Polyester resin composition, polyester film, and laminate for electronic device

1. A polyester film comprising a synthesized polyester resin comprising a diol residue and a dicarboxylic acid residue,

wherein the diol residue comprises a cyclohexanedimethanol residue and the dicarboxylic acid residue comprises an isophthalic acid residue and a terephthalic acid residue,

wherein an amount of the isophthalic acid residue is more than 0 mol % and 20 mol % or less when a total amount of the dicarboxylic acid residue is considered as 100 mol %,

wherein an amount of the cyclohexanedimethanol residue is 50 to 100 mol % when a total amount of the diol residue is considered as 100 mol %,

wherein the polyester film further comprises an antioxidant applied to the synthesized polyester resin,

wherein the antioxidant comprises a phenol-based antioxidant, a phosphorus-based antioxidant, and a sulfur-based antioxidant,

wherein a durability index (unit:/%) of the polyester film calculated from Equation 1 below is 0.12/% to 0.32/%:

Durability Index(/%)=ΔYI*10/ΔIV (%)  [Equation 1]

where, in Equation 1, ΔYI is a variation of yellow index before and after the polyester film is left for 60 minutes in an oven under a condition of 250° C., and ΔIV (%) is a ratio of intrinsic viscosity of the polyester film after a treatment of being left for 60 minutes in an oven of 250° C. expressed as % based on intrinsic viscosity of the polyester film before the treatment,

wherein the phosphorous-based antioxidant is selected from the group consisting of 3,9-bis (2,4-dicumylphenoxy)-2,4,8,10-tetraoxa-3,9-diphosphaspiro[5.5]undecane; tetrakis(2,4-di-tert-butylphenyl) 4,4′-biphenylene diphosphonate; and a combination thereof,

wherein the sulfur-based antioxidant is selected from the group consisting of dimyristyl-3,3′-thiodipropionic acid ester; distearyl-3,3′-thiodipropionic acid ester; lauryl stearyl-3,3′-thiodipropionic acid ester; pentaerythrityl tetrakis (3-laurylthio propion ester); and a combination thereof, and

wherein the phenol-based antioxidant is selected from the group consisting of tetrakis[methylene-3-(3,5-di-tert-butyl-4-hydroxyphenyl)propionate]methane; octadecyl-3-(3,5-di-tert-butyl-4-hydroxyphenyl)propionate; Benzenepropanoic acid, 3,5-bis(1,1-dimethylethyl)-4-hydroxy, alkyl ester (alkyl has 7 or 9 carbon atoms); triethylene glycol-bis-3-(3-tert-butyl-4-hydroxy-5-methylphenyl)propionate; tris(3,5-di-tert-butyl-4-hydroxybenzyl) isocyanurate; 1,3,5-trimethyl-2,4,6-tris(3,5-di-tert-butyl-4-hydroxybenzyl)benzene; and a combination thereof,

wherein the antioxidant comprises the phosphorus-based antioxidant and the sulfur-based antioxidant in a weight ratio of 1:0.8 to 1.2 and

wherein the polyester film further comprises an electrostatic agent in an amount of 300 to 1000 ppm based on the polyester resin of 100 parts by weight, and the electrostatic agent comprises a mixture of magnesium and potassium acetate.

2. The polyester film of claim 1 , wherein the variation of yellow index is less than 5.

3. The polyester film of claim 1 , wherein the ratio of the intrinsic viscosity of the polyester film after a treatment of being left for 60 minutes in an oven of 250° C. expressed as % based on the intrinsic viscosity of the polyester film before the treatment is 85% or more.

4. The polyester film of claim 1 , wherein the sulfur-based antioxidant is comprised in an amount of 30 parts by weight or more based on 100 parts by weight of the phenol-based antioxidant,

and

wherein the phosphorus-based antioxidant and the phenol-based antioxidant are comprised in a weight ratio of 1:0.1 to 4.

5. The polyester film of claim 1 , further comprising a residual catalyst.

6. The polyester film of claim 5 , wherein the residual catalyst is a titanium.

7. The polyester film of claim 1 ,

wherein the mixture contains a magnesium and potassium in an amount ratio (mole ratio) of 1:1 to 1:10.