JPH01227235A - 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 Ni, Gr, thereby forming the recording layer. CONSTITUTION:Sputtering sources 18, 19, 20 of the Ni, Gr, 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 Ni and Gr which reversibly induce the phase transitions of the crystal and amorphous states.

Description

Detailed Description of the Invention [Objective of the Invention] (Industrial Application Field) The present invention produces information by causing 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 reproduces information by repeatedly recording and erasing information and detecting changes in optical characteristics.

(Prior Art) Among the recordable and erasable information recording media that have been widely developed in the past, there are those that use 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 crystalline deafness). Next, a short, strong pulse of light is irradiated to heat and rapidly cool the recording layer. Then, the crystallinity of the pulse irradiated area begins to deteriorate (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.

Materials for the recording layer that record and erase information by changing the atomic arrangement depending on the light beam irradiation conditions are as follows:
Te and Se have particularly large reflectance changes.

Semiconductor amorphous materials containing chalcogenide-based elements such as Ge as a main component have been proposed. However, in addition to semiconductor device quality, G
In a binary alloy of r and Ni, when the Gr content is in the range of 15 atomic % or more and 85 atomic % or less, it repeatedly changes into metallic crystal and metallic amorphous depending on the difference in the light beam irradiation conditions as described above. 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.

(Problems to be Solved by the Invention) As detailed above, Ni and Gr (15 atomic %≦Gr≦8
5 at%), the crystallization temperature is low, the stability of the amorphous state at room temperature is poor, and the change in optical properties due to phase change is small, so it is not suitable as a material for information recording media. Couldn't use it.

In order to solve the above problems, the present invention adds chalcogenide elements Te, Se, and Ge to a binary alloy of Nl and G to increase the crystallization temperature and stabilize the amorphous state at room temperature. , change in optical properties due to phase change]
The purpose is to provide materials that can be used as information recording media.

[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 in order to prevent the optical recording layer 2 from deteriorating over time, and is made of a metal or metalloid oxide, fluoride, or sulfide.

Nitride such as SiO2, Al□03. A.I.N.

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 an 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. At the upper part of the vacuum container 11, a substrate 16 is supported horizontally on a support device 17 and can be rotated by the support device 17. Furthermore, sputtering sources 18, 19.20 made of a predetermined element are provided at the bottom of the vacuum chamber 11, and monitor devices 21, 22.2 are provided above each sputtering source.
3 is provided.

When forming a recording layer using this apparatus, first, the inside of the vacuum chamber 11 is heated to 10-6T o using the exhaust device 13.
Evacuate to a vacuum level of rr level. Next, gas introduction boat 1
Ar gas is introduced from 4 and the exhaust amount of the exhaust device 13 is adjusted to maintain the inside of the vacuum container 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 - Ni, Gr, and Te sputtering sources were provided in the vacuum container 11 shown in FIG. 2, and the inside of the container was evacuated to 5×1O−6 Torr. Next, introduce Ar gas to 5 x 1O-3T
The total pressure was adjusted to orr. A thoroughly cleaned disc-shaped polycarbonate substrate with an outer diameter of 130 nm and a plate thickness of 1.2 mm was used as the substrate, and this substrate was rotated 1 time at 60 rpm.
A recording layer was formed by monitoring the amount of sputtering of each element using a monitor and controlling the power applied to each sputtering source, and depositing each element until the total film thickness was LOOOA. The tellurium selenium content was gradually increased for 7 g of Ni2□Gr, and the crystallization temperature was measured using a high-sensitivity DSC (differential degree scanning calorimeter) at a heating rate of 10°C/ff1I11 to determine the tellurium and selenium contents and crystallization temperature. We investigated the relationship between The results are shown in FIG. The crystallization temperature was sufficiently high regardless of the tellurium and selenium contents. Also, Ge
However, the same effect was obtained.

Therefore, Ni, Gr, X (X-Te, Se.

It can be seen that the information recording medium made of Ge) has a sufficiently high crystallization temperature regardless of the composition ratio, and the amorphous state is stable.

1 Experiment 2 - Using the same method as Experiment 1, Ni, G' and X (X-Te,
A ternary recording layer of Se) was formed by a multi-component simultaneous sputtering method, and the surface reflectance was determined to be 11 by irradiating light with a wavelength of 790 nm. The results are shown in FIG. Chacogenite element T
It can be seen that as the content of e and Se increases, the amount of change in reflectance also increases. Similar effects were obtained by changing the composition ratio of Ni and Gr. Furthermore, Te.

A similar effect was obtained when Ge was added instead of Se. The above experimental results show that by adding a chalcogenide element to a binary alloy of Ni and G, the amount of change in reflectance due to phase change increases, and the amount of reproduced signal obtained also increases.

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

On a glass substrate, a layer of SiO21QOnm, an optical recording material of 1100n, SiO□100t+m, and a UV curable resin layer were formed by the sputtering method described above. The composition of the formed recording layer is (Ni 1oGr 70) 9oTe
lo+ (Ni 50GI” so), oTe lo+
(Ni 70 Gr 30) *oTe 10. This recording layer was first irradiated with a light beam over its entire surface, and then with short, intense pulsed light, and it was confirmed by X-ray structural diffraction 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 is -Ro, and the value of the reflectance over time is R, and the value of R/Ro is plotted for 4 hours (Fig. 5). (Ni
3oZr 70) 9oTe 1o, (Ni so
Zr so) '90"re IO+ (Ni
70 Zr 3o) 9°Te, It can be seen that there is almost no change in the reflectance even after 3 months of recording layer composition. Similar effects can also be obtained when Se or Ge is added instead of Te.

The above experimental results show that the amorphous state of a material made by adding chalcogenide elements such as Te, Se, and Ge to a binary alloy of Ni and Gr is sufficiently stable and can be used as an information recording medium. I understand.

[Effects of the invention] As detailed above, when chalcogenide elements Te, Se, and Ge are further added to a binary alloy of Ni and Gr that causes a reversible phase change between a crystalline state and an amorphous state, a phase change occurs. The accompanying change in reflectance increases, and an information recording medium with a large amount of reproduced signal can be obtained.

[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 amount of chalcogenide added and the crystallization. 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 amount of change in reflectance over time of a ternary recording layer of Ni, Gr, and Te. This is a graph showing. 1...Substrate 2...Recording layer 3...Inorganic protective layer 4...Organic protective layer Same 6 Figure

Claims (1)

[Claims] In an information recording medium having a recording layer capable of recording information by causing a change in atomic arrangement by irradiation with a light beam, the recording layer may include Ni, Gr, and X (X is an element selected from Se, Te, and Ge). ) An information recording medium comprising an alloy thin film containing.