JPS63106941A - Optical recording erasing method - Google Patents

Abstract

(57) [Abstract] This bulletin contains application data before electronic filing, so abstract data is not recorded.

Description

DETAILED DESCRIPTION OF THE INVENTION [Field of Industrial Application] The present invention relates to wavelength multiplexed optical recording with high recording density, and particularly to an optical recording erasing method using hole burning phenomenon.

[Conventional technology]

Challenges in information recording and reproducing methods using light include improving recording density, rewritability, and increasing input/output speed. Regarding the above issues.

In recent years, research has been actively conducted to search for new optical recording media and to wavelength multiplexing using multilayer structures. Among them, PHB memory (PHB memory) that utilizes hole burning phenomenon is attracting attention as a future information storage method.
o chemical hole burning
The hole burning phenomenon described above is academically interesting and is known as one of high-resolution spectroscopy methods. The above recording method was proposed by IBM in 1978 (Japanese Unexamined Patent Publication No. 53-99735), and the conventional 1000
This is a wavelength multiplexing optical memory that is expected to significantly improve the density by about 8 times as much. The principle will be described below.

When a photochemically active molecule is placed in a cold solid matrix, its absorption spectrum reflects subtle differences in the environment in which the molecule is placed, resulting in a non-uniform structure as shown in Figure 2(a). By irradiating a high-intensity laser beam with a narrow linewidth at a specific wavelength λ in the spectrum, which indicates the spectral width, only molecules resonating with the wavelength λ1 absorb the light and pass through the excited state. It moves to a metastable state different from the initial ground state. As for this metastable state.

1) Movement of protons within molecules due to light absorption.

2) Change in the orientation of molecules in the matrix due to light absorption, 3
) Photodissociation of molecules due to light absorption, etc. are considered.

When the above-mentioned metastable state is maintained, as shown in FIG. 2(b), a decrease in absorption intensity is observed only at the wavelength λ of light irradiation, and a hole is formed on the absorption spectrum showing a sharp spectral width. Furthermore, as shown in FIG. 2(c), the wavelength of light irradiation is sequentially changed to λ2. By changing λ, ... and forming a hole, a wavelength multiplexed optical memory can be formed.

As mentioned above, PHB memory is based on the basic principle of subtle state changes induced by light, so it is necessary to pay sufficient attention to the stability of holes in the recording, that is, the absorption spectrum. It is known that when the temperature of 20 to 30 degrees rises, optically recorded holes cannot be stably held and the holes disappear. Therefore, PHB
The entire recording medium used in the memory is stored at an extremely low temperature of liquid helium, at a temperature of 4.2, where there is little thermal fluctuation of molecules.

[Problem that the invention seeks to solve]

As mentioned above, research into PHB memory is conducted under strict conditions to search for recording mechanisms and recording media. However, regarding the method of erasing records, although it is possible to bring the entire recording medium to a high temperature and erase it all at once,
The problem of locally erasing a portion of a recording medium has so far remained largely unresolved.

The object of the present invention is to obtain a method that makes it possible locally to erase records in a PHB memory under cryogenic conditions.

[Means for solving problems]

The above object is achieved by mixing molecules with a light absorption wavelength region different from that of a recording medium used in a PHB memory into the recording medium, and irradiating the mixed recording medium with light having a wavelength that is absorbed by the molecules.

[Effect]

The recording medium used for PHB memory is a mixed recording medium in which molecules having different light absorption wavelength regions from that of the recording medium are mixed. Holes are formed by laser beam irradiation, that is, PHB recording is performed.The same laser spot where the PHB recording was performed is strongly irradiated with light having a wavelength that is absorbed by molecules responsible for erasing (hereinafter referred to as erasing molecules).

By this operation, the eraser molecules are photoexcited, and in the process of relaxation, they become thermally excited, in which lattice vibrations including the photomatrix are excited. The temperature of the entire light irradiated area increases due to the above heat, and as a result, the metastable state of PH8 molecules is disturbed.
Holes on the above absorption spectrum disappear. That is,
The light irradiation causes a local temperature rise, erasing the PHB recording.

The above phenomenon is a local phenomenon that occurs only within the light irradiation spot, and has no effect on the surrounding recorded areas other than the above-mentioned local area.Also, the area that was erased by the above method cannot be recorded again. It is also possible. Therefore, it is possible to erase and rewrite a portion of the recording on the recording medium.

The first desirable characteristic of the erasing molecule is that it is a molecule with a large absorption coefficient, and dye molecules, for example, are considered suitable. Second, molecules with large interactions with the host matrix are desirable, because large interactions with the matrix improve the heat transfer efficiency from the scavenging molecules and easily eliminate the metastable state of the PH8 molecules. This is because it is possible.

Further, the factors that influence the erasing efficiency include the intensity and time of light irradiation, and the density of erasing molecules in the recording medium. Among these, the density of the erasing molecules is an important factor, and in order to increase the erasing efficiency, it is desirable that the density is higher than that of the above-mentioned PH8 molecules.

〔Example〕

Next, embodiments of the present invention will be described with reference to the drawings.

FIG. 1 is a diagram showing an embodiment of the optical recording erasing method according to the present invention, in which (a) is the chemical formula of the dye molecule mixed for erasing, (b) is an absorption spectrum diagram of the recording medium, and (C) is is an absorption spectrum diagram showing the PHB memory before erasing operation,
(d) is an absorption spectrum diagram after the erasing operation. Metal-free phthalocyanine (hereinafter referred to as H2Pc) and the dye molecule shown in FIG. 1(a) (hereinafter referred to as dye)
at concentrations of 1X10-'M and 1X10-4M, respectively.
A recording medium dispersed in polymethyl methacrylate was prepared and stored at 4.2K. The absorption spectrum of the above mixed recording medium is as shown in FIG. 1(b). First, using a tunable dye laser.

Optical recording of <PHB memory was performed based on the movement of protons in the absorption band of 600 to 700 nI11, which is the non-uniform width of H2Pc. The above record is a binary code consisting of holes as shown in FIG. 1(c).

Next, a GaAf film that matches the absorption (800 to 900 nm) of the dye responsible for erasing is placed on the recording part in the first corridor of the laser spot.
Irradiation was performed with a lAs semiconductor laser. The duration and intensity of irradiation were increased 10 times that of recording. the result.

The holes in the PHB memory formed in the absorption band of H2Pc completely disappeared as shown in FIG. 1(d), and erasure of the PHB memory was achieved. Furthermore, PH is added to the erased part above.
It was also confirmed that it was possible to create (re-record) new holes in B memory. In addition, in the above erasing, the records of adjacent spots remained preserved.

〔Effect of the invention〕

As described above, the optical recording erasing method according to the present invention uses an optical recording medium made by mixing a substance capable of hole burning by light irradiation with molecules having a light absorption wavelength different from that of the substance, and burns the optical recording medium. The recorded data was irradiated with light that was absorbed by the molecules mentioned above.

By erasing the above records, there is no need to adjust the temperature of the entire recording medium, and it is possible to locally erase and rewrite records in the PHB memory with a simple operation of irradiating light from the outside. .

[Brief explanation of the drawing]

FIG. 1 is a diagram showing an embodiment of the optical recording erasing method according to the present invention, in which (a) is the chemical formula of the dye molecule mixed for erasing, (b) is an absorption spectrum diagram of the recording medium, and (c) is is an absorption spectrum diagram showing the PHB memory before erasing operation,
(d) is an absorption spectrum diagram after erasing operation, Figure 2 is a diagram explaining the basic principle of conventional PHB memory, (a) is an absorption spectrum diagram of photochemically active molecules, and (b) is a diagram of laser light. An absorption spectrum diagram showing hole burning due to irradiation, and (C) is a diagram showing an absorption spectrum when the wavelength of the light irradiation is sequentially changed.

Claims (1)

[Claims] 1. Using an optical recording medium made by mixing a substance that can be hole-burned by light irradiation with molecules having a different light absorption wavelength from the substance, the light absorbed by the molecules is applied to the burned record on the optical recording medium. An optical record erasing method that erases the above record by irradiating it.