JP2663881B2 - Magneto-optical recording medium and method of manufacturing the same - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a magneto-optical recording medium for recording, erasing, and reproducing data by irradiating a laser beam, and more particularly to a medium having excellent high-density recording and reducing medium noise in a low frequency region of a read signal. The present invention relates to a magneto-optical recording medium that can be reduced and a method for manufacturing the same.

[0002]

2. Description of the Related Art In general, a magneto-optical recording medium has attracted attention as a new storage medium replacing a magnetic recording medium which is frequently used at present because of its high density, large capacity and high-speed access. Further, since the magneto-optical recording medium can rewrite information once recorded, it has been actively studied in a wide range of application fields as a storage device for code data, image data, and the like.

For example, referring to FIG. 6, a conventional magneto-optical recording medium includes an organic resin substrate 11 made of a transparent polycarbonate resin having a spiral groove having a predetermined width and pitch on its surface, and an organic resin substrate 11 made of the same. Thickness 80 on top
Dielectric layer 1 made of silicon nitride formed in [nm]
2, a recording layer 13 made of a terbium-iron-cobalt alloy having an atomic ratio of 22: 70: 8 and formed on the dielectric layer 12 with a thickness of 80 [nm]; And a protective layer 14 of silicon nitride formed at 80 [nm].

In this conventional magneto-optical recording medium, an RF sputtering apparatus is used, and the inside of a chamber is 5.0 * 10 ^-5.
After evacuation to [Pa] or less, the layers are sequentially formed. For example, the dielectric layer 12 and the protective layer 14 each have a purity of 9%.
It is formed in a mixed gas atmosphere of argon gas and nitrogen using a 9.99% silicon sintered body as a target. The recording layer 13 is formed in an argon gas atmosphere using a composite target in which a terbium chip is disposed on an iron / cobalt alloy sheet having an atomic ratio of 90:10.

[0005]

However, when the relationship between a reproduction signal obtained by irradiating a laser beam on a magneto-optical recording medium manufactured by the above-mentioned conventional film forming method and medium noise is examined, It has been found that the medium noise increases in the low frequency range of the signal, especially in the frequency range of 5 [MHz] or less. Therefore, the jitter characteristic of the reproduced signal is deteriorated and the quality of the reproduced signal is remarkably reduced.

A main object of the present invention is to solve the above problems and reduce the medium noise in the low frequency region of the reproduction signal, particularly in the frequency region of 5 MHz or less, thereby improving the jitter characteristics of the reproduction signal. It is an object of the present invention to provide a magneto-optical recording medium capable of improving the quality of a reproduced signal and a method of manufacturing the same.

[0007]

According to the present invention, there is provided a magneto-optical recording medium comprising: an organic resin substrate whose surface is sputter-etched in a range not more than a first specified value; a first dielectric layer made of silicon nitride; A second dielectric layer made of tantalum oxide whose surface is sputter-etched in a range equal to or more than a second specified value, a recording layer made of an amorphous magnetic alloy, a third dielectric layer, and a metal reflective film Are sequentially laminated, and the total thickness of the first dielectric layer and the second dielectric layer is within a predetermined thickness range. Here, the first specified value is 0.5 [nm], the second specified value is 3 [nm], and the predetermined thickness is 100 to 1
50 [nm].

In the method of manufacturing a magneto-optical recording medium according to the present invention, the surface of the organic resin substrate is sputter-etched in a range of not more than a first specified value, and a first dielectric film made of silicon nitride is formed on the organic resin substrate. A first step of forming a body layer, and a step of forming the body layer from the tantalum oxide on the first dielectric layer so that the total thickness of the first dielectric layer and the first dielectric layer is within a predetermined thickness range. A second step of forming a second dielectric layer comprising: forming a second dielectric layer, and sputter-etching the surface of the second dielectric layer in a range equal to or more than a second prescribed value; and forming an amorphous layer on the second dielectric layer. And a third step of sequentially laminating a recording layer made of a high quality magnetic alloy, a third dielectric layer, and a metal reflection film.

[0009]

Next, an embodiment of the present invention will be described in detail with reference to the drawings.

Referring to FIG. 1, a magneto-optical recording medium according to one embodiment of the present invention has a spiral groove having a predetermined width and pitch on a surface thereof and has a thickness of 1.2 [m] made of a transparent polycarbonate resin. mm] and a diameter of 130 [mm], and a first layer of silicon nitride formed on the organic resin substrate 1 with a thickness of 30 to 140 [nm].
Dielectric layer 2, a second dielectric layer 3 of tantalum oxide formed on the first dielectric layer 2 with a thickness of 10 to 120 [nm], and a second dielectric layer 3, terbium, iron, cobalt, and
A recording layer 4 made of a titanium alloy, a third dielectric layer 5 made of silicon nitride formed on the recording layer 4 with a thickness of 30 [nm], and a thickness on the third dielectric layer 5 30 [n
m] and a metal reflective layer 6 made of an aluminum-titanium alloy.

The magneto-optical recording medium of this embodiment uses an in-line sputtering apparatus to move the inside of the chamber 1.0 * 10.
It is manufactured by evacuating to ^-5 [Pa] or less and forming each layer in order.

First, the surface of the organic resin substrate 1 is set to about 0.5 in an argon gas atmosphere at a gas pressure of 0.1 [Pa].
Sputter etching is performed in the range of [nm] or less. At this time, the power density of the sputtering apparatus was 0.15 [W / c].
m ² ], and the flow rate of the argon gas is 25 [SCCM]. The sputter etching amount on the organic resin substrate 1 of the present embodiment is set based on the experimental results of the sputter etching amount on the organic resin substrate 1 and the medium noise shown in FIG. These experimental data are obtained by measuring the medium noise of several magneto-optical recording media in which the same layer structure is formed on several substrates using the sputter etching amount as a parameter. According to this, when the sputter etching amount on the organic resin substrate 1 is about 0.5 [nm] or more, medium noise in a low frequency region of the reproduction signal becomes large. Therefore, in order to reduce the medium noise in the low frequency region of the reproduction signal, it is necessary to set the sputter etching amount on the organic resin substrate 1 to about 0.5 [nm] or less.

Subsequently, the first dielectric layer 2 made of silicon nitride is formed by using a silicon target in a mixed gas atmosphere of argon and nitrogen at a distance between target substrates of 15 cm and a gas pressure of 0.3 Pa. The film is formed inside. At this time, the power density of the sputtering device is 8.0 [W / cm ² ].
And the flow rates of argon gas and nitrogen gas are 10
0 and 55 [SCCM].

Next, the second dielectric layer 3 made of tantalum oxide is formed in a mixed gas atmosphere of argon and oxygen. At this time, the power density of the sputtering apparatus is 8.
At 0 [W / cm ² ], the flow rates of argon gas and oxygen gas are 70 and 30 [SCCM], respectively. Thereafter, in this embodiment, the surface of the second dielectric layer 3 is sputter-etched in an argon gas atmosphere at a gas pressure of 0.1 [Pa] in a range of about 3 [nm] or more. At this time, the power density of the sputtering apparatus was 0.15 [W / cm ² ], and the flow rate of the argon gas was 25 [SCCM]. The sputter etching amount for the second dielectric layer 3 of this embodiment is shown in FIG.
Are set based on the experimental results of the sputter etching amount for the second dielectric layer 3 and the medium noise shown in FIG. These experimental data are obtained by measuring the medium noise of several magneto-optical recording media having the same layer structure using the sputter etching amount as a parameter. According to this, when the sputter etching amount on the second dielectric layer 3 becomes about 3 [nm] or less, the medium noise in the low frequency region of the reproduction signal becomes large. for that reason,
In order to reduce the medium noise in the low frequency region of the reproduction signal, it is necessary to set the sputter etching amount on the second dielectric layer 3 to about 3 [nm] or more.

Further, in this embodiment, the first dielectric layer 2
The total thickness of the second dielectric layer 3 is set to about 100 to 150 [nm]. The sum of the film thicknesses of the first dielectric layer 2 and the second dielectric layer is:
This is set based on the experimental results of the sum of the thicknesses of the first dielectric layer 2 and the second dielectric layer shown in FIG. 4 and the medium noise. These experimental data were obtained by measuring the medium noise of several magneto-optical recording media having the same layer structure using the total thickness of the first dielectric layer 2 and the second dielectric layer 3 as a parameter. ing. According to this, the first
If the sum of the film thicknesses of the dielectric layer 2 and the second dielectric layer 3 is not more than about 100 [nm] or not less than about 150 [nm], the medium noise in the low frequency region of the reproduced signal becomes large. Therefore, in order to reduce medium noise in a low frequency region of a reproduction signal, the first dielectric layer 2 and the second
The total thickness of the dielectric layers 3 is about 100 [nm] or more and about 1 [nm].
It must be set to 50 [nm] or less. Here, the reason that the medium noise increases in the region where the total thickness is about 100 [nm] or less is that the total thickness of the first dielectric layer 2 and the second dielectric layer 3 is small. It is considered that the unevenness on the surface of the resin substrate 1 directly affects the recording layer 4 and causes distortion. The reason why the medium noise increases in the region where the total thickness is about 150 [nm] or more is that the first dielectric layer 2
It is also considered that the stress is increased between the second dielectric layer 3 and the organic resin substrate 1 and deformation occurs on the organic resin substrate 1 side.

Subsequently, the recording layer 4 made of a terbium / iron / cobalt / titanium alloy having a thickness of 25 [nm] is formed on a substrate by a binary magnetron sputtering method using a terbium target and an iron / cobalt / titanium alloy target. While rotating, the distance between target substrates is 10 cm,
The film is formed in an argon gas atmosphere having a gas pressure of 0.55 [Pa]. At this time, the power densities of the terbium target and the iron / cobalt / titanium alloy target in the sputtering apparatus are 1.5 [W / cm ² ] and 3.
0 [W / cm ² ] and the flow rate of argon gas is 50 [SC
CM].

Next, a thickness of 30 [n] made of silicon nitride is used.
m] of the third dielectric layer 5 was formed by using a silicon target, a distance between target substrates of 15 cm, and a gas pressure of 0.3 cm.
The film is formed in a mixed gas atmosphere of argon and nitrogen [Pa]. At this time, the power density of the sputtering apparatus is 8.
At 0 [W / cm ² ], the flow rates of the argon gas and the nitrogen gas are 100 and 55 [SCCM], respectively.

Finally, the metal reflective layer 6 of 30 nm thick made of aluminum / titanium alloy is made of aluminum / titanium.
Using a titanium alloy target, a film is formed in an argon gas atmosphere with a distance between target substrates of 15 [cm] and a gas pressure of 0.1 [Pa]. At this time, the power density of the sputtering device is 3.0 [W / cm ² ].

FIG. 5 shows the relationship between the medium noise and the frequency of the reproduced signal in the magnetic recording medium of this embodiment. According to this, compared to the graph 8 of the medium noise in the conventional magneto-optical recording medium, the graph 7 of the medium noise in the magneto-optical recording medium of the present embodiment is in the low frequency region of the reproduced signal, particularly 5 MHz or less. There is almost no change in the frequency domain. That is, it can be seen that the medium noise is considerably reduced. Therefore, by using the magnetic recording medium of this embodiment, the jitter characteristics of the reproduced signal can be improved, and the quality of the reproduced signal can be further improved. Here, the reason why the medium noise can be reduced is considered to be the surface shape of the second dielectric layer formed below the recording layer which is most caused by the medium noise. That is, in this embodiment, since the second dielectric layer is formed and then sputter-etched in an argon gas atmosphere in a range of about 3 nm or more, the surface shape of the second dielectric layer is uniform and This is considered to be because the direction of magnetization dispersion of the initial layer of the recording layer during the recording layer formation can be reduced when the recording layer is formed.

In the present invention, the organic resin substrate 1 can use an acrylic resin in addition to the polycarbonate resin. The recording layer 4 is made of a combination of a rare earth metal such as terbium, gadolinium, dysprosium, and holmium, and an iron group transition metal such as iron, cobalt, and nickel, in addition to the terbium-iron-cobalt-titanium alloy. Any amorphous magnetic alloy can be used. Further, for the third dielectric layer, in addition to silicon nitride, silicon dioxide, tantalum oxide, aluminum nitride, or the like can be used. The metal reflection layer may be made of aluminum, chromium, gold, aluminum chromium, or the like, in addition to the aluminum-titanium alloy.

Further, in this embodiment, an optical head for a magneto-optical disk having a wavelength of 830 [nm] was used to measure the medium noise. Prior to this measurement, in order to avoid the influence of the groove on the organic resin substrate on the medium noise, after forming the same layer structure on the entire flat organic resin substrate without the groove, the entire area of the medium is irradiated with DC light. At the same time, erasing was performed by applying an external magnetic field in the erasing direction. Also, the difference signal output from the optical head detector is taken into the spectrum analyzer,
The measurement of the medium noise level at each frequency was performed. Further, when measuring the medium noise, the irradiation power of the laser light of the optical head for the magneto-optical disk for irradiating the medium with the medium so that the amount of light returned to the optical head detector becomes constant even if the reflectance of the medium changes. Adjustments were made to measure the noise level.

[0022]

As described above, according to the present invention, the organic resin substrate 1 whose surface is sputter-etched within a range of about 0.5 nm or less, the first dielectric layer 2 made of silicon nitride, A second dielectric layer 3 made of tantalum oxide whose surface is about 3 [nm] or more, a recording layer 4 made of an amorphous magnetic alloy, and a third dielectric layer 5; And the metal reflective film 6 are sequentially laminated, and the total thickness of the first dielectric layer 2 and the second dielectric layer 3 is about 1
Since the magneto-optical recording medium is formed so as to fall within the range of 00 to 150 [nm], it is possible to reduce medium noise in the low frequency region of the reproduction signal, particularly in the frequency region of 5 [MHz] or less. . Therefore, the jitter characteristics of the reproduced signal can be improved, and the quality of the reproduced signal can be further improved.

[Brief description of the drawings]

FIG. 1 is a sectional view showing a structure of a magneto-optical recording medium according to one embodiment of the present invention.

FIG. 2 is a graph showing a relationship between a sputter etching amount on an organic resin substrate 1 and a medium noise in the present embodiment.

FIG. 3 is a graph showing a relationship between a sputter etching amount for a second dielectric layer 3 and a medium noise in the present embodiment.

FIG. 4 shows a first dielectric layer 2 and a second dielectric layer 2 in this embodiment.
6 is a graph showing the relationship between the total thickness of the dielectric layer 3 and the medium noise.

FIG. 5 is a graph showing a relationship between a frequency region of a reproduction signal and a medium noise in the magneto-optical recording medium manufactured in the embodiment.

FIG. 6 is a sectional view showing the structure of a conventional magneto-optical recording medium.

[Explanation of symbols]

 REFERENCE SIGNS LIST 1 organic resin substrate 2 first dielectric layer 3 second dielectric layer 4 recording layer 5 third dielectric layer 6 metal reflective layer

──────────────────────────────────────────────────続 き Continued on the front page (51) Int.Cl. ⁶ Identification code Agency reference number FI Technical display location G11B 11/10 541 G11B 11/10 541G

Claims (20)

(57) [Claims] An organic resin substrate whose surface is sputter-etched in a range of not more than a first specified value, a first dielectric layer made of silicon nitride, and a sputter-etched surface in a range of not less than a second specified value. A second dielectric layer made of tantalum oxide, a recording layer made of an amorphous magnetic alloy, a third dielectric layer, and a metal reflection film are sequentially laminated, and the first dielectric layer A magneto-optical recording medium, wherein the total thickness of the layers and the second dielectric layer is formed within a predetermined thickness range. 2. The magneto-optical recording medium according to claim 1, wherein the first specified value is 0.5 [nm]. 3. The magneto-optical recording medium according to claim 1, wherein the second specified value is 3 [nm]. 4. The predetermined thickness is 100 to 150.
2. The magneto-optical recording medium according to claim 1, wherein the thickness is [nm]. 5. The magneto-optical recording medium according to claim 1, wherein said organic resin substrate is made of a polycarbonate resin. 6. The magneto-optical recording medium according to claim 1, wherein said organic resin substrate is made of an acrylic resin. 7. The amorphous magnetic alloy is made of a combination of a rare earth metal containing terbium, gadolinium, dysprosium or holmium and an iron group transition metal containing iron, cobalt or nickel. 2. The magneto-optical recording medium according to 1. 8. The magneto-optical recording medium according to claim 1, wherein said third dielectric layer is made of silicon nitride. 9. The magneto-optical recording medium according to claim 1, wherein said third dielectric layer is made of silicon dioxide. 10. The magneto-optical recording medium according to claim 1, wherein said third dielectric layer is made of tantalum oxide. 11. The magneto-optical recording medium according to claim 1, wherein said third dielectric layer is made of aluminum nitride. 12. The magneto-optical recording medium according to claim 1, wherein said metal reflection layer is made of an aluminum-titanium alloy. 13. The magneto-optical recording medium according to claim 1, wherein said metal reflection layer is made of aluminum. 14. The magneto-optical recording medium according to claim 1, wherein said metal reflection layer is made of chromium. 15. The magneto-optical recording medium according to claim 1, wherein said metal reflection layer is made of gold. 16. The magneto-optical recording medium according to claim 1, wherein said metal reflection layer is made of aluminum chromium. 17. A first step in which a surface of an organic resin substrate is sputter-etched in a range equal to or less than a first prescribed value to form a first dielectric layer made of silicon nitride on the organic resin substrate; Forming a second dielectric layer made of tantalum oxide on the first dielectric layer such that the total thickness of the first dielectric layer and the first dielectric layer is within a predetermined thickness range; A second step of sputter etching the surface of the second dielectric layer in a range not less than a second specified value; a recording layer made of an amorphous magnetic alloy on the second dielectric layer; And a third step of sequentially laminating a body layer and a metal reflection film. 18. The method according to claim 1, wherein in the first step, the surface of the organic resin substrate is sputter-etched in an argon gas atmosphere at a gas pressure of 0.1 [Pa] in a range of 0.5 [nm] or less. Forming a first dielectric layer made of silicon nitride in a mixed gas atmosphere of argon and nitrogen having a distance between target substrates of 15 [cm] and a gas pressure of 0.3 [Pa]. A method for manufacturing a magneto-optical recording medium according to claim 17. 19. The method according to claim 19, wherein the total thickness of the second dielectric layer made of tantalum oxide and the first dielectric layer is 100 in a mixed gas atmosphere of argon and oxygen.
After being formed so as to be within the range of 150 to 150 [nm], the second layer is formed in an argon gas atmosphere at a gas pressure of 0.1 [Pa].
18. The method of manufacturing a magneto-optical recording medium according to claim 17, wherein the step of sputter-etching the surface of the dielectric layer is performed in a range of 3 [nm] or more. 20. The third step, wherein a terbium target and an iron-cobalt-titanium alloy target are used, a distance between target substrates is 10 cm, and a gas pressure is 0.55.
A recording layer of terbium / iron / cobalt / titanium alloy having a thickness of 25 [nm] and an inter-target substrate distance of 15 [cm] using a silicon target in an argon gas atmosphere of [Pa] at a gas pressure of 0.3 [cm] Pa] of a thickness of 3 made of silicon nitride in a mixed gas atmosphere of argon and nitrogen.
Using a third dielectric layer of 0 [nm] and an aluminum-titanium alloy target, a distance between target substrates of 15 [nm] is used.
[Cm] and a thickness of 30 [n] made of an aluminum-titanium alloy in an argon gas atmosphere having a gas pressure of 0.1 [Pa].
18. A method for manufacturing a magneto-optical recording medium according to claim 17, further comprising the step of sequentially laminating a metal reflective layer of [m].