KR101871293B1 - Solar cell backside protective sheet and solar cell - Google Patents

Abstract

Provided is a solar cell backing sheet and a solar cell module which are excellent in long term reliability and moisture resistance, excellent in adhesion under a low temperature environment, and excellent in cost and surface coverage. The solar cell backsheet of the present invention is characterized in that the adhesive layer for bonding at least one side of the thickest substrate among the outer layer substrate, the intermediate layer substrate and the inner layer substrate is a linear polyester polyol having a specific structure, a polyester polyurethane polyol and a bisphenol- And an adhesive containing a curing agent containing isocyanurate, and the adhesive contains 4 to 12 parts by weight of the solid of the curing agent with respect to 100 parts by weight of the solid matter of the subject.

Description

BACKGROUND OF THE INVENTION 1. Field of the Invention [0001] The present invention relates to a solar cell module,

BACKGROUND OF THE INVENTION 1. Field of the Invention [0002] The present invention relates to a solar cell back protection sheet used on the back side of a solar cell module, and a solar cell module having the protection sheet on the back side of the solar cell.

In recent years, photovoltaic (PV) power generation, which converts light energy into electrical energy using a quantum effect unique to semiconductors, is drawing attention. A solar cell module is used for solar power generation, and a protective sheet (so-called back sheet) is provided on the back side of the solar cell for protection and insulation purposes.

The solar cell module is required to have a long life time of several decades, and long-term reliability is likewise required for the back sheet for protecting it. In addition, the back sheet is required to have good insulation property against electricity generated in a power generation element called a cell, and good adhesion with an encapsulating material sealing the cell. In order to meet such a demand, there has been proposed a back sheet obtained by laminating a variety of conventional resin films or metal foils through an adhesive (for example, Patent Documents 1 and 2).

Further, an outdoor polyurethane-based adhesive containing a polyester polyol and a polyester polyurethane polyol has been proposed (Patent Document 3).

Japanese Patent Application Laid-Open No. 2010-278375 Japanese Patent Application Laid-Open No. 2009-290201 Japanese Patent Application Laid-Open No. 2010-043238

The backsheet is strongly required to have high long-term reliability. This requires good adhesion to the adhesive used in the backsheet and weatherability that can withstand long-term use. Further, it is required that the adhesive can be easily coated by a general coating method such as gravure coating, comma coating and the like, while being cost-effective. Further, it is required to be able to exhibit excellent adhesive force even in an environment of excellent heat and moisture resistance and a temperature lower than room temperature. Existing backsheets have room for further improvement in this respect.

The present invention has been made in view of the above background, and provides a solar cell backing sheet and a solar cell module which are excellent in long-term reliability and heat resistance, excellent in adhesion under a low temperature environment, The main purpose is.

The inventor of the present invention has made intensive studies to achieve the above object and as a result, it has been found that an adhesive containing a subject of a specific composition and a curing agent is used and the above object can be achieved by setting a specific amount of a specific curing agent for the subject And have completed the present invention.

That is, the solar cell backing sheet according to the present invention has at least 1) an outer layer substrate 2) an intermediate layer substrate having weatherability, and 3) an encapsulating material for sealing a power generating element used in a solar cell module, Wherein the adhesive layer for bonding at least one side of the thickest substrate among the outer layer substrate, the intermediate layer substrate and the inner layer substrate comprises a main layer containing the following (1) to (3) Which is formed by an adhesive,

The adhesive contains 4 to 12 parts by weight of the solid content of the curing agent relative to 100 parts by weight of the solid content of the subject.

(1) a dibasic acid component comprising 40 to 70 mol% of an aromatic dibasic acid and 30 to 60 mol% of an aliphatic dibasic acid having 9 to 10 carbon atoms and 30 to 40 mol% of an aliphatic divalent alcohol having 5 or more carbon atoms A straight chain polyester polyol having a weight average molecular weight of 70,000 to 80,000, which is obtained by reacting a dihydric alcohol component.

(2) a dibasic acid component comprising 60 to 80 mol% of an aromatic dibasic acid and 20 to 40 mol% of an aliphatic dibasic acid having 9 to 10 carbon atoms and 70 to 80 mol% of an aliphatic divalent alcohol having 5 or more carbon atoms A polyester polyurethane polyol having a weight average molecular weight of 30,000 to 40,000, which is obtained by reacting a polyester polyol obtained by reacting a dihydric alcohol component with an organic diisocyanate.

(3) Bisphenol-type epoxy resins having a number average molecular weight of 1,000 to 2,000.

(4) Polyisocyanates having isocyanurate of isophorone diisocyanate.

The thickness of the thickest substrate is preferably 125 to 350 μm, and the amount of the adhesive of the adhesive layer contacting the thickest substrate is preferably 5 g / m 2 or more and 30 g / m 2 or less.

In addition, it is preferable that a plurality of the above-mentioned intermediate layer base materials are bonded at least partially to each other through the adhesive layer.

It is preferable that the straight chain polyester polyol is 60 to 80% by weight of the total 100% by weight of the straight chain polyester polyol and the polyester polyol.

The solar cell module according to the present invention is equipped with a protective sheet in the case of the solar cell of the above-described type.

According to the protective sheet of the solar cell backing sheet of the present invention, a protective sheet for a solar cell excellent in long-term reliability and heat resistance, excellent in adhesion in a low-temperature environment, excellent in cost and excellent in coatability, and a solar cell module Can exhibit excellent effects.

1 is a view showing a layer structure of a protective sheet in the case of a solar cell manufactured in the embodiment of FIG.
2 is a view showing a layer structure of a protective sheet in the case of a solar cell manufactured in a comparative example.

Hereinafter, the present invention will be described in detail. Needless to say, other embodiments are also included in the scope of the present invention as long as the spirit of the present invention is satisfied. In the present specification, the phrase " any A to arbitrary number B " means a range that is larger than the number A and the number A and smaller than the number B and the number B.

The solar cell backing sheet of the present invention comprises at least 1) an outer layer substrate 2) an intermediate layer substrate having weather resistance, 3) an encapsulating material for sealing a power generating element used in the solar cell module, and an inner layer substrate having good adhesion. The solar cell backing sheet according to the present invention is characterized in that the adhesive layer for bonding at least one side of the thickest substrate among the outer layer substrate, the intermediate layer substrate and the innerlayer substrate comprises a base containing the following (1) to (3) By weight of a curing agent. Therefore, within the range that satisfies the above conditions, the protective sheet of the solar cell of the present invention can be bonded to each other by another adhesive. The inner layer substrate is disposed on the surface of the light emitting element side of the protective sheet in the case of a solar cell, and the outer layer substrate is disposed in the farthest position from the light emitting element. The intermediate layer substrate may be a single layer or a plurality of layers. In the case of a solar cell, the protective sheet is required to have a withstand voltage property. It is preferable that the withstand voltage property is mainly provided in the intermediate layer base material. However, when a plurality of intermediate-layer substrates are provided, all of the intermediate-layer substrates may not have a withstand voltage property. Hereinafter, the term " adhesive " refers to an adhesive of the present invention containing a subject containing the following (1) to (3) and a curing agent of the following (4)

It is preferable that the thickness of the thickest substrate among the outer layer substrate, the intermediate layer substrate and the inner layer substrate is 125 to 350 占 퐉. It is also preferable that the adhesive amount after drying of the adhesive layer in contact with the thickest substrate is in the range of 5 g / m 2 to 30 g / m 2. The reason will be described later. The thickest substrate may be an outer layer substrate, an intermediate layer substrate and an inner layer substrate, but it is preferable that the intermediate layer substrate is the thickest substrate. In the case where the outer layer substrate or the inner layer substrate is the thickest substrate, the coated surface of the adhesive amount becomes one surface, but in the case of the thickest substrate, the coating conditions are satisfied on at least one surface of the two bonded surfaces of the intermediate layer substrate . It is more preferable that the adhesive layer of the present invention is in the range of 5 g / m < 2 > to 30 g / m < 2 > in the case of the substrate having the thickest intermediate layer substrate. In addition, the above-mentioned adhesive can be suitably applied to the bonding of the substrates other than the thickest substrate. That is, the adhesive of the present invention can be suitably used for bonding of each substrate (for example, a plastic film, a metal foil, and the like) constituting the protective sheet as long as it is a solar cell.

The adhesive of the present invention is a polyurethane-based adhesive containing a base and a curing agent. The adhesive may be a two-liquid type adhesive which mixes a base and a curing agent at the time of use, or may be a one-part type adhesive in which a base and a curing agent are mixed in advance. Further, it is also possible to use a mixture of a plurality of themes and / or various curing agents when they are used.

The main theme of the adhesive is (1) a dibasic acid component comprising 40 to 70 mol% of aromatic dibasic acid and 30 to 60 mol% of aliphatic dibasic acid having 9 to 10 carbon atoms and 30 to 40 mol of aliphatic dihydric alcohol having 5 or more carbon atoms (2) an aromatic dibasic acid in an amount of from 60 to 80 mol% and an aliphatic dibasic acid in a carbon number of from 9 to 10 in an amount of from 20 to 40 mol%, wherein the polyester polyol has a weight average molecular weight of 70,000 to 80,000, % And a dihydric alcohol component containing 70 to 80 mol% of an aliphatic dihydric alcohol having 5 or more carbon atoms, with an organic diisocyanate is reacted with an organic diisocyanate to have a weight average molecular weight of 30,000 to 40,000 (3) a bisphenol-type epoxy resin having a number average molecular weight of 1,000 to 2,000.

The curing agent of the adhesive contains (4) a polyisocyanate having isocyanurate of isophorone diisocyanate. The adhesive of the present invention contains 4 to 12 parts by weight of the solid content of the curing agent relative to 100 parts by weight of the solid content of the subject. More preferably 6 to 12 parts by weight, and still more preferably 8 to 10 parts by weight.

[(1) Direct chain polyester polyol]

The straight chain polyester polyol (hereinafter simply referred to as " polyester polyol ") used in the present invention is a dibasic acid component comprising 40 to 70 mol% of an aromatic dibasic acid and 30 to 60 mol% of an aliphatic dibasic acid having 9 to 10 carbon atoms And 30 to 40 mol% of an aliphatic dihydric alcohol having 5 or more carbon atoms. And may include dibasic acids and polyhydric alcohol components having different structures as long as the above conditions are satisfied.

Examples of dibasic acids and ester compounds thereof include isophthalic acid, terephthalic acid, naphthalenedicarboxylic acid, phthalic anhydride, adipic acid, azelaic acid, sebacic acid, succinic acid, glutaric acid, anhydrous tetrahydrophthalic acid, Phthalic acid, maleic anhydride, itaconic anhydride and ester compounds thereof.

In the present invention, these can be appropriately used in combination. However, the aromatic dibasic acid in an amount of 40 to 70 mol% (preferably 50 to 60 mol%) and the aliphatic dibasic acid having 9 to 10 carbon atoms in an amount of 30 to 60 Mol% (preferably 40 to 50 mol%).

If the amount of the aromatic dibasic acid is less than 40 mol%, sufficient heat resistance and viscoelasticity may not be obtained. When the content is 70 mol% or less, the adhesive force can be exerted more effectively. In addition, when the aliphatic dibasic acid having 9 to 10 carbon atoms is contained in an amount of 30 mol% or more, it is possible to make the polyester polyol ester bonding degree suitable, thereby suppressing the hydrolysis starting point and leading to long-term moisture resistance. When the aliphatic dibasic acid having 9 to 10 carbon atoms is contained in an amount of 60 mol% or less, the heat resistance and viscoelasticity can be appropriately adjusted and the adhesive force can be more effectively expressed.

Of the above exemplified compounds, aromatic dibasic acids are preferably terephthalic acid, dimethyl terephthalate, isophthalic acid and phthalic anhydride from the viewpoint of reactivity in the transesterification reaction. As the aliphatic dibasic acids having 9 to 10 carbon atoms, azelaic acid having 9 carbon atoms and sebacic acid having 10 carbon atoms are preferred from the viewpoints of high lipophilicity, hydrophobicity, and suppression of absorption of the polymer.

Specific examples of polyhydric alcohols include ethylene glycol, diethylene glycol, triethylene glycol, propylene glycol, dipropylene glycol, 1,6-hexanediol, neopentyl glycol, 1,4-butylene glycol, 1,4- Cyclohexanedimethanol, 1,9-nonanediol, 3-methyl-1,5-pentanediol, and the like. These may be used singly or in combination of two or more, but an aliphatic divalent alcohol having 5 or more carbon atoms is used in a proportion of 30 to 40 mol% (preferably 32 to 38 mol%) with respect to the total amount of the polyhydric alcohol.

By setting the ratio of the dihydric alcohol component to the aliphatic divalent alcohol having 5 or more carbon atoms to 30 mol% or more, it is possible to suppress the increase of the hydrolytic cleavage point by suitably controlling the degree of polyester polyol ester bonding, have. When the proportion of the aliphatic dihydric alcohol is 40 mol% or less, the solubility of the product in the organic solvent is improved, and the coating property of the adhesive becomes good.

Of the above exemplified compounds, neopentyl glycol having 5 carbon atoms, 3-methyl-1,5-pentanediol having 6 carbon atoms and aliphatic dihydric alcohols having 5 or more carbon atoms having side chains and having improved solubility stability, And 1,6-hexanediol, which inhibits the absorption of the polymer, is preferred.

The weight average molecular weight of the polyester polyol is 70,000 to 80,000 from the viewpoint of securing cohesion, stretchability and adhesive strength. Among these, from the viewpoints of the solubility of the resin, the viscosity, and the coating property (handling property) of the adhesive, it is more preferable that it is 72,000 to 78,000.

The number average molecular weight of the present invention was measured by GPC (gel permeation chromatography) "HPC-8020" manufactured by TOSOH CORPORATION. It is a liquid chromatography that separates and quantifies a substance dissolved in a GPC solvent (THF; tetrahydrofuran) by a difference in the molecular size. In the measurement of the present invention, two columns of "LF-604" (GPC column for rapid analysis: 6MMID × 150MM size) were connected in series and a flow rate of 0.6ML / MIN and a column temperature of 40 ° C , And the weight average molecular weight (Mw) was determined in terms of polystyrene.

[(2) Polyester polyurethane polyol]

The polyester polyurethane polyol used in the present invention is a polyester polyurethane polyol having an aromatic dibasic acid content of 60 to 80 mol% (preferably 65 to 75 mol%) and an aliphatic dibasic acid having 9 to 10 carbon atoms in an amount of 20 to 40 mol% 35 mol%), and a dihydric alcohol component containing 70 to 80 mol% (preferably 72 to 78 mol%) of an aliphatic divalent alcohol having 5 or more carbon atoms to the polyester polyol Organic diisocyanate is reacted.

When the aromatic dibasic acid is used in an amount of 60 mol% or more, heat resistance and viscoelasticity can be effectively obtained. On the other hand, when the content is 80 mol% or less, the adhesive force can be more effectively exhibited. Further, when the aliphatic dibasic acid having 9 to 10 carbon atoms is contained in an amount of 20 mol% or more, the polyester polyol ester bonding degree can be suitably controlled to suppress the hydrolysis starting point and to lead to long-term moisture resistance. In addition, when the aliphatic dibasic acid having 9 to 10 carbon atoms is contained in an amount of 40 mol% or less, the effect of adjusting the heat resistance and viscoelasticity appropriately and exhibiting the adhesive force more effectively is obtained. In addition, by setting the ratio of the aliphatic dihydric alcohol having 5 or more carbon atoms to 70 mol% or more, it is possible to suppress the increase of the hydrolysis starting point by appropriately controlling the polyester polyol ester bonding degree, and to obtain the long-term moisture wettability more effectively. When the proportion of the aliphatic divalent alcohol is 80 mol% or less, the solubility of the product in the organic solvent becomes satisfactory, and the coating property of the adhesive becomes good.

The description of aromatic dibasic acids, aliphatic dibasic acids and aliphatic divalent alcohols having 5 or more carbon atoms is the same as described above.

The organic diisocyanate is not particularly limited. Specific examples include 2,4-tolylene diisocyanate, 2,6-tolylene diisocyanate, xylene diisocyanate, diphenylmethane diisocyanate, isophorone diisocyanate, 1,5-naphthalene diisocyanate, hexamethylene diisocyanate, And hydrogenated diphenylmethane diisocyanate. These may be used alone or in combination of two or more. From the viewpoint of reducing the yellowing of the adhesive over time, it is preferable to use an aliphatic or alicyclic isocyanate compound as the urethane crosslinking moiety.

By using the polyester polyurethane polyol and the polyester polyol in combination, the degree of ester bonding (as described later) of the entire polyol component can be lowered. As a result, the hydrolysis starting point can be reduced and the heat resistance can be improved.

The weight average molecular weight of the polyester polyurethane polyol is 30,000 to 40,000 in view of adjusting the viscosity of the polyester polyol with consideration of the weight average molecular weight of the polyester polyol and the high viscosity. And more preferably 32,000 to 38,000.

[(3) Bisphenol-type epoxy resin]

The bisphenol type epoxy resin used in the present invention preferably has a number average molecular weight of 1,000 to 2,000 and an epoxy equivalent of 500 to 1,000 g / eq. By including the bisphenol type epoxy resin, it is expected that the epoxy group reacts with the carboxyl group generated by the hydrolysis of the ester bond due to the hydrophobicity of the bisphenol skeleton, thereby suppressing the decrease in the molecular weight.

Among the bisphenol-type epoxy resins, bisphenol A type epoxy resins and bisphenol F type epoxy resins are preferable from the viewpoint of maintaining the shear strength, and they may be used alone or in combination of two or more kinds.

The number average molecular weight of the bisphenol-type epoxy resin may be 1,000 to 2,000 from the viewpoints of adjusting the heat resistance, viscoelasticity and solution viscosity of the adhesive cured film. If the number-average molecular weight of the bisphenol-type epoxy resin is less than 1,000, there is a fear that sufficient heat resistance may not be obtained. Further, when the number average molecular weight is 2,000 or less, the adhesive force can be exerted more effectively. In addition, in the present invention, since an epoxy resin having a low molecular weight is used in view of the use of a high molecular weight polyol, the viscosity of the adhesive solution is lowered and an effect of improving the coatability is expected. However, by setting the number average molecular weight to 2,000 or less, Can be effectively reduced. It is preferable that the number average molecular weight of the bisphenol-type epoxy resin is in the range of 1,200 to 1,800 in terms of balance between heat resistance and adhesion at low temperatures.

The content of the bisphenol-type epoxy resin is preferably 50% by weight or less, more preferably 20-40% by weight, from the viewpoint of adjusting the viscoelasticity of the adhesive cured coating, in consideration of adhesive strength.

[Subjects containing the above ingredients]

The composition ratio of the polyester polyol and the polyester polyurethane polyol (hereinafter collectively referred to as " polyol component ") is not particularly limited, but it is preferable that the polyester polyol is used in an amount of 60 to 80% , And it is more preferable to use 65 to 75 wt%. By setting the ratio of the polyester polyol as the polyol component to be 80% by weight or less, it is possible to more effectively obtain the heat and humidity resistance. On the other hand, when the ratio of the polyester polyol is 60% by weight or more, the adhesion at low temperature can be further improved. Therefore, it is preferable that the ratio of the polyester polyol of the polyol component is in the range of 60 to 80 wt% in balance of the wet heat resistance and the adhesive force at low temperature.

The present invention is designed so that the ratio of the ester bond by the reaction between the carboxyl group and the hydroxyl group of the polyol component (the reaction ratio of the carboxyl group and the hydroxyl group is 1: 1) is less than 1 when the ester linkage degree of the molecule (mol / . In other words, the degree of ester bonding can be lowered to lower the ratio of ester bonds to increase the hydrolysis resistance, thereby further suppressing deterioration of adhesive strength over time and improving the heat and humidity resistance of the organs. In this respect, in the present invention, since dibasic acids having 9 to 10 carbon atoms and polyhydric alcohols having 5 or more carbon atoms having a large molecular weight and having a large molecular weight are used as the dibasic acids, the degree of ester bonding in the unit weight (in 100 g) becomes small.

Particularly, considering both the bonding strength at room temperature and the bonding strength under high temperature (80 to 150 占 폚 and the like), the ester bonding degree of the polyol component is preferably in the range of 0.75 to 0.99. Such an ester bond degree can be achieved within the range of the aromatic dibasic acid ratio of the dibasic acid component of the adhesive used in the present invention and the carbon number of the polyhydric alcohol. The acid value (mgKOH / g) of the polyol component is preferably 5 or less, more preferably 2 or less.

The adhesive base may contain, in addition to the polyol component and the bisphenol-type epoxy resin, any additives insofar as the effect of the present invention is not impaired. Examples of the additive include a silane coupling agent reaction promoter, a leveling agent, and an antifoaming agent.

Examples of the silane coupling agent include trialkoxysilane having a vinyl group such as vinyltrimethoxysilane and vinyltriethoxysilane, 3-aminopropyltriethoxysilane, N- (2-aminoethyl) 3-aminopropyl Trialkoxysilane having an amino group such as trimethoxysilane; Trialkoxysilane having a glycidyl group such as 3-glycidoxypropyltrimethoxysilane, 2- (3,4-epoxycyclohexyl) ethyltrimethoxysilane and 3-glycidoxypropyltriethoxysilane, . These silane coupling agents may be used alone or in combination of two or more.

The amount of the silane coupling agent to be added is preferably 0.5 to 5% by weight, more preferably 1 to 3% by weight based on the whole amount of the base. When the amount is less than 0.5 wt%, the effect of improving the bonding strength is insufficient even when a silane coupling agent is added, and further improvement in performance is not recognized even if the amount exceeds 5 wt%.

Examples of the reaction accelerator include metal catalysts such as dibutyl tin diacetate, dibutyl tin dilaurate, dioctyltin dilaurate and dibutyl tin dimaleate; (5,4,0) undecene-7, 1,5-diazabicyclo (4,3,0) nonene-5,6-dibutylamino-1,8-di Tertiary amines such as carbacycl (5,4,0) undecene-7; And reactive tertiary amines such as triethanolamine. One or two or more reaction accelerators selected from these groups can be used.

Examples of the leveling agent include polyether-modified polydimethylsiloxane, polyester-modified polydimethylsiloxane, aralkyl-modified polymethylalkylsiloxane, polyester-modified hydroxyl-containing polydimethylsiloxane, polyetherester-modified hydroxyl-containing polydimethylsiloxane, , A methacrylic polymer, a polyether-modified polymethylalkylsiloxane, an acrylic acid alkyl ester copolymer, a methacrylic acid alkyl ester polymer, and lecithin.

Examples of the defoaming agent include a silicone resin, a silicone solution, a copolymer of an alkyl vinyl ether and an alkyl acrylate and methacrylate alkyl ester.

[Curing agent]

The curing agent used in the present invention includes a polyisocyanate having an isocyanurate of isophorone diisocyanate. This isocyanate has a long boat life after being mixed with the base, has good solution stability, and also has a long-term moist heat resistance of the adhesive. The content of isocyanurate is 50 to 100% by weight in the polyisocyanate. In addition, isocyanurate means trimer of isocyanate.

In the present invention, the curing agent may comprise any polyisocyanate in an amount of less than 50% by weight in addition to the polyisocyanate. However, it is preferably a low-yellowing aliphatic or alicyclic polyisocyanate in view of suppressing the yellowing of the adhesive.

Specifically, one or more selected from a low molecular weight polyisocyanate, a dimer of a low molecular weight isocyanate and a polyurethane isocyanate obtained by reacting a low molecular weight polyisocyanate with water or a polyhydric alcohol can be used in combination.

Examples of the low molecular weight polyisocyanate include hexamethylene diisocyanate, phenylene diisocyanate, 2,4- or 2,6-tolylene diisocyanate, diphenylmethane-4,4-diisocyanate, 3,3-dimethyl -4,4-biphenylene diisocyanate, dicyclohexylmethane-4,4-diisocyanate, isophorone diisocyanate, and mixtures thereof. Examples of polyhydric alcohols to be reacted with such low molecular weight polyisocyanates include those described above as raw materials for the polyester polyol of the preceding stage for producing the polyester polyurethane polyol.

The curing agent may be a known oxazoline compound such as 2,5-dimethyl-2-oxazoline, 2,2- (1,4-butylene) -bis (2-oxazoline) or hydrazide compounds such as isophthalic acid dihydrazide, sebacic acid dihydrazide, adipic acid dihydrazide, and the like.

As for the subject and the curing agent, the solid content of the curing agent is 4 to 12 parts by weight based on 100 parts by weight of the solid content of the subject. When the amount of the curing agent is 4 parts by weight or more, the resistance to moisture and humidity can be improved more effectively. Further, the curing agent is adjusted to 12 parts by weight or less, and the adhesive force at low temperature can be more effectively exhibited. Therefore, the amount of the curing agent is preferably 4 to 12 parts by weight in terms of wet heat resistance and adhesion at low temperature.

It is preferable that the isocyanate groups in the curing agent are blended in an equivalent ratio of 1.0 to 10.0 with respect to the total of the hydroxyl groups in the polyester polyol and the polyester polyurethane polyol in the subject. When the aging time after lamination is considered, it is preferably 3.0 to 7.0.

[Solar cell back protection sheet]

Examples of the outer layer substrate 1 having weather resistance include polyolefin resins such as polyethylene (PE) (high density polyethylene, low density polyethylene, linear low density polyethylene), polypropylene (PP) and polybutene, (meth) A polyvinylidene chloride resin, a polyvinylidene chloride resin, a vinyl resin, a polystyrene resin, a polyvinylidene chloride resin, an ethylene-vinyl acetate copolymer soap, a polyvinyl alcohol, a polycarbonate resin, a fluororesin, a polyvinylidene fluoride resin, A vinyl resin, an acetal resin, a polyester resin (polyethylene terephthalate (PET), polybutylene terephthalate, polyethylene naphthalate), a polyamide resin, and various other resin films or sheets. The film or sheet of such a resin may be stretched in the axial direction or in the two axial directions.

For the purpose of absorbing or reflecting ultraviolet rays, a white pigment such as titanium oxide or barium sulfate, or a black pigment such as carbon may be mixed into the outer layer substrate 1). In addition, known additives such as known ultraviolet absorbers, moisture absorbents (drying agents), oxygen absorbers, antioxidants and the like other than the coloring pigments may be incorporated.

The thickness of the outer layer substrate 1 is not limited, but may be, for example, about 10 to 350 탆, and preferably about 10 to 100 탆.

As the intermediate layer substrate 2, for example, a polyethylene terephthalate resin, an ethylene trifluoroethylene film and various other resin films or sheets can be used. The film or sheet of such a resin may be stretched in the axial direction or in the two axial directions.

The thickness of the intermediate layer substrate 2 is not particularly limited, but is preferably 30 to 350 占 퐉, more preferably 100 to 350 占 퐉, further preferably 125 to 350 占 퐉, particularly preferably 150 to 300 占 퐉.

The backsheet for solar cells may require a partial discharge voltage of 600 V or 1,000 V depending on the generating capacity of the solar cell in order to prevent the damage of the solar cell module due to voltage application. Since the partial discharge voltage depends on the thickness of the protective sheet in the case of a solar cell, the substrate constituting the protective sheet is required to be thicker than the substrate constituting the laminate for food packaging. The thickness of the intermediate layer substrate 2) responsible for the withstanding voltage in the substrate constituting the protective sheet is mainly responsible for the " thickness ". Therefore, the thickness of the intermediate layer 2) is preferably 100 to 350 占 퐉 as described above. On the other hand, when the thickness of the base material constituting the protective sheet becomes thick, the price of solar cells increases. Therefore, the thickness of the intermediate layer 2) is preferably 125 to 350 mu m.

(PE) (high density polyethylene, low density polyethylene, linear low density polyethylene), polypropylene (PP), poly (ethylene terephthalate), or the like, as an encapsulating material for sealing a power generating element used in a solar cell module and an inner layer substrate having good adhesiveness. (Meth) acrylic resin, polyvinyl chloride resin, polystyrene resin, polyvinylidene chloride resin, ethylene-vinyl acetate copolymer saponification, polyvinyl alcohol, polycarbonate resin, fluororesin, (PET), polybutylene terephthalate, polyethylene naphthalate), a polyamide-based resin, and various other resin films or sheets, such as polyvinyl chloride resin, polyvinyl chloride resin, polyvinyl acetate resin, acetal resin, polyester resin (polyethylene terephthalate Can be used. The film or sheet of such a resin may be stretched in the axial direction or in the two axial directions.

The thickness of the inner layer substrate is not particularly limited, but is, for example, 10 to 350 占 퐉, preferably about 30 to 250 占 퐉, and more preferably 30 to 100 占 퐉.

Further, the present invention may use at least the above-mentioned three layers, and in the case of other solar cells, any known layer may be further laminated with the protective sheet constitution. For example, a protective sheet for a solar cell made of a polyolefin layer of 125 to 350 占 퐉 as an inner layer substrate, a polyethylene terephthalate film layer of 125 to 350 占 퐉 as an intermediate layer substrate, and Teflon of 10 to 100 占 퐉 as an outer layer substrate is exemplified .

As described above, at least one surface of the thickest substrate of the outer layer substrate 1) the intermediate layer substrate 2) the inner layer substrate 3) is bonded by the adhesive. The bonding method is not particularly limited, but an adhesive may be applied on one side of the laminate substrate by gravure printing, a comma coat, dry lamination or the like, the solvent may be volatilized and then bonded to another laminate substrate and cured at room temperature or under heating. The thickness of the thickest substrate among the outer layer substrate, the intermediate layer substrate and the innerlayer substrate and the amount of the adhesive layer after drying can be appropriately designed. However, the thickness of the thickest substrate is preferably 125 to 350 占 퐉, The amount of the adhesive layer after drying is preferably 5 g / m 2 or more and 30 g / m 2 or less as described above. More preferably not less than 5 g / m 2 g / m 2, and still more preferably not less than 6 g / m 2 and not more than 20 g / m 2. Since the specific gravity of the adhesive excluding the organic solvent is about 1.1 g / cm 3, 1.1 g / m 2 can be converted into about 1 탆 / m 2. Accordingly, when the amount of the adhesive layer is converted into the thickness, it becomes about 4.5 to 27.3 mu m. By setting the amount of the adhesive layer after drying to 5 g / m 2 or more, the influence of hydrolysis on the adhesive layer can be more effectively reduced. Further, the amount of the adhesive layer is set to 30 g / m 2 or less so that the organic solvent of the adhesive can be easily volatilized sufficiently during drying before bonding to the substrate.

In the case of manufacturing the solar cell backing sheet of the present invention by industrially bonding various substrates and then curing the adhesive layer in a rolled state, the inventors of the present invention have conducted intensive studies. As a result, Productivity can be further improved. That is, the thickness of the thickest substrate among the outer layer substrate, the intermediate layer substrate and the innerlayer substrate is 125 to 350 占 퐉, and the amount of the adhesive layer is 5 g / m2 or more and 30 g / m2 or less, It is possible to more effectively inhibit the phenomenon of floating in a roll laminate (hereinafter referred to as tunneling) even when the laminate is wound on the roll in the process of developing the adhesive force after coating the adhesive while satisfying electrical insulation. As a result, it is possible to provide a protective sheet for a solar cell having high industrial productivity in the process of developing adhesive force after coating with an adhesive.

The solar cell back protection sheet of the present invention is attached to the solar cell module by bonding the inner layer substrate side to an encapsulating material sealing the power generating element of the solar cell module. The constitution of the solar cell module of the present invention is not particularly limited, and a known solar cell module can be used.

According to the solar cell backing sheet of the present invention, at least one of the outer layer substrate, the intermediate layer substrate and the thickest substrate among the built-in substrates is adhered by the above-mentioned specific adhesive, Weather resistance is obtained. As a result, it is possible to provide a protective sheet for a long-term stable solar cell. In addition, the adhesive used in the present invention is inexpensive in terms of cost, and can be easily coated by general coating methods such as gravure coating and comma coating. In addition, the solar cell backing sheet of the present invention is excellent in wet heat resistance and adhesion at low temperature by using an adhesive having a solid content of 4 to 12 parts by weight based on 100 parts by weight of the solid content of the base. That is, it is possible to provide a protective sheet for a solar cell excellent in long-term reliability and heat resistance, excellent in adhesion under a low-temperature environment, and excellent in cost and coatability.

Example

EXAMPLES Next, the present invention will be described in detail with reference to Examples and Comparative Examples. However, the present invention is not limited to the embodiments. In the examples, parts represent parts by weight.

Example 1

25 kg of titanium oxide particles were added to 100 kg of a low density polyethylene resin (LDPE) having a density of 0.91 g / cm 3 and sufficiently kneaded to prepare an LDPE resin composition. And then extruded in an extruder to produce a first film having a thickness of 50 탆.

Then, a polyethylene terephthalate film having a thickness of 250 占 퐉 (Toyoboseki Co., Ltd.: Toyo Ester Film E5102) was provided as a second film excellent in electrical insulation. Further, a PVF film (38 mu m, made by DuPont) was provided as the third film. These films were bonded by a dry lamination method using an adhesive for dry lamination.

The adhesive for dry lamination is as follows.

119.5 parts of dimethyl terephthalate, 92.2 parts of ethylene glycol, 72.2 parts of neopentyl glycol, and 0.02 part of zinc acetate were placed in a reaction vessel and heated under stirring in a nitrogen stream at 160-210 占 폚 to carry out an ester exchange reaction. Methanol 97% of the theoretical amount was discharged, and then 93.0 parts of isophthalic acid and 130.0 parts of azelaic acid were added and the esterification reaction was carried out by heating to 160 to 270 ° C. When the reaction vessel was gradually reduced to 1 to 2 Torr and the acid value became 0.8 mgKOH / g or less, the reaction was terminated under reduced pressure to obtain a polyester polyol having a weight average molecular weight of 75,000. The resin solution was diluted with ethyl acetate to obtain a polyester polyol concentration of 50%.

94.5 parts of neopentyl glycol, 91.7 parts of 1,6-hexanediol, 37.6 parts of ethylene glycol, 211.5 parts of isophthalic acid and 122.9 parts of sebacic acid were charged into a reaction vessel and heated to 160 to 250 DEG C while stirring under a nitrogen stream to effect an esterification reaction I did. When the reaction vessel was gradually reduced to 1 to 2 Torr and the acid value became 1 mgKOH / g or less, the reaction was terminated under reduced pressure to obtain a polyester polyol having a weight average molecular weight of 6,000. 22.9 parts of isophorone diisocyanate was gradually added to the obtained polyester polyol, and the mixture was reacted by heating at 100 to 150 ° C. After the reaction for 6 hours, a polyester polyurethane polyol having a weight average molecular weight of 35,000 was obtained. The resin solution having the concentration of the polyester polyurethane polyol obtained by diluting with ethyl acetate to 50% was designated as polyol B.

30 parts of a bisphenol A type epoxy resin having an epoxy equivalent weight of 600 g / eq and 3 parts of an epoxy group-containing organosilane coupling agent at 70 占 폚 were mixed with 100 parts of polyol A (solid content 50 parts), 40 parts of polyol B (solid content 20 parts) The resin solution with a solid content of 50% obtained by heating, dissolving, mixing and diluting with ethyl acetate was used as the subject 1.

The total ester bond degree of polyol A and polyol B in subject 1 is 0.89 as follows.

That is, reacted with dibasic acid: dihydric alcohol = 1: 1 (molar ratio), which is a raw material of each polyol, the number of ester bonds is 1. The average molecular weight (equivalent) of dibasic acid and dihydric alcohol of the polyol is calculated. (Obtained by removing dehydration and the like in the reaction) is molecular weight divided by ester bond.

Ester bond degree = 1 / molecular weight value (unit / g) = 100 / molecular weight value (unit / 100g)

Since the ester bond degree of polyol A is 0.93 and the ester bond of polyol B is 0.79, the ester bond degree of the subject 1 is

(0.93 x 100 + 0.79 x 40) / (100 +40) = 0.89

.

A trimer of isophorone diisocyanate was diluted with ethyl acetate to prepare a resin solution having a solid content of 50%.

A mixture of Topic 1 and Curing Agent 1 in a solid content of 100: 12 (weight ratio), diluted with ethyl acetate, and adjusted to a solid content of 30% was used as an adhesive solution.

The adhesive solution was dried to adjust the amount of the adhesive layer to 10 g / m < 2 > to carry out the first film to the third film laminate to obtain a laminate of 210 mm x 295 mm (A4 size). After laminating, the laminate of 210 mm x 295 mm (A4 size) was aged at 60 deg. C for 7 days in a substantially horizontal state, and the adhesive was cured to prepare a backsheet for a solar cell.

(25 占 폚, 15 占 폚), adhesion force after weathering test (25 占 폚), and tunneling were evaluated by the following method.

Example 2

Except that the curing agent 1 was changed to 10 parts (Example 2), 6 parts (Example 3) and 4 parts (Example 4) for 100 parts of Topic 1, And evaluated.

Comparative Example 1

A backsheet for a solar cell was prepared and evaluated in the same manner as in Example 1, except that the solid content of the curing agent 1 was changed to 14 parts with respect to 100 parts of the solid content.

Examples 5 to 11

(Example 5), 5 g / m 2 (Example 6), 15 g / m 2 (Example 7) and 20 g / m 2 (Example 8) after drying using the adhesive solution of Example 2 ), 25 g / m 2 (Example 9), 30 g / m 2 (Example 10) and 35 g / m 2 (Comparative Example 11) did.

Example 12

The same adhesive solution as in Example 2 was used as a second film, except that a polyethylene terephthalate film (Toyoboseki Co., Ltd.: Toyo Ester Film E5100) having a thickness of 100 占 퐉 was used instead of the polyethylene terephthalate film having a thickness of 250 占 퐉. A backsheet for a solar cell was prepared and evaluated in the same manner as in Example 1 except that the curing agent 1 was adjusted to 10 parts by weight.

Comparative Example 2, Examples 13 to 16

The kind of the resin film used was the same as in Example 1, and the adhesive to be used was changed.

30 parts of a bisphenol A type epoxy resin having an epoxy equivalent weight of 600 g / eq and 3 parts of an epoxy group-containing organosilane coupling agent were mixed at 70 DEG C (solid content: 20 parts), polyol B 100 parts (solid content 50 parts) The resin solution with a solid content of 50% obtained by heating, dissolving, mixing and diluting with ethyl acetate was defined as the subject 2.

14 parts (Comparative Example 2), 12 parts (Example 13), 10 parts (Example 14), 6 parts (Example 15) and 4 parts (Example 16) , A backsheet for a solar cell was produced in the same manner as in Example 1 and evaluated.

Examples 17 to 18

A bisphenol A type epoxy resin having a number average molecular weight of 1,400 and an epoxy equivalent weight of 700 g / eq (Example 17), a bisphenol A type epoxy resin having a number average molecular weight of 1,000, and an epoxy equivalent of 500 g / eq 18) were each used in place of 30 parts, and the backsheet for a solar cell was produced and evaluated in the same manner as in Example 2.

Comparative Example 3

A resin solution having a solid content of 50% was made in the same manner as in Comparative Example 1, except that 120 parts of polyol A (solid portion 60 parts) and 20 parts of polyol B (solid portion 10 parts) were used.

A protective sheet for a solar cell backing sheet was prepared and evaluated in the same manner as in Example 1 except that a mixture of Topic 3 and Curing Agent 1 in a weight ratio of 100: 14, diluted with ethyl acetate, and adjusted to a solid content of 30% did.

Comparative Example 4 (polyol B was not used)

A backsheet for a solar cell was prepared and evaluated in the same manner as in Comparative Example 1 except that polyol B was not used and 140 parts of polyol A (solids content: 70 parts) was used.

Comparative Example 5 (polyol A was not used)

A backsheet for a solar cell was prepared and evaluated in the same manner as in Comparative Example 1 except that polyol A was not used and polyol B was changed to 140 parts (solids content: 70 parts).

Comparative Example 6 (different hardener)

The isophorone diisocyanate trimer was diluted with ethyl acetate to prepare a resin solution having a solid content of 50% by diluting the TMP adduct of trilene diisocyanate with ethyl acetate instead of the resin solution having a solid content of 50%. Further, 14 parts of the solid content of the curing agent 2 was used for the subject 1 of 100 parts of the solid content. A backsheet for a solar cell was produced and evaluated in the same manner as in Example 1 except for this.

Comparative Examples 7 and 8 (polyol A was not used)

99.6 parts of dimethyl terephthalate, 92.2 parts of ethylene glycol, 72.2 parts of neopentyl glycol, and 0.02 parts of zinc acetate were placed in a reaction vessel and heated at 160 to 210 DEG C under stirring in a nitrogen stream to carry out an ester exchange reaction. After discharging, 77.5 parts of isophthalic acid and 129.6 parts of adipic acid were added, and the esterification reaction was carried out by heating at 160 to 240 ° C. The reaction vessel was gradually reduced to 1 to 2 Torr. When the acid value was 0.8 mgKOH / g or less, the decompression reaction was stopped to obtain a polyester polyol having a weight average molecular weight of 60,000 (ester bond degree 0.90 mol / 100 g). The resin solution having a solid content of 50% obtained by diluting with ethyl acetate was used as polyol C.

100 parts of polyol C was used instead of 100 parts of polyol A. Further, 14 parts (Comparative Example 7) or 10 parts (Comparative Example 8) of Curing Agent 1 was used for the subject 1 of 100 parts of solid content. A backsheet for a solar cell was produced and evaluated in the same manner as in Example 1 except for this.

The polyol C has a weight average molecular weight of 60,000 and does not contain an aliphatic dibasic acid having 9-10 carbon atoms, and therefore does not correspond to the polyester polyol A of the present invention.

Comparative Example 9 (not containing a bisphenol-type epoxy resin)

40 parts of polyol A (solid content 20 parts), 100 parts of polyol B (solid content 50 parts) and 3 parts of epoxy group-containing organosilane coupling agent were heated, dissolved, mixed and diluted with ethyl acetate to obtain a resin solution having a solid content of 50% Subject 4 was made. Further, 14 parts of Curing Agent 1 was used for 100 parts of Topic 4. Otherwise, the back surface protection sheet for a solar cell was produced and evaluated in the same manner as in Example 1.

Comparative Example 10

A backsheet for a solar cell was prepared and evaluated in the same manner as in Example 2 except that 30 parts of bisphenol A type epoxy resin having a number average molecular weight of 800 and an epoxy equivalent of 400 g / eq was used instead of the epoxy resin having a number average molecular weight of 1,200.

Hereinafter, the evaluation method will be described.

<25 ° C Initial adhesion 15 ° C Adhesion>

The protective sheet (sample) was cut into a length of about 15 mm in width and about 150 mm in length, and the adhesion (= peel strength) was measured in accordance with JIS K6854T type peeling test. Each resin film layer was peeled at 180 ° at a tensile speed of 100 mm / min under an atmosphere of 25 ° C and 15 ° C using a testing machine, and peel strength was measured and evaluated according to the following criteria.

◎: 12N / 15mm or more

○: 9N / 15mm or more and less than 12N

?: 6N / 15mm or more and less than 9N

X: less than 6N / 15 mm

&Lt; Adhesion after weathering test >

The adhesive strength after 1,000 hours and after 2,000 hours (equivalent to 10 years or more in outdoor room conditions) was measured in a dump heat (test conditions 85 ° C, 85%) and 25 ° C in the same manner as before testing, And the peel strength retention ratio (%) was calculated and evaluated according to the following criteria.

◎: Strength of 95% or more after 2,000 hours

○: After 2,000 hours, 85% or more and less than 95%

Δ: 60% or more and less than 85% strength after 2,000 hours

X: Less than 60% strength after 2,000 hours

<Tunneling (lifting of protective sheet in case of solar cell on roll)>

A laminate of the first film to the third film was used in Examples and Comparative Examples, and a long laminate having a length of 1 m was wound around a circumference of a paper tube having an outer diameter (diameter) of 170 mm by a length of 10 m to obtain a roll laminate. The roll laminate was set up in a state in which the core was in the vertical direction, and a protective sheet was obtained for an aging solar cell at 60 DEG C for 7 days. In the case of a solar cell of a roll, the presence or absence of lifting of the protective sheet was observed. The number of the parts where the lift occurred was evaluated based on the following criteria. &Quot; Lift " refers to a gap between the adhesive layer and the substrate.

○: No lift

△: Within 5 places

×: More than five locations

[Table 1A]

* 1: The description ... Thickest substrate

* 2: Unit of adhesive force (N / 15mm)

[Table 1B]

* 1: The description ... Thickest substrate

* 2: Unit of adhesive force (N / 15mm)

<Partial discharge>

IEC Partial Discharge Test (IEC61730-2, IEC60664-1) in air and in oil.

○: The measurement method in air or in oil is 1,000 V or more

△: It is 1,000 V or more only in measuring method in oil

X: Any measurement method less than 1,000 V

The evaluation of the partial discharge was not necessarily required for the protective sheet in the case of a solar cell, but a good result was obtained in all the samples except for the twelfth embodiment in which a polyethylene terephthalate film having a thickness of 100 占 퐉 was used instead of the 250 占 퐉 polyethylene terephthalate film .

This application claims priority based on Japanese patent application No. 2011-153066, filed on July 11, 2011, and inserts all of the disclosures therein.

Claims (5)

An outer layer substrate having at least 1) weather resistance, 2) an intermediate layer substrate, and 3) an inner layer substrate having good adhesion with an encapsulant for sealing a power generation element used in the solar cell module,
Wherein the adhesive layer for bonding at least one side of the outer layer substrate, the intermediate layer substrate and at least one of the thickest substrates of the inner layer substrates comprises a base containing the following (1) to (3) and an adhesive containing the curing agent of Lt; / RTI &gt;
Wherein the adhesive is a solar cell containing 4 to 12 parts by weight of the solid content of the curing agent with respect to 100 parts by weight of the solid content of the subject,
(1) a dibasic acid component comprising 40 to 70 mol% of an aromatic dibasic acid and 30 to 60 mol% of an aliphatic dibasic acid having 9 to 10 carbon atoms and 30 to 40 mol% of an aliphatic divalent alcohol having 5 or more carbon atoms A straight chain polyester polyol having a weight average molecular weight of 70,000 to 80,000 which is obtained by reacting a dihydric alcohol component,
(2) a dibasic acid component comprising 60 to 80 mol% of an aromatic dibasic acid and 20 to 40 mol% of an aliphatic dibasic acid having 9 to 10 carbon atoms and 70 to 80 mol% of an aliphatic divalent alcohol having 5 or more carbon atoms A polyester polyol polyol having a weight average molecular weight of 30,000 to 40,000, which is obtained by reacting a polyester polyol obtained by reacting a dihydric alcohol component with an organic diisocyanate,
(3) bisphenol-type epoxy resins having a number average molecular weight of 1,000 to 2,000,
(4) Polyisocyanates having isocyanurate of isophorone diisocyanate. The protective sheet according to claim 1, wherein the thickness of the thickest substrate is 125 to 350 占 퐉, and the amount of the adhesive of the adhesive layer in contact with the thickest substrate is in the range of 5 g / m 2 to 30 g / m 2. The protective sheet according to claim 1, wherein the intermediate layer base material is a plurality of, and at least a part of, the layers are bonded to each other through the adhesive layer. The protective sheet according to claim 1, wherein the straight chain polyester polyol is 60 to 80% by weight of the total of 100% by weight of the straight chain polyester polyol and the polyester polyurethane polyol. A solar cell module comprising a solar cell backsheet according to any one of claims 1 to 4.

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