JP2000099994A - Optical recording medium - Google Patents

Abstract

PROBLEM TO BE SOLVED: To enable to suppress corrosion and to improve durability by forming plural layers including a signal recording layer deposited within a vacuum chamber on a substrate and forming at least one layer formed on the layer upper than the signal recording layer among the plural layers so as to cover at least the signal recording layer. SOLUTION: A magneto-optical disk 1 is so formed that the second dielectric layer 6 is formed to cover the magneto-optical recording layer 5, that the deposition area of the second dielectric layer 6 is larger than the deposition area of the magneto-optical recording layer 5 and that the outer edge of the second dielectric layer 6 overhangs to the side outer than the outer edge of the magneto-optical recording layer 5. The occurrence of the corrosion in consequence of the oxidation, etc., of the magneto-optical recording layer 5 may be suppressed and the durability improved by forming the second dielectric layer in such a manner. In addition, the second dielectric layer 6 is preferably formed so as to cover the thermal diffusion layer 3 and the first dielectric layer 4. The occurrence of the corrosion is further suppressed and the durability is improved by forming the magneto-optical disk in the manner described above.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

[0001] 1. Field of the Invention [0002] The present invention relates to an optical recording medium for reproducing or recording / reproducing an information signal using light.

[0002]

2. Description of the Related Art Conventionally, a laminated film in which a signal recording layer, a dielectric layer, and the like are laminated on a substrate, such as a magneto-optical disk and a phase change optical disk, is formed. 2. Description of the Related Art Optical recording media on which information signals are read or written by irradiation are widely used.

[0003] In these optical recording media, recording densities have been actively increased in order to record as much information as possible.

With the increase in the recording density of the optical recording medium, the spot diameter of light applied to the signal recording layer is also reduced for an optical head that reads and writes information signals from and to the optical recording medium. Various studies have been made to reduce the size.

In particular, in recent years, the technology of a floating magnetic head in a hard disk drive or the like has been applied to form a floating optical head by mounting an objective lens on a slider, and the floating optical head is mounted on a substrate of an optical recording medium. Attempts have been made to read and write information signals from the side where the laminated film is formed on the optical recording medium by floating so as to face the laminated film formed on the optical recording medium.

[0006] As described above, the floating optical head is floated so as to face the laminated film formed on the substrate of the optical recording medium to read and write information signals. The distance from the signal recording layer can be significantly shortened as compared with the case where light from the optical head is applied to the signal recording layer via the substrate. Accordingly, it is possible to increase the NA of the objective lens, and it is possible to reduce the spot diameter of light applied to the signal recording layer.

As described above, when the flying optical head is floated so as to face the laminated film formed on the substrate of the optical recording medium to read or write information signals, the light from the optical head is Is irradiated from the laminated film side, so in this type of optical recording medium,
The order of forming the laminated film formed on the substrate is reverse to that of the optical recording medium of the type irradiated with light through the substrate.

[0008]

By the way, in an optical recording medium of a type irradiated with light through a substrate, a laminated film including a signal recording layer formed on the substrate is formed on the laminated film. It is covered with a protective coating film such as an ultraviolet curable resin film.

However, it is difficult to form such a protective coating film on an optical recording medium of the type in which light is irradiated from the side of the laminated film. In other words, in this type of optical recording medium, the floating optical head irradiates the signal recording layer with light at a position very close to the signal recording layer of the laminated film in order to reduce the spot diameter of the light applied to the optical recording medium. Therefore, if a dielectric layer is formed on the signal recording layer and a protective coating film is to be formed thereon, the distance between the surface of the optical recording medium and the floating optical head (working distance) ) Becomes too narrow, and the optical recording medium may collide with the flying optical head.

For this reason, in this type of optical recording medium, it is difficult to form a protective coating film, and there is a problem that corrosion is easily caused by oxidation of a signal recording film and the like formed on a substrate.

Therefore, the present invention provides an optical recording medium in which information signals are read or written by an optical head located near a signal recording layer, which suppresses corrosion and has high durability. The purpose is to do.

[0012]

SUMMARY OF THE INVENTION An optical recording medium according to the present invention has been developed to solve the above-mentioned problems.
In an optical recording medium in which a signal recording layer is irradiated with light to reproduce or record / reproduce an information signal, a plurality of layers including a signal recording layer formed in a vacuum chamber on a substrate are formed. At least one layer formed above the signal recording layer among the plurality of layers is formed so as to cover at least the signal recording layer.

According to this optical recording medium, since at least the signal recording layer is covered by another layer formed above the signal recording layer, corrosion caused by oxidation of the signal recording layer is reduced. It becomes possible.

In general, there is little room for selecting a material for the signal recording layer, and it is difficult to use a material that is resistant to corrosion. On the other hand, for example, a dielectric layer formed on the signal recording layer has a relatively large amount of room for selection of a material, so that a layer formed above the signal recording layer, such as the dielectric layer, may be used. If a material that is resistant to corrosion is used to cover the signal recording layer, corrosion due to oxidation or the like of the signal recording layer can be reduced.

Specifically, in an optical recording medium in which at least a heat diffusion layer, a first dielectric layer, a signal recording layer, and a second dielectric layer are formed in this order on a substrate, the signal recording layer At least the signal recording layer is covered by the second dielectric layer formed above the second dielectric layer.

In this case, it is desirable that the second dielectric layer is formed so as to cover not only the signal recording layer but also the heat diffusion layer and the first dielectric layer. As described above, if the second dielectric layer covers the thermal diffusion layer and the first dielectric layer, corrosion caused by oxidation of the thermal diffusion layer and the first dielectric layer is also suppressed. And durability can be further improved.

[0017]

Embodiments of the present invention will be described below with reference to the drawings.

Here, an example in which the present invention is applied to a magneto-optical disk in which a plurality of layers including a magneto-optical recording layer are formed on a disk substrate formed by molding a resin material into a disk shape will be described. Note that the present invention is not limited to this example. For example, a phase change type optical disk that performs recording and reproduction of a signal using a phase change of a signal recording layer, and other optical recording media having different recording methods and the like. It is also possible to apply to.

The magneto-optical disk to which the present invention is applied is irradiated with light from the signal recording layer side (the side opposite to the disk substrate) by an optical head close to the signal recording layer, for example, a floating optical head. This is a type of magneto-optical disk in which reading and writing of information signals are carried out.

As shown in FIG. 1, the magneto-optical disk 1 includes a heat diffusion layer 3, a first dielectric layer 4, a magneto-optical recording layer 5, and a second dielectric The layers 6 are sequentially laminated in this order.

The disk substrate 2 is formed by molding a resin material such as polycarbonate (PC) into a disk shape by injection molding or the like.

The thermal diffusion layer 3 diffuses heat due to the light applied to the magneto-optical recording layer 5 and improves the reflectivity of the light to improve the recording characteristics of the magneto-optical recording layer 5. For example, an Al film or the like is formed on the disk substrate 2 with a thickness of about 40 nm. In addition, between the disk substrate 2 and the heat diffusion layer 3, a base film serving as a base of each layer formed on the disk substrate 2 is formed, and the heat diffusion layer 3 is formed on the base film. You may.

The first dielectric layer 4 is for improving the optical efficiency of the magneto-optical disk 1, and includes, for example,
An SiN film or the like is formed on the thermal diffusion layer 3 with a thickness of about 20 nm.

The magneto-optical recording layer 5 is a layer that exhibits a magneto-optical effect. For example, a TbFeCo film using Tb as a rare earth element, Fe or Co as a transition metal, or the like is formed of a first dielectric material having a thickness of about 23 nm. It is formed on the layer 4.

The second dielectric layer 6, like the first dielectric layer 4, is used to improve the optical efficiency of the magneto-optical disk 1. For example, the SiN film or the like has a thickness of about 80 nm. It is formed on the magneto-optical recording layer 5 with a thickness of

The magneto-optical disk 1 of the present embodiment
In this case, as shown in FIG.
Are formed so as to cover at least the magneto-optical recording layer 5. That is, in the magneto-optical disk 1 according to the present embodiment, the film formation area of the second dielectric layer 6 is larger than the film formation area of the magneto-optical recording layer 5, and the outer edge of the second dielectric layer 6 Are formed so as to protrude outside the outer edge of the magneto-optical recording layer 5.

In the magneto-optical disk 1, since the second dielectric layer 6 is formed so as to cover the magneto-optical recording layer 5, corrosion of the magneto-optical recording layer 5 due to oxidation of the magneto-optical recording layer 5 occurs. And the durability can be improved.

Incidentally, in this magneto-optical disk 1,
As shown in FIG. 2, it is desirable that the second dielectric layer 6 be formed so as to cover the heat diffusion layer 3 and the first dielectric layer 4 as well. The magneto-optical disk 1 is thus formed such that the second dielectric layer 6 covers not only the magneto-optical recording layer 5 but also the thermal diffusion layer 3 and the first dielectric layer 4.
The occurrence of corrosion can be further suppressed, and the durability can be further improved.

The respective layers formed on the disk substrate 2 are formed by sequentially forming the materials constituting these layers on the disk substrate 2 by a thin film forming method such as sputtering. That is, as shown in FIG. 3, each of the above-mentioned layers is placed in a vacuum chamber 13 provided with a target 10 of a material constituting these layers and a mask 12 having an opening 11, respectively.
Are stacked and sequentially formed by carrying out sputtering or the like.

Each of these layers is, as described above, a mask 1
Since the film 12 is formed by sputtering or the like, the film is sequentially laminated on the disk substrate 2 as a film having an area corresponding to the opening diameter of the mask 12.

Therefore, when manufacturing the magneto-optical disk 1 of this embodiment, the second mask 12 having a larger opening diameter than the mask 12 used for forming the magneto-optical recording layer 5 is used. By forming the dielectric layer 6 described above, the second dielectric layer 6 formed so as to cover the magneto-optical recording layer 5 can be obtained.

The opening diameter of the opening 11 of the mask 12 used when forming the second dielectric layer 6 is determined by the opening diameter of the opening 11 of the mask 12 used when forming the thermal diffusion layer 3. By making the opening diameter of the opening 11 of the mask 12 used for forming the first dielectric layer 4 larger than that of the magneto-optical recording layer 5, the thermal diffusion layer 3 and the first dielectric layer 4
The second dielectric layer 6 formed so as to cover the second dielectric layer 6 can also be obtained.

When each of the above layers is formed, the target 10 and the mask 12 in the vacuum chamber 13 are exchanged each time each layer is formed by using one vacuum chamber 13. Although vacuuming may be performed to perform sputtering, a dedicated vacuum chamber 13 for forming each layer is prepared in a number corresponding to each layer, and the target 10 and the mask 12 are previously stored in each vacuum chamber 13. May be arranged, and the disk substrate 2 may be sequentially accommodated in these vacuum chambers 13 to perform sputtering to form each layer. Thus, a dedicated vacuum chamber 1 for forming each layer
By preparing the number 3 in accordance with each layer and sequentially performing sputtering, the time for manufacturing the magneto-optical disk 1 can be greatly reduced.

In the above description, the thermal diffusion layer 3 has a thickness of 40 nm.
And a first dielectric layer 4 having a thickness of 2
The magneto-optical recording film 5 is composed of a TbFeCo film having a thickness of about 23 nm,
Although the magneto-optical disk 1 in which the dielectric layer 6 is formed of a SiN film having a film thickness of about 80 nm has been described as an example, the material and film thickness of each layer of the magneto-optical disk 1 of the present embodiment are limited to this example. Not something.

For example, as a material of the heat diffusion layer 3 of the magneto-optical disk 1, besides Al, for example, AlTi or A
Mg, AlSi, or the like may be used. Also,
The thickness of the thermal diffusion layer 3 is not limited to the above example, but is desirably about 23 to 50 nm.

The material of the first dielectric layer 4 is as follows.
In addition to SiN, for example, ZnS or SiO ₂ may be used. Further, the thickness of the first dielectric layer 4 is not limited to the above example, but is desirably about 15 to 35 nm.

The material of the magneto-optical recording layer 5 is T
In addition to bFeCo, for example, Cr or Ni is added to TbFeCo.
And additives such as DyFeCo, GdFeCo
Or an alloy film of these.
The film thickness of the magneto-optical recording layer 5 is not limited to the above example, but is desirably about 15 to 120 nm. The magneto-optical recording layer 5 is formed by sputtering using an alloy target.
It may be formed by simultaneous sputtering using targets such as Tb, Dy, Gd, Fe, Co, and FeCo.

The material of the second dielectric layer 6 is as follows.
In addition to SiN, for example, ZnS or SiO ₂ may be used. Further, the thickness of the second dielectric layer 6 is not limited to the above example, but may be 40 to 110 nm.
It is desirable that the degree is about.

The power source for sputtering when forming the above layers may be either DC or RF.

[0040]

EXAMPLES In order to confirm the effects of the present invention, the following experiments were conducted. That is, a plurality of magneto-optical disks were actually produced while varying the sizes of a plurality of layers such as a signal recording layer formed on a substrate, and the relationship between the size of each layer and the state of corrosion was examined.

(Preparation of Magneto-Optical Disk) First, an Al target and a mask having a circular opening are set in a vacuum chamber. Then, a disk substrate made of polycarbonate is accommodated in the vacuum chamber, and the inside of the vacuum chamber is evacuated to about 5 × 10 ⁻⁵ Pa. Then, an Ar gas is introduced into the vacuum chamber at a gas pressure of about 0.2 to 0.8 Pa, and sputtering is performed using an Al target to form a thermal diffusion layer made of an Al film of about 40 nm.

Next, a Si target and a mask having a circular opening are set in a vacuum chamber. Then, the disk substrate on which the thermal diffusion layer is formed is housed in the vacuum chamber, and N ₂ gas is introduced into the vacuum chamber in addition to Ar gas, and the gas pressure is set to about 0.1 to 0.7 Pa. I do. Then, a first dielectric layer made of a SiN film of about 20 nm is formed by performing reactive sputtering using a Si target. In addition to forming the SiN film by reactive sputtering using a Si target, the SiN film may be formed by sputtering using a SiN target.

Next, a target of TbFeCo and a mask having a circular opening are set in the vacuum chamber.
Then, the disk substrate on which the heat diffusion layer and the first dielectric layer are formed is accommodated in the vacuum chamber, and the inside of the vacuum chamber is evacuated again to about 5 × 10 ⁻⁵ Pa.
Then, Ar gas is introduced into the vacuum chamber at a gas pressure of about 0.1 to 0.8 Pa, and sputtering is performed with a TbFeCo target to form a TbFe of about 23 nm.
A magneto-optical recording layer made of a Co film is formed.

Next, an Si target and a mask having a circular opening are set in a vacuum chamber. Then, the disk substrate on which the heat diffusion layer, the first dielectric layer and the magneto-optical recording layer are formed is accommodated in the vacuum chamber, and N ₂ gas is introduced into the vacuum chamber in addition to Ar gas, The pressure is set to about 0.1 to 0.7 Pa. Then, reactive sputtering using a Si target is performed to 80 nm.
A second dielectric layer made of a SiN film is formed. In addition, the reactive sputtering by the Si target
Instead of forming the N film, the SiN film may be formed by sputtering using a SiN target.

By the above method, 18 magneto-optical disks were manufactured. In each magneto-optical disk, the area of each layer formed on the disk substrate is made different by changing the opening diameter of the opening of the mask.

(Situation of Corrosion) The 18 magneto-optical disks prepared as described above were placed in a thermostat at a temperature of 80 ° C. and a humidity of 85%, and the occurrence of corrosion was observed. Table 1 shows the results
Shown in In Table 1, d1 indicates the diameter of the film formation surface of the thermal diffusion layer, d2 indicates the diameter of the film formation surface of the first dielectric layer, and d3 indicates the diameter of the film formation surface of the magneto-optical recording layer. Indicates that
d4 indicates the diameter of the deposition surface of the second dielectric layer. Then, ◎ indicates that there was no defect due to corrosion having a size of 30 μm or more, も の indicates that a slight defect was observed, and X indicates that other defect was observed.

[0047]

[Table 1]

From the results shown in Table 1, the magneto-optical disks (1) to (5), (9), (10), and (10) formed with the second dielectric layer covering the magneto-optical recording layer 13), (1
In 5) and (17), it was found that the generation of defects due to corrosion was suppressed.

Also, magneto-optical disks (2), (3), (5) in which the second dielectric layer covers the heat diffusion layer and the first dielectric layer in addition to the magneto-optical recording layer ), (9),
In (10), (13), and (17), the generation of defects due to corrosion is further suppressed. In particular, each layer of a heat diffusion layer, a first dielectric layer, a magneto-optical recording layer, and a second dielectric layer Is d1 ≦ d2
≦ d3 <d4, a magneto-optical disk (2),
In (3) and (5), it was found that no defect due to corrosion was observed at all.

Although a slight defect was observed in the magneto-optical disks (4) and (15), it was found that the defect was caused by dust and was very small. Was. It is possible to suppress the occurrence of the small defect caused by the inclusion of dust by adjusting the film forming conditions and the like.

On the other hand, magneto-optical disks (1), (6), (7), (8), (11), and (2) are not formed so that the second dielectric layer covers the magneto-optical recording layer. (1
In 2), (14), (16) and (18), it was found that the generation of defects due to corrosion was not suppressed.

From the above results, in the magneto-optical disk according to the present invention, since the second dielectric layer is formed so as to cover the magneto-optical recording layer, the occurrence of corrosion is suppressed and the durability is improved. Was found to be achieved.

Although the experiment using the magneto-optical disk using the magneto-optical recording film for the signal recording layer has been described above, the magneto-optical disk using the phase-change recording film for the signal recording layer also has a magneto-optical disk. It was confirmed that the same result as that of the disk was obtained.

[0054]

According to the optical recording medium of the present invention, at least one of a plurality of layers formed on a substrate in a vacuum chamber, which is formed above a signal recording layer, has at least a signal recording layer. , Corrosion is suppressed and durability is improved.

[Brief description of the drawings]

FIG. 1 is a sectional view of a main part of a magneto-optical disk.

FIG. 2 is a sectional view of an essential part showing an outer edge of the magneto-optical disk.

FIG. 3 is a schematic view of a vacuum chamber used for sputtering.

[Explanation of symbols]

REFERENCE SIGNS LIST 1 magneto-optical disk, 2 disk substrate, 3 thermal diffusion layer, 4 first dielectric layer, 5 magneto-optical recording layer, 6 second
Dielectric layer, 10 targets, 11 openings, 12
Mask, 13 vacuum chamber

Claims (3)

[Claims] 1. An optical recording medium in which a signal recording layer is irradiated with light to reproduce or record / reproduce an information signal, wherein a plurality of layers including the signal recording layer formed on a substrate in a vacuum chamber are provided. An optical recording medium comprising: a plurality of layers, wherein at least one layer formed above the signal recording layer is formed so as to cover at least the signal recording layer. 2. The method according to claim 1, wherein at least a heat diffusion layer is provided on the substrate.
Wherein the dielectric layer, the signal recording layer, and the second dielectric layer are formed in this order, and the second dielectric layer is formed so as to cover at least the signal recording layer. The optical recording medium according to claim 1, wherein 3. The optical device according to claim 1, wherein the second dielectric layer is formed so as to cover at least the heat diffusion layer, the first dielectric layer, and the signal recording layer. recoding media.