JP2772345B2 - Optical recording method - Google Patents

Description

Description: TECHNICAL FIELD The present invention relates to an optical recording system, and more particularly, to a stable and high-density optical recording system.

TECHNICAL BACKGROUND AND PROBLEMS OF THE INVENTION As a rewritable optical recording method, a method has been proposed which utilizes a change in absorption spectrum of a photochromic compound before and after a photoreaction. However, in this method, at the time of reading out a record, it is necessary to read out the light in a wavelength region having light absorption. Accordingly, the light used for reading such a record is not only the light for reading information but also the light for erasing information. Therefore, reproducing the information essentially destroys the information, and when reading the information recorded in the photochromic compound, the information is destroyed and it becomes impossible to read the information again. There was a point.

An object of the present invention is to solve the above-mentioned problems and to provide a stable and highly sensitive optical recording system capable of easily and stably performing writing, reading and rewriting of information. I have.

SUMMARY OF THE INVENTION An optical recording method according to the present invention is a method of dispersing an inorganic compound crystal, an organic compound crystal, a nematic liquid crystal, a ferroelectric liquid crystal, a polymer stretched film and a Langmuir-Blodgett film. Alternatively, by dissolving, the photochromic compound in which the transition moment of light absorption is oriented in a certain direction is used as an optical recording medium, and a light beam in the absorption wavelength region of the photochromic compound is irradiated to change the structure of the photochromic compound. Write or rewrite information, irradiate the photochromic compound with a light beam in a wavelength range where the photochromic compound does not absorb light as read light, and detect the difference in apparent optical rotation before and after light irradiation to write and read information. It is characterized by performing non-destructively.

DETAILED DESCRIPTION OF THE INVENTION Hereinafter, the optical recording system according to the present invention will be described in more detail.

In the present invention, when writing and reading information, a photochromic compound in which the transition moment of light absorption is oriented in a certain direction is used.

As described above, in the present invention, a photochromic compound in which the transition moment of light absorption is oriented in a certain direction is used, but a compound in which the transition moment of light absorption is oriented in a certain direction is used regardless of whether the compound itself has optical activity. In the absorption wavelength region and in the vicinity thereof. Therefore, if the transition moment of the light absorption of the photochromic compound is oriented in a certain direction, it is possible to write or rewrite information by changing the absorption spectrum by irradiating light in the absorption wavelength range, and at the same time, the apparent optical rotation. Can also be changed. Further, since the apparent optical rotation is also observed in the wavelength region where the photochromic compound does not absorb, as in the case of ordinary optical rotation, the photochromic compound is irradiated with readout light at a wavelength that does not absorb the photochromic compound, and the change in the optical rotation is detected. , Information can be read. In this way, the information written in the photochromic compound can be read without destroying the information.

In the present invention, as described above, the photochromic compound does not need to have optical activity in the molecule as described above. Therefore, any photochromic compound can be used, including spiropyran, fulgide, thioindigo, azobenzene, and derivatives thereof. As the photochromic compound, specifically, 1,3,3, -trimethylindolino-6'-nitrobenzospiropyran, 1,3,3, -trimethylindolino-6'-nitro-8'-
Methoxybenzospiropyran, 1,3,3-trimethylindolino-6,8'-dibromobenzospiropyran, 1,3,3-trimethylindolino-5'-nitro-8'-
Methoxybenzospiropyran benzothiazolinospiropyran, 1,3,3-trimethylspiro [indolino-2,3-naphtho (2,1-b) (1,4) oxazine], 1,3,3-trimethyl-5 Chlorospiro [indolino-
2,3-naphtho (2,1-b) (1,4) oxazine], 1- (octyl) 3,3-dimethylspiro [indolino-
2,3-naphtho (2,1-b) (1,4) oxazine], 1- (tetradecyl) 3,3-dimethylspiro [indolino-2,3-naphtho (2,1-b) (1,4 ) Oxazine], 1,3,3-trimethylspiro [indolino-2,3-phenanthro (9,10) (1,4) oxazine], 1,3,3-trimethyl-5-chlorospiro [indolino-
2,3-phenanthro (9,10) (1,4) oxazine], 1,3,3-trimethylspiro [indolino-2,3- (3,6)
Disulfonaphtho (2,1-b) (1,4) oxazine] disodium, 2-butylidene (diphenylmethylene) succinic anhydride, diphenylmethylene (isopropylidene) succinic anhydride, 2,5-dimethyl-3-furylethylidene ( (Isopropylidene) succinic anhydride, 2,5-dimethyl-3-thiophenylethylidene (isopropylidene) succinic anhydride, thioindigo perinaphthothioindigo azobenzene 4-methoxyazobenzene 2- (2,4-dinitrobenzyl) pyridine 4,4 Compounds such as', 4 "-tris (N, N-dimethylaminophenyl) methyl chloride can be used.

As a method of aligning such a photochromic compound, any method may be used as long as the photochromic compound can be aligned,
For example, a method of dispersing or dissolving the photochromic compound in a medium having anisotropy or a method of introducing a site that promotes molecular orientation into the structure of the photochromic compound itself can be used.

As an anisotropic medium that can be oriented by dispersing or dissolving a photochromic compound,
For example, any of an inorganic compound crystal or an organic compound crystal, a nematic liquid crystal, a ferroelectric liquid crystal, a stretched polymer film, and a Langmuir-Blodgett film is used. Such a medium itself also has an apparent optical rotation based on birefringence, and the apparent optical rotation based on the absorption of the photochromic compound can be observed in a form added to the apparent optical rotation of the medium itself.

Introducing a site that promotes molecular orientation into the photochromic compound itself is, for example, a method in which the photochromic compound is chemically bonded to liquid crystal molecules such that the transition moment of light absorption is oriented in a certain direction. With such a molecule, the photochromic compound can be oriented without using a medium. Examples of such molecules include those in which a photochromic compound is bonded to some of the molecules constituting the anisotropic medium in addition to the liquid crystal.

The optical recording medium according to the present invention uses the photochromic compound and the medium oriented as described above.

Writing or rewriting of information in the present invention is performed as follows. That is, a light beam in the absorption wavelength region of the photochromic compound (A) is irradiated to a desired portion of the recording medium as described above. As a result, a photochromic reaction occurs in the spot irradiated with the light beam, and the photochromic compound (A) reversibly changes to a different structure (B). On the other hand, such a change does not occur in a spot that has not been irradiated with a light beam. In this way, the two states (A) and (B) can be arranged in the optical recording medium according to the information, and thus the information can be written. When rewriting information,
The light beam in the absorption wavelength region of (B) is applied to the entire region to be rewritten, and the information that was originally recorded with all the photochromic compounds in the region as (A) is erased, and then the information is written again. Just do it.

Further, the reading of information in the present invention is performed as follows. That is, the information written or rewritten by the above method has an arrangement of (A) and (B) in the recording medium. Since (A) and (B) have different absorption spectra and thus have different apparent optical rotations, a change in optical rotation can be used as the readout light. By the way, as described above, since the apparent optical rotation is also recognized in the wavelength region where there is no absorption as in the case of the ordinary optical rotation, both (A) and (B) are different from the case where the change in the absorbance is used as the reading mode. Reading in a wavelength region having no absorption is possible. If the recording is read in either the absorption wavelength region (A) or (B), the recording is destroyed by the irradiation of the reading light, but in the present invention, the change in the optical rotation is set to the reading mode. Therefore, reading can be performed in a wavelength region in which neither (A) nor (B) has absorption, and reading can be performed without destroying information recorded in the photochromic compound.

Hereinafter, examples will be given to describe the present invention more specifically, but the present invention is not limited to these examples.

Example 1 In 0.3 ml of room-temperature nematic liquid crystal (ZLI 1132, MERCK), 6 mg of furyl fulgide (Structural formula 1 as shown below) was dissolved, and this was injected into a parallel alignment type liquid crystal cell to prepare an optical recording medium. It was formed, kept at 35 ° C., and irradiated with light in the absorption wavelength region of furilflugide to measure the change in optical rotation dispersion.

The result is shown in FIG.

When ultraviolet light (300 to 400 nm) is irradiated to the optical recording medium according to the present invention, furylfulgide changes from a ring-opened form (absorption peak wavelength 340 nm) to a closed-ring form (absorption peak wavelength 500 nm), and at this time, a photochromic reaction occurs. And the change in optical rotation dispersion is observed.

The change in optical rotation dispersion over a wide wavelength range,
It can also be read by light having a wavelength longer than 600 nm without the absorption of frillflugide.

Then, when firfulgide was irradiated with visible light (400 nm to long wavelength), the optical rotation dispersion was restored. Also, there is almost no absorption in the ring-opened and closed-ring forms of furilflugide
By irradiating the optical recording medium with light of 600 nm and observing the change in optical rotation, ultraviolet light (300-400 nm) and visible light (400 nm-
(Long wavelength), the reversible change in the optical rotation was observed as shown in FIG. As a result, it has been shown that according to the optical recording system of the present invention, information can be rewritten and non-destructively read. When the temperature was further increased to make the liquid crystal isotropic, the optical rotation was lost. This indicates that the orientation of the photochromic compound in the recording medium of the present invention is an essential factor in the optical rotation.

Example 2 In a ferroelectric liquid crystal (Structural Formula 2 as shown below), the photochromic compound used in Example 1 was dissolved in an amount of 0.01 mol per mol of the liquid crystal, and this was dissolved in a parallel alignment type liquid crystal cell. To form an optical recording medium.

When the same light irradiation as in Example 1 was performed while maintaining the temperature at 45 ° C., the optical rotation at 600 nm was changed by + 0.2 ° due to the ultraviolet light irradiation. Further, the optical rotation returned to the original value by irradiation with visible light. Further, when the temperature was raised to make the liquid crystal isotropic phase as in Example 1, the optical rotation was lost.

According to the optical recording method using the photochromic compound according to the present invention, the information written in the photochromic compound is non-destructively irradiated by irradiating the photochromic compound with light having a wavelength different from the recording light and the erasing light. Can be read out. Therefore, writing and reading of information can be performed with high sensitivity. Further, the recording medium can be manufactured without being limited to a special material.

[Brief description of the drawings]

FIG. 1 is a view showing a change in optical rotation when information recorded by irradiating an optical recording medium used in the present invention with ultraviolet light is read using visible light. FIG. 2 is a diagram showing a change in optical rotation when an optical recording medium used in the present invention is irradiated with ultraviolet light and visible light alternately.

Claims (1)

(57) [Claims] Claims: 1. An inorganic compound crystal, an organic compound crystal, a nematic liquid crystal, a ferroelectric liquid crystal, a polymer stretched film and a Langmuir-Blodgett film dispersed or dissolved in any one selected from the group consisting of: A photochromic compound in which the transition moment of light absorption is oriented in a certain direction is used as an optical recording medium, and a light beam in the absorption wavelength region of the photochromic compound is irradiated to write or rewrite information by changing the structure of the photochromic compound. Non-destructive writing and reading of information by irradiating a photochromic compound with a light beam in a wavelength region having no absorption of the photochromic compound as readout light and detecting a difference in apparent optical rotation before and after light irradiation. Characteristic optical recording system.