JPH04318324A - Polishing tape - Google Patents

Abstract

PURPOSE:To provide the polishing tape which is used for texturing of various kinds of rigid disks, can texture the disks without generating extraordinarily deep scratch flaws in the disks in spite of reducing the adrasive grain sizes of the polishing tape and is suitable for productin of the rigid disks having excellent high-density recording characteristics. CONSTITUTION:This polishing tape consists of the constitution formed by laminating a resin layer 11 which is softer than the above-mentioned finder resin 3 and is interposed between the abrasive grain layer 2 which is the mixture of a binder resin 3 and polishing abrasive grains 4 and face film 1 consisting of a polyethylene terephthalate resin, etc.

Description

[Detailed description of the invention]

0001

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an abrasive tape particularly suitable for texturing rigid disks (hereinafter referred to as magnetic disks), which are metal magnetic thin film media with excellent high-density recording characteristics.

0002

2. Description of the Related Art In recent years, magnetic disks have become mainstream as external storage devices for personal computers. There are three types of magnetic disks: coating type, plating type, and sputtering type. Recently, there has been a shift from coating type to plated type and sputtering type, which have excellent high-density recording characteristics.

Sputter type magnetic disks are textured using an abrasive tape to achieve a surface roughness Ra of 80.
~100 Å, the floating magnetic head (hereinafter abbreviated as magnetic head) can be moved 0.2 Å from the surface of the magnetic disk.
Since it can be levitated at a height of about 0.3 μm, a magnetic disk drive device with excellent high-density recording characteristics can be realized.

The purpose of texturing is to prevent the magnetic head and the magnetic disk from sticking together and to improve the magnetic properties of the magnetic disk. Generally, texturing is performed by bringing an abrasive tape called a lapping tape into contact with the mirror-polished surface of the NiP plating film and rotating the magnetic disk, thereby polishing the magnetic disk in the circumferential direction. By selecting the size of the abrasive grains of the polishing tape used at this time, the surface roughness of the textured surface can be controlled.

[0005] Conventional abrasive tapes will be explained below. FIG. 5 is a perspective view showing the surface condition of a conventional abrasive tape for texturing, and FIG. 6 is a sectional view of a main part of the conventional abrasive tape.

[0006] 1 is a base film made of a synthetic resin such as polyethylene terephthalate, and 2 is formed by coating and drying a resin liquid in which a binder resin 3 and abrasive grains 4 are mixed and suspended in a solvent on the base film 1. This is an abrasive layer. As the polishing abrasive grains 4, aluminum oxide, chromium oxide, silicon carbide, diamond, etc. are used.

Depending on the type, particle size, and shape of the abrasive grains, the surface shape of the abrasive tape can be flat (a) or hexagonal (b).
, donut shape (c).

The operation of the polishing tape constructed as described above will be explained below. FIG. 7 is a sectional view of the main part of the magnetic disk.

5 is an aluminum alloy substrate, and 6 is a NiP plating film applied to the surface of the aluminum alloy substrate 5. The polishing tape is used to polish the surface of the NiP plating film 6 to a mirror surface and further polish it in the circumferential direction of the magnetic disk.

The processing method of polishing in the circumferential direction is generally called texture processing. On this NiP plating film 6 which has been textured and polished to a surface roughness Ra of 80 to 100 Å, a Cr film 7 , a Co-based alloy magnetic film 8 , a protective film (Cr film) 9 , and a lubricating film (C film) 10 are sequentially deposited by sputtering to produce a magnetic disk with a flying height of 0.2 to 0.3 μm.

[0011]

[Problems to be Solved by the Invention] However, with the above conventional configuration, there is a problem that it is difficult to reduce the flying height of the magnetic head to 0.2 μm or less. It was not possible to provide the disc. In order to reduce the flying height of the magnetic head, it is necessary to reduce the surface roughness Ra of the magnetic disk as much as possible. R
In order to reduce a, it is effective to reduce the abrasive grain size of the abrasive tape for texturing, but conventional abrasive tapes have the problem of producing abnormally deep scratch marks in some places. If there are such abnormally deep scratch marks, when using a magnetic head with a flying height of 0.1 μm, there is a high probability that the magnetic head will come into contact with the magnetic disk and cause damage (crash). However, it was not possible to put it into practical use simply by reducing the abrasive grain size.

The present invention solves the above conventional problems, and provides an abrasive tape that can be textured without producing abnormally deep scratch marks even when the abrasive grain diameter of the abrasive tape is reduced. The purpose is to

[0013]

[Means for Solving the Problems] In order to achieve this object, the abrasive tape of the present invention has an abrasive grain layer which is a mixture of a binder resin and abrasive grains, and a base film, which is a mixture of binder resin and abrasive grains. It has a structure in which resin layers are laminated.

[0014]

[Operation] With this structure, even if the surface roughness Ra of the textured surface is small, texture processing can be performed while preventing the occurrence of abnormally deep scratches due to the buffering action of the soft resin. Furthermore, as a result, it is possible to realize a magnetic disk having ultra-high density recording characteristics in which the flying height of the magnetic head is 0.2 μm or less.

[0015]

DESCRIPTION OF THE PREFERRED EMBODIMENTS An embodiment of the present invention will be described below with reference to the drawings.

FIG. 1 is a sectional view of a main part of an abrasive tape according to an embodiment of the present invention, and FIG. 2 is a sectional view of a main part of an abrasive tape when texture processing is performed using the abrasive tape of the present invention. be.

1 is a base film having a thickness of 25 to 50 μm;
2 is an abrasive grain layer consisting of abrasive grains fixed in a binder resin with a thickness of 5 to 15 μm, 3 is a binder resin, and 4 is an abrasive grain; these are the same as in the conventional example, so they are given the same numbers. The explanation will be omitted.

11 is a soft resin layer of 10 to 50 μm; 12
is the disk substrate. The soft resin layer 11 has greater flexibility than the binder resin 3, and when a load is concentrated on the abnormal protrusion on the surface of the abrasive layer 2 as shown in FIG. It was found that the protruding portion sank into the base film and did not cause abnormally deep scratches on the processed disk substrate 12 coated with the NiP plating film 6.

(Example 1) A 15 μm thick soft resin layer 11 was laminated on one side of a 30 μm thick polyethylene terephthalate film as the base film 1.
50 parts by weight of Al2O3 grains (manufactured by Fujimi Abrasives Industry Co., Ltd.) with an average particle diameter of 2 μm as abrasive grains and 30 to 50 parts by weight as a binder resin 3 are uniformly dispersed in ethanol, and the suspension is used as a soft resin layer. After coating on 11, abrasive layer 2
The polishing tape (a) was coated to a thickness of 0 μm to obtain a polishing tape (a) in which the abrasive grain layer 2 had a flat shape. Using this polishing tape (a), a magnetic disk 5 was mirror-polished on an aluminum alloy substrate coated with a NiP plating film with an outer diameter of 3.5 inches.
Texture processing was performed on 0 sheets, and the frequency of occurrence of abnormal scratches was determined.

The frequency of occurrence was expressed as a percentage of the number of surfaces of the magnetic disks inspected and the number of surfaces on which abnormally deep scratches were visually detected.

The results are shown in (Table 1). (Examples 2 and 3) Polishing tapes (b), (
c) was obtained, texture processing was performed under the same conditions as in Example 1, and the frequency of occurrence of abnormal scratches was determined. The results are shown in (Table 1).

(Example 4) As the polishing abrasive grains 4, the average particle size was 1
μm Al2O3 grains (manufactured by Fujimi Abrasives Industry Co., Ltd.) 50
A polishing tape (d) was obtained in the same manner as in Example 1 except that the weight part was used and the shape of the abrasive layer 2 was made flat.
Texture processing was performed under the same conditions as above, and the frequency of occurrence of abnormal scratches was determined. The results are shown in (Table 1).

(Comparative Examples 1 to 4) Examples 1 to 4 were repeated except that the soft resin layer was not provided. c), flat type (d) conventional abrasive tapes were manufactured.

Using these polishing tapes (a) to (d), texture processing was carried out under the same conditions as in Example 1, and the frequency of occurrence of abnormal scratches was determined. The results are shown in (Table 1).

[0025]

[Table 1]

As is clear from Table 1, no abnormally deep scratches were observed in this example, regardless of the shape of the abrasive layer or the diameter of the abrasive grains.

On the other hand, it was found that in the conventional abrasive tape shown in the comparative example, abnormally deep scratches occurred with a high probability of 5 to 20%.

Next, a reliability test was conducted on magnetic disks textured with the abrasive tapes of Examples 1 to 4 and Comparative Examples 1 to 4.

Here, the reliability test was conducted using AE (Acoustic.
(mission) Evaluation was performed using the output voltage. As shown in FIG. 3, the AE output voltage is measured by attaching the AE element 16 to the fixed part (mount) 15 of the flexure 14, which is the supporting part of the magnetic head 13, and rotating the magnetic disk 18 mounted on the spindle 17. The AE element 16 measures the impact force that the magnetic head 13 receives from the scratch marks on the magnetic disk 18 and converts it into a voltage, and the noise level is 2.
The number of contacts between the magnetic head 13 and the magnetic disk 18 was evaluated by counting the number of times the output voltage was doubled or more.

[0030] The glide flying guarantee means that the flying height (for example, 0.1 μm) of the magnetic head used in a magnetic disk drive device is 60 to 80% of the flying height (for example, 0.1 μm).
For example, 0.06 μm).

The reliability test was carried out over a radius of 20 to 46 mm on the magnetic disk. The results are shown in (Table 2).

[0032]

[Table 2]

As is clear from this (Table 2), in this example, the lower limit flying height for glide flying guarantee is 0.06
While the number of AE counts per μm was 4 to 20 times, in the comparative example, the number of AE counts was 10 to 230 times that number.

This is thought to be due to the presence of many deep scratch marks that cannot be seen with the naked eye. Generally, when a deep scratch occurs, plastic deformation occurs, as shown in Figure 4.
It is well known that a phenomenon occurs in which both ends of a deep scratch mark 19 bulge and a protrusion 20 is formed as shown in FIG. This suggests that there are deep scratches that cannot be seen with the naked eye, and that abnormal protrusions that come into contact with the magnetic head have occurred on the magnetic disk. On the other hand, the magnetic disk textured using the abrasive tape of this example has a count number of 20 times or less by the AE element, as shown in (Table 2), and it is clear that the abrasive tape of the present invention is It can be seen that the texture processing is superior.

[0035]

As described above, the present invention has a synthetic resin layer that is softer than the binder resin of the abrasive layer and is laminated between the abrasive layer and the base film, thereby reducing the occurrence of scratches caused by abrasive particles during polishing. By significantly reducing the amount of friction, it is possible to realize an excellent abrasive tape that can provide magnetic disks with a low flying height and a stable flying state at a high yield.

[Brief explanation of drawings]

[Fig. 1] Cross-sectional view of essential parts of the abrasive tape of the present invention

[Figure 2] (a
) Cross-sectional view of the main part of the abrasive layer surface of the polishing tape (b) Cross-sectional view of the main part of the polishing tape during texture processing

[Figure 3] Principle diagram of AE output voltage measurement device

[Figure 4] Enlarged view of scratch marks on the magnetic disk surface

[Figure 5] Perspective view of conventional polishing tape

[Figure 6] Cross-sectional view of main parts of conventional polishing tape

[Figure 7] Cross-sectional view of main parts of a magnetic disk

[Explanation of symbols]

1 Base film 2 Abrasive grain layer 3 Binder resin 4. Abrasive grains 5 Aluminum alloy substrate 6 NiP plating film 7 Cr film 8 Co-based alloy magnetic film 9 Protective film 10 Lubricating film 11 Soft resin layer 12 Disc board 19 Scratch marks 20 Protrusion

Claims (1)

[Claims] 1. An abrasive tape characterized in that a synthetic resin layer softer than the binder resin is laminated between an abrasive grain layer made of a mixture of abrasive grains and a binder resin and a base film.