JP2016084419A - Silicone rubber composition for light condensing type solar cell, and fresnel lens and prism lens for light condensing type solar cell - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a silicone rubber composition having an ultraviolet ray-absorbing function which improves weather resistance of a light condensing type solar cell module.SOLUTION: The silicone rubber composition for forming a Fresnel lens or a prism lens of a light-condensing type solar cell includes: diorganopolysiloxane (A) having not less than 0.1 of a silicon atom-bonded alkenyl group on an average in 1 molecule; a liquid or solid organopolysiloxane (B) represented by the average composition formula RSiO(2), where R is a monovalent hydrocarbon group, an alkoxy group or a hydroxyl group and p is a positive number satisfying 1≤p<2, and having a SiOunit and a RSiOunit in the composition where the alkenyl group content is 0.01-1 mol to 100 g of the (B) constituent, and the viscosity at 23°C is not less than 10 mPa s; organohydrogenpolysiloxane (C) having not less than 2 of H bonded to a silicon atom in 1 molecule; a hydrosilylation catalyst (D); and a benzotriazole ultraviolet ray-absorbing agent (E).SELECTED DRAWING: None

Description

INDUSTRIAL APPLICABILITY The present invention can maintain an excellent ultraviolet cut property over a long period of time, and is obtained from a silicone rubber composition suitable for Fresnel lenses and prism lenses used in concentrating solar cells, and the silicone rubber composition. The present invention relates to a Fresnel lens and a prism lens for a concentrating solar cell.
In particular, the present invention relates to a concentrating solar power generation unit of a type in which high-energy solar light collected by primary optical system sunlight is irradiated to solar cells, and in particular, the concentrating solar power generation unit. It is related with the technology etc. which improve the durability and power generation stabilization.

  The concentrating solar power generation unit is attracting attention because it can reduce the number of solar cells that occupy a large portion of the cost composition ratio because it condenses sunlight and irradiates the solar cells. In this concentrating solar power generation unit, the condensed light collected in the primary optical system is non-uniform such that the intensity at the center is high and the intensity at the periphery is low. It has been pointed out that the power generation efficiency decreases when the solar cell is directly irradiated with the condensed light collected in (1). In view of this, a secondary optical system composed of a columnar optical member that generally mixes light collected in the primary optical system by advancing it while reflecting on the side surfaces has been proposed.

  A sunlight condensing part such as a Fresnel lens or prism lens which is a primary optical system uses a laminate of a transparent indicator substrate, a resin Fresnel lens and a prism lens. As the transparent substrate, optical glass and plastic are usually mentioned. From the viewpoint of scratch resistance, optical glass is preferred. By using optical glass, a surface that is exactly the same as a conventional lens and that does not have to worry about scratches can be obtained. Plastic materials include acrylic resins such as polymethyl methacrylate (polymethyl methacrylate, PMMA) used for optical lenses, polycarbonate, high-density polyethylene, polystyrene, polyvinyl chloride, polyacrylonitrile-styrene copolymer. And styrene-acrylic copolymer. As materials for Fresnel lenses, prism lenses, etc., acrylic resin, polymethyl methacrylate resin, and polycarbonate resin are generally used. However, in a concentrating solar cell panel that requires long-term durability of more than 20 years under sunlight, a silicone rubber having higher UV resistance and flexibility than these general-purpose resins is suitable.

  A concentrating solar power generation unit having a secondary optical system includes a primary optical system for concentrating sunlight, a solar battery cell, and a solar battery cell such that a lower end surface faces the solar battery cell. A columnar optical member made of sodium-containing glass for guiding the sunlight collected by the primary optical system to the solar cell, the columnar optical member, and the lower end surface thereof. A sealing resin or an adhesive covering the solar battery cell is provided.

  As the sealing resin and adhesive covering the solar battery cell, the solar battery cell may be easily deteriorated by moisture, which can prevent the ingress of moisture, and epoxy resin or acrylic resin with low water vapor permeability is used. Yes. However, since these resins deteriorate and discolor with ultraviolet rays of 350 nm or less, the ability as a solar cell has been reduced.

  In addition, the following are mentioned as prior literature relevant to the present invention.

JP-A-8-97457 JP 2007-201109 A JP 2007-212771 A JP 2007-271857 A JP 2011-243927 A JP 2012-149234 A International Publication No. 2012/160994

  The present invention protects against ultraviolet rays having a wavelength of 380 nm or less in order to improve the durability of the sealing resin and adhesive covering the columnar optical member of the concentrating solar cell unit and the solar cell facing the lower end surface thereof, It is an object of the present invention to provide a silicone rubber composition used in a sunlight condensing part such as a Fresnel lens and a prism lens, which is a primary optical system imparted with ultraviolet absorbing ability, and a Fresnel lens and a prism lens for a concentrating solar cell. To do.

  Silicone rubber is excellent in light transmittance in a wide wavelength region, and is widely used for LED sealing materials and various optical lenses. However, when this excellent characteristic is damaged, and it is used for Fresnel lenses and prism lenses of concentrating solar cells with silicone rubber, glass columnar optics provided in the secondary optical system of concentrating solar cell units Ultraviolet light including a short wavelength region of 380 nm or less enters the member directly, and the sealing resin or adhesive that covers the solar cell below the member is also exposed to ultraviolet light of a short wavelength region of 380 nm or less. End up. An organic resin such as an epoxy resin or an acrylic resin used for a sealing resin or an adhesive is discolored in a short time when exposed to ultraviolet light in a short wavelength region of 380 nm or less.

  In view of this, the present inventors have conducted extensive studies and as a result, absorbed light in the short wavelength region of 380 nm or less, prevented the penetration of ultraviolet light of 380 nm or less into the secondary optical system, and sealed the solar cell. For the purpose of improving the durability of the stop resin or adhesive, it has been found that it is effective to add a compound having a specific ultraviolet absorbing ability to the silicone rubber.

  That is, a general ultraviolet absorber has a structure suitable for a hydrocarbon-based organic resin, and an ultraviolet absorber suitable for silicone rubber is not known. Particularly, it has a solubility in a silicone rubber composition. There was difficulty. In contrast, the present inventors have confirmed that a benzotriazole-based ultraviolet absorber is suitable as a compound suitable for a UV absorption ability of 380 nm or less. Furthermore, as a UV absorber having excellent solubility in silicone rubber and excellent storage stability, a benzotriazole-based UV absorber that is liquid at room temperature is found to be excellent, and it is liquid at room temperature having a benzotriazole group. The organosilicon compound has been confirmed to have excellent compatibility and durability after curing.

〔式中、Ｒ³は、水素原子、炭素数１〜１０の非置換又は置換の１価炭化水素基、又は下記一般式（Ａ）で表されるベンゾトリアゾール基含有官能基であるが、Ｒ³の少なくとも１つは式（Ａ）のベンゾトリアゾール基含有官能基である。Ｒ⁴は、炭素数１〜１０の非置換又は置換の１価炭化水素基であり、ｍ≧０の整数、ｎ≧０の整数である。

（式中、Ｒ⁵、Ｒ⁶は炭素数１〜１０の非置換又は置換の２価炭化水素基であり、Ｘは、

である。＊は結合手を示す。）〕
〔６〕
〔１〕〜〔５〕のいずれかに記載のシリコーンゴム組成物の硬化物からなる集光型太陽電池用フレネルレンズ。
〔７〕
〔１〕〜〔５〕のいずれかに記載のシリコーンゴム組成物の硬化物からなる集光型太陽電池用プリズムレンズ。 Accordingly, the present invention provides the following inventions.
[1]
(A) Diorganopolysiloxane having an average of 0.1 or more alkenyl groups bonded to silicon atoms in one molecule: 100 parts by mass,
(B) The following average composition formula (2)
R _p SiO _{(4-p) / 2} (2)
(In the formula, R is the same or different unsubstituted or substituted monovalent hydrocarbon group, alkoxy group or hydroxyl group, and p is a positive number satisfying 1 ≦ p <2.)
It has a SiO ₂ unit and an R ₃ SiO _1/2 unit in the composition, 0.01 to 1 mol is an alkenyl group per 100 g of component (B), and a viscosity at 23 ° C. is 10 mPa · s or more. Liquid or solid organopolysiloxane: 5 to 50 parts by mass,
(C) Organohydrogenpolysiloxane having two or more hydrogen atoms bonded to silicon atoms in one molecule: silicon atom-bonded hydrogen atoms with respect to 1 mol of silicon atom-bonded alkenyl groups in components (A) and (B) In an amount of 0.1 to 4.0 mol,
(D) Hydrosilylation catalyst: 0.1 to 1,000 ppm as a platinum group metal with respect to the total mass of the components (A), (B) and (C),
(E) A benzotriazole ultraviolet absorber that is liquid at 25 ° C .: 0.01 to 10 parts by mass A silicone rubber composition for forming a Fresnel lens or prism lens for a concentrating solar cell .
[2]
[1] The silicone rubber composition according to [1], which gives a cured product having a light transmittance at a wavelength of 420 nm of 90% or more and a light transmittance at a wavelength of 380 nm of less than 10%.
[3]
[1] or [2], wherein the (E) component benzotriazole ultraviolet absorber is 2- (2H-benzotriazol-2-yl) -6-dodecyl-4-methylphenol Silicone rubber composition.
[4]
The silicone rubber composition according to [1] or [2], wherein the benzotriazole ultraviolet absorber as component (E) is an organosilicon compound having at least one benzotriazole group.
[5]
The silicone rubber composition according to [4], wherein the organosilicon compound having at least one benzotriazole group is represented by the following formula (i):

[Wherein R ³ is a hydrogen atom, an unsubstituted or substituted monovalent hydrocarbon group having 1 to 10 carbon atoms, or a benzotriazole group-containing functional group represented by the following general formula (A), ^At least one of ^{3 is} a benzotriazole group-containing functional group of the formula (A). R ⁴ is an unsubstituted or substituted monovalent hydrocarbon group having 1 to 10 carbon atoms, and is an integer of m ≧ 0 and an integer of n ≧ 0.

(In the formula, R ⁵ and R ⁶ are each an unsubstituted or substituted divalent hydrocarbon group having 1 to 10 carbon atoms, and X is

It is. * Indicates a bond. )]
[6]
A Fresnel lens for a concentrating solar cell comprising a cured product of the silicone rubber composition according to any one of [1] to [5].
[7]
A prism lens for a concentrating solar cell, comprising a cured product of the silicone rubber composition according to any one of [1] to [5].

  The silicone rubber composition for forming a Fresnel lens or a prism lens of a concentrating solar cell according to the present invention uses a sealing resin or an adhesive covering a solar cell used in a secondary optical system as an ultraviolet ray having a short wavelength of 380 nm or less. It is suitably used for protecting from light and as a result improving the weather resistance of the concentrating solar cell module.

As described above, the present invention proposes a silicone rubber composition for concentrating solar cells having the ability to absorb ultraviolet rays containing the following components (A) to (E).
(A) a diorganopolysiloxane having an average of 0.1 or more alkenyl groups bonded to silicon atoms in one molecule;
(B) The following average composition formula (2)
R _p SiO _{(4-p) / 2} (2)
(In the formula, R is the same or different unsubstituted or substituted monovalent hydrocarbon group, alkoxy group or hydroxyl group, and p is a positive number satisfying 1 ≦ p <2.)
A liquid or solid organopolysiloxane having a SiO ₂ unit and a R ₃ SiO _1/2 unit in the composition and containing an alkenyl group,
(C) an organohydrogenpolysiloxane having two or more hydrogen atoms bonded to silicon atoms in one molecule;
(D) a hydrosilylation catalyst,
(E) A benzotriazole ultraviolet absorber that is liquid at 25 ° C.

Hereinafter, the present invention will be described in more detail.
The component (A) curable diorganopolysiloxane contains an average of 0.1 or more silicon-bonded alkenyl groups in one molecule, more preferably an average of 0.5 or more, and still more preferably. An organopolysiloxane having an average of 0.8 or more, particularly an average of 2 or more silicon-bonded alkenyl groups is preferred.

Examples of such an alkenyl group-containing organopolysiloxane include those represented by the following average composition formula (1).
R ¹ _a SiO _{(4-a) / 2} (1)
Wherein R ¹ is an unsubstituted or substituted monovalent hydrocarbon group having the same or different carbon number of 1 to 10, preferably 1 to 8, and a is preferably 1.95 to 2.05. (It is preferably a positive number in the range of 2.00 to 2.02.)

Here, examples of the unsubstituted or substituted monovalent hydrocarbon group bonded to the silicon atom represented by R ¹ include a methyl group, an ethyl group, a propyl group, an isopropyl group, a butyl group, an isobutyl group, a tert-butyl group, Pentyl group, neopentyl group, hexyl group, cyclohexyl group, octyl group, nonyl group, alkyl group such as decyl group, aryl group such as phenyl group, tolyl group, xylyl group, naphthyl group, benzyl group, phenylethyl group, phenylpropyl Aralkyl groups such as groups, vinyl groups, allyl groups, propenyl groups, isopropenyl groups, butenyl groups, hexenyl groups, cyclohexenyl groups, octenyl groups and other alkenyl groups, and some or all of the hydrogen atoms of these groups are fluorine. Substituted with a halogen atom such as bromine, chlorine, cyano group, etc., such as chloromethyl group, chloro Propyl group, bromoethyl group, and a halogen-substituted alkyl group or cyanoethyl group such trifluoropropyl group.

In this case, an average of at least 0.1 of R ¹ , preferably an average of 0.5 or more, more preferably an average of 0.8 or more, and even more preferably an average of 2 or more is an alkenyl group (2 to 8 is preferable, more preferably 2 to 6. The content of the alkenyl group is 0.0001 to 20 mol%, preferably 0.001 to 10 mol%, particularly 0 in the total organic group (that is, the above-mentioned unsubstituted or substituted monovalent hydrocarbon group) R ^1. It is preferable to set it as about 0.01-5 mol%. The alkenyl group may be bonded to the silicon atom at the end of the molecular chain, may be bonded to the silicon atom in the middle of the molecular chain, or may be bonded to both. Those containing bonded alkenyl groups are preferred. R ¹ excluding the alkenyl group is preferably a methyl group or a phenyl group. The viscosity of the organopolysiloxane is preferably 10 to 500,000 mPa · s at 23 ° C., and particularly preferably 400 to 200,000 mPa · s. This is because when the viscosity at 23 ° C. is less than 10 mPa · s, the physical properties of the obtained silicone rubber tend to be remarkably deteriorated. On the other hand, when the viscosity exceeds 500,000 mPa · s, the resulting silicone rubber is obtained. This is because the handling workability of the steel tends to be remarkably lowered. In the present invention, the viscosity can be measured with a rotational viscometer or the like (hereinafter the same).

  The molecular structure of such an organopolysiloxane is a linear diorganopolysiloxane in which the main chain is basically composed of repeating diorganosiloxane units, and both ends of the molecular chain are blocked with triorganosiloxy groups. A part of the main chain may contain a small amount of a trifunctional siloxane unit. The organopolysiloxane is a single polymer having these molecular structures, a copolymer having these molecular structures, or a mixture of these polymers.

  Examples of the organopolysiloxane that can constitute such a base polymer include dimethylpolysiloxane blocked with dimethylvinylsiloxy group blocked at both ends of the molecular chain, dimethylpolysiloxane blocked with methyldivinylsiloxy group blocked at both ends of the molecular chain, and dimethylvinylsiloxy blocked at both ends of the molecular chain. Blocked dimethylsiloxane (80 mol%) / methylphenylsiloxane (20 mol%) copolymer, molecular chain both ends dimethylvinylsiloxy group blocked dimethylsiloxane (80 mol%) / diphenylsiloxane (20 mol%) copolymer, molecular chain both ends dimethylvinylsiloxy group Blocked dimethylsiloxane (90 mol%) / diphenylsiloxane (10 mol%) copolymer, trimethylsiloxy group-blocked dimethylsiloxane / methylvinylsiloxane copolymer Etc. The.

(B) component is the following average composition formula (2)
R _p SiO _{(4-p) / 2} (2)
(In the formula, R is the same or different unsubstituted or substituted monovalent hydrocarbon group, but a part of R may be an alkoxy group or a hydroxyl group. In particular, 0.025 mol% or less is preferably an alkoxy group or a hydroxyl group.), P is 0 ≦ p <2, preferably 0.5 ≦ p ≦ 1.8, and more preferably 0.7 ≦ p ≦. (It is a positive number satisfying 1.5.)
It has a SiO ₂ unit and an R ₃ SiO _1/2 unit in the composition, 0.01 to 1 mol is an alkenyl group per 100 g of component (B), and a viscosity at 23 ° C. is 10 mPa · s or more. It is an organopolysiloxane resin copolymer having a liquid or solid branched or three-dimensional network structure.

  In the above formula (2), the unsubstituted or substituted monovalent hydrocarbon group bonded to the silicon atom represented by R usually includes those having 1 to 12 carbon atoms, preferably about 1 to 8 carbon atoms. Specifically, alkyl groups such as methyl group, ethyl group, propyl group, isopropyl group, butyl group, isobutyl group, tert-butyl group, pentyl group, neopentyl group, hexyl group, cyclohexyl group, octyl group, nonyl group, decyl group, etc. Aryl group such as phenyl group, tolyl group, xylyl group, naphthyl group, aralkyl group such as benzyl group, phenylethyl group, phenylpropyl group, vinyl group, allyl group, propenyl group, isopropenyl group, butenyl group, hexenyl group , An alkenyl group such as a cyclohexenyl group and an octenyl group, and a part or all of the hydrogen atoms of these groups may be fluorine, bromine, Halogen atoms arsenide, those substituted with a cyano group or the like, such as chloromethyl group, chloropropyl group, bromoethyl group, and a halogen-substituted alkyl group or cyanoethyl group such trifluoropropyl group. In this case, at least two of R are preferably alkenyl groups (preferably having 2 to 8 carbon atoms, more preferably 2 to 6 carbon atoms). That is, the content of the alkenyl group is 0.1 to 80 mol%, preferably 0.5 to 50 mol% in the total organic group (that is, the above-mentioned unsubstituted or substituted monovalent hydrocarbon group) R. More preferably, it is about 1-30 mol%.

The (B) component organopolysiloxane has SiO ₂ units and R ₃ SiO _1/2 units, and may consist of only SiO ₂ units and R ₃ SiO _1/2 units. If necessary, R ₂ SiO _2/2 units and RSiO _3/2 units (R is as described above) may be 50% of the total mass of the organopolysiloxane resin copolymer of component (B) with the total amount of these units. Although it may be contained in a range of not more than mass% (50 to 0 mass%), preferably not more than 40 mass% (40 to 0 mass%), more preferably not more than 30 mass% (30 to 0 mass%), it is SiO ₂ unit The molar ratio [R ₃ SiO _1/2 / SiO ₂ ] to R ₃ SiO _1/2 units is preferably 0.5 to 1.5, particularly 0.7 to 1.3. If this molar ratio is smaller than 0.5 or larger than 1.5, the effect of improving the mechanical strength of the cured product may not be sufficiently exhibited. Further, the content of the alkenyl group bonded to the silicon atom in the component (B) is preferably in the range of 0.01 to 1 mol, and in the range of 0.05 to 0.5 mol, per 100 g of the component (B). It is more preferable. If the content of the alkenyl group is more than 1 mol per 100 g of component (B), the cured product may be hard and brittle, and if it is less than 0.01 mol, the effect of improving the mechanical strength may not be sufficiently exhibited.

The viscosity of the organopolysiloxane (B) at 23 ° C. is 10 mPa · s or more, preferably 100 mPa · s or more, more preferably 1,000 mPa · s or more. If the viscosity is lower than the above range, the cured product may be inferior in mechanical strength. There is no upper limit to the viscosity of component (B), and it may be solid at 23 ° C.
(B) The compounding quantity of the organopolysiloxane of a component is 5-50 mass parts with respect to 100 mass parts of (A) component, Preferably it is 5-40 mass parts, More preferably, it is 10-30 mass parts. If the blending amount of the component (B) is too small, the cured product may be inferior in mechanical strength, and if it is too much, the viscosity becomes high and the brittleness may be caused.

The component (C) is a curing agent (crosslinking component) that cures the organopolysiloxanes of the components (A) and (B). Two or more silicon-bonded hydrogen atoms (that is, one molecule) , Si-H group). This organohydrogenpolysiloxane acts as a crosslinking agent for curing the composition by the hydrosilylation addition reaction with the alkenyl group-containing organopolysiloxane of the above components (A) and (B), and the following average composition formula ( 3)
R ² _b H _c SiO _{(4-bc) / 2} (3)
(Wherein R ² is an unsubstituted or substituted monovalent hydrocarbon group having 1 to 10 carbon atoms, b is 0.7 to 2.1, c is 0.001 to 1.0, and b + c is a positive number satisfying 0.8 to 3.0.)
At least 2 (usually 2 to 300), preferably 3 or more (usually about 3 to 200), more preferably 4 to 100 silicon atom-bonded hydrogen atoms (Si) in one molecule. Those having -H group) are preferred. Here, examples of R ² include the same groups as R ¹ in formula (1), but those having no aliphatic unsaturated bond are preferred.

Examples of the organohydrogenpolysiloxane include 1,1,3,3-tetramethyldisiloxane, 1,3,5,7-tetramethylcyclotetrasiloxane, methylhydrogencyclopolysiloxane, methylhydrogensiloxane and dimethylsiloxane. Cyclic copolymer, tris (dimethylhydrogensiloxy) methylsilane, tris (dimethylhydrogensiloxy) phenylsilane, trimethylsiloxy group-blocked methylhydrogenpolysiloxane on both ends, trimethylsiloxy group-blocked dimethylsiloxane / methylhydrogensiloxane on both ends Polymer, both ends dimethylhydrogensiloxy-blocked dimethylpolysiloxane, both ends dimethylhydrogensiloxy-blocked dimethylsiloxane methylhydrogen Xanthene copolymer, both ends dimethylhydrogensiloxy group-blocked methylhydrogenpolysiloxane, both ends trimethylsiloxy group-blocked methylhydrogensiloxane diphenylsiloxane copolymer, both ends trimethylsiloxy group-blocked methylhydrogensiloxane diphenylsiloxane Dimethylsiloxane copolymer, a copolymer comprising (CH ₃ ) ₂ HSiO _1/2 units and SiO _4/2 units, (CH ₃ ) ₂ HSiO _1/2 units, SiO _4/2 units, and (C ₆ H ₅ ) Copolymers composed of SiO _3/2 units. The molecular structure of the organohydrogenpolysiloxane may be any of linear, cyclic, branched, and three-dimensional network structures, but the number of silicon atoms in one molecule (or the degree of polymerization) is 2 to 1. 1,000, especially 3 to 300, especially about 4 to 100 can be used. Further, the viscosity of the organohydrogenpolysiloxane at 23 ° C. is preferably 10 to 100,000 mPa · s, and particularly preferably 10 to 5,000 mPa · s.

  In this composition, the content of the organohydrogenpolysiloxane having a silicon atom-bonded hydrogen atom is such that the silicon atom in this component is 1 mol of the silicon atom-bonded alkenyl group in the component (A) and the component (B). The amount of bonded hydrogen atoms is 0.1 to 4.0 mol. This is because if the content of this component is less than the lower limit of the above range, the resulting composition may not be sufficiently cured, whereas if it exceeds the upper limit of the above range, it is obtained. This is because the cured product becomes very hard and may cause many cracks on the surface.

  Component (D) is a hydrosilylation catalyst (addition reaction catalyst) for accelerating the hydrosilylation addition reaction between the alkenyl group in components (A) and (B) and the Si-H group in component (C). This addition reaction catalyst includes platinum black, platinous chloride, chloroplatinic acid, a reaction product of chloroplatinic acid and a monohydric alcohol, a complex of chloroplatinic acid and an olefin, platinum bisacetoacetate, etc. And platinum group metal catalysts such as platinum-based catalysts, palladium-based catalysts, and rhodium-based catalysts. In addition, although the compounding quantity of this addition reaction catalyst can be made into a catalyst quantity, 0.1-1,000 ppm is normally with respect to the total mass of (A), (B) and (C) component as a platinum group metal. In particular, it is preferable to add about 0.5 to 500 ppm, more preferably about 1 to 200 ppm.

  The component (E), the benzotriazole-based ultraviolet absorber, is an ultraviolet ray having a short wavelength of 380 nm or less, which is a sealing resin or adhesive that covers the solar cell used in the secondary optical system in the concentrating solar cell system unit. It is a component added to protect from light. Considering the power generation efficiency of the solar cell, an ultraviolet absorber that cuts light with a wavelength of 380 nm or less without cutting light with a wavelength of 420 nm or more is suitable. UV absorber. Furthermore, in consideration of solubility with the component (A), by using a benzotriazole-based ultraviolet absorber that is liquid at room temperature, the composition does not become cloudy even when stored refrigerated and has excellent storage stability. Specifically, there is 2- (2H-benzotriazol-2-yl) -6-dodecyl-4-methylphenol. On the other hand, in order to further improve the solubility with the component (A), an organosilicon compound having a benzotriazole group is also exemplified. The organosilicon compound [general formula (i)] having a benzotriazole group is a compound in which a benzotriazole group is bonded to siloxane or silane via a hydrocarbon group. Specifically, the following compound (I) or compound (II) ) Is exemplified.

〔式中、Ｒ³は、水素原子、炭素数１〜１０のアルキル基、アリール基等の非置換又は置換の１価炭化水素基、又は下記一般式（Ａ）で表されるベンゾトリアゾール基含有官能基であるが、Ｒ³の少なくとも１つ、好ましくは１〜２個が式（Ａ）のベンゾトリアゾール基含有官能基である。Ｒ⁴は、炭素数１〜１０の非置換又は置換の１価炭化水素基であり、ｍ≧０の整数、ｎ≧０の整数、好ましくはｍは０〜５００、特に０〜１００、好ましくはｎは０〜２００、特に０〜５０である。

（式中、Ｒ⁵、Ｒ⁶は炭素数１〜１０の非置換又は置換の２価炭化水素基、特にアルキレン基であり、Ｘは、

である。＊は結合手を示す。）〕

[In the formula, R ³ is a hydrogen atom, an alkyl group having 1 to 10 carbon atoms, an unsubstituted or substituted monovalent hydrocarbon group such as an aryl group, or a benzotriazole group represented by the following general formula (A) Although it is a functional group, at least one, preferably 1-2 of R ³ is a benzotriazole group-containing functional group of the formula (A). R ⁴ is an unsubstituted or substituted monovalent hydrocarbon group having 1 to 10 carbon atoms, an integer of m ≧ 0, an integer of n ≧ 0, preferably m is 0 to 500, particularly 0 to 100, preferably n is 0 to 200, particularly 0 to 50.

(Wherein R ⁵ and R ⁶ are each an unsubstituted or substituted divalent hydrocarbon group having 1 to 10 carbon atoms, particularly an alkylene group, and X is

It is. * Indicates a bond. )]

  The blending amount of the component (E) is 0.01 to 10 parts by weight, preferably 0.05 to 5 parts by weight, particularly 100 parts by weight in total of the components (A), (B) and (C). It is preferable that it is 0.1-2 mass parts. If it is less than 0.01 part by mass, the effect as an ultraviolet absorber cannot be obtained, and if it is 10 parts by mass or more, it causes discoloration after heat resistance.

  Furthermore, since (E) component stabilizes by being taken in into hardened | cured material, it is preferable to have a silicon atom bond hydrogen atom. The amount of silicon atom-bonded hydrogen atoms contained in component (E) is 1 mol of silicon atom-bonded alkenyl groups in components (A) and (B), and the silicon atom-bonded hydrogen atoms in component (C). The amount is preferably 0.1 to 4 mol in total. When the amount is less than the lower limit of the above range, the resulting composition may not be sufficiently cured. On the other hand, when the upper limit of the above range is exceeded, the resulting cured product becomes very hard and has a large number of surfaces. There is a risk of cracking.

  The silicone rubber composition of the present invention comprises at least the above components (A) to (E), and the composition further includes other components as long as the purpose of the present invention is not impaired. Reinforcing fillers such as silica, wet fine powder silica, crystalline silica, and the like, and fillers obtained by hydrophobizing the surface of these fillers with an organosilicon compound, acetylene compounds, hydrazine compounds, phosphine compounds, You may contain addition reaction inhibitors, such as a mercaptan-type compound, a plasticizer, an adhesion | attachment imparting agent, etc.

  When the silicone rubber composition of the present invention is molded into a Fresnel lens or a prism lens, the molding method is not particularly limited, but generally, molding is used. Moreover, the curing conditions are not particularly limited. Generally, it can be heat-cured at 80 to 300 ° C., particularly 100 to 250 ° C. for 1 minute to 1 hour, particularly about 5 to 30 minutes. Moreover, you may post-cure about 10 minutes-10 hours at 100-200 degreeC.

  EXAMPLES Hereinafter, although an Example and a comparative example are shown and this invention is demonstrated concretely, this invention is not restrict | limited to the following Example.

[Synthesis example]
Organosilicon compound having a benzotriazole group (Compound I)
100 g (0.068 mol) of an organosilicon compound having a Si—H group only at the end and 32 mg of BHT were placed in a 0.5 L four-necked flask equipped with a conical tube cooler and a thermometer, and the temperature was raised to 80 ° C. After the temperature increase, 0.1 g of a 2-mass chloroplatinic acid 2-mass-2-ethylhexanol solution was added, and 2- [3- (2H-benzotriazol-2-yl) -4-hydroxyphenyl] ethyl 2- (2H) methacrylate was added. -Benzotriazol-2-yl) -4- [2- (methacryloyloxy) ethyl] phenol 22 g (0.068 mol) dissolved in toluene 198 g was added dropwise. After completion of dropping, the reaction was carried out at 80 to 90 ° C. for 2 hours. After the temperature was lowered to around 30 ° C., toluene was removed by concentration at 80 to 90 ° C./20 mmHg for 1 hour, and the precipitated solid was filtered. After filtration, 97.5 g of a pale yellow transparent liquid (Compound I) was obtained.

Organosilicon compound having a benzotriazole group (Compound II)
In a 0.5 L four-necked flask equipped with a serpentine condenser and a thermometer, 50 g (0.037 mol) of an organosilicon compound having Si—H groups at its ends and side chains, 30 mg of BHT, 2- [3 methacrylate] -(2H-benzotriazol-2-yl) -4-hydroxyphenyl] ethyl 2- (2H-benzotriazol-2-yl) -4- [2- (methacryloyloxy) ethyl] phenol 5.9 g (0.018 mol) ), 50 g of toluene was added, and the temperature was raised to 80 ° C. After raising the temperature, 0.1 g of a 2-mass chloroplatinic acid 2% by mass 2-ethylhexanol solution was added and reacted at 80 to 90 ° C. for 2 hours. After the temperature was lowered to around 30 ° C., toluene was removed by concentration at 80 to 90 ° C./20 mmHg for 3 hours, and after filtration, 50.3 g of a pale yellow transparent liquid (Compound II) was obtained.

[Examples and Comparative Examples]
The following components were prepared and silicone rubber compositions having the compositions shown in Table 1 were prepared. Each composition was cured at 120 ° C. for 1 hour. The transmittance measurement method was a spectrophotometer U-3310 (manufactured by Hitachi, Ltd.), and measured the light transmittances of 380 nm and 420 nm wavelengths at 25 ° C. for a cured product having an optical path length of 2.0 mm.
(A) Component organopolysiloxane (A-1) Molecular chain both ends vinyldimethylsiloxy group-capped dimethylpolysiloxane (viscosity at 23 ° C. 5,000 mPa · s, vinyl group content per 100 g is 0.006 mol) .
Component (B) Organopolysiloxane (B-1) Consists of Me ₃ SiO _0.5 unit, Me ₂ ViSiO _0.5 unit, SiO ₂ unit [(Me ₃ SiO _0.5 + Me ₂ ViSiO _0.5 ) / SiO ₂ = 0.8] Polysiloxane. The alkenyl group content was 0.1 mol per 100 g, solid at 23 ° C., Me: methyl group, Vi: vinyl group.
Component (C) Organohydrogenpolysiloxane (C-1) Trimethylsiloxy group-blocked dimethylsiloxane / methylhydrogensiloxane copolymer with both ends of molecular chain (viscosity at 23 ° C. is 100 mPa · s, content of silicon-bonded hydrogen atoms 0.5 mass%).
(D) Hydrosilylation catalyst (D-1) A dimethylsiloxane polymer solution of platinum 1,3-divinyl-1,1,3,3-tetramethyldisiloxane complex having a platinum content of 1% by mass.
(E) Benzotriazole ultraviolet absorber (E-1) 2- (2H-benzotriazol-2-yl) -6-dodecyl-4-methylphenol (liquid at 25 ° C.).
(E-2) An organosilicon compound having a benzotriazole group (Compound I) (liquid at 25 ° C.).
(E-3) An organosilicon compound having a benzotriazole group (Compound II) (liquid at 25 ° C.).
(Ultraviolet absorber-1) 2- [3- (2H-benzotriazol-2-yl) -4-hydroxyphenyl] methacrylate 2- (2H-benzotriazol-2-yl) -4- [2- ( Methacryloyloxy) ethyl] phenol (melting point 95 ° C.).
(Ultraviolet absorber-2) (p-methoxybenzylidene) dimethyl malonate (melting point 55 ° C.).
Control agent 1-ethynylcyclohexanol

※１ 反応性基比率：（Ａ）成分と（Ｂ）成分中に含まれるアルケニル基の合計のｍｏｌ数に対する（Ｃ）成分中のＳｉ−Ｈ基のｍｏｌ数
※２ 反応性基比率：（Ａ）成分と（Ｂ）成分中に含まれるアルケニル基の合計のｍｏｌ数に対する（Ｃ）成分と（Ｅ）成分中に含まれるＳｉ−Ｈ基の合計のｍｏｌ数

* 1 Reactive group ratio: Number of moles of Si-H groups in component (C) relative to the total number of moles of alkenyl groups contained in components (A) and (B) * 2 Reactive group ratio: (A ) Component and (B) the total number of moles of Si-H groups contained in component (C) and component (E) relative to the total number of moles of alkenyl groups contained in component

Claims (7)

(A) Diorganopolysiloxane having an average of 0.1 or more alkenyl groups bonded to silicon atoms in one molecule: 100 parts by mass,
(B) The following average composition formula (2)
R _p SiO _{(4-p) / 2} (2)
(In the formula, R is the same or different unsubstituted or substituted monovalent hydrocarbon group, alkoxy group or hydroxyl group, and p is a positive number satisfying 1 ≦ p <2.)
It has a SiO ₂ unit and an R ₃ SiO _1/2 unit in the composition, 0.01 to 1 mol is an alkenyl group per 100 g of component (B), and a viscosity at 23 ° C. is 10 mPa · s or more. Liquid or solid organopolysiloxane: 5 to 50 parts by mass,
(C) Organohydrogenpolysiloxane having two or more hydrogen atoms bonded to silicon atoms in one molecule: silicon atom-bonded hydrogen atoms with respect to 1 mol of silicon atom-bonded alkenyl groups in components (A) and (B) In an amount of 0.1 to 4.0 mol,
(D) Hydrosilylation catalyst: 0.1 to 1,000 ppm as a platinum group metal with respect to the total mass of the components (A), (B) and (C),
(E) A benzotriazole ultraviolet absorber that is liquid at 25 ° C .: 0.01 to 10 parts by mass A silicone rubber composition for forming a Fresnel lens or prism lens for a concentrating solar cell .   The silicone rubber composition according to claim 1, wherein a cured product having a light transmittance at a wavelength of 420 nm of 90% or more and a light transmittance at a wavelength of 380 nm of less than 10% is provided.   The silicone according to claim 1 or 2, wherein the benzotriazole ultraviolet absorber as component (E) is 2- (2H-benzotriazol-2-yl) -6-dodecyl-4-methylphenol. Rubber composition.   The silicone rubber composition according to claim 1 or 2, wherein the benzotriazole-based ultraviolet absorber as the component (E) is an organosilicon compound having at least one benzotriazole group. The silicone rubber composition according to claim 4, wherein the organosilicon compound having at least one benzotriazole group is represented by the following formula (i).

[Wherein R ³ is a hydrogen atom, an unsubstituted or substituted monovalent hydrocarbon group having 1 to 10 carbon atoms, or a benzotriazole group-containing functional group represented by the following general formula (A), ^At least one of ^{3 is} a benzotriazole group-containing functional group of the formula (A). R ⁴ is an unsubstituted or substituted monovalent hydrocarbon group having 1 to 10 carbon atoms, and is an integer of m ≧ 0 and an integer of n ≧ 0.

(In the formula, R ⁵ and R ⁶ are each an unsubstituted or substituted divalent hydrocarbon group having 1 to 10 carbon atoms, and X is

It is. * Indicates a bond. )]   The Fresnel lens for concentrating solar cells which consists of a hardened | cured material of the silicone rubber composition of any one of Claims 1-5.   The prism lens for concentrating solar cells which consists of a hardened | cured material of the silicone rubber composition of any one of Claims 1-5.