Background Art In general, a luminescent material for use in an organic electroluminescence device needs to be purified.

The purpose of the purification is to separate pure pigment elements from a mixed luminescent material and to use the pure elements for a thin film deposition. A development of a luminescent material purification technique increases a degree of purity and a luminous efficiency of purified materials, thus extending durability of an organic electroluminescence device using such purified materials.

In order to mass-produce organic electroluminescent materials, it is necessary to reduce a processing time and to improve a purification efficiency of the organic electroluminescent material purification technique.

The organic electroluminescent material device is conventionally purified by using a sublimation purification method. Sublimation refers to a direct transform from the solid to the gaseous state or from the gaseous to the solid state without becoming a liquid, which occurs under the conditions of a temperature and a pressure below a triple point in a phase equilibrium diagram. A material that may

be pyrolyzed at an atmospheric pressure is hardly decomposed at a low pressure below the triple point even by a comparatively higher temperature. Accordingly, a sublimation apparatus capable of controlling a temperature gradient is used for a vacuum sublimation method which applies heat to a mixed material so as to separate impurities having a different sublimation temperature therefrom without decomposing the material. Since the vacuum sublimation method is a genuinely physical method, any auxiliary reagent or chemical method are not used, and therefore, there is no contamination of the reagent.

Further, the vacuum sublimation method having a high separability is very useful for purifying an organic material for use in the organic electroluminescence device.

Currently, a train sublimation purification method is widely used for purifying the luminescent material for use in the organic electroluminescence device. This method involves mounting a material to be purified in one end of a hollow tube, vacuum-evacuating an inner portion of the tube by using a vacuum pump and heating the tube by using a heater to thereby generate a temperature gradient all over the tube. At this time, since a material to be separated and impurities have a different sublimation temperature, they are crystallized at different inner positions of the tube to be separated. In some cases, in order to make a. flow of sublimate gas efficient, a carrier gas flows from a high temperature to a low temperature within the scope of not significantly affecting a degree of vacuum of the tube, the carrier gas being nitrogen or inert gas showing no reaction with materials constituting the purifying apparatus.

Fig. 1 shows a schematic diagram of a conventional sublimation purifying apparatus for performing the above- described train sublimation purification method.

As illustrated in Fig. 1, a material to be purified is put into a cell 4, and the cell 4 is prepared at one end of

an inner tube 1. Connection members 3 interconnect separate sections of the inner tube 1, and an outer tube 2 covers the inner tube 1. A heater 5 is installed along the circumference of one end of the outer tube 2, wherein the end thereof corresponds to the end of the inner tube 1 where the cell 4 is positioned. A vacuum pump 6 is prepared at the other end of the inner tube 1 to vacuum-evacuate an inner portion thereof.

Fig. 2 illustrates a schematic perspective view of the cell 4 to hold therein the material to be purified.

Referring to Fig. 2, there is illustrated the cell 4 comprising a quartz tube 20 with both ends open and a pair of stainless steel caps 21 to be respectively fitted into each end of the tube 20, each of the caps 21 having a hole 22 formed at a substantially central portion thereof.

In order to use the conventional sublimation purifying apparatus configured as described above, the vacuum pump 6 vacuum-evacuates the inner portion of the inner tube 1, and the small amount of carrier gas is supplied thereinto, so that a slight pressure gradient is generated. Further, when the heater 5 slowly raises a temperature of the inner tube 1, a temperature gradient is generated. In this case, a temperature distribution shows a normal distribution curve.

Once the temperature thereof is higher than a sublimation temperature of the material to be purified therein, the material therein starts to be sublimated. Then, the sublimate material is discharged from the tube 20 through the holes 22 and moved toward the vacuum pump 6 due to the pressure gradient. At this time, impurities of which the sublimation temperature is higher than that of the material to be purified remain in the cell 4. In a section of the inner tube 2 where the temperature is lower than the sublimation temperature, the sublimate material changes its phase into solid and is crystallized on an inner surface of the inner tube 2. After heat is sufficiently applied to the

inner tube 1, the inner tube 1 is slowly cooled down. When a temperature thereof is equal to the room temperature, the inner tube 1 is disassembled and purified materials 25, i. e., materials crystallized on the inner surface of the inner tube 1, are collected and obtained.

Generally, a material for use in the organic electroluminescence device needs to be highly pure with the extremely small amount of impurities. Thus, a purification process should be performed multiple times to obtain high purity of the material. Since the purified materials are scratched from the inner surface of the inner tube 1 in order to be collected, a loss in quantity occurs. Further, whenever the purification process is repeated, the outer tube 2 needs to be disassembled, and therefore, the material to be purified may be contaminated or deteriorated by reacting with oxygen or water vapor. Moreover, a processing time of the purification is increased.

Disclosure of Invention It is, therefore, a primary object of the present invention to provide an improved apparatus for purifying an organic electroluminescent material.

It is another object of the present invention to provide an improved method for purifying the organic electroluminescent material.

In accordance with one aspect of the present invention, there is provided an apparatus for purifying an organic electroluminescent material, the apparatus including: one or more inner tubes for mounting material to be purified in one ends of the inner tubes; connection members for separating each of the inner tubes into a plurality of sections; a heat unit for heating the sections of respective inner tubes to more than a sublimation temperature of the material to be purified; and a vacuum pump for vacuum-evacuating the

sections of the inner tubes, wherein each of the connection members has a partition for partially closing space between two sections and a hole for making sublimate gas from the material to be purified pass therethrough, the hole being formed at a substantially central portion of the partition.

In accordance with another aspect of the present invention, there is provided a method for purifying an organic electroluminescent material, the method including the steps of: separating inner portions of one or more inner tubes into a plurality of sections being partially connected; supplying a material to be purified to one end of each inner tube; vacuum-evacuating each inner tube through the other end of each inner tube; and heating each inner tube sequentially from a section holding a material to be purified to neighboring sections to more than a sublimation temperature of the material to be purified.

Brief Description of Drawings The above and other objects and features-of the present invention will become apparent from the following description of preferred embodiments given in conjunction with accompanying drawings, in which: Fig. 1 is a schematic diagram of a conventional apparatus for purifying an organic electroluminescent material ; Fig. 2 illustrates an exploded perspective view of a conventional cell; Fig. 3 shows a schematic diagram of an apparatus for purifying an organic electroluminescent material in accordance with a first embodiment of the present invention; Figs. 4A and 4B provide views for explaining a coupling between connection members and an inner tube and a coupling between modified connection members and an inner tube, respectively, in accordance with the first embodiment

of the present invention; Figs. 5A to 5D depict graphs of temperature distributions in inner sections of the inner tube, respectively ; Fig. 6 describes a schematic diagram of an apparatus for purifying an organic electroluminescent material in accordance with a second preferred embodiment of the present invention; Figs. 7A and 7B offer views for explaining a coupling between connection members and inner tubes and a coupling between modified connection members and inner tubes, respectively, in accordance with the second embodiment of the present invention; Figs. 8A and 8B respectively set forth a front view and a side view of a carrier gas supply unit in accordance with the second preferred embodiment of the present invention; Fig. 9 demonstrates a schematic diagram of an organic electroluminescence device ; Fig. 10 presents a graph for comparing luminous efficiencies of the organic electroluminescence device using organic electroluminescent materials purified by the apparatus in accordance with the first preferred embodiment of the present invention and the conventional apparatus, respectively; Fig. 11 represents a graph for comparing purification efficiencies of the organic electroluminescence device using organic electroluminescent materials purified by the apparatus in accordance with the first preferred embodiment of the present invention and the conventional apparatus, respectively ; and Fig. 12 provides a graph for comparing processing times of the purification using the apparatus in accordance with the first and the second preferred embodiment of the present invention and the conventional apparatus,

respectively.

Best Mode for Carrying Out the Invention The present invention will be described in detail with reference to the accompanying drawings.

Fig. 3 schematically shows an apparatus for purifying an organic electroluminescent material in accordance with a first preferred embodiment of the present invention.

As can be seen from Fig. 3, the apparatus in accordance with the first preferred embodiment of the present invention includes an inner tube 31 made of quartz, an outer tube 32 covering the inner tube 31 and a first to a fourth heater 34a to 34d installed along the circumference of the outer tube 32. The inner tube 31 has therein a cell 35 for holding a material to be purified. Since a composition of the cell 35 is identical to that of the cell described with reference to Fig. 2, a detailed description thereof is omitted. A plurality of, e. g. , four connection members 33 separates an inner portion of the inner tube 31 into multiple, e. g., five sections of a first to a fifth section A to E, and interconnects the separate sections of the inner tube 31. Each of the heaters 34a to 34d corresponds to each of the sections A to D, respectively, and thus may heat its corresponding section at a certain temperature independently. If one of the heaters 34a to 34d heats its corresponding section, a temperature of sections adjacent thereto also increases. Since each heater corresponds to each section in the present invention, each section can be consecutively heated. Heating process of at least two sections of the tube may also be carried out by a sliding device for moving a heater against the tube or the tube against the heater.

Meanwhile, a vacuum pump 37 installed at one end of the inner tube 31 can vacuum-evacuate the inner portion

thereof. Further, a carrier gas supply unit 38 installed at the other end thereof can supply nitrogen or inert gas into the inner tube 31.

Fig. 4A explains a coupling between connection members 33 and the inner tube 31 in accordance with the first preferred embodiment of the present invention. Each of the connection members 33 is inserted into a portion of the inner tube 31 located between two sections of the inner tube 31. Each connection member 33 has a partition 42 for partially closing a space between two sections and a hole 41 formed at a substantially central portion of the partition 42.

Fig. 4B describes a coupling between modified connection members 33a and the inner tube 31. As can be seen from Fig. 4B, a configuration of the modified connection members 33a is similar to that of the connection members 33 illustrated in Fig. 4A. That is to say, each of the modified connection members 33a also has a partition 45 and a hole 46 formed at a central portion of the partition 45, except for a net 43 prepared at the hole 46.

The connection members 33 and 33a and the net 43 may be made of any material selected from quartz, stainless steel, aluminum, gold, silver, platinum, nickel, teflon, urethane and glass or a mixture of such materials. A diameter of the holes 41 and 46 is approximately more than 3mm but less than 10mm. Each graduation of the net 43 ranges from about 0. lmm x 0. 1mm to about 5mm x 5mm.

Hereinafter, a method for purifying a to-be-purified material by using the purifying apparatus in accordance with the first preferred embodiment of the present invention will be described.

The to-be-purified material containing impurities is inserted into the cell 35, and the cell 35 is arranged in the first section A of the inner tube 31. If the heater 34a is heated to more than a sublimation temperature of pure

materials included in the to-be-purified material, primarily purified materials are moved to the second section B. At this time, as can be seen from Fig. 5A, a temperature of the inner tube 31 is highest in the first section A and becomes lower in following sections B to D. When the material to be purified is sublimated and changes its phase into gas, the sublimate gas is discharged through a hole of the cell 35 and then moved to the second section B by a flow of carrier gas supplied by the carrier gas supply unit 38. In this case, the gas passes through the hole 41 of the partition 42 of the connection members 33 as illustrated in Fig. 4A or through the net 43 as shown in Fig. 4B. The holes 41 and 46 of the partition 42 and 45 and the net 43 are used for preventing impurities from moving to another section.

By controlling a temperature of the heater 34a and a flow rate of the carrier gas, it is possible to control a crystallized location of the sublimate gas on an inner surface of the second section B. It is most preferable that the purified materials are crystallized at a central portion of the second section B.

After a first purification process is completed, only impurities from the primarily purified material remain in the first section A. On the other hand, comparatively purified materials exist in the second section B. Next, the <BR> <BR> heater 34b heats its corresponding section, i. e. , the second section B. At this time, a temperature gradient is shown in Fig. 5B. The gas sublimated in the second section B flows into the third section C through the hole 41 of the connection members 33 or through the net 43 prepared at the hole 46 of the connection members 33a. As a result of a secondary purification process described above, impurities from the comparatively purified material remain in the second section B and more purified materials in the third section C.

In the same manner, the third heater 34a and the

fourth heater 34d are operated, and the to-be-purified material is more and more purified in the third section C and the fourth section D. Consequently, the most purified materials remain in the fifth section E.

The purifying apparatus in accordance with the first preferred embodiment of the present invention is applied to an experiment for purifying tris (8-hydroxyquinolinato) aluminum (Alq3) that is a luminescent material used for manufacturing an organic electroluminescence device, wherein a manufacturer of Alq3 guarantees more than 95% of purity of the Alq3 involved.

Experiment 1 20g of Alq3 are inserted into the cell 35, and the cell 35 is prepared in the first section A. Next, the inner tube 31 is vacuum-evacuated by the vacuum pump 37, and then 50cm3 of nitrogen flows thereinto per minute. A temperature of the first heater 34a is raised up to 340°C for three hours at room temperature, which is high enough to sublimate the organic electroluminescent material, and the raised temperature is maintained for six hours. At this time, a temperature of the second section B reaches approximately 220°C due to the high temperature of the first heater 34a.

The temperature of the second heater 34b is raised from 220°C to 340°C five hours later when the temperature of the first heater 34a reaches 340°C. From the moment the temperature of the second heater 34b reaches 340°C, the first heater 34a is naturally cooled down. The temperature of the second heater 34b is maintained at 340°C for six hours. Five hours later, the third heater 34c starts to be heated. The above-mentioned processes can be equally applied to the third and the fourth heater 34c and 34d. Further, in another case, at least two sections can be heated by moving a single heater against a single inner tube or the single

inner tube against the single heater.

In order to compare the method of the present invention with that of the conventional method, experiments may be differently carried out. In other word, after an operation of the second heater 34b is completed, purified materials crystallized on an inner surface of the third section C shown in Fig. 3 are collected. In another experiment, after an operation of the fourth heater 34d is completed, materials remaining in the fifth section E are collected. When the heating is finally completed, the inner tube 31 is naturally cooled down for three hours until its temperature reaches the room temperature. Next, a vacuum state of the inner tube 31 is released and purified Alq3 are collected. After the purification process is completed, there is found the small amount of dark brown impurities in the inner portion of the cell 35 and on inner surfaces of the second to the fourth section B to D of the inner tube 31.

In the first preferred embodiment of the present invention illustrated in Figs. 3,4A and 4B, if the amount of materials to be mounted in the cell increases, a heat transfer into materials in the cell becomes difficult, thus increasing the purification processing time and deteriorating the purification efficiency. Further, in case a large amount of materials need to be purified, the carrier gas may not be uniformly supplied into the inner tube.

In order to solve the above-mentioned problems, an apparatus for purifying an organic electroluminescent material in accordance with the second preferred embodiment of the present invention has a plurality of inner tubes and multiple connection members.

A total cross-sectional area of inner tubes in accordance with the second preferred embodiment of the present invention is approximately equal to that of the inner tube in accordance with the first preferred embodiment of the present invention.

Fig. 6 describes a schematic diagram of an apparatus for purifying an organic electroluminescent material in accordance with a second preferred embodiment of the present invention. Figs. 7A and 7B illustrate connection members 53 and 53a used in the purifying apparatus in accordance with the second embodiment of the present invention. Figs. 8A and 8B schematically show a carrier gas supply unit used in the purifying apparatus.

The purifying apparatus in accordance with the second preferred embodiment of the present invention includes a plurality of, e. g. , seven inner tubes 51 made of quartz, an outer tube 52 covering the inner tubes 51 and a first to a fourth heater 54a to 54d prepared along the circumference of the outer tube 52. Since each of the inner tubes 51 has a same configuration and function, a description thereof will be based on one inner tube.

The inner tube 51 has therein a cell 55 holding a material to be purified. Since a configuration of the cell 55 is same as that of the cell described with reference to Fig. 2, a detailed description thereon will be omitted. A plurality of, e. g. , four connection members separate an<BR> inner portion of the inner tube 51 into multiple, e. g. , five sections of a first to a fifth section A to E, and interconnect the separate sections of the inner tube 51.

The first to the fourth heater 54a to 54d correspond to the first to the fourth section of the inner tube 51, respectively, and thus, each heater can heat its corresponding section at a certain temperature. If one of the heaters 54a to 54d heats its corresponding section, a temperature of sections adjacent thereto is also increased.

Accordingly, each section can be consecutively heated in the present invention. Heating process of at least two sections of the tube may also be carried out by a sliding device for moving a heater against the tube or the tube against the heater.

Meanwhile, a vacuum pump 56 installed at one end of the outer tube 52 can vacuum-evacuate the inner tube 51.

Further, a carrier gas supply unit 57 installed at the other end of the outer tube 52 can supply nitrogen or inert gas into the inner tube 51.

Figs. 7A and 7B offer views for explaining a coupling between the connection members 53 and the inner tubes 51 and a coupling between the modified connection members 53a and the inner tubes 51, respectively, in accordance with the second embodiment of the present invention.

The connection members 53 and 53a in Figs. 7A and 7B connect seven inner tubes 51 at one time, and therefore, seven purification processes can be simultaneously executed.

Referring to Fig. 7A, there are illustrated the connection members 53 separating an inner portion of each inner tube 51 of quartz into multiple sections. The connection members 53 have seven partitions 47a for partially closing a space between two sections and seven holes 46a formed at substantially central portions of the partitions 47a. Each of the connection members 53 connects two sections prepared on a left and a right side thereof, and, further, forms the inner tube 51.

A configuration of connection members 53a shown in Fig.

7B is similar to that of the connection members 53 illustrated in Fig. 7A. That is to say, the connection members 53a also have a plurality of partitions 47b and holes 46b formed at substantially central portions of the partitions 47b, except for a net 48 prepared at each of the holes 46b.

The carrier gas supply unit 57 illustrated in Figs. 8A and 8B has a space 81 for containing the carrier gas and a plurality of holes 82 for making the carrier gas uniformly flow during multiple purification processes. The carrier gas supply unit 57 may be manufactured by using any material selected from quartz, stainless steel, aluminum, gold,

silver, platinum, nickel, teflon, urethane, glass or a mixture of such materials. A diameter of each hole 82 ranges from about 0.1 mm to about 5 mm.

A method for purifying the material to be purified by using the above-described purifying apparatus in accordance with the second preferred embodiment of the present invention is equal to that by using the apparatus in accordance with the first preferred embodiment of the present invention. The difference is in that multiple purification processes are simultaneously performed through a plurality of. inner tubes 51 in the second preferred embodiment of the present invention.

Although the above descriptions illustrate the inner tube 51 having a cross-section of a circular shape, a cross section of the inner tube 51 may be of a rectangular shape.

For example, a purification process may be performed in such a manner that an inner tube having a rectangular cross- section is prepared, and a material to be purified is uniformly distributed in a bottom portion of the inner tube, wherein a cross-sectional area of the rectangular inner tube is approximately equal to the total cross-sectional area of the aforementioned circular inner tubes.

The purifying apparatus in accordance with the second preferred embodiment of the present invention is applied to an experiment for purifying tris (8-hydroxyquinolinato) aluminum (Alq3) that is a luminescent material used for manufacturing an organic electroluminescence device, wherein a manufacturer of Alq3 guarantees more than 95% of purity of the Alq3 involved.

Experiment 2 Seven cells 55 holding 3g of Alq3 are arranged in the first section A of each inner tube 51. The vacuum pump 56 vacuum- evacuates each inner tube 51, and then, the carrier gas

supply unit 57 supplies thereinto nitrogen of 50 cm3 per minute. The first heater 54a is heated and raised up to 340°C for three hours at room temperature, and the raised temperature, which is high enough to sublimate the aforementioned organic electroluminescent material, is maintained for four hours. At this time, a temperature of the section B reaches 220°C due to the high temperature of the first heater 54a. The temperature of the second heater 34b is raised from 220°C to 340°C three hours later when the temperature of the first heater 34a reaches 340°C. From the moment the temperature of the second heater 54b reaches 340°C, the first heater 54a starts to be naturally cooled down. The temperature of the second heater 54b is maintained for four hours at 340°C. Three hours later, the third heater 54c starts to be heated. Such processes can be equally applied to the third and the fourth heater 54c and 54d. Heating process of at least two sections of the tube may also be carried out by a sliding device for moving a heater against the tube or the tube against the heater.

In this experiment, after an operation of the fourth heater 54d is completed, materials remaining in the fifth section E are collected. When the heating is completed, the inner tubes 51 are naturally cooled down for three hours until its temperature reaches the room temperature. Next, a vacuum state of the inner tubes 51 is released and purified Alq3 are collected. After the purification process is completed, there is found the small amount of dark brown impurities on inner surfaces of the second to the fourth section B to D as well as in inner portions of the cells 55.

In order to compare a conventional sublimation purifying apparatus with that of the first and the second preferred embodiment of the present invention, an experiment using the conventional apparatus is performed as follows.

Experiment 3 In the conventional sublimation purifying apparatus illustrated in Fig. 1, the cell 4 holds 20g of Alq3 to be purified and then is prepared at one end of an inner tube 1, wherein the end thereof corresponds to one end of an outer tube 2 where the heater 5 is installed. Further, conditions used in the apparatus of the present invention are equally applied to the-conventional apparatus. That is to say, the cell 4 is vacuum-evacuated by the vacuum pump 6 and the carrier gas is supplied therein. The heater 5 is heated for three hours at room temperature until its temperature reaches 340°C, and the raised temperature is maintained for six hours. For the next three hours, the cell 4 is cooled down until its temperature reaches the room temperature.

Subsequently, a vacuum state of the cell 4 is released and purified Alq3 are collected. At this time, there are found in the cell 4 dark brown impurities that have not been purified. After the cell 4 and the inner tube 1 are cleaned and dried, the purified Alq3 are inserted into the cell 4 again, and same purification processes are performed four times. In each purification process, a quantity of collected Alq3 and the processing time thereof are checked.

Fig. 9 provides a schematic diagram of an organic electroluminescence device using organic electroluminescent materials purified by the first preferred embodiment of the present invention.

Referring to Fig. 9, mounted on a surface of a glass substrate 61 are sequentially a transparent electrode layer <BR> <BR> 62 of, e. g. , ITO, a hole transport layer 63 of, e. g., triphenyl diamine (TPD), a luminescence/electron transport layer 64 of the purified organic electroluminescent materials (e. g., Alq3) and a metal electrode layer 65. A voltage is applied between the transparent electrode layer 62 and the metal electron layer 65.

Fig. 10 presents a graph for comparing luminous efficiencies of the organic electroluminescence device using organic electroluminescent materials purified by the conventional apparatus and the apparatus in accordance with the first preferred embodiment of the present invention, respectively.

A data point 71 indicates the luminous efficiency of the organic electroluminescence device using materials purified by the conventional apparatus described with reference to Fig. 1. In this case, the more frequently the purification process is performed, the higher the luminous efficiency becomes. A data point 73 represents the luminous efficiency of the organic electroluminescence device using materials purified by the apparatus in accordance with the first preferred embodiment of the present invention. At this time, only a first and a second heater 34a and 34b are operated and purified materials in a third section C are collected. Meanwhile, in case where every heater 34a to 34d is operated and purified materials in a fifth section E are collected, a data point 74 depicts the luminous efficiency of the organic electroluminescence device using materials purified by the apparatus in accordance with the first preferred embodiment of the present invention. As can be seen from Fig. 10, the materials purified by the apparatus in accordance with the first preferred embodiment of the present invention provide a higher luminous efficiency.

Fig. 11 represents a graph for comparing purification efficiencies of the organic electroluminescence device using organic electroluminescent materials purified by the apparatus in accordance with the first preferred embodiment of the present invention and the conventional apparatus, respectively.

A data point 91 indicates the amount of materials collected by using the conventional apparatus illustrated in Fig. 1. Data points 92 and 93 represent the amount of

materials collected in a third and a firth section C and E, respectively, of the apparatus of the present invention as shown in Fig. 3. As clearly can be seen from Fig. 11, in case 20g of materials to be purified are inputted, the purification process is performed four times in the conventional method thereby collecting 17. 2g (86% of the input) thereof. However, if the apparatus and method in accordance with the first preferred embodiment of the present invention are used, approximately 18. 6g (93% of the input) thereof are collected, which provides a higher purification efficiency than the conventional method.

Considering 95% of purity guaranteed by a manufacturer of an organic electroluminescent material to be purified, almost the total quantity of purified materials can be collected in a new purification method.

Fig. 12 provides a graph for comparing processing times of the purification using the apparatus in accordance with the first and the second preferred embodiment of the present invention and the conventional apparatus, respectively.

Referring to Fig. 12, the conventional apparatus requires approximately 14 hours in order to perform a purification process once: input time of materials to be purified (one hour), heating time (three hours), heating maintenance (six hours), cooling time (three hours), collecting and cleaning time (one hour) and re-input of materials to be purified. Accordingly, it takes 56 hours to carry out such process four times. However, the apparatus in accordance with the first preferred embodiment of the present invention needs 32 hours to perform the purification process: input time of materials to be purified (one hour), heating time (three hours), heating maintenance (24 hours, <BR> <BR> i. e. , six hours x four times), cooling time (three hours) and collecting and cleaning time (one hour). The apparatus in accordance with the second preferred embodiment of the

present invention requires 24 hours to carry out the purification process: input time of materials to be purified (one hour), heating time (three hours), heating maintenance (16 hours, i. e. , four hours x four times), cooling time (three hours) and collecting and cleaning time (one hour).

An apparatus and method for purifying an organic electroluminescent material in accordance with the present invention provides a higher luminous and purification efficiency than a conventional apparatus and method.

Further, when the same amount of materials needs to be purified, a processing time is reduced. In other words, a large amount of materials can be purified during the predetermined processing time. Since the present invention performs a plurality of processes at the predetermined time, materials in a cell can be distributed and a heat transfer becomes efficient. Consequently, an organic electroluminescence device using organic electroluminescent materials purified by the apparatus and method of the present invention is advantageous to a mass production and also provides a high quality.

While the invention has been shown and described with respect to the preferred embodiments, it will be understood by those skilled in the art that various changes and modifications may be made without departing from the spirit and scope of the invention as defined in the following claims.