Abstract: A polyester film roll is rolled on a core, wherein the difference R (m) between the maximum value and the minimum value of the diameters of the roll is not more than 2W×10?3 and not more than L×10?7, when the diameters of said roll are measured in the width direction of the roll, (therein, W is the width (m) of the film roll, and L is the length (m) of the rolled film). Alternatively, among the lengths of lines which are obtained by measuring the diameters of said roll in the width direction of the roll, drawing a straight line between both the ends of the curved line of the obtained roll diameters, the maximum distance on the convex portion between the curved and straight lines is not more than 500 ?m, and the maximum distance on the concave portion of the same is not more than 300 ?m.

Abstract: A biaxially oriented polyester film which has a Young's modulus (YMD) in the film machine direction (YMD) of 6.5 GPa or more and a Young's modulus in the width direction (YTD) of 8.2 to 9.8 GPa and is used as a base film for magnetic recording tapes of linear recording system, and a magnetic recording tape of linear recording system comprising the same as a base film. There are provided a biaxially oriented polyester film which has excellent dimensional stability, especially dimensional stability in the width direction and is suitable for use as a base film for magnetic recording tapes of linear recording system and a magnetic recording tape comprising the same.

Abstract: An object of the present invention is to provide a thin biaxially oriented film excellent in dimensional stability against humidity change, as well as a magnetic recording medium and a film capacitor using the same. The present invention provides a single layered or laminated biaxially oriented film comprising an aromatic polyester (a) and a polyolefin (b) having a melting point of from 230 to 280° C., wherein the ratio of the polyolefin (b) is from 5 to 30% based on the entire weight of the film, and the film thickness is from 1 to 10 ?m.

Abstract: A biaxially oriented laminated polyester film which has excellent dimensional stability to environmental changes such as temperature and humidity variations and excellent flatness and windability. A biaxially oriented laminated polyester film comprising a film layer B on one side of a film layer A and having a surface roughness (RaB) on the film layer B side which is 1.0 nm or more larger than the surface roughness (RaA) on the film layer A side, wherein at least one of the film layers comprises an aromatic polyester (I) composed of a glycol component and a dicarboxylic acid component containing 5 mol % or more and less than 80 mol % of a recurring unit represented by the following formula (A): wherein RA is an alkylene group having 1 to 10 carbon atoms.

Abstract: The polyester film roll, which is free from wrinkles and slacks generated with the passage of time and is having a good roll appearance, is provided without changing the characteristics of the film.

Abstract: An object of the present invention is to provide a thin biaxially oriented film excellent in dimensional stability against humidity change, as well as a magnetic recording medium and a film capacitor using the same. The present invention provides a single layered or laminated biaxially oriented film comprising an aromatic polyester (a) and a polyolefin (b) having a melting point of from 230 to 280° C., wherein the ratio of the polyolefin (b) is from 2 to 60% based on the entire weight of the film, and the film thickness is from 1 to 10 ?m.

Abstract: A thin biaxially oriented film excellent in dimensional stability against humidity change, as well as a magnetic recording medium and a film capacitor using the same. The present invention provides a laminated biaxially oriented film comprising: at least one layer comprising an aromatic polyester (a); and at least one layer of a polyolefin (b) having a melting point of from 230 to 280° C.; wherein the ratio of the polyolefin (b) is from 2 to 60% based on the entire weight of the film, and the film thickness is from 1 to 10 ?m.

Abstract: A biaxially oriented polyester film which has a Young's modulus (YMD) in the film machine direction (YMD) of 6.5 GPa or more and a Young's modulus in the width direction (YTD) of 8.2 to 9.8 GPa and is used as a base film for magnetic recording tapes of linear recording system, and a magnetic recording tape of linear recording system comprising the same as a base film. There are provided a biaxially oriented polyester film which has excellent dimensional stability, especially dimensional stability in the width direction and is suitable for use as a base film for magnetic recording tapes of linear recording system and a magnetic recording tape comprising the same.

Abstract: It is an object of the present invention to provide a biaxially oriented laminated polyester film which has excellent dimensional stability to environmental changes such as temperature and humidity variations and excellent flatness and windability. The present invention is a biaxially oriented laminated polyester film comprising a film layer B on one side of a film layer A and having a surface roughness (RaB) on the film layer B side which is 1.0 nm or more larger than the surface roughness (RaA) on the film layer A side, wherein at least one of the film layers comprises an aromatic polyester (I) composed of a glycol component and a dicarboxylic acid component containing 5 mol % or more and less than 80 mol % of a recurring unit represented by the following formula (A): wherein RA is an alkylene group having 1 to 10 carbon atoms.

Abstract: A biaxially oriented polyester film which has a Young's modulus (YMD) in the film machine direction (YMD) of 6.5 GPa or more and a Young's modulus in the width direction (YTD) of 8.2 to 9.8 GPa and is used as a base film for magnetic recording tapes of linear recording system, and a magnetic recording tape of linear recording system comprising the same as a base film. There are provided a biaxially oriented polyester film which has excellent dimensional stability, especially dimensional stability in the width direction and is suitable for use as a base film for magnetic recording tapes of linear recording system and a magnetic recording tape comprising the same.

Abstract: An object of the present invention is to provide a thin biaxially oriented film excellent in dimensional stability against humidity change, as well as a magnetic recording medium and a film capacitor using the same. The present invention provides a single layered or laminated biaxially oriented film comprising an aromatic polyester (a) and a polyolefin (b) having a melting point of from 230 to 280° C., wherein the ratio of the polyolefin (b) is from 2 to 60% based on the entire weight of the film, and the film thickness is from 1 to 10 ?m.

Abstract: A biaxially oriented polyester film for a high-density magnetic recording medium, particularly a high-density magnetic recoding medium of linear recording system, which has high strength in longitudinal and transverse directions, excellent dimensional stability in a crosswise direction and is flat and excellent in output characteristics and a process for producing the same. The biaxially oriented film is made from polyethylene-2,6-naphthalate and has a Young's modulus in a longitudinal direction of 8 GPa or more, a Young's modulus in a transverse direction of 6 GPa or more, a temperature expansion coefficient in the transverse direction (?t) of ?5×10?6/° C. to +12×10?6/° C., a humidity expansion coefficient in the transverse direction (?h) of 5×10?6/% RH to 12×10?6/% RH and a thermal shrinkage factor in the transverse direction at 105° C. of ?0.5 to +1.5%.

Abstract: A biaxially oriented polyester film, comprising a polyester containing inert particles, wherein (A) the smallest value of Young's modulus in the planar direction is 5 GPa or more, and the difference between the largest value and the smallest value is 1 GPa or less; (B) the largest value of thermal shrinkage factor when the film is heated at 105° C. for 30 minutes is 0.6% or less, and the difference between the largest value and the smallest value is 0.3% or less; (C) the center line average surface roughnesses (Ra) of the both surfaces of the film are in the range of 2 to 10 nm; and (D) the agglomeration ratio of the inert particles in the film is 30% or less. This film has a flat surface, few large projections formed by the agglomeration of particles, high strength, a small thermal shrinkage factor, rarely experienced an error (D/O), and had excellent head contact and dimensional stability as a base film for flexible disks, particularly high-density magnetic disks.

Abstract: A biaxially oriented polyester film for a high-density magnetic recording medium, particularly a high-density magnetic recoding medium of linear recording system, which has high strength in longitudinal and transverse directions, excellent dimensional stability in a crosswise direction and is flat and excellent in output characteristics and a process for producing the same. The biaxially oriented film is made from polyethylene-2,6-naphthalate and has a Young's modulus in a longitudinal direction of 8 GPa or more, a Young's modulus in a transverse direction of 6 GPa or more, a temperature expansion coefficient in the transverse direction (?t) of ?5×10?6/° C. to +12×10?6/° C., a humidity expansion coefficient in the transverse direction (?h) of 5×10?6/% RH to 12×10?6/% RH and a thermal shrinkage factor in the transverse direction at 105° C. of ?0.5 to +1.

Abstract: A biaxially oriented polyester film for a high-density magnetic recording medium, particularly a high-density magnetic recoding medium of linear recording system, which has high strength in longitudinal and transverse directions, excellent dimensional stability in a crosswise direction and is flat and excellent in output characteristics and a process for producing the same. The biaxially oriented film is made from polyethylene-2,6-naphthalate and has a Young's modulus in a longitudinal direction of 8 GPa or more, a Young's modulus in a transverse direction of 6 GPa or more, a temperature expansion coefficient in the transverse direction (?t) of ?5×10?6/° C. to +12×10?6/° C., a humidity expansion coefficient in the transverse direction (?h) of 5×10?6/% RH to 12×10?6/% RH and a thermal shrinkage factor in the transverse direction at 105° C. of ?0.5 to +1.

Abstract: The polyester film roll, which is free from wrinkles and slacks generated with the passage of time and is having a good roll appearance, is provided without changing the characteristics of the film.

Abstract: A biaxially oriented layered polyester film which is excellent in suitability for winding and processability while retaining the flatness of the flat surface and which gives a magnetic recording medium, especially a metal coating type high-recording-density magnetic recording medium, having excellent electromagnetic characteristics. The biaxially oriented layered polyester film comprises a second polyester layer and superposed on one side thereof a first polyester layer containing an ester of a C12 or higher aliphatic monocarboxylic acid with a polyhydric alcohol and three inert particulate materials differing in average particle diameter. In the film, one of the Young's moduli respectively in the longitudinal direction and transverse direction is 6 GPa or higher and the other is 4 GPa or higher.

Abstract: A biaxially oriented polyester film for magnetic recording media, which has (1) a dimensional change between before treated and after treated in a width direction of 0.40% or less when the film is treated at 49° C. and 90% RH under a load of 170 (g/12.65 mm) in a longitudinal direction for 72 hours, (2) a crystallinity of 27 to 45%, (3) a temperature expansion coefficient &agr;t (×10−6/° C.) and a humidity expansion coefficient &agr;h (×10−6/% RH) in a width direction of the film which satisfy the relationship (&agr;t+2&agr;h)≦45, (4) a heat shrinkage factor in a width direction of the film of 0 to 0.7%, and (5) a thickness of 3 to 7 &mgr;m. This film is useful particularly for digital data storage of a linear track system, is almost free from an error caused by track dislocation due to a dimensional change in the width of a tape and improves output characteristics.

Abstract: The polyester film roll, which is free from wrinkles and slacks generated with the passage of time and is having a good roll appearance, is provided without changing the characteristics of the film.

Abstract: A biaxially oriented layered polyester film which is excellent in suitability for winding and processability while retaining the flatness of the flat surface and which gives a magnetic recording medium, especially a metal coating type high-recording-density magnetic recording medium, having excellent electromagnetic characteristics. The biaxially oriented layered polyester film comprises a second polyester layer and superposed on one side thereof a first polyester layer containing an ester of a C12 or higher aliphatic monocarboxylic acid with a polyhydric alcohol and three inert particulate materials differing in average particle diameter. In the film, one of the Young's moduli respectively in the longitudinal direction and transverse direction is 6 GPa or higher and the other is 4 GPa or higher.