JPH02239182A - Method and apparatus for producing crystal material - Google Patents

Abstract

PURPOSE:To obtain the high-performance crystal material which has no gaps in the crystal with good reproducibility by applying the pressure to move a crystal material melt to a crystal growth side of the hollow body at the time of producing the crystal material by an inverted Stockbarger's method. CONSTITUTION:The bottom end of a hollow fiber 1 penetrated and held in a supporting part 24 is dipped into an org. optical material melt 22 put into a melt tank 23 in a stationary pressurizing vessel 26 disposed in, for example, a heating furnace 20. An inert gas 38 is then introduced into the vessel 26 from the bottom thereof to pressurize a space 39 and to rise the melt 22 up to the aperture at the top end of the fiber 1 previously disposed with the seed crystal. The heating furnace 20 and the upper furnace 21 above this furnace are lowered in this state by a moving mechanism 27 and the fiber 1 is inserted into a through-hole 44 at the center of the upper plate part of the heating furnace 20. the fiber is heated by a heater 41 and cooling water 48 is passed to allow the org. optical material of the single crystal to grow.

Description

[Detailed description of the invention] a. INDUSTRIAL APPLICATION FIELD The present invention relates to a method and apparatus for producing crystalline materials, such as nonlinear optical materials.

mouth. BACKGROUND OF THE INVENTION Since the nonlinear optical effect was discovered in 1961, research has been conducted on materials that have a nonlinear optical effect and devices that utilize the nonlinear optical effect. Such devices include, for example, wavelength conversion devices used in optical harmonic generators (especially used for wavelength conversion of laser light).
It has been known.

FIG. 7 shows an example of a waveguide, which has a hollow structure with an inner diameter of several tens of μm or less, for example, 3 μm, in which a nonlinear optical (conversion) material 2 is embedded in a glass fiber 1. Laser human radiation 3 from one end is wavelength-converted by a nonlinear optical effect while traveling through optical material 20, and is emitted as light 4. Such devices are known as phase matching conversion elements, Cerenkov type conversion elements, and the like. As the optical material 20, LiNbOs and K
Inorganic materials such as DP (KH.PO.) were known.

In recent years, organic materials, which have significantly higher nonlinear optical constants than these inorganic materials, have begun to attract attention. Examples of such substances include MNA (2-methyl-4-nitroaniline), mNA (metanitroaniline), and POM (3-nitroaniline).
methyl-4-nitroviridine-1-oxide).

As a method for manufacturing such optical materials, particularly organic materials, the Stockberger method is known, in which a low-molecular single-crystal organic optical material is grown inside a hollow fiber. The outline of this process is shown in FIG. 8. An optical material melt 12 is put into a hollow glass fiber 1 whose lower end is closed, and while it is transferred from a heating zone 5 to a cooling zone 6, a single crystal 2 is sequentially added from the lower end. Generate. The figure shows the various forces that occur in this system (the same applies to the following figures). However, with this method, sufficient material is not supplied to the single crystal forming interface.
A problem arises in that there are many voids.

An application of this Stockburger method is the Inverted Stockburger method (Journalof
Crystal Growth 68 (1984)
651-655). In this method, as schematically illustrated in FIG. 9, when forming an organic single crystal 2 in a fiber 1, a high temperature section 5 and a low temperature section 6 of the furnace are placed in opposite positions to those of the normal Stockberger method. This method is characterized by the fact that it is possible to obtain a single crystal without voids.

However, the first drawback of this separated Stockberger method is that it is practically difficult to stably obtain a void-free single crystal. The second drawback is that only fixed force relationships exist for various materials.
It is difficult to obtain a void-free single crystal by applying a force relationship suitable for each material. In particular, since the upper end of the fiber 1 is closed, the inner diameter may vary by several orders of magnitude depending on the atmospheric pressure.
Problems such as not being able to completely fill the fibers, which are extremely thin (less than 0 μm) with material, and not being able to place seed crystals in the closed tube region, exacerbate the above-mentioned drawbacks.

C. OBJECTS OF THE INVENTION It is an object of the present invention to provide a method and an apparatus therefor which enable crystal growth to obtain crystals without voids, and which can be easily operated with good reproducibility.

two. The constitution of the invention, that is, the present invention is such that the one end of a hollow body with at least one end opened is immersed in a crystal material melt, and the hollow body is moved to the other end side with respect to the crystal material melt. The present invention relates to a method for producing a crystalline material, in which the melt of the crystalline material in the hollow body is cooled from the other end side while applying pressure.

The present invention also provides a heating zone, a crystalline material melt container disposed in the heating zone, a cooling zone, and immersing the one end of the hollow body with at least one end open in the crystalline material melt. immersing means; pressure applying means for applying pressure to move the crystal material melt toward the other end of the hollow body in the immersed state; The present invention also provides an apparatus for manufacturing a crystal material, which includes a moving means for moving the crystal material.

Ho. Example Examples of the present invention will be described below.

1 to 4 show examples in which the present invention is applied to nonlinear organic optical materials.

The manufacturing apparatus used in this example basically consists of a heating furnace 20 for melting a low-molecular organic optical material to be single-crystallized.
, an upper furnace 21 disposed above the heating furnace 20 to cool and single-crystallize the existing optical material melt, and an upper furnace 21 disposed within the heating furnace 20 for accommodating the organic optical material melt 22. The melt tank 23 and the fiber support part (or the fiber support part for supporting the melt tank and penetrating and holding the hollow glass fiber 1 so that the lower end of the hollow glass fiber 1 is immersed in the melt 22) Means) A fixed pressurizing tank 26 in which 24 is provided on the upper plate 25, and a moving mechanism 27 for vertically moving the heating furnace 20 and the upper furnace 21 with respect to the pressurizing tank 26.
It is composed of.

As shown in FIG. 4, the heating furnace 20 and the upper furnace 21 are attached to a moving stage 28 using heat insulating screws 2, and are moved together. Movement of the moving stage 28 is performed by a feed screw mechanism 36 using a stamping motor 30 as a driving source. The motor 30 is computer controlled,
The moving stage 28 has a speed of 0.1 mm/hr to 2000 m/hr.
Move in steps at a speed of hr. In addition, each furnace 20, 21
Actually, the moving stage 2 is moved through the radiant heat shield 31.
8, and as a result, the entire structure is mounted on the support base 32 so as to be movable up and down while being guided by the temporary guide section 35.

The pressurized tank 26, which is a sample setting part, is made of Cu, for example, and is fixed on a support stand 33 via a support arm 34 (strictly speaking, it can be moved for sample setting).

Then, the material is heated by radiant heat from the heating furnace 20 and melted, and the hollow fiber 1 is filled with the melt 22 by capillary action and pressurization. Note that fiber 1 is
Heat conduction from sample installation section 26 and heating furnace 20. Heated by radiant heat from. An inert gas 38 is introduced into the pressurized tank 26 from the bottom via a pressurizing pipe 37, and the sample space 39 is maintained at a predetermined pressure (for example, 500 kg/cwt or less,
Especially 100 kg/d or less, and even 10 to 100 kg/d.
c+J is good. ), thereby causing the melt 22 to rise to the upper end opening of the fiber 1. In FIG. 1, the upper plate 25 is fixed by bolts 43, but they are not shown in FIG. 4.

Further, 46 indicates each thermocouple.

In FIG. 1, the heating furnace 20 is, for example, a cylindrical body 40 made of Cu.
Attach a surface heater 41 to the outer peripheral surface of the
Although it was configured to be heated to 0°C, as shown in Figure 4,
It is also possible to heat the cylindrical body 40 by winding the heater wire 42 around its outer peripheral surface. Additionally, an insertion hole 44 is provided at the center 1 of the upper plate of the heating furnace 20 for inserting the fiber 1 when the furnace moves up and down.

Above the heating zone 5 by the heating furnace 20, for example, 0.
1~3IIIIII! The upper furnace 21 is disposed with a micro gap 45 (actually, a heat insulating material is filled in this gap to form a temperature gradient in the vertical direction) of 0.1 to II[lII1]. The furnace 21 is cooled by discharging cooling water 48 at 0 to 70° C. from an inlet pipe 47 through an outlet pipe 49, and the temperature is monitored and controlled by a thermocouple 46. The shape of the furnace 21 may be a donut-shaped cylinder, the inside of which is a cooling zone 6, and the center thereof is an insertion hole 50 through which the fiber 1 can be inserted.

Regarding optical materials applicable to the above, especially organic substances having optical nonlinearity, see, for example, "Organic Nonlinear Optical Materials J (CMC Co., Ltd., published in 1985),"
'Nonlinear Optical Prope
rtiesof Organic Molecules
and Crystal Jvow. 1. 2
(Academic Press Inc. 1987
), described in the proceedings of the 1954-1956 Annual Meetings of the Chemical Society of Japan. Preferably used organic substances having optical nonlinearity include aromatic rings such as benzene and naphthalene substituted with electron-withdrawing groups and electron-donating groups represented by nitroaniline derivatives, heterocycles such as pyridine and pyrimidine, Mention may be made of stilbene, pyridine-N-oxide and urea.

Preferred examples of the organic substance having optical nonlinearity used in the present invention are shown below.

(The following is a blank space) Nα18 0I In the above, in consideration of single crystallinity and nonlinear optical effect, compounds with Nα10 to 16 are preferable, and more preferable are No. These are compounds No. 10, 11, 12, and 16.

A single crystal of an organic optical material is formed in the hollow part of the fiber 1 using the apparatus having the above-mentioned configuration.The operation method will be explained below.

That is, the heating temperature in the heating furnace 20 is set to the melting point of the optical material or higher, and the melt 22 is sufficiently formed. Then, the lower end opening 51 of the fiber 1 having an inner diameter of several ioom or less is immersed in this melt 22, and at the same time, a non-oxidizing gas, for example, an inert gas 38, is fed into the space 39.
The pressure of the melt 22 is increased, thereby forcing the melt 22 to rise through the hollow part of the fiber 1 to its upper end opening 52, completely filling the upper end of the fiber (see FIG. 3). Due to this pressurization, no air bubbles or the like are generated in the single crystal when the melt 22 is single crystallized. Further, pressure is applied so that the growing single crystal is not distorted.

A seed crystal 53 is placed in advance in the upper end opening 52 of the fiber 1 to facilitate single crystallization 2. This seed crystal 5
Even if 3 is present, the effect of the above-mentioned pressurization can be sufficiently exhibited and single crystallization can be performed reliably.

This single crystallization is achieved by gradually lowering the furnaces 20 and 21 from the state shown in FIG. 1 as shown in FIG. 2 to move the fiber 1 from the upper end from the heating zone 5 to the cooling zone 6.

As described above, the method and apparatus according to the present example is a two-zone, so-called high breath type, independent and stock burger type, and has the following excellent advantages.

(1). In addition to the capillary phenomenon, the operation is performed while pressurizing the space 39 to cause the melt 22 to rise toward the upper end of the fiber 1, so that the fiber 1 is sufficiently filled with the melt 22 and cooled. Even if volume contraction occurs due to single crystallization due to +F o)
. As a result, no voids are generated in the obtained single crystal, and a high-performance optical material can be produced with good reproducibility. This becomes even more certain because the upper end of the fiber 1 is open (in fact, there is a seed crystal). Instead of applying the above pressure to the lower end of the fiber 1, it would be possible to apply the same pressure to the upper end of the fiber 1 (i.e., pressurize the entire heating zone 5 without providing the space 39, or simply pressurize the heating zone 5 under atmospheric pressure). If the fiber is placed at <<), pressure is applied from both ends of the fiber, so the upward force of the melt is weak, making it impossible to prevent voids, and the single crystallinity may also deteriorate.

(2). Furthermore, since the seed crystal 53 can be placed at the upper end of the opened fiber as described above, single crystallization can easily occur from there. Furthermore, since single crystallization can proceed from the upper end, it is easy to set the level of the single crystal region.

(3). Further, since the furnaces 20 and 21 are gradually lowered to monocrystallize the melt in the fiber 1 from its upper end, single crystallization can be reliably achieved while forming a desired temperature gradient. In particular, since the fiber 1 has an extremely thin inner diameter and a wall that is thicker than this, in addition to the heat retention effect of the wall, the gap 45 between the furnaces 20 and 21 (relatively wide 0.1
~3n), if the descending speed of the furnace is too high, it will be difficult to form the desired temperature gradient in the fiber length direction, resulting in poor crystallinity of the single crystal, or crystallization at a location other than the upper end. This tends to result in a single crystal with insufficient purity or crystallinity.

However, the descending speed of the furnace is controlled by the stepping motor 3 mentioned above.
0 can be controlled with high precision (especially 0.
1 to 10 mm/hr), the temperature gradient described above can be made steep and a single crystal with good crystallinity can always be obtained.

FIG. 5 shows another manufacturing apparatus. This apparatus differs from the one shown in FIG. 1 in that it does not have an upper furnace 21, and above the heating furnace 20 is simply a cooling zone 6 consisting of space. The other parts are the same as those in FIG.

FIG. 6 shows an apparatus in which the fiber 1 and the furnace 26 are rotatable so that they can be moved up and down.

This method is particularly effective when using a fiber that uses a coupling agent around the core of the hollow fiber 1 or when the organic nonlinear optical material contains many impurities. Other substances are separated by rotation to obtain a good single crystal.

Similar to the above-mentioned example, this device sends non-oxidizing gas to the pressurized tank 26 to achieve the desired pressure, and then connects the connecting vibrator 37'.
It is made to be removable.

The pressurized tank 26 is placed on a high-speed rotation stage 60 and rotated at 100 to 1000 rpm by a known rotation stage mechanism 61. p
．． m. horizontally rotated at a rotation speed of Other parts are first
It is similar to the one shown in the figure.

Next, this embodiment will be described in more detail with regard to a specific example.

Vanillin was used as a low molecular weight organic material. And the first
As shown in the figure, in an apparatus provided with an upper furnace 21 and a lower furnace 20, the temperature of the upper furnace 21 was set to 20°C, and the temperature of the lower furnace 20 was set to (83°C).

The lower end of the hollow fiber 1, which is open at both ends, is put into the raw material melt tank 23, and the melt 2 is heated by capillary action and extremely slight pressure.
2 was filled into the hollow fiber 1. At this time, the hollow fiber 1 was heated by the lower furnace 20 in order to maintain the molten state. Incidentally, a vanillin seed crystal 53 was placed at the tip of the hollow fiber 1, and covered with a body-thermal epoxy resin or the like (not shown).

The inside of the pressurized tank 26 is pressurized with 40 kg/cd Ar gas, and the entire hollow fiber 1 except for the seed crystal 53 is transferred to the lower furnace 2.
0, then set the upper furnace 21 to the lower furnace 20 and 0.5
The price was lowered to +11,111. At this time, 0.
A ceramic heat insulating material with a thickness of 5.11111 mm was placed between both furnaces.

Next, the entire furnace was lowered at a rate of 1.0 s/hr to obtain crystals in the hollow fiber 1.

Furthermore, ethyl P-aminobenzoate was used as a low molecular weight organic material. Using the same equipment as in Example 1, the temperature of the upper furnace 21 was set to 3.
The temperature of the lower furnace 20 was 90°C.

A hollow fiber having one end (lower end) open and the other end (upper end) closed was filled with a raw material melt, and in the filled state was set in the raw material melt tank 23 with the closed end facing upward.

Place the entire hollow fiber 1 into the lower furnace 20, and
It was pressurized to 100 kg/Clll with r gas 38.

The entire furnace was lowered at a rate of 0.5 mm/hr to obtain crystals in the hollow fiber 1.

Example 1 Methyl p-hydroxybenzoate was used as a low molecular weight organic material.

There is one furnace as shown in Figure 5, and the temperature of this furnace is set to p-
Same melting point as methyl hydroxybenzoate (132°C)
And so.

The hollow fiber 1 was filled with the raw material melt 22 in the same manner as in Example 1, and a seed crystal was placed at the tip. The entire hollow fiber 1 except for the seed crystal part is set in the furnace, and Ar gas 38
The furnace was pressurized to 20 kg/cd and the entire furnace was lowered at a speed of 5 s/hr. Then, crystals were obtained in the hollow fiber 1.

Comparative Examples 1, 2, and 3 are Ar
Crystals were obtained within the hollow fiber using a method that did not use gas pressure.

The hollow fiber used in each of the above examples had an inner diameter of 7 μm.
It had an outer diameter of 1 barrel and a length of 50 mm.

Further, the hollow fibers used in Specific Example 2 and Comparative Example 2 corresponding thereto had an inner diameter of 7 μm and an outer diameter]. The length of the mln portion was 40 mm, and the inner diameter of 7 μm was gradually closed at one end (upper end) side with a certain slope, and the entire length of the fiber was 50 mm.

The evaluation results of the crystals within the hollow fibers obtained in each of the above examples are shown in the table below. The evaluation method was performed on 30 aun near the center of the hollow fiber. The evaluation consisted of examining extinction using a polarizing microscope to examine single crystallinity, and using a microscope (X2
00> was used to check the number of voids.

From this result, it is clear that by operating according to the present invention, a void-free crystal with excellent single crystallinity can be obtained.

Although the present invention has been illustrated above, the above-described examples can be further modified based on the technical idea of the present invention.

For example, the material, shape, etc. of the fiber 1 described above may be changed in various ways, and the hollow body may be in the shape of an ampoule or the like in addition to the fiber. Furthermore, various kinds of optical materials can be selected. In addition, the shape and structure of the pressurized tank, heating furnace, upper furnace, etc. may be modified in various ways, and the pressurizing medium used,
Various cooling media may also be employed.

Moreover, contrary to the above-mentioned example, it is also possible to grow a single crystal by moving the sample side (actually, the entire pressurized tank) up and down while keeping the furnace fixed. In addition, in the above example, the melt at the lower end of the fiber was pressurized by the pressure tank, but it is also possible to reduce the pressure in the space at the upper end of the fiber (inside the heating zone), specifically by suctioning it with a vacuum bomb. , the melt can rise in the fiber and fill it to the top. In this case, as in the case of pressurization, it is necessary to avoid straining the growing single crystal.

Note that the present invention is applicable not only to nonlinear optical materials as described above, but also to crystalline materials and devices that can be used for other purposes.

9. Effects of the Invention As described above, in the present invention, pressure is applied to move the melt to the other end side (crystal growth side) of the hollow body. Even if volume shrinkage occurs due to single crystallization due to cooling, the above-mentioned pressure acts to fill the volume (that is, to replenish the melt). As a result, no voids are generated in the obtained crystal, and a high-performance crystal material can be produced with good reproducibility.

Also, since a seed crystal can be placed on the other end of the hollow body,
Crystallization easily occurs from there, and by moving from the other end to the cooling zone, crystallization can be reliably achieved while forming a desired temperature gradient at the other end.

[Brief explanation of drawings]

1 to 6 show embodiments of the present invention. FIG. 1 is a cross-sectional perspective view of an apparatus for manufacturing a single crystal of a nonlinear organic optical material, and FIG. Figure 3 is a schematic cross-sectional view showing the state of force acting near the hollow fiber, Figure 4 is a schematic partial cross-sectional front view of the entire device including the drive system, Figure 5 FIG. 6 is a cross-sectional perspective view or sectional view of a manufacturing apparatus according to another example. 7 to 9 show conventional examples, in which FIG. 7 is a schematic perspective view of a wavelength conversion device, and FIGS. 8 and 9 are schematic diagrams showing a method for manufacturing a single crystal of a nonlinear optical material. FIG. In addition, in the symbols shown in the drawings, 1...Hollow fiber 2...Single crystal 5...Heating zone 6... ......Cooling zones 12, 22...Melt 20...Heating furnace 21...Upper furnace 23... ...Melt tank 24...Fiber support section, 26...
..... Pressurized tank 28 ..... Movement stage 29 ..... Insulation screw 30 ..... Stepping motor 38 ...
...Ar (pressurized) gas 39...
Pressurized space 4L 42... Heater 44, 50...
......Through hole 45...Gap 48...Cooling water 51, 52...Opening 53... ...It is a seed crystal.

Claims (1)

[Claims] 1. The one end of a hollow body with at least one end open is immersed in a crystal material melt, and the pressure is applied to move the crystal material melt toward the other end of the hollow body. A method for producing a crystal material, wherein the crystal material melt in the hollow body is cooled from the other end side in this state. 2. a heating zone, a crystalline material melt container disposed within the heating zone, a cooling zone, and an immersion means for immersing the one end of the hollow body having at least one open end in the crystalline material melt; Pressure applying means for applying pressure to move the crystal material melt toward the other end of the hollow body in this immersed state; and a pressure applying means for relatively moving the hollow body from the other end to the cooling zone. An apparatus for manufacturing a crystal material, comprising means.