JP2011178907A - Flame-retardant foamed polyester sheet - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a flame-retardant foamed polyester film which is an inexpensive thermoplastic resin sheet having excellent mechanical characteristics, heat resistance, gas barrier properties, and concealment properties, is excellent in environmental resistance, such as hydrolysis resistance and weather resistance, has high reflectance advantageous to electric conversion efficiency of sunlight, and achieves reduced current leakage; and to provide a solar cell utilizing the same. <P>SOLUTION: The flame-retardant foamed polyester film is not compatible with polyester and has fine bubbles using a resin composition as a nucleus, wherein the resin composition is obtained by mixing a flame retardant of which either a melting point or a decomposition point is 270°C or more therewith. The thermoplastic resin back sheet for a solar cell is composed of such a thermoplastic resin sheet for a solar cell and is suitably used also as a reflection sheet for liquid crystal. <P>COPYRIGHT: (C)2011,JPO&INPIT

Description

  The present invention relates to a flame retardant white film used for electronic parts and the like. More specifically, they are a white film incorporated into a backlight for liquid crystal displays, a sealing film for solar cell modules, a white film for a back sheet, and a white film for circuit materials.

  The present invention relates to a white film having a flame retardancy level equivalent to HB (F), VTM-2, which is defined in the United States Underwriters Laboratories (UL-94) standard UL-94.

  Conventionally, various films containing fine bubbles have been proposed, and these films are widely used in various applications such as labels, posters, thermal recording paper, and sublimation thermal recording paper due to the excellent properties of the film. It is used. In addition, as a characteristic of the film, by configuring the film itself with a layer containing fine bubbles, the hardness of the film is reduced, and a soft feeling and flexibility similar to paper are obtained, and a low specific gravity is achieved. It is known that As such a microbubble containing film, the film currently disclosed by patent document 1, patent document 2, patent document 3, patent document 4, etc. is known, for example.

  The layer containing fine bubbles in the interior is mainly composed of a polyester resin and a resin that is incompatible with the resin, and is a void having an incompatible resin as a core by stretching in biaxial directions after melt extrusion. And is disclosed in Patent Literature 5, Patent Literature 6, and the like.

  On the other hand, since many of these polyesters are inherently flammable, in order to use them as industrial materials, safety against flames, that is, flame retardancy is required in addition to the balance of general chemical and physical properties. There are many cases. Furthermore, in recent years, in order to overcome the drawbacks of halogen-based flame retardants, it has been strongly desired to use a flame retardant containing no halogen. Patent Document 7, Patent Document 8, Patent Document 9 and the like disclose methods for making polyester flame-retardant without using a halogen-based flame retardant.

JP-A-5-138844 JP-A-5-137871 JP-A-5-194773 JP-A-10-286920 Japanese Patent No. 3303983 Japanese Patent No.-03505050 Japanese Patent Laid-Open No. 10-25338 Japanese Patent Laid-Open No. 2003-082235 JP 2009-79123 A

  The polyester film containing fine bubbles has a problem that it easily burns because air is contained in the bubbles. Therefore, when using for the use which requires a flame retardance, it was necessary to add a flame retardant of a larger quantity than a normal polyester film.

  However, the conventional microbubble-containing film has a structure in which a layer having a high bubble content is centered and a layer having a lower bubble content than the substrate or a layer not containing bubbles is laminated on the surface. In addition, since it is necessary to add a flame retardant sufficient to make it flame retardant, the film properties tend to be reduced in strength, rigidity, etc., and as a result, the film becomes weak in practical use and lacks in handleability. was there. Furthermore, there is also a problem that when bent, the base layer having a high bubble content is buckled, and the surface layer is likely to be broken. Moreover, since such a phenomenon becomes more remarkable as the amount of fine bubbles in each layer of the laminated film increases, there is also a potential problem that it is difficult to apply to applications with a high degree of processing.

It is a polyester film having a polyester layer (A) having fine bubbles with a resin composition mixed with a flame retardant having a melting point or a decomposition point of 270 ° C. or higher, which is incompatible with polyester.

  According to the present invention, it is inexpensive and excellent in productivity, and has excellent flame resistance, mechanical / electrical properties, heat resistance, concealment properties, weather resistance and other environmental resistance, cleavage prevention, and solar cell conversion efficiency. It is possible to provide a thermoplastic resin sheet for solar cells having solar reflectivity that contributes to improvement of the solar cell.

  Such a thermoplastic resin sheet for solar cells can be suitably used not only for solar cells used as roofing materials but also for flexible solar cells and electronic components. In particular, since it has excellent properties as a protective sheet, it can be suitably used as a solar cell backsheet. By using the flame-retardant foamed polyester film of the present invention as a back sheet for a solar cell, a solar cell having excellent flame retardancy and conversion efficiency and less leakage current can be obtained. Moreover, the design property can be provided to a solar cell by making a thermoplastic resin sheet for solar cells contain a pigment and coloring it. Moreover, it can be used suitably also for the reflective sheet for liquid crystals with the same request | requirement.

  Further, the backlight lamp reflector of the present invention, the backlight and the backlight mounted with the LED are each configured using such a flame-retardant foamed polyester film, and as a solar cell backsheet member, As a flame-retardant foamed polyester sheet, flame retardancy and low dielectric constant can be effectively used.

This figure shows a cross-sectional view of a solar cell using the film of the present invention. This figure is a sectional view showing an example of the structure of a thermoplastic resin sheet for solar cells using the film of the present invention having a gas barrier layer on one side of the film. This figure is a cross-sectional view of another example showing the structure of a thermoplastic resin sheet for solar cells using a film of the present invention having a gas barrier layer between two films.

  The polyester film of the present invention needs to be a sheet having a thermoplastic resin layer containing a polyester resin (hereinafter sometimes referred to as a polyester layer (A)).

  In the present invention, the thermoplastic resin layer needs to contain a polyester resin which is a thermoplastic resin. Here, the polyester resin refers to a polymer that is a polycondensate of a dicarboxylic acid derivative and a diol derivative.

  Here, the diol is also called glycol, and is a kind of alcohol (polyol) having a structure in which one hydroxy group is substituted on each of two carbon atoms of a chain aliphatic hydrocarbon or a cyclic aliphatic hydrocarbon. It is a compound possessed. Those with adjacent hydroxy groups are called 1,2-glycols, and those with adjacent hydroxy groups through one methylene group are called 1,3-glycols. , 5-glycol, etc. In addition, ethylene glycol (1,2-ethanediol), which is the simplest 1,2-glycol, may be simply referred to as glycol. Representative diols include ethylene glycol, 1,2-propanediol, 1,3-propanediol, 1,4-butanediol, cyclohexanedimethanol, diethylene glycol, neopentyl glycol, polyalkylene glycol, and the like.

  Examples of the dicarboxylic acid include terephthalic acid, naphthalenedicarboxylic acid, isophthalic acid, diphenyldicarboxylic acid, diphenylsulfonedicarboxylic acid, diphenoxyethanedicarboxylic acid, 5-sodiumsulfonedicarboxylic acid, and aromatic dicarboxylic acid such as phthalic acid, Representative examples include oxalic acid, succinic acid, adipic acid, sebacic acid, dimer acid, maleic acid, fumaric acid and other aliphatic dicarboxylic acids, paraoxybenzoic acid and other oxycarboxylic acids, cyclohexanedicarboxylic acid and other alicyclic carboxylic acids. Is.

  Examples of the polyester resin include polyethylene terephthalate, polypropylene terephthalate, polybutylene terephthalate, polyethylene-2,6-naphthalate, poly 1,4-cyclohexanedimethylene terephthalate.

  Moreover, the thermoplastic resin layer of the present invention may contain a thermoplastic resin other than the polyester resin. Examples of thermoplastic resins other than polyester resins include polystyrene, acrylonitrile-styrene copolymers, styrene resins such as acrylonitrile-butadiene-styrene copolymers, polyolefins such as polyethylene and polypropylene, polycarbonates, polyamides, polyethers, polyurethanes, and polyphenylenes. Sulfides, polyesteramides, polyetheresters, polyvinyl chloride, polymethacrylic acid esters, modified polyphenylene ethers, polyarylate, polysulfone, polyetherimide, polyamideimide, polyimides and copolymers comprising these as main components, or of these resins A mixture etc. can be mentioned.

  In the present invention, since the thermoplastic resin is particularly preferably a polyester resin in terms of good dimensional stability and mechanical properties, it is preferable that the component ratio of the polyester resin in the thermoplastic resin layer is high. Specifically, when the entire thermoplastic resin layer is 100 parts by weight, the content of the polyester resin is preferably 55 parts by weight or more, and more preferably 65 parts by weight or more.

  Among polyester resins, in particular, polyethylene terephthalate (PET) is inexpensive, can be used for a wide variety of applications, and is highly effective. The melting point of the polyester resin preferably used is preferably 250 ° C. or higher in view of heat resistance, and preferably 300 ° C. or lower in terms of productivity. If it is in the above-mentioned range, other components may be copolymerized or blended.

  In the present invention, the polyester layer (A) needs to contain a flame retardant.

  The flame retardant that can be used in the present invention is a flame retardant that is incompatible with polyester and has a melting point or decomposition point of 270 ° C. or higher. The above-mentioned conditions are satisfied among organic flame retardants such as bromine compounds and phosphorus compounds, and inorganic flame retardants such as antimony compounds and metal hydroxides. Specifically, melamine phosphate melamine, melamine sulfate, melamine cyanurate, red phosphorus, zinc borate, boron oxide and the like are particularly useful.

  However, phosphates, phosphinates, phosphine oxides, ammonium polyphosphates, aromatic phosphates, pentabromodiphenyl ethers, octabromodiphenyl ethers, decabromodiphenyl ethers as non-halogen flame retardant compounds containing phosphorus atoms and / or bromine and nitrogen atoms , Tetrabromobisphenol A, or phosphate esters such as tricresyl phosphate, 2-ethylhexyl diphenyl phosphate, bisphenol A bis (diphenyl phosphate) 1,3 phenyl bis (diphenyl phosphate) are compatible with polyester Not a little, it is recognized, and moreover, thermal decomposition tends to occur at a high temperature when the polymer is melted. Therefore, there is a problem that the desired fine bubbles cannot be obtained and the reflection characteristics are inferior. Furthermore, with the occurrence of thermal decomposition, the film formation stability is poor and a smooth film cannot be obtained.

  As examples of metal hydroxides, flame retardants such as aluminum hydroxide, magnesium hydroxide, calcium aluminate hydrate and the like are usually stable up to 200 ° C, but the temperature rises to 200 ° C or higher. In many cases, a large endothermic reaction is caused by dehydrating and decomposing rapidly, and it is difficult to obtain a target polyester film having fine bubbles.

  These flame retardants will be placed adjacent to the voids in the film. Usually, in the foam film, air in the film is an adverse effect of flame retardancy, but in the flame retardant polyester film of the present invention, since the air layer and the flame retardant are adjacent to each other, it is possible to suitably block oxygen. .

  Moreover, the film of this invention may have layers other than a thermoplastic resin layer. As a layer other than the thermoplastic resin layer, a layer using an EVA resin for imparting adhesiveness with a filling resin, a metal oxide for imparting a gas barrier property, an oxide of silica, or an aluminum foil is used. And a gas barrier layer.

  Moreover, the film of this invention WHEREIN: It is a preferable aspect that the said polyester layer (A) is located in the outermost layer. This is because when the sheet of the present invention is used as a back sheet for a solar cell, it is used in one mode in which the solar cell filling resin and the sheet are in direct contact with each other. This is because it is possible to significantly improve.

  In addition, when another layer (for example, a gas barrier layer) is laminated on the surface of the polyester film of the present invention to form a new solar cell member, the void foam layer reduces the dielectric, making the film thinner and easier to handle. Productivity can be improved. In addition, the member for solar cells which is this new laminated body can also be used as a solar cell backsheet.

  In addition, as an example of bonding between films, Lumirror (registered trademark) E20 (made by Toray Industries, Inc.) containing titanium oxide, and PET (registered trademark) Barrier Rocks (Toray Film Processing Co., Ltd.) deposited with silica are used. Manufactured), aluminum foil, hydrolysis-resistant PET (registered trademark) X10S (manufactured by Toray Industries, Inc.), and the like.

  In the present invention, the above-mentioned flame retardant alone can be contained in the polyester layer (A) alone, but more preferably, a halogen-free flame retardant compound containing a phosphorus atom and / or bromine atom / nitrogen atom, metal A hydroxide and a metal oxide may be mixed and contained in the layer.

  In this invention, it does not specifically limit regarding the form which contains the above-mentioned flame retardant in the polyester layer (A), When you want to improve a flame retardance more, of the flame retardant in a polyester layer (A) A form in which the content can be further increased, for example, a method such as simply mixing with a resin for forming the polyester layer (A) may be used, and the flame retardant is used depending on the conditions for using the polyester film of the present invention, such as heat, light, and humidity. In order to prevent bleeding out from the polyester layer (A), for example, a method of adding an auxiliary agent that improves dispersion with the resin forming the polyester layer (A) may be used.

  Further, the thickness of the polyester film is preferably 20 μm or more, more preferably 50 μm or more, and particularly preferably 125 μm. Furthermore, when a single backsheet occupies the entire configuration, the partial discharge voltage can be improved by setting the film thickness to 250 μm or more. Although the upper limit is not particularly limited, the thickness of the sheet of the present invention is preferably 350 μm or less from the viewpoint of processability, lightness, and handling properties, and therefore 350 μm is a substantial upper limit. . In addition, when manufacturing the film of the present invention by co-extrusion of the polyester resin and other layers, the thickness of the thermoplastic resin layer is preferably 20 μm or more and 350 μm or less from the viewpoint of lamination accuracy and economy, More preferably, it is 50 μm or more and 300 μm or less.

  The film of the present invention preferably has a 90 ° peel strength of 4 N / 15 mm or more. When the peel strength is less than 4 N / 15 mm, when a stress is applied in the thickness direction (for example, when the installation location is moved after the solar cell using the film of the present invention is once applied), the thermoplastic resin for the solar cell. Cleavage occurs in the surface layer portion (particularly the thermoplastic resin layer portion) of the sheet, which causes a problem. Therefore, the peel strength is preferably 4 N / 15 mm or more, more preferably 5 N / 15 mm or more, and further preferably 6 N / 15 mm or more. The upper limit is not particularly limited, but the peel strength that can be achieved at present is 100 N / 15 mm or less. More preferably, it is 60 N / 15 mm or less. If the peel strength exceeds 100 N / 15 mm, members other than the film of the present invention may be destroyed first, resulting in overspec.

  The peel strength is correlated with the content of the alicyclic diol component in the thermoplastic resin layer and the content of the alicyclic dicarboxylic acid component, isophthalic acid component and naphthalenedicarboxylic acid component, and the peel strength increases as the content increases. Can be improved.

  However, if the content of the above components is simply increased, the thermoplastic resin layer has poor adhesion to the stretching roll and the dimensional stability of the thermoplastic resin sheet, so the concentration that can be practically added is 0.5 to 20 mol%. Within the range.

  The film of the present invention is preferably stretched at least uniaxially, and more preferably biaxially stretched. In biaxial stretching, an unstretched and non-oriented sheet obtained by melt molding the above polymer is stretched uniaxially in the longitudinal direction (film longitudinal direction) and uniaxially in the transverse direction (film width direction). 2 axes). Thereafter, the dimensional stability of the polyester film can be obtained by heat treatment. When extending | stretching, a flame retardant peels from a polyester resin and a void produces | generates by including a flame retardant incompatible with a polyester resin. For example, in the case of stretching in the uniaxial direction, the void generation direction is uniaxial in the vertical direction, and a void stretched in the vertical and horizontal directions is generated by performing vertical and horizontal biaxial stretching. The crystallinity of the film of the present invention (particularly the thermoplastic resin layer) can be easily controlled.

  In addition, the thickness of the film of the present invention is preferably in the range of 20 to 350 microns from the viewpoint of appropriate waist strength, processability, and light weight of the solar cell as a solar cell backside sealing sheet.

The film of the present invention preferably has a carboxyl end group concentration of 35 equivalents / 10 ⁶ g or less of polyester. More preferably, they are 2 equivalents or more and 20 equivalents or less, More preferably, they are 5 equivalents or more and 15 equivalents or less. Incidentally, the polyester carboxyl end group concentration is less than 2 equivalents / polyester 10 ⁶ g, since you can not substantially polymerized, 2 eq / polyester 10 ⁶ g is substantially the lower. When the carboxyl end group concentration exceeds 35 equivalents / 10 ⁶ g of polyester, the hydrolysis resistance is lowered, and the thermoplastic resin sheet for solar cells is rapidly deteriorated. That is, when the usage period extends for a long period of time, problems such as cracking of the film itself, cleavage of the interlayer, and cracking of the back sheet occur when used as a back sheet for solar cells.

The method for setting the carboxyl end group concentration of the film to 35 equivalents / polyester 10 ⁶ g or less is to apply a solid phase polymerization method or the like at the time of polymerization of a thermoplastic resin such as a polyester resin, thereby increasing the molecular weight of the thermoplastic resin. Examples thereof include a method for reducing the carboxyl end group concentration therein. It can also be achieved by containing a carboxyl group end-blocking agent.

  Moreover, the film of this invention can contain a ultraviolet absorber suitably. Examples of the method of incorporating the ultraviolet absorber include a method of incorporating the ultraviolet absorber in another layer constituting the composite layer of the film / back sheet for solar cell. Moreover, you may provide the layer containing a ultraviolet absorber on the surface of a film by methods, such as application | coating.

The film of the present invention is suitably used for solar cells. The solar cell referred to in the present invention refers to a system that converts sunlight into electricity and generates or stores the electricity, and preferably a high light transmissive material 1, a solar cell module 2, a filling resin 3, and a back surface sealing material 4. For example, the structure shown in FIG. 1 is used for a roof of a house, is used for an electric or electronic component, and has a flexible property.
Here, the high light-transmitting material is a material that efficiently allows sunlight to enter and protects the internal solar cell module, and glass, a high light-transmitting plastic, a film, or the like is preferably used.

  The solar cell module converts sunlight into electricity and stores it, and is the heart of the solar cell. The module is made of a semiconductor such as silicon, cadmium-tellurium, germanium-arsenic. There are single crystal, polycrystalline silicon, amorphous silicon, and the like that are widely used at present.

  The filling resin is used for the purpose of fixing and protecting the solar cell module in the solar cell and for electrical insulation, and among them, ethylene vinyl acetate resin (EVA) is preferably used in terms of performance and price.

  Since the sheet of the present invention has excellent mechanical properties, heat resistance, gas barrier properties, concealment properties, weather resistance, and other environmental resistances, and cleaving prevention properties, it is particularly suitably used as a back sheet for solar cells as a back surface sealing material. be able to. In this case, it is particularly preferable that the thermoplastic resin layer is used in a mode in which it is in contact with the filling resin. This is because it is difficult to cleave even if stress is applied in the thickness direction of the sheet by using in this mode.

  In addition, the back surface sealing material (back sheet for solar cell) referred to in the present invention is an important role for protecting the solar cell module on the back side of the solar cell, and at the same time, it is necessary to prevent deterioration of the sheet itself. In order to block the entry of water vapor from the outside, which is most hated by battery modules, those provided with a water vapor barrier layer 6 (water vapor barrier layer) are preferably used as shown in FIG.

  Furthermore, as shown in FIG. 3, gas barrier layers 6 may be provided on both sides of the sheet of the present invention to form a new solar cell member. It is also one of preferable embodiments to use such a new solar cell member as a back surface sealing material.

  Here, the gas barrier layer in the present invention refers to a layer having a water vapor barrier property in particular, and a water vapor transmission value measured according to the standard of JIS K7129-1992 is preferably 0.5 g / The layer which can achieve below m2 / 24Hr (thickness 0.1mm conversion) is said. When the water vapor transmission rate is inferior, hydrolysis of the thermoplastic resin sheet for solar cells is promoted, and both strength and elongation are lowered, so that it deteriorates and becomes brittle (hereinafter referred to as weakening). Furthermore, problems such as entering the circuit in the solar cell module and shorting the circuit occur.

  Here, the gas barrier layer is preferably a layer formed using silicon oxide, metal, metal oxide, or the like. When using a metal or metal oxide, it is preferable to use aluminum or aluminum oxide. By using these substances, the gas barrier properties of the gas barrier layer can be greatly improved.

  In addition, the gas barrier layer is preferably provided on the sheet surface by using a known method such as vacuum deposition or sputtering. In this case, the thickness of the gas barrier layer is preferably in the range of 100 to 200 angstroms.

  There is also a method in which a gas barrier layer is provided on an appropriate film (for example, a PET film) and this laminated film is laminated on the surface of the thermoplastic resin sheet for solar cells of the present invention.

  Moreover, the method of laminating | stacking metal foil (for example, aluminum foil) on the sheet | seat surface can also be used. In this case, the thickness of the metal foil is preferably in the range of 10 to 50 μm from the viewpoint of workability and gas barrier properties.

  The gas barrier layer is not necessarily arranged on the surface of the sheet of the present invention, and may be located inside the sheet as an inner layer, for example.

  The film of the present invention preferably has a high concealing property. Concealment can be quantified as optical density. That is, the higher the numerical value of the optical density, the higher the concealability. In this invention, it is preferable that the optical density of the film measured with the optical densitometer is 0.014 / micrometer or more in conversion of film thickness 1 micrometer, More preferably, it is 0.015 / micrometer or more. From the viewpoint of productivity and film strength, it is particularly preferably 0.2 / μm or less.

  By making the concealability of the film of the present invention within the above range, when the film is used as a back sheet for a solar battery, sunlight leaked from the lower part of the solar battery cell is reflected, and the reflected light is also electrically converted. In addition, the electrical conversion efficiency can be improved.

  In addition, improvement in concealment can be achieved by increasing the light reflectivity of the film or increasing the light absorption. In the former case, the color of the film is white, but in the latter case, the color of the film is black.

  The film of the present invention may be transparent, white, black, or other color, but it is colored white from the viewpoint of improving the conversion efficiency of the solar cell and the weather resistance of the film. Is particularly preferred. In that case, the light transmittance is preferably 35% or less, more preferably 20% or less. Further, the whiteness is preferably 75 to 130% or more, more preferably 80 to 125%, as measured by a color difference meter two-wavelength method. When the light transmittance and the whiteness are out of the above ranges, it does not contribute to the improvement of the electric conversion efficiency of the solar cell.

  On the other hand, when emphasizing the design property, it may be preferable to color it in black or the like.

  In this case, the film is preferably colored by adding an additive such as a dye such as carbon black or a phthalocyanine metal complex, a colorant, a pigment, or a fluorescent brightening agent.

  Moreover, when the film of this invention is blackened from a designable viewpoint, 5% or less of the light transmittance of a film is preferable, More preferably, it is 2% or less. The lower limit is not particularly limited, but 0% is a substantial lower limit. Note that if the additive content is increased too much in order to reduce the light transmittance, the productivity may be significantly deteriorated.

  In order to color the film of the present invention and make the optical density, whiteness, and light transmittance within the above ranges, the film of the present invention preferably contains a pigment. In the present invention, the pigment refers to organic / inorganic particles added for coloring.

  In addition, if within the range where there is no problem in terms of mechanical properties and productivity, the thermoplastic resin layer has at least one kind selected from the group consisting of carbon black, titanium oxide, barium sulfate, calcium carbonate and silicon dioxide as a pigment. The organic / inorganic particles are preferably contained in an amount of 0.5 to 50% by weight based on the entire thermoplastic resin layer. In particular, it is preferable to use titanium oxide when whitening the film, and carbon black when blackening the film.

  Inclusion of the pigment on the thermoplastic resin layer to increase the concealment, leaks incident light leaking from the solar cell module to the back surface sealing material (solar cell backsheet) located outside the solar cell. It is effective in preventing it from coming out. If the incident light is emitted to the outside of the solar cell, it cannot be used again for electrical conversion by the solar cell module, and therefore it is not preferable because improvement in electrical conversion efficiency cannot be expected. In addition, in the leaked light, there are UV (ultraviolet) region light rays that deteriorate the back surface sealing material (solar cell backsheet), but by adding a pigment to the thermoplastic resin layer, the film UV light can be blocked near the surface layer. Thereby, the penetration of UV light into the film can be reduced. Thereby, it can be set as the film which has little UV deterioration inside a film and is excellent in a weather resistance. When the weather resistance is improved, cleavage is less likely to occur even during a long period of use.

  On the other hand, in order to improve the concealability (that is, to increase the optical density), for example, simply increasing the amount of pigment added, a molten polyester filtration filter for removing foreign substances used in melting and extruding polyester It also causes clogging and unfavorable productivity.

  In addition to the pigments described above, the thermoplastic resin layer contains modifiers such as various types of inorganic particles such as silicon nitride, clay, talc, kaolin, and zirconium acid, and particles such as crosslinked polymer particles and various metal particles. May be.

  Further, the thermoplastic resin layer of the present invention is obtained by melt-kneading the resin and pigment particles constituting the thermoplastic resin layer to obtain a master batch, and then solid-phase polymerizing the master batch, the solid-phase polymerization The method of forming a film using the master batch which performed is preferable. Normally, in a system containing a large amount of polyester, the polyester resin is hydrolyzed during melt kneading with particles, and the carboxyl end group concentration becomes high. Therefore, after melting and kneading inorganic and organic particles into a masterbatch, A production method for polymerization is preferred.

Next, the manufacturing method of the film of this invention is demonstrated.
The polyester resin used for the thermoplastic resin layer of the present invention can be obtained, for example, by subjecting terephthalic acid or a derivative thereof and ethylene glycol to a transesterification reaction by a known method. Moreover, as a method of containing an alicyclic diol component, for example, when 1,4 cyclohexane dimethanol is contained, “PET-G 6763” manufactured by Eastman Chemical Co., Ltd. A method in which hexane dimethanol is copolymerized with 33 mol% of PET), and 1,4 cyclosandimethanol and / or an ester derivative of terephthalic acid and 1,4 cyclohexane dimethanol are added during polymerization. There exists the method of making it contain by transesterification by a method. Examples of the method of containing an alicyclic dicarboxylic acid component, an isophthalic component, and a naphthalenedicarboxylic acid component include, for example, a method of adding a copolymer of polyethylene terephthalate and cyclohexanedicarboxylic acid, or cyclohexanedicarboxylic acid during polymerization. There is a method in which an acid or the like is added and contained by a transesterification reaction by a known method.

  In addition, a conventionally known reaction catalyst (polymerization catalyst) (alkali metal compound, alkaline earth metal compound, zinc compound, lead compound, manganese compound, cobalt compound, aluminum compound, antimony compound, titanium compound, etc.) may be used for the polymerization. good. Furthermore, you may add a phosphorus compound etc. as a color tone regulator. More preferably, an antimony compound, a germanium compound, or a titanium compound is added as a polymerization catalyst at an arbitrary stage before the polyester production method is completed. As such a method, for example, when a germanium compound is taken as an example, it is preferable to add the germanium compound powder as it is.

  Next, a method for obtaining the film of the present invention from the polyester resin will be described. First, the polyester resin is dried as necessary, the polyester resin is extruded using a single extruder, and sent out from the flow path, and then discharged from a die to produce a single layer sheet, or two or more Using two extruders, two or more polyester resins and thermoplastic resins are extruded from different flow paths, and the resins are multi-layered using a multi-manifold die, feed block, static mixer, pinol, etc. There is a method of obtaining a laminated sheet by laminating and discharging from a die.

  The sheet discharged from the die is extruded onto a cooling body such as a casting drum, and is cooled and solidified to obtain a casting sheet. At this time, it is preferable to use a wire-like, tape-like, needle-like, or knife-like electrode, which is brought into close contact with a cooling body such as a casting drum by an electrostatic force and rapidly solidified.

  The casting sheet thus obtained must be stretched at least uniaxially. Stretching may be performed sequentially biaxially or simultaneously in two directions. Further, re-stretching may be performed in the longitudinal and / or transverse direction.

  Here, the stretching in the longitudinal direction refers to stretching for imparting molecular orientation in the longitudinal direction to the film, and is usually performed by a difference in peripheral speed between rolls. This stretching may be performed in one stage, or may be performed in multiple stages using a plurality of roll pairs. The stretching ratio varies depending on the type of resin, but is usually preferably 2 to 15 times. For example, when cyclohexanedimethanol-containing polyethylene terephthalate is used as the polyester resin, it is preferably 2 to 7 times. .

  The physical properties used in the present invention, the evaluation method thereof, and the evaluation criteria will be described below.

[Measurement of physical properties and evaluation method of effects]
The physical property value evaluation method and the effect evaluation method of the present invention are as follows.

(1) Carboxyl group end group concentration (equivalent / polyester 10 ⁶ g)
2 g of a polyester composition according to the Maurice method was dissolved in 50 ml of o-cresol / chloroform (weight ratio 7/3), titrated with an N / 20-NaOH methanol solution, and the carboxyl end group concentration was measured. The value is 10 ⁶ g.

(2) Whiteness (two-wavelength method)
The following numerical values were measured with a color difference meter (Nippon Denshoku: ND-300A). Whiteness (W) = 100 [(100-L) ² + a ² + b ² ] ^1/2
L: Lightness, a: Saturation, b: Hue.

(3) Optical density (1 μm thickness conversion value: F)
The transmitted light flux was measured with an optical densitometer (Macbeth: TR-524) and calculated according to the following formula.
Light source: Visible light spectral composition: Color temperature 3006 ° K tungsten bulb Measurement environment: Temperature 23 ° C ± 3 ° C, Humidity 65 ± 10% RH
Calculation formula: optical density = log ₁₀ (F ₀ / F) / d
F: transmitted light flux of sample, F ₀ : transmitted light flux without sample, d: film thickness (μm).

(4) Apparent density
The measurement was made with an electromagnetic balance (SD-120L manufactured by Kensei Kogyo Co., Ltd.).

(5) Relative reflectivity Using a Hitachi spectrophotometer U-3310, the equivalent of the standard white plate opening and the test piece opening were both made of alumina oxide as the standard white plate and the inclination angle of the test piece opening at 560 nm. The diffuse reflectance was measured at 10 ° (T ₀ ), and the reflectance at that time was 100%. Thereafter, the opening of the test piece was replaced with a test piece, and the diffuse reflectance was measured at 560 nm. Then, it converted into relative reflectance (R) by the following formula.

R (%) = T ₁ / T ₀ × 100
T ₀ : reflectance of standard white plate
T ₁ : reflectance of the test piece.

(6) Water vapor transmission rate
The water vapor transmission rate was measured according to JIS K7129. Measurement conditions were 24 hours, a temperature of 40 ° C., and 90% RH, and converted to m ² . (Thickness is converted to 0.1 mm).

(7) Moisture and heat resistance The film is aged in an atmosphere of 140 ° C., the elongation at break of the film is measured by ASTM-D61T, the elongation at break without aging is taken as 100%, and the ratio (retention ratio) to the elongation after aging ) Was calculated. And it determined on the following reference | standard.
◯: Retention ratio is 40% or more Δ: Retention ratio is 30 to less than 40% ×: Retention ratio is less than 30%

(8) Workability A 1 m square solar cell back surface sealing film was prepared, and the waist strength in consideration of the ease of incorporation into the solar cell system was determined according to the following criteria.
○: The waist strength is appropriate and it can be easily assembled.
Δ: A level where the waist is weak or too strong, and there are some difficulties in assembly processing.
X: Level at which the waist is too weak or too strong and clearly has difficulty in workability.

(9) Dielectric constant The dielectric constant was measured according to JIS C2151.

(10) Composite ratio of composite film The total thickness was measured in accordance with JIS C2151, and the laminated section was pretreated by cutting the section in the thickness direction with a microtome, and then a field emission scanning electron microscope (FE-SEM manufactured by Hitachi, Ltd.) ) Using S-800, the thickness section was imaged at a magnification (× 1000) at which the entire image was taken, and the composite ratio was calculated from the result of measuring the thickness ratio of the section photograph from the section photograph.

(11) Glossiness Using a digital gonio-gloss meter (UGU-4D) manufactured by Suga Test Instruments Co., Ltd., the incidence angle and the light reception angle were evaluated according to 60 ° according to JIS K7105.

(12) Average particle size of particles in film Cross-sectional photograph of magnification observation of cross section of layer A and / or layer C at 100,000 times using transmission electron microscope HU-12 type (manufactured by Hitachi, Ltd.) I asked for it. That is, the particle portion of the cross-sectional photograph is marked along the particle shape, and the particle portion is subjected to image processing using a high-definition image analysis processing apparatus PIAS-IV (manufactured by Pierce Co., Ltd.). The number average diameter when each particle was converted into a perfect circle was calculated and used as the average particle diameter of the particles.

(13) Total light transmittance According to JIS-K-7105-1981, the light transmittance of the thermoplastic resin sheet was measured using a haze meter (manufactured by Suga Test Instruments: IS-2B). The light incident surface was the film A layer surface.

(14) A test piece having a width of 12.7 mm, a length of 127 mm, and a thickness of 1.6 mm was prepared using a flame retardant three-stage press machine under the conditions of a temperature of 240 ° C., a heating time of 30 seconds, and a pressure of 30 MPa. A piece was used for testing and evaluation based on UL-94.

(15) Film formation stability Whether the film could be formed stably was evaluated according to the following criteria.
○: A film can be stably formed for 24 hours or more.
Δ: Film can be stably formed for 12 hours or more and less than 24 hours.
X: Breakage occurs within 12 hours, and stable film formation is not possible.

(16) Dispersion diameter The test film was cut in the thickness direction using a microtome to obtain a slice sample.

  The cross section of the slice sample was imaged at a magnification of 2000 using a Hitachi Field Emission Scanning Electron Microscope (FE-SEM) S-800, and the area of the void was marked and calculated from the photograph.

  In addition, the interface of the layer containing substantially no bubbles or the layer containing bubbles has a thickness of 0.5 μm as a measurement range, and the measurement range has an initial position as a thickness of 0.5 μm from the film surface. When the porosity at each time point is determined by moving from the center of the film to the center of the film, it is determined as a plane parallel to the film plane including the midpoint in the film thickness direction of the measurement range when the porosity exceeds 10%.

  The present invention will be described in more detail based on examples. However, the present invention is not construed as being limited by these examples.

Example 1
100 parts of dimethyl terephthalate (parts by weight: hereinafter simply referred to as parts) is mixed with 64 parts of ethylene glycol, 0.1 parts of zinc acetate and 0.03 part of antimony trioxide are added as a catalyst, and the reflux temperature of ethylene glycol is increased. Transesterification was performed. To this was added 0.08 part of trimethyl phosphate, and the temperature was gradually raised and reduced, and polymerization was carried out at a temperature of 271 ° C. for 5 hours. The intrinsic viscosity of the obtained polyethylene terephthalate was 0.55. This polymer was cut into chips having a length of 4 mm, and this was designated as PET-1. This PET-1 was put into a rotary vacuum apparatus (rotary vacuum dryer) having a temperature of 220 ° C. and a degree of vacuum of 0.5 mmHg, and heated while stirring for 20 hours. The intrinsic viscosity of the obtained PET was 0.78. This is designated as PET-2. Titanium dioxide was added to this polymer in an amount of 20% by weight based on the base polyester and 20% by weight of polymelamine phosphate MPP-B (registered trademark) (manufactured by Sanwa Chemical Co., Ltd.) having an average particle size of 10 μm.

  After drying at 180 ° C. for 3 hours, the mixture was supplied to an extruder α heated to around 280 ° C. (A layer) and formed into a sheet form from a T-die. Furthermore, the unstretched film obtained by cooling and solidifying this film with a cooling drum having a surface temperature of 25 ° C. was led to a roll group heated to 85 to 98 ° C., longitudinally stretched 3.5 times in the longitudinal direction, and cooled with a roll group at 21 ° C. . Subsequently, the film was stretched 3.8 times in the direction perpendicular to the longitudinal direction in an atmosphere heated to 120 ° C. while being guided to a tenter while holding both ends of the longitudinally stretched film with clips. Thereafter, heat setting was performed at 200 ° C. in a tenter, and after uniform cooling, the film was cooled to room temperature to obtain a film having a winding thickness of 225 μm. The characteristic evaluation of the obtained film was as shown in FIG.

Example 2
PET-2 obtained in Example 1: 33 wt%, barium sulfate: 47 wt%, polymelamine phosphate: 20 wt%, temperature 180 ° C, vacuum degree 0.5 mmHg, vacuum drying for 3 hours, PET-2: 91.994 wt%, barium sulfate: 5 wt%, UV absorber (triazine derivative): 3 wt%, silicon dioxide: 0 .006% by weight is fed into the B layer side with an extruder β, and is melted into a composite structure of A layer / B layer through a device (merging device) that can combine the two kinds of polymers in the melting flow path. The sheet was extruded from a T-die and cast by applying electrostatic force to a cooling drum maintained at 25 ° C. The thickness of the obtained sheet was 0.7 mm. The extrusion temperature was 270 to 290 ° C. for both polymers. Further, the diameter of the extruder α was 40 mm, and the diameter of the extruder β was 90 mm.

  This sheet was successively stretched 3.5 times in the longitudinal direction of the sheet at a temperature of 90 ° C. by successive biaxial stretching methods, and then the film was supplied to the subsequent tenter and stretched 3.8 times in the width direction at a temperature of 95 ° C. Further, heat treatment was then performed at 220 ° C. to obtain a film having a thickness of 50 μm.

Example 3
PET-2 obtained in Example 1: 80% by weight, melamine phosphate: 20% by weight, temperature 180 ° C., vacuum degree 0.5 mmHg, vacuum drying for 3 hours, and layer A in extruder β On the side, PET-2: 79.994 wt%, titanium dioxide: 20 wt%, and silicon dioxide 0.006 wt%, which were similarly vacuum-dried, were introduced into the B layer side with an extruder α, The melted sheet that is composed of B layer / A layer / B layer composite is extruded from the T-die through a device (combining device) that can combine the two types of polymer inside, and electrostatically applied to a cooling drum maintained at 25 ° C. Cast closely. The thickness of the obtained sheet was 0.7 mm. The extrusion temperature was 270 to 290 ° C. for both polymers. Further, the diameter of the extruder α was 40 mm, and the diameter of the extruder β was 90 mm.

  This sheet was successively stretched 3.5 times in the longitudinal direction of the sheet at a temperature of 90 ° C. by a continuous biaxial stretching method, and then the film was supplied to the subsequent tenter and stretched 3.8 times in the width direction at a temperature of 100 ° C. Further, heat treatment was then performed at 225 ° C. to obtain a film having a thickness of 50 μm.

Example 4
PET-2 obtained in Example 1: 80% by weight, melamine phosphate: 20% by weight, temperature 180 °, vacuum 0.5 mmHg, vacuum drying for 2 hours, and layer A in extruder β PET-2: 79.994% by weight, 20% by weight of titanium dioxide and 0.006% by weight of silicon dioxide, which were also vacuum-dried in the same manner, were introduced into the B layer side using an extruder α, and vacuum was applied in the same manner. PET-1 after drying: 89.994% by weight, titanium dioxide 5% by weight, barium sulfate: 5% by weight, silicon dioxide 0.006% by weight was charged into the C layer side with an extruder γ, and melt flow Through the device (merging device) that can combine the three kinds of polymers in the road, the molten sheet having a combined structure of B layer / A layer / C layer is extruded from the T die and electrostatically placed on a cooling drum maintained at 25 ° C. The cast was applied in close contact. The thickness of the obtained sheet was 0.7 mm. The extrusion temperature was 270 to 290 ° C. for both polymers. Further, the diameter of the extruder α was 40 mm, and the diameter of the extruder β was 90 mm. The diameter of the extruder γ was 30 mm.

Example 5
A 50 μm film was prepared in the same manner as in Example 3, except that the raw material composition to be added to the layer A side was changed to PET-2: 85 wt% obtained in Example 1 and polymelamine phosphate: 15 wt%. Obtained.

Example 6
A 50 μm film was prepared in the same manner as in Example 3, except that the raw material composition to be added to the layer A side was changed to PET-2: 65% by weight obtained in Example 1 and polymelamine phosphate: 35% by weight. Obtained.

Example 7
The raw material composition to be added to the layer A side is PET-2 obtained in Example 1: 80% by weight, and average particle size instead of 20 parts by weight of polymelamine phosphate MPP-B (registered trademark) (manufactured by Sanwa Chemical Co., Ltd.) A 50 μm film was obtained in the same manner as in Example 3 except that the diameter was changed to 15 μm zinc melamine oxalate apinone-901 (registered trademark).

Example 8
The raw material composition to be added to the layer A side is average particle size instead of PET-2: 80% by weight obtained in Example 1 and 20% by weight of polymelamine phosphate MPP-B (registered trademark) (manufactured by Sanwa Chemical Co., Ltd.) A 50 μm film was obtained in the same manner as in Example 3 except that the melamine cyanurate MC-860 (registered trademark) (manufactured by Sanwa Chemical Co., Ltd.) having a diameter of 2 μm was changed to 20% by weight.

Example 9
The raw material blended in the layer A side is PET-2: 80% by weight obtained in Example 1, and polyphosphoric melamine phosphate MPP-B (registered trademark) (manufactured by Sanwa Chemical Co., Ltd.) 20% by weight. A flame-retardant masterbatch of NOVA PELLET (registered trademark) (manufactured by Rin Chemical Industry Co., Ltd.) was used to obtain a 50 μm-thick film in the same manner as in Example 3 except that the flame retardant was changed to 20% by weight of red phosphorus It was.

Example 10
The raw material composition to be added to the layer A side is PET-2 obtained in Example 1: 80% by weight, and average particle size instead of 20 parts by weight of polymelamine phosphate MPP-B (registered trademark) (manufactured by Sanwa Chemical Co., Ltd.) A 50 μm film was obtained in the same manner as in Example 3, except that the diameter was changed to 20 parts by weight of zinc borate ALCANEX FRC (registered trademark) (manufactured by Mizusawa Chemical Co., Ltd.).

Example 11
Boron oxide instead of 20 parts by weight of PET-2: 80% by weight obtained in Example 1 and 20 parts by weight of melamine phosphate MPP-B (registered trademark) (manufactured by Sanwa Chemical Co., Ltd.) A 50 μm film was obtained in the same manner as in Example 3 except that the amount was changed to 20 parts by weight (manufactured by USBOLAX).

[Comparative Example 1]
20 parts by weight of polymethylpentene incompatible with polyester instead of 20 parts by weight of polymelamine phosphate MPP-B (registered trademark) (manufactured by Sanwa Chemical Co., Ltd.) as described in Table 1 A film having a thickness of 50 μm was obtained in the same manner as in Example 3 except that the thickness was changed to.

[Comparative Example 2]
As shown in Table 1, the laminated structure and raw material composition were changed to 20 parts by weight of brominated polyphenyl flame retardant instead of 20 parts by weight of polymelamine phosphate MPP-B (registered trademark) (manufactured by Sanwa Chemical Co., Ltd.) A film having a thickness of 225 μm was obtained in the same manner as in Example 3. This film does not provide the desired bubbles, has poor reflection performance, and has insufficient performance as a light reflecting substrate.

[Comparative Example 3]
As described in Table 1, the laminated structure and raw material composition were replaced with polyphenol melamine phosphate MPP-B (registered trademark) (manufactured by Sanwa Chemical Co., Ltd.) 20 parts by weight ammonium polyphosphate FR CROS 485P (registered trademark) (Buden A film having a thickness of 225 μm was obtained in the same manner as in Example 3, except that the flame retardant was changed to 20 parts by weight. Decomposition of ammonium polyphosphate occurs during film formation, a film containing bubbles cannot be obtained, reflection performance is poor, and performance as a substrate for light reflection is insufficient.

[Comparative Example 4]
Hexabromocyclododecane flame cut 130R (registered trademark) instead of 20 parts by weight of polymelamine phosphate MPP-B (registered trademark) (manufactured by Sanwa Chemical Co., Ltd.) A film having a thickness of 50 μm was obtained in the same manner as in Example 3 except that the flame retardant was changed to 20 parts by weight. The reflection performance is poor, and the performance as a light reflecting substrate is insufficient.

[Comparative Example 5]
Instead of 20 parts by weight of the polymelamine phosphate MPP-B (registered trademark) (manufactured by Sanwa Chemical Co., Ltd.) as shown in Table 1, the layer structure and raw material composition were trisdichloropropyl phosphate CRP (registered trademark) (Daihachi A film having a thickness of 225 μm was obtained in the same manner as in Example 3 except that the flame retardant was changed to 20 parts by weight. During film formation, decomposition of trisdichloropropyl phosphate occurred, and no film was obtained.

  In the films of the present invention in Examples 1 to 6, the flame retardance is confirmed by changing the lamination structure and the amount of the flame retardant added. In any configuration, flame retardancy and foamability are not particularly problematic. Furthermore, it can be seen that it has a low dielectric constant and excellent reflectivity compared to a polyethylene terephthalate film without voids. As other flame retardants, as shown in Examples 7 to 11, melamine sulfate, melamine cyanurate, red phosphorus, zinc borate, and boron oxide can be used. Moreover, the polymethylpentene of Comparative Example 1 in Table 1 has a problem that flame retardancy does not appear. The flame retardants shown in Comparative Examples 2 to 5 have a problem that voids do not appear and the effect of low dielectric constant cannot be obtained.

  Further, the flame retardant trisdichloropropyl phosphate of Comparative Example 5 has a problem that the flame retardant decomposes during the extrusion process and the film of the present invention cannot be obtained.

  The flame-retardant foamed polyester film of the present invention is suitably used not only for solar cells used as roofing materials, but also for applications that require design characteristics of flexible solar cells and electronic components, decorative panels, etc. be able to.

DESCRIPTION OF SYMBOLS 1 All light transmissive material 2 Solar cell module 3 Filling resin 4 Flame retardant foaming polyester film 5 Lead wire 6 Gas barrier layer 7 Film layer (1)
8 Film layer (2)

Claims (5)

A polyester film having a polyester layer (A) having fine bubbles with a resin composition mixed with a flame retardant having a melting point or a decomposition point of not less than 270 ° C. being incompatible with polyester. The polyester film according to claim 1, comprising at least two layers of a polyester layer (A) and a polyester layer (B). The polyester film according to claim 1 or 2, wherein the content of the flame retardant in the polyester layer (A) is 5 to 45% by weight with respect to the polyester layer (A). The polyester film according to claim 1, wherein the flame retardant has an average particle size of 0.1 μm or more and 10 μm or less. The polyester film in any one of Claims 1-4 used for a reflecting plate or a solar cell member.

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