Patent ID: 9375903
Filing Date: 2016-06-28
CPC Classification: B32B,Y10T

Claim Text:
1. A laminated polyester film comprising a polyester base film (layer S) with at least one surface laminated with a lamination layer (layer C) containing polyester resin as a primary component, the surface of the lamination layer (layer C) having a wetting tension of 35 to 45 mN/m, and the polyester resin contained in the lamination layer (layer C) meeting requirements (a) to (c): (a) the lamination layer (layer C) contains polyesters (A) with glass transition temperatures (Tg) of 110 to 140° C. and polyesters (B) with glass transition temperatures (Tg) of 40 to 90° C., (b) at least either polyesters (A) or polyesters (B) contain both a monomer having a sulfonic acid component and a monomer having a tri- or higher-valent, carboxylic acid component, and (c) a mixing ratio between polyesters (A) and polyesters (B) is 10/90 to 60/40 wherein: the polyesters contained in the lamination layer (layer C) include polyesters (A) with glass transition temperatures (Tg) of 110 to 140° C. and polyesters (B) with glass transition temperatures (Tg) of 40 to 90° C., polyesters (A) and polyesters (B) contain a monomer having a sulfonic acid component and a monomer having a tri- or higher-valent, carboxylic acid component, and equations (d) to (g) below are satisfied, where SA (parts by mole) represents content of the monomers having a sulfonic acid component while CA (parts by mole) represents content of the monomers having a tri- or higher-valent, carboxylic acid component, relative to the total content, which accounts for 100 parts by mole, of all the monomer components contained in polyesters (A), whereas SB (parts by mole) represents content of the monomers having a sulfonic acid component while CB (parts by mole) represents content of the monomers having a tri- or higher-valent, carboxylic acid component, relative to the total content, which accounts 100 parts by mole, of all the monomer components contained in polyesters (B):