JPS5870421A - Magnetic recording medium - Google Patents

Abstract

PURPOSE:To increase the surface electric resistance and to control the noise by covering the uppermost layer of a magnetic thin multilayer film with an oxidized magnetic layer. CONSTITUTION:A vapor-deposited Al layer or the like as an intermediate layer is laid on a base film of polyethylene terephthalate or the like. On the intermediate layer a vapor-deposited layer such as a magnetic thin Co.Ni alloy film is laid, and by repeating the stage, a vapor-deposited multilayer film is formed. A magnetic thin film of an oxidized alloy such as Co.Ni oxide is finally laid as the uppermost layer.

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to a high-density, high-resolution magnetic recording medium.

In recent years, as magnetic recording technology has progressed, high density and IWi resolution have been desired, and as compact VTRs, camera-integrated VTRs, and PCM compatible recorders have been proposed, new media for use in these devices have been proposed. is becoming necessary.

Under these circumstances, rlVl type film magnetic recording media using vacuum technology are attracting attention. Among these methods, research is being widely conducted on methods for forming magnetic recording media by directly forming a ferromagnetic layer on a non-magnetic substrate by blue vaporization, ion silating, sputtering, etc. for practical use.

However, there are many characteristics that should be taken into consideration when designing the vapor-deposited tape for use with all audio tapes, among which surface electrical resistance is an important item. Originally, coating type magnetic tape had an electrical resistance of 10@9 ohms or higher, since the negative layer was formed mainly from iron oxide and a polymeric binder. For this reason, the electrical resistance value becomes a problem because the electrical charge generated in various places during running is difficult to escape from the tape, and it is reflected in the audio signal as so-called discharge noise.
The main thing was that it was audible. To solve this problem, it is possible to mix conductive materials into magnetic paints, or to reverse (/C>η
A technology has been put into practical use that lowers the electrical resistance of the tape as a whole by installing a thin film on the back of the tape.

However, in the case of vapor-deposited tapes, etc., the magnetic layer is made of metal or alloy and does not contain a polymer binder, so the electrical resistance is extremely low, which causes problems during recording when using decks with poor sealing around the head. may occur. In other words, when a number of pieces of a so-called 5-head type tape deck with low electrical resistance are made, the circuit between the erasing head, recording head, and playback head is affected by the bias magnetic field generated by the recording head, and the erasing head. It has been found that noise is induced in the read head by the erase magnetic field from the magnetic field.

This phenomenon is also disclosed in Takekai 56-47924, for example. Therefore, the above-mentioned problems arise when manufacturing a deck.
It seems possible to read I many times, but l
Oxidation is also desired from the viewpoint of manufacturing +11 air tape. Furthermore, much of the noise can be reduced by using LF4K tape!
As disclosed in Japanese Patent Publication No. 56-47924, it has been proposed to provide cracks in the magnetic layer to create an insulating layer that is partially discontinuous.
Even if this technique is effective to some extent, it is extremely difficult to develop a technique for continuously forming cracks in the magnetic layer with good reproducibility.

This invention was made in view of the above situation, and by covering the top layer on the magnetic head side of a multi-layered magnetic layer with an oxidized magnetic layer, the surface of the magnetic tape can be improved. It was discovered that the electrical resistance can be controlled, and it is made of five or more strong 4B1 layers including an intermediate layer.
A thin film (a magnetic recording medium whose top layer is made of an oxide of the ferromagnetic material) can have a high surface electrical resistance, which reduces noise and improves electromagnetic conversion characteristics. This makes an excellent magnetic recording medium.

Hereinafter, embodiments of the present invention will be described in detail with reference to the accompanying drawings.

<Example> A base film of polyethylene terephthalate with a thickness of 15 μm was prepared, and a strong J of cobalt-nitrate alloy with an intermediate layer of aluminum was prepared on the base film by vacuum evaporation method.
i? , forming 4 sexual layers 1~.

The pressure during steaming Aj is 5 ×il]-5pa (approximately 2
1O-5 Torr), the control temperature was set to 0℃ using a cooling Guyan, the vapor aIIψ thickness was 250χ for the aluminum intermediate layer, and 1o for the cobalt-nickel alloy layer.
It was set as ooX.

The so-called open side 1 was made by the A method so that the coercive force in the longitudinal direction of the dage was approximately 61]00 el/g.

A multilayer steamed film including a nonmagnetic intermediate layer was entirely formed under the following conditions. The relationship between the number of layers and the sensitivity in this case is as shown in Figure 1. In Figure 1, the number of layers is
(The width of a cassette tape cut to 8 mm was found to have a relative output of 335 Hz at 4.75%.According to this paper, when the number of layers is 1 or 2, this tape does not have much power. However, it has been found that tapes consisting of five or more layers of magnetic I- exhibit better sensitivity.

When making my own samples, I made the second most layer a cobalt-nickel oxide layer and set the oxygen partial pressure at several levels of 11E to obtain samples with different degrees of oxidation. However, at this time, the incident angle during oblique deposition was adjusted so that the coercive force was approximately 6 oooo as in the case of the alloy. The oxygen partial pressure and electrical resistance of the tape surface at the time of forming the uppermost layer of the sample obtained as described above were as shown in FIG.

Here, the electrical resistance means that the tape has a width of 5.8 cm and a length of 20 Cr.
It refers to the electrical resistance measured at both ends of rL.

At this time, the sensitivity was 1 to 2 dB lower than each point in FIG. This is because the magnetic flux density is reduced due to the introduction of oxygen into the magnetic layer. In addition, when examining the relationship between the degree of oxidation and noise for the obtained samples, as mentioned above, the tape with low surface electrical resistance, conductivity, and properties has a 5-head quif of 0, while the tape with poor head sealing has When recording and playing back at the same time, the noise contained in the playback signal becomes louder than when it is simply written, but this is compensated for by forming the top layer of oxidized proboscis. That is, if the difference between the two noise levels is shown in relation to the electrical resistance on the surface of the tape, the result will be as shown in FIG.

Here, the noise level is the noise component of 555H1.

-J: gb i, lT According to Figure 5, the noise level difference of the tape with a resistance of more than 200 Ω is 1 dB or more, and there is no problem in practical use. At this time,
Since the 1st stop was only 1d"4M degrees lower than the hundreds of samples, the S/N ratio of the tape was improved by the amount that the noise level difference disappeared, and in practical terms it was ) is in a range with no 1 or ↓.

Note that this difference in noise level was concave everywhere in the audio frequency region. Even if the platform has four or more twisted magnetic layers, if the tjL pile is 200Ω or more, the noise level i1. Treasure is less than 2dB.

As explained above in detail, this invention (magnetic recording ((lj, body il- The IW decision was made, and the T business effect Q, 1 Guiwa 6
In the formation of the intermediate layer shown in Example 1 and 11, the force tk can be changed without departing from the gist of the present invention, and it is possible to use ion brating or other methods. Sputtering or the like can also be used.

In particular, the relationship between the oxygen atmosphere and the electrical resistance is influenced by other conditions, such as the evaporation rate and the movement rate of the substrate, so this does not limit the effective scope of the present invention.

[Brief explanation of drawings]

Figure 1 shows the relationship between the number of magnetic layers and the sensitivity of the magnetic tape obtained in the example of the present invention, and Figure 2 shows the relationship between the oxidation partial pressure in the vacuum chamber when forming the sixth layer and the surface of the finished tape. 'Relationship Diagram with Electrical Resistance, Figure 5 171: A diagram showing the relationship between surface electrical resistance and noise level difference when the top layer is an oxide layer in a five-layer magnetic layer. 'l-! fjFF Applicant Tokyo Denki Kagaku Kogyo Co., Ltd. Agent Patent Attorney Hide Sato

Claims (2)

[Claims] (1) In a magnetic recording medium comprising an intermediate layer and six or more ferromagnetic layers on a non-magnetic substrate in vacuum, the uppermost layer of the plurality of ferromagnetic layers is made of a ferromagnetic oxide. A magnetic recording medium characterized by: (2) The magnetic recording medium according to claim (1), wherein the electrical resistance measured at both ends of a width of 5.8 mm and a length of 20 cm is 200Ω or more. Medium.