Magnetic recording medium having narrow pulse width characteristics

#The present invention relates to magnetic recording media such as magnetic tapes, and more specifically to the magnetic layer of the media which contains particulate metallic pigments that have high magnetic coercivity and a high volume concentration. The media exhibit narrower pulsewidth characteristics and lowered remanence-thickness product.

#Magnetic recording media are widely used in audio tapes, video tapes, computer tapes, disks and the like. Magnetic media may use thin metal layers as the recording layers, or may comprise particulate magnetic compounds as the recording layer. The latter type of recording media employs particulate materials such as ferromagnetic iron oxides, chromium oxides, ferromagnetic alloy powders and the like dispersed in binders and coated on a substrate. In general terms, magnetic recording media generally comprise a magnetic layer coated onto at least one side of a non-magnetic substrate (e.g., a film for magnetic recording tape applications).

#In certain designs, the magnetic coating (or “front coating”) is formed as a single layer directly onto a non-magnetic substrate. In an effort to reduce the thickness of this magnetic recording layer, an alternative approach has been developed to form the front coating as a dual-layer construction, including a support layer (or “lower layer”) on the substrate and a reduced-thickness magnetic layer (or “upper layer”) formed directly on the support or lower layer. With this construction, the lower layer is typically non-magnetic or substantially non-magnetic, generally comprised of a non-magnetic powder and a binder. Conversely, the upper layer comprises a magnetic metal particle powder or pigment dispersed in a polymeric binder.

#The following detailed description describes certain embodiments and is not to be taken in a limiting sense. The scope of the present invention is defined by the appended claims. The magnetic recording medium includes a non-magnetic substrate, a magnetic upper layer, a lower support layer, or sublayer, and, typically, a back coat layer. The various components are described in greater detail below. In general terms, however, the magnetic upper layer includes a primary metallic pigment powder having a coercivity of greater than about 2000 Oe, and a binder system for the pigment. The lower support layer includes a primary powder material consisting of particles that are essentially nonmagnetic (although some magnetic particles having a coercivity of 300 Oe or less may be included) dispersed in a binder system.

#In accordance with the current invention, coated magnetic recording media have an orientation ratio of greater than about 2.0, preferably greater than about 2.2. The medium exhibits a narrowed PW50, i.e., the PW50 is less than about 500 nm, preferably less than about 450 nm.

#The Magnetic Recording Layer