JPWO2014115719A1 - Sheet heat treatment method and sheet heat treatment apparatus - Google Patents

Abstract

The present invention provides a sheet heat treatment method in which a sheet is supported by a plurality of conveying rollers in a heat treatment furnace, and at least one of the plurality of conveying rollers includes the following (a), (b), and (c): This is a heat treatment method for the sheet to be filled. (a) The ten-point average roughness of the portion in contact with the sheet is greater than 20 μm and less than 60 μm. (b) The portion in contact with the sheet is made of a material having a contact angle with water of 100 ° or more. (c) The roller, the conveyance roller on the upstream side in the sheet conveyance direction of the roller, and the conveyance roller on the downstream side in the sheet conveyance direction of the roller are in contact with the surface on the same side of the sheet. According to the present invention, there is provided a sheet heat treatment method capable of heat treating a sheet at a high temperature without causing the sheet to adhere to the conveyance roller.

Description

  The present invention relates to a sheet heat treatment method and a sheet heat treatment apparatus.

  Development of solar cells that directly convert sunlight into electrical energy has been promoted from the viewpoint of effective use of resources and prevention of environmental pollution. As shown in FIG. 3, the solar battery module generally includes a solar battery cell with a glass sheet side sealing sheet 3 a and a back sheet surface side sealing sheet 3 b between a glass substrate 1 and a back sheet 2. 4 is sealed.

  In such a solar cell module, the glass substrate 1, the sealing sheet 3a, the solar cell 4, the sealing sheet 3b, and the back sheet 2 are laminated in this order, and this laminate is vacuum laminated and heated. As shown in FIG. 4, it is manufactured by bonding and integration without bubbles.

  As a raw material of a sealing sheet used for a solar cell module (hereinafter referred to as a solar cell sealing sheet), an ethylene-vinyl acetate copolymer (EVA) is a main component from the viewpoint of transparency and fluidity. In many cases, a structure containing a crosslinking agent and a crosslinking aid is known. At the time of manufacturing the solar cell sealing sheet, the EVA resin composition is formed into a sheet in an uncrosslinked state, and at the time of manufacturing the solar cell module, the sealing sheet is cross-linked and solidified by heating at the time of vacuum lamination.

  However, the solar cell 4 may be damaged or bubbles may enter due to shrinkage and deformation of the sealing sheet (hereinafter referred to as heat shrinkage) due to heating during vacuum lamination. Therefore, the shrinkage of the sealing sheet is required to be small during heating during vacuum lamination.

  A general method for manufacturing a solar cell sealing sheet is to form a sheet by discharging a high-temperature resin melted by an extruder or the like with a die or by narrowing the pressure with a calendar roller. Taken over and solidified by cooling, and then rolled up on a winding core. Since the resin contains a crosslinking agent and a crosslinking aid, it is necessary to suppress the crosslinking reaction when the resin is formed into a sheet. For this reason, the molding temperature cannot be raised sufficiently, and a lot of distortion remains in the sealing sheet during sheet molding. Therefore, the sheet contracts greatly by heating during vacuum lamination. Particularly in recent years, there is a tendency to lower the crosslinking temperature in order to shorten the processing time of the vacuum laminating process. Therefore, the sheet forming temperature at the time of manufacturing the solar cell sealing sheet is inevitably lowered, and there is a problem that the residual strain of the sealing sheet at the time of sheet forming becomes large.

  Therefore, before the vacuum lamination process of the solar cell module, it is necessary to devise an annealing process for the sealing sheet to remove the residual distortion of the sheet. As a conventional method for reducing thermal shrinkage of a sealing sheet, for example, in Patent Document 1, in a manufacturing process of a sealing sheet, a sheet immediately after being formed into a sheet shape is conveyed by a plurality of conveying rollers, Is maintained at a temperature range lower than the crosslinking temperature and about 20 to 25 ° C. higher than the softening point for 1 to 2 minutes, and the peripheral speed of the roller on the inlet side of the conveying roller is higher than the peripheral speed of the roller on the outlet side. The annealing process is performed without applying a large tension. With such a method, residual distortion of the sheet is removed, and thermal shrinkage during vacuum lamination is reduced.

JP 2000-084996 A

  However, in recent years, solar electronic cells have become thin and become fragile, with a thickness of around 100 μm, due to the effective utilization of crystalline silicon resources and the demand for cost reduction for the spread of solar cell modules. Therefore, there is an increasing demand for reducing the thermal shrinkage of the sealing sheet. The annealing process of Patent Document 1 has a processing temperature as low as the melting point of the sealing sheet, and is insufficient to remove the residual strain of the sealing sheet formed at a low temperature as described above. In order to remove the residual strain of the encapsulating sheet, it is necessary to provide a sufficient temperature and time. However, if the annealing time is increased, productivity is lowered. On the other hand, when the temperature of the annealing treatment is increased, even if the temperature does not reach the crosslinking temperature, the adhesion between the sealing sheet and the conveyance roller in the annealing process increases. A tear occurs. In order to prevent this, when the tension is increased by the speed difference between the rollers, the peelability of the sealing sheet from the transport roller is improved, but distortion occurs again due to the speed difference. Thus, with the conventional annealing method, it is difficult to efficiently reduce the thermal shrinkage of the sealing sheet.

  In view of the above circumstances, the present invention provides a sheet heat treatment method capable of heat treating a sheet at a high temperature without causing the sheet to adhere to the conveyance roller. The present invention also provides a heat treatment apparatus capable of realizing this method. In addition, the present invention provides a method for producing a sealing sheet suitable for use as a solar cell sealing material, which has a small shrinkage due to heating during vacuum lamination.

The sheet heat treatment method of the present invention for solving the above problems is as follows.
In a heat treatment method for a sheet that is supported and conveyed by a plurality of conveyance rollers in a heat treatment furnace, heat treatment of the sheet in which at least one of the plurality of conveyance rollers satisfies the following (a), (b), and (c): Method.
(a) The ten-point average roughness of the portion in contact with the sheet is greater than 20 μm and less than 60 μm.
(b) The portion in contact with the sheet is made of a material having a contact angle with water of 100 ° or more.
(c) The roller, the conveyance roller on the upstream side in the sheet conveyance direction of the roller, and the conveyance roller on the downstream side in the sheet conveyance direction of the roller are in contact with the surface on the same side of the sheet.

In the present invention, “ten-point average roughness” refers to ten-average roughness measured based on Japanese Industrial Standard JIS B0601 (2001). The ten-point average roughness is a value measured with a contact-type surface roughness measuring instrument manufactured by Mitutoyo Corporation with a stylus material diamond, a stylus tip radius of 2 μm, and a measuring force of 0.75 mN. In this application, it is called “RzJIS”.
In the present invention, the “contact angle with water” is an angle formed by a tangent drawn to a water drop and the solid surface at the intersection of the surface of the water drop placed on the solid surface and the solid surface. That means. The contact angle with water was measured with a known automatic contact angle measuring instrument based on Japanese Industrial Standard JIS R3257 (1999).
In the present invention, the “upstream side” refers to the direction in which the sheet is conveyed, and the “downstream side” refers to the direction in which the sheet is conveyed.

  In the sheet heat treatment method of the present invention, the ten-point average roughness is preferably greater than 20 μm and not greater than 45 μm.

  In the sheet heat treatment method of the present invention, the sheet contains a crosslinking agent, and at least one of the conveying rollers satisfying the above (a), (b) and (c) is such that the temperature of the sheet is the melting point of the sheet +10 It is preferably in contact with the portion of the sheet having a melting point of + 40 ° C. or lower.

  In the present invention, the “melting point” refers to an endothermic peak value temperature in a temperature rising process in differential scanning calorimetry (DSC), and is a value measured based on Japanese Industrial Standard JIS K7121 (2012).

  In the sheet heat treatment method of the present invention, it is preferable that a contact distance between the sheet and at least one of the conveying rollers satisfying (a), (b) and (c) is 100 mm or less.

  In the present invention, the “contact distance with the sheet” refers to the roller circumferential length from the point where the sheet and the conveying roller start to contact to the point where the roller and the sheet peel.

  In the sheet heat treatment method of the present invention, it is preferable to perform an embossing treatment on one side of the sheet exiting the heat treatment furnace.

  In the present invention, the “embossing treatment” refers to a treatment for imparting an uneven shape to the surface of the sealing sheet in order to improve transportability and prevent blocking between the sealing sheets during winding.

  In the sheet heat treatment method of the present invention, the sheet is preferably composed of a resin composition containing an ethylene-vinyl acetate copolymer as a main component.

  In the sheet heat treatment method of the present invention, at least one portion of the transport roller that satisfies the above (a), (b), and (c) is in contact with the sheet, and is composed of a material containing baking silicone or a fluorine-based resin. It is preferable that

In the present invention, the “main component of the resin composition” is a component that occupies 50% by mass or more of the resin composition.
In the present invention, “baked silicone” refers to a silicone resin that has been subjected to a crosslinking reaction by heating, and the silicone resin refers to a generic term for synthetic resins having a siloxy acid bond composed of silicon (silicon) and oxygen.
In the present invention, the “fluororesin” is a general term for synthetic resins containing a part of a fluorine element such as ethylene hydrocarbon.

The sheet heat treatment apparatus of the present invention that solves the above problems is as follows.
A sheet heat treatment apparatus having a sheet heating unit, a sheet conveyance unit, and a sheet temperature holding unit, wherein the sheet conveyance unit includes a plurality of conveyance rollers, and at least one of the plurality of conveyance rollers includes the following (d), A sheet heat treatment apparatus satisfying (e) and (f).
(d) The ten-point average roughness of the portion in contact with the sheet being conveyed is greater than 20 μm and less than 60 μm.
(e) The portion in contact with the sheet being conveyed is made of a material having a contact angle with water of 100 ° or more.
(f) The roller, the conveyance roller on the upstream side in the sheet conveyance direction of the roller, and the conveyance roller on the downstream side in the sheet conveyance direction of the roller are in contact with the surface on the same side of the sheet being conveyed.

In the present invention, the “sheet heating means” means that when a solar cell sealing sheet is continuously conveyed, the sheet is heated to a predetermined temperature by irradiating or transferring heat energy to the sheet. This means.
In the present invention, “sheet conveying means” means means for conveying a solar cell sealing sheet continuous in the conveying direction from upstream to downstream of the production process, and in the present invention means a conveying roller.
In the present invention, the “sheet temperature holding means” refers to means for holding the sheet temperature at a high temperature for a predetermined time or longer when the solar cell sealing sheet is continuously conveyed.

  In the sheet heat treatment apparatus of the present invention, the ten-point average roughness is preferably greater than 20 μm and not greater than 45 μm.

  In the sheet heat treatment apparatus of the present invention, it is preferable that an embossing roller for embossing the sheet is disposed on the downstream side in the sheet conveying direction of the heat treatment apparatus.

  In the sheet heat treatment apparatus according to the present invention, the portion of the conveying roller that satisfies the above (d), (e), and (f) is in contact with at least one sheet being conveyed, and includes a material containing baking silicone or fluorine-based resin. It is preferable that it is comprised.

  Moreover, the manufacturing method of the sheet | seat for solar cell sealing of this invention which solves the said subject is as follows. In the method for producing a solar cell sealing sheet, a sheet containing a crosslinking agent is fed from a supply source, the sheet is subjected to a heat treatment in a heat treatment furnace, and then the sheet is wound up. The manufacturing method of the sheet | seat for solar cell sealing which uses this.

  In the present invention, the “supply source” includes not only a melt discharge source for forming a sheet but also a sheet unwinding machine such as an original roll.

Moreover, the manufacturing apparatus of the sheet | seat for solar cell sealing of this invention which solves the said subject is as follows.
A solar cell sealing sheet manufacturing apparatus for manufacturing a solar cell sealing sheet by forming a molten resin into a sheet shape, the solar cell sealing sheet manufacturing apparatus including the sheet heat treatment apparatus of the present invention.

  According to the present invention, even if the sealing sheet is transported at a temperature exceeding the melting point in the heat treatment apparatus, the sheet can be easily peeled off from the transport roller, so that without causing excessive distortion in the sealing sheet, The thermal contraction of the sealing sheet can be effectively removed.

FIG. 1 is a schematic diagram illustrating an example of a solar cell sealing sheet manufacturing apparatus according to the present invention. FIG. 2 is a schematic diagram illustrating an example of a solar cell sealing sheet manufacturing apparatus according to the present invention. FIG. 3 is a schematic diagram showing a member configuration of the solar cell module. FIG. 4 is a schematic diagram showing the member configuration of the solar cell module. FIG. 5 is an explanatory view schematically showing the surface of a conventional conveying roller immediately after contact with a sheet. FIG. 6 is an explanatory view schematically showing the surface of a conventional conveying roller immediately before sheet peeling. FIG. 7 is an explanatory view schematically showing the surface of the conveying roller of the present invention immediately after the sheet contact. FIG. 8 is an explanatory view schematically showing the surface of the conveying roller of the present invention immediately before sheet peeling and a partially enlarged view of the convex portion. FIG. 9A is a schematic diagram showing an example of a conveying roller that satisfies the conditions (a), (b), and (c). FIGS. 9B, 9C, and 9D are the conditions ( It is a schematic diagram which shows an example of the conveyance roller which does not satisfy | fill c).

  A preferred embodiment of the present invention will be described below with reference to the drawings, taking as an example a case where the present invention is applied to a method for producing a solar cell sealing sheet.

  FIG. 1 is a schematic view showing an embodiment of the production method of the present invention. FIG. 1 shows only the main part, and a part of the frame and the transport roller for fixing the structure is omitted.

  Here, the supply source of the sheet 3 to be conveyed by the exemplified solar cell sealing sheet manufacturing apparatus may be any source. As a preferred example, as shown in FIG. 1, an ethylene copolymer resin melted at a high temperature is mixed and melted by an extruder 11, and the melted resin is discharged from a die 12 to polishing rollers 13 a and 13 b to be solidified. And form into a sheet. The extruder 11 has a screw disposed inside the cylinder, and a twin-screw extruder having a small shear heat generation is more preferable for discharging the resin mixed with the crosslinking agent at a low temperature. The discharge temperature in this case varies depending on the selection of the resin and the crosslinking agent, but is preferably 90 ° C. or higher and 130 ° C. or lower, more preferably 100 ° C. or higher and 115 ° C. or lower. In addition to this, the sheet supply source may use a calendar device that forms by melting and stretching the molten resin between two rollers. At this time, either one of the polishing rollers 13a or 13b may be embossed on one side of the sealing sheet 3 during sheet forming. Or you may emboss both surfaces of the sheet | seat 3 at the time of sheet forming with both the polishing rollers 13a and 13b. By performing the embossing, the contact area between the sheet 3 and the roller in the downstream process can be reduced and the transportability can be improved.

  The sheet 3 sent out from the supply source in this way is sent to the heat treatment apparatus 14, heated by the heater 15 which is a sheet heating means, and conveyed by a plurality of conveying rollers 16a in a high temperature state. After exiting the heat treatment apparatus 14, the sheet 3 is preferably cooled by the cooling roller 20 and then taken up by a winder 32.

  FIG. 2 is a schematic view showing another embodiment of the production method of the present invention. As shown in the embodiment of FIG. 2, the sealing sheet may be wound as an intermediate product 34, the sheet 3 may be unwound by a rewinder 34 that is a subsequent process, and heat treatment may be performed by the heat treatment apparatus 14.

  The resin of the sheet 3 is not particularly limited as long as it is transparent and has adhesiveness and flexibility. Examples thereof include low-density polyethylene, ultra-low-density polyethylene, linear low-density polyethylene, medium-density polyethylene, high-density polyethylene, and polyethylene resins such as copolymers with other monomers mainly composed of ethylene. Here, the copolymer with other monomers mainly composed of ethylene is a copolymer in which 50% by mass or more of the copolymer is ethylene. Examples of the copolymer with another monomer having ethylene as a main component 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, ethylene-vinyl acetate copolymer (EVA), ethylene-methyl methacrylate copolymer (EMMA), and very low density polyethylene (VLDPE), which have good adhesion to glass and are excellent in cost, are sealed. It is suitable as a main component of the resin composition constituting the stop sheet. In addition, the present invention is particularly effective for resins having high adhesiveness at such high temperatures.

  When a resin composition mainly composed of EVA is used as the resin composition constituting the sheet, the vinyl acetate (VA) content in EVA is 15 to 35% by mass from the viewpoint of flexibility and moisture permeability. preferable. The melting point of EVA varies depending on the VA content. When the EVA is 15 to 35% by mass, the melting point is in the range of 60 to 90 ° C. Moreover, it is preferable that the melt flow rate of EVA is 2-50 g / 10min.

  When a resin composition mainly composed of EMMA is used as the resin composition constituting the sealing sheet, the content of methacrylic acid (MMA) in EMMA is 15 to 28% by mass from the viewpoint of flexibility and moisture permeability. It is preferable that The melting point of EMMA varies depending on the MMA content, and when it is 15 to 28% by mass, the melting point is in the range of 68 to 94 ° C. Moreover, it is preferable that the melt flow rate of EMMA is 2-50 g / 10min.

When a resin composition containing VLDPE as a main component is used as the resin composition constituting the sealing sheet, the density of the resin composition is 900 kg / m ³ or less and the melting point is 100 from the viewpoint of flexibility and transparency. It is preferable that it is below ℃. Moreover, it is preferable that the melt flow rate of VLDPE is 2-50 g / 10min.

  The sheet may be a single-layer sheet or a multilayer sheet in which two or more layers of resin compositions different in the thickness direction of the sheet are laminated. Even if it is a multilayer sheet, the present invention is effective if it has a layer made of the above-described resin composition having adhesiveness and flexibility on the surface in contact with the conveying roller.

  The resin composition used in the present invention has a crosslinked structure by blending a crosslinking agent as an additive for improving heat resistance. As this crosslinking agent, an organic peroxide that starts to initiate a crosslinking reaction at 100 to 120 ° C. or higher is generally used. Examples of such an organic peroxide include 2,5-dimethylhexane; 2,5-dihydroperoxide; 2,5-dimethyl-2,5-di (t-butylperoxy) hexane; -T-butyl peroxide; t-dicumyl peroxide; 2,5-dimethyl-2,5-di (t-butylperoxy) hexyne; dicumyl peroxide; α, α'-bis (t-butylperoxide Oxyisopropyl) benzene; n-butyl-4,4-bis (t-butylperoxy) butane; 2,2-bis (t-butylperoxy) butane; 1,1-bis (t-butylperoxy) cyclohexane 1,1-bis (t-butylperoxy) 3,3,5-trimethylcyclohexane; t-butylperoxybenzoate; benzoyl peroxide; Oxy-2-ethylhexyl carbonate or the like can be used. The compounding amount of these organic peroxides is generally 5 parts by mass or less, preferably 0.2 to 2 parts by mass with respect to 100 parts by mass of the resin composition.

  Furthermore, a crosslinking aid can be added to the resin composition as an additive for improving the crosslinking rate of the resin composition and improving the heat resistance. Examples of crosslinking aids provided for this purpose include triallyl isocyanurate; trifunctional crosslinking aids such as triallyl isocyanate, and bifunctional and monofunctional crosslinking aids such as NK ester. Can be mentioned. The compounding amount of these crosslinking aids is generally 5 parts by mass or less, preferably 1 to 3 parts by mass with respect to 100 parts by mass of the resin composition.

  Moreover, it is common to add a silane coupling agent to a resin composition as an additive for improving the adhesive force with glass or a power generation element as a sealing film of a solar cell. Known silane coupling agents for this purpose are, for example, γ-chloropropyltrimethoxysilane; vinyltrichlorosilane; vinyltriethoxysilane; vinyl-tris- (β-methoxyethoxy) silane; γ-methacryloxy. Propyltrimethoxysilane; β- (3,4-ethoxycyclohexyl) ethyltrimethoxysilane; γ-glycidoxypropyltrimethoxysilane; vinyltriacetoxysilane; γ-mercaptopropyltrimethoxysilane; γ-aminopropyltrimethoxysilane N-β- (aminoethyl) -γ-aminopropyltrimethoxysilane and the like can be mentioned. The compounding quantity of these silane coupling agents is generally 5 mass parts or less with respect to 100 mass parts of resin compositions, Preferably it is 0.1-1 mass part.

  Furthermore, hydroquinone; hydroquinone monomethyl ether; p-benzoquinone; methyl hydroquinone, and the like can be added as additives for improving the stability of the resin composition. The amount of these compounds is generally 100 parts by mass of the resin composition. Is 3 parts by mass or less.

  Furthermore, if necessary, an ultraviolet absorber, an antioxidant, a light stabilizer, and the like can be added as additives other than those described above. Examples of ultraviolet absorbers include 2-hydroxy-4-octoxybenzophenone; benzophenones such as 2-hydroxy-4-methoxy-5-sulfobenzophenone; 2- (2′-hydroxy-5-methylphenyl) benzotriazole Benzotriazoles; phenyl salsylates; hindered amines such as pt-butylphenyl salsylates. Antioxidants include di-t-butyl-p-cresol, n-octadecyl-3- (3,5-di-t-butyl-4-hydroxyphenylpropionate) and the like. Examples of the light stabilizer include bis (2,2,6,6-tetramethyl-4-piperazyl) sebacate.

  In the manufacturing method described above, the sheet 3 sent from the supply source retains distortion generated during sheet forming, and the distortion is removed by heat treatment in the heat treatment apparatus 14. The heat treatment apparatus 14 includes a sheet heating unit that reheats the sheet, a sheet conveyance unit that conveys the sheet, and a sheet temperature holding unit that holds the temperature of the heated sheet.

  The sheet heating means is disposed in at least a part of the conveyance direction region from the inlet to the outlet of the heat treatment apparatus 14 in order to heat the sheet to an appropriate temperature over the entire width in the width direction of the sheet. Yes. For this heating, a method of heating using heat transfer from a roller that conveys the sheet, a method of heating with radiant heat by bringing an infrared heater close to the sheet, or using heat transfer by blowing hot air on the sheet. Any method such as heating may be used.

  The sheet conveying means is constituted by a plurality of conveying rollers 16a, and conveys the sheet 3 in contact with the surface by rotating. These transport rollers 16a are preferably driven to rotate by a drive source such as a motor (not shown) via a drive transmission means such as a belt or a chain. For a portion that is difficult to drive, a roller that is not driven by being rotationally supported by a bearing having a low frictional resistance can be used.

  Here, in order for the sheet to be stably conveyed without being wound around the conveyance roller, it is necessary that the tension for peeling the sheet from the conveyance roller is large with respect to the force with which the sheet adheres to the conveyance roller. . The tension to be peeled is proportional to the speed difference between the conveying rollers and the rigidity of the sheet 3. The sheet softens when the temperature is high, and particularly when the melting point is exceeded, the molecular chain begins to slip, and a remarkable softening phenomenon occurs, so that the rigidity of the sheet decreases and the tension to be peeled decreases. Further, as described above, the sheet exhibits fluidity due to softening when the melting point is exceeded. Therefore, when the sheet contacts the conveying roller in such a state, as shown in FIG. Although it is in contact, the sheet 3 enters the concave portion of the macro unevenness on the surface of the conveying roller until the sheet is peeled off from the conveying roller, the contact area is increased, and the adhesive force is increased. Thus, when the melting point of the sealing sheet exceeds the melting point, the rigidity decreases due to softening, the tension to be peeled decreases, and the resin enters the irregularities due to the increase in fluidity, and the adhesive force increases, and the sheet is wound around the conveying roller. It becomes easy. On the other hand, the tension to be peeled is obtained by multiplying the sheet rigidity by the speed difference between the transport rollers. To avoid sticking and winding, the tension is reversed if the speed difference between the transport rollers is increased. In addition, since the sealing sheet is softened and the molecular chains of the sheet are stretched while slipping in the conveying direction, the original heat treatment furnace, instead of removing the distortion of the sheet, generates strain and increases thermal shrinkage.

  Therefore, in order to prevent the sealing sheet from being wrapped around the conveyance roller, the adhesive force of the portion of the conveyance roller that contacts the sheet is reduced, and the distance between the conveyance roller and the sheet during conveyance of the sheet is shortened. do it. Here, the portion of the conveying roller that comes into contact with the sheet refers to a portion of the surface of the conveying roller that comes into contact with the sheet while the sheet is being conveyed. Hereinafter, this portion is referred to as a sheet contact portion. The distance between the conveying roller and the sheet refers to the point at which the sheet starts to come into contact with the conveying roller when the conveying roller conveying the sheet is observed from the axial direction of the conveying roller to the point at which the sheet begins to peel from the conveying roller. The distance on the circumference of the transport roller. Hereinafter, this distance is referred to as a sheet contact distance.

  In particular, if the conveyance roller at the position where the temperature of the sheet exceeds the melting point has a small adhesive force at the sheet contact portion and the sheet contact distance is short, the sheet temperature can be increased to reduce the heat shrinkage, and accordingly. Can solve the problem of winding.

  In the present invention, as described below, in order to reduce the adhesive force of the sheet contact portion of the conveyance roller, the “contact angle with water” and the “ten-point average roughness” of the conveyance roller are set within appropriate ranges, and the conveyance roller In order to shorten the sheet contact distance between the roller and the sheet, a “conveyance path” of the sheet is defined.

(a) Contact angle with water In order for the transport roller to have excellent releasability with respect to the sheet, it is preferable to use a material having a large contact angle with water at the sheet contact portion of the transport roller. In particular, the sheet contact portion of the conveying roller is made of a material having a contact angle with water of 100 ° or more, thereby exhibiting excellent releasability. More preferably, the contact angle is 110 ° or more. The larger the contact angle with water, the smaller the intermolecular force at the sheet contact portion, so that the adhesive force can be suppressed even when the sheet is softened and the contact area is increased. If the contact angle is less than 100 °, the sheet sticks to the conveying roller, and a strong tension is required for peeling, so that a good heat shrinkage reduction effect cannot be obtained.

(b) Ten-point average roughness In order for the conveyance roller to have further excellent releasability with respect to the softened sheet, the ten-point average roughness of the sheet contact portion of the conveyance roller should be greater than 20 μm and less than 60 μm That's fine. The lower limit of the ten-point average roughness is preferably 25 μm or more. The upper limit of the ten-point average roughness is preferably 45 μm or less, and more preferably 40 μm or less.

  When the softened sheet having a ten-point average roughness within the above range is brought into contact with the conveying roller, as shown in FIG. And in the short time until it peels from a conveyance roller, the softened resin which comprises a sheet | seat enters the micro unevenness | corrugation of a convex part as FIG. However, since the macro unevenness is formed on the surface of the transport roller so that the sheet cannot enter during a short time while it is in contact with the surface of the transport roller, the sheet does not contact the macro uneven surface of the surface of the transport roller. Therefore, the contact area between the sheet and the conveyance roller can be reduced. On the other hand, although the resin of the sheet | seat exceeding melting | fusing point has entered the micro uneven | corrugated recessed part about the part which is contacting, since the contact angle with water is 100 degrees or more, adhesion of a sheet | seat can be prevented.

  When the ten-point average roughness is 20 μm or less, the softening sheet comes into contact with the conveyance roller, and the sealing sheet is formed on the concave and convex concave portions on the surface of the conveyance roller in a short time until the separation from the conveyance roller. The intrusion contact area cannot be reduced. For this reason, it is impossible to prevent the conveyance sheet from being wound around the melting point. Further, when the 10-point average roughness is 60 μm or more, the surface of the transport roller cannot be processed with high accuracy and clogging is likely to occur.

  Hereinafter, the “(a) contact angle with water” and “(b) ten-point average roughness” of the sheet contact portion both satisfy the conditions (a) and (b). It is referred to as “conveying roller”.

  The contact angle with water in the present invention is a value measured based on Japanese Industrial Standard JIS R3257 (1999) using a test piece made of the same material as the sheet contact portion of the transport roller. Direct measurement at the sheet contact portion of the conveying roller satisfying (a) and (b), that is, when measuring on the roller, it is on a curved surface and has roughness. Based on Japanese Industrial Standard JIS R3257 (1999) Measurement may be difficult. In this case, the contact angle with the water on the roller is determined by taking a picture of the water drop dripped on the roller with a camera, and the tangent line drawn on the water drop and the tangent line drawn on the roller at the intersection of the surface of the water drop and the roller surface. You may obtain | require by measuring the angle | corner which makes.

 The value of the contact angle with water measured on the transport roller satisfying (a) and (b) is larger than the value of the contact angle with water measured with the test piece, and becomes 110 ° or more.

  Further, the peeling force at the sheet contact portion of the conveying roller satisfying (a) and (b) is less than 2 N / 30 mm width. The measurement of peeling force is as having described in [peeling force] of the Example.

(c) Transport route
Further, in order to shorten the sheet contact distance between the conveying roller and the sealing sheet, the conveying roller satisfying (a) and (b), and the conveying roller satisfying (a) and (b) one upstream in the sheet conveying direction. Side conveyance roller and the conveyance roller that is one downstream in the sheet conveyance direction of the conveyance roller that satisfies (a) and (b) conveys the sheet through a conveyance path that contacts the same side surface of the sheet being conveyed. . By setting it as such a conveyance path | route, the winding angle of the sheet | seat to the conveyance roller which satisfies (a) and (b) can be made small, and a sheet contact distance can be shortened. Hereinafter, the conveyance rollers that satisfy (a) and (b) and are arranged to form such a conveyance path are referred to as “conveyance rollers that satisfy (a), (b), and (c)”.

  A specific example will be described with reference to FIG. 9A, the conveyance roller 16a2 that satisfies (a) and (b), the conveyance roller 16a1 that is one upstream in the sheet conveyance direction of the conveyance roller that satisfies (a) and (b), and (a) and ( The conveyance roller 16a3 which is one downstream in the sheet conveyance direction of the conveyance roller satisfying b) conveys the sheet 3 while being in contact with the same side surface of the sealing sheet 3 being conveyed. In FIG. 9B, the surface of the sheet 3 in contact with the transport roller 16a2 is different from the surface of the sheet 3 in contact with the transport roller 16a1 and the transport roller 16a2. 9C and 9D, the surface of the sheet 3 in contact with the conveyance roller 16a2 is different from the surface of the sheet 3 in contact with the conveyance roller 16a1 or the conveyance roller 16a2. As can be seen by comparing FIG. 9 (A) and FIGS. 9 (B) to (D), as shown in FIG. 9 (A), all of the transport rollers 16a1, 16a2, 16a3 are made of the sealing sheet 3. By conveying the sheet 3 so as to be in contact with the same surface, the wrapping angle of the sealing sheet around the conveying roller 16a2 satisfying (a) and (b) can be reduced, and the sheet contact distance can be shortened. Note that FIG. 9 is merely an example for explanation, and the arrangement of the conveyance rollers in the present invention is not limited to the arrangement of FIG. 9.

  If the sheet contact distance is shortened, the contact time is substantially shortened. Even if the sheet contacts the conveyance roller, the conveyance roller before the softened resin constituting the sheet enters the concave portion of the macro unevenness. Therefore, the sheet can be easily peeled off from the conveying roller. More preferably, as shown in FIGS. 1 and 2, all the conveying rollers in the heat treatment apparatus are arranged substantially horizontally, and all the conveying rollers are in contact with the same surface of the sheet to convey the sheet. It is good to do.

  In order to reduce the stretching distortion of the transport sheet, it is preferable that the transport roller satisfy (a), (b), and (c). Since the conveying sheet in the heat treatment apparatus exceeds the melting point and is softened, it is bent due to its own weight. As a result, the softened sheet stretches and generates distortion in the sheet. The longer the distance between the conveying rollers that support the sheet, the greater the deflection deformation, and the sheet expands. However, by using the conveyance rollers that satisfy (a), (b), and (c), the interval between the conveyance rollers that support the sheet can be shortened, and the extension distortion due to its own weight can be suppressed. In particular, as shown in FIGS. 1 and 2, when all the conveying rollers in the heat treatment apparatus are arranged substantially horizontally and all the conveying rollers are in contact with the same surface of the sheet, the sheet is conveyed. To be effective. However, if the distance between the conveying rollers is too short, handling is difficult because the number of rollers increases, and maintenance becomes complicated. Therefore, the roller center distance is preferably greater than 100 mm and 350 mm or less. The lower limit of the roller center distance is preferably 150 mm or more. The upper limit of the roller center distance is preferably 300 mm or less.

  By disposing the conveyance rollers satisfying (a), (b), and (c) in a region where the conveyance sheet in the heat treatment apparatus is at a high temperature, adhesion of the sheet to the conveyance roller can be prevented. As a result, even when the sheet is conveyed with a low tension, the sheet does not wrap around the conveying roller, and a sealing sheet with a small thermal shrinkage can be obtained. Preferably, a conveyance roller satisfying (a), (b) and (c) is disposed in a region where the sheet in the heat treatment apparatus is heated to the melting point or higher. More preferably, a conveying roller satisfying (a), (b) and (c) is disposed in a region where the temperature of the sheet in the heat treatment apparatus is the melting point + 10 ° C. or more and the melting point + 40 ° C. or less. Of course, all the transport rollers in the heat treatment apparatus may be transport rollers that satisfy (a), (b), and (c).

  The tension for pulling the sheet in the heat treatment apparatus is preferably 1 N / m or more and 15 N / m or less. More preferably, it is 1 N / m or more and 5 N / m or less. If the tension is 15 N / m or less, the sheet will not be excessively distorted. If a conveyance roller satisfying the above (a), (b) and (c) is used, the sheet can be peeled from the conveyance roller even with such a low tension.

  Of the width direction of the transport roller, the sheet contact portion is preferably made of a material containing fluororesin or baking silicone. Only the transport rollers satisfying the above (a), (b) and (c) may be made of such a material, and the other transport rollers may be made of such a material.

  Any method may be used to form the fluorine resin on the conveying roller. For example, it may be formed by impregnating or applying a fluororesin paint on the surface of the conveying roller by coating or spraying. Moreover, you may form by coat | covering a conveyance roller with a tape-shaped or tube-shaped fluororesin.

  Any method may be used for forming the baking silicone on the conveying roller. For example, it may be formed by impregnating or applying a silicone paint on a conveying roller by coating or spraying, and baking it using an electric furnace or the like.

  The base material of the transport roller is preferably steel, stainless steel, aluminum alloy, CFRP, or the like.

  The resin constituting the sheet generally contains resins having various molecular weights and melting points, and has a molecular weight distribution with a certain width. Accordingly, when the temperature of the sheet greatly exceeds the melting point and becomes higher than the melting point + 10 ° C., the molecular chain of the component having a high melting point in the molecular weight distribution also starts to slide, so that the adhesive force further increases. In such a situation, the conveyance roller of the present invention is particularly suitable and can be easily peeled off from the surface. Further, when the temperature of the sheet during the heat treatment becomes high and exceeds the melting point + 40 ° C., the cross-linking temperature of the sheet is reached. In order to sufficiently remove the residual distortion of the sheet, it is preferable to convey the sheet at a high temperature. Therefore, the temperature of the sheet during the heat treatment is at least partly in the conveying direction at + 10 ° C. or higher of the melting point of the sheet material and The melting point is preferably set to + 40 ° C. or lower. The lower limit of the sheet temperature is more preferably the melting point of the sheet material + 15 ° C. or more. The upper limit of the sheet temperature is more preferably the melting point of the sheet material + 25 ° C. or less. For example, when producing a sheet composed of EVA having a melting point of 75 ° C., the sheet temperature is preferably 85 ° C. or higher and 115 ° C. or lower, and more preferably 90 ° C. or higher and 100 ° C. or lower.

  If the surface temperature of the conveying roller is too low, the sheet is cooled and the residual distortion may not be sufficiently removed. On the other hand, if the surface temperature is too high, the sheet may stick to the transport roller and the sheet may not be transported satisfactorily. For this reason, the surface temperature of the conveying roller is preferably a sheet temperature of −30 ° C. or more and a sheet temperature + 30 ° C. or less. The lower limit of the surface temperature of the conveying roller is more preferably a sheet temperature of −15 ° C. or higher. The upper limit of the surface temperature of the conveying roller is more preferably the sheet temperature + 15 ° C. or less.

  The time during which the sheet is heat-treated by the heat treatment apparatus is preferably 20 seconds or longer and 2 minutes or shorter while the sheet is maintained at the melting point + 10 ° C. or higher. If it is 20 seconds or more, the residual distortion of the sheet can be sufficiently removed. If it is 2 minutes or less, the heat treatment apparatus 14 can be made compact and the equipment can be made inexpensive.

  In order to facilitate the peeling of the sheet, the distance between the upstream contact and the downstream contact of the conveying roller satisfying (a), (b) and (c) is preferably 100 mm or less. The distance between the contacts is more preferably 50 mm or less. It is particularly preferable that the distance between the contacts is 0 mm, that is, the upstream contact and the downstream contact coincide. The upstream contact is a common tangent corresponding to a position through which the sheet passes among the four common tangents that can be drawn between the transport roller and the upstream transport roller immediately preceding the transport roller, The contact point with this conveyance roller. The downstream contact is a common tangent corresponding to a position through which a sheet passes among four common tangents that can be drawn between the transport roller and the downstream transport roller immediately after the transport roller, The contact point with this conveyance roller. The distance between the contacts means the shorter one of the roller circumferential lengths from the upstream contact to the downstream contact.

  Furthermore, if the roller center interval is set to 350 mm or less and the conveyance roller is arranged so that the distance between the contacts is within the above range, from the point where the sheet and the conveyance roller start to contact to the point where the conveyance roller and the sheet peel off. The roller circumferential length, that is, the contact distance between the sheet and the conveying roller can be 100 mm or less, preferably 50 mm or less. Preferably, the conveying rollers are arranged substantially horizontally as shown in FIGS. In addition, as described above, since the adhesiveness of the sheet increases when the melting point is exceeded, the contact distance between the sheet and the conveying roller is preferably 100 mm or less in the region where the sheet in the heat treatment apparatus is heated to the melting point or more. . In a region where the sheet in the heat treatment apparatus has a melting point + 10 ° C. or higher and a melting point + 40 ° C. or lower, the contact distance between the sheet and the conveying roller is more preferably 100 mm or less.

  The sheet temperature holding means is disposed in at least a part of the region from the inlet to the outlet of the heat treatment apparatus. Any method may be used to maintain the temperature of the sheet. For example, a means for maintaining the temperature by ejecting hot air from the nozzle and controlling the atmospheric temperature in the furnace is preferable. Although various aspects of the hot air nozzle can be taken, in the present embodiment, the hot air nozzle is disposed at the lower part of the sheet, and a plurality of hot air nozzles are provided along the sheet conveying direction. Moreover, it is preferable to enclose the whole heat processing apparatus with the housing | casing with high heat insulation.

  Further, it is more desirable that there is a region for cooling the sheet in a region downstream of the region where the sheet reaches the maximum temperature and the outlet of the heat treatment apparatus 14. In this cooling, it is only necessary to have a function of reducing the sheet temperature to the melting point of the resin composition + 10 ° C. or lower so that the sheet coming out from the outlet of the heat treatment apparatus does not bend and deform due to its own weight.

  Preferably, the embossing roller 18 and the embossing counter roller 19 are disposed between the heat treatment apparatus and the cooling roller 20 described above, and the sheet is embossed by narrowing the pressure. In order to prevent a temperature drop of the sheet after passing through the heat treatment apparatus, the embossing roller and the embossing counter roller are preferably as close as possible to the heat treatment apparatus. The distance from the outlet of the heat treatment apparatus to the center of the embossing roller is preferably 250 mm to 2500 mm, more preferably 250 mm to 1500 mm.

  In performing the embossing process, it is preferable to control the temperature of the sheet exiting the heat treatment apparatus and the temperature of the sheet introduced into the embossing roller. Any method may be used to control the temperature of the sheet. For example, there is a method of controlling the temperature using heat transfer from a roller that conveys the sheet. Moreover, when arrange | positioning a roller between heat processing apparatuses and the embossing process, it is preferable to provide mold release property like the conveyance roller in a heat processing apparatus.

  The temperature of the sheet supplied to the embossing roller and the embossing counter roller is preferably in the temperature range from 10 ° C. below the melting point to 20 ° C. above the melting point.

  When embossed to some extent with a polishing roller, the embossed shape of the sheet surface will be lost when the sheet is heated to a melting point or higher with a heat treatment device, but the embossed shape will be maintained if embossing is performed after passing through the heat treatment device Therefore, the transportability is improved and blocking can be prevented.

  Furthermore, when there is an embossing treatment on the sheet surface, cushioning properties are enhanced when forming into a solar cell module, and there is also an effect of making it difficult for the problem of cell cracking to occur. Therefore, it is preferable to form a deep concavo-convex shape having a depth of 10 μm or more on the surface of the embossing roller by engraving or the like.

  In the present invention, the heat shrinkage at 80 ° C. of the sheet after the heat treatment is characterized by 30% or less, thereby, when manufacturing a solar cell module, particularly when handling a thin solar cell of 120 μm or less, The solar cell can be prevented from being displaced due to contraction deformation of the sheet, or cracking of the solar cell, and is preferable as a sealing material for the solar cell. More preferably, the heat shrinkage is 0 to 15%. The thermal shrinkage is calculated by measuring the dimensional change amount of the sheet when left in warm water of 80 ° C. for 1 minute, and the measurement and calculation method are as described in the examples.

  The result of manufacturing the sealing sheet using the solar cell sealing sheet manufacturing apparatus will be described.

[Example 1]
A sealing sheet was manufactured using the manufacturing apparatus schematically shown in FIG. 1 except that the embossing roller 18 and the embossing counter roller 19 were not used. EVA (vinyl acetate content: 28% by mass, melt flow rate: 15 g / 10 min, melting point: 71 ° C.) 100 parts by mass, t-butylperoxy-2-ethylhexyl monocarbonate (1 hour half-life temperature: 119 ° C.) A resin composition comprising 0.5 part by mass, 0.1 part by mass of 2,6-di-t-butyl-4-methylphenol and 0.3 part by mass of 2-hydroxy-4-methoxybenzophenone was prepared. This resin composition was supplied to the twin-screw extruder 11 and melt kneaded at 100 ° C., and the sealing sheet was extruded from the T die 12 held at 105 ° C. The lip width of the T die was 1300 mm and the lip gap was 1.0 mm.

  The sealing sheet was cooled and solidified by polishing rolls 13a and 13b held at 20 ° C. The sheet temperature when the sealing sheet was discharged from the T die was 107 ° C., and the sheet conveyance speed was 10 m / min.

Next, the sealing sheet was supplied to the heat treatment apparatus 14, and the sealing sheet was conveyed by the conveying roller 16a. The maximum temperature of the sheet passing through the heat treatment apparatus was 74 ° C., and the conditions were such that it passed through the heat treatment apparatus in 30 seconds. The contact distance between all the transport rollers 16a in the heat treatment apparatus 14 and the sealing sheet was set to 150 mm or less. All the transport rollers 16a in the heat treatment apparatus 14 satisfy the following conditions.
-Material of the part in contact with the sealing sheet: fluororesin-Contact angle with water in the part in contact with the sealing sheet: 103 °
-Ten-point average roughness of the portion in contact with the sealing sheet: 55 µm.

  The sheet thus heat-treated through the heat treatment apparatus 14 was cooled by the cooling roll unit 21 and wound up. The sheet temperature immediately after winding was 28 ° C.

[Example 2]
A sealing sheet was produced under the same conditions as in Example 1 except that the maximum temperature of the sheet passing through the heat treatment apparatus 14 was 85 ° C.

[Example 3]
A sealing sheet was produced under the same conditions as in Example 1 except that the maximum temperature of the sheet passing through the heat treatment apparatus 14 was set to 108 ° C.

[Example 4]
A sealing sheet was produced under the same conditions as in Example 3 except that a conveyance roller having a contact angle with water of 109 ° was used.

[Example 5]
A sealing sheet was produced under the same conditions as in Example 3 except that a conveyance roller having a contact angle with water of 121 ° was used.

[Example 6]
A sealing sheet was produced under the same conditions as in Example 5 except that a conveyance roller having a 10-point average roughness of 43 μm was used.

[Example 7]
A sealing sheet was produced under the same conditions as in Example 5 except that a 10-point average roughness of 29 μm was used.

[Example 8]
A sealing sheet was produced under the same conditions as in Example 7 except that the contact distance between the conveying roller 16a and the sealing sheet was 100 mm.

[Example 9]
A sealing sheet was manufactured under the same conditions as in Example 7 except that the contact distance between the conveying roller 16a and the sealing sheet was 70 mm.

[Example 10]
A sealing sheet was produced under the same conditions as in Example 9 except that the embossing roller 18 and the embossing counter roller 19 were installed immediately after the heat treatment apparatus 14.

[Example 11]
A sealing sheet was produced under the same conditions as in Example 10 except that a surface roller was baked silicone and a conveyance roller having a contact angle with water of 124 ° was used.

[Comparative Example 1]
A sealing sheet was produced under the same conditions as in Example 10 except that a conveyance roller having a contact angle with water of 103 ° and a ten-point average roughness of 15 μm was used.

[Comparative Example 2]
A sealing sheet was produced under the same conditions as in Example 10 except that a conveyance roller having a contact angle with water of 96 ° and a ten-point average roughness of 29 μm was used.

[Comparative Example 3]
A sealing sheet was produced under the same conditions as in Example 10 except that a conveyance roller having a contact angle with water of 96 ° and a 10-point average roughness of 15 μm was used.

[Comparative Example 4]
A sealing sheet was produced under the same conditions as in Example 10 except that the surface material was silicone, the contact angle with water was 90 °, and the 10-point average roughness was 15 μm.

[Comparative Example 5]
A sealing sheet was produced under the same conditions as in Comparative Example 4 except that the maximum temperature of the sheet passing through the heat treatment apparatus 14 was 85 ° C.

[Comparative Example 6]
A sealing sheet was produced under the same conditions as in Comparative Example 4 except that the maximum temperature of the sheet passing through the heat treatment apparatus 14 was set to 74 ° C.

[Comparative Example 7]
A sealing sheet was produced under the same conditions as in Comparative Example 4 except that the temperature of the sheet passing through the heat treatment apparatus 14 was set to 67 ° C. at the maximum.

  Table 1 shows the production conditions and evaluation results of each Example and Comparative Example. The evaluation method is as follows.

[blocking]
Check the occurrence of blocking of the rolled-up roll. If it was not seen at all, "A", if blocking was seen, "B". When it was not recognized, it was determined as “C”. If it is “A”, it is an excellent sealing sheet, and if it is “B”, there is no practical problem.

[Peeling force]
A 30 mm × 80 mm flat rectangular test piece was cut out from the obtained sealing sheet. The test piece is sandwiched between a substrate made of the same material as the sheet contact portion of the transport roller or a substrate cut out from the sheet contact portion of the transport roller and a PET sheet, and is pressed for 90 seconds at a pressure of 1 MPa and a press temperature of 80 ° by hot pressing. did. The PET sheet was pulled up and the load at that time was measured. When the peel force was less than 2N / 30 mm width, “A”, 2N / 30 mm width or more and less than 3N / 30 mm width was determined as “B”, and 3N / 30 mm width or more was determined as “C”.

[Heat shrinkage]
A planar square test piece having a side of 120 mm was cut out from the obtained sealing sheet. Two straight lines perpendicular to the running direction during production were drawn on the test piece. The distance between the straight lines at this time was 100 mm. Next, the test piece was immersed in warm water heated to 80 ° C., and after 60 seconds, the sealing sheet was taken out from the warm water to remove moisture on the sheet surface. An interval L (mm) between two straight lines drawn on the test piece was measured with a caliper at five points, and thermal shrinkage was calculated based on the following formula for each measurement point. The calculated average value of 5 points was used as the heat shrinkage value of the test piece.
Heat yield (%) = 100 × (100−L) / 100
Thermal shrinkage of less than 25% was judged as “A”, 25% or more and less than 30% as “B”, and 30% or more as “C”. If it is “A”, it is an excellent sealing sheet, and if it is “B”, there is no practical problem.

[Clogged roller]
Check the condition of the surface of the transport roller 16a after 20 hours of continuous use. If no clogging is observed, "A". If there is a slight clogging, "B". If it was, it was determined as “C”. If “A”, the productivity is good, and if “B”, there is no practical problem.

[Evaluation results]
In Examples 1 to 5, the ten-point average roughness of the surface of the transport roller and the contact angle with water were within appropriate ranges. As a result, the sealing sheet could be peeled off from the conveying roller 16a with a low tension, and a sealing sheet having a heat yield in a range having no practical problem was obtained. Some clogging was observed on the surface of the conveying roller, but there was no practical problem. Moreover, since there was no embossing on the surface of the sealing sheet, blocking was observed, but no deformation or breakage of the sheet occurred.

  In Examples 6 and 7, the roughness of the surface of the conveying roller was optimized more than in Example 5. As a result, clogging on the surface of the transport roller was eliminated.

  In Examples 8 and 9, the contact distance between the conveying roller and the sealing sheet was further shortened compared to Example 7. As a result, the adhesion between the conveying roller and the sealing sheet could be further reduced, and a sealing sheet with good heat shrinkage could be obtained.

  In Example 10, in addition to the manufacturing conditions of Example 9, an embossing roller and an embossing counter roller were installed, and the surface of the sealing sheet was embossed. As a result, blocking of the sealing sheet could be prevented.

  In Example 11, the surface material of the conveyance roller of Example 10 was baked silicone. As a result, a sealing sheet equivalent to that in Example 10 could be obtained.

  In Comparative Example 1, since the roughness of the surface of the transport roller was smaller than the appropriate range, the sealing sheet adhered to the transport roller. Therefore, since the tension was increased in order to prevent adhesion, the thermal shrinkage of the sealing sheet deteriorated.

In Comparative Example 2, since the contact angle of the surface of the transport roller with water was lower than the appropriate range, the sealing sheet adhered to the transport roller. Therefore, since the tension was increased to prevent adhesion, the thermal shrinkage of the sealing sheet deteriorated. In Comparative Examples 3 to 5, the surface roughness of the transport roller was smaller than the appropriate range, and Since the contact angle was also lower than the appropriate range, the sealing sheet adhered to the roller. In order to prevent adhesion, the tension had to be increased more than in Comparative Examples 1 and 2, and the heat shrinkage deteriorated. In Comparative Examples 4 and 5, the surface material of the conveying roller is changed to silicone, but the sealing sheet adheres to the roller. From this, it can be seen that, regardless of the type of the surface material of the transport roller, the releasability is not exhibited unless the surface roughness and the contact angle with water are within appropriate ranges. In Comparative Examples 6 and 7, the surface roughness of the transport roller was smaller than the appropriate range, and the contact angle with water was lower than the appropriate range. Therefore, in order to prevent adhesion between the sealing sheet and the roller, the temperature of the sealing sheet was lowered, so that the adhesive force was lowered. However, since the temperature of the sealing sheet was low, the residual strain could not be sufficiently removed, and the heat shrinkage was deteriorated.

  The heat treatment method and heat treatment apparatus of the present invention can be suitably used when annealing a web such as a sheet or film at a temperature exceeding its melting point, and its application range is not limited thereto. Especially, it is very useful for the manufacturing method of the sheet | seat for sealing used for a solar cell module.

DESCRIPTION OF SYMBOLS 1 Glass substrate 2 Back sheet 3 Sheet 3a Glass surface side sealing sheet 3b Back sheet surface side sealing sheet 4 Solar cell 5 Aluminum frame 6 Wiring box 11 Twin screw extruder 12 T die 13a Polishing roll 13b Polishing roll 14 Heat Treatment Device 15 Heater 16a Conveying Roller 16b Conveying Roller 16a1 Conveying Roller 16a3 Satisfying Conditions (a) and (b) Condition (a) and (b) Conveying roller satisfying a) and (b) in the sheet conveying direction one downstream conveying roller 17 Nozzle 18 Embossing roller 19 Embossing counter roller 20 Cooling roller 31 Gear pump 32 Winder 33 Sheet conveying direction 1
34 Unwinder 41 Transport roller base material 42 Surface material

Claims (13)

In a heat treatment method for a sheet that is supported and conveyed by a plurality of conveying rollers in a heat treatment furnace, heat treatment of the sheet in which at least one of the plurality of conveying rollers satisfies the following (a), (b), and (c): Method.
(a) The ten-point average roughness of the portion in contact with the sheet is greater than 20 μm and less than 60 μm.
(b) The portion in contact with the sheet is made of a material having a contact angle with water of 100 ° or more.
(c) The roller, the conveyance roller on the upstream side in the sheet conveyance direction of the roller, and the conveyance roller on the downstream side in the sheet conveyance direction of the roller are in contact with the surface on the same side of the sheet.   The sheet heat treatment method according to claim 1, wherein the ten-point average roughness is greater than 20 μm and equal to or less than 45 μm.   The sheet contains a cross-linking agent, and at least one of the conveying rollers satisfying the above (a), (b) and (c) is such that the temperature of the sheet is not less than the melting point of the sheet + 10 ° C., the melting point of the sheet + 40 ° C. The method for heat-treating a sheet according to claim 1 or 2, wherein the sheet is in contact with a portion which is the following.   The method for heat-treating a sheet according to any one of claims 1 to 3, wherein a contact distance between at least one conveyance roller satisfying (a), (b) and (c) and the sheet is 100 mm or less.   The sheet heat treatment method according to any one of claims 1 to 4, wherein an embossing process is performed on one side of the sheet that has exited the heat treatment furnace.   The method for heat-treating a sheet according to any one of claims 1 to 5, wherein the sheet comprises a resin composition containing an ethylene-vinyl acetate copolymer as a main component.   7. Any one of claims 1 to 6, wherein a portion of the conveying roller that satisfies the (a), (b), and (c) is in contact with at least one of the sheets, and is made of a material containing baking silicone or fluorine resin. A method for heat treatment of the sheet.   In the manufacturing method of the sheet | seat for solar cell sealing which sends out the sheet | seat containing a crosslinking agent from a supply source, heat-processes the said sheet | seat in the heat processing furnace, and then winds up the said sheet | seat, any of Claim 1 to 7 as said heat processing The manufacturing method of the sheet | seat for solar cell sealing using the heat processing method. A sheet heat treatment apparatus having a sheet heating unit, a sheet conveyance unit, and a sheet temperature holding unit, wherein the sheet conveyance unit includes a plurality of conveyance rollers, and at least one of the plurality of conveyance rollers includes the following (d), A sheet heat treatment apparatus satisfying (e) and (f).
(d) The ten-point average roughness of the portion in contact with the sheet being conveyed is greater than 20 μm and less than 60 μm.
(e) The portion in contact with the sheet being conveyed is made of a material having a contact angle with water of 100 ° or more.
(f) The roller, the conveyance roller on the upstream side in the sheet conveyance direction of the roller, and the conveyance roller on the downstream side in the sheet conveyance direction of the roller are in contact with the surface on the same side of the sheet being conveyed.   The sheet heat treatment apparatus according to claim 9, wherein the ten-point average roughness is greater than 20 μm and equal to or less than 45 μm.   The sheet heat treatment apparatus according to claim 9 or 10, wherein an embossing roller for embossing the sheet is disposed on the downstream side in the sheet conveyance direction of the heat treatment apparatus.   The portion of the conveying roller that satisfies the items (d), (e), and (f) that is in contact with at least one sheet being conveyed is made of a material containing baking silicone or a fluorine-based resin. To 11 heat treatment apparatus.   A solar cell sealing sheet manufacturing apparatus for manufacturing a solar cell sealing sheet by forming a molten resin into a sheet shape, the solar cell sealing sheet comprising the heat treatment device according to claim 9. Manufacturing equipment.

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