JPH09102120A - Substrate for recording medium - Google Patents

Abstract

PROBLEM TO BE SOLVED: To improve durability of a film formed on a substrate body by specifying the surface roughness of a chamfered part of the substrate. SOLUTION: This recording medium substrate 1 is chamfered on the edges of the inner and outer circumferences, and the surface roughness of the chamfered part 2, 3 is specified to <0.20μm. If the surface roughness of the chamfered part 2, 3 of the substrate body 1A is >=0.20μm, adhesion of films 1B-1I to be formed thereon decreases to easily cause peeling of films. Besides, an org. matter such as a detergent intrudes into recesses on the rough surface of the chamfered part 2, 3 in a working process of the substrate body 1A and remains in a large amt. if the recesses are large (the roughness is large). As a result, adhesion strength of films 1B to 1I to be formed on the contaminated part decreases to easily cause peeling of films.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a recording medium substrate of various recording systems (magnetic, magneto-optical, optical).

[0002]

2. Description of the Related Art A substrate for a recording medium typified by a hard disk (HD) substrate is a lapping process for roughly polishing the surface of a substrate body, a chamfering process for chamfering the inner and outer peripheral end faces to be chamfered, and a final polishing for the surface. It is manufactured through a polishing process. Then, this substrate further has a texture step of forming a texture layer on the surface of the substrate body to appropriately roughen the surface, an underlayer forming step of forming an underlayer on the surface, and a magnetic layer formed on the surface. Magnetic layer forming step, a protective layer forming step of forming a protective layer on the magnetic layer,
A product is formed by forming a film on the surface of the substrate body in a lubricating layer forming step of forming a lubricating layer on the protective layer, and then performing a burnishing step of removing abnormal protrusions on the film surface.

[0003]

However, in the conventional substrate, film peeling occurs between the chamfered chamfered portion on the inner and outer peripheral end faces of the substrate body and the texture layer or the like formed thereon. , It was sometimes defective.

An object of the present invention is to improve the durability of a film formed on a substrate body.

[0005]

According to a first aspect of the present invention, in a recording medium substrate having inner and outer peripheral end faces chamfered, the chamfered portion has a surface roughness Ra of less than 0.20 μm. Is.

According to a second aspect of the present invention, in addition to the first aspect of the present invention, the substrate is a substrate made of a brittle material.

According to a third aspect of the present invention, in addition to the second aspect of the present invention, the substrate is a carbon substrate.

According to the present invention described in claim 1, the following operational effects are obtained. Since the surface roughness of the chamfered portion of the substrate body is as small as less than 0.20 μm, the adhesion of the film such as the texture layer formed thereon is improved and the film is not peeled off. In addition, organic substances (detergent, etc.) that enter the valleys of the surface roughness of the chamfered portion during the substrate body processing process have a small depth of the valleys (small roughness).
Therefore, a small amount or good removal is easy, and as a result, the adhesion of the film such as the texture layer formed on the clean chamfered portion is improved, and the film is not peeled off.

According to the second aspect of the present invention, there are the following operational effects. Even in a substrate made of a brittle material such as a carbon substrate or a glass substrate, film peeling does not occur due to the above.

According to the third aspect of the present invention, there are the following operational effects. A carbon substrate also has excellent impact resistance.

[0011]

1 is a schematic diagram showing a substrate, FIG. 2 is a schematic diagram showing a film structure of the substrate, FIG. 3 is a schematic diagram showing a chamfer processing device, FIG. 4 is a schematic diagram showing a polishing device, and FIG. 5 is a schematic view showing a film structure of a substrate according to an example of the present invention.

A glassy carbon substrate for a magnetic disk (G
The C substrate 1 has the substrate body 1A processed by the following (1) to (3). (1) Lapping step The surface of the substrate body 1A is roughly polished with loose abrasive grains.

(2) Chamfer processing step The inner and outer peripheral end faces of the substrate body 1A are ground and chamfered. FIG.
2 is an outer peripheral chamfered portion, and 3 is an inner peripheral chamfered portion.

(3) Polishing Step The surface of the substrate body 1A is finish-polished.

Here, the chamfer processing apparatus used in the chamfer processing step (2) will be described (FIG. 3).

The chamfer processing apparatus 10 includes a chuck stage 11, a clamp 12, diamond grinding stones 13 and 14.
Is configured.

The chuck stage 11 applies a vacuum pressure to the concentric convex portion 11A for supporting the substrate body 1A, a vacuum suction groove 11B for vacuum suctioning the substrate body 1A around the convex portion 11A, and a vacuum suction groove 11B. A vacuum supply path 11C is provided. As a result, the chuck stage 11 moves to the substrate body 1
A can be vacuum-adsorbed.

The clamp 12 is a high-pressure water jet port 12A for applying high-pressure water to the substrate body 1A on the chuck stage 11.
The substrate body 1A can be pressed and held on the chuck stage 11.

The diamond grindstone 13 can chamfer and grind the outer peripheral end surface of the substrate body 1A, and the diamond grindstone 14 can chamfer and grind the inner peripheral end surface of the substrate body 1A.

The polishing apparatus 30 used in the polishing step (3) will be described (FIG. 4). The polishing device 30 includes an upper polishing plate 31, a lower polishing plate 32, and a carrier 3.
3. The upper polishing plate 31 and the lower polishing plate 3
A pad is attached to the surface of 2 (the surface in contact with the substrate body).

In the polishing apparatus 30, the lower polishing plate 32 rotates in the direction of arrow A. Further, above the lower polishing plate 32,
A sun gear 34 rotating in the direction of arrow B and an internal gear 35 rotating in the direction of arrow C are provided with a planetary gear-shaped carrier 33 that rotates while revolving, and holds a plurality of works. The substrate body 1A is set in the hole 36. An upper polishing plate 31 is provided above the lower polishing plate 32 and the carrier 33. The upper polishing plate 31 is moved up and down by an air cylinder (not shown), and is engaged with a rotor 37 that rotates in the direction of arrow D when it is lowered. Combine and rotate in the same direction. Then, a slurry containing abrasive grains is supplied between the upper polishing platen 31 and the lower polishing platen 32 by a slurry supply pipe (not shown).

As a result, in the polishing apparatus 30, by lowering the upper polishing platen 31, the substrate body 1A held by the carrier 33 is sandwiched between the upper polishing platen 31 and the lower polishing platen 32, and the abrasive grains intervene. Both upper and lower sides are polished below.

Further, in the GC substrate 1, the above-mentioned substrate body 1A is subjected to, for example, the following film formation, and finally the following burnishing process is performed to obtain a product (FIG. 2). Ti layer forming step The Ti layer 1B is formed on the substrate body 1A.

Texture step An Al-Si uneven layer 1C (texture layer) is formed on the Ti layer 1B, and the surface is appropriately roughened.

Carbon Layer Forming Step A carbon layer 1D is formed on the texture layer 1C.

Underlayer forming step: Ti underlayer 1E and Cr underlayer 1F are formed on the carbon layer 1D.
Are formed in order.

Magnetic Layer Forming Step A magnetic layer (recording layer) 1G is formed on the Cr underlayer 1F.

Protective Layer Forming Step A carbon protective layer 1H is formed on the magnetic layer 1G.

Lubricating Layer Forming Step A lubricating layer 1I is formed on the protective layer 1H.

Burnishing step Abnormal protrusions on the surface are removed.

However, the present inventor has found that in the GC substrate 1, chamfered portions 2 and 3 chamfered on the inner and outer peripheral end faces of the substrate body 1A, and the film-forming layers 1B to 1 formed thereon.
Regarding the prevention of film peeling that tends to occur with I, the following (A)
The knowledge of (C) was obtained. (A) Processing Roughness of Chamfered Parts 2 and 3 of Substrate Main Body 1A In the polishing process by the polishing device 30, the upper and lower surfaces of the substrate main body 1A are in contact with the upper and lower polishing plates 31 and 32 via abrasive grains. It is sufficiently polished and mirror-finished. Further, the outer peripheral surface of the substrate body 1A (a straight cylindrical surface between the upper and lower chamfered portions 2) is sufficiently polished by being in contact with the carrier 33 via abrasive grains, and is given a mirror surface. However,
The chamfered portions 2 and 3 of the substrate body 1A include upper and lower polishing plates 31,
Since it does not come into contact with either 32 or carrier 33,
Not sufficiently polished, resulting in a large roughness.

(B) Relationship between roughness and film peeling If the surface roughness of the chamfered portions 2 and 3 of the substrate body 1A is as large as 0.20 μm or more, the film forming layers 1B to
The adhesion of a film such as 1I is poor, and film peeling easily occurs. Also, a large amount of organic substances (detergent etc.) that enter the valleys of the surface roughness of the chamfered portions 2 and 3 in the processing step of the substrate body 1A remain when the depth of the valleys is large (roughness). As a result, the adhesion of the films such as the film forming layers 1B to 1I formed on the contaminated portion is deteriorated, and film peeling easily occurs.

(C) Relationship between Material of Substrate Body 1A and Film Peeling When the substrate body 1A is made of a brittle material as in the GC substrate 1, the grindstones 13 and 1 of the chamfering machine 10 are used.
A diamond grindstone is used as 4, but the surface roughness of the conventional chamfered portions 2 and 3 is as rough as 0.4 μm or more. For this reason, in combination with (A), the roughness of the chamfered portions 2, 3 of the substrate body 1A is likely to be particularly large, and film peeling due to (B) above is likely to occur remarkably.

Therefore, in the present invention, the substrate body 1A
By setting the surface roughness Ra of the chamfered portions 2 and 3 to be less than 0.20 μm, the film forming layer 1 formed on the chamfered portions 2 and 3 is formed.
The adhesion of the films B to 1I is improved, and the occurrence of film peeling can be avoided. Further, this shows a remarkable effect in the substrate made of a brittle material such as the GC substrate 1 and the glass substrate.

[0035]

【Example】

(Example 1) (Table 1) An Al substrate, a hard glass substrate, and an amorphous carbon substrate were manufactured by the following (1) and (2), and a film peeling test of the following (3) was carried out. (1) Substrate body processing The above-mentioned lapping process, chamfering process,
Polished. At this time, after chamfering the substrate main body, the roughness of the chamfered portion of the inner and outer peripheral end surfaces is 0.05 μm, 0.10 μm, 0.15 μm by polishing with a polishing tape.
It was adjusted to 0.20 μm and 0.5 μm, respectively.

The roughness measuring method was as follows. Stylus type roughness meter (manufactured by TENCOR, model P2) Stylus diameter: 0.6 μm (needle curvature radius) Stylus pressing pressure: 7 mg Measuring length: 250 μm x 8 points Tracing speed: 2.5 μm / sec Cutoff: 1.25 μm (low pass filter)

(2) Film formation on the substrate body (FIG. 5) An Al-10 wt% Si alloy texture layer having a thickness of 20 nm and an average surface roughness of 9.2 angstrom was provided by DC magnetron sputtering under Ar gas pressure of 2 mTorr.

Next, a first underlayer made of amorphous carbon and having a thickness of 25 nm was formed by DC magnetron sputtering under the conditions of Ar gas pressure of 2 mTorr and substrate heating temperature of 250 ° C.

Further, the substrate heating temperature is set to 180 ° C. and Ar
Under a gas pressure of 10 mTorr, a second underlayer made of Ti having a thickness of 50 nm, a third underlayer made of Cr having a thickness of 25 to 50 nm, and a Co-Cr-Pt-B layer having a thickness of 15 to 35 nm (magnetic Layers) were successively deposited.

Next, the disk substrate is placed in a chamber of an in-line type sputtering apparatus, the chamber is evacuated, and then Ar (partial pressure of 1.6 mTorr) and oxygen (partial pressure of 0.4 mTorr) are introduced to target graphite. As a result, sputtering was performed to form a 15 nm protective layer on the magnetic layer.

Finally, after burnishing, a lubricant was dipped and applied on the protective layer to a thickness of 2 nm.

(3) Film peeling test (tape test method) A film forming disk was left at 80 ° C. and a humidity of 85% for 2 weeks, then taken out and cut into 10 mm × 10 mm cellophane tape (“Cellotape” manufactured by Nichiban Co., Ltd.). (Registered trademark)). At this time, air bubbles were prevented from entering the pasted part. Then, it was quickly pulled up in the vertical direction to measure the peeled area of the film. The evaluation criteria were as follows. ◯: No peeling occurred. △: The peeled area is greater than 0% of the pasted area and 50%
Less than ×: 50% or more peeled area

The results of the film peeling test of each substrate are shown in Table 1, and the effect of the present invention was confirmed in any of the Al substrate, the hard glass substrate and the amorphous carbon substrate.

[0044]

[Table 1]

The effects of the present invention can be obtained regardless of the constitution and composition of the film provided on the substrate body.

In the practice of the present invention, the end face portion of the substrate body is (1) lapping step, (2) fixed abrasive grain grinding step, (3) chamfer processing step, (4) finishing polishing step (can be omitted). Processed by (1) fixed grinding wheel grinding process, (2) chamfer processing process, (3) lapping process,
It may be processed by (4) polishing step, (1) chamfer processing step, (2) lapping step, or (3) polishing step.

[0047]

As described above, according to the present invention, the durability of the film formed on the substrate body can be improved.

[Brief description of the drawings]

FIG. 1 is a schematic view showing a substrate.

FIG. 2 is a schematic diagram showing a film configuration of a substrate.

FIG. 3 is a schematic diagram showing a chamfer processing device.

FIG. 4 is a schematic view showing a polishing apparatus.

FIG. 5 is a schematic view showing a film structure of a substrate according to an example of the present invention.

[Explanation of symbols]

 1 substrate 1A substrate body 2 and 3 chamfer

Claims (3)

[Claims] 1. A recording medium substrate having chamfered inner and outer peripheral end faces, wherein the chamfered portion has a surface roughness Ra of less than 0.20 μm. 2. The substrate for a recording medium according to claim 1, wherein the substrate is a substrate made of a brittle material. 3. The carbon substrate as the substrate.
The recording medium substrate described.