JPH02308455A - Magneto-optical recording medium - Google Patents

Abstract

PURPOSE:To facilitate the adjustment of a recording sensitivity and to maintain the S/N of the signal to be reproduced at a high value by forming the recording layer of the magneto-optical recording medium of alloys consisting of light rare earths, heavy rare earths and transition metals and constituting the reflecting layers thereof of two layers consisting of one among Au, Ag, Pt, and Cu, and Al. CONSTITUTION:A 1st dielectric layer 104, the recording layer 103, a 2nd dielectric layer 102, and the reflecting layers 101, 101' are successively laminated on an insulating substrate 105 and the recording layer 103 is formed of the alloy constituted of the light rare earths, heavy rare earths and the transition metals. The reflecting films are constituted of the two layers consisting of one among the Au, Ag, Pt, and Cu, and the Al. Further, the Au, Ag, Pt, Cu of the recording layer are provided on the recording layer side. The dielectric layers 104, 102 are formed of aluminum nitride silicon, the recording layer 103 is formed of NdDyFeCo or aluminum nitride silicon and the recording layer 103 is formed of NdDyTbFeCo.

Description

DETAILED DESCRIPTION OF THE INVENTION [Field of Industrial Application] The present invention relates to the structure of an optical recording medium that records, reproduces, and erases information using light.

[Prior Art] As shown in Patent Application Publication No. 62-27458, dielectric layers are provided on both sides of a recording film in order to increase the Kerr rotation angle or to improve the corrosion resistance of the recording film. , forming a reflective layer. In addition, as a recording film, patent application publication No. 59-159509.59
-159510 etc., TbFeCo is generally used.

[Problems to be Solved by the Invention] In recording and reproducing a magneto-optical recording medium, it is necessary to obtain as large a rotation of the plane of polarization as possible and a large reflection during reproducing. The required characteristic is that there must be a sufficient margin for power. However, it has been extremely difficult for conventional magneto-optical recording media to achieve sufficient characteristics to meet these requirements.

Therefore, in order to improve such conventional drawbacks, it is an object of the present invention to provide a magneto-optical recording medium that can obtain a high signal S/N ratio and has high recording sensitivity. Means] The present invention provides a magneto-optical recording medium in which a dielectric layer, a recording layer, a dielectric layer, and a reflective layer are laminated in the order of a dielectric layer, a recording layer, a dielectric layer, and a reflective layer on a glass or plastic substrate. An alloy composed of transition metals, and the reflective layer is A.
It is characterized by being composed of two layers of one of U, Ag, Pt, and CU and Al, and that Au, Ag, Pt, and Cu are provided on the recording layer side.

[Example] FIG. 1 is a sectional view showing the structure of a recording medium of the present invention. The V-shaped groove in FIG. 0 is a guide groove for an optical head to perform tracking servo.

A recording medium having this structure was used in the following examples.

105 substrate with a diameter of 130 mm and a thickness of 1.
Using 2 mm polycarbonate, aluminum silicon nitride was used as the dielectric layer 104, NdDyFeCo was used as the recording film 103, the same dielectric layer as 104 was used as 105, and silver (Ag) was sputtered as the reflective film of aluminum 101' as 101. The thickness of the aluminum reflective layer was varied and the change in recording sensitivity was measured. 1
The film thickness of each layer except the 01 reflective layer is 2.
The dielectric layer No. 104 was fixed at 60 nm, the recording layer No. 103 was fixed at 25 nm, and the dielectric layer No. 102 was fixed at 30 nm.

To measure the recording sensitivity, a laser wavelength of 830 nanometers was used.
An optical head with an objective lens NA of 0.55 was used and two types of linear speeds were used. The linear velocity of each is 5゜6m/s and l1
m/s. Furthermore, the recording signal at each linear velocity was 3.7 MHz with a duty of 33% when the linear velocity was low, and 3.7 MHz with a duty of 50% when the linear velocity was high. The optimal recording sensitivity is the point where the second harmonic is the lowest. Figure 2 shows the results of an experiment with 0 or more. The data in Figure 2 is at a linear velocity of 11 m.
/S, the sensitivity of a medium without a reflective layer is normalized to 1. The recording power at that time was 4.5 mW. The recording sensitivity monotonically decreases as the thickness of the reflective layer increases. Therefore, the thinner the reflective layer is, the better the recording sensitivity is. By changing the thickness of the reflective layer in this way, recording sensitivity can be adjusted.

However, the reflectance cannot be ensured unless the total reflective layer has a certain thickness. FIG. 3 is a diagram showing the relationship between the thickness of the reflective layer and the reflectance.

This data was obtained by forming 20 nanometers of platinum (PT) on a glass substrate, and then forming aluminum by sputtering, and measuring the reflectance for light with a wavelength of 830 nanometers. (Indicated by a black circle in the figure) For comparison, we also measured a sample made only of aluminum. (Indicated by a white square in the figure) From this figure, it can be seen that the reflectance is approximately 10% higher than when only aluminum is used.

In addition, Figure 4 shows the linear velocity of disks with different reflective films at 5.6 m.
The recording characteristics at /s are shown. The data in the black circles in the figure shows the results of the disk according to the present invention, in which the reflective layer is made of copper (Cu) and aluminum each having a thickness of 20 nanometers. For comparison, the data shown by the open squares is for using only aluminum (film thickness: 40 nanometers) as the reflective film. From this figure, it can be seen that the sensitivity of the disk according to the present invention has a sharper recording threshold and a higher KazuCZN ratio compared to a disk made only of aluminum.

Therefore, the margin for reproduction power is widened, and the stability of recorded data is further improved.

Next, in a recording medium having the structure shown in FIG.
The recording film of 103 is 25 nanometers, the dielectric material of 104 is aluminum nitride silicon 30 nanometers, and 10
Aluminum 30 nm as reflective layer of 101
A recording medium with 20 nanometers of gold (AU) added as ' was prepared, the composition of the recording film was changed, and the C/N ratio and recording sensitivity were measured. The results are shown in FIG. 5. As shown in FIG. 5, the recording medium of the present invention has high recording sensitivity and
It can be seen that a high value of C/N ratio can also be obtained.

[Effects of the Invention] As shown in the embodiments above, in the magneto-optical recording medium according to the present invention, the recording sensitivity can be easily adjusted and a high S/N ratio of the reproduced signal can be obtained. Furthermore, the recording medium has a large margin for reproduction power and can be used as a recording medium with excellent long-term stability.

[Brief explanation of the drawing]

FIG. 1 is a sectional view showing the structure of a magneto-optical recording medium according to the present invention. FIG. 2 is a diagram showing the relationship between the thickness of the reflective layer of the recording medium according to the present invention and the recording sensitivity. FIG. 3 is a diagram showing the relationship between the film thickness of the reflective layer and the reflectance. FIG. 4 is a diagram showing the relationship between the structure of the reflective layer and recording characteristics. FIG. 5 is a diagram showing the relationship between recording sensitivity and C/N ratio of a magneto-optical recording medium according to the present invention and a conventional recording medium. Applicant Seiko Epson Co., Ltd. Representative Patent Attorney Kizobe Meiki (and 1 other person) 105 Board Figure 1 Figure 2 Recording power [mW Figure 4

Claims (3)

[Claims] (1) In a magneto-optical recording medium in which a dielectric layer, a recording layer, a dielectric layer, and a reflective layer are laminated in this order on a glass or plastic substrate, the recording layer is composed of a light rare earth, a heavy rare earth, and a transition metal. and the reflective layer is Au,
A magneto-optical recording medium comprising two layers of one of Ag, Pt, and Cu and Al, and characterized in that Au, Ag, Pt, and Cu are provided on the recording layer side. (2) The magneto-optical recording medium according to item 1, wherein the dielectric layer is made of aluminum silicon nitride, and the recording layer is made of NdDyFeCo. (3) The magneto-optical recording medium according to item 1, wherein the dielectric layer is made of aluminum silicon nitride, and the recording layer is made of NdDyTbFeCo.