JPH0240132A - Reproduction of substrate for hard disk - Google Patents

Abstract

PURPOSE:To remove a magnetic layer securely without damaging a base layer and to improve the yield of reproduction of substrates for hard disks by using a solution of inorganic acid or of inorganic acid with organic compounds added. CONSTITUTION:The magnetic layer 3 in the hard disk 8 which is composed of the substrate 1, base layer 2 and the magnetic layer 3 is removed by the solution of inorganic acid or of inorganic acid with organic compound added. Namely, an enamel, ceramic or metal bath equipped with a pipe 5 to agitate the solution by air in the bottom of the bath is charged with the solution, for example, an organic acid solution 7 to the specified amount. A mounting member 9 on which hard disks 8 are fixed at specified intervals is dipped in the solution 7 and rotated in the direction of the disk circumference to effect uniformly the electrochemical reaction of the disk 8 and the solution 7. Thereby, the protective layer and the magnetic layer are completely removed without damaging the base layer, and the yield of the reproduction of substrates is improved.

Description

DETAILED DESCRIPTION OF THE INVENTION [Industrial Application Field] The present invention relates to a method for reclaiming a hard disk substrate, which involves removing a magnetic layer formed on the substrate and reclaiming the hard disk substrate.

[Summary of the invention] The present invention uses an inorganic acid solution or a solution in which an organic substance is added to an inorganic acid to remove the magnetic layer of a hard disk without damaging the underlying layer [conventional technology]

For example, disk-shaped magnetic disks that can be randomly accessed are widely used as storage media for computers, etc., and because of their excellent responsiveness and large storage capacity, A1 alloy and AI are used as substrates. ! , -Magnetic disks made of hard materials such as Mg alloys, glass plates, plastic plates, etc. are now being used as fixed disks or external disks.

The above-mentioned hard disk is, for example, Aj! for magnetic disks.
- An Nj-P plating layer or alumite treatment layer is formed as a base layer on a Mg alloy substrate, etc., and a magnetic layer involved in recording and reproduction and a protective film layer such as a carbon film that protects the magnetic layer are sequentially formed on top of this. It is formed by being deposited by sputtering, vapor deposition, or the like. This hard disk rotates at high speed in the circumferential direction to record and reproduce information on a large number of concentric tracks.

By the way, hard disks formed in this manner have a high rate of defective products due to deprinting of the magnetic layer, generation of cracks, etc., and there is a problem in terms of yield. here,
If the defective hard disk is simply thrown away, the manufacturing cost will be significantly increased because the AN-Mg alloy substrate that constitutes the hard disk is very expensive. For this reason, only the substrate is recycled and used.

In order to reproduce the defective hard disk, it is necessary to remove the above-mentioned magnetic layer and protective film layer, which are involved in the recording and reproduction characteristics, and to expose the N1-P plating layer as the underlayer again. In order to expose the N1-P plating layer, for example, a polishing process in which the protective film layer and the magnetic layer are scraped off using an abrasive material can be used.

[Problems to be Solved by the Invention] However, when attempting to remove the protective film layer and the magnetic layer by the polishing process, the abrasive material slips and is easily removed due to the high hardness of the carbon film layer, which is the protective film layer. The protective film layer cannot be removed, and uneven polishing caused by polishing remains on the substrate surface. Particularly, when the unevenness of the boring is large, there is a risk that even the substrate will be scraped off.

Therefore, the present invention has been proposed in view of the conventional situation, and is intended to improve the yield of recycled hard disk substrates by reliably removing the protective film layer and the magnetic layer without damaging the underlying layer. The object of the present invention is to provide a method for reproducing a hard disk substrate.

(Means for Solving the Problems) In order to achieve the above object, the present inventors have conducted extensive research and found that an inorganic acid solution or a solution containing an organic substance added to an inorganic acid is used to remove the magnetic layer. The present invention was completed based on the knowledge that the method is effective.

The method for reproducing a hard disk substrate of the present invention includes removing the magnetic layer of a hard disk formed by forming a magnetic layer on the substrate via an underlayer using an inorganic M solution or a solution prepared by adding an organic substance to fI# organic acid. It is characterized by:

Examples of the inorganic acids include phosphoric acid, sulfuric acid, hydrochloric acid, chromic anhydride, and birophosphoric acid.

On the other hand, examples of organic substances include glycine and glycerin.

To remove the magnetic layer, you can simply immerse the defective hard disk in an inorganic acid solution or a solution containing an organic substance added to an inorganic acid, or you can immerse it in these solutions and apply a voltage. It's okay.

For example, when simply immersing the hard disk,
The following inorganic acid solution or a solution prepared by adding an organic substance to an inorganic acid may be used. Examples of such solutions include: (1) A solution consisting of water, phosphoric acid, and chromic anhydride and having a temperature of 80 to 95°C. In the case of this solution, it is recommended to soak the hard disk for 10 to 60 seconds.

■It consists of water and sulfuric acid, and the sulfuric acid accounts for 40 to 50% of the entire solution.
A solution having a temperature of 50 to 75°C. In the case of this solution, the hard disk should be
It is best to soak it for a minute.

■It consists of water, hydrochloric acid, and glycerin, and the hydrochloric acid accounts for 4% of the entire solution.
0 to 50%, the temperature of the solution is room temperature to
Solution at 50°C.

(2) A solution consisting of water and hydrochloric acid, in which the hydrochloric acid accounts for 20% of the total solution, and the temperature of the solution is room temperature. In the case of this solution, it is preferable to immerse the hard disk for 3 to 10 seconds.

(2) A solution consisting of water, sulfuric acid, and Rochelle's salt, in which the sulfuric acid accounts for 10% of the total solution and Rochelle's salt is 98 g/l, and the temperature of the solution is 70 to 80°C.

■It consists of water and hydrochloric acid, and the hydrochloric acid accounts for 10 to 50% of the entire solution.
% solution. In the case of this solution, the temperature of the solution is 70°C.
It is preferable to set the temperature to 80°C.

etc.

On the other hand, when performing regeneration by applying a voltage, the following solutions are suitable, for example. Examples of such solutions include: (1) A solution consisting of water, phosphoric acid, sulfuric acid, and chromic anhydride.

In the case of this solution, the temperature of the solution is 70-110°C.
It is preferable to apply a current density of 1 to IOA/dm2.

(2) A solution consisting of water and sulfuric acid, in which the sulfuric acid accounts for 70% of the total solution. In the case of this solution, the temperature of the solution is room temperature, and 1
Preferably, a current density of ~5 A/dm2 is applied.

(2) A solution saturated with water, sulfuric acid, and chromic acid, the sulfuric acid being 60%. In the case of this solution, the temperature of the solution is preferably room temperature.

(2) A solution consisting of hydrochloric acid and glycerin, an organic substance, in which the hydrochloric acid accounts for 25% of the total solution and the glycerin accounts for 75%. In the case of this solution, the temperature of the solution is room temperature and 1.5A/
Preferably, a current density of dm2 is applied.

(2) Consists of water, sulfuric acid, pyrophosphoric acid, and chromic anhydride; sulfuric acid accounts for 15% of the total solution, and pyrophosphoric acid accounts for 63%.

A solution that is 10% chromic anhydride. For this solution,
The temperature of the solution is 50-70°C, and the flow rate is 10-2OA/d.
Preferably, a current density of m2 is applied.

■It consists of water and sulfuric acid, and the sulfuric acid accounts for 25 to 50% of the entire solution.
solution. In the case of this solution, it is preferable to keep the temperature of the solution at room temperature and apply a current density of 10 to 20 A/dm''.

Although both aqua regia and nitric acid are inorganic acids, they are not suitable for reproducing hard disks. That is, when aqua regia or nitric acid is used, nitrate radicals (No, -) remain on the substrate, which causes AI! .

This adversely affects the quality (physical properties) of the Mg alloy substrate, sputtering equipment, etc. Furthermore, there is a risk that even the Al base layer may be corroded, and a base layer must be formed on the substrate again, which requires an extra work process and makes it impossible to improve productivity.

[Effect]

When a node disk on which a magnetic layer is formed is immersed in an inorganic acid solution or a solution in which an organic substance is added to an inorganic acid, a chemical reaction (etching) occurs between the solution and the magnetic layer, causing the node The magnetic layer formed on the substrate of the hard disk is reliably removed.

Furthermore, there is no risk that the surface of the substrate from which the magnetic layer has been removed, that is, the underlayer, will be corroded by the solution, and furthermore, no acid roots or the like will remain on the underlayer.

Therefore, the magnetic layer and the like can be removed from the underlayer of the hard disk without any adverse effects, so that the yield of recycled hard disk substrates obtained is improved.

〔Example〕

Hereinafter, a specific embodiment to which the present invention is applied will be described with reference to the drawings.

First of all, the node disc to be played in this embodiment is the first one.
As shown in the figure, a base layer (2) consisting of a NiP plating layer or an alumite treatment layer is formed on a disk-shaped substrate (1) made of a hard material such as A1 alloy, AIV, -Mg alloy, etc. A magnetic layer (3) involved in recording and reproduction is coated by sputtering, vapor deposition, or the like. A protective film layer (4) made of, for example, a carbon film layer is formed on the magnetic layer (3) to protect the magnetic layer (3).

For the magnetic layer (3), any conventionally known material can be used, such as Co, Co-Cr alloy, and C.

Ni alloy, Co-Ni-Cr alloy, Co-Ni oxide, etc. are used.

This hard disk has excellent responsiveness and allows random access, and rotates at high speed in the circumferential direction to record and reproduce information on a large number of concentric tracks.

To reproduce the above hard disk, it is performed as follows.

First, as shown in FIG. 2, a bathtub (6) made of enamel, ceramics, metal, etc. is prepared, and a bath stirring pipe (5) for discharging air is disposed on the bottom of the bathtub (6).
6) Do not fill the inorganic acid solution (7) until the predetermined liquid level is reached.

Since the bath stirring pipe (5) is for stirring the inorganic acid solution (7) in the bathtub (6), the air released from the bath stirring pipe (5) is for stirring the inorganic acid solution (7) in the bathtub (6). )
It may be emitted from either the peripheral surface or the end surface. By disposing this bath stirring pipe (5) on the bottom of the bathtub (6), the inorganic acid solution (7) is always kept in the bathtub (6).
6) will be stirred within.

In addition, to stir the inorganic acid solution (7) in the bathtub (6), use not only the bath stirring pipe (5) but also a propeller or the like to stir the inorganic acid solution (7). Furthermore, the inorganic acid solution (
7) may be circulated. Further, these may be used alone or in combination.

The inorganic acid solution (7) contains 300 to 500 m of phosphoric acid.
l/l, sulfuric acid 300-400ml/l, chromic anhydride 5-10g/42. Water 200mfl/1. The temperature of the bath was set at 70 to 110°C. Since the above-mentioned phosphoric acid, sulfuric acid, and chromic anhydride are all commonly used acids, the inorganic acid solution (7) can be produced at low cost, unlike aqua regia, etc., and the bath can be easily managed.

Next, the hard disk mounting member (9), in which a plurality of hard disks (8) are arranged and fixed at predetermined intervals, is immersed in the inorganic acid solution (7).

For the above-mentioned hard disk mounting, the member (9) is made of, for example, a conductive material and formed into a rod shape, and is inserted through the center hole of the previous hard disk (8), and then the hard disk (8) is mounted by means such as chucking. It is fixed. In addition, the above hard disk installation member (9) is
As a result, the hard disk (8) and the hard disk mounting member (9) rotate in the circumferential direction in the inorganic acid solution (7). According to this, the electrochemical reaction between the hard disk (8) and the inorganic acid solution (7) is performed evenly. In addition, the above hard disk installation is done using the member (9).
) is connected to one end of the positive electrode (10), thereby establishing electrical continuity with the hard disk (8). That is, the hard disk (8) is the substrate (1)
Since it is made of an AN-Mg alloy, it can be electrically connected to the positive electrode (10).

Next, a negative electrode (11) is placed between the hard disks (8) so as to sandwich each of the hard disks (8), and a voltage is applied between the positive electrode (10) and the negative electrode (11). .

In this example, a current density of 1 to IOA/dm2 was applied between the positive electrode (10) and the negative electrode (11), and the processing time was 3 to 10 minutes.

As a result, the hard disk (8) and the inorganic acid solution (7)
) causes an electrochemical reaction (electropolishing), and the protective film layer (4) and magnetic layer (3) of the hard disk (8) are reliably removed by the inorganic acid solution (7). As a result, the hard disk (8) is reproduced with the underlying layer (2) on the substrate (1) exposed, and becomes a node disk substrate. Further, according to this embodiment, the protective film layer (4)
In addition, the removal point of the magnetic layer (3) can be accurately determined. Therefore, if the removal points of the protective film layer (4) and the magnetic layer (3) are measured in advance, workability, productivity, etc. can be improved.

Here, the surface roughness was measured when the above-mentioned recycled hard disk substrate, that is, the alumite treated layer was used as the base layer (2). The results are shown in FIG.

In this example, the surface roughness of a hard disk substrate whose base layer (2) is an alumite treated layer before forming a magnetic layer was also measured in the same manner. The results are shown in FIG.

The base layer of the hard disk substrate that has undergone the above recycling treatment (
The surface roughness of 2) is approximately the same value as the surface roughness of the base layer (2) of the hard disk substrate before forming the magnetic layer (3). From this result, the protective film layer (4) and the magnetic N (3) are reliably removed from the underlayer (2),
It also shows that the base layer (2) is not corroded by the inorganic acid solution (7). In other words, it can be said that the hard disk substrate subjected to the above-mentioned regeneration process has been regenerated to approximately the same state as the hard disk substrate before the formation of the magnetic layer (3). Therefore, the yield of recycled hard disk substrates is improved, and since the Al base is not corroded, there is no need to form the base layer (2) again, and productivity can be improved.

Furthermore, the surface roughness of the hard disk substrate having the N1-P plating layer as the base layer (2) was similarly measured.

As a result, the surface roughness of the hard disk substrate subjected to the regeneration process shown in FIG. 5 was approximately the same as the surface roughness of the hard disk substrate before formation of the magnetic layer (3) shown in FIG. In other words, even if the hard disk substrate is formed with the N1-P plating layer as the underlayer (2), the state of the hard disk substrate before the magnetic layer is formed is the same as the hard disk substrate with the alumite treatment layer described above. It can be said that it has been reborn. Therefore, according to the regeneration method of this embodiment, even if the base layer (2) is an alumite-treated layer, N
Even with a 1-P plating layer, the reproduction is to the same extent as the state of the hard disk substrate before the magnetic layer is formed.

Sharp Disc I Reproduction of a hard disk according to this embodiment is performed as follows.

First, a protective film layer (
4) and remove the magnetic layer (3). Note that this reproduction method is the same as the previous reproduction method, so its explanation will be omitted.

Next, the hard disk substrate from which the protective film layer (4) and magnetic layer (3) have been removed is washed with water to remove the inorganic acid solution (7).

Then phosphoric acid 35 ml/l, chromic anhydride 2
The hard disk substrate is simply immersed in a bath having a concentration of 0 to 30 g/l and a bath temperature of 80 to 95° C. without applying a voltage. In addition, when immersing the hard disk substrate, it is preferable to perform a rocking operation such as vertically moving or rotating the substrate.

Since the above-mentioned phosphoric acid, chromic acid anhydride, etc. are all commonly used acids, baths can be made at low cost and baths can be easily managed. In this example, the hard disk substrate was immersed in a bath having the above composition for 10 to 60 seconds.

As a result, surface oxides and the like that could not be completely removed from the base layer (2) of the hard disk substrate are reliably removed by the bath having the above composition, and a stable treated surface is obtained. Therefore, a hard disk substrate is reproduced that is even closer to the state of the hard disk substrate before the magnetic layer is formed. Furthermore, when the surface roughness of the hard disk substrate after the above-mentioned reproduction treatment was measured, as in Example 1, a value substantially the same as the surface roughness of the hard disk substrate before the magnetic layer was formed was obtained. Therefore, according to this regeneration method, no base layer (
2) without damaging the protective film layer (4) and the magnetic layer (3).
) can be reliably removed.

The regeneration method of this embodiment can be applied not only to regenerating hard disk substrates, but also to electrolytic polishing of iron or Ni alloys, which is performed on boats.

The reproduction of the hard disk according to this embodiment is performed as follows.

First, a bathtub filled with an inorganic acid solution to a predetermined level is prepared.

The inorganic acid solution is a bath consisting of water and sulfuric acid, in which the sulfuric acid accounts for 40 to 50% of the entire bath, and the bath temperature is 50 to 50%.
It is at 75°C.

Since the above-mentioned sulfuric acid is a commonly used acid, the bath can be made at low cost and the bath can be easily managed. In addition, the same bathtub as in Example 1 is used, but since no voltage is applied in this example, the positive electrode (10) and negative electrode (11) shown in FIG. 2 are removed. use. Therefore, in this embodiment, it is possible to simplify the equipment and improve workability.

Next, the hard disk (8) is immersed in the bath. Note that in this embodiment, the hard disk (8
) was immersed for 3 to 15 minutes, and the bath was stirred as in the first example above.

As a result, a chemical reaction (etching) occurs between the hard disk (8) and the inorganic acid solution, and the protective film layer (4) and magnetic layer (3) of the hard disk (8) are reliably removed by the inorganic acid solution. be done. As a result, the hard disk (8) becomes a reproduced hard disk substrate with the base layer (2) on the substrate (1) exposed.

Next, the hard disk substrate is washed with water to wash away the inorganic acid solution and the like.

Next, it consists of water, hydrochloric acid, and the organic substance glycerin.
The hydrochloric acid accounts for 40-50% of the entire bath, and glycerin accounts for 20g/j.
A bath according to No. 2 was prepared, and the bath temperature was set to room temperature to 50°C until the bath reached a predetermined liquid level.

The above-mentioned organic substance does not attack the underlying layer (2) of the hard disk in any way, and furthermore, it is non-toxic. Furthermore, it is sufficient to add a small amount of the organic substance described in 1. to the entire bath.

Then, the hard disk substrate is immersed in the bath. In order to immerse the hard disk substrate, a rocking operation such as vertically moving or rotating the hard disk substrate is performed in the bathtub.

This ensures that residues, surface oxides, etc. that could not be removed in the previous step are removed, and a stable treated surface is obtained. According to this, the hard disk substrate is further reproduced to the same state as the hard disk substrate before the magnetic layer is formed.

Finally, the hard disk substrate is dried to remove water and the like, and the reproduction is completed.

As for the surface roughness of the hard disk substrate reproduced in this example, the surface roughness and path distance values of the hard disk substrate before the formation of the magnetic layer were obtained, as in the previous example. Therefore, according to the recycling method of this embodiment, the protective film layer (4) and the magnetic layer (3) can be reliably removed without damaging the base layer (2), and the recycled hard disk substrate can be reliably removed. The yield is improved.

[Effects of the Invention] As is clear from the above description, according to the hard disk substrate recycling method of the present invention, the base layer is removed by immersing the hard disk in an inorganic acid solution or a solution containing an organic substance added to an inorganic acid. The protective film layer and the magnetic layer can be reliably removed without damaging the magnetic layer, and the state between the hard disk substrate and the track before the magnetic layer is formed can be reproduced. Therefore, the reproduction yield of the hard disk substrate is improved, and its industrial value is great.

[Brief explanation of the drawing]

FIG. 1 is an enlarged sectional view of a main part showing an example of a hard disk to be reproduced. FIG. 2 is a schematic diagram showing an example of a bathtub used for recycling hard disk substrates. Figures 3 and 4 are characteristic diagrams showing the surface roughness of a hard disk substrate whose underlayer is an alumite treated layer. Figure 3 shows the surface roughness after recycling treatment, and Figure 4 shows the surface roughness before magnetic layer formation. are shown respectively. 5 and 6 are characteristic diagrams showing the surface roughness of a hard disk substrate whose underlayer is an N1-P plating layer. Roughness is shown respectively.・Substrate, Underlayer, Magnetic layer, Protective layer, Inorganic acid solution, Hard disk

Claims (1)

[Claims] A method for recycling a hard disk substrate, which comprises removing the magnetic layer of a hard disk formed by forming a magnetic layer on a substrate via an underlayer using an inorganic acid solution or a solution containing an inorganic acid and an organic substance.