JP2002032908A - Magnetic recording medium - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a magnetic recording medium using a substrate made of synthetic resin and having high recording density. SOLUTION: The magnetic recording medium constituted of a base layer, a magnetic layer, a protective layer and a lubricating layer laminated on at least one side of the substrate made of the synthetic resin is provided with a seed layer formed in an island shape and has a portion where the seed layer is not formed between the substrate made of the synthetic resin and the base layer.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a removable magnetic recording medium used for an auxiliary recording device or an image recording device of a computer, and has a high recording density of 1.6 terabits per square meter (gigabits per square inch) or more. And a floppy (registered trademark) disk.

[0002]

2. Description of the Related Art Tape-shaped magnetic recording media such as digital video tapes have been used as high-density recording media for large-capacity digital information such as auxiliary storage of computers. There is a demand for higher capacity and higher recording or reproduction speed. Due to these demands, a removable hard disk has recently been used as a large-capacity, high-density digital recording medium. However, the existing gigabyte-class removable media uses rigid disc-shaped substrates such as glass and aluminum, so when an impact is applied to the device, the media itself cannot absorb the impact, causing a head crash. However, both the magnetic recording medium and the head were sometimes seriously damaged. For this reason, those using a rigid substrate such as a removable hard disk have not yet solved the problem of impact resistance, and have problems in using a magnetic recording medium using the rigid substrate in a portable device. This is one of the problems in the spread of portable devices such as digital disk cameras using a magnetic recording medium using a rigid base.

[0003] By changing a rigid base to a flexible base, a magnetic recording medium can be reduced in weight of a recording portion, reduced in damage at the time of head crash, and realized a high-density removable magnetic recording medium excellent in impact resistance. It is possible. Therefore, the applicant has
We are developing ultra-high recording density recording media using synthetic resin substrates with low height, especially flexible substrates. The magnetic layer for high density recording is formed by a vacuum film forming method. When a vacuum film forming method is used for forming a magnetic layer of a floppy disk, a magnetic layer having a high magnetic recording density can be manufactured. In a manufacturing process of a rigid magnetic recording medium by a vacuum film forming method, the temperature of the substrate may rise to a region of 50 to 300 ° C. A metal such as aluminum, silicon oxide, a ceramic disk, or the like is used for the substrate. With these materials, the amount of gas emitted by heating the substrate is small, and the material is hardly affected by the gas emitted from the substrate due to the temperature rise of the substrate.

[0004] Synthetic resin substrates, particularly flexible substrates, contain gases such as water and hydrogen in the manufacturing process. Therefore, when the substrate is heated, a large amount of gas is generated, and the adhesion between the substrate and the deposited film is reduced when the underlayer or the magnetic layer is formed by vacuum film formation. When the adhesion was reduced, the running durability of the magnetic recording medium was significantly reduced. On the other hand, in order to improve the adhesion, it is effective to provide an adhesion layer below the nonmagnetic underlayer. However, since the adhesion layer affects the crystal orientation of the underlayer and the magnetic layer, or even the electromagnetic conversion characteristics, there is a limitation that an optimum material is selected in consideration of lattice matching. In the case of a magnetic recording medium using a synthetic resin substrate, which is often degassed from the substrate, materials that can be used as the adhesion layer are limited. Therefore, there is a problem that matching of lattice orientation between the underlayer and the magnetic layer cannot be optimized.

[0005]

SUMMARY OF THE INVENTION The present invention provides a magnetic recording medium using a synthetic resin substrate, which prevents a decrease in adhesion between a magnetic layer or the like formed by vacuum film formation and the synthetic resin substrate. An object of the present invention is to provide a magnetic recording medium in which matching of lattice orientation between a magnetic layer and an underlayer is optimized.

[0006]

SUMMARY OF THE INVENTION An object of the present invention is to provide an underlayer, a magnetic layer, a protective layer,
In a magnetic recording medium having a configuration in which a lubricating layer is laminated, a seed layer is provided between a synthetic resin substrate and a base layer, and the seed layer has an island-like structure, and a portion where the synthetic resin substrate and the base layer are in direct contact is formed. The problem can be solved by a magnetic recording medium having the above. In addition, the thickness of the synthetic resin substrate is 30 to 1
The magnetic recording medium is in the range of 00 μm. The above magnetic recording medium, wherein the thickness of the seed layer is in the range of 5 to 25 nm. The seed layer is formed in an island shape, and the area occupancy of the seed layer material is 80% to 9% of the surface area of the synthetic resin substrate.
The magnetic recording medium is 8%. The above magnetic recording medium uses an alloy containing Co as a main component and having a Cr concentration in a range of 10 to 30 at% as a magnetic layer. C as base layer
The above magnetic recording medium using a Cr alloy having an r concentration of 77 to 100 at%. The above magnetic recording medium is formed on both surfaces of a synthetic resin substrate.

[0007]

BEST MODE FOR CARRYING OUT THE INVENTION In a magnetic recording medium having a structure in which an underlayer, a magnetic layer, a protective layer, and a lubricating layer are laminated on at least one of a synthetic resin substrate, the present inventors have an island between the synthetic resin substrate and the underlayer. The present inventors have found that the provision of the seed layer having the shape of a letter can improve both the adhesion between the synthetic resin substrate and the metal thin film and the crystal orientation of the metal thin film at the same time. When forming by vacuum film formation on a synthetic resin substrate, it is necessary to heat the substrate at a temperature of 50 to 250 ° C. in order to secure magnetostatic characteristics and electromagnetic conversion characteristics. A metal such as aluminum or a disk such as glass, silicon oxide or ceramic is used for a substrate of a hard disk. These materials have basically high adhesion between deposited films, and also emit less gas from the substrate when the substrate is heated during film formation. For this reason, there was almost no decrease in adhesion due to heating, and in the case of a hard disk, the decrease in adhesion during substrate heating did not become a major problem.

However, in the case of a synthetic resin substrate, the substrate contains a gas such as water or hydrogen. Therefore, when the substrate is heated, gas is generated, and the adhesion between the substrate and the deposited film is reduced. When the adhesion is reduced, the running durability of the magnetic recording medium may be significantly reduced. In order to improve the adhesion, it is effective to form an adhesion layer under a seed layer formed on a synthetic resin substrate. However, since the adhesion layer affects the crystal orientation of the seed layer, the underlayer, and the magnetic layer and, at the very least, the electromagnetic conversion characteristics, there is a limitation that an optimum material is selected in consideration of lattice matching. For these reasons, in a magnetic recording medium using a synthetic resin substrate, a material that can be used as an adhesion layer is limited. Therefore, the underlayer
The lattice matching of the magnetic layer could not be optimized.

Therefore, the present invention provides a seed layer formed on a synthetic resin substrate in an island shape so as not to completely cover the synthetic resin substrate surface. In part, the substrate is brought into direct contact with the surface of the synthetic resin substrate, and the adhesion of the underlying layer is fully utilized. In particular, when a Cr alloy is used as the underlayer, a high adhesion is obtained, so that the effect of enhancing the adhesion is increased. In addition, the seed layer having an island structure can be formed by changing film forming conditions such as adjusting a partial pressure of gas in an atmosphere during vacuum film formation. Instead, they form island structures. By forming the nonmagnetic underlayer after the seed layer is formed in an island shape, a region where the synthetic resin substrate and the nonmagnetic underlayer are bonded across the seed layer can be realized.

If the area occupancy of the island portion of the seed layer is small relative to the surface area of the synthetic resin substrate, the adhesion is improved,
The effect of improving the crystal orientation by the seed layer is reduced. Conversely, if the area occupancy of the islands is too high, the effect of improving the crystal orientation is improved, but the adhesion is reduced.
In the magnetic recording medium of the present invention, both the crystal orientation and the adhesion are excellent by using a CrTi alloy having an excellent adhesion as a base layer together with a Ta seed layer or the like having an excellent crystal orientation and a low adhesion. A magnetic recording medium can be obtained. The area occupancy of the island portion of the seed layer of the present invention with respect to the area of the synthetic resin substrate is preferably in the range of 75% to 98%, more preferably 80% to 95%.

The synthetic resin substrate that can be used in the magnetic recording medium of the present invention includes polyethylene terephthalate, polyethylene naphthalate, polyetherimide, polyimide, polyamide, polyamideimide,
A synthetic resin material such as polybenzoxazole can be used. As a material of these synthetic resin substrates, the Young's modulus is 1.96 × 10 ^{3 to} 15.7 × 10 ³ MPa (2
00 to 1600 kg / mm ² ), and particularly preferably 2.94 × 10 ^{3 to} 7.85 × 10 ³ MPa (300
８００800 kg / mm ² ). The thickness of the synthetic resin substrate is preferably from 20 to 150 μm, more preferably from 30 to 80 μm. As the synthetic resin substrate, a disk-shaped member formed by punching a band-shaped member made of these synthetic resins or a disk formed by injection-molding these synthetic resin materials may be used.

Further, a flat layer may be provided on the synthetic resin substrate in order to improve the flatness of the synthetic resin substrate. A heat-resistant polymer material can be used as the flat layer material. Specifically, silicone resin, polyamide resin,
Materials such as polyamide imide resin and polyimide resin can be given. These materials are not only excellent in heat resistance, but also can achieve good properties in surface properties and magnetostatic properties. The coating thickness of the flat layer is preferably 0.1 to 5.0 μm, more preferably 0.5 to 3.0 μm.
m, more preferably 0.8 to 2.0 μm. Also,
Fine projections may be provided on the surface of the synthetic resin substrate. Examples of the minute projections provided on the surface of the synthetic resin substrate include fine particles of an inorganic substance such as SiO ₂ , Al ₂ O ₃ , and TiO ₂ , or fine particles of an organic substance. The particle size of these fine particles is in the range of 5 to 40 nm, preferably 10 to 35 nm, particularly preferably 15 to 30 nm. The height of the protrusions on the surface of the prepared undercoat film is preferably 30 nm or less.

As a material for the seed layer, Ta, Mo, W,
V, Zr, Cr, Rh, Hf, Nb, Mn, Ni, A
Alloys selected from l, Ru, Ti, and Si or compounds of these with nitrogen, oxygen, and the like can be given. Specifically, TaSi, NiSi, CrSi, NiAl,
NiP, CrTaSi, CrW, CrTi, CrMo,
TaSi is preferred. The seed layer thickness is 5 nm to 25
nm, and particularly preferably 10 to 20 nm.
When the thickness of the underlayer is reduced to 5 nm or less, the area occupancy of the seed layer decreases, and the crystal orientation of the magnetic layer decreases.
If the thickness is more than m, the adhesion will be reduced. The area occupancy of the island portion of the seed layer with respect to the area of the synthetic resin substrate is preferably in the range of 75% to 98%.
% To 95%. The distance between the islands is preferably in the range of 1 nm to 20 nm. More preferably, it is in the range of 1 nm to 5 nm. The size of the islands is preferably in the range of 5 nm to 100 nm. More preferably, it is in the range of 10 nm to 50 nm. The seed layer forming temperature is in the range of 5 to 250C, particularly preferably 10 to 200C. As a method of controlling the island portion, it is effective to change the substrate temperature and the seed layer sputtering pressure.

As a material of the underlayer, Cr, Ti,
W, Mo, V, Ta, B, Si, Nb, Zr, Al, M
An alloy of at least one of n and Cr is preferable. The Cr concentration of the underlayer is 77 to 100 at%, particularly preferably the Cr concentration is 80 to 95 at%, and the balance is a metal of another element. Underlayer thickness 5 nm to 500
nm, more preferably 10 to 10 nm.
0 nm. When the thickness of the underlayer is increased to 500 nm or more, the grain size of the magnetic layer becomes large, and when a magnetic recording medium is used, noise occurs.

As the magnetic material, a CoCr alloy or barium ferrite is preferable, and Pt, Ta, Ni, Si,
C containing at least one selected from B, Ni and Pd
An oCr alloy or one containing oxygen therein is more preferable. Above all, CoCrPt, CoCrPtTa
Is preferred. The Cr concentration in the magnetic layer is preferably from 10 to 30 at%, particularly preferably from 15 to 25 at%. The thickness of the magnetic layer is preferably 10 to 300 nm,
Particularly preferably, it is 10 to 60 nm. The underlayer and the magnetic layer are preferably formed by a vacuum film formation method. In particular, sputtering is preferable because a film can be formed without changing the composition of many elements. The seed layer, the underlayer, and the magnetic layer
It is preferable to form a film continuously while maintaining the degree of reduced pressure in the film forming apparatus.

On the magnetic layer, it is preferable to provide, as a protective layer, a carbon protective layer made of an amorphous, graphite, diamond structure or a mixture thereof prepared by a plasma CVD method, a sputtering method or the like.
Particularly preferred is a hard amorphous carbon film called diamond-like carbon. This hard carbon film has a Vickers hardness of at least 9.81 × 10 ³ MPa (1000 kg / mm ² ), preferably 19.6 × 10 ³ MPa (2000 kg).
/ Mm ² ) or more. The thickness of the protective layer is preferably from 2.5 to 30 nm, particularly preferably from 5 to 30 nm.
25 nm.

In the magnetic recording medium of the present invention, running durability
In order to improve the corrosion resistance and corrosion resistance,
It is preferable to provide a lubricant or a rust inhibitor on the protective layer. Jun
Lubricants include hydrocarbon-based lubricants, fluorine-based lubricants,
Pressure additives and the like can be used. As hydrocarbon lubricants
Carboxylic acids such as stearic acid and oleic acid, stearyl
Esters such as butyl phosphate, octadecylsulfonic acid, etc.
Phosphoric acid such as sulfonic acids and monooctadecyl phosphate
Steals, stearyl alcohol, oleyl alcohol
And carboxylic acids such as stearamide
Amides and amines such as stearylamine and the like.
It is. As the fluorine-based lubricant, the above-mentioned hydrocarbon-based lubricant
Part or all of the alkyl group may be a fluoroalkyl group.
Lubricants substituted with perfluoropolyether groups
I can do it. Perfluoropolyether group
Fluoromethylene oxide polymer, perfluoroethylene
Oxide polymer, perfluoro-n-propyleneoxy
Polymer (CF_TwoCF_TwoCF_TwoO)_n, Perfluoroisop
Propylene oxide polymer (CF (CF_Three) CF_TwoO)_nMa
Or copolymers of these. Extreme pressure additives
Phosphoric acid esters such as trilauryl phosphite, triphosphorous acid
Phosphites such as lauryl, trithiophosphorous acid
Thiolphosphoric acid esters such as lirauryl and thiophosphoric acid ester
Examples include sulfur-based extreme pressure agents such as ters and dibenzyl disulfide.
I can do it. The above lubricants can be used alone or in combination.
Used. Apply these lubricants on the magnetic layer or protective layer.
As a method of applying, a lubricant is dissolved in an organic solvent,
Yerber method, gravure method, spin coating method, dipco
Or by vacuum evaporation.
I just need. The amount of lubricant to be applied is 1 to 30 mg / m ^Two But
Preferably, 2 to 20 mg / m^Two Is particularly preferred. The present invention
Benzotriazole, benzene
Nitrogen-containing complexes such as zimidazole, purine and pyrimidine
Alkyl side chains are introduced into rings and their nuclei
Derivatives, benzothiazole, 2-mercapton benzothi
Azole, tetrazaindene ring compound, thiouracillation
Compounds and other nitrogen- and sulfur-containing heterocycles and derivatives thereof
Body and the like.

[0018]

The present invention will be described below with reference to examples and comparative examples. Example 1 75 in which a 1 μm thick polyimide resin was applied as a flat layer
μm polyimide resin substrate, argon partial pressure 1.06
Pa (8.0 mTorr), input power 11.4 W / cm
^2. TaSi (atomic ratio 85:15) was used as a seed layer by DC sputtering at a substrate temperature of 20 ° C.
It was formed to a thickness of 0 nm. Then, an argon partial pressure of 2.0
0 Pa (15 mTorr), input power 11.4 W / cm
^{2. Under} conditions of a substrate temperature of 200 ° C., C
An rTi alloy (atomic ratio 80:20) was formed into a film with a thickness of 60 nm by DC sputtering. Next, an argon partial pressure of 0.20 Pa (1.5 mTorr) and an input power of 11.
Under the conditions of 4 W / cm ² and a substrate temperature of 20 ° C., a CoCrPt alloy (atomic ratio of 78: 20: 1) was used as a magnetic layer on the underlayer.
2) was formed into a film having a thickness of 30 nm by DC sputtering. Next, an argon partial pressure of 0.40 Pa (3 mTorr)
r), input power 5.71 W / cm ² , substrate temperature 200 ° C.
Under the conditions described above, a protective layer made of carbon having a thickness of 20 nm was formed. A magnetic recording medium was manufactured using a mixed lubricant of monooctadecyl phosphate and stearylamine as a lubricant. For the obtained magnetic recording medium, the film thickness and the like are measured by the following evaluation methods for each film forming step, and the obtained magnetic recording medium is evaluated for adhesion, crystal orientation, and the like. It is shown in Table 1.

Example 2 A film was fabricated in the same manner as in Example 1 except that the thickness of the seed layer was changed to 5 nm, and evaluated in the same manner as in Example 1. The results are shown in Table 1.

Example 3 A semiconductor device was manufactured in the same manner as in Example 1 except that the thickness of the seed layer in Example 1 was changed to 25 nm, evaluated in the same manner as in Example 1, and the results are shown in Table 1.

Example 4 The procedure of Example 1 was repeated except that the synthetic resin substrate of Example 1 was changed to a polyetherimide substrate having a thickness of 0.6 mm, and evaluation was performed in the same manner as in Example 1. Table 1
Shown in

Example 5 A film was prepared in the same manner as in Example 1 except that the temperature for forming the seed layer in Example 1 was changed to 77 K, evaluated in the same manner as in Example 1, and the results are shown in Table 1.

COMPARATIVE EXAMPLE 1 A sample was prepared in the same manner as in Example 1 except that no seed layer was provided.
Evaluation was performed in the same manner as in Example 1, and the results are shown in Table 1. Comparative Example 2

Except that the thickness of the seed layer in Example 1 was changed to 2 nm, it was manufactured in the same manner as in Example 1, evaluated in the same manner as in Example 1, and the results are shown in Table 1. Comparative Example 3

Except that the seed layer thickness in Example 1 was changed to 30 nm, it was manufactured in the same manner as in Example 1, evaluated in the same manner as in Example 1, and the results are shown in Table 1. Comparative Example 4 A seed layer was prepared in the same manner as in Example 1 except that the seed layer forming temperature in Example 1 was changed to 300 ° C., evaluated in the same manner as in Example 1, and the results are shown in Table 1.

(Evaluation Method) Seed layer area occupancy Atomic force microscope (Digital Instrumentum)
ts: Nanoscope-III) was used. 1
The surface of the sample after the formation of the seed layer is observed in μm square, and an image is formed by projecting the particle shape from a direction perpendicular to the synthetic resin substrate. The area occupancy is calculated from the ratio between the image area and the scan area. The same measurement is performed at ten locations, and the average area occupancy is calculated. 2. Measurement of Seed Layer Thickness Using a silicon substrate as a standard sample, marking is performed, a film is formed for 10 minutes, washed with acetone, and the marking portion is removed. The film thickness step generated in this portion is measured with a contact type step meter, and the sputtering rate is calculated from the relationship between the film thickness and the sputtering time. The seed layer film thickness is calculated from the film formation time × sputtering rate.

3. Adhesive force of adhesive layer Adhesive tape (Polyethylene naphthalate te manufactured by Nitto Denko Corporation)
18mm x 20mm
About 4.9 N / m ^Two(50
0gf / cm^Two) Rub more than 3 times with more force
Adhere. Then peel off at once. Do this 5 times
Perform the test in a different place.
No screeching.

4. Crystal Orientation The crystal orientation of the underlayer and the magnetic layer was observed with a biaxial X-ray diffractometer (RINT 2500H, manufactured by Rigaku Corporation).
The measurement was performed by the θ-2θ method, and Cu was used as the radiation source. The applied voltage was 50 kV and the tube current was 300 mA. As a measure of crystal orientation, a magnetic layer (110) which is an in-plane orientation component;
The axis of easy magnetization grows obliquely to the film surface (10
1) Define the diffraction intensity ratio of the plane. I (110) / I (1
01) The case where the intensity ratio was 2.5 or more was regarded as good, and the case where the intensity ratio was less than 2.5 was regarded as bad.

[0029]

Table 1 Area occupancy ratio Seed layer thickness Adhesion Crystal orientation (%) (nm) I (110) / I (101) Example 1 93 20 No peeling 7.6 (good) Example 2 8655 No peeling 3.8 (good) Example 3 97 25 No peeling 6.2 (good) Example 4 92 20 No peeling 5.3 (good) Example 5 82 20 No peeling 4.6 (good) Comparative Example 100 No peeling 0.3 (bad) Comparative Example 2 78 2 No peeling 0.9 (bad) Comparative Example 3 100 30 Peeled 6.5 (Good) Comparative Example 4 100 20 Peeled 3.5 (Good)

[0030]

According to the present invention, a synthetic resin substrate is used as a base, a seed layer is provided between nonmagnetic underlayers provided as an underlayer of a magnetic layer, and the seed layer is formed in an island shape. Since the direct contact portion is formed, it is possible to obtain a magnetic recording medium having both excellent adhesion and crystal orientation characteristics.

Claims (7)

[Claims] 1. A magnetic recording medium having a structure in which an underlayer, a magnetic layer, a protective layer, and a lubricating layer are laminated on at least one surface of a synthetic resin substrate, wherein a seed layer is provided between the synthetic resin substrate and the underlayer. A magnetic recording medium, wherein the seed layer has an island structure, and has a portion where the synthetic resin substrate and the underlayer are in direct contact. 2. The synthetic resin substrate has a thickness of 30 to 100 μm.
2. The magnetic recording medium according to claim 1, wherein the distance is in the range of m. 3. The magnetic recording medium according to claim 1, wherein the thickness of the seed layer is in the range of 5 to 25 nm. 4. The magnetic recording medium according to claim 1, wherein the area occupancy of the island structure of the seed layer is 80% to 98% of the surface of the synthetic resin substrate. 5. A magnetic layer having a Cr concentration of 10 to 30 at.
5. The magnetic recording medium according to claim 1, wherein an alloy containing Co as a main component in the range of% is used. 6. The underlayer having a Cr concentration of 77 to 100 a
6. The magnetic recording medium according to claim 1, wherein a Cr alloy in the range of t% is used. 7. The magnetic recording medium according to claim 1, wherein the magnetic recording medium is formed on both sides of a synthetic resin substrate.