JPH0710699A - Production of organic nonlinear optical crystal - Google Patents

Abstract

PURPOSE:To provide a method for producing a large organic nonlinear optical crystal in a short time by melt-raising a specific organic nonlinear optical crystal material in an inert gas atmosphere. CONSTITUTION:A method for producing an organic nonlinear optical crystal comprises receiving an organic nonlinear optical crystal material in a crucible 5 disposed in a chamber 6, thermally melting the optical crystal material to produce the melted liquid 4, immersing a seed crystal 3 in the melted liquid 4 and subsequently raising the seed crystal at a raising rate of 0.1-5.0mm/hr in an inert gas atmosphere. The organic nonlinear optical crystal material comprises a 4'-nitrobenzylidene-3-alkanoylamino-4-methoxyaniline or a 4'- nitrobenzylidene-3-halogenoalkanoylamino-4-methoxyaniline of the formula [R is <=2C (halogenated) alkyl] or their derivative wherein at least a part of the H atoms of the compound of the formula is replaced by deuterium atom, which are purified by a gas chromatography method, a recrystallization method or a sublimation method comprising heating the compound under a pressure of <=10<-3>Torr.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a method for producing a single crystal of an organic nonlinear optical material used for a nonlinear optical element used in the fields of optical communication and optical information processing.

[0002]

[Prior art]

 General formula:

[Chemical 2] The organic nonlinear optical crystal material represented by (where R is an alkyl or alkyl halide having a carbon number of 2 or less) has high nonlinear optical performance and, in addition, mutually heteroepitaxially grown, a waveguide type nonlinear optical. It is a material having advantageous characteristics for producing an element. As a method for producing a single crystal of the organic nonlinear optical material, an example using a melting method or a solution method has been reported. The crystal growth by the solution method has an advantage that it can be performed by a simple growth apparatus and can be grown at room temperature, but it has drawbacks such as long growth time and difficulty in increasing the size of the crystal. Also, no specific conditions for the melt-pulling method were shown.

An example in which a single crystal of an organic nonlinear optical crystal material is produced by the Czochralski method is an example in which benzyl and benzophenone are grown (Journal of Cry).
stal Growth, vol. 43,589; 19
77) Example of growing 2-methyl-4-nitroaniline (MNA) (Fukuda et al .; Journal of Japan Society for Crystal Growth, vol16,
No. 1, 26; 1989).

The high sublimability of MNA has been an obstacle in the melt-pulling method. Benzyl and benzophenone had the drawback of low nonlinear optical performance.

[0005]

SUMMARY OF THE INVENTION An object of the present invention is to provide a manufacturing method for growing a large single crystal of a high-performance organic nonlinear optical crystal material in a short period of time.

[0006]

In order to solve the above problems, the present invention has the following constitution.

"General formula:

[Chemical 3] (However, R is alkyl having 2 or less carbon atoms or alkyl halide) 4′-nitrobenzylidene-3
-Alkanoylamino-4-methoxyaniline, 4'-
In a method for producing a single crystal of an organic nonlinear optical crystal material selected from the group consisting of nitrobenzylidene-3-halogenoalkanoylamino-4-methoxyaniline and a compound in which at least a part of the hydrogen contained therein is deuterium-substituted, And a manufacturing method characterized by manufacturing by a melt-pulling method in an inert gas atmosphere. In the present invention, 4′-nitrobenzylidene-3-alkanoylamino-4-methoxyaniline, 4′-nitrobenzylidene-3-halogenoalkanoylamino-4-methoxyaniline, and at least a part of hydrogen contained therein are heavy. The hydrogen-substituted compound means 4'-nitrobenzylidene-3-acetamino-4-methoxyaniline (MNBA), 4'-nitrobenzylidene-3-ethylcarbonylamino-4-methoxyaniline (MNBA-).
Et), 4'-nitrobenzylidene-3-chloroacetamino-4-methoxyaniline (MNBA-Cl),
4'-nitrobenzylidene-3-bromoacetamino-
4-Methoxyaniline (MNBA-Br), 4'-nitrobenzylidene-3- (β-chloroethyl) carbonylamino-4-methoxyaniline (MNBA-ClEt)
And the like, -NHCOR representing an alkanoylamino group or a halogenoalkanoylamino group, R is alkyl having 2 or less carbon atoms, alkyl halides, and compounds in which at least part of them is deuterium-substituted (hereinafter , These are collectively referred to as benzylidene aniline-based materials). The crystals of these compounds are all large second-order nonlinear optical crystal materials (Japanese Patent Laid-Open No. 63-113429). Further, as described later, the present invention has revealed that the material has a preferable characteristic for melt growth that sublimation from the melt state is significantly suppressed under normal pressure or under pressure.

The melt-pulling method as used in the present invention means that a seed crystal is brought into contact with a raw material melt, and then a crystal grown in the same direction from a single crystal part of the crystal is pulled while rotating. Is a method of producing a single crystal by solidifying (Czochralski method), and is superior to other production methods in that it has a high growth rate and can obtain a large-sized and low-defect crystal.

Although it is not the Czochralski method in a strict sense, while the seed crystal is kept in contact with the raw material melt, the seed crystal is rotated in the same direction from the single crystal part of the crystal. A method for producing a single crystal in which a crystal is grown and then pulled from a melt is also included in the production method by the melt-pulling method of the present invention.

The seed crystal in the present invention serves as a nucleus for crystal growth, and may be the same substance as the organic nonlinear optical crystal material for the purpose of production or a different substance. As different substances, substances that mutually heteroepitaxially grow are considered. When the seed crystal is not a single crystal, the single crystal can be grown after contact with the melt, but in this case, it is difficult to control the single crystal orientation. Therefore, the seed crystal is preferably a single crystal. When the seed crystal is a single crystal, a crystal having the same orientation as the intended single crystal may be selected.

The raw material benzylideneaniline-based material used in the production method of the present invention is preferably purified by a combination of a column chromatography method, a recrystallization method and a sublimation method. According to the purification method,
This is because it is possible to remove impurities that cause deterioration and coloring of the raw material due to thermal decomposition, thermal polymerization, etc. that are observed during heating and melting.

In the purification by column chromatography, it is preferable to use a neutral or basic alumina column. This is because MNBA-Et easily reacts with an acidic substance and decomposes.

The sublimation purification is preferably carried out under a vacuum of 10 ^-3 torr or less. This is because the benzylideneaniline-based material can be prevented from being colored by thermal decomposition or the like due to heating and melting in the air, and when it is performed under reduced pressure, the sublimation rate is increased and the efficiency of purification can be increased. Sublimation purification is preferably performed at least twice. This is because if the number of times of sublimation purification is only once, the purification purity may be insufficient and the raw material melt may deteriorate. In order to accelerate the sublimation rate, the benzylideneaniline-based material may be heated to a temperature equal to or higher than the melting point for purification. In this case, strictly speaking, it should be called vacuum distillation rather than sublimation purification.
Vacuum distillation purification is also included in the present invention because it can be carried out by the same procedure.

The crystal pulling rate in the manufacturing method of the present invention is preferably 0.1 to 5.0 mm / hour.
If it is too fast, the contact between the crystal and the melt is cut off, so growth does not occur in the pulling axis direction.If it is too slow, it is difficult to control the speed, and the growth rate is too slow, which is not practical. Because.

The rotation speed of the crystal is preferably 20 rpm or less. A more preferable rotation speed is 12 rpm or less. This is because if the rotation speed is too fast, the solid-liquid interface between the crystal and the melt will be convex upward, and defects will easily occur in the single crystal, which is not preferable.

It is preferable that the inside of the growth vessel is once deaerated in vacuum and then replaced with an inert gas. This is because vacuum deaeration can remove oxygen, carbon dioxide, water vapor, and the like in the atmosphere, which are considered to be the causative substances of thermal deterioration. By substituting the inside of the growth container with an inert gas, it is possible to suppress the reduction of the raw material and the sublimation of the raw material which causes unnecessary generation of crystal growth nuclei.

The inert gas used in the present invention does not react with the organic nonlinear optical crystal material intended for production,
Alternatively, any gas may be used as long as it does not cause a deterioration reaction. Ar and N ₂ are preferably used.

[0018]

The present invention will be described in more detail by the following examples.

Example 1 Purification of MNBA-Et The raw material MNBA-Et was purified by repeating twice a procedure in which a dichloromethane solution of MNBA-Et was passed through a neutral alumina column and then recrystallized by a solvent evaporation method. The obtained powder was further subjected to sublimation purification three times.

Purification by column chromatography was carried out by passing through a column having an inner diameter of 8 cm and a height of about 20 cm, which was manufactured by Merck and made of neutral alumina having a particle size of 70 to 230 mesh.

Sublimation purification is carried out by filling MNBA-Et powder in a glass container and reducing the pressure to 1 × 10 ⁻³ torr or less.
The heating was performed to 175 ° C., which is a molten state.

FIG. 2 shows the analysis results of the MNBA-Et purified product by the high performance liquid chromatography method. MNBA-
Only the peak corresponding to Et is detected, and MNBA-E
It was found that the t purified product was extremely high in purity.

The MNBA-Et obtained by the above procedure was filled in a glass container, and once the inside of the container was 1 × 10 ⁻⁴ to.
After degassing to about rr, Ar substitution was performed. After heating and melting at 175 ° C. using an oil bath, the state was maintained for 8 hours and then cooled to solidify the melt. The solidified product obtained at this time had an orange color, and no thermal deterioration was observed.

From this example, it was shown that high-purity MNBA-Et does not cause thermal decomposition or the like even when it is heated and melted, and can be melt-grown.

Single Crystal Growth by Melting Method Using MNBA-Et Seed Crystals Purification of MNBA-Et used as a raw material was performed according to the procedure described above.

The raw material was filled in a glass crucible and placed in an oil bath. The crucible had an inner diameter of 20 mm and a depth of 30 mm. Silicon oil was used as the heat medium. The inside of the growth vessel was deaerated at one end by an oil diffusion pump and then replaced with Ar gas. The pressure during vacuum deaeration was 2 × 10 ⁻⁶ torr, and the pressure inside the container after the substitution was about 1 atm at room temperature.

The seed crystal used in this experiment is obtained by cutting a single crystal part from a polycrystal obtained by heating and melting the raw material purified by the above-mentioned method and then solidifying by cooling. did.

For melting the raw materials and controlling the temperature during growth,
A programmable oil bath with a temperature accuracy of ± 0.01 ° C was used, and silicone oil was used as the heat medium.

The temperature of the oil bath was set to 173 ° C. and the raw material was heated and melted. After the raw material is completely melted, increase the temperature to 1
The temperature was lowered to 70 ° C., and when the temperature became stable, the seed crystal was brought into contact with the melt and rotated at about 15 rpm. After keeping the oil bath temperature at 170 ° C for 30 minutes, 1 at the rate of 2 ° C / hour.
The temperature was lowered to 67 ° C., and subsequently, the temperature was maintained at 167 ° C. for 3 hours, then, the grown crystal was immediately pulled up and cut from the melt.

It was confirmed by visual observation that the pulled crystal had a single domain. The size of the crystal is
The diameter was about 6 mm and the length was about 3 mm.

This example corresponds to the initial growth process of the melt pulling method, and it has been shown that the MNBA-Et single crystal can be grown in the same direction as the seed crystal by the melting method.

Example 2 Single Crystal Growth of MNBA-Et by Melt Lifting Method MNBA-Et used as a raw material was purified by the same procedure as in Example 1. FIG. 1 shows the apparatus configuration of the melt pulling apparatus used in the present invention.

After charging the raw material into a glass crucible, it was heated in an electric furnace. The atmosphere in the growing apparatus is nitrogen flow.
And The temperature control was performed by visually confirming that the raw materials melted.

After the raw materials were completely melted, the seed crystals were brought into contact with the melt. While rotating the seed crystal at 6 rpm,
Crystals were grown by pulling at a rate of 0.5 mm / hour.
When the length of the grown crystal was about 1 cm, the pulling rate was increased and the grown crystal was cut off from the melt.

The size of the pulled crystal is 6 mm in diameter,
The length was about 1 cm.

According to this embodiment, the MNB is prepared by the melt pulling method.
It has been demonstrated that it is possible to produce single crystals of A-Et.

[0037]

According to the present invention, it is possible to provide a manufacturing method for growing a large single crystal of a high-performance organic nonlinear optical crystal material in a short period of time.

[Brief description of drawings]

FIG. 1 is a diagram showing an apparatus configuration of a melt pulling apparatus used in the present invention.

FIG. 2 is a diagram showing the results of analysis of the purity of MNBA-Et purified product by a high performance liquid chromatography method.

[Explanation of symbols]

 1: Pulling shaft 2: Electric furnace 3: Seed crystal 4: Raw material melt 5: Pyrex glass crucible 6: Chamber-7: Inflow nitrogen 8: Outflow nitrogen

Claims (10)

[Claims] 1. A general formula: (However, R is alkyl having 2 or less carbon atoms or alkyl halide) 4′-nitrobenzylidene-3
-Alkanoylamino-4-methoxyaniline, 4'-
In a method for producing a single crystal of an organic nonlinear optical crystal material selected from the group consisting of nitrobenzylidene-3-halogenoalkanoylamino-4-methoxyaniline, and a compound in which at least a part of the hydrogen contained therein is deuterium-substituted And a manufacturing method characterized by manufacturing by a melt-pulling method in an inert gas atmosphere. 2. The method according to claim 1, wherein the organic nonlinear optical material is 4′-nitrobenzylidene-3-ethylcarbonylamino-4-methoxyaniline (hereinafter abbreviated as MNBA-Et). 3. The production method according to claim 1, wherein the raw material compound is purified by a combination of a column chromatography method, a recrystallization method and a sublimation method. 4. The method according to claim 3, wherein the purification by column chromatography is carried out by passing a dichloromethane solution of the starting compound through a neutral or basic alumina column. 5. The production method according to claim 3, wherein the recrystallization method uses dichloromethane as a recrystallization solvent. 6. Purification by a sublimation method produces 10 starting compounds.
^The method according to claim 3, wherein the heating is performed at a pressure of ^-3 torr or less. 7. When a single crystal is grown by the melt pulling method,
The method according to claim 1, wherein the seed crystal is grown while rotating at a rotation speed of 20 or less per minute. 8. The manufacturing method according to claim 1, wherein the pulling rate is 0.1 to 5.0 mm / hour. 9. The manufacturing method according to claim 1, wherein the inside of the growth container is deaerated in vacuum and then replaced with an inert gas. 10. The manufacturing method according to claim 1, wherein the inert gas is Ar or N ₂ .