JPH0980681A - Photochromic optical recording medium - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a rewritable photochromic optical recording medium having high stability in repeated reproduction. SOLUTION: This rewritable photochromic optical recording medium has a photochromic recording layer 2 formed of a ring opening and closing type photochromic compound having a heterocycle having dimethylamino group and an acid anhydride part, an organic acid, and a resin binder. Therefore, since the ring opening reaction quantum yield of decoloring reaction in the acid-added photochromic recording layer is extremely low, compared with the case of a conventional diarylethene derivative, nondestructive read or long-time reproduction can be attained, decoloration can be performed with a light of low power, and a rewritable photochromic optical recording medium with high S/N can be provided.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a photochromic optical recording medium, and more particularly to a so-called rewritable photochromic optical memory having a recording layer containing a ring-opening ring-closing photochromic compound.

[0002]

2. Description of the Related Art A photochromic optical disk utilizing the reversible light and thermal isomerization reaction of an organic photochromic material is known as a rewritable optical disk capable of recording, reproducing and erasing information. Such a rewritable photochromic optical disc has a transparent substrate 1 as shown in FIG.
A photochromic recording layer 2 containing an organic photochromic material is formed, a reflective layer 3 made of aluminum or the like is formed on the recording layer 2, and the protective layer 4 protects this. On the main surface of the substrate 1, guide grooves for tracking, pre-pits for controlling writing or reading of data, pre-address 5 and the like are formed in advance. The laser beam 6 is emitted from the substrate 1 side.

The organic photochromic material is a compound which is repeatedly colored and decolored in response to light. For example, as shown in the light absorption spectrum distribution chart of FIG. 2, it absorbs light of wavelength B in the first wavelength absorption band. Then, the stable state X (first state) is changed to the metastable state Y (second state) and colored (coloring reaction), and in the metastable state Y, the wavelength A of the second wavelength absorption band is obtained.
When it absorbs the light or heat of (color erasing reaction), it returns to the original substance and erases the color, so-called photochromism. Using this photochromism, information can be recorded, reproduced, and erased by a laser beam. Examples of such an organic photochromic material include a material that uses a photoisomerization reaction such as thioindigo, a spiropyran compound that uses a ring-opening and ring-closing reaction, and a redox reaction, and a fulgide compound.

To record information on these optical disks, light energy is applied to the recording layer 2 in spots by a writing laser beam having a specific wavelength via a pickup optical system.
It is carried out by positively causing a color-forming reaction to form a color-recorded portion. The reproduction of information from this optical disk is performed by irradiating a laser beam of another wavelength and reading the recorded portion. Information is erased by irradiating another laser beam having a specific wavelength to cause a decoloring reaction in the recorded portion. Therefore, in the rewritable photochromic optical disk, when the signal state of the photochromic recording layer in the first state is set to “0” as the initial state, the wavelength modulation of the laser beam and the blinking thereof cause Writing can be performed in the state of "1" and erasing can be performed by the laser beam of the second wavelength. That is, in the rewritable photochromic optical disk of this embodiment, binary logic recording of "0" and "1" is possible.

As described above, attempts have been made to apply an organic photochromic compound exhibiting a reversible color-decoloring reaction to a rewritable recording medium for an optical disk.
As such recording medium materials, spiropyran compounds, fulgide compounds, diarylethene compounds, and the like have been investigated. However, to date, no recording medium material having a nondestructive read function in which recording is not destroyed by reading light has not been obtained. Since the photoreaction in the photochromic compound has no threshold value and the reaction occurs in proportion to the amount of absorbed light, when a normal photochromic compound is used as an optical recording medium, light irradiation for reading the presence or absence of light absorption (recording information) This is because the recorded information is gradually erased by repeating (reproduction).

Therefore, since the recording / reproducing is performed by the repeated irradiation of the laser beam, the recording / reproducing can be performed by the laser beam having the non-destructive reading function and the low power in order to extend the life of the recording medium. A rewritable photochromic optical disk is desired.

[0007]

SUMMARY OF THE INVENTION An object of the present invention is to provide a rewritable photochromic optical recording medium having a nondestructive reading function and capable of recording / reproducing even with a low power laser beam.

[0008]

The rewritable photochromic optical recording medium of the present invention comprises a ring-opening ring-closing photochromic compound having a heterocyclic ring having a dimethylamino group and an acid anhydride moiety, an organic acid, and a resin binder. It has a photochromic recording layer consisting of.

One of the ring-opening ring-closing photochromic compounds comprises a protonated ring-opened compound and a non-protonated ring-opened compound, each of which has a short wavelength absorption band. The body is a protonated ring-closed body and a non-protonated ring-closed body each having a long-wavelength absorption band that is biased to a longer wavelength side than the short-wavelength absorption band when responding to writing light of a common wavelength in the short-wavelength absorption band. And the ring-opening reaction quantum yield of the non-protonated ring-closed compound upon reacting to the wavelength reading light in the long-wavelength absorption band of the non-protonated ring-closed body is The ring-opening reaction quantum yield of the above-mentioned protonated ring-closed compound is smaller than that of the above-mentioned protonated ring-closed compound when it is reacted with the erasing light having the wavelength of.

The ring-opening ring-closing photochromic compound having a ring-opening reaction quantum yield smaller than the quantum yield of the ring-opening reaction upon reaction with the light of the third wavelength is represented by the following formula:

[0011]

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(In the formula, Me represents a methyl group, and the same applies hereinafter)
Is a diarylethene anhydrous compound represented by. Furthermore, the ring-opening ring-closing photochromic compound having a ring-opening reaction quantum yield smaller than the quantum yield of the ring-opening reaction when reacted with the light of the third wavelength is represented by the following formula:

[0013]

[Chemical 6]

Is a fulgide compound represented by: Further, the other of the ring-opening ring-closing photochromic compound,
Each of them consists of a protonated ring-opened body and a non-protonated ring-opened body having a short wavelength absorption band, and the protonated ring-opened body and the non-protonated ring-opened body write a common wavelength in the short wavelength absorption band. At least one of which has a long-wavelength absorption band having an absorbance higher than that of the short-wavelength absorption band when at least one side is biased to the long-wavelength side when reacted with light.

The ring-opening ring-closing photochromic compound which is the deprotonated ring-closed compound is represented by the following formula:

[0016]

[Chemical 7]

An anhydrous diarylethene compound represented by: The ring-opening ring-closing photochromic compound to be the deprotonated ring-closed compound has the following formula:

[0018]

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An anhydrous diarylethene compound represented by: The organic acid is trichloroacetic acid, dichloroacetic acid,
Chloroacetic acid, P-toluenesulfonic acid, or phosphoric acid is preferable. The resin binder is preferably polystyrene, polymethylmethacrylate, polycarbonate or polyvinyl chloride.

According to the present invention, the quantum yield of the decolorization reaction in the acid-added photochromic recording layer is lower than that in the case of the conventional diarylethene derivative, so that nondestructive read-out or long-time reproduction can be achieved. Decolorization can be performed with light of low power, and S / N can be increased.

[0021]

Embodiments of the present invention will be described below with reference to the drawings. The rewritable photochromic optical disk of this example is the same as the conventional one shown in FIG. 1 except for the recording layer, and includes a transparent substrate 1 such as polymethylmethacrylate (PMMA) or polycarbonate (PC), and an organic photochromic material. It comprises a photochromic recording layer 2, a reflective layer 3 made of aluminum or the like, and a protective layer 4.

The photochromic recording layer of the first embodiment is
A fulgide compound (5-dimethylaminoindolyl fulgide fulgide) having an indole ring having a dimethylamino group at the 5-position and an acid anhydride moiety, and trichloroacetic acid, dichloroacetic acid, chloroacetic acid, P-toluenesulfonic acid, or Organic acids such as phosphoric acid, polymethylmethacrylate,
It is a thin film of a mixture of a resin binder such as polystyrene, polycarbonate, or polyvinyl chloride.

The photochromic recording layer is prepared by mixing such 5-dimethylaminoindolyl fulgide and trichloroacetic acid with, for example, polymethylmethacrylate, dissolving them in a methylethylketone (MEK) solvent to prepare a dispersion solution, and spin-coating the transparent solution. A film is formed on the substrate. The photochromic recording layer can also be formed by spin coating with a polystyrene solution using toluene as a solvent. The photochromic recording layer can be formed by the same method in the following examples. In addition to polymethylmethacrylate, polystyrene, polycarbonate or polyvinyl chloride can be used by combining a resin binder with an appropriate solvent.

FIG. 3 shows an aprotonated ring-opened compound, a protonated ring-opened compound H +, an aprotic ring-closed compound C, and a protonated ring-closed compound CH + in the acid-base equilibrium system of acid-added 5-dimethylaminoindolylfulgide. The optical absorption spectrum distribution map of is shown. A rewritable photochromic optical disk with a non-destructive read-out function that utilizes acid-base equilibrium in 5-dimethylaminoindolyl fulgide and the wavelength dependence of the quantum yield of the ring-opening reaction operates as shown in the formula below. To do.

[0025]

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As shown in FIG. 3 and the above formula, the aprotonated ring-opened product of 5-dimethylaminoindolylfulgide (upper left in the above formula) becomes an aprotic ring-closed product C by light having a wavelength of 403 nm, and its wavelength absorption. The maximum band is 673 nm,
Although it has an absorption edge of 900 nm or more, it does not change even when irradiated with light in this absorption region. When trichloroacetic acid is added to this system, a proton is added to the dimethylamino group and 5-dimethylaminoindolyl fulgide is a protonated ring-closure compound CH +.
Therefore, the wavelength absorption band is shortened, and light can be converted into a protonated ring-opened product H + having a proton attached to the ring-opened product. That is, when the protonated ring-closed product CH + absorbs 554 nm light, it becomes a protonated ring-opened product H + with a high quantum yield (0.1). The ring-closed body C of 5-dimethylaminoindolyl fulgide and the protonated ring-closed body CH + and the ring-opened body of 5-dimethylaminoindolyl fulgide and the protonated ring-opened body H + are in acid-base equilibrium. Body CH
When + decreases, the closed ring C decreases and protonated open ring H +
Increase. Since the protonated ring-opened product H + is converted into a protonated ring-closed product CH + by ultraviolet light, 5-dimethylaminoindolyl fulgide ring-opened product and protonated ring-opened product H + are converted.
When the equilibrium system of 1 is irradiated with ultraviolet light, the equilibrium system of the ring-closed body C and the protonated ring-closed body CH + is formed. Nondestructive read optical recording can be realized by using this four-component balanced system. That is, for writing of 403 nm light for recording, 5
54 nm light is used for erasing recording. 7 to read records
With 80 nm light, the record is not destroyed.

The second embodiment is the same as the first embodiment except that an indole ring having a dimethylamino group at the 5-position, a benzothiophene ring and a diarylethene anhydride compound having an acid anhydride portion are used in the photochromic recording layer. is there.
Difference in acid-base equilibrium between an organic acid and a diarylethene anhydride compound having an indole ring having a dimethylamino group at the 5-position, a benzothiophene ring, and an acid anhydride moiety in the second example, and the ring-opening reaction quantum yield of this system. The rewritable photochromic optical disk that achieves the nondestructive read function utilizing the above-described method operates in the same manner as in the first example using 5-dimethylaminoindolylflugide, but a specific acid-base equilibrium system will be described later.

The ring-opening ring-closing photochromic compounds having an indole ring having a dimethylamino group at the 5-position of the first and second examples are all protonated having a first wavelength absorption band in acid-base equilibrium upon addition of acid. It becomes a ring-opened body and an aprotonated ring-opened body, and has a first wavelength absorption band on the short wavelength side. When it reacts to the light of the short wavelength of the first wavelength,
These compounds undergo a ring closure reaction to become a protonated ring-closed body and an aprotonated ring-closed body having second and third wavelength absorption bands which are biased to a longer wavelength side than the first wavelength absorption band. In both cases, the ring-opening reaction quantum yield in the case of reacting to the light of the second wavelength having the longer wavelength in the second wavelength absorption band is higher than that in the case of reacting to the light of the third wavelength having the longer wavelength in the third wavelength absorption band. It is smaller than the ring-opening reaction quantum yield. These first and second
The anhydrous diarylethene compounds and 5-dimethylaminoindolyl fulgide of Examples utilize acid-base equilibrium and wavelength dependence of the ring-opening reaction quantum yield by introducing a dimethylamino group having a strong electron donating property. It is a material that has achieved the non-destructive readout function used.

Next, the third embodiment is the same as the first embodiment except that a benzothiophene ring having a dimethylamino group at the 6-position and a diarylethene anhydride compound having an acid anhydride portion are used as the photochromic recording layer. is there. Next, in the fourth embodiment, as a photochromic recording layer, 6
The same as Example 1 except that an indole ring having a dimethylamino group at the position and a diarylethene anhydrous compound having an acid anhydride portion were used.

The diarylethene anhydride compounds having a benzothiophene ring having a dimethylamino group and an indole ring at the 6-positions in the third and fourth examples were protonated with a first wavelength absorption band in acid-base equilibrium upon addition of an acid. It becomes a ring body and a non-protonated ring-opened body, and has a first wavelength absorption band on the short wavelength side. When reacted with light having a short wavelength of the first wavelength, a ring-closing reaction occurs in these compounds, both of which are deviated to the longer wavelength side from the first wavelength absorption band and have a second absorbance higher than that of the first wavelength absorption band. It becomes a deprotonated closed ring compound having a wavelength absorption band.

Here, in a further embodiment, instead of the dimethylamino group (CH ₃ ) ₂ N— in each formula of the diarylethene anhydrous compounds in the second, third and fourth embodiments,
Strong electron-donating group such as diethylamino group (C ₂ H ₅ ) ₂
A diarylethene anhydride compound derivative having a dialkylamino group such as N- or an amino group H ₂ N can also be used in the photochromic recording layer. (Experiment) The inventors of the present invention, in order to impart a non-destructive read-out function to a diarylethene compound, which is said to substantially satisfy the requirements for a recording medium other than the non-destructive read-out function and the durability, have a benzothiophene ring and an indole ring as aryl groups. Focusing on a material in which a dimethylamino group was introduced into a diarylethenoic acid anhydride having, the effect of the introduction position on photochromism and the ring-opening reaction quantum yield was studied and studied, and the present invention was accomplished. As a result of an experiment, the ring-opening reaction quantum yield and the molar extinction coefficient of various acid-added diarylethene derivative mixtures were found to be extremely low in the ring-opening reaction quantum yield of the acid-added diarylethene anhydride derivative mixture b. However, it was found that the molar extinction coefficient of the mixtures a and c was extremely high. By introducing a dimethylamino group having a strong electron donating property of the present invention into a heterocyclic ring of a benzothiophene ring and an indole ring, acid-base equilibrium is utilized and non-destructive utilizing the wavelength dependence of the ring-opening reaction quantum yield. Since the photochromic optical recording medium having the reading function was obtained, the experimental process will be described in detail. (Sample) As recording materials, Samples 1 to 5 of the compound represented by the left unprotonated ring-opened product of the following general formula were used.
On the right side of the general formula is the unprotonated closed ring form of the colored body.

[0032]

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In the above formula, R ^{1 to} R ⁴ represent the group of groups shown in the table below.

[0034]

[Table 1] ━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━ R ¹ R ² R ³ R ⁴ ━━━━━━━━ ━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━ Compound 1 H H H H Compound 2 Me ₂ N H H H Compound 3 H Me ₂ N H H Compound 4 H H Me ₂ N H Compound 5 H H H Me ₂ N ━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━ Compound 1, 2, 3, Ad solutions were prepared with the following solvents of 4 and 5 and enclosed in a quartz cell having an optical path length of 10 mm, and a series of light irradiation experiments were conducted.

A: 5 × 10 ^-5 mol / 1 benzene solution b: 5 × 10 ^-5 mo to which 50 equivalents of trichloroacetic acid was added
l / 1 benzene solution c: 5 × 10 ⁻⁵ mol / 1 toluene: hexane = 1: 1 solution d: 5 × 10 ⁻⁵ mo added with 50 equivalents of trichloroacetic acid
l / 1 toluene: hexane = 1: 1 solution In addition, among compounds 1, 2, 3, 4 and 5, compound 4,
3 and 5 are diarylethenoic anhydrides used in the second, third and fourth examples, respectively. Hereinafter, compounds 1, 2,
3, 4 and 5 initial state unprotonated ring-opened compounds, respectively,
Simply indicated by their numbers 1, 2, 3, 4 and 5, their protonated ring-openings are simply 1H +, 2H +, 3H +,
4H + and 5H +, their unprotonated ring closures at 1C, 2C, 3C, 4C and 5C, their protonated ring closures at 1CH +, 2CH +, 3CH +,
Shown at 4CH + and 5CH +. (Light irradiation) A 500 W xenon lamp is used as a light source,
Monochromatic light having a predetermined wavelength was extracted by an interference filter having a half-value width of 10 nm, and the sample was irradiated with light.
(Measurement of Spectral Characteristics and Molar Absorption Coefficient) First, the spectroscopic characteristics and molar absorption coefficient of the above sample (100% ring-opened body) were measured using a spectrophotometer. Next, a ring-closed body was obtained by irradiating the sample with light having an absorption peak wavelength. However, a 100% ring-closed product could not be obtained only by irradiating the above sample with light.
After separation into a 0% ring-closed body and a 100% ring-closed body, only the ring-closed body was separated, and the eluent was removed and dissolved in a predetermined solvent to obtain a 100% ring-closed body sample. Then 100
The spectral characteristics and molar extinction coefficient were measured in the same manner as for the% ring-opened product.
The series of operations was performed at a constant temperature (23 ° C.) in a completely dark place.

FIG. 4 shows absorption spectra of the spectral characteristics of 1 and 1C. 1 is absorption peak wavelength 462 in benzene
nm and maximum molar extinction coefficient 9600. 1 is 460
nm absorption was performed and the ring was closed, resulting in an absorption peak wavelength of 596 nm and a maximum molar absorption coefficient of 11700, which was 1C. The absorption spectra of the samples (1H + and 1CH +) added with trichloroacetic acid showed no difference from the absorption spectra of 1 and 1C, respectively.

FIG. 5 shows absorption spectra of 2,2H +, 2C and 2CH +. No. 2 had an absorption peak wavelength of 465 nm and a maximum molar extinction coefficient of 9900 in benzene. 2 in benzene hardly closed even when irradiated with light of 460 nm, but slightly closed in a solution of toluene: hexane = 1: 1, and became 2C with an absorption peak wavelength of 630 nm and a maximum molar absorption coefficient of 9100. In addition, the absorption spectrum of 2H + and 2CH + of the sample to which trichloroacetic acid was added was completely different from 2 and 2C. Two
H + is absorption peak wavelength 468 nm and maximum molar extinction coefficient
9100, 2CH + showed an absorption peak wavelength of 620 nm and a maximum molar extinction coefficient of 9800.

FIG. 6 shows the absorption spectra of 3,3H +, 3C and 3CH +. 3 also showed an absorption peak wavelength of 455 nm and a maximum molar extinction coefficient of 8900 in benzene. 3 in benzene hardly closed even when irradiated with light of 460 nm, but slightly closed in a solution of toluene: hexane = 1: 1, and became 3C with an absorption peak wavelength of 612 nm and a maximum molar absorption coefficient of 17500. Also, although 3H + obtained by adding trichloroacetic acid is different from 3, 2H +
And 3CH + have the same absorption spectrum as 3C. 3H + is absorption peak wavelength 468
nm and the maximum molar extinction coefficient 9100, and 3CH + showed an absorption peak wavelength of 612 nm and the maximum molar extinction coefficient 17200.

FIG. 7 shows absorption spectra of 4, 4H +, 4C and 4CH +. With respect to 4 in benzene having an absorption peak wavelength of 467 nm and a maximum molar extinction coefficient of 7800, no change was observed in the absorption spectrum even when irradiated with light of 460 nm, and the result was the same in toluene: hexane = 1: 1. 4C is 4H + obtained by adding trichloroacetic acid
Is closed by irradiation with 440 nm light to form 4CH +,
Obtained by removing the proton by adding triethylamine to 4CH +. 4H + indicates an absorption peak wavelength of 437 nm and a maximum molar extinction coefficient of 9100, and
CH + showed an absorption peak wavelength of 596 nm and a maximum molar absorption coefficient of 9500, and 4C showed an absorption peak wavelength of 680 nm and a maximum molar absorption coefficient of 7400.

FIG. 8 shows absorption spectra of 5, 5H +, 5C and 5CH +. With respect to 5 in benzene having an absorption peak wavelength of 530 nm and a maximum molar extinction coefficient of 5400, no change was observed in the absorption spectrum upon irradiation with light. For the first time, 5C having an absorption peak wavelength of 612 nm and a maximum molar extinction coefficient of 27800 was obtained in the same manner as in 4. 5H + obtained by adding trichloroacetic acid has the same absorption spectrum as 4H +,
H + has the same absorption spectrum as 5C. 5H + showed an absorption peak wavelength of 437 nm and a maximum molar absorption coefficient of 10300, and 5CH + showed an absorption peak wavelength of 612 nm and a maximum molar absorption coefficient of 27800.

As mentioned above, the compounds 4 and 5 are acid (H
No change in absorption spectrum due to the ring-closing reaction was observed in any solvent without +). Further, by adding trichloroacetic acid to the benzene solution of the compounds 1, 2, 3, 4 and 5, 1 did not show any change in the absorption spectrum, but 2 and 3 and 4 and 5 did not show the absorption spectrum. Differences were noted. It is considered that 1 does not have a dimethylamino group, and it is considered that the protonation by trichloroacetic acid does not occur on the nitrogen of the indole ring but on the nitrogen of the dimethylamino group. . 2H + and 3
The absorption spectra of H + and 4H + are the same as those of 5H +, which is considered to be because protonation by trichloroacetic acid occurred on the nitrogen of the dimethylamino group, and the strong electron donating property of the dimethylamino group was lost. The influence of the amino group on the absorption spectrum depends on the 5 and 6 positions of the indole ring or the 5 and 6 positions of the benzothiophene ring.
It suggests that there is no difference in rank.

Further, the ring-closed compounds 3C and 3CH + and 5C and 5CH + of the compounds 3 and 5 each having a dimethylamino group at the 6-position, whether an indole ring or a benzothiophene ring, have the same absorption whether or not an acid is added. Showing a spectrum and having a maximum molar extinction coefficient of 3C and 3
It was observed that CH + was about twice other than that of 5C and 5CH +, and about three times greater.

The fact that the protonated substance and the non-protonated substance show the same absorption spectrum is unlikely to be coincidental. Therefore, it is expected that one of the causes of the above phenomenon is that 3H + and 5H + are ring-closed by light irradiation, and at the same time, a deprotonation reaction occurs, and the obtained ring-closed bodies are all 3C and 5C. In order to investigate the occurrence of the deprotonation reaction, it was made difficult to cause deprotonation by adding 100 times or more of trichloro acid in 5H + as compared with a normal protonated sample. Opening easily in place,
It was confirmed that it would return to 5H +. This suggests that the unstable ring-closed compound obtained by light irradiation in the presence of a large excess of acid, which is hard to undergo deprotonation reaction, is the protonated ring-closed compound 5CH +.
The closed ring that was thought to be H + was deprotonated 5C
Can be confirmed. Even if a large excess of acid was added, no phenomenon considered to be a side reaction was observed.

As described above, in general, in the case of a diarylethene compound having no electron-donating group, the molar absorption coefficient of the ring-closed compound is as small as about 10,000, so that the material concentration should be increased to increase the S / N ratio of the recording medium. Although it is necessary to increase the cost, the cost of the recording medium is high because it is an expensive material. However, according to the third and fourth examples, when the dimethylamino group is introduced at the 6-position of the benzothiophene ring, the molar absorption coefficient of the ring-closed body is 1
When a dimethylamino group is introduced at the 6-position of the indole ring at 7500 (1.5 times), the molar extinction coefficient becomes 28000 (2.4 times).
N is obtained. (Measurement of Quantum Yield) The ring-opening reaction quantum yield of a sample partially ring-closed by light irradiation was measured at a constant temperature (23 ° C.) using an automatic quantum yield measuring device. The measurement wavelength was limited to the long wavelength region where the ring-opened body did not absorb.

The ring-opening reaction quantum yields of the ring-closed compounds of Compounds 1, 2, 3, 4 and 5 and their protonated ring-closed compounds by light irradiation at the absorption peak wavelength are shown in the table below.

[0046]

[Table 2] Quantum yield of ring-opening reaction (in benzene) at absorption peak wavelength of ring-closed sample ━━━━━━━━━━━━━━━━━━━━━━━━━━━━ ━━━━━━ Sample 1C 2C 3C 4C 5C Quantum yield 0.16 0.13 0.18 0.0015 0.095 ━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━ ━━━━Sample 2CH + 3CH + 4CH + 5CH + Quantum yield 0.13 0.19 0.22 −−− * ━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━ ━━━ *: Not measured because the absorption edges of 5CH + and 5C are almost the same as shown in FIG.

It was found that the quantum yield of 4C was 0.0015, which is two orders of magnitude smaller than the others. 4C also has an absorption peak wavelength of 50 nm from 4CH + as shown in FIG.
As mentioned above, the wavelength is becoming longer. Since similar photostabilization of the ring-closed body and lengthening of the absorption peak wavelength of the ring-closed body can be seen also in 5-dimethylaminoindolyl fulgide, by introducing a dimethylamino group at the 5-position of the indole ring, diarylethene The same effect as that of the fulgide compound was obtained with the compound of the type.

Further, the wavelength dependence of the quantum yield as shown in FIG. 9 which was not observed at 4C was confirmed. FIG.
Shows the absorption spectrum of the absorption band on the long wavelength side at 4C and the ring-opening reaction quantum yield. Although such wavelength dependence that the ring-opening reaction quantum yield decreases as the wavelength absorbed by the ring-opened product becomes longer is reported for the fulgide-based compound, it is the first time for the diarylethene-based compound.

FIG. 10 shows the relationship between the absorption spectrum and the ring-opening reaction quantum yield in various photochromic compounds (colored materials). Line a in FIG. 10 shows changes in the ring-opening reaction quantum yield of a conventional diarylethene compound. The change in the ring-opening reaction quantum yield of 4C corresponds to the line b in FIG. 10, and since the ring-opening reaction quantum yield exceeds zero at wavelengths Z and below, the absorption wavelength Even if the recorded information is reproduced by using, the recorded information will be gradually erased. However, compared to most of the conventional diarylethene compounds being the line a in FIG. 10, since the 4C is changed to the line b, even the diarylethene compound is line c (wavelength Z
In the following, the quantum yield becomes zero, which suggests that a nondestructive readout function using light between wavelengths Y and Z in the wavelength absorption band on the long wavelength side can be obtained.

Since 4C cannot be produced without protonation with trichloroacetic acid and deprotonation with triethylamine, nondestructive readout using the wavelength dependence of quantum yield as described above may be difficult in practice. By creating a state in which protonated compounds and non-protonated compounds coexist, it is considered that the optical memory utilizing acid-base equilibrium is sufficiently possible.

The following formula represents an optical recording medium having 4C as a recording medium (a diarylethene anhydride compound having an indole ring having a dimethylamino group at the 5-position and a benzothiophene ring at the 5-position and an acid anhydride moiety and an organic acid). The acid-base equilibrium system of the recording layer of the rewritable photochromic optical disk which achieves the nondestructive read-out function by utilizing the acid-base equilibrium and the difference in the ring-opening reaction quantum yield of this system. It can be seen that an optical recording medium can be obtained by using three light sources of 440 nm light (recording), 600 nm light (erasing) and 780 nm light (reproducing). Although the reproducing operation of this optical recording medium cannot be said to be a perfect nondestructive read function, since the ring-opening reaction quantum yield is extremely low, it is possible to reproduce for a long time by adjusting the amount of read light.

[0052]

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First, in the initial state (erased state), an unprotonated ring-opening body 4 and a protonated ring-opening body 4 of an indole ring having a dimethylamino group at the 5-position, a benzothiophene ring, and a diarylethene anhydride compound having an acid anhydride moiety are firstly formed. Body 4H +
Coexist. By irradiation with 440 nm light for writing and recording, the protonated ring-opened product 4H + changes to the protonated ring-closed product 4CH +, and by acid-base equilibrium, the non-protonated ring-opened product 4 changes to the protonated ring-opened product 4H + and the protonated ring-closed product. Change from body 4CH + to unprotonated ring closure 4C.

In the recording state (recording portion), the unprotonated ring-opened body 4, the protonated ring-opened body 4H +, the protonated ring-closed body 4CH +, and the non-protonated ring-closed body 4C coexist and are not irradiated with light. In the recording portion, the initial state (the non-protonated ring-opened body 4 and the protonated ring-opened body 4H + coexist) remains unchanged. The protonated ring-closed body 4CH + changed to a protonated ring-opened body 4H + (quantum yield 0.22) by irradiation with 600 nm light for erasure, and the acid-base equilibrium changed from the non-protonated ring-opened body 4 to the protonated ring-closed body 4CH +. It changes from the protonated ring-opened body 4H + to the non-protonated ring-opened body 4 and quickly returns to the initial state.

In the recorded portion in the erased state, the non-protonated ring-opened body 4 and the protonated ring-opened body 4H + coexist, and in the unrecorded portion in the erased state, the protonated ring-opened body 4H + does not absorb light of 600 nm. The protonated ring-opener 4 does not react to 600 nm light, and therefore remains in the initial state. Non-protonated closed ring 4C by 780 nm light irradiation for readout and reproduction
Changes from aprotonated ring-opened compound 4 (quantum yield 0.001)
Then, by acid-base equilibrium, the protonated ring-closed body 4CH + changes to the non-protonated ring-closed body 4C and the unprotonated ring-opened body 4C.
To the protonated ring-opened product 4H +.

In the recording portion in the read / reproduced state, the quantum yield is extremely low, so that the recording state slowly shifts to the initial state, and in the unrecorded portion in the reproduced state, the 780 nm light is not absorbed, and the state remains in the initial state. As described above, according to the present invention, when a dimethylamino group is introduced into the 6-position of a benzothiophene ring or an indole ring, and a dimethylamino group is introduced into the 6-position of a benzothiophene ring, the molar absorption coefficient of a ring-closed compound is about 1.5. If the dimethylamino group is introduced at the 6-position of the indole ring, the molar absorptivity of the ring-closed product will be about 2.4 times, and the same S / N can be obtained with a small amount of material, leading to cost reduction of the medium.

Further, since a ring-opening and ring-closing photochromic material having both an acid anhydride part and an indole ring having a dimethylamino group introduced at the 5-position and an acid (H +) are mixed in a binder, Since two types of closed ring compounds, a protonated closed ring and a non-protonated closed ring, exist while maintaining an equilibrium relationship, they are eliminated by using the absorption wavelength light of the protonated closed ring with a large ring-opening reaction quantum yield. Non-destructive read-out or long-time reproduction is possible by performing reproduction by using absorption wavelength light of a non-protonated ring-closure material having an extremely small rate (does not absorb protonated compounds).

[0058]

According to the present invention, a rewritable photochromic optical recording medium comprises a ring-opening ring-closing photochromic compound having a heterocyclic ring having a dimethylamino group and an acid anhydride portion, an organic acid, and a binder. Since the photochromic recording layer is provided, the ring-opening reaction quantum yield of the decoloring reaction in the acid-added photochromic recording layer is extremely lower than that in the case of the conventional diarylethene derivative, so that nondestructive readout or long-time reproduction can be achieved. Further, it is possible to obtain a rewritable photochromic optical disk having a high S / N, which can be decolorized with light of low power.

[Brief description of drawings]

FIG. 1 is an enlarged partial sectional view of a rewritable photochromic optical disk.

FIG. 2 is a light absorption spectrum distribution chart of an organic photochromic material.

FIG. 3 is a light absorption spectrum distribution chart of the organic photochromic material of the photochromic optical recording medium of the present embodiment.

FIG. 4 is a light absorption spectrum distribution chart of the organic photochromic material of the photochromic optical recording medium of the present embodiment.

FIG. 5 is a light absorption spectrum distribution chart of the organic photochromic material of the photochromic optical recording medium of the present embodiment.

FIG. 6 is a light absorption spectrum distribution chart of the organic photochromic material of the photochromic optical recording medium of the present embodiment.

FIG. 7 is a light absorption spectrum distribution chart of the organic photochromic material of the photochromic optical recording medium of the present embodiment.

FIG. 8 is a light absorption spectrum distribution chart of the organic photochromic material of the photochromic optical recording medium of the present embodiment.

FIG. 9 is a graph showing optical absorption spectrum distribution and absorption wavelength versus quantum yield of the organic photochromic material of the photochromic optical recording medium of this example.

FIG. 10 is a graph showing light absorption spectrum distribution and absorption wavelength versus quantum yield of an organic photochromic material of a photochromic optical recording medium.

[Explanation of symbols]

 1 substrate 2 photochromic recording layer 3 reflective layer 4 protective layer 5 guide groove 6 laser beam

Claims (9)

[Claims] 1. A rewritable photochromic layer comprising a photochromic recording layer comprising a ring-opening ring-closing photochromic compound having a heterocyclic ring having a dimethylamino group and an acid anhydride portion, an organic acid, and a resin binder. Optical recording medium. 2. The ring-opening ring-closed photochromic compound comprises a protonated ring-opened compound and a non-protonated ring-opened compound, each of which has a short wavelength absorption band. Is a protonated ring-closed body and an aprotonated ring-closed body each having a long-wavelength absorption band biased to the long-wavelength side from the short-wavelength absorption band when reacted with light having a common wavelength in the short-wavelength absorption band. , The ring-opening reaction quantum yield of the non-protonated ring-closed product when reacted with light having a wavelength in the long-wavelength absorption band of the non-protonated ring-closed product is the wavelength of light in the long-wavelength absorption band of the protonated ring-closed product. 2. The rewritable photochromic optical recording medium according to claim 1, wherein the rewritable photochromic optical recording medium is smaller than the ring-opening reaction quantum yield of the protonated ring-closure product when reacted with. 3. The ring-opening ring-closing photochromic compound is represented by the following formula: The rewritable photochromic optical recording medium according to claim 2, which is a diarylethene anhydrous compound represented by the formula (Me represents a methyl group). 4. The ring-opening ring-closing photochromic compound has the following formula: The rewritable photochromic optical recording medium according to claim 2, which is a fulgide compound represented by the formula (Me represents a methyl group). 5. The ring-opening ring-closing photochromic compound comprises a protonated ring-opened compound and a non-protonated ring-opened compound, each of which has a short wavelength absorption band. When reacting to light of a common wavelength in the short-wavelength absorption band, at least one of the long-wavelength absorption band of the absorbance higher than the short-wavelength absorption band is biased to the long-wavelength side. The rewritable photochromic optical recording medium according to claim 1, which comprises: 6. The ring-opening ring-closing photochromic compound is represented by the following formula: The rewritable photochromic optical recording medium according to claim 5, which is a diarylethene anhydrous compound represented by the formula (Me represents a methyl group). 7. The ring-opening ring-closing photochromic compound is represented by the following formula: The rewritable photochromic optical recording medium according to claim 5, which is a diarylethene anhydrous compound represented by the formula (Me represents a methyl group). 8. The rewritable photochromic optical recording medium according to claim 1, wherein the organic acid is trichloroacetic acid, dichloroacetic acid, chloroacetic acid, P-toluenesulfonic acid, or phosphoric acid. 9. The rewritable photochromic optical recording medium according to claim 1, wherein the resin binder is polystyrene, polymethylmethacrylate, polycarbonate or polyvinyl chloride.