JPS58155541A - Information recording medium - Google Patents

Abstract

PURPOSE:To enable piercing with low energy beams and to obtain an iformation recording medium undergoing little change with the passage of time and having low toxicity by depositing a thin film consisting of under and upper layers of elements or alloys which form a eutectic on a substrate. CONSTITUTION:A film 2 as an under layer and a film 3 as an upper layer are deposited on a substrate 1 of glass, plastics or the like. The combination of the films is selected so that the constituent elements form a eutectic. When the elements are mixed, the m.p. is made lower than the m.p. of each of the elements. The 2-layered film is then irradiated with energy beams such as laser beams from an upper part. By the irradiation the elements are mixed at the interface of the 2-layered film and converted into a eutectic to form a eutectic layer 4. The m.p. is suddenly lowered when the eutectic is formed, so the 2- layered film adjacent to the eutectic layer 4 is rapidly melted or evaporated to pierce a hole 5.

Description

[Detailed Description of the Invention] The present invention makes it possible to record information such as video, audio signals, computer data, etc. onto a recording medium provided on a predetermined substrate using an energy beam such as a laser beam. This invention relates to a recording member.

In recent years, an information recording method in which information is written on a metal thin film provided on a substrate using a laser era has been attracting attention. This type of recording method is performed by forming holes or recesses in a metal thin film using the thermal energy of a processing beam such as a laser beam. This metal thin film is
It has a thickness of 100 to 100 OA and is attached to a substrate such as glass or plastic by vapor deposition or the like. Conditions for making this metal thin film material for information recording are safe: (1) holes or recesses can be easily formed with a low-energy beam; (2) the shape of the hole or recess is close to the cross-sectional shape of the energy beam and has a smooth periphery. and (3) no change in film quality over time during long-term storage or thermal cycles of about 0 to 100C. In addition to these conditions for tfcJM, secondary conditions include (4) being able to produce a homogeneous film with a thickness of F0 for more than 1000 people with good reproducibility, and (5) being non-toxic.

Te is known as a typical material for conventionally used films. This material has a low melting point of 4,500 and poor thermal conductivity, so when irradiated with an energy beam such as a laser, it has a melting point of 1.2 nJ/μm! Holes can be easily drilled with a low amount of energy. Furthermore, alloys in which elements such as As and Se are added to Te are also used in order to improve the shape of the pores formed and to increase stability in high humidity environments. However, the sensitivity is still not high enough.

Further, Te, As, and F3e are heavy metals, and care must be taken when handling them in terms of toxicity.

The present invention was made in order to solve these problems, and its purpose is to provide a material for information recording that can perform hole drilling with a relatively low energy beam, has little change in film quality over time, and is less toxic. The goal is to provide a membrane. The basic principle of the present invention will be explained below.

FIG. 1 is a detailed explanatory diagram of the present invention. 2mM films 2 and 3 are layered on a substrate 1 made of glass, plastic, or the like. Here, the combination of two types of films is such that the respective constituent elements form a eutectic with each other. That is, by mixing the constituent elements, a combination is selected in which the melting point thereof is lower than the melting point of each element alone. For example, specific examples of element combinations and eutectic point temperatures are as follows. Here, the eutectic composition indicates the proportion of the second element in atomic percent. That is, Ag 26Qe (651
C), Ag-95Bi (271c).

Ag-41Sb (485C), Ag-67Te (35
1C), At-30,3Ge (424G>.

At-11,3S i (597U), At-87F
e (414C), Au-27Ge (356c).

Au-348i (37 (N:'), B-45Ni (
990C), Sn-43B i (139
C), B 1-90.3Te (413C), Cu
-71Te (340c).

Mn-53Ge (697C), 5b-17Ge (59
0C), Ge-85Te (375tl.

Mn-81Sb (570G), Pb-17,5Sb (
252C), Pb-85,5Te (405C).

Pb-89Sb (590C), Pd-4581 (72
0C), 5b-89Te (424C), etc. As shown in FIG. 1(a), a film of each element in the above combination is deposited on the lower film 2 and the upper film 3. Here, separating into two films and attaching each element in the form of a film is as follows.
Due to reasons. The melting point of a film containing only the constituent elements is much higher than that of a film containing three elements. For example, At-
In the case of Ge, the melting point is At (660C), Ge (940C
).

It is At-30,3Ge (424C), and the melting point of the single element is 200C or more higher than that of the alloy composition.

When the melting point is high, diffusion of elements is difficult to occur, so that changes over time during heating cycles and long-term storage of the film can be reduced. Next, when an energy beam such as a laser beam is irradiated from above this two-layer film, the image shown in Fig. 1(b)
As shown in the figure, two elements are mixed at the interface of the two-layer film, eutectic formation occurs, and a eutectic layer 4 is generated. When it becomes eutectic, the melting point drops rapidly, so the two-layer film rapidly melts or evaporates, forming holes 5 as shown in FIG. 1(C).

By using such a two-layer membrane structure, 0-10
01: By utilizing the eutectic phenomenon, it is possible to create a film for information recording that does not change over time even after several heating cycles or long-term storage, and can be used to form holes or recesses with a relatively low energy beam. Here, as the lower layer of the two-layer film, in order to prevent heat from diffusing into the substrate during energy beam irradiation, it is desirable to use a film of an element with poor thermal conductivity among the two types of elements. Generally, it is desirable to use elements that have good oxidation resistance and contact resistance, such as Mg and Ca, which are active against oxygen and the like.

Elements such as art are undesirable. If toxicity is an issue, it is necessary to select a combination of elements with low toxicity. Furthermore, a lower layer film and an upper layer film are basically used, each consisting of a single element, but in order to improve the aging characteristics of the information recording film, the shape of the hole made by the energy beam, etc. Adding other elements is also effective.

For example, in the case of a kl-Ge double layer film, At and Si are used.

Add a few percent of Bi to Qe to make A4,8i-Qe
, 13i makes it possible to make holes with a lower energy beam.

Further, it is preferable that there is a difference of 200 C or more between the melting points of each of the three elements or alloys and the temperature of their eutectic point.

The present invention will be explained below using Examples.

Example 1 This example relates to an information recording film using an At(S i )-Ge two-layer film. A transparent plastic disk with a diameter of 30 holes and a thickness of 1 m was used as a deposition substrate.

Approximately 100 Qe films were deposited in a vacuum of 10-' to 10-' Torr using an X-vacuum deposition method, followed by At-10
A Si film having a thickness of about 70 atomic % was deposited to form a two-layer film consisting of a lower layer of Qe and an upper layer of At containing Si. Here, a small amount of KSi in At was added as the upper layer because
This is to prevent the laser beam from being reflected by At when drilling with a laser beam in a later step.

Next, this disk was attached to a recording/writing device and information was written on it. While rotating the disk at 180 rpm, the recording laser beam head was brought close to the disk surface while maintaining a constant distance. Next, information was recorded by irradiating pulsed argon laser light with a wavelength of 488 OA focused to approximately 0.8 μmφ on the surface of the two-layer film. The power of the laser beam required to advance eutectic formation and create a hole at the interface of this two-layer film was about 15 mW. Further, the laser energy sensitivity required to melt this two-layer film was 1.5 nJ 7 μm2. These values are almost equivalent to those of conventional Te-based recording materials.

It was possible to form an oval hole with a short diameter of about 1 μmφ.

The disc on which information was recorded was subjected to a repeated heating test from 0 to 60 tll'. After applying 104 heating cycles, the state of the two-layer film was examined, and it was confirmed that the film quality had hardly changed and the recorded information was well maintained.

Example 2 This example relates to the evaluation of various types of 2-layer films, and the power of the laser beam required to make holes, the laser energy sensitivity, and the state of the 2-layer film after repeated heating tests were compared and studied.

A two-layer film was formed by depositing a metal film of 100 A as a lower layer film and a metal film of about 70 A as an upper layer film on a 30 w x 60 m x 1+ m glass substrate by sputtering or vapor deposition. Regarding these films, the power of the laser beam necessary to make the hole, the laser energy sensitivity, and the heating cycle characteristics of 10' times from 0 to 60 C were examined in the same manner as in Example 1. The results are summarized in Table 1. As a result of repeated heating, if no abnormality occurred at all, it is marked O, and if some abnormality occurred, it is marked Δ.

As is clear from this example, by using a two-layer film structure, there is almost no change over time, and information can be recorded in almost the same way as with conventional Te-based films. It is possible to realize a film of

-Thorns

[Brief explanation of the drawing]

FIGS. 1(a), 1(b), and 1(C) are diagrams for explaining the present invention in detail. DESCRIPTION OF SYMBOLS 1... Substrate, 2... Lower layer film, 3... Upper layer film, 4...
...eutectic layer, 224- Figure 1 (a) (C)

Claims (1)

[Claims] 1. An information recording medium consisting of a substrate and a thin film for information recording attached to the substrate, in which the thin film has 28 parts of the lower skin and the upper layer.
1. An information recording medium comprising a stack of thin films of the same type, characterized in that the respective elements or alloys forming the two layers form a eutectic at at least one location in the binary phase diagram.