JPS63306090A - Optical information memory medium - Google Patents

Abstract

PURPOSE:To perform a recording medium of a multilayer structure in which colored parts are recorded without superposing on first and second photochromatic materials to increase its recording density twice or more in density by specifying the first and second materials, and irradiating beams having different optical energies. CONSTITUTION:First and second photochromatic materials are laminated, the first material is made of spiropyrane compound represented by a formula I (where R1, R2, R3 include at least one of hydrogen atom, hydroxyl group, halogen group, nitro group, amino group, alkyl group, alkoxy group, and aryl group), the second material is made of fulgide compound represented by a formula 11 (where R4, R5 include at least one of hydrogen atom, hydroxyl group, halogen group, nitro group, amino group, alkyl group, alkoxy group, and aryl group, an optical energy required to color the second material is large, and the colored parts of the first and second materials are not superposed each other.

Description

[Detailed description of the invention] [Industrial application field]

This invention relates to a storage medium used in, for example, an optical disk storage/playback device, and in particular to an optical information storage device in which information can be written by a photo-induced reaction when using a laser beam, and this written information can be read out using a laser beam. It's about the medium.

[Conventional technology]

Conventionally, disk-shaped storage carriers (hereinafter referred to as optical disks) as optical information storage media used in optical disk devices usually have a recording function, but after recording information, the recorded information cannot be erased. A write-once optical disc that cannot be erased, and a write-once optical disc that can erase information after it has been recorded.
Erasable optical discs are known in which information can be re-stored in the erased portions. Optical disk devices using such optical disks are used as external storage devices for electronic computers. A write-once optical disk device using a write-once optical disk uses a write-once optical disk formed by forming a vapor-deposited film of a low melting point metal such as tellurium as a light absorption layer on the surface of a glass or plastic substrate as a storage medium. While rotating this write-once optical disc at high speed, a laser beam modulated according to the information to be written is focused on the metal vapor-deposited film, which is the light absorption layer, and thermal processing is performed using the focused light. Information is written by punching holes in the metal-deposited film. In this method, information is written on a write-once optical disk by thermal processing, so it is impossible to erase information once recorded on the metal vapor deposited film and stored. On the other hand, erasable optical disc devices using erasable optical discs include systems that utilize magneto-optical effects such as the Kerr effect or crystal/amorphous phase transition. This phase-transfer type system uses an erasable optical disk in which a tellurium-based amorphous metal layer is formed as a storage medium on the surface of a glass substrate. While rotating this erasable optical disk at high speed, laser light modulated according to the information to be written is focused on the amorphous metal layer, and the heat of the modulated laser light causes a phase transition in the amorphous metal layer. By writing information. When erasing this written information, the heat of the laser beam is used to cause a phase transition in the amorphous metal layer again, thereby returning the optical disc to its original state. 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 diameter that can focus laser light, and it is difficult to write information. Because it relies on thermal processing, there are problems in that the storage density is theoretically limited to 10" bits/-, and it is impossible to increase the storage density any further.Such problems In order to solve this problem, for example, as shown in Fig. 8, information can be recorded multiplexed in an area of about 1 μm in diameter that can be focused by a laser beam through a photo-induced reaction, and the storage density can be greatly improved. An optical information storage medium has already been proposed in an invention filed on January 17, 1985. In FIG. , are laminated in multiple layers. 2 is a wavelength tunable laser device, 3 is a laser beam output from the wavelength tunable laser device 2, 4 is a written bit written by the laser beam 3, and 5 is an unwritten bit. Next, the operation will be explained.The wavelength tunable laser device 2 uses photoreactive materials II to 1n.
A laser beam 3 having a wavelength corresponding to each layer is output. As a result, information is selectively written into the unwritten bits 5 in any layer of the photoreactive materials 11 to 1n and stored as written bits 4. Furthermore, by irradiating any written bit 4 with a laser beam 3 having a wavelength depending on the layer, the stored information is read out.

[Problems to be solved by the invention]

Since the conventionally proposed optical information storage medium shown in FIG. 8 has the structure described above, at present, most of the drive systems including the laser system and photoreactive materials for realizing the above idea have not been developed. Regarding the latter, for example, even if photochromic materials are used, there are still many problems in making multi-layering possible. In addition, due to multilayering, materials interact with each other at the interface, resulting in spectral behavior that is completely different from that of the individual materials. This invention was made in order to solve the above-mentioned problems, and it is possible to increase the recording density of an optical disk by more than double the density by using photochromism, and to realize an inexpensive multi-layered recording medium. The objective is to obtain a high-density optical information storage medium.

[Means to solve the problem]

An optical information storage medium according to the present invention is provided by laminating a first photochromic material and a second photochromic material on a substrate having at least a light-transmitting property or a light-reflecting property,
The first photochromic material has the following general formula (in the above formula, R1, R,, R, are hydrogen atoms, hydroxyl groups,
At least one of a halogen group, nitro group, amino group, alkyl group, alkoxyl group, or aryl group
The second photochromic material is composed of a spiropyran compound represented by the following general CH8 (in the above formula, R, R, is a hydrogen atom, a hydroxyl group, a halogen group, a nitro group, an amino group). , an alkyl group, an alkoxyl group, or an aryl group).
The light energy required to color the second photochromic material is greater than the light energy required to color the photochromic material, and the light absorption spectra of the first photochromic material and the second photochromic material after coloring do not overlap with each other. This is what I did.

[Function] In the optical information storage medium of the present invention, when the first photochromic material and the second photochromic material are irradiated with light having different light energies, the first and second photochromic materials
Colored portions are recorded on each of the photochromic materials without overlapping each other. [Embodiment] An embodiment of the present invention will be described below with reference to the drawings. 1st
The figure is a sectional view of an optical information storage medium according to an embodiment of the present invention, and FIG. 2 is a sectional view for explaining its operation. In the figure, reference numeral 8 denotes a substrate having at least either light-transmitting or light-reflecting properties, and is glass. It is made of a material with excellent light transmittance or light reflection, such as ceramic, metal, or plastic. A first photochromic material 9 is laminated on the substrate 8 and records data in response to irradiation light, and is made of a spiropyran compound represented by the following formula (1). CH. In the above formula (1), RI, Rz, and R3 are hydrogen atoms, hydroxyl groups, halogen groups, nitro groups, amino groups, alkyl groups,
Contains at least one of an alkoxyl group and an aryl group. 10 is a second photochromic material that is laminated on the first photochromic material 9 and records data in response to irradiation light having a different optical energy from the irradiation light;
It consists of a fulgide compound represented by the following formula (2). In the above formula (2), R o IR is a hydrogen atom, a hydroxyl group,
At least one of a halogen group, nitro group, amino group, alkyl group, alkoxyl group, or aryl group
Contains more than one. Reference numeral 11 indicates light irradiated onto the second photochromic material 10 with light energy hv capable of coloring (data recording) the second photochromic material 10; The light is transmitted and irradiated to the first photochromic material 9 with a light energy hv2 that can color only the first photochromic material 9.
The light energy hν2 of the light 11 and the light energy hν of the light 11
, hv,>hv2, and are selected so that the light absorption spectra of the first photochromic material 9 and the second photochromic material 10 do not overlap with each other after coloring. 13 is a colored portion colored and recorded on the second photochromic material 10 by the light 11; 14 is a colored portion colored and recorded on the first photochromic material 9 by the light 12; 15 is a colored portion recorded on the first photochromic material 9 and the first photochromic material 9; The light 16.17 is irradiated with light energy hv, +hvt that can simultaneously color both of the second photochromic materials 10 and the first photochromic material 9 by its tip 15. These are the respective colored parts recorded in color. More specifically, the first and second photochromic materials 9 and 10 exhibit a so-called photochromic reaction in which they become colored when light is reflected and return to their original colorless state when exposed to light and heat again. Although this photochromic reaction is a competitive reaction between a photoreaction and a thermal reaction, the first photochromic material 9
is 3,3-dimethylindolino-6゛-nitrobenzobyrillospiran (RI, Rz, R3=H in the above formula (1)
The compound group in the case of ) consists of a series of compounds. Further, the second photochromic material 10 is (E)-α-(
2-methyl-3-furylethylidene) (isopropylidene) succinic anhydride (R in the above formula (2)
a, compound group in the case of R5-H). Such first and second photochromic materials 9,
All of the above compounds in No. 10 have relatively good storage stability at room temperature and in the dark in both colored and colorless forms, and when repeatedly changed between the colored form and the -colorless form by irradiation with light, A material with excellent repeated stability is used. The most important thing is the optical wavelength of the spectrum change of both the first and second photochromic materials 9 and 10. As an example, Fig. 4 shows the above (1).
1.1.3-trimethylindolino- in the compounds of formula
The spectra of 6'-nitrobenzopyrillospiran in the colorless state A and the colored state B are shown in FIG.
(E)-α-(2,5-dimethyl-
Colorless Bc and colored state of 3-furylethylidene) (isopropylidene) succinic anhydride,
The spectrum of D is shown. Here, in FIG. 4, the spiropyran compound in the colorless state A (the first photochromic material 9
) becomes colored BB when irradiated with light having a wavelength shorter than about 450 nm, and returns to colorless BA when irradiated with light having a wavelength of about 550 to 600 nm. On the other hand, in FIG. 5, a fulgide-based compound (second photochromic material 1
0), about 39 to make colorless state C-colored state QD
It can be seen that light with a wavelength shorter than 0 nm is effective, and light with a wavelength of approximately 430 nm to 520 nm is effective for producing the colored state gD-colorless state C. Therefore, as shown in FIGS. 1 and 2 and described above, the optical information storage medium in which the first and second photochromic materials 9 and 10 are laminated on the substrate 8 is suitable for data recording (data writing). For example, when the light energy hJ/
, light with a wavelength shorter than 390 nm is used, and the light energy hv2 is between 390 nm and 430 nm.
m light is used. Furthermore, when erasing recorded data, for example, as shown in FIG. To erase the colored portion 14 of the photochromic material 9, light with a wavelength longer than 550 nm may be used. Next, the operation will be explained. When recording data, as shown in FIG. 2, when the second photochromic material 10 is irradiated with light 11, the second photochromic material 10 is colored by the light energy hv, and the first photochromic material 9 A colored portion 13 is recorded. After this recording, the light 1
1 loses the optical energy hv1 and stays inside this second photochromic material 10. On the other hand, the second photochromic material 1 is added to the first photochromic material 9.
When light 12 is irradiated through 0, the light 12 passes through the second photochromic material 10 with its own light energy hv2, and colors only the first photochromic material 9, thereby changing the color of this photochromic material 9.
A colored portion 14 is recorded on the image. Also, (hν, +hν2)
When the light 15 having a light energy of
is recorded. If the first photochromic material 9 and the second photochromic material 10 are arranged in reverse, both the first and second photochromic materials 9 and 10 are Since the image will be colored, multiple recording is not possible. Note that the film thickness of the second photochromic material 10 needs to be determined based on the light intensity hv and the absorbance of the second photochromic material 10, and the film thickness of the first photochromic material 9 can be determined with a large degree of freedom. Needless to say. As described above, reading out the information recorded on the first and second photochromic materials 9 and 10 is carried out using the colored section 1.
3.14 by irradiating it with weak light that does not destroy (delete color). In that case, the colored portion 13 in FIG. 14. 15°16.17 and unwritten colored areas can be detected using transmitted light or reflected light. In this case, it is necessary that the light absorption spectra of the colored portions 13 and 14 do not overlap with each other. In the above, the first and second photochromic materials 9.10 include azobenzene-based, spiropyran-based,
Fulgide type, polycyclic aromatic compound type, etc.
240 pages "Photochromic Materials"Jun'etsu Seto) 1. In the present invention, materials that satisfy the above requirements are selected from these material groups and used in combination. That is, in the compounds of formulas (1) and (2) above,
R2 to R2 can be appropriately changed into a group containing at least one of a hydrogen atom, a hydroxyl group, a halogen group, a nitro group, an amino group, an alkyl group, an alkoxyl group, and an aryol group. . In this case, introduction of a group with a large molecular weight as a substituent improves the storage stability, repetition stability, etc. of photochromism. However, when substituents at positions other than R or R2 are changed, the symmetry of the molecule is disrupted, photochromism is lost, and the spectrum is significantly shifted, thereby achieving the object of the present invention. It is not possible. The photochromic material can be laminated using the usual solvent casting method, vacuum evaporation method, Langmuir-Prodgett method, etc., and the photochromic material itself can be used alone, or with the purpose of stabilization, depending on the spectra of the photochromic material and the like. It may be used in combination with other polymeric materials that do not adversely affect spectral changes. In addition, as light sources for writing, reading, and erasing information (for example, lights 11, 12, and 15 in FIG. 2),
In addition to laser light, a normal light source such as a mercury lamp, a xenon lamp, a halogen lamp, or a tungsten lamp may be arbitrarily selected and used depending on the purpose. FIG. 3 shows another embodiment of the invention. In this embodiment, the degree of freedom in the thickness of the second photochromic material 10 in FIGS. 1 and 2 described above is increased, and the interaction between the first and second photochromic materials 9 and 10 is increased. In order to increase the degree of freedom in material selection,
An optical short wavelength absorption filter 18 whose cut wavelength range is between the light wavelengths corresponding to hv1 and hv2 is inserted between the first and second photochromic materials 9.10. Here, the first photochromic material 9 and the second photochromic material 10 are expressed by the above formula (1) and (
Since it is made of the compound of formula 2), the optical short wavelength absorption filter 18 has a cut wavelength in a range of 350 nm to 450 nm, and a filter with a cut wavelength of 390 nm is suitable, for example. This filter selection is performed based on spectra as shown in FIGS. 4 and 5, for example. The optical short wavelength absorption filter 18 may be made of any material (for example, glass, plastic, other resins, etc.) as long as it fully exhibits its function. In the invention, the colored portions 13, 14, 15, 16 of the first and second photochromic materials 9, 10 are both colored by ultraviolet light, and the color is erased by visible light or near-infrared light. The reason for this is that both the first and second photochromic materials 9.10 are transparent in the unwritten state, and if they are colored by writing, they can be read out with excellent safety and are easy to use. This is because not only a variety of visible light to near-infrared light is used for the light source, but also the individual spectrum changes are large, and a good S/N ratio can be obtained.In each of the embodiments described above, Although the first and second photochromic materials 9 and 10 are provided on the substrate 8 to form a two-layer structure, it is also possible to use three or more photochromic materials to form a structure of three or more layers. It can also be applied to devices.Next, an experimental example of the present invention will be described below. [Experimental Example 1] 1.
．． 3. 3-1-limethylindolino-6'-nitrobenzovirillopyran is vacuum-deposited to a thickness of about 2000 g, and the first photochromic material 9 is laminated;
Furthermore, (E)-α-(2,5-dimethyl-3-furylethylidene) (isopropylidene) succinic anhydride was vacuum-deposited on top of it to a thickness of approximately 2,000 nm to create optical information storage. A medium (hereinafter referred to as the first medium) was obtained. [Experimental Example 2] On the transparent quartz plate of Experimental Example 1 above, ■-isopropyl 3
,3-dimethylindolino-6'-nitrobenzopyrillospiran, and then (E)-α-(2,4,5-trimethyl-3-furylethylide) were vacuum-deposited in the same manner as in Experimental Example 1 above and optically deposited. [Experimental Example 3] In Experimental Example 1, 1,3.3-)limethylindolino-6'-nitrobenzopyrillospiran was vacuum-deposited. After that, bis[
Acryloxyethyl] orthophthalate was applied to a thickness of about 10 μm and cured with ultraviolet rays, and then (E)-α-(2,5-dimethyl-3-furylethylidene) (isopropylidene ) Succinic anhydride was vacuum-deposited to obtain a multi-structured optical information storage medium (hereinafter referred to as the third medium). Next, examples of measuring characteristics in Experimental Examples 1 to 3 will be described below. The spiropyran compounds and fulgide compounds in Experimental Examples 1 to 3 are similar to those shown in FIGS. 4 and 5, respectively, and the ultraviolet-cured thickness of Experimental Example 3 is about 1.
It was found that 0μ poly-bis[acryloxyethyl]orthophthalate functions as an optical short wavelength absorption filter 18 with a cut wavelength of 390 nm. The optical information storage medium obtained in Experimental Examples 1 to 3 above was coated with 500
W Cefnon lamp (USHIO INC. UXL-500D)
The results of examining the color changes of the first to third media by irradiating them with light in the following order are shown in FIGS. 6 and 7 and will be described below. (1) Short wavelength absorption filter with a cut wavelength of 45 nm (
When irradiated with light passing through Toshiba Glass (V-Y45) for 3 minutes, the first to third media had spectra shown by curve AI in FIG. 6, and all became colorless and transparent. (2) Ultraviolet transmission visible absorption filter (Toshiba Glass UV
-D 33 S) was irradiated for 1 minute.
The first to third media had spectra shown by dotted curve B1 in FIGS. 6 and 7, and were all colored purple. (3) When irradiated with light through a 470 nm band pass filter (KL-47 manufactured by Toshiba Glass) for 2 minutes, the first
- The third medium had a spectrum shown by curve B2 in FIG. 7, and all of the mediums changed color to blue. (4) Regarding the purple colored sample in (2) above, 58
0nm bandpass filter (KL-58 manufactured by Toshiba Glass)
) When irradiated with light for 2 minutes, the first to third media had spectra shown by the curves in FIG. 7, and all of them changed color to red. (5) When the samples colored in (2) to (5) above were irradiated for 3 minutes with the light that had passed through the filter used in (1) above, the spectrum became as shown by curve A1 in Figure 6. The sample also became colorless and transparent again. (6) When irradiated with light through a 370 nm band pass filter (KL-37 manufactured by Toshiba Glass) for 30 seconds, the first to third media had the spectrum shown by curve A3 in Figure 7, and both It was colored red. (7) For the colorless transparent sample in (5) above, 400 nm
When irradiated with light through a band pass filter (KL-40 manufactured by Toshiba Glass Co., Ltd.) for 30 seconds, the first to third media had the following properties.
The spectrum was shown by curve B2 in FIG. 7, and both were colored blue. From the above characteristic measurement results, the optical information storage medium to which photochromism according to the present invention is applied is capable of multiple recording.
It is obvious that this will result in a high density recording medium.

【Effect of the invention】

As described above, according to the present invention, a first photochromic material made of a spiropyran compound and a second photochromic material made of a fulgide compound are laminated on a substrate having at least light-transmitting or light-reflecting properties. However, at least the light energy required for coloring the second photochromic material is greater than the light energy required for coloring the first photochromic material, and moreover, the light energy required for coloring the first photochromic material and the second photochromic material is greater than the light energy required for coloring the first photochromic material. Since the structure is configured so that the absorption spectra do not overlap with each other, multiplexing of recording using a multilayer structure can be easily performed, and the storage capacity of high-density optical information is more than double that of conventional optical information storage media. This has the effect of providing a storage medium.

[Brief explanation of drawings]

FIG. 1 is a sectional view of an optical information storage medium according to an embodiment of the present invention, and FIG. 2 is a sectional view for explaining its operation.
FIG. 3 is a cross-sectional view of an optical information storage medium showing another embodiment of the present invention, FIG. 4 is a diagram showing changes in the light absorption spectrum of the spiropyran compound of the optical information storage medium, and FIG. 5 is an optical Figures 6 and 7 are diagrams showing changes in the optical absorption spectrum of fulgide-based compounds for optical information storage media, Figures 6 and 7 are diagrams showing changes in the optical absorption spectrum according to experimental results for optical information storage media, and Figure 8 is for conventional optical information storage media. FIG. 1 is a perspective view showing an optical information storage medium. In the figure, 8 is a substrate, 9 is a first photochromic material, and 1o is a second photochromic material. Patent applicant Manufactured by Mitsubishi Electric Co., Ltd.

Claims (2)

[Claims] (1) A substrate that is at least translucent or reflective;
Laminated on this substrate, there are the following general formulas ▲ mathematical formulas, chemical formulas, tables, etc. ▼ (In the above formula, R_1, R_2, R_3 are hydrogen atoms, hydroxyl groups, halogen groups, nitro groups, amino groups, alkyl groups,
A spiropyran-based compound containing at least one of either an alkoxyl group or an aryl group), in which a colored portion having a predetermined light absorption spectrum is recorded by light irradiation with a predetermined light energy. 1 photochromic material, and is laminated on this first photochromic material, and has the following general formula ▲ Numerical formula, chemical formula, table, etc. ▼ (In the above formula, R_4 and R_5 are hydrogen atoms, hydroxyl groups, halogen groups, nitro by irradiation with light having a light energy greater than the above-mentioned predetermined light energy.
an optical information storage medium comprising: a second photochromic material on which a colored portion having a light absorption spectrum that does not overlap with the predetermined light absorption spectrum is recorded; (2) Between the first photochromic material and the second photochromic material, each light energy required to record the colored portion on each of the first and second photochromic materials and the corresponding light wavelength is 2. The optical information storage medium according to claim 1, wherein an optical short wavelength absorption filter having a cut wavelength range between 1 and 2 is inserted.