JP3215123B2 - Multi-level recording method using optical recording medium - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a multi-value recording using an optical recording medium.
Recording method .

[0002]

2. Description of the Related Art In recent years, with the development of information processing technology, the need for a large-capacity memory has been increasing more and more. An optical recording medium and an optical recording method using the same have attracted attention as a technique satisfying the demand. The optical recording method refers to means for recording and reproducing information by utilizing the interaction between light and a substance. The principle of the optical recording includes a photon mode using a direct change of a substance caused by a photon and a heat mode using a morphological change of a substance caused by heat energy converted from light energy.

An optical recording medium currently in practical use includes an optical disk memory, which is based on a heat mode principle. One is to form small holes or bubble-like bulges in the recording film by using the light energy of the irradiation laser light as a heat source, that is, to change the shape of the recording film. The other one is to change optical characteristics such as light transmittance, refractive index, and reflectance using the thermal phase transition of the recording film material. However, in these heat mode recordings, it is difficult to obtain high spatial resolution because heat energy is diffused on the recording medium, and in order to obtain high resolution, strong light must be incident in a short time. is there.

On the other hand, in the photon mode, the irradiated light is used for direct recording, so that the diffusion of light energy is small and generally high spatial resolution is exhibited. However, since this method uses a photochemical reaction in the recording process, the change in optical characteristics before and after light irradiation is small, and detection during reproduction is generally difficult. In addition, since the reproducing means utilizes the difference between the reflectances before and after recording, deterioration of the recording medium due to light irradiation at that time is a serious problem.

For the reasons described above, the optical disk memory using the photon mode has not been put to practical use so far, and the principle of the photon mode recording is only used for a photographic film, a photoresist, a photochromic material and the like. .

[0006]

As described above, an optical recording medium has attracted attention as a large-capacity memory. However, an optical disk memory currently in practical use uses the principle of heat mode recording, and therefore has a large capacity. There are many problems in terms of reliability. An object of the present invention is to provide a multi-value recording method using an optical recording medium capable of large-capacity recording by photon mode multi-value recording based on a novel principle.

[0007]

A multi-value recording method using an optical recording medium according to the present invention uses an optical recording medium having a recording film made of 4'-octylazobenzene-4-oxybutyric acid formed on a substrate, Multi-level recording is performed by irradiating the recording film with two or more types of light having different wavelengths from each other, and forming two or more types of light-irradiated portions having a transmittance different from that of an unirradiated portion in the recording film. Is performed. In the present invention, the substrate may be any material such as metal, glass, ceramics, and plastic.

In the present invention, 4'-octylazobenzene-4-oxybutyric acid is used as a material constituting the recording film. This substance has a wide light absorption band in the visible or ultraviolet region, and the quantum yield of the photochemical reaction changes by changing the wavelength of the irradiation light, and as a result, the transmittance changes.

Methods for depositing such a recording film material on a substrate include a vapor deposition method, a dipping method, a coating method, and an LB method. In particular, the LB method is useful because a small amount of material molecules can be uniformly accumulated.

In the present invention, the light source used for optical recording is preferably a monochromatic light source whose wavelength can be changed within the absorption band of the recording film material. Such light sources include tunable dye lasers, spectroscopic xenon lamps,
Examples thereof include a hydrogen or deuterium lamp and a halogen lamp.

In order to record information on the optical recording medium of the present invention, the light from the light source as described above is applied for several μm by a lens or the like.
The irradiation is controlled by turning on / off the beam spot to a few hundred μm. To read the recorded information,
Using a monitor light having the same spot diameter as the incident light,
The change in light absorption intensity is read as information. The intensity of the monitor light needs to be sufficiently low so that the film molecules do not react during reading. In addition, the wavelength of the monitor light may be tuned to the light absorption band of the reactant to read the amount of decrease in absorption intensity, or may be tuned to the light absorption band of the product to read the amount of increase in absorption intensity. . Which should be used may be determined by comparing the absolute value of the absorption intensity between the reactant and the product. In the former case, the intensity of the irradiation light used for recording can be reduced and used as it is as the monitor light.

[0012]

In the present invention, 4'-
Octylazobenzene-4-oxybutyric acid
Used. When this substance is photoexcited, it undergoes a post-excitation process.
Cause a photochemical reaction. This substance is visible or ultraviolet
It has a wide wavelength absorption band in the region, and the excitation wave
Choice of length alters the quantum yield of photochemical reactions
You. As a result, depending on the ratio of reaction products and unreacted substances,
To control the light transmittance.

By utilizing this principle, it is possible to form portions having different light transmittances between the light-irradiated portion and the non-irradiated portion. When a plurality of portions having different light transmittances are formed by irradiating light of a plurality of different wavelengths when irradiating light, multi-value recording becomes possible, and a large capacity optical memory can be realized by using this. . In this method, high-density recording is possible because there is no influence of thermal energy diffusion in the heat mode.

In the present invention, since there is no restriction on the substrate and the film forming method, it is only necessary to employ a means suitable for the recording film material in the manufacture. In particular, if the LB method is used, a small amount of material can be formed uniformly. An inexpensive recording medium can be manufactured.

[0015]

FIG. 1 is a sectional view of an optical recording medium according to this embodiment. In this optical recording medium, a recording film 2 made of 4′-octylazobenzene-4-oxybutyric acid, which is a long-chain fatty acid composed of an azobenzene group, is formed on both surfaces of a quartz substrate 1. This substance undergoes photoisomerization upon irradiation with light. Specifically, a chloroform solution of 4'-octylazobenzene-4-oxybutyric acid is spread on a clean water surface, and a single-layer or multiple-layer recording film 2 is formed on the substrate 1 using the LB method. I do.

For writing information on the optical recording medium, a dye laser capable of selectively exciting a specific wavelength within the wavelength range of the light absorption band of the recording film 2 is used.
This is performed by controlling irradiation / non-irradiation of the light. As a result, in the recording film 2, a portion where the light transmittance has changed is formed in a dot shape. At this time, by forming a plurality of portions having different light transmittances by changing the wavelength of the laser light, multi-value recording can be performed.

For reading information recorded on the optical recording medium, a laser beam whose intensity has been reduced to a level that does not cause a chemical change of the recording film 2 is irradiated as monitor light, and transmitted light or reflected light from the recording film 2 is emitted. Is detected by an optical sensor.

FIG. 2 shows the result of actually measuring the light absorption spectrum of the recording film after irradiating the optical recording medium with laser light of a specific wavelength. In FIG. 2, a solid line A indicates a portion where laser light was not irradiated, and a broken line B indicates a wavelength 3
The portion irradiated with the laser beam of 20 nm, the broken line C indicates the wavelength 3
It is a light absorption spectrum of the part irradiated with the laser beam of 70 nm. Note that the irradiation time is set sufficiently long until the change in absorbance is completed in order to suppress the influence of the difference in the intensity of the laser light for each wavelength.

In FIG. 2, focusing on the change in the absorbance near 320 nm, the decrease in the absorbance in the portion irradiated with the 320 nm laser light is about 25%, whereas the decrease in absorbance is about 25%.
In the portion irradiated with the laser beam of 0 nm, the decrease in absorbance is about 50%. Conversely, the light transmittance is increased in the portion irradiated with the 370 nm laser light.

Therefore, the first wavelength (for example, 370n
Information can be written by setting a portion irradiated with the laser light of m) as information "0" and a portion irradiated with the laser light of the second wavelength (for example, 320 nm) as information "1". Then, by irradiating 320 nm laser light whose intensity has been reduced by a filter or the like as monitor light and detecting transmitted light or reflected light, information “0” and “1” can be discriminated reliably.

The portion irradiated with the laser light of the first wavelength is information “−1”, the portion not irradiated with the laser light is “0”, and the portion irradiated with the laser light of the second wavelength is information “1”. As 1 ", ternary recording becomes possible. Further, by irradiating a laser beam having a wavelength such that the light transmittance has a different value from those described above, multi-level recording becomes possible and the capacity of the optical recording medium can be increased.

[0022]

As described in detail above, according to the present invention,
4'-octylazobenzene-4-oxybutylic acid
Using an optical recording medium with a recording film made of SID
Enables highly reliable multi-level recording, and as a result
Capability can be achieved.

[Brief description of the drawings]

FIG. 1 is a sectional view of an optical recording medium according to an embodiment of the present invention.

FIG. 2 shows an optical recording medium according to an embodiment of the present invention.
It is a characteristic view which shows the light absorption spectrum of the part which has not irradiated the laser beam, the part which irradiated the laser beam of 320 nm wavelength, and the part which irradiated the laser beam of 370 nm wavelength.

[Explanation of symbols]

 1. Quartz substrate, 2. Recording film, 3. Laser light.

──────────────────────────────────────────────────続 き Continuation of front page (56) References JP-A-62-164591 (JP, A) JP-A-62-165749 (JP, A) JP-A-2-94137 (JP, A) JP-A-2-162 251840 (JP, A) JP-A-1-259353 (JP, A) JP-A-2-147286 (JP, A) JP-A-3-261947 (JP, A) JP-A-3-200957 (JP, A) JP-A-3-282450 (JP, A) (58) Fields investigated (Int. Cl. ⁷ , DB name) G11B 7/24 B41M 5/26 G11B 7/00

Claims (1)

(57) [Claims] 1. The method according to claim 1, wherein 4'-octylazobenzene-
An optical recording medium having a recording film made of 4-oxybutyric acid is used, and the recording film has different wavelengths from each other.
Performing multi-level recording by irradiating more than one kind of light to form two or more kinds of light-irradiated portions having a transmittance different from that of an unirradiated portion in the recording film; Multi-value recording method using a medium.