JP2646739B2 - Magnetic recording / reproducing method - Google Patents

Description

Description: BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a magnetic recording / reproducing method having excellent short-wavelength recording performance.

2. Description of the Related Art At present, the magnetic recording / reproducing method having the highest recording density involves sliding a magnetic recording layer and a ring-type magnetic head at a high speed to record / reproduce a high frequency. However, it is well known that the technical progress of the head and tape largely depends on the elemental technology. The magnetic material used for the tape is Co-γ-Fe ₂ from γ-Fe ₂ O _3.
Due to generational changes of O ₃ , metal powder, Co-Ni-O obliquely deposited film, track width is 10 μm, recording wavelength is 0.5 μm at shortest.
m is approaching. On the other hand, from where we teach magnetic recording,
Higher density is achieved by narrowing the track width and shortening the recording wavelength, but shortening the recording wavelength requires increasing the coercive force of the tape, To cope with this, the transition from ferrite heads, which have excellent reliability and performance to alloys, is being forced (for example, "Magnetic Recording" (Magnetic Recording vol.III, C
hapter 2. See McGraw-Hill Book Company 1988)).

FIG. 8 is an enlarged sectional view of a main part of a tape head which is important as an element of magnetic recording and reproduction. In FIG. 8, 1 is a ring-type magnetic head, 7 is a magnetic tape, and both perform relative motion, and operate so as to convert an electric signal in recording and reproduction. In the magnetic head, 2 is an alloy magnetic material having a large saturation magnetic flux density, such as an Fe-based sendust alloy or a Co-based amorphous alloy, 3 is a ferrite, 4 is a spacer glass for determining a gap interval, and 5 is a bonding glass. , 6 are coils. Numeral 8 denotes a magnetic recording layer, and a coating type magnetic layer in which alloy magnetic powder is dispersed and an oblique deposition type magnetic layer such as Co-Ni-O are beginning to be used for short wavelength recording.
No. 9 has variously devised the constitution of the deep in a polymer film typified by a polyethylene terephthalate film as required. Especially Co-Ni-O
A magnetic tape having a magnetic recording layer made of a thin film or a ferromagnetic metal thin film such as a Cc-Cr perpendicular magnetization film has been devised with a focus on surface lubrication because of severe friction and wear [Japanese Patent Laid-Open No. 61-142525, See JP-A-61-151837, JP-A-61-220116, JP-A-64-8506, etc.] The pursuit of high-density recording performance has been continued.

Problems to be Solved by the Invention However, when a ferromagnetic metal thin film is used as a magnetic recording layer, so-called modulation noise, which is generally generated by recording a signal rather than DC erasing or noise or AC erasing noise, is large. Is considered to be the occurrence of so-called zigzag domains in the magnetization transition region.To improve this, the surface is made smoother, the coercive force is increased, and the fine particles forming the thin film are formed. It is devised to weaken the ferromagnetic coupling between the crystals (for example, "IEE Transactions on Magnetics" IEEE TRANSACTIONS ON MAGNEETICS Vo
l.MAG-24. No. 6, pp 2979 to 2981 (1988 No. V)))
However, as the recording wavelength becomes shorter,
It is difficult to secure C / N and improvement is desired.

The present invention has been made in view of the above circumstances, and 0.5 μm
The purpose is to secure C / N in a magnetic recording system using a wavelength range of m or less.

Means for Solving the Problems In order to solve the above-mentioned problems, the present invention provides a composite head using an alloy thin film having a gap length gl of 0.25 μm or less and a fine protrusion having a spread of the protrusion in the range of 1.3 gl to 0.6 gl. The recording / reproduction is performed using the ferromagnetic metal thin film.

The magnetic recording / reproducing method of the present invention has the above-described configuration,
While maintaining the durability improvement effect of the ferromagnetic metal thin film with the protrusion shape, the magnetic non-uniformity becomes difficult for the head to detect as noise due to loss similar to gap loss,
C / N will be improved.

Embodiments Hereinafter, embodiments of the present invention will be described in detail with reference to the drawings. FIG. 1 is an enlarged sectional view of a magnetic recording medium used in an embodiment of the present invention.

In FIG. 1, reference numeral 10 denotes a polymer film of polyethylene terephthalate, polyethylene naphthalate, polyphenylene sulfide, polyether ether ketone, etc., and reference numeral 11 denotes catalyst residue particles or a filler such as SiO ₂ , TiO ₂ , CaCO ₃ which is positively added. Depending on the shape, size, amount, stretching conditions, etc. of the filler used, either a film having loose projections formed on the surface of the film 10 or an almost flat surface is used. At about 10 ³ pieces / mm ² , those with a height of up to about 200 mm hardly cause a decrease in C / N even in short wavelength recording.

However, it is preferable that a film having no added particles has a uniform C / N ratio even when combined with various heads.
Should be adopted in terms of security. 12 is Co, Co-Ni, Co-
Ferromagnetic metal thin film of Cr, Co-Ti, Co-Mo, Co-W, Co-O, Co-Ni-O, etc., formed by electron beam evaporation, sputtering, etc. May be any.
Reference numeral 13 denotes fine particles which serve as nuclei of protrusions for securing durability by arranging minute protrusions on a ferromagnetic metal thin film.
As for the material, an optimum system must be selected from the recording / reproducing performance and durability to be obtained by the magnetic recording medium.

More importantly, the relation with the gap length of the recording / reproducing head is optimized as described later.

Generally, the higher the density in a certain range, the better the durability, but the noise tends to increase and the C / N tends to decrease,
According to the present invention, both durability and C / N can be made satisfactory. The selection range of the fine particles is 0.5 to 50 in the form of particles such as oxides and organic substances, oval spheres, and the like.
In the range of ケ (μm) ² , the finally required parameter is the extension of the protrusion of the ferromagnetic metal thin film. The spread is determined by the combination of the conditions for forming the ferromagnetic metal thin film 14 and the conditions for fine particles. The ferromagnetic metal thin film 14 may be selected from the same group as the ferromagnetic metal thin film 12. Reference numeral 15 denotes a protective lubrication layer, which is a combination of a plasma polymerized film, a carbon film, a fat film, a perfluoropolyether, a perfluorocarboxylic acid, etc., which minimizes spacing between the head and the operating environment. It is devised so as not to be limited. FIG. 2 is an enlarged sectional view of a main part between the head and the magnetic tape.

In FIG. 2, the protrusion 16 formed on the ferromagnetic metal thin film 14 is shown.
When viewed from the magnetic head between the A ₁ and A ₂ portions (indicated by arrows) rising from the flat portion of the ferromagnetic metal thin film 14 having the spread D ₁ , the magnetic poles opposed by the spacer 17 (length gl) 18
In the gap (in the present invention, an alloy thin film is used), the change in magnetic flux cannot be widened (the same as the well-known gap loss), and the noise cause of the protrusion can be effectively removed. The effect is that experimentally, the geometry is ideally determined and has a distribution, so that D ₁ is
The minimum noise can be set between 0.6 gl and 1.3 gl.

The gap length means an effective gap length, and does not indicate an optical or physical gap length.

Hereinafter, more specific examples will be described in comparison with comparative examples.

[Example-1] A polyethylene terephthalate film having a thickness of 10.2 µm and containing no added particles, on an ultra-smooth surface having an average roughness of 20 mm and a maximum roughness of 40 mm, along a cylindrical can having a diameter of 1 mm,
In oxygen of 9 × 10 ^{-6 to} 9 × 10 ^-5 (Torr), the minimum incident angle is 30
(Degree)-49 (degree), average deposition rate 800 (800 / sec)-3300
(Å / sec), a first ferromagnetic metal thin film is formed by e-beam evaporation of Co in the above range at a can temperature of −50 ° C. to + 50 ° C., and SiO ₂ fine particles having a diameter of 10 ° are formed thereon. Axis 300
ポ リ, 100 ス ル polysulfone elliptical spheres with short axis
Electron beam deposition of CoNi (Co80wt%) within the same range as the deposition conditions of the layer to form a ferromagnetic metal thin film with various projections, and furthermore, commercially available Montefluos as pearl fluoropolyether Humblin Z
-25 was applied at 0.3 (mg / m ² ), a 0.5 μm backcoat layer was provided, and an 8 mm wide magnetic tape was formed. Metal-in-gap type (MIG type) amorphous heads and laminated alloy type amorphous heads with different gap lengths (gl) using each tape [Journal of the Japan Society of Applied Magnetics Vol12, No.2, pp97]
-106 (1988)], and modified the 8 mm video, and changed the carrier frequency to compare C / N. The range of the tape composition conditions is as follows: the thickness of the first layer is 350 to 1000 mm, the thickness of the second layer is 400 to 1300 mm, and the spreading in the head moving direction D ₁
Is 780Å to 3300Å and the density is 0.3 / (μm) ^{2 to} 25 /
(Μm) ² . Using these magnetic tapes,
Among the MIG type heads having gap lengths of 0.25 μm, 0.2 μm, 0.15 μm, and 0.1 μm, [Fe4.5 wt%, Co7
0.5wt%, Zr10wt%, B15wt%] [Al5.4, Si9.6, Fe85wt%]
A composite type head with ferrite using a sendust sputtered film as an alloy film was prepared, and a laminated alloy type head of a 10 μm track in which five similar materials were laminated was prepared, and λ _C = 0.36 μm was recorded. FIG. 3 shows the result of comparing the modulation noise levels.

From this figure, it can be seen that when λ _C = 0.36 μm, the favorable condition is that the spread in the head moving direction is from 0.6 gl to 1.4 gl.

Similarly, the noise level when λ _C = 0.3 μm is recorded by the above-mentioned head group is as shown in FIG. 4. In this range, the optimum condition is narrower from 0.6 gl to 1.3 gl than in FIG. Recognize. If λ _C = 0.3 μm or less, the output is insufficient, and the practical range of the invention is 0.3 μm or less, which is difficult to realize at present. It can be considered that the condition is optimal in the range of gl.

It is apparent from the results in FIG. 5 that the ferromagnetic thin film should not be formed into two layers. That is, FIG. 5 shows oblique deposition of Co-Cr (Co: 80 wt%), and TiO ₂ fine particles having a diameter of 130 ° on a smooth polyimide film (10 μm).
4 pieces / (μm) ² sets and sets the can temperature to 200 ° C.
^In a vacuum of ^-6 (Torr) with a minimum incident angle of 59 degrees, a Co-Cr film with a projection spread of 1600 ° is provided with 0.11 μm, and Fomblin Z-25 is provided with 0.26 (mg / m ² ). Λ obtained by
_C = 0.34 µm, λ _C = 0.4 µm noise level,
It is estimated that the preferable range of the single-layer film is in the range of 0.6 gl to 1.3 gl.

Example 2 Polyamideimide film having a thickness of 12 μm [average roughness 30
{Maximum roughness 50 °]], 1 to 16 polysulfone spheres of 300 to 450 ° are arranged at ² to 16 pieces / (μm), and they are placed along a cylindrical can (diameter of 155 ° C) with a diameter of 50cm. : 80wt%)
Target, Ar pressure 0.01 to 0.07 (Torr), RF condition 13.
Set the conditions in the range of 56 (MHz) and 0.65 to 3 (KW) and set D ₁
Of Co-Cr perpendicular magnetization films of 0.1 μm and 0.15 μm different from each other, and 0.3 (mg /
m ² ) was applied, a 0.4 μm back coat layer was provided, and an 8 mm wide tape was prepared.

These tapes have a gl of 0.25 μm, 0.22 μm, 0.17 μm, 0.12 μm.
FIG. 6 and FIG. 7 show the modulation noise level as a result of recording and reproduction with a μm, 0.08 μm laminated alloy type head and a MIG type head.

In order to ensure durability, the height of the protrusion is also required. In view of the output, the embodiment is configured in the range of 150 to 250 mm. In any case, the medium described above has a steal characteristic at 23 ° C. and 70% RH of 60 minutes or more. Therefore, it is possible to provide a magnetic recording medium suitable for achieving higher density with a practical level configuration. It is easily conceivable that the present invention is not limited to the tape alone.

Even if the shape of the projections is not limited to one type but is a combination with a mountain shape or the like, those having a high density of projections satisfying the requirements of the present invention can provide a preferable C / N. still,
Spread in the head movement direction is large and height is 25
The ones up to 0 ° have the disadvantage that the running performance becomes unstable and the noise increases, and the fluctuation range is large depending on the design conditions of the recording / reproducing apparatus.

As described above, according to the present invention, there is an excellent effect that high-density magnetic recording / reproducing can be performed with a narrow gap head of 0.25 μm or less in a range where durability is ensured and modulation noise is suppressed.

[Brief description of the drawings]

FIG. 1 is an enlarged sectional view of a magnetic recording medium used in an embodiment of the present invention, FIG. 2 is an enlarged sectional view of a main part of a head medium, and FIGS. 3, 4, 5, and 6 are shown. 7, FIG. 7 is a characteristic diagram of the relative noise level, and FIG. 8 is an enlarged sectional view of a main part of the magnetic tape head. 10 …… Polymer film, 12,14 …… Ferromagnetic metal thin film, 13
... fine particles, 16 ... ferromagnetic metal thin film projections, 18 ... magnetic poles.

Claims (1)

(57) [Claims] 1. A recording / reproducing method using a composite head using an alloy thin film having a gap length gl of 0.25 μm or less and a ferromagnetic metal thin film having fine projections having a projection spread of 0.6 gl to 1.3 gl. Characteristic magnetic recording / reproducing method.