JP2009289299A - Cleaning method of aluminum substrate for magnetic recording medium - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a substrate for a magnetic recording medium having high cleanness, while securing a smooth data surface. <P>SOLUTION: In a cleaning method of an aluminum substrate for the magnetic recording medium subjected to Ni-P plating, the substrate is immersed in an acid electrolyte; the substrate is brought into contact with an anode; an insoluble electrode (cathode) is disposed in the vicinity of an end surface of the substrate; and only the end surface of the substrate is selectively subjected to etching treatment, by applying DC voltage between both electrodes to clean the end surface of the substrate. <P>COPYRIGHT: (C)2010,JPO&INPIT

Description

  The present invention relates to a method for cleaning an aluminum substrate for a magnetic recording medium mounted on various magnetic recording devices including an external storage device of a computer.

  An aluminum substrate plated with Ni-P for a magnetic recording medium generates dust if particles are present on the inner peripheral surface of the substrate when it is incorporated into a hard disk drive, and needs to be cleaned to cause defects.

  Also, the contamination on the outer peripheral end surface of the substrate moves to the data surface and causes an error when performing immersion ultrasonic cleaning in the final cleaning before sputtering film formation.

  The cause of the contamination of the substrate end face, which is a problem, is abrasive grains such as alumina and colloidal silica, and most of them are not only adhered but remain due to sticking.

  Conventionally, removal is performed by rubbing with a sponge made of PVA, urethane, or the like (for example, see Patent Document 1) or chemical solution immersion ultrasonic cleaning with acid (for example, see Patent Document 2).

Japanese Patent Laid-Open No. 62-141634 JP 2005-44488 A

  However, in the sponge scrubbing as described in Patent Document 1, the cleaning effect decreases due to accumulation of dirt on the sponge. Further, such sponge scrubbing is not sufficient for removing abrasive grains sticking to the substrate.

  In addition, in the ultrasonic cleaning with a chemical solution such as an acid described in Patent Document 2, the removal effect is high for the pierced abrasive grains due to the etching effect, but when treated with a high acid or a strong acid for a long time, the aluminum substrate The roughness Ra of the data surface increases, making it difficult to apply as a high recording density medium substrate. Further, the inner peripheral end face has a drawback that ultrasonic waves are difficult to hit and it is difficult to clean.

  The present invention has been made in view of such circumstances, and the method for cleaning an aluminum substrate for a magnetic recording medium of the present invention is a method for cleaning an aluminum substrate subjected to Ni-P plating for a magnetic recording medium, and is acidic. The substrate is immersed in the electrolyte and the substrate is brought into contact with the anode. On the other hand, an insoluble electrode (cathode) is disposed in the vicinity of the substrate end surface, and a DC voltage is applied between both electrodes to selectively select only the substrate end surface. Etching is performed to clean the end face of the substrate.

  According to the method for cleaning an aluminum substrate for a magnetic recording medium of the present invention, by selectively etching the end surface portion of the Ni-P plated aluminum substrate, deposits on the end surface portion of the substrate can be removed without impairing the roughness of the data surface. Can be removed.

According to the cleaning method of the present invention, a Ni-P plated aluminum substrate for a magnetic recording medium is immersed in an acidic electrolyte solution, and the substrate is brought into contact with the anode, while an insoluble electrode (cathode) is provided in the vicinity of the substrate end face. And a DC voltage is applied between both electrodes to selectively etch only the substrate end face. As shown in FIG. 1, this substrate is a circular disk-shaped substrate having a center hole. In the cleaning method of the present invention, the edge of the center hole and the edge of the outer periphery are cleaned by etching.
An insoluble electrode means an electrode in which electrode components do not elute into the electrolyte when a voltage is applied. Examples of such an electrode include a stainless steel electrode, a platinum electrode, a titanium electrode, and a carbon electrode.
Examples of the acidic electrolytic solution used here include inorganic acid aqueous solutions such as phosphoric acid, hydrochloric acid, nitric acid, and sulfuric acid, and organic acid aqueous solutions such as citric acid and tartaric acid.

  In the present invention, the substrate is brought into contact with the anode. The portion of the substrate in contact with the anode may be the inner peripheral end surface of the substrate or the outer peripheral end surface of the substrate. In either case, the anode may be used as a substrate holder.

  When the anode is brought into contact with the outer peripheral end surface of the substrate as shown in FIG. 2, the insoluble electrode (cathode) is arranged at the center of the circle formed by the inner peripheral end surface of the substrate so as not to contact the substrate. When a voltage is applied between the two electrodes in this state, the inner peripheral surface of the substrate closest to the cathode is etched, and particles such as abrasive grains adhering to or stuck into the inner peripheral surface of the substrate are removed. The

  In addition, when the anode is brought into contact with the inner peripheral end surface of the substrate as shown in FIG. 3, a ring-shaped or cylindrical insoluble electrode (cathode) having a larger circumference than the circle formed by the outer peripheral end surface of the substrate is concentric with the substrate. And so as not to contact the substrate. When a voltage is applied between the two electrodes in this state, the substrate outer peripheral end surface closest to the cathode is etched, and particles such as abrasive grains adhering to the substrate outer peripheral end surface or sticking to the substrate outer peripheral end surface are removed.

  The voltage applied between the two electrodes is preferably 5 to 60 V, and the current to be applied is preferably 3 to 20A. The temperature of the acidic electrolyte for immersing the substrate is preferably 20 to 50 ° C., and the etching treatment time is preferably 30 to 150 seconds. If the voltage, current, and processing time are less than the above lower limit, the particle removal effect is insufficient, and if the voltage, current, and processing time exceeds the upper limit, etching proceeds excessively, and the data surface (see FIG. 1) may be damaged. There is.

  The present invention will be further described below with reference to examples.

<Example 1>
As shown in FIG. 2, an acidic electrolyte solution was prepared by placing a phosphoric acid aqueous solution at 45 ° C. and pH 2.5 in a resin water tank. In this aqueous solution, the Ni-P plated substrate was held by a SUS316 jig that also held the Ni-P plated substrate and the anode, and was immersed until the jig in contact with the substrate and the peripheral edge of the substrate was completely immersed.

  Next, a cathode made of a rod-shaped SUS316 is inserted into the hole in the center of the substrate so as to etch the inner peripheral end surface of the substrate by applying a voltage of 50 V and a current of 5 A for 100 seconds with direct current and etching the inner peripheral end surface of the substrate. Particles such as abrasive grains adhering to the top or sticking to the inner peripheral edge of the substrate were removed.

  Thereafter, the substrate was lifted from the water tank, and the outer peripheral end surface of the substrate was scrubbed with a sponge, subjected to ultrasonic immersion cleaning with a cleaning agent, rinsed with pure water several steps, and then dried. The number of particles of 500 nm or more on the inner peripheral end face of the substrate within the measurement field of view after the cleaning was examined by appearance inspection using an electron microscope. The result is shown in FIG. FIG. 4 shows a substrate after a combination of normal cleaning (rubbing of the end surface with a sponge soaked with pure water) and cleaning with phosphoric acid only (rubbing of the end surface with a sponge soaked with phosphoric acid aqueous solution) and normal cleaning. The number of particles of 500 nm or more on the inner peripheral end face is shown for comparison.

<Example 2>
As shown in FIG. 2, an acidic electrolyte solution was prepared by placing a phosphoric acid aqueous solution at 45 ° C. and pH 2.5 in a resin water tank.

  Prepare an anode rod made of SUS316 with grooves in a comb shape, and insert this anode rod into the center hole of the Ni-P plated substrate to hook the substrate and fix the substrate at the same time as contacting the inner peripheral end surface of the substrate I let you.

  Next, a ring-shaped cathode made of SUS316 and having a circumference larger than the circle formed by the outer peripheral end face of the substrate was arranged so as to be concentric with the substrate and not in contact with the substrate. Next, a DC voltage of 50 V and a current of 5 A were applied for 100 seconds to etch the inner peripheral end surface of the substrate, and particles such as abrasive grains adhering to or stuck into the inner peripheral end surface of the substrate were removed.

  Thereafter, the substrate was lifted from the water tank, and the outer peripheral end surface of the substrate was scrubbed with a sponge, subjected to ultrasonic immersion cleaning with a cleaning agent, rinsed with pure water several steps, and then dried. The number of particles of 500 nm or more on the outer peripheral end face of the substrate within the measurement field of the substrate after cleaning was examined by appearance inspection using an electron microscope. The result is shown in FIG. FIG. 5 shows, for comparison, the number of particles of 500 nm or more on the outer peripheral end face of the substrate after the combination of normal cleaning and ultrasonic cleaning in a phosphoric acid aqueous solution and normal cleaning.

  4 and 5, it can be seen that the cleaning method of the present invention exhibits higher cleaning properties than the combination of normal cleaning and ultrasonic cleaning in a phosphoric acid aqueous solution and normal cleaning.

The polishing method of the present invention makes it possible to obtain a magnetic recording medium substrate with higher cleanliness while ensuring a smooth data surface.
Further, since the quality of the magnetic recording medium is improved by improving the cleaning property, it is possible to provide a higher quality magnetic recording medium.

It is a schematic diagram which shows the aluminum substrate for magnetic recording media. It is a figure which shows the board | substrate inner peripheral end surface washing | cleaning by this invention. It is a figure which shows the board | substrate outer periphery end surface washing | cleaning by this invention. It is a figure which shows the washability of the board | substrate inner peripheral end surface washing | cleaning by this invention. It is a figure which shows the washability of the board | substrate outer periphery end surface washing | cleaning by this invention.

Explanation of symbols

1: substrate inner peripheral end surface 2: substrate outer peripheral end surface 3: data surface 10: substrate (anode)
11: Jig (anode)
12: Cathode 13: Water tank 14: Phosphoric acid aqueous solution

Claims (3)

  A method for cleaning a Ni-P plated aluminum substrate for a magnetic recording medium, wherein the substrate is immersed in an acidic electrolyte and the substrate is brought into contact with the anode, while an insoluble electrode (cathode) is formed near the substrate end face. ), And a DC voltage is applied between the electrodes to selectively etch only the substrate end face, thereby cleaning the end face of the magnetic recording medium.   The disposition of the insoluble electrode (cathode) in the vicinity of the substrate end surface means that the insoluble electrode (cathode) is disposed at the center of the circle formed by the inner peripheral end surface of the substrate so as not to contact the substrate, and the anode is the substrate. The method for cleaning an aluminum substrate for a magnetic recording medium according to claim 1, wherein the cleaning method is provided so as to be in contact with an outer peripheral end face.   Arranging the insoluble electrode (cathode) in the vicinity of the substrate end surface is such that the ring-shaped or cylindrical insoluble electrode (cathode) having a circumference larger than the circle formed by the substrate outer peripheral end surface is concentric with the substrate. 2. The magnetism according to claim 1, wherein the anode is disposed in a circle formed by the inner peripheral end surface of the substrate so as to be in contact with the entire inner peripheral end surface of the substrate. Cleaning method for aluminum substrate for recording media.

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