Claims
[Claim 1]
Polyester film having a stress at 5% elongation (F5 value) and a stress at 10% elongation (F10 value)
at 25°C in the longitudinal direction (MD) and those in the transverse direction (TD) that satisfy
formulae (I) and (II) given below:
1.5>F10MD/F5MD>1 ffi
1.5>F10TD/F5TD>1 (II)
[Claim 2]
Polyester film as defined in claim l wherein the stress at 10% elongation (F10 value) at 25°C in the
longitudinal direction (MD) and that in the transverse direction (TD) satisfy formulae (III) and (IV)
given below:
F10MD>120MPa (III)
F10TD>120MPa (IV)
[Claim 3]
Polyester film as defined in claim 2 wherein 95 mol% or more of the glycol units are structural units
derived from ethylene glycol and 95 mol% or more of the dicarboxylic acid units are structural units
derived from terephthalic acid.
[Claim 4]
Polyester film as defined in any one of claims 1 to 3 wherein the stress at 10% elongation at 25°C in
the longitudinal direction and that in the transverse direction satisfy formula (V) given below:
1.2>F10MD/F10TD>0.8 (V)
[Claim 5]
Polyester film as defined in any one of claims 1 to 4 wherein the degree of heat shrinkage at 200°C is
-5 to 5% both in the longitudinal direction and in the transverse direction.
[Claim 6]
Polyester film as defined in any one of claims 1 to 5 wherein at least either of its surfaces has a
dynamic friction coefficient Lid of 0.3 to 0.8.
[Claim 7]
Polyester film as defined in any one of claims 1 to 6 intended to be used for forming.
[Claim 8]
Polyester film as defined in any one of claims 1 to 7 intended to be laminated with metal foil.
[Claim 9]
Polyester film as defined in any one of claims 1 to 8 intended to be used for exterior packages of
batteries.
[Claim 10]
Polyester film as defined in any one of claims 1 to 8 intended to be used for medical packaging
containers.
[Claim 11]

Laminates comprising polyester film as defmed in any one of claims 1 to 10 wherein at least either of
the surfaces is laminated with aluminum foil with a thickness of 10 um or more and 60 \im or less.
[Claim 12]
Laminates as defined in claim 11 intended to be used for exterior packages of batteries.
[Claim 13]
Laminates as defined in claim 11 intended to be used for medical packaging containers.

[Title of the document] Abstract
Provided is a polyester film, which is suitable for use in battery packages, particularly for use in deep
drawn packages of lithium ion secondary batteries that comprise an electrolyte (in a solid state or in a
liquid state), and which is also suitable for use in packages of pharmaceutical products that have
various shapes.
The polyester film is characterized in that the stresses at 5% elongation (F5 values) and the stresses
at 10% elongation (F10 values) of the film in the longitudinal direction and in the transverse
direction at 25°C respectively satisfy the following formulae (I) and (II).
1.5>F10MD/F5MD>1 0) 1.5>F10TD/F5TD>1 (II)