JPH0641109B2 - Polishing tool for disk substrate processing - Google Patents

Description

Description: TECHNICAL FIELD The present invention relates to a polishing tool for obtaining a high-precision flat magnetic disk substrate, for example, in which a magnetic head can be stably levitated to a very small clearance.

(Prior Art and Its Problems) Generally, a magnetic disk substrate is formed on an aluminum alloy surface or a non-magnetic nickel-phosphorus-plated surface formed on the aluminum alloy surface or an aluminum alloy surface corresponding to the type of recording medium. The anodized surface is used as a highly precise flat surface.

In the magnetic disk device, the smaller the floating amount of the magnetic head that floats on the surface of the magnetic disk that rotates at a high speed, the higher the recording density and the larger the output that can be obtained.

Therefore, the levitation amount of a magnetic head in a normal coated magnetic disk is 0.4 to 0.5 μ, whereas the levitation amount of a magnetic head is 0.2 in a high density magnetic disk (for example, a thin film medium disk formed by plating or sputtering). μ
The magnetic head is levitated to a very small gap of m.

As described above, it is necessary to improve the plane accuracy of the magnetic disk substrate as the flying height of the magnetic head is reduced. Since the magnetic head uses a leaf spring for supporting the magnetic head, the magnetic head can follow long-period waviness on the surface of the magnetic disk substrate.
However, it is difficult for the magnetic head to follow waviness of a short cycle (one cycle is three times or less the length of the magnetic head) on the surface of the magnetic disk substrate. Therefore, the short-period undulation height on the magnetic disk substrate surface is 20% or less of the magnetic head levitation amount, that is, when the levitation amount is 0.2 μm, the short-period undulation height is 0.04 μm or less. There is. FIG. 1 shows a cross section of the waviness of the magnetic disk substrate 11 before polishing. The waviness of the substrate 11 has a shape in which a short-period waviness 13 is placed on a long-period waviness 12, and this short-period waviness 13 needs to be removed by polishing.

Conventionally, cast iron wraps have been generally used for polishing metal materials (for example, Precision Machinery Handbook), and cast iron wraps (rigid body polishing tools) have also been used as polishing tools for magnetic disk substrates. However, when the magnetic disk substrate 21 is polished by using a rigid polishing tool, the short-period undulations 22 located at the peaks of the long-period undulations are removed by pressure contact with the rigid polishing tool as shown in FIG. However, the short-period undulations 23 located in the valleys of the long-period undulations have a drawback that they are not removed and remain when the amount of processing is smaller than the height of the long-period undulations (difference between peak and valley). For this reason, when polishing a magnetic disk substrate using a rigid polishing tool such as cast iron wrap, it is necessary to make the processing amount larger than the long cycle waviness height value, resulting in a longer processing time and lower productivity. It has drawbacks and is not always satisfactory.

(Object of the Invention) The present invention eliminates such conventional defects, and efficiently corrects short cycle undulations of a disk substrate with a small processing amount.
An object is to provide an abrasive tool for removal.

(Structure of the Invention) According to the present invention, an elastic body having a small Young's modulus (Young's modulus E <10 ³ g / mm ² ) is provided on the tool base, and the polishing surface is flat on the elastic body and divided into small pieces. And a hard abrasive body with a large Young's modulus that is different from the elastic body (Young's modulus E> 10 ⁴
A polishing tool for processing a disk substrate is obtained which is characterized by having g / mm ² ).

(Operation / Principle of the Present Invention) When the height of the undulation portion of the magnetic disk substrate is a ₀ and the lateral width of the undulation portion is 1, when the surface is polished with a polishing tool, the processing amount h and the undulation portion height a are Is a theoretical formula
It can be represented by (1).

Here, p is the average processing pressure, E ₁ is the Young's modulus of the magnetic disk substrate, E ₂ is the Young's modulus of the polishing tool, ν ₁ is the Poisson's ratio of the magnetic disk substrate, and ν ₂ is the Poisson's ratio of the polishing tool.

FIG. 3 shows short cycle waviness (width 1 = 15 mm, height a ₀ ) of a magnetic disk substrate (surface Ni-P plated surface) using three kinds of polishing tools having elastic properties shown in FIG. = 0.
The relationship between the amount of work and the height of the waviness at the time of surface polishing (5 μm) is calculated using the formula (1) (calculation result is shown by a solid line), and the result is compared with the experimental value. As can be seen from FIG. 3, polishing tool A or B having a small Young's modulus
In the case of using, the height of the short-period waviness of the magnetic disk substrate is slightly modified even if the surface is polished. However, when the polishing tool C having a large Young's modulus was used, the height of the short-period waviness on the magnetic disk substrate was significantly corrected and removed, and the height of the short-period waviness was 0.02 μm at the processing amount of 2 μm.
Is achieved.

However, the phenomenon described above with reference to FIG. 2, that is, the phenomenon in which the valleys of the long-period waviness of the magnetic disk substrate are not polished, is caused when polishing with a polishing tool C having a large Young's modulus with a small amount of processing. woke up.

Next, according to the present invention, a hard material having a large Young's modulus different in material from the elastic body having a flat polishing surface and being divided into small pieces on an elastic body having a small Young's modulus (Young's modulus E <10 ³ g / mm ² ). The operation and principle of a polishing tool characterized by having a polishing body (Young's modulus E> 10 ⁴ g / mm ² ) will be described. As described above with reference to FIG. 3, when a polishing body having a large Young's modulus (Young's modulus E> 10 ⁴ g / mm ² ) is used as a polishing tool, the height of the short cycle waviness of the magnetic disk substrate is Will be fixed.
This polished body with a large Young's modulus (Young's modulus E> 10 ⁴ g / mm ² )
Is divided into small pieces, and an elastic body with a small Young's modulus (Young's modulus E <
10 ³ g / mm ² ), the surface of the polished body with a large Young's modulus divided into small pieces follows the long-period waviness of the magnetic disk substrate due to the deformation of the elastic body with a small Young's modulus, Can be corrected or removed. This solves the conventional problem that the valley of the long-period waviness of the magnetic disk substrate is not polished when a polishing tool having a large Young's modulus is used.

(Example) Hereinafter, an example of the present invention will be described in detail with reference to the drawings. FIG. 4 is a sectional view showing an embodiment of the present invention, in which polyurethane having a small Young's modulus (Young's modulus E ₂
= 2 × 10 ² g / mm ² ) 42, and polyurethane 4
It is a polishing tool in which a grindstone with a large Young's modulus (Young's modulus E ₂ = 4 × 10 ⁴ g / mm ² ) 43, which is divided into small pieces, is adhered to the upper part of 2. An average processing pressure of 250 g / mm ² and an average relative speed, using the above-mentioned polishing tool, using a magnetic disk substrate (surface Ni-P plated surface) as an example.
Polished under the processing conditions of 20 m / mm.

(Effect of the invention) As a result of polishing the magnetic disk substrate (surface Ni-P plated surface) under the above processing conditions using the polishing tool of the present invention,
As shown in FIG. 5, the short-period undulations on the long-period undulations of the magnetic disk substrate 51 could be efficiently removed. According to the measurement results of the magnetic disk substrate undulation, the short cycle undulation height of 0.3 μm before processing was polished by 1.5 μm with the average processing amount, and the short cycle undulation height was 0.02 μm. I confirmed that it was achieved. In FIG. 5, reference numeral 52 shows the undulation of the magnetic disk substrate before processing, 53 shows the undulation of the magnetic disk substrate after processing, and 54 shows the distribution of the processing amount, which follow the long-period undulation of the magnetic disk substrate. , The short cycle undulations have been corrected / removed. It was possible to stably levitate the magnetic head on the surface of the magnetic disk processed according to this example to a minute clearance of 0.2 μm.

As described above, the elastic body having a small Young's modulus (Young's modulus E <10 ³ g / mm ² ) is provided with the abrasive body having a large Young's modulus (Young's modulus E> 10 ⁴ g / mm ² ) divided into small pieces. By processing the magnetic disk substrate with the polishing tool, there is an advantage that the magnetic head can efficiently obtain a highly accurate flat magnetic disk substrate capable of stably levitating even a minute clearance.

It should be noted that the magnetic disk substrate has been described in the embodiment, but it goes without saying that the same effect can be obtained in polishing of another disk substrate such as an optical disk.

[Brief description of drawings]

FIG. 1 is a partial sectional view of the substrate showing the undulations of the magnetic disk substrate before polishing, FIG. 2 is a partial sectional view of the substrate when the magnetic disk substrate is processed by a rigid polishing tool, and FIG. 3 is shown in FIG. Fig. 4 is a graph showing the relationship between the amount of processing when processed with a polishing tool and the height of the short-period waviness of the substrate. Fig. 4 is a sectional view of the polishing tool of the present invention. Fig. 5 shows a magnetic disk substrate with the polishing tool of the present invention. FIG. 6 is a diagram showing a partial cross-sectional view of the substrate when processed, and FIG. 6 is a diagram showing examples of three types of polishing tools having elastic properties. In the drawing, 11, 21, 41 and 51 are magnetic disk substrates, 12 is a long cycle undulation of the magnetic disk substrate, 13 is a short cycle undulation of the magnetic disk substrate, 22 and 23 are short cycle undulations, 41
Is a tool stand, 42 is an elastic body with a small Young's modulus, 43 is a small-piece abrasive body with a large Young's modulus, 52 is a magnetic disk substrate undulation before processing, 53 is a magnetic disk substrate undulation after processing, and 54 is a processing amount. Distribution.

Claims (1)

[Claims] 1. An elastic body having a small Young's modulus (Young's modulus E <10 ³ g / mm ² ) is provided on a tool table, and a polishing surface is flat on the elastic body and the elastic body and the material are divided into small pieces. Hard abrasive with different Young's modulus (Young's modulus E> 10 ⁴ g / mm
² ) A polishing tool for processing disk substrates, which is provided with.