JP2002037826A - Cross-linked product and optical recording medium of photochromic compound - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a material which retains optical anisotropy over a wide temperature range and has a high optical response speed, and finally satisfies the characteristics required as a rewritable optical recording medium. SOLUTION: The cross-linked product is obtained from a compound having one or more photochromic site and one or more polymerizable group in the molecule. The medium contains the product.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a crosslinked product useful as an optical recording medium and an optical recording medium using the crosslinked product.

[0002]

2. Description of the Related Art In recent years, with the development of computers and the advancement and versatility of information, recording media have been required to have higher capacities. Until now, recording media such as magnetic disks, CDs (compact disks), and DVDs (digital versatile disks) have become widespread, and their recording capacities have been improved. However, the recording density of these media has almost reached the theoretical limit. It is said that it has reached. As a method for achieving higher capacity in the future, recording in a photon mode is expected to replace recording in a conventional heat mode. As one of the candidate materials, a polymer containing a photochromic group has been proposed.

[0003] When a polymer containing a photochromic group is irradiated with polarized light, optically anisotropic is developed in the irradiated portion. When the polymer is stored at a glass transition temperature (Tg) or lower, the optical anisotropy can be maintained. On the other hand, the developed optical anisotropy is
It can be erased by heating it to polarized light or a temperature higher than the glass transition temperature of the polymer. Such a reversible change in the optical properties of the polymer using light can be used not only as an optical recording material but also as a material for an optical switch or an optical shutter.

As optical recording, it is required that 1) recording / erasing can be performed in a short time (high speed), 2) recording can be clearly read (high contrast), and 3) recording can be held stably for a long period of time. In response, the optical recording medium
It is necessary that 1) have high-speed light responsiveness, 2) have high optical anisotropy, and 3) be able to stably maintain optical anisotropy for a long period of time. Conventionally, research on optical recording media using an inorganic material or a semiconductor material has been made, but in recent years, research using an organic material has begun due to the easiness of material design and synthesis and high-speed response. Above all, there has been an increasing movement to use polymers as media because they can impart processability.

[0005] In 1987, the group of Eich, Wendorff et al. Reported optical recording properties using liquid crystal polymers containing azobenzene (Makromol. Chem., Rapid Commun., 8,
467 (1987)). Subsequently, high optical anisotropy and excellent stability have been achieved by introducing various modifying groups into the azobenzene-containing liquid crystal polymer (Makromol. Chem.,
Rapid Commun., 12, 709 (1991), Science, 268, 1873
(1995)). Recently, it has been reported that a material having more practical characteristics can be obtained by using an amorphous polymer in which an azobenzene group and a liquid crystal group are independently introduced into a side chain of the polymer (US 5,641,846). Also, Natansoh
n, Rochon et al.'s group reported that by adding electron donating and electron-withdrawing groups to both ends of azobenzene and generating a high dipole moment, optical anisotropy can be expressed at a high response speed, and it is rewritable It has shown usefulness as an optical recording medium (Macromolecules, 25, 2268 (199
2), Macromolecules, 25, 5531 (1992), US5,173,38
1). Further, it has been suggested that the phase morphology of the polymer, the azobenzene content concentration, the absorption wavelength, and the like are also important factors in the optical recording characteristics.

However, in many conventional polymers, even when the medium is stored at a temperature lower than Tg, a phenomenon in which the optically induced optical anisotropy is relaxed is observed, which is a cause of a decrease in recording stability. Has become. As a result, the boundary (contrast) between the recording portion and the non-recording portion is reduced, which may cause a reading error. Photochromic moieties can be introduced into the polymer chain rather than dispersed in the polymer, or bulky substituents can be introduced into the photochromic moieties or the polymer backbone can be made bulky.
The method of increasing Tg (Macromolecules, 32, 8572 (1999)) can improve stability, but has adverse effects on other properties such as slow response of optical properties and inability to obtain high optical anisotropy. Is seen.

[0007]

As described above, the conventional technology does not sufficiently satisfy all the characteristics. In particular, compatibility between long-term stability of optical anisotropy and high optical response speed is an important issue to be solved in optical recording materials. Further, since it is assumed that such an optical recording medium is used in a wide temperature range, the optical recording medium needs to have characteristics equivalent to characteristics at room temperature even at a high temperature.

Accordingly, an object of the present invention is to provide all the required characteristics as an optical recording medium which has a stable optical anisotropy over a wide temperature range, has a high optical response speed, and is finally rewritable. It is to provide a satisfactory material.

[0009]

Means for Solving the Problems In order to solve the problems in the conventional optical recording medium using a polymer, the inventors of the present invention have conducted intensive studies. As a result, a photochromic site and a polymerizable reactive group have been formed in the molecule. A rewritable optical recording material in which a crosslinked product obtained by using a compound having at least one compound can maintain stable optical anisotropy over a wide temperature range, and has high optical anisotropy and a fast response speed. The present invention has been found to be useful as such, and has led to the present invention.

That is, the present invention provides a crosslinked product of a compound having one or more photochromic sites and one or more polymerizable reactive groups in a molecule. Also,
The present invention provides a rewritable optical recording medium containing the crosslinked body.

[0011]

BEST MODE FOR CARRYING OUT THE INVENTION The starting compound of the crosslinked product of the present invention comprises at least one or more photochromic sites in the molecule,
It has one or more polymerizable reactive groups.

Examples of the photochromic moiety include azobenzene, stilbene, spiropyran, fulgide, cyclophane, and diarylethene-based moieties, and preferably have an azobenzene skeleton for ease of design and preparation. Further, it is more preferable that the compound has an azobenzene moiety, and an electron-donating substituent and an electron-withdrawing substituent are bonded to each of the benzene rings at both ends thereof. In particular, the photochromic site is represented by the following formula (1)
Or (2)

[0013]

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[Wherein, -A- is -N (R ¹ )-(where R ¹ represents an alkyl group, an aromatic group or a heterocyclic group which may have a substituent, or A condensed heterocyclic ring may be formed together with the nitrogen atom and the benzene ring.),-
O—, —S— or —S (＝ O) ₂ —, and —B ¹ represents —N
Represents O ₂ or —CN, and —B ² — represents —S (＝ O) ₂ —,
—C (＝ O) — or —N (R ² ) — (where R ² represents an alkyl group, an aromatic group or a heterocyclic group which may have a substituent, (A condensed heterocyclic ring may be formed together with the benzene ring.)). Equation (1) above
Of structure, the ^{-A- -N (R 1) -,} - S
(= O) ₂ - or -O-. Examples of -B ¹ is -NO ₂ or -CN, -B ² - The -S (= O) ₂ - or -N
(R ¹⁾ - is preferred. Here, among R ¹ and R ² , the alkyl group is preferably an alkyl group having 1 to 10 carbon atoms such as a methyl group, an ethyl group or a propyl group, and the substituted alkyl group is a hydroxyethyl group or a hydroxypropyl group. A hydroxyalkyl group having 2 to 10 carbon atoms is preferred. Examples of the aromatic group include a phenyl group and a naphthyl group. Examples of the heterocyclic group include a pyridyl group. Examples of the condensed heterocyclic ring formed by R ¹ or R ² with an adjacent nitrogen atom and a benzene ring include a carbazole group. Incidentally, a non-polymerizable group such as an alkyl group and an aromatic hydrocarbon group, or a polymerizable reactive group described later may be bonded to -B ^2- in the formula (2).

Specific examples of the structure of the formula (1) or (2) include the structures of the following formulas (3) to (8).

[0016]

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The polymerizable reactive group in the raw material compound of the crosslinked product of the present invention means a reactive group that can be polymerized by heat and / or light or a group that can react with a polyfunctional compound. Examples are selected from vinyl, isopropenyl, oxiranyl, epoxycyclohexyl, styryl, isocyanate, hydroxy, amino, alkylamino, carboxyl, halogenocarbonyl, mercapto, and oxetanyl groups. Groups. The structures of these groups are more specifically shown as follows.

[0018]

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(Wherein R ³ is a hydrogen atom or CH ₃ , R ⁴
Represents a hydrogen atom or an alkyl group, and R ⁵ represents a hydroxyl group or a halogen atom, respectively.

Specific examples of the starting compound (monomer) of the present invention include compounds represented by the following formulas (9) to (12).

[0021]

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Among the starting compounds of the present invention, oligomers,
Examples of the polymer include a polymer containing a photochromic site and a polymerizable reactive group in the same side chain of the polymer as represented by, for example, formulas (13) to (16). In this case, the polymerizable reactive group and the photochromic portion, may be bonded directly or, for example, ^{-R 7 -, - COOR 8 -} , - CONHR
^It may be bonded via a divalent group such as 9- (where R ⁷ , R ⁸ and R ⁹ are respectively an alkylene group and a divalent aromatic hydrocarbon group). A specific example of obtaining such a polymer is, for example, Macromolecules, 26, 5303 (1993).

[0023]

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(Wherein, n represents one or more repeating units)

The oligomer or polymer may be a polymer having a photochromic site and a polymerizable reactive group in separate side chains as represented by, for example, formulas (17) and (18). In this case, the polymer can be obtained by a method such as copolymerization, polycondensation, or polyaddition, and the obtained oligomer or polymer can have any of block, random, graft, and alternating structures. Specific examples of obtaining such a polymer include, for example, J. Appl.
Polym. Sci., 74, 974 (1999), Macromolecules, 32, 5
277 (1999), J. Appl. Polym. Sci., 71, 1081 (1999), M
As described in acromol. RapidCommun., 15, 741 (1994), a random copolymerization of a methacrylate containing a photochromic site and a methacrylate containing a polymerizable reactive group may be used.

[0026]

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(In the formula, m and n each represent one or more repeating units. It means that the compound is formed by random copolymerization of two kinds of monomers.)

Further, as shown by the formula (19), the position of the photochromic site and the position of the polymerizable reactive group are not limited to oligomers and polymer side chains as described above. Is also good.

[0029]

Embedded image

(Wherein, n represents one or more repeating units)

The compound represented by the above formula (9), (12), (14) or (16) is reacted by adding a polyfunctional compound such as a polyol, polyisocyanate, polyamine, or polycarboxylic acid. Can be done.

The raw material compound of the present invention has a number average molecular weight of 2,000 or more, especially 3.0,
It is preferably an oligomer or polymer of 00 or more. When the molecular weight is less than 2,000, when a composition containing the present compound is applied on a recording substrate, there may be a problem that a uniform coating film cannot be obtained. In this case, the number average molecular weight means a molecular weight in terms of polystyrene by gel permeation chromatography. As the compound having a number average molecular weight of 3,000 or more, for example, oligomers or polymers such as the compounds (13) to (19) described above are preferable. In this case, it is preferable that both the photochromic site and the polymerizable reactive group are present in the side chain of the polymer from the viewpoint of the light response speed.

In the raw material compound of the present invention, it is preferable to introduce a photochromic moiety and a polymerizable reactive group in a molar ratio of (photochromic group) / (polymerizable reactive group) = 0.05 to 19. , Especially when the ratio is 0.15
-6 is preferable. If this ratio is less than 0.05, sufficient optical anisotropy cannot be obtained, and if this ratio exceeds 19, stable optical anisotropy may not be obtained in a wide temperature range.

The crosslinked product of the present invention is preferably formed such that the polymerizable reactive group in the above-mentioned raw material compound is polymerized by irradiation of heat and / or radiation or reacted with a polyfunctional compound. Here, radiation means, for example, infrared rays, visible light rays, ultraviolet rays, X-rays, electron beams, α
Means ionizing radiation such as radiation, β-rays, γ-rays. In either case, an initiator that cleaves by heat and / or radiation can be added as needed, and further a sensitizer can be added as needed.

In this case, if necessary, in addition to the raw material compound, a compound capable of reacting with a polymerizable reactive group in the raw material compound, optional components such as monomers, oligomers and polymers, and additives are recorded. It can be added to such an extent that the properties are not deteriorated.

The crosslinked product may be formed in a solvent or in a bulk. When the finally obtained crosslinked product has a glass transition point, its temperature (Tg) is determined by DS
C (scanning differential calorimeter), 100
It is preferable that the temperature is not lower than ° C. When the Tg of the crosslinked product is lower than 100 ° C., a problem may occur in the long-term stability of the recording characteristics.

[0037]

EXAMPLES The present invention will be described below in more detail with reference to examples, but the present invention is not limited to these examples.

Monomer Synthesis 4 '-(2-methacryloyloxyethyl) ethylamido
In a reaction vessel equipped with a no-4-nitroazobenzene stirrer, 4 ′-(2-hydroxyethyl) ethylamino-4-nitroazobenzene (Ald
Rich red, disperse red 1) 5.0
g, 2.6 mL of triethylamine and 60 mL of dry tetrahydrofuran (THF) were added, and the mixture was cooled to 5 ° C. or lower in an ice bath while being dissolved and stirred. A solution obtained by mixing 1.9 mL of methacryloyl chloride and 20 mL of THF was slowly dropped into the reaction vessel. After dropping, the mixture was
The mixture was stirred for 5 hours while being cooled to 5 ° C. or lower, and then stirred at room temperature for 12 hours. After stirring, the precipitate was removed, the filtrate was concentrated by an evaporator, and the concentrate was poured into cooling water. After the precipitated precipitate was subjected to suction filtration while washing with water, the precipitate was dried by heating under reduced pressure. The obtained product was recrystallized from ethanol to give a final yield of 61%.
% Of the desired product. ¹ H-NMR (CDCl ₃ ): 1.2
_{8 (CH 3 - (CH 2} -)), 1.92 (CH 3 - (C =
_{CH 2)), 3.55 (-CH} 2 -N), 3.69 (-C
_{H 2 -N), 4.36 (-CH} 2 -O -), 5.59 (C
_{H 2 = C -), 6.09} (CH 2 = C -), 6.92 ( aromatic H), 7.90 (aromatic H), 8.30 (aromatic H)

In a reaction vessel equipped with an ortho-methacryloyloxyphenol stirrer, 3.4 g of 1,2-benzenediol (Catechol, manufactured by Aldrich) was added.
5.1 mL of triethylamine and 40 mL of dry tetrahydrofuran (THF) were added, and the mixture was cooled to 5 ° C. or lower in an ice bath while being dissolved and stirred. A solution in which 3.0 mL of methacryloyl chloride and 30 mL of THF were mixed was slowly dropped into the reaction vessel. After the dropwise addition, the mixture was stirred for 4 hours while cooling to 5 ° C. or lower. After stirring, the precipitate deposited by filtration was removed while washing with THF. After the filtrate was concentrated by an evaporator, it was separated by silica gel column chromatography using an eluent of ethyl acetate: hexane = 1: 4 (ml / ml), and then a second component was recovered. The solution of the second component was concentrated and dried with an evaporator, and then recrystallized with ethanol. Finally, the desired product was obtained with a yield of 34%. ¹ H-N
MR (CDCl ₃ ): 2.11 (CH _3- (C = C
_{H 2)), 5.57 (HO} -), 5.83 (CH 2 = C
−), 6.42 (CH ₂ ＣC—), 6.96 (aromatic H), 7.02 (aromatic H), 7.15 (aromatic H)

Polymer Synthetic 1 ampoule of 4 '-(2-methacryloyloxyethyl) per ampoule
0.48 g of ethylamino-4-nitroazobenzene, 0.16 g of hydroxyethyl methacrylate, 2,2′-azobisisobutyronitrile (AI
0.06 g of BN) and 5 mL of dry toluene
Dissolved. The mixture was degassed under reduced pressure, and the ampoule was purged with argon gas, sealed, and stirred at 65 ° C. for 2 days. This mixture was dropped into 500 mL of hexane,
The precipitate was collected by vacuum filtration. After dissolving the recovered precipitate with a small amount of THF, it was dropped again into hexane and recovered by filtration under reduced pressure. The obtained precipitate was dried under reduced pressure to obtain a polymer intermediate having a yield of 89%.

Subsequently, in a reaction vessel equipped with a stirrer, 0.35 g of the obtained polymer intermediate and 0.1 mL of triethylamine were added.
31 mL, 0.02 g of hydroquinone and 30 mL of dry tetrahydrofuran (THF) were added, and the mixture was cooled to 5 ° C. or lower in an ice bath while being dissolved and stirred. A solution obtained by mixing 0.02 mL of acryloyl chloride and 10 mL of THF was slowly dropped into the reaction vessel. After the dropwise addition, the mixture was stirred for 1 hour while being cooled to 5 ° C. or lower, and then the stirring was continued at room temperature for 12 hours. After stirring, the THF solution containing the precipitate was poured into water, and the precipitate was collected by filtration under reduced pressure. After the precipitate was dissolved in THF, it was added dropwise to hexane, and the precipitate was collected by filtration under reduced pressure. The precipitate was dried under reduced pressure to finally obtain Polymer 1 (number average molecular weight: 8,000) with a yield of 63%. ¹ H-NMR (d ₆ -DM
_{SO): 0.5-1.4 (CH 3 -} ), 1.4-1.9
_{(-CH 2 -), 3.4-4.4 (} -CH 2 -), 4.7
-4.9 (HO-), 5.8-6.0 (H-C =),
6.0-6.2 (H-C =), 6.2-6.4 (H-C
=), 6.5-7.0 (aromatic H), 7.5-8.0
(Aromatic H), 8.0-8.4 (aromatic H)

4 '-(2-methacryloyloxyethyl) in 2 ampoules of polymer
0.49 g of ethylamino-4-nitroazobenzene, 0.49 g of hydroxyethyl methacrylate, 0.10 g of AIBN which is a thermal polymerization initiator, and 10 parts of dry toluene
mL was added and dissolved. The mixture was degassed under reduced pressure, and the ampoule was purged with argon gas, and then sealed.
Stirred at 5 ° C. for 2 days. This mixed solution is hexane 500m
The mixture was dropped into L, and the precipitate was collected by filtration under reduced pressure. After dissolving the recovered precipitate with a small amount of THF, it was dropped again into hexane and recovered by filtration under reduced pressure. The obtained precipitate was dried under reduced pressure to obtain a polymer intermediate having a yield of 74%.

Subsequently, in a reaction vessel equipped with a stirrer, 0.40 g of the obtained polymer intermediate and 0.1 mL of triethylamine were added.
61 mL, 0.05 g of hydroquinone and 30 mL of dry tetrahydrofuran (THF) were added, and the mixture was cooled to 5 ° C. or lower in an ice bath while being dissolved and stirred. A solution obtained by mixing 0.35 mL of acryloyl chloride and 20 mL of THF was slowly dropped into the reaction vessel. After the dropwise addition, the mixture was stirred for 2 hours while being cooled to 5 ° C. or lower, and then the stirring was continued at room temperature for 12 hours. After stirring, the THF solution containing the precipitate was poured into water, and the precipitate was collected by filtration under reduced pressure. After the precipitate was dissolved in THF, it was added dropwise to hexane, and the precipitate was collected by filtration under reduced pressure. The precipitate was dried under reduced pressure to finally obtain Polymer 2 (number average molecular weight 7,500) with a yield of 73%. ¹ H-NMR (d ₆ -DM
_{SO): 0.5-1.4 (CH 3 -} ), 1.5-2.1
_{(-CH 2 -), 3.4-4.4 (} -CH 2 -), 4.7
-4.9 (HO-), 5.7-5.9 (H-C =),
5.9-6.1 (H-C =), 6.1-6.3 (H-C
=), 6.4-6.9 (aromatic H), 7.4-7.9
(Aromatic H), 7.9-8.2 (aromatic H)

4 '-(2-methacryloyloxyethyl) in 3 ampoules of polymer
0.48 g of ethylamino-4-nitroazobenzene, 0.18 g of glycidyl methacrylate, 0.07 g of AIBN as a thermal polymerization initiator, and 5 mL of dry toluene were added and dissolved. The mixture was degassed under reduced pressure, and the ampoule was purged with argon gas, and then sealed and sealed at 65 ° C for 2 hours.
Held for days. This mixture was dropped into 500 mL of methanol, and the precipitate was collected by filtration under reduced pressure. After dissolving the recovered precipitate with a small amount of THF, the precipitate was dropped into methanol again and recovered by filtration under reduced pressure. The resulting precipitate was dried under reduced pressure to finally obtain Polymer 3 (number average molecular weight 6,900) with a yield of 91%. ¹ H-NMR (d ₆ -DMS
_{O): 0.5-1.4 (CH 3 -} ), 1.4-2.0
(-CH ₂ -), 2.4-2.8 (epoxy H), 2.
9-3.3 (epoxy H), 3.3-4.4 (-CH ₂
-), 6.6-7.0 (aromatic H), 7.5-8.0
(Aromatic H), 8.0-8.4 (aromatic H)

4 '-(2-methacryloyloxyethyl) in 4 ampoules of polymer
0.48 g of ethylamino-4-nitroazobenzene, 0.22 g of ortho-methacryloyloxyphenol, 0.07 g of AIBN as a thermal polymerization initiator, and 5 mL of dry toluene were added and dissolved. The mixture was degassed under reduced pressure, and the ampoule was purged with argon gas, sealed, and stirred at 65 ° C. for 2 days. This mixture was dropped into 500 mL of methanol, and the precipitate was collected by filtration under reduced pressure. After dissolving the recovered precipitate with a small amount of THF, the precipitate was dropped into methanol again and recovered by filtration under reduced pressure. The obtained precipitate was dried under reduced pressure to obtain a polymer intermediate having a yield of 90%.

Subsequently, the obtained product was placed in a reaction vessel equipped with a stirrer.
0.45 g of the obtained polymer intermediate, 0.1 ml of triethylamine.
53 mL, 0.02 g of hydroquinone and dry tetrahydride
Add 30 mL of lofuran (THF), dissolve and stir.
The mixture was cooled to 5 ° C. or lower in an ice bath. Acryroy
Mix 0.31 mL of luchloride and 20 mL of THF
The solution was dropped slowly into the reaction vessel. After dripping, the mixture
Is stirred for 2 hours while cooling to 5 ° C. or less, and then
Stirring was continued at temperature for 12 hours. After stirring,
The THF solution was poured into water, and the precipitate was collected by filtration under reduced pressure.
Was recovered. After dissolving the precipitate in THF,
The precipitate was collected by filtration under reduced pressure. Settling
The product was dried under reduced pressure to give a final 74% yield of polymer 4 (number
(Average molecular weight: 3,600).¹H-NMR (d₆-D
MSO): 0.5-1.4 (CH _Three-), 1.4-2.
1 (-CH_Two-), 3.4-4.3 (-CH_Two−), 5.
7-6.1 (H-C =), 6.1-6.6 (H-C
=), 6.6-7.0 (H-C =), 7.0-7.4.
(Aromatic H), 7.4-8.0 (aromatic H), 8.0-
8.4 (aromatic H)

4 '-(2-methacryloyloxyethyl) in 5 ampoules of polymer
0.96 g of ethylamino-4-nitroazobenzene, 0.09 g of AIBN as a thermal polymerization initiator, and 5 mL of dry toluene were added and dissolved. The mixture was degassed under reduced pressure, and the ampoule was purged with argon gas, sealed, and stirred at 65 ° C. for 2 days. This mixture was dropped into 500 mL of methanol, and the precipitate was collected by filtration under reduced pressure. After dissolving the recovered precipitate with a small amount of THF, the precipitate was dropped into methanol again and recovered by filtration under reduced pressure. The resulting precipitate was dried under reduced pressure to finally obtain Polymer 5 (number average molecular weight: 4,000) with a yield of 90%. ¹ H-NMR
_{(D 6 -DMSO): 0.5-1.4 (} CH 3 -), 1.
_{5-2.1 (-CH 2 -), 3.4-4.4} (-CH
_2- ), 6.4-6.9 (aromatic H), 7.4-7.9
(Aromatic H), 7.9-8.2 (aromatic H)

Film Preparation Examples 1-5 0.05 g of polymer 1 and 0.002 g of AIBN were added to TH
F1 mL, the solution was spread on a slide glass plate, and a polymer film having a thickness of 400 nm was obtained by spin coating (1,000 rpm × 30 seconds). The obtained film was kept at 120 ° C. for 2 days under an argon atmosphere to obtain a crosslinked product of Polymer 1 (Example 1). Crosslinked products were obtained for Polymers 2 and 4 by the same method and conditions (Examples 2 and 4). For Polymer 3, instead of AIBN, boron trifluoride monoethylamine was added to 0.03.
After adding 02 g, a crosslinked product was obtained by the same method and under the same conditions (Example 3). Further, with respect to polymer 4, 2-methyl-1- [4- (methylthio) phenyl] -2-morpholino-propan-2-one was used in place of AIBN.
004 g was added, and a polymer film was obtained by spin coating.
Irradiation with mW / cm ² UV light (using a high-pressure mercury lamp) was performed to obtain a crosslinked product (Example 5).

Comparative Examples 1 and 2 Polymer 5 was dissolved in 1 mL of THF, and the solution was applied on a slide glass plate and spin-coated (1,000 rpm).
(pm × 30 seconds) to obtain a polymer film having a thickness of 400 nm. The obtained film was dried under reduced pressure at 50 ° C. for 12 hours (Comparative Example 1). 0.07 g of bisphenol A polyethoxylated diacrylate (average molecular weight 512)
And 2,2-dimethoxybenzylacetophenone 0.00
4 g was dissolved in 1 mL of THF, the solution was spread on a slide glass plate, and spin-coated (1,000 rpm × 3).
0 second), and then irradiated with UV light (using a high-pressure mercury lamp) having an illuminance of 50 mW / cm ² for 5 minutes at room temperature under a nitrogen atmosphere to obtain a polymer film (Comparative Example 2). .

Glass transition temperature measurement Using a differential scanning calorimeter, the heating / cooling rate was set at 10 ° C. /
In minutes, the change in calorific value of the polymer was measured. The glass transition temperature was determined from the second heating measurement.

Confirmation test of crosslinked product The polymer films of Examples 1 to 5 and Comparative Examples 1 and 2 were immersed in THF at 25 ° C. for 48 hours, and the shape was maintained without dissolving the film. The case where the film dissolved and disappeared was defined as "x".

Optical Recording Characteristics A measuring device was prepared assuming the optical recording characteristics evaluation as shown in FIG. For optical recording, the polymer film was irradiated with a linearly polarized argon laser having an illuminance of 160 mW / cm ² and a wavelength of 488 nm. For light erasure, a circularly polarized argon laser having the same wavelength and the same illuminance was irradiated. The optical anisotropy was detected by using a 674 nm laser as a probe through a polarizer at +/− 45 ° before and after the polymer film, and the birefringence was detected. The linearly polarized light was applied for 300 seconds, and after stopping the linearly polarized light, the film was kept in that state for 300 seconds and then irradiated with circularly polarized light for 200 seconds. A typical characteristic curve is shown in FIG. The measurement was performed while the temperature of the film was adjusted to 25 ° C. and 80 ° C. by a temperature controller.

In FIG. 2, the maximum value of the birefringence during irradiation of linearly polarized light is represented by a, and the birefringence immediately before irradiation of circularly polarized light is represented by b. To define the decay rate. The smaller the value of the attenuation rate, the higher the stability.

(Equation 1) Attenuation rate (%) = 100 × (ab) / a

As erasing characteristics of the recording, when a circularly polarized laser was irradiated, the case where the birefringence completely disappeared was defined as “○”, and the case where the birefringence did not disappear was defined as “x”. The light response speed was measured by irradiating linearly polarized light and measuring the time until the birefringence reached 95% of the maximum value.

Table 1 shows the obtained results. As shown in Table 1, the crosslinked product obtained by using the polymer having both the photochromic site and the polymerizable reactive group showed a small temperature dependence of the birefringence and a low decay rate at a high temperature. In addition, it can be seen that optical anisotropy can be expressed and erased at a high light response speed. Therefore, this crosslinked product was found to be useful as a rewritable recording medium.

[0057]

[Table 1]

[0058]

The crosslinked product of the present invention can exhibit optical anisotropy at a high response speed with polarized light of a specific wavelength and can be eliminated. Therefore, the crosslinked product of the present invention is useful as a rewritable optical recording medium, since the temperature dependence of optical anisotropy is small and excellent stability is obtained, particularly in a wide temperature range.

[Brief description of the drawings]

FIG. 1 is a diagram schematically illustrating an apparatus for measuring optical recording (birefringence) characteristics.

FIG. 2 is a diagram showing a typical curve of birefringence characteristics.

──────────────────────────────────────────────────続 き Continued on the front page (51) Int.Cl. ⁷ Identification symbol FI Theme coat ゛ (Reference) G03C 1/73 503 G03C 1/73 503 G11B 7/24 516 G11B 7/24 516 F-term (Reference) 2H123 AA00 AA03 AA30 4J027 AA02 AB02 AB05 AJ01 CB01 CC02 CC05 CC06 CC08 CD05 4J029 AA07 AB07 AD01 AE04 AE05 BH01 DA01 DA03 DA07 GA11 4J100 AL08P AL62Q AL66P AL69Q BA03P BA16P BA28P BA41P BA45P BA58P BC43 JA01

Claims (6)

[Claims] 1. A crosslinked product of a compound having one or more photochromic sites and one or more polymerizable reactive groups in a molecule. 2. A photochromic moiety represented by the formula (1) or (2): [In the formula, -A- is -N (R ¹ )-(where R ¹ represents an alkyl group, an aromatic group, or a heterocyclic group which may have a substituent, or an adjacent nitrogen atom and with a benzene ring may form a fused heterocycle), -. O -, - S- or -S (= O) ₂ - indicates, -B ¹ is -NO ₂ or -C
N, -B ² -is -S (= O) _2- , -C (= O)-
Or —N (R ² ) — (where R ² represents an alkyl group, an aromatic group, or a heterocyclic group which may have a substituent,
A condensed heterocyclic ring may be formed together with an adjacent nitrogen atom and a benzene ring. The crosslinked product according to claim 1, which has a structure represented by the following formula: 3. The polymerizable reactive group includes a vinyl group, an isopropenyl group, an oxiranyl group, an epoxycyclohexyl group, a styryl group, an isocyanate group, a hydroxy group,
3. The crosslinked product according to claim 1, which is an amino group, an alkylamino group, a carboxyl group, a halogenocarbonyl group, a mercapto group or an oxetanyl group. 4. The crosslinked product according to claim 1, which is a crosslinked product of an oligomer or a polymer having a number average molecular weight of 2,000 or more. 5. polymerizing a polymerizable reactive group in a compound having one or more photochromic sites and one or more polymerizable reactive groups in a molecule by heat and / or radiation, or The crosslinked product according to any one of claims 1 to 4, which is obtained by reacting the compound with a polyfunctional compound. 6. A rewritable optical recording medium comprising the crosslinked product according to claim 1. Description: