Aromatic amine derivatives and organic electroluminescent device using same

Abstract

The present invention provides a novel aromatic amine derivative having a specific structure and an organic electroluminescence device in which an organic thin film layer comprising a single layer or plural layers including at least a light emitting layer is interposed between a cathode and an anode, wherein at least one layer in the above organic thin film layer, particularly a hole injecting layer contains the aromatic amine derivative described above in the form of a single component or a mixed component. Use of the aromatic amine derivative described above materialize an organic electroluminescence device which reduces an operating voltage and makes molecules less liable to be crystallized and which enhances a yield in producing the organic EL device and has a long lifetime.

Description

BACKGROUND OF THE INVENTION [0001] The present invention relates to an aromatic amine derivative and an organic electroluminescence (EL) device using the same, specifically to an aromatic amine derivative which reduces the operating voltage and inhibits the molecules from being crystallized by using an aromatic amine derivative having a specific substituent for a hole transporting material and which enhances a yield in producing an organic EL device and improves a lifetime of the organic EL device. RELATED ART [0002] An organic EL device is a spontaneous light emitting device making use of the principle that a fluorescent substance emits light by recombination energy of holes injected from an anode and electrons injected from a cathode by applying an electric field. Since an organic EL device of a laminate type driven at a low voltage was reported by C. W. Tang et al. of Eastman Kodak Company (C. W. Tang and S. A. Vanslyke, Applied Physics Letters, Vol. 51, p. 913, 1987 and the like...

AI Technical Summary

Benefits of technology

[0008] The present invention has been made in order to solve the problems described above, and an object thereof is to provide an organic EL device which reduces an operating voltage and makes molecules less liable to be crystallized and which is improved in a yield in producing the organic EL device and has a long lifetime and an aromatic amine derivative which materializes the same.

[0010] Further, it has been found that an amino group substituted with an aryl group having a thiophene structure represented by Formula (2) is suited as an amine unit having the specific substituent. The above amine unit has a polar group, so that it can be interacted with an electrode, and therefore it has the effects that charges are readily injected and that the operating voltage is reduced due to a high mobility since it has a thiophene structure. In addition thereto, the above amine unit has a steric hindrance, so that interaction between the molecules is small, and therefore it has the effects that crystallization thereof is inhibited to enhance a yield in producing an organic EL device and that the organic EL device obtained is extended in a lifetime. In particular, it has been found that a marked reduction in the voltage and an effect of extending the lifetime are obtained by combining it with a blue light emitting device. Further, in the compounds having a large molecular weight, the compounds having an asymmetric structure can be reduced in a vapor deposition temperature, and therefore they can be inhibited from being decomposed in vapor deposition and can be extended in a lifetime.

[0014] The aromatic amine derivative of the present invention and the organic EL device obtained by using the same are reduced in an operating voltage, less liable to be crystallized in molecules, improved in a yield in producing the organic EL device and extended in lifetimes.

Problems solved by technology

Usually, when an organic EL device is operated or stored under high temperature environment, brought about are adverse effects such as a change in a color of emitted light, a reduction in a current efficiency, a rise in an operating voltage and a reduction in an emission lifetime.

However, if they have a lot of aromatic groups in a molecule, crystallization is liable to be caused in forming a thin film using the above hole transporting materials to produce an organic EL device, and the problems that an outlet of a crucible used for vapor deposition is clogged and that defects of a thin film originating in crystallization are caused to bring about a reduction in a yield of an organic EL device have been brought about.

Further, compounds having more aromatic groups in a molecule have usually a higher glass transition temperature (Tg) but have a higher sublimation temperature, and it is considered that the phenomena that decomposition is caused in vapor deposition and that a deposited film is unevenly formed are brought about, so that the problem that the lifetime is short has been involved therein.

These compounds are unstable and hard to be refined, and therefore a purity thereof is not enhanced.

When thiophene is bonded directly to amine, an electron state of amine is varied to a large extent, and therefore the satisfactory performances are not exhibited.

A 2-position or a 3-position in thiophene has a high reactivity and is electrically unstable.

Further, polar groups necessary for polymerization reduce the performances of the device such as a lifetime and the like, and therefore the above compounds are not preferred.

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