JPS6022731A - magnetic recording medium - Google Patents

Abstract

PURPOSE:To obtain a magnetic recording medium which has an excellent electromagnetic conversion characteristic over a wide frequency range and is suitable for use in a metal position by forming a thin ferromagnetic metallic film layer on the magnetic coating layer formed by dispersing pulverous magnetic powder in a binder and coating such powder in a non-magnetic base and regulating the coercive force, residual magnetic flux density and thickness of the respective layers in a prescribed range. CONSTITUTION:A thin ferromagnetic metallic film layer is formed on a magnetic coating layer and the coercive force of the magnetic coating layer is made 1,000-1,200 oersted (Oe), the residual magnetic flux density 2,500-3,500 gauss and the thickness 2-8mum. On the other hand the coercive force of the thin ferromagnetic metallic film layer is made 700-1,500 oersted (Oe), the residual magnetic flux density 8,000-12,000 gauss and the thickness 50-4,000Angstrom . The magnetic ink formed by dispersing fine particulate magnetic powder of Fe into a binder is uniformly coated on, for example, a polyethylene terephthalate film having 9mum thickness and after orientation and drying, the coating is finished to a specular surface by which the coating is finished to 4.5mum thickness and 0.15mum Rz surface roughness.

Description

DETAILED DESCRIPTION OF THE INVENTION Field of Industrial Application The present invention relates to a magnetic recording medium having a two-layer structure.

Conventional structure and its problems Conventionally, γ-F e 203. cr
o2゜Co -r -F e 20 s or Fe
A magnetic ink obtained by dispersing magnetic fine powders such as, etc., in a binder such as a polyurethane resin using a solvent together with various additives such as a dispersant and an antistatic agent is applied onto a non-magnetic support such as polyethylene terephthalate. A coated magnetic recording medium obtained by mirror-finishing after orientation and drying, and a ferromagnetic material such as Fe, Co, Ni, etc. is directly formed on a non-magnetic support by vapor deposition or sputtering in a vacuum. There is a thin film magnetic recording medium.

Further, as a multilayer magnetic recording medium, many proposals have already been made for a two-layer structure with coated magnetic layers, and some of them have also been put into practical use. Furthermore, a few two-layer structures in which a ferromagnetic metal thin film layer is formed on a coated magnetic layer have been proposed, and some have even been put into practical use.

However, although a coated magnetic layer with a two-layer structure can improve performance to some extent compared to a one-layer structure, the magnetic layer essentially becomes thicker, so losses during recording and reproduction are unavoidable. In addition, proposals for magnetic recording media in which a ferromagnetic metal thin film layer is formed on a coated magnetic layer have been made and put into practical use to some extent for bi-position tapes; There are almost no concrete proposals regarding the tape, and of course, it has not been put to practical use.

Purpose of the Invention The present invention provides a ferromagnetic metal thin film layer formed on a coated magnetic layer.
Based on the recognition that the layer structure can be a magnetic recording medium with inherently excellent electromagnetic conversion characteristics, we have conducted detailed studies on the formation of a ferromagnetic metal thin film layer on a coated magnetic layer. By setting the coercive force, residual magnetic flux density, and thickness of the ferromagnetic metal thin film layer within a predetermined range and creating a two-layer structure, we have created a magnetic recording medium for metal positions that has excellent electromagnetic conversion characteristics over the entire frequency band. This is what we are trying to provide.

Structure of the Invention In the present invention, a ferromagnetic metal thin film layer is formed on a coated magnetic layer, and the coated magnetic layer has a coercive force of 1,000 to 1,200 oersteds (Os) and a residual magnetic flux density of 2,500 to 3.500. Gauss, with a thickness of 2-8 μm,
- The coercive force of the ferromagnetic metal thin film layer is 700 to 1.500 Oe, and the residual magnetic flux density is 8,000 to 12.
000 Gauss, thickness 50-4,00
By setting the number to 0, a magnetic recording medium for metal positions that exhibits excellent electromagnetic conversion characteristics over the entire frequency band is realized.

DESCRIPTION OF EMBODIMENTS The magnetic recording medium of the present invention achieves an expanded frequency band and improved sensitivity over the entire frequency band compared to conventional products under the same usage conditions as conventional coated metal tapes. It has very good properties. Note that the surface of the coated magnetic layer, which is the surface on which the ferromagnetic metal is deposited, is the element that governs the large high-frequency output that is a characteristic of the ferromagnetic metal thin film layer. (JIS
) 0.
A 16 μm thick film was used.

An embodiment of the present invention will be described below with reference to the drawings.

FIG. 1 is a diagram showing the structure of a magnetic recording medium according to the present invention, in which 1 is a non-magnetic support made of a polyester film or the like, 2 is a coated magnetic layer provided on the surface thereof, and 3 is a coated magnetic layer. This is a ferromagnetic metal thin film layer formed on the surface of 2. FIG. 2 shows the frequency characteristics when the characteristics of the ferromagnetic metal thin film layer 3 are fixed and the coercive force of the coated magnetic layer 2 is varied.

The residual magnetic flux density of the coated magnetic layer 2 is 3.0OOGauss
, the thickness is 4.15 μm, the coercive force of the ferromagnetic metal thin film layer 3 is 1.2000e, and the residual magnetic flux density is 10,000G.
auss.

For the combination of thickness 800 and curve A in the figure, when the coercive force of the coated magnetic layer 2 is 9000e, curve B is 1.10.
00e t7), curve C shows the case of 1,3000e. As is clear from FIG. 2, the coercive force of the coated magnetic layer 2 is required to be 1.1000 @ or more in order to obtain sufficient sensitivity from the middle to high ranges.

Note that sensitivity in this frequency range can be achieved by increasing the thickness of the ferromagnetic metal thin film layer 3, and if the coercive force of the coated magnetic layer is 1,0000@, the thickness of the ferromagnetic metal thin film layer 3 can be increased. It has also been confirmed that the target can be achieved by setting the number to 4,000. The upper limit needs to be suppressed to about 1.2000 e in order to obtain sufficient bias characteristics, erase characteristics, etc. Note that the lower limit of the residual magnetic flux density of the coated magnetic layer 2 is limited by sensitivity, saturation output, etc., and the upper limit is limited by the physical strength of the layer itself.

Furthermore, the lower limit of thickness is limited by saturation output, etc., and the upper limit is limited by flexibility, etc., but these are not fundamentally different from existing coating-type magnetic recording media, and the experimental results here A detailed explanation will be omitted.

FIG. 3 shows the frequency characteristics when the characteristics of the coated magnetic layer 2 are fixed and the thickness of the ferromagnetic metal thin film layer 3 is varied. The coercive force of the coated magnetic layer 2 is 1,1000e.

The residual magnetic flux density is 3,000 Gauss, and the thickness is 4
．． '57 Jm, and the coercive force of the ferromagnetic metal thin film layer 3 is 1
, 2000e, residual magnetic flux density is 10,000 Gauss
The curved line in the figure is the combination of ferromagnetic metal thin film layer 3.
The thickness of curve E is 100 people, and the thickness of curve E is 2,000 people.
The case of a person is shown. As is clear from FIG. 3, when the thickness of the ferromagnetic metal thin film layer 3 is 100 people, only the high-frequency output is emphasized and the sound becomes difficult to hear, and due to the thin thickness, the film may be missing during endurance running. It is easy to cause

As a result of further detailed study, we found that the high-frequency output is also greatly affected by the coercive force of the ferromagnetic metal thin film, and that the coercive force is 7.
In the case of 000e, it has become clear that if the thickness is 6e8 or more, the minimum characteristics required as a magnetic recording medium can be secured.

The upper limit is mainly limited by physical characteristics, and if it exceeds 4,000 OOA, the rigidity becomes too strong and the state of contact with the head becomes unstable.

In the end, in order to ensure comprehensive characteristics such as excellent electromagnetic conversion characteristics, runnability, and durability over all frequency bands, the thickness of the ferromagnetic metal thin film layer 3 should be in the range of 60 to 4,000 mm. It is necessary that there be.

On the other hand, the coercive force of the ferromagnetic metal thin film layer 3 can be arbitrarily set by oblique evaporation in an oxygen gas atmosphere, but a magnetic recording medium of this configuration requires a coercive force of 700 to 1,500 e. If it is less than 700 Oe, sufficient high frequency output cannot be obtained, and if it is more than 1.6 ooOe, there are problems such as insufficient erasure. Compared to a coated magnetic layer, a ferromagnetic metal thin film layer can provide high high-frequency output even with a low coercive force, and good erasing characteristics even with a high coercive force, so it can be put to practical use in a wide range of applications as described above.

Furthermore, regarding the residual magnetic flux density, in order to obtain sufficient sensitivity and saturation output in the high range, it is 8,000 to 12,0 O.
OGauss is required, but these are basically not particularly different from existing vapor-deposited magnetic recording media, and a detailed explanation of the experimental results will be omitted here.

Next, a specific example will be described. On a polyethylene terephthalate film with a thickness of 9 μm, a magnetic ink containing fine magnetic particles of Fe dispersed in a binder was uniformly applied, and after orientation and drying, a mirror polishing treatment was performed to give a thickness of 4.6 μm2 surface roughness Rzo, Finish to 15 μm. The coercive force of this is 1,
10o Oe, residual magnetic flux density is 3. ooo Gauss
Met. Further, on top of this, p
Co-Ni alloy (Ni-20%) was obliquely deposited in an oxygen atmosphere to a thickness of 1.0OOA and a coercive force of 1,2000e.
A ferromagnetic metal thin film with a residual magnetic flux density of 11.000 Gauss was formed.

The wide two-layer magnetic recording medium obtained in this way was cut to a width of 3.81 tan to form the final magnetic recording medium, and the bias position was metal and the input level was -10 dB. The frequency characteristics were measured and the results obtained are shown in FIG. In FIG. 4, curve F shows the characteristics of this example, and for comparison, curve G shows the general characteristics of commercially available metal tapes.

As is clear from FIG. 4, the magnetic recording medium according to the present invention can expand the frequency band and improve sensitivity compared to commercially available coated metal tapes, and exhibits extremely superior characteristics. Yes, its industrial value is extremely large.

Effects of the Invention As described above, in the present invention, magnetic fine powder is dispersed in a binder on a non-magnetic support, and a ferromagnetic metal thin film layer is formed on a magnetic coating layer coated with the fine powder, and each coercive force, By setting the residual magnetic flux density and thickness within predetermined ranges, it is possible to obtain a magnetic recording medium suitable for use in a metal position that has excellent electromagnetic conversion characteristics over a wide frequency range.

[Brief explanation of drawings]

Fig. 1 is a cross-sectional configuration diagram showing one embodiment of the present invention, Fig. 2 is a frequency characteristic diagram when the coercive force of the coated magnetic layer is changed,
FIG. 3 is a frequency characteristic diagram when the thickness of the ferromagnetic metal thin film is changed, and FIG. 4 is a frequency characteristic diagram comparing this embodiment with a conventional metal tape. 1...Nonmagnetic support, 2...Coating magnetic layer, 3...Ferromagnetic metal thin film layer.

Claims (1)

[Claims] A structure in which a first layer is formed by coating a non-magnetic support with magnetic powder dispersed in a binder, and a second layer made of a ferromagnetic metal thin film is formed on the first layer. No, the coercive force of the first layer is 1, OOO~1.200 oersted, the residual magnetic flux density is 2,500~300 Gauss, the thickness is 2~8 μm, and the coercive force of the second layer is 700 Oe. ~1,50
0 oersted, residual magnetic flux density is 8,000-12,0
A magnetic recording medium having a thickness of 60-4.00 Gauss.