JP4701403B2 - Sublimation purification equipment for organic compounds - Google Patents

Description

  The present invention relates to a sublimation purification apparatus for organic compounds exhibiting sublimation properties. The present invention particularly relates to a sublimation purification apparatus useful for obtaining a high-purity electroluminescent chelate complex compound that can be used as a light-emitting material of an organic electroluminescence (EL) element.

  In recent years, organic EL elements have attracted attention as thin light emitting elements for constituting various light emitting devices such as display devices, flat light emitters, and electronic paper.

  The structure of a typical organic EL element has a basic configuration in which a first electrode layer, an organic light emitting material layer, and a second electrode layer are laminated in this order on a substrate. An electron transport layer or a hole transport layer is disposed as a functional auxiliary layer between each electrode layer and the organic light emitting material layer as necessary.

There are various problems in the development of organic EL elements. Among them, it is not easy to produce organic EL elements that exhibit sufficient durability, and it is not easy to ensure a sufficient amount of light emission. It has been a problem. Among these, as for the latter problem, a chelate complex compound represented by tris- (8-hydroxyquinolinato) aluminum, which is usually called Alq ₃ , has already been developed as a light-emitting material exhibiting a high light emission amount. . However, even in the case of Alq ₃ described above, there is a problem that a sufficient amount of light emission cannot be obtained, and the cause thereof is that a mixture of impurities generated in the Alq ₃ manufacturing process has already been pointed out. Yes.

  Patent Document 1 describes a method of purifying an organic compound typified by a chelate complex compound used as a light emitting material of an organic EL element by sublimation. The invention described in Patent Document 1 is an invention characterized in that, when an organic compound is purified by sublimation, the organic compound is stirred or vibrated. By using this invention, the sublimation efficiency is improved and the sublimation time is increased. It is said that this can be shortened. An apparatus for realizing sublimation purification specifically described in Patent Document 1 is a general sublimation apparatus, that is, a bowl-type container containing an organic compound to be sublimated and an upper part of the container. It is an apparatus comprised from the container (it is equipped with the cooling device) provided with the surface which deposits the arranged sublimate.

  In Patent Document 2, as a sublimation purification apparatus particularly useful for purification of a light emitting material of an organic electroluminescent element, a heat source is installed in a vacuum chamber, and an organic compound heated by the heat source is separated from the heat source in the vacuum chamber. A sublimation purification apparatus is described which consists of sublimation collection in a collection chamber arranged in position.

  Patent Document 3 describes an organic material sublimation purification apparatus in which a collection tube for supplementing an organic material to be sublimated is arranged in a reaction tube.

Patent Document 4 discloses a sublimation tube capable of generating heat by electromagnetic induction as a device for efficiently sublimating and purifying a solid material having poor thermal stability, and a collection having a plurality of zones arranged on the downstream side of the sublimation tube. The sublimation purification apparatus which consists of a part is described.
Japanese Patent Laid-Open No. 11-171801 JP 2003-88704 A JP 2003-95992 A JP 2000-93701 A

As described above, commercially available products (reagents) of the above-described chelate complex compounds such as Alq ₃ used as organic EL light-emitting materials usually contain several percent of impurities. It is known that the chelate complex compound does not exhibit sufficient light emission that can be originally exhibited. For this reason, research on the sublimation purification method of chelate complex compounds has already been conducted as described above.

  This time, the inventors' research has revealed that there is a problem that it is difficult to obtain a chelate complex compound exhibiting sufficient luminescence characteristics by purification using a conventionally known sublimation purification apparatus. And this problem is not just a skillful problem of sublimation purification technology, but a configuration of a conventionally known sublimation purification apparatus, that is, a configuration in which a sublimation chamber and a collection chamber or a collection surface are simply arranged, In particular, the thermal stability is not sufficient, and the sublimation temperature of the mixed impurities is often close to the sublimation temperature of the chelate complex compound, realizing a highly purified electroluminescent chelate complex compound that can be obtained as a reagent. Proved difficult to do.

  For the above reasons, the present inventor has developed a sublimation purification apparatus that makes it possible to achieve a high degree of purification of a chelate complex compound exhibiting electroluminescence properties at a level that can be obtained as a reagent. And when the sublimation purification of the chelate complex compound which shows the light emission characteristic of the level which can be obtained as a reagent was tried using the developed sublimation purification apparatus, the light emission characteristic improved remarkably compared with the chelate complex compound of the reagent level. It has been found that a highly pure chelate complex compound can be obtained.

  The present invention relates to a heat-resistant glass cylindrical body provided with an inert gas inlet at the lower part and an inert gas outlet at the upper part, and an organic compound to be sublimated accommodated in the inner lower part of the cylindrical body. A container (hereinafter also referred to as a sublimable organic compound), a thermally conductive outer tube disposed on the outer periphery of the cylindrical body so as to cover the periphery of the container and extend upward, and the container of the outer tube A heating tool installed in a region covering the periphery, and three or more circular or polygonal elements arranged in a stepwise manner in parallel with each other at intervals inside the cylindrical body and above the container It exists in the sublimation refinement | purification apparatus of the sublimable organic compound which comprises the multistage sublimation plate which consists of a plate.

By using the sublimation purification apparatus of the present invention, from a sublimable organic compound having insufficient thermal stability and an organic compound product in which the sublimation temperature of mixed impurities is close to the sublimation temperature of the target organic compound. The desired high-purity organic compound can be obtained. Therefore, the sublimation purification apparatus of the present invention can be used particularly advantageously for sublimation purification of an electroluminescent chelate complex compound such as Alq ₃ used as a light emitting material of an organic EL element, and has the same problems as described above. It is extremely useful for obtaining a desired high purity organic compound from an organic compound product having a reagent level purity.

A preferred embodiment of the sublimation purification apparatus of the present invention will be described next.
(1) The sublimable organic compound is a chelate complex compound.
(2) The sublimable organic compound is a chelate complex compound exhibiting electroluminescence.
(3) The sublimable organic compound is tris- (8-hydroxyquinolinato) aluminum (Alq ₃ ).
(4) The multi-stage sublimation plate is composed of 5 to 50 plates.
(5) The multistage sublimation plate is composed of 10 to 30 plates.
(6) The plate of the multi-stage sublimation plate is made of heat-resistant glass or metal material (particularly aluminum).
(7) Each plate of the multi-stage sublimation plate is sequentially suspended from the upper part of the cylindrical body by a suspension rope.
(8) It is arranged so that the top part of the thermally conductive outer tube arranged on the outer periphery of the cylindrical body is positioned below the top part of the cylindrical body, and this arrangement allows the top part of the cylindrical body to be exposed to the outside. An exposed surface is formed, and the uppermost stage of the plate is disposed at an internal position of the cylindrical body corresponding to the exposed surface.

  Next, the sublimation purification apparatus of the present invention will be described in detail with reference to the accompanying drawings.

  FIG. 1 attached herewith is a diagram showing a typical configuration of the sublimation purification apparatus of the present invention. That is, in the sublimation purification apparatus of the present invention, the heat-resistant glass cylindrical body 13 in which the inert gas inlet 11 is provided in the lower part and the inert gas outlet 12 is provided in the upper part; A container 14 of a chelate complex compound to be sublimated, which is accommodated in the tube; a thermally conductive outer tube 15 disposed on the outer periphery of the cylindrical body 13 so as to cover the periphery of the container 14 and extend upward; A heating tool 16 installed in a portion covering the periphery of 14; and three or more circular shapes arranged in a stepwise manner in parallel with each other at intervals inside the cylindrical body 13 and above the container 14; It comprises a multi-stage sublimation plate 17 comprising polygonal plates 17a, 17b, 17c,.

  The sublimation purification apparatus of the present invention first requires a cylindrical body 13 that performs a sublimation operation inside. This cylindrical body is manufactured from heat-resistant glass such as Pyrex glass or quartz glass. As this cylindrical body, a cylinder is usually used, but a cylindrical body having a polygonal or elliptical cross section may be used. An inert gas inlet 11 for introducing an inert gas (for example, argon, helium, nitrogen) for sending an organic compound to be sublimated upward is provided at the bottom of the cylindrical body 13. The upper part is inert to discharge inert gas (part of the sublimated organic compound, impurities mixed in the organic compound, and possibly thermal decomposition products) sent from the lower part. An active gas outlet 12 is provided. The upper part of the cylindrical body 13 means the top part of the cylindrical body or the vicinity thereof, and the lower part means the bottom part of the cylindrical body or the vicinity thereof. And the sublimation purification apparatus of this invention is normally used by the perpendicular | vertical arrangement | positioning as shown in FIG. 1, but can also be arrange | positioned diagonally or horizontally as needed. In the latter case, the lower part of the cylindrical body means the end part on the side where the inert gas is introduced or its vicinity, and the upper part means the end part on the side where the inert gas is discharged or its vicinity.

  A container 14 of a chelate complex compound to be sublimated is accommodated in the inner lower portion of the cylindrical body 13. The container 14 is made of, for example, heat-resistant glass, and is formed by a tubular support 18 (provided with a hole for passing an inert gas in the middle) 18 raised from the bottom of the tubular body 13. Supported.

  On the outer periphery of the cylindrical body 13, a heat conductive outer tube 15 is provided so as to cover the periphery of the container 14 and to be extended upward. As a material of the heat conductive outer tube 15, iron is usually used, but other materials may be used as long as they exhibit heat conductivity. In addition, the top part of the heat conductive sheath 15 is arrange | positioned so that it may be located below the top part of the cylindrical body 13, and the exposed surface to the outside is formed in the upper part of this cylindrical body Is preferred. The meaning of this configuration will be described later.

  A heating tool 16 is installed in the outer tube 15 at a site covering the periphery of the container 14. The heating tool 16 is usually configured to cover the entire periphery of the container 14. In addition, although a heating tool may be independent, you may install additional heating tools (auxiliary heating tools) 16a and 16b above the heating tool 16. FIG. This is particularly useful because the sublimation purification can be effectively performed by forming a wide temperature gradient in the vertical direction of the cylindrical body 13 by installing the auxiliary heating tool. A typical example of the heating tool and the auxiliary heating tool is a ribbon heater.

  Inside the cylindrical body 13 and above the container 14 are composed of three or more circular or polygonal plates 17a, 17b, 17c,... Arranged in a stepped manner in parallel with each other at intervals. A multi-stage sublimation plate 17 is accommodated. In FIG. 1, each plate in the multistage sublimation plate 17 is sequentially suspended from the inert gas discharge port 12 by a suspension line. Note that the multi-stage sublimation plate 17 may be provided with a support in the middle of the tubular body 13 and fixedly erected by this support. The number of plates of the multistage sublimation plate 17 is not particularly limited as long as it is 3 or more, but is usually 5 to 50, preferably 10 to 30. Each plate is preferably made of a heat conductive material, and is preferably made of a heat-resistant glass capable of suppressing the mixing of impurities into the organic compound to be purified, or a metal material (especially aluminum) that is lightweight and excellent in durability. preferable.

  It is desirable for the plate above the multi-stage sublimation plate to transmit less heat from the outer tube heated by the heating means. For this purpose, the top part of the thermally conductive outer tube arranged on the outer periphery of the cylindrical body is arranged so as to be located below the top part of the cylindrical body. And at least the uppermost plate (preferably 2-5 on the uppermost side) is disposed at the internal position of the cylindrical body corresponding to the exposed surface. Is preferred.

Examples of organic compounds suitable for purification using the sublimation purification apparatus of the present invention include electroluminescent chelate complex compounds. A typical example of the electroluminescent chelate complex compound is the aforementioned tris- (8-hydroxyquinolinato) aluminum (Alq ₃ ), but in addition, various metal complex compounds of quinoline derivatives can also be mentioned, Moreover, a phthalocyanine-type metal complex compound can also be mentioned. Specific examples of these organic compounds suitable for purification by the sublimation purification apparatus of the present invention are described in Patent Document 1 described above.

  Next, an organic compound purification method using the sublimation purification apparatus of the present invention will be described as a purification method using the sublimation purification apparatus shown in FIG.

  First, an organic compound to be purified is placed in a container 14 (for example, a dish-shaped container made of heat-resistant glass) that has been removed in advance, and is held inside the tubular body 13 by the form placed on the tubular support 18. Next, the multistage sublimation plate 17 is mounted inside the cylindrical body 13. Then, an inert gas supply source (not shown) is connected to the inert gas introduction port 11 at the lower part of the cylindrical body 13, and a vacuum device (not shown) is connected to the upper inert gas exhaust port 12.

  Next, exhaust is started from the inert exhaust port 12, and at the same time, an inert gas such as argon is introduced from the inert gas introduction port 11. At the same time before or after the introduction of the inert gas, heating by the heating means 16 and the auxiliary heating means 16a and 16b is started. The heating temperature varies depending on the organic compound to be purified, and also varies depending on the pressure inside the cylindrical body 13. Usually, the heating temperature by the auxiliary heating means 16 a and 16 b is set lower than the heating temperature by the heating means 16.

  The organic compound filled in the container 14 heated through the outer tube 15 and the wall of the cylindrical body 13 by the heating means 16 starts sublimation, and the main part of the organic compound is once the lowermost stage of the multistage sublimation plate 17. It adheres to the lower surface of the plate. The organic compound adhering to the lower surface of the lowermost plate further sublimates, and sequentially adheres to the lower surface of each plate of the upper step to repeat sublimation. The organic compound is thus repeatedly attached and sublimated to the lower surface of each plate, and purification is realized by repeating the repetition, and the organic compound deposited on the lower surface of the plate near the uppermost stage of the multi-stage sublimation plate 17 is of high purity.

[Example 1]
A Pyrex glass tube (cylindrical body 13) having a diameter of 40 mm (wall thickness: 2 mm) and a length of about 1100 mm and an open top and bottom, and an iron outer tube 15 having a length of 700 mm were prepared, respectively. It was arranged in the form shown in. Next, heating means 16 and auxiliary heating means 16a and 16b, each of which is a band heater, were wound around the outer periphery of the outer tube 15. Next, the organic compound (Tris- (8-hydroxyquinolinato) to be purified placed in a cylindrical body 13 on a support tube (height 20 mm) 18 and filled in a glass dish (container 14). ) Aluminum (Alq ₃ ) reagent (manufactured by Tokyo Chemical Industry Co., Ltd., guaranteed purity of 95% or more)) was accommodated. From the upper part of the cylindrical body 13, a multi-stage sublimation plate 17 (distance between each plate is 40 mm) of 20 stages (20 plates: all made of aluminum) was suspended. Next, argon gas was continuously introduced from the inert gas inlet 11, and argon gas was continuously exhausted from the inert gas outlet 12. The flow rate of argon gas was 120 mL / min, and the pressure inside the cylindrical body 13 was almost normal pressure (1.0 × 10 ⁵ Pa). After the introduction of the argon gas was started, current was supplied to each of the band heaters 16, 16a and 16b to heat the band heater 16 to 350 ° C. and the band heaters 16a and 16b to 330 ° C. By this heating, the outer tube 15 reached 313 ° C. at the position closest to the container 14, and the temperature gradually decreased above the outer tube 15 and reached 53 ° C. at the top of the outer tube 15. This heating started the sublimation of Alq ₃ . After performing this sublimation operation (heating operation) for 67 hours continuously, the heating was terminated.
When the cylindrical body 13 and the outer tube 15 are cooled to room temperature, the upper portion of the cylindrical body 13 is cut in the diametrical direction, and then sublimation deposition is performed from the second to third stage plates from above the multistage sublimation plate 17. The product was recovered (yield: about 50%).

[Example 2]
According to the method of Example 1, except that the flow rate of argon gas was changed to about 200 mL / min, the pressure inside the cylindrical body 13 was changed to 3.3 × 10 ² Pa, and the sublimation operation time was changed to 2 hours. Alq ₃ was purified by sublimation (yield: about 60%).

[Comparative example]
The Alq ₃ reagent (manufactured by Tokyo Chemical Industry Co., Ltd., guaranteed purity of 95% or more) used in the sublimation purification experiments in Examples 1 and 2 was prepared and used as a comparative sample.

[Evaluation of purity of Alq ₃ ]
Because it is accurately quantify the purity of Alq ₃ at high purity levels difficult, Example 1 and Alq ₃ was purified by sublimation at 2, and incorporates each of Alq ₃ reagent of Comparative Example in the organic EL device Then, the light emission characteristics of the organic EL element were measured, and Alq ₃ of each example was evaluated.

(1) Evaluation test method as an organic EL element On a glass substrate having an ITO electrode (thickness: 150 nm) on the surface, α-NPD (known hole layer forming material: described in JP-A-2004-253209) The vapor deposition layer (thickness: 50 nm) was formed. Next, Alq ₃ of each example was vapor-deposited with a thickness of 50 nm on this vapor deposition layer to form a light emitting layer, and a LiF / Al (0.5 nm / 200 nm) electrode was further formed on the light emitting layer. An organic EL element for evaluation test was created.

(2) Evaluation test result A voltage was applied between both electrodes of the organic EL element for the evaluation test, light emitted from the light emitting layer was taken out of the glass substrate, and the amount of light was measured. FIG. 2 shows the results of measuring the amount of light with various applied voltages.
As is clear from the results of FIG. 2, Alq ₃ purified using the sublimation purification apparatus of the present invention showed a luminescence with much higher luminance than Alq ₃ before purification.

It is drawing which shows the structure of the sublimation purification apparatus of this invention. Alq ₃ before the sublimation purification is a graph showing the difference in the light emission characteristics of (commercially available reagent) and Alq ₃ was purified by sublimation using a sublimation purification apparatus of the present invention.

Explanation of symbols

DESCRIPTION OF SYMBOLS 11 Inert gas introduction port 12 Inert gas exhaust port 13 Cylindrical body 14 Container 15 Outer tube 16 Heating means 16a Auxiliary heating means 16b Auxiliary heating means 17 Multistage sublimation plate 17a Plate 17b Plate 17c Plate 18 Support pipe

Claims (7)

  A heat-resistant glass cylindrical body provided with an inert gas inlet at the lower part and an inert gas outlet at the upper part, a container of an organic compound to be sublimated accommodated in an inner lower part of the cylindrical body, A heat conductive outer tube that is disposed on the outer periphery of the tubular body so as to cover the periphery of the container and extend upward, a heating tool installed in a portion of the outer tube covering the periphery of the container, and the tube Sublimation of an organic compound comprising a multi-stage sublimation plate composed of three or more circular or polygonal plates arranged in a step-like manner in parallel with each other at intervals inside the container and above the container Purification equipment.   The sublimation purification apparatus according to claim 1, wherein the organic compound is a chelate complex compound.   The sublimation purification apparatus according to claim 1 or 2, wherein the multi-stage sublimation plate comprises 5 to 50 plates.   The sublimation purification apparatus according to claim 3, wherein the multi-stage sublimation plate comprises 10 to 30 plates.   The sublimation purification apparatus according to any one of claims 1 to 4, wherein the plate of the multistage sublimation plate is made of heat-resistant glass or a metal material.   The sublimation purification apparatus according to any one of claims 1 to 5, wherein each plate of the multistage sublimation plate is sequentially suspended from an upper portion of the cylindrical body by a suspension rope.   It arrange | positions so that the top part of the heat conductive sheath tube arrange | positioned on the outer periphery of the said cylindrical body may be located below the top part of this cylindrical body, and the exposed surface to the outside on the upper part of this cylindrical body by this arrangement | positioning The sublimation purification apparatus according to any one of claims 1 to 6, wherein an uppermost stage of the plate is disposed at an internal position of the cylindrical body corresponding to the exposed surface.

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