JPH0935261A - 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 or silicon substrate, the substrate is textured by irradiation with laser beams from UV laser in a circular band shape before a magnetic layer, etc., are formed.

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, it improves sliding durability between a magnetic disk (hereinafter referred to as HD) and a magnetic head. The present invention relates to a method for manufacturing a magnetic recording 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 introducing 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 to lower the coefficient of friction, including the improvement in material strength and lubricity. However, from the HD perspective, the conventional topcoat technology [diamond-like carbon ( Efforts have been made to reduce the coefficient of friction 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 important elemental technology of HD manufacturing technology.

[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. 88). 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 relates to a method of manufacturing a magnetic recording medium using a glass substrate or a silicon substrate, and is represented by a harmonic of a YAG laser, an excimer laser, or the like. The present invention relates to a method for manufacturing a magnetic recording medium, characterized in that the substrate is irradiated with the laser beam in the form of a ring using an ultraviolet laser.

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 inventors have found that the structure having the desired shape shown in FIGS. 2A and 2B can be appropriately formed by devising the energy density distribution, and the present invention has been completed.

That is, according to the present invention, a projection having a desired shape as shown in FIG. 2A is formed by irradiating a substrate with an ultraviolet laser such as YAG or excimer changed into a ring-shaped beam and irradiating the substrate. Yes, start-up between magnetic head and HD-
The substrate is subjected to a texture treatment which is excellent in so-called CSS characteristics in which sliding-floating-sliding-stop is repeated. FIG. 3 shows the glass surface processed by the annular laser beam used in the present invention and the conventional spot laser beam.
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 with a spot-shaped laser beam, the concentration of energy is not constant, so the formation of irregularities is unstable, making it difficult to selectively form the desired protrusions required by the present invention. is there. On the other hand, in the present invention, since the substrate is irradiated with a laser beam having an annular energy density distribution, the spread of the projections formed is controlled, and the deposits due to explosion erosion are easily collected in the center. However, there is an advantage that a protrusion having a higher height and less unevenness in shape is formed. There are several methods for shaping laser light into such a ring-shaped beam, and each has its advantages, but from a comprehensive point of view, methods such as an axicon prism method, a mask method, and a method of producing converged light by a grating are available. It has been found useful in the present case. Especially in the former two cases, selection of axicon prism and mask,
By adjusting the geometrical conditions of beam irradiation, the laser energy density, and the like, the size and shape of the protrusions to be formed can be controlled appropriately. It is desirable to process the protrusions within a range in which the irradiation intervals of the annular beams 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, when the height of the protrusion is set to a certain height or more, collision between the magnetic head and the HD easily occurs, and sliding durability deteriorates. The size of the protrusion suitable for practical use (as the texture of the substrate surface of 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. 1-9
It is desirable to be 9.9%. Although the present invention is intended for glass substrates, silicon substrates, etc., such texturing can also be applied to roughening a magnetic layer or a carbon protective layer. In addition, conventional Ni-P
It can also be applied to a coated Al substrate.

As described above, a glass substrate, a silicon substrate, or the like is formed by converting an ultraviolet laser into a ring-shaped beam, irradiating the substrate to give a texture, and then sequentially forming an underlayer, a magnetic layer and the like to form a magnetic layer. The recording medium has excellent sliding durability and does not cause cracks or the like even when it is used, which requires high durability, so it contributes to the production of highly reliable magnetic recording devices such as magnetic disk devices. can do. Each layer formed on a glass substrate, a silicon substrate, or the like,
The undercoating film, magnetic film, protective film, lubricating film, etc. are not particularly limited in material, composition, film forming method, etc., and known materials and known methods can be appropriately selected and used in combination. .

[0009]

EXAMPLES Examples of the present invention will be shown below. In addition, the stylus 0.5μ was used for the measurement of the surface roughness using a stylus type roughness meter.
m, cutoff 0.25 mm.

Example 1 Using a fourth harmonic (266 nm) of a YAG laser and an axicon prism, an energy density of 0.2 J / cm was applied to the surface of a soda-lime glass substrate.
^2. 50 pulses were applied with a pulse width of 20 ns. The outer diameter of the annular beam was 10 μm and the annular width was 2 μm. 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 95%. 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 applied to form a film to obtain the magnetic recording medium of Example 1. It was made.

Example 2 KrF excimer laser (24
8 nm) and a mask, and a pulse width of 15 n under the conditions of an energy density of 0.1 J / cm ² , an annular beam outer diameter of 10 μm and an annular width of 2 μm on the surface of a soda lime glass substrate.
As a result of irradiating the s pulse beam 80 times, Rp23n
m, Rv ≧ -1 nm, outer radius 6 μm, and Sm-35 μm surface protrusions were obtained at a rate of 90%. Subsequently, a magnetic recording medium of Example 2 was manufactured in the same manner as in Example 1.

<Embodiment 3> The fourth harmonic (266 nm) of a YAG laser and an axicon prism are used, the substrate is a silicon substrate, and the energy density of laser light is 0.02 J.
/ Except that the cm ² is a result of to the laser beam irradiation in the same manner as in Example 1, Rp27nm, Rv ≧ -1.5n
m, outer radius 5.5 μm, 8 surface protrusions of Sm-40 μm
Obtained at a rate of 5%. Subsequently, a magnetic recording medium of Example 3 was manufactured in the same manner as in Example 1.

Example 4 KrF excimer laser (24
Laser beam irradiation was performed in the same manner as in Example 2 except that the substrate was a silicon substrate and the energy density was 0.03 J / cm ² , using Rp30.
nm, Rv ≧ -2 nm, outer radius 5.5 μm, Sm-40
80 μm surface protrusions of μm were obtained. Subsequently, the magnetic recording medium of Example 4 was manufactured in the same manner as in Example 1.

COMPARATIVE EXAMPLE 1 A YAG laser beam of the fourth harmonic (266 nm) having a diameter of 10 μm was applied to the surface of a soda-lime glass substrate for 50 pulses at an energy density of 0.2 J / cm ² and a pulse width of 20 ns. Rp28n
m, Rv ≧ -1 nm, outer radius 7 μm, and surface protrusions with Sm to 35 μm were obtained at a rate of 50%, and the balance was Rv-1.
The concave shape was 00 nm. Subsequently, a magnetic recording medium of Comparative Example 1 was manufactured in the same manner as in Example 1.

<Comparative Example 2> A beam of a YAG laser fourth harmonic (266 nm) having a diameter of 10 μm was applied to the surface of a silicon substrate at an energy density of 0.02 J / cm ² and a pulse width of 20 n.
S s was irradiated for 50 pulses. Rp25nm, Rv ≧ -1
nm, the outer radius was 5.5 μm, and the surface protrusions with Sm to 35 μm were obtained at a rate of 40%, and the rest were concave with Rv-150 nm. Subsequently, a magnetic recording medium of Comparative Example 2 was produced in the same manner as in Example 1 above.

<Comparative Example 3> KrF excimer laser (24
8 nm) and a mask, an energy density of 0.2 J / cm ² , a diameter of 10 μm, and a soda lime glass substrate surface,
As a result of irradiation with a laser beam having a pulse width of 15 nm 80 times, Rp27 nm, Rv ≧ -1 nm, outer radius 6 μm, S
The surface protrusions of m to 40 μm were obtained at a rate of 40%,
The rest was a concave shape of Rv-150 nm. . Subsequently, a magnetic recording medium of Comparative Example 3 was prepared in the same manner as in Example 1.

<Comparative Example 4> KrF excimer laser (24
8 nm) and a mask, the energy density is 0.03 J / cm ² , the diameter is 10 μm, and the pulse width is 15 on the surface of the silicon substrate.
As a result of irradiating 80 times at 80 nm, Rp23 nm, Rv ≧ −
Surface protrusions having a diameter of 1 nm, an outer radius of 5.5 μm, and Sm of 40 μm were obtained at a rate of 30%, and the balance was Rv-100 nm.
It was a concave shape. Subsequently, a magnetic recording medium of Comparative Example 4 was produced in the same manner as in Example 1.

<Comparative Example 5> A conventional mechanical texture is applied to an aluminum substrate so that Rp is 25 nm, Rv-30 nm or more, and Sm is 2.2 μm.
A magnetic recording medium of Comparative Example 5 was produced in the same manner as in.

Table 1 shows stiction values after CSS 10,000 times as CSS characteristics of the magnetic disks of Examples 1, 2, 3, 4 and Comparative Examples 1, 2, 3, 4, 5. In addition, the CSS measuring machine uses a commercially available CSS tester,
An Al ₂ O ₃ —TiC slider head was used as the magnetic head.

[0020]

[Table 1]

As is clear from Table 1, Example 1 of the present invention
It can be seen that the magnetic recording media of Nos. 4 to 4 have markedly lower stiction values as compared with the magnetic recording media of Comparative Examples 1 to 5, and have better CSS characteristics than the disks manufactured by the conventional technique.

Although the present invention has been described based on the embodiments, the present invention is not limited to the above embodiments, and can be carried out in any manner as long as the configuration described in the claims is not changed. it can.

[0023]

As described above, the present invention provides a magnetic recording medium (HD) in which an underlayer, a magnetic layer, a protective layer, a lubricating layer and the like are sequentially formed on a glass substrate, a silicon substrate or the like. Regarding a manufacturing method, the present invention provides a laser texture technique for forming a roughened surface having a desired shape on a substrate by using a laser beam. According to the present invention, it is possible to completely prevent the non-controllability of the uneven shape and the depth and the occurrence of burrs, which are 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. On the other hand, with a spot-shaped laser beam, which is a conventional laser processing method, the uneven shape is unstable because the energy concentration on the glass substrate, silicon substrate, etc. is not constant, and the desired projection shape can be selectively formed. Although it is difficult and often causes dents due to excessive ablation to cause cracks in a substrate that is thin and requires high durability, in the present invention using a ring-shaped laser beam, the energy density in the substrate is reduced. Since it is distributed in the shape of a band, it is easy to perform outstanding texturing of protrusions with less unevenness. According to the present invention, a texture processing technique with high efficiency and excellent controllability can be obtained in a next-generation HD requiring high recording density and 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 substrate in the present invention, (A) a shape of a protrusion formed in the present invention, and (B) a shape of a recess formed with an energy density equal to or higher than a processing threshold. Is.

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

Claims (4)

[Claims] 1. A method of manufacturing a magnetic recording medium using a glass substrate or a silicon substrate, wherein an ultraviolet laser is used to irradiate the substrate with the laser beam in a ring shape prior to film formation of a magnetic layer or the like. A method for manufacturing a magnetic recording medium, characterized in that: 2. The method of manufacturing a magnetic recording medium according to claim 1, wherein a laser beam of an annular beam obtained by passing through the axicon prism is irradiated. 3. A method for manufacturing a magnetic recording medium according to claim 1, wherein laser light of a ring-shaped beam obtained by interposing a mask is irradiated. 4. The size of the protrusion formed on the substrate surface by the laser beam has an outer radius of 1 to 50 μm and a height of 1 to
4. The method for manufacturing a magnetic recording medium according to claim 1, wherein the thickness of the magnetic recording medium is 100 nm, and the ratio of the area occupied by the protrusion to the substrate surface is 0.1 to 99.9%.