Water-based non-organic coolant for texturing hard disk

Abstract

A water-based non-organic coolant contains a texturing surfactant, a wetting surfactant, a lubricating surfactant and a bacterial growth inhibitor each of a specified composition and each in an amount within a specified range. As a hard disk is rotated, slurry containing abrading particles and such a coolant is applied to its surface as a polishing tape is pressed on it to obtain a textured surface of a high quality.

Description

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 is a micromax visual picture of circumferential lines on the surface of a hard disk textured by a method of this invention.

FIG. 2 is an atomic force microscope (AFM) picture showing circumferential lines on the surface of a hard disk textured by a method of this invention.

FIG. 3 is an AFM three-dimensional picture of the circumferential lines of FIG. 2.

DETAILED DESCRIPTION OF THE INVENTION

The invention relates to a water-based non-organic coolant characterized as containing a texturing surfactant, a wetting surfactant, a lubricating surfactant and a bacterial growth inhibitor each of a special kind and each in an amount within a specified range. The texturing surfactant is preferably sodium tripolyphosphate and is contained at a rate of 0.50%-1.50% and preferably by about 0.10%.

The wetting surfactant is preferably polyoxyethylene and is contained at a rate of 1.5%-2.0% and preferably by about 1.8%. It may additionally contain polyethylene glycol and/or dinonylphenyl polyoxyethylene.

The lubricating surfactant is preferably polyalkylene and is contained at a rate of 1.8%-2.3% and preferably by about 2.12%. It may additionally contain propylene glycol and/or propylene oxide polymer.

The bacterial growth inhibitor is benzyldimethylhexadecyl ammonium chloride (CH₃(CH₂)₁₅N(Cl)(CH₃)₂CH₂C₆H₅) and is contained at a rate of 0.05%-0.10% and preferably by a bout 0.08%

These components are dissolved in 94%-97% of water or preferably deionized water.

If the content of the texturing surfactant is below the stated range, conglomerations of abrading particles will occur. If it is over the stated range, on the other hand, the intended effects of the other components will be overpowered and neutralized.

If the content of the wetting surfactant is below the stated range, the contact on the disk surface will not be established and stock removed efficiently. If it is over the stated range, on the other hand, the other components will become ineffective.

If the content of the lubricating surfactant is below the stated range, the stock removal of the coolant will be adversely affected after freezing and thawing. If it is over the stated range, there will be more deep cuts and valleys as the result of the texturing.

If the content of the bacterial growth inhibitor is below the stated range, bacterial or fungal growth will occur. If it is over the stated range, pits and unwanted blisters will come to be observed on the treated surface.

The invention relates also to a method of texturing a hard disk. A prior art texturing machine of a known type provided with a spindle to which a disk may be mounted and nozzles for supply a liquid may be used for the purpose of this invention. A method according to this invention may be characterized as comprising the steps of rotating a hard disk, preparing-slurry by mixing a coolant of this invention with abrading particles having diameters in the range of 0.10 nm-0.15 nm on a surface of this hard disk and pressing a running tape on the surface while the hard disk is rotated.

In a typical texturing process as explained above, the hardness of the rollers with which the tape is pressed may be 30-60 durometer, the force by the rollers may be 1.0-4.0 lbs, the supply speed of the polishing tapes may be 1.5-3.0 inches/minute, the rotary speed of the hard disk may be 300-1600 rpm, the tension in the tapes may be 0.5-1.5 lbs, the oscillation frequency may be 4.0-5.0 Hz, the oscillation amplitude may be 0.05-0.1 inch, the time of texturing process may be 7.0-15 seconds and the slurry flow rate may be 10.0-30 ml/minute. These, however, are merely examples and are not intended to limit the scope of the invention.

The invention is explained next by way of results of experiments performed by using the coolant and the method of this invention. Sample hard disk substrates were textured by using a texturing machine of a known type by applying slurry made of a coolant of this invention together with three different kinds of diamond abrading particles having diameters 0.10 nm, 0.12 nm and 0.15 nm. In all experiments, the texturing time was less than 10 seconds.

Table 1 shows the average surface roughness Ra, maximum roughness Rmax, peak ridge height Rp, deep of valley Rv and line density of texturing marks on the sample substrates.

Table 2 shows the measured values of stock removal as diamond abrading particles having diameters 0.10 nm were used in the slurry in 5 minutes of texturing process.

TABLE 1
	Diameter of
Disk	abrading	Ra	Rmax	Rp	Rv	Line density
No.	particles (nm)	(Å)	(Å)	(Å)	(Å)	(μm)
1	0.10	1.96	29.34	13.39	−15.95	25.800
2	0.10	1.88	40.89	27.44	−13.45	22.990
3	0.10	1.83	35.95	23.99	−11.96	20.440
4	0.10	2.05	47.77	33.82	−13.95	19.596
1	0.12	1.60	35.09	14.08	−21.01	20.800
2	0.12	1.37	48.62	35.45	−13.17	21.400
3	0.12	2.40	44.85	21.05	−13.69	20.437
4	0.12	2.27	40.80	17.44	−23.37	15.900
1	0.15	3.45	57.51	32.08	−25.43	20.943
2	0.15	3.25	72.83	34.57	−38.26	24.897
3	0.15	2.80	50.94	29.05	−21.89	19.137
4	0.15	3.02	46.79	29.05	−19.06	18.400

TABLE 2
	Weight before	Weight after texturing	Difference
Disk No.	texturing (gr)	(gr)	(gr)
1	23.021	23.015	0.006
2	23.015	23.008	0.007
3	23.018	23.010	0.008
Average	23.018	23.011	0.007
Standard deviation	0.003	0.004	0.001
Maximum	23.021	23.015	0.008
Minimum	23.015	23.008	0.006

FIG. 1 is a micromax visual picture of circumferential lines on the surface of a hard disk textured by a method of this invention. FIG. 2 is an atomic force microscope (AFM) picture showing circumferential lines on the surface of a hard disk textured by a method of this invention. FIG. 3 is an AFM three-dimensional picture of the circumferential lines of FIG. 2. FIGS. 1-3 and Table 1 and 2 clearly show that texturing lines of a high quality can be formed on the surface of a

In summary, the experiments have shown that the coolants according to this invention wet the hard disk surface easily, carry the abrading particles to the tape and easily wash off the disk surface without the use of any chemical, in addition to having the merit of inhibiting bacterial and fungal growth.

Claims

1. A water-based non-organic coolant comprising: sodium tripolyphosphate by 0.50%-1.50%;polyoxyethylene by 1.5%-2.0%;polyalkylene by 1.8%-2.3%;benzyldimethylhexadecyl ammonium chloride by 0.05%-0.10%; anddeionized water by 94%-97%.

2. The water-based non-organic coolant of claim 1 further including polyethylene glycol nonylphenyl ether.

3. The water-based non-organic coolant of claim 1 further including ethylene oxide.

4. The water-based non-organic coolant of claim 1 further including propylene oxide polymer.

5. A method of texturing a hard disk, said method comprising the steps of: rotating said hard disk;spraying slurry made of a coolant and abrading particles on a surface of this hard disk; andpressing a tape on said surface while said hard disk is rotated; wherein said coolant comprises:sodium tripolyphosphate by 0.50%-1.50%;polyoxyethylene by 1.5%-2.0%;polyalkylene by 1.8%-2.3%;benzyldimethylhexadecyl ammonium chloride by 0.05%-0.10%; anddeionized water by 94%-97%.

6. The method of claim 5 wherein said abrading particles have diameters of 0.10 nm-0.15 nm.

7. The method of claim 5 wherein said coolant further includes polyethylene glycol nonylphenyl ether.

8. The method of claim 5 wherein said coolant further includes ethylene oxide.

9. The method of claim 5 wherein said coolant further includes propylene oxide polymer.