JPH01241040A - Information recording medium - Google Patents

Abstract

PURPOSE:To obtain the information recording medium having a large reproduction signal quantity by forming the recording layer of a thin film of an alloy consisting Ca, Ga and X (X is an element selected from Se, Te and Ge). CONSTITUTION:The information recording medium is constituted of a substrate 1 and by providing an inorg. protective layer 3, the optical recording layer 2, an inorg. protective layer 3, and an org. protective layer 4 successively on the substrate 1. Sputtering sources of Ca and Ga and Te or Se are provided in a vacuum vessel 11 and the inside of the vessel is evacuated down to 5X10<-6>Torr in case of forming the recording layer. Gaseous Ar is then introduced into the vessel to control the pressure over the entire part in the vessel to 5X10<-3>Torr. The disk-shaped polycarbonate substrate is used and while this substrate is rotated at 60rpm, the sputtering rates of the respective elements are detected by a monitor and the electric power to be thrown to the respective sputtering sources is controlled to deposit the respective elements until the entire part attains 1,000Angstrom film thickness. The recording layer is thus formed. The information recording medium which is stable in the recording state, is increased in the reflectivity change arising from a phase transition and has the large reproduction signal quantity is thereby obtd.

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) Some recordable and erasable information recording media, which have been widely developed in the past, utilize changes in atomic arrangement caused by irradiation with a light beam.

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 a particularly large change in reflectance, are used as materials for the recording layer that records and erases information by changing the atomic arrangement depending on the irradiation conditions with the light beam.

Semiconductor amorphous materials containing chalcogenide-based elements such as Ge as a main component have been proposed. However, in addition to semiconductor amorphous materials, C
In a binary alloy of a and Ga, when the Ca content is in the range of 30 atomic % to 80 %, the alloy repeatedly changes into metallic crystal and metallic amorphous due to 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. Furthermore, it has drawbacks such as low crystallization temperature and poor stability of the amorphous state at room temperature, and cannot be used as an information recording medium.

(Problem to be solved by the invention) As detailed above, Ca and Ga (30 atomic%≦Ca
≦80 at. It cannot be used as t2.

In order to solve the above problems, the present invention adds chalcogenide elements Te, Se, and Ge to a binary alloy of Ca and Ga 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.

[Configuration of the Invention (Means and Effects for Solving the Problems) The information recording medium of the present invention has a cross section as shown in FIG. 1, for example. In FIG. 1, the information recording medium includes a substrate 1, an inorganic protective layer 3, an 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 Si 02+ A1203. 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, the substrate 16 is supported horizontally on a support device 17.
;Can be driven more rotationally. Moreover, at the bottom of the vacuum container 11,
Sputter sources 18, 19, 20 made of a predetermined element are provided, and monitor devices 21, 22, .
23 are provided.

When forming a recording layer using this apparatus, first, the inside of the vacuum chamber 11 is heated to 1O-6 Torr using the exhaust device 13.
Evacuate to a vacuum level of R. Next, the gas introduction boat 14
Ar gas is then introduced and the exhaust amount of the exhaust device 13 is adjusted to maintain the inside of the vacuum container 11 at 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) An example of the information recording medium having the above structure will be specifically described below.

Embodiment 1 - Ca, Ga, Te or Se are contained in the vacuum vessel 11 shown in FIG.
A sputtering source of
Exhausted until. Next, introduce Ar gas to 5x 1o-”
The total pressure was adjusted to r orr. Using a thoroughly cleaned disc-shaped polycarbonate substrate with an outer diameter of 130 nm and a plate thickness of 1.2H as the substrate, the amount of sputtering of each element was detected by a monitor while rotating this substrate at 60 rpm, and the power input to each sputtering source was determined. control, and the total film thickness is 1000
The recording layer was formed by depositing each element until it became a human. C
The content of Te sSe was gradually increased for a4oGa6o, and the crystallization temperature was measured using a high-sensitivity DSC (differential scanning calorimeter) at a heating rate of 10°C/■. I investigated the relationship. The results are shown in FIG.

The crystallization temperature was sufficiently high regardless of the composition ratio of Ca and Ga. Similar effects were also obtained with Ge.

Therefore, it was found that an information recording medium composed of Ca, Ga, and X (X-Te, Se, Ge) has a sufficiently high crystallization temperature and a stable amorphous state regardless of the composition ratio of Ca and Ga. .

Example 2 Ca, Ga, and X (X-T e
, Se) was formed by a multi-component simultaneous sputtering method, and its surface reflectance was measured by irradiating it with light having a wavelength of 790 r+m. The results are shown in FIG. It can be seen that as the content of the chalcogenide elements Te and Se increases, the amount of change in reflectance also increases. Similar effects were obtained even when the composition ratio of Ca and Ga was changed. Furthermore, Ge instead of Te and Se
A similar effect was obtained when adding .

The above experimental results revealed that by adding a chalcogenide element to a binary alloy of Ca and Ga, the amount of change in reflectance due to phase change increases, and the amount of reproduced signal also increases.

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

On a glass substrate, 100nIIl of SiO2, 100nIIl of optical recording material, 1100n of SiO□, and a UV curable resin layer were formed by the sputtering method described above. The composition of the formed recording layer is (Ca 4oGa 60) 9oTe
IO+ (Ca 5oGa 50)goTe 10.
(Ca 70Ga30) 9oTe 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 reflectance value over time is R, and the value of R/Ro is plotted against time (Figure 6) o (C
a 4oGa 6G), oTe Ion (Ca
5oGa so) 9oTe i. , (Ga to Ga
30) It was found that there was almost no change in the reflectance of the recording layer of any of the compositions of oTelo even after 3 months. Similar effects can also be obtained when Se or Ge is added instead of Te.

From the above experimental results, a binary alloy consisting of Ca and Ga,
It has been found that materials to which chalcogenide elements such as Te, Se, and Ge are added have stable reflectance over time and can be used as information recording media.

Example 4 In this example, an information recording medium having a film-formed recording layer was mounted on a practical test device as shown in FIG. 7, and the amount of reproduced signal was measured.

The light emitted by the semiconductor laser source 34 passes through a collimator lens 35 and becomes parallel light. Subsequently, the light passes through the beam splitter 36, passes through the λ/4 plate 3 and the metal plate 7, and is focused onto the sample 31 by the objective lens 38. The light reflected from the sample 31 passes through the λ/4 plate 3 and the beam splitter 36.
reflected.

This reflected light is collected by the detection lens 39, enters the light receiver 40, and becomes a detection signal.

Further, the detection signal is converted into an electric current through a servo system 42, which flows through a drive coil 41, which drives an objective lens to accurately focus the light onto the groove (guide groove) on the sample 31 in which information is recorded. Ru.

Using the method shown in Example 1, a recording layer was created in which the content of Te was increased relative to Ca4°Ga6o, and a medium sample was created in which both sides of this recording layer were sandwiched between 5IO2 (film thickness 1000A). The amount of reproduced signal was measured by installing it in the above-mentioned device.

As a result, it was found that as the Te content increased, the amount of reproduced signals also increased.

Furthermore, similar effects were obtained even when the composition ratio of Ca and Ga was changed. Furthermore, similar effects were obtained when 5eSGe was added instead of Te.

From the above experimental results, it has been found that by adding chalcogenide elements Te, Se, and Ge to a binary alloy of Ca and Ga, an information recording medium with a larger amount of reproduced signal can be obtained.

[Effect of the invention] As detailed above, when chalcogenide elements Te, Se, and Ge are further added to a binary alloy of Ca and Ga that causes a reversible phase change between a crystalline state and an amorphous state, the crystallization temperature increases. increases, the recording state is stable, the change in reflectance due to phase change 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 Ca, Ga, and Te. It is a graph showing the correlation. FIG. 7 is a schematic diagram of a practical test apparatus. 1...Substrate 2...Recording layer 3...Inorganic protection layer 4...Organic protection layer

Claims (1)

[Claims] The recording layer that can record information by causing a change in atomic arrangement by irradiation with a light beam is composed of Ca, Ga, and X (X is Se, Te
, Ge).