JP2012018954A - Method for sealing solar cell and sealing device - Google Patents

Abstract

PROBLEM TO BE SOLVED: To solve such problems that the conventional sealing method requires heating for long period of time for thermally curing a sealing resin and, even in sealing with a thermoplastic resin, processes for long period of time, such as vacuum pressurization and autoclave pressurization, are performed.SOLUTION: In a method and device for sealing a solar cell in which top and bottom sides are formed of a rigid object such as a glass sheet, a pressing pressure is applied on a layered product, which is laminated, in the atmospheric pressure, and thereby, a sealing resin is plastically fluidized to seal the solar cell. The layered product is preliminarily heated, and then the layered product is subjected to press working in the atmosphere, so that sealing is performed while bubbles are eliminated.

Description

  The present invention provides a module for a crystalline solar cell such as a single crystal solar cell or a polycrystalline solar cell, a thin film solar cell using a microcrystalline silicon or amorphous silicon thin film, a compound solar cell such as a chalcopyrite system or a CdTe-CdS system, etc. The sealing method used for the sealing process in the manufacturing process of a solar cell module in which the light-receiving side surface layer is formed of a glass plate and the back side of the module is formed of a rigid plate material such as a glass plate, a metal plate, a ceramic plate, and the like It relates to a stop device.

  In general, a crystalline solar cell is formed as a solar cell by diffusing and doping various impurities on a hard substrate such as a polycrystalline silicon substrate or a single crystal silicon substrate. Therefore, a solar cell module using this is also a hard module. . In general, a glass plate with high transparency is used on the surface side.

  On the other hand, a back sheet or a glass plate in which various resin films are laminated with an adhesive on an aluminum foil, PET, or a fluorine resin film having low moisture permeability on the back side is used. When installing on the roof or outside of the outer wall, the former is preferred because it does not expect appearance from the back or light transmission, but when installing the solar cell module on the window or the solar cell module itself is the roof plate In order to enhance the appearance from the back side, a module using a glass plate on the back side is used. In these sealings, EVA (ethylene vinyl acetate copolymer) is widely used as the sealing resin.

In conventional thin-film solar cells and compound solar cells, the above situation has not changed. However, in recent years, in the CdTe-CdS solar cells, it is expected to improve the strength of laminated glass by using a glass plate as the back side material. The method of omitting the peripheral reinforcing aluminum frame, which was essential for solar cells, is accepted.
This structure uses a glass plate on the back side as a strength member to maintain strength without using an aluminum reinforcing frame, and by utilizing the high oxygen barrier performance and steam barrier performance peculiar to glass, by laminating various films By omitting the backsheet, significant cost reduction has been realized.

  As an example of a conventional sealing process using EVA, as described in Patent Document 1, preheating to below the softening point of EVA (for example, 80 degrees or more) while performing vacuum evacuation, and further heating, EVA softens The temperature is raised to a temperature (for example, 110 ° C. or higher), further heated to a temperature at which crosslinking proceeds satisfactorily (for example, about 150 ° C.) and pressed in a vacuum. A cure method is known.

  This method requires a long heating process with evacuation and is disadvantageous in cost. In crystalline solar cells with a lot of past results, independent cells are connected by soldering and sealed, and it is necessary to completely polymerize EVA and transform it into a thermosetting resin. It was adopted.

  On the other hand, there is also a method using PVB which is a sealing resin with a proven record in automotive laminated glass. As a laminated glass process, for example, as described in Patent Document 2, a material that manages the moisture content of PVB suitable for the conventional method using an autoclave, the method using a nip roll, and the method using a vacuum bag is provided. ing. In Patent Document 2, in the above-described mechanical fixing method, the laminated plate fixed by temporary fixing for a short time is completely bonded by heating from approximately 150 ° C. to 220 ° C. at approximately atmospheric pressure.

  In this method, the nip roll method that does not use a vacuum requires a bonding process by heating after the temporary fixing process, and since the process time becomes long, a heating process using a large number of heating furnaces is necessary. / The consistency with the solar cell module production line, which is often produced in a short tact time of the module, is poor, and the production tact is likely to be extended. In the method using a vacuum bag, the vacuum process and the temperature raising process are used in combination as in the EVA vacuum superposition method, so that there is a limit to shortening the processing time.

  In Patent Document 2, names such as an expansion bag, a press using a platen, a continuous belt, a multiplex or a staggered roller can be seen as a temporary fixing method, but a detailed process has not been studied.

Japanese Patent Laid-Open No. 11-238898 Japanese Patent Publication No. 2008-536785

  The object of the present invention is to manufacture a low-cost, nip roller type tactile glass for a laminated glass, which replaces the high-cost vacuum heating process based on the long-time thermosetting treatment that has been used for solar cells in the past. It is an object of the present invention to provide a short-time sealing process and a sealing apparatus that do not use a heat treatment process using a batch heating furnace that is easy to extend.

  In order to achieve the above object, at least a front glass plate, a sealing resin sheet represented by PVB, and a back glass plate are laminated to form a laminate, and preheating is performed to preheat the laminate. This can be achieved by performing sealing by performing a process and a welding process in which pressure is uniformly heated by a flat press heater in an atmospheric pressure atmosphere. The sealing device at this time has at least an overlapping portion, a preheating portion, and a flat press portion in an atmospheric pressure atmosphere.

  According to the present invention, a low-cost, heat treatment using a batch heating furnace for laminated glass, which replaces the high-cost vacuum heating process based on the long-time heat curing process that has been used for conventional solar cells in EVA, etc. It is possible to provide a short-time sealing process and a sealing apparatus that do not use the long-time process.

It is a figure which shows the process flow of 1st Example of this invention. It is a figure which shows the process apparatus structure of 1st Example of this invention. It is a figure which shows the shape of the laminated body in the process of the 1st Example of this invention. It is a figure which shows the process conditions of the 1st Example of this invention. It is a figure which shows the shape of the laminated body in the process of the 2nd Example of this invention. It is a figure which shows the process conditions of the 2nd Example of this invention. It is a figure which shows the process apparatus structure of the other Example of this invention.

Hereinafter, a first solar cell sealing method and a solar cell sealing device according to the present invention will be described with reference to FIGS.
FIG. 1 is a process flow of a sealing process according to a first embodiment of the present invention. The sealing process is centered on a process called a post-process in a general semiconductor process. The glass substrate 1 on which the solar cell element is formed in the solar cell forming step 101 which is the previous step is made and put into the main sealing process.
The first step of the sealing process is a lamination step 102, in which the glass substrate 1, the sealing resin 2, and the glass plate 3 on the back side are overlaid. In this process, mutual positioning is carried out but bonding is not performed.

  The next step is a preheating step 103. The stacked body 10 stacked in the stacking step 102 is heated, and the sealing resin 2 is preheated below the softening point. At this time, if the preheating temperature is too high, heat shrinkage occurs in the sealing resin, resulting in displacement. On the other hand, when the preheating temperature is low, the rate of temperature increase in the subsequent atmospheric pressure atmosphere pressing step 104 becomes too fast, the temperature unevenness of the sealing resin 2 becomes large, and stable sealing becomes difficult. Appropriate temperature is required according to the formulation.

The subsequent atmospheric pressure atmosphere pressing step 104 is divided into two steps: step 1 in which the sealing resin 2 is heated to a temperature at which the softening point is exceeded and plastic flow begins; Is formed in Step 2 in which the resin is dissolved in the sealing resin 2.
In step 1, a slight press pressure is applied to increase the contact area with each other by elastic deformation of each member and to suppress displacement due to heat shrinkage of the sealing resin 2.
In step 2, a strong press pressure is applied so as to dissolve the sealing resin 2 by pressurizing air remaining in the recesses of the member by helping smooth plastic flow of the sealing resin and filling the gap.

  At this time, the press pressure is maintained at a pressure exceeding the vapor pressure at the workpiece temperature of the sealing resin 2 so that water vapor bubbles are not generated by evaporation of moisture contained in the sealing resin. As a result, the sealing resin 2 becomes a laminated body 10 in which the glass substrate 1 and the glass substrate 3 on the back surface side are firmly adhered and integrated without bubbles.

  In the next discharging step 105, the laminated body 10 is pulled out into a room temperature atmosphere and quickly cooled, so that the temperature becomes lower than the flow temperature of the sealing resin 2, and the laminated body 10 is not deformed and is carried out to the next step 106. The In general, the next step 106 is a peripheral coking step.

  FIG. 2 shows a sealing device for realizing the present sealing method. The input stage is a stage composed of a roller conveyor 201, on which a cell-formed glass substrate 1, a sheet of sealing resin 2, and a glass plate 3 on the back side are sequentially laminated. In addition, it is also possible to perform lamination | stacking by an external setup and to mount the laminated body 10 on which it laminated | stacked on the roller conveyor 201 of an input stage.

As the roller conveyor 201 rotates, the laminate 10 is transferred to the conveyor belt 202 and carried to the preheating stage. The conveyor belt 202 is formed of a silicon rubber sheet reinforced with glass fibers because it needs to withstand repeated sealing temperatures and pressures. The conveyor belt 202 is held flat by a driven roller 203 in the middle of the stage and is driven to rotate by a driving roller 204 on the back side.
A lower heater 210 and an upper heater 211 are provided on the preheating stage, and the laminated body 10 is evenly heated to a temperature equal to or lower than the softening temperature of the sealing resin 2. At this time, since the lower heater 210 is heated through the conveyor belt 202 and the upper heater 211 is proximity heating that does not contact the laminate 10, the set temperature of each heater needs to be adjusted by experiment.

  Next, the laminated body 10 is carried into the heat press stage by the conveyor belt 202. The heat press stage includes a lower heating plate 220, an upper heating plate 221, and a servo jack mechanism 223 that performs pressure control. An EPDM rubber sheet 222 having a thickness of 3 mm, which is a hard heat resistant rubber thick plate, is attached to the surface of the upper heating plate 221. The servo jack mechanism 223 has a built-in sensor for monitoring the pressurization in real time and adjusts the pressurizing force to prevent fluctuations in the pressurizing force. Further, the pressure can be adjusted at an arbitrary timing based on a process command from a host controller (not shown).

  In the short-time heating and pressurizing process which is the purpose of this sealing method, it is not realistic to raise the temperature and cool the upper heating plate 221 and the lower heating plate 220 having a large heat capacity during the heating process time. The temperature control of the plate must be done mainly with constant heat. Although it is possible to adjust the set temperature of the heater during the process, the effect is low. Since the difference between the heater set temperature and the actual workpiece temperature causes uneven temperature, the upper heat plate 221 and the lower heat plate 220 have good heat conduction and press a thick aluminum cast plate with a rib structure that can secure a sufficient heat capacity. It has a structure that prevents deformation due to pressure.

  Here, since the pressing is performed in an atmospheric pressure atmosphere, it is not necessary to pressurize after waiting for evacuation as in the conventional vacuum pressurizing process, which contributes to the realization of the short time process. In addition, since the pressure is controlled in real time by the servo jack 223, the pressure does not decrease below the target value due to the flow of the sealing resin, and the flow is partially reduced as in the hydrostatic pressure method. The entire shape after sealing is not uneven.

  Finally, the bonded laminate 10 is pulled out to the take-out stage. The take-out stage is constituted by a roller conveyor 205, and the laminate 10 is carried out by a carry-out mechanism (not shown) while being quickly cooled by natural cooling. Here, since the work temperature at the end of the atmospheric pressure atmosphere pressing step 104 is 115 degrees and the temperature difference from room temperature is less than 100 degrees, the roller conveyor 205 is not provided with a heater, but is operated at a higher temperature. It is preferable to provide a roller conveyor 205 with a heater so that excessive thermal shock is not applied to the glass substrate 1 on the surface side of the laminate 10.

  Here, the state before pressurization heating of the laminated body 10 was shown with typical sectional drawing in FIG. The glass substrate 1 is formed by forming a solar cell thin film 1b on a glass plate 1a made of white glass having a thickness of 3 mm and excellent in transparency, and joining a collector copper foil wiring 1d. Here, the solar cell thin film 1b is formed with a cell gap 1c by laser scribing for the purpose of insulation between the cells, and is a recess. In addition, dents are also formed in the corners of the current collector copper foil wiring 1d, and the sealing resin 2 just placed by its own weight is in a partially floating state.

  Here, the sealing resin 2 is a PVB sheet kept at a moisture content of 0.5% or less, preferably 0.3% or less, and exhibits considerable rigidity at room temperature even when a plasticizer is added. Furthermore, in order to prevent adhesion due to stacking on the sealing resin 2, the surface layer is provided with fine irregularities as a textured process, and the surface is not smooth. In this state, even if the glass plate 3 on the back surface side is stacked on top, a large amount of air is contained in the gaps of the laminated body 10. It is necessary to fill this gap by plastic flow of the sealing resin 2 by pressure heating.

  FIG. 4 shows the process conditions. When PVB exceeds 90 ° C., it starts to show fluidity and further starts to shrink by heating. Therefore, in the preheating step, the work temperature of the sealing resin 2 is only raised to 90 ° C. This preheating reduces the uneven temperature during the temperature rise of the sealing resin 2.

  After this, in the atmospheric pressure atmosphere press, a slight pressurization is applied until the workpiece temperature reaches 100 ° C. in Step 1 to promote heat transfer and prevent the sealing resin 2 from being displaced due to heat shrinkage. ing. During this time, the sealing resin 2 softens and fills the large gaps in the laminate 10, while the air in the gaps is pushed out. At this time, the embossing on the surface of the sealing resin 2 serves as a remaining air flow path to prevent large bubbles from remaining.

In step 2, the temperature is raised to 115 ° C. where the fluidity of the sealing resin 2 is increased. Here, the embossing is crushed by the pressure, and the unevenness on the surface of the solar cell element is filled. The remaining air becomes isolated bubbles. During this time, the vapor pressure of the water contained in the sealing resin 2 exceeds the atmospheric pressure, but the generation of water vapor bubbles is prevented because the applied pressure is increased above the vapor pressure. At the ultimate temperature of 115 ° C., the vapor pressure is 1.7 atm. However, the pressure received by the sealing resin 2 by the atmospheric pressure and the pressurizing force of the press is 2 atm. It can be crushed and dissolved in the sealing resin 2 in a short time. At this time, the disappearance of the bubbles is accelerated because the closed cells are fine due to the embossing of the surface of the sealing resin 2.
Thereafter, when the press is completed, the cooling proceeds promptly, and the sealing resin 2 cools, so that the sealing process is completed without causing the generation of bubbles.

  In the examples so far, a thin film solar cell is taken as an example, and the solar cell element is described as being formed on the glass plate 1 on the surface side. However, the glass plate 1 such as a crystalline solar cell or a CIGS solar cell is used. If there is a separate solar cell element and the element is thick, it is necessary to adjust the process.

  FIG. 5 shows a cross-sectional structure of the stacked body 10 ′ in the crystalline solar cell. The glass plate 1 on the front surface side is a plate material of white plate glass excellent in transparency, and fine irregularities are provided on the inner surface side for the purpose of reducing interface reflection with the sealing resin 2. On this, the sealing resin 2 on the surface side is temporarily fixed in advance by roller pressure. Although most of the gaps between the glass plate 1 and the sealing resin 2 are crushed by the temporary fixing, fine bubbles due to the embossing of each surface layer remain.

A cell string 5 formed by connecting solar cells 5a in series with tab copper wires 5b is disposed thereon, and further, a back side sealing resin 2 is placed thereon, and a back side glass plate 3 is placed thereon. Needless to say, the sealing resin 2 on the back surface side forms a gap with the cell string 5 and also forms a gap with the glass plate 3.
Here, in the crystalline solar cell, the substrate thickness is about 0.15 mm, and the tab copper wire 5 b is also flattened, but the thickness is about 0.1 mm. Since it is necessary to fill this gap with the plastic flow of the sealing resin 2, it is necessary to make the thickness of the sealing resin 2 thicker than that of the first embodiment. Here, the thickness of the sealing resin 2 on the front and back is 0.5 mm. Increasing the thickness increases the flow margin.

  On the other hand, in the case of a crystalline solar cell, since the silicon substrate is weak against local pressurization, it is difficult to extremely increase the applied pressure, so the process conditions are changed as shown in FIG. The atmospheric pressure atmosphere press process has three steps, and the pressure during the temperature rise from 100 ° C to 110 ° C is slowly increased from 0.01 MPa to 0.05 Ma, thereby promoting the evaporation of water vapor along the way and sealing. Local pressurization to the string 5 of the solar cell due to pressurization before the resin 2 is sufficiently softened is prevented.

  In addition, since the moisture concentration of the sealing resin decreases during this period, the generation of water vapor bubbles at high temperatures is prevented. Thereafter, the workpiece temperature of the sealing resin 2 is raised to 120 ° C., which is higher than that of the first embodiment. Here, since the sealing resin 2 is sufficiently softened, smooth plastic flow can be expected. Therefore, even if the applied pressure is increased, the cell string 5 is not forced to concentrate stress.

  In the examples so far, the atmospheric pressure atmosphere pressing step was directly performed after preheating. However, in the solar cell having excellent flexibility such as a thin film solar cell and a film substrate solar cell, an atmospheric pressure atmosphere pressing is performed by adding a nip roll process. The effect of reducing the remaining bubbles inside can be expected. This embodiment is shown in FIG. A nip roll 230 is provided between the preheating stage and the pressure heating stage. By handling the sealing resin 2 that has been softened to some extent, the gap between the laminates 10 is reduced, and the introduction of air into the atmospheric pressure atmosphere pressing process is reduced. is doing.

  As mentioned above, several examples of the present invention have been shown. In the present invention, PVB is exemplified as a thermoplastic resin that does not require a long-time process by heat crosslinking. However, several resins having similar characteristics are known for laminated glass. It is possible to apply any resin that can obtain a sufficient adhesive force without being changed into a thermosetting resin such as an olefin resin, an ester resin, an ionomer resin, or a composite resin thereof.

  DESCRIPTION OF SYMBOLS 1 ... Glass plate, 2 ... Sealing resin, 3 ... Glass plate, 5 ... Cell string, 101 ... Solar cell formation process, 102 ... Lamination process, 103 ... Preheating Process 104 ... Atmospheric pressure atmosphere pressing process 105 ... Unloading process 106 ... Next process 201 ... Roller conveyor 202 ... Conveyor belt 203 ... Driving roller 204 ... Drive roller, 210 ... lower heater, 211 ... upper heater, 220 ... lower heating plate, 221 ... upper heating plate, 222 ... rubber plate, 223 ... servo jack, 205. ..Roller conveyor, 230 ... nip roll

Claims (8)

  In the solar cell module sealing method in which the front and back are made of a hard plate and sealed with a thermoplastic resin, the sealing resin is preheated in a preheating temperature range in which heat shrinkage does not occur, and the plastic flow temperature range of the sealing resin A method for sealing a solar cell module, wherein bubbles are eliminated by pressurizing to a pressure equal to or higher than a vapor pressure in the sealing resin by pressurizing with an atmospheric pressure press.   The method for sealing a solar cell module according to claim 1, wherein generation of water vapor is prevented by pressurization by an atmospheric pressure atmospheric press during temperature rise between the preheating temperature range and the plastic flow temperature range. A method for sealing a solar cell module.   2. The method for sealing a solar cell module according to claim 1, wherein during the temperature rise between the preheating temperature range and the plastic flow temperature range, pressurization by an atmospheric pressure atmospheric press is restricted to prevent generation and outflow of water vapor. A method for sealing a solar cell module, characterized by being promoted.   4. The method for sealing a solar cell module according to claim 1, wherein a gap is reduced by roller pressurization during a temperature rise between the preheating temperature range and the plastic flow temperature range. A method for sealing a solar cell module.   In a sealing device for a solar cell module in which the front and back are made of a hard plate material and sealed with a thermoplastic resin, a transport mechanism for transporting the stacked members, a preheating unit for preheating the stacked members, and an atmospheric pressure atmosphere A sealing device for a solar cell module, comprising an atmospheric pressure atmosphere press section that pressurizes and heats at an arbitrary pressure.   6. The solar cell module sealing device according to claim 5, wherein the transport mechanism includes a roller conveyor portion on which the laminate is placed, a conveyor belt portion on which the laminate is placed on the preheating and pressure heating unit, and after sealing. A solar cell module sealing device comprising a roller conveyor portion for discharging the solar cell module.   7. A sealing device for a solar cell module according to claim 5, wherein the atmospheric pressure atmosphere pressing unit realizes command pressurization with a rigid hot plate having a heater, a controller unit for controlling a pressurizing force according to a process time. A sealing device for a solar cell module, comprising:   8. The solar cell module sealing device according to claim 5, further comprising a nip roll portion that pressurizes the laminated body between the preheating portion and the atmospheric pressure press portion. Module sealing device.

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