Classifications

• • B—PERFORMING OPERATIONS; TRANSPORTING
  • B29—WORKING OF PLASTICS; WORKING OF SUBSTANCES IN A PLASTIC STATE IN GENERAL
  • B29C—SHAPING OR JOINING OF PLASTICS; SHAPING OF MATERIAL IN A PLASTIC STATE, NOT OTHERWISE PROVIDED FOR; AFTER-TREATMENT OF THE SHAPED PRODUCTS, e.g. REPAIRING
  • B29C55/00—Shaping by stretching, e.g. drawing through a die; Apparatus therefor
  • B29C55/02—Shaping by stretching, e.g. drawing through a die; Apparatus therefor of plates or sheets
  • B29C55/10—Shaping by stretching, e.g. drawing through a die; Apparatus therefor of plates or sheets multiaxial
  • B29C55/12—Shaping by stretching, e.g. drawing through a die; Apparatus therefor of plates or sheets multiaxial biaxial
• • C—CHEMISTRY; METALLURGY
  • C08—ORGANIC MACROMOLECULAR COMPOUNDS; THEIR PREPARATION OR CHEMICAL WORKING-UP; COMPOSITIONS BASED THEREON
  • C08J—WORKING-UP; GENERAL PROCESSES OF COMPOUNDING; AFTER-TREATMENT NOT COVERED BY SUBCLASSES C08B, C08C, C08F, C08G or C08H
  • C08J5/00—Manufacture of articles or shaped materials containing macromolecular substances
  • C08J5/18—Manufacture of films or sheets
• • B—PERFORMING OPERATIONS; TRANSPORTING
  • B29—WORKING OF PLASTICS; WORKING OF SUBSTANCES IN A PLASTIC STATE IN GENERAL
  • B29K—INDEXING SCHEME ASSOCIATED WITH SUBCLASSES B29B, B29C OR B29D, RELATING TO MOULDING MATERIALS OR TO MATERIALS FOR MOULDS, REINFORCEMENTS, FILLERS OR PREFORMED PARTS, e.g. INSERTS
  • B29K2067/00—Use of polyesters or derivatives thereof, as moulding material

Definitions

• Polyamide is widely used as the base material for the above-mentioned laminates due to its excellent formability. In addition to formability, moisture resistance, sealing properties, and chemical resistance may also be required, and a structure consisting of, from the outer layer onwards, polyester film/polyamide film/metal foil/sealant film is also being considered.
• Patent Documents 3 and 4 discuss the use of polyester films primarily composed of polybutylene terephthalate, which has good formability, as battery exterior materials.
• Patent Documents 5 to 7 also discuss the use of polyester films containing polybutylene terephthalate as battery exterior materials.
• the present invention aims to provide a polyester film for forming that has good puncture resistance.
• PET/PBT polyethylene terephthalate content to polybutylene terephthalate content
• polyester film for extrusion molding according to any one of [1] to [10] above, wherein the intrinsic viscosity of the polyester film is 0.6 dL/g or more and 0.85 dL/g or less.
• [18] The method for producing a shaping polyester film according to any one of [13] to [17] above, wherein the transverse stretching ratio is 3.5 times or more and 5.5 times or less.
• a laminate comprising the polyester film for molding according to any one of [1] to [12] above and at least one of a resin layer and a metal layer.
• An exterior packaging material comprising the polyester film according to any one of [1] to [12] above or the laminate according to [19] above.
• the packaging material according to [20] above which is a packaging material for a battery.
• a battery comprising the packaging material according to [20] or [21] above.
• the present invention provides a polyester film for extrusion molding that has good puncture resistance.
• the shaping polyester film of the present invention contains polybutylene terephthalate (hereinafter sometimes referred to as "PBT”) and polyethylene terephthalate (hereinafter sometimes referred to as "PET").
• PBT polybutylene terephthalate
• PET polyethylene terephthalate
• the PBT constituting the polyester film is a polycondensate of a dicarboxylic acid component and a diol component, and is a polyester containing terephthalic acid as the dicarboxylic acid component and 1,4-butanediol as the diol component.
• the PBT is mainly composed of terephthalic acid and 1,4-butanediol, and preferably contains 50 mol % or more of terephthalic acid as the dicarboxylic acid component and 50 mol % or more of 1,4-butanediol (BDO) as the diol component.
• the proportion of terephthalic acid in the dicarboxylic acid component of PBT is more preferably 70 mol% or more, even more preferably 90 mol% or more, and most preferably 100 mol%.
• the proportion of 1,4-butanediol in the diol component of PBT is more preferably 70 mol% or more, even more preferably 90 mol% or more, and most preferably 100 mol%. Therefore, homo-PBT is most preferred as PBT.
• the dicarboxylic acids other than terephthalic acid are not particularly limited, and examples include aromatic dicarboxylic acids such as phthalic acid, isophthalic acid, 4,4'-diphenyldicarboxylic acid, 4,4'-diphenyletherdicarboxylic acid, 4,4'-benzophenonedicarboxylic acid, 4,4'-diphenoxyethanedicarboxylic acid, 4,4'-diphenylsulfonedicarboxylic acid, and 2,6-naphthalenedicarboxylic acid; alicyclic dicarboxylic acids such as 1,2-cyclohexanedicarboxylic acid, 1,3-cyclohexanedicarboxylic acid, and 1,4-cyclohexanedicarboxylic acid; and aliphatic dicarboxylic acids such as malonic acid, succinic acid, glutaric acid, adipic acid, pimelic acid, suberic acid, azelaic acid, and
• the diol component other than BDO is not particularly limited, and examples thereof include aliphatic diols such as ethylene glycol, 1,2-propanediol, 1,3-propanediol, 1,5-pentanediol, neopentyl glycol, 1,6-hexanediol, 1,8-octanediol, and dibutylene glycol; alicyclic diols such as 1,2-cyclohexanediol, 1,4-cyclohexanediol, 1,1-cyclohexanedimethylol, and 1,4-cyclohexanedimethylol; and aromatic diols such as xylylene glycol, 4,4'-dihydroxybiphenyl, 2,2-bis(4-hydroxyphenyl)propane, and bis(4-hydroxyphenyl)sulfone.
• aliphatic diols such as ethylene glycol, 1,2-
• PBT can use one or more copolymerization components, such as hydroxycarboxylic acids such as lactic acid, glycolic acid, m-hydroxybenzoic acid, p-hydroxybenzoic acid, 6-hydroxy-2-naphthalenecarboxylic acid, and p- ⁇ -hydroxyethoxybenzoic acid; alkoxycarboxylic acids; monofunctional components such as stearyl alcohol, benzyl alcohol, stearic acid, benzoic acid, t-butylbenzoic acid, and benzoylbenzoic acid; and trifunctional or higher polyfunctional components such as tricarballylic acid, trimellitic acid, trimesic acid, pyromellitic acid, gallic acid, trimethylolethane, trimethylolpropane, glycerol, and pentaerythritol.
• hydroxycarboxylic acids such as lactic acid, glycolic acid, m-hydroxybenzoic acid, p-hydroxybenzoic acid, 6-hydroxy-2-na
• the intrinsic viscosity of PBT is not particularly limited, but is preferably 0.7 dL/g to 1.4 dL/g, more preferably 0.73 dL/g to 1.37 dL/g, even more preferably 0.77 dL/g to 1.33 dL/g, and even more preferably 0.8 dL/g to 1.3 dL/g. Setting the intrinsic viscosity of PBT within the above range facilitates improving the heat resistance, productivity, and film-forming properties of the polyester film.
• the intrinsic viscosity of PBT can be appropriately set within the above range, and may be, but is not limited to, for example, 0.8 dL/g to 1.2 dL/g, 0.8 dL/g to 1.1 dL/g, or 0.8 dL/g to 1 dL/g.
• the intrinsic viscosity refers to the intrinsic viscosity of the mixed polyester.
• the intrinsic viscosity can be measured according to standard methods, for example, using an Uperohde viscometer at 30°C with a phenol:tetrachloroethane (1:1) solvent.
• the PET constituting the present film is a polycondensate of a dicarboxylic acid component and a diol component, and is a polyester containing terephthalic acid as the dicarboxylic acid component and ethylene glycol as the diol component.
• the PET is primarily composed of terephthalic acid and ethylene glycol, and preferably contains 50 mol % or more of terephthalic acid as the dicarboxylic acid component and 50 mol % or more of ethylene glycol as the diol component.
• the proportion of terephthalic acid in the dicarboxylic acid component of PET is more preferably 70 mol% or more, even more preferably 90 mol% or more, and most preferably 100 mol%.
• the proportion of ethylene glycol in the diol component is more preferably 70 mol% or more, even more preferably 90 mol% or more, and most preferably 100 mol%. Therefore, homo-PET is most preferred as PET.
• PET terephthalic acid and ethylene glycol in PET
• the crystallinity of the polyester film is increased, which facilitates an increase in the degree of planar orientation, etc. It also facilitates imparting a certain level of mechanical strength, which in turn facilitates increasing the puncture resistance, Martens hardness, indentation hardness, elastic deformation power, etc.
• dicarboxylic acid other than terephthalic acid there are no particular limitations on the dicarboxylic acid other than terephthalic acid, and examples of dicarboxylic acids other than terephthalic acid are as listed above for PBT.
• the dicarboxylic acid other than terephthalic acid may be used alone or in combination of two or more.
• diol component other than ethylene glycol there are no particular limitations on the diol component other than ethylene glycol, and specific examples include 1,4-butanediol and the diols other than ethylene glycol listed above for PBT.
• one or more of hydroxycarboxylic acids, monofunctional components, trifunctional or higher polyfunctional components, etc. may be used as copolymer components, and specific examples of these are as described above for PBT.
• the intrinsic viscosity of PET is not particularly limited, but is preferably 0.5 dL/g to 1 dL/g, more preferably 0.53 dL/g to 0.96 dL/g, even more preferably 0.57 dL/g to 0.93 dL/g, and even more preferably 0.6 dL/g to 0.9 dL/g. Setting the intrinsic viscosity of PET within the above range facilitates improving the heat resistance, productivity, and film-forming properties of the polyester film.
• the intrinsic viscosity of PET can be set appropriately within the above range, and may be, for example, but not limited to, 0.6 dL/g to 0.8 dL/g, or 0.6 dL/g to 0.75 dL/g.
• the ratio of the polyethylene terephthalate content to the polybutylene terephthalate content is preferably 55/45 or more and 95/5 or less by mass.
• the mass ratio 55/45 or more the mechanical strength of the present polyester film is increased, and the puncture resistance is further improved. Furthermore, the heat resistance is also easily improved.
• the mass ratio 95/5 or less it is easy to ensure elongation and to increase the amount of displacement during puncture, as described below.
• the mass ratio is more preferably 60/40 or more, even more preferably 63/37 or more, even more preferably 65/35 or more, and particularly preferably 72/28 or more, and is more preferably 90/10 or less, even more preferably 85/15 or less, and even more preferably 82/18 or less.
• the polyester film may contain resins other than the above-mentioned PET and PBT, as long as the effects of the present invention are not impaired.
• resins other than the above-mentioned PET and PBT include polyester resins other than PET and PBT, and resins other than polyester resins.
• resins other than polyester resins include polystyrene resins, polyvinyl chloride resins, polyvinylidene chloride resins, chlorinated polyethylene resins, polycarbonate resins, polyamide resins, polyacetal resins, acrylic resins, ethylene-vinyl acetate copolymers, polymethylpentene resins, polyvinyl alcohol resins, cyclic olefin resins, polylactic acid resins, polybutylene succinate resins, polyacrylonitrile resins, polyethylene oxide resins, cellulose resins, polyimide resins, polyurethane resins, polyphenylene sulfide resins, polyphenylene ether resins, polyvinyl acetal resins, polybutadiene resins, polybutene resins, polyamideimide resins, polyamide bismaleimide resins, polyetherimide resins, polyetheretherketone resins, polyetherketone resins, polyethersulfone resins, polyketone resins,
• PBT and PET are preferably the main components.
• the combined amount of PBT and PET is preferably 50% by mass or more, more preferably 70% by mass or more, more preferably 90% by mass or more, and even more preferably 95% by mass or more, based on the total amount of the polyester film.
• the combined amount of PBT and PET There are no particular upper limits on the combined amount of PBT and PET, as long as it is 100% by mass or less. However, from the perspective of incorporating additives, etc., it is preferable that the combined amount be less than 100% by mass, based on the total amount of the polyester film.
• the thickness of the polyester film is not particularly limited as long as it can be formed into a film, but is, for example, in the range of 6 ⁇ m to 90 ⁇ m, preferably 8 ⁇ m to 70 ⁇ m, more preferably 9 ⁇ m to 50 ⁇ m, and even more preferably 10 ⁇ m to 40 ⁇ m.
• the polyester film is preferably a biaxially stretched polyester film. By using a biaxially stretched polyester film, it is easier to achieve a certain degree of planar orientation, as described below, and it is also easier to adjust
• the polyester film may have a single layer structure (single layer film) or a multilayer structure (multilayer film) having two or more layers. In the case of a multilayer structure, it may have a surface layer and a core layer.
• the surface layer is a layer that constitutes one surface of the polyester film
• the core layer is a layer that is disposed inside the surface layer.
• the polyester film may have a surface layer that constitutes the other surface of the polyester film in addition to the surface layer and core layer that constitute one surface.
• the polyester film may have a multilayer structure, which may be a two-layer structure (surface layer/core layer), a three-layer structure (surface layer/core layer/surface layer), or a four-layer or more layer structure, but preferably has a three-layer structure (surface layer/core layer/surface layer).In a four-layer or more layer structure, it is preferable that the core layer has two or more layers.
• each layer may contain PET and PBT, and the ratio of the PET to PBT content in each layer may be as described above. Furthermore, the ratio of the PET to PBT content in some of the layers may be as described above, or the ratio of the PET to PBT content in all of the layers may be as described above. Furthermore, the ratio of the PET to PBT content in the entire multilayer structure may be as described above. Furthermore, each layer may contain a resin other than PET and PBT as described above, and the total content of PET and PBT in each layer may be as described above based on each layer instead of the total amount of the polyester film.
• the core layer may contain PET and PBT, while the surface layer may contain PET but not PBT.
• the material composition (e.g., resin composition) constituting one surface layer may be different from the material composition constituting at least one of the other layers, for example, the material composition constituting the surface layer may be different from the material composition constituting the core layer.
• the contents of PET and PBT in each layer may be adjusted so that the contents at the surface and the central part in the thickness direction of the film are as shown in a preferred embodiment described below.
• each surface layer is preferably 0.2 ⁇ m or more and 10 ⁇ m or less, more preferably 0.4 ⁇ m or more and 7.5 ⁇ m or less, even more preferably 0.8 ⁇ m or more and 6 ⁇ m or less, and even more preferably 1 ⁇ m or more and 4 ⁇ m or less.
• the core layer preferably constitutes the central portion of the polyester film in the thickness direction, and the thickness of the core layer is preferably 65% to 98% of the total thickness of the polyester film, more preferably 70% to 96%, and even more preferably 75% to 94%.
• the thickness of the core layer is preferably 7 ⁇ m or more and 88 ⁇ m or less, more preferably 10 ⁇ m or more and 70 ⁇ m or less, and even more preferably 15 ⁇ m or more and 55 ⁇ m or less.
• the thickness ratio of each surface layer to the core layer is, for example, 1/99 to 40/60, preferably 2/98 to 35/65, more preferably 4/96 to 30/70, and even more preferably 6/94 to 25/75.
• the thickness ratio is preferably 1-20:65-98:1-20, more preferably 2-15:70-96:2-15, and even more preferably 3-12.5:75-94:3-12.5.
• the thickness of the core layer referred to here is the total thickness of the core layers when the core layer is two or more layers.
• the PET content on at least one surface of the polyester film (hereinafter also referred to as “content (A1)”) is greater than the PET content in the central region of the film thickness (hereinafter also referred to as “content (A2)”), based on a mass ratio.
• content (A1) the PET content on at least one surface of the polyester film
• content (A2) the PET content in the central region of the film thickness
• the battery When used as a battery exterior material, the battery is less likely to break even if damaged due to an accident or other reasons. Furthermore, the high Martens hardness and indentation hardness reduce swelling of the battery when heated, preventing contact with the battery casing, for example, outside the battery exterior material. Furthermore, when the polyester film contains both PBT and PET and the PET content (A1) on the surface is greater than the PET content (A2), the elastic deformation power can also be increased. A high value of the elastic deformation power means that a molded article can easily return to its original shape even if it is deformed. This makes it easier for the shape of the molded article to be maintained during molding, resulting in a molded article with excellent design and shape recovery properties and less prone to molding defects.
• the PET content (A1) on one surface may be greater than the PET content (A2) in the central portion of the film, but it is preferable that the PET content (A1) on both surfaces is greater than the PET content (A2).
• the PET content (A1) on at least one surface of the polyester film is, for example, 70% by mass or more, preferably 80% by mass or more, more preferably 85% by mass or more, even more preferably 89% by mass or more, and even more preferably 92% by mass or more.
• the PET content (A1) may be 100% by mass or less. However, when PBT is contained on one surface, for example, it is preferably 99% by mass or less, more preferably 98% by mass or less, and even more preferably 97% by mass or less.
• the PET content (A1) on the surface having a higher PET content than the above-mentioned content (A2) may be at least the lower limit and at most the upper limit as described above.
• the PET content (A1) on both surfaces be at least the lower limit and at most the upper limit as described above.
• the PET content (A2) in the central portion of the polyester film in the thickness direction may be, for example, 50% by mass or more, but is preferably 55% by mass or more, more preferably 60% by mass or more, even more preferably 63% by mass or more, still more preferably 65% by mass or more, and particularly preferably 72% by mass or more, and is preferably 95% by mass or less, more preferably 90% by mass or less, even more preferably 85% by mass or less, and still more preferably 82% by mass or less.
• the PET content (A1) on at least one surface is greater than the PET content (A2) in the central region, but the difference (A1-A2) between the content (A1) and the content (A2) is preferably within a certain range, specifically, 3% by mass or more and 35% by mass or less.
• the content difference (A1-A2) is more preferably 5% by mass or more, even more preferably 8% by mass or more, even more preferably 10% by mass or more, and more preferably 30% by mass or less, even more preferably 25% by mass or less, and even more preferably 22% by mass or less.
• the ratio (B1/A1) of the PBT content (B1) to the PET content (A1) on at least one surface of the polyester film is, by mass, preferably 20/80 or less, more preferably 15/85 or less, even more preferably 10/90 or less, and still more preferably 8/92 or less.
• the content ratio (B1/A1) is at or below the above-mentioned certain value, the Martens hardness, indentation hardness, elastic deformation power, etc. can be easily increased.
• the polyester film may not contain PBT on at least one surface, and therefore the content ratio (B1/A1) may be 0/100 or more.
• the polyester film may contain PBT on at least one surface, and in that case, the content ratio (B1/A1) is preferably 1/99 or more, more preferably 2/98 or more, and even more preferably 3/97 or more, by mass.
• the content ratio (B1/A1) may be equal to or less than the upper limit value and equal to or more than the lower limit value on the surface where the content (A1) is greater than the content (A2), but it is preferable that the content ratio (B1/A1) on both surfaces is equal to or less than the upper limit value and equal to or more than the lower limit value.
• the polyester film has a mass ratio (B2/A2) of the PBT content (B2) to the PET content (A2) in the central portion of the film thickness direction of 5/95 or more and 45/55 or less.
• a mass ratio of 45/55 or less enhances the mechanical strength of the polyester film, making it easier to improve pinhole resistance, breaking strength, and the like, and also to improve heat resistance.
• a mass ratio of 5/95 or more improves elongation and shape recovery, and also makes it easier to improve shape recovery, and the like.
• the ratio (B2/A2) is more preferably 40/60 or less, even more preferably 35/65 or less, even more preferably 30/70 or less, and is more preferably 10/90 or more, even more preferably 15/85 or more, and even more preferably 18/82 or more.
• the PET content (A1) and the PBT content (B1) in one surface refer to the PET and PBT contents in the surface layer of a multilayer film.
• the blending may vary along the thickness direction near the surface, resulting in changes in the PET content and PBT content.
• the PET content and PBT content in the region from the film surface to 5% of the total thickness may be defined as the content (A1) and the content (B1), respectively.
• the PET content (A2) and the PBT content (B2) in the central portion in the thickness direction may be the PET content and the PBT content, respectively, in the core layer of a multilayer film.
• the PET content (A2) and the PBT content (B2) are defined as the PET content and the PBT content, respectively, in a region that is 10% of the total thickness centered on the center of the film in the thickness direction.
• the PET and PBT may have a concentration gradient in the thickness direction, and by providing a concentration gradient, the PET contents (A1) and (A2) and the PBT contents (B1) and (B2) may be adjusted to fall within the ranges specified in the above preferred embodiment.
• the PET content may have a concentration gradient that decreases from one surface of the film toward the center in the thickness direction.
• the PET content decreases from one surface of the film toward the center in the thickness direction, and then increases again toward the other surface.
• the PET content it is sufficient for the PET content to have a region with a high content (first region) and a region with a low content (second region) from one surface to the other, but it is preferable for the region with a high content (first region), a region with a low content (second region), and a region with a high content (first region) to be provided in this order.
• the PBT content may have a concentration gradient that increases from one surface of the film toward the center in the thickness direction. It is also preferable that the PBT content increases from one surface toward the center of the film, and then increases again toward the other surface.
• a region with a low content (first region) and a region with a high content (second region) may be provided from one surface toward the other, but it is preferable that the region with a low content (first region), a region with a high content (second region), and a region with a low content (first region) are provided in this order.
• the low PBT content region is a concept that also encompasses regions that do not contain PBT.
• the polyester film may contain particles.
• the inclusion of particles in the polyester film can impart properties such as easy slippage and improve the film's handleability.
• particles include, but are not limited to, inorganic particles such as silica, calcium carbonate, magnesium carbonate, barium carbonate, calcium sulfate, calcium phosphate, magnesium phosphate, kaolin, aluminum oxide, and titanium oxide; crosslinked polymers such as crosslinked silicone resin particles, crosslinked acrylic resin particles, crosslinked styrene-acrylic resin particles, and crosslinked polyester particles; and organic particles such as calcium oxalate and ion exchange resins.
• silica and aluminum oxide are preferred, and silica is more preferred.
• the average particle size is generally in the range of 0.05 ⁇ m to 10 ⁇ m, preferably 0.1 ⁇ m to 6 ⁇ m, more preferably 0.3 ⁇ m to 5 ⁇ m, and even more preferably 0.6 ⁇ m to 4.5 ⁇ m.
• the average particle size is the particle size at a cumulative volume fraction of 50% (d50) in the equivalent sphericity distribution measured using a centrifugal sedimentation particle size distribution analyzer.
• the particles may be contained throughout the entire polyester film, but are preferably contained on at least one surface of the polyester film. Therefore, in the multilayer structure described above, it is sufficient to contain particles in at least one surface layer, but when the film has surface layers on both sides, it is more preferable to contain particles in both surface layers.
• the particle content is not particularly limited, but is usually less than 5% by mass, preferably 0.0003% by mass to 3% by mass, more preferably 0.001% by mass to 2.5% by mass, and even more preferably 0.01% by mass to 1% by mass.
• the film has excellent transparency.
• the film has improved slipperiness and good handleability.
• the film transparency can be sufficiently ensured as long as the particle content is less than 5% by mass.
• the particle content should be within the above range at least in a region from the surface of the film to a depth of 1 ⁇ m in the thickness direction.
• the particle content in the surface layer should be within the above range.
• the particle content relative to the entire film should be within the above range.
• the particle content relative to the entire film is preferably 0.0001 mass % or more and 2 mass % or less, more preferably 0.0005 mass % or more and 1.5 mass % or less, even more preferably 0.001 mass % or more and 1 mass % or less, and still more preferably 0.005 mass % or more and 0.7 mass % or less.
• the amount of particles present is not particularly limited, but is preferably about 3 mg/ m2 or more, more preferably 4 mg/ m2 to 15 mg/ m2 , and even more preferably 5 mg/ m2 to 14 mg/ m2 .
• the particles present on the surface of the polyester film may be particles exuded from the resin constituting the polyester film, or particles coated on the surface of the polyester film.
• the polyester film may also contain conventionally known antioxidants, ultraviolet absorbers, antistatic agents, heat stabilizers, lubricants, and colorants such as dyes and pigments, as needed.
• One or both surfaces of the polyester film may be appropriately surface-treated.
• the surface treatment may be a known modification treatment performed on the surface of a resin film, such as corona treatment or plasma treatment.
• the functional layer described below, may be formed on a surface of the polyester film that has been surface-treated, or on a surface of the polyester film that has not been surface-treated. However, it is preferable that the surface treatment be performed on the surface on which the functional layer is not formed.
• the polyester film has a functional layer on one surface and no functional layer on the other surface, which is a corona-treated surface.
• the polyester film may have a functional layer such as an easy-adhesion layer, a release layer, an antistatic layer, a coating layer such as an antiblocking layer, a hard coat layer, an inorganic vapor deposition layer, or a printed layer on at least one surface, as long as the effects of the present invention are not impaired.
• a coating layer is preferred, and an easy-adhesion layer is more preferred.
• the easy-adhesion layer is a layer provided to adhere other layers or films to the polyester film, and is preferably formed from a resin such as a polyurethane resin, a vinyl resin, a polyamide resin, a polyester resin, an acrylic resin, or a polyvinyl acetal resin.
• the resin in the easy-adhesion layer may be appropriately blended with additives such as various crosslinking agents and particles.
• additives such as various crosslinking agents and particles.
• the functional layer preferably has a thickness such that the mass per unit area is 1 mg/ m2 or more and 1000 mg/ m2 or less.
• the mass per unit area is within the above range, the functional layer does not become thicker than necessary, and when it is made into functional layer X described below, the surface free energy and/or the water droplet contact angle can be easily adjusted to desired values.
• the mass per unit area of the functional layer is more preferably 5 mg/m 2 or more and 500 mg/m 2 or less, even more preferably 10 mg/m 2 or more and 300 mg/m 2 or less, and even more preferably 15 mg/m 2 or more and 150 mg/m 2 or less.
• the mass per unit area of the functional layer can be determined from the amount of nonvolatile components applied when forming the resin composition for forming the functional layer, and when drying and stretching are performed, it is the mass per unit area of the functional layer after drying and stretching. Furthermore, when functional layers are provided on both sides of the present film, the mass per unit area of the functional layer is the mass per unit area of the functional layer provided on each surface of the present film.
• the thickness of the functional layer is, for example, 0.001 ⁇ m or more and 1 ⁇ m or less, preferably 0.005 ⁇ m or more and 0.5 ⁇ m or less, 0.01 ⁇ m or more and 0.4 ⁇ m or less, preferably 0.01 ⁇ m or more and 0.3 ⁇ m or less, and more preferably 0.01 ⁇ m or more and 0.2 ⁇ m or less. If necessary, the aforementioned particles, etc. may be contained to improve slip properties.
• the polyester film when the polyester film is placed in a mold such as a die, the film slides appropriately, making it easier to follow the mold, and uniform pressure is easily applied during extrusion molding, making it easier for the entire film to stretch uniformly. This makes it easier to obtain molded products that are less likely to deform and have little thickness variation.
• a functional layer having the above-described surface free energy and/or water droplet contact angle is generally also called a release layer.
• the functional layer having the above-described surface free energy and/or water droplet contact angle will be referred to as functional layer X.
• the surface of the functional layer X has a surface free energy of 49 mN/m or less and a water droplet contact angle of 63° or more.
• the surface free energy of the surface of the functional layer X is more preferably 40 mN/m or less, even more preferably 30 mN/m or less, and even more preferably 27 mN/m or less.
• the surface free energy of the surface of the functional layer X is not particularly limited in terms of its lower limit, but from the viewpoint of ease of obtaining it by adjusting the composition of the functional layer X, it is, for example, 5 mN/m or more, preferably 10 mN/m or more, more preferably 15 mN/m or more.
• the water droplet contact angle on the surface of the functional layer X is more preferably 75° or more, even more preferably 90° or more, and even more preferably 100° or more.
• the upper limit of the surface free energy of the surface of the functional layer X is not particularly limited and is, for example, 140° or less, but from the viewpoint of ease of obtaining it by adjusting the composition of the functional layer X, it is preferably 130° or less, more preferably 120° or less.
• the water droplet contact angle and surface free energy are measured as follows.
• Method for measuring water droplet contact angle The contact angle is measured using a contact angle meter when 1 ⁇ L of pure water is dropped onto the surface of the functional layer of a film that has been conditioned for 24 hours or more in an environment of 23°C and 50% RH. The contact angle is measured 60 seconds after the drop onto the film.
• a contact angle meter (DMo-501 model) manufactured by Kyowa Interface Science Co., Ltd. may be used.
• Surface free energy is composed of the sum of the components of intermolecular forces. Intermolecular forces are classified into dispersion forces, orientation forces, induction forces, and hydrogen bonding forces, which respectively make up the surface free energy as a dispersion component (Dispersion), polar component (Polar), induction component (Induction), and hydrogen bonding component (Hydrogen). Of these components, the induction component is very weak and can be ignored, while the hydrogen bonding component can be lumped together with the polar component.
• the components of the surface free energy ⁇ SV are values determined by the following measurement and calculation methods: First, the contact angle ( ⁇ 1 ) between a first liquid, whose ⁇ LV1 , ⁇ LV1d , and ⁇ LV1p below are known, and the surface to be measured, and the contact angle ( ⁇ 2 ) between a second liquid, whose ⁇ LV2 , ⁇ LV2d , and ⁇ LV2p below are known, and the surface to be measured are measured.
• ⁇ SV d Dispersion component of the surface free energy ⁇ SV of the surface to be measured
• ⁇ SV p Polar component of the surface free energy ⁇ SV of the surface to be measured
• ⁇ LV1 Surface tension of the first liquid ⁇ LV2 : Surface tension of the second liquid ⁇ 1 : Contact angle of the first liquid ⁇ 2 : Contact angle of the second liquid ⁇ LV1 d : Dispersion component of the surface tension of the first liquid ⁇ LV1 p : Polar component of the surface tension of the first liquid ⁇ LV2 d : Dispersion component of the surface tension of the second liquid ⁇ LV2 p : Polar component of the surface tension of the second liquid
• compounds containing a long-chain alkyl group are preferred as release agents, as they make it difficult for the release agent to transfer to a mold such as a die during molding, while also making it easier to adjust the surface free energy and/or water droplet contact angle to the specified values described above. Furthermore, it is preferable to use a compound having a long-chain alkyl group as the main component in functional layer X.
• the release agent contains a long-chain alkyl group, it has good compatibility with components other than the release agent in the functional layer, and can exhibit good release properties even with a small amount.
• the term "main component” here refers to the component with the highest content among the release agents.
• wax, a fluorine compound, a silicone compound, etc. may also be used as a release agent.
• the compound having a long-chain alkyl group refers to a compound having a linear or branched alkyl group having 4 or more carbon atoms.
• the number of carbon atoms in the alkyl group is preferably 9 or more, more preferably 12 or more, even more preferably 15 or more, and particularly preferably 18 or more.
• Increasing the number of carbon atoms in the alkyl group as described above can impart appropriate mold releasability to the functional layer X, lower the surface free energy of the functional layer X, and/or increase the water droplet contact angle.
• There is no particular limit to the upper limit of the number of carbon atoms in the alkyl group and it is usually about 30, but preferably 25.
• Examples of compounds having a long-chain alkyl group include various long-chain alkyl group-containing polymer compounds, long-chain alkyl group-containing amine compounds, long-chain alkyl group-containing ether compounds, long-chain alkyl group-containing quaternary ammonium salts, etc. From the viewpoint of exhibiting good mold releasability, long-chain alkyl group-containing polymer compounds are preferred.
• the long-chain alkyl group-containing polymer compound is preferably a polymer compound having a long-chain alkyl group on the side chain, and the method for producing the polymer compound is as follows: (1) A method of polymerizing a monomer having a long-chain alkyl group, or copolymerizing a monomer having a long-chain alkyl group with a monomer copolymerizable with said monomer; (2) A method of reacting a polymer having a reactive group with a compound having a long-chain alkyl group that can react with the reactive group.
• the compound having a long-chain alkyl group can be preferably produced by the above method (2).
• the monomer having a long-chain alkyl group is preferably a (meth)acrylic monomer, for example, a (meth)acrylic acid ester having an alkyl group having 4 to 30 carbon atoms. More specific examples include (meth)acrylic acid esters such as isobutyl (meth)acrylate, t-butyl (meth)acrylate, n-amyl (meth)acrylate, isoamyl (meth)acrylate, n-hexyl (meth)acrylate, 2-ethylhexyl (meth)acrylate, n-heptyl (meth)acrylate, octyl (meth)acrylate, decyl (meth)acrylate, lauryl (meth)acrylate, stearyl (meth)acrylate, and isostearyl (meth)acrylate, as well as various octadecyl (meth)acrylates such as behenyl (
• the alkyl group preferably has 9 or more carbon atoms, more preferably 12 or more, even more preferably 15 or more, and particularly preferably 18 or more.
• the long-chain alkyl group-containing polymer compound obtained by the above method (1) is preferably a (meth)acrylic acid ester (co)polymer, and the content of the structural unit derived from the monomer having the long-chain alkyl group is preferably in the range of 10% by mass to 100% by mass, more preferably in the range of 20% by mass to 80% by mass, and even more preferably in the range of 30% by mass to 60% by mass.
• the monomer copolymerizable with the monomer having a long-chain alkyl group is not particularly limited, but (meth)acrylic monomers, vinyl group-containing monomers, and the like are preferred.
• the (meth)acrylic monomer include hydroxyl group-containing monomers such as hydroxyalkyl (meth)acrylates, such as 2-hydroxyethyl (meth)acrylate, 2-hydroxypropyl (meth)acrylate, 2-hydroxybutyl (meth)acrylate, 4-hydroxybutyl (meth)acrylate, and 6-hydroxyhexyl (meth)acrylate; carboxy group-containing monomers such as (meth)acrylic acid, itaconic acid, carboxyethyl acrylate, mono(2-acryloyloxyethyl) succinate, ⁇ -carboxy-dicarolactone monoacrylate, and monohydroxyethyl acrylate phthalate; and alkyl (meth)acrylates having less than 4 carbon atoms other than the compounds
• vinyl group-containing monomers examples include styrene, vinyl acetate, vinyl propionate, and divinylbenzene.
• the copolymerizable monomer preferably includes a monomer containing a functional group such as a hydroxyl group-containing monomer or a carboxy group-containing monomer, from the viewpoint of contributing to the reaction with the crosslinking agent described later, and more preferably includes a carboxy group-containing monomer such as (meth)acrylic acid.
• (meth)acrylic means acrylic or methacrylic.
• examples of the reactive group of the polymer having a reactive group include a hydroxyl group, an amino group, a carboxy group, and an acid anhydride.
• Specific examples of polymers having a reactive group include polyvinyl alcohol, polyethyleneimine, polyethyleneamine, reactive group-containing polyester resins, and reactive group-containing poly(meth)acrylic resins. Of these, from the standpoints of releasability and ease of handling, polyvinyl alcohol and reactive group-containing poly(meth)acrylic resins are preferred, with polyvinyl alcohol being even more preferred.
• the reactive groups may be neutralized.
• a stabilizer can be used to neutralize the reactive groups.
• basic stabilizers include inorganic basic compounds such as calcium hydroxide, magnesium hydroxide, lithium hydroxide, potassium hydroxide, and sodium hydroxide, as well as amine compounds such as ammonia, trimethylamine, triethylamine, diethylamine, and dimethylaminoethanol.
• inorganic basic compounds such as calcium hydroxide, magnesium hydroxide, lithium hydroxide, potassium hydroxide, and sodium hydroxide
• amine compounds such as ammonia, trimethylamine, triethylamine, diethylamine, and dimethylaminoethanol.
• it is preferable to use inorganic basic compounds and specifically, calcium hydroxide, magnesium hydroxide, and lithium hydroxide are preferred.
• Examples of compounds having a long-chain alkyl group capable of reacting with the above-mentioned reactive groups include long-chain alkyl group-containing isocyanates such as various octadecyl isocyanates such as octyl isocyanate, decyl isocyanate, lauryl isocyanate, isostearyl isocyanate, and stearyl isocyanate, and behenyl isocyanate; long-chain alkyl group-containing acid chlorides such as hexanoyl chloride, octanoyl chloride, decanoyl chloride, lauroyl chloride, octadecanoyl chloride, and behenoyl chloride; long-chain alkyl group-containing amines; and long-chain alkyl group-containing alcohols.
• long-chain alkyl group-containing isocyanates are preferred, with steary
• the number average molecular weight (Mn) of the long-chain alkyl group-containing polymer compound obtained by the above methods (1) and (2) is preferably 1,000 to 100,000, and more preferably 2,000 to 80,000.
• Mn The number average molecular weight
• the functional layer resin composition is easily dissolved in a solvent contained in a coating liquid, which is a preferred form of the functional layer resin composition, and can be easily applied to a polyester film.
• the melting point of the long-chain alkyl group-containing compound is preferably 0°C or higher and 100°C or lower, more preferably 10°C or higher and 100°C or lower, and even more preferably 20°C or higher and 90°C or lower.
• waxes examples include natural waxes, synthetic waxes, and waxes made by combining these.
• Natural waxes include vegetable waxes, animal waxes, mineral waxes, and petroleum waxes.
• Vegetable waxes include candelilla wax, carnauba wax, rice wax, Japan wax, and jojoba oil.
• Animal waxes include beeswax, lanolin, and spermaceti wax.
• Mineral waxes include montan wax, ozokerite, and ceresin. Petroleum waxes include paraffin wax, microcrystalline wax, and petrolatum.
• Examples of synthetic waxes include synthetic hydrocarbons, modified waxes, hydrogenated waxes, fatty acids, fatty acid amides, amines, imides, ester waxes, and ketones.
• Examples of synthetic hydrocarbons include Fischer-Tropsch wax (Sazol wax), polyethylene wax, oxidized polyethylene wax, oxidized polypropylene wax, etc.
• low molecular weight polymers such as polypropylene, ethylene-acrylic acid copolymer, polyethylene glycol, polypropylene glycol, and block or graft bonded polyethylene glycol and polypropylene glycol.
• Examples of modified waxes include montan wax derivatives, paraffin wax derivatives, and microcrystalline wax derivatives. The derivatives herein refer to compounds obtained by any of the following treatments: purification, oxidation, esterification, and saponification, or a combination thereof.
• Hydrogenated waxes include hydrogenated castor oil and hydrogenated castor oil derivatives.
• the number average molecular weight (Mn) of the wax is preferably in the range of 1,000 to 100,000, and the weight average molecular weight (Mw) is preferably in the range of 2,000 to 80,000.
• the melting point or softening point of the wax is preferably 80°C or higher, more preferably 110°C or higher, taking into consideration factors such as durability against heat treatment during use. From the perspective of controlling release performance after heat treatment, it is preferably 200°C or lower, more preferably 170°C or lower, and even more preferably 150°C or lower.
• the melting point or softening point of the wax can be measured using a differential scanning calorimeter (DSC).
• the fluorine compound may be any polymeric compound containing a fluorine atom in the molecule, such as a perfluoroalkyl group-containing polymeric compound, a polymer of an olefin compound containing a fluorine atom, etc. From the viewpoint of being able to exhibit releasability with a small content, a perfluoroalkyl group-containing polymeric compound is preferred.
• a perfluoroalkyl group-containing polymeric compound is preferred.
• the monomer for forming the perfluoroalkyl group-containing polymer compound a perfluoroalkyl group-containing (meth)acrylate, a perfluoroalkyl group-containing vinyl ether, or the like is preferred.
• perfluoroalkyl group-containing (meth)acrylates examples include perfluoroalkyl (meth)acrylate, perfluoroalkylmethyl (meth)acrylate, 2-perfluoroalkylethyl (meth)acrylate, 3-perfluoroalkylpropyl (meth)acrylate, 3-perfluoroalkyl-1-methylpropyl (meth)acrylate, and 3-perfluoroalkyl-2-propenyl (meth)acrylate.
• perfluoroalkyl group-containing vinyl ethers examples include perfluoroalkylmethyl vinyl ether, 2-perfluoroalkylethyl vinyl ether, 3-perfluoropropyl vinyl ether, 3-perfluoroalkyl-1-methylpropyl vinyl ether, and 3-perfluoroalkyl-2-propenyl vinyl ether. These may be polymerized singly or in combination of two or more. From the viewpoint of exhibiting releasability with a small content, the perfluoroalkyl group preferably has 3 to 11 carbon atoms.
• the number-average molecular weight (Mn) of the fluorine compound (polymer compound) is preferably in the range of 1,000 or more and 100,000 or less, and the weight-average molecular weight (Mw) is preferably in the range of 2,000 or more and 80,000 or less.
• the silicone compound is a compound having a siloxane bond (—Si—O—) in the molecule, and examples thereof include silicone emulsion, acrylic-grafted silicone, silicone-grafted acrylic, amino-modified silicone, perfluoroalkyl-modified silicone, alkyl-modified silicone, etc. From the viewpoints of releasability, heat resistance, etc., curable silicone resins are preferred.
• the types of curable silicone resins include addition type, condensation type, ultraviolet curable type, and electron beam curable type, and any of the curable types can be used.
• the number-average molecular weight (Mn) of the silicone compound is preferably in the range of 100 or more and 100,000 or less, and the weight-average molecular weight (Mw) is preferably in the range of 200 or more and 80,000 or less.
• the functional layer X i.e., the resin composition for the functional layer described below, preferably further contains a crosslinking agent.
• crosslinking agents include melamine compounds, oxazoline compounds, epoxy compounds, isocyanate compounds, carbodiimide compounds, and silane coupling agents.
• melamine compounds are preferred because they have high crosslink density and elastic modulus while providing good mold releasability. Therefore, the functional layer X, i.e., the resin composition for the functional layer described below, preferably contains a long-chain alkyl group-containing compound and a crosslinking agent, and more preferably contains a long-chain alkyl group-containing compound and a melamine compound.
• Melamine compounds are compounds that contain a melamine skeleton within the compound. Examples include alkylolated melamine derivatives, compounds obtained by reacting alkylolated melamine derivatives with alcohol to partially or completely etherify them, and mixtures of these. Suitable alcohols for etherification include methanol, ethanol, isopropyl alcohol, n-butanol, and isobutanol. Furthermore, melamine compounds may be either monomers or dimers or higher polymers, or mixtures of these may be used. Furthermore, melamine partially co-condensed with urea or the like may also be used, and a catalyst can also be used to increase the reactivity of the melamine compound.
• Oxazoline compounds are compounds that contain an oxazoline group in the molecule, and polymers containing oxazoline groups are particularly preferred. Polymers containing oxazoline groups can be synthesized by polymerizing oxazoline group-containing monomers alone or with other monomers. Examples of oxazoline group-containing monomers include 2-vinyl-2-oxazoline, 2-vinyl-4-methyl-2-oxazoline, 2-vinyl-5-methyl-2-oxazoline, 2-isopropenyl-2-oxazoline, 2-isopropenyl-4-methyl-2-oxazoline, and 2-isopropenyl-5-ethyl-2-oxazoline.
• Epoxy compounds are compounds that contain an epoxy group in the molecule. Examples include condensation products of epichlorohydrin with the hydroxyl or amino groups of ethylene glycol, polyethylene glycol, glycerin, polyglycerin, bisphenol A, etc., as well as polyepoxy compounds, diepoxy compounds, monoepoxy compounds, and glycidylamine compounds.
• isocyanate compounds include tolylene diisocyanate compounds such as 2,4-tolylene diisocyanate and 2,6-tolylene diisocyanate; xylylene diisocyanate compounds such as 1,3-xylylene diisocyanate, 1,4-xylylene diisocyanate and tetramethylxylylene diisocyanate; aromatic isocyanate compounds such as 1,5-naphthalene diisocyanate and triphenylmethane triisocyanate; hexamethylene diisocyanate, isophorone diisocyanate, and adducts of these isocyanate compounds with polyol compounds such as trimethylolpropane; and biuret and isocyanurate forms of these polyisocyanate compounds.
• tolylene diisocyanate compounds such as 2,4-tolylene diisocyanate and 2,6-tolylene diisocyanate
• xylylene diisocyanate compounds such as 1,3-xy
• Carbodiimide compounds include monocarbodiimide compounds such as dicyclohexylcarbodiimide, diisopropylcarbodiimide, dimethylcarbodiimide, diisobutylcarbodiimide, dioctylcarbodiimide, t-butylisopropylcarbodiimide, diphenylcarbodiimide, di-t-butylcarbodiimide, and di- ⁇ -naphthylcarbodiimide; and isocyanate-terminated polycarbodiimides obtained by the condensation reaction of diisocyanates accompanied by the decarbonation of carbon dioxide.
• monocarbodiimide compounds such as dicyclohexylcarbodiimide, diisopropylcarbodiimide, dimethylcarbodiimide, diisobutylcarbodiimide, dioctylcarbodiimide, t-butylisopropylcarbodiimide, diphen
• Silane coupling agents include gamma-mercaptopropyltrimethoxysilane, gamma-isocyanatepropyltriethoxysilane, gamma-isocyanatepropyltrimethoxysilane, and N-(1,3-dimethylbutylidene)-3-(triethoxysilyl)-1-propanamine.
• the functional layer X preferably contains a long-chain alkyl group-containing compound and a crosslinking agent.
• the content of the long-chain alkyl group-containing compound is 5% by mass or more and 95% by mass or less
• the content of the crosslinking agent is 5% by mass or more and 95% by mass or less, relative to the total non-volatile components of the functional layer X (the resin composition for the functional layer).
• the content of the long-chain alkyl group-containing compound is 5% by mass or more, appropriate releasability can be imparted to the functional layer X, the surface free energy of the functional layer surface can be kept below a certain level, and the water droplet contact angle can be easily adjusted to a predetermined value or higher.
• the content is 95% by mass or less, it becomes easier to incorporate appropriate amounts of components other than the long-chain alkyl group-containing compound, such as crosslinking agents, into the functional layer X.
• the content of the long-chain alkyl group-containing compound is more preferably 15% by mass or more and 80% by mass or less, even more preferably 30% by mass or more and 70% by mass or less, and even more preferably 40% by mass or more and 65% by mass or less.
• the crosslinking agent can appropriately crosslink the functional layer X, improving the performance of the functional layer X and making it easier to adjust the surface free energy and water droplet contact angle of the functional layer surface to desired values.
• the content is 95% by mass or less, it is easier to incorporate appropriate amounts of components other than the crosslinking agent, such as a long-chain alkyl group-containing compound, into the functional layer X.
• the content of the crosslinking agent is more preferably 10% by mass or more and 80% by mass or less, even more preferably 20% by mass or more and 70% by mass or less, and even more preferably 30% by mass or more and 50% by mass or less.
• the functional layer X i.e., the resin composition for the functional layer, may contain components other than the release agent and the crosslinking agent, such as a binder resin.
• the binder resin makes it easier to impart film-forming properties to the functional layer X.
• the binder resin is not particularly limited, and conventionally known binder resins such as polyester resins, (meth)acrylic resins, polyurethane resins, polyvinyl resins (such as polyvinyl alcohol and vinyl chloride-vinyl acetate copolymers), polyalkylene glycols, polyalkyleneimines, methyl cellulose, hydroxycellulose, and starches can be used.
• polyester resins from the viewpoints of film-forming properties and adhesion to polyester films, at least one selected from polyester resins, (meth)acrylic resins, and polyurethane resins is preferred.
• One binder resin may be used alone, or two or more binder resins may be used in combination.
• the functional layer X i.e., the resin composition for the functional layer, may further contain particles and additives in addition to the above components.
• the particles are added to improve blocking properties and slip properties, and their type, shape, average particle size, and content are the same as those of the particles that may be incorporated into the polyester film described above.
• additives include antistatic agents, UV absorbers, antioxidants, antifoaming agents, lubricants, foaming agents, dyes, and pigments.
• the functional layer resin composition preferably contains a solvent to form a liquid coating solution, which is then applied to the surface of a polyester film, and dried and cured as necessary to form the functional layer X.
• each component forming the functional layer X may be dissolved in the solvent or may be dispersed in the solvent.
• the solvent is a volatile component.
• the solvent may be either water or an organic solvent, or a mixed solvent of water and an organic solvent.
• organic solvent examples include aromatic hydrocarbons such as toluene; aliphatic hydrocarbons such as hexane, heptane, and isooctane; esters such as ethyl acetate and butyl acetate; ketones such as ethyl methyl ketone and isobutyl methyl ketone; alcohols such as ethanol and 2-propanol; and ethers such as diisopropyl ether and dibutyl ether.
• aromatic hydrocarbons such as toluene
• aliphatic hydrocarbons such as hexane, heptane, and isooctane
• esters such as ethyl acetate and butyl acetate
• ketones such as ethyl methyl ketone and isobutyl methyl ketone
• alcohols such as ethanol and 2-propanol
• ethers such as diisopropyl ether and dibutyl
• the surface roughness (Ra) of the functional layer X is not particularly limited, but is, for example, 1 nm to 100 nm, preferably 5 nm to 50 nm, and more preferably 10 nm to 30 nm.
• the film has an appropriately good sliding processability when the polyester film is placed in a mold or the like, and also has good sliding properties when the film is unwound for lamination with other films, etc., and the film tends to have excellent handleability.
• the present polyester film has an absolute value (
• the present polyester film contains PBT and PET, and by setting
• the film has small variations in displacement and puncture strength upon puncture, and more uniform elongation in the thickness direction, making it more suitable for use as an exterior packaging material.
• the anisotropy of the film is suppressed by lowering
• a puncture force from a needle or the like is applied to a film, the film stretches and deforms in the thickness direction so that it is caught by the needle or the like, and this degree of stretching of the film (the degree to which the film is caught by the needle or the like) tends to be similar in the longitudinal and transverse directions of the film, thereby reducing the variation in puncture displacement and puncture strength depending on the puncture position.
• is preferably 50 or less, more preferably 45 or less, and even more preferably 40 or less.
• is not particularly limited as long as it is 0 or more, but in practice it is sufficient if it is 5 or more, preferably 10 or more, and more preferably 15 or more.
• the polyester film preferably has a planar orientation degree ( ⁇ P) of 100 or more, more preferably 120 or more, even more preferably 140 or more, and even more preferably 150 or more.
• ⁇ P planar orientation degree
• the crystallinity of the film is enhanced, making it easier to increase the puncture strength.
• the planar orientation degree is not particularly limited, but is preferably 200 or less, more preferably 180 or less, and even more preferably 170 or less.
• the present polyester film typically has a transverse orientation degree ( ⁇ nv) greater than its longitudinal orientation degree ( ⁇ np).
• the transverse orientation degree ( ⁇ nv) is not particularly limited, but is, for example, 50 to 130, preferably 60 to 120, more preferably 70 to 110, and even more preferably 75 to 105.
• the longitudinal orientation degree ( ⁇ np) is also not particularly limited, but is, for example, 20 to 100, preferably 30 to 90, more preferably 40 to 80, and even more preferably 45 to 70.
• , transverse orientation ( ⁇ nv), longitudinal orientation ( ⁇ np), and planar orientation ( ⁇ P) of the polyester film can be adjusted to the above ranges by adjusting the stretching ratio, stretching temperature, preheating temperature and time of the polyester film, and heat setting temperature and time during the process of manufacturing the polyester film.
• the planar orientation degree ( ⁇ P), longitudinal orientation degree ( ⁇ np), and transverse orientation degree ( ⁇ nv) of the present polyester film can be determined as follows.
• the refractive index (nx), refractive index (ny), and refractive index (nz) of the polyester film in the longitudinal direction and the transverse direction are measured using an Abbe refractometer with sodium D-line as a light source according to JIS K 7142:2014 5.1 (Method A).
• the measurement results are applied to the following formula to calculate the degree of planar orientation (also referred to as the planar orientation coefficient; ⁇ P), the degree of longitudinal orientation (also referred to as the longitudinal plane orientation coefficient; ⁇ np), and the degree of transverse orientation (also referred to as the transverse plane orientation coefficient; ⁇ nv).
• ⁇ P ((nx+ny)/2-nz) ⁇ 1000
• ⁇ np (nx-(ny+nz)/2) ⁇ 1000
• ⁇ nv (ny-(nx+nz)/2) ⁇ 1000
• the longitudinal direction of the film is the MD (machine direction), which is the direction in which the film advances during the film manufacturing process, i.e., the direction in which the film roll is wound.
• the transverse direction of the film is the TD (transverse direction), which is the direction parallel to the film surface and perpendicular to the longitudinal direction, i.e., the direction parallel to the central axis of the roll when the film is rolled.
• the present polyester film preferably has a puncture strength of 480 N/mm or more.
• a puncture strength of 480 N/mm or more provides high puncture resistance, making it suitable for use as an exterior material, such as an exterior material for a battery.
• the puncture strength is more preferably 490 N/mm or more, even more preferably 500 N/mm or more, even more preferably 510 N/mm or more, even more preferably 520 N/mm or more, and even more preferably 530 N/mm or more.
• the puncture strength is not particularly limited, but is, for example, 1000 N/mm or less, preferably 800 N/mm, more preferably 700 N/mm or less, even more preferably 650 N/mm or less, even more preferably 590 N/mm or less, even more preferably 585 N/mm or less, even more preferably 580 N/mm or less, and even more preferably 575 N/mm or less.
• the puncture strength is below the above upper limit, the elongation of the present polyester film is easily improved.
• the puncture strength is set to be equal to or less than the above upper limit, when the film is made into an actual product such as a battery exterior material by, for example, extrusion molding, the restoring force of the film trying to return to its original shape is kept low, and the shape retention of the actual product tends to be improved.
• deformation of the exterior material due to post-processing such as heat fusion or heat generation from an electricity storage device element housed inside can be more effectively suppressed.
• the present polyester film preferably has a displacement amount at the time of piercing of 4 mm or more.
• the displacement amount at the time of piercing is 4 mm or more, the film has good extensibility, and is sufficiently stretched during shaping, making it easy to increase the molding depth, etc.
• the displacement amount at the time of piercing is more preferably 4.2 mm or more, and even more preferably 4.3 mm or more.
• the displacement amount at the time of piercing is not particularly limited, but may be, for example, 8 mm or less, 6 mm or less, or 5 mm or less.
• the present polyester film preferably has a coefficient of variation in puncture strength of 0.036 or less, more preferably 0.034 or less, even more preferably 0.032 or less, even more preferably 0.03 or less, even more preferably 0.028 or less, even more preferably 0.026 or less, even more preferably 0.024 or less, even more preferably 0.022 or less, and even more preferably 0.02 or less.
• a smaller coefficient of variation reduces the variation in puncture strength of the present polyester film, resulting in uniform elongation in the thickness direction, making it suitable for use as an exterior packaging material.
• the coefficient of variation in puncture strength indicates the variation in puncture strength and is calculated by dividing the standard deviation by the mean value.
• the mean value and standard deviation are the mean and standard deviation of the puncture strength measured at 12 points on the polyester film sample.
• the coefficient of variation of the displacement upon puncture which will be described later, indicates the variation in the displacement upon puncture and can be calculated in the same way, except that the measured value is replaced by the displacement upon puncture.
• the present polyester film preferably has a coefficient of variation of the displacement amount upon piercing of 0.034 or less, more preferably 0.03 or less, even more preferably 0.027 or less, even more preferably 0.025 or less, even more preferably 0.023 or less, even more preferably 0.021 or less, and even more preferably 0.019 or less.
• the reduced coefficient of variation of the displacement amount upon piercing reduces the variation in the displacement amount, resulting in uniform elongation in the thickness direction, making the film suitable for use as an exterior packaging material. Furthermore, the film tends to stretch uniformly during shaping, resulting in good formability.
• the polyester film preferably has a Martens hardness of 132 N/ mm2 or more, more preferably 135 N/ mm2 or more, and even more preferably 138 N/ mm2 or more.
• the upper limit of the Martens hardness is not particularly limited, but may be, for example, 300 N/ mm2 or 200 N/ mm2 .
• the polyester film preferably has an indentation hardness of 200 N/ mm2 or more, more preferably 210 N/ mm2 or more, and even more preferably 215 N/ mm2 or more.
• the upper limit of the indentation hardness is not particularly limited, but may be, for example, 400 N/ mm2 or 300 N/ mm2 .
• the elastic deformation power of the polyester film is preferably 42% or more, more preferably 43% or more, and even more preferably 44% or more. Having a certain level of elastic deformation power or higher makes it easier to obtain molded articles with excellent design and shape recovery.
• the upper limit of the elastic deformation power of the polyester film is not particularly limited, but may be, for example, 60%, 57%, 53%, or 50%.
• the Martens hardness, indentation hardness, and elastic deformation power should be equal to or greater than the lower limit values when measured on at least one surface of the polyester film. Specifically, it is sufficient that the values measured on the surface of the polyester film where the PET content (A1) is greater than the PET content (A2) in the central portion of the film are equal to or greater than the lower limit values, but it is preferable that the values measured on both surfaces are equal to or greater than the lower limit values. Furthermore, the Martens hardness, indentation hardness, and elastic deformation power can be measured by performing a load-unload test on the surface of the polyester film using a microhardness measurement method in which an indenter is pressed with a force of 20 mN. Specifically, they can be measured by the method described in the Examples below.
• the haze of the polyester film is preferably 10% or less, more preferably 8% or less, even more preferably 5% or less, and particularly preferably 3% or less. By setting the haze to the above lower limit or less, sufficient transparency is obtained.
• the haze is not particularly limited, and may be, for example, 0.01% or more, 0.1% or more, or 0.7% or more.
• the polyester film has a heat shrinkage rate of less than 5% in either the longitudinal or transverse direction of the polyester film and a heat shrinkage rate of more than 2% in the other direction after heat treatment at 160°C for 15 minutes.
• the polyester film has excellent heat resistance. Therefore, when the polyester film is laminated onto other films by lamination, dimensional deformation is reduced, making it easier to laminate onto other films. Furthermore, when the polyester film is laminated onto other films to form a laminate, shrinkage stress is less likely to remain, and secondary processability is improved without shrinkage during secondary processing into battery exterior materials, etc.
• the sealant layer is, for example, 10 ⁇ m or more and 100 ⁇ m or less, preferably 15 ⁇ m or more and 80 ⁇ m or less, or 20 ⁇ m or more and 60 ⁇ m or less.
• An adhesive layer may be present between each layer (for example, between a resin layer and the polyester film, between a resin layer and a metal layer, or between the polyester film and a metal layer), and each layer may be bonded via the adhesive layer.
• the adhesive layer is not particularly limited, but may be composed of a known adhesive such as a polyether adhesive, polyester adhesive, polyurethane adhesive, epoxy adhesive, phenolic resin adhesive, polyamide adhesive, polyolefin adhesive, polyacrylic adhesive, amino resin adhesive, rubber adhesive, or silicone adhesive.
• each layer may be bonded using a known lamination method such as a dry lamination method, although this is not particularly limited.
• the present polyester film is preferably disposed as the outermost layer of a laminate.
• the present polyester film is preferably used as the outermost layer of a battery exterior material.
• the outermost layer of a laminate is easily damaged by external forces during molding or use, but the present polyester film, as described above, has good puncture resistance. Furthermore, the Martens hardness and indentation hardness can be increased, resulting in excellent pinhole resistance and breaking strength. Therefore, using the present polyester film as the outermost layer of a laminate makes it easier to appropriately prevent damage to the laminate during molding and damage to a battery exterior material containing the laminate.
• the exterior material may have any configuration as long as it contains the polyester film or the laminate described above. However, it is preferable that the exterior material contain the laminate described above.
• the present invention also provides a battery exterior material comprising the polyester film or laminate described above, and a battery comprising the battery exterior material.
• Tg Glass transition temperature
• Tm melting point
• the peak top temperature of each endothermic peak observed during the first heating process (1st run) and the second heating process (2nd run) was taken as the melting point, and the values are shown in Table 2.
• the melting point column indicates one endothermic peak
• two values in the melting point column indicate two endothermic peaks.
• the melting point is the temperature at the top of the maximum peak.
• Heat shrinkage Rate ⁇ (L0 - L1) / L0 ⁇ ⁇ 100 (In the above formula, L0 is the sample length before heat treatment, and L1 is the sample length after heat treatment) Measurements were taken at five points in each of the machine direction (MD) and the transverse direction (TD) of the film, and the average value was calculated for each.
• Indenter used Diamond regular triangular pyramid indenter (edge angle: 115)
• Measurement mode Load-unload test Test force: 20.00 mN Minimum test force: 0.20 mN Load speed: 0.1464mN/sec Load holding time: 2sec Unloading holding time: 0sec Measurement atmosphere: 23 ⁇ 2°C, relative humidity 50 ⁇ 5% Number of measurements: 11
• Example 1 As shown in Table 2, PBT-A, PET-A, and PET-C were dry-blended in a mass ratio of 20:70:10 as the raw materials for the surface layer, and PBT-A and PET-A were dry-blended in a mass ratio of 20:80 as the raw materials for the core layer.
• the mixed raw materials for the surface layer and the core layer were each fed into separate twin-screw extruders, kneaded at 280°C, and co-extruded at 280°C.
• the materials were then cooled and solidified on a cooling roll set at 25°C using an electrostatic adhesion method, yielding an unstretched film with two types and three layers (surface layer/core layer/surface layer).
• the resulting unstretched film was then stretched 3.5 times in the machine direction (MD) at 73°C using a roll stretching machine. It was then introduced into a tenter stretching machine, preheated at 75°C for 6 seconds in the tenter, and then stretched 4.5 times in the transverse direction (TD) at 85°C. After stretching, the film was subsequently heat-set at 210°C for 8 seconds and cooled to 140°C with 2% relaxation in the transverse direction (TD) to obtain a biaxially stretched polyester film with a thickness of 25 ⁇ m (each surface layer: 2.5 ⁇ m, core layer: 20 ⁇ m). The biaxially stretched polyester film was wound into a film roll. The resulting polyester film was evaluated. The evaluation results are shown in Table 2.
• the PET/PBT mass ratio shown in Table 2 is the mass ratio of PET and PBT contained in the entire three-layer biaxially oriented polyester film. Specifically, the PET/PBT mass ratio in the entire polyester film is calculated from the blending ratio of PET and PBT in each layer and the ratio of the thickness of each layer, and the mass ratio is rounded to one decimal place.
• Example 2 (Examples 2 to 4, 6, and 7, and Comparative Examples 1 and 2) The same procedures as in Example 1 were carried out, except that the compositions of the surface layer and core layer and the film production conditions were changed as shown in Table 2.
• Example 8 the Martens hardness, indentation hardness, and elastic deformation power of the obtained polyester film were measured, and the results were a Martens hardness of 140 N/mm 2 , an indentation hardness of 220 N/mm 2 , and an elastic deformation power of 45%.
• Example 5 The same procedures as in Example 1 were carried out except that the compositions of the surface layer and core layer and the film production conditions were changed as shown in Table 2, the preheating time after longitudinal stretching was changed to 7 seconds, the heat setting treatment time was changed to 10 seconds, and an easy-adhesion layer was formed by in-line coating after longitudinal stretching and before transverse stretching, by applying a coating liquid for an easy-adhesion layer having the following formulation to one side of the polyester film so that the coating amount (after dry stretching) was 0.05 g/ m2 .
• Example 8 The same procedure as in Example 1 was repeated except that the compositions of the surface layer and core layer and the film production conditions were changed as shown in Table 2, the preheating time after longitudinal stretching was changed to 7 seconds, and the heat setting treatment time was changed to 10 seconds.
• the polyester films of the above examples contained both PBT and PET, and the absolute value of the difference between the horizontal orientation degree ( ⁇ nv) and the vertical orientation degree ( ⁇ np) was 57 or less. Therefore, they had high puncture strength, a large amount of displacement upon puncture, and small variations in the amount of displacement and strength upon puncture, and were therefore excellent in puncture resistance.
• the polyester films of Comparative Examples 1 and 2 contained both PBT and PET, but the absolute value of the difference between the transverse orientation degree ( ⁇ nv) and the longitudinal orientation degree ( ⁇ np) was greater than 57, resulting in large variations in the amount of displacement or strength upon puncture, and the films were unable to achieve excellent puncture resistance.
• the polyester film of Example 8 contained both PBT and PET, and the PET content (A1) at the surface was higher than the PET content (A2) at the center (core layer) in the thickness direction, so that the puncture strength, Martens hardness, indentation hardness, and elastic deformation power were all high. Therefore, it can be understood that the polyester film of Example 8 has excellent pinhole resistance, is less likely to break when an external force is applied, and also has excellent design and shape recovery properties, making it particularly suitable for battery exterior materials.

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