JPH03252920A - Magnetic recording medium - Google Patents

Abstract

PURPOSE:To improve corrosion resistance even in a corrosive atmosphere containing SO2 gas, etc., by forming a ferromagnetic metal thin film on a nonmagnetic supporting body and covering the ferromagnetic metal thin film with specified naphthalene deriv. CONSTITUTION:A ferromagnetic metal thin film formed on a nonmagnetic supporting body is covered with a naphthalene deriv. as a rust preventive expressed by formula I which contains one or more nitro groups, a hydroxyl group and an acyloxy group. In the formula I, (n) is an integer >=1 and R is hydrocarbon group. The amt. of the rust preventive applied is preferably 0.5-100 mg/m<2>, and more preferably 1-20 mg/m<2>. If the amt. is too small, the effect to improve the corrosion resistance cannot be obtained, but with too large amt., sticking between the sliding member and the ferromagnetic metal thin film is caused to reduce the traveling property. By this method, the obtd. medi um has excellent corrosion resistance even in a corrosive atmosphere containing SO2 gas, etc.

Description

[Detailed Description of the Invention] [Industrial Application Field] The present invention relates to magnetic recording of a so-called ferromagnetic metal thin film type in which a ferromagnetic metal thin film is formed on a nonmagnetic support by vapor deposition, ion blating, sputtering, etc. It's about the medium.

[Summary of the Invention] The present invention provides a magnetic recording medium formed by forming a ferromagnetic metal thin film as a magnetic layer on a non-magnetic support, in which the ferromagnetic metal thin film serving as the magnetic layer has one or more nitro groups, and The present invention aims to provide a magnetic recording medium that exhibits excellent corrosion resistance under all conditions of use by depositing a naphthalene derivative having a hydroxyl group and an acyloxy group as a rust preventive agent.

[Conventional technology]

Conventionally, as a magnetic recording medium, 7-
7-FezO, +, Fe' containing Fe2O3, Co
, 04, Co-containing Fe, O4,7-Fe2Ch and Fe, , Oa-containing heldride compounds, CO-containing heldride compounds, oxide magnetic powders such as CrO□, or main components such as Fe, Co, Ni, etc. A coated magnetic material obtained by coating and drying a magnetic paint in which a powdered magnetic material such as an alloy magnetic powder is dispersed in an organic binder such as a vinyl chloride/vinyl acetate copolymer, polyester resin, or polyurethane resin. Recording media are widely used.

In recent years, with the increasing demand for high-density magnetic recording, metal magnetic thin films made of ferromagnetic metals have been directly deposited on non-magnetic supports using techniques such as vacuum evaporation, sputtering, ion blating, and plating. Deposited ferromagnetic metal thin film magnetic recording media are attracting attention. This ferromagnetic metal thin film magnetic recording medium not only has high coercive force H6 and residual magnetic flux density B, but also allows the thickness of the magnetic layer to be made extremely thin, so there is less thickness loss during recording demagnetization and reproduction. It has many advantages in terms of magnetic properties, such as being extremely small and being able to increase the packing density of the magnetic material because it is not necessary to mix organic binder, which is a non-magnetic material, into the magnetic layer.

However, the above-mentioned ferromagnetic metal thin film type magnetic recording medium has a problem in that it lacks corrosion resistance.

Therefore, attempts have been made to improve the corrosion resistance by coating the surface of the ferromagnetic metal thin film, which is the magnetic layer of the magnetic recording medium, with a rust preventive agent to form a protective film. For example, in JP-A-57, a magnetic recording medium with improved corrosion resistance was created by coating a ferromagnetic metal thin film with a rust preventive agent mainly composed of naphthols.
-152520.

[Problems to be Solved by the Invention] However, the metal thin film magnetic recording medium coated with the above-mentioned rust preventive agent still has insufficient corrosion resistance depending on its storage environment, and further improvement has been desired. . An object of the present invention is to provide a magnetic recording medium that has excellent corrosion resistance even in a corrosive atmosphere containing SO2 gas and the like.

[Means for Solving the Problems] The present invention uses a naphthalene derivative having one or more nitro groups and a hydroxyl group and an acyloxy group as a rust preventive agent in a ferromagnetic metal thin film formed on a non-magnetic support. A deposited magnetic recording medium.

In the present invention, naphthalene derivatives having one or more nitro groups and hydroxyl and acyloxy groups are synthesized by the general formula below, and 5-nitro-2-hydroxy-3acetoxynaphthalene is synthesized by the following reaction formula. It is synthesized in (2).

It is a compound represented by However, n is an integer of 1 or more, R
is a hydrocarbon group.

The compound represented by general formula (I) can be prepared, for example, by the method of Thomson et al. (J, Cham, Soc, PP350.1947).
can be synthesized as follows.

For example, 2,4-dinitro-5-acetoxy-1-hydroxynaphthalene is expressed by the following reaction formula (1), where Ac represents an acetyl group.

The method of forming the layer made of the rust preventive agent according to the present invention includes applying or spraying a solution obtained by dissolving the rust preventive agent in a solvent such as Freon, toluene, isooctane, hexane, etc. onto the surface of the metal ferromagnetic thin film; Alternatively, the metal ferromagnetic thin film may be immersed in this solution and dried.

In the present invention, the amount of rust preventive applied is 0.5 to 1100a.
/m2, preferably 1-20mg/m2
It is more preferable that

If the coating amount is too small, the effect of improving the corrosion resistance of the present invention will not be realized, while if it is too large, a sticking phenomenon will occur between the sliding member and the metal ferromagnetic thin film, resulting in poor running properties.

Materials for the non-magnetic support include polyesters such as polyethylene terephthalate, polyolefins such as polyethylene and polypropylene, cellulose triacetate,
Cellulose derivatives such as cellulose diacetate and cellulose acetate butyrate, vinyl resins such as polyvinyl chloride and polyvinylidene chloride, plastics such as polycarbonate, polyimide, and polyamideimide, light metals such as aluminum alloys and titanium alloys, and aluminum alloys such as aluminum alloys, etc. Examples include ceramics. The nonmagnetic support may be in any form such as a film, tape, sheet, disk, card, or drum.

Materials for the ferromagnetic metal thin film include Fe, Co, and Ni.
metals such as Co-Ni alloy, Fe-Co alloy, F
e-C.

N1 alloy, Fe-co-B alloy, Co-N1-Fe-B
Examples include alloys or alloys containing metals such as Cr and A1.

Examples of the means for depositing the ferromagnetic metal thin film material include vacuum evaporation, ion blasting, and sputtering.

In the vacuum evaporation method, the ferromagnetic metal material is evaporated by resistance heating, high frequency heating, electron beam heating, etc. under a vacuum of lo-4 to 10-'' Torr, and the evaporated metal (ferromagnetic metal material) is deposited on a non-magnetic support. ), and is roughly divided into oblique deposition method and vertical deposition method. In the oblique deposition method, the ferromagnetic metal material is deposited diagonally on a non-magnetic support in order to obtain high coercive force. It also includes those that are vapor deposited and that the vapor deposition is performed in an oxygen atmosphere in order to obtain higher coercive force.

In the vertical deposition method, Bi is pre-coated on a non-magnetic support in order to improve deposition efficiency and productivity and to obtain high coercive force.
,,5bXPb, Sn, Ga, In, Cd,
A base metal layer of Ge, Si, T1, etc. is formed in advance, and the ferromagnetic metal material is vertically deposited on the base metal layer. The ion blating method is also a type of vacuum evaporation, in which DC glow discharge or RF glow discharge is caused in an inert gas atmosphere of 10-4 to IF 3 Torr, and the ferromagnetic metal is evaporated during the discharge. be. The sputtering method uses 103 to 10'-'
A glow discharge is generated in an atmosphere mainly composed of Torr arbogas, and the generated argon ions are used to knock out atoms on the target surface. There is also a magnetron sputtering method that uses magnetron discharge.

(Function) By depositing a naphthalene derivative having one or more nitro groups and a hydroxyl group and an acyloxy group on a ferromagnetic metal thin film formed on a nonmagnetic support as described above, S02 gas, etc. A magnetic recording medium with excellent corrosion resistance can be obtained even in a corrosive atmosphere.

(Examples) Hereinafter, specific examples of the present invention will be described, but the present invention is not limited to these examples.

Example 1 Co was deposited on a 14 μm thick polyethylene terephthalate film by oblique evaporation to form a 1000 μm thick ferromagnetic metal thin film.

Next, 2,4-dinitro5-
The amount of acetoxy-1-hydroxynaphthalene applied is 5 m.
A sample tape was prepared by coating the sample tape at a concentration of g/m2 and cutting it into a 2-inch width.

Example 2 Co was deposited on a 14 μm thick polyethylene terephthalate film by oblique vapor deposition to form a ferromagnetic metal thin film with a thickness of 1000 μm.

Next, a coating amount of 5 mg/m2 of 5-nitro-2-hydroxy-3-acetoxynaphthalene was applied to the surface of this ferromagnetic metal thin film.
A sample tape was prepared by coating the sample so as to have the following properties and cutting it into a 3-inch width.

Example 3 Co was deposited on a 14 μm thick polyethylene terephthalate film by oblique evaporation to form a 1000 μm thick ferromagnetic metal thin film.

Next, 5-acetoxy-1-hydroxy-2,4,7-trinitronaphthalene was applied to the surface of this ferromagnetic metal thin film at a coating amount of 5 mg/m2, and the sample tape was cut into 3-inch widths. Created.

Comparative Example 1 Co was deposited on a 14 μm thick polyethylene terephthalate film by an oblique evaporation method to form a 1000 μm thick ferromagnetic metal thin film.

Next, 1-nitroso-2-naphthol was applied to the surface of this ferromagnetic metal thin film at a coating amount of 5 mg/m''.
Sample tapes were prepared by cutting into inch width pieces.

Comparative Example 2 Co was deposited on a 14 μm thick polyethylene terephthalate film by oblique vapor deposition to form three ferromagnetic metal films with a thickness of 1000.

Next, 2-nitroso-1 naphthol was applied to the surface of this ferromagnetic metal thin film at a coating amount of 5 mg/m2.
Sample tapes were prepared by cutting into inch width pieces.

Comparative Example 3 Co was deposited on a 14 μm thick polyethylene terephthalate film by oblique vapor deposition to form a 100 μm thick ferromagnetic metal thin film.

Next, this was cut to a width of 3 inches to produce a sample tape.

After measuring the initial coercive force (HCI) and saturation magnetization (Is+) of each of the sample tapes prepared above, the tape was divided into two, and one was placed in an atmosphere of 45"C and 80% relative humidity. Coercive force (HC2) after being left for one week
) and the saturation magnetization (Isz) were measured. The other tape was heated at 40°C containing SOz (0.3ppm).
The coercive force (HCI) and saturation magnetization (Is:,) after being left for 24 hours in a 502 gas atmosphere with a relative humidity of 90% were measured.

The rate of change after standing was determined by the following formula.

Hc (DK rate = (Hen Hc+) / I(
c+xlooo (X)1, (7) Rate of change - (r S,,
-I 31) / f 5IX100 ($) However, n
=2.3 The measurement results of the rate of change are shown in the table.

As is clear from the results shown in the margin below, the magnetic recording medium of the example of the present invention has more stable magnetic properties than the magnetic recording medium of the comparative example using the conventional technology, both in high humidity and in an atmosphere containing SO2 gas. ing.

〔Effect of the invention〕

As explained above, in the present invention, a naphthalene derivative having one or more nitro groups and a hydroxyl group and an acyloxy group is used as a rust preventive agent for a ferromagnetic metal thin film type magnetic recording medium. It is possible to obtain an excellent magnetic recording medium with little change in properties upon oral administration.

Claims (1)

[Claims] A magnetic recording medium characterized in that a ferromagnetic metal thin film is formed on a nonmagnetic support, and a naphthalene derivative having one or more nitro groups and a hydroxyl group and an acyloxy group is deposited on the ferromagnetic metal thin film. .