Carbonaceous protective layer, magnetic recording medium, production method thereof, and magnetic disk apparatus

• US 6,974,642 B2
• Filed: 05/04/2001
• Issued: 12/13/2005
• Est. Priority Date: 03/15/2000
• Status: Expired due to Fees

• Current Assignee: Fujitsu Limited
• Original Assignee: Fujitsu Limited
• Inventors: Yamamoto, Takayuki, Hyodo, Hiroyuki
• Primary Examiner(s): Resan, Stevan A.
• Application Number:
  US09/849,966
• Publication Number:
  US 20010029051A1
• Time in Patent Office: 1,684 Days
• Field of Search: 428/408, 428/694.TC
• US Class Current: 428/835.4
• CPC Class Codes: C23C 14/0605 Carbon
• CPC Class Codes: C23C 14/22 characterised by the process of coating
• CPC Class Codes: C23C 14/325 Electric arc evaporation
• CPC Class Codes: G11B 5/727 Inorganic carbon protective coating, e.g. graphite, diamond like carbon or doped carbon
• CPC Class Codes: G11B 5/8408 protecting the magnetic layer
• CPC Class Codes: H01J 37/32055 Arc discharge

Abstract

A carbonaceous protective layer particularly suitable for use in magnetic recording media. The carbonaceous protective layer is formed by a Filtered Cathodic Arc process, and contains nitrogen distributed therein. A process for the production of a carbonaceous protective layer as well as a magnetic recording medium and a magnetic disk apparatus are also disclosed.

Claims

1. A carbonaceous protective layer having a controlled hardness of at least 18 GPa and a controlled adsorption of a liquid lubricant evaluated from a contact angle to water of not greater than 35°

for protecting an underlying material, which is a layer formed by a nitrogen ion beam-assisted Filtered Cathodic Arc process, and contains nitrogen distributed therein.

2. A carbonaceous protective layer according to claim 1,

wherein nitrogen is not contained in a substantially lower half portion, occupying substantially one half of the thickness-wise distance from a bottom surface of said carbonaceous protective layer, and

wherein a nitrogen concentration is gradually increased from substantially one half of the thickness-wise distance from a bottom surface of said carbonaceous protective layer to a top surface side in said carbonaceous protective layer.

3. A carbonaceous protective layer according to claim 1 or 2, wherein a nitrogen content of said carbonaceous protective layer is 2 to 20 at %.

4. A carbonaceous protective layer according to claim 1 or 2, wherein said carbonaceous protective layer is positioned over a magnetic recording layer of the magnetic recording medium.

5. A magnetic disk apparatus according to claim 1, wherein nitrogen is distributed in an inclined concentration in said carbonaceous protective layer, and a nitrogen concentration is gradually increased from a bottom surface side to a top surface side in said carbonaceous protective layer.

6. A magnetic recording medium comprising a non-magnetic substrate having applied thereon a magnetic recording layer, in which said magnetic recording layer has a carbonaceous protective layer having a controlled hardness of at least 18 GPa and a controlled adsorption of a liquid lubricant evaluated from a contact angle to water of not greater than 35°

formed thereon by a nitrogen ion beam-assisted Filtered Cathodic Arc process, and said carbonaceous protective layer contains nitrogen distributed therein.

7. A magnetic recording medium according to claim 6, wherein nitrogen is substantially not contained in a lower half portion, occupying substantially one half of the thickness-wise distance from a bottom surface of said carbonaceous protective layer.

8. A magnetic recording medium according to claim 6 or 7, wherein a nitrogen content of said carbonaceous protective layer is 2 to 20 at %.

9. A magnetic recording medium according to claim 6, wherein nitrogen is distributed in an inclined concentration in said carbonaceous protective layer, and a nitrogen concentration is gradually increased from a bottom surface side to a top surface side in said carbonaceous protective layer.

10. A magnetic disk apparatus comprising a recording head for recording information and a reproducing head for reproducing information to and from a magnetic recording medium, in which said magnetic recording medium comprises a non-magnetic substrate having applied thereon a magnetic recording layer, and said magnetic recording layer has a carbonaceous protective layer having a controlled hardness of at least 18 GPa and a controlled adsorption of a liquid lubricant evaluated from a contact angle to water of not greater than 35°

, formed thereon by a nitrogen ion beam-assisted Filtered Cathodic Arc process, which contains nitrogen distributed therein.

11. A magnetic disk apparatus according to claim 10,

wherein nitrogen is substantially not contained in a lower half portion, occupying a substantially one half of the thickness-wise distance from a bottom surface of said carbonaceous protective layer, and

wherein a nitrogen concentration is gradually increased from substantially one half of the thickness-wise distance from a bottom surface of said carbonaceous protective layer to a top surface side in said carbonaceous protective layer.

12. A magnetic disk apparatus according to claim 10, wherein nitrogen is distributed in an inclined concentration in said carbonaceous protective layer, and a nitrogen concentration is gradually increased from a bottom surface side to a top surface side in said carbonaceous protective layer.