JPH0619802B2 - Magnetic recording method - Google Patents

Description

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a magnetic recording medium, and more particularly to a magnetic recording method using a metal thin film type magnetic recording medium.

2. Description of the Related Art Prior Art and Problems There have been developed magnetic recording media for video, audio, etc. which have a metal thin film type magnetic layer because of their compactness when formed into a tape and wound.

As a magnetic layer of such a metal thin film type medium, vapor deposition of Co-based, Co-Ni-based, or the like, which is formed by a so-called oblique vapor deposition method in which vapor deposition is performed at a predetermined inclination angle with respect to the normal line of the substrate, is characteristic. Membranes are preferred.

Since the characteristics of such a medium are largely deteriorated by the spacing loss, it is necessary to smooth the surface as much as possible.

However, if the surface is made too flat, friction will increase, which will hinder the head touch and the running surface.

By the way, in the metal thin film type medium, the magnetic layer is 0.05 to
Since it is as thin as 0.5 μm, the surface property of the medium depends on the surface property of the substrate.

Therefore, it has been proposed to provide comparatively gentle so-called wrinkle-shaped or earth-shaped protrusions on the substrate surface (Japanese Patent Laid-Open No. 53-116115, etc.).

Further, in JP-A-58-68227 and JP-A-58-100221, fine particles are arranged on the surface of a substrate so that they can be observed with an optical microscope at a magnification of 50 to 400 times, and actually measured with a stylus type surface roughness measuring device. It has been proposed to provide unevenness with a height that can be achieved.

However, even these are still insufficient in terms of physical properties such as running friction, running durability and running stability, and electromagnetic conversion characteristics.

On the other hand, Japanese Patent Publication No. 39-25246 and the like propose that a top coat layer made of an organic lubricant is provided on the surface of a ferromagnetic metal thin film to reduce running friction.

However, when an organic lubricant is used, adhesion of the lubricant to the head and clogging of the head occur, which poses a serious problem in practical use.

That is, under the present circumstances, a technology has not yet been realized in which traveling friction is reduced, head adhesion and head clogging are eliminated within a range where traveling is not affected, and inconvenience does not occur in terms of electromagnetic conversion characteristics.

II Object of the invention The object of the present invention is to improve the physical properties such as friction, durability running property, running stability, etc. in a magnetic recording method using a metal thin film type magnetic recording medium, and to the extent that the physical properties are not hindered. It is to eliminate head adhesion and clogging, and to prevent any inconvenience in terms of electromagnetic conversion characteristics.

Such an object is achieved by the present invention described below.

That is, the present invention uses a magnetic head to record a magnetic recording medium in which a ferromagnetic metal thin film layer containing Co as a main component is provided on a flexible substrate and an organic topcoat layer is provided on the surface of the ferromagnetic metal thin film layer. In the magnetic recording method of reproducing, when the organic topcoat layer contains an antioxidant and a lubricant, the ferromagnetic metal thin film layer contains oxygen, and the gap length of the magnetic head is a μm,
a is 0.1 to 0.5, the medium surface has an average of 10 ⁵ / a ² to 10 ⁹ / a ² or more protrusions per 1 mm ² , and the protrusions have a height of 30 to 300 Å. The magnetic recording method is characterized in that at least the end surface of the gap portion of the magnetic head is made of a metal ferromagnetic material.

III Specific Structure of the Invention Hereinafter, the specific structure of the present invention will be described in detail.

The ferromagnetic metal thin film layer as the magnetic layer in the present invention is C
o is the main component, O is included in this, and if necessary N
It has a composition containing i and / or Cr.

That is, in a preferred embodiment, it may consist of Co alone or Co and Ni. When Ni is contained, the Co / Ni polymerization ratio is preferably 1.5 or more.

Further, Cr may be contained in the ferromagnetic metal thin film layer.

When Cr is contained, electromagnetic conversion characteristics are improved, output and S / N ratio are improved, and film strength is also improved.

In such a case, Cr / Co or Cr / (Co + N
The weight ratio of i) is 0.001-0.1, more preferably,
It is preferably 0.005 to 0.05.

Further, O is contained in the ferromagnetic metal thin film.

The average oxygen content in the ferromagnetic metal thin film is the atomic ratio, especially O /
The atomic ratio of (Co or Co + Ni) is preferably 0.5 or less, more preferably 0.05 to 0.5.

In this case, oxygen forms an oxide with the ferromagnetic metal (Co, Ni) on the surface of the ferromagnetic metal thin film layer.

That is, a peak showing an oxide is recognized by Auger spectroscopic analysis in the surface portion, particularly in the range of 50 to 500 Å, more preferably 50 to 200 Å from the surface. The oxygen content of this oxide layer is about 0.5 to 1.0 in atomic ratio.

In such a ferromagnetic metal thin film, other trace components, especially transfer elements such as Fe, Mn, V, Zr,
Nb, Ta, Ti, Zn, Mo, W, Cu, etc. may be contained.

In a preferred embodiment, such a ferromagnetic metal thin film layer is composed of an aggregate of columnar crystal grains containing Co as the main component.

In this case, the thickness of the ferromagnetic metal thin film layer is 0.05 to 0.
The thickness is 5 μm, preferably 0.07 to 0.3 μm.

The columnar crystal grains have a length extending over almost the entire area in the thickness direction of the thin film, and the longitudinal direction is inclined in the range of 10 to 70 ° with respect to the normal line of the main surface of the substrate. Preferably.

It should be noted that oxygen is present in the form of a compound as described above on the surface of the cast crystal grains in the surface portion.

Further, there is no particular limitation on the oxygen concentration gradient of the ferromagnetic metal thin film layer.

Further, the minor axis of the crystal grains preferably has a length of about 50 to 500 Å.

The substrate on which such a ferromagnetic metal thin film layer is formed is not particularly limited as long as it is a non-magnetic substrate, but a particularly flexible substrate, particularly a resin such as polyester or polyimide is preferable. preferable.

Further, the thickness thereof may be various, but it is particularly preferably 5 to 20 μm.

In this case, on the back surface of the ferromagnetic metal thin film layer forming surface of the substrate,
Various known back coat layers may be formed.

On the surface of the magnetic recording medium of the present invention thus configured, fine protrusions are provided with a predetermined density.

The fine protrusions are 30 to 300Å, more preferably 50 to
It has a height of 250Å.

That is, the projections of the present invention can be observed with an optical microscope and can be observed with a scanning or transmission electron microscope, not with a stylus type surface roughness meter.

If the projection height exceeds 300Å and can be observed with an optical microscope, electromagnetic conversion characteristics deteriorate and running stability deteriorates.

Further, if it is less than 50Å, the improvement of physical properties is not effective.

And the density is an average of 10 ⁵ / a ² per 1 mm ² ~
10 ⁹ / a ² pieces, more preferably 2 × 10 ⁶ / a ² to 1 pieces
× 10 ⁹ / a ² pieces.

In this case, a represents the gap length of the magnetic head used in μm unit.

And, a is 0.1 to 0.5 μm, particularly 0.1 to 0.
4 μm.

If the protrusion density is less than 10 ⁵ / a ² / mm ² , more preferably less than 2 × 10 ⁶ / a ² mm ² , noise increases, still characteristics deteriorate, and head clogging occurs frequently. It deteriorates and cannot be put to practical use.

Further, if it exceeds 10 ⁹ / a ² / mm ² , the effect on the physical properties will be reduced.

In order to provide such protrusions, it is usually sufficient to dispose fine particles on the substrate. The particle size is 30-300Å, especially 5
It may be set to 0 to 250Å, whereby fine protrusions corresponding to the particle diameter are formed.

The fine particles used are those generally known as colloidal particles, for example, SiO ₂ (colloidal silica), Al ₂ O ₃ (alumina sol), MgO, Ti.
O ₂ , ZnO, Fe ₂ O ₃ , zirconia, CdO, Ni
O, CaWO ₄ , CaCO ₃ , BaCO ₃ , CoC
O ₃ , BaTiO ₃ , Ti (titanium black), Au,
Ag, Cu, Ni, Fe, various hydrosols, resin particles and the like can be used. In this case, it is particularly preferable to use an inorganic substance.

Such fine particles may be used as a coating solution using various solvents, which may be coated on a substrate and dried, or a coating solution to which a resin component such as various aqueous emulsions is added may be coated and dried. Good.

In some cases, the projections may be provided by adding fine particles to the top coat layer instead of disposing the coating liquid on the substrate.

Further, when a resin component is used, it is possible to provide a gentle protrusion by superposing on the fine protrusion based on these fine particles, but it is not usually necessary to do so.

If necessary, various known underlayers may be interposed between the substrate and the ferromagnetic metal thin film layer.

If necessary, the ferromagnetic metal thin film layer may be divided into a plurality of layers, and the non-ferromagnetic metal thin film layer may be interposed therebetween.

In the present invention, the magnetic layer may be formed by electrolytic vapor deposition, ion plating, plating or the like, but it is preferably formed by a so-called oblique vapor deposition method.

In this case, the minimum value of the incident angle of the vapor deposition substance with respect to the normal to the substrate is preferably 20 ° or more.

If the incident angle is less than 20 °, the electromagnetic conversion characteristics deteriorate.

The vapor deposition atmosphere is usually an atmosphere containing oxygen gas in an inert atmosphere such as argon, helium, or vacuum.
And ^-5 to 10 0 ^Pa pressure of about, also deposition distance, groups to the conveying direction, the structure of the can and the mask, arrangement and the like may be the same as known conditions.

Then, a metal oxide film is formed on the surface by vapor deposition in an oxygen atmosphere. The oxygen gas partial pressure at which the metal oxide is formed can be easily obtained from experiments.

Various oxidation treatments can be performed to form a metal oxide film on the surface.

The following oxidation treatments can be applied.

1) Dry treatment a. Energetic particle treatment As described in Japanese Patent Application No. 58-76640, in the latter stage of vapor deposition, oxygen is energized to the magnetic layer as energetic particles by an ion gas or a neutral gun.

b. Glow treatment O ₂ , H ₂ O, O ₂ + H ₂ O and the like and an inert gas such as Ar and N ₂ are used to glow discharge this to generate plasma, and the surface of the magnetic film is exposed to this plasma. .

c. Oxidizing gas A gas that blows an oxidizing gas such as ozone or heated steam.

d. Heat treatment A substance that is oxidized by heating. Heating temperature is 60-150
℃ degree.

2) Wet treatment a. Anodization b. Alkaline treatment c. Acid treatment Chromate treatment, permanganate treatment, phosphate treatment, etc. are used.

d. Oxidant treatment H ₂ O ₂ or the like is used.

A specific organic topcoat layer is provided on such a magnetic layer.

The top coat layer of the present invention contains an antioxidant and a lubricant.

The antioxidant used in the present invention may be any one as long as it can prevent metal oxidation.

As the antioxidant used in the present invention, usual antioxidants are used, and these are: 1) phenolic antioxidants 2) amine antioxidants, 3) phosphorus antioxidants, 4) sulfur compounds Structurally roughly classified as antioxidants, 5) organic acids, alcohols, ester-based antioxidants, 6) quinone-based antioxidants, 7) inorganic acids, inorganic salt-based antioxidants.

Specific examples of the above various antioxidants are as follows: 1) Examples of phenolic antioxidants are 2,6-di-tert-butyl-p-cresol, 2,6-di-tert-butyl-phenol, 2 , 4-di-methyl-6-tert-butyl-phenol, butylhydroxyanisole, 2,2'-methylenebis (4-methyl-6-tert-butylpheninol), 4,
4'-butylidene bis (3-methyl-6-tert-butylphenol), 4,4'-thiobis (3-methyl-6-tert-butylphenol), tetrakis [methylene-3 (3,5-di-tert-butyl-phenol) 4-hydroxyphenyl) propionate]
There are methane, 1,1,3-tris (2-methyl-4-hydroxy-5-tert-butylphenyl) butane, dibutylhydroxytoluene, propyl gallate, guaiac butter, nordihydroguaiaretinic acid and the like.

As a radiation curable type, monoglycol salicylate,
Examples thereof include methacrylate and acrylate types such as 2,5-di-tert-butylhydroquinone, 2,4-dihydroxybenzophenone, 2,4,5-trihydroxybutyrophenone and hydroquinone.

2) Amine-based antioxidants include phenyl-β-naphthylamine, α-naphthylamine, N, N'-di-tert-butyl-p-phenylenediamine, phenothiazine,
In addition to N, N'-diphenyl-p-phenylenediamine,
Examples thereof include alkanolamine and phospholipid.

Among amine-based radiation-curable types, there are radiation-curable types such as dimethylaminoethyl methacrylate and acrylate.

3) As the phosphorus-based antioxidant, a radiation-curable type or a non-radiation-curable type is used, and R of the phosphate ester part contains an alkyl group, an alkylphenyl group, other ethylene oxide, or propylene oxide. As R, C is preferably 1-26, and more preferably 1-2.
It is 2.

The phosphoric acid ester includes mono, di, and triesters, and may have a large amount of mono or di components,
Tri-type may be cut.

The phosphoric acid ester also includes NH ₄ type, methacrylate type, and acrylate type.

Specifically, triphenyl phosphite, trioctadecyl phosphite, tridecyl phosphite, phosphite esters such as trilauryl trithiophosphite, hexamethyphosphoric amide, butyl phosphate, cetyl phosphate, butoxyethyl phosphate, 2- Ethylhexyl phosphate, β-chloroethyl phosphate, butoxyethyl phosphate diethylamine salt,
Di (2-ethylhexyl) phosphate, ethylene glycol acid phosphate, (2-hydroxyethyl) methacrylate phosphate, butyl hydroxymethacrylate phosphate, capryl hydroxymethacrylate phosphate, myristyl hydroxymethacrylate phosphate, stearyl hydroxymethacrylate phosphate, cetyl hydroxymethacrylate. Phosphates, butylphenyl hydroxymethacrylate phosphates, amylphenylhydroxymethacrylate phosphates, noniphenylhydroxymethacrylate phosphates, and their acrylate types, phenylphosphates, other alcohols, and phenylphosphates such as nonylphenyl, vanadium-based Phosphoric acid esters such as sexual phosphoric acid esters.

4) Examples of sulfur-based antioxidants include dilauryl thiodipropionate, distearyl thiodipropionate, lauryl stearyl thiodipropionate, dimyristyl thiodipropionate, distearyl β, β′-thiobutyrate, 2- In addition to mercaptobenzimidazole and dilauryl sulfide, 4,4'-
Examples of the radiation-curable type include methacrylates such as thio-bis (3-methyl-6-tert-butyl-phenol) and 2,2'-thio-bis (4-methyl-6-tert-butyl-phenol) and acrylates. To be

Moreover, these may contain ethylene oxide and propylene oxide.

5) Examples of organic substances, alcohols, and ester-based antioxidants include sorbitol, glycerin, propylene glycol, adipic acid, citric acid, and ascorbic acid, which may be radiation-curable.

6) Examples of the quinone antioxidant include hydroquinone and tocopherol, and of these, radiation type may be used.

7) Typical examples of inorganic acids and inorganic salt antioxidants include phosphoric acid.

Among the above antioxidants, radiation curable ones having an acrylic double bond in the molecule, for example, monoglycol salicylate methacrylate (acrylate), 4 Tert-butyl catechol methacrylate (acrylate), dimethylaminoethyl methacrylate (acrylate), ethyl hydroxymethacrylate (acrylate) phosphate, cetyl hydroxyphosphate methacrylate (acrylate), stearyl methacrylate (acrylate) phosphate, and phenyl type of the above, 2,2 'Thio-
Bis (4-methyl-6-tert-butyl-phenol) methacrylate (acrylate) and the like are preferable.

The phosphoric acid ester can be produced by a known method, and the method described in JP-B-57-44223 can also be used.

Since the radiation-curable inhibitor can be cured online on the ferromagnetic thin film, the surface property is not deteriorated due to the back mold transfer due to winding tightness at the time of heat curing, and therefore the output is not reduced.

The top coat on the ferromagnetic thin film is 100Å as described later.
The following is preferable, and if the thickness is further increased, the characteristics are deteriorated. Also, if it is too thick, the top coat layer will be scraped. This is the first finding of the present invention. By using radiation-curable antioxidants, it is possible to prevent dropouts, to reduce the difference in output due to the internal and external parts when wound into a roll, and to manufacture online. It can also increase the curing in processing.

As the lubricant used in the present invention, as a lubricant conventionally used in this type of magnetic recording medium, silicone oil,
Fluorine oil, fatty acid, fatty acid ester, paraffin,
Liquid paraffin, a surfactant and the like can be used, but it is preferable to use a fatty acid and / or a fatty acid ester.

As the fatty acid, caprylic acid, capric acid, lauric acid, myristic acid, palmitic acid, stearic acid, behenic acid, oleic acid, elaidic acid, linolenic acid, stearolic acid or the like having 12 or more carbon atoms (RCOOH, R
Is an alkyl group having 11 or more carbon atoms).

Examples of the fatty acid ester include fatty acid esters composed of monobasic fatty acids having 12 to 16 carbon atoms and monohydric alcohol having 3 to 12 carbon atoms, monobasic fatty acids having 17 or more carbon atoms and carbon numbers of fatty acids. In total, a fatty acid ester or the like composed of a monohydric alcohol having 21 to 23 carbon atoms is used.

As the silicone, those which are modified with fatty acids and those which are partially modified with fluorine are used.

As the alcohol, a higher alcohol is used, and as the fluorine, one obtained by electrolytic substitution, telomerization, oligomerization or the like is used.

Among the lubricants, it is convenient to use radiation-curable lubricants.

Since these suppress back-side transfer to the ferromagnetic thin film, they can prevent dropout, reduce the output difference due to the inner and outer diameters when wound in a roll, and can be manufactured online. Have an advantage.

As the radiation-curable lubricant, a compound having a molecular chain exhibiting lubricity and an acrylic double bond in the molecule, for example, acrylic acid ester, methacrylic acid ester, vinyl acetate ester, acrylic acid amide compound, vinyl alcohol ester , Methyl vinyl alcohol ester, allyl alcohol ester, glyceride and the like.

When these lubricants are represented by structural formulas, Etc.

Here, R is a linear or branched saturated or unsaturated hydrocarbon group having a carbon number of 7 or more, preferably 12 or more 23
Below, these can also be made into the fluorine substitution product.

As the fluorine substitution product, Etc.

Specific preferred examples of these radiation-curable lubricants include:
Examples thereof include stearic acid methacrylate (acrylate), stearyl alcohol methacrylate (acrylate), glycerin methacrylate (acrylate), glycol methacrylate (acrylate), and silicone methacrylate (acrylate).

As a method of providing a top coat layer containing an antioxidant and a lubricant on the surface of the ferromagnetic thin film, the additive is diluted with a solvent and thinly coated on the ferromagnetic metal thin film, or the additive is not exposed to the atmosphere or the atmosphere. There are means such as vaporizing in active gas or in vacuum and applying the vapor to the ferromagnetic metal surface, and these can be applied.

The thickness of the top coat layer is preferably 10 to 100Å. If it is too thick, the characteristics of the battery may be deteriorated or the battery may be damaged. If it is too thin, clogging will occur.

In this case, the thickness is preferably 10 to 50Å.

The weight ratio of the antioxidant to the lubricant is 10:
0.1-10: 40, more preferably 10: 1-10:
It is about 20.

The lubricant and antioxidant contained in the top coat layer of the present invention are preferably radiation-curable.

In this case, as the active energy ray used for the crosslinking, an electron beam having a radiation accelerator as a radiation source, γ-rays having Co60 as a radiation source, β-rays having Sr90 as a radiation source, and an X-ray generator are radiation rays. X-rays or ultraviolet rays used as a source are used.

Particularly, as a radiation source, a method of using radiation by a radiation heater is advantageous from the standpoints of controlling absorbed dose, introducing it into a manufacturing process line, and shielding ionizing radiation.

As the radiation characteristics used for curing the top coat layer, from the viewpoint of penetrating power, an irradiation voltage of 100 to 750 KV, preferably 150 to 300 KV is used so that the absorbed dose is 0.5 to 20 megarats. It is convenient to do this.

At the time of radiation curing of the present invention, a low-dose type radiation accelerator (electro curtain system) manufactured by US Energy Science Co., Ltd. is shielded from secondary X-rays inside the accelerator introduced into the tape coating processing line. Etc. is extremely advantageous.

Alternatively, a van de Graaff type accelerator, which has been widely used for radiation acceleration, may be used.

Further, at the time of radiation crosslinking, it is important to irradiate the backcoat layer and the topcoat layer with radiation in an inert gas stream such as N ₂ gas or He gas.

Irradiation with radiation in the air is extremely disadvantageous because radicals generated in the polymer under the influence of O _{3 and the} like generated by radiation advantageously inhibit the crosslinking reaction during crosslinking of the binder component.

Therefore, the atmosphere of the part irradiated with active energy rays is
In particular, it is important to keep the atmosphere of an inert gas such as N ₂ , He or CO ₂ having an oxygen concentration of 5% at the maximum.

The top coat layer of the present invention can be ultraviolet-cured by adding a photopolymerization sensitizer.

The photopolymerization sensitizer may be a conventionally known one, for example,
Benzoin-based compounds such as benzoin methyl ether, benzoin ethyl ether, α-methylbenzoin and α-chlordeoxybenzoin; ketones such as benzophenone, acetophenone and bisdialkylaminoenzophenone; quinones such as anthraquinone and phenanthraquinone; benzyl disulfide. And sulfides such as tetramethylthylium monosulfide, and the like.

The photopolymerization sensitizer is preferably in the range of 0.1 to 10% by weight based on the solid content.

On the other hand, as the magnetic head used, at least the end surface of the gap portion is made of a magnetic metal material.

In this case, the entire core can be formed of a metal ferromagnetic material, and if necessary, a part of the core including the end face of the gap can be formed of a metal ferromagnetic material.

In FIG. 1, for example, metallic half ferromagnetic bodies 31 and 32 having a thickness of about 1 to 5 μm are deposited on the end surfaces of the gaps of the core halves 21 and 22 made of a ferromagnetic material such as ferrite by sputtering or the like, and the glass Core half 2 through gap 4 of quality etc.
An example is shown in which the magnetic head 1 is configured by associating 1 and 22.

By using a head using such a metal magnetic material, extremely good electromagnetic conversion characteristics can be obtained, and running durability is good, and head adhesion and head clogging are also good.

The shape, structure, etc. may be known.

However, the gap length a is 0.1 to 0.5 as described above.
μm, particularly 0.1 to 0.4 μm, and the track width is usually 10 to 50 μm, especially 10 to 20 μm.

Various kinds of metal ferromagnetic materials can be used, such as amorphous magnetic metal, sendust, hard permalloy,
Any thin film such as permalloy or a thin plate can be used.

However, among these, the amorphous magnetic alloy containing Co as a main component has particularly small head clogging or adhesion and good electromagnetic conversion characteristics.

As such an amorphous magnetic alloy, Co70 to 95 at
%, Zr, Nb, Ta, Hf,
Rare earth elements, Si, B, P, C, Al, etc., especially those containing 5 to 20 at% of Zr and / or Nb are preferable.

Alternatively, Co of 65 to 85 at% and Si and / or B of 15 to 35 at% as a vitrifying element are also preferable. In this case, Fe of 10 at% or less, 2
5 at% or less Ni, total 20 at% or less Cr, Ti, R
One or more of u, W, Mo, Ti, Mn and the like may be contained.

These amorphous magnetic alloys are formed as core halves or gaps by using sputtering or rapid quenching.

Recording and reproduction on the above-mentioned medium using such a magnetic head may be performed according to a known video recording system such as a so-called VHS system, beta system, 8 mm video system, U standard system.

IV Specific Actions and Effects of the Invention According to the present invention, running friction is extremely reduced and stabilized.

Further, the running durability is remarkably improved, the running friction is not increased even after a number of runnings, the number of times of repeated recording and reproduction is remarkably improved, and the still characteristic is remarkably improved.

It also has high running stability and exhibits extremely high stability under a wide range of conditions from high temperature and high humidity to low temperature and low humidity.

Furthermore, the reproduction output based on the spacing loss is extremely small.

Also, there is very little noise.

Also, there is very little clogging of the head and adhesion of the head.

Such an effect is enhanced when a metal ferromagnetic head is used.

Further, such an effect is further enhanced in high density recording with a minimum recording wavelength of less than 1 μm.

II Specific Examples of the Invention Examples of the present invention are shown below.

Example 1 Colloidal silica was applied onto a smooth polyester film (thickness: 12 μm) containing substantially no fine particles to obtain a substrate having fine protrusions.

The protrusion height was about 150Å, and the protrusion density was about 10 ⁷ pieces / mm ² . (1) Formation of magnetic layer Ferromagnetic thin film 1 The above substrate was moved along the circumferential surface of the cylindrical cooling can, and O ₂ + Ar (volume ratio 1: 1) was flowed at a speed of 800 cc / min to obtain a vacuum degree. In a chamber with a pressure of 1.0 × 10 ⁻⁴ Torr, an alloy of Co80 and Ni20 was melted and obliquely vapor-deposited only at the incident angle of 90 ° to 30 ° to obtain a film thickness of 0.15
A μm Co-Ni-O thin film was formed.

A large amount of oxygen was unevenly distributed on the interface with the base and on the surface opposite to the base.

The surface opposite to the base was almost covered with only oxide.

Hc = 1000 Oe.

The average oxygen content in the film is the atomic ratio of Co and Ni. Was 40%.

Ferromagnetic Thin Film 2 The substrate was moved along the peripheral surface of the cylindrical cooling can, and vapor deposition was performed in the same manner as in the case of the ferromagnetic thin film 1 in the chamber where the degree of vacuum was 5.0 × 10 ⁻⁶ Torr. The film thickness is 0.
It has a thickness of 15 μm and is substantially made of Co—Ni.

This tape was forcibly oxidized in a 20% RH atmosphere at 90 ° C., and the surface opposite to the base was made of only oxide.

Hc = 900 Oe. The average oxygen content in the film is Co and Ni.
Was 45% in terms of atomic ratio.

Ferromagnetic thin film 3 Like the ferromagnetic thin film 2, except that the oxidation step by oxygen is omitted, the substrate is moved along the peripheral surface of the cylindrical cooling can and the degree of vacuum is 5.0 × 10 ⁻⁶ Torr. In the above chamber, vapor deposition was performed as in the case of the ferromagnetic thin film 1. The film thickness was 0.15 μm and consisted essentially of Co—Ni.

Hc = 950 Oe. (2) Formation of topcoat layer Topcoat composition Topcoat composition 1 part by weight 2,6 Di-tert-butyl p-cresol 2 Fluorine-modified silicone stearate 0.4 MEK 100 Coromate L 0.2 Topcoat composition 2 Monoglycol Salicylate acrylate 5 Myristic acid 0.3 Myristyl alcohol methacrylate 1.0 MEK / toluene (1/1) 100 Topcoat composition 3 Dimethylaminomethacrylate 3 Fluorine (electrolysis method) 0.3 MEK / toluene (1/1) 100 Topcoat composition 4 Hydroxyethylmethacrylate phosphate 3 Stearic acid 0.5 Stearic acid modified silicone 0.5 Toluene 100 Topcoat composition 5 parts by weight Stearyl alcohol methacrylate phosphate 3 Stearic acid acrylate 0.6 MEK / toluene (1/1) 100 Production and properties of top coat layer 1. For the top coat layer 1, the top coat composition 1 was directly applied on the ferromagnetic thin film and cured at 80 ° C. for 24 hours.

The film thickness was 20Å.

2. The top coat layer 2 is formed by applying the top coat composition 2 on a ferromagnetic thin film, accelerating voltage 150 KeV, electrode current 6 m.
Irradiation was performed in A, 3 Mrad, N ₂ gas.

The film thickness was 80Å.

3. The top coat layer 3 is obtained by applying the top coat composition 3 on a ferromagnetic thin film, accelerating voltage 150 KeV, and electrode current 10 m.
Irradiation was carried out in A, 5 Mrad, N ₂ gas.

The film thickness was 40Å.

4. The top coat layer 4 is formed by applying the top coat composition 4 on a ferromagnetic thin film, accelerating voltage 150 KeV, and electrode current 10 m.
Irradiation was carried out in A, 5 Mrad, N ₂ gas.

The film thickness was 30Å.

5. The top coat layer 5 is obtained by applying the top coat composition 5 on a ferromagnetic thin film, accelerating voltage 150 KeV, and electrode current 10 m.
Irradiation was carried out in A, 5 Mrad, N ₂ gas.

The film thickness was 40Å.

6. Topcoat composition 6 parts by weight a. Dimethylaminomethacrylate 3 MEK / toluene (1/1) 100 Coating this on a ferromagnetic thin film, accelerating voltage 150 KeV,
Irradiation was performed in an electrode current of 10 mA, 5 Mrad, and N ₂ gas.

On top of that, b. Stearyl methacrylate 0.3 Fluorine oil (telomerization method) 0.2 MEK 100 was applied, acceleration voltage 150 KeV, electrode current 4 mA, 2 Mra
Irradiation was performed in d, N ₂ gas.

The film thickness was 30Å.

7. 4 x 1 on top of a top coat composition 6 on the ferromagnetic film
Stearyl alcohol was adsorbed in an atmosphere of 0 ^-3 Torr.

The film thickness was 40Å.

8. 4 x 1 on top of a top coat composition 6 on the ferromagnetic film
The fluorine-modified oil was adsorbed in an atmosphere of 0 ^-3 Torr.

The film thickness was 40Å.

9. Comparative topcoat layer Stearic acid was applied to a thickness of 30Å to form a layer.

Using these ferromagnetic thin films and top coat films, Table 1
The medium shown in was created.

The characteristics are shown below.

The magnetic head used is that shown in Table 1 and has a gap length of 0.25 μm and a track length of 20 μm. In this case, the core halves 21 and 22 are made of ferrite, and the gap end faces are formed by sputtering.
μm thick Co0.8NiO. 1Zr0.1 (atomic ratio), and the gap material was glass.

For comparison, a ferrite magnetic head was used.

In addition, 10 ⁵ / a ² is 1.6 × 10 ⁶ .

The method of measuring the above characteristics will be described below.

1. Observation of protrusions SEM (scanning electron microscope) and TEM (transmission electron microscope) are used. Still characteristics Record at 5MHz and measure the still characteristics of playback output.

Set the OK level for 10 minutes or longer.

3. Magnetic surface side friction measurement Wrap the magnetic tape so that it comes to the cylinder side, apply a load of 20 g to one end surface, and read the change in tension when the cylinder is rotated 90 ° to measure friction.

4. Output Indicates the S / N ratio (relative value) when recording / reproducing at a center frequency of 5 MHz.

Modify VHS VTR to measure up to 5MHz.

5. Clogging Using a VHS VTR deck, clogging was measured during 50 runs.

6. Head Adhesion After a predetermined number of running tests, the head drum was removed, and the contact surface with the tape was observed with an optical microscope.

7. Guide Adhesion After a predetermined number of running tests, the adhesion to the guide pin was observed with an optical microscope.

8. Topcoat abrasion The tape after a predetermined number of running tests was measured by observing with an optical microscope.

Example 2 The following table shows the relationship between the height and density of protrusions on the surface of the magnetic film and the characteristics.

The test was conducted using a signal with the shortest recording wavelength of 0.7 μm. As the magnetic head, in addition to the amorphous head of Example 1, a sendust head and a ferrite head for comparison were used. The gap length is the same as in Example 1.

The top coat is the top coat layer 4 of Example 1.
The thin film 1 of Example 1 was used as the magnetic film manufacturing conditions.

Also, as a result of Auger spectroscopic analysis, it was found that the surface of these magnetic layers was covered with an oxide layer of 100 to 200 Å.

In the above examples, colloidal silica was used as the inorganic fine particles, but it goes without saying that other substances such as alumina sol, titanium black, zirconia or various hydrosols may be used.

It should be noted that the same results were obtained when a head made of Co-Fe-Ru-Cr-Si-B based amorphous was used, and the characteristics were superior to those of the ferrite head.

However, when a head made of Sendust was used, the effect was slightly less than that in the above case.

[Brief description of drawings]

FIG. 1 is a front view showing an example of a magnetic head used in the present invention. 1 ... Magnetic head, 21, 22 ... Core half body, 31, 32 ... Metal ferromagnetic body, 4 ... Gap

Claims (7)

[Claims] 1. A magnetic recording medium in which a ferromagnetic metal thin film layer containing Co as a main component is provided on a flexible substrate and an organic top coat layer is provided on the surface of the ferromagnetic metal thin film layer by using a magnetic head. In a magnetic recording method for recording / reproducing, when the organic topcoat layer contains an antioxidant and a lubricant, the ferromagnetic metal thin film layer contains oxygen, and the gap length of the magnetic head is a μm. ,
a is 0.1 to 0.5, the medium surface has an average of 10 ⁵ / a ² to 10 ⁹ / a ² protrusions per 1 mm ² , and the protrusions have a height of 30 to 300Å, A magnetic recording method characterized in that at least the end face of the gap of the magnetic head is made of a metal ferromagnetic material. 2. The magnetic recording method according to claim 1, wherein the metal ferromagnet is an amorphous magnetic alloy containing Co as a main component. 3. A flexible substrate is made of a polymer, and fine particles having a diameter of 30 to 300 Å are arranged on this substrate, and a ferromagnetic metal thin film layer and an organic top coat layer are formed thereon. The magnetic recording method according to claim 1 or 2, which is provided. 4. The magnetic recording method according to claim 1, wherein the ferromagnetic metal thin film has a ferromagnetic metal oxide layer on its surface. 5. The magnetic recording method according to any one of claims 1 to 4, wherein the antioxidant of the top coat layer is a radiation curing type. 6. A lubricant according to claim 1, wherein the lubricant of the top coat layer contains a radiation curing agent.
The magnetic recording method according to any one of paragraphs. 7. The magnetic recording method according to any one of claims 1 to 6, wherein the thickness of the top coat layer is 10 to 100Å.