JPH03260908A - Magnetic recording medium - Google Patents

Abstract

PURPOSE:To obtain good corrosion resistance not only in high temp. and high humidity but in a corrosive gaseous atmosphere and to reduce changes with the lapse of time in the coercive force, and saturation magnetization, etc., of the medium by forming a ferromagnetic metal thin film on a nonmagnetic supporting body and applying naphthalenediol having one nitroso group or one or more nitro groups on the metal thin film. CONSTITUTION:The ferromagnetic metal thin film such as Fe, Co, Ni, is formed on a nonmagnetic supporting body composed of polyesters such as polyethylene terephthalate or polyolefins such as polyethylene, polypropylene. Then 1- nitroso-2,7-naphthalene-diol is applied by coating it on this thin film. Thus, magnetic property of the medium is stabilized even in an any atmosphere including high humidity or gaseous SO2.

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 in which a ferromagnetic metal thin film is formed 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 nitroso groups. The purpose of the present invention is to provide a magnetic recording medium on which naphthalene diol having a nitro group is deposited as a rust preventive agent, and exhibits excellent corrosion resistance under all conditions of use.

[Conventional technology]

Conventionally, as a magnetic recording medium, 7-
7-FezO containing Fe2O,, Co:+, Fe5
Powders such as 0+1, Co-containing Fe3O4, bertolide compounds of r-FezO3 and Fe3O4, Co-containing bertolide compounds, oxide magnetic powders such as CrO7, or alloy magnetic powders whose main components are Fe, CO1Ni, etc. Painted magnetic recording media, which are obtained by coating and drying a magnetic paint in which a magnetic material is dispersed in an organic binder such as vinyl chloride/vinyl acetate copolymer, polyester resin, or polyurethane resin, are widely used. There is.

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 Br, but also allows the thickness of the magnetic layer to be made extremely thin, resulting in significant thickness loss during recording demagnetization and reproduction. It has many advantages in terms of magnetic properties, such as being small and being able to increase the packing density of the magnetic material because there is no need to mix an 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 corrosion resistance of the metal thin film magnetic recording medium coated with the above-mentioned rust preventive agent is still not sufficient depending on the storage environment, and further improvement is desired. Ta. 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 to solve the problem]

The present invention is a magnetic recording medium in which naphthalene diol having one nitroso group or one or more nitro groups is coated as a rust preventive agent on a ferromagnetic metal thin film formed on a nonmagnetic support.

In the present invention, the naphthalene diol having one nitroso group or one or more nitro groups is a compound represented by the general formula: or (where n=an integer of 1 or more).

Naphthalene diol having one nitroso group can be synthesized by the following method. For example, 1-nitroso-2,7
- Naphthalene diol was reported by M, D, 5offer et al. (J, Am, Chem, Soc, 72 (1950)
pp 3704), the following reaction formula (1) 1-nitroso-2,3-naphthalenediol can be synthesized from 2,3-naphthalenediol by the same method as above.

Moreover, naphthalene diol having one or more nitro groups can be synthesized by the following method. For example, 2,4-dinitro-1,5-naphthalenediol is R,H,Thom
son et al. (J, Chem, Soc, (194
7) According to pp. 350), as shown in the following reaction formula (2), an equimolar amount of caustic soda was added to 2,7-naphthalene diol and stirred, and an equimolar amount of sodium nitrite and 42% by weight were added to 2,7-naphthalene diol. of concentrated sulfuric acid is gradually added dropwise. After the dropwise addition is completed, the crystals formed are thoroughly washed with water and diluted hydrochloric acid. For example, as shown in , it can be obtained by acetylating 1,5-naphthalenediol with acetic anhydride, nitrating it with acetic acid, and then hydrolyzing it with an alkaline aqueous solution (containing alcohol). In addition, by a similar method, for example, 2,4-dinitro-1,7-naphthalenediol,
It can be synthesized from 17 naphthalene diol. Also, for example, 2,6-sinitro-1,5-naphthalenediol is R
o)1. Thomson et al. (J, Chem, S.
oc, (1947) pp350) 2 Therefore, a platform can be formed as shown in the following reaction formula (3).

Furthermore, for example, 1,5-dinitro-2,6-naphthalenediol has been reported by H. Paul et al. (J. Prakt.
Chem, 18 (1962) pp219), it can be synthesized as shown in the following reaction formula (4).

Also, for example, tonitro-2,6-naphthalenediol is S, N, C: reported by hakravarti et al. (J
, Chem, Soc.

(1937) pp1859), the following reaction formula (5)
The bottom can be created as shown in .

For example, 2,4.7-)dinitro-1,5-naphthalene diol can be produced as shown in reaction formula (6).

(6) In the above reaction formula, Ac represents an acetyl group.

The method for forming a layer made of a rust preventive agent according to the present invention involves dissolving the rust preventive agent in a solvent such as Freon, toluene, isooctane, hexane, etc., applying or dipping the resulting solution onto the surface of a metal ferromagnetic thin film, and drying. do it.

In the present invention, the amount of rust preventive applied is 0.5 to 100 mg.
/m2 is preferable, and 1 to 20 mg/m2 is more preferable.

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, polycod, and polyamideimide, light metals such as aluminum alloy and titanium alloy, alumina glass, 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, Go, and Ni.
metals such as Go-Ni alloy, Re-Co alloy, F
e-C.

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

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 10-4 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 evaporation method, Bi is deposited on a non-magnetic support in advance in order to improve the evaporation efficiency and productivity and to obtain high coercive force.
,,Sb, Pb, Sn, ,Ga, In5Cd,
Ge, Si.

A base metal layer such as TI 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 10-Torr, and the ferromagnetic metal is evaporated during the discharge. It is. The sputtering method involves generating a glow discharge in an atmosphere containing argon gas as a main component at 10 3 to 10 Torr, and using the generated argon ions to knock out atoms on the target surface. There are pole and three-pole sputtering methods, high-frequency sputtering methods, and magnetron sputtering methods that utilize magnetron discharge.

[Effect]

As mentioned above, by coating naphthalene diol with one nitroso group or one or more nitro groups on a ferromagnetic metal thin film formed on a nonmagnetic support, the corrosion resistance of magnetic recording media can be significantly improved. be done. Although the exact reason is unknown, Natsuta 1 2 diols are effective in improving corrosion resistance under high temperature conditions, and they also passivate the surface of the magnetic layer by introducing nitroso or nitro groups. It is believed that corrosion resistance is improved especially in a corrosive gas 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, 1-nitroso-2°7 was applied to the surface of this ferromagnetic metal thin film.
- A sample tape was prepared by applying naphthalene diol in an amount of 5 mg/m 2 and cutting it into % 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, 1-nitroso2.3-
A sample tape was prepared by applying naphthalene diol in an amount of 5 mg/m 2 and cutting it into a 4-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, 2,4-dinitro 1.
A sample tape was prepared by applying 5-naphthalene diol in an amount of 5 mg/m'' and cutting it into a 2-inch width.

Example 4 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, 2,4-dinitro 1.
A sample tape was prepared by applying 7-naphthalene diol in an amount of 5 mg/m 2 and cutting it into a 3-inch width.

Example 5 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, 2,4-dinitro 2.
A sample tape was prepared by applying 6-naphthalene diol in an amount of 5 mg/m 2 and cutting it into a 3-inch width.

Example 6 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, 2,6-dinitro 1.
A sample tape was prepared by applying 5-naphthalene diol in an amount of 5 mg/m 2 and cutting it into a 3-inch width.

Example 7 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, 4-nitro-2,3-naphthalene diol was coated on the surface of this ferromagnetic metal thin film in an amount of 5 mg/m<2 >and cut into 3-inch widths to prepare sample tapes.

Example 8 Go was deposited on a 14 μm thick polyethylene terephthalate film by oblique vapor deposition to form a 1000 μm thick ferromagnetic metal thin film.

Next, 1-nitro-2,6-naphthalene diol was coated on the surface of this ferromagnetic metal thin film in an amount of 5 mg/m<2 >and cut into 2-inch widths to prepare sample tapes.

Example 9 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/7-trinitro-1,5-naphthalene diol was applied to the surface of this ferromagnetic metal thin film.
A sample tape was prepared by applying the sample to a thickness of m25 6 and cutting it into a 3-inch width.

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 in an amount of 5 mg/m2,
A sample tape was prepared by cutting it into a 2-inch width.

Comparative Example 2 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, 2-nitroso-1-naphthol was coated on the surface of this ferromagnetic metal thin film in an amount of 5+ng/m 2 and cut into 3-inch widths to prepare sample tapes.

Comparative Example 3 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, this was cut into a 2-inch width to produce a sample tape.

After measuring the initial coercive force (I c + ) and saturation magnetization (Is+) of each of the sample tapes prepared above, the tape was divided into two, and one was heated at 45°C.
The coercive force (8,2) and saturation magnetization (Isz) after being left in an atmosphere of 80% relative humidity for one week were measured. For the other tape, 4 containing 5Oz (0.3ppm)
Coercive force (IC3) and saturation magnetization N (Is3) after being left for 24 hours in an SO2 gas atmosphere at 0'C relative humidity 90%
was measured.

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

Rate of change in Hc - (HC,, -HCI) /Hc+X10
0 (X) ■, rate of change - (I s - 1s +) / I
s+X100 (%) However, n=2.3 The measurement results of the rate of change are shown in the table.

7 As is clear from the above results, 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 prior art, both in high humidity and in an atmosphere containing SOz gas. There is.

〔Effect of the invention〕

As explained above, in the present invention, naphthalene diol having one nitroso group or one or more nitro groups is used as a rust preventive agent for ferromagnetic metal thin film type magnetic recording media. Corrosion resistance is improved not only under corrosive gas atmospheres, but also in corrosive gas atmospheres, and an excellent magnetic recording medium with little change in magnetic properties such as coercive force and saturation magnetization can be obtained.

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Claims (1)

[Claims] 1. A magnetic recording medium comprising: a ferromagnetic metal thin film formed on a non-magnetic support; and naphthalene diol having one nitroso group or one or more nitro groups deposited on the ferromagnetic metal thin film.