JPS633376B2 - - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to a magnetic recording medium that is highly durable, prevents noise due to charging and tape winding, and has good electromagnetic conversion characteristics.

With the increasing density and performance of magnetic recording, methods such as using fine magnetic powder and mirror-finishing the surface of the magnetic coating are being used to improve the contact between the magnetic tape and the head. .

However, in such cases, due to increased adhesion and friction between the magnetic head and tape, normal recording and playback are likely to become impossible, and the durability of the magnetic recording medium itself is still insufficient. It was difficult to describe.

To improve the durability of magnetic recording media, there are methods that include non-magnetic powder such as chromium oxide (Cr ₂ O ₃ ) in the media (Japanese Patent Publication No. 47-18572).
No.) and those containing α-alumina (Special Publication No. 52
-49961) is known.

The present inventor is currently considering the industrial use of a series of metal borides. Focusing on the high hardness and high electrical conductivity that are the characteristics of metal borides, the present inventor has determined that when such a substance is included in a magnetic recording medium, magnetic tape We discovered that it is effective in improving the durability of magnetic tapes and at the same time preventing static electricity associated with reducing recording/reproducing noise and magnetic tape winding, that is, reducing the surface electrical resistance of magnetic tapes.
This has led to the present invention. Boron and metals form a group of over 200 compounds called borides.
Although classified as ceramics, they are substances that do not exist in nature like oxides, but among various borides,
BACKGROUND ART BACKGROUND OF THE INVENTION It is known that borides of transition metal elements of Groups, Groups, and Groups of La or La have properties such as particularly high hardness, high electrical conductivity, and high melting point.

Highly hard chromium oxide (Cr ₂ O ₃ ) and alumina (Al ₂ O ₃ ) are used to improve the durability of magnetic recording media, but in such cases, magnetic recording media cannot be used because of their high surface resistance. During high-speed contact with the magnetic head and guide roller, a charging phenomenon occurs, causing problems such as ^noise or tape winding. For example, a method of further incorporating carbon into the medium is known. However, carbon has an extremely strong cohesive force, so it is generally difficult to incorporate it into a medium in a desirable state, and there are problems in that it tends to cause product variations, and of course it does not significantly contribute to improving durability. Furthermore, in order to place the highest priority on magnetic properties, it is not preferable for magnetic recording media to contain essentially non-magnetic substances, and it is necessary for practical purposes to include them in order to improve durability and prevent static electricity. In this regard, the use of a material having high hardness and high electrical conductivity is extremely beneficial as it is effective for both improving durability and preventing static electricity. There are various metal borides, among which the borides of Ti, Zr, and Hf, which belong to the group, have a microhardness of 2250.
~3250Kg/mm ² , electrical conductivity 7~15μΩ-cm, and borides of V, Nb, and Ta belonging to the group also have a conductivity of 2000~
2100Kg/mm ² , 12~60μΩ-cm, Cr belonging to the group,
Mo, W boride is 1900~2650Kg/mm ² , 18~50μ
Ω-cm Furthermore, the boride of La is 2770Kg/mm ² , 15μΩ-
Conventionally used metal oxides, such as cm, have high hardness and electrical conductivity close to that of metals.
It exhibits properties not found in metal carbides or metal nitrides.

In view of these points, the present invention provides a magnetic recording medium that can improve the durability of the tape and at the same time significantly reduce the surface electrical resistance of the tape.

In the present invention, a group transition metal or a boride of La is added to the magnetic powder at a ratio of 0.5 to the magnetic powder.
~10 wt percent and the desired curable adhesive are applied onto a support to obtain a magnetic recording medium.

The magnetic material used in the present invention may include conventionally used magnetic materials such as γ-
Examples include Fe ₂ O ₃ , Fe ₃ O ₄ , Co-γ-Fe ₂ O ₂ , magnetic alloys, etc., and examples of curable resins include conventionally used thermoplastic resins and thermosetting resins. It can be used.

This will be further explained below with reference to Examples.

Example 1 Magnetic paints were manufactured with the following weight mixing ratios.

Ferromagnetic iron oxide (γ-Fe ₂ O ₃ ) 400 parts by weight Titanium boride (TiB ₂ ) 0 to 80 Vinyrite VYHH (trade name) 100 Dibutyl phthalate (DBP) 15 Methyl ethyl ketone 300 Toluene 300 Here, ferromagnetic iron oxide (γ −Fe ₂ O ₃ ) to titanium boride (purity 99.5%, average particle size 2μ)
I tried changing it by 20wt%. After mixing and dispersing the above magnetic paint in a ball mill for 20 hours, it was coated on a polyester film support to a coating thickness of about 6 μm, dried, and cut into a predetermined width for measurement.

The results are shown in FIGS. 1 and 2. In addition,
Still life and surface electrical resistance were measured under the following conditions.

(a) Still life The time taken for the output signal to drop by 10 dB relative to the tape's input signal when a VTR is turned into a still image was defined as the still life as a proxy for tape durability.

(b) Surface electrical resistance Magnetic tape 50 mm long and 1/2 inch wide
Apply a voltage of 1000 VDC and measure the surface electrical resistance.

As is clear from Figure 1, the still life is
Addition of 0.5wt% or more gives good results, while the effect on surface electrical resistance is significant when 1wt% or more is added.
Moreover, from FIG. 2, the amount added is preferably 10 wt % or less, taking into account the decrease in magnetic flux density.

Example 2 Magnetic paints were manufactured with the following weight mixing ratios.

Ferromagnetic iron oxide (γ-Fe ₂ O ₃ ) 400 Vanadium boride (VB ₂ ) 0~80 Vinyrite VYHH (trade name) 100 Dibutyl phthalate (DBP) 15 Methyl ethyl ketone 300 Toluene 300 Here, ferromagnetic iron oxide (γ-Fe ₂ O ₃ ) to vanadium boride (99% purity, average particle size 1 μ)
I tried changing it by 20wt%. Others are the same as in Example 1.
As shown in FIGS. 3 and 4, almost the same effects were obtained.

Example 3 Magnetic paints were manufactured with the following weight mixing ratios.

Ferromagnetic iron oxide (γ-Fe ₂ O ₃ ) 400 Chromium boride (CrB ₂ ) 0 to 80 Vinyrite VAGH (product name) 100 Hiker (product name) 10 Dibutyl phthalate (DBP) 5 Methyl ethyl ketone 300 Toluene 300 Here, ferromagnetic Chromium boride (purity 99.8%, average particle size 0.5μ) is added to iron oxide (γ-Fe ₂ O ₃ ) from 0 to 0.
I tried changing it by 20wt%. Others are the same as in Example 1.
The results are shown in FIGS. 5 and 6. The same effects as in Example 1 were obtained.

Example 4 Magnetic paints were manufactured with the following weight mixing ratios.

Ferromagnetic iron oxide (γ-Fe ₂ O ₃ ) 400 Lanthanum boride (LaB ₆ ) 0~80 Vinyrite VAGH (product name) 100 Hiker (product name) 10 Dibutyl phthalate (DBP) 5 Methyl ethyl ketone 300 Toluene 300 Here, ferromagnetic Lanthanum boride (purity 99%, average particle size 3.0μ) was added to iron oxide (γ-Fe ₂ O ₃ ) from 0 to
I tried changing it by 20wt%. Others are the same as in Example 1.
The results are as shown in Figures 7 and 8.
The results were almost the same as in Example 1.

[Brief explanation of the drawing]

FIG. 1 shows changes in still life and surface electrical resistance with respect to changes in the amount of titanium boride (TiB ₂ ) added, and FIG. 2 shows changes in magnetic flux density with respect to the same changes. Figures 3 and 4 are similar measurement results for vanadium boride (VB ₂ ), Figure 6 for chromium boride (CrB ₂ ), Figure 7 for lanthanum boride (LaB 6 ), and Figure 8 for lanthanum boride (LaB ₆ ). shows.

Claims (1)

[Claims] 1. A magnetic recording medium comprising magnetic powder, 0.5 to 10 wt% of at least one boride of Ti, V, Cr, or La based on the magnetic powder, and a desired curable resin.