JPS62165749A - Optical information recording medium - Google Patents

Abstract

PURPOSE:To attain high density in storage information by storing information by the optical characteristic change when a light substance causes a light induction reaction by a light irradiated to a storage substance and the optical characteristic such as absorbed spectrum or refractive index changes by the induced reaction. CONSTITUTION:Laser light 4 sufficient in strength for causing light induction reaction is collected to an information storage medium layer 3. When the laser light 4 having a wavelength near a maximum value of an absorption spectrum curve 9 of a sensing base 6 as the storage substance is irradiated, the base 6 causes the light induction reaction, the degree of light absorption is reduced, the spectrum curve 9 changes into a curve 9a and the information is stored in an information storage medium layer 3. The storage of information is similar to that of the light sensing base 6 as to other light sensing bases 7, 8. Through the above constitution, high density and large capacity of the storage information are attained.

Description

[Detailed Description of the Invention] [Field of Industrial Application] The present invention is directed to a storage medium used for example in an optical disk storage/playback device, in which information is written by a photo-induced reaction when laser light is used, and this written information is processed. The present invention relates to an optical information storage medium that can be read using laser light.

[Conventional technology]

Conventionally, a disk-shaped storage carrier (hereinafter referred to as an optical disk) 1 is used as an optical storage information medium used in an optical disk device.
There are write-once optical discs that normally have a recording function, but cannot erase the recorded information after recording information, and write-once optical discs that can erase the information after recording it and write the information again on the erased part. Erasable optical disks that can record information are known, and optical disk devices using such optical disks are used as external storage devices for electronic computers.

In a write-once optical disk device using a write-once optical disk, a write-once optical disk on which a low-melting-point metal vapor deposited film such as tellurium is formed on the surface of a glass or plastic substrate as a storage medium is rotated at high speed, and during this rotation, writing is performed. A laser beam that has been optically modulated according to the information to be stored is focused on the above-mentioned metal vapor deposited film, which is a light absorption layer, and this focused light is thermally processed to create a hole in the metal vapor deposited film. Write. In this method, information is written onto a write-once optical disk by thermal processing, so it is impossible to erase the information once recorded and stored in the metal vapor deposited film.

On the other hand, some erasable optical disc devices using erasable optical discs use a system that utilizes a magneto-optical effect such as the Kerr effect or a crystal/amorphous phase transition. for example,
In the phase change type method, an erasable optical disk with a tellurium-based amorphous metal layer formed as a storage medium on the surface of a glass substrate is rotated at high speed, and a laser beam that is optically modulated according to the information to be written is focused on the amorphous metal layer. The heat of the modulated laser light causes a phase transition in the amorphous metal layer to write information, and when erasing this written information, the heat of the laser light is used to cause the amorphous metal layer to undergo phase transition again. Causes metastasis and returns the optical disc to its original state.

[Problem that the invention seeks to solve]

Conventional optical information storage media are configured as described above, so they can only store one piece of information recorded in an area of about 1 μm in diameter that can be focused by a laser beam, and it is difficult to write information. Because it relies on thermal processing, the storage density is theoretically limited to 108 bits/)2.
There were problems such as the inability to increase the memory density any further.

This invention was made in order to solve the above-mentioned problems, and it is possible to store information recorded multiple times in a diameter of about 1 μm, for example, where light can be focused by photo-induced reaction, and to significantly improve storage density. The purpose of this invention is to obtain an optical information storage medium that can perform

[Means for solving problems]

The optical information storage medium according to the present invention uses two or more types of storage materials each having a certain absorption spectrum width, and combines these storage materials with a molecular structure that is transparent to light having a wavelength within the absorption spectrum width of the storage materials. Introduced in a substantially planar dimension into a matrix material, when the storage material is irradiated with light of a wavelength within the absorption spectrum width of the storage material, the storage material causes a photo-induced reaction and stores information. This is what I did.

[For production]

In the optical information storage medium of the present invention, when the storage material is irradiated with a light beam, the storage material undergoes a photo-induced reaction due to the heat, and this induced reaction changes optical properties such as absorption spectrum and refractive index. By taking advantage of the property of storing information by using each beam of each wavelength within the absorption spectrum of each storage material, information can be stored multiplexed in a diameter of about 1 μm that can be focused by light.

〔Example〕

An embodiment of the present invention will be described below with reference to the drawings.

FIG. 1 is a cross-sectional side view showing writing and reading of information using a laser beam into an optical information storage medium according to an embodiment of the present invention. In the figure, reference numeral 1 denotes an optical information storage medium, which is composed of components indicated by reference numerals 2 and 3, which will be described below.

2 is a substrate; 3 is an information storage medium layer on the substrate 2 that has two or more types of storage materials that cause a photo-induced reaction and store information when irradiated with light having a wavelength within the absorption spectrum width; laser light used for writing and reading;
Reference numeral 5 denotes an objective lens for condensing the laser beam 4 onto the information storage medium layer 3. The material of the substrate 2 is not particularly limited, but glass, polymethyl methacrylate, polycarbonate, etc. are usually preferably used.

FIG. 2 is an enlarged view showing an example of the information storage medium layer 3. As shown in FIG.

In FIG. 2, 6, 7, and 8 are different photosensitive groups as memory substances, and in this example, they are present as polymer side chains. Furthermore, Fig. 3 is a light absorption spectrum diagram shown by the photosensitive group, where 9 and fQil correspond to the photosensitive groups 6 and 7.8, respectively, and the photoinduced reaction at a diameter of about 1 μm where the laser beam is focused. Corresponds to the previous optical absorption spectrum curve.

Further, 9a shows an absorption spectrum curve after the photosensitive group 6 undergoes a photoinduced reaction. Here, the photosensitive groups 6 to 8 are:
When the photosensitive group receives light of a wavelength within the width of the light absorption spectrum, it causes irreversible photoreactions (photopolymerization reactions, photoisomerization reactions, photodegradation reactions, etc.) or reversible photoisomerization reactions, etc. It is a photoreactive group that causes an induced reaction and causes changes in absorption spectrum intensity and refractive index. When using a photosensitive group that causes an irreversible reaction in the information storage medium layer 3, once information is recorded on the information storage medium layer 3 using laser light,
That information cannot be deleted.

On the other hand, if a photosensitive group that causes a reversible photoisomerization reaction is used in the information storage medium layer 3, it becomes possible to record and erase information on the optical information storage medium 1 many times. Examples of reversible photoisomerization reactions include photochromic reactions and azobenzene reactions.

There are compounds such as spirobenzobilane, fulgide type, polycyclic aromatized metal compound type, and spironaphthoxazine type, but of course they are not limited to these.Absorption spectrum curve 9 of photosensitive groups 6 to 8 in Figure 3 -11 are uniform absorption spectrum curves, and for multiple storage, it is desirable that their absorption spectra do not overlap as shown in Figure 3, but it is preferable that they have portions where their absorption spectra do not overlap. Good.

In this example, photosensitive groups 6 to 8 are introduced into the side chains of polymeric substances such as plastics and ceramics, but of course,
It may be introduced into the main chain of a polymeric substance. Alternatively, the information storage medium layer may be formed by dispersing a photosensitive substance in a polymeric substance. Furthermore, after introducing a photosensitive group into the polymer main chain or side chain, there is no problem in using it as an information storage medium layer by combining it with other polymer substances. As mentioned above, when a photosensitive group is introduced into a polymer main chain or side chain, and when a photosensitive substance is further dispersed in a matrix of a polymeric substance, the polymeric substance exhibits at least a photosensitive group or a photosensitive substance. Care must be taken not to inhibit photoinduced reactions in the light absorption spectral region. For example, when dispersing a photosensitive substance in a polymeric substance, polycarbonate,
It is preferable to use a material that is highly transparent to at least light in its light absorption spectrum, such as polymethyl methacrylate or silicone resin. If the polymer containing the photosensitive group or photosensitive substance exhibits sufficient strength, the substrate 2 in FIG.
It is also possible to combine the optical information storage medium 1 and the information storage medium layer 3 to form the optical information storage medium 1.

Next, an example of a method for writing and reading information will be explained.

To record information, a laser beam 4 of sufficient intensity to cause a photoinduced reaction is focused on the information storage medium layer 3 in the manner shown in FIG. Here, if the laser beam 4 having a wavelength near the maximum value of the absorption spectrum curve 9 of the photosensitive group 6 shown in FIG. 3 is irradiated, the photosensitive group 6 will undergo a photo-induced reaction and its absorbance will decrease. , information is stored in the information storage medium layer 3 as shown in the absorption spectrum curves 9 to 9a. The information storage of the other photosensitive groups 7 and 8 is similar to that of the photosensitive group 6.

Next, regarding the reading of information, if a laser beam having the same wavelength as that causing the photo-induced reaction and an intensity that hardly causes the photo-induced reaction is applied to the optical information storage medium 1, the absorbance of the light Alternatively, it is possible to determine whether information has been written or not based on the degree of transparency. In addition, if photoisomerization occurs through a photoinduced reaction such as a photochromic reaction and an absorption spectrum appears in a wavelength region different from the original absorption spectrum region, information can be obtained using the newly appeared absorption spectrum. can be read, but in this case,
It is important to ensure that the absorption spectra after the photo-induced reaction do not overlap each other, and the absorption spectrum after the photo-induced reaction and the absorption spectrum of the storage medium before the photo-induced reaction do not overlap with each other. It is also important to have a part.

FIG. 3 shows an example in which the multiplicity is 3. For example, if only the photosensitive group 6 undergoes a photoinduced reaction, information of (1,0°0) will be stored. Furthermore, if the photosensitive group γ is also subjected to a photoinduced reaction,
(1,,1,O) information is stored. Furthermore, if the photosensitive group 8 is also subjected to a photoinduced reaction, the information of (1, 1, 1) can be stored, and this information is stored in the information storage medium layer 3 within a condensed diameter of about 1 μm of the laser beam 4. recorded in Therefore, three pieces of information are stored corresponding to the area of the information storage medium layer 3 having a diameter of approximately 1 μm. Considering it as a combination of 3 bits, 28=8
Type information can be stored within a 1-bit storage area.

Note that during actual use, the optical information storage medium 1 is coated with silicon dioxide, acrylic resin, silicone resin, polycarbonate resin, or tricarbonate resin on the storage medium layer 3 for the purpose of stabilizing the information storage medium layer 3. A highly transparent protective film such as cellulose acetate may be provided.

In the above embodiments, information is stored by changing the absorption spectrum, but it may also be done by changing other optical properties, such as changing the refractive index.

〔Effect of the invention〕

As described above, according to the present invention, two or more types of storage substances that have absorption spectral widths and which cause a photoinduced reaction when receiving light of a wavelength within these absorption spectral widths can be used to absorb at least light within the absorption spectral widths. However, since the information storage medium is constructed by placing it in a transparent matrix material, multiple pieces of information can be stored multiplexed in an area of about 1 μm in diameter that can focus laser light, resulting in a high density of stored information. This has the effect of being able to achieve larger capacity and larger capacity.

[Brief explanation of drawings]

FIG. 1 is a cross-sectional view showing writing with a laser beam on an optical information storage medium according to an embodiment of the present invention, FIG. 2 is an enlarged view of an example of the information storage medium layer shown in FIG. 1, and FIG. is an absorption spectrum diagram shown by a photosensitive group of an information storage medium layer. In the figure, 1 is an optical information storage medium, 2 is a substrate, 3 is an information storage medium layer, 6.7.8 is a photosensitive group, 9.10.1
1 is an absorption spectrum curve shown before the photo-induced reaction, and 9a is an absorption spectrum curve shown after the photo-induced reaction. In addition, in the figures, the same reference numerals indicate the same or equivalent parts. Patent Applicant: Mitsubishi Electric Corporation (2 others) Figure 1 1: Mynah's Injury Mine, 1 view, 5 female fruit I, 1 scale, Figure 2 6, 7, 8: Round storage and curtain Figure 3, J ＼Human helmet wavelength, −

Claims (10)

[Claims] (1) It has at least two types of storage materials that have a certain absorption spectral width and cause a photo-induced reaction to store information when irradiated with light having a wavelength within this absorption spectral width;
An optical information storage medium configured to store information in a substantially planar dimension by incorporating these storage substances into a matrix material that is transparent to at least light within the above-mentioned absorption spectrum width and has a matrix-like molecular structure. (2) The optical information storage medium according to claim 1, wherein the photo-induced reaction is reversible. (3) The optical information storage medium according to claim 1, wherein the photo-induced reaction is irreversible. (4) The optical information storage medium according to claim 1 or 2, wherein the photo-induced reaction is a photochromic reaction. (5) The optical information storage medium according to any one of claims 1 to 4, characterized in that the absorption spectra of the storage material before photoinduced reaction have portions that do not overlap with each other. . (6) The optical information storage medium according to any one of claims 1 to 4, characterized in that the absorption spectra of the storage material after the photo-induced reaction have a portion that does not overlap with each other. . (7) Claims 1 to 4 characterized in that the absorption spectrum of the storage material has a portion that does not overlap either before the photo-induced reaction or after the photo-induced reaction.
The optical information storage medium according to any one of the above items. (8) The optical information storage medium according to any one of claims 1 to 7, wherein the matrix material is a polymeric substance. (9) The optical information storage medium according to claim 8, wherein the storage substance is introduced into the main chain of the polymeric substance. (10) The optical information storage medium according to claim 8, wherein the storage substance is introduced into a side chain of the polymer substance.