KR100236418B1 - Magneto-optical recording medium for short wavelength - Google Patents

Abstract

The present invention relates to a short-wavelength magneto-optical recording medium. More specifically, the dielectric film 2, the recording film 3, the insulating film 4 and the reflective film 5 are sequentially formed on the substrate 1, In a magneto-optical recording medium, the recording film 3 is formed of two layers of an NdTbFeCo reproducing layer 31 and a TbFeCo recording layer 33, and between the NdTbFeCo reproducing layer 31 and the TbFeCo recording layer 33. By forming the intermediate layer 32 on the optical fiber, a shorter wavelength of the magnetoelectric recording medium is superior to the conventional recording medium, and the coercivity and the C / N ratio are hardly reduced in terms of reliability due to changes over time. will be.

Description

Short-wavelength magneto-optical recording media

1 is a schematic cross-sectional view of a conventional magneto-optical recording medium,

2 is a schematic cross-sectional view of the short wavelength magneto-optical recording medium of the present invention,

3 is a graph showing a change in the coercivity with respect to the number of repetitive reproduction times of the short wavelength magneto-optical recording medium according to the present invention and the comparative example,

4 is a graph showing a change in C / N ratio (carrier to noise ratio) according to the number of repetitive reproduction times of the short wavelength magneto-optical recording medium according to the present invention and the comparative example.

* Explanation of symbols for main parts of the drawings

1, 11 substrate 2, 21 dielectric film

3: recording film 31: reproduction layer

32: intermediate layer 33: recording layer

4, 41 insulation film 5, 51 reflection film

The present invention relates to a short-wavelength magneto-optical recording medium, and more particularly, to manufacturing a recording film which is a magnetic film of a magneto-optical recording medium, comprising a two-layer film for recording and a reproducing layer for magneto-optical effects. Therefore, the present invention relates to a short wavelength magneto-optical recording medium having excellent recording and reproducing characteristics even with a short wavelength laser.

A magneto-optical recording medium is an apparatus for recording and reproducing information. The magneto-optical characteristic is used for information recording and the magneto-optical characteristic for information reproducing.

Magneto-optical recording is a technique for recording, reproducing, and erasing information by forming a perpendicular magnetization film on a substrate and irradiating a laser beam on the recording film to form a magnetic domain in which the recording film is parallel or antiparallel to the vertical direction. In other words, when the integrated laser light is irradiated onto the recording film of the magneto-optical recording medium, the temperature is locally raised above the Curie temperature and the magnetization is lost. When the external magnetic field is applied, the laser light is irradiated. Since the magnetization of the magnetic field forms a magnetic domain in the same direction as the external magnetic field, the information can be recorded. Also, the reproduction of information on the magneto-optical recording medium utilizes the Kerr effect.

On the other hand, when the incident laser beam is reflected on the recording film, the rotation of the polarization plane varies depending on the magnetization state of the recording film. That is, in the case where the recording film is magnetized upward, the polarization plane is + If k is rotated, the polarization plane is-when it is magnetized in the downward direction of the recording film. k will rotate. Therefore, the reflected laser lights along the direction of magnetization are two The polarization plane of k is rotated. Reproducing this difference as an electrical signal in the photodetector is the principle of reproduction of the magneto-optical recording medium.

In general, a magneto-optical recording medium has an outer diameter of 180 mm (or 90 mm) and a dielectric film / recording film / insulating film / reflective film is sputtered on a substrate formed with grooves of 1.6 μm intervals, and the recording capacity thereof is 10E8. The memory capacity is very high, about byte / cm 2. On the other hand, the recording film of the magneto-optical recording medium is made of an alloy thin film composed of rare earth elements and transition elements, and the transition elements of such rare earth elements are antiparallel to each other so that the total magnetization value thereof is the sublattice of the rare earth element and the transition element. Ferri is a car of armor.

FIG. 1 shows a schematic cross-sectional view of a conventional magneto-optical recording medium, in which a dielectric film 2, a recording foil 3, an insulating film 4 and a reflective film 5 are sequentially stacked on a substrate 1. .

However, when the recording film of the conventional magneto-optical recording medium having such a structure is made of a TbFeCo thin film, the recording angle is about 0.3 ° and excellent in recording and reproducing characteristics at a wavelength of 830 nm. However, as the wavelength becomes shorter, the angle of rotation becomes larger. This decreases and the characteristics deteriorate. That is, when recording and reproducing using a laser diode having a wavelength of 830 nm (or 780 nm) as a light source on a recording film made of TbFeCo, the rotation angle is about 0.3 °, but as the wavelength gradually decreases, the rotation angle is increased. When the wavelength is reduced to 415 nm or less, which is half of the wavelength, the recording and reproducing characteristics deteriorate significantly.

Accordingly, it is an object of the present invention to provide a short wavelength magneto-optical recording medium in which the above problems are solved as well as improved in characteristics over the conventional ones.

The short-wavelength magneto-optical recording medium of the present invention for achieving the above object is a magneto-optical recording medium in which a dielectric film, a recording film, an insulating film, and a reflective film are sequentially formed on a substrate, wherein the recording film is an NdTbFeCo reproducing layer and a TbFeCo. It is formed by forming two layers of the recording layer and forming an intermediate layer between the NdTbFeCo reproducing layer and the TbFeCo recording layer.

Hereinafter, the configuration of the present invention will be described in more detail with reference to the accompanying drawings.

In the case of a magneto-optical recording medium, the high data rate and high density remain to be solved, and the research is actively being conducted in the US, Japan and Europe.

On the other hand, in order to achieve high density, the laser wavelength must be shortened first, and the rotation angle is large at the short wavelength, so the recording and reproduction characteristics must be excellent.

However, in the case of using the recording film made of the TbFeCo thin film as described above, the recording and reproduction characteristics are excellent with the rotation angle of about 0.3 ° at the wavelength of 830 nm, but the wavelength becomes shorter and becomes less than 415 nm, which is half the wavelength. There was a problem that the recording and reproducing characteristics were significantly worsened at 0.2 degrees or less.

The present inventors have conducted studies to solve these problems. As a result, the above-described problems are formed by forming a recording film of a magneto-optical recording medium into two layers of a reproduction layer and a recording layer and forming an intermediate layer between the reproduction layer and the recording layer. It has been found that the solution of the present invention is to develop a short wavelength magneto-optical recording medium of the present invention.

2 is a schematic cross-sectional view of a short wavelength magneto-optical recording medium of the present invention, wherein reference numeral 11 denotes a substrate made of 2P (Photo-polymer) glass or PC (Polucatbonate) material, 21 is a dielectric film of SiN component, 31 Is a reproducing layer of NdTbFeCo component, 32 is an intermediate layer, 33 is a recording layer of TbFeCo component, 41 is an insulating film of SiN component, and 51 is an Al-Ti reflective film.

Referring to FIG. 2, the manufacturing process and structure of the shortwave magneto-optical recording medium of the present invention are as follows.

First, a SiN-containing dielectric film 21 is formed on the substrate 11 to a thickness of 500 to 600 kHz by DC magnetron sputtering. On top of that, the reproduction layer 31 of the NdTbFeCo component, the intermediate layer 32 and the recording layer 33 of the TbFeCo component are sequentially stacked. At this time, the thickness of the NdTbFeCo regeneration layer 31 is 100 to 500 mW, the thickness of the intermediate layer 32 is 10 to 100 mW, and the thickness of the TbFeCo recording layer 33 is 150 to 1000 mW.

On the other hand, the intermediate layer 32 serves to prevent the reduction of the coercive force and the C / N ratio after the aging test (aging test), the intermediate layer material used is SiN, TiN, AlN, etc., preferably SiN to be.

Next, the insulating film 41 of the SiN component and the reflective film 51 of the Al-Ti component were formed on the TbFeCo recording layer 33 by the same sputtering method as described above, respectively, to about 300 mW and 400 mW, and thus the short wavelength of the present invention. A magneto-optical recording medium is produced.

On the other hand, argon gas is generally used in the production of the NdTbFeCo regenerating layer 31, the TbFeCo recording layer 33 and the Al-Ti reflecting film 51, but in the case of manufacturing the SiN dielectric layer 21 and the SiN intermediate layer 32, A mixed gas of (Ar + N ₂ ) is used, and the initial vacuum at the time of preparation of the cornea is 3 × 10 E-7 mbar.

Therefore, the structure of the short-wavelength magneto-optical recording medium of the present invention manufactured through the above manufacturing process is a dielectric film 2, the recording film 3, the insulating film 4 and the reflective film 5 sequentially on the substrate (1) In the magneto-optical recording medium, the recording film 3 is formed of two layers, the NdTbFeCo reproduction layer 31 and the TbFeCo recording layer 33, and the NdTbFeCo reproduction layer 31 and the TbFeCo recording layer 33 The intermediate layer 32 is formed in between.

The present invention will be described in more detail with reference to the following Examples, which however do not limit the scope of the present invention.

Example 1

A SiN dielectric film was formed to a thickness of 500 mW on a 2P glass substrate by DC magnetron sputtering, and an NdTbFeCo regenerated layer, a SiN intermediate layer, and a TbFeCo recording layer were sequentially stacked thereon. At this time, the thickness of the NdTbFeCo reproducing layer was 100 kPa, the thickness of the SiN intermediate layer was 50 kPa, and the thickness of the TbFeCo recording layer was 200 kPa.

Then, the SiN insulating film and the Al-Ti reflecting film were formed on the TbFeCo recording layer in the same manner as described above with a thickness of 300 mW and 400 mW, respectively, to prepare the short wavelength magneto-optical recording medium of the present invention.

On the other hand, argon gas was used for the production of the NdTbFeCo regeneration layer, TbFeCo recording layer, and Al-Ti reflective film, but (Ar + N ₂ ) mixed gas was used for the production of the SiN dielectric layer and the SiN intermediate layer. The degree of vacuum was 3 × 10 E-7 mbar.

Example 2

In this embodiment, a short wavelength magneto-optical recording medium was fabricated using the same conditions and methods as in Example 1, except that an intermediate layer was formed using TiN instead of SiN in Example 1.

Example 3

In this embodiment, a short wavelength magneto-optical recording medium was fabricated using the same conditions and methods as in Example 1 except that the intermediate layer was formed using AIN instead of the SiN of Example 1.

Comparative Example 1

Introduced for the purpose of comparison with the present invention, unlike the above-described embodiments, the intermediate layer was not formed, but the magneto-optical recording medium was manufactured using the same conditions and methods as those of the above-described embodiments.

The magnetic properties (coercive force) of the magneto-optical recording media produced by the above examples and comparative examples were measured using a Vibrating Sample Magnetometer (VSM), and the dynamic characteristics (C / N ratio) of the disk (DISK) were measured by the dynamic tester. Measurements were made and the results are compared with each other as described in FIGS. 3 and 4.

3 is a graph showing the change in the coercive force according to the number of repetitive reproduction times of the short wavelength magneto-optical recording medium according to the present invention and the comparative example, and FIG. 4 is the number of repetition reproduction times of the short wavelength magneto-optical recording medium according to the present invention and the comparative example A graph showing a change in C / N ratio according to the above, wherein the indication "X" described in the graph means a state in which no intermediate layer is formed.

As shown in FIG. 3, the coercive force was most remarkably reduced in the absence of the intermediate layer (Comparative Example 1), and almost no decrease in coercive force was observed in the case of forming SiN in the intermediate layer (Example 1). Can be.

Further, as shown in FIG. 4, in the absence of the intermediate layer (Comparative Example 1), the C / N ratio of the recording medium rapidly decreased, and in the case of the recording medium having the intermediate layer, the C / N ratio was decreased. The decrease was relatively small, and especially in the case of the recording medium using SiN as an intermediate layer (Example 1), it can be seen that there is almost no change in the C / N ratio.

Therefore, in the short wavelength magneto-optical recording medium of the present invention, since the recording film is produced by separating the recording layer into two layers, the Kerr rotation angle of the short wavelength laser is superior to that of the conventional recording medium.

In addition, since the intermediate layer is formed between the reproduction layer and the recording layer, the coercivity and the C / N ratio are hardly reduced even in the reliability test according to the time-dependent change (change in physical property over time).

Claims (1)

In a magneto-optical recording medium in which a dielectric film 2, a recording film 3, an insulating film 4 and a reflective film 5 are sequentially formed between a (correction) substrate 1, the recording film 3 is The intermediate layer 32 is formed by forming two layers of the NdTbFeCo reproducing layer 31 and the TbFeCo recording layer 33 and between the NdTbFeCo reproducing layer 31 and the TbFeCo recording layer 33. Is a material selected from the group consisting of SiN, TiN, and AlN, the thickness of which is 10 kPa to 100 kPa, the thickness of the regeneration layer 31 is 100 kPa to 500 kPa, and the thickness of the recording layer 33 is 150 kPa to 1000 kPa. Short-wavelength magneto-optical recording media.