JPH03197380A - Production of organic crystal - Google Patents

Abstract

PURPOSE:To obtain the subject organic crystal useful for a wave changing device showing a high second-order nonlinear optical effect by growing a crystal of an organic crystalline material in a glass capillary having the inner wall surface treated with trimethylchlorosilane. CONSTITUTION:The inner wall of a glass capillary is subjected to a surface treatment with trimethylchlorosilane and a crystal of an organic crystalline material is subsequently grown in the glass capillary to obtain the objective organic crystal. The inner wall surface of the glass capillary is generally covered with hydroxyl groups. And, by the surface treatment thereof with trimethylchlorosilane, trimethylchlorosilane is bonded to a hydroxyl group on the surface of the inner wall of the glass capillary 20 and the surface of the inner wall of the glass capillary 20 is modified from the hydrophilic nature to the hydrophobic nature due to formation of a trimethylchlorosilane molecular layer. As the organic crystalline material for use, 2-methyl-4-nitroaniline, 4,5- dimethyl-1,3-dithiol-2-ylidene cyanoacetate, etc., are exemplified.

Description

[Detailed Description of the Invention] <Industrial Application Field> The present invention relates to a method for manufacturing an organic crystal, and more specifically, an organic crystal suitable for manufacturing a wavelength conversion element etc. that exhibits a second-order nonlinear optical effect. The present invention relates to a manufacturing method of.

<Prior art and problems to be solved by the invention> FIG. 4 shows a core 11 made of an organic nonlinear optical crystal having a second-order nonlinear optical effect, and a glass cladding 12 having no second-order nonlinear optical effect. This shows a fiber-type wavelength conversion element composed of.

This fiber type wavelength conversion element has the formula: (where n
(2ω) is the refractive index of the lad cladding at the second harmonic, n (ω) is the effective refractive index of the core at the fundamental wave, n (ω) is the refractive index of the cladding at the fundamental wave) When the following conditions are satisfied, the second harmonic (arrow A)
1 to the cladding 12, Cerenkov radiation is generated.

At this time, from the fundamental wave (arrow B) to the second harmonic (arrow A)
In order to improve the conversion efficiency, it is necessary to match the polarization direction of the fundamental wave with the direction of the maximum nonlinear optical constant of the organic crystal forming the core 11.

However, in the conventional method, an organic crystal exhibiting a second-order nonlinear optical effect becomes a core in a thin tube that becomes a cladding.
Methyl-4-nitroaniline (hereinafter referred to as MNA)
G.P. Llpscosb et al., J.
Chem, 75.1509 (1981)), 4'
-nitropendiritin-4-methylaniline (0,S
, Flllpenko et.

al,,Sov,Phys,Crystallogra
phy, 22.805 (1977)), 2-(α-methylbenzylamino)-5-nitroviridine (T, Ko
ndo et, al., 5PIE Proc.

971, 83 (198g)) have good molecular orientation within the crystal, and di among the components of the second-order nonlinear optical tensor
When i is large, dii of the resulting organic crystal
There was a problem in that the direction of the crystal coincided with the long axis direction of the glass capillary, and the polarization direction of the incident fundamental wave could not be made to coincide with the direction of the maximum nonlinear optical constant of the crystal.

This is considered to be because, as shown in FIG. 5, a material that easily forms hydrogen bonds, such as MNA, forms hydrogen bonds with the hydroxyl groups on the inner wall surface of the glass capillary tube 20.

As a method for controlling the orientation of an organic crystal material, there is a method as disclosed in Japanese Patent Publication No. 61-208038. That is, after treating the surface of the glass substrate 21 with (4-nitrophenyl)dimethylchlorosilane and modifying the inner wall surface of the glass capillary 20 as shown in FIG. 6, the organic crystal material is treated with ion beam irradiation. There is a technique to vacuum evaporate and deposit a thin film to create a thin film with good orientation.

This is because, as shown in the figure, (4-nitrophenyl)dimethylchlorosilane molecules, which are surface treatment agents, line up on the substrate surface, and material molecules with a similar structure also have their principal axes perpendicular to the substrate surface. This is because the orientation changes, and molecules attached in a different direction will move to a stable state due to the energy received from the ion beam.

However, with the above-mentioned surface treatment agents, the hydrophilicity of the inner wall surface of the glass capillary tube may be affected due to the three-dimensional structure of the surface treatment agent (i.e., the presence of a bulky 4-nitrophenyl group, etc.) and its reactivity with hydroxyl groups. The modification to hydrophobicity is not sufficient,
The problem of matching the polarization power direction of the incident fundamental wave with the direction of the maximum nonlinear optical constant of the crystal remained.

The present invention has been made to make the surface modification effect of the inner wall of a glass capillary more remarkable, and uses various organic crystal materials to improve wavelengths that exhibit nonlinear optical effects, particularly high second-order nonlinear optical effects. An object of the present invention is to provide a method for producing an organic crystal that can produce an organic crystal used as a conversion element.

Means and Effects for Solving the Problems> In order to solve the above problems, the method for producing an organic crystal of the present invention includes surface-treating the inner wall of a glass capillary with trimethylchlorosilane, and then adding an organic crystal material into the glass capillary. It is characterized by growing crystals.

That is, in the method for producing organic crystals of the present invention, the inner wall of the glass capillary is surface-treated with trimethylchlorosilane having the following characteristics.

(1) High reactivity with hydroxyl groups.

■Since it has only one functional group (halogen atom) that can react with the inner wall of the glass capillary, no complicated reactions occur.

[3) Since all the it substituents are methyl groups, the molecules themselves are small, and therefore a large amount can be packed onto the substrate.

The inner wall surface of the glass capillary tube is generally covered with hydroxyl groups, but when the surface is treated with trimethylchlorosilane, as shown in FIG. is formed, and the inner wall surface of the glass capillary tube 20 is modified from hydrophilic to hydrophobic.

This modification of the inner wall surface of the glass capillary from hydrophilic to hydrophobic causes a change in the interaction at the interface between the organic crystal and the inner wall surface of the glass capillary. That is,
Hydrogen bonding with the glass inner wall surface that occurs when a material that easily forms hydrogen bonds, such as MNA, is used is eliminated.

Utilizing this fact, it becomes possible to freely change the crystal orientation depending on the degree of hydrogen bonding with the glass inner wall surface.

In addition, in the surface-treated glass tube, the crystal di
When growing a single crystal of an organic crystal material with a large i, that is, the direction of dii and the direction of the main axis of the molecule are close to each other, the angle between the direction of dii and the long axis of the fiber approaches 90°. By performing such treatment, it is possible to obtain a single crystal that can utilize the maximum nonlinear optical constant.

Hereinafter, the method for producing organic crystals of the present invention will be explained in detail.

As a method for surface treatment of the inner wall of a glass capillary, there is a method of contacting the inner wall of the glass capillary with a solution of trimethylchlorosilane for a predetermined period of time, or a method of immersing the glass capillary in a solution of trimethylchlorosilane for a predetermined period of time.

The glass capillary tube is made of heat-resistant quartz glass, lead glass, soda glass, etc. that does not exhibit nonlinear optical effects, and those having an inner diameter of 1 to 3 μm are usually used.

The method for producing organic crystals is by capillary phenomenon, etc.
A capillary tube is filled with a melt of the organic crystal material, and the capillary tube is cooled to crystallize it, and the crystals in the capillary tube are melted again, and then the capillary tube is sequentially cooled from one end toward the other end. Precipitating polycrystals as seed crystals by a melt method in which a single crystal is grown in a capillary tube, or by rapidly lowering the temperature of one end of a solution containing an organic crystal material contained in a heated glass capillary tube, Then, a so-called solution method can be used in which a single crystal is grown based on the seed crystal by sequentially cooling slowly toward the other end.

As the organic crystal material, for example, 2-methyl-4-
Nitroaniline (MNA), 4,5-dimethyl-1,
3-dithiol-2-ylidene cyanoacetate, 1.
3-dithiol-2-ylidene cyanoacetate-I', 3
．． 5-dimethyl-1-(4-nitrophenyl)pyrazole, 3-(2-cyano-2-ethoxycarbonylvinyl)indole, 2-(2-cyanoethoxy)-5-nitropyridine-4'-nitropenzylidene-3 Examples include -acetamino-4-methoxyaniline and molecular salts represented by the following general formula: (wherein, X represents a methyl group or a chlorine atom).

In addition to water, examples of solvents containing the organic crystal material in the solution method include toluene, methanol, acetonitrile, dimethylformamide, nitrobenzene, dimethyl sulfoxide, dioxane, ethanol, acetone, ethyl acetate, chloroform, benzene, Examples include organic solvents such as carbon chloride, tetrahydrofuran, and pyridine.

<Example> Examples of the present invention will be described below.

Example 2 A 5% by weight hexane solution 2 of trimethylchlorosilane was put into the upper liquid reservoir 1 of a cell 4 as shown in Fig. 2, the tube was sealed, and the entire cell 4 was heated to 80°C. A processing solution was injected into the glass capillary tube 3. After continuing the treatment in this state for 3 hours, the cell 4 was thoroughly washed and dried, and the MNA crystals were transferred to the glass capillary tube 3 using this cell 4.
I let it grow within me. The growth conditions at that time were: 0.1 mJ of benzene was added to 0.05 g of the organic crystal material, and the furnace temperature was 1.
The solution was dissolved at 00℃, and the crystal growth temperature was 0.2m.
m/hour.

Comparative Example 1 Crystals were grown using the solution method in the same manner as in Example except that a glass capillary tube without surface treatment was used.

Comparative Example 2 Crystals were grown by a melt method using a glass capillary tube surface-treated with dimethylphenylchlorosilane.

Comparative Example 3 Crystals were grown using the same solution method as in Example 1 using a glass capillary tube surface-treated with methylphenylchlorosilane in the same manner as in Comparative Example 2.

The MNA fiber obtained in the example was examined using an optical microscope for extinction in the dark field and dichroism in the bright field, and as shown in Figure 3 (al), the crystal axis (X axis) It was found that the trimethylchlorosilane was oriented at 90 degrees from the center, making it suitable for wavelength conversion devices.This is because trimethylchlorosilane completely modified the inner wall of the glass capillary from hydrophilic to hydrophobic, and completely controlled the crystal orientation. .

On the other hand, the MNA fiber of Comparative Example 1 was not suitable for a wavelength conversion element because the dii direction was oriented in the long axis direction of the fiber, as shown in FIG. 3+b+.

In Comparative Example 2, as shown in FIG. 3(C), the crystal axis was oriented at only 80° from the long axis of the fiber, and the effect was lower than that of the Example. This is presumed to be because dimethylphenylchlorosilane cannot completely cover the inner wall of the glass capillary due to the bulky phenyl group, so free hydroxyl groups remain and these are hydrogen bonded with MNA.

Furthermore, Comparative Example 3 using the solution method showed the same results as Comparative Example 1 shown in Section 3). This shows that the solution method has no effect at all when dimethylphenylchlorosilane is used as a surface treatment agent.

Note that in FIGS. 3A to 3C, 11 and 12 are the same core and cladding as in FIG. 4, respectively.

<Effects of the Invention> As described above, according to the method for producing organic crystals of the present invention,
Since the crystal orientation of the resulting single crystal can be controlled, it is possible to obtain a single crystal that exhibits a second-order nonlinear optical effect and is suitable for use as a wavelength conversion element. This has the excellent effect of making it possible to manufacture a single crystal that can make use of the maximum nonlinear optical constant of the organic crystal material by matching the direction of the maximum nonlinear optical constant of the organic crystal material.

[Brief explanation of drawings]

Fig. 1 is an explanatory diagram showing a state in which trimethylchlorosilane is bonded to the inner wall surface of a capillary, Fig. 2 is a schematic cross-sectional view showing an embodiment of the method for producing organic crystals of the present invention, and Fig. An explanatory diagram showing the crystal orientation of the single crystal obtained in the example of
Figure 4 is an explanatory diagram showing Chenkov radiation, and Figure 5 is an explanatory diagram showing the crystal orientation of the single crystals obtained in Comparative Examples 1 and 2. Figure 6 is an explanatory diagram showing the hydrogen bonding of (
FIG. 4 is an explanatory diagram showing a state in which nitrophenyldimethylchlorosilane (4nitrophenyl) is bonded. DESCRIPTION OF SYMBOLS 1... Upper liquid pool, 2... Solution, 3... Glass capillary, 4... Cell, 11... Core,
12...Clad, 20...Glass.

Claims (1)

[Claims] 1. A method for producing organic crystals, which comprises surface-treating the inner wall of a glass capillary with trimethylchlorosilane, and then growing crystals of an organic crystal material inside the glass capillary.