JPH0388122A - Polishing tape for magnetic disk - Google Patents

Abstract

PURPOSE:To reduce the dispersion in surface roughness by providing a polyshing layer consisting of the fine particles of a polyshing material and a binder on one surface of a long-sized base material and providing a backing layer consisting of conductive particles and a binder on the rear surface of the polishing layer of the long-sized base material. CONSTITUTION:The polishing layer consisting of the fine particles of the polishing material and the binder is provided on one surface of the long-sized base material. The backing layer consisting of conductive film particles and the binder is provided on the rear surface of the polishing layer of the long-sized base material. The conductive fine particles are preferably a carbon black having 30 to 140cc/100g oil absorption. The conductive fine particles are preferably conductive titanium having <=50OMEGAcm powder resistance when made into the compressed powder of 100kg/cm<2>. The magnetic disk subjected to the surface polishing by using this polishing tape is reduced in the dispersion of the surface roughness. The good reproduced output envelope when signal are actually written is obtd.

Description

DETAILED DESCRIPTION OF THE INVENTION A6 Object of the Invention [Field of Industrial Application] The present invention relates to a polishing tape used for polishing the surface of a magnetic disk.

[Conventional technology]

Normally, in a magnetic disk in which a magnetic recording layer made of magnetic powder, a binder, etc. is provided on a non-magnetic support, in order to further improve the surface properties, after forming the magnetic recording layer, the surface is Polishing is done.

By applying such surface polishing treatment, it is possible to significantly reduce the recording/reproducing spacing loss between the magnetic head and the magnetic disk, and as a result, the electromagnetic characteristics are oil-free and the running stability is improved. An excellent magnetic disk can be obtained.

Surface polishing of the magnetic disk in the circumferential direction is generally performed using a polishing tape provided with a polishing layer made of abrasive fine particles and a binder on one surface of a flexible support. It is true.

When polishing the surface of a magnetic disk using such a polishing tape, a magnetic disk surface polishing apparatus is used. In this device, the polishing tape is pressed against the rotating magnetic disk surface by an elastic backup roll, and as a result, the surface of the magnetic disk is polished.

This is the most widely used magnetic disk surface polishing method, and the most important factor in obtaining a high-quality polished surface is to make the contact of the polishing tape uniform with the magnetic disk. is well known.

[Problem to be solved by the invention]

Factors that hinder the uniformity of the abrasive tape's contact with the magnetic disk include the lack of dimensional accuracy of the backup roll made of elastic material, and the inaccuracy of the design of hardness, diameter, etc. Even if it is satisfied, if the polishing tape's slipperiness is insufficient, the elastic roll may be deformed during the polishing process, or the polishing tape's feeding speed may fluctuate, resulting in a slippage in the radial direction of the magnetic disk. Also, there is a problem in that the surface roughness in the circumferential direction becomes uneven, and the electromagnetic conversion characteristics of the magnetic disk vary.

The present invention has been made in view of the current situation. That is, an object of the present invention is to provide a polishing tape that has excellent sliding properties with a backup roll when polishing the magnetic recording surface of a magnetic disk, and to obtain a magnetic disk that has excellent electromagnetic conversion characteristics. be.

8. Structure of the Invention [Means for Solving the Problems] The present invention provides an abrasive tape used for surface polishing of magnetic disks, which comprises a polishing layer made of fine particles of abrasive material and a binder on one surface of a long base material. On the other hand, a backing layer made of conductive fine particles and a binder is formed on the back side of the polishing layer of the long base material, and the conductive fine particles have an oil absorption of 30 cc.
/100 g to 140 cc/100 g of carbon black, or conductive titanium oxide with a specific resistance of 50 Ω C1 or less when made into a compressed powder of 100 kg/cm, and the surface resistance of the backing layer conforms to ASTM D257.
This abrasive tape for magnetic disks is characterized in that it has a resistance of 9×10 9 Ω or less when measured by a method prescribed in the Act.

That is, the present invention provides: 1. An abrasive tape used for surface polishing of magnetic disks, which has a polishing layer made of abrasive fine particles and a binder on one surface of a long base material, and a polishing layer of the long base material. On the back,
An abrasive tape for magnetic disks characterized by having a backing layer made of conductive fine particles and a binder.

2. The conductive fine particles have an oil absorption of 30cc/100g
The abrasive tape for magnetic disks according to claim 1, characterized in that the abrasive tape is carbon black of 140 cc/100 g.

3. The magnetic disk according to claim 1, wherein the conductive fine particles are conductive titanium oxide having a powder specific resistance of 50 Ωcm or less when compressed into a powder of 100 kg/cm2. polishing tape.

4. The surface resistance of the backing layer is a value determined by a two-terminal constant current method using a ring electrode in accordance with ASTM D257 method,
The present invention relates to an abrasive tape for a magnetic disk according to claims 1, 2, and 3, characterized in that the abrasive tape has a resistance of 9×10 9 Ω or less.

[Effect]

In the present invention, since a running stabilizing layer is provided on the surface of the abrasive tape base material that comes into contact with the backup roll, a discontinuous adsorption phenomenon of the abrasive tape to the backup roll occurs, that is, contact between the abrasive tape and the backup roll. It is possible to reduce fluctuations in the frictional force that sometimes occur, and prevent uneven running of the polishing tape and distortion of the backup roll that occur when the frictional force fluctuates. In addition, since the running stabilizing layer has conductivity, dust can be attracted by charging.
Prevent entanglement. As a result, a magnetic disk with a uniform surface is obtained.

In the present invention, the surface roughness of the backing layer is defined as center line roughness (Ra)
The thickness is preferably in the range of 0.008 μm to 0.25 μm. If the center line roughness is 0.008 μm or less, the formation of an air layer during contact with the backup roll will be insufficient, so the desired improvement in running stability cannot be expected.
If it is 0.25 μm or more, it is not preferable because it causes deterioration in the polishing accuracy of the magnetic disk.

The carbon black used in the present invention has an oil absorption of 30cc.
/ 100 g to 140 cc/100 g. If the oil absorption amount is less than 30 cc/100 g, it will be difficult to secure the desired conductivity, so it is not preferable, and if it is more than 140 cc/100 g, the surface roughness of the coating film may occur. This is not preferable because it makes it difficult to control the temperature.

The conductive titanium oxide fine powder that can be used in the present invention may have a powder resistance of 50 ncm or less at a value of 100 kg/cm" compressed powder, and the molecular formula is Ti.
, , 02n, or white conductive titanium oxide in which a tin oxide-based conductive layer is provided on the surface of titanium oxide (TiO2) can be used. If the specific resistance of the powder exceeds 50 nC, it will be difficult to obtain the desired conductivity, so care must be taken.

In addition, the surface resistance of the polishing tape backing layer in the present invention is A
According to the two-terminal constant current method using a ring electrode, which is a measurement method of the STM D257 method, it is desirable that the value is 9 x 10 9 Ω or less, and if it is higher than that, the antistatic effect of the present invention cannot be fully expected. Can not.

Note that the value of the powder resistivity of the conductive titanium oxide fine powder may be any value as long as the value satisfies the condition of 50 Ωcit or less. Therefore, even if a powder with conductive properties similar to those of a metal conductor is used, the same result as in the present invention will be achieved. It is natural that the following effects can be obtained.

〔Example〕

Next, embodiments of the present invention will be described with reference to the drawings.

Example 1 Fused alumina fine powder 84 parts by weight (average particle size 1
μm) Epoxy resin 9 parts by weight (solid content) Polyurethane resin 7 parts by weight (solid content) Methyl ethyl ketone 45 parts by weight Toluene
50 parts by weight cyclohexanone 25
Parts by Weight The above composition was kneaded in a ball mill for 45 hours to obtain an abrasive layer paint. This was placed on a polyethylene terephthalate (PET) film with a thickness of 50 μm, and the thickness after drying was 1
The polishing tape was coated to a thickness of 5 μm to obtain an original polishing tape.

Next, after kneading the following composition in a ball mill for 72 hours,
24 parts by weight of a curing agent (isocyanate compound) was added and kneaded for an additional hour to obtain a coating material for a conductive backing layer.

Carbon black 169 parts by weight (RAVEN1255 manufactured by Cologne Yankee Co., Ltd./oil absorption 5
8cc/100g) Vinyl chloride-vinyl acetate-vinyl alcohol copolymer 81 parts by weight (solid content) 69 parts by weight (solid content) 600 parts by weight 615 parts by weight 330 parts by weight Saturated polyester resin Methyl ethyl ketone Toluene cyclohexanone This was added to the back side of the polishing tape The thickness after drying is 0.7
After applying the coating to a thickness of .mu.m and curing at 60'C for 72 hours, the sample was slit to a width of 24 mm to obtain a sample. The surface resistance of the resulting polishing tape was 4×10 7 Ω.

Example 2 A sample was prepared in the same manner as in Example 1, except that the coating composition for the conductive backing layer in Example 1 was changed to the one shown below.

White conductive titanium oxide fine powder 427 parts by weight (powder resistivity: 3ΩC1, average particle size: 0.2ttm) Nitrocellulose resin 54 parts by weight (solid content) Polyurethane resin H @ 126 parts by weight (solid content) Methyl ethyl ketone 600 parts by weight part toluene
615 parts by weight cyclohexanone 3
The surface resistance of the abrasive tape obtained by 30 parts by weight is 7
IQ was 8Ω.

Comparative Example 1 A sample was prepared in the same manner as in Example 1 except that the conductive backing layer in Example 1 was omitted.

The surface resistance of the resulting polishing tape was 9×10 12 Ω or more.

Each sample obtained was placed in a magnetic disk polishing device having the mechanism shown in Fig. 1, and was polished to a diameter of 3 mm under the processing conditions shown in Table 1.
．． A 5" flexible magnetic disk was subjected to surface polishing treatment.

Table 1 The magnetic disk obtained here was evaluated as shown below.

1) Surface gloss variation 60'-60@ using a gloss meter, measure the circumferential direction (radius 30cm) and radial direction (radius 20~4cm) of the magnetic disk.
The glossiness of 0■- was measured at 5-question intervals, the maximum value and minimum value were selected from both data, and the difference therebetween was defined as ΔG.

2) Reproduction output envelope Frequency 50 on the circumference of each magnetic disk with a radius of 30o+m
After recording a 0 kHz signal, the reproduced output envelope was observed using an oscilloscope.

The evaluation results regarding the above test are shown in Table 2.

Table 2 As can be seen from this table, magnetic disks whose surfaces were polished using the polishing tape of the present invention had less variation in surface gloss (surface roughness) than when conventional polishing tapes were used. It has become.

The playback output envelope when the signal is actually written is also good.

Effects of the Invention [Effects of the Invention] As described above, according to the present invention, there is provided a magnetic disk surface polishing tape that can produce magnetic disks with less variation in surface roughness and good electromagnetic conversion characteristics. Obtained.

[Brief explanation of drawings]

"FIG. 1 is a perspective view showing a magnetic disk surface polishing apparatus used to evaluate magnetic tape polishing tapes in Examples and Comparative Examples of the present invention. 1...Magnetic disk, 2 ... Polishing tape, 3...
Backup roll, 4a, 4b...Guide roll, 5...Slit air nozzle.

Claims (1)

[Scope of Claims] 1. An abrasive tape used for surface polishing of a magnetic disk, which has a polishing layer made of abrasive fine particles and a binder on one surface of a long base material, and the polishing layer of the long base material. on the back of
An abrasive tape for magnetic disks characterized by having a backing layer made of conductive fine particles and a binder. 2. The conductive fine particles have an oil absorption of 30cc/100g
The abrasive tape for magnetic disks according to claim 1, characterized in that it is carbon black of 140 cc/100 g. 3. The conductive fine particles are conductive titanium oxide having a powder specific resistance of 50 Ωcm or less when compressed into powder of 100 kg/cm^2, Claim 1
Abrasive tape for magnetic disks as described in . 4. The surface resistance of the backing layer is 9× as determined by the two-terminal constant current method using a ring electrode according to ASTM D257 method.
The abrasive tape for magnetic disks according to claims 1, 2, and 3, characterized in that it has a resistance of 10^9Ω or less.