JPH0366047A - Magneto-optical recording medium - Google Patents

Abstract

PURPOSE:To improve characteristics of recording, erasing and reproducing of the recording medium by gradually increasing the amt. of Nb in the recording film from the inner circumferential area to the outer circumferential area. CONSTITUTION:The recording medium has a recording film formed on a substrate. The recording film consists of 25 - 27 atm % Tb and substantially the balance Fe in which Nb is incorporated in a manner that the amt. of Nb gradually increases from the inner area to the outer area within 0 - 5 atm % range. By this constitution, deterioration of recording pits caused by thermal diffusion of power for reproducing, and decrease in the Kerr rotation angle with increase of film temp. can be prevented in the inner circumferential area having less Nb, even when the line speed is low in this area. In the outer circumferential area, where the line speed is high, good recording can be performed with not so much laser power.

Description

DETAILED DESCRIPTION OF THE INVENTION [Field of Industrial Application] The present invention relates to a magneto-optical record carrier that records, reproduces and erases information using a laser beam and an external magnetic field.

[Conventional technology]

2. Description of the Related Art Consumer optical discs, such as compact discs and video discs (hereinafter referred to as optical discs), which read signals using laser light and play back music and videos, are widely used. However, for these optical disks, in order to obtain an optical disk that cannot be recorded or erased by the user and is rewritable, a magneto-optical recording film has been proposed that utilizes rotation of the plane of polarization due to the orientation of magnetic moments.

In this magneto-optical recording film, Tb and Gd are used.

There are known alloys of rare earth elements such as Nd and D7 and transition metals such as Fe and co.

[Problem to be solved by the invention]

However, such recording films have different Curie temperatures depending on their composition, and the sensitivity of the laser power of the optical disk is determined by the Curie temperature. Therefore, in the case of optical discs such as CDV, in which a single disc has a high linear velocity region and a low linear velocity region, or an optical disc with a constant rotational speed, a composition with a high Curie temperature of the recording film is used. This makes recording difficult in the high linear velocity region. On the other hand, if a composition with a low Curie temperature is used, there will be problems such as deterioration of recording focus due to the heat of the reproducing power when reproducing a low linear velocity region, and a decrease in the Kerr rotation angle due to an increase in film temperature. Ta.

Therefore, the present invention has been made with the object of providing a magneto-optical record carrier having good recording, erasing and reproducing characteristics over the entire surface of the disk.

[Means to solve the problem]

Therefore, in the present invention, a recording film of terbium (25 to 27 at% cobal) 1
Using a composition of 1 to 12 at%, the balance being substantially more powerful than iron,
This magneto-optical record carrier is characterized in that the niobium content continuously changes in the range of 0 to 5 at% from the inner circumference where the linear velocity is slow to the outer circumference where the linear velocity is high.

[Effect]

In Figure 2, (T bzhF bhsco ++)
+@@4 Figure 3 shows the NbO composition in the radial direction of a magneto-optical recording medium having a recording film of Nbx.
This figure shows the dependence of the optimum recording power on the composition of niobium at 000e. As shown in this figure, it can be seen that as the amount of niobium increases, the optimum recording power decreases. As a result, even if the linear velocity is low in the inner periphery where niobium is less, it is possible to prevent the recording bit from deteriorating due to the influence of thermal diffusion of the reproducing power and from decreasing the Kerr rotation angle due to the rise in film temperature. In addition, in the outer peripheral portion where the amount of niobium is large, even if the linear velocity is high, good recording is possible without requiring a very large laser power.

〔Example〕

Glass, polycarbonate as shown in Figure 1.

Alternatively, a typical example of a film &IItc is Tbzs'FebaC on the inner peripheral portion of the substrate 3 formed of acrylic resin or the like.

A target adjusted to have a film thickness of about 1,000 is deposited by magnetron sputtering. Then, towards the outer periphery, the film composition at the outermost periphery is (T bxsF
e, 4G O11) 9SN bs Deposit in such a way that it changes gradually.

On the thus formed recording layer 4, an I retention film 5 made of ZnS, 5iN8, etc. is deposited over the entire surface of the disk to a thickness of about 1000 layers.

CAV180 on the magneto-optical disk created in this way.
When a frequency signal of 1 MHz was recorded with an external magnetic field of 4000 e and an output of 0 rpm, a wavelength of 780 ns, and a power of 3 H, pits were accurately formed. When this was reproduced with a laser power of 1.0-, a constant CNR was obtained over the entire surface of the disk.

〔Effect of the invention〕

As described above, according to the present invention, good recording and reproduction signals can be obtained in CAV recording without greatly changing the laser power.

[Brief explanation of drawings]

FIG. 1 is a cross-sectional view for explaining the present invention in detail, FIG. 2 is a diagram showing the niobium composition in the radial direction of the magneto-optical recording medium according to the present invention, and FIG. 3 is a Tb-Fe-Co-Nb non- FIG. 3 is a diagram showing Nb concentration dependence of a crystalline perpendicularly magnetized film. ■... Recording light beam 2... External magnetic field 3...
Substrate 4... Recording layer 5... Protective layer.

Claims (1)

[Claims] In a magneto-optical recording carrier having a substrate and a recording thin film formed on the substrate, the recording thin film is a film consisting of 25 to 27 at% Tb, the balance substantially Fe, and 0 to 5 at% Nb from the inner circumference to the outer circumference. A magneto-optical record carrier characterized in that the recording medium gradually increases in the range of .