JPH01227236A - Information recording medium - Google Patents

Abstract

PURPOSE:To increase the crystallization temp. so as to stabilize the amorphous state at room temp. and to obtain the recording medium having a large reflectivity change with a phase transition by adding Te of a chalcogenite element to a binary alloy of Mg, Ca, thereby forming the recording layer. CONSTITUTION:Sputtering sources 18, 19, 20 of the Mg, Ca, Te are provided in a vacuum vessel and further monitors 21, 22, 23 are provided. The inside of the vessel 1 is then evacuated to a vacuum and gaseous Ar is introduced therein. The entire part of the pressure therein is controlled. A substrate 16 is rotated and the electric power to be thrown to the sputtering sources 18-20 is controlled while the sputtering rates of the respective elements are monitored by the monitors 21-23 to deposit the respective elements on the substrate 16, by which the recording layer is formed. The recording medium having the large reflectivity change with the phase transition is obtd. by adding the chalcogenite elements Te, Se, Ge to the binary element of the Mg and Ca which reversibly induce the phase transitions of the crystal and amorphous states.

Description

[Detailed Description of the Invention] [Purpose of the Invention (Industrial Application Field) The present invention produces a change in optical properties due to a change in the atomic arrangement of the recording layer by irradiation with a recording light beam, The present invention relates to an information recording medium that repeatedly records and erases information, detects changes in optical characteristics, and reproduces information.

(Prior Art) Among recordable and erasable information recording media that have been widely developed in the past, there is one that uses light beam irradiation to change the atomic arrangement.

When recording information on such an information recording medium, the information recording layer is first irradiated with a light beam over the entire surface and heated to bring the recording layer into a highly crystalline state (hereinafter referred to as a crystalline state). Next, a short, strong pulse of light is irradiated to heat and rapidly cool the recording layer. Then, the pulse irradiated area becomes in a state where the crystallinity is reduced (hereinafter referred to as an amorphous state), and information is recorded. The optical properties (reflectance, transmittance) change between the crystalline state and the amorphous state because the atomic arrangement is different, so information can be reproduced by detecting changes in these optical properties. .

To erase the written information, the material is heated and slowly cooled by irradiation with long, weak pulsed light to change the atomic arrangement and return to a crystalline state.

As a material for the recording layer that records and erases information by repeatedly changing the atomic arrangement depending on the irradiation conditions of the light beam, Te has a particularly large change in reflectance.

A semiconductor amorphous i whose main component is a chalcogenide element such as Se has been proposed. However, in addition to the semiconductor device mass, M
In a binary alloy of g and Ca, when the Ca content is in the range from 15 atomic % to 85 atomic %, it repeatedly changes into metallic crystal and metallic amorphous due to the difference in the light beam irradiation conditions as described above. The scales were discovered. However, in these metal alloys, changes in optical properties due to phase change are not large enough to allow them to be used as recording materials. In addition, there are problems such as low crystallization temperature and poor stability of the amorphous state at room temperature, making it impossible to use it as an information recording medium.

(Problem to be solved by the invention) As detailed above, Mg and Ca (15 atomic%≦Ca
≦85 at. could not be used.

In order to solve the above problems, in the present invention, a chalcogenide element Te is added to a binary alloy of Mg and Ca.

By adding Se and Ge, the crystallization temperature is increased to stabilize the amorphous state at room temperature, and the amount of change in optical properties due to phase change is increased, thereby providing a material that can be used as an information recording medium. The purpose is to

[Structure of the Invention] (Means and Effects for Solving the Problems) The information recording medium of the present invention has a cross-sectional structure as shown in FIG. 1, for example. In FIG. 1, the information recording medium includes a substrate 1 and an inorganic protective layer 3 on the substrate 1. Optical recording layer 2. Inorganic protective layer 3. It is constructed by sequentially comprising organic protection layers 4.

The substrate 1 is made of glass or plastic material (eg, polyolefin, epoxy, polycarbonate, polymethacrylate, etc.).

The inorganic protective layer 3 has a structure sandwiching both sides of the optical recording layer 2 to prevent the optical recording layer 2 from deteriorating over time, and is made of a metal or semimetal oxide, fluoride, or sulfide.

Nitride such as 5i02, A1203, AIN.

It is made of dielectric material such as ZnS. This inorganic protective layer also has the function of amplifying reflected light. The organic protection layer 4 is made of ultraviolet curing resin and is provided to prevent scratches and dust on the surface when handling this information recording medium.

A recording layer having such a composition is formed by a multi-source simultaneous sputtering method. That is, the sputtering equipment used is as shown in FIGS. 2 and 3. Reference numeral 11 in FIG. 2 is a vacuum container, which is connected to an exhaust device 13 via a gas exhaust boat 12 and to an argon gas cylinder 15 via a gas introduction boat 14. In the upper part of the vacuum container 11,
The substrate 16 is supported horizontally on the support device 17 .
It can be rotated by Moreover, at the bottom of the vacuum container 11,
Sputter sources 18, 19 and 20 made of a predetermined element are provided, and monitor devices 2'l and 22 are provided above each sputter source.
．． 23 are provided.

When forming a recording layer using this apparatus, first, the inside of the vacuum chamber 11 is heated to 10''T using the exhaust device 13.
Evacuate to a vacuum level of orr level. Next, Ar gas is introduced from the gas introduction boat 14 and the exhaust amount of the exhaust device 13 is adjusted to maintain the inside of the vacuum vessel 11 under a predetermined reduced pressure. Then, while rotating the substrate 16, power is applied to the sputtering sources 18, 19, and 20 for a predetermined period of time. As a result, a recording layer is formed on the substrate 16.

(Example) The experimental results of testing the characteristics of the information recording medium having the above structure will be described below.

Experiment 1 - Mg, Ca, and Te sputtering sources were provided in the vacuum container 11 shown in FIG. 2, and the inside of the container was evacuated to 5×1G-6 Torr. Next, introduce Ar gas to 5 x 1O-3T
The total pressure was adjusted to orr. Using a thoroughly cleaned disc-shaped polycarbonate substrate with an outer diameter of 130 nm and a plate thickness of 1.2+ nm as the substrate, the amount of sputtering of each element was monitored while rotating this substrate at 80 rpm, and each sputtering source was introduced. The recording layer was formed by controlling the electric power and depositing each element until the total film thickness was 1000 Å. Tellurium,
The relationship between selenium content and crystallization temperature was investigated. The results are shown in FIG. It can be seen that as the content of Te and Se increases, the crystallization temperature gradually increases. Mg and C
A similar effect was obtained when the composition ratio with a was changed. Similar effects were also obtained when Ge was added instead of Te and Se.

From the above experimental results, it was found that by adding chalcogenide elements Te, Se, and Ge to a binary alloy of Mg and Ca, the crystallization temperature increases and the amorphous state at room temperature becomes stable.

-Experiment 2- Mg, Ca and X (X-Te, S
The ternary recording layer of e) was formed by a multi-component simultaneous sputtering method, and the wavelength was 7.
It was irradiated with 90 nm light and the surface reflectance was determined by DJ.

The results are shown in FIG. Chacogenite element Te
, the amount of change in reflectance gradually increased as the Se content increased. Similar effects were obtained by changing the composition ratio of Mg and Ca. Similar effects were also obtained when Ge was added instead of Te and Se. The above experimental results revealed that the amount of change in reflectance increases by adding chalcogenide elements Te, Se, and Ge to a binary alloy with Mg and Ca.

Experiment 3 - Here, the safety of the amorphous state of the formed alloy thin film was investigated.

Si 02100rv, optical recording material 1100n, Si 021100n, UV- under the glass substrate
A cured resin layer was formed by the sputtering method described above. The composition of the formed recording layer is (Mg 3oca 70)
9oSe Ion (Mg 5oCa 50
) ease Ion (Mg 7oca 30),
There are 3 types of ose 10. This recording layer is first irradiated with a light beam over the entire surface, then with a short strong pulse of light,
Linear structure diffraction confirmed that it was amorphous.

Next, this sample was subjected to an environment of 45° C. and 70% RH, and changes in reflectance were measured. The initial value of the surface reflectance on the substrate side was set as Ro, and the value of the reflectance over time was set as R, and the value of R/Ro was plotted over a 4-time period (FIG. 6). (Mg3
oca 70) 9ose Ion (Mg, o
ca so) 9oSe lot (Mg
7oca 30) 9ose1o It can be seen that there is almost no change in the reflectance of the recording layer of any composition even after three months.

Similar effects were obtained when Te and Ge were added instead of Se. From the above experimental results, T
It has been found that by adding chalcogenide elements such as e, Se, and Ge, it is possible to obtain a stable information recording medium that does not change over time and is in an amorphous state.

[Effects of the invention] As detailed above, when chalcogenide elements Te, Se, and Ge are further added to a binary alloy of Mg and Ca that causes a reversible phase change between a crystalline state and an amorphous state, a phase change occurs. The change in reflectance associated with this increased, and the crystallization temperature also increased, resulting in an information recording medium that was stable in an amorphous state at room temperature.

[Brief explanation of the drawing]

FIG. 1 is a cross-sectional structural diagram of the information recording medium of the present invention, FIG. 2 is a side view of the sputtering device, FIG. 3 is a bottom view of the sputtering device, and FIG. 4 is the doping rate of chalcogenide elements and crystals. Figure 5 is a graph showing the correlation between the amount of chalcogenide added and the amount of change in reflectance. Figure 6 is the change in reflectance over time of a ternary recording layer of Mg, Ca, and Se. It is a graph showing the correlation of quantities. 1...Substrate 2...Recording layer 3...Inorganic protective layer 4...Organic protective layer

Claims (1)

[Claims] In an information recording medium having a recording layer capable of recording and erasing information by causing a change in atomic arrangement by irradiation with a light beam, the recording layer may contain Mg, Ca, and X (X is Se, Te, Ge,
An information recording medium comprising an alloy thin film containing an element selected from the group consisting of: