Abstract: A magnetic tape favorably employable for recording computer data has a support, and on one side of the support, a essentially non-magnetic layer composed of a non-magnetic powder and a binder, and a magnetic layer composed of a ferromagnetic powder and a binder superposed in order, and on the other side, a back-coating layer containing carbon black, wherein the magnetic layer has a thickness of 0.08 to 0.28 &mgr;m and a magnetic flux of 0.02 to 0.1 G·cm.

Abstract: A magnetic recording medium composed of an aromatic polyamide support, a magnetic recording layer arranged on one surface side of the support, and a back-coating layer arranged on the other surface side of the support is improved in its running durability, by forming the back-coating layer from solid particles and a binder in amounts of the range of 8/10 to 20/10, and further by placing a subbing layer of polyester resin or polyurethane resin having a Tg of 40.degree. C.-80.degree. C. and a polar group such as --SO.sub.3 M, --OSO.sub.3 M, --COOM and --OPO.sub.3 MM.sup.1 (each of M and M.sup.1 is hydrogen, an alkaline metal ion or an ammonium ion) between the support and the back-coating layer.

Abstract: A magnetic recording tape favorably employable for computer data storage has a flexible polymer web, a magnetic recording layer arranged on one surface side of the web, and a backing layer arranged on another surface side of the web, characterized in that the recording tape has a thickness of 2 to 8 .mu.m and shows a Young's modulus of not less than 1,200 kg/mm.sup.2 in its longitudinal direction; and the backing layer has a thickness of 0.2 to 1 .mu.m and is composed of a binder, a carbon black, a non-magnetic powder I having Mohs' scale of hardness of 3 to 4.5 and another non-magnetic powder II having Mohs' scale of hardness of 5 to 9. Between the magnetic layer and the flexible polymer web, a non-magnetic undercoating layer composed of a binder and a non-magnetic powder can be provided.

Abstract: A magnetic recording disk having a good overwriting characteristic and an excellent electromagnetic characteristic, as well as superior running durability. The magnetic recording disk comprises a non-magnetic support having coated thereon, in the order, a non-magnetic layer comprising mainly a non-magnetic powder and a binder resin and a magnetic layer comprising mainly a ferromagnetic powder and a binder resin, wherein the magnetic layer is formed by applying a magnetic layer coating solution onto the coated non-magnetic layer while the non-magnetic layer remains in a wet condition, the average thickness of the magnetic layer is 0.5 .mu.m or less, and the maximum thickness and the minimum thickness thereof fall within the range of .+-.15% of the average thickness of the magnetic layer.

Abstract: Disclosed is a magnetic recording medium comprising a nonmagnetic support having thereon a magnetic layer comprising a ferromagnetic powder and a binder resin as the main components together with abrasive particles. The ferromagnetic powder is a hexagonal ferrite fine powder having particle sizes of from 0.01 to 0.2 .mu.m and a coercive force of from 600 to 2,000 Oe. The binder resin is composed of a polyurethane resin and/or a vinyl chloride resin each having at least one kind of a polar group, the abrasive particles are composed of a fine particle abrasive having a mean particle size of from 0.1 to 0.39 .mu.m and a coarse particle abrasive having a mean particle size of from 0.4 to 1.0 .mu.m, and the density of the coarse particle abrasive distributed in the vicinity of the surface of the magnetic layer is higher than that of the coarse particle abrasive distributed in the other region of the magnetic layer.

Abstract: A flexible magnetic disk is disclosed, which comprises a non-magnetic support having thereon a non-magnetic layer comprising mainly a non-magnetic powder and a binder resin, and a magnetic layer comprising mainly a ferromagnetic layer and a binder resin, in this order, wherein at least a part of the non-magnetic powder in the non-magnetic layer is an electrically conductive powder, and therein the product Et.sup.3 of Young's modulus (E) of the flexible magnetic disk and the cube of the thickness (t) thereof is 50 to 210 g.multidot.mm. The magnetic layer preferably has a thickness of not more than 0.5 .mu.m and the ferromagnetic powder preferably is ferromagnetic metallic powder or ferromagnetic hexagonal ferrite powder.

Abstract: There is disclosed a flexible magnetic recording disk which is suitable as a high capacity magnetic disk for data recording and has an excellent durability. The flexible magnetic recording disk comprises a non-magnetic support having thereon a non-magnetic layer comprising a non-magnetic powder and a binder resin, and a magnetic layer comprising a ferromagnetic powder and a binder resin, in this order, wherein the magnetic layer has a thickness of 1 .mu.m or less, which is 1/2 or less of the thickness of the non-magnetic layer; and the magnetic layer further contains the abrasive particles which comprise a first abrasive particles having a Mohs' hardness of 6 or more and an average particle size of 0.8 to 1.4 times as large as the average particle size of the magnetic powder and a second abrasive particles having a Mohs' hardness of 6 or more and an average particle size of 2 to 4 times as large as the average particle size of the ferromagnetic powder.

Abstract: A novel magnetic recording disc is provided comprising, a nonmagnetic support having thereon a nonmagnetic layer comprising nonmagnetic particles and a binder resin, and a magnetic layer comprising ferromagnetic particles and a binder resin, in this order. The nonmagnetic particles in the nonmagnetic layer are partially or entirely electrically conductive particles, the thickness of the magnetic layer is in the range of 0.5 .mu.m or less, and the orientation ratio of the ferromagnetic particles in the magnetic layer is 0.85 or more.A novel process for preparing the magnetic recording disc is provided. Further, a novel process for recording and reproduction of a signal having a shortest recordable wavelength of 1.5 .mu.m or less is provided, which utilizes the magnetic recording disc in conjunction with a magnetic head having a gap length (.delta.) of 0.50 .mu.m or less.

Abstract: A magnetic recording disc is disclosed which comprises a disc container with a liner comprising nonwoven fabric in which a flexible magnetic disc comprising a flexible non-magnetic support having on at least one side thereof a magnetic layer mainly comprising a ferromagnetic powder and a binder resin is rotably set, wherein said liner comprises (1) a nonwoven fabric layer mainly comprising rayon fiber on at least the side in contact with the magnetic layer, and (2) a nonwoven fabric layer mainly comprising polypropylene fiber, and said liner comprises from 70 to 80% by weight based on the liner of rayon fiber and from 20 to 30% by weight based on the liner of polypropylene fiber.

Abstract: A magnetic recording medium comprising (A) a non-magnetic support; (B) a non-magnetic layer comprising mainly a non-magnetic powder and a binder resin; and (C) a magnetic layer comprising mainly a ferromagnetic powder and a binder resin, wherein said non-magnetic layer is coated on said non-magnetic support; and said magnetic layer is coated over the previously formed non-magnetic layer while the previously formed non-magnetic layer is still wet; the thickness of the magnetic layer is 0.6 .mu.m or less; the Young's Modulus of the magnetic layer is from 50% to 95% of the Young's Modulus of the non-magnetic layer, and the glass transition temperature of the magnetic layer is lower than that of the non-magnetic layer. The magnetic recording medium has good electromagnetic characteristics and excellent running stability and running durability. It is suitable as a disc medium for high-density recording at a shortest recording wavelength of 1.5 .mu.

Abstract: The present invention relates to a magnetic recording medium comprising, in the following order:(a) a nonmagnetic support;(b) a nonmagnetic layer comprising nonmagnetic particles and a binder resin; and(c) a magnetic layer comprising ferromagnetic particles and a binder resin;wherein said magnetic layer has a thickness of 0.8 .mu.m or less and said nonmagnetic layer and said magnetic layer are formed by a process which comprises the steps of coating a nonmagnetic layer coating solution on said nonmagnetic support, and then subsequently coating a magnetic layer coating solution on said nonmagnetic layer coating solution wile said nonmagnetic layer is wet and, further, wherein the solvent used in said nonmagnetic layer coating solution has a higher boiling point than the solvent used in said magnetic layer coating solution.

Abstract: A magnetic disc having excellent running durability is disclosed, which comprises a non-magnetic support and a magnetic layer on the non-magnetic support, the layer being composed mainly of a ferromagnetic metal powder and a binder resin, wherein the ferromagnetic metal powder has a pH value of less than 7.0 and a specific surface area as determined by the BET method of at least 40 m.sup.2 /g, and the glass transition temperature of the magnetic layer is at least 75.degree. C.

Abstract: A magnetic recording medium comprising a non-magnetic support having thereon a magnetic layer comprising ferromagnetic metal powder and a binder, the magnetic layer further comprising carbon black having an average particle diameter of 250 m.mu. or more in an amount of from 1 to 10 parts by weight per 100 parts by weight of the ferromagnetic metal powder, and an ester of tridecyl alcohol with stearic acid and/or an ester of tridecyl alcohol with palmitic acid in an amount of from 5 to 20 parts by weight per 100 parts by weight of the ferromagnetic metal powder.

Abstract: A magnetic disk comprising a non-magnetic support having provided thereon a magnetic layer comprising ferromagnetic particles, and a binder resin, wherein said magnetic layer is such that when sputtering is conducted on said magnetic layer from the surface of the magnetic layer in the direction of the depth of the magnetic layer by the Auger electron spectroscopic method, and the concentration of carbon atoms resulting from the sputtering is measured, a sputtering time (T.sub.1) required for the carbon atom concentration to be (C.sub.0 +C.sub.2)/2 is in the range of from 8 to 98 minutes, wherein C.sub.0 is a carbon atom concentration value obtained at the initiation of the sputtering and C.sub.2 is a carbon atom concentration value after the carbon atom concentration becomes constant.

Abstract: A novel flexible magnetic disc is provided comprising a protective layer on the periphery of a central hole, wherein the protective layer comprises of two layers, the lower one of the two layers being a composition mainly composed of a printing ink and the upper one being a composition mainly composed of a resin obtained by irradiating a radiation-polymerizable compound with radiation so that it cures.

Abstract: A magnetic recording medium comprising a nonmagnetic support having thereon a magnetic layer comprising a binder and ferromagnetic particles dispersed therein, wherein the binder comprises (a) a vinyl chloride resin, (b) a phenoxy resin, (c) a polycarbonate polyurethane resin and (d) a polyisocyanate; and said magnetic layer further comprises at least one lubricating agent selected from the group consisting of polyalkylnenoxide alkylphosphate, an alkali salt thereof, and lecithin.

Abstract: A magnetic recording medium is disclosed, comprising a nonmagnetic support having thereon a magnetic layer, wherein at least one of ester compounds represented by formula (I) is present in or on the magnetic layer, ##STR1## wherein R.sub.1 represents a straight chain, saturated alkyl group having 6 to 12 carbon atoms, R.sub.2 represents a straight chain, saturated alkyl group having 4 to 10 carbon atoms, and R represents a branched or straight chain alkyl group having 4 to 22 carbon atoms.

Abstract: A magnetic recording medium is described, comprising a nonmagnetic support having thereon a magnetic layer containing ferromagnetic particles which are a hexagonal system tabular particle, and which have an axis of easy magnetization in a direction of perpendicular to the major axis of the plate and are dispersed in a binder, wherein said ferromagnetic particles have a saturation magnetization of 60 emu/g or higher, a specific surface area (BET method) of from 25 to 70 m.sup.2 /g, an average particle diameter of from 0.01 to 0.2 .mu.m, and a coercive force of from 400 to 2000 oersteds, and said biner contains a resin having at least one kind of polar group in an amount of 1.times.10.sup.-5 eq/g or more of the polar group.

Abstract: A flexible disk jacket for accommodating therein a disk-like magnetic recording medium to form a flexible disk is formed by folding and bonding a plastic sheet into a bag-like shape. The plastic sheet is of a composite sheet material formed by laminating an outer layer and an inner layer respectively consisting of at least one plastic layer. The outer layer is colored and has heat sealability and heat resistance. The inner layer has heat sealability and antistatic properties.

Abstract: A smoothing apparatus which includes at least one set of two rolls at least one of which is a metal roll, and a high-frequency dielectric heater positioned prior to the rolls. A magnetic recording medium is first heated by the high-frequency dielectric heater and then pressed between the rolls to smooth the surface of the magnetic layer of the magnetic recording medium.