JPS60125944A - Recording medium - Google Patents

Abstract

PURPOSE:To record or read out information by producing a frog-shaped recording medium containing needle-shaped projections from a form storage alloy and deciding the presence or absence of the information in response to the bent or straight form said projections. CONSTITUTION:A disk substrate 1 made of a form storage alloy is heated and then quanched. A photoresist layer 2 is formed and then a pattern of a resist 3 is formed by the exposure and development processes. Then the substrate 1 is etched vertically and the resist 3 is dissolved to obtain a frog-shaped recording medium 4 where needle- shaped metals 11 of microdiameters are arrayed. The erasion processing is applied to the medium 4 prior to the record of information. In this case, the substrate 1 is revolved to bend the tip of the metal 11 by an erasion stylus 6. Under such conditions, the maximum reflection factor is obtained. When the information is written, a laser is selectively irradiated to heat the irradiated area 12 up to a level higher than the phase transition temperature of the form storage metal. Thus the area 12 is reset to its upright state. Under such conditions, the reflection factor of the laser light is minimum. For read-out of the information, the laser light having such a level of electric power that causes no phase transition. Then the intensity of the reflected laser light is read by a detector.

Description

DETAILED DESCRIPTION OF THE INVENTION (a) Technical Field of the Invention The present invention relates to the structure of a recording medium formed using a shape memory alloy.

(b) Technology background Titanium-nickel (TI-Ni) is a shape memory alloy.
Alloy, copper/aluminum, (CusAt) alloy, copper/aluminum/
Nickel (Cu-At-N1) alloy, gold-cadmium (Au
・Cd) alloy, iron-platinum (Fe, Pt) alloy, indium-thallium (In-Tt) alloy, etc. are known.

These alloys have the property of behaving as elastic bodies above the phase transition temperature determined by their composition, and as plastic bodies at room temperature. For example, the phase transition temperature of Ti-Ni alloy is 50 to 70 [℃
], and if it is held above this temperature and molded into an arbitrary shape, then rapidly cooled, returned to room temperature, and deformed, it behaves as a shape memory alloy.

That is, heating to a temperature above the phase transition temperature can restore the original molded state.

The present invention relates to a recording medium made using such a shape memory alloy.

(c) Prior Art and Problems Optical discs are a method of recording and reproducing information using laser light.

That is, a thin film of tellurium (To), bismuth (Bi), etc. is formed on a transparent substrate such as glass or acrylic resin,
A method of drilling holes by irradiating laser light or using tellurium oxide (
Information is recorded by utilizing the change in reflectance that occurs when an amorphous thin film such as TeOX) or germanium oxide (GeOx) is irradiated with laser light to cause a phase transition to crystalline. There is.

However, when using a method that involves punching holes in a thin film, information cannot be erased, and on the other hand, when using a method that uses changes in reflectance, the amorphous state may change over time and become crystalline, resulting in poor long-term storage. There is a problem.

(d) Purpose of the Invention An object of the present invention is to provide a recording medium in which information can be rewritten using a shape memory alloy.

(e) Structure of the Invention The object of the present invention is to use, as a storage medium, a large number of minute metal needles formed by selectively etching the surface of a disk substrate made of a shape memory alloy into a crest shape, and to move the needles in a certain direction. The state in which the needle-shaped metal is tilted down is defined as the OFF state, and the state in which the needle metal returns to an upright state by locally irradiating a laser beam to raise the temperature above the transition temperature of the alloy is defined as the ON state, and information is recorded. This can be achieved using a memory alloy characterized by irradiating a storage medium with a laser beam of very low power and reading information from changes in reflectance.

(f) Embodiments of the Invention The present invention uses a shape memory alloy to produce a recording medium in the shape of a pincushion having needle-like protrusions, and the shape of the needle-like protrusions varies depending on whether they are curved or upright. Information is recorded in correspondence with the presence or absence of information.

The present invention will be described below with reference to an example in which a T1/N1 alloy is used as the shape memory alloy.

A disk substrate 1 made of a Ti-Ni alloy having a diameter of 20 (z) and a thickness of 3 [degrees] is heat treated at 100 [° C.] and then rapidly cooled. Here, the phase transition temperature of T1/N1 alloy is 5
The temperature is 0 to 70 [°C].

Figure 1 (
4) After forming the photoresist layer 2 as shown in the same figure (
Exposure and development were performed as shown in B) to obtain a diameter of approximately 1.5 (μ
Patterns made of resists 3 of 3 CA-] are formed alternately over the entire surface of the disk substrate 1 at intervals of 3 CA-].

Next, reactive ion etching is performed using argon (Ar) gas and carbon tetrachloride (CCt) gas to vertically etch the disk substrate 1 to a depth of approximately 5 μm. By melting 3, a recording medium 4 in which needle-like metals of minute diameter are arranged in a crest shape is completed.

Figure 2 shows a disk substrate 1 with a recording medium 4 on its surface.
The disk substrate 1 is rotated by a motor 5, and above there is an eraser 7 equipped with an erasing needle 6, an objective lens 81 for recording and reproducing information, and a reflecting mirror 9. A laser beam 10 from a laser light source (not shown) is reflected by a reflecting mirror 9, focused onto the disk substrate 1 by an objective lens 8, and is configured to be movable in the radial direction.

Now, information is recorded on the recording medium according to the present invention by turning ON when the metal needle is upright with respect to the disk substrate 1, and OFF when it is curved, and detecting information from the difference in reflectance. It is.

FIG. 3 shows this state. Prior to recording information, it is necessary to erase the information. This is done by lowering the erasing needle 6 until it touches the needle metal 11 while rotating the disk substrate 1. This is done by curving the tip of the metal 11.

In other words, in this case, the laser beam is projected onto the back surface of the curved part of the needle-like metal 11 and is reflected, resulting in little light absorption and maximum reflectance. The recording medium made of the metal 11 may be selectively irradiated with a laser to raise the irradiated portion 12 to a temperature equal to or higher than the phase transition temperature of the shape memory alloy.

This method uses a semiconductor laser or helium neon (H
a-No) If the output of the laser is about 20 [mw], the light should be focused by the objective lens 8 and heated for several [m seconds]. As it is heated and easily exceeds the phase transition temperature, it returns to its original upright state. In this state, the laser beam is repeatedly reflected and absorbed within the etching hole, so that the reflectance becomes minimum.

In this way, information is transmitted through ON and O using changes in reflectance.
Recorded by FF signal.

Note that the information is read by irradiating a laser beam with a power that does not cause a phase transition, that is, in the case of this embodiment, approximately 1 [mw], and reading the intensity of this reflected light with a detector.

Further, information can be erased by using the erasing needle 6 to bend the needle metal 11 which is in an upright state again.

(g) Effects of the Invention The present invention provides a recording medium using a shape memory alloy, and by using the present invention, it becomes possible to form a memory that can be used repeatedly.

[Brief explanation of drawings]

Figures 1-C) are cross-sectional views showing the process of forming a recording medium according to the present invention, Figure 2 is a perspective view illustrating the writing and erasing method, and Figure 3 (5) shows the state of information being erased. Diagram (B)
FIG. 2 is a cross-sectional view showing a written state. In the figure, 1 is a disk substrate, 2 is a photoresist layer,
4 is a recording medium, 6 is an erasing needle, 8 is an objective lens, 10 is a laser beam, 11 is a needle-like metal, and 12 is an irradiated part.

Claims (1)

[Claims] A large number of minute needle-shaped metals formed by selectively etching the surface of a disk substrate made of a shape memory alloy into a crest shape is used as a storage medium, and the state in which the needle-shaped metals are tilted in a certain direction is the OFF state. Light is irradiated locally to raise the temperature above the transition temperature of the alloy, and the state in which the acicular metal returns to an upright state is set as the ON state to record information, and the storage medium is irradiated with a laser beam of very low power. A recording medium made of a memory alloy, characterized in that information is read out from changes in reflectance.