TWI474925B - Resin sealing sheet and solar cell module - Google Patents

Description

Resin sealing sheet and solar battery module

The present invention relates to a resin sealing sheet and a solar battery module using the same.

In recent years, new energy systems that raise environmental awareness due to global warming and do not generate greenhouse gases such as carbon dioxide have attracted attention. The energy generated by solar cells does not generate carbon dioxide gas or the like. Therefore, it is attracting attention as a green energy source, and research and development of industrial and household energy are carried out.

Representative examples of the solar cell include those using a single crystal or a polycrystalline germanium battery (crystalline silicon battery), and an amorphous silicon or a compound semiconductor (thin film battery). How long does the solar cell be exposed to the wind and rain outside the house, and the power generation part is laminated with a glass plate and a back sheet to form a module, and the water is prevented from intruding from the outside, thereby protecting the power generation portion and Prevent leakage and so on.

The member for protecting the power generation portion is a transparent glass and a transparent resin for the member on the light incident side in order to ensure light penetration required for power generation. The member on the opposite side (back side) is processed by a barrier coat such as aluminum foil, polyvinyl fluoride resin (PVF), polyethylene terephthalate (PET), and cerium oxide called a back sheet. Layered sheets. Then, the power-generating element is sandwiched by the resin sealing sheet, and the glass and the back sheet are covered with the outer surface, and the resin sealing sheet is melted by performing heat treatment to integrally seal (modulate) the whole.

The above resin sealing sheet requires the following characteristics (1) to (3). That is, (1) good adhesion to glass, power generation element, and back sheet, and (2) prevention of melting of the resin sealing sheet in the high temperature state, causing the power generation element to flow (creep resistance), (3) not Blocks the transparency of sunlight incident.

From such a viewpoint, the resin sealing sheet is blended with an ultraviolet absorber which is resistant to ultraviolet rays in an ethylene-vinyl acetate copolymer (EVA), a coupling agent for improving adhesion to glass, and cross-linking. An additive such as an organic peroxide is used, and a film is formed by calender molding and T-die casting. In addition, in view of the need to expose to sunlight for a long period of time, various additives such as a light stabilizer are blended in order to prevent deterioration of optical characteristics due to deterioration of the resin.

As a method of molding a solar cell with a resin sealing sheet as described above, a method using a dedicated solar cell vacuum laminator or the like can be mentioned. Specifically, a method in which a power generating element such as a glass/resin sealing sheet/crystalline enamel battery/resin sealing sheet/backing plate is laminated in the order of resin melting temperature or higher (in the case of EVA, about 150° C.) The temperature preheating step and the press step are performed, and the resin sealing sheet is melted and bonded.

In the above method, the resin of the resin sealing sheet is first melted in the preheating step, and the member in contact with the molten resin is adhered to the molten resin in a press step, and laminated by vacuum. In the laminating step, (i) thermally decomposing a crosslinking agent (for example, an organic peroxide) contained in the resin sealing sheet and promoting crosslinking of the EVA, (ii) contacting the coupling agent contained in the resin sealing sheet. The components are covalently bonded. Thereby, the adhesion between the two is improved, and the power generation element is prevented from flowing (durability resistance) due to melting of the resin sealing sheet in a high temperature state, and the glass, the power generating element, and the back sheet are excellent in adhesion.

Patent Document 1 discloses a sheet for solar cell encapsulation which is made of a vinyl-based copolymer resin and which is crosslinked by radiation to a certain degree of gel fraction. Further, Patent Document 2 discloses a sheet for solar cell encapsulation which is made of a vinyl-based copolymer resin in which a decane coupling agent is blended.

[Previous Technical Literature]

[Patent Literature]

[Patent Document 1] Japanese Patent Laid-Open Publication No. 2010-031232

[Patent Document 2] Japanese Patent Laid-Open Publication No. 2005-019975

However, in recent years, it is required to increase the power output of the solar cell module, and to reduce the power loss by thickening a metal connecting wire such as a tab wire connecting power generating elements such as a crystallization battery, and to reduce the power. From the viewpoint of the requirements of the loss module, there is room for improvement in the filling property of the resin sealing sheet in the gap of the power generating element having a large unevenness. In the past, in order to improve the above-mentioned resistance to latent deformation, the resin sealing sheet is gelled, etc., but if gelled, the thermal fluidity deteriorates when the solar cell is modularized, and the gel is accompanied by the module. The problem of cracking gas is generated. Therefore, sufficient gap filling property cannot be obtained. This problem is more remarkable in the case of a solar cell having a large-concave power generating element connected by a thick metal wire.

From the viewpoint of power generation efficiency, the solar cell sealing material is preferably colorless and transparent, and the crosslinked structure and gelation rate may affect it. Since the cross-linking structure and the gelation rate are mainly designed to improve the gap filling property and the latent denaturation resistance, the stability of transparency and chromatic aberration has not been fully reviewed.

The present invention has been made in view of the above circumstances, and a main object of the present invention is to provide a resin sealing sheet which is excellent in gap-filling property and latent resistance, and which is excellent in transparency and chromatic aberration stability.

As a result of intensive research to solve the above problems, the present inventors have found that a resin sealing sheet containing a polyethylene resin having a specific density and containing no crosslinking agent and controlling specific physical properties can achieve gap filling property and resistance to latent denaturation. A resin sealing sheet which is excellent in transparency and excellent in stability of chromatic aberration.

That is, the present invention is as follows:

[1] A resin sealing sheet comprising a polyethylene resin having a density of 0.860 to 0.910 g/cm ³ and containing no crosslinking agent, and having a shrinkage ratio of 0 to 25% when suspended at a temperature of 150 ° C, and a glue The chemical conversion rate is 0% by mass or more and less than 1% by mass.

[2] A resin sealing sheet comprising a polyethylene-based resin having a density of 0.860 to 0.910 g/cm ³ and containing no crosslinking agent, and a Mooney viscosity of 70 to 90 M.

[3] A resin sealing sheet comprising a polyethylene resin having a density of 0.860 to 0.910 g/cm ³ and containing no crosslinking agent, and satisfying the conditions (1) and (2) below.

(1) The activation energy calculated by measuring the melt viscoelasticity of 150 to 250 ° C is 75 to 90 kJ/mol.

(2) The storage modulus (G') measured at 1 rad/sec at 150 ° C was 6,000 to 12,000 Pa.

[4] The resin sealing sheet according to any one of [1] to [3] which is subjected to a crosslinking treatment.

[5] The resin sealing sheet according to [4], wherein the crosslinking treatment is performed by irradiating ionizing radiation.

[6] The resin sealing sheet according to [5], wherein the ionizing radiation irradiation amount of the irradiated ionizing radiation is 30 kGy or more and 60 kGy or less.

[7] A solar cell module comprising: a translucent insulating substrate; a back insulating substrate disposed opposite to the translucent insulating substrate; and disposed between the translucent insulating substrate and the back insulating substrate A power-generating element, and a resin sealing sheet according to any one of [1] to [6], wherein the power generating element is sealed.

[8] The solar cell module according to the above [7], wherein the resin sealing sheet contained in the solar cell module has a gelation ratio of 0% by mass or more and less than 1% by mass.

[9]. A method of producing a resin sealing sheet, comprising the step of irradiating a sheet with ionizing radiation of 30 kGy or more and 60 kGy or less, the sheet containing a polyethylene resin having a density of 0.860 to 0.910 g/cm ³ and containing no crosslinking Agent.

According to the present invention, it is possible to provide a resin sealing sheet which is excellent in gap filling property and latent resistance, and excellent in transparency and chromatic aberration stability.

Hereinafter, the mode for carrying out the invention (hereinafter simply referred to as "this embodiment") will be described in detail. The following embodiments are illustrative for the purpose of illustrating the invention, but are not intended to limit the invention. The present invention can be carried out with appropriate modifications within the scope of the gist of the invention. In addition, in the drawings, the positional relationship of the up, down, left, and right directions is based on the positional relationship shown in the drawing unless otherwise specified. And the dimensional ratio of the drawings is not limited to the ratios shown in the drawings.

<Resin sealing sheet>

The first type of the resin sealing sheet of the present embodiment contains a polyethylene resin having a density of 0.860 to 0.910 g/cm ³ and does not contain a crosslinking agent, and shrinkage at a temperature of 150 ° C (hereinafter referred to as " The resin sealing sheet having a suspension shrinkage ratio of 0 to 25% and a gelation ratio of 0% by mass or more and less than 1% by mass.

The lower limit of the shrinkage ratio (hereinafter referred to as "suspension shrinkage ratio") when the sheet is suspended at a temperature of 150 ° C is 0% or more, preferably 1% or more. The upper limit of the suspension shrinkage ratio may be 25% or less, preferably 15% or less. The suspension shrinkage ratio can be measured by the method described in the examples below.

In addition, the molecular motion caused by thermal relaxation causes the residual stress in the resin sealing sheet to be released, resulting in shrinkage due to suspension. Therefore, the suspension shrinkage ratio can be controlled by adjusting the molecular weight of the resin component such as the polyethylene resin and the branched structure (crosslinking density). When the degree of branching of the branched structure is high and the molecular motion caused by thermal relaxation is suppressed, for example, if the polyethylene resin having a high molecular weight is irradiated by the ionizing radiation having a high ionizing radiation irradiation amount, the crosslinking treatment can be performed, thereby reducing the suspension. Shrinkage. On the other hand, when the degree of branching of the branched structure is low and the molecular motion caused by thermal relaxation is difficult to suppress, for example, if the polyethylene resin having a low molecular weight is irradiated by the ionizing radiation having a low ionizing radiation amount, the crosslinking treatment can be improved. Suspension shrinkage rate.

The resin sealing sheet of the present embodiment is subjected to a crosslinking treatment in which the gelation ratio is 0% by mass or more and less than 1% by mass. The lower limit of the gelation ratio may be 0% by mass or more, and preferably 0.2% by mass or more, from the viewpoint of resistance to latent denaturation. The upper limit of the gelation ratio may be less than 1% by mass, and preferably 0.8% by mass, from the viewpoint of the gap filling property, in particular, the filling of the gap between the power generating elements having large irregularities connected by the thick metal connecting wires. the following. The gelation rate can be measured by the method described in the examples below.

In addition, the gelation ratio can be controlled by adjusting the molecular weight of the resin component such as the polyethylene resin and the branched structure (crosslinking density, etc.) which will be described later. For example, if a polyethylene resin having a high molecular weight is irradiated by ionizing radiation having a high ionizing radiation irradiation amount and cross-linking treatment is performed, the gelation rate can be increased. On the other hand, if the polyethylene resin having a low molecular weight is irradiated by ionizing radiation having a low ionizing radiation amount to carry out a crosslinking treatment, the gelation rate can be lowered.

The second form of the resin sealing sheet of the present embodiment contains a polyethylene resin having a density of 0.860 to 0.910 g/cm ³ and a resin sealing sheet having a crosslinking agent and a Mui viscosity of 70 to 90 M. The resin sealing sheet may have a Mui viscosity of 70 to 90 M, preferably 75 to 85 M, more preferably 78 to 82 M. The viscosity of the Mooney viscosity at high temperature can be used as an index of the ease of molecular motion in accordance with the crosslinked structure of the resin. When the Mooney viscosity is 70 M or more, the fluidity can be suppressed and the creep resistance can be improved, and when it is 90 M or less, the gap embedding property can be improved.

In addition, the Mooney viscosity can be controlled by adjusting the molecular weight of the resin component such as a polyethylene resin and the branched structure (crosslinking density, etc.) which will be described later. For example, if the polyethylene resin having a high molecular weight is irradiated by ionizing radiation having a high ionizing radiation amount to carry out a crosslinking treatment, the Mooney viscosity can be improved. Conversely, if the polyethylene resin having a low molecular weight is irradiated by ionizing radiation having a low ionizing radiation amount to carry out a crosslinking treatment, the Mooney viscosity can be lowered.

The third type of the resin sealing sheet of the present embodiment contains a polyethylene resin having a density of 0.860 to 0.910 g/cm ³ and does not contain a crosslinking agent, and satisfies the conditions of the following (1) and (2). Resin sealing sheet.

(1) The activation energy calculated by measuring the melt viscoelasticity of 150 to 250 ° C is 75 to 90 kJ/mol.

(2) The storage modulus (G') measured at 1 rad/sec at 150 ° C was 6,000 to 12,000 Pa.

The activation energy and the storage modulus (G') can be used as an index of the ease of molecular motion in accordance with the crosslinked structure of the resin, and the resin gelation ratio of the crosslinked structure of the resin is only slightly different. When the activation energy is 75 kJ/mol or more, the fluidity can be suppressed and the latent denaturation resistance can be further enhanced, and by setting the activation energy to 90 kJ/mol or more, the gap filling property can be further improved. Then, by making both the activation energy and the storage modulus (G') in the above range, the balance between the latent resistance and the gap filling property can be further improved.

In the third form, the activation energy may be from 75 to 90 kJ/mol, more preferably from 78 to 88 kJ/mol, still more preferably from 80 to 85 kJ/mol. The storage modulus (G') may be 6,000 to 12,000 Pa, and more preferably 7,000 to 10,000 Pa.

In addition, the activation energy is affected by the ease of molecular motion of the polymer chain. Therefore, the activation energy can be controlled by adjusting the molecular weight of the resin component such as the polyethylene resin and the branched structure (crosslinking density, etc.) which will be described later. For example, when a polyethylene-based resin having a high molecular weight is irradiated by ionizing radiation having a high electron beam irradiation amount and subjected to a crosslinking treatment, the activation energy can be improved. On the other hand, if the polyethylene resin having a low molecular weight is irradiated by ionizing radiation having a low electron beam irradiation amount to carry out a crosslinking treatment, the activation energy can be lowered.

In addition, the storage modulus (G') is affected by the ease of molecular motion of the polymer chain. Therefore, the storage modulus (G') can be controlled by adjusting the molecular weight of the resin component such as the polyethylene resin and the branched structure (crosslinking density). For example, when a polyethylene resin having a high molecular weight is irradiated by ionizing radiation having a high electron beam irradiation amount to carry out a crosslinking treatment, the storage modulus (G') can be improved. On the other hand, if the polyethylene resin having a low molecular weight is irradiated by the ionizing radiation having a low electron beam irradiation amount and the crosslinking treatment is carried out, the storage modulus (G') can be lowered.

Even if the resin sealing sheet has any one of a single layer structure or a multilayer structure which will be described later, unless otherwise specified, the above-mentioned suspension shrinkage ratio, gelation ratio, Mooney viscosity, activation energy, and storage modulus (G') are various physical properties. Both represent the overall average of the resin sealing sheets. In the above-described range, the resin sealing sheet has the following properties: the performance (gap-filling property) and the resistance to latent denaturation which are excellent in sealing the gap between the power-generating element and the sealed object such as the wiring without gaps. And transparency and color stability are also excellent.

Then, by satisfying the conditions of the respective physical properties by satisfying the first type, the second type, and the third type, it is possible to exhibit more excellent effects. For example, it is possible to exhibit a more excellent effect by the configuration shown below.

For example, a combination of the first type and the second type may be a polyethylene-based resin satisfying a density of 0.860 to 0.910 g/cm ³ and containing no crosslinking agent, and satisfying the following conditions (a) and ( b) The resin sealing sheet.

(a) When the sheet was hung at a temperature of 150 ° C, the shrinkage ratio was 0 to 25%, and the gelation ratio was 0% by mass or more and less than 1% by mass.

(b) Mooney viscosity is 70 to 90M.

For example, a combination of the second type and the third type may be a polyethylene-based resin satisfying a density of 0.860 to 0.910 g/cm ³ and containing no crosslinking agent, and satisfying the following conditions (b), ( The resin sealing sheets of c) and (d).

(b) Mooney viscosity is 70 to 90M.

(c) The activation energy calculated by measuring the melt viscoelasticity of 150 to 250 ° C is 75 to 90 kJ/mol.

(d) The storage modulus (G') measured at 1 rad/sec at 150 ° C was 6,000 to 12,000 Pa.

For example, a combination of the first type, the second type, and the third type may be a polyethylene-based resin that satisfies a density of 0.860 to 0.910 g/cm ³ and does not contain a crosslinking agent, and satisfies the following conditions. The resin sealing sheets of (a) to (d).

(a) When the sheet was hung at a temperature of 150 ° C, the shrinkage ratio was 0 to 25%, and the gelation ratio was 0% by mass or more and less than 1% by mass.

(b) Mooney viscosity is 70 to 90M.

(c) The activation energy calculated by measuring the melt viscoelasticity of 150 to 250 ° C is 75 to 90 kJ/mol.

(d) The storage modulus (G') measured at 1 rad/sec at 150 ° C was 6,000 to 12,000 Pa.

In the present embodiment, it is preferred to subject the resin sealing sheet to a crosslinking treatment. By performing the crosslinking treatment, the above physical properties can be controlled with high precision. In the present embodiment, "crosslinking treatment" means a state in which at least a part of the polymer constituting the resin is physically or chemically crosslinked.

Since the resin sealing sheet of the present embodiment does not contain a crosslinking agent, the heat curing step can be omitted. Further, since the temperature limitation during the production of the sheet can be alleviated, the sheet temperature can be set to a high temperature at the time of sheet film formation and emboss processing to be described later. As a result, the film forming speed and the imprint processing speed can be improved, which is advantageous for productivity. By the thermal decomposition of the organic peroxide used as the crosslinking agent, the generation of gas can be suppressed, and corrosion damage, oil stain, and the like of the vacuum pump and the like can be suppressed. Further, the meaning of "there is no crosslinking agent" in the present embodiment includes those which do not substantially contain a crosslinking agent, and those which do not contain a positive crosslinking agent.

The crosslinking treatment of the resin sealing sheet of the present embodiment is preferably carried out by irradiating ionizing radiation. The ionizing radiation used in the present embodiment may, for example, be α-ray, β-ray, γ-ray, neutron beam, electron beam or the like. The electron beam irradiation amount can be adjusted by adjusting the irradiation intensity (acceleration voltage) and the irradiation density of the ionizing radiation, and the suspension shrinkage rate, the gelation rate, the Mooney viscosity, the activation energy, and the storage in the thickness direction of the sheet can be controlled with high precision. Modulus (G'). By adjusting the irradiation intensity (acceleration voltage), the depth of arrival of electrons in the thickness direction of the sheet can be controlled, and by adjusting the irradiation density, the amount of electrons irradiated per unit area of the sheet can be controlled. The accelerating voltage of the ionizing radiation can be appropriately adjusted in accordance with the resin to which the crosslinking treatment is applied, and the irradiation amount of the ionizing radiation varies depending on the resin to be used, but the resin sealing sheet is uniformly crosslinked uniformly. Look, it is generally preferred to be 3kGy to 100kGy. More preferably, it is 30 kGy to 60 kGy, and more preferably 40 kGy to 50 kGy. Further, the accelerating voltage is preferably from 250 kV to 2000 kV, more preferably from 500 kV to 1000 kV.

The effects obtained by the resin sealing sheet of this embodiment are not fully understood, but it is presumed as follows.

First, considering the relationship between the gap filling property and the latent resistance to the trade-off, it is difficult to balance. However, since the resin sealing sheet of the present embodiment does not contain a crosslinking agent such as an organic peroxide, the polar group generated by the crosslinking agent can be suppressed, and it is considered whether the gap filling property and the latent resistance can be balanced. In particular, since the crosslinking treatment is carried out without using a crosslinking agent, the adverse effects of the crosslinking agent and the radical initiator can be eliminated, whereby the intermolecular structure of the resin component can be formed only by the chemical structure derived from the resin component. Cross-linking, it is presumed that the balance between gap filling property and latent resistance can be more excellent. The complex cause is crosslinked by irradiation with ionizing radiation, and it is presumed that the compatibility between the gap filling property and the latent resistance is more excellent.

More specifically, in the prior art using a crosslinking agent such as an organic peroxide, a radical species (for example, RO‧, etc.) generated by a dissociation reaction of a crosslinking agent and a radical initiator is also used in the resin. Cross-linking reaction of the components (refer to the following formula). As a result, the radical species derived from the crosslinking agent and the radical initiator are reacted with the resin to form a crosslinked structure, and thus the terminal group of the crosslinking agent and the radical initiator is contained in the intermolecular crosslinking (for example) -OR, etc., which is considered to have an adverse effect on gap filling and resistance to latent denaturation.

R-O-O-R→R-O‧+‧O-R

However, in the resin sealing sheet of the present embodiment, the crosslinking reaction is carried out by electrolytic dissociation of a hydrogen atom of [-(CH ₂ )-] contained in a repeating unit such as a polyethylene resin (refer to the following). Said). As a result, since the radical species derived only from the resin component are related to the crosslinking reaction, the intermolecular crosslinking is composed only of the chemical structure derived from the resin component, and the gap filling property and the latent denaturation resistance are considered to be compatible. It is more excellent (but the effect of the present embodiment and the like is not limited to this).

-CH ₂ -CH ₂ -CH ₂ -CH ₂ -→H‧+-CH ₂ -C‧H-CH ₂ -CH ₂ -

Further, the resin component in the resin sealing sheet is crystallized by heat treatment to cause optical scattering, which causes a problem that the haze is deteriorated and the chromatic aberration is unstable. However, in the resin sealing sheet of the present embodiment, the crosslinking treatment is carried out by irradiating the ionizing radiation, and it can be considered as a difficult position (for example, tertiary carbon) on the molecular chain of the resin component for steric reasons or the like. Upper) produces a crosslinking point that does not have a polar group. By this, it is considered that the molecular motion caused by the crystallization by heating is suppressed, the haze deterioration can be effectively suppressed, and the chromatic aberration stability can be maintained (however, the effects of the present embodiment and the like are not limited thereto).

In the past, the hydrogen atom in the resin is detached by irradiation of ionizing radiation to generate a conjugated double bond, because this conjugated double bond functions as a chromophor and has a problem of increasing chromatic aberration. However, in the resin sealing sheet of the present embodiment, the resin sealing sheet can be designed in an appropriate color difference range by adjusting the irradiation amount of the ionizing radiation to a specific range. Further, it is surprising that the resin sealing sheet of the present embodiment can suppress an increase in chromatic aberration caused by thermal deterioration due to heat treatment. The reason for this is not certain. It is considered that the crosslinking reaction does not use an organic peroxide, and does not form a polar group (hydroxyl group, carbonyl group, peroxy group, or epoxy group) caused by a peroxide, so that the polyethylene can be maintained. The polyethylene-based resin such as a resin or the like has high weather resistance and heat resistance (however, the effects of the present embodiment and the like are not limited thereto).

Next, a material relating to the resin sealing sheet which can be used in the present embodiment will be described.

The resin sealing sheet of this embodiment contains a polyethylene resin having a density of 0.860 to 0.910 g/cm ³ or less. The polyethylene resin means an ethylene homopolymer or a copolymer of ethylene and one or more other monomers. By using a polyethylene resin having a density of 0.910 g/cm ³ or less, the gap filling property and transparency (especially the total light transmittance) at the time of heat lamination can be greatly improved. Light emitted from the lift dip transmittance haze increase of the viewpoint, the lower limit of density was 0.860g / cm ³ or more, preferably 0.880g / cm ³ or more, more preferably 0.890g / cm ³ or more. From the viewpoint of further improving the transparency, it is more preferable to use a different type of resin such as a high-density polyethylene resin in combination with a low-density polyethylene-based resin. More specifically, it is more preferable to add a high-density polyethylene-based resin to the low-density polyethylene-based resin in a ratio of from 1 to 50% by mass.

The polyethylene resin is more preferably a chain-shaped low-density polyethylene. By using a chain-shaped low-density polyethylene, the polarity can be further suppressed, and more excellent insulation properties can be obtained. The re-water vapor barrier property is excellent, and the sealed object can be reliably sealed even under high temperature and high humidity. This advantage is especially pronounced when cross-linking is applied.

The melting point of the chain-shaped low-density polyethylene is preferably 110 ° C or less from the viewpoint of the processability of the resin sealing sheet and the suitability of the heat-storing layer. Further, the melt flow rate (MFR; 190 ° C, 2.16 kg) measured on the basis of JIS K 7210 is preferably from 0.5 to 30 g/10 min, more preferably from 0.8 to 30 g/10 min, still more preferably from 1.0 to 25 g. /10 minutes.

The chain-shaped low-density polyethylene can be polymerized using a known catalyst such as a single-site catalyst or a multi-site catalyst. Among them, from the viewpoint of suppressing the content of the low molecular component and efficiently synthesizing the low-density resin, it is preferred to carry out the polymerization using a single-point catalyst. The single-point catalyst is not particularly limited, and a known one can be used. For example, a metal complex having cyclopentadiene can be mentioned. These can be used as a commercial item.

The resin sealing sheet may be composed of a resin composition containing a resin other than a polyethylene resin having a density of 0.860 to 0.910 g/cm ³ . In the entire resin composition, the other resin content is preferably 10% by mass or less, more preferably 5% by mass or less, and still more preferably 3% by mass or less.

The melting point of the other resin is preferably 100 ° C or lower, more preferably 80 ° C or lower, still more preferably 75 ° C or lower. Thereby, sufficient heat fluidity of the resin sealing sheet can be imparted. When the resin composition contained in the resin sealing sheet contains a plurality of resins, the melting point of the entire resin composition is preferably 100 ° C or lower. The melting point can be measured by the method described in the examples below.

The other resin may, for example, be any one selected from the group consisting of ethylene-vinyl acetate copolymer, ethylene-aliphatic unsaturated carboxylic acid copolymer, ethylene-aliphatic unsaturated carboxylic acid ester copolymer, and ethylene. a vinyl acetate copolymer saponified product, an ethylene-vinyl acetate-acrylate copolymer saponified product, and a polyolefin-based resin. These may be used alone or in combination of two or more.

The ethylene-vinyl acetate copolymer means a copolymer obtained by copolymerizing an ethylene monomer with a vinyl acetate monomer. The ratio of vinyl acetate in the entire monomer constituting the ethylene-vinyl acetate copolymer is preferably from 10 to 40% by mass, more preferably from 13 to 35% by mass, from the viewpoints of optical properties, adhesion, and flexibility. More preferably, it is 15 to 30% by mass. From the viewpoint of the processability of the resin sealing sheet, the MFR (190 ° C, 2.16 kg) measured based on JIS K 7210 is preferably from 0.3 to 30 g/10 min, more preferably from 0.5 to 30 g/10 min. More preferably, it is 0.8 to 25 g/10 minutes.

The ethylene-aliphatic unsaturated carboxylic acid copolymer means a copolymer obtained by copolymerizing an ethylene monomer with an aliphatic unsaturated carboxylic acid monomer. The aliphatic unsaturated carboxylic acid monomer may, for example, be acrylic acid, methacrylic acid or the like. The copolymer may be a multicomponent copolymer obtained by copolymerizing a monomer having three or more components. In all the monomers constituting the ethylene-aliphatic unsaturated carboxylic acid copolymer, the proportion of the aliphatic unsaturated carboxylic acid monomer is preferably from 3 to 35 mass%. The MFR (190 ° C, 2.16 kg) is preferably from 0.3 to 30 g/10 min, more preferably from 0.5 to 30 g/10 min, still more preferably from 0.8 to 25 g/10 min.

The ethylene-aliphatic unsaturated carboxylic acid ester copolymer means a copolymer obtained by copolymerizing an ethylene monomer with an aliphatic unsaturated carboxylic acid ester monomer. The aliphatic unsaturated carboxylic acid ester monomer may, for example, be an ester of acrylic acid or methacrylic acid with an alcohol having 1 to 8 carbon atoms such as methanol or ethanol. The copolymer may be a multicomponent copolymer obtained by copolymerizing a monomer having three or more components. In all of the monomers constituting the ethylene-aliphatic unsaturated carboxylic acid ester copolymer, the proportion of the aliphatic unsaturated carboxylic acid ester is preferably from 3 to 35 mass%. The MFR (190 ° C, 2.16 kg) is preferably from 0.5 to 30 g/10 min, more preferably from 0.8 to 30 g/10 min, still more preferably from 1 to 25 g/10 min.

The ethylene-vinyl acetate copolymer saponified product may, for example, be a partial or complete saponified product of an ethylene-vinyl acetate copolymer. The ethylene-vinyl acetate-acrylate copolymer saponified product may, for example, be a partial or complete saponified product of an ethylene-vinyl acetate-acrylate copolymer. The upper limit of the hydroxyl group content in the saponified product is preferably 10% by mass or less, more preferably 5% by mass or less, and still more preferably 3% by mass or less. Further, the lower limit is preferably 0.1% by mass or more. When the hydroxyl group content is in the above range, the adhesion and compatibility are further improved, and the whitening of the obtained resin sealing sheet can be effectively suppressed. The saponification resin and the saponified resin (saponified product) can be measured by NMR to determine the vinyl acetate copolymerization ratio (VA%), the degree of saponification of the saponified product, and the content of the saponified product in the resin composition.

The vinyl acetate-vinyl acetate copolymer or the ethylene-vinyl acetate-acrylate copolymer before saponification preferably has a vinyl acetate content of 10 to 40% by mass, more preferably from the viewpoints of optical properties, adhesion, and flexibility. It is 13 to 35 mass%, and more preferably 15 to 30 mass%. The degree of saponification of each saponified product is preferably from 10 to 70%, more preferably from 15 to 65%, still more preferably from 20 to 65%, from the viewpoints of transparency and adhesion.

Examples of the saponification method include a method in which an ethylene-vinyl acetate copolymer, an ethylene-vinyl acetate-acrylate copolymer pellet and a powder are placed in a lower alcohol such as methanol, a saponification using an alkali catalyst, and a copolymer. A method in which an organic solvent such as toluene, xylene or hexane is dissolved in advance, and then saponified with a small amount of an alcohol or a base catalyst. Further, a monomer having a functional group other than a hydroxyl group may be subjected to graft copolymerization to a saponified copolymer. The saponified compound exemplified herein has a hydroxyl group in the side chain, so that the adhesion can be further improved as compared with the copolymer before saponification. Physical properties such as transparency and adhesion can be controlled by adjusting the degree of saponification.

The polyolefin-based resin may be a polyolefin-based resin other than the polyethylene-based resin having a density of 0.860 to 0.910 g/cm ³ . From the viewpoint of corrosiveness and water vapor barrier properties, at least one selected from the group consisting of a polyethylene resin, a polypropylene resin, and a polybutene resin is preferred, and it is more preferable from the viewpoint of cost. Vinyl resin. The polypropylene resin means a homopolymer of propylene or a copolymer of propylene and one or two other monomers. The polybutene resin represents a homopolymer of butene, or a copolymer of butene and one or more other monomers.

In addition to the above, in order to impart adhesion to the resin sealing sheet, it is preferred to contain at least one resin selected from the group consisting of olefin-based copolymers having a hydroxyl group, modified ends or grafting moieties with acidic functional groups. The modified polyolefin and the ethylene copolymer containing glycidyl methacrylate (hereinafter abbreviated as "GMA").

When the above-mentioned adhesive resin is contained, for example, when the ethylene copolymer containing glycidyl methacrylate is contained, since the reactivity of the glycidyl methacrylate is high, the stability of the stability can be exhibited.

The olefin constituting the olefin-based copolymer having a hydroxyl group is preferably ethylene. The hydroxyl group can be obtained by saponifying an acetic acid group of an ethylene-vinyl acetate copolymer or an ethylene-vinyl acetate-acrylate copolymer to form a hydroxyl group. The olefin-based copolymer having a hydroxyl group may specifically be a partial or complete saponified product of an ethylene-vinyl acetate copolymer or a partial or complete saponified product of an ethylene-vinyl acetate-acrylate copolymer.

The modified polyolefin which is modified with an acidic functional group or a grafted portion may, for example, be a compound having a polar group such as maleic anhydride, nitro group, hydroxyl group or carboxyl group, etc., modified polyethylene resin and poly The end or graft portion of the propylene resin. Among them, from the viewpoint of the stability of the polar group, a maleic acid-modified polyolefin in which the terminal or graft portion of the maleic anhydride is modified is preferable. The polyethylene resin or the polypropylene resin described herein can be the same as those described for the polyolefin resin described later.

The ethylene copolymer containing glycidyl methacrylate represents a copolymer of glycidyl methacrylate and ethylene having an epoxy group as a reaction site, and a terpolymer with ethylene, for example, Examples: ethylene-glycidyl methacrylate copolymer, ethylene-glycidyl methacrylate-vinyl acetate copolymer, ethylene-glycidyl methacrylate-methyl acrylate copolymer, and the like. Since the reactivity of glycidyl methacrylate is high, the above compound can exhibit stable adhesion.

The resin composition used for the resin sealing sheet may further contain an ionizing radiation degradation type resin. The ionizing radiation-cleaving type resin refers to a resin having a property of being cracked by irradiation with ionizing radiation such as α rays, β rays, γ rays, neutron rays, and electron beams.

The ionizing radiation cleavage type resin may, for example, be a cleavage type resin in which a functional group is bonded to the α position of the main chain C-C bond. The functional group may, for example, be at least one selected from the group consisting of a halogen atom, a hydroxyl group, a nitro group, a substitutable alkyl group, a substitutable alkoxy group, a substitutable amine group, a substitutable carboxyl group, An amine group which may be substituted, and an aryl group which may be substituted.

Here, one or two or more substituents may be substituted at the substitutable positions of the alkyl group, the alkoxy group, the amine group, the carboxyl group, the decylamino group and the aryl group. Examples of the related substituent include a halogen atom (for example, a fluorine atom, a chlorine atom, and a bromine atom), and an alkyl group having 1 to 6 carbon atoms (for example, methyl group, ethyl group, propyl group, isopropyl group, butyl group, and isobutyl group). Base, second butyl, tert-butyl, pentyl, hexyl), aryl (eg phenyl, naphthyl), aralkyl (eg benzyl, phenethyl), alkoxy (eg methoxy) , ethoxy) and so on.

Specifically, the ionizing radiation-cleaving type resin may, for example, be at least one selected from the group consisting of polypropylene, polyisobutylene, poly-α-methylstyrene, polytetrafluoroethylene, and polymethyl methacrylate. Ester, polypropylene decylamine, polymethyl methacrylate methacrylate and cellulose.

The resin constituting the resin sealing sheet may contain an ionizing radiation cross-linking cleavage resin having both a crosslinkable portion and a cleavable portion. Examples of such resins include ethylene copolymers containing glycidyl methacrylate, ethylene copolymers containing polypropylene, ethylene copolymers containing methyl methacrylate, and ethylene copolymers containing isoprene rubber. An ethylene copolymer containing butadiene rubber, an ethylene copolymer containing a styrene-butadiene copolymer rubber, and the like.

The ethylene copolymer containing propylene methacrylate is a copolymer of propylene glycol methacrylate and ethylene having an epoxy group as a reaction site, and a terpolymer with ethylene, or a multicomponent copolymer. Things. For example, an ethylene-glycidyl methacrylate copolymer, an ethylene-glycidyl methacrylate-vinyl acetate copolymer, an ethylene-glycidyl methacrylate-methyl acrylate copolymer, etc. are mentioned. Since the reactivity of glycidyl methacrylate is high, these compounds exhibit a stable adhesive property, and tend to lower the glass transition temperature and provide good flexibility.

The copolymerization of each of the above copolymers can be carried out by a known method such as a high pressure method or a melting method depending on the type of the monomer constituting the copolymer, and the catalyst for the polymerization can be used with a plurality of sites and a single point contact. Media and so on. Further, in the above copolymer, the bonding shape of each monomer is not particularly limited, and a resin having a bonding shape such as random bonding or block bonding can be used. Further, from the viewpoint of optical properties, the above copolymer is preferably a copolymer which is polymerized by random bonding using a high pressure method.

In the resin sealing sheet of this embodiment, a coupling agent, an antifogging agent, a plasticizer, an antioxidant, a surfactant, and a colorant may be added within a range that does not impair the original characteristics. (coloring agent), ultraviolet absorber, antistatic agent, crystal nucleating agent, slip agent, antiblocking agent, inorganic filler (inorganic filler) ), a crosslinking regulator, an antitarnish agent, and the like. These additives can be used by a known person. In particular, when it is necessary to maintain transparency and adhesion for a long period of time, the total amount of such additives is preferably from 0 to 10% by mass based on the total amount of the resin, and the addition method is more preferably from 0 to 5% by mass. The resin can be introduced by adding a liquid to the molten resin, directly kneading the target resin layer, and applying a known additive method such as coating after film formation.

For example, a coupling agent may be added to ensure stable adhesion in the resin sealing sheet of this embodiment. The amount of the coupling agent to be added is preferably from 0.01 to 5% by mass, more preferably from 0.03 to 4% by mass, still more preferably 0.05 to the total amount of the resin, depending on the degree of the desired adhesion and the type of the substrate to be subjected. 3 mass%.

The coupling agent is preferably added to the ethylene-based copolymer, and it is preferred to impart a good adhesion to a solar cell, glass, or the like. The ethylene-based copolymer is, for example, an ethylene-vinyl acetate copolymer or an ethylene-aliphatic unsaturated carboxylic acid. The acid copolymer, the ethylene-aliphatic unsaturated carboxylic acid ester copolymer is selected from at least one resin of a vinyl copolymer. Specific examples of the coupling agent include an organic decane compound, an organic decane peroxide, and an organic titanate compound. Among the above, preferred coupling agents include those having an unsaturated group and an epoxy group: γ-chloropropyl methoxy decane, vinyl trichloro decane, vinyl triethoxy decane, and vinyl-tri ( --methoxyethoxy methoxy decane, γ-methacryloxypropyltrimethoxysilane, β-(3,4-ethoxycyclohexyl)ethyltrimethoxydecane , γ-glycidoxypropyltrimethoxysilane, vinyltriacetoxysilane, γ-mercaptopropyltrimethoxysilane, γ-amine Propyltriethoxydecane, N-β-(aminoethyl)-γ-aminopropyltrimethoxydecane, glycidoxypropyltriethoxydecane, and the like.

Further, the coupling agent can be added unobstructed by a known addition method, and the known method can be exemplified by injecting and mixing a coupling agent into a resin in an extruder, in an extruder hopper. The coupling agent is mixed and introduced, and the coupling agent is masterbatch, mixed and added. However, since it passes through the extruder, the original function is hindered by heat and pressure in the extruder, and it is necessary to increase or decrease the amount of addition according to the type of the coupling agent. Further, when mixed with a resin, the kind of the coupling agent can be suitably selected from the viewpoints of transparency of the resin, degree of dispersion, corrosion to an extruder, and extrusion stability.

Preferred ultraviolet absorbers are as follows: 2-hydroxy-4-n-octyloxydiphenyl ketone, 2-hydroxy-4-n--5-sulfonyldiphenyl ketone, 2-hydroxy-4- Methoxydiphenyl ketone, 2,2'-dihydroxy-4,4'-dimethoxydiphenyl ketone, 2-hydroxy-4-n-dodecyloxydiphenyl ketone, 2 , 4-dihydroxydiphenyl ketone, 2,2'-dihydroxy-4-methoxydiphenyl ketone, and the like.

Preferred antioxidants are phenol-based, sulfur-based, phosphorus-based, amine-based, hindered phenol-based, hindered amine-based, hydrazine-based, and the like.

These ultraviolet absorbers, antioxidants, and the like may be added not only to the ethylene copolymer but also to other resins constituting the resin layer, and the additive is preferably 0 to 10% by mass, more preferably the resin constituting each resin layer. It is 0 to 5 mass%.

In the case of a polyethylene-based resin, the resin having a sterol group can be granulated and mixed to further improve the adhesion.

The resin sealing sheet of the present embodiment may be either a single layer structure or a multilayer structure. The following description pertains to each configuration. Here, when the resin sealing sheet has a multilayer structure, the layer on the surface of the resin sealing sheet is referred to as a "surface layer", and is also referred to as an "inner layer" (in the case of three or more layers). That is, both layers forming the both surfaces of the resin sealing sheet are "surface layers". For example, when the two-layer structure is composed of two layers, the structure is composed of two surface layers, and the surface layer on one side and the surface layer on the other side may be the same component or may be different components.

[single layer structure]

The resin sealing sheet of this embodiment can satisfy any specific conditions of suspension shrinkage and gelation rate; Mui viscosity; or activation energy and storage modulus (G'), and has a density of 0.860 to 0.910 g/cm ³ A polyethylene resin, and a single layer resin sealing sheet containing no crosslinking agent. From the viewpoint of ensuring good adhesion to the substrate to be attached, it is preferred to contain at least one resin selected from the group consisting of olefin-based copolymers having a hydroxyl group, modified ends with an acidic functional group or A grafted portion of a modified polyolefin, an ethylene copolymer containing propylene glycol methacrylate.

[Multilayer construction]

The resin sealing sheet of the present embodiment preferably has a multilayer structure. The multilayer structure can impart different functions to the respective layers (resin layers), and the physical properties of the resin sealing sheets can be improved. When the resin sealing sheet has a multilayer structure, the sheet as a whole can satisfy a specific suspension shrinkage ratio, a gelation ratio, a viscoelasticity or a Mooney viscosity. Further, at least one of the resin sealing sheets of the multilayer structure may contain a polyethylene resin having a density of 0.860 to 0.910 g/cm ³ . In the entire resin sealing sheet having a multilayer structure, the content of the polyethylene resin having a density of 0.860 to 0.910 g/cm ³ is not particularly limited, but is preferably 70% by mass or more, more preferably 80% by mass or more, and still more preferably 90% by mass or more. The following description pertains to each layer.

(surface layer)

In the case of a multilayer structure, the layer (surface layer) which is in contact with the object to be sealed is preferably a resin layer containing at least one adhesive resin selected from the group consisting of an olefin-based copolymer having a hydroxyl group and an acidic functional group. A modified polyolefin having a modified terminal or grafting portion, an ethylene copolymer containing propylene glycol methacrylate.

The surface layer may be a layer formed only of the above-mentioned adhesive resin, but from the viewpoint of ensuring good transparency, flexibility, adhesion to the substrate, and handleability, the above-mentioned adhesive resin is preferably used. A layer formed by mixing a resin of at least one selected from the group consisting of a polyethylene resin having a density of 0.860 to 0.910 g/cm ³ , an ethylene-vinyl acetate copolymer, and an ethylene-aliphatic unsaturated carboxylic acid copolymerization. , an ethylene-aliphatic unsaturated carboxylic acid ester copolymer, an ethylene-vinyl acetate copolymer saponified product, an ethylene-vinyl acetate-acrylate copolymer saponified product, and a polyolefin-based resin. These resins can be used as the other resins. For example, the ethylene-aliphatic unsaturated carboxylic acid copolymer can be used, and specifically, an ethylene-acrylic acid copolymer, an ethylene-methacrylic acid copolymer, or the like can be used. The polyolefin resin may be used as the polyolefin resin, and specific examples thereof include a polyethylene resin, a polypropylene resin, and a polybutene resin.

The content of the adhesive resin in the surface layer is not particularly limited, but is preferably from 5 to 50% by mass, more preferably from 5 to 40% by mass, still more preferably from 5 to 35% by mass, from the viewpoint of adhesion.

When the resin sealing sheet has a multilayer structure, the ionizing radiation-cleaving type resin is preferably contained in a layer (surface layer) which is in contact with the object to be sealed. When the layer which is in contact with the to-be-sealed material of the resin sealing sheet contains the ionizing radiation-cracking resin, the performance (gap filling property) of sealing the gap between the power generating element and the wiring without gaps tends to be good. .

When the surface layer contains the ionizing radiation-cracking resin, the content of the ionizing radiation-cracking resin in the surface layer is preferably from 5 to 80% by mass, more preferably from 7 to 70% by mass, still more preferably from 8 to 60% by mass.

When the layer in contact with the object to be sealed contains the ionizing radiation-cracking resin, the gelation rate of the surface layer is preferably less than 3% by mass, more preferably 0.1% by mass to 2% by mass, still more preferably 0.1% by mass. The above is 1% by mass or less. When the gelation rate of the surface layer is less than 3% by mass, the gap filling property tends to be good. When the content is 0.1% by mass or more, the resin is not melted in the high temperature state such as summer to cause the sealed object to flow. , can have a tendency to stabilize the seal.

The density of the surface layer is preferably 0.870 g/cm ³ or more from the viewpoint of preventing blocking, and is preferably 0.960 g/cm ³ or less from the viewpoint of cushioning property and transparency. It is also effective to use a known imprint method as a method of preventing clogging to reduce the contact area of the surface. From the viewpoint of ensuring good adhesion, the layer ratio of the surface layer in contact with the object to be sealed is preferably at least 5% or more with respect to the entire thickness of the resin sealing sheet. When the thickness is 5% or more, the same adhesiveness as in the case of the above-described single layer structure tends to be obtained.

(inner layer)

The inner layer is preferably a layer containing a polyethylene resin having a density of 0.860 to 0.910 g/cm ³ or a layer formed of other resins, and the other resin is selected from the group consisting of at least one selected from the group consisting of ethylene-acetic acid. An ethylene copolymer, an ethylene-aliphatic unsaturated carboxylic acid copolymer, an ethylene-aliphatic unsaturated carboxylic acid ester copolymer, and a polyolefin-based resin.

For the purpose of imparting other functions, a resin material, a mixture, an additive, or the like can be appropriately selected in the inner layer. For example, a layer containing a thermosetting resin may be provided as an inner layer for the purpose of newly imparted cushioning properties. Examples of the thermoplastic resin used as the inner layer include a polyolefin resin, a styrene resin, a vinyl chloride resin, a polyester resin, a polyurethane resin, a chlorine-based polyethylene resin, and a polyamide. Resin or the like. It contains biodegradable and plant-derived raw materials. Among the above, from the viewpoint of good compatibility with the crystalline polyethylene resin and good transparency, a hydrogenated cerium segment copolymer resin, a propylene copolymer resin, and a vinyl copolymer resin are preferable. It is a hydrogenated oxime copolymer resin and a propylene-based copolymer resin.

The hydrogenated hydrazine segment copolymer resin is preferably a fluorene copolymer of a vinyl aromatic hydrocarbon and a conjugated diene. Examples of the vinyl aromatic hydrocarbons include styrene, o-methyl styrene, p-methyl styrene, p-tert-butyl styrene, 1,3-dimethyl styrene, α-methyl styrene, and vinyl naphthalene. Ethylene hydride, 1,1-diphenylethylene, N,N-dimethyl-p-aminoethylstyrene, N,N-diethyl-p-aminoethylstyrene, etc., particularly preferably benzene Ethylene. These may be used alone or in combination of two or more. The conjugated diene has a diolefin having a conjugated double bond thereto, and examples thereof include 1,3-butadiene, 2-methyl-1,3-butadiene (isoprene), and 2 , 3-dimethyl-1,3-dibutene, 1,3-pentadiene, 1,3-hexadiene, and the like. These may be used alone or in combination of two or more.

The propylene-based copolymer resin is preferably a copolymer of propylene and ethylene or an α-olefin having 4 to 20 carbon atoms. The content of the ethylene or the 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, and 3-methyl-1. -pentene, 1-decene, 1-dodecene, 1-tetradecene, 1-hexadecene, 1-octadecene, 1-icosene, and the like.

The propylene-based copolymer resin can be polymerized using a multi-site catalyst, a single-point catalyst, and any other catalyst. A vinyl copolymer having a resin crystal/non-crystalline structure (morphology) controlled by a nano order can be used.

The ethylene-based copolymer resin can be polymerized by a multi-site catalyst, a single-point catalyst, and any other catalyst. Further, a vinyl-based copolymer which controls the resin crystal/non-crystalline structure (morphology) by nano-ordering can be used.

Further, the resin sealing sheet may have a structure in which one or two or more layers of the same composition are laminated on both sides of the central layer (the layer located at the central position of the multilayer structure) so as to be symmetric with respect to the central layer. The resin sealing sheet may be, for example, a resin sealing sheet comprising two surface layers (hereinafter referred to as "surface layer") and three inner layers, wherein the surface layers of the two layers are the same component. The inner layer (hereinafter referred to as "base layer") of the two layers adjacent to the surface layer is formed of the same component.

In the resin sealing sheet having the above-described 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 preferably 50 to 50 with respect to the film thickness of the entire resin sealing sheet. 90%, the film thickness of the inner layer (hereinafter referred to as "core layer") sandwiched by the base layer is preferably 5 to 40% with respect to the film thickness of the entire resin sealing sheet.

The resin sealing sheet of this embodiment is preferably subjected to imprint processing at least a part of the surface. Blocking (blocking resistance) is prevented by imprint processing. The method of performing the imprint processing is not particularly limited, and a known method can be used. For example, the surface of the softened resin sealing film can be pressed by a platen roller to give an embossed shape. Alternatively, an embossed release paper may be used to impart an embossed shape. From the viewpoint of transfer precision of imprinting, it is preferred that the resin is formed into a sheet shape and then cooled and solidified at one time, and the resin sealing sheet after cooling and solidification is heated and softened, and then imprinted. machining. Here, "softening" (also referred to as "softening") refers to a state in which a shape can be imparted by imprinting with a platen roller, and it is usually softened by heating to a temperature higher by about 10 ° C than the melting point of the resin.

The shape and size of the embossing are not particularly limited, and suitable conditions can be selected depending on the use of the resin sealing sheet or the like. The shape (pattern) of the embossing is not particularly limited, and examples thereof include a striped shape, a woven pattern, a satin finished surface, a dermatoglyph, a diamond lattice, a synthetic leather pattern, and a wrinkle pattern. , four-cornered vertebra (ie, pyramid pattern), quadrilateral pyramidal (pyramid frustum) (ie trapezoidal cup pattern). The embossed portion preferably has a small number of planar portions, and more preferably the embossed convex portion has a ratio of 5 to 50% of the total area of the embossed portion.

It is sufficient to apply at least a part of the resin sealing sheet to the embossing process, but it is also possible to apply embossing to both sides of the resin sealing sheet. The embossing depth is preferably from 5 to 300 μm from the viewpoint of the blocking resistance of the resin sealing sheet. The embossing depth here means the depth from the convex portion of the embossed shape to the concave portion.

The resin sealing sheet of this embodiment can be used as a sealing material for sealing various members, but is particularly suitable as a resin sealing sheet for solar cells. Since the resin sealing sheet of the present embodiment is excellent in gap filling property and latent resistance, it is suitably used as a sealing material for a power generating element for sealing a solar cell.

The resin sealing sheet of the present embodiment can be obtained in various forms as described above, and the production method can be suitably adapted. For example, a method for producing a resin sealing sheet is as follows: a sheet containing a polyethylene resin having a density of 0.860 to 0.910 g/cm ³ and containing no crosslinking agent, and irradiating an ionizing radiation of 30 kGy or more and 60 kGy or less. . The irradiation conditions of the ionizing radiation can be appropriately selected from the above suitable conditions. Further, various preparation steps, processing steps, and the like described above may be appropriately combined before and after the irradiation step of the ionizing radiation.

<Solar battery module>

The resin sealing sheet of this embodiment can be used for a solar cell module. Fig. 1 is a schematic cross-sectional view showing the same state of the solar cell module of the present embodiment. In other words, the solar cell module 1 of the present embodiment includes at least a translucent insulating substrate 2, a back insulating substrate 3, a power generating element 4 disposed between the translucent insulating substrate 2 and the back insulating substrate 3, and sealing the foregoing. The resin sealing film 5 of the power generating element 4.

When the solar cell module is used, the gelation rate of the resin sealing sheet contained in the solar cell module (the gelation rate of the resin sealing sheet during solar cell module formation) is not particularly limited, but is preferably 0% by mass or more. Full 1% by mass. In other words, if the first type of resin sealing sheet is taken as an example, not only the gelation rate of the resin sealing sheet before the solar cell module can be controlled, but also the resin sealing sheet after the solar cell moduleization can be controlled. (The resin sealing sheet contained in the solar cell module) has a gelation rate, so that the gap filling property, the latent deformation resistance, the transparency, and the chromatic aberration stability can be further improved. Further, the above-mentioned second type and third type of resin sealing sheets can further improve the gap filling property, the latent denaturation resistance, the transparency, and the stability of the chromatic aberration, and need not be said. The lower limit of the gelation rate of the solar cell module is preferably 0% by mass or more, and more preferably 0.2% by mass or more from the viewpoint of resistance to latent denaturation. The upper limit of the gelation rate of the solar cell module is preferably less than 1% by mass, more preferably from the viewpoint of the gap filling property, in particular, the gap of the power generating element which is connected by the thick metal wire. It is 0.8% by mass or less. The gelation rate of the solar cell module can be measured by the method described in the examples below.

(translucent insulating substrate)

The translucent insulating substrate is not particularly limited. However, since it is located at the outermost layer of the solar cell module, it is preferable to have weather resistance, hydrophobicity, stain resistance, and mechanical strength to ensure that the solar cell is exposed to the outside. Long-term reliability performance. Further, in order to effectively utilize sunlight, a member having less optical loss and high transparency is preferable.

Examples of the light-transmitting insulating substrate material include a resin film formed of a polyester resin, a fluororesin, an acrylic resin, a cyclic olefin (co)polymer, and an ethylene-vinyl acetate copolymer, and a glass substrate, and the like, wherein weather resistance is obtained. From the viewpoint of impact resistance and cost balance, a glass substrate is preferred. The resin film is particularly suitable for polyester resins excellent in transparency, strength, cost, and the like, and particularly polyethylene terephthalate resins.

Further, it is also suitable to use a fluororesin which is particularly excellent in weather resistance. Specific examples thereof include tetrafluoroethylene-ethylene copolymer (ETFE), polyvinyl fluoride resin (PVF), polyvinylidene fluoride resin (PVDF), polytetrafluoroethylene resin (TFE), and tetrafluoroethylene-hexafluorocarbon. Propylene copolymer (FEP), polychlorotrifluoroethylene resin (CTFE). From the viewpoint of weather resistance, a polyvinylidene fluoride resin is preferred, but a tetrafluoroethylene-ethylene copolymer is preferred from the viewpoint of achieving both weather resistance and mechanical strength. Further, in order to improve the adhesion to the material constituting the other layer such as the resin sealing sheet, it is preferable to perform a corona treatment or a plasma treatment on the translucent insulating substrate. In order to increase the mechanical strength, a sheet subjected to elongation treatment such as a biaxially stretched polyethylene sheet may be used.

When a glass substrate is used as the light-transmitting insulating substrate, the total light transmittance of light having a wavelength of 350 to 1400 nm is preferably 80% or more, and more preferably 90% or more. In general, white glass having a small absorption in the infrared portion is used as the glass substrate. However, even if the thickness is 3 mm or less, the thickness of the green glass has little influence on the output characteristics of the solar cell module. Further, in order to increase the mechanical strength of the glass substrate, the tempered glass may be obtained by heat treatment, but a float glass having no heat treatment may be used. In order to suppress reflection, a coating for preventing reflection can be applied to the light-receiving surface of the glass substrate.

(back insulating substrate)

The back insulating substrate is not particularly limited. However, since it is located on the outermost layer of the solar cell module, it is required to have properties such as weather resistance and mechanical strength similarly to the above-mentioned translucent insulating substrate. Therefore, the back insulating substrate can be formed of the same material as that of the translucent insulating substrate. That is, the above various materials which can be used for the translucent insulating substrate can be used for the back insulating substrate. In particular, a polyester resin and a glass substrate are preferably used, and from the viewpoint of weather resistance and cost, polyethylene terephthalate resin (PET) is more preferable.

Since the back insulating substrate does not have to transmit sunlight, it is not necessary to require transparency (transparency) required for the translucent insulating substrate. Here, in order to increase the mechanical strength of the solar cell module, or to prevent bending and warping caused by temperature changes, a reinforcing plate may be laid. For example, a steel plate, a plastic plate, an FRP (glass fiber reinforced plastic) plate or the like can be preferably used.

The back insulating substrate may have a multilayer structure composed of two or more layers. The multilayer structure may have, for example, a structure in which one or two or more layers of the same composition are laminated on both sides of the center layer as a symmetrical central layer. Examples of such a structure include PET/aluminum vapor deposition PET/PET, PVF (trade name "Tedlar")/PET/PVF, PET/AI foil/PET, and the like.

(power generation component)

The power generating element is not particularly limited as long as it is a photovoltaic effect that can utilize a photovoltaic effect, and for example, germanium (single crystal system, polycrystalline system, amorphous), compound semiconductor (3-5 group) can be used. , 2-6, others, etc., among which polycrystalline germanium is preferred from the viewpoint of power generation performance and cost balance.

(Method of manufacturing solar cell module)

The manufacturing method of the solar cell module of the present embodiment is not particularly limited, and can be manufactured, for example, in the order of the translucent insulating substrate/resin sealing sheet a/the power generating element/resin sealing sheet b/back insulating substrate. The layers were superposed by vacuum lamination using a vacuum laminating apparatus at 150 ° C for 15 minutes. In particular, it is preferable that the resin sealing sheet of the present embodiment is used at least as a resin sealing sheet a which fills a gap between the power generating element and the light-transmitting insulating substrate. Since the sunlight passes through the resin sealing sheet of this embodiment and reaches the power generating element, it can contribute significantly to the improvement of power generation efficiency.

In the solar battery module, the thickness of each member is not particularly limited, but the thickness of the light-transmitting insulating substrate is preferably 3 mm or more from the viewpoint of weather resistance and impact resistance, and the back surface is viewed from the viewpoint of insulation. The thickness of the insulating substrate is preferably 75 μm or more; the thickness of the power generating element is preferably from 140 to 250 μm from the viewpoint of balance between power generation performance and cost; and the thickness of the resin sealing sheet is preferably from the viewpoint of cushioning property and sealing property. It is 250 μm or more.

(Example)

The present embodiment will be described in detail by way of the following examples, but the present embodiment is not limited to the following examples.

The resins used in this example are as follows:

(1) Chain-shaped low-density polyethylene 1 trade name "AFFINITY EG8200G", manufactured by The Dow Chemical Co., Ltd. (density = 0.870 g/cm ³ , MFR = 5.0 g/10 min, melting point = 63 ° C)

(2) Chain-shaped low-density polyethylene 2, trade name "AFFINITY PF1140G", manufactured by The Dow Chemical Co., Ltd. (density = 0.898 g/cm ³ , MFR = 1.6 g/10 min, melting point = 96 ° C)

(3) Chain-shaped low-density polyethylene 3 trade name "AFFINITY KC8852G", manufactured by The Dow Chemical Company (density = 0.877 g/cm ³ , MFR = 3.0 g/10 min, melting point = 68 ° C)

(4) Chain-shaped low-density polyethylene 4, trade name "ENGAGE 8403", manufactured by The Dow Chemical Company (density = 0.913 g/cm ³ , MFR = 30 g/10 min, melting point = 107 ° C)

(5) An ethylene copolymer containing propylene glycol methacrylate (GMA) under the trade name "Bondfast 7B", manufactured by Sumitomo Chemical Co., Ltd. (GMA = 12% by mass, VA = 5% by mass, density = 0.950 g/cm ³ , MFR =7.0 g/10 min, melting point = 95 ° C)

(6) The decane coupling agent "KBM503", manufactured by Shin-Etsu Chemical Co., Ltd. (3-methacryloxypropyltrimethoxydecane, specific gravity: 1.04), was measured for the density of the resin based on JIS K 7112.

The melting point of the resin was measured in accordance with JIS K 7121.

The melt flow rate of the resin (MFR; 190 ° C, 2.16 k kg) was measured in accordance with JIS K 7210.

<Examples 1 to 3, Comparative Examples 1 to 8, 10 (Production of Resin Sealing Sheet)>

The resin shown in Tables 1 and 2 was used, and the resin was melted using three extruders, and the resin was extruded in a tubular shape from a ring die attached to the extruder. The formed tube was extruded upward, and a molten resin sealing sheet was obtained by a direct inflation method. The resin sealing sheet was obtained by blowing it with cold air to cool and solidify it. Next, the cooled and cured resin sealing sheet is mainly heated by an infrared heater, and the softened resin sealing film is passed between a back-up roller and an impression roller, thereby performing imprint processing. (embossed shape: four-corner pedestal, embossing depth: 50 μm). The obtained resin sealing sheet (embossing sheet) was subjected to crosslinking treatment by irradiating an electron beam with an EPS-800 electron beam irradiation apparatus (manufactured by Nisshin Electric Co., Ltd.). Thus, a resin sealing sheet of the three-layer structure of Examples 1 to 3 and Comparative Examples 1 to 8 was obtained. Similarly, the resin shown in Table 3 was used, and a resin of the same composition was melt-extruded using three extruders to obtain a resin sealing sheet of the single layer structure of Comparative Example 10.

<Comparative Example 9 (Preparation of a resin sealing sheet using a decane-modified resin)>

Compared with chain low density polyethylene 2 ("AFFINITY PF1140G"; (density = 0.897 g/cm ³ , MFR = 1.6 g/10 min, melting point = 96 ° C) 98% by mass, a decane coupling agent was mixed therein ("KBM503" 2% by mass of 3-methacryloxypropyltrimethoxydecane) and 0.1% by mass of dicumyl peroxide of a radical generator, and heated and melted at 200 ° C to obtain The decane-modified resin was mixed with a decane-modified resin of 5% by mass and a chain-shaped low-density polyethylene 2 ("AFFINITY PF1140G") of 95% by mass, and the same operation as in Comparative Example 10 was carried out to obtain a single layer of Comparative Example 9. The resulting resin sealing sheet was constructed, and the resin sealing sheet was not subjected to crosslinking treatment.

<Making a solar cell module>

A solar cell module was produced using the following materials: a resin sealing sheet obtained by an AGC company, and a whiteboard glass for embossed solar cells (thickness 3.2 mm × width 700 mm × length 1000 mm, pressure of 150 μm on the sealing material surface) As a transparent protective material, a polycrystalline silicon battery (6 吋 square × thickness 200 μm) manufactured by E-TON Co., Ltd. as a power generation element, PVF (thickness 40 μm) / PET (thickness 250 μm) / PVF (thickness) manufactured by Mitsubishi Aluminum Packaging Co., Ltd. 40 μm) as a backing material (backsheet). 16 (4 columns × 4) 6-inch polycrystalline batteries are arranged, and a transparent substrate (transparent protective material) / resin sealing sheet (a) / power generating element (200 μm) / resin sealing sheet (b) / back sheet (back) In the order of the protective material), the LM type vacuum laminating apparatus (manufactured by NPC Co., Ltd.) was used to preheat the film at 150 ° C for 5 minutes and the laminate was pressed for 10 minutes to form a solar cell module, and each evaluation was performed. test.

<gelation rate>

Based on JIS K 6796, the sample was boiled in p-xylene for 8 hours ± 5 minutes and then extracted. The ratio of the insoluble portion of the sample after extraction to the sample before extraction was the gelation rate. The gelation rate is used as a basis for the degree of crosslinking of the resin sealing sheet.

Gelation rate (% by mass) = (sample quality after extraction / sample quality before extraction) × 100

Further, using an oven, the resin sealing sheet was subjected to a thermal history of 15 minutes at 150 ° C, and its gelation ratio was obtained by the same operation as described above. This gelation rate is used as a benchmark for the degree of crosslinking of the resin sealing sheet after the solar cell module is fabricated.

<150°C suspension shrinkage>

The obtained resin sealing sheet was cut into a width of 20 mm × a length of 130 mm, and a central portion of 100 mm in length after leaving 10 mm and 20 mm at both ends in the longitudinal direction, and a line was indicated by an oily stroke having a thickness of 0.5 to 1.0 mm. Then, the end portion of the long direction remaining 20 mm was sandwiched by a clip, and hung in an oven at 150 ° C, and taken out after the oven temperature indicating value returned to 150 ° C for 10 minutes, and the measurement showed a dimensional change of 100 mm between the lines, and the following The formula is used to reduce the shrinkage rate. Those who have an elongation of more than twice (the shrinkage rate is -100% or less) are recorded as "flowing".

Shrinkage (%) = 100 - after the test, the length between the lines (mm)

<Evaluating the gap filling of the power generation part>

Glass plate for solar cell (manufactured by AGC, white plate glass 5 cm × 10 cm square: thickness 3 mm) / resin sealing sheet (thickness 600 μm) / power generation portion / resin sealing sheet / glass plate for solar cell overlap, using LM50 vacuum The lamination device (NPC Co., Ltd.) was vacuum-laid at 150 ° C, and the contact state of the single crystal germanium battery of the power generation portion with the resin sealing sheet was visually confirmed. Two connecting wires (thickness: 300 μm) were respectively wired on both sides of a single crystal germanium battery (thickness: 200 μm) in the power generating portion. The shape of the power generating portion was a part of both sides of the battery having a thickness of 200 μm, and a 300 μm convex portion was present. The overall thickness of the power generating portion is made 200 μm to 800 μm. The contact condition of the power generation portion was visually determined and performed by the following criteria.

○: The single crystal germanium battery and the connecting wire of the power generating portion were all in good contact with the resin sealing sheet.

X: The single crystal germanium battery of the power generation portion and the connecting wire have a gap with the contact portion of the resin sealing sheet. Or when the laminate is laminated, the sealing sheet extends beyond the end of the glass sheet due to heat flow.

<Evaluation of latent resistance>

Glass plate for solar cell (manufactured by AGC, white plate glass 5 cm × 10 cm square: thickness 3 mm) / resin sealing sheet / power generation portion (single crystal neodymium battery (thickness: 250 μm)) / resin sealing sheet / glass plate for solar cell The LM50 vacuum laminator (NPC Co., Ltd.) was used for vacuum lamination, and the glass plate on one side of the laminated solar cell was fixed to the wall surface of the thermostat set at 85 ° C for 24 hours, and the sliding of the other glass plate was measured.

○: The sliding of the glass plate was less than 3 mm.

×: The sliding of the glass plate was 3 mm or more.

<Measurement of melt viscoelasticity and activation energy>

Melt viscoelasticity was carried out using a multi-function SMT rheometer (ARES) manufactured by TA Instruments, in the range of 150 to 250 ° C (scale 50 ° C) with a frequency dispersion of 0.1 to 100 radians / sec. (Measurement of storage modulus (G')). The sample was adjusted to a diameter of 50 mm Φ and a parallel plate was used.

The activation energy (ΔH) was calculated according to the following (1) to (3) by the obtained storage modulus (G').

(1) The storage modulus (G') was measured at 150 ° C, 200 ° C, and 250 ° C in the frequency range of 10-1 to 102 rad / sec.

(2) The master curve of the reference temperature of 150 ° C is created by the principle of overlapping the stored modulus curves of the respective temperatures. Thereby, a shift factor (a _T ) of each temperature is obtained.

(3) The activation energy (ΔH) is obtained from the obtained translation factor by the Arrhenius plot. (Refer to equation (1))

Log(a _T )=(ΔH/R)‧(1/T-1/T0) (1)

a _T = translation factor of temperature T relative to the reference temperature

ΔH=activation energy (KJ/mol)

R=8.31447 (J‧K ^-1 ‧mol ^-1 )

T = measured temperature (K)

T ₀ = reference temperature (K)

<Muni viscosity>

Based on JIS K 6300-1, it was measured by the Murray Viscometer (MVR) MODEL VR-1130 manufactured by Ueshima Manufacturing Co., Ltd. The roll shape was measured by an L-shaped roll at a test temperature of 100 ° C for 1 minute, a measurement time of 4 minutes, and a rotation number of 2 RPM. Further, the values obtained from the test results of one time are rounded to the integer position in accordance with JIS Z 8401 to indicate the test results.

<Full light transmittance and haze>

The measurement was carried out by a haze meter (turbidity meter) NDH2000 manufactured by Nippon Denshoku Industries Co., Ltd. based on ASTM D-1003. The evaluation sample was prepared by laminating a glass plate for a solar cell (manufactured by AGC, white plate glass 5 cm × 10 cm square: thickness 3 mm) / resin sealing sheet / glass plate for solar cell, and using LM type vacuum laminate A device (manufactured by NPC Co., Ltd.) performs vacuum lamination.

Total light transmittance Tt (=Td+Tp)

Dip light transmittance Td(Dfs)

Parallel light transmittance Tp(P.t)

Haze Hz (haze): scattered light transmittance [= (total light transmittance - parallel light transmittance) / total light transmittance]

The haze of the initial resin sealing sheet was measured by the above method, and then the haze was measured again in the oven at 120 ° C for 120 hours.

<color difference>

The b value was measured by a color difference meter Z-300A manufactured by Nippon Denshoku Industries Co., Ltd. based on the JIS Z 8722 color measurement method. The evaluation sample was prepared by laminating a glass plate for a solar cell (manufactured by AGC, white plate glass 5 cm × 10 cm square: thickness 3 mm) / resin sealing sheet / back sheet (back surface protective material), and using the LM type. A vacuum laminator (NPC) performs vacuum lamination.

The color difference of the original resin sealing sheet was measured by the above method, and then the color difference was measured again in the oven at 120 ° C for 120 hours.

Further, as an example, in Example 3, the storage modulus (G') of the sheets obtained at temperatures of 150 ° C, 200 ° C, and 250 ° C is plotted as a graph and shown in FIG. 2 . The translation factor (a _T ) thus obtained is shown in Table 4, and the Arrhenius diagram of the obtained translation factor is shown in Fig. 3. The activation energy values thus obtained are shown in Table 1. In the other examples and comparative examples, the obtained activation energy (ΔH) was obtained by the same operation, and the values are shown in Table 1, Table 2, and Table 3.

The production conditions and evaluation results of the respective examples and comparative examples are shown in Table 1, Table 2, and Table 3.

As shown in Table 1, it was confirmed that the resin sealing sheets of the respective examples were excellent in gap filling property, latent resistance, haze after heat treatment, and chromatic aberration. On the other hand, as shown in Table 2 and Table 3, the evaluation results of the resin sealing sheets of the respective comparative examples were confirmed, and at least one of them was defective.

(industrial availability)

The resin sealing sheet of the present embodiment has the following industrial applicability as a sealing material for sealing various members such as a power generating element constituting a solar battery.

1. . . Solar battery module

2. . . Translucent insulating substrate

3. . . Back insulating substrate

4. . . Power generation component

5. . . Resin sealing sheet

Fig. 1 is a schematic cross-sectional view showing the same state of the solar battery module of the present embodiment.

Fig. 2 is a graph in which the storage modulus (G') of the sheet obtained at each of 150 ° C, 200 ° C, and 250 ° C was plotted in Example 3.

Fig. 3 is a graph showing the Arrhenius plot of the translation factor obtained in Example 3.

1. . . Solar battery module

2. . . Translucent insulating substrate

4. . . Power generation component

5. . . Resin sealing sheet

Claims (8)

A resin sealing sheet comprising a polyethylene resin having a density of 0.860 to 0.910 g/cm ³ and containing no crosslinking agent, having a shrinkage ratio of 0 to 25% when suspended at a temperature of 150 ° C, and a gelation rate of 0 The mass% or more and less than 1 mass%. A resin sealing sheet containing a polyethylene resin having a density of 0.860 to 0.910 g/cm ³ and containing no crosslinking agent and having a Mui viscosity of 70 to 90 M. A resin sealing sheet containing a polyethylene resin having a density of 0.860 to 0.910 g/cm ³ and containing no crosslinking agent, and satisfying the following conditions (1) and (2) (1) by measuring 150 to 250 The activation energy calculated by the melt viscoelasticity of °C is 75 to 90 kJ/mol; and (2) the storage modulus (G,) measured at 1 rad/sec at 150 ° C is 6,000 to 12,000 Pa. The resin sealing sheet according to any one of claims 1 to 3, which is subjected to a crosslinking treatment. The resin sealing sheet according to claim 4, wherein the crosslinking treatment is carried out by irradiation with ionizing radiation. The resin sealing sheet according to claim 5, wherein the ionizing radiation irradiated by the ionizing radiation is 30 kGy or more and 60 kGy or less. A solar cell module comprising: a translucent insulating substrate; a back insulating substrate disposed opposite to the translucent insulating substrate; and a power generating disposed between the translucent insulating substrate and the back insulating substrate The resin sealing sheet according to any one of the items 1 to 6 of the invention of the present invention. The solar cell module according to claim 7, wherein the resin sealing sheet contained in the solar cell module has a gelation ratio of 0% by mass or more and less than 1% by mass.