Abstract: There is provided a membrane switch film comprising polyethylene 2, 6-naphthalenedicarboxylate as the major component and having excellent handling properties and durability, and particularly a film which is suitable for a membrane switch to be used in automobile interior devices which are potentially exposed to high temperature. The film is a membrane switch film having a refractive index in the range of 1.770–1.790 on both surfaces in either or both the film processing direction and the widthwise direction and an absolute value of no greater than 0.015 for the difference between the refractive indexes of both surfaces.

Abstract: A film which is a biaxially oriented film comprising polyethylene-2,6-naphthalenedicaboxylate as a principal component, having a thermal strain ratio RMD (150) in the machine direction of the film at a temperature of 150° C. is ?1.5%?RMD (150)?0.0% when the thermal strain ratio RMD (T) in the machine direction of the film at a temperature T° C. based on the length LMD (t) in the machine direction (MD) of the film at a temperature t° C. is defined by RMD(T)={[LMD(T)?LMD(35)]/LMD(35)}×100(%), excellent in insulation characteristics without lowering processing characteristics, especially the characteristics during hot-pressing and suitable as a dielectric for capacitors.

Abstract: There is provided a membrane switch film comprising polyethylene-2,6-naphthalenedicarboxylate as the major component and having excellent handling properties and durability, and particularly a film which is suitable for a membrane switch to be used in automobile interior devices which are potentially exposed to high temperature. The film is a membrane switch film having a refractive index in the range of 1.770-1.790 on both surfaces in either or both the film processing direction and the widthwise direction and an absolute value of no greater than 0.015 for the difference between the refractive indexes of both surfaces, or having a melting sub-peak temperature of between 220° C. and 250° C. as measured with a differential scanning calorimeter (DSC) and an absolute value of no greater than 6° C. for the difference between the melting sub-peak temperature on one surface and the melting sub-peak temperature on the other surface.

Abstract: A biaxially oriented polyester film which has excellent productivity while ensuring a transferred image having excellent shape reproducibility and gradation and is particularly suitable for use as a base film for a heat-sensitive transfer ribbon. This film is formed by simultaneous biaxial orientation and contains 0.1 to 2 wt % of inert inorganic particles having an average particle diameter of 0.5 to 5 &mgr;m. This biaxially oriented polyester film has a value of 0.028 or less obtained by dividing the heat shrinkage factor (HS) (%) in a longitudinal direction at 200° C. by the F-5 value (N/mm2) (F5) in the longitudinal direction measured at normal temperature (about 23° C.) of the film.

Abstract: A biaxially oriented polyester film which has excellent productivity while ensuring a transferred image having excellent shape reproducibility and gradation and is particularly suitable for use as a base film for a heat-sensitive transfer ribbon. This film is formed by simultaneous biaxial orientation and contains 0.1 to 2 wt % of inert inorganic particles having an average particle diameter of 0.5 to 5 &mgr;m. This biaxially oriented polyester film has a value of 0.028 or less obtained by dividing the heat shrinkage factor (HS) (%) in a longitudinal direction at 200° C. by the F-5 value (N/mm2) (F5) in the longitudinal direction measured at normal temperature (about 23° C.) of the film.

Abstract: A film which is a biaxially oriented film comprising polyethylene-2,6-naphthalenedicaboxylate as a principal component, having a thermal strain; ratio RMD (150) in the machine direction of the film at a temperature of 150° C. is −1.5%≦RMD (150)≦0.0% when the thermal strain ratio RMD (T) in the machine direction of the film at a temperature T° C. based on the length LMD (t) in the machine direction (MD) of the film at a temperature t ° C.

Abstract: A biaxially oriented polyester film for a thermal transfer ribbon characterized in that the biaxially oriented polyester film comprises a copolymerized polyethylene-2,6-naphthalate obtained by polycondensing 90 to 99.9 mole % of 2,6-naphthalenedicarboxylic acid and 0.1 to 10 mole % of isophthalic acid as dicarboxylic acid component, and 97 to 100 mole % of ethylene glycol component and 0 to 30 mole % of diethylene glycol component as diol component, the alternating current volume resistivity of the molten product of the film is 66×108 &OHgr;cm or less, the plane orientation coefficient of the film is 0.230 or more and 0.275 or less, and the density of the film is 1.3450 g/cm3 or more.

Abstract: An aromatic polyester film, which comprises an aromatic polyester comprising 2,6-naphthalenedicarboxylic acid as the main dicarboxylic acid component and 1,3-propanediol as the main diol component and having a density of at least 1.310 g/cm3. A laminated film comprising another polyester layer can be formed from this aromatic polyester film. An aromatic polyester containing a small amount of a sulfonic acid phosphonium salt used as one of the aromatic polyesters forming this laminated film is excellent in electrostatic casting properties and resistance to the contamination of an electrostatic wire, and an aromatic polyester containing an inorganic anti-fungus agent is used for antifungal application.

Abstract: A polyester film which is excellent in uniform light diffusibility, heat-resistant dimensional stability and luminance and suitable as a substrate of a light-diffusing plate of a liquid crystal display device. The film comprises a polyester containing polyethylene-2,6-naphthalene dicarboxylate as a main component and has a heat shrinkage in two directions perpendicular to each other in the surface of the film of not higher than 0.3% when heat-treated at 105° C. for 30 minutes, a dimensional change rate in two directions perpendicular to each other in the surface of the film under a stress of 0.37 MPa within a temperature range of 30 to 150° C. of not higher than 1.0%, a density of not lower than 1.350 g/cm3, a total light transmittance of not lower than 87%, a haze value of lower than 1.5% and a thickness of 50 to 150 &mgr;m.

Abstract: A composite film for a film condenser, which comprises a biaxially oriented film made of polyethylene-2,6-naphthalenedicarboxylate as a main polymer component and an electrically conductive metal thin layer formed on the surface of the biaxially oriented film, wherein the number of flyspecks having an average diameter of 60 &mgr;m or greater in the surface of said biaxially oriented film is 20/m2 or less and the number of portions failing to satisfy a dielectric breakdown voltage of 200 V/&mgr;m (electrical insulation defects) in said composite film is 20/m2 or less, and a biaxially oriented film therefor. According to the present invention, there is provided a high-quality composite film for a film condenser, which has excellent physical properties and electric characteristics. Further, there is provided a very thin biaxially oriented film excellent in processability and surface properties and usable for the composite film.

Abstract: A laminate film for preventing glass from shattering, which comprises: (A) a biaxially oriented polyester film of a copolyester containing ethylene-2,6-naphthalenedicarboxylate recurring units in an amount of at least 80 mol % of all recurring units, (B) an adhesive coating film on at least one side of the above biaxially oriented polyester film, (C) a hard coat layer on the above adhesive coating film, and (D) an antireflection layer on the above hard coat layer. This laminate film has not only excellent adhesive properties, surface hardness and abrasion resistance but also sufficient transparency, antireflection property and glass shatterproof performance.

Abstract: A biaxially oriented polyester film for thermal transfer use produced by using a polyester composed of a dicarboxylic acid component and a diol component as a constituent component characterized in that said film contains a sulfonic acid quaternary phosphonium salt having an ester-forming functional group in an amount of 0.1 to 40 mmol % based on said dicarboxylic acid component, the alternate current volume resistivity of the film is 6×108 &OHgr;·cm or below in molten state and the endothermic subpeak temperature of the film other than the melting point and determined by DSC is between 225° C. and the melting point, a laminated film produced by forming an adhesiveness improving layer on at least one surface of the biaxially oriented polyester film, and its production process.

Abstract: A base film for photographic films formed from a copolyester comprising 97 to 100 mol % of 2,6-naphthalenedicarboxylic acid and 0 to 3 mol % of a dicarboxylic acid other than 2,6-naphthalenedicarboxylic acid and (i) 87 to 99.8 mol % of ethylene glycol, 0.2 to 10 mol % of bis[4-(.omega.-hydroxyalkoxy)phenyl]sulfone and 0 to 3 mol % of a glycol other than ethylene glycol and bis[4-(.omega.-hydroxyalkoxy)phenyl]sulfone or (ii) 97 to 100 mol % of ethylene glycol, 0 to 3 mol % of a diol other than ethylene glycol and 1 to 7 mol % of an oxycarboxylic acid. This base film has an endothermic peak having a peak top temperature, measured by a differential scanning calorimeter, of 120 to 160.degree. C. and showing an endothermic energy of 0.3 mJ/mg or more.

Abstract: A biaxially oriented polyester film for a membrane switch, which is made from a polyester containing at least 80 mol % of ethylene-2,6-naphthalene dicarboxylate recurring units and which has an endothermic peak with an endothermic energy of at least 0.4 mJ/mg at a temperature of 110 to 160.degree. C.This film is produced by subjecting a biaxially oriented polyester film produced from the above polyester in accordance with a method known per se to the following steps in the order named:(1) the step of heating the film under no strain at a temperature of 150 to 180.degree. C. for 1 to 5 hours; and(2) the step of heating the film in an unrolled or rolled state at a temperature of 80 to 122.degree. C. for 5 to 200 hours.

Abstract: A biaxially oriented film (1) which is substantially formed from a polyethylene naphthalate copolymer comprising ethylene-2,6-naphthalate units in an amount of 90 to 99.9 mol % based on the total of all recurring units and an isophthalic acid component or a decalin-2,6-dicarboxylic acid component in an amount of 0.1 to 10 mol % based on the total of all dicarboxylic acid components and which has (2) Young's modulus of 500 kg/mm.sup.2 or more in each of a longitudinal direction and a transverse direction, (3) a plane orientation coefficient of 0.230 to 0.275 and (4) a density of 1.350 g/cm.sup.3 or more.

Abstract: A laminated base film for a photographic film, (A) which is a laminated film comprising a first layer formed substantially of polyethylene-2,6-naphthalenedicarboxylate and a second layer formed substantially of a polymer composition containing a 2,6-naphthalenedicarboxylate unit ##STR1## and an ethylene unit (--CH.sub.2 CH.sub.2 --) in a total amount of at least 50% by weight, and (B) which has a haze value of 3.0% or less, (C) in which the first layer has a plane orientation coefficient (NS.sub.1) of 0.270 or less, and (D) in which the first layer thickness/second layer thickness ratio is in the range of from 3/7 to 7/3 wherein the laminated film has a curl degree f.sub.2 in the longitudinal direction of 0 to 70%. This base film is provided with a proper curling which can be cured by the contraction of a photosensitive emulsion and has various suitable properties as a base film for a photographic film, such as transparency, lubricity, and the like.