Organic electroluminescent element

Abstract

An object of the present invention is to provide an organic EL device having (1) high luminous efficiency and high power efficiency, (2) low turn on voltage, (3) low actual driving voltage, and (4) particularly a long lifetime by combining various materials for an organic EL device having excellent hole and electron injection / transport performances, electron blocking ability, stability in a thin-film state, and durability so as to allow the respective materials to effectively reveal their characteristics. The organic EL device has at least an anode, a hole transport layer, a light emitting layer, an electron transport layer and a cathode in this order, the hole transport layer includes an aryl amine compound represented by the following general formula (1), and the electron transport layerincludes a compound having a benzoazole ring structure represented by the following general formula (2).

Description

technical field [0001] The present invention relates to an organic electroluminescent element as a self-luminous element suitable for various display devices, and in particular, relates to an organic electroluminescent element using a specific arylamine compound and a specific compound having a benzoxazole ring structure element (hereinafter sometimes referred to as an organic EL element). Background technique [0002] Since the organic EL element is a self-luminous element, it is brighter than a liquid crystal element, has excellent visibility, and can perform a clear display, so active research has been conducted. [0003] In 1987, C.W.Tang of Eastman Kodak Co., Ltd. developed a layered structure element in which various functions are shared by each material, thereby making an organic EL element using an organic material a practical element. They layered a phosphor capable of transporting electrons and an organic substance capable of transporting holes, injected the charg...

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Problems solved by technology

NPD has good hole transport ability, but the glass transition temperature (Tg) as an index of heat resistance is as low as 96°C, and the degradation of device characteristics occurs due to crystallization under high temperature conditions (for example, refer to Non-Patent Document 4 )

In addition, in the aromatic amine derivatives described in the above-mentioned patent documents, the mobility of holes is 10 -3 cm 2 Compounds having excellent mobility above / Vs (for example, refer to Patent Document 1 and Patent Document 2), but electron blocking property is insufficient, therefore, a part of electrons passes through the light-emitting layer, and improvement of luminous efficiency cannot be expected. To further improve efficiency, search for materials with higher electron barrier properties, more stable films, and high heat resistance

In addition, there are reports of highly durable aromatic amine derivatives (for example, refer to Patent Document 3), but they are used as charge transport materials used in electrophotographic photoreceptors, and there are no examples of use as organic EL devices.

[0010] Arylamine compounds having a substituted carbazole structure have been proposed as compounds having improved properties such as heat resistance and hole injection properties (for example, refer to Patent Document 4 and Patent Document 5), and the use of these compounds in the hole injection layer For components of the hole transport layer or the hole transport layer, although heat resistance and luminous efficiency have been improved, they are still not sufficient, and further low driving voltage and further high luminous efficiency are sought.

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