JPH0770044B2 - Magnetic recording medium - Google Patents

Description

Description: TECHNICAL FIELD The present invention relates to a magnetic recording medium using a metal magnetic powder as a magnetic recording element, and more particularly to the above magnetic recording medium having excellent durability.

[Prior Art] A magnetic recording medium is usually produced by applying a magnetic coating material consisting of a magnetic powder, a binder component, an organic solvent and other necessary components onto a substrate such as a polyester film and drying it. When a material is required, a magnetic metal powder such as metallic iron powder is used as the magnetic recording element.

However, since magnetic metal powders such as metallic iron powders are softer than oxide magnetic powders such as iron oxide powders, a magnetic recording medium using this kind of metallic magnetic powder as a magnetic recording element is not yet durable enough. In order to improve this, the abrasive particles, which are superior in hardness to the metal magnetic powder, are mixed in the magnetic layer, or the binder resin that binds the metal magnetic powder to the substrate is made into a high molecular weight compound to form a magnetic layer. Strengthening is being done.

[Problems to be solved by the invention]

However, in the method of mixing the polishing agent into the magnetic layer, the amount of the polishing agent mixed by the amount of the soft metal magnetic powder must be increased, so that the packing density of the metal magnetic powder is rather lowered and the electromagnetic conversion characteristics are improved. There is a drawback that it deteriorates, and in the method of strengthening the strength of the magnetic layer by increasing the molecular weight of the binder resin, it becomes difficult to disperse the metal magnetic powder, which is relatively difficult to disperse, and the magnetic layer becomes brittle. is there.

[Means for solving problems]

The present invention has been made as a result of various studies in order to improve such drawbacks. It is mainly composed of iron, contains 0.5% by weight or more and 20% by weight or less of aluminum, and 0.1% by weight or more and 5% by weight of nickel. By using a metal magnetic powder containing less than or equal to wt%, the metal magnetic powder to be used is made sufficiently hard, and the metal magnetic powder of sufficient hardness makes the magnetic layer tough and adversely affects electromagnetic conversion characteristics. In other words, the durability of the obtained magnetic recording medium is sufficiently improved.

The metal magnetic powder used in the present invention is mainly composed of iron, and 0.5% by weight or more and 20% by weight or more of aluminum with respect to iron.
It is preferable to contain the following and also contain nickel in an amount of 0.1% by weight or more and 5% by weight or less. When iron and aluminum and nickel are included in such a range, the metallic magnetic powder mainly containing iron becomes sufficiently hard. The metal magnetic powder itself having sufficient hardness exerts the same action and effect as the abrasive particles and sufficiently reinforces the mechanical strength of the magnetic layer. Therefore, when this type of metal magnetic powder is used and coated on a substrate together with a binder resin, etc., a tough magnetic layer is formed,
A magnetic recording medium having excellent durability can be obtained. In addition, since the magnetic layer can be made tough with the metal magnetic powder having sufficient hardness as described above, it is possible to reinforce the strength of the magnetic layer by using a large amount of an abrasive or to polymerize the binder resin. Therefore, the electromagnetic conversion characteristics are not deteriorated.

Such iron is the main component, and aluminum is less than aluminum.
The magnetic metal powder containing 5% by weight or more and 20% by weight or less and 0.1% by weight or more and 5% by weight or less of nickel is used when synthesizing goethite, which is a raw material of the metallic magnetic powder mainly containing iron,
Iron ions and nickel ions are co-precipitated to produce goethite in which Nikel is dissolved, and an aluminum compound is deposited on the surface of this nickel-dissolved goethite, or the nickel compound and aluminum are deposited on the surface of goethite. Compounds are deposited, and then these goethites and α-Fe ₂ O obtained by reducing these goethites are obtained.
Made by methods such as reducing ₃ in a hydrogen stream,
Further, goethite containing only nickel or goethite coated with only a nickel compound and α-Fe ₂ O ₃ obtained by reducing these goethites are reduced in a hydrogen stream, and then an aluminum compound such as aluminum oxide is added thereto. It is made by a method such as coating on the surface of particles.
In particular, when aluminum is present as an oxide or acid hydroxide on the particle surface of the metal powder, a uniform and dense film is formed. Therefore, aluminum oxide, aluminum hydroxide, or another oxide or acid hydroxide is used as the metal powder. It is preferable that they are present on the surface of the particles.

As described above, when the content of nickel contained in the metal magnetic powder mainly composed of iron is less than 0.1% by weight relative to iron, branching occurs in the powder particles, and the durability of the magnetic layer obtained by using this is improved. It cannot be sufficiently improved, and if it exceeds 5% by weight, the saturation magnetization amount of the metal magnetic powder becomes small. Therefore, it is preferable to set it within the range of 0.1 to 5% by weight relative to iron, and 0.1 to 3.5% by weight. It is more preferable to set it within the range. On the other hand, if the content of aluminum is less than 0.5% by weight with respect to iron, the hardness of the metal magnetic powder is not sufficiently improved, and the durability cannot be improved. 20% by weight
If the content is higher, the residual magnetic flux density of the magnetic layer obtained by using this kind of metal magnetic powder cannot be sufficiently increased, and the output level will be low, so within the range of 0.5 to 20% by weight relative to iron. Is preferable, and more preferably within the range of 0.5 to 10% by weight.

Such iron is the main component, and aluminum is less than aluminum.
The production of a magnetic recording medium using a metal magnetic powder containing 5% by weight or more and 20% by weight or less and 0.1% by weight or more and 5% by weight or less of nickel as a magnetic recording element is performed according to a conventional method. This kind of metallic magnetic powder is dispersed and mixed with a binder resin, an organic solvent and other necessary components to prepare a magnetic paint, and the magnetic paint is sprayed or roll-coated on a substrate such as polyester film. Is applied and dried.

Here, as the binder resin, a polyvinyl chloride resin,
Vinyl chloride-vinyl acetate based copolymers, fibrin based resins, butyral based resins, polyurethane based resins, polyester based resins, epoxy based resins, polyether based resins, isocyanate compounds, etc. Is also used.

Further, as the organic solvent, a ketone solvent such as cyclohexanone, methyl ethyl ketone and methyl isobutyl ketone, an ester solvent such as ethyl acetate and butyl acetate, an aromatic hydrocarbon solvent such as benzene, toluene and xylene, and a sulfoxide such as dimethyl sulfoxide. System solvent,
Solvents suitable for dissolving the binder resin used, such as ether solvents such as tetrahydrofuran and dioxane, may be used alone or in combination of two or more without particular limitation.

In addition, various additives that are usually used in the magnetic paint,
For example, a lubricant, an abrasive, an antistatic agent, etc. may be added appropriately.

〔Example〕

 Next, an embodiment of the present invention will be described.

Examples 1 to 8 Consist of iron, aluminum and nickel, containing aluminum and nickel in a ratio shown in Table 1 below with respect to iron,
Moreover, the metal magnetic powder having a specific surface area as shown in Table 1 by the BET method is used, and 80 parts by weight of the metal magnetic powder VAGH (manufactured by UCC, vinyl chloride-vinyl acetate-vinyl alcohol copolymer) 10〃Nipporan N3113 ( Nippon Polyurethane Industry Co., Ltd., polyurethane resin) 6〃 Coronate L (Nippon Polyurethane Industry Co., Ltd., trifunctional low molecular weight isocyanate compound) 4
A magnetic paint was prepared by mixing and dispersing a composition of α-Al ₂ O ₃ powder (average particle size 0.7 μm) 16 〃 oleyl oleate 8 〃 cyclohexanone 95 〃 toluene 95 〃 in a ball mill for 96 hours. This magnetic paint was applied to both sides of a 75 μm-thick polyester film so that the dry thickness would be 2.5 μm, dried and surface-treated, and then punched into a disk shape to form a magnetic disk.

Comparative Examples 1 to 9 Magnetic disks were prepared in the same manner as in Examples 1 to 8 except that the same amounts of the metal magnetic powders shown in Table 1 below were used in the compositions of the magnetic paints in Examples 1 to 8.

For each magnetic disk obtained in each example and each comparative example, in the magnetic recording and reproducing device, while observing the decrease in the reproduction output level due to wear of the magnetic layer of the magnetic disk while sliding the magnetic disk to the magnetic head, The playback output is 70% of the original
The durability was examined by measuring the running time until it decreased to 100 ° C. An output level at 40 kfci was measured with a magnetic head using a magnetic core made of iron-nickel alloy (Sendust) at a gap length of 0.3 μm, a track width of 30 μm, and a relative speed of 3.1 m / sec.

The results are shown in Table 2 below.

As is clear from Table 2 above, the magnetic tapes obtained in the present invention (Examples 1 to 8) have higher sensitivity and better durability than the conventional magnetic tapes (Comparative Examples 1 to 9). From this, it can be seen that the magnetic recording medium obtained by the present invention has good electromagnetic conversion characteristics and excellent durability.

Claims (2)

[Claims] 1. Mainly iron, aluminum to iron
A magnetic recording medium comprising a magnetic magnetic powder containing 0.5 wt% or more and 20 wt% or less and 0.1 wt% or more and 5 wt% or less of nickel in a magnetic layer as a magnetic recording element. 2. The magnetic recording medium according to claim 1, wherein the magnetic recording medium is a magnetic disk having magnetic layers formed on the front and back surfaces of a substrate.