Tdk Corporation

Takayoshi Kuwajima

Akihiko Seki

Kenichi Kitamura

Naoto Yajima

Hiroyuki Yamada

Sadafumi Iijima

Akira Saitoh

Tsunehiko Ikarashi

Yuko Motegi

Hideki Sasaki

Tsutomu Aoyama

Akimasa Kaizu

Osamu Inoue

Yasufumi Takasugi

Katsuhiko Yamazaki

Satoru Tsuchida

A high recording density magnetic recording medium and a manufacturing method therefor are provided. The dilution stability during preparation of magnetic paint is improved and, thereby, even when the magnetic paint concentration is lowered, no problem occurs with the surface roughness and the output of the thin magnetic layer. The magnetic recording medium includes at least a magnetic layer on one surface of a non-magnetic support, wherein the magnetic layer contains a magnetic powder, a vinyl chloride resin having a degree of polymerization of at least 270 and an aliphatic polyester polyurethane resin to serve as binder resins, an aromatic compound having a substituent R (where R is &#x2014;COOH, &#x2014;(COOH), &#x2014;OPO(OH), &#x2014;PO(OH), or &#x2014;SOH), and a phosphoric acid ester. The ratio of binder resins in the magnetic paint is set at 2.0 percent by weight or less relative to a total sum of the binder resins and a solvent.

Magnetic recording medium and method for manufacturing the same

The present invention provides a magnetic recording medium comprising a magnetic layer with excellent surface smoothness, which comprises a thin film magnetic layer of thickness in a range from 0.03 to 0.30 &#x3bc;m that is ideal for short wavelength recording, and displays superior electromagnetic conversion characteristics. The magnetic recording medium comprises a magnetic layer containing at least a ferromagnetic powder and a binder resin on one surface of a non-magnetic support, wherein the thickness of the magnetic layer is within a range from 0.03 to 0.30 &#x3bc;m, and the number of concavities with a depth of 30 nm or greater in the surface of the magnetic layer is 5 per 1 cmof surface area or less. Preferably, the value of the average depth Rv6 of the surface of the magnetic layer, as measured by a contact type surface roughness meter, is 12 nm or less.

Magnetic recording medium

The present invention provides a magnetic recording medium which has a back coat layer excellent in surface smoothness and durability and is excellent in electromagnetic conversion property. A magnetic recording medium, comprising at least a non-magnetic support, a lower non-magnetic layer on one surface of the non-magnetic support, an upper magnetic layer on the lower non-magnetic layer, and a back coat layer on the other surface of the non-magnetic support, wherein the lower non-magnetic layer contains at least carbon black, a non-magnetic inorganic powder other than carbon black, and a binder resin material, the upper magnetic layer contains at least a ferromagnetic powder, and a binder resin material, and the back coat layer contains at least carbon black, a non-magnetic inorganic powder other than carbon black, a carboxylic acid amine salt, a phosphate amine salt, and a binder resin material.

Magnetic recording medium utilizing a back coat layer containing a carboxylic acid amine salt and a phosphate amine salt

The present invention provides a magnetic recording medium comprising a thin film magnetic layer of thickness in a range from 0.03 to 0.30 &#x3bc;m, and having excellent surface smoothness and superior electromagnetic conversion characteristics. The magnetic recording medium comprises a lower non-magnetic layer containing at least a non-magnetic powder and a binder resin on one surface of a non-magnetic support, an upper magnetic layer containing at least a ferromagnetic powder and a binder resin on the lower non-magnetic layer, and a back coat layer on the other surface of the non-magnetic support, wherein the thickness of the upper magnetic layer is within the range from 0.03 to 0.30 &#x3bc;m, the AFM surface roughness Ra of the upper magnetic layer is 6 nm or less, and the number of concavities with a depth of 30 nm or greater in the surface of the upper magnetic layer is 5 per 1 cmof surface area or less.

The present invention provides a high recording density magnetic recording medium with excellent surface smoothness, as well as excellent electromagnetic conversion characteristics and durability. A magnetic recording medium comprising a lower non-magnetic layer containing at least a non-magnetic powder and a binder resin on a non-magnetic support, and an upper magnetic layer with a thickness of 0.2 &#x3bc;m or less on said lower non-magnetic layer, wherein said lower non-magnetic layer contains an acicular powder of hydrated iron oxide as the non-magnetic powder, and said lower non-magnetic layer contains a fatty acid and a fatty acid amide. Preferably the acicular powder of hydrated iron oxide is goethite with an average long axial length of 0.15 &#x3bc;m or less.

A magnetic recording medium is prepared by coating a dispersion of non-magnetic powder and ferromagnetic powder in a binder and a dispersion of ferromagnetic powder in a binder to a non-magnetic substrate by a wet-on-wet coating technique to form subordinate and magnetic layers on the substrate, and subjecting the layers to magnetic field orientation. The subordinate layer has a Br of 80 to 400 gauss, and the magnetic layer has a thickness of 0.1 to 0.4 &#x3bc;m. The medium has surface smoothness and good electromagnetic characteristics and lends itself to recording and reproducing signals having a minimum wavelength of 0.2 to 0.7 &#x3bc;m.

The average major-axis length (L) of a ferromagnetic alloy powder primarily contained together with a binder in a magnetic layer provided on at least one surface of a non-magnetic support is less than 0.10 &#x3bc;m, and the ferromagnetic alloy powder contains Co at a content of 15 to 28 at % relative to Fe, and furthermore, contains Y at a content of 22 &#x3bc;mol/m2 or more with respect to a specific surface area (Sc) calculated from the above-mentioned average major-axis length (L) and the crystallite diameter (d). A coating-type high-recording-density magnetic recording medium has excellent surface properties, an excellent electromagnetic transducing characteristic especially in short wavelength regions and high reliability.

The present invention provides a high recording density magnetic recording medium with improved dropout and excellent surface smoothness and electromagnetic conversion characteristics, as well as a process for producing such a medium. A magnetic recording medium comprising a lower non-magnetic layer containing at least a non-magnetic powder and a binder resin on one surface of a non-magnetic support, an upper magnetic layer containing at least a ferromagnetic powder and a binder resin on said lower non-magnetic layer, and a back coat layer on an opposite surface of said non-magnetic support, wherein said lower non-magnetic layer contains an acicular powder of hydrated iron oxide as the non-magnetic powder, said ferromagnetic powder has an average long axial length of 0.1 &mgr;m or less, and said upper magnetic layer has a surface roughness (center line average roughness: Ra) of 2.4 nm or less. After curing the lower non-magnetic layer, the magnetic layer is applied and formed.

Magnetic recording medium and process for producing the same

A magnetic recording medium comprising a non-magnetic base having on at least one side a non-magnetic layer (undercoat) containing electron beam-curable resins which in turn is over-laid with a magnetic layer (topcoat) containing an iron (Fe) based magnetic powder, said magnetic layer having a glass transition temperature (Tg) of at least 65.degree. C. and said non-magnetic layer being an electron beam cured coating that is formed by coating the non-magnetic base with a non-magnetic coating mix containing electron beam curable resins, the yet to be cured coating having a glass transition temperature (Tg) of 30-53.degree. C. and said electron beam curable resins comprising an electron beam curable vinyl chloride based resin having a sulfur-containing polar group and an electron beam curable urethane resin having a phosphorus-containing polar group. Also disclosed is a process for producing the magnetic recording medium, which has good electromagnetic conversion characteristics in a high-frequency range and which can be manufactured at high production rate.

Magnetic recording medium and a process for producing the same

A magnetic recording medium having an intermediate layer excellent in conductivity, surface properties and strength, and excellent in electromagnetic characteristics, physical properties, etc., which comprises a non-magnetic intermediate layer having a thickness of 0.5 .mu.m to 3.0 .mu.m formed on at least one surface of a non-magnetic support, and a magnetic layer formed on the intermediate layer, the magnetic layer being mainly composed of a ferromagnetic powder and a binder and having a thickness of 0.1 .mu.m to 0.5 .mu.m, in which said magnetic layer is formed on the intermediate layer at least in a dry state, and the intermediate layer comprises

Magnetic recording medium having a magnetic layer and an intermediate

A magnetic layer is provided on a nonmagnetic base with a non-ferromagnetic layer interposed between them. Non-ferromagnetic particulate iron oxide is incorporated in the non-ferromagnetic layer. In addition to, or in place of, this iron oxide, non-structural carbon having a mean particle diameter of 10 to 60 nm, a specific surface area of 150 m2/g as measured by the BET method and a DBP oil absorption of 100 ml/100 g or less may be used. This makes it possible to achieve a magnetic recording medium having excellent surface properties and good-enough electromagnetic transducing characteristics.

A magnetic recording medium has a magnetic layer on a non-magnetic substrate. The magnetic layer contains ferromagnetic powder dispersed in a binder and a lubricant which is an unsaturated fatty acid diester of a dihydric alcohol and an unsaturated fatty acid, preferably a C.sub.2-6 dihydric alcohol and a C.sub.14-24 unsaturated fatty acid, typically neopentyl glycol dioleate. The lubricant remains effective in low-temperature, high-temperature, and thermal cycling environments without bleed-out. The medium is low in rotational torque, abrasion resistant and durable.

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Tokyo, Japan

Takayoshi Kuwajima