JP4691725B2 - Optical information recording medium - Google Patents

Description

  The present invention relates to a photoresponsive recording material comprising a copolymer obtained from a monomer containing an azo compound, and an optical information recording material using the same.

Society is facing a remarkable wave of advanced information technology, and social demands and importance of technologies and materials related to information processing and recording are increasing. However, in the optical (or magnetic) recording by the current digital recording method, even if future technological progress is expected, it is considered that 1 [TB / inch ² ] is the limit, and this limit will be reached after 5 to 10 years. There are concerns about reaching this. Therefore, it is necessary to find a new ultra-high density recording method and establish a technology that can overcome this limitation.

The holographic memory is a technology that enables three-dimensional information to be recorded in three dimensions as it is, and two-dimensional planar data to be multilayered and recorded in three dimensions using light interference. In particular, the method of recording / reproducing two-dimensional data in page units is highly compatible with the current digital recording signal processing system, and has high potential in that high-speed transfer of recording / reproduction is possible. This technology enables ultra-high density and ultra-large capacity that greatly exceed 1 [TB / inch ² ].

  So far, photorefractive materials, photopolymerizable photopolymers, and photochromic organic materials (particularly polymers) are known as optical information recording media for realizing holographic memories. Photorefractive materials are known to be representative of inorganic crystalline materials (barium titanate, lithium niobate, etc.), but they have low sensitivity, are difficult to read nondestructively in principle, and are selective to the wavelength of the writing light. There are disadvantages such as poor resistance, brittleness, poor workability, and difficulty in thinning. In addition, photopolymerizable photopolymers are promising because the material design that avoids the above-mentioned drawbacks can be made relatively freely, and this is promising. . On the other hand, in the case of using a photochromic organic material, a polymer containing an azobenzene structure is already known as a representative one, and is based on various physical principles such as interference exposure, multiphoton reaction, local thermal excitation, and surface deformation. Information can be recorded. However, no material has yet been found that satisfies all the various characteristics such as sensitivity, response speed, long-term storage stability, and repeated durability of the material.

WO00 / 54111 Publication WO00 / 54112 Publication JP 2001-294652 Chem. Rev., vol.5 (1993) p.403-411 Macromol. Chem. Arys., Vol.196 (1995) p.1375-1390 ACS Symposium Series, vol.672 (1997) p.236-250 Macromolecules, vol.31 (1998) p.1155-1161

Non-patent document 1 describes the light-induced birefringence and hologram recording using the same, and the usefulness of a copolymerized polymer material composed of two types of photosensitive azobenzene and a liquid crystalline part having high shape anisotropy. Is stated. Non-Patent Document 2 describes the knowledge about the formation and relaxation dynamics of a hologram in a copolymer polymer material composed of two types of photo-sensitive azobenzene and a liquid crystalline part having high shape anisotropy. Non-Patent Documents 3 and 4 show that in an azobenzene polymer, the molecular orientation is controlled by irradiation with linearly polarized light, information can be recorded using birefringence distribution, and the molecular orientation is disturbed by circularly polarized light. It is clearly stated that the information can be deleted. Furthermore, the influence of the dipole of the copolymer component with high shape anisotropy on the properties is also discussed.
Patent Documents 1 to 3 disclose that an azobenzene structure-containing copolymer is used as a rewritable optical recording medium, particularly as a holographic optical recording medium. However, these materials have insufficient photoinduced birefringence, and the performance as an optical recording material for this purpose is insufficient.

  An object of the present invention is to provide an optical information recording material or a photoresponsive recording material that improves various properties such as light-induced birefringence, long-term storage stability, and repeated durability in holographic optical information recording.

  As a result of intensive research on materials capable of recording / reproducing ultra-large volume data at high speed, the present inventors have clarified the chemical structure of an azo compound that is conventionally representative and known to exhibit relatively good characteristics at present. Based on the intention of modifying and optimizing the combination of their dipole moments, by developing a new copolymer material with azo compounds and bisazo compounds with longer π-conjugated electron systems in the side chain, The inventors have found that various properties such as light-induced birefringence, long-term storage stability, and repeated durability in holographic optical information recording can be improved, and the present invention has been achieved based on this finding.

（式中、Ar¹〜Ar⁵はベンゼン環構造を示し、Ｒ¹〜Ｒ⁵は各々同一または別異に前記ベンゼン環構造に結合する水素原子、炭素数１〜６のアルキル基またはアルコキシ基を示し、m、nおよびｓ〜uはその結合数を示し、該結合数は０、１または２であり、Ｘ¹およびＸ³はコポリマーの主鎖または側鎖に連結する連結基を示し、該連結基は、エステル、チオエステル、エーテル、チオエーテル、アミン、アミド、スルホン、スルホニル、スルホンアミド、イミン、アゾ、または炭化水素鎖からなる結合基を含む基であり、Ｘ²およびＸ⁴は水素原子または-F、-Cl、-Br、-I、-CN、-NO₂、-CF₃、-CCl₃、-N⁺(CH₃)₃、-S⁺(CH₃)₃、-NH₂、-CH₃、及び-OHから選ばれる末端基を示す。）で表わされる構成単位を主鎖および側鎖の少なくとも一方に有するコポリマーであること、及び
該コポリマーは、平均分子量（Mn)として、１０００〜１０００００の範囲であり、このコポリマーは、式（１）及び（２）で表される構成単位を５０モル％以上含み、式（１）で表される構成単位と式（２）表される構成単位のコポリマー中における存在モル比は、４：６〜６：４の範囲にあること。 The present invention is a medium that enables optical information recording by changing the absorption characteristic or refractive index of light generated by light irradiation , and uses the following copolymer as a photoresponsive recording material. It is a recording medium.
As photoresponsive sites, the following formulas (1) and (2)

(In the formula, Ar ^{1 to} Ar ⁵ each represent a benzene ring structure, and R ^{1 to} R ⁵ each independently represent a hydrogen atom, an alkyl group having 1 to 6 carbon atoms, or an alkoxy group bonded to the benzene ring structure. M, n and s to u represent the number of bonds, the number of bonds is 0, 1 or 2, X ¹ and X ³ represent a linking group linked to the main chain or side chain of the copolymer, The linking group is a group containing a linking group consisting of ester, thioester, ether, thioether, amine, amide, sulfone, sulfonyl, sulfonamido, imine, azo, or a hydrocarbon chain , and X ² and X ⁴ are hydrogen atoms or -F, -Cl, -Br, -I, -CN, -NO 2, -CF 3, -CCl 3, -N + (CH 3) 3, -S + (CH 3) 3, -NH 2, - CH _3, and copoly having at least one of the main chain and side chain a structural unit represented by.) showing a terminal group selected from -OH And the copolymer has an average molecular weight (Mn) in the range of 1000 to 100,000, and the copolymer contains 50 mol% or more of the structural units represented by the formulas (1) and (2), The molar ratio of the structural unit represented by the formula (1) and the structural unit represented by the formula (2) in the copolymer is in the range of 4: 6 to 6: 4 .

The invention of claim 2 and the following is as follows.
a) The above-mentioned photoresponsive recording material, wherein the copolymer is an oligomer or polymer having a molecular weight of 700 to 1,000,000.
b) The above-mentioned photoresponsive recording material wherein the abundance ratio (molar ratio) of the structural units represented by the formulas (1) and (2) is in the range of 2: 8 to 8: 2.
c) The above-mentioned component containing 80 mol% or less of a structural unit other than the structural unit (hereinafter also referred to as other structural unit) at a site corresponding to the site to which the structural units represented by formulas (1) and (2) are linked. Photoresponsive recording material.
d) A liquid crystalline group for promoting photo-induced molecular reorientation in any of R ^{1 to} R ⁵ and X ^{1 to} X ⁴ in formulas (1) and (2), photoresponsive molecular reorientation state of photoresponsiveness Functional group having a function of stably maintaining, functional group having large optical anisotropy, or functional group for improving solvent solubility and film-forming property of the copolymer (hereinafter collectively referred to as modified functional group) The above-mentioned photoresponsive recording material.
e) The above-mentioned photoresponsive recording material in which at least a part of other structural units has a modified functional group.
f) The above light wherein the linking group is a group containing a linking group comprising an ester, a thioester, an ether, a thioether, an amine, an amide, a sulfone, a sulfonyl, a sulfonamide, an imine, an azo, a hydrocarbon chain, or one or more combinations thereof. Responsive recording material.
g) The photoresponsive recording material as described above, wherein the copolymer has a carbon chain as the main chain and the structural units of the formulas (1) and (2) in the main chain or side chain.
h) The carbon chain of the main chain is copolymerized with a monomer having a polymerizable reactive group that gives the structural units represented by the above formulas (1) and (2), or other monomers having a polymerizable reactive group with these monomers. The above-mentioned photoresponsive recording material, which is formed by copolymerization with a monomer.

（式中、X²、X⁴、Ar¹〜Ar⁵、Ｒ¹〜Ｒ⁵、m、nおよびｓ〜uは、式（１）および（２）と同じ意味であり、Ｒ⁶、Ｒ⁷は水素原子またはメチル基を示す。Xは結合基COOと共に連結基X¹またはX³を構成する。）で表わされるモノマーを必須成分として含むモノマーを共重合して得られたものであることを特徴とする上記の光応答性記録材料。
j)上記の光応答性記録材料の製造方法であって、式（１）および（２）の構成単位を与えるモノマーを必須成分として含むモノマーを共重合することを特徴とする光応答性記録材料の製造方法。
k)上記の光応答性記録材料の製造方法であって、式（３）および（４）で表わされるモノマーを必須成分として含むモノマーを共重合することを特徴とする光応答性記録材料の製造方法。
l)改質官能基を有する１種以上のモノマーを使用する上記の光応答性記録材料の製造方法。
m)光照射または局所加熱により発生する光の吸収特性変化または屈折率変化による光情報記録を可能とする媒体であって、上記の応答性記録材料を使用することを特徴とする光情報記録材料。
n)書き換えが可能な体積ホログラムメモリとして用いられる上記の光情報記録用材料。
o)書き換えが可能な表面レリーフ型メモリとして用いられる上記の光情報記録用材料。 i) The following equations (3) and (4)

(In the formula, X ² , X ⁴ , Ar ^{1 to} Ar ⁵ , R ^{1 to} R ⁵ , m, n and s to u have the same meanings as in the formulas (1) and (2), and R ⁶ , R ⁷ Represents a hydrogen atom or a methyl group, and X constitutes a linking group X ¹ or X ³ together with a linking group COO.) The photoresponsive recording material as described above.
j) A method for producing the above-mentioned photoresponsive recording material, characterized in that the photoresponsive recording material is obtained by copolymerizing a monomer containing a monomer that gives the structural units of formulas (1) and (2) as an essential component Manufacturing method.
k) A method for producing a photoresponsive recording material as described above, wherein the monomer comprising the monomers represented by formulas (3) and (4) as an essential component is copolymerized. Method.
l) The method for producing the above-mentioned photoresponsive recording material using one or more monomers having a modified functional group.
m) An optical information recording material that is capable of recording optical information by a change in absorption characteristics or refractive index of light generated by light irradiation or local heating, wherein the responsive recording material described above is used. .
n) The above optical information recording material used as a rewritable volume hologram memory.
o) The above optical information recording material used as a rewritable surface relief type memory.

The photoresponsive recording material of the present invention has a unit having a bisazo structure represented by the general formula (2) (referred to as a bisazo unit) in the copolymer. It is presumed that this unit exhibits superior performance as compared with a conventionally known unit having an azo structure represented by the general formula (1) (referred to as an azo unit) for the following reason.
1) A bisazo unit exhibits photoisomerization efficiency equivalent to that of an azo unit, and itself has a property of causing photo-alignment when irradiated with linearly polarized light.
2) Since the bisazo unit has a longer π-conjugated electron system than the azo unit, the birefringence value expressed when the molecules are oriented becomes large.
3) Liquid crystallinity is imparted to the copolymer by introducing a bisazo unit into the side chain, and two types of side chains or main chains of the azo unit and the bisazo unit spontaneously and undergo photoalignment in a molecular coordination manner.
As a comprehensive result of these, it is possible to realize a large light-induced birefringence value that was not obtained in the case of the polymer of each unit alone.

First, the manufacturing method of the photoresponsive recording material of the present invention will be described.
The photoresponsive recording material of the present invention comprises a copolymer having the structural units represented by the above formulas (1) and (2) as photoresponsive sites. Here, the term “copolymer” is used in the sense of including an oligomer, and the average molecular weight (Mn) may be 700 to 1,000,000, preferably 1000 to 100,000, more preferably 3000 to 30,000.

  This copolymer may be composed of only the structural units represented by the formulas (1) and (2), or may contain one or more other structural units (other structural units). When other monomers containing other structural units are used, the amount is 80 mol% or less, preferably 50 mol% or less, more preferably 20 mol% or less.

  The molar ratio of the structural unit represented by the formula (1) and the structural unit represented by the formula (2) in the copolymer is in the range of 2: 8 to 8: 2, preferably 4: 6 to 6: 4. There should be. Outside this range, it becomes difficult to obtain a thin film with low optical solubility and high optical quality.

In the formulas (1) and (2), Ar ^{1 to} Ar ⁵ represent a benzene ring or a heteroaromatic ring structure, and a preferable heteroaromatic ring structure is a monocyclic structure having one heteroatom. Preferred Ar ^{1 to} Ar ⁵ are benzene rings. R ^{1 to} R ⁵ each independently represent a hydrogen atom or a substituent bonded to the ring structure, and m, n, and su represent the number of bonds, preferably a hydrogen atom or a carbon number of 1 to 6 alkyl groups or alkoxy groups. m, n and s to u are 4 when Ar ^{1 to} Ar ⁵ are benzene rings, but the number of substituents is preferably 0, 1 or 2. X ^{1 to} X ⁴ are terminal groups or linking groups, and at least one of each formula is linked to the main chain or side chain of the copolymer as a linking group. X ¹ and X ³ are preferably linking groups, and X ² and X ⁴ are preferably end groups. However, all of X ^{1 to} X ⁴ can be linking groups. The terminal group is a hydrogen atom or a substituent, but is preferably a hydrogen atom, an alkyl group having 1 to 6 carbon atoms, or an alkoxy group.

  Preferred examples of the linking group include a group containing a linking group comprising an ester, a thioester, an ether, a thioether, an amine, an amide, a sulfone, a sulfonyl, a sulfonamide, an imine, an azo, a hydrocarbon chain, or one or more combinations thereof. The

  The main chain of the copolymer includes a hydrocarbon chain formed by polymerization of carbon-carbon unsaturated double bonds, a polyester chain, a polyamide chain, and the like, and a hydrocarbon chain is exemplified as a preferable one.

An example of a method for producing a copolymer constituting the photoresponsive recording material of the present invention is shown below.
Two kinds of polymerizable monomers represented by the general formulas (5) and (6), or one or more other copolymerizable monomers having these modified functional groups represented by the general formula (7) The monomer is polymerized in the presence of a polymerization initiator (AIBN or the like) to obtain a random copolymer having the general formulas (8) and (9) as repeating units.

Moreover, it is also possible to obtain the copolymer containing a repeating unit like General formula (10) as needed.

In the above formulas (5) to (9), Ar ^{1 to} Ar ⁵ , R ^{1 to} R ⁵ , m, n, s to t, and X ² and X ⁴ are as defined above. L ¹ and L ³ correspond to the aforementioned X ¹ and X ³ , but are divalent linking groups including a bonding group including X ¹ and X ³ .
Preferably, R ^{1 to} R ² and R ^{3 to} R ⁵ are hydrogen atoms or electron withdrawing or electron donating substituents. The end groups X ² and X ⁴ are —H, —F, —Cl, —Br, —I, —CN, —NO ₂ , —CF ₃ , —CCl ₃ , —N ⁺ (CH ₃ ) ₃ , Groups such as -S ⁺ (CH ₃ ) ₃ , -NH ₂ , -CH ₃ , -OH. The linking groups X ¹ and X ³ are —O—, —S—, — (NR ⁸ ) —, — (CR ⁹ R ¹⁰ ) —, — (CO) —, — (CO—O) —, — (CO-NR ⁸ )-,-(SO ₂ )-,-(SO ₂ -O)-,-(SO ₂ -NR ⁸ )-,-(C = NR ¹¹ )-,-(CNR ¹¹ -NR ⁸ )-)-,-(CR ⁹ = CR ¹⁰ )-,-(C≡C)-,-(N = N)-, C ₁ -C ₂₀ alkylene group, C ₃ -C ₁₀ cycloalkylene group, A divalent group containing a C _{2 to} C ₂₀ alkenylene group, a C _{6 to} C ₁₀ arylene group, or a combination thereof. Since this linking group to give a degree of freedom of rotation of the main chain and side chain, preferably we have a certain length, for this purpose it is advantageous to have an alkylene group C ₁ -C _5.
R ⁸ and R ¹¹ each represent a C _{1 to} C ₂₀ alkyl group, a C _{3 to} C ₁₀ cycloalkyl group, a C _{2 to} C ₂₀ alkenyl group, a C _{6 to} C ₁₀ aryl group, R ⁹ and R ¹⁰ is a hydrogen atom, a halogen atom, a C _{1 to} C ₂₀ alkyl group, a C _{1 to} C ₂₀ alkoxy group, a C _{3 to} C ₁₀ cycloalkyl group, a C _{2 to} C ₂₀ alkenyl group, C _{6, respectively.} an aryl group having -C _10.

In the formulas (5) to (7), M represents a functional group having polycondensation reactivity, polyaddition reactivity, addition polymerization property, isomerization polymerization property, or ring-opening polymerization property. It may be the same or different as long as it is copolymerizable with M in the formula or a monomer added separately. For example, when M has an ethylenically unsaturated bond, all M may be the same. When constituting a main chain such as polyester, M has at least two functional groups such as OH and COOH. In the case of an oligomer, a polyfunctional condensing agent such as tetracarboxylic acid may be used. In Formula (7), Y ¹ represents an arbitrary side chain or substituent, and is a photoresponsive group via a liquid crystal group for promoting photoinduced molecular reorientation of the photoresponsive azobenzene moiety or a hydrogen bond. Functional groups having the function of stably maintaining the photo-induced molecular reorientation state, functional groups having a large optical anisotropy, or functional groups for improving the solvent solubility and film-forming properties of the copolymer (modified) A functional group). Note that by a portion of the R ¹ to R ⁵ the same reforming functional groups Y ^1, the same effect without the use of monomers of formula (7) are expected.

In formulas (8) to (10), P ¹ , P ² , and P ³ each represent a main chain skeleton structure after polymerization. x, y and z represent the number of repetitions of each monomer in the copolymerization and are integers of 1 or more. These repeating units may be present randomly or in blocks.

  Advantageously, there is a method of copolymerizing monomers containing the monomers represented by the above formulas (3) and (4) as essential components. In this case, the main chain is a hydrocarbon chain and the linking group is -COOX-.

  According to the present invention, it is possible to obtain an optical information recording material that improves various characteristics such as light-induced birefringence, long-term storage stability, and repeated durability in holographic optical information recording.

  Hereinafter, the present invention will be described in more detail based on examples and comparative examples.

Synthesis example 1
A methacrylate monomer having a cyanoazobenzene group was synthesized according to the following reaction formula.

  4-Cyanoaniline 4.25g (36mmol) was dissolved in 2M hydrochloric acid and stirred in an ice bath. Thereto, 2.5 g (36 mmol) of sodium nitrite dissolved in distilled water was slowly added dropwise. To this was slowly added dropwise 2.8 g (30 mmol) of phenol dissolved in an aqueous sodium hydroxide solution, stirred at 0 ° C. for 2 hours, then at room temperature for 3 hours, and then filtered to take out an orange precipitate. . Further, this was thoroughly washed with distilled water, recrystallized from an ethanol / water mixture, filtered and dried under reduced pressure. Yield 67%.

Subsequently, a methylene spacer was introduced into this azo compound by the following method.

2.23 g (10 mmol) of the above azo compound, 2.5 g (20 mmol) of 2-bromoethanol and 2.76 g (20 mmol) of potassium carbonate were dissolved in 100 ml of acetone, and the mixture was refluxed at 50 ° C. for 72 hours to be reacted.
After the reaction, the mixture was cooled to room temperature, and the solvent was removed with an evaporator. The crude product was extracted with chloroform and a saturated aqueous potassium carbonate solution, and further extracted again with chloroform and an aqueous sodium chloride solution. Subsequently, it was washed 3 times with distilled water, dried over magnesium sulfate, and filtered.
Chloroform was removed under reduced pressure and purified by recrystallization from ethanol. By this method, a yellow-orange solid was obtained. (Yield: 60%)

Next, a polymerizable group was introduced at the terminal according to the following formula.

Dissolve 0.7 g (2.62 mmol) of the compound obtained in the above reaction and 0.53 g (5.24 mmol) of triethylamine in dichloromethane and slowly add 0.57 g (5.24 mmol) of methacryloyl chloride while stirring in an ice bath under a nitrogen gas atmosphere. It was dripped. After stirring for 2 hours, the mixture was returned to room temperature and further stirred for 24 hours.
Thereafter, triethylamine and the like were removed by an evaporator, followed by extraction with chloroform and a saturated aqueous potassium carbonate solution, and further extraction with chloroform and an aqueous sodium chloride solution. Subsequently, it was washed 3 times with distilled water, dried over magnesium sulfate, and filtered.
Chloroform was removed under reduced pressure and purified by recrystallization from n-hexane. By this method, a yellow-orange solid was obtained. (Yield: 51%)

  The ultraviolet-visible absorption spectrum of the obtained polymerizable azobenzene monomer is shown in FIG.

Synthesis example 2
A methacrylate monomer having a bisazobenzene group (4- [2- (methacryloyloxy) ethyloxy-2-methyl-4- (phenylazo)] azobenzene) was synthesized according to the following formula.

Disperse Yellow 7 (1 g, 3.16 mmol), 2-bromoethanol (0.79 g, 6.32 mmol) and potassium carbonate (0.87 g, 6.32 mmol) were dissolved in 50 ml acetone and refluxed at 50 ^° C. for 72 h.
After the reaction, the mixture was cooled to room temperature, and the solvent was removed with an evaporator. The crude product was extracted with chloroform and a saturated aqueous potassium carbonate solution, and further extracted again with chloroform and an aqueous sodium chloride solution. Subsequently, it was washed 3 times with distilled water, dried over magnesium sulfate, and filtered.
Chloroform was removed under reduced pressure and purified by recrystallization from ethanol. By this method, a brown solid was obtained. (Yield: 74%)
H ¹ -NMR data (600 MHz, JEOL Model, CDCl ₃ ) is shown in FIG.

Next, reaction which introduce | transduces a polymeric group into the terminal of the compound obtained by the said reaction was performed according to following Formula.

The compound (0.288 g, 0.8 mmol) obtained in the above reaction and triethylamine (0.162 g, 1.6 mmol) were dissolved in dichloromethane and cooled to 0 ^° C. under a dry nitrogen atmosphere. To this was slowly added methacrylic acid chloride (0.167 g, 1.6 mol), and the mixture was allowed to react at 0 ^° C. for 2 hours at room temperature with stirring for 24 hours.
Thereafter, triethylamine and the like were removed by an evaporator, followed by extraction with chloroform and a saturated aqueous potassium carbonate solution, and further extraction with chloroform and an aqueous sodium chloride solution. Subsequently, it was washed 3 times with distilled water, dried over magnesium sulfate, and filtered.
Chloroform was removed under reduced pressure and purified by recrystallization from n-hexane. By this method, a reddish brown solid was obtained. (Yield: 50%)
The ¹ H NMR data (600 MHz, JEOL Model, CDCl ₃ ) of this compound is shown in FIG. Moreover, the ultraviolet visible absorption spectrum of this compound is shown in FIG.

Synthesis example 3
A methacrylate monomer having a trifluoromethylazobenzene group was synthesized according to the following formula.

4.83 g (30 mmol) of 4-trifluoromethylaniline was dissolved in 2M hydrochloric acid and stirred in an ice bath. Thereto was slowly added dropwise 1.8 g (30 mmol) of sodium nitrite dissolved in distilled water. A solution of 4.13 g (25 mmol) of 2- (N-ethylanilino) ethanol dissolved in an aqueous sodium hydroxide solution was slowly added dropwise thereto, followed by stirring at 0 ° C. for 2 hours and then at room temperature for 6 hours, followed by filtration. An orange precipitate was removed. Further, this was thoroughly washed with distilled water, recrystallized from an ethanol / water mixture, filtered and dried under reduced pressure. Yield 60%.
FIG. 5 shows ¹ H NMR data (600 MHz, JEOL Model, DMSO) of this compound.

Subsequently, a polymerizable group was introduced into this azo compound by the following method.

Dissolve 3.13 g (9.3 mmol) of the azo compound obtained in the above reaction and 1.8 g (18.6 mmol) of triethylamine in tetrahydrofuran and stir 1.944 g (18.6 mmol) of methacryloyl chloride while stirring in an ice bath under a nitrogen gas atmosphere. Slowly dripped. After stirring for 2 hours, the mixture was returned to room temperature and further stirred for 24 hours.
Thereafter, triethylamine and the like were removed by an evaporator, followed by extraction with chloroform and a saturated aqueous potassium carbonate solution, and further extraction with chloroform and an aqueous sodium chloride solution. Subsequently, it was washed 3 times with distilled water, dried over magnesium sulfate, and filtered.
Chloroform was removed under reduced pressure to give a red viscous solid. (Yield: 50%)
The compound ¹ H NMR data (600 MHz, JEOL Model, CDCl ₃ ) is shown in FIG. Further, an ultraviolet-visible absorption spectrum of this polymerizable azobenzene monomer is shown in FIG.

Synthesis example 4
A methacrylate monomer having a cyanoazopyridine group was synthesized according to the following formula.

  2-Cyano-5-aminopyridine (5.236 g, 44 mmol) was dissolved in 2M hydrochloric acid and stirred in an ice bath. To this, 3.036 g (44 mmol) of sodium nitrite dissolved in distilled water was slowly added dropwise. To this, 3.6 g (40 mmol) of phenol dissolved in an aqueous sodium hydroxide solution was slowly added dropwise, stirred at 0 ° C. for 2 hours and then at room temperature for 6 hours, and then filtered to take out an orange precipitate. . Further, this was thoroughly washed with distilled water, recrystallized from an ethanol / water mixture, filtered and dried under reduced pressure. Yield 53%.

Subsequently, a methylene spacer was introduced into this azo compound by the following method.

2.23 g (10 mmol) of the above azo compound, 2.5 g (20 mmol) of 2-bromoethanol and 2.76 g (20 mmol) of potassium carbonate were dissolved in 100 ml of acetone, and the mixture was refluxed at 50 ° C. for 72 hours to be reacted.
After the reaction, the mixture was cooled to room temperature, and the solvent was removed with an evaporator. The crude product was extracted with chloroform and a saturated aqueous potassium carbonate solution, and further extracted again with chloroform and an aqueous sodium chloride solution. Subsequently, it was washed 3 times with distilled water, dried over magnesium sulfate, and filtered.
Chloroform was removed under reduced pressure and purified by recrystallization from ethanol. By this method, a yellow-orange solid was obtained. (Yield: 60%)

Next, a polymerizable group was introduced into this compound according to the following formula.

Dissolve 0.7 g (2.62 mmol) of the compound obtained in the above reaction and 0.53 g (5.24 mmol) of triethylamine in dichloromethane and slowly add 0.57 g (5.24 mmol) of methacryloyl chloride while stirring in an ice bath under a nitrogen gas atmosphere. It was dripped. After stirring for 2 hours, the mixture was returned to room temperature and further stirred for 24 hours.
Thereafter, triethylamine and the like were removed by an evaporator, followed by extraction with chloroform and a saturated aqueous potassium carbonate solution, and further extraction with chloroform and an aqueous sodium chloride solution. Subsequently, it was washed 3 times with distilled water, dried over magnesium sulfate, and filtered.
Chloroform was removed under reduced pressure and purified by recrystallization from n-hexane. By this method, a yellow-orange solid was obtained. (Yield: 51%)

The methacrylate monomer having a cyanoazobenzene group obtained in Synthesis Example 1 and the methacrylate monomer having a bisazobenzene group obtained in Synthesis Example 2 were polymerized according to the following formula.

A mixture of 0.05 g (0.15 mmol) of a methacrylate monomer having a cyanoazobenzene group and 0.064 g (0.15 mmol) of a methacrylate monomer having a bisazobenzene group is dissolved in 1 ml of tetrahydrofuran. To this was added 2.28 mg of 2,2′-azobisisobutyronitrile at 2 wt%, and after deaeration using liquid nitrogen, the system was sealed and polymerization was carried out at 65 ° C. After 24 hours, the polymer was taken out and purified by reprecipitation twice in methanol. As a result, a 1: 1 random copolymer (number average molecular weight 12000) of yellow-orange powder was obtained. The glass transition temperature of this copolymer DSC analysis was 120 ° C., and its absorption spectrum (5 × 10 ⁻⁵ mol / L in THF) was as shown in FIG.
Similarly, random copolymers having a monomer ratio of 4: 1, 3: 2, 2: 3, and 1: 4 (number average molecular weight of 10,000 to 20000) were also obtained.

Polymerization of the methacrylate monomer having a trifluoromethylazobenzene group obtained in Synthesis Example 3 and the methacrylate monomer having a bisazobenzene group obtained in Synthesis Example 2 was performed according to the following formula.

In the same manner as in Example 1, 0.061 g (0.15 mmol) of a methacrylate monomer having a trifluoromethylazobenzene group and 0.064 g (0.15 mmol) of a methacrylate monomer having a bisazobenzene group were mixed and dissolved in 1 ml of tetrahydrofuran. To this was added 2.28 mg of 2,2′-azobisisobutyronitrile at 2 wt%, and after deaeration using liquid nitrogen, the system was sealed and polymerization was carried out at 65 ° C. After 24 hours, the polymer was taken out and purified by reprecipitation twice in methanol. As a result, a 1: 1 random copolymer (number average molecular weight 8000) of yellowish orange powder was obtained. The glass transition temperature of this copolymer by DSC analysis was 110 ° C., and its absorption spectrum (5 × 10 ⁻⁵ mol / L in THF) was as shown in FIG. Similarly, random copolymers (number average molecular weight 7000 to 18000) having monomer ratios of 4: 1, 3: 2, 2: 3 and 1: 4 were also obtained.

The methacrylate monomer having a cyanoazopyridine group obtained in Synthesis Example 4 and the methacrylate monomer having a bisazobenzene group obtained in Synthesis Example 2 were polymerized according to the following formula.

In the same manner as in Example 1, 0.05 g (0.15 mmol) of a methacrylate monomer having a cyanoazopyridine group and 0.064 g (0.15 mmol) of a methacrylate monomer having a bisazobenzene group were mixed and dissolved in 1 ml of tetrahydrofuran. To this was added 2.28 mg of 2,2′-azobisisobutyronitrile at 2 wt%, and after deaeration using liquid nitrogen, the system was sealed and polymerization was carried out at 65 ° C. After 24 hours, the polymer was taken out and purified by reprecipitation twice in methanol. As a result, a 1: 1 random copolymer (number average molecular weight 10000) of yellow-orange powder was obtained. The glass transition temperature of this copolymer by DSC analysis was 125 ° C., and its absorption spectrum (5 × 10 ⁻⁵ mol / L in THF) was as shown in FIG. Similarly, random copolymers (number average molecular weight of 10,000 to 20000) having molar ratios of 4: 1, 3: 2, 2: 3 and 1: 4 were also obtained.

The light-induced birefringence properties of the 1: 1 molar ratio copolymers obtained in Examples 1-3 were measured.
The optical system for evaluating the light-induced birefringence characteristics of each material was as shown in FIG. The excitation light is set to 488 nm linearly polarized light, the probe light is set to 633 nm linearly polarized light, and the direction is set to 45 degrees. A filter is installed so that only 633 nm probe light enters the polarimeter placed behind the sample, and the birefringence value photoinduced by the azo compound thin film is analyzed by analyzing the state of elliptically polarized light measured by the polarimeter. Asked.

The thickness of each copolymer thin film is about 1 μm, the excitation light irradiation time is 170 seconds, and the excitation light intensity is 1 W / cm ² . The measurement results are shown in FIG. In the figure, (a), (b), and (c) are the photoresponse dynamics for the copolymers of Examples 1, 2, and 3 (copolymerization ratio 1: 1), respectively, and Example 2 shows the light of a known azobenzene copolymer. It shows a value close to the induced birefringence value, and it can be seen that Example 1 gives a large light-induced birefringence value that is about 20% higher than the known value. Further, it is an excellent feature that the photoinduced birefringence value after the photoexcitation is stopped is not relaxed (reduced) in any material. In the figure, “pump on” and “off” indicate timings of starting and stopping the irradiation of excitation light, respectively, and Δn indicates light-induced birefringence (the magnitude of birefringence generated by light irradiation). In the case of Example 3, the value was low, but the relaxation was found to be very small compared to the known one.
As described above, the light-induced birefringence value is larger than that of the known material and the relaxation is small (the initial relaxation value is 1% or less), which is a very suitable characteristic as an optical recording medium.

The dependency of the light-induced birefringence value of the copolymer of Example 1 on the polymerization ratio was measured according to the measurement conditions described above. Six copolymers of Example 1 (cyanoazobenzene group: bisazobenzene group = 4: 1, 2: 1, 3: 2, 1: 1, 2: 3, 1: 2) and two homopolymers of each monomer FIG. 13 shows the result of comparison of the light-induced birefringence values for.
As is clear from FIG. 13, it was found that the light-induced birefringence value was maximum near the 1: 1 polymerization ratio. This means that when a cyanoazobenzene group and a bisazobenzene group are present in the polymer in an appropriate ratio, each molecule (side chain) cooperatively responds to light stimulation and achieves a highly ordered orientation state. It has been found remarkably in the present invention to improve the performance of the optical information recording material by utilizing such a molecular joint phenomenon, and is a unique and effective method.

  When the polymerization ratio dependence of the light-induced birefringence value of the copolymer of Example 3 was measured, an increase in the light-induced birefringence value based on the molecular cooperative movement similar to that in Example 5 was observed in the material system of Example 3. After all, the maximum was observed around the copolymerization ratio of 1: 1. Therefore, it can be considered that this phenomenon is caused by a common bisazobenzene moiety. The results are shown in FIG.

Fig. 11 shows the excitation wavelength dependence of the light-induced birefringence value shown by the 1: 1 polymer of Example 1 in terms of the change in the light-induced birefringence value when the wavelength of the excitation light is changed not only at 488 nm but also variously. As shown in FIG.
As a result, the maximum photoinduced birefringence value was obtained under the excitation condition of 458 nm. The solid line is a plot of the absorption spectrum considered to be based on the n-π ^* transition of the material, but the wavelength dependence of the photoinduced birefringence value is relatively well matched with this absorption spectrum. It has been found that efficient excitation is preferable for optical information recording.

Ultraviolet-visible absorption spectrum of polymerizable azobenzene monomer of Synthesis Example 1 H ¹ -NMR data of intermediate of Synthesis Example 2 H ¹ -NMR data of the bisazobenzene monomer of Synthesis Example 2 UV-visible absorption spectrum of bisazobenzene monomer in Synthesis Example 2 H ¹ -NMR data of intermediate of Synthesis Example 3 H ¹ -NMR data of the polymerizable azobenzene monomer of Synthesis Example 3 UV-visible absorption spectrum of polymerizable azobenzene monomer of Synthesis Example 3 Absorption spectrum of the copolymer of Example 1 Absorption spectrum of the copolymer of Example 2 Absorption spectrum of the copolymer of Example 3 Schematic diagram of optical system for evaluating photoinduced birefringence characteristics The figure which shows the relationship between the birefringence value of each copolymer and time Figure showing polymerization ratio dependence of photoinduced birefringence of copolymer Figure showing polymerization ratio dependence of photoinduced birefringence of copolymer Diagram showing excitation wavelength dependence of photoinduced birefringence value

Claims (5)

It is a medium that enables optical information recording by changing the absorption characteristics or refractive index of light generated by light irradiation, and as a photoresponsive recording material,
As photoresponsive sites, the following formulas (1) and (2)

(In the formula, Ar ^{1 to} Ar ⁵ each represent a benzene ring structure, and R ^{1 to} R ⁵ each independently represent a hydrogen atom, an alkyl group having 1 to 6 carbon atoms, or an alkoxy group bonded to the benzene ring structure. M, n and s to u represent the number of bonds, the number of bonds is 0, 1 or 2, X ¹ and X ³ represent a linking group linked to the main chain or side chain of the copolymer, The linking group is a group containing a linking group consisting of an ester, a thioester, an ether, a thioether, an amine, an amide, a sulfone, a sulfonyl, a sulfonamide, an imine, an azo or a hydrocarbon chain , and X ² and X ⁴ are a hydrogen atom or — F, -Cl, -Br, -I, -CN, -NO 2, -CF 3, -CCl 3, -N + (CH 3) 3, -S + (CH 3) 3, -NH 2, -CH _3, and to a terminal group selected from -OH. of the main chain and the side chain a structural unit represented by) copolymer having at least one , And the and the copolymer, the average molecular weight (Mn), is in the range of 1,000 to 100,000, wherein the copolymer has the formula (1) and (2) a structural unit represented by at least 50 mol%, the formula ( The molar ratio of the structural unit represented by 1) and the structural unit represented by formula (2) in the copolymer satisfies the range of 4: 6 to 6: 4.
An optical information recording medium characterized by using a copolymer. 2. The optical information recording medium according to claim 1, wherein the copolymer has a carbon chain as a main chain and has structural units of formula (1) and formula (2) in the main chain or side chain . The copolymer has the following formulas (3) and (4)

(Where X ² , X ^Four , Ar ¹ ~ Ar ^Five , R ¹ ~ R ^Five , M, n and s to u have the same meaning as in formulas (1) and (2), and R ⁶ , R ⁷ Represents a hydrogen atom or a methyl group. X is a linking group XO together with a linking group COO. ¹ Or X ^Three Configure. 2. The optical information recording medium according to claim 1, wherein the optical information recording medium is obtained by copolymerizing a monomer containing a monomer represented by formula (1) as an essential component. The optical information recording medium according to claim 1, which is used as a rewritable volume hologram memory. The optical information recording medium according to claim 1, wherein the optical information recording medium is used as a rewritable surface relief type memory.

Images