Fuji Photo Film Company, Limited

Rank Xerox Ltd.

Xerox Corporation

Mitsubishi Gas Chemical Company, Inc.

Yasuo Tamai

Hiroshi Ogawa

Masashi Aonuma

Chiaki Mizuno

Shinji Saito

Matsuaki Nakamura

Tatsuji Kitamoto

Satoru Honjo

Goro Akashi

Masaaki Suzuki

Toshio Ono

Ryuji Shirahata

Sadao Osawa

Kouichi Masaki

Hajime Miyatuka

Nobuo Tsuji

Akira Kasuga

Noburo Hibino

Hiromi Nakahara

Fumio Kodama

Hiroshi Agawa

Masaaki Fujiyama

Yasuyuki Yamada

Masatoshi Takahashi

Masato Satomura

Akihiro Matsufuji

Nobuo Yamazaki

Eiichi Tadokoro

Tsunehiko Sato

Toshio Kawamata

Toshihiko Miura

Masaaki Takimoto

Hideaki Kosha

Shinichi Funabashi

Shin-ichiro Dezawa

Naomitsu Takashina

Chiaki Osada

Hiroshi Amari

Masahiko Furukawa

Masaaki Igarashi

Koshu Kurokawa

Tutomu Nishina

Wakio Nagashima

Teruya Shinjo

Kazuhide Ishii

Masashi Anonuma

Koozi Kamiyama

A magnetic recording medium is described, comprising a non-magnetic support having thereon a magnetic layer containing ferromagnetic particles dispersed in a binder, the ferromagnetic layer containing abrasive agent particles alone or in combination with lubricating agent particles, wherein the weight ratio of (a) the abrasive agent particles which are present, or each of the abrasive agent particles and lubricating agent particles which are present, within 1 .mu.m in a thickness direction from the surface of the magnetic layer to (b) the abrasive agent particles or each of the abrasive agent particles and lubricating agent particles which are present, within the whole magnetic layer is at least 100/(thickness of the magnetic layer -1) % in which the 'thickness of the magnetic layer' represents the thickness in '.mu.m' and is 2 .mu.m or more. A method for preparing a magnetic recording medium comprising: coating on a non-magnetic support a first coating composition having ferromagnetic particles dispersed in a binder, and simultaneously or successively coating thereon a second coating composition having a binder in which there is despersed abrasive agent particles alone or in combination with lubricating agent particles.

Magnetic recording medium and the method for preparing the same

A magnetic recording medium comprising a non-magnetic support having provided thereon an underlayer containing non-magnetic particles and a binder and an upper layer containing ferromagnetic particles and a binder, wherein the underlayer contains a thermoplastic binder and has a dry thickness of 0.5 .mu.m or more.

Magnetic recording medium

A single two-shaft continuous kneading and mixing machine, which is provided with a pair of shafts having blade members secured thereto, and a barrel accommodating the shafts such that they can be rotated, carries out kneading of a mixture of magnetic grains and a solution, which contains a binder in an organic solvent, in a normal kneading region and thereafter carries out dilution kneading of the mixture, which resulted after kneading in the normal kneading region was carried out, and an organic solvent in a dilution kneading region. The solids concentration in the mixture subjected to kneading in the normal kneading region is adjusted so that it falls within the range of 65 to 95 wt %. The solids concentration in the mixture subjected to dilution kneading is adjusted so that it falls within the range of 30 to 60 wt %. The width of a gap between blade members, which are secured to different shafts and which face each other, and the width of a gap between each blade member and the inner surface of the barrel in the dilution kneading region are made smaller than the widths of corresponding gaps in the normal kneading region.

Method for preparing magnetic coating compositions

A magnetic recording medium comprises a nonmagnetic support and a magnetic recording layer provided on the support which comprises two layers including a first magnetic recording layer and a second magnetic recording layer. Each of the two magnetic recording layers contains a ferromagnetic powder having a coercive force of not less than 500 Oe dispersed therein. The first magnetic recording layer is provided on the support has a Young's modulus of 500 to 1,000 kg/mm.sup.2 ; and the second magnetic recording layer provided on the first magnetic recording layer has a Young's modulus of not less than 1,300 kg/mm.sup.2 ; and the magnetic recording layers as a whole show a Young's modulus of not less than 900 kg/mm.sup.2.

A magnetic recording medium is disclosed which comprises a non-magnetic support having coated thereon two magnetic layers, wherein an under layer of the magnetic layers contains ferromagnetic metal particles having a coercive force of 550 to 700 Oe, and wherein an upper layer of the magnetic layers contains a ferromagnetic particles having a specific surface area determined by the BET method of 25 to 35 m.sup.2 /g, a coercive force of 700 to 800 Oe and a thickness of 0.5 to 2.5 .mu.m, wherein the entire magnetic layer including the upper layer and the under layer have a coervice force of 580 to 750 Oe, a residual magnetic flux density of 2200 to 3200 gauss and a thickness of 3.0 to 5.0 .mu.m.

A magnetic recording medium comprising a nonmagnetic support and a magnetic recording layer provided on said support, in which said magnetic recording layer comprises:

A magnetic tape having a leader tape excellent in cleaning effect and free from change of the apppearance and decrease of the cleaning effect even after storage at high temperatures is provided. This magnetic tape has a leader tape at at least one end of the tape, the leader tape comprising a coating layer provided on the one or both sides of a support, and is characterized in that the coating layers contains an inorganic pigment powder with a grain size of 0.01 to 10 .mu.m or a mixture of an inorganic pigment powder with a grain size of 0.01 to 5 .mu.m and a resin powder with a grain size of 0.1 to 10 .mu.m, and a binder, the support has a haze of 20 to 80% and the leader tape has a percent photo-transmission of at least 20%.

Magnetic tape having a leader tape

A magnetic recording medium such as an audio-tape or a video-tape comprising a flexible support and a magnetic recording layer provided on a surface of said support, which is characterized in that the ratio of Young's modulus of said magnetic recording layer in the longitudinal direction (Em) to Young's modulus of said support in the longitudinal direction (Eb), namely Em/Eb, is in the range of 1.20-3.20.

A magnetic recording medium comprising a flexible support having coated thereon a magnetic layer is disclosed. The support has a surface roughness of from 0.01 to 0.1 .mu.m, the magnetic recording medium has a percent heat shrinkage of 1% or less in the direction of maximum shrinkage thereof after standing at 110.degree. C. for 4 hours, and the magnetic layer contains a metal or alloy fine powder as a ferromagnetic powder. The magnetic recording medium has a excellent running property after repeated use and a small percent heat shrinkage.

A magnetic recording medium such as an audio cassette tape or a video cassette tape comprising a flexible nonmagnetic support and a magnetic recording layer which contains a ferromagnetic cobalt-containing iron oxide, in which the nonmagnetic support has a surface of a center line average height in the range of 0.01 to 0.1 .mu.m on both sides and the magnetic recording medium has a heat shrinkage ratio of not higher than 1%, the heat shrinkage ratio being determined after allowing to stand at 110.degree. C. for 4 hours.

A magnetic recording medium such as an audio-tape or a video-tape comprising a flexible support and a magnetic recording layer provided on one surface of said support, which is characterized in that the total of the thickness of said magnetic recording layer (dM) and the thickness of said support (dB), namely dM plus dB, is not larger than 14 .mu.m; the ratio of the thickness of said magnetic recording layer (dM) to the thickness of said support (dB), namely dM/dB, is in the range of 0.6-1.0; and said magnetic recording medium has F-3 tensile strength in the range of 6.0-8.5 kg/mm.sup.2.

A magnetic recording medium in the form of tape such as an audio-tape or a video-tape comprising a flexible support and a magnetic recording layer provided on said support, said magnetic recording layer comprising a ferromagnetic powder dispersed in a binder, which is characterized in that said magnetic recording medium has dynamic modulus of not lower than 4.5.times.10.sup.10 dyne/cm.sup.2 in the longitudinal direction at 110.degree. C.

An improvement of a process for producing a magnetic recording medium comprising coating a non-magnetic support with a magnetic paint comprising a magnetic layer forming component containing ferromagnetic powder and a resin component dispersed in an organic solvent and drying the coated layer. The improvement resides in the preparation of the magnetic paint. In the improvement, the magnetic paint is obtained by kneading said magnetic layer forming component and a first solvent having a solubility parameter of not lower than 9.5[cal..multidot.cm.sup.-3 ].sup.1/2 as measured by Small method and adding a second solvent to the resulting kneaded product so that the mixed organic solvent in the magnetic paint has a solubility parameter of lower than 9.5[cal.multidot.cm.sup.-3 ].sup.1/2 to thereby disperse the magnetic layer forming component in the organic solvent.

Process for producing magnetic recording medium

A magnetic recording medium comprising a nonmagnetic support and a magnetic recording layer provided on said support, said magnetic recording layer comprising a ferromagnetic powder dispersed in a binder, in which H.sub.1 in terms of oersted which is a value of external magnetic field determined when a magnetic flux density of a magnetic hysteresis curve determined in the direction of orientation of the ferromagnetic powder in the magnetic recording layer in the fourth quadrant is equivalent to one-third of the maximum magnetic flux density of said magnetic hysteresis curve in the third quadrant; H.sub.2 in terms of oersted which is a value of external magnetic field determined when a magnetic flux density of said magnetic hysteresis curve in the first quadrant is equivalent to one-third of the maximum magnetic flux density of said magnetic hysteresis curve in the first quadrant; Hc in terms of oersted which is a coercive force of the magnetic recording layer; and Br in terms of gauss which is a residual magnetic flux density of the magnetic recording layer, have the relationship defined by the following inequality:

A magnetic recording medium having a heat shrinkage ratio of not higher than 1% and comprising a nonmagnetic support in the form of a tape which has a heat shrinkage ratio of not higher than 1.8%, a Young's modulus of 450 to 650 kg/mm.sup.2 in the longitudinal direction and a Young's modulus of 450 to 550 kg/mm.sup.2 in the width direction, and a magnetic recording layer provided on the support which comprises a binder and a ferromagnetic powder dispersed therein and has a squareness ratio of not less than 0.89. All the heat shrinkage ratios are values determined after being allowed to stand at 110.degree. C. for 4 hours.

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Odawara, Japan

Yasuo Tamai