JPH1092028A - Optical recording medium formed by using grooveless substrate and its manufacture - Google Patents

Abstract

PROBLEM TO BE SOLVED: To carry out the tracking servo operation by a push-pull method of an optical recording medium formed using a grooveless substrates. SOLUTION: The film of magnetic garnet added with bismuth(Bi) is formed as a recording layer 3 on the flat substrate 1 on which grooves for tracking servo do not exist. This recording layer 3 is irradiated with a laser beam to change the crystalline structure or compsn. ratio of the parts irradiated with the laser beam of the recording layers, by which the track-like regions varied in reflectivity and magnetic properties from the non-irradiated parts are formed.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an optical recording technique, and more particularly to an optical recording medium capable of forming a tracking guide track on a recording layer of an optical recording medium using a substrate having no grooves. The present invention relates to a manufacturing method thereof.

[Summary of the Invention] The present invention relates to video, audio,
Also, it is related to optical recording for recording data information etc. on optical recording media such as disks and cards. Laser recording is performed on an optical recording medium using a substrate on which tracking servo grooves are not processed. By irradiating the laser beam, the laser-irradiated portion of the recording material is transformed into a region having no perpendicular magnetization, thereby producing a track that can be used for tracking servo.

[0003]

2. Description of the Related Art In a compact disk and a magneto-optical disk which are currently in practical use, a push-pull method utilizing a phase difference of reflected light from peaks and valleys of concave and convex grooves is adopted as a tracking servo method. (For example, "Erasable Optical Disk Technology", page 195, Trikeps Co., Ltd., 1991).

[0004] In addition, a method of forming a groove in a glass substrate includes: 1) a method using a high-molecular polymer and a metal stamper, which is cured by irradiation with ultraviolet rays, called a photosensitive resin method (2P method) (for example, An easy-to-understand optical disk ", p. 172, Optronics, 1990), and 2) a direct cutting method, which is a method of directly cutting a groove in a glass substrate by ion milling.

[0005]

By the way, 600 nm
A magnetic garnet having a large signal intensity in the following wavelength range is known as a magneto-optical recording material capable of performing high-density recording by shortening a light source wavelength. However, in order to crystallize this magnetic garnet during film formation, the substrate temperature must be set at 5 ° C.
It must be at least 00 ° C (for example, T. Okuda et a
l .; IEEE Trans. Mag., MAG-23, 3491 (1987)). Even when crystallizing by heat treatment after film formation, heat treatment must be performed at 580 ° C. or more, depending on the composition ratio of bismuth (Bi) as an additive element (for example, Y. Braik and H. Le Gal).
l: J. Appl. Phys. 76, 7633 (1994)). Therefore, when garnet is used for the recording layer, the method of grooving the substrate is as follows.
There was a problem that the direct cutting method had to be used.

The present invention has been made in view of the above circumstances, and an object of the present invention is to enable tracking servo by a push-pull method on an optical recording medium using a substrate having no groove.

[0007]

In order to achieve the above object, the invention of claim 1 is to provide a recording layer comprising bismuth (Bi) as a recording layer on a flat substrate having no groove serving as a groove for tracking servo. The additive magnetic garnet is formed into a film.

According to a second aspect of the present invention, in the optical recording medium according to the first aspect, the recording layer is irradiated with a laser beam to change a crystal structure or a composition ratio of a portion of the recording layer irradiated with the laser beam. As a result, a track-shaped region having different reflectivity and magnetic properties from the non-irradiated portion is formed.

According to a third aspect of the present invention, in the optical recording medium according to the first aspect, the recording layer has a Bi composition ratio excluding oxygen (O) between 15 at.% And 45 at.%. The film is formed on the substrate using a target having the following.

According to a fourth aspect of the present invention, in the optical recording medium according to the first aspect, the optical density or the light absorptance of the recording layer in an uncrystallized state is yttrium (Y), gallium (Ga), The composition ratio including iron (Fe) and oxygen (O) and excluding oxygen (O) is Y = 46 at.%, Ga =
It is characterized by being at least 1.5 times the Bi-free film formed using a target having 13 at.% And Fe = 41 at.%.

According to a fifth aspect of the present invention, in the optical recording medium according to the first aspect, as the substrate on which the recording layer is laminated,
Quartz glass, alkali-free glass, Corning 7059,
Glass such as Corning 0317, and non-magnetic garnet or a metal such as platinum (Pt), chromium (Cr), aluminum (Al), or an alloy of these metals laminated on these glasses, or gadolinium. A single crystal such as gallium garnet (GGG) or neodymium gallium garnet (NGG) is used.

According to a sixth aspect of the present invention, bismuth (Bi), yttrium (Y) and gallium (G) are formed on a flat substrate having no groove serving as a groove for tracking servo.
a) a nonmagnetic garnet underlayer containing iron (Fe) and oxygen (O) is laminated, and then, under predetermined film forming conditions, bismuth (Bi), dysprosium (Dy),
It contains gallium (Ga), iron (Fe) and oxygen (O), and the composition ratio of each element when oxygen (O) is excluded is Bi = 38a.
t.%, Dy = 8 at.%, Ga = 13 at.%, Fe = 41 at.%
An amorphous film made of bismuth (Bi), dysprosium (Dy), gallium (Ga), iron (Fe), and oxygen (O) is formed from a sintered target such as The amorphous film is crystallized under a predetermined heat treatment condition to produce a recording layer composed of a bismuth-added magnetic garnet film, and the recording layer is irradiated with laser light under a predetermined irradiation condition to obtain a reflectance and a magnetic property. It is characterized in that a track-shaped region having a property different from that of the non-irradiated portion is formed.

According to a seventh aspect of the present invention, bismuth (Bi) and dysprosium (D) are formed on a flat substrate having no groove serving as a groove for tracking servo under a predetermined film forming condition.
y), gallium (Ga), iron (Fe), oxygen (O), and the composition ratio of each element when oxygen (O) is excluded is Bi =
32 at.%, Dy = 14 at.%, Ga = 13 at.%, Fe = 4
From a sintered target of 1 at.%, Bismuth (Bi), dysprosium (D
y), a recording layer of an amorphous film composed of gallium (Ga), iron (Fe), and oxygen (O) is prepared, and the recording layer is irradiated with laser light under predetermined irradiation conditions to obtain a reflectance and a crystal. And forming a track-shaped region whose magnetic properties after formation are different from those of the non-irradiated portion.

The method specifically used in the present invention to solve the problem will be described below. By irradiating a laser beam to an optical recording medium having a recording layer formed on a non-grooved substrate, and changing the crystal structure or the composition ratio of the laser beam-irradiated portion of the recording layer, the reflectance, and the magnetic properties are increased. A track-shaped region different from the non-irradiated portion is formed.

In order to obtain a sufficient amount of heat to change the crystal structure or the composition ratio, it is necessary to increase the light absorption or optical density of the recording layer at the wavelength of the laser to be irradiated. For that purpose, for example, the composition ratio when yttrium (Y), gallium (Ga), iron (Fe) and oxygen (O) are included and oxygen (O) is excluded is Y = 46 at.
%, Ga = 13 at.%, And Fe = 41 at.%. Bismuth (Bi), a rare earth element, gallium (Ga) exhibiting a light absorption rate or an optical density of 1.5 times or more that of a film formed from a target. A garnet film obtained by crystallizing a film containing iron (Fe) and oxygen (O) is used for the recording layer.

[0016]

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

<First Embodiment> FIG. 1 is a diagram showing a configuration of an optical recording medium used in a first embodiment according to the present invention. A substrate 1 using non-alkali glass, and a nonmagnetic garnet base film 2 containing bismuth (Bi), yttrium (Y), gallium (Ga), iron (Fe), and oxygen (O) laminated on the substrate 1 And bismuth (Bi), dysprosium (Dy), gallium (G
a), iron (Fe), oxygen (O), and the composition ratio of each element when oxygen (O) is excluded is Bi = 38 at.%, Dy =
The recording layer 3 is formed by a high-frequency sputtering method from a sintered target in which 8 at.%, Ga = 13 at.%, And Fe = 41 at.%.

<< Method of Manufacturing Optical Recording Medium (Method of Manufacturing Guide Track for Tracking) >> Next, methods of manufacturing the optical recording medium and the method of manufacturing the guide track for tracking shown in FIG. 1 are shown in Tables 1 to 3. This will be described with reference to FIG. Table 1 shows sputtering conditions when the recording layer 3 is formed on the substrate 1, Table 2 shows heat treatment conditions when the recording layer 3 is crystallized, and Table 3 shows the first embodiment. Shows the conditions for irradiating a laser beam to produce a guide track for tracking on the optical recording medium used in the above.

[0019]

[Table 1]

[Table 2]

[Table 3] First, a nonmagnetic garnet is laminated as a base film 2 on a non-alkali glass substrate 1, and bismuth (Bi), dysprosium (Dy), and bismuth (Dy) are deposited on the substrate 1 on which the base film 2 is laminated under the conditions shown in Table 1. An amorphous film made of gallium (Ga), iron (Fe), and oxygen (O) was formed. As shown in FIG. 2, the optical density of the recording layer 3 in an uncrystallized state is such that yttrium (Y), gallium (Ga), iron (Fe), oxygen (O ), And the composition ratio excluding oxygen (O) is Y = 46 at.%, Ga =
It is 1.5 times or more that of a film formed from a target with 13 at.% And Fe = 41 at.%.

Next, heat treatment was performed under the conditions shown in Table 2 to crystallize the recording layer 3 as garnet. The optical recording medium manufactured in this manner has a wavelength of 514.
When a laser beam of 5 nm was irradiated, a track having a width of 1.5 μm and showing no perpendicular magnetization was formed as a result of heat generation due to absorption. Since this region is convex on the film surface side,
It was confirmed that the reflectance itself was lower than that of the peripheral region due to scattering even when the reading light was irradiated from either the film surface side or the substrate side.

Further, it was found that when magneto-optical recording was performed on the optical recording medium shown in FIG. 1, a CN ratio of 40 dB or more was secured. Therefore, it can be understood that the difference in signal intensity between the track on which magneto-optical recording is performed and the guide track that does not exhibit perpendicular magnetization is also 40 dB or more.

<Second Embodiment> FIG. 3 is a diagram showing a configuration of an optical recording medium used in a second embodiment according to the present invention. This optical recording medium contains a substrate 4 using non-alkali glass, bismuth (Bi), dysprosium (Dy), gallium (Ga), iron (Fe), and oxygen (O), and excludes oxygen (O). When the composition ratio of each element is Bi = 32 at.%, Dy = 14 at.%, Ga = 13 a.
The recording layer 5 is composed of an amorphous film formed from a sintered target having t.% and Fe = 41 at.%.

<< Method of Manufacturing Optical Recording Medium (Method of Manufacturing Guide Track for Tracking) >> Next, a method of manufacturing the optical recording medium and a method of manufacturing the guide track for tracking shown in FIG. 3 will be described.

[0024]

[Table 4]

[Table 5] Here, Table 4 shows conditions for irradiating a laser beam in order to produce a guide track for tracking on the optical recording medium used in the second embodiment.
Indicates heat treatment conditions when the recording layer 5 of the optical recording medium used in the second embodiment is crystallized.

The conditions for forming the amorphous film constituting the recording layer 5 are the same as those shown in Table 1. That is, the substrate 1
Alkali-free glass was used as a material, and the film forming conditions (sputtering conditions) shown in Table 1 were formed on the alkali-free glass substrate 1.
It contains bismuth (Bi), dysprosium (Dy), gallium (Ga), iron (Fe), and oxygen (O), and the composition ratio of each element when oxygen (O) is excluded is Bi = 32 at.
%, Dy = 14 at.%, Ga = 13 at.%, Fe = 41 at.%
An amorphous film composed of bismuth (Bi), dysprosium (Dy), gallium (Ga), iron (Fe), and oxygen (O) is formed from a sintered target such as Layer 5 was obtained.

Next, under the conditions shown in Table 4, the wavelength is 514.5 nm.
As a result, a track having a width of 1 μm was formed, which became more convex on the film surface side than the surrounding amorphous region.
When the sample on which the tracks were printed in this manner was heat-treated under the conditions shown in Table 5, the track portions remained as convex regions not exhibiting perpendicular magnetization, and the regions other than the tracks were garnets capable of rewritable magneto-optical recording. And crystallized.

In the first embodiment and the second embodiment, in order to form a guide track for tracking, the wavelength of a laser beam applied to the optical recording medium is set to 5 wavelengths.
Although it was 14.5 nm, as shown in FIG. 2, bismuth (Bi), rare earth element, gallium (Ga), iron (F
e) The difference between the optical density of the amorphous film 5 containing oxygen (O) and the optical density of the film containing yttrium (Y), gallium (Ga), iron (Fe) and oxygen (O) is a short wavelength. Therefore, the wavelength may be 514.5 nm or less, and the laser power at this time is as shown in Table 3, that is, 13 mW,
Alternatively, it may be the value shown in Table 4, that is, 7 mW or less. When the irradiation laser power is 13 mW or 7 mW or more, the optical density of the amorphous film 5 becomes yttrium (Y),
A laser having a wavelength between 514.5 nm and 650 nm, which is twice to 1.5 times the value of a film containing gallium (Ga), iron (Fe), and oxygen (O), may be used.

Next, these grounds will be described. FIG.
As shown in (1), the laser power required for the additional recording of the amorphous film (the guide track for tracking is a spatially continuous bit at this time) is lower for a film having a higher Bi concentration and a higher optical density. . Therefore, when a laser having a wavelength of 514.5 nm or less, at which the optical density of the Bi-added film is further increased, the laser power can be low, but Bi is used.
The difference in optical density between the added film and the non-added film is reduced to 514.5n.
When using a laser with a wavelength between m and 650 nm,
The laser power must be high.

In the first and second embodiments, the Bi composition ratio of the target used for forming the recording layers 3 and 5 is set to 38 at.% And 32 at.%.
The i composition ratio may be a value between 15 at.% and 45 at.%. Bi
When the composition ratio is 0 at.%, The heat generation required for track formation cannot be obtained, and the heat treatment temperature required for crystallization becomes 800 ° C. or more, which may exceed the heat resistant temperature of the glass used for the substrate. We have a target Bi composition ratio of 25a
At t.%, a garnet single-phase film was obtained without damaging the alkali-free glass substrate by heat treatment at 750 ° C. for 1 hour. Considering these facts, the lower limit of the Bi composition ratio of the target is set to 15 at.%.

In the first and second embodiments, the non-alkali glass is used as the substrate, but quartz glass, Corning 0317 and Corning 7 are used.
059, etc., and the underlying film at this time is not only non-magnetic garnet but also platinum (P
t), metals such as chromium (Cr) and aluminum (Al), or alloys thereof. Alternatively, a single crystal such as gadolinium gallium garnet (GGG) or neodymium gallium garnet (NGG) may be used as the substrate.

As described above, according to the embodiments of the present invention, tracks having no perpendicular magnetization and having a low reflectivity are arranged at intervals by the width of a track for performing magneto-optical recording. Even when a flat substrate without grooves is used, it is possible to manufacture a magneto-optical recording medium capable of performing tracking servo by the push-pull method.

Further, the optical recording medium is placed on the apparatus for evaluating the dynamic characteristics of the optical recording medium, and a laser of a recording / reproducing light source is irradiated on the optical recording medium to form a guide track for tracking on the recording layer itself. Therefore, according to the present embodiment, an ion milling device for direct cutting,
Since the process of applying the photoresist in the 2P method and the curing process using ultraviolet rays are not required, the process of manufacturing the substrate for the optical recording medium can be simplified, and the ratio of the substrate processing cost to the cost of the optical recording medium can be reduced.

[0033]

As described above, according to the present invention, tracks having no perpendicular magnetization and having a low reflectance are arranged at intervals by the width of a track for performing magneto-optical recording. Accordingly, even when a flat substrate having no groove is used, an optical recording medium capable of performing tracking servo by the push-pull method can be manufactured.

Further, according to the present invention, since an ion milling apparatus for direct cutting, a photoresist coating in the 2P method, and a curing process by ultraviolet rays are not required, the process of manufacturing a substrate for an optical recording medium is simplified. In addition, the ratio of the substrate processing cost to the cost of the optical recording medium can be reduced.

[Brief description of the drawings]

FIG. 1 is an explanatory diagram showing a structure of an optical recording medium used in a first embodiment of the present invention.

FIG. 2 is an explanatory diagram showing the light source wavelength dependence of the optical density of an amorphous film containing Bi, a rare earth element, Ga, Fe, and O.

FIG. 3 is an explanatory diagram showing a structure of an optical recording medium used in a second embodiment of the present invention.

FIG. 4 is an explanatory diagram showing the recording power dependence of the CN ratio when write-once optical recording is performed on an amorphous film with light having a wavelength of 514.5 nm.

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 1 Substrate 2 Underlayer film (non-magnetic garnet film) 3 Recording layer (bismuth-added magnetic garnet film) 4 Substrate (alkali-free glass) 5 Recording layer (amorphous film)

──────────────────────────────────────────────────の Continued on the front page (51) Int.Cl. ⁶ Identification code FI G11B 7/24 511 G11B 7/26 7/26 B41M 5/26 X

Claims (7)

[Claims] 1. An optical recording medium characterized in that a magnetic garnet containing bismuth (Bi) is formed as a recording layer on a flat substrate on which no groove serving as a groove for tracking servo is present. 2. The optical recording medium according to claim 1, wherein the recording layer is irradiated with a laser beam, and the crystal structure or the composition ratio of a portion of the recording layer irradiated with the laser beam is changed, so that the reflectance and the reflectance are improved. An optical recording medium characterized by forming a track-shaped region having a magnetic property different from that of a non-irradiated portion. 3. The optical recording medium according to claim 1, wherein the recording layer uses a target having a Bi composition ratio excluding oxygen (O) between 15 at.% And 45 at.%. An optical recording medium, wherein the optical recording medium is formed on the substrate. 4. The optical recording medium according to claim 1, wherein the optical density or the optical absorptance of the recording layer in an uncrystallized state is yttrium (Y), gallium (Ga), iron (F).
e) and oxygen (O), and excluding oxygen (O), the composition ratio is Y = 46 at.%, Ga = 13 at.%, Fe =
B deposited using a target such as 41 at.
An optical recording medium characterized by being 1.5 times or more the thickness of the i-free film. 5. The optical recording medium according to claim 1, wherein the substrate on which the recording layer is laminated is quartz glass, non-alkali glass, Corning 7059, and Corning 031.
7 or a nonmagnetic garnet, a metal such as platinum (Pt), chromium (Cr), aluminum (Al), or an alloy of these metals, or gadolinium gallium -An optical recording medium using a single crystal such as garnet (GGG) or neodymium gallium garnet (NGG). 6. A nonmagnetic material containing bismuth (Bi), yttrium (Y), gallium (Ga), iron (Fe), and oxygen (O) on a flat substrate having no grooves serving as tracking servo grooves. Then, under predetermined film forming conditions, bismuth (Bi), dysprosium (Dy), gallium (G)
a), containing iron (Fe) and oxygen (O), and excluding oxygen (O), the composition ratio of each element is Bi = 38 at.%, Dy = 8
Bismuth (Bi), dysprosium (Dy), gallium (G) were obtained from a sintered target having at.%, Ga = 13 at.%, and Fe = 41 at.% by a high frequency sputtering method.
a) An amorphous film made of iron (Fe) and oxygen (O) is formed, and then the amorphous film is crystallized under a predetermined heat treatment condition to form a recording layer made of a bismuth-added magnetic garnet film. And irradiating the recording layer with a laser beam under predetermined irradiation conditions to form a track-shaped region having a reflectance and a magnetic property different from those of the non-irradiated portion. . 7. Bismuth (Bi), dysprosium (Dy), gallium (Ga), iron (Fe), oxygen on a flat substrate having no groove serving as a groove for tracking servo under a predetermined film forming condition. (O), containing oxygen (O)
When the composition ratio of each element is Bi = 32 at.%, Dy
= 14 at.%, Ga = 13 at.%, And Fe = 41 at.%, Bismuth (Bi), dysprosium (Dy), gallium (Ga), iron (Fe), A recording layer of an amorphous film made of oxygen (O) is formed, and the recording layer is irradiated with a laser beam under predetermined irradiation conditions to obtain a track whose reflectance and magnetic properties after crystallization are different from those of the non-irradiated part. Forming an optical recording medium.