Abstract: Disclosed is a biaxially oriented polyester film composed mainly of a polymer blend comprising [A] a polyester having recurring units of the following general formula (I): ##STR1## wherein n is 2, 4 or 6 and R is at least one member selected from the group consisting of ##STR2## in which X is H or Cl and at least one X is Cl, and [B] a copolyester having units represented by the general formula (I) and units represented by the following general formula (II) and/or the following general formula (III): ##STR3## wherein R.sup.I, R.sub.II and R.sup.III stand for at least one member selected from the group consisting of 1,3-phenylene, 1,4-phenylene, 2,6-naphthalene, 2,7-naphthalene, ##STR4## and having a flow-initiating temperature not higher than 350.degree. C. and a melt anisotropy-forming capacity, the molar ratio of the units represented by the general formula (II) and/or the general formula (III) being 0.5 to 18 mole % based on the total polymer blend.

Abstract: The present invention relates to a composite film comprising a plastic film and a protective layer which is formed on at least one surface of the film, wherein the protective layer is made of a mixture comprising (a) an inorganic swellable silicate having a layered structure and (b) a compound containing a silanol group at a weight ratio of (a) to (b) of between 1:1000 and 2:1 and an antistatic composite film comprising a plastic film and a coating layer which is formed on at least one surface of the film, wherein said coating layer is made of a mixture comprising (a) a swellable inorganic silicate having a layered structure and containing at least one ion selected from among aliphatic ammonium ions having at most 6 carbon atoms, sodium ion, silver ion and lithium ion as an interlayer ion and (b) at least one member selected from among water-soluble compounds and water-dispersible resins at a weight ratio of (a) to (b) of between 1:1000 and 2:1.

Abstract: The present invention relates to a polyethylene terephthalate film having the sum of F-5 values in longitudinal and transverse directions of 3500 to 5000 kg/cm.sup.2, absolute heat shrinkages in longitudinal and transverse directions at 100.degree. C. of up to 2.5% and amorphous orientation factor of -1.5 to 0.5, a process for the production thereof and a magnetic recording medium containing the film as a base. The polyethylene terephthalate film useful as a magnetic recording medium having super high-tensile-strength in both longitudinal and transverse directions and a low heat shrinkage is provided, while it has been considered that such properties could not be obtained in polyethylene terephthalate film.

Abstract: The present invention relates to a polyethylene terephthalate film having the sum of F-5 values in longitudinal and transverse directions of 3500 to 5000 kg/cm.sup.2, absolute heat shrinkages in longitudinal and transverse directions at 100.degree. C. of up to 2.5% and amorphous orientation factor of -1.5 to 0.5, a process for the production thereof and a magnetic recording medium containing the film as a base. The polyethylene terephthalate film useful as a magnetic recording medium having super high-tensile-strength in both longitudinal and transverse directions and a low heat shrinkage is provided, while it has been considered that such properties could not be obtained in polyethylene terephthalate film.

Abstract: The present invention relates to a polyethylene terephthalate film having the sum of F-5 values in longitudinal and transverse directions of 3500 to 5000 kg/cm.sup.2, absolute heat shrinkages in longitudinal and transverse directions at 100.degree. C. of up to 2.5% and amorphous orientation factor of -1.5 to 0.5, a process for the production thereof and a magnetic recording medium containing the film as a base. The polyethylene terephthalate film useful as a magnetic recording medium having super high-tensile-strength in both longitudinal and transverse directions and a low heat shrinkage is provided, while it has been considered that such properties could not be obtained in polyethylene terephthalate film.

Abstract: A polyester laminated film which comprises a transparent layer and delustered layer(s) laminated at least on one side face of the transparent layer is provided. The transparent layer is formed by a biaxially stretched polyester film mainly composed of polyethylene terephthalate, while the delustered layer is made of an at least uniaxially stretched polyester film which is mainly composed of a polyethylene terephthalate copolymer containing, as a copolymer composition, 1 to 20 mole % of ##STR1## wherein n is an integer from 2 to 140, and x represents ##STR2## and which also contains inert inorganic particles of 0.3 to 20 microns at 3 to 40% by weight.The film of the present invention as described above is roughened on the surface, and is superior in the writability and transcribability by pencils, ink, indian ink, etc., with an excellent transparency, and therefore, very useful for tracing films and the like.

Abstract: A diffusion transfer photographic film, in which a film of a polyethylene terephthalate copolymer is a part of the constituents thereof, the polyethylene terephthalate containing about 3 to about 20% by weight of a polyalkylene glycol, as a glycol component comonomer, based on the weight of the polyethylene terephthalate copolymer.

Abstract: Polyester film for magnetic tape including discrete polyester particles containing lithium, calcium and phosphorus, said particles having an average size in the range from 0.1 to 3.0 .mu.m and inert pigments having an average size of 1.0 to 10.0 .mu.m.Magnetic tape from this film has improved abrasion resistance and reduced the occurrence of "drop out".