Oriented polyester film and manufacturing method therefor

An oriented polyester film, which comprises a polyester resin in which a diol component and a dicarboxylic acid component are polymerized,

• wherein when a sample of the oriented polyester film obtained by subjecting the oriented polyester film to a first heat treatment at 70° C., a preliminary heat treatment at 160° C., and then cutting it into 1 cm×1 cm is mixed with a sample of polyethylene terephthalate (PET) obtained by passing a polyethylene terephthalate (PET) container through a 12.5-mm mesh sieve at a weight ratio of 3:97, which is heat-treated at 195° C. for 90 minutes, and the heat-treated mixed sample is passed through the sieve to evaluate the crystallinity of the polyester oriented film, the crystalline fraction represented by the following Equation 2 is 30% or more:
• Crystalline
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• fraction
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• %
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• (
• F
• T
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• F
• m
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• 1
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• 0
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• Equation
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• 2
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• in Equation 2, FT is the ratio ((Ss/MT)×100, %) of the weight (Ss) of the sample that has passed through the 12.5-mm mesh sieve among the heat-treated mixed sample to the total weight (MT) of the heat-treated mixed sample, and Fm is the ratio ((Cs/MT)×100, %) of the weight (Cs) of the agglomerated sample that remains on the 12.5-mm mesh sieve among the heat-treated mixed sample to the total weight (MT) of the heat-treated mixed sample.

A process for preparing an oriented polyester film, which comprises:

• polymerizing a diol component and a dicarboxylic acid component to prepare a polyester resin;
• preparing an oriented polyester sheet from the polyester resin;
• and
• heat-setting the oriented sheet,
• wherein when the film is subjected to a first heat treatment and a second heat treatment and is then analyzed by differential scanning calorimetry (DSC), a first melting temperature (Tm1) and a second melting temperature (Tm2) appear, and
• the ratio (H2/H1) of the second heat of fusion (H2) at the second melting temperature (Tm2) to the first heat of fusion (H1) at the first melting temperature (Tm1) is 0.1 or more.