JP2001126313A - Optical information recording medium and method for producing same - Google Patents

Abstract

PROBLEM TO BE SOLVED: To obtain a carbon protective layer excellent in wear and corrosion resistances and less liable to absorb light. SOLUTION: At least a recording-reproducing layer and a carbon protective film are successively laminated on a substrate to obtain the objective optical information recording medium in which information is recorded and reproduced by irradiation with light from the protective film side. The extinction coefficient of the carbon protective film at 300-500 nm wavelength is <=0.1. The protective film contains hydrogen and has 25-30 at.% hydrogen content. The recording- reproducing layer is, e.g. a magneto-optical recording layer. The carbon protective film is formed by DC sputtering using carbon as a target in an inert gaseous atmosphere containing 10-15% gaseous hydrogen or gaseous hydrocarbon.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an optical information recording medium and a method for manufacturing the same, and more particularly to an improvement in a method for forming a carbon protective film.

[0002]

2. Description of the Related Art For example, components requiring a large number of slidable properties, such as industrial machines and various devices, are required to have properties such as wear resistance, heat resistance, and corrosion resistance. In particular, as the speed of these machines and devices has increased, the sliding parts have been operating at higher speeds with respect to other members, this requirement has become even stronger.

[0003] In order to satisfy these requirements, a protective film made of ceramics or the like formed on the surface of a sliding component has been eagerly developed.

[0004] This also applies to the field of information recording such as a magnetic recording medium such as a magnetic disk and a magnetic tape included in a hard disk drive, and an optical information recording medium such as a magneto-optical disk and a phase change disk.

[0005] The magnetic recording medium has a laminated film in which a signal recording layer made of a magnetic recording material is laminated on a substrate or a film, and a magnetic head reads and writes information signals from the signal recording layer side. Will be

In these magnetic recording media, high recording densities have been actively promoted in order to record as much information as possible.

With the increase in the density of the magnetic recording medium, the flying height of the flying magnetic head with respect to the magnetic recording medium is decreasing year by year. Therefore, there is a possibility that the magnetic recording medium may be damaged or worn due to collision or contact between the flying magnetic head and the magnetic recording medium. To prevent this, a carbon protective film is used as a protective film on the outermost surface of the magnetic recording medium.

On the other hand, 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, and the signal recording layer is irradiated with light. As with magnetic recording media, high recording densities are also being actively studied in optical information recording media in which information signals are read and written.

With the increase in the recording density of the optical information recording medium, the optical spot for irradiating the signal recording layer with respect to the optical head for reading and writing the information signal from and to the optical information recording medium is also required. Various studies have been made to reduce the diameter.

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

The floating type optical head is floated so as to face the laminated film formed on the substrate of the optical information recording medium to read and write information signals, thereby recording the signal between the objective lens and the optical information recording medium. The distance from the layer can be greatly reduced as compared with the case where the 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.

When the light from the conventional optical head is applied to the signal recording layer through the substrate, the distance between the objective lens and the signal recording layer of the optical information recording medium is long, and the optical head and the optical information recording medium have to be long. Collision or contact with the medium is not a problem. Also, even if the optical head and the optical information recording medium collide or come into contact with each other, since the optical head is installed so as to be opposed from the substrate side, damage or wear to the laminated film itself does not occur. Absent.

On the other hand, when reading and writing information signals by floating the flying optical head so as to face the laminated film of the optical information recording medium, the distance between the objective lens and the signal recording layer of the optical information recording medium is increased. Since the length is greatly shortened, there is a problem that the laminated film is damaged or worn due to collision or contact between the floating optical head and the laminated film.

For this reason, it has been studied to use a carbon protective film on the outermost surface of the laminated film of the optical information recording medium by applying the technology of the protective layer of the magnetic recording medium.

[0015]

However, although the conventional carbon protective film has sufficient mechanical strength to withstand collision or contact with the magnetic head, it is not suitable for optical information recording media. Are dissatisfied with respect to the transmittance of light emitted from the floating optical head.

In particular, when the wavelength of the recording / reproducing light is shortened in order to further increase the recording density, the light transmittance sharply decreases,
The lack of light transmittance is a significant problem.

Accordingly, the present invention is to provide an optical information recording medium which realizes a carbon protective layer which is excellent in abrasion resistance and corrosion resistance and has little light absorption, and which can cope with high recording density. Aim. Furthermore, the present invention provides a technique for forming a carbon protective film having less light absorption as described above,
An object of the present invention is to provide a method for manufacturing an optical information recording medium that can cope with high recording density.

[0018]

In order to achieve the above object, an optical information recording medium of the present invention comprises at least a recording / reproducing layer and a carbon protective film sequentially laminated on a substrate,
In an optical information recording medium for recording and / or reproducing information by irradiating light from the carbon protective film side, the carbon protective film has an extinction coefficient at a wavelength of 300 nm to 500 nm of 0.1 or less. Things.

Further, according to the manufacturing method of the present invention, there is provided a method for manufacturing an optical information recording medium in which at least a recording / reproducing layer and a carbon protective film are sequentially formed on a substrate. A film is formed by direct current (DC) sputtering using carbon as a target in an inert gas atmosphere containing a gas.

When a carbon protective film is formed, direct current sputtering is adopted, and the ratio of hydrogen gas or hydrocarbon gas contained in an inert gas atmosphere is set to an appropriate value, so that it can be used even in a short wavelength region. A film with a small extinction coefficient and excellent light transmittance is obtained.

Specifically, the wavelength of the carbon protective film is 300
The extinction coefficient at nm to 500 nm can be 0.1 or less. Such light transmission has never been realized before.

In an optical information recording medium having such a carbon protective film, when recording or reproduction is performed by irradiating light from the carbon protective film side, the carbon protective film does not adversely affect the signal characteristics, thus impairing signal characteristics. The abrasion resistance is improved without.

[0023]

DESCRIPTION OF THE PREFERRED EMBODIMENTS Hereinafter, an optical information recording medium to which the present invention is applied and a method for manufacturing the optical information recording medium will be described 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 of a resin material and formed into a disk shape will be described. The present invention is not limited to this example. For example, the present invention is applicable to other optical information recording media having different recording methods, such as a phase change type disc that records and reproduces a signal using a phase change. Is also possible.

A 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 has a surface on a disk substrate 2 reversely sputtered, and then a base layer 3, a thermal diffusion layer 4, a second dielectric layer 5, and a magneto-optical disk. The recording layer 6, the first dielectric layer 7, and the carbon protective film 8 are laminated in this order.

Further, in the magneto-optical disk 1, the first dielectric layer 7 includes the dielectric layer 7A and the dielectric protection layer 7A.
It is desirably formed of a two-layer film of B and B. Also,
In the case of a magneto-optical disk whose recording film is optically sufficiently thick, as in the case of using magnetic super-resolution, for example, the second dielectric layer 5 may be better not provided.

The disk substrate 2 is formed by molding a resin material such as ZEONEX or polycarbonate into a disk shape by a technique such as injection molding.

The surface of the disk substrate 2 is reverse-sputtered before each layer of the recording film is formed. This reverse sputtering has a function of improving the adhesion between the disk substrate 2 and the underlayer 3.

The underlayer 3 serves to reduce the corrosion of the disk by suppressing the moisture from the disk substrate 2 from reaching the thermal diffusion layer 4 or the second dielectric layer 5 and the magneto-optical recording layer 6. For example, a film of SiO ₂ or SiN having a thickness of about 10 nm is formed.

The thermal diffusion layer 4 controls the size of the recording mark of the magneto-optical recording layer 6 by diffusing the heat generated by irradiating the magneto-optical recording layer 6 with light.
This is for improving the recording / reproducing characteristics. For example, an Al film having a thickness of about 40 nm is formed.

The magneto-optical recording layer 6 is a layer exhibiting a magneto-optical effect. For example, a TbFeCo film using Tb as a rare earth element and Fe or Co as a transition metal is formed on the thermal diffusion layer 4 to a thickness of about 20 nm. It is formed into a film. Note that a second dielectric layer 5 made of SiN or the like and having a thickness of about 20 nm for the purpose of optical enhancement may be interposed between the thermal diffusion layer 4 and the magneto-optical recording layer 6.

The dielectric layer 7A constituting the first dielectric layer 7
Is for improving the optical efficiency of the magneto-optical disk 1. For example, SiN is formed on the magneto-optical recording layer 6 to a thickness of about 30 nm, and a dielectric protection layer is further formed thereon. ZnS.SiO _{2 of} 7B is formed to a thickness of about 60 nm. As described above, the first dielectric layer 7 is formed by the dielectric layer 7A (SiN) and the dielectric protection layer 7B (ZnS.Si).
By using a two-layer film of O ₂ ), the thickness can be made smaller than in the case where the first dielectric layer 7 is made of a single SiN layer, and there is an effect of reducing stress. Further, by reducing the film thickness, there is also an effect of improving tact.

The carbon protective film 8 is for improving the resistance to damage and abrasion of the magneto-optical disk 1 at the time of collision or contact with the flying optical head.
It is formed on the dielectric protection layer 7B with a thickness of about 0 nm.

In the magneto-optical disk 1 of the present invention, the carbon protective film 8 has a wavelength of 300 nm to 500 nm.
The extinction coefficient at m is 0.1 or less.

By providing such a carbon protective film 8, not only the damage and wear of the magneto-optical disk 1 at the time of collision or contact with the flying optical head can be suppressed, but also the light of the carbon protective film 8 can be suppressed. Since the absorption is small, the signal characteristics of the magneto-optical disk 1 can be improved at the same time. Therefore, for example, light having a wavelength of 300 nm to 500 nm can be used as the recording / reproducing light.

The carbon protective film 8 contains hydrogen, and its content is preferably 25 to 30 atomic%. If the content of hydrogen exceeds 30 atomic%, the hardness decreases rapidly and the extinction coefficient also increases rapidly. vice versa,
When the content of hydrogen is less than 25 atomic%, the extinction coefficient sharply increases again, and becomes the largest when the flow ratio of hydrogen gas and hydrocarbon gas in the inert gas atmosphere is 0%.

The carbon protective film 8 as described above can be formed by direct current (DC) sputtering with controlled atmosphere.

That is, it can be formed by DC sputtering in an inert gas atmosphere containing hydrogen gas or hydrocarbon gas.

At this time, examples of the carrier gas (inert gas) include Ar gas, Ne gas, Xe gas, and Kr gas.
An inert gas such as a gas can be used.

As the hydrocarbon gas, a hydrocarbon gas such as methane, ethylene, acetylene, and propane can be used. Furthermore, it is also possible to use a mixed gas of hydrogen gas and hydrocarbon gas.

At the time of film formation, the ratio of hydrogen gas or hydrocarbon gas in the inert gas atmosphere needs to be properly set, and the flow rate ratio of the hydrogen gas and the hydrocarbon gas in the inert gas atmosphere is 10 to 15%. And

By satisfying these conditions, it is possible to realize a carbon protective film having an unprecedented light transmittance.

For example, in high frequency (RF) sputtering, the extinction coefficient at a wavelength of 300 nm to 500 nm cannot be made 0.1 or less even if the ratio of hydrogen or hydrocarbon is 10 to 15%. In RF sputtering, a decrease in the extinction coefficient is observed in the direction of increasing the ratio of the hydrogen gas. In this case, however, the hardness is reduced. Cannot be less than 0.1.

In DC sputtering, the light transmittance is sharply improved at a specific hydrogen gas ratio, and the hardness is maintained at a high level.

Each of the layers formed on the disk substrate 2 is formed by sequentially forming the materials constituting these layers on the disk substrate 2 by a thin film forming method such as sputtering.

The material and thickness of each layer of the magneto-optical disk 1 are not limited to this example.

For example, as a material of the thermal diffusion layer 4 of the magneto-optical disk 1, in addition to Al, for example, AlTi, AlMg,
AlSi, AgPdCu or the like may be used.
The thickness of the thermal diffusion layer 4 is not limited to the above example, but is desirably about 23 to 50 nm.

The material of the second dielectric layer 5 is S
In addition to iN, for example, ZnS.SiO ₂ , SiO _2, or the like may be used, or may be omitted.

The material of the magneto-optical recording layer 6 is TbFe
In addition to Co, for example, a material obtained by adding an additive such as Cr or Ni to TbFeCo, DyFeCo, GdFeCo, or an alloy film thereof may be used. Further, the thickness of the magneto-optical recording layer 6 is not limited to the above example, but is desirably about 15 to 120 nm. The magneto-optical recording layer 6 is formed by sputtering using an alloy target.
It may be formed by simultaneous sputtering using targets such as b, Dy, Gd, Fe, Co, and FeCo.

Further, the magneto-optical recording layer 6 is a multilayer film composed of a plurality of magneto-optical recording films having different properties or a multilayer film other than the magneto-optical recording film to perform magnetic super-resolution and magnetic domain expansion reproduction. What you do may be.

The thickness of the dielectric layer 7A constituting the first dielectric layer 7 is not limited to the above example.
It is desirable that the thickness be about 10 to 30 nm.

The power source for sputtering for forming each of the above layers may be either a DC power source or a high frequency power source except for the carbon protective film 8.

[0054]

The present invention will be described below with reference to specific experimental examples.

Experiment 1 In this experiment, a carbon protective film was prepared by varying the flow ratio of Ar gas and hydrogen gas in each of DC sputtering and high frequency sputtering, and the wavelength dependence of the extinction dispersion k of the formed carbon protective film was determined. The sex was examined.

First, a carbon target was set in a vacuum chamber. And, in this vacuum chamber, Si
After accommodating the substrate and evacuating to 1 × 10 ⁻⁵ Pa, hydrogen gas was introduced into the vacuum chamber in addition to Ar gas, and the gas pressure was set to about 0.5 Pa. And 1
DC power or high-frequency power of kW was applied to perform DC sputtering and high-frequency sputtering with a carbon target to form a carbon protective film having a thickness of about 200 nm.

FIG. 2 shows the result of measurement of the extinction coefficient k of the carbon protective film produced by DC sputtering, and FIG. 3 shows the result of measurement of the extinction coefficient k of the carbon protective film produced by high frequency sputtering. Extinction extinction is 300 wavelength
The measurement was performed centering on light of nm to 600 nm.

As is clear from comparison of these figures,
It can be seen that the carbon protective film produced by direct-current sputtering has extremely low light absorption at an appropriate flow ratio of Ar gas and hydrogen gas.

FIG. 4 shows the results of analyzing the hydrogen content in the carbon protective film formed by DC sputtering. As the hydrogen gas flow ratio increases, the hydrogen content in the carbon protective film also increases. At the appropriate hydrogen gas flow ratio (10 to 15%), the hydrogen content in the carbon protective film becomes 25%. -30 atomic%.

Experiment 2 In this experiment, as an example to which the present invention was applied, a magneto-optical disk in which a carbon protective film was formed by DC sputtering in an inert gas (Ar gas) atmosphere containing hydrogen gas was produced, and a magneto-optical disk was produced. The signal characteristics of the disk were measured.

First, a disk substrate made of Zeonex was set in a vacuum chamber. Ar gas is introduced into the vacuum chamber at a gas pressure of about 0.2 to 0.8 Pa,
Reverse sputtering of the disk substrate was performed.

Next, an SiO ₂ target was set in the vacuum chamber. Then, the disk substrate subjected to reverse sputtering is accommodated in this vacuum chamber, and 0.2 to 0.8
Ar gas was introduced at a Pa of about gas pressure, to form a base layer made of about 10nm in thickness of the SiO ₂ film by performing a sputtering by SiO2 target.

Subsequently, an AlMg target was set in the vacuum chamber. Then, after accommodating the disk substrate on which the underlayer is formed in the vacuum chamber, 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 AlMg target. A heat spreading layer made of an AlMg film having a thickness of about 40 nm was formed.

Next, a Si target was set in the vacuum chamber. Then, the disk substrate on which the base layer and the thermal diffusion layer are formed is accommodated in the vacuum chamber, and N ₂ gas is introduced in addition to Ar gas, and the gas pressure is adjusted to 0.1 to 0.7 P.
After setting the thickness to about a, the second dielectric layer made of SiN having a thickness of about 20 nm was formed by performing reactive sputtering using a Si target. In addition, in addition to forming SiN by reactive sputtering using a Si target,
SiN may be formed by sputtering with an N target.

Further, TbFeCo is placed in a vacuum chamber.
Was set up. Then, the disk substrate on which the underlayer, the thermal diffusion layer and the second dielectric layer are formed is accommodated in this vacuum chamber, and the inside of the vacuum chamber is again filled with 5 × 10
^It was evacuated to about ^-5 Pa. In this state, Ar gas was introduced into the vacuum chamber at a gas pressure of about 0.1 to 0.8 Pa, and sputtering was performed with a TbFeCo target to form a TbFeCo film having a thickness of about 20 nm as a magneto-optical recording layer.

Next, the Si target was set in the vacuum chamber again. Then, the disk substrate on which the underlayer, the thermal diffusion layer, the second dielectric layer, and the magneto-optical recording layer are formed is housed in the vacuum chamber, and N ₂ gas is added in addition to Ar gas.
Gas was introduced and the gas pressure was set at about 0.1 to 0.7 Pa. Then, a dielectric layer made of a SiN film having a thickness of about 30 nm was formed as a dielectric layer constituting the first dielectric layer by performing reactive sputtering using a Si target. Note that, other than forming SiN by reactive sputtering using a Si target, an SiN film may be formed by sputtering using a SiN target.

Subsequently, ZnS.Si is placed in a vacuum chamber.
An O ₂ target was set. Then, the disk substrate on which the dielectric layers of the underlayer, the thermal diffusion layer, the second dielectric layer, the magneto-optical recording layer and the first dielectric layer are formed is accommodated in the vacuum chamber, and Ar gas is introduced. , The gas pressure is 0.1-0.
It was set to about 7 Pa. Then, to form a ZnS · SiO ₂ film having a thickness of about 60nm performing sputtering with ZnS · SiO ₂ target as dielectric protective layer constituting the first dielectric layer.

Finally, a carbon target was set in the vacuum chamber. The underlayer, the thermal diffusion layer, the second dielectric layer, the magneto-optical recording layer, and the first
The disk substrate on which the dielectric layer (dielectric layer + dielectric protective layer) was formed was housed, and hydrogen gas was introduced in addition to Ar gas, and the gas pressure was set to about 0.5 Pa. And 1k
DC power of W was applied to perform DC sputtering with a carbon target to form a carbon protective film having a thickness of about 10 nm.

When the signal characteristics of the magneto-optical disk were measured, the extinction coefficient k of the carbon protective film was 3 wavelengths.
It was 0.1 or less in the range of 00 nm to 500 nm, and the same signal characteristics as those without forming the carbon protective film were obtained.

For comparison, a similar measurement was attempted on a magneto-optical disk on which a carbon protective film was formed by RF sputtering, but the extinction coefficient k of the carbon protective film exceeded 0.1 at a wavelength of 300 nm to 500 nm.
Sudden deterioration of signal characteristics was observed.

[0071]

As is apparent from the above description, according to the present invention, it is possible to obtain a carbon protective film having excellent wear resistance and corrosion resistance and sufficiently low light absorption.

Therefore, even in an optical information recording medium in which a flying type optical head is floated so as to face a laminated film formed on a substrate to perform recording / reproduction, abrasion resistance and corrosion resistance can be greatly improved. It is possible to read and write information signals without deteriorating optical characteristics.

[Brief description of the drawings]

FIG. 1 is a schematic cross-sectional view of a main part showing a configuration example of a magneto-optical disk applied to the present invention.

FIG. 2 is a characteristic diagram showing a hydrogen gas flow ratio dependency of an extinction coefficient k of a carbon protective film formed by DC sputtering.

FIG. 3 is a characteristic diagram showing a hydrogen gas flow ratio dependency of an extinction coefficient k of a carbon protective film formed by high frequency sputtering.

FIG. 4 is a characteristic diagram showing an analysis result of hydrogen content in a carbon protective film produced by DC sputtering.

[Explanation of symbols]

1 magneto-optical disk, 2 disk substrate, 3 underlayer,
4 thermal diffusion layer, 5 second dielectric layer, 6 magneto-optical recording layer,
7 first dielectric layer, 7A dielectric layer, 7B dielectric protective layer, 8 carbon protective film

Continued on the front page (51) Int.Cl. ⁷ Identification symbol FI Theme coat II (reference) G11B 11/105 531 G11B 11/105 531D 546 546F (72) Inventor Makoto Watanabe 6-7-35 Kita Shinagawa, Shinagawa-ku, Tokyo No. Sony Corporation F term (reference) 5D029 LA12 LB04 LC05 LC21 5D075 EE03 FG04 GG03 GG16 5D121 AA04 EE03 EE13 EE17

Claims (6)

[Claims] 1. An optical information recording medium comprising a substrate, on which at least a recording / reproducing layer and a carbon protective film are sequentially laminated, and recording and / or reproducing information by irradiating light from the carbon protective film side. An optical information recording medium, wherein the protective film has an extinction coefficient at a wavelength of 300 nm to 500 nm of 0.1 or less. 2. The recording and / or reproducing method according to claim 1, wherein the wavelength is 300
2. The optical information recording medium according to claim 1, wherein the optical information recording medium is performed using light of nm to 500 nm. 3. The carbon protective film contains hydrogen,
2. The optical information recording medium according to claim 1, wherein the hydrogen content is 25 to 30 atomic%. 4. The optical information recording medium according to claim 1, wherein said recording / reproducing layer is a magneto-optical recording layer. 5. A method for manufacturing an optical information recording medium, wherein at least a recording / reproducing layer and a carbon protective film are sequentially formed on a substrate, wherein the carbon protective film is formed of an inert gas atmosphere containing hydrogen gas and / or hydrocarbon gas. A method for manufacturing an optical information recording medium, wherein a film is formed by DC sputtering in which carbon is used as a target. 6. The method for manufacturing an optical information recording medium according to claim 5, wherein a flow ratio of hydrogen gas and / or hydrocarbon gas in said inert gas atmosphere is 10 to 15%.