JPH0624052B2 - Magnetic recording method - Google Patents

Description

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a magnetic recording method, and more particularly to a magnetic recording method using a magnetic recording medium having a continuous thin film type magnetic layer by a so-called oblique evaporation method.

Prior art and its problems Active development of a magnetic recording medium for video, audio, etc. having a continuous thin film type magnetic layer on a long substrate due to its compactness when wound into a tape and wound. Has been done.

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

The ferromagnetic metal thin film layer formed by the oblique deposition method as described above is an aggregate of columnar crystal grains that are inclined with respect to the normal line of the main surface of the substrate and have a longitudinal diameter extending over the entire thickness direction of the ferromagnetic metal thin film layer. It is formed.

Then, Co, Ni and the like are present in the columnar crystal grains, and O introduced in a preferred embodiment is present by forming an oxide on the surface of the columnar crystal grains.

However, such a ferromagnetic metal thin film layer has a shape anisotropy in the longitudinal direction of the substrate, that is, in the traveling direction of the medium. It has the drawback of occurring.

Therefore, the present inventors previously measured the coercive force as a medium having no such input / output difference while changing the direction on a plane defined by the longitudinal direction of the substrate and the normal direction of the main surface of the substrate. (Hc max−Hc min) / Hc (O) ≦ 0.9 [where Hc max is the maximum value of coercive force, Hc min is the minimum value of coercive force, and Hc (O) is the longitudinal direction of the substrate. Represents the coercive force at. ] A magnetic recording medium characterized by having the following relationship is proposed.

As a result, it was possible to obtain a magnetic recording medium having no difference in input / output characteristics due to the forward and reverse directions of the medium.

By the way, since such a medium has a large characteristic deterioration due to spacing loss, it is necessary to make the surface as smooth as possible.

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

In this case, 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.

For this reason, in order to reduce the friction on the surface, it has been attempted to perform surface treatment on the substrate or dispose fine particles, but even with these, physical properties such as running friction, running durability and running stability, and electromagnetic characteristics It is still insufficient in terms of conversion characteristics.

That is, it is a magnetic recording medium that does not cause a difference in the input / output characteristics due to the forward and reverse of the running direction of the medium, has low running friction, high running durability, and high running stability, and is a magnetic recording medium that can eliminate head adhesion and head clogging. The recording method has not been realized yet.

II Object of the Invention The object of the present invention is to improve the physical properties such as friction durability running property and running stability in a magnetic recording method using a metal thin film type magnetic recording medium, and to the extent of not hindering the physical properties. It is an object of the present invention to provide a magnetic recording method that eliminates adhesion and clogging, and that does not cause any inconvenience in terms of electromagnetic conversion characteristics, and that has a small difference between input and output with respect to the forward and reverse directions of the medium.

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

That is, the present invention provides a magnetic recording method for recording / reproducing a magnetic recording medium having a ferromagnetic metal thin film layer containing Co as a main component on a flexible substrate by using a magnetic head. a is 0.
1 to 0.5, and the medium surface has an average of 10 ⁵ / mm ²
a Has ^two or more protrusions, and the protrusion is 30 to 300Å
Furthermore, when the coercive force is measured while changing the direction on a plane defined by the longitudinal direction of the base and the normal to the main surface of the base, (Hc max-Hc min) / Hc ( O) ≦ 0.9 [Here, Hc max represents the maximum value of coercive force, Hc min represents the minimum value of coercive force, and Hc (O) represents coercive force in the longitudinal direction of the substrate. ] It is a magnetic recording method characterized by having the following relationship.

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

The magnetic recording medium used in the present invention has a ferromagnetic metal thin film layer on a substrate.

The ferromagnetic metal thin film layer in the present invention is made of Co, Co-Ni, Co-Cr, Co-Ti, Co-M.
o, Co-V, Co-W, Co-Re, Co-Ru, C
Various known compositions such as o-Mn, Co-Fe, and Fe may be used, and the formation method thereof may be vapor deposition, ion plating, or the like.

However, the effect of the present invention is greatest when the magnetic layer has a composition containing Co as a main component and optionally 1 to 3 of Ni, Cr, and O contained therein.

That is, it may be composed of Co alone or may be composed of Co and Ni.

When Co + Ni, the weight ratio of Co / Ni is 1.5.
The above is preferable.

Further, O may be contained in addition to Co or Co + Ni. When O is contained, more preferable results can be obtained in terms of changes in electromagnetic conversion characteristics over time and running durability.

In such a case, the atomic ratio of O / Co (when Ni is not included) or O / (Co + Ni) is preferably 0.5 or less, more preferably 0.01 to 0.5.

On the other hand, in the ferromagnetic metal thin film layer, Co, Co + Ni, C
When Cr is contained in addition to o + O or Co + Ni + O, even more preferable results are obtained.

This is because the electromagnetic conversion characteristics are improved, the output and the S / N ratio are improved, and the film strength is further improved.

In such a case, Cr / Co (when Ni is not included)
Alternatively, the weight ratio of Cr / (Co + Ni) is preferably 0.1 or less, and particularly preferably 0.001 to 0.1.

Then, a more preferable result is obtained when the weight ratio of Cr / Co or Cr / (Co + Ni) is 0.005 to 0.05.

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

Such a ferromagnetic metal thin film layer usually has a thickness of 0.05-0.
The thickness is 5 μm, more preferably 0.07 to 0.3 μm.

Usually, such a ferromagnetic metal thin film layer is preferably composed of an aggregate of cast crystal grains inclined with respect to the normal line of the main surface of the substrate.

In such a case, the columnar crystal grains are preferably inclined at an angle of 30 ° or more with respect to the normal line of the main surface of the base.

Each columnar crystal grain has a length over the entire thickness direction of the ferromagnetic metal thin film layer, and its minor axis is about 50 to 500Å.

The inclination angle of the columnar crystal grains on the substrate side with respect to the normal to the substrate main surface is preferably larger than the inclination angle of the columnar crystal grains on the side opposite to the substrate with respect to the normal to the substrate main surface.

Co, Ni, Cr, etc. are present in the crystal grains, and O is mainly present on the surface of each columnar crystal grain.

In this case, O is preferably present in the form of oxide on the surface of the ferromagnetic metal thin film layer.

Under such a premise, when the coercive force is measured while changing the direction on a plane defined by the longitudinal direction of the base body and the normal direction of the main surface of the base body, Hc max, Hc min, and Hc (O) Must be (Hc max −Hc min) / Hc (O) ≦ 0.9.

If this value exceeds 0.9, a large input / output difference of 2 dB or more will occur when the traveling direction of the medium is changed, which is not practical.

When this value is 0.6 or less, the input / output difference with respect to the forward / reverse traveling is extremely small.

On the other hand, if this value exceeds 0.6, the corrosion resistance will be critically lowered and it will not be practical.

When this value is 0.4 or less, the input / output difference with respect to the forward and reverse running is extremely small, and the corrosion resistance is extremely high.

On the surface of such a ferromagnetic metal thin film layer, if necessary,
Various top coat layers can be provided.

The substrate for forming the ferromagnetic metal thin film layer is not particularly limited as long as it is a long and non-magnetic substrate, and is particularly flexible substrate, particularly made of resin such as polyester or polyimide. It is 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 used in the present invention having such a structure, 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 not be measured with a stylus type surface roughness meter, but can be observed with a scanning or transmission electron microscope.

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 ,
More preferably, it is 2 × 10 ⁶ / a ² to 1 × 10 ⁹ / a ² .

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

And, a is 0.1 to 0.5 μm, especially 0.1 to 0.4
μm.

When the protrusion density is 10 ⁵ / a ² pieces / mm ² , more preferably less than 2 × 10 ⁶ / a ² pieces mm ² , noise increases and still characteristics deteriorate, resulting in deterioration of physical properties. Can not stand.

On the other hand, 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 may be 30 to 300 Å, especially 50 to 250 Å, whereby fine protrusions corresponding to the particle size are formed.

The fine particles used are those generally known as colloidal particles, for example, SiO ₂ (colloidal silica), Al ₁ 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 coating liquid may be provided as a top coat layer instead of being provided 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 nonmagnetic 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.

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

Usually, a vapor-deposited cylindrical can is used for vapor deposition, and a vapor deposition mask is interposed between the can and 90 to 20 °, more preferably 90 to 40, with respect to the normal to the main surface of the substrate.
It is preferable to gradually reduce the incident angle during film formation so that the incident angle becomes °.

In such a case, in order to have the above-mentioned angular dependence of the coercive force, for example, a plurality of hearths or crucibles are arranged in a direction perpendicular to the feeding direction of the base body, that is, in the width direction of the base body. There are methods such as changing the evaporation rate.

In addition, vapor deposition conditions other than this are not particularly limited.

That is, the deposition atmosphere is usually argon, helium,
An inert atmosphere such as vacuum, and 10 ^-5 to 10 0 ^Pa pressure of about, also deposition distance, the substrate transport direction, the structure of the can and the mask, arrangement and the like may be the same as known conditions.

However, it is preferable that oxygen is contained in the vapor deposition atmosphere to improve electromagnetic conversion characteristics and corrosion resistance.

In addition, oxygen can be introduced into the ferromagnetic metal thin film layer at any magnetism during vapor deposition by various methods.

Then, various oxidation treatments can be performed even after the ferromagnetic metal thin film layer is formed.

Furthermore, heat treatment can be performed after the ferromagnetic metal thin film layer is formed.

On the other hand, various magnetic heads can be used.

In this case, as the magnetic head, it is preferable that at least the end surface of the gap portion is made of a magnetic metal material.

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

As a result, it becomes extremely good, and head adhesion and head clogging become good.

The shape, structure, etc. may be known.

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

Various ferromagnetic materials can be used, and any of amorphous magnetic metals, sendust, hard permalloy, thin films such as permalloy, and thin plates 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 The magnetic recording method of the present invention is useful as a medium for video, audio, computer, and the like. According to the invention,
The difference between input and output due to the forward and reverse of the traveling direction of the medium is extremely small.

Further, the 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 further 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.

V Specific Examples of the Invention Hereinafter, specific examples of the present invention will be described in detail.

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 with a height of 150Å and a density of 10 ⁷ pieces / mm ² .

Next, when the weight ratio of Co and Co / Ni is 4/1,
And an alloy having a Co / Ni / Cr weight ratio of 65/30/5 was used.
A 15 μm ferromagnetic metal thin film layer was formed.

The substrate is continuously transported by a can, and the incident angle of the vapor deposition substance is set to 90.
Taper to ~ 40 °. The distance between the evaporation source and the can is 2
It was set to 00 mm. Then, vapor deposition was performed in an atmosphere in which P = 5 × 10 ⁻³ Pa and oxygen of P = 2 × 10 ⁻¹ Pa were introduced into this.

In this case, the melting area of the hearth was set to 25 cm ^2, and three hearths were arranged, one at the center of the substrate and one at two points 20 mm apart from the center of the substrate.

Of the evaporation rates from these three hearths, the evaporation rates of both hearths in the end direction of the substrate are the same, and the ratio of the evaporation rate of the hearths in the end direction and the evaporation rate of the central hearth is changed as shown in Table 1 below. went.

(Hc max-Hc mi of the sample prepared in this way
n) / Hc (O) is shown in Table 1.

In each of the samples, the magnetic layer has a length over the entire thickness direction of the magnetic layer and is composed of an aggregate of columnar crystal grains inclined with respect to the normal to the substrate. The tilt angle with respect to the line was larger than that of the surface side portion.

The oxygen content of each sample was obtained by introducing O ₂ into the atmosphere, and O / (Co or Co + Ni) = 18 to 20
%, Without introducing O ₂ , it was about 1%.

Next, each sample was cut into a 1/2 inch width, and a tape was produced from the central portion.

The magnetic head used is that shown in FIG. 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.
The thickness was Co0.8Ni0.1Zr0.1 (atomic ratio) with a thickness of μm, and the gap material was glass.

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

Then, the following measurements were performed on each sample.

(1) Input / output difference The input / output at 4.5 MHz in both running directions was measured by mounting it on a commercially available VHS type VCR, and the difference between the maximum values was determined.

The results are shown in Table 1.

Example 2 The sample of Example 1 was heat-treated in air at 85 ° C. for 1 hour.

Table 2 shows the input / output difference.

Further, each sample was allowed to stand at 60 ° C. and 90% relative humidity for 7 days, and −Δφm / φ (%) per cm ² was measured.

The results are shown in Table 2.

From the results shown in Table 1 and Table 2, the effect of the coercive force distribution in the present invention is clear.

Example 3 In a sample obtained by vapor deposition of the Co / Ni alloy of Example 1 in an oxygen atmosphere, colloidal silica was applied onto a substrate,
The fine protrusions shown in Table 3 below were provided.

In the sample of the present invention, the effect of colloidal silica coating was not detected by observation with an optical microscope and measurement with a stylus type surface roughness meter, but when observed at a high magnification by a scanning electron microscope, protrusions were formed on the magnetic film. Seen, the size is
It corresponded to the size of the applied colloidal silica.

Table 3 shows the relationship between the height and density of the protrusions on the surface of the magnetic layer and the characteristics.
Shown in.

Experiments were conducted using signals having characteristics and the shortest recording wavelength of 0.7 μm.

The magnetic head used is that shown in FIG. 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 Co0.8, Ni0.1, Zr0.1 (at%)
The gap material was glass.

10 ⁵ / a ² is 1.6 × 10 ⁶ (mm ² ) ^-1 .

A ferrite head was used as a magnetic head for comparison.

The method of measuring the characteristics is as follows.

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. 1
Set the OK level to 0 minutes or more.

3. 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.

4. Noise Measure the noise (dB) at 4MHz in the playback output measurement.

5. Surface condition after endurance running test The condition of the tape surface after running for 50 passes is observed with an optical microscope.

○: No change △: Damage to magnetic surface ×: Missing magnetic layer As a result of Auger spectroscopic analysis, it was found that the surface of the magnetic layer in each of these Examples was covered with an oxide layer of 100 to 200 Å.

Sample No. Reference numeral 33 denotes a magnetic layer containing no oxygen by vapor deposition in an atmosphere containing no oxygen.

In each of the above examples, colloidal silica was used as the inorganic fine particles, but the same result was obtained even if other substances such as alumina sol, titanium black, zirconia or various hydrosols were used.

Similar results were obtained when a head made of Co-Fe-Ru-Cr-Si-B based amorphous was used.

It should be noted that when a head made of Sendust was used, the effect was slightly less than that in the above case.

The combination of the tape and the head according to the present invention was superior to the other combinations in terms of physical properties, the friction coefficient in each atmosphere was stable and low, and the durability and running characteristics were far superior.

[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 (14)

[Claims] 1. A magnetic recording method for recording and reproducing a magnetic recording medium having a ferromagnetic metal thin film layer containing Co as a main component on a flexible substrate by using a magnetic head. a is 0.
1 to 0.5, and the medium surface has an average of 10 ⁵ / mm ²
a Has ^two or more protrusions, and the protrusion is 30 to 300Å
Furthermore, when the coercive force is measured while changing the direction on a plane defined by the longitudinal direction of the base and the normal to the main surface of the base, (Hc max-Hc min) / Hc ( O) ≦ 0.9 [Here, Hc max represents the maximum value of coercive force, Hc min represents the minimum value of coercive force, and Hc (O) represents coercive force in the longitudinal direction of the substrate. ] The magnetic recording method characterized by having the following relationship. 2. The magnetic recording method according to claim 1, wherein at least the end surface of the gap portion of the magnetic head is made of a metal ferromagnetic material. 3. The magnetic recording method according to claim 2, wherein the metal ferromagnet is an amorphous magnetic alloy containing Co as a main component. 4. A magnetic recording medium, wherein a flexible substrate is made of a polymer, fine particles having a diameter of 30 to 300Å are arranged on the substrate, and a ferromagnetic metal thin film layer is formed thereon. The magnetic recording method according to any one of claims 1 to 3, which is provided. 5. The ferromagnetic metal thin film layer is Co or Co
5. The magnetic recording method according to any one of claims 1 to 4, which contains 1 to 3 of Ni, Cr and O as main components. 6. A ferromagnetic metal thin film layer containing Ni, Co /
The magnetic recording method according to any one of claims 1 to 5, wherein the weight ratio of Ni is 1.5 or more. 7. The ferromagnetic metal thin film layer contains Cr, and Cr /
(Co or Co + Ni) weight ratio is 0.001 to 0.
7. The magnetic recording method according to claim 1, wherein the magnetic recording method is 1. 8. The ferromagnetic metal thin film layer contains O, and O / (C
8. The magnetic recording method according to claim 1, wherein the atomic ratio of o or Co + Ni) is 0.45 or less. 9. The magnetic recording method according to claim 8, wherein the atomic ratio of O / (Co or Co + Ni) is 0.01 to 0.5. 10. The magnetic recording method according to claim 1, wherein the ferromagnetic metal thin film has a layer of an oxide of a ferromagnetic metal on the surface. 11. A ferromagnetic metal thin film having a thickness of 0.05 to 0.
The magnetic recording method according to any one of claims 1 to 10, which has a thickness of 5 μm. 12. The magnetic recording according to claim 1, wherein the ferromagnetic metal thin film layer is composed of an aggregate of columnar crystal grains inclined with respect to the normal line of the main surface of the substrate. Method. 13. A tilt angle of a columnar crystal grain on a substrate side with respect to a normal line of a substrate main surface is larger than a tilt angle of a columnar crystal grain on a side opposite to a substrate with respect to a normal line of a substrate main surface. 13. The magnetic recording method as described in any one of 1 to 12 above. 14. The magnetic recording method according to any one of claims 1 to 13, wherein (Hc max-Hc min) / Hc (O) ≦ 0.6.