JP2006185490A - Information recording medium and its manufacturing method - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide an information recording medium wherein high speed data transfer is made possible and lightness in weight and the thinness of a disk and the power saving of a drive apparatus are made possible. <P>SOLUTION: In the information recording medium formed by forming an information recording layer 3 on a substrate 1, the substrate 1 is composed of magnesium or a magnesium based alloy. <P>COPYRIGHT: (C)2006,JPO&NCIPI

Description

  The present invention relates to an information recording medium such as a hard magnetic disk and an optical disk and a manufacturing method thereof, and more particularly to a substrate of the recording medium.

  In recent years, in order to meet the demand for larger capacity of information recording media such as hard magnetic disks, it is required to increase the disk rotation speed so as to increase the recording capacity per unit area and improve the data transfer speed with the disk. It has been.

  On the other hand, personal computers and handy-type terminal devices are becoming increasingly popular, and recording / playback devices including hard magnetic disks are becoming smaller, lighter, and thinner, reducing the power consumption of drive systems such as motors, and using the same battery There is a growing demand for energy-saving types that can be used for a longer period of time.

  Conventionally, aluminum or glass has been used as a substrate for a hard magnetic disk. When the hard magnetic disk is inserted into the recording / reproducing apparatus, the central portion thereof is sandwiched by the clamping means and rotated at high speed, and information is recorded / reproduced between the recording layer and the magnetic head.

For example, the following patent documents can be cited as a method for manufacturing a hard magnetic disk substrate.
JP-A-1-223629 Japanese Patent Laid-Open No. 2-246019

  By the way, when aluminum or glass is used as the disk substrate, the surface shake occurs during high-speed rotation due to the warping or bending of the substrate, resulting in poor contact between the head and the disk, and the desired access speed can be obtained. There is a problem that there is no problem, and this is a hindrance to an increase in recording capacity per unit area.

  In order to reduce the deflection of the disk during high-speed rotation, measures such as increasing the thickness of the substrate or providing a reinforcing part have been taken, all of which make the disk lighter, thinner, and drive device Is an obstacle to power saving. Further, the glass substrate is liable to be cracked or chipped, and there is an inconvenience that it requires careful handling.

  SUMMARY OF THE INVENTION An object of the present invention is to solve the above-mentioned drawbacks of the prior art, to enable high-speed data transfer, and to reduce the weight and thickness of the disc and to reduce the power consumption of the drive device, and its manufacture It is to provide a method.

  In order to achieve the above object, a first means of the present invention is an information recording medium in which an information recording layer is formed on a substrate, wherein the substrate is made of magnesium or a magnesium-based alloy.

  According to a second means of the present invention, there is provided a method of manufacturing an information recording medium having an information recording layer formed on a substrate, a step of rolling magnesium or a magnesium-based alloy into a thin plate having a predetermined thickness, and a predetermined step from the rolled thin plate. And a step of anodizing the substrate, and a step of forming the information recording layer on the anodized film.

  According to a third means of the present invention, in the second means, a flat mold surface is provided between the step of rolling the magnesium or the magnesium-based alloy and the step of punching the rolled thin plate into a predetermined substrate shape. The method includes a step of pressing the rolled sheet with a press die maintained at a high temperature, and a step of cooling the rolled sheet after the pressing step.

  The present invention is configured as described above, and since magnesium or a magnesium-based alloy (hereinafter abbreviated as magnesium material) is lighter than aluminum, it has good rise and fall characteristics during rotation of the recording medium. It can be adapted for high-speed data transfer and requires less motor power during high-speed rotation.

  In addition, magnesium materials have superior mechanical properties such as tensile strength, hardness, dent resistance, high specific rigidity, and dimensional stability compared to aluminum. Even if the rotational speed is increased, the recording medium hardly bends during high-speed rotation. In addition, since the vibration absorption is excellent, there is almost no occurrence of surface vibration during high-speed rotation. In addition, since the magnesium material is less likely to spring back, warpage as a substrate can be reduced compared to aluminum or the like. Therefore, it is difficult for surface deflection due to the warpage of the substrate to occur. For this reason, the contact with the head is always good, a desired access speed can be obtained, and the recording capacity per unit area can be increased.

  The following embodiments of the present invention will be described with reference to the drawings. FIG. 1 is an enlarged cross-sectional view of a hard magnetic disk according to the embodiment, FIG. 2 is a flowchart for explaining a manufacturing process of the hard magnetic disk, and FIG. 3 is for explaining a process of pressing a disk substrate from a rolled plate. It is a schematic block diagram.

  In the present invention, pure magnesium having a purity of 99.9% by weight or a magnesium-based alloy mainly composed of magnesium is used as the disk substrate.

  Examples of magnesium-based alloys include Mg—Al—Zn alloys, Mg—Zn—Zr alloys, Mg—Al alloys, Mg—rare earth elements alloys, Mg—Al—Zr alloys, and Mg—Al—Mn alloys. There are alloys, Mg—Al—Si alloys, Mg—Al—rare earth elements alloys, and the like.

  Specific examples of the Mg—Al—Zn alloy include AZ21, AZ31A, Z31B, AZ31C, AZ61A, AZ80A, and AZ91, and the substrate can be strengthened by solid solution hardening and work hardening.

  Specific examples of the Mg—Zn—Zr alloy include ZK10, ZK40, ZK60, and the like. By adding a small amount of Zr, crystal grains can be refined and warm workability is improved. This type of alloy is improved in proof stress by heat treatment, and therefore the specific strength of proof stress / specific gravity is increased.

  Specific examples of the Mg—Al based alloy include AM100A, which is excellent in mechanical properties.

  Specific examples of the Mg—Al—Zn alloy include AZ63A, AZ81A, AZ91E, and AZ92A, which are excellent in mechanical properties, and in particular, AZ91E is excellent in corrosion resistance.

Specific examples of the Mg-rare earth element alloy include EZ33A, ZE41A, QE22A, WE54A, and WE43A. By adding rare earth elements (RE: misch metal or didymium, mainly Ce or Nb), Mg ₁₂ RE is generated in a network form at the grain boundaries. Excellent creep resistance and pressure resistance.

  Specific examples of the Mg—Al—Zr alloy include ZK10 and ZK40. Specific examples of the Mg—Al—Mn alloy include Am60, Am50, Am20, and the like. Specific examples of the Mg—Al—Si alloy include As41 and As21. Specific examples of the Mg-Al-rare earth element alloy include As42.

Specific chemical component examples of typical magnesium-based alloys are as follows.
AZ91: Al 8.3 to 9.7 wt%, Zn 0.35 to 1.0 wt%, Mn 0.
15% by weight or more, Mn 0.15% by weight or more, Si 0.5% by weight or more,
Cu 0.1% by weight or more, Mg balance AZ31: Al 2.5-3.3% by weight, Zn 0.5-1.5% by weight, Mn 0.5
% By weight or more, Fe 0.01% by weight or less, Si 0.1% by weight or less, Cu
0.1 wt% or less, Ni 0.005 wt% or less, other 0.3 wt%
Hereinafter, Mg balance ZK10: Zn 0.8 to 1.5 wt%, Zr 0.4 to 0.8 wt%, Cu 0.0
3 wt% or less, Ni 0.005 wt% or less, other 0.3 wt% or less,
Mg balance AZ21: Al 1.5 to 2.4% by weight, Zn 0.5 to 1.5% by weight, Mn 0.0
5 wt% or more, Fe 0.01 wt% or less, Si 0.1 wt% or less, C
u 0.1 wt% or less, Ni 0.005 wt% or less, other 0.3 wt%
% Or less, Mg balance FIG. 2 is a flowchart for explaining the manufacturing process of a hard magnetic disk. As shown in the figure, the magnesium material is rolled in step (hereinafter abbreviated as S) 1. Magnesium is a close-packed hexagonal metal and is more suitable for warm rolling than cold rolling.

  This rolling process includes a rough rolling process, a subsequent warm main rolling process, and a subsequent finish rolling process. A specific example of the rolling conditions of AZ31 (Mg—Al—Zn alloy) will be described. The starting temperature of the rough rolling process is 425 ° C. to 450 ° C., the rolling reduction (% / heating) is 90 to 95, and the rolling reduction (% / Pass) is 10-20. The starting temperature of the warm main rolling process is 350 ° C. to 440 ° C., the rolling reduction (% / heating) is 25 to 50, and the rolling reduction (% / pass) is 5 to 20. The starting temperature of the finish rolling step is 250 ° C. or less, the rolling reduction (% / heating) is 15 to 25, and the rolling reduction (% / pass) is 5. In the case of pure magnesium or a low concentration alloy, the finish rolling process may be performed by cold rolling.

  The warm rolling method includes a heated roll method in which a roll is heated and a cold roll method in which a roll is not heated. By passing through the rolling process as described above, a working texture is formed in which the bottom surface of the hexagonal crystal is arranged parallel to the surface of the rolled plate, thereby further improving the mechanical properties.

  Next, in S2, the rolled plate material is punched out by pressing to obtain a donut-shaped substrate having a predetermined diameter. FIG. 3 is a schematic configuration diagram for explaining a process until a disk substrate is punched from a rolled plate.

  As shown in the figure, a rolled plate 11 (for example, 1 mm in thickness) wound in a roll shape is fed out by a pair of feed rolls 12 and flattened by a press die so as to have a predetermined flatness as a substrate. Is done. The press die 13 shown as an example is composed of a lower die 13a whose upper surface is fixed in a flat state and an upper die 13b whose lower surface is flat and which can move up and down. Built-in.

  The rolled-out rolled sheet 11 is strongly pressed for a predetermined time by the heated molds 13a and 13b and heated to around 250 ° C. By this pressing, the thickness of the rolled plate 11 is reduced to, for example, 0.8 mm. The strong pressure by the press mold 13 is repeated once or a plurality of times, and the rolled plate 11 is work-hardened.

  Next, the rolled plate 11 is guided to the cooling unit 15 and cooled. In view of the quenching effect, for example, a low-temperature nitrogen gas or a liquid such as water may be used as the refrigerant 16. After cooling, a donut-shaped disk substrate having a predetermined size is continuously punched by the punching dies 17a and 17b. The punched donut-shaped disk substrate is mounted on a turret type planar polishing apparatus (not shown), and deburring and planar polishing are performed.

  Returning again to FIG. 2, anodizing is performed in S3. This anodizing treatment includes three steps of pretreatment, oxidation treatment, and posttreatment. The pretreatment is a step of removing processing oil and the like adhering to the surface of the disk substrate, and specifically includes alkali cleaning and acid cleaning. Since magnesium is resistant to alkali, it can be cleaned effectively at high temperature using a highly alkaline cleaning solution. In the case of acid cleaning, a cleaning solution having a low acidity that does not damage the surface of the disk substrate may be used for a short time.

  The pretreated disk substrate is made of, for example, a mixed aqueous solution of sodium hydroxide, ethylene glycol, and sodium oxalate, immersed in an electrolytic bath maintained at 75 ° C. to 80 ° C., and subjected to predetermined energization. Next, after the oxidation treatment, the disk substrate is washed with water, washed with hot water, and dried. By this anodizing treatment, a dense anodized film is formed on the entire surface of the disk substrate, and this anodized film functions as an anticorrosive film.

  In S4, a nickel-cobalt magnetic thin film is formed on one surface of the disk substrate by a thin film forming means such as sputtering or vapor deposition. Further, in S5, a protective film made of amorphous carbon or the like is formed on the magnetic thin film. Make a disc. If necessary, a lubricant such as PFPE may be applied onto the amorphous carbon film.

  FIG. 1 is a partially enlarged cross-sectional view of the hard magnetic disk thus obtained. In the figure, reference numeral 1 denotes a disk substrate made of a magnesium material, the entire surface of which is covered with an anodized film 2.

  A nickel-cobalt magnetic thin film 3 is formed on one surface of the disk substrate 1, and a protective film 4 made of amorphous carbon or the like is further formed on the magnetic thin film 3. In addition, since moderate unevenness | corrugation generate | occur | produces on the surface by anodic oxidation, the said board | substrate does not require a texturing process in particular.

  FIG. 4 is a characteristic diagram showing the relationship between vibration damping coefficient and tensile strength of pure magnesium plate, magnesium-based alloy plate, and aluminum-based alloy plate. The vibration damping coefficient is measured using X as the magnitude of the tensile stress corresponding to 0.2% permanent strain of the material, and using a shear stress amplitude that is 1/10 of the magnitude X of the tensile stress.

  In the figure, A is pure magnesium, B is an Mg—Zr alloy containing 0.6% by weight of Zr, C is an Mg—Al—Zn alloy containing 8% by weight of Al and 1% by weight of Zn, and D is an aluminum base. An alloy is shown.

  A heavy material has a higher vibration damping capability, which is a general material characteristic. As is apparent from the results of FIG. 4, magnesium is lighter and has a much higher vibration damping capability than an aluminum-based alloy. .

  The specific gravity of magnesium is 1.74, which is about two-thirds lighter than that of aluminum (specific gravity: 2.74), the tensile strength of magnesium is 98 MPa, stronger than aluminum (tensile strength: 88 MPa), and the hardness of magnesium is 30 HB. Harder than aluminum (hardness: 23HB).

  The specific gravity of the magnesium-based alloy is about 1.79 to 1.81, which is lighter than the aluminum-based alloy (specific gravity: 2.8), and the vibration-absorbing property (loss factor) of the magnesium-based alloy is 0.005, which is aluminum (loss factor). : 0.0001), the dent resistance (weight drop energy: 20 ft · 1b) of the magnesium-based alloy is 0.12, which is superior to aluminum (0.19), and the specific rigidity of the magnesium-based alloy The height (rigidity / specific gravity) is 9.56, which is superior to aluminum (rigidity / specific gravity: 8.58). Further, the magnesium-based alloy is hardly deformed even when left at a high temperature (for example, 100 to 150 ° C.) for a long time, and has excellent dimensional stability.

  Thus, magnesium is lighter than aluminum (aluminum-based alloy), so it has good rise and fall characteristics during disk rotation, can be used for high-speed transfer, and consumes less motor power during high-speed rotation. That's it.

  Magnesium has superior mechanical properties such as tensile strength, hardness, dent resistance, high specific rigidity, and dimensional stability compared to aluminum (aluminum-based alloy). Moreover, even if the number of revolutions of the disk is increased, the disk hardly bends during high-speed rotation. Moreover, since it has excellent vibration absorption, it hardly causes self-excited vibration during high-speed rotation. In addition, since the magnesium material is less likely to spring back, the warpage of the substrate can be reduced compared to aluminum or the like. Therefore, it is difficult for surface deflection due to the warpage of the substrate to occur. For this reason, the contact with the head is always good, a desired access speed can be obtained, and the recording capacity per unit area can be increased.

  In the above-described embodiment, the case of a hard magnetic disk has been described. However, the present invention is not limited to this, and any information recording medium that requires high-speed rotation can use the same substrate even if a substrate made of a magnesium material is used. An effect is obtained. For example, the present invention can be applied to an optical information recording medium such as a read-only reflective optical disc or a write-only reflective optical disc. When applied to a write-only reflective optical disk, it is obtained by forming signal pits on the surface of a substrate made of magnesium or a magnesium-based alloy by pressing or etching, and forming a transparent protective film on the signal surface.

1 is a partially enlarged cross-sectional view of a hard magnetic disk according to an embodiment of the present invention. 4 is a flowchart for explaining a manufacturing process of the hard magnetic disk. It is a schematic block diagram for demonstrating to the process of punching a disk substrate out of a rolled plate. It is a characteristic view which shows the relationship between the vibration damping coefficient and tensile strength of a pure magnesium plate, a magnesium base alloy plate, and an aluminum base alloy plate.

Explanation of symbols

  1: disk substrate, 2: anodized film, 3: magnetic thin film, 4: protective film, 11: rolled plate, 12: pair of feed rolls, 13: press die, 13a: lower die, 13b: upper die, 14: heater, 15: cooling section, 16: refrigerant, 17a, 17b: punching mold.

Claims (3)

  An information recording medium having an information recording layer formed on a substrate, wherein the substrate is made of magnesium or a magnesium-based alloy. In a method for manufacturing an information recording medium in which an information recording layer is formed on a substrate,
Rolling magnesium or a magnesium-based alloy into a thin plate having a predetermined thickness;
A process of punching the rolled sheet into a predetermined substrate shape;
A process of anodizing the substrate;
And a step of forming the information recording layer on the anodized film. The method for manufacturing an information recording medium according to claim 2, wherein the step of rolling the magnesium or magnesium-based alloy and the step of punching into a predetermined substrate shape from the rolled thin plate,
A step of strongly pressing the rolled sheet with a press mold having a flat mold surface and maintained at a high temperature;
And a step of cooling the rolled sheet after the strong pressing step.

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