JP2848835B2 - Nonlinear optical element - Google Patents

Description

Description: BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a device made of a nonlinear optical material, and particularly to a device using a nonlinear optical material suitable for forming a portion such as a thin film or a fiber waveguide. Related to the element.

[Prior Art] Conventionally, as a nonlinear optical material, an inorganic single crystal such as KDP or LiNbO ₃ or an organic single crystal such as urea has been known and used for a wavelength conversion element of a laser, for example. However, it is technically difficult to obtain a single crystal having a sufficient size with such a single crystal, and an inexpensive single crystal cannot be obtained.

Furthermore, it is known that if a thin film or fiber waveguide is formed from a nonlinear optical material, incident light can be focused and the nonlinear optical effect can be improved. Is not easy to form. For example, in LiNbO ₃ , diffusion and exchange of Ti and H are performed on a single crystal, which is time-consuming and difficult to control.

Further, for example, attempts have been made to obtain a large thin film or fiber single crystal by a vapor deposition method or zone melting in a capillary. [Naya B.K., "AS CS Symposia" (Nayar, B.
K .; ACS sym.) 153, 1983]. However, in such a method, the second harmonic generation (SH
G), it is not easy to control the single crystal to the phase-matched orientation necessary for efficiently obtaining the third harmonic generation (THG).

As described above, the nonlinear optical element composed of only a single crystal has problems in workability, cost, and the like. Therefore, as one means for solving such a problem, a nonlinear optical element in which a fine nonlinear optical compound is dispersed and oriented in a polymer has been proposed. The polymer is usually called a host polymer, and the dispersed compound is called a guest compound.

As an optical material comprising a host polymer and a guest compound, for example, after dissolving an azo dye in a polymethyl methacrylate resin to form a thin film, heating to a glass transition point or higher,
Some are formed by applying voltage and cooling while arranging the azo dye molecules to fix the structure, and a nonlinear optical constant of 6 × 10 ⁻⁹ esu has been observed in this material. [Singer K.D., Thorn J.E., Larama S.J. "Applied Physics Letters" (Singer, KD, Sohn, JEand Lalam
a, SJ; Appl. Phys. Lett., 49 , 248, 1986].

For example, JP-A-62-84139 discloses a nonlinear optical element using an acrylamide resin as a host polymer and using a nonlinear optically responsive organic compound as a guest compound.

Further, for example, JP-A-57-45519, U.S. Pat.
No. 8873 also discloses an element using a host polymer and a guest compound which is a nonlinear optically responsive organic compound.

For example, Japanese Patent Application Laid-Open No. 62-246962 discloses an element formed by growing a compound having a chiral center (guest compound) in a polyoxyalkylene oxide (host polymer).

The device including the host polymer and the guest compound as described above is superior to a single crystal device in terms of workability, cost, and the like, and is suitable for device fabrication.

However, such an element has the following problems. That is, in order to increase the nonlinear optical effect of the element, the content of the guest compound in the solid solution is increased. However, a large amount of the low molecular polar compound, which is a guest, is added to the polymer, for example, at least 20% by weight or more. It is difficult to perform uniform blending at the molecular level, and a defect such as partial crystallization of the guest molecule and crystallization may occur.

Further, in such a blend polymer, particularly when the content of the low-molecular polar guest molecule is increased, the flexibility of the polymer itself is lost, and the mechanical strength tends to be greatly reduced.

Regarding the second-order nonlinear optical effect, even if the guest molecule has a large polarizability β, if it is a non-oriented centrally symmetric crystal, it can be mixed with a conventional polymer by SHG.
No activity or negligible activity. for that reason,
It was necessary to form a film, apply an electric or magnetic field, or stretch and orient the film.

Furthermore, as shown in the report of Zinger K. D. et al., The energy of the electric field is smaller than the thermal energy, that is, the tendency of the thermal diffusion is strong, so that even when the electric field is applied to near the dielectric breakdown, a good molecule is obtained. Orientation and a large nonlinear susceptibility could not be obtained much. In order to solve such a problem, a proposal has been made to use a polymer having liquid crystallinity as a host polymer.

For example, an attempt has been made to arrange polar molecules using a polymer liquid crystal as a host and polar molecules as a guest by using the electric field orientation of the polymer liquid crystal, and SHG has been observed by applying a voltage [Meredith G.R. Macromolecules "(Meredith, GRet al; Macromolecule
s,) 15 , p. 1385, 1982].

In addition, in order to solve the above-described problem, it has been proposed that a liquid crystal polymer itself be given nonlinear optical properties and that no guest compound be used.

For example, JP-A-62-190230, JP-A-62-190233
JP-A-62-190208 and JP-A-62-201419 disclose liquid crystalline polymers having nonlinear optical properties such as polyvinyl-based polymers, polyoxyalkyl-based polymers, and polycyclohexane-based polymers. Is disclosed.

However, even in the devices using these liquid crystalline polymers, the molecular orientation and the nonlinear optical property obtained from the orientation are not yet sufficient, and a large nonlinear optical effect cannot be obtained.

On the other hand, in order to further improve the asymmetric central molecular orientation,
JP-A-63-192030 discloses a side chain type polymer liquid crystal having a nonlinear optical side chain having a chiral group. This side-chain type polymer liquid crystal has a structure similar to that of dimethylaminonitrostilbene, and has a similarly large molecular nonlinear susceptibility (about 10 times as large as 2-methyl-4-nitroaniline (MNA)). It is an inorganic material that is practically used by copolymerizing chains, and has been confirmed to be about 500 times the KDP and the same level of nonlinearity as the MNA. However, the molecular nonlinear susceptibility of the side chain having nonlinearity used here is still small, and the degree of molecular orientation is insufficient. Also,
The side-chain type polymer liquid crystal used here is not a ferroelectric liquid crystal having a chiral smectic C phase, and thus has poor memory of molecular orientation.

Japanese Patent Application Laid-Open No. 63-204235 discloses a nonlinear optical element in which a ferroelectric side-chain type polymer liquid crystal exhibiting a chiral smectic C phase is used in the core or cladding of an optical fiber in order to obtain asymmetric central alignment. Is disclosed,
No non-linear molecular structure has been introduced, and the non-linearity is only about 10 times that of an amorphous polymer doped with dimethylaminonitrostilbene and subjected to electric field alignment.

[Problems to be Solved by the Invention] The present invention has already disclosed in Japanese Patent Application No. 63-179097 that a guest organic compound having a large non-linear polarizability can be easily and uniformly contained in a host polymer liquid crystalline compound. Compatible, and the second and third order nonlinear optical effects of the guest organic compound are not reduced by blending with the liquid crystal compound of the host polymer, and are flexible even when a large amount of the guest organic compound is contained. To provide a novel solid solution having excellent mechanical strength and processability, and in the second-order nonlinear optical effect, β is large, but the guest organic compound alone is a centrally symmetric crystal, and exhibits no SHG activity. The purpose of the present invention is to provide a solid solution capable of expressing a large SHG activity by blending a guest organic compound (not shown) with the liquid crystal compound of the host polymer. It showed a nonlinear optical material comprising a polymer liquid crystal compound and a non-linear compounds.

Compared with such a conventional method, the present invention has a large degree of asymmetric central alignment, exhibits a large nonlinearity due to the structure peculiar to the ferroelectric polymer liquid crystal, and has excellent moldability. It is an object of the present invention to provide a nonlinear optical material showing the following.

It is another object of the present invention to provide a nonlinear optical element which has a portion formed by subjecting the nonlinear optical material to an orientation treatment, is easy to produce, has high memory properties, and exhibits excellent properties having switching characteristics. is there.

Means for Solving the Problems The present inventors have conducted intensive studies to achieve the above object, and as a result, have found that a material containing a ferroelectric polymer liquid crystal and a nonlinear optical compound has a large nonlinearity. Heading The present invention has been completed.

That is, in the present invention, a non-linear optical material containing a side chain type ferroelectric polymer liquid crystal and a non-linear optical compound is sandwiched as a non-linear optical waveguide between an upper electrode and a lower electrode at least one of which has an alignment film. Is a nonlinear optical element.

 Hereinafter, the present invention will be described in detail.

It is considered that the nonlinear optical material of the present invention shows good orientation and nonlinearity for the following reasons.

That is, a side chain type ferroelectric polymer liquid crystal (hereinafter, abbreviated as “ferroelectric polymer liquid crystal”) generally has its inversion symmetry center removed in the liquid crystal structure. A polarization component parallel to the twice rotation axis appears. This is important for second-order nonlinear optics,
Due to the presence of such a polarization component, a second-order nonlinear susceptibility is generated even in the ferroelectric polymer liquid crystal alone, and good nonlinearity as a whole material is exhibited in combination with the nonlinearity of the nonlinear optical compound.

The above-mentioned conventional liquid crystal host polymer (for example, the one reported by Meredit Giar et al.) Is a polymer liquid crystal compound that is not ferroelectric.

As the guest organic compound which is a nonlinear optical compound having nonlinear optical characteristics used in the present invention, a guest organic compound having a secondary molecular nonlinear susceptibility β of 10 × 10 ⁻³⁰ esu or more is desirable. This is because the guest organic compound effectively aligns with respect to the internal electrolysis accompanying the alignment of the ferroelectric polymer liquid crystal, and more preferably, the secondary molecular nonlinear susceptibility of 20 × 10 ⁻³⁰ esu or more. Is used.

In the nonlinear optical compound, it is desirable that the anisotropy due to the molecular shape developed when combined with the host polymer liquid crystal and the anisotropy of the transition moment thereof match. As a result, control for performing phase matching is facilitated, and the degree of freedom in device implementation is improved. The coincidence of the anisotropy of the nonlinear optical compound can be estimated from the dichroic ratio, and is preferably 0.3 or more.

Next, as the ferroelectric polymer liquid crystal used in the present invention, a side chain polymer liquid crystal can be used. The side chain type polymer liquid crystal used in the present invention has the following structure.

(* Is asymmetric carbon, R is H, Cl, CH ₃ , n = 5 to 50,000, m =
0-30, p = 1-20, q = 1-20. The ferroelectric polymer liquid crystal used in the present invention is not limited to the above structure.

Next, the nonlinear optical compound having a secondary molecular nonlinear susceptibility of 10 × 10 ⁻³⁰ esu or more used in the nonlinear optical material of the present invention has an electron-donating group or an electron-withdrawing group in a skeleton having a π-atom system. It is a structure having at least one.

Examples of the skeleton having a π-electron system include monosubstituted benzene derivatives, disubstituted benzene derivatives, trisubstituted benzene derivatives, tetrasubstituted benzene derivatives, monosubstituted biphenyl derivatives, disubstituted biphenyl derivatives, trisubstituted biphenyl derivatives, tetrasubstituted biphenyl derivatives, monosubstituted Substituted naphthalene derivative, di-substituted naphthalene derivative, tri-substituted naphthalene derivative, tetra-substituted naphthalene derivative, mono-substituted pyridine derivative, di-substituted pyridine derivative, tri-substituted pyridine derivative, tetra-substituted pyridine derivative, mono-substituted pyrazine derivative, di-substituted pyrazine derivative, tri-substituted Substituted pyrazine derivatives, tetra-substituted pyrazine derivatives, mono-substituted pyrimidine derivatives, di-substituted pyrimidine derivatives, tri-substituted pyrimidine derivatives, tetra-substituted pyrimidine derivatives, mono-substituted azulene derivatives, di-substituted azure Derivatives, trisubstituted azulene derivatives, tetrasubstituted azulene derivatives, mono-substituted pyrrole derivative, disubstituted pyrrole derivatives, trisubstituted pyrrole derivatives,
Tetra-substituted pyrrole derivative, mono-substituted thiophene derivative, di-substituted thiophene derivative, tri-substituted thiophene derivative, tetra-substituted thiophene derivative, mono-substituted furan derivative, di-substituted furan derivative, tri-substituted furan derivative, tetra-substituted furan derivative, mono-substituted pyrylium salt derivative , Di-substituted pyrylium salt derivatives, tri-substituted pyrylium salt derivatives, tetra-substituted pyrylium salt derivatives, mono-substituted quinoline derivatives, di-substituted quinoline derivatives, tri-substituted quinoline derivatives, tetra-substituted quinoline derivatives, mono-substituted pyridazine derivatives, di-substituted pyridazine derivatives, tri- Substituted pyridazine derivatives, tetra-substituted pyridazine derivatives, mono-substituted triazine derivatives, di-substituted triazine derivatives, tri-substituted triazine derivatives, mono-substituted tetrazine derivatives, di-substituted tetrazine derivatives, mono-substituted Surasen derivatives, disubstituted anthracene derivatives, trisubstituted anthracene derivatives, can be used tetrasubstituted anthracene derivatives.

Examples of the electron donating substituent bonded to these include an amino group, an alkyl group (methyl, ethyl, isopropyl, n
-Propyl, n-butyl, t-butyl, sec-butyl,
n-octyl, t-octyl, n-hexyl, cyclohexyl, etc.), alkoxy group (methoxy, ethoxy, propoxy, butoxy, etc.), alkylamino group (N-methylamino, N-ethylamino, N-propylamino,
N-butylamino, etc.), hydroxyalkylamino groups (N-hydroxymethylamino, N- (2-hydroxyethyl) amino, N- (2-hydroxypropyl) amino, N- (3-hydroxypropyl) amino, N- (4-hydroxy) butylamino, etc.), dialkylamino group (N, N-dimethylamino, N, N-diethylamino, N, N-dipropylamino, N, N-dipropylamino, N-methyl-N-ethylamino, N-methyl-
A hydroxyalkyl-alkylamino group (N-hydroxymethyl-N-methylamino, N-hydroxymethyl-N-ethylamino,
N-hydroxymethyl-N-ethylamino, N- (2
-Hydroxyethyl) -N-methylamino, N- (2
-Hydroxyethyl) -N-ethylamino, N- (3
-Hydroxypropyl) -N-methylamino, N-
(2-hydroxypropyl) -N-ethylamino, N
-(4-hydroxybutyl) -N-butylamino and the like) dihydroxyalkylamino group (N, N-dihydroxymethylamino, N, N-di- (2-hydroxyethyl) amino, N, N-di- (2-hydroxypropyl) amino, N, N-di- (3-hydroxypropyl)
Amino, N-hydroxymethyl-N- (2-hydroxyethyl) amino, etc.), a mercapto group, a hydroxy group, or the like can be used.

Examples of the electron-withdrawing substituent include a nitro group, a cyano group, a halogen atom (a chlorine atom, a bromine atom, an iodine atom,
A fluorine atom), a trifluoromethyl group, a carboxyl group, a carboxyester group, a carbonyl group or a sulfonyl group.

Next, specific examples of the nonlinear optical compound used in the present invention include the following compounds (1) to (33).

(1) o-nitroaniline (2) p-nitroaniline (33) Poly-γ-benzyl-L-glutamate The non-linear optical material of the present invention comprises an electron-donating group and an electron-withdrawing compound in the ferroelectric polymer liquid crystal described in detail above. It can be obtained by, for example, dispersing one or two or more kinds of non-linear optical compounds typified by the above-mentioned examples of compounds having a sexual group, uniformly.

When the nonlinear optical material of the present invention is dissolved in a solvent, a thin film is used because the viscosity can be easily adjusted and a uniform thin film can be easily obtained by a spin coating method, a dipping method, a casting method, or the like. Suitable for nonlinear optical elements.

When the ferroelectric polymer liquid crystal and the non-linear optical compound are heated and melted and mixed, it is possible to obtain a fiber-like or film-like material by extruding from a die. Good fibers and films can also be obtained.

One or more of the above various methods can be combined, and a good film can be obtained also by a method in which a film obtained by casting is hot-pressed and melt-mixed. The thickness of the nonlinear optical material layer used as a thin film varies depending on the application, but is usually 0.01 μm to 10 μm.
0 mm, preferably 0.1 μm to 1 mm is used. 0.01μm
Below this, it is difficult to trap light effectively,
If it exceeds 0 mm, it is not effective because the nonlinear optical effect occurs only in a part of the element.

The amount of the nonlinear optical compound added to the ferroelectric polymer liquid crystal is 0.1 to 80% by weight. If the content is less than 0.1% by weight, the nonlinear optical effect of the nonlinear optical compound is reduced, which is not effective. On the other hand, if it exceeds 80% by weight, it has an adverse effect.
More preferably, it is desirable to add the nonlinear optical compound at a ratio of 1 to 50% by weight.

Further, in the nonlinear optical material of the present invention, the nonlinear optical compound is uniformly dispersed in the ferroelectric polymer liquid crystal to form a solid solution.

The non-linear optical material of the present invention obtained as described above shows a large second-order non-linear effect even without performing an alignment treatment. In particular, even a non-linear optical compound such as P-nitroaniline, which has central symmetry as a single crystal and does not exhibit second harmonic (SHG) activity, is blended with a ferroelectric polymer liquid crystal. As a result, a very large SHG activity is expressed. One of the reasons for this is that strong interaction between the ferroelectric polymer liquid crystal having the liquid crystal structure from which the inversion symmetry center is removed and the guest molecule makes it difficult for the guest molecule to have the central symmetry. Is probably working.

In addition, the ferroelectric polymer liquid crystal used in the present invention is a polymer, and therefore has high stability in terms of maintaining an alignment normal state. Similarly, a low-molecular ferroelectric liquid crystal having a liquid crystal structure in which the center of symmetry has been removed. Dielectric liquid crystal also has a function of maintaining the alignment state, but is excellent in that it is a low molecular weight compound, and thus is easily disturbed by shock or the like.

Also, compared to materials using other polymers, since they are ferroelectric liquid crystals, they are very excellent in that they have memory properties. These factors greatly contribute to the stability of nonlinearity of the nonlinear optical material of the present invention with time, and in fact, the nonlinear optical material containing the ferroelectric polymer liquid crystal of the present invention and the nonlinear optical compound has a high nonlinearity. The properties are stored semi-permanently at room temperature.

In the nonlinear optical material of the present invention, it is desirable to form a nonlinear optical element of the present invention by forming a thin film waveguide or a fiber as a nonlinear optical portion on a substrate and performing an orientation treatment so that phase matching can be performed.

The nonlinear optical material of the present invention is formed on a substrate made of any material such as glass, plastic or metal, and if necessary, a transparent electrode such as an ITO film or a patterned electrode is formed on the substrate. To form a recording medium or a display element.

In order to give the characteristic for orienting the non-linear optical material of the present invention provided on the substrate as described above, the following methods can be mentioned.

(1) Horizontal alignment (the molecular axis direction of the ferroelectric polymer liquid crystal is oriented horizontally with respect to the substrate surface) Rubbing method A solution coating method, vapor deposition, sputtering, or the like on the substrate, for example, silicon monoxide, silicon dioxide , Aluminum oxide, zirconia, magnesium fluoride, cerium oxide, cerium fluoride, inorganic insulating materials such as silicon nitride, silicon carbide, boron nitride, polyvinyl alcohol, polyimide, polyamideimide, polyesterimide, polyparaxylerin, polyester , Forming a film of organic insulating material such as polycarbonate, polyvinyl acetal, polyvinyl chloride, polyamide, polystyrene, cellulose resin, melamine resin, urea resin and acrylic resin, then velvet the surface, unidirectionally with cloth or paper Rubbing Te to form an alignment control film.

Oblique evaporation method An oxide such as SiO or a fluoride or a metal such as Au or Al and an oxide thereof are deposited from an oblique angle of the substrate to form an orientation control film.

The organic or inorganic insulating film shown by the oblique etching method is etched by irradiating an ion beam or oxygen plasma from obliquely to form an orientation control film.

Use of stretched polymer film A polymer film such as polyester or polyvinyl alcohol is stretched.

Grating method A groove is formed on the substrate surface by using photolithography, stamper, or injection. In this case, the ferroelectric polymer liquid crystal is oriented in the groove direction.

(2) Vertical alignment (the molecular axis direction of the ferroelectric polymer liquid crystal is aligned perpendicular to the substrate surface) A vertical alignment film is formed.

A layer having a vertical orientation such as organosilane, lecithin, or polytetrafluoroethylene is formed on the surface of the substrate.

Oblique evaporation The vertical orientation can be provided by appropriately selecting the evaporation angle while rotating the substrate by the oblique evaporation method described in (1)-. Further, after oblique deposition, a vertical alignment agent shown by may be applied.

And further, applying a DC electric field at or above the liquid crystal phase temperature simultaneously with or separately from the alignment treatment to this nonlinear optical element, and cooling the liquid crystal phase temperature or below while applying the voltage,
Better performance is obtained. As a method of applying a vertical electric field, electrodes may be provided on both surfaces of the film, or corona discharge or the like may be used.

Further, the nonlinear optical element of the present invention has excellent memory properties because it has bistability due to interaction with the substrate interface without using an electric field. In order to eliminate the spiral for achieving bistability without using an electric field, the film thickness may be made smaller than the spiral period of the chiral smectic, and specifically, it is preferably 50 μm or less. Also, at that time, the nonlinear optical element of the present invention,
Since each of the bistable states can be stably and rapidly switched by the electric field, the emitted SHG signal can be changed accordingly. Conventional SHG elements
Almost only SHG was generated, and the SHG signal could not be easily modulated by using an electric field in this way. In this respect, the nonlinear optical element of the present invention is excellent and can be used as a high-speed switch light modulation element of a future computer.

EXAMPLES Hereinafter, the present invention will be described in more detail with reference to Examples.

Synthesis Example 1 In this synthesis example, poly-4- [4 ′-(11-acryloyloxyundecanyloxy) bezoyloxy] which is a ferroelectric polymer liquid crystal according to the present invention represented by the following formula (I)
The production of 2-methyl-3-hexyloxyethyl benzoate is illustrated.

Step 1 Synthesis of 4-hydroxybenzoic acid 2-methyl-3-hexyloxyethyl ester 3.2 g of 4-hydroxybenzoic acid and 18.7 g of optically active 2-methyl-3-hexyloxyethanol in benzene together with 1 ml of sulfuric acid for 20 hours Heated to reflux. After concentration of the reaction solution, 6.2 g of the product was obtained by column chromatography (yield
91%).

Step 2 Synthesis of 4- (11-hydroxyundecanyloxy) benzoic acid 5.4 g of p-hydroxybenzoic acid was added to a mixed solvent of ethanol and dioxane, and an aqueous solution containing 6.6 g of potassium hydroxide was added. Bromoundecanol 12.5g
Was added dropwise, and the mixture was heated and circulated for 12 hours. Acidify and extract with ethyl acetate, column chromatography, product 7.
3 g (53% yield) was obtained.

Step 3 Synthesis of 4- (11-acryloyloxyundecanyloxy) benzoic acid 4- (11-hydroxyundecanyloxy) benzoic acid
6.4 g and 5.8 g of acrylic acid were heated under reflux in benzene for 80 hours in the presence of hydroquinone. The solvent was distilled off, and the product was subjected to column chromatography to obtain 2.9 g of the product (yield: 38%).

Step 4 Synthesis of 4- [4 '-(11-acryloyloxyundecanyloxy) benzoyl] benzoic acid 2-methyl-3-hexyloxyethyl ester 4- (11-acryloyloxyundecanyloxy) benzoic acid 1.6 g was heated and refluxed for 3 hours in 20 ml of thionyl chloride in the presence of 2,6-di-t-butylphenol.
The remaining thionyl chloride was distilled off, and anhydrous THF 20m
l and 5 ml of triethylamine were added, and to this was added 1.0 g of 2-methyl-3-hexyloxyethyl 4-hydroxybenzoate at 5 ° C., followed by stirring at 50 ° C. for 4 hours. The mixture was acidified, extracted with ethyl acetate, and subjected to column chromatography to obtain 1.5 g (yield: 48%) of a product.

Polymerization Step 4- [4 '-(11-Acryloyloxyundecanyloxy) benzoyl] benzoic acid 2-methyl-3-hexyloxyethyl ester 0.500 g, 3 mol% azobisisobutyronitrile (AIBN) Was deaerated by freeze-drying in 5 ml of anhydrous toluene, and then polymerized at 60 ° C. for 24 hours. Repeated reprecipitation from methanol, 0.32 g (64%) of the desired polymer
I got

Synthesis Example 2 In this synthesis example, poly-4 ′-(6-acryloyloxyhexyloxy) biphenyl-4-carboxylic acid 2 which is a ferroelectric polymer liquid crystal according to the present invention represented by the following formula (II):
-Illustrates the synthesis of methyl butyl ester.

Step 1 Synthesis of 2-methylbutyl 4'-hydroxybiphenyl-4-carboxylic acid 10.0 g of 4'-hydroxybiphenyl-4-carboxylic acid
And 20.5 g of optically active 2-methylbutanol were heated and refluxed in benzene with 1 ml of sulfuric acid for 20 hours. After filtration and concentration, the product was recrystallized to obtain 11.0 g of the product (83% yield).

Step 2 4 '-(6-hydroxyhexyloxy) biphenyl-
Synthesis of 4-carboxylic acid 2-methylbutyl ester 4'-hydroxybiphenyl-4-carboxylic acid 2-methylbutyl ester 2.84 g, potassium carbonate 4.14 g, 6-chloro-1-hexanol 4.10 g and potassium iodide 4.28 g The mixture was refluxed for 48 hours in acetone. After filtration and concentration, 1.31 g of the product (yield 3
4%).

Step 3 Synthesis of 4 '-(6-acryloyloxyhexyloxy) biphenyl-4-carboxylic acid 2-methylbutyl ester 1.60 g of 4'-(6-hydroxyhexyloxy) biphenyl-4-carboxylic acid 2-methylbutyl ester Was added dropwise in anhydrous benzenetriethylamine in the presence of 2,6-di-t-butylphenol at 4.53 g of acryloyl chloride at 5 ° C., and stirring was continued for 2 hours. The mixture was acidified, extracted with ethyl acetate, and subjected to column chromatography to obtain 1.20 g (yield: 66%) of a product.

Polymerization Step 4 '-(6-Acryloyloxyhexyloxy) biphenyl-4-carboxylic acid 2-methylbutyl ester 1.20 g
Was freeze-degassed in 12 ml of anhydrous toluene together with 3 mol of AIBN, and then polymerized at 60 ° C. for 24 hours. Repeated reprecipitation with methotanol, 1.02 g of the desired polymer (85% yield)
I got

[Measurement of SHG intensity] Next, the SHG intensity was measured in order to examine the nonlinear optical effect of the solid solution obtained in the following example.

Using a Nd: YAG laser as the light source, irradiate light with a wavelength of 1.06 μm (output 17 mJ / pulse) to generate SHG light (0.53
μm) was observed with a photomultiplier.

Reference Example 1 Poly 4- [4 '-(11-acryloyloxyundecanyloxy) benzol] benzoic acid 2-methyl-3-hexyloxyethyl ester (75) produced according to Synthesis Example 1
Wt.) And p-nitroaniline (25 wt.
And homogeneously mixed, and cooled to room temperature. The obtained solid solution was irradiated with an Nd: YAG laser, and the second harmonic was measured by a method based on the powder method. As a result, SHG having an intensity about 25 times that of urea was observed by a photomultiplier. This nonlinearity did not change at all after three months.

Reference Example 2 Poly 4- [4 '-(11-acryloyloxyundecanyloxy) benzoyl] benzoic acid 2-methyl-3-hexyloxyethyl ester (75% by weight) produced according to Example 1 and P -Nitroaniline (25% by weight) was dissolved in dimethylformamide to prepare a cast film.

The obtained solid solution was irradiated with a Nd: YAG laser, and the second harmonic was measured by a method based on the powder method. As a result, SHG having an intensity about 18 times that of urea was observed by a photomultiplier. This nonlinearity did not change at all after three months.

Reference Example 3 Poly (4 '-(6-acryloyloxyhexyloxy) biphenyl-4-carboxylic acid 2-methylbutyl ester (75% by weight) produced by Synthesis Example 2 and P-nitroaniline (25% by weight) Was melted and mixed at 170 ° C., and cooled to room temperature. The obtained solid solution was irradiated with an Nd: YAG laser, and the second harmonic was measured by a method based on the powder method. As a result, SHG having about 17 times the intensity of urea was observed by a photomultiplier. This nonlinearity did not change at all for two months.

Reference Example 4 Poly-4 '-(6-acryloyloxyhexyloxy) biphenyl-4-carboxylic acid 2-methylbutyl ester (75% by weight) produced by Synthesis Example 2 and P-nitroaniline (25% by weight) Was dissolved in THF to prepare a cast film.

The obtained solid solution was irradiated with a Nd: YAG laser, and the second harmonic was measured by a method based on the powder method.
SHG about 15 times stronger than urea was observed by photomultiplier. This nonlinearity did not change at all for two months.

Example 1 The nonlinear optical element 1 shown in FIG. 1 was produced as follows. An ITO film was formed on a glass substrate 11 having a thickness of 1 mm, and Al was evaporated to a thickness of 5000 mm to form a lower electrode 12.
A polyamic acid solution (manufactured by Hitachi Chemical Co., Ltd.)
PIO: nonvolatile content of 3% by weight) was applied by spin coating, and heated at 20 ° C. for 30 minutes, 200 ° C. for 60 minutes, and 350 ° C. for 30 minutes to form a polyimide alignment film layer 13. This was rubbed to give uniaxial orientation.

Next, the non-linear optical material used in Reference Example 2 was spin-coated on the alignment film layer 13 to a thickness of about 1 μm, dried, and Al was deposited thereon to a thickness of 1000 ° The optical waveguide 14 and the upper electrode 15 were formed. Next, cooling was performed at 130 ° C. while applying a DC voltage of 100 V to the lower electrode 12 and the upper electrode 15.

The optical element 1 of the present invention produced as described above was irradiated with a laser beam of 1.06 μm from a laser light source 16 via a modulator 17 and a condenser lens 18 as shown in FIG. Harmonic generation was observed by a photomultiplier.

[Effects of the Invention] As described above, the nonlinear optical material of the present invention exhibits large nonlinearity and excellent moldability due to the structure peculiar to the ferroelectric polymer liquid crystal.

Further, a nonlinear optical element having a portion formed by subjecting the nonlinear optical material to an orientation treatment is easy to produce, and exhibits excellent properties having high memory properties and switching characteristics.

[Brief description of the drawings]

FIG. 1 is a sectional view showing a thin film waveguide type nonlinear optical element produced in Example 1. DESCRIPTION OF SYMBOLS 1 ... Nonlinear optical element, 11 ... Substrate 12 ... Lower electrode, 13 ... Orientation film layer 14 ... Nonlinear optical waveguide, 15 ... Upper electrode 16 ... Laser light source, 17 ... Modulator 18 ... Condenser lens

──────────────────────────────────────────────────続 き Continuation of the front page (56) References JP-A-64-90414 (JP, A) JP-A-1-269926 (JP, A) JP-A-64-40508 (JP, A) (58) Investigation Field (Int.Cl. ⁶ , DB name) G02F 1/35 504 G02F 1/37 JICST

Claims (5)

(57) [Claims] 1. A non-linear optical waveguide comprising a non-linear optical material containing a side-chain type ferroelectric polymer liquid crystal and a non-linear optical compound between an upper electrode and a lower electrode at least one of which has an alignment film. Characteristic nonlinear optical element. 2. The addition amount of the nonlinear optical compound to the side chain type ferroelectric polymer liquid crystal is 1 to 50% by weight.
The non-linear optical element according to the above. 3. The nonlinear optical element according to claim 1, wherein said side chain type ferroelectric polymer liquid crystal and said nonlinear optical compound form a solid solution. 4. The nonlinear optical element according to claim 1, further comprising a portion formed by subjecting a nonlinear optical material containing a side chain type ferroelectric polymer liquid crystal and a nonlinear optical compound to an alignment treatment. 5. The addition amount of the nonlinear optical compound to the side chain type ferroelectric polymer liquid crystal is 1 to 50% by weight.
The non-linear optical element according to the above.