KR20040102877A - Method for Purifying Organic Compounds Used in Organic Electroluminescence Device - Google Patents

Abstract

PURPOSE: A method for purifying organic materials with ultra-high purity used for organic electroluminescent(OEL) element is provided to effectively remove free metal ions, thereby reducing black spots generated during OEL manufacturing and improving electric and optical properties and the service life of the resulted element. CONSTITUTION: The method for purifying organic materials used for OEL element comprises contacting the organic materials used for OEL element with a solution of a chelating agent and zeolite, wherein the chelating agent is selected from DTPA (diethylenetriaminepentaacetic acid), EDTA (ethylenediaminetetraacetic acid), NTA (nitrilotriacetic acid), TTHA (triethylenetetraaminehexaacetic acid), HIDA (dimethyliminodiacetic acid), gluconic acid soda and Dimercaprol (2,3-dimercapto-1-propanol).

Description

Method for Purifying Organic Compounds Used in Organic Electroluminescence Device

The present invention relates to an ultrahigh purity purification method of an organic material used in an organic electroluminescent device, and more particularly, to an ultrahigh purity purification method of an organic material used in an organic electroluminescent device and an organic electroluminescent device including the organic material thus purified.

In the 21st century, information exchange through the Internet has been actively progressed to the extent that it is not an exaggeration to say that it is an information society, and the information display device that can use information contents, text, voice, and image information without restriction of time and place As a result, display devices for displaying such information are diversifying from large screens such as TVs to small screens for communication that can be carried and carried.

CRT (Cathode Ray Tube) has become the mainstream of the display device as such information display media, but it is gradually increasing as FPD (Flat Panel Display) in terms of high functionalization and ergonomics. Among these flat panel displays, liquid crystal displays (LCDs) are widely used as flat panel displays to replace CRTs because they have advantages of light weight and thinness and low power consumption.

However, LCD is a light-receiving device that requires a separate light source, not a self-light emitting device, and there are technical limitations in brightness, contrast, viewing angle, and large area. Therefore, efforts are being actively made to develop a new flat panel display that can overcome this disadvantage. Recently, organic electroluminescent display (OELD) displays, which have advantages such as low voltage driving, self-luminous, thin film type, fast response speed, and wide viewing angle, have been gradually emerging.

ELDs are largely divided into inorganic ELDs using inorganic materials as light emitting materials and organic ELDs using monomolecular and polymer organic materials as light emitting materials. Organic ELDs do not require high driving voltages required by inorganic ELDs. Due to the ease of multicolor has the advantage.

Organic ELDs were first discovered in anthracene single crystals by Pope et al. In 1963.Tang and Van Slyke's work by Eastman Kodak in 1987 ( Appl. Phys. Lett) ., 51: 913 (1987)) and in 1990 from the University of Cambridge to the use of PPV as a light-emitting polymer materials continues research on organic ELD.

The organic ELD generates excitons in which holes injected from the anode and electrons injected from the cathode are excited by recombination in the light emitting layer, and light of a specific wavelength is generated by energy from the excitons formed. Refers to an element emitting light. Currently, studies on materials applied to organic ELD are being actively conducted. Generally, hole transport layers include TPD (3-methylphenyl-biphenyl-diamine) and NPD (4,4 -bis [N- (1-napthyl)). N-phenylamino] bipheny), CuPc (copper phthalocyanine), MTDATA (4,4 ', 4' '-tris (3-methylphenylphenyl-amino) triphenylamin), etc. are used, and Alq3 (tris (tris ( 8-hydroxyquinoline) aluminum), DPVBi (4,4-Bis (2,2-diphenyl-ethen-1-yl) -bipheyl), PBD (2- (4-biphenylyl) -5- (4-tert-butyl- phenyl) -1,3,4-oxadiazole) and the like are used. In addition, Alq3 or the like is used as a material for the light emitting layer, or a mixed layer using coumarine derivatives, quinacridone derivatives, DCM derivatives, rubrene, etc. as a doping material. The emission color is adjusted.

In particular, the light emitting material, the hole transporting material and the electron transporting material are manufactured by a chemical company and delivered to the device manufacturer, and have excellent chemical purity. There is a case that does not represent. This cause is not only solved by the compound manufacturer or device manufacturer alone, but also significantly affects the device manufacturing yield. Therefore, much research is being conducted to improve the purity of organic electroluminescent materials and transfer materials.

The present inventors have made diligent research efforts to solve the above-mentioned conventional problems, and as a result, it is difficult to remove them by conventional purification methods (e.g., recrystallization method and sublimation purification method), and the stability of the organic materials used in the organic electroluminescent device and The present invention has been completed by developing a purification method capable of efficiently removing free metal ions adversely affecting optical properties and improving purity to near 100%.

Accordingly, it is an object of the present invention to provide a method for purifying organic materials used in organic electroluminescent devices.

Another object of the present invention is to provide an organic electroluminescent device comprising an organic substance purified by the purification method of the present invention between an anode and a cathode.

Other objects and advantages of the present invention will become apparent from the following detailed description, claims and drawings.

1 is a schematic diagram of an apparatus for practicing the method of the present invention; And

2 is a view showing the performance of an organic electroluminescent device fabricated using a light emitting material purified according to the method of the present invention.

According to an aspect of the present invention, the present invention provides a method for purifying organic materials used in an organic electroluminescent device comprising contacting an organic material used in the organic electroluminescent device with a chelating agent solution and zeolite.

To date, in the art, in order to purify organic materials used in organic electroluminescent devices, sublimation purification is generally used. However, the sublimation purification method can reduce the amount of impurities affecting the device, such as free metal ions. However, since the removal is difficult, the properties of the device are deteriorated. . In addition, even when the recrystallization method, which is a chemical purification method generally used in the pretreatment, is difficult to remove such impurities, there is no fundamental solution.

Therefore, the present inventors have conducted an in-depth study for the perfect removal of impurities affecting the device, such as free metal ions, and as a result, it is possible to remove impurities that affect the properties of the device and to purify the material with ultra high purity. The method was established.

The basic strategy of the process of the invention is to purify the organics used in the organic electroluminescent device using chelating agents and zeolites.

According to a preferred embodiment of the present invention, the chelating agent is DTPA (diethylenetriaminepentaacetic acid), EDTA (ethylenediaminetetraacetic acid) NTA (Nitrilotriacetic acid), TTHA (triethylenetetraaminehexaacetic acid), HIDA (Dimethyliminodiacetic acid), Hose mixed acid, Sodium gluconate , Dimercaprol (2,3-dimercapto-1-propanol), more preferably DTPA and EDTA, most preferably DTPA.

According to a preferred embodiment of the present invention, zeolites suitable for the present invention may have the form of powder, granule and slurry, and most preferably have the form of powder, the type of which is preferably A-4 type and P-type, P-type zeolites are most preferred.

In the process of the invention, the zeolite can exist in various phases, most preferably in the colloidal phase.

As used herein, the term "organic material used in an organic electroluminescent device" means any material placed between the anode and the cathode of the organic electroluminescent device. For example, the organic substance used for an organic electroluminescent element contains an organic electroluminescent material, a hole injection / transfer material, an electron injection / transfer material, and a hole transfer obstruction material.

In the process of the invention, the contacting step can be carried out by adding the organic material used in the organic electroluminescent device to a mixture of the chelating agent solution and the zeolite or to the chelating agent solution and the zeolite, respectively, preferably It is performed by adding the organic substance used for an organic electroluminescent element to the mixture of a chelating agent solution and a zeolite.

According to a preferred embodiment of the present invention, before or after the contacting step of the present invention, purification methods commonly used in the art, such as recrystallization, sublimation purification, reprecipitation, zone melting, column purification and their Further purification is selected from the group consisting of combinations. More preferably, recrystallization and sublimation purification are further carried out before or after the contacting step, and most preferably, recrystallization and sublimation purification are carried out sequentially after the contacting step. As described above, in the case of carrying out in the same manner as usual purification, it is preferable to carry out in a continuous step. The accompanying Figure 1 illustrates an apparatus that enables this continuous process. As illustrated in FIG. 1 and the embodiment, an impurity inside the organic electroluminescent material is formed by a device fabricated so that the material having the organic electroluminescent property can be automatically circulated through the DTPA solution, the chloroform solution and the zeolite colloidal phase. Efficiently and completely removed

The purity of the organics purified by the purification method of the present invention described above is at least 99%, preferably at least 99.99, more preferably 99.9999%. Such purity can be said to be 100% purity considering the range of error.

The method of the present invention is difficult to remove by conventional purification methods (e.g., recrystallization method and sublimation purification method), and efficiently removes free metal ions that adversely affect the stability and electrical and optical properties of organic materials used in organic electroluminescent devices. By removing and improving the purity to nearly 100%, it has the advantages of reducing the occurrence of black spots generated during the fabrication of the organic electroluminescent device, improving the electrical and optical properties of the device, and extending the life of the device.

According to another aspect of the present invention, the present invention provides an organic electroluminescent device comprising an organic material purified according to the method of the present invention described above.

The organic electroluminescent device of the present invention can be manufactured in various configurations, for example, i) a substrate / anode / light emitting layer / cathode; Ii) substrate / anode / hole injection layer / light emitting layer / cathode; Iii) substrate / anode / light emitting layer / electron injection layer / cathode; Iii) substrate / anode / hole injection layer / light emitting layer / electron injection layer / cathode; Or iii) a substrate / anode / hole injection layer / hole transport layer / light emitting layer / electron transport layer / electron injection layer / cathode.

As a substrate suitable for the organic electroluminescent device of the present invention, any one used in the art may be used, for example, indium tin oxide (ITO) glass may be used. Specific examples of device fabrication using Indium Tin Oxide (ITO) glass are as follows: Substrate is impregnated in aqueous sodium chloride solution, isopropyl alcohol, acetone, ultrapure water and ultrasonic cleaning. The treated ITO substrate is then nitrogenized again to make it clean. The ITO substrate is attached to a vacuum evaporator, and the organic electroluminescent material purified according to the present invention is added and deposited. The aluminum is put again here to manufacture a device.

In the device of the present invention, the anode may be a metal, alloy, electrically conductive compound having a high work function (4 eV or more), and includes, for example, Au, CuI, ITO and SnO ₂ . The formation of the anode can be performed by vapor deposition or sputtering.

In the device of the present invention, as the organic electroluminescent material constituting the light emitting layer, various organic compounds may be used depending on the color tone (red, blue, green, yellow, white, etc.). For example, Alq3 (tris (8-hydroxyquiloline) aluminum) or the like may be used alone, or a coumarin derivative, quinacridone derivative, or DCM (4- (Dicyanomethylene) -2-methyl-6- ( julolidin-4-yl-vinyl) -4H-pyran) is a mixed layer using a derivative, rubrene and the like as a doping material, and the emission color is controlled. Formation of a light emitting layer can be performed by well-known methods, such as a vapor deposition method, a spin coating method, and an LB method.

In the organic electroluminescent device of the present invention, materials that can be used for the hole injection and transfer layer include triazole derivatives (US Pat. No. 3,112,197), oxadiazole derivatives (US Pat. No. 3,189,447), polyarylalkane derivatives (US) Patent 3,615,402), arylamine derivatives (US Pat. No. 4,232,103), silazane derivatives (US Pat. No. 4,950,950), oxazole derivatives (US Pat. No. 3,257,203), and the like. The hole injection and transfer layer can be formed by vacuum deposition, spin coating, casting, LB, or the like.

In the light emitting device of the present invention, examples of materials that can be used for the electron injection and transport layer include Alq3 (tris (8-hydroxyquiloline) aluminum), DPVBi (4,4-Bis (2,2-diphenyl-ethen-1- yl) -bipheyl), PBD (2- (4-biphenyl) -5- (4-tert-butyl-phenyl) -1,3,4-oxadiazole) and TPD (N, N'-diphenyl-N, N ' -(3-methylphenyl) -1,1-biphe-nyl-4,4'-diamine).

In the light emitting device of the present invention, the cathode may be a metal, alloy, or electrically conductive compound having a small work function (4 eV or less), for example, sodium, magnesium, lithium, aluminum / lithium alloy, indium, sodium / potassium alloy. Etc. The cathode may be manufactured by forming a thin film on the electrode material by deposition or sputtering.

In the device of the present invention, the organic material placed between the anode and the cathode is purified according to the method of the present invention, and preferably has a purity of at least 99%, more preferably at least 99.99%, and most preferably at least 99.999%. Have

Hereinafter, the present invention will be described in more detail with reference to Examples. These examples are only for illustrating the present invention in more detail, it will be apparent to those skilled in the art that the scope of the present invention is not limited by these examples in accordance with the gist of the present invention. .

Example

According to the method of the present invention, organic electroluminescent material was purified by passing through DTPA (diethylenetriaminepentaacetic acid, Aldrich) and zeolite colloid phase. As the organic electroluminescent material, tris (8-hydroxyquiloline) aluminum (Alq ₃ ) (TCI, Tokyo Kasei Kogyo Co., LTD, Japan) was used.

Chloroform and normal hexane (Aldrich) were used as a solvent, and impurities were removed by distillation. 5 g of Alq ₃ was taken and dissolved in 250 mL of purified chloroform solution. 1 g of DTPA was dissolved in 1 L of ultrapure water, and the undissolved material was separated using a glass filter, and the remaining solution was used.

In the device of FIG. 1 manufactured by the present inventors, a zeolite colloidal phase in chloroform was first added with 1 g of zeolite powder (Powder, P-type, Degussa, Germany) and 1 ml of surfactant (SDS (Sodium Dodecyl Sulfate), Aldrich). Was prepared. Then 250 ml of Alq ₃ dissolved in chloroform were added and an appropriate amount of DTPA solution was added. The DTPA solution filled in the three-necked flask is boiled and vaporized and condensed in the condenser and falls along the tube to the part with chloroform + Alq ₃ + zeolite, which moves upwards due to the difference in specific gravity and back to the three-necked flask. The circulated DTPA solution and zeolite remove the metal impurities of Alq ₃ in chloroform. Then, the chloroform solution in which Alq ₃ was dissolved was evaporated to dryness at 50 ° C. and 1 atm in an evaporator to remove the chloroform solution, recrystallized with normal hexane, filtered through a glass filter, and then dried for a predetermined time to obtain only Alq _3. .

Then, it was put in a sublimation apparatus and purified once again through sublimation. Purified Alq ₃ was placed in a glass tube in a sublimation instrument (SIBATA GLASS TUBE OVEN GTO-350 RD). The temperature for sublimation was 320 ° C., and the pressure was 1 × 10 ⁻⁵ Torr. As the fluid for sublimation, Alq ₃ was sublimed again using sublimated water at 4 ° C. The so eoteonaen Alq ₃ was produced by using the device.

In order to fabricate the device, ITO (indium-tin-oxide) glass (Ashai glass, 10 로 /?) Was cut into 2 cm × 2 cm in size, and then in order of 1 mole aqueous solution of KOH, acetone, isopropyl alcohol and deionized water. Each was cleaned with an ultrasonic cleaner (Branson model 8910) for 30 minutes and then vacuum dried. The prepared ITO glass was put into a vacuum vapor deposition machine (ULVAC VPC-260F), and vacuum deposition was carried out under the condition of 1 × 10 ^-5 Torr with a thickness of Alq ₃ deposition surface of 1000 kPa, followed by Al (Aluminum) 2000. Raised to jab.

Experimental Example

Using a produced couple plasma (ICP) atomic emission spectrometer (Thermo Jarrell-Ash ARIS-AP, USA), Alq ₃ purified by the purification process of the above example was pulverized in 5% nitric acid solution, and then the clean filtered solution was preferentially The calibration curve in the instrument for the standard was obtained by targeting the component analysis in the material targeting Al, Fe ⁺² and Cu ⁺² . Based on the calibration curves obtained at each concentration (0 ppm, 10 ppm and 100 ppm), they were analyzed under conditions suitable for isotopes and spin, and the results are shown in Table 1 below.

impurities Number of attempts Raw material After purification process Copper content One 0.2421 ppm 0.0015 ppm 2 0.2427 ppm 0.0031 ppm 3 0.2432 ppm 0.0034 ppm 4 0.2399 ppm 0.0014 ppm Iron content One 4.688 ppm 0.0315 ppm 2 4.695 ppm 0.0355 ppm 3 4.628 ppm 0.0309 ppm 4 4.685 ppm 0.0324 ppm

As can be seen in Table 1, the Alq ₃ treated according to the method of the present invention can be seen that the copper and iron content is greatly reduced.

In addition, HPLC (High Performance Liquid Chromatography) using Jasco RI930 (Sungjin I & T) to measure the purity of the purified organic electroluminescent material, Alq _{3 in} the examples at a flow rate of 0.8 mm / min and pressure 82 kg / m ² The results are shown in Table 2.

Number of attempts water Raw material One 98.1092% 2 98.0568% 3 98.2135% 4 98.1568% After completion of purification process One 99.9992% 2 99.9983% 3 100% 4 99.9997%

In Table 2, less than two decimal places fall within the error range of the machine. As can be seen in Table 2, it can be seen that the purity of Alq ₃ treated according to the method of the present invention is 99.99% or more.

So by using the obtained Alq ₃ crude and Alq ₃ we have seen, at the VL (Voltage-Luminescence) characteristic of the device through a vacuum vapor deposition to evaluate the characteristics on the devices. In the vacuum evaporator (ULVAC VPC-260F), the Alq ₃ deposition surface was 1000 Å (ULVAC CRTM-5000) under the conditions of 1 × 10 ^-5 Torr, and vacuum deposition was performed thereon. Raised to 2000 Hz (ULVAC CRTM-5000). The device thus made was measured for luminescence through the Minolta LS-100 while giving electricity. The data obtained is shown in FIG.

As can be seen in Figure 2, it can be seen that the device using the purified (q. 99.999%) Alq ₃ in the turn-on voltage is lower, the light emission indicating the brightness of the light is higher.

Having described the specific part of the present invention in detail, it is apparent to those skilled in the art that the specific technology is merely a preferred embodiment, and the scope of the present invention is not limited thereto. Thus, the substantial scope of the present invention will be defined by the appended claims and equivalents thereof.

As described above in detail, the present invention provides a method for purifying organic materials used in organic electroluminescent devices. The present invention also provides an organic electroluminescent device comprising an organic substance purified by the purification method of the present invention between an anode and a cathode. The method of the present invention is a conventional purification method (e.g., recrystallization method and sublimation purification method). By removing the free metal ions that are difficult to remove and adversely affect the stability and electrical and optical properties of the organic materials used in the organic electroluminescent device, thereby reducing the occurrence of black spots generated during the fabrication of the organic electroluminescent device. Has the advantage of improving the electrical and optical properties and extending the life of the device.

Claims (10)

A method for purifying organic materials used in an organic electroluminescent device, comprising contacting an organic material used in the organic electroluminescent device with a chelating agent solution and zeolite. The chelating agent of claim 1, wherein the chelating agent is diethylenetriaminepentaacetic acid (DTPA), ethylenediaminetetraacetic acid (EDTA), nitrilotriacetic acid (NTA), triethylenetetraaminehexaacetic acid (TTHA), dimethyliminodiacetic acid (HIDA), hose blend acid, gluconate, and dimercaprol (2,3-dimercapto-1-propanol) The organic substance purification method used for the organic electroluminescent element characterized by the above-mentioned. 3. The method of claim 2, wherein the chelating agent is DTPA. The organic electroluminescent device according to claim 1, wherein the contacting step is performed by adding an organic material used in the organic electroluminescent device to a mixture of a chelating agent solution and a zeolite or to a chelating agent solution and a zeolite, respectively. Organic substance purification method used. The method of claim 4, wherein the contacting step is performed by adding an organic material used in the organic electroluminescent device to a mixture of a chelating agent solution and a zeolite. The organic material used in an organic electroluminescent device according to claim 1, wherein the organic material used in the organic electroluminescent device is an organic electroluminescent material, a hole injection / transmission material, an electron injection / transmission material, or a hole transport obstruction material. Purification method. The method according to claim 1, further comprising a refining method selected from the group consisting of recrystallization, sublimation refining, reprecipitation, zone melting, column refining, and combinations thereof, before or after the contacting step. Organic substance purification method used for organic electroluminescent element. 8. The method of claim 7, further comprising recrystallization and sublimation purification before or after the contacting step. 9. The method of claim 8, wherein the purity of the organic substance purified by the organic substance purification method is at least 99.999%. An organic electroluminescent device comprising an organic substance purified according to any one of claims 1 to 9.