KR20010015513A - organic electroluminescence device - Google Patents

Abstract

PURPOSE: Provided is an organo-electronic luminescence element, which improves luminescence efficiency and luminescence color by using indole derivatives as luminescence material. CONSTITUTION: The organo-electronic luminescence element is characterized by containing a first electrode, a second electrode and one or more luminescence layer that is composed of a below compound or mixture containing the following compound. In the compound, A is PhN having two substitution group or sulfur atom; B is PhC having two substitution group or nitrogen atom; R1 and R6 is respectively one material selected from the group consisting of H, alkyl, substituted alkyl, alkoxy, aryl, substituted aryl, halogen, alkylsulfur, arylsulfur, alkylamino, arylamino and cyano group, or material that one more of R1 and R2, R3 and R4, and R5 and R6 are coupled each other to form aryl group; and R is one material selected from the group consisting of H, alkyl, substituted alkyl, alkoxy, aryl and substituted aryl group.

Description

Organic electroluminescence device

The present invention relates to an organic electroluminescent device which emits green light by using an organic electroluminescent device, specifically an indole compound, etc. as a light emitting material.

Recently, as the size of display devices (displays) increases, the demand for flat display devices with less space is increasing. One of such flat display devices is an electroluminescent device.

The electroluminescent device is classified into inorganic electroluminescent device and organic electroluminescent device according to the material used.

In general, the inorganic electroluminescent device is a device that accelerates electrons by applying a high electric field to a light emitting part, and thus emits light by exciting the light emitting center by colliding the accelerated electrons with the light emitting center.

In the organic electroluminescent device, the excitons generated by combining the injected electrons and holes by injecting electrons and holes from the electron injection electrode (cathode) and the hole injection electrode (anode) into the light emitting unit are respectively grounded from the excited state. It is a device that emits light when falling.

The inorganic electroluminescent device having the above operating principle requires a high voltage of 100-200V as a driving voltage because a high electric field is required, whereas the organic electroluminescent device can be driven at a low voltage of about 5-20V. There is an advantage, and research is being actively conducted.

In addition, the organic light emitting display device has excellent characteristics such as wide viewing angle, high speed response and high contrast, so it can be used as a pixel of a graphic display, a pixel of a television image display or a surface light source. They are thin, light, and have good color, making them suitable for next-generation flat panel displays.

The organic light emitting diode may include a first electrode, a second electrode, and an organic light emitting medium. The organic light emitting medium includes two separate organic layers, that is, one layer for injecting and transporting electrons and one layer for forming an area for injecting and transporting holes in the device. It may be further included. The layer for injecting and transporting electrons and the layer for injecting and transporting holes may be divided into an electron injection layer, an electron transport layer, a hole injection layer, and a hole transport layer, respectively. The organic light emitting medium may further include a light emitting layer in addition to the electron injection and transport layer and the hole injection and transport layer. The structure of the organic light emitting device having a simple structure

First electrode / charge transport layer and light emitting layer / second electrode

It can be configured as. In addition, by separating each organic functional layer

The organic light emitting diode may be configured as a first electrode / hole injection layer / hole transport layer / light emitting layer / electron transport layer / electron injection layer / second electrode.

The second electrode of the organic light emitting device having such a structure injects electrons through an electron injection and transport layer (or an electron injection layer and an electron transport layer, respectively), and the first electrode is a hole injection and transport layer (or a hole injection layer, respectively). By injecting holes through the hole transport layer, electrons and holes are paired in the organic light emitting medium and then disappear, and energy is emitted as light.

Currently, many researches are being conducted on materials applied to the organic light emitting device, and the following materials are generally used in the device.

The hole transport layer is N, N'-diphenyl-N, N'-bis (3-methylphenyl)-(1,1'-biphenyl) -4,4'-diamine (TPD) or N, N'-dinap Triphenylamine derivatives, such as thi-N, N'-phenyl- (1,1'-biphenyl) -4,4'-diamine (NPD) and the like.

As the electron transporting layer, alkyl metal complex compounds such as tris (8-hydroxyquinolate) aluminum (Alq ₃ ) are generally used.

The material used as a component of the remaining organic light emitting diodes may be selected and used among materials known to perform a function as a corresponding component.

On the other hand, the light emitting layer may be used alone in the case of a parent material known to emit light when holes and electrons are injected, and when Alq ₃ or the like is used as the parent material, the light emitting material may be doped into the parent material to control the emission color. Can be.

That is, the light emitting layer emits light when the holes and electrons are combined in the organic matrix material that can support the injection of holes and electrons. Change occurs.

From the physical point of view, if the parent material and the luminescent material are completely dispersed and a physically affinity mixing is possible, it is a means of extending the life of the device.

Selecting a luminescent material that can provide the desired color tone upon light emission necessarily involves a relationship between the nature of the luminescent material and the nature of the parent material.

Holes and electrons recombine in the parent material to emit light. The light energy is absorbed by the light emitting material, which is excited to emit light inherent in the light emitting material.

The important relationship for selecting a luminescent material that exists in the parent material and that can specify the hue of the light emission is:

First is the comparison of the reduction potentials of the two materials. Luminescent materials that have been demonstrated to shift the wavelength of light emission exhibit negative reduction potentials than the parent material. Various techniques for measuring the reduction potential measured by eV have already been described extensively in the literature. Since what is required here is the difference between the reduction potentials rather than the absolute values of the two materials, any technique capable of measuring the reduction potential can be applied if the reduction potentials of the luminescent material and the parent material are measured in the same way.

Secondly, when selecting the light emitting material, the difference in the bandgap potential between the two materials is considered. Luminescent materials that have been demonstrated to shift the wavelength of light emission exhibit lower bandgap potentials than the parent material. The bandgap potential of a molecule is obtained as the difference between its ground state, measured in eV, and the potential separating the first single state. Bandgap potentials and their measurement methods are also described extensively in the literature. Since what is required is the difference between the bandgap potentials rather than the absolute values of the two materials, if the bandgap of the luminescent material and the parent material are measured in the same way, all the techniques allowed for the measurement of the bandgap potential can be used.

In a parent material that can emit light directly, when spectral coupling between the parent and the luminescent material is obtained, there is a shift in the light emission energy at the characteristic wavelength of the parent material alone and enhanced emission at the characteristic wavelength of the luminescent material. do. This means that by spectral coupling there is an overlap between the wavelength of the characteristic emission of the parent material alone and the wavelength of the absorption of the luminescent material.

Transferring the function of light emission to a luminescent material has more stringent restrictions on the choice of parent material. For example, a material selected to emit light is basically required that light of the wavelength emitted by the material exhibit a low extinction coefficient that avoids internal absorption.

On the other hand, it is possible to use any technique that is convenient for dispersing the light emitting material into the parent material, it is preferable that the light emitting material can be deposited with the parent material.

In the case of green light emitting devices, coumarine 6, quinacridone, or N-substituted quinacridone derivatives are used as light emitting materials.

It has been found that when the luminescent materials are dispersed in the parent material such as Alq ₃ by vacuum vapor deposition, the luminous efficiency of the mixture is much higher than when the mother material Alq _{3 is used} alone, and thus the electroluminescent efficiency of the mixture Can be greatly improved.

However, the above-mentioned conventional light emitting materials have some problems. Among them, the problems of the typical organic light emitting device using quinacridone are as follows. Therefore, a new type of light emitting material to be applied to the organic light emitting device is developed. This industry is being asked.

First, the conventional quinacridone molecular formula has N-H groups, which can form unstable hydrogen bonds with neighboring molecules having carbonyl groups and other groups. Such internal molecular coordination generates dimers of excited states between adjacent quinacridone molecules, which is undesirable for the operation of electroluminescence.

Second, the conventional N-alkylquinacridone also has a problem that the hydrogen bonding problem has been solved, but the need to improve the electroluminescent efficiency itself has been continuously raised, and the problem of improving the stability of the electroluminescent device life has been raised.

The present invention has been made to improve the above-mentioned problems, the object of the present invention is to apply a new type of light emitting material instead of the conventional light emitting material to improve the luminous efficiency and emission color green organic electroluminescence It is to provide a device.

1 is a cross-sectional view showing the structure of an organic light emitting display device;

2 is a cross-sectional view showing the structure of an organic light emitting display device according to the present invention.

Explanation of symbols for main parts of the drawings

1 substrate 2 first electrode

3: organic film layer 4: second electrode

5: hole injection layer 6: hole transport layer

7: organic light emitting layer 8: electron transport layer

9: electron injection layer

In order to achieve the above object, a feature of the present invention is an organic electroluminescent device composed of a first electrode, a second electrode and at least one organic film layer, a mixture containing an isobenzofuran derivative or isobenzofuran derivative of the following structure It is to provide an organic light emitting device comprising a light emitting layer consisting of.

Structural Formula 1

Wherein R ₁ to R ₁₀ are each hydrogen, an alkyl group, a substituted alkyl group, an alkoxy (alkoxyl) group, an aryl group, a substituted aryl group, a halogen group, an alkylsulfur group , An arylsulfur group, an alkylamino group, an arylamino group, and a cyano group. Wherein the R ₁ and R _2, R ₃ and R _4, R ₅ and R _6, R ₇ and R _8` and at least one of R ₉ and R ₁₀ are each interconnected and may form an aryl group (aryl).

Throughout this specification, it is understood that each of one or more of R ₁ and R ₂ , R ₃ and R ₄ , R ₅ and R ₆ , R ₇ and R _8, and R ₉ and R ₁₀ are each interconnected to form an aryl group, It means that two paired substituents are positioned immediately adjacent to form one aryl group.

In addition, the present invention, in addition to the above compounds, isobenzopyrrole derivative in which the oxygen atom of the hetero ring is substituted with nitrogen atom in the molecular skeleton of isobenzofuran, isobenzoimidazole derivative having two nitrogen atom substituents, Isobenzoisoxazole derivatives containing oxygen and nitrogen atoms, isobenzothiophene derivatives containing sulfur atoms, isobenzothiazole derivatives containing nitrogen atoms together with sulfur atoms, and indole derivatives And quinoline derivatives are applied to organic electroluminescent devices. Hereinafter, the derivatives will be described in detail.

The present invention also provides an organic electroluminescent device comprising a light emitting layer comprising a mixture containing an isobenzopyrrole derivative or an isobenzopyrrole derivative in which the oxygen atom of the hetero ring is replaced with a nitrogen atom in the molecular skeleton of isobenzofuran. to provide.

The structural formula of the isobenzopyrrole derivative is as follows.

Structural Formula 2

R ₁ to R ₁₀ are each hydrogen, alkyl group, substituted alkyl group, alkoxy group, aryl group, substituted aryl group, halogen group, alkylsulfur group, arylsulfur group, alkylamino group, arylamino group and cyano group It is either chosen. At least _one of R ₁ and R ₂ , R ₃ and R ₄ , R ₅ and R ₆ , R ₇ and R _8, and R ₉ and R ₁₀ may be connected to each other to form an aryl group. Meanwhile, R represents hydrogen, an alkyl group, a substituted alkyl group, an alkoxyl group, an aryl group or a substituted aryl group.

In addition, the present invention provides an organic electroluminescent device comprising a first electrode, a second electrode and at least one organic film layer, wherein the mixture containing isobenzothiophene derivative or isobenzothiophene derivative having the following structure is an organic light emitting layer An organic electroluminescent device composed of an electroluminescent medium is provided.

Structural Formula 3

R ₁ to R ₁₀ are each hydrogen, alkyl group, substituted alkyl group, alkoxy group, aryl group, substituted aryl group, halogen group, alkylsulfur group, arylsulfur group, alkylamino group, arylamino group and cyano group At least one selected from R ₁ and R ₂ , R ₃ and R ₄ , R ₅ and R ₆ , R ₇ and R _8, and R ₉ and R ₁₀ may be connected to each other to form an aryl group.

In addition, the present invention is an organic electroluminescent device composed of a first electrode, a second electrode and at least one organic film layer, characterized in that it comprises a light emitting layer consisting of a material having the following structural formula or a mixture containing the material An organic electroluminescent device is provided.

Structural Formula 4

A is a PhN or sulfur atom having two substituents, B is a PhC or nitrogen atom having two substituents, and R ₁ to R ₆ are each hydrogen, an alkyl group, a substituted alkyl group, and alkoxy ), Aryl group, substituted aryl group, halogen group, alkylsulfur group, arylsulfur group, alkylamino group, arylamino group and cyano or one or more of R ₁ and R ₂ , R ₃ and R _4, and R ₅ and R ₆ may be connected to each other to form an aryl group. Meanwhile, R is one selected from the group consisting of hydrogen, an alkyl group, a substituted alkyl group, an alkoxyl group, an aryl group and a substituted aryl group.

PhC as used throughout this specification means C ₆ H ₅ C, and PhN means C ₆ H ₅ N.

In addition, the present invention is indole having the following structural formula wherein A is PhN having two substituents (R ₇ , R ₈ ) in the formula 4, B is PhC having two substituents (R ₉ , R ₁₀ ) An organic electroluminescent device comprising a light emitting layer comprising a mixture containing a derivative or an indole derivative is provided.

Structural Formula 5

R ₇ to R ₁₀ are each selected from the group consisting of hydrogen, an alkyl group, a substituted alkyl group, an alkoxy group, an aryl group, a substituted aryl group, a halogen group, an alkylsulfur group, an arylsulfur group, an alkylamino group, an arylamino group and a cyano group At least one selected from R ₁ and R ₂ , R ₃ and R ₄ , R ₅ and R ₆ , R ₇ and R _8, and R ₉ and R ₁₀ may be connected to each other to form an aryl group.

In addition, the present invention is composed of a mixture containing an isobenzothiazole derivative or an isobenzothiazole derivative having the following structural formula wherein A is a sulfur atom, B is a nitrogen atom, and R is a hydrogen atom in the formula (4) It provides an organic light emitting device comprising a light emitting layer.

Structural Formula 6

The present invention also provides an isobenzoimidazole derivative or an isobenzoimidazole derivative having the following structural formula wherein A is PhN having two substituents, B is a nitrogen atom, and R is a hydrogen atom. An organic electroluminescent device comprising a light emitting layer comprising a mixture is provided.

Structural Formula 7

R ₇ and R ₈ are each hydrogen, alkyl group, substituted alkyl group, alkoxy group, aryl group, substituted aryl group, halogen group, alkylsulfur group, arylsulfur group, alkylamino group, arylamino group and cyano group It is either chosen. Meanwhile, at least _one of R ₁ and R ₂ , R ₃ and R ₄ , R ₅ and R _6, and R ₇ and R ₈ may be interconnected to form an aryl group.

The present invention also provides an organic electroluminescent device comprising a first electrode, a second electrode, and at least one organic film layer, wherein the organic light emitting layer comprises a light emitting layer comprising a quinoline derivative or a mixture containing a quinoline derivative having the following structure: It is an electroluminescent device.

Structural Formula 8

R ₁ to R ₉ are hydrogen, an alkali group, a substituted alkyl group, an alkoxy group, an aryl group, a substituted aryl group, a halogen group, an alkylsulfur group, an arylsulfur group, an alkylamino group, an arylamino group and a cyano group, respectively. At least one selected from R ₁ and R ₂ , R ₃ and R ₄ , R ₅ and R _6, and R ₇ and R ₈ may be connected to each other to form an aryl group.

In addition, the present invention is an organic electroluminescent device composed of a first electrode, a second electrode and at least one organic film layer, wherein the isobenzoxazole derivative having the following structure or a mixture containing the isobenzoxisoxazole derivative is a light emitting layer An organic electroluminescent device composed of an organic electroluminescent medium.

Structural Formula 9

R ₁ to R ₈ are each hydrogen, alkyl group, substituted alkyl group, alkoxy group, aryl group, substituted aryl group, halogen group, alkylsulfur group, arylsulfur group, alkylamino group, arylamino group and cyano group It is any one selected, wherein at least one of R ₁ and R ₂ , R ₃ and R ₄ , R ₅ and R _6, and R ₇ and R ₈ may be connected to each other to form an aryl group.

Preferred compounds of the present invention mentioned above include compounds of the following structural formulas.

Structural Formula 10

The organic light emitting medium of the organic electroluminescent device of the present invention to which the above compounds are applied may include two separate organic layers, that is, a layer for injecting and transporting electrons and a hole for transporting and transporting holes in the device. However, the organic light emitting device to which the present invention is applied will be described in detail below.

It is common to use a transparent anode in organic electroluminescent devices. This is possible by providing a transparent insulating support such as a metal having a relatively high work function through which conductive light is transmitted and a metal oxide layer deposited thereon to form an anode thereon.

A general organic electroluminescent device is composed of a first electrode and a second electrode on a transparent insulating support, and an organic light emitting medium therebetween. The organic light emitting medium may be composed of a plurality of stacked layers, such as a hole injection layer, a hole transport layer, an electron injection layer, a light emitting layer and an electron transport layer. The first electrode and the second electrode are each connected to an external energy source by a conductor.

The second electrode may be conveniently formed by depositing on the upper layer of the organic light emitting medium. The hole injection layer and the hole transport layer may be different layers, or may be a hole injection and transport layer in which the function is performed in one layer, and the electron injection layer and the electron transport layer are the same. At this time, the light emitting materials according to the present invention are used as the light emitting layer itself or as a dopant in the parent material of the light emitting layer to control the light emitting color.

In order to evaluate the electroluminescence of the organic light emitting device to which the compound of the present invention is applied, tetraphenoxybenzofuran (TPB) of Structural Formula 10 was used as a dopant of the light emitting layer.

First electrode / hole injection layer / hole transport layer / doped light emitting layer / electron transport layer / electron injection layer / second electrode

At this time, Alq ₃ was used as a parent material of the light emitting layer, and the TPB was used as a dopant to co-deposit the Alq ₃ layer at 1 to 1.5% by mass.

The organic light emitting diode configured as described above exhibited 4000 Cd / m ² when the voltage of 9 V was applied, and the emission spectrum showed the maximum peak of 530 nm.

This means that TPB used as a luminescent material has a much better luminous performance than coumarin, quinacridone and N-methylquinacridone, which have been used as a conventional light emitting material. An organic light emitting display device emitting green light can be manufactured.

Claims (4)

An organic electroluminescent device comprising a first electrode, a second electrode and at least one organic film layer, the organic electroluminescent device comprising a light emitting layer comprising a material having the following structural formula or a mixture containing the material: A is PhN or a sulfur atom having two substituents; B is PhC or a nitrogen atom having two substituents; R ₁ to R ₆ are each hydrogen, an alkyl group, a substituted alkyl group, an alkoxyl group, an aryl group, a substituted aryl group, a halogen group, an alkylsulfur group, An arylsulfur group, an alkylamino group, an arylamino group, and a cyano group; or R ₁ and R ₂ , R ₃ and R ₄ and R ₅ At least one of R ₆ and R ₆ interconnected to form an aryl group: R is selected from the group consisting of hydrogen, an alkyl group, a substituted alkyl group, an alkoxyl group, an aryl group and a substituted aryl group. The method of claim 1, Wherein A is PhN having two substituents, and B is PhC having two substituents, wherein the organic light emitting device comprises an indole derivative or a mixture containing an indole derivative having the following structural formula: R ₇ to R ₁₀ are each selected from the group consisting of hydrogen, an alkyl group, a substituted alkyl group, an alkoxy group, an aryl group, a substituted aryl group, a halogen group, an alkylsulfur group, an arylsulfur group, an alkylamino group, an arylamino group and a cyano group Or a material selected from one or more of R ₁ and R ₂ , R ₃ and R ₄ , R ₅ and R ₆ , R ₇ and R _8, and R ₉ and R ₁₀ are interconnected to form an aryl group. The method of claim 1, Wherein A is a sulfur atom, B is a nitrogen atom, and R is a hydrogen atom, and an organic light emitting layer comprising an isobenzothiazole derivative or a mixture containing an isobenzothiazole derivative having the following structural formula Electroluminescent Devices: The method of claim 1, A is PhN having two substituents, B is a nitrogen atom, and R is a hydrogen atom, and includes an emission layer comprising an isobenzoimidazole derivative or an isobenzoimidazole derivative having the following structural formula An organic light emitting display device characterized in that: R ₇ and R ₈ are each hydrogen, alkyl group, substituted alkyl group, alkoxy group, aryl group, substituted aryl group, halogen group, alkylsulfur group, arylsulfur group, alkylamino group, arylamino group and cyano group Or a material selected from one or more of R ₁ and R ₂ , R ₃ and R ₄ , R ₅ and R _6, and R ₇ and R ₈ are interconnected to form an aryl group.