JP2010222545A - Method for producing resinous sealed sheet, and resinous sealed sheet - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a method for producing a resinous sealed sheet which is excellent in creep resistance, does not cause blocking between the resinous sealed sheets, is handled favorably, and hardly causes thermal shrinkage. <P>SOLUTION: The method for producing a resinous sealed sheet includes the following processes: (i) a process for sheeting a thermoplastic resin by thermal melting; (ii) a process for embossing the sheet obtained by process (i); and (iii) a process for subjecting the sheet embossed by process (ii) to crosslinking by ionizing radiation. <P>COPYRIGHT: (C)2011,JPO&INPIT

Description

  The present invention relates to a resin sealing sheet manufacturing method and a resin sealing sheet manufactured by the method.

In recent years, the global warming phenomenon has heightened awareness of the environment, and a new energy system that does not generate greenhouse gases such as carbon dioxide is attracting attention. Since the energy generated by solar cell power generation does not emit carbon dioxide and other gases that cause global warming, research and development has been conducted as clean energy, and has attracted attention as industrial energy. Representative examples of solar cells include those using single crystal and polycrystalline silicon cells (crystalline silicon cells), those using amorphous silicon, and compound semiconductors (thin film cells). Solar cells are often used outdoors exposed to wind and rain for a long period of time, and the power generation part is modularized by attaching a glass plate, back sheet, etc. to prevent moisture from entering from outside. We tried to protect the parts and prevent leakage.
As a member for protecting the power generation portion, transparent glass or transparent resin is used on the light incident side in order to ensure light transmission necessary for power generation. For the opposite member, an aluminum foil called a back sheet, a polyvinyl fluoride resin (PVF), polyethylene terephthalate (PET), or a laminated sheet with a barrier coating such as silica is used. The power generation element is sandwiched between resin sealing sheets, the outside is further covered with glass or a back sheet, and heat treatment is performed to melt the resin sealing sheet, and the whole is integrally sealed (modularized).
The following (1) to (3) are required as characteristics of the resin-encapsulated sheet described above. That is, (1) good adhesion to glass, power generation element and back sheet, (2) flow prevention (creep resistance) of power generation element due to melting of resin-sealed sheet at high temperature, (3) sun Transparency that does not hinder the incidence of light. From this point of view, the resin encapsulated sheet is made of an ethylene-vinyl acetate copolymer (EVA), an ultraviolet absorber as a countermeasure for ultraviolet deterioration, a coupling agent for improving adhesion to glass, and an organic material for crosslinking. Additives such as peroxide are blended to form a film by calendar molding or T-die casting. Further, in view of exposure to sunlight for a long period of time, various additives such as a light-proofing agent are blended in order to prevent a decrease in optical properties due to deterioration of the resin. Thereby, the transparency which does not inhibit sunlight incidence for a long time is maintained.
As a form of modularizing solar cells with the resin-encapsulated sheet as described above, glass / resin encapsulated sheet / power generation element such as crystalline silicon cell / resin encapsulated sheet / back sheet are stacked in this order, and the glass surface is Using a dedicated solar cell vacuum laminator, the resin sealing sheet is melted and pasted through a preheating step and a pressing step above the melting temperature of the resin (150 ° C in the case of EVA). There is. In this method, first, the resin of the resin sealing sheet is melted in the preheating process, and is in close contact with the member in contact with the melted resin in the pressing process and vacuum laminated. In this laminating step, (ii) after the crosslinking agent contained in the resin sealing sheet, for example, the organic peroxide is thermally decomposed and the crosslinking of EVA is promoted, (ii) it is contained in the resin sealing sheet. The coupling agent is covalently bonded to the member in contact. As a result, the mutual adhesiveness is further improved, the flow of the power generation part due to the melting of the resin sealing sheet in a high temperature state is prevented (creep resistance), and the excellent adhesion to glass, power generation element and back sheet Is realized.

Patent Document 1 discloses a module in which an organic polymer resin encapsulating sheet crosslinked by electron beam irradiation is laminated on an amorphous silicon solar cell. In this organic polymer resin encapsulating sheet, ethylene-vinyl acetate copolymer (EVA), ethylene-methyl acrylate (EMA) or the like is used, and the organic polymer resin sheet has an antioxidant, an ultraviolet absorber, A module is made by vacuum lamination at 150 ° C with a power generation part and a back sheet using a resin sealing sheet blended with a light stabilizer and a silane coupling agent and sheeted by extrusion molding from a slit. . Patent Document 1 uses a resin-encapsulated sheet that is irradiated with an electron beam at an acceleration voltage of 500 kV and an irradiation dose of 300 kGy from the light receiving surface of the module, or that has been previously subjected to a crosslinking process by electron beam irradiation. It is described that a solar cell module excellent in creep resistance and weather resistance can be provided by carrying out vacuum lamination at 180 ° C. to produce a module.
Patent Document 2 discloses a solar cell element sealing material made of an ethylene copolymer subjected to electron beam irradiation. As a typical example of an ethylene copolymer, a resin selected from an ethylene-vinyl acetate copolymer (EVA), an ethylene-unsaturated carboxylic acid ester copolymer, and an ethylene-unsaturated carboxylic acid copolymer is used for crosslinking. It is described that by providing a high degree of crosslinking with a gelation rate of 65% or more, it is possible to provide a solar cell element sealing material having creep resistance that prevents the sealing material from flowing or deforming. Yes.
Patent Document 3 discloses an example of a sheet made of an ethylene vinyl acetate copolymer blended with a crosslinking agent and a silane coupling agent, which is subjected to radiation crosslinking to a certain gel fraction after embossing. ing.

JP-A-6-334207 JP 2001-119047 A JP-A-8-283696

However, a sheet whose surface has been activated by electron beam irradiation has too strong an adhesive force (hereinafter also referred to as blocking), and it becomes difficult to peel off the sheet when it is formed into a roll. Patent Documents 1 and 2 do not describe blocking measures and cannot withstand actual use.
In Patent Document 3, there is no description regarding details such as an embossed pattern and a winding tension, and a specific solution to a blocking measure for the scroll is not specified. Moreover, although there is description that heat shrinkage is improved by electron beam irradiation, the heat shrinkage rate of the sheet before irradiation is high, and therefore the processing stability at the time of electron beam irradiation is insufficient.

  In view of the above circumstances, in addition to having excellent creep resistance, the present invention provides a method for producing a resin-encapsulated sheet that has good handling without blocking between sheets and is less likely to shrink due to heat. For the purpose.

  As a result of intensive studies to solve the above-mentioned problems, the present inventors have heated and melted the thermoplastic resin constituting the resin-encapsulated sheet to form a sheet, and then embossed and ionized the resulting sheet. The present inventors have found that the above-mentioned problems can be solved by carrying out crosslinking treatment with actinic radiation in this order, and completed the present invention.

That is, the present invention is as follows.
[1]
A method for producing a resin-encapsulated sheet comprising the following steps (i) to (iii) in this order:
(I) a step of heating and melting the thermoplastic resin to form a sheet;
(Ii) a step of embossing the sheet obtained in the step (i),
(Iii) A step of subjecting the sheet embossed in the step (ii) to a crosslinking treatment with ionizing radiation.
[2]
The method for producing a resin sealing sheet according to the above [1], wherein the orientation of the resin sealing sheet is relaxed by heat applied during the embossing.
[3]
The method for producing a resin-encapsulated sheet according to the above [1], wherein the orientation of the resin-encapsulated sheet is relaxed by heat generated during the crosslinking treatment with the ionizing radiation.
[4]
The method for producing a resin-encapsulated sheet according to the above [1], further comprising a step of cooling the sheet after the embossing.
[5]
The method for producing a resin-encapsulated sheet according to the above [1], further comprising a step of winding the sheet into a roll, wherein the winding tension is 3 to 200 N / 1000 mm width.
[6]
The method for producing a resin-encapsulated sheet according to the above [1], wherein the thermal contraction rate of the sheet obtained by the step (i) is 0 to 15% at {(Tm) −10} ° C. (where Tm is Indicates the melting point of the thermoplastic resin).
[7]
In the step (ii), an embossing roll is disposed between the two pairs of nip rolls, and when the speed of the embossing roll is 1, the speed ratio of the two pairs of nip rolls is in the range of 0.8 to 1.2. The method for producing a resin-sealed sheet according to the above [1], which is adjusted.
[8]
The method for producing a resin-encapsulated sheet according to the above [1], wherein the thermoplastic resin does not substantially contain a crosslinking agent.
[9]
The method for producing a resin-encapsulated sheet according to the above [1], wherein the gel fraction of the sheet after the crosslinking treatment with the ionizing radiation is 2 to 65% by mass.
[10]
The resin sealing sheet manufactured by the method of said [1] description.

  According to the present invention, it is possible to provide a method for producing a resin-encapsulated sheet that has excellent creep resistance, has good handling without blocking sheets, and is unlikely to shrink by heat.

  Hereinafter, a mode for carrying out the present invention (hereinafter referred to as “the present embodiment”) will be described in detail. In addition, this invention is not limited to the following embodiment, It can implement by changing variously within the range of the summary.

The manufacturing method of the resin sealing sheet of this Embodiment is a manufacturing method which contains the process of the following (i)-(iii) in this order.
(I) a step of heating and melting the thermoplastic resin to form a sheet;
(Ii) a step of embossing the sheet obtained in the step (i),
(Iii) A step of subjecting the sheet embossed in the step (ii) to a crosslinking treatment with ionizing radiation.

  The manufacturing method of the present embodiment includes (i) a sheet forming step by heating and melting, (ii) an embossing step, and (iii) a crosslinking treatment step by ionizing radiation irradiation, and these steps are performed in this order. In addition to the above steps, steps such as heat setting and annealing may be included, but the step of heating the sheet is preferably performed after the crosslinking treatment step from the viewpoint of maintaining the embossed pattern. These steps may be performed continuously in a series of lines, or may be performed separately for each step. As the order of the steps, the crosslinking treatment is performed after embossing. This is because when the ionizing radiation is applied, the sheet surface is activated and the sheets are more easily blocked, and it is difficult to peel off the wound sheet. Further, even when the embossing is continuously performed after the crosslinking treatment, there is a problem that the processing stability is deteriorated because it is easily stuck to a roll or the like in the process. Moreover, the sheet | seat after bridge | crosslinking also has a problem also from the point that embossing becomes difficult to enter.

  In order to prevent the resin-encapsulated sheet from shrinking due to heat, it is important not to apply tension to the sheet when the sheet temperature is high. This is common in all processes. For example, in (i) the step of forming a sheet by heat melting, there is a stage until the sheet is cooled after the resin is heated and melted to form a sheet. (Ii) In the embossing process, in addition to the stage until the sheet is cooled after embossing, this stage is also included when a preheating process is included. (Iii) In the cross-linking treatment step with ionizing radiation, a portion heated by irradiation with ionizing radiation can be mentioned. Furthermore, when a heat setting process or an annealing process is included, these stages are also targeted. From the viewpoint of suppressing the thermal shrinkage of the sheet, it is preferable to adjust the tension at a location where the sheet temperature becomes {(Tm) −40} ° C. or higher. The method for adjusting the tension is not particularly limited, but it is preferable to adjust the speed ratio of the roll from the viewpoint of control accuracy in the low tension and minus tension (slack) ranges. In this case, the roll means a nip roll or a drive roll. In this case, when the speed of the roll disposed upstream in the process is 1, the downstream roll speed is preferably 0.8 to 1.2. When the speed of each roll is within the above range, thermal contraction tends to be more suppressed while preventing meandering of the sheet.

  The resin sealing sheet is finally wound up in a roll shape. When all the steps are continuously performed in a series of lines, a step of winding the sheet into a roll (winding step) is performed after the crosslinking treatment step. Moreover, when each process is implemented separately, a winding process will be implemented for each process. The winding tension at this time is preferably 3 to 200 N and more preferably 5 to 150 N with respect to a product width of 1000 mm from the viewpoint of product winding deviation and blocking prevention. In addition, when finally producing a solar cell module, the roll of the resin-encapsulated sheet may be used as it is, or the roll cut out to a desired size (single-sheet processed product) may be used. Good.

[Step (i)]
Step (i) is a step of heating and melting the thermoplastic resin to form a sheet. Here, “sheeting” refers to molding a heat-melted resin into a sheet shape. Examples of the sheet forming method include, but are not limited to, an extrusion molding method using a T die or an annular die, an inflation molding method, an injection molding method, a hot press molding method, a calendar molding method, and the like. Examples of the method for cooling the sheet after heating and melting include cooling with cold water (water cooling), cooling with wind (air cooling), and cooling with a roll, but are not limited thereto. In addition, embossing may be performed after cooling and forming into a sheet and before cooling. The sheet may be a single layer or a multilayer, and in the case of a multilayer, examples of the multilayering method include extrusion with a multilayer die and bonding (laminating) a film, but are not limited thereto.

  The thermal contraction rate of the sheet obtained by the step (i) is preferably 0 to 15%, more preferably 0 to 10% at {(Tm) -10} ° C., where Tm is the melting point of the thermoplastic resin. When the thermal contraction rate of the sheet is in the above range, the thermal contraction rate of the embossed sheet can be easily suppressed to a lower level. Further, from the viewpoint of the thermal contraction rate of the sheet, the resin temperature at the time of heating and melting is preferably {(Tm) +10} to {(Tm) +150} ° C., and {(Tm) +20} to {(Tm) +130} ° C. More preferred. Here, the melting point Tm of the thermoplastic resin is obtained by using a differential scanning calorimeter, heating about 5 mg of the resin from 0 ° C. to 200 ° C. at a rate of 20 ° C./min, and melting and holding at 200 ° C. for 5 minutes. The temperature of the endothermic peak accompanying melting obtained when rapidly cooled to −50 ° C. or lower and then heated from 0 ° C. to 200 ° C. at 20 ° C./min.

  Furthermore, as described above, it is preferable to adjust the tension until the sheet temperature is cooled to {(Tm) −40} ° C. or lower after forming into a sheet. The tension adjusting method is not particularly limited, but it is preferable to adjust the speed ratio of the roll from the viewpoint of control accuracy in the low tension and minus tension (slack) ranges. In this case, the roll means a nip roll or a drive roll. In this case, when the speed of the roll disposed upstream in the process is 1, the downstream roll speed is preferably 0.8 to 1.2. When the speed of each roll is within the above range, thermal contraction tends to be more suppressed while preventing meandering of the sheet.

  As for the thickness of the sheet | seat obtained by process (i), 50-1500 micrometers is preferable. More preferably, it is 100-1000 micrometers, More preferably, it is 150-800 micrometers. When the thickness of the sheet is within the above range, the productivity of the sheet is good, and the cushioning property, which is a necessary physical property of the sealing sheet, tends to be excellent. The sheet thickness variation rate is preferably 0.5 to 30%, and more preferably 0.5 to 25%. The thickness variation rate refers to a ratio (R / t) of a sheet thickness variation value (difference between maximum thickness and minimum thickness: R) to sheet thickness (t). When the thickness variation rate is in the above range, the processing depth at the time of embossing tends to be uniform, and meandering at the time of sheet conveyance in each process is less likely to occur, and the processing stability tends to be better.

[Step (ii)]
Step (ii) is a step of embossing the sheet obtained in step (i). The embossing may be performed from the sheet forming process by heat melting until the sheet is wound, or may be performed off-line after being temporarily wound in the sheet forming process. Since a sheet that has not been embossed is likely to be blocked, it is preferable that the embossing be performed during the period from the sheeting step to winding.

  As the embossing method, as described above, in the sheet forming step, in addition to the method of processing before cooling, a method of applying preheating to the sheet with an IR heater, a temperature control roll, or the like, A method of performing processing with a heated embossing roll without using preheating is exemplified, but the method is not limited thereto. In the embossing process, although the heating medium varies depending on the processing method, the sheet always receives heat in any case. With this heat, the orientation of the sheet generated in the sheet forming process by heat melting is relaxed, and the shrinkage due to heat tends to be reduced. From the viewpoint of the effect of relaxing the orientation of the sheet, the embossing method is preferably a method of preheating the sheet. The sheet temperature at the time of preheating is preferably {(Tm) -20} to {(Tm) +40} ° C., from the viewpoint of orientation relaxation effect, embossing depth and embossing stability, and {(Tm) -15} to {(Tm) +35} ° C. is more preferable.

  As described above, the sheet is heated in the embossing process. At this time, if a tension is applied to the sheet, the sheet is stretched and heat shrinkage increases. Therefore, when embossing is performed, it is preferable to adjust the tension applied to the sheet within an appropriate range. The tension adjustment method is not particularly limited, but from the viewpoint of control accuracy in the low tension and minus tension (slack) range, an embossing roll is arranged between two pairs of nip rolls, and the speed ratio of these rolls can be adjusted. preferable. Specifically, the speed ratio of each nip roll when the speed of the embossing roll is 1 is preferably 0.8 to 1.2. When the speed ratio of each roll is within the above range, heat shrinkage tends to be more easily suppressed while maintaining embossing stability.

  Moreover, lowering the sheet temperature as soon as possible after embossing is also effective in suppressing thermal shrinkage. From this viewpoint, it is preferable that the manufacturing method of the present embodiment further includes a step of cooling the sheet after embossing. Examples of the method for cooling the sheet include cooling with a water-cooled roll or chill roll, cooling with cold air, and the like, but are not limited thereto.

  Examples of the material of the embossing roll to be embossed include metal, rubber, paper and the like, but are not particularly limited. Further, for the purpose of preventing the sheet from sticking, the roll surface may be subjected to a high release treatment using Teflon (registered trademark), silicon, or the like.

  The embossing may be performed on at least one side of the resin sealing sheet, and both sides may be processed. From the viewpoint of the anti-blocking performance of the sheet, the embossing depth is preferably 10 μm or more, more preferably 15 μm or more. The processing depth is preferably 300 μm or less, more preferably 200 μm or less. When producing a solar cell module, it is necessary to seal the gap between cells, but when the processing depth is in the above range, the fluidity of the resin sheet during heating is reduced by electron beam crosslinking. However, it tends to be better sealed. Although it does not specifically limit as a pattern of embossing, For example, a stripe, a texture, a satin, a skin pattern, a diamond lattice, a synthetic leather-like wrinkle pattern, a pyramid pattern (square weight) etc. are mentioned. From the standpoint of preventing blocking of the sheet, it is preferable that the embossed sheet has fewer flat portions, and the area ratio of the convex portion to the total area is preferably 5 to 50%.

[Step (iii)]
Step (iii) is a step of subjecting the sheet embossed in step (ii) to a crosslinking treatment with ionizing radiation. The crosslinking treatment with ionizing radiation is to irradiate the resin-encapsulated sheet with ionizing radiation such as α-rays, β-rays, γ-rays, neutron rays, and electron beams to crosslink the polymer constituting the sheet. Irradiating with ionizing radiation such as α rays, β rays, γ rays, neutron rays, electron rays, etc. to crosslink, thermoplastic resins such as ethylene-vinyl acetate copolymer, ethylene-aliphatic unsaturated carboxylic acid Preventing unreacted components such as organic acids and peroxides from remaining in the resin due to elimination of side chain parts such as copolymers and copolymers of ethylene-aliphatic unsaturated carboxylic acid ester copolymers, It is possible to prevent adverse effects of the unreacted components on the solar battery cell, the conductive functional layer, or the wiring.

  In the manufacturing method of the present embodiment, the sheet is cross-linked by ionizing radiation irradiation after the embossing process. The cross-linking treatment may be performed between embossing and winding of the sheet, and may be performed off-line after being temporarily wound in the embossing process, but is always performed after embossing. This is because the sheet surfaces are activated by irradiation with ionizing radiation and the sheets are more likely to be blocked, so that if the sheet is wound without being embossed, it is difficult to peel off the sheet. Even when embossing is performed continuously after crosslinking, there is a problem that processing stability is lowered because it is easy to stick to a roll or the like in the process. Moreover, the sheet | seat after bridge | crosslinking also has a problem also from the point that embossing becomes difficult to enter.

  By carrying out crosslinking by irradiation with ionizing radiation, the sheet can be provided with excellent creep resistance, and has an effect of reducing the thermal shrinkage rate of the sheet. This is because the orientation of the sheet is relaxed by the heat generated during the crosslinking treatment. Furthermore, suppression of the movement of the polymer chain due to cross-linking is also cited as a reason for the effect of reducing thermal shrinkage.

  The degree of crosslinking of the sheet can be evaluated by measuring the gel fraction. The gel fraction of the resin-encapsulated sheet after the crosslinking treatment in the present embodiment is preferably 2 to 65% by mass, more preferably 3 to 65% by mass, and further preferably 3 to 60% by mass. When the gel fraction is in the above range, the balance between the uniformity of the degree of crosslinking and the gap filling property and fluidity (creep resistance) when sealing the gaps between cells of the solar cell module is good.

Here, the gel fraction of the resin sealing sheet is obtained by extracting a sample in boiling p-xylene for 12 hours and displaying the ratio of the insoluble portion by the following formula. Used.
Gel fraction (wt%) = (sample mass after extraction / sample mass before extraction) × 100

  The cross-linking distribution in the thickness direction of the sheet can be adjusted by the acceleration voltage of ionizing radiation such as an electron beam. For example, it is possible to crosslink uniformly in the thickness direction by increasing the acceleration voltage, or to crosslink only one side of the sheet by decreasing the acceleration voltage. Therefore, the acceleration voltage of the ionizing radiation may be appropriately adjusted so as to obtain a desired cross-linking distribution in consideration of the thickness of the sheet, and is not particularly limited.

  Since the crosslinking reaction by ionizing radiation irradiation is affected by stabilizers and weathering agents added to the thermoplastic resin, even if the same resin is irradiated under the same conditions, the degree of crosslinking varies depending on the additive formulation. Therefore, the irradiation dose of ionizing radiation may be appropriately adjusted so as to have a desired gel fraction, and is not particularly limited. Further, as a method for adjusting the gel fraction, in addition to the irradiation dose of ionizing radiation, a difference in the degree of crosslinking depending on the type of resin, crosslinking promotion by a transfer agent or the like, and the effect of inhibiting crosslinking may be used. For example, a linear low density polyethylene (LLDPE) having a surface layer of a resin having a polar group such as saponified olefin copolymer, ethylene monomer and vinyl acetate, aliphatic unsaturated carboxylic acid, aliphatic unsaturated carboxylic acid ester, etc. When the inner layer is a linear ultra-low density polyethylene (called “VLDPE” or “ULDPE”) resin, the gel fraction of the surface layer is sufficient even if the acceleration voltage is sufficient to allow all layers to permeate. Is high and the gel fraction of the inner layer can be low. Furthermore, by adjusting the acceleration voltage, an uncrosslinked layer that does not crosslink the inner layer of linear low density polyethylene (LLDPE) or linear ultra low density polyethylene (called “VLDPE” or “ULDPE”) resin layer While being constructed, a crosslinking treatment by electron beam irradiation can be performed. Moreover, when a polypropylene resin is arranged as the inner layer, the polypropylene resin is not crosslinked by an electron beam or the like, and therefore an uncrosslinked layer can be constructed.

  Moreover, the thermoplastic resin of this Embodiment may have added the crosslinking agent. Examples of the crosslinking agent include organic peroxides, which are blended in or impregnated in a resin for thermal crosslinking. In this case, an organic peroxide having a half-life at 100 to 130 ° C. of 1 hour or less is preferable.

  As the organic peroxide, a good compatibility with the ethylene copolymer is obtained, and the organic peroxide has the half-life. For example, 1,1-bis (t-butylperoxy) 3, 3, 5-trimethylcyclohexane, 1,1-bis (t-butylperoxy) cyclohexane, n-butyl-4,4-bis (t-butylperoxy) valerate, 2,2-bis (t-butylperoxy) butane Etc. 0-10 mass% is preferable with respect to ethylene-type copolymer, and, as for content of an organic peroxide, 0-5 mass% is more preferable. However, when these cross-linking agents are added, there is a concern that the sheet may be cross-linked by heat when the resin is melted in the sheet forming step. In order to carry out embossing more stably and under mild conditions that do not cause heat shrinkage, it is preferable that the degree of crosslinking of the sheet before embossing is low, so these crosslinking agents are not added (substantially It is preferable that it is not included.

  Next, the thermoplastic resin which comprises the resin sealing sheet of this Embodiment is demonstrated. As the thermoplastic resin, from the viewpoint of adhesiveness and sealing performance, ethylene-vinyl acetate copolymer, ethylene-aliphatic unsaturated carboxylic acid copolymer, ethylene-aliphatic carboxylic acid ester copolymer, and polyolefin series It is preferable to contain at least one resin selected from the group consisting of resins.

  The ethylene-vinyl acetate copolymer refers to a copolymer obtained by copolymerization of an ethylene monomer and vinyl acetate. The ethylene-aliphatic unsaturated carboxylic acid copolymer refers to a copolymer obtained by copolymerization of an ethylene monomer and at least one monomer selected from aliphatic unsaturated carboxylic acids. Furthermore, the ethylene-aliphatic unsaturated carboxylic acid ester copolymer refers to a copolymer obtained by copolymerization of an ethylene monomer and at least one monomer selected from aliphatic unsaturated carboxylic acid esters.

  The copolymerization can be performed by a known method such as a high pressure method or a melting method, and a multisite catalyst, a single site catalyst, or the like can be used as a catalyst for the polymerization reaction. Moreover, in the said copolymer, the bond shape of each monomer is not specifically limited, The polymer which has bond shapes, such as a random bond and a block bond, can be used. From the viewpoint of optical properties, the copolymer is preferably a copolymer polymerized by random bonding using a high-pressure method.

  In the ethylene-vinyl acetate copolymer, the ratio of vinyl acetate in all monomers constituting the copolymer is preferably 10 to 40% by mass from the viewpoint of optical properties, adhesiveness, and flexibility. More preferably, it is -35 mass%, and it is still more preferable that it is 15-30 mass%. Further, from the viewpoint of workability of the resin-encapsulated sheet, a melt flow rate value (hereinafter also abbreviated as “MFR”) (190 ° C., 2.16 kg) measured according to JIS-K-7210 is obtained. It is preferably 0.3 g / 10 min to 30 g / 10 min, more preferably 0.5 g / min to 30 g / min, and still more preferably 0.8 g / min to 25 g / min.

  Examples of the ethylene-aliphatic unsaturated carboxylic acid copolymer include an ethylene-acrylic acid copolymer (hereinafter also abbreviated as “EAA”) and an ethylene-methacrylic acid copolymer (hereinafter, “EMAA”). Abbreviated as well)). Examples of the ethylene-aliphatic unsaturated carboxylic acid ester copolymer include an ethylene-acrylic acid ester copolymer and an ethylene-methacrylic acid ester copolymer. Here, as acrylic acid ester and methacrylic acid ester, ester with C1-C8 alcohols, such as methanol and ethanol, is used suitably.

  These copolymers may be multi-component copolymers obtained by copolymerizing three or more monomers. Examples of the multi-component copolymer include a copolymer obtained by copolymerizing at least three types of monomers selected from ethylene, aliphatic unsaturated carboxylic acid, and aliphatic unsaturated carboxylic acid ester.

  In the ethylene-aliphatic unsaturated carboxylic acid copolymer, the proportion of the aliphatic unsaturated carboxylic acid in all monomers constituting the copolymer is preferably 3 to 35% by mass. Further, MFR (190 ° C., 2.16 kg) is preferably 0.3 g / 10 min to 30 g / 10 min, more preferably 0.5 g / 10 min to 30 g / 10 min, and 0.8 g / 10 min to More preferably, it is 25 g / 10 min.

  Moreover, in the resin which comprises a resin sealing sheet, the ethylene copolymer containing glycidyl methacrylate may be contained. The ethylene copolymer containing glycidyl methacrylate refers to an ethylene copolymer and an ethylene terpolymer with glycidyl methacrylate having an epoxy group as a reaction site. For example, ethylene-glycidyl methacrylate copolymer, ethylene-glycidyl methacrylate-vinyl acetate copolymer And an ethylene-glycidyl methacrylate-methyl acrylate copolymer. Since the above compounds have high reactivity of glycidyl methacrylate, they can exhibit stable adhesion, and have a low glass transition temperature and tend to have good flexibility.

  As the polyolefin resin, polyethylene resin, polypropylene resin, and polybutene resin are preferable. Here, the polyethylene resin refers to a homopolymer of ethylene or a copolymer of ethylene and one or more other monomers. The polypropylene resin refers to a homopolymer of propylene or a copolymer of propylene and one or more other monomers.

  Examples of the polyethylene resin include polyethylene and ethylene-α-olefin copolymers.

  Examples of the polyethylene include low density polyethylene (LDPE), linear low density polyethylene (LLDPE), and linear very low density polyethylene (referred to as “VLDPE” and “ULDPE”).

  The ethylene-α-olefin copolymer is preferably a copolymer composed of ethylene and at least one selected from α-olefins having 3 to 20 carbon atoms, and includes ethylene and 3 to 12 carbon atoms. More preferred is a copolymer comprising at least one selected from α-olefins. Examples of the α-olefin include propylene, 1-butene, 1-pentene, 1-hexene, 1-octene, 4-methyl-1-pentene, 3-methyl-1-pentene, 1-decene, and 1-decene. Examples include dodecene, 1-tetradecene, 1-hexadecene, 1-octadecene, 1-eicosane and the like, and these can be used alone or in combination. Moreover, it is preferable that the ratio (based on preparation monomer) of the alpha olefin in all the monomers which comprise a copolymer is 6-30 mass%. Further, the ethylene-α-olefin copolymer is preferably a soft copolymer, and preferably has a crystallinity of 30% or less by an X-ray method.

  In addition, as the ethylene-α-olefin copolymer, a copolymer of ethylene and at least one comonomer selected from propylene comonomer, butene comonomer, hexene comonomer, and octene comonomer is generally easily available. It can be used suitably.

The polyethylene resin can be polymerized using a known catalyst such as a single site catalyst or a multisite catalyst, and is preferably polymerized using a single site catalyst. The above polyethylene-based resin, from the viewpoint of cushioning properties, it is preferable that a density of 0.860~0.920g / cm ^3, more preferably 0.870~0.915g / cm ^3, 0. More preferably, it is 870-0.910 g / cm < ³ >. When the density is 0.920 g / cm ³ or less, the cushioning property tends to be good. If the density exceeds 0.920 g / cm ³ , the transparency may be deteriorated. When a high-density polyethylene-based resin is used, the transparency can be improved by adding a low-density polyethylene-based resin at a ratio of about 30% by mass, for example.

  The polyethylene resin preferably has an MFR (190 ° C., 2.16 kg) of 0.5 g / 10 min to 30 g / 10 min, preferably 0.8 g / 10 min to 30 g / min, from the viewpoint of processability of the resin encapsulated sheet. 10 min is more preferable, and 1.0 g / 10 min to 25 g / 10 min is still more preferable.

  As said polyethylene-type resin, the polyethylene-type copolymer which controlled crystal / amorphous structure (morphology) by nano order can also be used.

  Examples of the polypropylene resin include polypropylene, propylene-α-olefin copolymer, and terpolymer of propylene, ethylene, and α-olefin.

  The propylene-α-olefin copolymer refers to a copolymer composed of at least one selected from propylene and α-olefin. The propylene-α-olefin copolymer is preferably a copolymer composed of propylene and at least one selected from ethylene and an α-olefin having 4 to 20 carbon atoms, and propylene, ethylene and 4 to 8 carbon atoms. A copolymer comprising at least one selected from α-olefins is more preferable. Examples of the α-olefin having 4 to 20 carbon atoms include propylene, 1-butene, 1-pentene, 1-hexene, 1-octene, 4-methyl-1-pentene, and 3-methyl-1-pentene. , 1-decene, 1-dodecene, 1-tetradecene, 1-hexadecene, 1-octadecene, 1-eicosane and the like, and these can be used alone or in combination. Moreover, it is preferable that the content rate (charged monomer reference | standard) of ethylene and / or alpha-olefin in all the monomers which comprise the said propylene-alpha-olefin copolymer is 6-30 mass%. Furthermore, the propylene-α-olefin copolymer is preferably a soft copolymer, and preferably has a crystallinity of 30% or less by an X-ray method.

  As the propylene-α-olefin copolymer, a copolymer of propylene and at least one comonomer selected from ethylene comonomer, butene comonomer, hexene comonomer, and octene comonomer is generally easily available, and preferably Can be used.

The polypropylene resin can be polymerized using a known catalyst such as a single-site catalyst or a multi-site catalyst, and is preferably polymerized using a single-site catalyst. Also the polypropylene-based resin, from the viewpoint of cushioning properties, it is preferable that a density of 0.860~0.920g / cm ^3, more preferably 0.870~0.915g / cm ^3, 0. More preferably, it is 870-0.910 g / cm < ³ >. When the density is 0.920 g / cm ³ or less, the cushioning property tends to be good. If the density exceeds 0.920 g / cm ³ , the transparency may be deteriorated.

  The polypropylene resin preferably has an MFR (230 ° C., 2.16 kgf) of 0.3 g / 10 min to 15.0 g / 10 min from the viewpoint of processability of the resin-encapsulated sheet, preferably 0.5 g / 10 min. 12 g / 10 min is more preferable, and 0.8 g / 10 min to 10 g / 10 min is still more preferable.

  As the polypropylene resin, a polypropylene copolymer in which the crystal / amorphous structure (morphology) is controlled in nano order can also be used.

  Examples of the polypropylene resin include copolymers of propylene and α-olefins such as ethylene, butene, hexene, and octene, or ternary compounds of propylene, ethylene and α-olefins such as butene, hexene, and octene. A copolymer etc. can be used conveniently. These copolymers may be in any form such as a block copolymer, a random copolymer, etc., preferably a random copolymer of propylene and ethylene, or a random copolymer of propylene, ethylene and butene. is there.

  The polypropylene resin is not limited to a resin polymerized with a catalyst such as a Ziegler-Natta catalyst, but may be a resin polymerized with a metallocene catalyst, for example, syndiotactic polypropylene, isotactic polypropylene, etc. it can. Moreover, it is preferable that the ratio (based on preparation monomer) of the propylene in all the monomers which comprise a polypropylene resin is 60-80 mass%. Furthermore, from the viewpoint of excellent heat shrinkability, the propylene content ratio (based on the charged monomer) in all monomers constituting the polypropylene resin is 60 to 80% by mass, and the ethylene content ratio (based on the charged monomer) is 10 to 30. A ternary copolymer having a butene content ratio (based on charged monomers) of 5 to 20% by mass is preferable.

  As the polypropylene resin, a resin obtained by uniformly finely dispersing a rubber component having a high concentration of 50% by mass or less with respect to the total amount of the polypropylene resin can be used.

  When the resin constituting the resin sealing sheet contains the polypropylene resin, properties such as hardness and heat resistance tend to be further improved.

  In addition, since the polybutene resin is particularly excellent in compatibility with the polypropylene resin, the polybutene resin is preferably used in combination with the polypropylene resin for the purpose of adjusting the hardness and waist of the resin sealing sheet. The polybutene resin is crystalline and is a copolymer of butene and at least one selected from ethylene, propylene and an olefin compound having 5 to 8 carbon atoms, and constitutes a polybutene resin. A high molecular weight polybutene resin having a butene content of 70 mol% or more in all monomers can be suitably used.

  The polybutene resin preferably has an MFR (190 ° C., 2.16 kg) of 0.1 g / 10 min to 10 g / 10 min. Moreover, it is preferable that a Vicat softening point is 40-100 degreeC. Here, the Vicat softening point is a value measured according to JIS K7206-1982.

  The resin sealing sheet of the present embodiment may have either a single layer structure or a multilayer structure. Hereinafter, each structure will be described.

[Single layer structure]
When the resin encapsulating sheet has a single layer structure, ethylene-vinyl acetate copolymer, ethylene-aliphatic unsaturated carboxylic acid is used from the viewpoint of ensuring good transparency, flexibility, adhesion of adherends and handleability. A layer made of at least one resin selected from the group consisting of an acid copolymer, an ethylene-aliphatic unsaturated carboxylic acid ester copolymer, and a polyolefin resin is preferable.

[Multilayer structure]
The resin sealing sheet in the present embodiment may have a multilayer structure of at least two layers including a surface layer and an inner layer laminated on the surface layer. Here, the two layers forming both surfaces of the resin sealing sheet are referred to as “surface layers”, and the other layers are referred to as “inner layers”.

  When it has a multilayer structure, the surface layer uses a resin with good adhesion to glass and backsheet, and the inner layer contains a resin excellent in cushioning and water vapor barrier properties and water and / or a gas scavenger. By using such a resin, it is possible to achieve high functionality without impairing the adhesiveness or the step embedding property. In addition, when an inexpensive resin is used for the inner layer or an inexpensive raw material such as a sealing sheet recycling material is used, the cost is reduced.

  As the surface layer, ethylene-vinyl acetate copolymer, ethylene-aliphatic unsaturated carboxylic acid copolymer, ethylene-, from the viewpoint of ensuring good transparency, flexibility, adhesion of the adherend and handleability. It is preferable to include at least one resin selected from the group consisting of aliphatic unsaturated carboxylic acid ester copolymers and polyolefin resins.

  The layer ratio of the surface layer in contact with the object to be sealed preferably has a thickness of at least 5% with respect to the total thickness of the resin sealing sheet from the viewpoint of ensuring good adhesiveness. When the thickness is 5% or more, the same adhesiveness as in the case of the single layer structure described above tends to be obtained.

  The resin constituting the inner layer is not particularly limited, and any other resin may be used in addition to the resin contained in the surface layer described above. For the purpose of imparting other functions to the inner layer, resin materials, mixtures, additives, and the like can be appropriately selected. For example, for the purpose of newly imparting cushioning properties, a layer containing a thermoplastic resin may be provided as the inner layer.

  Examples of the thermoplastic resin used as the inner layer include polyolefin resins, styrene resins, vinyl chloride resins, polyester resins, polyurethane resins, chlorine ethylene polymer resins, polyamide resins, and the like. Those possessed and those derived from plant-derived materials are also included. Among the above, a hydrogenated block copolymer resin, a propylene copolymer resin, and an ethylene copolymer resin that have good compatibility with the crystalline polypropylene resin and good transparency are preferable, and a hydrogenated block copolymer. A resin and a propylene-based copolymer resin are more preferable.

  As the hydrogenated block copolymer resin, a block copolymer of vinyl aromatic hydrocarbon and conjugated diene is preferable. Examples of vinyl aromatic hydrocarbons include styrene, o-methylstyrene, p-methylstyrene, p-tert-butylstyrene, 1,3-dimethylstyrene, α-methylstyrene, vinylnaphthalene, vinylanthracene, and 1,1-diphenyl. Examples thereof include ethylene, N, N-dimethyl-p-aminoethylstyrene, N, N-diethyl-p-aminoethylstyrene, and styrene is particularly preferable. These may be used alone or in combination of two or more. The conjugated diene is a diolefin having a pair of conjugated double bonds, such as 1,3-butadiene, 2-methyl-1,3-butadiene (isoprene), 2,3-dimethyl-1,3- Examples include butadiene, 1,3-pentadiene, and 1,3-hexadiene. These may be used alone or in combination of two or more.

  As the propylene-based copolymer resin, a copolymer obtained from propylene and ethylene or an α-olefin having 4 to 20 carbon atoms is preferable. The content of the ethylene or α-olefin having 4 to 20 carbon atoms is preferably 6 to 30% by mass. Examples of the α-olefin having 4 to 20 carbon atoms include 1-butene, 1-pentene, 1-hexene, 1-octene, 4-methyl-1-pentene, 3-methyl-1-pentene and 1-decene. 1-dodecene, 1-tetradecene, 1-hexadecene, 1-octadecene, 1-eicosane and the like.

  The propylene-based copolymer resin may be polymerized using a multi-site catalyst, a single-site catalyst, or any other catalyst. Further, a propylene-based copolymer in which the crystal / amorphous structure (morphology) of the polymer is controlled in nano order can be used.

  The ethylene copolymer resin may be polymerized with any of a multisite catalyst, a single site catalyst, and other catalysts. Further, an ethylene copolymer in which the crystal / amorphous structure (morphology) of the polymer is controlled in nano order can be used.

When a polyethylene resin is used as the material for the inner layer, the density of the polyethylene resin is preferably 0.860 to 0.920 g / cm ³ from the viewpoint of obtaining appropriate cushioning properties, and 0.870 to 0.915 g. / Cm ³ is more preferable, and 0.870 to 0.910 g / cm ³ is still more preferable. When a resin layer having a density of 0.920 g / cm ³ or more is formed as a layer (inner layer) that does not contact the object to be sealed, the transparency tends to deteriorate.

  Moreover, the resin sealing sheet may have a structure in which one or two or more layers of the same component are laminated on both surfaces of the center layer so as to be symmetrically arranged with respect to the center layer. As such a resin sealing sheet, for example, a resin sealing sheet composed of two surface layers (hereinafter sometimes referred to as “skin layer”) and three inner layers, Examples thereof include a resin-encapsulated sheet in which the surface layer is composed of the same component, and two inner layers adjacent to the surface layer (hereinafter sometimes referred to as “base layer”) are composed of the same component.

  In the resin sealing sheet having the above structure, the film thickness of the surface layer is preferably 5 to 40% with respect to the film thickness of the entire resin sealing sheet, and the film thickness of the base layer is the resin sealing sheet. The film thickness of the inner layer (hereinafter sometimes referred to as “core layer”) sandwiched between the base layers is preferably 50% to 90% with respect to the entire film pressure. It is preferable that it is 5 to 40% with respect to the film thickness.

  Next, the viewpoint of resin-encapsulated sheet processability is examined. The MFR (190 ° C., 2.16 kg) of the resin constituting the resin sealing sheet is preferably 0.5 to 30 g / 10 min from the viewpoint of ensuring good workability, and 0.8 to 30 g / 10 min. It is more preferable that it is 1.0 to 25 g / 10 min. When the resin sealing sheet has a multilayer structure of two or more layers, the MFR of the resin constituting the inner layer (base layer or core layer) is preferably lower than the MFR of the surface layer from the viewpoint of resin sealing sheet processability.

  In the resin-encapsulated sheet in the present embodiment, various additives such as a coupling agent, an antifogging agent, a plasticizer, an antioxidant, a surfactant, a colorant, and an ultraviolet absorber are provided as long as the characteristics are not impaired. Further, an antistatic agent, a crystal nucleating agent, a lubricant, an antiblocking agent, an inorganic filler, a crosslinking regulator, and the like may be added.

  A coupling agent may be added to the resin sealing sheet for the purpose of ensuring stable adhesion. The addition amount and type of the coupling agent can be appropriately selected depending on the desired degree of adhesion and the type of adherend. The addition amount of the coupling agent is preferably 0.01 to 5% by mass, more preferably 0.03 to 4% by mass, based on the total mass of the resin layer to which the coupling agent is added. More preferably, the content is 0.05 to 3% by mass. As the kind of the coupling agent, a substance that gives the resin layer good adhesion to a solar battery cell or glass is preferable, and examples thereof include organic silane compounds, organic silane peroxides, and organic titanate compounds. . These coupling agents may be added by a known addition method such as injection and mixing into a resin in an extruder, mixing and introducing into an extruder hopper, masterbatching, mixing and adding. it can. However, when passing through an extruder, the function of the coupling agent may be hindered by heat, pressure, etc. in the extruder, so the amount of addition needs to be adjusted appropriately depending on the type of coupling agent. In addition, the type of the coupling agent may be appropriately selected in consideration of the transparency of the resin-encapsulated sheet and the degree of dispersion, the corrosion on the extruder, and the viewpoint of extrusion stability. Preferred coupling agents include γ-chloropropylmethoxysilane, vinyltrichlorosilane, vinyltriethoxysilane, vinyl-tris (β-methoxyethoxy) silane, γ-methacryloxypropyltrimethoxysilane, β- (3,4- Ethoxycyclohexyl) ethyltrimethoxysilane, γ-glycidoxypropyltrimethoxysilane, vinyltriacetoxysilane, γ-mercaptopropyltrimethoxysilane, γ-aminopropyltriethoxysilane, N-β- (aminoethyl) -γ- Examples thereof include those having an unsaturated group or an epoxy group such as aminopropyltrimethoxysilane glycidoxypropyltriethoxysilane.

  Moreover, an ultraviolet absorber, antioxidant, discoloration inhibitor, etc. can be added to a resin sealing sheet. In particular, when it is necessary to maintain transparency and adhesiveness over a long period of time, it is preferable to add an ultraviolet absorber, an antioxidant, a discoloration inhibitor and the like. When these additives are added to the resin, the amount added is preferably 10% by mass or less, more preferably 5% by mass or less, based on the total amount of the resin to be added.

  Examples of the ultraviolet absorber include 2-hydroxy-4-n-octoxybenzophenone, 2-hydroxy-4-n-5-sulfobenzophenone, 2-hydroxy-4-methoxybenzophenone, and 2,2′-dihydroxy-4. , 4′-dimethoxybenzophenone, 2-hydroxy-4-n-dodecyloxybenzophenone, 2,4-dihydroxybenzophenone, 2,2′-dihydroxy-4-methoxybenzophenone, and the like. Examples of the antioxidant include phenol-based, sulfur-based, phosphorus-based, amine-based, hindered phenol-based, hindered amine-based, and hydrazine-based antioxidants.

  These ultraviolet absorbers, antioxidants, discoloration inhibitors and the like are preferably added in an amount of 0 to 10% by mass, more preferably 0 to 5% by mass, in the resin constituting the resin sealing sheet. When added to an ethylene-based resin, adhesiveness can be further imparted by mixing a resin having a silanol group into a master batch. The addition method is not particularly limited, and examples thereof include a method of adding to a molten resin in a liquid state, directly kneading and adding to the target resin layer, and applying after sheeting.

  The resin sealing sheet preferably has a thickness of 50 to 1500 μm, more preferably 100 to 1000 μm, and still more preferably 150 to 800 μm. When the thickness is less than 50 μm, there is a tendency for problems in durability and strength from the viewpoint of structurally poor cushioning properties or workability. On the other hand, when the thickness exceeds 1500 μm, there is a tendency that a problem of reducing productivity and adhesion is caused.

  Next, the optical characteristics of the resin sealing sheet will be described. A haze value is used as an index of optical characteristics. When the haze value is 10.0% or less, the sealed object sealed with the resin sealing sheet can be visually confirmed, and at the same time, when used as a solar cell sealing material, a practically sufficient power generation efficiency Is preferable. From the above viewpoint, the haze value is preferably 9.5% or less, and more preferably 9.0% or less. Here, the haze value can be measured according to ASTM D-1003.

  Further, the resin encapsulating sheet preferably has a total light transmittance of 85% or more and 87% or more in order to ensure practically sufficient power generation efficiency when used as a sealing material for solar cells. More preferably, it is more preferably 88% or more. Here, the total light transmittance can be measured in accordance with ASTM D-1003.

  Hereinafter, the present embodiment will be described in detail based on examples and comparative examples. However, the present embodiment is not limited to the present examples unless it exceeds the gist of the present invention. The evaluation method used in this example is as follows. Moreover, the part and% in a present Example are a mass reference | standard unless there is particular notice.

<VA of thermoplastic resin>
It measured based on JIS-K-7129.

<MFR of thermoplastic resin>
It measured based on JIS-K-7210.

<Density of thermoplastic resin>

  It measured based on JIS-K-7112.

<Melting point of thermoplastic resin>
Using a differential scanning calorimeter “MDSC 2920 type” manufactured by TI Instruments Inc., about 5 mg of resin was heated from 0 ° C. to 200 ° C. at a rate of 20 ° C./min, and melted and held at 200 ° C. for 5 minutes. The temperature of the endothermic peak that accompanies the melting obtained when the sample was rapidly cooled to -50 ° C. or lower and then heated from 0 ° C. to 200 ° C. at 20 ° C./min was defined as the melting point.

<Gel fraction>
A sample was extracted for 12 hours in boiling p-xylene, and the proportion of the insoluble portion was expressed by the following formula, and used as a measure of the degree of crosslinking of the resin-encapsulated sheet.
Gel fraction (wt%) = (sample mass after extraction / sample mass before extraction) × 100

<Heat shrinkage>
{(Melting point of resin) -10} After putting a 100mm square sample in a thermostatic chamber set at 10 ° C for 5 minutes, measure the dimensions in each of the sample flow direction and width direction. The rate of change was defined as the heat shrinkage rate.

<Evaluation of peelability (anti-blocking property) of scroll>
The scroll-like product after the completion of all processes was peeled off, and the ease of peeling was evaluated.
◎: Naturally peels ○: Easy to peel by hand ×: Difficult to peel

<Solar evaluation of solar cell power generation unit>
Glass plate for solar cell (white glass made by AGC 150 cm × 100 cm square: thickness 3 mm) / resin sealing sheet / power generation part (single crystal silicon cell (thickness 250 μm): arranged in 6 × 8 rows) / resin Stacking in the order of sealing sheet / glass plate for solar cell, and using an LM-SA220 type vacuum laminator (NPC), vacuum lamination (lamination time: vacuum time 5 minutes, press time 10 minutes) at 150 ° C. The deviation of the single crystal silicon cell in the power generation part was measured.
A: Deviation from the original position is 0 to 3 mm
○: Deviation from the original position is 3 to 8 mm
×: Deviation from the original position is 8 mm or more

<Solar cell power generation partial gap evaluation>
Glass plate for solar cell (white glass made by AGC, 5 cm × 10 cm square: thickness 3 mm) / resin sealing sheet / power generation part (single crystal silicon cell (thickness 250 μm) / resin sealing sheet / solar cell glass plate) Then, vacuum lamination was performed at 150 ° C. using an LM50 type vacuum laminating apparatus (NPC), and the contact state of the power generation portion with the resin sealing sheet of the single crystal silicon cell was visually confirmed.
A: Even when the laminating time is 2 minutes in vacuum and the press time is 5 minutes, the contact part between the single crystal silicon cell and the resin sealing sheet is all good. (No gap)
○: All contact portions between the single crystal silicon cell and the resin encapsulating sheet are good when the lamination time is 5 minutes in vacuum and the press time is 10 minutes. (No gap)
X: A gap occurred at the contact portion between the single crystal silicon cell and the resin sealing sheet. (Almost all have gaps)

<Creep resistance evaluation>
Glass plate for solar cell (white glass made by AGC, 5 cm × 10 cm square: thickness 3 mm) / resin sealing sheet / power generation part (single crystal silicon cell (thickness 250 μm) / resin sealing sheet / solar cell glass plate) , Vacuum laminate using LM50 type vacuum laminator (NPC), and fix one glass plate of the laminated solar cell on the wall surface of a thermostat set at 85 ° C., let stand for 24 hours, Was measured.
A: There is no deviation of the glass plate. O: The deviation of the glass plate is 3 mm or less. X: The deviation of the glass plate is 3 mm or more.

The materials used in the examples and comparative examples are as follows.
<Thermoplastic resin>
(1) Ethylene-vinyl acetate copolymer (Examples 1-17, Examples 24-31, Comparative Examples 1-4)
Tosoh Ultrasen 751
(Example 18)
Tosoh Ultrasen 631
(Example 19)
Tousoh Ultrasen YX13
(2) Linear ultra low density polyethylene Engage 8180 manufactured by Dow Chemical Japan
(3) Low density polyethylene Suntec M2004 manufactured by Asahi Kasei Chemicals
(4) Ethylene-propylene copolymer 5C30F manufactured by Sun Allomer
(5) Ethylene-acrylic acid copolymer EAA449 manufactured by Dow Chemical Japan
<Crosslinking agent>
Lupelocks 101 made by Arkema Yoshitomi

Tables 1 and 2 show examples in which ethylene-vinyl acetate copolymer was used as the thermoplastic resin and all steps were performed continuously.
[Example 1]
The resin was melt-extruded using an extruder and after passing through a cooling step, embossing and cross-linking by electron beam irradiation were performed, and the product was wound into a roll. As the embossing conditions, the sheet was preheated using an IR heater, embossed, and cooled with a water-cooled roll. The nip rolls before and after the embossing roll were set at the same speed as the embossing roll. The embossing roll nip pressure was adjusted so that the embossed pattern was a pyramid pattern and the processing depth was 100 μm. As crosslinking conditions, the irradiation voltage was adjusted so that the acceleration voltage was 500 kV and the gel fraction was 15% by mass. The winding tension at the time of winding after the crosslinking step was set to 5 N / 1000 mm width. The resulting resin-encapsulated sheet had good roll releasability and had no problems in heat shrinkage, gap filling and creep resistance during lamination, and had both handling and practicality.

[Examples 2 to 17]
As shown in Examples 2 to 4, as the embossing method, when preheating is applied using a heating roll (Example 2), when processing is performed with a heated embossing roll without preheating (Example 3), the resin is melted. After extruding and before embossing before cooling (Example 4), a good sheet is obtained in which the roll peelability is good and the solar cell generator cell does not shift due to heat shrinkage. It was. Moreover, as shown in Examples 5 to 8, the tension conditions before and after the embossing roll were changed, but a good resin-sealed sheet such as heat shrinkage was obtained in the same manner. Furthermore, as shown in Examples 9 to 10, the cooling process after embossing was changed and excluded, but a good resin-encapsulated sheet such as heat shrinkage was obtained in the same manner. As shown in Examples 11 to 14, although the degree of crosslinking (gel fraction) was changed, there were no significant problems with respect to gap filling properties or creep resistance. As shown in Examples 15 to 17, the winding tension after the crosslinking step was changed, but there was no significant problem with winding slippage or roll peelability, and a good resin-sealed sheet was obtained.

[Examples 18 to 24]
Table 3 shows an example in which the thermoplastic resin is changed. The implementation conditions are the same as in Example 1 (however, the resin melting temperature, embossing preheating temperature, irradiation conditions, etc. are adjusted to be the same as in Example 1 in accordance with the melting point and crosslinking characteristics of the resin) . As shown in Examples 18 to 23, even when ethylene-vinyl acetate copolymers having different VA contents and other olefin-based resins were used, there was no problem in blocking and heat shrinkage, gap filling properties, A resin encapsulated sheet excellent in creep resistance was obtained. Furthermore, as shown in Example 24, when the crosslinking agent was added to the thermoplastic resin used in Example 1, a good resin-encapsulated sheet was obtained in the same manner.

[Examples 25 to 31]
Table 4 shows an example in which part of the process is performed offline. From the sheet formation to embossing, when the cross-linking process was carried out after forming into a roll once (Examples 25 to 27), after the sheet was wound up once, the embossing to cross-linking process was carried out continuously. In each case (Example 28), sheet formation, embossing, and crosslinking (Examples 29 to 31) were carried out separately (Examples 29 to 31), there was no problem in blocking and thermal shrinkage, and excellent gap filling and creep resistance. A resin encapsulated sheet was obtained.

[Comparative Examples 1-4]
A comparative example is shown in Table 5. As shown in Comparative Example 1, when embossing was not performed, sheet blocking was severe and it was difficult to peel off the scroll. Moreover, as shown in Comparative Example 2, when crosslinking by electron beam irradiation was not performed, the creep resistance was inferior. Furthermore, as shown in Comparative Examples 3 to 4, when the cross-linking step is performed after the sheet forming step and then the embossing is performed, the sheet whose surface is activated is in-process regardless of continuous or offline. A problem such as sticking to a roll or the like occurred, and there was a problem in processing stability. Further, after the cross-linking, embossing is difficult to enter, resulting in poor roll peelability.

  INDUSTRIAL APPLICABILITY The present invention has industrial applicability as a manufacturing method for providing a sealing material that protects a semiconductor element or the like of a solar cell.

Claims (10)

A method for producing a resin-encapsulated sheet comprising the following steps (i) to (iii) in this order:
(I) a step of heating and melting the thermoplastic resin to form a sheet;
(Ii) a step of embossing the sheet obtained in the step (i),
(Iii) A step of subjecting the sheet embossed in the step (ii) to a crosslinking treatment with ionizing radiation.   The method for producing a resin sealing sheet according to claim 1, wherein the orientation of the resin sealing sheet is relaxed by heat applied during the embossing.   The method for producing a resin-encapsulated sheet according to claim 1, wherein the orientation of the resin-encapsulated sheet is relaxed by heat generated during the crosslinking treatment with the ionizing radiation.   The manufacturing method of the resin sealing sheet of Claim 1 which further includes the process of cooling a sheet | seat after the said embossing.   The method for producing a resin-encapsulated sheet according to claim 1, further comprising a step of winding the sheet into a roll shape, wherein the winding tension is 3 to 200 N / 1000 mm width.   2. The method for producing a resin-encapsulated sheet according to claim 1, wherein the thermal contraction rate of the sheet obtained by the step (i) is 0 to 15% at {(Tm) −10} ° C. (where Tm is heat). Indicates the melting point of the plastic resin).   In the step (ii), an embossing roll is disposed between the two pairs of nip rolls, and when the speed of the embossing roll is 1, the speed ratio of the two pairs of nip rolls is in the range of 0.8 to 1.2. The manufacturing method of the resin sealing sheet of Claim 1 to adjust.   The manufacturing method of the resin sealing sheet of Claim 1 with which the said thermoplastic resin does not contain a crosslinking agent substantially.   The manufacturing method of the resin sealing sheet of Claim 1 whose gel fraction of the sheet | seat after the crosslinking process by the said ionizing radiation is 2-65 mass%.   The resin sealing sheet manufactured by the method of Claim 1.