JPH11259844A - Magnetic recording medium - Google Patents

Abstract

PROBLEM TO BE SOLVED: To obtain a magnetic recording medium usable as a large-capacity removable magnetic recording medium having good magnetic characteristics and surface characteristics. SOLUTION: This magnetic recording medium is constituted by forming a planarization layer 0.1 to 5.0 μm thick consisting of a heat resistant high- polymer material, a barrier layer consisting of a Cr-O based thin film contg. 5 to 40 atom.% oxygen and a ferromagnetic layer consisting of a nonmagnetic ground surface layer consisting of a Cr alloy and a Co-Cr based alloy deposited by a sputtering method in this order on at least one surface of a flexible nonmagnetic base 30 to 100 μm thick.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

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 medium having a high recording density, which relates to a removable magnetic recording medium used for an auxiliary storage device and an image storage device of a computer.

[0002]

2. Description of the Related Art Along with the increase in the capacity of electronic data created by a personal computer or the like, a removable disk comprising a high-capacity magnetic recording medium for storing and backing up a large amount of electronic data is desired. In addition, digital video tapes have been mainly used as ultra-high-density recording media for business use.
There is a demand for recording and playback speed. In view of the above, instead of the current mainstream video tape, a removable disk having an excellent recording / reproducing speed is being studied as a digital recording medium for business use.

[0003] Existing gigabyte-class large-capacity removable magnetic recording media use a hard disk using a glass or aluminum disk as a substrate. Therefore, if a large impact is applied during operation of the apparatus, a head crash occurs, and both the magnetic recording medium and the head are greatly damaged. This problem of shock resistance has not been solved yet in the case of a removable hard disk, and it is considered that this is one of the causes of the spread of configurable devices using a removable large-capacity recording medium.

When a flexible member similar to a floppy disk is used as a support for a removable high-density magnetic recording medium, vibrations may be applied when the removable disk is transported in a plastic cartridge or the like. Alternatively, it is considered that a device capable of stably storing data can be obtained without causing a displacement of the magnetic head and a crash of the magnetic layer surface due to an impact of the magnetic head due to the insertion / removal into / from the driving device. In a high-density recording medium of the order of 100 Mbytes, similar to a floppy disk using a flexible support, in order to achieve a large capacity and a high recording density, the spacing loss between the head and the magnetic recording medium is minimized. It is necessary. Therefore, the magnetic recording medium is required to have improved surface properties.

However, since the flexible support used as the substrate is made of synthetic resin, the surface is not good,
It is difficult to obtain surface properties equivalent to those of a substrate for a hard disk only by processing such as polishing of the surface of the flexible support.
Therefore, a heat-resistant polymer resin is applied on the support to provide a flattening layer to improve the surface properties of the support.

On the other hand, in a high-density magnetic recording medium, a ferromagnetic layer formed on the surface of the magnetic recording medium forms a magnetic film by using a vacuum film forming method. There are various methods for vacuum film formation. In a rotating recording medium such as a floppy disk, the orientation of magnetic particles constituting the ferromagnetic layer is randomly or preferably circumferentially oriented in the plane of the ferromagnetic layer. However, such a magnetic thin film is manufactured by sputtering.

[0007] In sputtering, the support is 50 to 25
Although there is a step of heating to 0 ° C., when the temperature of the support increases due to the heat applied to the nonmagnetic support in such a step, the adhesion between the support and the flat layer is reduced, and the film is peeled off. In addition, the heat applied to the support deforms the support, and the deformation of the support or the deformation of the support significantly reduces durability and electromagnetic conversion characteristics. In addition, when a large amount of gas is released from the support by heating in the film forming process, this gas affects the formation of the underlayer and the ferromagnetic layer during vacuum film formation, and the magnetostatic properties, surface properties,
Electromagnetic conversion characteristics have remarkably deteriorated, and deterioration of characteristics as a magnetic recording medium has been a serious problem.

[0008]

SUMMARY OF THE INVENTION An object of the present invention is to provide a magnetic recording medium which can be used in a removable mass storage device.
It is an object of the present invention to provide a magnetic recording medium having a ferromagnetic layer having good surface properties.

[0009]

According to the present invention, a thickness of 30 to 30 mm is provided.
At least one surface of the flexible non-magnetic support having a thickness of 100 μm is made of a heat-resistant polymer and has a thickness of 0.1 to 5.0 μ.
m-leveling layer, Cr- containing 5 to 40 atomic% oxygen
This is a magnetic recording medium in which an O-based barrier layer, a non-magnetic underlayer made of a Cr alloy, and a ferromagnetic layer made of a Co-Cr-based alloy formed by a sputtering method are formed in this order.

[0010]

BEST MODE FOR CARRYING OUT THE INVENTION The present inventors provided an underlayer on a nonmagnetic support, and formed a flat layer on the underlayer in order to improve the surface properties of the ferromagnetic layer formation surface. In addition, by providing a barrier layer between the underlayer and the flattening layer, the peeling of the film, deformation of the support, underlayer and magnetostatic properties, granularity of the ferromagnetic layer, and surface roughness are significantly improved. The present invention has been found. That is, the present invention provides a flattening layer made of a heat-resistant polymer having a thickness of 0.1 to 5.0 μm on at least one surface of a flexible support having a thickness of 30 to 100 μm; An oxide barrier layer made of chromium or chromium alloy containing 5 to 40 atomic% of oxygen, a nonmagnetic underlayer made of a chromium alloy, and a cobalt-chromium alloy ferromagnetic layer formed on the nonmagnetic underlayer And a protective layer and a lubricating layer are further formed on the magnetic recording medium. Since the magnetic recording medium of the present invention has the barrier layer, the magnetic recording medium has excellent characteristics by preventing the gas generated from the support from adversely affecting the crystal orientation of the ferromagnetic layer due to heat applied during the manufacture of the magnetic recording medium. It is characterized in that a film can be formed.

[0011] The support of the magnetic recording medium of the present invention includes:
Materials such as polyethylene terephthalate, polyethylene naphthalate, polyimide, polyamide, polyamide imide, and polybenzoxazole can be given. The Young's modulus of the support of the magnetic recording medium of the present invention is 20
It is preferably from 0 to 1600 kg / mm ² , and particularly preferably from 300 to 800 kg / mm ² . Support thickness is 20
To 150 μm, more preferably 30 to 80 μm
m.

In order to improve the surface properties of the support, a flattening layer is provided on the support. A heat-resistant polymer material can be widely used for the flattening layer. Particularly preferably silicone resin, polyamide resin, polyamide imide resin,
It is a material such as a polyimide resin. These materials are not only excellent in heat resistance, but also can achieve good surface properties and magnetostatic properties. The coating thickness of the flattening layer is 0.1
５5.0 μm, preferably 0.5-3.0 μm,
Particularly preferably, it is in the range of 0.8 to 2.0 μm. Minute protrusions such as SiO ₂ , Al ₂ O ₃ , T
iO ₂ etc. or organic fine particles are or organic fine particles may be provided.

As a material of the Cr—O-based thin film of the barrier layer,
A chromium oxide and a chromium alloy oxide containing oxygen in a chromium alloy can be given. As the chromium alloy oxide, for example, Ti, W, Mo, V, Ta, B, Si, N
An alloy oxide containing at least one element of b, Zr, and Mo is preferable. The amount of oxygen contained is 5
It is 40 at%, preferably 7 to 30 at%, more preferably 10 to 20 at%. The Cr concentration is 42 to 95 atomic%, preferably 49 to 93 atomic%, more preferably 56%.
９０90 at%.

The Cr—O-based thin film of the barrier layer can be formed by sputtering in an atmosphere containing argon and oxygen. The total partial pressure of argon and oxygen in the sputtering atmosphere is 1 to 20 mTorr, preferably 1 to 20 mTorr.
8 mTorr. The degree of oxidation in the chromium oxide or chromium alloy oxide can be adjusted by the oxygen partial pressure in the total pressure. The ratio of oxygen partial pressure to total pressure is 5 to 75
%, Desirably 10 to 65%. If the oxygen content of the Cr—O-based thin film is less than 5 atomic%, the heat resistance becomes insufficient and the function of the barrier layer is not fulfilled. On the other hand, if it exceeds 40 atomic%, the adhesion to the underlying layer formed thereon is undesirably reduced.

The thickness of the barrier layer is 10 to 100 nm, preferably 15 to 80 nm, and more preferably 20 to 100 nm.
６０60 nm. When the thickness of the underlayer is reduced to 10 nm or less, the barrier layer structure becomes discontinuous and does not serve as a barrier. If the thickness is more than 100 nm, the film stress of the barrier layer increases, and cracks, film peeling, etc. occur on the magnetic recording medium. The oxide barrier layer can be formed by direct-current sputtering of an underlayer metal in an atmosphere of argon and oxygen. The amount of oxygen added in the barrier layer is adjusted by the oxygen partial pressure during sputtering. The temperature of the support during the preparation of the barrier layer is 5 to 8
0 ° C., preferably 10 to 70 ° C., particularly preferably 20 to 60 ° C.

As a material for the underlayer, chromium or chromium and Ti, W, Mo, V, Ta, B, Si, Nb, Z
An alloy containing at least one metal of r and Mo is preferable. The Cr concentration of the underlayer is 70 to 100 at%,
It is preferably from 75 to 98 at%, particularly preferably from 80 to 98 at%.
95 at%, with the balance being other elemental metals.

The chromium alloy serving as the underlayer may contain a small amount of a nonmetallic component other than the above metal component. For example, there are gas components such as oxygen, nitrogen, and argon contained in the atmosphere during the film formation, and impurity components in the metal raw material. However, it is particularly necessary to ensure that the gaseous components do not exceed 5 atomic% in the alloy. The thickness of the nonmagnetic underlayer is 5 nm to 500 nm, preferably 10 to 300 nm.
nm, more preferably 20 to 100 nm. When the thickness of the underlayer is increased to 100 nm or more, the grain size of the ferromagnetic layer increases, and the medium noise increases.

As the magnetic material, a cobalt chromium alloy is preferable, and in particular, Pt, Ta, Ni, Si, B, Ni, P
d-containing cobalt-chromium alloy. Among these, CoCrPt and CoCrPtTa are particularly preferred. This is because both output and noise characteristics are excellent. Barium ferrite other than the cobalt chromium alloy can be used. The Cr concentration in the ferromagnetic layer is 1
0 to 30 atomic%, preferably 12 to 28 atomic%,
More preferably, it is 15 to 25 atomic%. By specifying the Cr concentration of the underlayer made of a chromium alloy within the above range, it is possible to make the crystal orientation of the ferromagnetic layer formed thereon a preferable mode and realize good magnetic properties. The thickness of the ferromagnetic layer is 5 to 300 nm, preferably 10 to 140 nm.
nm, more preferably 15 to 60 nm.

The barrier layer, the underlayer and the ferromagnetic layer are preferably provided by a vacuum film forming method. In particular, sputtering is preferable because a film can be formed without changing the composition of many elements.
It is preferable that the barrier layer, the underlayer, and the ferromagnetic layer be continuously formed in a vacuum state.

On the magnetism, a plasma CV is used as a protective film.
It is preferable to provide a carbon film made of an amorphous structure, a graphite structure, a diamond structure, or a mixture thereof prepared by the method D, the sputtering method, or the like. Particularly preferred is a hard amorphous carbon film generally called diamond-like carbon. This hard carbon film has a Vickers hardness of 1000 kg / mm ² or more, preferably ² kg / mm ² or more.
It is a hard carbon film of 000 kg / mm ² or more.

In the magnetic recording medium of the present invention, in order to improve running durability and corrosion resistance, it is preferable to add a lubricant or a rust inhibitor to the magnetic film or the protective film. As the lubricant, known hydrocarbon-based lubricants, fluorine-based lubricants, extreme pressure additives and the like can be used. Examples of the hydrocarbon-based lubricant include carboxylic acids such as stearic acid and oleic acid, esters such as butyl stearate, sulfonic acids such as octadecylsulfonic acid, phosphoric esters such as monooctadecyl phosphate, stearyl alcohol, oleyl alcohol and the like. Alcohols, carboxylic acid amides such as stearic acid amide, and amines such as stearylamine.

Examples of the fluorine-based lubricant include lubricants in which part or all of the alkyl group of the hydrocarbon-based lubricant is replaced 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 ) C
F ₂ O) _n or a copolymer thereof.

Examples of extreme pressure additives include phosphates such as trilauryl phosphate, phosphites such as trilauryl phosphite, thiophosphites and thiophosphates 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 a magnetic film or a protective film, a lubricant is dissolved in an organic solvent and applied by a wire bar method, a gravure method, a spin coating method, a dip coating method, or a vacuum evaporation method. What is necessary is just to make it adhere. The amount of the lubricant to be applied is 1 to 30 mg / m ^2.
Preferably, 2 to 20 mg / m ² is particularly preferred.

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

[0026]

The present invention will be described below with reference to examples and comparative examples of the present invention. Example 1 A flattening layer made of a silicone resin was formed on both surfaces of a film made of a polyethylene naphthalate resin having a thickness of 63 μm.
On a flexible support coated to a thickness of 0 μm, by direct current sputtering, 2.5 mTorr of argon and 0.1 m 2 of oxygen were added.
5mTorr, input power 1400W, support temperature 20 ° C
Under the conditions described above, a (CrTi ₂₀ ) ₈₅ O ₁₅ oxide containing 15 atomic% of oxygen was formed to a thickness of 50 nm as a barrier layer. Next, a chromium alloy containing 20 atomic% of titanium was coated as a nonmagnetic underlayer to a thickness of 60 nm by DC sputtering. Next, a 30 nm-thick cobalt-chromium alloy thin film containing 20 atomic% of chromium and 12 atomic% of Pt was coated as a metal magnetic medium on the metal underlayer by DC sputtering. For the protective layer, carbon was sputtered at an argon pressure of 3 mTorr and an input power of 700 W to form an amorphous carbon film having a thickness of 20 nm. The temperature of the support for preparing the underlayer, ferromagnetic layer and protective layer is 1
The temperature was 50 ° C., and the underlayer was formed by a partial pressure of argon of 8 mTorr.
r, input power 1400W. When producing a ferromagnetic layer, an argon partial pressure of 1.5 mTorr and an input power of 1 were used.
The test was performed under the condition of 400 W. The protective layer has an Ar partial pressure of 3 mTo.
rr, the input power was 700 W. The properties of the obtained magnetic recording medium were evaluated by the evaluation methods described below, and the results are shown in Tables 1 and 2.

Example 2 A magnetic recording medium was manufactured in the same manner as in Example 1 except that the barrier layer was changed to (CrTi ₂₀ ) ₇₅ O ₂₅ , and evaluated in the same manner as in Example 1. Are shown in Tables 1 and 2.

EXAMPLE 3 A polyimide support having a thickness of 75 μm was coated on both sides with a polyimide resin flattening layer of 1.2 μm on a flexible support.
2.5 mTorr of argon by DC sputtering
r, oxygen 0.5 mTorr, input power 1400 W, support temperature 20 ° C., containing 15 atomic% of oxygen (C
A barrier layer of rTi ₁₀ ) ₈₅ O ₁₅ oxide having a thickness of 50 nm was formed. Next, 10 atomic% of titanium is used as a nonmagnetic underlayer.
Chromium alloy containing 60nm by direct current sputtering
Coated. Next, a ferromagnetic layer having a thickness of 20 nm was formed on the metal underlayer by a direct current sputtering method. The ferromagnetic layer was a chromium-cobalt alloy thin film containing 17 atomic% of chromium, 9 atomic% of platinum, and 4 atomic% of tantalum.

The substrate temperature at the time of forming the underlayer, the ferromagnetic layer, and the protective layer was 150 ° C.
The test was performed under the conditions of mTorr and input power of 1400 W. The ferromagnetic layer was formed under the conditions of an argon partial pressure of 1.5 mTorr and an input power of 1400 W. The protective layer was formed under the conditions of an Ar partial pressure of 3 mTorr and an input power of 700 W. The properties of the obtained magnetic recording medium were evaluated by the evaluation methods described below, and the results are shown in Tables 1 and 2.

Comparative Example 1 A magnetic recording medium was manufactured under the same conditions as in Example 1 except that the barrier layer was changed to CrTi ₂₀ alloy, and the characteristics were evaluated by the same evaluation method as in Example 1. The results are shown in Tables 1 and 2.

Comparative Example 2 A magnetic recording medium was manufactured under the same conditions as in Example 1 except that the barrier layer was changed to an oxide composed of (CrTi ₂₀ ) ₅₅ O _45, and the same evaluation method as in Example 1 was used. Evaluate the characteristics,
The results are shown in Tables 1 and 2.

Comparative Example 3 A magnetic recording medium was manufactured under the same conditions as in Example 1 except that the thickness of the barrier layer was changed to 5 nm, and the characteristics were evaluated by the same evaluation method as in Example 1. Are shown in Tables 1 and 2.

Comparative Example 4 A magnetic recording medium was manufactured under the same conditions as in Example 1 except that no barrier layer was provided, and the characteristics were evaluated by the same evaluation method as in Example 1. The results were shown in Tables 1 and 2. It is shown in FIG.

Comparative Example 5 A magnetic recording medium was manufactured under the same conditions as in Example 1 except that the temperature of the support at the time of manufacturing the barrier layer was 150 ° C.
The characteristics were evaluated by the same evaluation methods as those described above, and the results are shown in Tables 1 and 2.

Comparative Example 6 Example 1 except that the thickness of the barrier layer was changed to 150 nm.
A magnetic recording medium was manufactured under the same conditions as in Example 1, and the characteristics were evaluated by the same evaluation method as in Example 1. The results are shown in Tables 1 and 2.

Comparative Example 7 Example 3 except that the barrier layer was changed to CrTi ₁₀ alloy.
A magnetic recording medium was manufactured under the same conditions as in Example 1, and the characteristics were evaluated by the same evaluation method as in Example 1. The results are shown in Tables 1 and 2.

Comparative Example 8 A magnetic recording medium was manufactured under the same conditions as in Example 3 except that the barrier layer was changed to (CrTi ₁₀ ) ₄₀ O ₆₀ oxide, and the characteristics were evaluated by the same evaluation method as in Example 1. Was evaluated, and the results are shown in Tables 1 and 2.

Comparative Example 9 A magnetic recording medium was manufactured under the same conditions as in Example 3 except that no barrier layer was provided, and the characteristics were evaluated by the same evaluation method as in Example 1. It is shown in Table 2.

Comparative Example 10 Except that the temperature of the support at the time of preparing the barrier layer was set to 150 ° C.
A magnetic recording medium was manufactured under the same conditions as in Example 1, and the characteristics were evaluated by the same evaluation method as in Example 1. The results are shown in Tables 1 and 2.

(Evaluation Method) Evaluation test of adhesion a. Peeling test A 18 mm × 20 mm polyethylene naphthalate tape (Nitto Denko No. 31B) was applied to the prepared magnetic recording medium.
Adhering to the sample surface, peeling it off at once by hand, repeating this operation 5 times, peeling off the film that has never been peeled off "No", peeling off the film that has been peeled off once "Yes". b. Hard ball wear test A glass ball was used as a hard ball, and measurement was performed in two passes and 15 tracks. The weight was changed in 10 g weight increments. Each time a load was applied, the occurrence of scratches on the differential interference optical microscope was observed.

2. Measurement of Deformation The magnetic recording medium was punched into the same shape as the magnetic recording medium for a 3.5-inch floppy disk, and was punched to the same inner diameter as the 3.5-inch floppy disk. Insert into the bar placed in. A holding plate was installed from above, and the magnetic recording medium was fixed vertically to eliminate the influence of gravity. Using a micrometer installed in parallel with the bar to which the magnetic recording medium is fixed, measure the horizontal position of the most convex part and the most concave part of the magnetic recording medium, measure the difference as the amount of deformation, and An evaluation was performed.

3. Observation of magnetostatic characteristics Using a sample vibration magnetometer (hereinafter VSM), the coercive force (H
c), squareness ratio (SQ), and coercive force squareness ratio (S *) were measured. 4. The particle state and surface roughness (Ra) of the ferromagnetic layer were observed with an atomic force microscope (AFM).

[0043]

[Table 1]

[0044]

Table 2 Hc SQ S * Particle size Surface roughness (Oe) (nm) (nm) Example 1 3025 0.86 0.82 21 0.386 Example 2 2760 0.87 0.79 25 0.392 Example 3 2535 0.82 0.71 20 0.367 Comparative Example 1 2439 0.83 0.75 28 0.427 Comparative Example 2 2730 0.68 0.65 31 0.542 Comparative Example 3 2758 0.72 0 .70 30 0.695 Comparative Example 4 2119 0.68 0.70 38 0.725 Comparative Example 5 2907 0.81 0.79 25 0.672 Comparative Example 6 3010 0.85 0.79 27 0.432 Comparative Example 7 2350 0.72 0.65 23 0.524 Comparative Example 8 2218 0.75 0.51 22 0.325 Comparative Example 9 1928 0.75 0.69 31 0.61 Comparative Example 10 2390 0.81 0.75 24 0.327

[0045]

According to the present invention, by providing a barrier layer on a flattened layer formed on a non-magnetic support, gas components are generated from the non-magnetic support in the film forming process under vacuum, and the film is formed. It is possible to obtain a magnetic recording medium having good magnetic properties and good surface properties of the magnetic material without adversely affecting the properties.

Claims (1)

[Claims] 1. A flattening layer having a thickness of 0.1 to 5.0 μm made of a heat-resistant polymer material on at least one surface of a flexible nonmagnetic support having a thickness of 30 to 100 μm. A barrier layer composed of a Cr—O-based thin film containing 40 atomic% of oxygen,
A magnetic recording medium comprising a non-magnetic underlayer made of a Cr alloy and a ferromagnetic layer made of a Co-Cr alloy formed by a sputtering method in this order.