JPH01224938A - Information recording medium - Google Patents

Abstract

PURPOSE:To increase a crystallization temp. and to stabilize the amorphous state at room temp. by adding chalcogenite elements Te, Se and Ge further to a binary alloy of Ca and Zn which reversibly induce a phase change between a crystal state and the amorphous state. CONSTITUTION:The recording medium is constituted by providing a substrate 1 and an inorg. protective layer 3, an optical recording layer 2, an inorg. protective layer 3, and an org. protective layer 4 successively on this substrate 1. The substrate 1 consists of a glass or plastic material and the inorg. protective layer 3 is made into the structure in which both sides of the optical recording layer 2 are sandwiched in order to prevent the deterioration of the optical recording layer 2 with age. Said protective layer consists of the dielectrics such as the oxide, fluoride, sulfide or nitride of metals or semimetals. The org. protective layer 4 consists of a UV curing resin and is disposed in order to prevent flawing and dust on the surface. The recording layer 2 having such compsn. is formed by a multielement simultaneous sputtering method which forms the film by adding the chalcogenite elements such as Te, Se and Ge to the binary element consisting of the Ca and the Zn. The crystallization temp. is thereby increased and the amorphous state at room temp. is stabilized.

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 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 crystallinity of the pulse irradiated area becomes 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.

Te and Se, which have particularly large reflectance changes, are used as materials for the recording layer that records and erases information by changing the atomic arrangement depending on the light beam irradiation conditions.

Semiconductor amorphous materials mainly composed of chalcogenide elements such as qe have been proposed. However, in addition to the mass of the semiconductor device, C
In a binary alloy of a and Zn, when the Zn content is in the range of 10 at. I found out that it works. 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, so that it cannot be used as an information recording medium.

(Problems to be Solved by the Invention) As detailed above, in the binary alloy of Ca and Zn, (1
(0 atomic%≦Zn≦85 atomic%) It is used as a material for information recording media because 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. could not.

In order to solve the above problems, the present invention adds chalcogenide elements Te, Se, and Ge to a binary alloy of Ca and Zn to increase the crystallization temperature and stabilize the amorphous state at room temperature. The purpose of this invention is to provide a material that increases the amount of change in optical properties due to phase change and can be used as an information recording medium.

[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, polymeric methacrylate, 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 S10□, 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. In the upper part of the vacuum container 11, a substrate 16 is horizontally supported by a support device 17 and can be rotated by the support device 17. Further, 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, 20 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 by 10-'To
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 sputterers [18, 19, 20] for a predetermined 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 - Ca, Zn, 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 L of 30 nm and a plate thickness of 1.2 cm was used as the substrate, and this substrate was rotated at 80 rpa+ for 1 time.
A recording layer was formed by monitoring the amount of sputtering of each element using a monitor and controlling the power input to each sputtering source, and depositing each element to a total film thickness of 1000 Å. The content of tellurium selenium was gradually increased relative to Ca 7oZn 30, and the crystallization temperature was raised to 1lllJ at a heating rate of 10°C/mn+ using high-sensitivity DSC (differential scanning calorimetry).
The relationship between the tellurium-9-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. Similar effects were obtained even when the composition ratio Se of Ca and Zn was changed. Furthermore, similar effects were obtained when Te, Se, and Ge were added instead.

From the above experimental results, T
It was found that adding chalcogenide elements such as e, Se, and Ge increases the crystallization temperature and stabilizes the amorphous state at room temperature. (X-Te,
A recording layer consisting of the three elements Se) was formed by a multi-element simultaneous sputtering method, and its surface reflectance was measured by irradiating it with light having a wavelength of 790 nIIl. The results are shown in FIG.

It can be seen that as the content of the chacogenite elements Te and Se increases, the amount of change in reflectance also increases. Similar effects were obtained by changing the composition ratio of Ca and Zn. Furthermore, similar effects were obtained when Ge was added instead of Te and Se. Based on the above experimental results, Ca.

It can be seen that when a chalcogenide element such as Te, Se, or Ge is added to a recording layer made of a binary alloy made of Zn, the amount of change in reflectance increases and a recording layer with a large amount of reproduced signal can be obtained.

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

S102100na+, optical recording material 100rv, SI0O2100n, and a UV curable resin layer were formed on a glass substrate by the sputtering method described above. The composition of the formed recording layer is (Ca 1oZn To) 9oSe Ion
(Ca 5oZn so) *oSe Ion (C
There are three ways: a To Zn 30) and ose to. 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 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). (Ca 1
oZn 70), ose Ion (Ca so
Zn 5o) eose Ion (Ca
70 Zn 30) e.

It can be seen that there is almost no change in the reflectance of any recording layer having a composition of Se even after 3 months. Similar effects were also obtained when Te and Ge were further added.

The above experimental results show that when chalcogenide elements such as Te, Se, and Ge are added to an information recording medium made of a binary alloy of Ca and Zn, there is almost no change in reflectance over time and the recording state is stable. I found out that you can get

[Effect of the invention] As detailed above, when chalcogenide elements Te, Se, and Ge are further added to a binary alloy of Ca and Zn that causes a reversible phase change between a crystalline state and an amorphous state, a phase change occurs. The accompanying change in reflectance increases, the crystallization temperature also increases, and an information recording medium with a stable amorphous state at room temperature 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 apparatus, Fig. 3 is a bottom view of the sputtering apparatus, and Fig. 4 is the addition amount and crystallization of chalcogenide elements. Figure 5 is a graph showing the correlation between temperature; Figure 5 is a graph showing the correlation between the amount of chalcogenide added and the change in reflectance; Figure 6 is the reflectance over time of the ternary recording layer of Ca, Zn, and Se. It is a graph showing the correlation of the amount of change. 1...Substrate 2...Recording layer 3...Inorganic protection layer 4...Organic protection layer

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 is composed of Ca, Zn, and X (X is an element selected from Se, Te, and Ge). ) An information recording medium comprising an alloy thin film containing.