JPH09190652A - Magneto-optical recording medium - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a magneto-optical recording medium with which the sure execution of overwriting of information is possible. SOLUTION: This recording medium consists of at least a memory layer 5, a writing layer 6, a switching layer 7 and an initialized layer 8. These layers are exchange-bonded at room temp. to allow the overwriting of the information. At this time, test patterns for finding low level recording power are recorded on the initialized layer 8 of data track exclusive of a user data region 2.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a magneto-optical recording medium capable of overwriting information by irradiating a light beam.

[0002]

2. Description of the Related Art Conventionally, a magneto-optical recording medium has been known as an optical recording medium capable of recording / reproducing information by irradiating a light beam. The magneto-optical recording medium has the advantage that information can be rewritten any number of times, but since it is necessary to erase information by irradiating an erasing light beam and applying an erasing magnetic field before recording information, It had a drawback that the recording speed of information was slightly slow. However, this drawback has also been overcome by the invention of an overwritable magneto-optical recording medium as disclosed in JP-A-63-268103. This magneto-optical recording medium has an exchange coupling four-layer film including a memory layer, a writing layer, a switching layer and an initialization layer. Then, by controlling the recording light beam, the temperature of the recording film is switched between a temperature at which a high temperature process (or a recording process) occurs and a temperature at which a low temperature process (or an erasing process) occurs to overwrite information.

[0003]

However, in an overwritable magneto-optical recording medium, information reproduction is performed by irradiating a low energy light beam so that neither high temperature process nor low temperature process occurs. Must be irradiated under the control of information to record a light beam of high energy enough for a high temperature process and a light beam of a medium energy for a low temperature process but not a high temperature process. Therefore, when using an overwritable magneto-optical recording medium, the energy of the light beam must be controlled with higher accuracy than when erasing, recording, or reproducing information on a non-overwritable magneto-optical recording medium. I have to. In particular, in order to surely overwrite the information, the energy of the light beam must be controlled so that the low temperature process and the high temperature process do not occur at the temperature of the low temperature process portion.
As a method of finding the optimum value of the light beam energy in the low temperature process part, for example, first, after recording a test pattern, the power of the light beam for the low temperature process is changed to irradiate the test pattern to erase the pattern. There is a way to ask. However, there is a problem that the power obtained by such a method does not guarantee that the mark recorded with a power larger than the power for recording the test pattern can be erased. Furthermore, it is difficult for the drive device to detect that the mark has been completely erased.

An object of the present invention is to solve the above problems,
An object of the present invention is to provide a magneto-optical recording medium capable of surely overwriting information.

[0005]

The object of the present invention is to consist of at least a memory layer, a writing layer, a switching layer and an initialization layer, and these layers are exchange-coupled at room temperature so that information can be overwritten. In a possible magneto-optical recording medium, an overwritable magneto-optical recording medium in which a test pattern for obtaining a low level recording power is recorded in an initialization layer of a data track other than a user data area is achieved.

[0006]

BEST MODE FOR CARRYING OUT THE INVENTION Embodiments of the present invention will be described in detail in the following examples.

[0007]

Embodiments of the present invention will be described below in detail with reference to the drawings. Example 1 FIG. 1 is a schematic plan view showing an example of an optical disc of the present invention. In FIG. 1, reference numeral 1 is a magneto-optical disk having a diameter of 86 mm in which a magneto-optical recording layer is formed on a transparent substrate, and the back surface is coated with a protective layer made of an ultraviolet curable resin. The magneto-optical disk 1 has data tracks formed at a track pitch of 1.1 μm between a radius of 22.5 mm and a radius of 41.5 mm. 2 radius 23.7
The range from mm to 41.0 mm is the user data area,
User data and information for managing the user data are recorded in this area. Reference numeral 3 denotes an area in which a test pattern for obtaining a low level recording power is recorded in the initializing layer, and the track is provided on the inner circumference side and the outer circumference side of the user data area 2 for one turn. In this embodiment, areas where a test pattern for obtaining a low level recording power is recorded in the initialization layer are provided at the radial positions of the radius of 23.5 mm and the radius of 41.2 mm over the entire circumference of the disc. FIG. 2 shows an enlarged schematic view of the cross section of the region 3. Four
Is a transparent substrate, 5 is a memory layer for holding and reading information, and 6 is a small coercive force and high Curie at room temperature with respect to the memory layer 5 for transferring information to the memory layer 5 for overwriting. A writing layer having temperature, 7 is a switching layer having the lowest Curie temperature among four layers for controlling the transfer of magnetization from the initialization layer 8 to the writing layer 6, and 8 is for initializing the writing layer 6. It is an initialization layer that is magnetized in advance in a predetermined magnetization direction and has the highest Curie temperature among the four layers.
The initialization layer 8 is magnetized with a test pattern for obtaining a low level recording power. This test pattern was magnetized with the same recording method and the same format when the user data was recorded in order to facilitate detection of the low level recording power in the drive device. In this embodiment, (1,
7) After being modulated, the data was magnetized to form a repeating pattern of 6T mark-6T space. The test pattern was magnetized using a recording device capable of producing a particularly high recording power. The overwritable magneto-optical disk used in this example was rotated at 3000 rpm and a low level recording power of 3.6 mW and a high level recording of 8.5 mW were used for normal recording on a track at a radius of 23.5 mm. Low level recording power of 4.6 mW and high level recording power of 10.6 mW on the track at 41.2 mm position
You can do normal recording with. This overwritable magneto-optical disk is rotated at 3000 rpm, and a track at a radius of 23.5 mm has a low level recording power of 3.6 mW and a high level recording power of 17.5 mW for 500.
A recording magnetic field of Oe was applied to record a mark on the initialization layer by the optical modulation recording method. On the track at the radius of 41.2 mm, a recording magnetic field of 500 Oe was applied at a low level recording power of 4.6 mW and a high level recording power of 21.8 mW to record a mark on the initialization layer by the optical modulation recording method.

Next, a procedure for obtaining a low level recording power using this magneto-optical disk will be described with reference to FIGS. 3, 4 and 5. 3A is a diagram illustrating a step of initializing the memory layer, FIG. 3B is a diagram illustrating a step of transferring a test pattern to the memory layer, and FIG. 4 is a block of a procedure for obtaining a low level recording power. FIG. 5 and FIG. 5 are block diagrams of a drive device used for obtaining a low level recording power. First, step 1 of initializing the memory layer
In the region 3 where the test pattern for obtaining the low level recording power is recorded in the initialization layer of the magneto-optical disk 1, the laser is applied while applying the recording magnetic field Hw from the magnetic field applying device 14 as shown in FIG. Light is continuously emitted with high level recording power. Here, the high level recording power does not invert the initialization layer 8 and the memory layer 5
And the recording power sufficient to direct the magnetization of the writing layer 6 in the direction of the recording magnetic field Hw. This step 1
Thus, the magnetization of the memory layer 5 is uniformly arranged in the direction of the recording magnetic field Hw. At this time, the test pattern magnetized in the initialization layer 8 is transferred to the writing layer 6 by the functions of the initialization layer 8 and the switching layer 7 after passing through the laser light irradiation portion. Next, in step 2 in which the test pattern is transferred to the memory layer 5, laser light is emitted at a power lower than the high level recording power as shown in FIG. At this time, the power of laser light to be irradiated was changed for each sector. The range in which the power of the laser light is changed varies from a power smaller than the laser power assumed to transfer the test pattern to the memory layer 5 (this value is determined by the characteristics and recording linear velocity of the magneto-optical disk) to a large power. I will let you. In this embodiment, a track at a radius of 23.5 mm is changed from 2.6 mW to 4.6 mW in steps of 0.1 mW, and a radius of 41.
The track at the 2 mm position was changed from 3.6 mW to 5.6 mW in 0.1 mW steps. After irradiating the laser beam, this region is irradiated with the reproducing laser beam to try to reproduce the test pattern (step 3), and a sector from which the test pattern can be read without error is searched. To find a sector from which the test pattern can be read, the reproduction signal processing circuit 12 shown in FIG.
The same process as reading user data was performed by searching for a sector in which data recorded as a test pattern can be read without error. In step 4, the smallest recording power among the recording powers applied to the sectors from which the test pattern can be read is detected. The recording power thus obtained is the low-level recording power required to perform overwriting on this medium. If no sector where the test pattern can be read without an error is found in step 3, it means that there is no overwritable low-level recording power within the range of the laser power assumed in advance. I do. As the error processing, the range of laser power to be irradiated in step 2 is changed, and the process is repeated from step 1.
Alternatively, processing such as notifying an error and interrupting the processing may be performed. In this way, the low level recording power required for this magneto-optical disk can be obtained. In the above series of tests, the control of the laser power and the detection of the low level recording power are controlled by the CPU 13 of FIG. The drive device may perform overwriting with the value of the low level recording power thus obtained. Furthermore, in consideration of the uneven recording sensitivity of the magneto-optical disk, the focus of the drive device, the fluctuation of the track servo, the fluctuation of the temperature, etc., overwrite with a low level recording power value that is a margin added to this value at a fixed ratio. If you do, you can perform more reliable recording. Margin ratio is 1.0
It is preferably about 5 to 1.2 times. Further, by using the low-level recording power value obtained in the region where the test patterns on the inner and outer circumferences are magnetized, the low-level recording power value at other radial positions can be obtained by interpolation. Moreover,
In the above test, even if the sector irradiated with the smallest laser power in step 2 can be read out without error in step 3, there should be no overwritable low-level recording power within the range of laser power assumed in advance. Therefore, error processing may be performed in this case as well.

The above embodiment is an example of the present invention. An intermediate layer for adjusting the exchange coupling force is provided between the memory layer and the writing layer for facilitating the production of the medium, and the reproducing layer is provided. It goes without saying that other auxiliary layers not shown in the examples, such as a reproduction layer for improving the characteristics, may be provided.

[0010]

As described above, when the magneto-optical recording medium of the present invention is used, the drive device is not provided with any special detecting means, and only the data detecting mechanism normally provided in the drive device is used for the medium. A suitable low level recording power can be obtained. Therefore, it becomes possible to reliably overwrite the information.

[Brief description of the drawings]

FIG. 1 is a schematic plan view showing an optical disc which is an example of a magneto-optical recording medium of the present invention.

FIG. 2 is a schematic cross-sectional view of a region in which a test pattern for obtaining a low level recording power of the present invention is recorded.

FIG. 3A is a diagram illustrating a step of initializing a memory layer in a region for recording a test pattern,
(B) is a figure explaining the step which transfers a test pattern to a memory layer.

FIG. 4 is a block diagram of a procedure for obtaining a low level recording power according to the present invention.

FIG. 5 is a block diagram of a drive device used to obtain a low level recording power of the present invention.

[Explanation of symbols]

 1 optical disk (magneto-optical recording medium) 2 user data area 3 test pattern magnetized area 4 transparent substrate 5 memory layer 6 writing layer 7 switching layer 8 test pattern magnetized initialization layer

Claims (2)

[Claims] 1. A magneto-optical recording medium comprising at least a memory layer, a writing layer, a switching layer and an initialization layer, and these layers being exchange-coupled at room temperature so that information can be overwritten. An overwritable magneto-optical recording medium in which a test pattern for obtaining a low level recording power is recorded on an initialization layer of a data track other than the area. 2. The test pattern for determining the low level recording power recorded in the initialization layer is a pattern modulated by the same modulation method as the pattern used in the user data area. Magneto-optical recording medium.