JP2015134502A - polyolefin resin multilayer film - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a polyolefin resin multilayer film that has high elasticity, excellent blocking resistance, little curling, low powdering property, and weather resistance, and is suitable for packaging materials for foods and beverages, pharmaceutical products and medical products, optical films, liquid crystal members, electronic or electric components, and precision components, and for back sheets for solar cells.SOLUTION: The multilayer film has a three-layer structure of A-layer/B-layer/C-layer. The A-layer and the C-layer comprise a resin composition prepared by mixing 100 parts by weight of an ethylene α-olefin copolymer having a density of 0.920 to 0.938 g/cmand 5 to 20 parts by weight of a mixed resin of a low density polyethylene and a propylene resin. The B-layer essentially comprises an ethylene α-olefin copolymer having a density of less than 0.920 g/cm, to which a phosphorus-phenolic compound antioxidant is added and mixed by 0.01 to 0.3 wt.%. The C-layer has a thickness of 2/3 or less of the thickness of the A-layer.

Description

  The present invention relates to a polyolefin resin multilayer film. More specifically, it is strong, has excellent blocking resistance, has low curl, low powder and UV resistance, food / beverage, pharmaceutical / medical product, optical film, liquid crystal component, electronic / electrical component, precision component It is a polyolefin resin multilayer film suitable for a packaging material such as a solar cell and a back protective sheet for solar cells.

  Conventionally, polyolefin resin films such as polyethylene and polypropylene have excellent strength, transparency, heat sealability, moisture resistance, chemical resistance, and low temperature impact strength, so that they can be used in food / beverages, pharmaceuticals / medical products, and industries. It is widely used as various packaging materials such as materials and daily life materials.

  By the way, in recent years, photovoltaic power generation has shown remarkable growth against the background of national policy and assistance. The solar cell usually has a structure of glass sheet of front sheet / ethylene-vinyl acetate copolymer resin (hereinafter abbreviated as EVA) / power generation cell / EVA / back surface protection sheet material of sealing material. As a back surface protection sheet material for the solar cell, development of a polyolefin-based resin film having adhesion to EVA and weather resistance is desired. In outdoor applications such as these solar cells, it is a polyolefin resin film that is inherently weak to ultraviolet rays. Its weather resistance, reflectivity, design by coloring, curling and misalignment do not occur during secondary processing such as lamination, etc. The handling of the machine is also required.

  As a method of whitening for the purpose of imparting design properties to a polyolefin-based resin film, a method of kneading titanium oxide is generally known, but when adding high concealability and reflectance, the amount added is increased. There must be. In this case, a defect of foreign matter called fish eye is generated due to poor dispersion of titanium oxide. Moreover, when it shape | molds by the T-die casting method, dies will become dirty, and problems, such as eyes and a streak, will arise. In addition, there is a problem that a titanium oxide dispersant volatilizes to generate gas.

Further, in Patent Document 1, as the back sheet for a solar cell, density 0.940 g / cm ³ or more, 0.970 g / cm ³ or less polyethylene method of using the added film sunscreen and antioxidants in resin of It is disclosed. However, since a resin having a density of 0.940 g / cm ³ or more has a high density, when the present film is molded by the T-die casting method, there is a problem that the film curls due to crystallization. Further, polyethylene having a density of 0.940 g / cm ³ or more and 0.970 g / cm ³ or less is generally classified as a high density polyethylene (hereinafter sometimes abbreviated as HDPE). This HDPE has high crystallinity and the surface is likely to be rough, and scraping occurs due to friction with the take-up roll after casting and the roll during the winding process, and the scraping powder adheres to the metal roll. May cause problems such as damage to the film and contamination of the film forming process. In addition, since the surface of the polyethylene resin film having a density of 0.940 g / cm ³ or more is not smooth, bubbles are likely to enter the interface during lamination with other substrates, and when used as a back surface protection sheet for solar cells. In addition, there is a problem that it is inferior in melt adhesion with EVA as a sealing material.

  In addition, Patent Document 2 discloses a method for producing a laminated film in which a polyethylene film is strong and difficult to curl. However, an addition of an antioxidant, an ultraviolet blocking agent, an antioxidant or the like is added to the polyethylene film. However, there is a problem that productivity is deteriorated due to generation of gels and streaks on the surface, and there is a problem that the Young's modulus is low and the blocking resistance is inferior, so that the laminating property with other substrates is inferior.

  Therefore, it has a high Young's modulus, excellent blocking resistance, small curl, low powder, weather resistance, food / beverage, pharmaceutical / medical products, optical films, liquid crystal components, electronic / electrical parts, precision parts, etc. Development of a polyolefin resin multilayer film suitable for a packaging material and particularly suitable for a back surface protection sheet for solar cells is desired.

JP-A-11-261085 JP 2008-73854 A

  An object of the present invention is to solve the above-described problems. That is, the object of the present invention is a food / beverage, a pharmaceutical / medical product, an optical film, a liquid crystal member, an electronic / electrical part, having a strong back, excellent blocking resistance, small curl, low powder and weather resistance. Another object of the present invention is to provide a polyolefin-based resin multilayer film suitable for packaging materials such as precision parts, and a back protective sheet for solar cells.

The above-described problems are solved by the polyolefin resin multilayer film according to the present invention. That is, a film having a three-layer structure of A layer / B layer / C layer, wherein the A layer and the C layer have an ethylene / α-olefin copolymer weight in the range of 0.920 to 0.938 g / cm ^3. It consists of a resin composition in which 5 to 20 parts by weight of a mixed resin of low density polyethylene and propylene resin is mixed with 100 parts by weight of the coalescence, and the B layer is an ethylene / α-olefin having a density of less than 0.920 g / cm ^3. Copolymer as the main component, 0.01-0.3 wt% of phosphorus-phenolic compound antioxidant is added and mixed, and the thickness of the C layer is 2/3 or less of the thickness of the A layer. It is a certain polyolefin resin multilayer film.

  The polyolefin-based resin multilayer film of the present invention is strong, has excellent blocking resistance, has low curl, and has low powder and weather resistance. Therefore, it is a food / beverage, pharmaceutical / medical product, optical film, liquid crystal member, electronic -It can use suitably for packaging materials, such as an electrical component and a precision component, and the back surface protection sheet for solar cells.

The present invention is a film having a three-layer structure of A layer / B layer / C layer, wherein the A layer and the C layer have an ethylene / α-olefin having a density in the range of 0.920 to 0.938 g / cm ^3. It consists of a resin composition in which 5 to 20 parts by weight of a mixed resin of low density polyethylene and propylene resin is mixed with 100 parts by weight of the copolymer, and the layer B has an ethylene / α having a density of less than 0.920 g / cm ^3. -An olefin copolymer as a main component, 0.01-0.3 wt% of an antioxidant of a phosphorus-phenol compound is added and mixed, and the thickness of the C layer is 2/3 of the thickness of the A layer. It is the polyolefin resin multilayer film which is the following.

  The A layer and the C layer of the present invention are made from a resin composition in which 5 to 20 parts by weight of a mixed resin of low density polyethylene and a propylene resin is mixed with 100 parts by weight of an ethylene / α-olefin copolymer having a specific density. Become. The ethylene / α-olefin copolymer used in the A layer and the C layer in the present invention is a linear low density polyethylene (hereinafter referred to as LLDPE) obtained by random copolymerization of ethylene and a small amount of α-olefin. Abbreviated).

  The α-olefin is not particularly limited, but is an α-olefin having 4 to 10 carbon atoms, preferably 4 to 8 carbon atoms, and specifically includes 1-butene, 1-pentene, 4-methyl. Examples include -1-pentene, 1-hexene, 1-heptene, 1-octene, 1-nonene, and 1-decene. These α-olefins can be used alone or in combination. Particularly, 1-butene, 1-hexene, 1-octene and the like are preferably used from the viewpoint of polymerization productivity.

The density of the ethylene / α-olefin copolymer of the A layer and the C layer used in the present invention is 0.920 to 0.938 g / cm ³ . If the density is higher than 0.938 g / cm ³ , the resin is likely to fall off during rubbing with a metal roll or a rubber roll, which causes generation of white powder. Further, when the density is higher than 0.938 / cm ³ , when used as a back sheet for a solar cell, the laminate strength with EVA of the sealing material for the power generation cell of the solar cell is practically required 40N. / 10mm or more cannot be obtained.

When it is lower than 0.920 g / cm ³ , desired slipping property and handling property cannot be obtained, and winding slip and wrinkle are easily generated during film formation and lamination. Moreover, when it uses as a back surface sheet for solar cells, a partial discharge voltage becomes low and is inferior to practicality. Furthermore, in relation to the density of the B layer described later, the density of the A layer and the C layer needs to be higher than the density of the B layer, but the density of one of the A layer and the C layer is higher than the density of the B layer. If the density is low in the order of A layer / B layer / C layer, the curl of the film increases due to the difference in the crystallization behavior of each layer.

In the present invention, the content of α-olefin in the ethylene / α-olefin copolymer of the A layer and the C layer is preferably 0.5 to 10 mol%, more preferably 2.0 to 8.0 mol%. is there. By setting the α-olefin content to 0.5 to 10 mol%, the density of the ethylene / α-olefin copolymer can be set to a range of 0.920 to 0.938 g / cm ³ .

  The melt index (hereinafter abbreviated as MFR) at 190 ° C. of the ethylene / α-olefin copolymer of the A layer and the C layer used in the present invention is preferably 1.0 to 10.0 g / 10 min, more preferably Is 1.5 to 7.0 g / 10 min. If the MFR is larger than 10.0 g / 10 minutes, necking down and uneven lamination with other layers are likely to occur during film production. Moreover, when MFR becomes lower than 1.0 g / 10min, the fluidity | liquidity at the time of melt extrusion will fall, it will be inferior to extrusion stability, and it will become easy to produce the thickness nonuniformity of a film.

  The ethylene / α-olefin copolymer of layer A and layer C used in the present invention is produced by a conventional synthesis method using a multisite catalyst or a synthesis method using a single site catalyst (Kaminsky catalyst, metallocene catalyst). be able to. The production method of the ethylene / α-olefin copolymer is preferably a multi-site catalyst from the viewpoint of improving slipperiness and imparting strength.

  In the present invention, in the A layer and the C layer, it is necessary to mix 5 to 20 parts by weight of a mixed resin of low density polyethylene and propylene resin with respect to 100 parts by weight of the ethylene / α-olefin copolymer. If the mixed resin of low-density polyethylene and propylene resin is less than 5 parts by weight, the Young's modulus will be low and the film will be weak. Therefore, the film will be stretched at the time of film winding or laminating, and wound into a roll When the film is unwound, the flatness deteriorates. Moreover, slipperiness with a metal falls, wrinkles generate | occur | produce in a film and process passability worsens. On the other hand, if it exceeds 20 parts by weight, crystallization of the resin component constituting the A layer and the C layer is accelerated, the adhesion to the casting drum is deteriorated and the smoothness of the film surface is deteriorated. Shaving powder is generated by friction with a metal roll during the process. Moreover, when laminating another base material on the polyolefin-based resin multilayer film of the present invention, air bubbles are caught in the interface with the other base material because of poor flatness. Furthermore, since the crystallization proceeds on the layer side laminated with EVA, the laminate strength with EVA decreases.

  The blending ratio of the low density polyethylene and the propylene resin in the mixed resin is preferably 90 to 60% by weight of the propylene resin with respect to 10 to 40% by weight of the low density polyethylene. In particular, the blending ratio is more preferably 85 to 70% by weight with respect to 15 to 30% by weight of the low density polyethylene due to the problem of workability (preventing adhesion during lamination).

  Here, the roles of the low density polyethylene and the propylene resin of the mixed resin will be described. By adding the low density polyethylene, the crystallinity of the LLDPE is improved and the Young's modulus of the film is improved. On the other hand, slipping property and blocking resistance are improved by adding a propylene-based resin.

Examples of the low density polyethylene (hereinafter sometimes abbreviated as LDPE) resin include those obtained by polymerization using a Ziegler-Natta type or a metallocene catalyst. The density of the low density polyethylene resin is preferably 0.890 to 0.920 g / cm ³ . Although slipperiness and handling properties of the density of the low density polyethylene resin is desired if 0.890 g / cm ³ or more is obtained, the density is higher than 0.920 g / cm ^3, scraping the metal roll and rubber roll In this case, the resin is easily scraped off and becomes a factor in generating white powder.

  Examples of the propylene-based resin include homopolypropylene and random or block copolymers of ethylene and propylene, including heat resistance, slipperiness, film handling, scratch resistance, and curl resistance. To homopropylene are most preferred.

  In the case of using a copolymer of ethylene and propylene, an ethylene content in the range of 1 to 7 mol% is preferable because it can maintain heat resistance and improve slipperiness. Moreover, when it is desired to impart strength to the film, it is preferable to add a nucleating agent as necessary.

  The propylene-based resin preferably has an MFR at 230 ° C. of 3 to 15 g / 10 min, and the low-density polyethylene has an MFR at 190 ° C. of preferably 5 to 30 g / 10 min. By setting the MFR of the propylene-based resin and the low-density polyethylene within the above range, the mixing property of the low-density polyethylene and the propylene-based resin is improved, and the performance of the film of the present invention is improved.

  In addition, it is preferable to reduce the addition of inorganic and / or organic fine particles and organic compound lubricants to the A layer as much as possible, because the laminate strength with EVA becomes high. It is preferable to add only to the C layer, because slipping is good in the lap winding with the A layer, and winding property and laminating property are improved.

  In order to improve the handleability and slipperiness of the film, 0.1 to 5% by weight of inorganic and / or organic fine particles having an average particle diameter of 1 to 5 μm is added as a resin component of the C layer to the C layer. Is preferred.

  Examples of the fine particles to be added include inorganic particles such as wet silica, dry silica, colloidal silica, aluminum silicate, calcium carbonate, and styrene, silicone, acrylic acid, methacrylic acid, divinylbenzene, and the like as crosslinked components. Particles can be used. Among these, the use of aluminum silicate is preferable because of its good dispersibility in the resin, a high effect of improving slipperiness with a low addition amount, and low cost.

  When the average particle diameter of the inorganic and / or organic fine particles is 1 μm or more, the slipperiness of the film is improved, which is preferable. On the other hand, if the average particle diameter is larger than 5 μm, the particles fall off from the film and cause contamination and scratches, which is not preferable.

  Moreover, when the addition amount of particle | grains is less than 0.1 weight%, the improvement power of slipperiness is weak and is not preferable. On the other hand, when the added amount exceeds 5% by weight, the particles easily fall off from the film and are not preferable because they are caused by contamination and scratches.

  Further, an organic compound lubricant may be added, and examples thereof include stearic acid amide and calcium stearate. Further, an antioxidant, an ultraviolet absorber, a pigment, an antistatic agent, a nucleating agent, and the like may be appropriately added to the A layer and the C layer. You may add these individually or in combination of 2 or more types.

  The average surface roughness Ra of the C layer in the present invention is preferably 0.10 to 0.30 μm because the film handling function during processing is satisfied.

  The B layer in the present invention is mainly composed of an ethylene / α-olefin copolymer having a specific density, and 0.01 to 0.3% by weight of a phosphorus-phenol antioxidant is added and mixed as a B layer resin component. It is necessary to become. The ethylene / α-olefin copolymer here is a linear polyethylene obtained by random copolymerization of ethylene and a small amount of α-olefin similar to those in the A layer and the C layer.

It is important that the density of the B layer is less than 0.920 g / cm ³ , and more preferably 0.910 to 0.920 g / cm ³ . When the density is higher than 0.920 g / cm ³ , problems such as cracking and cracking of the film occur when it is laminated with another substrate due to crystallization. When the density is lower than 0.910 g / cm ³ , the Young's modulus of the film is lowered, and the film may be stretched at the time of winding after processing such as film formation and lamination, and the winding shape may be deteriorated.

  In the present invention, the α-olefin used in the B layer is not particularly limited, but is an α-olefin having 4 to 10 carbon atoms, preferably 4 to 8 carbon atoms. Examples include butene, 1-pentene, 4-methyl-1-pentene, 1-hexene, 1-heptene, 1-octene, 1-nonene and 1-decene. These α-olefins can be used alone or in combination.

  In the present invention, the α-olefin content in the ethylene / α-olefin copolymer used in the B layer is preferably 0.5 to 10 mol%, more preferably 2.0 to 8.0 mol%. However, the Young's modulus of the film is high, and the secondary workability such as lamination becomes good. If the α-olefin content is less than 0.5 mol%, the crystallinity is low, and if it exceeds 10 mol%, the film becomes brittle.

  In the present invention, the MFR of the ethylene / α-olefin copolymer used for the B layer is preferably 1.0 to 10.0 g / 10 minutes, more preferably 1.5 to 7.0 g / 10 minutes. If the viscosity is larger than 1.0 g / 10 min and the viscosity is lowered, it causes a neck-down during film production and uneven lamination with other layers.

  Further, in order to maintain the strength against ultraviolet rays and temperature and humidity, it is necessary to add a phosphorus-phenol antioxidant in the range of 0.01 to 0.3% by weight as the B layer resin component. . Antioxidants other than phosphorus-phenolic antioxidants have a problem of yellowing although they are satisfactory in weather resistance against oxidative deterioration due to ultraviolet rays and temperature and humidity. Moreover, since antioxidants other than phosphorus-phenol type | system | group have high heat volatility, they may adhere to a nozzle | lip lip | rip part at the time of heating extrusion, and may become a factor of the surface defect of a film. If the amount of the phosphorus-phenolic antioxidant added is less than 0.01% by weight, the effect is low, and if it exceeds 0.3% by weight, the dispersibility is deteriorated. It adheres and causes surface defects. Moreover, when producing the back surface protection sheet for solar cells produced using this film, the bubble defect occurs at the interface with the polyester film due to the surface defects.

  As an antioxidant for phosphorus-phenol compounds, for example, 2,10-dimethyl-4,8-di-t-butyl-6- [3- (3,5-di-t-butyl-4-hydroxyphenyl) ) Propoxy] -12H-dibenzo [d, g] [1,3,2] dioxaphosphocin, 2,4,8,10-tetra-t-butyl-6- [3- (3,5-di- t-butyl-4-hydroxyphenyl) propoxy] dibenzo [d, f] [1,3,2] dioxaphosphine, 2,4,8,10-tetra-t-butyl-6- [3- ( 3,5-di-t-butyl-4-hydroxyphenyl) propionyloxy] -dibenzo [d, f] [1,3,2] dioxaphosphine, among others 2,4,8 , 10-Tetra-t-butyl-6- [3- (3,5-di-t-butyl-4-hydroxyphenyl) propionyloxy] -dibenzo [d, f] [1,3,2] dioxaphos Fepin (“Sumilyzer” GP manufactured by Sumitomo Chemical Co., Ltd.) is preferable because of its good dispersibility in the resin and high effect of addition. In addition, antioxidants other than phosphorus-phenolic antioxidants such as phosphorus antioxidants, phenolic antioxidants, amine antioxidants, sulfur antioxidants can be used in combination. The addition amount is preferably 0.05% by weight or less from the viewpoint of preventing volatilization and coloring.

  Further, when 5-30% by weight of rutile-type titanium oxide particles coated with an inorganic oxide having an average particle diameter of 150 to 500 nm is added as a resin component of the B layer, excellent light reflectivity is obtained. When used as a back surface protective sheet, light leaking from between the power generation cells of the solar battery is reflected, which is preferable because power generation efficiency is increased. When the amount added is 5% by weight or more, the light reflection effect can be exhibited. When the amount added is less than 30% by weight, good dispersibility in the resin can be secured, and during film formation and processing such as laminating. It is possible to avoid problems such as sometimes breaking of the film, fine cracks in the film, deterioration of electrical characteristics, and increased discoloration.

  The titanium oxide particles used in the B layer of the present invention are not particularly limited, but as the crystal type, rutile type, anatase type, brookite type and the like are known, and excellent whiteness and weather resistance and The rutile type is preferable from the characteristics such as light reflectivity.

  Since the titanium oxide used in the B layer of the present invention may deteriorate the resin by photocatalytic action, it is preferably surface-coated for the purpose of stabilizing the photocatalytic action, and the composition is not limited. Inorganic oxides such as silicon oxide, alumina, or zinc oxide are preferable. The coating method of the surface coating agent is not particularly limited, and titanium oxide particles obtained by a known method can be used.

  The average particle diameter of the titanium oxide particles used in the present invention is preferably 150 to 500 nm, and more preferably 180 to 350 nm. If the average particle diameter is smaller than 150 nm, the activity of the titanium oxide particles is high, which is not preferable because it causes resin deterioration. On the other hand, if the average particle diameter exceeds 500 nm, the dispersibility in the resin is deteriorated, and this may cause clogging of a filter used in film production, which is not preferable.

  Moreover, the slit waste etc. which generate | occur | produce when manufacturing this film can also be used as a collection | recovery raw material. Specifically, slit scraps and the like are pelletized, and 5 to 50% by weight can be added to the B layer of the present film as a resin component of the B layer. The pelletizing method is generally a method in which a cut material is melt-extruded and then cut, but is not limited to this method.

  Further, the A layer, the B layer, and the C layer in the present invention may contain other additives in addition to those described above. As said other additive, a light stabilizer, a ultraviolet absorber, or a heat stabilizer can be mentioned.

  As the light stabilizer, one that captures the active species at the start of photodegradation in the resin and prevents photooxidation can be used. Specifically, one or a combination of two or more selected from hindered amine compounds, hindered piperidine compounds, and the like can be used. Among these, it is preferable to use a hindered amine compound. Specific examples of hindered amine compounds include “MARK” LA-57, LA-62, LA-67 manufactured by Adeka Argus Chemical Co., Ltd., “Tinuvin” 144, 622LD manufactured by Ciba-Gigi Co., Ltd., and the like. Can do. In particular, when a light stabilizer is mixed in the B layer as a resin component of the B layer in a range of 0.005 to 0.2% by weight, titanium oxide is stabilized and long-term weather resistance is imparted. If the addition amount is less than 0.005% by weight, the effect as a light stabilizer is insufficient, and if it exceeds 0.2% by weight, aggregation of inorganic particles such as bleed out and titanium oxide is not preferable.

  As the above-mentioned ultraviolet absorber, it absorbs harmful ultraviolet rays in sunlight, converts them into innocuous heat energy in the molecule, and prevents the activation of active species that initiate photodegradation in the resin. Can be used. Specifically, benzophenone, benzotriazole, salicylate, acrylonitrile, metal complex, hindered amine, and ultrafine titanium oxide (particle size: 10 nm to 60 nm) or ultrafine zinc oxide (particle size: 10 nm) At least one selected from the group consisting of inorganic UV absorbers such as (˜40 nm) can be used.

  Examples of the heat stabilizer include tris (2,4-di-tert-butylphenyl) phosphite, bis [2,4-bis (1,1-dimethylethyl) -6-methylphenyl] ethyl ester phosphorous acid. Acid, tetrakis (2,4-di-tert-butylphenyl) [1,1-biphenyl] -4,4'-diylbisphosphonite, and bis (2,4-di-tert-butylphenyl) penta List phosphorus-based heat stabilizers such as erythritol diphosphite and lactone-based heat stabilizers such as the reaction product of 8-hydroxy-5,7-di-tert-butyl-furan-2-one and o-xylene. Can do. Moreover, these can also use 1 type or 2 types or more.

  As content of the said ultraviolet absorber, heat stabilizer, etc. in this invention, it may add suitably in the range of 0.01 weight%-5 weight% as a resin component of each layer according to the objective.

  The film of the present invention is composed of A layer / B layer / C layer, and the thickness of the film varies depending on the application used, but is preferably in the range of 10 to 200 μm, and more preferably in the range of 20 to 150 μm. It is preferable from the surface and the laminating property with other base materials.

  The lamination ratio is preferably 3 to 30% for the A layer, 60 to 96% for the B layer, and 1 to 10% for the C layer. Further, the thickness of the C layer is thinner than the A layer from the viewpoint of suppressing curling of the film, and is required to be 2/3 or less with respect to the thickness of the A layer, and 1/5 to 2/3. It is more preferable to set the range.

  For example, when the film of the present invention is formed by the melt T-die molding method, when the melt-extruded sheet is cooled and cast on the cooling drum, the layer A is used as the cooling drum surface, and the film is quenched from the cooling drum surface. The non-drum surface side of the C layer is gradually cooled, causing curling due to the difference in crystallization, and curling occurs on the inner surface of the C layer side. Therefore, as described above, the thickness of the C layer on the slow cooling side is preferably thinner than the A layer on the quenching side. When the thickness of the C layer exceeds 2/3 of the A layer, the curl of the film becomes large, and film slippage in the take-off process or secondary processing may occur.

  In addition, the value of each Young's modulus in the longitudinal direction and the width direction of the film of the present invention is in the range of 150 to 400 MPa, preferably in the range of 250 to 350 MPa. Good handling at the time of secondary processing is preferable. If the value of Young's modulus is less than 150 MPa, the film stretches due to the winding property during film formation and the tension during secondary processing such as laminating, the workability is poor, and the winding shape is also deteriorated. On the other hand, if it exceeds 400 MPa, the film becomes too hard, and the film may be cracked or cracked during secondary processing such as winding property during lamination or lamination.

  In addition, the film of the present invention can be used by laminating with another base material by a method such as an adhesive or heat fusion depending on the application. Examples of other base materials include aluminum foil, paper, and a thermoplastic resin film. The thermoplastic resin is not particularly limited as long as it is a thermoplastic resin capable of forming a film by melt extrusion. Preferred examples include polyethylene terephthalate (hereinafter abbreviated as PET), polyethylene-2,6-naphthalene dicarboxylate. Polyester such as polypropylene terephthalate, polybutylene terephthalate, poly-1,4-cyclohexylenedimethylene terephthalate, styrene resin such as polystyrene and acrylonitrile-styrene copolymer, polycarbonate, polyamide, polyether, polyurethane, polyphenylene sulfide, polyester Amides, polyether esters, polyvinyl chloride, polymethacrylic acid esters, modified polyphenylene ethers, polyarylate, polysulfone, polyether ether De, polyamideimide copolymer to the polyimide and those composed mainly or can be exemplified mixtures thereof and the like resins. Particularly in the present invention, polyester is preferable from the viewpoint of good dimensional stability and mechanical properties, and PET is particularly preferable.

  Hereinafter, the method for producing the polyolefin resin multilayer film of the present invention will be specifically described. In addition, the manufacturing method of the film of this invention is not limited to this.

  As a resin used for the A layer, a resin composition in which 100 parts by weight of an ethylene / α-olefin copolymer and 5 to 20 parts by weight of a mixed resin of low density polyethylene and a propylene resin are mixed is put into a twin screw extruder. And compounded in the range of 180 to 280 ° C. to form chips.

  As the resin used for the B layer, rutile-type titanium oxide particles coated with an inorganic oxide having an average particle diameter of 150 to 500 nm on an ethylene / α-olefin copolymer or an ethylene / α-olefin copolymer Then, a phosphorus-phenol antioxidant is mixed as an antioxidant and compounded in the range of 180 to 280 ° C. using a twin screw extruder to form chips.

  As the C layer resin, 100 parts by weight of an ethylene / α-olefin copolymer, 5 to 20 parts by weight of a mixture of a low density polyethylene and a propylene-based resin, or an inorganic having an average particle diameter of 1 to 5 μm as necessary, and / or A resin composition in which organic particles are mixed as a resin component is compounded in a range of 180 to 280 ° C. using a twin screw extruder to form chips.

  The compound chips of the mixed resin of each layer prepared in this way are each supplied to a uniaxial melt extruder, and melt extrusion is performed in the range of 220 to 280 ° C., respectively. After removing foreign substances and coarse inorganic particles through a filter installed in the middle of the polymer tube, a multi-manifold type T die or a feed block installed on top of the T die is used for A layer / B layer / C layer type. Three-kind three-layer lamination is performed, and a non-stretched sheet is obtained by discharging from a T die onto a rotating metal roll with the A layer side facing the metal roll surface. At this time, it is preferable that the surface temperature of the rotating metal roll is controlled to 20 to 60 ° C., because adhesion to the metal roll of the A layer is not caused and the crystallinity is improved. Moreover, in order to make a molten polymer contact | adhere to a metal roll, it is preferable to use the method of spraying air from a nonmetallic roll side, or a nip roll.

  The A layer and / or C layer of the film of the present invention thus obtained are subjected to corona discharge treatment in air or in one or more atmospheres of nitrogen gas and carbon dioxide gas for bonding to other substrates. It is preferable that the surface is wound with a wetting tension of 35 mN / m or more.

  The polyolefin-based resin multilayer film of the present invention can be suitably used for food / beverage, pharmaceutical / medical products, optical films, liquid crystal members, packaging materials for electronic / electrical parts, precision parts, etc., and back protection sheets for solar cells. it can.

  The back surface protection sheet for solar cells is a back surface protection sheet of a solar cell module, for example, a hydrolysis resistant PET film (Toray Industries, Inc .: “Lumirror” X10S) having a thickness of 25 to 250 μm and the polyolefin of the present invention. A multi-layer laminated film is dry-laminated using a known adhesive.

  For example, as described in Japanese Utility Model Laid-Open No. 6-38264, a solar cell generally includes a plurality of plate-like solar cell power generation cells sandwiched between a light-receiving side glass substrate and a back surface protection sheet, thereby generating a power generation cell. As a cell sealing resin, EVA is filled as a cell sealing resin, and a protective sheet is stacked on the back surface on the opposite side of the glass substrate. For the back protective sheet, a plastic film having excellent mechanical properties, heat resistance, moisture resistance, weather resistance (ultraviolet ray resistance, discoloration resistance) is used, and in order to effectively use sunlight, A film with high light reflectance may be used.

  Hereinafter, the present invention will be described in detail by way of examples. The characteristics were measured and evaluated by the following methods.

(1) Density of resin The density was cut into cubes each having a side of 2 mm in accordance with the density gradient tube method specified in JIS K7112-1980. Next, put 3 or more glass floats of known density into a density gradient tube made using ethyl alcohol and purified water in a water tank controlled at 25 ° C. ± 0.5 ° C. Produced. Thereafter, the sample was placed in a density gradient tube and allowed to stand for 24 hours, the position of the sample was measured, and the density was determined from the calibration curve.

(2) Film Thickness and Thickness Composition Ratio The film thickness was measured for 5 sheets at any 10 locations on the film using a dial gauge according to JIS K7130 (1992) A-2 method. . The average value was divided by 10 to obtain the film thickness. The thickness of each layer in the case of a laminated film is determined by embedding the laminated film in an epoxy resin, cutting out the film cross section with a microtome, observing the cross section with a scanning electron microscope at a magnification of 5,000 times, The thickness ratio was determined.

(3) Light reflectivity With the spectrophotometer (U-3410, manufactured by Hitachi, Ltd.) and a φ60 integrating sphere (130-0632, manufactured by Hitachi, Ltd.) and a 10-degree inclined spacer attached, the layer A surface of the film of the present invention is placed on the surface. 3 points were measured and the average value of the light reflectance at a wavelength of 560 nm was defined as the light reflectance of the film.

(4) Young's modulus A sample film was cut into a size of 120 mm × 10 mm in the longitudinal direction and the width direction in accordance with JIS K7113 (1995/05/01 revised edition). The cut sample film was pulled at a speed of 300 mm / min using a “Tensilon” RTG-1210 manufactured by A & I Co., Ltd. in an atmosphere of 23 ° C. at a pulling speed of 300 mm / min. Asked. The average value was calculated by setting n number to 5.

(5) Curl A sample film was cut into a 300 mm square, and the interfacial distance that floated from the lithographic plate on the four sides of the film was measured with a caliper on a flat plate with the curled inner surface of the cut sample film facing upward. The average value was calculated by setting n number to 5.
The upper limit of the curl that can be used without causing wrinkles or winding slip during laminating is 6 mm.

(6) Blocking resistance The sample film is cut into 120 mm × 30 mm, and the cast drum surface and the non-drum surface are overlapped at a position of 40 mm from the edge of the cut sample film. A 500 g weight was placed on the overlapped 40 mm × 30 mm surface, left in an oven at 40 ° C./84% RH for 24 hours, and then allowed to cool in a room at 23 ° C./55% RH for 30 minutes. Then, using a tensile and compression tester TG-500N (Minebea Co., Ltd.), the both ends of the stacked film were pulled at a peeling speed of 300 mm / min, and the integrated average of the shear peeling force when the stacked film was peeled off The value was defined as blocking shear force (N / 12 cm ² ). The average value was calculated by setting n number to 5. When the blocking shearing force is 5 N / 12 cm ² or more, when the film is wound up in a roll shape and unwound, a peeling mark is formed on the surface, bubbles are formed at the interface when the solar cell back sheet is formed, and the surface appearance is Deteriorate.

(7) Weather resistance As a weather resistance test, an ultraviolet deterioration accelerating tester (I Super UV Tester SUV-W131: manufactured by Iwasaki Electric Co., Ltd.) was used under the following conditions. Ultraviolet irradiation (UV illuminance: 100 mW / cm ² , temperature and humidity: 60 ° C. × 50% RH) was carried out for 144 hours, the appearance of the film was visually observed, and the following determinations were made.
++: There is no discoloration of the resin, and no cracks or cracks are observed.
+: The resin is slightly discolored, but no cracks or cracks are observed.
-: Discoloration of the resin is large, cracks are generated, and some cracks are confirmed.
The film evaluated as “−” in the above evaluation cannot be practically used as a solar cell application.

(8) Low powderiness (antifouling property of film forming process)
In the film forming process, the metal roll used from the cast drum to the winder was observed for white powder, and judged according to the following criteria. The determination was made after 30 minutes of film-forming experiments for each film.
++: No white powder adheres to all observed rolls.
-: White powder adhered to some or all of the observed rolls.
The film evaluated as “−” in the above evaluation is inferior in film-forming stability due to the film-forming process, and the polyester of the following (9) is formed by the white powder that is scraped on the film surface during the production of the back surface protection sheet for solar cells. When laminating with a film, there is a high possibility of causing problems such as fouling the laminating process and biting bubbles at the interface with the polyester film.

(9) Manufacturing method of back surface protection sheet for solar cell Two-component cured adhesive (LX-903 / manufactured by Dainippon Ink & Chemicals, Inc.) on biaxially stretched PET film ("Lumirror" X10S 125 μm, manufactured by Toray Industries, Inc.) KL-75 = 8/1) was applied at a solid content coating thickness of 6 μm, dried at 80 ° C., and then superimposed on the corona-treated surface of the polyolefin resin multilayer film and passed through a pair of pressure rolls. Created the body. The laminated film was aged at a temperature of 40 ° C. for 72 hours to promote the curing reaction of the adhesive layer, thereby obtaining a back protective sheet for solar cells.

(10) The number of bubbles in the interface after lamination The biaxial stretching of the back protective sheet for solar cells obtained in (9) with a width of 1 m and a length of 1650 m using a reflective defect detector made by Hutec Co., Ltd. The measurement was performed from the polyester film side, and the number of bubbles (pieces) having a length of 1 mm or more on one side at the film interface was determined over the entire area, and the following evaluation was performed.
++: The number of bubbles is 9 or less +: The number of bubbles is 10 to 29-: The number of bubbles is 30 or more In the above evaluation, the film evaluated as “−” is used as a solar cell, the partial discharge voltage decreases, or the product Because the value is lowered, it is not practical.

(11) Laminate strength Glass (thickness 5 mm, 200 mm × 200 mm square) / EVA (PVC-45FR00S manufactured by Sanbic Co., Ltd., 450 μm) so that the A layer of the back protective sheet for solar cells prepared in (9) is in contact with EVA. ) / Copper plate (2 mm width × thickness 0.6 mm) / EVA (450 μm) / Solar cell module laminator (LM-50X50-S, manufactured by NPC Corporation) ) Was subjected to thermocompression bonding under the conditions of a vacuum time of 4 minutes, a control time of 1 minute, a press time of 15 minutes, and a temperature of 140 ° C. After crimping, the module was cooled at room temperature to create a pseudo module. Thereafter, it was stored in an oven at a temperature of 85 ° C. and a humidity of 85% for 1000 hours. From the pseudo module stored for 1000 hours, EVA and the laminated film were peeled off to a width of 15 mm and a length of 50 mm for the back protective sheet for solar cells to prepare five laminate strength measurement samples. Then, the laminate strength between the back protective sheet for solar cells and EVA was peeled off at a peeling angle of 180 ° and a peeling speed of 300 mm / min using “Tensilon” PTM-50 manufactured by ORIENTEC under a room temperature condition of 23 ° C. The following judgment was made.
++: Laminate strength is 50 N / 10 mm or more +: Laminate strength is 40 N / 10 mm or more and less than 50 N / 10 mm −: Laminate strength is less than 40 N / 10 mm.
In the above evaluation, the film “-” does not withstand practical use because of interfacial peeling when used in solar cell applications.

(12) Partial discharge voltage The solar cell back surface protective sheet of (9) was measured under the following conditions and evaluated as follows.
Testing machine: KPD2050 (manufactured by Kikusui Industry Co., Ltd.)
Measurement environment conditions: Temperature 23 ° C, humidity 50%
Maximum applied voltage: 1.10 to 1.25 kV
Voltage application time: 22.0 s
Starting voltage: 0.71 to 0.98 kV
Annihilation voltage: 0.86 to 1.07 kV
++: Partial discharge voltage is 800 V or more +: Partial discharge voltage is 700 V or more and less than 800 V-: Partial discharge voltage is less than 700 V
The film evaluated as “−” in the above evaluation cannot be practically used as a solar cell application.

(13) Sliding property The film is cut into a size of 100 mm × 50 mm, and two films are set so that the A layer and the C layer overlap each other, and the JISK7125 plastic film and sheet friction coefficient test method (revised 1999/08/20) ), The static friction coefficient was measured, and the average value of n number 5 was calculated. The following evaluation was performed from the calculated value.
++: Static friction coefficient is less than 1.0 +: Static friction coefficient is 1.0 or more and less than 1.5-: Static friction coefficient is 1.5 or more.
The film evaluated as “−” in the above evaluation is likely to cause problems when producing a back surface protective sheet for solar cells due to wrinkles and misalignment in process passability and rollability.

(14) Laminating workability In the laminating process at the time of producing the solar cell back sheet of (9), the following evaluation was performed by observing the occurrence of wrinkles, winding deviation, film breakage, and the like.
++: No winding misalignment, wrinkles, film breakage during laminating, and the winding shape was beautiful.
+: Slight winding deviation was observed at the end of the back sheet wound up during the laminating process.
−: Winding misalignment, wrinkle generation, or film breakage occurred during laminating, and the laminate processability was poor.

(15) Comprehensive evaluation The following comprehensive evaluation was performed by integrating the evaluation results as the above-mentioned solar cell back surface protective sheet.
++: All cases show ++ performance.
−: When the evaluation of − is 1 or more.
The film evaluated as “−” in the above evaluation cannot be practically used as a solar cell application.

  Examples of the present invention and comparative examples will be described below.

Method for Producing Phosphorus-Phenolic Antioxidant Masterbatch A 90% by weight of ethylene / α-olefin copolymer having a density of 0.922 g / cm ³ obtained by copolymerizing 6 mol% of 1-hexene having 6 carbon atoms, 6- [3- (3-t-butyl-4-hydroxy-5-methylphenyl) propoxy] -2,4,8,10-tetra-t-butyldibenz [d, f] as a phenolic antioxidant After melt-kneading 10% by weight of [1,3,2] -dioxaphosphepine (Sumitomo Chemical Co., Ltd. “Sumizer” GP) with a twin screw extruder, the strand was cut, and the antioxidant master batch A Manufactured.

Method for producing hindered amine light stabilizer master batch B 90% by weight of ethylene / α-olefin copolymer having a density of 0.922 g / cm ³ obtained by copolymerizing 6 mol% of 1-hexene having 6 carbon atoms, and hindered amine light 10% by weight of a stabilizer (“MARK” LA-57 manufactured by Adeka Argus Chemical Co., Ltd.) was melt-kneaded with a twin screw extruder, and then cut into strands to produce a hindered amine light stabilizer master batch B.

Method for producing titanium oxide master batch C Surface treatment with 40% by weight of an ethylene / α-olefin copolymer having a density of 0.922 g / cm ³ obtained by copolymerizing 6 mol% of 1-hexene having 6 carbon atoms and an inorganic oxide 60% by weight of rutile type titanium oxide having an average particle diameter of 200 nm (“FTR” 700 manufactured by Sakai Chemical Industry) was melt-kneaded with a twin screw extruder, and then the strand was cut to produce a titanium oxide master batch C.

Manufacturing method of inorganic particle master batch D 90% by weight of an ethylene / α-olefin copolymer having a density of 0.922 g / cm ³ obtained by copolymerizing 6 mol% of 1-hexene having 6 carbon atoms and a silica having an average particle diameter of 2 μm After melt-kneading 10% by weight of inorganic particles made of aluminum oxide ('Silton' JC30, manufactured by Mizusawa Chemical) with a twin screw extruder, the strand was cut to produce a titanium oxide master batch D.

Example 1
As a resin used for the A layer, an ethylene / α-olefin copolymer (LLDPE) having a density of 0.935 g / cm ³ and an MFR of 5 g / 10 min obtained by copolymerizing 6 mol% of 1-butene having 4 carbon atoms is 100 weight. to parts, density 0.900g ^/ cm 3, MFR7g ^/ 10 min of the low density polyethylene (LDPE) and 3.5 parts by weight, density 0.900 g ^/ cm 3 as the propylene resin, MFR8g / 10 min homopolypropylene ( (Hereinafter abbreviated as H-PP) 10.5 parts by weight were mixed and charged into a twin screw extruder heated to 220 ° C. to be compounded.

The resin used for the B layer is phosphorus-phenolic antioxidant for 100 parts by weight of LLDPE having a density of 0.918 g / cm ³ and MFR of 5 g / 10 min copolymerized with 6 mol% of 1-hexene having 6 carbon atoms. The master batch A was mixed with 0.5 parts by weight and compounded using a twin screw extruder heated to 220 ° C. The amount of the phosphorus-phenolic antioxidant added to the B layer resin is 0.05% by weight.

As C layer resin, the A layer resin Similarly, for LLDPE100 parts of density 0.935g ^/ cm 3, MFR5g ^/ 10 min ethylene · alpha-olefin copolymer, density 0.900g ^/ cm 3, MFR7g ^/ Inorganic composed of aluminum silicate having a density of 0.900 g / cm ³ and a MFR of 8 g / 10 minutes and 10.5 parts by weight of H-PP as a propylene resin, and 3.5 parts by weight of LDPE for 10 minutes. A resin composition prepared by mixing 6 parts by weight of a master batch D of particles ('Silton “JC30, manufactured by Mizusawa Chemical)” (the amount of inorganic particles added to layer C is 0.5% by weight) was heated to 220 ° C. Compounded with a shaft extruder.

  The A layer, B layer, and C layer compound resins prepared in this way are each supplied to a uniaxial melt extruder, and melted at 220 ° C., respectively, so that A layer / B layer / C layer type multi-manifold type It is led to a T-die, extruded onto a casting drum maintained at 30 ° C., and cooled and solidified by blowing cold air of 25 ° C. from the non-drum surface side. The thickness composition ratio of each layer is 100% of the total thickness of the film. A layer / B layer / C layer = 15% / 75% / 10% A polyolefin resin multilayer film having a film thickness of 150 μm was obtained. The C layer of the multilayer film was subjected to corona discharge treatment and wound up with a surface wetting tension of 40 mN / m. Next, a two-component curing type adhesive (LX-903 / KL-75 = 8/1, manufactured by Dainippon Ink & Chemicals, Inc.) is added to a biaxially stretched PET film (“Lumirror” X10S 125 μm manufactured by Toray Industries, Inc.) as a solid content. After coating and drying at a coating thickness of 6 μm, the polyolefin-based resin multilayer film is laminated, and then subjected to aging at a temperature of 40 ° C. for 72 hours to promote the curing reaction of the adhesive layer and foaming in the adhesive layer. It was set as the back surface protection sheet for solar cells.

  As shown in Table 1, this film has cleared all the necessary requirements of the present invention, and it can be seen that the film has excellent characteristics when used in a back protective sheet for solar cells.

(Example 2)
As a B layer composition component of Example 1, 0.2 part by weight of a master batch A of phosphorus-phenolic antioxidant (addition amount of phosphorus-phenolic antioxidant to B layer resin is 0.02% by weight) Except for mixing, a polyolefin resin multilayer film was obtained in the same manner as in Example 1. Moreover, it carried out similarly to Example 1, and was set as the back surface protection sheet for solar cells.

  As shown in Table 1, this film cleared all the necessary requirements, and no problem in practical use was observed. However, when this film was used for a back sheet for solar cells, a slight discoloration was observed.

(Example 3)
As a B layer resin component of Example 1, 3 parts by weight of a master batch A of phosphorus-phenolic antioxidant (the amount of phosphorus-phenolic antioxidant added to the B layer resin is 0.29% by weight). ) A polyolefin-based resin multilayer film was obtained in the same manner as in Example 1 except for mixing. Moreover, it carried out similarly to Example 1, and was set as the back surface protection sheet for solar cells.

  As shown in Table 1, the present film has cleared all necessary requirements, and it can be seen that the film has excellent characteristics when used in a back sheet for solar cells.

Example 4
As a B layer composition, 0.1 part by weight of a phosphorus-phenol antioxidant masterbatch A is mixed with 100 parts by weight of the resin composition of Example 1 (to a B layer resin of a phosphorus-phenol antioxidant). Furthermore, 33 parts by weight of master batch C of rutile-type titanium oxide was mixed (addition amount of titanium oxide to layer B was 14.9% by weight), and hindered amine light A polyolefin-based resin multilayer film having a film thickness of 150 μm was obtained in the same manner as in Example 1 except that 0.1 part by weight of the master batch B of the stabilizer was mixed. Moreover, it carried out similarly to Example 1, and was set as the back surface protection sheet for solar cells.

  As shown in Table 1, the present film clears all necessary requirements, has high light reflectivity, and has excellent characteristics when used in a back protective sheet for solar cells.

(Example 5)
As resin used for the A layer, with respect to 100 parts by weight of LLDPE of Example 1, LDPE of 1.25 parts by weight of density 0.900 g / cm ³ and MFR 7 g / 10 min, and ethylene copolymerization amount 4 mol% as propylene resin A mixed resin composition of 3.75 parts by weight of an ethylene / propylene random copolymer having a density of 0.900 g / cm ³ and an MFR of 7 g / 10 minutes is mixed into 5 parts by weight, and the same mixed resin composition is used for the C layer. A polyolefin resin multilayer film having a film thickness of 150 μm was obtained in the same manner as in Example 1 except that 5 parts by weight of the product and 6 parts by weight of the master batch D were mixed. Moreover, it carried out similarly to Example 1, and was set as the back surface protection sheet for solar cells. As shown in Table 1, the present film has cleared all necessary requirements, and it can be seen that the film has excellent characteristics when used in a back protective sheet for solar cells.

(Example 6)
As resin used for the A layer, 5 parts by weight of LDPE of Example 1 and 15 parts by weight of H-PP of Example 1 are mixed with 100 parts by weight of LLDPE of Example 1, and the same mixed resin composition is also used for the C layer. A polyolefin resin multilayer film having a film thickness of 150 μm was obtained in the same manner as in Example 1 except that 20 parts by weight and 6 parts by weight of master batch D were mixed. Moreover, it carried out similarly to Example 1, and was set as the back surface protection sheet for solar cells.

  As shown in Table 1, the present film has cleared all necessary requirements, and it can be seen that the film has excellent characteristics when used in a back protective sheet for solar cells.

(Example 7)
In Example 1, the composition ratio of thickness was A layer / B layer / C layer = 20% / 75% / 5%, and a polyolefin-based resin multilayer film having a film thickness of 150 μm was obtained. Moreover, it carried out similarly to Example 1, and was set as the back surface protection sheet for solar cells.

  It can be seen from Table 1 that this film has cleared all necessary requirements as shown in Table 1 and has excellent characteristics when used in a back protective sheet for solar cells.

(Example 8)
In Example 1, except that the density of LLDPE obtained by copolymerizing 6 mol% of 1-hexene having 6 carbon atoms in layer A was 0.925 g / cm ³ , the film thickness was A 150 μm polyolefin resin multilayer film was obtained. Moreover, it carried out similarly to Example 1, and was set as the back surface protection sheet for solar cells.
As shown in Table 1, this film has cleared all the necessary requirements of the present invention, and it can be seen that the film has excellent characteristics when used for a back sheet for solar cells.

Example 9
In Example 4, the film thickness was set in the same manner as in Example 4 except that the density of LLDPE obtained by copolymerizing 6 mol% of 1-octene having 8 carbon atoms in layer B was 0.912 g / cm ^3. A 150 μm polyolefin resin multilayer film was obtained. Moreover, it carried out similarly to Example 1, and was set as the back surface protection sheet for solar cells.
As shown in Table 1, the present film clears all the necessary requirements of the present invention, and it can be seen that the film has excellent characteristics when used in a back protective sheet for solar cells.

(Comparative Example 1)
In Example 1, LLDPE obtained by copolymerizing 6 mol% of 1-octene having 8 carbon atoms having a density of 0.912 g / cm ³ in the A layer and carbon atoms having a density of 0.942 g / cm ^{3 in} the C layer was used. A polyolefin resin multilayer film having a film thickness of 150 μm was obtained in the same manner as in Example 1 except that LLDPE obtained by copolymerizing 4 mol% of 1-hexene of Formula 6 was used. Moreover, it carried out similarly to Example 1, and was set as the back surface protection sheet for solar cells.

Table 2 shows the evaluation results of each physical property. This film has insufficient slipperiness because the density of LLDPE in layer A is lower than 0.920 g / cm ³ , and the ethylene / α-olefin copolymer in each layer in the order of layer A / layer B / layer C Since the density of the resin is high, the curl of the film is large, and when laminating with a polyester film to produce a back protective sheet for a solar cell, winding misalignment and wrinkles occur and the laminating workability is poor. . Moreover, since the density of LLDPE of C layer was high, generation | occurrence | production of the shaving powder was seen by the friction with a metal roll, and the biting of the bubble was seen in the interface with a polyester film. Furthermore, the density of LLDPE in the C layer was high, and the laminate strength with EVA was insufficient.

(Comparative Example 2)
In Example 1, without laminating the A layer, the resin composition of the B layer and the C layer was extruded by two types and two layers of a multi-manifold type T die, and the thickness composition ratio was A layer / B layer / C. A polyolefin-based resin multilayer film having a film thickness of 150 μm was obtained in the same manner as in Example 1 except that the layer = 0% / 90% / 10%. Table 2 shows the evaluation results of each physical property. Since this film has two layers, the curl of the film is large, the slipperiness of the surface of layer B is insufficient, and the film is misaligned and wrinkled in the secondary processing of the laminate, resulting in poor laminating properties. It was. In addition, entrapment of bubbles was observed at the interface with the polyester film.

(Comparative Example 3)
In Example 1, a film was prepared in the same manner as in Example 1 except that LLDPE obtained by copolymerizing 6 mol% of 1-octene having 8 carbon atoms and a density of 0.912 g / cm ³ was used for the A layer and the C layer. A polyolefin resin multilayer film having a thickness of 150 μm was obtained. Table 2 shows the evaluation results of each physical property. This film had low density of the A layer and C layer, was inferior in slipperiness, and was inferior in blocking resistance. Further, since the Young's modulus was low, it was difficult to control the tension during winding, and wrinkles were generated, resulting in poor laminating properties. Furthermore, since the crystallinity is low, the partial discharge voltage is low.
(Comparative Example 4)
A polyolefin-based resin having a film thickness of 150 μm in the same manner as in Example 1 except that the resin composition of the A layer and the C layer in Example 1 was changed to 1 part by weight of LDPE and 3 parts by weight of H-PP. A multilayer film was obtained. Moreover, it carried out similarly to Example 1, and was set as the back surface protection sheet for solar cells.
This film has low LDPE and H-PP components in the resin components of the A layer and the C layer, so the crystallinity is low and the slipperiness is poor. It was inferior. Further, bubbles were observed at the interface with the polyester film, and the partial discharge voltage was also low.

(Comparative Example 5)
Polyolefin having a film thickness of 150 μm in the same manner as in Example 1, except that 9 parts by weight of LDPE and 21 parts by weight of H-PP were mixed as the resin component of the A layer and the C layer in Example 1. -Based resin multilayer film was obtained. Moreover, it carried out similarly to Example 1, and was set as the back surface protection sheet for solar cells.
This film has high crystallinity due to the large amount of mixed resin of LDPE and H-PP in the resin component of the A layer and the C layer, and the curling of the film at the time of casting becomes large. The adhesion decreased and the flatness of the film deteriorated. Further, scraping powder adhered to the metal roll in the film forming process or the secondary processing of the laminate. When scraping powder adhered to the film surface and produced the back sheet for solar cells, air bubbles were observed at the interface with the polyester film. Moreover, since the crystallinity is high, the laminate strength with EVA decreased.

(Comparative Example 6)
In Example 1, as a resin component of the A layer and the C layer, a polyolefin system having a film thickness of 150 μm was obtained in the same manner as in Example 1 except that LDPE was not added and only 14 parts by weight of H-PP was added. A resin multilayer film was obtained. Moreover, it carried out similarly to Example 1, and obtained the back surface protection sheet for solar cells. Since this film does not add LDPE as a resin component of the A layer and the C layer, the crystallinity is lowered and the Young's modulus is lowered, the film is stretched by the tension at the time of winding, and the planarity is deteriorated. When manufacturing the back surface protection sheet for a film, the film | wound misalignment and a wrinkle generate | occur | produced and it was inferior to the lamination process. Moreover, since the crystallinity was low, the partial discharge voltage was low.

(Comparative Example 7)
In Example 1, as a resin component of the A layer and the C layer, a polyolefin system having a film thickness of 150 μm was obtained in the same manner as in Example 1 except that H-PP was not added and only 14 parts by weight of LDPE was added. A resin multilayer film was obtained. Moreover, it carried out similarly to Example 1, and obtained the back surface protection sheet for solar cells. Since this film is inferior in slipping property and blocking resistance because H-PP is not added as a resin component of the A layer and the C layer, the film is misaligned when producing a back sheet for solar cells. A wrinkle occurred and it was inferior to laminating.

(Comparative Example 8)
In Example 1, 4 parts by weight of a master batch A of phosphorus-phenolic antioxidant was added as a resin component of the B layer (the amount of phosphorus-phenolic antioxidant added was 0.4% by weight) Obtained a polyolefin resin multilayer film having a film thickness of 150 μm in the same manner as in Example 1. Moreover, it carried out similarly to Example 1, and obtained the back surface protection sheet for solar cells.
Since this film had a large amount of phosphorus-phenolic antioxidant added, the dispersibility deteriorated, bleeded out, adhered to the slits of the die, and became a surface defect. Moreover, when producing the back surface protection sheet for solar cells produced using this film, the bubble defect was seen in the interface with a polyester film due to the surface defect.

(Comparative Example 9)
In Example 1, instead of the master batch A of the phosphorus-phenolic antioxidant added as the resin component of the B layer, a phenolic antioxidant (“Irganox 1010” manufactured by Ciba Geigy Co., Ltd.) was added ( A polyolefin resin multilayer film having a film thickness of 150 μm was obtained in the same manner as in Example 1 except that 0.05 wt% of a phenolic antioxidant was added as the resin component of the B layer. Moreover, it carried out similarly to Example 1, and was set as the back surface protection sheet for solar cells.
This film is low in antioxidant effect and weather resistance improving effect of the antioxidant, and when measuring the laminate strength of the back protective sheet for solar cells prepared using this film, the film is brittle and breaks. The strength was low.

(Comparative Example 10)
In Example 3, the amount of addition of master batch C of titanium oxide in layer B was 200 parts by weight (the amount of addition of titanium oxide was 40% by weight), and the amount of addition of master batch A of phosphorus-phenolic antioxidant Having a film thickness of 150 μm in the same manner as in Example 3, except that 0.2 part by weight (the addition amount of the phosphorus-phenolic antioxidant in layer B is 0.007% by weight) -Based resin multilayer film was obtained. Moreover, it carried out similarly to Example 1, and was set as the back surface protection sheet for solar cells.
This film has a titanium oxide concentration that is too high, dispersibility is reduced, fine cracks are formed in the film, and the film is brittle because the amount of phosphorus-phenolic antioxidant added is small and the weather resistance is poor. Laminate strength and laminate processability decreased. Moreover, since there were cracks in the film, the partial discharge voltage was lowered.

(Comparative Example 11)
In Example 1, a polyolefin resin multilayer film having a film thickness of 150 μm was obtained except that the thickness constitution ratio of each layer was changed to A layer / B layer / C layer = 10% / 80% / 10%. Moreover, it carried out similarly to Example 1, and was set as the back surface protection sheet for solar cells.
Since this film had a thicker C layer than the A layer, the curl was large, and when the back protective sheet for solar cells was produced, the film was wound and wrinkled, and the laminate processability was poor.

Claims (6)

A film having a three-layer configuration of A layer / B layer / C layer, wherein the A layer and the C layer have an ethylene / α-olefin copolymer 100 having a density in the range of 0.920 to 0.938 g / cm ^3. It consists of a resin composition in which 5 to 20 parts by weight of a mixed resin of low density polyethylene and a propylene resin is mixed with respect to parts by weight, and the B layer is an ethylene / α-olefin copolymer having a density of less than 0.920 g / cm ^3. It is composed of a coalescence as a main component, and 0.01 to 0.3% by weight of an antioxidant of a phosphorus-phenol compound is added and mixed. The lamination ratio is 3 to 30% for the A layer and 60 to 96% for the B layer. A polyolefin resin multilayer film, wherein the C layer is 1 to 10%, and the adhesion strength at 140 of the A layer and the ethylene / vinyl acetate copolymer resin sheet is 40 N / 10 mm or more. The polyolefin resin multilayer film according to claim 1, wherein the thickness of the C layer is 2/3 or less of the thickness of the A layer. The polyolefin resin multilayer film according to claim 1 or 2, wherein the Young's modulus in the longitudinal direction and the width direction of the film is in the range of 150 to 400 MPa. The polyolefin resin multilayer film according to any one of claims 1 to 3, comprising 0.1 to 5% by weight of particles having an average particle diameter of 1 to 5 µm as a resin component of the C layer. The polyolefin resin multilayer film according to any one of claims 1 to 4, comprising 5 to 30% by weight of rutile-type titanium oxide particles having an average particle diameter of 150 to 500 nm as a resin component of the B layer. The polyolefin resin multilayer film according to any one of claims 1 to 5, which is used as a solar cell back sheet.