Teijin Limited

Teijin Dupont Films Japan Limited

Shinji Muro

Ieyasu Kobayashi

Hirofumi Murooka

Takeshi Ishida

Tetsuo Yoshida

Mitsuo Tojo

Katsuyuki Hashimoto

Tsuyonari Nohira

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&#xd7;10and not more than L&#xd7;10, 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 &#x3bc;m, and the maximum distance on the concave portion of the same is not more than 300 &#x3bc;m.

Polyester film roll

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.

Biaxially oriented polyester film and magnetic recording tape

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&#xb0; 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 &#x3bc;m.

Biaxially oriented film

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. The polyester film roll is a polyester film roll in which a polyester film is rolled on a core, characterized in that the difference R (m) between the maximum value and the minimum value is not more than 2 W&#xd7;10and not more than L&#xd7;10, 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 rolled length (m) of the film roll), or a polyester film roll in which a polyester film is rolled on a core, characterized in that, 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, and then vertically drawing the lines from said curved line to said straight line, the maximum length (maximum convex portion) on the convex portion side from said straight line is not more than 500 &#x3bc;m, and the maximum length (maximum concave portion) on the concave portion side from said straight line is not more than 300 &#x3bc;m.

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&#xb0; 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 &#x3bc;m.

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 (&#x3b1;t) of &#x2212;5&#xd7;10/&#xb0; C. to +12&#xd7;10/&#xb0; C., a humidity expansion coefficient in the transverse direction (&#x3b1;h) of 5&#xd7;10/% RH to 12&#xd7;10/% RH and a thermal shrinkage factor in the transverse direction at 105&#xb0; C. of &#x2212;0.5 to +1.5%.

Biaxially oriented polyester film and production process therefor

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 (&#x3b1;t) of &#x2212;5&#xd7;10/&#xb0; C. to +12&#xd7;10/&#xb0; C., a humidity expansion coefficient in the transverse direction (&#x3b1;h) of 5&#xd7;10/% RH to 12&#xd7;10/% RH and a thermal shrinkage factor in the transverse direction at 105&#xb0; C. of &#x2212;0.5 to +1.5%

Biaxially oriented polyester film and method for production thereof

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 C 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.

Growing community of inventors

Sagamihara, Japan

Shinji Muro