Stock material or miscellaneous articles – Composite – Of inorganic material
Reexamination Certificate
2002-03-12
2004-12-28
Yamnitzky, Marie (Department: 1774)
Stock material or miscellaneous articles
Composite
Of inorganic material
C428S917000, C313S504000, C257S040000, C257S088000
Reexamination Certificate
active
06835471
ABSTRACT:
BACKGROUND OF THE INVENTION
1. Field of the Invention
This invention relates to a porphyrin derivative compound, and a light emitting device and a display unit which make use of same. More particularly, it relates to a light emitting device and a display unit which have as a constituent material a porphyrin derivative compound which is a porphyrin metal coordination compound or a porphyrin compound and exhibits liquid crystal properties or exhibits phosphorescent or fluorescent light emission properties. This invention also relates to a material having high charge injection performance, utilizing such liquid crystal properties.
2. Related Background Art
In the research on porphyrin derivative compounds, it is hitherto known that porphyrin derivative compounds made to have a long side chain are capable of controlling intermolecular mutual action. For example, it is also known that the porphyrin derivative compounds having a long side chain exhibit a discotic liquid crystal phase. With regard to discotic liquid crystal properties of a porphyrin compound itself, however, the number of compounds exhibiting liquid crystal properties are not large, because it has not been long since the research was commenced.
As an example of such discotic liquid crystal compounds using the porphyrin skeleton, there is a Brian A. Gregg et al paper, Journal of American Chemical Society 1989, 111, 3024-3029, which discloses the structure of compounds using hydrogen (H), zinc (Zn), Copper (Cu), palladium (Pd) or cadmium (Cd) for the central metal and a temperature range in which a discotic liquid crystal phase is exhibited.
In the case of the compound using zinc as the central metal, there is an example in which the temperature at which a phase transition into the discotic liquid crystal phase is caused is at least 61° C. In other examples, however, the temperature is 84° C. or above, and the compounds that exhibit the discotic liquid crystal phase at around room temperature are still unknown.
An example is also disclosed in which, utilizing a regularity the discotic liquid crystal has, a high mobility has been achieved as an electron mobile layer of an organic EL (organic electroluminescence) device (e.g., Japanese Patent Application Laid-open No. 11-97176). In this example, it is disclosed that, as attempted in solid electrolytes, a structure in which the discotic liquid crystal has been oriented in a specific direction is made up so as to improve charge transportability due to hopping conduction. In the text of this publication, the porphyrin skeleton is described as one of the core structures of compounds for the charge transporting materials. Namely, it is stated that a good charge transport layer can be formed using the discotic liquid crystal. However, the disclosure is limited to the utilization as a charge transport layer having a large charge mobility.
With regard to organic EL devices using porphyrin compounds, the following publications 1 and 2 disclose devices making use of a platinum-porphyrin complex (PtEP) as a light emitting material and show the effectiveness of porphyrin materials as light emitting materials. In particular, devices are studied which utilize not fluorescent light emission via a singlet exciton but phosphorescent light emission via a triplet exciton, and are expected to be effective to improve light emission efficiency.
Publication 1: “Improved Energy Transfer in Electrophosphorescent Devices” (D.F. O'Brien et al., Applied Physics Letters, vol. 74, No. 3, p.
442 (1999))
.
Publication 2: “Very High-Efficiency Green Organic Light-Emitting Devices Based on Electrophosphorescence” (M.A. Baldo et al., Applied Physics Letters, vol. 75, No. 1, p.
4 (1999
)).
Here, the construction of commonly available organic EL devices is shown in
FIGS. 3A and 3B
. In these devices, a plurality of organic layers are present between a transparent electrode
14
on a transparent substrate
15
and a metal electrode
11
. In the device shown in
FIG. 3A
, the organic layers consist of a light emitting layer
12
and a hole transport layer
13
. As the transparent electrode
14
, a material having a large work function, such as ITO (indium-tin oxide), is used so that it can be endowed with good hole injection performance from the transparent electrode into the hole transport layer. As the metal electrode
11
, a metallic material having a small work function, such as aluminum, magnesium or an alloy formed using these, is used so that it can be endowed with good electron injection performance into the organic layer. These electrodes are formed in a layer thickness of 50 to 200 nm.
In the light emitting layer, an aluminum-quinolinol complex or the like (a typical example is Alq3 shown below) having electron transport properties and light emission properties is used.
In the hole transport layer, a material having electron-donating properties as exemplified by a biphenyldiamine derivative (a typical example is &agr;-NPD shown below) is used.
In the device shown in
FIG. 3B
, an electron transport layer
16
is further provided between the metal electrode
11
and the light emitting layer
12
which are shown in FIG.
3
A. The light emission is separated from the electron transport and hole transport to provide a more effective carrier blocking construction, so that an effective light emission can be performed. As materials for the electron transport layer, an oxadiazole derivative or the like may be used.
In the above publications 1 and 2, such a four-layer organic-layer construction as shown in
FIG. 4
is chiefly used. It is constituted of, in this order from the anode side, a hole transport layer
25
, a light emitting layer
24
, an exciton diffusion preventive layer
23
and an electron transport layer
22
. Materials used are carrier transport materials and phosphorescent light emitting materials as shown below.
Alq3: Aluminum-quinolinol complex.
&agr;-NPD:N4,N4′-di-naphthalen-1-yl-N4,N4′-diphenyl-bi phenyl-4,4′-diamine.
CBP: 4,4′-N,N′-dicarbazole-biphenyl.
BCP: 2,9-Dimethyl-4,7-diphenyl-1,10-phenanthroline.
PtOEP: platinum-octaethylporphyrin complex.
Ir(ppy)
3
: Iridium-phenylpyrimidine complex.
In both the above publications 1 and 2, the device construction which contributes to the high efficiency is the construction that, as host materials, the &agr;-NPD is used in the hole transport layer, the Alq3 in the electron transport layer, the BCP in the exciton diffusion preventive layer and the CBP in the light emitting layer, and the phosphorescent light emitting material PtOEP or Ir(ppy)
3
is mixed in a concentration of about 6%.
However, the PtOEP disclosed in the above publication has two carbon atoms in the side chain, and has no liquid crystal properties by itself. It is only used as a light emitting material. Also, its concentration with respect to the host materials is 6%. Accordingly, in order to allow the device to have a higher efficiency, it is expected to be used in a much higher concentration.
As stated above, it is shown that an organic EL device having a high light emission efficiency can be provided using the compound having phosphorescent light emission properties. The device, however, is still not one which can be satisfactory, inclusive of its emission luminance. In general, phosphorescence is often observable at a low temperature of about 77 K, and is not observable at room temperature. The phosphorescent light emitting material or compound herein referred to indicates a compound whose phosphorescent light emission is perceivable within a temperature range near room temperature (0° C. or above), required in practical use.
SUMMARY OF THE INVENTION
The present invention was made taking into account conventionally known techniques. Accordingly, an object of the present invention is to provide a light emitting device such as an organic EL device, making use of a porphyrin derivative compound.
Another object of the present invention is to provide a porphyrin derivative compound having a high stability as a light emitting material especial
Furugori Manabu
Kamatani Jun
Miura Seishi
Moriyama Takashi
Okada Shinjiro
Canon Kabushiki Kaisha
Fitzpatrick ,Cella, Harper & Scinto
Yamnitzky Marie
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