KR20020086842A - Light-emitting compound and display device adopting light-emitting compound as color-developing substance - Google Patents

Abstract

PURPOSE: Provided are a blue light emitting compound comprising benzooxazinone having improved luminous efficiency and an organic electroluminescence device using the same as color developer. CONSTITUTION: The blue light emitting compound has a benzooxazinone group represented by formula 1. In the formula 1, Ar is selected from the group consisting of aryl group having C6-C20 such as anthracene, dibenzothiophene 5,5-dioxide, aryl group of C6-C20 having C1-C20 alkyl group, and aryl group of C6-C20 having C1-C20 alkoxy group. The compound is useful for color developer of display. The compound forms an organic film such as luminescent layer of organic electroluminescence device. The organic film is a dopant of the luminescent layer.

Description

Light-emitting compound and display device adopting light-emitting compound as color-developing substance

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a blue light emitting compound having benzooxazinone having excellent luminescence properties and a display device employing the same as a color developing material.

An electroluminescence device (EL device) is a self-luminous display device having advantages of wide viewing angle, excellent contrast and fast response time.

Recently, due to the rapid growth of the optical communication and multimedia fields, the development into a highly information society has been accelerated. Accordingly, optoelectronic devices that use photon-to-electron conversion or electron-to-photon conversion have become the core of the modern information electronics industry. Such semiconductor optoelectronic devices can be broadly classified into electroluminescent devices, light receiving devices, and devices in which these are combined. Until now, most displays are light-receiving, while self-emissive electroluminescence displays are fast responding and self-luminous, so they do not require backlighting and have excellent brightness. It is attracting attention as a display element. Electroluminescent devices are classified into inorganic and organic light emitting devices according to materials for forming the light emitting layer. In general, inorganic electroluminescent devices made of pn junctions of inorganic semiconductors such as GaN, ZnS, and SiC have a small area display and light emitting diode due to advantages of high efficiency, small size, long life, and low power consumption. It is used for lamps, semiconductor lasers and the like. However, in the case of an electroluminescent (EL) device made of an inorganic material, a driving voltage is required to be 200 V or more, and the manufacturing method of the device is made by vacuum deposition, which makes it difficult to enlarge the size and to obtain high efficiency blue color. In order to overcome this problem, a method of manufacturing an electroluminescent device using organic electroluminescence has been reported (Appl. Phys. Letter., 51, p913 (1987); Nature, 347, p539 (1990)). Organic electroluminescence (EL) is a phenomenon in which when an electric field is applied to an organic material, electrons and holes are transferred from the cathode and the anode, respectively, to be combined within the material, and the energy generated is emitted as light. The electroluminescence of these organic materials was reported by Pope et al in 1963, and in 1987 by Tang et al at Eastmann Kodak, π-, called alumina-quinone. Many studies have been conducted since a light emitting device having a multilayer structure having a quantum efficiency of 1% and a luminance of 1000 cd / m 2 at 10 V or less as a device manufactured with a conjugated dye having a structure. They have the advantage of easy synthesis and synthesis of various types of materials and simple color tuning. However, when the processability and thermal stability are low and the voltage is applied, Joule heat is generated in the light emitting layer, and as the molecules are rearranged, the device is destroyed as it causes problems in luminous efficiency or life of the device. Substitution is proceeding with organic electroluminescent devices having a compound structure.

1 is a cross-sectional view illustrating a structure of a general organic electroluminescent device manufactured from a substrate / anode / hole transport layer / light emitting layer / electron transport layer / cathode. In the figure, an anode 12 is formed on the substrate 11. The hole transport layer 13, the light emitting layer 14, the electron transport layer 15, and the cathode 16 are sequentially formed on the anode 12. The hole transport layer 13, the light emitting layer 14, and the electron transport layer 15 are organic thin films made of organic compounds. The driving principle of the organic electroluminescent device of the above structure is as follows:

When a voltage is applied between the anode 12 and the cathode 16, holes injected from the anode 12 are moved to the light emitting layer 14 via the hole transport layer 13. Meanwhile, electrons are injected into the light emitting layer 14 from the cathode 16 via the electron transport layer 15, and carriers are recombined in the light emitting layer 14 to generate excitons. This exciton is changed from the excited state to the ground state, whereby the fluorescent molecules of the light emitting layer emit light to form an image.

In 1987, Eastman kodak, for the first time, developed an organic electroluminescent device using a low molecular weight aromatic diamine and an aluminum complex as a material for forming a light emitting layer (Appl. Phys. Lett. 51 , 913, 1987). On the other hand, as a blue light emitting material, compounds such as diphenyl anthracene, tetraphenylbutadiene and distyrylbenzene derivatives have been developed, but are known to have a tendency to crystallize easily due to poor film stability. Idemitsu Co., Ltd. has developed a diphenyl distyryl-based blue luminescent material that improves thin film stability by inhibiting crystallization of phenyl groups on side branches [H. Tokailin, H. Higashi, C. Hosokawa, EP 388,768 (1990)], and Kuju University have developed distyryl anthracene derivatives with improved electron beam stability and electron donor. SPIE, 1910, 180 (1993)]

However, these compounds also have lower luminous efficiency than other luminescent compounds and the thin film stability should be further improved. Therefore, development of a new blue luminescent compound is an urgent task to develop a blue light emitting device or a full color light emitting device.

The technical problem to be achieved by the present invention is to provide a new blue light emitting compound comprising benzooxazinone improved luminous efficiency characteristics.

Another technical problem of the present invention is to provide a blue light emitting compound having the benzooxazinone and a display device employing the same as a light emitting material.

1 is a cross-sectional view illustrating a structure of a general organic electroluminescent device manufactured from a substrate / anode / hole transport layer / light emitting layer / electron transport layer / cathode.

FIG. 2 is a diagram illustrating UV absorption and PL (Photoluminescence) spectra in a solution state of the electroluminescent compound represented by Chemical Formula 2 of the present invention and a PL spectrum in a film state.

* Description of the symbols for the main parts of the drawings *

11: substrate

12: anode

13: hole transport layer

14 light emitting layer

15: electron transport layer 16: cathode (cathode)

In order to achieve the first technical problem, the present invention provides a blue light emitting compound having a new benzooxazinone represented by the formula (1).

In the formula, Ar is an aryl having 6 to 20 carbon atoms while having an aryl group having 6 to 20 carbon atoms and an alkyl group having 1 to 20 carbon atoms, such as anthracene and dibenzothiophene 5,5-dioxide. The group is selected from the group consisting of aryl groups having 6 to 20 carbon atoms having an alkoxy group having 1 to 20 carbon atoms.

A second object of the present invention is achieved by a display device characterized in that a blue luminescent compound having the above benzooxazinone is employed as a coloring material. As a preferable aspect of this invention, the organic electroluminescent element which employ | adopts the blue luminescent compound which has the said benzooxazinone as a coloring material is mentioned.

That is, the second object of the present invention is also an organic electroluminescent device comprising an organic film provided between a pair of electrodes,

The organic film is made of an organic electroluminescent device, characterized in that it comprises a compound of formula (1).

In the formula, Ar is an aryl having 6 to 20 carbon atoms, having an aryl group having 6 to 20 carbon atoms, an alkyl group having 1 to 20 carbon atoms, such as anthracene and dibenzothiophene 5,5-dioxide. The group is selected from the group consisting of aryl groups having 6 to 20 carbon atoms having an alkoxy group having 1 to 20 carbon atoms.

Preferably, Ar of the blue light emitting compound of Formula 1 according to the present invention is

Is a compound of formula (2).

The benzooxazinone group at the terminal of the formula (2) having the structure as described above can improve the blue light emission efficiency as the electron donor material.

Hereinafter, a method of manufacturing an organic electroluminescent device according to the present invention will be described. First, an anode electrode material is coated on the substrate. Herein, a substrate used in a conventional organic electroluminescent device is used, and a glass substrate or a transparent plastic substrate having excellent transparency, surface smoothness, ease of handling, and waterproofness is preferable. In addition, as the anode electrode material, indium tin oxide (ITO), tin oxide (SnO 2), zinc oxide (ZnO), or the like, which is transparent and has excellent conductivity, is used. As the cathode forming metal, lithium (Li), magnesium (Mg), aluminum (Al), Al: Li, etc. having a small work function are used. The organic electroluminescent device of the present invention may further include a hole transport layer and / or an electron transport layer as well as the most common device configuration of the anode / light emitting layer / cathode.

In this case, the light emitting layer may be formed by spin coating, the thickness is preferably in the range of 10 ~ 10,000 Å. The hole transport layer is formed on the anode, and the electron transport layer is formed on the light emitting layer before forming the cathode. The hole transport layer and the electron transport layer may be formed by vacuum deposition, sputtering, or spin coating. In this case, the hole transport layer and the electron transport layer may be a material commonly used in the art or a material of the formula (1), the layer thickness is preferably 10 to 10,000 kPa.

As the hole transport material, N, N'-bis (3-methylphenyl) -N, N-diphenyl- [1,1'-biphenyl] -4,4'-diamine (TPD) is used, and the electron transport layer is used. Materials include aluminum trihydroxyquinoline (Alq3), 1,3,4-oxadiazole derivative PBD (2- (4-biphenylyl) -5-phenyl-1,3,4-oxadiazole), quinox TPQ (1,3,4-tris [(3-penyl-6-trifluoromethyl) quinoxaline-2-yl] benzene), which is a saline derivative, is used. The electron transport layer and the hole transport layer increase the probability of light emitting coupling in the light emitter by efficiently transporting the carriers to the light emitter. The organic electroluminescent device may be manufactured in the order described above, that is, in the order of anode / hole transporting layer / light emitting layer / electron transporting layer / cathode, and vice versa, that is, in the order of cathode / electron transporting layer / light emitting layer / hole transporting layer / anode. You may manufacture.

The present invention can be more clearly understood by the following examples, which are only intended to illustrate the present invention and are not intended to limit the scope of the invention.

Example 1

An indium-tin oxide (ITO) electrode was formed on a glass substrate, and a light emitting layer having a thickness of 600 하여 was formed by spin coating a compound of Formula 2 on the ITO electrode. Al: Li was vacuum-deposited on the emission layer to form an aluminum-lithium electrode of 1200 Å thickness to fabricate an organic electroluminescent device.

Example 2

Characterization of Organic Electroluminescent Compounds

The driving start voltage, the L-I efficiency, the highest luminous luminance and color characteristics of the organic electroluminescent device manufactured according to Example 1 were investigated and shown in Table 1 below.

From the Table 1, the organic electroluminescent device according to Example 1 was able to implement blue color, and it was confirmed that the driving start voltage and the luminance characteristics were excellent.

The compound of Formula 1 according to the present invention is a blue light emitting material containing a benzooxazinone group, and has excellent luminous efficiency, and is useful as a coloring material of a display device.

In addition, the organic electroluminescent device according to the present invention forms an organic film such as a light emitting layer using the compound of Formula 1, and the luminous efficiency and luminance characteristics are improved compared with the case of using a conventional blue light emitting compound.

Claims (2)

A blue light emitting compound having a benzooxazinone group represented by Formula 1: In the formula, Ar is an aryl having 6 to 20 carbon atoms, having an aryl group having 6 to 20 carbon atoms, an alkyl group having 1 to 20 carbon atoms, such as anthracene and dibenzothiophene 5,5-dioxide. The group is selected from the group consisting of aryl groups having 6 to 20 carbon atoms having an alkoxy group having 1 to 20 carbon atoms. The organic electroluminescent device according to claim 1, wherein the organic film is a dopant of a light emitting layer.