JP2000306234A - Washing method of hard substrate for magnetic recording medium - Google Patents

Abstract

PROBLEM TO BE SOLVED: To realize a washing method of a hard substrate in order to obtain such a magnetic recording medium that a <= several tens of Å low flying height of a head at a surface of the hard substrate for the magnetic recording medium is realized. SOLUTION: A low frequency ultrasonic wave washing step is incorporated in a washing method of a hard substrate having a texture formed on a surface of a Ni-P film formed on a hard member plate. For example, a washing method wherein the surface of the substrate is scrubbing washed, ultrasonically washed by a 20-50 kHz low frequency ultrasonic wave in an alkaline detergent solution, successively washed with warm pure water, a pure water and an ultra pure water in this order and finally dryed by using IPA vapor is applied.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a method for cleaning a hard substrate in the manufacture of a magnetic recording medium using a hard substrate using a non-magnetic hard member such as a hard glass plate or various ceramic plates as a substrate member.

[0002]

2. Description of the Related Art A hard disk drive (hereinafter, referred to as an HDD) used as an information storage device of an information processing apparatus such as a computer is provided with a magnetic recording medium (hereinafter, also simply referred to as a medium) serving as a heart, and disposed opposite to the magnetic recording medium. A magnetic head for writing an information signal on a medium or reading an information signal written on the medium via the magnetic head.

In the HDD, the CSS method is usually employed. When driving to write and read an information signal, the magnetic head slightly floats on the medium rotating at high speed due to the air flow generated by the rotation of the medium. However, when the drive is stopped, the magnetic head is brought into contact with the surface of the medium that has been stopped, and when the drive is started and stopped, the magnetic head is brought into transient contact with the medium surface and slides. In order for information signals to be written and read satisfactorily, the medium surface is smooth and free from abnormal protrusions that hinder the stable and smooth flying of the magnetic head, and the contact sliding of the magnetic head is smooth. It must be reasonably fine and rough to be performed. The recording density of an information signal on a medium largely depends on the distance between a magnetic layer of the medium and a magnetic head flying above the medium (hereinafter simply referred to as a head flying height), and the smaller the amount, the higher the recording density. .

[0004] A medium is generally formed on a disk-shaped non-magnetic member plate by electroless plating, sputtering or the like.
After a P film is formed, the surface thereof is mirror-finished, and then a textured process for forming fine irregularities along the circumferential direction is performed.
An underlayer made of a non-magnetic metal such as a Cr alloy, a magnetic layer made of a Co alloy, and a protective layer made of carbon are sequentially formed by a VD method or the like, and a lubricating layer coated with a liquid lubricant is further formed thereon. Be formed.

[0005] In recent years, the head flying height has been increasingly reduced to the order of several tens of thousands in order to satisfy the demand for increasing the recording density of HDDs. In order to realize such a small head flying height, it is important that the medium surface is as flat as possible and that there are no abnormal protrusions that hinder the running of the magnetic head. Various causes of abnormal projections have been considered and measures have been taken.However, recently, among the deposits such as polishing residue and abrasive residue generated during the texturing of the substrate, they cannot be completely removed in the substrate cleaning process. Kimono has come to be taken up as a major cause of abnormal projections that hinder the stable floating flight of the head.

Conventionally, a plate made of an aluminum-based alloy which is inexpensive and easily available has been used as a non-magnetic member plate of a substrate. As a method of cleaning the substrate, a method of dipping in an alkaline detergent, a scrub method using a brush, and the like have been studied and implemented. Above all, scrubbing, for example, a method of soaking a sponge brush with a cleaning agent to scrub the substrate surface has been said to be effective, but the brush used, for example, the sponge brush itself, has been considered effective. Since it is soft, it cannot be removed to a sufficiently satisfactory level, and when scrubbing with a brush made of a hard member, the substrate surface is damaged and the texture is disturbed.

Recently, it has been studied to employ ultrasonic cleaning as a method of cleaning a substrate. When a low frequency ultrasonic wave of 28 kHz to 50 kHz used in normal ultrasonic cleaning is used, a very large cleaning effect can be obtained by an impact action caused by a strong cavitation effect. Since the aluminum-based alloy plate is used, it is mechanically damaged and the surface shape of the substrate becomes rough, which is a problem. Therefore, the frequency of ultrasonic waves used for cleaning has been studied, for example,
Japanese Patent Application Laid-Open No. 4-212716 discloses that the wavelength is 200 kHz.
It is disclosed that a large cleaning effect can be obtained by using ultrasonic waves having a relatively high frequency of up to 1600 kHz without damaging the surface roughness of the substrate.

In recent years, the use of computers has been expanded due to the miniaturization and high performance of computers, and portable notebook computers have become widespread. There is a strong demand for higher density and higher speed, and therefore, it has been required to eliminate surface runout of the medium even at high speed rotation. In order to meet these demands, hard members such as crystallized glass, chemically strengthened glass, and various ceramic plates have been used as hard and flat member plates.

[0009]

The use of a hard substrate greatly improves the performance in terms of mechanical strength and runout. However, the above-described ultrasonic cleaning step using an ultrasonic wave having a relatively high frequency is required. With the cleaning method that includes, it is not possible to sufficiently remove the deposits on the substrate surface, and in order to achieve a low head flying height that can respond to the high recording density required in the market recently, the remaining small deposits can be ignored. Is gone.

The present invention has been made in view of the above points, and has as its object to provide a cleaning method capable of sufficiently cleaning a substrate using a hard substrate as a nonmagnetic substrate. .

[0011]

According to the present invention, there is provided, according to the present invention, a method for forming a Ni-P film on a hard member plate and forming irregularities on the surface thereof when manufacturing a medium using a hard substrate. The problem is solved by applying a cleaning method including a step of ultrasonically cleaning the surface of the substrate using low-frequency ultrasonic waves in a liquid in cleaning a medium hard substrate produced by performing texture processing.

By irradiating the substrate surface with low-frequency ultrasonic waves, it is possible to effectively remove solid deposits on the substrate surface by an impact force generated by a strong cavitation effect. Much higher cleanliness is obtained than when ultrasonic cleaning is performed using sound waves. Moreover, in the case of a hard substrate using a hard member plate, the surface of the substrate on which the Ni-P film is formed is hardly mechanically damaged even by such low-frequency ultrasonic cleaning, and the irregularities formed on the substrate surface are hardly damaged. It was confirmed that the texture of was hardly disturbed.

As the ultrasonic wave, it is preferable to use an ultrasonic wave having a frequency of 20 kHz to 50 kHz having a large cavitation effect. Further, the liquid may be pure water or the like, but it is preferable to use an alkaline detergent solution.

[0014]

FIG. 1 is a schematic sectional view of a medium according to the present invention, in which a Ni-P film 1b is formed on a hard member plate 1a.
Is formed on a hard substrate 1 having a textured surface, a Cr alloy base layer 2, a Co alloy magnetic layer 3, a carbon-based protective layer 4, and a lubricating layer 5 coated with a liquid lubricant. It is of the formed configuration.

As the hard member plate 1a, crystallized glass,
Hard members such as chemically strengthened glass and various ceramic plates are used. After smoothing the surface of the hard member plate 1a, Ni surface is formed on the surface by electroless plating or sputtering.
The P substrate 1b is formed, and its surface is subjected to texture processing to form fine irregularities, thereby forming the hard substrate 1.

The hard substrate 1 is cleaned to remove extraneous matter on the surface and to clean the substrate. FIG. 2 is a cleaning process diagram of an example of substrate cleaning according to the present invention, in which a hard substrate surface is subjected to a normal scrub-type cleaning by rubbing with a sponge brush containing a detergent or water and then an alkaline detergent. Or, it is immersed in a bath of pure water or the like and subjected to ultrasonic cleaning according to the present invention using low-frequency ultrasonic waves. This ultrasonic cleaning also removes strong deposits. Subsequently, after performing each of the usual cleaning steps of warm pure water immersion, pure water immersion, and ultrapure water shower, drying with IPA vapor is performed.

The hard substrate 1 having been subjected to such a cleaning step
An underlayer made of a Cr alloy, a magnetic layer made of a Co-based alloy, and a carbon-based protective layer 4 are sequentially formed thereon by a sputtering method, a CVD method, or the like, and a liquid lubricant is applied thereon by a coating method. By forming the lubrication layer 5 in this manner, a medium that can realize a low head flying height that satisfies the market requirements is obtained.

[0018]

Next, specific embodiments of the present invention will be described. Example 1 A 2.5-inch disk-shaped tempered glass plate for media (inner diameter 10 mm, outer diameter 65 mm) was used as a hard member plate, and a Ni-P film was formed on the surface by electroless plating, and a Ni-P film was formed on the surface. Texture processing was performed using diamond abrasive grains in order to form irregularities in the circumferential direction, thereby producing a non-magnetic hard substrate having a surface roughness of about 1 nm with _a center line average roughness Ra.

On the surface of the hard substrate, cleaning is performed to remove adhering substances such as polishing residue and abrasive residue after texture processing and to clean the surface. First, scrub cleaning is performed by rubbing the substrate surface with a sponge brush containing an alkaline detergent. Then, immersed in an alkaline detergent tank and
Ultrasonic cleaning using ultrasonic waves of 600 Hz and output of 600 W is performed for 3 minutes. Subsequently, it is immersed in warm pure water of 45 ° C. for 2 minutes, immersed in normal temperature pure water for 2 minutes, showered with ultrapure water, and finally
The substrate surface was dried by exposing it to PA vapor for about 1 minute to obtain a substrate of Example 1. No mechanical damage was observed on the substrate surface due to low frequency ultrasonic waves.

Example 2 A substrate was prepared in the same manner as in Example 1 except that the frequency of the ultrasonic wave used for immersion in the alkaline detergent bath during the cleaning of the substrate was changed to 39 kHz. I do. Similar to the substrate of Example 1, no mechanical damage was observed on the substrate surface due to low-frequency ultrasonic waves.

Comparative Example 1 A substrate of Comparative Example 1 was prepared in the same manner as in Example 1, except that ultrasonic cleaning was not performed in the alkaline detergent immersion at the time of cleaning the substrate, and mere immersion cleaning was performed.

COMPARATIVE EXAMPLE 2 In Example 1, the ultrasonic wave used for the ultrasonic cleaning at the frequency of 750 kHz and the output of 1 was immersed in the alkaline detergent bath for cleaning the substrate.
A substrate of Comparative Example 2 was made in the same manner as in Example 1 except that the ultrasonic wave was changed to 75 W. Also in this case, Embodiments 1 and 2
Similarly, no mechanical damage was observed on the substrate surface due to ultrasonic waves.

For each of the ten substrates of the four types obtained in the above-described different washing steps, the number of adhering substances having a surface average diameter of about 0.5 μm or more remaining on one surface of the substrate is determined by the appearance. Inspection equipment (Hitachi Electronics Engineering Co., Ltd.)
(RS-1350). The result is shown in FIG.
Is shown in the graph of FIG.

As can be seen from FIG. 3, the substrates of Examples 1 and 2 had a very small number of deposits as compared with the substrate of Comparative Example 1, and the ultrasonic waves were applied by low-frequency ultrasonic waves during immersion cleaning in an alkaline detergent bath. The effect of adding washing is clear. In addition, the substrate of Comparative Example 2 which was subjected to ultrasonic cleaning with ultrasonic waves having a frequency of 750 kHz had a smaller number of deposits than the substrate of Comparative Example 1 which was not subjected to ultrasonic cleaning. The number of deposits is much larger than that of the substrate of the second embodiment. It is clear that ultrasonic cleaning using a low frequency is effective for removing deposits.

Example 1 in which the above-described cleaning process was performed
2 on the surface of each substrate by sputtering,
o When a magnetic layer and a carbon protective layer are sequentially formed and a liquid lubricant is applied thereon to form a lubricating layer to produce a medium, it is possible to achieve a low head flying height that sufficiently satisfies the market requirements. did it.

[0026]

According to the present invention, Ni can be deposited on the hard member plate.
In a method of cleaning a hard substrate for a magnetic recording medium manufactured by performing a texturing process for forming a P film and forming irregularities on the surface thereof, an ultrasonic wave of low frequency is applied to the surface of the substrate in a liquid. The cleaning method includes a cleaning step.
By cleaning using low frequency ultrasonic waves, strong deposits can also be removed, and by using such a hard substrate, a magnetic recording medium with a low head flying height that can respond to market requirements can be obtained. Becomes possible.

[Brief description of the drawings]

FIG. 1 is a schematic sectional view of an example of a medium according to the present invention.

FIG. 2 is a diagram illustrating a cleaning process of an example of substrate cleaning according to the present invention.

FIG. 3 is a diagram showing the relationship between the presence or absence of ultrasonic cleaning in substrate cleaning, the ultrasonic frequency used, and the number of adhered substances after cleaning;

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 1 Hard substrate 1a Hard member plate 1b Ni-P film 2 Underlayer 3 Magnetic layer 4 Protective layer 5 Lubrication layer

Claims (4)

[Claims] In a method for cleaning a hard substrate for a magnetic recording medium, a Ni-P film is formed on a hard member plate and a texture process for forming irregularities on the surface is performed. Cleaning a hard substrate for a magnetic recording medium, comprising a step of ultrasonically cleaning the surface of the substrate using the substrate. 2. The method for cleaning a hard substrate for a magnetic recording medium according to claim 1, wherein ultrasonic cleaning is performed using low-frequency ultrasonic waves having a wavelength of 20 kHz to 50 kHz. 3. The method for cleaning a hard substrate for a magnetic recording medium according to claim 1, wherein ultrasonic cleaning is performed in an alkaline detergent solution. 4. The method for cleaning a hard substrate for a magnetic recording medium according to claim 1, wherein the hard member plate is made of hard glass.