JP7283200B2 - Resin composition, backside protective sheet for solar cell, and solar cell module - Google Patents

Description

TECHNICAL FIELD The present invention relates to a resin composition used for forming a urethane resin layer such as a solar cell back surface protection sheet, a solar cell back surface protection sheet, and a solar cell module.

The solar cell used as a clean energy source is, for example, an embodiment using a plurality of solar cell modules, which is a laminate of surface protective sheet/surface sealing material/solar cell element/back surface sealing material/back surface protective sheet. is common, and the back protective sheet often has a structure in which resin films such as polyester resin, fluororesin, olefin resin, and ethylene/vinyl acetate copolymer resin are laminated with an interlayer adhesive.

In addition, solar cells are sometimes installed on the roof of houses, and from the viewpoint of design that creates a sense of unity with the frequently used dark-colored roofing materials, the exterior of the back protective sheet when viewed from the light-receiving side is made black. It is often colored. Furthermore, the wavelength range absorbed by solar cell elements is generally 300 to 800 nm for amorphous silicon solar cell elements and 400 to 1200 nm for crystalline silicon solar cell elements. can be reflected by the reflective layer of the back surface protective sheet, the reflected light will enter the solar cell element again, improving the photoelectric conversion efficiency.

Therefore, as a near-infrared transparent dark ink having a dark appearance for design, Patent Document 1 discloses a polyol main agent / polyisocyanate curing agent, an oxazine pigment / phthalocyanine A dark adhesive containing a specific ratio of pigment/isoindoline pigment/quinacridone pigment, and a back protective sheet for solar cells characterized by having a dark adhesive layer formed from the adhesive are disclosed.
Further, in Patent Document 2, one kind selected from the group consisting of phthalocyanine pigments and dioxazine pigments and diketopyrrolopyrrole pigments are contained in a specific ratio, and have excellent black appearance and heat shielding properties, and can be reduced in cost. An adhesive composition capable of forming a black adhesive layer of a back protective sheet for solar cells is disclosed.

JP 2016-069586 A JP 2015-015414 A

However, although the invention described in Patent Document 1 contains a quinacridone-based red pigment, it does not contain the specific purple pigment of the present application, and the content of the yellow pigment is small. There is a problem in that the peel strength after a wet heat resistance test under a high-temperature and high-humidity environment of 120° C. and 100% RH is low.
In addition, the invention described in Patent Document 2 does not contain the specific purple pigment of the present application, and the configuration during use is significantly different from that of the present application, and is used as an adhesive layer between white PET and LLDPE. Therefore, there is a problem that the initial peel strength and the peel strength after moist heat resistance are inferior.

Therefore, an object of the present invention is to transmit near-infrared rays, exhibit excellent stability over time, exhibit excellent adhesive strength even at the initial stage and after a moisture and heat resistance test, and be able to form a black adhesive layer having excellent reflectance and black appearance. An object of the present invention is to provide a resin composition, a solar cell back surface protective sheet and a solar cell module using the resin composition.

The present inventors propose the following inventions [1] to [5] in order to solve the above problems.

[1] A resin composition used for forming a urethane resin layer of a back protective sheet for solar cells comprising a light reflective film and a urethane resin layer,
The resin composition contains a polyol component, a polyisocyanate component, and a colorant,
10 to 40% by mass of the coloring agent in 100% by mass of the non-volatile content of the resin composition,
In 100% by mass of the coloring agent,
A total of 10 to 50% by mass of at least one purple pigment (A) selected from the group consisting of quinacridone-based purple pigments (A1) and perylene-based purple pigments (A2),
20 to 50% by mass of phthalocyanine blue pigment (B), and at least one yellow pigment (C) selected from the group consisting of isoindoline yellow pigment (C1) and isoindolinone pigment (C2) in total of 30 A resin composition containing ~60% by mass.

[2] The resin composition according to [1], wherein the polyol component contains a polyether urethane polyol.

[3] The resin composition according to [1] or [2], further comprising a bisphenol A type epoxy resin.

[4] A sheet for protecting the back surface of a solar cell comprising a light-reflective film, a urethane resin layer and a plastic film,
The urethane resin layer contains a polyol component, a polyisocyanate component, and a colorant,
The urethane resin layer contains 10 to 40% by mass of the coloring agent,
In 100% by mass of the coloring agent,
A total of 10 to 50% by mass of at least one purple pigment (A) selected from the group consisting of quinacridone-based purple pigments (A1) and perylene-based purple pigments (A2),
20 to 50% by mass of phthalocyanine blue pigment (B), and at least one yellow pigment (C) selected from the group consisting of isoindoline yellow pigment (C1) and isoindolinone pigment (C2) in total of 30 ~ 60% by mass,
Sheet for protecting the back of solar cells.

[5] A solar cell module comprising a surface protective member, a front side sealant, a power generation cell, a back side sealant, and a back surface protective member formed from the sheet for solar cell back surface protection described in [4].

According to the present invention, it transmits near-infrared rays, has excellent aging stability after 2 months at 60 ° C., exhibits excellent adhesive strength not only at the initial stage, but also after a moisture and heat resistance test at 120 ° C. 100% RH, and has a reflectance. , a resin composition capable of forming a black adhesive layer having an excellent black appearance, and a solar cell backside protective sheet and a solar cell module using the resin composition.

The present invention relates to a resin composition containing a polyol component, a polyisocyanate component and a colorant, which is used for forming a urethane resin layer of a back protective sheet for solar cells having a light reflective film and a urethane resin layer, and a nonvolatile resin composition. 10 to 40% by mass of a coloring agent in the components, and a total of 10 purple pigments (A) selected from the group consisting of quinacridone-based purple pigments (A1) and perylene-based purple pigments (A2) in the total amount of coloring agents. ~50% by mass, 20 to 50% by mass of phthalocyanine blue pigment (B), and yellow pigment (C) selected from the group consisting of isoindoline yellow pigment (C1) and isoindolinone pigment (C2) in total It is characterized by containing 30 to 60% by mass.
By containing the specific colorant in a specific ratio, it exhibits excellent dispersibility in the components constituting the resin composition, such as the polyol component and the polyisocyanate component, thereby exhibiting good stability over time. . In addition, the dispersibility is maintained even under high humidity conditions, and by suppressing unevenness in pigment concentration over time, excellent adhesive strength is exhibited even after the heat and humidity resistance test.

The present invention will be described in detail below.
In this specification, the numerical range specified using "to" includes the numerical values before and after "to" as the range of lower and upper values.
Further, in this specification, "film" and "sheet" shall not be distinguished by thickness. In other words, the "sheet" in this specification includes a thin film-like thing, and the "film" in this specification also includes a thick sheet-like thing.
In the present specification, the term "(meth)acrylic copolymer" includes "acrylic copolymer", "methacrylic copolymer", and "acrylic-methacrylic copolymer". Yes, "(meth)acryloyl" includes "acryloyl" and "methacryloyl", and "(meth)acryl" includes "acryl" and "methacryl".
The degree of blackness means that the external appearance of the urethane resin layer is not as black as carbon black, but black enough to be visually recognized as black. Solar cells are also called photovoltaics.

<Resin composition>
The resin composition of the present invention contains a polyol component, a polyisocyanate component, and a coloring agent, and contains 10 to 40% by weight of the coloring agent in 100% by weight of the non-volatile matter of the resin composition, and 100% by weight of the coloring agent. inside,
A total of 10 to 50% by mass of a purple pigment (A) selected from the group consisting of a quinacridone-based purple pigment (A1) and a perylene-based purple pigment (A2),
20 to 50% by mass of a phthalocyanine blue pigment (B) and a total of 30 to 60% by mass of a yellow pigment (C) selected from the group consisting of an isoindoline yellow pigment (C1) and an isoindolinone pigment (C2) include.

<Polyol component>
The polyol component should just have a hydroxyl group, and may use 2 or more types together. Polyol components include polyester polyols, polyether polyols, polyurethane polyols, acrylic polyols, polycarbonate polyols, polyhydroxyl alkanes, castor oil, and mixtures thereof. Polyols are preferably used. As polyurethane polyol, for example, polyether urethane polyol which is a reaction product of polyalkylene glycol and organic diisocyanate can be used.

[Polyether polyurethane polyol]
(polyalkylene glycol)
Examples of polyalkylene glycol include polyethylene glycol, polytrimethylene glycol, polypropylene glycol, polytetramethylene glycol, polybutylene glycol and the like. Polyalkylene glycols having repeating units with 3 or 4 carbon atoms are preferred. When the number of carbon atoms is 3 or 4, the hydrophilicity and crystallinity are well balanced, the water resistance and moisture resistance are improved, and the adhesive is easily adjusted, which is preferable.
Polytrimethylene glycol, polypropylene glycol, polytetramethylene glycol, and polybutylene glycol are preferably used as the polyalkylene glycol having a repeating unit with 3 or 4 carbon atoms, and polytetramethylene glycol is particularly preferred.

The number average molecular weight of the polyalkylene glycol is preferably in the range of 600-3,500, more preferably in the range of 1,000-3,000. By setting the number average molecular weight within the above range, sufficient flexibility can be imparted to the polyether polyurethane polyol which is a reaction product with the organic diisocyanate described later. Thereby, the adhesive strength of the adhesive composition to the substrate can be improved. In addition, by setting the number average molecular weight of the polyalkylene glycol to the above range, the solubility in various solvents and the compatibility with other resin components are improved, and good low-temperature stability is exhibited, making it suitable for practical use. A resin composition can be obtained.

The polyalkylene glycol may be either linear or branched, preferably linear. Linear polyalkylene glycol has moderate crystallinity, and the obtained polyether polyurethane polyol also has moderate crystallinity. The agent layer has a relatively high density and is suitable as a member that requires long-term moist heat resistance.

(alkanediol)
Moreover, when reacting a polyalkylene glycol and an organic diisocyanate to obtain a polyether polyurethane polyol, an alkanediol may be used in combination as an alcohol component. Alkanediols include ethylene glycol, 1,2-propanediol, 1,3-propanediol, 3-methyl-1,5-pentanediol, 1,4-butanediol, neopentyl glycol, and 1,6-hexanediol. , 2-methyl-1,3-propanediol, 2,4-diethyl-1,5-pentanediol, 2-butyl-2-ethyl-1,3-propanediol, 1,9-nonanediol and the like. . One of these can be used, or two or more of them can be used in combination.

The number of carbon atoms in the alkanediol is preferably in the range of 2-9, particularly preferably in the range of 2-6. Within the above range, the density of urethane bonds forming the hard segments in the polyether polyurethane polyol obtained can be increased, and the cohesive strength of the resin composition can be increased. In particular, by using an alkanediol having a carbon number of 2 to 6, it is preferable because the urethane bond equivalent of the polyether polyurethane polyol can be easily adjusted to 600 g/eq or less as described later. Accordingly, alkanediols include ethylene glycol, 1,2-propanediol, 1,3-propanediol, 3-methyl-1,5-pentanediol, 1,4-butanediol, neopentyl glycol, and 1,6-hexane. It is preferable to use at least one selected from the group consisting of diols and 2-methyl-1,3-propanediol.

(organic diisocyanate)
Examples of organic diisocyanates include diphenylmethane diisocyanate, tolylene diisocyanate, 1,6-hexamethylene diisocyanate, 2,2,4-trimethylhexamethylene diisocyanate, xylylene diisocyanate, tetramethylxylylene diisocyanate, lysine diisocyanate, isophorone diisocyanate, hydrogenated xyl diisocyanate, hydrogenated diphenylmethane diisocyanate, methylcyclohexylene diisocyanate, isopropylidenedicyclohexyl-4,4'-diisocyanate, derivatives thereof, and the like, and any one or more of these may be used in combination. can be done.

Derivatives include polyurethane diisocyanates obtained by reacting the above organic diisocyanates with polyhydric alcohols. As the polyhydric alcohol, the alkanediol or the like mentioned as the raw material for synthesizing the polyether polyurethane polyol can be used.

Preferred organic diisocyanates are aliphatic or alicyclic diisocyanates whose isocyanate groups are not directly bonded to aromatic rings, or derivatives thereof. Aliphatic or alicyclic diisocyanates are preferable because they are less likely to polymerize due to irradiation with ultraviolet rays or the like, and can suppress discoloration of the black adhesive layer over time.

The reaction ratio between the polyalkylene glycol and the alkanediol and the organic diisocyanate is preferably 0.7 or more and less than 1 in terms of equivalent ratio (NCO/OH), more preferably in the range of 0.7 to 0.99, A range of 0.8 to 0.95 is particularly preferred.
Within the above range, it is possible to obtain a polyether polyurethane polyol that has an optimum molecular weight for exhibiting adhesion to a substrate, suitably prevents gelation, and has a hydroxyl group at the end of the main chain.

Either solution polymerization method or bulk polymerization method may be used for the reaction of polyalkylene glycol and alkanediol with organic diisocyanate. In the solution polymerization method, each component is dissolved in an organic solvent such as ethyl acetate and then reacted. The reaction temperature is set below the boiling point of the organic solvent. In this case, since the concentration of reactive groups is low, a catalyst such as an organic tin compound is generally used. On the other hand, in the bulk polymerization method, the reaction is carried out without dissolving each component in a solvent. In this case, since the reaction temperature can be set relatively high, the reaction can be carried out in a short time without using a catalyst.

The weight average molecular weight (Mw) of the polyether polyurethane polyol preferably ranges from 20,000 to 70,000, more preferably from 30,000 to 60,000. When it is 20,000 or more, the initial cohesive force is sufficient, which is preferable. When 70,000 or less, not only the initial cohesive force is sufficient, but also the viscosity can be set within a suitable range, which is preferable. Also, the number average molecular weight (Mn) of the polyether polyurethane polyol is preferably in the range of 5,000 to 35,000. Thereby, the viscosity and initial cohesive force of the resin composition can be set in more suitable ranges.
Furthermore, the polydispersity (Mw/Mn), which is the ratio of the weight average molecular weight (Mw) to the number average molecular weight (Mn) of the polyether polyurethane polyol, is preferably in the range of 1.5-4.

The urethane bond equivalent of the polyether polyurethane polyol is preferably in the range of 320-600 g/eq, more preferably in the range of 350-500 g/eq. Within the above range, sufficient initial cohesive strength of the resin composition is ensured, and sufficient adhesive strength is exhibited even to the substrate.

[Bisphenol A type epoxy resin]
The polyol component may contain a bisphenol A type epoxy resin. A resin that is solid or semi-solid at room temperature is preferable as the bisphenol A type epoxy resin. The resin not only has a high compatibility with the polyether polyurethane polyol, but also has a highly hydrophobic chemical structure, which improves the water resistance and imparts high long-term durability to the black adhesive layer. can be done.
In the present specification, “normal temperature” means “23° C.” unless otherwise specified, and “solid or semi-solid at normal temperature” means “viscosity of 25 Pa·s or more at 23° C.”.

The number average molecular weight of the bisphenol A type epoxy resin is preferably in the range of 400-5,000, more preferably in the range of 800-3,000. When the number average molecular weight is 400 or more, the bisphenol A type epoxy resin becomes solid or semi-solid at room temperature, and can sufficiently improve the water resistance and moist heat resistance of the black adhesive layer. When the number average molecular weight is 5,000 or less, the resin composition has appropriate flexibility and viscosity.

The content of the bisphenol A epoxy resin is preferably 60% by mass or less, more preferably 10 to 40% by mass, and particularly preferably 20 to 35% by mass. By setting the amount of the bisphenol A type epoxy resin to 60% by mass or less, the flexibility of the resin composition can be more suitably adjusted. can be enhanced.

[Other ingredients]
The polyol component may further contain known additives for adhesives. Examples of additives include silane coupling agents and reaction accelerators. When the polyol component contains a silane coupling agent, the adhesion to a substrate made of a metal material (for example, metal foil) is improved. Moreover, when the polyol component contains a reaction accelerator, the time required for curing the resin composition (aging time) can be shortened.

Examples of the silane coupling agent include trialkoxysilanes having a vinyl group such as vinyltrimethoxysilane and vinyltriethoxysilane; 3-aminopropyltriethoxysilane, N-(2-aminoethyl)3-aminopropyltrimethoxysilane; trialkoxysilanes having amino groups such as silane; and the like, and can be used alone or in combination of any two or more.
The content of the silane coupling agent is preferably 0.5 to 5% by mass, more preferably 1 to 3% by mass, based on the total nonvolatile matter of the polyol component. Within the above range, the adhesive strength to a substrate made of a metal material (for example, metal foil) can be further enhanced.

Examples of reaction accelerators include metallic catalysts such as dibutyltin diacetate, dibutyltin dilaurate, dioctyltin dilaurate, and dibutyltin dimaleate; 1,8-diaza-bicyclo(5,4,0)undecene-7,1, 5-diazabicyclo(4,3,0)nonene-5,6-dibutylamino-1,8-diazabicyclo(5,4,0)undecene-7-party tertiary amines; reactive tertiary amines such as triethanolamine and the like, and any one of them or two or more of them can be used in combination.

In addition, polyether polyurethane is generally known to discolor (yellowing) at high temperatures of 150° C. or higher. may contain. Examples of heat stabilizers include hindered phenol-based antioxidants, phosphorus-based and hydroxylamine-based processing heat stabilizers, and the like. Among these, hindered phenol-based antioxidants are preferred.

Hindered phenol antioxidants include 2,4-dimethyl-6-t-butylphenol, 2,6-di-t-butylphenol, 2,6-di-t-butyl-p-cresol, hydroxymethyl- 2,6-di-t-butylphenol, 2,6-di-t-α-dimethylamino-p-cresol, 2,5-di-t-butyl-4-ethylphenol, 4,4′-bis(2 ,6-di-t-butylphenol), 2,2′-methylene-bis-4-methyl-6-t-butylphenol, 2,2′-methylene-bis(4-ethyl-6-t-butylphenol), 4 , 4′-methylene-bis(6-t-butyl-o-cresol), 4,4′-methylene-bis(2,6-di-t-butylphenol), 2,2′-methylene-bis(4- methyl-6-cyclohexylphenol), 4,4′-butylidene-bis(3-methyl-6-t-butylphenol), 4,4′-thiobis(6-t-butyl-3-methylphenol), bis(3 -methyl-4-hydroxy-5-t-butylbenzyl)sulfide, 4,4'-thiobis(6-t-butyl-o-cresol), 2,2'-thiobis(4-methyl-6-t-butylphenol ), 2,6-bis(2′-hydroxy-3′-t-butyl-5′-methylbenzyl)-4-methylphenol, diethyl of 3,5-di-t-butyl-4-hydroxybenzenesulfonate ester, 2,2′-dihydroxy-3,3′-di(α-methylcyclohexyl)-5,5′-dimethyl-diphenylmethane, α-octadecyl-3(3′,5′-di-t-butyl-4 '-hydroxyphenyl) propionate, 6-(hydroxy-3,5-di-t-butylanilino)-2,4-bis-octyl-thio-1,3,5-triazine, hexamethylene glycol-bis[β-( 3,5-di-t-butyl-4-hydroxyphenol)propionate], N,N′-hexamethylene-bis(3,5-di-t-butyl-4-hydroxyhydrocinnamic acid amide), 2,2 -thio[diethyl-bis-3(3,5-di-t-butyl-4-hydroxyphenyl)propionate], dioctadecyl ester of 3,5-di-t-butyl-4-hydroxybenzenephosphonic acid, tetrakis [ methylene-3(3,5-di-t-butyl-4-hydroxyphenyl)propionate]methane, 1,3,5-trimethyl-2,4,6-tris(3,5-di-t-butyl-4 -hydroxybenzyl)benzene, 1,1,3-tris(2-methyl-4-hydroxy-5-di-t-butylphenyl)butane, tris(3,5-di-t-butyl-4-hydroxyphenyl) isocyanurate, tris[β-(3,5-di-t-butyl-4-hydroxyphenyl)propionyl-oxyethyl]isocyanurate and the like.

Among these, hindered phenol-based antioxidants having a molecular weight of 500 or more, such as tetrakis[methylene-3(3,5-di-t-butyl-4-hydroxyphenyl)propionate]methane, are preferably used. be done.
Moreover, the content of the heat stabilizer is preferably about 1 to 5 parts by mass with respect to 100 parts by mass of the total nonvolatile matter of the polyol component. Thereby, the effect of preventing discoloration due to heating of the polyether polyurethane polyol is further improved.

Additionally, the polyol component may contain known wetting agents or defoamers. This makes it possible to improve the laminate appearance of a laminate produced using a resin composition containing a polyol component.
Examples of wetting agents include polyether-modified polydimethylsiloxane, polyester-modified polydimethylsiloxane, aralkyl-modified polymethylalkylsiloxane, polyester-modified hydroxyl group-containing polydimethylsiloxane, polyether ester-modified hydroxyl group-containing polydimethylsiloxane, and acrylic copolymers. , methacrylic copolymers, polyether-modified polymethylalkylsiloxanes, acrylic acid alkyl ester copolymers, methacrylic alkyl ester copolymers, lecithin and the like.

Antifoaming agents include known compounds such as silicone resins, silicone solutions, and copolymers of alkyl vinyl ethers, alkyl acrylates and alkyl methacrylates.

<Polyisocyanate component>
The polyisocyanate component should just have two or more isocyanate groups, and polyfunctional polyisocyanates are particularly preferred.
Polyfunctional polyisocyanates include, for example, low molecular weight polyisocyanates, polyurethane isocyanates (adducts) obtained by reacting low molecular weight polyisocyanates with water or polyhydric alcohols, biuret or allophanate forms of polyurethane isocyanates, and low molecular weight polyisocyanates. Uretdione bodies (dimers) and isocyanurate bodies (trimers) of isocyanates can be mentioned, and one of them or any two or more of them can be used in combination.
Examples of the low-molecular-weight polyisocyanate include those similar to those described as the organic diisocyanate described above, and one or more of these can be used in combination. Polyhydric alcohols to be reacted with these low-molecular-weight polyisocyanates when obtaining polyurethane isocyanates (adducts) include, for example, tri- or higher-functional polyhydric alcohols such as trimethylolpropane and sorbitol, and the above polyethers. The alkanediol mentioned as a raw material for synthesizing the polyurethane polyol and the like can be mentioned.

Polyfunctional polyisocyanates are roughly classified into aromatic polyfunctional polyisocyanates and aliphatic or alicyclic polyfunctional polyisocyanates, and aliphatic or alicyclic polyfunctional polyisocyanates are preferably used. Aliphatic or alicyclic polyfunctional polyisocyanate does not have an aromatic ring in its structure, so even if it is irradiated with light such as ultraviolet rays, it is difficult to polymerize. Therefore, even if a laminate produced using the resin composition is left outdoors for a long period of time, it is possible to suitably prevent the polyisocyanate component of the resin composition from discoloring over time.

Moreover, the polyfunctional polyisocyanate preferably contains at least a polyfunctional polyisocyanate having an isocyanurate structure. Since the isocyanurate structure has high heat resistance and high hydrophobicity, by using such a polyfunctional polyisocyanate as the polyisocyanate component, the cured product of the resin composition can exhibit moist heat resistance for a longer period of time. can.
The content of polyfunctional polyisocyanate having an isocyanurate structure is preferably about 50 to 100% by mass, more preferably about 60 to 100% by mass, in the curing agent. By setting the blending amount of the polyfunctional polyisocyanate having an isocyanurate structure in the polyisocyanate component within the above range, the resistance to moist heat of the cured product of the resin composition can be further improved.
For these reasons, in the present invention, a polyisocyanate component containing 50 to 100% by mass of an aliphatic or alicyclic polyfunctional polyisocyanate having an isocyanurate structure is particularly preferably used.

A specific example of the polyfunctional polyisocyanate having an isocyanurate structure is 3-isocyanatomethyl-3,5,5-trimethylcyclohexyl isocyanate (hereinafter referred to as "isophorone diisocyanate"), which is an alicyclic diisocyanate. and isocyanurate of hexamethylene diisocyanate which is an aliphatic diisocyanate. These isocyanurates are preferable because they have a long pot life after being mixed with the polyether polyurethane polyol and the solution stability of the resin composition is good.
Among these, the isocyanurate of isophorone diisocyanate is more preferably used. Such isocyanurate is preferable because it has higher heat resistance.

In addition, the content of the polyisocyanate component is preferably about 3 to 20 parts by mass, more preferably about 7 to 18 parts by mass, with respect to 100 parts by mass of the polyol component. By setting the amount of the resin composition in the above range, it is possible to improve the initial cohesive strength of the resin composition, and even when the laminate produced using the resin composition is left outdoors for a long time, the resin composition It is possible to suitably prevent the peel strength of the cured product from lowering.

<Colorant>
In the present invention, three colorants are used to obtain black tones instead of carbon black.
The coloring agent includes a purple pigment (A) selected from the group consisting of a quinacridone-based purple pigment (A1) and a perylene-based purple pigment (A2), a phthalocyanine-based blue pigment (B), an isoindoline-based yellow pigment (C1), and and a yellow pigment (C) selected from the group consisting of isoindolinone pigments (C2) as essential components.
When the purple pigment (A) selected from the group consisting of the quinacridone-based purple pigment (A1) and the perylene-based purple pigment (A2) is included, the dispersibility of the entire coloring agent is improved, color separation is less likely to occur after long-term storage, and the resin The storage stability of the composition is improved.
When the yellow pigment (C) selected from the group consisting of the isoindoline-based yellow pigment (C1) and the isoindolinone pigment (C2) is included, it is possible to suppress a decrease in adhesion between the urethane resin layer and the substrate after the durability test. shows an amazing effect.
Although the cause is not clear, it is believed that the isoindole skeleton portion contained in (C1) or (C2) contributes to adhesion by strengthening the intermolecular force between the surrounding pigment, resin and substrate. I'm guessing. In addition, the isoindole skeletal site is compatible with the aromatic ring skeletal sites of the phthalocyanine blue pigment (B), the quinacridone violet pigment (A1), and the perylene violet pigment (A2), and strengthens the intermolecular force, thereby improving adhesion. is expected to strengthen the

Furthermore, the resin composition of the present invention contains 10 to 40% by mass of a coloring agent based on 100% by mass of the non-volatile matter of the resin composition. When the content of the colorant is 40% by mass or less, the adhesion to the substrate is further improved, and when it is 10% by mass or more, the blackness of the appearance is further improved. More preferably 15 to 35% by mass.

Further, the colorant is a purple pigment (A) selected from the group consisting of quinacridone-based purple pigment (A1) and perylene-based purple pigment (A2) in a total amount of 10 to 50% by mass,
20 to 50% by mass of a phthalocyanine blue pigment (B) and a total of 30 to 60% by mass of a yellow pigment (C) selected from the group consisting of an isoindoline yellow pigment (C1) and an isoindolinone pigment (C2) include.
By including the above-mentioned specific colorant in this ratio, an appropriate degree of blackness is obtained, the storage stability of the resin composition is improved, the adhesion to the substrate after the durability test is good, and the A urethane resin layer having excellent peel strength can be obtained.

(Quinacridone purple pigment (A1))
The quinacridone-based purple pigment (A1) is a purple pigment having a quinacridone skeleton, such as Pigment Violet 19. The purple pigment referred to herein means C.I. I. It is a pigment classified as Pigment Violet.

(Perylene purple pigment (A2))
The perylene purple pigment (A2) is a purple pigment having a perylene skeleton, and examples thereof include Pigment Violet 29, Pigment Violet 31 and Pigment Violet 33. The purple pigment referred to herein means C.I. I. It is a pigment classified as Pigment Violet.

(Phthalocyanine blue pigment (B))
The phthalocyanine-based blue pigment (B) is a pigment having a phthalocyanine skeleton. :6, Pigment Blue 16, Pigment Blue 17:1, Pigment Blue 75, Pigment Blue 79. Among these, Pigment Blue 15, Pigment Blue 15:1, Pigment Blue 15:2, Pigment Blue 15:3, Pigment Blue 15:4 and Pigment Blue 75 are preferred in terms of weather resistance and color tone.

(Isoindolinone yellow pigment (C2))
The isoindolinone-based yellow pigment (C2) is a yellow pigment having an isoindolinone skeleton, and examples thereof include Pigment Yellow 109, Pigment Yellow 110 and Pigment Yellow 173. Incidentally, the yellow pigment referred to here means C.I. I. It is a pigment classified as Pigment Yellow.

(Isoindoline yellow pigment (C1))
The isoindoline-based yellow pigment (C1) is a yellow pigment having an isoindoline skeleton, and examples thereof include Pigment Yellow 139 and Pigment Yellow 185. Incidentally, the yellow pigment referred to here means C.I. I. It is a pigment classified as Pigment Yellow. Among these, Pigment Yellow 139 is particularly preferable in terms of color tone.

Moreover, the total content of the isoindoline-based yellow pigment (C1) and the isoindolinone-based yellow pigment (C2) is preferably larger than that of the phthalocyanine-based blue pigment (B). By setting it as such a compounding ratio, the adhesion improvement effect with respect to a base material can be heightened more.

The resin composition may contain other colorants as long as the problem can be solved. Blackness and the like can be adjusted by including other colorants. Other colorants include, for example, insoluble azo pigments, condensed azo pigments, anthraquinone pigments, dioxazine pigments, and dyes. The content of the other coloring agent is preferably 10% by mass or less, more preferably 5% by mass or less, based on 100% by mass of the coloring agent.

<Method for producing resin composition>
[Dispersant]
The colorant is preferably subjected to a dispersion treatment together with the above-mentioned polyol component and the below-mentioned solvent, or together with a part thereof. This further improves the dispersion stability of the colorant in the resin composition. Also, a dispersant may be used in the dispersion treatment. Dispersants include basic dispersants, acidic dispersants or amphoteric dispersants. Since the pigment surface is often slightly acidic, a basic dispersant is preferred from the viewpoint of acid-base affinity. When the dispersant is a resin-type dispersant, the main skeleton includes, for example, a polyurethane skeleton, a polyacrylic skeleton, a polyester skeleton, a polyamide skeleton, a polyimide skeleton, or a polyurea skeleton. , a polyacrylic backbone or a polyester backbone are preferred. The structure of the resin-type dispersant is not limited, and may be random structure, block structure, comb structure, star structure, or the like. From the viewpoint of storage stability, block structure or comb structure is preferably used. . The mass average molecular weight of the dispersant used in the present invention is preferably 1,000 to 70,000, more preferably 2,000 to 60,000, and particularly preferably 3,000 to 50,000. By setting the molecular weight within the above range, both dispersibility and peel strength before and after the moisture and heat resistance test can be achieved.

Examples of basic dispersants include 101, 102, 103, 106, 108, 109, 110, 111, 112, 116, 130, 140, 142, and 145 of DISPER BYK series of wetting and dispersing agents commercially available from BYK Chemie. , 161, 162, 163, 164, 166, 167, 168, 170, 171, 174, 180, 182, 183, 184, 185, 2000, 2001, 2020, 2050, 2070, 2096, 2150, BYKJET series 9130, 9131, 9132, 9133, 9150, LP-N-22252, EFKA series 4008, 4009, 4010, 4015, 4020, 4046, 4047, 4050, 4055, 4060, 4080 commercially available from Ciba Specialty Chemicals; 4300, 4330, 4340, 4400, 4401, 4402, 4403, 4406, 4800, 5010, 5044, 5054, 5055, 5063, 5064, 5065, 5066, 5070, 5244, Solsperse series 3000 commercially available from Lubrizol , 11200, 13240, 13650, 13940, 16000, 17000, 18000, 20000, 21000, 24000SC, 24000GR, 26000, 28000, 31845, 32000, 32500, 32550, 32600, 33000, 347 50, 35100, 35200, 36000, 36600, 37500 , 38500, 39000, 41000, 53000, 53095, 54000, 55000, 56000, 71000, 76400, 76500, J100, J200; 2100, 2150, 2200, 7004, KS-260, KS-273N, KS-860, KS-873N, PW-36, DN-900, DA-234, DA-325, DA-375, DA-550, DA- 1200, DA-1401, DA-7301, PB-711, PB-821, PB-822, PB-824, PB-827, PB-711, PN of the Ajisper series commercially available from Ajinomoto Fine-Techno Co., Ltd. -411, PA-111 and the like.
In the present invention, basic resin type dispersants DISPER-BYK162, 167, 168, LP-N-22252, Solsperse 24000SC, 24000GR, 32000, 33000, 35000, 39000, 76400, 76500, J100, J200, Ajisper PB-821 , 822, 824, 827 are preferred.

Dispersion treatment is not particularly limited. A known dispersing device such as a medialess dispersing device that utilizes cavitation due to sonic vibration can be used.

The resin composition may further contain organic or inorganic fine particles. Microparticles|fine-particles can be used individually or in combination of 2 or more types. When fine particles are contained, tackiness on the surface of the urethane resin layer can be reduced. The shape of the fine particles includes powdery, granular, granular, tabular, fibrous, dendritic, and the like, and may contain impurities to the extent that their properties are not impaired.

Organic particles are, for example, polymer particles such as acrylic resin, polystyrene resin, nylon (registered trademark) resin, melamine resin, guanamine resin, phenol resin, urea resin, silicone resin, or cellulose powder, nitrocellulose powder, wood flour. , waste paper powder, rice husk powder, starch, and the like. Polymer particles can be synthesized by known polymerization methods such as emulsion polymerization, suspension polymerization, dispersion polymerization, soap-free polymerization, seed polymerization, and microsuspension polymerization.

The organic particles are preferably particles having a melting point or softening point of 150° C. or higher. When a solvent having a melting point or softening point of 150° C. or higher is used, it is difficult to soften due to the heat during drying of the solvent, and the anti-blocking property is difficult to decrease.

Examples of inorganic particles include oxides, hydroxides, sulfates, carbonates and silicates of metals such as magnesium, calcium, barium, zinc, zirconium, molybdenum, silicon, antimony and titanium. Specific compounds of inorganic particles include silica gel, aluminum oxide, calcium hydroxide, calcium carbonate, magnesium oxide, magnesium hydroxide, magnesium carbonate, zinc oxide, lead oxide, diatomaceous earth, zeolite, and aluminosilicate. , Talc, White Carbon, Mica, Glass Fiber, Glass Powder, Glass Beads, Clay, Wallacenite, Iron Oxide, Antimony Oxide, Titanium Oxide, Litpon, Pumice Powder, Aluminum Sulfate, Zirconium Silicate, Barium Carbonate, Dolomite, Molybdenum Disulfide , iron sand, carbon black and the like.

Among the fine particles, inorganic particles are preferable because the adhesion to the substrate is further improved, and talc, hydrotalcite, mica, and kaolin are more preferable.

[solvent]
The resin composition may further contain a solvent. A solvent can be used individually or in combination of 2 or more types. Examples of solvents include alcohols such as methanol, ethanol, propanol, butanol, ethylene glycol methyl ether and diethylene glycol methyl ether; ketones such as acetone, methyl ethyl ketone, methyl isobutyl ketone and cyclohexanone; ether; hydrocarbons such as hexane, heptane and octane; aromatics such as benzene, toluene, xylene and cumene; esters such as ethyl acetate and butyl acetate;

The solvent preferably has a boiling point of 50°C to 200°C. When the boiling point is in the appropriate range, it is easy to achieve both dryness during coating and surface smoothness of the urethane resin layer.

The resin composition of the present invention may contain other components as long as the problem can be solved. Other components include, for example, fillers, thixotropy-imparting agents, antioxidants, antioxidants, antistatic agents, flame retardants, thermal conductivity modifiers, plasticizers, anti-sagging agents, antifouling agents, preservatives, Bactericides, antifoaming agents, leveling agents, thickeners, silane coupling agents and the like are included.

<Solar cell back surface protection sheet>
The solar cell backside protective sheet of the present invention comprises a light reflective film, a urethane resin layer and a plastic film. The light-reflecting film reflects the light that passes through the urethane resin layer that has been received by the solar cell module and has not been fully utilized by the solar cell elements. The reflected light passes through the urethane resin layer and enters the solar cell element again, thereby improving the power generation efficiency of the solar cell element.

The light-reflecting film is preferably capable of reflecting light with a wavelength of 400 to 1200 nm that can be used by the solar cell element for power generation. In order to reflect light, for example, it is preferable to blend titanium dioxide having a predetermined average particle size. It is preferable to blend two or more types of titanium dioxide with different diameters. Further, the light reflecting film may have a multilayer structure in which one of two types of titanium dioxide having different average particle sizes is used as the first light reflecting film and the other is used as the second light reflecting film. In place of or in combination with titanium dioxide, a foamed film obtained by foaming a film to impart a light reflecting function can also be used.
The content of titanium dioxide is preferably 5 to 40% by mass based on 100% by mass of the light-reflective film.

The base material of the light reflective film includes, for example, polyester resin films such as polyethylene terephthalate, polybutylene terephthalate, and polyethylene naphthalate; olefin films such as polyethylene, polypropylene, and polycyclopentadiene; fluorine-based films such as tetrafluoroethylene films and ethylene-tetrafluoroethylene copolymer films; acrylic films; and cellulose-based films such as triacetylcellulose films. Among these, from the viewpoint of film rigidity and cost, a polyester resin film is preferable, and a polyethylene terephthalate film is more preferable.

The plastic film can be appropriately selected from the substrates of the light-reflecting film described above according to the required physical properties, and is preferably capable of transmitting light with a wavelength of 400 to 1200 nm that can be used by the solar cell element for power generation.

A single layer or a laminate of two or more layers can be used as the substrate. Also, the base material may have an inorganic layer formed by vapor deposition or sputtering of a metal oxide or a non-metal inorganic oxide. Moreover, the thickness of the substrate is preferably 25 to 300 μm.

The urethane resin layer is preferably formed by coating the resin composition of the present invention on a light-reflecting film and drying it. Coating can be performed using a coating device such as comma coating, gravure coating, reverse coating, roll coating, lip coating, and spray coating. For drying, for example, hot air drying, an infrared heater, or the like can be used. The drying temperature is usually preferably 80 to 200° C., and the thickness of the urethane resin layer is preferably 0.1 to 30 μm.
In addition, the solar cell back surface protective sheet can be obtained by coating the resin composition of the present invention on another base material in place of the light reflective film, drying the base material, and then attaching the base material to the light reflective film via an adhesive. It can also be manufactured by pasting together.

Solar cell back surface protection sheet is used to protect solar cell modules formed from elements such as crystalline silicon solar cell elements, compound semiconductors such as copper indium selenide, and amorphous silicon, in which electrodes are provided on the photoelectric conversion layer. can do. The urethane resin layer formed from the resin composition of the present invention can be used for back sealing in a thermocompression bonding process for producing a solar cell module using a surface protective sheet, a surface sealing material, a solar cell element, and a back sealing material. It is preferable to closely contact the back sealing material by stacking and crimping so as to be in contact with the sealing material.
EVA, olefin film, and the like are examples of the back sealing material that constitutes the solar cell module. It may contain an oxide or the like.

EXAMPLES The present invention will be described in more detail below with reference to examples, but the present invention is not limited by the following examples. In the examples, "parts" and "%" represent "mass parts" and "mass%", respectively. Also, the glass transition temperature and hydroxyl value were measured as described below. In addition, the compounding amounts in the table are parts by mass.

<Measurement of glass transition temperature (Tg)>
The measurement of glass transition temperature was obtained by differential scanning calorimetry (DSC) method. A sample for measurement was prepared by heating a resin solution to be measured at 150° C. for about 15 minutes to dry it.

<Measurement of mass average molecular weight (Mw) and number average molecular weight (Mn)>
The mass average molecular weight and number average molecular weight of the polyester polyol are values converted to polystyrene by gel permeation chromatography (GPC), model: Shodex (manufactured by Showa Denko Co., Ltd.), column: KF-805L, KF-803L, and KF-802 (manufactured by Showa Denko Co., Ltd.) at a column temperature of 40 ° C., using THF as an eluent, a flow rate of 0.2 ml / min, detection of RI, sample concentration of 0.02%, standard It was measured using polystyrene as a sample.

<Measurement of hydroxyl value (OHV)>
For the measurement of the hydroxyl value (OHV), first, about 1 g of a sample was accurately weighed into a stoppered Erlenmeyer flask, and 100 ml of a toluene/ethanol (volume ratio: toluene/ethanol=2/1) mixed solution was added and dissolved. Exactly 5 ml of an acetylating agent (a solution of 25 g of acetic anhydride dissolved in pyridine to a volume of 100 ml) was further added and stirred for about 1 hour. To this, phenolphthalein test solution was added as an indicator and maintained for 30 seconds. After that, the solution was titrated with 0.5N alcoholic potassium hydroxide solution until it turned pink.
The hydroxyl value was determined by the following formula. The hydroxyl value was the numerical value of the dry state of the resin (unit: mgKOH/g).
Hydroxyl value (mgKOH/g)
= [{(ba) × F × 28.05} / S] / (non-volatile concentration / 100) + D
However, S: sample collection amount (g)
a: consumption of 0.5N alcoholic potassium hydroxide solution (ml)
b: Consumption (ml) of 0.5N alcoholic potassium hydroxide solution in blank experiment
F: Potency of 0.5N alcoholic potassium hydroxide solution D: Acid value (mgKOH/g)

<Production of polyol component>
[Synthesis Example 1] Urethane-based polyol (U1)
73 parts of polytetramethylene glycol having a number average molecular weight of 2,000 (“PTG2000SN” manufactured by Hodogaya Chemical Co., Ltd., hereinafter abbreviated as “PTMG2000”), and 3-methyl-1,5-pentanediol (hereinafter referred to as “ abbreviated as MPD”) and 20 parts of diphenylmethane diisocyanate (hereinafter abbreviated as “MDI”) were placed in a synthesis vessel equipped with a stirrer, and then reacted at 170° C. for 2 hours to achieve a glass transition. A polyurethane polyol U1 having a temperature of −35° C., a mass average molecular weight of 40,000 and a hydroxyl value of 8.0 mgKOH/g was synthesized. The equivalent ratio (NCO/OH) is 0.85.

[Synthesis Example 2] Urethane-based polyol (U2)
67 parts of polytetramethylene glycol having a number average molecular weight of 2000 (“PTG2000SN” manufactured by Hodogaya Chemical Co., Ltd., hereinafter abbreviated as “PTMG2000”) and 3-methyl-1,5-pentanediol (hereinafter “MPD”) ) and 23 parts of isophorone diisocyanate (hereinafter abbreviated as “IPDI”) were placed in a synthesis vessel equipped with a stirrer and reacted at 170 ° C. for 2 hours to obtain a glass transition temperature of −30. °C, a mass average molecular weight of 45,000, and a hydroxyl value of 7.2 mgKOH/g, a polyurethane polyol U2 was synthesized. The equivalent ratio (NCO/OH) is 0.92.

[Synthesis Example 3] Polyester polyol (P1)
15 parts of isophthalic acid, 15 parts of terephthalic acid, 28 parts of adipic acid, 6 parts of ethylene glycol, 17 parts of neopentyl glycol, 17 parts of 1,6-hexanediol, 2 parts of trimethylolpropane, and 0.13 parts of tetraisobutyl titanate are charged. , 170 to 250° C. for 15 hours, the pressure reduction was started when the acid value was 10 mgKOH/g or less, and the esterification reaction was further carried out at 250° C. and 100 Torr for 1 hour. Thereafter, the pressure was gradually reduced, and transesterification was performed at 1 to 4 Torr and 230 to 250°C for 4 hours to obtain polyester polyol P1 having a glass transition temperature of -25°C, a mass average molecular weight of 45,000, and a hydroxyl value of 7.5 mgKOH/g. Obtained.

[Synthesis Example 4] (Meth)acrylic polyol (R1)
A 4-necked flask equipped with a condenser, a nitrogen inlet tube, a dropping funnel and a thermometer was charged with 100 parts of ethyl acetate and heated to 80°C. Then, a monomer liquid prepared by previously mixing 68 parts of butyl methacrylate, 30 parts of butyl acrylate, 2 parts of 2-hydroxyethyl methacrylate and 0.8 parts of azobisisobutylnitrile was added dropwise from the dropping funnel over 2 hours.
After that, react for 1 hour, then add 0.2 parts of azobisisobutylnitrile and react for 1 hour until the conversion of the monomer reaches 98% or more, then cool to obtain a glass transition temperature of -3°C. , a mass average molecular weight of 70,000 and a hydroxyl value of 8.6 mgKOH/g (meth)acrylic polyol R1 was obtained.

[Synthesis Example 5] (Meth)acrylic polyol (R2)
100 parts of toluene was introduced into a four-necked flask equipped with a condenser, a stirrer, a thermometer and a nitrogen inlet tube, and the temperature was raised to 80°C. Then, a monomer solution obtained by pre-mixing 18 parts of methyl methacrylate, 78 parts of n-butyl methacrylate, 2 parts of 2-hydroxyethyl methacrylate, 2 parts of glycidyl methacrylate, and 0.075 parts of azobisisobutyronitrile was added from a dropping funnel for 2 hours. dripped over. Next, 0.07 part of azobisisobutyronitrile was added and the polymerization reaction was further carried out for 2 hours, and further 0.07 part of azobisisobutyronitrile was added and the polymerization reaction was further carried out for 2 hours.
Then, 0.03 parts of hydroquinone, 0.8 parts of dimethylbenzylamine, and 1 part of acrylic acid (glycidyl methacrylate: the amount required for modification of 2 parts) were added, and the mixture was heated and stirred at 100° C. for 15 hours. After confirming that the acid value was 2 or less, a (meth)acrylic polyol R2 having a number average molecular weight of 75,000, a hydroxyl value of 18.0 mgKOH/g, a glass transition temperature of 30°C and a solid content concentration of 50% was obtained.

Table 1 lists the glass transition temperature, mass average molecular weight, number average molecular weight and hydroxyl value of the obtained polyol component.

Abbreviations in Table 1 are shown below.
PTMG2000: Polytetramethylene glycol with a number average molecular weight of 2,000 (“PTG2000SN” manufactured by Hodogaya Chemical Co., Ltd.)
・MPD: 3-methyl-1,5-pentanediol ・MDI: diphenylmethane diisocyanate ・IPDI: isophorone diisocyanate ・IPA: isophthalic acid ・TPA: terephthalic acid ・AdA: adipic acid ・EG: ethylene glycol ・NPG: neopentyl glycol ・1,6-HD: 1,6-hexanediol BMA: butyl methacrylate BA: butyl acrylate HEMA: 2-hydroxyethyl methacrylate MMA: methyl methacrylate GMA: glycidyl methacrylate

<Production of polyisocyanate component>
(Polyisocyanate curing agent N1)
A solution of 85% non-volatile content of isocyanurate form of hexamethylene diisocyanate was used as polyisocyanate curing agent N1. The isocyanurate form of hexamethylene diisocyanate corresponds to an aliphatic multifunctional polyisocyanate having an isocyanurate structure.

(Polyisocyanate curing agent N2)
A 75% non-volatile solution of an isocyanurate form of hexamethylene diisocyanate blocked with 3,5-dimethylpyrazole was used as polyisocyanate curing agent N2.

<Production of resin composition>
[Examples 1 to 15, Comparative Examples 1 to 16]
A colorant, a polyol component, a basic resin-type dispersant, and a bisphenol A-type epoxy resin were blended so as to have the non-volatile content ratio shown in Table 2, and the colorant was uniformly dispersed by bead dispersion using glass beads. . Next, a polyisocyanate component was added, and the non-volatile content was adjusted to 30% with ethyl acetate to obtain each resin composition.

<Evaluation of Resin Composition>
The obtained resin composition was evaluated for solution stability. Using the resin solution, a laminate was produced by the method described later, and the peel strength, reflectance, and appearance blackness were evaluated at the initial stage and after the moisture and heat resistance test. Table 2 shows the results.

<Solution stability evaluation>
At the initial stage of the resin solution and after 2 months at 60° C., the rotational viscosity was measured using a Brookfield type rotational viscometer BH manufactured by Tokimec Co., Ltd. Solution stability was determined as follows from the rotational viscosity at the initial stage and after the lapse of time.
A: Rotational viscosity change rate after aging Less than 20% (good)
B: Rotational viscosity change rate after aging 20% or more to less than 30% (practical range)
C: Rotational viscosity change rate after aging 30% or more (not practical)

<Method for producing laminate>
A resin composition was applied to the corona-treated surface of a white PET (polyethylene terephthalate) film having a thickness of 50 μm at a coating amount of 5 g/m ² ·dry, and then dried to remove the solvent to form an adhesive layer. . Then, a corona-treated surface of a 100 μm-thick LLDPE film was laminated on the adhesive layer under lamination conditions of 60° C. and 0.5 MPa. Then, aging treatment was performed at 60° C. for 48 hours to obtain a laminate.

<Initial peel strength>
The laminate was cut into a size of 200 mm×15 mm to obtain a test piece. For each test piece, according to the test method of ASTM D1876-61, using a tensile tester, in an atmosphere of 23 ° C., perform a T-type peel test at a load rate of 300 mm / min, and peel between the white PET film and the LLDPE film. The strength (N/15 mm width) was measured. The average value of 5 test pieces was taken as the initial peel strength.
S: 20N/15mm or more (excellent)
A: 15 N/15 mm or more to less than 20 N/15 mm (good)
B: 10N/15mm or more to less than 15N/15mm (practical range)
C: less than 10N/15mm (not practical)

<Peel strength after moist heat resistance test>
A pressure cooker test was performed for 72 hours by exposing the laminate to an atmosphere of 120° C. and 100% relative humidity using a highly accelerated life tester (EMD-211MD) manufactured by Espec Corporation. After that, the peel strength between the white PET film and the LLDPE film (average value of 5 test pieces) was obtained in the same manner as the initial peel strength evaluation.
S: 20N/15mm or more (excellent)
A: 15 N/15 mm or more to less than 20 N/15 mm (good)
B: 10N/15mm or more to less than 15N/15mm (practical range)
C: less than 10N/15mm (not practical)

<Reflectance (blackness)>
The reflectance of the laminate was measured from the LLDPE film side using a UV-visible spectrophotometer V-570 manufactured by JASCO Corporation. The average reflectance was calculated in the range from 380 nm to 780 nm, and the degree of blackness was determined as follows.
A: Average reflectance less than 15% (good)
B: Average reflectance 15% or more to less than 30% (practical range)
C: Average reflectance 30% or more (not practical)

<Appearance blackness (hue)>
L ^* a ^* b ^* of the laminate was measured from the LLDPE film side using a fluorescence spectrodensitometer FD-5 manufactured by Konica Minolta, Inc., and the hue was evaluated from the a ^* b ^* values.
A: Both a ^* b ^* values are less than ±5 (good)
B: Either one of the a ^* b ^* values is ±5 or more and less than ±10 (practical range)
C: Either one of the a ^* b ^* values is ±10 or more (not practical)

Abbreviations in Table 2 are shown below.
PB-822: Ajinomoto Fine Techno Co., Ltd. Ajisper PB-822
JER1002: bisphenol A type epoxy resin manufactured by Mitsubishi Chemical Corporation

Examples 1 to 15 using the resin composition of the present invention are excellent in solution stability, and the laminate formed using the resin composition has excellent peel strength, reflectance and appearance after the initial and wet heat resistance tests. It was excellent in black taste. In particular, in Examples 5, 7 and 14, the polyol component is a highly flexible urethane resin at room temperature. It becomes a tough coating film that has both adhesion and heat and humidity resistance, and has excellent peel strength and reflectance before and after heat and humidity resistance. Furthermore, the blackness of the appearance is excellent due to the optimum ratio of the purple pigment, the blue pigment and the yellow pigment in the coloring agent.

In Comparative Examples 1 and 12, the content of the purple pigment (A) in 100% by mass of the coloring agent in the adhesive layer was less than 10%, so the appearance was inferior in blackness. On the other hand, in Comparative Examples 5 and 13, since the content of the purple pigment (A) exceeds 50%, the peel strength after the wet heat resistance test is inferior.
In Comparative Examples 3 and 8, the content of the yellow pigment (C) exceeds 60%, so the appearance is inferior in blackness. On the other hand, in Comparative Examples 5, 6, 9 and 13, since the content of the yellow pigment (C) is less than 30%, the peel strength after the wet heat resistance test is inferior. Moreover, since Comparative Example 4 contains a benzimidazolone-based yellow pigment, it is inferior in solution stability and peel strength after the heat and humidity resistance test.
In Comparative Example 7, since the phthalocyanine-based blue pigment (B) is less than 20%, the appearance is inferior in blackness. On the other hand, in Comparative Example 2, since the phthalocyanine blue pigment (B) exceeds 60%, the solution stability is poor.
In Comparative Example 10, since the content of the coloring agent in 100% by mass of the non-volatile matter of the resin composition exceeds 40%, the solution stability and peel strength after initial and wet heat resistance are inferior. On the other hand, in Comparative Example 11, since the content of the coloring agent is less than 10%, the reflectance is inferior.
In Comparative Examples 14 to 16, since none of the specific pigments of the present application is contained in a specific ratio, the affinity between the pigment and the resin is reduced, and the interfacial force is reduced. Inferior.

<Production of sheet for protecting back surface of solar cell>
[Example 16]
Using the resin composition obtained in Example 5, a laminate having a structure of white PET/adhesive layer/LLDPE was obtained in the same manner as the laminate produced in the evaluation of the resin composition.
An EVA film (Ultra Pearl PV-45FR00S, Sanvic Co., Ltd.) and a white plate glass plate were laminated in this order on the LLDPE of the obtained laminate, and the module laminator PVL0505S (Nisshinbo Mechatronics Co., Ltd.) was heated to 140°C. The plate was placed on the plate with the white glass plate facing downward, and the plate was evacuated to about 1 Torr and left for 5 minutes. Next, while maintaining the temperature at 140° C., the sheet was pressed at atmospheric pressure and allowed to stand for 15 minutes to obtain a solar cell back surface protective sheet.

[Example 17]
A solar cell back surface protective sheet was obtained in the same manner as in Example 16, except that the resin composition of Example 14 was used instead of the resin composition obtained in Example 5.

<Evaluation of sheet for protecting back surface of solar cell>
The obtained solar cell back surface protective sheet was subjected to peel strength evaluation before and after moist heat resistance, reflectance evaluation, and appearance blackness evaluation in the same manner as the evaluation of the laminate. It was confirmed that the solar cell backside protective sheets of Examples 16 and 17 were excellent in peel strength, reflectance, and blackness of appearance in the initial stage and after the moist heat resistance test, and could be suitably used as a solar cell module.

Claims (5)

A resin composition used for forming a urethane resin layer of a back protective sheet for solar cells comprising a light reflective film and a urethane resin layer,
The resin composition contains a polyol component, a polyisocyanate component, and a colorant,
10 to 40% by mass of the coloring agent in 100% by mass of the non-volatile content of the resin composition,
In 100% by mass of the coloring agent,
A total of 10 to 50% by mass of at least one purple pigment (A) selected from the group consisting of quinacridone-based purple pigments (A1) and perylene-based purple pigments (A2),
20 to 50% by mass of phthalocyanine blue pigment (B), and at least one yellow pigment (C) selected from the group consisting of isoindoline yellow pigment (C1) and isoindolinone pigment (C2) in total of 30 ~ 60% by mass,
The resin composition, wherein the content of the colorant other than (A), (B), and (C) in 100% by mass of the colorant is 10% by mass or less. 2. The resin composition of Claim 1, wherein the polyol component comprises a polyether urethane polyol. 3. The resin composition according to claim 1, further comprising a bisphenol A type epoxy resin. A solar cell back surface protection sheet comprising a light reflective film, a urethane resin layer and a plastic (excluding urethane resin) film,
The urethane resin layer contains a polyol component, a polyisocyanate component, and a colorant,
The urethane resin layer contains 10 to 40% by mass of the coloring agent,
In 100% by mass of the coloring agent,
A total of 10 to 50% by mass of at least one purple pigment (A) selected from the group consisting of quinacridone-based purple pigments (A1) and perylene-based purple pigments (A2),
20 to 50% by mass of phthalocyanine blue pigment (B), and at least one yellow pigment (C) selected from the group consisting of isoindoline yellow pigment (C1) and isoindolinone pigment (C2) in total of 30 ~ 60% by mass,
A sheet for protecting the back surface of a solar cell, wherein the content of the colorant other than (A), (B), and (C) in 100% by mass of the colorant is 10% by mass or less. A solar cell module comprising a surface protective member, a front side sealant, a power generation cell, a back side sealant, and a back surface protective member formed from the sheet for solar cell back surface protection according to claim 4 .