JPH01199333A - Information recording medium - Google Patents

Abstract

PURPOSE:To form an information recording medium having excellent recording and erasing characteristics by specifying the average compsn. of a recording layer. CONSTITUTION:The average compsn. of the recording layer is MxTe100-x (where M is a metal selected from Ag, Au, Pd, Pt and the total content of the metal expressed by M is 0atom.%<x<10atom.%). Of the constituting components, a chalcogen element such as Te is capable of stably maintaining an amorphous state by allowing with the metal expressed by M. The metal expressed by M exhibits the excellent corrosion resistance by alloying with Te. Further, the element expressed by M has the effect of constituting a crystal nucleus at the time of crystallization and allows the crystallization at a high speed. The recording and erasing characteristics are thereby improved, the recording state is stabilized and the quantity of reproduction signals is relatively increased.

Description

Detailed Description of the Invention [Objective of the Invention] (Industrial Field of Application) The present invention is capable of recording information by causing a change in optical properties due to a change in atomic arrangement in a recording layer by irradiation with a light beam. The present invention relates to an information recording medium that reproduces information by repeatedly performing erasing and detecting changes in optical characteristics.

(Prior Art) Information recording media that utilize phase change caused by light beam irradiation have been developed as information recording media that can repeatedly record and erase information.

When recording information on such an information recording medium, first, the entire surface of the recording medium is irradiated with a light beam to bring the recording layer into a highly crystalline state (hereinafter referred to as a crystalline state). Next, in order to record information, the recording layer is irradiated with short, strong pulsed light to heat it and rapidly cool it, thereby bringing the recording layer into a state in which the atomic arrangement is disordered (hereinafter referred to as an amorphous state). When erasing recorded information, the recording layer is irradiated with long, weak pulsed light to heat it and slowly cool it to a crystalline state again. Since optical properties such as reflectance and transmittance change between the crystalline state and the amorphous state due to changes in atomic arrangement, information can be reproduced by detecting changes in these optical properties. ing.

An example of the disclosure of the above technology is Japanese Patent Application Laid-Open No. 60-179952.
No., JP-A-60-179953, JP-A-61-680
There are publications such as Publication No. 6. In these publications, Au x T
(3too-x * Ag x Te 5on-x(1
0≦X≦40 atomic %), etc. have been proposed.

However, although these materials provide stability in the recording state, problems remain in terms of recording and erasing characteristics because the energy required for recording is large.

(Problem to be solved by the invention) As detailed above, the conventional Ag x Te +oo-x
Information recording media using (10≦X≦40) as materials have drawbacks such as poor erasing characteristics and large energy requirements for recording.

An object of the present invention is to eliminate the above-mentioned drawbacks and provide an information recording medium with excellent recording and erasing characteristics.

[Structure of the Invention] (Means and Effects for Solving the Problems) The information recording medium of the present invention has a recording layer having an average composition of Mz Te 1oo-x, where M is selected from Ag, Au, Pd, and Pt. The total content of metals represented by M is 0 atomic %<x<1
It is characterized by being 0 atomic %.

Among the constituent components, chalcogen elements such as Te can stably maintain an amorphous state by alloying with the metal represented by M. The metal represented by M exhibits excellent corrosion resistance when alloyed with Te. Furthermore, the element represented by M above serves as a crystal nucleus during crystallization, and high-speed crystallization can be expected.

In addition, an alloy consisting of Te and M absorbs pulsed light and easily changes from amorphous to crystalline, resulting in optical properties (reflectance,
The amount of change in transmittance (transmittance) is very large.

However, if the composition range of M exceeds 10 atomic %, a sufficient amount of optical change cannot be obtained. Also, crystalline state,
The energy required for phase change between amorphous states also increases when the composition range of M exceeds 10 at %. Therefore, the composition range of M must be less than 10 atomic %.

A sectional view showing the structure of the information recording medium used in the present invention is shown in FIG.

Reference numeral 12 in FIG. 1 is a substrate made of glass or plastic material (for example, polymethyl methacrylate resin, polycarbonate resin, etc.).A recording layer 13 is formed on this substrate 12, which undergoes a layer change when irradiated with a light beam. An organic protective layer 14 made of ultraviolet curing resin or the like is formed on the recording layer 13. Furthermore, the information recording medium used in the present invention may have a structure as shown in FIGS. 2 and 3. In FIG. 2, in order to prevent the recording layer 13 from deteriorating over time, the recording layer 13 is sandwiched between an inorganic protective layer 15 made of metal or metalloid oxide, fluoride, sulfide, nitride, etc. In FIG. 3, the structure has a composite layer 16 in which the material forming the recording layer 13 is dispersed in the material forming the inorganic protective layer 15.

Next, a method for manufacturing the information recording medium will be explained with reference to FIGS. 4 and 5. FIG. 4 is a side view of the film forming apparatus used in the present invention, and FIG. 5 is a bottom view of the film forming apparatus.

The vacuum container 17 is an exhaust bag via the exhaust boat 18! ! 19
It is also connected to an argon gas cylinder 21 via a gas introduction boat 20. Vacuum container 1
A support device 22 and a substrate 12 horizontally supported by the support device are provided at the middle upper portion of the substrate 7, and the substrate 12 can rotate around the support device 22. Also, vacuum container 1
A sputtering source 23.2 is installed at the bottom of 7, facing the substrate 12.
4 are provided, and a high frequency power source is connected to these sputter sources. Additionally, monitor devices 25 and 26 are installed above the sputter sources 23 and 24.

When forming a recording layer on the substrate 12 using this apparatus, first the air in the container is exhausted by the exhaust device 19, and then argon gas is introduced from the argon gas cylinder 21 to bring the inside of the container to a predetermined pressure. Hold. Then, while rotating the substrate 12, power is applied to the sputtering sources 23 and 24 for a predetermined period of time. The monitor devices 25 and 26 are adapted to monitor the amount of element sputtered from each sputtering source, and adjust the power applied to each sputtering source so that the monitored amount becomes a predetermined value. As a result, a substrate 121; a recording layer is formed.

(Example) Experiment 1 - In this experiment, a recording film was formed by a multi-source simultaneous sputtering method.

Sputtering sources for desired metals and Te were provided in a vacuum container, and the inside of the container was evacuated to 5×10-' Torr. Next A
r gas was introduced and the overall pressure was adjusted to 5 x 10-' Torr. Outer diameter 130 mm, thoroughly cleaned as a substrate
Using a disk-shaped carbonate substrate with a thickness of 1.21 mm, the amount of sputtering of each element was monitored while rotating the substrate at 6 Orpm, and the power input to each sputtering source was controlled to determine the overall film thickness. A recording layer was formed by depositing each element until the number of participants reached 1,000.

Furthermore, an ultraviolet curable resin was overcoated as an organic protective layer on this recording layer to a thickness of about 10 μm using a spin coater, and was cured by irradiation with ultraviolet rays to form an information recording medium having a desired composition.

Here, changes in the atomic arrangement of the recording film due to light beam irradiation were confirmed.

In Experiment 1, a sample with a recording layer composition of Ag s Te 95 was formed using Te and Ag as a sputtering source (unirradiated area). A 5mW 15μ beam focused to a beam diameter of 1μ was applied to this sample.
When irradiated with pulsed light of s, the reflectance of the irradiated area changed (unrecorded area). Next, when pulsed light of 13+aW of 300 ns was applied, it was confirmed that the reflectance of the irradiated area returned to its original value (recording area). Next, in order to compare the crystalline state of the unrecorded area and the recorded area, the diffraction pattern was observed using a transmission electron microscope. When the protective layer was peeled off from the sample and the state of the recording layer was observed from a diffraction pattern, a halo pattern characteristic of amorphous materials was observed in the areas not irradiated with laser light. Moreover, in the unrecorded part of the laser beam irradiated part, diffraction rings and spots indicating a crystal structure were observed, and in the recorded part, a halo pattern peculiar to an amorphous substance near the unirradiated part was observed.

Similar changes in reflectance changes and diffraction patterns were observed for recording layers with other compositions.

Experiment 3 - In this experiment, the crystallization temperature was measured in order to evaluate the stability of the recording state. Using the same method as shown in Experiment 1, using Te and Au as sputtering sources, the recording layer composition was made to be Au.
XTet. 0.6,1 Au to Te in ox
A sample was prepared in which 5.20 atomic % was added. These samples were thermally analyzed by differential scanning calorimetry (DSC) (
Figure 6). It can be seen that when Al is added, the crystallization temperature is higher and the amorphous state is stable compared to a recording film containing only Te. Furthermore, similar effects were obtained when PtPd and Ag were added instead of Au.

Experiment 4--Here, the stability of the recording state was evaluated based on changes in reflectance over time.

By the method shown in Experiment 1, the composition of the recording layer was changed to Te and Au.
Two types of samples of g Te 92 were prepared. These samples were exposed to an environment of 65°C and 90% RH for 500 hours, and the ratio (Rt/R1) of the initial reflectance (R1) to the reflectance over time (Rt) was plotted against the exposure time of 5. (Figure 7).

As can be seen from the figure, the reflectance of the sample with Te composition gradually decreases, but the reflectance of the sample with Au added to ``re'' remained stable over time, almost unchanged from the initial reflectance.

Furthermore, similar effects were obtained when Pt, Pd, and Ag were added instead of Au.

-Experiment 5- In this experiment, the erasing characteristics of the recorded portion were evaluated. The recording layer composition is Pd, 're, o. -, in Tej,
: Samples were prepared in which Pd was added at a ratio of 6.9 and 15.30 atomic %.

The recording layer was crystallized by applying pulsed light of 5 mW and 5 μs to this sample until the reflectance became constant. In FIG. 8, the number of pulsed light irradiations until the reflectance becomes constant is plotted against the amount of Pd added. It has been found that when the amount of Pd added is 10 atomic % or more, the number of irradiations is required to be increased.

From this result, it is desirable that the amount of Pd added is less than 10 atoms and 96 atoms.

Further, similar effects can be obtained even when Au Pt or Ag is added instead of Pd.

-Experiment 6- In this experiment, we used a practical test device.

FIG. 9 is a schematic diagram of the apparatus used in the test. The sample 31 is fixed on a spindle motor 32 and can be rotated. On the sample 31, semiconductor laser sources 34. Collimator lens 3
5. Beam splitter 36. λ/4 plate 37. The objective lens 38 is arranged in a straight line. Also, objective lens 3
A drive coil 41 is installed at both ends of the coil 8.

Furthermore, the beam splitter 36 causes a detection lens 39. A light receiver 40 is installed, and a servo system 42 is installed vertically below the light receiver 40 in a direction parallel to the sample 31 from the objective lens.

The light emitted from the semiconductor laser source 34 passes through the collimator lens 3
5 and becomes parallel light. Next, the light passes through the beam splitter 36, passes through the λ/4 plate 37, and passes through the objective lens 38.
The light is focused onto the sample 31. The light reflected from the sample 31 passes through the λ/4 plate 37 and is reflected by the beam splitter 36. This reflected light is collected by the detection lens 39, enters the light receiver 40, and becomes a detection signal. Furthermore, the detection signal is converted into a current through the servo system 42, which flows through the drive coil 41, and this current drives the objective lens.
The light is accurately focused on the groove (guide groove) on the sample 31 in which information is recorded.

Using the method shown in Experiment 1, both sides of the recording layer were coated with 5102 (
A media sample sandwiched with a film thickness of 1000×) was prepared, and an experiment was conducted by mounting it in the above-mentioned apparatus. The recording layer composition is Pdz
Te EPd at Te Zoo-X 5.11.18
It was added in an amount of atomic percent. This sample was fixed to a spindle motor and rotated at 700 rpm. In this state, continuous light of 6i+W was irradiated onto the sample until the reflectance became constant (
Crystalline 8). FIG. 10 is a plot of the minimum energy required for the reflectance to return to its original value in samples with different amounts of Pd added. It has been found that when the amount of Pd added is 10 atomic % or more, the energy required for recording increases. From the above experimental results, it can be said that the amount of Pd added is preferably less than 10%. Furthermore, Au, Ag instead of Pd
, Similar paste results were obtained when Pt was added.

Experiment 7 - In this experiment, the amount of reproduced signal was tested. The composition of the recording layer was set to Au x Te in the same manner as in Experiment 1.

0.5, 11.18 atomic% Au to Te in ox
was added to form a sample.

This sample was set in the apparatus shown in Experiment 6, and the rotation speed was set to 90.
It was rotated with Orpm. Furthermore, from above this 5■W15μ
s pulsed light was irradiated, and the amount of change in reflectance was measured. Figure 11 shows the value obtained by dividing the amount of change by the initial value (contrast ratio)
and the amount of Au added were plotted. It can be seen that the contrast ratio increases by adding Au. Furthermore, Au
Similar effects can be obtained even when Pt, Pd, or Ag is added instead. Based on the above results, Te has Ag, Au
By adding , Pt, and Pd, the crystal state is stable,
A recording film with a large amount of optical change can be obtained.

Furthermore, considering the recording and erasing characteristics, the above-mentioned Ag.

The amount of Au, PL, and Pd added is suitably less than 10 atomic %.

[Effects of the Invention] As detailed above, according to the present invention, the recording and erasing characteristics are good, the recording state is stable, and the amount of reproduced signal is relatively large.
It is possible to provide an information recording medium that is sufficiently practical.

[Brief explanation of the drawing]

1 to 3 are cross-sectional views showing the layer structure of the information recording medium used in the present invention, FIG. 4 is a side view of the film forming apparatus, and FIG.
The figure is a bottom view of the film forming apparatus, Figure 6 is a graph showing the amount of Au added and crystallization temperature, Figure 7 is a graph showing the exposure time and reflectance ratio, and Figure 8 is the graph showing the amount of Pd added and the number of irradiations. 9 is a schematic diagram of a practical recording device, FIG. 10 is a graph showing the amount of Pd added and recording energy, and FIG. 11 is a graph showing the amount of Au added and contrast ratio. 12...Substrate 13...Recording layer

Claims (1)

[Claims] An information recording medium having a recording layer in which information is recorded and erased by causing a change in atomic arrangement by irradiation with a light beam, wherein the average composition of the recording layer is MxTe_1_0_0_-_x, where M is An information recording medium characterized in that 0 atomic %<x<10 atomic % of a metal selected from Ag, Au, Pd, and Pt.