JPH03183045A - magneto-optical recording medium - Google Patents

Abstract

(57) [Summary] This bulletin contains application data before electronic filing, so abstract data is not recorded.

Description

DETAILED DESCRIPTION OF THE INVENTION [Field of Industrial Application] The present invention relates to a magneto-optical recording medium used for magneto-optical recording, and more particularly to the structure of its multilayer film and the material of the magneto-optical recording film.

[Prior Art 1 As shown in Patent Application Publication No. 62-27458,
In order to increase the Kerr rotation angle or to improve the weather resistance of the magneto-optical recording film, protective films or reflective layers have been provided on both sides of the magneto-optical recording film. Also magneto-optic! ! As for III, patent application publication period 59-1
59509.59-159510 etc., T
bFeCo is generally used.

[Problems to be Solved by the Invention] In the conventional technology, in order to improve the C/N ratio of information signals, an alloy consisting of heavy rare earths and transition metals is used as a first protective film and an optical Magnetic recording film/Second protective film/
It had a four-layer structure in which reflective films were laminated in this order. However, if a heavy rare earth such as Tb is used for the magneto-optical distribution Ba, there is a drawback that the sensitivity to recording power becomes poor and high recording power is required. At the same time, the sensitivity to the recording bias magnetic field is poor and a larger recording bias magnetic field is required.
There were six problems in terms of power consumption and heat generation. Therefore, attempts were made to improve the recording power sensitivity and recording magnetic field sensitivity by adding Nd, which is a light rare earth element, to the magneto-optical recording film. Therefore, in the present invention, an alloy consisting of light rare earth Nd, heavy rare earth glue, y, and transition metals Fe and CO is used for the magneto-optical recording film.
The purpose is to provide a magneto-optical recording medium that can record with low laser power and a low magnetic field and reproduce signals with a high C/N ratio by optimizing the composition ratio of Nd and the composition ratio of all rare earth elements. .

[Means for Solving the Problems] The magneto-optical recording medium of the present invention is a magneto-optical recording medium in which at least a first protective film, a magneto-optical recording film, a second protective film and a reflective film are laminated in this order on a substrate. The composition of the magnetic recording film is light rare earth Nd, heavy rare earth Dy, and transition metals Fe and CO.
and the composition of the magneto-optical recording film is Ndx D:Jy (FeCo) +0O-x-IT
It is characterized in that 2≦x≦5 and 25≦x+y≦30 when expressed as follows.

〔Example] The present invention will be described in detail below based on examples.

(Example 1) Ndx Dy2t, *-*Fe*m, mCOx.

The magneto-optical recording film is an amorphous film with a composition of
A magneto-optical recording medium was prepared by forming a first protective film, a magneto-optical recording film, a second protective film, and a reflective film in this order on a polycarbonate substrate of m. FIG. 1 shows the membrane structure of this embodiment. The first protective film/second protective film is aluminum silicon nitride.0 The reflective film uses an aluminum tank.0 As an example of the present invention, among the above compositions, X=3, Oa
From t% x=5. A magneto-optical recording medium having a recording film with a thickness between Oat% was produced. As a comparative example, a magneto-optical recording medium having a value of X other than that region was produced. Table 1 shows the relationship between sample numbers and recording film compositions.

Below, the results of evaluating the electrical properties of the produced magneto-optical recording medium will be described. The evaluation was performed by recording a 4.9 MHz signal at a linear velocity of 7.5 m/sec.

First, the relationship between recording laser power and C/N ratio will be described. Signals were recorded under a bias field of 3000e. FIG. 2 shows the relationship between recording laser power and carrier wave-to-noise ratio (C/N ratio) when the Nd composition ratio X is changed.

It can be seen that the C/N ratio at saturation reaches its maximum value when X is 3 at%. At this time, it can be seen that the recording sensitivity of the medium to the recording laser power is 0.5 mW worse than that of the embodiment of the present invention when X is fat%.

Next, the value of the Nd composition ratio X is changed more finely to examine the relationship between the recording laser power and the C/N ratio.

FIG. 3 shows the relationship between X and the C/N ratio with respect to the recording laser power. C/N when X is 2 at% to 5 at%
The ratio exceeds 50 dB, and compared to other composition regions,
It can be seen that the value is higher than dB. In Figure 4, Nd
The relationship between the composition ratio X and the recording laser power when the C/N ratio is saturated is shown. It can be seen that when X is less than 2 at%, the recording power sensitivity deteriorates.

FIG. 5 shows the relationship between the recording magnetic field and the C/N ratio.

The composition ratio X of Nd is in the composition range of the present invention, that is, 2 to 5 at%
When it deviates from this, the recording bias magnetic field at saturation becomes high, which is shown in more detail in FIG. FIG. 6 shows the bias magnetic field at which the C/N ratio is saturated when the value of X is changed by 0.5 at%. It can be seen that when X is 2 to 5 at%, the C/N ratio is saturated at a low bias magnetic field of 1250e to 1500e.

(Example 2) Ndx D yy (F e CO) +oo-++
An amorphous film with a composition of −y is used as a magneto-optical recording film, and a diameter of 13
A magneto-optical recording medium was prepared by forming a first protective film/magneto-optical recording film/second protective film/reflective film in this order on a 0 mm polycarbonate substrate. FIG. 1 shows the membrane structure of this embodiment. The first protective film/second protective film was made of aluminum silicon nitride, and the zero-reflection film was made of aluminum tantalum.

Below, the evaluation results regarding the electrical characteristics of the produced magneto-optical recording medium will be described. The evaluation was performed by recording a 4.9 MHz signal at a speed of 7.5 m/5 eclr3.

FIG. 7 shows the relationship between the rare earth composition ratio x+y and the C/N ratio when saturated with the recording laser power. X+
When y falls to 24 at% or exceeds 30 at%, C
/N ratio is 25at%≦x+, which is within the range of the embodiment of the present invention.
It can be seen that the value decreases by more than 1 dB from the value when y≦30at%.

FIG. 8 shows the relationship between the rare earth composition ratio x+y and the recording saturation magnetic field. x+y drops to 24at% or 30at%
If the recording saturation magnetic field exceeds 25 at%, the recording saturation magnetic field will be 250 e
It gets bigger than that.

It should be noted that the present invention should not be considered limited to these embodiments, and various modifications can be made without departing from the gist of the present invention.

For example, the first protective film and the second protective film may be made of nitride or oxide ceramic, and the reflective film may be made of aluminum titanium and have the same characteristics as the six embodiments. Further, the substrate may be made of glass.

[Effects of the Invention] As described above, according to the present invention, it is possible to provide a magneto-optical recording medium that can record with low laser power and a low magnetic field and can reproduce signals with a high C/N ratio.

[Brief explanation of drawings]

FIG. 1 is a diagram showing the structure of the magneto-optical recording medium of the present invention. FIG. 2 is a diagram showing the relationship between the recording laser power and the C/N ratio when the Nd composition ratio X is changed. X is x=1a
t%, ○ is x=3at%, ■ is x=5at%, △ is x=
It is 7at%. FIG. 3 is a diagram showing the relationship between the Nd composition ratio X and the C/N ratio. FIG. 4 is a diagram showing the relationship between the Nd composition ratio X and the recording laser power when the C/N ratio is saturated. FIG. 5 is a diagram showing the relationship between the recording bias magnetic field and the C/N ratio when the Nd composition ratio X is changed. X is X=lat%, ○ is x=3at%, ■ is X=5at
%, Δ is x=7at%. FIG. 6 is a diagram showing the relationship between the Nd composition ratio X and the saturation magnetic field. FIG. 7 is a diagram showing the relationship between the rare earth composition ratio x+y and the C/N ratio. For X, x=2at%, and for ○, X=5at%. FIG. 8 is a diagram showing the relationship between the rare earth composition ratio x+y and the saturation bias magnetic field. X is x=2 a t%. O is x=5at%.・Substrate ・First protective film Magneto-optical recording layer ・Second protective film ・Reflective film and above

Claims (3)

[Claims] (1) At least the first protective film, magneto-optical recording film,
In a magneto-optical recording medium in which a second protective film and a reflective film are laminated in this order, the composition of the magneto-optical recording film is an alloy consisting of Nd as a light rare earth, Dy as a heavy rare earth, and Fe and Co as transition metals, and The composition of the magneto-optical recording film is Nd_xDy_y (FeCo)_1_0_0_-_x_
A magneto-optical recording medium characterized in that, when expressed as −_y, 2≦x≦5 25≦x+y≦30. (2) The magneto-optical recording medium according to claim 1, wherein the first protective film and the second protective film are made of nitride. (3) The magneto-optical recording medium according to claim 2, wherein the first protective film and the second protective film are aluminum silicon nitride.