U.S. patent application number 11/905737 was filed with the patent office on 2008-07-03 for benzofluorene compound, emission materials and organic electroluminescent device.
Invention is credited to Akiko Kageyama, Toshihiro Koike, Manabu Uchida, Guofang Wang.
Application Number | 20080160347 11/905737 |
Document ID | / |
Family ID | 39532992 |
Filed Date | 2008-07-03 |
United States Patent
Application |
20080160347 |
Kind Code |
A1 |
Wang; Guofang ; et
al. |
July 3, 2008 |
Benzofluorene compound, emission materials and organic
electroluminescent device
Abstract
Provided is a benzofluorene compound which exhibits excellent
performances when applied to an organic electroluminescent device.
In the benzofluorene compound, a central five-membered ring in a
benzofluorene skeleton is substituted with aryl, and a benzene ring
condensed to the five-membered ring is substituted with aryl,
diarylamino and the like.
Inventors: |
Wang; Guofang; (Chiba,
JP) ; Kageyama; Akiko; (Chiba, JP) ; Koike;
Toshihiro; (Chiba, JP) ; Uchida; Manabu;
(Chiba, JP) |
Correspondence
Address: |
WENDEROTH, LIND & PONACK, L.L.P.
2033 K STREET N. W., SUITE 800
WASHINGTON
DC
20006-1021
US
|
Family ID: |
39532992 |
Appl. No.: |
11/905737 |
Filed: |
October 3, 2007 |
Current U.S.
Class: |
428/704 ;
428/411.1; 564/321; 570/129; 585/27 |
Current CPC
Class: |
C07C 2601/14 20170501;
C07C 13/66 20130101; C09K 2211/1011 20130101; H01L 51/0058
20130101; H01L 51/0071 20130101; H01L 51/0039 20130101; H01L 51/006
20130101; H01L 51/0094 20130101; H01L 51/0072 20130101; C09K
2211/1007 20130101; C09K 11/06 20130101; C07C 2603/26 20170501;
Y10T 428/31504 20150401; C07C 2603/40 20170501; H01L 51/0054
20130101; H01L 51/0081 20130101; H05B 33/14 20130101 |
Class at
Publication: |
428/704 ;
564/321; 570/129; 428/411.1; 585/27 |
International
Class: |
C07C 211/54 20060101
C07C211/54; C07C 25/18 20060101 C07C025/18; H01J 1/63 20060101
H01J001/63; B32B 11/04 20060101 B32B011/04; C07C 13/66 20060101
C07C013/66 |
Foreign Application Data
Date |
Code |
Application Number |
Oct 5, 2006 |
JP |
2006-273809 |
Apr 27, 2007 |
JP |
2007-118535 |
Claims
1. A benzofluorene compound represented by the following Formula
(1): ##STR00040## (wherein Ar.sup.1 and Ar.sup.2 are aryl which may
be substituted; R.sup.1 and R.sup.2 each are independently
hydrogen, alkyl which may be substituted, cycloalkyl which may be
substituted or aryl which may be substituted, and at least one of
R.sup.1 and R.sup.2 is aryl which may be substituted).
2. The benzofluorene compound as described in claim 1, wherein
Ar.sup.1 and Ar.sup.2 are aryl having 6 to 30 carbon atoms which
may be substituted; R.sup.1 and R.sup.2 each are independently
hydrogen, alkyl having 1 to 24 carbon atoms which may be
substituted, cycloalkyl having 3 to 12 carbon atoms which may be
substituted or aryl having 6 to 30 carbon atoms which may be
substituted, and at least one of R.sup.1 and R.sup.2 is aryl having
6 to 30 carbon atoms which may be substituted; and substituents in
Ar.sup.1, Ar.sup.2, R.sup.1 and R.sup.2 each are independently
alkyl having 1 to 24 carbon atoms, cycloalkyl having 3 to 12 carbon
atoms or aryl having 6 to 30 carbon atoms.
3. The benzofluorene compound as described in claim 1, wherein
Ar.sup.1 and Ar.sup.2 are aryl having 6 to 16 carbon atoms which
may be substituted; R.sup.1 and R.sup.2 are aryl having 6 to 24
carbon atoms which may be substituted; and substituents in
Ar.sup.1, Ar.sup.2, R.sup.1 and R.sup.2 each are independently
alkyl having 1 to 12 carbon atoms, cycloalkyl having 3 to 6 carbon
atoms or aryl having 6 to 20 carbon atoms.
4. The benzofluorene compound as described in claim 1, wherein
Ar.sup.1 and Ar.sup.2 are aryl having 6 to 12 carbon atoms which
may be substituted; R.sup.1 and R.sup.2 are aryl having 6 to 20
carbon atoms which may be substituted; and substituents in
Ar.sup.1, Ar.sup.2, R.sup.1 and R.sup.2 each are independently
methyl, ethyl, propyl, t-butyl, cyclobutyl, cyclopentyl,
cyclohexyl, phenyl, biphenylyl or naphthyl.
5. The benzofluorene compound as described in claim 1, wherein
Ar.sup.1 and Ar.sup.2 each are independently phenyl or biphenylyl;
and R.sup.1 and R.sup.2 each are independently phenyl, biphenylyl,
terphenylyl, quaterphenylyl, naphthyl or phenanthryl.
6. The benzofluorene compound as described in claim 1, wherein
Ar.sup.1 and Ar.sup.2 are aryl having 6 to 16 carbon atoms which
may be substituted; one of R.sup.1 and R.sup.2 is hydrogen, and the
other is aryl having 6 to 24 carbon atoms which may be substituted;
and substituents in Ar.sup.1, Ar.sup.2, R.sup.1 and R.sup.2 each
are independently alkyl having 1 to 12 carbon atoms, cycloalkyl
having 3 to 6 carbon atoms or aryl having 6 to 20 carbon atoms.
7. The benzofluorene compound as described in claim 1, wherein
Ar.sup.1 and Ar.sup.2 are aryl having 6 to 12 carbon atoms which
may be substituted; one of R.sup.1 and R.sup.2 is hydrogen, and the
other is aryl having 6 to 20 carbon atoms which may be substituted;
and substituents in Ar.sup.1, Ar.sup.2, R.sup.1 and R.sup.2 each
are independently methyl, ethyl, propyl, t-butyl, cyclobutyl,
cyclopentyl, cyclohexyl, phenyl, biphenylyl or naphthyl.
8. The benzofluorene compound as described in claim 1, wherein
Ar.sup.1 and Ar.sup.2 each are independently phenyl or biphenylyl;
and one of R.sup.1 and R.sup.2 is hydrogen, and the other is
phenyl, biphenylyl, terphenylyl, quaterphenylyl, naphthyl or
phenanthryl.
9. The benzofluorene compound as described in claim 1, wherein
Ar.sup.1 and Ar.sup.2 are phenyl; R.sup.1 is 4-biphenylyl, and
R.sup.2 is 4-biphenylyl.
10. The benzofluorene compound as described in claim 1, wherein
Ar.sup.1 and Ar.sup.2 are phenyl; R.sup.1 is 2-naphthyl, and
R.sup.2 is 2-naphthyl.
11. The benzofluorene compound as described in claim 1, wherein
Ar.sup.1 and Ar.sup.2 are phenyl; R.sup.1 is 4-biphenylyl, and
R.sup.2 is 2-naphthyl.
12. The benzofluorene compound as described in claim 1, wherein
Ar.sup.1 and Ar.sup.2 are phenyl; R.sup.1 is 2-naphthyl, and
R.sup.2 is 4-biphenylyl.
13. A benzofluorene compound represented by the following Formula
(1'): ##STR00041## (wherein Ar.sup.1 and Ar.sup.2 are aryl which
may be substituted; R.sup.1 is diarylamino having aryl which may be
substituted; and R.sup.2 is hydrogen, alkyl which may be
substituted, cycloalkyl which may be substituted, aryl which may be
substituted or diarylamino having aryl which may be
substituted).
14. The benzofluorene compound as described in claim 13, wherein
Ar.sup.1 and Ar.sup.2 are aryl having 6 to 30 carbon atoms which
may be substituted; R.sup.1 is diarylamino having aryl having 6 to
30 carbon atoms which may be substituted; R.sup.2 is hydrogen,
alkyl having 1 to 24 carbon atoms which may be substituted,
cycloalkyl having 3 to 12 carbon atoms which may be substituted,
aryl having 6 to 30 carbon atoms which may be substituted or
diarylamino having aryl having 6 to 30 carbon atoms which may be
substituted; and substituents in Ar.sup.1, Ar.sup.2, R.sup.1 and
R.sup.2 each are independently alkyl having 1 to 24 carbon atoms,
aryl having 6 to 30 carbon atoms or heteroaryl having 2 to 30
carbon atoms.
15. The benzofluorene compound as described in claim 13, wherein
Ar.sup.1 and Ar.sup.2 are aryl having 6 to 16 carbon atoms which
may be substituted; R.sup.1 is diarylamino having aryl having 6 to
16 carbon atoms which may be substituted; R.sup.2 is hydrogen, aryl
having 6 to 24 carbon atoms which may be substituted or diarylamino
having aryl having 6 to 16 carbon atoms which may be substituted;
and substituents in Ar.sup.1, Ar.sup.2, R.sup.1 and R.sup.2 each
are independently alkyl having 1 to 12 carbon atoms, aryl having 6
to 12 carbon atoms or heteroaryl having 2 to 10 carbon atoms.
16. The benzofluorene compound as described in claim 13, wherein
Ar.sup.1 and Ar.sup.2 are aryl having 6 to 12 carbon atoms which
may be substituted; R.sup.1 is diarylamino having aryl having 6 to
12 carbon atoms which may be substituted; R.sup.2 is hydrogen, aryl
having 6 to 20 carbon atoms which may be substituted or diarylamino
having aryl having 6 to 12 carbon atoms which may be substituted;
and substituents in Ar.sup.1, Ar.sup.2, R.sup.1 and R.sup.2 each
are independently methyl, ethyl, propyl, t-butyl, phenyl,
biphenylyl, naphthyl, pyridyl or thienyl.
17. The benzofluorene compound as described in claim 13, wherein
Ar.sup.1 and Ar.sup.2 each are independently phenyl or biphenylyl;
R.sup.1 is diphenylamino, dibiphenylamino, dinaphthylamino or
phenylnaphthylamino; and R.sup.2 is phenyl, biphenylyl,
terphenylyl, quaterphenylyl, naphthyl, phenanthryl, diphenylamino,
dibiphenylamino, dinaphthylamino or phenylnaphthylamino.
18. The benzofluorene compound as described in claim 13, wherein
Ar.sup.1 and Ar.sup.2 are phenyl; and R.sup.1 and R.sup.2 are
diphenylamino.
19. A material for an emission layer in a light emitting device and
which contains the benzofluorene compound as described in claim
1.
20. The material for an emission layer as described in claim 19,
further containing at least one selected from the group consisting
of perylene derivatives, borane derivatives, amine-containing
styryl derivatives, aromatic amine derivatives, coumarin
derivatives, pyran derivatives, iridium complexes and platinum
complexes.
21. An organic electroluminescent device comprising a pair of
electrodes comprising an anode and a cathode and an emission layer
which is disposed between a pair of the electrodes and which
contains the material for an emission layer as described in claim
19.
22. The organic electroluminescent device as described in claim 21,
further comprising an electron transport layer and/or an electron
injection layer disposed between the cathode and the emission
layer, wherein at least one of the electron transport layer and
electron injection layer contains at least one selected from the
group consisting of quinolinol metal complexes, pyridine
derivatives and phenanthroline derivatives.
23. A display unit comprising the organic electroluminescent device
as described in claim 21.
24. A lighting instrument comprising the organic electroluminescent
device as described in claim 21.
25. A material for an emission layer in a light emitting device and
which contains the benzofluorene compound as described in claim 13.
Description
FIELD OF THE INVENTION
[0001] The present invention relates to a benzofluorene compound, a
material for an emission layer using the compound and an organic
electroluminescent device.
BACKGROUND OF THE INVENTION
[0002] An organic electroluminescent device is a light emitting
device which is a spontaneous emission type and is expected as a
light emitting device for display or lighting. A display unit using
an electroluminescent light emitting device has so far been
researched in various cases because of possibility of small power
consumption and reduction in a thickness. Further, an organic
electroluminescent device comprising organic materials has so far
been actively investigated since reduction in a weight and increase
in a size are easy. In particular, developments of organic
materials having light emitting characteristics including a blue
color which is one of three primary colors and developments of
organic materials endowed with charge transport ability (having
possibility of being derived into semiconductors and
superconductors) of holes and electrons have so far been actively
researched regardless of high molecular compounds and low molecular
compounds.
[0003] An organic electroluminescent device has a structure
comprising a pair of electrodes comprising an anode and a cathode
and a single layer or plural layers which are disposed between a
pair of the electrodes and which contain organic compounds. The
layer containing organic compounds includes an emission layer and a
charge transport/injection layer which transports or injects
charges such as a hole and an electron, and various organic
materials have been developed as the organic compounds (for
example, International Publication No. 2004/061047 pamphlet and
International Publication No. 2004/061048 pamphlet (JP H18-512395
(through PCT) A/2006): refer to a patent document 1 and a patent
document 2). However, only high molecular compounds of
benzofluorene are disclosed in the examples of the patent
documents. Also, International Publication No. 2003/051092 pamphlet
(JP H17-513713 (through PCT) A/2005), for example, describes
dibenzofluorene compounds having amino substituted with aryls
(refer to a patent document 3). However, the document describes
only structural formulas thereof, and does not describe the
specific characteristics thereof.
Patent document 1: International Publication No. 2004/061047
pamphlet Patent document 2: International Publication No.
2004/061048 pamphlet (JP H18-512395 (through PCT) A/2006) Patent
document 3: International Publication No. 2003/051092 pamphlet (JP
H17-513713 (through PCT) A/2005)
[0004] However, even if the organic materials described above are
used, organic electroluminescent devices having satisfactory
performances in terms of heat resistance, luminous efficiency,
current efficiency, device life and external quantum efficiency
have not yet been obtained. Under the situation described above,
desired to be developed is an organic electroluminescent device
having further better performances in terms of heat resistance,
luminous efficiency, current efficiency, device life and external
quantum efficiency, that is, a compound which can provide the
device.
[0005] Further, in order to meet commercial production of light
emitting devices, desired are organic materials which are more
easily synthesized and organic materials which can accept any
processing conditions in applying to devices. For example, organic
materials having an excellent solubility in a solvent are
relatively easily synthesized and have the merit that they are not
limited to a vapor deposition method in forming layers.
SUMMARY OF THE INVENTION
[0006] Intensive investigations repeated by the present inventors
in order to solve the problems described above have resulted in
successfully producing a benzofluorene compound represented by
Formula (1) shown below. Further, the present inventors have found
that an organic electroluminescent device which is improved in
luminous efficiency, current efficiency, device life and external
quantum efficiency is obtained by disposing a layer containing the
benzofluorene compound between a pair of electrodes to constitute
the organic electroluminescent device, and thus they have completed
the present invention.
[0007] That is, the present invention provides the following
benzofluorene compound.
[0008] [1] A benzofluorene compound represented by the following
Formula (1):
##STR00001##
(wherein Ar.sup.1 and Ar.sup.2 are aryl which may be substituted;
R.sup.1 and R.sup.2 each are independently hydrogen, alkyl which
may be substituted, cycloalkyl which may be substituted or aryl
which may be substituted, and at least one of R.sup.1 and R.sup.2
is aryl which may be substituted).
[0009] [2] The benzofluorene compound as described in [1], wherein
Ar.sup.1 and Ar.sup.2 are aryl having 6 to 30 carbon atoms which
may be substituted;
R.sup.1 and R.sup.2 each are independently hydrogen, alkyl having 1
to 24 carbon atoms which may be substituted, cycloalkyl having 3 to
12 carbon atoms which may be substituted or aryl having 6 to 30
carbon atoms which may be substituted, and at least one of R.sup.1
and R.sup.2 is aryl having 6 to 30 carbon atoms which may be
substituted; and substituents in Ar.sup.1, Ar.sup.2, R.sup.1 and
R.sup.2 each are independently alkyl having 1 to 24 carbon atoms,
cycloalkyl having 3 to 12 carbon atoms or aryl having 6 to 30
carbon atoms.
[0010] [3] The benzofluorene compound as described in [1], wherein
Ar.sup.1 and Ar.sup.2 are aryl having 6 to 16 carbon atoms which
may be substituted;
R.sup.1 and R.sup.2 are aryl having 6 to 24 carbon atoms which may
be substituted; and substituents in Ar.sup.1, Ar.sup.2, R.sup.1 and
R.sup.2 each are independently alkyl having 1 to 12 carbon atoms,
cycloalkyl having 3 to 6 carbon atoms or aryl having 6 to 20 carbon
atoms.
[0011] [4] The benzofluorene compound as described in [1], wherein
Ar.sup.1 and Ar.sup.2 are aryl having 6 to 12 carbon atoms which
may be substituted;
R.sup.1 and R.sup.2 are aryl having 6 to 20 carbon atoms which may
be substituted; and substituents in Ar.sup.1, Ar.sup.2, R.sup.1 and
R.sup.2 each are independently methyl, ethyl, propyl, t-butyl,
cyclobutyl, cyclopentyl, cyclohexyl, phenyl, biphenylyl or
naphthyl.
[0012] [5] The benzofluorene compound as described in [1], wherein
Ar.sup.1 and Ar.sup.2 each are independently phenyl or biphenylyl;
and
R.sup.1 and R.sup.2 each are independently phenyl, biphenylyl,
terphenylyl, quaterphenylyl, naphthyl or phenanthryl.
[0013] [6] The benzofluorene compound as described in [1], wherein
Ar.sup.1 and Ar.sup.2 are aryl having 6 to 16 carbon atoms which
may be substituted;
one of R.sup.1 and R.sup.2 is hydrogen, and the other is aryl
having 6 to 24 carbon atoms which may be substituted; and
substituents in Ar.sup.1, Ar.sup.2, R.sup.1 and R.sup.2 each are
independently alkyl having 1 to 12 carbon atoms, cycloalkyl having
3 to 6 carbon atoms or aryl having 6 to 20 carbon atoms.
[0014] [7] The benzofluorene compound as described in [1], wherein
Ar.sup.1 and Ar.sup.2 are aryl having 6 to 12 carbon atoms which
may be substituted;
one of R.sup.1 and R.sup.2 is hydrogen, and the other is aryl
having 6 to 20 carbon atoms which may be substituted; and
substituents in Ar.sup.1, Ar.sup.2, R.sup.1 and R.sup.2 each are
independently methyl, ethyl, propyl, t-butyl, cyclobutyl,
cyclopentyl, cyclohexyl, phenyl, biphenylyl or naphthyl.
[0015] [8] The benzofluorene compound as described in [1], wherein
Ar.sup.1 and Ar.sup.2 each are independently phenyl or biphenylyl;
and
one of R.sup.1 and R.sup.2 is hydrogen, and the other is phenyl,
biphenylyl, terphenylyl, quaterphenylyl, naphthyl or
phenanthryl.
[0016] [9] The benzofluorene compound as described in [1], wherein
Ar.sup.1 and Ar.sup.2 are phenyl;
R.sup.1 is 4-biphenylyl, and R.sup.2 is 4-biphenylyl.
[0017] [10] The benzofluorene compound as described in [1], wherein
Ar.sup.1 and Ar.sup.2 are phenyl;
R.sup.1 is 2-naphthyl, and R.sup.2 is 2-naphthyl.
[0018] [11] The benzofluorene compound as described in [1], wherein
Ar.sup.1 and Ar.sup.2 are phenyl;
R.sup.1 is 4-biphenylyl, and R.sup.2 is 2-naphthyl.
[0019] [12] The benzofluorene compound as described in [1], wherein
Ar.sup.1 and Ar.sup.2 are phenyl;
R.sup.1 is 2-naphthyl, and R.sup.2 is 4-biphenylyl.
[0020] [13] A benzofluorene compound represented by the following
Formula (1'):
##STR00002##
(wherein Ar.sup.1 and Ar.sup.2 are aryl which may be substituted;
R.sup.1 is diarylamino having aryl which may be substituted; and
R.sup.2 is hydrogen, alkyl which may be substituted, cycloalkyl
which may be substituted, aryl which may be substituted or
diarylamino having aryl which may be substituted).
[0021] [14] The benzofluorene compound as described in [13],
wherein Ar.sup.1 and Ar.sup.2 are aryl having 6 to 30 carbon atoms
which may be substituted;
R.sup.1 is diarylamino having aryl having 6 to 30 carbon atoms
which may be substituted; R.sup.2 is hydrogen, alkyl having 1 to 24
carbon atoms which may be substituted, cycloalkyl having 3 to 12
carbon atoms which may be substituted, aryl having 6 to 30 carbon
atoms which may be substituted or diarylamino having aryl having 6
to 30 carbon atoms which may be substituted; and substituents in
Ar.sup.1, Ar.sup.2, R.sup.1 and R.sup.2 each are independently
alkyl having 1 to 24 carbon atoms, aryl having 6 to 30 carbon atoms
or heteroaryl having 2 to 30 carbon atoms.
[0022] [15] The benzofluorene compound as described in [13],
wherein Ar.sup.1 and Ar.sup.2 are aryl having 6 to 16 carbon atoms
which may be substituted;
R.sup.1 is diarylamino having aryl having 6 to 16 carbon atoms
which may be substituted; R.sup.2 is hydrogen, aryl having 6 to 24
carbon atoms which may be substituted or diarylamino having aryl
having 6 to 16 carbon atoms which may be substituted; and
substituents in Ar.sup.1, Ar.sup.2, R.sup.1 and R.sup.2 each are
independently alkyl having 1 to 12 carbon atoms, aryl having 6 to
12 carbon atoms or heteroaryl having 2 to 10 carbon atoms.
[0023] [16] The benzofluorene compound as described in [13],
wherein Ar.sup.1 and Ar.sup.2 are aryl having 6 to 12 carbon atoms
which may be substituted;
R.sup.1 is diarylamino having aryl having 6 to 12 carbon atoms
which may be substituted; R.sup.2 is hydrogen, aryl having 6 to 20
carbon atoms which may be substituted or diarylamino having aryl
having 6 to 12 carbon atoms which may be substituted; and
substituents in Ar.sup.1, Ar.sup.2, R.sup.1 and R.sup.2 each are
independently methyl, ethyl, propyl, t-butyl, phenyl, biphenylyl,
naphthyl, pyridyl or thienyl.
[0024] [17] The benzofluorene compound as described in [13],
wherein Ar.sup.1 and Ar.sup.2 each are independently phenyl or
biphenylyl;
R.sup.1 is diphenylamino, dibiphenylamino, dinaphthylamino or
phenylnaphthylamino; and R.sup.2 is phenyl, biphenylyl,
terphenylyl, quaterphenylyl, naphthyl, phenanthryl, diphenylamino,
dibiphenylamino, dinaphthylamino or phenylnaphthylamino.
[0025] [18] The benzofluorene compound as described in [13],
wherein Ar.sup.1 and Ar.sup.2 are phenyl; and
R.sup.1 and R.sup.2 are diphenylamino.
[0026] [19] A material for an emission layer in a light emitting
device and which contains the benzofluorene compound as described
in any of [1] to [18].
[0027] [20] The material for an emission layer as described in
[19], further containing at least one selected from the group
consisting of perylene derivatives, borane derivatives,
amine-containing styryl derivatives, aromatic amine derivatives,
coumarin derivatives, pyran derivatives, iridium complexes and
platinum complexes.
[0028] [21] An organic electroluminescent device comprising a pair
of electrodes comprising an anode and a cathode and an emission
layer which is disposed between a pair of the electrodes and which
contains the material for an emission layer as described in [19] or
[20].
[0029] [22] The organic electroluminescent device as described in
[21], further comprising an electron transport layer and/or an
electron injection layer disposed between the cathode and the
emission layer, wherein at least one of the electron transport
layer and electron injection layer contains at least one selected
from the group consisting of quinolinol metal complexes, pyridine
derivatives and phenanthroline derivatives.
[0030] [23] The organic electroluminescent device as described in
[21], further comprising an electron transport layer and/or an
electron injection layer disposed between the cathode and the
emission layer, wherein at least one of the electron transport
layer and electron injection layer contains quinolinol metal
complexes.
[0031] [24] The organic electroluminescent device as described in
[21], further comprising an electron transport layer and/or an
electron injection layer disposed between the cathode and the
emission layer, wherein at least one of the electron transport
layer and electron injection layer contains pyridine
derivatives.
[0032] [25] The organic electroluminescent device as described in
[21], further comprising an electron transport layer and/or an
electron injection layer disposed between the cathode and the
emission layer, wherein at least one of the electron transport
layer and electron injection layer contains phenanthroline
derivatives.
[0033] [26] A display unit comprising the organic
electroluminescent device as described in any of [21] to [25].
[0034] [27] A lighting instrument comprising the organic
electroluminescent device as described in any of [21] to [25].
[0035] According to the preferred embodiment of the present
invention, for example, a benzofluorene compound having excellent
characteristics as a material for an emission layer can be
provided. Also, an organic electroluminescent device which is
improved in heat resistance, luminous efficiency, current
efficiency, device life and external quantum efficiency can be
provided. Further, the benzofluorene compound according to the
preferred embodiment of the present invention is an organic
material having an excellent solubility in a solvent and therefore
is relatively readily synthesized, and it has the merit that it is
not limited to a vapor deposition method in forming layers. As a
result thereof, a material for a light emitting device which is
suited to commercial production of light emitting devices can be
provided.
DETAILED DESCRIPTION OF THE INVENTION
[0036] The benzofluorene compound of the present invention shall be
explained in details.
[0037] The benzofluorene compound according to the present
invention is the benzofluorene compound represented by Formula (1)
described above.
1. Benzofluorene Compound Represented by Formula (1)
[0038] First, the benzofluorene compound represented by Formula (1)
shall be explained.
[0039] "Aryl" of "aryl which may be substituted" in Ar.sup.1,
Ar.sup.2, R.sup.1 and R.sup.2 of Formula (1) includes, for example,
aryl having 6 to 30 carbon atoms. "Aryl" in Ar.sup.1 and Ar.sup.2
is preferably aryl having 6 to 16 carbon atoms, more preferably
aryl having 6 to 12 carbon atoms. "Aryl" in R.sup.1 and R.sup.2 is
preferably aryl having 6 to 24 carbon atoms, more preferably aryl
having 6 to 20 carbon atoms and further preferably aryl having 6 to
12 carbon atoms.
[0040] The specific "aryl" includes phenyl, (o-, m- or p-)tolyl,
(2,3-, 2,4-, 2,5-, 2,6-, 3,4- or 3,5-)xylyl, mesityl and (o-, m- or
p-)cumenyl which are monocyclic aryls, (2-, 3- or 4-)biphenylyl
which is dicyclic aryl, (1- or 2-)naphthyl which is condensed
dicyclic aryl, terphenylyl(m-terphenyl-2'-yl, m-terphenyl-4'-yl,
m-terphenyl-5'-yl, o-terphenyl-3'-yl, o-terphenyl-4'-yl,
p-terphenyl-2'-yl, m-terphenyl-2-yl, m-terphenyl-3-yl,
m-terphenyl-4-yl, o-terphenyl-2-yl, o-terphenyl-3-yl,
o-terphenyl-4-yl, p-terphenyl-2-yl, p-terphenyl-3-yl and
p-terphenyl-4-yl) which are tricyclic aryls, acenaphthylene-(1-,
3-, 4- or 5-)yl, fluorene-(1-, 2-, 3-, 4- or 9-)yl, phenalene-(1-
or 2-)yl and (1-, 2-, 3-, 4- or 9-)phenanthryl which are condensed
tricyclic aryls, quaterphenylyl (5'-phenyl-m-terphenyl-2-yl,
5'-phenyl-m-terphenyl-3-yl, 5'-phenyl-m-terphenyl-4-yl and
m-quaterphenylyl) which are tetracyclic aryls, triphenylene-(1- or
2-)yl, pyrene-(1-, 2- or 4-)yl and naphthacene-(1-, 2- or 5-)yl
which are condensed tetracyclic aryls, perylene-(1-, 2- or 3-)yl
and pentacene-(1-, 2-, 5- or 6-)yl which are condensed pentacyclic
aryls and the like.
[0041] The particularly preferred "aryl" in Ar.sup.1 and Ar.sup.2
is phenyl and 4-biphenylyl. Ar.sup.1 and Ar.sup.2 may be the same
or different, and Ar.sup.1 and Ar.sup.2 are preferably the same. If
Ar.sup.1 and Ar.sup.2 are aryl, the benzofluorene compound
represented by Formula (1) is characterized by that it is increased
in rigidity and excellent in heat resistance and that it is
extended in life.
[0042] The particularly preferred "aryl" in R.sup.1 and R.sup.2 is
phenyl, biphenylyl, terphenylyl, quaterphenylyl, naphthyl and
phenanthryl, and among them, phenyl, 4-biphenylyl, 1-naphthyl and
2-naphthyl are preferred. R.sup.1 and R.sup.2 may be the same or
different, and R.sup.1 and R.sup.2 are preferably the same. If
R.sup.1 and R.sup.2 are aryl, the benzofluorene compound
represented by Formula (1) is characterized by that it is excellent
in heat resistance, luminous efficiency and life.
[0043] "Alkyl" of "alkyl which may be substituted" in R.sup.1 and
R.sup.2 of Formula (1) may be either linear or branched and
includes, for example, linear alkyl having 1 to 24 carbon atoms or
branched alkyl having 3 to 24 carbon atoms. The preferred "alkyl"
is alkyl having 1 to 18 carbon atoms (branched alkyl having 3 to 18
carbon atoms). More preferred "alkyl" is alkyl having 1 to 12
carbon atoms (branched alkyl having 3 to 12 carbon atoms). Further
preferred "alkyl" is alkyl having 1 to 6 carbon atoms (branched
alkyl having 3 to 6 carbon atoms). Particularly preferred "alkyl"
is alkyl having 1 to 4 carbon atoms (branched alkyl having 3 to 4
carbon atoms).
[0044] The specific "alkyl" includes methyl, ethyl, n-propyl,
isopropyl, n-butyl, isobutyl, s-butyl, t-butyl, n-pentyl,
isopentyl, neopentyl, t-pentyl, n-hexyl, 1-methylpentyl,
4-methyl-2-pentyl, 3,3-dimethylbutyl, 2-ethylbutyl, n-heptyl,
1-methylhexyl, n-octyl, t-octyl, 1-methylheptyl, 2-ethylhexyl,
2-propylpentyl, n-nonyl, 2,2-dimethylheptyl, 2,6-dimethyl-4-heptyl,
3,5,5-trimethylhexyl, n-decyl, n-undecyl, 1-methyldecyl, n-dodecyl,
n-tridecyl, 1-hexylheptyl, n-tetradecyl, n-pentadecyl, n-hexadecyl,
n-heptadecyl, n-octadecyl, n-eicosyl and the like.
[0045] "Cycloalkyl" of "cycloalkyl which may be substituted" in
R.sup.1 and R.sup.2 of Formula (1) includes, for example,
cycloalkyl having 3 to 12 carbon atoms. The preferred "cycloalkyl"
is cycloalkyl having 3 to 10 carbon atoms. More preferred
"cycloalkyl" is cycloalkyl having 3 to 8 carbon atoms. Further
preferred "cycloalkyl" is cycloalkyl having 3 to 6 carbon
atoms.
[0046] The specific "cycloalkyl" includes cyclopropyl, cyclobutyl,
cyclopentyl, cyclohexyl, methylcyclopentyl, cycloheptyl,
methylcyclohexyl, cyclooctyl, dimethylcyclohexyl and the like.
[0047] The "substituents" in Ar.sup.1, Ar.sup.2, R.sup.1 and
R.sup.2 of Formula (1) include alkyl, cycloalkyl and aryl, and the
preferred groups thereof include the same groups as the groups
explained in the column of the "alkyl" in R.sup.1 and R.sup.2, the
groups explained in the column of the "cycloalkyl" in R.sup.1 and
R.sup.2 and the groups explained in the column of the "aryl" in
Ar.sup.1, Ar.sup.2, R.sup.1 and R.sup.2.
[0048] The "substituents" in Ar.sup.1, Ar.sup.2, R.sup.1 and
R.sup.2 include, to be specific, alkyl such as methyl, ethyl,
n-propyl, isopropyl, n-butyl, isobutyl, s-butyl, t-butyl, n-pentyl,
isopentyl, neopentyl, t-pentyl, n-hexyl, n-heptyl, n-octyl,
t-octyl, n-nonyl, n-decyl, n-undecyl, n-dodecyl, n-tridecyl,
n-tetradecyl, n-pentadecyl, n-hexadecyl, n-heptadecyl, n-octadecyl
and the like; cycloalkyl such as cyclopropyl, cyclobutyl,
cyclopentyl, cyclohexyl, cycloheptyl, cyclooctyl and the like; aryl
such as phenyl, biphenylyl, naphthyl, terphenylyl, phenanthryl and
the like; and alkylaryl such as methylphenyl, ethylphenyl,
s-butylphenyl, t-butylphenyl, 1-methylnaphthyl, 2-methylnaphthyl,
1,6-dimethylnaphthyl, 2,6-dimethylnaphthyl, 4-t-butylnaphthyl and
the like. The number of the substituents is, for example, a maximum
substitutable number, and it is preferably 0 to 3, more preferably
0 to 2 and further preferably 0 (non-substituted).
[0049] The specific examples of the compound represented by Formula
(1) described above include, for example, compounds represented by
the following Formulas (I-1) to (1-86). Among the compounds shown
below, particularly preferred are the compounds represented by the
following Formula (1-1), Formula (1-3), Formula (1-4), Formula
(1-7), Formula (1-12), Formula (1-13), Formula (1-14), Formula
(1-19), Formula (1-23), Formula (1-24), Formula (1-29), Formula
(1-31), Formula (1-33), Formula (1-34), Formula (1-41), Formula
(1-43), Formula (1-44), Formula (1-49), Formula (1-51), Formula
(1-53), Formula (1-54), Formula (1-59), Formula (1-61), Formula
(1-63), Formula (1-64), Formula (1-65), Formula (1-84) and Formula
(1-86). Further, more preferred are the compounds represented by
the following Formula (1-1), Formula (1-4), Formula (1-7), Formula
(1-12), Formula (1-13), Formula (1-14), Formula (1-24), Formula
(1-29), Formula (1-31), Formula (1-34), Formula (1-44), Formula
(1-59), Formula (1-61), Formula (1-63) and Formula (1-65).
##STR00003## ##STR00004## ##STR00005## ##STR00006## ##STR00007##
##STR00008## ##STR00009## ##STR00010## ##STR00011##
2. Benzofluorene Compound Represented by Formula (1')
[0050] Next, the benzofluorene compound represented by Formula (1')
shall be explained.
[0051] Explanations in Ar.sup.1 and Ar.sup.2 of Formula (1) can be
quoted for "aryl which may be substituted" in Ar.sup.1 and Ar.sup.2
of Formula (1'). Further, explanations in R.sup.1 and R.sup.2 of
Formula (1) can be quoted for "alkyl which may be substituted",
"cycloalkyl which may be substituted" and "aryl which may be
substituted" in R.sup.2 of Formula (1').
[0052] "Diarylamino having aryl which may be substituted" in
R.sup.1 and R.sup.2 of Formula (1') is amino substituted with two
"aryls which may be substituted". The "aryls which may be
substituted" may be the same or different, and they are preferably
the same. "Aryl" of "aryl which may be substituted" includes, for
example, aryl having 6 to 30 carbon atoms, and it includes
preferably aryl having 6 to 24 carbon atoms, more preferably aryl
having 6 to 20 carbon atoms, further preferably aryl having 6 to 16
carbon atoms and particularly preferably aryl having 6 to 12 carbon
atoms.
[0053] To be specific, "aryl" of "aryl which may be substituted"
includes, for example, the "aryls" described above, and more
preferred "aryl" is phenyl, biphenylyl, naphthyl and the like, and
the particularly preferred "aryl" is phenyl.
[0054] The "substituents" for "aryl which may be substituted" are
alkyl, aryl, heteroaryl or the like, and the preferred examples of
the alkyl and the aryl include the "alkyls" and the "aryls" each
described above. Further, the preferred examples of heteroaryl
include the following groups.
[0055] The "heteroaryl" includes, for example, heteroaryl having 2
to 30 carbon atoms. The preferred "heteroaryl" is heteroaryl having
2 to 25 carbon atoms, and it is more preferably heteroaryl having 2
to 20 carbon atoms, further preferably heteroaryl having 2 to 15
carbon atoms and particularly preferably heteroaryl having 2 to 10
carbon atoms.
[0056] Further, the "heteroaryl" includes, for example,
heterocyclic groups containing 1 to 5 hetero atoms selected from
oxygen atoms, sulfur atoms and nitrogen atoms other than carbon
atoms as ring constitutional atoms, and it includes, for example,
aromatic heterocyclic groups.
[0057] The "heterocyclic group" includes, for example, pyrrolyl,
oxazolyl, isooxazolyl, thiazolyl, isothiazolyl, imidazolyl,
oxadiazolyl, thiadiazolyl, triazolyl, tetrazolyl, pyrazolyl,
pyridyl, pyrimidinyl, pyridazinyl, pyrazinyl, triazinyl, indolyl,
isoindolyl, 1H-indazolyl, benzimidazolyl, benzoxazolyl,
benzothiazolyl, 1H-benzotriazolyl, quinolyl, isoquinolyl, cinnolyl,
quinazolyl, quinoxalinyl, phthalazinyl, naphthyridinyl, purinyl,
pteridinyl, carbazolyl, acridinyl, phenoxazinyl, phenothiazinyl,
phenazinyl, indolidinyl and the like, and imidazolyl, pyridyl,
carbazolyl and the like are preferred.
[0058] The "aromatic heterocyclic group" includes, for example,
furyl, thienyl, pyrrolyl, oxazolyl, isooxazolyl, thiazolyl,
isothiazolyl, imidazolyl, pyrazolyl, oxadiazolyl, furazanyl,
thiadiazolyl, triazolyl, tetrazolyl, pyridyl, pyrimidinyl,
pyridazinyl, pyrazinyl, triazinyl, benzofuranyl, isobenzofuranyl,
benzo[b]thienyl, indolyl, isoindolyl, 1H-indazolyl, benzimidazolyl,
benzoxazolyl, benzothiazolyl, 1H-benzotriazolyl, quinolyl,
isoquinolyl, cinnolyl, quinazolyl, quinoxalinyl, phthalazinyl,
naphthyridinyl, purinyl, pteridinyl, carbazolyl, acridinyl,
phenoxazinyl, phenothiazinyl, phenazinyl, phenoxathienyl,
thianthrenyl, indolidinyl and the like, and thienyl, imidazolyl,
pyridyl, carbazolyl and the like are preferred.
[0059] The specific examples of the compound represented by Formula
(1') described above include, for example, compounds represented by
the following Formulas (1'-1) to (1'-16). Among the compounds shown
below, particularly preferred are the compounds represented by the
following Formula (1'-1), Formula (1'-2), Formula (1'-6), Formula
(1'-9) and Formula (1'-15).
##STR00012## ##STR00013## ##STR00014## ##STR00015##
3. Production Process for Benzofluorene Compound
<Benzofluorene Compound Represented by Formula (1)>
[0060] The benzofluorene compound represented by Formula (1) can be
produced by using a known synthetic method such as, for example, a
Suzuki coupling reaction. The Suzuki coupling reaction is reaction
in which aromatic halide or triflate is subjected to coupling with
aromatic boronic acid or aromatic boronic ester under the presence
of a base using a palladium catalyst. A specific example of a
reaction route for obtaining the compound represented by Formula
(1) by the reaction is shown below (schemes 1 to 3). Ar.sup.1,
Ar.sup.2, R.sup.1 and R.sup.2 in the respective schemes are the
same as described above, and Tfo is triflate.
##STR00016##
##STR00017##
##STR00018##
[0061] The specific examples of the palladium catalyst used in the
reaction are Pd(PPh.sub.3).sub.4, PdCl.sub.2(PPh.sub.3).sub.2,
Pd(OAc).sub.2, tris(dibenzylideneacetone)dipalladium (0),
tris(dibenzylideneacetone)dipalladium (0) chloroform complex,
bis(dibenzylideneacetone)palladium (0) and the like. A phosphine
compound may be added, if necessary, to the palladium compounds in
order to accelerate the reaction. The specific examples of the
phosphine compound include tri(t-butyl)phosphine,
tricyclohexylphosphine,
1-(N,N-dimethylaminomethyl)-2-(di-t-butylphosphino)ferrocene,
1-(N,N-dibutylaminomethyl)-2-(di-t-butylphosphino)ferrocene,
1-(methoxymethyl)-2-(di-t-butylphosphino)ferrocene,
1,1'-bis(di-t-butylphosphino)ferrocene,
2,2'-bis(di-t-butylphosphino)-1,1'-binaphthyl,
2-methoxy-2'-(di-t-butylphosphino)-1,1'-binaphthyl and the
like.
[0062] The specific examples of the base used in the reaction are
sodium carbonate, potassium carbonate, cesium carbonate, sodium
hydrogencarbonate, sodium hydroxide, potassium hydroxide, barium
hydroxide, sodium ethoxide, sodium t-butoxide, sodium acetate,
tripotassium phosphate, potassium fluoride and the like.
[0063] Further, the specific examples of the solvent used in the
reaction are benzene, toluene, xylene, N,N-dimethylformamide,
tetrahydrofuran, diethyl ether, t-butyl methyl ether, 1,4-dioxane,
methanol, ethanol, isopropyl alcohol and the like. These solvents
can suitably be selected according to the structures of aromatic
halide, triflate, aromatic boronic ester and aromatic boronic acid
which is subjected to the reaction. The solvent may be used alone
or in the form of a mixed solvent.
<Benzofluorene Compound Represented by Formula (1')>
[0064] When R.sup.1 and R.sup.2 are diarylamino having aryl which
may be substituted in Formula (1'), the benzofluorene compound
represented by Formula (1') can be produced by using an existing
reaction such as a Buchwald-Hartwig reaction or a Ullmann reaction.
The Buchwald-Hartwig reaction is reaction in which aromatic halide
is subjected to coupling with primary aromatic amine or secondary
aromatic amine under the presence of a base using a palladium
catalyst or a copper catalyst. A specific example of a reaction
route for obtaining the compound represented by Formula (1') by the
reaction is shown below (schemes 4 to 7).
[0065] Ar.sup.1 and Ar.sup.2 in the respective schemes are the same
as described above, and R.sup.1 and R.sup.2 are diarylamino having
aryl which may be substituted. R.sup.3 and R.sup.4 are "aryl which
may be substituted" constituting "diarylamino having aryl which may
be substituted".
##STR00019##
##STR00020##
##STR00021##
##STR00022##
[0066] The specific examples of the palladium catalyst, the base
and the solvent which are used in the reaction can be selected from
those used in the Suzuki coupling reaction. A phosphine compound
may be added, if necessary, to the palladium compounds in order to
accelerate the reaction. The specific examples of the phosphine
compound can be selected as well from the same compounds as the
specific examples shown in the Suzuki coupling reaction. In
addition to the compounds, 1,1'-bis(diphenylphosphino)ferrocene,
bis(diphenylphosphino)binaphthyl and the like can be used as
well.
[0067] The Ullmann reaction is reaction in which aromatic halide is
subjected to coupling with primary aromatic amine or secondary
aromatic amine under the presence of a base using a copper
catalyst. The specific examples of the copper catalyst used in the
reaction are copper powder, copper chloride, copper bromide, copper
iodide and the like. The specific examples of the base used in the
reaction can be selected from the same compounds as in the Suzuki
coupling reaction. The specific examples of the solvent used in the
reaction are nitrobenzene, dichlorobenzene, N,N-dimethylformamide
and the like.
[0068] Also, in a case where R.sup.1 is diarylamino having aryl
which may be substituted and where R.sup.2 is hydrogen, alkyl which
may be substituted, cycloalkyl which may be substituted or aryl
which may be substituted in Formula (1'), the compound represented
by Formula (1') can be produced by the scheme 5.
[0069] In the case, R.sup.2 in the scheme 5 is hydrogen, alkyl
which may be substituted, cycloalkyl which may be substituted or
aryl which may be substituted. Ar.sup.1 and Ar.sup.2 in the scheme
5 are the same as described above, and R.sup.3 and R.sup.4 are
"aryl which may be substituted" constituting "diarylamino having
aryl which may be substituted".
[0070] The benzofluorene compounds represented by Formula (1) and
Formula (1') are compounds having strong fluorescence in a solid
state and can be used for emission of various colors, and they are
suited particularly to emission of a blue color. Among the
benzofluorene compounds represented by Formula (1) and Formula
(1'), the compounds having an asymmetric molecular structure are
liable to form an amorphous state in producing an organic EL
device. Further, they are excellent in heat resistance and stable
in applying an electric field.
[0071] The benzofluorene compound represented by Formula (1) is
effective as a host emission material. The benzofluorene compound
has a shorter emission wavelength, and it is excellent particularly
as a blue host emission material but can be used as well for
emission of colors other than a blue color. When the benzofluorene
compound is used as a host material, energy transfer is efficiently
carried out, and a light emitting device having high efficiency and
long life can be obtained.
[0072] Further, the benzofluorene compound represented by Formula
(1') is effective particularly as a dopant material.
[0073] The benzofluorene compounds represented by Formula (1) and
Formula (1') comprise benzo[c]fluorene in a fluorene skeleton and
therefore are excellent in solubility in solvents as compared with
compounds having a benzo[.alpha.]fluorene skeleton. Accordingly,
width in selecting a solvent in synthesis is broad, and therefore
freedom of the synthesis can be enhanced, and mass production can
be easy. Further a spin coating method using various solvents can
readily be employed.
[0074] The benzofluorene compound represented by Formula (1') is
substituted with diaryl amino in a R.sup.1 position without fail.
This compound has high heat resistance as compared with the
compound substituted with diaryl amino only in a R.sup.2 position,
and it is improved in luminous efficiency when applied to a
device.
4. Organic Electroluminescent Device
[0075] The benzofluorene compound according to the present
invention can be used, for example, as a material for an organic
electroluminescent device.
[0076] The organic electroluminescent device according to this
embodiment shall be explained in details with reference to a
drawing. FIG. 1 is an outline cross-sectional drawing showing the
organic electroluminescent device according to the present
embodiment.
<Structure of Organic Electroluminescent Device>
[0077] An organic electroluminescent device 100 shown in FIG. 1
comprises a substrate 101, an anode 102 provided on the substrate
101, a hole injection layer 103 provided on the anode 102, a hole
transport layer 104 provided on the hole injection layer 103, an
emission layer 105 provided on the hole transport layer 104, an
electron transport layer 106 provided on the emission layer 105, an
electron injection layer 107 provided on the electron transport
layer 106 and a cathode 108 provided on the electron injection
layer 107.
[0078] The organic electroluminescent device 100 may be turned
upside down in a preparation order and may assume a structure in
which it comprises, for example, the substrate 101, the cathode 108
provided on the substrate 101, the electron injection layer 107
provided on the cathode 108, the electron transport layer 106
provided on the electron injection layer 107, the emission layer
105 provided on the electron transport layer 106, the hole
transport layer 104 provided on the emission layer 105, the hole
injection layer 103 provided on the hole transport layer 104 and
the anode 102 provided on the hole injection layer 103.
[0079] All the respective layers described above do not necessarily
have to be present, and the hole injection layer 103, the hole
transport layer 104, the electron transport layer 106 and the
electron injection layer 107 are layers which are optionally
provided, wherein a minimum structural unit assumes a structure
comprising the anode 102, the emission layer 105 and cathode 108.
The respective layers described above each may comprise a single
layer or plural layers.
[0080] The mode of the layers constituting the organic
electroluminescent device may be, in addition to the structural
mode of "substrate/anode/hole injection layer/hole transport
layer/emission layer/electron transport layer/electron injection
layer/cathode" described above, the structural modes of
"substrate/anode/hole transport layer/emission layer/electron
transport layer/electron injection layer/cathode",
"substrate/anode/hole injection layer/emission layer/electron
transport layer/electron injection layer/cathode"
"substrate/anode/hole injection layer/hole transport layer/emission
layer/electron injection layer/cathode", "substrate/anode/hole
injection layer/hole transport layer/emission layer/electron
transport layer/cathode", "substrate/anode/emission layer/electron
transport layer/electron injection layer/cathode",
"substrate/anode/hole transport layer/emission layer/electron
injection layer/cathode", "substrate/anode/hole transport
layer/emission layer/electron transport layer/cathode",
"substrate/anode/hole injection layer/emission layer/electron
injection layer/cathode", "substrate/anode/hole injection
layer/emission layer/electron transport layer/cathode",
"substrate/anode/hole injection layer/hole transport layer/emission
layer/cathode", "substrate/anode/hole injection layer/emission
layer/cathode", "substrate/anode/hole transport layer/emission
layer/cathode", "substrate/anode/emission layer/electron transport
layer/cathode", "substrate/anode/emission layer/electron injection
layer/cathode" and "substrate/anode/emission layer/cathode".
<Substrate in the Organic Electroluminescent Device>
[0081] The substrate 101 is a base for the organic
electroluminescent device 100, and quartz, glass, metal, plastics
and the like are usually used therefor. The substrate 101 is formed
in the shape of a plate, a film or a sheet according to the
purposes, and a glass plate, a metal plate, a metal foil, a plastic
film or a plastic sheet is used therefor. Among them, a glass plate
and a plate made of a transparent synthetic resin such as
polyester, polymethacrylate, polycarbonate and polysulfone are
preferred. Soda lime glass, non-alkali glass and the like are used
for the glass substrate. The thickness thereof may be such a
thickness as enough for maintaining the mechanical strength, and
therefore it is, for example, 0.2 mm or more. An upper limit value
of the thickness is, for example, 2 mm or less, preferably 1 mm or
less. The material of glass is preferably non-alkali glass since
ions eluted from glass are preferably fewer. Soda lime glass which
is provided with a barrier coat such as SiO.sub.2 is commercially
available, and therefore it can be used. The substrate 101 may be
provided at least on one face thereof with a gas barrier film such
as a minute silicon oxide film in order to enhance gas barrier
property thereof. Particularly when a plate, a film or a sheet made
of a synthetic resin having low gas barrier property is used for
the substrate 101, a gas barrier membrane is preferably provided
thereon.
<Anode in the Organic Electroluminescent Device>
[0082] The anode 102 plays a role of injecting holes into the
emission layer 105. When the hole injection layer 103 and/or the
hole transport layer 104 are provided between the anode 102 and the
emission layer 105, holes are injected into the emission layer 105
via these layers.
[0083] A material for forming the anode 102 includes inorganic
compounds and organic compounds. The inorganic compounds include,
for example, metals (aluminum, gold, silver, nickel, palladium,
chromium and the like), metal oxides (oxide of indium, oxide of
tin, indium-tin oxide (ITO) and the like), halogenated metals
(copper iodide and the like), copper sulfide, carbon black, ITO
glass, nesa glass and the like. The organic compounds include, for
example, polythiophene such as poly(3-methylthiophene) and
electrically conductive polymers such as polypyrrole, polyaniline
and the like. In addition thereto, those suitably selected from
materials used for an anode of an organic electroluminescent device
can be used.
[0084] A resistance of the transparent electrode shall not be
restricted as long as an electric current sufficient for emission
of the light emitting device can be supplied, and it is preferably
a low resistance from the viewpoint of power consumption of the
light emitting device. For example, an ITO substrate having a
resistance of 300 K/square or less functions as a device electrode.
At present, a substrate having a resistance of about 10
.OMEGA./square can be supplied, and therefore a product having a
low resistance of, for example, 100 to 5 .OMEGA./square, preferably
50 to 5 .OMEGA./square is particularly preferably used. A thickness
of ITO can optionally be selected depending on a resistance value
thereof, and it is usually used in a range of 100 to 300 nm in many
cases.
<Hole Injection Layer and Hole Transport Layer in the Organic
Electroluminescent Device>
[0085] The hole injection layer 103 plays a role of efficiently
injecting holes moving from the anode 102 into the emission layer
105 or the hole transport layer 104. The hole transport layer 104
plays a role of efficiently transporting holes injected from the
anode 102 or holes injected from the anode 102 via the hole
injection layer 103 to the emission layer 105. The hole injection
layer 103 and the hole transport layer 104 are formed respectively
by laminating or mixing one or more hole injecting or transporting
material(s) or from a mixture of the hole injecting or transporting
material(s) with a high molecular binder. Further, inorganic salt
such as iron chloride (III) may be added to the hole injecting or
transporting material to form the layers.
[0086] The hole injecting or transporting material has to
efficiently inject or transport holes from a positive electrode
between the electrodes to which an electrical field is applied, and
it is desirable that the hole injection efficiency is high and that
the holes injected are efficiently transported. Accordingly,
preferred is the material which has small ionization potential and
large hole mobility and is excellent in stability and in which
impurities trapped are less liable to be generated in producing and
using.
[0087] Optional compounds selected from compounds which have so far
conventionally been used as a charge transport material for a hole
in a photoconductive material, p type semiconductors and publicly
known compounds used for a hole injection layer and a hole
transport layer in an organic electroluminescent device can be used
as materials for forming the hole injection layer 103 and the hole
transport layer 104. The specific examples thereof are preferably
carbazole derivatives (N-phenylcarbazole, polyvinylcarbazole and
the like), biscarbazole derivatives such as bis(N-allylcarbazole)
and bis(N-alkylcarbazole), triarylamine derivatives (polymers
having aromatic tertiary amine on a main chain or a side chain),
triphenylamine derivatives such as
1,1-bis(4-di-p-tolylaminophenyl)cyclohexane,
N,N'-diphenyl-N,N'-di(3-methylphenyl)-4,4'-diaminobiphenyl,
N,N'-diphenyl-N,N'-dinaphthyl-4,4'-diaminobiphenyl (hereinafter
abbreviated as NPD),
N,N'-diphenyl-N,N'-di(3-methylphenyl)-4,4'-diphenyl-1,1'-diamine,
N,N'-dinaphthyl-N,N'-diphenyl-4,4'-diphenyl-1,1'-diamine and
4,4',4''-tris(3-methylphenyl(phenyl)-amino)triphenylamine,
starburst amine derivatives and the like, stilbene derivatives,
heterocyclic compounds such as phthalocyanine derivatives
(non-metal phthalocyanines, copper phthalocyanine and the like),
pyrazoline derivatives, hydrazone compounds, benzofuran
derivatives, thiophene derivatives, oxadiazole derivatives and
porphylin derivatives, polysilane and the like. In polymer
compounds, polycarbonate, styrene derivatives, polyvinylvcarbazole,
polysilane and the like which have the monomers described above on
side chains are preferred, but they shall not specifically be
restricted as long as they are compounds which can form a thin film
necessary for preparing a light emitting device and which can
inject holes from an anode and can transport the holes.
[0088] It is know as well that electrical conductivity of an
organic semiconductor is strongly influenced by doping thereof.
Such organic semiconductor matrix substance is constituted from a
compound having good electron donating property or a compound
having good electron accepting property. Strong electron acceptors
such as tetracyanoquinonedimethane (TCNQ) or
2,3,5,6-tetrafluorotetracyano-1,4-benzoquinonedimethane (F4TCNQ)
are known for doping electron donating substances (refer to, for
example, a document "M. Pfeiffer, A. Beyer, T. Fritz, K. Leo, Appl.
Phys. Lett., 73 (22), 3202 to 3204 (1998)" and a document "J.
Blochwitz, M. Pfeiffer, T. Fritz, K. Leo, Appl. Phys. Lett., 73
(6), 729 to 731 (1998)"). They produce so-called holes by an
electron moving process in an electron donating type base material
(hole transport material). Conductivity of the base material is
changed to a considerably large extent by the number and mobility
of holes. Known as a matrix substance having hole transport
property are, for example, benzidine derivatives (TPD and the
like), starburst amine derivatives (TDATA and the like) and
specific metal phthalocyanines (particularly zinc phthalocyanine
ZnPc and the like) (JP H17-167175 A/2005).
<Emission Layer in the Organic Electroluminescent Device>
[0089] The emission layer 105 emits light by recombining holes
injected from the anode 102 with electrons injected from the
cathode 108 between the electrodes to which an electrical field is
applied. A material for forming the emission layer 105 may be any
compounds as long as they are compounds (luminescent compounds)
which are excited by recombination of holes with electrons to emit
light, and they are preferably compounds which can form a stable
thin film shape and which show strong emission (luminescence and/or
phosphorescence) efficiency in a solid state.
[0090] The emission layer may comprise either a single layer or
plural layers and is formed by an emission material (host material
and dopant material). This may be either a mixture of a host
material and a dopant material or a host material alone. That is,
only the host material or the dopant material may emit light or
both the host material and the dopant material may emit light in
the respective layers of the emission layer. The host material and
the dopant material each may comprise either one kind or
combination of two or more kinds thereof. The dopant material may
be contained in either the whole part or a part of the host
material. A use amount of the dopant is varied depending on the
dopant and can be determined so that the use amount meets the
characteristics of the dopant (for example, a too large use amount
of the dopant is likely to bring about a concentration quenching
phenomenon). A standard of a use amount of the dopant is preferably
0.001 to 50% by weight, more preferably 0.1 to 10% by weight and
further preferably 1 to 5% by weight based on the whole emission
material. In a doping method, the emission layer can be formed by a
method of co-depositing with the host material, or the dopant
material may be mixed in advance with the host material and then
deposited at the same time.
[0091] Further, the emission material for the light emitting device
according to the present embodiment may be either fluorescent or
phosphorescent.
[0092] The benzofluorene compound represented by Formula (1)
described above can be used as the host material. In particular,
preferably used are the compounds represented by the foregoing
Formula (1-1), Formula (1-3), Formula (1-4), Formula (1-7), Formula
(I-12), Formula (1-13), Formula (1-14), Formula (1-19), Formula
(1-23), Formula (1-24), Formula (1-29), Formula (1-31), Formula
(1-33), Formula (1-34), Formula (1-41), Formula (1-43), Formula
(1-44), Formula (1-49), Formula (1-51), Formula (1-53), Formula
(1-54), Formula (1-59), Formula (1-61), Formula (1-63), Formula
(1-64), Formula (1-65), Formula (1-84) and Formula (1-86). Further,
more preferably used are the compounds represented by the foregoing
Formula (1-1), Formula (1-4), Formula (1-7), Formula (1-12),
Formula (1-13), Formula (1-14), Formula (1-24), Formula (1-29),
Formula (1-31), Formula (1-34), Formula (1-44), Formula (1-59),
Formula (1-61), Formula (1-63) and Formula (1-65). A use amount of
the benzofluorene compound represented by the foregoing Formula (1)
as the host material is preferably 50 to 99.999% by weight, more
preferably 80 to 99.95% by weight and further preferably 90 to 99.9
by weight based on the whole emission material.
[0093] Other host materials shall not specifically be restricted,
and suitably used are condensed ring derivatives such as
anthracene, pyrene and the like which have so far been known as an
emission material, metal chelated oxynoid compounds including
tris(8-quinolinolate)aluminum, bisstyryl derivatives such as
bisstyrylanthracene derivatives, distyrylbenzene derivatives and
the like, tetraphenylbutadiene derivatives, coumarin derivatives,
oxadiazole derivatives, pyrrolopyridine derivatives, perinone
derivatives, cyclopentadiene derivatives, oxadiazole derivatives,
thiadiazolopyridine derivatives, pyrrolopyrrole derivatives and
polymers such as polyphenylenevinylene derivatives,
polyparaphenylene derivatives and polythiophene derivatives.
[0094] In addition to the compounds, compounds suitably selected
from compounds described in Kagaku Kogyo (Chemical Industry) issued
in June 2004 edition, p. 13 and references cited therein can be
used as the host material.
[0095] The benzofluorene compound represented by Formula (1')
described above can be used as the dopant material, and in
particular, more preferably used are the compounds represented by
the foregoing Formula (1'-1), Formula (1'-2), Formula (1'-6),
Formula (1'-9) and Formula (1'-15). A use amount of the
benzofluorene compound represented by the foregoing Formula (1') as
the dopant material is preferably 0.001 to 50% by weight, more
preferably 0.05 to 20% by weight and further preferably 0.1 to 10%
by weight based on the whole emission material. In a doping method,
the emission layer can be formed by a method of co-depositing with
the host material, or the dopant material may be mixed in advance
with the host material and then deposited at the same time.
[0096] Other dopant materials shall not specifically be restricted,
and known compounds can be used. They can be selected from various
compounds according to emission colors desired. To be specific,
they include, for example, condensed ring derivatives such as
phenanthrene, anthracene, pyrene, tetracene, pentacene, perylene,
naphthopyrene, dibenzopyrene, rubrene and the like, benzoxazole
derivatives, benzothiazole derivatives, benzimidazole derivatives,
benzotriazole derivatives, oxazole derivatives, oxadiazole
derivatives, thiazole derivatives, imidazole derivatives,
thiadiazole derivatives, triazole derivatives, pyrazoline
derivatives, stilbene derivatives, thiophene derivatives,
tetraphenylbutadiene derivatives, cyclopentadiene derivatives,
bisstyryl derivatives (JP H1-245087 A/1989) such as
bisstyrylanthracene derivatives, distyrylbenzene derivatives and
the like, bisstyrylarylene derivatives (JP H2-247278 A/1990),
diazaindacene derivatives, furan derivatives, benzofuran
derivatives, isobenzofuran derivatives such phenylisobenzofuran,
dimesitylisobenzofuran, di(2-methylphenyl)isobenzofuran,
di(2-trifluoromethylphenyl)isobenzofuran, phenylisobenzofuran and
the like, dibenzofuran derivatives, coumarin derivatives-such as
7-dialkylaminocoumarin derivatives, 7-piperidinocoumarin
derivatives, 7-hydroxycoumarin derivatives, 7-methoxycoumarin
derivatives, 7-acetoxycoumarin derivatives,
3-benzothiazolylcoumarin derivatives, 3-benzimidazolylcoumarin
derivatives, 3-benzoxazolylcoumarin derivatives and the like,
dicyanomethylenepyran derivatives, dicyanomethylenethiopyran
derivatives, polymethine derivatives, cyanine derivatives,
oxobenzanthracene derivatives, xanthene derivatives, rhodamine
derivatives, fluorescein derivatives, pyrylium derivatives,
carbostyryl derivatives, acridine derivatives, oxazine derivatives,
phenylene oxide derivatives, quinacridone derivatives, quinazoline
derivatives, pyrrolopyridine derivatives, ferropyridine
derivatives, 1,2,5-thiadiazolopyrene derivatives, pyrromethene
derivatives, perinone derivatives, pyrrolopyrrole derivatives,
squarylium derivatives, violanthrone derivatives, phenazine
derivatives, acridone derivatives, deazaflavin derivatives and the
like.
[0097] To give the examples thereof by color of emission, the blue
to bluish green dopant materials include aromatic hydrocarbon
compounds and derivatives thereof such as naphthalene, anthracene,
phenanthrene, pyrene, triphenylene, perylene, fluorene, indene and
the like, aromatic heterocyclic compounds and derivatives thereof
such as furan, pyrrole, thiophene, silole, 9-silafluorene,
9,9'-spirobisilafluorene, benzothiophene, benzofuran, indole,
dibenzothiophene, dibenzofuran, imidazopyridine, phenanthroline,
pyrazine, naphthylidine, quinoxaline, pyrrolopyridine, thioxanthene
and the like, distyrylbenzene derivatives, tetraphenylbutadiene
derivatives, stilbene derivatives, aldazine derivatives, coumarin
derivatives, azole derivatives and metal complexes thereof such as
imidazole, thiazole, thiadiazole, carbazole, oxazole, oxadiazole,
triazole and the like and aromatic amine derivatives represented by
N,N'-diphenyl-N,N'-di(3-methylphenyl)-4,4'-diphenyl-1,1'-diamine.
[0098] The green to yellow dopant materials include coumarin
derivatives, phthalimide derivatives, naphthalimide derivatives,
perinone derivatives, pyrrolopyrrole derivatives, cyclopentadiene
derivatives, acridone derivatives, quinacridone derivatives,
naphthacene derivatives (such as rubrene) and the like. Further,
the suitable examples thereof include compounds obtained by
introducing substituents which can shift wavelengths to a longer
side such as aryl group(s), heteroaryl group(s), arylvinyl
group(s), amino group(s), cyano group(s) and the like into the
compounds given as the examples of the blue to bluish green dopant
materials described above.
[0099] Further, the orange to red dopant materials include
naphthalimide derivatives such as bis(diisopropylphenyl)perylene
tetracarboxylic imide, perinone derivatives, rare earth complexes
such as Eu complexes having acetylacetone, benzoylacetone and
phenanthroline as ligands,
4-(dicyanomethylene)-2-methyl-6-(p-dimethylaminostyryl)-4H-pyran
and analogous compounds thereof, metal phthalocyanine derivatives
such as magnesium phthalocyanine, aluminum chlorophthalocyanine and
the like, rhodamine derivatives, deazaflavin derivatives, coumarin
derivatives, quinacridone derivatives, phenoxazine derivatives,
oxazine derivatives, quinazoline derivatives, pyrrolopyridine
derivatives, squarylium derivatives, violanthrone derivatives,
phenazine derivatives, phenoxazone derivatives, thidiazolopyrene
and the like. Further, the suitable examples thereof include
compounds obtained by introducing substituents which can shift
wavelengths to a longer side such as aryl group(s), heteroaryl
group(s), arylvinyl group(s), amino group(s), cyano group(s) and
the like into the compounds given as the examples of the blue to
bluish green and green to yellow dopant materials described above.
Further, the suitable examples thereof include phosphorescent metal
complexes comprising iridium and platinum as central metals
represented by tris(8-phenylpyridine)iridium (III).
[0100] Among the dopant materials described above, the dopant
materials which are suited to the material for the emission layer
according to the present invention are particularly preferably the
benzofluorene compound represented by Formula (1'), perylene
derivatives, borane derivatives, amine-containing styryl
derivatives, aromatic amine derivatives, coumarin derivatives,
pyran derivatives, iridium complexes or platinum complexes.
[0101] The perylene derivatives include, for example,
3,10-bis(2,6-dimethylphenyl)perylene,
3,10-bis(2,4,6-trimethylphenyl)perylene, 3,10-diphenylperylene,
3,4-diphenylperylene, 2,5,8,11-tetra-t-butylperylene,
3,4,9,10-tetraphenylperylene,
3-(1'-pyrenyl)-8,11-di(-t-butyl)perylene,
3-(9'-anthryl)-8,11-di(-t-butyl)perylene,
3,3'-bis(8,11-di(-t-butyl)perylenyl) and the like.
[0102] Further, perylene derivatives described in JP H11-97178
A/1999, JP H12-133457 A/2000, JP H12-26324 A/2000, JP H13-267079
A/2001, JP H13-267078 A/2001, JP H13-267076 A/2001, JP H12-34234
A/2000, JP H13-267075 A/2001, JP H13-217077 A/2001 and the like may
be used as well.
[0103] The borane derivatives include, for example,
1,8-diphenyl-10-(dimesitylboryl)anthracene,
9-phenyl-10-(dimesitylboryl)anthracene,
4-(9'-anthryl)dimesitylborylnaphthalene,
4-(10'-phenyl-9'-anthryl)dimesitylborylnaphthalene,
9-(dimesitylboryl)anthracene,
9-(4'-biphenylyl-10-(dimesitylboryl)anthracene,
9-(4'-(N-carbazolyl)phenyl)-10-(dimesitylboryl)anthracene and the
like.
[0104] Further, borane derivatives described in International
Publication No. 2000/40586 pamphlet and the like may be used as
well.
[0105] The amine-containing styryl derivatives include, for
example, N,N,N',N'-tetra(4-biphenylyl)-4,4'-diaminostilbene,
N,N,N',N'-tetra(1-naphthyl)-4,4'-diaminostilbene,
N,N,N',N'-tetra(2-naphthyl)-4,4'-diaminostilbene,
N,N'-di(2-naphthyl)-N,N'-diphenyl-4,4'-diaminostilbene,
N,N'-di(9-phenanthryl)-N,N'-diphenyl-4,4'-diaminostilbene,
4,4'-bis[4''-bis(diphenylamino)styryl]-biphenyl,
1,4-bis[4'-bis(diphenylamino)styryl]-benzene,
2,7-bis[4'-bis(diphenylamino)styryl]-9,9-dimethylfluorene,
4,4'-bis(9-ethyl-3-carbazovinylene)-biphenyl,
4,4'-bis(9-phenyl-3-carbazovinylene)-biphenyl and the like.
[0106] Further, amine-containing styryl derivatives described in JP
H15-347056 A/2003, JP H13-307884 A/2001 and the like may be used as
well.
[0107] The aromatic amine derivatives include, for example,
N,N,N,N-tetraphenylanthracene-9,10-diamine,
9,10-bis(4-diphenylamino-phenyl)anthracene,
9,10-bis(4-di(1-naphthylamino)phenyl)anthracene,
9,10-bis(4-di(2-naphthylamino)phenyl)anthracene,
10-di-p-tolylamino-9-(4-di-p-tolylamino-1-naphthyl)anthracene,
10-diphenylamino-9-(4-diphenylamino-1-naphthyl)anthracene,
10-diphenylamino-9-(6-diphenylamino-2-naphthyl)anthracene,
[4-(4-diphenylamino-phenyl)naphthalene-1-yl]-diphenylamine,
[4-(4-diphenylamino-phenyl)naphthalene-1-yl]-diphenylamine,
[6-(4-diphenylamino-phenyl)naphthalene-2-yl]-diphenylamine,
4,4'-bis[4-diphenylaminonaphthalene-1-yl]biphenyl,
4,4'-bis[6-diphenylaminonaphthalene-2-yl]biphenyl,
4,4''-bis[4-diphenylaminonaphthalene-1-yl]-p-terphenyl,
4,4''-bis[6-diphenylaminonaphthalene-2-yl]-p-terphenyl and the
like.
[0108] Further, aromatic amine derivatives described in JP
H18-156888 A/2006 and the like may be used as well.
[0109] The coumarin derivatives include coumarin-6, coumarin-334
and the like.
[0110] Further, coumarin derivatives described in JP H16-43646
A/2004, JP H13-76876 A/2001, JP H6-298758 A/1994 and the like may
be used as well.
[0111] The pyran derivatives include DCM and DCJTB shown below.
##STR00023##
[0112] Further, pyran derivatives described in JP H17-126399
A/2005, JP H17-097283 A/2005, JP H14-234892 A/2002, JP H13-220577
A/2001, JP H13-081090 A/2001, JP H13-052869 A/2001 and the like may
be used as well.
[0113] The iridium complexes include Ir(ppy).sub.3 shown below.
##STR00024##
[0114] Further, iridium complexes described in JP H18-089398
A/2005, JP H18-080419 A/2006, JP H17-298483 A/2005, JP H17-097263
A/2005, JP H16-111379 A/2004 and the like may be used as well.
[0115] The platinum complexes include PtOEP shown below.
##STR00025##
[0116] Further, platinum complexes described in JP H18-190718
A/2006, JP H18-128634 A/2006, JP H18-093542 A/2006, JP H16-335122
A/2004, JP H16-331508 A/2004 and the like may be used as well.
[0117] In addition to the compounds, compounds suitably selected
from compounds described in Kagaku Kogyo (Chemical Industry) issued
in June 2004 edition, p. 13 and references cited therein can be
used as the dopant material.
<Electron Injection Layer and Electron Transport layer in the
organic electroluminescent device>
[0118] The electron injection layer 107 plays a role of efficiently
injecting electrons moving from the cathode 108 into the emission
layer 105 or the electron transport layer 106. The electron
transport layer 106 plays a role of efficiently transporting
electrons injected from the cathode 108 or electrons injected from
the cathode 108 via the electron injection layer 107 to the
emission layer 105. The electron transport layer 106 and the
electron injection layer 107 are formed respectively by laminating
or mixing one or more electron transporting or injecting
material(s) or from a mixture of the electron transporting or
injecting material(s) with a high molecular binder.
[0119] An electron injection or transport layer is a layer into
which electrons are injected from the cathode and which controls
transportation of the electrons, and it is desirable that the
electron injection efficiency is high and that the electrons
injected are efficiently transported. Accordingly, preferred is the
material which has large electron affinity and large electron
mobility and is excellent in stability and in which impurities
trapped are less liable to be generated in producing and using.
However, when considering a transport balance between a hole and an
electron, the material is provided, even if electron transport
ability is not so high, with an effect of enhancing luminous
efficiency to the same extent as that of a material having high
electron transport ability in the case of playing principally a
role of efficiently inhibiting holes coming from the anode from
moving to a cathode side without recombination. Accordingly, the
electron injection and transport layer in the present embodiment
may be provided as well with a function of a layer which can
efficiently inhibit holes from moving.
[0120] Compounds optionally selected from compounds which have so
far been conventionally used as electron transport materials in
photoconductive materials and publicly known compounds used for an
electron injection layer and an electron transport layer of an
organic electroluminescent device can be used as the materials used
for the electron transport layer and the electron injection
layer.
[0121] To be specific, the compounds include pyridine derivatives,
naphthalene derivatives, anthracene derivatives, phenanthroline
derivatives, perynone derivatives, coumarin derivatives,
naphthalimide derivatives, anthraquinone derivatives,
diphenoquinone derivatives, diphenylquinone derivatives, perylene
derivatives, thiophene derivatives, thiadiazole derivatives,
quinoxaline derivatives, polymers of quinoxaline derivatives,
benzazole compounds, pyrazole derivatives, perfluorinated phenylene
derivatives, triazine derivatives, pyrazine derivatives,
imidazopyridine derivatives, borane derivatives, benzoxazole
derivatives, benzothiazole derivatives, quinoline derivatives,
aldazine derivatives, carbazole derivatives, indole derivatives,
phosphorus oxide derivatives, bisstyryl derivatives and the like.
Further, they include oxazole derivatives
(1,3-bis[(4-t-butylphenyl)-1,3,4-oxadiazolyl]phenylene and the
like), triazole derivatives (N-naphthyl-2,5-diphenyl-1,3,4-triazole
and the like), benzoquinoline derivatives
(2,2'-bis(benzo[h]quinoline-2-yl)-9,9'-spirobifluorene and the
like), benzimidazole derivatives
(tris(N-phenylbenzimidazole-2-yl)benzene and the like), bipyridine
derivatives, terpyridine derivatives
(1,3-bis(4'-(2,2',:6',2''-terpyridinyl))benzene and the like),
naphthyridine derivatives
(bis(1-naphthyl)-4-(1,8-naphthyridine-2-yl)phenylphosphine oxide
and the like) and the like. The materials may be used alone or in a
mixture with different materials.
[0122] Further, metal complexes having electron accepting nitrogen
can be used as well and include, for example, quinolinol metal
complexes, hydroxyazole complexes such as hydroxyphenyloxazole
complexes, azomethine complexes, tropolone metal complexes,
flavonol metal complexes, benzoquinoline metal complexes and the
like. The materials may be used alone or in a mixture with
different materials.
[0123] Among the compounds, the quinolinol metal complexes, the
pyridine derivatives or the phenanthroline derivatives are
preferred.
[0124] The quinolinol metal complexes are compounds represented by
Formula (E-1) shown below:
##STR00026##
wherein R.sub.1 to R.sub.6 are hydrogen or a substituent; M is Al,
Ga, Be or Zn; and n is an integer of 2 or 3.
[0125] The specific examples of the quinolinol metal complexes
include tris(8-quinolinolate)aluminum (hereinafter abbreviated as
ALQ), tris(4-methyl-8-quinolinolate)aluminum,
tris(5-methyl-8-quinolinolate)aluminum,
tris(3,4-dimethyl-8-quinolinolate)aluminum,
tris(4,5-dimethyl-8-quinolinolate)aluminum,
tris(4,6-dimethyl-8-quinolinolate)aluminum,
bis(2-methyl-8-quinolinolate)(phenolate)aluminum,
bis(2-methyl-8-quinolinolate)(2-methylphenolate)aluminum,
bis(2-methyl-8-quinolinolate)(3-methylphenolate)aluminum,
bis(2-methyl-8-quinolinolate)(4-methylphenolate)aluminum,
bis(2-methyl-8-quinolinolate)(2-phenylphenolate)aluminum,
bis(2-methyl-8-quinolinolate)(3-phenylphenolate)aluminum,
bis(2-methyl-8-quinolinolate)(4-phenylphenolate)aluminum,
bis(2-methyl-8-quinolinolate)(2,3-dimethylphenolate)aluminum,
bis(2-methyl-8-quinolinolate)(2,6-dimethylphenolate)aluminum,
bis(2-methyl-8-quinolinolate)(3,4-dimethylphenolate)aluminum,
bis(2-methyl-8-quinolinolate)(3,5-dimethylphenolate)aluminum,
bis(2-methyl-8-quinolinolate)(3,5-di-t-butylphenolate)aluminum,
bis(2-methyl-8-quinolinolate)(2,6-diphenylphenolate)aluminum,
bis(2-methyl-8-quinolinolate)(2,4,6-triphenylphenolate)aluminum,
bis(2-methyl-8-quinolinolate)(2,4,6-trimethylphenolate)aluminum,
bis(2-methyl-8-quinolinolate)(2,4,5,6-tetramethylphenolate)aluminum,
bis(2-methyl-8-quinolinolate)(1-naphtholate)aluminum,
bis(2-methyl-8-quinolinolate)(2-naphtholate)aluminum,
bis(2,4-dimethyl-8-quinolinolate)(2-phenylphenolate) aluminum,
bis(2,4-dimethyl-8-quinolinolate)(3-phenylphenolate)aluminum,
bis(2,4-dimethyl-8-quinolinolate)(4-phenylphenolate)aluminum,
bis(2,4-dimethyl-8-quinolinolate)(3,5-dimethylphenolate)aluminum,
bis(2,4-dimethyl-8-quinolinolate)(3,5-di-t-butylphenolate)aluminum,
bis(2-methyl-8-quinolinolate)aluminum-.mu.-oxo-bis(2-methyl-8-quinolinola-
te)aluminum,
bis(2,4-dimethyl-8-quinolinolate)aluminum-.mu.-oxo-bis(2,4-dimethyl-8-qui-
nolinolate)aluminum,
bis(2-methyl-4-ethyl-8-quinolinolate)aluminum-.mu.-oxo-bis(2-methyl-4-eth-
yl-8-quinolinolate) aluminum,
bis(2-methyl-4-methoxy-8-quinolinolate)aluminum-1-oxo-bis(2-methyl-4-meth-
oxy-8-quinolinolate)aluminum,
bis(2-methyl-5-cyano-8-quinolinolate)aluminum-.mu.-oxo-bis(2-methyl-5-cya-
no-8-quinolinolate) aluminum,
bis(2-methyl-5-trifluoromethyl-8-quinolinolate)aluminum-p-oxo-bis(2-methy-
l-5-trifluoromethyl-8-quinolinolate)aluminum,
bis(10-hydroxybenzo[h]quinoline)beryllium and the like.
[0126] The pyridine derivatives are compounds represented by
Formula (E-2-1) or (E-2-2) shown below:
##STR00027##
wherein R.sub.1 to R.sub.5 are hydrogen or a substituent, and the
adjacent groups may be combined with each other to form condensed
ring(s); G represents a mere bond or an n-valent linkage group; and
n is an integer of 2 to 8.
[0127] G in Formula (E-2-2) includes, for example, groups shown by
the following structural formulas. R(s) in the following structural
formulas each are independently hydrogen, methyl, ethyl, isopropyl,
cyclohexyl, phenyl, 1-naphthyl or 2-naphthyl.
##STR00028## ##STR00029##
[0128] The specific examples of the pyridine derivative include,
for example,
2,5-bis(2,2'-bipyridyl-6-yl)-1,1-dimethyl-3,4-diphenylsilole,
2,5-bis(2,2'-bipyridyl-6-yl)-1,1-dimethyl-3,4-dimesitylsilole
(hereinafter abbreviated as ET1),
9,10-di(2,2'-bipyridyl-6-yl)anthracene,
9,10-di(2,2'-bipyridyl-5-yl)anthracene,
9,10-di(2,3'-bipyridyl-6-yl)anthracene,
9,10-di(2,3'-bipyridyl-5-yl)-2-phenylanthracene,
9,10-di(2,2'-bipyridyl-5-yl)-2-phenylanthracene,
3,4-diphenyl-2,5-di(2,2'-bipyridyl-6-yl)thiophene,
3,4-diphenyl-2,5-di(2,3'-bipyridyl-5-yl)thiophene,
6',6''-di(2-pyridyl)-2,2':4',4'':2'':2'''-quaterpyridine and the
like.
[0129] The phenanthroline derivatives are compounds represented by
Formula (E-3-1) or (E-3-2) shown below:
##STR00030##
wherein R.sub.1 to R.sub.5 are hydrogen or a substituent, and the
adjacent groups may be combined with each other to form condensed
ring(s); G represents a mere bond or an n-valent linkage group; and
n is an integer of 2 to 8. G in Formula (E-3-2) includes, for
example, the same groups as explained in the column of the pyridine
derivatives.
[0130] The specific examples of the phenanthroline derivative
include 4,7-diphenyl-1,10-phenanthroline,
2,9-dimethyl-4,7-diphenyl-1,10-phenanthroline,
9,10-di(1,10-phenanthroline-2-yl)anthracene,
2,6-di(1,10-phenanthroline-5-yl)pyridine,
1,3,5-tri(1,10-phenanthroline-5-yl)benzene,
9,9'-difluoro-bis(1,10-phenanthroline-5-yl), bathocuproine,
1,3-bis(2-phenyl-1,10-phenanthroline-9-yl)benzene and the like.
[0131] In particular, a case where the phenanthroline derivative is
used for the electron transport layer or the electron injection
layer shall be explained. Materials which are excellent in thermal
stability and thin film forming property are desired in order to
obtain stable light emitting for a long time, and among the
phenanthroline derivatives, preferred are compounds in which a
substituent itself has a three-dimensional steric structure,
compounds having a three-dimensional steric structure due to steric
repulsion against a phenanthroline skeleton or an adjacent
substituent and compounds obtained by linking plural phenanthroline
skeletons. Further, in the case of the compounds obtained by
linking plural phenanthroline skeletons, more preferred are the
compounds containing a conjugate bond, substituted or
non-substituted aromatic hydrocarbon or substituted or
non-substituted aromatic heterocycle in a linkage unit.
<Cathode in the Organic Electroluminescent Device>
[0132] The cathode 108 plays a role of injecting electrons into the
emission layer 105 via the electron injection layer 107 and the
electron transport layer 106.
[0133] A material for forming the cathode 108 shall not
specifically be restricted as long as it is a material which can
efficiently inject electrons into the organic layers, and the same
materials as the materials for forming the anode 102 can be used.
Among them, preferred are metals such as tin, magnesium, indium,
calcium, aluminum, silver, copper, nickel, chromium, gold,
platinum, iron, zinc, lithium, sodium, potassium, and cesium and
alloys thereof (magnesium-silver alloys, magnesium-indium alloys
and aluminum-lithium alloys such as lithium fluoride/aluminum
alloys) and the like. Lithium, sodium, potassium, cesium, calcium,
magnesium and alloys containing the metals having a low work
function are effective for elevating the electron injection
efficiency to enhance the device characteristics. However, the
metals having a low work function are usually instable in the air
in many cases. In order to solve this issue a method in which a
small amount of lithium, cesium or magnesium is doped in an organic
layer to use an electrode having high stability is known. As other
dopants, inorganic salts such as lithium fluoride, cesium fluoride,
lithium oxide and cesium oxide can be used as well. However, it
shall not be restricted to the materials.
[0134] Further, a preferred example for protecting the electrodes
includes lamination of metals such as platinum, gold, silver,
copper, iron, tin, aluminum and indium, alloys using these metals,
inorganic substances such as silica, titania and silicon nitride,
polyvinyl alcohol, polyvinyl chloride, hydrocarbon high molecular
compounds and the like. A method for preparing the electrodes shall
not specifically be restricted as long as the electrodes can
conduct electricity and comprises resistance heating, electron
beam, sputtering, ion plating, coating and the like.
<Binder which May be Used in the Respective Layers>
[0135] The materials used for the hole injection layer, the hole
transport layer, the emission layer, the electron transport layer
and the electron injection layer each described above can form
alone the respective layers, and the materials which are dispersed
in solvent-soluble resins such as polyvinyl chloride,
polycarbonate, polystyrene, poly(N-vinylcarbazole), polymethyl
methacrylate, polybutyl methacrylate, polyester, polysulfone,
polyphenylene oxide, polybutadiene, hydrocarbon resins, ketone
resins, phenoxy resins, polysulfone, polyamide, ethyl cellulose,
vinyl acetate resins, ABS resins and polyurethane resins; curing
resins such as phenol resins, xylene resins, petroleum resins, urea
resins, melamine resins, unsaturated polyester resins, alkyd
resins, epoxy resins and silicon resins; and the like as high
molecular binders can be used as well.
<Preparing Method for the Organic Electroluminescent
Device>
[0136] The respective layers constituting the organic
electroluminescent device can be formed by forming thin films from
the materials for constituting the respective layers by methods
such as a vapor deposition method, resistance heating deposition,
electron beam deposition, sputtering, a molecular lamination
method, a printing method, a spin cast method, a cast method and a
coating method. The film thicknesses of the respective layers thus
formed shall not specifically be restricted and can suitably be set
according to the properties of the materials, and they fall usually
in a range of 2 nm to 5000 nm. The film thickness can usually be
measured by means of a quartz oscillation type film thickness
measuring apparatus and the like. When a thin film is formed by a
deposition method, deposition conditions thereof are varied
depending on the kind of the materials, the crystal structure and
the aggregate structure which are aimed by the film, and the like.
In general, the deposition conditions can suitably be set
preferably in the ranges of a boat heating temperature of 50 to
400.degree. C., a vacuum degree of 10.sup.-6 to 10.sup.-3 Pa, a
deposition rate of 0.01 to 50 nm/second, a substrate temperature of
-150 to +300.degree. C. and a film thickness of 2 nm to 5
.mu.m.
[0137] Next, a preparing method for an organic electroluminescent
device comprising an anode/a hole injection layer/a hole transport
layer/an emission layer comprising a host material and a dopant
material/an electron transport layer/an electron injection layer/a
cathode shall be explained as one example of a preparing method for
the organic electroluminescent device. A thin film of an anode
material is formed on a suitable substrate by a vapor deposition
method and the like to prepare an anode, and then the thin films of
a hole injection layer and a hole transport layer are formed on the
anode. A host material and a dopant material are co-deposited
thereon to form a thin film, whereby an emission layer is prepared,
and an electron transport layer and an electron injection layer are
formed on the emission layer. Further, a thin film comprising a
substance for a cathode is formed thereon by a vapor deposition
method and the like to prepare a cathode, whereby the targeted
organic electroluminescent device is obtained. In preparing the
organic electroluminescent device described above, the preparing
order can be turned upside down to prepare it as well in the order
of the cathode, the electron injection layer, the electron
transport layer, the emission layer, the hole transport layer, the
hole injection layer and the anode.
[0138] When direct voltage is applied to the organic
electroluminescent device thus obtained, it may be applied with the
anode being set to a polarity of + and the cathode being set to a
polarity of -, and when a voltage of 2 to 40 V is applied, emission
can be observed from a transparent or translucent electrode side
(the anode or the cathode and both). This organic
electroluminescent device emits light as well when applying a pulse
current and an alternating current. A waveform of the alternating
current applied may be optional.
<Application Examples of the Organic Electroluminescent
Device>
[0139] The present invention can be applied as well to display
units equipped with an organic electroluminescent device, lighting
instruments equipped with an organic electroluminescent device and
the like.
[0140] The display units or lighting instruments equipped with an
organic electroluminescent device can be produced by such publicly
known methods that the organic electroluminescent device according
to the present embodiment is connected with publicly known drive
apparatuses, and they can be driven by suitably using publicly
known drive methods such as direct current drive, pulse drive,
alternating current drive and the like.
[0141] The display unit includes, for example, panel displays such
as color flat panel displays and flexible displays such as flexible
color electroluminescent (EL) displays (refer to, for example, JP
H10-335066 A/1998, JP H15-321546 A/2003, JP H16-281086 A/2004 and
the like). A display system of the displays includes, for example,
a matrix and/or segment display system and the like. A matrix
display system and a segment display system may be coexistent in
the same panel.
[0142] A matrix means a state in which pixels for display are
two-dimensionally arranged in a lattice form, a mosaic form and the
like, and characters and images are displayed by aggregate of the
pixels. The form and the size of the pixels are determined by
applications. For example, square pixels having a side of 300 .mu.m
or less are usually used for display of images and characters in
personal computers, monitors and TV. In the case of a large-sized
display such as display panels, pixels having a side of mm order
are used. In the case of monochrome display, pixels having the same
color are arranged, and in the case of color display, red, green
and blue pixels are arranged for display. In this case, to be
typical, a delta type and a stripe type are available. A drive
method of this matrix may be either a linear sequential drive
method or an active matrix. The linear sequential drive method has
the advantage that it has a simpler structure. However, considering
the operation characteristics, the active matrix is more excellent
in a certain case, and therefore this has to be used separately
depending on the applications.
[0143] In the segment system (type), patterns are formed so that
informations determined in advance are displayed, and light is
emitted in a determined area. It includes, for example, display of
time and temperature in digital watches and thermometers, display
of operation states in audio instruments and electromagnetic
cookers and display of panels in automobiles.
[0144] The lighting instrument includes, for example, lighting
instruments such as indoor lighting instruments, backlights for
liquid crystal displays and the like (refer to, for example, JP
H15-257621 A/2003, JP H15-277741 A/2003, JP H16-119211 A/2004 and
the like). The backlights are used principally for a purpose of
enhancing a visibility of display equipments which do not
spontaneously emit light, and they are used for liquid crystal
displays, watches, audio instruments, car panels, display boards,
indicators and the like. In particular, considering that backlights
of a conventional system for uses in liquid crystal displays,
especially, personal computers in which a reduction in a size is a
problem comprise fluorescent lumps and optical waveguides, so that
it is difficult to reduce in a thickness thereof, a backlight using
the light emitting device according to the present embodiment is
characterized by that it is reduced in a thickness and has a
lightweight.
<Synthetic Example of Benzofluorene Compound>
[0145] Next, the physical property values of some of the
benzofluorene compounds synthesized are shown in Table 1. The
respective physical property values are measured by the following
methods. The glass transition temperatures which are quideposts for
the melting points and the heat resistances were measured by means
of Diamond DSC manufactured by Perkin Elmer Co., Ltd. (measuring
conditions: cooling rate 200.degree. C./minute, heating rate
10.degree. C./minute). The UV absorption wavelengths were measured
by means of a V-560 type spectrophotometer manufactured by JASCO
Corporation, in which an excitation wavelength was set to 254
nm.
TABLE-US-00001 TABLE 1 UV absorption wave- length Solubility
maximum (25.degree. C.) Solubility Melting value g/100 ml
(25.degree. C.) point (nm) (ethyl g/100 ml Compound (.degree. C.)
Tg (.degree. C.) (MeOH) acetate) (toluene) ##STR00031## 270 151 360
1 8 ##STR00032## 318 155 360 -- -- ##STR00033## 301 140 349 0.2 0.9
##STR00034## 61 53 360 -- -- ##STR00035## 64 54 348 -- --
##STR00036## 284.9 129.2 406 -- -- ##STR00037## -- -- 392 -- --
[0146] It can be found from the above-mentioned results that the
glass transition temperatures of the compound (1-13) and the
compound (1-4) are apparently higher than those of the compound
(2), (3) and (4). The compound (1-13) and the compound (1-4) have
higher glass transition temperature than those of the compounds (3)
and (4), because substitution with alkyl in a five-membered ring of
the benzofluorene skeleton provides the lower glass transition
temperature than in substitution with aryl such as phenyl. The same
tendency shall be observed in the case of the compound (1'-1) in
which a substituent on a five-membered ring of the benzofluorene
skeleton is phenyl.
[0147] Further, it can be found that the compound (1-13) is
apparently more excellent in solubility in the solvents than the
compound (2). This is considered to be attributed to the fact that
the compound (1-13) has a benzo[c] skeleton. It is estimated that
the same tendency shall be observed in the case of the compound
(1-4) and the compound (1'-1) having the benzo[c] skeleton.
[0148] In Table 1, the benzofluorene compounds according to the
present invention are only the compound (1-13), the compound (1-4),
the compound (1'-1) and the compound (1'-15) in which Ar.sup.1 and
Ar.sup.2 in Formula (1) described above are phenyl, and when the
compounds in which Ar.sup.1 and Ar.sup.2 are, for example,
biphenylyl are applied to a light emitting device, they have the
same performances as those of the compound (1-13), the compound
(1-4), the compound (1'-1) and the compound (1'-15). Also, the
compound (1-13) is the compound in which R.sup.1 and R.sup.2 in
Formula (1) described above are 2-naphthyl, and when all the
compounds in which R.sup.1 and R.sup.2 are suitably selected from,
for example, phenyl, biphenylyl, terphenylyl, quaterphenylyl,
naphthyl and phenanthryl are applied to a light emitting device,
they have the same performances as that of the compound (1-13). As
a result of further experiment, when the compound (1-4), for
example, in which R.sup.1 and R.sup.2 are selected from biphenylyl
is applied to a light emitting device, it has the same performances
as that of the compound (1-13). Further, the compound (1'-1) is the
compound in which R.sup.1 and R.sup.2 in Formula (1') described
above are N,N-diphenylamino, and when all the compounds in which
R.sup.1 and R.sup.2 are suitably selected from, for example,
N,N-di(biphenylyl)amino and N,N-dinaphthylamino are applied to a
light emitting device, they have the same performances as that of
the compound (1'-1). Also, the compound (1'-15) is the compound in
which R.sup.1 in Formula (1') described above is N,N-diphenylamino,
and when all the compounds in which R.sup.1 is suitably selected
from, for example, N,N-di(biphenylyl)amino and N,N-dinaphthylamino
are applied to a light emitting device, they have the same
performances as that of the compound (1'-15).
[0149] The synthetic examples of the compound (1-13), the compound
(1-4), the compound (2), the compound (3), the compound (4), the
compound (1'-1) and the compound (1'-15) shall be explained
below.
<Synthetic Example of the Compound (1-13)>
[0150]
7,7-Diphenyl-5,9-bis(trifluoromethanesulfonyloxy)-7H-benzo[c]fluore-
ne 6.66 g and 2-naphthyleneboronic acid 5.16 g were dissolved in
100 ml of a mixed solvent of tetrahydrofuran and isopropyl alcohol
(tetrahydrofuran/isopropyl alcohol=1/4 (volume ratio)) under
nitrogen atmosphere, and 1.16 g of
tetrakis(triphenylphosphine)palladium (0) was added thereto, and
the mixture was stirred for 5 minutes. Then, 12.7 g of potassium
phosphate was added thereto, and the mixture was refluxed for 4
hours. After finishing the reaction, 50 ml of the solvent was
removed. Water 100 ml was added thereto, and the precipitate was
filtered. The precipitate was further washed with water and
methanol to obtain a crude product of the compound (1-13). The
crude product was subjected to column refining (solvent:
heptane/toluene=3/1 (volume ratio)) with silica gel and then
refined by sublimation to obtain 5.0 g of the targeted compound
(1-13) (yield: 80.5%).
[0151] The structure of the compound (1-13) was confirmed by an MS
spectrum and NMR measurement.
[0152] .sup.1H-NMR (CDCl.sub.3) .sigma.=8.93 (d, 1H), 8.53 (d, 1H),
8.06 to 8.04 (m, 2H), 7.93 to 7.21 (m, 28H)
<Synthetic Example of the Compound (1-4)>
[0153] 5,9-Dibrome-7,7-diphenyl-7H-benzo[c]fluorene 5.26 g and
biphenyl boronic acid 4.36 g were dissolved in 50 ml of a mixed
solvent of toluene and ethanol (toluene/ethanol=4/1 (volume ratio))
under nitrogen atmosphere, and 0.69 g of
tetrakis(triphenylphosphine)palladium (0) was added thereto, and
the mixture was stirred for 5 minutes. Then, 20 ml of 2M sodium
hydrogencarbonate aqueous solution was added thereto, and the
mixture was refluxed for 8 hours. After finishing the heating, the
reaction mixture was cooled, and the organic layer was isolated and
washed with saturated saline and then dried with anhydrous
magnesium sulfate. Then, the desiccant agent was removed and the
solvent was distilled away under reduced pressure to obtain a solid
material. The solid material was subjected to column refining
(solvent: heptane/toluene=3/1 (volume ratio)) with silica gel and
then refined by sublimation to obtain 3.9 g of the targeted
compound (1-4) (yield: 58%).
[0154] The structure of the compound (1-4) was confirmed by an MS
spectrum and NMR measurement.
[0155] .sup.1H-NMR (CDCl.sub.3) .sigma.=8.91 (d, 1H), 8.49 (d, 1H),
8.11 (d, 1H), 7.79 to 7.77 (m, 2H), 7.73 to 7.20 (m, 31H)
<Synthetic Example of the Compound (2)>
[0156] Synthesis of
3,9-dinaphthalene-2-yl-11,11-diphenyl-11H-benzo[a]fluorene was
carried out by the following method.
[0157]
11,11-Diphenyl-3,9-bis(trifluoromethanesulfonyloxy)-11H-benzo[a]flu-
orene 6.66 g and 2-naphthyleneboronic acid 5.16 g were dissolved in
100 ml of a mixed solvent of tetrahydrofuran and isopropyl alcohol
(tetrahydrofuran/isopropyl alcohol=1/4 (volume ratio)) under
nitrogen atmosphere, and 1.16 g of
tetrakis(triphenylphosphine)palladium (0) was added thereto, and
the mixture was stirred for 5 minutes. Then, 12.7 g of potassium
phosphate was added thereto, and the mixture was refluxed for 4
hours. After finishing the reaction, 50 ml of the solvent was
removed. Water 100 ml was added thereto, and the precipitate was
filtered. The precipitate was further washed with water and
methanol to obtain a crude product of the compound (2). The crude
product was subjected to column refining (solvent:
heptane/toluene=3/1 (volume ratio)) with silica gel and then
refined by sublimation to obtain 4.2 g of the targeted compound (2)
(yield: 67.6%).
[0158] The structure of the compound (2) was confirmed by an MS
spectrum and NMR measurement.
[0159] .sup.1H-NMR (CDCl.sub.3) .sigma.=8.23 (d, 1H), 8.1 to 8.08
(m, 3H), 7.98 to 7.67 (m, 14H), 7.51 to 7.42 (m, 8H), 7.27 to 7.22
(m, 6H)
<Synthetic Example of the Compound (3)>
[0160] Synthesis of
7,7-Dihexyl-5,9-di-naphthalene-2-yl-7H-benzo[c]fluorene was carried
out by the following method.
[0161] 5,9-Dibromo-7,7-dihexyl-7H-benzo[c]fluorene 5.42 g and
2-naphtylene boronic acid 3.78 g were dissolved in 50 ml of a mixed
solvent of toluene and ethanol (toluene/ethanol=4/1 (volume ratio))
under nitrogen atmosphere, and 0.69 g of
tetrakis(triphenylphosphine)palladium (0) was added thereto, and
the mixture was stirred for 5 minutes. Then, 20 ml of 2M sodium
hydrogencarbonate aqueous solution was added thereto, and the
mixture was refluxed for 7 hours. After finishing the heating, the
reaction mixture was cooled, and the organic layer was isolated and
washed with saturated saline and then dried with anhydrous
magnesium sulfate. Then, the desiccant agent was removed and the
solvent was distilled away under reduced pressure to obtain a crude
product. The crude product was subjected to column refining
(solvent: heptane/toluene=3/1 (volume ratio)) with silica gel and
then refined by sublimation to obtain 4.4 g of the targeted
compound (3) (yield: 69%).
[0162] The structure of the compound (3) was confirmed by an MS
spectrum and NMR measurement.
[0163] .sup.1H-NMR (CDCl.sub.3) .sigma.=8.89 (d, 1H), 8.46 (d, 1H),
8.17 to 7.25 (m, 20H), 2.20 to 2.10 (m, 4H), 1.14 to 1.00 (m, 12H),
0.76 to 0.69 (m, 10H)
<Synthetic Example of the Compound (4)>
[0164] Synthesis of
11,11-Dihexyl-3,9-di-naphthalene-2-yl-11H-benzo[a]fluorene was
carried out by the following method.
[0165]
11,11-Dihexyl-3,9-bis(trifluoromethanesulfonyloxy)-11H-benzo[a]fluo-
rene 6.81 g and 2-naphthyleneboronic acid 4.13 g were dissolved in
100 ml of a mixed solvent of tetrahydrofuran and isopropyl alcohol
(tetrahydrofuran/isopropyl alcohol=1/4 (volume ratio)) under
nitrogen atmosphere, and 1.16 g of
tetrakis(triphenylphosphine)palladium (0) was added thereto, and
the mixture was stirred for 5 minutes. Then, 12.7 g of potassium
phosphate was added thereto, and the mixture was refluxed for 5
hours. After finishing the reaction, 50 ml of the solvent was
removed. Water 100 ml was added thereto, and the precipitate was
filtered. The precipitate was further washed with water and
methanol to obtain a crude product of the compound (4). The crude
product was subjected to column refining (solvent:
heptane/toluene=5/1 (volume ratio)) with silica gel and then
refined by sublimation to obtain 5.1 g of the targeted compound (4)
(yield: 80%).
[0166] The structure of the compound (4) was confirmed by an MS
spectrum and NMR measurement.
[0167] .sup.1H-NMR (CDCl.sub.3) .sigma.=8.34 (d, 1H), 8.31 (d, 1H),
8.23 (d, 1H), 8.15 (d, 1H), 8.01 to 7.87 (m, 12H), 7.80 to 7.77 (m,
2H), 7.56 to 7.49 (m, 4H), 2.60 to 2.33 (m, 4H), 1.03 to 0.93 (m,
12H), 0.71 to 0.68 (t, 6H), 0.60 to 0.48 (m, 4H)
<Synthetic Example of the Compound (1'-1)>
[0168] 5,9-Dibromo-7,7-diphenyl-7H-benzo[c]fluorene 2.5 g and
diphenylamine 1.6 g were dissolved in 100 ml of dehydrated xylene
under nitrogen atmosphere, and palladium acetate 1.5 mg, sodium
t-butoxide 0.98 g and tri(t-butyl)phosphine 14 mg was added thereto
and refluxed for 4 hours. After finishing the reaction, water 100
ml was added thereto, and the organic layer was washed with water
in a separating funnel. The aqueous layer was removed, and then the
organic layers were put together and concentrated by means of a
rotary evaporator to obtain a crude product. The crude product was
subjected to column refining (solvent: heptane/toluene=3/1 (volume
ratio)) with silica gel and then refined by sublimation to obtain
450 mg of the targeted compound (1'-1) (yield: 13%)
[0169] The structure of the compound (1'-1) was confirmed by an MS
spectrum and NMR measurement.
[0170] .sup.1H-NMR (CDCl.sub.3) .sigma.=8.70 (d, 1H), 8.16 (d, 1H),
8.02 (d, 1H), 7.56 (t, 1H), 7.37 to 7.34 (m, 2H), 7.58 to 6.86 (m,
32H)
<Synthetic Example of the Compound (1'-15)>
[0171] 5-Bromo-9-phenyl-7,7-diphenyl-7H-benzo[c]fluorene 1.4 g and
diphenylamine 0.5 g were dissolved in 30 ml of dehydrated xylene
under nitrogen atmosphere, and palladium acetate 3.0 mg, sodium
t-butoxide 0.89 g and tri(t-butyl)phosphine 15 mg was added thereto
and refluxed for 4 hours. After finishing the reaction, water 30 ml
was added thereto, and the organic layer was washed with water in a
separating funnel. The aqueous layer was removed, and then the
organic layers were put together and concentrated by means of a
rotary evaporator to obtain 1.1 g of the targeted compound (1'-15)
(yield: 64%). The structure of the compound (1'-15) was confirmed
by an MS spectrum.
[0172] The other benzofluorene compounds of the present invention
can be synthesized according to the synthetic examples described
above by suitably selecting the compounds of the raw materials.
EXAMPLES
[0173] Organic electroluminescent devices according to Examples 1,
2, 3, 4 and 5 and Comparative Example 1, 2, 3 and 4 were prepared
to measure voltage (V) which is a characteristic in emission of 100
cd/m.sup.2, current density (mA/cm.sup.2), luminous efficiency
(lm/W), current efficiency (cd/A), emission wavelength (nm),
chromaticity (x, y), external quantum efficiency (%) and luminance
retention rate (%) after 200 hours in an initial luminance of 1000
cd/m.sup.2 or elapsed time at luminance retention rate 70% in an
initial luminance of 2000 cd/m.sup.2. Examples 1, 2, 3, 4 and 5 and
Comparative Example 1, 2, 3 and 4 shall be explained below in
details.
[0174] The material compositions of the respective layers in the
organic electroluminescent devices prepared in Examples 1, 2, 3 and
4 and Comparative Example 1, 2 and 3 are shown in the following
Table 2.
TABLE-US-00002 TABLE 2 Hole Hole Electron injection transport
transport layer layer Host Dopant layer Example 1 CuPc NPD Compound
D1 ALQ 1-13 Example 2 CuPc NPD Compound D1 ET1 1-13 Example 3 CuPc
NPD Compound D1 ALQ 1-4 Example 4 CuPc NPD Compound D1 ET2 1-4
Example 5 CuPc NPD BH1 Compound ALQ 1'-1 Comparative CuPc NPD
Compound D1 ALQ Example 1 2 Comparative CuPc NPD Compound D1 ALQ
Example 2 3 Comparative CuPc NPD Compound D1 ET2 Example 3 3
Comparative CuPc NPD Compound D1 ET2 Example 4 4
[0175] In Table 2, Compound (1-13), Compound (1-4), Compound
(1'-1), Compound (2), Compound (3) and Compound (4) each show
Compound (1-13), Compound (1-4), Compound (1'-1), Compound (2),
Compound (3) and Compound (4) in Table 1. In Table 2, CuPc is
copper phthalocyanine; NPD is
N,N'-di(1-naphthyl)-N,N'-diphenylbenzidine; D1 is
N,N,N',N'-tetra(4-biphenylyl)-4,4-diaminostilbene; ALQ is
tris(8-quinolinolate)aluminum; ET1 is
2,5-bis(2,2'-bipyridyl-6-yl)-1,1-dimethyl-3,4-dimesitylsilole; ET2
is 2,21,2''-(1,3,5-phenylene)tris(1-phenyl-1H-benzimidazole); and
BH1 is
9-phenyl-10-(6-[1,1':3',1'']terphenyl-5'-yl-naphthalene-2-yl)-anthracene.
They each have the following chemical structural formulas.
##STR00038## ##STR00039##
Example 1
[0176] A glass substrate of 26 mm.times.28 mm.times.0.7 mm on which
ITO was deposited in a thickness of 150 nm was used as a
transparent substrate. This transparent substrate was fixed on a
substrate holder of a commercial deposition system, and loaded
therein were a molybdenum-made boat for deposition containing CuPc,
a molybdenum-made boat for deposition containing NPD, a
molybdenum-made boat for deposition containing the compound (1-13),
a molybdenum-made boat for deposition containing D1, a
molybdenum-made boat for deposition containing ALQ, a
molybdenum-made boat for deposition containing lithium fluoride and
a tungsten-made boat for deposition containing Aluminum.
[0177] A vacuum chamber was reduced in pressure up to
5.times.10.sup.-4 Pa, and the boat for deposition containing CuPc
was heated to deposit it in a layer thickness of 20 nm, whereby a
hole injection layer was formed. Then, the boat for deposition
containing NPD was heated to deposit it in a layer thickness of 30
nm, whereby a hole transport layer was formed. Next, the
molybdenum-made boat for deposition containing Compound (1-13) and
the molybdenum-made boat for deposition containing D1 were heated
to co-deposit both compounds in a layer thickness of 30 nm, whereby
an emission layer was formed. In this regard, a doping
concentration of D1 was about 5% by weight. Next, the boat for
deposition containing ALQ was heated to deposit it in a layer
thickness of 20 nm, whereby an electron transport layer was formed.
The deposit rates of the layers described above were 0.01 to 1
nm/second.
[0178] Thereafter, the boat for deposition containing lithium
fluoride was heated to deposit it at a deposition rate of 0.003 to
0.1 nm/second so that a layer thickness was 0.5 nm, and then the
boat for deposition containing aluminum was heated to deposit it at
a deposition rate of 0.01 to 10 nm/second so that a layer thickness
was 100 nm, whereby an organic EL device was obtained.
[0179] With the ITO electrode set to an anode and the lithium
fluoride/aluminum electrode set to a cathode, the characteristics
in emission of 100 cd/m.sup.2 were measured to find that the
voltage was 4.8 V; the current density was 1.7 mA/cm.sup.2; the
luminous efficiency was 3.7 .mu.m/W; the current efficiency was 5.7
cd/A; the emission wavelength was 455 nm; and the chromaticity was
(0.145, 0.162). Further, the external quantum efficiency was 5.0%,
and the current density in the external quantum efficiency was 10
mA/cm.sup.2. A constant current operation test was carried out at
current density for obtaining an initial luminance of 1000
cd/m.sup.2 to find that the luminance retention rate was 89.0%
after 200 hours passed.
Example 2
[0180] An organic EL device was obtained by a method according to
Example 1, except that ALQ used for the electron transport layer in
Example 1 was changed to ET1. With the ITO electrode set to an
anode and the lithium fluoride/aluminum electrode set to a cathode,
the characteristics in emission of 100 cd/m.sup.2 were measured to
find that the voltage was 3.7 V; the current density was 1.6
mA/cm.sup.2; the luminous efficiency was 5.4 .mu.m/W; the current
efficiency was 6.3 cd/A; the emission wavelength was 455 nm; and
the chromaticity was (0.145, 0.168). Further, the external quantum
efficiency was 4.9%, and the current density in the external
quantum efficiency was 10 mA/cm.sup.2. The constant current
operation test was carried out at current density for obtaining an
initial luminance of 1000 cd/m.sup.2 to find that the luminance
retention rate was 76.2% after 200 hours passed.
Example 3
[0181] A glass substrate of 26 mm.times.28 mm.times.0.7 mm on which
ITO was deposited in a thickness of 150 nm was used as a
transparent substrate. This transparent substrate was fixed on a
substrate holder of a commercial deposition system, and loaded
therein were a molybdenum-made boat for deposition containing CuPc,
a molybdenum-made boat for deposition containing NPD, a
molybdenum-made boat for deposition containing the compound (1-4),
a molybdenum-made boat for deposition containing D1, a
molybdenum-made boat for deposition containing ALQ, a
molybdenum-made boat for deposition containing lithium fluoride and
a tungsten-made boat for deposition containing Aluminum.
[0182] A vacuum chamber was reduced in pressure up to
5.times.10.sup.-4 Pa, and the boat for deposition containing CuPc
was heated to deposit it in a layer thickness of 50 nm, whereby a
hole injection layer was formed. Then, the boat for deposition
containing NPD was heated to deposit it in a layer thickness of 30
nm, whereby a hole transport layer was formed. Next, the
molybdenum-made boat for deposition containing Compound (1-4) and
the molybdenum-made boat for deposition containing D1 were heated
to co-deposit both compounds in a layer thickness of 35 nm, whereby
an emission layer was formed. In this regard, a doping
concentration of D1 was about 5% by weight. Next, the boat for
deposition containing ALQ was heated to deposit it in a layer
thickness of 15 nm, whereby an electron transport layer was formed.
The deposit rates of the layers described above were 0.01 to 1
nm/second.
[0183] Thereafter, the boat for deposition containing lithium
fluoride was heated to deposit it at a deposition rate of 0.003 to
0.1 nm/second so that a layer thickness was 0.5 nm, and then the
boat for deposition containing aluminum was heated to deposit it at
a deposition rate of 0.01 to 10 nm/second so that a layer thickness
was 100 nm, whereby an organic EL device was obtained.
[0184] With the ITO electrode set to an anode and the lithium
fluoride/aluminum electrode set to a cathode, the characteristics
in emission of 100 cd/m.sup.2 were measured to find that the
voltage was 4.6 V; the current density was 1.9 mA/cm.sup.2; the
luminous efficiency was 3.6 .mu.m/W; the current efficiency was 5.3
cd/A; the emission wavelength was 455 nm; and the chromaticity was
(0.141, 0.140). Further, the external quantum efficiency was 5.1%,
and the current density in the external quantum efficiency was 2
mA/cm.sup.2. A constant current operation test was carried out at
current density for obtaining an initial luminance of 2000
cd/m.sup.2 to find that the elapsed time at luminance retention
rate 70% was 165 hours.
Example 4
[0185] An organic EL device was obtained by a method according to
Example 3, except that ALQ used for the electron transport layer in
Example 3 was changed to ET2. With the ITO electrode set to an
anode and the lithium fluoride/aluminum electrode set to a cathode,
the characteristics in emission of 100 cd/m.sup.2 were measured to
find that the voltage was 4.4 V; the current density was 1.8
mA/cm.sup.2; the luminous efficiency was 4.0 .mu.m/W; the current
efficiency was 5.6 cd/A; the emission wavelength was 455 nm; and
the chromaticity was (0.141, 0.142). Further, the external quantum
efficiency was 5.4%, and the current density in the external
quantum efficiency was 2 mA/cm.sup.2. The constant current
operation test was carried out at current density for obtaining an
initial luminance of 2000 cd/m.sup.2 to find that the elapsed time
at luminance retention rate 70% was 88 hours.
Example 5
[0186] An organic EL device was obtained by a method according to
Example 1, except that the compound (1-13) used as the host in
Example 1 was changed to BH1 and that D1 used as the dopant was
changed to the compound (1'-1). With the ITO electrode set to an
anode and the lithium fluoride/aluminum electrode set to a cathode,
the characteristics in emission of 100 cd/m.sup.2 were measured to
find that the voltage was 5.3 V; the current density was 1.8
mA/cm.sup.2; the luminous efficiency was 3.3 .mu.m/W; the current
efficiency was 5.5 cd/A; the emission wavelength was 460 nm; and
the chromaticity was (0.140, 0.159). Further, the external quantum
efficiency was 5.2%, and the current density in the external
quantum efficiency was 10 mA/cm.sup.2. The constant current
operation test was carried out at current density for obtaining an
initial luminance of 1000 cd/m.sup.2 to find that the luminance
retention rate was 90.0% after 200 hours passed.
Comparative Example 1
[0187] An organic EL device was obtained by a method according to
Example 1, except that the compound (1-13) used as the host in
Example 1 was changed to the compound (2). With the ITO electrode
set to an anode and the lithium fluoride/aluminum electrode set to
a cathode, the characteristics in emission of 100 cd/m.sup.2 were
measured to find that the voltage was 5.2 V; the current density
was 1.7 mA/cm.sup.2; the luminous efficiency was 3.5 .mu.m/W; the
current efficiency was 5.8 cd/A; the emission wavelength was 456
nm; and the chromaticity was (0.145, 0.168). Further, the external
quantum efficiency was 4.8%, and the current density in the
external quantum efficiency was 10 mA/cm.sup.2. The constant
current operation test was carried out at current density for
obtaining an initial luminance of 1000 cd/m.sup.2 to find that the
luminance retention rate was 88.5% after 200 hours passed.
Comparative Example 2
[0188] An organic EL device was obtained by a method according to
Example 3, except that the compound (1-4) used as the host in
Example 3 was changed to the compound (3). With the ITO electrode
set to an anode and the lithium fluoride/aluminum electrode set to
a cathode, the characteristics in emission of 100 cd/m.sup.2 were
measured to find that the voltage was 5.3 V; the current density
was 19.5 mA/cm.sup.2; the luminous efficiency was 0.31 lm/W; the
current efficiency was 0.5 cd/A; the emission wavelength was 520
nm; and the chromaticity was (0.239, 0.523). Further, the external
quantum efficiency was 0.2%, and the current density in the
external quantum efficiency was 17.2 mA/cm.sup.2. Also, the organic
EL device has very low efficiency because it has ALQ
luminescence.
Comparative Example 3
[0189] An organic EL device was obtained by a method according to
Example 4, except that the compound (1-4) used as the host in
Example 4 was changed to the compound (3). With the ITO electrode
set to an anode and the lithium fluoride/aluminum electrode set to
a cathode, the characteristics in emission of 100 cd/m.sup.2 were
measured to find that the voltage was 4.7 V; the current density
was 2.6 mA/cm.sup.2; the luminous efficiency was 2.6 lm/W; the
current efficiency was 3.8 cd/A; the emission wavelength was 450
nm; and the chromaticity was (0.142, 0.114). Further, the external
quantum efficiency was 4.6%, and the current density in the
external quantum efficiency was 3.2 mA/cm.sup.2. The constant
current operation test was carried out at current density for
obtaining an initial luminance of 2000 cd/m.sup.2 to find that the
elapsed time at luminance retention rate 70% was 1 hour.
Comparative Example 4
[0190] An organic EL device was obtained by a method according to
Example 4, except that the compound (1-4) used as the host in
Example 4 was changed to the compound (4). With the ITO electrode
set to an anode and the lithium fluoride/aluminum electrode set to
a cathode, the characteristics in emission of 100 cd/m.sup.2 were
measured to find that the voltage was 4.8 V; the current density
was 2.4 mA/cm.sup.2; the luminous efficiency was 2.7 lm/W; the
current efficiency was 4.2 cd/A; the emission wavelength was 450
nm; and the chromaticity was (0.142, 0.120). Further, the external
quantum efficiency was 4.7%, and the current density in the
external quantum efficiency was 2.2 mA/cm.sup.2. The constant
current operation test was carried out at current density for
obtaining an initial luminance of 2000 cd/m.sup.2 to find that the
elapsed time at luminance retention rate 70% was 29 hours.
[0191] The performance evaluation results of the organic
electroluminescent devices prepared in Examples 1, 2, 3, 4 and 5
and Comparative Example 1, 2, 3 and 4 are summarized in the
following Table 3.
TABLE-US-00003 TABLE 3 Life Elapsed time External luminance at
luminance quantum retention rate retention rate Characteristics in
emission of 100 cd/m.sup.2 efficiency after 200 hours 70% (initial
Current Luminous Current Emission Current passed (initial
luminance: Voltage density efficiency efficiency wavelength
Chromaticity density luminance: 2000 cd/m.sup.2) V mA/cm.sup.2 lm/W
cd/A nm (x, y) % mA/cm.sup.2 1000 cd/m.sup.2) % hour Ex. 1 4.8 1.7
3.7 5.7 455 0.145, 0.162 5.0 10 89.0 -- Ex. 2 3.7 1.6 5.4 6.3 455
0.145, 0.168 4.9 10 76.2 -- Ex. 3 4.6 1.9 3.6 5.3 455 0.141, 0.140
5.1 2 -- 165 Ex. 4 4.4 1.8 4.0 5.6 455 0.141, 0.142 5.4 2 -- 88 Ex.
5 5.3 1.8 3.3 5.5 460 0.140, 0.159 5.2 10 90.0 -- Comp. 5.2 1.7 3.5
5.8 456 0.145, 0.168 4.8 10 88.5 -- Ex. 1 Comp. 5.3 19.5 0.3 0.5
520 0.239, 0.523 0.2 17.2 -- -- Ex. 2 Comp. 4.7 2.6 2.6 3.8 450
0.142, 0.114 4.6 3.2 -- 1 Ex. 3 Comp. 4.8 2.4 2.7 4.2 450 0.140,
0.120 4.7 2.2 -- 29 Ex. 4
[0192] It can be found from the result of Comparative Examples 2, 3
and 4 that substitution with alkyl in a five-membered ring of the
benzofluorene skeleton provides low luminous efficiency and current
efficiency of the EL devices, and short life.
INDUSTRIAL APPLICABILITY
[0193] According to the preferred embodiment of the present
invention, broader width in selecting the solvents in the synthesis
makes it possible to enhance freedom in the synthesis of the
compounds and employ free layer-forming means in forming the layers
of the light emitting device. Further, capable of being provided
are an organic electroluminescent device having better performances
in at least one of heat resistance, luminous efficiency, current
efficiency, device life and external quantum efficiency, a display
unit equipped with the same, a lighting instrument equipped with
the same and the like.
BRIEF EXPLANATION OF THE DRAWING
[0194] FIG. 1 is an outline cross-sectional drawing showing the
organic electroluminescent device according to the present
embodiment.
EXPLANATIONS OF CODES
[0195] 100 Organic electroluminescent device [0196] 101 Substrate
[0197] 102 Anode [0198] 103 Hole injection layer [0199] 104 Hole
transport layer [0200] 105 Emission layer [0201] 106 Electron
transport layer [0202] 107 Electron injection layer [0203] 108
Cathode
* * * * *