Toda Kogyo Corporation

Toshiharu Harada

Kazuyuki Hayashi

Keisuke Iwasaki

Seiji Okazaki

Haruki Kurokawa

Yuji Mishima

Manabu Matsumoto

Hidetomo Unemoto

Kazuyoshi Murashige

Tadashi Kanasaku

Hiroko Morii

Yasuyuki Tanaka

Minoru Ohsugi

Masaru Isoai

Kazushi Takama

Spherical tetragonal barium titanate particles of the present invention have a perovskite crystal structure, an average particle diameter of 0.05 to 0.5 &#x3bc;m, a particle size distribution &#x3c3;g of not less than 0.70, and a ratio of Ba to Ti of 0.99:1 to 1.01:1. The spherical tetragonal barium titanate particles exhibit an excellent dispersibility as well as a high denseness, a high purity and excellent permittivity properties.

Coated spherical tetragonal barium titanate particles and process for producing the same

Spherical tetragonal barium titanate particles of the present invention have a perovskite crystal structure, an average particle diameter of 0.05 to 0.5 &mgr;m, a particle size distribution &sgr;g of not less than 0.70, and a ratio of Ba to Ti of 0.99:1 to 1.01:1. The spherical tetragonal barium titanate particles exhibit an excellent dispersibility as well as a high denseness, a high purity and excellent permittivity properties.

Spherical tetragonal barium titanate particles and process for producing the same

A magnetic recording medium of the present invention comprises: a base film; a non-magnetic undercoat layer formed on said base film and comprising a binder resin and non-magnetic acicular particles containing iron as a main component, comprising iron and titanium of 0.05 to 50% by weight, calculated as Ti, based on the total weight of the particles, which is present within the particle; and a magnetic recording layer formed on said non-magnetic undercoat layer and comprising magnetic particles and a binder resin. Such a magnetic recording medium has a low light transmittance, an excellent smooth surface, a high mechanical strength and an excellent durability.

Magnetic recording medium comprising non-magnetic acicular particles

Disclosed herein are non-magnetic particles for a non-magnetic undercoat layer of a magnetic recording medium, comprising acicular or spindle-shaped .alpha.-Fe.sub.2 O.sub.3 particles coated with at least one selected from the group consisting of an A1 compound, a silane coupling agent, a titanate coupling agent, an aluminate coupling agent and a zirconate coupling agent; a non-magnetic undercoating layer containing such non-magnetic particles; and magnetic recording medium having such an undercoating layer.

Non-magnetic particles for non-magnetic undercoating layer of magnetic

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Ube, Japan

Toshiharu Harada