JPH05250672A - Method for positioning recording of information - Google Patents

Abstract

PURPOSE:To provide the optical recording medium which has excellent mass productivity and enables ultra-high density recording by detecting a difference in the reflectivity measured via a substrate and determining the position where information is recorded, reproduced or erased. CONSTITUTION:A metallic layer 5 having the parts of an equal refractive index concentrically or spirally with a substrate 1 is formed on the recording medium provided with a first dielectric layer 2, a magneto-optical recording layer 3 and a second dielectric layer 4 on the substrate 1. The difference in the distribution of the refractive index within the recording medium is detected and the position where the information is recorded, reproduced or erased is determined. Then, there is no need for forming guide grooves on the surface of the substrate and therefore, the recording medium is easily produced and the mass production is enabled. The information is recordable in any part of the recording medium and the control of the size of at the recording point is easily executed without receiving the interference between the tracksand, therefore, the high-density optical recording is executed.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an optical recording for recording, reproducing or erasing at least a laser beam,
In particular, it relates to a method of recording and positioning information by a simple method.

[0002]

2. Description of the Related Art The needs for a high-density and large-capacity file memory have been increasing with the progress of the advanced information society in recent years, and among them, optical recording has attracted attention as a means for meeting this. At present, it is broadly divided into a read-only type represented by a CD and a laser disc, a write-once type capable of recording only once, and a rewritable type capable of rewriting any number of times, and they are widely used in fields utilizing their respective characteristics. .. In these optical recordings, high density recording is possible because recording and reproduction are performed by using a lens to squeeze the laser light with a minute light spot. However, it is necessary to record and position the information in order to record it on the disc or reproduce the recorded information. At that time, a method of performing more precise positioning that exceeds the limit of the mechanical method has been required. 2. Description of the Related Art In current optical discs, a technique is widely used in which an uneven guide groove is provided on the surface of a substrate, light is irradiated to this portion, and the recording position of information is determined by using the interference of the generated light.

[0003]

In the above prior art, although the method is excellent, the track pitch is narrowed in order to improve the recording capacity, the mass production of the disk is taken into consideration, and further, the substrate is used. There was a limit to improving the characteristics of the disk by increasing the shape of the uneven grooves formed and the flatness of the surface.

It is an object of the present invention to provide an optical recording which is rich in mass productivity and is capable of ultra-high density recording by providing a method for determining a position for recording information by a simple method.

[0005]

The object of the present invention is achieved by providing a distribution of reflectances in a recording medium and determining the difference between them in order to determine the position where information is recorded, reproduced or erased. To be done. In particular, the reflectance distribution provided in the recording medium may be formed so that there are concentric or spiral portions having the same reflectance with respect to the disk substrate. The recording medium may have at least an information recording layer and a metal layer on the substrate, and this metal layer may be formed concentrically or spirally with respect to the disc substrate to provide a reflectance distribution in the medium. A specific manufacturing process for formation includes a mask method, a lift-off method, an ion beam method, and the like, but the effect obtained by the present invention does not depend on the manufacturing process.

Further, a dielectric layer is provided between the substrate and the information recording layer or between the information recording layer and the metal layer in order to increase the optical effect, and the difference in reflectance is further clarified to improve the tracking accuracy. Can be improved.

The information positioning method of the present invention can be applied to any of recording systems such as read-only optical recording, write-once optical recording, and rewritable optical recording such as magneto-optical recording and phase change recording. .. Further, the effect of the present invention does not depend on the recording method or the manufacturing process.

The structure of the disk is sufficient if it has at least an information recording layer and a metal layer on the substrate. The light path is such that the light incident from the substrate side passes through the information recording layer and the metal layer is formed. Therefore, there is a portion where the light is reflected and returned and a portion where the light is not transmitted and is not returned because there is no metal layer. What is important here is that the information recording layer has a film thickness capable of transmitting light having a wavelength used for recording, reproduction, or erasing and reflecting light at the metal layer.

Information recorded in a portion having a high light reflectance is
The information is included in the reflected light. Also,
The reproduction of information at a portion having a low reflectance, that is, at a portion where the metal layer is not formed includes information in the light transmitted through the disc. The part relating to the recorded information and the part relating to the tracking coexist, and may be separated at the time of reproduction or recording. Further, since the recording medium has a portion where the metal layer exists and a portion where the metal layer does not exist, the heat flow in the recording medium can be controlled, so that the size of the recording point can be easily controlled. In particular, by controlling the pitch between the part where the metal layer is present and the part where it is not present,
The size of recording points can be controlled.

[0010]

According to the present invention, since the guide grooves having irregularities are not formed, the disk can be easily manufactured. Also,
The optical system can be simplified by detecting the difference in reflectance and performing tracking. At the same time, information can be recorded on any part of the recording medium,
Since the size of the recording point can be easily controlled without receiving interference between the tracks, high density optical recording can be realized.

[0011]

EXAMPLES The present invention will be described in detail with reference to Examples 1-3.

Example 1 In this example, a substrate (glass,
Plastic etc.) / SiNx / TbFeCoNb / Si
This is a case where a recording medium of four layers of Nx / AlTi is used and the information at the recording point is reproduced from the magneto-optical type disc while tracking the change in the reflectance from the medium and performing the tracking.

FIG. 1 is a schematic view of the sectional structure of the magneto-optical disk used in this embodiment. First, a silicon nitride layer 2 having a film thickness of 550 Å was formed on a flat substrate 1 made of glass or plastic by a sputtering method. Pure silicon was used as the target and Ar / N ₂ mixed gas was used as the discharge gas. The discharge gas pressure was 10 mTorr and the input RF power density was 6.6.
Sputtering was performed at mW. Next, the magneto-optical recording film 3 was formed without breaking the vacuum. Tb ₂₄ Fe _{58 as a} target
Co ₁₅ Nb ₃ alloy, Ar is used as the discharge gas,
The discharge gas pressure was 5 mTorr, and the sputtering was performed at an input RF power density of 4.2 mW. Then, again, the silicon nitride layer 4 was formed to a film thickness of 100 Å by using the sputtering method. The sputtering conditions at that time are the same as those of the silicon nitride film 2 described above. Then, finally, the metal layer 5 was formed. Al ₇₀ Ti ₃₀ alloy was used as the target and Ar was used as the discharge gas. The discharge gas pressure was 15 mTorr and the input RF power density was 3.6 m.
Sputtering was performed with W 2. In that case, the AlTi layer was formed so as to exist concentrically using a photoresist method.

The effect of the present invention is exerted irrespective of the manufacturing method of the AlTi layer as long as the above layers are concentrically present on the disk.

With respect to the magneto-optical disk manufactured as described above in FIG. 2, after confirming that information can be positioned, information was recorded at the position where the metal layer exists. The schematic diagram of the disk drive device at that time is shown. First, the positioning of information is no different from that of the conventional disc having a concave and convex guide groove, and good tracking can be achieved. In addition, when a signal (information) is recorded at a constant cycle in a portion having a high reflectance measured through the substrate of the disc (corresponding to a portion where the metal layer is present), the recorded signal is reproduced. Code data The information could be reproduced well. When the pitch of the metal layer is 0.8 μm, it is easy to form a recording magnetic domain of 0.5 μm.
Good recording and erasing could be performed without causing interference between tracks during recording and erasing.

Example 2 In this example, a high reflectance portion (corresponding to a portion where the metal layer exists) and a low reflectance portion (where the metal layer does not exist) measured through the substrate are used. (Corresponding to the part) is the case where information is recorded in both. The structure of the disk used is the same as that of the first embodiment.

FIG. 3 shows a schematic diagram of the disk drive device used. The positioning of information was not different from that of the first embodiment as well as the conventional disc having the uneven guide groove. A signal (information) measured at a constant cycle through the substrate of the disc has a low reflectance portion (corresponding to a portion where the metal layer does not exist) and a high reflectance portion (a portion where the metal layer exists). Corresponding) both recorded. After that, when the recorded signal was reproduced, the code data information could be reproduced well. When the pitch of the metal layer is set to 0.8 μm, a recording magnetic domain of 0.5 μm can be easily formed, and good recording and erasing can be performed without causing interference between tracks during recording and erasing. It was

<Embodiment 3> In this embodiment, a dye is used for the information recording layer. FIG. 4 shows a schematic diagram of the cross-sectional structure of the disk used in this example. A phthalocyanine dye layer was formed as an information recording layer 3 on a flat glass or plastic disk substrate 1 by a spin coating method. The film thickness is about 1 μm. Next, Al ₉₀ Ta _{10 is formed} as the metal layer 5.
The alloy layer was formed by the sputtering method. Al as a target
Sputtering was performed on a ₉₀ Ta ₁₀ alloy using Ar as a discharge gas at a discharge gas pressure of 15 mTorr and an input RF power density of 3.6 mW. In that case, the lift-off method is used to
It was prepared so that the 1Ta layer existed concentrically. The effect of the present invention may be concentrically present on the disk without depending on the method of forming the AlTa layer.

With respect to the optical disc manufactured in this manner, after first confirming that information can be positioned,
Information was recorded at the location where the metal layer was present. FIG. 5 shows a schematic diagram of the disk drive device at that time. First, the positioning of information is no different from that of the conventional disc having a concave and convex guide groove, and good tracking can be achieved. In addition, after recording a signal (information) at a high reflectance portion (corresponding to a portion where the metal layer is present) measured through the substrate of the disc at a constant cycle, the recorded signal is recorded as a change in reflectance. Upon reproduction, the recorded code data information could be reproduced well. In addition, the reproduction may be performed by using the change in the light absorption wavelength of phthalocyanine after recording.
Also, when the pitch of the metal layer is 0.8 μm,
The size of the recording point was about 0.5 μm, and it was easy to form the recording point. In the case of this system, there is no particular problem even if recording is performed on both a portion having no metal layer and a portion having no metal layer. Of course, the portion where the metal layer is not formed may be reproduced by using the change of the absorption wavelength of the transmitted light or the change of the light absorptance.

[0020]

According to the present invention, a disk can be manufactured by a simple method without forming an uneven guide groove.
Mass production of disks can be achieved. Further, the optical system can be simplified by detecting the difference in reflectance and performing tracking. At the same time, information can be recorded on any part of the recording medium, and the size of the recording point can be easily controlled without receiving interference between tracks, so that high-density optical recording can be realized.

[Brief description of drawings]

FIG. 1 is a sectional view of an optical disc according to an embodiment of the present invention.

FIG. 2 is a schematic block diagram of a disk drive device used in an embodiment of the present invention.

FIG. 3 is a schematic block diagram of a disk drive device used in an embodiment of the present invention.

FIG. 4 is a sectional view of an optical disc according to an embodiment of the present invention.

FIG. 5 is a schematic block diagram of a disk drive device used in an embodiment of the present invention.

[Explanation of symbols]

1 ... Substrate, 2 ... First dielectric layer, 3 ... Magneto-optical recording layer, 4 ...
Second dielectric layer, 5 ... Metal layer.

Claims (8)

[Claims] 1. Information is recorded using at least laser light,
In optical recording for reproduction or erasure, the reflectance measured through the substrate has a distribution in its value within the disk, and more advantageously, the reflectance value is concentric, or
An information recording and positioning method characterized in that the values are spirally equal, and the position at which information is recorded, reproduced, or erased is determined by detecting the difference in reflectance. 2. The information recording and positioning method according to claim 1, wherein information is recorded at least in a portion having a low reflectance in the reflectance distribution existing in the disk. 3. The reflectivity distribution according to claim 1, wherein the structure of the recording medium has at least an information recording layer and a metal layer on a substrate, and the metal layer is formed concentrically or spirally. A method for recording and positioning information. 4. The light reflected by the information recording layer at the portion where the metal layer is present, according to claim 3,
With respect to the portion where the metal layer does not exist, the light transmitted through the information recording layer is provided with information, respectively,
Recording and reproducing information by detecting the difference in reflectance,
Alternatively, a method for recording and positioning information that has been positioned for erasing. 5. The method according to claim 1, 2, 3 or 4, wherein the information is recorded by using a magneto-optical effect or a change in reflectance associated with the formation of a recording point of the information recording layer. An information recording and positioning method using the thermomagnetic properties of the information recording layer or changes in reflectance and light absorptivity associated with phase transition. 6. A method for recording and positioning information according to claim 1, 2, 3 or 4, wherein the recording, reproducing or erasing of information is carried out by using a change in absorption wavelength of light contained in the information recording layer. 7. A film thickness according to claim 1, 2, 3, 4, 5 or 6, which is capable of transmitting at a wavelength of light used for recording, reproducing or erasing the information recording layer and reflecting light at the metal layer. A method for recording and positioning information. 8. The heat flow of the information recording layer or the entire recording medium is controlled by forming the metal layer in a concentric or spiral shape according to claim 1, 2, 3, 4, 5, 6 or 7. A method for recording and positioning information by controlling the size of recording points formed on the disc.