Abstract: A biaxially oriented polyester film containing 0.05 to 3 wt % of agglomerates of primary particles of aluminum oxide having an average particle size of 5 to 40 nm, the agglomerates having an average particle size of 50 to 400 nm. The film of the present invention is excellent in the wear resistance against various members such as a metal pin, and suitable for various industrial purposes including a base film of a magnetic recording medium.

Abstract: A biaxially oriented polyester film containing 0.01 to 4 wt %, based on the polyester film, of inorganic particles, the volumetric shape parameter being 0.02 to 0.2, the weight-average particle size being 0.05 to 3 .mu.m, and the ratio (Dw/Dn) of the weight-average particle size (Dw) and the number-average particle size (Dn) being not more than 1.1 is disclosed. The film of the present invention has a uniform surface and shows excellent running property and wear resistance so that it is useful as a base film for a magnetic tape, for example. Thus, the film of the present invention has a high industrial value.

Abstract: Disclosed herein is a polyester composition which comprises a polyester with a terminal carboxyl group content of 40 to 80 equivalents/10.sup.6 and 0.0 to 5 wt %, based on the total amount of the polyester composition, aluminum oxide particles of 0.005 to 5 .mu.m in average particle diameter and which has a melt resistivity of 6 x 10.sup.6 to 5 x 10.sup.8 .OMEGA..cm.By using the polyester composition, it is possible to successively produce a film having excellent wear resistance and flatness over a long production run.

Abstract: Disclosed in this invention is a polyester film for magnetic recording media, containing 0.05 to 5% by weight of inactive inorganic particles (A) having a Mohs hardness of 6 or above and an average particle size of 0.005 to 1.0 .mu.m and 0.01 to 2.0% by weight of inactive particles (B) having an average particle size which is greater than that of the particles (A) and in the range of 0.1 to 3.0 .mu.m, the polyester film having an intrinsic viscosity in the range of 0.52 to 0.65. The polyester film of this invention is excellent in abrasion resistance, scuff resistance and slitting qualities and useful as a base film for magnetic recording media.

Abstract: Disclosed herein is a uniaxially or biaxially oriented polyphenylene sulfide film wherein the number of n-order of interference fringes Hn (per mm.sup.2) as measured by a multiple interference method satisfies the following relations (1) and (2) at the same time:30.ltoreq.H.sub.1 .ltoreq.300 (1)10.ltoreq.H.sub.3 .ltoreq.

Abstract: A polyester film suitable for use as the magnetic tape base for video recording, capable of high density recording and having stable slidability or running characteristics. The polyester film is made of a polyester which contains 0.05-1 wt % particles containing calcium and phosphorus and of which the number n of the second interference fringes (number/mm.sup.2) and the average centerline roughness (.mu.m) satisfy the following relationships:n<30 (1)0.005.ltoreq.R.sub.a .ltoreq.0.

Abstract: There is disclosed a polyester film suitable for use in magnetic tapes having the characteristics represented by the following equations: ##EQU1## wherein N.sub.1 is the number of peaks of surface projections per millimeter;h is the average height in .mu.m of the surface projections;.theta. is the average steepness in degree of the surface projections;H.sup.2 is the mean square height in .mu.m.sup.2 of the surface projections; andn is the average refractive index.

Abstract: Disclosed herein is a biaxially oriented polyethylene naphthalate film having a center line average roughness [Ra(.mu.m)] and a film thickness [T(.mu.m)] which satisfy the following formula: ##EQU1## produced by the electrostatic cooling method from polymethylene naphthalate having a resistivity of 1.times.10.sup.7 to 5.times.10.sup.8 .OMEGA..cm as measured in the molten state.

Abstract: Disclosed herein is an electrical insulating material which comprises biaxially oriented polyethylene naphthalate film having a center line average roughness of 0.008 to 0.08 .mu.m as measured on the surface thereof and a resistivity of 5.times.10.sup.7 to 5.times.10.sup.10 .OMEGA..multidot.cm as measured in the molten state.

Abstract: There is disclosed a polyester film containing from 0.001% to 4% by weight fine particles of a crosslinked polymer having an average diameter of 0.1 to 5.mu., said fine particles being derived by pulverization from a crosslinked polymer having a specific surface area of at least 1 m.sup.2 /g and a pore volume of at least 0.1 ml/g. The films of the present invention are useful as high grade films and afford many advantages in various applications, for example, as magnetic tapes, capacitors, photography, printing plate making, releasing and the like.

Abstract: A polyester film is disclosed which comprises a polyester mainly consisting of polyethylene terephthalate and an additive amount of granular calcium terephthalate anhydride particles having a specific volume shape factor. The average particle diameter and additive amount of the granular calcium terephthalate anhydride particles may be controlled so that the film is particularly suitable as a metallized film or a condenser film.

Abstract: A polyester film is disclosed which comprises (a) a polyester mainly consisting of polyethylene terephthalate which includes first inert particles being precipitated in the polyester-forming reaction system and having an average particle diameter of 1 to 3 microns and which shows a solution haze of 25 to 75% and (b) an additive amount of second inert substance particles which are added to said polyester (a) insoluble in said polyester (a), inert to the polyester-forming reaction and have an average particle diameter of 1 to 5 microns. The film is useful as a base of a magnetic tape.