JPS63152020A - Magnetic recording medium - Google Patents

Abstract

PURPOSE:To obtain an excellent electromagnetic conversion characteristic over a wide frequency range by providing a 1st magnetic layer formed by dispersing ferromagnetic alloy powder in a binder on a nonmagnetic base and further, providing the 2nd magnetic layer consisting of a thin magnetic film contg. specific iron nitride thereon. CONSTITUTION:The 1st magnetic layer formed by dispersing the ferromagnetic alloy powder into the binder is provided on the nonmagnetic base and the 2nd magnetic layer consisting of the thin magnetic film contg. the iron nitride expressed by FexN (x is 2-8) is further provided thereon. The compsn. of the ferromagnetic alloy powder to be used for the 1st magnetic layer is pure iron and alloy such as Fe, Fe-Ni, Fe-Ni-Co and FexN (x: 2-8) and further, a slight amt. of nonmagnetic or nonmetallic elements such as B, C and N may be incorporated therein in order to improve the characteristics. The magnetic recording medium of the double layer type which has the excellent output in the wide frequency range from a low to high range and has the excellent corrosion resistance is thereby obtd.

Description

[Detailed Description of the Invention] [Field of Industrial Application] The present invention relates to a magnetic recording medium with excellent electromagnetic conversion characteristics over a wide frequency band from low to high frequencies, particularly a coated magnetic layer and a vapor deposited thin film magnetic layer. The present invention relates to a magnetic recording medium having a magnetic recording medium.

[Conventional technology]

Conventionally, r-Fez was used as a ferromagnetic powder for magnetic recording media such as audio tapes, video tapes, and magnetic disks.
A magnetic layer is used in which O3, Fe, Oa or their intermediate oxides, Co-containing chromium dioxide, ferromagnetic alloy powder, etc. are dispersed in a binder. In particular, ferromagnetic alloy powder, which is also known as metal powder, has a high coercive force. Since high output can be obtained, it is excellent as a high-density magnetic recording medium. However, magnetic recording media using ferromagnetic alloy powder have a drawback in that the maximum output in the high frequency range is low.

On the other hand, with the increasing density of magnetic recording, magnetic recording media have been proposed in which Co, Ni, or an alloy of Co, Ni, Fe, etc. is provided as a thin film magnetic layer on a non-magnetic substrate by vapor deposition, sputtering, etc. being developed. This type of magnetic recording medium has a high output in a high frequency band and is suitable for high density recording, but it has the disadvantage that the maximum output in a low frequency band is low.

In order to overcome these drawbacks, the above-mentioned Co is applied on a magnetic layer in which ferromagnetic alloy powder is dispersed in a binder.

It has been proposed to compensate for the drawbacks of both magnetic layers by forming a thin film magnetic layer made of Ni or an alloy thereof by vapor deposition or the like (Japanese Unexamined Patent Publication No. 56-34145).

[Problem that the invention seeks to solve]

Although the problem of the decrease in the maximum output of each magnetic layer was solved by the above-mentioned multilayer system, the Co
and other co as stated in the specification.

When a vapor-deposited film of an alloy or oxide such as Ni or Fe is provided, there is a problem that the magnetic film rusts during long-term storage or use, resulting in poor corrosion resistance.

Therefore, an object of the present invention is to provide a multilayer magnetic recording medium that has excellent output over a wide frequency band from low to high frequencies and has excellent corrosion resistance.

[Means for solving problems]

The above objects are achieved by the invention described below.

That is, the present invention comprises a first magnetic layer in which ferromagnetic alloy powder is dispersed in a binder on a non-magnetic support, and a FexN layer on the first magnetic layer.
The present invention is a magnetic recording medium characterized by having a second magnetic layer made of a magnetic thin film containing iron nitride represented by (x is 2 to 8).

The present invention will be explained in detail below.

The composition of the ferromagnetic metal powder used for the first magnetic layer in the present invention is Fe, Fe-Ni, or Fe-Ni-Co.

Pure iron and alloys such as FexN (x: 2 ~ B), and BSC, N,, A! , $11P-,
S % T iSCr % M n SCu −, Z
A small amount of a nonmagnetic or nonmetallic element such as n can also be included. In addition, in order to effectively achieve the object of the present invention and to exhibit the effects of the method of the present invention, the specific surface area of the ferromagnetic powder particles must be 30 m"/gr or more, and further 40 m"/gr. It is preferable that there be.

In addition, the saturation magnetic ratio of the metal magnetic material is 120 e m u /
gr or more, preferably 125 emu/gr or more (measuring external magnetic field 10 kve). By using a magnetic material with high saturation magnetization, it is possible to increase the remanence (Br) of the magnetic layer and obtain a magnetic recording medium with high video sensitivity.

The ferromagnetic alloy powder used in the present invention can be manufactured as follows.

(1) A method of reducing acicular oxyhydroxides, acicular oxyhydroxides containing other metals, or acicular iron oxides obtained from these oxyhydroxides (iron oxide reduction method).

(2) A method in which ferromagnetic metal is evaporated in a low-pressure inert gas (low-vacuum evaporation method).

(3) A method of obtaining ferromagnetic powder by reducing an aqueous solution of a metal salt capable of forming a ferromagnetic substance using a reducing substance (borohydride compound, hypophosphite, hydrazine, etc.).

(4) A method of thermally decomposing an organic acid salt of a ferromagnetic metal and reducing it with a reducing gas.

(5) A method of thermally decomposing a metal carbonyl compound.

(6) A method of electrodepositing ferromagnetic metal powder using a mercury cathode and then separating it from mercury.

In the present invention, the ferromagnetic metal powders produced by the above methods (1), (2), and (3) are easy to use, and among them, the powder obtained by method (1) is the most desirable in terms of cost and quality. Furthermore, when producing the ferromagnetic metal powder of the present invention, it is desirable to provide an oxide film on the particle surface in order to improve the chemical stability of the fine metal powder.

Further, iron nitride powder is obtained by nitriding and, if necessary, post-oxidizing, metal powder obtained according to the above method.

The above ferromagnetic powder is kneaded with a binder to form a magnetic coating liquid.

As for the mixing ratio of the ferromagnetic metal powder and the binder, the binder used for the first magnetic layer may be a thermosetting resin, a thermosetting resin, a reactive resin, etc., which are generally used in coated magnetic recording media. can.

Organic solvents used for dispersion and application of magnetic coating liquid include acetone, methyl ethyl ketone, methyl isobutyl ketone,
Ketones such as cyclohexanone; esters such as methyl acetate, ethyl acetate, butyl acetate, ethyl lactate, glycol acetate monoethyl ether; ethyl ether, glycol dimethyl ether, glycol monoethyl ether,
Ethers such as dioxane and tetrahydrofuran; aromatic hydrocarbons such as benzene, toluene, and xylene; chlorinated hydrocarbons such as methylene chloride, ethylene chloride, tetracarbon L chloroform, ethylene chlorohydrin, and dichlorobenzene, etc. are selected. It can be used as

Further, additives such as a lubricant, an abrasive, a dispersant, an antistatic agent, and a rust preventive may be added to the magnetic coating liquid of the present invention.

Materials for the support to which the magnetic coating liquid is applied include polyesters such as polyethylene terephthalate and polyethylene 2,6-naphthalate; polyolefins such as polyethylene and polypropylene; cellulose derivatives such as cellulose triacetate; plastics such as polycarbonate, polyimide, and polyamideimide. In addition, depending on the purpose, the nonmagnetic support may be in the form of a film, tape, sheet, disk, etc.

After applying and drying the magnetic layer, if necessary, after performing surface treatment such as calendering, FeN is deposited on the magnetic layer by vapor deposition.
A thin magnetic layer of x (x=2-8) is formed by vacuum deposition.

FIG. 1 is a schematic diagram of a vacuum evaporation apparatus for forming the second magnetic layer in the present invention. 5X10-'~5X10
A support 3 on which the first magnetic layer described above is formed is continuously running along a cylindrical drum 2 provided in a vacuum tank evacuated to -2 Pa. A crucible 5 containing an iron material 4 is placed below the drum 2 , and the iron material 4 is heated and evaporated by the electron beam generated by the electron gun 6 , and the vapor flow passes through a mask 7 to the support 3 . directed at an angle.

At the same time, an ion beam mainly composed of nitrogen ions generated by the ion gun 8 is directed toward the support so as to intersect with the vapor flow, thereby forming an iron thin film containing iron nitride.

In order to control the magnetic properties of this second magnetic layer, a gas introduction port 9 is provided in the vacuum chamber. 10. A gas such as oxygen, nitrogen, argon, ammonia helium, etc. is introduced as appropriate through a gas such as 11 or the like.

In the above example, in order to incorporate nitrogen atoms into the iron thin film,
I showed an example using an ion gun, but without using an ion gun,
Vapor deposition in nitrogen gas plasma of about 10-' to 10 Pa,
Methods such as ion blasting and sputtering may also be used.

The thickness of the deposited film is 0.03 to 2 μm, preferably 0.05 μm.
~1 μm. Furthermore, the angle of incidence of the Fe vapor stream directed toward the support is at least 20 degrees, preferably at least 45 degrees.

The composition of the formed iron nitride varies depending on the degree of vacuum, the amount of nitrogen ions supplied, the ion acceleration voltage, the power of the electron beam, etc., but it is preferable that Fe2-3N be 50% or less. A magnetic film with a large magnetic force HC can be obtained.

After providing the second magnetic layer, an overcoat such as a carbon value material may be provided over the layer by vapor deposition, spuckling, or the like.

Furthermore, after providing the first magnetic layer in the magnetic recording medium of the present invention, a back layer conventionally used in coated magnetic recording media may be provided, and the layer composition and additives of the bank layer may be are used.

〔Example〕

Hereinafter, the present invention will be explained by examples.

Example First Magnetic Layer 300 parts of ferromagnetic metal powder and the following composition were mixed and dispersed in a ball mill for 10 hours.

Polyester polyurethane (reactant of ethylene adipate and 2.4-)lylene diisocyanate, styrene equivalent average molecular weight approximately 130,000) 35 parts Vinyl chloride-vinyl acetate-maleic anhydride copolymer (contains maleic acid! 3.0%, Degree of polymerization: approx. 400) 30 parts α-alumina 15 parts carbon blank
Tripartite butyl acetate
300 parts methyl isobutyl ketone
300 parts Furthermore, 22 parts of triisocyanate compound [3
Adduct of 1 mol of tolylene diisocyanate and 1 mol of trimethylolpropane (molecular weight approximately 760, NGO content 43.3%, trade name: Bayer A).

A magnetic coating solution was prepared by adding a 75% ethyl acetate solution of "Desmodinil L-75J" manufactured by Co., Ltd. and dispersing it under high-speed shearing for 1 hour.The obtained magnetic coating solution was dried on a 9.0 μm thick polyethylene terephthalate plate. It was coated and dried to a film thickness of 3.0 μm. After drying, it was calendered to form a first magnetic layer.

Second Magnetic Layer Next, an iron nitride thin film (thickness: 0.15 μm) was formed on the first magnetic layer using a winding type vapor deposition apparatus as shown in FIG. 1 under the following conditions.

Pressure 1X10-'Pa Incident angle θ = 70° Vapor deposition rate 40 people/S The obtained data were examined for output and corrosion resistance as shown below, and the results are summarized in the following table.

Layer configuration IMHz output 6MHz output Contact resistance example Fe coating layer/FexN vapor deposition layer +0.5d
B +4. odBO Comparative Example I Fe coating layer
OdB OdB O2Fe,N
Vapor deposition 11 -3.5dn +5.2da
O3Fe coating layer/CoNi vapor deposition layer -0.7dB
+5.6 dB x The above CoNi vapor deposited layer was formed as follows.

The Go-2ONi alloy was vapor-deposited by operating only the electron gun in the above-mentioned apparatus and introducing oxygen gas from the vicinity of the mask.

Output: -3mm VTR (Fujifilm FUJ I
Output resistance when recording and reproducing IMHz and 6MHz signals with
Visual inspection of electromagnetic conversion characteristics after being left at RH for 3 days [Effects of the invention] As is clear from the above results, the magnetic recording medium of the present invention has a large output in both the low frequency range and the high frequency range, and has excellent contact resistance. I can see that it is excellent.

[Brief explanation of the drawing]

FIG. 1 is a schematic diagram of a vacuum deposition apparatus used to form the second magnetic layer of the present invention. 2...Cooling can 3...Tape 4...Fe
Source 6...Electronic statistics...Ion gunkyu No. 1 for nitrogen ion source Figure Toin pump

Claims (1)

[Claims] (1) A first magnetic layer in which ferromagnetic alloy powder is dispersed in a binder on a non-magnetic support, and a first magnetic layer on which Fe_xN(x
A magnetic recording medium comprising a second magnetic layer made of a magnetic thin film containing iron nitride represented by 2 to 8).