U.S. patent application number 13/585132 was filed with the patent office on 2012-12-06 for organic electroluminescence device and display.
This patent application is currently assigned to Idemitsu Kosan Co., Ltd.. Invention is credited to Chishio HOSOKAWA, Kiyoshi Ikeda, Takayasu Sado.
Application Number | 20120305908 13/585132 |
Document ID | / |
Family ID | 39759489 |
Filed Date | 2012-12-06 |
United States Patent
Application |
20120305908 |
Kind Code |
A1 |
HOSOKAWA; Chishio ; et
al. |
December 6, 2012 |
ORGANIC ELECTROLUMINESCENCE DEVICE AND DISPLAY
Abstract
In an organic electroluminescence device including a cathode and
an anode, at least an emitting layer and an electron transporting
layer are provided between the cathode and the anode. The emitting
layer contains a host material formed of a naphthacene derivative
represented by the following formula (1) and a dopant material
formed of a compound having a pyrromethene skeleton represented by
the following formula (2) or a metal complex of the compound. The
electron transporting layer is preferably a benzoimidazole
derivative. ##STR00001##
Inventors: |
HOSOKAWA; Chishio;
(Sodegaura-shi, JP) ; Sado; Takayasu;
(Sodegaura-shi, JP) ; Ikeda; Kiyoshi;
(Sodegaura-shi, JP) |
Assignee: |
Idemitsu Kosan Co., Ltd.
Chiyoda-ku
JP
|
Family ID: |
39759489 |
Appl. No.: |
13/585132 |
Filed: |
August 14, 2012 |
Related U.S. Patent Documents
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Application
Number |
Filing Date |
Patent Number |
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12044436 |
Mar 7, 2008 |
8278819 |
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13585132 |
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Current U.S.
Class: |
257/40 ;
257/E51.026 |
Current CPC
Class: |
H01L 51/008 20130101;
C07C 15/38 20130101; H01L 51/5012 20130101; H01L 51/0065 20130101;
C09K 2211/1055 20130101; H01L 51/0072 20130101; H01L 51/0054
20130101; C09K 11/06 20130101; C07C 15/62 20130101; C09K 2211/1011
20130101; C07C 2603/44 20170501 |
Class at
Publication: |
257/40 ;
257/E51.026 |
International
Class: |
H01L 51/54 20060101
H01L051/54 |
Foreign Application Data
Date |
Code |
Application Number |
Mar 9, 2007 |
JP |
2007-061091 |
Claims
1-20. (canceled)
21. An organic electroluminescence device, comprising: a cathode;
an anode; and an emitting layer provided between the cathode and
the anode, wherein the emitting layer comprises a host and a
dopant, the host is a naphthacene derivative represented by a
formula (1) as follows, and the dopant is a compound having a
pyrromethene skeleton represented by a formula (2) as follows or a
metal complex of the compound, ##STR00064## in the formula (1),
Q.sup.10, Q.sup.40, Q.sup.50, Q.sup.60, Q.sup.70, Q.sup.80,
Q.sup.110, Q.sup.120, Q.sup.130 and Q.sup.140 each representing a
hydrogen atom, a substituted or unsubstituted alkyl group having 1
to 20 carbon atoms, a substituted or unsubstituted aryl group
having 6 to 30 carbon atoms, a substituted or unsubstituted amino
group, a substituted or unsubstituted alkoxy group having 1 to 20
carbon atoms, a substituted or unsubstituted alkylthio group having
1 to 20 carbon atoms, a substituted or unsubstituted aryloxy group
having 6 to 30 carbon atoms, a substituted or unsubstituted
arylthio group having 6 to 30 carbon atoms, a substituted or
unsubstituted alkenyl group having 1 to 20 carbon atoms, a
substituted or unsubstituted aralkyl group having 7 to 30 carbon
atoms or a substituted or unsubstituted heterocyclic group,
Q.sup.10, Q.sup.40, Q.sup.50, Q.sup.60, Q.sup.70, Q.sup.80,
Q.sup.110, Q.sup.120, Q.sup.130 and Q.sup.140 being allowed to be
mutually the same or different, Q.sup.20 and Q.sup.30 in the
formula (1) each representing a substituted or unsubstituted
heterocylic group, Q.sup.20 and Q.sup.30 being allowed to be
mutually the same or different, in the formula (2): at least one of
R.sup.15 to R.sup.21 being a substitute containing an aromatic ring
or forming a condensed ring with an adjacent substituent while the
rest of R.sup.15 to R.sup.21 each representing a hydrogen atom, an
alkyl group, a cycloalkyl group, an aralkyl group, an alkenyl
group, a cycloalkenyl group, an alkynyl group, a hydroxyl group, a
mercapto group, an alkoxy group, an alkylthio group, an arylether
group, an arylthioether group, an aryl group, a heterocyclic group,
a halogen, a haloalkane, a haloalkene, a haloalkyne, a cyano group,
an aldehyde group, a carbonyl group, a carboxyl group, an ester
group, a carbamoyl group, an amino group, a nitro group, a silyl
group or a siloxanyl group, the rest of R.sup.5 to R.sup.21 each
being allowed to form a condensed ring or an aliphatic ring with an
adjacent substituent, the groups listed above each having 1 to 20
carbon atoms, R.sup.15 to R.sup.21 being allowed to be mutually the
same or different and being allowed to be substituted or
unsubstituted; X representing a carbon atom or a nitrogen atom on a
condition that R.sup.21 above does not exist when X represents a
nitrogen atom; and a metal in the metal complex is at least one
metal selected from the group consisting of boron, beryllium,
magnesium, chromium, iron, cobalt, nickel, copper, zinc and
platinum.
22. The organic electroluminescence device according to claim 21,
wherein the substituted or unsubstituted heterocyclic group
represented by Q.sup.20 and Q.sup.30 is a condensed polycyclic
aromatic heterocyclic group having 2 to 20 carbon atoms.
23. The organic electroluminescence device according to claim 21,
wherein the heterocyclic group represented by Q.sup.20 and Q.sup.30
comprises a substituent, the substituent forming a condensed ring,
and the condensed ring is substituted or unsubstituted.
24. The organic electroluminescence device according to claim 21,
wherein the substituted or unsubstituted heterocyclic group
represented by Q.sup.20 and Q.sup.30 is at least one substituted or
unsubstituted condensed polycyclic aromatic heterocyclic group
selected from the group consisting of quinoline, isoquinoline,
quinoxaline, phenazine, acridine, indole, carbazole, phenoxazine,
phenothiazine, benzothiazole, benzothiophen, benzofuran, acridone,
benzoimidazole, coumarin and flavone.
25. The organic electroluminescence device according to claim 21,
wherein the metal complex represented by the formula (2) is a metal
complex having a pyrromethene skeleton represented by a formula
(2-1) as follows, ##STR00065## where: at least one of R.sup.22 to
R.sup.28 is a substituent having an aromatic ring or forms a
condensed aromatic ring together with an adjacent substituent while
the rest of R.sup.22 to R.sup.28 each represent a hydrogen atom, an
alkyl group, a cycloalkyl group, an aralkyl group, an alkenyl
group, a cycloalkenyl group, an alkynyl group, a hydroxyl group, a
mercapto group, an alkoxy group, an alkylthio group, an arylether
group, an arylthioether group, an aryl group, a heterocyclic group,
halogen, haloalkene, haloalkene, haloalkyne, a cyan group, an
aldehyde group, a carbonyl group, a carboxyl group, an ester group,
a carbamoyl group, an amino group, a nitro group, a silyl group or
a siloxanyl group, the rest of R.sup.22 to R.sup.28 each being
allowed to form a condensed ring or an aliphatic ring with an
adjacent substituent, R.sup.22 to R.sup.28 being allowed to be
mutually the same or different and being allowed to be substituted
or unsubstituted; R.sup.29 and R.sup.30 are allowed to be mutually
the same or different and each are selected from the group
consisting of halogen, a hydrogen atom, substituted or
unsubstituted alkyl, substituted or unsubstituted aryl and a
substituted or unsubstituted heterocyclic group; and X representing
a carbon atom or a nitrogen atom on a condition that R.sup.21 above
does not exist when X represents a nitrogen atom.
26. The organic electroluminescence device according to claim 25,
wherein at least one of R.sup.22 to R.sup.28 in the metal complex
having the pyrromethene skeleton represented by the formula (2-1)
is a substituent having an aromatic ring.
27. The organic electroluminescence device according to claim 25,
wherein at least one of R.sup.22 to R.sup.28 in the metal complex
having the pyrromethene skeleton represented by the formula (2-1)
forms a condensed aromatic ring together with an adjacent
substituent.
28. The organic electroluminescence device according to claim 21,
wherein at least one of Q.sup.10 and Q.sup.40 in the naphthacene
derivative represented by the formula (1) is a substituted or
unsubstituted aryl group having 6 to 30 carbon atoms.
29. The organic electroluminescence device according to claim 21,
wherein the dopant is contained in the emitting layer at a doping
concentration of 0.1 to 10 mass %.
30. The organic electroluminescence device according to claim 29,
wherein the dopant is contained in the emitting layer at a doping
concentration of 0.5 to 2 mass %.
31. The organic electroluminescence device according to claim 21,
further comprising: an electron transporting layer provided between
the cathode and the anode, wherein the electron transporting layer
comprises a compound represented by a formula (4) as follows,
(A).sub.m-(B).sub.n (4) where: A represents a substituted or
unsubstituted condensed aromatic hydrocarbon group having three or
more rings; B represents a substituted or unsubstituted
heterocyclic group; and m and n each represent an integer in a
range of 1 to 6.
32. The organic electroluminescence device according to claim 31,
wherein A in the compound represented by the formula (4) has a
skeleton in its molecule, the skeleton selected from the group
consisting of anthracene, phenanthrene, naphthacene, pyrene,
chrysene, benzoanthracene, pentacene, dibenzoanthracene,
benzopyrene, fluorene, benzofluorene, fluoranthene,
benzofluoranthene, naphthofluoranthene, dibenzofluorene,
dibenzopyrene and dibenzofluoranthene.
33. The organic electroluminescence device according to claim 31,
wherein B in the compound represented by the formula (4) is a
nitrogen-containing heterocyclic group.
34. The organic electroluminescence device according to claim 33,
wherein B in the compound represented by the formula (4) has a
skeleton in its molecule, the skeleton selected from the group
consisting of pyridine, pyrimidine, pyrazine, pyridazine, triazine,
quinoline, quinoxaline, acridine, imidazopyridine,
imidazopyrimidine, phenanthroline, pyrazole, imidazole and
benzoimidazole.
35. The organic electroluminescence device according to claim 34,
wherein the compound represented by the formula (4) is a
benzoimidazole derivative represented by a formula (5) or a formula
(6) as follows, ##STR00066## where: R represents a hydrogen atom, a
substituted or unsubstituted aryl group having 6 to 60 carbon
atoms, a substituted or unsubstituted pyridyl group, a substituted
or unsubstituted quinolyl group, a substituted or unsubstituted
alkyl group having 1 to 20 carbon atoms or a substituted or
unsubstituted alkoxy group having 1 to 20 carbon atoms; p
represents an integer in a range of 1 to 4; R.sup.11 represents a
substituted or unsubstituted aryl group having 6 to 60 carbon
atoms, a substituted or unsubstituted pyridyl group, a substituted
or unsubstituted quinolyl group, a substituted or unsubstituted
alkyl group having 1 to 20 carbon atoms or an alkoxy group having 1
to 20 carbon atoms; R.sup.12 represents a hydrogen atom, a
substituted or unsubstituted aryl group having 6 to 60 carbon
atoms, a substituted or unsubstituted pyridyl group, a substituted
or unsubstituted quinolyl group, a substituted or unsubstituted
alkyl group having 1 to 20 carbon atoms or a substituted or
unsubstituted alkoxy group having 1 to 20 carbon atoms; L
represents a substituted or unsubstituted arylene group having 6 to
60 carbon atoms, a substituted or unsubstituted pyridinylene group,
a substituted or unsubstituted quinolinylene group or a substituted
or unsubstituted fluorenylene group; and Ar.sup.1 represents a
substituted or unsubstituted aryl group having 6 to 60 carbon
atoms, a substituted or unsubstituted pyridyl group or a
substituted or unsubstituted quinolyl group, at least one of R,
R.sup.11, R.sup.12, L and Ar.sup.1 corresponding to A in the
compound represented by the formula (4) and being a condensed
aromatic hydrocarbon group having three or more rings.
36. The organic electroluminescence device according to claim 21,
wherein the emitting layer emits light of orange to red.
37. A display, comprising the organic electroluminescence device
according to claim 21.
Description
BACKGROUND OF THE INVENTION
[0001] 1. Field of the Invention
[0002] The present invention relates to an organic
electroluminescence device (organic EL device) and a display that
use a naphthacene derivative and a compound having a pyrromethene
skeleton or a metal complex of the compound together.
[0003] 2. Description of Related Art
[0004] Organic electroluminescence (EL) devices have been known.
Organic EL devices formed from organic materials have been
vigorously studied since a report on a low voltage-driven organic
EL device formed by laminating layers was made by C. W. Tang et al.
of Eastman Kodak Company (see Document 1: Applied Physics Letters,
vol. 51, page 913, by C. W. Tang and S. A. Vanslyke, 1987).
[0005] Known examples of an emitting material used for an organic
EL device are a chelate complex such as a
tris(8-quinolinol)aluminum (Alq) complex, a coumarin complex, a
tetraphenylbutadiene derivative, a bisstyrylarylene derivative, an
oxadiazole derivative or the like. These emitting materials, which
have been reported to emit blue to red light in a visible region,
are expected to be applied to color-display devices (e.g., Document
2: JP-A-08-239655, Document 3: JP-A-07-138561, Document 4:
JP-A-03-200889 and the like). However, luminous efficiency and
lifetime of such a device has been so insufficient that the device
has not been practically applicable. While a full color display
requires three primary colors of blue, green and red, among them, a
red-emitting device with high efficiency has been demanded.
[0006] For instance, Document 5 (JP-A-08-311442) has recently
disclosed a red-emitting device whose emitting layer is added with
a naphthacene derivative or a pentacene derivative. However,
although the red-emitting device is excellent in purity of red
color, the red-emitting device requires voltage of 11V to be
applied, and time lapsed until the luminescent intensity decreases
to half is approximately 150 hours, i.e., the performance of the
device is insufficient. Document 6 (JP-A-03-162481) discloses a
device whose emitting layer is added with a dicyanomethylene
(DCM)-based compound. However, the device exhibits insufficient
purity of red color. Document 7 (JP-A-2001-81451) discloses a
red-emitting device whose emitting layer is added with an
amine-based aromatic compound. However, although the emitting
device exhibits excellent CIE (Commission Internationale
d'Eclairage) chromaticity (0.64, 0.33) and chromatic purity, the
device requires high voltage for driving. Document 8 (WO/01/23497)
and Document 9 (JP-A-2003-40845) disclose devices in which an
amine-based aromatic compound and an Alq compound are used for the
emitting layer. However, although emitting red light, the device
exhibits low efficiency and short lifetime.
[0007] Document 10 (JP-A-2003-81924) discloses devices in which an
amine-based aromatic compound and DPVDPAN are used for the emitting
layer. However, high-efficient one of the devices emits orange
light while red-emitting one of the devices exhibits low
efficiency.
[0008] Document 11 (JP-A-2001-307885) discloses a device in which a
dicyanoanthracene derivative and an indenoperylene derivative are
used for the emitting layer while a metal complex is used for the
electron transporting layer. However, the device emits light of red
orange color.
[0009] Document 12 (JP-A-2003-338377) discloses a device in which a
fluoranthene derivative and an indenoperylene derivative are used
for the emitting layer while a fluoranthene derivative is used for
the electron transporting layer. However, the device does not
exhibit practically-applicable efficiency.
SUMMARY OF THE INVENTION
[0010] An object of the present invention is to provide an
practically-applicable organic EL device and a
practically-applicable display excellent in efficiency, lifetime
and chromatic purity.
[0011] After conducting concentrated studies in order to achieve
such an object, the inventors have found that an organic EL device
exhibits longer lifetime and higher efficiency by using a
naphthacene derivative and a compound having a pyrromethene
skeleton or a metal complex of the compound in at least one layer
of organic compound layers of the organic EL device, and reached
the present invention.
[0012] An organic electroluminescence device according to an aspect
of the present invention includes: a cathode; an anode; and an
emitting layer provided between the cathode and the anode, in which
the emitting layer comprises a host and a dopant, the host is a
naphthacene derivative represented by a formula (1) as follows, and
the dopant is a compound having a pyrromethene skeleton represented
by a formula (2) as follows or a metal complex of the compound.
##STR00002##
[0013] In the formula (1), Q.sup.10, Q.sup.20, Q.sup.30, Q.sup.40,
Q.sup.50, Q.sup.60, Q.sup.70, Q.sup.80, Q.sup.110, Q.sup.120,
Q.sup.130 and Q.sup.140 each represent a hydrogen atom, a
substituted or unsubstituted alkyl group having 1 to 20 carbon
atoms, a substituted or unsubstituted aryl group having 6 to 30
carbon atoms, a substituted or unsubstituted amino group, a
substituted or unsubstituted alkoxy group having 1 to 20 carbon
atoms, a substituted or unsubstituted alkylthio group having 1 to
20 carbon atoms, a substituted or unsubstituted aryloxy group
having 6 to 30 carbon atoms, a substituted or unsubstituted
arylthio group having 6 to 30 carbon atoms, a substituted or
unsubstituted alkenyl group, a substituted or unsubstituted aralkyl
group having 7 to 30 carbon atoms or a substituted or unsubstituted
heterocyclic group. Q.sup.10, Q.sup.20, Q.sup.30, Q.sup.40,
Q.sup.50, Q.sup.60, Q.sup.70, Q.sup.80, Q.sup.110, Q.sup.120,
Q.sup.130 and Q.sup.140 may be mutually the same or different.
[0014] In the formula (2), at least one of R.sup.15 to R.sup.21 is
a substitute having an aromatic ring or forms a condensed ring
together with an adjacent substituent while the rest of R.sup.15 to
R.sup.21 each represent a hydrogen atom, an alkyl group, a
cycloalkyl group, an aralkyl group, an alkenyl group, a
cycloalkenyl group, an alkynyl group, a hydroxyl group, a mercapto
group, an alkoxy group, an alkylthio group, an arylether group, an
arylthioether group, an aryl group, a heterocyclic group, halogen,
a haloalkane, a haloalkene, a haloalkyne, a cyano group, an
aldehyde group, a carbonyl group, a carboxyl group, an ester group,
a carbamoyl group, an amino group, a nitro group, a silyl group or
a siloxanyl group. The rest of R.sup.15 to R.sup.21 each may form a
condensed ring or an aliphatic ring with an adjacent substituent
(the groups listed above each have 1 to 20 carbon atoms). R.sup.15
to R.sup.21 may be mutually the same or different and may be
substituted or unsubstituted. X represents a carbon atom or a
nitrogen atom on a condition that R.sup.21 above does not exist
when X represents a nitrogen atom. A metal in the metal complex is
at least one metal selected from a group consisting of boron,
beryllium, magnesium, chrome, iron, cobalt, nickel, copper, zinc
and platinum.
[0015] The metal in the metal complex is particularly preferably
boron.
[0016] The substituted or unsubstituted alkyl group is preferably
an alkyl group having 1 to 20 carbon atoms, more preferably an
alkyl group having 1 to 10 carbon atoms, further preferably an
alkyl group having 1 to 5 carbon atoms. The alkyl group may be
linear or branched. The alkyl group may be a primary alkyl group, a
secondary alkyl group or a tertiary alkyl group.
[0017] Preferable examples of the alkyl group are a methyl group,
an ethyl group, an n-propyl group, an isopropyl group, an n-butyl
group, a sec-butyl group, a tert-butyl group, an n-pentyl group, an
n-hexyl group, an n-heptyl group, an n-octyl group, an n-nonyl
group and an n-decyl group.
[0018] The substituted or unsubstituted aryl group is preferably an
aryl group having 6 to carbon atoms, more preferably an aryl group
having 6 to 20 carbon atoms. Examples of the aryl group are a
phenyl group, a phenylphenyl group (4-phenylphenyl group,
3-phenylphenyl group, 2-phenylphenyl group), a naphthylphenyl group
(4-(1-naphthyl)phenyl group, 4-(2-naphthyl)phenyl group), a
naphthyl group (1-naphthyl group, 2-naphthyl group), a
phenylnaphthyl group (6-phenyl-2-naphthyl group,
4-phenyl-1-naphthyl group), a naphthylnaphthyl group
(6-naphthyl-2-naphthyl group, 4-naphthyl-1-naphthyl group), an
anthranil group, a phenantyl group, a pyrenyl group and a chrysenyl
group.
[0019] The amino group may be an amino group, a substituted or
unsubstituted monoalkyl-aryl group having 1 to 20 carbon atoms, a
substituted or unsubstituted dialkyl-aryl group having 1 to 20
carbon atoms, a substituted or unsubstituted monoaryl-aryl group
having 6 to 30 carbon atoms, or a substituted or unsubstituted
bisaryl-aryl group having 6 to 30 carbon atoms. Examples of the
amino group are a dimethylamino group, a diethylamino group, a
diphenylamino group, a ditolylamino group and a dixylylamino
group.
[0020] The substituted or unsubstituted alkoxy group is preferably
an alkoxy group having 1 to 20 carbon atoms, examples of which are
a methoxy group, an ethoxy group and a propoxy group.
[0021] The substituted or unsubstituted alkylthio group is
preferably an alkylthio group having 1 to 20 carbon atoms, examples
of which are a methylthio group and an ethylthio group.
[0022] The substituted or unsubstituted aryloxy group is preferably
an aryloxy group having 6 to 30 carbon atoms, an example of which
is a phenoxy group.
[0023] The substituted or unsubstituted aryloxythio group is
preferably an aryloxythio group having 6 to 30 carbon atoms, an
example of which is a phenylthio group.
[0024] The substituted or unsubstituted alkenyl group is preferably
an alkenyl group having 1 to 20 carbon atoms, examples of which are
a vinyl group and a propenyl group.
[0025] The substituted or unsubstituted aralkyl group is preferably
an aralkyl group having 7 to 30 carbon atoms, an example of which
is a benzyl group.
[0026] The substituted or unsubstituted heterocyclic group is
preferably a heterocyclic group having 5 to 30 carbon atoms,
examples of which are a pyridyl group, a furyl group, a thienyl
group, a pyrazyl group, a pyrimidyl group and a quinolyl group.
[0027] According to the aspect of the present invention, since the
emitting layer contains the host formed of a naphthacene derivative
and the dopant formed of a compound having a pyrromethene skeleton
or a metal complex of the compound, the organic EL device having
practically-applicable efficiency and lifetime can be realized.
[0028] According to the aspect of the present invention, it is
preferable that the compound having the pyrromethene skeleton
represented by the formula (2) or the metal complex of the compound
is a metal complex having a pyrromethene skeleton represented by a
formula (2-1) as follows.
##STR00003##
[0029] In the formula (2-1), at least one of R.sup.22 to R.sup.28
is a substitute having an aromatic ring or forms a condensed
aromatic ring together with an adjacent substituent while the rest
of R.sup.22 to R.sup.28 each represent a hydrogen atom, an alkyl
group, a cycloalkyl group, an aralkyl group, an alkenyl group, a
cycloalkenyl group, an alkynyl group, a hydroxyl group, a mercapto
group, an alkoxy group, an alkylthio group, an arylether group, an
arylthioether group, an aryl group, a heterocyclic group, halogen,
haloalkane, haloalkene, haloalkyne, a cyano group, an aldehyde
group, a carbonyl group, a carboxyl group, an ester group, a
carbamoyl group, an amino group, a nitro group, a silyl group or a
siloxanyl group. The rest of R.sup.22 to R.sup.28 each may form a
condensed ring or an aliphatic ring with an adjacent substituent.
R.sup.22 to R.sup.28 may be mutually the same or different and may
be substituted or unsubstituted. R.sup.29 and R.sup.30 may be
mutually the same or different and each are selected from a group
consisting of halogen, a hydrogen atom, substituted or
unsubstituted alkyl, substituted or unsubstituted aryl and a
substituted or unsubstituted heterocyclic group. X represents a
carbon atom or a nitrogen atom on a condition that R.sup.28 above
does not exist when X represents a nitrogen atom.
[0030] According to the aspect of the present invention, it is
preferable that at least one of R.sup.22 to R.sup.28 in the metal
complex having the pyrromethene skeleton represented by the formula
(2-1) is a substituent having an aromatic ring.
[0031] According to the aspect of the present invention, it is
preferable that at least one of R.sup.22 to R.sup.28 in the metal
complex having the pyrromethene skeleton represented by the formula
(2-1) forms a condensed aromatic ring together with an adjacent
substituent.
[0032] According to the aspect of the present invention, it is
preferable that at least one of R.sup.22 to R.sup.24 in the metal
complex having the pyrromethene skeleton represented by the formula
(2-1) forms a substituted or unsubstituted condensed aromatic ring
together with an adjacent substituent and/or at least one of
R.sup.25 to R.sup.27 in the metal complex having the pyrromethene
skeleton represented by the formula (2-1) forms a substituted or
unsubstituted condensed aromatic ring together with an adjacent
substituent.
[0033] According to the aspect of the present invention, it is
preferable that the metal complex having the pyrromethene skeleton
represented by the formula (2-1) is a metal complex having a
pyrromethene skeleton represented by a formula (2-2) as
follows.
##STR00004##
[0034] In the formula (2-2), R.sup.31 to R.sup.39 each represent a
hydrogen atom, an alkyl group, a cycloalkyl group, an aralkyl
group, an alkenyl group, a cycloalkenyl group, an alkynyl group, a
hydroxyl group, a mercapto group, an alkoxy group, an alkylthio
group, an arylether group, an arylthioether group, an aryl group, a
heterocyclic group, halogen, haloalkane, haloalkene, haloalkyne, a
cyano group, an aldehyde group, a carbonyl group, a carboxyl group,
an ester group, a carbamoyl group, an amino group, a nitro group, a
silyl group or a siloxanyl group. R.sup.31 to R.sup.39 may be
mutually the same or different and may be substituted or
unsubstituted. R.sup.40 and R.sup.41 may be mutually the same or
different and each are selected from a group consisting of halogen,
a hydrogen atom, substituted or unsubstituted alkyl, substituted or
unsubstituted aryl and a substituted or unsubstituted heterocyclic
group. X represents a carbon atom or a nitrogen atom on a condition
that R.sup.39 above does not exist when X represents a nitrogen
atom.
[0035] According to the aspect of the present invention, it is
preferable that the metal complex having the pyrromethene skeleton
represented by the formula (2-1) is a metal complex having a
pyrromethene skeleton represented by a formula (2-3) as
follows.
##STR00005##
[0036] In the formula (2-3), R.sup.42 to R.sup.52 each represent a
hydrogen atom, an alkyl group, a cycloalkyl group, an aralkyl
group, an alkenyl group, a cycloalkenyl group, an alkynyl group, a
hydroxyl group, a mercapto group, an alkoxy group, an alkylthio
group, an arylether group, an arylthioether group, an aryl group, a
heterocyclic group, halogen, haloalkane, haloalkene, haloalkyne, a
cyano group, an aldehyde group, a carbonyl group, a carboxyl group,
an ester group, a carbamoyl group, an amino group, a nitro group, a
silyl group or a siloxanyl group. R.sup.42 to R.sup.52 may be
mutually the same or different and may be substituted or
unsubstituted. R.sup.53 and R.sup.54 may be mutually the same or
different and each are selected from a group consisting of halogen,
a hydrogen atom, a substituted or unsubstituted alkyl, a
substituted or unsubstituted aryl and a substituted or
unsubstituted heterocyclic group. X represents a carbon atom or a
nitrogen atom on a condition that R.sup.52 above does not exist
when X represents a nitrogen atom.
[0037] According to the aspect of the present invention, it is
preferable that at least one of Q.sup.10, Q.sup.20, Q.sup.30 and
Q.sup.40 in the naphthacene derivative represented by the formula
(1) is a substituted or unsubstituted aryl group having 6 to 30
carbon atoms.
[0038] According to the aspect of the present invention, it is
preferable that the naphthacene derivative represented by the
formula (1) is a naphthacene derivative represented by a formula
(3) as follows.
##STR00006##
[0039] In the formula (3), Q.sup.10, Q.sup.21 to Q.sup.25, Q.sup.31
to Q.sup.35, Q.sup.40 to Q.sup.80 and Q.sup.110 to Q.sup.140 each
represent a hydrogen atom, a substituted or unsubstituted alkyl
group, a substituted or unsubstituted aryl group, a substituted or
unsubstituted amino group, a substituted or unsubstituted alkoxy
group, a substituted or unsubstituted alkylthio group, a
substituted or unsubstituted aryloxy group, a substituted or
unsubstituted arylthio group, a substituted or unsubstituted
alkenyl group, a substituted or unsubstituted aralkyl group, or a
substituted or unsubstituted heterocyclic group. Q.sup.10, Q.sup.21
to Q.sup.25, Q.sup.31 to Q.sup.35, Q.sup.40 to Q.sup.80 and
Q.sup.110 to Q.sup.140 may be mutually the same or different.
[0040] Adjacent two or more of Q.sup.21 to Q.sup.25 and Q.sup.31 to
Q.sup.35 may be mutually bonded to form a cyclic structure.
[0041] According to the aspect of the present invention, it is
preferable that at least one of Q.sup.21, Q.sup.25, Q.sup.31 an
Q.sup.35 in the naphthacene derivative represented by the formula
(3) represents a substituted or unsubstituted alkyl group, a
substituted or unsubstituted aryl group, a substituted or
unsubstituted amino group, a substituted or unsubstituted alkoxy
group, a substituted or unsubstituted alkylthio group, a
substituted or unsubstituted aryloxy group, a substituted or
unsubstituted arylthio group, a substituted or unsubstituted
alkenyl group, a substituted or unsubstituted aralkyl group, or a
substituted or unsubstituted heterocyclic group.
[0042] According to the above structure, the naphthacene derivative
represented by the formula (3) has a substituent in at least one
ortho position of two benzene rings bonded to naphthacene.
[0043] By introducing substituent(s) to ortho position(s) of the
two benzene rings bonded to naphthacene, a steric hindrance is
caused between the introduced substituent(s) and the naphthacene
skeleton. The steric hindrance directs the introduced
substituent(s) to face in an out-of-plane direction of the
naphthacene skeleton. Then, the substituent(s) directed in the
out-of-plane direction prevents association of naphthacene
derivatives with each other.
[0044] When two or more of Q.sup.21, Q.sup.25, Q.sup.31 and
Q.sup.35 are substituents, the substituents may be mutually the
same or different. In addition, adjacent two or more of Q.sup.21 to
Q.sup.25 and Q.sup.31 to Q.sup.35 may be mutually bonded to form a
cyclic structure.
[0045] An example of the substituent is a substituted or
unsubstituted phenyl group.
[0046] Two or more of the ortho positions of the two benzene rings
bonded to naphthacene are preferably substituted.
[0047] According to the aspect of the present invention, it is
preferable that at least one of Q.sup.21 and Q.sup.25 in the
naphthacene derivative represented by the formula (3) represents a
substituted or unsubstituted aryl group or a substituted or
unsubstituted heterocyclic group while at least one of Q.sup.31 and
Q.sup.35 in the naphthacene derivative represents a substituted or
unsubstituted aryl group or a substituted or unsubstituted
heterocyclic group.
[0048] According to the aspect of the present invention, it is
preferable that the dopant is contained in the emitting layer at a
doping concentration of 0.1 to 10 mass %. It is more preferable
that the dopant is contained in the emitting layer at a doping
concentration of 0.5 to 2.0 mass %.
[0049] According to the aspect of the present invention, it is
preferable that the organic EL device further includes an electron
transporting layer provided between the cathode and the anode, in
which the electron transporting layer comprises a compound
represented by a formula (4) as follows.
(A).sub.m-(B).sub.n (4)
[0050] In the formula, A represents a substituted or unsubstituted
condensed aromatic hydrocarbon group having three or more rings,
and B represents a substituted or unsubstituted heterocyclic group.
In addition, m and n each represent an integer in a range of 1 to
6.
[0051] According to the aspect of the present invention, it is
preferable that A in the compound represented by the formula (4)
has a skeleton in its molecule, the skeleton selected from a group
consisting of anthracene, phenanthrene, naphthacene, pyrene,
chrysene, benzoanthracene, pentacene, dibenzoanthracene,
benzopyrene, fluorene, benzofluorene, fluoranthene,
benzofluoranthene, naphthofluoranthene, dibenzofluorene,
dibenzopyrene and dibenzofluoranthene.
[0052] According to the aspect of the present invention, it is
preferable that B in the compound represented by the formula (4) is
a nitrogen-containing heterocyclic group.
[0053] According to the aspect of the present invention, it is
preferable that B in the compound represented by the formula (4)
has a skeleton in its molecule, the skeleton selected from a group
consisting of pyridine, pyrimidine, pyrazine, pyridazine, triazine,
quinoline, quinoxaline, acridine, imidazopyridine,
imidazopyrimidine, phenanthroline, pyrazole, imidazole and
benzoimidazole.
[0054] According to the aspect of the present invention, it is
preferable that the compound represented by the formula (4) is a
benzoimidazole derivative represented by a formula (5) or a formula
(6) as follows.
##STR00007##
[0055] In the formulae: R represents a hydrogen atom, a substituted
or unsubstituted aryl group having 6 to 60 carbon atoms, a
substituted or unsubstituted pyridyl group, a substituted or
unsubstituted quinolyl group, a substituted or unsubstituted alkyl
group having 1 to 20 carbon atoms or a substituted or unsubstituted
alkoxy group having 1 to 20 carbon atoms; p represents an integer
in a range of 1 to 4; R.sup.11 represents a substituted or
unsubstituted aryl group having 6 to 60 carbon atoms, a substituted
or unsubstituted pyridyl group, a substituted or unsubstituted
quinolyl group, a substituted or unsubstituted alkyl group having 1
to 20 carbon atoms or an alkoxy group having 1 to 20 carbon atoms;
R.sup.12 represents a hydrogen atom, a substituted or unsubstituted
aryl group having 6 to 60 carbon atoms, a substituted or
unsubstituted pyridyl group, a substituted or unsubstituted
quinolyl group, a substituted or unsubstituted alkyl group having 1
to 20 carbon atoms or a substituted or unsubstituted alkoxy group
having 1 to 20 carbon atoms; L represents a substituted or
unsubstituted arylene group having 6 to 60 carbon atoms, a
substituted or unsubstituted pyridinylene group, a substituted or
unsubstituted quinolinylene group or a substituted or unsubstituted
fluorenylene group; and Ar.sup.1 represents a substituted or
unsubstituted aryl group having 6 to 60 carbon atoms, a substituted
or unsubstituted pyridyl group or a substituted or unsubstituted
quinolyl group.
[0056] At least one of R, R.sup.11, R.sup.12, L and Ar.sup.1
corresponds to A in the compound represented by the formula (4) and
is a condensed aromatic hydrocarbon group having three or more
rings.
[0057] According to the aspect of the present invention, it is
preferable that the emitting layer emits light of orange to
red.
[0058] A display according to another aspect of the present
invention includes the above-described organic electroluminescence
device.
[0059] According to the above arrangement, since the display is
formed from the above-described organic electroluminescence device,
the display can exhibit high efficiency, long lifetime and
excellent chromatic purity.
[0060] The present invention can provide a practically-applicable
organic EL device that exhibits high efficiency, long life and
excellent chromatic purity.
[0061] In addition, according to the present invention, by
selecting a suitable compound for the materials of the electron
transporting layer and the emitting layer, the organic EL device
can exhibit higher efficiency. Specifically, with the arrangement
according to the present invention, generation of exciters in the
electron transporting layer can be prevented, thereby providing a
highly chromatically-pure organic EL device whose micro emission
from the electron transporting layer is further reduced In
addition, for the same reason(s), the lifetime of the device can be
prolonged.
BRIEF DESCRIPTION OF THE DRAWINGS
[0062] FIG. 1 shows a first embodiment of an organic EL device
according to the present invention.
DETAILED DESCRIPTION OF PREFERRED EMBODIMENT(S)
Arrangement of Organic EL Device
[0063] Representative exemplary arrangements of an organic EL
device usable in the present invention will be described below. As
a matter of course, the present invention is not limited
thereto.
(1) anode/emitting layer/electron transporting layer/cathode (2)
anode/hole transporting layer/emitting layer/electron transporting
layer/cathode (3) anode/hole injecting layer/hole transporting
layer/emitting layer/electron transporting layer/cathode (4)
anode/hole transporting layer/emitting layer/electron transporting
layer/electron injecting layer/cathode (5) anode/hole injecting
layer/hole transporting layer/emitting layer/electron transporting
layer/electron injecting layer/cathode (FIG. 1) (6)
anode/insulating layer/hole transporting layer/emitting
layer/electron transporting layer/cathode (7) anode/hole
transporting layer/emitting layer/electron transporting
layer/insulating layer/cathode (8) anode/insulating layer/hole
transporting layer/emitting layer/electron transporting
layer/insulating layer/cathode (9) anode/hole injecting layer/hole
transporting layer/emitting layer/electron transporting
layer/insulating layer/cathode (10) anode/insulating layer/hole
injecting layer/hole transporting layer/emitting layer/electron
transporting layer/electron injecting layer/cathode (11)
anode/insulating layer/hole injecting layer/hole transporting
layer/emitting layer/electron transporting layer/electron injecting
layer/insulating layer/cathode
[0064] Among the above, the arrangement (2), (3), (4), (5), (8),
(9) or (11) is typically preferable.
[0065] The organic EL device according to the present invention
includes an anode, a cathode and a single-layered or plural-layered
organic layer including an emitting layer. At least one layer of
the organic layer contains a host formed of a naphthacene
derivative and a dopant formed of a compound having a pyrromethene
skeleton or a metal complex of the compound.
[0066] An exemplary arrangement of the organic EL device according
to the present invention is shown in FIG. 1. In FIG. 1, the organic
EL device 1 includes an anode 20, a hole injecting layer 30, a hole
transporting layer 40, an emitting layer 50, an electron
transporting layer 60, an electron injecting layer 70 and a cathode
80, which are all laminated on a substrate 10 in this order. The
hole injecting layer 30, the hole transporting layer 40, the
emitting layer 50, the electron transporting layer 60 and the
electron injecting layer 70 correspond to the organic layer
interposed between the cathode 80 and the anode 20. At least one of
the above layers contains a host material formed of a naphthacene
derivative and a dopant material formed of a compound having a
pyrromethene skeleton or a metal complex of the compound.
Preferably, the emitting layer contains a naphthacene derivative
and a compound having a pyrromethene skeleton or a metal complex of
the compound.
[0067] Functions or the like of the layers of the organic EL device
will be described below.
[Light-Transmissive Substrate]
[0068] When the organic EL device is to emit light through the
substrate (i.e., when the organic EL device is bottom-emission
type), the organic EL device according to the present invention is
manufactured on a light-transmissive substrate. The
light-transmissive plate, which supports the organic EL device, is
preferably a smoothly-shaped substrate that transmits 50% or more
of light in a visible region of 400 nm to 700 nm.
[0069] The light-transmissive plate is exemplarily a glass plate, a
polymer plate or the like. For the glass plate, such materials as
soda-lime glass, barium/strontium-containing glass, lead glass,
aluminosilicate glass, borosilicate glass, barium borosilicate
glass, quartz and the like can be used. For the polymer plate, such
materials as polycarbonate, acryl, polyethylene terephthalate,
polyether sulfide, polysulfone and the like can be used. In
addition, the light-transmissive plate may be a TFT substrate on
which a TFT (thin film transistor) for driving is formed.
[0070] On the other hand, when the organic EL device is to emit
light from its top portion (i.e., when the organic EL device is
top-emission type), the light-transmissive plate is required to be
provided with a light reflector, an exemplary material of which is
a metal such as aluminum.
[Anode]
[0071] The anode of the organic EL device is used for injecting
holes into the hole transporting layer or the emitting layer. It is
effective that the anode includes a work function of 4.5 eV or
more. Exemplary materials for the anode are indium-tin oxide (ITO),
tin oxide (NESA), indium zinc oxide alloy (IZO), gold, silver,
platinum and copper.
[0072] One of the above materials may be singularly used, or alloys
formed by mixing the above materials and materials formed by adding
other element(s) to the above material(s) may be suitably selected
as the material of the anode.
[0073] The anode may be made by forming a thin film from the above
electrode materials through methods such as vapor deposition and
sputtering.
[0074] When the organic EL device is bottom-emission type, the
anode preferably transmits more than 10% of light emitted by the
emitting layer. Sheet resistance of the anode is preferably several
hundreds .OMEGA./square or lower. Although depending on the
material of the anode, thickness of the anode is typically in a
range of 10 nm to 1 .mu.m, and preferably in a range of 10 to 200
nm.
[Emitting Layer]
[0075] The emitting layer of the organic EL device has functions
described below. Specifically, the emitting layer has:
(i) injecting function: a function for accepting, when an
electrical field is applied, the holes injected by the anode or the
hole injecting/transporting layer, or the electrons injected by the
cathode or the electron injecting/transporting layer; (ii)
transporting function: a function for transporting injected
electric charges (the electrons and the holes) by the force of the
electrical field; and (iii) emitting function; a function for
providing a condition for recombination of the electrons and the
holes to emit light.
[0076] Although injectability of the holes may differ from that of
the electrons and transporting capabilities represented by
mobilities of the holes and the electrons may differ from each
other, the emitting layer preferably transports at least either one
of the electric charges.
[0077] As a method to form the emitting layer, known methods such
as vapor deposition, spin coating and an LB (Langmuir Blodgett)
method may be employed. The emitting layer is preferably a
molecular deposit film.
[0078] The molecular deposit film means a thin film formed by
depositing a material compound in gas phase or a film formed by
solidifying a material compound in a solution state or in liquid
phase. The molecular deposit film is generally distinguished from a
thin film formed by the LB method (molecular accumulation film) by
differences in aggregation structures, higher order structures and
functional differences arising therefrom.
[0079] As disclosed in JP-A-57-51781, the emitting layer can be
formed from a thin film formed by spin coating or the like, the
thin film being formed from a solution prepared by dissolving a
binder (e.g. a resin) and a material compound in a solvent.
[0080] The emitting layer of the present invention contains a host
and a dopant.
[0081] The emitting layer is preferably doped with a dopant
material at a doping concentration of 0.1 to 10 mass %, more
preferably 0.5 to 2.0 mass %.
[0082] The emitting layer preferably emits light of orange to
red.
[0083] The host is a naphthacene derivative represented by the
above formula (1).
[0084] In the formula (1), Q.sup.10, Q.sup.20, Q.sup.30, Q.sup.40,
Q.sup.50, Q.sup.60, Q.sup.70, Q.sup.80, Q.sup.110, Q.sup.120,
Q.sup.130 and Q.sup.140 each represent a hydrogen atom, a
substituted or unsubstituted alkyl group having 1 to 20 carbon
atoms, a substituted or unsubstituted aryl group having 6 to 30
carbon atoms, a substituted or unsubstituted amino group, a
substituted or unsubstituted alkoxy group having 1 to 20 carbon
atoms, a substituted or unsubstituted alkylthio group having 1 to
20 carbon atoms, a substituted or unsubstituted aryloxy group
having 6 to 30 carbon atoms, a substituted or unsubstituted
arylthio group having 6 to 30 carbon atoms, a substituted or
unsubstituted alkenyl group, a substituted or unsubstituted aralkyl
group having 7 to 30 carbon atoms or a substituted or unsubstituted
heterocyclic group. Q.sup.10, Q.sup.20, Q.sup.30, Q.sup.40,
Q.sup.50, Q.sup.60, Q.sup.70, Q.sup.80, Q.sup.110, Q.sup.120,
Q.sup.130 and Q.sup.140 may be mutually the same or different.
[0085] In the above formula (1), Q.sup.10, Q.sup.20, Q.sup.30 and
Q.sup.40 (collectively referred to as Q.sup.10 to Q.sup.40) are
each preferably selected from a group consisting of a hydrogen
atom, a substituted or unsubstituted alkyl group having 1 to 20
carbon atoms, a substituted or unsubstituted aryl group having 6 to
30 carbon atoms, a substituted or unsubstituted amino group, a
substituted or unsubstituted heterocyclic group and a substituted
or unsubstituted alkenyl group having 1 to 20 carbon atoms. More
preferably, Q.sup.10 to Q.sup.40 are aryl groups. Particularly, a
structure where Q.sup.10 and Q.sup.40 are hydrogen atoms while
Q.sup.20 and Q.sup.30 are the above substituents is also
preferable.
[0086] In addition, although a structure where Q.sup.10 and
Q.sup.40 are the same while Q.sup.20 and Q.sup.30 are the same is
preferable, Q.sup.10 to Q.sup.40 may be mutually different.
[0087] In the above formula, Q.sup.50, Q.sup.60, Q.sup.70 and
Q.sup.80 (collectively referred to as Q.sup.50 to Q.sup.80) are
each preferably selected from a group consisting of a hydrogen
atom, a substituted or unsubstituted alkyl group having 1 to 20
carbon atoms, a substituted or unsubstituted aryl group having 6 to
30 carbon atoms, a substituted or unsubstituted amino group, a
substituted or unsubstituted alkenyl group having 1 to 20 carbon
atoms and a substituted or unsubstituted heterocyclic group. More
preferably, Q.sup.50 to Q.sup.80 are each a hydrogen atom or a
substituted or unsubstituted aryl group having 6 to 30 carbon
atoms. In addition, although a structure where Q.sup.50 and
Q.sup.60 are the same while Q.sup.70 and Q.sup.80 are the same is
preferable, Q.sup.50 to Q.sup.80 may be mutually different.
Q.sup.10, Q.sup.120, Q.sup.130 and Q.sup.140 (collectively referred
to as Q.sup.110 to Q.sup.140) are each preferably a hydrogen
atom.
[0088] The alkyl group(s) represented by Q.sup.10 to Q.sup.40,
Q.sup.50 to Q.sup.80 and Q.sup.110 to Q.sup.140 may be substituted
or unsubstituted, or may be linear or branched. Preferable examples
of the alkyl group are a methyl group, an ethyl group, a (n,
i)-propyl group, a (n, i, sec, tert)-butyl group, and (n, i, neo,
tert)-pentyl group.
[0089] The aryl group(s) represented by Q.sup.10 to Q.sup.40,
Q.sup.50 to Q.sup.80 and Q.sup.110 to Q.sup.140 may monocyclic or
polycyclic, or may be of a condensed-ring structure or of a
ring-assembly structure. The aryl group(s) represented by Q.sup.10
to Q.sup.40, Q.sup.50 to Q.sup.80 and Q.sup.110 to Q.sup.140 may be
substituted or unsubstituted. The aryl group(s) represented by
Q.sup.10 to Q.sup.40, Q.sup.50 to Q.sup.80 and Q.sup.110 to
Q.sup.140 is preferably a phenyl group, an (o-, m-, p-) tolyl
group, a pyrenyl group, a perylenyl group, a coronenyl group, a
(1-, and 2-) naphthyl group, an anthryl group, a (o-, m-, p-)
biphenyl group, a taphenyl group and a phenanthryl group.
[0090] Although the amino group(s) represented by Q.sup.10 to
Q.sup.40, Q.sup.50 to Q.sup.80 and Q.sup.10 to Q.sup.140 may be
substituted or unsubstituted, the amino group(s) is preferably
substituted and may be an alkylamino group, an arylamino group, an
aralkylamino group or the like. The above amino groups each
preferably contain fatty series having 1 to 6 carbon atoms in total
and/or an aromatic carbon ring having 1 to 4 rings. Examples of
such an amino group are a dimethylamino group, a diethylamino
group, an abutyl-amino group, a diphenylamino group, a ditolylamino
group, a bis-diphenylamino group and a bis-naphtylamino group.
[0091] The heterocyclic group(s) represented by Q.sup.10 to
Q.sup.40, Q.sup.50 to Q.sup.80 and Q.sup.110 to Q.sup.140 may be
substituted or unsubstituted. Examples of the heterocyclic group(s)
are a five- or six-membered aromatic heterocyclic group containing
O, N and S as heteroatoms and a condensed polycyclic aromatic group
having 2 to 20 carbon atoms. Examples of the aromatic heterocyclic
group and the condensed polycyclic aromatic heterocyclic group are
a thienyl group, a furyl group, a pyronyl group, a pyridyl group, a
quinolyl group and a quinoxalyl group.
[0092] Preferable Examples of the substituted or unsubstituted
alkenyl group(s) having 1 to 20 carbon atoms represented by
Q.sup.10 to Q.sup.40, Q.sup.50 to Q.sup.80 and Q.sup.110 to
Q.sup.140 are a (1- and 2-) phenylalkenyl group, a (1,2- and 2,2-)
diphenylalkenyl group and a (1,2,2-)triphenylalkenyl group that are
each substituted by at least one phenyl group. Each of the above
examples may be unsubstituted.
[0093] The alkoxy group(s) or the alkylthio group(s) represented by
Q.sup.10 to Q.sup.40, Q.sup.50 to Q.sup.80 and Q.sup.110 to
Q.sup.140 may be substituted or unsubstituted. The alkoxy group(s)
or the alkylthio group(s) preferably contains the above-described
alkyl group.
[0094] The aryloxy group(s) or the arylthio group(s) represented by
Q.sup.10 to Q.sup.40, Q.sup.50 to Q.sup.80 and Q.sup.110 to
Q.sup.140 may be substituted or unsubstituted. The aryloxy group(s)
or the arylthio group(s) preferably has an aryl group. An example
of the aryloxy group(s) is an (o-, m-, p-) phenoxy group while an
example of the arylthio group(s) is an (o-, m-, p-) phenylthio
group.
[0095] The aralkyl group(s) represented by Q.sup.10 to Q.sup.40,
Q.sup.50 to Q.sup.80 and Q.sup.110 to Q.sup.140 may be substituted
or unsubstituted, examples of which are a benzyl group and a
phenethyl group.
[0096] When Q.sup.10 to Q.sup.40, Q.sup.50 to Q.sup.80, and
Q.sup.110 to Q.sup.140 are substituted, at least two of the
substituents contained, particularly, in Q.sup.10 to Q.sup.40 are
each preferably an aryl group, an amino group, a heterocyclic
group, an alkenyl group or an aryloxy group, more preferably an
aryl group. The same as described in relation to Q.sup.10 to
Q.sup.40 applies to the aryl group, the amino group, the
heterocyclic group and the alkenyl group.
[0097] Two or more of the above substituents may form a condensed
ring. The above substituents may be further substituted, preferable
substituents for which are the same as in the above
description.
[0098] When Q.sup.10 to Q.sup.40, Q.sup.50 to Q.sup.80, and
Q.sup.110 to Q.sup.140 are substituted, at least two, particularly,
of Q.sup.10 to Q.sup.40 each preferably contain the above
substituent. The substitution positions are not subject to any
specific limitations. When Q.sup.10 to Q.sup.40 contains phenyl,
the substitution positions may be any one of meta, para and ortho
positions.
[0099] In the above formula (1), at least one of Q.sup.10 to
Q.sup.80 is preferably a substituted or unsubstituted aryl group.
More preferably, at least one of Q.sup.10 to Q.sup.40 is a
substituted or unsubstituted aryl group.
[0100] Specifically, the naphthacene derivative is more preferably
represented by the above formula (3).
[0101] In the formula (3), Q.sup.10, Q.sup.21 to Q.sup.25, Q.sup.31
to Q.sup.35 Q.sup.40 to Q.sup.80 and Q.sup.110 to Q.sup.140 each
represent a hydrogen atom, a substituted or unsubstituted alkyl
group, a substituted or unsubstituted aryl group, a substituted or
unsubstituted amino group, a substituted or unsubstituted alkoxy
group, a substituted or unsubstituted alkylthio group, a
substituted or unsubstituted aryloxy group, a substituted or
unsubstituted arylthio group, a substituted or unsubstituted
alkenyl group, a substituted or unsubstituted aralkyl group, or a
substituted or unsubstituted heterocyclic group. Q.sup.10, Q.sup.21
to Q.sup.25, Q.sup.31 to Q.sup.35, Q.sup.40 to Q.sup.80 and
Q.sup.110 to Q.sup.140 may be mutually the same or different.
Adjacent two or more of Q.sup.21 to Q.sup.25 and Q.sup.31 to
Q.sup.35 may be mutually bonded to form a cyclic structure.
[0102] The same as described in relation to Q.sup.10 and the like
of the formula (1) applies to examples of these groups.
[0103] In the formula (3), Q.sup.21 to Q.sup.25 and Q.sup.31 to
Q.sup.35 are each preferably selected from a group consisting of a
hydrogen group, an aryl group, an amino group, a heterocyclic
group, an aryloxy group and an alkenyl group, more preferably an
aryl group. In addition, at least one of Q.sup.21 to Q.sup.25 and
Q.sup.31 to Q.sup.35 is preferably substituted by an aryl group, an
amino group, a heterocyclic group or an aryloxy group, more
preferably by an aryl group. Adjacent two or more of the above may
form a condensed ring. The same as described in relation to
Q.sup.10 to Q.sup.40 applies to preferable examples of the aryl
group, the amino group, the heterocyclic group and the alkenyl
group.
[0104] In addition, although a structure where Q.sup.21 to Q.sup.25
and Q.sup.31 to Q.sup.35 are the same is preferable, Q.sup.21 to
Q.sup.25 may be different from Q.sup.31 to Q.sup.35. Examples of
the amino group for substituting Q.sup.21 to Q.sup.25 and Q.sup.31
to Q.sup.35 are an alkylamino group, an arylamino group and an
aralkylamino group. The above amino groups each preferably contain
fatty series having 1 to 6 carbon atoms in total and/or an aromatic
carbon ring having 1 to 4 rings. Examples of such an amino group
are a dimethylamino group, a diethylamino group, an abutyl-amino
group, a diphenylamino group, a ditolylamino group, a
bis-diphenylamino group and a bis-naphtylamino group.
[0105] Examples of the condensed ring formed as above are indene,
naphthalene, anthracene, phenanthrene, quinoline, isoquinoline,
quinoxaline, phenazine, acridine, indole, carbazole, phenoxazine,
phenothiazine, benzothiazole, benzothiophen, benzofuran, acridone,
benzoimidazole, coumarin and flavone.
[0106] Q.sup.10, Q.sup.40 and Q.sup.110 to Q.sup.140 are each
particularly preferably a hydrogen atom.
[0107] Examples of the aromatic compound represented by the general
formula (1) according to the present invention will be shown below.
However, the present invention is not limited to the exemplary
compounds shown below.
##STR00008## ##STR00009## ##STR00010## ##STR00011##
##STR00012##
[0108] The dopant is a compound having the pyrromethene skeleton
represented by the formula (2) or a metal complex of the
compound.
[0109] The compound having the pyrromethene skeleton represented by
the formula (2) or the metal complex of the compound is preferably
a compound having a pyrromethene skeleton represented by the
following formula (2-1) or a metal complex of the compound.
##STR00013##
[0110] In the formula (2-1), at least one of R.sup.22 to R.sup.28
is a substitute having an aromatic ring or forms a condensed
aromatic ring together with an adjacent substituent while the rest
of R.sup.22 to R.sup.28 each represent a hydrogen atom, an alkyl
group, a cycloalkyl group, an aralkyl group, an alkenyl group, a
cycloalkenyl group, an alkynyl group, a hydroxyl group, a mercapto
group, an alkoxy group, an alkylthio group, an arylether group, an
arylthioether group, an aryl group, a heterocyclic group, halogen,
haloalkane, haloalkene, haloalkyne, a cyano group, an aldehyde
group, a carbonyl group, a carboxyl group, an ester group, a
carbamoyl group, an amino group, a nitro group, a silyl group or a
siloxanyl group. The rest of R.sup.22 to R.sup.28 each may form a
condensed ring or an aliphatic ring with an adjacent substituent.
R.sup.22 to R.sup.28 may be mutually the same or different and may
be substituted or unsubstituted. R.sup.29 and R.sup.30 may be
mutually the same or different and each are selected from a group
consisting of halogen, a hydrogen atom, substituted or
unsubstituted alkyl, substituted or unsubstituted aryl and a
substituted or unsubstituted heterocyclic group. X represents a
carbon atom or a nitrogen atom on a condition that R.sup.28 above
does not exist when X represents a nitrogen atom.
[0111] When one or more of R.sup.22 to R.sup.28 forms a condensed
aromatic ring(s) together with adjacent substituent(s), the
condensed aromatic ring(s) is preferably formed by a pair of
R.sup.22 and R.sup.23, a pair of R.sup.23 and R.sup.24, a pair of
R.sup.25 and R.sup.26 and/or a pair of R.sup.26 and R.sup.27. The
condensed aromatic ring(s) is particularly preferably formed by the
pair of R.sup.22 and R.sup.23 and/or the pair of R.sup.26 and
R.sup.27. Examples of the condensed aromatic ring(s) are a benzo
ring and a naphtho ring.
[0112] The compound having the pyrromethene skeleton represented by
the formula (2) or the metal complex of the compound is preferably
a compound having a pyrromethene skeleton represented by the
following formula (2-2) or a metal complex of the compound.
##STR00014##
[0113] In the formula (2-2), R.sup.31 to R.sup.39 each represent a
hydrogen atom, an alkyl group, a cycloalkyl group, an aralkyl
group, an alkenyl group, a cycloalkenyl group, an alkynyl group, a
hydroxyl group, a mercapto group, an alkoxy group, an alkylthio
group, an arylether group, an arylthioether group, an aryl group, a
heterocyclic group, halogen, haloalkane, haloalkene, haloalkyne, a
cyano group, an aldehyde group, a carbonyl group, a carboxyl group,
an ester group, a carbamoyl group, an amino group, a nitro group, a
silyl group or a siloxanyl group. R.sup.31 to R.sup.39 may be
mutually the same or different and may be substituted or
unsubstituted. R.sup.40 and R.sup.41 may be mutually the same or
different and each are selected from a group consisting of halogen,
a hydrogen atom, substituted or unsubstituted alkyl, substituted or
unsubstituted aryl and a substituted or unsubstituted heterocyclic
group. X represents a carbon atom or a nitrogen atom on a condition
that R.sup.39 above does not exist when X represents a nitrogen
atom.
[0114] According to the present invention, the compound having the
pyrromethene skeleton represented by the formula (2-1) or the metal
complex of the compound is preferably a metal complex having a
pyrromethene skeleton represented by the following formula
(2-3).
##STR00015##
[0115] In the formula (2-3), R.sup.42 to R.sup.52 each represent a
hydrogen atom, an alkyl group, a cycloalkyl group, an aralkyl
group, an alkenyl group, a cycloalkenyl group, an alkynyl group, a
hydroxyl group, a mercapto group, an alkoxy group, an alkylthio
group, an arylether group, an arylthioether group, an aryl group, a
heterocyclic group, halogen, haloalkane, haloalkene, haloalkyne, a
cyano group, an aldehyde group, a carbonyl group, a carboxyl group,
an ester group, a carbamoyl group, an amino group, a nitro group, a
silyl group or a siloxanyl group. R.sup.42 to R.sup.52 may be
mutually the same or different and may be substituted or
unsubstituted. R.sup.53 and R.sup.54 may be mutually the same or
different and each are selected from a group consisting of halogen,
a hydrogen atom, a substituted or unsubstituted alkyl, a
substituted or unsubstituted aryl and a substituted or
unsubstituted heterocyclic group. X represents a carbon atom or a
nitrogen atom on a condition that R.sup.52 above does not exist
when X represents a nitrogen atom.
[0116] Examples of the aromatic compound represented by the general
formula (2) according to the present invention will be shown below.
However, the present invention is not limited to the exemplary
compounds shown below.
##STR00016## ##STR00017## ##STR00018## ##STR00019## ##STR00020##
##STR00021## ##STR00022## ##STR00023## ##STR00024## ##STR00025##
##STR00026## ##STR00027## ##STR00028## ##STR00029## ##STR00030##
##STR00031## ##STR00032## ##STR00033## ##STR00034## ##STR00035##
##STR00036## ##STR00037## ##STR00038## ##STR00039## ##STR00040##
##STR00041## ##STR00042##
[0117] In the above formulae, Q.sup.10 to Q.sup.140 and R.sup.15 to
R.sup.54 may be substituted or unsubstituted, a substituent for
each of which is preferably an alkyl group, an aryl group or an
alkoxy group.
[0118] The alkyl group is preferably an alkyl group having 1 to 20
carbon atoms, more preferably an alkyl group having 1 to 10 carbon
atoms, further preferably an alkyl group having 1 to 5 carbon
atoms. The alkyl group may be linear or branched. The alkyl group
may be a primary alkyl group, a secondary alkyl group or a tertiary
alkyl group.
[0119] Preferable examples of the alkyl group are a methyl group,
an ethyl group, an n-propyl group, an isopropyl group, an n-butyl
group, a sec-butyl group, a tert-butyl group, an n-pentyl group, an
n-hexyl group, an n-heptyl group, an n-octyl group, an n-nonyl
group and an n-decyl group.
[0120] The aryl group is preferably an aryl group having 6 to 30
carbon atoms, more preferably an aryl group having 6 to 20 carbon
atoms. Examples of the aryl group are a phenyl group, a tolyl
group, a xylyl group, a phenylphenyl group (4-phenylphenyl group,
3-phenylphenyl group, 2-phenylphenyl group), a naphthylphenyl
group, a naphthyl group (1-naphthyl group, 2-naphthyl group), a
phenylnaphthyl group, a naphthylnaphthyl group, a taphenyl group,
an anthranil group, a phenantyl group, a pyrenyl group and a
chrysenyl group.
[Hole Transporting Layer and Hole Injecting Layer]
[0121] The hole transporting layer helps injection of the holes
into the emitting layer and transports the holes to an emitting
region, in which the hole mobility is large and the energy of
ionization is typically small (5.5 eV or smaller). A material of
the hole transporting layer is preferably such a material that
transports the holes to the emitting layer with a low field
intensity, and more preferably such a material that transports the
holes with the hole mobility of at least 10.sup.-4 cm.sup.2/V*sec
when the exemplary electrical field of 10.sup.4 to 10.sup.6 V/cm is
applied.
[0122] A material for the hole transporting layer is not
specifically limited as long as the material has the above
preferable characteristics. Any materials conventionally used for
transporting charges of the holes in photoconducting materials or
any materials publicly known to be applicable to the hole
transporting layers of the EL devices may be used.
[0123] Examples of the material are a triazole derivative (see, for
instance, the specification of U.S. Pat. No. 3,112,197), an
oxadiazole derivative (see, for instance, the specification of U.S.
Pat. No. 3,189,447), an imidazole derivative (see, for instance,
the publication of JP-B-37-16096), a polyarylalkane derivative
(see, for instance, the specifications of U.S. Pat. No. 3,615,402,
No. 3,820,989 and No. 3,542,544 and the publications of
JP-B-45-555, JP-B-51-10983, JP-A-51-93224, JP-A-55-17105,
JP-A-56-4148, JP-A-55-108667, JP-A-55-156953, and JP-A-56-36656), a
pyrazoline derivative and a pyrazolone derivative (see, for
instance, the specifications of U.S. Pat. No. 3,180,729 and No.
4,278,746 and the publications of JP-A-55-88064, JP-A-55-88065,
JP-49-105537, JP-A-55-51086, JP-A-56-80051, JP-A-56-88141,
JP-A-57-45545, JP-A-54-112637 and JP-A-55-74546, a phenylenediamine
derivative (see, for instance, the specification of U.S. Pat. No.
3,615,404 and the publications of JP-B-51-10105, JP-B-46-3712,
JP-B-47-25336 and JP-A-54-119925), an arylamine derivative (see,
for instance, the specifications of U.S. Pat. No. 3,567,450, No.
3,240,597, No. 3,658,520, No. 4,232,103, No. 4,175,961 and No.
4,012,376 and the publications of JP-B-49-35702, JP-B-39-27577,
JP-A-55-144250, JP-A-56-119132 and JP-A-56-22437 and the
specification of West Germany Patent No. 1,110,518), an
amino-substituted chalcone derivative (see, for instance, the
specification of U.S. Pat. No. 3,526,501), an oxazole derivative
(disclosed in, for instance, the specification of U.S. Pat. No.
3,257,203), a styrylanthracene derivative (see, for instance, the
publication of JP-A-56-46234), a fluorenone derivative (see, for
instance, the publication of JP-A-54-110837), a hydrazone
derivative (see, for instance, the specification of U.S. Pat. No.
3,717,462 and the publications of JP-A-54-59143, JP-A-55-52063,
JP-A-55-52064, JP-A-55-46760, JP-A-57-11350, JP-A-57-148749 and
JP-A-2-311591), a stilbene derivative (see, for instance, the
publications of JP-A-61-210363, JP-A-61-228451, JP-A-61-14642,
JP-A-61-72255, JP-A-62-47646, JP-A-62-36674, JP-A-62-10652,
JP-A-62-30255, JP-A-60-93455, JP-A-60-94462, JP-A-60-174749 and
JP-A-60-175052), a silazane derivative (see the specification of
U.S. Pat. No. 4,950,950), a polysilane type (see the publication of
JP-A-2-204996), an aniline-based copolymer (see the publication of
JP-A-02-282263), and a conductive high-molecular oligomer
(particularly, thiophene oligomer).
[0124] Preferably, a material represented by the following formula
(7) may be used.
Q.sub.1-G-Q.sup.2 (7)
[0125] In the formula (7), Q.sup.1 and Q.sup.2 each represent a
portion having at least one tertiary amine while G represents a
linking group.
[0126] More preferable material is an amine derivative represented
by the following formula (8).
##STR00043##
[0127] In the above formula (8), Ar.sup.21 to Ar.sup.24 each
represent a substituted or unsubstituted aromatic ring having 6 to
50 carbon atoms forming the ring or a substituted or unsubstituted
heteroaromatic ring having 5 to 50 atoms forming the ring. R.sup.21
and R.sup.22 each represent a substituent while s and t each
represent an integer in a range of 0 to 4.
[0128] Ar.sup.21 and Ar.sup.22 may be bonded together to form a
cyclic structure while Ar.sup.23 and Ar.sup.24 may also be bonded
together to form a cyclic structure. R.sup.21 and R.sup.22 may also
be bonded together to form a cyclic structure.
[0129] The substituent for Ar.sup.21 to Ar.sup.24 each, and
R.sup.21 and R.sup.22 are selected from a group consisting of a
substituted or unsubstituted aromatic ring having 6 to 50 carbon
atoms forming the ring, a substituted or unsubstituted
heteroaromatic ring having 5 to 50 atoms forming the ring, an alkyl
group having 1 to 50 carbon atoms, an alkoxy group having 1 to 50
carbon atoms, an alkylaryl group having 1 to 50 carbon atoms, an
aralkyl group having 1 to 50 carbon atoms, a styryl group, an amino
group substituted by an aromatic ring having 6 to 50 carbon atoms
forming the ring or by a heteroaromatic ring having 5 to 50 atoms
forming the ring, an aromatic ring having 6 to 50 carbon atoms
forming the ring substituted by an amino group substituted by an
aromatic ring having 6 to 50 carbon atoms forming the ring or by a
heteroaromatic ring having 5 to 50 atoms forming the ring, and a
heteroaromatic ring having 5 to 50 atoms forming the ring
substituted by an amino group substituted by an aromatic ring
having 6 to 50 carbon atoms forming the ring or by a heteroaromatic
ring having 5 to 50 atoms forming the ring.
[0130] In order to aid the injection of the holes, a hole injecting
layer may be provided in addition to the hole transporting layer.
The above materials for the hole transporting layer can be used as
the materials of the hole injecting layer, preferable examples of
which are a porphyrin compound (disclosed in JP-A-63-295695), an
aromatic tertiary amine compound and a styrylamine compound (see,
for instance, the specification of U.S. Pat. No. 4,127,412,
JP-A-53-27033, JP-A-54-58445, JP-A-55-79450, JP-A-55-144250,
JP-A-56-119132, JP-A-61-29558, JP-A-61-98353 and JP-A-63-295695).
Among these, use of an aromatic tertiary amine compound is
particularly preferable.
[0131] In addition, 4,4'-bis(N-(1-naphthyl)-N-phenylamino)biphenyl
(hereinafter, abbreviated as NPD) having in the molecule two
condensed aromatic rings disclosed in U.S. Pat. Nos. 5,061,569,
4,4',4''-tris(N-3-methylphenyl-N-phenylamino)triphenylamine
(hereinafter, abbreviated as MTDATA) in which three triphenylamine
units disclosed in JP-A-04-30868 are bonded in a starbust form and
the like may also be used.
[0132] As another example, a nitrogen-containing heterocyclic
derivative represented by the following formula (9), which is
disclosed in Japanese Patent No. 03571977, may be used.
##STR00044##
[0133] In the formula (9), R.sub.1 to R.sub.6 each represent a
substituted or unsubstituted alkyl group, a substituted or
unsubstituted aryl group, a substituted or unsubstituted aralkyl
group, or a substituted or unsubstituted heterocyclic group.
R.sub.1 to R.sub.6 may be mutually the same or different. A pair of
R.sub.1 and R.sub.2, a pair of R.sub.3 and R.sub.4 or a pair of
R.sub.5 and R.sub.6 may form a condensed ring(s). Alternatively, a
pair of R.sub.1 and R.sub.6, a pair of R.sub.2 and R.sub.3 or a
pair of R.sub.4 and R.sub.5 may form a condensed ring(s).
[0134] As another example, a compound represented by the following
formula (10), which is disclosed in US 2004/113547A1, may be
used.
##STR00045##
[0135] In the formula (10), R1 to R6 each represent a substituent,
a preferable example of which is an electron-attracting group such
as a cyano group, a nitro group, a sulfonyl group, a carbonyl
group, a trifluoromethyl group and halogen.
[0136] In addition to aromatic dimethylidyne-based compounds,
inorganic compounds such as p-type Si and p-type SiC can be used as
the material of the hole injecting layer.
[0137] The hole injecting layer and the hole transporting layer can
be formed by forming thin films from the compounds listed above by
known methods such as vacuum deposition, spin coating, casting and
the LB method. Although the thickness of the hole injecting layer
and the hole transporting layer is not particularly limited, the
thickness is typically in the range from 5 nm to 5 .mu.m. The hole
injecting layer and the hole transporting layer may be formed by a
single layer formed of at least one of the above materials as long
as the hole injecting layer and the hole transporting layer
contains the above compound(s) in the hole transporting region.
Alternatively, the hole injecting layer and the hole transporting
layer may be formed by laminating layers respectively formed of a
different material.
[0138] In addition, an organic semiconductor layer, which is a part
of the hole transporting layer, aids the injection of the holes or
the electrons into the emitting layer. The organic semiconductor
layer preferably has electric conductivity of 10.sup.-10 S/cm or
more. Examples of a material for the organic semiconductor layer
are a conductive oligomer such as a thiophene-containing oligomer
or an arylamine-containing oligomer (disclosed in JP-A-08-193191),
and a conductive dendrimer such as an arylamine-containing
dendrimer.
[Electron Injecting/Transporting Layers (Electron Transport
Zone)]
[0139] The electron transporting layer, which aids injection of the
electrons into the emitting layer, has a high electron mobility.
The thickness of the electron transporting layer is suitably
selected from the range of several nanometers to several
micrometers. However, especially when the thickness of the electron
transporting layer is large, the electron mobility, in order to
prevent voltage from rising, is preferably at least 10.sup.-5
cm.sup.2/Vs or higher with the electrical field of 10.sup.4 to
10.sup.6 V/cm applied.
[0140] The electron transporting layer preferably contains a
compound represented by any one of the following formulae (4), (5)
and (6).
[0141] In the formulae (5) and (6), R represents a hydrogen atom, a
substituted or unsubstituted aryl group having 6 to 60 carbon
atoms, a substituted or unsubstituted pyridyl group, substituted or
unsubstituted quinolyl group, a substituted or unsubstituted alkyl
group having 1 to 20 carbon atoms, or a substituted or
unsubstituted alkoxy group having 1 to 20 carbon atoms while p
represents an integer in a range of 1 to 4.
[0142] Preferable examples of the aryl group having 6 to 60 carbon
atoms are a phenyl group, 1-naphthyl group, 2-naphthyl group,
1-anthryl group, 2-anthryl group, 9-anthryl group, 1-phenanthryl
group, 2-phenanthryl group, 3-phenanthryl group, 4-phenanthryl
group, 9-phenanthryl group, 1-naphthacenyl group, 2-naphthacenyl
group, 9-naphthacenyl group, 1-pyrenyl group, 2-pyrenyl group,
4-pyrenyl group, 2-biphenylyl group, 3-biphenylyl group,
4-biphenylyl group, p-ta-phenyl-4-yl group, p-ta-phenyl-3-yl group,
p-ta-phenyl-2-yl group, m-ta-phenyl-4-yl group, m-ta-phenyl-3-yl
group, m-ta-phenyl-2-yl group, o-tolyl group, m-tolyl group,
p-tolyl group, p-t-butylphenyl group, p-(2-phenylpropyl)phenyl
group, 3-methyl-2-naphthyl group, 4-methyl-1-naphthyl group,
4-methyl-1-anthryl group, 4'-methylbiphenylyl group,
4''-t-butyl-p-ta-phenyl-4-yl group, fluoranthenyl group and
fluorenyl group. More preferable examples thereof are a phenyl
group, naphthyl group, biphenyl group, anthracenyl group,
phenanthryl group, pyrenyl group, crycenyl group, fluoranthenyl
group and fluorenyl group.
[0143] Preferable examples of the alkyl group having 1 to 20 carbon
atoms are a methyl group, ethyl group, propyl group, isopropyl
group, n-butyl group, s-butyl group, isobutyl group, t-butyl group,
n-pentyl group, n-hexyl group, n-heptyl group, n-octyl group,
hydroxymethyl group, 1-hydroxyethyl group, 2-hydroxyethyl group,
2-hydroxyisobutyl group, 1,2-dihydroroxyethyl group,
1,3-dihydroxyisopropyl group, 2,3-dihydroxy-t-butyl group,
1,2,3-trihydroxypropyl group, chloromethyl group, 1-chloroethyl
group, 2-chloroethyl group, 2-chloroisobutyl group,
1,2-dichloroethyl group, 1,3-dichloroisopropyl group,
2,3-dichloro-t-butyl group, 1,2,3-trichloropropyl group,
bromomethyl group, 1-bromoethyl group, 2-bromoethyl group,
2-bromoisobuthyl group, 1,2-dibromoethyl group,
1,3-dibromoisopropyl group, 2,3-dibromo-t-butyl group,
1,2,3-tribromopropyl group, iodomethyl group, 1-iodoethyl group,
2-iodoethyl group, 2-iodoisobutyl group, 1,2-diiodoethyl group,
1,3-diiodoisopropyl group, 2,3-diiodo-t-butyl group,
1,2,3-triiodopropyl group, aminomethyl group, 1-aminoethyl group,
2-aminoethyl group, 2-aminoisobutyl group, 1,2-diaminoethyl group,
1,3-diaminoisopropyl group, 2,3-diamino-t-butyl group,
1,2,3-triaminopropyl group, cyanomethyl group, 1-cyanoethyl group,
2-cyanoethyl group, 2-cyanoisobutyl group, 1,2-dicyanoethyl group,
1,3-dicyanoisopropyl group, 2,3-dicyano-t-butyl group,
1,2,3-tricyanopropyl group, nitromethyl group, 1-nitroethyl group,
2-nitroethyl group, 2-nitroisobutyl group, 1,2-dinitroethyl group,
1,3-dinitroisopropyl group, 2,3-dinitro-t-butyl group,
1,2,3-trinitropropyl group, cyclopropyl group, cyclobutyl group,
cyclopentyl group, cyclohexyl group, 4-methylcyclohexyl group,
1-adamantyl group, 2-adamantyl group, 1-norbornyl group and
2-norbornyl group.
[0144] The alkoxy group having 1 to 20 carbon atoms is a group
represented by --OY'''. Examples of Y''' are the same as those of
the above alkyl group.
[0145] Examples of the substituent for the aryl group, the pyridyl
group, the quinolyl group, the alkyl group or the alkoxy group are
a substituted or unsubstituted aryl group having 6 to 50 carbon
atoms forming the ring, a substituted or unsubstituted aromatic
heterocyclic group having 5 to 50 atoms forming the ring, a
substituted or unsubstituted alkyl group having 1 to 50 carbon
atoms, a substituted or unsubstituted alkoxy group having 1 to 50
carbon atoms, a substituted or unsubstituted aralkyl group having 1
to 50 carbon atoms, a substituted or unsubstituted aryloxy group
having 5 to 50 atoms forming the ring, a substituted or
unsubstituted arylthio group having 5 to 50 atoms forming the ring,
a substituted or unsubstituted carboxyl group having 1 to 50 carbon
atoms, a halogen group, a cyano group, a nitro group and a hydroxyl
group.
[0146] In the formulae (5) and (6), p represents an integer in a
range of 1 to 4. Preferably, p is any one of 1 to 3, more
preferably 1 or 2.
[0147] R preferably represents a hydrogen atom.
[0148] R.sup.11 represents a substituted or unsubstituted aryl
group having 6 to 60 carbon atoms, a substituted or unsubstituted
pyridyl group, a substituted or unsubstituted quinolyl group, a
substituted or unsubstituted alkyl group having 1 to 20 carbon
atoms or an alkoxy group having 1 to 20 carbon atoms. Examples of
each group and substituent are the same as R.
[0149] R.sup.12 represents a hydrogen atom, a substituted or
unsubstituted aryl group having 6 to 60 carbon atoms, a substituted
or unsubstituted pyridyl group, a substituted or unsubstituted
quinolyl group, a substituted or unsubstituted alkyl group having 1
to 20 carbon atoms or a substituted or unsubstituted alkoxy group
having 1 to 20 carbon atoms. Examples of each group and substituent
are the same as R.
[0150] L represents a substituted or unsubstituted arylene group
having 6 to 60 carbon atoms, a substituted or unsubstituted
pyridinylene group, a substituted or unsubstituted quinolinylene
group, or a substituted or unsubstituted fluorenylene group.
[0151] Preferable examples of the arylene group having 6 to 60
carbon atoms are divalent substituents formed by further removing
one hydrogen atom from the substituents listed in the description
of the aryl group having 6 to 60 carbon atoms. More preferable
examples thereof are a phenylene group, naphthylene group,
biphenylene group, anthracenylene group, phenantolylene group,
pyrenylene group, chrysenylene group, fluoranthenylene group and
fluorenylene group.
[0152] Examples of the substituent for each of the arylene group,
the pyridinylene group, the quinolinylene group or the fluorenylene
group are the same as R.
[0153] Ar.sup.1 represents a substituted or unsubstituted aryl
group having 6 to 60 carbon atoms (preferably, 6 to 30 carbon
atoms), a substituted or unsubstituted pyridyl group or a
substituted or unsubstituted quinolyl group.
[0154] Examples of the substituent for each of the aryl group
having 6 to 60 carbon atoms, the aryl group, the pyridyl group or
the quinolyl group are the same as R.
[0155] Preferably in the benzoimidazole derivative represented by
the formula (5): R represents a hydrogen atom; R.sup.11 represents
an aryl group; L represents an arylene group having 6 to 30 carbon
atoms (preferably, 6 to 20 carbon atoms); and Ar.sup.1 represents
an aryl group having 6 to 30 carbon atoms.
[0156] Preferably in the benzoimidazole derivative represented by
the formula (6): R represents a hydrogen atom; R.sup.12 represents
an aryl group; L represents an arylene group having 6 to 30 carbon
atoms (preferably, 6 to 20 carbon atoms); and Ar.sup.1 represents
an aryl group having 6 to 30 carbon atoms.
[0157] Although the compound(s) represented by the formulae (4),
(5) and (6) are preferably applicable to the electron transporting
layer, the material of the electron transporting layer is not
limited thereto. Compounds containing 8-hydroxyquinoline, a metal
complex of its derivative, or a nitrogen-containing heterocycle may
be preferably applicable to the electron transporting layer.
[0158] An example of the 8-hydroxyquinoline or the metal complex of
its derivative is a metal chelate oxinoid compound containing a
chelate of oxine (typically 8-quinolinol or 8-hydroxyquinoline).
For example, an Alq complex having Al as its central metal can be
used for the electron transporting layer.
[0159] On the other hand, examples of the oxadiazole derivative are
electron transporting compounds represented by the following
general formulae.
##STR00046##
[0160] In the formulae, Ar.sup.321, Ar.sup.322, Ar.sup.323,
Ar.sup.325, Ar.sup.326 and Ar.sup.329 each represent a substituted
or unsubstituted aryl group, which may be mutually the same or
different. Ar.sup.324, Ar.sup.327 and Ar.sup.328 each represent a
substituted or unsubstituted arylene group, which may be mutually
the same or different.
[0161] Examples of the aryl group are a phenyl group, a biphenyl
group, an anthranil group, a perylenyl group, and a pyrenyl group.
Examples of the arylene group are a phenylene group, a naphthylene
group, a biphenylene group, an anthranylene group, a perylenylene
group and a pyrenylene group. Examples of the substituent therefor
are an alkyl group having 1 to 10 carbon atoms, an alkoxy group
having 1 to 10 carbon atoms or a cyano group. The electron
transporting compounds are preferably compounds that exhibit
favorable performance in forming a thin film.
[0162] Examples of the electron transporting compounds are as
follows.
##STR00047##
[0163] Me represents a methyl group while Bu represents a butyl
group.
[0164] A silacyclopentadiene derivative represented by the
following formula (disclosed in JP-A-09-087616) is also preferably
applicable to the electron transporting layer.
##STR00048##
[0165] In the formula, X.sup.351 and Y.sup.351 may each represent a
saturated or unsaturated hydrocarbon group having 1 to 6 carbon
atoms, an alkoxy group, an alkenyloxy group, an alkynyloxy group, a
hydroxy group, a substituted or unsubstituted aryl group or a
substituted or unsubstituted heterocycle, or X.sup.351 and
Y.sup.351 may be bonded together to form a saturated or unsaturated
ring. R.sup.351 to R.sup.354 may each represent hydrogen, halogen,
a substituted or unsubstituted alkyl group having 1 to 6 carbon
atoms, an alkoxy group, an aryloxy group, a perfluoroalkyl group, a
perfluoroalkoxy group, an amino group, an alkylcarbonyl group, an
arylcarbonyl group, an alkoxycarbonyl group, an aryloxycarbonyl
group, an azo group, an alkylcarbonyloxy group, an arylcarbonyloxy
group, an alkoxycarbonyloxy group, an aryloxycarbonyloxy group, a
sulfinyl group, a sulfonyl group, a sulfanyl group, a silyl group,
a carbamoyl group, an aryl group, a heterocyclic group, an alkenyl
group, an alkynyl group, a nitro group, a formyl group, a nitroso
group, a formyloxy group, an isocyano group, a cyanate group, an
isocyanate group, a thiocyanate group, an isothiocyanate group or
cyano group, or an adjacent set of R.sup.351 to R.sup.354 may be
condensed to form a substituted or unsubstituted ring.
[0166] A silacyclopentadiene derivative represented by the
following formula (disclosed in JP-A-09-194487) is also preferably
applicable to the electron transporting layer.
##STR00049##
[0167] In the formula, X.sup.361 and Y.sup.361 may each represent a
saturated or unsaturated hydrocarbon group having 1 to 6 carbon
atoms, an alkoxy group, an alkenyloxy group, an alkynyloxy group, a
substituted or unsubstituted aryl group or a substituted or
unsubstituted heterocycle, or X.sup.361 and Y.sup.361 may be bonded
together to form a saturated or unsaturated ring. R.sup.361 to
R.sup.364 may each represent hydrogen, halogen, a substituted or
unsubstituted alkyl group having 1 to 6 carbon atoms, an alkoxy
group, an aryloxy group, a perfluoroalkyl group, a perfluoroalkoxy
group, an amino group, an alkylcarbonyl group, an arylcarbonyl
group, an alkoxycarbonyl group, an aryloxycarbonyl group, an azo
group, an alkylcarbonyloxy group, an arylcarbonyloxy group, an
alkoxycarbonyloxy group, an aryloxycarbonyloxy group, a sulfinyl
group, a sulfonyl group, a sulfanyl group, a silyl group, a
carbamoyl group, an aryl group, a heterocyclic group, an alkenyl
group, an alkynyl group, a nitro group, a formyl group, a nitroso
group, a formyloxy group, an isocyano group, a cyanate group, an
isocyanate group, a thiocyanate group, an isothiocyanate group or
cyano group, or an adjacent set of R.sup.361 to R.sup.364 may be
condensed to form a substituted or unsubstituted ring. However,
when R.sup.361 and R.sup.364 are phenyl groups, neither X.sup.361
nor Y.sup.361 is an alkyl group or a phenyl group. When R.sup.361
and R.sup.364 are thienyl groups, X.sup.361 and Y.sup.361 are each
a univalent hydrocarbon group provided that neither R.sup.362 nor
R.sup.363 is an alkyl group, an aryl group or an alkenyl group, or
that R.sup.362 and R.sup.363 are not bonded together to form an
aliphatic ring group. When R.sup.361 and R.sup.364 are silyl
groups, none of R.sup.362, R.sup.363, X.sup.361 and Y.sup.361 is a
univalent hydrocarbon group having 1 to 6 carbon atoms or a
hydrogen atom. When R.sup.361 and R.sup.362 are of a condensed
benzene-ring structure, neither of X.sup.361 nor Y.sup.361 is an
alkyl group or a phenyl group.
[0168] A borane derivative represented by the following formula
(disclosed in JP-A1-2000-040586) is also preferably applicable to
the electron transporting layer.
##STR00050##
[0169] In the formula, R.sup.371 to R.sup.378 and Z.sup.372 each
represent a hydrogen atom, a saturated or unsaturated hydrocarbon
group, an aromatic group, a heterocyclic group, a substituted amino
group, a substituted boryl group, an alkoxy group or an aryloxy
group; X.sup.371, Y.sup.371 and Z.sup.371 each represent a
saturated or unsaturated hydrocarbon group, an aromatic group, a
heterocyclic group, a substituted amino group, an alkoxy group or
an aryloxy group; substituent groups of Z.sup.371 and Z.sup.372 may
be bonded to form a condensed ring; and n represents an integer in
a range of 1 to 3, where when n is equal to or larger than 2,
Z.sup.371 does not have to be the same. However, the above does not
apply when: n is 1; X.sup.371, Y.sup.371 and R.sup.372 are the
methyl groups; and R.sup.378 is the hydrogen atom or the
substituted boryl group, or when: n is 3; and Z.sup.371 is the
methyl group.
[0170] A compound represented by the following formula (disclosed
in JP-A-10-088121) is also preferably applicable to the electron
transporting layer.
##STR00051##
[0171] In this formula, Q.sup.381 and Q.sup.382 each represent a
ligand shown by the formula below. L.sup.381 represents a ligand
which may be a halogen atom, a substituted or unsubstituted alkyl
group, a substituted or unsubstituted cycloalkyl group, a
substituted or unsubstituted aryl group, a substituted or
unsubstituted heterocyclic group, or L.sup.381 represents a ligand
represented by --OR.sup.391 (R.sup.391 representing a hydrogen
atom, a substituted or unsubstituted alkyl group, a substituted or
unsubstituted cycloalkyl group, a substituted or unsubstituted aryl
group or a substituted or unsubstituted heterocyclic group) or a
ligand represented by --O--Ga-Q.sup.391 (Q.sup.392) (Q.sup.391 and
Q.sup.392 being the same as Q.sup.381 and Q.sup.382).
##STR00052##
[0172] In the above formula, rings A.sup.401 and A.sup.402 are
bonded together to form a substituted or unsubstituted aryl ring or
a heterocycle.
[0173] Examples of the substituent groups of the ring A.sup.401 and
the ring A.sup.402 that form the ligands in the formula above are:
halogen atoms such as chlorine, bromine, iodine and fluorine;
substituted or unsubstituted alkyl groups such as a methyl group,
an ethyl group, a propyl group, a butyl group, a sec-butyl group, a
tert-butyl group, a pentyl group, a hexyl group, a heptyl group, an
octyl group, a stearyl group and a trichloromethyl group;
substituted or unsubstituted aryl groups such as a phenyl group, a
naphthyl group a 3-methylphenyl group, a 3-methoxyphenyl group, a
3-fluorophenyl group, a 3-trichloromethylphenyl group, a
3-trifluoromethylphenyl group and a 3-nitrophenyl group;
substituted or unsubstituted alkoxy groups such as a methoxy group,
a n-butoxy group, a tert-butoxy group, a trichloromethoxy group, a
trifluoroethoxy group, a pentafluoropropoxy group, a
2,2,3,3-tetrafluoropropoxy group, a
1,1,1,3,3,3-hexafluoro-2-propoxy group and a
6-(perfluorohethyl)hexyloxy group; substituted or unsubstituted
aryloxy groups such as a phenoxy group, a p-nitrophenoxy group, a
p-tert-butylphenoxy group, a 3-fluorophenoxy group, a
pentafluorophenyl group and a 3-trifluoromethylphenoxy group;
substituted or unsubstituted alkylthio groups such as a methylthio
group, an ethylthio group, a tert-butylthio group, a hexylthio
group, an octylthio group and a trifluoromethylthio group;
substituted or unsubstituted arylthio groups such as a phenylthio
group, a p-nitrophenylthio group, a p-tert-butylphenylthio group, a
3-fluorophenylthio group, a pentafluorophenylthio group and a
3-trifluoromethylphenylthio group; mono- or disubstituted amino
groups such as a cyano group, a nitro group, an amino group, a
methylamino group, a diethylamino group, an ethylamino group, a
diethylamino group, a dipropylamino group, a dibutylamino group and
a diphenylamino group; acylamino groups such as a
bis(acetoxymethyl)amino group, a bis(acetoxyethyl)amino group, a
bis(acetoxypropyl)amino group and a bis(acetoxybutyl)amino group; a
hydroxyl group; a siloxy group; an acyl group; carbamoyl groups
such as a methylcarbamoyl group, a dimethylcarbamoyl group, an
ethylcarbamoyl group, a diethylcarbamoyl group, a propylcarbamoyl
group, a butylcarbamoyl group, and a phenylcarbamoyl group; a
carboxylic acid group; a sulfonic acid group; an imide group;
cycloalkyl groups such as a cyclopentane group and a cyclohexyl
group; aryl groups such as a phenyl group, a naphthyl group, a
biphenyl group, an anthranil group, a phenanthryl group, a
fluorenyl group and a pyrenyl group; and heterocyclic groups such
as a pyridyl group, a pyrazinyl group, a pyrimidinyl group, a
pyridazinyl group, a triazinyl group, an indolinyl group, a
quinolyl group, an acridinyl group, a pyrrolidinyl group, a
dioxanyl group, a piperidinyl group, a morpholidinyl group, a
piperazinyl group, a carbazolyl group, a furanyl group, a
thiophenyl group, an oxazolyl group, an oxadiazolyl group, a
benzoxazolyl group, a thiazolyl group, a thiadiazolyl group, a
benzothiazolyl group, a triazolyl group, an imidazolyl group and a
benzoimidazolyl group. In addition, the substituent groups listed
above may be bonded together to form a 6-membered aryl ring or a
heterocycle.
[0174] As a preferred embodiment of the organic EL device according
to the present invention, there is known a device containing a
reductive dopant at a boundary between a region transporting the
electrons or the cathode and an organic layer. The reductive dopant
is defined as a substance capable of reducing an electron
transporting compound. Thus, various substances having a certain
level of reducibility can be used, preferable examples of which are
at least one substance selected from a group consisting of: alkali
metal, alkali earth metal, rare earth metal, an oxide of the alkali
metal, a halogenide of the alkali metal, an oxide of the alkali
earth metal, a halogenide of the alkali earth metal, an oxide of
the rare earth metal, a halogenide of the rare earth metal, an
organic complex of the alkali metal, an organic complex of the
alkali earth metal and an organic complex of the rare earth
metal.
[0175] Specifically, the reductive dopant is preferably a
substance(s) having the work function of 2.9 eV or lower, which is
exemplified by at least one alkali metal selected from a group
consisting of Na (work function: 2.36 eV), K (work function: 2.28
eV), Rb (work function: 2.16 eV) and Cs (work function: 1.95 eV) or
at least one alkali earth metal selected from a group consisting of
Ca (work function: 2.9 eV), Sr (work function: 2.0 to 2.5 eV) and
Ba (work function: 2.52 eV). Among these, the reductive dopant is
more preferably at least one alkali metal selected from a group
consisting of K, Rb and Cs, among which Rb and Cs are even more
preferable and Cs is the most preferable. These alkali metals have
particularly high reducibility, so that addition of a relatively
small amount of these alkali metals to an electron injecting zone
can enhance luminescence intensity and lifecycle of the organic
electroluminescence device. In addition, as the reductive dopant
having the work function of 2.9 eV or lower, a combination of two
or more of these alkali metals is also preferable, and a
combination including Cs is particularly preferable (e.g.
combinations of Cs and Na, Cs and K, Cs and Rb or Cs, Na and K).
The combinations including Cs can effectively exert the
reducibility, so that the addition of such reductive dopant to the
electron injecting zone can enhance the luminescence intensity and
the lifecycle of the organic electroluminescence device.
[0176] According to the present invention, an electron injecting
layer formed from an insulator or a semiconductor may be provided
between the cathode and the organic layer. With the arrangement,
leak of electric current can be effectively prevented and the
electron injecting capability can be enhanced. As the insulator, it
is preferable to use at least one metal compound selected from a
group consisting of an alkali metal chalcogenide, an alkali earth
metal chalcogenide, a halogenide of alkali metal and a halogenide
of alkali earth metal. By forming the electron injecting layer from
the alkali metal chalcogenide or the like, the electron injecting
capability can preferably be further enhanced. Specifically,
preferable examples of the alkali metal chalcogenide are Li.sub.2O,
LiO, Na.sub.2 S, Na.sub.2 Se and NaO, while preferable example of
the alkali earth metal chalcogenide are CaO, BaO, SrO, BeO, BaS and
CaSe. Preferable examples of the halogenide of the alkali metal are
LiF, NaF, KF, LiCl, KCl and NaCl. Preferable examples of the
halogenide of the alkali earth metal are fluorides such as
CaF.sub.2, BaF.sub.2, SrF.sub.2, MgF.sub.2 and BeF.sub.2, and
halogenides other than the fluoride.
[0177] Examples of the semiconductor for forming the electron
injecting layer are one of or a combination of two or more of an
oxide, a nitride or an oxidized nitride containing at least one
element selected from a group consisting of Ba, Ca, Sr, Yb, Al, Ga,
In, Li, Na, Cd, Mg, Si, Ta, Sb and Zn. An inorganic compound for
forming the electron injecting layer is preferably a
microcrystalline or amorphous semiconductor film. When the electron
injecting layer is formed of such semiconductor film, more uniform
thin film can be formed, thereby reducing pixel defects such as a
dark spot. Examples of such an inorganic compound are the
above-described alkali metal chalcogenide, alkali earth metal
chalcogenide, halogenide of the alkali metal and halogenide of the
alkali earth metal.
[Cathode]
[0178] In order to inject the electrons into the electron injecting
and transporting layers or the emitting layer, a material whose
work function is small (4 eV or lower) is used as an electrode
material for the cathode, examples of the material being metals,
alloys, electrically conductive compounds and mixtures thereof.
Examples of the electrode material are sodium, a sodium-potassium
alloy, magnesium, lithium, a magnesium-silver alloy,
aluminium/aluminium oxide, an aluminium-lithium alloy, indium, rare
earth metal and the like.
[0179] The cathode is made by forming a thin film from the
electrode material by vapor deposition and sputtering.
[0180] When the organic EL device is top-emission type, the cathode
preferably transmits more than 10% of light emitted by the emitting
layer.
[0181] The sheet resistance as the cathode is preferably several
hundreds .OMEGA./square or lower, and the thickness of the film is
typically in a range from 10 nm to 1 .mu.m, preferably 50 to 200
nm.
[Insulating Layer]
[0182] Since the electrical field is applied to ultra thin films in
the organic electroluminescence device, pixel defects resulted from
leak or short circuit are likely to occur. In order to prevent such
defects, it is preferable to interpose an insulating thin film
layer between a pair of electrodes.
[0183] Examples of a material used for the insulating layer are
aluminum oxide, lithium fluoride, lithium oxide, cesium fluoride,
cesium oxide, magnesium oxide, magnesium fluoride, calcium oxide,
calcium fluoride, cesium fluoride, cesium carbonate, aluminium
nitride, titanium oxide, silicon oxide, germanium oxide, silicon
nitride, boron nitride, molybdenum oxide, ruthenium oxide, vanadium
oxide and the like.
[0184] Mixtures or laminates thereof may also be used.
[Manufacturing Example(s) of Organic EL Device]
[0185] The organic EL device can be manufactured by forming the
anode, the emitting layer and the cathode (in addition to the
above, forming the hole injecting layer, the hole transporting
layer, the electron injecting layer and the electron transporting
layer as necessary) from the materials listed above by the
above-described formation methods. The organic EL device can also
be manufactured by forming the above elements in the inverse order
of the above, namely from the cathode to the anode.
[0186] The following is a manufacturing example of the organic EL
device in which the anode, the hole transporting layer, the
emitting layer, the electron transporting layer and the cathode are
sequentially formed on the light-transmissive substrate.
[0187] A thin film is formed of the anode material on a suitable
light-transmissive substrate by vapor deposition or sputtering such
that the thickness of the thin film is 1 m or smaller, preferably
in a range from 10 nm to 200 nm, thereby forming the anode. Then,
the hole transporting layer is formed on the formed anode. The hole
transporting layer may be formed by a method such as vacuum
deposition, spin coating, casting and the LB method as described
above, among which vacuum deposition is preferable in forming the
hole transporting layer because the method can easily form
homogeneous films and can prevent generation of pin holes. When the
hole transporting layer is formed by vacuum deposition, conditions
for conducting vacuum deposition depend on the compounds to be used
(i.e., the material of the hole transporting layer), a crystal
structure of the targeted hole transporting layer, and a
recombination structure of the targeted hole transporting layer.
Generally, conditions are preferably set so as to satisfy
deposition-source temperature of 50 to 450 degrees C., vacuum of
10.sup.-7 to 10.sup.-3 torr, deposition speed of 0.01 to 50
nm/second, substrate temperature of -50 to 300 degrees C., film
thickness of 5 nm to .mu.m.
[0188] Then, the emitting layer is formed on the hole transporting
layer. The emitting layer may also be formed of a desirable
material by a method such as vacuum deposition, sputtering, spin
coating and casting, among which vacuum deposition is preferable in
forming the emitting layer because the method can easily form
homogeneous films and can prevent generation of pin holes. When the
emitting layer is formed by vacuum deposition, deposition
conditions for forming the emitting layer can be generally set in
the same manner as the hole transporting layer although the
deposition conditions may vary depending on compounds used for
forming the emitting layer.
[0189] Next, the electron transporting layer is formed on the
emitting layer. As with the hole transporting layer and the
emitting layer, the electron transporting layer is also preferably
formed by vacuum deposition so as to form a homogeneous film.
Deposition conditions for forming the electron transporting layer
can be set in the same manner as the hole transporting layer and
the emitting layer.
[0190] Lastly, the cathode is laminated thereon.
[0191] The cathode can be formed from a metal by a method such as
vapor deposition and sputtering. In order to protect the organic
layers deposited under the cathode from being damaged, the vacuum
deposition is preferable.
[0192] The above-described organic EL device is preferably
manufactured such that all layers from the anode to the cathode are
formed in one vacuuming.
[0193] The methods for forming each layer of the organic EL device
are not particularly limited. Conventionally-known methods such as
vacuum deposition, molecular-beam deposition, spin coating,
dipping, casting, bar coating and roll coating are applicable to
forming the layers.
[0194] Although the thickness of each organic layer of the organic
EL device is not particularly limited, the thickness is generally
preferably in a range of several nanometers to 1 .mu.m because
excessively-thinned film likely entails defects such as a pin hole
while excessively-thickened film requires high voltage to be
applied and deteriorates efficiency.
[0195] When a voltage is applied to the organic EL device, the
light-emission can be observed by applying a voltage of 3 to 40V
with the anode having the positive polarity and the cathode having
the negative polarity. When the voltage is applied with the
inversed polarity, no current flows, so that no light is emitted.
When an alternating voltage is applied, the uniform light-emission
can be observed only when the anode has the positive polarity and
the cathode has the negative polarity. A waveform of the
alternating current to be applied may be suitably selected.
EXAMPLE
[0196] Next, the present invention will be further described in
detail by exemplifying Examples. However, the present invention is
not limited to such Examples.
Example 1
[0197] A 130 nm-thick transparent electrode formed of indium tin
oxide was formed on a glass substrate having a size of 25 mm by 75
mm by 0.7 mm. After the transparent substrate was ultrasonically
cleaned in isopropyl alcohol for five minutes, the substrate was
further cleaned with UV (ultraviolet) ozone for thirty minutes, and
then the substrate was mounted on a vapor deposition apparatus.
[0198] Initially,
N,N'-bis[4-(N,N-diphenylamino)phenyl-1-yl]-N,N'-diphenyl-4,4'-benzidine
was deposited on the substrate to form a 60 nm-thick hole injecting
layer, and subsequently
N,N'-bis[4'-{N-(naphthyl-1-yl)-N-phenyl}aminobiphenyl-4-yl]-N-phenylamine
was deposited thereon to form a 10 nm-thick hole transporting
layer. Then, the following compound (A-1), a naphthacene
derivative, and the following compound (B-1), a compound having a
pyrromethene skeleton, were simultaneously deposited thereon by
weight ratio of 40 to 0.4 (=0.99 wt %) to form a 40 nm-thick
emitting layer.
##STR00053##
[0199] Next, the following compound (C-1) was deposited thereon to
form a 30 nm-thick electron transporting layer.
##STR00054##
[0200] After 0.5 nm-thick lithium fluoride was subsequently
deposited thereon, 150 nm-thick aluminum was deposited further
thereon. The layer of aluminum/lithium fluoride served as the
cathode. The organic EL device was manufactured by the
above-described manner.
[0201] When a current test was conducted on the obtained device,
the organic EL device was driven by a voltage of 4.7 V to emit red
light having a luminescence intensity of 711 cd/m.sup.2 at a
current density of 10 mA/cm.sup.2, a trichromatic coordinate of the
emitted light was (0.66, 0.33), and efficiency of the device was
7.11 cd/A. In addition, when a continuous direct-current test was
conducted with the initial luminescence intensity set at 5,000
cd/m.sup.2, time elapsed until the luminescence intensity was
reduced by half (i.e., time until half-life) was 1,800 hours.
Example 2
[0202] An organic EL device was manufactured in the same manner as
in Example 1 except that the following compound (A-2) was used in
place of the compound (A-1) for forming the emitting layer.
##STR00055##
[0203] When a current test was conducted on the obtained device,
the organic EL device was driven by a voltage of 4.8 V to emit red
light having a luminescence intensity of 720 cd/m.sup.2 at a
current density of 10 mA/cm.sup.2, a trichromatic coordinate of the
emitted light was (0.66, 0.33), and efficiency of the device was
7.20 cd/A. In addition, when a continuous direct-current test was
conducted with the initial luminescence intensity set at 5,000
cd/m.sup.2, time elapsed until the luminescence intensity was
reduced by half was 2,000 hours.
Example 3
[0204] An organic EL device was manufactured in the same manner as
in Example 1 except that the following compound (A-3) was used in
place of the compound (A-1) for forming the emitting layer.
##STR00056##
[0205] When a current test was conducted on the obtained device,
the organic EL device was driven by a voltage of 4.8 V to emit red
light having a luminescence intensity of 737 cd/m.sup.2 at a
current density of 10 mA/cm.sup.2, a trichromatic coordinate of the
emitted light was (0.66, 0.33), and efficiency of the device was
7.37 cd/A. In addition, when a continuous direct-current test was
conducted with the initial luminescence intensity set at 5,000
cd/m.sup.2, time elapsed until the luminescence intensity was
reduced by half was 3,200 hours.
Example 4
[0206] An organic EL device was manufactured in the same manner as
in Example 1 except that the following compound (B-2) was used in
place of the compound (B-1) for forming the emitting layer.
##STR00057##
[0207] When a current test was conducted on the obtained device,
the organic EL device was driven by a voltage of 4.8 V to emit red
light having a luminescence intensity of 698 cd/m.sup.2 at a
current density of 10 mA/cm.sup.2, a trichromatic coordinate of the
emitted light was (0.66, 0.33), and efficiency of the device was
6.98 cd/A. In addition, when a continuous direct-current test was
conducted with the initial luminescence intensity set at 5,000
cd/m.sup.2, time elapsed until the luminescence intensity was
reduced by half was 1,900 hours.
Example 5
[0208] An organic EL device was manufactured in the same manner as
in Example 1 except that the following compound (B-3) was used in
place of the compound (B-1) for forming the emitting layer.
##STR00058##
[0209] When a current test was conducted on the obtained device,
the organic EL device was driven by a voltage of 4.8 V to emit red
light having a luminescence intensity of 710 cd/m.sup.2 at a
current density of 10 mA/cm.sup.2, a trichromatic coordinate of the
emitted light was (0.66, 0.33), and efficiency of the device was
7.10 cd/A. In addition, when a continuous direct-current test was
conducted with the initial luminescence intensity set at 5,000
cd/m.sup.2, time elapsed until the luminescence intensity was
reduced by half was 1,500 hours.
Example 6
[0210] An organic EL device was manufactured in the same manner as
in Example 1 except that the following compound (B-4) was used in
place of the compound (B-1) for forming the emitting layer.
##STR00059##
[0211] When a current test was conducted on the obtained device,
the organic EL device was driven by a voltage of 4.7 V to emit red
light having a luminescence intensity of 676 cd/m.sup.2 at a
current density of 10 mA/cm.sup.2, a trichromatic coordinate of the
emitted light was (0.66, 0.33), and efficiency of the device was
6.76 cd/A. In addition, when a continuous direct-current test was
conducted with the initial luminescence intensity set at 5,000
cd/m.sup.2, time elapsed until the luminescence intensity was
reduced by half was 1,600 hours.
Example 7
[0212] An organic EL device was manufactured in the same manner as
in Example 1 except that the following compound (C-2) was used in
place of the compound (C-1) for forming the electron transporting
layer.
##STR00060##
[0213] When a current test was conducted on the obtained device,
the organic EL device was driven by a voltage of 5.6 V to emit red
light having a luminescence intensity of 564 cd/m.sup.2 at a
current density of 10 mA/cm.sup.2, a trichromatic coordinate of the
emitted light was (0.64, 0.34), and efficiency of the device was
5.64 cd/A. In addition, when a continuous direct-current test was
conducted with the initial luminescence intensity set at 5,000
cd/m.sup.2, time elapsed until the luminescence intensity was
reduced by half was 1,000 hours.
[Comparative 1]
[0214] An organic EL device was manufactured in the same manner as
in Example 7 except that the following compound (C-2) was used in
place of the compound (A-1) for forming the emitting layer.
[0215] When a current test was conducted on the obtained device,
the organic EL device was driven by a voltage of 6.1 V to emit red
light having a luminescence intensity of 434 cd/m.sup.2 at a
current density of 10 mA/cm.sup.2, a trichromatic coordinate of the
emitted light was (0.63, 0.35), and efficiency of the device was
4.34 cd/A. In addition, when a continuous direct-current test was
conducted with the initial luminescence intensity set at 5,000
cd/m.sup.2, time elapsed until the luminescence intensity was
reduced by half was 500 hours.
[Comparative 2]
[0216] An organic EL device was manufactured in the same manner as
in Example 1 except that the following compound (B-5) was used in
place of the compound (B-1) for forming the emitting layer.
##STR00061##
[0217] When a current test was conducted on the obtained device,
the organic EL device was driven by a voltage of 4.7 V to emit red
light having a luminescence intensity of 385 cd/m.sup.2 at a
current density of 10 mA/cm.sup.2, a trichromatic coordinate of the
emitted light was (0.64, 0.37), and efficiency of the device was
3.85 cd/A. In addition, when a continuous direct-current test was
conducted with the initial luminescence intensity set at 5,000
cd/m.sup.2, time elapsed until the luminescence intensity was
reduced by half was 700 hours.
[Comparative 3]
[0218] An organic EL device was manufactured in the same manner as
in Example 1 except that the following compound (C-2) was used in
place of the compound (A-1) for forming the emitting layer.
[0219] When a current test was conducted on the obtained device,
the organic EL device was driven by a voltage of 5.2 V to emit red
light having a luminescence intensity of 451 cd/m.sup.2 at a
current density of 10 mA/cm.sup.2, a trichromatic coordinate of the
emitted light was (0.65, 0.33), and efficiency of the device was
4.51 cd/A. In addition, when a continuous direct-current test was
conducted with the initial luminescence intensity set at 5,000
cd/m.sup.2, time elapsed until the luminescence intensity was
reduced by half was 600 hours.
Example 8
[0220] An organic EL device was manufactured in the same manner as
in Example 1 except that the following compound (B-6) was used in
place of the compound (B-1) for forming the emitting layer.
##STR00062##
[0221] When a current test was conducted on the obtained device,
the organic EL device was driven by a voltage of 4.4 V to emit red
light having a luminescence intensity of 1,081 cd/m.sup.2 at a
current density of 10 mA/cm.sup.2, a trichromatic coordinate of the
emitted light was (0.65, 0.34), and efficiency of the device was
10.81 cd/A. In addition, when a continuous direct-current test was
conducted with the initial luminescence intensity set at 5,000
cd/m.sup.2, time elapsed until the luminescence intensity was
reduced by half was 3,500 hours.
Example 9
[0222] An organic EL device was manufactured in the same manner as
in Example 1 except that the following compound (B-7) was used in
place of the compound (B-1) for forming the emitting layer.
##STR00063##
[0223] When a current test was conducted on the obtained device,
the organic EL device was driven by a voltage of 4.5 V to emit red
light having a luminescence intensity of 852 cd/m.sup.2 at a
current density of 10 mA/cm.sup.2, a trichromatic coordinate of the
emitted light was (0.67, 0.33), and efficiency of the device was
8.52 cd/A. In addition, when a continuous direct-current test was
conducted with the initial luminescence intensity set at 5,000
cd/m.sup.2, time elapsed until the luminescence intensity was
reduced by half was 3,300 hours.
TABLE-US-00001 TABLE 1 time Drive luminescence Luminous until
Voltage intensity trichromatic Efficiency half- (V) (cd/m.sup.2)
coordinate (cd/A) life (hr) Example 1 4.7 711 (0.66, 0.33) 7.11
1,800 Example 2 4.8 720 (0.66, 0.33) 7.20 2,000 Example 3 4.8 737
(0.66, 0.33) 7.37 3,200 Example 4 4.8 698 (0.66, 0.33) 6.98 1,900
Example 5 4.8 710 (0.66, 0.33) 7.10 1,500 Example 6 4.7 676 (0.66,
0.33) 6.76 1,600 Example 7 5.6 564 (0.64, 0.34) 5.64 1,000 Compar-
6.1 434 (0.63, 0.35) 4.34 500 ative 1 Compar- 4.7 385 (0.64, 0.37)
3.85 700 ative 2 Compar- 5.2 451 (0.65, 0.33) 4.51 600 ative 3
Example 8 4.4 1,081 (0.65, 0.34) 10.81 3,500 Example 9 4.5 852
(0.67, 0.33) 8.52 3,300
[0224] It is understood from a comparison between Example 7 and
Comparative 1 that Example 7, in which the compound (A-1) was used
as the host, is more excellent in drive voltage, luminescence
intensity, chromaticity and time until half-life.
[0225] In other words, a combination of the compound (A-1) and the
compound (B-1) as the combination of the host and the dopant is
more excellent than a combination of the compound (C-2), a general
host material, and the compound (B-1).
[0226] In Examples 1 to 6 and Comparatives 2 and 3, the compound
(C-1) was used as the electron transporting layer. The compound
(B-5) was used as the dopant in Comparative 2 while the compound
(C-2) was used as the host in Comparative 3. In contrast, the
combination of the host and the dopant according to the present
invention was used in Examples 1 to 6.
[0227] Consequently, the combination of the host and the dopant
according to the present invention is excellent in terms of drive
voltage, luminescence intensity, chromaticity, luminous efficiency
and time until half-life.
[0228] In other words, irrespective of what compound is used for
forming the electron transporting layer, the combination of the
host material and the dopant material according to the present
invention is excellent in terms of drive voltage, luminescence
intensity, chromaticity, efficiency and time until half-life.
[0229] It is understood from a comparison between Examples 1 to 6
and Example 7 that, by using such a material as represented by the
compound (C-1) according to the present invention for the electron
transporting material, the device can exhibit excellent performance
in terms of drive voltage, luminescence intensity, chromaticity,
efficiency, time until half-time and the like.
[0230] The emitting region is typically preferably located within
the emitting layer in the organic EL device.
[0231] On the other hand, an emitting material for emitting red
light tends to cause electron traps because an energy gap of the
dopant is small. Accordingly, the electrons injected into the
emitting layer from the electron transporting layer tend to be
trapped in the dopant located adjacent to the electron transporting
layer, thereby moving the emitting region toward the electron
transporting layer.
[0232] In Example 7, the chromaticity was shifted toward green, and
the compound (C-2) emitted light. It can be deduced from the above
with respect to Example 7 that the holes were more strongly
injected into the emitting layer than the electrons, and that many
of the holes penetrated the emitting layer to reach the electron
transporting layer, thereby generating exciters in the compound
(C-2) forming the electron transporting layer. In addition, since
the compound (C-2) emitted light, the time elapsed until the
lifetime of the organic EL device was reduced by half is short.
[0233] In this respect, the electron transporting material
according to the present invention, a representative example of
which is the compound (C-1), is excellent in transporting
electrons. The electron transporting layer formed of such an
electron transporting material can strongly inject the electrons
into the emitting layer, thereby preventing the holes from
penetrating the emitting layer to reach the electron transporting
layer.
[0234] In other words, the organic EL device according to the
present invention can emit light of high chromaticity with high
efficiency while preventing generation of exciters in the electron
transporting layer, and lifetime of the entire device is long.
[0235] In addition, when a naphthacene derivative and a compound
having pyrromethene skeleton or the like are respectively used for
the host and the dopant, the electron transporting material can
exhibit above-described excellent effects and advantages.
[0236] Lifetime of Example 3 is much longer than those of Examples
1 and 2 because the compound A-3 was used for the host in Example
3. It has been revealed from the above that substituent(s) in ortho
position(s) of benzene rings bonded to the naphthacene skeleton
prevents molecular association, thereby contributing to longer
lifetime.
[0237] The present invention is not limited to the above examples,
but includes modifications and improvements made within a scope
where an object of the present invention can be achieved.
[0238] For instance, ruburene, which is an example of the host
material of Example 1, may be substituted or unsubstituted. In
addition, the compounds used in the other Examples may be
substituted or unsubstituted.
[0239] The priority application Number JP2007-061091 upon which
this patent application is based is hereby incorporated by
reference.
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