U.S. patent application number 11/994046 was filed with the patent office on 2009-02-12 for organic electroluminescent element material, organic electroluminescent element, display device and lighting device.
This patent application is currently assigned to KONICA MINOLTA HOLDINGS, INC.. Invention is credited to Eisaku Katoh, Tomohiro Oshiyama, Noriko Yasukawa.
Application Number | 20090039771 11/994046 |
Document ID | / |
Family ID | 37604255 |
Filed Date | 2009-02-12 |
United States Patent
Application |
20090039771 |
Kind Code |
A1 |
Oshiyama; Tomohiro ; et
al. |
February 12, 2009 |
ORGANIC ELECTROLUMINESCENT ELEMENT MATERIAL, ORGANIC
ELECTROLUMINESCENT ELEMENT, DISPLAY DEVICE AND LIGHTING DEVICE
Abstract
This invention provides an organic EL element, which can control
luminescence wavelength, exhibits high luminescence efficiency, and
has a prolonged emission life, and a lighting equipment and a
display device. They can be realized by an organic
electroluminescent element material characterized by a metal
complex having a structure represented by the following general
formula (A) as a partial structure.
Inventors: |
Oshiyama; Tomohiro; (Tokyo,
JP) ; Katoh; Eisaku; (Tokyo, JP) ; Yasukawa;
Noriko; (Tokyo, JP) |
Correspondence
Address: |
CANTOR COLBURN, LLP
20 Church Street, 22nd Floor
Hartford
CT
06103
US
|
Assignee: |
KONICA MINOLTA HOLDINGS,
INC.
Tokyo
JP
|
Family ID: |
37604255 |
Appl. No.: |
11/994046 |
Filed: |
June 6, 2006 |
PCT Filed: |
June 6, 2006 |
PCT NO: |
PCT/JP2006/311260 |
371 Date: |
December 27, 2007 |
Current U.S.
Class: |
313/504 ;
548/402; 556/1; 556/136 |
Current CPC
Class: |
C09K 2211/1088 20130101;
C09K 2211/1092 20130101; C07D 403/04 20130101; C09K 2211/1033
20130101; H01L 51/0042 20130101; C09K 2211/1011 20130101; C07D
409/14 20130101; C07D 401/14 20130101; C07D 417/14 20130101; C07D
413/14 20130101; C07D 231/12 20130101; H01L 51/0071 20130101; C07F
15/0086 20130101; H01L 51/0059 20130101; C07D 233/58 20130101; H01L
51/0081 20130101; H01L 51/5016 20130101; H01L 51/0087 20130101;
H01L 2251/308 20130101; C07D 413/04 20130101; C09K 2211/1022
20130101; H05B 33/14 20130101; C07F 15/0033 20130101; C07D 405/14
20130101; C09K 2211/185 20130101; H01L 51/0069 20130101; H01L
51/5012 20130101; C09K 2211/1007 20130101; H01L 51/0085 20130101;
C07D 405/04 20130101; C09K 2211/186 20130101; C09K 2211/1037
20130101; C07D 417/04 20130101; C09K 11/06 20130101; H01L 51/006
20130101; C09K 2211/1044 20130101; C09K 2211/1029 20130101; C07D
409/04 20130101 |
Class at
Publication: |
313/504 ; 556/1;
548/402; 556/136 |
International
Class: |
H01L 51/50 20060101
H01L051/50; C07F 15/00 20060101 C07F015/00; C07D 207/00 20060101
C07D207/00; C07D 403/04 20060101 C07D403/04 |
Foreign Application Data
Date |
Code |
Application Number |
Jul 1, 2005 |
JP |
2005-193697 |
Claims
1. An organic electroluminescent element material comprising a
metal complex having a partial structure represented by Formula
(A): ##STR00036## wherein Xa, Xb, Xc, Xd, Xe, and Xf each represent
a carbon atom, CRa, a nitrogen atom, NRb, an oxygen atom or a
sulfur atom, provided that at least one of them represents CRa; Ya,
Yb, and Yc each represent a carbon atom or a nitrogen atom and Yd
represents a nitrogen atom; when Ya and Yb represent the same atom,
Yc does not represent a nitrogen atom; Ra and Rb represent a
hydrogen atom or a substituent, provided that one of Ra represents
an aromatic hydrocarbon ring group or an aromatic heterocyclic ring
group; Ma represents a metal of the 8th-10th groups in a periodic
table of elements; and rings Z1 and Z2 each represent a single
five-membered ring, and bonds to form each of the rings Z.sub.1 and
Z.sub.2 each represent a single bond or a double bond, rings
Z.sub.1 and Z.sub.2 each being a single ring.
2. The organic electroluminescent element material of claim 1
comprising a metal complex having a partial structure represented
by Formula (1): ##STR00037## wherein X.sub.01, X.sub.02, X.sub.03,
X.sub.04, X.sub.05, and X.sub.06 each represent CR.sub.01, a
nitrogen atom, NR.sub.02, an oxygen atom or a sulfur atom, provided
that at least one of them represents CR.sub.01; Y.sub.01 and
Y.sub.02 each represent a carbon atom or a nitrogen atom; R.sub.01
and R.sub.02 each represent a hydrogen atom or a substituent,
provided that at least one of R.sub.01 represents an aromatic
hydrocarbon ring group or an aromatic heterocyclic ring group; Mol
represents a transition metal element of the 8th-10th groups in the
periodic table of elements; rings A and B each represent a single
five-membered ring, and bonds to form each of rings A and B
represent a single bond or a double bond.
3. The organic electroluminescent element material of claim 1
comprising a metal complex having a partial structure represented
by Formula (2): ##STR00038## wherein X.sub.11, X.sub.12, X.sub.13,
X.sub.14, X.sub.15, and X.sub.16 each represent CR.sub.11, a
nitrogen atom, NR.sub.12, an oxygen atom or a sulfur atom, provided
that at least one of them represents CR.sub.11; R.sub.11 and
R.sub.12 each represent a hydrogen atom or a substituent, provided
that at least one of R.sub.11 represents an aromatic hydrocarbon
ring group or an aromatic heterocyclic ring group; M.sub.11
represents a transition metal element of the 8th-10th groups in the
periodic table of elements; rings C and D each represent a single
five-membered ring, and bonds to form each of rings C and D each
represent a single bond or a double bond.
4. The organic electroluminescent element material of claim 1
comprising a metal complex having a partial structure represented
by Formula (3): ##STR00039## wherein X.sub.21, X.sub.22, X.sub.23,
X.sub.24, X.sub.25, and X.sub.26 each represent CR.sub.21, a
nitrogen atom, NR.sub.22, an oxygen atom or a sulfur atom, provided
that at least one of them represents CR.sub.21; R.sub.21 and
R.sub.22 each represent a hydrogen atom or a substituent, provided
that at least one of R.sub.21 represents an aromatic hydrocarbon
ring group or an aromatic heterocyclic ring group; M.sub.21
represents a transition metal element of the 8th-10th groups in the
periodic table of elements; rings E and F each represent a single
five-membered ring, and bonds to form each of rings E and F
represent a single bond or a double bond.
5. The organic electroluminescent element material of claim 1
comprising a metal complex having a partial structure represented
by Formula (4): ##STR00040## wherein X.sub.31, X.sub.32, X.sub.33,
X.sub.34, X.sub.35, and X.sub.36 each represent CR.sub.31, a
nitrogen atom, NR.sub.32, an oxygen atom or a sulfur atom, provided
that at least one of them represents CR.sub.31; X.sub.37 and
X.sub.38 each represent a carbon atom or a nitrogen atom; R.sub.31
and R.sub.32 each represent a hydrogen atom or a substituent,
provided that at least one of R.sub.31 represents an aromatic
hydrocarbon ring group or an aromatic heterocyclic ring group;
M.sub.31 represents a transition metal element of the 8th-10th
groups in the periodic table of elements; rings G and H each
represent a single five-membered ring, and bonds to form each of
rings G and H represent a single bond or a double bond.
6. The organic electroluminescent element material of claim 1,
wherein Ma in Formula (A) is iridium or platinum.
7. The organic electroluminescent element material of claim 2,
wherein M.sub.01 in Formula (1) is iridium or platinum.
8. The organic electroluminescent element material of claim 3,
wherein M.sub.11 in Formula (2) is iridium or platinum.
9. The organic electroluminescent element material of claim 4,
wherein M.sub.21 in Formula (3) is iridium or platinum.
10. The organic electroluminescent element material of claim 5,
wherein M.sub.31 in formula (4) is iridium or platinum.
11. An organic electroluminescent element comprising the organic
electroluminescent element materials of claim 1.
12. An organic electroluminescent element comprising an emission
layer as a constituting layer of the element, wherein the emission
layer comprises the organic electroluminescent element materials of
claim 1.
13. An organic electroluminescent element comprising an electron
inhibition layer as a constituting layer of the element, wherein
the electron inhibition layer comprises the organic
electroluminescent element materials of claim 1.
14. The organic electroluminescent element of claim 11, comprising
an emission layer as a constituting layer of the element, the
emission layer containing: a carboline derivative; or a condensed
ring compound having a structure derived from carboline, wherein at
least one of carbon atoms of a hydrocarbon ring in a carboline ring
is substituted with a nitrogen atom.
15. The organic electroluminescent element of claim 11, comprising
a positive hole inhibition layer as a constituting layer of the
element, the positive hole inhibition layer containing: a carboline
derivative; or a condensed ring compound having a structure derived
from carboline, wherein at least one of carbon atoms of a
hydrocarbon ring in a carboline ring is substituted with a nitrogen
atom.
16. A display device comprising the organic electroluminescent
elements of claim 11.
17. A lighting device comprising the organic electroluminescent
elements of claim 11.
Description
TECHNICAL FIELD
[0001] The present invention relates to an organic
electroluminescent element material, an organic electroluminescent
element, a display device and a lighting device.
BACKGROUND
[0002] Conventionally, an emission type electronic display device
includes an electroluminescence display (hereinafter, referred to
as an ELD). A constituent element of ELD includes such as an
inorganic electroluminescent element and an organic
electroluminescent element (hereinafter, referred to as an organic
EL element). An inorganic electroluminescent element has been
utilized as a flat light source, however, requires a high voltage
of alternating current to operate an emission element. An organic
electroluminescent element is an element provided with a
constitution comprising an emission layer containing a emitting
substance being sandwiched with a cathode and an anode, and an
exciton is generated by an electron and a positive hole being
injected into the emission layer to be recombined, resulting
emission utilizing light release (fluorescence-phosphorescence) at
the time of deactivation of said exciton; the emission is possible
at a voltage of approximately a few to a few tens volts, and an
organic electroluminescent element is attracting attention with
respect to such as superior viewing angle and high visual
recognition due to a self-emission type as well as space saving and
portability due to a completely solid element of a thin layer
type.
[0003] However, in an organic electroluminescence in view of the
future practical application, desired has been development of an
organic EL element which efficiently emits at a high luminance with
a low electric consumption.
[0004] In Japanese Patent No. 3093796, a slight amount of a
fluorescent substance has been doped in a stilbene derivative,
distyrylarylene derivative or a tristyrylarylene derivative, to
achieve improved emission luminance and a prolonged life of an
element.
[0005] Further, there are known such as an element having an
organic emission layer comprising a 8-hydroxyquinoline aluminum
complex as a host compound which is doped with a slight amount of a
fluorescent substance (for example, JP-A 63-264692 (hereinafter,
JP-A refers to Japanese Patent Publication Open to Public
Inspection No.)) and an element having an organic emission layer
comprising a 8-hydroxyquinoline aluminum complex as a host compound
which is doped with quinacridone type dye (for example, JP-A
3-255190).
[0006] In the case of utilizing emission from an excited singlet as
described above, since a generation ratio of a singlet exciton to a
triplet exciton is 1/3, that is, a generation probability of an
emitting exciton species is 25% and a light taking out efficiency
is approximately 20%, the limit of a quantum efficiency (next) of
taking out is said to be 5%.
[0007] However, since an organic EL element which utilizes
phosphorescence from an excited triplet has been reported from
Princeton University (M. A. Baldo et al., Nature vol. 395, pp.
151-154 (1998)), researches on materials exhibiting phosphorescence
at room temperature have come to be active.
[0008] For example, it is also disclosed in A. Baldo et al.,
Nature, vol. 403, No. 17, pp. 750-753 (2000), and U.S. Pat. No.
6,097,147.
[0009] Since the upper limit of internal quantum efficiency becomes
100% by utilization of an excited triplet, which is principally 4
times of the case of an excited singlet, it may be possible to
achieve almost the same ability as a cooled cathode ray tube to
attract attention also for an illumination application.
[0010] For example, in such as S. Lamansky et al., J. Am. Chem.
Soc., vol. 123, p. 4304 (2001), many compounds mainly belonging to
heavy metal complexes such as iridium complexes have been
synthesized and studied.
[0011] Further, in aforesaid, A. Baldo et al., Nature, vol. 403,
No. 17, pp. 750-753 (2000), utilization of tris(2-phenylpyridine)
iridium as a dopant has been studied.
[0012] In addition to these, M. E. Tompson et al., at The 10th
International Workshops on Inorganic and Organic
Electroluminescence (EL'00, Hamamatsu), have studied to utilize
L.sub.2Ir(acac) such as (ppy).sub.2Ir(acac) as a dopant, Moon-Jae
Youn. Og., Tetsuo Tsutsui et al., also at The 10th International
Workshops on Inorganic and Organic Electroluminescence (EL'00,
Hamamatsu), have studied utilization of such as
tris(2-(p-tolyl)pyridine)iridium (Ir(ptpy).sub.3) and
tris(benzo[h]quinoline)iridium (Ir(bzq).sub.3) (herein, these metal
complexes are generally referred to as orthometalated iridium
complexes.).
[0013] Further, in also the aforesaid, S. Lamansky et al., J. Am.
Chem. Soc., vol. 123, p. 4304 (2001), studies have been carried out
to prepare an element utilizing various types of iridium
complexes.
[0014] Further, to obtain high emission efficiency, Ikai et al., at
The 10th International Workshops on Inorganic and Organic
Electroluminescence (EL'00, Hamamatsu) utilized a hole transporting
compound as a host of a phosphorescent compound. Further, M. E.
Tompson et al. utilized various types of electron transporting
materials as a host of a phosphorescent compound doped with a new
iridium complex.
[0015] An orthometalated complex provided with platinum instead of
iridium as a center metal is also attracting attention. With
respect to these types of complexes, many examples having a
characteristic ligand are known (for example, refer to Patent
Documents 1-5 and Non-Patent Document 1.).
[0016] In any case, emission luminance and emission efficiency are
significantly improved compared to conventional elements because
the emitting light arises from phosphorescence, however, there has
been a problem of a poor emission life of the element compared to
conventional elements. It is hard to achieve an emission of a short
wavelength and an improvement of an emission life of the element
for a phosphorescent emission material provided with a high
efficiency. At present state, it cannot be achieved a level of a
practical use.
[0017] With respect to shortening of emission wavelength,
heretofore, there have been known introduction of an electron
attracting group such as a fluorine atom, a trifluoromethyl group,
or a cyano group as a substituent group into phenylpyridine, and
introduction of a ligand of such as picolinic acid or of a
pyrazabole type. However, when an emission wavelength is shortened
to achieve blue color by utilizing these substitution effects, a
high efficiency may be achieved while emission life will be greatly
deteriorated, which requires further improvement to overcome the
trade-off relationship.
[0018] There are known some iridium complexes containing a ligand
having a specific partial structure combining two carbon atoms of
two five membered ring. However, in the disclosed compounds, at
least one of the five membered rings is condensed with other ring.
In addition, there are disclosed only the use for a red emission
element (refer to Patent Document 11.)
[0019] [Patent Document 1] JP-A 2002-332291
[0020] [Patent Document 2] JP-A 2002-332292
[0021] [Patent Document 3] JP-A 2002-338588
[0022] [Patent Document 4] JP-A 2002-226495
[0023] [Patent Document 5] JP-A 2002-234894
[0024] [Patent Document 6] WO 02/15645
[0025] [Patent Document 7] JP-A 2003-123982
[0026] [Patent Document 8] JP-A 2002-117978
[0027] [Patent Document 9] JP-A 2003-146996
[0028] [Patent Document 10] WO 04/016711
[0029] [Patent Document 11] JP-A 2003-252888
[0030] [Non-patent Document 1] Inorganic Chemistry, 41 (12),
3055-3066 (2002)
[0031] [Non-patent Document 2] Applied Physics Letters, 79, 2082
(2001)
[0032] [Non-patent Document 3] Applied Physics Letters, 83, 3818
(2003)
[0033] [Non-patent Document 4] New Journal of Chemistry, 26, 1171
(2002)
DISCLOSURE OF THE INVENTION
Problems to be Solved by the Invention
[0034] This invention has been made in view of these problems, and
an object of this invention is to provide an organic EL element
material with a controlled emission wavelength which have high
emission efficiency and long emission life, a lighting device and a
display device by utilizing said element material.
Means to Solve the Problems
[0035] An object of the present invention described above has been
achieved by the following constitutions 1-15.
(1) An organic electroluminescent element material characterized by
a metal complex having a structure represented by Formula (A) as a
partial structure.
##STR00001##
[0036] wherein Xa, Xb, Xc, Xd, Xe, and Xf each represent a carbon
atom, CRa, a nitrogen atom, NRb, an oxygen atom, or a sulfur atom,
but at least one of them represents CRa. Ya, Yb, and Yc each
represent a carbon atom or a nitrogen atom and Yd represents a
nitrogen atom. When Ya and Yb represent the same atom, Yc does not
represent a nitrogen atom. Ra and Rb represent a hydrogen atom or a
substituent, but at least one of Ra represents an aromatic
hydrocarbon ring group or an aromatic heterocyclic ring group. Ma
represents a metal of the 8th-10th groups of the periodic table of
elements. Rings Z1 and Z2 each represent a single five-membered
ring, and the bonds to form each of the rings Z.sub.1 and Z.sub.2
each represent a single bond or a double bond, the rings Z.sub.1
and Z.sub.2 each being a single ring.
(2) The organic electroluminescent element material described in
item (1) characterized by a metal complex having a structure
represented by Formula (1) as a partial structure.
##STR00002##
[0037] wherein X.sub.01, X.sub.02, X.sub.03, X.sub.04, X.sub.05,
and X.sub.06 each represent CR.sub.01, a nitrogen atom, NR.sub.02,
an oxygen atom, or a sulfur atom, but at least one of them
represents CR.sub.01. Y.sub.01 and Y.sub.02 each represent a carbon
atom or a nitrogen atom. R.sub.01 and R.sub.02 each represent a
hydrogen atom or a substituent, but at least one of R.sub.01
represents an aromatic hydrocarbon ring group or an aromatic
heterocyclic ring group. M.sub.01 represents a transition metal
element of the 8th-10th groups of the periodic table of elements.
Rings A and B each represent a single five-membered ring, and the
bonds to form each of the rings A and B represent a single bond or
a double bond.
(3) The organic electroluminescent element material described in
item (1) characterized by a metal complex having a structure
represented by Formula (2) as a partial structure.
##STR00003##
wherein X.sub.11, X.sub.12, X.sub.13, X.sub.14, X.sub.15, and
X.sub.16 each represent CR.sub.11, a nitrogen atom, NR.sub.12, an
oxygen atom, or a sulfur atom, but at least one of them represents
CR.sub.11. R.sub.11 and R.sub.12 each represent a hydrogen atom or
a substituent, but at least one of R.sub.11 represents an aromatic
hydrocarbon ring group or an aromatic heterocyclic ring group.
M.sub.11 represents a transition metal element of the 8th-10th
groups of the periodic table of elements. Rings C and D each
represent a single five-membered ring, and the bonds to form each
of the rings C and D each represent a single bond or a double bond.
(4) The organic electroluminescent element material described in
item (1) characterized by a metal complex having a structure
represented by Formula (3) as a partial structure.
##STR00004##
[0038] wherein X.sub.21, X.sub.22, X.sub.23, X.sub.24, X.sub.25,
and X.sub.26 each represent CR.sub.21, a nitrogen atom, NR.sub.22,
an oxygen atom, or a sulfur atom, but at least one of them
represents CR.sub.21. R.sub.21 and R.sub.22 each represent a
hydrogen atom or a substituent, but at least one of R.sub.21
represents an aromatic hydrocarbon ring group or an aromatic
heterocyclic ring group. M.sub.2, represents a transition metal
element of the 8th-10th groups of the periodic table of elements.
Rings E and F each represent a single five-membered ring, and the
bonds to form each of the rings E and F represent a single bond or
a double bond.
(5) The organic electroluminescent element material described in
item (1) characterized by a metal complex having a structure
represented by Formula (4) as a partial structure.
##STR00005##
[0039] wherein X.sub.31, X.sub.32, X.sub.33, X.sub.34, X.sub.35,
and X.sub.36 each represent CR.sub.31, a nitrogen atom, NR.sub.32,
an oxygen atom, or a sulfur atom, but at least one of them
represents CR.sub.31. X.sub.37 and X.sub.38 each represent a carbon
atom or a nitrogen atom. R.sub.31 and R.sub.32 each represent a
hydrogen atom or a substituent, but at least one of R.sub.31
represents an aromatic hydrocarbon ring group or an aromatic
heterocyclic ring group. M.sub.31 represents a transition metal
element of the 8th-10th groups of the periodic table of elements.
Rings G and H each represent a single five-membered ring, and the
bonds to form each of the rings G and H represent a single bond or
a double bond.
(6) The organic electroluminescent element material described in
item (1), wherein Ma in Formula (A) is iridium or platinum. (7) The
organic electroluminescent element material described in item (3),
wherein M.sub.01 in Formula (1) is iridium or platinum. (8) The
organic electroluminescent element material described in item (3),
wherein M.sub.11 in Formula (2) is iridium or platinum. (9) The
organic electroluminescent element material described in item (4),
wherein M.sub.21 in Formula (3) is iridium or platinum. (10) The
organic electroluminescent element material described in item (5),
wherein M.sub.31 in Formula (4) is iridium or platinum. (11) An
organic electroluminescent element comprising any one of the
organic electroluminescent element materials described in items
(1)-(10). (12) An organic electroluminescent element comprising an
emission layer as a constituting layer of the element, wherein the
emission layer comprises any one of the organic electroluminescent
element materials described in items (1)-(10). (13) An organic
electroluminescent element comprising an electron inhibition layer
as a constituting layer of the element, wherein the electron
inhibition layer comprises any one of the organic
electroluminescent element materials described in items (1)-(10).
(14) The organic electroluminescent element of any one of the
above-described items (11)-(13), comprising an emission layer as a
constituting layer of the element, the emission layer
containing:
[0040] a carboline derivative; or
[0041] a condensed ring compound having a structure derived from
carboline, wherein at least one of carbon atoms of a hydrocarbon
ring in a carboline ring is substituted with a nitrogen atom.
(15) The organic electroluminescent element of any one of the
above-described items (11)-(14), comprising a positive hole
inhibition layer as a constituting layer of the element, the
positive hole inhibition layer containing;
[0042] a carboline derivative; or
[0043] a condensed ring compound having a structure derived from
carboline, wherein at least one of carbon atoms of a hydrocarbon
ring in a carboline ring is substituted with a nitrogen atom.
(16) A display device comprising any one of the organic
electroluminescent elements described in items (11)-(15). (17) A
lighting device comprising any one of the organic
electroluminescent elements described in items (11)-(15).
EFFECTS OF THE INVENTION
[0044] This invention has been able to provide an organic EL
element material for and an organic EL element, and it has been
achieved to provide an organic EL element, a lighting device and a
display device having high emission efficiency and long emission
life utilizing said organic EL element material.
BRIEF DESCRIPTION OF THE DRAWINGS
[0045] FIG. 1 is a schematic drawing to show an example of a
display device constituted of an organic EL element.
[0046] FIG. 2 is a schematic drawing of display section A.
[0047] FIG. 3 is an equivalent circuit diagram of an image
pixel.
[0048] FIG. 4 is a schematic drawing of a full color display device
according to a passive matrix mode.
[0049] FIG. 5 is a schematic drawing of a lighting device.
[0050] FIG. 6 is a schematic cross-sectional view of a lighting
device.
DESCRIPTION OF SYMBOLS
[0051] 1 display [0052] 3 pixel [0053] 5 scanning line [0054] 6
data line [0055] 7 electrical power line [0056] 10 organic EL
element [0057] 11 switching transistor [0058] 12 operating
transistor [0059] 13 capacitor [0060] A display section [0061] B
control section [0062] 107 glass substrate having a transparent
electrode [0063] 106 organic EL layer [0064] 105 cathode [0065] 102
glass cover [0066] 108 nitrogen gas [0067] 109 desiccant
BEST MODES TO CARRY OUT THE INVENTION
[0068] In the organic EL element material of the present invention,
molecular designing of an organic EL element material for use in an
organic EL element has been realized via the embodiment set forth
by any one of items (1)-(8). Further, by use of the organic EL
element material, there has been provided an organic EL element
exhibiting high emission efficiency and having a prolonged emission
life, lighting equipment, and a display device.
[0069] Each of the constituent elements of the present invention
will now be detailed successively.
<Metal Complex Having a Structure Represented by any One of
Formulas (A) and (1)-(4) as a Partial Structure>
[0070] A metal complex relevant to the organic EL element material
of the present invention is described.
[0071] The inventors of the present invention have conducted
diligent investigation on the above problems and made the following
findings: emission efficiency was significantly enhanced employing
an organic EL element containing a metal complex material having a
specific partial structure as the organic EL element material,
wherein as the ligand of the metal complex, the mother nucleus of a
commonly used phenylpyridine (being structured of two six-membered
rings joining each other via a carbon-carbon bond) was coordinated
to the mother nucleus having a structure in which "the
five-membered aromatic heterocyclic rings", represented by Formulas
(A) and (1)-(4), joined each via a carbon-carbon bond or a
carbon-nitrogen bond.
[0072] However, such a ligand, in which two five-membered rings
each join via a carbon-carbon bond or a carbon-nitrogen bond, tends
to be electron-deficient as a whole, resulting in the problem in
that the stability of a compound is likely to decrease, and
therefore in order to enhance the stability of the compound, a
breakthrough in molecular designing has been further demanded.
[0073] The inventors of the present invention have found that, by
introducing an aromatic hydrocarbon ring or an aromatic
heterocyclic ring as a substituent of the ligand having a structure
in which two five-membered rings each join via a carbon-carbon bond
or a carbon-nitrogen bond in such a manner as in the metal complex
of the present invention, an emission life was able to be prolonged
which had been a problem of the organic EL element produced
employing an organic EL element material exhibiting an emission
wavelength controlled to be in the short wavelength side only via a
conventional blue metal complex, specifically via an
electron-attracting group, whereby compatibility of emission
efficiency and an emission life has been realized.
[0074] Specifically, in molecular designing a
phosphorescence-emitting blue dopant used preferably as a blue
light-emitting dopant, molecular designing via a viewpoint
different from the conventional one has been realized, and at the
same time a greatly prolonged emission life of the organic EL
element has been achieved.
[0075] Further, the following findings have been made: even when
the ligand has a structure in which two five-membered rings each
join via a carbon-carbon bond or a carbon-nitrogen bond, a long
emission wavelength might be realized depending on the structure of
the ligand, and also in molecular designing for adding a function
to enable the emission wavelength of the metal complex to be in the
long wavelength region, an appropriate partial structure was able
to be selected by employing the partial structure of the present
invention represented by Formulas (A) and (1)-(4) or a partial
structure expressed as a tautomer of each partial structure
represented by Formulas (A) and (1)-(4) as a starting material for
designing the original skeleton.
(Ligand)
[0076] The metal complex of the present invention is characterized
by having one of the partial structure represented by Formulas (A)
and (1)-(4) and a partial structure expressed as a tautomer of each
partial structure represented by Formulas (A) and (1)-(4)
(specifically by having the partial structure as a coordination
structure), wherein any of the metal complex may be composed of
only the partial structure represented by Formulas (A) and (1)-(4)
or a partial structure expressed as a tautomer of each partial
structure represented by Formulas (A) and (1)-(4), and also, as the
ligand, any of the metal complex may have a ligand (also called a
coordination compound), if necessary, which is known among persons
skilled in the art as a so called ligand used to prepare metal
complexes known in the art.
[0077] In view of achieving preferable results in desired effects
of the present invention, the ligand in complexes is composed of 1
or 2 types, but is preferably composed of only one type.
[0078] Ligands employed in conventional metal complexes known in
the art include various types. Examples include ligands (for
example, halogen ligands, being preferably a chlorine ligand, and
nitrogen containing heterocyclic ligands such as bipyridyl or
phenanthroline, and diketone ligands) described, for example, in H.
Yersin, "Photochemistry and Photophysics of Coordination Compounds"
Springer-Verlag Co., published in 1987, and in Akio Yamamoto, "Yuki
Kinzoku Kagaku--Kiso to Oyo-- (Organic Metal Chemistry--Bases and
Applications--)" Shokabo Sha, published in 1982.
(Transition Metal Elements of Groups 8-10 of the Periodic Table of
Elements)
[0079] Employed as a metal used to form the metal complexes
containing a partial structure represented by one of Formulas (A),
and (1)-(4) (more definitely, containing as a ligand) according to
the present invention, the transition metal elements (also simply
referred to as transition metals) of Groups 8-10 of the periodic
table. Of these, iridium and platinum are
listed as a preferable transition metal element.
[0080] The layer in which the metal complexes containing a partial
structure represented by one of Formulas (A), and (1)-(4) is
preferably an emission layer and/or an electron inhibition layer.
Further, when incorporated in the emission layer, by employing them
as an emission dopant in the emission layer ("an emission dopant"
will be explained later), it is possible to achieve an increase in
the quantum efficiency (to realize high luminance) to be taken out
and the extension of luminescent lifetime of the organic EL
elements of the present invention.
[0081] Further, by employing such organic EL element materials, it
became possible to provide organic EL elements which exhibit high
luminescent efficiency and long luminescent lifetime, a lighting
device and a display device.
[0082] Each of the constituting components according to the present
invention will now be successively detailed.
[0083] Metal complexes which are organic EL element materials of
the present invention will be described first.
[0084] Preferred as a layer incorporating the metal complexes
containing a partial structure represented by one of Formulas (A)
and (1)-(4) according to the present invention is an emission layer
and/or an electron inhibition layer. Further, when incorporated in
the emission layer, by employing them as an emission dopant in the
emission layer, it is possible to achieve an increase in the
quantum efficiency (to realize high luminance) to be taken out and
the extension of luminescent lifetime of the organic EL elements of
the present invention.
[0085] The partial structures represented by Formulas (A) and
(1)-(4) and contained in the metal complexes of the present
invention will be described next.
<<A Partial Structure Represented by Formula (A)>>
[0086] In Formula (A), Xa, Xb, Xc, Xd, Xe, and Xf each represents a
carbon atom, CRa, a nitrogen atom, NRb, an oxygen atom or a sulfur
atom. At least one of them represents CRa.
[0087] Examples of substituents represented by Xa, Xb, Xc, Xd, Xe,
and Xf; Ra of CRa; and Rb of NRb in Formula (A) are as follows.
Examples of such a substituent include an alkyl group (for example,
a methyl group, an ethyl group, a propyl group, an isopropyl group,
a tert-butyl group, a pentyl group, a hexyl group, an octyl group,
a dodecyl group, a tridecyl group, a tetradecyl group, and a
pentadecyl group), a cycloalkyl group (for example, a cyclopentyl
group and a cyclohexyl group), an alkenyl group (for example, a
vinyl group and an allyl group), an alkynyl group (for example, an
ethynyl group and a propargyl group), an aromatic hydrocarbon ring
group (also called an aromatic carbon ring group or an aryl group
such as a phenyl group, a p-chlorophenyl group, a mesityl group, a
tolyl group, a xylyl group, a naphthyl group, an anthryl group, an
azulenyl group, an acenaphthenyl group, fluorenyl group, a
phenanthryl group, an indenyl group, a pyrenyl group, or a biphenyl
group), an aromatic heterocyclic group (for example, a pyridyl
group, a pyrimidinyl group, a furyl group, a pyrrolyl group, an
imidazolyl group, a benzimidazolyl group, a pyrazolyl group, a
piradinyl group, a triazolyl group (for example, a
1,2,4-triazole-1-yl group and a 1,2,3-triazole-1-yl group), an
oxazolyl group, a benzoxazolyl group, a thiazolyl group, an
isooxazolyl group, an isothiazolyl group, a furazanyl group, a
thienyl group, a quinolyl group, a benzofuryl group, a dibenzofuryl
group, a benzothienyl group, a dibenzothienyl group, an indolyl
group, a carbazolyl group, a carbolynyl group, a diazacarbazoyl
group (which shows that one of the carbon atoms which constitute a
carboline ring of the above carbolinyl group is replaced with a
nitrogen atom), a quinoxythalinyl group, a pyridazinyl group, a
triazinyl group, a quinazolinyl group, a phthalazinyl group), a
heterocyclic group (for example, a pyrrolidinyl group, an
imidazolidyl group, a morpholyl group, and an oxazolidyl group), an
alkoxy group (for example, a methoxy group, an ethoxy group, a
propyloxy group, a pentyloxy group, a hexyloxy group, an octyloxy
group, and a dodecyloxy group), a cycloalkoxy group (for example, a
cyclopentyloxy group and a cyclohexyloxy group), an aryloxy group
(for example, a phenoxy group and a naphthyloxy group), an
alkylthio group (for example, a methylthio group, an ethylthio
group, a propylthio group, a pentylthio group, a hexylthio group,
an octylthio group, and a dodecylthio group), a cycloalkylthio
group (for example, a cyclopentylthio group and a cyclohexylthio
group), an arylthio group (for example, a phenylthio group and a
naphthylthio group), an alkoxycarbonyl group (for example, a
methyloxycarbonyl group, an ethyloxycarbonyl group, a
butyloxycarbonyl group, an octyloxycarbonyl group, and a
dodecyloxycarbonyl group), an aryloxycarbonyl group (for example, a
phenyloxycarbonyl group and a naphthyloxycarbonyl group), a
sulfamoyl group (for example, an aminosulfonyl group, a
methylaminosulfonyl group, a dimethylaminosulfonyl group, a
butylaminosulfonyl group, a hexylaminosulfonyl group, a
cyclohexylaminosulfonyl group, an octylaminosulfonyl group, a
dodecylaminosulfonyl group, a phenylaminosulfonyl group, a
naphthylaminosulfonyl group, and a 2-pyridylaminosulfonyl group),
an acyl group (for example, an acetyl group, an ethylcarbonyl
group, a propylcarbonyl group, a pentylcarbonyl group, a
cyclohexylcarbonyl group, an octylcarbonyl group, a
2-ethylhexylcarbonyl group, a dodecylcarbonyl group, a
phenylcarbonyl group, a naphthylcarbonyl group, a pyridylcarbonyl
group), an acyloxy group (for example, an acetyloxy group, an
ethylcarbonyloxy group, a butylcarbonyloxy group, an
octylcarbonyloxy group, a dodecylcarbonyloxy group, and a
phenylcarbonyloxy group), an amido group (for example, a
methylcarbonylamino group, an ethylcarbonylamino group, a
dimethylcarbonylamino group, a propylcarbonylamino group, a
pentylcarbonylamino group, a cyclohexylcarbonylamino group, a
2-ethylhexylcarbonylamino group, an octylcarbonylamino group, a
dodecylcarbonylamino group, a phenylcarbonylamino group, and a
naphthylcarbonylamino group), a carbamoyl group (for example, an
aminocarbonyl group, a methylaminocarbonyl group, a
dimethylaminocarbonyl group, a propylaminocarbonyl group, a
pentylaminocarbonyl group, a cyclohexylaminocarbonyl group, an
octylaminocarbonyl group, a 2-ethylhexylaminocarbonyl group, a
dodecylaminocarbonyl group, a phenylaminocarbonyl group, a
naphthylaminocarbonyl group, and a 2-pyridylaminocarbonyl group),
an ureido group (for example, a methylureido group, an ethylureido
group, a pentylureido group, a cyclohexylureido group, an
octylureido group, a dodecylureido group, a phenylureido group, a
naphthylureido group, and a 2-pyridylaminoureido group), a sulfinyl
group (for example, a methylsulfinyl group, an ethylsulfinyl group,
a butylsulfinyl group, a cyclohexylsulfinyl group, a
2-ethylhexylsulfinyl group, a docecylsulfinyl group, a
phenylsulfinyl group, a naphthylsulfinyl group, and a
2-pyridylsulfinyl group), an alkylsulfonyl group (for example, a
methylsulfonyl group, an ethylsulfonyl group, a butylsulfinyl
group, a-cyclohexylsulfonyl group, a 2-ethylhexylsulfonyl group,
and a dodecylsulfonyl group), an arylsulfonyl group or a
heteroarylsulfonyl group (for example, a phenylsulfonyl group, a
naphthylsulfonyl group, and a 2-pyridylsulfonyl group), an amino
group (for example, an amino group, an ethylamino group, a
dimethylamino group, a butylamino group, a cyclopentylamino group,
a 2-ethylhexylamino group, a dodecylamino group, an anilino group,
a cyclopentylamino group, a 2-ethylhexylamino group, a dodecylamino
group, an anilino group, a naphthylamino group, and a
2-pyridylamino group), a halogen atom (for example, a fluorine
atom, a chlorine atom, and a bromine atom), a fluorinated
hydrocarbon group (for example, a fluoromethyl group, a
trifluoromethyl group, a pentafluoroethyl group, and a
pentafluorophenyl group), a cyano group, a nitro group, a hydroxyl
group, a mercapto group, and a silyl group (for example, a
trimethylsilyl group, a triisopropylsilyl group, a triphenylsilyl
group, and a phenyldiethylsilyl group).
[0088] These substituents may be substituted with the above
substituents. Further, these substituents may be bound together to
form a ring.
[0089] Ra represents a hydrogen atom or a substituent. The
substituent is a group similar to each substituent represented by
Ra and Rb, but at least one of Ra and Rb is an aromatic hydrocarbon
ring group or an aromatic heterocyclic ring group. As the aromatic
hydrocarbon ring group or the aromatic heterocyclic ring group, a
phenyl group, thienyl group, pyridyl group, imidazolyl group, and
pyrazolyl group are preferable, but of these, a phenyl group is
more preferably utilized.
[0090] Ya, Yb, and Yc each represent a carbon atom or a nitrogen
atom, and Yd represents a nitrogen atom. When Ya and Yb represent
the same atom, Yc does not represent a nitrogen atom.
[0091] In Formula (A), Ma represents a transition metal element of
the 8th-10th groups of the periodic table of elements, but of
these, iridium and platinum are preferably utilized.
[0092] In Formula (A), the rings Z.sub.1 and Z.sub.2 each represent
a single five-membered ring, and the bonds to each form the rings
Z.sub.1 and Z.sub.2 are a single bond or a double bond.
[0093] Examples of a carbon ring of the single five-membered ring
utilized as the ring Z.sub.1 include a cyclopentane ring and a
cyclopentadiene ring.
[0094] As a heterocyclic ring of the single five-membered ring
utilized as the ring Z.sub.1, there are preferably utilized a furan
ring, thiophene ring, selenophene ring, tellurophene ring, oxazole
ring, isoxazole ring, oxadine ring, pyrrole ring, pyrazole ring,
oxadiazole ring, triazole ring, imidazole ring, pyrazole ring,
thiazole ring, isothiazole ring, pyrrolidine ring, pyrazolidine
ring, imidazolidine ring, isoxazolidine ring, and isothiazolidine
ring.
[0095] The single five-membered ring utilized as the ring Z.sub.2
is synonymous with the heterocyclic ring of the single
five-membered ring described as the ring Z.sub.1.
[0096] The single five-membered rings each formed with the rings
Z.sub.1 and Z.sub.2 in Formula (A) incorporate Xa, Xb, Xc, Xd, Xe,
and Xf, which may further have a substituent each represented by Ra
or Rb contained in CRa or NRb.
[0097] Further, the bonds to each form the rings Z.sub.1 and
Z.sub.2 are a single bond or a double bond, but may also be a bond
with a bond order such as 1.5 positioned between the single bond
and the double bond.
<A Partial Structure Represented by Formula (1)>
[0098] In Formula (1), at least one of X.sub.01, X.sub.02,
X.sub.03, X.sub.04, X.sub.05, and X.sub.06 is represented by
CR.sub.01.
[0099] Examples of substituents represented by X.sub.01, X.sub.02,
X.sub.03, X.sub.04, X.sub.05, X.sub.06; R.sub.01 of CR.sub.01; and
R.sub.02 of NR.sub.02 in Formula (1) are as follows. Examples of
such a substituent include an alkyl group (for example, a methyl
group, an ethyl group, a propyl group, an isopropyl group, a
tert-butyl group, a pentyl group, a hexyl group, an octyl group, a
dodecyl group, a tridecyl group, a tetradecyl group, and a
pentadecyl group), a cycloalkyl group (for example, a cyclopentyl
group and a cyclohexyl group), an alkenyl group (for example, a
vinyl group and an allyl group), an alkynyl group (for example, an
ethynyl group and a propargyl group), an aromatic hydrocarbon ring
group (also called an aromatic carbon ring group or an aryl group
such as a phenyl group, a p-chlorophenyl group, a mesityl group, a
tolyl group, a xylyl group, a naphthyl group, an anthryl group, an
azulenyl group, an acenaphthenyl group, fluorenyl group, a
phenanthryl group, an indenyl group, a pyrenyl group, or a biphenyl
group), an aromatic heterocyclic group (for example, a pyridyl
group, a pyrimidinyl group, a furyl group, a pyrrolyl group, an
imidazolyl group, a benzimidazolyl group, a pyrazolyl group, a
piradinyl group, a triazolyl group (for example, a
1,2,4-triazole-1-yl group and a 1,2,3-triazole-1-yl group), an
oxazolyl group, a benzoxazolyl group, a thiazolyl group, an
isooxazolyl group, an isothiazolyl group, a furazanyl group, a
thienyl group, a quinolyl group, a benzofuryl group, a dibenzofuryl
group, a benzothienyl group, a dibenzothienyl group, an indolyl
group, a carbazolyl group, a carbolynyl group, a diazacarbazoyl
group (which shows that one of the carbon atoms which constitute a
carboline ring of the above carbolinyl group is replaced with a
nitrogen atom), a quinoxythalinyl group, a pyridazinyl group, a
triazinyl group, a quinazolinyl group, a phthalazinyl group), a
heterocyclic group (for example, a pyrrolidinyl group, an
imidazolidyl group, a morpholyl group, and an oxazolidyl group), an
alkoxy group (for example, a methoxy group, an ethoxy group, a
propyloxy group, a pentyloxy group, a hexyloxy group, an octyloxy
group, and a dodecyloxy group), a cycloalkoxy group (for example, a
cyclopentyloxy group and a cyclohexyloxy group), an aryloxy group
(for example, a phenoxy group and a naphthyloxy group), an
alkylthio group (for example, a methylthio group, an ethylthio
group, a propylthio group, a pentylthio group, a hexylthio group,
an octylthio group, and a dodecylthio group), a cycloalkylthio
group (for example, a cyclopentylthio group and a cyclohexylthio
group), an arylthio group (for example, a phenylthio group and a
naphthylthio group), an alkoxycarbonyl group (for example, a
methyloxycarbonyl group, an ethyloxycarbonyl group, a
butyloxycarbonyl group, an octyloxycarbonyl group, and a
dodecyloxycarbonyl group), an aryloxycarbonyl group (for example, a
phenyloxycarbonyl group and a naphthyloxycarbonyl group), a
sulfamoyl group (for example, an aminosulfonyl group, a
methylaminosulfonyl group, a dimethylaminosulfonyl group, a
butylaminosulfonyl group, a hexylaminosulfonyl group, a
cyclohexylaminosulfonyl group, an octylaminosulfonyl group, a
dodecylaminosulfonyl group, a phenylaminosulfonyl group, a
naphthylaminosulfonyl group, and a 2-pyridylaminosulfonyl group),
an acyl group (for example, an acetyl group, an ethylcarbonyl
group, a propylcarbonyl group, a pentylcarbonyl group, a
cyclohexylcarbonyl group, an octylcarbonyl group, a
2-ethylhexylcarbonyl group, a dodecylcarbonyl group, a
phenylcarbonyl group, a naphthylcarbonyl group, a pyridylcarbonyl
group), an acyloxy group (for example, an acetyloxy group, an
ethylcarbonyloxy group, a butylcarbonyloxy group, an
octylcarbonyloxy group, a dodecylcarbonyloxy group, and a
phenylcarbonyloxy group), an amido group (for example, a
methylcarbonylamino group, an ethylcarbonylamino group, a
dimethylcarbonylamino group, a propylcarbonylamino group, a
pentylcarbonylamino group, a cyclohexylcarbonylamino group, a
2-ethylhexylcarbonylamino group, an octylcarbonylamino group, a
dodecylcarbonylamino group, a phenylcarbonylamino group, and a
naphthylcarbonylamino group), a carbamoyl group (for example, an
aminocarbonyl group, a methylaminocarbonyl group, a
dimethylaminocarbonyl group, a propylaminocarbonyl group, a
pentylaminocarbonyl group, a cyclohexylaminocarbonyl group, an
octylaminocarbonyl group, a 2-ethylhexylaminocarbonyl group, a
dodecylaminocarbonyl group, a phenylaminocarbonyl group, a
naphthylaminocarbonyl group, and a 2-pyridylaminocarbonyl group),
an ureido group (for example, a methylureido group, an ethylureido
group, a pentylureido group, a cyclohexylureido group, an
octylureido group, a dodecylureido group, a phenylureido group, a
naphthylureido group, and a 2-pyridylaminoureido group), a sulfinyl
group (for example, a methylsulfinyl group, an ethylsulfinyl group,
a butylsulfinyl group, a cyclohexylsulfinyl group, a
2-ethylhexylsulfinyl group, a docecylsulfinyl group, a
phenylsulfinyl group, a naphthylsulfinyl group, and a
2-pyridylsulfinyl group), an alkylsulfonyl group (for example, a
methylsulfonyl group, an ethylsulfonyl group, a butylsulfinyl
group, a cyclohexylsulfonyl group, a 2-ethylhexylsulfonyl group,
and a dodecylsulfonyl group), an arylsulfonyl group or a
heteroarylsulfonyl group (for example, a phenylsulfonyl group, a
naphthylsulfonyl group, and a 2-pyridylsulfonyl group), an amino
group (for example, an amino group, an ethylamino group, a
dimethylamino group, a butylamino group, a cyclopentylamino group,
a 2-ethylhexylamino group, a dodecylamino group, an anilino group,
a cyclopentylamino group, a 2-ethylhexylamino group, a dodecylamino
group, an anilino group, a naphthylamino group, and a
2-pyridylamino group), a halogen atom (for example, a fluorine
atom, a chlorine atom, and a bromine atom), a fluorinated
hydrocarbon group (for example, a fluoromethyl group, a
trifluoromethyl group, a pentafluoroethyl group, and a
pentafluorophenyl group), a cyano group, a nitro group, a hydroxyl
group, a mercapto group, and a silyl group (for example, a
trimethylsilyl group, a triisopropylsilyl group, a triphenylsilyl
group, and a phenyldiethylsilyl group).
[0100] These substituents may be substituted with the above
substituents. Further, these substituents may be bound together to
form a ring.
[0101] At least one of R.sub.01 is an aromatic hydrocarbon ring or
an aromatic heterocyclic ring, but a phenyl group, thienyl group,
pyridyl group, imidazolyl group, and pyrazolyl group are
preferable. Of these, a phenyl group is more preferably
utilized.
[0102] Further, Y.sub.01 and Y.sub.01 each represent a carbon atom
or a nitrogen atom.
[0103] In Formula (1), M.sub.01 represents a transition metal
element of the 8th-10th groups of the periodic table of elements,
but of these, iridium and platinum are preferably utilized.
[0104] In Formula (1), the rings A and B each represent a single
five-membered ring, and the bonds to each form the rings A and B
represent a single bond or a double bond.
[0105] Examples of a carbon ring of the single five-membered ring
utilized as the ring A include a cyclopentane ring and a
cyclopentadiene ring.
[0106] As a heterocyclic ring of the single five-membered ring
utilized as the ring A, there are preferably utilized a furan ring,
thiophene ring, selenophene ring, tellurophene ring, oxazole ring,
isoxazole ring, oxadine ring, pyrrole ring, pyrazole ring,
oxadiazole ring, triazole ring, imidazole ring, pyrazole ring,
thiazole ring, isothiazole ring, pyrrolidine ring, pyrazolidine
ring, imidazolidine ring, isoxazolidine ring, and isothiazolidine
ring.
[0107] The single five-membered ring utilized as the ring B is
synonymous with the heterocyclic ring of the single five-membered
ring described as the ring Z.sub.1.
[0108] The single five-membered rings each formed with the rings A
and B in Formula (1) incorporate X.sub.01, X.sub.02, X.sub.03,
X.sub.04, X.sub.05, and X.sub.06, which may further have a
substituent each represented by R.sub.01 or R.sub.02 contained in
CR.sub.01, or NR.sub.02.
[0109] Further, the bonds to each form the rings A and B are a
single bond or a double bond, but may also be a bond with a bond
order such as 1.5 positioned between the single bond and the double
bond.
<Metal Complex Having a Partial Structure Represented by Formula
(2)>
[0110] The substituent each expressed in terms of R.sub.11 or
R.sub.12 contained in CR.sub.11 or NR.sub.12 each represented by
X.sub.11, X.sub.12, X.sub.13, X.sub.14, X.sub.15, and X.sub.16 in
Formula (2) is synonymous with the substituent each expressed in
terms of R.sub.01 or R.sub.02 contained in CR.sub.01 or NR.sub.02
each represented by X.sub.01, X.sub.02, X.sub.03, X.sub.04,
X.sub.05, and X.sub.06 in Formula (1).
[0111] In Formula (2), at least one of X.sub.11, X.sub.12,
X.sub.13, X.sub.14, X.sub.15, and X.sub.16 is CR.sub.11.
[0112] The transition metal element of the 8th-10th groups of the
periodic table of elements represented by M.sub.11 in Formula (2)
is synonymous with the transition metal element of the 8th-10th
groups of the periodic table of elements each represented by Ma or
M.sub.01 in Formula (A) or (1)
[0113] The single five-membered ring represented by the ring C in
Formula (2) is synonymous with the single five-membered ring
represented by the ring A in Formula (1).
[0114] The single five-membered ring represented by the ring D in
Formula (2) is synonymous with the single five-membered ring
represented by the ring B in Formula (1).
<Metal Complex Having a Partial Structure Represented by Formula
(3)>
[0115] The substituent each expressed in terms of R.sub.21 or
R.sub.22 contained in CR.sub.21 or NR.sub.22 each represented by
X.sub.21, X.sub.22, X.sub.23, X.sub.24, X.sub.25, and X.sub.26 in
Formula (3) is synonymous with the substituent each expressed in
terms of R.sub.01 or R.sub.02 contained in CR.sub.01 or NR.sub.02
each represented by X.sub.01, X.sub.02, X.sub.03, X.sub.04,
X.sub.05, and X.sub.06 in Formula (1).
[0116] In Formula (3), at least one of X.sub.21, X.sub.22,
X.sub.23, X.sub.24, X.sub.25, and X.sub.26 is CR.sub.21.
[0117] The transition metal element of the 8th-10th groups of the
periodic table of elements represented by M.sub.21 in Formula (3)
is synonymous with the transition metal element of the 8th-10th
groups of the periodic table of elements each represented by Ma or
M.sub.01 in Formula (A) or (1).
[0118] The single five-membered rings represented by the rings E
and F in Formula (3) are synonymous with the single five-membered
ring represented by the ring B in Formula (1).
<Metal Complex Having a Partial Structure Represented by Formula
(4)>
[0119] The substituent each expressed in terms of R.sub.31 or
R.sub.32 contained in CR.sub.31 or --NR.sub.32 each represented by
X.sub.31, X.sub.32, X.sub.33, X.sub.34, X.sub.35, and X.sub.36 in
Formula (4) is synonymous with the substituent each expressed in
terms of R.sub.01 or R.sub.02 contained in CR.sub.01 or NR.sub.02
each represented by X.sub.01, X.sub.02, X.sub.03, X.sub.04,
X.sub.05, and X.sub.06 in Formula (1).
[0120] In Formula (4), at least one of X.sub.31, X.sub.32,
X.sub.33, X.sub.34, X.sub.35, and X.sub.36 is CR.sub.31.
[0121] The transition metal element of the 8th-10th groups of the
periodic table of elements each represented by M.sub.31 in Formula
(4) is synonymous with the transition metal element of the 8th-10th
groups of the periodic table of elements each represented by Ma or
M.sub.01 in Formula (A) or (1).
[0122] The single five-membered rings each represented by the rings
G and H in Formula (4) are synonymous with the single five-membered
rings each represented by the rings E and F in Formula (3).
[0123] Specific examples of the metal complex having, as a partial
structure, at least one of the structures represented by Formulas
(A) and (1)-(4) will now be listed, but the present invention is
not limited thereto.
##STR00006## ##STR00007## ##STR00008## ##STR00009## ##STR00010##
##STR00011## ##STR00012## ##STR00013## ##STR00014## ##STR00015##
##STR00016## ##STR00017## ##STR00018## ##STR00019## ##STR00020##
##STR00021## ##STR00022## ##STR00023## ##STR00024##
##STR00025##
[0124] A synthetic example of Compound 4-2 will now be shown as one
synthetic example of specific examples of the metal complex, but
the present invention is not limited thereto.
<Synthesis of Compound 4-2>
[0125] Compound (A), compound (B), compound (C) and compound (D)
used in a synthetic process of Compound 4-2 are listed below.
##STR00026##
[0126] 3-Bromo-2-phenylthiophene was prepared by introducing one
equivalent of phenylboronic acid to 2,3-dibromothiophene via the
Suzuki Coupling. The compound (A) was prepared by converting
3-bromo-2-phenylthiophene into a boronic acid via a method
conventionally known in the art.
[0127] The compound (B) was prepared by allowing the compound (A)
thus obtained to react with 2-bromo-1-methyl-1H-imidazole via a
method conventionally known in the art employing the Suzuki
Coupling.
[0128] A solution of 2-ethoxyethanol and water (a mixture ratio of
3 to 1) containing iridium chloride trihydrate and 4 equivalent,
based on the same, of the compound (B) was heated to reflux at
120.degree. C. for 6 hours, and then the resultant solid was
filtered to give iridium .mu. complex. A solution containing the
thus obtained indium .mu. complex was prepared by adding 3
equivalent, based on the same, of each of acetylacetone and sodium
carbonate and by adding 2-ethoxyethenol, followed by being heated
to reflux at 120.degree. C. for 4 hours. The resultant organic
layer was extracted with water added, followed by removal of the
solvent to give the compound (C) via purification employing silica
column chromatography. Tow equivalents, based on the compound (C)
of the compound (D) were added to the compound (C) in glycerin,
followed by being heated while stirring at 140.degree. C. for 4
hours. The organic layer was extracted with water added, followed
by removal of the solvent to give Compound 4-2 via purification
employing silica column chromatography.
[0129] Metal complexes according to an organic EL element material
of this invention can be synthesized by applying a method described
in such as Organic Letter, vol. 3, No. 16, pp. 2579-2581 (2001),
Inorganic Chemistry vol. 30, No. 8, pp. 1685-1687 (1991), J. Am.
Chem., Soc., vol. 123, p. 4304 (2001), Inorganic Chemistry vol. 40,
No. 7, pp. 1704-1711 (2001), Inorganic Chemistry vol. 41, No. 12,
pp. 3055-3066 (2002), New Journal of Chemistry, vol. 26, p. 1171
(2002), European Journal of Organic Chemistry Vol. 4, pp. 95-709
(12004), and reference documents described in these documents.
<Application of Organic EL Element Material Containing Metal
Complex to Organic EL Element>
[0130] In the case of preparing an organic EL element by utilizing
an organic EL element material of this invention, said material is
preferably utilized in an emission layer or an electron inhibition
layer among constituent layers (details will be described later) of
the organic EL element. Further, the material is preferably
utilized as an emission dopant in an emission layer as described
above.
(Emission Host and Emission Dopant)
[0131] A mixing ratio of an emission dopant against an emission
host as a primary component in an emission layer, is preferably
adjusted to a range of 0.1-30 weight %.
[0132] However, plural types of compounds may be utilized in
combination as an emission dopant, and the partner to be mixed may
be a metal complex having a different structure, and a
phosphorescent dopant or a fluorescent dopant having other
structures.
[0133] Here, a dopant (such as a phosphorescent dopant and a
fluorescent dopant) which may be utilized together with a metal
complex employed as an emission dopant will be described.
[0134] An emission dopant is roughly classified into two types,
that is, a fluorescent dopant which emits fluorescence and a
phosphorescent dopant which emits phosphorescence.
[0135] A typical example of the former (a fluorescent dopant)
includes coumarin type dye, pyran type dye, cyanine type dye,
croconium type dye, squarylium type dye, oxobenzanthracene type
dye, fluorescein type dye, rhodamine type dye, pyrylium type dye,
perylene type dye, stilbene type dye, polythiophene type dye or
rare earth complex type fluorescent substances.
[0136] A typical example of the latter (a phosphorescent dopant) is
preferably a complex type compound containing metal of the 8th-10th
groups of the periodic table, more preferably an iridium compound
and an osmium compound and most preferable among them is an iridium
compound.
[0137] Specifically, listed are compounds described in the
following patent publication:
[0138] Such as WO 00/70655, JP-A Nos. 2002-280178, 2001-181616,
2002-280179, 2001-181617, 2002-280180, 2001-247859, 2002-299060,
2001-313178, 2002-302671, 2001-345183 and 2002-324679, WO 02/15645,
JP-A Nos. 2002-332291, 2002-50484, 2002-322292 and 2002-83684,
Japanese Translation of PCT International Application Publication
No. 2002-540572, JP-A Nos. 2002-117978, 2002-338588, 2002-170684
and 2002-352960, WO 01/93642 pamphlet, JP-A Nos. 2002-50483,
2002-100476, 2002-173674, 2002-359082, 2002-175884, 2002-363552,
2002-184582 and 2003-7469, Japanese Translation of PCT
International Application Publication No. 2002-525808, JP-A
2003-7471, Japanese Translation of PCT International Application
Publication No. 2002-525833, JP-A Nos. 2003-31366, 2002-226495,
2002-234894, 2002-235076, 2002-241751, 2001-319779, 2001-319780,
2002-62824, 2002-100474, 2002-203679, 2002-343572 and
2002-203678.
[0139] A part of examples thereof will be shown below.
##STR00027## ##STR00028## ##STR00029## ##STR00030##
(Emission Hosts (or Called as Host Compounds))
[0140] A host compound, employed in the present invention, refers
to a compound, among those incorporated in the emission layer,
which results in a phosphorescent quantum yield of less than 0.01
during emitting phosphorescence.
[0141] Structures of the emission host (host compound) employed in
the present invention are not particularly limited. Representative
compounds include those having a basic skeleton such as carbazole
derivatives, triarylamine derivatives, aromatic borane derivatives,
nitrogen-containing heterocyclic compounds, thiophene derivatives,
furan derivatives, or oligoarylene compounds, or derivatives having
a ring structure in which at least one of the carbon atoms of the
hydrocarbon ring, which constitutes carboline derivatives and the
carboline ring of the above carboline derivatives, is substituted
with a nitrogen atom.
[0142] Of these, preferably employed are carbazole derivatives,
carboline derivatives and their derivatives which have a structure
in which at least one carbon atom composing the hydrocarbon ring in
the carboline ring is substituted with a nitrogen atom.
[0143] Specific examples of emission hosts will now be listed,
however the present invention is not limited thereto. It is also
preferable to employ these compounds as a positive hole inhibition
material.
##STR00031## ##STR00032## ##STR00033##
[0144] In the emission layer according to the present invention,
prior art host compounds may be employed in combinations of a
plurality of types. The use of a plurality of host compounds
enables regulation of migration of electrons to make organic EL
elements more efficient. Preferred as these prior art host
compounds are those which exhibit positive hole transportability
and electron transportability, minimize the variation of
luminescent wavelength to a longer wavelength, and attain a high Tg
(being a glass transition temperature).
[0145] Further, an emission host of this invention may be either a
low molecular weight compound or a polymer compound having a
repeating unit, in addition to a low molecular weight compound
provided with a polymerizing group such as a vinyl group and an
epoxy group (an evaporation polymerizing emission host).
[0146] An emission host is preferably a compound having a positive
hole transporting ability and an electron transporting ability, as
well as preventing elongation of an emission wavelength and having
a high Tg (a glass transition temperature).
[0147] As specific examples of an emission host, compounds
described in the following Documents are preferable: For example,
JP-A Nos. 2001-257076, 2002-308855, 2001-313179, 2002-319491,
2001-357977, 2002-334786, 2002-8860, 2002-334787, 2002-15871,
2002-334788, 2002-43056, 2002-334789, 2002-75645, 2002-338579,
2002-105445, 2002-343568, 2002-141173, 2002-352957, 2002-203683,
2002-363227, 2002-231453, 2003-3165, 2002-234888, 2003-27048,
2002-255934, 2002-260861, 2002-280183, 2002-299060, 2002-302516,
2002-305083, 2002-305084 and 2002-308837. Specific examples of an
emission host are shown below; however, this invention is not
limited thereto.
[0148] The emission layer may further incorporate, as a host
compound, a compound which exhibits a maximum fluorescent
wavelength. In such a case, luminescence is also generated from the
other host compound, resulting in the maximum fluorescent
wavelength in the form of electromagnetic luminescence as an
organic EL element due to energy transfer from the other host
compound and a phosphorescent compound to the fluorescent compound.
Preferred as such host compounds resulting in the maximum
fluorescent wavelength are those which attain a high fluorescent
quantum yield. Herein, the fluorescent quantum yield is preferably
at least 10%, but is more preferably at least 30%. Specific
examples of host compounds resulting in the maximum fluorescent
wavelength include coumarin based dyes, pyran based dyes, cyanine
based dyes, croconium based dyes, suqualium based dyes,
oxobenzanthracene based dyes, fluorescein based dyes, ROHDAMINE
based dyes, pyrylium based dyes, perylene based dyes, stilbene
based dyes, and polythiophene based dyes. The fluorescent quantum
yield can be determined based on the method described on page 362
of Bunko (Spectroscopy) II of aforesaid Zikken Kagaku Koza (Lecture
on Experimental Chemistry) 7, 4th Edition (published by Maruzen,
1992).
[0149] Next, a typical constitution of an organic EL element will
be described.
<Constituent Layers of Organic EL Element>
[0150] Constituent layers of an organic EL element of this
invention will now be explained.
[0151] Specific examples of a preferable layer constitution of an
organic EL element of this invention are shown below; however, this
invention is not limited thereto.
(i) anode/positive hole transport layer/emission layer/positive
hole inhibition layer/electron transport layer/cathode, (ii)
anode/electron inhibition layer/emission layer/positive hole
inhibition layer/electron transport layer/cathode, (iii)
anode/positive hole transport layer/electron inhibition
layer/emission layer/positive hole inhibition layer/electron
transport layer/cathode, (iv) anode/positive hole transport
layer/electron inhibition layer/emission layer/positive hole
inhibition layer/electron transport layer/cathode, (v)
anode/positive hole transport layer/electron inhibition
layer/emission layer/positive hole inhibition layer/electron
transport layer/cathode buffer layer/cathode, (vi) anode/anode
buffer layer/positive hole transport layer/electron inhibition
layer/emission layer/positive hole inhibition layer/electron
transport layer/cathode buffer layer/cathode, (vii) anode/anode
buffer layer/positive hole transport layer/electron inhibition
layer/emission layer/positive hole inhibition layer/electron
transport layer/cathode buffer layer/cathode.
<Inhibition Layer (Electron Inhibition Layer, Positive Hole
Inhibition Layer)>
[0152] An inhibition layer (such as an electron inhibition layer, a
positive hole inhibition layer) according to this invention will
now be explained.
[0153] In this invention, an organic EL element material of this
invention is preferably utilized in such as a positive hole
inhibition layer and an electron inhibition layer, and specifically
preferably in a positive hole inhibition layer.
[0154] In the case of an organic EL element material of this
invention being contained in a positive hole inhibition layer and
an electron inhibition layer, a metal complex according to this
invention, which is described in any one of the above-described
embodiments 1-7, may be contained in a state of 100 weights as a
layer constituent component of such as a positive hole inhibition
layer and an electron inhibition layer, or may be contained by
being mixed with another organic compound (such as compounds
utilized in a constituent layer of an organic EL element of this
invention).
[0155] The layer thickness of an inhibition layer according to this
invention is preferably 3-100 nm and more preferably 5-30 nm.
<Positive Hole Inhibition Layer>
[0156] A positive hole inhibition layer, in a broad meaning, is
provided with a function of electron transport layer, being
comprised of a material having a function of transporting an
electron but a very small ability of transporting a positive hole,
and can improve the recombination probability of an electron and a
positive hole by inhibiting a positive hole while transporting an
electron.
[0157] As a positive hole inhibition layer, for example, a positive
inhibition layer described in such as JP-A Nos. 11-204258 and
11-204359 and p. 273 of "Organic EL Elements and Industrialization
Front Thereof (Nov. 30 (1998), published by N. T. S Corp.)" is
applicable to a positive hole inhibition (hole block) layer
according to this invention. Further, a constitution of an electron
transport layer described later can be appropriately utilized as a
positive hole inhibition layer according to this invention.
[0158] It is preferable that the organic EL layer of the present
invention incorporates a positive hole layer, which incorporates
derivatives having a ring structure, in which at least one carbon
atom of the hydrocarbon ring constituting the above carboline
derivative or the carboline ring of the above carboline derivative
is substituted with a nitrogen atom.
<Electron Inhibition Layer>
[0159] On the other hand, an electron inhibition layer is, in a
broad meaning, provided with a function of a positive hole
transport layer, being comprised of a material having a function of
transporting a positive hole but a very small ability of
transporting an electron, and can improve the recombination
probability of an electron and a positive hole by inhibiting an
electron while transporting a positive hole. Further, a
constitution of a positive hole transport layer described later can
be appropriately utilized as an electron inhibition layer.
[0160] Further, in this invention, it is preferable to utilize an
organic EL element material of this invention described above in an
adjacent layer neighboring to an emission layer, that is in a
positive hole inhibition layer and an electron inhibition layer,
and specifically preferably in a positive hole inhibition
layer.
<Positive Hole Transport Layer>
[0161] A positive hole transport layer contains a material having a
function of transporting a positive hole, and in a broad meaning, a
positive hole injection layer and an electron inhibition layer are
also included in a positive hole transport layer. A single layer of
or plural layers of a positive hole transport layer may be
provided.
[0162] A positive hole transport material is not specifically
limited and can be arbitrary selected from those such as generally
utilized as a charge injection transporting material of a positive
hole in a conventional photoconductive material and those which are
well known in the art and utilized in a positive hole injection
layer and a positive hole transport layer of an EL element.
[0163] A positive hole transport material is those having any one
of a property to inject or transport a positive hole or a barrier
property to an electron, and may be either an organic substance or
an inorganic substance. For example, listed are a triazole
derivative, an oxadiazole derivative, an imidazole derivative, a
polyallylalkane derivative, a pyrazolone derivative, a
phenylenediamine derivative, a allylamine derivative, an amino
substituted chalcone derivative, an oxazole derivatives, a
styrylanthracene derivative, a fluorenone derivative, a hydrazone
derivative, a stilbene derivative, a silazane derivative, an
aniline type copolymer, or conductive polymer oligomer and
specifically preferably such as thiophene oligomer.
[0164] As a positive hole transport material, those described above
can be utilized, however, it is preferable to utilized a porphyrin
compound, an aromatic tertiary amine compound and a styrylamine
compound, and specifically preferably an aromatic tertiary amine
compound.
[0165] Typical examples of an aromatic tertiary amine compound and
a styrylamine compound include
N,N,N',N'-tetraphenyl-4,4'-diaminophenyl;
N,N'-diphenyl-N,N'-bis(3-methylphenyl)-(1,1'-biphenyl)-4,4'-diamine
(TDP); 2,2-bis(4-di-p-tolylaminophenyl)propane;
1,1-bis(4-di-p-tolylaminophenyl)cyclohexane;
N,N,N',N'-tetra-p-tolyl 4,4'-diaminobiphenyl;
1,1-bis(4-di-p-tolylaminophenyl)-4-phenylcyclohexane;
bis(4-dimethylamino-2-methyl)phenylmethane;
bis(4-di-p-tolylaminophenyl)phenylmethane;
N,N'-diphenyl-N,N'-di(4-methoxyphenyl)-4,4'-diaminobiphenyl;
N,N,N',N'-tetraphenyl-4,4'-diaminophenylether;
4,4'-bis(diphenylamino)quarterphenyl; N,N,N-tri(p-tolyl)amine;
4-(di-p-tolylamino)-4'-[4-(di-p-triamino)styryl]stilbene;
4-N,N-diphenylamino-(2-diphenylvinyl)benzene;
3-methoxy-4'-N,N-diphenylaminostilbene; and N-phenylcarbazole, in
addition to those having two condensed aromatic rings in a molecule
described in U.S. Pat. No. 5,061,569, such as
4,4'-bis[N-(1-naphthyl)-N-phenylamino]biphenyl (NDP), and
4,4',4''-tris[N-(3-methylphenyl)-N-phenylamino]triphenylamine
(MDTDATA), in which three of triphenylamine units are bonded in a
star burst form, described in JP-A 4-308688.
[0166] Polymer materials, in which these materials are introduced
in a polymer chain or constitute the main chain of polymer, can be
also utilized.
[0167] Further, an inorganic compound such as a p type-Si and a p
type-SiC can be utilized as a positive hole injection material and
a positive hole transport material
[0168] This positive hole transport layer can be prepared by
forming a thin layer made of the above-described positive hole
transport material according to a method well known in the art such
as a vacuum evaporation method, a spin coating method, a cast
method, an inkjet method and a LB method. The layer thickness of a
positive hole transport layer is not specifically limited, however,
is generally 5-5,000 nm. This positive transport layer may have a
single layer structure comprised of one or not less than two types
of the above described materials.
<Electron Transport Layer>
[0169] An electron transfer layer is comprised of a material having
a function to transfer an electron, and an electron injection layer
and a positive hole inhibition layer are included in an electron
transfer layer in a broad meaning. A single layer or plural layers
of an electron transfer layer may be provided.
[0170] Conventionally, as an electron transfer material utilized in
a single layer of an electron transfer layer, and in an electron
transfer layer adjacent to the cathode side against an emission
layer in the case of utilizing plural electron transfer layers, the
following materials are known.
[0171] Further, an electron transfer layer is provided with a
function to transmit an electron injected from a cathode to an
emission layer, and compounds conventionally well known in the art
can be utilized by arbitrarily selection as a material thereof.
[0172] Examples of a material utilized in this electron transfer
layer (hereinafter, referred to as an electron transfer material)
include such as a nitro-substituted fluorene derivative, a
diphenylquinone derivative, a thiopyradineoxide derivative, a
heterocyclic tetracarbonic acid anhydride such as
naphthaleneperylene, carbodiimide, a fluorenylidenemethane
derivative, anthraquinonedimethane and anthrone derivatives, and an
oxadiazole derivative. Further, a thiazole derivative in which an
oxygen atom in the oxadiazole ring of the above-described
oxadiazole derivative is substituted by a sulfur atom, and a
quinoxaline derivative having a quinoxaline ring which is known as
an electron attracting group can be utilized as an electron
transfer material.
[0173] Polymer materials, in which these materials are introduced
in a polymer chain or these materials form the main chain of
polymer, can be also utilized.
[0174] Further, a metal complex of a 8-quinolinol derivative such
as tris(8-quinolinol)aluminum (Alq),
tris(5,7-dichloro-8-quinolinol)aluminum,
tris(5,7-dibromo-8-quinolinol)aluminum,
tris(2-methyl-8-quinolinol)aluminum,
tris(5-methyl-8-quinolinol)aluminum and bis(8-quinolinol)zinc
(Znq); and metal complexes in which a central metal of the
aforesaid metal complexes is substituted by In, Mg, Cu, Ca, Sn, Ga
or Pb, can be also utilized as an electron transfer material.
Further, metal-free or metal phthalocyanine, or those the terminal
of which is substituted by an alkyl group and a sulfonic acid
group, can be preferably utilized as an electron transfer material.
Further, distyrylpyrazine derivative, which has been exemplified as
a material of an emission layer, can be also utilized as an
electron transfer material, and, similarly to the case of a
positive hole injection layer and a positive hole transfer layer,
an inorganic semiconductor such as an n-type-Si and an n-type-SiC
can be also utilized as an electron transfer material.
[0175] This electron transport layer can be prepared by forming a
thin layer made of the above-described electron transport material
according to a method well known in the art such as a vacuum
evaporation method, a spin coating method, a cast method, an inkjet
method and a LB method. The layer thickness of an electron
transport layer is not specifically limited; however, is generally
5-5,000 nm. This electron transport layer may have a single layer
structure comprised of one or not less than two types of the above
described materials.
[0176] Next, an injection layer which is known as a constituent
layer of an organic EL element of this invention will be
explained.
<Injection Layer>: Electron Injection Layer, Positive Hole
Injection Layer
[0177] An injection layer is appropriately provided and includes an
electron injection layer and a positive hole injection layer, which
may be arranged between an anode and an emission layer or a
positive transfer layer, and between a cathode and an emission
layer or an electron transfer layer, as described above.
[0178] An injection layer is a layer which is arranged between an
electrode and an organic layer to decrease an operating voltage and
to improve an emission luminance, which is detailed in volume 2,
chapter 2 (pp. 123-166) of "Organic EL Elements and
Industrialization Front thereof (Nov. 30, 1998, published by N. T.
S Corp.)", and includes a positive hole injection layer (an anode
buffer layer) and an electron injection layer (a cathode buffer
layer).
[0179] An anode buffer layer (a positive hole injection layer) is
also detailed in such as JP-A 9-45479, 9-260062 and 8-288069, and
specific examples include such as a phthalocyanine buffer layer
comprising such as copper phthalocyanine, an oxide buffer layer
comprising such as vanadium oxide, an amorphous carbon buffer
layer, and a polymer buffer layer employing conductive polymer such
as polythiophene.
[0180] A cathode buffer layer (an electron injection layer) is also
detailed in such as JP-A 6-325871, 9-17574 and 10-74586, and
specific examples include a metal buffer layer comprising such as
strontium and aluminum, an alkali metal compound buffer layer
comprising such as lithium fluoride, an alkali earth metal compound
buffer layer comprising such as magnesium fluoride, and an oxide
buffer layer comprising such as aluminum oxide.
[0181] The above-described buffer layer (injection layer) is
preferably a very thin layer, and the layer thickness is preferably
in a range of 0.1-100 nm although it depends on a raw material.
[0182] This injection layer can be prepared by forming a thin layer
made of the above-described material according to a method well
known in the art such as a vacuum evaporation method, a spin
coating method, a cast method, an inkjet method and a LB method.
The layer thickness of an injection layer is not specifically
limited; however, is generally 5-5,000 nm. This injection layer may
have a single layer structure comprised of one or not less than two
types of the above described materials.
<Anode>
[0183] As an anode according to an organic EL element of this
invention, those comprising metal, alloy, a conductive compound,
which is provided with a large work function (not less than 4 eV),
and a mixture thereof as an electrode substance are preferably
utilized. Specific examples of such an electrode substance include
a conductive transparent material such as metal like Au, CuI,
indium tin oxide (ITO), SnO.sub.2 and ZnO. Further, a material such
as IDIXO (In.sub.2O.sub.3--ZnO), which can prepare an amorphous and
transparent electrode, may be also utilized. As for an anode, these
electrode substances may be made into a thin layer by a method such
as evaporation or spattering and a pattern of a desired form may be
formed by means of photolithography, or in the case of requirement
of pattern precision is not so severe (not less than 100 .mu.m), a
pattern may be formed through a mask of a desired form at the time
of evaporation or spattering of the above-described substance. When
emission is taken out of this anode, the transmittance is
preferably set to not less than 10% and the sheet resistance as an
anode is preferably not more than a few hundreds
.OMEGA./.quadrature.. Further, although the layer thickness-depends
on a material, it is generally selected in a range of 10-1,000 nm
and preferably of 10-200 nm.
<Cathode>
[0184] On the other hand, as a cathode according to this invention,
metal, alloy, a conductive compound and a mixture thereof, which
have a small work function (not more than 4 eV), are utilized as an
electrode substance. Specific examples of such an electrode
substance includes such as sodium, sodium-potassium alloy,
magnesium, lithium, a magnesium/copper mixture, a magnesium/silver
mixture, a magnesium/aluminum mixture, a magnesium/indium mixture,
an aluminum/aluminum oxide (Al.sub.2O.sub.3) mixture, indium, a
lithium/aluminum mixture and rare earth metal. Among them, with
respect to an electron injection property and durability against
such as oxidation, preferable are a mixture of electron injecting
metal with the second metal which is stable metal having a work
function larger than electron injecting metal, such as a
magnesium/silver mixture, a magnesium/aluminum mixture, a
magnesium/indium mixture, an aluminum/aluminum oxide
(Al.sub.2O.sub.3) mixture and a lithium/aluminum mixture, and
aluminum. As for a cathode, these electrode substances may be made
into a thin layer by a method such as evaporation or spattering.
Further, the sheet resistance as a cathode is preferably not more
than a few hundreds .OMEGA./.quadrature. and the layer thickness is
generally selected in a range of 10-1,000 nm and preferably of
10-200 nm. Herein, to transmit emission, either one of an anode or
a cathode of an organic EL element is preferably transparent or
translucent to improve the mission luminance.
<Substrate (Also Referred to as Base Plate, Base Material or
Support)>
[0185] A substrate according to an organic EL element of this
invention is not specifically limited with respect to types of such
as glass and plastics provided being transparent, however, a
substrate preferably utilized includes such as glass, quartz and
transparent resin film. A specifically preferable substrate is
resin film capable of providing an organic EL element with a
flexible property.
[0186] Resin film includes such as film comprised of polyethylene
terephthalate (PET), polyethylene naphthalate (PEN), polyether
sulphone (PES), polyether imide, polyether etherketone,
polyphenylene sulfide, polyallylate, polyimide, polycarbonate (PC)
and cellulose acetate propionate (CAP).
[0187] On the surface of resin film, an inorganic or organic cover
layer or a hybrid cover layer comprising the both may be formed,
and the film is preferably provided with a high barrier ability
having a vapor transmittance of not more than 0.01 g/m.sup.2dayat a
temperature of 25.+-.0.5.degree. C., relative humidity (90.+-.2)%
RH, measured based on JIS K 7129-1992.
[0188] The taking out efficiency of emission of an organic EL
element of this invention at room temperature is preferably not
less than 1% and more preferably not less than 2%. Herein, taking
out quantum efficiency (%)=photon number emitted out of organic EL
element/electron number flown into organic EL
element.times.100.
[0189] Further, a hue improving filter such as a color filter may
be utilized in combination.
[0190] In the case of an illumination application, roughening
processed film (such as anti-glare film) can be also utilized in
combination to decrease emission unevenness.
[0191] In the case of an application as a multi-color display
device, the display is comprised of at least two types of organic
EL elements having different emission maximum wavelengths, and a
preferable example to prepare an organic EL element will now be
explained.
<Preparation Method of Organic EL Element>
[0192] As an example of a preparation method of an organic EL
element of this invention, a preparation method of an organic EL
element, comprising anode/positive hole injection layer/positive
hole transport layer/emission layer/positive hole inhibition
layer/electron transport layer/cathode buffer layer/cathode, will
be explained.
[0193] First, on an appropriate substrate, a thin layer comprising
a desired electrode substance such as an anode electrode substance
is formed by means of evaporation or spattering so as to make a
layer thickness of not more than 1 .mu.m and preferably of 10-200
nm, whereby an anode is prepared. Next, on this layer, thin layers
containing organic substances of such as a positive hole injection
layer, a positive hole transport layer, an emission layer, a
positive hole inhibition layer and an electron transport layer are
formed.
[0194] A thin layer forming method of these layers containing the
organic substances includes such as a spin coat method, a cast
method, an inkjet method, an evaporation method and a printing
method as described before, however, a vacuum evaporation method or
a spin coat method is specifically preferable with respect to easy
preparation of a homogeneous layer and bare generation of pinholes.
Further, a different layer forming method depending on each layer
may be applied. In the case of employing an evaporation method in
layer formation, the evaporation condition depends on such as the
type of a utilized compound, however, is generally appropriately
selected in a range of 50-450.degree. C. as a boat heating
temperature, 10.sup.-6-10.sup.-2 Pa as a vacuum degree, 0.01-50
nm/sec as a deposition rate, -50-300.degree. C. as a substrate
temperature and 1 nm-5 .mu.m as a layer thickness.
[0195] After formation of these layers, a thin layer comprising a
cathode electrode substance is formed thereon by means of such as
evaporation or spattering so as to make a layer thickness in a
range of 50-200 nm to provide a cathode, whereby a desired organic
EL element can be prepared. This preparation of an organic EL
element is preferably carried out with one time evacuation to
prepare all through from a positive hole injection layer to a
cathode, however, different layer forming method may be also
applied by taking out the element on the way. At that time, it is
preferable to take consideration such as to perform the operation
under a dry inert gas environment.
<Display Device>
[0196] A display device of this invention will now be explained.
The display device of this invention includes the above-described
organic EL element.
[0197] A display device of this invention may be either
monochromatic or multi-colored. Here explained will be a multicolor
display device. In the case of a multicolor display device, a
shadow mask is provided only at the time of emission layer
formation, and layers can be formed all over the surface by such as
an evaporation method, a cast method, a spin coat method, an inkjet
method and a printing method.
[0198] When patterning is performed only with an emission layer,
the method is not specifically limited; however, preferable are an
evaporation method, an inkjet method and a printing method. And
patterning employing a shadow mask is preferred in the case of an
evaporation method.
[0199] Further, reversing the preparation order, it is also
possible to prepare layers in the order of a cathode, an electron
transport layer, a positive hole inhibition layer, an emission
layer, a positive hole transport layer and an anode.
[0200] When a direct current voltage is applied on the multicolor
display device thus prepared, emission can be observed by
application of a voltage of approximately 2-40 V setting an anode
to + polarity and a cathode to - polarity. Further, no current
flows and no emission generate at all even when a voltage is
applied with a reversed polarity. Further, in the case of alternate
current voltage being applied, emission generates only in a state
of an anode being + and a cathode being -. Herein, the wave shape
of alternate current may be arbitrary.
[0201] A multicolor display device can be utilized as a display
device, a display and various types of emission light sources. In a
display device and a display, full-colored display is possible by
employing three types of organic EL elements providing blue, red
and green emissions.
[0202] A display device and a display include a TV, a personal
computer, a mobile instrument, an AV instrument, a character
broadcast display and an information display in a car.
Particularly, the display device and the display may be also
utilized as a display to playback still images and moving images,
and may adopt either a simple matrix (a passive matrix) mode or an
active matrix mode when being utilized as a display device for
moving image playback.
[0203] An illumination light source includes a home use
illumination, a car room illumination, a backlight of a watch or a
liquid crystal, a panel advertisement, a signal, a light source of
an optical memory medium, a light source for an electrophotographic
copier, a light source for an optical telecommunication processor
and a light source for a photo-sensor, however, is not limited
thereto.
<Lighting Device>
[0204] A lighting device of this invention will now be explained.
The lighting device of this invention includes the above-described
organic EL element.
[0205] An organic EL element of this invention can be utilized as
an organic EL element provided with a resonator structure, and a
utilization purpose of such an organic EL element provided with a
resonator structure includes such as a light source for an optical
memory medium, a light source for an electrophotographic copier, a
light source for a optical telecommunication processor and a light
source for a photo-sensor, however, is not limited thereto.
Further, the organic EL element may be utilized for the
above-described applications by being made to perform laser
emission.
[0206] Further, an organic EL element of this invention may be
utilized as one type of a lamp like an illumination and an exposure
light, and may be also utilized as a display device of a projector
of an image projecting type and a display device (a display) of a
type to directly view still images and moving images. An operating
mode in the case of being utilized as a display device for playback
of moving images may be either a simple matrix (a passive matrix)
mode or an active matrix mode. In addition, a full-color display
device can be prepared by utilizing at least two types of organic
EL elements of this invention which emit different emitting
colors.
[0207] In the following, one example of a display device provided
with an organic EL element of this invention will be explained.
[0208] FIG. 1 is a schematic drawing to show an example of a
display device constituted of an organic EL element. It is a
schematic drawing of a display, which displays image information by
emission of an organic EL element, such as a mobile phone.
[0209] Display 1 is constituted of such as display section A having
plural number of pixels and control section B which performs image
scanning of display section A based on image information.
[0210] Control section B, which is electrically connected to
display section A, sends a scanning signal and an image data signal
to plural number of pixels based on image information from the
outside and pixels of each scanning line successively emit
depending on the image data signal by a scanning signal to perform
image scanning, whereby image information is displayed on display
section A.
[0211] FIG. 2 is a schematic drawing of display section A.
[0212] Display section A is provided with such as a wiring part,
which contains plural scanning lines 5 and data lines 6, and plural
pixels 3 on a substrate. Primary part materials of display section
A will be explained in the following.
[0213] In the drawing, shown is the case that light emitted by
pixel 3 is taken out along the white allow (downward).
[0214] Scanning lines 5 and plural data lines 6 in a wiring part
each are comprised of a conductive material, and scanning lines 5
and data lines 6 are perpendicular in a grid form and are connected
to pixels 3 at the right-angled crossing points (details are not
shown in the drawing).
[0215] Pixel 3 receives an image data from data line 6 when a
scanning signal is applied from scanning line 5 and emits according
to the received image data. Full-color display device is possible
by appropriately arranging pixels having an emission color in a red
region, pixels in a green region and pixels in a blue region, side
by side on the same substrate.
[0216] Next an emission process of a pixel will be explained.
[0217] FIG. 3 is a schematic drawing of a pixel.
[0218] A pixel is equipped with such as organic EL element 10,
switching transistor 11, operating transistor 12 and capacitor 13.
Red, green and blue emitting organic EL elements are utilized as
organic EL element 10 for plural pixels, and full-color display
device is possible by arranging these side by side on the same
substrate.
[0219] In FIG. 3, an image data signal is applied on the drain of
switching transistor 11 via data line 6 from control section B.
Then, when a scanning signal is applied on the gate of switching
transistor 11 via scanning line 5 from control section B, operation
of switching transistor is on to transmit the image data signal
applied on the drain to the gates of capacitor 13 and operating
transistor 12.
[0220] Operating transistor 12 is on, simultaneously with capacitor
13 being charged depending on the potential of an image data
signal, by transmission of an image data signal. In operating
transistor 12, the drain is connected to electric source line 7 and
the source is connected to the electrode of organic EL element 10,
and an electric current is supplied from electric source line 7 to
organic EL element 10 depending on the potential of an image data
applied on the gate.
[0221] When a scanning signal is transferred to next scanning line
5 by successive scanning of control section B, operation of
switching transistor 11 is off. However, since capacitor 13 keeps
the charged potential of an image data signal even when operation
of switching transistor 11 is off, operation of operating
transistor 12 is kept on to continue emission of organic EL element
10 until the next scanning signal is applied. When the next
scanning signal is applied by successive scanning, operating
transistor 12 operates depending on the potential of an image data
signal synchronized to the scanning signal and organic EL element
10 emits.
[0222] That is, emission of each organic EL element 10 of plural
pixels 3 is performed by providing switching transistor 11 and
operating transistor 12 against each organic EL element 10 of
plural pixels 3. Such an emission method is called as an active
matrix mode.
[0223] Herein, emission of organic EL element 10 may be either
emission of plural gradations based on a multiple-valued image data
signal having plural number of gradation potentials or on and off
of a predetermined emission quantity based on a binary image data
signal.
[0224] Further, potential hold of capacitor 13 may be either
continuously maintained until the next scanning signal application
or discharged immediately before the next scanning signal
application.
[0225] In this invention, emission operation is not necessarily
limited to the above-described active matrix mode but may be a
passive matrix mode in which organic EL element is emitted based on
a data signal only when a scanning signal is scanned.
[0226] FIG. 4 is a schematic drawing of a display device based on a
passive matrix mode. In FIG. 4, plural number of scanning lines 5
and plural number of image data lines 6 are arranged grid-wise,
opposing to each other and sandwiching pixels 3.
[0227] When a scanning signal of scanning line 5 is applied by
successive scanning, pixel 3 connected to scanning line 5 applied
with said signal emits depending on an image data signal.
[0228] Since pixel 3 is provided with no active element in a
passive matrix mode, decrease of manufacturing cost is
possible.
[0229] An organic EL element material of this invention can be also
applied to an organic EL element to generate emission of
practically white color as a lighting device. Plural emission
colors are simultaneously emitted by plural number of emission
materials to obtain white light by mixing colors. A combination of
plural emission colors may be either the one, in which three
emission maximum wavelengths of three primary colors of blue, green
and red are contained, or the other, in which two emission maximum
wavelengths, utilizing a relationship of complimentary colors such
as blue and yellow, or blue and orange, are contained.
[0230] Further, a combination of emission materials to obtain
plural number of emission colors may be either a combination
comprising plural number of materials which emit phosphoresce or
fluorescence, or a combination of a material which emits
phosphoresce or fluorescence and a dye material which emits by
light from an emission material as exiting light, however, in a
white organic electroluminescent element according to this
invention, it is enough only to mix plural emission dopants in
combination. A mask is provided only at the time of forming such as
an emission layer, a positive hole transport layer or an electron
transport layer, to only simply arrange the plural emission dopants
such as by separately painting through the mask, while other layers
are commonly utilized to require no patterning such as a mask.
Therefore, such as an electrode can be formed all over the plane by
such as an evaporation method, a cast method, a spin coat method,
an inkjet method and a printing method, resulting in improvement of
productivity. According to this method, different from a white
organic EL device in which plural colors of emission elements are
arranged parallel in an alley form, an element itself is white
emitting.
[0231] An emission material utilized in an emission layer is not
specifically limited, and in the case of a backlight of a liquid
crystal display element, any combination by arbitrary selection
among platinum complexes according to this invention or emission
materials well known in the art can be utilized so as to be fitted
to the wavelength range corresponding to CF (color filter)
characteristics, whereby white emission can be obtained.
[0232] In this manner, a white emitting organic EL element of this
invention is usefully utilized as one type of a lamp such as a home
use illumination, a car room illumination or an exposure light
source as various emission light sources or lighting devices, in
addition to the aforesaid display device and a display, and is
further usefully applied for a display as such as a backlight of a
liquid crystal display.
[0233] In addition to these, listed is a wide range of applications
such as a backlight of a watch, an advertising board, a signal, a
light source of an optical memory medium, a light source of an
electrophotographic copier, a light source of an optical
telecommunication processor and a light source of an optical
sensor, and further general home use electric instruments which
require a display device.
EXAMPLES
[0234] In the following, this invention will be explained with
reference to examples, however, is not limited thereto. The
compounds employed in the examples are shown below.
##STR00034## ##STR00035##
Example 1
Preparation of Organic EL Element 1-1
[0235] After a substrate, in which ITO had been deposited at nm on
a glass plate as an anode (NA-45 produced by NH Techno Glass Co.
Ltd.) was subjected to patterning, the transparent support
substrate was washed with isopropyl alcohol by use of ultrasonic
waves, followed by being dried with a dry nitrogen gas, and was
subjected to UV ozone washing for 5 minutes. This transparent
support substrate was fixed on a substrate holder of a vacuum
evaporation system available on the market, and on the other hand,
each of five resistance heating boats made of tantalum was charged
with A-NPD, CA-1, Ir-12, BCP and Alq.sub.3, respectively, which was
attached in the vacuum evaporation system (in the first vacuum
chamber).
[0236] Further, a resistance heating boat made of tantalum was
charged with lithium fluoride and a resistance heating boat made of
tungsten was charged with aluminum, respectively, and these boats
were attached in the second chamber of the vacuum evaporation
system.
[0237] First, after the first vacuum chamber was evacuated down to
4.times.10.sup.-4 Pa, the aforesaid heating boat charged with A-NPD
was heated with an electric current to deposit A-NPD on a support
substrate at a deposition rate of 0.1-0.2 nm/sec so as to make a
layer thickness of 30 nm, whereby a positive hole
injection/transport layer was formed.
[0238] Further, the aforesaid heating boat charged with CA-1 and
the boat charged with Ir-12 were independently supplied with an
electric current to deposit CA-1 as an emission host and Ir-12 as
an emission dopant so as to make a layer thickness of 30 nm while
adjusting the deposition rates thereof to 100:6, whereby an
emission layer was formed.
[0239] Next, the aforesaid heating boat charged with BCP was heated
with an electric current to provide a positive hole inhibition
layer having a layer thickness of 10 nm at a deposition rate of
0.1-0.2 nm/sec. Further, the aforesaid heating boat charged with
Alq.sub.3 was heated with an electric current to provide an
electron transport layer having a layer thickness of 40 nm at a
deposition rate of 0.1-0.2 nm/sec.
[0240] Next, after an element having been deposited with up to an
electron injection layer as described before was transferred into
the second vacuum chamber while keeping vacuum, a mask, which was
made of stainless steel and had rectangular holes, was arranged on
the electron injection layer by means of remote control from
outside of the system.
[0241] After the second vacuum chamber was evacuated down to
2.times.10.sup.-4 Pa, a boat charged with lithium fluoride was
supplied with an electric current to provide a cathode buffer layer
having a layer thickness of 0.5 nm at a deposition rate of
0.01-0.02 nm/sec, and then a boat charged with aluminum was
supplied with an electric current to provide a cathode having a
layer thickness of 150 nm at a deposition rate of 1-2 nm/sec to
obtain Organic EL Element 1-1.
<Preparation of Organic EL Elements 1-2 to 1-16>
[0242] Organic EL elements 1-2 to 1-16 each were prepared in a
similar manner to preparation of organic EL element 1-1 described
above, except that an emission host and an emission dopant was
changed as shown in Table 1.
<<Evaluation of Organic EL Elements>>
[0243] When resulting Organic EL Elements 1-1 to 1-16 were
evaluated, after their preparation, the non-luminescent side was
covered with a glass case, and a 300 .mu.m thick glass substrate
was employed as a sealing substrate. Further, an epoxy based
radiation curable type adhesive (LAXTRACK C0629B, produced by
TOAGOSEI Co., Ltd.) was applied to the periphery as a sealing
agent. The resulting substrate was overlapped onto the above anode
to come into close contact with the above transparent supporting
substrate. Subsequently, UV radiation was exposed to the glass
substrate side to result in curing and sealing. Thus, the lighting
device as shown in FIGS. 5 and 6 was formed and evaluation was then
carried out.
[0244] FIG. 5 is a schematic view of a lighting device. Organic EL
element 101 is covered with glass cover 102 (sealing operation
employing the glass cover was carried out in a globe box (under an
atmosphere of high purity nitrogen gas at a purity of at least
99.999%) without contact with atmospheric air). FIG. 6 is a
sectional view of the lighting device, in which numeral 105
represents a cathode, 106 represents an organic EL layer, and 107
represents a glass substrate having a transparent electrode.
Further, nitrogen gas 108 is fed into glass cover 102, and
desiccant 109 is provided.
<Quantum Efficiency of Taking Out>
[0245] Each of organic EL elements was lighted under a constant
current condition of 2.5 mA/cm.sup.2 at room temperature
(approximately 23-25.degree. C.), and an emission luminance (L)
[cd/m.sup.2] immediately after turning on was measured, whereby a
quantum efficiency of taking out (.eta.) was calculated. Herein,
CS-1000 (produced by Konica Minolta Sensing Inc.) was utilized for
measurement of emission luminance. Further, each of the quantum
efficiency of taking out was expressed as a relative value when
that of organic EL element 1-1 was set to 100.
<Emission Life>
[0246] Each of organic EL elements was continuously lighted under a
constant current condition of 2.5 mA/cm.sup.2 at room temperature
(approximately 23-25.degree. C.), and time to reach a half of the
initial luminance (.tau..sub.1/2) was measured. Further, each
emission life was expressed as a relative value when that of
organic EL element 1-1 was set to 100.
[0247] The obtained results are shown in Table 1.
TABLE-US-00001 TABLE 1 Organic Taking- Lumines- EL out cent Element
Emission Emission Quantum Lifetime No. host dopant Yield
(.tau..sub.1/2) Remarks 1-1 CA-1 Ir-12 100 100 Comp. 1-2 CA-1
Comparison 91 109 Comp. 1 1-3 CA-1 Comparison 90 88 Comp. 2 1-4
CA-1 Comparison 105 79 Comp. 3 1-5 CA-1 1-1 130 255 Inv. 1-6 CA-1
1-2 134 314 Inv. 1-7 CA-1 1-8 131 240 Inv. 1-8 CA-1 1-21 127 270
Inv. 1-9 CA-1 1-25 125 261 Inv. 1-10 CA-1 1-28 132 312 Inv. 1-11
CA-1 1-39 130 230 Inv. 1-12 CA-1 1-44 129 232 Inv. 1-13 CA-1 4-2
122 213 Inv. 1-14 CA-1 4-5 120 204 Inv. 1-15 CA-23 1-1 135 330 Inv.
1-16 CA-23 1-44 132 298 Inv.
[0248] Based on Table 1, it is clear that the organic EL elements
prepared via the metal complexes according to the present invention
attain high luminescent efficiency and extended luminescent
lifetime, compared to the EL element of the Comparative
Examples.
[0249] Further, it was noticed that by simultaneously employing, in
the emission layer, a carboline derivative or its derivative having
a ring structure in which at least one carbon atom of the
hydrocarbon ring constituting the carboline derivative was
substituted with a nitrogen atom, targeted effects of the present
invention were further enhanced.
Example 2
Preparation of Organic EL Element 2-1
[0250] After a substrate, in which ITO had been deposited at 150 nm
on a glass plate as an anode (NA-45 produced by NH Techno Glass Co.
Ltd.) was subjected to patterning, the transparent support
substrate was washed with isopropyl alcohol by use of ultrasonic
waves, followed by being dried with a dry nitrogen gas, and was
subjected to UV ozone washing for 5 minutes.
[0251] This transparent support substrate was fixed on a substrate
holder of a vacuum evaporation system available on the market, and
on the other hand, each of five resistance heating boats made of
tantalum was charged with A-NPD, CA-1, Ir-13, BCP and Alq.sub.3,
respectively, which was attached in the vacuum evaporation system
(in the first vacuum chamber).
[0252] Further, a resistance heating boat made of tantalum was
charged with lithium fluoride and a resistance heating boat made of
tungsten was charged with aluminum, respectively, and these boats
were attached in the second chamber of the vacuum evaporation
system.
[0253] First, after the first vacuum chamber was evacuated down to
4.times.10.sup.-4 Pa, the aforesaid heating boat charged with
.alpha.-NPD was heated with an electric current to deposit
.alpha.-NPD on a support substrate at a deposition rate of 0.1-0.2
nm/sec so as to make a layer thickness of 30 nm, whereby a positive
hole injection/transport layer was formed.
[0254] Further, the aforesaid heating boat charged with CA-1 and
the boat charged with Ir-13 were independently supplied with an
electric current to deposit CA-1 as an emission host and Ir-13 as
an emission dopant so as to make a layer thickness of 30 nm while
adjusting the deposition rates thereof to 100:6, whereby an
emission layer was formed.
[0255] Next, the aforesaid heating boat charged with BCP was heated
with an electric current to provide a positive hole inhibition
layer having a layer thickness of 10 nm at a deposition rate of
0.1-0.2 nm/sec. Further, the aforesaid heating boat charged with
Alq.sub.3 was heated with an electric current to provide an
electron transport layer having a layer thickness of 40 nm at a
deposition rate of 0.1-0.2 nm/sec.
[0256] Next, after an element having been deposited with up to an
electron injection layer as described before was transferred into
the second vacuum chamber while keeping vacuum, a mask, which was
made of stainless steel and had rectangular holes, was arranged on
the electron injection layer by means of remote control from
outside of the system.
[0257] After the second vacuum chamber was evacuated down to
2.times.10.sup.-4 Pa, a boat charged with lithium fluoride was
supplied with an electric current to provide a cathode buffer layer
having a layer thickness of 0.5 nm at a deposition rate of
0.01-0.02 nm/sec, and then a boat charged with aluminum was
supplied with an electric current to provide a cathode having a
layer thickness of 150 nm at a deposition rate of 1-2 nm/sec to
obtain Organic EL Element 2-1.
<Preparation of Organic EL Elements 2-2 to 2-15>
[0258] Organic EL elements 2-2 to 2-15 each were prepared in a
similar manner to preparation of organic EL element 2-1 described
above, except that an emission dopant was changed as shown in Table
2.
<<Evaluation of Organic EL Elements>>
[0259] When resulting Organic EL Elements 2-1 to 2-15 were
evaluated, after their preparation, the non-luminescent side was
covered with a glass case, and a 300 .mu.m thick glass substrate
was employed as a sealing substrate. Further, an epoxy based
radiation curable type adhesive (LAXTRACK C0629B, produced by
TOAGOSEI Co., Ltd.) was applied to the periphery as a sealing
agent. The resulting substrate was overlapped onto the above anode
to come into close contact with the above transparent supporting
substrate. Subsequently, UV radiation was exposed to the glass
substrate side to result in curing and sealing. Thus, the lighting
device as shown in FIGS. 5 and 6 was formed and evaluation was then
carried out.
[0260] FIG. 5 is a schematic view of a lighting device. Organic EL
element 101 is covered with glass cover 102 (sealing operation
employing the glass cover was carried out in a globe box (under an
atmosphere of high purity nitrogen gas at a purity of at least
99.999%) without contact with atmospheric air). FIG. 6 is a
sectional view of the lighting device, in which numeral 105
represents a cathode, 106 represents an organic EL layer, and 107
represents a glass substrate having a transparent electrode.
Further, nitrogen gas 108 is fed into glass cover 102, and
desiccant 109 is provided.
[0261] Taking-out quantum efficiency was evaluated in the same
manner as for Example 1. The taking-out quantum efficiency was
expressed by relative values when each value of Organic EL Element
2-1 was 100.
<Emission Life>
[0262] Each of organic EL elements was continuously lighted under a
constant current condition of 2.5 mA/cm.sup.2 at room temperature
(approximately 23-25.degree. C.), and time to reach 90% of the
initial luminance (.tau..sub.1/9) was measured. Further, each
emission life was expressed as a relative value when that of
organic EL element 2-1 was set to 100.
[0263] Table 2 shows the results.
TABLE-US-00002 TABLE 2 Organic Taking- Lumines- EL out cent Element
Emission Emission Quantum Lifetime No. host dopant Yield
(.tau..sub.1/9) Remarks 2-1 CA-1 Ir-13 100 100 Comp. 2-2 CA-1
Comparison 83 103 Comp. 1 2-3 CA-1 Comparison 90 98 Comp. 2 2-4
CA-1 Comparison 100 77 Comp. 3 2-5 CA-1 2-2 130 241 Inv. 2-6 CA-1
2-7 128 255 Inv. 2-7 CA-1 2-9 124 279 Inv. 2-8 CA-1 2-13 129 288
Inv. 2-9 CA-1 2-14 129 203 Inv. 2-10 CA-1 2-17 122 277 Inv. 2-11
CA-1 2-20 135 298 Inv. 2-12 CA-1 2-23 124 282 Inv. 2-13 CA-1 4-12
120 230 Inv. 2-14 CA-23 2-2 133 345 Inv. 2-15 CA-23 2-7 134 314
Inv.
[0264] Based on Table 2, it is clear that the organic EL elements
prepared via the metal complexes according to the present invention
attain high luminescent efficiency and extended luminescent
lifetime, compared to the EL element of the Comparative
Examples.
[0265] Further, it was noticed that by simultaneously employing, in
the emission layer, a carboline derivative or its derivative having
a ring structure in which at least one carbon atom of the
hydrocarbon ring constituting the carboline derivative was
substituted with a nitrogen atom, targeted effects of the present
invention were further enhanced.
Example 3
Preparation of organic EL Element 3-1
[0266] After a substrate, in which ITO had been deposited at 150 nm
on a glass plate as an anode (NA-45 produced by NH Techno Glass Co.
Ltd.) was subjected to patterning, the transparent support
substrate was washed with isopropyl alcohol by use of ultrasonic
waves, followed by being dried with a dry nitrogen gas, and was
subjected to UV ozone washing for 5 minutes.
[0267] This transparent support substrate was fixed on a substrate
holder of a vacuum evaporation system available on the market, and
on the other hand, each of five resistance heating boats made of
tantalum was charged with m-MTDATXA, CA-2, Ir-12, BCP and
Alq.sub.3, respectively, which was attached in the vacuum
evaporation system (in the first vacuum chamber).
[0268] Further, a resistance heating boat made of tantalum was
charged with lithium fluoride and a resistance heating boat made of
tungsten was charged with aluminum, respectively, and these boats
were attached in the second chamber of the vacuum evaporation
system.
[0269] First, after the first vacuum chamber was evacuated down to
4.times.10.sup.-4 Pa, the aforesaid heating boat charged with
m-MTDATXA was heated with an electric current to deposit m-MTDATXA
on a support substrate at a deposition rate of 0.1-0.2 nm/sec so as
to make a layer thickness of 40 nm, whereby a positive hole
injection/transport layer was formed.
[0270] Further, the aforesaid heating boat charged with CA-2 and
the boat charged with Ir-12 were independently supplied with an
electric current to deposit CA-2 as an emission host and Ir-12 as
an emission dopant so as to make a layer thickness of 30 nm while
adjusting the deposition rates thereof to 100:6, whereby an
emission layer was formed.
[0271] Next, the aforesaid heating boat charged with BCP was heated
with an electric current to provide a positive hole inhibition
layer having a layer thickness of 10 nm at a deposition rate of
0.1-0.2 nm/sec. Further, the aforesaid heating boat charged with
Alq.sub.3 was heated with an electric current to provide an
electron transport layer having a layer thickness of 20 nm at a
deposition rate of 0.1-0.2 nm/sec.
[0272] Next, after an element having been deposited with up to an
electron injection layer as described before was transferred into
the second vacuum chamber while keeping vacuum, a mask, which was
made of stainless steel and had rectangular holes, was arranged on
the electron injection layer by means of remote control from
outside of the system.
[0273] After the second vacuum chamber was evacuated down to
2.times.10.sup.-4 Pa, a boat charged with lithium fluoride was
supplied with an electric current to provide a cathode buffer layer
having a layer thickness of 0.5 nm at a deposition rate of
0.01-0.02 nm/sec, and then a boat charged with aluminum was
supplied with an electric current to provide a cathode having a
layer thickness of 150 nm at a deposition rate of 1-2 nm/sec to
obtain Organic EL Element 3-1.
<Preparation of Organic EL Elements 3-2 to 3-18>
[0274] Organic EL elements 3-2 to 3-18 each were prepared in a
similar manner to preparation of organic EL element 3-1 described
above, except that an emission dopant was changed as shown in Table
3.
<<Evaluation of Organic EL Elements>>
[0275] When resulting Organic EL Elements 3-1 to 3-18 were
evaluated, after their preparation, the non-luminescent side was
covered with a glass case, and a 300 .mu.m thick glass substrate
was employed as a sealing substrate. Further, an epoxy based
radiation curable type adhesive (LAXTRACK C0629B, produced by
TOAGOSEI Co., Ltd.) was applied to the periphery as a sealing
agent. The resulting substrate was overlapped onto the above anode
to come into close contact with the above transparent supporting
substrate. Subsequently, UV radiation was exposed to the glass
substrate side to result in curing and sealing. Thus, the lighting
device as shown in FIGS. 5 and 6 was formed and evaluation was then
carried out.
[0276] FIG. 5 is a schematic view of a lighting device. Organic EL
element 101 is covered with glass cover 102 (sealing operation
employing the glass cover was carried out in a globe box (under an
atmosphere of high purity nitrogen gas at a purity of at least
99.999%) without contact with atmospheric air). FIG. 6 is a
sectional view of the lighting device, in which numeral 105
represents a cathode, 106 represents an organic EL layer, and 107
represents a glass substrate having a transparent electrode.
Further, nitrogen gas 108 is fed into glass cover 102, and
desiccant 109 is provided.
[0277] Taking-out quantum efficiency was evaluated in the same
manner as for Example 1. The taking-out quantum efficiency was
expressed by relative values when each value of organic EL Element
3-1 was 100.
[0278] Table 3 shows the results.
TABLE-US-00003 TABLE 3 Organic Taking- Lumines- EL out cent Element
Emission Emission Quantum Lifetime No. host dopant *1 Yield
(T.sub.1/2) Remarks 3-1 CA-2 Ir-12 BCP 100 100 Comp. 3-2 CA-2
Comparison BCP 80 104 Comp. 1 3-3 CA-2 Comparison BCP 91 95 Comp. 2
3-4 CA-2 Comparison BCP 103 80 Comp. 3 3-5 CA-2 3-1 BCP 130 271
Inv. 3-6 CA-2 3-6 BCP 124 277 Inv. 3-7 CA-4 3-10 BCP 126 256 Inv.
3-8 CA-4 3-11 BCP 128 255 Inv. 3-9 CA-2 3-13 BCP 129 280 Inv. 3-10
CA-10 4-8 BCP 120 235 Inv. 3-12 CA-10 4-9 BCP 122 245 Inv. 3-13
CA-10 3-2 CA-23 133 320 Inv. 3-14 CA-6 3-8 CA-29 129 314 Inv. 3-15
CA-6 3-10 CA-23 129 302 Inv. 3-16 CA-6 3-12 CA-29 122 262 Inv. 3-17
CA-2 3-13 CA-5 128 319 Inv. 3-18 CA-4 4-9 CA-29 126 283 Inv. *1:
Positive Hole Blocking Material
[0279] Based on Table 3, it is clear that the organic EL elements
prepared via the metal complexes according to the present invention
attain high luminescent efficiency and extended luminescent
lifetime, compared to the EL element of the Comparative
Examples.
[0280] Further, it was noticed that by simultaneously employing,
both in the emission layer and in the hole inhibition layer, a
carboline derivative or its derivative having a ring structure in
which at least one carbon atom of the hydrocarbon ring constituting
the carboline derivative was substituted with a nitrogen atom,
targeted effects of the present invention were further
enhanced.
Example 4
Preparation of Organic EL Element 4-1
[0281] After a substrate, in which ITO had been deposited at 150 nm
on a glass plate as an anode (NA-45 produced by NH Techno Glass Co.
Ltd.) was subjected to patterning, the transparent support
substrate was washed with isopropyl alcohol by use of ultrasonic
waves, followed by being dried with a dry nitrogen gas, and was
subjected to UV ozone washing for 5 minutes. This transparent
support substrate was fixed on a substrate holder of a vacuum
evaporation system available on the market, and on the other hand,
each of five resistance heating boats made of tantalum was charged
with .alpha.-NPD, Comparison 4, CA-1, Ir-1, BCP and Alq.sub.3,
respectively, which was attached in the vacuum evaporation system
(in the first vacuum chamber).
[0282] Further, a resistance heating boat made of tantalum was
charged with lithium fluoride and a resistance heating boat made of
tungsten was charged with aluminum, respectively, and these boats
were attached in the second chamber of the vacuum evaporation
system.
[0283] First, after the first vacuum chamber was evacuated down to
4.times.10.sup.-4 Pa, the aforesaid heating boat charged with
.alpha.-NPD was heated with an electric current to deposit
.alpha.-NPD on a support substrate at a deposition rate of 0.1-0.2
nm/sec so as to make a layer thickness of 40 nm, whereby a positive
hole injection/transport layer was formed.
[0284] Then, after the first vacuum chamber was evacuated down to
4.times.10.sup.-4 Pa, the aforesaid heating boat charged with
Comparison 4 was heated with an electric current to deposit
Comparison 4 on a support substrate at a deposition rate of 0.1-0.2
nm/sec so as to make a layer thickness of 20 nm, whereby an
electron inhibition layer was formed.
[0285] Further, the aforesaid heating boat charged with CA-1 and
the boat charged with Ir-1 were independently supplied with an
electric current to deposit CA-1 as an emission host and Ir-1 as an
emission dopant so as to make a layer thickness of 30 nm while
adjusting the deposition rates thereof to 100:7, whereby an
emission layer was formed.
[0286] Next, the aforesaid heating boat charged with BCP was heated
with an electric current to provide a positive hole inhibition
layer having a layer thickness of 15 nm at a deposition rate of
0.1-0.2 nm/sec. Further, the aforesaid heating boat charged with
Alq.sub.3 was heated with an electric current to provide an
electron transport layer having a layer thickness of 20 nm at a
deposition rate of 0.1-0.2 nm/sec.
[0287] Next, after an element having been deposited with up to an
electron injection layer as described before was transferred into
the second vacuum chamber while keeping vacuum, a mask, which was
made of stainless steel and had rectangular holes, was arranged on
the electron injection layer by means of remote control from
outside of the system.
[0288] After the second vacuum chamber was evacuated down to
2.times.10.sup.-4 Pa, a boat charged with lithium fluoride was
supplied with an electric current to provide a cathode buffer layer
having a layer thickness of 0.5 nm at a deposition rate of
0.01-0.02 nm/sec, and then a boat charged with aluminum was
supplied with an electric current to provide a cathode having a
layer thickness of 150 nm at a deposition rate of 1-2 nm/sec to
obtain Organic EL Element 4-1.
<Preparation of Organic EL Elements 4-2 to 4-9>
[0289] Organic EL elements 4-2 to 4-9 each were prepared in a
similar manner to preparation of organic EL element 4-1 described
above, except that an electron inhibition material was changed as
shown in Table 4.
<<Evaluation of Organic EL Elements>>
[0290] When resulting Organic EL Elements 4-1 to 4-9 were
evaluated, after their preparation, the non-luminescent side was
covered with a glass case, and a 300 .mu.m thick glass substrate
was employed as a sealing substrate. Further, an epoxy based
radiation curable type adhesive (LAXTRACK C0629B, produced by
TOAGOSEI Co., Ltd.) was applied to the periphery as a sealing
agent. The resulting substrate was overlapped onto the above anode
to come into close contact with the above transparent supporting
substrate. Subsequently, UV radiation was exposed to the glass
substrate side to result in curing and sealing. Thus, the lighting
device as shown in FIGS. 5 and 6 was formed and evaluation was then
carried out.
[0291] FIG. 5 is a schematic view of a lighting device. Organic EL
element 101 is covered with glass cover 102 (sealing operation
employing the glass cover was carried out in a globe box (under an
atmosphere of high purity nitrogen gas at a purity of at least
99.999%) without contact with atmospheric air). FIG. 6 is a
sectional view of the lighting device, in which numeral 105
represents a cathode, 106 represents an organic EL layer, and 107
represents a glass substrate having a transparent electrode.
Further, nitrogen gas 108 is fed into glass cover 102, and
desiccant 109 is provided.
[0292] Taking-out quantum efficiency was evaluated in the same
manner as for Example 1. The taking-out quantum efficiency was
expressed by relative values when each value of Organic EL Element
4-1 was 100.
[0293] Table 4 shows the results.
TABLE-US-00004 TABLE 4 Organic EL Electron Takingout Luminescent
Element inhibition Quantum Lifetime No. material Yield
(.tau..sub.1/2) Remarks 4-1 Comparison 100 100 Comp. 4 4-2 1-8 115
278 Inv. 4-3 1-16 113 291 Inv. 4-4 2-10 120 201 Inv. 4-5 3-13 122
245 Inv. 4-6 4-2 116 288 Inv. 4-7 4-15 121 285 Inv.
[0294] Based on Table 4, it is clear that the organic EL elements
prepared via the metal complexes according to the present invention
attain high luminescent efficiency and extended luminescent
lifetime, compared to the EL element of the Comparative
Examples.
Example 5
Preparation of Organic EL Element 5-1
[0295] A cathode (at a thickness of 200 nm) composed of an indium
tin oxide (ITO at an indium/tin=95/5 mol ratio) was formed on a 25
mm.times.25 mm.times.0.5 mm glass substrate under application of a
direct electric current, employing a sputtering method. The surface
resistance of the resulting cathode was 10.OMEGA./.quadrature.. The
above surface was coated with a dichloroethane solution in which
polyvinylcarbazole (being a positive hole transporting binder
polymer)/Ir-13 (being a blue fluorescent ortho metal
complex)/2-(4-biphenylyl-5(4-t-butylphenyl)-1,3,4-oxazole (being an
electron transport material)=200/2/50 mole ratio were dissolved,
employing a spin coater, whereby a 100 nm emission layer was
prepared. On the resulting organic compound layer, a mask (being a
mask resulting in a luminescent area of 5 mm.times.5 mm), which was
subjected to patterning, was arranged and an anode was arranged in
such a manner that in a vacuum evaporation device, 0.5 mm lithium
fluoride was evaporated as an anode buffer layer and 150 nm
aluminum as a cathode was evaporated, whereby Blue Luminescent
Organic EL Element 5-1 was prepared.
<preparation of Organic EL Elements 5-2 to 5-5>
[0296] Organic EL Elements 5-2 to 5-5 were prepared in the same
manner as Organic EL Element 5-1, except that the emission dopant
was changed as described in Table 5.
<<Evaluation of Organic EL Elements>>
[0297] When resulting Organic EL Elements 5-1 to 5-5 were
evaluated, after their preparation, the non-luminescent side was
covered with a glass case, and a 300 .mu.m thick glass substrate
was employed as a sealing substrate. Further, an epoxy based
radiation curable type adhesive (LAXTRACK C0629B, produced by
TOAGOSEI Co., Ltd.) was applied to the periphery as a sealing
agent. The resulting substrate was overlapped onto the above anode
to come into close contact with the above transparent supporting
substrate. Subsequently, UV radiation was exposed to the glass
substrate side to result in curing and sealing. Thus, the lighting
device as shown in FIGS. 5 and 6 was formed and evaluation was then
carried out.
[0298] FIG. 5 is a schematic view of a lighting device. Organic EL
element 101 is covered with glass cover 102 (sealing operation
employing the glass cover was carried out in a globe box (under an
atmosphere of high purity nitrogen gas at a purity of at least
99.999%) without contact with atmospheric air). FIG. 6 is a
sectional view of the lighting device, in which numeral 105
represents a cathode, 106 represents an organic EL layer, and 107
represents a glass substrate having a transparent electrode.
Further, nitrogen gas 108 is fed into glass cover 102, and
desiccant 109 is provided.
[0299] Subsequently, luminance and luminescent efficiency were
determined as described below.
(Luminance and Luminescent Efficiency)
[0300] By employing SOURCE MAJOR UNIT Type 2400, produced by Toyo
Technica Inc., DC voltage was applied to an organic EL element to
result in luminescence. Luminance (cd/m.sup.2) in the case in which
10 V DC voltage was applied, was determined and luminescent
efficiency (lm/W). In the case in which an electric current of 2.5
mA/cm.sup.2 was run, was also determined.
[0301] Table 5 shows the results.
TABLE-US-00005 TABLE 5 Organic EL Luminescent Element Emission
Luminance Efficiency No. dopant (cd/m.sup.2) (lm/W) Remarks 5-1
Ir-13 100 100 Comparative Example 5-2 1-2 118 185 Present Invention
5-3 2-8 113 190 Present Invention 5-4 3-11 114 189 Present
Invention 5-5 4-2 115 173 Present Invention
[0302] Based on Table 5, it is evident that the organic EL elements
prepared by employing the metal complexes according to the present
invention attained high luminescent efficiency and high luminance,
compared to the EL element of the Comparative Example.
Example 6
Preparation of Full-Color Display Device
(Preparation of Blue Emission Element)
[0303] Organic EL element 1-5 of example 1 was utilized as a blue
emission element.
(Preparation of Green Emission Element)
[0304] Organic EL element 4-7 of example 4 was utilized as a green
emission element.
(Preparation of Red Emission Element)
[0305] A red emission element was prepared by substituting Ir-13
used in Organic EL element 2-1 of Example 2 with Ir-9.
[0306] Each of red, green and blue organic EL elements prepared
above was arranged parallel on the same substrate to prepare an
active matrix mode full-color having a form as described in FIG. 1,
and only display section A of said display device is schematically
shown in FIG. 2. That is, a wiring section containing plural lines
of scanning line 5 and data line 6, and plural pixels 3 (such as a
pixel having an emission color of a red region, a pixel of a green
region and a pixel of a blue region) arranged parallel are provided
on the same substrate, and scanning lines 5 and data lines 6 in a
wiring section, which are comprised of a conductive material,
respectively, cross each other at a right angle in a grid form to
be connected to pixels 3 at the right-angled crossing points
(details being not shown in the drawing). The aforesaid plural
pixels 3 each are operated in an active matrix mode, in which an
organic EL element, a switching transistor and an operating
transistor are provided corresponding to each emission color, and
receive an image data signal from data line 6 when a scanning
signal is applied from scanning line 5 to emit based on the
received image data. Each red, green and blue pixel was
appropriately arranged parallel in this manner, whereby a
full-color display device was prepared.
[0307] It has been proved that a full-color moving image display
device exhibiting a high luminance, a high durability and a highly
visibility can be achieved by operating said full-color
display.
Example 7
Preparation of White Emitting Element and White Lighting Device
[0308] A transparent electrode substrate of example 1 was subjected
to patterning of an electrode having an area of 20 mm.times.20 mm,
and .alpha.-NPD was deposited thereon at a layer thickness of 25 nm
as a positive hole injection/transport layer in a similar manner to
example 1; and further the aforesaid heating boat charged with
CA-1, boat containing Example compound (1-11) and boat containing
Ir-9 were supplied with an electric current to deposit an emission
layer having a layer thickness of 30 nm, while adjusting the
evaporation rates of CA-1 as an emission host, Example compound
(1-11) and Ir-9 as emission dopants to be 100:5:0.6.
[0309] Successively, BCP was deposited at 10 nm to provide a
positive hole inhibition layer. Further, Alq.sub.3 was deposited at
40 nm to provide an electron transport layer.
[0310] Next, similar to example 1, a mask with square holes having
a shape nearly same as a transparent electrode made of stainless
steel was arranged on an electron injection layer, and 0.5 nm of
lithium fluoride as a cathode buffer layer and 150 nm of aluminum
as a cathode were deposited.
[0311] This element was equipped with a sealed can, which had a
similar structure and was prepared in a similar method to example
1, to prepare flat lamps shown in FIGS. 5 and 6. FIG. 5 shows a
schematic view of a lighting device, and FIG. 6 shows a
cross-sectional view of a lighting device.
[0312] FIG. 5 is a schematic view of a lighting device. Organic EL
element 101 is covered with glass cover 102 (sealing operation
employing the glass cover was carried out in a globe box (under an
atmosphere of high purity nitrogen gas at a purity of at least
99.999%) without contact with atmospheric air). FIG. 6 is a
sectional view of the lighting device, in which numeral 105
represents a cathode, 106 represents an organic EL layer, and 107
represents a glass substrate having a transparent electrode.
Further, nitrogen gas 108 is fed into glass cover 102, and
desiccant 109 is provided.
[0313] Nearly white light was obtained when these lamps were
supplied with an electric current to prove that said lamp can be
utilized as a lighting device.
* * * * *