Polyester film, method for manufacturing polyester film, laminated metal sheet, method for manufacturing laminated metal sheet, and laminated metal container

A polyester film comprising:

• a first polyester containing polyethylene terephthalate as a component;
• and a second polyester containing polybutylene terephthalate as a component,
• wherein the first polyester is polyethylene terephthalate or a polyethylene terephthalate copolymer of polyethylene terephthalate and a copolymer component,
• the second polyester is polybutylene terephthalate or a polybutylene terephthalate copolymer of polybutylene terephthalate and a copolymer component,
• a ratio of the first polyester to the second polyester is from 20:80 to 50:50 on a mass % basis, and
• net intensities in pole figures satisfy formulas (1) and (2) below:
• 0.2
• ≤
• I
• 100
• (
• 60
• ,
• 0
• )
• /
• I
• 100
• (
• 60
• ,
• 90
• )
• ≤
• 0.6
• (
• 1
• )
• 0.3
• ≤
• I
• 100
• (
• 50
• ,
• 0
• )
• /
• I
• 100
• (
• 50
• ,
• 90
• )
• ≤
• 0.85
• (
• 2
• )
• wherein, in X-ray diffraction measurement using Cu Kα radiation, a diffraction peak appearing at 2θ=24.0±1.0° is attributed to (100) diffraction, and a diffraction peak appearing at 2θ=17.5±0.5° is attributed to (010) diffraction,
• the pole figures are measured with α=0° defined as a grazing angle at which a bisector of an angle between an incident X-ray and a reflected X-ray is parallel to a film plane, and
• β=90° is defined as an in-plane rotation angle at which a maximum diffraction intensity is observed at α=60° in the pole figure of the (100) diffraction,
• I100(60,0) is a net intensity at α=60° and β=0° in a pole figure of intensity of the (100) diffraction,
• I100(60,90) is a net intensity at α=60° and β=90° in the pole figure of intensity of the (100) diffraction,
• I010(50,0) is a net intensity at α=50° and β=0° in a pole figure of intensity of the (010) diffraction, and
• I010(50,90) is a net intensity at α=50° and β=90° in the pole figure of intensity of the (010) diffraction.

A method for manufacturing a polyester film including a first polyester containing polyethylene terephthalate as a component and a second polyester containing polybutylene terephthalate as a component,

• wherein the first polyester is polyethylene terephthalate or a polyethylene terephthalate copolymer of polyethylene terephthalate and a copolymer component,
• the second polyester is polybutylene terephthalate or a polybutylene terephthalate copolymer of polybutylene terephthalate and a copolymer component,
• the method comprising:
• a non-stretched film forming step of extruding a resin composition containing the first polyester and the second polyester in a ratio of 20:80 to 50:50 on a mass % basis through a T-die using an extruder to obtain a non-stretched film;
• and
• a longitudinally uniaxially stretched film forming step of longitudinally stretching the non-stretched film by using a longitudinal uniaxial stretching machine equipped with preheating rolls and one or more stretching rolls to obtain a longitudinally uniaxially stretched film,
• wherein, in the longitudinally uniaxially stretched film forming step, a draw ratio in the longitudinal stretching is 3.0 or more and 7.0 or less, and a final preheating roll in the longitudinal stretching has a temperature of 40° C. or higher and 80° C. or lower.

A method for manufacturing a polyester film including a first polyester containing polyethylene terephthalate as a component and a second polyester containing polybutylene terephthalate as a component,

• wherein the first polyester is polyethylene terephthalate or a polyethylene terephthalate copolymer of polyethylene terephthalate and a copolymer component,
• the second polyester is polybutylene terephthalate or a polybutylene terephthalate copolymer of polybutylene terephthalate and a copolymer component,
• the method comprising:
• a non-stretched film forming step of extruding a resin composition containing the first polyester and the second polyester in a ratio of 20:80 to 50:50 on a mass % basis through a T-die using an extruder to obtain a non-stretched film;
• and
• a longitudinally uniaxially stretched film forming step of longitudinally stretching the non-stretched film by using a longitudinal uniaxial stretching machine equipped with preheating rolls and one or more stretching rolls to obtain a longitudinally uniaxially stretched film,
• wherein, in the longitudinally uniaxially stretched film forming step, a draw ratio in the longitudinal stretching is 3.0 or more and 7.0 or less, and a stretching temperature in the longitudinal stretching is 50° C. or higher and 80° C. or lower.