JPS62202320A - Magnetic recording medium - Google Patents

Abstract

PURPOSE:To obtain a magnetic recording medium having excellent electrostatic charge preventiveness and durability, high packing density of magnetic powder and excellent recording and reproducing output by constituting a binder of a high-polymer complex. or high-polymer material contg. the high-polymer complex. CONSTITUTION:The binder of the magnetic recording medium having the magnetic layer contg. the magnetic powder and binder on a nonmagnetic substrate is constituted of the high-polymer complex or the high-polymer material contg. the high-polymer complex. The complex obtd. by bringing part or the whole of the cyano group of the high-polymer material contg. the cyano group into reaction with copper sulfide is suitable as such high-polymer complex. A polyacrylonitrile, acrylonitrile/styrene copolymer, etc., are used for the high- polymer material contg. the cyano group. A high-polymer material having no cyano group in the molecule is also usable by incorporating the cyano group therein. A polycarbonate, PVA, etc., are used for such high-polymer material.

Description

[Detailed Description of the Invention] [Object of the Invention] (Technical Field of the Invention) The present invention relates to a magnetic recording medium, and particularly relates to the durability of a magnetic layer,
The present invention relates to a magnetic recording medium that has excellent antistatic properties, is highly packed with magnetic powder, and has excellent recording and reproducing output.

(Prior art) In recent years, as various electronic and electrical devices have become lighter, thinner, and more compact, magnetic recording devices and magnetic recording media have also become smaller and more sophisticated. Media development is required.

In order to improve the magnetic properties of a magnetic recording medium, it is sufficient to increase the packing density of magnetic powder. Conversely, if the packing density of magnetic powder is low, the recording and reproducing output will decrease, making high-density recording difficult. Become.

(Problems to be Solved by the Invention) In order to promote high-density recording in magnetic recording media, it is necessary to improve not only the magnetic properties but also the antistatic properties and durability of the magnetic recording media. Must be. If anti-static properties are insufficient, dust will easily adhere to the magnetic recording medium, and therefore, when the magnetic layer of the magnetic recording medium approaches the magnetic head, these dust will be trapped between the magnetic layer and the recording medium head. This results in damage to the magnetic layer of the magnetic recording medium and the magnetic head, resulting in decreased durability. In particular, as the recording density increases, the distance between the magnetic layer and the magnetic head becomes narrower, so that even small particles of dust can easily damage the magnetic layer. Therefore, in high-density recording media, even a small scratch on the magnetic layer tends to cause drop defects 1 to occur.

Therefore, an object of the present invention is to solve the above-described problems and provide a magnetic recording medium that has excellent antistatic properties and durability, has a high packing density of magnetic powder, and has excellent recording and reproducing output.

[Configuration of the Invention (Means for Solving the Problems)] The magnetic recording medium of the present invention has a magnetic layer containing magnetic powder and a binder on a non-magnetic support, in which the binder is a polymer complex. Alternatively, it is characterized by being composed of a polymer substance containing a polymer complex.

As the J, Una polymer mirror, a composite obtained by reacting some or all of the cyano groups of a polymer substance containing cyano groups with sulfurized steel is suitable. In addition, as an example of a polymer mirror body, a polymer material containing cyano groups in which some or all of the cyano groups form a composite with sulfurized steel will be explained below. It is not limited to complexes.

Examples of polymeric substances containing cyano groups that can be used in the present invention include polyacrylonitrile-1-lyl, acrylonitrile-lyru-styrene copolymer, acrylonitrile-butadiene-styrene copolymer, acrylonitrile-butadiene copolymer, etc. Ru.

Furthermore, a polymer substance that does not have a cyano group in its molecule can also be used by introducing a cyano group by the method described below. Examples of such polymeric substances7 include polycarbonate, polyvinyl alcohol, polybutyral, polyvinyl chloride, polyvinyl acetate, polyvinylidene chloride, polyvinylpyrrolidone, polyurethane, polyamide, polystyrene, polybutadiene, polyacrylic acid, and polyacrylic ester. , polymethacrylic acid, polymethacrylic acid ester, epoxy resin, phenoxy resin, phenol resin, fluororesin, melamine resin, urea resin, furan resin,
Examples thereof include xylene resins, ketone resins, mixtures of two or more thereof, and copolymers of two or more heptamers constituting these polymeric substances.

Methods for introducing cyano groups into the above-mentioned polymeric substances include (a) a method of introducing cyano groups through a polymerization reaction using a monomer containing a cyano group;

(b) A method of carrying out a polymerization reaction using a polymerization initiator, emulsifier, or terminator containing a cyano group during polymerization of these polymeric substances.

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The above-mentioned polymeric substances having a cyano group may be used alone or in combination of two or more types as a binder, or may be used in combination with a polymeric substance not having a cyano group. In either case, cyano groups should account for 0.05% to 50% by weight of the total polymer material in the magnetic layer.

If the cyano group is less than 0.05%, it will be difficult to obtain sufficient conductivity required in the present invention,
On the other hand, if it exceeds 50 weight m3, the mechanical properties such as adhesion and durability of the magnetic layer will deteriorate.

The magnetic powder used in the present invention may be of any kind as long as it contains a metal element exhibiting ferromagnetism, and its shape is not limited, such as needle-like or hexagonal plate-like.

Examples of such magnetic powder include Ferray 1, which is commonly used in magnetic recording media, chromium dioxide, iron powder, iron nitride, and metallic cobalt.

The above-mentioned ferrites include T-ferrite, cobalt-modified ferrite, barium ferrite 1~, and s-1 rhodium ferrite, among others, the following general formula % formula %) (However, Mx is barium or strontium, MY
Group J consisting of cobalt, titanium, Tsukuru, indicium, copper, germanium, niobium and zirconium:
represents one or more elements selected from
In a magnetic recording medium using hexagonally modified ferrite powder (n represents a positive number from 5.4 to 6.0), the effect of the present invention is particularly remarkable because the magnetic layer has a large electrical resistance value. appear.

This hexagonal device type ferrite has a hexagonal plate shape, and the length of the diagonal of the hexagonal plate is preferably 0.2 μm or less.

If the thickness exceeds 0.2 μm, the C/N characteristics during recording and reproduction will deteriorate.

These magnetic powders are mixed with the above-mentioned binder and an organic solvent, and applied onto a non-magnetic substrate such as an aluminum plate or a polymer film to form a magnetic layer on the surface of the non-magnetic substrate.

Examples of the above organic solvents include methyl alcohol, ethyl alcohol, 1SO-propyl alcohol, n-
Propyl alcohol, tert-butyl alcohol, furfuryl alcohol, tetrahydrofurfuryl alcohol, 1,2-propylene oxide, 1,4-dioxane, trioxane, tetrahydrofuran, tetrahydrofuran, methylal, acetone, methylacetone, methyl alcohol, acetonylacetone, Diaretonyl alcohol, methyl cyclohexane formate, etc. can be mentioned. Among these, methyl alcohol, ethyl alcohol, and acetone are particularly preferred.

Note that these organic solvents may be used alone or in an appropriate mixture of two or more.

The magnetic recording medium of the present invention is manufactured, for example, as follows.

First, magnetic powder and a binder containing, for example, a polymeric substance having a cyano group are mixed with an appropriate organic solvent, and a dispersion operation is performed using a normal dispersion means such as a ball mill or a sand grinder to prepare a coating material. Apply on top and let dry. Next, this magnetic recording medium is placed in an aqueous solution containing cupric ions, and an aqueous solution of hydrosulfide is added to the aqueous solution containing cupric ions, so that the cyano groups in the polymer substance in the magnetic recording medium and the sulfide The magnetic recording medium of the present invention can be manufactured by reacting with steel to form a composite. In addition, instead of forming a complex in the subsequent treatment, a polymer material containing cyano groups that has already formed a complex with the sulfurized steel is used as a binder, and this is mixed with magnetic powder in an organic solvent to form a non-complex. It can also be manufactured by coating on a magnetic substrate.

(Function) The magnetic recording medium of the present invention has excellent antistatic properties and durability because the binder itself is made of a conductive polymer complex or a polymer material containing a polymer complex. Therefore, it is possible to significantly reduce the amount of carbon, which was conventionally added for the purpose of preventing static electricity, and this increases the packing density of magnetic powder and improves the recording/reproducing output and C.
/N characteristics can be significantly improved. Furthermore, since the amount of carbon used in the production of magnetic paint is small or unnecessary, the paint has good dispersibility and there is little increase in viscosity, making it extremely easy to manufacture.

(Example) Examples of the present invention will be described below.

Example 1 A magnetic paint having the composition shown in Table 1 was coated on one side of a polyester film having a thickness of 10 μm to form a magnetic layer. Next, this was immersed in a 3% sulfuric acid aqueous solution, and a 5% hydrofulphite aqueous solution was added to this aqueous solution and stirred to cause a sufficient reaction.The magnetic recording medium was then taken out, washed with water, dried, and its characteristics were measured. . The results are shown in Table 2.

Example 2 A magnetic recording medium of the present invention was produced in the same manner as in Example 1, except that the magnetic powder in Example 1 was replaced with Balircumferai 1 powder having an average particle size of 0.05 μm, and the characteristics were measured. . The results are shown in Table 2.

Example 3 A magnetic recording medium of the present invention was produced in the same manner as in Example 1, except that the polymer material of Example 2 was replaced with a polyacrylonitrile-butadiene resin containing 20% by weight of nitrile groups based on the total amount of the polymer material. It was manufactured and its characteristics were measured. The results are shown in Table 2.

Comparative Example A magnetic paint having the composition shown in Table 1 plus 3 parts of carbon was coated on one side of a 10 μm thick polyester film to form a magnetic layer to prepare a magnetic recording medium and its properties were measured. The results are shown in Table 2.

Table 2 however Δ: Surface electrical resistance B: Relative recording/playback output Head-medium relative speed; 3.5 m/sec.

Carrier frequency: 5.0M112 C: C/N characteristics Same conditions as relative recording and reproducing output [Effects of the invention] As is clear from the above examples, the magnetic recording medium of the present invention has a binder itself that is electrically conductive. Since it is composed of a polymer complex or a polymer substance containing a polymer complex, it has excellent antistatic properties and durability. Therefore, the amount of carbon, which is conventionally added for the purpose of preventing static electricity, can be significantly reduced, thereby increasing the filling of the magnetic powder and greatly improving the recording/reproducing output and C/N characteristics. can.

Therefore, the magnetic recording medium of the present invention includes a cassette deck,
It greatly contributes to improving the characteristics and downsizing of VTRs, floppy disk devices, etc.

Claims (4)

[Claims] (1) A magnetic recording medium comprising a magnetic layer containing magnetic powder and a binder formed on a non-magnetic support, characterized in that the binder is made of a polymer complex or a polymer substance containing a polymer complex. magnetic recording medium. (2) The magnetic recording medium according to claim 1, wherein the polymer complex is a polymer material containing cyano groups, in which some or all of the cyano groups form a composite with sulfurized steel. (3) The magnetic recording medium according to claim 2, wherein the amount of cyano groups in the polymer substance is 0.05% to 50% by weight. (4) Any one of claims 1 to 3, wherein the magnetic powder is hexagonal ferrite powder containing a substituent element.
Magnetic recording medium described in Section 1.