KR20140040765A - Solar cell backside protective sheet and solar cell - Google Patents

Abstract

Provided are a solar cell back protective sheet and a solar cell module that are excellent in long-term reliability and wet heat resistance, have excellent adhesion in low temperature environments, and are excellent in cost and coating properties. In the solar cell back protective sheet of the present invention, 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 straight-chain polyester polyol, a polyester polyurethane polyol, and a bisphenol-type epoxy resin having a specific structure. It adhere | attaches with the main body containing and the adhesive agent containing the hardening | curing agent containing an isocyanurate, The said adhesive contains 4-12 weight part of solids of the said hardening | curing agent with respect to 100 weight part of solids of a main body.

Description

Solar cell back protection sheet and solar cell module {SOLAR CELL BACKSIDE PROTECTIVE SHEET AND SOLAR CELL}

The present invention relates to a solar cell back protective sheet used for the back side of a solar cell module, and a solar cell module having the solar cell back protective sheet.

Recently, attention has been paid to solar power generation that converts light energy into electrical energy using quantum effects peculiar to semiconductors. A solar cell module is used for photovoltaic power generation, on which the solar cell back protective sheet (so-called back sheet) is installed for the purpose of protection and insulation.

The solar cell module requires a long life of several decades, and the long-term reliability is also required for the back sheet to protect it. In addition, the back sheet is required for insulation against electricity generated in a power generation element called a cell and good adhesion to an encapsulant for sealing the cell. In order to meet such a demand, the back sheet obtained by laminating | stacking existing various resin films and metal foils through an adhesive agent is proposed (for example, patent document 1, 2 etc.).

Moreover, the outdoor polyurethane type adhesive agent containing polyester polyol and polyester polyurethane polyol is proposed (patent document 3).

Japanese Patent Publication No. 2010-278375 Japanese Patent Publication No. 2009-290201 Japanese Patent Publication No. 2010-043238

The back sheet is strongly required to have high long-term reliability. This requires good adhesion to the adhesive used in the back sheet and weather resistance to withstand long term use. In addition, it is required that the adhesive is inexpensive and can be easily coated by general coating methods such as gravure coating and comma coat. In addition, it is required to be excellent in wet heat resistance and to exhibit excellent adhesive strength even in an environment at a temperature lower than room temperature. Existing back sheets had room for further improvement in this respect.

SUMMARY OF THE INVENTION The present invention has been made in view of the above background, and provides a solar cell back protective sheet and a solar cell module that are excellent in long-term reliability and wet heat resistance, have excellent adhesion in a low temperature environment, and are excellent in cost and coatability. It is a main purpose.

MEANS TO SOLVE THE PROBLEM As a result of earnestly researching in order to achieve the said objective, the present inventor uses the adhesive agent containing the subject matter of a specific composition and a hardening | curing agent, and can achieve the said objective by making a specific amount of specific hardening | curing agent with respect to a subject. It has been found and the present invention has been completed.

That is, the solar cell back protective sheet according to the present invention has good adhesiveness with at least 1) an outer layer substrate having weather resistance, 2) an intermediate layer substrate, and 3) an encapsulant for sealing a power generating element used for the solar cell module. The adhesive layer which consists of an inner layer base material which has, and joins at least one side of the thickest base material of an outer layer base material, an intermediate | middle layer base material, and an inner layer base material contains the main material containing (1)-(3) below, and the hardening | curing agent of below (4) Formed by an adhesive,

The said adhesive agent contains 4-12 weight part of solid content of a hardening | curing agent with respect to 100 weight part of solid content of a subject.

(1) a dibasic acid component comprising 40 to 70 mol% of aromatic dibasic acids and 30 to 60 mol% of aliphatic dibasic acids having 9 to 10 carbon atoms, and 30 to 40 mol% of aliphatic dihydric alcohols having 5 or more carbon atoms. A linear polyester polyol having a weight average molecular weight of 70,000 to 80,000 formed by reacting a dihydric alcohol component.

(2) a dibasic acid component containing 60 to 80 mol% of aromatic dibasic acids and 20 to 40 mol% of aliphatic dibasic acids having 9 to 10 carbon atoms, and 70 to 80 mol% of aliphatic dihydric alcohols having 5 or more carbon atoms. The polyester polyurethane polyol whose weight average molecular weights which make organic diisocyanate react with the polyester polyol obtained by making a dihydric alcohol component react is 30,000-40,000.

(3) Bisphenol-type epoxy resin of the number average molecular weight 1,000-2,000.

(4) Polyisocyanate with isocyanurate of isophorone diisocyanate.

It is preferable that the thickness of the said thickest base material shall be 125-350 micrometers, and it is preferable that the adhesive amount of the said adhesive bond layer in contact with the said thickest base material shall be 5 g / m <2> or more and 30g / m <2> or less.

In addition, it is preferable that the said intermediate | middle layer base material is plural and at least partially adhere | attached each other through the said adhesive layer.

Moreover, it is preferable that the said linear polyester polyol is 60-80 weight% in a total of 100 weight% of the said linear polyester polyol and the said polyester polyurethane polyol.

The solar cell module which concerns on this invention is equipped with the solar cell back surface protection sheet of the said form.

According to the solar cell back surface protective sheet of this invention, it is excellent in long-term reliability and wet heat resistance, and it is excellent in adhesiveness in a low temperature environment, and it is excellent in cost, and it is excellent in coatability, and provides a solar cell back surface protective sheet, and a solar cell module. Can show excellent effect.

It is a figure which shows the laminated constitution of the solar cell back surface protection sheet produced by the Example.
It is a figure which shows the laminated constitution of the solar cell back surface protective sheet produced by the comparative example.

Hereinafter, the present invention will be described in detail. It goes without saying that other embodiments also fall within the scope of the present invention as long as it is in accordance with the spirit of the present invention. In addition, in this specification, "any A-arbitrary number B" means the range larger than the number A and the number A, and means the range smaller than the number B and the number B.

The solar cell back protective sheet of the present invention is composed of at least 1) an outer layer substrate having weather resistance, 2) an intermediate layer substrate, and 3) an encapsulant for sealing a power generating element used for a solar cell module and an inner layer substrate having good adhesion. And the solar cell back surface protective sheet of this invention has the main body and the bottom which the adhesive bond layer which joins at least one surface of the thickest base material of an outer layer base material, an intermediate | middle layer base material, and an inner layer base material contains (1)-(3) below. It is formed by the adhesive agent containing the hardening | curing agent of. Therefore, in the range which satisfy | fills the said conditions, the solar cell back surface protective sheet of this invention can also join together base materials with another adhesive agent. The inner layer substrate is disposed on the surface of the light emitting element side in the solar cell back protective sheet, and the outer layer substrate is disposed at the position farthest from the light emitting element. Although the intermediate | middle layer base material may be single, plural may be sufficient as it. The solar cell back protective sheet is required to have a withstand voltage. It is preferable to provide withstand voltage mainly to an intermediate | middle layer base material. However, in the case where a plurality of intermediate layer substrates are provided, all of the intermediate layer substrates do not have to have voltage resistance. In addition, when it mentions "adhesive agent" afterwards separately, it shall refer to the adhesive agent of this invention containing the subject matter containing (1)-(3) below, and the hardening | curing agent of (4) below.

As for the solar cell back surface protection sheet of this invention, it is preferable that the thickness of the thickest base material of an outer layer base material, an intermediate | middle layer base material, and an inner layer base material shall be 125-350 micrometers. Moreover, it is preferable that the adhesive amount after drying of the adhesive bond layer which contact | connects the thickest base material exists in the range of 5 g / m <2> or more and 30g / m <2> or less. The reason will be described later. Although the thickest base material may be an outer layer base material, an intermediate | middle layer base material, and an inner layer base material, it is preferable that an intermediate | middle layer base material is the thickest base material. In addition, in the case of the thickest base material of the outer base material or the inner base material, the coating surface of the adhesive amount becomes one side, but in the case of the thickest base material of the intermediate layer base material, the coating conditions are satisfied on at least one side of the two bonding surfaces of the intermediate layer base material. It is desirable to. In the case where the intermediate layer substrate is the thickest substrate, it is more preferable that the adhesive layer of the present invention is in the range of 5 g / m 2 or more and 30 g / m 2 or less from both bonding surfaces. Moreover, the said adhesive agent can also be preferably applied also to joining of substrates other than the thickest substrate. That is, the adhesive agent of this invention can be used suitably for both bonding of each base material (for example, plastic film, metal foil, etc.) which comprises a solar cell back surface protection sheet.

The adhesive of the present invention is a polyurethane-based adhesive containing a main agent and a curing agent. The adhesive may be a two-liquid type adhesive that mixes the main material and the curing agent in use, and may be a one-liquid type adhesive in which the main material and the curing agent are mixed in advance. Moreover, the type which mixes various subjects and / or several hardening | curing agents when using may be sufficient.

The main subject 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. A linear polyester polyol having a weight average molecular weight of 70,000 to 80,000 formed by reacting a dihydric alcohol component containing%, (60) 60 to 80 mol% of aromatic dibasic acids and 20 to 40 mol of aliphatic dibasic acids having 9 to 10 carbon atoms. The weight average molecular weight which consists of making organic diisocyanate react the polyester polyol obtained by making the dibasic acid component containing% and the dihydric alcohol component containing 70-80 mol% of C5 or more aliphatic dihydric alcohols 30,000-40,000 Polyester polyurethane polyol and (3) The number average molecular weight contains bisphenol-type epoxy resin of 1,000-20,000.

The hardening | curing agent of the said adhesive contains the polyisocyanate which has the isocyanurate of (4) isophorone diisocyanate. The adhesive agent of this invention contains 4-12 weight part of solid content of the said hardening | curing agent with respect to 100 weight part of solid content of a main subject. More preferably, it is 6-12 weight part, More preferably, it is 8-10 weight part.

[(1) straight chain polyester polyol]

The linear polyester polyol used in the present invention (hereinafter simply referred to as "polyester polyol") is a dibasic acid component containing 40 to 70 mol% of aromatic dibasic acids and 30 to 60 mol% of aliphatic dibasic acids having 9 to 10 carbon atoms. And a dihydric alcohol component containing 30 to 40 mol% of aliphatic dihydric alcohols having 5 or more carbon atoms. As long as it is a range which satisfy | fills the said conditions, you may contain the dibasic acid and polyhydric alcohol component of another structure.

Examples of the dibasic acid and its ester compound include isophthalic acid, terephthalic acid, naphthalene dicarboxylic acid, phthalic anhydride, adipic acid, azelaic acid, sebacic acid, succinic acid, glutaric acid, tetrahydrophthalic anhydride, and hexahydroanhydride. Phthalic acid, maleic anhydride, itaconic anhydride and ester compounds thereof can be exemplified.

In the present invention, these can be used in combination as appropriate, but, based on the total amount of dibasic acids, 40 to 70 mol% of aromatic dibasic acids (preferably 50 to 60 mol%) and 30 to 60 aliphatic dibasic acids having 9 to 10 carbon atoms. Combine to mole% (preferably 40 to 50 mole%).

If the amount of the aromatic dibasic acid is less than 40 mol%, sufficient heat resistance and viscoelasticity may not be obtained. Moreover, adhesive force can be exhibited more effectively by setting it as 70 mol% or less. In addition, by setting the aliphatic dibasic acid having 9 to 10 carbon atoms to 30 mol% or more, the polyester polyol ester bond can be appropriately used to suppress the point of hydrolysis and lead to long-term moist heat resistance more effectively. In addition, by setting the aliphatic dibasic acid having 9 to 10 carbon atoms to 60 mol% or less, heat resistance and viscoelasticity can be appropriately adjusted, and adhesive force can be more effectively expressed.

Among the above exemplary compounds, as the aromatic dibasic acid, terephthalic acid, dimethyl terephthalate, isophthalic acid and phthalic anhydride are preferable from the viewpoint of reactivity in the transesterification reaction. As aliphatic dibasic acids having 9 to 10 carbon atoms, azela acid having 9 carbon atoms and sebacic acid having 10 carbon atoms are preferable from the viewpoint of high lipophilic property, hydrophobicity, and suppression of absorption of the polymer.

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

By setting the ratio of aliphatic dihydric alcohol having 5 or more carbon atoms in the dihydric alcohol component to 30 mol% or more, the polyester polyol ester bond can be appropriately suppressed to suppress the increase of the hydrolysis origin and lead to long-term moist heat resistance more effectively. have. Moreover, when the ratio of aliphatic dihydric alcohol is 40 mol% or less, the solubility with respect to the organic solvent of a product will become favorable and adhesive coatability will become favorable.

Among the above-mentioned compounds, neopentyl glycol of 5 carbon atoms, 3-methyl-1,5-pentanediol of 6 carbon atoms, hydrophobic high lipophilic property which has a side chain as a C5 or more aliphatic dihydric alcohol, and improves dissolution stability 1,6-hexanediol etc. which suppress the absorption of a polymer are preferable.

The weight average molecular weight of polyester polyol shall be 70,000-80,000 from a viewpoint of ensuring cohesion force, stretchability, and adhesive strength. Among these, it is more preferable that they are 72,000-78,000 from a viewpoint of the solubility of resin, a viscosity, and the coating property (handling property) of an adhesive agent.

In addition, the number average molecular weight measurement of this invention used GPC (gel permeation chromatography) "HPC-8020" by Tosoh Corporation. Liquid chromatography that separates and quantifies a substance dissolved in a GPC solvent (THF; tetrahydrofuran) by a difference in molecular size. In the measurement of the present invention, two columns of “LF-604” (manufactured by Showa Denko: GPC column for rapid analysis: 6MMID × 150MM size) were connected in series, and the flow rate was 0.6ML / MIN, and the column temperature was 40 ° C. It carried out on condition of, and determined the weight average molecular weight (Mw) in polystyrene conversion.

[(2) Polyester Polyurethane Polyol]

The polyester polyurethane polyols used in the present invention are 60 to 80 mol% of aromatic dibasic acids (preferably 65 to 75 mol%) and 20 to 40 mol% of aliphatic dibasic acids having 9 to 10 carbon atoms (preferably 25 to 25). To a polyester polyol obtained by reacting a dibasic acid component containing 35 mol%) with a dihydric alcohol component containing 70 to 80 mol% (preferably 72 to 78 mol%) of an aliphatic dihydric alcohol having 5 or more carbon atoms. It is made to react organic diisocyanate.

By setting the amount of the aromatic dibasic acid to 60 mol% or more, heat resistance and viscoelasticity can be effectively obtained. On the other hand, by setting it as 80 mol% or less, adhesive force can be exhibited more effectively. Further, by setting the aliphatic dibasic acid having 9 to 10 carbon atoms to 20 mol% or more, the polyester polyol ester bond can be suitably controlled to suppress the hydrolysis origin and lead to long-term moist heat resistance more effectively. In addition, by setting the aliphatic dibasic acid having 9 to 10 carbon atoms to 40 mol% or less, it is possible to appropriately adjust the heat resistance and viscoelasticity and to more effectively express the adhesive force. Further, by setting the proportion of aliphatic dihydric alcohols having 5 or more carbon atoms to 70 mol% or more, the polyester polyol ester bond can be appropriately suppressed to increase the hydrolysis origin and the long-term moist heat resistance can be more effectively elicited. Moreover, when the ratio of aliphatic dihydric alcohol is 80 mol% or less, the solubility with respect to the organic solvent of a product will become favorable and adhesive coatability will become favorable.

The description of the aromatic dibasic acid, aliphatic dibasic acid and aliphatic dihydric alcohol having 5 or more carbon atoms is the same as described above.

It does not specifically limit as organic diisocyanate. Specifically, 2,4-triylene diisocyanate, 2,6-triylene diisocyanate, xylene diisocyanate, diphenylmethane diisocyanate, isophorone diisocyanate, 1,5-naphthalene diisocyanate, hexamethylene diisocyanate, Hydrogenated diphenylmethane diisocyanate etc. are mentioned. These may be used alone or in combination of two or more. In addition, from the viewpoint of reducing the yellowing over time of the adhesive, it is preferable that the urethane crosslinked portion uses an aliphatic or alicyclic isocyanate compound.

By using polyester polyurethane polyol and polyester polyol in combination, it is possible to lower the ester bonding degree (described later) of the entire polyol component, and as a result, it is possible to reduce the origin of hydrolysis and to improve the heat and moisture resistance.

The weight average molecular weight of the polyester polyurethane polyol is 30,000 to 40,000 in view of the fact that the weight average molecular weight of the polyester polyol is large and the viscosity is high, and the viscosity is adjusted with an adhesive. Among these, 32,000-38,000 are more preferable.

[(3) Bisphenol-type epoxy resins]

The number average molecular weights of the bisphenol-type epoxy resin used by this invention are 1,000-2,000, and it is preferable that epoxy equivalent is 500-1,000 g / eq. By including a bisphenol type epoxy resin, it is expected that the hydrophobicity of the bisphenol skeleton reacts with the carboxyl group generated by the hydrolysis of the ester bond to suppress the molecular weight decrease.

Among bisphenol type epoxy resins, bisphenol A type epoxy resins, bisphenol F type epoxy resins and the like are preferable from the viewpoint of maintaining the shear strength, and these can be used alone or in combination of two or more thereof.

The number average molecular weight of the bisphenol-type epoxy resin may be 1,000 to 2,000 from the viewpoint of heat resistance and viscoelasticity adjustment and solution viscosity adjustment of the adhesive cured film. If the number average molecular weight of a bisphenol-type epoxy resin is less than 1,000, there exists a possibility that sufficient heat resistance may not be obtained. Moreover, adhesive force can be exhibited more effectively by setting it as number average molecular weight 2,000 or less. Moreover, in this invention, since the high molecular weight polyol is used, the effect of reducing the viscosity of an adhesive bond solution by the low molecular weight epoxy resin and improving coating property is anticipated, but by setting it as number average molecular weight 2,000 or less, solution viscosity Can be effectively reduced. It is preferable that the number average molecular weight of a bisphenol-type epoxy resin is 1,200-1,800 in the balance of wet heat resistance and the adhesive force at low temperature.

The content of the bisphenol-type epoxy resin is preferably 50% by weight or less in 100% by weight of the main solid content from the viewpoint of adjusting the viscoelasticity of the adhesive cured film, and more preferably 20 to 40% by weight in consideration of the adhesive force.

[Subject containing the above components]

Although the composition ratio of the said polyester polyol and polyester polyurethane polyol (henceforth collectively called a "polyol component") is not specifically limited, 60-80 weight% of polyester polyol is used in 100 weight% of total polyol components. It is preferable to use, and it is more preferable to use 65-75 weight%. By setting the ratio of the polyester polyol of the polyol component to 80% by weight or less, the moist heat resistance can be more effectively elicited. On the other hand, the adhesive force at low temperature can be made more favorable by making the ratio of polyester polyol into 60 weight% or more. Therefore, it is preferable that the ratio of the polyester polyol of the polyol component is in the range of 60 to 80% by weight in the balance between wet heat resistance and adhesion at low temperature.

The present invention is designed to be less than 1 when the ratio of ester bonds by the reaction of the carboxyl group and the hydroxyl group of the polyol component (the reaction ratio of the carboxyl group and the hydroxyl group is 1 to 1) is expressed by the ester bond degree (mole / 100g) of the molecule. It is desirable to. In other words, the ester bond degree is less than 1, the ratio of ester bonds is lowered to increase the hydrolysis resistance, further suppressing the deterioration of the adhesive strength over time and improving the long-term moisture resistance. In this respect, in the present invention, since the dibasic acid having 9 to 10 carbon atoms having a high molecular weight and the polyhydric alcohol having 5 or more carbon atoms having a high molecular weight are used as the dibasic acid, the degree of ester bonding in the unit weight (in 100 g) is reduced.

In particular, considering the compatibility between the adhesive strength at room temperature and the adhesive strength under high temperature (80 to 150 ° C, etc.), the ester bond degree of the polyol component is preferably in the range of 0.75 to 0.99. Such ester bond degree can be achieved within the range of the ratio of the aromatic dibasic acid of the dibasic acid component of the adhesive agent used by this invention, and carbon number of a polyhydric alcohol. Moreover, it is preferable that it is 5 or less, and, as for the acid value (mgKOH / g) of a polyol component, it is more preferable that it is two or less.

The adhesive subject may include, in addition to the polyol component and the bisphenol type epoxy resin, any additives within a range that does not impair the effects of the present invention. As an additive, a silane coupling agent reaction promoter, a leveling agent, an antifoamer, etc. are mentioned, for example.

As a silane coupling agent, Trialkoxy silane which has vinyl groups, such as vinyl trimethoxy silane and vinyl triethoxy silane, 3-aminopropyl triethoxy silane, N- (2-aminoethyl) 3-aminopropyl, for example. Trialkoxy silanes having amino groups such as trimethoxy silane; Trialkoxy silane which has glycidyl groups, such as 3-glycidoxy propyl trimethoxy silane, 2- (3, 4- epoxy cyclohexyl) ethyl trimethoxy silane, and 3-glycidoxy propyl triethoxy silane, is mentioned. Can be. These silane coupling agents may be used alone or in combination of two or more.

It is preferable that it is 0.5-5 weight% with respect to a main quantity, and, as for the addition amount of a silane coupling agent, it is more preferable that it is 1-3 weight%. If it is less than 0.5 weight%, even if it adds a silane coupling agent, the adhesive strength improvement effect will become inadequate, Even if it adds more than 5 weight%, the further performance improvement is not recognized.

As a reaction promoter, For example, Metal-type catalysts, such as a dibutyltin diacetate, a dibutyltin dilaurate, a dioctyltin dilaurate, a dibutyltin dimaleate; 1,8-diaza-bicyclo (5,4,0) undecene-7, 1,5-diazabicyclo (4,3,0) nonene-5,6-dibutylamino-1,8-dia Tertiary amines such as xabicyclo (5,4,0) undecene-7; Reactive tertiary amines such as triethanol amine, and the like, and one or two or more reaction promoters selected from these groups can be used.

As the leveling agent, for example, polyether-modified polydimethyl siloxane, polyester-modified polydimethyl siloxane, aralkyl-modified polymethylalkyl siloxane, polyester-modified hydroxyl group-containing polydimethyl siloxane, polyetherester-modified hydroxyl group-containing polydimethyl siloxane, acrylic polymer And methacrylic polymers, polyether-modified polymethylalkyl siloxanes, acrylic acid alkyl ester copolymers, methacrylic acid alkyl ester polymers, lecithin and the like.

Examples of the antifoaming agent include silicone resins, silicone solutions, copolymers of alkyl vinyl ethers with acrylic acid alkyl esters and methacrylic acid alkyl esters.

[Curing agent]

Curing agents used in the present invention include polyisocyanates having isocyanurates of isophorone diisocyanate. This isocyanate has a long boat life after mixing with the main body, good solution stability, and long-term moist heat resistance of the adhesive. The content of isocyanurate is 50 to 100% by weight in polyisocyanate. In addition, isocyanurate means the trimer of isocyanate.

The present invention may include a curing agent in an amount of less than 50% by weight of any polyisocyanate in addition to the polyisocyanate. However, it is preferable that it is a low yellow aliphatic or alicyclic polyisocyanate from the point which suppresses yellowing of an adhesive agent.

Specifically, 1 or more types chosen from the polyurethane isocyanate obtained by making low molecular weight polyisocyanate, low molecular weight polyisocyanate, water, or polyhydric alcohol, the dimer of a low molecular weight isocyanate, etc. can be used together.

As the low molecular weight polyisocyanate, for example, hexamethylene diisocyanate, phenylene diisocyanate, 2,4- or 2,6-trilene diisocyanate, diphenyl methane-4,4-diisocyanate, 3,3-dimethyl -4,4-biphenylene diisocyanate, dicyclohexylmethane-4,4-diisocyanate, isophorone diisocyanate and mixtures thereof. As a polyhydric alcohol made to react with such low molecular weight polyisocyanate, the above-mentioned thing is mentioned as a raw material of the polyester polyol of the previous stage which manufactures the said polyester polyurethane polyol, for example.

Curing agents are known oxazoline compounds, such as 2,5-dimethyl-2-oxazoline, 2,2- (1,4-butylene) -bis, within the scope of not impairing the effects of the present invention. (2-oxazoline) or hydrazide compounds such as isophthalic acid dihydrazide, sebacic acid dihydrazide, adipic acid dihydrazide and the like.

As mentioned above, a main body and a hardening | curing agent make 4-12 weight part of hardening | curing agent solids with respect to 100 weight part of solids of a main body. By setting the amount of the curing agent to 4 parts by weight or more, the moist heat resistance can be more effectively improved. Moreover, the hardening | curing agent can be 12 weight part or less, and the adhesive force in low temperature can be exhibited more effectively. Therefore, the amount of curing agent in the balance between wet heat resistance and low temperature adhesion force is 4 to 12 parts by weight.

Moreover, it is preferable to mix | blend so that the isocyanate group in a hardening | curing agent may be 1.0-10.0 by an equivalence ratio with respect to the sum total of the hydroxyl groups of the polyester polyol and polyester polyurethane polyol in a subject, and the loss of isocyanate group by reaction with moisture in air, In consideration of the aging time after lamination, it is preferably 3.0 to 7.0.

[Solar cell back protection sheet]

As the outer layer base material 1) having weather resistance, for example, polyolefin resin such as polyethylene (PE) (high density polyethylene, low density polyethylene, linear low density polyethylene), polypropylene (PP), polybutene, (meth) acrylic resin, polychlorinated Vinyl resin, polystyrene resin, polyvinylidene chloride resin, ethylene-vinyl acetate copolymer saponified material, polyvinyl alcohol, polycarbonate resin, fluorine resin, polyvinylidene fluoride resin, polyvinyl fluoride resin, polyacetic acid Vinyl resins, acetal resins, polyester resins (polyethylene terephthalate (PET), polybutylene terephthalate, polyethylene naphthalate), polyamide resins, and various other resin films or sheets can be used. The film or sheet of such a resin may be stretched in the axial or two axial directions.

In order to absorb or reflect an ultraviolet-ray, the outer layer base material 1) may mix white pigments, such as a titanium oxide and barium sulfate, and black pigments, such as carbon. Moreover, you may mix well-known additives, such as a well-known ultraviolet absorber other than a coloring pigment, a moisture absorber (drying agent), an oxygen absorber, and antioxidant.

Although the thickness of the outer layer base material 1) is not limited, For example, it can be said that it is 10-350 micrometers, Preferably it is about 10-100 micrometers.

As the intermediate | middle layer base material 2), polyethylene terephthalate resin, ethylene trifluoro ethylene film, and other various resin films or sheets can be used, for example. The film or sheet of such a resin may be stretched in the axial or two axial directions.

Although the thickness of the intermediate | middle layer base material 2) is not limited, 30-350 micrometers is preferable, It is more preferable that it is 100-350 micrometers, It is further more preferable that it is 125-350 micrometers, It is especially preferable that it is 150-300 micrometers.

In order to prevent the solar cell module from being damaged by voltage application, the back protective sheet for a solar cell may require resistance of a partial discharge voltage of 600 V or 1,000 V depending on the power generation capacity of the solar cell. Since the partial discharge voltage depends on the thickness of the solar cell back protective sheet, the substrate constituting the solar cell back protective sheet is required to be thicker than the substrate constituting the laminate for food packaging. The intermediate | middle layer base material 2) which bears a withstand voltage among the base materials which comprise a solar cell back surface protection sheet mainly plays a "thickness". Therefore, it is preferable that the thickness of the intermediate | middle layer base material 2) is 100-350 micrometers as mentioned above. On the other hand, if the base material which comprises a solar cell back surface protection sheet becomes thick, a price will become high. Therefore, it is preferable that the thickness of the intermediate | middle layer base material 2) is 125-350 micrometers.

Examples of the encapsulant that seals the power generation element used in the solar cell module and an inner layer substrate having good adhesiveness include polyethylene (PE) (high density polyethylene, low density polyethylene, linear low density polyethylene), polypropylene (PP), poly Polyolefin resins such as butene, (meth) acrylic resins, polyvinyl chloride resins, polystyrene resins, polyvinylidene chloride resins, ethylene-vinyl acetate copolymer saponifications, polyvinyl alcohols, polycarbonate resins, fluorine resins, Polyvinyl fluoride resin, polyvinyl acetate resin, acetal resin, polyester resin (polyethylene terephthalate (PET), polybutylene terephthalate, polyethylene naphthalate), polyamide resin, various other resin films or sheets Can be used. The film or sheet of such a resin may be stretched in the axial or two axial directions.

Although the thickness of an inner layer base material is not limited, For example, it is 10-350 micrometers, about 30-250 micrometers is preferable and it is more preferable than 30-100 micrometers.

In the present invention, at least three layers may be used, and any other known layer may be further laminated in the solar cell back protective sheet configuration. For example, the solar cell back surface protection sheet which consists of a polyolefin layer of 125-350 micrometers as an inner layer base material, the polyethylene terephthalate film layer of 125-350 micrometers as an intermediate layer base material, and a Teflon of 10-100 micrometers as an outer layer base material is illustrated. Can be.

As described above, at least one side of the thickest substrate among the outer layer substrate 1) the intermediate layer substrate 2) the inner layer substrate 3) is bonded by the adhesive. Although the adhesion method is not specifically limited, On the other hand, an adhesive is apply | coated to one side of a laminate base material with a gravure printing, a comma coat, a dry laminate, etc., and a solvent is made to volatilize, and it joins with another laminate base material, and may harden under normal temperature or warming. Although the thickness of the thickest of the outer substrate, the intermediate substrate and the inner substrate and the amount of the adhesive layer after drying can be appropriately designed, the thickness of the thickest substrate is applied to at least one side of the laminate substrate at 125 to 350 μm, After drying, the amount of the adhesive layer is preferably 5 g / m 2 or more and 30 g / m 2 or less. More preferably, they are 5 g / m <2> or more and g / m <2> or less, More preferably, they are 6g / m <2> or more and 20g / m <2> or less. Since the specific gravity of the adhesive except the organic solvent is about 1.1 g / cm 3, 1.1 g / m 2 can be converted to about 1 μm / m 2. Therefore, when the quantity of the said adhesive bond layer is converted into thickness, it will be about 4.5-27.3 micrometers. By setting the amount of the adhesive layer after the drying to 5 g / m 2 or more, the influence of the hydrolysis received by the adhesive layer can be more effectively reduced. In addition, the amount of the adhesive layer can be 30 g / m 2 or less, so that the organic solvent of the adhesive can be easily volatilized sufficiently before bonding to the substrate.

When the solar cell back protective sheet of the present invention is manufactured by industrially bonding a plurality of substrates and then completing the curing of the adhesive layer in a rolled state, the present inventors have diligently studied the following examples. It has been shown to improve productivity further. That is, the thickness of the thickest substrate among the outer substrate, the intermediate substrate and the inner substrate is 125 to 350 µm, while the amount of the adhesive layer is 5 g / m 2 or more and 30 g / m 2 or less to effectively light-emitting elements disposed in the solar cell module. After applying the adhesive while satisfying the electrical insulation, it was found that even if the laminate was wound on the roll during the development of adhesive force, the phenomenon of floating on the roll laminate (hereinafter referred to as tunneling) can be more effectively suppressed. As a result, it is possible to provide a solar cell back protective sheet having high industrial productivity in the process of developing adhesive force after adhesive coating.

The solar cell back surface protection sheet of this invention is attached to a solar cell module by adhering the inner side base material side to the sealing material which seals the power generation element of a solar cell module. The structure of the solar cell module of this invention is not specifically limited, A well-known solar cell module can be used.

According to the solar cell back surface protective sheet of this invention, at least one side of the thickest base material of an outer layer base material, an intermediate | middle layer base material, and a built-in base material is adhere | attached by the specific adhesive mentioned above, and it can endure good adhesive and long-term use by adhesive performance. Weather resistance that can be obtained is obtained. As a result, a long-term stable solar cell back surface protection sheet can be provided. In addition, the adhesive used in the present invention is inexpensive in terms of cost, and also has properties that can be easily coated by general coating methods such as gravure coating and comma coat. Moreover, the solar cell back surface protection sheet of this invention is excellent in wet heat resistance and adhesiveness at low temperature using the adhesive whose ratio of a main body and a hardening | curing agent is 4-12 weight part of hardening | curing agent solids content with respect to 100 weight part of main solids content. That is, the solar cell back surface protection sheet which is excellent in long-term reliability and wet heat resistance, excellent in adhesiveness in a low temperature environment, and excellent in cost and coatability can be provided.

Example

Next, an Example and a comparative example are shown and this invention is demonstrated concretely. However, the present invention is not limited to the embodiment. 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 kneaded sufficiently to prepare an LDPE resin composition. Next, it extruded in the extruder and produced the 1st film of 50 micrometers in thickness.

Then, a 250-micrometer-thick polyethylene terephthalate film (Toyo Boseki company: Toyo ester film E5102) was prepared as a 2nd film excellent in electrical insulation. Furthermore, PVF film (made by Dupont, 38 micrometers) was provided as the 3rd film. This film was bonded by the dry lamination method using the adhesive for dry lamination.

In addition, the adhesive for dry laminates is as follows.

119.5 parts of dimethyl terephthalate, 92.2 parts of ethylene glycol, 72.2 parts of neopentyl glycol, and 0.02 parts of zinc acetate were easily added and heated to 160-210 ° C while stirring under a nitrogen stream to carry out a transesterification reaction. After 97% of the theoretical amount of methanol was distilled off, 93.0 parts of isophthalic acid and 130.0 parts of azelaic acid were added thereto, and the esterification reaction was performed by heating to 160-270 ° C. The reaction vessel was gradually depressurized to 1-2 Torr and the reaction was stopped under reduced pressure when the acid value became 0.8 mgKOH / g or less to obtain a polyester polyol having a weight average molecular weight of 75,000. The resin solution which makes 50% of the concentration of the polyester polyol obtained by diluting with ethyl acetate was made into polyol A.

Neopentyl glycol 94.2 parts, 11.7-hexane diol 91.7 parts, ethylene glycol 37.6 parts, isophthalic acid 211.5 parts and sebacic acid 122.9 parts were put into the reaction vessel and heated to 160 ~ 250 ℃ while stirring under nitrogen stream to esterification reaction Done. The reaction vessel was gradually depressurized to 1 to 2 Torr and the reaction was stopped under reduced pressure when the acid value became 1 mgKOH / g or less to obtain a polyester polyol having a weight average molecular weight of 6,000 steps. 22.9 parts of isophorone diisocyanate were gradually added to the obtained polyester polyol, and it heated and reacted at 100-150 degreeC. After 6 hours of reaction, a polyester polyurethane polyol having a weight average molecular weight of 35,000 was obtained. The polyol B was used as a resin solution having a concentration of 50% of the polyester polyurethane polyol obtained by dilution with ethyl acetate.

100 parts of polyol A (50 parts of solid content), 40 parts of polyol B (20 parts of solid content), 30 parts of bisphenol A type epoxy resin having an epoxy equivalent of 600 g / eq and an epoxy group-containing organic silane coupling agent at 70 ° C. at a number average molecular weight of 1,200. The resin solution of 50% of solid content obtained by heat-dissolving and mixing and diluting with ethyl acetate was made into the main subject 1.

In addition, the total ester bond degree of the polyol A and the polyol B of the subject 1 is 0.89 calculated as follows.

That is, suppose that it reacted with dibasic acid: dihydric alcohol = 1: 1 (molar ratio) which is a raw material of each polyol, and makes the ester bond number 1. The average molecular weight (equivalent) of the dibasic acid and dihydric alcohol of this polyol is computed. The molecular weight divided by the number of ester bonds (except dehydration at the time of reaction) is prescribed | regulated as ester bond degree.

Equation of ester = 1 / molecular weight value (unit / g) = 100 / molecular weight value (unit / 100g)

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

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

.

The trimer of isophorone diisocyanate was diluted with ethyl acetate to give a resin solution having a solid content of 50% as a curing agent 1.

The solution which mix | blended the subject 1 and the hardening | curing agent 1 in solid content at 100: 12 (weight ratio), diluted with ethyl acetate, and adjusted to 30% of solid content was used as the adhesive solution.

After drying the said adhesive solution so that the quantity of an adhesive bond layer might be set to 10 g / m <2>, 1st film-3rd film lamination was performed and the laminated body of 210 mm x 295 mm (A4 size) was obtained. After lamination, aging was carried out at 60 ° C. for 7 days while the above laminate of 210 mm × 295 mm (A4 size) was placed almost horizontally, and the adhesive was cured to produce a solar cell back protective sheet.

The adhesive force (25 degreeC, 15 degreeC), the adhesive force (25 degreeC) after a weather resistance test, and tunneling were evaluated by the method of mentioning later.

Example 2

The back protective sheet for solar cells was prepared in the same manner as in Example 1 except that the curing agent 1 was made into 10 parts (Example 2), 6 parts (Example 3), and 4 parts (Example 4) for 100 parts of the subject 1, respectively. It produced and evaluated.

Comparative Example 1

About the subject 1 of 100 parts of solid content, it carried out similarly to Example 1 except having set the solid content of the hardening | curing agent 1 to 14 parts, and produced and evaluated the back surface protective sheet for solar cells.

Examples 5-11

The amount of the adhesive layer after drying using the adhesive solution of Example 2 was 3 g / m 2 (Example 5), 5 g / m 2 (Example 6), 15 g / m 2 (Example 7), 20 g / m 2 (Example 8 ) And 25 g / m 2 (Example 9), 30 g / m 2 (Example 10), and 35 g / m 2 (Comparative Example 11) except that the values were adjusted to be the same as in Example 2 to fabricate and evaluate a solar cell back protective sheet. did.

Example 12

The same adhesive solution as in Example 2 was used as a second film using a polyethylene terephthalate film (Toyo Boseki Co., Ltd .: Toyo ester film E5100) having a thickness of 100 μm instead of a 250 μm thick polyethylene terephthalate film. And except having adjusted the hardening | curing agent 1 to 10 weight part, it carried out similarly to Example 1, and produced and evaluated the back surface protective sheet for solar cells.

Comparative Example 2, Examples 13-16

The kind of resin film to be used was similar to Example 1, and changed the adhesive agent to be used.

40 parts of polyol A (20 parts of solid content), 100 parts of polyol B (50 parts of solid content), 30 parts of bisphenol A type epoxy resin having a number average molecular weight of 1,200 and epoxy equivalent of 600 g / eq and 3 parts of an epoxy group-containing organic silane coupling agent at 70 ° C. The resin solution of 50% of solid content obtained by heat-dissolving and mixing and diluting with ethyl acetate was made into the main subject 2.

To 100 parts of the subject 2, the curing agent 1 was divided into 14 parts (Comparative Example 2), 12 parts (Example 13), 10 parts (Example 14), 6 parts (Example 15), and 4 parts (Example 16). A solar cell back protective sheet was produced and evaluated in the same manner as in Example 1 except for the above.

Examples 17-18

Bisphenol A type epoxy resin of the number average molecular weight 1,400, epoxy equivalent 700g / eq (Example 17) instead of the number average molecular weight 1,200 epoxy resin (Example 17), bisphenol A type epoxy resin of the number average molecular weight 1,000, and epoxy equivalent 500g / eq (Example Except having used 30 parts 18 each, it carried out similarly to Example 2, and produced and evaluated the solar cell back protective sheet.

Comparative Example 3

The resin solution of 50% of solid content was made into the subject 3 similarly to the comparative example 1 except having made polyol A into 120 parts (solid content 60 parts) and polyol B to 20 parts (solid content 10 parts).

A solar cell back protective sheet was produced and evaluated in the same manner as in Example 1, except that a solution in which the main ingredient 3 and the curing agent 1 were mixed at 100: 14 (weight ratio), diluted with ethyl acetate, and adjusted to a solid content of 30% was used as the adhesive solution. did.

Comparative Example 4 (without Polyol B)

Without using polyol B and making polyol A 140 parts (solid content 70 parts), it carried out similarly to the comparative example 1, and produced the solar cell back protective sheet and evaluated.

Comparative Example 5 (Without Polyol A)

Without using polyol A and making polyol B 140 parts (solid content 70 parts), it carried out similarly to the comparative example 1, and produced the solar cell back surface protection sheet, and evaluated.

Comparative Example 6 (Different Curing Agent)

The trimer of isophorone diisocyanate was diluted with ethyl acetate to substitute the TMP adduct of triylene diisocyanate with ethyl acetate instead of a resin solution having a solid content of 50% to give a resin solution having a solid content of 50% as curing agent 2. In addition, 14 parts of solid content of the hardening | curing agent 2 were used with respect to the theme 1 of 100 parts of solid content. Except this, it carried out similarly to Example 1, and produced and evaluated the solar cell back surface protective sheet.

Comparative Example 7, 8 (without Polyol A)

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 added to the reaction vessel and heated to 160-210 ° C. while stirring under a nitrogen stream to carry out a transesterification reaction. After discharging, 77.5 parts of isophthalic acid and 129.6 parts of adipic acid were added thereto, and the esterification reaction was performed by heating to 160 to 240 ° C. The reaction vessel was gradually reduced to 1 to 2 Torr. The reaction was stopped at an acid value of 0.8 mg KOH / g or less to obtain a polyester polyol having a weight average molecular weight of 60,000 (ester bonding degree of 0.90 mol / 100 g). The resin solution of 50% of solid content obtained by dilution with ethyl acetate was made into polyol C.

100 parts polyol C was used instead of 100 parts polyol A. In addition, 14 parts (comparative example 7) or 10 parts (comparative example 8) of the hardening | curing agent 1 was used for the subject 1 of 100 parts of solid content. Except this, it carried out similarly to Example 1, and produced and evaluated the solar cell back surface protective sheet.

In addition, since the said polyol C has a weight average molecular weight of 60,000 and does not contain the aliphatic dibasic acid of 9-10 carbon atoms, it does not correspond to the polyester polyol A of this invention.

Comparative Example 9 (Does not contain bisphenol type epoxy resin)

A resin solution of 50% solids obtained by diluting 40 parts of polyol A (20 parts of solids), 100 parts of polyol B (50 parts of solids) and 3 parts of an epoxy group-containing organic silane coupling agent at 70 ° C. by heating, dissolving and mixing with ethyl acetate Made with topic 4. In addition, 14 parts of curing agent 1 were used for 100 parts of the subject 4. Otherwise, it carried out similarly to Example 1, and produced and evaluated the back surface protective sheet for solar cells.

Comparative Example 10

A solar cell back protective sheet was produced and evaluated in the same manner as in Example 2, except that 30 parts of a 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 number average molecular weight of 1,200.

Hereinafter, the evaluation method will be described.

<25 ℃ Initial Adhesion 15 ℃ Adhesion>

The solar cell back surface protective sheet (sample) produced by the Example and the comparative example was cut into 15 mm width about 150 mm length, and adhesive force (= peel strength) was measured in compliance with JISK6854T type peel test. Peel strength was measured by peeling each resin film layer 180 degrees at a tensile rate of 100 mm / min in the atmosphere of 25 degreeC and 15 degreeC using the test machine, and evaluated on the following criteria.

◎: 12N / 15mm or more

○: 9 N / 15 mm or more less than 12 N

△: 6N / 15mm or more but less than 9N

×: less than 6N / 15mm

<Adhesion after weathering test>

Adhesion after dump heat (test conditions 85 ° C., 85%), after 1,000 hours, after 2,000 hours (equivalent to 10 years or more in an indoor room exposure state) was measured in the same manner as before the test under an atmosphere of 25 ° C., and the initial stage was 100%. The peel strength retention ratio (%) was computed and evaluated by the following criteria.

◎: 95% strength after 2,000 hours

○: After 2,000 hours, strength is greater than 85% and less than 95%

(Triangle | delta): It maintains intensity | strength 60% or more and less than 85% after 2,000 hours.

×: less than 60% strength after 2,000 hours

<Tunneling (lifting of protective sheet on the back of solar cell on roll)>

In the Example and the comparative example, the lamination | stacking of the 1st film-the 3rd film was carried out, and the long laminate of 1 m width was wound around the outer periphery of the paper barrel of outer diameter (diameter) 170 mm, and the roll laminate was obtained. The roll laminate was placed in a state in which the core was in the vertical direction to obtain an aging solar cell back protective sheet at 60 ° C. for 7 days. The presence or absence of the protection sheet of the solar cell back surface of a roll was observed. The number of the part which lifted up was evaluated by the following criteria. "Lift" refers to the creation of a gap between the adhesive layer and the substrate.

○: no lifting

△: up to 5 places

×: 5 or more places

[Table 1A]

* 1: substrate; Thickest substrate

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

[Table 1B]

* 1: substrate; Thickest substrate

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

<Partial discharge>

It measured in air and in the oil by the method based on IEC partial discharge test (IEC61730-2, IEC60664-1).

(Circle): What is 1,000 V or more in the measuring method in air and oil.

(Triangle | delta): What is 1000 V or more only in the measuring method in oil.

X: What is less than 1,000V in any measuring method

Partial discharge evaluation is not necessarily an essential characteristic for the solar cell back protective sheet, but a good result in all samples except Example 12 in which a polyethylene terephthalate film having a thickness of 100 μm is used instead of a 250 μm polyethylene terephthalate film as the second film. Got.

This application claims the priority based on Japanese application 2011-153066 for which it applied on July 11, 2011, and inserts all of that publication here.

Claims (5)

At least 1) an outer layer substrate having weather resistance; 2) an intermediate layer substrate; and 3) an encapsulant for sealing a power generation element used in a solar cell module, and an inner layer substrate having good adhesion.
The adhesive layer which bonds at least one side of the thickest base material among the said outer layer base material, the said intermediate | middle layer base material, and the said inner layer base material to the adhesive agent containing the main material containing (1)-(3) below and the hardening | curing agent of below (4) Formed by
The solar cell back surface protection sheet which the said adhesive agent contains 4-12 weight part of solid content of the said hardening | curing agent with respect to 100 weight part of main solid content:
(1) a dibasic acid component comprising 40 to 70 mol% of aromatic dibasic acids and 30 to 60 mol% of aliphatic dibasic acids having 9 to 10 carbon atoms, and 30 to 40 mol% of aliphatic dihydric alcohols having 5 or more carbon atoms. A linear polyester polyol having a weight average molecular weight of 70,000 to 80,000 formed by reacting a dihydric alcohol component,
(2) a dibasic acid component containing 60 to 80 mol% of aromatic dibasic acids and 20 to 40 mol% of aliphatic dibasic acids having 9 to 10 carbon atoms, and 70 to 80 mol% of aliphatic dihydric alcohols having 5 or more carbon atoms. Polyester polyurethane polyol with a weight average molecular weight of 30,000-40,000 formed by making organic diisocyanate react with the polyester polyol obtained by making a dihydric alcohol component react,
(3) bisphenol-type epoxy resins having a number average molecular weight of 1,000 to 2,000,
(4) Polyisocyanate with isocyanurate of isophorone diisocyanate. The solar cell back protective sheet according to claim 1, wherein the thickness of the thickest substrate is 125 to 350 µm, and the adhesive amount 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 solar cell back protective sheet according to claim 1 or 2, wherein the interlayer substrate is plural and at least partially bonded to each other through the adhesive layer. The solar cell back protective sheet according to any one of claims 1 to 3, wherein the linear polyester polyol is 60 to 80% by weight in a total of 100% by weight of the linear polyester polyol and the polyester polyurethane polyol. . The solar cell module provided with the solar cell back surface protection sheet in any one of Claims 1-4.

Images