JP5464051B2 - Curable resin composition, protective sheet for solar cell, and solar cell module - Google Patents

Description

  In recent years, solar cells that directly convert sunlight into electric energy have attracted attention and are being developed from the viewpoint of effective use of resources and prevention of environmental pollution.

  In general, a solar cell is an EVA (ethylene-vinyl acetate copolymer, usually a mixture with an organic peroxide) film sealing material between a light-receiving side transparent protective member and a back side protective member. It is the structure which sealed the cell for solar cells, such as a silicon power generation element, and is the sheet-like sealing material arranged on the light-receiving side transparent protective member, the surface side, the cell for solar cells, and the sheet shape arranged on the back side The sealing material and the back surface side protective member are laminated in this order, heated and pressurized, and EVA is crosslinked and cured to be bonded and integrated.

  Since solar cell modules are used outdoors, the members used are required to have high durability and weather resistance. In particular, since the light-receiving surface side transparent protective member is constantly exposed to sunlight, high light resistance is required. For these reasons, a glass plate is usually used, but many attempts have been made to use a plastic substrate from the viewpoint of weight reduction and flexibility of the solar cell.

  For the purpose of enhancing the weather resistance, weather resistance, and antifouling properties of plastic substrates, metal compound particles having a particle diameter of 1 nm to 400 nm, hydrolyzable silicon compounds, and vinyl monomer having a glass transition point of −20 ° C. to 80 ° C. A light-receiving surface side transparent protective member obtained by coating a plastic substrate with a coating composition containing core-shell type polymer emulsion particles obtained by emulsion polymerization with a body is known (see, for example, Patent Document 1). However, the coating composition can withstand the weather resistance evaluation after 2000 hours of exposure, but in the weather resistance evaluation after 3000 hours of exposure, which corresponds to long-term exposure of 10 years or more outdoors, the coating film is insufficient due to lack of stretchability. There is a risk of cracks on the surface.

JP 2009-253203 A JP 2006-328354 A

  The problem to be solved by the present invention is to provide a curable resin composition for coating having high durability and weather resistance, a protective sheet for solar cell using the same, and a solar cell module.

  As a result of intensive studies, the present inventors have made a composite resin having a silanol group and / or a hydrolyzable silyl group, a polysiloxane segment having a polymerizable double bond, and a polymer segment other than the polysiloxane, The curable resin composition for coating to which polyisocyanate and metal oxide are added has been found to have both long-term outdoor weather resistance (specifically, crack resistance) and excellent coating protection performance, and has solved the above problems. .

By setting the polysiloxane segment in the curable resin composition within a specific range, even a coating film obtained by curing with active energy rays such as ultraviolet rays without heating at high temperature has excellent scratch resistance. And high adhesion to the plastic substrate.
In addition, by allowing alcoholic hydroxyl groups and isocyanate groups to coexist in the curable resin composition, long-term outdoor exposure is possible even for coating films obtained by curing with active energy rays such as ultraviolet rays without heating at high temperatures. It was found that the occurrence of cracks in the coating film can be prevented.

That is, the present invention relates to a polysiloxane segment (a1) having a structural unit represented by the general formula (1) and / or the general formula (2), a silanol group and / or a hydrolyzable silyl group, and an alcoholic hydroxyl group. Containing a composite resin (A), a polyisocyanate (B), and a metal oxide (C) bonded by a bond represented by the general formula (3), and a vinyl polymer segment (a2) having
The content of the polysiloxane segment (a1) is 10 to 60% by weight with respect to the total solid content of the curable resin composition, and the content of the polyisocyanate (B) is the total solid of the curable resin composition. A curable resin composition that is 5 to 50% by weight based on the amount is provided.

（１）

(1)

（２）

(2)

(In the general formulas (1) and (2), R ¹ , R ² and R ³ are each independently -R ⁴ -CH = CH ₂ , -R ⁴ -C (CH ₃ ) = CH ₂ ,- A group having one polymerizable double bond selected from the group consisting of R ⁴ —O—CO—C (CH ₃ ) ═CH ₂ and —R ⁴ —O—CO—CH═CH ₂ (where R ⁴ is Represents a single bond or an alkylene group having 1 to 6 carbon atoms.), An alkyl group having 1 to 6 carbon atoms, a cycloalkyl group having 3 to 8 carbon atoms, an aryl group, or 7 to 7 carbon atoms. 12 represents an aralkyl group, and at least one of R ¹ , R ² and R ³ is a group having the polymerizable double bond)

（３）

(3)

(In the general formula (3), carbon atoms constitute a part of the vinyl polymer segment (a2), and silicon atoms bonded only to oxygen atoms constitute a part of the polysiloxane segment (a1). To do)

  Moreover, this invention provides the coating agent which uses the said curable resin composition.

  Moreover, this invention provides the protective sheet for solar cells which provides the protective layer which hardened the said curable resin composition on the single side | surface of the plastic substrate.

  Moreover, this invention provides the solar cell module which provides the said protective sheet for solar cells in the light reception side front surface of a solar cell module so that the protective layer which hardened | cured the said curable resin composition may become the outermost layer.

  Since the curable resin composition of the present invention has long-term weather resistance outdoors and excellent coating protection performance, it is a protection for solar cells, in which a protective layer obtained by curing the curable resin composition is provided on one surface of a plastic substrate. By providing the sheet on the solar cell module such that the protective layer obtained by curing the curable resin composition is the outermost layer, a solar cell module having excellent weather resistance can be obtained.

(Composite resin (A))
The composite resin (A) used in the present invention is a polysiloxane having a structural unit represented by the general formula (1) and / or the general formula (2), and a silanol group and / or a hydrolyzable silyl group. Segment (a1) (hereinafter simply referred to as polysiloxane segment (a1)) and vinyl polymer segment (a2) having alcoholic hydroxyl group (hereinafter simply referred to as vinyl polymer segment (a2)) This is a composite resin (A) bonded by a bond represented by formula (3). The bond represented by the general formula (3) is particularly excellent in acid resistance and alkali resistance of the resulting coating film.

（３）

(3)

The silanol group and / or hydrolyzable silyl group possessed by the polysiloxane segment (a1) described later and the silanol group and / or hydrolyzable silyl group possessed by the vinyl polymer segment (a2) described below undergo a dehydration condensation reaction. Thus, the bond represented by the general formula (3) is generated. Accordingly, in the general formula (3), carbon atoms constitute a part of the vinyl polymer segment (a2), and silicon atoms bonded only to oxygen atoms constitute a part of the polysiloxane segment (a1). And
The form of the composite resin (A) is, for example, a composite resin having a graft structure in which the polysiloxane segment (a1) is chemically bonded as a side chain of the polymer segment (a2), or the polymer segment (a2). And a composite resin having a block structure in which the polysiloxane segment (a1) is chemically bonded.

(Polysiloxane segment (a1))
The polysiloxane segment (a1) in the present invention is a segment having a structural unit represented by the general formula (1) and / or the general formula (2), a silanol group and / or a hydrolyzable silyl group. The structural unit represented by the general formula (1) and / or the general formula (2) includes a group having a polymerizable double bond.

(Structural unit represented by general formula (1) and / or general formula (2))
The structural unit represented by the general formula (1) and / or the general formula (2) has a group having a polymerizable double bond as an essential component.
Specifically, R ¹ , R ² and R ³ in the general formulas (1) and (2) are each independently —R ⁴ —CH═CH ₂ , —R ⁴ —C (CH ₃ ) = A group having one polymerizable double bond selected from the group consisting of CH ₂ , —R ⁴ —O—CO—C (CH ₃ ) ═CH ₂ , and —R ⁴ —O—CO—CH═CH ₂ ( R ⁴ represents a single bond or an alkylene group having 1 to 6 carbon atoms), an alkyl group having 1 to 6 carbon atoms, a cycloalkyl group having 3 to 8 carbon atoms, an aryl group, or the number of carbon atoms. 7 to 12 aralkyl groups are represented, and at least one of R ¹ , R ² and R ³ is a group having the polymerizable double bond. Examples of the alkylene group having 1 to 6 carbon atoms in R ⁴ include a methylene group, an ethylene group, a propylene group, an isopropylene group, a butylene group, an isobutylene group, a sec-butylene group, a tert-butylene group, Pentylene group, isopentylene group, neopentylene group, tert-pentylene group, 1-methylbutylene group, 2-methylbutylene group, 1,2-dimethylpropylene group, 1-ethylpropylene group, hexylene group, isohesylene group, 1-methylpentylene Len group, 2-methylpentylene group, 3-methylpentylene group, 1,1-dimethylbutylene group, 1,2-dimethylbutylene group, 2,2-dimethylbutylene group, 1-ethylbutylene group, 1,1 , 2-trimethylpropylene group, 1,2,2-trimethylpropylene group, 1-ethyl-2 -A methylpropylene group, 1-ethyl-1-methylpropylene group, etc. are mentioned. Among these, R ⁴ is preferably a single bond or an alkylene group having 2 to 4 carbon atoms because of easy availability of raw materials.

Examples of the alkyl group having 1 to 6 carbon atoms include methyl, ethyl, propyl, isopropyl, butyl, isobutyl, sec-butyl, tert-butyl, pentyl, and isopentyl. Group, neopentyl group, tert-pentyl group, 1-methylbutyl group, 2-methylbutyl group, 1,2-dimethylpropyl group, 1-ethylpropyl group, hexyl group, isohexyl group, 1-methylpentyl group, 2-methylpentyl Group, 3-methylpentyl group, 1,1-dimethylbutyl group, 1,2-dimethylbutyl group, 2,2-dimethylbutyl group, 1-ethylbutyl group, 1,1,2-trimethylpropyl group, 1,2 , 2-trimethylpropyl group, 1-ethyl-2-methylpropyl group, 1-ethyl-1-methylpropyl group, and the like.
Examples of the cycloalkyl group having 3 to 8 carbon atoms include a cyclopropyl group, a cyclobutyl group, a cyclopentyl group, and a cyclohexyl group. Examples of the aryl group include a phenyl group, a naphthyl group, a 2-methylphenyl group, a 3-methylphenyl group, a 4-methylphenyl group, a 4-vinylphenyl group, and a 3-isopropylphenyl group.
Examples of the aralkyl group having 7 to 12 carbon atoms include a benzyl group, a diphenylmethyl group, and a naphthylmethyl group.

In addition, at least one of R ¹ , R ² and R ³ is a group having a polymerizable double bond, specifically, the polysiloxane segment (a1) is represented by the general formula (1). When only having a structural unit, R ¹ is a group having the polymerizable double bond, and when the polysiloxane segment (a1) has only the structural unit represented by the general formula (2), R ² and When R ³ is a group having the polymerizable double bond and the polysiloxane segment (a1) has both of the structural units represented by the general formula (1) and the general formula (2), R It shows that at least one of ¹ , R ² and R ³ is a group having a polymerizable double bond.

  The structural unit represented by the general formula (1) and / or the general formula (2) is a three-dimensional network polysiloxane structural unit in which two or three of the silicon bonds are involved in crosslinking. Since a dense network structure is not formed while a three-dimensional network structure is formed, gelation or the like does not occur during production, and the long-term storage stability of the resulting composite resin is improved.

(Silanol group and / or hydrolyzable silyl group)
In the present invention, the silanol group is a silicon-containing group having a hydroxyl group directly bonded to a silicon atom. Specifically, the silanol group is a silanol group formed by combining an oxygen atom having a bond with a hydrogen atom in the structural unit represented by the general formula (1) and / or the general formula (2). Preferably there is.

  In the present invention, the hydrolyzable silyl group is a silicon-containing group having a hydrolyzable group directly bonded to a silicon atom, and specifically includes, for example, a group represented by the general formula (4). .

（４）

(4)

(In the general formula (4), R ⁵ is a monovalent organic group such as an alkyl group, an aryl group or an aralkyl group, and R ⁶ is a halogen atom, an alkoxy group, an acyloxy group, a phenoxy group, an aryloxy group, a mercapto group, (It is a hydrolyzable group selected from the group consisting of an amino group, an amide group, an aminooxy group, an iminooxy group and an alkenyloxy group, and b is an integer of 0 to 2.)

Examples of the alkyl group in R ⁵ include a methyl group, an ethyl group, a propyl group, an isopropyl group, a butyl group, an isobutyl group, a sec-butyl group, a tert-butyl group, a pentyl group, an isopentyl group, a neopentyl group, and a tert group. -Pentyl group, 1-methylbutyl group, 2-methylbutyl group, 1,2-dimethylpropyl group, 1-ethylpropyl group, hexyl group, isohexyl group, 1-methylpentyl group, 2-methylpentyl group, 3-methylpentyl Group, 1,1-dimethylbutyl group, 1,2-dimethylbutyl group, 2,2-dimethylbutyl group, 1-ethylbutyl group, 1,1,2-trimethylpropyl group, 1,2,2-trimethylpropyl group 1-ethyl-2-methylpropyl group, 1-ethyl-1-methylpropyl group and the like.
Examples of the aryl group include a phenyl group, a naphthyl group, a 2-methylphenyl group, a 3-methylphenyl group, a 4-methylphenyl group, a 4-vinylphenyl group, and a 3-isopropylphenyl group.
Examples of the aralkyl group include a benzyl group, a diphenylmethyl group, and a naphthylmethyl group.

In R ⁶ , examples of the halogen atom include a fluorine atom, a chlorine atom, a bromine atom, and an iodine atom.
Examples of the alkoxy group include a methoxy group, an ethoxy group, a propoxy group, an isopropoxy group, a butoxy group, a second butoxy group, and a third butoxy group.
Examples of the acyloxy group include formyloxy, acetoxy, propanoyloxy, butanoyloxy, pivaloyloxy, pentanoyloxy, phenylacetoxy, acetoacetoxy, benzoyloxy, naphthoyloxy and the like.
Examples of the aryloxy group include phenyloxy and naphthyloxy.
Examples of the alkenyloxy group include a vinyloxy group, allyloxy group, 1-propenyloxy group, isopropenyloxy group, 2-butenyloxy group, 3-butenyloxy group, 2-petenyloxy group, 3-methyl-3-butenyloxy group, 2 -A hexenyloxy group etc. are mentioned.

By hydrolyzing the hydrolyzable group represented by R ⁶ , the hydrolyzable silyl group represented by the general formula (4) becomes a silanol group. Among these, a methoxy group and an ethoxy group are preferable because of excellent hydrolyzability.
The hydrolyzable silyl group specifically includes an oxygen atom having a bond in the structural unit represented by the general formula (1) and / or the general formula (2) bonded to the hydrolyzable group. Or it is preferable that it is the hydrolyzable silyl group substituted.

The silanol group and the hydrolyzable silyl group are converted into the hydroxyl group in the silanol group or the hydrolyzable silyl group in parallel with the curing reaction when forming a coating film by active energy rays or heat curing. Since the hydrolysis condensation reaction proceeds between the functional groups, the cross-linking density of the polysiloxane structure of the obtained coating film is increased, and a coating film having excellent solvent resistance and the like can be formed.
In addition, the polysiloxane segment (a1) containing the silanol group or the hydrolyzable silyl group and the vinyl polymer segment (a2) having an alcoholic hydroxyl group described later are represented by the general formula (3). Used when connecting via

The polysiloxane segment (a1) is not particularly limited except that it has a structural unit represented by the general formula (1) and / or the general formula (2), and a silanol group and / or a hydrolyzable silyl group. Other groups may be included. For example,
Polysiloxanes R ¹ in the general formula (1) is a structural unit is a group having a polymerizable double bond, R ¹ in the general formula (1) coexist and the structural unit is an alkyl group such as methyl It may be segment (a1)
A structural unit R ¹ is an alkyl group such as a methyl group and structural units R ¹ is a group having a polymerizable double bond in the formula (1), the formula in (1), the general formula It may be a polysiloxane segment (a1) in which R ² and R ³ in (2) coexist with a structural unit that is an alkyl group such as a methyl group,
A structural unit in which R ¹ in the general formula (1) is a group having the polymerizable double bond, and a structural unit in which R ² and R ³ in the general formula (2) are alkyl groups such as a methyl group. The polysiloxane segment (a1) which coexists may be used, and there is no particular limitation.
Specifically, examples of the polysiloxane segment (a1) include those having the following structures.

  The present invention is characterized in that the polysiloxane segment (a1) is contained in an amount of 10 to 60% by weight based on the total solid content of the curable resin composition, and achieves both weather resistance and excellent coating protection performance. It becomes possible.

(Vinyl polymer segment (a2) having an alcoholic hydroxyl group)
The vinyl polymer segment (a2) in the present invention is a vinyl polymer segment such as an acrylic polymer having an alcoholic hydroxyl group, a fluoroolefin polymer, a vinyl ester polymer, an aromatic vinyl polymer, and a polyolefin polymer. Among them, an acrylic polymer segment obtained by copolymerizing a (meth) acrylic monomer having an alcohol hydroxyl group is preferable because the obtained coating film is excellent in transparency and gloss.

Specific examples of the (meth) acrylic monomer having an alcohol hydroxyl group include 2-hydroxyethyl (meth) acrylate, 2-hydroxypropyl (meth) acrylate, 3-hydroxypropyl (meth) acrylate, and 2-hydroxybutyl (meth) ) Acrylate, 3-hydroxybutyl (meth) acrylate, 4-hydroxybutyl (meth) acrylate, 3-chloro-2-hydroxypropyl (meth) acrylate, di-2-hydroxyethyl fumarate, mono-2-hydroxyethyl mono Various α such as butyl fumarate, polyethylene glycol mono (meth) acrylate, polypropylene glycol mono (meth) acrylate, “Placcel FM or Plaxel FA” [Caprolactone addition monomer manufactured by Daicel Chemical Industries, Ltd.] Hydroxyalkyl esters of β- ethylenically unsaturated carboxylic acid or an adduct thereof with ε- caprolactone, and the like.
Of these, 2-hydroxyethyl (meth) acrylate is preferable because it is easy to react.

Since the content of the polyisocyanate (B) described later is in the range of 5 to 50% by weight with respect to the total solid content of the curable resin composition, the alcoholic hydroxyl group content is that of the actual polyisocyanate (B). It is preferable to calculate from the amount added and to determine appropriately.
Further, as described later, in the present invention, it is more preferable to use an active energy ray-curable monomer having an alcoholic hydroxyl group in combination. Accordingly, the amount of alcoholic hydroxyl group in the vinyl polymer segment (a2) having an alcoholic hydroxyl group can be determined in consideration of the amount of the active energy ray-curable monomer having an alcoholic hydroxyl group to be used in combination. It is preferably contained so as to be substantially in the range of 30 to 300 in terms of the hydroxyl value of the vinyl polymer segment (a2).

  There is no limitation in particular as another (meth) acryl monomer which can be copolymerized, It is possible to use a well-known monomer. Vinyl monomers can also be copolymerized. For example, methyl (meth) acrylate, ethyl (meth) acrylate, n-propyl (meth) acrylate, n-butyl (meth) acrylate, isobutyl (meth) acrylate, tert-butyl (meth) acrylate, 2-ethylhexyl (meth) Alkyl (meth) acrylates having an alkyl group having 1 to 22 carbon atoms such as acrylate and lauryl (meth) acrylate; aralkyl (meth) acrylates such as benzyl (meth) acrylate and 2-phenylethyl (meth) acrylate Cycloalkyl (meth) acrylates such as cyclohexyl (meth) acrylate and isobornyl (meth) acrylate; ω-alkoxyalkyl such as 2-methoxyethyl (meth) acrylate and 4-methoxybutyl (meth) acrylate ( A) Acrylates; aromatic vinyl monomers such as styrene, p-tert-butylstyrene, α-methylstyrene, vinyltoluene, etc .; vinyl acetates such as vinyl acetate, vinyl propionate, vinyl pivalate, vinyl benzoate Alkyl esters of crotonic acid such as methyl crotonic acid and ethyl crotonic acid; dialkyl esters of unsaturated dibasic acids such as dimethyl malate, di-n-butyl maleate, dimethyl fumarate, dimethyl itaconate; ethylene, propylene Α-olefins such as vinylidene fluoride, tetrafluoroethylene, hexafluoropropylene, chlorotrifluoroethylene, etc .; fluoroolefins such as ethyl vinyl ether, n-butyl vinyl ether; cyclopentyl Cycloalkyl vinyl ethers such as nyl ether and cyclohexyl vinyl ether; Tertiary amide group-containing monomers such as N, N-dimethyl (meth) acrylamide, N- (meth) acryloylmorpholine, N- (meth) acryloylpyrrolidine and N-vinylpyrrolidone Etc.

  There are no particular limitations on the polymerization method, solvent, or polymerization initiator for copolymerizing the monomers, and the vinyl polymer segment (a2) can be obtained by a known method. For example, 2,2′-azobis (isobutyronitrile), 2,2′-azobis (2,4-) can be obtained by various polymerization methods such as bulk radical polymerization, solution radical polymerization, and non-aqueous dispersion radical polymerization. Dimethylvaleronitrile), 2,2′-azobis (2-methylbutyronitrile), tert-butylperoxypivalate, tert-butylperoxybenzoate, tert-butylperoxy-2-ethylhexanoate, di- The vinyl polymer segment (a2) can be obtained by using a polymerization initiator such as tert-butyl peroxide, cumene hydroperoxide, diisopropyl peroxycarbonate or the like.

  The number average molecular weight of the vinyl polymer segment (a2) is preferably in the range of 500 to 200,000 in terms of number average molecular weight (hereinafter abbreviated as Mn), and the composite resin (A) is produced. It is possible to prevent thickening and gelation at the time of carrying out, and excellent durability when used as a coating film. Mn is more preferably in the range of 700 to 100,000, and still more preferably in the range of 1,000 to 50,000.

  In addition, the vinyl polymer segment (a2) is a vinyl polymer segment (A) in order to form a composite resin (A) bonded by the bond represented by the general formula (3) with the polysiloxane segment (a1). It has a silanol group and / or a hydrolyzable silyl group directly bonded to the carbon bond in a2). Since these silanol groups and / or hydrolyzable silyl groups become bonds represented by the general formula (3) in the production of the composite resin (A) described later, the composite resin (A ) In the vinyl polymer segment (a2). However, there is no problem even if silanol groups and / or hydrolyzable silyl groups remain in the vinyl polymer segment (a2), and in parallel with the active energy ray curing reaction when a coating film is formed by active energy ray curing. Since the hydrolysis condensation reaction proceeds between the hydroxyl group in the silanol group and the hydrolyzable group in the hydrolyzable silyl group, the crosslinking density of the polysiloxane structure of the resulting coating film is increased, and the solvent resistance is increased. An excellent coating film can be formed.

Specifically, the vinyl polymer segment (a2) having a silanol group and / or a hydrolyzable silyl group directly bonded to a carbon bond is a (meth) acryl monomer having the alcohol hydroxyl group, the general-purpose monomer, and It is obtained by copolymerizing a vinyl monomer containing a silanol group and / or a hydrolyzable silyl group directly bonded to a carbon bond.
Examples of vinyl monomers containing a silanol group and / or a hydrolyzable silyl group directly bonded to a carbon bond include vinyltrimethoxysilane, vinyltriethoxysilane, vinylmethyldimethoxysilane, and vinyltri (2-methoxyethoxy) silane. , Vinyltriacetoxysilane, vinyltrichlorosilane, 2-trimethoxysilylethyl vinyl ether, 3- (meth) acryloyloxypropyltrimethoxysilane, 3- (meth) acryloyloxypropyltriethoxysilane, 3- (meth) acryloyloxypropyl Examples include methyldimethoxysilane and 3- (meth) acryloyloxypropyltrichlorosilane. Among these, vinyltrimethoxysilane and 3- (meth) acryloyloxypropyltrimethoxysilane are preferable because the hydrolysis reaction can easily proceed and by-products after the reaction can be easily removed.

(Production method of composite resin (A))
Specifically, the composite resin (A) used in the present invention is produced by the methods shown in the following (Method 1) to (Method 3).

(Method 1) (Meth) acrylic monomer having alcohol hydroxyl group, general-purpose (meth) acrylic monomer, etc., and vinyl monomer containing silanol group and / or hydrolyzable silyl group directly bonded to carbon bond To obtain a vinyl polymer segment (a2) containing a silanol group and / or a hydrolyzable silyl group directly bonded to a carbon bond. A silane compound having both a silanol group and / or a hydrolyzable silyl group and a polymerizable double bond, and, if necessary, a general-purpose silane compound are mixed and subjected to a hydrolysis condensation reaction.
In this method, a silanol group and / or hydrolyzable silyl group and a silanol group or hydrolyzable silyl group of a silane compound having both a polymerizable double bond and a silanol group and / or hydrolyzed directly bonded to a carbon bond. The silanol group and / or hydrolyzable silyl group of the vinyl polymer segment (a2) containing a functional silyl group undergoes a hydrolytic condensation reaction to form the polysiloxane segment (a1), and the polysiloxane The composite resin (A) in which the segment (a1) and the vinyl polymer segment (a2) having an alcoholic hydroxyl group are combined by the bond represented by the general formula (3) is obtained.

(Method 2) In the same manner as in Method 1, a vinyl polymer segment (a2) containing a silanol group and / or a hydrolyzable silyl group directly bonded to a carbon bond is obtained.
On the other hand, a polysiloxane segment (a1) is obtained by subjecting a silane compound having both a silanol group and / or a hydrolyzable silyl group and a polymerizable double bond and, if necessary, a general-purpose silane compound to a hydrolysis condensation reaction. Then, the silanol group and / or hydrolyzable silyl group of the vinyl polymer segment (a2) and the silanol group and / or hydrolyzable silyl group of the polysiloxane segment (a1) are hydrolyzed and condensed. Let

  (Method 3) Similarly to Method 1, a vinyl polymer segment (a2) containing a silanol group and / or a hydrolyzable silyl group directly bonded to a carbon bond is obtained. On the other hand, the polysiloxane segment (a1) is obtained in the same manner as in Method 2. Furthermore, a silane compound containing a silane compound having a polymerizable double bond and a general-purpose silane compound as necessary are mixed and subjected to a hydrolysis condensation reaction.

  Specific examples of the silane compound having both a silanol group and / or a hydrolyzable silyl group and a polymerizable double bond used in the (Method 1) to (Method 3) include, for example, vinyltrimethoxysilane, Vinyltriethoxysilane, vinylmethyldimethoxysilane, vinyltri (2-methoxyethoxy) silane, vinyltriacetoxysilane, vinyltrichlorosilane, 2-trimethoxysilylethyl vinyl ether, 3- (meth) acryloyloxypropyltrimethoxysilane, 3- (Meth) acryloyloxypropyltriethoxysilane, 3- (meth) acryloyloxypropylmethyldimethoxysilane, 3- (meth) acryloyloxypropyltrichlorosilane and the like. Among these, vinyltrimethoxysilane and 3- (meth) acryloyloxypropyltrimethoxysilane are preferable because the hydrolysis reaction can easily proceed and by-products after the reaction can be easily removed.

  Examples of the general-purpose silane compound used in the (Method 1) to (Method 3) include methyltrimethoxysilane, methyltriethoxysilane, methyltri-n-butoxysilane, ethyltrimethoxysilane, and n-propyl. Various organotrialkoxysilanes such as trimethoxysilane, iso-butyltrimethoxysilane, cyclohexyltrimethoxysilane, phenyltrimethoxysilane, phenyltriethoxysilane; dimethyldimethoxysilane, dimethyldiethoxysilane, dimethyldi-n-butoxysilane Various diorganodialkoxysilanes such as diethyldimethoxysilane, diphenyldimethoxysilane, methylcyclohexyldimethoxysilane, and methylphenyldimethoxysilane; Chill trichlorosilane, phenyl trichlorosilane, vinyl trichlorosilane, dimethyl dichlorosilane, chlorosilane such as diethyl dichlorosilane or diphenyl dichlorosilane and the like. Of these, organotrialkoxysilanes and diorganodialkoxysilanes that can easily undergo a hydrolysis reaction and easily remove by-products after the reaction are preferable.

  In addition, a tetrafunctional alkoxysilane compound such as tetramethoxysilane, tetraethoxysilane or tetra n-propoxysilane or a partial hydrolysis condensate of the tetrafunctional alkoxysilane compound may be used in combination as long as the effects of the present invention are not impaired. it can. When the tetrafunctional alkoxysilane compound or a partially hydrolyzed condensate thereof is used in combination, the silicon atoms of the tetrafunctional alkoxysilane compound are 20 with respect to the total silicon atoms constituting the polysiloxane segment (a1). It is preferable to use together so that it may become the range which does not exceed mol%.

  In addition, a metal alkoxide compound other than a silicon atom such as boron, titanium, zirconium or aluminum can be used in combination with the silane compound as long as the effects of the present invention are not impaired. For example, it is preferable to use the metal alkoxide compound in combination in a range not exceeding 25 mol% with respect to all silicon atoms constituting the polysiloxane segment (a1).

  In the hydrolysis condensation reaction in the (Method 1) to (Method 3), a part of the hydrolyzable group is hydrolyzed under the influence of water or the like to form a hydroxyl group, and then the hydroxyl groups or the hydroxyl group and the hydrolysis are hydrolyzed. This refers to a proceeding condensation reaction that proceeds with a functional group. The hydrolysis-condensation reaction can be performed by a known method, but a method in which the reaction is advanced by supplying water and a catalyst in the production process is simple and preferable.

  Examples of the catalyst used include inorganic acids such as hydrochloric acid, sulfuric acid and phosphoric acid; organic acids such as p-toluenesulfonic acid, monoisopropyl phosphate and acetic acid; inorganic bases such as sodium hydroxide and potassium hydroxide; tetraisopropyl titanate , Titanates such as tetrabutyl titanate; 1,8-diazabicyclo [5.4.0] undecene-7 (DBU), 1,5-diazabicyclo [4.3.0] nonene-5 (DBN), 1 Compounds containing various basic nitrogen atoms, such as 1,4-diazabicyclo [2.2.2] octane (DABCO), tri-n-butylamine, dimethylbenzylamine, monoethanolamine, imidazole, 1-methylimidazole; Tetramethylammonium salt, tetrabutylammonium salt, dilauryldimethylammonium Quaternary ammonium salts having chloride, bromide, carboxylate or hydroxide as a counter anion; dibutyltin diacetate, dibutyltin dioctoate, dibutyltin dilaurate, dibutyltin diacetylacetate Examples thereof include tin carboxylates such as narate, tin octylate and tin stearate. A catalyst may be used independently and may be used together 2 or more types.

  The amount of the catalyst to be added is not particularly limited, but generally it is preferably used in the range of 0.0001 to 10% by weight with respect to the total amount of each compound having the silanol group or hydrolyzable silyl group. , More preferably in the range of 0.0005 to 3% by weight, and particularly preferably in the range of 0.001 to 1% by weight.

The amount of water to be supplied is preferably 0.05 mol or more with respect to 1 mol of the silanol group or hydrolyzable silyl group of each compound having the silanol group or hydrolyzable silyl group, The above is more preferable, and particularly preferably 0.5 mol or more.
These catalyst and water may be supplied collectively or sequentially, or may be supplied by previously mixing the catalyst and water.

  The reaction temperature for carrying out the hydrolytic condensation reaction in the above (Method 1) to (Method 3) is suitably in the range of 0 ° C to 150 ° C, and preferably in the range of 20 ° C to 100 ° C. The reaction can be carried out under any conditions of normal pressure, increased pressure, or reduced pressure. Moreover, you may remove the alcohol and water which are the by-products which can be produced | generated in the said hydrolysis-condensation reaction by methods, such as distillation, as needed.

  The charging ratio of each compound in the (Method 1) to (Method 3) is appropriately selected depending on the desired structure of the composite resin (A) used in the present invention. Especially, since the durability of the obtained coating film is excellent, it is preferable to obtain the composite resin (A) such that the content of the polysiloxane segment (a1) is 30 to 80% by weight, and 30 to 75% by weight. Further preferred.

  In the above (Method 1) to (Method 3), as a specific method for conjugating the polysiloxane segment and the vinyl polymer segment in a block form, the above-mentioned silanol group and Using a vinyl polymer segment having a structure having a hydrolyzable silyl group as an intermediate, for example, in the case of (Method 1), a silanol group and / or hydrolysis is added to the vinyl polymer segment. And a silane compound having both a polymerizable silyl group and a polymerizable double bond, and a general-purpose silane compound as required, followed by a hydrolysis condensation reaction.

  On the other hand, in the above (Method 1) to (Method 3), as a specific method of complexing the polysiloxane segment to the vinyl polymer segment in a graft form, the main chain of the vinyl polymer segment is The vinyl polymer segment having a structure in which silanol groups and / or hydrolyzable silyl groups are randomly distributed is used as an intermediate. For example, in the case of (Method 2), the vinyl polymer segment is Examples thereof include a method in which a hydrocondensation reaction is carried out between the silanol group and / or hydrolyzable silyl group possessed and the silanol group and / or hydrolyzable silyl group possessed by the polysiloxane segment.

(Polyisocyanate (B))
The curable resin composition of the present invention contains 5 to 50% by weight of polyisocyanate (B) with respect to the total solid content of the curable resin composition.
By containing the polyisocyanate in this range, a coating film having particularly excellent long-term weather resistance outdoors (specifically, crack resistance) can be obtained. This is because the polyisocyanate reacts with a hydroxyl group in the system (this is a hydroxyl group in the active energy ray-curable monomer having a hydroxyl group in the vinyl polymer segment (a2) or an alcoholic hydroxyl group described later). Thus, it is estimated that a urethane bond, which is a soft segment, is formed and functions to relieve stress concentration due to curing derived from a polymerizable double bond.

  When the content of the polyisocyanate (B) is less than 5% by weight with respect to the total solid content of the curable resin composition, cracks are generated in the cured coating film obtained from the composition upon long-term exposure outdoors. The problem occurs. On the other hand, when the content of the polyisocyanate (B) is higher than 50% by weight with respect to the total solid content of the curable resin composition, there arises a problem that the scratch resistance of the cured coating film is remarkably lowered.

  The polyisocyanate (B) to be used is not particularly limited and known ones can be used, but aromatic diisocyanates such as tolylene diisocyanate and diphenylmethane-4,4′-diisocyanate, meta-xylylene diisocyanate, Since polyisocyanates mainly composed of aralkyl diisocyanates such as α, α, α ′, α′-tetramethyl-meta-xylylene diisocyanate have a problem that a cured coating film is yellowed after long-term outdoor exposure. It is preferable to minimize the amount used.

  From the viewpoint of long-term outdoor use, the polyisocyanate used in the present invention is preferably an aliphatic polyisocyanate containing an aliphatic diisocyanate as a main raw material. Examples of the aliphatic diisocyanate include tetramethylene diisocyanate, 1,5-pentamethylene diisocyanate, 1,6-hexamethylene diisocyanate (hereinafter abbreviated as “HDI”), 2,2,4- (or 2,4,4). Trimethyl-1,6-hexamethylene diisocyanate, lysine isocyanate, isophorone diisocyanate, hydrogenated xylene diisocyanate, hydrogenated diphenylmethane diisocyanate, 1,4-diisocyanate cyclohexane, 1,3-bis (diisocyanate methyl) cyclohexane, 4,4 Examples include '-dicyclohexylmethane diisocyanate, etc. Among them, HDI is particularly preferable from the viewpoint of crack resistance and cost.

  Examples of the aliphatic polyisocyanate obtained from the aliphatic diisocyanate include allophanate type polyisocyanate, biuret type polyisocyanate, adduct type polyisocyanate, and isocyanurate type polyisocyanate, and any of them can be suitably used.

  In addition, as the above-described polyisocyanate, so-called blocked polyisocyanate compounds blocked with various blocking agents can be used. Examples of the blocking agent include alcohols such as methanol, ethanol and lactic acid esters; phenolic hydroxyl group-containing compounds such as phenol and salicylic acid esters; amides such as ε-caprolactam and 2-pyrrolidone; oximes such as acetone oxime and methyl ethyl ketoxime Active methylene compounds such as methyl acetoacetate, ethyl acetoacetate and acetylacetone can be used.

The isocyanate group in the polyisocyanate (B) is preferably 3 to 30% by weight based on the total solid content of the polyisocyanate from the viewpoint of crack resistance and scratch resistance of the resulting cured coating film. When the isocyanate group in (B) is less than 3%, the reactivity of the polyisocyanate is low, and the scratch resistance of the cured coating film is remarkably reduced. When it exceeds 30%, the molecular weight of the polyisocyanate is reduced. Care must be taken because crack resistance due to stress relaxation does not appear.
The reaction between the polyisocyanate and the hydroxyl group in the system (this is a hydroxyl group in the active energy ray-curable monomer having a hydroxyl group in the vinyl polymer segment (a2) or an alcoholic hydroxyl group described later) is particularly heated. For example, when the cured form is UV, it reacts gradually by being left at room temperature after coating and UV irradiation. Moreover, you may accelerate | stimulate reaction of alcoholic hydroxyl group and isocyanate by heating for several minutes-several hours (20 minutes-4 hours) at 80 degreeC after UV irradiation as needed. In that case, you may use a well-known urethanation catalyst as needed. The urethanization catalyst is appropriately selected according to the desired reaction temperature.

(Metal oxide (C))
The present invention is characterized by containing the composite resin (A), the polyisocyanate (B), and a metal oxide (C) having an ultraviolet shielding ability. By adding the metal compound (C), it is possible to maintain the ultraviolet shielding ability for a long time even when exposed outdoors.
The metal oxide (C) is not particularly limited, but silicon dioxide, aluminum oxide, antimony oxide, titanium oxide, indium oxide, tin oxide, zirconium oxide, lead oxide, iron oxide, calcium silicate, magnesium oxide, niobium oxide, Examples thereof include cerium oxide. Of these, zinc oxide or titanium oxide is preferably used from the viewpoints of ultraviolet shielding ability and cost.

  As the number average particle diameter of the metal oxide (C) (a mixture of primary particles and secondary particles may be used, or only primary particles or secondary particles may be used) Although it does not have a restriction | limiting in particular as long as it has shielding ability, Preferably it is 0.5 nm-500 nm from viewpoints, such as productivity and a weather resistance. When the particle diameter is smaller than 0.5 nm, the viscosity of the curable resin composition is extremely increased and it is difficult to use. On the other hand, if the particle diameter exceeds 500 nm, it may be difficult to ensure the ultraviolet shielding ability.

(Curable resin composition)
Since the curable resin composition of the present invention has a polymerizable double bond as described above, it can be cured by active energy rays such as ultraviolet rays or heat. It is also possible to include both. In the case of a protective sheet for a solar cell in which a protective layer obtained by curing the curable resin composition is provided on one side of a plastic substrate, ultraviolet curing is preferable because the substrate is plastic. Hereinafter, an example in the case of UV curing will be described as a specific embodiment of the present invention.

When the curable resin composition of the present invention is UV-cured, it is preferable to use a photopolymerization initiator. Known photopolymerization initiators may be used, and for example, one or more selected from the group consisting of acetophenones, benzyl ketals, and benzophenones can be preferably used. Examples of the acetophenones include diethoxyacetophenone, 2-hydroxy-2-methyl-1-phenylpropan-1-one, 1- (4-isopropylphenyl) -2-hydroxy-2-methylpropan-1-one, 4 -(2-hydroxyethoxy) phenyl- (2-hydroxy-2-propyl) ketone and the like. Examples of the benzyl ketals include 1-hydroxycyclohexyl-phenyl ketone and benzyl dimethyl ketal. Examples of the benzophenones include benzophenone and methyl o-benzoylbenzoate. Examples of the benzoins include benzoin, benzoin methyl ether, and benzoin isopropyl ether. A photoinitiator (B) may be used independently and may use 2 or more types together.
The amount of the photopolymerization initiator (B) used is preferably 1 to 15% by weight and more preferably 2 to 10% by weight with respect to 100% by weight of the composite resin (A).

Moreover, when making it ultraviolet-harden, it is preferable to contain polyfunctional (meth) acrylate as needed. As described above, the polyfunctional (meth) acrylate is preferably one having an alcoholic hydroxyl group because it is reacted with the polyisocyanate (B). For example, 1,2-ethanediol diacrylate, 1,2-propanediol diacrylate, 1,4-butanediol diacrylate, 1,6-hexanediol diacrylate, dipropylene glycol diacrylate, neopentyl glycol diacrylate, Tripropylene glycol diacrylate, trimethylolpropane diacrylate, trimethylolpropane triacrylate, tris (2-acryloyloxy) isocyanurate, pentaerythritol triacrylate, pentaerythritol tetraacrylate, di (trimethylolpropane) tetraacrylate, di (penta Erythritol) pentaacrylate, di (pentaerythritol) hexaacrylate, etc. have two or more polymerizable double bonds in one molecule That polyfunctional (meth) acrylate. Moreover, urethane acrylate, polyester acrylate, epoxy acrylate, etc. can be illustrated as polyfunctional acrylate. These may be used alone or in combination of two or more.
In particular, pentaerythritol triacrylate and dipentaerythritol pentaacrylate are preferred from the viewpoint of scratch resistance of the cured coating film and the improvement of crack resistance due to reaction with polyisocyanate.

  In addition, a monofunctional (meth) acrylate can be used in combination with the polyfunctional (meth) acrylate. For example, hydroxyethyl (meth) acrylate, hydroxypropyl (meth) acrylate, hydroxybutyl (meth) acrylate, caprolactone-modified hydroxy (meth) acrylate (for example, “Plexel” manufactured by Daicel Chemical Industries), phthalic acid and propylene Mono (meth) acrylate of polyester diol obtained from glycol, mono (meth) acrylate of polyester diol obtained from succinic acid and propylene glycol, polyethylene glycol mono (meth) acrylate, polypropylene glycol mono (meth) acrylate, pentaerythritol Tri (meth) acrylate, 2-hydroxy-3- (meth) acryloyloxypropyl (meth) acrylate, (meth) acrylate of various epoxy esters Hydroxyl group-containing (meth) acrylic acid esters such as phosphoric acid adducts; carboxyl group-containing vinyl monomers such as (meth) acrylic acid, crotonic acid, itaconic acid, maleic acid, fumaric acid; vinyl sulfonic acid, styrene sulfone Sulfonic acid group-containing vinyl monomers such as acid and sulfoethyl (meth) acrylate; 2- (meth) acryloyloxyethyl acid phosphate, 2- (meth) acryloyloxypropyl acid phosphate, 2- (meth) acryloyloxy-3- Examples thereof include acidic phosphate ester vinyl monomers such as chloro-propyl acid phosphate and 2-methacryloyloxyethylphenyl phosphoric acid; vinyl monomers having a methylol group such as N-methylol (meth) acrylamide. These can use 1 type (s) or 2 or more types. Considering the reactivity of the polyfunctional isocyanate (b) with the isocyanate group, the monomer (c) is particularly preferably a (meth) acrylic acid ester having a hydroxyl group.

  As the usage-amount in the case of using the said polyfunctional acrylate (C), 1 to 85 weight% is preferable with respect to the total solid content of the curable resin composition of this invention, and 5 to 80 weight% is more preferable. By using the polyfunctional acrylate within the above range, the coating film properties such as hardness of the coating film obtained can be improved.

(Active energy rays)
Examples of active energy rays used when the adhesive of the present invention is cured with active energy rays include electron beams, ultraviolet rays, and infrared rays. Ultraviolet rays are simple and preferable. For example, a low-pressure mercury lamp, a high-pressure mercury lamp, a metal halide lamp, a xenon lamp, an argon laser, or a helium / cadmium laser can be used as the light used for ultraviolet curing. Using these, the coating film can be cured by irradiating the application surface of the adhesive with ultraviolet rays having a wavelength of about 180 to 400 nm. The irradiation amount of ultraviolet rays is appropriately selected depending on the type and amount of the photopolymerization initiator used.

On the other hand, when thermosetting the curable resin composition of the present invention, the reaction temperature and reaction time of the polymerizable double bond reaction in the composition and the urethanization reaction between the alcoholic hydroxyl group and the isocyanate are taken into consideration. Thus, it is preferable to select each catalyst.
Moreover, it is also possible to use a thermosetting resin together. Examples of the thermosetting resin include vinyl resins, unsaturated polyester resins, polyurethane resins, epoxy resins, epoxy ester resins, acrylic resins, phenol resins, petroleum resins, ketone resins, silicon resins, and modified resins thereof.

  Moreover, in order to adjust the viscosity at the time of coating, you may contain the organic solvent. Examples of the organic solvent include aliphatic or alicyclic hydrocarbons such as n-hexane, n-heptane, n-octane, cyclohexane and cyclopentane; aromatic hydrocarbons such as toluene, xylene and ethylbenzene. Alcohols such as methanol, ethanol, n-butanol, ethylene glycol monomethyl ether, propylene glycol monomethyl ether; ethyl acetate, butyl acetate, n-butyl acetate, n-amyl acetate, ethylene glycol monomethyl ether acetate, propylene glycol monomethyl Esters such as ether acetate; Ketones such as acetone, methyl ethyl ketone, methyl isobutyl ketone, methyl n-amyl ketone and cyclohexanone; diethylene glycol dimethyl ether, diethylene glycol dibuty Polyalkylene glycol dialkyl ethers such as ethers; ethers such as 1,2-dimethoxyethane, tetrahydrofuran and dioxane; N-methylpyrrolidone, dimethylformamide, dimethylacetamide or ethylene carbonate used alone or in combination of two or more Can be used.

  In addition, the curable resin composition of the present invention includes an organic solvent, an inorganic pigment, an organic pigment, an extender pigment, a clay mineral, a wax, a surfactant, a stabilizer, a flow regulator, a dye, a leveling agent, if necessary. Various additives such as a rheology control agent, an ultraviolet absorber, an antioxidant, or a plasticizer can also be used.

  In the curable resin composition of the present invention, since the composite resin (A) contained has both the polysiloxane segment (a1) and the vinyl polymer segment (a2), the surface smoothness of the coating film is improved. Can be relatively compatible with acrylic resins and active energy ray-curable monomers. Therefore, a composition having good compatibility can be obtained.

  The curable resin composition of the present invention can be used in various shapes. Specific examples include a solution dissolved in an organic solvent, a dispersion dispersed in an organic solvent, a dispersion dispersed in water, a solution that does not use a solvent, a powder, and the like.

  The curable resin composition of the present invention can be used as it is as a curable coating such as active energy rays. Moreover, you may add additives, such as an above described organic pigment and an inorganic pigment.

(Protective sheet for solar cell)
A protective sheet for solar cells can be obtained by providing the curable resin composition on one side of a plastic substrate and curing it.

(Plastic substrate)
The plastic sheet used in the present application is, for example, polyethylene (PE) (high density polyethylene, low density polyethylene, linear low density polyethylene), polypropylene (PP), polyolefin resin such as polybutene, (meth) acrylic resin, poly Vinyl chloride resin, polystyrene resin, polyvinylidene chloride resin, saponified ethylene-vinyl acetate copolymer, polyvinyl alcohol, polycarbonate resin, fluororesin, polyvinyl acetate resin, acetal resin, polyester resin (polyethylene Films or sheets of terephthalate (PET), polybutylene terephthalate, polyethylene naphthalate), polyamide resin, polyphenylene sulfide (PPS) resin, and other various resins can be used. These resin films or sheets may be stretched uniaxially or biaxially. Moreover, what laminated | stacked the said resin film in multiple layers may be sufficient, and the metal and the metal oxide, and the inorganic compound may be vapor-deposited. In addition, when these resin films are used as a protective sheet on the back side of a solar cell module, white pigments such as titanium oxide and barium sulfate or carbon are used for the purpose of absorbing or reflecting light incident on the module. Black pigments may be added, and known additives such as known UV absorbers, moisture absorbers (drying agents), oxygen absorbers and antioxidants other than colored pigments may be added. . In particular, considering the performance of the protective sheet for solar cells such as transparency, polyolefin resins such as polyethylene (PE) (high density polyethylene, low density polyethylene, linear low density polyethylene), polypropylene (PP), polybutene, (meta) Acrylic resins, polyester resins (polyethylene terephthalate (PET), polybutylene terephthalate, polyethylene naphthalate), polyphenylene sulfide (PPS) resins and the like are preferably used.

A curable resin composition layer made of the curable resin composition is provided on one side of the plastic sheet. The curable resin composition layer may be formed by a known method, for example, a calendar method, a flow coater method, a roll coater method, a spray method, an airless spray method, an air spray method, a brush coating, a roller coating, a trowel coating, or a dipping process. Examples thereof include a method of forming by a method, a pulling method, a nozzle method, a winding method, a sink method, a piling method, a patching method, and the like.
The film thickness of the curable resin composition layer is preferably in the range of 0.05 μm to 150 μm. If the thickness is less than 0.05 μm, the ultraviolet shielding ability may be insufficient, and if the thickness exceeds 150 μm, the coating film may be cracked in the subsequent step.

A solar cell protective sheet having a cured protective layer can be obtained by curing the curable resin composition layer by curing with the aforementioned active energy ray curing, thermosetting, or active energy ray. .
The haze of the protective layer may be selected comprehensively from the viewpoint of the strength and durability of the coating film and the conversion efficiency of the solar cell, but is preferably 20 or less, more preferably 10 from the viewpoint of the conversion efficiency of the solar cell. Hereinafter, it is more preferably 5 or less.

The solar cell protective sheet can be suitably used for either the light-receiving surface side protective sheet or the back surface side protective sheet of the solar cell module.
For example, when using as a light-receiving surface side protective sheet, it is preferable to use highly transparent zinc oxide as the metal oxide (C). In this case, the amount of zinc oxide to be used is preferably 1 to 25%, and most preferably 1.5 to 20%. On the other hand, since transparency is not calculated | required when using as a back surface side protection sheet, a metal oxide with low transparency can also be used. Specific examples include titanium oxide.

(Solar cell module)
An example of a specific aspect of the solar cell module in the case where the solar cell protective sheet of the present application is used as a light-receiving surface side protective sheet is shown in FIG. Needless to say, the present invention includes various embodiments not described herein.
In the solar cell module shown in FIG. 1, a solar cell light-receiving surface side protective sheet 1, a first sealing material 2, a solar cell group 3, a second sealing material 4, and a solar cell protective sheet 5 are sequentially laminated. Consists of. The solar cell light-receiving surface side protective sheet 1 is a state in which the plastic substrate of the protective sheet 1 (the surface opposite to the cured surface of the curable resin composition of the present invention) and the first sealing material 2 are combined. That is, the protective layer obtained by curing the curable resin composition is laminated so that it becomes the outermost layer.

  The 1st sealing material 2 and the 2nd sealing material 4 seal the solar cell group 3 between the light-receiving surface side protection sheet 1 for solar cells of this invention, and the protection sheet 5 for batteries. As the 1st sealing material 2 and the 2nd sealing material 4, translucent resin, such as EEA, PVB, silicon | silicone, urethane, an acryl, an epoxy other than EVA, can be used. Moreover, the 1st sealing material 2 and the 2nd sealing material 4 contain crosslinking agents, such as a peroxide. Accordingly, the first sealing material 2 and the second sealing material 4 are heated to a predetermined crosslinking temperature or higher to be softened and then crosslinked.

  The solar cell group 3 includes a plurality of solar cells and a wiring material. The plurality of solar cells are electrically connected to each other by a wiring material.

  Thereafter, the first sealing material 2 and the second sealing material 4 laminated by the laminating apparatus are fully cured by heating, whereby a solar cell module can be obtained.

  Next, the present invention will be specifically described with reference to examples and comparative examples. Unless otherwise indicated, “parts” and “%” are based on weight.

(Synthesis Example 1 [Preparation Example of Polysiloxane (a1-1)])
A reaction vessel equipped with a stirrer, a thermometer, a dropping funnel, a condenser tube and a nitrogen gas inlet is charged with 415 parts of methyltrimethoxysilane (MTMS) and 756 parts of 3-methacryloyloxypropyltrimethoxysilane (MPTS). The temperature was raised to 60 ° C. with stirring under aeration of gas. Next, a mixture consisting of 0.1 part of “A-3” (iso-propyl acid phosphate manufactured by Sakai Chemical Co., Ltd.) and 121 parts of deionized water was added dropwise over 5 minutes. After completion of the dropwise addition, the reaction vessel was heated to 80 ° C. and stirred for 4 hours to carry out a hydrolysis condensation reaction, thereby obtaining a reaction product.
By removing methanol and water contained in the obtained reaction product under conditions of 40 to 60 ° C. under reduced pressure of 1 to 30 kilopascals (kPa), the number average molecular weight is 1000 and the active ingredient is 75. 1000 parts of polysiloxane (a1-1) which is 0.0% was obtained.
The "active ingredient" is a value obtained by dividing the theoretical yield (parts by weight) when all the methoxy groups of the silane monomer used undergo hydrolysis condensation reaction by the actual yield (parts by weight) after hydrolysis condensation reaction, That is, it is calculated by the formula [theoretical yield when all methoxy groups of the silane monomer undergo hydrolysis condensation reaction (parts by weight) / actual yield after hydrolysis condensation reaction (parts by weight)].

(Synthesis Example 2 [Preparation Example of Vinyl Polymer (a2-1)])
In a reaction vessel similar to Synthesis Example 1, 20.1 parts of phenyltrimethoxysilane (PTMS), 24.4 parts of dimethyldimethoxysilane (DMDMS), and 107.7 parts of n-butyl acetate were charged under a nitrogen gas flow. The temperature was raised to 80 ° C. while stirring. Next, 15 parts of methyl methacrylate (MMA), 45 parts of n-butyl methacrylate (BMA), 39 parts of 2-ethylhexyl methacrylate (EHMA), 1.5 parts of acrylic acid (AA), 4.5 parts of MPTS, 2-hydroxyethyl A mixture containing 45 parts of methacrylate (HEMA), 15 parts of n-butyl acetate and 15 parts of tert-butylperoxy-2-ethylhexanoate (TBPEH) was stirred at the same temperature under a stream of nitrogen gas. And dropped into the reaction vessel in 4 hours. After further stirring at the same temperature for 2 hours, a mixture of 0.05 part of “A-3” and 12.8 parts of deionized water was added dropwise to the reaction vessel over 5 minutes, and the mixture was kept at the same temperature for 4 hours. By stirring, the hydrolysis condensation reaction of PTMS, DMDMS, and MPTS was advanced. When the reaction product was analyzed by ¹ H-NMR, almost 100% of the trimethoxysilyl group of the silane monomer in the reaction vessel was hydrolyzed. Subsequently, the vinyl polymer (a2-1) which is a reaction product with a residual amount of TBPEH of 0.1% or less was obtained by stirring at the same temperature for 10 hours.

Synthesis Example 3 [Preparation Example of Vinyl Polymer (a2-2)]
In a reaction vessel similar to Synthesis Example 1, 20.1 parts of phenyltrimethoxysilane (PTMS), 24.4 parts of dimethyldimethoxysilane (DMDMS), and 107.7 parts of n-butyl acetate were charged under a nitrogen gas flow. The temperature was raised to 80 ° C. while stirring. Next, 14.5 parts of methyl methacrylate (MMA), 2 parts of n-butyl methacrylate (BMA), 105 parts of cyclohexyl methacrylate (CHMA), 7.5 parts of acrylic acid (AA), 4.5 parts of MPTS, 2-hydroxyethyl While stirring a mixture containing 15 parts of methacrylate (HEMA), 15 parts of n-butyl acetate and 6 parts of tert-butylperoxy-2-ethylhexanoate (TBPEH) at the same temperature under aeration of nitrogen gas And dropped into the reaction vessel in 4 hours. After further stirring at the same temperature for 2 hours, a mixture of 0.05 part of “A-3” and 12.8 parts of deionized water was added dropwise to the reaction vessel over 5 minutes, and the mixture was kept at the same temperature for 4 hours. By stirring, the hydrolysis condensation reaction of PTMS, DMDMS, and MPTS was advanced. When the reaction product was analyzed by ¹ H-NMR, almost 100% of the trimethoxysilyl group of the silane monomer in the reaction vessel was hydrolyzed. Subsequently, by stirring for 10 hours at the same temperature, a vinyl polymer (a2-2) which was a reaction product having a residual amount of TBPEH of 0.1% or less was obtained.

(Synthesis Example 4 [Preparation Example of Composite Resin (A-1)])
162.5 parts of the polysiloxane (a1-1) obtained in Synthesis Example 1 is added to 307 parts of the vinyl polymer (a2-1) obtained in Synthesis Example 2 and stirred for 5 minutes. 27.5 parts of ionic water was added and the mixture was stirred at 80 ° C. for 4 hours to carry out a hydrolysis condensation reaction between the reaction product and polysiloxane. The obtained reaction product was distilled under reduced pressure of 10 to 300 kPa under conditions of 40 to 60 ° C. for 2 hours to remove the produced methanol and water, and then 150 parts of methyl ethyl ketone (MEK), n-acetate -Butyl resin 27.3 parts, 600 parts of composite resin (A-1) having a polysiloxane segment (a1-1) and a vinyl polymer segment (a2-1) having a nonvolatile content of 50.0% Got.

(Synthesis Example 5 [Preparation Example of Composite Resin A-2])
After adding 562.5 parts of the polysiloxane (a1-1) obtained in Synthesis Example 1 to 307 parts of the vinyl polymer (a2-1) obtained in Synthesis Example 2, the mixture was stirred for 5 minutes, and then removed. 80.0 parts of ionic water was added, and the mixture was stirred at 80 ° C. for 4 hours to carry out hydrolysis condensation reaction between the reaction product and polysiloxane. The obtained reaction product was distilled under reduced pressure of 10 to 300 kPa under conditions of 40 to 60 ° C. for 2 hours to remove the produced methanol and water, and then 128.6 parts of MEK, n-acetate 5.8 parts of butyl were added to obtain 857 parts of a composite resin (A-2) composed of a polysiloxane segment having a nonvolatile content of 70.0% and a vinyl polymer segment.

(Synthesis Example 6 [Preparation Example of Composite Resin A-3])
162.5 parts of the polysiloxane (a1-1) obtained in Synthesis Example 1 is added to 307 parts of the vinyl polymer (a2-2) obtained in Synthesis Example 3 and stirred for 5 minutes. 27.5 parts of ionic water was added, and the mixture was stirred at 80 ° C. for 4 hours to carry out a hydrolysis condensation reaction between the reaction product and polysiloxane. The obtained reaction product was distilled under reduced pressure of 10 to 300 kPa under conditions of 40 to 60 ° C. for 2 hours to remove the produced methanol and water, and then 150 parts of methyl ethyl ketone (MEK), n-acetate -Butyl resin 27.3 parts, 600 parts of composite resin (A-3) having a polysiloxane segment (a1-1) and a vinyl polymer segment (a2-2) having a nonvolatile content of 50.0% Got.

(Preparation of solar cell encapsulant)
100 parts EVA (ethylene / vinyl acetate copolymer (vinyl acetate content 28% by weight)) and 1.3 parts 2,5-dimethyl-2,5-di (2-ethylhexanoylperoxy) hexane as a crosslinking agent The mixture for solar cell encapsulant was prepared by kneading at 70 ° C. with a roll mill. The solar cell encapsulant composition was calendered at 70 ° C. and allowed to cool to produce a solar cell encapsulant (thickness 0.6 mm).

(Examples 1 to 11 and Comparative Examples 1 to 5) Examples of adjusting the curable resin composition
According to the composition described in Table 1, the curable resin compositions of Examples 1 to 11 and the curable resin compositions of Comparative Examples 1 to 5 were prepared. In addition, the zinc oxide or titanium oxide used as a metal oxide (C) was mixed as follows. That is, when mixing zinc oxide, all raw materials are put into a cup and then T.I. K. A curable resin composition was obtained by mixing for 4 minutes at 500 rpm using a HOMO MIXER.
When mixing titanium oxide, the composite resin and titanium oxide were charged into a brown bottle, glass beads having a diameter of about 1.5 mm were charged in an amount equal to the weight of the raw material, and mixed for 30 minutes using a paint conditioner. Thereafter, other raw materials were added, and T.I. K. A curable resin composition was obtained by mixing for 4 minutes at 500 rpm using a HOMO MIXER.

(Preparation of solar cell protective sheet)
A curable resin composition for Examples 1 to 10 was applied to a transparent PET film (thickness 125 μm) treated with corona treatment manufactured by Toyobo Co., Ltd., and Example 11 was applied to a transparent PP film manufactured by DIC Filtech Co., Ltd. Each curable resin composition was applied using the bar coater # 22, and then heated at 80 ° C. for 4 minutes to remove the solvent component. A peeling film was placed on the coating surface, and UV was irradiated from the peeling film side under the condition of 1000 mJ / cm ^{2 with} a UV irradiation apparatus F-6100V manufactured by FUSION. Through the curing period, the urethanization reaction in the adhesive layer proceeds, and the solar cell protective sheets (F-1) to (F-11) and the comparative solar cell protective sheets (HF-1) to (HF-5). Got.

(Production of super straight type solar cell module)
A hot plate of a laminating apparatus (manufactured by Nisshinbo Mechatronics Co., Ltd.) is adjusted to 150 ° C., and on the hot plate, white plate tempered glass, solar cell sealing material, polycrystalline silicon solar cell, solar cell sealing Materials, solar cell protective sheets (F-1) to (F-11) and comparative solar cell protective sheets (HF-1) to (HF-5) (however, the solar cell protective sheet is a peelable film). After peeling, the curable resin composition application surface is overlapped so that the outermost layer is the outermost layer), with the lid of the laminating apparatus being closed, degassing 3 minutes, pressing 8 minutes in order, and then 10 minutes The super straight solar cell modules (SM-1) to (SM-11) and (HSM-1) to (HSM-5) were taken out after being held.

(Production of back straight type solar cell module)
A hot plate of a laminating apparatus (manufactured by Nisshinbo Mechatronics Co., Ltd.) is adjusted to 150 ° C., and on the hot plate, a stainless steel plate, the solar cell encapsulant, a polycrystalline silicon solar cell, and the solar cell encapsulant , Solar cell protective sheets (F-1) to (F-5), (F-7) to (F-9), (F-11) and comparative solar cell protective sheets (HF-1) to ( HF-5) (However, the protective sheet for solar cells is overlapped in the order of peeling the peelable film and then the curable resin composition coated surface is the outermost layer) and the lid of the laminating apparatus is closed. Then, deaeration 3 minutes, press 8 minutes in order, then hold for 10 minutes, then take out, back straight type solar cell modules (BM-1) to (BM-5), (BM-7) to (BM-) 9), (BM-11) and (HBM-1) to (H M-5) and the.

(Evaluation of yellowing after accelerated light resistance test)
An accelerated light resistance test was conducted using an ultraviolet deterioration accelerating tester (eye super UV tester SUV-W131: manufactured by Iwasaki Electric Co., Ltd.) with a UV irradiation intensity of 100 mW / cm ² .
The degree of yellowing of the film before and after the 200 hour accelerated test of the solar cell protective sheets (F-1) to (F-11) and the comparative solar cell protective sheets (HF-1) to (HF-5) The b value indicating the yellowish color of the Lab display color was measured using a color difference meter CR-100 manufactured by Gretag Macbeth. When the difference Δb between the b values before and after the test was 0-1, the degree of yellowing was evaluated as ◯, when 1-5, Δ when the value was 5 or more, and x.

(Weather resistance evaluation)
Accelerated weathering test (3000 hours) using a sunshine weatherometer for solar cell protective sheets (F-1) to (F-11) and comparative solar cell protective sheets (HF-1) to (HF-5) The appearance change before and after the test was observed. The weather resistance was evaluated by evaluating the appearance characteristics according to the following criteria.
5; No change 4; State 3 in which hair cracks (thin cracks) are scattered 3; State 2 in which cracks having a width of 1 mm or more are observed; State 1 in which the coating film is partially peeled and missing 1; Most of the coating film Missing state

(Evaluation method Evaluation of power generation efficiency of solar cell module)
Super straight type solar cell modules (SM-1) to (SM-11) and (HSM-1) to (HSM-5), back straight type solar cell modules (BM-1) to (BM) obtained above. -5), (BM-7) to (BM-9), (BM-11), and (HBM-1) to (HBM-5), module temperature using Wacom Denso solar simulator The power generation efficiency was measured under the conditions of 25 ° C., radiation intensity 1 kW / m ² , and spectral distribution AM1.5G.

  Each raw material composition and evaluation results are shown in the table.

PETA; pentaerythritol triacrylate polyisocyanate; DN-902S [manufactured by DIC Corporation]
Photopolymerization initiator; hydroxycyclohexyl phenyl ketone zinc oxide 1; ZD019 manufactured by Teika Co., Ltd.
Titanium oxide 1; MT-500HD manufactured by Teika Co., Ltd.
Titanium oxide 2; JR-805 manufactured by Teika Co., Ltd.
UVa1; RUVA-93 manufactured by Otsuka Chemical Co., Ltd.
UVa2; 2- [4-[(2-hydroxy-3- (2′-ethyl) hexyl) oxy] -2-hydroxyphenyl] -4,6-bis (2,4-dimethylphenyl) -1,3 5-triazine

  As a result, the solar cell protective sheets (F-1) to (F-11) of Examples 1 to 11 were not yellowed even after the accelerated light resistance test and cracks due to the weather resistance test did not occur, and the sheets were used. The solar cell module showed a power generation efficiency of 10% or more. The comparative solar cell protective sheets (HF-1) to (HF-4) are examples in which the content of the polysiloxane segment (a1) is out of the range, or the content of the polyisocyanate (B) is out of the range. In either case, the weather resistance was inferior. Moreover, although the protective sheet for solar cells (HF-5) of the comparative example 5 is an example which does not contain zinc oxide, it has turned yellow.

: An example of a super straight type solar cell module.

1: Solar cell protective sheet 2: First sealing material 3: Solar cell group 4: Second sealing material 4
5: Back side protective material

Claims (6)

A polysiloxane segment (a1) having a structural unit represented by the general formula (1) and / or the general formula (2), a silanol group and / or a hydrolyzable silyl group, and a vinyl heavy polymer having an alcoholic hydroxyl group. The combined segment (a2) contains a composite resin (A), a polyisocyanate (B), and a metal oxide (C) bonded by a bond represented by the general formula (3),
The content of the polysiloxane segment (a1) is 10 to 60% by weight with respect to the total solid content of the curable resin composition, and the content of the polyisocyanate (B) is the total solid of the curable resin composition. I 5 to 50% by weight der respect to quantity,
A curable resin composition, wherein the metal oxide (C) is zinc oxide .

(1)

(2)
(In the general formulas (1) and (2), R ₁ , R ₂ and R ₃ are each independently -R ₄ -CH = CH ₂ , -R ₄ -C (CH ₃ ) = CH ₂ ,- A group having one polymerizable double bond selected from the group consisting of R ₄ —O—CO—C (CH ₃ ) ═CH ₂ and —R ₄ —O—CO—CH═CH 2 (provided that R ₄ is a single group) Represents a bond or an alkylene group having 1 to 6 carbon atoms.), An alkyl group having 1 to 6 carbon atoms, a cycloalkyl group having 3 to 8 carbon atoms, an aryl group, or 7 to 12 carbon atoms. And at least one of R ₁ , R ₂ and R ₃ is a group having the polymerizable double bond)

(3)
(In the general formula (3), carbon atoms constitute a part of the vinyl polymer segment (a2), and silicon atoms bonded only to oxygen atoms constitute a part of the polysiloxane segment (a1). To do) The curable resin composition according to claim 1, wherein an average particle diameter of the metal oxide (C) is in a range of 0.5 nm to 500 nm. The content rate of the said metal oxide (C) is 1-25 weight% with respect to the total solid content of a curable resin composition, The curable resin composition of Claims 1-2. The curable resin composition in any one of Claims 1-3 is used, The coating agent characterized by the above-mentioned. A polysiloxane segment (a1) having a structural unit represented by the general formula (1) and / or the general formula (2), a silanol group and / or a hydrolyzable silyl group on one side of the plastic substrate, and an alcoholic property Contains a composite resin (A), a polyisocyanate (B), and a metal oxide (C) in which a vinyl polymer segment (a2) having a hydroxyl group is bonded by a bond represented by the general formula (3). ,
The content of the polysiloxane segment (a1) is 10 to 60% by weight with respect to the total solid content of the curable resin composition, and the content of the polyisocyanate (B) is the total solid of the curable resin composition. A protective sheet for a solar cell, comprising a protective layer obtained by curing a curable resin composition, which is 5 to 50% by weight based on the amount .

(1)

(2)
(In the general formulas (1) and (2), R ₁ , R ₂ and R ₃ are each independently -R ₄ -CH = CH ₂ , -R ₄ -C (CH ₃ ) = CH ₂ ,- A group having one polymerizable double bond selected from the group consisting of R ₄ —O—CO—C (CH ₃ ) ═CH ₂ and —R ₄ —O—CO—CH═CH 2 (provided that R ₄ is a single group) Represents a bond or an alkylene group having 1 to 6 carbon atoms.), An alkyl group having 1 to 6 carbon atoms, a cycloalkyl group having 3 to 8 carbon atoms, an aryl group, or 7 to 12 carbon atoms. And at least one of R ₁ , R ₂ and R ₃ is a group having the polymerizable double bond)

(3)
(In the general formula (3), carbon atoms constitute a part of the vinyl polymer segment (a2), and silicon atoms bonded only to oxygen atoms constitute a part of the polysiloxane segment (a1). To do) A solar cell module comprising the solar cell protective sheet according to claim 5 provided on a solar cell module such that a protective layer obtained by curing the curable resin composition is an outermost layer.

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