JPH0935257A - Production of magnetic recording medium - Google Patents

Abstract

PURPOSE: To provide a method for producing a magnetic recording medium by which the sliding durability of the substrate of the medium and a magnetic head is improved. CONSTITUTION: When a magnetic recording medium is produced using a glass substrate, the substrate is textured by continuous irradiation with pulsating laser beams from UV laser at energy density between 0.01J/cm<2> and working threshold value before a magnetic layer, etc., are formed. The irradiation is repeated 2-1000 times.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a method for manufacturing a magnetic recording medium such as a magnetic disk device, and more particularly to a magnetic recording having improved sliding durability between a magnetic disk (hereinafter referred to as HD) and a magnetic head. The present invention relates to a method of manufacturing a medium.

[0002]

2. Description of the Related Art The progress of high-density magnetic recording has been steadily increasing, and the speed of improving the recording density of a hard disk drive (HDD), which was once said to be 10 times in 10 years, has recently been 100 times in 10 years. Voices have also been heard.
HDD is commonly referred to as Winchester style, HD /
The CSS (contact start / stop) method, which has a basic operation of contact sliding between magnetic heads, head levitation, and contact sliding, is the mainstream.
This method is an epoch-making method that accelerates the increase in the recording density of HDDs at the same time, but on the other hand, it has also become the beginning of bringing serious tribological problems. The recent increase in recording density is accompanied by an increase in disk rotation speed and a decrease in the flying height of the magnetic head, and the demand for CSS-based sliding durability / stability and HD surface smoothness is increasing. It is the present situation. The key to improving the sliding durability between the magnetic head and the HD is the improvement of the material strength and the reduction of the friction coefficient including the lubricity. However, from the HD side, the conventional top coat technology is considered (diamond-like carbon ( Efforts have been made to reduce the friction coefficient by roughening the HD surface along with DLC) protective film, various coating lubricants, etc.). This is called texturing, and is intended to lower the coefficient of friction and increase CSS durability / stability by effectively reducing the contact area. The roughening is basically forming unevenness having a height difference within a predetermined range on the HD surface. This texture processing is an indispensable elemental technology in HD manufacturing.

[0003] The above-mentioned texture technique is, of course, inseparable from the material of the substrate.
In the case of 1 substrate, a method of forming irregularities by mechanical polishing using a polishing powder or the like has been mainly used. Further, for glass substrates and the like, lithography, etching techniques combining printing techniques with it, and the like have been proposed, and some have been put to practical use.

[0004]

As can be said of the texture technology in general, the efficiency of the process is a necessary requirement along with the precise unevenness control, but the two are often in an antagonistic relationship, and in particular, as described above, Under the current trend of high recording density of HDDs, which is proceeding at an amazing speed, the conventional technology cannot not only satisfy the specified specifications, but also various problems that can no longer be covered by accumulating ideas and improvements. The point is being revealed. For example, the mechanical polishing method is already near the limit of fine processing control, and not only the height of the unevenness but also the precision control of the texture area, which is important in zone texturing and the like, has encountered fundamental difficulties. Specifically, it is the occurrence of irregularities (overpolishing, burrs, etc.) that show height differences outside a predetermined range that occur at a fixed rate, and blurring of texture boundaries. In addition, although the lithographic technique has no problem in terms of precision control, the complexity of the process is inevitable, which is the Achilles tendon in terms of efficiency. On the other hand, higher recording capacity and higher quality of the HDD necessarily implies higher cleanliness of the HD manufacturing environment, and removal / elimination of various contaminants and dust at a high level is the highest goal for each process. It is the present situation. From this point of view, it is desirable that each process is dry, and there are great expectations for this dry texturing. Attempts to apply laser light to material processing and measurement can be said to have begun since the beginning of the invention of the laser, but the recent development / development of laser light sources has brought about remarkable improvements in basic characteristics and handling properties. It forms a wide base of application technology up to precise measurement. The material is deposited by laser beam,
Alternatively, laser ablation (erosion) or laser etching for processing a material surface has been actively studied since the 1980's, and a so-called laser texture technique for performing texturing by using the technique has recently attracted attention (for example, US Pat. No. 5,620,221). JP-A-62-2097
No. 98). This has the advantage that it is possible to precisely control the individual surface irregularities formed utilizing the characteristics of the laser beam and that it is basically a dry process. Further, it can be said that it has a degree of freedom / versatility that a laser type or wavelength and an energy density can be selected according to the substrate material. However, in the case of a so-called alternative substrate such as glass and silicon, irradiation / ablation of a simple laser beam that does not limit the laser type, wavelength, and energy density causes irregularities in irregularities due to reattachment of scattering fine particles or excessive corrosion, and the like. There is a high probability that problems such as cracks and CSS characteristics will be worsened.

[0005]

The present invention has been proposed in view of the above, and in a method of manufacturing a magnetic recording medium using a glass substrate, prior to forming a magnetic layer or a protective layer,
0.01 J / cm ^{2 with} respect to the substrate by using a harmonic of YAG laser and an ultraviolet laser typified by an excimer laser
The present invention relates to a method for manufacturing a magnetic recording medium, characterized in that texture processing is performed by continuously irradiating the laser pulse beam having an energy density equal to or less than a processing threshold value twice or more and 1000 times or less.

Generally, when a material such as ceramics or polymer material is irradiated with a laser beam, if the energy density of the laser beam exceeds a certain threshold value, the working depth rapidly increases (laser damage as shown in FIG. 1). Non-linearity)
However, it is known that when the pulse beam irradiation is continuously performed in a region below the threshold value, a conical projection called a conical structure is formed (for example, Journal of
Applied Physics, 49, 453, 19
1986). Regarding the above-mentioned problems, the inventors of the present invention have made a detailed study on laser irradiation conditions, irradiation atmospheres, etc., and as a result, the key to solving the problem is the shape control of the unevenness on the substrate formed by the laser beam, The present invention has been completed by discovering that the structure having the desired shape shown in FIGS. 2A and 2B can be appropriately formed by devising the energy density distribution.

That is, according to the present invention, an ultraviolet laser of YAG, excimer or the like is continuously irradiated to the substrate in a pulse form at an energy density of 0.01 J / cm ² or more and a processing threshold value or less for 2 times or more and 1000 times or less. The substrate is subjected to a texture treatment which is capable of forming a protrusion having an intended shape as shown in (A) and which repeats start-sliding-floating-sliding-stop between the magnetic head and HD, which is so-called excellent CSS characteristics. It is a thing. It is not preferable to continuously irradiate the laser pulse beam 1000 times or more in terms of throughput.
FIG. 3 shows the glass surface processed by the laser pulse beam and the laser single beam used in the present invention.
The appearance frequency of the uneven shape shown by (A) and (B) is shown.
When the energy density of the laser beam exceeds a certain value,
The frequency of appearance of the protrusion [FIG. 2 (A)] decreases sharply. When a substrate is processed by irradiating a laser single beam, it is necessary to concentrate excessive energy exceeding a processing threshold value, and it is difficult to selectively form desired projections required by the present invention. On the other hand, in the present invention, since the substrate is continuously irradiated with the laser pulse beam, not only the unevenness is sufficiently formed even by the laser irradiation with the energy density of 0.01 J / cm ² or more and the processing threshold or less, but also the size of the protrusion is increased. There is an advantage that the appearance frequency can be set selectively. Although the processing itself is possible even with an energy density of less than 0.01 J / cm ^2, it is not suitable for practical use (as the texture of the substrate surface of the magnetic recording medium) because a sufficiently large protrusion cannot be obtained. It is desirable to process the protrusions in a range where the laser beam irradiation intervals do not overlap. If the beams overlap with each other, irregular irregularities are likely to be formed and the sliding durability of the HD is deteriorated. On the contrary, when the irradiation interval of the beam is widened to a certain value or more, the area where no concavities and convexities are formed expands and the contact area between the magnetic head and the HD increases, which deteriorates the sliding durability. Similarly, if the height of the protrusion is a certain height or more, the magnetic head and HD
And the sliding durability is deteriorated. The size of the protrusion formed on the surface of the substrate as the magnetic recording medium is preferably an outer radius of 1 to 50 μm and a height of 1 to 100 nm, and the ratio of the area occupied by the protrusion to the substrate surface is 0.1 to 99. 9% is desirable. Although the present invention is intended for a glass substrate which is originally difficult to be subjected to laser texturing, such a texturing can be applied to roughening a magnetic layer or a carbon protective film. It can also be applied to conventional Ni-P coated Al substrates, silicon substrates, and the like.

As described above, a glass substrate is irradiated with an ultraviolet laser at an energy density of 0.01 J / cm ² or more and an energy density of a processing threshold or less and textured, and then a base layer, a magnetic layer, and the like are sequentially formed. The formed magnetic recording medium has excellent sliding durability and does not cause cracks or the like even when it is used for which high durability is required. Therefore, magnetic recording devices such as magnetic disk devices having high reliability can be used. Can contribute to fabrication. In addition, each layer, base film, magnetic film, protective film, lubricating film, and the like formed on the glass substrate are not particularly limited in terms of material, composition, film forming method, and the like, and known materials and known methods can be used. It can be appropriately selected and used in combination.

[0009]

EXAMPLES Examples of the present invention will be shown below. The roughness was measured using a stylus type roughness meter with a stylus of 0.5 μm and a cutoff of 0.25 mm.

Example 1 On the surface of a soda lime glass substrate, the diameter 1 of the fourth harmonic (266 nm) of the YAG laser was measured.
0 μm beam with an energy density of 0.05 J / cm ² ,
Irradiation was performed for 100 pulses with a pulse width of 20 ns. As a result, Rp (protrusion height) 25 nm, Rv (recess depth) ≧
-1 nm, outer radius 7 μm, Sm (average spacing between protrusions) ~ 2
Surface protrusions of 5 μm were obtained at a rate of 60%. Subsequently, at a substrate temperature of 200 ° C., Cr100n was used as an underlayer.
m, a Co ₁₇ Cr ₄ Ta alloy 20 nm as a magnetic layer, and a carbon 20 nm as a protective layer are sequentially sputter-deposited, and a PFPE (perfluoropolyether) -based lubricant is further applied to form a film to obtain the magnetic recording medium of Example 1. It was made.

Example 2 Using a KrF (248 nm) excimer laser and a mask, an energy density of 0.02 J / cm ² and a pulse width of 15 ns were applied to the surface of soda lime glass.
The continuous pulse beam was irradiated 80 times. as a result,
Rp20 nm, Rv ≧ -1 nm, outer radius 6 μm, Sm-
A surface protrusion of 35 μm was obtained at a rate of 70%. Subsequently, a magnetic recording medium of Example 2 was manufactured in the same manner as in Example 1.

COMPARATIVE EXAMPLE 1 A YAG laser fourth harmonic (266 nm) beam having a diameter of 10 μm was applied to the surface of a soda-lime glass substrate for one pulse at an energy density of 5 J / cm ^{2, and} as a result, an outer radius was 8 μm and Rv- A 100 nm concave shape [FIG. 2 (B)] was formed. Subsequently, a magnetic recording medium of Comparative Example 1 was manufactured in the same manner as in Example 1.

<Comparative Example 2> An aluminum substrate was subjected to a conventional mechanical texture method so as to have Rp of 26 nm, Rv-30 nm or more and Sm of 2.2 μm, and subsequently, in the same manner as in Example 1, the magnetic property of Comparative Example 2 was determined. A recording medium was produced.

Table 1 shows Examples 1 and 2 and Comparative Examples 1 and 2.
1000 as CSS characteristics of each magnetic disk
The stiction value after 0 times is shown. A commercially available CSS tester was used as the CSS measuring device, and Al ₂ O was used as the magnetic head.
_{A 3-} TiC slider head was used.

[0015]

[Table 1]

As can be seen from Table 1, the magnetic recording media of Examples 1 and 2 of the present invention had a significantly lower stiction value than the magnetic recording media of Comparative Examples 1 and 2, and were manufactured by the conventional technique. The disk had better CSS characteristics than the disk.

The present invention has been described above based on the embodiments, but the present invention is not limited to the above embodiments, and can be carried out in any manner without changing the constitution described in the claims. it can.

[0018]

As described above, the present invention relates to a method for manufacturing a magnetic recording medium (HD) in which an underlayer, a magnetic layer, a protective layer, a lubricating layer and the like are successively formed on a glass substrate, It is intended to provide a laser texture technique for forming a required protrusion-shaped rough surface on a substrate by using a laser beam. The texturing method using laser abrasion can completely prevent the uneven shape and the non-controllability of the depth and the occurrence of burrs which have been problems in the conventional mechanical texture. Moreover, since many processes such as lithography technology and generation of waste such as resist and cleaning liquid are not involved, the facility cost can be reduced. However, when the substrate is processed by irradiating it with a laser single beam, it is necessary to excessively concentrate energy exceeding the processing threshold value, and it is difficult to selectively form the desired protrusions required in the present invention. In addition, since a recess is often generated due to excessive ablation and a crack is generated in a substrate that is thin and requires high durability. In the present invention, a laser pulse beam is continuously applied to the substrate.
Irradiation with a laser having an energy density of not less than 01 J / cm ^{2 and not} more than the processing threshold not only forms a sufficient uneven shape,
There is an advantage that the size and appearance frequency of the protrusions having excellent S characteristics can be selectively set. INDUSTRIAL APPLICABILITY By the present invention, a highly efficient and highly controllable texture processing technique can be obtained in the next-generation HD that requires high recording density / high durability.

[Brief description of drawings]

FIG. 1 is a correlation diagram showing the relationship between laser energy density and processing depth in substrate processing.

FIG. 2 is an enlarged side view of a texture formed on a glass substrate in the present invention, showing (A) a shape of a protrusion formed in the present invention, and (B) a recess formed with an energy density equal to or higher than a processing threshold. The shape.

FIG. 3 shows the difference in texture formed on the surface of soda lime glass between the laser pulse beam and the laser single beam, and shows the relationship between the ratio of the uneven shape shown in FIG. 2 and the laser energy density applied to the substrate. It is a correlation diagram shown.

Claims (1)

[Claims] 1. A method of manufacturing a magnetic recording medium using a glass substrate, wherein an ultraviolet laser is used prior to the formation of a magnetic layer or the like, and an energy density of 0.01 J / cm ² or more and a processing threshold or less is applied to the substrate. The laser pulse beam is 2
A method for producing a magnetic recording medium, characterized in that texturing is performed by continuously irradiating the magnetic recording medium once or more and 1,000 times or less.