WO2012133196A1

WO2012133196A1 - Process for producing solar cell sealing sheet

Info

Publication number: WO2012133196A1
Application number: PCT/JP2012/057531
Authority: WO
Inventors: 岡善之; 中原誠; 佐藤誠; 一ノ宮崇
Original assignee: 東レ株式会社
Priority date: 2011-03-31
Filing date: 2012-03-23
Publication date: 2012-10-04
Also published as: KR20140010961A; CN103442880B; CN103442880A

Abstract

The present invention is a process for producing a solar cell sealing sheet, the process comprising conducting the following steps (a), (b), and (c) in the this order: a step (a) in which a resin composition that has been melted by heating is formed into a sheet and then cooled to obtain a web sheet; a step (b) in which at least one surface of the web sheet obtained in the step (a) is heated for 22-55 seconds to elevate, during this heating, the temperature of this surface to a temperature not lower than the melting point of the resin composition that constitutes this surface; and a step (c) in which the surface of the web sheet which has been heated in the step (b) is made to have a temperature within a specific range, and an embossing roller is subsequently pushed against this surface to form an embossed pattern in the surface. Thus, a solar cell sealing sheet which suffers little heat shrinkage and in which a distinct embossed pattern has been formed can be efficiently produced at low cost.

Description

Method for producing solar cell encapsulant sheet

The present invention relates to a method for producing a solar cell encapsulant sheet. In particular, the present invention relates to a method for producing a sheet suitably used for producing a solar cell encapsulant sheet having a small heat shrinkage and having a clear protrusion formed on the surface.

In recent years, solar cells that directly convert sunlight into electrical energy have attracted attention and are being developed in various ways from the viewpoint of effective use of resources and prevention of environmental pollution. Generally, a solar cell is a solar cell sealing material sheet (hereinafter referred to as a sealing material sheet) between a light-receiving surface protective material typified by a glass substrate and a back surface protective material called a back sheet. The cell is sealed.

Crystalline silicon solar cells, which are mainstream as solar cell modules, are generally manufactured as follows. First, a glass substrate, a sealing material sheet, a solar battery cell (silicon power generation element), a sealing material sheet, and a back sheet are laminated in this order. This sealing material sheet is generally composed of an ethylene-vinyl acetate copolymer (hereinafter referred to as EVA). Subsequently, this laminated body is heated under vacuum with a vacuum laminator, and the sealing material sheet is heated and melted to be cured by crosslinking. In this way, a solar cell module in which the constituent members are bonded without bubbles is manufactured.

In the manufacture of such a solar cell module, if the shrinkage when the encapsulant sheet is heated is large, the shrinkage deformation may damage the silicon power generation element or shift the position of the cell. Therefore, the encapsulant sheet is required to have small shrinkage during heating. Further, in recent years, the thickness of silicon power generation elements has been reduced to about 100 μm and is more likely to be damaged due to effective utilization of crystalline silicon resources and cost reduction for the spread of solar cell modules. Therefore, the request | requirement which makes heat shrinkage of a sealing material sheet small is still stronger. For this reason, various methods for reducing the heat shrinkage rate of the encapsulant sheet have been studied. (For example, patent document 1).

Moreover, in addition to the above requirements for manufacturing, since the solar cell module is used for a long time after manufacturing, its reliability is extremely important. Typical defects that occur in a solar cell module that has been used for a long period of time include peeling between the solar cells and the sealing material sheet, poor appearance such as swelling, and a corresponding decrease in the amount of power generation. The reason for these malfunctions is not necessarily clarified, but studies have been made from the raw material side constituting the encapsulant sheet. For example, a method of adjusting the viscosity of EVA constituting the encapsulant sheet (Patent Document 2) and a method of adding a silane coupling agent to improve the adhesive strength between the solar battery cell and the encapsulant sheet (Patent Document) 3) etc. are being studied.

Furthermore, various studies have been conducted from the structural aspect of the encapsulant sheet. In order to prevent swelling and the like associated with long-term use, it is important that each component in the module immediately after manufacture is bonded in a state free from bubbles as much as possible. Therefore, attempts have been made to form various protrusions and depressions such as an embossed shape on the surface of the encapsulant sheet for the purpose of facilitating air removal during vacuum lamination. In addition, these protrusions and depressions may be formed for the purpose of preventing the solar cell from being damaged by the pressing pressure during lamination, or for improving the handling property of the sealing material sheet. About the embossed pattern, the detailed proposal is made about the shape, depth, etc. (patent documents 4 and 5).

As described above, when producing a sealing material sheet, it is important to form a clear embossed shape on the surface of the sealing material sheet while reducing heat shrinkage of the sealing material sheet. As a method proposed so far, when a sheet extruded from a T-die is cast using an extruder such as a twin-screw extruder, an embossed shape is formed on the sheet directly under the die, and then as necessary. A method of performing an annealing process for reducing heat shrinkage is disclosed (Patent Document 6).

JP 2000-084996 A JP 2002-170971 A JP 2000-183382 A JP 2006-134970 A JP 2002-185027 A JP 2010-100032 A

In the manufacturing method of Patent Document 6, after forming an embossed shape on the surface of a sheet in the manufacturing process (hereinafter referred to as a process sheet), the process sheet is annealed. Therefore, when the process sheet is sufficiently heated to reduce the heat shrinkage of the encapsulant sheet, the embossed shape formed on the surface of the process sheet is broken by the heating. Conversely, if the heating of the process sheet is loosened in order to maintain the embossed shape, the annealing process becomes insufficient. As described above, in the manufacturing method of Patent Document 6, it is very difficult to achieve both reduction in heat shrinkage and clear formation of an embossed shape.

Moreover, as a method of reducing the heat shrinkage of the encapsulant sheet, generally, as disclosed in Patent Document 1, when the resin film is conveyed by a conveyor having a plurality of rollers, the entrance side A method of reducing the heat shrinkage by shrinking the process sheet, for example, by making the peripheral speed of the roller faster than the peripheral speed of the roller on the outlet side is used. However, in this method, since the sheet is stretched during the annealing treatment, the heat shrinkage is not sufficiently removed, and it is necessary to carry out the annealing treatment for a long time of 1 to 2 minutes.

In addition, the encapsulant sheet composed of EVA often contains a cross-linking agent, and the molding temperature of the process sheet becomes low, so that a lot of residual distortion remains in the process sheet. Moreover, the residual strain is often not uniform in the width direction of the wide process sheet. When the process sheet in such a state is annealed as described above, the flatness of the sheet is impaired, the thickness becomes non-uniform, and problems such as the process sheet meandering during the annealing process occur. Furthermore, it is very difficult to continuously press and emboss the process sheet in such a state with a plurality of rollers.

Therefore, an object of the present invention is to provide a production method capable of forming a clear embossed shape on the surface of the encapsulant sheet while sufficiently reducing the heat shrinkage of the encapsulant sheet.

In order to solve the above problems, the method for producing a solar cell encapsulant sheet of the present invention is characterized in that the following step (a), step (b) and step (c) are performed in this order.
Step (a): Forming a resin composition melted by heating into a sheet shape, and then cooling to obtain a step sheet Step (b): At least one surface of the step sheet obtained in the step (a) Is heated for 22 to 55 seconds, and during this heating, the temperature of the surface reaches a temperature not lower than the melting point of the resin composition constituting the surface portion. Step (c): Heated in the step (b) The surface of the process sheet is brought to a temperature of (the melting point of the resin composition constituting the surface portion−10 ° C.) to (the melting point of the resin composition constituting the surface portion + 20 ° C.), and then an embossing roller is pressed against the surface Bumping and forming an embossed shape on this surface

According to the present invention, a solar cell encapsulant sheet having a small heat shrinkage and a clear embossed shape can be efficiently produced at low cost.

FIG. 1 is a schematic diagram showing an example of a method for producing a solar cell encapsulant sheet of the present invention. FIG. 2 is a schematic diagram showing an example of a conventional method for producing a solar cell encapsulant sheet. FIG. 3 is a diagram for explaining a method of measuring the height of the protrusions of the solar cell encapsulant sheet having protrusions formed on one side. FIG. 4 is a diagram for explaining a method for measuring the height of the protrusions of the solar cell encapsulant sheet having protrusions formed on both sides. FIG. 5 is a diagram illustrating the length D of the bottom side of the protrusion.

[Method for producing solar cell encapsulant sheet]
The manufacturing method of the solar cell sealing material sheet of this invention performs the following process (a), a process (b), and a process (c) in this order.
Step (a): A step of forming a resin composition melted by heating into a sheet and then cooling to obtain a process sheet.
Step (b): At least one surface of the process sheet obtained in the step (a) is heated for 22 to 55 seconds, and during this heating, the temperature of the surface is set to the melting point of the resin composition constituting the surface portion. The process of reaching the above temperature.
Step (c): The surface of the process sheet heated in the step (b) is changed from (the melting point of the resin composition constituting the surface portion−10 ° C.) to (the melting point of the resin composition constituting the surface portion + 20). C.), and then an embossing roller is pressed against the surface to form an embossed shape on the surface.

Hereinafter, the manufacturing method of the solar cell sealing material sheet of this invention is demonstrated, referring drawings. FIG. 1 is a schematic diagram showing one embodiment of the production method of the present invention.

[Step (a): Film-forming step]
First, the step (a) will be described. Step (a) is a step of forming a raw material resin into a sheet and cooling it to obtain a process sheet. Hereinafter, the step (a) is referred to as a film forming step.

The film forming process in FIG. 1 includes an extruder 11 that melts and kneads the raw resin and additives at high temperature, a gear pump 31 that reduces the pressure fluctuation of the resin and stabilizes the thickness of the sheet, and the kneaded molten resin into the sheet. A die 12 to be extruded into a shape and

polishing rollers

13a, 13b and 13c for cooling and solidifying the extruded high-temperature process sheet to form a solid process sheet are installed.

As the extruder 11, a single screw extruder or a twin screw extruder can be used. The use of a twin screw extruder is preferred from the viewpoints of productivity, kneadability of resin and additive, and the like. In the case of using a single screw extruder, since the inside of the extruder is filled with resin, the pressure fluctuation at the die portion at the tip of the extruder is relatively small, and therefore it is not always necessary to install a quantitative supply device such as the gear pump 31. . When a twin screw extruder is used, the inside of the extruder is not filled, and therefore it is preferable to install a quantitative supply device such as a gear pump 31 between the extruder and the die.

The raw material resin and the additive to be charged into the extruder 11 may be mixed in advance using a mixer or a blender, or may be individually charged. Moreover, you may use the method etc. which side-feed an additive from the middle of an extruder, or add with an injection pump etc., if it is a liquid additive.

The temperature at which the raw material resin and the additive are kneaded depends on the type and viscosity of the resin used, but is preferably in the range of (melting point of raw material resin + 10 ° C.) to (melting point of raw material resin + 60 ° C.). In the present invention, the melting point is an endothermic peak value temperature when the temperature is raised at 10 ° C./min in differential scanning calorimetry (DSC). In the case of an EVA sheet generally used as a sealing material sheet, an organic peroxide is often contained as an additive in order to crosslink EVA. Therefore, it should be noted that the organic peroxide is kneaded without being decomposed as much as possible. Therefore, the resin temperature is preferably in the range of 80 to 130 ° C., for example, in the case of EVA having a melting point of about 70 ° C. More preferably, it is in the range of 100 to 120 ° C. If it is less than 80 degreeC, kneadability becomes inadequate and the uniform dispersibility of an additive may fall. As a result, the appearance of the encapsulant sheet may be deteriorated. When it exceeds 130 ° C., when an organic peroxide is blended, the organic peroxide is decomposed, the quality of the sealing material sheet is not stabilized, and the continuous productivity may be lowered.

In addition, in the process of FIG. 1, although the extruder is installed as a method of forming the process sheet into a film, a known different method such as molding with a calendar roller may be used.

The molten resin kneaded by melting the raw resin and the additive in the extruder 11 or the like is extruded into a sheet shape using the die 12. As the die 12, a T die, a circular die, or the like can be used. Since a flat die has a wide shape in accordance with the sheet width to be extruded, it becomes a T shape when attached to an extruder, and is collectively called a T die. In addition, since the residence time and flow rate differ in the die width direction in the T die, problems such as uneven thickness and uneven thickness in the width direction occur when the process sheet is heated in step (b). It's easy to do. In order to solve this, it is also preferable to use a cylindrical circular die. The circular die is a cylindrical die for extruding a resin into a cylindrical shape and cutting it into a sheet shape, and the physical properties in the width direction of the sheet tend to be relatively uniform.

Also, when using a T-die, different resin compositions are extruded using a plurality of extruders, and the process sheet can be laminated by a co-extrusion method such as a feed block method or a multi-die method. By setting it as such a laminated structure, a function required as a sealing material sheet can be isolate | separated for every layer, and cost can be reduced by adjusting the amount of additives.

The process sheet extruded using the die 12 is formed into a sheet shape by polishing

rollers

13a, 13b, and 13c. The polishing roller is a process sheet conveying apparatus composed of a plurality of rollers for simultaneously pressing the molten resin between a pair of rollers and shaping the sheet thickness and surface properties. Each configured roller includes a mechanism that adjusts the temperature to a temperature suitable for cooling and shaping of the molten resin, and a mechanism that adjusts the gap between the rollers and the pressure. Moreover, it is preferable to prevent sticking of the process sheet and improve the moldability by flowing temperature-controlled water such as cooling water as necessary. The temperature of the cooling water is preferably adjusted in the range of 0 to 30 ° C. Of the polishing rollers, the polishing roller 13a located on the most upstream side is likely to stick high temperature resin to the surface of the roller depending on the composition of the resin used. It is preferable to improve the property. In order to further improve the transportability, it is also preferable that the opposite roller 13b of the polishing roller 13a located on the most upstream side is a metal roller having a matte surface shape. The satin-like surface roughness preferably has a 10-point average roughness Rz defined by JIS B 0601-1994 in the range of about 2 to 10 μm. When silicon rubber or the like is wound around the surface of the polishing roller 13a and the counter roller 13b is a metal roller having a satin surface shape, the thickness of the silicon rubber on the surface of the polishing roller 13a is 3 to 10 mm. It is preferably 4 to 8 mm. When the thickness of the silicon rubber is less than 3 mm, the transfer of the textured pattern becomes insufficient, and the process sheet may adhere to a free roller or the like for conveying the process sheet. If the thickness of the silicon rubber exceeds 10 mm, the heat from the molten resin is stored on the rubber surface, and the resin may stick to the roller.

[Process (b): Annealing process]
Next, the step (b) will be described. The purpose of the step (b) is to remove the residual strain of the process sheet formed in the film forming process and reduce the heat shrinkage of the process sheet. In the step (b), a method of passing the process sheet on the plurality of conveying rollers 17 while heating with the heater 16 installed in the annealing furnace 15 can be mentioned. Hereinafter, the step (b) is referred to as an annealing step.

The heater 16 for heating the process sheet is not particularly limited as long as it can heat the process sheet, and a known method such as a ceramic heater, a stainless steel heater, or a sheath heater can be used. In particular, the method of heating the sheet with infrared rays is preferable because the sheet can be heated uniformly in the thickness direction of the sheet. Further, heating with a heat medium such as hot air or steam, a method of contacting with a heated roll, or the like can also be preferably used. These heating methods may be used alone or in combination of several methods.

It is preferable that the conveyance roller 17 for conveying the process sheet is excellent in releasability in order to convey the heated process sheet. For this reason, fluorocarbon resins such as polytetrafluoroethylene, perfluoroethylene propene copolymer, and perfluoroalkoxyalkane are coated on metal rollers that have uneven surfaces by embossing or thermal spraying of compounds such as metals and metal oxides. You may use the roller which did. Or you may use the roller which wound the paper, the film, etc. which performed the releasable coating process on the surface of the metal roller. These means for imparting releasability need not be particularly limited, and conventionally known methods can be used. The degree of releasability of these rollers is preferably a material having a peel strength of 5 N / mm or less with respect to the cellophane tape manufactured by Nichiban Co., Ltd. according to the method specified in JIS Z0237-2009. Moreover, it is preferable for the conveyance roller 17 in a furnace to be able to control the speed | rate separately according to shrinkage | contraction of a process sheet | seat, in order to remove a heating shrinkage efficiently.

It is preferable that the heater 16 and the transport roller 17 are installed in the annealing furnace 15 and the contact with the outside air is minimized as the temperature in the furnace is stabilized and the heat treatment of the process sheet is stabilized. Moreover, it is one of the preferable aspects to supply hot air into a furnace in order to stabilize the temperature in a furnace uniformly.

Furthermore, it is preferable to provide a pair of nip rollers 14 upstream of the annealing furnace 15 as necessary. Providing the nip roller 14 is preferable because the influence of the annealing process on the film forming process can be blocked. Specifically, shrinkage when heating the process sheet can be prevented from affecting the film forming process, and the supply of the process sheet to the annealing process can be stabilized.

Further, it is preferable to provide a sheet take-out roller 18 between the outlet of the annealing furnace 15 and the embossing roller 20. The sheet take-out roller 18 plays a role of taking out the process sheet from the annealing furnace 15. If the sheet take-out roller 18 is not provided, the process sheet may be pulled between the most outlet side roller 17 and the embossing roller 20 among the rollers 17 in the annealing furnace to cause distortion. Further, in the annealing treatment, wrinkles or the like may occur if there is unevenness in the heat shrinkage of the process sheet in the width direction of the process sheet. Therefore, in order to remove the wrinkle, the sheet take-out roller 18 is an expander roller (an arch-shaped curved roller). ) Is also preferable. The sheet take-out roller 18 is preferably provided with releasability in the same manner as the transport roller 17 in the furnace.

Further, if the surface temperature of the sheet take-out roller 18 is too low, the process sheet supplied to the embossing roller is cooled, and the embossed shape transferability may be lowered. On the other hand, if the surface temperature is too high, the process sheet may stick to the sheet take-out roller 18 and it may be difficult to convey the process sheet. Therefore, it is preferable that the surface temperature of the sheet take-out roller 18 is adjusted in the range of 20 to 80 ° C. Furthermore, it is preferable that the surface temperature is equal to or lower than the temperature of the process sheet at the exit of the annealing furnace. If the surface temperature of the sheet take-out roller 18 is higher than the surface temperature of the process sheet taken out of the annealing furnace, the process sheet may stick to the roller.

In order to prevent the temperature of the process sheet from decreasing, the distance between the annealing furnace 15 and the embossing roller 20 is preferably as short as possible. For this reason, a plurality of sheet take-out rollers 18 can be installed, but it is preferable that the number is less, and it is preferable that the number be at most 3 or less, and more preferably 1 or 2.

Controlling the surface temperature of the process sheet exiting the annealing furnace 15 and the surface temperature of the process sheet introduced into the embossing roller in the process (c) when performing the annealing process and the next process (c) continuously. Is preferred. Therefore, in order to correctly grasp the surface temperature of the process sheet, it is preferable to provide a non-contact infrared thermometer 33 for measuring the surface temperature of the exit part of the annealing furnace 15 and the process sheet immediately before embossing. Further, it is preferable to install a plurality of non-contact thermometers in the annealing furnace 15 and measure the surface temperature of the process sheet.

In the annealing process, heating is performed until the maximum temperature of at least one surface of the process sheet reaches a temperature equal to or higher than the melting point of the resin composition constituting the surface portion. The surface on the heated side is embossed in the next step (c). Here, when the process sheet is a single layer sheet, the “resin composition constituting the surface portion” is a resin composition constituting the process sheet, and the process sheet is a laminated sheet in which a plurality of layers are laminated. In this case, it is a resin composition constituting the layer on the surface on the heated side. Even if an annealing process is performed in which the maximum temperature is only a temperature lower than the melting point of the resin composition, the effect of reducing the heat shrinkage rate is insufficient, or a long-time process is required. The maximum surface temperature is within the temperature range of (the melting point of the resin composition constituting the heated surface portion + 5 ° C.) to (the melting point of the resin composition constituting the heated surface portion + 35 ° C.). preferable. If the temperature during the annealing process becomes too high, the process sheet may adhere to the transport roller, the flatness may deteriorate, or wrinkles may occur in the next process (c) due to these reasons. For example, in the case of a process sheet made of EVA resin having a melting point of 71 ° C., the highest surface temperature in the annealing process is preferably in the range of 76 to 106 ° C.

The time for heating the process sheet, that is, the time for retaining the process sheet in the annealing furnace is in the range of 22 to 55 seconds. This heating time is the time required for the process sheet cooled by the polishing roller 13 to reach the surface temperature of the process sheet above the melting point temperature, and the annealing treatment to reduce the heat shrinkage after reaching the melting point temperature or more. It is the total with the time to do. If the heating time is less than 22 seconds, removal of the heat shrinkage is insufficient. Even if the heating time exceeds 55 seconds, the effect is saturated, and the length of the annealing furnace is merely increased unnecessarily. The lower limit of the heating time is preferably 22 seconds or more, and more preferably 25 seconds or more. The upper limit of the heating time is preferably shorter as long as the heat shrinkage can be sufficiently removed, preferably 45 seconds or shorter, and more preferably 40 seconds or shorter.

[Process (c): Embossing process]
Next, step (c) will be described. Step (c) is a step of embossing the process sheet that has been brought to a high temperature state by heating in the annealing process to form an embossed shape on the surface of the process sheet. In the step (c), an embossing roller 20, an embossing counter roller 19, and a cooling roller 21 for forming an embossed shape on the process sheet are provided. Hereinafter, this step (c) is referred to as an embossing step.

The surface of the embossing roller 20 is engraved with the embossed shape inverted corresponding to the embossed shape desired to be formed on the process sheet. What is necessary is just to determine the emboss shape formed in a process sheet | seat as needed, such as a random shape and a geometric pattern. However, if the embossed shape is insufficiently formed, blocking is likely to occur when the process sheet is conveyed and rolled, or air is difficult to escape when creating a solar cell module. May cause air bubbles. The engraving pattern applied to the surface of the embossing roller can be a hemispherical shape, a triangular pyramid shape, a quadrangular pyramid shape, a hexagonal pyramid shape, a conical shape such as a conical shape, or a trapezoidal shape with a flat top. Moreover, the pattern in which these shapes were mixed may be sufficient. Among these, a hemispherical shape and / or a quadrangular pyramid shape are preferable. Here, “hemispherical and quadrangular pyramid” means sculpture with a pattern in which hemispherical and quadrangular pyramid are mixed. A hemispherical shape is preferable in that concentrated load is not easily applied when the encapsulant sheet is pressed against the solar battery cell, and the load can be uniformly dispersed. Further, a quadrangular pyramid shape is preferable in that unevenness of reflected light of the encapsulant sheet hardly occurs and the surface quality is excellent. And since both hemispherical and quadrangular pyramid features can be produced, a pattern in which hemispherical and quadrangular pyramid shapes are mixed is also preferable. When the hemispherical shape and the quadrangular pyramid shape are mixed, the ratio of each may be arbitrarily determined according to which feature is to be obtained. Particularly preferably, all are hemispherical patterns.

If the surface of the embossing roller is too deep, a large press pressure is required during embossing, resulting in a large equipment. Therefore, the engraving depth of the emboss roller is preferably in the range of 65 to 350 μm, although it depends on the thickness of the process sheet. The depth of engraving of the embossing roller is the distance from the center of the embossing roller to the surface of the embossing roller (the part not engraved) and the deepest of the engraving recess (the valley part) from the center of the embossing roller. Indicates the difference from the distance to the part. The depth of this sculpture is indicated by the maximum height Pz (μm) measured using a surface roughness measuring machine in accordance with JIS B0601 (2001).

The surface of the embossing roller is preferably further recessed with a depth of 1 to 20 μm. By embossing with an embossing roller provided with such minute depressions, minute projections are formed on the surface of the sheet. As a result, the slipperiness of the sheet is improved and handling is facilitated, and light is scattered by minute projections, and the whiteness of the sheet is improved, so that it is easy to inspect adhered foreign matters and the like. Such a minute depression can be easily formed by carrying out a known blasting process after engraving the embossing roller surface. The depth of the minute recess can be adjusted by the particle size at the time of blasting and the pressure condition.

The embossing counter roller 19 facing the embossing roller is preferably a rubber roller wrapped around a metal roller in order to improve transferability of the embossing roller surface to the engraving process sheet. The type of rubber is not particularly limited, such as silicone rubber, nitrile rubber, and chloroprene rubber, but rubber having a type A hardness in the range of 65 to 85 ° in accordance with JIS K 6253-2006 is preferable. Even if the angle is less than 65 ° or exceeds 85 °, the transfer property of the embossed shape may be deteriorated. Among these rubbers, silicon rubber is most preferable because of its good releasability from a process sheet that is easily adhered at high temperatures.

In the embossing process, the temperature of the surface heated in the annealing process of the process sheet supplied to the embossing roller is set to (melting point of the resin composition constituting this surface−10 ° C.) to (of the resin composition constituting this surface). (Melting point + 20 ° C.). If it is less than (the melting point of the resin composition−10 ° C.), the transferability of the embossed shape is lowered. If it exceeds (the melting point of the resin composition + 20 ° C.), the temperature of the process sheet in the annealing process becomes too high, and wrinkles and the like are likely to occur in the annealing process. For example, when the surface layer is made of EVA resin having a melting point of 71 ° C., the surface temperature during embossing is in the range of 61 to 91 ° C.

Furthermore, the pressing pressure of the embossing roller 20 is preferably set so that the linear pressure applied to the process sheet is in the range of 150 to 500 N / cm. More preferably, it is in the range of 200 to 450 N / cm. If the linear pressure is less than 150 N / cm, the embossed shape transferability may be lowered. If an attempt is made to apply a linear pressure exceeding 500 N / cm, it is necessary to increase the size of the equipment, and in this case, the life of the opposing rubber roller is reduced.

In the conventional technique shown in FIG. 2, a linear pressure of about 100 N / cm is sufficient even if the pressing pressure of the embossing roller 13b 'is high. This is because the temperature of the resin extruded from the T die is, for example, in the range of 100 to 120 ° C. when EVA resin having a melting point of 71 ° C. is used. It is estimated that a pressure of about 100 N / cm is sufficient. On the other hand, in the production method of the present invention, as described above, embossing is performed within the temperature range of (melting point of resin composition−10 ° C.) to (melting point of resin composition + 20 ° C.). As described above, when the surface temperature of the process sheet at the time of embossing becomes low, it becomes difficult to transfer the embossed shape. Therefore, it is preferable to increase the pressing pressure necessary for the embossing. That is, the linear pressure is preferably 150 N / cm or more. In addition, the linear pressure said by this invention is the value which remove | divided the pressing load of the roller by the surface length of the roller.

Furthermore, in the embossing process at a relatively low temperature as described above, it is preferable that the process sheet is held by the embossing roller 20 in order to improve the transferability of the embossed shape. Specifically, the hugging angle to the embossing roller is preferably in the range of 30 to 270 °. If only shallow embossing is to be applied, the hugging angle may be less than 30 °. However, in order to give a deep and well-defined embossing, it is preferable to set the hugging angle to 30 ° or more. Note that the hugging angle can be simply calculated from the ratio between the arc length of the portion where the process sheet 32 is in contact with the embossing roller 20 and the circumference of the embossing roller. For example, when the hugging angle is 90 °, it means that the process sheet is in contact with a portion corresponding to ¼ of the circumference of the embossing roller.

The surface temperature of the embossing roller 20 in this embossing process is preferably (the melting point of the resin composition constituting the surface portion on the side to which the embossed shape is transferred−20 ° C.) or less. When the temperature of the embossing roller is low, the releasability of the process sheet is improved, and the process sheet is difficult to wind around the roller. As a result, the load when the process sheet is peeled off from the embossing roller is reduced, and a solar cell encapsulant sheet with better quality can be obtained.

After releasing the process sheet from the embossing roller, the process sheet is cooled by the cooling roller 21, and the surface temperature of the process sheet is quickly lowered to near room temperature.

After forming the film in this way, removing the heat shrinkage by annealing, and forming the embossed shape, the process sheet 32 is adjusted to a desired width by a defect inspection and then rolled into a roll shape by a winder or the like. Or cut into a cut sheet having a desired length and used for manufacturing a solar cell module.

[Solar cell encapsulant sheet]
Next, the solar cell encapsulant sheet will be described. The encapsulant sheet preferably has an independent protrusion having a height of 60 to 300 μm on the surface. By having independent protrusions with a height of 60 μm or more on the surface of the encapsulant sheet, the air remaining between the encapsulant sheet and the solar cells is multi-directional during vacuum lamination when manufacturing a solar cell module. It is possible to efficiently remove the bubbles and suppress the generation of bubbles. Furthermore, it is possible to disperse the pressing force of the encapsulant sheet to the solar battery cells and suppress the occurrence of cell cracking. If the shape of the surface of the sealing material sheet is not an independent protrusion but a continuous groove shape, deaeration in a direction perpendicular to the groove becomes insufficient, and the remaining air becomes bubbles. Further, when the height of the protrusion is 300 μm or less, the concentration of the load on the top of the protrusion during vacuum lamination is suppressed, and the solar battery cell can be prevented from cracking. Here, the “independent protrusion” refers to a protrusion having a bottom length D to be described later in the range of 70 to 6000 μm when attention is paid to the bottom surface of the protrusion.

In addition, the independent protrusions are sandwiched between flat plates, applied with a pressure of 50 kPa in the thickness direction and compressed to deform the protrusions, and when the area where the tops of the protrusions contact the flat plate expands, It is preferable that a gap of 20 to 800 μm is secured between the two regions derived from the protrusions.

The independent protrusion preferably has a ratio (T / D) of the protrusion height (T) to the base length (D) of 0.05 to 0.80. More preferably, it is 0.15 to 0.80. If the T / D ratio is less than 0.05, the cushioning property of the encapsulant sheet may be insufficient. When the T / D ratio exceeds 0.80, a concentrated load on the top of the protrusion occurs, and cell cracking may occur. The height T of the protrusion is measured as follows. First, the case where there is a protrusion on one side will be described. The surface of the encapsulant sheet having the protrusions is referred to as A surface, and the surface having no protrusion is referred to as B surface. As shown in FIG. 3, the distance from the apex of the protrusion on the A surface to the B surface is Tmax, and the distance from the portion having no protrusion on the A surface to the B surface is Tmin. The difference between Tmax and Tmin is the height T of the protrusion. Next, the case where both have projections will be described. One side of the encapsulant sheet is referred to as A side and the other side is referred to as B side. As shown in FIG. 4, the distance from the apex of the protrusion on the A surface to the portion without the protrusion on the B surface is TAmax, the distance from the apex of the protrusion on the B surface to the portion without the protrusion on the A surface is TBmax, The distance from the portion having no protrusion to the portion having no protrusion on the B surface is defined as Tmin. The difference between TAmax and Tmin is the height TA of the projection on the A surface, and the difference between TBmax and Tmin is the height TB of the projection on the B surface. The length of the bottom of the protrusion is the outer diameter D of the protrusion shown in FIG. When the shape of the bottom surface of the protrusion is a polygon such as a triangle or a hexagon or an ellipse, the length of the bottom of the protrusion is the diameter of the smallest perfect circle including the shape of the bottom surface. The above Tmax, Tmin, and D can be measured by observing the sheet with a stereomicroscope.

Desirable protrusion height T is 60 to 300 μm as described above. When the height T of the protrusion is 60 μm, the length of the base D of the protrusion is preferably 75 to 1200 μm, more preferably 75 to 400 μm. When the height T of the protrusion is 300 μm, the length of the base D of the protrusion is preferably 375 to 6000 μm, more preferably 375 to 2000 μm.

The number of independent protrusions is preferably 40 to 2300 per 1 cm ² area on one side of the sheet. More preferably, it is 40 to 1100. If the number of independent protrusions is less than 40 / cm ² , cell cracks or bubbles may occur. If it exceeds 2300 pieces / cm ² , the T / D ratio increases, and cell cracking may occur due to the concentrated load on the top of the protrusion.

The encapsulant sheet preferably has a heat shrinkage rate of 30% or less in the sheet flow direction when left in warm water at 80 ° C. for 1 minute. More preferably, it is 25% or less. Here, “Leave in warm water” means that when the specific gravity of the encapsulant sheet is small and the encapsulant sheet floats on the surface of the warm water, the encapsulant sheet is pressed from above and submerged in the warm water. Instead, leave it in its floating state. On the other hand, when the specific gravity of the encapsulant sheet is large and the encapsulant sheet sinks in warm water, the encapsulant sheet is not allowed to be supported from below but is left in its submerged state. The “sheet flow direction” is a direction in which the process sheet flows in the manufacturing process of the sealing material sheet. In a general vacuum laminating process in the manufacture of a solar cell module, vacuuming is performed without applying pressure to the sealing material sheet until the sealing material sheet is sufficiently melted, and the sealing material sheet is melted and removed. Do care. At this time, since the encapsulant sheet is exposed to a no-load state at a high temperature of about 80 ° C., the encapsulant sheet contracts, and as a result, cell cracks and displacement occur. As a result of investigations by the inventors focusing on cell cracks and misalignment, when the process sheet is left for 1 minute in a no-load state that reproduces the inside of the vacuum laminator, the heat shrinkage rate in the sheet flow direction is 30. It was found that the cell cracking can be further suppressed if it is at most%. The state where the inside of the vacuum laminator is reproduced is a state where the process sheet is left in 80 ° warm water. The heat shrinkage rate in the direction orthogonal to the flow direction of the sheet is not particularly limited because it is minute compared to the flow direction, but is preferably 5% or less.

The shape of the independent protrusion is preferably a hemispherical shape, a pyramid shape such as a triangular pyramid, a quadrangular pyramid, a hexagonal pyramid, or a cone, or a trapezoidal shape in which the tops thereof are flattened. Moreover, the state in which these protrusion shapes are mixed may be used. Among these, a hemispherical shape and / or a quadrangular pyramid shape are preferable. Here, “hemispherical and quadrangular pyramid” means a surface shape in which hemispherical protrusions and quadrangular pyramidal protrusions are mixed. A hemispherical shape is preferable in that a concentrated load on the solar battery cell is difficult to be applied and the load can be uniformly dispersed when the pressure is applied to the solar battery cell. Further, a quadrangular pyramid shape is also preferable in that unevenness of reflected light hardly occurs and the surface quality is excellent. And since both hemispherical and quadrangular pyramid features can be obtained, a shape in which a hemispherical shape and a quadrangular pyramid shape are mixed is also preferable. When the hemispherical shape and the quadrangular pyramid shape are mixed, the ratio of each may be arbitrarily determined according to which feature is to be obtained. Particularly preferably, all are hemispherical patterns.

The sealing material sheet of the present invention preferably further has a protrusion having a height of 1 to 15 μm on the surface having an independent protrusion. By having such a minute protrusion, the slipperiness of the sheet is improved and the handling becomes easy. In addition, light is scattered by the minute protrusions, and the whiteness of the sheet is improved, so that it is easy to inspect adhered foreign matter and the like.

Such fine protrusions can be achieved by the manufacturing method of the present invention in which embossing is performed after the annealing step. In the conventional method in which annealing is performed by heating after embossing, large protrusions with a height of several tens of μm may remain on the sheet even after the heat treatment, but they are very small with a height of several μm. The protrusion disappears with the heat treatment.

The height of the minute protrusion is a numerical value measured as follows. The surface of the sheet is photographed at a magnification of 400 using a well-known laser microscope such as a laser microscope VK-X100 manufactured by Keyence Corporation in accordance with JIS B0601 (2001). In the roughness curve of the obtained image, the Rz value when the cutoff value is 0.080 mm is defined as the height of the minute protrusion.

In the present application, as an index for evaluating the cushioning property of the encapsulant sheet for suppressing cell cracking of the solar battery, the repulsive stress of the sheet when the surface having the projection of the encapsulant sheet is compressed 100 μm in the thickness direction is used. adopt. As a result of intensive studies on the relationship between the cell cracking property of the solar battery and the cushioning property of the sealing material sheet, it was found that the repulsive stress at which cell cracking is suppressed is preferably 70 kPa or less. The above repulsive stress is a sealing material sheet using a compression test apparatus having a resolution of 5 μm or less as a compression displacement and 100 Pa or less as a compression load, and a flat pressure terminal at a pressure rate of 0.02 mm / s. It is obtained by measuring the repulsive stress (kPa) of the sheet when the surface having the protrusions is pressed 100 μm in the thickness direction. When the repulsive stress of the encapsulant sheet is 70 kPa or less, the solar cell can be prevented from cracking by laminating the surface having the protrusion so as to be in contact with the solar cell and performing vacuum lamination. The shape of the surface opposite to the surface having the projection of the encapsulant sheet is not particularly limited, but it is about 2 to 10 μm in height from the viewpoint of preventing adhesion of the encapsulant sheet when manufacturing the solar cell module. It is preferable to have minute protrusions.

The thickness of the sealing material sheet is preferably 50 to 1500 μm. More preferably, it is 100 to 1000 μm, particularly preferably 200 to 800 μm. If it is less than 50 μm, the cushioning property of the solar cell encapsulant sheet may be poor, or a problem may occur from the viewpoint of workability. On the other hand, if the thickness exceeds 1500 μm, a decrease in productivity and a decrease in adhesion may be a problem. In addition, the thickness of a sealing material sheet is the distance from the vertex of a processus | protrusion to the surface on the opposite side to the surface which has a processus | protrusion, when the processus | protrusion is formed only in the single side | surface of the encapsulant sheet. When protrusions are formed on both surfaces of the encapsulant sheet, the distance is from the top of the protrusion on one surface to the top of the protrusion on the opposite surface.

Thus, in order to accurately form independent protrusions on the surface of the encapsulant sheet, or to suppress the heat shrinkage rate of the encapsulant sheet within a specific range, the encapsulant sheet is used in the production method of the present invention. It is preferable to manufacture.

[Raw material constituting solar cell encapsulant sheet]
Next, the resin composition which comprises a sealing material sheet is demonstrated. In addition, it is preferable that the resin composition which comprises the surface part by the side in which a processus | protrusion is formed satisfy | fills the composition etc. of the resin composition demonstrated below. Of course, it is more preferable that all resin compositions constituting the process sheet satisfy the composition of the resin composition described below.

It is preferable that the resin composition which comprises a sealing material sheet contains polyolefin resin. Polyolefin resins include homopolypropylene, copolymers with other monomers based on propylene, polypropylene resins such as ethylene-propylene-butene terpolymers, low density polyethylene, ultra low density polyethylene, straight Examples thereof include chain-type low-density polyethylene, medium-density polyethylene, high-density polyethylene, polyethylene resins such as copolymers with other monomers mainly composed of ethylene, and polyolefin-based thermoplastic elastomers. Examples of the copolymer with other monomers mainly composed of ethylene include an ethylene-α-olefin copolymer and an ethylene-unsaturated monomer copolymer. As the α-olefin, α-olefin is ethylene, propylene, 1-butene, isobutylene, 1-pentene, 2-methyl-1-butene, 3-methyl-1-butene, 1-hexene, 1-heptane, 1 -Octene, 1-nonene, 1-decene and the like. Examples of the unsaturated monomer include vinyl acetate, acrylic acid, methacrylic acid, methyl acrylate, methyl methacrylate, ethyl acrylate, and vinyl alcohol. In addition, it is one of preferred embodiments that these polyolefin resins are copolymerized or modified in a small amount using a silane compound, a carboxylic acid, a glycidyl compound, or the like, if necessary.

Among these polyolefin-based resins, ethylene vinyl acetate copolymer, ethylene methyl methacrylate copolymer, and low density polyethylene are used from the viewpoint of transparency that is important as a solar cell encapsulant and adhesion to solar cells. It is preferable to use one modified with an ethylenically unsaturated silane compound. When an ethylene vinyl acetate copolymer or an ethylene methacrylate copolymer is used, the content of the copolymer component is preferably in the range of 15 to 40% by mass.

Moreover, it is preferable that the resin composition constituting the sealing material sheet contains an organic peroxide. Any organic peroxide can be used as long as it decomposes at a temperature of 100 ° C. or higher to generate radicals. The temperature at which the solar cell encapsulant sheet is produced, the solar cell What is necessary is just to select in consideration of the heating and laminating temperature at the time of producing a module, the storage stability of the crosslinking agent itself, and the like. In particular, those having a decomposition temperature of 70 hours or more with a half-life of 10 hours are preferred. Examples of such organic peroxides include 1,1-di (t-hexylperoxy) cyclohexane, n-butyl 4,4-di- (t-butylperoxy) valerate, 2,5-dimethyl- 2,5-di (t-butylperoxy) hexane, di-t-butyl peroxide, di-t-hexyl peroxide, 2,5-dimethyl-2,5-di (t-butylperoxy) hexyne-3 Disuccinic acid peroxide, di (4-t-butylcyclohexyl) peroxydicarbonate, 1,1,3,3-tetramethylbutylperoxy-2-ethylhexanoate, t-hexylperoxy-2-ethylhexa Noate, t-butylperoxy-2-ethylhexanoate, t-hexylperoxyisopropyl monocarbonate, di (4-t-butylcyclohexyl) Syl) peroxydicarbonate, t-butylperoxy-3,5,5-trimethylhexanoate, t-butylperoxylaurate, t-butylperoxy-2-ethylhexyl monocarbonate, t-butylperoxy- 2-ethylhexanoate, t-butylperoxyisobutyrate, t-butylperoxyacetate, t-butylperoxyisononanoate, t-amylperoxy-2-ethylhexanoate, t-amylperoxy Normal octoate, t-amylperoxyoxynononanoate, t-amylperoxy-2-ethylhexyl carbonate, di-t-amyl peroxide, 1,1-di (t-butylperoxy) cyclohexane, ethyl 3,3 -Di (t-butylperoxy) butyrate, 1,1-di (t-amyl) Peroxy) cyclohexane and the like. These organic peroxides may be used in combination of two or more. The content of these organic peroxides is preferably 0.1 to 5 parts by mass with respect to 100 parts by mass of the polyolefin resin. The amount is more preferably 0.1 to 3 parts by mass, particularly preferably 0.2 to 2 parts by mass. If the content of the organic peroxide is less than 0.1 part by mass, the polyolefin resin may not be crosslinked. Even if the content exceeds 5 parts by mass, the content effect is low, and undecomposed organic peroxide may remain in the encapsulant sheet, which may cause deterioration over time.

The resin composition constituting the encapsulant sheet may further contain a crosslinking aid, a silane coupling agent, a light stabilizer, an ultraviolet absorber, an antioxidant, and the like.

The crosslinking aid is a polyfunctional monomer having a plurality of unsaturated bonds in the molecule and reacts with the active radical compound generated by the decomposition of the organic peroxide to uniformly and efficiently crosslink the polyolefin resin. Used for. Examples of these crosslinking aids include triallyl isocyanurate, triallyl cyanurate, trimethylolpropane tri (meth) acrylate, pentaerythritol tri (meth) acrylate, tris [(meth) acryloyloxyethyl] isocyanurate, Dimethylolpropane tetra (meth) acrylate, pentaerythritol tetra (meth) acrylate, pentaerythritol ethoxytetra (meth) acrylate, dipentaerystol penta (meth) acrylate, dipentaerystol hexa (meth) acrylate, divinylbenzene, etc. Can be mentioned. These crosslinking aids may be used alone or in combination of two or more. In the present invention, “(meth) acrylate” means “acrylate or methacrylate”.

Among these crosslinking aids, triallyl isocyanurate and trimethylolpropane tri (meth) acrylate are particularly preferable. The content in the case of adding these crosslinking aids is preferably 0 to 5 parts by mass with respect to 100 parts by mass of the polyolefin resin. The amount is more preferably 0.1 to 3 parts by mass, particularly preferably 0.3 to 3 parts by mass. Even if the content exceeds 5 parts by mass, the effect is only slightly improved, which causes a cost increase.

The silane coupling agent is preferably used for improving the adhesion between the solar cell encapsulant sheet and various members such as solar cells, a back sheet, and glass. The content in the case of adding the silane coupling agent is preferably in the range of 0.05 to 2 parts by mass with respect to 100 parts by mass of the polyolefin resin. When the amount is less than 0.05 parts by mass, the content effect is small. Even if it contains more than 2 parts by mass, the effect of improving adhesiveness is small. Although it does not specifically limit as a silane coupling agent, For example, at least 1 sort (s) chosen from methacryloxy group, acryloxy group, an epoxy group, a mercapto group, a ureido group, an isocyanate group, an amino group, and a hydroxyl group. Examples include alkoxysilane compounds having a functional group. Specific examples thereof include methacryloxy group-containing alkoxysilane compounds such as γ-methacryloxypropylmethyldimethoxysilane, γ-methacryloxypropyltrimethoxysilane, γ-methacryloxypropylmethyldiethoxysilane, and γ-methacryloxypropyltrimethoxysilane. , Acryloxy group-containing alkoxysilane compounds such as γ-acryloxypropyltrimethoxysilane, γ-glycidoxypropyltrimethoxysilane, γ-glycidoxypropyltriethoxysilane, β- (3,4-epoxycyclohexyl) ethyl Epoxy group-containing alkoxysilane compounds such as trimethoxysilane, mercapto group-containing alkoxysilane compounds such as γ-mercaptopropyltrimethoxysilane and γ-mercaptopropyltriethoxysilane Ureido group-containing alkoxysilane compounds such as γ-ureidopropyltriethoxysilane, γ-ureidopropyltrimethoxysilane, γ-isocyanatopropyltriethoxysilane, γ-isocyanatopropyltrimethoxysilane, γ-isocyanatopropylmethyl Isocyanato group-containing alkoxysilane compounds such as dimethoxysilane, amino such as γ- (2-aminoethyl) aminopropylmethyldimethoxysilane, γ- (2-aminoethyl) aminopropyltrimethoxysilane, γ-aminopropyltrimethoxysilane Examples thereof include a hydroxyl group-containing alkoxysilane compound such as a group-containing alkoxysilane compound, γ-hydroxypropyltrimethoxysilane, and γ-hydroxypropyltriethoxysilane. Among these, a methacryloxy group-containing alkoxysilane compound is preferable from the viewpoint of compatibility with a polyolefin resin, and γ-methacryloxypropyltrimethoxysilane is more preferable.

It is preferable that the resin composition constituting the encapsulant sheet further contains an ultraviolet absorber. The UV absorber absorbs harmful UV rays in the irradiated light and converts them into innocuous heat energy within the molecule, preventing the active species that initiate photodegradation in the polymer from being excited. . Known ultraviolet absorbers can be used. For example, benzophenone series, benzotriazole series, triazine series, salicylic acid series, cyanoacrylate series, etc. can be used. One of these may be used, or two or more may be used in combination.

Examples of the benzophenone ultraviolet absorber include 2,2′-dihydroxy-4,4′-di (hydroxymethyl) benzophenone, 2,2′-dihydroxy-4,4′-di (2-hydroxyethyl) benzophenone, 2,2'-dihydroxy-3,3'-dimethoxy-5,5'-di (hydroxymethyl) benzophenone, 2,2'-dihydroxy-3,3'-dimethoxy-5,5'-di (2-hydroxy Ethyl) benzophenone, 2,2′-dihydroxy-3,3′-di (hydroxymethyl) -5,5′-dimethoxybenzophenone, 2,2′-dihydroxy-3,3′-di (2-hydroxyethyl)- Examples include 5,5′-dimethoxybenzophenone and 2,2-dihydroxy-4,4-dimethoxybenzophenone.

Examples of the benzotriazole ultraviolet absorber include 2- [2′-hydroxy-5 ′-(hydroxymethyl) phenyl] -2H-benzotriazole, 2- [2′-hydroxy-5 ′-(2-hydroxyethyl). ) Phenyl] -2H-benzotriazole, 2- [2'-hydroxy-5 '-(3-hydroxypropyl) phenyl] -2H-benzotriazole, 2- [2'-hydroxy-3'-methyl-5'- (Hydroxymethyl) phenyl] -2H-benzotriazole, 2- [2′-hydroxy-3′-methyl-5 ′-(2-hydroxyethyl) phenyl] -2H-benzotriazole, 2- [2′-hydroxy- 3′-methyl-5 ′-(3-hydroxypropyl) phenyl] -2H-benzotriazole, 2- [2′-hydroxy- '-T-butyl-5'-(hydroxymethyl) phenyl] -2H-benzotriazole, 2- [2'-hydroxy-3'-t-butyl-5 '-(2-hydroxyethyl) phenyl] -2H- Benzotriazole, 2- [2'-hydroxy-3'-t-octyl-5 '-(hydroxymethyl) phenyl] -2H-benzotriazole, 2- [2'-hydroxy-3'-t-octyl-5' -(2-hydroxyethyl) phenyl] -2H-benzotriazole, 2- [2'-hydroxy-3'-t-octyl-5 '-(3-hydroxypropyl) phenyl] -2H-benzotriazole, etc., or 2 , 2'-methylenebis [6- (2H-benzotriazoly-2-yl) -4- (hydroxymethyl) phenol], 2,2'-methylenebis [6 (2H-benzotriazoly-2-yl) -4- (2-hydroxyethyl) phenol], 2,2′-methylenebis [6- (2H-benzotriazoly-2-yl) -4- (3-hydroxypropyl) phenol] 2,2′-methylenebis [6- (2H-benzotriazoly-2-yl) -4- (4-hydroxybutyl) phenol], 3,3- {2,2′-bis [6- (2H-benzotriazoly 2-yl) -1-hydroxy-4- (2-hydroxyethyl) phenyl]} propane, 2,2- {2,2′-bis [6- (2H-benzotriazoly-2-yl) -1-hydroxy- 4- (2-hydroxyethyl) phenyl]} butane, 2,2′-oxybis [6- (2H-benzotriazoly-2-yl) -4- (2-hydroxyethyl) phenol 2,2'-bis [6- (2H-benzotriazoly-2-yl) -4- (2-hydroxyethyl) phenol] amine and the like.

Examples of triazine ultraviolet absorbers include 2- (2-hydroxy-4-hydroxymethylphenyl) -4,6-diphenyl-s-triazine, 2- (2-hydroxy-4-hydroxymethylphenyl) -4, 6-bis (2,4-dimethylphenyl) -s-triazine, 2- [2-hydroxy-4- (2-hydroxyethyl) phenyl] -4,6-diphenyl-s-triazine, 2- [2-hydroxy -4- (2-hydroxyethyl) phenyl] -4,6-bis (2,4-dimethylphenyl) -s-triazine, 2- [2-hydroxy-4- (2-hydroxyethoxy) phenyl] -4, 6-diphenyl-s-triazine, 2- [2-hydroxy-4- (2-hydroxyethoxy) phenyl] -4,6-bis (2,4-dimethylphenyl) -S-triazine, 2- [2-hydroxy-4- (3-hydroxypropoxy) phenyl] -4,6-diphenyl-s-triazine, 2- [2-hydroxy-4- (3-hydroxypropoxy) phenyl] -4,6-bis (2,4-dimethylphenyl) -s-triazine, 2- [2-hydroxy-4- (4-hydroxybutyl) phenyl] -4,6-diphenyl-s-triazine, 2- [ 2-hydroxy-4- (4-hydroxybutyl) phenyl] -4,6-bis (2,4-dimethylphenyl) -s-triazine, 2- [2-hydroxy-4- (4-hydroxybutoxy) phenyl] -4,6-diphenyl-s-triazine, 2- [2-hydroxy-4- (4-hydroxybutoxy) phenyl] -4,6-bis (2,4-dimethylphenyl) -S-triazine, 2- (2-hydroxy-4-hydroxymethylphenyl) -4,6-bis (2-hydroxy-4-methylphenyl) -s-triazine, 2- [2-hydroxy-4- (2 -Hydroxyethyl) phenyl] -4,6-bis (2-hydroxy-4-methylphenyl) -s-triazine, 2- [2-hydroxy-4- (2-hydroxyethoxy) phenyl] -4,6-bis (2-hydroxy-4-methylphenyl) -s-triazine, 2- [2-hydroxy-4- (3-hydroxypropyl) phenyl] -4,6-bis (2-hydroxy-4-methylphenyl) -s -Triazine, 2- [2-hydroxy-4- (3-hydroxypropoxy) phenyl] -4,6-bis (2-hydroxy-4-methylphenyl) -s-triazine , Etc.

Examples of the salicylic acid ultraviolet absorber include phenyl salicylate, p-tert-butylphenyl salicylate, p-octylphenyl salicylate and the like.

Examples of the cyanoacrylate ultraviolet absorber include 2-ethylhexyl-2-cyano-3,3′-diphenyl acrylate, ethyl-2-cyano-3,3′-diphenyl acrylate, and the like.

Of these ultraviolet absorbers, benzophenone-based ultraviolet absorbers are most preferable from the viewpoints of the ultraviolet absorption effect and coloring of the ultraviolet absorber itself.

In the case of adding the above ultraviolet absorber, 0.05 to 3 parts by mass is preferable with respect to 100 parts by mass of the polyolefin resin. More preferably, it is 0.05 to 2.0 parts by mass. When the content is less than 0.05 parts by mass, the content effect is low, and when it exceeds 3 parts by mass, a coloring tendency occurs.

It is preferable that the resin composition which comprises a sealing material sheet contains a light stabilizer further. The light stabilizer captures radical species that are harmful to the polymer and prevents the generation of new radicals. As the light stabilizer, a hindered amine light stabilizer is preferably used.

Hindered amine light stabilizers include bis (2,2,6,6-tetramethyl-1 (octyloxy) -4-piperidinyl) ester, 1,1-dimethylethyl hydroperoxide and octane produced by reaction with decanedioic acid 70% by mass of a product and 30% by mass of polypropylene, bis (1,2,2,6,6-pentamethyl-4-piperidyl) [[3,5-bis (1,1-dimethylethyl) -4-hydroxy Phenyl] methyl] butyl malonate, bis (1,2,2,6,6-pentamethyl-4-piperidyl) sebacate and methyl-1,2,2,6,6-pentamethyl-4-piperidyl sebacate mixture, bis (2,2,6,6-tetramethyl-4-piperidyl) sebacate, tetrakis (2,2,6,6-tetramethyl-4-piperidyl ) -1,2,3,4-butanetetracarboxylate, tetrakis (1,2,2,6,6-pentamethyl-4-piperidyl) -1,2,3,4-butanetetracarboxylate, 2,2 , 6,6-Tetramethyl-4-piperidyl-1,2,3,4-butanetetracarboxylate and tridecyl-1,2,3,4-butanetetracarboxylate, 1,2,2,6 A mixture of 6-pentamethyl-4-piperidyl-1,2,3,4-butanetetracarboxylate and tridecyl-1,2,3,4-butanetetracarboxylate, poly [{6- (1,1,3, 3-tetramethylbutyl) amino-1,3,5-triazine-2,4-diyl} {(2,2,6,6-tetramethyl-4-piperidyl) imino} hexamethylene {(2,2,6 6-tetramethyl-4-piperidyl) imino}], dimethyl succinate and 4-hydroxy-2,2,6,6-tetramethyl-1-piperidineethanol, N, N ′, N ″, N ″ '-Tetrakis- (4,6-bis- (butyl- (N-methyl-2,2,6,6-tetramethylpiperidin-4-yl) amino) -triazin-2-yl) -4,7-diazadecane 1,10-diamine, dimethyl succinate and 4-hydroxy-2,2,6,6-tetramethyl-1-piperidineethanol polymer mixture, dibutylamine, 1,3,5-triazine, N, Polycondensation of N'-bis (2,2,6,6-tetramethyl-4-piperidyl-1,6-hexamethylenediamine and N- (2,2,6,6-tetramethyl-4-piperidyl) butylamine Thing And so on. The above-mentioned hindered amine light stabilizers may be used alone or in combination of two or more.

Among these, hindered amine light stabilizers include bis (1,2,2,6,6-pentamethyl-4-piperidyl) sebacate and methyl-1,2,2,6,6-pentamethyl-4-piperidyl seba. It is preferred to use a mixture of ketates, as well as methyl-4-piperidyl sebacate, bis (2,2,6,6-tetramethyl-4-piperidyl) sebacate. Moreover, it is preferable to use a hindered amine light stabilizer having a melting point of 60 ° C. or higher.

When the hindered amine light stabilizer is added, the content is preferably 0.05 to 3.0 parts by mass with respect to 100 parts by mass of the polyolefin resin. More preferably, it is 0.05 to 1.0 part by mass. If the content is less than 0.05 parts by mass, the stabilizing effect is insufficient, and even if the content exceeds 3.0 parts by mass, coloring and cost increase are caused.

In addition, an antioxidant, a flame retardant, a flame retardant aid, a plasticizer, a lubricant, a colorant, and the like may be included as necessary within the range not impairing the effects of the present invention.

[Solar cell module]
The solar cell module is composed of a light-receiving surface protective material, a back surface protective material, and a layer in which the solar cells are sealed with a sealing material sheet disposed between the light-receiving surface protective agent and the back surface protective material. Has been. As a sealing material sheet used here, you may use the sealing material sheet obtained by the manufacturing method of this invention, and use the sealing material sheet which has the processus | protrusion independent on the surface mentioned above. Also good.

The encapsulant sheet obtained by the production method of the present invention has small heat shrinkage when the above-structured materials are laminated and integrated. Therefore, the residual stress at the time of molding between the solar battery cell and the encapsulant sheet, between the light-receiving surface protective material and the encapsulant sheet, and between the back surface protector and the encapsulant sheet is small, and long-term durability Becomes an excellent solar cell module.

Moreover, since the sealing material sheet having independent protrusions on the surface described above can disperse the pressing force to the solar battery cells when the materials having the above-mentioned configuration are laminated and integrated, the solar battery cells and the sealing material Residual stress between the sheet and the sheet can be reduced. In addition, no bubbles remain in the sealing material. Therefore, the solar cell module is excellent in durability over a long period of time.

The measurement method used in this example is shown below. Unless otherwise specified, the number of measurement n was 5, and the average value was adopted.

(1) Thickness of sheet The 20-point thickness of the molded encapsulant sheet was measured in the width direction to obtain an average thickness. As a measuring instrument, a thickness gauge (type 547-301) manufactured by Mitutoyo Corporation was used. The thickness of the sealing material sheet was measured by measuring the distance from the top of the protrusion to the surface opposite to the surface having the protrusion when the protrusion was formed only on one side of the sealing material sheet. When protrusions were formed on both surfaces of the encapsulant sheet, the distance from the top of the protrusion on one surface to the top of the protrusion on the opposite surface was measured.

(2) Protrusion height The sealing material sheet was cut so as to pass the top of the protrusion in a direction (width direction) perpendicular to the traveling direction of the sheet at the time of manufacture (hereinafter abbreviated as MD direction). A cross section in the thickness direction of the cut sealing material sheet was observed over the entire width of the sheet with a stereomicroscope.
When there is a projection on one side of the encapsulant sheet, the side of the encapsulant sheet with the projection is A side, and the side without the projection is B side. As shown in FIG. 3, the distance from the apex of the protrusion on the A surface to the B surface is Tmax, and the distance from the portion having no protrusion on the A surface to the B surface is Tmin. Then, the height T of the protrusion was calculated by the formula (i).
T (μm) = Tmax−Tmin (i)
When there are protrusions on both sides of the encapsulant sheet, one side of the encapsulant sheet is A side and the other side is B side. As shown in FIG. 4, the distance from the apex of the protrusion on the A surface to the portion without the protrusion on the B surface is TAmax, the distance from the apex of the protrusion on the B surface to the portion without the protrusion on the A surface is TBmax, The distance from the portion having no protrusion to the portion having no protrusion on the B surface is defined as Tmin. Then, the height TA of the projection on the A surface was calculated by the equation (ii), and the height TB of the projection on the B surface was calculated by the equation (iii).
TA (μm) = TAmax−Tmin (ii)
TB (μm) = TBmax−Tmin (iii).

(3) Pattern depth of embossing roller The surface of the embossing roller was measured under the measurement conditions of a standard length of 20 mm, a load of 0.75 mN, and a measurement speed of 0.3 mm / s in accordance with JIS B0601 (2001). The measurement was performed by using a small surface roughness measuring device SJ401 manufactured by Mitutoyo Corporation and a diamond stylus having a cone of 60 ° and a tip curvature radius of 2 μm. This measured value was taken as the pattern depth Pz value (μm) of the embossing roller.

(4) Embossing transfer rate Embossing roller in which the protrusion height T (μm) (or protrusion height TA (μm) or protrusion height TB (μm)) measured in (2) above is measured in (3) above. The value divided by the pattern depth Pz was used as the emboss transfer rate.
Emboss transfer rate (%) = T / Pz × 100.

(5) Heat shrinkage rate A flat square test piece having a side of 120 mm was cut out from the encapsulant sheet. On this test piece, two parallel straight lines (5 cm) in the TD direction were drawn at a distance of 100 mm at the center in the TD direction during production. And the mark was attached | subjected to the position (each 5 places) which divides each straight line into 6 equal parts.
Next, the test piece was left in warm water heated to 80 ° C. for 60 seconds. When the specific gravity of the encapsulant sheet was small and the encapsulant sheet floated on the surface of the hot water, the encapsulant sheet was left in the floated state. When the specific gravity of the encapsulant sheet was large and the encapsulant sheet sank in warm water, the encapsulant sheet was left as it was. After 60 seconds, the test piece was taken out from the warm water, immersed in room temperature water at 20 ° C. for 10 seconds and cooled, and then moisture on the sheet surface was removed.
The distance A (mm) from each of the five marks attached to one straight line drawn on the test piece to the opposing marks attached to the other straight line was measured with a caliper, and the heat shrinkage rate based on the following formula Was calculated, and the average value of 5 locations was obtained.
Heat shrinkage rate (%) = (100−A) / 100 × 100

(6) Melt flow rate of resin composition constituting sealing material sheet The resin composition was tested in accordance with JIS K7210 (1999) “Plastic-thermoplastic melt mass flow rate (MFR) and melt volume flow rate (MVR)”. According to “Method”, the measurement was performed under the test conditions of a temperature of 190 ° C. and a load of 2.16 kg.

(7) Bottom length of protrusion (D)
The surface having the protrusions on the sheet is observed with a stereomicroscope, and the base length (D) is measured. When the shape of the bottom surface of the protrusion is a polygon such as a triangle or a hexagon, or an ellipse, the diameter of the smallest perfect circle including the shape was measured.

(8) Cell cracking property Two plane square test pieces having a side of 180 mm were cut out from the encapsulant sheet. An interconnector (thickness: 280 μm, width: 2 mm) was soldered to a polycrystalline solar cell (3 bus bars, size: 156 mm square, thickness: 200 μm) to produce a solar cell with an interconnector. A glass plate (size 180 mm square, thickness 3 mm) and a polyester solar cell backsheet (size 180 mm square, thickness 240 μm) were prepared. On the glass plate, it laminated | stacked in order of the sealing material sheet | seat, the photovoltaic cell, the sealing material sheet | seat, and the back sheet | seat. At this time, the sealing material sheet was laminated so that the surface having the protrusions was in contact with the solar battery cell. This laminate was vacuum laminated under the conditions of a temperature of 145 ° C., evacuation for 30 seconds, pressing for 1 minute, and pressure holding for 10 minutes to produce a solar cell module. The obtained solar cell module was photographed with a solar cell EL image inspection device, and a light emission image was taken, and the total crack length (mm) of the cell crack portion was measured. This test was repeated three times to obtain the average value of the total crack length.

(9) Number of bubbles The number of bubbles in the solar cell module produced in (8) above was counted visually. The average of three tests was determined.

(10) Repulsive stress A flat square test piece having a side of 120 mm was cut out from the encapsulant sheet. Next, using a compression tester KES FB-3 manufactured by Kato Tech Co., Ltd., the sealing material sheet was pressed at a speed of 20 μm / second from the surface having the protrusion of the test piece with a flat pressure terminal having a diameter of 16 mm in the thickness direction. The repulsive stress (kPa) of the sheet when pressed by 100 μm was measured. This test was repeated three times, and the average value of the rebound stress was determined.

Example 1
A solar cell encapsulant sheet was prepared according to the production method shown in FIG. 1. Step (a): Film-forming step EVA (vinyl acetate content: 28% by mass, melt flow rate) using a twin-screw extruder as the extruder 11 : 15 g / 10 min, melting point: 71 ° C.) 100 parts by mass, t-butylperoxy-2-ethylhexyl monocarbonate (1 hour half-life temperature: 119 ° C.) 0.7 parts by mass, triallyl isocyanurate 0.3 parts by mass Parts, 0.2 parts by weight of γ-methacryloxypropyltrimethoxysilane, 0.3 parts by weight of 2-hydroxy-4-methoxybenzophenone, bis (1,2,2,6,6-pentamethyl-4-piperidyl) sebacate 0 The resin composition consisting of 1 part by mass was supplied to the extruder 11 set at 80 ° C. and melt-kneaded. The kneaded resin composition was extruded from a T-die 12 connected to an extruder 11 and maintained at 105 ° C. The T die used had a lip width of 1300 mm and a lip gap of 0.8 mm.
The resin composition thus extruded was cooled and solidified by polishing

rollers

13a, 13b, and 13c maintained at 20 ° C. to form a sheet. In addition, the temperature of the process sheet | seat at the time of discharging from T die was 107 degreeC. At this time, the width of the process sheet was 1150 mm, the thickness was 450 μm, and the conveyance speed was 10 m / min.

Step (b): Annealing Step Next, annealing was performed under the conditions shown in Table 1.
A ceramic heater 16 is used for heating, and a metal roller whose surface is coated with “Teflon (registered trademark)” and having a diameter of 150 mm is used as the transport roller 17 at intervals such that the distance between the centers of the rollers is 200 mm. It was. The annealing furnace 15 used was a SUS casing wrapped with a heat insulating material. Hot air was blown from the lower part of the entrance and the lower part of the outlet of the annealing furnace 15 at a wind speed of 1 m / sec.

Step (c): Embossing step In accordance with the conditions described in Table 1, embossing was performed continuously with the annealing treatment.
The embossing was carried out by passing the process sheet conveyed from the annealing furnace between the embossing roller 20 with a pattern depth of 120 μm and the embossing counter roller 19 wound with silicon rubber having a hardness of 75 ° with a thickness of 10 mm. .

The heat shrinkage rate and emboss transfer rate of the obtained solar cell encapsulant sheet were evaluated. The results are shown in Table 1. As shown in Table 1, a solar cell encapsulant sheet having a very small heat shrinkage and an embossed pattern clearly transferred was obtained.

(Example 2)
A sealing material sheet was prepared in the same manner as in Example 1 except that the hot air temperature in the step (b) was 87 ° C., the heater temperature was 320 ° C., and the residence time in the furnace was 29 seconds. Since the surface temperature of the process sheet was lowered, the heat shrinkage rate was slightly increased and the emboss transfer rate was slightly lowered, but the heat shrinkage rate was very small as in Example 1 and the embossed pattern was clearly transferred. A solar cell encapsulant sheet was obtained.

(Example 3)
A sealing material sheet was prepared in the same manner as in Example 1 except that the hot air temperature in step (b) was 80 ° C., the heater temperature was 300 ° C., the residence time in the furnace was 30 seconds, and the linear pressure was 450 N / cm. did. Since the surface temperature of the process sheet was further lowered, the heat shrinkage rate was slightly increased and the emboss transfer rate was slightly lowered, but the heat shrinkage rate was very small as in Example 1 and the embossed pattern was clearly transferred. A solar cell encapsulant sheet was obtained.

Example 4
A sealing material sheet was prepared in the same manner as in Example 3 except that the linear pressure in the step (c) was 200 N / cm. Although the emboss transfer rate was slightly low, a solar cell encapsulant sheet in which the emboss pattern was clearly transferred as in Example 3 was obtained.

(Example 5)
A sheet was prepared in the same manner as in Example 1 except that the hot air temperature in the step (b) was 110 ° C., the residence time in the furnace was 27 seconds, and the linear pressure in the step (c) was 200 N / cm. Since the surface temperature of the process sheet increased, the solar cell encapsulant sheet with a very small heating shrinkage and a clear emboss transfer rate was obtained.

(Example 6)
A sealing material sheet was prepared in the same manner as in Example 5 except that the hugging angle to the embossing roller in the step (c) was 45 °. The embossing transfer rate was slightly shallow due to the shallow hugging angle, but the sheet had a good appearance.

(Example 7)
The process sheet conveyance speed in step (b) is 7 m / min, the hot air temperature is 110 ° C., the heater temperature is 300 ° C., the residence time in the furnace is 39 seconds, and the linear pressure in step (c) is 120 N / cm. Produced a sealing material sheet in the same manner as in Example 1. Since the heating time of the process sheet became longer and the surface temperature increased, the heat shrinkage ratio was greatly reduced, and a clear embossed sheet could be produced even when the linear pressure was low.

(Comparative Examples 1 to 5)
A solar cell encapsulant sheet was prepared in the same manner as in Example 1 except that the conditions shown in Table 2 were applied.

(Comparative Examples 6 and 7)
Immediately after extrusion from the T die by the conventional manufacturing method shown in FIG. 2, embossing was performed, followed by annealing. The annealing apparatus was the same as in Example 1, and a roller having a pattern depth of 120 μm was used as the embossing roller 13b ′ immediately after the T die.

(result)
As shown in Table 1, the solar cell encapsulant sheets prepared in Examples 1 to 7 had a low heat shrinkage rate and a high emboss transfer rate, and the emboss shape was clearly transferred.
Using these solar cell encapsulant sheets, a solar cell module was created by a conventionally known method. At the time of module creation, problems such as cell displacement, cell cracking, and air bubbles were introduced. I did not.

In Comparative Example 1, since the temperature during annealing and the sheet temperature at the entrance of the embossing roller 20 were both low, the heat shrinkage rate was large and the embossing transfer rate was low. In Comparative Example 3, since the space between the annealing furnace outlet and the embossing roller inlet was widened, the sheet temperature was lowered and the embossing transfer rate was lowered. In Comparative Example 4, since the sheet surface temperature in the annealing furnace was low, the heat shrinkage rate could not be sufficiently reduced.
In Comparative Example 2, the process sheet was wound around the embossing roller, and a sample could not be obtained.
In Comparative Example 5, since the annealing treatment time was short, the heat shrinkage of the solar cell encapsulant sheet could not be sufficiently reduced.
In Comparative Examples 6 and 7, the embossed shape was given by the polishing roller, so the embossed shape was clear. However, when trying to reduce the heat shrinkage, the embossed shape collapsed, and when trying to maintain the embossed shape, the heat shrinkage was reduced. could not.

(Example 8)
Step (a): Film-forming step EVA (vinyl acetate content: 28% by mass, melt flow rate: 15 g / 10 min (190 ° C.), melting point: 71 ° C.) 100 parts by mass, t-butylperoxy-2-ethylhexyl Monocarbonate (1 hour half-life temperature: 119 ° C) 0.7 parts by mass, triallyl isocyanurate 0.3 parts by mass, γ-methacryloxypropyltrimethoxysilane 0.2 parts by mass, 2-hydroxy-4-methoxybenzophenone A resin composition comprising 0.3 part by mass and 0.1 part by mass of bis (1,2,2,6,6-pentamethyl-4-piperidyl) sebacate is supplied to a twin screw extruder set at 80 ° C. and melted. Kneaded. The kneaded resin composition was extruded from a T die connected to a twin screw extruder and held at 105 ° C. The lip width of the T die was 1300 mm, and the lip gap was 0.8 mm.

The EVA sheet was cooled and solidified by a polishing roll maintained at 20 ° C. The sheet temperature when the EVA sheet was discharged from the T die was 107 ° C. At this time, the sheet width was 1150 mm, the sheet thickness was 450 μm, and the sheet conveyance speed was 10 m / min. Next, annealing treatment and embossing were continuously performed.

Step (b): Annealing treatment step An annealing treatment is performed by installing a ceramic heater with a surface temperature set at 350 ° C., a metal roller having a diameter of 150 mm and coated with “Teflon (registered trademark)” on the surface, and the distance between the centers of the rollers is It was performed by passing through an annealing furnace in which a heat insulating material was wound around a SUS casing, which was installed at intervals of 250 mm. Hot air was blown from the lower part of the entrance and the lower part of the furnace at a wind speed of 1 m / sec.

Process (c): Embossing process The embossing process is performed by embossing the sheet taken out of the annealing furnace with an embossing roller having a pattern depth of 180 μm, a diameter of 460 μm and 450 hemispherical concave engraving patterns / cm ^2, and a hardness of 75 °. This was carried out by passing it between opposed rollers wound with a thickness of 10 mm.

The details of the manufacturing conditions are as follows.
Sheet surface temperature at the annealing furnace entrance: 23 ° C
Hot air temperature: 93 ° C
Maximum temperature of sheet surface in annealing furnace: 90 ° C
Sheet surface temperature at annealing furnace outlet: 90 ° C
Sheet residence time in the annealing furnace: 28 seconds Sheet speed at the outlet of the annealing furnace 15: 9.6 m / min
Sheet surface temperature at the embossing roller entrance: 78 ° C
Embossing roller temperature: 15 ° C
Embossed roller linear pressure: 350 N / cm
Hang angle to emboss roller: 120 °.

The heat shrinkage rate, rebound stress, cell cracking property during module production, and the number of bubbles of the obtained encapsulant sheet were evaluated. The results are shown in Table 3. As shown in Table 3, the sheet was a sealing material sheet having a small sheet heat shrinkage ratio and having few cell cracks and bubbles during module production.

Example 9
The embossing roller in step (c) was sealed in the same manner as in Example 8 except that the embossing roller was changed to an embossing roller having a pattern depth of 120 μm, a diameter of 460 μm, and 450 hemispherical concave engraving patterns / cm ^2. A material sheet was created.
As shown in Table 3, the obtained encapsulant sheet was a encapsulant sheet having a small sheet heat shrinkage ratio and few cell cracks and bubbles during module production.

(Example 10)
The embossing roller in the step (c) was sealed in the same manner as in Example 8 except that the embossing roller was changed to an embossing roller having a pattern depth of 300 μm, a diameter of 460 μm, and 450 hemispherical concave engraving patterns / cm ^2. A material sheet was created.
As shown in Table 3, the obtained encapsulant sheet was a encapsulant sheet having a small sheet heat shrinkage ratio and few cell cracks and bubbles during module production.

(Example 11)
The embossing roller in the step (c) was sealed in the same manner as in Example 8 except that the embossing roller was changed to an embossing roller having a pattern depth of 300 μm and a diameter of 330 μm and a hemispherical concave engraving pattern of 980 pieces / cm ^2. A material sheet was created.
As shown in Table 3, the obtained encapsulant sheet was a encapsulant sheet having a small sheet heat shrinkage ratio and few cell cracks and bubbles during module production.

(Example 12)
In the same manner as in Example 8, except that the embossing roller in the step (c) was changed to an embossing roller having a pattern depth of 180 μm, an outer diameter of 460 μm and a rectangular pyramid-shaped concave engraving pattern of 840 pieces / cm ^2. A sealing material sheet was prepared.
As shown in Table 3, the obtained encapsulant sheet was a encapsulant sheet having a small sheet heat shrinkage rate and few bubbles, although some cell cracking during module production occurred.

(Example 13)
A sealing material sheet was prepared in the same manner as in Example 8 except that the annealing was not performed and the sheet surface temperature was heated to 90 ° C. with an infrared heater and embossing was performed.
As shown in Table 3, the obtained encapsulant sheet was a encapsulant sheet with a small number of bubbles, although the sheet had a large heat shrinkage rate and cell cracking occurred slightly during module production.

(Example 14)
A sealing material sheet was prepared in the same manner as in Example 8 except that the EVA resin was changed to an EVA resin having a melt flow rate of 10 g / 10 min. As shown in Table 3, the obtained encapsulant sheet was a encapsulant sheet having a small sheet heat shrinkage rate and few bubbles, although some cell cracking during module production occurred.

(Example 15)
In the same manner as in Example 8, except that the embossing roller in the step (c) was changed to an embossing roller having a pattern depth of 180 μm, an outer peripheral diameter of 2000 μm, and 45 pyramidal concave engraving patterns / cm ^2. A sealing material sheet was prepared.
As shown in Table 3, the obtained encapsulant sheet was a encapsulant sheet with a small number of bubbles, although the sheet heat shrinkage rate was small and cell cracking during module production was slightly generated.

(Reference Example 1)
Except not embossing, the sealing material sheet which implemented by annealing method by the method similar to Example 8 was created, and it used for evaluation.
As shown in Table 4, the obtained encapsulant sheet was a encapsulant sheet in which the heat shrinkage rate of the sheet was small, but a large number of cell cracks and bubbles were generated during module production.

(Reference Example 2)
Example 8 except that the embossing roller in the step (c) was changed to an embossing roller having a pattern depth of 180 μm and an engraving pattern of a semicircular groove (groove width 460 μm) continuous in the rotation direction of the roll. A sealing material sheet was prepared in the same manner.
As shown in Table 4, the obtained encapsulant sheet was a encapsulant sheet having a small sheet heat shrinkage rate and few cell cracks during module production, but having many bubbles.

(Reference Example 3)
The embossing roller in the step (c) was sealed in the same manner as in Example 8 except that the embossing roller was changed to an embossing roller having a pattern depth of 50 μm, a diameter of 460 μm, and 450 hemispherical concave engraving patterns / cm ^2. A material sheet was created.
As shown in Table 4, the obtained encapsulant sheet had a small sheet heat shrinkage rate, but was a encapsulant sheet having many cell cracks and bubbles during module production.

(Reference Example 4)
The embossing roller in the step (c) was sealed in the same manner as in Example 8 except that the embossing roller was changed to an embossing roller having a pattern depth of 180 μm and a diameter of 150 μm and a hemispherical concave engraving pattern of 4500 pieces / cm ^2. A material sheet was created.
As shown in Table 4, the obtained encapsulant sheet was a encapsulant sheet having a small sheet heat shrinkage rate and a small number of bubbles, but many cell cracks during module production.

(Reference Example 5)
The embossing roller in step (c) was sealed in the same manner as in Example 8 except that the embossing roller was changed to an embossing roller having a pattern depth of 180 μm, a diameter of 3800 μm, and 7 hemispherical concave engraving patterns / cm ^2. A material sheet was created.
As shown in Table 4, the obtained encapsulant sheet had a small sheet heat shrinkage rate, but was a encapsulant sheet with many cell cracks and bubbles during module production.

The present invention can be used very suitably for a method for producing a solar cell encapsulant sheet. In particular, it has reduced heat shrinkage and has a clear embossed pattern, so it can prevent cell misalignment and air bubbles in the module during module manufacturing, and can significantly improve module productivity. .

1 process sheet 11 twin screw extruder 12 die 13a polishing roller (no engraving on the surface)
13b Polishing roller (no engraving on the surface)
13b 'Embossed roller (with engraving on the surface)
13c Polishing roller (no engraving on the surface)
14 Nip roller 15 Annealing furnace 16 Heater 17 Conveying roller 18 Sheet take-out roller 19 Embossed opposed roller 20 Embossed roller 21 Cooling roller 31 Gear pump 32 Sheet conveying direction 33 Non-contact infrared thermometer

Claims

The manufacturing method of the solar cell sealing material sheet which performs the following process (a), a process (b), and a process (c) in this order.
Step (a): Forming a resin composition melted by heating into a sheet shape, and then cooling to obtain a step sheet Step (b): At least one surface of the step sheet obtained in the step (a) Is heated for 22 to 55 seconds, and during this heating, the temperature of the surface reaches a temperature not lower than the melting point of the resin composition constituting the surface portion. Step (c): Heated in the step (b) The surface of the process sheet is brought to a temperature of (the melting point of the resin composition constituting the surface portion−10 ° C.) to (the melting point of the resin composition constituting the surface portion + 20 ° C.), and then an embossing roller is pressed against the surface Bumping and forming an embossed shape on this surface
The method for producing a solar cell encapsulant sheet according to claim 1, wherein, in the step (c), when the surface of the process sheet is pressed by the embossing roller, a linear pressure applied to the surface is set to 150 to 500 N / cm. .
In the step (c), when the surface of the process sheet is pressed with the embossing roller, the surface temperature of the embossing roller is set to (the melting point of the resin composition constituting the surface portion −20 ° C.) or less. The manufacturing method of the solar cell sealing material sheet of claim | item 1 or 2.
The solar cell encapsulant according to any one of claims 1 to 3, wherein in the step (a), the resin composition melted by the heating is extruded from a die using a single-screw or twin-screw extruder and formed into a sheet shape. Sheet manufacturing method.
The method for producing a solar cell encapsulant sheet according to any one of claims 1 to 4, wherein the resin composition constituting the surface portion contains a polyolefin resin and an organic peroxide.
A solar cell encapsulant sheet obtained by the production method according to any one of claims 1 to 5,
The resin composition constituting the surface portion includes a polyolefin resin,
Surface wherein the embossed shape is formed, a separate high protrusions 60 ~ 300μm 40 ~ 2300 pieces / cm 2 has, and the height of the independent projections (T) and bottom lengths (D) and A solar cell encapsulant sheet having a ratio (T / D) of 0.05 to 0.80.
The solar cell sealing material according to claim 6, wherein when the solar cell sealing material sheet is left in warm water at 80 ° C for 1 minute, the heat shrinkage rate of the sealing material sheet in the sheet flow direction is 30% or less. Sheet.
The solar cell encapsulant sheet according to claim 6 or 7, wherein the independent protrusion has a hemispherical shape and / or a quadrangular pyramid shape.
The solar cell according to any one of claims 6 to 8, wherein when the surface having the protrusions of the solar cell encapsulant sheet is compressed by 100 µm in the thickness direction of the encapsulant sheet, the repulsive stress of the sheet is 70 kPa or less. Battery encapsulant sheet.
10. The solar cell encapsulant sheet according to claim 6, wherein the surface of the solar cell encapsulant sheet having a protrusion further has a protrusion having a height of 1 to 15 μm.
A light-receiving surface protective material;
Back surface protection material,
A layer disposed between the light-receiving surface protective material and the back surface protective material, wherein the solar cells are sealed with the solar cell sealing material sheet according to any one of claims 6 to 10,
A solar cell module composed of