JPH09274719A - Magnetic recording medium - Google Patents

Abstract

PROBLEM TO BE SOLVED: To increase S/N and output in a high range and to decrease the error rate by forming a lower magnetic film and an upper magnetic film on a supporting body in such a manner that the upper magnetic film is made thicker than the lower magnetic film. SOLUTION: A lower magnetic film 21 and an upper magnetic film 22 are formed on a base body 1 in such a manner that the upper magnetic film 22 is 1.1 to 3 times as thick as the lower magnetic film 21. The upper magnetic film 22 is formed to 600 to 2200Å, while the lower magnetic film 21 is formed to 200 to 2000Å to obtain 800 to 4200Å sum thickness. Further, the thickness of the upper magnetic film 22 is controlled to 1/6 to 1/4 of the recording wavelength. Bs of the lower magnetic film 21 is controlled to 4000 to 8000G, while Bs in the upper magnetic film 22 is controlled large as 5000 to 10000G. Then. a protective film 3 is formed on the upper magnetic film 22 and a lubricant layer 4 is formed thereon. Thereby, when the medium is used for 15MHz or higher main recording wavelength, the S/N and output in a high range can be improved and the error rate can be decreased.

Description

Detailed Description of the Invention

[0001]

[0001] The present invention relates to a magnetic recording medium.

[0002]

In a magnetic recording medium such as a magnetic tape, a magnetic layer provided on a support is not a coating type using a binder resin, but a binder. A metal thin film type using no resin has been proposed. That is, there has been proposed a magnetic recording medium having a magnetic layer formed by a wet plating means such as electroless plating or a dry plating means such as vacuum deposition, sputtering or ion plating. And this kind of magnetic recording medium has a high packing density of a magnetic material,
This is suitable for high-density recording.

However, even in such a metal thin film type magnetic recording medium, the S / N is improved, the output is increased in the high range,
Furthermore, it is required to reduce the error rate. Therefore,
An object of the present invention is to provide a magnetic recording medium with improved S / N, increased output in the high frequency range, and further reduced error rate.

[0004]

The above-mentioned object of the present invention is a magnetic recording medium comprising a support and a plurality of magnetic films provided thereon, wherein the upper magnetic film has a thickness smaller than that of the lower magnetic film. It is solved by a magnetic recording medium characterized by being thick.
In particular, it is a magnetic recording medium in which a plurality of magnetic films are provided on a support, wherein the thickness of the upper magnetic film is 1.1 to 3 times the thickness of the lower magnetic film. It is solved by a magnetic recording medium.

Further, the upper magnetic film has a thickness of 600 to 2200.
Å, a magnetic recording medium further satisfying the requirement that the thickness of the lower magnetic film is 200 to 2000Å and the total thickness is 800 to 4200Å. Further, the thickness of the upper magnetic film can be solved by a magnetic recording medium which further satisfies the requirement of 1/6 to 1/4 of the recording wavelength.

That is, by making the magnetic film of a two-layer type and setting the thickness of the upper magnetic film and the thickness of the lower magnetic film as described above, the Bs of the lower magnetic film is 40.
Bs of the upper magnetic film, while it is 0.00 to 8000G
Is as large as 5000 to 10000G, which results in S / N
Is improved, the output is increased in the high frequency range, and the error rate is reduced.

The magnetic recording medium of the present invention preferably has a magnetic film provided with a protective film and / or a lubricating film.
The magnetic recording medium of the present invention is preferably used for applications where the main recording frequency is 15 MHz or higher.

[0008]

BEST MODE FOR CARRYING OUT THE INVENTION The magnetic recording medium of the present invention is a magnetic recording medium in which a plurality of magnetic films are provided on a support, and the upper magnetic film is thicker than the lower magnetic film. .
In particular, in a magnetic recording medium in which a plurality of magnetic films are provided on a support, the thickness of the upper magnetic film is 1.1 to 3 times the thickness of the lower magnetic film, particularly 1.2 to 2 Double. The thickness of the upper magnetic film is 600-2200Å, especially 800-1600
Å, the thickness of the lower magnetic film is 200-2000Å, especially 40
0 to 1200Å, the total thickness is 800 to 4200Å,
Particularly, it is 1200 to 2400Å. The thickness of the upper magnetic film is 1/6 to 1/4 of the recording wavelength. Bs of the upper magnetic film is 5000 to 10000G. Bs of the lower magnetic film is 4
000-8000G. Bs in the entire magnetic film in which the lower magnetic film and the upper magnetic film are laminated is 4800 to 80.
00G and Hc is 1000 to 1800 Oe.
The magnetic recording medium of the present invention is used for applications where the main recorded video frequency is 15 MHz or higher.

A more detailed description will be given below. FIG. 1 is a schematic diagram of a magnetic recording medium according to the present invention. The magnetic recording medium support 1 of the present invention may be magnetic or non-magnetic. Typical examples include polyethylene terephthalate (PET), polybutylene terephthalate, polyethylene naphthalate, polycyclohexylene dimethylene terephthalate, polyesters such as polyethylene bisphenoxycarboxylate, polyolefins such as polyethylene and polypropylene, cellulose acetate butyrate, Cellulose derivatives such as cellulose acetate propionate, polyvinyl chloride,
Examples thereof include vinyl resins such as polyvinylidene chloride and non-magnetic plastic materials such as polyamide and polycarbonate. Of course, it is not limited to these. Also, various kinds of processing may be performed. For example, corona discharge,
Alternatively, surface treatment is performed by other appropriate means.
Further, polyester, polyurethane or oligomer for improving the adhesiveness may be applied.

A plurality of metal thin film type magnetic films, especially two layers, are provided on the support 1 by a PVD (Physical Vapor Deposition) method such as oblique deposition. Examples of the material forming the metal magnetic films 2 ₁ and 2 ₂ include Fe and C
o, Ni, and other metals, Co-Ni alloy, Co-Pt
Alloy, Co-Ni-Pt alloy, Fe-Co alloy, Fe-
Ni alloy, Fe-Co-Ni alloy, Fe-Co-B alloy, Co-Ni-Fe-B alloy, Co-Cr alloy, etc. are used. As the metal magnetic film, a nitride film (for example, Fe—N, Fe—N—O) or a carbonized film (for example, Fe—C—O) of the above materials can also be used.

The average thickness of the metal magnetic films 2 ₁ and 2 ₂ is as described above. That is, the average thickness of a ₁ in the lower magnetic layer 2 ₁ 200～2000A average thickness a ₂ of the upper magnetic film 2 ₂ 600～2200A, a ₁ + a ₂ is from 800 to 42
By setting 00Å, a ₂ > a ₁ , the lower magnetic film 2 ₁
Whereas the Bs is 4000～8000G, and Bs of the upper magnetic film 2 ₂ can be increased and 5000～10000G, whereby improved S / N, also the output of the high frequency band is up, even error The rate is reduced.

A protective film 3 is provided on the uppermost magnetic film provided by oblique vapor deposition or the like. As a material for forming the protective film 3, for example, Al, Si, Ti, Cr, Zr, N
Oxides, nitrides and carbides of metals such as b, Mo, Ta and W, diamond-like carbon and boron nitride are used. CVD (chemical vapor deposition) or PVD is used as a film forming method. The thickness of the protective film is 10 to 500Å, especially 30 to 200Å.

A lubricant film 4 is provided on the protective film 3.
You. For example, the fluorine lubricant film is dipped or
It is provided with a thickness of about 20 to 70Å by means such as spraying.
You. As the lubricant, for example,-(C (R) F-CF_Two-O)_p-(However
And R is F, CF_Three, CH_ThreeSuch as HOOC-CF)_Two
(O-C_TwoF_Four)_p(OCF_Two)_q -OCF_Two-COOH, F- (CF_TwoCF_TwoCF_TwoO)_n-C
F_TwoCF_TwoCarboxyl group-modified perfluoro such as COOH
Oropolyether, HOCH _Two-CF_Two(O-C_TwoF_Four)_p(OCF_Two)_q -OC
F_Two-CH_TwoOH, HO- (C_TwoH_Four-O)_m-CH_Two-(O-C_TwoF_Four)_p(OCF _Two)_q -
OCH_Two-(OCH_TwoCH_Two)_n-OH, F- (CF_TwoCF_TwoCF_TwoO)_n-CF_TwoCF_TwoCH_TwoOH
Alcohol-modified perfluoropolyate
Or an alkyl group or the like on one or a part of the molecule.
Saturated hydrocarbon group, or unsaturated hydrocarbon group, or
Examples include aromatic hydrocarbon groups and those with other functional groups.
You can Specifically, FOMBL of Montecatini
IN Z DIAC, FOMBLIN Z DOL,
Demnum SA of Ikin Industries Co., Ltd. and the like.

A back coat film 5 is provided on the other surface side of the support 1. When the back coat film is formed by coating, carbon black having a particle size of 10 to 100 nm is dispersed in a binder resin such as a PVC-based resin or a urethane-based resin, and is dried by a gravure method, a reverse method, a die coating method, or the like. Is applied so as to be 0.4 to 1 μm. When the back coat film is formed by PVD means such as vapor deposition, Al
Place a metallic material such as a Cu alloy in the evaporation source and deposit evaporated metal particles to a thickness of 0.05-1 μm. Then, a top coat layer may be provided on such a back coat film in order to improve running properties and durability.

[0015]

Example 1 A lower magnetic film (Co film) 2 ₁ having an average thickness a ₁ = 800 Å was provided on a PET film 1 having a thickness of 6.3 μm. The lower magnetic layer 2 ₁ is obtained by depositing using a conventional oblique deposition apparatus. The conditions of the oblique deposition are as follows: the output of the electron gun for vaporizing the Co metal is 20 kw, the traveling speed of the PET film 1 is 20 m / min, and the oxygen gas supply amount is 6
It is 00 SCCM. Then, the Hc ₁ of the lower magnetic film 2 ₁ examined at the stage of only the lower magnetic film 2 ₁ before the upper magnetic film 2 ₂ to be described later was 1600 Oe, and the Bs ₁ was 4800.
G.

[0016] After the lower magnetic film 2 ₁ is deposited, without issuing from the vacuum vessel, followed average on the lower magnetic film 2 ₁ a thickness of a
₂ = 1200Å The upper magnetic film 2 ₂ was provided. The upper magnetic film (Co film) 2 ₂ is also formed by using a normal oblique vapor deposition apparatus. The conditions of the oblique deposition are as follows: the output of the electron gun for evaporating the Co metal is 30 kw, the traveling speed of the PET film 1 is 20 m / min, and the oxygen gas supply amount is 650 S.
CCM. The Hc ₂ of the upper magnetic film 2 _{2 formed under the} same conditions without the lower magnetic film 2 ₁ is 1230O.
e and Bs ₂ were 6900G.

After the lower magnetic film 2 ₁ and the upper magnetic film 2 ₂ were provided, Hc was 1400 Oe and Bs was 6100G. The protective film 3 is made of benzene as a raw material and is made of ECR-CV.
It is a 100Å thick diamond-like carbon film formed by D. Lubricant (FOMBLIN AM200
The film 4 has a thickness of 20 Å, and the back coat film 5 has a thickness of 0.5 μm.

[0018]

[Embodiment 2] In Embodiment 1, a ₁ = 600Å, Hc
₁ = 1700 Oe, Bs ₁ = 5000 G Lower magnetic film 2
₁ , a ₂ = 750Å, Hc ₂ = 1420 Oe, Bs ₂ =
And the upper magnetic film 2 ₂ 6200G, Hc = 1530O
A magnetic tape for Hi8VTR was obtained in the same manner as in Example 1 except that e and Bs were set to 5550G.

[0019]

Third Embodiment In the first embodiment, a ₁ = 500Å, Hc
₁ = 1650 Oe, Bs ₁ = 4850 G Lower magnetic film 2
₁ , a ₂ = 1000Å, Hc ₂ = 1350 Oe, Bs ₂
= 6700G as the upper magnetic film 2 ₂ and Hc = 1490O
A magnetic tape for Hi8VTR was obtained in the same manner as in Example 1 except that e and Bs were set to 5700G.

[0020]

Comparative Example 1 In Example 1, a ₁ = 1000Å, H
c ₁ = 1400 Oe, Bs ₁ = 6500 G lower magnetic film 2 ₁ , a ₂ = 800 Å, Hc ₂ = 1550 Oe, Bs ₂
= 5000 G as the upper magnetic film 2 ₂ and Hc = 1450 O
A magnetic tape for Hi8VTR was obtained in the same manner as in Example 1 except that e and Bs were set to 5800G.

[0021]

Comparative Example 2 In Example 1, a ₁ = 1100Å, H
c ₁ = 1500 Oe, Bs ₁ = 5000 G lower magnetic film 2 ₁ , a ₂ = 1100 Å, Hc ₂ = 1500 Oe, Bs
₂ = 5000 G, the upper magnetic film 2 ₂ , Hc = 1520
A magnetic tape for Hi8VTR was obtained in the same manner as in Example 1 except that Oe and Bs were set to 5000 G.

[0022]

[Characteristics] The output, S / N and error rate of the 8 mm VTR magnetic tape obtained in each of the above examples were examined. The results are shown in Table-1. Table-1 Output (dB) S / N (dB) Error rate 1MHz 7MHz 15MHz 20MHz Example 1 +0.1 +0.8 +1.5 +1.3 +1.9 6.3 × 10 ^-6 Example 2 0 +0.3 +1.7 +1.8 +1.4 7.1 × 10 ^-6 Example 3 0 +0.2 +1.7 +1.6 +1.6 5.9 × 10 ^-6 Comparative Example 1 0 0 0 0 0 0 5.6 × 10 ^-5 Comparative Example 2 -0.3 -0.2 -0.4 -0.4 -0.4 5.1 × 10 ^{-5 From} these results, the one according to the present invention has an improved S / N and an improved output in the high range,
Furthermore, the error rate is being reduced.

[0023]

The S / N ratio is improved, the output in the high range is also improved, and the error rate is reduced.

[Brief description of drawings]

FIG. 1 is a schematic diagram of a magnetic recording medium of the present invention.

[Explanation of symbols]

1 Support 2 ₁ Lower magnetic film 2 ₂ Upper magnetic film 3 Protective film

 ─────────────────────────────────────────────────── ─── Continuation of front page (72) Inventor Katsumi Endo 2606 Akabane, Kaiga-cho, Haga-gun, Tochigi Prefecture Kao Co., Ltd.

Claims (8)

[Claims] 1. A magnetic recording medium comprising a support and a plurality of magnetic films provided thereon, wherein the upper magnetic film is thicker than the lower magnetic film. 2. The magnetic recording medium according to claim 1, wherein the thickness of the upper magnetic film is 1.1 to 3 times the thickness of the lower magnetic film. 3. The thickness of the upper magnetic film is 600 to 2200.
3. The magnetic recording medium according to claim 1, wherein the lower magnetic film has a thickness of 200 to 2000, and the total thickness is 800 to 4200. 4. The thickness of the upper magnetic film is about 1/6 of the recording wavelength.
It is 1/4, The magnetic recording medium in any one of Claim 1- Claim 3 characterized by the above-mentioned. 5. The Bs of the upper magnetic film is 5000 to 1000.
It is 0G, The magnetic recording medium in any one of Claims 1-4. 6. The Bs of the lower magnetic film is 4000 to 8000.
4. The magnetic recording medium according to claim 1, wherein the magnetic recording medium is G. 7. The magnetic recording medium according to claim 1, wherein a protective film and / or a lubricating film is provided on the magnetic film. 8. The magnetic recording medium according to claim 1, wherein the main recording frequency is 15 MHz or higher.