JPH07248515A - Production of organic nonlinear optical crystal - Google Patents

Abstract

PURPOSE:To grow a large-sized high quality single crystal in a short period of time with satisfactory reproducibility by using a metallic bar as a seed when a single crystal of an org. nonlinear optical crystalline material selected from among specified compds. is pulleced up from a melt. CONSTITUTION:A metallic bar is used as a seed when a single crystal of an org. nonlinear optical crystalline material selected from among 4'- nitrobenzylidene-3-alkanoylamino-4-methoxyaniline represented by the formula, 4'-nitrobenzylidene-3-halogenoalkanoylamino-4-methoxy aniline represented by the formula and compds. each obtd. by substituting deuterium for at least part of hydrogen atoms in each of the compds. is produced by a melting and pulling method. In the formula, R is <=2C alkyl or a halogenated alkyl. The metallic bar is a cooling bar for depositing a crystal of the optical crystalline material and it is made of a metal which does not melt or react with the material at the growth temp. of the crystal. A stainless steel or platinum bar is preferably used.

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 nonlinear optical crystal material represented by (wherein R is an alkyl having 2 or less carbon atoms or an alkyl halide) has high nonlinear optical performance and, in addition, mutually heteroepitaxially grown, a waveguide. Is a material having advantageous characteristics for producing a non-linear optical 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.

In the melt-pulling method, it is usually necessary to prepare crystals as seeds. As a method for producing seed crystals, a solution method or another melting method can be considered. The solution method has the advantage that a suitable size for use as seed crystals can be obtained relatively easily, but 4'-nitrobenzylidene-3-ethylcarbonylamino-4-methoxyaniline (hereinafter referred to as MNBA-E).
In the case of abbreviated as t), the seed crystal produced by the solution method has a defect that not only deterioration occurs during heating but also a deterioration component flows back into the raw material melt. On the other hand, although the melting method does not cause thermal deterioration, it has a problem that it is difficult to obtain a material having an appropriate size and shape with good reproducibility. .

In order to grow good quality crystals,
It is said that it is more preferable to perform an operation called necking, but when an organic crystal is used as a seed crystal, conditions for necking with good reproducibility have not been found.

[0005]

SUMMARY OF THE INVENTION An object of the present invention is to provide an unnecessary production method of a seed crystal for growing a large-sized, high-quality single crystal of a high-performance organic nonlinear optical crystal material with good reproducibility in a short period of time. To do.

[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′-nitrobenzylidene-3-halogenoalkanoylamino A metal rod is used as a seed in a method for producing a single crystal of an organic nonlinear optical crystal material selected from -4-methoxyaniline and a compound in which at least part of these hydrogens is deuterium-substituted, by a melt pulling method. A manufacturing method characterized by the above.

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-E)
t) 4'-nitrobenzylidene-3- (β-chloroethyl) carbonylamino-4-methoxyaniline (MN
BA-ClEt) and the like, which represents an alkanoylamino group or a halogenoalkanoylamino group, -NHCOR
In, R refers to an alkyl having 2 or less carbon atoms, an alkyl halide, or a compound in which at least a part of them is deuterium-substituted (hereinafter, these are collectively referred to as a benzylideneaniline-based material). 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 is a material having a preferable characteristic for melt growth that sublimation from a melt state is significantly suppressed under normal pressure or under pressure.

The melt-pulling method referred to in the present invention is to produce a single crystal by bringing seed crystals or other rod-shaped substances into contact with the raw material melt and then pulling them while rotating to solidify the melt. This method is superior to other manufacturing methods in that it has a high growth rate and that large-sized and low-defect crystals can be obtained.

The metal rod used in the present invention serves as a cooling rod for precipitating crystals of the material, and may be any material as long as it does not react with the material or melt at the growth temperature. . Preferably, stainless steel or platinum is used.

As for the inorganic crystals, an example has heretofore been known in which crystals are grown by a melt pulling method using a metal rod as a seed (Japanese Patent Laid-Open No. 4-243998). However, the present invention is based on the fact that there is no example in which a metal rod is used as a seed when growing an organic crystal by a melt-pulling method, and the invention can be applied to a specific organic nonlinear optical crystal material such as the present invention.

The raw material benzylidene aniline 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. This is because the purification method can remove impurities that cause deterioration and coloring of the raw material due to thermal decomposition, thermal polymerization, etc., which 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. 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 vacuum distillation purification is included in the present invention because execution is processing by the same apparatus and the same procedure.

An example of a melt pulling apparatus used for producing the organic nonlinear optical crystal of the present invention is shown in FIG.

The melt pulling apparatus mainly comprises a chamber 6, a crucible, and a pulling shaft (rotating shaft) 1. A metal rod 2 used as a seed is attached to the tip of the pulling shaft 1. The raw material is melted by heating silicon oil or the like filled in the copper crucible (inner) 4 and circulating in the copper crucible (outer) 5. Here, 3 is the raw material melt, 7
Is an oil inlet and 8 is an oil outlet. The inside of the chamber 6 is evacuated from the exhaust port 9 through the exhaust valve 11, and the inert gas is introduced from the gas inlet port 10 through the gas inlet valve 12.

In the manufacturing method of the present invention, it is preferable to change the crystal pulling rate during the growth. At the initial stage of growth, a polycrystalline body attached to a metal rod is thinly stretched to form a single crystal portion, and thereafter, the single crystal portion is thickened by decreasing the pulling rate, and a large single crystal can be obtained. Because.

The pulling rate is 2.0 at the initial stage of growth.
It is desirable to be 20.0 mm / hour. If it is too slow, it is difficult to stretch the precipitated crystal finely to form a single crystal site, and if it is too fast, the melt and the crystal may lose contact. Because.

The pulling rate after the change is preferably slower than that at the initial stage of growth, and more 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 rate of change of the pulling rate may be any value.

The rotation speed of the crystal is preferably 20 rpm or less. A more preferable rotation speed is 6 rotations per minute 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 container is once deaerated in vacuum and then replaced with an inert gas. This is because vacuum deaeration can remove oxygen, carbon dioxide, water and the like in the atmosphere, which are considered to be the causative substances 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 for the purpose of production,
Alternatively, any gas that does not serve as a catalyst for the reaction may be used.
Ar and N ₂ are preferably used.

The high-purity crystal obtained by the melt-pulling method using the metal rod of the present invention can be used again as a seed crystal.

[0025]

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

Example 1 MNBA using a stainless steel rod
-Et crystal growth Purification of the raw material MNBA-Et used in this experiment was performed 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 to 175 ° C. under a 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.

The raw material was filled in a copper crucible and placed in a growth vessel. The crucible has an inner diameter of 25 mm and a depth of 25.
It was mm. Silicon oil was used as the heat medium. The inside of the growth vessel was once evacuated by a rotary pump and a turbo molecular pump and then replaced with Ar gas.
The degree of vacuum during vacuum deaeration was 2 × 10 ⁻⁶ torr, and the pressure inside the container after the substitution was about 3 atm at room temperature.

In this experiment, a metal rod having a diameter of 2 mm and a length of 2 was used.
A 0 mm stainless rod was used and attached to the seed chuck.

A temperature accuracy of ± 0.01 ° C. and a programmable oil bath were used to control the temperature of the crucible during melting of the raw materials and growth, and silicon oil was used as the heat medium. Further, in order to control the temperature of the growth container atmosphere, the growth container itself was heated with a sheath heater.

The temperature of the oil bath was set to 177 ° C. and the temperature of the sheath heater was set to 160 ° C., and the raw materials were heated and melted. After the raw material was completely melted, the stainless steel rod was brought into contact with the melt and lowered to 8 mm below the liquid surface, and immediately after that, pulling was started at a speed of 5 mm / hour.

After 12 hours, the crystal in the vicinity of the solid-liquid interface had a diameter of about 2 mm and a neck portion could be formed. After that, in order to increase the crystal diameter, the pulling rate is 0.5 mm / hour, and the set value of the sheath heater is 158 ° C.
At the same time, the crystals started to rotate. Rotation speed is 1
It was 0 rpm.

After 20 hours, the crystal was rapidly cut off from the melt by increasing the pulling rate to stop the growth.

The pulled crystal was transparent by visual observation. The crystal size was 6 mm in diameter and 15 mm in length.

D ₁₁ which is the maximum component of the second-order nonlinear optical constant of the crystal prepared this time is determined by the maker fringe method (Jouna
l of Applied Physics. vol.
41.1667: 1970) showed that the performance was more than four times higher than d _33, which is the maximum component of lithium niobate, which is a typical material having high second-order optical nonlinearity.

From this example, it was confirmed that single crystal growth was possible using a stainless steel rod.

Example 2 MNBA-Et Crystal Growth by Seed Crystal Produced Using Stainless Steel Rod From the crystal produced by Example 1, a portion having a diameter of 2 mm and a length of 2 cm formed by necking was cut out and attached to a seed chuck. , Used as seed crystals.

The procedures of raw material purification, raw material filling, degassing / substitution in the growth vessel, and raw material melting were the same as in Example 1.

After the raw material was completely melted, the sheath heater setting value was set to 165 ° C., and after the temperature was stabilized, the seed crystal was lowered and brought into contact with the melt. After the contact, it was quickly raised by 0.5 mm. Then, lower the sheath heater setting value to 158 ° C over 20 minutes, and then
Lifting was started at a speed of mm / hour, and rotation was started at a speed of 10 rpm.

After 30 hours, the pulling rate was increased to quickly cut off the crystal to stop the growth.

The obtained crystals were visually transparent and had a diameter of 6 mm and a length of 15 mm.

As a result of evaluating d ₁₁ which is the maximum component of the second-order nonlinear optical constant of the crystal prepared this time by the maker fringe method as in Example 1, it is a typical material having a high second-order optical nonlinearity. D, which is the maximum component of lithium niobate
_The performance was four times higher than ₃₃ .

The present example shows that the crystal produced by using the metal rod can be used as a seed crystal.

[0044]

According to the present invention, when a high-performance organic nonlinear optical crystal material is grown by the melt-pulling method, necking can be performed with good reproducibility, and a large-sized, high-quality single crystal can be reproducible within a short period of time. It is possible to provide a manufacturing method that grows well and easily.

[Brief description of drawings]

FIG. 1 is a diagram showing an example of a melt pulling apparatus used for producing an organic nonlinear optical crystal of the present invention.

[Explanation of symbols]

 1 Pull-up shaft 2 Metal rod 3 Raw material melt 4 Copper crucible (inner) 5 Copper crucible (outer) 6 Chamber 7 Oil inlet 8 Oil outlet 9 Exhaust port 10 Gas inlet port 11 Exhaust valve 12 Gas inlet valve

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′-nitrobenzylidene-3-halogenoalkanoylamino A metal rod is used as a seed in a method for producing a single crystal of an organic nonlinear optical crystal material selected from -4-methoxyaniline and a compound in which at least part of these hydrogens is deuterium-substituted, by a melt pulling method. A method of manufacturing an organic nonlinear optical crystal, which is characterized by the above. 2. The method for producing an organic nonlinear optical crystal according to claim 1, wherein the metal rod is stainless steel. 3. The method for producing an organic nonlinear optical crystal according to claim 1, wherein the organic nonlinear optical material is 4′-nitrobenzylidene-3-ethylcarbonylamino-4-methoxyaniline. 4. The method for producing an organic nonlinear optical crystal 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. 5. The method for producing an organic nonlinear optical crystal according to claim 1, wherein the crystal is pulled while rotating at a rotation speed of 20 or less per minute when the single crystal is grown by the melt pulling method. 6. The method for producing an organic nonlinear optical crystal according to claim 1, wherein the pulling rate is changed during the growth. 7. The initial pulling speed is 2.0 to 20.0 m.
The method for producing an organic nonlinear optical crystal according to claim 6, wherein m / hour. 8. The pulling speed after the change is 0.1 to 5.0 m.
The method for producing an organic nonlinear optical crystal according to claim 6, wherein m / hour. 9. 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. 10. The method for producing an organic nonlinear optical crystal according to claim 9, wherein the inert gas is Ar or N ₂ .