JP2006018113A - Organic photorefractive material and optical recording material using same - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To obtain a photorefractive material which is excellent in phase stability of the material, exhibits excellent photorefractive characteristics for a long period of time, and has a long working life. <P>SOLUTION: The organic photorefractive material includes components of A, B, C and D groups mentioned below. Here, A is an organic polymer compound, B is a combination of N-(4-nitrophenyl)-L-prolinol and at least a kind of compound selected from a group of compounds mentioned below as electric field sensitive optical functional compounds, C is a photosensitizer, and D is a plasticizer. The above mentioned group of compounds consists of N-(4-nitrophenyl)-L-prolinol methyl ether, (s)-(-)-N-(5-nitro-2-pyridyl) prolinol, [[4-(hexahydro-1H-azepin-1-yl) phenyl] methylene] propanedinitrile, 4-(2,2-dicyanovinyl)-N-ethyl-N-(5-hydroxypentyl) aniline, and 4-(2,2-dicyanovinyl)-N,N-bis(2-methoxyethyl) aniline. <P>COPYRIGHT: (C)2006,JPO&NCIPI

Description

The present invention relates to photorefractive materials. The photorefractive material of the present invention can provide a photorefractive characteristic without applying a voltage without using a photoconductive compound, and can be a spatial light modulator excellent in optical communication and optical information processing.
A photorefractive material is a material whose refractive index changes upon irradiation with light. That is, when a photorefractive material is irradiated with light, electrons and holes (hereinafter referred to as carriers) are generated, and a spatial electric field is generated by the movement of the carriers. Then, the refractive index in the material changes corresponding to this spatial electric field, and refractive index modulation becomes possible.

  When the photorefractive material is irradiated with interference light of two coherent light beams that are not uniform in intensity, for example, carriers are generated only in the bright part of the interference light, so that a spatial electric field corresponding to the light intensity distribution of the interference light is generated. Then, the material undergoes refractive index modulation corresponding to the spatial electric field to form a diffraction grating.

  In addition, unlike other diffraction grating formation mechanisms (such as photochromic), the diffraction grating formed by the photorefractive material is out of phase (π / 2) with the intensity distribution of interference light (interference fringes). Energy transfer occurs between one light beam incident on the material and the other light beam.

  Therefore, by using such characteristics, application to an optical modulation element that performs nonlinear signal processing on signal light is possible. In other words, hologram recording materials and optical multiplexers / demultiplexers using diffraction grating formation, optical switching elements using energy transfer, beam amplifiers, image correlation processing, associative memory elements, etc. Since it is a phase conjugate, it can also be used as a phase conjugate mirror (Yepouch, Photorefractive Nonlinear Optics, Maruzen, 1995).

(Inorganic photorefractive material)
As photorefractive materials that have been known for a long time, there are those obtained by doping metal ions or the like into inorganic single crystals such as lithium niobate and barium titanate. These are studied as light modulation elements that perform the above-described nonlinear signal processing, and are also used as materials for studying the mechanism of the expression of photorefractive characteristics. However, their use is limited because it is difficult to grow an inorganic single crystal containing a dopant, and since the crystal is hard and brittle, it is difficult to form.

(Organic photorefractive material)
From such a background, a photorefractive material (hereinafter referred to as an organic photorefractive material) using an amorphous organic compound that is low in cost and excellent in moldability is demanded. For organic photorefractive materials, an organic photoconductive compound for forming a spatial electric field and an electric field response optical functional compound (such as a nonlinear optical dye) that causes a refractive index change corresponding to the spatial electric field are essential. Further, a sensitizer or a plasticizer may be added to improve the molding processability in order to efficiently absorb the irradiation light.

  In the past research, we have mainly blended non-linear optical dye compounds and other field-responsive optical functional compounds with polymers with photoconductive functions, and conversely low-molecular compounds with photoconductive functions in non-linear optical dye-containing polymers. In addition, a polymer compound such as polymethylmethacrylate or polystyrene, which is inert to photorefractive properties, is used as a binder, and a photoconductive function and a non-linear optical dye compounded in low molecules are proposed. Has been.

Depending on the molecular orientation, not only the Pockels effect but also birefringence contributes to the refractive index modulation. For this reason, the photorefractive material having a low glass transition temperature is not limited in the molecular motion of the nonlinear optical dye even near room temperature, has a large electro-optic characteristic, and exhibits a high photorefractive characteristic exceeding that of an inorganic material.
As described above, the organic photorefractive material is expected to be applied to an optical modulation element, and active research and development are currently being performed reflecting the recent optical information communication situation.

W.E.Moerner and S.M.Silence, Chemistry Review, 94, 127-155, 1994

As described above, the organic photorefractive material is generally a mixture of various functional compounds, and a part of the components are likely to precipitate, and the phase stability is low, so that the pot life is short. In order to eliminate such drawbacks, for example, there is a proposal that all functional compounds are incorporated into one molecule by copolymerization, but there are difficulties such as complicated compound synthesis operations. It is also conceivable to increase the blending amount of a solvent, a compatibilizer, or a plasticizer excellent in compatibility with the functional compound in the organic photorefractive material. However, in such a method, the concentration of other functional compounds required in the photorefractive material is lowered, and the photorefractive characteristics are lowered. An object of the present invention is to provide a photorefractive material that is excellent in phase stability of the material, exhibits excellent photorefractive characteristics over a long period of time, and has a long pot life.
As a result of intensive studies on such problems, the present inventors can use a two or more types of electric field response optical functional compounds to inhibit the crystallization or prolong the time until crystallization. As a result, the present invention was completed. According to the technique of the present invention, the concentration of the functional compound does not decrease unlike the method for increasing the blending amount of the plasticizer.

That is, the present invention provides an organic photorefractive material comprising the following A, B, C and D group components.
A: Organic polymer compound B: Combination of N- (4-nitrophenyl) -L-prolinol as an electric field response optical functional compound and at least one compound selected from the following compound group:
N- (4-nitrophenyl) -L-prolinol methyl ether, (s)-(−)-N- (5-nitro-2-pyridyl) prolinol, [[4- (hexahydro-1H-azepine-1 -Yl) phenyl] methylene] propanedinitrile, 4- (2,2-dicyanovinyl) -N-ethyl-N- (5-hydroxypentyl) aniline, and 4- (2,2-dicyanovinyl) -N, N-bis (2-methoxyethyl) aniline C: sensitizer D: plasticizer Further, the preferred organic photorefractive material of the present invention is such that the organic polymer compound is polymethyl methacrylate and the sensitizer is 2, 4,7-trinitro-9-fluorenone and the plasticizer is 2- (1,2-cyclohexanedicarboximido) ethyl propionate. Moreover, each compounding quantity of the component of A, B, C, and D in the organic photorefractive material of the present invention is 10 to 50% by weight of the organic polymer compound, 0.01 to 50% by weight of the electric field response optical functional compound, and increased. It is preferably 0.01 to 25% by weight of the sensitizer and 50% by weight or less of the plasticizer. In particular, the compounding amount of N- (4-nitrophenyl) -L-prolinol in the electric field response optical functional compound is preferably 50 to 90% by weight. Furthermore, the present application provides an optical recording material and a recording element using the photorefractive material.

  According to the present invention, an organic photorefractive material exhibiting stable characteristics can be obtained without requiring a complicated synthesis operation in the production of the photorefractive material, and can be used over a long period of time.

Detailed description of the invention

(A) Organic polymer compound The material of the present invention requires an electric field responsive optical functional compound and a sensitizer that forms a charge transfer complex therewith. These are low molecular crystalline compounds (powder). For this reason, the charge transfer complex is hardly formed by simple mixing, and is not suitable for practical use because of no molding processability. For this reason, an organic polymer compound in which these compounds are uniformly mixed and dispersed is used. As such an organic polymer compound, it is necessary that both the electric field response optical functional compound and the sensitizer have good compatibility, and these compounds are uniformly dispersed and mixed to be transparent and free from scattering.

  In addition, an organic polymer compound that forms a charge transfer complex between an electric field response optical functional compound and a sensitizer is not preferable because it may increase light absorption loss. Further, an organic polymer compound that does not absorb a large amount in the absorption region of the charge transfer complex formed from the electric field response optical functional compound and the sensitizer is preferable. Accordingly, the organic polymer compound has good compatibility, good moldability, optical transparency, and does not have the polar functional group described for the electric field response optical functional compound and sensitizer. Is preferred.

  As such an organic polymer compound, polymethyl methacrylate (PMMA) is particularly preferable. Other poly t-butyl methacrylate (PtBuMA), polypropyl methacrylate (PPMA), poly (vinyl butyral) (PVB), poly (vinyl acetate) ) (PVAc), polycarbonate (PC), etc. may be used.

  Further, in order to maintain stable photorefractive characteristics, an organic polymer compound excellent not only in transparency but particularly in heat resistance and weather resistance is preferable. As such a highly transparent and highly heat-resistant polymer compound, polyimides, polyether ketones, polyether sulfones and the like are preferable. The thermodynamic properties of photorefractive materials made from a mixture of several compounds are thought to reflect the thermodynamic properties of the added organic polymer compound. Therefore, in order to maintain stable photorefractive properties, it is particularly resistant to heat. Organic polymer compounds having excellent properties and weather resistance are preferred.

  When these organic polymer compounds are incorporated in a small amount, the compatibility is lowered. On the other hand, when the amount is too large, the concentration of other functional compounds may be lowered and the properties may be lowered. Accordingly, the blending amount is preferably 10 to 50% by weight based on the total composition.

(B: electric field response optical functional compound)
The refractive index of the electric field-responsive optical functional compound used in the present invention varies depending on the strength of the spatial electric field formed by the function of the component of the group A. Such a phenomenon in which the refractive index changes is presumed to be caused by the molecular orientation of molecules having large birefringence being changed by an electric field, or by the Pockels effect or Kerr effect. Examples of such electric field responsive optical functional compounds include those having large birefringence such as nonlinear optical dyes, liquid crystal compounds, and imides.

  In the present invention, different compounds are used as electric field response optical functional compounds. Such a combination improves the phase stability. Examples of the field response optical functional compound used in the material of the present invention include N- (4-nitrophenyl) -L-prolinol (formula B1), N- (4-nitrophenyl) -L-prolinol methyl ether (formula B2), (s)-(−)-N- (5-nitro-2-pyridyl) prolinol (formula B3), [[4- (hexahydro-1H-azepin-1-yl) phenyl] methylene] propanedi Nitrile (formula B4), 4- (2,2-dicyanovinyl) -N-ethyl-N- (5-hydroxypentyl) aniline (formula B5), 4- (2,2-dicyanovinyl) -N, N- Bis (2-methoxyethyl) aniline (formula B6) is preferred.

  In the organic photorefractive material, the blending amount of the electric field response optical functional compound is preferably 10 to 50% by weight, more preferably 10 to 30% by weight in consideration of compatibility with other components. If the blending amount is less than this, the electric field response optical function is lowered. On the other hand, if the blending amount is larger than this range, the concentration of other components is low and the photorefractive characteristics are deteriorated.

In the organic photorefractive material of the present invention, two or more kinds of electric field responsive optical functional compounds are used. Thus, by using together different kinds of electric field response optical functional compounds, it is possible to prevent a decrease in phase stability due to crystallization. This is presumably because the material of the present invention is in a solid state called a solid solution. As a preferable electric field response optical functional compound used here, N- () exhibits excellent photorefractive characteristics even when used alone, and it is easy to obtain a solid solution from two similar compounds (pigments). Examples of the field-responsive optical functional compound include 4-nitrophenyl) -L-prolinol (formula B1) and N- (4-nitrophenyl) -L-prolinol methyl ether (formula B2). Since these are similar in structure and each compound alone exhibits photorefractive properties, it is preferable to select them.
In combining these electric field response optical functional compounds, the above-mentioned other dyes are added to N- (4-nitrophenyl) -L-prolinol having the highest photorefractive characteristics when used alone in the dye. Inhibits crystallization. Therefore, 50 to 90% by weight of N- (4-nitrophenyl) -L-prolinol is blended in the total amount of the compounded field response optical functional compound, and the remaining 10 to 50% is combined with other field response optical functional compounds. It is preferable to do this.

(C: sensitizer)
In order to generate carriers, it is necessary to absorb irradiation light to the photoconductive compound. A single photoconductive compound usually generates carriers efficiently only for light having a wavelength of 350 nm or less. Therefore, in the photorefractive material, a sensitizer is necessary for improving absorption of long wavelength light having a visible wavelength (300 to 800 nm) or longer. The sensitizer is known to form a charge transfer complex together with the photoconductive compound, absorbs light up to about 800 nm, generates carriers, and the generated carriers are transported by the photoconductive material.

The sensitizer used in the present invention is preferably one that forms a charge transfer complex with the photoconductive compound. Such sensitizers include 2,4,7-trinitro-9-fluorenone (formula C1), 2,4,7-trinitro-9-fluorenylidene malonitrile (formula C2), dimethyl terephthalate (formula C3), p-dicyanobenzene (formula C4), and C ₆₀ (formula C5), although such C ₇₀ (formula C6) are known, among these, considering the compatibility of the blend components with one another, 2, 4,7-trinitro-9-fluorenone is preferred.

    Other sensitizers include fluorene derivatives such as 2,4-dinitrofluorene, 9-oxo-9H-thioxanthene-3-carboxylic acid-10,10 dioxide and 9-oxo-9H-thioxanthene-3-carboxy. Thioxanthenes such as amide-10,10 dioxide, and cyanoethylenes such as tetracyanoethylene and 7,7,8,8-tetracyanoquinodimethane may also be used.

  The blending amount of the sensitizer is 0.01 to 20% by weight, preferably 0.1 to 20% by weight in the organic photorefractive material. When the amount of the sensitizer is less than this range, the carrier generation efficiency is low. On the other hand, if the amount exceeds this range, the amount of charge generation increases, but the light absorption of the charge transfer complex generated from the sensitizer and the organic photoconductive compound becomes too strong, and the signal is generated when the photorefractive material is a light modulation element. It causes a decrease in light intensity.

また、リン酸トリクレジル、フタル酸ジオクチルエステル、フタル酸ブチルベンジルエステル、ジブチルスズジラウリン酸エステルなど一般的な可塑剤及び下記の式Ｄ６、式Ｄ７の化合物が挙げられる。 (D: Plasticizer)
In the present invention, the plasticizer serves as a solvent or compatibilizer for uniformly mixing the above-described components, and improves the moldability of the material. As such a plasticizer, those having characteristics similar to those of the organic polymer compound are preferable, and 2- (1,2-cyclohexanedicarboximido) ethyl propionate (AX22) is particularly preferable as a plasticizer exhibiting excellent compatibility. ) (Formula D1) is preferred. Other plasticizers include 2- (1,2-cyclohexanedicarboximido) ethyl butyrate (AX23) (formula D2), 2- (1,2-cyclohexanedicarboximido) ethyl benzoate (AXPH) ( Formula D3), 2- (1,2-cyclohexanedicarboximido) ethyl acrylate (AX14) (Formula D4), 2- (phthalimido) ethyl propionate (AX24) (Formula D5).

Further, general plasticizers such as tricresyl phosphate, dioctyl phthalate, butyl benzyl phthalate, and dibutyltin dilaurate, and compounds of the following formulas D6 and D7 may be mentioned.

  In the photorefractive material of the present invention, the blending amount of the plasticizer is usually preferably 5 to 70% by weight and more preferably 10 to 65% by weight in consideration of compatibility with other components. Phase separation may occur if the plasticizer content is outside this range.

(Preparation of photorefractive molding)
Next, a method for producing a photorefractive molded body using each of the above components will be described. The photorefractive material of the present invention exhibits photorefractive characteristics even when there is no applied voltage. It should be noted that in forming, a transparent and uniform film is finally obtained.

(Uniform mixing method)
The solid content in the photorefractive molded body needs to be mixed uniformly. Therefore, the solid content is dissolved in a highly polar solvent and sufficiently stirred and mixed until uniform. The solid content concentration in the solvent may be a concentration that enables uniform dissolution, but the solid content concentration is 1 to 20% by weight so that operations such as solution viscosity at the time of mixing and drying necessary for film formation are easy. It is preferable to dissolve.

(Molding method)
Using the mixed solution thus obtained, a film is produced by a casting method or the like to produce a practical photorefractive material. In addition, the form of the photorefractive material of this invention is not limited to a film, It can change suitably according to the intended purpose.
For example, in order to create a film by a casting method, a smooth film surface is obtained by directly applying a film on a substrate such as a glass plate by spin coating or dripping, and casting a solution according to a desired film thickness and shape. Get. Next, the solvent is removed from the cast solution by heating or the like under reduced pressure to form a film.

Next, the present invention will be described more specifically with reference to examples and comparative examples.
[Examples 1 to 7, Comparative Example 1]
The components of the following groups were blended in the proportions shown in Table 1 to prepare organic photorefractive materials.

(Sample preparation)
(A) Organic polymer compound The polymethylmethacrylate used by Wako Pure Chemical Industries was used as it was.

(B) Electric field response optical functional compound
N- (4-Nitrophenyl) -L-prolinol (formula B1)
(s)-(−)-N- (5-nitro-2-pyridyl) prolinol (formula B3)
A product made by Tokyo Chemical Industry Co., Ltd. was purchased and used as it was.

[[4- (Hexahydro-1H-azepin-1-yl) phenyl] methylene] propanedinitrile (formula B4) was synthesized according to the following method:
25.1 g (340 mmol) of lithium carbonate, 8.9 g (72 mmol) of 4-fluorobenzaldehyde and 7.2 g (72 mmol) of hexahydroazepine were added to 200 ml of anhydrous DMF and stirred at 50 ° C. for 24 hours. 300 ml of water was added to the reaction solution, extracted with chloroform, and the organic layer was washed with saturated brine. The reaction mixture obtained by distilling off the solvent was produced by column chromatography (filler Wakogel C300 (manufactured by Wako Pure Chemical Industries, Ltd.), developing solvent hexane: ethyl acetate mixed solvent) to produce 1-formyl-4- (hexahydro-1H -Azepin-1-yl) benzene (4.53 g) was obtained.
1-Formyl-4- (hexahydro-1H-azepin-1-yl) benzene (4.53 g, 22 mmol), malonitrile (2.3 g, 34 mmol) and dimethylaminopyridine (1.37 g) were added to methanol (15 ml) at 40 ° C. for 24 hours. Stir. The reaction mixture obtained by distilling off the solvent was recrystallized and purified with methylene chloride to obtain the desired product. Yield 78%

4- (2,2-dicyanovinyl) -N, N-bis (2-methoxyethyl) aniline (formula B6) was synthesized according to the following:
N, N-bis (2-methoxyethyl) aniline (13.9 g, 55.5 mmol) was added to anhydrous dimethylformamide, which was added with 5.8 ml of phosphorus oxychloride under ice-cooling and stirred at room temperature for 30 minutes. Stir at 20 ° C. for 20 hours. 600 ml of water was poured into the reaction solution, and extracted with ether and chloroform in this order. After drying the organic layer over anhydrous magnesium sulfate, the solvent was distilled off and the reaction mixture obtained was purified by column chromatography to obtain 11.8 g of N, N-bis (2-methoxyethyl) -4-formylaniline. It was. Yield 77%
Finally, 3.3 g (50 mmol) of dicyanomalonic acid, 10.8 g (45.6 mmol) of N, N-bis (2-methoxyethyl) -4-formylaniline, and 0.7 g (4. 4 of N, N-dimethylaminopyridine). 3 mmol) was added to 60 ml of isopropyl and stirred at 40 ° C. for 3 days. The reaction mixture obtained by distilling off the solvent was added to ether and washed with water. The organic layer was dried over magnesium sulfate, the solvent was distilled off, and the residue was further purified by column chromatography to obtain 12.5 g of the target substance. Yield 67%

N- (4-nitrophenyl) -L-prolinol methyl ether (formula B2) was synthesized according to the following synthesis method:
Oily sodium hydride (0.53 g, 13.5 mmol) was washed with hexane and dried by vacuum drying. After making the atmosphere nitrogen, 30 ml of N- (4-nitrophenyl) -L-prolinol (1.0 g, 4.5 mmol), iodomethane (1.1 ml, 2.55 g, 18 mmol) and anhydrous tetrahydrofuran was added, and 1 at room temperature. Stir for hours. After the reaction, brine was added and the aqueous phase was extracted with tetrahydrofuran. After drying the organic phase with magnesium sulfate, 1.0 g (yield 94%) of yellow powder was obtained by silica gel column chromatography using dichloromethane as a developing solvent. Further, recrystallization was performed with methanol to obtain 0.65 g of yellow crystals.

4- (2,2-dicyanovinyl) -N-ethyl-N- (5-hydroxypentyl) aniline (formula B5) was synthesized according to the following method:
N-ethylaniline (16 ml), acetic acid (5-bromo) pentyl (20 ml, 119.6 mmol) and triethylamine (20 ml) were added to toluene (125 ml), and the mixture was stirred at 120 ° C. for 19 hours. After the precipitate contained in the reaction mixture is filtered off, the low-boiling product is distilled off and further purified by column chromatography to obtain 14.8 g of N-ethyl-N- (5-acetyloxy) pentylaniline. It was. Yield 50%
Next, 5.8 ml of phosphorus oxychloride was added to anhydrous dimethylformamide and the mixture was stirred for 30 minutes at room temperature, and then 13.9 g (55.5 mmol) of N-ethyl-N- (5-acetyloxy) pentylaniline was added. And stirred at 90 ° C. for 20 hours. 600 ml of water was poured into the reaction solution, and extracted with ether and chloroform in this order. After drying the organic layer over anhydrous magnesium sulfate, the solvent was distilled off and the resulting reaction mixture was purified by column chromatography to obtain 11.8 g of N-ethyl-N- (5-acetyloxy) pentyl-4-formylaniline. Got. Yield 77%
Finally, 3.3 g (50 mmol) of dicyanomalonic acid, 10.8 g (45.6 mmol) of N-ethyl-N- (5-acetyloxy) pentyl-4-formylaniline, 0.7 g of N, N-dimethylaminopyridine ( 4.3 mmol) was added to 60 ml of isopropyl and stirred at 40 ° C. for 3 days. The reaction mixture obtained by distilling off the solvent was added to ether and washed with water. The organic layer was dried over magnesium sulfate, the solvent was distilled off, and the residue was further purified by column chromatography to obtain 12.5 g of the target substance. Yield 67%

(C) Sensitizer 2,4,7-trinitro-9-fluorenone (formula C1) was purchased from Tokyo Chemical Industry Co., Ltd. and used as it was.

(D) Plasticizer 2- (1,2-cyclohexanedicarboximido) ethyl pyropionate (formula D1) was synthesized according to the following method.
To 149 g (967 mmol) of phthalic anhydride, 200 ml of toluene and 62 g (1000 mmol) of ethanolamine were added and stirred at 80 ° C. for 2 hours, and then 15 g (44 mmol) of titanium butanate was added and refluxed for 19 hours. After cooling, 100 ml of water was added to the reaction solution, and the white precipitate precipitated was separated by filtration to recover the organic layer. The reaction mixture obtained by distilling off the solvent was purified by column chromatography (filler: silica gel, developing solvent: mixed solvent of n-hexane and ethyl acetate) to obtain N- (2-hydroxyethyl) cyclohexanedicarboximide. Obtained (200 g).

  To 52 g (272 mmol) of N- (2-hydroxyethyl) cyclohexanedicarboximide, 57 ml of pyridine, 200 ml of toluene and 30 ml (347 mmol) of propionic acid chloride were added and stirred at 90 ° C. for 19 hours. The reaction mixture was washed with diluted hydrochloric acid, sodium bicarbonate aqueous solution, and brine in this order to recover the organic layer. The reaction mixture obtained by distilling off the solvent was purified by column chromatography (filler: silica gel, developing solvent: mixed solvent of n-hexane and ethyl acetate) to obtain the desired product. Yield 45g, Yield 65%

(Method for evaluating photorefractive characteristics)
In order to evaluate the photorefractive effect of the organic material obtained in the present invention, irradiation with coherent light was performed without applying voltage. The evaluation apparatus shown in FIG. 1 was used for these evaluations. That is, the obtained material 1 was sandwiched between a glass plate 2 and a spacer 3 of glass beads having a particle diameter of 100 μm (SPM-100 manufactured by Union), heated, and depressurized to remove microbubbles in the material.

As evaluation characteristics of the photorefractive molded article, diffraction efficiency, response time, and phase stability were evaluated by the following methods.
(Diffraction efficiency)
The diffraction efficiency indicates the ratio of the intensity of transmitted light and diffracted light when a light beam is incident on a diffraction grating formed by the photorefractive effect. Diffraction efficiency was determined by degenerate four-wave mixing using a 10 mW helium-neon laser as a light source and P-polarized writing and S-polarized reading. At this time, the writing light was incident at ± 9.6 ° with respect to the normal of the sample plane. After the measurement for a predetermined time, the point at which the diffracted light intensity was maximum was determined, and the diffraction efficiency (%) was calculated from the following formula 1 from the ratio to the transmitted light intensity.
Diffraction efficiency = {diffracted light intensity / (diffracted light intensity + transmitted light intensity)} × 100 (Equation 1)
(Response time)
The response time means the time until the diffracted light intensity becomes maximum.
(Phase stability evaluation)
The sample was stored at 60 ° C., and when visually observed, the case where there was no crystal deposition after standing for more than 2 months was evaluated as “◎”, about 1 to 2 months ○, and the case where crystal deposition occurred in about 1 month was evaluated as “x”.
(result)
As is clear from Table 1, the photorefractive material of the present invention using two or more types of field response optical functional compounds has high phase stability unlike the photorefractive material of the comparative example using one type. Of these compounds, those containing a large amount of N- (4-nitrophenyl) -L-prolinol can provide high photorefractive characteristics. Particularly in Examples 1 and 3, conventional photorefractive materials are excellent. The same characteristics were obtained.

It is the schematic of the measuring apparatus which performs the characteristic evaluation of a photorefractive material.

Explanation of symbols

1 Photorefractive material 2 Glass plate 3 Spacer

Claims (6)

An organic photorefractive material comprising the following A, B, C and D group components.
A: Organic polymer compound B: Combination of N- (4-nitrophenyl) -L-prolinol as an electric field response optical functional compound and at least one compound selected from the following compound group:
N- (4-nitrophenyl) -L-prolinol methyl ether, (s)-(−)-N- (5-nitro-2-pyridyl) prolinol, [[4- (hexahydro-1H-azepine-1 -Yl) phenyl] methylene] propanedinitrile, 4- (2,2-dicyanovinyl) -N-ethyl-N- (5-hydroxypentyl) aniline, and 4- (2,2-dicyanovinyl) -N, N-bis (2-methoxyethyl) aniline C: sensitizer D: plasticizer The organic polymer compound is polymethyl methacrylate, the sensitizer is 2,4,7-trinitro-9-fluorenone, and the plasticizer is 2- (1,2-cyclohexanedicarboximido) ethyl propionate. The organic photorefractive material according to claim 1. The compounding amounts of the components A, B, C, and D in the organic photorefractive material are 10 to 50% by weight of the organic polymer compound, 0.01 to 50% by weight of the electric field response optical functional compound, and 0. The organic photorefractive material according to claim 1 or 2, wherein the organic photorefractive material is 01 to 25% by weight and the plasticizer is 50% by weight or less. The organic photorefractive material according to any one of claims 1 to 3, wherein the compounding amount of N- (4-nitrophenyl) -L-prolinol in the electric field response optical functional compound is 50 to 90% by weight. An optical recording material comprising the material according to claim 1. A recording element comprising the material according to claim 1.

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