This invention provides an improved method and apparatus for manufacturing magnetic recording media; specifically, that which is to be used in the manufacture of flexible, magnetic recording disks. The process provides a sequence of disorienting magnetic fields in different directions and of diminishing strengths to form a magnetic media in which the magnetic particles are essentially disoriented and the media is, thereby, devoid of modulated signal envelopes.
A magnetic coating composition comprising a binder dissolved in a solvent and magnetic grains dispersed therein is applied onto a surface of a non-magnetic substrate continuously moved. The coating film thus overlaid on the non-magnetic substrate is subjected to a preliminary orientation step for orientating the magnetic grains in the coating film, and then to a preliminary drying step. A final orientation step is then conducted while intermediate drying is carried out. Thereafter, final drying is effected.
The invention seeks to provide a magnetized coating suitable for exerting durable magnetic forces. To do this, the method of the invention consists in spreading conductive particles (13) on a medium (11), the particles being directed by prior magnetization along an inducing magnetic field and being embedded in a binder (12). The coating apparatus for implementing the method of the invention comprises means (10, 15) for feeding the medium (11) onto a conveyor (20), means for applying a main binder (12) via presser rollers (40) and via at least one nozzle (30), said means being coupled to heater means, a tank (50) of particles (13) coupled to a duster (51) for dispensing the fill of particles, means for spreading the fill of particles within the main binder, electromagnetic means (60) for producing an anisotropic magnetic field for magnetizing the particles, a sprayer (80) for depositing an additional binder, dryer means (100), demagnetizer means (110), and winder means (120). The invention is applicable to media particularly in paper-making, games, decoration, or building.
An apparatus and method are provided for magnetically disorienting magnetic particles in a magnetic layer of a web coated recording medium that is designed to be used in the manufacture of flexible disks. Disorientation is achieved by subjecting the particles in a fluid pigment carried on a linear web to a rotating magnetic field that projects into the plane of the fluid layer and is rotated about an axis perpendicular to the plane. The interaction of the rotating field with the magnetic particles also has a smoothing effect on the outer surface of the magnetic layer.
A process for the production of magnetic recording media having stochastic orientation of the magnetic anisotropic particles in the magnetic layer with the aid of a magnetic drum rotating above the still fluid dispersion layer and containing radially arranged permanent magnets of alternating polarity, and a corresponding apparatus for carrying out the process.
The present invention provides a disc-shaped magnetic recording medium particularly suitable for high density recording obtainable a high output power with low noise. In the disc-shaped magnetic recording medium according to the present invention, a ferromag netic powder having a coercive force of about 1,000 Oe or higher and a BET specific surface area in the range from about 25 to 70 m.sup.2 /g is employed. This allows a decrease in noise level and satisfies the electromagnetic performance requirements for high density recording. A random (unoriented) orientation or a circumferential orientation of the ferromagnetic powder in the magnetic layer provides high output power without causing a variation in output power.
