JPH0422256B2 - - Google Patents

Description

[Detailed Description of the Invention] [Technical Field of the Invention] The present invention relates to an optical recording medium such as an optical disk memory.By using a biological material as an optical recording medium, it is possible to write and read information as a gradation signal. The present invention relates to an optical recording medium that is easy and rewritable.

[Prior art]

Conventionally, as an optical recording medium, there has been one shown in FIG. In the figure, 1 is a metal vapor deposited film, 2 is a pore formed by irradiating the metal vapor deposited film 1 with a laser beam, 3 is a portion not irradiated with the laser beam, and 4 is a glass substrate. In this conventional optical recording medium, the temperature of the part irradiated with the laser beam rises, and the metal part melts and desorbs, creating pores 2. This causes the part 3 not irradiated with the laser beam to become "0", and the laser beam The two can be distinguished by setting the beam irradiation part to "1", and a binary value as a digital memory can be obtained.

Conventional optical recording media are structured as described above, so once a signal has been recorded, it cannot be rewritten, and the signal can only take on two values, "0" and "1", and therefore the gradation is different. Recording, ie analog recording, was impossible.

[Summary of the invention]

This invention was made to eliminate the above-mentioned drawbacks of conventional optical recording media, and it consists of a thin film of bacteriorhodopsin, a pigment protein present in the biological membranes of highly halophilic bacteria, on a substrate. The purpose of the present invention is to provide a completely new optical recording medium that is formed by forming a thin film and that makes it possible to record gradations and is rewritable by utilizing changes in optical properties due to cyclic photoreactions of the thin film. There is.

[Embodiments of the invention]

First, the principle and operation of this invention will be explained with reference to the drawings.

Bacteriorhodopsin is a pigment protein present in the biomembrane of highly halophilic bacteria (Halobacterium halobium), and is known to perform photoreactions. Although the full details of this photoreaction have not yet been elucidated, several types of photoreaction intermediates have been discovered.

Therefore, the present invention focused on the fact that a bacteriorhodopsin film can be used as an optical recording medium if it is made to function as a stable solid film and the progress of a photoreaction can be controlled. In particular, the bacteriorhodopsin membrane has a cyclic photoreaction, and the progress of the reaction may be controlled by the intensity of the irradiated light. It has been discovered that a rewritable optical recording medium can be obtained.

That is, as a result of intensive research based on the above considerations, the present invention has been made by producing an optical recording medium by forming a thin film of bacteriorhodopsin on a substrate such as glass or silicon wafer, and by producing an optical recording medium by forming a thin film of bacteriorhodopsin on a substrate such as a glass or silicon wafer. This invention was created by focusing on the fact that a state in which optical properties have changed due to a reaction can be used as an information recording or reproduction signal.

FIGS. 3 and 4 show experimental results regarding the light absorption spectrum of bacteriorhodopsin membranes, which were conducted by the present inventor based on the above-mentioned points of interest.

FIG. 3 shows the light absorption spectrum of the bacteriorhodopsin membrane before photoreaction, and the absorption spectrum was measured at -60°C. Figure 4 shows the difference absorption spectrum, which is the difference between the absorbance of the bacteriorhodopsin membrane before and after the photoreaction.
500 nm).

From FIGS. 3 and 4, the bacteriorhodopsin membrane has a strong absorption band in the wavelength range of 500 to 600 nm before photoreaction, but the reaction intermediate of bacteriorhodopsin, which is stable at -60°C after photoreaction, 380～
It has a strong absorption band in the 450 nm wavelength range, and it can be seen that the absorbance significantly decreases after the reaction in the 500-600 nm wavelength range, which is the main absorption band before the photoreaction. In addition, experiments have shown that when the temperature of the optical recording medium is set to around room temperature by irradiating the optical recording medium with a laser beam and heating it, this reaction intermediate returns to its pre-reaction state and has the absorption spectrum shown in Figure 3. I found out that it becomes

Furthermore, it has been found that by controlling the intensity or irradiation time during irradiation with green irradiation light, the difference in absorbance in the absorption spectrum before and after the photoreaction shown in FIG. 4 can be made into a desired characteristic.

From the above experimental results, it has been found that the following method can be used to record, reproduce, or rewrite information in gradations using an optical recording medium in which a bacteriorhodopsin film is formed on a substrate.

(1) To record information, laser light (green light or blue light) is used as the recording irradiation light that causes a cyclic photoreaction in the bacteriorhodopsin membrane.
Use.

(2) irradiating the thin film with the recording irradiation light while holding the optical recording medium using the bacteriorhodopsin film at a constant temperature in the range of -120°C to -30°C to cause a writing light reaction; The state after the photoreaction is set as a writing state, and the optical medium in the writing state is maintained at a constant temperature in the range of -120°C to -30°C, thereby stably maintaining the writing state.

(3) To reproduce the recorded information after optical writing,
The optical recording medium is irradiated with reproduction irradiation light having a wavelength range of 500 to 600 nm or 380 to 450 nm, and the recorded information is reproduced from the reflectance or transmittance of the light.

(4) To erase the information signal after optical writing,
All you have to do is irradiate the area to be erased with a laser beam and heat the area.This causes a cyclic photoreaction to locally proceed, and the reaction intermediate returns to its initial state before optical writing, resulting in the writing being completed. The signal is locally canceled.

(5) To perform gradation recording of information, it is sufficient to control the intensity or irradiation time of the irradiation light for optical writing.

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

FIG. 2 schematically shows an optical recording medium according to an embodiment of the present invention. In the figure, 5 is a bacteriorhodopsin thin film formed on a glass substrate 10, and 6 is a thin film of bacteriorhodopsin that has not been irradiated with a laser beam. Part, 7, 8, 9
is a laser beam irradiation part.

To record information on the above optical recording medium, -120℃
At a constant temperature of -30 DEG C., the parts of the bacteriorhodopsin thin film 5 that are to become the irradiation parts 7, 8, and 9 are irradiated with blue laser light of high intensity in this order. As a result, the optical properties of the irradiating parts 7, 8, and 9, such as light reflectance and transmittance, change significantly in the order of the irradiating parts 7, 8, and 9, and information on the state in which the optical properties have changed is generated. As a recording state, gradation recording of information is realized.

To reproduce information from the optical recording medium,
The optical recording medium is irradiated with reproduction irradiation light having a wavelength range of 500 to 600 nm or 380 to 450 nm. Then, the reflectance or transmittance of the reproduction irradiation light in the laser beam irradiation parts 7, 8, and 9 differs from the reflectance or transmittance in the unirradiated part 6 depending on the signal strength, and therefore, from now on, Information can be played back.

Furthermore, in order to erase the recorded information on the optical recording medium, it is sufficient to irradiate a laser beam to the part of the optical recording medium where the information is to be erased and heat it locally, thereby causing the reflection of the light on the thin film 5. The rate or transmittance returns to the value before the information was recorded, and the recorded information can be erased. Then, if the information is recorded again using the above-mentioned recording method, rewriting of the information can be realized.

Note that the bacteriorhodopsin thin film is not limited to a pure bacteriorhodopsin film, and may be a bacteriorhodopsin thin film containing, for example, a lipid or a synthetic polymeric substance such as polystyrene.

〔Effect of the invention〕

As described above, according to the present invention, an optical recording medium is constructed by forming a film of bacteriorhodopsin, which is a pigment protein of highly halophilic bacteria, on a substrate. This has the effect of providing an optical recording medium that is capable of recording and reproducing information in gradations and rewriting information by skillfully utilizing changes in properties.

[Brief explanation of drawings]

FIG. 1 is a perspective view of a conventional optical recording medium, FIG. 2 is a perspective view of an optical recording medium according to an embodiment of the present invention, and FIG. 3 is a characteristic diagram showing the absorption spectrum of bacteriorhodopsin membrane before photoreaction. FIG. 4 is a characteristic diagram showing the difference absorption spectrum of light before and after photoreaction. 5...Bacteriorhodopsin thin film, 10...Glass substrate.

Claims (1)

[Claims] 1. An optical recording medium comprising a thin film of bacteriorhodopsin whose optical properties change by photoreaction on a substrate.