JP2001101648A - Floppy disk and magnetic recording system using it - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a floppy disk and a magnetic recording system with high recording density. SOLUTION: The floppy disk is constituted such that a ferromagnetic metallic thin film, a protective film and a lubricating film are laminated on both sides of a flexible non-magnetic support and that minute projections having a diameter of 30-200 nm and a height of 10-70 nm are provided on the surface at a density of 1-100 pieces per one square μm; and the magnetic recording system is such that both front and rear sides of the floppy disk are held between magnetic head arms provided with a slider each of which has an MR head at the tip end and that, while the floppy disk is rotated at the number of revolution of 2,000 rpm or higher, a slider is made to run with the floppy disk for recording and reproduction.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

The present invention relates to a floppy disk medium having a high areal recording density and a magnetic recording system using the same as a recording medium.

[0002]

2. Description of the Related Art In a magnetic recording medium such as a magnetic tape or a hard disk, a magnetic recording medium such as a vapor-deposited tape or a thin-film hard disk having a recording layer of a ferromagnetic metal thin film produced by a vacuum film forming method such as a sputtering method or a vapor-deposition method. The medium has been put to practical use. In such a magnetic recording medium, high magnetic energy can be easily obtained, and smooth surface properties can be easily achieved by smoothing the surface of the non-magnetic substrate. Because of its characteristics, it is suitable for high-density recording materials. In particular, the sputtering method can further increase the magnetic energy than the vapor deposition method, and is therefore used for a medium such as a hard disk, which requires a high surface recording density.

On the other hand, floppy disk type magnetic recording media have been widely used mainly in the 2HD class because of their excellent impact resistance and low cost as compared with hard disks. Zi using coating technology
High-density magnetic recording media such as p (Iomega) are also used. In such a magnetic recording medium, 3
By performing recording and reproduction at a high speed of about 000 rpm, a high-speed transfer speed close to that of a hard disk is achieved. However, the recording density is still less than 1/20 that of a hard disk. This is because a floppy disk-type magnetic recording medium in which the magnetic layer is formed by a sputtering method, such as a hard disk, has not yet been put to practical use.Furthermore, a floppy disk consists of a magnetoresistive element that is effective for improving the recording density. A major factor is that it is technically difficult to use an MR head.

There are various reasons why it is difficult to use an MR head, and the biggest reason is the problem of so-called thermal asperity generated when the disk and the MR head come into contact with each other. Thermal asperity is a phenomenon in which the temperature of the MR element changes due to the influence of frictional heat or the like generated when the disk and the head come into contact with each other, causing a change in the output of the reproducing head unrelated to the magnetic signal. The output of this thermal asperity can reach several times the magnetic signal reproduction output. In such a case, saturation of the head amplifier is caused, signal cannot be read, and a reading error occurs.

[0005] In a hard disk using an MR head, when the rotational speed of the disk is increased, the head flies due to the effect of the floating force acting on the head, and the head is used in a state in which the hard disk does not come into contact with the head. Has not been a problem, but recently, the flying height of the head has become extremely low, and the head collides with the disk, which has become a problem. On the other hand, in the case of a floppy disk, if the number of rotations of the disk is increased in the same manner as a hard disk, the disk cannot be stably levitated due to the large vibration (runout) of the disk. The thermal asperity is a very serious problem because of the frequent contact.

[0006]

SUMMARY OF THE INVENTION Accordingly, an object of the present invention is to provide a magnetic recording system in which the areal recording density is greatly improved by mounting an MR head as compared with the prior art, and a floppy disk used therefor. Therefore, the generation of thermal asperity is suppressed, and sufficient practical reliability is achieved.

[0007]

An object of the present invention is to provide a floppy disk medium having a structure in which a ferromagnetic metal thin film, a protective film, and a lubricating film are laminated on both surfaces of a flexible non-magnetic support. Height 10nm ~ 7
This is achieved by a floppy disk having 0 nm microprojections at a density of 1 to 100 per square μm. Further, both sides of the floppy disk medium are sandwiched between a pair of assemblies each having a slider having an MR head attached to the tip of a leaf spring.
This is achieved by a magnetic recording method in which recording and reproduction are performed by causing a medium and a slider to contact and run while rotating at a rotation speed of pm or more.

[0008]

DESCRIPTION OF THE PREFERRED EMBODIMENTS The present invention enables stable recording and reproduction in recording and reading information on a magnetic recording medium using an MR head by making the surface of a floppy disk a specific surface texture. Things.

The present invention will be described below with reference to the drawings.
FIG. 1 is a view for explaining a floppy disk drive used in the magnetic recording system of the present invention, and is a perspective view with a part cut away. The floppy disk drive 1 used in the magnetic recording system of the present invention has an insertion port 4 for a disk cartridge 3 in which a floppy disk 2 made of a magnetic disk is incorporated, and the disk cartridge 3 is mounted through the insertion port 4. As a result, the floppy disk 2 in the disk cartridge 3 is rotated by connecting the center core 5 to a rotating mechanism such as a spindle motor. Further, a pair of upper and lower head arms 8 having a head slider 7 provided with a head through a head window 6 provided in the disk cartridge 3 at the tip.
Is inserted by the head moving mechanism 9, and a pair of upper and lower heads are symmetrically pressed against the surface of the floppy disk to read and write a recording signal of a predetermined track.

FIG. 2 is a sectional view for explaining a floppy disk drive. The floppy disk drive 1 used in the magnetic recording system according to the present invention is characterized in that it is rotated at a high speed of 2000 rpm or more by a spindle motor 10 coupled to the center core 5. For this purpose, a small and lightweight magnetic head 12 such as an MR head made of a magnetoresistive element is attached to the head slider 7. Head arm 8 with head slider 7 attached
Is mounted on a head moving mechanism 9 driven by a head positioning signal via a leaf spring 12 for load adjustment, and a high speed of 2000 rpm or more in a state where the magnetic head 11 is in contact with the upper and lower symmetric positions of the floppy disk. Rotated by

FIG. 3 is a diagram illustrating a head and a head slider. The head slider 7 attached to the head arm 8 is provided with a magnetic head 11 such as an MR head. An MR head having a structure similar to that used in a hard disk can be used. For example, in addition to a general MR head, a G-MR head, a dual stripe type MR head, or the like can be used. Above all, a dual stripe type MR head is preferable because thermal asperity can be reduced by the structure of the head.

The head slider 7 of the floppy disk drive used in the magnetic recording system of the present invention may have the same structure as that used for a hard disk. For example, a taper flat type positive pressure slider, one with a slot in this rail, a tri-pad slider, a negative pressure slider, etc. can be used, and among them, a taper flat type positive pressure slider or one with a slot in this rail is a floppy A combination with a disk is preferable because it is less susceptible to runout of the disk. The head slider 7 is made of a ceramic material such as Al ₂ O ₃ —TiC, for example, and has a hard amorphous carbon protective film such as diamond-like carbon on its surface to prevent abrasion. This diamond-like carbon can be produced in the same manner as the disk protective film, but it is preferable to set the hardness higher than that of the disk protective film in consideration of the balance between the head and the disk wear.

The head arm or the like to which the head slider is attached is suitably one having a proper weight of about 1 to 6 gf by a leaf spring or the like. If the weight is lighter than this, the head is more likely to jump from the disk, causing a dropout of the reproduced signal. Conversely, if the load is heavier than this, the disk is likely to be worn and the life of the disk is shortened.

As the moving device of the head arm, both an in-line type and a trans-perspective type can be used, but when the disk diameter is relatively large such as 3.5 inches, the transverse type is preferable. This is because the head window of the shell can be reduced by using the transverse type head assembly, and the disk runout can be reduced.

Next, a floppy disk used in the magnetic recording system of the present invention will be described. FIG. 4 is a diagram illustrating a cross section of a floppy disk used in the magnetic recording system of the present invention. The floppy disk 2 shown in FIG. 4A has an undercoat film 22 and an undercoat film 2 on both sides of a flexible support 21.
3. A ferromagnetic metal thin film 24, a protective film 25, and a lubricating film 26 are laminated. The surface has a diameter of 30 nm to 200 nm formed by the fine particles 27 and a height of 10 n.
1 to 100 per square μm
Have a density of. More preferably, the diameter is 50 nm to 150 nm, the height is 20 nm to 50 nm, and the density is 1 μm square.
Range from 3 to 30 pieces. In the floppy disk 4 shown in FIG. 4B, a ferromagnetic metal thin film 24 is provided directly on a flexible support without providing an underlayer, and a protective film 25 and a lubricating film 26 are formed thereon. Things.

If the height of the minute projections provided on the surface of the floppy disk is too high, the spacing loss between the recording / reproducing head and the medium increases, thereby deteriorating the electromagnetic conversion characteristics. It becomes easier to cause head jump and thermal asperity. If the density of the fine projections is too low, the effect of improving the sliding characteristics is reduced, and if it is too high, the number of high projections increases due to the increase in aggregated particles, and the electromagnetic conversion characteristics deteriorate. The size and height of the projection can be measured by a surface analyzer such as a scanning electron microscope or an atomic force microscope. The projections are formed by applying fine particles to any one of a support, an undercoat film, a magnetic film, and a protective film as described later.

Further, it is preferable that the surface projections have a uniform height. If the heights of the projections are widely distributed or locally high projections are present, only the high components of the projections come into contact with each other, which leads to deterioration of life due to local wear and generation of thermal asperity. Such a height distribution can be examined using an atomic force microscope. In other words, the area where a sufficient number of protrusions exist to know the distribution is measured with an atomic force microscope, and when a threshold surface with a specific height from the average reference surface is provided, the number of protrusions existing there is calculated. This is a method of measuring and measuring the distribution of the protrusion height. In the measurement of the distribution of protrusions, observation by a scanning electron microscope is also used in order to detect protrusions that are not actively provided protrusions, such as particles of a magnetic film, in low components of 10 nm or less. The density of protrusions (D) provided positively in a scanning electron microscope is measured, and the protrusion height corresponding to the protrusion density (D) is obtained from the distribution of protrusions of an atomic force microscope. Can be measured. It is preferable that most of the protrusions exist in a range from the HL to a height of 30 nm. In other words, 30 nm more than HL
The protrusion density (D30) on the high plane (HL + 30 nm) is
Preferably D30 / D <0.10, more preferably D
30 / D <0.01.

In order to achieve stable running as a floppy disk drive, the run-out of the disk must be 100 μm or less, preferably 50 μm or less when the head is not in contact with the floppy disk surface. This runout is mainly caused by static deformation of the floppy disk. Therefore, a floppy disk having a small curl is required, and the static curl amount is preferably 1 mm or less.

The flexible non-magnetic support 21 is made of polyethylene terephthalate, polyethylene naphthalate, polyimide film, polyamide film, etc., having a thickness of 20 μm.
To 100 μm films can be used. If the thickness is too small, the magnetic film or the protective film will affect the static curl and deformation. If the thickness is too large, the impact when the head and the disk come into contact cannot be reduced.

When the non-magnetic support is close to the mirror surface and is smooth, fine particles 27 for forming surface protrusions may be directly provided on the non-magnetic support. However, when the non-magnetic support is not sufficiently smooth, It is preferable to first form an undercoat film 22 for the purpose of smoothing on the surface of the nonmagnetic support. As a material of the undercoat film, it is preferable to use a thermosetting imide or a thermosetting silicone resin having a high smoothing effect. The thickness of the undercoat film is preferably 0.1 to 3 μm. The thermosetting resin can be produced, for example, by a method of applying a silane coupling agent having an epoxy group or a monomer containing a thermosetting imide, followed by thermosetting.

The thus obtained smooth nonmagnetic support 21, undercoat film 22, magnetic film 23, protective film 24
On one of the above, a small projection with a uniform height is provided.
Above all, on the non-magnetic support 21 or on the undercoat film 22 is preferable. As a method for producing such a fine projection structure, a method of applying spherical silica particles dispersed in a solvent or a method of forming an organic substance projection by applying an emulsion is used. Although a method and the like can be used, silica particles are preferable in order to achieve a uniform particle size. It is also possible to use a binder to fix the projection to the surface. It is particularly preferable to use a thermosetting imide or a thermosetting silicone resin as such a material. The microprojections have a diameter of 30 on the disk surface.
The thickness ranges from 1 nm to 200 nm, the height ranges from 15 nm to 70 nm, and the density ranges from 1 to 100 per square μm. To form such protrusions, the thickness of the magnetic film or the protective film formed thereon must be reduced. It is necessary to determine the particle size taking into account. When a general underlayer, a magnetic film, and a protective film are formed, the number of particles is about 5 nm to 50 nm in spherical particles, and the density is 1 to 100 per 1 μm 2.

As the ferromagnetic metal thin film to be a magnetic layer in the magnetic recording medium of the present invention, a ferromagnetic metal thin film formed by vacuum film formation can be used, and a film formed by a sputtering method is particularly preferable. As the composition, an alloy mainly containing cobalt or a material obtained by adding a nonmagnetic substance such as silicon oxide to the alloy can be used. Specific examples of the alloy include Co-Cr, Co-Ni-Cr, Co-Cr-Ta, C
o-Cr-Pt, Co-Cr-Ta-Pt, Co-Cr
-Pt-Si, Co-Cr-Pt-B and the like can be used.
In particular, Co-Cr-Pt for improving the electromagnetic conversion characteristics,
Co-Cr-Pt-Ta is preferred. The thickness of the magnetic layer is 1
It is desirable to set it to 0 to 30 nm. Further, in this case, it is preferable to provide a base film for improving the magnetostatic characteristics of the magnetic film, and a known metal or alloy can be used as the composition of the base film. Specifically, Cr, V, Ti, T
a, W, Si and the like or alloys thereof can be used, and among them, Cr, Cr-Ti, and Cr-V are particularly preferable. The thickness of the underlayer is 5 nm to 50 nm, preferably 10 nm to 30 nm. Further, in order to control the crystal orientation of the underlayer, a seed layer may be used under the underlayer. Specifically, Ta, Mo, W, V, Zr, Cr, R
h, Hf, Nb, Mn, Ni, Al, Ru, Ti or an alloy thereof, particularly preferably Ta, Cr, Ti or an alloy thereof, and has a thickness of 15 to 60 nm. When a magnetic film is formed by a sputtering method, the film is preferably formed while the substrate is heated, and the temperature at that time is 20 ° C. to 300 ° C., and more preferably 15 ° C.
0 ° C to 250 ° C.

In the magnetic recording medium of the present invention, a protective film is formed on the ferromagnetic metal thin film in order to improve running durability and corrosion resistance. Examples of the protective film include oxides such as silica, alumina, titania, zirconia, cobalt oxide, and nickel oxide; nitrides such as titanium nitride, silicon nitride, and boron nitride; carbides such as silicon carbide, chromium carbide, and boron carbide; graphite; A protective film made of carbon such as fixed carbon can be used, but among them, a hard carbon film called diamond-like carbon (DLC), which hardly causes seizure during sliding and whose effect is stably maintained, is preferable. The diamond-like carbon film is an amorphous carbon film formed by a plasma CVD method, a sputtering method, etc.
This is a mixture of clusters formed by p2 bonds and clusters formed by sp3 bonds. The hardness of this film is 1 in Vickers hardness.
000 kg / mm ² or more, preferably 2000 kg / m
m ² or more. When measured by Raman spectroscopy of the diamond-like carbon film, a main peak called a G peak near 1540 cm ^-1 was 1390.
This can be confirmed by detecting a shoulder-like portion called a so-called D peak at cm ^-1 . These diamond-like carbon films are formed by sputtering or CV.
Although it can be manufactured by the D method, it can be manufactured by the CVD method because productivity, stability of quality, and good abrasion resistance can be ensured even with an ultrathin film having a thickness of 10 nm or less, and generation of pinholes can be reduced. Preferably
A negative bias voltage is applied to the substrate, especially when the plasma decomposes carbon-containing compounds such as alkane such as methane, ethane, propane, and butane, or alkenes such as ethylene and propylene, or alkyne such as acetylene. The method of accelerating and depositing is preferred.

Further, by introducing nitrogen gas into the reaction gas, nitrogen is contained in the protective film, whereby the coefficient of friction of the film can be reduced. When the thickness of the hard carbon protective film is large, the electromagnetic conversion characteristics are deteriorated and the adhesion to the magnetic layer is reduced, and when the thickness is small, the abrasion resistance is insufficient. Preferably 5 to 20
nm.

In the magnetic recording medium of the present invention, it is preferable to form a lubricating film on the protective film in order to improve running durability and corrosion resistance. As the lubricant, a hydrocarbon-based lubricant, a fluorine-based lubricant, an extreme pressure additive and the like can be used.

As the hydrocarbon lubricant, stearic acid,
Carboxylic acids such as oleic acid, esters such as butyl stearate, sulfonic acids such as octadecylsulfonic acid, phosphoric esters such as monooctadecyl phosphate, alcohols such as stearyl alcohol and oleyl alcohol, and carboxylic acids such as stearamide. Examples thereof include acid amides and amines such as stearylamine.

Examples of the fluorine-based lubricant include lubricants in which part or all of the alkyl groups of the hydrocarbon-based lubricant are substituted with a fluoroalkyl group or a perfluoropolyether group. Examples of the perfluoropolyether group include a perfluoromethylene oxide polymer, a perfluoroethylene oxide polymer, a perfluoro-n-propylene oxide polymer (CF ₂ CF ₂ CF ₂ O) _n , and a perfluoroisopropylene oxide polymer (CF ( CF ₃ ) CF
₂ O) _n or a copolymer thereof. Further, a compound having a phosphazene ring into which a fluorine or fluorinated alkyl group is introduced can be used as a lubricant because it is thermally and chemically stable.

Examples of extreme pressure additives include phosphoric esters such as trilauryl phosphate, phosphites such as trilauryl phosphite, thiophosphites and thiophosphoric esters such as trilauryl trithiophosphite, and the like. And sulfur-based extreme pressure agents such as dibenzyl sulfide.

The above lubricants are used alone or in combination of two or more. As a method of applying these lubricants on the protective film, a lubricant is dissolved in an organic solvent, a wire bar method,
It is good to apply by a gravure method, a spin coating method, a dip coating method, or the like, or to adhere by a vacuum evaporation method. The amount of the lubricant to be applied is preferably 1 to 30 mg / m ² ,
To 20 mg / m ² is particularly preferred.

Examples of the rust preventives usable in the present invention include nitrogen-containing heterocycles such as benzotriazole, benzimidazole, purine, pyrimidine and tetrazaindene ring compounds, and derivatives having an alkyl side chain introduced into the mother nucleus thereof.
Benzothiazole, 2-mercaptobenzothiazole,
Nitrogen- and sulfur-containing heterocycles such as thiouracil compounds and derivatives thereof.

When the medium of the present invention is used as a floppy disk, it is used with the disk incorporated in a shell. The shell is very important not only for preventing the attachment of dirt from the outside, but also for ensuring the rotational stability of the floppy disk.

It is preferable that a liner is provided inside the shell, on the surface which comes into contact with the disk. The liner has the effect of removing dust from the surface of the floppy disk for cleaning, and also has the function of preventing adhesion of the floppy disk to the shell of the present invention. As the liner, a non-woven fabric containing polyester fibers and acrylic fibers, mainly cellulose fibers such as rayon fibers, polynosic fibers, cupra fibers, and acetate fibers can be used. Also, the liner may contain a rust inhibitor, a lubricant, an antistatic agent, a fungicide, etc.
Since the floppy disk is applied to the surface of the floppy disk during use, the floppy disk can be used stably for a long period of time.

In the magnetic recording system of the present invention, the same material as the hard disk can be used for the magnetic film and the head. Therefore, by maintaining the same low spacing loss as the hard disk in the head / floppy disk / interface, it is possible to stably maintain the same. In spite of a floppy disk, a surface recording density comparable to that of a hard disk can be achieved. Also, at this time, despite the fact that the head and the floppy disk are considered to be in contact sliding, thermal asperity hardly occurs, so that even if an MR head is used, reading and writing errors are small.

There are several possible reasons for this. Even when the floppy disk is combined with the slider used for the floating type head, the slider does not float, and it is assumed that the slider makes stable contact sliding or pseudo contact sliding in which the slider and the disk frequently contact very little. . For example, when magnetic spacing is calculated using metal thin film media having different protective film thicknesses, the amount of spacing is approximately equal to the sum of the thickness of the protective film and the surface roughness, and the flying amount is approximately 0. In addition, when the surface of the floppy disk after running for a short time is observed with a time-of-flight secondary ion mass spectrometer (TOF-SIMS), traces of the solid lubricant spread over almost the entire circumference of the running track are observed. It can be inferred from what can be done. However, in order to obtain such stable sliding, it is necessary to reduce the runout of the disk during high-speed rotation and prevent the head from jumping.

It is also considered that the contact force between the floppy disk and the head is extremely small as compared with the hard disk, despite the fact that the floppy disk and the head are in sliding contact with each other. In the case of a floppy disk, even if the head and the floppy disk come into contact, not only the head but also the floppy disk will be deformed,
It is considered that the impact of the contact can be reduced.

Further, the floppy disk of the present invention differs from the conventional coating type floppy disk in that the head and the floppy disk are kept in a stable contact state by the presence of a large number of sharp and uniform projections on the surface. There are things. This is because a plurality of projections of the same height always contact the slider or the head, so that low and stable friction can be obtained. It is considered that thermal asperity is hardly generated. On the other hand, the height of surface bumps of conventional coating media and laser bumps of hard disks is low,
It is considered that the protrusions having a large spread in the plane direction are likely to intermittently contact the slider or the head at a low frequency, so that abrasion and thermal asperity due to the contact are likely to occur.

Further, the floppy disk used in the present invention has a low coefficient of friction on the disk surface and can form a protective film having excellent wear resistance and a lubricating film having excellent lubricity, so that the above-mentioned low and stable friction is maintained for a long time. That is possible. This can be inferred from the fact that traces of the smoothed solid lubricant can be observed. However, in order to obtain such stable sliding, it is necessary to reduce the runout of the disk during high-speed rotation and prevent the head from jumping.

[0038]

The present invention will be described below with reference to examples and comparative examples. (Production of Floppy Disk) Examples 1 to 9, Comparative Examples 1 to 3 A thermosetting imide resin (BANI-NB manufactured by Maruzen Petrochemical Co.) was applied on both sides of a polyimide film having a maximum projection roughness of 200 nm and a thickness of 75 μm on both sides. A solution dissolved in a mixed solvent of isopropanol, ethanol and cyclohexanone (1: 1: 2 weight ratio) was filtered through a membrane filter having a pore diameter of 0.1 μm, and then applied by a dip coating method.
The mixture was heated at 0 ° C. for 12 hours to prepare a 1.7 μm-thick undercoat film. A liquid having a particle diameter and a concentration as shown in Table 1 was applied by dip coating with an organosilica sol dispersed in cyclohexanone by dip coating, and dried at 250 ° C. for 1 hour to form fine projections formed on the surface. A plurality of supports having different sizes, densities, etc. were produced. The particle diameter was measured with a scanning electron microscope, and an average value of 20 particles was obtained.

Next, the support was placed in a sputtering apparatus for forming a magnetic film while being sandwiched between holders, and the support was heated to 200 ° C., and then Cr—Ti, Ta, Cr—Ti was formed by DC magnetron sputtering. Underlayer films of 30 nm, 20 nm and 60 nm are formed, respectively,
An o-Cr-Pt magnetic film was formed to a thickness of 25 nm. The base film and the magnetic film were formed on both sides of the support. After further cleaning this magnetic film surface with argon glow,
With a bias of -500 V applied to the magnetic film, ethylene 150 ccm and argon 150 ccm
By using an RF plasma CVD method with a substrate bias voltage of -500 V and an RF output of 500 W
A diamond-like carbon protective film having a thickness of 20 nm was formed.

Next, the sample was taken out of the holder, and a phosphazene ring compound (X-1 manufactured by Dow Chemical Co.) in which a perfluoropolyether-based lubricant (FOMBLIN Z-DOL manufactured by Ausimont) and fluorine were introduced onto the protective film.
P) with a fluorinated solvent (HFE-7200 manufactured by Sumitomo 3M)
Was filtered through a filter having a pore diameter of 0.1 μm, and then applied by dip coating to form a lubricating film having a thickness of 1 nm. And this sample was 3.7
Floppy disks were produced by punching into an inch magnetic disk shape and incorporating them into a shell provided with a liner made of rayon fibers, and Examples 1 to 9 and Comparative Examples 1 to 3. Next, the characteristics of the floppy disk were measured by the following evaluation methods, and the results are shown in Table 1.

The surface of the floppy disk obtained in Example 1 was examined with a scanning electron microscope at an accelerating voltage of 20 kV.
An image was taken at a magnification of 20,000 times, and the results are shown in FIG. The surface of the floppy disk obtained in Example 1 was measured with an atomic force microscope, and the results are shown in FIG. FIG. 7 shows a projection height distribution curve obtained from the result of measuring the surface of the floppy disk of Example 1 with an atomic force microscope. The horizontal axis represents the protrusion height in nm,
The vertical axis indicates the number of peaks per unit area (μm ² ).

Comparative Example 4 An undercoat film, a magnetic film, a protective film, and a lubricating film were directly formed on a polyimide film without applying an undercoat film and an organosilica sol in Example 1, and a floppy disk was manufactured in the same manner as in Example 1. did. In this sample, many coarse protrusions due to the internal filler of the film were observed. The characteristics of the floppy disk were measured by the following evaluation methods, and the results are shown in Table 1.

Comparative Example 5 In Example 1, an organosilica sol, a base film, a magnetic film,
A protective film and a lubricating film were prepared, and a floppy disk was prepared in the same manner as in Example 1. As in Comparative Example 4, many coarse projections due to the internal filler of the film were observed in this sample.
The characteristics of the floppy disk were measured by the following evaluation methods, and the results are shown in Table 1.

Comparative Example 6 An undercoat film was prepared by mixing the undercoat film with an organosilica sol having a diameter of 40 nm in Example 1 so that the solid content was 5% by weight based on the entire undercoat film. A base film, a magnetic film, a protective film, and a lubricating film were formed on the undercoat film, and
A floppy disk was prepared in the same manner as described above. In this sample, very smooth fine protrusions formed by swelling of the undercoat resin by the filler of the undercoat film were observed. The characteristics of the floppy disk were measured by the following evaluation methods, and the results are shown in Table 1. The filler diameter indicates the diameter of the filler added to the undercoat film.

Comparative Example 7 A mirror-polished glass substrate was used as a nonmagnetic support.
After forming an organosilica sol on a substrate without forming an undercoat film, a base film, a magnetic film, a protective film, and a lubricating film were formed, and a hard disk was prepared in the same manner as in Example 1.
The characteristics of the floppy disk were measured by the following evaluation methods, and the results are shown in Table 1.

(Evaluation Method) Evaluation of protrusions The prepared floppy disk was observed by scanning electron microscope (SEM) observation and atomic force microscope (AFM) observation to determine the protrusion diameter L (nm) and protrusion density D (pieces / μ).
m ² ) was determined. The diameters of the projections were arbitrarily selected from 20 projections from a scanning electron microscope photograph taken at a magnification of 50,000 times, and the average value was obtained. Next, for an area of 30 μm × 30 μm, an atomic force microscope (DIGITAL INSTRUMENTS) was used.
Scanning was performed in the contact mode using NANOSCOPE 3) manufactured by the company. In this AFM image, the number of protrusions when the slice was sliced at an arbitrary height was measured using a surface in which the volume of the protrusion and the volume of the depression are equal as a reference surface. The projection height corresponding to the projection density D is obtained from the projection height distribution, and the reference projection height HL is obtained.
And To check the distribution of protrusion height, 3
The projection density D30 on the plane higher by 0 nm and the height HH of the highest observed projection were defined as the height HH.

2. Evaluation by MR head Track width: 2.2 μm, head gap: 0.26 μ
A negative pressure slider to which a m MR head was attached was attached to a transverse head arm to produce a pair of head assemblies. The floppy disk was sandwiched so that the weights of the heads above and below the head arm were both 3.5 gf. The head loading position was adjusted so that the center height of the head arm coincided with the height of the innermost circumference of the floppy disk. In this state, the disk is rotated at 3600 rpm, and signals are recorded and reproduced at a linear recording density of 100 KFCI at a radius of 32 mm using the upper head.
N (signal / noise ratio) was measured. C / N is Example 1
Was standardized as 0 dB. Next, the head was scanned at intervals of 0.1 mm in a radius of 20 mm to 30 mm where no signal was recorded, and the head output was measured. In this head output, the same voltage as the output value at the time of the C / N measurement is set as a threshold level, and a portion where the output equal to or higher than the threshold level is observed is regarded as thermal asperity, and the number of occurrences is measured. The number of occurrences was described as “TA”.

[0048]

Table 1 Sample Filler Sole Concentration LDHL D30 HHC / NTA Number Size (nm) Weight% nm / μm ² nm / μm ² nm dB Example 1 18 0.15 80 9.4 16 0 35 0 3 Example 2 18 0.30 80 18.2 17 0 45 -0.5 10 Example 3 18 1.00 80 65.1 17 0 55 -0.7 14 Example 4 18 0.05 80 3.1 16 0 35 +0.2 5 Example 5 25 0.10 90 3.0 22 0 50 -1.5 8 Example 6 25 1.0 90 28.5 23 0.001 55 -1.9 8 Example 7 40 0.20 110 1.2 37 0 65 -4.0 19 Example 8 12 0.10 70 8.4 12 0 30 -1.8 35 Example 9 12 1.00 70 75.0 12 0 30 -0.9 20 Comparative Example 1 18 2.00 80 132.0 19 0.02 80 -2.5 204 Comparative Example 2 18 0.01 80 0.5 16 0 35 -1.6 120 Comparative Example 3 100 2.00 160 1.4 85 0.03 125 -8.4 89 Comparative Example 4 2000 0.003 100 -9.5 481 Comparative Example 5 18 0.15 80 9.5 16 0.003 100 -8.8 282 Comparative Example 6 (40) 300 0.03 15 0 40 -3.2 181

It can be seen that the use of the floppy disk and the magnetic recording method of the present invention can provide good results with very little generation of thermal asperity despite running with the MR head. Example 1
The C / N of the hard disk produced in the same manner as in Example 1 was -1.1 dB as compared with Example 1. This indicates that the floppy disk of Example 1 has a smaller physical spacing than the hard disk produced in the same manner and has good electromagnetic conversion characteristics.

[0050]

According to the present invention, the occurrence of thermal asperity due to collision between a floppy disk and a head, which occurs when an MR head is used, is suppressed, and a highly reliable floppy disk and a magnetic recording system capable of high-density recording can be obtained. .

[Brief description of the drawings]

FIG. 1 is a diagram illustrating a floppy disk drive used for a magnetic recording system according to the present invention.

FIG. 2 is a cross-sectional view illustrating a floppy disk drive used in the magnetic recording system of the present invention.

FIG. 3 is a diagram illustrating a head and a head slider.

FIG. 4 is a diagram illustrating a cross section of the floppy disk of the present invention.

FIG. 5 is a photograph of the surface of the floppy disk obtained in Example 1 taken with a scanning electron microscope.

FIG. 6 is a surface image obtained by photographing the surface of the floppy disk obtained in Example 1 with an atomic force microscope.

FIG. 7 is a diagram illustrating a distribution curve of the height of protrusions of the floppy disk obtained in Example 1.

[Explanation of symbols]

DESCRIPTION OF SYMBOLS 1 ... Floppy disk device, 2 ... Floppy disk, 3 ... Disk cartridge, 4 ... Insertion opening, 5 ... Center core, 6 ... Head window, 7 ... Head slider, 8 ... Head arm, 9 ... Head moving mechanism, 10 ... Spindle motor , 11: magnetic head, 12: leaf spring for load adjustment,
21: flexible support, 22: undercoat film, 23: base film,
24: ferromagnetic metal thin film, 25: protective film, 26: lubricating film,
27 ... fine particles

 ────────────────────────────────────────────────── ─── Continuing on the front page (72) Inventor Shin Nobu 2-12-1, Ogimachi, Odawara-shi, Kanagawa Prefecture Fuji Photo Film Co., Ltd. F-term (reference) 5D006 BB01 CB07 DA02 FA00

Claims (2)

[Claims] 1. A floppy disk having a structure in which a ferromagnetic metal thin film, a protective film, and a lubricating film are laminated on both sides of a flexible non-magnetic support, the surface has a diameter of 30 nm to 200 nm.
1 μm square micro projections with a height of 10 nm to 70 nm
A floppy disk having a density of 1 to 100 pieces per floppy disk. 2. A floppy disk having a structure in which a ferromagnetic metal thin film, a protective film, and a lubricating film are laminated on both sides of a flexible non-magnetic support in a magnetic recording system, the surface of which has a diameter of 30 nm to 200 nm and a high thickness. 10 nm to 70 nm
Of a floppy disk having a density of 1 to 100 per micrometer squared between the front and back surfaces of the floppy disk with a magnetic head arm having a slider having an MR head attached to the tip, and rotating the floppy disk at a rotation speed of 2000 rpm or more. A magnetic recording system characterized by performing recording and reproduction by causing a slider to travel.