JP3606106B2 - Magnetic recording medium and method for manufacturing the same - Google Patents

Description

[0001]
BACKGROUND OF THE INVENTION
The present invention relates to a magnetic recording medium mounted on a hard disk drive device used as an external storage device of an information processing apparatus such as a computer, and a manufacturing method thereof.
[0002]
[Prior art]
A hard disk drive device (hereinafter referred to as HDD) includes a magnetic recording medium (hereinafter simply referred to as medium) and a magnetic head disposed so as to face the magnetic recording medium, and information signals can be written to or read from the medium via the magnetic head. Done.
[0003]
The HDD usually employs a CSS (contact start / stop) system, and the magnetic head is driven by the air flow generated by the rotation of the medium on the medium that rotates at high speed when the information signal is written and read. It flies slightly and stops contacting the surface of the medium that is stopped when driving is stopped, and the magnetic head slides in contact with the surface of the medium transiently when starting and stopping driving. In order to write and read information signals satisfactorily, the surface of the medium is smooth, there is no abnormal protrusion that prevents stable and smooth flying when the device is driven, and when the drive is stopped, It is necessary that the surface of the medium is appropriately finely roughened so that the magnetic head is not attracted to the surface of the medium, and the contact and sliding of the magnetic head is smoothly performed at the start and stop of driving.
[0004]
The medium usually has a disk-like non-magnetic member plate surface made of an aluminum alloy or the like smoothed, and then a Ni-P film is formed on the surface to prevent the magnetic head from adhering to the medium surface. In order to improve the magnetic anisotropy of the medium and increase the coercive force, the unevenness of the Ni-P film is mechanically finely uneven along the circumferential direction. A rough alloy surface (mechanical texturing) is applied, and a Cr alloy underlayer, a Co alloy magnetic layer, a carbon-based protective layer, and liquid lubrication are formed on the nonmagnetic substrate on which such a texture is formed. A lubricant layer of the agent is sequentially formed and laminated. Since each layer formed on the substrate is a thin layer, the shape of the Ni-P film surface of the substrate becomes the shape of the medium surface as it is.
[0005]
The recording density of the information signal on the medium greatly depends on the distance between the magnetic layer of the medium and the magnetic head flying above (hereinafter simply referred to as the head flying height), and the recording density increases as the amount decreases. . In recent years, there is a strong demand for higher recording density of HDDs, and the flying height of the magnetic head is required to be further reduced, and the flying height of the head of 20 nm or less has been demanded. Conventionally, as described above, the Ni-P film surface formed on the substrate surface has been textured by mechanical texturing (hereinafter referred to as mechanical texture), but abnormal in mechanical texturing. The occurrence of protrusions is inevitable, and the height of the abnormal protrusions on the surface of the medium restricts the head flying height. In order to eliminate such problems, the unevenness caused by mechanical texturing in the data recording area of the medium is made as small as possible within the range where the effect of improving magnetic anisotropy can be obtained, and the height of the abnormal protrusion generated is reduced. Lowering the flying height of the head by lowering it, in the CSS area, forming a large number of bumps by laser processing on this mechanical texture, forming LZT (Laser Zone Texture) to prevent the medium surface and the magnetic head from being attracted, A method for improving the sliding characteristics has been developed (for example, JP-A-10-64055).
[0006]
[Problems to be solved by the invention]
In the laser processing as described above, the mechanical texture of the Ni-P film surface is irradiated with a pulse laser, and is substantially circular when viewed from above, and the side cross section is as shown in FIG. 2 (a) or FIG. 2 (b). A large number of bumps having a shape as shown in the schematic sectional view are formed. The shape of the bump depends on the laser frequency and the laser power. The relationship shown in the explanatory diagram of FIG. 3 is among the bump shape, bump diameter, and bump height (bump height) by the laser power using the laser frequency as a parameter. In FIG. 3, the vertical axis indicates the bump height, the horizontal axis indicates the laser power, and a, b. c3 types of laser are shown. Here, the level of the laser frequency is in the order of a <b <c. As shown in FIG. 3, at the same frequency, there is a region I where the bump diameter and bump height increase rapidly as the laser power increases, and then there is a region II where the bump height hardly increases even if the power increases. As shown in FIG. 2A, the bump formed in the region I has a V-shaped cross section, and the bump bulge is rounded at the tip, and the bump height changes greatly by slightly increasing or decreasing the laser power. As shown in FIG. 2B, the bump formed in the region II has a W-shaped cross section, the bump periphery has a sharp tip, and the bump height does not increase much even when the laser power increases. Further, as seen in FIG. 3, the bump height depends on the laser frequency, and as the frequency increases, the formed bump height increases.
[0007]
Conventionally, normally formed bumps have a bump diameter of about 10 μm for the V shape and about 15 μm for the W shape when the bump height is about 20 nm to 25 nm.
[0008]
When bumps are formed by laser processing as described above, the bump diameter and the bump height can be variously changed by changing the power in the laser power region I, but the bump diameter and the bump height are changed by a slight change in power. In the laser power region II, there is almost no variation in the bump diameter and bump height due to the variation in power. Therefore, in mass production, it is desirable to form bumps in the region II because it is easy to form bump shapes uniformly. Further, the W-shaped bump formed in the region II or the bulging tip at the upper periphery of the bump is sharper than the V-shaped bump formed in the region I, and the W-shaped bump is slid when the medium surface slides with the magnetic head. This is more preferable because the sliding characteristics are more stable than the V-shaped bump.
[0009]
However, in order to form a W-shaped bump having a low bump height in order to realize a low flying height, as shown in FIG. 3, it is necessary to reduce the frequency of the laser, resulting in inferior mass productivity. There is. For example, a bump with a bump height of about 20 nm or less can be formed with a laser having a frequency of 70 kHz to 90 kHz in the V shape, but must be a low frequency laser with a frequency of 10 kHz to 30 kHz in the W shape, which greatly improves the workability. To become impractical.
[0010]
The present invention has been made in view of the above-described points, and is a medium that can reduce the flying height of the head, at the same time, has good sliding characteristics between the magnetic head and the medium surface, and can prevent the magnetic head from being attracted. It aims at providing the manufacturing method.
[0011]
[Means for Solving the Problems]
According to the present invention, the above-described problem is that a nonmagnetic metal underlayer, a magnetic layer, a protective layer, and a lubricating layer are sequentially formed on a substrate in which a Ni-P film is formed on a disk-shaped nonmagnetic member plate. In the magnetic recording medium, the problem is solved by making the P concentration of the Ni-P film higher than that in the film from the surface to a depth of at least several nanometers.
[0012]
In such a medium, a Ni-P film is formed on a disk-shaped nonmagnetic member plate to form a substrate, and mechanically fine irregularities are formed along the circumferential direction on the surface of the Ni-P film of the substrate. A large number of fine bumps are formed on the uneven surface by laser processing, and a nonmagnetic metal underlayer, a magnetic layer, a protective layer, and a lubricating layer are sequentially laminated on the roughened substrate surface. In a method of manufacturing a magnetic recording medium, the method includes a step of immersing a substrate having a large number of fine irregularities formed on the surface of the Ni-P film in water and then forming a large number of fine bumps by laser processing. It is obtained by adopting the manufacturing method.
[0013]
Alternatively, the problem can be solved by adopting a manufacturing method including a step of forming a large number of fine bumps by laser processing after immersing a substrate having mechanically fine irregularities formed on the Ni-P film surface in a weak acid solution. .
[0014]
The Ni—P film is usually Ni ₄ P and has a composition with a Ni concentration of 60% and a P concentration of 40%. The Ni—P film formed on the substrate surface is usually washed with water for cleaning and the like, and as shown by the dotted line in the explanatory diagram of FIG. However, although the P concentration is increased and a very shallow region (about several nm or less), a high region of P concentration of 40% or more is generated, but the Ni-P film is actively immersed in water or a weak acid solution. As a result, as shown by the solid line in FIG. 1, the P concentration on the surface of the Ni-P film is further increased, and the depth from the surface of the region where the P concentration is as high as 40% or more (hereinafter referred to as P-rich layer). (Hereinafter referred to as the P-rich layer thickness) increases. The amount of increase in the P concentration and film thickness of the P-rich layer varies depending on the type, temperature, and immersion time of the liquid in which the Ni-P film is immersed, but the laser depends on the P concentration and film thickness of the formed P-rich layer. It was found that the bump height on the surface of the Ni-P film formed by processing can be controlled.
[0015]
When a substrate with a very fine mechanical texture formed on the Ni-P film surface is immersed in water or a weak acid solution to increase the thickness of the P-rich layer on the Ni-P film surface, A low W-shaped bump can be formed, and a fine LZT with a bump height of 20 nm or less can be formed. By sequentially laminating a nonmagnetic metal underlayer, magnetic layer, protective layer, and lubricating layer on the roughened substrate in this way, the head flying height can be reduced, and at the same time, sliding between the magnetic head and the medium surface is possible. A medium having good characteristics and capable of preventing the magnetic head from being attracted can be obtained.
[0016]
DETAILED DESCRIPTION OF THE INVENTION
FIG. 4 is a schematic cross-sectional view of a medium according to the present invention. On a substrate 1 in which a Ni-P film 12 is formed on a disk-like nonmagnetic member plate 11, an underlayer 2, a magnetic layer 3, A protective layer 4 and a lubricating layer 5 are sequentially formed.
As the nonmagnetic member plate, an aluminum alloy plate, a hard glass plate or a ceramic plate is used.
[0017]
The surface of the nonmagnetic member plate is processed smoothly and washed, and then a Ni-P film is formed on the surface by an electroless plating method or a sputtering method to obtain a substrate. The film thickness of the Ni—P film is usually about 10 μm. After this Ni-P film surface is processed and washed smoothly, a mechanical texture composed of fine irregularities along the circumferential direction is formed on the Ni-P film surface while rotating the substrate, and then washed and cleaned. To.
[0018]
The substrate having the mechanical texture formed and cleaned is immersed in water or a weak acid solution. By immersing in water or a weak acid solution, the P concentration and film thickness of the P-rich layer on the Ni-P film surface of the substrate increase. The amount of increase is greater in the weak acid solution than in water, and increases as the liquid temperature is higher and the immersion time is longer. In the weak acid solution, the higher the weak acid concentration, the greater. By selecting the type of immersion liquid, the liquid temperature, and the immersion time, it is possible to control the amount of increase in P concentration and film thickness of the P-rich layer. In the case of water immersion, the thickness of the P-rich layer is about 100 nm or more. In the case of the weak acid solution immersion, the thickness of the P-rich layer is about 10 nm or more. It becomes possible to form LZT composed of bumps as low as 20 nm or less.
[0019]
By using a substrate on which an extremely fine mechanical texture is formed on the surface of the Ni-P film, and on which a LZT made of W-shaped bumps having a bump height of 20 nm or less is formed, the head flying height is lowered to 20 nm or less. At the same time, it is possible to obtain a medium that has good sliding characteristics between the magnetic head and the medium surface and that can prevent the magnetic head from being attracted.
[0020]
【Example】
Examples of the present invention will be specifically described below.
Example 1
After the surface of the disk-shaped member plate made of an aluminum alloy is processed smoothly, a Ni—P film is formed to a thickness of about 10 μm by an electroless plating method, and the surface is polished and washed smoothly to obtain a substrate. While rotating this substrate, the surface of the Ni-P film is pressed by a polishing roller with a roller and roughened to form a mechanical texture having extremely fine irregularities along the circumferential direction. To do.
[0021]
When the substrate on which the mechanical texture was formed was immersed in warm pure water at 66 ° C. for 20 hours, the P-rich layer thickness increased by about 130 nm compared to when no water immersion was performed. Thereafter, laser texturing was performed on the substrate surface using a semiconductor laser having a frequency of 60 kHz and a power of 250 μW. As a result, a W-shaped bump was formed, and the bump height was reduced by about 12 nm to about 13 nm.
[0022]
The water immersion time was changed, and the relationship between the film thickness of the P-rich layer formed on the Ni-P film surface at that time, the immersion time, and the formed bump height was examined. The bump height was measured with an optical Micro-XAM (manufactured by PHASE SHIFT). The results are shown in the diagram of FIG.
[0023]
As can be seen from FIG. 5, the film thickness of the P-rich layer on the surface of the Ni-P film increases as the immersion time increases, and the bump height formed decreases as the film thickness of the P-rich layer increases.
[0024]
Example 2
A substrate having a mechanical texture formed and cleaned in the same manner as in Example 1 was immersed in a malic acid solution having a liquid temperature of 27 ° C. and a concentration of 0.1%. The immersion time was 450 seconds and the P-rich layer thickness was 4 nm. Increased. Subsequently, when a bump was formed by a semiconductor laser having a frequency of 60 kHz and a power of 250 μW, a W-shaped bump could be formed, and the bump height decreased by about 3 nm to about 17 nm.
[0025]
The immersion time was changed, and the relationship between the immersion time, the P-rich layer thickness on the Ni-P film surface, and the bump height formed was examined. The results are shown in the diagram of FIG.
As seen in FIG. 6, the same tendency as in the water immersion of Example 1 is observed between the immersion time, the P-rich layer thickness, and the bump height, but the malic acid solution immersion is more than in the water immersion. It can be seen that an increase in the film thickness of the P-rich layer is observed with a shorter immersion time, and a bump with a low bump height can be obtained.
[0026]
Example 3
When a substrate having a texture formed and cleaned in the same manner as in Example 1 was immersed in a malic acid solution having a liquid temperature of 50 ° C. and a concentration of 0.1% for 150 seconds, the P-rich layer thickness increased by about 6 nm. Subsequently, as in Example 2, when bumps were formed by a semiconductor laser having a frequency of 60 kHz and a power of 250 μW, the bump height was reduced by about 6 nm to about 14 nm.
[0027]
The liquid temperature was changed, and the relationship between the P-rich layer thickness and the formed bump height was examined. The results are shown in the diagram of FIG. The formed bumps were all W-shaped as in Example 2.
As can be seen from FIG. 7, as the liquid temperature increases, the P-rich layer thickness increases and the bump height decreases.
[0028]
In Example 2 and Example 3 described above, when the relationship between the P-rich layer thickness and the bump height when the substrate was immersed in the malic acid solution was examined, there was a correlation as shown in the diagram of FIG. It is understood that the bump height can be lowered by increasing the rich layer thickness, and in order to reduce the bump height to 20 nm or less with a W-shaped bump, the P rich layer thickness should be about 10 nm or more. .
[0029]
Example 4
A substrate having a mechanical texture formed and cleaned in the same manner as in Example 1 was immersed in a malic acid solution, a succinic acid solution, and a phosphoric acid solution having a concentration of 1% and a liquid temperature of 50 ° C. for 10 minutes. Subsequently, as in Example 2, when bumps were formed by a semiconductor laser having a frequency of 60 kHz and a power of 250 μW, bump height bumps as shown in the graph of FIG. 9 were formed. FIG. 9 also shows the bump height of the bump formed on the substrate that was not immersed in the acid solution for comparison.
[0030]
As seen in FIG. 9, the bump height of the bump formed when not immersed in an acid solution is as high as 20.5 nm, but by immersing in a weak acid organic acid such as malic acid or succinic acid or weak phosphoric acid, It can be seen that the thickness of the P-rich layer on the surface of the Ni-P film is increased, and a bump having a low bump height can be formed.
[0031]
【The invention's effect】
According to the present invention, in a magnetic recording medium in which an underlayer, a magnetic layer, a protective layer, and a lubricating layer are sequentially laminated on a substrate having a Ni-P film formed on a disk-shaped nonmagnetic member plate, By using a medium in which a P-rich region having a P concentration higher than the inside of the film is formed from the surface of the Ni-P film formed on the nonmagnetic member plate to a depth of at least several nm or more, the head flying height is 20 nm. It is possible to obtain a medium that can be reduced to the following, and at the same time, has good sliding characteristics between the magnetic head and the medium surface and can prevent the magnetic head from being attracted.
[0032]
Thus, it is possible to increase the thickness of the P-rich region on the surface of the Ni-P film by immersing the substrate on which the Ni-P film is formed in water or a weak acid solution.
[Brief description of the drawings]
FIG. 1 is an explanatory diagram for explaining changes in the P concentration of a Ni—P film due to liquid immersion. FIG. 2 is a schematic cross-sectional view of a bump shape formed by laser texturing. FIG. FIG. 4 is a schematic cross-sectional view of the medium according to the present invention. FIG. 5 is a diagram showing the relationship between the water immersion time, the P-rich layer thickness, and the bump height to be formed. Diagram showing the relationship between malic acid solution immersion time, P-rich layer thickness, and formed bump height [Fig. 7] Diagram showing the relationship between malic acid solution temperature, P-rich layer thickness, and formed bump height [ FIG. 8 is a diagram showing the relationship between the P-rich layer thickness formed by dipping malic acid solution and the bump height to be formed. FIG. 9 is a graph showing an example of bump height of bumps formed when dipped in various weak acids. Figure Description of]
DESCRIPTION OF SYMBOLS 1 Substrate 11 Nonmagnetic member plate 12 Ni-P film 2 Underlayer 3 Magnetic layer 4 Protective layer 5 Lubrication layer

Claims (3)

In a magnetic recording medium in which a nonmagnetic metal underlayer, a magnetic layer, a protective layer, and a lubricating layer are sequentially laminated on a substrate having a Ni-P film formed on a disk-shaped nonmagnetic member plate, the disk-shaped nonmagnetic member A magnetic recording medium, wherein a P-rich region having a P concentration higher than the inside of the film is formed from the surface of the Ni-P film formed on the plate to a depth of at least several nm or more. A Ni-P film is formed on a disk-like non-magnetic member plate to form a substrate, mechanically fine irregularities are formed along the circumferential direction on the Ni-P film surface of the substrate, and a laser is formed on the irregular surface. In a method of manufacturing a magnetic recording medium, after forming a large number of fine bumps by processing, a nonmagnetic metal underlayer, a magnetic layer, a protective layer, and a lubricating layer are sequentially stacked on the roughened substrate surface. A method for producing a magnetic recording medium, comprising: immersing a substrate having fine irregularities mechanically formed on the Ni-P film surface in water and then forming fine bumps by laser processing. A Ni-P film is formed on a disk-like non-magnetic member plate to form a substrate, mechanically fine irregularities are formed along the circumferential direction on the Ni-P film surface of the substrate, and a laser is formed on the irregular surface. In the method of manufacturing a magnetic recording medium, after forming fine bumps by processing, a nonmagnetic metal underlayer, a magnetic layer, a protective layer, and a lubricating layer are sequentially laminated on the roughened substrate surface. A method for producing a magnetic recording medium, comprising: immersing a substrate having mechanically fine irregularities formed on a Ni-P film surface in a weak acid solution and then forming fine bumps by laser processing.

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