JP2001049244A - Photochromic material and optical recording medium - Google Patents

Abstract

PROBLEM TO BE SOLVED: To obtain a photochromic material that can be synthesized by relatively few reactions in relatively high yields and can give a ring-opening product having an absorption band reaching the vicinity of the visible region by using a diarylethene compound. SOLUTION: The diarylethene compound is represented by formula 1-5 (wherein R1 and R2 are each H, an alkyl, or an alkoxy; and A is a fused polycyclic aromatic group or a group derived by the removal of one H atom from a polyphenyl group). When a photochromic material is utilized in an optical recording medium, it needs to exhibit good repetition durability and thermal irreversibility in the recording, deletion, and reproduction of information. The diarylethene compound, especially, a diarylethene compound composed of a perfluorocyclopentene ring and two aryl groups bonded thereto satisfies the above requirements, is relatively simple in the route and step of synthesizing the material, and can be synthesized in high yields. The objective diarylethene compound can be obtained through a route of synthesis including steps of 1-1 to 1-5.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

The present invention relates to a photochromic material and an optical recording medium using the same.

[0002]

2. Description of the Related Art When recording and erasing information on a recording medium, a rewritable recording medium is usually used. As an information rewritable recording medium, an optical recording medium using a photochromic material photoreaction, that is, a photochromic reaction has been proposed.

[0003] The photochromic reaction means that a photochromic material in the state A is irradiated with light having a wavelength λ1 in which the state A absorbs, thereby producing a state B in which light of a different wavelength is absorbed. Is a reversible reaction that returns to the original state of A by irradiating the photochromic material in the state of state A with light having a wavelength λ2 in which the state B absorbs. In an optical recording medium utilizing a photochromic reaction, one of the states A and B is in an information unrecorded state (a state where information is not recorded), and the other is an information recorded state (an information is recorded). An optical recording medium on which information can be rewritten can be obtained by associating the optical recording medium.

In an optical recording medium on which information can be rewritten using a photochromic reaction, when the recorded information is reproduced, the difference between the physical property value in the state A and the physical value in the state B is different. Should be detected. Since the light absorption spectrum before and after the photochromic reaction, that is, the state of A and the state of B are greatly different, for example, the difference between the light absorption intensity in the state A and the light absorption intensity in the state B at the wavelength λ2 , It is possible to read the information recorded state or the information unrecorded state, that is, to reproduce the information.

In order to use a photochromic material for an optical recording medium, good repetition durability and thermal irreversibility are required for recording, erasing and reproducing information. Diarylethene-based compounds have attracted attention as a photochromic material satisfying such requirements. In particular, a diarylethene-based compound in which two aryl groups are connected to a perfluorocyclopentene ring satisfies the above-mentioned required performance, and the route and steps for material synthesis are relatively simple and the synthesis yield is high.

In the photochromic reaction of a diarylethene-based compound having a perfluorocyclopentene ring (hereinafter simply referred to as a diarylethene-based compound), the above-mentioned A state and B state are often called ring-opened and ring-closed bodies, respectively. The closed form can absorb light of a longer wavelength than the open form, in other words, has an absorption band up to a long wavelength range. In many diarylethene compounds, the absorption band of the closed ring is in the visible range, but the absorption band of the open ring is in the ultraviolet range. For this reason, in an optical recording apparatus that accommodates an optical recording medium using a diarylethene-based compound and records, reproduces, and / or erases information on the optical recording medium, the wavelength λ at which the ring-opened body has absorption is used.
A light source such as a semiconductor laser that emits ultraviolet light is required as a light source that emits one light.

[0007]

However, at present, no light source such as a semiconductor laser that operates stably in the ultraviolet region has been found. Even if such a light source is developed in the future, it is advantageous that the absorption band of the ring-opened body is as close to the visible region as possible. Because the shorter the wavelength of the light that the ring-opened body has absorption, that is, the light used for recording, reproducing and erasing information, the special optical components in the optical recording device must be used to cope with it. This is because the optical recording device becomes expensive. Therefore, as the diarylethene-based compound used for the optical recording medium, it is desirable to adopt a compound in which the ring-opened body has an absorption band in a longer wavelength region and closer to a visible light region.

As a diarylethene compound having a ring-opened compound having an absorption band in a relatively long wavelength range, for example, Japanese Patent Application Laid-Open No.
As disclosed in Japanese Patent No. 89954, there is a diarylethene-based compound having a conjugated double bond chain.
There is a possibility that a cis form and a trans form occur at the double bond portion. Only the cis-form causes a photochromic reaction from the ring-opened form to the closed-form, and therefore, when the cis-form is changed to the trans-form, it is not possible to react with the closed-form. This causes a reduction in sensitivity (reduction in signal intensity) during reproduction, and is therefore inconvenient when used as a recording material. Also,
A diarylethene compound having a different structure of two aryl groups, that is, an asymmetric diarylethene compound, is also considered to be advantageous in that the absorption band of the ring-opened compound is relatively long, but according to this compound, the photochromic Since the number of reactions in synthesizing a material is increased, and the yield of the overall synthesis reaction tends to be low, the cost of material synthesis is increased accordingly.

Therefore, the present invention relates to a photochromic material comprising a diarylethene compound, which is convenient for use as a recording material, requires a relatively small number of reactions in synthesizing the material, and has a high yield in the overall synthesis reaction. It is an object of the present invention to provide a photochromic material having a relatively high absorption and having an absorption band of a ring-opened body near the visible region.

[0010] The present invention also relates to an optical recording medium for recording, reproducing and / or erasing information by light using a photochromic material. It is an object of the present invention to provide an optical recording medium which is excellent in medium quality and can keep down the production cost of the medium and the cost of the optical recording apparatus for accommodating the medium.

[0011]

The present invention provides the following photochromic material and optical recording medium to solve the above-mentioned problems. (1) Photochromic material A photochromic material comprising a diarylethene compound, wherein the diarylethene compound has a general formula

[0012]

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(Wherein R ₁ and R ₂ each represent a hydrogen atom or an optionally substituted alkyl group, or a hydrogen atom or an optionally substituted alkoxy group, and A represents a condensed polycyclic aromatic group, or A group in which one hydrogen atom is removed from a polyphenyl group in which two or more benzene rings are connected by a single bond. A may have a substituent.)
A photochromic material, which is a compound represented by the formula: (2) Optical recording medium An optical recording medium for recording, reproducing and / or erasing information by light using a photochromic material, comprising the photochromic material of (1). . In the photochromic materials according to the present invention, the alkyl group of the general formula C _n H _{2n + 1} - are denoted by. The range of n of the alkyl group is not particularly limited and does not affect the main photochromic reaction characteristics. Examples of the alkyl group include a methyl group, an ethyl group, a propyl group,
A butyl group and the like can be mentioned. The alkoxy group is denoted formula C _n H _{2n + 1} O- in. N of the alkoxy group
Is not particularly limited and does not affect the main photochromic reaction characteristics. Examples of the alkoxy group include a methoxy group, an ethoxy group, a propoxy group, and a butoxy group.

Examples of the substituent of A include naphthalene, anthracene, pyrene, chrysene, phenanthrene, biphenyl, terphenyl and the like. The photochromic material according to the present invention comprises a diarylethene-based compound represented by the above general formula, and causes a photochromic reaction by the diarylethene-based compound. That is,
In the ring-opened diarylethene-based compound,
By irradiating the light of wavelength λ1 in which the ring-opened body has absorption, a ring-closed body having absorption of light of a different wavelength is generated, and the diarylethene-based compound in the state of a ring-closed body is
Irradiation with light having a wavelength of λ2, in which the ring-closure has absorption, causes a reversible reaction to return to the original ring-opened state.

According to the photochromic material of the present invention,
Since the diarylethene-based compound is a compound having no conjugated double bond chain as shown in the general formula,
It does not cause inconvenience like the diarylethene-based compound taught in Japanese Patent No. 89954 and is convenient for use as a recording material. Further, since the diarylethene-based compound is a compound having a bilaterally symmetric structure as shown in the above general formula, the number of reactions in synthesizing the material is relatively small, and the yield in the whole synthesis reaction is relatively high. further,
The absorption band of the ring-opened form of the diarylethene-based compound extends to a longer wavelength region than that of the conventional one, that is, to a region near the visible region.

The optical recording medium according to the present invention contains the photochromic material according to the present invention, and one of the ring-opened and ring-closed states of the diarylethene compound of the photochromic material is in an unrecorded state. An optical recording medium on which information can be rewritten by making the other correspond to the information recording state. According to the optical recording medium of the present invention,
Since a diarylethene-based compound is used as the photochromic material, it has excellent repetition durability and thermal irreversibility in recording, erasing, and reproducing information. Further, this diarylethene-based compound is a diarylethene-based compound represented by the above-mentioned general formula, and as described above, the number of reactions when synthesizing a material is relatively small and the yield in the whole synthesis reaction is relatively high. Accordingly, the cost of material synthesis can be kept low, and the cost of manufacturing the medium can be kept low. Further, this diarylethene-based compound is a diarylethene-based compound represented by the above general formula, and as described above, since the absorption band of the ring-opened body reaches near the visible region, the light in which the ring-opened body has absorption, that is, information Light near the visible region can be adopted as light used for recording, reproducing, and erasing. Therefore, it is not necessary to use a special optical component in the optical recording device that accommodates the medium, and the cost of the optical recording device can be reduced accordingly.

The "optical recording medium on which information is recorded, reproduced and / or erased" is an optical recording medium on which information can be recorded, reproduced and erased, and information is already recorded. Any of optical recording media capable of reproducing information is included.

[0018]

Embodiments of the present invention will be described below with reference to the drawings. FIG. 1 is a diagram showing an example of a route at the time of material synthesis for obtaining a photochromic material according to the present invention. FIG. 1 shows steps (1-1) to (1-
5 shows the chemical structural formula of the material synthesized in 5).

The photochromic material according to the present invention comprises a diarylethene compound, and the diarylethene compound has a general formula

[0020]

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(Wherein R ₁ and R ₂ each represent a hydrogen atom or an optionally substituted alkyl group, or a hydrogen atom or an optionally substituted alkoxy group, and A represents a condensed polycyclic aromatic group, or A group in which one hydrogen atom is removed from a polyphenyl group in which two or more benzene rings are connected by a single bond. A may have a substituent.)
It is a compound shown by this.

This compound can be obtained as a target product in the step (1-5) by sequentially synthesizing the materials in the steps (1-1) to (1-5) shown in FIG. it can. As an example of the present invention, a method for synthesizing the following two diarylethene compounds will be described. Example 1: 1,2-bis- (2-methyl-5- (4-biphenyl) thiophen-3-yl) perfluorocyclopentene Example 2: 1,2-bis- (2,4-dimethyl-5-)
(1-pyrenyl) thiophen-3-yl) perfluorocyclopentene (Method for synthesizing the material of Example 1) a) Synthesis of 3,5-dibromo-2-methylthiophene In a 1000 ml container, 25 g (0.25 mol) of 25 g (0.25 mol) was added. 2
-After adding methylthiophene and 300 ml of acetic acid and stirring, the mixture was cooled to 0 ° C, and 84 g of bromine (0.53
mol) was added dropwise. Thereafter, the temperature was returned to room temperature, and the mixture was stirred and reacted for 48 hours. After completion of the reaction, water was added, and the organic layer was extracted with chloroform. The organic layer was washed with water, neutralized with an aqueous solution of sodium hydrogen carbonate, reduced with unreacted bromine with an aqueous solution of sodium thiosulfate, and dried over anhydrous magnesium sulfate. After drying, the magnesium sulfate was removed and the solvent was distilled off under reduced pressure. The obtained reaction product was purified by silica gel chromatography, and the following structural formula 1
43.3 g (yield 67%) was obtained (see steps (1-1) to (1-2) shown in FIG. 1). (Structural formula 1)

[0023]

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B) Synthesis of boric acid (3-bromo-2-methylthiophen-5-yl) In a 1000 ml three-necked flask purged with argon,
2,6.9 g of 3,5-dibromo-2-methylthiophene
(0.105 mol) and 500 ml of diethyl ether. After cooling to −78 ° C. while stirring, 68.9 ml of a hexane solution of n-butyl lithium.
(0.11 mol) was added dropwise, and the mixture was stirred for 30 minutes. Further, 37.7 ml of tri (n-butyl) borate (0.14 mol) was added.
l) was added dropwise and stirred for 4 hours. After returning to room temperature,
After stirring was continued for 4 hours, methanol, diluted hydrochloric acid and water were added to stop the reaction. An aqueous sodium hydroxide solution was added thereto to make the mixture alkaline, and the aqueous layer was taken out.
Concentrated hydrochloric acid was added. Thereafter, the precipitate is collected by suction filtration and dried, and 14.1 g of the compound of the following structural formula 2 is obtained.
(61% yield) (from (1-2) shown in FIG. 1 to (1)
-3)). (Structural formula 2)

[0025]

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C) 3-bromo-2-methyl-5- (4-
Synthesis of biphenyl) thiophene In a 500 ml container, 10 g (0.045 mol) of boric acid (3-bromo-2-methylthiophen-5-yl),
10.5 g of 4-bromobiphenyl (0.045 mo
l), tetrakis (triphenylphosphine) palladium (0) 1.73g (0.0015mol) and 120m
l of tetrahydrofuran was added and stirred to dissolve the solid content. 120 ml of 20% aqueous sodium carbonate solution
, And the mixture was refluxed for 48 hours under a nitrogen atmosphere. After completion of the reaction, the temperature was returned to room temperature, and the organic layer was extracted with chloroform. After the organic layer was washed and dried, the solvent was distilled off under reduced pressure. The obtained reaction product was purified by silica gel chromatography to obtain 7.1 g (yield 48%) of a compound of the following structural formula 3 (from (1-3) to (1-
See step 4)). (Structural formula 3)

[0027]

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D) 1,2-bis- (2-methyl-5-)
Synthesis of (4-biphenyl) thiophen-3-yl) perfluorocyclopentene 3-argon in a 200 ml three-necked flask purged with argon
5.0 g (0.015 mol) of bromo-2-methyl-5- (4-biphenyl) thiophene and 100 ml of tetrahydrofuran were added. After cooling to −78 ° C. while stirring, hexane solution 1 of n-butyllithium 1 was added.
1.3 ml (0.018 mol) was added dropwise and stirred for 30 minutes, and 1.6 ml of perfluorocyclopentene was further added.
(0.025 mol) was added in three portions. Then 2
After stirring for an hour, methanol, diluted hydrochloric acid and water were added to stop the reaction. After extracting the organic layer with diethyl ether, the organic layer was washed and dried, and the solvent was distilled off under reduced pressure. The obtained reaction product was purified by silica gel chromatography to obtain a compound 2.6 of the following structural formula 4.
g (yield 51%) was obtained (see steps (1-4) to (1-5) shown in FIG. 1). (Structural formula 4)

[0029]

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(Synthesis Method of Material of Example 2) e) Synthesis of 3,5-dibromo-2,4-dimethylthiophene In the synthesis method a) of the material of Example 1, 2,4 was used instead of 2-methylthiophene. -Using dimethylthiophene, 2,4 by the same method as in the synthesis method a) of the material of Example 1
-From 28 g (0.025 mol) of dimethylthiophene, 47.2 g (yield 70%) of a compound of the following structural formula 5 was obtained (see steps (1-1) to (1-2) shown in Fig. 1). (Structural formula 5)

[0031]

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F) Boric acid [5- (3-bromo-2,4-
Synthesis of dimethylthienyl)] 3,5-Dibromo- in place of 3,5-dibromo-2-methylthiophene in the synthesis method b) of the material of Example 1
Using 2,4-dimethylthiophene, 3,5-dibromo- was obtained in the same manner as in the synthesis method b) of the material of Example 1.
25 g of 2,4-dimethylthiophene (0.093 mol
1), 13.5 g of the compound of the following structural formula 6 (yield: 62)
%) (See steps (1-2) to (1-3) shown in FIG. 1). (Structural formula 6)

[0033]

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G) 3-bromo-2,4-dimethyl-5-
Synthesis of (1-pyrenyl) thiophene Boric acid [5- (3-bromo-2,4-dimethylthienyl)] 10.6 g (0.045 mol), 1-bromopyrene 12.7 g (0.045 mol), tetrakis (triphenyl) 1.73 g of phosphine) palladium (0)
(0.0015 mol) and 120 ml of tetrahydrofuran were added and stirred to dissolve the solid content. 20 more
After the addition of 120 ml of a 20% aqueous sodium carbonate solution, the mixture was refluxed for 48 hours under a nitrogen atmosphere. After completion of the reaction, the temperature was returned to room temperature, and the organic layer was extracted with chloroform. After washing and drying the organic layer, the solvent was distilled off under reduced pressure. The obtained reaction product is purified by silica gel chromatography,
7.0 g (yield 40%) of the compound of the following structural formula 7 was obtained (see steps (1-3) to (1-4) shown in FIG. 1). (Structural formula 7)

[0035]

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H) 1,2-bis- (2,4-dimethyl-)
Synthesis of 5- (1-pyrenyl) thiophen-3-yl) perfluorocyclopentene In a 1000 ml three-necked flask purged with argon, 3
5 g (0.013 mol) of -bromo-2,4-dimethyl-5- (1-pyrenyl) thiophene and 100 ml of tetrahydrofuran were added. While stirring this, -78 ° C
After cooling to hexane solution of n-butyllithium 1
0 ml (0.016 mol) was added dropwise, and the mixture was stirred for 30 minutes. Further, 1.5 ml (0.02 mol) of perfluorocyclopentene was added.
3 mol) was added in three portions. After stirring for 2 hours, methanol, diluted hydrochloric acid and water were added to stop the reaction. And after extracting the organic layer with diethyl ether,
After washing and drying the organic layer, the solvent was distilled off under reduced pressure. The obtained reaction product was purified by silica gel chromatography to obtain 2.1 g (yield: 41%) of a compound of the following structural formula 8 (from (1-4) to (1-5) shown in FIG. 1).
Step). (Structural formula 8)

[0037]

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The photochromic material produced in this manner is composed of a diarylethene compound represented by the above-mentioned structural formula 4 or 8, and causes a photochromic reaction by the diarylethene compound. That is, by irradiating the ring-opened diarylethene-based compound with light having a wavelength λ1 in which the ring-opened body has absorption, a ring-closed body having absorption of light of a different wavelength is generated, and the state of the closed-ring body is also obtained. The diarylethene-based compound according to
Irradiation with light having a wavelength of λ2, in which the ring-closure has absorption, causes a reversible reaction to return to the original ring-opened state.

According to this photochromic material, since the diarylethene compound is a compound having no conjugated double bond chain as shown in the structural formula 4 or 8,
There is no inconvenience such as the diarylethene-based compound taught in JP-A-7-89954, which is convenient for use as a recording material. Further, since the diarylethene-based compound is a compound having a bilaterally symmetric structure as shown in the structural formula 4 or 8, the number of reactions in synthesizing the material is relatively small, and the yield in the overall synthesis reaction is low. Relatively high. Further, the absorption band of the ring-opened form of this diarylethene compound is longer than the conventional one,
That is, it reaches the vicinity of the visible region.

FIG. 2 is a cross-sectional view of a schematic configuration of a part of an example of an optical recording medium manufactured using the photochromic material comprising the diarylethene compound of Example 1 or Example 2, and FIG. FIG. 2 is a side view of a schematic configuration of an example of an optical recording apparatus that accommodates the optical recording medium shown in the drawings and performs recording, erasing, and reproduction of information on the medium. As shown in FIG. 2, the optical recording medium 94 has a recording layer 942 for recording information by applying the diarylethene-based compound of Example 1 or 2 and a polystyrene resin by spin coating on a glass substrate 941. The prepared product, more specifically, 2.5 parts by weight of a diarylethene compound, 2.5 parts by weight of a polystyrene resin, and 95 parts by weight of toluene were used as coating liquids at 3000 rpm.
The recording layer 9 is formed on the substrate 941 rotated by the spin coating method.
42 is formed. In this example, in the recording layer 9
The layer thickness of 42 is about 150 nm.

In the optical recording medium 94, one of the ring-opened and ring-closed states of the diarylethene compound is recorded in an information unrecorded state and the other is recorded in an information recorded state. By associating the unrecorded state and the closed body state with the information recorded state, an optical recording medium on which information can be rewritten is obtained. The optical recording apparatus shown in FIG. 3 includes a light source 91 for information erasure and reproduction, a light source 97 for information recording, a wavelength selection mirror 92, condenser lenses 93 and 95, and a photodiode 96.
And a storage unit 100 for an optical recording medium, and can perform any of recording, erasing, and reproducing information on the optical recording medium 94.

The light source 91 for information erasure and reproduction includes an ND filter 91 ′ capable of adjusting the intensity of light, and has a wavelength of 54 nm.
3 nm light 91a can be emitted. Thereby, the light source 91
Has a wavelength of 543n as information erasing light when information is erased.
m, a light 91a having an irradiation light power of about 500 μW on the recording medium can be emitted. Note that this information erasing light is applied to the medium 9.
4 is light having a wavelength at which the ring-closed form of the diarylethene-based compound has absorption. At the time of information reproduction, light 91a having a wavelength of 543 nm and an irradiation light power of about 10 μW on a recording medium can be emitted as information reproduction light. Since the information reproducing light has a low irradiation light power of about 10 μW, information on the medium 94 is hardly erased.

The information recording light source 97 includes an ND filter 97 'capable of adjusting the intensity of light, and has a wavelength of 337 nm.
Light 97a can be emitted. Accordingly, the light source 97 can emit light 97a having a wavelength of 337 nm and an irradiation light power of about 300 μW on the recording medium as information recording light during information recording. The information recording light is light having a wavelength at which the ring-opened body of the diarylethene compound in the medium 94 has absorption.

The wavelength selection mirror 92 transmits a part of the light 91 a from the light source 91, reflects the light 97 a from the light source 97, and makes the light enter the condenser lens 93. The condenser lens 93 can irradiate the light from the wavelength selection mirror 92 to the optical recording medium 94. The condenser lens 95 is provided for the optical recording medium 9.
4 can enter the light receiving portion of the photodiode 96.

The photodiode 96 includes a light quantity detection circuit (not shown). Also, the photodiode 9
Numeral 6 can photoelectrically convert the light from the condenser lens 95 into an electric signal, and can detect a signal corresponding to the light intensity as a light amount by a light amount detection circuit (not shown). The accommodating section 100 is provided with a rotation drive device (not shown), and can accommodate a disk-shaped optical recording medium 94. The medium surface of the medium 94 is moved by the rotation of the rotation driving device.

According to this optical recording apparatus, when recording information, the light source 97 emits the light 97a as information recording light. The light 97a from the light source 97 is transmitted to a wavelength selection mirror 92.
Is reflected by the optical recording medium 94 via the condenser lens 93.
Irradiated on top. In the recording layer 942 of the medium 94, when the diarylethene-based compound in the ring-opened state is irradiated with light having a wavelength that the ring-opened body has absorption as information recording light, in this example, light having a wavelength of 337 nm, Ring forms with different wavelengths of light absorption are produced. Thus, information is recorded on the medium 94.

In erasing information, the light source 91 emits light 91 a as information erasing light. Light 91 a from a light source 91 passes through a wavelength selection mirror 92 and is collected by a condenser lens 93.
Irradiates the optical recording medium 94 through the optical recording medium 94. In the recording layer 942 of the medium 94, when the diarylethene-based compound in a closed-ring state is irradiated with light having a wavelength at which the closed-ring has absorption as information erasing light, in this example, light having a wavelength of 543 nm, the original light is irradiated. Return to ring-opened form. Thus, the information on the medium 94 is erased.

In reproducing information, light 91a is emitted from the light source 91 as information reproducing light. Light 91 a from a light source 91 passes through a wavelength selection mirror 92 and is irradiated onto an optical recording medium 94 via a condenser lens 93. The transmitted light 91b from the optical recording medium 94 is incident on the photodiode 96 via the condenser lens 95. In the recording layer 942 of the medium 94, the light absorption spectrum is greatly different between the information unrecorded state, that is, the state of the ring-opened diarylethene compound, and the information recording state, that is, the state of the ring-closed body of the diarylethene compound. The wavelength of the information reproducing light (here, the wavelength 543)
nm), it is possible to read out the information recorded state or the information unrecorded state by detecting the difference between the light absorption intensity in the open-ring state and the light absorption intensity in the closed-ring state. It becomes possible.

According to the optical recording medium 94, since a diarylethene compound is employed as a photochromic material, it is excellent in repetition durability and thermal irreversibility in recording, erasing and reproducing information. Further, this diarylethene-based compound is a diarylethene-based compound represented by the structural formula 4 or 8, and as described above, the number of reactions for synthesizing a material is relatively small, and the yield in the entire synthesis reaction is small. Since the ratio is relatively high, the cost of material synthesis can be kept low, and the cost of manufacturing the medium can be kept low. The diarylethene-based compound is a diarylethene-based compound represented by Structural Formula 4 or Structural Formula 8, and as described above, the absorption band of the ring-opened body extends to near the visible region. , That is, light in the vicinity of the visible region (in this example, a wavelength of 33
7 nm light). Therefore, it is not necessary to use special optical components in the optical recording apparatus shown in FIG. 3 that accommodates the medium 94, and the cost of the optical recording apparatus can be reduced accordingly.

Next, performance evaluation experiments were performed on the photochromic material and the optical recording medium of the present invention. In addition, the measurement experiment of the light absorption spectrum was performed about the photochromic material, and the optical recording experiment was performed about the optical recording medium. <Measurement Experiment of Light Absorption Spectra> In the experiment, Examples 1 and 2 were used as photochromic materials 1 and 2 for evaluation experiments.
And a material composed of 1,2-bis- (2-methyl-5-phenylthiophen-3-yl) perfluorocyclopentene represented by the following structural formula 9 was used as a photochromic material for comparative experiments. (Structural formula 9)

[0051]

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The materials for evaluation 1 and 2 and the material for comparative experiment were prepared by dissolving them in hexane. The experiments measured the light absorption spectra of these solutions. The molarity of each solution was adjusted to be approximately equal. The measurement was performed in a state where almost all of the diarylethene compound in the solution could be regarded as a ring-opened product.

FIG. 4 shows the measurement results of the light absorption spectrum. The solid line, dashed line and chain line in the figure show the light absorption spectra in the ring-opened state of the diarylethene-based compounds of the materials for evaluation experiments 1 and 2 and the material for comparative experiments in a hexane solution, respectively. As shown in FIG. 4, the solutions of the materials for evaluation experiments 1 and 2 were different from the solutions of the materials for comparative experiments.
It can be seen that the ring-opened product has an absorption band in a longer wavelength range and has a high light absorption intensity.

Next, these solutions were irradiated with ultraviolet light from a mercury lamp, and the light absorption spectra were measured again. This ultraviolet light is a light having a wavelength at which the ring-opened diarylethene-based compounds of the evaluation experiment materials 1 and 2 and the comparative experiment material all have absorption. FIGS. 5, 6, and 7 show changes in the light absorption spectra of the solutions of the materials for evaluation experiments 1 and 2 and the solution of the material for comparison experiment before and after irradiation with ultraviolet light, respectively. The solid line and broken line in FIGS. 5, 6, and 7 show the light absorption spectrum before and after the ultraviolet light irradiation, respectively. In the materials for evaluation experiments 1 and 2 and the material for comparative experiments, the ring-opened diarylethene-based compound is irradiated with light having a wavelength at which the ring-opened body has absorption, thereby generating a closed-ring state. FIGS. 8, 9 and 10 show the state of the structural formula change due to the photochromic reaction.

As shown in FIGS. 5, 6, and 7, it can be seen that a new absorption band has been generated in the visible region due to the irradiation of ultraviolet light. From this, the photochromic reactions shown in FIGS. 8, 9 and 10 proceed in the solutions of the materials for evaluation experiments 1 and 2 and the solution of the materials for comparative experiments by irradiation with ultraviolet light, respectively. It can be seen that a closed body shown on the right side in FIG. 10 is produced. <Optical recording experiment> The diarylethene compounds of Examples 1 and 2 were combined with the 1,2-bis- (2-
Optical recording media were prepared using diarylethene compounds of methyl-5-phenylthiophen-3-yl) perfluorocyclopentene, and optical recording experiments described below were performed.

The optical recording medium used in the experiment was produced by the same method as that for producing the optical recording medium 94 shown in FIG.
That is, as an optical recording medium used in the experiment, as shown in FIG. 2, a recording layer 942 for recording information was formed by applying a diarylethene-based compound and a polystyrene resin on a glass substrate 941 by spin coating. thing,
More specifically, 2.5 parts by weight of a diarylethene compound,
A recording liquid 942 formed by a spin coating method on a substrate 941 rotating at 3000 rpm using 2.5 parts by weight of a polystyrene resin and 95 parts by weight of toluene as a coating liquid was used. The optical recording media prepared using the diarylethene-based compounds of Examples 1 and 2 were referred to as optical recording media 1 and 2 for evaluation experiments, respectively.
An optical recording medium manufactured using a diarylethene-based compound of (2-methyl-5-phenylthiophen-3-yl) perfluorocyclopentene was used as an optical recording medium for comparative experiments. The thickness of each of the recording layers 942 was about 150 nm. In addition, the recording layer 94 in the optical recording medium after fabrication.
2 are colorless, and almost all of the diarylethene compounds in the recording layer 942 can be regarded as ring-opened compounds.

In this optical recording experiment, the optical recording media 1 and 2 for evaluation experiment and the optical recording medium for comparative experiment were respectively housed in the optical recording device shown in FIG. In the initial state, that is, the light 91a having a wavelength of 543 nm from the light source 91 is applied to the optical recording medium 94 of the colorless recording layer 942.
And the intensity T1 of the light 91b transmitted through the optical recording medium by the photodiode 96 was measured. At this time, the irradiation light power of the light 91a from the light source 91 was about 10 μW on the optical recording medium. The optical recording medium 94 has a wavelength of 337 n from the light source 97.
m of light 97a was irradiated. This process is referred to as a recording process.
At this time, the irradiation light power of the light 97a from the light source 97 was about 300 μW on the optical recording medium, and the irradiation time was 1 msec. The transmitted light intensity T2 at the time of recording was measured in the same manner as described above. The optical recording medium 94 has a wavelength of 543n from the light source 91.
m of light 91a was applied. This process is called an erasing process.
At this time, the irradiation light power of the light 91a from the light source 91 was about 500 μW on the optical recording medium, and the irradiation time was 1 msec. The transmitted light intensity T3 at the time of erasing was measured in the same manner as described above. By repeating the operations up to this point, the transmitted light intensity T4
To T10. That is, the transmitted light intensity T4, T6, T8, T10 during recording, and the transmitted light intensity T during erasure.
5, T7 and T9 were measured.

The light intensity is adjusted by the ND filter 9.
This was performed using 1 'and 97'. Figure 1 shows the results of the optical recording experiment.
It is shown in FIG. FIG. 11 is a graph showing the results of an optical recording experiment using the optical recording media 1 and 2 for the evaluation experiment and the optical recording medium for the comparative experiment. Is a graph obtained by plotting the ratio of the transmitted light intensity to the transmitted light intensity and connecting the plots with a line. The solid line, the broken line, and the chain line in the figure show the experimental results using the optical recording media 1 and 2 for the evaluation experiment and the optical recording medium for the comparative experiment, respectively.

According to this experiment, information can be recorded and erased on each of the optical recording media 1 and 2 for the evaluation experiment and the optical recording medium for the comparative experiment, and the intensity of the transmitted light is detected by the photodiode 96. Confirmed that information can be reproduced. However, according to the graph of FIG. 11, it can be seen that the reproduction signal difference between the recorded state and the unrecorded state of the optical recording media for evaluation experiment 1 and 2 is larger than that of the optical recording media for comparative experiment. This means that the recording has not proceeded sufficiently in the recording process in the optical recording media for comparative experiment compared to the optical recording media for evaluation experiment 1 and 2. This is shown in FIG.
As can be seen from the light absorption spectrum shown in FIG. 3, the ring-opened diarylethene compound of the optical recording medium for comparative experiment hardly absorbs light having a wavelength of 337 nm, whereas the diarylethene compound of optical recording media 1 and 2 for evaluation experiment. The ring-opened body easily absorbs light having a wavelength of 337 nm. In other words, the absorption intensity at a wavelength of 337 nm of the ring-opened body of the optical recording medium for comparative experiments is 337 nm for the ring-opened bodies of the optical recording media for evaluation experiments 1 and 2. Is smaller than the absorption intensity at Therefore, the ring-opened form of the diarylethene compound of the optical recording media for evaluation experiments 1 and 2 has an absorption band up to a longer wavelength range than the ring-opened form of the diarylethene compound of the optical recording medium for comparative experiment, and has an absorption intensity. Since the optical recording media for evaluation experiments 1 and 2 are strong, light having a wavelength of 337 nm can be favorably absorbed, and it is considered that favorable recording is progressing.

[0060]

As described above, according to the present invention, a photochromic material comprising a diarylethene compound is convenient for use as a recording material, and the number of reactions when synthesizing the material is relatively small. It is possible to provide a photochromic material having a relatively high yield in the whole synthesis reaction and having an absorption band of a ring-opened body near the visible region.

According to the present invention, an optical recording medium for recording, reproducing and / or erasing information by light using a photochromic material is provided. It is possible to provide an optical recording medium which is excellent in performance and can keep down the production cost of the medium and the cost of the optical recording apparatus for containing the medium.

[Brief description of the drawings]

FIG. 1 is a diagram showing an example of a route at the time of material synthesis for obtaining a photochromic material according to the present invention.

FIG. 2 is a cross-sectional view of a part of a schematic configuration of an example of an optical recording medium manufactured using a photochromic material comprising a diarylethene-based compound of Example 1 or 2.

FIG. 3 is a side view of a schematic configuration of an example of an optical recording device that accommodates the optical recording medium shown in FIG. 2 and records, erases, and reproduces information on the medium.

FIG. 4 shows evaluation materials 1 and 2 in a hexane solution.
4 is a graph showing the results of measuring light absorption spectra of a ring-opened diarylethene compound as a material for comparative experiments.

FIG. 5 is a graph showing the measurement results of light absorption spectra of a diarylethene-based compound of Evaluation Material 1 in a hexane solution before and after irradiation with ultraviolet light.

FIG. 6 is a graph showing the measurement results of the light absorption spectrum of a diarylethene compound of Evaluation Material 2 in a hexane solution before and after irradiation with ultraviolet light.

FIG. 7 is a graph showing measurement results of light absorption spectra of a diarylethene compound as a comparative experimental material before and after irradiation with ultraviolet light in a hexane solution.

FIG. 8 is a structural formula based on a photochromic reaction in which a ring-opened body is irradiated with light having a wavelength that the ring-opened body absorbs to a ring-opened diarylethene compound in the evaluation experiment material 1. It is a figure showing a state of change.

FIG. 9 is a structural formula based on a photochromic reaction in which a ring-opened state is generated by irradiating a light of a wavelength having an absorption of the ring-opened body to a diarylethene-based compound in a ring-opened state in Evaluation Experiment Material 2 It is a figure showing a state of change.

FIG. 10 shows a structural formula of a photochromic reaction in which a ring-opened state is generated by irradiating a diarylethene-based compound in a ring-opened state in a comparative experimental material with light having a wavelength that the ring-opened body has absorption. It is a figure showing a state of change.

FIG. 11 is a graph showing the results of optical recording experiments using the optical recording media 1 and 2 for the evaluation experiment and the optical recording media for the comparative experiment, where the transmitted light intensity T1 (medium initial state) Is a graph obtained by plotting the ratio of the transmitted light intensity with respect to the transmitted light intensity and connecting each plot with a line.

[Explanation of symbols]

 Reference Signs List 91 Light source for information erasing and reproduction 91 'ND filter 91a Light for information erasing or light for information reproduction 91b Transmitted light from optical recording medium 94 Wavelength selection mirror 93, 95 Condensing lens 94 Optical recording medium 941 Glass substrate 942 Recording layer 96 Photodiode 97 Light source for information recording 97 'ND filter 97a Light for information recording 100 Housing for optical recording medium

Claims (2)

[Claims] 1. A photochromic material comprising a diarylethene compound, wherein the diarylethene compound has a general formula: (Wherein R ₁ and R ₂ each represent a hydrogen atom or an optionally substituted alkyl group, or a hydrogen atom or an optionally substituted alkoxy group, and A represents a condensed polycyclic aromatic group or a benzene ring. It represents a group obtained by removing one hydrogen atom from a polyphenyl group connected by two or more single bonds.
A may have a substituent. A photochromic material characterized by being a compound represented by the formula: 2. An optical recording medium for recording, reproducing and / or erasing information by light using a photochromic material, comprising the photochromic material according to claim 1.