JP2012238491A - Polyester film for battery outer package, laminate for battery outer package including the same, and constitutional body - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a polyester film for a battery outer package, capable of being used for a battery outer package, specifically used suitable for a lithium ion secondary battery having an electrolyte (solid, liquid).SOLUTION: In a polyester film for a battery outer package, a thermal shrinkage stress Yin an MD direction and a thermal shrinkage stress Yin a TD direction at 200°C satisfy the following expressions, and at least one surface of the polyester film is subjected to corona discharge treatment or surface coating treatment. 50≤Y≤120 g/10 mm and 5≤Y≤80 g/10 mm.

Description

  TECHNICAL FIELD The present invention relates to a battery exterior polyester film, and more particularly to a battery exterior polyester film that can be suitably used for a lithium ion secondary battery having an electrolyte (solid, liquid).

  A lithium battery, also called a lithium secondary battery, is a battery that has a liquid, gel-like polymer, solid polymer, polymer electrolyte, etc., and generates current by the movement of lithium ions. Including those consisting of molecules. The configuration of the lithium secondary battery is as follows: positive electrode current collector (aluminum, nickel) / positive electrode active material layer (polymer positive electrode material such as metal oxide, carbon black, metal sulfide, electrolyte, polyacrylonitrile) / electrolyte layer ( Carbonate electrolytes such as propylene carbonate, ethylene carbonate, dimethyl carbonate, ethylene methyl carbonate, inorganic solid electrolytes made of lithium salts, gel electrolytes) / negative electrode active material layers (lithium metals, alloys, carbon, electrolytes, polyacrylonitrile, etc. Polymer negative electrode material) / negative electrode current collector (copper, nickel, stainless steel) and an outer package for packaging them. In recent years, lithium batteries have been widely used because of their high volumetric efficiency and weight efficiency. PCs, mobile terminal devices (cell phones, PDAs, etc.), video cameras, electric vehicles, energy storage batteries, robots, satellites It is used as a small and large capacity power source.

  As the exterior body of a lithium battery, a metal can obtained by pressing a metal into a cylindrical or rectangular parallelepiped container or a multilayer film composed of an outermost layer / aluminum / sealant layer in a bag shape is used. ing. However, since the outer wall of the container in a metal can is rigid, the shape of the battery itself is determined, and the hardware side using the battery is determined by the battery in order to design the hardware side to match the battery. As a result, there is a problem that the design can be restricted, for example, so that a bag-like exterior body made of a multilayer film has been favored. Physical properties and functions required for the exterior of lithium batteries are moisture resistance, content resistance (resistance to compounds such as electrolytes used as contents), moldability, etc. As what is used, for example, a polyamide film, a polyethylene naphthalate film, or polyethylene terephthalate is used (see, for example, Patent Document 1). However, when the battery is sealed, it cannot withstand dimensional changes due to heat, and delamination may occur between the film layer and the aluminum layer, and improvements have been demanded. Moreover, examination using a polyester film is also performed (for example, refer patent document 2). However, the proposed polyester film also has a large thermal shrinkage at the time of sealing processing, and the adhesion between the film layer and the aluminum layer is reduced, and delamination may occur.

JP 2006-331897 A Japanese Patent Laid-Open No. 2004-362953

  An object of the present invention is to eliminate the above-described problems. In other words, a lithium battery exterior polyester film that ensures excellent moldability in lithium battery packaging materials that involve drawing with a mold as a processing step and eliminates delamination between the film layer and the aluminum layer during sealing processing is provided. There is to do.

The present invention for solving the above problems has the following configuration.
(1) Battery exterior in which heat shrinkage stress Y _MD in MD direction at 200 ° C., heat yield stress Y _{TD in} TD direction satisfies the following formulas (i) and (ii), and at least one side of diiodomethane contact angle is 22 ° or more Polyester film.

50 ≦ Y _MD ≦ 120 g / 10 mm (i)
5 ≦ Y _TD ≦ 80 g / 10 mm (ii)
(2) It has at least a polyester film layer and a resin layer, and at least one outermost layer is a resin layer, and the resin layer is a polyurethane resin, a polyester resin, a polyester acrylate resin, a polyurethane acrylate resin, or a polyepoxy. The polyester film for battery exterior according to (1), which has at least one selected from an acrylate resin and a titanate compound.
(3) 5% elongation stress (F5 value) and 10% elongation stress (F10 value) in the longitudinal direction (MD) and width direction (TD) of the film at 25 ° C. are the following (I), (II) The polyester film for battery exterior as described in (1) or (2) which satisfy | fills Formula.
1.5 ≧ F10 _MD / F5 _MD ≧ 1 (I)
1.5 ≧ F10 _TD / F5 _TD ≧ 1 (II)
(4) The polyester film for battery exterior according to any one of (1) to (3), wherein the dynamic friction coefficient μd of at least one surface is 0.3 to 0.8.
(5) It contains particles, the average particle diameter of the particles is 0.01 to 5 μm, and the content of the particles is 1.5 to 5% by weight based on the whole film (1) to (4) A polyester film for battery exterior according to any one of the above.
(6) A laminate obtained by laminating an aluminum foil having a thickness of 10 μm or more and 60 μm or less on at least one surface of the battery exterior polyester film according to any one of (1) to (5), the polyester film and aluminum A laminate for battery exterior having a peel strength between the foil of 2 N / 15 mm or more.
(7) A battery exterior structure using the battery exterior laminate according to (6).

Polyester film for a battery case of the present invention, the thermal shrinkage stress Y _MD in the MD _direction, the TD direction of NetsuOsamu stress Y _TD exist in a specific range at 200 ° C., and at least one side corona discharge treatment, or surface coating treatment By being done, since the delamination resistance after laminating | stacking aluminum foil is favorable, it can be used conveniently for the structure for battery exterior.

  The battery exterior polyester film of the present invention has at least a polyester film layer.

  The polyester film layer of the present invention is composed of polyester. In the present invention, the term “polyester” is a general term for polymer compounds in which the main bond in the main chain is an ester bond. The polyester can be usually obtained by polycondensation reaction of dicarboxylic acid or its derivative with glycol or its derivative.

  In the present invention, 60 mol% or more of the glycol unit constituting the polyester is a structural unit derived from ethylene glycol from the viewpoint of molding followability after the aluminum foil is laminated, heat resistance, dimensional stability, and electrolytic solution resistance. It is preferable that 60 mol% or more of the dicarboxylic acid units are structural units derived from terephthalic acid. Here, the dicarboxylic acid unit (structural unit) or the diol unit (structural unit) means a divalent organic group from which a portion to be removed by polycondensation is removed, and is represented by the following general formula. .

Dicarboxylic acid unit (structural unit): —CO—R—CO—
Diol unit (structural unit): —O—R′—O—
(Here, R and R ′ are divalent organic groups. R and R ′ may be the same or different.)
The same applies to the meaning of units (structural units) of trivalent or higher carboxylic acids such as trimellitic acid units and glycerin units, alcohols, and derivatives thereof.

  Examples of glycols or derivatives thereof that give the polyester used in the present invention include 1,2-propanediol, 1,3-propanediol, 1,3-butanediol, 1,4-butanediol, 1, other than ethylene glycol. Aliphatic dihydroxy compounds such as 5-pentanediol, 1,6-hexanediol and neopentyl glycol, polyoxyalkylene glycols such as diethylene glycol, polyethylene glycol, polypropylene glycol and polytetramethylene glycol, 1,4-cyclohexanedimethanol, spiro Examples thereof include alicyclic dihydroxy compounds such as glycol, aromatic dihydroxy compounds such as bisphenol A and bisphenol S, and derivatives thereof.

  In addition to terephthalic acid, the dicarboxylic acid or derivative thereof that provides the polyester used in the present invention includes isophthalic acid, phthalic acid, 2,6-naphthalenedicarboxylic acid, diphenyldicarboxylic acid, diphenylsulfonedicarboxylic acid, diphenoxyethanedicarboxylic acid. Acids, aromatic dicarboxylic acids such as 5-sodiumsulfone dicarboxylic acid, oxalic acid, succinic acid, adipic acid, sebacic acid, dimer acid, maleic acid, fumaric acid and other aliphatic dicarboxylic acids, 1,4-cyclohexanedicarboxylic acid, etc. Alicyclic dicarboxylic acids, oxycarboxylic acids such as paraoxybenzoic acid, and derivatives thereof. Examples of dicarboxylic acid derivatives include dimethyl terephthalate, diethyl terephthalate, 2-hydroxyethyl methyl terephthalate, dimethyl 2,6-naphthalenedicarboxylate, dimethyl isophthalate, dimethyl adipate, diethyl maleate, and dimethyl dimer. An esterified product can be mentioned.

From the point of delamination resistance after laminating a film layer and an aluminum foil layer, the polyester film for battery exterior according to the present invention has a thermal shrinkage stress Y _MD in the MD direction at 200 ° C. and a heat yield stress Y _{TD in the} TD direction represented by the following formulas: It is necessary to satisfy (i) and (ii).

50 ≦ Y _MD ≦ 120 g / 10 mm (i) 5 ≦ Y _TD ≦ 80 g / 10 mm (ii)
Preferably, 55 ≦ Y _MD ≦ 115 g / 10 mm, 6 ≦ Y _TD ≦ 75 g / 10 mm, more preferably 60 ≦ Y _MD ≦ 110 g / 10 mm, and 7 ≦ Y _TD ≦ 70 g / 10 mm.

The battery exterior polyester film of the present invention is preferably used as a battery exterior structure such as a polyester film / aluminum foil / sealant film, but when heated to heat seal the sealant film part, and In some cases, heat resistance in a high-temperature environment after battery products are required. By setting the heat shrinkage stress Y _MD and Y _TD in the longitudinal direction and the width direction at 200 ° C. within the above ranges, the shrinkage of the polyester film is small during heat sealing, so curling as a constituent can be suppressed. It becomes. Further, even when the battery product is exposed to a high temperature environment, peeling between the polyester film and the aluminum foil due to the shrinkage force of the film can be suppressed.

  Examples of the method for setting the heat shrinkage stress at 200 ° C. of the polyester film for battery exterior of the present invention in the above range include a method of adjusting the heat treatment conditions of the film after biaxial stretching. From the viewpoint of heat resistance and film quality, the heat treatment temperature after biaxial stretching is preferably 200 ° C to 240 ° C, more preferably 210 ° C to 230 ° C. In addition, the heat processing temperature of a polyester film is calculated | required from the micro endothermic peak resulting from a heat history in the DSC curve when it measures with the temperature increase rate of 20 degree-C / min in nitrogen atmosphere in a differential scanning calorimeter (DSC). it can. Moreover, as preferable heat processing time, Preferably it is 5 to 60 second, More preferably, it is good to carry out for 7 to 30 second. Further, the heat treatment may be performed by relaxing the film in the longitudinal direction and / or the width direction. Further, the heat treatment is preferably performed while relaxing in the longitudinal direction and / or the width direction, since the heat shrinkage stress can be reduced. A preferable relaxation rate (relaxation rate) at the time of heat treatment is 3% or more. From the viewpoint of dimensional stability and productivity, 3% to 10% is preferable, and 3% to 7% is most preferable. preferable.

  Also, a method of heat treatment under two or more conditions is very preferable. After heat treatment at a high temperature of 200 ° C. to 240 ° C., the heat shrinkage rate can be further reduced by performing heat treatment at a temperature lower than the heat treatment temperature while relaxing in the longitudinal direction and / or the width direction. The heat treatment temperature in the second stage at this time is preferably 120 ° C. to 180 ° C., more preferably 150 ° C. to 180 ° C.

  Moreover, in the heat treatment process of the film, a method of performing the heat treatment process after lowering the film to a glass transition point (Tg) or lower once through the cooling process after the transverse stretching process is particularly preferable. By lowering the film below the glass transition point (Tg), the heat shrinkage stress of the film is relaxed, and then the heat shrinkage stress can be adjusted to the above range by performing heat treatment.

The polyester film for battery exterior according to the present invention needs to have a diiodomethane contact angle of at least 22 ° on at least one side from the viewpoint of adhesion to an aluminum foil. Thereby, the improvement of the outstanding adhesiveness and adhesive strength can be aimed at. The method for setting the diiodomethane contact angle to 22 ° or more is not particularly limited, but in terms of productivity and recoverability, a method of subjecting the film surface to corona discharge treatment can be preferably used. By performing the treatment at an intensity of min / m ² , preferably 10 to 65 W · min / m ² , the surface free energy can be made a preferable range. Here, E value is corona discharge treatment intensity, applied voltage (Vp, unit: V), applied current (Ip, unit: A), processing speed (S, unit: m / min), processing width (Wt). , Unit: m), and expressed as E = Vp × Ip / S × Wt.

  A method of laminating a resin layer on the surface of the polyester film layer is also used. The method of providing the resin layer is not particularly limited, but the resin is coated on the film surface (composite melt extrusion method, hot melt coating method, solvent other than water, in-line, off-line coating from water-soluble and / or water-dispersible resin) And the like, and the same composition or surface lamination method of blended products thereof. Among them, a coating material containing a resin is applied and dried on one surface of a film (polyester film layer) before orientation crystallization is completed, and is stretched in at least one direction and heat-treated to complete orientation crystallization. The in-line coating method is preferable for uniform film formation and industrial use. When the resin layer is provided by coating, the resin has at least one selected from polyurethane resins, polyester resins, polyester acrylate resins, polyurethane acrylate resins, polyepoxy acrylate resins, and titanate compounds. It is preferable that From the viewpoint of adhesion, it is preferable to use a polyester resin, an acrylic resin, or a urethane resin. When the polyester resin is used as an aqueous coating liquid, a water-soluble or water-dispersible polyester resin is used. For such water-solubilization or water-dispersion, a compound containing a sulfonate group or a carboxyl group is used. It is preferable to copolymerize a compound containing an acid base. When an acrylic resin is used as an aqueous coating liquid, it needs to be dissolved or dispersed in water, and as an emulsifier, a surfactant (for example, a polyether compound, etc. can be mentioned, but it is not limited. Not.) May be used.

  In the resin layer used in the present invention, various crosslinking agents can be used in combination with the resin in order to further improve the adhesion. As the crosslinking agent resin, melamine-based, epoxy-based, and oxazoline-based resins are generally used.

  The resin layer of the present invention may contain particles. Examples of the particles to be contained include inorganic particles and organic particles, but inorganic particles are more preferable because easy slipping and blocking resistance are improved. As the inorganic particles, silica, alumina, kaolin, talc, mica, calcium carbonate, titanium and the like can be used.

  From the viewpoint of developing easy adhesion, it is preferable that at least one outermost layer of the polyester film for battery exterior is a resin layer.

The polyester film for battery exterior of the present invention has a 5% elongation stress (F5 value) and a 10% elongation stress in the longitudinal direction and the width direction of the film at 25 ° C. from the viewpoint of molding followability after laminating the aluminum foil. (F10 value) must satisfy the following formulas (I) and (II), respectively.
1.5 ≧ F10 _MD / F5 _MD ≧ 1 (I)
1.5 ≧ F10 _TD / F5 _TD ≧ 1 (II)
Here, F10 _MD , F5 _MD , F10 _TD , and F5 _TD are tensile tests at a strain rate of 300 mm / min under the conditions of 25 ° C. and 63% Rh on a film sample cut into a rectangular shape having a test length of 50 mm. The stress at the time of performing 10% elongation in the longitudinal direction, the stress at the time of 5% elongation, and the stress at the time of 10% elongation in the width direction, and the stress at the time of 5% elongation, respectively, are expressed in MPa. Here, the longitudinal direction and the width direction of the film are any one direction (0 °) of the film, 15 °, 30 °, 45 °, 60 °, 75 °, 90 °, 105 °, 120 from the direction. The refractive index in the directions of °, 135 °, 150 °, and 165 ° was measured, the direction having the highest refractive index was defined as the width direction, and the direction orthogonal to the width direction was defined as the longitudinal direction.
In the present invention, the other physical properties are defined in the longitudinal direction and the width direction as described above.

  Satisfying the expressions (I) and (II) means that the stress does not drop greatly during the initial stage of deformation, that is, it does not show a clear yield point. In order for a polyester film to exhibit such physical properties, it is important that the molecular chain orientation is uniform and highly advanced, and by forming such a structure, it is difficult to stretch the film. Deformation and non-uniform deformation hardly occur, and the film does not show a clear yield point.

  The present inventors have found that, at the initial stage of deformation, by not showing a clear yield point, the molding followability when the aluminum foil is molded after lamination is significantly improved. Although this mechanism has not been clearly clarified, the present inventors presume as follows. Since aluminum foil is originally a material that is very difficult to deform, it deforms following the film, but there is a clear yield point when the film is deformed, that is, if there is an inflection point where the stress changes greatly, the aluminum foil It is not easy to follow the stress change and breaks easily. For this reason, it is presumed that the aluminum foil can be deformed following the deformation of the film by satisfying the expressions (I) and (II) and not showing a clear yield point at the initial stage of deformation.

When F10 _MD / F5 _MD and F10 _TD / F5 _TD are less than 1, molding followability after laminating aluminum foil is inferior, while F10 _MD / F5 _MD and F10 _TD / F5 _TD are 1.5. When trying to make it larger, the orientation of the molecular chain needs to be advanced to a very high degree. Therefore, even if there are a few foreign substances and defects, the film is torn during the film formation, and the film forming property is remarkably lowered.

The polyester film for battery exterior according to the present invention has a 5% elongation stress (F5 value) in the longitudinal direction and the width direction of the film at 25 ° C. at a temperature of 25 ° C. % Elongation stress (F10 value) preferably satisfies the following formulas (I) ′ and (II) ′, and most preferably satisfies the formulas (I) ″ and (II) ″.
1.2 ≧ F10 _MD / F5 _MD ≧ 1.05 (I) ′
1.2 ≧ F10 _TD / F5 _TD ≧ 1.05 (II) ′
1.2 ≧ F10 _MD / F5 _MD ≧ 1.1 (I) ”
1.2 ≧ F10 _TD / F5 _TD ≧ 1.1 (II) ”
In the battery exterior polyester film of the present invention, as a method of satisfying the formulas (I) and (II), 90 mol% or more of glycol units are preferably structural units derived from ethylene glycol, more preferably 95 mol% or more. It is. Further, 90 mol% or more of the dicarboxylic acid units are preferably structural units derived from terephthalic acid, and more preferably 95 mol% or more. By setting it as the above compositions, since it becomes a composition close | similar to a homopolyethylene terephthalate, since the component which inhibits the uniform orientation of a molecular chain decreases, it is preferable.

  Moreover, in the process of forming the film of the present invention, an unstretched sheet is obtained by discharging and extruding into a sheet from a T-die on a cooling drum. At that time, a wire electrode, a tape electrode or a needle electrode is obtained. The sheet-like polymer is brought into close contact with the cooling drum by a method of applying electrostatic force to the cooling drum, a casting method in which a water film is provided between the cooling drum and the extruded polymer sheet, or a combination of these methods. And cooled and solidified to obtain an unstretched film.

  In the casting process, the film for battery exterior according to the present invention preferably lowers the temperature of the cooling drum in order to achieve the formulas (I) and (II). Specifically, it is preferable to control the casting temperature to 0 to 10 ° C, more preferably 0 to 5 ° C. Furthermore, when adopting a method in which electrostatic application is applied to the cooling drum, the voltage is preferably 10 kV to 20 kV, and more preferably 12 kV to 18 kV. Moreover, it is preferable to set it as 30 mm-50 mm between a nozzle | lip lip and a cooling drum. By adopting the conditions as described above in the casting process, it is possible to prevent the formation of an ordered structure in the unstretched film. Therefore, in the stretching process after the casting process, the molecular chains are more uniformly and more highly advanced. Since it can be oriented, it is possible to satisfy the formulas (I) and (II).

  Further, the polyester film for battery exterior of the present invention is obtained by stretching the unstretched film obtained in the casting step in the longitudinal direction and then stretching in the width direction, or stretching in the longitudinal direction after stretching in the width direction. Although it can be obtained by stretching by a biaxial stretching method or by a simultaneous biaxial stretching method that stretches the film in the longitudinal direction and the width direction almost simultaneously, as the stretching ratio in such a stretching method, Preferably, 3.5 to 4.5 times, more preferably 3.6 to 4.2 times, and particularly preferably 3.7 to 4 times are employed in the direction of. In addition, the stretching temperature is preferably low enough to prevent stretching unevenness. For example, when a sequential biaxial stretching method in which stretching is performed in the width direction after stretching in the longitudinal direction is employed, the preheating temperature in the longitudinal direction is The temperature is preferably 50 to 60 ° C., the stretching temperature is preferably 80 to 90 ° C., the preheating temperature in the width direction is preferably 70 to 80 ° C., and the stretching temperature is preferably 90 to 100 ° C. Moreover, you may perform extending | stretching in multiple times with respect to each direction.

  In this stretching process, the film for battery outer packaging of the present invention is stretched in the longitudinal direction using a heating roll in the longitudinal direction using the difference in speed of the roll from the viewpoint of productivity, and then stretched in the width direction by a tenter-type lateral stretching machine. The sequential biaxial stretching method is preferably used. In order to achieve the formulas (I) and (II), the preheating temperature is as low as 50 to 60 ° C. and the stretching temperature is 80 to 90 ° C. in the longitudinal stretching. It is preferable to control the temperature of the film, and it is preferable that the film is rapidly cooled using a cooling roll after stretching. At this time, it is preferable that the temperature of a cooling roll is low temperature, specifically 0-15 degreeC, More preferably, it is preferable to set it as 5-10 degreeC. In order to further increase the cooling efficiency, the cooling roll preferably has 6 or more rolls having a roll diameter of 150 mm or more, preferably 170 mm or more, preferably 8 or more. By using the above technique, by performing rapid cooling at once after stretching in the longitudinal direction, it is possible to suppress the formation of an ordered structure of amorphous parts that are not oriented and crystallized, so at the time of stretching in the width direction after stretching in the longitudinal direction, Since the orientation of the molecular chains proceeds more uniformly and highly, it becomes possible to satisfy the formulas (I) and (II).

  In addition, in order to achieve the formulas (I) and (II), the battery exterior film of the present invention has a preheating temperature as low as 70 to 80 ° C. and a stretching temperature as 90 to 100 ° C. when stretching in the width direction. It is preferable to do. Further, in order to make the molecular chain orientation proceed more uniformly, a method of increasing the number of sections in each step of the preheating step and the stretching step in the tenter and controlling the temperature uniformly is preferable. Specifically, a method of controlling the temperature of each section by preferably providing three or more rooms in the preheating process and three or more rooms in the stretching process and attaching a shielding plate and a fan for blocking hot air in each section is preferably employed. Furthermore, the length of one section is preferably 4000 mm or less. By performing stretching in the width direction using the tenter as described above, the orientation of the molecular chains proceeds uniformly and further to a high degree, so that the formulas (I) and (II) can be satisfied.

  Moreover, it is preferable that the film for battery exterior of this invention performs heat processing of a film after extending | stretching to the width direction. The heat treatment can be performed by any conventionally known method such as in an oven or on a heated roll. It is preferable that heat processing shall be 180 degreeC-240 degreeC. The heat treatment time can be arbitrarily set within a range not deteriorating the characteristics, and is preferably 10 to 60 seconds, more preferably 15 to 30 seconds. Further, the heat treatment may be performed by relaxing the film in the longitudinal direction and / or the width direction.

  The polyester film for battery exterior of the present invention preferably has a dynamic friction coefficient μd of 0.3 to 0.8 from the viewpoint of moldability. The battery exterior structure using the battery exterior polyester fill of the present invention is formed by male-female press molding, but the sliding with the press mold is controlled by setting the dynamic friction coefficient μd to 0.3 to 0.8. Therefore, it becomes possible to mold smoothly. More preferably, it is 0.3 to 0.7, and most preferably 0.3 to 0.6. In the present invention, the dynamic friction coefficient refers to a dynamic friction coefficient between an arbitrary surface of the film and a surface opposite to the surface.

Examples of the method of setting the dynamic friction coefficient μd of the polyester film for battery exterior of the present invention include a method of incorporating particles in the film. Although it does not specifically limit as particle | grains to contain, An internal particle, an inorganic particle, or an organic particle with an average particle diameter of 0.01-5 micrometers is mentioned, It is preferable to contain 1.5-5 weight% by making the whole film into 100 weight%. . The average particle diameter of the particles used is preferably 0.05 to 3 μm, more preferably 0.1 to 2.5 μm. Here, the average particle diameter refers to the average particle diameter, which is the number average diameter D obtained by observing the cross section of the film and obtained by the following formula. D = ΣDi / N (Di: equivalent circle diameter of particles, N: number of particles)
Examples of the internal particle precipitation method include the techniques described in JP-A-48-61556, JP-A-51-12860, JP-A-53-41355, JP-A-54-90397, and the like. Can be adopted. In addition, other particles such as JP-B-55-20496 and JP-A-59-204617 can be used in combination. Examples of inorganic particles that can be used include wet and dry silica, colloidal silica, aluminum silicate, titanium oxide, calcium carbonate, calcium phosphate, barium sulfate, aluminum oxide, mica, kaolin, and clay. Moreover, as organic particles, particles containing styrene, silicone, acrylic acids, methacrylic acids, polyesters, divinyl compounds and the like as constituent components can be used. Among them, it is preferable to use inorganic particles such as wet and dry silica and alumina, and particles containing styrene, silicone, acrylic acid, methacrylic acid, polyester, divinylbenzene and the like as constituent components. Furthermore, these internal particles, inorganic particles, and organic particles may be used in combination of two or more.

  The polyester film for battery exterior of the present invention is preferably used as a laminate for battery exterior by laminating an aluminum foil having a thickness of 10 μm or more and 60 μm or less on at least one surface. As a material of the aluminum foil, for example, a pure aluminum-based or aluminum-iron-based alloy material can be used. By making the thickness of the aluminum foil 10 μm or more and 60 μm or less, it becomes possible to achieve both mold followability and barrier properties of oxygen and moisture, which is preferable. More preferably, the thickness is 20 μm or more and 50 μm or less, and most preferably 25 μm or more and 45 μm or less. The aluminum foil may be subjected to a pretreatment such as an undercoat such as a silane coupling agent or a titanium coupling agent, or a corona discharge treatment for the purpose of improving the adhesion performance of the laminate. In addition, at least one side of the polyester film for battery exterior of the present invention is subjected to corona discharge treatment, or a resin layer is provided, and an aluminum foil is laminated on the side on which the corona treatment surface or the resin layer is provided. preferable.

  The method for laminating the polyester film for battery exterior and the aluminum foil of the present invention is not particularly limited, but dry lamination using an adhesive is preferably used from the viewpoint of adhesion. The adhesive used may be a thermosetting type or a thermoplastic type, but a thermosetting type is preferred. For example, polyurethane resins, polyester resins, polyvinyl chloride resins, styrene-butadiene copolymers, acrylonitrile-butadiene copolymers, methyl methacrylate-butadiene copolymers, rubber resins such as chloroprene and polybutadiene, poly From acrylic ester resins, polyvinylidene chloride resins, polybutadiene, or carboxyl modified products of these resins, epoxy resins, cellulose derivatives, ethylene vinyl acetate copolymers, polyethylene oxide, acrylic resins, lignin derivatives, etc. The adhesive which becomes is mentioned. From the viewpoint of adhesion between the polyester film and the polyolefin film, an adhesive composed of a polyurethane resin or a polyester resin is preferable.

  In the laminate for battery exterior of the present invention, the peel strength between the polyester film for battery exterior and the aluminum foil is preferably 2 N / 15 mm or more, more preferably 2.1 N / 15 mm, most preferably 2.2 N. / 15 mm. In the case of 2N / 15 mm or less, delamination of the battery exterior polyester film and the aluminum foil occurs at the time of molding or sealing, which is not preferable. The method for setting the peel strength in the above range is as described above.

  In the battery exterior laminate of the present invention, a sealant film is preferably further laminated on the aluminum foil. Examples of sealant films include low density polyethylene, medium density polyethylene, high density polyethylene, linear low density polyethylene, ethylene resins such as ethylene-butene copolymer, homopolypropylene, ethylene-propylene copolymer, ethylene-propylene-butene. A simple substance or a mixture of propylene resins such as a copolymer can be appropriately selected and used.

  In order to improve the adhesion between the aluminum foil and the sealant film, a method in which a modified polyolefin resin is interposed between the aluminum foil and the sealant film is also preferably used. Here, the modified polyolefin resin refers to a polyolefin resin containing one or more polar groups at least one of one end, both ends, and the inside of the polyolefin resin. Here, the polar group is a functional group containing an atom having a large electronegativity such as an oxygen atom or a nitrogen atom. Specifically, a functional group such as an amide group, a carboxyl group, or a hydroxyl group, and these functional groups It is a substituent containing.

  Such a modified polyolefin resin is preferably a polyolefin resin modified with an unsaturated dicarboxylic acid or modified by oxidative decomposition of the resin, and more preferably a modified polyolefin resin modified with an unsaturated dicarboxylic acid. Specifically, low density polyethylene, medium density polyethylene, high density polyethylene, linear low density polyethylene, ethylene-α / olefin copolymer polymerized using metallocene catalyst, polypropylene, ethylene-propylene copolymer, methylpentene A modified polyolefin resin obtained by modifying a polyolefin resin such as a random copolymer or block copolymer composed of a polymer or other α-olefin monomer with an unsaturated dicarboxylic acid such as acrylic acid, methacrylic acid, maleic anhydride, or fumaric acid. It is preferable in terms of interlayer adhesion with the polyester layer (A layer). As the unsaturated dicarboxylic acid, maleic anhydride is particularly preferable, that is, a modified polyolefin resin obtained by modifying a polyolefin resin with maleic anhydride is particularly preferable.

  Examples of such modified polyolefin resin with unsaturated dicarboxylic acid include “Yumex” manufactured by Sanyo Kasei, “Admer” manufactured by Mitsui Chemicals, “Modic” manufactured by Mitsubishi Chemical, “Orebak” manufactured by Arkema, “Rotada, manufactured by Toyo Kasei Examples of the modified polyolefin resin modified by oxidative decomposition of the resin include “Viscol” and “Sunwax” manufactured by Sanyo Chemical.

  The characteristics are measured and evaluated by the following methods.

(1) Film Thickness A film sample was cut into a size of 100 mm × 100 mm using an SD-type lever-type sample cutting machine SDL-100 (manufactured by Dumbbell Co., Ltd.), 10 sheets were prepared and calibrated digital micrometer (M-30, manufactured by Sony Precision Technology Co., Ltd.), the thickness of 8 points per sheet was measured and averaged to calculate the thickness.

(2) Composition of polyester film layer The polyester film layer was dissolved in hexafluoroisopropanol (HFIP), and the content of each monomer residue and by-product diethylene glycol was quantified using ¹ H-NMR and ¹³ C-NMR.

(3) Birefringence (Δn), plane orientation coefficient (fn)
Using a sodium D line (wavelength 589 nm) as a light source, using methylene iodide as a mounting solution, and using an Abbe refractometer at 25 ° C., MD, TD, and refractive index in the thickness direction of the biaxially oriented polyester film for packaging (respectively, _nMD , _nTD , _nZD ). The plane orientation coefficient (fn) and the birefringence index (Δn) were calculated from the obtained refractive index by the following formula. In addition, the measurement was performed on the surface side in close contact with the cooling drum after discharging from the T-die at the time of film formation, and the average of measured values at arbitrary three locations was evaluated.
Δn = (n _MD −n _TD ) × 1000
fn = (n _MD + n _TD ) / 2-n _ZD
(4) Heat shrinkage stress at 200 ° C. The film is cut into a strip shape having a width of 10 mm, both ends are fixed to a jig so that the sample length is 100 mm, and one side is connected to a load cell. The sample was placed in an oven and adjusted so that the initial stress of the film at 45 ° C. was 30 g / 10 mm. Thereafter, the temperature was increased at a rate of 10 ° C. per minute, and the stress at 200 ° C. was measured.

(5) F10 _MD / F5 _MD , F10 _TD / F5 _TD
Under the conditions of 25 ° C. and 63% Rh, the film was cut into a rectangular shape having a length of 150 mm × width of 10 mm in the longitudinal direction and the width direction to obtain a sample. Using a tensile tester (Orientec Tensilon UCT-100), a tensile test was conducted in the longitudinal direction and the width direction of the film with a crosshead speed of 300 mm / min, a width of 10 mm, and a sample length of 50 mm. stress _F10 MD, 5% elongation stress during the _{F5 MD} of, also, and the stress at 10% elongation in the width direction and _F10 TD, 5% elongation stress during the _{F5 TD.} Each measurement was performed 5 times, and the average was used.

(6) Coefficient of dynamic friction μd
According to JIS K7125 (1999), the dynamic friction coefficient (μd) was measured using a slip tester under the following conditions. In addition, the measurement was performed by bringing an arbitrary surface of the film into contact with the surface opposite to the surface.
Sample size: 75 mm (width) x 100 mm (length)
Sliding speed: 150 mm / min Load: 1.96 N.

(7) Diiodomethane contact angle Static contact with the film surface using a contact angle meter (Kyowa Interface Science Co., Ltd. CA-D type) using diiodomethane as a measurement solution under the conditions of 25 ° C. and 63% Rh. I asked for a corner. The measurement was performed 5 times, and the average contact angle (θ) was adopted.

(8) The film having an average particle diameter is cut, the cut surface of the film is observed at a magnification of 10,000 using a transmission electron microscope (TEM H7100, manufactured by Hitachi, Ltd.), and the image of the particles is processed with an image analyzer. The number average diameter D obtained by performing the following numerical processing with the number of particles of 1000 with different observation locations was defined as the average particle size.
D = ΣDi / N (Di: equivalent circle diameter of particles, N: number of particles)
(9) Peel strength between polyester film and aluminum foil The polyester film of the present invention and aluminum foil (thickness 40 μm) were urethane adhesive (AD-502, CAT10L, Toyo Morton Co., Ltd., 15: 1.5: 25 (mass ratio)) was dry laminated by a conventional method to prepare a laminate for battery exterior. After standing at 40 ° C. for 48 hours, it is cut into strips of 150 mm length × 15 mm width, gripped so that the aluminum foil is in a straight line and the polyester film is bent at an acute angle, and 180 ° peel test 1 using an Instron type tensile tester (Tensilon UCT-100 manufactured by Orientec Co., Ltd.) at 25 ° C. and 50% RH atmosphere at a peeling speed of 300 mm / min in the direction of the arrow in FIG. Measurements were made. The average value of the strength between the measurement lengths of 50 mm and 100 mm was taken as the peel strength.

(10) Molding followability of battery exterior component The polyester film / aluminum foil battery exterior component obtained in the same manner as in (9) is coated with maleic acid-modified polypropylene resin and polypropylene as a sealant. A two-layer co-extruded film (maleic acid-modified polypropylene resin layer: 15 μm, polypropylene resin layer: 30 μm) was co-extruded with the maleic acid-modified polypropylene resin layer on the aluminum foil side, and heat-pressed using a laminator ( 120 ° C., 0.3 MPa, 2 m / min) to form a battery exterior structure. The obtained structure was cut into a size of 200 mm × 200 mm, and a gold consisting of a 150 mm × 150 mm rectangular male mold (R: 2 mm) and a female mold (R: 2 mm) with a clearance of 0.5 mm between the male mold. Using the mold, the battery exterior component was set on the female mold so that the sealant side was on the male mold side, and press molding (pressurization: 0.1 MPa) was performed to obtain a molded body for battery exterior. The obtained molded body for battery exterior was evaluated according to the following criteria.
A: Molded at 10 mm or more (no damage)
○: Breakage occurred at 7 m or more and less than 10 mm Δ: Breakage occurred at 5 mm or more and less than 7 mm x: Breakage occurred at less than 5 mm

(11) Delamination resistance characteristics of battery exterior component Two battery exterior molded bodies obtained in the same manner as in (10) were prepared, the respective sealant sides were overlapped, and thermocompression bonding (200 ° C, 0.3 MPa, 2 m / min). The thermocompression bonding was performed so that the end portion where the molding of each molded article for battery exterior rises was sealed. In the molded article for battery exterior after sealing, the polyester film and aluminum foil were visually checked for delamination.
○: No delamination occurred ×: Delamination occurred

  Hereinafter, the present invention will be described in detail by way of examples. The specific example of manufacture of the polyester film for battery exteriors of this invention is described below.

(Manufacture of polyester)
The polyester resin used for film formation was prepared as follows.

(Polyester A)
0.04 parts by mass of manganese acetate is added to a mixture of 100 parts by mass of dimethyl terephthalate and 70 parts by mass of ethylene glycol, the temperature is gradually raised, and finally transesterification is performed while distilling methanol at 220 ° C. It was. Next, 0.025 parts by mass of 85% phosphoric acid aqueous solution and 0.02 parts by mass of germanium dioxide were added, and a polycondensation reaction was performed at 290 ° C. under a reduced pressure of 1 hPa, the intrinsic viscosity was 0.65, and by-produced diethylene glycol 1 A mol% copolymerized polyethylene terephthalate resin was obtained.

(Particle Master)
Polyethylene terephthalate particle master (intrinsic viscosity 0.65) containing polyester A with aggregated silica particles having an average particle diameter of 1.9 μm at a particle concentration of 2 mass%.

(Coating agent A)
Acrylic resin having a copolymer composition of methyl methacrylate / ethyl acrylate / acrylic acid / N-methylolacrylamide = 63/35/1/1% by weight: 3.00% by mass
・ Melamine crosslinking agent: 0.75% by mass
Colloidal silica particles (average particle size: 80 nm): 0.15% by mass
・ Hexanol: 0.26% by mass
・ Butyl cellosolve: 0.18% by mass
・ Water: 95.66 mass%
(Coating agent B)
Polyester having a copolymer composition of terephthalic acid / isophthalic acid / trimellitic acid / sebacic acid / ethylene glycol / neopentyl glycol / 1,4-butanediol = 28/9/10/3/15/18/17 mol% Resin: 6.0% by mass
・ Melamine crosslinking agent: 0.3% by mass
Colloidal silica particles (average particle size: 80 nm): 0.06% by mass
-Butyl cellosolve: 1.36% by mass
・ Water: 92.28% by mass
Example 1
Each polyester resin is dried in a vacuum dryer at 180 ° C. for 4 hours, after sufficiently removing moisture, supplied to the single screw extruder at the composition shown in the table, melted at 280 ° C., passed through a filter and gear pump, Then, the amount of extrusion was leveled, and the sheet was discharged from a T-die onto a cooling drum whose temperature was controlled at 4 ° C. to obtain an unstretched film. At that time, the distance between the lip of the T die and the cooling drum was set to 35 mm, and a wire-like electrode having a diameter of 0.1 mm was used for electrostatic application at a voltage of 14 kV to adhere the cooling drum.

  Next, before stretching in the longitudinal direction, the film temperature is increased with a heated roll, the preheating temperature is 105 ° C., the stretching temperature is 120 ° C. and the film is stretched 3.95 times in the longitudinal direction, and the roll surface temperature is immediately increased to 30 ° C. Rapid cooling was performed using the set eight cooling rolls.

  Next, preheating is performed at 112 ° C. in a tenter-type transverse stretching machine, and the film is stretched 3.65 times in the width direction at 110 ° C., and then the film is lowered to 70 ° C. so as to be equal to or lower than the glass transition point (Tg). Then, heat treatment was performed at 215 ° C. for 7 seconds while relaxing 5% in the width direction. The film coming out of the tenter was subjected to corona discharge treatment on the upper surface of the film with an E value of 30 while being wound with a winder to obtain a biaxially oriented polyester film having a film thickness of 25 μm. The E value is the corona discharge treatment intensity, which is a function of the applied voltage (Vp), the applied current (Ip), the treatment speed (S), and the treatment width (Wt), and E = (Vp × Ip) / ( S × Wt).

(Example 2)
A biaxially oriented polyester film having a film thickness of 25 μm was obtained in the same manner as in Example 1 except that the draw ratio in the longitudinal direction was 3.85 times and the E value of the corona discharge treatment was 20.

(Example 3)
A biaxially oriented polyester film having a film thickness of 25 μm was obtained in the same manner as in Example 2 except that the heat treatment temperature in the tenter was 225 ° C. and the E value of the corona discharge treatment was 60.

Example 4
Each polyester resin is dried in a vacuum dryer at 180 ° C. for 4 hours, after sufficiently removing moisture, supplied to the single screw extruder at the composition shown in the table, melted at 280 ° C., passed through a filter and gear pump, Then, the amount of extrusion was leveled, and the sheet was discharged from a T-die onto a cooling drum whose temperature was controlled at 4 ° C. to obtain an unstretched film. At that time, the distance between the lip of the T die and the cooling drum was set to 35 mm, and a wire-like electrode having a diameter of 0.1 mm was used for electrostatic application at a voltage of 14 kV to adhere the cooling drum.

  Next, before stretching in the longitudinal direction, the film temperature is increased with a heated roll, the preheating temperature is 105 ° C., the stretching temperature is 120 ° C. and the film is stretched 3.95 times in the longitudinal direction, and the roll surface temperature is immediately increased to 30 ° C. Rapid cooling was performed using the set eight cooling rolls. Example 1 except that this uniaxially stretched film was subjected to corona discharge treatment in the air, and the coating surface A was mixed while ultrasonically dispersing as a resin layer on the treated surface and uniformly applied with a # 6 metering bar. In the same manner as described above, a 25 μm-thick biaxially oriented polyester film in which a 0.2 μm resin layer was laminated on one side was obtained.

(Example 5)
A biaxially oriented polyester film having a thickness of 25 μm in which a 0.2 μm resin layer was laminated on one side was obtained in the same manner as in Example 4 except that the coating material was changed to the coating material B.

(Example 6)
A biaxially oriented polyester film having a film thickness of 25 μm was obtained in the same manner as in Example 1 except that the heat treatment temperature in the tenter was 200 ° C.

(Example 7)
A biaxially oriented polyester film having a film thickness of 25 μm was obtained in the same manner as in Example 1 except that the draw ratio in the longitudinal direction was 3.50 times and the heat treatment temperature in the tenter was 225 ° C.

EG: ethylene glycol DEG: diethylene glycol TPA: terephthalic acid (Comparative Example 1)
A biaxially oriented polyester film having a film thickness of 25 μm was obtained in the same manner as in Example 1 except that the corona discharge treatment was not performed.

(Comparative Example 2)
A biaxially oriented polyester film having a film thickness of 25 μm was obtained in the same manner as in Example 1 except that the E value of the corona discharge treatment was set to 10.

(Comparative Example 3)
A biaxially oriented polyester film having a film thickness of 25 μm was obtained in the same manner as in Example 1 except that the draw ratio in the longitudinal direction and the width direction were 3.40 times and the heat treatment temperature in the tenter was 225 ° C.

(Comparative Example 4)
A biaxially oriented polyester film having a film thickness of 25 μm was obtained in the same manner as in Example 1 except that the heat treatment temperature in the tenter was 180 ° C.

(Comparative Example 5)
A biaxially oriented polyester film having a film thickness of 25 μm was obtained in the same manner as in Example 1 except that the composition was changed as shown in the table.

  Since the polyester film for battery exterior of the present invention has good delamination resistance after the aluminum foil is laminated, it can be suitably used for a battery exterior structure.

Claims (7)

A polyester film for battery exterior, wherein the heat shrinkage stress Y _MD in the MD direction at 200 ° C. and the heat yield stress Y _{TD in} the TD direction satisfy the following formulas (i) and (ii), and the contact angle of diiodomethane on at least one side is 22 ° or more. .
50 ≦ Y _MD ≦ 120 g / 10 mm (i)
5 ≦ Y _TD ≦ 80 g / 10 mm (ii) It has at least a polyester film layer and a resin layer, and at least one outermost layer is a resin layer, and the resin layer is a polyurethane resin, a polyester resin, a polyester acrylate resin, a polyurethane acrylate resin, or a polyepoxy acrylate resin. The polyester film for battery exteriors of Claim 1 which has at least 1 type chosen from the titanate type compound. The 5% elongation stress (F5 value) and 10% elongation stress (F10 value) in the longitudinal direction (MD) and width direction (TD) of the film at 25 ° C. are the following (I) and (II), respectively. The polyester film for battery exteriors according to claim 1 or 2 satisfying a formula.
1.5 ≧ F10 _MD / F5 _MD ≧ 1 (I)
1.5 ≧ F10 _TD / F5 _TD ≧ 1 (II) The polyester film for battery exterior according to any one of claims 1 to 3, wherein a dynamic friction coefficient μd of at least one surface is 0.3 to 0.8. 5. The particle according to claim 1, wherein the particle has an average particle diameter of 0.01 to 5 μm, and the content of the particle is 1.5 to 5% by weight with respect to the entire film. The polyester film for battery exterior as described. It is a laminated body formed by laminating an aluminum foil having a thickness of 10 µm or more and 60 µm or less on at least one surface of the battery exterior polyester film according to any one of claims 1 to 5, wherein the polyester film and the aluminum foil are between the polyester film and the aluminum foil. A laminate for battery exterior having a peel strength of 2 N / 15 mm or more. A battery exterior structure using the battery exterior laminate according to claim 6.