JP2729664B2 - Magneto-optical recording medium - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION [Industrial Application Field] The present invention is used for an optical disk or the like, and particularly relates to a magneto-optical recording medium.

〔Overview〕

The present invention relates to a magneto-optical recording medium comprising a recording layer and a transparent dielectric film for protecting the recording layer, wherein the transparent dielectric film comprises at least two elements of silicon, aluminum and titanium. A recording / reproducing characteristic and a protection characteristic are improved by using a dielectric film having a specific range of composition with a nitrogen compound containing boron as a compound.

[Conventional technology]

Conventionally, a rare earth transition metal alloy thin film is generally used for a recording layer of a magneto-optical recording medium. Rare earth transition metal alloy is Tb
FeCo, GdTbFeCo, NdDyFeCo, NdTbFeCo, PrTbFeCo and the like are known. This rare earth transition metal thin film is very susceptible to oxidation and degrades immediately when left in the air.
Recording characteristics gradually disappear. Therefore, in order to prevent this, the recording layer is sandwiched from both sides by a transparent dielectric film called a protective film so as not to come into direct contact with the air.

Further, the rare earth transition metal alloy has a disadvantage that the magnitude of the Kerr effect, which is an important factor of the magneto-optical recording characteristics, is as small as 0.3 to 0.4 mm, and it is necessary to improve this. The improvement of the Kerr effect is called Kerr effect enhancement, and is intended to improve the reproduction characteristics by using a light interference phenomenon and increasing the apparent Kerr rotation angle. The increase in the Kerr rotation angle is more effective as the refractive index of the protective film is larger, which leads to an improvement in signal quality.

[Problems to be solved by the invention]

By the way, the transparent dielectric films conventionally used have many drawbacks, such as being weak to moisture and easily scratched, even if the refractive index is large, and some of them are not practical.

The object of the present invention is to eliminate the disadvantages mentioned above,
It is an object of the present invention to provide a magneto-optical recording medium having a sufficient magneto-optical effect and having protection characteristics excellent in corrosion resistance and moisture resistance.

[Means for solving the problem]

The present invention relates to a magneto-optical recording medium comprising a recording layer and a transparent dielectric film for protecting the recording layer, wherein the transparent dielectric film is made of silicon (Si), aluminum (Al) and titanium (Ti). ) Is a nitrogen compound containing boron (B) in at least two or more kinds of elemental compounds, and (Si _1-Y Al _Y ) _1-XZ Ti _X B _Z N 0 ≦ X ≦ 0.5 (atomic weight ratio) 0 ≦ It is characterized by comprising a composition in a range represented by Y ≦ 0.70 <Z ≦ 0.1.

[Function] SiAlTiBN is a high melting point material, extremely stable,
Excellent weather resistance. Further, since it is a nitride, a dense film can be formed as compared with an oxide film or a conventional nitride film.

Since a dense film can be formed, a film having a high refractive index can be easily formed by setting the composition within a specific range as compared with an oxide-based film.

Since the SiAlTiBN does not contain oxygen as a component, there is no danger of oxidation during or after its preparation even on extremely corrosive metal surfaces.

Therefore, by forming a transparent dielectric film of SiAlTiBN, it is possible to realize a magneto-optical recording medium having a sufficient magneto-optical effect and having protection characteristics excellent in corrosion resistance and moisture resistance.

Embodiment An embodiment of the present invention will be described below with reference to the drawings.

FIG. 1 is a sectional view showing a main part of one embodiment of the present invention.

In this embodiment, TbFeCo is used as a recording layer on a glass substrate 1.
A layer 2 is provided, on which SiAlTiBN is used as a transparent dielectric film.
A membrane 3 is provided.

The composition of the SiAlTiBN film 3 is in the following range.

(Si _1-Y Al _Y ) _1-XZ Ti _X B _Z N 0 ≦ X ≦ 0.5 (atomic weight ratio) 0 ≦ Y ≦ 0.7 0 <Z ≦ 0.1 The SiAlTiBN film 3 is made of glass with the TbFeCo layer 2 interposed therebetween. It may be provided directly above the substrate 1.

The feature of the present invention resides in that a SiAlTiBN film 3 is provided in FIG.

Next, a film forming method for changing the refractive index of the SiAlTiBN film will be described with an example of the film forming method.

The film is formed by a sputtering method. The sputtering method may be any method such as a two-pole magnetron sputtering method, an ion beam sputtering method, and a facing target type sputtering method.

A two-electrode RF sputtering apparatus was used to make the examples. As a target material, a high-purity Si having a diameter of 5 inches was used, and a composite target in which required numbers of high-purity 10 mm × 10 mm square, 1 mm thick Ti chips, Al chips, and BN chips were placed thereon was used. Gas using a mixed gas of Ar and N _2,
A SiAlTiBN film was formed by reactive sputtering.

FIG. 2 shows the refractive indexes of the SiTiBN films produced under various sputtering conditions. As can be seen from this figure, the refractive index of SiTiBN film is dependent on the ratio and the gas pressure of Ar and N _2, it was deposited in the condition of low gas pressure becomes high refractive index, the higher the gas pressure Decreases the refractive index. FIG. 3 shows the result of adding Al to this. In FIG. 3, the same result as in FIG. 2 was obtained. Next, the same applies to SiAlBN.
Shown in the figure. In any case, a film having a desired refractive index can be formed by changing the gas pressure and the mixing ratio of the sputtering gas.

In the case of SiAlTiBN, it is also possible to form a film by changing the refractive index by changing the amount of B. This situation is shown in Fig. 5 for SiTiBN, and Fig. 6 for SiAlBN.
FIG. 7 shows the case of SiAlTiBN. The measurement was performed by X-ray photoelectron spectroscopy (XPS).

Therefore, a film having a desired refractive index can be formed by appropriately selecting the mixing amount of Al, Ti and B. However, if the added amount of Ti exceeds 50 at% with respect to the amount of SiAl, the effect of the decrease in transmittance increases. Therefore, it is desirable to use Ti below this amount. Similarly, the added amount of B is 10 at% with respect to SiAlTi.
% Is desirable.

Next, in order to evaluate the protection characteristics, the evaluation was performed using a TbFeCo alloy thin film in the case of magneto-optical storage. A 100 nm TbFeCo film is formed on a Corning # 7059 glass substrate by sputtering.
Sample I on which a 100 nm SiTiBN film was formed, and TbF
Sample II with 100 nm SiAlBN film deposited on 100 nm eCo and Sample III with 100 nm SiAlTiBN film deposited on TbFeCo 100 nm
And, as a comparative example, a TbFeCo 100 nm film formed on a glass substrate,
Sample IV with 100 nm of aluminum nitride deposited thereon was immersed in 1N saline at 25 ° C to evaluate corrosion resistance by measuring changes in light transmittance and changes in corroded area using an image processing device. did.

As a result, even after 500 hours, the transmittance using the SiTiBN film did not change, and the SiAlBN film and the SiAlTiBN film did not change.
No change was observed in the transmittance using the membrane. On the other hand, the aluminum nitride film showed a remarkable change in transmittance. In addition, Sample I was compared in detail with Sample II and Sample III, but all were inferior and all showed excellent protection characteristics.

Next, disks using various protective films continuously formed on a polycarbonate resin substrate (PC) using an in-line type sputtering apparatus were prepared and compared. These examples are shown in the table. The recording / reproducing characteristics are the results measured at a recording frequency of 2 MHz, a duty of 50%, an optimum recording power, and a recording position radius = 33 mm.

The embodiments shown in the table will be described in order. The No. 1 medium is a comparative example using silicon nitride (SiN) that is commonly used. The Kerr rotation angle θ _k is 0.89 ° and the CNR is 52.8 dB.
Met. In comparison, No. 2 of the example using SiTiBN
No. 3 medium has a car rotation angle of 1.14 to 1.16 ゜, which is a comparative example.
A large value was obtained compared to No. 1, and the CNR was 2.0 compared to No. 1.
From 2.4dB. The media No. 4 to No. 5 using the SiAlBN film had a large Kerr rotation angle of 1.14 to 1.17 °, the CNR was improved by 1.0 to 2.4 dB, and the No. 4 media using the SiAlTiBN film did not.
As for the media Nos. 6 to No. 7, the media with a large Kerr rotation angle of 1.20 to 1.22 ° were obtained, and the media with improved CNR of 2.9 to 3.0 dB were obtained.

Although the embodiment has been described, the present invention is not limited to this. That is, a sintered target of SiAlTiBN may be sputtered, or a sintered target of SiAlTiBN and TiAl
It may be formed by binary simultaneous sputtering using two B sintered targets. In short, any manufacturing method in which the refractive index can be changed by changing the sputtering conditions and the amounts of titanium, aluminum, and boron can be applied to the present invention.

The film formation method is not limited to the sputtering method, and any method capable of forming a film, such as an electron beam evaporation method, may be used.

[Effects of the Invention] As described above, according to the present invention, by using a SiTiBN film or a SiAlTiBN film having a predetermined composition as a transparent dielectric film, a magneto-optical device having excellent recording / reproduction characteristics and excellent protection characteristics is provided. A recording medium can be provided, and the effect is great.

[Brief description of the drawings]

FIG. 1 is a sectional view showing the configuration of one embodiment of the present invention. FIG. 2 is a characteristic diagram showing a change in the refractive index when the sputtering conditions of the SiTiBN film are changed. FIG. 3 is a characteristic diagram showing a change in the refractive index when the sputtering conditions of the SiAlTiBN film are changed. FIG. 4 is a characteristic diagram showing a change in the refractive index when the sputtering conditions of the SiAlBN film are changed. FIG. 5 is a characteristic diagram showing a change in the refractive index when the B concentration of the SiTiBN film is changed. FIG. 6 is a characteristic diagram showing a change in the refractive index when the B concentration of the SiAlBN film is changed. FIG. 7 is a characteristic diagram showing a change in the refractive index when the B concentration of the SiAlTiBN film is changed. 1 ... Glass substrate, 2 ... TbFeCo layer (recording layer), 3 ...
SiAlTiBN film (transparent dielectric film).

Claims (1)

(57) [Claims] 1. A magneto-optical recording medium comprising a recording layer and a transparent dielectric film for protecting the recording layer, wherein the transparent dielectric film comprises silicon (Si), aluminum (Al), and titanium ( Ti) is a nitrogen compound containing boron (B) in at least two or more types of elemental compounds, and (Si _1-Y Al _Y ) _1-XZ Ti _X B _Z N 0 ≦ X ≦ 0.5 (atomic weight ratio) 0 ≦ Y ≦ 0.70 <Z ≦ 0.1 A magneto-optical recording medium comprising a composition in a range represented by the following range.