JP2000105920A - Magnetic recording medium and its production - Google Patents

Abstract

PROBLEM TO BE SOLVED: To produce a magnetic recording medium using a glass substrate, having good magnetic characteristics, capable of reducing the levitation height of a magnetic head and also having good durability. SOLUTION: A Cr layer 2 and an NiP layer 3 are successively formed on a glass substrate 1 by sputtering and the surface of the NiP layer 3 is subjected to texturing so as to form fine grooves mainly along the circumferential direction. A Cr alloy underlayer 4, a Co alloy type magnetic layer 5 and a protective layer 6 are successively formed on the NiP layer 3 by sputtering and a liquid lubricant layer 7 is formed on the protective layer 6 by coating to produce the objective magnetic recording medium.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

[0001] The present invention relates to a magnetic recording device,
In particular, the present invention relates to a magnetic recording medium mounted on a hard disk drive and the like and a method of manufacturing the same.

[0002]

2. Description of the Related Art A magnetic recording medium (hereinafter, simply referred to as a medium) mounted on a hard disk drive or the like is formed on a non-magnetic substrate by, for example, a non-magnetic metal underlayer made of Cr or the like by a sputtering method, Co or a Co alloy. Magnetic layer composed of C
And the like, and a liquid lubricant layer is provided thereon.

[0003] Magnetic recording devices such as hard disk drives have been developed to have higher densities, higher transfer speeds and smaller sizes.
Chemically strengthened glass and crystallized glass have come to be used as a medium for the medium. Substrates made of these glasses have higher strength than conventional substrates made of Al alloys, so they have excellent impact resistance and
In addition to the advantages of being able to be used at a high speed rotation of more than 0000 rpm, the surface smoothness is high and the magnetic head flying height required for high recording density can be easily reduced.
However, it is difficult to roughen the surface of the substrate to form fine grooves mainly along the circumferential direction, which is generally called texturing, which is applied to the surface of the substrate to secure the durability of the medium. The magnetic properties such as the magnetic force Hc, the squareness ratio S, and the coercive force squareness ratio S ^* are inferior to those of a medium using a substrate made of an Al alloy. Further, glass has a large heat capacity as compared with metal, making it difficult to heat the substrate during manufacture, and because a substrate bias cannot be applied because the substrate is an insulator, a medium using a substrate made of an Al alloy. It was difficult to improve the magnetic characteristics as compared with the above.

[0004] As a method of solving such a problem,
In Japanese Patent Application Laid-Open No. 3-125322, NiP, T is deposited on a glass substrate having a smooth surface by vapor deposition or sputtering.
A non-magnetic metal thin film made of i, Al, Cr, Cu, Mo, Ta, W, stainless steel, or an alloy containing these as a main component is provided as a substrate, and after texturing the surface thereof, the substrate is subjected to texturing. A method is disclosed in which an underlayer, a magnetic layer, and a protective layer made of a metal or an alloy are sequentially formed thereon to form a medium. The thickness of the nonmagnetic metal thin film is 0.0
3 μm or more and 5 μm or less are considered suitable.

[0005]

However, in the above-mentioned method, the adhesion and wettability between the glass substrate and the non-magnetic metal thin film were insufficient, and it was difficult to form a non-magnetic metal thin film having a uniform thickness. The thickness of the nonmagnetic metal thin film is 0.03 μm.
m and 5 μm or less, but the surface smoothness inherent to the glass is impaired to a certain extent, and there is a problem in realizing an extremely low flying height of the magnetic head (for example, about 1 μ inch or less). It becomes.

The present invention eliminates the above-mentioned drawbacks, uses a glass substrate, has good magnetic properties, can greatly reduce the flying height of a magnetic head, and has good durability, and its production. The aim is to provide a method.

[0007]

According to the present invention, there is provided a magnetic recording medium comprising at least a non-magnetic metal base layer, a magnetic layer, and a protective layer sequentially laminated on a non-magnetic substrate. Magnetic recording in which a magnetic substrate is made of a glass substrate, a Cr layer and a NiP layer are sequentially formed thereon, and a groove mainly along the circumferential direction is formed on the surface of the NiP layer by texturing. It is solved by using a medium.

[0008] By first forming a Cr layer on a glass substrate and then forming a NiP layer thereon, an extremely thin NiP layer can be provided very uniformly on the glass substrate with good adhesion. Since the Cr layer and the NiP layer are each formed as an extremely thin film, the degree of impairing the surface smoothness of the glass substrate due to the provision of these layers is extremely small. As the glass substrate, chemically strengthened glass or crystallized glass is preferably used.

It is preferable that the thickness of the Cr layer provided on the glass substrate is in the range of 3 nm to 30 nm.
In order to fulfill the function of improving the adhesion of the NiP layer,
If it is less than 3 nm, it is insufficient, while it is not necessary to make it too thick, and 30 nm or less is enough. The thickness of the NiP layer is 2
It is preferable that the thickness be in the range of 0 nm or more and 200 nm or less. If the film thickness is less than 20 nm, the texturing process cannot be performed because the film thickness is too thin, and if the film thickness exceeds 200 nm, the NiP layer surface roughness after sputtering increases, and
It is not preferable because the production cost is increased.

The P concentration of the NiP layer is desirably in the range of 15 at% to 30 at%. Concentration 1
If it is less than 5 atomic%, the NiP layer tends to have magnetism and may affect the magnetic properties of the magnetic layer, and if it exceeds 30 atomic%, the hardness of the NiP layer becomes high, making texturing difficult. In addition, phosphate ions are easily eluted, which is inappropriate.

Further, it is preferable and the surface roughness of the NiP layer after texturing treatment is within 15Å the range over 3Å center line average roughness R _a. If _Ra is less than 3 [deg.], The durability of the medium is reduced, which is not preferable. If _Ra exceeds 15 [deg.], The flying height of the magnetic head cannot be sufficiently reduced (for example, 1 [mu] inch or less). In such a magnetic recording medium, in a method for manufacturing a magnetic recording medium in which at least a nonmagnetic metal underlayer, a magnetic layer, and a protective layer are sequentially laminated on a nonmagnetic substrate, a glass substrate is used as the nonmagnetic substrate. An ultra-thin Cr layer, N
It is obtained by forming an iP layer, performing a texturing process for forming a groove mainly along the circumferential direction on the surface of the NiP layer, and then sequentially forming a nonmagnetic metal base layer, a magnetic layer, and a protective layer.

Preferably, the texturing treatment includes a mechanochemical processing step in which an acidic solution is used as a polishing accelerator and polishing is performed using alumina abrasive grains or diamond abrasive grains. By using this, a more uniform surface without abnormal projections can be obtained. For example, the texturing process is divided into two stages, the first stage is ground using alumina abrasive grains or diamond abrasive grains, and the second stage is alumina abrasive grains or diamond abrasive grains having a smaller particle size than the first stage. It is preferable to perform mechanochemical processing using granules and using an acidic solution as a polishing accelerator. As the acidic solution, an aluminum nitrate solution is preferably used.

[0013]

FIG. 1 is a schematic sectional view of a medium according to the present invention. Cr layer 2, Ni on non-magnetic substrate 1
A P layer 3 is sequentially provided, on which a Cr alloy underlayer 4 is provided.
A Co alloy magnetic layer 5, a protective layer 6, and a liquid lubricant layer 7 are sequentially formed. As the nonmagnetic substrate 1, crystallized glass or chemically strengthened glass is used.

A Cr layer 2 and a NiP layer 3 are sequentially formed on the non-magnetic substrate 1 by a sputtering method. The thickness of the Cr layer 2 is 3
The thickness is preferably from 30 nm to 30 nm. Also, the NiP layer 3
It is necessary to set the P concentration in the film of 15 to 30 atomic% or less, and the film thickness is preferably in the range of 20 to 200 nm, more preferably 40 to 10 nm.
It is within the range of 0 nm or less. The surface of the NiP layer 3 is subjected to texturing directly, that is, without performing precision polishing such as polishing, and fine grooves are formed mainly along the circumferential direction. Surface roughness after texturing treatment is preferably in the range of 5Å or 15Å or less in the center line average roughness R _a. In the texturing process, polishing is performed using a slurry in which alumina abrasive grains or diamond abrasive grains are used as polishing abrasive grains. However, in order to form a more uniform surface roughness with few abnormal projections, an acidic solution is added to the slurry to a polishing accelerator. It is preferable to carry out a mechano-thematic process of adding and polishing.

In this manner, a Cr alloy underlayer 4, a Co alloy magnetic layer 5, and a carbon protective layer 6 are formed by sputtering on the NiP layer which has been subjected to the texturing treatment on the nonmagnetic substrate. A liquid lubricant layer 7 is formed by applying a perfluoropolyether-based lubricant thereon to obtain a medium.

[0016]

Embodiments Hereinafter, specific embodiments will be described. Example 1 Non-magnetic substrate having an outer diameter of 2.5 inches and a thickness of 0.635 m
m of a disk-shaped chemically strengthened glass, which was introduced into the sputtering apparatus after cleaning, and was supplied with an argon gas pressure of 5 mTorr.
film thickness of 10 nm by DC magnetron sputtering under
Then, a NiP thin film having a thickness of 80 nm was continuously formed. At this time, the composition of the NiP target was changed to form a NiP thin film having a different P concentration in the NiP thin film, and the hardness of the NiP thin film was measured using a microhardness meter.
In addition, the phosphate ion concentration extracted when the substrate after forming the NiP thin film was immersed in pure water at 80 ° C. was measured to evaluate the amount of eluted phosphoric acid, and the dependence of both on the P concentration of the NiP thin film was determined. Examined.

The results are shown in the diagram of FIG. From FIG.
When the P concentration exceeds 30 atomic%, the film hardness sharply increases,
In addition, it can be seen that the amount of eluted phosphoric acid also increases. Also, it was found that when the P concentration was 15 atomic% or less, the NiP thin film was magnetized even immediately after film formation. Such a tendency was similarly observed when crystallized glass was used as the nonmagnetic substrate.

Example 2 A non-magnetic substrate having an outer diameter of 2.5 inches and a thickness of 0.635 m
m of a disk-shaped chemically strengthened glass, which was introduced into the sputtering apparatus after cleaning, and was supplied with an argon gas pressure of 5 mTorr.
film thickness of 10 nm by DC magnetron sputtering under
Then, a NiP thin film having a P concentration of about 25 atomic% was continuously formed using a Ni-25 atomic% P target while changing the film thickness from 10 nm to 400 nm.

[0019] Thus the center line average roughness R _a of the surface of the NiP film thus obtained was measured using an atomic force microscope (AFM), was examined NiP film thickness dependence of R _a. The results are shown in the diagram of FIG. From FIG. 3, the NiP film thickness is 200
It can be seen that up to nm, the surface roughness is as smooth as 1 nm or less in _Ra , but when the film thickness exceeds 200 nm, _Ra rapidly increases. Such a tendency was similarly observed even when the composition of the NiP film was changed.

Example 3 A non-magnetic substrate having an outer diameter of 2.5 inches and a thickness of 0.635 m
m of a disk-shaped chemically strengthened glass, which was introduced into the sputtering apparatus after cleaning, and was supplied with an argon gas pressure of 5 mTorr.
film thickness of 10 nm by DC magnetron sputtering under
Then, a NiP thin film having a P concentration of about 25 atomic% was continuously formed to a film thickness of 50 nm using a Ni-25 atomic% P target.

Thereafter, the substrate is taken out of the sputtering apparatus, and the surface of the NiP thin film is subjected to texturing. At this time, the texturing process is not a normal one-step process but is divided into two stages, the first stage is performed using diamond abrasive grains, and the second stage is performed using diamond abrasive grains having an average particle size of 0.5 μm. A mechanochemical process using an acidic aluminum nitrate solution as a polishing accelerator is performed to form a surface shape mainly composed of grooves along the circumferential direction. At this time, the surface roughness after the texturing treatment was changed by changing the particle size and texture conditions of the diamond abrasive used in the first stage.

After the texturing process and the cleaning, the substrate is introduced into a sputtering apparatus, and an argon gas pressure of 5% is applied.
Under mTorr, a 30-nm thick CrMo underlayer, a 20-nm thick CoCrTaPt magnetic layer, and a 10-nm thick D
After the LC protective layer is sequentially formed and laminated, it is taken out from the sputtering apparatus, and then a liquid lubricant of perfluoropolyether is applied to the protective layer surface to a thickness of 2 nm to form a lubricating layer. A medium having the structure shown in FIG.

The center line average roughness _Ra (Å) is defined as the medium surface roughness between the minimum magnetic head flying height (GH) (μ inch) of the medium and the coercive force squareness ratio S ^* of the medium thus obtained. )
(A value measured with a contact-type surface roughness meter using a stylus having a tip curvature radius of 0.5 μm) was examined. FIG. 4 shows the results. In FIG. 4, for comparison, measured values of a medium manufactured in a process in which only the above-described texturing of the NiP layer surface is omitted are shown on the axis of R _a = 0. As can be seen from FIG. 4, the coercivity squareness ratio S ^* is as small as about 0.65 in the medium not subjected to texturing,
It can be seen that a medium having a large coercive force squareness ratio S ^* of 0.8 or more can be obtained by performing the texturing process.

COMPARATIVE EXAMPLE In the same manner as in Example 3, except that the normal texturing was performed as the texturing treatment of the substrate, that is, the grinding was performed only in one step without using the polishing accelerator of the acidic solution. A medium was prepared. In this case, the magnetic properties are good, but was small minimum head flying height, the medium surface R _a
Is less than 15 °, the minimum head flying height is 1
It did not go below μ inch. It can be seen that it is effective to apply mechanochemical processing to texturing in order to greatly reduce the minimum head flying height.

[0025]

According to the present invention, a Cr layer and a NiP layer are formed on a glass substrate by a sputtering method, and the NiP layer is subjected to a texturing process for forming a groove mainly along the circumferential direction on the surface thereof. By sequentially laminating a non-magnetic metal underlayer, a magnetic layer and a protective layer to produce a magnetic recording medium,
It is possible to obtain a magnetic recording medium having good magnetic properties, a significantly reduced flying height of the magnetic head, and good durability.

[Brief description of the drawings]

FIG. 1 is a schematic sectional view of an example of a medium according to the present invention.

FIG. 2 is a diagram showing the relationship between the film hardness and the amount of extracted phosphoric acid with respect to the P concentration in the film of the NiP layer.

FIG. 3 is a diagram showing a relationship between _a NiP layer thickness and a NiP layer surface roughness Ra.

[4] the coercive force squareness ratio with respect to the surface roughness R _a of the medium S ^*, graph showing the relationship between minimum head flying height

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 1 Non-magnetic base 2 Cr layer 3 NiP layer 4 Cr alloy base layer 5 Co alloy magnetic layer 6 Protective layer 7 Liquid lubricant layer

 ──────────────────────────────────────────────────続 き Continuing on the front page (72) Inventor Toyoji Ataka 1-1, Tanabe-Nitta, Kawasaki-ku, Kawasaki-shi, Kanagawa Prefecture Inside Fuji Electric Co., Ltd. (72) Inventor Noboru Kurata 1, Tanabe-Nitta, Kawasaki-ku, Kawasaki-ku, Kanagawa Prefecture No. 1 Fuji Electric Co., Ltd. F term (reference) 5D006 CB04 CB07 CB08 DA03 FA02 FA09 5D112 AA02 AA11 AA24 BA03 BA05 GA02 GA14 GA26

Claims (10)

[Claims] 1. A magnetic recording medium comprising at least a non-magnetic metal underlayer, a magnetic layer, and a protective layer sequentially laminated on a non-magnetic substrate, wherein the non-magnetic substrate comprises a glass substrate, and a Cr layer, NiP A magnetic recording medium, wherein layers are sequentially formed, and grooves are formed on the surface of the NiP layer by texturing mainly along a circumferential direction. 2. The magnetic recording medium according to claim 1, wherein the substrate is made of chemically strengthened glass or crystallized glass. 3. The magnetic recording medium according to claim 1, wherein the thickness of the Cr layer is in the range of 3 nm to 30 nm. 4. The NiP layer according to claim 1, wherein the P concentration is in the range of 15 at% to 30 at%.
Or the magnetic recording medium according to 3. 5. The NiP layer has a thickness of not less than 20 nm and not more than 200 nm.
4. The method according to claim 1, wherein the distance is within the following range.
Or the magnetic recording medium according to 4. 6. The NiP layer after texturing has a surface roughness within a range of not less than 3 ° and not more than 15 ° in center line average roughness _Ra . The magnetic recording medium according to the above. 7. A method for manufacturing a magnetic recording medium comprising a non-magnetic substrate and a non-magnetic metal underlayer, a magnetic layer, and a protective layer sequentially laminated on the non-magnetic substrate, wherein the non-magnetic substrate comprises a glass substrate, and A Cr layer and a NiP layer are formed by a method, and a texturing process for forming a groove mainly along the circumferential direction is performed on the surface of the NiP layer. Then, a nonmagnetic metal base layer, a magnetic layer, and a protective layer are sequentially laminated. A method for manufacturing a magnetic recording medium, characterized by being manufactured by: 8. The magnetic treatment according to claim 7, wherein the texturing includes a mechanochemical processing step of polishing using an alumina solution or a diamond abrasive using an acidic solution as a polishing accelerator. Manufacturing method of recording medium. 9. A texturing process is performed in two stages, the first stage grinding using alumina abrasive grains or diamond abrasive grains, and the second stage alumina grinding having a smaller particle size than the first stage. 9. The method for producing a magnetic recording medium according to claim 8, wherein mechanochemical processing is performed using grains or diamond abrasive grains and using an acidic solution as a polishing accelerator. 10. The method for manufacturing a magnetic recording medium according to claim 8, wherein the acidic solution is an aluminum nitrate solution.