KR20170063474A - Method and apparatus for single crystal growth of organic materials using ionic liquid - Google Patents

Abstract

The present invention relates to a method and an apparatus for growing a high purity organic material single crystal using an ionic liquid, comprising a mixing step of mixing an organic material with an ionic liquid, a step of heat treating the organic material in an ionic liquid, A nucleation step in which a seed is put into an ionic liquid containing the solubilized organic material in a second condition, a single crystal growth step in which a single crystal is grown in a third condition, and a grown organic material single crystal And separating the organic material from the ionic liquid so as to obtain an organic material single crystal purified to a higher purity than before mixing with the ionic liquid. According to the present invention, an organic material single crystal of high purity can be grown at a low cost by a simple process.

Description

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a method and apparatus for growing an organic material single crystal using an ionic liquid,

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a method and apparatus for growing an organic material single crystal, and more particularly, to a method and apparatus for growing an organic material after mixing an organic material with an ionic liquid.

2. Description of the Related Art As examples of using organic materials for electronic devices such as organic electroluminescence (EL) devices, organic semiconductor devices, organic photoelectric conversion devices, and organic sensor devices have been increasingly increasing, attention has been focused on single crystal organic materials. However, organic materials having an amorphous state are mostly used in organic electronic devices due to the lack of efficient organic material single crystal growth technology.

As a conventional method for growing an organic material single crystal, there is a method in which a single crystal is grown by dissolving an organic material in a solvent and gradually evaporating the solvent at a constant temperature. However, this method has a problem that not only the single crystal growth time is too long, but also the process control necessary for growing a high quality single crystal is difficult. These problems eventually lead to an increase in the cost of growth of single crystals, and thus organic materials monocrystals are becoming obstacles to industrial use.

Further, the conventional organic material single crystal growth method has a problem that impurity removal is not easy. Therefore, in order to obtain a high purity single crystal, the organic material must first be purified to a high purity by the sublimation purification method disclosed in HJ Wagner, el al., Journal of Materials Science, 17, 2781 (1982) There was a hassle.

Accordingly, there is a need for a new method for solving various problems of the prior art and for growing a single crystal while refining an organic material with a simple process at low cost.

H. J. Wagner, el al., Journal of Materials Science, 17, 2781 (1982)

It is another object of the present invention to provide a new organic material single crystal growth method and apparatus capable of solving the problems of the above conventional purification method.

Specifically, it is an object of the present invention to provide a single crystal growth method and apparatus capable of growing a high purity organic material single crystal of 99% or more, preferably 99.5% or more, and more preferably 99.9% or more, by a single process.

It is another object of the present invention to provide a single crystal growth method and apparatus capable of efficiently growing a single crystal of a high purity organic material at low cost.

Another object of the present invention is to provide a method and apparatus for growing a single crystal which can be easily designed and controlled in process, and can cope with various organic materials.

According to an aspect of the present invention, there is provided an organic material single crystal growth method comprising: mixing an organic material with an ionic liquid; A solubilization step of heat-treating the organic material mixed with the ionic liquid in a solution condition in a first condition; A nucleation step of injecting a seed into the ionic liquid containing the solubilized organic material in a second condition and generating nuclei on the seed surface; A single crystal growing step of growing a single crystal in a third condition; And a separation step (S50) of separating the grown organic material single crystal from the ionic liquid to obtain an organic material single crystal purified to a higher purity than before mixing with the ionic liquid. Here, the first condition, the second condition, or the third condition may be a condition that changes with time.

In the present invention, the seed injected into the ionic liquid may be a single crystal of the same material as the organic material to be crystallized, or may be a hollow microtube, and the solubilization may be at least one of dissolution or melting.

Further, a single high purity single crystal organic material of 99% or more can be obtained by performing the mixing step, the solubilization step, the nucleation step, the single crystal growth step and the separation step once, and the organic material single crystal And then washing and drying.

Wherein the separating step further includes a step of performing a suwetting process for removing surface impurities of the separated organic material single crystal and a filtering step for filtering the organic material that has not been solubilized between the solubilizing step and the nucleation step . ≪ / RTI >

An organic material single crystal growth apparatus according to another aspect of the present invention includes: a stage; A container body supported by the stage and containing a mixture of an organic material and an ionic liquid; A temperature controller for heating a mixture of the organic material and the ionic liquid contained in the container body; And a seed holder to which a seed to be fed into a mixture of the organic material and the ionic liquid accommodated in the container body is fixed to the end portion, wherein the container body and the seed holder are movable relative to each other.

Here, the seed may be a single crystal or hollow microtube of the same material as the organic material, and the relative movement may be at least one of up-down movement and rotational movement.

A gas inlet for introducing gas into the container body; And a gas discharging unit for discharging gas from the inside of the container body.

Organic single crystal material according to still another aspect of the present invention can be grown by the method of any one of the aforementioned methods, may be up to the X-ray full width at half maximum is 0.1 ^o.

According to the present invention, by using a method of mixing an organic material with an ionic liquid to form a solution and then growing a single crystal, various problems of the conventional purification method can be solved.

Concretely, the organic material single crystal can be grown with a high purity of 99% or more, preferably 99.5% or more, and more preferably 99.9% or more with only one step.

Further, according to the present invention, there is an effect that the high purity organic material single crystal can be efficiently grown at low cost.

Further, according to the present invention, there is an effect that process design and control are easy and can cope with various organic materials.

1 is a main flowchart of a method for growing an organic material single crystal using an ionic liquid according to the present invention.
2 is an example of a temperature change curve for proceeding the organic material single crystal growth method according to the present invention.
3 is a schematic cross-sectional view of an organic material single crystal growing apparatus according to the present invention.
FIG. 4 is an exemplary view of using a microtube for self-seed formation. FIG.
5 (a) shows the XRD analysis results of the NPB single crystal grown according to the present invention, and FIG. 5 (b) shows the XRD analysis results of the NPB polycrystal.
Fig. 6 (a) shows the XRD analysis results of the Alq3 single crystal grown according to the present invention, and Fig. 6 (b) shows the XRD analysis results of the Alq3 polycrystal.
Fig. 7 (a) is an Alq3 single crystal grown according to the present invention, and Fig. 7 (b) is a scanning electron micrograph of an Alq3 polycrystal.

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS Reference will now be made in detail to the embodiments of the present invention. The following description includes specific embodiments, but the present invention is not limited to or limited by the embodiments described. DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS Hereinafter, the present invention will be described in detail with reference to the accompanying drawings.

The method for growing an organic material single crystal according to the present invention is a method for growing an organic material in an ionic liquid by mixing the organic material to be grown with a single crystal, And a single crystal is grown in a third condition to grow a single crystal of high purity organic material. Here, the first, second and third conditions refer to process conditions such as temperature, pressure, process atmosphere, and the like.

The ionic liquid refers to a liquid composed of only ions, and is generally a molten salt which is composed of a large cation and a smaller anion, and is not particularly limited, but the cation constituting the ionic liquid includes the following [ 1] can be used. In formula (1), R 1, R 2, R 3 and R 4 may be linear or branched alkyl groups having n carbon atoms.

 [Chemical Formula 1]

In addition, the anions constituting the ionic liquid together with the cations include Cl ^- , Br ^- , NO ₃ ^- , BF ₄ ^- , PF ₆ ^- , AlCl ₄ ^- , Al ₂ Cl ₇ ^- , AcO ^- , CH ₃ COO ^{- _{3 COO -, CH 3 SO 3}} -, CF 3 SO 3 -, (CF 3 SO 2) 2 N -, (CF 3 SO 2) 3 C -, (CF 3 CF 2 SO 2) 2 N -, C 4 _{^{F 9 SO 3 -, C 3}} F 7 COO -, (CF 3 SO 2) (CF 3 CO) N -, C 4 F 10 N -, C 2 F 6 NO 4 S 2 -, C 2 F 6 NO 6 S ₂ ^- , C ₄ F ₁₀ NO ₄ S ₂ ^- , CF ₃ SO ₂ ^- , C ₄ F ₉ SO ₂ ^- , C ₂ H ₆ NO ₄ S ₂ ^- , C ₃ F ₆ NO ₃ S ^- , CH ₃ CH (OH) CO ₂ ^-, and the like.

The ionic liquid has a low melting point due to its structural characteristics and has a very low vapor pressure and is present as a stable liquid in a wide temperature range. In addition, it is excellent in thermal stability and ionic conductivity, can dissolve various organic, inorganic and polymeric substances having hydrophilic and hydrophobic properties, is low in volatility, low in flammability, and low in explosibility, thus being environmentally friendly.

1 is a main flowchart of a method for growing an organic material single crystal using an ionic liquid according to the present invention.

1, a method of growing an organic material single crystal according to the present invention will be described. In the mixing step (S10) of mixing an organic material to be grown with an ionic liquid, a first step of heat- A nucleation step (S30) of injecting the seed into the ionic liquid containing the organic material dissolved in the second condition and generating nuclei on the seed surface, a step of forming a single crystal in the third condition And a separation step (S50) of separating the grown organic material single crystal from the ionic liquid.

More specifically, the mixing step (S10) of mixing the organic material with the ionic liquid is a step of mixing and mixing the organic material to be grown in the ionic liquid. At this time, stirring may be performed by mechanical stirring, magnetic stirring or the like so that the solid organic material can be more uniformly mixed with the ionic liquid. The organic material is an organic material for growing a high-purity single crystal using the method according to the present invention. However, the material is not specifically limited, but an electron injection layer, an electron transport layer, a hole injection layer, Layer, a light emitting layer, a light absorbing layer of an organic photoelectric conversion element, an organic semiconductor layer of an organic semiconductor device, or the like. Further, the organic material to be mixed with the ionic liquid may be a low-purity organic material containing an impurity.

Also, the ionic liquid can be appropriately selected according to the organic material to be mixed, and an imidazolium-based ionic liquid having a long alkyl substituent is suitable as the ionic liquid of the present invention. For example, 1-octyl-3-methylimidazolium bis (trifluoromethylsulfonyl) imide (hereinafter abbreviated as '[Omim] [TFSI]') 1-butyl-3-methylimidazolium bis (trifluoromethylsulfonyl) imide], 1-ethyl-3-methylimidazolium trifluoromethylsulfonylamide [(1-Ethyl-3-methylimidazolium bis (trifluoromethylsulfonyl) amide], 1-decyl-3-methylimidazolium bis Dodecyl-3-methylimidazolium bis (trifluoromethylsulfonyl) amide] and the like can be used.

The ionic liquid can cope with a variety of organic materials because of the myriad combinations of up to 10 ¹⁸ theoretically due to the combination of cations and anions. That is, it is possible to select and use an ionic liquid having characteristics suitable for an organic material to which a high purity single crystal is to be grown. Particularly, conductive organic materials for commercial use, such as conductive organic materials for organic electroluminescent devices, have a similar basic structure and polarity, and since a part of reactors are substituted on the basis of this basic structure, similar crystallization behavior is exhibited. Even without designing various ionic liquids, the single crystal growth method according to the present invention can be used for various conductive organic materials by optimizing process conditions using some ionic liquids such as [Omim] [TFSI].

After the organic material and the ionic liquid are mixed, the solution is subjected to a heat treatment under the first condition to perform a dissolving step (S20) for dissolving the organic material in the ionic liquid. Here, the solubilization may mean dissolution or melting, and may be a mixture of dissolution and melting. Whether the dissolution or the melting is the main mechanism of solubilization can be determined by the organic material and the ionic liquid pair and the first condition. The first condition means a heat treatment process condition such as a first temperature, a first pressure, and a first atmospheric condition, and may be a condition that changes with time instead of any fixed condition. For example, the organic material may be solubilized while the organic material and the ionic liquid are mixed and maintained at the first temperature for a predetermined time, but they may be dissolved while changing the temperature at a predetermined rate. Also, the first condition does not require uniformity depending on the position. For example, the container in which the organic material and the ionic liquid are mixed may be heat-treated to have a predetermined temperature gradient depending on the position.

For the single crystal growth, the organic material must first be solubilized in the ionic liquid, so that for a high process yield, the first condition is 80% or more, preferably 90% or more, more preferably 90% or more of the organic material mixed in the ionic material Can be set to a condition in which substantially all of the organic material is dissolved, which can be achieved by setting the first temperature condition at a high enough temperature to allow the entire amount of the organic material to be dissolved.

After the solubilization step (S20), a nucleation step (S30) is performed in which a seed is put into an ionic liquid containing a solubilized organic material and nuclei are formed on the seed surface. It should be understood that introducing the seed here does not necessarily mean that the seed is completely immersed in the ionic liquid, but that at least a portion of the seed is in contact with the ionic liquid.

The nucleation step is carried out under a second condition, which may be a condition in which nucleation of the organic material crystals at the seed surface is facilitated. For example, if the main mechanism of solubilization is dissolution, the second condition may be a condition of lower temperature than the first condition. In the case of organic materials whose solubility decreases at low temperatures, the driving force for crystallization increases under the second condition, which is lower than the first condition, so nucleation can be easily performed on the seed surface. Further, when the main mechanism of solubilization is melting, the second condition may be a condition of a temperature higher than the first condition. Depending on the organic material-ionic liquid pair, the driving force for crystallization may increase at a temperature higher than the melting temperature, so that nucleation can be easily performed on the seed surface under the second condition higher than the first condition.

On the other hand, the second condition does not necessarily mean a fixed condition, but it may be a condition that changes with time. That is, after the heat treatment in the first condition, nucleation may be caused to occur while maintaining the temperature lower or higher than the lower temperature. Alternatively, nucleation may be performed while gradually decreasing or increasing the temperature. Also, the second condition does not require uniformity depending on the position. For example, a predetermined temperature gradient may be generated in accordance with the seeding direction.

The seed may be a high-purity single crystal of the same material as the molten organic material, or a hollow microtube may be used for self-seed formation. When a microtube is used, the molten organic material may be crystallized as capillary rises to the hollow portion of the microtube, and may serve as a seed. For this purpose, the diameter of the hollow region of the microtube may be 800 탆 or less.

After the nucleation step (S30), a single crystal growth step of growing a single crystal under the third condition is performed (S40). Here, the third condition means a process condition for growing a single crystal of an organic material dissolved in an ionic liquid such as a third temperature, a third pressure and a third atmospheric condition, and it is not a fixed condition, It may be a changing condition. The third condition does not require uniformity depending on the position. For example, a predetermined temperature gradient may be generated in accordance with the seeding direction.

The third condition may be a condition in which at least one of temperature, pressure and atmosphere is different from the first condition and / or the second condition, and it is preferable that the pressure and the atmosphere are the same and the temperature is different. If the main mechanism of solubilization is dissolution, the third temperature may be a temperature lower than the first temperature or the second temperature, and if the main mechanism of dissolution is melting, the third temperature may be higher than the first temperature or the second temperature Lt; / RTI >

On the other hand, in the nucleation step (S20) and / or the single crystal growing step (S30), the injected seed can be moved relative to the container containing the organic material and the ionic liquid. Here, the relative movement may include rotation or up and down movement. For example, the seed may be moved upward at a speed of less than 2 mm per hour while rotating the seed at a speed of less than or equal to 9 rph, and in this process, a single crystal may be induced to grow from the seed.

In the above description, the example in which the organic material is solubilized and the single crystal is grown by changing the temperature has been described. However, by changing the pressure instead of the temperature or changing both the temperature and the pressure, You may.

In the single crystal growth step S30, the organic material dissolved or melted in the ionic liquid is precipitated in a high-purity single crystal in which impurities are excluded. Therefore, if the organic material single crystal is separated from the ionic liquid containing impurities, A single crystal can be obtained (S50).

1, the organic material single crystal separated from the ionic liquid may be cleaned and dried. Alternatively, the organic material may be heated to an appropriate temperature to remove impurities contained in the surface of the organic material monocrystal, It is possible to further carry out a sweeting process such as slightly melting only the portion. Further, when the organic material mixed in the ionic liquid is not completely dissolved in the solubilization step S20 and a single crystal is grown in a state in which a part of the organic material is not dissolved or melted, in the separation step (S50) Since it may be mixed with the single crystal, a filtering step may be further carried out between the solubilization step (S20) and the nucleation step (S30) to filter off the undissolved organic material.

At a high temperature at which a large amount of organic material is dissolved or melted, a common organic solvent is often volatile and does not exist in a stable liquid phase. Even if it exists as a liquid, its ratio to an organic material is not maintained constant, And the like. On the other hand, since the ionic liquid can be heat-treated to a relatively high temperature because the temperature range in which the ionic liquid is stably present in a liquid is wide, it is possible to dissolve or melt a large amount of organic material, and the characteristic change is small even at such a high temperature. Since the amount of the organic material to be dissolved or melted eventually affects the yield of the single crystal process, it is possible to grow the organic material single crystal at low cost according to the present invention of growing a single crystal using an ionic liquid.

Particularly, according to the present invention, by growing a single crystal using an ionic liquid, it is possible to grow a high-purity single crystal even without a pre-purification step. According to the embodiments described later, the organic material single crystal can be grown at a high purity of 99.9% or more only by one step of growing the single crystal after solving the low purity organic material in the ionic liquid.

In addition, the ionic liquid has a very low vapor pressure, and even when it is heat-treated at a high temperature, the ratio with the organic material is kept constant, so that the process design and control are easy, and the amount of impurities contained in the organic material crystal is negligible . These effects are characteristics that can not be expected in a conventional single crystal growth method using a common organic solvent.

2 is an example of a temperature change curve for proceeding the organic material single crystal growth method according to the present invention. Referring to FIG. 2, an organic material is mixed with an ionic liquid, and then heated to a first temperature (T1) at a predetermined rate to hold the organic material for a predetermined time (t2-t1). The first temperature can be set to a temperature at which the organic material can be dissolved as much as possible depending on the combination of the organic material and the ionic liquid, and the solubilization temperature of the organic material is greatly reduced by using the ionic liquid . Also, since the mixed organic material may contain initial crystals of low quality, it is preferable to set the time for maintaining the first temperature (T1) to a time sufficient for the organic material including the initial crystals to be completely dissolved.

After the end of the holding time at the first temperature T1, the temperature is lowered to a second temperature T2 which is a single crystal growth temperature after the seeding, and a certain time t4-t3 is maintained at the second temperature T2 . Depending on the second temperature (T2), the growth rate of the single crystal and the quality of the grown single crystal may be different from each other, and the purity of the crystal may be different. In order to form a single crystal of high purity, it is preferable that the second temperature (T2) is as high as possible. On the other hand, since the nucleation and the growth of the single crystal proceeds during the process of cooling at the first temperature T1 at the second temperature T2 or during the process of maintaining at the second temperature T2, It is preferable to set the time sufficient for the solubilized organic material to be mostly crystallized.

 After growing the single crystal at the second temperature T2, the temperature may be lowered at a predetermined rate so that the separation step S50 may be performed.

The temperature change curve in Fig. 2 is merely an example, and the present invention is not limited thereto. For example, instead of maintaining the organic material at a first temperature for a certain period of time for solubilizing the organic material, the organic material may be made to be dissolved in a process of raising the temperature to a first temperature at a predetermined rate. In this case, good. Although the second temperature is shown as being lower than the first temperature in FIG. 2, the second temperature may be a temperature higher than the first temperature, and in the process of changing the temperature at a predetermined speed instead of maintaining the temperature at the second temperature for a predetermined time So that single crystal growth can be achieved. The temperature at which the mixing step S10 and the separation step S50 are performed is not limited to room temperature. For example, the organic material may be mixed with the ionic liquid at the first temperature T1.

According to the method for growing an organic material single crystal according to the present invention described above, since an organic material is mixed and dissolved in an ionic liquid and seeding is carried out to proceed the single crystal growth, a high- Lt; / RTI > In particular, according to the method of the present invention, high purity single crystal growth of about 99.9% or more is possible by only one process as described in the embodiments.

In addition, such a process using an ionic liquid can be performed at a normal pressure or a low vacuum in a short time, and there is little loss of raw materials, and the process yield is high, which is advantageous in terms of cost compared to the conventional single crystal growth or purification method.

The present invention is also advantageous in terms of ease of design and control of process conditions. That is, since the general organic solvent is volatile, it is difficult to apply it to an organic material requiring a high temperature for solution, and since the organic solvent is volatilized during the heat treatment process, The liquid is compatible with most organic materials and is not only present in a liquid phase over a wide temperature range but also chemically stable so that the mixing ratio of the ionic liquid and the organic material remains substantially the same in the heat treatment process.

3 is a schematic cross-sectional view of an organic material single crystal growth apparatus according to another aspect of the present invention. 3, an organic material single crystal growing apparatus 100 according to the present invention includes a stage 110, a container body 120 supported by the stage and containing a mixture 200 of an organic material and an ionic liquid, A temperature regulating unit 130 provided around the container body 120 for heating a mixture 200 of an organic material and an ionic liquid, a gas inlet for introducing gas into the container body 120 A gas discharge unit 150 for discharging gas from the inside of the container body 120, a container cover 160 for covering and sealing the container body 120, a seed holder for fixing the seed 310, (300).

More specifically, the stage 110 can be configured to support the container body 120 and to move up and down and / or rotate. The container body 120 accommodates therein an ionic liquid mixed with an organic material to which a single crystal is to be grown. The container body 120 may be formed of a material having excellent heat resistance, such as ceramics, and formed of a material that does not react with the ionic liquid and the organic material when heated at a high temperature. The temperature regulating unit 130 may be a resistance heating type heater for heating the organic material to be dissolved in the ionic liquid. 3 shows a coil shape heater in which the temperature adjusting unit 130 surrounds the container body 120. However, the shape, type, and installation position of the temperature adjusting unit 130 are not limited thereto. The temperature controller 130 may be a heater capable of raising the temperature of 400 ° C or more and may be designed to have a constant temperature gradient in all directions of the container body 120.

The gas introducing part 140 and the gas discharging part 150 are configured to control the gas atmosphere inside the container body 140. For example, the gas inlet 140 may be connected to an inert gas source such as nitrogen or argon, and the inside of the container body 140 may be maintained in an inert gas atmosphere. A vacuum pump may be connected to the gas discharging unit 150 so that the inside of the container body 140 is maintained in a vacuum atmosphere. In order to maintain the atmosphere or pressure inside the container body 140, it is necessary to form a closed space. The container cover 160 covers the top of the container body 140 to form a closed space.

The seed holder 300 may be configured to allow the seed 310 to be fixed to the end of the seed holder 300 to feed the seed into the ionic liquid, and to move up and down and / or rotate. The seed 310 may be a high-purity single crystal of the same material as the organic material to be grown.

Instead of fixing the seed 310 to the end of the seed holder 300, a microtube for forming a self-seed may be fixed and injected into the ionic liquid, as shown in FIG. As shown in FIG. 4, a hollow micro tube 320 is fixed to an end of the seed holder 300 instead of the seed 310, and the diameter of the hollow region may be 800 μm or less. When the microtube is put into the ionic liquid in which the organic material is dissolved, the organic material solution rises to the hollow region of the microtube by the capillary phenomenon and crystallizes due to a minute temperature difference to form the seed 330. By using the microtube as described above, it is possible to grow the organic material single crystal without using the separate single crystal seed 310.

In the single crystal growth step, the container body 12 and the seed holder 300 can be moved up and down or in the rotating direction, and the up and down movement speed can be 2 mm or less per hour and the rotation speed can be 9 rph or less. In FIG. 3, both the stage 110 and the seed holder 300 are shown to be movable up and down and rotated. However, the stage 110 and the seed holder 300 can be configured to move up and down or rotate only as needed.

It should be understood that the apparatus of Fig. 3 is an example, and that the organic material single crystal growing apparatus according to the present invention is not limited to the configuration of Fig. 3 may be omitted or changed, or a configuration not shown in Fig. 3 may be added. For example, the container body 120 or the container cover 160 may be provided with a measuring unit capable of measuring process conditions such as temperature and pressure, and may receive the measurement result of the measuring unit and control the temperature controlling unit 130 and the like May be provided.

Hereinafter, results of growing a high purity organic material single crystal using an ionic liquid according to the present invention will be described with reference to examples.

< Example  1>

Example 1 is a method of preparing a conductive organic material which is used as a material of an organic electroluminescent device, such as N, N'-bis- (1-naphyl) -N, N'-diphenyl-1,1'-biphenyl-4,4'-diamine (Hereinafter abbreviated as 'NPB') was grown by single crystal growth using [Omim] [TFSI] ionic liquid. The formula of NPB is shown in the following formula (2).

(2)

Observation of Scanning Electron Microscope (SEM) showed that the NPB particles before mixing with the ionic liquid had an amorphous shape of 1 ~ 2 ㎛ and low purity of 82.4% as a result of HPLC (High Performance Liquid Chromatography) purity analysis.

The low purity NBP before refining was milled and mixed at a mixing ratio of 10 wt% in [Omim] [TFSI] ionic liquid. Then, in a heat treatment furnace maintained in an argon (Ar) gas atmosphere, Lt; / RTI &gt; and the NPB was allowed to dissolve. After the next microtube was introduced, nucleation was induced by gradual cooling to 230 deg. C at a rate of 10 deg. C / h and isothermal treatment at 230 deg. C for 12 hours to grow single crystals. The formed NPB single crystal was separated from the ionic liquid, washed with isopropyl alcohol (IPA) and dried in an oven at 60 DEG C for 24 hours to obtain the final NPB crystal. The crystallinity of the crystals thus obtained was analyzed by X-ray diffractometry (XRD) and its purity was confirmed by HPLC.

5 (a) shows the XRD analysis results of the NPB single crystal grown by Example 1, and FIG. 5 (b) shows the XRD analysis results of the NPB polycrystals for comparison. As shown in Fig. 5, an excellent NPB single crystal having an X-ray half width of 0.1 ^o or less was grown by the method of the present invention. Also, HPLC purity analysis showed that the grown NPB single crystal had a high purity of 99.92%. That is, according to the method of the present invention, it can be seen that a high purity NPB single crystal having a purity of 99.9% or more can be obtained through only one simple heat treatment process.

< Example  2>

Example 2 was an example in which tris- (8-hydroxyquinoline) aluminum (hereinafter abbreviated as Alq3), which is a conductive organic material used as a material of an organic electroluminescent device, was purified using [Omim] [TFSI] ionic liquid to be. Compared with Example 1, the organic material was changed from NPB to Alq3, and the remaining process conditions were the same. The formula of Alq3 is shown in the following formula (3).

(3)

6 (a) shows the XRD analysis results of the Alq3 single crystal grown by Example 2, and FIG. 6 (b) shows the XRD analysis results of the Alq3 polycrystal for comparison. As shown in Fig. 6, excellent Alq3 single crystals having an X-ray half width of 0.1 ^o or less were grown by the method of the present invention. Also, HPLC purity analysis showed that the purity of the grown Alq3 single crystal was similar to that of NPB single crystal.

7 (a) and 7 (b) are scanning electron micrographs of Alq3 single crystals and Alq3 polycrystals grown by Example 2, respectively. From FIG. 7, it is confirmed that the Alq3 polycrystal is a needle-shaped particle having a size of several micrometers or less, while a crystal growth of several hundreds of micrometers or more is achieved after the single crystal growth process according to the present invention.

From the above results, it can be seen that when the single crystal growth method using the ionic liquid disclosed in the present invention is used, it is possible to grow the organic material into a high-purity single crystal of about 99.9% through a simple and low- , Which is very significant in that it overcomes the fundamental limitations of conventional methods. In the embodiment, only the results of purification of NPB and Alq3 have been disclosed. However, the single crystal growth method according to the present invention can be effectively applied to most organic materials used in organic electroluminescent devices, organic photoelectric conversion devices, organic semiconductor devices, . The reason why such an excellent effect is exhibited by the single crystal growth method using an ionic liquid is not fully clarified. However, in the case of a conductive organic material used for an organic electroluminescent device or the like, the ionic liquid has a similar composition and molecular weight, , It is very advantageous in terms of kinetics in the solution, and it can be assumed that it exhibits excellent behavior in crystallization.

It will be apparent to 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. For example, it should be understood that the present invention does not preclude the use of a mixture of a plurality of ionic liquids with an ionic liquid or mixing with another solvent. Accordingly, the scope of protection of the present invention should be determined by the description of the claims and their equivalents.

100: Organic material single crystal growth apparatus
120: container body
130: Temperature control unit
140: gas inlet
150:
160: container cover
200: mixture of organic material and ionic liquid
300: seed holder
310, 330: seed
320: micro tube

Claims (14)

Mixing the organic material with an ionic liquid;
A lyophilizing step of heat-treating the organic material mixed in the ionic liquid in a first condition to form a solution;
A nucleation step of injecting a seed into the ionic liquid containing the solubilized organic material in a second condition and generating nuclei on the seed surface;
A single crystal growing step of growing a single crystal in a third condition; And
A separation step (S50) of separating the grown organic material single crystal from the ionic liquid;
Including,
A method for growing an organic material single crystal using an ionic liquid, characterized by obtaining an organic material single crystal purified with high purity before mixing with an ionic liquid. The method according to claim 1,
Wherein the seed is a single crystal or hollow microtube of the same material as the organic material. The method according to claim 1,
Wherein the solubilization is at least one of dissolution and melting. The method according to claim 1,
Wherein a high purity single crystal organic material of 99% or more is obtained by performing the mixing step, the solubilization step, the nucleation step, the single crystal growth step and the separation step once. The method according to claim 1,
Further comprising the step of washing and drying the organic material single crystal separated from the ionic liquid. The method according to claim 1,
Wherein the first condition, the second condition, or the third condition is a condition that changes with time. The method according to claim 1,
Wherein the organic material single crystal is further subjected to a swelling step for removing surface impurities of the separated organic material single crystal after the separation step. The method according to claim 1,
Between the solubilization step and the nucleation step,
Further comprising a filtering step for filtering the organic material that has not been solubilized. stage;
A container body supported by the stage and containing a mixture of an organic material and an ionic liquid;
A temperature controller for heating a mixture of the organic material and the ionic liquid contained in the container body;
A seed holder in which a seed to be fed into a mixture of an organic material and an ionic liquid accommodated in the container body is fixed to an end thereof;
/ RTI &gt;
Wherein the container body and the seed holder are movable relative to each other. 10. The method of claim 9,
Wherein the seed is a single crystal or hollow microtube of the same material as the organic material. 10. The method of claim 9,
Wherein the relative movement is at least one of up-down movement and rotation movement. 10. The method of claim 9,
A gas inlet for introducing gas into the container body; And
And a gas discharging portion for discharging gas from the inside of the container main body. Section 1 9. An organic material monocrystal grown by the method according to any one of claims 1 to 8. 14. The method of claim 13,
X-ray full width at half maximum is 0.1 ^o organic single crystal material, characterized in that not more than.

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