JPH02183450A - Magneto-optical recording medium - Google Patents

Abstract

PURPOSE:To prevent the formation of magnetic domains to a teardrop type even with the short recording domains and to lessen the decrease in C/N to lower the error rate of the medium by forming at least one layer of dielectric layers of a specific metal oxide. CONSTITUTION:The above medium is obtd. by forming the dielectric layers 101, magnetic layers 102 consisting of TbFeCo films, etc., and the dielectric layers 103 respectively by a sputtering method, etc., on two sheets of substrates 104 consisting of polycarbonate, etc., and sticking the layer 103 side thereof by using a thermosetting resin. At least one layer of the layers 101 and the layers 103 are formed of any among BeO, SrO and BaO. the combination of the above-mentioned metal oxides and AlN, Si3N4, etc., as the dielectrics can be used.

Description

[Detailed description of the invention] [Industrial application field]

The present invention utilizes focused light such as laser light to record, erase, and
It relates to magneto-optical recording media used in magneto-optical recording for reproduction, and particularly relates to improving the recording and reproduction characteristics of the medium. [Prior Art] Magneto-optical recording is an erasable optical recording system, and research on media, devices, etc. is being actively conducted. The medium used is a film of a rare earth transition metal amorphous alloy represented by TbFeCo formed by a sputtering method on a transparent substrate such as glass or polycarbonate.
At this time, in order to prevent oxidation of the magnetic layer, a dielectric layer made of an oxide or nitride of aluminum or silicon is laminated on top of the magnetic layer, or a structure is adopted in which the magnetic layer is sandwiched between dielectric layers on both sides. This is common. Further, depending on the case, a metal film such as aluminum may be further laminated as a reflective layer. [Problem to be Solved by the Invention 1] By the way, recording domains in the magneto-optical recording method are formed using the distribution of magnetic properties resulting from the temperature distribution of minute regions of the magnetic layer heated by the recording beam. On the other hand, since a focused beam with a width similar to that of the recording domain is used for reproduction, it is desirable that the width of the recording domain is constant.However, in actual recording, when the recording domain is short, the width of the magnetic layer during recording is It is known that the temperature distribution becomes asymmetric between the front and rear of the bit, resulting in the formation of so-called mold-making magnetic domains. In such a recording domain, the degree of modulation of the reproduction signal is not sufficient, so when the recording frequency becomes high, sufficient reproduction characteristics cannot be obtained, and the reproduction signal may be misaligned with respect to the time axis, causing errors. It has been known. Furthermore, it has been pointed out that this is a fatal drawback in the bit edge recording method proposed for the purpose of improving recording density. The present invention is intended to solve these problems, and its purpose is to be able to form magnetic domains of uniform width without molding even when the recording domain is short, and to improve the carrier-to-noise ratio (C) at high frequencies. An object of the present invention is to provide a highly reliable recording medium with a small decrease in /N) and a low error rate. [Measures to Solve the Problems Fi1] The magneto-optical recording medium of the present invention is a magneto-optical recording medium in which a magnetic layer and at least one dielectric layer are laminated on a substrate. One layer is beryllium oxide (
BeO), strontium oxide (SrO), or barium oxide (BaO). [Operation] Applicants investigated the recording and reproducing characteristics by changing the type of dielectric layer in the magneto-optical recording medium, and found that BaO11
We discovered that by using this method, a shorter recording domain can be manufactured into a mold compared to the conventionally used silicon nitride film or aluminum nitride film. Furthermore, when other materials were investigated, a similar tendency was confirmed when using a Bad film or a SrO film. The cause of this is not clear, but by analogy, although the temperature of the magnetic layer increases once due to beam irradiation, the thermal conductivity of these oxides is as high as that of metals and is also higher than that of the magnetic layer, so the heat of the magnetic layer increases. This is thought to be due to the fact that the magnetic layer escapes through the dielectric layer, and as a result, the magnetic layer quickly cools down to its original temperature, resulting in a symmetrical temperature distribution in the front and rear portions of the recording domain. It is also thought that the temperature gradient that occurs in the recording layer when the temperature rises becomes steeper, which also has an effect. [Example] The present invention will be explained in detail below by giving specific examples. Example 1: Polycarbonate (PC) with a guide groove of 130 mm in diameter
A magneto-optical recording medium was fabricated using a substrate with the configuration shown in FIG. That is, the BaO film 101, the TbFeCo film 102, and the BaO film 103 are respectively 80 nm, 90 nm, and 80 nm thick.
A film of 0nm was sequentially formed on the PC board 104 by sputtering, and then two of the same films were bonded together using a thermosetting resin on the III side to form a reflective double-sided magneto-optical recording medium. Created. Using this medium, the dependence of C/N on recording frequency at a linear velocity of 5 m/s was investigated using a measurement system using a semiconductor laser with a wavelength of 780 nm. The results are shown in Figure 2, and when IMH2 (domain length 2.5 μm), 57
．． At 0 dB and 3 MHz (domain length 0°8, clm), the C/N drop was 52.5 dB and 4.5 dB. For comparison, a recording medium manufactured with the same configuration as the above example except that the dielectric layer was made of Si3N4 was prepared. The third factor is the frequency dependence of the C/N of this recording medium.
57.2 dB at MHz (domain length 2.5 μm)
Although no significant difference was observed between the results and the examples of the present invention, 3M
51.0 dB at Hz (domain length 0.8 μm)
The drop in C/N was 6.2 dB, indicating that this was not suitable for high-density recording. Furthermore, when the recording domains of the media of the examples of the present invention and the comparative examples were observed using a polarizing microscope, the recording domains of the former had a neat elliptical shape, but the recording domains of the latter were liquid. Example 2: A recording medium having exactly the same configuration as Example 1 was produced using BeOSrO as the material of the dielectric film. That is, the dielectric film, TbFeCo11, and the dielectric film were each 80%
PC by sputtering method to film thickness of nm, 90nm, 80nm
Films were sequentially formed on the substrate. Next, two sheets of the same material were bonded together using a thermosetting resin on the machine side to produce a reflective double-sided magneto-optical recording medium. Wavelength 78 using these media as in implementation g41
The measurement system uses a 0 nm semiconductor laser, and the linear velocity is 5 m.
The dependence of C/N on the recording frequency was investigated at /s. As a result, the medium using BeO had a C/N drop of 4°1 dB, which was 56.8 dB at IMHz (domain length 2.5 μm) and 52.7 dB at 3 MHz (domain length 0.8 μm). When the medium was IMHz, it was 5
7.3dB, 53.0dB and C/N at 3MHz
The reduction was 4.3 dB, which was found to be suitable for high-density recording. Example 3: Recording media having various configurations as shown in Table 1 were fabricated using Bed, SrO, and BaO as dielectric films. Samples 1-5
Samples 6 to 8 are reflective media having a reflective layer, and Samples 9 and 10 are transmissive media that utilize the Faraday effect for reproduction. Table 1 When a random pattern of 2-7 codes was recorded on these media samples 1 to 10 and the error rate of the reproduced signal was measured, all samples showed a value of 10-@ or less.
For comparison, recording media having the configurations shown in Table 2 were produced. Here, the samples y411.12.13 are a normal reflective medium, a reflective medium having a reflective layer, and a transmissive medium, respectively. Similarly to Table 2, when a random pattern of 2-7 codes was recorded on the media numbered 11-13 and the error rate of the reproduced signal was measured, all samples had a value of 104 or more.

【Effect of the invention】

As described above, according to the present invention, the temperature distribution of the recording layer becomes highly symmetrical during the thermomagnetic writing process of magneto-optical recording, so that even when the recording domain is short, it does not become shaped. , it is possible to reduce the drop in C/H at high frequencies, reduce the error rate of the medium, and provide a highly reliable recording medium. Note that these effects do not only appear in recording media with the combination of substrate, recording material, and dielectric film shown in the examples; for example, when a glass or acrylic resin substrate is used as the substrate, or when the recording material is D y F
e Co, G d T b Fe, N d
It goes without saying that the same effect can be obtained even if a material such as T b Fe CO is used, or if a dielectric material such as Al5iN or 5i02 is used in combination.

[Brief explanation of the drawing]

FIG. 1 is a schematic diagram showing the configuration of a medium according to Example 1 of the present invention. 101...Ba0 102...TbFeC0 103...Ba0 104...Polycarbonate substrate The second factor is a diagram showing the frequency dependence of the reproduction C/N of the magneto-optical recording medium of the present invention in Example 1. . FIG. 3 is a diagram showing the frequency dependence of the reproduction C/N of the conventional magneto-optical recording medium in Example 1. Applicant Seiko Epson Co., Ltd. Representative Patent Attorney Masayoshi Kamikushi and 1 other person Figure 1 Figure 2 3-3-5 Seiko Epson stock % formula % Seiko Epson stock

Claims (1)

[Claims] In a magneto-optical recording medium formed by laminating a magnetic layer and at least one dielectric layer on a substrate, at least one of the dielectric layers is made of beryllium oxide (BeO), strontium oxide (SrO), or barium oxide (BaO). A magneto-optical recording medium characterized by being any of the above.