Fuji Photo Film Company, Limited

Takamitsu Asai

Masaaki Fujiyama

Tatsuji Kitamoto

Goro Akashi

Fumihiro Tokunaga

Yasuyuki Yamada

Takahito Miyoshi

Tsunehiko Sato

Toshihiko Miura

Hiroshi Chikamasa

Minoru Kanazawa

Haruo Masuda

Nobuo Aoki

A magnetic recording medium whose output is increased over a wide range of from long wavelengths to short wavelengths and whose output fluctuation with rotation period is decreased when rotating and reproducing in the form of a disk is provided comprising a non-magnetic support and a magnetic layer provided thereon containing a ferromagnetic substance, the magnetic layer having a multilayer structure consisting of a lower layer containing a ferromagnetic substance in an ellipsoidal shape with ##EQU1## and a saturation magnetization of at least 60 emu/g and an upper layer containing a ferromagnetic substance of plate-shaped hexagonal system having the axis of easy magnetization in the vertical direction to the plate surface.

Magnetic recording medium

A magnetic recording medium is described which has, on a non-magnetic support, a magnetic layer comprising a ferromagnetic substance dispersed in a binder, wherein the ferromagnetic substance is a hexagonal tabular ferromagnetic substance having an axis of easy magnetization in the direction perpendicular to the plain thereof and the ratio of the bulk density to true density (bulk densy/true density) is at least 0.16. The magnetic recording medium has improved output and C/N.

Magnetic recording media

A magnetic recording medium is described, comprising a non-magnetic support having provided thereon a magnetic layer having magnetic particles being ferromagnetic hexagonal crystallized tabular shape particles having an axis of easy magnetization in a direction vertical to a flat surface thereof, said binder being present in an amount of from 10 to 30 wt % based on the weight of the magnetic particles, and said binder comprising a polycarbonate polyurethane being present in an amount of from 20 to 60 wt %, a vinyl chloride and vinyl acetate type copolymer being present in an amount of from 20 to 70 wt %, and a polyisocyanate being present in an amount of from 10 to 60 wt %, based on the total amount of binder.

A magnetic recording medium is described, comprising a non-magnetic support, a magnetic recording layer on one side of the support, and a backing layer on the opposite side of the support to the magnetic recording layer, wherein said backing layer comprising a binder and a powder dispersed in the binder, wherein the powder is a powdered oxide represented by the formula M.sup.1.M.sup.2.O.sub.2+x (wherein M.sup.1 is at least one element selected from the group consisting of Ba, Sr, Pb and Ca, M.sup.2 is at least one element selected from the group consisting of Ti, Zr and Sn, and x is in the range of from 0 to 0.9) or a mixture of said powdered oxide and carbon black. This magnetic recording medium has a decreased coefficient of friction, is free from formation of scratches, has good durability, and furthermore, maintains good S/N characteristics.

The perpendicular magnetic orientation of a magnetic layer containing platelet-form ferromagnetic particles coated on a web support is effectively performed by passing a web having thereon the coated magnetic layer in an undried state through a magnetic field formed by plural pairs of opposite pole type magnets disposed in the travelling direction of the web with a gap between adjacent pairs of magnets, while supplying drying air through each gap onto the surface of the travelling web to substantially complete the drying of the coated layer while the web is in the magnetic field. A partition may be inserted in each gap so that the lower end of the partition is close to the upper surface of the travelling web to divide the gap into a front section and a back section, and the drying air may be passed through these sections.

Process for producing magnetic recording medium

A magnetic recording medium having an improved surface smoothness of the coating layer, improved degree of orientation in a magnetic field and increased output is provided which comprises a non-magnetic support and a magnetic recording layer provided thereon containing a ferromagnetic substance of plate-shaped hexagonal system, and having a surface gloss value of 180% or more.

A magnetic recording medium is described, comprising a non-magnetic support having provided thereon a magnetic layer containing magnetic particles and a binder, wherein the magnetic particles comprise (1) ferromagnetic hexagonal crystallized tabular shape particles having an axis of easy magnetization in a direction vertical to the tabular plane thereof and (2) ferromagnetic ellipsoidal particles having an acicular ratio (length/width) of 1.5/1 to 10/1 and having a saturation magnetization of 60 emu/g or more.

A magnetic recording medium is disclosed. The medium is comprised of a support base having provided thereon a non-magnetic metal layer and a magnetic layer. The magnetic layer is comprised of plate-shaped magnetic particles having an axis of easy magnetization perpendicular to the plane of the plate-shaped magnetic particles dispersed in a binder. The non-magnetic metal layer is preferably comprised of a metal selected from the group consisting of Al, Cu, Zn, Sn, Ti and alloys thereof. The recording medium has high S/N ratio, reduced drop out, high output, excellent durability and running properties.

A magnetic recording medium is disclosed. The medium comprises a non-magnetic support having provided thereon a magnetic layer comprising a binder, a magnetic powder and a powder of an oxide represented by the formula:

A magnetic recording medium is described, comprising a non-magnetic support having provided thereon a magnetic layer containing ferromagnetic particles and a binder, wherein said ferromagnetic particles have a tabular ratio (table diameter/table thickness) of 2 or more, a table diameter of from 0.01 to 10 .mu.m, and a lamination degree of the magnetic particles in the magnetic layer in a cross-section thereof of 2 or more.

Magnetic recording medium having laminated hexagonal ferrite platelets

A magnetic recording material is disclosed which is comprised of a single magnetic layer comprised of plate-shaped ferromagnetic particles wherein the plate-shaped ferromagnetic particles are present in greater number in the surface part of the magnetic layer than in the inner part and/or the plate-shaped ferromagnetic particles are aligned such that an average horizontal axis component of the particles with respect to the surface of magnetic layer is larger in the surface part than in the inner part. The location and alignment of the particles make is possible to increase output with short-wave recording.

Magnetic recording material using plate-shaped ferromagnetic particles

The present invention relates to an improved method for preparing a magnetic recording method having excellent magnetic orientation comprising the steps of (1) dispersing ferromagnetic fine particles which are plate-shaped and which have an axis of magnetization perpendicular to the plates of the particles in a binder and (2) coating a magnetic coating layer on a non-magnetic support wherein the method comprises, after coating the magnetic coating layer and before drying it, subjecting the surface of the magnetic layer to a magnetic field from the direction perpendicular to the support to produce a magnetic orientation while contacting the surface of the magnetic layer with a flexible smoothening sheet.

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Kanagawa, Japan

Takamitsu Asai