WO2012081243A1

WO2012081243A1 - Radiation curable adhesive and back surface-protecting sheet for solar batteries

Info

Publication number: WO2012081243A1
Application number: PCT/JP2011/006997
Authority: WO
Inventors: 諭志前田; 梅沢　三雄; 瑛齋藤; 猛吉川
Original assignee: 東洋インキＳｃホールディングス株式会社
Priority date: 2010-12-15
Filing date: 2011-12-14
Publication date: 2012-06-21
Also published as: KR20140014091A; CN103314070A; JPWO2012081243A1; TW201229177A; JP5849968B2

Abstract

Provided is a radiation curable adhesive with superior inter-sheet adhesive strength and resistance to moist heat, high quality and yield, and high producibility. This radiation curable adhesive contains an epoxy resin (E) and a (meth)acryloyl group-containing urethane resin (D) obtained by reacting: a polyol component (A) that does not contain (meth)acryloyl groups, which has a polyether polyol (A1) of 500-5,000 number average molecular weight as an essential component; a polyol component (B) having a (meth)acryloyl group and two or more hydroxyl groups; and a polyisocyanate component (C).

Description

Active energy ray-curable adhesive and solar cell back surface protective sheet

The present invention relates to an active energy ray-curable adhesive containing a urethane resin having a (meth) acryloyl group. Moreover, it is related with the back surface protection sheet for solar cells containing the above-mentioned active energy ray hardening adhesive. Furthermore, it is related with the urethane resin which has a (meth) acryloyl group used suitably for adhesives etc., such as ink, a coating material, and a back surface protection sheet for solar cells.

In recent years, solar cells have attracted attention as a clean energy source free from environmental pollution, and have been intensively studied as a useful energy resource and are being put into practical use. The solar cell element provided in the solar cell is provided with a back protective sheet for solar cell on the surface opposite to the sunlight incident surface for the purpose of protecting the solar cell element. This back protective sheet for solar cells is usually laminated with several kinds of sheet-like members via an adhesive in order to satisfy performance such as weather resistance, water vapor barrier property, electrical insulation, mechanical properties, mounting workability, etc. is doing. As an adhesive used for laminating the sheet-like member, Patent Document 1 proposes a polyurethane adhesive having hydrolysis resistance.

Moreover, in patent document 2, as a preferable example of the adhesive between the sheet-like members of the surface protection sheet for solar cell modules arranged for the purpose of protecting the solar cell element on the irradiation surface side of sunlight, urethane resin is used. Is listed. Patent Document 3 discloses an unsaturated group-containing urethane resin that is suitably applied to inks, paints, adhesives, and the like, and an active energy ray-curable resin composition containing the unsaturated group-containing urethane resin.

Polyurethane resins have been put into practical use in various fields such as paint products, adhesives, urethane foam, textile products, shoe products such as artificial leather, automobile parts, etc. A structure has been proposed (for example, Patent Documents 4 and 5).

JP 2007-320218 A JP 2007-253463 A JP 2008-127475 A Japanese Patent Laid-Open No. 57-8218 JP 2003-40965 A

By the way, when manufacturing the back surface protection sheet for solar cells industrially, after laminating | stacking a some sheet-like member, there exists a process of winding up the thing of a long state in roll shape. However, since the polyurethane-based adhesive has a slow curing reaction, there is a problem that the adhesive layer in the laminated body wound up in a roll shape tends to be insufficiently cured, and the sheet-like member is easily displaced. For this reason, the defective product generation rate is high due to the displacement of the sheet-like member, and the yield is poor.
Further, in order to sufficiently cure the polyurethane-based adhesive, it was necessary to maintain it at a high temperature and age it for several days in a warehouse. For this reason, there is a problem in that the productivity is low and the production cost is high, such as the cost of electricity for maintaining the temperature of the warehouse.
Furthermore, the isocyanate compound as the curing agent has a problem that it reacts not only with the hydroxyl group-containing resin as the main agent but also with water in the air. That is, there has been a problem that a decarboxylation reaction occurs by reacting with water, and bubbles are generated in the adhesive layer after laminating the sheet-like members, resulting in poor appearance and delamination.

Moreover, when using as an adhesive agent for back surface protection sheets for solar cells, excellent adhesive strength between sheet-like members and heat-and-moisture resistance are required, which is more than the active energy ray-curable resin composition described in Patent Document 3. An excellent adhesive was desired.

The present invention has been made in view of the above background, and its purpose is excellent in adhesive strength between sheets and wet heat resistance, high quality, high yield, and high productivity active energy ray curability. It is providing the adhesive agent and the back surface protection sheet for solar cells.

The active energy ray-curable adhesive according to the present invention comprises a polyol component (A) having no (meth) acryloyl group, which essentially comprises a polyether polyol (A1) having a number average molecular weight of 500 to 5,000, ) Urethane resin (D) having a (meth) acryloyl group obtained by reacting a polyol component (B) having an acryloyl group and having two or more hydroxyl groups with a polyisocyanate component (C), and an epoxy resin ( E) is contained.
As preferred examples of the polyether polyol (A1) having a number average molecular weight of 500 to 5,000,
Formula (1): HO (—R—O) _n —H
(In the formula, R represents a hydrocarbon group having 3 to 8 carbon atoms which may have a side chain substituent, and n represents an arbitrary integer. Examples of the side chain substituent include a methyl group and an ethyl group. .) Can be mentioned.
The number average molecular weight of the urethane resin (D) is preferably 5,000 to 150,000.
A preferable range of the urethane bond equivalent of the urethane resin (D) is 200 to 3,000.
A preferable range of the (meth) acryloyl group equivalent in the urethane resin is 500 to 40,000.
A preferred range of the number average molecular weight of the epoxy resin (E) is 450 to 5,000.
A preferable content of the urethane resin (D) is 50 to 85% by weight and a preferable content of the epoxy resin (E) is 5 to 40% by weight based on the solid content of the active energy ray-curable adhesive. is there.
Preferable examples of the polyol component (B) include those having two or more (meth) acryloyl groups.
A preferred example of the polyol component (B) is a compound in which (meth) acrylic acid is added to the epoxy group of a compound having two or more epoxy groups.

Moreover, the back surface protection sheet for solar cells which concerns on this invention is a back surface protection sheet for solar cells which protects the surface on the opposite side to the sunlight incident surface of the solar cell element provided in the solar cell, 2 A laminate of two or more sheet-like members is provided. An active energy ray-cured adhesive layer formed from the active energy ray-curable adhesive of the above aspect is used for at least a part of the adhesion between the sheet-like members constituting the laminate.
The sheet-like member constituting the laminate preferably has a water vapor barrier layer. The water vapor barrier layer is preferably selected from the group consisting of a metal foil, a plastic film with a metal oxide layer, and a plastic film with a non-metal oxide layer.
A preferable range of the glass transition temperature of the active energy ray-cured adhesive layer is −50 to 30 ° C.

ADVANTAGE OF THE INVENTION According to this invention, it is excellent in moisture resistance, productivity, quality, and the adhesive force between sheet-like members, and also the active energy ray-curable adhesion containing the urethane resin (D) which has a (meth) acryloyl group with good yield. It has the outstanding effect that an agent and the back surface protection sheet for solar cells can be provided.

The typical sectional view which is an example of the outline of the solar cell module concerning the present invention. The typical sectional view explaining the example of the back protection sheet for solar cells concerning the present invention. The typical sectional view explaining the example of the back protection sheet for solar cells concerning the present invention. The typical sectional view explaining the example of the back protection sheet for solar cells concerning the present invention. The typical sectional view explaining the example of the back protection sheet for solar cells concerning the present invention. The typical sectional view explaining the example of the back protection sheet for solar cells concerning the present invention. The typical sectional view explaining the example of the back protection sheet for solar cells concerning the present invention.

Hereinafter, embodiments of the present invention will be described in detail. In the present specification and claims, when the expression “(meth) acrylo” is used for a certain compound, the compound is obtained by replacing “(meth) acrylo” with “acrylo” and “ Any compound in which “(meth) acrylo” is replaced with “methacrylo” is included. The same definition is applied to “(meth) acryl” and “(meth) acrylate”.
In this specification, the description “any number A to any number B” means a range larger than the numbers A and A but smaller than the numbers B and B. Moreover, the ratio of each member in a figure is for convenience of explanation, and is not limited at all.

The urethane resin (D) having a (meth) acryloyl group of the present invention (hereinafter, also simply referred to as “urethane resin (D)”) requires a polyether polyol (A1) having a number average molecular weight of 500 to 5,000 as an essential component. Obtained by reacting a polyol component (A) having no (meth) acryloyl group, a polyol component (B) having a (meth) acryloyl group and having two or more hydroxyl groups, and a polyisocyanate component (C) It is something that can be done.

Moreover, the active energy ray-curable adhesive of the present invention contains the urethane resin (D) and epoxy resin (E) having the (meth) acryloyl group described above.
Furthermore, the back surface protection sheet for solar cells of this invention is a back surface protection sheet for solar cells which protects the surface on the opposite side to the sunlight incident surface of the solar cell element provided in the solar cell, A laminate of the above sheet-like members is provided. And the active energy ray hardening-processed adhesive bond layer formed from the above-mentioned active energy ray hardening adhesive is used for at least one part of adhesion | attachment between the sheet-like members which comprise a laminated body.

The number average molecular weight (Mn) of the urethane resin (D) is preferably 5,000 to 150,000, more preferably 10,000 to 100,000, more preferably 15,000 to 90,000, particularly 20,000 to 85. Is more preferable. By setting the number average molecular weight to 5,000 or more, swelling due to water vapor caused by insufficient cohesive strength of the cured adhesive layer during the moisture and heat resistance test is suppressed, and the adhesive force between the sheet-like members is kept better. be able to. In addition, when the number average molecular weight is 150,000 or less, the increase in viscosity is suppressed, the coating property becomes better, and further the effect of deterioration of solubility with other components constituting the active energy ray-curable adhesive is effective. Can be suppressed. And when the active energy ray-curable adhesive is stacked on the sheet-like member, the wettability of the adhesive layer to the sheet-like member is kept good, and as a result, the adhesive force between the sheet-like members can be more effectively kept. it can.
The value of the number average molecular weight in the present specification is a value obtained by standard polystyrene conversion using GPC (gel permeation chromatography) “HPC-8020” manufactured by Tosoh Corporation and using tetrahydrofuran as a solvent.

The urethane resin (D) preferably has a (meth) acryloyl group equivalent of 500 to 40,000, preferably 1,000 to 30,000, from the viewpoint of compatibility between the adhesion between the sheet-like members and heat and heat resistance. Is more preferable. From the standpoint of achieving both excellent adhesion between sheet-like members and heat-and-moisture resistance, it is more preferably 1,200 to 20,000, more preferably 2,000 to 10,000, particularly 2,400 to 8,000. It is preferable that The (meth) acryloyl group equivalent referred to here is the number average molecular weight per (meth) acryloyl group in the urethane resin molecule. In other words, the (meth) acryloyl group equivalent is obtained by dividing the number average molecular weight of the urethane resin (D) by the average number of (meth) acryloyl groups contained in one molecule of the urethane resin (D). Value.
By setting the (meth) acryloyl group equivalent to 500 or more, it is possible to effectively suppress a decrease in the adhesive force between the sheet-like members due to curing shrinkage during active energy ray curing. In addition, by setting the (meth) acryloyl group equivalent to 40,000 or less, swelling due to water vapor caused by insufficient cohesive strength of the cured adhesive layer during the moisture and heat resistance test is suppressed, and the adhesive force between the sheet-like members Can be kept better.

The urethane resin (D) can have a hydroxyl group terminal, an isocyanate terminal, a saturated hydrocarbon group containing an ethylenically unsaturated group, an unsaturated hydrocarbon group, or the like. If the urethane resin (D) has an isocyanate group, the isocyanate group may react with moisture in the air, resulting in an increase in viscosity or gelation. For this reason, it is preferable not to have an isocyanate group in a terminal or a side chain from a viewpoint of improving the temporal stability of a urethane resin more effectively.
In order to make the terminal of the urethane resin (D) a hydroxyl group, for example, a polyol component (A) having no (meth) acryloyl group and a polyol component (B) having a (meth) acryloyl group and having two or more hydroxyl groups (B) ) And the polyisocyanate component (C) may be reacted under conditions with relatively few isocyanate groups. Further, the urethane component having an isocyanate group is obtained by reacting under relatively few conditions as compared with the isocyanate group of the polyisocyanate component (C), in which the total of hydroxyl groups in the polyol components (A) and (B) is relatively small. By reacting an isocyanate group with, for example, a compound having one hydroxyl group or amino group, a compound having a terminal sealed with a saturated hydrocarbon group or an unsaturated hydrocarbon group can be obtained.

In addition, the urethane resin (D) preferably has a urethane bond equivalent of 200 to 3,000, more preferably 250 to 2,000 from the viewpoints of adhesive strength between sheet-like members and heat and humidity resistance. Further, 300 to 1,500, particularly 350 to 1250 is more preferable. The urethane bond equivalent referred to here is the number average molecular weight per urethane bond in one molecule of the urethane resin (D). In other words, the urethane bond equivalent is a value obtained by dividing the number average molecular weight of the urethane resin (D) by the average value of the number of urethane bonds contained in one molecule of the urethane resin (D).
By setting the urethane bond equivalent to 200 or more, the cohesive force of the curable adhesive layer or the cured adhesive layer is suppressed, and the sheet-like member is stacked on the upper layer of the curable adhesive layer or the cured adhesive layer. The wettability of the adhesive layer with respect to the sheet-like member at the time can be made good, and the adhesive force can be effectively maintained. In addition, by setting the urethane bond equivalent to 3,000 or less, it is possible to keep the heat and moisture resistance good and to suppress the decrease in the adhesive force between the sheet-like members even after the moisture and heat resistance test. The “curable adhesive layer” refers to an adhesive layer before irradiation with active energy rays, and the “cured adhesive layer” refers to a cured adhesive layer after irradiation with active energy rays.

The number of atoms in the main chain skeleton between urethane bonds is preferably 3 or more, and more preferably 5 or more. By setting the number of atoms of the main chain skeleton between urethane bonds to 3 or more, the distance between the hard segment due to aggregation of the urethane bond and the hard segment due to crosslinking of the (meth) acryloyl group in the adhesive film is appropriately maintained. The cohesive force can be exhibited in each segment better. As a result, swelling due to water vapor can be suppressed during the moisture and heat resistance test, and the adhesive force between the sheet-like members can be kept better.

As the polyol component (A) having no (meth) acryloyl group, which is essential for the polyether polyol (A1) having a number average molecular weight of 500 to 5,000, used for the formation of the urethane resin (D), the number average The polyether polyol (A1) having a molecular weight of 500 to 5,000 is essential, and other polyols (A2) can be used in combination.

As the polyether polyol (A1) having a number average molecular weight of 500 to 5,000 used for forming the urethane resin (D), a known polyether polyol can be used.
As the polyether polyol (A1), a hydroxyl group obtained by ring-opening polymerization of an alkylene oxide using a polyhydric alcohol such as ethylene glycol, propylene glycol, diethylene glycol, dipropylene glycol, trimethylolpropane, glycerin or the like using an alkali catalyst or a cation catalyst is used. Two or more things are mentioned. The materials for synthesizing the polyether polyol (A1) can be used alone or in combination of two or more. The alkylene oxide is preferably an alkylene oxide having 3 or more carbon atoms, and examples thereof include propylene oxide, 1,2-butylene oxide, 2,3-butylene oxide, epichlorohydrin, oxetane, tetrahydrofuran, and the like. Combinations of more than one species can be used. 1,3-propanediol, 2-methyl-1,3-propanediol, 2,2-dimethyl-1,3-propanediol, 1,4-butanediol, 1,5-pentanediol, 1,6 -Hexanediol, 1,7-heptanediol, 1,8-octanediol, trimethylolpropane, glycerin, and other polyhydric alcohols or mixtures of these having two or more hydroxyl groups obtained by dehydration condensation. Single or a combination of two or more can be used.
Above all,
Formula (1): HO (—R—O) _n —H
(Wherein R is a hydrocarbon group having 3 to 8 carbon atoms which may have a side chain substituent, and n is an arbitrary integer. Examples of the side chain substituent include a methyl group and an ethyl group. Is preferable because it has good heat and humidity resistance, and examples thereof include polypropylene glycol and polytetramethylene glycol.
By using the polyether polyol (A1) having a number average molecular weight of 500 or more, the urethane bond group equivalent is suppressed from being reduced, and the cohesive force of the curable adhesive layer or the cured adhesive layer becomes too large. Can be prevented. As a result, when the sheet-like member is stacked on the curable adhesive layer or the cured adhesive layer, the wettability of the adhesive layer to the sheet-like member is improved, and the adhesive force between the sheet-like members is kept better. be able to. Moreover, by making the number average molecular weight of polyether polyol (A1) 5,000 or less, cohesion force can be made appropriate and the adhesive force between sheet-like members can be kept better.

Examples of the polyol component (A2) other than the polyether polyol (A1) having a number average molecular weight of 500 to 5,000 include so-called prepolymers such as polyester polyol, polycarbonate polyol, polybutadiene polyol, polyolefin polyol, and acrylic polyol, ethylene glycol, Diethylene glycol, triethylene glycol, propylene glycol, dipropylene glycol, 1,6-hexanediol, neopentyl glycol, 1,4-butylene glycol, 1,9-nanonediol, 3-methyl-1,5-pentanediol, etc. Aliphatic diol, 1,3-cyclohexanediol, 1,4-cyclohexanediol, 1,4-cyclohexanedimethanol, 2-bis (4-hydroxycyclohexyl) Propane, hydrogenated bisphenol A, diol having an alicyclic structure such as hydrogenated bisphenol F, diols having a carboxyl group such as dimethylol butanoic acid, trimethylol propane, pentaerythritol, polyols such as glycerin. (A2) A component may be individual or may use 2 or more types together. When the diol component having an alicyclic structure is used, the wet strength and heat resistance of the adhesive strength is excellent, but the initial bond strength (adhesive strength before the wet heat resistance test) tends to decrease. Therefore, an alicyclic structure can be appropriately introduced as required.
When the polyol components (A1) and (A2) are used in combination, the proportion of the polyol component (A2) other than (A1) in the total amount thereof is preferably 40% by weight or less in the total polyol component (A). 30% by weight or less, and more preferably 20% by weight or less. In other words, the proportion of the polyol component (A1) is preferably 60% by weight or more, more preferably 70% by weight or more, and further preferably 80% by weight or more. By making the ratio of (A1) 60% by weight or more, the effect of the polyether polyol skeleton on the adhesive force can be kept good, and both excellent heat and moisture resistance and excellent adhesive force can be achieved more effectively. When a low molecular polyol is used as (A2), the urethane bond equivalent is increased by increasing the proportion of (A1), the deterioration of solubility is suppressed, and the curable adhesive layer or the cured adhesive is used. An increase in the cohesive force of the layer can be suppressed. And when a sheet-like member is accumulated on the curable adhesive layer or the cured adhesive layer, the wettability of the adhesive layer with respect to the sheet-like member can be kept good, and the adhesive force can be more effectively kept.

The polyol component (B) having a (meth) acryloyl group has two or more hydroxyl groups. By using the polyol component (B), a (meth) acryloyl group can be introduced not only into the terminal of the main chain of the urethane resin (D) but also into the side chain. By controlling the composition of the polyol components (A1), (A2) and the polyol component (B), the amount of (meth) acryloyl group introduced can be controlled.
When a polyol component (B) having two or more (meth) acryloyl groups is used, even if it is a high molecular weight urethane resin (D), the (meth) acryloyl groups can be efficiently introduced. Therefore, there is an excellent merit that active energy ray curability is improved and moisture and heat resistance can be improved.

As a polyol component (B) having a (meth) acryloyl group and two or more hydroxyl groups in one molecule, a compound in which (meth) acrylic acid is added to the epoxy group of a compound having two or more epoxy groups ( B1), glycerin mono (meth) acrylate, trimethylolethane mono (meth) acrylate, trimethylolpropane mono (meth) acrylate, pentaerythritol mono (meth) acrylate, pentaerythritol di (meth) acrylate, dipentaerythritol tetra (meth) ) Acrylate, dipentaerythritol tri (meth) acrylate, and the like. These may be used alone or in combination of two or more.

As the compound (B1) in which (meth) acrylic acid is added to the epoxy group of a compound having two or more epoxy groups, for example, a (meth) acrylic acid adduct of propylene glycol diglycidyl ether, 1,6-hexane (Meth) acrylic acid adduct of diol diglycidyl ether, (meth) acrylic acid adduct of ethylene glycol diglycidyl ether, (meth) acrylic acid adduct of 1,4-butanediol diglycidyl ether, 1,5-pentane (Meth) acrylic acid adduct of diol diglycidyl ether, (meth) acrylic acid adduct of 1,6-hexanediol diglycidyl ether, (meth) acrylic acid adduct of 1,9-nonanediol diglycidyl ether, Neo With (meth) acrylic acid of pentyl glycol diglycidyl ether Things, (meth) acrylic acid adduct of bisphenol A diglycidyl ether, (meth) acrylic acid adduct of hydrogenated bisphenol A diglycidyl ether, and (meth) acrylic acid adduct of glycerin diglycidyl ether.

Examples of the polyisocyanate component (C) used in the present invention include 2,4-tolylene diisocyanate, 2,6-tolylene diisocyanate, xylylene diisocyanate, diphenylmethane diisocyanate, isophorone diisocyanate, 1,5-naphthalene diisocyanate, Examples include an adduct, a burette, and an isocyanurate formed of a single isocyanate compound selected from hexamethylene diisocyanate, hydrogenated diphenylmethane diisocyanate, and the like, or at least one selected from the above isocyanate compounds. More than one type may be used in combination. From the viewpoint of weather resistance, the diisocyanate component is preferably an alicyclic diisocyanate.

The urethane resin (D) having a (meth) acryloyl group of the present invention may be produced by reacting raw materials in the absence of a solvent or may be produced by reacting in an organic solvent.
Organic solvents include ketone compounds such as acetone, methyl ethyl ketone, methyl isobutyl ketone and cyclohexanone, ester compounds such as methyl acetate, ethyl acetate, butyl acetate, ethyl lactate and methoxyethyl acetate, ethers such as diethyl ether and ethylene glycol dimethyl ether. Various solvents such as aromatic compounds such as a series compound, aromatic compounds such as toluene and xylene, aliphatic compounds such as pentane and hexane, and halogenated hydrocarbon compounds such as methylene chloride, chlorobenzene, and chloroform can be used.

In addition, a catalyst can be added as necessary during the synthesis of the urethane resin (D) of the present invention. For example, metal catalysts such as dibutyltin diacetate, dibutyltin dilaurate, dioctyltin dilaurate, dibutyltin dimaleate; 1,8-diaza-bicyclo (5,4,0) undecene-7,1,5-diazabicyclo (4,3 , 0) tertiary amines such as nonene-5,6-dibutylamino-1,8-diazabicyclo (5,4,0) undecene-7; and reactive tertiary amines such as triethanolamine. These may be used alone or in combination of two or more.

Next, the active energy ray-curable adhesive of the present invention will be described.
The active energy ray-curable adhesive of the present invention contains the aforementioned urethane resin (D) and epoxy resin (E).

As the epoxy resin (E) used in the present invention, bisphenol A type epoxy resin, bisphenol F type epoxy resin, bisphenol S type epoxy resin, brominated bisphenol A type epoxy resin, hydrogenated bisphenol A type epoxy resin, biphenol type Epoxy resin, bixylenol type epoxy resin, phenol novolac type epoxy resin, cresol novolac type epoxy resin, brominated phenol novolak type epoxy resin, bisphenol A novolac type epoxy resin, trihydroxyphenylmethane type epoxy resin, tetraphenylolethane type Glycidyl ether compounds such as epoxy resins, naphthalene skeleton-containing phenol novolac epoxy resins, dicyclopentadiene skeleton-containing phenol novolac epoxy resins; Glycidyl ester compounds such as diglycidyl rephthalate; Alicyclic epoxy resins such as EHPE-3150 manufactured by Daicel Chemical Industries; heterocyclic epoxy resins such as triglycidyl isocyanurate; N, N, N ′, N Examples thereof include glycidylamines such as' -tetraglycidylmetaxylenediamine, and epoxy compounds such as a copolymer of glycidyl (meth) acrylate and a compound having an ethylenically unsaturated double bond. These may be used alone or in combination of two or more.

By including the resin (E) in the active energy ray-curable adhesive, the functional group generated by the decomposition of the urethane resin during the moisture and heat resistance test can be reacted with the epoxy group, and the decrease in the molecular weight of the adhesive layer can be suppressed. It is possible to suppress a decrease in adhesive strength.

From the viewpoint of wet heat resistance of the adhesive layer and compatibility with the urethane resin (D), the epoxy resin (E) is preferably a bisphenol type epoxy resin having a number average molecular weight of 450 to 5,000, preferably 450 to 5,000. Bisphenol-type epoxy resins are more preferred, 500-5,000 bisphenol-type epoxy resins are more preferred, and 800-4,000 bisphenol-type epoxy resins are more preferred. By setting the number average molecular weight of the epoxy resin to 450 or more, it is possible to prevent the adhesive layer from becoming soft and the heat-and-moisture resistance cannot be obtained, and better moisture-and-heat resistance can be obtained. By setting the number average molecular weight of the epoxy resin to 5,000 or less, it is possible to suppress deterioration of compatibility with other components of the active energy ray-curable adhesive and effectively prevent the adhesive from becoming cloudy. .

The active energy ray-curable adhesive of the present invention can contain a compound having a (meth) acryloyl group other than the urethane resin (D). Examples of the compound having a (meth) acryloyl group other than the urethane resin (D) contained in the active energy ray-curable adhesive of the present invention include a relatively low molecular weight (meth) acrylate monomer and a certain molecular weight. There are large so-called prepolymers and polymers.
Examples of relatively low molecular weight (meth) acrylate monomers include monofunctional (meth) acrylate monomers such as 4-hydroxybutyl (meth) acrylate, isobornyl (meth) acrylate, lauryl (meth) acrylate, and acryloylmorpholine; 1,9-nonanediol di (meth) acrylate, bisphenol A di (meth) acrylate, pentaerythritol tri (meth) acrylate, tris ((meth) acryloxyethyl) isocyanurate, and dipentaerythritol hexa (meth) A polyfunctional (meth) acrylate monomer such as acrylate can be exemplified.
Examples of the prepolymer and polymer include radical polymerization having a (meth) acryloyl group such as polyester (meth) acrylate, polyurethane (meth) acrylate, polyepoxy (meth) acrylate, and (meth) acrylated maleic acid-modified polybutadiene. Mention may be made of prepolymers or polymers.
These may be used alone or in combination of two or more.

The active energy ray-curable adhesive of the present invention can appropriately contain a photopolymerization initiator, a sensitizer, a compound having no active energy ray curability, and the like.

A known photopolymerization initiator can be used as the photopolymerization initiator. For example, benzophenone, 1-hydroxycyclohexyl phenyl ketone, 2,2-dimethoxy-1,2-diphenylethane-1-one, 2,4,6-trimethylbenzoyldiphenylphosphine oxide, 2-benzyl-2-dimethylamino- 1- (4-morpholinophenyl) butanone-1,2-hydroxy-2-methyl-1-phenylpropan-1-one, 2-methyl-1- (4-methylthiophenyl) -2-morpholinopropane-1 -One, benzoin methyl ether, benzoin ethyl ether, benzoin isobutyl ether, benzoin isopropyl ether, bis (2,4,6-trimethylbenzoyl) -phenylphosphine oxide, 2-hydroxy-2-methyl- (4- (1- Methylvinyl) phenyl) propa Oligomer, isopropylthioxanthone, (4- (methylphenylthio) phenyl) phenylmethane, 2,4-diethylthioxanthone, 2-chlorothioxanthone, ethyl anthraquinone, etc., and these may be used alone or in combination of two or more. .
In addition to the photopolymerization initiator, aliphatic amines such as n-butylamine, triethylamine, ethyl p-dimethylaminobenzoate, and aromatic amines may be used in combination as a sensitizer.

The active energy ray-curable adhesive of the present invention can further contain other compounds having no active energy ray curability. Compounds that do not have active energy ray curability include acrylic resins, polyester resins, amino resins, xylene resins, petroleum resins and other curing agents, isocyanate compounds, aziridine compounds and other curing agents, aluminum chelate compounds, silane coupling agents, and ultraviolet rays. Absorbers, antioxidants, leveling agents, antifoaming agents, adhesion aids, dispersants, drying regulators, antifriction agents, and the like can be blended.

The active energy ray-curable adhesive of the present invention is based on the solid content of the active energy ray-curable adhesive, 50 to 85% by weight of the urethane resin (D), 5 to 40% by weight of the epoxy resin (E), It is preferable to contain 0 to 30% by weight of a compound having a (meth) acryloyl group other than the urethane resin (D), 60 to 85% by weight of the urethane resin (D), and 10 to 34% by weight of the epoxy resin (E). It is more preferable to contain 0 to 15% by weight of a compound having a (meth) acryloyl group other than the urethane resin (D).
By setting the urethane resin (D) to 50% by weight or more, a decrease in the cohesive force of the adhesive layer can be suppressed, and the adhesive force and heat and humidity resistance can be more effectively maintained. Moreover, moisture-heat-resistance can be kept more favorable by setting it as 85 weight% or less.
By making the epoxy resin (E) 5% by weight or more, the moisture and heat resistance is made better, and by making it 40% by weight or less, the urethane resin (D) having a (meth) acryloyl group is sufficiently cured, Thermal properties and adhesive strength can be kept better.
By setting the compound having a (meth) acryloyl group other than the urethane resin (D) to 30% by weight or less, it is possible to effectively prevent a decrease in adhesive force due to shrinkage during curing.

The active energy ray-cured adhesive layer constituting the solar cell back surface protective sheet of the present invention preferably has a glass transition temperature of −50 ° C. to 30 ° C. In other words, the active energy ray-curable adhesive is capable of forming a cured adhesive layer having a glass transition temperature of −50 ° C. to 30 ° C. when cured by irradiation with active energy rays. preferable. Further, it is more preferably −40 ° C. to 25 ° C., more preferably −35 ° C. to 20 ° C., further preferably −35 ° C. to 10 ° C., particularly preferably −35 ° C. to 5 ° C.
By setting the glass transition temperature to 30 ° C. or lower, when the sheet-like member is stacked on the curable adhesive layer or the cured adhesive layer, the wettability of the adhesive layer with respect to the sheet-like member is suppressed. The adhesive force between the sheet-like members can be kept better. In addition, by setting the glass transition temperature to −50 ° C. or higher, it is possible to suppress a decrease in the cohesive strength of the adhesive layer, and to more effectively maintain the adhesive strength and wet heat resistance.

Next, the back surface protection sheet for solar cells of the present invention will be described. First, FIG. 1 shows a schematic cross-sectional view which is an example of the outline of the solar cell module according to the present invention. As shown in the figure, the solar cell module 100 includes a solar cell 1, which is a solar cell element, a solar cell surface protective sheet 2, a light-receiving surface side sealing material layer 3, a non-light-receiving surface side sealing material layer 4, The back surface protection sheet 5 for solar cells is provided. As shown in FIG. 1, the solar cell 1 includes a light-receiving surface side sealing material layer 3 positioned on the light-receiving surface side of the solar cell 1 and a non-light-receiving surface side positioned on the non-light-receiving surface side of the solar cell 1. It is sandwiched and sealed between the sealing material layers 4. And the light-receiving surface side sealing material layer 3 is protected by the surface protection sheet 2 for solar cells, and the non-light-receiving surface side sealing material 4 is protected by the back surface protection sheet 5 for solar cells. In addition, the structure of the solar cell module which concerns on this invention is not limited to the structure of FIG. 1, A various deformation | transformation is possible.

The back surface protective sheet 5 for solar cells is usually composed of a laminate of a plurality of sheet-like members in order to satisfy performances such as weather resistance, water vapor barrier properties, electrical insulation properties, mechanical properties, and mounting workability. .

2A to 2F are schematic cross-sectional views for explaining an example of the solar cell back surface protective sheet 5 according to the present invention. The back surface protection sheet 5a for solar cells in FIG. 2A has a two-layer sheet-shaped member of a first sheet-shaped member 11 and a second sheet-shaped member 12. The first sheet-like member 11 and the second sheet-like member 12 include an active energy ray-cured adhesive layer 51 (hereinafter also simply referred to as “adhesive layer 51”) formed from an active energy ray-curable adhesive. Are joined through. The first sheet-like member 11 and the second sheet-like member 12 are a plastic film, a metal foil, a plastic film with a metal layer, a plastic film with a metal oxide layer, a plastic film with a non-metal oxide layer, and a plastic with a silicon nitride layer It can be formed by a film or the like. The metal layer, metal oxide layer, nonmetal oxide layer, and silicon nitride layer can be formed by vapor deposition or the like.

As a suitable example of FIG. 2A, for example, the first sheet-like member 11 is formed of a plastic film, and the second sheet-like member 12 is made of a metal oxide such as aluminum, a metal oxide such as alumina, or a non-metal oxide such as silicon dioxide. Examples include a plastic film 21 provided with a vapor deposition layer 22 made of a material, silicon nitride, or the like. Moreover, like the back surface protection sheet 5b for solar cells of FIG. 2B, the vapor deposition layer 22 which consists of metal oxides, such as an alumina, nonmetal oxides, such as a silicon dioxide, etc. of the 2nd sheet-like member 12, is the adhesive bond layer 51. It may be provided on the side. Furthermore, as shown in FIG. 2C, a metal foil 23 such as an aluminum foil can be used as the second sheet-like member 12. In this case, a coating layer 24 such as a white coat layer can be provided on the non-light-receiving surface side of the metal foil 23. The coating layer 24 can be colored as necessary.
2A to 2C, the second sheet-like member 12 functions as a water vapor barrier layer. Of course, both the 1st sheet-like member 11 and the 2nd sheet-like member may be comprised with the plastic film etc. By laminating two sheets of sheets, it is possible to effectively satisfy a plurality of characteristics required for the back surface protection sheet for solar cells. In addition, there is no restriction | limiting in particular in the thickness of the film as used in this specification.

2D has a three-layered sheet-like member including a first sheet-like member 11, a second sheet-like member 12, and a third sheet-like member 13. The first sheet-like member 11 and the second sheet-like member 12 are bonded via the first adhesive layer 51, and the second sheet-like member 12 and the third sheet-like member 13 are interposed via the second adhesive layer 52. Are joined. A preferred example of FIG. 2D is an example in which the first sheet-like member 11 to the third sheet-like member 13 are all made of a plastic film. Further, as shown in FIGS. 2A and 2B, a plastic film on which a metal, a metal oxide, or a nonmetal oxide is deposited may be used for any sheet-like member. Moreover, as shown in FIG. 2C, the sheet-like member itself may be a metal foil such as an aluminum foil. By laminating three layers of sheets, the sheet can be designed to more effectively satisfy a plurality of characteristics required for the back surface protection sheet for solar cells.

2E has a four-layered sheet-like member including a first sheet-like member 11, a second sheet-like member 12, a third sheet-like member 13, and a fourth sheet-like member 14. The first sheet-like member 11 and the second sheet-like member 12 are bonded via the first adhesive layer 51, and the second sheet-like member 12 and the third sheet-like member 13 are interposed via the second adhesive layer 52. The third sheet-like member 13 and the fourth sheet-like member 14 are joined via the third adhesive layer 53. As a suitable example of FIG. 2E, for example, the first sheet-like member 11, the second sheet-like member 12, and the fourth sheet-like member 14 are made of a plastic film, and the third sheet-like member 13 is a metal such as an aluminum foil. The example which comprises with foil is given. In this case, the third sheet-like member 13 functions as a barrier layer. By laminating four layers of sheets, the characteristics of the back surface protective sheet for solar cells can be made more excellent. As the third sheet-like member 13, a non-metal oxide layer 31 made of silicon oxide or the like deposited on a plastic film 32 may be used as in the solar cell back surface protection sheet 5f shown in FIG. 2F. Instead of the non-metal oxide layer, a metal or metal oxide layer deposited on the plastic film 32 can be used. 2A to 2F are merely examples, and various modifications are possible.

As the plastic film, for example, a polyester resin film such as polyethylene terephthalate, polynaphthalene terephthalate,
Polyethylene resin film, polypropylene resin film, polyvinyl chloride resin film, polycarbonate resin film, polysulfone resin film, poly (meth) acrylic resin film,
Fluorine resins such as polyvinyl fluoride, polyvinylidene fluoride, polychlorotrifluoroethylene, polyethylene tetrafluoroethylene, polytetrafluoroethylene, tetrafluoroethylene perfluoroalkyl vinyl ether copolymer, tetrafluoroethylene-hexafluoropropylene copolymer A film etc. are mentioned.
Using these plastic films as a support, a film formed by coating acrylic or fluorine-based paint, a multilayer film obtained by laminating polyvinylidene fluoride, acrylic resin, or the like by coextrusion can be used. Furthermore, you may use the sheet-like member by which multiple said plastic films were laminated | stacked through the urethane type adhesive bond layer.

Examples of the metal foil include aluminum foil and copper foil.
Examples of the metal oxide or non-metal inorganic oxide to be deposited include oxides such as silicon, aluminum, magnesium, calcium, potassium, tin, sodium, boron, titanium, lead, zirconium, and yttrium.

Among these, polyethylene terephthalate, polynaphthalene terephthalate, etc. that have resistance to temperature in order to satisfy performance such as weather resistance, water vapor barrier property, electrical insulation, mechanical properties, mounting workability when used as a solar cell module Polyester-based resin film, polycarbonate-based resin film, and plastic film or aluminum foil on which a metal oxide or non-metal inorganic oxide having a water vapor barrier property is deposited in order to prevent a decrease in output due to the influence of water on the solar battery cell In order to prevent appearance defects due to photodegradation and the like, and a fluorine-based resin film having good weather resistance, a back protective sheet for solar cells is preferable.

Among them, as a combination of the sheet-like members of the laminated body, from the incident surface side of sunlight, the light receiving surface side sealing material layer 4 and the polyethylene-based resin film, the polypropylene-based resin film, the fluororesin film and the like having good adhesion A polyester resin film having a polyolefin resin film or corona treatment, a polyester resin layer or an acrylic resin layer formed thereon is laminated, and then a polyester resin film thicker than 100 μm is laminated for the purpose of providing electrical insulation, Next, in some cases, a metal film such as a plastic film or aluminum foil on which a metal oxide or nonmetal inorganic oxide having a water vapor barrier property is deposited is laminated, and then weather resistance is good to prevent appearance defects due to light deterioration Fluorine-based resin film, weather resistant resin layer may be formed Ester-based resin film is laminated solar cell back surface protective sheet is preferred.

The solar cell back surface protection sheet of the present invention can be obtained, for example, by the following production method.
[1] An active energy ray-curable adhesive is applied to one arbitrary sheet-like member, and another sheet-like member is stacked on the formed active energy ray-curable adhesive layer, and then one sheet-like member Active energy rays are irradiated from the side or from both sheet-like members, and an active energy ray-cured adhesive layer is formed between both sheet-like members, or
[2] An active energy ray-curable adhesive layer is applied to any one sheet-like member to form an active energy ray-curable adhesive layer, and / or from the active energy ray-curable adhesive layer side After irradiating active energy rays from the side of the member and forming the active energy ray-cured adhesive layer, another sheet-like member is laminated on the active energy ray-cured adhesive layer, or
[3] An active energy ray curable adhesive is applied to any one sheet-like member to form an active energy ray curable adhesive layer, and / or from the active energy ray curable adhesive layer side. After irradiating an active energy ray from the side of the member and forming an active energy ray-cured adhesive layer, another sheet-like member forming coating liquid is applied to the active energy ray-cured adhesive layer. The back surface protection sheet for solar cells of the present invention can be produced by forming other sheet-like members by heat or active energy rays.
Other sheet-form member forming coating solutions used in the method of [3] include polyester resin solutions, polyethylene resin solutions, polypropylene resin solutions, and polyvinyl chloride resin solutions that can be used to form plastic films. Preferred examples include polycarbonate resin solutions, polysulfone resin solutions, poly (meth) acrylic resin solutions, and fluorine resin solutions.

In the method of [1], the active energy ray-curable adhesive layer is irradiated with the active energy ray-curable adhesive layer sandwiched between two sheet-like members. It has the advantage of being less susceptible to oxygen inhibition. However, on the other hand, since the active energy ray-curable adhesive layer is irradiated with the active energy ray through the sheet-like member, regardless of whether the active energy ray-curable adhesive is radically polymerizable, It is important to use a sheet-like member that can transmit active energy rays without being attenuated as much as possible.
The method [2] has completely opposite characteristics to the method [1]. That is, the active energy ray is irradiated in a situation where oxygen inhibition is likely to occur, but it has the advantage that the options of sheet-like members that can be used are widened.
In the method of [3], the active energy ray is irradiated in a situation where it is susceptible to oxygen inhibition in the first step, but on the other hand, another sheet-like member forming coating liquid is applied to the formed adhesive layer, Since another sheet-like member is formed, there is an advantage that it is easy to ensure the adhesive force between the adhesive layer and the other sheet-like member.
Various manufacturing methods can be selected or further combined in consideration of performance, price, productivity and the like required for the back surface protection sheet for solar cells.
In the case of [1] and [2], when another sheet-like member is overlaid on the curable adhesive layer or the cured adhesive layer, it can be overlaid under heating and / or pressure conditions.

When the active energy ray-curable adhesive is applied to the sheet-like member, a solvent may be included within a range that does not affect the sheet-like member in the drying step in order to adjust the coating liquid to an appropriate viscosity. . When the active energy ray-curable adhesive contains a solvent, after the solvent is volatilized, the active energy ray-curable adhesive can be cured by irradiation with active energy rays.
Solvents include ketone compounds such as acetone, methyl ethyl ketone, methyl isobutyl ketone and cyclohexanone, ester compounds such as methyl acetate, ethyl acetate, butyl acetate, ethyl lactate and methoxyethyl acetate, ethers such as diethyl ether and ethylene glycol dimethyl ether. Compounds, aromatic compounds such as toluene and xylene, aliphatic compounds such as pentane and hexane, halogenated hydrocarbon compounds such as methylene chloride, chlorobenzene and chloroform, alcohols such as ethanol, isopropyl alcohol and normal butanol, and water It is done. These solvents may be used alone or in combination of two or more.

In the present invention, the active energy ray-curable adhesive is applied to the sheet-like member as a comma coater, dry laminator, roll knife coater, die coater, roll coater, bar coater, gravure roll coater, reverse roll coater, blade. Examples include coaters, gravure coaters, and micro gravure coaters.

The amount of adhesive applied to the sheet-like member is preferably about 0.1 to 50 g / m ^{2 in} terms of dry film thickness.

Examples of active energy rays irradiated for curing the active energy ray-curable adhesive include ultraviolet rays, electron beams, γ rays, infrared rays, and visible rays.

<Example>
Hereinafter, the present invention will be described more specifically with reference to examples. However, the present invention is not limited to the following examples. In the examples, all parts and% indicate parts by weight and% by weight.
Below, it shows about the synthesis | combination of the urethane resin which has a (meth) acryloyl group, an active energy ray hardening adhesive, and the preparation methods of the back surface protection sheet for solar cells.

Example 1 (Synthesis of urethane resin having (meth) acryloyl group)
800.0 parts of methyl ethyl ketone (MEK) and polytetramethylene ether glycol PTMG-2000 (Mitsubishi Chemical) in a polymerization reactor of a polymerization reactor equipped with a polymerization vessel, a stirrer, a thermometer, a reflux condenser, a nitrogen introduction tube, and a dropping vessel 857.4 parts, 31.2 parts of epoxy ester 70PA (manufactured by Kyoeisha Chemical Co., Ltd.), a compound obtained by adding 2 mol of acrylic acid to propylene glycol diglycidyl ether, and dibutyltin dilaurate (DBTDL) as a catalyst. 0.5 part, 0.3 part of hydroquinone as a radical polymerization inhibitor and 0.1 part of IRGANOX 1010 (manufactured by BASF) as an antioxidant were charged, and the temperature in the polymerization tank was 80 ° C. with stirring in a nitrogen stream. I raised it. When the temperature reached 80 ° C., a mixture of 111.4 parts of isophorone diisocyanate (IPDI) and 200.0 parts of MEK was dropped from the dropping tank into the polymerization tank over 2 hours. Thereafter, the reaction was continued at 80 ° C. for 4 hours, and the reaction was terminated after confirming that the absorption peak of the isocyanate group had completely disappeared with an infrared spectrophotometer, and a urethane having a (meth) acryloyl group having a solid content of 50%. Resin D-1 was obtained. The properties of D-1 are shown in Table 1A.

Examples 2 to 10, Examples 101 to 103
According to the composition of Table 1A or 1B, the reaction was carried out in the same manner as in Synthesis Example 1 to obtain urethane resins D-2 to D-10 and urethane resins D-14 to D-16 having (meth) acryloyl groups. . The properties of urethane resins D-2 to D-10 and urethane resins D-14 to D-16 are shown in Table 1A or Table 1B.

Comparative Example 1
800.0 parts of methyl ethyl ketone (MEK) and polytetramethylene ether glycol PTMG-2000 (Mitsubishi Chemical) in a polymerization reactor of a polymerization reactor equipped with a polymerization vessel, a stirrer, a thermometer, a reflux condenser, a nitrogen introduction tube, and a dropping vessel 907.2 parts, 0.5 parts of dibutyltin dilaurate (DBTDL) as a catalyst, 0.3 parts of hydroquinone as a radical polymerization inhibitor, 0.1 parts of IRGANOX 1010 (manufactured by BASF) as an antioxidant. The temperature in the polymerization tank was raised to 80 ° C. while stirring under a nitrogen stream. When the temperature reached 80 ° C., a mixture of 92.8 parts of isophorone diisocyanate (IPDI) and 200.0 parts of MEK was dropped from the dropping tank into the polymerization tank over 2 hours. Thereafter, the reaction was continued at 80 ° C. for 4 hours, and the primary reaction was completed after confirming that the absorption peak of the isocyanate group had completely disappeared with an infrared spectrophotometer.
Next, 3.6 parts of acrylic acid and 1.0 part of tetrabutylammonium bromide as a catalyst were added to the reaction tank, and the temperature in the polymerization tank was raised to 100 ° C. to continue the reaction. The reaction is continued until the acid value becomes 1.0 mgKOH / g or less. When the acid value becomes 1.0 mgKOH / g or less, the reaction is terminated to obtain a urethane resin D-11 having a (meth) acryloyl group having a solid content of 50%. It was. Properties of the urethane resin D-11 are shown in Table 1B.

Comparative Example 2
According to the composition shown in Table 1B, the reaction was conducted in the same manner as in Comparative Example 1 to obtain a urethane resin D-12 having a (meth) acryloyl group. Properties of the urethane resin D-12 are shown in Table 1B.

Comparative Example 3
According to the composition shown in Table 1B, the reaction was carried out in the same manner as in Synthesis Example 1 to obtain a urethane resin D-13 having a (meth) acryloyl group. Properties of the urethane resin D-13 are shown in Table 1B.

Details of each component in Table 1A and Table 1B are as follows.
PTMG-3000: Polytetramethylene ether glycol number average molecular weight 3,000 manufactured by Mitsubishi Chemical Corporation
PTMG-2000: polytetramethylene ether glycol number average molecular weight 2,000 manufactured by Mitsubishi Chemical Corporation
PTMG-1000: polytetramethylene ether glycol number average molecular weight 1,000 manufactured by Mitsubishi Chemical Corporation
EXCENOL-2020: Polypropylene glycol manufactured by Asahi Glass Co., Ltd. Number average molecular weight 2,000
C-1090: manufactured by Kuraray Co., Ltd., polycarbonate diol number average molecular weight = 1,000
MPD: 3-methyl-1,5-pentanediol 1,9-ND: 1,9-nonanediol CHDM: cyclohexane dimethanol epoxy ester 70AP: manufactured by Kyoeisha Chemical Co., Ltd., 2 mol of acrylic acid is added to propylene glycol diglycidyl ether Added compound DBTDL: Dibutyltin dilaurate IRGANOX 1010: Hindered phenol antioxidant manufactured by BASF IPDI: Isophorone diisocyanate AA: Acrylic acid TBAB: Tetrabutylammonium bromide MEK: Methyl ethyl ketone

<Mn, Mw>
For the measurement of Mn and Mw, GPC (gel permeation chromatography) “HPC-8020” manufactured by Tosoh Corporation was used, and tetrahydrofuran was used as a solvent. Mn and Mw were calculated in terms of polystyrene.

Examples 11 to 20, Examples 104 to 106, Comparative Examples 4 to 6 (production of active energy ray-curable adhesive)
Resin solution of urethane resin (D) having (meth) acryloyl group obtained by the above synthesis, epoxy resin (E), active energy ray-curable compound other than urethane resin (D) having (meth) acryloyl group, light A polymerization initiator and other components are blended according to parts by weight shown in Table 2A or Table 2B, and active energy ray-curable adhesives 1 to 7, 12 to 17 (above, Examples 11 to 20, Examples 104 to 106). Active energy ray-curable adhesives 8 to 10 (Comparative Examples 4 to 6) were obtained.

Details of each component in Tables 2A and 2B are as follows.
Epicoat 834: Epoxy resin (manufactured by Japan Epoxy Resin) Number average molecular weight 470 Epicoat 1001: Epoxy resin (manufactured by Japan Epoxy Resin) Number average molecular weight 900
Epicoat 1009: Epoxy resin (Japan Epoxy Resin Co., Ltd.) Number average molecular weight 3,800
M210: EO-modified bisphenol A diacrylate (manufactured by Toagosei Co., Ltd.)
M305: Pentaerythritol triacrylate (manufactured by Toagosei Co., Ltd.)
Irgacure 184: 1-hydroxy-cyclohexyl ruphenyl ketone (Ciba Specialty Chemicals)

The glass transition temperature (Tg) of the cured product of each adhesive shown in Table 2A and Table 2B was determined as follows. A cured adhesive sheet having a thickness of about 200 μm was prepared and measured using a dynamic viscoelasticity measuring apparatus DVA-200 (manufactured by IT Measurement Control Co., Ltd.), and the temperature at the peak value of tan δ was defined as the glass transition temperature.

The cured adhesive sheet was prepared by applying an adhesive to a polyester film having a silicone release layer with a blade coater, drying the solvent, and then applying ultraviolet rays (120 W metal halide lamp, integrated light quantity of 500 mJ / UV-A region). cm ² ), an active energy ray-curable adhesive layer was formed, and the polyester film was peeled off.

(Methods 1 to 6 for manufacturing a back surface protection sheet for solar cells)
Manufacturing method 1
After applying the active energy ray-curable adhesive to the sheet-like member (S1) and volatilizing the solvent, the other sheet-like member (S2) was passed between the two rolls set at 60 ° C. . After stacking, the other sheet-like member (S1) side is irradiated with ultraviolet rays (120 W metal halide lamp, integrated light amount of 500-mJ / cm ^{2 in the} UV-A region) to form an active energy ray-cured adhesive layer to form a solar cell. A back protective sheet was prepared. The amount of the adhesive layer was 8 to 10 g / m ² .

Manufacturing method 2
The active energy ray-curable adhesive is applied to the sheet-like member (S2), and the solvent is volatilized, followed by irradiation with ultraviolet rays (120 W high-pressure mercury lamp, integrated light amount of 200 mJ / cm ^{2 in the} UV-A region) from the coated surface side. Then, an active energy ray-cured adhesive layer was formed. Then, the other sheet-like member (S1) was piled up, and the laminated body was produced by passing between two rolls set to 60 degreeC, and laminating | stacking.
Next, an active energy ray-curable adhesive was applied to the S2 side of the laminate, and the solvent was volatilized. Then, an ultraviolet ray (120 W high-pressure mercury lamp, UV-A region integrated light quantity 200 mJ / cm ^{2 was} applied from the coated surface side. ) To form an adhesive layer that has been subjected to the active energy ray curing treatment. Thereafter, another sheet-like member (S3) was stacked while passing between two rolls set to 60 ° C., and after lamination, a solar cell back surface protective sheet was produced. The amount of the two adhesive layers was 8 to 10 g / m ² .

Manufacturing method 3
Apply active energy ray-curable adhesive to the sheet-like member (S4), volatilize the solvent, and then irradiate with ultraviolet rays (120W high-pressure mercury lamp, integrated light quantity of UV-A region 200mJ / cm ² ) from the coated surface side. Then, an active energy ray-cured adhesive layer was formed. Then, while laminating other sheet-like members (S3), it was passed between two rolls set at 60 ° C., and a laminate was produced after lamination.
Next, an active energy ray-curable adhesive was applied to the S3 side of the laminate, and the solvent was volatilized. Then, an ultraviolet ray (120 W high-pressure mercury lamp, UV-A region integrated light quantity 200 mJ / cm ^{2 was} applied from the coated surface side. ) To form an adhesive layer that has been subjected to the active energy ray curing treatment. Thereafter, another sheet-like member (S2) was stacked while passing between two rolls set at 60 ° C., and after lamination, a laminate was produced.
Next, an active energy ray-curable adhesive was applied to the S2 side of the laminate, and the solvent was volatilized. Then, an ultraviolet ray (120 W high-pressure mercury lamp, UV-A region integrated light quantity 200 mJ / cm ^{2 was} applied from the coated surface side. ) To form an adhesive layer that has been subjected to the active energy ray curing treatment, and then passed between two rolls set at 60 ° C. while laminating another sheet-like member (S1). Then, the back surface protection sheet for solar cells was produced. The amount of the two adhesive layers was 8 to 10 g / m ² .

Manufacturing method 4
After applying a thermosetting urethane-based adhesive to the sheet-like member (S1) and volatilizing the solvent, the other sheet-like member (S2) is stacked and passed between two rolls set at 60 ° C. Laminated. Thereafter, this was aged for 1 week in an environment of 60 ° C. to obtain a back surface protection sheet for solar cells. The amount of the adhesive layer was 8 to 10 g / m ² .

Manufacturing method 5
After applying a thermosetting urethane-based adhesive to the sheet-like member (S2) and volatilizing the solvent, while passing another sheet-like member (S1), let it pass between two rolls set at 60 ° C, A laminate was made.
Next, after applying a thermosetting urethane-based adhesive on the S2 side of the laminate and evaporating the solvent, another sheet-like member (S3) is stacked and between two rolls set at 60 ° C. And passed through. Thereafter, this was aged for 1 week in an environment of 60 ° C. to obtain a back surface protection sheet for solar cells. The amount of the two adhesive layers was 8 to 10 g / m ² .

Manufacturing method 6
After applying a thermosetting urethane-based adhesive to the sheet-like member (S4) and volatilizing the solvent, while passing another sheet-like member (S3), let it pass between two rolls set at 60 ° C, A laminate was made.
Next, after applying a thermosetting urethane-based adhesive on the S3 side of this laminate and volatilizing the solvent, another sheet-like member (S2) is stacked, and between the two rolls set at 60 ° C. Passed through to make a laminate.
Next, after applying a thermosetting urethane-based adhesive on the S2 side of this laminate and volatilizing the solvent, another sheet-like member (S1) was stacked and the two rolls set at 60 ° C. were sandwiched. Passed and laminated. Thereafter, this was aged for 1 week in an environment of 60 ° C. to obtain a back surface protection sheet for solar cells. The amount of the two adhesive layers was 8 to 10 g / m ² .

(Examples 21 to 33, 107 to 109, Comparative Examples 7 to 15)
A solar cell back surface protective sheet was obtained by a combination of the active energy ray-curable adhesive shown in Tables 3A, 3B, and 4 and the solar cell back surface protective sheet production method and sheet-like member. According to the method described later, the adhesiveness, heat and humidity resistance, productivity, and presence of bubbles were evaluated. The results are shown in Table 3A, Table 3B, and Table 4. In addition, Example 21 and Comparative Examples 7, 12, and 16 are examples of the laminated structure shown in FIG. 2C, and Example 22, Comparative Examples 8, 13, and 17 are examples of the laminated structure shown in FIG. Examples 23, 25 to 33, 107 to 109, and Comparative Examples 9, 11, 14, and 18 are examples of the laminated structure shown in FIG. 2E. Examples 24 and Comparative Examples 10, 15, and 19 are shown in FIG. 2F. It is an example of the laminated structure shown.

(Comparative Examples 16 to 19)
Polyester diol P-3010 (manufactured by Kuraray Co., Ltd.) is reacted with isophorone diisocyanate, and a polyurethane having a hydroxyl group with a number average molecular weight of 15,000 so that a burette of hexamethylene diisocyanate has a solid content ratio of 10: 1. Furthermore, Epicoat 1001 was blended at a solid content ratio of 30% by weight to produce a thermosetting urethane-based adhesive 11. Using this, the back surface protection sheet for solar cells was obtained with the combination of the thermosetting urethane type adhesive shown in Table 5, the production method of the back surface protection sheet for solar cells, and a sheet-like member. According to the method described later, the adhesiveness, heat and humidity resistance, productivity, and presence of bubbles were evaluated. The results are shown in Table 5.

The meanings of the abbreviations of the sheet-like members (S1 to S4) in Tables 3A to 5 are as follows.
PET (250): transparent polyethylene terephthalate film (thickness 250 μm)
PET (188): Transparent polyethylene terephthalate film (thickness: 188 μm)
PET (125): Transparent polyethylene terephthalate film (thickness 125 μm)
PET (50): transparent polyethylene terephthalate film (thickness 50 μm)
Vapor deposition PET (12): A film obtained by vapor-depositing a mixture of silicon oxide and magnesium fluoride in a ratio of 90/10 to a thickness of 500 mm (50 nm) on one side of a polyethylene terephthalate film (thickness 12 μm) .
AL (white coat): A 10 μm weather resistant resin layer * provided on one side of an aluminum foil (thickness 30 μm).
Weather resistant resin layer *: Obligato PS2012 (white) Main agent: Curing agent (13: 1) (manufactured by AGC Co-Tech)
AL (20): Aluminum foil (thickness 20 μm).
PVF (30): polyvinyl fluoride film (thickness 30 μm)
・ LLDPE (50): Polyethylene film (thickness 50 μm)
EVA: Ethylene / vinyl acetate copolymer resin film (thickness 100 μm)

The evaluation methods and evaluation criteria in Tables 3A to 5 are as follows.
(1) Adhesive The back protection sheet for solar cells is cut to a size of 200 mm x 15 mm, and a T-type peel test is performed at a load rate of 300 mm / min using a tensile tester according to the test method of ASTM D1876-61. It was. The peel strength (N / 15 mm width) between each sheet-like member was shown by the average value of five test pieces.
◎ ・・・ 6N or more ○ ・・・ 4N or more to less than 6N △ ・・・ 2N or more to less than 4N × ・・・ less than 2N

(2) Moist heat resistance The back surface protection sheet for solar cells was preserve | saved for 1000 hours in 85 degreeC and 85% RH atmosphere. The stored back protective sheet for solar cells was cut into a size of 200 mm × 15 mm, and a T-type peel test was performed at a load speed of 300 mm / min using a tensile tester in accordance with the test method of ASTM D1876-61. The peel strength (N / 15 mm width) between each sheet-like member was shown by the average value of five test pieces.
◎ ・・・ 6N or more ○ ・・・ 4N or more to less than 6N △ ・・・ 2N or more to less than 4N × ・・・ less than 2N

(3) Productivity A roll-like product of a back protective sheet for solar cells having a width of 50 cm and a length of 500 m was produced, and the core was placed in the vertical direction, and the outer periphery was grasped and lifted.
○: No deviation occurred in the bonded sheet, and the shape of the roll could be maintained.
X: Deviation occurred in the adhered sheet, and the shape of the roll could not be maintained.

(4) Presence / absence of bubbles and floats A 50 cm wide, 500 m long back protection sheet for solar cells was produced, and the roll was placed in a vertical orientation and stored in an environment at 60 ° C. for 1 week.
The state of the adhesive layer was observed through the transparent sheet-like member, and the presence or absence of lifting of the sheet-like member was observed.
○ ・・・ No abnormality △ ・・・ Small bubbles or small floats occurred.
X: Large bubbles or large bubbles are generated.

Further, the following supplementary notes are disclosed.
[Appendix 1]
A polyol component (A) having no (meth) acryloyl group, which essentially comprises a polyether polyol (A1) having a number average molecular weight of 500 to 5,000,
A polyol component (B) having a (meth) acryloyl group and having two or more hydroxyl groups;
Urethane resin (D) having a (meth) acryloyl group obtained by reacting with a polyisocyanate component (C).
[Appendix 2]
The polyether polyol (A1) having a number average molecular weight of 500 to 5,000 is
Formula (1): HO (—R—O) _n —H
(Wherein R represents a hydrocarbon group having 3 to 8 carbon atoms which may have a side chain substituent, and n represents an arbitrary integer), Urethane resin (D) having a (meth) acryloyl group.
[Appendix 3]
The urethane resin (D) having a (meth) acryloyl group according to appendix 1 or appendix 2, wherein the number average molecular weight is 5,000 to 150,000.
[Appendix 4]
The urethane resin (D) having a (meth) acryloyl group according to any one of appendices 1 to 3, wherein the urethane bond equivalent is 200 to 3,000.
[Appendix 5]
5. The urethane resin (D) having a (meth) acryloyl group according to any one of appendices 1 to 4, wherein the (meth) acryloyl group equivalent is 500 to 40,000.
[Appendix 6]
The urethane resin (D) having a (meth) acryloyl group according to any one of appendices 1 to 5, wherein the (meth) acryloyl group equivalent is 1,200 to 20,000.
[Appendix 7]
The urethane resin having a (meth) acryloyl group according to any one of appendices 1 to 6, wherein the terminal is a hydroxyl group, a saturated hydrocarbon group, or an unsaturated hydrocarbon group (D)
[Appendix 8]
8. The urethane resin (D) having a (meth) acryloyl group according to any one of appendices 1 to 7, wherein the number of atoms of the main chain skeleton between urethane bonds is 3 or more.
[Appendix 9]
The urethane resin (D) having a (meth) acryloyl group according to any one of appendices 1 to 8, wherein the polyol component (B) has two or more (meth) acryloyl groups.
[Appendix 10]
(Meth) acrylic acid is added to an epoxy group of a compound having two or more epoxy groups, and the polyol component (B) is a compound according to any one of appendices 1 to 9, ) Urethane resin (D) having an acryloyl group.

This application is based on the priority based on Japanese Patent Application No. 2010-278715 filed on Dec. 15, 2010 and the Japanese Application No. 2011-235723 filed on Oct. 27, 2011. Claim priority and incorporate all of its disclosure here.

The active energy ray-curable adhesive containing the (meth) acryloyl group-containing urethane resin (D) of the present invention is excellent in adhesiveness to various substrates such as plastic films and metal films, and is under conditions of high temperature and high humidity. Excellent resistance. Then, it uses suitably for the back surface protection sheet manufacture for solar cells. Moreover, you may apply to the surface protection sheet for solar cells. In other fields, for example, plastic lenses, prisms, optical members such as optical fibers, solder resists for flexible printed wiring boards, interlayer insulating films for multilayer printed wiring boards, and packaging films for lithium ion battery packs. In addition, it can be widely used as a coating agent for paper and plastic film in general, and an adhesive for food packaging. Further, the urethane resin (D) having a (meth) acryloyl group of the present invention can be used in the fields of ink, paint, etc. in addition to the use as an adhesive described above.

DESCRIPTION OF SYMBOLS 1 Solar cell 2 Surface sealing sheet 3 for solar cells Light-receiving surface side sealing material layer 4 Non-light-receiving surface side sealing material layer 5 Back surface protection sheet 11 for solar cells 1st sheet-like member 12 2nd sheet-like member 13 1st 3 sheet-like member 14 4th sheet-like member 21 Plastic film 22 Deposition layer 23 Metal foil 24 Coating layer 31 Non-metal oxide layer 51 First adhesive layer 52 Second adhesive layer 53 Third adhesive layer 100 Solar cell module

Claims

A polyol component (A) having no (meth) acryloyl group, which essentially comprises a polyether polyol (A1) having a number average molecular weight of 500 to 5,000,
A polyol component (B) having a (meth) acryloyl group and having two or more hydroxyl groups;
A polyisocyanate component (C);
A urethane resin having a (meth) acryloyl group obtained by reacting (D),
And an active energy ray-curable adhesive containing the epoxy resin (E).
The polyether polyol (A1) having a number average molecular weight of 500 to 5,000 is
Formula (1): HO (—R—O) n —H
2. The activity according to claim 1, wherein R represents a hydrocarbon group having 3 to 8 carbon atoms which may have a side chain substituent, and n represents an arbitrary integer. Energy ray curable adhesive.
The active energy ray-curable adhesive according to claim 1 or 2, wherein the urethane resin (C) has a number average molecular weight of 5,000 to 150,000.
4. The active energy ray-curable adhesive according to claim 1, wherein the urethane resin (D) has a urethane bond equivalent of 200 to 3,000.
The active energy ray-curable adhesive according to any one of claims 1 to 4, wherein the (meth) acryloyl group equivalent in the urethane resin is 500 to 40,000.
The active energy ray-curable adhesive according to any one of claims 1 to 5, wherein the epoxy resin (E) has a number average molecular weight of 450 to 5,000.
The active energy ray-curable adhesive according to any one of claims 1 to 6, wherein the epoxy resin (E) has a number average molecular weight of 500 to 5,000.
The urethane resin (D) is contained in an amount of 50 to 85% by weight and the epoxy resin (E) is contained in an amount of 5 to 40% by weight based on the solid content of the active energy ray-curable adhesive. 8. The active energy ray-curable adhesive according to any one of 7 above.
The active energy ray-curable adhesive according to any one of claims 1 to 8, wherein the polyol component (B) has two or more (meth) acryloyl groups.
10. The compound according to claim 1, wherein the polyol component (B) is a compound in which (meth) acrylic acid is added to an epoxy group of a compound having two or more epoxy groups. Active energy ray curable adhesive.
A solar cell back surface protection sheet for protecting a surface opposite to the solar light incident surface of a solar cell element provided in a solar cell,
Comprising a laminate of two or more sheet-like members,
The active energy ray-cured adhesive formed from the active energy ray-curable adhesive according to any one of claims 1 to 10 at least a part of the adhesion between the sheet-like members constituting the laminate. The back surface protection sheet for solar cells in which the agent layer is used.
At least one of the sheet-like members constituting the laminate has a water vapor barrier layer,
The back protective sheet for a solar cell according to claim 11, wherein the water vapor barrier layer is selected from the group consisting of a metal foil, a plastic film with a metal oxide layer, and a plastic film with a non-metal oxide layer.
The solar cell back surface protective sheet according to claim 11 or 12, wherein the active energy ray-cured adhesive layer has a glass transition temperature of -50 to 30 ° C.