JPH05307747A - Magnetic disk - Google Patents

Abstract

PURPOSE:To improve wear resistance by forming a solid lubricant layer which consists of a satd. fatty acid salt and is solid at ordinary temp. and a liquid lubricant layer which consists of perfluoropolyether and is liquid at ordinary temp. on a protective film consisting of carbon. CONSTITUTION:A ground surface film 3 consisting of Cr, a magnetic layer 4, the protective film 5 and the lubricant layer 6 are successively laminated on an aluminum substrate 7 formed with an Ni-P plating film 2 on the surface. The protective film 5 provided to protect the magnetic layer 4 against the impact by the contact with a magnetic head is formed of a carbon film or SiO2 film and the lubricant layer 6 is formed on this protective film 5 in order to assure the wear resistance and wear resistance to the magnetic head. The lubricant layer 6 is formed of the two-layered constitution consisting of the solid lubricant 7 and the liquid lubricant layer 8 consisting of the perfluoropolyether. A sufficient lubricating effect is obtd. by forming the solid lubricant layer 7 as a thick film if the lubricant layer 6 is formed of the two- layered constitution consisting of the layer 7 and the layer 8 in such a manner. In addition, a self-restoration effect is obtd. and a lubricating effect is secured long by the liquid lubricant layer 8 of the perfluoropolyether.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a magnetic disk,
In particular, it relates to a magnetic disk having excellent CSS (contact start / stop) characteristics.

[0002]

2. Description of the Related Art As a storage medium for, for example, a computer, a disc-shaped magnetic disk which can be randomly accessed is widely used. Among them, since it is excellent in response and has a large storage capacity, it is made of aluminum or the like. A magnetic disk (hard disk) in which a recording magnetic layer is formed on a substrate made of a hard material is used.

The magnetic disk as described above rotates at a high speed to record and reproduce information on a large number of tracks concentrically.

By the way, when recording / reproducing on / from the magnetic disk, the magnetic head and the magnetic layer surface are mounted in contact with each other at the start of the operation, and then the magnetic disk is rotated by a predetermined amount. A minute vacant layer is formed between the magnetic layer surface and recording / reproducing in this state C
The SS method (contact start stop method) is generally used.

In such a CSS system, the magnetic head is in contact friction with the magnetic layer surface at the start and end of the operation, and the frictional force generated between the head and the magnetic disk causes the magnetic head and the magnetic disk to wear. Cause. Alternatively, depending on the surface properties of the magnetic disk, the magnetic head may stick to the magnetic disk and give a large impact to the magnetic disk. Therefore, it is necessary for the magnetic disk to have a small coefficient of friction with respect to the head, have wear resistance, and be able to withstand impact when contacting the head.

Therefore, the hard disk has a structure in which a nonmagnetic undercoat film, a recording magnetic layer, a protective film, and a lubricant layer are sequentially laminated on a substrate. That is, the non-magnetic undercoating film and the protective film ensure durability to withstand impacts due to contact with the magnetic head, and the lubricant layer has abrasion resistance and wear resistance against sliding with the head. To improve.

[0007]

A liquid lubricant such as PFPE (perfluoropolyether) is conventionally used as the lubricant used in the lubricant layer.

However, when a liquid lubricant is used, since the liquid is present between the magnetic head and the disk, the head and the disk easily stick to each other. The lubricant is scattered by the centrifugal force of the disk rotation (rotation). Therefore, there is a problem that the lubrication effect is lost. In particular, when sticking between the head and the disk occurs, the coefficient of friction between the head and the disk increases and the running performance of the head deteriorates.
A head crash occurs, causing troubles such as buckling of the head gimbal spring and damage of the magnetic disk.

Here, in the liquid lubricant layer, the wear resistance effect improves as the film thickness increases, but the sticking phenomenon tends to occur as the film thickness increases. Therefore, it is difficult to optimize the thickness of the liquid lubricant layer, and it is difficult to achieve both wear resistance and prevention of sticking even if the amount and type of lubricant are adjusted. is there.

It is considered that if the solid lubricant is used as the lubricant, the sticking phenomenon and the rotation loss as described above can be avoided, but the solid lubricant does not have a self-repairing action due to surface diffusion unlike the liquid lubricant. However, there is a drawback that abrasion (sliding loss) due to sliding cannot be recovered, and further progresses to deteriorate the lubricating effect at an accelerated rate.

Therefore, the present invention has been proposed in view of such a conventional situation, sticking of the head hardly occurs, and the lubricant layer is not lost even when it is repeatedly used,
An object is to provide a magnetic disk having excellent CSS durability.

[0012]

In order to achieve the above object, the magnetic disk of the present invention is a magnetic disk in which a metal magnetic thin film and a carbon protective film are formed on a non-magnetic substrate. A solid lubricant layer formed of a saturated fatty acid salt in a solid state at room temperature and a liquid lubricant layer formed of perfluoropolyether in a liquid state at room temperature are formed thereon.

Further, a metal magnetic thin film, Si, is formed on the non-magnetic substrate.
In a magnetic disk having an O ₂ protective film formed thereon, a solid lubricant layer made of a silane coupling agent in a solid state at room temperature and a liquid lubricant made of perfluoropolyether in a liquid state in a normal state are formed on the Si ₂ O protective film. It is characterized in that an agent layer is formed. Further, the saturated fatty acid salt is a saturated fatty acid salt represented by Formula 4.

CF ₃ (CF ₂ ) _n COONH ₃ C _m H _{2m + 1} Formula 4 (where m is an integer of 18 or more and n is an integer of 6 to 8) Further, the silane cup is also used. The ring agent is a silane coupling agent represented by Formula 5. _{(C k H 2k + 1 O} ) 3 Si (CH 2) n C m F 2m + 1 ··· Equation 5 (where, k is 1 or 2, m is an integer of from 1 to 10, n represents 2
Or 3. In addition, the perfluoropolyether is a perfluoropolyether represented by the formula (6).

RCF ₂ (CF ₂ O) _n (CF ₂ CF ₂ O) _m CF ₂ R (Formula 6) (wherein R is alcohol, glycol, glycerin, phenol, carboxylic acid or fluorine substitution product thereof, m
+ N is an integer of 10 to 50. ) Further, the film thickness D _s of the solid lubricant layer is 20Å ≦ D _s ≦ 7.
It is characterized by being 00Å.

Furthermore, the film thickness D of the liquid lubricant layer
_L is 5Å ≦ D _L ≦ 15Å.

[0017]

When only the liquid lubricant layer is provided on the magnetic disk, the liquid lubricant layer induces sticking between the head and the disk as the layer thickness increases, and increases the static friction coefficient between the disk and the head. Therefore, the thickening of the lubricant layer is limited, and the lubricating effect cannot be sufficiently obtained.

On the other hand, when only the solid lubricant layer is provided, the solid lubricant layer does not have a self-repairing action due to surface diffusion unlike liquid lubricants, so that the sliding loss is large and the lubricating effect is rapidly deteriorated.

In the present invention, the lubricant layer has a two-layer structure of a solid lubricant layer and a liquid lubricant layer. When the lubricant layer has a two-layer structure including a solid lubricant layer and a liquid lubricant layer, a sufficient lubricating effect can be obtained by forming the solid lubricant layer as a thick film. Further, since the liquid lubricant layer has a self-repairing action, the sliding loss is small and the lubricating effect is maintained for a long time.

Further, in the present invention, perfluoropolyether is used as the liquid lubricant, and as the solid lubricant, a saturated fatty acid salt is used when the protective film is a carbon protective film, and a protective film is a SiO ₂ protective film. In some cases, a silane coupling agent is used. As a result, the protective film, the solid lubricant layer, and the liquid lubricant layer are evenly and firmly adhered to each other, and a more stable lubricating effect can be obtained.

[0021]

EXAMPLES Specific examples of the present invention will be described below.

As shown in FIG. 1, the magnetic disk of this embodiment has a Cr base film 3, a magnetic layer 4, a protective film 5, and a lubricant on an aluminum substrate 1 having a Ni-P plated film 2 formed on the surface thereof. The layers 6 are sequentially laminated.

The Ni-P plated film 2 is formed on the aluminum substrate 1
Is provided for the purpose of increasing the surface hardness of the hard disk and ensuring the adhesion to the magnetic layer 4. Therefore, in the hard disk, the aluminum substrate 1 formed on the surface of the Ni-P plated film 2 serves as a rigid substrate. Will be treated. Further, the Cr underlayer 3 is provided to control the crystallinity and the like when the magnetic layer 4 is formed by vapor deposition sputtering or the like, and has the effect of improving the magnetic characteristics (for example, coercive force).

The magnetic layer 4 is made of Co--Cr--Ta.
Any conventionally known metal magnetic thin film such as a system alloy thin film can be applied. The protective film 5 is provided to protect the magnetic layer 4 from an impact due to contact with the magnetic head, and a carbon film or a SiO ₂ film is used. Further, the lubricant layer 6 provided on the protective film 5 is for ensuring abrasion resistance and abrasion resistance for the magnetic head.

Here, perfluoropolyether (P) which is usually used as a lubricant for magnetic disks is used.
There are liquid lubricants such as FPE) and solid lubricants, but they have their respective drawbacks. The liquid lubricant layer causes sticking between the head and the disk when the film thickness is too large. Therefore, there is a limitation in increasing the film thickness, and a sufficient lubricating effect cannot be obtained. On the other hand, the solid lubricant layer does not induce the sticking phenomenon described above, but does not have the self-repairing action due to surface diffusion unlike the liquid lubricant, so that the wear easily progresses and the lubricating effect deteriorates quickly.

In the present invention, the lubricant layer 6 has a two-layer structure including a solid lubricant layer 7 and a liquid lubricant layer 8 made of perfluoropolyether (PFPE).

When the lubricant layer 6 has a two-layer structure of the solid lubricant layer 7 and the PFPE liquid lubricant layer 8, the solid lubricant layer 7 having a thick film provides a sufficient lubricating effect. Also, PF
Since the PE liquid lubricant layer 8 has a self-repairing action, it is difficult for the sliding loss to progress and the lubricating effect is maintained for a long period of time.

Further, in the present invention, in order to make the mutual coupling of the protective film 5 and the lubricant layer 6 uniform and strong, the solid lubricant used in the solid lubricant layer 7 is as follows. regulate.

Here, the solid lubricant that achieves a strong bond depends on whether the protective film 5 is a carbon protective film or a SiO ₂ protective film.

First, when the protective film 5 is a carbon protective film, a saturated fatty acid salt is used as a solid lubricant. The surface of the carbon film has a very high electric conductivity and an extremely high affinity with polar groups. Therefore, as shown in FIG. 2, the protective film 5 and the solid lubricant layer 7 are firmly bonded by the polar terminal group 21 (COOH, COONH _3, etc.) of the saturated fatty acid salt.
In addition, the van der Waals force acts between the adjacent saturated hydrocarbon groups 23 to stabilize the existing state of the saturated fatty acid salt. [Saturated hydrocarbons having polar end groups include ester compounds and amide compounds in addition to saturated fatty acid salts, but the ester compounds and amide compounds have weaker adsorptive power to the carbon film than saturated fatty acid salts, and thus the above solid lubrication It is insufficient as a drug. ]

Considering that the temperature inside the drive device rises to about 60 ° C. due to the rotation of the disk, it is preferable to select a saturated fatty acid salt having a melting point of 80 ° C. or higher.

On the other hand, when the protective film is a SiO ₂ film, a silane coupling agent is used as a solid lubricant. Figure 3
In the SiO ₂ film surface as shown, silanol group (Si
OH) is present, the SiOH groups chemically react with the silane coupling agent. As a result, the protective film 5 and the solid lubricant layer 7 are firmly bonded.

Further, in the SiO ₂ film, the SiOH group takes in water, so that sticking is easily induced. However, when the SiOH group and the silane coupling agent are chemically bonded, sticking is easily caused. SiO
This is also advantageous in this respect because the H group is drastically reduced.

The silane coupling agent is used as the protective film 5.
Since it is via a chemical bond with the solid lubricant layer, it can exist stably as a solid lubricant layer even if its melting point is as low as about 30 ° C.

In both of the saturated fatty acid and the silane coupling agent, when a fluorocarbon group is introduced, the lubricity is increased and the solid lubricant layer 7 and the liquid lubricant layer 8 are firmly adhered to each other. Good lubrication effect can be obtained. Examples of the saturated fatty acid having a fluorocarbon group introduced therein and the silane coupling agent include those represented by Formulas 7 and 8, respectively.

CF ₃ (CF ₂ ) _n COONH ₃ C _m H _{2m + 1} ... Equation 7 (C _k H _{2k + 1} O) ₃ Si (CH ₂ ) _n C _m F _{2m + 1} ... Equation 8

In the formula 7, the number m of carbon atoms in the hydrocarbon group is 1
It is preferably 8 or more. By setting m to be 18 or more, the van der Waals force becomes sufficient, and even when the temperature in the drive rises (about 60 ° C.), it can exist in a more stable solid state. The carbon number n of the fluorocarbon group is preferably 6-8. The longer the chain length of the fluorocarbon group is, the more advantageous it is in terms of the lubrication effect, but if it is too long, the stabilization of the hydrocarbon group by the van der Waals force may sterically hinder the fluorocarbon group. ..

In the formula 8, the carbon number n is preferably 2-3, and the carbon number m of the fluorocarbon group is preferably 1-10. In the silane coupling agent of Chemical formula 5, the fluorocarbon group contributes to the stabilization of the orientation property, and by setting the carbon number m to 1 to 10, the orientation stabilization effect is sufficiently exerted. Become.

The saturated fatty acid salt is diluted with an organic solvent and applied on the carbon protective film by a dipping method (immersion method) to form a solid lubricant layer. Here, the layer thickness of the solid lubricant layer is several molecule thickness to several tens of minutes (20 to several hundred Å)
It is preferable that If the solid lubricant layer is too thin, the anti-friction and anti-wear effects cannot be sufficiently obtained, and even if the solid lubricant layer is too thick, the above effects cannot be obtained when the thickness is in the above range, and the lubricant is wasted. Incidentally, in the usual case, when the saturated fatty acid salt is applied so as to have a concentration of 50 to 500 mg / m ² , a solid lubricant layer having the above layer thickness is obtained.

On the other hand, the silane coupling agent is diluted with a solvent such as Freon and spin-coated to form a solid lubricant layer. Also in this case, the layer thickness is preferably several molecule thickness to several tens of minutes (20 to several hundred Å) for the same reason as in the case of the saturated fatty acid salt.

On the other hand, PFPE is used as the liquid lubricant used in the liquid lubricant layer. As PFPE, the one shown in Formula 9 is preferable. R ¹ CF ₂ (CF ₂ O) _n (CF ₂ CF ₂ O) _m CF ₂ R ² ... Formula 9 (wherein R ¹ and R ² are any of alcohol, glycol, glycerin, phenol and carboxylic acid) Residues, or fluorine-substituted products thereof, m + n is an integer of 10 to 50.) PFPE represented by the formula 9 is, for example, Fombl.
inAM2001, Z-DOL and the like.

The above-mentioned PFPE is made into a liquid lubricant by diluting it in a solvent such as Freon and spin-coating it.
At this time, the layer thickness is preferably several Å to 15 Å. When the liquid lubricant layer is too thin, the self-repairing action is not sufficiently exerted, while when it is thick, sticking between the disk and the head is induced. Incidentally, in the usual case, when the silane coupling agent is applied in an amount of several mg / m ² , a liquid lubricant layer having the above layer thickness is obtained.

Next, the above magnetic disk was actually manufactured,
The abrasion resistance was examined.

Example 1 C was formed on an aluminum substrate having a Ni-P plating film formed on the surface.
r Underlayer film, metal magnetic thin film, SiO ₂ protective film are formed, and S
A magnetic disc was produced by forming an aminosilane solid lubricant layer having a film thickness of 10 Å and a PFPE liquid lubricant layer having a film thickness of 8 Å on the iO ₂ protective film by spin coating.

Comparative Example 1 A magnetic disk was prepared in the same manner as in Example 1 except that only a 20Å-thick PFPE liquid lubricant layer was formed on the SiO ₂ protective film.

With respect to the magnetic disk thus manufactured, Mn--Zn was used under the environment of temperature 50 ° C. and relative humidity 60%.
Run the ferrite slider for 40 hours to obtain a friction coefficient μ
Was measured.

As a result, the friction coefficient μ was μ <0.2 in the magnetic disk of Example 1 and μ> 0.4 in the magnetic disk of Comparative Example 1. Therefore, from this, it was confirmed that in the magnetic disk, it is effective to improve the abrasion resistance by forming the lubricant layer into the two-layer structure of the solid lubricant layer and the liquid lubricant layer. In this example,
The thickness of the solid lubricant layer was set to a relatively low value of 10Å,
It is considered that when the thickness is further increased, the abrasion resistance is further improved.

[0048]

As is apparent from the above description, in the magnetic disk of the present invention, since the lubricant layer has the two-layer structure of the solid lubricant layer and the liquid lubricant layer, sticking of the magnetic head hardly occurs. The lubricant layer is not lost even after repeated use, and has excellent abrasion resistance and wear resistance. Further, since the molecular constitution of the lubricant used for the solid lubricant layer is regulated, the lubricant layer can be uniformly and firmly adhered to the disk, and a stable lubricating effect can be obtained.

[Brief description of drawings]

FIG. 1 is a schematic cross-sectional view of essential parts showing a configuration example of a magnetic disk of the present invention.

FIG. 2 is a schematic view showing a bonded state of a carbon protective film and a solid lubricant, and a solid lubricant and a liquid lubricant.

FIG. 3 is a schematic diagram showing a bonded state of a SiO ₂ protective film and a solid lubricant, and a solid lubricant and a liquid lubricant.

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 1 ... Substrate 2 ... Ni-P film 3 ... Cr base film 4 ... Magnetic layer 5 ... Protective film 6 ... Lubricant layer 7 ... Solid lubricant layer 8 ...・ Liquid lubricant layer

Claims (7)

[Claims] 1. A magnetic disk comprising a nonmagnetic substrate on which a metal magnetic thin film and a carbon protective film are formed, wherein a solid lubricant layer made of a saturated fatty acid salt in a solid state at room temperature and a perfluoropolycarbon layer are formed on the carbon protective film. A magnetic disk comprising a liquid lubricant layer formed of ether in a liquid state at room temperature. 2. A metal magnetic thin film, SiO ₂ on a non-magnetic substrate.
In a magnetic disk having a protective film formed thereon, a solid lubricant layer made of a silane coupling agent and solid at room temperature and a liquid lubricant layer made of perfluoropolyether in a liquid state at normal temperature are formed on the Si ₂ O protective film. A magnetic disk characterized by being formed with. 3. The magnetic disk according to claim 1, wherein the saturated fatty acid salt is a saturated fatty acid salt represented by formula 1. _{CF 3 (CF 2) n COONH} 3 C m H 2m + 1 ··· Formula 1 (where, m is 18 or more integer, n is an integer of 6-8.) 4. The magnetic disk according to claim 2, wherein the silane coupling agent is a silane coupling agent represented by formula 2. _{(C k H 2k + 1 O} ) 3 Si (CH 2) n C m F 2m + 1 ··· formula 2 (where, k is 1 or 2, m is an integer of from 1 to 10, n represents 2
Or 3. ) 5. The magnetic disk according to claim 1, wherein the perfluoropolyether is a perfluoropolyether represented by formula 3. R ¹ CF ₂ (CF ₂ O) _n (CF ₂ CF ₂ O) _m CF ₂ R ² ... Formula 3 (wherein R ¹ and R ² are any of alcohol, glycol, glycerin, phenol and carboxylic acid) Residues or fluorine-substituted products thereof, m + n is an integer of 10 to 50.) 6. The thickness D _s of the solid lubricant layer is 20Å ≦ D
3. The magnetic disk according to claim 1, wherein _s ≦ 700Å. 7. The film thickness D _L of the liquid lubricant layer is 5Å ≦ D _L
3. The magnetic disk according to claim 1, wherein ≦ 15Å.