Biaxially stretched polyester film and method for producing same, and optical sheet
Disclosed is a biaxially stretched polyester film containing an antimony compound as a catalyst component, and a magnesium compound and a phosphorus compound as additives, in which an amount of metal antimony included in residues on a membrane filter having an average pore diameter of 0.1 μm, after a solution in which 1 g of the biaxially stretched polyester is dissolved in 5 ml of hexafluoroisopropanol is filtered by the filter, is 10 to 100 mg per 1 kg of the biaxially stretched polyester.
1. A biaxially stretched polyester film containing an antimony compound as a catalyst component, and a magnesium compound and a phosphorus compound as additives,
wherein an amount of metal antimony included in residues on a membrane filter having an average pore diameter of 0.1 μm, after a solution in which 1 g of the biaxially stretched polyester is dissolved in 5 ml of hexafluoroisopropanol is filtered by the filter, is 10 to 100 mg per 1 kg of the biaxially stretched polyester.
2. The biaxially stretched polyester film according to claim 1 ,
wherein a micro heat absorption peak temperature Tmeta (° C.) of the biaxially stretched polyester film obtained by differential scanning calorimetry (DSC) satisfies the following Expression 1:
210° C.≤ T meta≤230° C. (Expression 1).
3. The biaxially stretched polyester film according to claim 1 ,
wherein the biaxially stretched polyester film contains diethylene glycol, and a content of the diethylene glycol is from 1.0 mol % to 1.5 mol %.
4. The biaxially stretched polyester film according to claim 1 ,
wherein the biaxially stretched polyester film further satisfies a relationship denoted by the following Expression 2:
20 ppm≤ W P ≤W Mg ≤55 ppm (Expression 2)
wherein in Expression 2, W P represents a content (ppm) of phosphorus in the biaxially stretched polyester film, and W Mg represents a content (ppm) of magnesium in the biaxially stretched polyester film.
5. The biaxially stretched polyester film according to claim 1 ,
wherein the biaxially stretched polyester film is used in an optical sheet.
6. An optical sheet, comprising:
the biaxially stretched polyester film according to claim 1 ; and
an easily adhesive layer which is disposed on at least one surface of the biaxially stretched polyester film, and contains at least one type of resin selected from a polyester resin, a urethane resin, an acrylic resin, or a melamine resin, in an amount of greater than or equal to 50 mass %.