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: 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 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 laminated polyester film excellent in blocking resistance and processing suitability and exhibiting excellent electromagnetic transducing characteristics and excellent travel durability, when processed into a magnetic recording medium, and an electromagnetic recording medium using the laminated polyester film as a base film, are provided. This laminated polyester film comprises a polyester layer B containing a cyclic trimer in an amount of not more than 0.8 percent by weight, having a terminal carboxyl group concentration of not more than 35 eq/106 g and containing inactive particles B having an average particle diameter of 50 to 100 nm, and a polyester layer A laminated to one side of the polyester layer B and not containing inactive particles or containing inactive particles A having a smaller average particle diameter than that of the inactive particles B.

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: 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 multilayer film which comprises a first layer comprising a polyethylene-2,6-naphthalene dicarboxylate and a second layer comprising a thermoplastic resin having a lower refractive index than the polyethylene-2,6-naphthalene dicarboxylate constituting the first layer, wherein:

Abstract: A base film for magnetic recording media, comprising a film layer containing inert fine particles and having an agglomeration rate of the inert fine particles on the surface of the film of 4 to 20%, or a film layer containing inert fine particles and an ester wax of an aliphatic monocarboxylic acid having 8 or more carbon atoms and a polyhydric alcohol and having a water contact angle of the exposed surface of 70 to 90°. A magnetic recording medium, particularly a metal deposited thin film magnetic recording medium comprising this base film is excellent in electromagnetic conversion characteristics.

Abstract: There is provided a multilayer film which is useful as a refractive polarizer film or a semi-transparent film. The multilayer film comprises a first layer comprising of a polyester whose main recurring unit is ethylene-2,6-naphthalene dicarboxylate and a second layer comprising mainly of a thermoplastic resin which is different from the polyester of the first layer, wherein at least one of the first and second layers contains 0.001 to 0.5 wt % of inert fine particles having an average particle diameter of 0.01 to 2 &mgr;m; the first and second layers each have a thickness of 0.05 to 0.3 &mgr;m and are laminated alternately to form a laminate comprising at least 11 layers; the laminate is oriented at least in one direction; and the second layer has a lower refractive index than the first layer at least in one direction. This multilayer film has excellent handling properties such as film formability and windability and an easily adjustable reflectance.

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 laminated polyester film excellent in blocking resistance and processing suitability and exhibiting excellent electromagnetic transducing characteristics and excellent travel durability, when processed into a magnetic recording medium, and an electromagnetic recording medium using the laminated polyester film as a base film, are provided.

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 (&agr;t) of −5×10−6/° C. to +12×10−6/° C., a humidity expansion coefficient in the transverse direction (&agr;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 to be laminated onto a metal plate and molded, (A) which comprises a copolyester comprising (a) terephthalic acid in an amount of 82 to 100 mol % and 2,6-naphthalenedicarboxylic acid or a combination of 2,6-naphthalenedicarboxylic acid and other dicarboxylic acid in an amount of 0 to 18 mol % of the total of all dicarboxylic acid components and (b) ethylene glycol in an amount of 82 to 100 mol % and cyclohexanedimethanol or a combination of cyclohexanedimethanol and other diol in an amount of 0 to 18 mol % of the total of all diol components, having (c) a glass transition temperature of 78° C. or more and (d) a melting point of 210 to 250° C., and containing (e) porous silica particles with a pore volume of 0.5 to 2.0 ml/g which are agglomerates of primary particles having an average particle diameter of 0.001 to 0.1 &mgr;m; and (B) which has the following relationship between the highest peak temperature (Te, °C.

Abstract: The invented film comprises a layer A composed of a copolyester A, a layer B composed of a copolyester B, and a layer C composed of copolyester C. Layer A is laminated to one side of the layer B. Layer C is laminated to the other side of Layer B. Copolyester A contains 0-15 wt % of rutile titanium oxide (average particle diameter 0.1-0.5 &mgr;m). Copolyester B contains 10-50 wt % of the rutile titanium oxide. Copolyester C contains 0-15 wt % of the rutile titanium oxide. Each of Copolyester A, B, and C has a melting point of 210-245° C. The intrinsic viscosity (&eegr;A) of the polymer part of copolyester A, the intrinsic viscosity (&eegr;B) of the polymer part of copolyester B, and the intrinsic viscosity (&eegr;C) of the polymer part of copolyester C satisfy the following relationship. 0.46≦&eegr;B≦0.66, |&eegr;A-&eegr;B|<0.15, |&eegr;C-&eegr;B|<0.15, and |&eegr;A-&eegr;C|<0.15.

Abstract: A biaxially oriented polyester film: (A) which comprises a composition comprising at least two thermoplastic polyesters; (B) which has at least two melting peaks which satisfy difference between being in range of 5 to 20° C. and average of the both melting peak temperature being in range of 200 to 230° C. when measured by DSC at a temperature elevation rate of 2° C./min by superimposing a periodic temperature variation of ±1° C./min; the highest melting peak temperature (° C.) and the lowest melting peak temperature (° C.); (C) which has on the film plane two crossing directions having a thermal shrinkage factor at 100° C. for 10 minutes of 16 to 25%; and (D) which has a thickness of 0.2 to 7 &mgr;m.

Abstract: Provided is a polyester film containing a lubricant having an average particle diameter of 0.001 to 2.5 .mu.m in an amount of 0.01 to 5.0% by weight and suited for the lamination onto the surface that comes in contact with the contents of an easy-open can cap. The polyester film has a plane orientation coefficient of 0.115 to 0.140, two or more endothermic peaks in DSC curve in the range of 170 to 270.degree. C., a peak temperature of 60 to 120.degree. C. of a complex elastic modulus (E") in water and an intrinsic viscosity of 0.50 to 0.64 dl/g. Having these features, the polyester film laminated onto a metal sheet is excellent in can-capping processability and in corrosion resistance even after holding at high temperature.

Abstract: A biaxially oriented polyester film to be laminated onto a metal plate and molded, which comprises a copolyester, said copolyester comprising (a) terephthalic acid in an amount of 82 to 100 mol % and 2,6-naphthalenedicarboxylic acid or a combination of 2,6-naphthalenedicarboxylic acid and other dicarboxylic acids in an amount of 0 to 18 mol % of the total of all dicarboxylic acid components and (b) ethylene glycol in an amount of 82 to 100 mol % and cyclohexanedimethanol or a combination of cyclohexanedimethanol and other diols in an amount of 0 to 18 mol % of the total of all diol components, and having (c) a glass transition temperature of 78.degree. C. or higher and (d) a melting point of 210 to 250.degree. C. The said film has the following relationship between the highest peak temperature (Te, .degree. C.) of loss elastic modulus and the glass transition temperature (Tg, .degree. C.): Te-Tg.ltoreq.30, or its content of a free dicarboxylic acid diol ester is 50 ppm or less.