Abstract: A film roll in which the distance from the center line of the film roll to the edge of the film extending in a film winding direction is slightly changed in a film breadthwise direction.

Abstract: A biaxially oriented polyester film has a first layer of an aromatic polyester containing inert fine particles having an average particle diameter of 1.0 .mu.m or less in an amount of 0.01 to 2% by weight and a second layer of an aromatic polyester. The ratio (t/d) of the thickness t of the first layer to the average particle diameter d of the inert fine particles is 5 to 30. The exposed surface of the first layer has a dynamic friction coefficient (.mu.k.sub.1) against a metal of 0.15 to 0.50, the exposed surface of the second layer has a dynamic friction coefficient (.mu.k.sub.2) against a metal of 0.24 to 0.60, and the ratio .mu.k.sub.2 /.mu.k.sub.1 is 1.2 to 4.0. The film has a thickness of 2 to 8 .mu.m.

Abstract: A laminate film comprises a base film and a second film layer containing core-shell particles and a hydrophilic resin. The laminate film is useful for a base film for a magnetic recording medium.

Abstract: A laminate film comprises a base layer A formed of a thermoplastic resin A and a coating film layer B present on one surface of the base layer A. The coating film layer B contains a binder resin, inert fine particles and a surfactant. The surfactant consists essentially of 0.1 to 15% by weight of a surfactant X having an HLB value of 10 to 14 and 10 to 40% by weight of a surfactant Y having an HLB value of 16 to 18.5 based on the solid content of the coating film layer B to ensure that the average HLB value defined by the following equation be 15 to 18:average HLB=HLB(X).times.(P)X+HLB(Y).times.P(Y)wherein HLB(X) is an HLB value of the surfactant X, P(X) is a weight fraction of the surfactant X with respect to the total weight of the surfactants X and Y, HLB(Y) is an HLB value of the surfactant Y, and P(Y) is a weight fraction of the surfactant Y with respect to the total weight of the surfactants X and Y.The laminate film is useful as a base for a magnet recording medium.

Abstract: A biaxially oriented laminate polyester film consisting of a polyester layer A containing lubricant particles I and II and a polyester layer B laminated on one side of the polyester A, wherein each of the lubricant particles I and II contains non-agglomerated particles in a proportion of 80 to 100%; the lubricant particles I are selected from the group consisting of silica, calcium carbonate and crosslinked polymer particles and have an average particle diameter of 0.3 to 1.0 .mu.m and are contained in an amount of 0.005% by weight or more but less than 0.1% by weight; the lubricant particles II are selected from the group consisting of silica and crosslinked polymer particles and have an average particle diameter which satisfies the following expression (1):1<d.sub.I /d.sub.II .ltoreq.10 (1)wherein d.sub.I is an average particle diameter of the lubricant particles I and d.sub.II is an average particle diameter of the lubricant particles II,and are contained in an amount of 0.

Abstract: A biaxially oriented laminate film comprising a thermoplastic resin layer A and a thermoplastic resin layer B which is laminated on one side of the thermoplastic resin layer A. The surface of the thermoplastic resin layer A has protrusions having an average height of 2 to 85 nm and an average width of 20 to 500 .mu.m, at a density of 4 to 2,500/mm.sup.2. The thermoplastic resin layer B contains inert fine particles, and the surface of the thermoplastic resin layer B is rougher than the surface of the thermoplastic resin layer A. The laminate film can have furher a layer C on the thermoplastic resin layer A. The surface of the thermoplastic resin layer C has protrusions having an average height of 2 to 85 nm and an average width of 20 to 500 .mu.m, at a density of 4 to 2,500/mm.sup.2. These laminate film are useful as a base film for magnetic recording medium.

Abstract: A polyester film having low electrostatic and high adhesion properties and having formed on at least one side thereof a primer layer which has a softening point of 100.degree. to 170.degree. C. and essentially consists of (1) water-dispersible polyester resin containing, as a copolymer component, a sulfonic acid metal salt group-containing compound in an amount of 0.01 mol % or more and less than 0.5 mol % of the whole dicarboxylic acid compound (component A) and (2) polyethylene oxide-monoalkyl ether or a mixture of the same and a polyethylene oxide-polypropylene oxide block copolymer (component B). This adherent polyester film has low electrostatic properties and high heat resistance and is useful as a base film for a magnetic recording medium.

Abstract: There is provided a polyester film useful for production of a magnetic recording medium excellent in runnability, electromagnetic conversion characteristics and storage stability. In the polyester film, a continuous thin film which contains a resin as a matrix and acts as a primer layer for a magnetic layer is coated on one surface of a support film composed of a polyester. According to one embodiment thereof, the surface of the continuous thin film has (A) small protuberances each containing particles with an average particle size of less than 0.06 micrometer as a nucleus and having a height of 13 nm or less, (B) large protuberances each containing particles with an average particle size of 0.06 micrometer or more as a nucleus and having a height of 30 nm or less, and (C) micro-protuberances composed of a matrix resin alone, the numbers, per mm.sup.2 of the film, of these protuberances satisfying the formulas,An=1.0.times.10.sup.4 -1.0.times.10.sup.8 /mm.sup.2,Bn=0-4.times.10.sup.4 /mm.sup.2, andCn.ltoreq.4.