JP3801040B2 - Method for manufacturing magnetic recording medium - Google Patents

Description

[0001]
BACKGROUND OF THE INVENTION
The present invention relates to a method for manufacturing a hard disk magnetic recording medium constituting a hard disk device, and more particularly to a method for manufacturing a magnetic recording medium in which a lubricating layer is formed by a vacuum evaporation method.
[0002]
[Prior art]
The hard disk device is a main external recording device of a computer, and with the progress of multimedia, the recording density, the transfer speed, and the miniaturization are rapidly progressing. As a result, the magnetic recording medium, which is the main component of the hard disk device, is required to maintain the tribological mechanical strength as well as the recording density.
[0003]
A magnetic recording medium is a component that magnetically records information. A base film, a magnetic film, and a protective film are laminated on a substrate, and a lubricant is further applied. Usually, the substrate is made of an Al alloy, and the surface of the substrate is protected by applying a NiP plating layer. In order to improve the impact resistance, a glass substrate is used.
[0004]
The magnetic film for recording information is made of a Co-based ferromagnetic material, and a Cr underlayer is inserted in order to improve the magnetic characteristics. In addition, in order to protect the magnetic film, a hard carbon-based protective film called diamond-like carbon (DLC) which is excellent in lubricity and hardly worn is coated. Usually, the carbon protective film is deposited by sputtering in the same manner as the Cr underlayer film and the magnetic film.
[0005]
Perfluoropolyether (PFPE) is mainly used for the lubricating layer applied on the protective film. This is diluted with a solvent and formed by dipping or spin coating. The thickness of the lubricating layer is about 1 nm to several nm.
[0006]
The lubricating layer on the protective film is divided into two types. One is a layer bonded to the protective film (bonded lubricating layer), and the other is a layer not bonded (free lubricating layer). If the free lubricating layer is thick, it adheres to the head and affects the head flying height, or the disk medium and the head adsorb and the disk does not rotate. Further, since the disk medium rotates at a high speed, the free lubricating layer moves to the outer peripheral side by centrifugal force, and is easily worn. For this reason, it is desired to make the free lubricating layer thin, and hence the bonded lubricating layer thick.
[0007]
By forming the lubricating layer without exposing the surface of the carbon protective film to the atmosphere, it is possible to increase the component of the lubricant bonded to the protective film. As the technique, a method of forming a protective film and a lubricating layer by a consistent vacuum process has been reported. A sputtering method or a plasma CVD method is used to produce a carbon-based protective film, and a vacuum deposition method is used for a lubricant that is a liquid.
[0008]
[Problems to be solved by the invention]
In the process of continuously forming the protective film and the lubricating layer in vacuum, when the lubricant is vacuum-deposited, as shown in FIG. 5, the thickness of the bonded lubricating layer is determined by the total thickness of the deposited lubricating layer. There is a problem that the ratio of the bonded lubricating layer to the total thickness of the lubricating layer cannot be controlled.
[0009]
The present invention has been made in view of such problems, and its purpose is to deposit a lubricant on a substrate heated to a constant temperature, or to expose a substrate to be deposited to an oxygen atmosphere before vapor deposition. It is another object of the present invention to provide a method for manufacturing a magnetic recording medium in which the lubricant is deposited by controlling the bonding rate between the carbon protective film and the liquid lubricant molecules.
[0010]
[Means for Solving the Problems]
The present invention, in order to achieve the above object, an invention according to claim 1, on a nonmagnetic substrate, sequentially laminated magnetic film and the carbon protective film of each of the at least one layer and a liquid lubricant layer And after forming the carbon protective film, in the method of manufacturing a magnetic recording medium in which the liquid lubricating layer is continuously formed in a vacuum, the liquid lubricating layer includes a first layer combined with the carbon protective film, A non-bonded second layer that is not bonded to the carbon protective film, and the non-magnetic substrate is heated at a predetermined temperature within a range of 80 ° C. to 140 ° C. when the liquid lubricant layer is formed by a vacuum deposition method. The ratio of the film thickness of the first layer of the liquid lubrication layer to the total film thickness of the liquid lubrication layer is controlled according to the predetermined temperature .
[0011]
The invention according to claim 2 has a magnetic film, a carbon protective film, and a liquid lubricating layer, which are sequentially laminated on a nonmagnetic substrate, respectively, and after forming the carbon protective film, In the method of manufacturing a magnetic recording medium in which the liquid lubricating layer is continuously formed in a vacuum, the liquid lubricating layer includes a first layer bonded to the carbon protective film and a second layer not bonded to the carbon protective film. Before the deposition of the liquid lubrication layer, the surface of the carbon protective film is exposed to an oxygen atmosphere at a certain pressure for a certain time, and the liquid lubrication layer according to at least one of the pressure and the time The ratio of the film thickness of the first layer of the liquid lubricant layer to the total film thickness is controlled.
[0014]
That is, according to the present invention, a lubricant is deposited on a substrate heated to a constant temperature, or a lubricant is deposited in a state where the deposited substrate is exposed to an oxygen atmosphere before deposition, so that the carbon protective film and the liquid lubricant are deposited. The molecular bond rate is controlled.
[0015]
With this configuration, the lubricating layer deposited on the heated substrate has a higher ratio of the bonded lubricating layer to the total thickness of the lubricating layer than that without heating, and the ratio can be controlled by the heating temperature. The lubricating layer deposited on the substrate exposed to an oxygen atmosphere before vapor deposition has a lower ratio of the bonded lubricating layer to the total thickness of the lubricating layer than that without exposure, and the ratio can be controlled by the exposure pressure and the exposure time.
[0016]
DETAILED DESCRIPTION OF THE INVENTION
Embodiments of the present invention will be described below with reference to the drawings.
FIG. 1 is a cross-sectional view of a magnetic recording medium produced by the method of manufacturing a magnetic recording medium of the present invention. In FIG. 1, reference numeral 1 denotes a magnetic recording medium, and this magnetic recording medium 1 is sequentially placed on a nonmagnetic substrate 2. The magnetic film 5, the carbon protective film 6, and the liquid lubricating layer 7 are laminated. The nonmagnetic substrate 2 may be any conventional nonmagnetic substrate such as an aluminum alloy, glass, or plastic substrate. Specific examples of the plastic substrate include substrates made of polycarbonate, polyolefin, polyethylene terephthalate, polyethylene naphthalate, polyimide, and the like.
[0017]
Further, the non-magnetic substrate 2 may be a disk substrate having a size of 2.5 inches, 3 inches, 3.3 inches, 3.5 inches, or 5 inches, and the form thereof is also a disk. It is not limited to a shape, and any shape such as a card shape or a belt shape may be used. In addition, it should be understood that the size shown here is a nominal value and is widely used in the art.
[0018]
The magnetic film 5 includes a ferromagnetic metal that can be used as a recording layer, and specifically includes CoCrTaPt, CoCrTaPt—Cr ₂ O ₃ , CoCrTaPt—SiO ₂ , CoCrTaPt—ZrO ₂ , CoCrTaPt—TiO ₂ , CoCrTaPt—Al ₂ O. _{3 and the} like.
[0019]
The thickness of the magnetic film 5 is 20 nm or less, preferably 10 to 20 nm. A plurality of magnetic films may be used to form a multilayered recording layer.
[0020]
Further, the base film 4 may be formed between the magnetic film 5 and the substrate 2. The base film 4 may be formed of any conventional component for forming the base film, and is not particularly limited. Specifically, it consists of Cr, Cr-W, Cr-V, Cr-Mo, Cr-Si, Ni-Al, Co-Cr, Mo, W, Pt, and the like. The thickness of the base film is 20 nm or less, preferably 10 to 20 nm.
[0021]
The carbon protective film 6 has a function of protecting the magnetic film forming the recording layer from the impact of the head and the corrosion of corrosive substances in the outside world. The thickness of the protective film is 8 nm or less, preferably 2 to 8 nm. The film forming method may be any method such as sputtering or plasma CVD. The carbon film quality may be formed from any conventional component such as hydrogenated amorphous carbon or nitrogen added amorphous carbon.
[0022]
The lubricant is perfluoropolyether and may be any liquid lubricant such as Z-dol, Z-tetraol, Z-dolTX, and AM. The film thickness of the lubricating layer was measured by infrared spectroscopy, and was determined from absorption near 1270 cm ⁻¹ due to —CF vibration. The film thickness of the bonded lubricating layer was determined by the same measurement by infrared spectroscopy after ultrasonic cleaning in a fluorocarbon solvent to remove the free lubricating layer.
[0023]
By heating and holding the substrate at 80 to 140 ° C. during vapor deposition of the lubricant, the bonded lubricating layer was thicker than that without heating, that is, the ratio of the bonded lubricating layer to the total thickness of the lubricating layer could be increased. . FIG. 2 is a diagram showing the relationship between the substrate temperature and the film thickness of the bonded lubricating layer in the present invention.
[0024]
When the substrate temperature is 80 ° C. or lower, the thickness of the bonded lubricating layer is hardly changed as compared with the case without heating, and when the substrate temperature is 140 ° C. or higher, the deposited lubricant is redeposited.
[0025]
Also, by exposing the substrate to an oxygen atmosphere before the deposition of the lubricant, the bonded lubricating layer was thinner than that without exposure, that is, the ratio of the bonded lubricating layer to the total thickness of the lubricating layer could be reduced. . FIG. 3 is a diagram showing the relationship between the pressure during exposure to oxygen and the thickness of the bonded lubricating layer in the present invention.
[0026]
Hereinafter, the present invention will be described with reference to examples. However, the present invention is not limited to the examples.
[0027]
[Example 1]
As shown in FIG. 1, Ni-P plating 3 is applied on an aluminum alloy substrate 2, and a 20 nm Cr underlayer 4, a 20 nm Co magnetic layer 5 and an 8 nm nitrogen-added amorphous carbon protective film are formed thereon by sputtering. 6 was deposited. Further, a liquid lubricant (Z-dol: trade name Ausimont) was formed on the carbon film by a vapor deposition method described in detail below.
[0028]
FIG. 4 is a schematic diagram of a film forming apparatus used in this experiment. The crucible 15 for heating the lubricant stock solution, the shutter 17 and the substrate 11 are configured, and the distance between the crucible and the substrate is 200 mm. A certain amount of lubricant was put in a crucible, and after the formation of the carbon protective film, a liquid lubricant was vapor-deposited at a pressure of 3 × 10 ⁻⁴ Pa or less on a substrate transported in vacuum. At this time, the substrate was heated and maintained at 140 ° C.
[0029]
When the total film thickness of the lubricating layer and the film thickness of the combined lubricating layer of the magnetic recording medium obtained were measured, the total film thickness was about 2 nm, and the combined lubricating layer was about 1.4 nm. The ratio of the bonded lubrication layer to about 70% was about 70%. In the conventional manufacturing method without heating the substrate, when the total film thickness is about 2 nm, the bonded lubricating layer is about 1.1 nm, and the ratio of the bonded lubricating layer to the total thickness of the lubricating layer is about 55%. By maintaining the temperature at 0 ° C., the ratio of the bonded lubricating layer to the total thickness of the lubricating layer could be increased.
[0030]
[Example 2]
As in Example 1, Ni—P plating 3 is applied on an aluminum alloy substrate 2, and a 20 nm Cr underlayer 4, a 20 nm Co magnetic layer 5, and an 8 nm nitrogen-added amorphous carbon protective film are formed thereon by sputtering. 6 was deposited. Further, a liquid lubricant (Z-dol: trade name Ausimont) was formed on the carbon film by a vapor deposition method described in detail below.
[0031]
After the formation of the carbon protective film, the substrate that was vacuum transferred was exposed to an oxygen atmosphere at a pressure of 10,000 Pa for 2 hours. The substrate temperature at this time was RT.
[0032]
When the total film thickness of the lubricating layer and the film thickness of the combined lubricating layer of the obtained magnetic recording medium were measured, the total film thickness was about 2 nm and the combined lubricating layer was about 0.82 nm. The ratio of the bonded lubrication layer to about 40% was about 40%. In the conventional manufacturing method without heating the substrate, the combined lubricating layer is about 1.1 nm when the total film thickness is about 2 nm, and the ratio of the combined lubricating layer to the total film thickness of the lubricating layer is about 55%. By exposing to the atmosphere, the ratio of the bonded lubricating layer to the total thickness of the lubricating layer could be lowered.
[0033]
【The invention's effect】
As described above, according to the present invention, in a manufacturing method in which a carbon protective film and a liquid lubricating layer are continuously formed in a vacuum, a lubricant is deposited on a substrate heated to a constant temperature, and then exposed to an oxygen atmosphere and then lubricated. By depositing the agent, the bonding rate between the carbon protective film and the liquid lubricant molecule is controlled. Thereby, a lubricating layer corresponding to any design of the magnetic recording medium can be formed.
[Brief description of the drawings]
FIG. 1 is a cross-sectional view of a magnetic recording medium produced by a magnetic recording medium manufacturing method of the present invention.
FIG. 2 is a diagram showing a relationship between a substrate temperature and a film thickness of a bonded lubricating layer in the present invention.
FIG. 3 is a diagram showing the relationship between the pressure during exposure to oxygen and the film thickness of a bonded lubricating layer in the present invention.
FIG. 4 is a schematic view of a film forming apparatus used in the present invention.
FIG. 5 is a diagram showing the relationship between the total thickness of the lubricating layer and the bonded lubricating layer in a conventional vapor deposition method.
[Explanation of symbols]
DESCRIPTION OF SYMBOLS 1 Magnetic recording medium 2 Nonmagnetic board | substrate 3 Plating layer 4 Underlayer 5 Magnetic layer 6 Carbon protective film 7 Liquid lubricating layer 8 Protective film deposition chamber 9 Lubricating layer vapor deposition chamber 10 Transport chamber 11 Substrate 12 Carbon target 13 DC power supply 14 Lubricant 15 Crucible 16 Heater 17 Shutter 18 Gas introduction part

Claims (2)

The non-magnetic substrate has at least one magnetic film, a carbon protective film, and a liquid lubricating layer that are sequentially stacked. After the carbon protective film is formed, the liquid lubricating layer is continuously formed in a vacuum. In the method of manufacturing a magnetic recording medium,
The liquid lubrication layer has a first layer bonded to the carbon protective film and a second layer not bonded to the carbon protective film,
When the liquid lubricant layer is formed by a vacuum deposition method, the non-magnetic substrate is heated at a predetermined temperature within a range of 80 ° C. to 140 ° C., and the total of the liquid lubricant layer is increased according to the predetermined temperature. A method of manufacturing a magnetic recording medium, comprising controlling a ratio of a film thickness of the first layer of the liquid lubricant layer to a film thickness . The non-magnetic substrate has at least one magnetic film, a carbon protective film, and a liquid lubricating layer that are sequentially stacked. After the carbon protective film is formed, the liquid lubricating layer is continuously formed in a vacuum. In the method of manufacturing a magnetic recording medium,
The liquid lubrication layer has a first layer bonded to the carbon protective film and a second layer not bonded to the carbon protective film,
Before vapor deposition of the liquid lubrication layer, the surface of the carbon protective film is exposed to an oxygen atmosphere at a constant pressure for a certain time, and according to at least one of the pressure and the time, the total film thickness of the liquid lubrication layer, A method of manufacturing a magnetic recording medium, comprising controlling a film thickness ratio of the first layer of the liquid lubricant layer.

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