Teijin Limited

Shigeyoshi Masuda

Kinji Hasegawa

Masami Etchu

Dai Nakagawa

Masanori Nishiyama

Tatsuya Ogawa

Yukio Mitsuishi

Kohei Endo

Yoshimichi Hase

Provided is a highly insulating film having excellent electrical characteristics (breakdown voltage), heat resistance, and handling properties such as windability and processability. The highly insulating film is a biaxially stretched film made of a styrene polymer having a syndiotactic structure as a main component. The highly insulating film contains specific inert fine particles A, antioxidant, and polymer Y having a glass transition temperature Tg by DSC of 130&#xb0; C. or more each in a specific amount, and has a refractive index in the thickness direction of 1.5750 or more and 1.6350 or less.

Insulating film

The present invention is to provide an insulating film having a high breakdown voltage and excellent heat resistance and handling properties. The present invention is a biaxially oriented insulating film which contains (i) a styrene-based polymer having a syndiotactic structure and (ii) particles and which has a refractive index in the thickness direction of 1.6050 to 1.6550.

The polylactic acid film is obtained by melt extruding polylactic acid (A) prepared by melt kneading together polylactic acid (B) which comprises an L-lactic acid unit as the main ingredient and polylactic acid (C) which comprises a D-lactic acid unit as the main ingredient in a specific weight ratio, wherein the polylactic acid film has:

Polylactic acid film

A biaxially oriented laminated polyester film comprises a polyester substrate layer (A) and a polyester surface layer (B) containing inert particles wherein the polyester surface layer (B) has a thickness of 0.2 to 3 .mu.m with the thickness of the polyester surface layer (B) varying along the film width direction so that the surface layer (B) is thicker at the edges of the film and thinner at the center of the film. The thickness of the surface layer (B) also satisfies specified relationships based on surface layer thickness, birefringence, and orientation angle values at two different points along the film width direction in order to obtain a film whose surface layer (B) has a uniform surface roughness in the film width direction wherein the polyester surface layer (B) has a surface roughness Ra of 3 to 40 nm and a surface roughness Ra fluctuation ratio of 5% or less when measured along a distance of 500 mm in the film width direction. The laminated film can be slit and easily wound into pancake rolls.

Biaxially oriented laminated polyester film

A biaxially oriented laminated polyester film comprising a first polyester surface layer having (a1) a central line average roughness R.sub.aA of 1 to 7.9 nm, (b1) a 10-points average roughness R.sub.ZA of 15 to 400 nm and (c1) an R.sub.ZA /R.sub.aA ratio of 11-51, and a second polyester surface layer having (a2) a central line average roughness R.sub.aB which is greater than R.sub.aA and is 5 to 40 nm, (b2) a 10-points average roughness R.sub.ZB of 75 to 600 nm and (c2) an R.sub.ZB /R.sub.aB ratio of 20 or less, and satisfying the relationship between the first polyester surface layer and the second polyester surface layer, which is represented by the following expressions,

A biaxially oriented laminated polyester film comprising:

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Gifu, Japan

Shigeyoshi Masuda