JPS6022732A - 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 250- 400 oersted (Oe), the residual magnetic flux density 1,000-1,700 gauss and the thickness 2-8mum. On the other hand the coercive force of the thin ferromagnetic metallic film layer is made 300-700 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.

Structure of conventional example and its problems Conventionally, γ-Fe203. Cr
O2゜Go-r-Fe20. Alternatively, a magnetic ink obtained by dispersing magnetic fine powder such as Fe in a binder such as polyurethane resin together with various additives such as a dispersant and an antistatic agent using a solvent is applied onto a non-magnetic support such as polyethylene terephthalate. A coated magnetic recording medium obtained by applying, aligning, drying, and mirror-finishing treatment, and Fe, Go, etc.
There are thin film magnetic recording media in which a ferromagnetic material such as Ni is directly formed on a nonmagnetic support by a method such as vapor deposition or sputtering.

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 single-layer structure, essentially the magnetic layer becomes thicker, so losses during recording and reproduction cannot be avoided. do not have. 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 creating a two-layer structure with the coercive force, residual magnetic flux density, and thickness of the ferromagnetic metal thin film layer within a predetermined range, we will provide a magnetic recording medium for normal position that has excellent electromagnetic conversion characteristics over the entire frequency band. That is.

Structure of the Invention This invention forms a ferromagnetic metal thin film layer on a coated magnetic layer and increases the coercive force of the coated magnetic layer from 260 to 400 Oe.
), the residual magnetic flux density is 1000 to 1 γ'o.

Gauss, the thickness is 2 to 8 μm, and the coercive force of the ferromagnetic metal thin film layer is 300 to 700 Oerste.
Node (Oe), residual magnetic flux density8. ○OO~12.000
Gauss x and thickness of 60 to 4.0 OOA, we have realized a magnetic recording medium for normal points that exhibits excellent electromagnetic conversion characteristics over the entire frequency band.1.
It is something that

DESCRIPTION OF EMBODIMENTS The magnetic recording medium of the present invention has an expanded frequency band and improved sensitivity over the entire frequency band compared to conventional products under the same usage conditions as conventional coated normal 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
) Rz specified in Bo601 "Surface roughness" is 0.
A 15 μm thick one 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 2. This is a ferromagnetic metal thin film layer formed on the surface of the ferromagnetic metal. 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 coated magnetic layer 2 has a residual magnetic flux density of 1500 Gauss and a thickness of 4.6 μm, and the ferromagnetic metal thin film layer 3 has a coercive force of 6oo0e and a residual magnetic flux density of 10,000 Gauss.
, the thickness is 5ooA, and the curved line in the figure is 3ooO when the coercive force of the coated magnetic layer 2 is 2000e.
When e, curve C shows the case of 5000e. This second
As is clear from the figure, the coercive force of the coated magnetic layer 2 is required to be 5oooe or more in order to obtain sufficient sensitivity from the mid to high range.

In order to obtain sensitivity in this frequency range, it is possible to increase the thickness of the ferromagnetic metal thin film layer 3. If the coercive force of the coated magnetic layer is 2E500s, the thickness of the ferromagnetic metal thin film layer 3 can be increased to 400OA. It has also been confirmed that the goal can be achieved by doing so. In order to obtain sufficient bias characteristics, erase characteristics, etc., it is necessary to suppress the second limit to about 4000e.

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 coated 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 35006, and the residual magnetic flux density is 150.
0 Gauss, the thickness is 4.6 pm, the coercive force of the ferromagnetic metal thin film layer 3 is 5000 e, and the residual furrow degree is 10. O
OO Gauss combination, the curved line in the figure shows the case where the thickness of the ferromagnetic metal thin film layer 3 is 100^, and the curve E shows the case where the thickness is 2000^. As is clear from FIG. 3, when the thickness of the ferromagnetic metal thin film layer 3 is 10 OA, only the high-frequency output is emphasized, resulting in a sound that is difficult to hear, and the thinness of the layer 3 causes problems such as chipping of the film during endurance running. 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 3.
In the case of 000e, it has become clear that if the thickness is 5e8 or more, the minimum characteristics required as a magnetic recording medium can be achieved.

The upper limit is mainly limited by physical characteristics, and if it exceeds 400 Å, the rigidity becomes too strong and the state of contact with the head becomes unstable. After all, in order to ensure excellent electromagnetic conversion characteristics over the entire frequency band and comprehensive characteristics such as runnability and durability, the thickness of the ferromagnetic metal thin film layer 3 should be in the range of 60 to 4000 nm. is necessary.

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 it is required to be 300 to 000e for the magnetic recording body of this configuration. 3
Below 000e, sufficient high-frequency output cannot be obtained, and the
If the number is 0006 or more, there are problems such as insufficient erasing.

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, s, o o is required.

~12,000 Gauss is required, but these are basically not particularly different from existing vapor-deposited magnetic recording media, and a detailed explanation of the experimental results here will be omitted.

Next, a specific example will be described. On a polyethylene terephthalate film with a thickness of g/1 m, a magnetic ink containing fine particle magnetic powder of γ-Fe20x dispersed in a binder was applied uniformly, and after orientation and drying, mirror polishing was performed to obtain a film with a thickness of 4 g/1 m.
．． Finished to 6 μm, surface roughness RZo, 16 μm. Its coercive force is 3600e and residual magnetic flux density is 1500G.
It was 2Lu5s. Furthermore, a Cro-Ni alloy (N1 = 20%) was obliquely deposited on top of this in an oxygen atmosphere by a continuous deposition method in a vacuum to a thickness of 1000 mm and a coercive force of 500.
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 into 1 mm widths (s, a) to obtain the final magnetic recording medium.The bias position was normal and the frequency at an input level of -10 dB was cut into 1 mm widths. The characteristics were measured and the obtained results are shown in Figure 4.In this Figure 4, curve F shows the characteristics of this example, and for comparison, curve G shows the general characteristics of a commercially available normal tape. Indicated.

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

Effects of the Invention As described above, the present invention involves dispersing magnetic fine powder in Bi/Goo on a non-magnetic support, and forming a ferromagnetic metal thin film layer on the magnetic coating layer coated with the powder, each of which has a coercive force. , 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 and 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 layer is changed, and FIG. 4 is a frequency characteristic diagram comparing this embodiment with a conventional Q-P. 1...Nonmagnetic support, 2...Coated magnetic layer,
3...Ferromagnetic metal thin film layer. Name of agent: Patent attorney Toshio Nakao and 1 other person No. 1
Figure 2 500uoo, 5ooOtoooo Of course θθO number of cycles (Hsu 3 500 2000 5007) 100Oθ 2ooo
. Frequency (fh) Figure 4

Claims (1)

[Claims] It consists of a first layer in which magnetic powder is dispersed in a binder and coated on a non-magnetic support, and a second layer made of a ferromagnetic metal thin film is formed on this first layer, 1st
The coercive force of the layer is 250 to 400 Oersted, the residual magnetic flux density is 1.000 to 1.700 Gauss, and the thickness is 2 to 8μ.
m, the second layer has a coercive force of 300 to 700 oersted, a residual magnetic flux density of 8,000 to 12,000 Gauss, and a thickness of 6Q to 4.00 OA.