JPS62102416A - Magnetic recording medium - Google Patents

Abstract

PURPOSE:To obtain a magnetic recording medium having excellent magnetic characteristics and excellent durability by forming plural layers of thin ferromagnetic metallic films on a nonmagnetic base having micro-projections on the surface. CONSTITUTION:>=1 kinds of projections such as peak-shaped projections, wrinkle-shaped projections or granular projections are formed as projections 3 on the surface of a substrate 1 and the surface roughness thereof is preliminarily controlled in the stage of forming a magnetic recording medium of plural layers of the thin ferromagnetic metallic film type formed as the magnetic layer on the substrate 1 consisting of a nonmagnetic material. The peak-shaped projections are formed by internally adding pulverized inorg. particles of calcium carbonate, silica, alumina, etc. in the stage of forming a high-polymer film. The wrinkle-shaped projections are formed by coating a dilute soln. of a resin, for which, for example, a specific solvent mixture is used, on the substrate and drying the coating. The surface characteristic of the thin ferromagnetic metallic films is thereby controlled and the runnability and durability are improved. Excellent characteristics are thus obtd. in the magnetic characteristics and electromagnetic conversion characteristic.

Description

[Detailed Description of the Invention] [Industrial Application Field] The present invention relates to a so-called ferromagnetic metal thin film type magnetic recording medium in which a ferromagnetic thin film is formed as a magnetic layer on a substrate by a vacuum evaporation method. It is.

[Summary of the invention]

The present invention aims to provide a magnetic recording medium with excellent magnetic properties and durability by forming multiple layers of ferromagnetic metal thin films on a non-magnetic support having microprotrusions on the surface. be.

[Conventional technology]

Conventionally, as a magnetic recording medium, γ-F8203 containing γ-Fe20= and Co on a substrate made of a non-magnetic material has been used.
1F13304. Pe5o containing Co,,'r
Hertolide compound of FezO3 and Fe3O4 + C
Heldride compound containing o, oxide magnetic powder such as Cr[1□, or Pe, Co.

A magnetic layer is formed by dispersing a powder magnetic material such as an alloy magnetic powder containing Ni etc. as a main component in an organic binder such as vinyl chloride-vinyl acetate copolymer, polyester resin 1 polyurethane resin, coating, and drying. So-called coated magnetic recording media have been widely used.

On the other hand, with the increasing demand for high-density magnetic recording, ferromagnetic metal iN films are being formed on substrates using vacuum thin film formation techniques such as vacuum evaporation, sputtering, and ion blating, and techniques such as plating. ferromagnetic metal thin film type magnetic recording media that are directly deposited using magnetic materials are attracting attention. This type of magnetic recording medium has large coercive force He and residual magnetic flux density Br, and the thickness of the magnetic layer can be made extremely thin, so the thickness loss during recording and reproduction is significant. It has many advantages, such as being small and being able to dramatically increase the packing density of the material since there is no need to mix an organic binder, which is a non-6(i) material, into the magnetic layer.

Conventionally, in order to further improve the magnetic properties such as coercive force and squareness ratio of the above-mentioned ferromagnetic metal thin film type magnetic recording medium, a multilayer structure as described in JP-A No. 1-113318, for example, has been developed. That is, a magnetic recording medium in which multiple layers of ferromagnetic thin films are formed has been proposed.

[Problem that the invention seeks to solve]

By the way, in the field of magnetic recording, with the progress of higher density recording and higher quality recording, it goes without saying that magnetic recording media are required to further improve their magnetic properties. There is also a demand for improvements in practical properties such as durability and running properties. The multilayered magnetic recording medium described above is no exception.

The present invention has been proposed in view of such conventional circumstances, and has excellent magnetic properties and
The object of the present invention is to provide a magnetic recording medium that also has excellent practical properties such as durability and runnability.

Means for Solving Problem C] In order to achieve the above-mentioned object, the magnetic recording medium of the present invention includes a nonmagnetic support having microprotrusions on the surface, and a plurality of ferromagnetic metal thin films formed on the l- It is characterized by what it did.

[Effect]

The microprotrusions provided on the surface of the nonmagnetic support control the surface properties of the ferromagnetic metal TiN film, improving runnability and durability. Furthermore, since the magnetic layer is composed of multiple layers of ferromagnetic metal thin films, it exhibits excellent fd magnetic characteristics and electromagnetic conversion characteristics.

〔Example〕

The present invention will be explained in detail below.

As shown in FIG. 1, a magnetic recording medium to which the present invention is applied includes a substrate (1) made of a non-magnetic material; second, a plurality of layers (two layers in this example) of ferromagnetic thin films (2a )
, (2b) is a so-called ferromagnetic metal thin film type magnetic recording medium.

As the substrate (1), a heat-resistant polymer film such as polyimide or polyamide is used.

In the magnetic recording medium of the present invention, the base (
One or more types of microprotrusions (3) such as mountain-like protrusions, wrinkle-like protrusions, and ladle-like protrusions are formed on the surface of 1), and the surface roughness thereof is controlled.

The above-mentioned mountain-like protrusions have a particle size of 500 when forming a polymer film.
It is formed by internally adding ~3000 inorganic fine particles, and the height from the polymer film surface is 5' O0~1
000 people, density is lXl0'~10XIO' pieces/recommendation 8
shall be. Inorganic fine particles used to form mountain-like protrusions include calcium carbonate (CaCO3), silica,
Alumina etc. are suitable.

- The wrinkle-like protrusions described in - are undulations formed by applying and drying a dilute solution of resin using a specific mixed solvent, and the height thereof is 0.01 to 10 μm, preferably 0.03 to 10 μm. 0.5μm, minimum distance between protrusions 0.1~20
Let it be pm. Examples of resins used to form these wrinkle-like projections include saturated polyesters such as polyethylene terephthalate and polyethylene naphthalate, polyamides, polystyrene, polycarbonates, polyacrylates, polysulfones, polyethersulfones, polyvinyl chloride, polyvinylidene chloride, and polyvinyl butyral. A single substance, a mixture, or a copolymer of various resins such as polyphenylene oxide, phenoxy resin, etc., and those having a soluble solvent are suitable. Then, to a solution in which these resins were dissolved in the good solvent at a resin concentration of 1 to 11,000 ppp, a solvent that was a poor solvent for the resin and had a boiling point higher than the good solvent was added 10 to 100 times the amount of the resin. By applying the solution to the surface of the polymer film and drying it, a layer ii1 having very fine wrinkle-like irregularities can be obtained.

The granular protrusions are formed by attaching organic ultra-fine particles such as acrylic resin or inorganic ultra-fine particles such as silica or metal powder in a spherical or hemispherical shape.

The height of this granular projection is 50 to 500 people, and the pumpkin is I
10'~50X] 06 pieces/approximately 2 pieces.

If at least one of these protrusions is formed, the surface P1 of the ferromagnetic metal thin film (2a), (2b) that is the magnetic layer is controlled, but the effect is increased by combining the ferromagnetic metal thin films (2a) and (2b). If two granular wrinkle-like projections are formed on a base film provided with projections, durability and runnability can be greatly improved.

The overall height of the above-mentioned microprotrusions (3) is 100~
Preferably 2000 people, the density is ln+”
It is preferable that the number of IXIO' to 1XlO is 7 on average.

On the other hand, the ferromagnetic thin films (2a) and '(2b) are formed as magnetic layers by directly depositing a ferromagnetic metal material onto the substrate (1) by vacuum deposition.

The ferromagnetic metal material constituting this ferromagnetic thin film (2) is metal such as Fe, Co, Ni, or Fe-C.
o.

Fe-Ni, Go-Ni + Fe-Co-N
i, re-Cu, Go-Cu, Co-Au
, Co-PL.

Mn-B1. Mn-A1, Fe-Cr, Co
-Cr, Ni-Cr, Pe-Go-Cr, Co-
Examples include ferromagnetic alloys such as Ni-Cr and Fe-co-Ni-Cr.

The ferromagnetic metal thin films (2a) and (2b) are deposited obliquely onto the moving substrate (1) while continuously changing the evaporated atoms from the evaporation source from a high incident angle to a low incident angle. It has a curved and inclined columnar structure. Furthermore, in this embodiment, the inclination directions of the ferromagnetic metal thin films (2a) and (2b) are the same.

In this way, by forming multiple layers of ferromagnetic metal thin films (2a) and (2b) with the tilted columnar structures aligned in the same direction,
A magnetic recording medium with excellent magnetic properties, especially reproduction output, noise, etc., can be obtained.

The above-mentioned multi-layered ferromagnetic metal thin film (2a), (2b)
is formed by diagonal deposition according to a conventional method using a vacuum deposition apparatus as shown in FIG.

This vacuum evaporation apparatus includes an evaporation source (12) heated by heating means such as electron beam heating, and an unwinding roll ( 13), a take-up roll (4) and a cooling cylindrical can (15) are arranged, and the base body (1
) is continuously run (moved) along the can (15), the evaporated atoms from the evaporator a (12) are deposited on the surface of the substrate (1), and a continuous film of the evaporated atoms is formed. is formed as a magnetic layer.

Here, a shielding plate (16) is provided between the evaporation source (I2) and the moving substrate (1) to regulate the vapor flow of the evaporated atoms deposited on the substrate (1). There is.

That is, the evaporation source (1) is attached to the base (1).
The evaporated atoms from 2) are deposited while changing continuously from a high incident angle to a low incident angle.

Therefore, by repeating the oblique deposition twice using the above-mentioned apparatus, a magnetic recording medium having a two-layer structure as shown in FIG. 1 can be obtained.

By the way, -1- mentioned method number (more ferromagnetic VW film (2a
).

(2b), the substrate (1) and the ferromagnetic thin film (2b) are formed.
a) or between each ferromagnetic metal thin film (2a), (2
b) In order to improve the adhesion between and control the coercive force, etc.
A base layer or an intermediate layer may be provided. These base layers or intermediate layers include 8ft, Si, Cr, Mn, Zn+B.
Examples include i, Ti, Cu+In, Ni, Go, Fe, and oxides and nitrides thereof.

Further, a protective film may be formed on the ferromagnetic thin film (2h) in order to improve the corrosion resistance and runnability of the ferromagnetic thin film (2b). As this protective film,
An inorganic protective film made of metals or their oxides, nitrides, etc. as mentioned in the previous base layer, fatty acids, metal soaps that are alkali metal salts or alkaline earth metal salts of fatty acids,
High class alcohol.

Examples include organic protective films such as fatty acid esters, fluorine-containing compounds, and silicone oil.

According to the method described above, the ferromagnetic metal thin film (2a) and (
Sample tapes were created by changing the film thickness of 2b).

This was designated as Example 1 and Example 2. The incident angle during vapor deposition was 50° to 90°, and the ferromagnetic metal material was C.
o was used. In addition, a sample tape was prepared using a substrate having no small protrusions on its surface, and this was designated as Comparative Example 1.

Regarding these Examples and Comparative Examples, magnetic properties (coercive force H
The C9 residual magnetic flux density B r and squareness ratio R8) and practical characteristics were investigated. The results are shown in Table 1.

In addition, in the table, the still characteristics are 4.2 Mllz for the tape.
A video signal was recorded, and the time required for the playback output to attenuate to 50% was measured. In addition, the shuttle characteristics are 25℃,
The output fluctuation was investigated after running 200 times at a relative humidity of 50%.

Table 1 From this Table 1, it can be seen that by making the ferromagnetic metal thin film have a two-layer structure, magnetic properties are ensured, and since the base is provided with minute protrusions, durability is also greatly improved. Recognize.

By the way, the ferromagnetic metal thin film (2a) and (2
The directions of inclination of the inclined columnar structures in b) may be opposite to each other, as shown in FIG. In this case, as shown in FIG. 2, the ferromagnetic metal thin film (2a) is obliquely deposited while the substrate (1) is first fed out in the six directions of arrows, and then the alibi plate (16) is deposited as shown in FIG. The ferromagnetic metal thin film (2b) may be obliquely deposited while the substrate (1) is fed out from the take-up roll (13) in the direction of arrow B.

In this way, by oriented the tilted columnar structures of the ferromagnetic metal thin films (2a) and (2b) in opposite directions, the phase shift is eliminated, which is extremely advantageous when performing digital recording. In other words, when a conventional obliquely evaporated film is digitally recorded (square wave) with a ring head, the reproduced waveform becomes asymmetrical, so the reproduction circuit (equalizer circuit) adjusted with a longitudinal recording medium cannot be used as is, and the circuit scale The larger the value, the more difficult it is to make optimum adjustments specifically for the vapor-deposited tape. On the other hand, a ferromagnetic metal with a two-layer structure! If the tilted columnar structures of the four films (2a) and (2h) are oriented in opposite directions, the asymmetry of the reproduced waveform can be improved and the error rate can be kept low even when using a circuit adjusted for a longitudinal recording medium. This also makes it easier to make optimal adjustments.

In fact, by using the same method as in the previous embodiment, FIGS.
Ferromagnetic metal thin II# (2a) and (
A sample tape was prepared by reversing the direction of inclination of the inclined columnar structure in 2b), and the magnetic properties and practical characteristics, as well as the phase shift in the forward direction, were measured. The improvement was remarkable.

(Margins below) Table 2: Although the present invention has been described with reference to specific examples, the present invention is not limited to these examples. For example, the present invention is not limited to these examples. It goes without saying that various forms may be taken without departing from the gist of the present invention, such as a structure with more than one layer.

〔Effect of the invention〕

As is clear from the following explanation, the magnetic recording medium of the present invention is composed of a plurality of ferromagnetic metal thin films as magnetic layers, and has microprotrusions on a non-magnetic support, so it has excellent properties. In addition to having magnetic properties and electromagnetic conversion properties,
It also has excellent practical properties such as durability and runnability.

In particular, if the tilted columnar structure of the ferromagnetic metal thin film consisting of multiple layers is deposited obliquely so that the tilt directions are opposite to each other,
Phase shifts are also eliminated, the error rate can be kept low, and adjustments can be made easily.

BRIEF DESCRIPTION OF THE DRAWINGS FIG. 1 is a schematic enlarged sectional view of essential parts showing an example of a magnetic recording medium to which the present invention is applied. FIG. 2 is a schematic diagram showing the configuration of a vacuum evaporation apparatus used for forming a ferromagnetic metal thin film. FIG. 3 is a schematic enlarged sectional view of essential parts showing another example of a magnetic recording medium to which the present invention is applied. FIG. 4 is a schematic diagram showing the configuration of a vacuum evaporation apparatus for making the tilted horns of the tilted columnar structure of the ferromagnetic metal thin film reverse in direction. l...Substrate (non-magnetic support) 2a,'lb・
...Ferromagnetic thin film 3 ...Minute protrusions

Claims (1)

[Claims] A magnetic recording medium characterized in that a plurality of layers of ferromagnetic metal thin films are formed on a nonmagnetic support having microprotrusions on the surface.