JP2012151170A - Manufacturing method of back sheet material for solar cell module - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a method capable of reducing occurrence of warpage on a cut back sheet without causing an increase in a manufacturing cost.SOLUTION: A manufacturing method of a back sheet material for a solar cell module comprises: a step (a) of obtaining a long laminate 108 by bonding a film F1 and a film F2 with an adhesive under heating; a step (b) of winding the laminate 108 into a rolled shape; a step (c) of performing aging processing for promoting curing of the adhesive with the laminate 108 wound into the rolled shape; and a step (d) of cutting the laminate to which the aging processing was applied to a requested size. If contractility of the film F2 is larger than contractility of the film F1, in the step (b), the laminate is wound with the film F2 facing outward.

Description

  The present invention relates to a solar cell module, and more particularly to a backsheet disposed on the back side of the solar cell module.

Solar cell modules have been applied to various electronic devices, starting with those originally used in calculators. In particular, due to the recent increase in awareness of environmental problems, solar cell modules that supply power as clean energy are gaining attention as household and industrial power supply sources.
The solar cell module mainly includes a solar cell element made of crystalline silicon and amorphous silicon. For example, a surface protective layer called a front sheet, a filler layer, a solar cell element as a photovoltaic element, and a filler It is manufactured by a lamination method in which a layer and a back surface protective layer called a back sheet are laminated in this order, and vacuum suction is performed to perform thermocompression bonding.

In the solar cell module, on the assumption that the backsheet has electrical insulation, it is provided for the purpose of providing water vapor and other gas barrier properties and preventing deterioration of the solar cell element mounted inside. . For this purpose, a laminated film in which a thick aluminum foil is initially used as an intermediate layer and both front and back surfaces are laminated with a resin film containing a white pigment has been used.
However, although the back sheet in which the aluminum foil is laminated on the intermediate layer is excellent in gas barrier properties, the cost is high, which hinders widespread use of solar cell modules. Moreover, since aluminum foil has electroconductivity, there exists a possibility that a short circuit (short circuit) may arise in a solar cell circuit by accident etc. during use. Accordingly, various backsheets that do not use aluminum foil have been proposed. For example, Patent Document 1 discloses a back sheet having a structure in which a base film having light reflectivity, an adhesive layer, a vapor deposition layer of an inorganic oxide, and a weather resistant resin film are sequentially laminated from the side arranged on the solar cell element side. Is described. This back sheet can be made excellent in light reflectivity and gas barrier properties without using a metal foil such as an aluminum foil, and is said to have long-term reliability such as performance and weather resistance.

Such a back sheet mainly composed of a resin film is prepared by cutting long film materials to a required length after the film materials are bonded together with an adhesive. However, as described in Patent Document 2, for example, the back sheet after cutting may be warped.
In the process of manufacturing the solar cell module, members constituting the solar cell module may be handled by a machine. The backsheet is no exception. If the back seat is warped, there is a problem that it cannot be handled well. Therefore, it is desirable that the back sheet after cutting is flat.
Patent document 2 addresses this problem by laminating a pressure-sensitive adhesive layer on the surface of the release material layer having releasability, and manufacturing a fluororesin directly on the pressure-sensitive adhesive layer by a melt extrusion method. A base film layer is laminated on the pressure-sensitive adhesive layer surface of the two-layer film after peeling off and removing the release material layer from the three-layer film obtained by laminating the fluorine-based film layer. The manufacturing method of the back sheet | seat base material called.

JP 2000-114565 A JP 2008-204997 A

According to the manufacturing method of Patent Document 2, warping after cutting can be reduced, but a step of peeling and removing the release material layer is added. This process leads to an increase in the manufacturing cost of the backsheet.
Accordingly, an object of the present invention is to provide a method capable of reducing the occurrence of warping after cutting without causing an increase in manufacturing cost.

Patent Document 2 states that the entire laminated structure is heated at a high temperature in the dry laminating process at the time of manufacturing the back sheet is a factor of warpage. However, according to the experience of the present inventors, it was felt that high temperature heating alone would not be the cause of warping. Therefore, the present inventors examined the warpage occurring in the back sheet after cutting. As a result, the following was found.
(1) Warpage becomes conspicuous when a resin film substrate of a different material is bonded, compared to a case of bonding a resin film substrate of the same material.
(2) When a resin film base material having a high heat shrinkage rate and a resin film base material having a low heat shrinkage rate are bonded together via an adhesive, a warp that causes the resin film base material having a high heat shrinkage rate to be inside occurs.

By the way, after laminating two resin film base materials through an adhesive to obtain a laminate, the laminate is wound into a roll. And the laminated body is maintained in the wound state until the adhesive is cured and sufficient adhesive force is obtained.
The present inventor wound up a resin film having a high heat shrinkage rate on the inside of the warp and wound it in a roll shape and maintained the state. As a result, it was confirmed that the warp generated after cutting can be remarkably reduced.

The manufacturing method of the solar cell module backsheet material of the present invention made there is a step (a) for obtaining a long laminate, a step (b) for winding the laminate into a roll, and promoting the curing of the adhesive. The process (c) which performs the aging process to perform, and the process (d) which unwinds the laminated body which passed through the aging process, and cut | disconnects it to the requested | required size.
In the step (a), the laminate is obtained by laminating the first resin film substrate and the second resin film substrate through an adhesive under heating.
In the step (c), the aging treatment is performed in a state where the laminate is wound into a roll.
In the step (d), the cutting is performed in a flat state by unwinding the laminate subjected to the aging treatment from the roll shape.
In the manufacturing method of the back sheet material according to the present invention, when the second resin film base material is more contractible than the first resin film base material, in the step (b), the laminate is the second resin film. It is characterized by being wound up with the substrate facing outward.

In the step (a), the first resin film substrate and the second resin film substrate are inserted between the heated first roll and the second roll disposed to face the first roll. Thus, when the first resin film substrate and the second resin film substrate are bonded together, the first resin film substrate is coated with an adhesive. It is preferable that the first resin film substrate is disposed in direct contact with one roll.
In order to sufficiently obtain the adhesive strength of the adhesive, it is necessary to apply heat necessary for the adhesive. However, it is preferable for reducing the warp that the first resin film substrate having a high shrinkage property, in particular, the heat shrinkage rate, is not set to a very high temperature. Therefore, the heated first roll is indirectly brought into contact with the second resin film substrate via the first resin film substrate. On the other hand, since the heated first roll is in direct contact with the first resin film substrate coated with the adhesive, the heat necessary for the adhesive can be applied.

  In the present invention, a polyester resin can be used as the first resin film substrate, and a fluororesin can be used as the second resin film substrate. Since the fluororesin has a considerably higher heat shrinkage rate than the polyester resin, the effect of reducing warpage by applying the present invention is great.

  According to the present invention, it is possible to reduce warping after cutting by winding the second resin film base material having a large shrinkability outside. Winding the second resin film substrate having a large shrinkage outside is not a new step, and therefore the present invention does not increase the manufacturing cost.

It is a figure which shows schematic structure of the bonding apparatus in this Embodiment. It is a fragmentary sectional view which shows schematic structure of a solar cell module. It is a fragmentary sectional view which shows schematic structure of a back seat | sheet. It is a figure for demonstrating the cause which a curvature produces after a cutting | disconnection. It is a figure for demonstrating the effect | action of this invention. In the present embodiment, (a) is a diagram showing a measurement position of warpage, and (b) shows a measurement result of warpage corresponding to a layer positioned on the outside during winding. In this Embodiment, (a) shows the measurement result of the curvature corresponding to the temperature of a heat roll, (b) shows the measurement result of the joining strength corresponding to the temperature of a heat roll.

Hereinafter, the present invention will be described in detail based on embodiments shown in the accompanying drawings.
First, a schematic configuration of a solar cell module 10 in which a back sheet for a solar cell module (hereinafter simply referred to as a back sheet) is used will be described.
As shown in FIG. 2, the solar cell module 10 includes a front sheet 1, a filler layer 2 made of a resin layer, a solar cell element 3 as a photovoltaic element, and a filler layer similar to the filler layer 2. 4 and the back sheet 5 are sequentially laminated. In addition, this structure is an example of a solar cell module to the last, Comprising: The object to which the back seat | sheet in this invention is applied is not limited.

<Front seat 1>
The front sheet 1 protects the solar cell element 3 as a photovoltaic element. In order for the irradiated sunlight to reach the solar cell element 3, the front sheet 1 needs to be excellent in light transmittance. Moreover, since it protects the solar cell element 3, it must be excellent in weather resistance, water vapor and other gas barrier properties. As the front sheet 1, a known material, typically glass, can be used.

<Filler layers 2, 4>
The filler layers 2 and 4 are provided so as to sandwich the solar cell element 3 in order to embed and stabilize the solar cell element 3 made of amorphous silicon, crystalline silicon, or the like. For the filler layers 2 and 4, resin compositions mainly composed of various thermoplastic resins excellent in thermal fluidity and thermal adhesiveness can be used. For example, a resin composition composed of one or more of a polyethylene resin, a polypropylene resin, a fluorine resin, a cyclic polyolefin resin, a poly (meth) acrylic resin, or a silicone resin is used. can do. All of these resins have transparency and transmit sunlight, and are excellent in scratch resistance and impact absorption. In addition, these resins have heat resistance that is unlikely to deteriorate or decompose due to the action of heat. The heat resistance is required for a heating operation in a lamination method in which a vacuum suction is performed when the solar cell module 10 is manufactured, and for a heating operation by irradiation of sunlight while the solar cell module 10 is used. Is done.
The thickness of the filler layers 2 and 4 is preferably 200 to 1000 μm, and more preferably 350 to 600 μm.

<Solar cell element 3>
As the solar cell element 3 as a photovoltaic element constituting the solar cell module 10, a conventionally known single crystal silicon type solar cell element, a crystalline silicon solar electronic element represented by a polycrystalline silicon type solar cell element, a single junction Well-known ones such as amorphous silicon solar cell elements of a type or tandem structure type can be widely applied.

<Back sheet 5>
As shown in FIG. 3, the backsheet 5 has a three-layer structure except for the adhesive layer 54. That is, the white PET layer 51, the vapor-deposited PET layer 52, and the fluororesin layer 53 are laminated via the adhesive layer 54 from the solar cell element 3 (filler layer 4) side. However, this configuration is merely an example, and does not exclude application of the present invention to the backsheet 5 having another configuration. PET is an abbreviation for polyethylene terephthalate.

The white PET layer 51 mainly has a function of reflecting the light transmitted through the filler layers 2 and 4 toward the solar cell element 3 in the back sheet 5. The white PET layer 51 also has electrical insulation. The white PET layer 51 is composed of a PET film in which a white pigment such as titanium dioxide is kneaded in order to have light reflectivity.
The vapor-deposited PET layer 52 has a gas barrier property that prevents water vapor and other gases from penetrating the solar cell element 3 mainly in the backsheet 5. Therefore, the vapor deposition PET layer 52 is formed with a vapor deposition layer made of an inorganic compound on either one of the front and back surfaces of the PET film, preferably on both surfaces. As the inorganic compound, aluminum oxide, silicon oxide, magnesium oxide, tin oxide, or a mixture thereof can be used. Among these, aluminum oxide is preferable. Although the thickness of a vapor deposition film is suitably set by the kind and structure of an inorganic compound to be used, it is normally selected from the range of 5-300 nm.
The fluororesin layer 53 disposed as the outermost layer in the backsheet 5 mainly bears weather resistance.

The back sheet 5 can be obtained, for example, by cutting a laminate produced by the bonding apparatus 100 shown in FIG. A procedure for bonding the first resin film substrate F1 (hereinafter referred to as film F1) and the second resin film substrate F2 (hereinafter referred to as film F2) by the bonding apparatus 100 will be described.
The laminating apparatus 100 includes a first base material roll 101 around which a film F1 is wound around a core material, and a second base material roll 105 around which a film F2 is wound around the core material. The film F1 is unwound from the first substrate roll 101, and the film F2 is unwound from the second substrate roll 105. In addition, tension | tensile_strength is given to the film F1 and the film F2 which are pulled out until it is wound up by the winding roll 109.

  The laminating apparatus 100 applies an adhesive to the film F1 drawn from the first base material roll 101. For this purpose, the bonding apparatus 100 includes an adhesive tank 102. The adhesive tank 102 contains an adhesive containing a solvent. The adhesive tank 102 is provided with a gravure roll 103, a part of which is immersed in the adhesive. The adhesive in the adhesive tank 102 is applied to the film F <b> 1 by transfer accompanying the rotation of the gravure roll 103. The solvent is used to facilitate the application of the adhesive to the film F1.

  The bonding apparatus 100 includes a drying furnace 104. The film F1 coated with the adhesive passes through the drying furnace 104, and the solvent in the adhesive applied to the film F1 is removed in the process of passing through the drying furnace 104. The film F1 that has passed through the drying furnace 104 is supplied toward a bonding portion that includes a heat roll 106 and a counterpart roll 107 that is arranged to face the heat roll 106. On the other hand, the film F2 drawn from the second base material roll 105 is supplied to the bonding portion.

Film F1 and film F2 are overlapped and inserted between heat roll 106 and counterpart roll 107. The film F1 has an adhesive-coated surface facing the film F2. Also, the film F1 is in direct contact with the heat roll 106, the film F2 is in direct contact with the counterpart roll 107, and the superimposed film F1 and film F2 are at a pressure adjusted by the heat roll 106 and the counterpart roll 107. Pressed. The heat roll 106 is heated to the adjusted temperature, and gives necessary heat to the adhesive via the film F1.
The film F1 and the film F2 that have passed through the heat roll 106 and the counterpart roll 107 become a laminate 108 and are taken up by a take-up roll 109. In FIG. 1, the broken-line laminate 108 indicates that the film F1 is disposed outside and wound, and the practical laminate 108 indicates that the film F2 is disposed outside and wound.

  The laminate 108 wound up in a roll shape is subjected to an aging treatment for promoting the curing of the adhesive. In the aging treatment, the laminate 108 wound up in a roll shape is left in a temperature range (for example, 30 to 60 ° C.) higher than normal temperature for several days (for example, 2 to 5 days). The adhesive begins to harden after passing through the heat roll 106 and the counterpart roll 107, and is cured through this aging treatment, thereby exhibiting the necessary adhesive force.

  The procedure for bonding the two film base materials has been described above, but in order to obtain the three-layer back sheet 5, two of the three layers are bonded by the bonding apparatus 100 to produce the laminate 108. The film base material constituting the remaining layers may be bonded to the laminate 108. In the case of the back sheet 5, for example, the vapor-deposited PET layer 52 and the fluororesin layer 53 are bonded together via an adhesive layer 54 to form a laminate, and then the laminate and the white PET layer 51 are interposed via the adhesive layer 54. Can be laminated to form a three-layer laminate. Further, the white PET layer 51 and the fluororesin layer 53 are bonded together through an adhesive layer 54 to form a laminated body, and then a base film constituting the laminated body and the vapor-deposited PET layer 52 is bonded through the adhesive layer 54. It can also be set as a laminated body of 3 layers in total. Even when it has a configuration of four or more layers, a laminate can be obtained in the same manner as described above.

Now, as shown to Fig.4 (a), suppose that two films F1 and film F2 from which shrinkage differs were laminated | stacked through the adhesive agent. In this case, the heat shrinkage rate α2 of the film F2 is larger than the heat shrinkage rate α1 of the film F1 (α1 <α2), so that the shrinkage properties of the film F1 and the film F2 are different. In addition, the white arrow in FIG. 4 has shown the magnitude | size of the heat shrinkage rate (the following is also the same).
The film F1 and the film F2 are heated with the adhesion. Therefore, although the film F1 and the film F2 cause heat shrinkage, from the relationship of α1 <α2, when the adhesive is cured and the adhesion is completed, the shrinkage amount of the film F2 is large as shown in FIG. 4B. Moreover, the warp with the film F2 on the inside occurs in the laminate.

4 assumes that the film F1 and the film F2 are flat, but as described with reference to FIG. 1, in the process of producing the back sheet 5, the film F1 and the film F2 are wound in a roll shape. The adhesive is cured while maintaining that state. Therefore, next, the warpage of the roll-shaped laminate 108 will be examined with reference to FIG.
FIG. 5A shows a part of the laminate 108 (film F1 and film F2) in a state of being wound on the winding roll 109. FIG. The film F1 and the film F2 are tensioned and extend compared to the unloaded state. However, the film F1 located on the outer side is longer in the circumferential direction than the film F2 located on the inner side. It is getting longer. That is, the residual stress of the film F1 is larger than the residual stress of the film F2. Therefore, when the difference in the thermal contraction rate is ignored and only the residual stress is taken into account, if the laminate 108 is cut after unwinding, a warp with the film F1 on the inside occurs. In FIG. 5, a patterned arrow indicates the magnitude of the residual stress (the same applies to the following). FIG. 5A shows the case where the film F1 is the outside and the film F2 is the inside, but the relationship of the residual stress is the same even when the film F1 is the inside and the film F2 is the outside.

Since the film F1 and the film F2 have a difference in heat shrinkage rate, the difference in heat shrinkage rate is also considered next.
By the way, the laminated body 108 wound up by the winding roll 109 requires a considerable time until the adhesive is completely cured. Therefore, it is understood that the film (F1 or F2) positioned on the outer side contracts in the circumferential direction while sliding with respect to the film (F2 or F1) positioned on the inner side so that the residual stress is reduced.

FIG. 5 (b) shows the case where the film F1 (low heat shrinkage rate) is arranged outside, and FIG. 5 (c) shows the case where the film F2 (high heat shrinkage rate) is arranged outside and wound up. Show. In FIGS. 5B and 5C, the magnitude of the heat shrinkage rate and the magnitude of the residual stress are indicated by arrows following the examples so far.
When the film F1 (small heat shrinkage rate) is arranged on the outside, as shown in FIG. 5B, the outer film F1 has a large residual stress and the heat shrinkage rate is large on the inside film F2. Therefore, at first glance, the warping after cutting is reduced by offsetting the residual stress of the film F1 and the heat shrinkage rate of the film F2. However, the residual stress is released by the outer film F1 slipping with respect to the inner film F1 during the curing process of the adhesive. Therefore, the influence of the heat shrinkage rate of the film F2 is greatly reflected, and it is not possible to reduce the warp with the film F2 inside after cutting.
On the other hand, when the film F2 (large heat shrinkage rate) is arranged on the outside, as shown in FIG. 5 (c), both the residual stress and the heat shrinkage rate are large on the outside film F2. Therefore, at first glance, the film F2 is greatly warped after being cut. However, the residual stress is released by the sliding of the outer film F2 during the curing process of the adhesive. Then, the warp after cutting is reduced by balancing the heat shrinkage rate (large) of the outer film F2 with the sum of the heat shrinkage rate (small) and the residual stress (small) of the inner film F1.
Here, the heat shrinkage rate has been described as one of the shrinkage properties. However, the shrinkability in the present invention is not limited to the heat shrinkage rate. Obviously, when the elasticity of the film F2 is larger than that of the film F1, it can be understood in the same manner as described above.

  The reason why the warp can be reduced by the present invention has been described above. In the following, the back sheet 5 in which the white PET layer 51, the vapor-deposited PET layer 52, and the fluororesin layer 53 are actually laminated with the adhesive layer 54 interposed therebetween will be described. The example which manufactured and observed generation | occurrence | production of curvature is shown.

The material constituting each layer and the adhesive for joining the layers were as follows.
White PET layer 51: Lumirror E20 manufactured by Toray Industries, Inc.
Thickness: 50 μm Heat shrinkage (150 ° C x 30 minutes); 1.4 (JIS C2151)
Deposition PET layer 52: manufactured by Toray Film Processing Co., Ltd. Barrier Rocks 1031HGT
Thickness: 12 μm Heat shrinkage (150 ° C x 30 minutes); 1.5 (JIS C2151)
Fluororesin layer 53: DuPont Tedlar film TWH15BL3
Thickness: 38μm Heat shrinkage (150 ℃ × 30min); 4.0 (JIS C2151)
Adhesive: Urethane adhesive manufactured by Mitsui Chemicals, Inc.
Main agent; A-910-A Curing agent; A-3

  The backsheet 5 is bonded to the vapor-deposited PET layer 52 and the fluororesin layer 53 by the bonding apparatus 100 described in FIG. The PET layer 51 was prepared by the procedure of bonding (second bonding). However, the laminate after the second bonding was wound in two ways: an example in which the fluororesin layer 53 was placed outside (invention example) and an example in which the white PET layer 51 was placed outside (comparative example).

The conditions at the time of the first bonding and the second bonding and the aging conditions are as follows.
First bonding:
Tension: vapor deposition PET layer 52 = 13 kg / cm ² fluororesin layer 53 = 11 kg / cm ²
Drying furnace 104 (temperature): 50 to 70 ° C
Heat roll 106 (temperature): 70 ° C.
Second bonding:
Tension: Laminate = 13 kg / cm ² White PET layer 51 = 50 kg / cm ²
Drying furnace 104 (temperature): 50 to 70 ° C
Heat roll 106 (temperature): 50 ° C, 70 ° C, 90 ° C
50 ° C. and 90 ° C. make the fluororesin layer 53 outside.
Implemented only in the case of the example (example of the present invention) Aging: 40 ° C. × 5 days (implemented in the wound state)

  After the aging was completed, the laminate unwound from each of the inventive examples and the comparative examples was cut to obtain an A4 size sheet S. Each sheet S was placed on a flat surface, and the distances from the flat surface to the four vertices A, B, C, and D (see FIG. 6A) were measured. Each sheet S is placed so that the white PET layer 51 is in contact with the flat surface when the distance is measured. Moreover, about the example which changed the temperature of the heat roll 106, the joint strength by each temperature was also measured. The bonding strength was measured according to JIS K6854. However, the measurement width is 15 mm, and the measurement speed is 200 mm / min. It was. The results are shown in FIGS. 6 (a), 7 (a), and 7 (b).

As shown in FIG. 6A, the warping after cutting can be remarkably reduced by winding the fluororesin layer 53 outside.
Further, the warp after cutting can be remarkably reduced by lowering the temperature of the heat roll 106. However, when the temperature of the heat roll 106 is lowered, the bonding strength is reduced. This suggests the following in addition to lowering the temperature of the heat roll 106 itself. That is, the heat roll 106 is not brought into direct contact with the fluororesin layer 53 having a large heat shrinkage rate, but is bonded so that the heat roll 106 is brought into direct contact with the white PET layer 51 (first resin film substrate). By performing, the temperature rise of the fluororesin layer 53 can be suppressed, so that the warp after cutting can be reduced.

In the said embodiment, the specific example was shown about the back sheet 5 in which the white PET layer 51, the vapor deposition PET layer 52, and the fluororesin layer 53 were laminated | stacked through the adhesive bond layer 54. As shown in FIG. However, it is obvious that the present invention can be widely applied when the second resin film substrate is more contractible than the first resin film substrate, as is clear from the reason that the above-described warpage can be reduced.
The white PET layer 51, the vapor-deposited PET layer 52, and the fluororesin layer 53 are not limited to the materials specifically shown, and the present invention can be widely applied to materials used for back sheets.
Other than this, as long as the gist of the present invention is not deviated, the configuration described in the above embodiment can be selected or changed to another configuration as appropriate.

DESCRIPTION OF SYMBOLS 5 ... Back sheet 51 ... White PET layer, 52 ... Deposition PET layer, 53 ... Fluorine resin layer 100 ... Laminating apparatus 101 ... 1st base material roll, 104 ... Drying furnace, 105 ... 2nd base material roll 106 ... Heat roll , 107 ... Counter roll, 108 ... Laminate 109 ... Winding roll F1 ... First resin film substrate (film)
F2 ... Second resin film substrate (film)

Claims (3)

A step (a) of obtaining a long laminate by bonding the first resin film substrate and the second resin film substrate through an adhesive under heating;
A step (b) of winding the laminate into a roll;
A step (c) of performing an aging treatment for accelerating the curing of the adhesive in a state where the laminate is wound into a roll;
A step (d) of unwinding the laminate subjected to the aging treatment and cutting it to a required size,
When the second resin film substrate is more contractible than the first resin film substrate,
In the step (b), the laminate is wound up with the second resin film substrate outside, and a method for producing a backsheet material for a solar cell module. In the step (a),
By inserting the first resin film substrate and the second resin film substrate between the heated first roll and the second roll disposed to face the first roll, Bonding the first resin film substrate and the second resin film substrate,
The first resin film substrate coated with the adhesive is disposed so as to be in direct contact with the heated first roll.
The manufacturing method of the backsheet raw material for solar cell modules of Claim 1. The first resin film substrate is made of a polyester resin,
The second resin film substrate is made of a fluororesin,
The manufacturing method of the backsheet raw material for solar cell modules of Claim 1 or 2.

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