JPH08161737A - Texture treatment method for amorphous carbon substrate for magnetic disk - Google Patents

Abstract

PURPOSE: To obtain a texture treatment method for an amorphous carbon substrate for a magnetic disk which enables texture treatment for the amorphous carbon substrate. CONSTITUTION: After the mirror finished grinding of an amorphous carbon substrate, the amorphous carbon substrate is ground by a grinding liquid in which 0.1-10% of aluminum nitrate is added to grits with a particle size thereof 2-8μm to perform a texture treatment. This eliminates probable cause of recording/reproduction errors.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a texture treatment method for an amorphous carbon substrate for a magnetic disk, which is texture-treated in order to prevent an adsorption phenomenon between the air bearing surface of the magnetic head and the surface of the magnetic disk.

[0002]

2. Description of the Related Art Conventionally, magnetic disks are Ni (nickel)
A magnetic film is formed on an Al (aluminum) substrate coated with a -P (phosphorus) plating material or the like. Then, in the magnetic disk reproducing apparatus, a floating magnetic head is arranged on the magnetic disk, and the magnetic head is levitated by rotating the magnetic disk. To do.

However, when writing to and reproducing from a magnetic disk, adsorption may occur between the magnetic head levitating surface and the magnetic disk surface when the disk is stationary. This phenomenon is caused by the fact that when the magnetic head levitation surface and the magnetic disk surface are extremely smooth and both face each other with a minute gap, the gap is filled with molecules of 0 ₂ , N ₂ or H ₂ 0 and the surface tension is increased. Due to the generation of a larger suction force. If such an adsorption phenomenon occurs, it causes an inconvenience that a large amount of electric power is consumed when the motor for driving the magnetic disk is activated.

Therefore, in order to prevent the above-mentioned adsorption phenomenon, in the Al substrate for a magnetic disk, before the magnetic film is deposited, the surface of the substrate is once mirror-finished and then subjected to a texture treatment to reduce its surface roughness. I am adjusting.
The following texture processing methods are available. That is, while the Al substrate (Ni-P plated material) is rotated, the polishing tape is pressed against the Al substrate by a roller so as to be in contact with the Al substrate, and the polishing tape is moved in the radial direction of the Al substrate to roughen the entire surface. A surface-roughening method and a method of providing a rotating platen facing the Al substrate, interposing free abrasive grains between the Al substrate and the platen, and polishing the entire surface of the Al substrate to roughen the surface. is there. Silicon carbide, alumina, diamond or the like is used as the abrasive grains.

As described above, by performing the mechanical texture treatment, concentric circular scratches are formed on the surface of the Al substrate for the magnetic disk, and a rough surface in which the scratches are oriented in the circumferential direction can be obtained. It is possible (for example, JP-A-62-120374).
No. 8).

As a conventional magnetic disk substrate, an amorphous carbon substrate is chemically treated by polishing the substrate surface to a predetermined surface roughness and then heat-treating it at a predetermined temperature in an oxidizing atmosphere. A chemical texture treatment is performed to form fine irregularities (Japanese Patent Laid-Open Nos. 02-410434 and 02-410436).

[0007]

However, since amorphous carbon is a brittle material, in the conventional texture treatment method for an Al substrate for a magnetic disk, the substrate surface causes brittle fracture and the surface roughness is made appropriate. Adjustment is extremely difficult and causes a recording error. Further, in the method of performing texture treatment by heating the amorphous carbon substrate in an oxidizing atmosphere, it is difficult to perform stable texture treatment because excessive oxidation occurs due to poor cleaning or the like.

The present invention has been made in view of the above problems, and does not cause a defect on the surface of the substrate that causes a recording error and does not cause a problem such as excessive oxidation. An object of the present invention is to provide a texture treatment method for an amorphous carbon substrate for a magnetic disk, which can obtain a textured surface of the amorphous carbon substrate.

[0009]

According to the method for texturing an amorphous carbon substrate for a magnetic disk according to the present invention, a polished amorphous carbon substrate is polished with abrasive grains having an average grain size of 2 to 8 μm. It is characterized by performing.

In this case, the polishing step using the abrasive grains is
With the amorphous carbon substrate rotated, 0.1
% To less than 10% of aluminum nitrate is used to form concentric scratches on the surface of the amorphous carbon substrate by the abrasive grains.

[0011]

The inventors of the present application paid attention to the properties of the amorphous carbon substrate and conducted various studies on the texture treatment method. As a result, they have found that the amorphous carbon substrate can be processed to have an appropriate surface roughness as a magnetic disk substrate by polishing the amorphous carbon substrate to a predetermined surface roughness and then polishing in a ductile mode.

That is, when the amorphous carbon is machined, the cutting depth is 60 nm (critical cutting depth).
If it exceeds, the machined surface will cause brittle fracture, but if machined below this critical depth of cut, it will be machined in ductile mode, and the material will be removed without causing brittle fracture. Conference Proceedings, Proceedings 19 and 20 pages). When polishing, it is not possible to directly control the actual cutting amount of each abrasive grain, abrasive grain size, pad material type,
The depth of cut is determined by conditions such as processing pressure.

According to experiments conducted by the inventors of the present application, the largest factor that governs the actual cutting amount is the abrasive grain size, and when polishing an amorphous carbon substrate using abrasive grains,
The maximum grain size of the abrasive grain that achieves the critical cutting depth is 8 μm
Met. The abrasive grain count is # 1500. Therefore, the abrasive grain size is 8 μm or less, and the abrasive grain count is # 1.
By polishing with 500 or more abrasive grains, the amorphous carbon substrate can be roughened by processing in a ductile mode.

If the cut amount is too small, a predetermined surface roughness cannot be obtained, so that the magnetic head is likely to be attracted. In order to obtain the surface roughness of 20 ÅRa required as a textured surface, it is necessary to polish the amorphous carbon with abrasive grains having an average grain size of 2 μm or more (abrasive grain count # 6000 or less).

Therefore, the average grain size of the polishing abrasive grains is 2 to 8
μm (abrasive grain count # 1500 to # 6000).

Further, according to experiments conducted by the inventors of the present invention, when an amorphous carbon substrate is polished by using the above-mentioned abrasive grains, by adding 0.1% or more of aluminum nitrate to the polishing liquid, It is possible to obtain an optimal surface roughness as a carbon substrate and also to obtain a carbon substrate having an appropriate substrate surface property.

If the surface of the substrate is roughened more than necessary and the surface is sagging, a head crash easily occurs. Up to 1 to achieve proper substrate surface texture
It is necessary to stop adding 0% aluminum nitrate. Therefore, the addition amount of aluminum nitrate to be added is 0.1
To 10%.

[0018]

EXAMPLES Hereinafter, a method for manufacturing an amorphous carbon substrate for a magnetic disk according to an example of the present invention will be described in comparison with a comparative example which is out of the scope of the claims of the present application.

First, a mixed resin of a thermosetting resin that becomes amorphous carbon after carbonization and firing and a phenol formaldehyde resin is molded into a magnetic disk shape by hot pressing, and then this molded body is subjected to, for example, an N ₂ gas atmosphere. Preheat by heating to 1450 ° C.

Then, the pre-fired body is heated to, for example, about 2350 ° C. by using a hot isostatic pressing (HIP) apparatus, and isotropic pressure of, for example, about 1800 atmosphere is applied to the HI.
P process. As a result, an amorphous carbon substrate (untreated) is obtained. This amorphous carbon substrate is mirror-polished to obtain a substrate having a surface roughness of 10ÅRa.

Then, while the mirror-polished amorphous carbon substrate is rotated, for example, by a surface plate that rotates facing the substrate, the loose abrasive grains are intervened between the substrate and the surface plate to form a texture. Perform processing.

In this embodiment, the average grain size of the abrasive grains is 2 to 8 μm (abrasive grain count # 1500 to # 6000).
Is. The texture conditions are, for example, as follows.

Substrate rotation speed: 180 rpm Surface plate rotation speed: 20 rpm Applied pressure: 20 PSI Processing time: 30 seconds Abrasive grain count: # 1500 to # 6000 Polishing liquid: 0.1 to 10% aluminum nitrate added.

Although alumina abrasive grains were used as the material for the abrasive grains, similar effects can be obtained with abrasive grains having a hardness higher than that of amorphous carbon such as diamond and silicon carbide.

By performing the texture treatment as described above, the surface of the substrate is processed in the ductile mode, and the material is removed without causing brittle fracture. Therefore, a defect such as a data error may occur after the magnetic film is formed on the substrate. It does not occur on the surface. Further, this roughening treatment can prevent the magnetic head from being attracted.

Next, the results of evaluating the characteristics of the amorphous carbon substrate textured under the above conditions will be described. First, the surface roughness Ra of the substrate after the texture treatment was measured using a surface roughness meter. The results are shown in Tables 1 and 2 below. The surface roughness meter is WYKO.
TOP03D (trade name) manufactured by the company was used. The presence or absence of head crash is also shown in Tables 1 and 2 below.

However, Table 1 shows that the abrasive grains # 1500 to # 6000 were used and polishing was performed using a polishing liquid containing 1% aluminum nitrate. Table 2 shows # 50
No. 00 abrasive grains are used and a polishing liquid containing 0.1 to 10% aluminum nitrate is used. Table 1 also shows comparative examples in which the abrasive grain count is out of the range of the present invention, and Table 2 also shows comparative examples in which the concentration of aluminum nitrate is out of the range of the present invention.

[0028]

[Table 1]

[0029]

[Table 2]

Next, the amorphous carbon substrates for magnetic disks according to these examples and comparative examples were precisely cleaned, and then a media layer (magnetic film) made of CoNiCr was formed on the amorphous carbon substrates using a magnetron sputtering device. A carbon protective film was sequentially formed, and a lubricant was applied to the surface to prepare a magnetic disk.

Then, recording / reproducing was performed using a disc certifier (trade name) manufactured by Pquip Co., the state of occurrence of head crush was evaluated, and a recording / reproducing test was conducted using a head tester. In addition, magnetic disk and MIG
The head flying height from the (Metal In Gap) head was set to about 0.03 μm.

As is clear from Tables 1 and 2, the head flying height of the amorphous carbon substrates for magnetic disks according to Examples 2 to 5 and Examples 8 to 12 was as low as about 0.03 μm. However, head crash did not occur, and head adsorption did not occur.

[0033]

As described above, according to the present invention,
The surface of the amorphous carbon substrate for a magnetic disk has an average grain size of 2 to 8 μm (abrasive grain numbers # 1500 to # 6).
Since the abrasive grains of No. 000) are used for polishing, defects that cause recording / reproducing errors do not occur and stable texture processing can be performed. Further, by adding aluminum nitrate having a concentration of 0.1 to 10% and polishing, the surface roughness can be optimized as an amorphous carbon substrate for a magnetic disk. Therefore, the magnetic head can be prevented from being attracted to the magnetic disk, and the flying height of the magnetic head can be made smaller than before.

Claims (2)

[Claims] 1. A method of texture-treating an amorphous carbon substrate for a magnetic disk, which comprises polishing a polished amorphous carbon substrate with abrasive grains having an average grain size of 2 to 8 μm. 2. The polishing step using the abrasive grains is 0.1% or more and 10% or more when the amorphous carbon substrate is rotated.
% Of aluminum nitrate is used to form concentric scratches on the surface of the amorphous carbon substrate with the abrasive grains. A texture treatment method for an amorphous carbon substrate.