JPH03171450A - Optical recording medium - Google Patents

Abstract

PURPOSE:To enhance the heating efficiency of the medium and a recording sensitivity and to allow the high-speed transfer of data by aggregating and forming the many grain lumps of a thin film material along the surface of a substrate and forming heat propagation releasing regions between the adjacent grain lumps. CONSTITUTION:The thin film of the optical recording medium which allows the recording of information by irradiating the thin film formed on a transparent substrate 3 with a laser beam thereby heating the thin film and changing the magnetization, crystallinity or shape of the thin film is constituted of the columnar or planar grain lumps 1 of 5 to 100nm sizes on the base and the heat propagation releasing regions of such gaps 2 or the like which hinder the propagation of the heat between the grain lumps are provided between the grain lumps and the grain lumps. Such film is small in thermal conductivity as compared with ordinary films. The heating efficiency by the laser beam is enhanced if this film is used for the heat mode optical recording medium. The optical information medium having the high heating efficiency and the excellent recording sensitivity is obtd. in this way.

Description

[Detailed description of the invention] [Industry” second field of use] The present invention relates to an optical recording medium with excellent recording sensitivity.

[Conventional technology]

By irradiating a thin film formed on a transparent substrate with a laser beam and heating the thin film, the magnetization state of the thin film can be changed.
2. Description of the Related Art Optical recording media that record information by crystallinity or by changing shape have recently attracted attention as high-capacity recording media.

Optical recording media include magneto-optical disks, which use a magnetic material in the recording film, record information by partially reversing the direction of magnetization by heating with laser light, and reproduce signals using the magneto-optic effect, and laser light. Phase change disks record information by causing a phase change from crystal to non-quality or from non-quality to crystal by heating, and reproduce signals based on the difference in reflectance between crystal and non-quality, or by heating holes in 14 films. There are some that form protrusions. In addition, disk-shaped media, card-shaped media, and tape-shaped media have also been proposed.

Recording films used in optical recording media include rare earth and transition metal alloys, which are mainly used in magneto-optical recording, chalcogenite alloys, which are used in phase change media, and cyanine-based organic dyes. A method for forming these films is spuck vacuum evaporation. Spincoal l. etc. are used.

[Problem to be solved by the invention]

When handling large amounts of data, it is required not only that the capacity of the recording medium be large, but also that the data be transferred in as short a time as possible. However, in all of the above-mentioned optical recording media, information is recorded by irradiating the medium with laser light and heating the medium to several hundred degrees Celsius or higher, but there is a limit to the output of the semiconductor laser used as the light source. Unfortunately, current optical recording media have slower data transfer speeds than hard disks and magnetic tape.

SUMMARY OF THE INVENTION An object of the present invention is to provide an optical recording medium that has high recording sensitivity and is capable of high-speed data transfer by increasing the heating efficiency of the medium.

[Means and effects for solving the problem] Therefore, the present invention provides an optical recording medium in which a thin film formed on a transparent substrate is irradiated with a laser beam to record information on the thin film, wherein the thin film is formed on the transparent substrate. The solution is that a large number of grains of the thin film material adhered and formed on the substrate are formed in aggregation along the surface of the substrate, and a heat propagation relaxation region is formed between adjacent grains. It is used as a means.

That is, in view of the above-mentioned current state of optical recording media, the present inventors conducted various experiments and found that a thin film formed on a transparent substrate is irradiated with laser light to heat the thin film. In an optical recording medium that records information by changing the magnetization, crystallinity, or shape of the thin film, the thin film
It is composed of columnar or plate-shaped grains with a bottom surface size of 5 to 100 nm, and between these grains there is a heat propagation relaxation region such as a void that prevents at least the propagation of heat between the grains. It has been found that the above problem can be solved by having the following.

According to the present invention, depending on the method and conditions for shaping the thin film, the formed film has a bottom surface size of 5 to 100 nm.
It is composed of columnar or plate-like particles, and may have a structure with voids at the boundaries between the particles that at least hinder the propagation of heat between the particles.
The thermal conductivity is lower than that of a normal film, and by using this film in a heat mode optical recording medium, it is possible to provide a heat mode optical recording medium with high heating efficiency by laser light and excellent recording sensitivity. can.

In the method of forming a thin film in the present invention, the formed film is composed of columnar or plate-like grains with a bottom surface size of 5 to 100 nm, and at least grains are present between the grains. There are no particular restrictions as long as the method creates a structure with voids that prevent the propagation of heat between the lumps, but when forming a film by sputtering, the pressure of Ar used as sputtering gas may be set to 10
If sputtering is performed at mTorr or more, such a film can be formed with relatively good reproducibility. Further, in the vacuum evaporation method, such a film can be formed by intentionally introducing a gas such as Ar or N into the evaporation chamber.

When the size of the grains constituting the film exceeds 100 nm,
The voids at the boundaries of the grains are undesirable because they cause noise during signal reproduction. Furthermore, although it was not possible to produce particles with a particle diameter of less than 5 nm within the scope of the tests conducted by the present inventors, when a magnetic material is used in a thin film such as in magneto-optical recording, it is possible to If it becomes small, it is not preferable because there is a risk that the thin film will become unmagnetized due to so-called superparamagnetism.

Thin film materials that can be used in the present invention are particularly suitable for use in optical recording media. Although there is no such restriction, it is preferable that the film can be formed by a sputtering method or a vacuum evaporation method. Examples of such materials include TbFe and Gd, which are used for the recording film of magneto-optical media.
Pe, NdFe, DyFe, GdCo, TbFeCo,
NdFeCo, DyPeCo, NdDyFeCo1 or these to which Cr, Ti, In, Pt, Ta, etc. are added,
Sin, SiN, AIN, ZnS, used for the protective film
SiAION, BN, A+ used for reflective film, GeTe, GeTeSe, GaTeSe, Pd used for phase change medium
'l''eo etc.

In the present invention, the voids between the grain agglomerates may be filled with other substances other than air, the composition of which is different from that of the grain agglomerates. The other substances mentioned here include gas molecules in the vacuum chamber that are fixed at the boundaries between grain agglomerates and those that are formed previously when the medium is a multilayer film. Refers to the constituent materials of the next layer deposited in the voids of the Noko layer.

Example C] The present invention will be explained in more detail using Examples below.
The present invention is not limited to these examples.

Example I First, a T b 22 F e 70 C O B thin film used as a recording film of a magneto-optical disk was coated at various Ar gas pressures using a Magne 1 Ron sputtering device for electron microscopic observation. It was produced by sputtering and observed using a transmission electron microscope. The film thickness was set to 500 people1.

The film sputtered at an Ar gas pressure of 1 to 8 mTorr was a substantially continuous film as shown in FIG. Conventional optical recording media use such continuous thin films.

On the other hand, the film sputtered at an Ar gas pressure of 12 to 20 mTorr is not shown in Figure 1. l7
It was clearly recognized that voids existed as heat propagation regions.

7. FIG. 2 is a cross-sectional view of this example, in which 1 indicates a grain agglomerate, 2 indicates a void, and 3 indicates a substrate (colonone film).

In addition, G e 9B i 33T e 611.
S i 3N4 (protective film) was formed by sputtering at various gas pressures and observed with a transmission electron microscope. As expected, most of the films sputtered at gas pressures of I O mTorr or higher had a thickness of several tens of nanometers. The structure was composed of columnar or plate-like grain agglomerates with a size of

Example 2 Table 1 shows the results of measuring the thermal conductivity of a film formed to a thickness of 15 μm on a 75 μm thick glass substrate by AC force lolimetry under the same conditions as Example I.

Transmission electron microscopy revealed that the membrane was composed of columnar to plate-like grains with a size of several tens of nanometers, and it was clearly observed that there were voids at the boundaries between the grains. The thermal conductivity of the film-coated products of the present invention (both are 8% lower than that of conventional products of the same set).

Table 1 “Evaluation as an optical recording medium” Glass substrate with group/S 1 3 N 4 (
10006) / T b 22F e vnC O e
(800 people) / S i 3 N 4 (800 people)
A magneto-optical disk having a structure of
The input/output characteristics were compared between mTorr and 3 mTorr.

Disc rotation speed 1800 rpm, recording radius 30 mm
Recording frequency 3. When measured at 7 MHz and a duty ratio of 33%, both disks had the same CN ratio of 48.0 dB. The optimal recording power was 68 mW for the conventional product with an Ar gas pressure of 3 mTorr, whereas the optimal recording power was as low as 6.0 mW with the present invention product with an Ar gas pressure of 20 mTorr, and the recording sensitivity was improved.

In other words, the recording film of the present invention with an Ar gas pressure of 20 mTorr is composed of columnar or plate-like particles with a size of several tens of nanometers, as shown in Fig. 1, and consists of grains and grains. The structure clearly shows the existence of voids at the boundaries, and these voids impede the propagation of heat between the particles, reducing the thermal conductivity of the film, and therefore preventing the recording film from being exposed to laser light 7. Heating efficiency has increased, and recording sensitivity has improved.

Although the embodiments have been described above, various design changes can be made to the present invention depending on the gist of its configuration.

For example, in each of the above-mentioned embodiments, voids are formed as heat propagation relaxation regions, but other materials with low thermal conductivity may be interposed between grain agglomerates.

Furthermore, the present invention is not limited to the methods and materials used in the above-described embodiments.

〔Effect of the invention〕

As is clear from the above description, the present invention has the effect of providing an optical recording medium with high heating efficiency by laser light and excellent recording sensitivity.

[Brief explanation of the drawing]

Figure 1 shows Tb2. Fe,. A transmission electron micrograph of the Coo thin film (first example), Figure 2 is a cross-sectional view of the first example, and Figure 3 is a transmission electron microscope photograph of a conventional example prepared by magnetron sputtering at an Ar gas pressure of 3 mTorr. be. +1- Figure 3 Enlarged photograph of conventional example 0.1 μm April 1990 258 ■. Display of the case 1999 Patent Application No. 309687 2 Name of the invention Optical recording medium 3 Person making the amendment Relationship to the case

Claims (1)

[Claims] (1) In an optical recording medium in which information is recorded on a thin film formed on a transparent substrate by irradiating the thin film with a laser beam, the thin film is composed of agglomerates of a thin film material attached and formed on the transparent substrate. An optical recording medium characterized in that a large number of grains are formed along the surface of the substrate, and a heat propagation relaxation region is formed between adjacent grains.