JPH10114890A - Organic light emitting element - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide an organic light emitting element having high light emitting efficiency and long life. SOLUTION: On an optically abrasion finished glass base 11, a 1,500Å indium tin oxide(ITO) film is formed as a transparent electrode 12 by spattering, on which a charge transfer layer 13 and an electron transfer layer 14, 500Å each, are formed by vacuum vapor deposition using a resistance heating method. Then, an Al/Li electrode with a film thickness of 2000Å is formed as a cathode 15. For an organic light emitting element 10, when the charge transfer layer 13 is formed, an organic compd. shown by the formula is simultaneously vapor deposited by a resistance heating method. An external voltage is applied by direct current or alternative current electric field between the transparent electrode 12 and the cathode 15.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an organic light emitting device used as a light emitting display or a backlight for a liquid crystal display.

[0002]

2. Description of the Related Art Electroluminescent (EL) panels have high visibility, excellent display capability, and high-speed response. In recent years, reports have been made on organic light-emitting devices using an organic compound as a constituent material (for example, see the related paper “Applied Physics Letters”, Vol.
1, 913, 1987 (Applied Physics Letters, 51,
1987, P.913.)). This report describes an organic light emitting device having a structure in which an organic light emitting layer and a charge transport layer are laminated.
A tris (8-quinolinol) aluminum complex (hereinafter Alq) has been developed as a luminescent material, and is an excellent luminescent material having both high luminous efficiency and electron transport.

[0003] Also, "Journal of Applied
Physics, Vol. 65, p. 3610, 1989 (Journal
of Applied Physics, 65, 1989, p.3610.), a device in which Alq forming an organic light emitting layer is doped with a coumarin derivative or a fluorescent dye such as DCM1, and the emission color changes by appropriate selection of the dye. Was found. Furthermore, it was clarified that the luminous efficiency was increased as compared with the undoped one.

[0004]

The biggest problem for practical use of an organic light emitting device is to prolong its life. The organic thin film constituting the device has an amorphous property in order to maintain a highly efficient light emitting function. When driving the element,
Joule heat is generated, and the amorphous property of the film is impaired.
Therefore, in order to extend the life, it is necessary to increase the luminous efficiency of the element and reduce the input power.

An object of the present invention is to solve the above-mentioned conventional problems, and an object of the present invention is to provide an organic light emitting device having a high luminous efficiency and a long life.

[0006]

In order to achieve the above object, the present invention provides an organic light emitting device, wherein the charge transport layer is composed of an organic compound represented by the formula (3), and the charge transport layer or the electron transport layer is Or an organic dye having an organic light emitting layer, an organic dye represented by Chemical Formula 4 was added to the organic light emitting layer.

[0007]

Embedded image

[0008]

Embedded image

The compound (Chem. 3) constituting the charge transport layer of the organic light-emitting device according to the present invention is an organic compound having a triphenylamine tetramer structure and a large molecular weight. Therefore, the glass transition point (Tg), which is a measure for starting the loss of the amorphous property of the organic thin film, is as high as 152 ° C. Thereby, thermal degradation of the element is suppressed, and a longer life can be achieved.

Further, by adding an organic dye represented by the formula (4) to at least one of the charge transport layer and the electron transport layer, the luminous efficiency is increased. Accordingly, the input power for obtaining a desired luminance is reduced, and the influence of Joule heat is reduced, so that the life can be prolonged.

[0011]

BEST MODE FOR CARRYING OUT THE INVENTION

(Embodiment 1) FIG. 1 shows a configuration of an organic light emitting device according to Embodiment 1 of the present invention. As shown in FIG.
0 is 1500 ° as a transparent electrode 12 on a 10 cm × 10 cm optically polished glass substrate 11 by sputtering.
Of indium tin oxide (ITO). After the charge transport layer 13 and the electron transport layer 14 are formed thereon by vacuum deposition using a resistance heating method, an Al / Li electrode having a thickness of 2000 ° is provided as the negative electrode 15.

In the organic light emitting device 10, when forming the charge transport layer 13, (Formula 4) is co-deposited by a resistance heating method.
The concentration of (Chem. 4) is 0.1 to 10% by weight based on (Chem. 3)
Is preferred. In the organic light emitting device 10 of the present embodiment, the concentration of (Chem. 4) contained in the charge transport layer 13 is set to 1.0% by weight.
And The charge transport layer 13 is composed of (Chem. 3). An example of the organic compound forming the electron transport layer 14 is shown in (Chem. 5).

[0013]

Embedded image

The thickness of the charge transport layer 13 and the electron transport layer 14 is preferably 5 to 5000 degrees. A DC or AC electric field is applied between the transparent electrode 12 and the negative electrode 15 as an external voltage.

The case where (Chem. 4) is not added is defined as (A),
(B) the organic light emitting device 10 added to the charge transport layer 13
(C) shows a case where a dye was added to the electron transporting layer 14 in the same manner as the organic light emitting layer 10, and Table 1 shows measurement results of light emission luminance when a DC voltage was applied.

[0016]

[Table 1]

From the results shown in Table 1, (B) and (C)
It can be seen that the light emission luminance of (A) is much higher than that of (A) where the same drive voltage is applied. When a dye was added to the charge transport layer 13 or the electron transport layer 14, the luminous efficiency was increased. In particular, when the dye was added to the charge transport layer 13, high luminance at a low driving voltage became possible.

(Embodiment 2) FIG. 2 shows another configuration of an organic light emitting device according to Embodiment 2 of the present invention. As shown in the figure, an organic light emitting device 20 is formed on a 10 cm × 10 cm optically polished glass substrate 21 similarly to the organic light emitting device 10 shown in FIG.
A film of indium tin oxide (ITO) of 1500 ° is formed as the transparent electrode 22 by using a sputtering method.
The charge transporting layer 23, the organic light emitting layer 24, and the electron transporting layer 25 are further formed on the respective layers by vacuum evaporation using a resistance heating method.
After the film is formed at 0 ° each, the film thickness is set to 2000 ° as the negative electrode 26.
Al / Li electrodes are provided.

In the organic light emitting device 20, the main material of the organic light emitting layer 24 is (Chem. 3), and when this is formed into a film, (Chem. 4) is simultaneously deposited by the resistance heating method. The concentration of (Chem. 4) is (Chem. 3)
Is preferably 0.1 to 10% by weight. In the organic light-emitting device 20 of the present embodiment, the concentration of (Chem. 4) contained in the organic light-emitting layer 24 was set to 1.0% by weight. A DC or AC electric field is applied between the transparent electrode 22 and the negative electrode 26 as an external voltage.

When a DC voltage is applied to the organic light emitting device 20 of the second embodiment, the current density becomes 100 mA / cm ² or more when the applied DC voltage is 5 V or more. At this time, the emission luminance is 10
0 cd / m ^2, and at an applied voltage of 10 v, about 1
An emission luminance of 000 cd / m ² was obtained.

An environmental reliability test of the organic light emitting device 20 of the second embodiment was performed. After standing for 96 hours in a high-temperature and high-humidity environment at an ambient temperature of 60 ° C. and a humidity of 90%, the above-mentioned electrical characteristics and light-emitting characteristics were evaluated at room temperature.

[0022]

As described above, the present invention has, as a charge transport layer, a layer composed of an organic compound of triphenylamine tetramer having excellent heat resistance and durability, and further comprises a charge transport layer or an electron transport layer. By adding the organic dye shown in (Chem. 4) to at least one of them, an organic light-emitting device having high luminous efficiency and long life can be obtained.

[Brief description of the drawings]

FIG. 1 is a cross-sectional view illustrating a configuration of an organic light emitting device according to a first embodiment of the present invention.

FIG. 2 is a cross-sectional view showing a configuration of the organic light-emitting device of Embodiment 2.

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 10 Organic light emitting element 11 Glass substrate 12 Transparent electrode 13 Charge transport layer 14 Electron transport layer 15 Negative electrode 20 Organic light emitting element 21 Glass substrate 22 Transparent electrode 23 Charge transport layer 24 Organic light emitting layer 25 Electron transport layer 26 Negative electrode

Claims (4)

[Claims] An organic light-emitting device having a positive electrode, a charge transport layer, an electron transport layer, and a negative electrode, wherein the charge transport layer comprises an organic compound represented by the following chemical formula (1). Light emitting element. Embedded image 2. The organic light emitting device according to claim 1, wherein an organic dye represented by the formula (2) is added to at least one of the charge transport layer and the electron transport layer. Embedded image 3. An organic light emitting device having a positive electrode, a charge transport layer, an organic light emitting layer, an electron transport layer, and a negative electrode, wherein the charge transport layer is composed of an organic compound represented by the following chemical formula (1). Organic light-emitting device characterized by the following. 4. An organic light-emitting layer comprising, as a main material, one of an organic compound constituting a charge transport layer and an electron transport layer;
The organic light emitting device according to claim 3, wherein an organic dye represented by the following formula (2) is added.