JPH06295433A - Production of magnetic recording medium - Google Patents

Abstract

PURPOSE:To provide a method for producing a magnetic recording medium by which satisfactory productivity and satisfactory quality of a worked part are ensured when the surface of a magnetic recording medium is made rugged. CONSTITUTION:A magnetic layer and a protective layer are successively laminated on the surface of a nonmagnetic substrate to produce a magnetic recording medium. At this time, the surface of the substrate or one of the layers laminated on the substrate, that is, a body A to be irradiated is irradiated with UV laser beams L to cause abrasion and recesses B each with a protrusion C made of a deposit of atoms or molecules generated by the abrasion at the edge of the opening are formed in the surface of the body A at prescribed intervals. The substrate or layer irradiated with UV laser beams is made preferably of a nonmetallic material.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a method for forming irregularities on the surface of a magnetic recording medium for reducing frictional resistance with a magnetic head and for reducing the flying height.

[0002]

2. Description of the Related Art In recent years, a magnetic layer formed of a Co alloy having uniaxial crystal magnetic anisotropy such as CoNiCr or CoCrTa has been used as a Cr underlayer on a non-magnetic substrate in accordance with high density recording of a magnetic recording medium. A metal thin film type magnetic recording medium formed through the above has come to be used.

As the non-magnetic substrate, an Al alloy plate on which an amorphous Ni-P plating layer is formed to secure hardness (hereinafter, simply referred to as an aluminum substrate) or a glass substrate is used. On the surface of the substrate, usually, minute irregularities called texture are formed along the circumferential direction. When the unevenness is formed on the substrate, the thickness of the magnetic layer or the like laminated on the substrate is thin, so that the unevenness is formed on the surface of each layer and also on the medium surface. As a result, contact frictional resistance between the surface of the medium and the magnetic head is reduced, and adsorption between the magnetic head and the medium is prevented, so that durability is improved. Further, since the shape magnetic anisotropy in the circumferential direction of the magnetic layer is improved, the coercive force is improved and the recording density is increased. Conventionally, such irregularities have been mechanically formed by lapping tape or loose abrasive grains.

On the other hand, in order to increase the recording density, it is necessary to fly the magnetic head as close as possible to the surface of the medium. However, in order to reduce the frictional force and the attraction force, the roughness of the unevenness should be as large as possible. On the other hand, the unevenness should be as small as possible in order to reduce the flying height of the head. There is. Further, according to the conventional method, even if the average roughness of the unevenness is suppressed to a small value, protrusions having a height higher than the average roughness are formed on the medium surface. If the magnetic head comes into contact with this protrusion, a crash accident occurs, and thus there is a limit to reducing the flying height of the head.

Therefore, in recent years, as disclosed in Japanese Unexamined Patent Publication No. Hei 4-85725, fine irregularities having a specific structure are regularly formed on the surface of a medium to achieve reduction of frictional resistance and low flying height. Magnetic recording media have been provided. As a means for regularly forming specific minute irregularities, a lithography technique or a processing technique using a YAG or CO ₂ laser is applied as disclosed in the publication.

[0006]

However, in order to form a convex portion having a desired size and shape by the lithography technique, complicated steps such as resist coating, exposure, baking and etching must be performed. However, there is a problem that quality control is difficult because of the large number of products, large capital investment is required, and productivity is low. On the other hand, in the thermal processing using the YAG or CO ₂ laser, the quality of the periphery of the processed portion changes due to heat, and processing defects such as burrs and burrs occur at the opening edge of the processed recess, which causes a head crash accident. There was a fear.

The present invention has been made in view of the above problems, and provides a method of manufacturing a magnetic recording medium which has good productivity and good quality of a processed portion when forming irregularities on the surface of the magnetic recording medium. With the goal.

[0008]

A method of manufacturing a magnetic recording medium according to the present invention is a method of manufacturing a magnetic recording medium in which a magnetic layer and a protective layer are laminated in the same order on the surface side of a non-magnetic substrate. On the surface of any layer laminated on the substrate,
Irradiation with an ultraviolet laser beam causes ablation, and recesses having protrusions made of deposits of atoms and molecules generated by the ablation on the opening edge are formed at predetermined intervals on the surface of the object to be irradiated. At this time, the surface of the substrate or layer formed of a non-metallic material may be irradiated with an ultraviolet laser beam.

[0009]

As shown in FIG. 1A, when the surface of the substrate or one of the layers (irradiation object) laminated on the substrate is irradiated with the ultraviolet laser beam L, the irradiated portion of the irradiation object A is photochemically irradiated. A reaction occurs, the bonds between the atoms and molecules in the irradiated area are cut off, and as shown in FIG. 2B, atoms and molecules momentarily disperse at the same level, causing a phenomenon called ablation. By this ablation, a recess B is formed in the laser beam irradiation portion (such processing is referred to as "ablation processing"). At this time, atoms and molecules scattered by ablation are made difficult to gasify in the atmosphere of the irradiation portion of the laser beam, so that atoms scattered by ablation at the opening edge of the recess B as shown in FIG. , A convex portion (referred to as “debris”) C made of a deposit of molecules is formed. Ablation is an optical phenomenon, and unlike a thermal processing process using an infrared laser such as a YAG or CO ₂ laser, the convex portion C is different from an irregular processing defect such as a flash or a return,
It fits in a certain size.

By irradiating the surface of the object A to be irradiated with an ultraviolet laser beam at a predetermined interval, concaves and convexes having the convex portions are formed at predetermined intervals. Concavities and convexities due to the irregularities are also formed on the surfaces of various layers formed thereon, and thus predetermined irregularities are formed on the surface of the medium. Of course, since ablation and debris are formed by directly irradiating the irradiation object A with the ultraviolet laser beam L, there is no need for complicated steps such as lithography technology and consumables such as resists and cleaning liquids. Low and excellent in productivity.

As the object A to be irradiated, a non-metallic material is more likely to ablate than a metallic material even if the energy density of the ultraviolet laser beam on the beam reaching surface is low, and the processing is easy.

[0012]

EXAMPLE FIG. 2 is a conceptual view of a radial cross section of a metal thin film magnetic recording medium according to an example, in which a Cr underlayer 2, a magnetic recording layer 3 and a nonmagnetic substrate 1 are formed on a nonmagnetic substrate 1. A magnetic protective layer 4 and a lubricating layer 5 are laminated in this order, and minute irregularities are regularly formed at predetermined intervals on the surface of the substrate 1 and each layer 2, 3, 4, 5. There is.

As the material of the non-magnetic substrate 1, a material having an amorphous Ni-P plating layer formed on an Al alloy plate, a metal material such as titanium, or a non-metal material such as glass, ceramics, carbon or polymer. Material is used. In this embodiment, an ultraviolet laser beam is radiated onto the substrate 1 to perform ablation processing, and convex portions called debris are formed at predetermined intervals on the surface of the substrate 1 by forming concave portions on the edge of the opening. Concavities and convexities are formed, and the respective layers 2, 3, 4, 5 formed on the substrate 1 are sequentially formed with concavities and convexities due to the concavities and convexities formed on the substrate 1.

The ultraviolet laser beam preferably has a wavelength of 500 nm or less and an energy density of 1 × 10 ⁻⁹ J / cm ² or more when the beam reaches an object to be irradiated. If it exceeds 500 nm, it is close to the infrared region, and there is a possibility that the effect of thermal processing may occur. If the energy density upon arrival is less than 1 × 10 ⁻⁹ J / cm ² , ablation is unlikely to occur and processing becomes difficult. An excimer laser is suitable as the ultraviolet laser, and for example, ArF (wavelength 193 nm) and KrF (wavelength 248 n) are used as excitation species.
m), XeCl (wavelength 308 nm), XeF (wavelength 35)
0nm) halogenated rare gas laser can be mentioned.

It is necessary that the atmosphere of the laser beam irradiation section is such that atoms and molecules scattered by ablation are difficult to gasify. For this purpose, it is preferable that the atmosphere of the irradiation section is an inert gas atmosphere and the gas pressure is high. Further, as the inert gas, it is preferable to use a gas having a large atomic weight such as argon gas. When the ablation process is performed under such an atmosphere, the atoms and molecules scattered by the ablation are deposited on the opening edge of the recess to form the protrusion. The height of this convex portion can be easily and accurately controlled by the irradiation time of the laser beam, the energy density in the irradiation portion, the type of atmospheric gas, and the pressure.

FIG. 3 shows that the surface of the carbon substrate was blown with argon gas and irradiated with a KrF excimer laser having a wavelength of 248 nm to perform ablation processing, and the surface roughness of the processed substrate was measured by a stylus roughness meter. This is an example.
At this time, the energy density on the substrate surface is 0.08J.
/ Cm ² . From the figure, the depth of the recess is about 230
Å, convex height is about 150Å, convex width is about 100 μm, and concave / convex average spacing is 400 μm. Irregular processing defects such as burrs and burrs are not recognized on the opening edge of the concave.

The depth of the concave portion generated by the irradiation of the ultraviolet laser beam can be easily controlled by the irradiation time of the laser beam and the energy density. An ordinary laser device can emit a beam at a frequency of 100 to 300 pulses per second. The object to be irradiated is glass, ceramics,
In the case of inorganic non-metallic materials such as carbon, it is possible to process submicrons per pulse by irradiation with energy density of 10 J / cm ² , and usually the processing speed can be increased to 10 μm / sec or more. Is high. In the case of polymer, submicron processing per pulse is possible by irradiation with 1 J / cm ² . When a metal material such as an aluminum substrate or a titanium substrate is used as the substrate, it is necessary to increase the laser output (energy density on the surface of the object to be irradiated) as compared with a non-metal material.

For example, when a glass substrate is used, the depth of the recess formed on the surface of the substrate is usually 0.1 μm or less. Therefore, the laser beam is applied to the surface of the substrate 1 through the mask having a predetermined recess pattern. By irradiating the surface of the substrate, predetermined irregularities can be formed on the entire surface of the substrate in 1 second or less, and the production efficiency is extremely good. Incidentally, by providing an appropriate lens system between the laser light source and the mask and between the mask and the object to be irradiated, the laser beam emitted from the laser light source was expanded and applied to the entire surface of the mask, and passed through the mask. The laser beam can be easily focused on the substrate surface having a predetermined size. Further, without using the mask, the laser beam emitted from the laser light source is narrowed down by a lens system, the focused laser beam is applied to the irradiation target, and the irradiation target is moved in a two-dimensional direction. An uneven pattern may be formed.

The Cr underlayer 2 is formed to improve the in-plane orientation of the Co alloy of the magnetic layer 3 formed thereon. As described above, the magnetic layer 3 is made of C
It is formed of a Co alloy exhibiting uniaxial crystal magnetic anisotropy such as oNiCr, CoCrTa, and CoCrPt. A nonmagnetic protective layer 4 made of carbon, SiC or the like is formed on the magnetic layer 3, and a fluorinated polyether,
Lubricating layer 5 made of lubricant such as perfluoropolyether
Is formed by coating. The Cr underlayer 2, the magnetic layer 3,
The protective layer 4 is formed by a physical vapor deposition method such as sputtering, ion beam sputtering, or vacuum vapor deposition.

The Cr underlayer 2 and the lubricating layer 5 may be formed as needed and may be omitted. Also,
The magnetic layer 3 is not limited to a single layer of Co alloy, but may be C
It may be formed by alternately forming a plurality of o alloy layers and Cr layers (the top layer is a Co alloy layer). The thickness of the Cr underlayer 2 is 50
0 to 2000Å, the magnetic layer 3 (total of Co alloy layers) is 40
0-800Å, protective layer 4 is 200-400Å, lubrication layer 5
Is about 20 to 40Å (monomolecular thickness).

In the above embodiment, the substrate 1 was ablated, but the object to be irradiated is not limited to the substrate 1 and may be the surface of the protective layer 4 as shown in FIG. In this case, the surfaces of the layers 3 and 2 below the protective layer 4 and the substrate 1 remain flat. When the substrate 1 is made of a metallic material, it can be directly ablated, but as shown in FIG. 5, the intermediate layer 6 is formed on the substrate 1 with an inorganic non-metallic material such as carbon Ablation processing may be applied on the top. By forming such an intermediate layer, it is possible to perform a predetermined uneven processing with a low-power laser.

Next, specific examples will be given. (1) A carbon substrate with a smooth polished surface (outer diameter 2.5
Using an inch (6.35 cm) and a thickness of 0.635 mm, an ultraviolet laser beam was irradiated through a mask having a concave pattern formed on its surface to perform ablation processing. The UV laser used was KrF with a wavelength of 248 nm.
It is an excimer laser, and the energy density on the substrate surface was 0.08 J / cm ² . Argon gas was blown on the laser beam irradiation part. As a result, irregularities having a concave depth of 300Å, a convex height of 200Å, and an average concave interval of 50 μm were formed. (2) After that, a Cr underlayer of 60 is formed by sputtering.
0 Å, a magnetic layer (CoCrTa alloy single layer) of 700 Å and a protective layer (carbon) of 200 Å were deposited, and perfluoropolyether was further coated thereon in an amount of 20 Å to obtain a magnetic recording medium having the structure shown in FIG. .. (3) For comparison, a magnetic recording medium having the same structure was manufactured under the same method and conditions as in Example, except that the texture was formed on the surface of the substrate by using a polishing tape. Abrasive grains of the polishing tape were No. 7000, and irregularities of Ra = 50Å were formed. The roughness measurement conditions were a stylus diameter of 0.5 μm, a scan length of 2.5 mm, and a cutoff of 0.25 mm. (4) The friction coefficient and the glide height with respect to the number of CSS (constant start / stop) were measured using the magnetic recording medium and the thin film head of the examples and conventional examples. (5) The measurement results are shown in FIGS. 6 and 7. From FIG. 6, in the magnetic recording medium of the example, the friction coefficient was about 0.4 regardless of the number of CSSs, but in the conventional example, it increased to about twice the initial value. Further, as shown in FIG. 7, the glide height of the magnetic recording medium of the example could be lowered by about 0.02 μm as compared with the conventional example.

[0023]

As described above, according to the method of manufacturing a magnetic recording medium of the present invention, the surface of the substrate or any layer laminated on the substrate is irradiated with an ultraviolet laser beam to cause ablation, Since convexes made of deposits of atoms and molecules generated by ablation are provided on the surface of the irradiated object at predetermined intervals, convexes made of deposits of atoms and molecules are formed at a predetermined interval. Since no consumables such as cleaning liquid are required, the equipment cost is low and the productivity is excellent. Also, YA
Unlike a thermal processing process using an infrared laser such as a G or CO ₂ laser, it does not cause processing defects such as burrs and burrs on the surface of the object to be irradiated, and does not cause alteration, resulting in high quality.

[Brief description of drawings]

FIG. 1 is a conceptual explanatory view of ablation processing.

FIG. 2 is a conceptual sectional view of a main part of a magnetic recording medium according to an example.

FIG. 3 is a roughness measurement diagram of a substrate surface after ablation processing.

FIG. 4 is a conceptual cross-sectional view of a main part of a magnetic recording medium according to another example in which a protective layer is ablated.

FIG. 5 is a conceptual cross-sectional view of a main part of a magnetic recording medium according to another embodiment in which an intermediate layer formed on a substrate is ablated.

FIG. 6 is a graph showing a CSS test result according to an example.

FIG. 7 is a graph showing a measurement result of glide height according to an example.

[Explanation of symbols]

 1 Non-magnetic Substrate 2 Cr Underlayer 3 Magnetic Layer 4 Protective Layer 5 Lubricating Layer 6 Intermediate Layer

Claims (2)

[Claims] 1. A method of manufacturing a magnetic recording medium comprising a magnetic layer and a protective layer laminated in the same order on the surface side of a non-magnetic substrate, wherein an ultraviolet laser is formed on the surface of the substrate or any layer laminated on the substrate. Irradiate the beam to cause ablation,
A method of manufacturing a magnetic recording medium, characterized in that recesses having protrusions made of a deposit of atoms and molecules generated by ablation are provided at an opening edge portion on a surface of an object to be irradiated at predetermined intervals. 2. The method of manufacturing a magnetic recording medium according to claim 1, wherein the surface of the substrate or layer formed of a non-metallic material is irradiated with an ultraviolet laser beam.