JP2943606B2 - Magneto-optical recording medium and manufacturing method thereof - Google Patents

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, such as a magneto-optical disk, for recording information by means of a magneto-optical effect and for rewriting the information. The present invention relates to a medium and a method for manufacturing the medium.

[0002]

2. Description of the Related Art In recent years, optical disks have been receiving attention as one of large-capacity file memories. Above all, magneto-optical disks have the advantage of being able to rewrite recorded information, and a wide range of applications, such as code data file memories and image file memories, are being actively studied in various places. Therefore, with the expansion of such applications, further improvement in recording density and speeding up are expected.

FIG. 3 shows an example of such a magneto-optical disk. In the figure, a resin substrate 2 made of polycarbonate or the like is used.
On the first dielectric layer 202, a first dielectric layer 202 made of SiN is formed, and the surface of the first dielectric layer 202 is subjected to a sputter etching process 203. In addition, T formed by a combination of a rare earth metal and an iron group transition metal thereon.
Recording layer 2 made of an amorphous magnetic alloy film such as bFeCo
04 is formed thereon, and a second dielectric layer 205 made of SiN is further formed thereon. Further, a reflective layer 206 of Al or the like is formed thereon.

In this magneto-optical disk, as is well known,
By heating with a laser beam or the like in a state where an external magnetic field is applied, information is recorded as the direction of magnetization in the recording layer 205, information is reproduced by the polarization direction associated with this direction of magnetization, and the magnetic field in the opposite direction is generated. The addition enables erasure of information.

[0005]

However, the above-described magneto-optical disk has a problem that the medium noise level is large in a low frequency region of the reproduction signal, particularly in a frequency region of 5 MHz or less. For this reason, the jitter of the reproduced signal is large, and the window margin at the time of signal reproduction is narrowed, which hinders the improvement of the recording density. In addition, there is a problem that thermal stability is easily deteriorated such that information recorded on the magneto-optical disk is lost by heat.

[0006]

SUMMARY OF THE INVENTION It is an object of the present invention to provide a magneto-optical recording medium in which the polarization noise is reduced to reduce the medium noise level. Another object of the present invention is to provide a magneto-optical recording medium having improved thermal stability. It is a further object of the present invention to provide a method of manufacturing a magneto-optical recording medium having a reduced medium noise level and improved thermal stability.

[0007]

The magneto-optical recording medium of the present invention comprises a first dielectric layer, a second dielectric layer, and a recording layer made of an amorphous magnetic alloy on an organic resin substrate. , A third dielectric layer and a reflective layer are sequentially laminated, and the surface of the second dielectric layer and the surface of the recording layer are each subjected to sputter etching. For example, the organic resin substrate is made of polycarbonate, the first dielectric layer is made of TaOx (x = 1 to 2.5) , the second dielectric layer is made of SiN, and the recording layer is made of rare earth metal. The third dielectric layer is formed of SiN, and the reflective layer is formed of an AlTi alloy, in combination with an iron group transition metal.

In the method of manufacturing a magneto-optical recording medium according to the present invention, a step of forming a first dielectric layer made of TaOx (x = 1 to 2.5) on an organic resin substrate; Forming a second dielectric layer made of SiN on the dielectric layer, sputter etching the surface of the second dielectric layer, and forming a rare earth metal on the second dielectric layer; Forming a recording layer composed of an amorphous magnetic alloy in which the recording layer is combined with an iron-group transition metal; sputter etching the surface of the recording layer;
Forming a third dielectric layer made of AlTi alloy, and forming a reflective layer made of an AlTi alloy on the third dielectric layer. Here, the sputter etching amount of the recording layer surface is in the range of 20 ° to 50 °.

[0009]

According to the present invention, by subjecting the surface of the recording layer to sputter etching, the polarization noise can be reduced and the noise level of the recording medium can be reduced. At the same time, the thermal stability can be improved.

[0010]

Next, an embodiment of the present invention will be described with reference to the drawings. FIG. 1 is a sectional view of a magneto-optical recording medium according to the present invention.
A 300 - mm thick first dielectric layer 102 made of TaOx (x = 1 to 2.5) is formed on the surface of a polycarbonate substrate 101 having a thickness of 1.2 mm and a diameter of 130 mm. A second dielectric layer 103 having a thickness of 800 ° is formed. This second dielectric layer 1
The surface of No. 03 is sputter-etched by a thickness of about 7 °, so that the surface is subjected to sputter etching 104. In addition, TbFeCoTi
The recording layer 105 having a thickness of 250 ° is formed, and the surface thereof is sputter-etched by a thickness of 20 to 50 °, and a sputter etching process 106 is performed. A third dielectric layer 10 made of SiN and having a thickness of 320 ° is formed thereon.
7 is formed thereon, and a thickness 3 of AlTi is further formed thereon.
A metal reflective layer 108 of 00 ° is formed. Note that a protective layer 109 made of an ultraviolet curable resin is formed thereon.

Each of the above layers is formed using an in-line sputtering apparatus. That is, the first dielectric layer (TaOx layer (x =
1 to 2.5) ) 102 is a Ta target, the distance between the target and the substrate 101 is 15 (cm), the power density is 8 (W / cm2), and the gas flow ratio of Ar and O2 is Ar / O2. = 100/55 (SCCM) and a film is formed under the condition of a sputtering gas pressure of 0.2 (Pa).

The second dielectric layer (SiN layer) 103 is made of S
Using an i target, the distance between the target and the substrate 101 was 15 (cm), the power density was 8 (W / cm 2), and the gas flow ratio of Ar and N 2 was Ar / N 2 = 100/5.
5 (SCCM) and a film is formed under the condition of a sputtering gas pressure of 0.3 (Pa). The surface of the second dielectric layer 103 has a power density of 0.15 (W / cm 2) and Ar = 25.
(SCCM), sputter etching under the conditions of a gas pressure of 0.1 (Pa), and etching by about 7 ° to perform sputter etching processing 104.

The recording layer (TbFeCoTi layer) 105 is
Tb target and FeCoTi alloy target (Fe
The film is formed by rotating the substrate 101 by a binary DC magnetron sputtering method using Co Ti atm%). At this time, the distance between the target and the substrate is 10 (c).
m), the power densities of the Tb target and the FeCoTi alloy target are 1.5 (W / cm 2),
3.0 (W / cm2), Ar = 50 (SCCM),
This is performed under the condition of a gas pressure of 0.14 (Pa). The surface of the recording layer 105 is sputter-etched under the same conditions as the sputter-etching of the surface of the second dielectric layer 103 to form a sputter etching process 106. However, the etching amount is in the range of 20 to 50 °.

The third dielectric layer (SiN layer) 107 is formed under the same conditions as the second dielectric layer 103.

The metal reflection layer (AlTi alloy layer) 108
Using an AlTi alloy target containing 1 Wt% of Ti and using an Ar gas as a sputtering gas and the target and the substrate 1
01 is 15 (cm) and the power density is 3.0.
(W / cm 2) and a film is formed under the conditions of a gas pressure of 0.1 (Pa). The protective layer (ultraviolet curable resin layer) 109 is formed by applying an ultraviolet curable resin by spin coating.

Here, in order to confirm the effect of the sputter etching process 106 formed by treating the surface of the recording layer 105 in the present invention, the samples in which the sputter etching amount was variously changed from 0 to 70 ° were used. Create In this case, eight types of samples changed in units of 10 ° were prepared. Then, these samples were attached to a magnet hub in a single plate state, and the polarization noise was measured. The polarization noise is measured by initializing the sample and then measuring the difference signal output of the MO head detector under the following measurement conditions. In this case, since the reflectance is different due to the difference in the respective sputter etching amounts,
The power at the time of reproduction is adjusted so that the amount of return light is constant.

Conditions for measuring polarization noise (a) Linear velocity (m / sec): 9.4 (b) Frequency (MHz): 1.0 to 10.0 (c) Reproduction power (mW): 1.0 1.9 (d) VBW (Hz): 100 (e) RBW (kHz): 30

The thermal stability (ΔC / N) of the recording signal was evaluated for each sample. In this evaluation, after a signal was recorded on each sample, a magnetic field of 500 (Oe) was externally applied to the portion in the information erasing direction, and simultaneously, 2.5 (mW)
Is irradiated for 3 minutes, and the difference between the reproduced signals before and after the irradiation is taken as the evaluation result.

The measurement result of the polarization noise at 1 MHz is shown in the lower part of FIG. Similarly, the evaluation results of the thermal stability are shown in the upper part of FIG. The polarization noise is reduced as the sputter etching amount increases from 0 ° to 20 °.
Above values are almost constant. On the other hand, the thermal stability is not changed even when the sputter etching amount is increased from 0 °, but increases rapidly when the amount exceeds 60 °, and the thermal stability is rapidly deteriorated.

From the above, the sputter etching amount when performing the sputter etching process 106 is set to 20 ° to 50 °.
By adjusting to the range of Å, a magneto-optical disk having excellent thermal stability while suppressing polarization noise can be obtained. In particular, by suppressing polarization noise,
It can reduce the jitter of the reproduction signal on the magneto-optical disk,
The window margin at the time of signal reproduction can be expanded, and the density of the magneto-optical disk can be increased.

Although the above embodiment shows an example in which the present invention is applied to a magneto-optical disk, the present invention can be similarly applied to other types of recording media such as a magneto-optical card. Further, the composition and thickness of the recording layer or the composition and thickness of the other layers are not limited to those of the above-described embodiment, and can be appropriately changed in order to obtain a desired magneto-optical recording medium. It is.

[0022]

As described above, the magneto-optical recording medium of the present invention has a structure in which the surface of the recording layer formed on the organic resin substrate is sputter-etched to reduce the polarization noise and to perform recording. There is also an effect that the medium noise level can be reduced and the thermal stability of the recording medium can be increased.

In the method of manufacturing a magneto-optical recording medium according to the present invention, after forming a recording layer, the surface of the recording layer is sputter-etched by a required amount, thereby reducing polarization noise and improving thermal stability. Can be manufactured.

Further, according to the method of the present invention, by controlling the sputter etching amount of the recording layer surface in the range of 20 ° to 50 °, it is possible to preferably improve both the polarization noise reduction and the thermal stability. Become.

[Brief description of the drawings]

FIG. 1 is a sectional view of a magneto-optical recording medium of the present invention.

FIG. 2 is a diagram showing the results of measurement of polarization noise and thermal stability of samples of the magneto-optical recording medium of the present invention with different sputter etching amounts.

FIG. 3 is a sectional view of a conventional magneto-optical recording medium.

DESCRIPTION OF SYMBOLS 101 Polycarbonate substrate 102 TaOx layer (first dielectric layer) 103 SiN layer (second dielectric layer) 104 Sputter etching processing 105 TbFeCoTi alloy layer (recording layer) 106 Sputter etching processing 107 SiN layer ( Third dielectric layer) 108 AlTi layer (metal reflective layer) 109 Protective layer

──────────────────────────────────────────────────続 き Continued on front page (58) Field surveyed (Int.Cl. ⁶ , DB name) G11B 11/10

Claims (4)

(57) [Claims] And 1. A organic resin substrate, a first dielectric layer formed thereon, and the first Ru is formed on the dielectric layer <br/> second dielectric layer, the Formed on the second dielectric layer
A recording layer made of an amorphous magnetic alloy, a third dielectric layer formed on the recording layer, and a reflective layer formed on the third dielectric layer . Table of 2 dielectric layers
The surface and the surface of the recording layer are sputter-etched.
Magneto-optical recording medium characterized configured der Rukoto was. Wherein said organic resin substrate is formed of polycarbonate, the first dielectric layer TaOx (x =. 1 to
2.5) is formed in said second dielectric layer is formed of SiN, the recording layer is formed by a combination of rare earth metals and iron group transition metals, said third dielectric layer is Si
Is formed by N, the reflective layer is formed of AlTi alloy
The magneto-optical recording medium according to claim 1 . 3. An organic resin substrate comprising a TaOx (x = 1 to 1)
2.5) forming a first dielectric layer made of SiN, forming a second dielectric layer made of SiN on the first dielectric layer, and forming the second dielectric layer Forming a recording layer made of an amorphous magnetic alloy in which a rare earth metal and an iron group transition metal are combined on the second dielectric layer; and forming a recording layer on the second dielectric layer. A step of sputter etching the surface, a step of forming a third dielectric layer made of SiN on the recording layer, and a step of forming a reflective layer made of an AlTi alloy on the third dielectric layer And a method for manufacturing a magneto-optical recording medium. 4. The method for manufacturing a magneto-optical recording medium according to claim 3 , wherein the sputter etching amount of the recording layer surface is 20 ° to 50 °.