JPS5922232A - Production of aluminium substrate for magnetic disc - Google Patents

Abstract

PURPOSE:To produce a substrate of which smoothness and cleanliness are improved on the surface by adhering high-purity >=99.0% Al with the prescribed thickness to the surface of a blank plate prior to mechanical or chemical surface smoothing processing to the blank plate or after the surface smoothing processing. CONSTITUTION:After planning the Al alloy blank plate by a required method and executing thermal correction for the purposes of the removal of distortion, etc., mechanical or chemical surface smoothing processing is applied to adjust the surface and to finish the objective magnetic disc substrate. Prior to or after the surface smoothing processing, high purity >=99.0% Al is adhered to the surface of the blank plate to form the high-purity Al layer with the prescribed thickness on the surface of the blank plate. The adhesion of the high-purity Al to the blank plate surface is generally performed by various methods such as physical and chemical vapor deposition methods, but the physical vapor-deposition method such as vacuum vapor deposition, ion plating method and sputtering method is properly adopted.

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to a method of manufacturing an aluminum substrate (substrate) for magnetic tissue, and in particular, it prevents the occurrence of surface defects due to non-metallic inclusions and intermetallic compounds present in the substrate material, and The present invention relates to an economically advantageous method for obtaining an aluminum substrate useful for high-density magnetic disks, which has improved smoothness and cleanliness.

Traditionally, magnetic disks have been widely used as one of the recording media in electronic calculators, and these magnetic disks consist of a substrate of a predetermined thickness made of an aluminum (A6)-based alloy whose surface is coated with a magnetic coating film. The device stores signals by magnetizing this magnetic coating.

By the way, the A-substrate used for such magnetic disks is produced by machining the surface of an A-substrate alloy plate (base plate) obtained by rolling to a predetermined thickness, and then machining the surface to a predetermined thickness. Although it is a polished product, it is generally considered to have the following characteristics.

(a) In order to keep the gap between the magnetic head and the magnetic disk substrate constant during magnetization operation and stabilize the storage characteristics, the surface accuracy after polishing (roughness, waviness, etc.) must be good; (b) There should be no protrusions or hole-like depressions on the substrate surface that could cause defects in the magnetic coating; (0) It should have sufficient mechanical strength against high-speed rotation during use; (1) Corrosion resistance. ((+) It must be non-magnetic, lightweight, and inexpensive.

On the other hand, the most commonly used substrate for magnetic disks at present is a plate made of Ag-based alloy of AA standard 5086, but it has not been able to fully meet the recent demands for larger capacity and higher density magnetic disks. It's disappearing. That is,
In order to increase the capacity and density, it is desired to further miniaturize the magnetized area per bit and narrow the gap between the magnetic head and the magnetic disk. This is because the above-mentioned A and A3086 substrates do not have sufficient surface accuracy.

For this reason, various studies have been made to improve the surface condition of such Ae substrates.
-39699, JP-A-56-10'5846, etc., describe nonmetallic inclusions and intermetallic compounds (for example, A5-Fc-MnJ% and Mg-
8i-based crystallized substances, etc.) by adjusting alloy components, etc., to reduce them as much as possible, make them fine, and disperse them uniformly, thereby reducing protrusions and hole-like depressions. However, even if these methods are adopted, there are limits to the miniaturization of nonmetallic inclusions and intermetallic compounds, and it is also difficult to completely eliminate them from the surface of the fund. As a result, the limit was to limit the size of the nonmetallic inclusions and intermetallic compounds to about 1 to 10 μ+n. Moreover, in the manufacturing process, the use of high-purity AI metal is required from the perspective of preventing inclusions, and strict alloy composition adjustment is also required. Various conditions and operations are required, such as the need for filtration through a high-density filter and the need for testing to confirm the effectiveness of such filters, which increases the final manufacturing cost of the substrate. It was inviting him to ascend.

As mentioned above, considering the demand for larger capacity and higher density of magnetic disks, the ultimate goal is to completely eliminate nonmetallic inclusions and intermetallic compounds and completely eliminate their influence on the substrate surface. There is an urgent need to eliminate them.

The present invention has been made against this background, and its objective is to provide a method for economically obtaining an Ad substrate for magnetic disks with excellent surface properties. It is in.

Another object of the present invention is to use ordinary substrates used for various purposes as base plates before being finished into magnetic disk substrates, where no special measures are taken to remove non-metallic inclusions and intermetallic compounds. The object of the present invention is to provide a method for manufacturing a substrate with improved surface smoothness and cleanliness by using an Ad-based alloy sheet metal as it is.

Still another object of the present invention is to satisfy all of the characteristics (a) to (e) required for the magnetic disk, and to substantially eliminate the problem of surface protrusion caused by nonmetallic inclusions and intermetallic compounds. An object of the present invention is to provide a method for manufacturing an AI substrate for magnetic disks that solves the problem.

In order to achieve these objects, the present invention uses an Add alloy blank plate of a predetermined thickness to produce an Aβ substrate for a magnetic disk with a smooth surface, and the present invention provides mechanical or chemical treatment to the blank plate. Prior to or after the surface smoothing treatment, 99.0% of the surface of the base plate is coated.
It is characterized in that the above-mentioned high-purity AI is deposited to a predetermined thickness.

According to the present invention, high-purity A4 containing no non-metallic inclusions or intermetallic compounds is newly added to the A4 base alloy base plate.
Since the d layer is formed and covers the base plate,
The quality of the raw sheet, in other words, the presence of non-metallic inclusions and intermetallic compounds is no longer an important issue, and even if surface irregularities caused by these non-metallic inclusions and intermetallic compounds are present on the raw sheet. However, such surface irregularities can now be effectively filled with the high-purity AI that is attached.
Furthermore, by applying surface smoothing treatment as necessary, an extremely smooth surface can be easily obtained, and therefore the influence of unevenness on the surface of the raw plate can be almost ignored. be.

As a result, the present invention can be used as a base plate before being finished into a magnetic disk substrate in various applications where special measures to remove non-metallic inclusions and intermetallic compounds have not been taken as in the past. It became possible to use the conventional Ag-based alloy as it is, thereby significantly reducing the cost of the blank plate. When producing blanks and blank plates, the conventional use of high-purity Al ingots, strict control of alloy composition, use of high-density filters during casting, and inspections to confirm filter effectiveness are no longer necessary. This is because there is no need to use a special material (alloy composition).

Furthermore, according to the method of the present invention, a uniform high-purity A4 layer can be deposited with the minimum necessary thickness in accordance with the surface roughness of the A5 blank sheet, which is profitable, so it can be used for reliable magnetic disks. In addition to being able to manufacture substrates, the high-purity A layer that is deposited does not contain nonmetallic inclusions or intermetallic compounds, so the smoothness and cleanliness of the surface can be significantly improved, and the disk manufacturing process can be improved. This can effectively prevent the occurrence of surface irregularities before painting.

By the way, the A5-based alloy material plate used in the present invention is generally intended to be a plate material made of an A4-based alloy, which has been conventionally known as a substrate material for magnetic disks, but the present invention also uses non-metallic materials. This makes it possible to use plate materials made of other Ad-based alloys, which were considered unsuitable due to inclusions and intermetallic compounds. In particular, the present invention uses high-purity base metal, strict alloy composition control, use of high-density filters during casting, etc. when manufacturing blank plates of a predetermined thickness from these Al-based alloys by casting and rolling. This has the great advantage that even blank plates obtained without performing this process can be used.

Then, such an A4 base alloy blank plate is subjected to desired turning, heat straightening for the purpose of removing distortion, etc., and then subjected to mechanical or chemical surface smoothing treatment. Then, the surface is adjusted and the target substrate for magnetic disk is finished. However, in the present invention, the raw substrate is processed before or after such surface smoothing treatment. High purity A4 of 99.0% or more is adhered to the surface of the base plate, and a predetermined thickness of high purity Ag is deposited on the surface of the base plate.
It forms a layer.

E-coating on the surface of such a high-purity A5 base plate can generally be performed using various methods such as physical vapor deposition and chemical vapor deposition, but in the present invention, deposition using vacuum vapor deposition, ion deposition, etc. Physical vapor deposition methods such as the brating method and sputtering method are preferably adopted, and among them, the ion blating method is the most recommended because it does not have the problem of dimensional changes due to increases in the temperature of the base plate and also has a self-cleaning effect. It is. In addition, the purity of this A4 (=J) is 9.
A product of high purity of 90% or more, preferably 99.9% or more, and in some cases reaching 99.9999% or more, so that it does not contain non-metallic inclusions or intermetallic compounds. A uniform A4 layer is formed on the surface of the blank.

The thickness of the high-purity Ag layer formed on the surface of the A4 blank plate is determined appropriately depending on the surface roughness of the A4 blank plate, but if the thickness is too thick, The upper limit is approximately 50μ since it increases the cost of the board.
It is desirable to stop it at about m. The lower limit is also related to the surface roughness, but is generally about 1 μrn, preferably about 5 μm.

Further, according to the present invention, the surface smoothing treatment performed before or after the formation of the high purity 11 layer has been conventionally performed on A5
It is similar to that used in the manufacture of substrates, and provides the smoothness required for magnetic disk substrates, and is generally carried out by mechanical or chemical methods, such as cutting, This includes grinding, polishing, surface mirror finishing, and polishing operations. More specifically, a method of grinding to a predetermined thickness with a grindstone and further polishing, a surface mirror finishing method using an ultra-precision lathe using a diamond viper 14, etc. are suitably employed.

By the way, the order of execution of the high-purity 11 layer formation step and the surface smoothing treatment step according to the present invention can be interchanged. That is, a process (A) of forming a predetermined high-purity A/layer on a base plate and then subjecting the surface of the high-purity Ae layer to a surface smoothing process (A); , Process of forming a high-purity A5 layer after sufficiently smoothing the surface of the base plate (B)
It is possible to adopt these processes, and these processes are selected depending on the surface condition of the blank plate and the purity of the AI to be coated (=J), but in general, when the surface roughness of the blank plate is small or When the purity of the Ad line is low, the former process A is preferably adopted, and when the surface roughness of the blank is large or the purity of AI is high, the latter process B is preferably adopted. After the process, if necessary, the surface of the high-purity A4 layer formed on the base plate can be subjected to the same surface smoothing treatment as described above, thereby improving the surface characteristics of the manufactured substrate. It is possible to further improve this.

The A4 substrate thus obtained generally has an average surface roughness (Ra) of approximately 0.02 μm or less, and a maximum surface roughness (R) of approximately 0.02 μm or less.
+nax,μ) is 0.2μ! It has a surface precision of about n or less, and in particular, because its surface is formed of a high-purity A/layer that is substantially free of nonmetallic inclusions and intermetallic compounds, it is possible to Even through the pretreatment (chemical conversion film formation) process that precedes the magnetic coating process employed in the manufacture of magnetic disks, there is almost no deterioration of the surface properties.

Examples are shown below to clarify the present invention more specifically, but the present invention is not limited in any way by the description of these Examples. Note that the percentages in the examples are shown on a weight basis.

Example I Alloy composition according to AA5086 standard, namely Mg: 4.2%,
Fe: 0.18%, Si: 0.06%, Mn: 037%
, Cr: 0.08%, Cu: 0.04%, Ti: 0.0
A4 consisting of 8%, Zn: 0.01% or less, A4: remainder
The molten alloy was semi-continuously cast according to the usual method without strict filtration or alloy composition adjustment, and the plate thickness was reduced to knee 5.
A slab of 00 mm was obtained.

Next, both sides of this slab were side-faced, and then hot rolling and cold rolling were performed according to a conventional method to obtain a rolled plate having a thickness of 2.2 marks. Furthermore, both sides of this rolled plate were turned, and then 32
Heat straightening was performed by holding at a temperature of 0°C for 5 hours.

The thus obtained A4 alloy plate (base plate) with a thickness of 1.9 mm was coated with AI with a purity of 9999% by the ion blating method under the following conditions, and approximately I
High purity A4 layers with a thickness of Q p m were each formed. That is, for the ion blating method, the degree of vacuum: 1
0' to IQ' Torr, and Ar
The 11 alloy plate was placed in a chamber maintained in an atmosphere, and 99.99% aluminum was evaporated by an electron beam, and then using a high frequency excitation method,
The method of vapor deposition on the A.1 alloy plate was adopted.

Next, the Ag alloy plate to which the high-purity A4 was attached was cut using a single-crystal diamond cutting tool, spindle rotation speed: 2000 rl) approximately II+, cutting depth: 10
[μ■] A substrate according to the present invention was obtained by mirror finishing and surface smoothing under the following conditions.

On the other hand, for comparison, after subjecting Ad molten metal having the above alloy composition to a strict filtration operation as in the conventional method, an A4 alloy plate (base plate) obtained in the same manner as above was subjected to high purity A
A comparative substrate was obtained by immediately performing mirror finishing using a diamond tool to smooth the surface without applying d.

For the two types of substrates obtained in this way, the roughness after mirror finishing: Ita and Rmax were measured using a stylus roughness meter (Tokyo Seimitsu Co., Ltd.: 8URF-20 model) according to the method of the present invention. The obtained substrate had an Ra of 0.008μIII.

Rmax is 0.08μIn, and the comparison substrate's temperature a = Q, Q I Q Itrn, Rmax
= Q, l Q It was found that the surface smoothness was superior to that of Itm.

In addition, in order to manufacture magnetic disks from such substrates, ordinary chemical conversion treatment is applied to the substrates as a pre-cleaning process before magnetic coating is applied to form a chemical conversion film on the surface. However, in the substrate according to the present invention, the surface roughness is 1La=Q, Q l 5 μmXRma
x = Q, l 5 lzm, and the occurrence of surface defects due to non-metallic inclusions and intermetallic compounds present in the substrate material is effectively suppressed, and the smoothness and cleanliness of the surface are also significantly improved. It was something I was forced to do. On the other hand, the surface roughness of the comparative substrate subjected to chemical conversion treatment is 几a"'0.02077 Ill, Rrnax
= 0.20 μm Tear is recognized as a surface defect caused by the influence of nonmetallic inclusions and intermetallic compounds present in the substrate material, and the surface smoothness and cleanliness are sufficient. It was acknowledged that this was not the case.

As described above, the substrate according to the present invention obtained in this example has the following characteristics compared to the conventional substrate 1.
Not only is it superior in terms of surface defects, surface smoothness, and cleanliness, but it also eliminates other unnecessary or troublesome operations, such as preparing alloy components, strengthening molten metal filtration,
It also has great advantages, such as completely eliminating the need for tests to confirm its filtration effectiveness.

Example 2 1 with a plate thickness of about 1.9 mm obtained in the same manner as in Example 1
1 alloy plate was subjected to bio6 plating in the same manner as in Example 1, and the purity was 99.99% on both sides.
A high-purity A5 layer of about IO μm thick made of AI was formed respectively.

Next, the surface of the Ad alloy plate (base plate) to which the thus obtained high-purity Afi was adhered was subjected to surface polishing including grinding with a whetstone and polishing with free abrasive grains, and the surface was smoothed to form a book. Substrate A according to the invention was obtained.

In addition, different from the above order, the A4 alloy plate (base plate) is first subjected to the surface polishing treatment to smooth the surface of the alloy plate, and then the high purity A4 is attached. Another sub-stray according to the present invention)B
t[ta.

For comparison, the high purity A4 alloy plate as described above was compared with the one obtained by subjecting the A4 alloy plate to strict filtration treatment.
Substrate C was obtained by surface polishing as it was without performing any adhesion operation.

For these three types of substrates obtained, the surface roughness Ra and Rma were measured using a stylus roughness meter.
x), and the surface roughness after the chemical conversion treatment was also measured in the same way.

As a result, for both substrates A and H, R
a==Q, Q 187z+n, Rmax = Q, l
Regarding substrate C, which showed a surface smoothness of 8 μm, high purity A4 was not attached.
Ra, = 0.020 p m, Rmax = Q20/
1 m, and it was observed that the surface was affected by nonmetallic inclusions and intermetallic compounds in the material.

Further, after the chemical conversion treatment, the substrates A and B according to the present invention each have Ra = 0.03 tim
.

■+na, x = about 0.3μ, whereas for comparison substrate C, Ra = 0.041t
m, ILmax = Q, about 4 p m,
It was observed that the latter Substrate C was more affected by the chemical conversion treatment than the former, and its surface was roughened.

In addition, high purity A4 obtained by the ion blating method
Instead of forming a layer, sputtering or other vapor deposition methods can also be used to deposit high-purity A1 onto the target AI base plate.
It was observed that a layer was formed and the same excellent effects as described above were achieved.

As described above, according to the present invention, high-purity A4 containing no non-metallic inclusions or intermetallic compounds is newly formed on the Ag-based alloy blank.
Since a layer is formed to cover the base plate, the material of the base plate does not matter at all, and its surface smoothness can be significantly improved. As a result, by using the substrate according to the present invention, a high-density magnetic disk can be advantageously manufactured.

Applicant: Sumitomo Light Metal Industries, Ltd.

Claims (6)

[Claims] (1) UA using an aluminum-based alloy blank of a specified thickness
When manufacturing an aluminum substrate for a magnetic disk with a smooth surface, the surface of the blank is coated with a 99-90% coating before or after mechanical or chemical surface smoothing treatment. A method for producing an aluminum substrate for a magnetic disk, characterized in that a predetermined thickness of high-purity aluminum of .0% or more is deposited. (2) The deposition of the high-purity aluminum is performed by a vacuum evaporation method,
The method according to claim 1, which is carried out by a sputtering method or an ion blating method. 3. The method of claim 1 or claim 2, wherein said high purity aluminum is deposited to a thickness not exceeding about 50 μIn. (4) The surface smoothing treatment includes a grinding step and a honing step 1.
the method of. (5) Is the surface flat? 2. The method according to claim 1, wherein the Vk treatment includes a step of mirror-finishing the surface using a lathe using several diamond hides. (6) Following a predetermined surface treatment for the blank plate, applying the high-purity aluminum,
2. The method according to claim 1, further comprising subsequently performing said surface smoothing treatment.