KR20030006682A - Organic luminescent compound, and organic electroluminescence device using the same - Google Patents

Abstract

PURPOSE: An organic luminescent compound and an organic electroluminescence device using the compound are provided to improve the heat resistance and to allow the luminescent color to be controlled easily. CONSTITUTION: The organic luminescent compound is represented by the formula 4, wherein R1 is an alkyl group of C1-C10, an aryl group or a heteroaryl group; R2 is H, an alkyl group of C1-C10 or a five or six-membered carbocyclic ring connected with R1; R3, R4, R5, R6 and R7 are independent each another and are H, an alkyl or alkoxy group of C1-C10, an aryl group, or a heteroaryl group; M is a mono, di or tri-valent metal; and n is 1, 2 or 3. The organic electroluminescence device comprises a first electrode with high work function; a second electrode with low work function; and at least one organic electroluminescence layer containing the organic luminescent compound of the formula 4.

Description

Organic luminescent compound, and organic electroluminescence device using the same

The present invention relates to an organic light emitting compound having a novel structure, and more particularly, to an organic light emitting compound having high heat resistance and easily controlling a light emission color and an organic electroluminescence device using the same. It is about.

Electroluminescence devices, commonly referred to as EL, are representative flat panel displays such as liquid crystal displays (LCDs), plasma display panels (PDPs), field emission displays (FEDs), and the like. As one of the devices, there is no need for a backlight as in an LCD, a fast response speed, and a spontaneous light emitting device, which has excellent brightness and viewing angle characteristics. In particular, the organic electroluminescent device forms an organic light emitting layer that exhibits strong light emission between a transparent electrode such as ITO having a large work function and an electrode such as Mg having a small work function, and applies a voltage to the electrodes to generate the organic light emitting layer. When holes and electrons are combined in the organic light emitting layer, the organic light emitting layer generates light, and the device can be manufactured in a thin film and a bendable form, and pattern formation and mass production by the film fabrication technology can be easily performed. In addition, the driving voltage is low, and in theory, all colors can be emitted in the visible region.

Conductive, non-conductive or semiconducting organic monomolecules, oligomers, or polymers may be used as the material capable of forming the organic light emitting layer, and the organic monomolecule having luminescence may be conjugated with a plurality of benzene rings. Conjugated organic host materials and conjugated organic activators are known. Typical examples of the organic host material include naphthalene, anthracene, phenanthrene, pyrene, benzopyrene, chrisene, picene, carbazole (carbazole), fluorene, biphenyl, terphenyl, qurterphenyl, triphenylene oxide, dihalobiphenyl, transstilbene ), 1,4-diphenyl butadiene, and the like, anthracene, tetracene, pentacene, and the like are known. However, the light emitting layer formed by using such a typical light emitting organic single molecule has a disadvantage that the thickness of the light emitting layer is 1 μm or more, and the light emitting layer has a high resistance and a high driving voltage.

Therefore, various types of organic monomolecules have been developed to reduce the thickness of the light emitting layer and to lower the resistance and driving voltage of the light emitting layer. Metal complex compounds such as ZnPBO and Balq which luminesce at (460 nm), and 4- (dicymethylene) -2-methyl-6- (p-dimethylaminostyryl) -4H which luminesce at 590 nm which is a red region -Pyran (4- (dicyanomethylene) -2-methyl-6- (p-dimethyl aminostyryl) -4H-pyran: DCM), a DCM-based DCJTB that emits light at 630 nm, and the like are known. Recently, a color light emitting layer has been developed and used to improve the luminous efficiency and durability by forming a guest-host doping system by mixing a host material having sufficient electron, hole mobility, and luminescence with a dopant having various hues. have.

As an example of forming such a guest-host doping system, US Pat. No. 4,769,292 discloses tris- (8-hydroxyquinolinato) aluminum (Alq3) of Formula 1 as a host material. 4- (dicyanomethylene) -2-methyl-6- (p-dimethylaminostyryl) -4H-pyran (4- (dicyanomethylene) -2-methyl- of formula 2) By using 6- (p-dimethylaminostyryl) -4H-pyran (DCM), an electron-hole recombination is induced by Alq3, and DCM emits red light by receiving energy emitted by electron-hole recombination. It is starting.

However, DCM represented by Chemical Formula 2 shows an emission peak at about 590 nm, and thus emits orange color rather than red, and has a disadvantage in that the purification process is complicated and the reactivity with other compounds is high. Thus, US Patent No. 5,935,720 has an improved DCM. As a fluorescent substance, a compound of Formula 3 is disclosed.

In Formula 3, R ₁ and R ₂ are each an alkyl group having 1 to 20 carbon atoms, an aryl, a carbocyclic or heterocyclic group, and R ₃ and R ₄ are each an alkyl group having 1 to 10 carbon atoms, or each of R ₁ and Together with R ₂ form a 5 or 6 branched or unbranched ring, R ₅ is an alkyl group of 2-20 carbon atoms or a structurally protected aryl or heteroaryl group, and R ₆ is 1 carbon atom; Together with alkyl of -10 or R ₅ form a 5 or 6 carbon ring.

However, such a DCM-based red fluorescent substance has a low heat resistance and is easy to deteriorate because alkyl groups such as methyl groups are substituted with nitrogen atoms, and not only reduce the lifespan of the organic electroluminescent device, but also emit only orange or orange / red light. There is a disadvantage in that the emission color can not be arbitrarily adjusted.

Accordingly, an object of the present invention is to provide an organic light emitting compound having excellent heat resistance and an organic electroluminescent device using the same. Another object of the present invention is to provide an organic light emitting compound capable of controlling various emission colors and an organic electroluminescent device using the same.

1 is a cross-sectional view of an organic electroluminescent device according to an embodiment of the present invention.

2 is a cross-sectional view of an organic electroluminescent device according to another embodiment of the present invention

In order to achieve the above object, the present invention provides a novel organic light emitting compound represented by the following formula (4). The present invention also includes a first electrode having a high work function, a second electrode having a low work function, and a compound represented by the following Chemical Formula 4, wherein at least one organic light emitting layer is disposed between the first and second electrodes. It provides an organic electroluminescent device comprising.

Wherein R ₁ is an alkyl group having 1-10 carbon atoms, an aryl group, or a heteroaryl group, and R ₂ is a 5 or 6 membered carbo linked to hydrogen, an alkyl group having 1-10 carbon atoms, or R ₁ Is a cyclic ring, R ₃ to R ₇ are each independently the same or different hydrogen, an alkyl or alkoxy group having 1 to 10 carbon atoms, an aryl group, or a heteroaryl group, and M is 1, 2 or It is a trivalent metal, n is an integer of 1, 2 or 3.

Hereinafter, the present invention will be described in detail with reference to the accompanying drawings.

The organic light emitting compound according to the present invention is a compound which emits light by receiving energy generated by recombination of electron-holes and has a structure of the following formula.

In the above formula, R ₁ is an alkyl group having ₁ to 10 carbon atoms, an aryl group, or a heteroaryl group, preferably a t-butyl group, a phenyl group or a trimethylphenyl group, and R ₂ is hydrogen or a 1-carbon group. 10 alkyl group, or a cyclic 5 or 6 atoms connected to the carbonyl ring and R _1, R ₃ to R ₇ are each independently the same or different hydrogen, alkyl group or alkoxy group having a carbon number of 1-10 groups, aryl (aryl) group, or Heteroaryl group. M may be a 1, 2 or trivalent metal, specifically, Li, Na, K, Be, Mg, Zn, Al and the like may be used, wherein n is an integer of 1, 2 or 3. More preferred among the organic light emitting compounds according to the present invention is that in Formula 4 R ₁ is a phenyl or trimethylphenyl group, M is Li, Be, Zn, or Al, n is 1, 2, or 3. Since the organic light emitting compound has a structure in which a DCM compound is chelated to the metal M as a ligand, the emission color of the organic light emitting compound can be appropriately adjusted by appropriately selecting a ligand and a metal to be used.

The organic light emitting compound according to the present invention can be prepared by a variety of known organic synthesis method, an example of which is shown in Scheme 1.

As shown in Scheme 1, in order to prepare the organic light emitting compound according to the present invention in the state of slowly dropping POCl ₃ in a solvent such as dimethylformamide (DMF) in an ice bath (vilsmeier reagent), 8 Hydroxyquinoline is added to form the aldehyde of Compound B, and then reacted with 4,4-dicyanomethylene-4H-pyran in a solvent such as ethanol to synthesize Compound C. Next, the target compound D can be synthesized by reacting a halogenated metal such as AlCl _{3 or} MgCl ₂ with compound C in a solvent such as ethanol.

1 is a cross-sectional view of an organic electroluminescent device according to an embodiment of the present invention. As shown in FIG. 1, an organic electroluminescent device includes a first electrode having a high work function on a substrate 10. 12) is formed as a hole injection layer (anode), and at least one light emitting layer 14 including the organic light emitting compound according to the present invention is formed on the first electrode 12. A second electrode 16 having a low work function is formed on the emission layer 14 so as to face the first electrode as an electron injection layer (cathode). When voltage is applied to the first and second electrodes 12 and 16 of the organic electroluminescent device, holes and electrons generated by the first and second electrodes 12 and 16 are injected into the light emitting layer 14, In the molecular structure of the emission layer 14, electrons and holes are combined to emit light, and the emitted light passes through the first electrode 12 and the substrate 10 made of a transparent material to display an image.

The organic light emitting compound of the present invention may be used as a host material as the organic light emitting layer 14 by forming a layer alone between the first and second electrodes 12 and 16, and a conventional host material inducing hole-electron recombination. In addition, the organic light emitting layer 14 may be used as a dopant, which is a guest material forming the organic emission layer 14. As a host material capable of forming the organic light emitting layer 14 together with the organic light emitting compound of the present invention, it is preferable to use a material whose energy level is larger than the HOMO and LUMO energy levels of the organic light emitting compound according to the present invention. Depending on the type of light emitting compound, a conventional host material such as tris- (8-hydroxyquinolinato) aluminum (Alq 3) may be used. When the organic light emitting layer 14 is formed together with the host material, the content of the organic light emitting compound according to the present invention is preferably 1 to 10% by weight. When the content of the organic light emitting compound exceeds 10% by weight, the electron-hole recombination induction property by the host material may not be exhibited smoothly.

The substrate 10 of the organic electroluminescent device is electrically insulative, and in particular, when fabricating a device emitting light toward the first electrode 12, the substrate 10 is made of a transparent material, preferably made of glass or transparent plastic film. The first electrode 12 functions as a hole injection layer (anode), and is made of indium tin oxide (ITO), polyaniline, silver (Ag), or the like having a high work function without limitation. The second electrode 16 may be formed of a metal alloy, such as Al, Mg, Ca, or LiAl, Mg-Ag, which functions as an electron injection layer and has a low work function. Can be.

FIG. 2 is a cross-sectional view of an organic electroluminescent device according to another exemplary embodiment of the present invention. In the organic electroluminescent device shown in FIG. 2, holes and electrons generated in the first and second electrodes 12 and 16, respectively, may be formed. Further, hole injection and transport layers 21 and 22 and electron injection and transport layers 25 and 26 are further formed between the first and second electrodes 12 and 16 and the light emitting layer 14 so as to be easily injected into the 14. This point is different from the organic electroluminescent device shown in FIG. 1. The hole injection and transport layers 21 and 22 serve to facilitate hole injection from the hole injection electrode 12, to transport holes stably, and to block electrons, and to the hole injection layer 21. A non-limiting example may be a porphyrinic compound such as phthalocyanine copper disclosed in US Pat. No. 4,356,429, and the hole transport layer 22 may include a triphenyldiamine derivative, a styrylamine derivative, and N, N'-. An amine derivative having an aromatic condensed ring such as bis- (1-naphthyl) -N, N'-diphenylbenzidine can be used. The electron injection and transport layers 25 and 26 are functions of facilitating injection of electrons from the electron injection electrode 16, stably transporting electrons, and blocking holes, and are not limited to chinoline. It is also possible to use derivatives, in particular tris (8-chinolinorate) aluminum (aluminaquinone, Alq3). These layers function to augment, confine, and combine holes and electrons injected into the light emitting layer 14, and to improve luminous efficiency. The thickness of the light emitting layer 14, the hole injection and transport layers 21 and 22, and the electron injection and transport layers 25 and 26 is not particularly limited and may vary depending on the formation method, but usually has a thickness of about 5 to 500 nm.

The organic light emitting compound according to the present invention may be included in the hole injection and transport layers 21 and 22 and / or the electron injection and transport layers 25 and 26, and the organic compound layers are commonly used in the fabrication of organic electroluminescent devices. It may be formed by a vacuum deposition method or a spin coating method. The organic light emitting compound of the present invention can be applied not only to the organic electroluminescent device of the structure shown in FIG. 1 or 2, but also to the organic electroluminescent device of various structures exhibiting light emission phenomenon by hole-electron coupling.

Hereinafter, preferred examples are described in order to describe the present invention in more detail, but the present invention is not limited to the following examples.

Example 1

Organic light emitting compound (R _One = CH ₃ , R ₂ To R ₇ Silver hydrogen, a compound of formula 4 wherein M = Al, n = 3)

Process 1: ₃ mmol (0.458 g) of POCl ₃ was dropped and 2 mmol (0.29 g) of 8 was maintained while keeping the reactor containing dimethylformamide (DMF) at 10 ° C. or lower in an ice bath. Hydroxyquinoline was added dropwise, and then reacted at 40 to 45 ° C for 12 hours. The reaction was poured into iced water, neutralized to pH <8 or less by adding sodium acetate saturated in water, then refrigerated overnight, filtered and dried.

Step 2: 0.173 g (1 mmol) of the compound obtained in Step 1 and 0.172 g (1 mmol) of 4,4-dicyanomethylene-2,6-dimethyl-4H-pyran are added to 5 ml of ethanol, followed by 0.12 g of piperidine. Was added and refluxed for 5-6 hours. The reaction was cooled, filtered, washed with cold methanol and dried.

Step 3: 0.327 g (1 mmol) of the compound obtained in Step 2 and 0.044 g (0.33 mmol) of AlCl ₃ were added to ethanol, refluxed, cooled, filtered, washed with cold methanol, and dried to obtain the target compound.

Example 2

Organic light emitting compound (R _One = Phenyl, R ₂ To R ₇ Is hydrogen, a compound of formula 4 wherein M = Li, n = 1

Instead of using 4,4-dicyanomethylene-2,6-dimethyl-4H-pyran, 0.234 g (1 mmol) of 4,4-dicyanomethylene-2-phenyl-6-methyl-4H-pyran was used. The reaction was carried out in the same manner as in Example 2, except that 0.389 g (1 mmol) of the compound obtained in the process and 0.023 g (1 mmol) of LiOH were reacted instead of using AlCl ₃ . The reaction was carried out in the same manner as in Step 3, to obtain the target compound.

Example 3

Fabrication of Organic Electroluminescent Devices.

The glass substrate coated with indium tin oxide (ITO) was ultrasonically cleaned using a cleaning agent, and then washed again with deionized water, then degreased with toluene gas and dried. Next, a hole injecting layer is formed by vacuum depositing phthalocyanine copper to a thickness of 150 kPa on the ITO electrode, and N, N'-bis- (1-naphthyl) -N, N'-di on the hole injecting layer. Phenylbenzidine was vacuum deposited to a thickness of 600 mm 3 to form a hole transport layer. 95% by weight of Alq3 and 5% by weight of the organic light emitting compound according to Example 1 were vacuum deposited on the hole transport layer to form an organic light emitting layer, and Alq3 was vacuum deposited on the organic light emitting layer to a thickness of 380 kV to form an electron transport layer. Formed. Finally, an organic electroluminescent device was manufactured by depositing silver (Ag) on the upper portion of the electron transport layer at a thickness of 2000 kV to form a cathode.

As described above, the organic light emitting compound according to the present invention has excellent heat resistance, thereby improving reliability and lifespan of the organic electroluminescent device using the same, and variously controlling the emission color by modifying the metal or ligand of the organic light emitting compound. There are advantages to it.

Claims (6)

An organic light emitting compound represented by Chemical Formula 4, which emits light by receiving energy generated by recombination of electron-holes. [Formula 4] Wherein R ₁ is an alkyl group having 1-10 carbon atoms, an aryl group, or a heteroaryl group, and R ₂ is a 5 or 6 membered carbo linked to hydrogen, an alkyl group having 1-10 carbon atoms, or R ₁ Is a cyclic ring, R ₃ to R ₇ are each independently the same or different hydrogen, an alkyl or alkoxy group having 1 to 10 carbon atoms, an aryl group, or a heteroaryl group, and M is 1, 2 or It is a trivalent metal, n is an integer of 1, 2 or 3. The organic light emitting compound according to claim 1, wherein R ₁ is a t-butyl group, a phenyl group or a trimethylphenyl group, M is Al, and n is 3. A first electrode having a high work function; A second electrode having a low work function; And An organic electroluminescent device positioned between the first and second electrodes and comprising at least one organic light emitting layer comprising an organic light emitting compound represented by Formula 4. [Formula 4] Wherein R ₁ is an alkyl group having 1-10 carbon atoms, an aryl group, or a heteroaryl group, and R ₂ is a 5 or 6 membered carbo linked to hydrogen, an alkyl group having 1-10 carbon atoms, or R ₁ Is a cyclic ring, R ₃ to R ₇ are each independently the same or different hydrogen, an alkyl or alkoxy group having 1 to 10 carbon atoms, an aryl group, or a heteroaryl group, and M is 1, 2 or It is a trivalent metal, n is an integer of 1, 2 or 3. The organic electroluminescent device according to claim 3, further comprising a hole injection layer for injecting holes into the organic light emitting layer and a hole transporting layer for transporting holes between the first electrode and the organic light emitting layer. . The organic electroluminescent device according to claim 3, further comprising an electron injection layer for injecting electrons into the organic light emitting layer and an electron transporting layer for transporting electrons between the organic light emitting layer and the second electrode. . The organic electroluminescent device according to claim 3, wherein the organic light emitting compound is used as a host or guest material of the organic light emitting layer.