JP2675139B2 - Method for producing amorphous material having nonlinear optical effect - Google Patents

Description

The present invention relates to a method for producing an amorphous material having a nonlinear optical effect.

[Conventional technology]

Non-linear optical material is a material that shows a large optical phenomenon (non-linear effect) in which a higher-order effect of square or higher appears, which is not proportional to the amplitude of incident light. It is expressed as the following equation (1), and P = ε ₀ χ ⁽¹⁾ E + ε ₀ χ ⁽²⁾ E ² + ε ₀ χ ⁽³⁾ E ³ … + ε ₀ χ ⁽ⁿ⁾
E ⁿ (1) χ ⁽²⁾ is called the second-order nonlinear susceptibility, and χ ⁽³⁾ is called the third-order nonlinear susceptibility.

As such an inorganic material as a nonlinear optical material, Li
_{NbO 3, KH 2 PO 4,} BaTiO 3 or the like, and in organic materials known 2-methyl-4-nitroaniline, urea, m- nitroaniline, and the like. Organic crystal 2-methyl-4-nitroaniline (MNA) is famous as a second-order nonlinear material. It has been found that polyvinylidene fluoride has a third-order nonlinear effect in polymer materials.

Such non-linear optical materials are expected to be applied to higher information recording densities and optical computers, and in particular, interest in organic materials having a non-linear effect is increasing.

[Problems to be solved by the invention]

As a material having a non-linear optical effect, an organic material having an order of magnitude higher performance than an inorganic material has been found.
When an organic material is used as a device, it is often used in a single crystal state. However, organic crystals have the problems of low heat resistance and low mechanical strength. Further, the second-order nonlinear effect is possessed only by a substance having no inversion symmetry. Even for an organic molecule having a large second-order nonlinear effect, the crystal does not always have the nonlinear effect.

In such a case, a substance serving as a binder may be doped with an organic molecule and used as a composite material. Polymer materials are often used as binders at that time,
The range of use of polymer materials is limited in terms of weather resistance and translucency. Further, as described above, the quadratic nonlinear effect appears only in a system having no center of inversion symmetry, but if randomly doped, the molecules cancel each other even if each molecule has a nonlinear effect. Therefore, the structure is isotropic and the non-linear effect does not appear.

Therefore, it is necessary to align and dope organic molecules in a specific direction in order to develop a second-order nonlinear effect.
There is also a problem that the organic molecules in the polymer material are difficult to be oriented.

The present invention has been made in view of the above problems, and is a composite material obtained by doping an organic molecule having a nonlinear optical effect, and can provide a device having excellent optical characteristics and weather resistance when used. It is an object of the present invention to provide a method for producing an amorphous material having such a nonlinear optical effect.

Another object of the present invention is to provide a method for producing an amorphous material having a non-linear optical effect that allows organic molecules having a non-linear effect to be doped and then easily oriented. .

[Means for solving the problem]

The inventors of the present invention, in the course of various studies to achieve the above-mentioned object, apply an electrostatic field in the process of hydrolyzing / gelling a silicon tetraalkoxide mixed with an organic molecule having a nonlinear optical effect. The inventors have found that amorphous silica having molecules aligned in one direction can be easily obtained and have reached the present invention.

That is, the present invention synthesizes an amorphous material by adding water and alcohol to a silicon alkoxide represented by the general formula Si (OR) ₄ [wherein R is an alkyl group], and hydrolyzing and gelling the mixture. In the method described above, an amorphous material having a nonlinear optical effect is characterized in that an organic molecule having a nonlinear optical effect is added to the composite liquid at the time of the hydrolysis and gelled while applying an electrostatic field after completion of the hydrolysis. Is a manufacturing method.

It can be mentioned as a particularly preferred embodiment of the present invention that the Yuki molecule having a nonlinear optical effect is an organic molecule having a secondary nonlinear optical effect.

The composite amorphous silica produced according to the present invention is 2
It has the following nonlinear optical effect, excellent translucency and weather resistance, and the organic molecules that are dopants are not affected by the surrounding atmosphere at all, and are oriented in a fixed direction, so stable nonlinear optical It can be used as a material.

[Action]

Glass is considered to be a desirable material as a medium for optically functional organic molecules, but since conventional glass production requires a high temperature of 1000 ° C. or higher, thermal decomposition occurs even when organic molecules are mixed, It could not be added.

By the way, in recent years, a low temperature synthesis process of glass called a sol-gel method has been developed. This sol-gel method synthesizes a gel body by hydrolyzing a silicon alkoxide at room temperature, so by adding an organic molecule to a hydrolysis solution, the organic molecule is not transformed into a silica gel body. It can be dispersed and added. Compared with normal silica glass, the silica gel obtained at this room temperature,
It has a high content of water and alcohol and a low density, but its light-transmitting property and strength are close to those of silica glass, and it can be used as an optical material.

The production method of the present invention utilizes this sol-gel method to hydrolyze a silicon alkoxide mixed solution containing a nonlinear optical organic molecule, and by applying an electrostatic field in the process of obtaining a gel body, a mixed solution of the nonlinear optical organic molecule is obtained. Further, it is possible to obtain an amorphous material having a non-linear optical effect by aligning in one direction in the gel body. The degree of orientation <cosΘ> when the dipole moment of the organic molecule is oriented at an angle of Θ with the direction of the electrostatic field is given by the following equation (2).

<Cos Θ> = cotha−1 / a (2) a = μg · E / kT where μg is the dipole moment [Coulomb · m], E
Electrostatic field [V / m], k is Boltzmann's constant [Joule Kelvin], T is temperature [Kelvin], and a is dimensionless.

From this equation (2), it can be seen that the lower the temperature, the higher the orientation.

When gelled without applying an electric field, the organic molecules are randomly doped in the gel and the second-order nonlinear effect cannot be expressed.

Further, when a polymer material is used as the binder, it is necessary to bring the polymer material into a molten state at a high temperature for electric field orientation, which is not preferable for organic molecules that are easily decomposed at a high temperature. Further, since the molten state of the polymer is high in viscosity and the movement of organic molecules is suppressed, it is difficult to increase the degree of orientation.

On the other hand, in the present invention, at the start of the reaction, the solution is a solution containing alcohol and water as the main components, and the reaction proceeds at a low temperature of about room temperature. Therefore, the electric field is effectively utilized as described in the above equation (2). Can be oriented. With the gelation of alkoxide, the added organic molecules are
Since it is fixed in the matrix, it does not change its orientation once it is oriented.

Examples of suitable non-linear optical organic molecules in the present invention include dimethylaminonitrobenzene, p-nitroaniline, dimethylaminonitroazobenzene, cyanine dyes and azo dyes.

As the alkyl group of the silicon alkoxide represented by the general formula Si (OR) _{4 of the} present invention [wherein R is an alkyl group],
Examples thereof include a methyl group, an ethyl group, a propyl group and a butyl group.

In the present invention, the hydrolysis of silicon alkoxide is
It can be performed according to a usual method of a so-called sol-gel method.

Examples of alcohols include methyl alcohol, ethyl alcohol, propyl alcohol and the like.

As an example of the hydrolysis conditions, high temperature 10 ~ 30 ℃, PH1
It is ~ 7 mag. To adjust the pH, a suitable alkali or acid can be added to the solution of silicon alkoxide, water and alcohol.

An organic molecule having a nonlinear optical effect is added to this hydrolysis solution. The amount of organic molecules added is, for example, ~ 30% by weight.
It is a degree, but the more the better.

After completion of hydrolysis, the reaction vessel is sealed, for example, 10 kV / cm to 1
While applying an electrostatic field of 000kV / cm, for example, the temperature is 60-80 ℃
Warm to a certain degree to cause gelation. After gelation, a small hole is opened in the lid of the container, and heating is further continued at about 60 to 80 ° C. to dry the gel body to obtain an amorphous material having a nonlinear optical effect of the present invention. it can.

Further details of the method of the invention are illustrated in the examples below.

〔Example〕

Example 1 As shown in the perspective view of FIG. 1 (a) and the sectional view of FIG. 1 (b), a quartz glass plate (20 mm × 10 mm × 1 mm) 3, on the surface of which transparent conductor films 1 and 2 are formed, A cell (thickness 3 mm) 6 composed of 4 and a quartz cell frame 5 and a power supply 7 connected to the conductive films 1 and 2 by connecting wires 8 and 9 were used to remove the amorphous material of the present invention. Manufactured. Silicon methoxide 4 ml, H ₂ O 2.3 ml HCl0.0
In 6 ml of ethanol and 5.1 ml of ethanol, 17 mg of 2-methyl-4-nitroaniline, which is a non-linear organic molecule, was dissolved and sufficiently stirred. This mixed solution 10 was poured into the cell 6 as shown in FIGS. 1 (a) and 1 (b), and gelled while applying an electric field from the power supply 7. The applied voltage was 6 × 10 ⁵ V / cm. When this cell 6 was allowed to stand at room temperature for 3 days, it gelated and a yellow transparent dry gel was obtained. NdYAG was added to this dried gel.
When a laser (λ = 1.062 μm) was incident, it was confirmed that green light was emitted. This is called the second harmonic and is due to the secondary light effect. Therefore, it can be seen that this dried gel is a substance having a second-order nonlinear effect.

On the other hand, in the dried gel obtained by gelling the mixed solution having the same composition as in the above example without applying an electric field, generation of the above second harmonic was not observed (comparative example).

Therefore, it can be said that the generation of the second harmonic is due to the non-linear organic molecules being oriented by the electrostatic field and fixed in the gel body.

Example 2 40 mg of para-nitroaniline, which is a non-linear organic molecule, was dissolved in a mixed solution containing 10 ml of silicon ethoxide, 4.4 ml of H ₂ O, 0.1 ml of HCl and 11 ml of ethanol, and a dry gel was obtained in the same manner as in Example 1 below. However, it was confirmed that this substance also has a second-order nonlinear effect.

Example 3 A mixture of 10 ml of silicon methoxide, 6 ml of H ₂ O, 0.15 ml of HCl and 12 ml of methanol was added to a mixture of non-linear organic molecules 3-
When 20 ml of methyl-4-nitropyridine-1-oxide was dissolved and a dried gel was obtained in the same manner as in Example 1, it was confirmed that this was also a substance having a second-order nonlinear effect.

〔The invention's effect〕

As described above, the present invention makes it possible to easily manufacture an amorphous material having a nonlinear optical effect by orienting the nonlinear organic molecules in the amorphous material by an electric field. It can be advantageously used in the field of circuit elements and display elements that can replace liquid crystal displays.

[Brief description of the drawings]

1 (a) and 1 (b) are a perspective view and a cross-sectional view schematically explaining an embodiment of the present invention. 1, 2 are conductive films, 3 and 4 are quartz glass plates, 5 is a cell frame, 6 is a cell, 7 is a power source, 8 and 9 are connection lines, and 10 is a sol or gel body.

Claims (2)

(57) [Claims] 1. A general formula Si (OR) ₄ [wherein R is an alkyl group]
In the method of synthesizing an amorphous material by hydrolyzing / gelling a mixture of water and alcohol added to a silicon alkoxide represented by, an organic molecule having a nonlinear optical effect in the mixture during the hydrolysis. Is added, and after completion of hydrolysis, gelation is carried out while applying an electrostatic field, and a method for producing an amorphous material having a nonlinear optical effect. 2. The organic molecule having the nonlinear optical effect is 2
The method for producing an amorphous material having a nonlinear optical effect according to claim 1, having the following nonlinear optical effect.