Laminated polyester film for magnetic recording medium

A magnetic recording tape comprising of a magnetic recording layer and a biaxially oriented laminated polyester base film wherein the base film comprises a layer (A) of a polyester consisting essentially of 2,6-naphthalenedicarboxylic acid and ethylene glycol components, and a layer (B) of a copolyester consisting essentially of 2,6-naphthalenedicarboxylic acid, ethylene glycol, and diethylene glycol components, the copolyester containing 1-5% by weight of the diethylene glycol component, based on the weight of the layer (B) copolyester, the layer (A) being provided with the layer (B) on one surface or both surfaces thereof, wherein the laminated polyester film has a total thickness of 3 to 12 .mu.m and Young's moduli of at least 500 kg/mm.sup.2 in both the machine and transverse directions.

A magnetic recording disk comprising of a magnetic recording layer and a biaxially oriented laminated polyester base fill wherein the base film comprises a layer (A) of a polyester consisting essentially of 2,6-naphthalenedicarboxylic acid and ethylene glycol components, and a layer (B) of a copolyester consisting essentially of 2,6-naphthalenedicarboxylic acid, ethylene glycol, and diethylene glycol components, the copolyester containing 1-5% by weight of the diethylene glycol component, based on the weight of the layer (B) copolyester, the layer (A) being provided with the layer (B) on one surface or both surfaces of the layer (A), wherein the laminated polyester film has a total thickness of 30 to 80 .mu.m and Young's moduli of at least 500 kg/mm.sup.2 in both the machine and transverse directions.

A magnetic recording medium comprising of a magnetic recording layer and a biaxially oriented laminated polyester base film wherein the base film comprises a layer (A) of a polyester consisting essentially of 2,6-naphthalenedicarboxylic acid and ethylene glycol components and a layer (B) of a copolyester consisting essentially of 2,6-naphthalenedicarboxylic acid, ethylene glycol and diethylene glycol components, the copolyester containing 1 to 2.0% by weight of the diethylene glycol component, based on the weight of the layer (B) copolyester, the layer (A) being provided with the layer (B) on one surface or both surfaces of layer (A).

A magnetic recording tape comprising of a magnetic recording layer and a biaxially oriented laminated polyester base film wherein the base film comprises a layer (A) of a polyester consisting essentially of 2,6-naphthalenedicarboxylic acid and ethylene glycol components and a layer (B) of a copolyester consisting essentially of 2,6-naphthalenedicarboxylic acid, ethylene glycol and diethylene glycol components, the copolyester containing 1 to 2.0% by weight of the diethylene glycol, based on the weight of the layer (B) copolyester, the layer (A) being provided with the layer (B) on one surface or both surfaces of layer (A), wherein the laminated polyester film has a total thickness of 3 to 12 .mu.m and Young's moduli of at least 500 kg/mm.sup.2 in both the machine and transverse directions.

A magnetic recording disk comprising of a magnetic recording layer and a biaxially oriented laminated polyester base film wherein the base film comprises a layer (A) of a polyester consisting essentially of 2,6-naphthalenedicarboxylic acid and ethylene glycol components and a layer (B) of a copolyester consisting essentially of 2,6-naphthalenedicarboxylic acid, ethylene glycol and diethylene glycol components, the copolyester containing 1 to 2.0% by weight of the diethylene glycol, based on the weight of the layer (B) copolyester, the layer (A) being provided with the layer (B) on one surface or both surfaces of layer (A), the layer (B) having the thickness of 0.2 to 5 .mu.m, wherein the laminated polyester film has a total thickness of 30 to 80 .mu.m and Young's moduli of at least 500 kg/mm.sup.2 in both the machine and transverse directions.