JPH0792511A - Production of organic nonlinear optical crystal - Google Patents

Abstract

PURPOSE:To effectively grow a plate single crystal of a large area of a high- performance org. nonlinear optical crystal material by producing the single crystal by a melting and pulling up method using a capillary die in an inert gaseous atmosphere. CONSTITUTION:This org. nonlinear optical crystal is produced by the melting and pulling up method using the capillary die in the inert gaseous atmosphere. The org. nonlinear optical crystal material is an org. nonlinear optical crystal material selected from among 4'-nitrobenzylidene-3-alkanoylamino-4- methoxyaniline expressed by the formula, etc., and compds. in which a part of hydrogen of these compounds are replaced with deuterium. In the formula, R denotes <=2C alkyl, alkyl halide, etc. The melding and pulling up method is a method of producing the single crystal by bringing a seed crystal into contact with a raw material melt, then pulling up the crystal grown in the same bearing from the single crystal section of the crystal to solidify the melt. The crystal which is high in growth speed, large in size and low in defect is obtd.

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]

2. Description of the Related Art General formula;

[Chemical 2] The organic non-linear optical crystal material represented by (where R is an alkyl or alkyl halide having 2 or less carbon atoms) has high non-linear optical performance and, in addition, mutually heteroepitaxially grows. 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. In order to use it as a substrate for heteroepitaxial growth, it is necessary to prepare a large-area plate-shaped single crystal. The crystal growth by the solution method has the advantage that it can be performed with 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. It cannot be said that the method is suitable for the purpose of obtaining a large-area substrate. The Czochralski method, which is a type of melting method, is capable of producing large crystals in a short period of time and is suitable for increasing the area of a substrate. However, the crystals produced by the Czochralski method are plate-shaped. However, there is a problem in that many parts are lost as chips and shavings when the substrate is processed. On the other hand, EFG (edge-defined fid) which is one of the melt growth methods.
The lm-fed growth method is capable of directly growing a plate-shaped single crystal and is a suitable method for manufacturing a substrate. However, the method used to manufacture a single crystal of an organic material has hitherto been used. There was no.

[0003]

An object of the present invention is to provide a manufacturing method for efficiently growing a large-area plate-shaped single crystal of a high-performance organic nonlinear optical crystal material.

[0004]

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

"A method for producing a single crystal of an organic optical crystal material, which is characterized in that it is produced by a melt pulling method using a capillary die in an inert gas atmosphere. The organic optical crystal material referred to in the present invention may be any organic crystal material used for optical applications, but an organic nonlinear optical crystal, which has recently been noted for its usefulness, is desirable.

4'-Nitrobenzylidene-referred to in the present invention
3-alkanoylamino-4-methoxyaniline, 4 '
-Nitrobenzylidene-3-halogenoalkanoylamino-4-methoxyaniline, and a compound in which at least a part of the hydrogen contained therein is deuterium-substituted,
4'-nitrobenzylidene-3-acetamino-4-methoxyaniline (MNBA), 4'-nitrobenzylidene-3-ethylcarbonylamino-4-methoxyaniline (MNBA-Et), 4'-nitrobenzylidene-3
-Chloroacetamino-4-methoxyaniline (MNB
A-Cl), 4'-nitrobenzylidene-3-bromoacetamino-4-methoxyaniline (MNBA-B)
r), 4'-nitrobenzylidene-3- (β-chloroethyl) carbonylamino-4-methoxyaniline (MN
BA-ClEt) and the like, -NHCOR representing an alkanoylamino group or a halogenoalkanoylamino group, wherein R is alkyl having 2 or less carbon atoms or an alkyl halide, and at least a part of them is deuterium-substituted. Refers to compounds (hereinafter, these are collectively referred to as benzylideneaniline-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 will be described later, it has a preferable characteristic for melt growth that sublimation from the melt state is significantly suppressed under normal pressure or under pressure. Such a benzylidene aniline material is more preferably used.

The melt-pulling method referred to in the present invention is to solidify the melt by bringing seed crystals into contact with the raw material melt and then pulling up the crystals grown in the same direction from the single crystal part of the crystal. It is a method for producing a single crystal by using the above method, and is superior to other production methods in that it has a high growth rate and that a large-sized and low-defect crystal can be obtained.

The seed crystal in the present invention serves as a nucleus for crystal growth, and it may be the same substance as or a different substance from the organic nonlinear optical crystal material for the purpose of production. 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 capillary die used in the manufacturing method of the present invention is used for controlling the shape of the crystal to be grown, and it has a dot-shaped or slit-shaped opening depending on the desired crystal shape. The raw material melt is sucked up into the opening of the die by a capillary phenomenon. In order to grow a plate crystal, it is desirable to have a slit-shaped opening or a plurality of dot-shaped openings arranged in a straight line. It is also desirable to use a capillary die with openings of appropriate length depending on the desired crystal size.

It is desirable that the capillary die has good wettability with MNBA-Et and is made of a material that does not react with MNBA-Et. For example, it may be made of metal, ceramic, or glass. Even with a metal capillary die, a copper die whose surface is oxidized and deteriorated cannot be used. It is desirable to use a metal die that has been subjected to a surface treatment (such as plating) to prevent oxidative deterioration. More preferably, quartz glass is used.

The opening interval of the capillary die is 0.3 to 1.0.
mm is desirable. The opening distance of the capillary die regulates the thickness of the plate-shaped single crystal.If it is too thick, the suction height due to the capillary phenomenon will be small, and if it is too thin, the crystal will easily break during pulling growth. Is.

The crystal pulling rate in the production 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.

It is preferable that the inside of the growth container is once deaerated in vacuum and then replaced with an inert gas. This is because vacuum deaeration makes it possible to remove oxygen, carbon dioxide, water, etc. in the container, which is considered to be the causative substance of thermal deterioration. By replacing the inside of the growth vessel with an inert gas,
It is possible to suppress the sublimation of the raw material which causes a decrease in the raw material and generation of unnecessary 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 that does not serve as a catalyst for the reaction may be used.
Ar and N ₂ are preferably used.

In the present invention, when the raw material is melted, it is desirable to gradually melt the raw material organic substance in the crucible in order to avoid increase in sublimation due to excessive heating of the raw material organic substance and promotion of thermal deterioration. As an example, the crucible temperature is raised to about 10 ° C. lower than the melting point of the raw material, and then gradually raised at a rate of 2 ° C. or less per minute until the raw material starts melting. If the melting of the raw materials is insufficient after the temperature is stopped, the raw materials are completely melted by further increasing the temperature by 1 ° C. at most. In this way, unnecessary overheating can be prevented without being affected by the difference in the position of the thermometer.

As the raw material benzylidene aniline material used in the production method of the present invention, it is preferable to use a material 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.

For 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.

Sublimation purification is preferably carried out under a pressure 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. 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, but since it can be carried out with the same apparatus and the same procedure, vacuum distillation purification is also included in the present invention.

[0020]

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

Example 1 Crystal Growth of MNBA-Et by EFG Method Purification of the raw material MNBA-Et used in this experiment was carried out using MNB.
A solution of A-Et in dichloromethane was passed through a neutral alumina column and then recrystallized by a solvent evaporation method. This procedure was repeated twice, and the obtained powder was filled in a glass container.
Sublimation purification performed by heating at 175 ° C. under reduced pressure of × 10 ^-3 torr or less was repeated 3 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.

FIG. 1 is a schematic diagram of a growth apparatus used in the present invention, and FIG. 2 shows the outer shape of a capillary die. The material of the die was quartz glass, and the slit width of the opening was 0.5 mm. The atmosphere in the growth vessel was nitrogen flow.

The raw material MNBA-Et was filled in the crucible portion,
The electric crucible was once heated to 165 ° C in an electric furnace, and then the temperature was raised by 1 ° C until the raw material was completely melted.
The temperature was raised to 5 ° C.

After melting, the seed crystals were lowered and brought into contact with the melt sucked up in the slit of the die due to the capillary phenomenon, and then the seed crystals were pulled up at a speed of 1 mm / hour to grow plate-like crystals, Crystals having a thickness of 0.5 mm, a width of 10 mm and a length of 20 mm were obtained. The grown crystal had an ac plane on the wide side.

According to this embodiment, MNBA is obtained by the EFG method.
It was shown that it is possible to grow a plate-shaped single crystal of -Et.

Example 2 Crystal growth of MNBA-Et by the EFG method It was carried out except that the growth container was once evacuated to a nitrogen flow atmosphere and the seed crystals were pulled up at a rate of 0.5 mm / hour. Crystal growth was performed in the same manner as in Example 1.

The size of the plate-like crystals obtained is 0.
It was 5 mm, width 10 mm, and length 10 mm. The grown crystal had an ac plane on the wide side.

According to this embodiment, MNBA is obtained by the EFG method.
It was shown that it is possible to grow a plate-shaped single crystal of -Et.

[0030]

According to the present invention, it is possible to provide a manufacturing method for growing a large-area plate-shaped 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 a configuration of a growth apparatus used in the present invention.

FIG. 2 is a diagram showing a configuration of a capillary die used in the present invention.

[Explanation of symbols]

 1: Pulling shaft 2: Electric furnace 3: Seed crystal 4: Raw material melt 5: Pyrex glass crucible 6: Chamber-7: Inflowing nitrogen 8: Outflowing nitrogen 9: Capillary die

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Claims (10)

[Claims] 1. A method for producing a single crystal of an organic optical crystal material, which comprises producing by a melt-pulling method using a capillary die in an inert gas atmosphere. . 2. The organic optical crystal material has a general formula: (Wherein R is alkyl having 2 or less carbon atoms, alkyl halide) 4'-nitrobenzylidene-3-alkanoylamino-4-methoxyaniline, 4'-nitrobenzylidene-3-halogenoalkanoylamino-4
-Methoxyaniline, and an organic nonlinear optical crystal material selected from compounds in which at least a part of the hydrogen contained therein is deuterium-substituted.
A method for producing the described organic nonlinear optical crystal. 3. The organic nonlinear optical crystal according to claim 1, wherein the organic optical material is 4′-nitrobenzylidene-3-ethylcarbonylamino-4-methoxyaniline (hereinafter abbreviated as MNBA-Et). Production method. 4. The method for producing an organic nonlinear optical crystal according to claim 1, wherein the material of the capillary die is quartz. 5. The method for producing an organic nonlinear optical crystal according to claim 1, wherein the capillary die has a slit-shaped opening or a plurality of point-shaped openings arranged in a straight line. 6. The method for producing an organic nonlinear optical crystal according to claim 5, wherein the distance between the die openings is 0.3 to 1.0 mm. 7. The method for producing an organic nonlinear optical crystal according to claim 1, wherein the pulling rate is 0.1 to 5.0 mm / hour. 8. The method for producing an organic nonlinear optical crystal according to claim 1, wherein the inside of the growth container is deaerated in vacuum and then replaced with an inert gas. 9. The method for producing an organic nonlinear optical crystal according to claim 1, wherein the inert gas is Ar or N ₂ . 10. The method for producing an organic nonlinear optical crystal according to claim 1, wherein the raw material organic compound is purified by a combination of a column chromatography method, a recrystallization method and a sublimation method.