Abstract: A magnetic recording disk having a flexible non-magnetic support, an intervening non-magnetic layer of 0.5 to 5 .mu.m thick which contains as binder and anon-magnetic inorganic powder, and a magnetic layer of 0.02 to 0.5 .mu.m thick containing a binder, a ferromagnetic powder, carbon black and a lubricant to reduced in its tendency to make a magnetic head of a magnetic recording/reproducing device corrosive without reducing its running endurance, by employing a binder polymer containing no chlorine atom in its molecular structure for both the non-magnetic layer and the magnetic layer and by making the magnetic layer to have an upper surface having a Knoop hardness of 14 to 25.

Abstract: Information is recorded on a floppy disk in a state in which the confidentiality of the information is maintained. An ID signal representing ID information is magnetically recorded down to the lower layer of a floppy disk when data is recorded. A data signal representing information (a data file) to be recorded is also magnetically recorded down to the lower layer of the floppy disk. A security signal is magnetically recorded on the upper layer of the floppy disk over at least the data signal that has been recorded on the lower layer of the floppy disk. At the time of data reproduction, the ID signal is reproduced from the floppy disk and the ID information represented by the reproduced ID signal is compared with entered ID information. When the two items of compared ID information agree, the security signal that has been recorded on the upper layer of the floppy disk is erased. The data signal that has been recorded on the lower layer of the floppy disk is then reproduced.

Abstract: A magnetic recording medium is described, which comprises a nonmagnetic support having on at least one side thereof a lower layer and an upper layer, in which the upper layer is a magnetic layer mainly comprising ferromagnetic particles and a binder resin, and the lower layer is adjacent to the magnetic layer and is either a magnetic layer mainly comprising ferromagnetic particles and a binder resin or a nonmagnetic layer mainly comprising nonmagnetic particles and a binder resin, wherein the upper layer has a thickness of from 0.05 to less than 1.0 .mu.m the lower layer has a thickness of from 1 to 5 .mu.m and contains unsaturated alkyl carbonate having from 17 to 45 total carbon atoms represented by the following formula in an amount of from 1.8 to 100% by weight based on the amount of the binder resin: ##STR1## wherein R.sub.1 and R.sub.2 are the same or different and each represents a chain hydrocarbon group having from 8 to 22 carbon atoms, provided that at least one of R.sub.1 and R.sub.

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: 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 novel magnetic disc and process for the preparation thereof is disclosed, comprising a nonmagnetic support having thereon a magnetic layer comprising ferromagnetic metal particles and a binder resin containing at least a vinyl chloride copolymer, wherein the crystallite size of the ferromagnetic metal particles as determined by X-ray diffraction method is 300 .ANG. or less, and the ratio .alpha. at the surface of the magnetic layer of the integrated intensity of the Cl-2P spectrum as determined by X-ray photoelectron spectroscopy to that of the Fe-2P(3/2) spectrum is in the range of from 0.50 to 0.90. In a preferred embodiment, the vinyl chloride copolymer contains at least one polar group selected from the group consisting of --SO.sub.3 M, --OSO.sub.3 M, --PO.sub.3 M.sub.2, and --CO.sub.2 M wherein M represents hydrogen, an alkali metal or ammonium and at least one epoxy ring in the copolymer molecule.

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 recording medium is disclosed, comprising a nonmagnetic support having thereon a magnetic layer comprising ferromagnetic metal particles and binder resins, in which 35 to 55% by weight of said binder resins are a polar group-containing vinyl chloride copolymer and 10 to 25% by weight of said binder resins are a polyurethane resin obtained by the reaction of a polyisocyanate with a polyester polyol that is a product of the reaction of at least one of an alicyclic dihydric alcohol and an aromatic dihydric alcohol with at least one of an alicyclic dicarboxylic acid and an aromatic dicarboxylic acid, said polyurethane resin containing a polar group selected from the group consisting of --SO.sub.3 M, --COOM, --PO.sub.3 M wherein M is an H, Na, or K atom, and --NH.sub.2 in an amount of from 0.03 to 2% by weight, the amount of said binder resin in the magnetic layer being from 15 to 30 parts by weight per 100 parts by weight of said ferromagnetic metal particles.

Abstract: A magnetic recording medium is disclosed, comprising a nonmagnetic support having thereon a magnetic layer comprising mainly ferromagnetic metal particles of a specific surface area and binder resins, wherein at least part of said binder resins is a cellulosic resin having in side chains of the molecules thereof a polar group which is a sulfonic acid group, a metal sulfonate group, a phosphoric acid group, or a metal phosphate group.

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 having on a non-magnetic support a magnetic layer mainly composed of a ferromagnetic metal powder and a binder resin is disclosed, wherein the specific surface area S (m.sup.2 /g) of the ferromagnetic metal powder is from 30 to 65 and the magnetic layer further contains a fatty acid ester in a content Y (% by weight) to the ferromagnetic metal powder of the range of 0.05S+5.5.ltoreq.Y.ltoreq.-0.2S+24 when the specific surface area S is from 30 to less than 50 and the range of 0.06S+4.7.ltoreq.Y.ltoreq.-0.13S+21 when the specific surface area S is from 50 to 65. The magnetic recording medium is suitable for high density recording and exhibits excellent running durability.

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 magnetic recording medium is disclosed, comprising a nonmagnetic support having thereon a magnetic layer containing ferromagnetic particles which are dispersed in a binder and have a tabular hexagonal crystal shape with an axis of easy magnetization perpendicular to the plate, wherein said ferromagnetic particles have a specific surface area of from 50 to less than 70 m.sup.2 /g, and further said magnetic layer contains abrasive agents having a Mohs' hardness of 6 or more and having an average particle diameter of from 0.3 to 1.0 .mu.m in an amount of from 7 to 15 parts by weight per 100 parts by weight of the ferromagnetic particles.

Abstract: In an infrared sensor having a pyroelectric element and a FET in a high frequency electric field and infrared radiation shielding case, a capacitor is located in the case and connected to at least one of the drain and source electrodes of the FET in order to remove an influence due to an external high-frequency electric field.

Abstract: A capacitance type push-button switch which includes a movable member carried by the lower end of a key stem and including a holding member made of an elastic material of high compressibility and having a convex lower surface, a movable electrode made of an electrically conductive and flexible material held to the lower surface of the holding member, a dielectric film carried by the movable electrode and comprised of a synthetic resin of a fluoride type which can be brought into contact with two stationary electrodes to vary the capacitance therebetween, means including a pair of suspending pieces each carrying at their lower end portions a respective pawl adapted to engage the holding member when it is raised to its upper position for holding it in place, and means for releasing the pawls to bring the dielectric film into pressed contact with the stationary electrodes.

Abstract: An ultrasonic image device such as may be used in a holography system or scanning system and having a piezoelectric transducer in which the conversion efficiency and phase are substantially constant over a wide frequency range. A piezoelectric sheet 5 .mu.m to 1000 .mu.m thick is used for a piezoelectric element. The piezoelectric sheet is constructed of a macromolecular material including polymers and copolymers of polar monomers. A high frequency signal input device applies to the electrodes coupled to the piezoelectric sheet high frequency signals of different frequencies in a range around a fundamental resonance of the piezoelectric sheet of .+-.10 to .+-.70% of the fundamental resonance frequency.

Abstract: The laminated electric element is composed of a plastic film having at least one of electric properties including dielectric, pyroelectric and piezoelectric properties, and carrying a conductive layer on at least one surface thereof, the plastic film being laminated with a foam layer. Between the plastic film having the conductive layer and the foam layer is provided a middle layer to permit a flat surface on the conductive layer-carrying plastic film. The provision of the middle layer can render the surface of the conductive layer-carrying plastic film or layer flat without causing deformation on the surface thereof by the curved or waved surface of the foam layer and permit an effective utilization of such electric properties in addition to an effective prevention of the electrode layer provided thereon from coming off. Where the electrode layer is provided inside the conductive layer-carrying plastic film, the corrosion of the electrode layer can be prevented effectively.