U.S. patent application number 13/358284 was filed with the patent office on 2012-05-17 for organic electroluminescent element material, organic electroluminescent element, method of manufacturing organic electroluminescent element, display device, and illuminating device.
This patent application is currently assigned to KONICA MINOLTA HOLDINGS, INC.. Invention is credited to Rie KATAKURA, Hiroshi KITA, Hideo TAKA, Tatsuo TANAKA.
Application Number | 20120123073 13/358284 |
Document ID | / |
Family ID | 40638609 |
Filed Date | 2012-05-17 |
United States Patent
Application |
20120123073 |
Kind Code |
A1 |
TANAKA; Tatsuo ; et
al. |
May 17, 2012 |
ORGANIC ELECTROLUMINESCENT ELEMENT MATERIAL, ORGANIC
ELECTROLUMINESCENT ELEMENT, METHOD OF MANUFACTURING ORGANIC
ELECTROLUMINESCENT ELEMENT, DISPLAY DEVICE, AND ILLUMINATING
DEVICE
Abstract
In the present invention, provided is an organic
electroluminescent element material having a high externally
taking-out quantum efficiency, which is suitable for manufacturing
an element exhibiting long light emission lifetime, and also
provided is an organic electroluminescent element possessing the
material, a method of manufacturing the organic electroluminescent
element, and a display as well as an illuminating device fitted
with the organic electroluminescent element.
Inventors: |
TANAKA; Tatsuo; (Kanagawa,
JP) ; KITA; Hiroshi; (Tokyo, JP) ; KATAKURA;
Rie; (Tokyo, JP) ; TAKA; Hideo; (Tokyo,
JP) |
Assignee: |
KONICA MINOLTA HOLDINGS,
INC.
Tokyo
JP
|
Family ID: |
40638609 |
Appl. No.: |
13/358284 |
Filed: |
January 25, 2012 |
Related U.S. Patent Documents
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Application
Number |
Filing Date |
Patent Number |
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12742127 |
May 10, 2010 |
|
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PCT/JP2008/069878 |
Oct 31, 2008 |
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13358284 |
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Current U.S.
Class: |
526/241 ;
526/259; 526/310 |
Current CPC
Class: |
H01L 51/0025 20130101;
H01L 51/0059 20130101; H01L 51/0088 20130101; H01L 51/0037
20130101; H01L 51/5012 20130101; H01L 51/006 20130101; H01L 51/56
20130101; H01L 51/0071 20130101; H01L 51/0043 20130101; H01L
2251/308 20130101; C09K 11/06 20130101; H01L 51/0087 20130101; C09K
2211/1425 20130101; H01L 51/0081 20130101; H01L 27/3244 20130101;
H01L 51/0085 20130101; H01L 51/0039 20130101; H01L 51/0086
20130101; C09K 2211/1433 20130101 |
Class at
Publication: |
526/241 ;
526/259; 526/310 |
International
Class: |
C08F 236/22 20060101
C08F236/22; C08F 126/06 20060101 C08F126/06; C08F 136/20 20060101
C08F136/20 |
Foreign Application Data
Date |
Code |
Application Number |
Nov 14, 2007 |
JP |
2007-295326 |
Claims
1. A method of manufacturing a polymer contained in an organic
electroluminescent element material, comprising the steps of:
synthesizing the polymer from at least one monomer having an
impurity content of 1000 ppm or less; and recovering the
polymer.
2. The method of claim 1, wherein the at least one monomer
comprises a reactive substituent.
3. The method of claim 2, wherein the reactive substituent
comprises any of the following partial structures: ##STR00031##
4. The method of claim 1, wherein the polymer comprises a partial
structure represented by the following Formula (1):
--Ar1-N(Ar3)-Ar2- Formula (1) wherein each of Ar1 and Ar2
independently represents an arylene group or a heteroarylene group,
and Ar3 represents an aromatic hydrocarbon group or an aromatic
heterocyclic group.
Description
CROSS REFERENCE TO RELATED APPLICATIONS
[0001] This is a Continuation of U.S. application Ser. No.
12/742,127, filed May 10, 2010, which was a U.S. National Phase
Application under 35 U.S.C. 371 of International Application
PCT/JP2008/069878, filed Oct. 31, 2008, which claims the priority
of Japanese Application No. 2007-295326, filed Nov. 14, 2007, the
entire content of all three applications are hereby incorporated by
reference.
TECHNICAL FIELD
[0002] The present invention relates to an organic
electroluminescent element material, an organic electroluminescent
element, a method of manufacturing an organic electroluminescent
element, a display device and an illuminating device.
BACKGROUND
[0003] As an emission type electronic displaying device, there is
an electroluminescent display (hereinafter referred to as ELD). As
devices constituting the ELD, there are mentioned an inorganic
electroluminescent element and an organic electroluminescent
element (hereinafter referred to as organic EL element).
[0004] The inorganic electroluminescent element has been used for a
plane-shaped light source, but a high voltage alternating current
has been required to drive the element.
[0005] An organic EL element has a structure in which a light
emission layer containing a light emission compound is arranged
between a cathode and an anode, and an electron and a hole are
injected into the light emission layer and recombined to form an
exciton. The element emits light, utilizing light (fluorescent
light or phosphorescent light) generated by inactivation of the
exciton, and the element can emit light by applying a relatively
low voltage of from several volts to several decade volts. The
element has a wide viewing angle and high visualization since the
element is of self light emission type. Further, the element is a
thin, complete solid device, and therefore, the element is noted
from the viewpoint of space saving and portability.
[0006] However, development of an organic EL element for practical
use is demanded which efficiently emits light with high luminance
at a lower power.
[0007] High emission luminance and long lifetime is attained in
Japanese Patent No. 3093796 by doping a slight amount of a phosphor
in stilbene derivatives, distyrylarylene derivatives or
tristyrylarylene derivatives.
[0008] An element is known which comprises an organic light
emission layer containing an 8-hydroxyquinoline aluminum complex as
a host compound doped with a slight amount of a phosphor in
Japanese Patent O.P.I. Publication No. 63-264692, and an element is
known which comprises an organic light emission layer containing an
8-hydroxyquinoline aluminum complex as a host compound doped with a
quinacridone type dye in Japanese Patent O.P.I. Publication No.
3-255190.
[0009] When light emitted through excited singlet state is used as
in the above, the upper limit of externally taking-out quantum
efficiency (.eta.) is considered to be at most 5%, as the
generation ratio of singlet excited species to triplet excited
species is 1:3, that is, the generation probability of excited
species capable of emitting light is 25%, and further, external
light emission efficiency is 20%.
[0010] Since an organic EL element, employing phosphorescence
through the excitation triplet, was reported by Prinston University
(see M. A. Baldo et al., Nature, 395, p. 151-154 (1998)), study on
materials emitting phosphorescence at room temperature has been
actively made.
[0011] For example, such an organic EL element is disclosed in M.
A. Baldo et al., Nature, 403, 17, p. 750-753 (2000) or U.S. Pat.
No. 6,097,147.
[0012] As the upper limit of the internal quantum efficiency of the
excitation triplet is 100%, the light emission efficiency of the
excitation triplet is theoretically four times that of the excited
singlet. Such an organic EL element has possibility that exhibits
the same performance as a cold cathode tube, and its application to
illumination is watched.
[0013] Many compounds, mainly heavy metal complexes such as iridium
complexes are synthesized and studied in for example, S. Lamansky
et al., J. Am. Chem. Soc., 123, 4304 (2001).
[0014] An example employing tris(2-phenylpyridine)iridium as a
dopant is studied in M. A. Baldo et al., Nature, 403, 17, p.
750-753 (2000) above.
[0015] Further, M. E. Tompson et. al. studies an example employing
as a dopant L.sub.2Ir(acac) such as (ppy).sub.2Ir(acac) in The
10.sup.th International Workshop on Inorganic and Organic
Electroluminescence (EL '00, Hamamatsu), and Moon-Jae Youn. Og,
Tetsuo Tsutsui et. al. an example employing as a dopant
tris(2-p-tolylpyridine)iridium {Ir(ptpy).sub.3} or
tris(benzo-[h]-quinoline)iridium {Ir(bzq).sub.3} in The 10.sup.th
International Workshop on Inorganic and Organic Electroluminescence
(EL '00, Hamamatsu). In addition, these metal complexes are
generally called orthometalated iridium complexes.
[0016] As described above, attempt for preparing an element
employing various iridium complexes is made in S. Lamansky et al.,
J. Am. Chem. Soc., 123, 4304 (2001) or in Japanese Patent O.P.I.
Publication No. 2001-247859.
[0017] Further, to obtain high emission efficiency, lkai et al.
utilized a hole transporting compound as a host of a phosphorescent
compound at The 10th International Workshops on Inorganic and
Organic Electroluminescence (EL '00, Hamamatsu). Further, M. E.
Tompson et al. utilized various types of electron transporting
materials doped with a new iridium complex as a host of a
phosphorescent compound.
[0018] An organic EL element fitted with the iridium complex is
prepared generally via evaporation. Studies of an organic EL
element prepared by a coating method have been actively done, but
it is presently difficult to prepare the organic EL element via
coating since the iridium complex exhibits low solubility. Thus, it
is desired to improve solubility of the iridium complex.
[0019] Further, orthometalated complexes in which iridium as a
center metal is replaced by platinum are also watched. Regarding
these complexes, there are known many kinds of complexes having
characteristics in the ligands, which are disclosed in Japanese
Patent O.P.I. Publication Nos. 2002-332291, 2002-332292,
2002-338588, 2002-226495, and 2002-234894, for example.
[0020] Light emission elements employing the above compounds
exhibit greatly improved emission luminance and emission efficiency
as compared to conventional elements, because the light emission
arises from phosphorescence, but they have a problem in that
emission lifetime is low as compared to conventional elements. In
this way, in the case of a light emitting material exhibiting high
phosphorescence efficiency, it is difficult to improve realization
of shorter light emission wavelength as well as emission lifetime,
whereby presently, practically sufficient tolerable performance has
not yet been achieved.
[0021] As a material to improve the performance, for example, known
is an Ir complex or a Pt complex each having a phenyl imidazole
derivative as a ligand in WO 02/15645 and WO 05/7767. However,
light emission efficiency and lifetime of the element of each of
these complexes are not sufficiently satisfactory, and further
improvement of the light emission efficiency and the lifetime are
desired to be improved.
[0022] A vacuum evaporation method is conventionally utilized as a
method of manufacturing an organic EL element, but since in the
case of the conventional vacuum evaporation method, high vacuum is
required for the operation, the manufacturable member is limited in
size, and a step of taking a member in and out is also required at
the same time. Thus, the conventional vacuum evaporation method is
rejected as unsuitable for the continuous production.
[0023] On the other hand, as a continuously manufacturable means, a
method of employing an EL material solution is disclosed (refer to
Patent Document 1, for example), and a low-molecular material and a
polymeric material are to be usable as the EL material.
[0024] However, in the case of coating with a low-molecular
material, a lower layer and an upper layer are difficult to be
incorporated during formation of a multilayer, resulting in
difficulty of obtaining an EL element exhibiting high
performance.
[0025] Further, in the case of a polymeric material, there appears
a problem such that a refining method available with a
low-molecular material such as a recrystallization method, a
sublimation refining method, and a silica column refining method
can not be utilized, and impurities contained in a monomer as raw
material to prepare a polymer are difficult to be removed. Thus,
this reason leads to a factor to degrade light emission lifetime.
[0026] Patent Document 1: Japanese Patent O.P.I. Publication No.
2001-297882
DISCLOSURE OF THE INVENTION
Problems to be Solved by the Invention
[0027] It is an object of the present invention to provide an
organic electroluminescent element material having a high
externally taking-out quantum efficiency, which is suitable for
manufacturing an element exhibiting long light emission lifetime,
and also to provide an organic electroluminescent element
possessing the material, a method of manufacturing the organic
electroluminescent element, and a display as well as an
illuminating device fitted with the organic electroluminescent
element.
Means to Solve the Problems
[0028] The above-described object of the present invention is
accomplished by the following Structures.
[0029] (Structure 1) An organic electroluminescent element material
comprising a synthesized polymer from at least one monomer having
an impurity content of 1000 ppm or less.
[0030] (Structure 2) The organic electroluminescent element
material of Structure 1, wherein the at least one monomer has an
impurity content of 100 ppm or less.
[0031] (Structure 3) The organic electroluminescent element
material of Structure 1 or 2, wherein the at least one monomer
comprises a reactive substituent.
[0032] (Structure 4) The organic electroluminescent element
material of any one of Structures 1-3, the polymer comprises a
partial structure represented by the following Formula (1):
--Ar1-N(Ar3)-Ar2- Formula (1)
wherein each of Ar1 and Ar2 independently represents an arylene
group or a heteroarylene group, and Ar3 represents an aromatic
hydrocarbon group or an aromatic heterocyclic group.
[0033] (Structure 5) An organic electroluminescent element
comprising the organic electroluminescent element material of any
one of Structures 1-4.
[0034] (Structure 6) The organic electroluminescent element of
Structure 5, comprising a phosphorescence emission compound.
[0035] (Structure 7) The organic electroluminescent element of
Structure 5 or 6, prepared with a solution comprising the organic
electroluminescent element material of any one of Structures
1-4.
[0036] (Structure 8) The organic electroluminescent element of any
one of Structures 5-7, producing white light emission.
[0037] (Structure 9) A method of manufacturing an organic
electroluminescent element, comprising the step of using a reaction
solution for a polymer to be synthesized from at least one monomer
having an impurity content of 1000 ppm or less to prepare the
organic electroluminescent element of any one of Structures
5-8.
[0038] (Structure 10) A display device comprising the organic
electroluminescent element of any one of Structures 5-8.
[0039] (Structure 11) An illuminating device comprising the organic
electroluminescent element of any one of Structures 5-8.
Effect of the Invention
[0040] In the present invention, provided can be an organic
electroluminescent element material having a high externally
taking-out quantum efficiency, which is suitable for manufacturing
an element exhibiting long light emission lifetime, and also
provided can be an organic electroluminescent element possessing
the material, a method of manufacturing the organic
electroluminescent element, and a display as well as an
illuminating device fitted with the organic electroluminescent
element.
BRIEF DESCRIPTION OF THE DRAWINGS
[0041] FIG. 1 is a schematic diagram showing an example of a
display device composed of an organic EL element.
[0042] FIG. 2 is a schematic diagram showing display section A.
[0043] FIG. 3 is a schematic diagram showing a pixel.
[0044] FIG. 4 is a schematic diagram showing a passive matrix
system full color display device.
[0045] FIG. 5 is an appearance diagram showing an illuminating
device.
[0046] FIG. 6 is a schematic diagram showing an illuminating
device.
EXPLANATION OF NUMERALS
[0047] 1 Display [0048] 3 Pixel [0049] 5 Scanning line [0050] 6
Data line [0051] 7 Power supply line [0052] 10 Organic EL element
[0053] 11 Switching transistor [0054] 12 Drive transistor [0055] 13
Condenser [0056] A Display section [0057] B Control section [0058]
101 Organic EL element [0059] 102 Glass cover [0060] 105 Cathode
[0061] 106 Organic EL layer [0062] 107 Glass substrate provided
with transparent electrode [0063] 108 Nitrogen gas [0064] 109 Water
refilling agent
DESCRIPTION OF THE PREFERRED EMBODIMENTS
[0065] As to an organic electroluminescent element material of
Structure 1 or 2 in the present invention, provided is a polymer
synthesized from at least one monomer having an impurity content of
1000 ppm or less, or an organic electroluminescent element material
containing a synthesized polymer from at least one monomer having
an impurity content of 1000 ppm or less, and also provided can be
an organic electroluminescent element exhibiting high externally
taking-out quantum efficiency and long light emission lifetime via
use of the foregoing element material, and a display device and an
illuminating device fitted with the foregoing element.
[0066] Next, each of constituent elements in the present invention
will be described is detailed in order.
<<Monomer Having Impurity Content of 1000 ppm or
Less>>
[0067] A monomer having comprised in an organic electroluminescent
element material of the present invention will be described.
[0068] The monomer of the present invention is referred to also as
an organic compound having a reactive substituent, and has an
impurity content of 1000 ppm or less, but preferably has an
impurity content of 100 ppm or less.
[0069] Herein, to achieve the impurity content of 1000 ppm or less
means that a monomer of the present invention (an organic compound
having a reactive substituent) is designed to have a purity content
of 99.9% by weight or more.
[0070] In the present invention, it is inhibited by using an
organic electroluminescent element material containing a
high-purity polymer synthesized from the above-described
high-purity monomer (organic compound having a reactive
substituent) to contain the impurity to possibly induce poor
performance variation of an organic electroluminescent element,
whereby light emission efficiency and lifetime of the element
become possible to be largely improved.
{Measurement of Impurity Content (Referred to Also as Measurement
of Polymer Purity)}
[0071] The purity of a monomer of the present invention (an organic
compound having a reactive substituent) can be measured and
determined by a commercially available HPLC (high performance
liquid chromatography).
[0072] The monomer purity measured by HPLC will be described in
detail in synthetic examples of the after-mentioned monomer.
(Reactive Substituent)
[0073] The reactive substituent of the present invention will be
described.
[0074] Specific examples of the reactive substituent of the present
invention include groups each having the following partial
structure.
##STR00001##
[0075] As organic compounds each having the above-described
reactive substituent, preferable compounds are those having the
above-described reactive group as mother compounds such as
compounds used for forming a host compound, an emission dopant, a
fluorescence dopant, an election injection layer and a hole
injection layer; compounds used for forming a hole blocking layer
and an electron blocking layer; compounds used for forming a hole
transport layer; and compounds used for forming an electron
transport layer, which are utilized to form a constituent layer of
the after-mentioned organic electroluminescent element (organic EL
element).
[0076] Further, these can also be appropriately selected from
compounds described as a hole transport material, an electron
blocking material, an emission host (referred to as a host
compound), an emission dopant (referred to simply as a dopant), an
electron transport material and a hole blocking material, and
compounds disclosed in patent documents.
[0077] Specific examples of the compound having a reactive
substituent are shown below, but the present invention is not
limited thereto.
##STR00002## ##STR00003## ##STR00004## ##STR00005## ##STR00006##
##STR00007## ##STR00008## ##STR00009## ##STR00010## ##STR00011##
##STR00012## ##STR00013## ##STR00014## ##STR00015##
[0078] Next, a synthetic example of the monomer relating to an
organic electroluminescent element material of the present
invention (an organic compound having a reactive substituent) will
be shown, but the present invention is not limited thereto.
Synthetic Example
Synthesis of Compound 1-2
##STR00016##
[0080] Into a 200 mL three-necked flask, added were 0.5 g of
palladium acetate, 100 mL of xylene, and 1.0 g of
tri-tert-butylphosphine, and the system was replaced by introducing
nitrogen, followed by stirring at room temperature for 30 minutes.
Thereafter, 5.2 g of 4,4'-diiodobiphenyl, 5.0 g of
3-formylcarbazole (compound described in J. Chem. Soc., 1957,
2210-2212), and 3.0 g of tert-buthoxy sodium were added therein,
and heated to reflux for 5 hours.
[0081] After completing the reaction, the system was cooled to room
temperature, and an insoluble substance was removed via diatomite
filtration. It was washed with saturated saline and dried with
sodium sulfate, and was subsequently concentrated at reduced
pressure with a rotary evaporator.
[0082] A residue was purified by silica gel chromatography to
obtain 5.5 g of compound 1-2 as a formyl substance {referred to
also as compound 1-2 (formyl)}.
[0083] Next, 4.0 g of methyltriphenylphosphonium bromide and 80 mL
of tetrahydrofuran were added in a 200 mL three-necked flask, and
the inside of the system was cooled to -70.degree. C. or less after
replacing the reaction system with nitrogen. Then, after 6.0 mL of
a 2 mol/L LDA were added into the system, it was once raised up to
a temperature of 0.degree. C.
[0084] After cooling this reaction system to -70.degree. C. or less
again, 20 mL of a THF solution obtained from 5.5 g of compound 1-2
as a formyl substance {referred to also as compound 1-2 (formyl)}
were dropped at -70.degree. C. or less while stirring for one
hour.
[0085] After completion of stirring, the system was heated back to
room temperature. The reaction solution was washed with saturation
saline, dried with magnesium sulfate, and subsequently concentrated
at reduced pressure with a rotary evaporator.
[0086] The residue was purified by silica gel chromatography to
obtain 2.2 g of a white solid, and it was confirmed via
determination of the mass-spectrum and .sup.1H-NMR spectrum that
the resulting was compound 1-2.
(Preparation of Compound 1-2 Having Different Purity Content)
[0087] The purity of this target material was measured via HPLC,
resulting in a purity content of 96.30% (compound 1-2a). This white
solid was purified again via silica gel chromatography, resulting
in a purity content of 98.02% (compound 1-2b) obtained via
HPLC.
[0088] Recrystallization was subsequently repeated 3 times
(1.sup.st time: a purity content of 99.53% obtained via HPLC
(compound 1-2c), 2.sup.nd time: a purity content of 99.92% obtained
via HPLC (compound 1-2d), and 3.sup.rd time: a purity content of
99.99% obtained via HPLC (compound 1-2d). Compounds 1-2 each having
a different purity content were obtained.
[0089] Next, the measurement conditions of HPLC employed in the
present invention are shown below.
Measurement Conditions of HPLC
[0090] Measuring apparatus: LC-2000 Series (manufactured by Japan
Analytical Industry Co., Ltd.) Utilized column: ODS-3 (GL Science)
Developing solvent: acetonitrile/water=3/7 Developing flow: 1
mL/min
Temperature: 40.degree. C.
[0091] Detection wavelength: 254 nm
[0092] A monomer having an impurity content of 1000 ppm in the
present invention (referred to also as an organic compound having a
reactive substituent) can be synthesized by using, for example, a
method disclosed in Japanese Patent O.P.I. Publication No.
2004-327454 or the reference described in the foregoing
documents.
<<Polymer Having Partial Structure Represented by Formula
(1)>>
[0093] Further, a polymer of the present invention, synthesized by
using at least one monomer having an impurity content of 1000 ppm
or less, preferably has a partial structure represented by
foregoing Formula (1).
[0094] Examples of an arylene group independently represented at
each of Ar1 and Ar2 in Formula (1) include an o-phenylene group, a
m-phenylene group, a p-phenylene group, a naphthalenediyl group, an
anthracenediyl group, a naphthacenediyl group, a pyrenediyl group,
a naphthylnaphthalenediyl group, a biphenyldiyl group (for example,
a [1,1'-biphenyl]-4,4'-diyl group and a 3,3'-biphenyldiyl group,
and a 3,6-biphenyldiyl group), terphenyldiyl group,
quaterphenyldiyl group, a quinquephenyldiyl group, a sexiphenyldiyl
group, a septiphenyldiyl group, an octiphenyldiyl group, a
nobiphenyldiyl group, and a deciphenyldiyl group. Further, The
foregoing arylene group may also have a substituent.
[0095] As the heteroarylene group independently represented at each
of Ar1 and Ar2 in Formula (1), provided is a divalent group derived
from the group consisting of a carbazole group, a carboline ring, a
diazacarbazole ring (also referred to as a monoazacarboline group,
indicating a ring structure formed in such a manner that one of the
carbon atoms constituting the carboline ring is replaced with a
nitrogen atom), a triazole ring, a pyrrole ring, a pyridine ring, a
pyrazine ring, a quinoxaline ring, a thiophene ring, an oxadiazole
ring, a dibenzofuran ring, a dibenzothiophene ring and an indole
ring.
[0096] Further, The foregoing heteroarylene group may also have a
substituent.
[0097] Examples of the aromatic hydrocarbon ring group (referred to
also as aromatic hydrocarbon group or aryl group) represented at
Ar3 in Formula (1) include a phenyl group, a p-chlorophenyl group,
a mesityl group, a tolyl group, a xylyl group, a naphthyl group, an
anthryl group, an azulenyl group, an acenaphthenyl group, a
fluorenyl group, a phenanthryl group, an indenyl group, a pyrenyl
group, and a biphenyl group. These groups each may be
unsubstituted, or may have a substituent.
[0098] Examples of the aromatic heterocyclic group represented at
Ar3 in Formula (1) include a pyridyl group, a pyrimidinyl group, a
furyl group, a pyrrolyl group, an imidazolyl group, a
benzimidazolyl group, a pyrazolyl group, a pyrazinyl group, a
triazolyl group (for example, a 1,2,4-triazole-1-yl group or a
1,2,3-triazole-1-yl group), an oxazolyl group, a benzoxazolyl
group, a thiazolyl group, an isooxazolyl group, an isothiazolyl
group, a furazanyl group, a thienyl group, a quinolyl group, a
benzofuryl group, a dibenzofuryl group, a benzothienyl group, a
dibenzothienyl group, an indolyl group, a carbazolyl group, a
carbolinyl group, a diazacarbazolyl group (in which one of the
carbon atoms constituting the carboline ring of the carbolinyl
group is substituted with a nitrogen atom), a quinoxalinyl group, a
pyridazinyl group, a triazinyl group, a quinazolinyl group, and a
phthalazinyl group.
[0099] These groups each may be unsubstituted, or may have a
substituent.
[0100] Next, specific examples of the polymer having a partial
structure represented by Formula (1) in the present invention will
be shown, but the present invention is not limited thereto.
##STR00017## ##STR00018##
<<Method of Manufacturing Organic EL Element>>
[0101] The method of manufacturing an organic EL element of the
present invention will be described.
[0102] As an example of the method of manufacturing an organic EL
element of the present invention, a method of manufacturing an
organic EL element composed of anode/hole injection layer/hole
transport layer/light emission layer/hole blocking layer/electron
transport layer/cathode buffer layer/cathode will be described. A
specific method of manufacturing an organic EL element will be
described in Example in detail.
[0103] A monomer (organic compound having a reactive substituent)
having an impurity content of 1000 ppm or less, concerning an
organic electroluminescent element material (organic EL element
material) of the present invention, is usable to form any one of a
hole injection layer, a hole transport layer, a light emission
layer, a hole blocking layer, an electron transport layer and a
cathode buffer layer described above, if desired.
[0104] First, a thin film made of a desired electrode material such
as an anode material, for example, is formed on a substrate via
evaporation or sputtering so as to give a film thickness of not
more than 1 .mu.m, but preferably 10-200 nm to prepare an anode.
Next, a thin layer containing an organic compound as an element
material constituting a hole injection layer, a hole transport
layer, a light emission layer, a hole blocking layer or an electron
transport layer is formed thereon.
[0105] Examples of the method of forming a thin film containing the
organic compound (referred to also as an organic compound layer or
an organic layer) include a spin coating method, a cast method, an
inkjet method, a vacuum evaporation method and a printing method,
but a vacuum evaporation method or a spin coating method is
specifically preferable in view of easy preparation of a
homogeneous layer and reduced generation of pinholes.
[0106] Further, a different film formation method may be separately
applied to each layer. When the evaporation method is applied for
film formation, the evaporation conditions depend on kinds of
utilized compounds, but in general, preferably selected are a boat
heating temperature of 50-450.degree. C., a vacuum degree of
10.sup.-6-10.sup.-2 Pa, a deposition rate of 0.01-50 nm/sec, a
substrate temperature of -50-300.degree. C. and a film thickness of
0.1-5 .mu.m.
[0107] After forming these layers, a 1 .mu.m or less thick thin
film made of a cathode material is formed thereon via evaporation
or sputtering so as to preferably give a film thickness of 50-200
nm to obtain a desired organic EL element via formation of a
cathode.
[0108] This organic EL element is preferably prepared in one time
of evacuation for all steps of from a hole injection layer to a
cathode, but a different film formation method may also be allowed
to be used after removing the sample in the preparation on the way.
In this case, the operation is preferably conducted in dry inert
gas atmosphere.
<<Constituent Layer of Organic EL Element>>
[0109] As an element prepared by a method of manufacturing an
organic thin film element of the present invention, provided is an
organic electroluminescent element (organic EL element) as an
example.
[0110] The constituent layer of an organic EL element of the
present invention (referred to also as an organic layer or an
organic compound layer), and an inorganic layer (referred to also
as an inorganic compound layer) will be described. In the present
invention, preferred examples of layer configuration of the organic
EL element of the present invention will be specifically shown
below, but the present invention is not limited thereto.
(i) anode/light emission layer/electron transport layer/cathode
(ii) anode/hole transport layer/light emission layer/electron
transport layer/cathode (iii) anode/hole transport layer/light
emission layer/hole blocking layer/electron transport layer/cathode
(iv) anode/hole transport layer/light emission layer/hole blocking
layer/electron transport layer/cathode buffer layer/cathode (v)
anode/anode buffer layer/hole transport layer/light emission
layer/hole blocking layer/electron transport layer/cathode buffer
layer/cathode
[0111] In the organic EL element of the present invention, a blue
emission layer preferably has an emission maximum wavelength of
430-480 nm, a green emission layer preferably has an emission
maximum wavelength of 510-550 nm, and a red emission layer
preferably has an emission maximum wavelength of 600-640 nm, and a
display employing these layers is preferred. At least these three
layers may be laminated in order to prepare a white emission layer.
A non-light emission layer may be provided as an intermediate layer
between these emission layers. It is preferred that the organic EL
element of the invention is a white emission layer or an
illuminating device employing the same.
[0112] Each layer constituting the organic EL element of the
present invention will be described.
<<Light Emission Layer>>
[0113] The light emission layer in the present invention is a layer
where electrons and holes, injected from electrodes, an electron
transport layer or a hole transport layer, are recombined to emit
light. The portions where light emits may be in the light emission
layer or at the interface between the light emission layer and the
layer adjacent thereto.
[0114] The total thickness of the light emission layer is not
specifically limited. In view of improving layer uniformity and
stability of emission color against driving electric current
without requiring unnecessary high voltage on light emission, the
above thickness is adjusted to be in the range of preferably from 2
nm to 5 .mu.m, more preferably from 2 nm to 200 nm, and still more
preferably from 10 nm to 20 nm.
[0115] Employing an emission dopant or a host compound each
described later, the light emission layer is formed according to a
known thin layer formation method such as a vacuum evaporation
method, a spin coating method, a cast method, an LB method or an
inkjet method.
[0116] The light emission layer of the organic EL element of the
present invention preferably contains a host compound and at least
one kind of an emission dopant (referred to also as phosphorescence
dopant or a phosphorescence emission dopant) and a fluorescence
dopant.
{Host Compound (Referred to Also as Emission Host)}
[0117] The host compound used in the present invention will be
described below.
[0118] Herein, the host compound in the present invention is
defined as a compound which is contained in the light emission
layer in an amount of 20% by weight or more and which has a
phosphorescence quantum yield at room temperature (25.degree. C.)
of less than 0.1. The phosphorescence quantum yield of the host
compound is preferably less than 0.01. The content of the host
compound in the light emission layer is preferably 20% by weight or
more.
[0119] As a host compound, a commonly known host compound may be
used singly, or in combination with plural kinds. It is possible to
control the transfer of charges by making use of a plurality of
host compounds, resulting in high efficiency of an organic EL
element. In addition, it is possible to mix different emission
lights by making use of a plurality of the after-mentioned emission
dopants. Any emission color can be appropriately obtained
thereby.
[0120] The structure of the emission host in the present invention
is not specifically limited, but typical examples thereof include
carbazole derivatives, triarylamine derivatives, aromatic borane
derivatives, nitrogen-containing heterocyclic compounds, thiophene
derivatives, furan derivatives, those having a moiety such as an
oligoarylene compound, carboline derivatives, and derivatives each
having a ring structure in which at least one of the carbon atoms
of the hydrocarbon ring constituting a carboline ring of the
foregoing carboline derivatives is replaced by a nitrogen atom.
[0121] Of these, preferable usable are carbazole derivatives,
carboline derivatives, and derivatives each having a ring structure
in which at least one of the carbon atoms of the hydrocarbon ring
constituting a carboline ring of the foregoing carboline
derivatives is replaced by a nitrogen atom.
[0122] Specific examples are shown below, but the present invention
is not limited thereto. It is preferable that these compounds are
also used as the hole blocking material.
##STR00019## ##STR00020## ##STR00021## ##STR00022##
[0123] A commonly known host compound which may be used in
combination is preferably a compound having hole transporting
ability and electron transporting ability, as well as preventing
longer light emission wavelength and having a high Tg (a glass
transition temperature).
[0124] As specific examples of the commonly known host compound,
compounds described in the following documents are cited.
[0125] For example, Japanese Patent O.P.I. Publication Nos.
2001-257076, 2002-308855, 2001-313179, 2002-319491, 2001-357977,
2002-334786, 2002-8860, 2002-334787, 2002-15871, 2002-334788,
2002-43056, 2002-334789, 2002-75645, 2002-338579, 2002-105445,
2002-343568, 2002-141173, 2002-352957, 2002-203683, 2002-363227,
2002-231453, 2003-3165, 2002-234888, 2003-27048, 2002-255934,
2002-260861, 2002-280183, 2002-299060, 2002-302516, 2002-305083,
2002-305084, and 2002-308837.
(Emission Dopant)
[0126] The emission dopant in the present invention will be
described.
[0127] As the emission dopant in the present invention, a compound
having a partial structure represented by the foregoing Formula (1)
or a compound having a partial structure represented by the
foregoing Formula (2) is preferably usable as a phosphorescence
dopant.
[0128] Further, as the emission dopant in the present invention,
commonly known fluorescence dopant (also referred to as a
fluorescent compound) and phosphorescence dopant (also referred to
as a phosphorescence emitter, a phosphorescent compound or a
phosphorescence emission compound) are usable.
(Phosphorescence Dopant)
[0129] The phosphorescence dopant in the present invention will be
described.
[0130] The phosphorescence dopant in the present invention is a
compound which emits light from the excitation triplet, can emit
phosphorescence at room temperature (25.degree. C.), and has a
phosphorescent quantum yield at 25.degree. C. of 0.01 or more. The
phosphorescent quantum yield at 25.degree. C. is preferably 0.1 or
more.
[0131] The phosphorescent quantum yield can be measured according
to a method described in the fourth edition "Jikken Kagaku Koza 7",
Bunko II, page 398 (1992) published by Maruzen. The phosphorescent
quantum yield can be measured in a solution employing various kinds
of solvents. The phosphorescence dopant in the present invention is
a compound, in which the phosphorescent quantum yield measured
employing any one of the solvents satisfies the above-described
definition (at least 0.01).
[0132] The light emission of the phosphorescence dopant is divided
into two types in principle, one is an energy transfer type in
which recombination of a carrier occurs on the host to which the
carrier is transported to excite the host, the resulting energy is
transferred to the phosphorescence dopant, and light is emitted
from the phosphorescence dopant, and the other is a carrier trap
type in which recombination of a carrier occurs on the
phosphorescence dopant, a carrier trap material, and light is
emitted from the phosphorescence dopant. However, in each type, it
is desired that energy level of the phosphorescence dopant in
excited state is lower than that of the host compound in excited
state.
[0133] The phosphorescence dopant can be suitably selected from
those commonly known, which are used in the light emission layer of
an organic EL element.
[0134] The phosphorescence dopant in the present invention is
preferably a complex compound containing a metal belonging to
groups 8 to 10 of the periodic table, and is more preferably an
iridium compound, an osmium compound, a platinum compound (a
platinum complex) or a rare earth compound, and most preferably an
iridium compound.
[0135] Specifically listed are compounds described in the following
patent publication.
[0136] WO 00/70655, Japanese Patent O.P.I. Publication No.
2002-280178, Japanese Patent O.P.I. Publication No. 2001-181616,
Japanese Patent O.P.I. Publication No. 2002-280179, Japanese Patent
O.P.I. Publication No. 2001-181617, Japanese Patent O.P.I.
Publication No. 2002-280180, Japanese Patent O.P.I. Publication No.
2001-247859, Japanese Patent O.P.I. Publication No. 2002-299060,
Japanese Patent O.P.I. Publication No. 2001-313178, Japanese Patent
O.P.I. Publication No. 2002-302671, Japanese Patent O.P.I.
Publication No. 2001-345183, Japanese Patent O.P.I. Publication No.
2002-324679, WO 02/15645, Japanese Patent O.P.I. Publication No.
2002-332291, Japanese Patent O.P.I. Publication No. 2002-50484,
Japanese Patent O.P.I. Publication No. 2002-322292, Japanese Patent
O.P.I. Publication No. 2002-83684, Japanese Patent O.P.I.
Publication No. 2002-540572, Japanese Patent O.P.I. Publication No.
2002-117978, Japanese Patent O.P.I. Publication No. 2002-338588,
Japanese Patent O.P.I. Publication No. 2002-170684, Japanese Patent
O.P.I. Publication No. 2002-352960, WO 01/93642, Japanese Patent
O.P.I. Publication No. 2002-50483, Japanese Patent O.P.I.
Publication No. 2002-100476, Japanese Patent O.P.I. Publication No.
2002-173674, Japanese Patent O.P.I. Publication No. 2002-359082,
Japanese Patent O.P.I. Publication No. 2002-175884, Japanese Patent
O.P.I. Publication No. 2002-363552, Japanese Patent O.P.I.
Publication No. 2002-184582, Japanese Patent O.P.I. Publication No.
2003-7469, Japanese Patent O.P.I. Publication No. 2002-525808,
Japanese Patent O.P.I. Publication No. 2003-7471, Japanese Patent
O.P.I. Publication No. 2002-525833, Japanese Patent O.P.I.
Publication No. 2003-31366, Japanese Patent O.P.I. Publication No.
2002-226495, Japanese Patent O.P.I. Publication No. 2002-234894,
Japanese Patent Publication No. 2002-235076, Japanese Patent O.P.I.
Publication No. 2002-241751, Japanese Patent O.P.I. Publication No.
2001-319779, Japanese Patent O.P.I. Publication No. 2001-319780,
Japanese Patent O.P.I. Publication No. 2002-62824, Japanese Patent
O.P.I. Publication No. 2002-100474, Japanese Patent O.P.I.
Publication No. 2002-203679, Japanese Patent O.P.I. Publication No.
2002-343572, and Japanese Patent O.P.I. Publication No.
2002-203678.
[0137] Specific examples of compounds used as the commonly known
phosphorescence dopant are shown below, but the present invention
is not limited thereto. In addition, these compounds are possible
to be synthesized by the method described in Inorg. Chem. Vol. 40,
1704-1711.
##STR00023## ##STR00024## ##STR00025## ##STR00026## ##STR00027##
##STR00028##
{Fluorescence Dopant (Referred to Also as a Fluorescent
Compound)}
[0138] Examples of the fluorescence dopant (fluorescent compound)
include a coumarin based dye, a pyrane based dye, a cyanine based
dye, a chloconium based dye, a squarylium based dye, an
oxobenzanthracene based dye, a fluorescene based dye, a rhodamine
based dye, a pyrylium based dye, a perylene based dye, a stilbene
based dye, a polythiophene based dye, and rare earth complex based
phosphor.
[0139] Next, an injection layer, a blocking layer, and an electron
transport layer used in the constituent layer of the organic EL
element of the present invention will be described.
<<Injection Layer: Electron Injection Layer and Hole
Injection Layer>>
[0140] The injection layer is optionally provided, for example, an
electron injection layer or a hole injection layer, and may be
provided between the anode and the light emission layer or hole
transport layer, and between the cathode and the light emission
layer or electron transport layer as described above.
[0141] The injection layer herein means a layer provided between
the electrode and an organic layer in order to reduce the driving
voltage or to improve of light emission efficiency, which is
detailed in "Electrode Material", Div. 2 Chapter 2, pp. 123-166 of
"Organic EL element and its frontier of industrialization"
(published by NTS Corporation, Nov. 30, 1998). As the injection
layer, there are a hole injection layer (anode buffer layer) and an
electron injection layer (cathode buffer layer).
[0142] The anode buffer layer (hole injection layer) is described
in Japanese Patent O.P.I. Publication Nos. 9-45479, 9-260062, and
8-288069, and examples thereof include a phthalocyanine buffer
layer represented by a copper phthalocyanine layer, an oxide buffer
layer represented by a vanadium oxide layer, an amorphous carbon
buffer layer, a polymer buffer layer employing a conductive polymer
such as polyaniline (emeraldine) or polythiophene.
[0143] The cathode buffer layer (electron injection layer) is
described in detail in Japanese Patent O.P.I. Publication Nos.
6-325871, 9-17574, and 10-74586, and examples thereof include a
metal buffer layer represented by a strontium or aluminum layer, an
alkali metal compound buffer layer represented by a lithium
fluoride layer, an alkali earth metal compound buffer layer
typified by a magnesium fluoride layer, and an oxide buffer layer
typified by an aluminum oxide. The buffer layer (injection layer)
is preferably very thin and has a thickness of preferably from 0.1
nm to 5 .mu.m depending on kinds of the material used.
<<Blocking Layer: Hole Blocking Layer and Electron Blocking
Layer>>
[0144] The blocking layer is a layer provided if desired in
addition to the fundamental constituent layer as described above,
and is, for example, a hole blocking layer as described in Japanese
Patent O.P.I. Publication Nos. 11-204258, and 11-204359, and on
page 237 of "Organic EL element and its frontier of
industrialization" (published by NTS Corporation, Nov. 30,
1998).
[0145] The hole blocking layer is an electron transport layer in a
broad sense, and is comprised of material having ability of
transporting electrons but extremely poor ability of holes, which
can increase recombination probability of electrons and holes by
transporting electrons and blocking holes.
[0146] Further, the constitution of an electron transport layer
described later can be used in the hole blocking layer in the
present invention, if desired.
[0147] The hole blocking layer in the organic EL element of the
present invention is preferably provided so as to be in contact
with a light emission layer.
[0148] It is preferred that the hole blocking layer contains an
azacarbazole derivative as the foregoing host compound.
[0149] Further, in the present invention, when there are a
plurality of light emission layers which emit a plurality of
different color lights, it is preferable that a light emission
layer emitting light having emission maximum in the shortest
wavelength of all the light emission layers is provided closest to
the anode. In such a case, it is preferred that a hole blocking
layer is additionally provided between the light emission layer
emitting a light having emission maximum in the shortest wavelength
and a light emission layer provided closest to the anode excluding
the above light emission layer emitting a light having emission
maximum in the shortest wavelength.
[0150] Further, it is preferred that at least 50% by weight of
compounds, which are incorporated in the hole blocking layer
arranged in the above location, have an ionization potential 0.3 eV
higher than that of the host compound contained in the light
emission layer emitting a light having emission maximum in the
shortest wavelength.
[0151] Ionization potential is defined as energy required to
transfer an electron in an HOMO (highest occupied molecular
orbital) level to the vacuum level, and can be determined by the
methods described below.
[0152] (1) The ionization potential can be determined via
calculation by performing structural optimization employing
Gaussian 98 (Gaussian 98, Revision A. 11.4, M J. Frisch, et al.,
Gaussian, Inc., Pittsburgh Pa., 2002), which is a software for
molecular orbital calculation of Gaussian, Inc., and B3LYP/6-31G*
as a key word, and the calculated value (being the value in terms
of eV unit) is rounded off at the second decimal place. Background
in which the calculated value above is effective is that the
calculated value obtained by the above method and experimental
values exhibit high correlation.
[0153] (2) It is also possible to obtain ionization potential via a
direct measurement method employing a photoelectron spectroscopy.
For example, it is possible to appropriately employ a low energy
electron spectrometer "Model AC-1", produced by Riken Keiki Co.,
Ltd., or a method known as ultraviolet photoelectron
spectroscopy.
[0154] On the other hand, the electron blocking layer is a hole
transport layer in a broad sense, and is comprised of material
having ability of transporting holes but extremely poor ability of
electrons, which can increase recombination probability of
electrons and holes by transporting holes and blocking
electrons.
[0155] The constitution of the hole transport layer as described
later can be used as that of the electron blocking layer. The
thickness of the hole blocking layer or electron transport layer is
preferably 3-100 nm, and more preferably 5-30 nm.
<<Hole Transport Layer>>
[0156] The hole transport layer is comprised of a hole transport
material having ability of transporting holes, and a hole injection
layer and an electron blocking layer are included in the hole
transport layer in a broad sense. The hole transport layer may be
provided as a single layer or plural layers.
[0157] The hole transport material has hole injecting ability, hole
transporting ability or ability to form a barrier to electrons, and
may be either an organic substance or an inorganic substance.
Examples thereof include a triazole derivative, an oxadiazole
derivative, an imidazole derivative, a polyarylalkane derivative, a
pyrazoline derivative and a pyrazolone derivative, a
phenylenediamine derivative, an arylamine derivative, an amino
substituted chalcone derivative, an oxazole derivative, a styryl
anthracene derivative, a fluorenone derivative, a hydrazone
derivative, a stilbene derivative, a silazane derivative, an
aniline copolymer, and a conductive oligomer, particularly a
thiophene oligomer.
[0158] As the hole transport material, those described above are
used, but a porphyrin compound, an aromatic tertiary amine
compound, or a styrylamine compound is preferably used, and an
aromatic tertiary amine compound is more preferably used.
[0159] Typical examples of the aromatic tertiary amine compound and
styrylamine compound include
N,N,N',N'-tetraphenyl-4,4'-diaminophenyl,
N,N'-diphenyl-N,N'-bis(3-methylphenyl)-[1,1'-biphenyl]-4,4'-diamine
(TPD), 2,2'-bis(4-di-p-tolylaminophenyl)propane,
1,1-bis(4-di-p-tolylaminophenyl)cyclohexane,
N,N,N',N'-tetra-p-tolyl-4,4'-diaminobiphenyl,
1,1-bis(4-di-p-tolylaminophenyl)-4-phenylcyclohexane,
bis(4-dimethylamino-2-methylphenyl)-phenylmethane,
bis(4-di-p-tolylaminophenyl)phenylmethane,
N,N'-diphenyl-N,N'-di(4-methoxyphenyl)-4,4'-diaminobiphenyl,
N,N,N',N'-tetraphenyl-4,4'-diaminodiphenyl ether,
4,4'-bis(diphenylamino)quardriphenyl, N,N,N-trip-tolyl)amine,
4-(di-p-tolylamino)-4'-[4-(di-p-tolylamino)styryl]stilbene,
4-N,N-diphenylamino(2-diphenylvinyl)benzene,
3-methoxy-4'-N,N-diphenylaminostylbenzene, N-phenylcarbazole,
compounds described in U.S. Pat. No. 5,061,569 which have two
condensed aromatic rings in the molecule thereof such as
4,4'-bis[N-(1-naphthyl)-N-phenylamino]biphenyl (NPD), and compounds
described in Japanese Patent O.P.I. Publication No. 4-308688 such
as 4,4',4''-tris[N-(3-methylphenyl)-N-phenylamino]-triphenylamine
(MTDATA) in which three triphenylamine units are bonded in a
starburst form.
[0160] A polymer in which the material mentioned above is
introduced in the polymer chain or a polymer having the material as
the polymer main chain can be also used. As the hole injection
material or the hole transport material, inorganic compounds such
as p-type-Si and p-type-SiC are usable.
[0161] So-called p-type hole transport materials as disclosed in
Japanese Patent O.P.I. Publication No. 11-251067 or described in
the literature of J. Huang et al. (Applied Physics Letters 80
(2002), p. 139) are also applicable. In the present invention,
these materials are preferably used since an emitting element
exhibiting a higher efficiency is obtained.
[0162] The hole transport layer can be formed by layering the hole
transport material by a commonly known method such as a vacuum
evaporation method, a spin coating method, a cast method, an inkjet
method, and an LB method. The thickness of the hole transport layer
is not specifically limited, but is conventionally 5 nm-5 .mu.m,
and preferably 5-200 nm. The hole transport layer may be composed
of a single layer structure comprising one kind or at lest two
kinds of the materials mentioned above.
[0163] A positive hole transport layer having a high p-type
property doped with impurity can be utilized. Examples thereof
include those described in Japanese Patent O.P.I. Publication Nos.
4-297076, 2000-196140 and 2001-102175, and J. Appl. Phys., 95, 5773
(2004).
[0164] It is preferable in the present invention to employ such a
positive hole transport layer having a high p-type property, since
an element with lower power consumption can be prepared.
<<Electron Transporting Layer>>
[0165] The electron transport layer comprises a material (electron
transport material) having electron transporting ability, and in a
broad sense refers to an electron injection layer or a hole
blocking layer. The electron transport layer can be provided as a
single layer or plural layers.
[0166] An electron transport material (which serves also as a hole
blocking material) used in a single electron transport layer or in
the electron transport layer closest to the cathode of plural
electron transporting layers has a function of incorporating
electrons injected from a cathode to a light emission layer, and
can be selected from commonly known compounds. Examples thereof
include a nitro-substituted fluorene derivative, a diphenylquinone
derivative, a thiopyran dioxide derivative, a carbodiimide, a
fluolenylidenemethane derivative, an anthraquinodimethane, an
anthrone derivative, and an oxadiazole derivative.
[0167] Moreover, a thiadiazole derivative which is formed by
substituting the oxygen atom in the oxadiazole ring of the
foregoing oxadiazole derivative with a sulfur atom, and a
quinoxaline derivative having a quinoxaline ring known as an
electron withdrawing group are usable as the electron transport
material. A polymer in which the material mentioned above is
introduced in the polymer side chain or a polymer having the
material as the polymer main chain can also be used.
[0168] A metal complex of an 8-quinolynol derivative such as
aluminum tris-(8-quinolynol) (Alq.sub.3), aluminum
tris-(5,7-dichloro-8-quinolynol), aluminum
tris-(5,7-dibromo-8-quinolynol), aluminum
tris-(2-methyl-8-quinolynol), aluminum
tris-(5-methyl-8-quinolynol), or zinc bis-(8-quinolynol)
(Znq.sub.2), and a metal complex formed by replacing the central
metal of the foregoing complexes with another metal atom such as
In, Mg, Cu, Ca, Sn, Ga or Pb, can be used as the electron transport
material.
[0169] Furthermore, a metal-free or metal-containing
phthalocyanine, and a derivative thereof, in which the molecular
terminal is replaced by a substituent such as an alkyl group or a
sulfonic acid group, are also preferably used as the electron
transport material. The distyrylpyrazine derivative exemplified as
a material for the light emission layer may preferably be employed
as the electron transport material. An inorganic semiconductor such
as n-type-Si and n-type-SiC may also be used as the electron
transport material in the same manner as in the hole injection
layer or in the hole transport layer.
[0170] The electron transport layer can be formed employing the
above-described electron transport materials and a known method
such as a vacuum evaporation method, a spin coating method, a cast
method, a printing method including an inkjet method or an LB
method. The thickness of the electron transport layer is not
specifically limited, but is conventionally 5 nm-5 .mu.m, and
preferably 5-200 nm. The electron transport layer may be composed
of a single layer comprising one kind or at least two kinds of the
electron transport material.
[0171] An electron transport layer having a high n property doped
with impurity can be utilized. Examples thereof include those
described in Japanese Patent O.P.I. Publication Nos. 4-297076,
10-270172, 2000-196140, 2001-102175, and J. Appl. Phys., 95, 5773
(2004).
[0172] It is preferred in the present invention that use of such an
electron transport layer having a high n property can provide an
element with lower power consumption.
<<Anode>>
[0173] For the anode of the organic EL element, a metal, an alloy,
or a conductive compound each having a high working function (4 eV
or more), and mixture thereof are preferably used as the electrode
material. Specific examples of such an electrode material include a
metal such as Au, and a transparent conductive material such as
CuI, indium tin oxide (ITO), SnO.sub.2 or ZnO.
[0174] A material such as IDIXO (In.sub.2O.sub.3--ZnO) capable of
forming an amorphous and transparent conductive layer may be used.
The anode may be prepared by forming a thin layer of the electrode
material according to a evaporation or sputtering method, and by
forming the layer into a desired pattern according to a
photolithographic method. When precision of the pattern is not
desired to be not so high (roughly 100 .mu.m or more), the pattern
may be formed via evaporation or sputtering of the electrode
material through a mask having a desired form.
[0175] When a coatable material such as an organic conductive
compound is used, a wet coating method such as a printing method or
a coating method can be used. When light is emitted through the
anode, transmittance of the anode is preferably 10% or more, and
the sheet resistance of the anode is preferably several hundreds
.OMEGA./.quadrature. or less. The thickness of the layer is
conventionally 10-1000 nm, and preferably 10-200 nm, depending on
kinds of materials used.
<<Cathode>>
[0176] On the other hand, for the cathode, a metal (referred to
also as an electron injecting metal), an alloy and a conductive
compound each having a low working function (4 eV or less), and a
mixture thereof is used as the electrode material.
[0177] Specific examples of such an electrode material include
sodium, a sodium-potassium alloy, magnesium, lithium, a
magnesium/copper mixture, a magnesium/silver mixture, a
magnesium/aluminum mixture, a magnesium/indium mixture, an
aluminum/aluminum oxide (Al.sub.2O.sub.3) mixture, indium, a
lithium/aluminum mixture, and a rare-earth metal.
[0178] Among them, a mixture of an electron injecting metal and a
metal higher in the working function than that of the electron
injecting metal, such as a magnesium/silver mixture, a
magnesium/aluminum mixture, a magnesium/indium mixture, an
aluminum/aluminum oxide (Al.sub.2O.sub.3) mixture, a
lithium/aluminum mixture, or aluminum is suitable in view of
durability against electron injection and oxidation.
[0179] The cathode can be prepared forming a thin layer of such an
electrode material by a method such as a deposition or sputtering
method. The sheet resistance as the cathode is preferably several
hundreds .OMEGA./.quadrature. or less, and the thickness of the
layer is conventionally 10 nm-5 .mu.m, and preferably 50-200
nm.
[0180] It is preferred in increasing emission luminance that either
the anode or the cathode of the organic EL element, through which
light passes, is transparent or semi-transparent.
[0181] After a layer of the metal described above as a cathode is
formed to give a thickness of 1-20 nm, the transparent conductive
material as described in the anode is layered thereon, whereby a
transparent or semi-transparent cathode can be prepared. Employing
this cathode, an element can be manufactured in which both anode
and cathode are transparent.
<<Supporting Substrate>>
[0182] The supporting substrate (referred to also as a base body, a
substrate, a base material or a support) employed for the organic
EL element of the present invention is not limited to specific
kinds of materials such as glass and plastic, as long as it is
transparent. When light is taken out from the side of a substrate,
the substrate is preferably transparent. Preferable examples of the
usable substrate include glass, quartz and a transparent resin
film. Specifically preferred supporting substrate is a resin film
capable of providing flexibility to the organic EL element.
[0183] Examples of materials for the resin film include polyesters
such as polyethylene terephthalate (PET) and polyethylene
naphthalate (PEN), polyethylene, polypropylene, cellophane,
cellulose esters and their derivatives such as cellulose diacetate,
cellulose triacetate, cellulose acetate butylate, cellulose acetate
propionate (CAP), cellulose acetate phthalate (TAC), and cellulose
nitrate, polyvinylidene chloride, polyvinylalcohol,
polyethylenevinylalcohol, syndiotactic polystyrene, polycarbonate,
norbornane resin, polymethylpentene, polyetherketone, polyimide,
polyether sulfone (PES), polyphenylene sulfide, polysulfones,
polyether imide, polyetherketone imide, polyamide, fluorine resin,
nylon, polymethyl methacrylate, acryl or polyarylates, and
cyclo-olefin resins such as ARTON (commercial name, manufactured by
JSR Corp.) or APEL (commercial name, manufactured by Mitsui
Chemicals Inc.).
[0184] On the surface of the resin film, an inorganic or organic
cover film or a hybrid cover film comprising the both may be
formed, and the cover film is preferably one with a barrier ability
having a water vapor permeability of 0.01 g/(m.sup.224 h) or less
(at 25.+-.0.5.degree. C. and at (90.+-.2) % RH), measured by a
method in accordance with JIS K 7129-1992, and is more preferably
one with a high barrier ability having an oxygen permeability of
10.sup.-3 mL/(m.sup.224 hrMPa) or less as well as a water vapor
permeability of 10.sup.-5 g/(m.sup.224 h) or less, measured by a
method in accordance with JIS K 7126-1987.
[0185] Any materials capable of preventing penetration substances
such as moisture and oxygen causing degradation of the element are
usable for forming the barrier film, and for example, silicon
oxide, silicon dioxide and silicon nitride are usable. It is more
preferred that the barrier film has a multi-layered structure
composed of a layer of the inorganic material and a layer of an
organic material for improving fragility of the film. It is
preferred that the both layers are alternatively laminated several
times though there is no limitation as to the lamination order of
the inorganic layer and the organic layer.
[0186] The method to form the barrier film is not specifically
limited, and for example, a vacuum evaporation method, a sputtering
method, a reaction sputtering method, a molecular beam epitaxy
method, a cluster ion beam method, an ion plating method, a plasma
polymerization method, an atmospheric pressure plasma
polymerization method, a plasma CVD method, a laser CVD method, a
heat CVD method and a coating method are applicable, and the
atmospheric pressure plasma polymerization method as described in
Japanese Patent O.P.I. Publication No. 2004-68143 is specifically
preferable.
[0187] As the opaque supporting substrate, for example, a metal
plate such as an aluminum plate and a stainless steel plate, a film
or an opaque resin substrate and a ceramic substrate are cited.
[0188] The taking-out efficiency of light emission of an organic EL
element of the present invention at room temperature is preferably
1% or more, and more preferably 5% or more.
[0189] Herein, taking-out quantum yield (%) is as follows.
Taking-out quantum yield (%)=(the number of photons emitted to the
exterior of the organic electroluminescent element.times.100)/(the
number of electrons supplied to the organic electroluminescent
element)
[0190] A hue-improving filter such as a color filter may be used in
combination or a color conversion filter which can convert from
emission light color from an organic EL element to multi-color
employing a phosphor may be used in combination. In cases where the
color conversion filter, the .lamda.max of light emitted from the
organic EL element is preferably 480 nm or less.
<<Sealing>>
[0191] As the sealing means used in the present invention, there is
a method in which adhesion of a sealing member to an electrode and
a supporting substrate is carried out employing an adhesive
agent.
[0192] The sealing member is formed so as to cover the displaying
region of an organic EL element and may have a flat plate shape or
a concave plate shape, and transparency and an electrical
insulation property thereof are not specifically limited.
[0193] Specific examples of the sealing member include a glass
plate, a polymer plate, a polymer film, a metal plate and a metal
film. As the glass plate, a plate of soda-lime glass, barium
strontium-containing glass, lead glass, aluminosilicate glass,
boron silicate glass, barium boron silicate glass or quartz is
usable.
[0194] As the polymer plate, a plate of polycarbonate, acryl resin,
polyethylene terephthalate, polyether sulfide or polysulfone is
usable. As the metal plate, a plate composed of one or more kinds
of metals selected from the group consisting of stainless steel,
iron, copper, aluminum, magnesium, nickel, zinc, chromium,
titanium, molybdenum, silicon, germanium and tantalum, and alloys
thereof is provided.
[0195] In the present invention, the polymer film and the metal
film are preferably used since the element formed from a thinner
film can be prepared.
[0196] The polymer film is preferably one having an oxygen
permeability of 1.times.10.sup.-3 mL/(m.sup.224 hrMPa) or less,
measured by a method in accordance with JIS K 7126-1987, and a
water vapor permeability {at 25.+-.0.5.degree. C. and at (90.+-.2)
% RH} of 1.times.10.sup.-3 g/(m.sup.224 h) or less, measured by a
method in accordance with JIS K 7129-1992.
[0197] For processing the sealing material in the form of the
concave, a sandblast treatment and a chemical etching treatment are
used.
[0198] As the adhesive agent, there are mentioned a photo-curable
or thermo-curable adhesive agent containing a reactive vinyl group
such as an acrylic acid based oligomer or a methacrylic acid based
oligomer, and a moisture curable adhesive agent such as
2-cyanoacrylate. Examples of the adhesive agent include an epoxy
based thermally and chemically (two liquid type) curable adhesive
agents, a hot-melt type polyamide, polyester or polyolefin adhesive
agents, and a cationic curable type UV-curable epoxy adhesive.
[0199] The organic EL element is degraded by a heat treatment in
some cases, and therefore, an adhesive agent capable of being cured
within the temperature range of from room temperature to 80.degree.
C. is preferred. A drying agent may be dispersed in the adhesive
agent. Coating of the adhesive agent onto the adhering portion may
be performed by a dispenser available on the market or by printing
such as screen printing.
[0200] It is preferred that a layer made of an inorganic or organic
material is formed as a sealing layer on an electrode placed on the
side facing a supporting substrate an organic layer provided
between the substrate and the electrode, so as to cover the
electrode and the organic layer and contact with the substrate. In
such a case, a material to form the sealing layer may be a material
having a function to inhibit permeation substances such as water
and oxygen causing degradation of the element, and for example,
silicon oxide, silicon dioxide and silicon nitride are usable.
[0201] The sealing layer preferably has a multi-layered structure
composed of a layer made of an inorganic material and a layer made
of an organic material to improve fragility of the layer. The
method of forming the layer is not specifically limited, and for
example, a vacuum evaporation method, a sputtering method, a
reaction sputtering method, a molecular beam epitaxy method, a
cluster-ion beam method, an ion plating method, a plasma
polymerization method, an atmospheric pressure plasma
polymerization method, a plasma CVD method, a laser CVD method, a
heat CVD method and a coating method are applicable.
[0202] In the spacing between the sealing layer and the displaying
portion of the organic EL element, an inactive gas such as nitrogen
or argon or an inactive liquid such as fluorinated hydrocarbon or
silicone oil is preferably injected in the form of gas or liquid
phase. It is also possible that vacuum is provided in the spacing.
A hygroscopic compound can also be enclosed inside.
[0203] Examples of the hygroscopic compound include metal oxide
such as sodium oxide, potassium oxide, calcium oxide, barium oxide,
magnesium oxide or aluminum oxide; sulfate such as sodium sulfate,
calcium sulfate, magnesium sulfate or cobalt sulfate; metal halide
such as calcium chloride, magnesium chloride, cesium fluoride,
tantalum fluoride, cerium bromide, magnesium bromide, barium iodide
or magnesium iodide; and perchlorate such as barium perchlorate or
magnesium perchlorate. Anhydride of the sulfate, halide and
perchlorate is preferably usable.
<<Protective Layer and Protective Plate>>
[0204] A protective layer or a protective plate may be provided on
the foregoing sealing layer formed on the side facing the substrate
through the organic layer or outside the sealing layer in order to
raise mechanical strength of the element. Specifically when sealing
is carried out by the sealing layer as described above, such a
protective layer or plate is preferably provided, since strength of
the element is not so high. As materials for the protective layer
or plate, the same glass plate, polymer plate, polymer film, metal
plate and metal film as those described above to be used for
sealing are usable. The polymer film is preferably used from the
viewpoint of light weight and a thin layer formation property.
<<Taking-Out of Light>>
[0205] It is generally said that, in the organic EL element, light
is emitted in a layer whose refractive index (the refractive index
is about 1.7-2.1) is higher than that of air, and only 15 to 20% of
the light emitted in the light emission layer can be taken out.
This is because light which enters a boundary (a boundary between a
transparent substrate and the atmosphere) at an angle .theta.
larger than a critical angle is totally reflected and cannot be
taken out from the element, or because light is totally reflected
at a boundary between the transparent substrate and the transparent
electrode or between the transparent substrate and the light
emission layer, so that the light exits from the side of the
element through the transparent electrode or the light emission
layer.
[0206] As methods to improve the light taking-out efficiency, there
are a method to form concavity and convexity on the surface of the
transparent substrate to prevent total internal reflection at a
boundary between the transparent substrate and atmospheric air (see
U.S. Pat. No. 4,774,435); a method to provide light focusing
properties to the substrate to improve the efficiency (see Japanese
Patent O.P.I. Publication No. 63-314795); a method to form a
reflection surface on the side of the element (see Japanese Patent
O.P.I. Publication No. 1-220394); a method to form a flat layer
having an intermediate refractive index between the substrate and
the light emission layer to form an anti-reflection layer (see
Japanese Patent O.P.I. Publication No. 62-172691); a method to form
a flat layer having a low refractive index between the substrate
and the light emission layer (see Japanese Patent Publication No.
2001-202827); and a method to form a diffraction lattice at a
boundary between any two of the substrate, the transparent
electrode and the light emission layer (including a boundary
between the substrate and atmospheric air) (see Japanese Patent
O.P.I. Publication No. 11-283751).
[0207] In the present invention, these methods can be used in
combination with the organic electroluminescent element of the
present invention. Also, a method of forming a flat layer having a
lower refractive index than that of the substrate between the
substrate and the light emission layer, or a method of forming a
diffraction lattice at a boundary between any of the substrate,
transparent electrode and light emission layer (including a
boundary between the substrate and the atmosphere) can be
preferably used.
[0208] In the present invention, an element exhibiting further
higher luminance and durability can be obtained by using these
methods in combination.
[0209] When a low refractive index medium with a thickness greater
than light wavelength is formed between a transparent electrode and
a transparent substrate, the taking-out efficiency of light, which
comes out of the transparent electrode, increases, as the
refractive index of the medium decreases.
[0210] As a low refractive index layer, acrogel, porous silica,
magnesium fluoride and a fluorine-containing polymer are cited, for
example. Since refractive index of the transparent substrate is
conventionally 1.5-1.7, the refractive index of the low refractive
index layer is preferably 1.5 or less and more preferably 1.35 or
less.
[0211] The thickness of a low refractive index medium is preferably
twice or more of the wavelength of light in the medium, because
when thickness of the low refractive index medium is such that the
electromagnetic wave exuding as an evanescent wave enters the
transparent substrate, the effect of the low refractive index layer
is reduced.
[0212] A method to provide a diffraction lattice at a boundary
where the total internal reflection occurs or in some of the media
has a feature that the effect of enhancing the light extraction
efficiency increases.
[0213] The intension of this method is to provide a diffraction
lattice at a boundary between any of the layers or in any of the
mediums (in the transparent substrate or in the transparent
electrode) and extract light which cannot exit due to total
reflection occurring at a boundary between the layers among lights
emitted in the light emission layer, which uses the property of the
diffraction lattice that can change the direction of light to a
specific direction different from the direction of reflection due
to so-called Bragg diffraction such as primary diffraction or
secondary diffraction.
[0214] It is preferred that the diffraction lattice to be provided
has a two-dimensional periodic refractive index. This is because,
since light generated in the light emission layer is emitted
randomly in all the directions, only the light proceeding in a
specific direction can be diffracted when a general one-dimensional
diffraction lattice having a periodic refractive index distribution
only in a specific direction is used, which does not greatly
increase the light taking-out efficiency.
[0215] However, a refractive index distribution is
two-dimensionally distributed, whereby the light proceeding in all
the directions can be diffracted, and then the light taking-out
efficiency is increased.
[0216] The position where the diffraction lattice is introduced, as
previously described, is any of boundaries each between layers or
in a medium (in the transparent substrate or in the transparent
electrode), but it is preferably provided in the vicinity of the
organic light emission layer where the light is emitted.
[0217] In this case, the period of the diffraction lattice is
preferably about 1/2 to 3 times the wavelength of light in the
medium.
[0218] The array of the diffraction lattice is preferably two
dimensionally repeated as in the shape of a square lattice, a
triangular lattice, or a honeycomb lattice.
<<Light Collection Sheet>>
[0219] In the organic EL element of the present invention,
luminance in a specified direction can be increased, for example,
by providing a structure in the form of a micro-lens array on the
light taking-out side surface of the substrate or in combination
with a so-called light collection sheet, whereby light is focused
in a specific direction, for example, in the front direction to the
light emitting plane of the element.
[0220] As an example of a micro-lens array, there is one in which
quadrangular pyramids having a side of 30 .mu.m and having a vertex
angle of 90.degree. are two-dimensionally arranged on the light
taking-out side surface of the substrate. The side of the
quadrangular pyramids is preferably 10-100 .mu.m. When the length
of the side is shorter than the above range, the light is colored
via producing of the effect of diffraction, while when it is longer
than the above range, it becomes unfavorably thick.
[0221] As the light collection sheet, one practically applied for
an LED backlight of a liquid crystal display is applicable. Usable
examples of such a sheet include a brightness enhancing film (BEF)
produced by SUMITOMO 3M Inc.
[0222] As shape of a prism sheet, there may be included one in
which a triangle-shaped strip having a vertex angle of 90.degree.
and a pitch of 50 .mu.m provided on a substrate, one having round
apexes, one having a randomly changed pitch or other ones.
[0223] In order to control an emission angle of light emitted from
the light emitting element, a light diffusion plate or film may be
used in combination with the light collection sheet. For example, a
diffusion film (Light-Up, produced by KIMOTO Co., Ltd.) is
usable.
<<Use of Organic Thin Film Element>>
[0224] The organic thin film element of the present invention can
be used as an organic EL element, a display device, a display, or
various light emission sources. Examples of the light emission
sources include an illuminating device (a home lamp or a room lamp
in a car), a backlight for a watch or a liquid crystal, a light
source for boarding advertisement, a signal device, a light source
for a photo memory medium, a light source for an
electrophotographic copier, a light source for an optical
communication instrument, and a light source for an optical sensor,
but the present invention is not limited thereto. Specifically, it
is effectively usable as a backlight for a liquid crystal or a
light source for illumination.
[0225] Further, in preparation of an organic thin film element of
the present invention, patterning may be carried out with a metal
mask or by an inkjet printing method, if desired. The patterning
may be carried out only in electrodes, in both electrodes and light
emission layers, or in all the layers of the element. Further, the
element can also be prepared according to a commonly known
method.
[0226] Color of light emitted from the organic EL element of the
present invention or from the compounds in the present invention is
specified with color obtained when measurements determined by a
spectral radiance luminance meter CS-1000 (produced by Konica
Minolta Sensing Co., Ltd.) are applied to the CIE chromaticity
coordinates in Fig. 4.16 on page 108 of "Shinpen Shikisai Kagaku
Handbook (edited by The Color Science Association of Japan,
University of Tokyo Press, 1985).
[0227] When the organic EL element of the present invention is a
white light element, "white" means that when front luminance of a
2.degree. viewing angle is determined via the above method,
chromaticity in the CIE 1931 Chromaticity System at 1,000
Cd/m.sup.2 is in the range of X=0.33.+-.0.07 and Y=0.33.+-.0.1.
<<Illuminating Device>>
[0228] An illuminating device of the present invention will be
described. The illuminating device of the present invention
possesses the above-described organic EL element.
[0229] The organic EL element of the present invention may be
employed as one having a resonator structure. As intended use of
the aforesaid organic EL element having such a resonator structure
include, provided are a light source for an optical memory medium,
a light source for an electrophotographic copier, a light source
for an optical communication processor, and a light source for an
optical sensor, but the present invention is not limited thereto.
Further, laser oscillation may also be applied for the
above-described intended use.
[0230] Further, the organic EL element of the present invention may
also be employed as a type of lamp for lighting or an exposure
light source, a projection device to project images, and a display
device (display) to directly visualize still images and moving
images. A drive system employed as a display for reproduction of
moving images may be allowed to be a simple matrix (passive matrix)
system, and also allowed to be an active matrix system.
Alternatively, it is possible to prepare a full-color display
device by using at least two types of the organic EL elements of
the present invention having different light emitting colors,
[0231] One example of a display device possessing an organic EL
element of the present invention, will be described referring to
figures.
[0232] FIG. 1 is a schematic diagram showing one example of a
display device possessing an organic EL element. It is a schematic
diagram of a display such as a cellular phone display, for example,
to display image information via light emission of an organic EL
element.
[0233] Display 1 is composed of display section A having a
plurality of pixels and control section B to conduct image scanning
of display section A, based on image information.
[0234] Control section B is electrically connected to display
section A; scanning signals and image data signals are transmitted
to each of the plural pixels based on the image information from
the exterior; and pixels of each scanning line sequentially emit
light in response to image data signals through scanning signals to
display image information on display section A via scanning of
images.
[0235] FIG. 2 is a schematic diagram of display section A.
[0236] Display section A possesses a substrate and provided
thereon, a wiring section possessing plural scanning lines 5 and
data lines 6, and plural pixels 3. The major members of display
section A will be described below.
[0237] In the figure, shown is the case where light emitted by
pixel 3 is taken out in the white arrow direction (in the lower
direction).
[0238] Each of scanning lines 5 and plural data lines 6 in a wiring
section is made of a conductive material and scanning lines 5;
scanning lines 5 and plural data lines 6 are orthogonal in the form
of a lattice, and are connected to pixel 3 (not shown in the figure
in detail).
[0239] When a scanning signal is applied from scanning line 5,
pixel 9 receives an image data signal from data line 6 to produce
luminescence in response to the receiving image data.
It is possible to display full color by appropriately placing
pixels in the red region, pixels in the green region and pixels in
the blue region in parallel for light emission colors on the same
substrate.
[0240] Next, the light emission process will be described.
[0241] FIG. 3 shows a schematic diagram of a pixel.
[0242] The pixel possesses organic EL element 10, switching
transistor 11, drive transistor 12, and condenser 13. As organic EL
element 10, red, green and blue light emitting organic EL elements
are employed for plural pixels, and these are placed in parallel on
the same substrate to display full color.
[0243] In FIG. 3, image data signals are applied to the drain of
switching transistor 11 via data line 6 from control section B.
Subsequently, when a scanning signal is applied to the gate of
switching transistor 11 via scanning line 5 from control section B,
the drive of switching transistor 11 is activated, and an image
data signal applied to the drain is transmitted to the gate of
condenser 13 and drive transistor 12.
[0244] Through transmission of the image data signal, condenser 13
is charged depending on the electrical potential of the image data
signal, and simultaneously, the drive of drive transistor 12 is
activated. In drive transistor 12, the drain is connected to power
supply line 7; the source is connected to the electrode of organic
EL element 10; and electric current is supplied to organic EL
element 10 from power supply line 7, depending on the electric
potential of the image data signal applied to the gate.
[0245] When a scanning signal is transferred to the following
scanning line 5 via sequential scanning of control section B, the
drive of switching transistor 11 is deactivated. However, since
condenser 13 maintains the electrical potential of a charged image
data signal even though the drive of switching transistor 11 is
deactivated, the drive of drive transistor 12 is kept activated,
and light emission of organic EL element 10 is continued until the
following scanning signal is applied. When the following scanning
signal is applied via sequential scanning, drive transistor 12 is
driven depending on the electrical potential of the next image data
signal synchronized with a scanning signal, whereby organic EL
element 10 produces luminescence.
[0246] That is, as to light emission of organic EL element 10,
switching transistor 11 and drive transistor 12 as the active
element are provided with respect to organic EL element 10 for each
of the plural pixels, and organic EL element 10 for each of plural
pixels 3 produces luminescence. Such the light emitting method is
called an active matrix system.
[0247] Herein, light emission of organic EL element 10 may be light
emission exhibiting a plurality of gradations obtained via a
multi-valued image data signal having a plurality of gradation
potentials, or may be on-and-off of a prescribed light emitting
amount obtained via a binary image data signal. Further, the
electrical potential of condenser 13 may be continuously maintained
until the next scanning signal is applied, or may be discharged
immediately before the next scanning signal is applied.
[0248] In the present invention, in addition to the above-described
active matrix system, may be allowed to be used is a light emission
drive of a passive matrix system in which an organic EL element
emits light, depending on the data signal, only when a scanning
signal is scanned.
[0249] FIG. 4 is a schematic diagram of a display device of a
passive matrix system. In FIG. 4, plural scanning lines 5 and
plural image data lines 6 sandwiching pixel 3 and facing to each
other are provided in the form of a lattice.
[0250] When the scanning signal of scanning lines 5 are applied via
sequential scanning, pixels 3 connected to applied scanning lines 5
emit light in response to the image data signal.
[0251] In the case of a passive matrix system, pixels 3 have no
active element, resulting in reduction of manufacturing cost.
[0252] Further, the organic EL material of the present invention
can be applied to an organic EL element substantially emitting
white light. A plurality of light emitting colors are
simultaneously emitted from a plurality of light emitting materials
to obtain white light emission via color mixture. A combination
with a plurality of light emitting colors may be one including
three light emission maximum wavelengths of the three primary
colors of blue, green and red, or maybe one including two light
emission maximum wavelengths utilizing the complementary color
relationship such as blue and yellow or bluish-green and
orange.
EXAMPLE
[0253] Next, the present invention will be described referring to
Examples, but the present invention is not limited thereto. In
addition, compounds used in Examples are shown below.
##STR00029##
Example 1
Preparation of Organic EL Element
<<Preparation of Coating Solutions 1-1 to 1-8>>
[0254] Under nitrogen atmosphere, 600 mg of 1-2a prepared in the
foregoing synthetic example and 30 mg of Ir-1 were dissolved in
dehydrated dichloroethane, while stirring and exposed to UV rays
employing a high pressure mercury lamp for 120 seconds to obtain
coating solution 1-1.
[0255] Coating solutions 1-2 to 1-8 were prepared similarly to
preparation of coating solution 1-1, except that compound 1-2a was
replaced by compounds shown in Table 1.
[0256] It was possible to be confirmed that a polymer had been
prepared from the monomer contained therein by analyzing a part of
each of coating solutions 1-1 to 1-8 employing a commercially
available LC-Mass.
<<Preparation of Organic EL Element 1-1>>
[0257] A substrate (NA45, produced by NH Techno Glass Corp.),
prepared by forming a 100 nm thick ITO (indium tin oxide) film as
an anode on a glass plate having a size of 100.times.100.times.1.1
mm, was subjected to patterning, and a transparent supporting
substrate provided with this ITO transparent electrode was cleaned
with isopropyl alcohol via ultrasonic waves, followed by being
dried employing dry nitrogen gas and being cleaned for 5 minutes
employing UV ozone.
[0258] This substrate was placed on a spin coater, and a solution
prepared by diluting
poly(3,4-ethylenedioxythiophene)-polystyrenesulfonate (PEDOT/PSS,
produced by Bayer Co., BAYTRON P A1 4083) by 70% with pure water
was coated by a spin coating method to form a film at 3,000 rpm for
30 seconds, followed by drying at 200.degree. C. for one hour,
resulting in formation of a hole transport layer having a film
thickness of 30 nm.
[0259] After completing a drying treatment, a substrate was placed
on the spin coater again, and coating solution 1-1 was spin-coated
at 1000 rpm for 30 seconds, so as to give a film thickness of 40
mm, followed by drying in vacuum at 60.degree. C. for one hour to
obtain a light emission layer.
[0260] Next, this substrate was fixed on a substrate holder in a
vacuum evaporator, and inside the vacuum evaporator, 200 mg of
bathocuproine (BCP) were charged in a molybdenum resistance heating
boat; 200 mg of Alq.sub.3 were charged in another molybdenum
resistance heating boat. After depressurizing the vacuum chamber to
4.times.10.sup.-4 Pa, the foregoing heating boat in which BCP was
charged was heated via electricity application to conduct
evaporation on the foregoing light emission layer at a deposition
rate of 0.1 nm/sec, and a hole blocking layer having a film
thickness of 10 nm was further provided.
[0261] Subsequently, the foregoing heating boat in which Alq.sub.3
was charged was heated via electricity application, and evaporation
was conducted on the foregoing hole blocking layer at a deposition
rate of 0.1 nm/sec to further form an electron transport layer
having a film thickness of 40 nm. In addition, the substrate
temperature during evaporation was room temperature.
[0262] Subsequently, lithium fluoride and aluminum were deposited
so as to give thicknesses of 0.5 nm and 110 nm, respectively to
form a cathode. Thus, organic EL element 1-1 was prepared.
<<Preparation of Organic EL Elements 1-2 to 1-8>>
[0263] Organic EL elements 1-2 to 1-8 were prepared similarly to
preparation of organic EL element 1-1, except that coating solution
1-1 was replaced by coating solutions 1-2 to 1-8, respectively.
<<Evaluation of Organic EL Elements 1-1 to 1-8>>
[0264] The resulting organic EL elements 1-1 to 1-8 were evaluated
as shown below.
<<Externally Taking-Out Quantum Efficiency>>
[0265] The externally taking-out quantum efficiency (%) of each of
the resulting organic EL elements 1-1 to 1-8 during application of
a constant current of 2.5 mA/cm.sup.2 under dried nitrogen
atmosphere was measured, and shown in Table 1. In addition, a
spectrum radiation luminance meter CS-1000, manufactured by Konica
Minolta Sensing, Inc., was employed for the measurements.
[0266] The measured results of the externally taking-out quantum
efficiency shown in Table 1 are represented by the relative value
when the measured value of organic EL element 1-1 is set to
100.
<<Light Emission Lifetime>>
[0267] Time necessary for reducing luminance to half of the
luminance immediately after emission at the initial time (initial
luminance) was measured when driving with a constant current of 2.5
mA/cm.sup.2, and was designated as a measure of half-lifetime
(.tau..sup.0.5).
[0268] A spectrum radiation luminance meter CS-1000, manufactured
by Konica Minolta Sensing, Inc., was employed for the
measurements.
[0269] The measured results of the light emission lifetime shown in
Table 1 are represented by the relative value when the measured
value of organic EL element 1-1 is set to 100.
[0270] Obtained results are shown in Table 1.
TABLE-US-00001 TABLE 1 Host Externally Light compound taking-out
emission Element (Purity) quantum efficiency lifetime Remarks 1-1
1-2a (99.30%) 100 100 Comparative example 1-2 1-2b (98.02%) 106 113
Comparative example 1-3 1-2c (99.53%) 112 182 Comparative example
1-4 1-2d (99.92%) 126 245 Present invention 1-5 1-2e (99.99%) 132
388 Present invention 1-6 1-1 (99.98%) 122 353 Present invention
1-7 1-12 (99.99%) 142 398 Present invention 1-8 1-19 (99.99%) 138
402 Present invention
[0271] As is clear from Table 1, organic EL elements of the present
invention exhibit longer light emission lifetime in comparison to
organic EL elements in Comparative examples.
Example 2
Preparation of Organic EL Element
(Preparation of Coating Solutions 2-1A to 2-3A)
[0272] The following coating solutions 2-1A to 2-3A were prepared
employing the compound shown in Table 2.
[0273] Under nitrogen atmosphere, 600 mg of exemplified compound
4-1a (a purity content of 98.85% by weight) were dissolved in 60 mL
of dehydrated xylene, and heated at 130.degree. C. for 30 minutes
to prepare coating solution 2-1A.
[0274] Subsequently, under nitrogen atmosphere, 600 mg of
exemplified compound 1-21a (a purity content of 98.23% by weight)
and 30 mg of exemplified compound 2-25a (a purity content of 99.31%
by weight) were dissolved in 60 mL of dehydrated xylene, and heated
at 130.degree. C. for 30 minutes to prepare coating solution
2-2A.
[0275] Further, under nitrogen atmosphere, 600 mg of exemplified
compound 3-14a (a purity content of 99.18% by weight) were
dissolved in 60 mL of dehydrated xylene, and heated at 130.degree.
C. for 30 minutes to prepare coating solution 2-3A.
(Preparation of Coating Solutions 2-1B to 2-3B)
[0276] Coating solutions 2-1B to 2-3B were prepared similarly to
preparation of coating solutions 2-1A to 2-3A, by utilizing
materials shown in Table 2.
[0277] It was possible to be confirmed that a polymer had been
prepared from the monomer contained therein by analyzing a part of
each coating solution employing a commercially available
LC-Mass.
<<Preparation of Organic EL element 2-1>>
[0278] A substrate (NA45, produced by NH Techno Glass Corp.),
prepared by forming a 100 nm thick ITO (indium tin oxide) film as
an anode on a glass plate having a size of 100.times.100.times.1.1
mm, was subjected to patterning, and a transparent supporting
substrate provided with this ITO transparent electrode was cleaned
with isopropyl alcohol via ultrasonic waves, followed by being
dried employing dry nitrogen gas and being cleaned for 5 minutes
employing UV ozone.
[0279] This substrate was placed on a spin coater, and a solution
prepared by diluting
poly(3,4-ethylenedioxythiophene)-polystyrenesulfonate (PEDOT/PSS,
produced by Bayer Co., BAYTRON P A1 4083) by 70% with pure water
was coated by a spin coating method to form a film at 3,000 rpm for
30 seconds, followed by drying at 200.degree. C. for one hour,
resulting in formation of a hole injection layer having a film
thickness of 30 nm.
[0280] After completing a drying treatment, a substrate was placed
on the spin coater again, and coating solution 2-1A was spin-coated
at 1000 rpm for 30 seconds to form a hole transport layer.
Subsequently, coating solution 2-2A was spin-coated at 1000 rpm for
30 seconds to form a light emission layer, and further, coating
solution 2-3A was spin-coated at 1000 rpm for 30 seconds to form an
electron transport layer.
[0281] Next, this substrate was fixed on a substrate holder in a
vacuum evaporator, and inside the vacuum evaporator, 200 mg of
Alq.sub.3 were charged in a molybdenum resistance heating boat.
[0282] After depressurizing the vacuum chamber to 4.times.10.sup.-4
Pa, the foregoing heating boat in which Alq.sub.3 was charged was
heated via electricity application to conduct evaporation on the
foregoing electron transport layer at a deposition rate of 0.1
nm/sec, and an electron injection layer having a film thickness of
40 nm was further provided. In addition the substrate temperature
during evaporation was room temperature.
[0283] Subsequently, lithium fluoride and aluminum were deposited
so as to give thicknesses of 0.5 nm and 110 nm, respectively to
form a cathode. Thus, organic EL element 2-1 was prepared.
(Preparation of Organic EL Element 2-2)
[0284] Organic EL element 2-2 was prepared similarly to preparation
of organic EL element 2-1A, by utilizing coating solutions 2-1B,
2-2B, and 2-3B.
[0285] When electricity was applied to these elements, light
emission of blue color was obtained, whereby it was confirmed that
these elements were usable as an organic EL display.
<<Evaluation of Organic EL Elements 2-1 and 2-2>>
[0286] Similarly to the evaluation of organic EL element 1-1 in
Example 1, results shown in Table 2 were obtained. In addition, the
measured results of the light emission lifetime shown in Table 2
are represented by the relative value when the measured value of
organic EL element 2-1 is set to 100.
TABLE-US-00002 TABLE 2 Hole transport Light material Light emitting
Electron transport emission Element Purity (%) material Purity (%)
material Purity (%) lifetime Remarks 2-1 4-1a 1-21a (98.23%)/ 3-14a
(99.18%) 100 Comparative (98.85%) 2-25a (99.31%) example 2-2 4-1b
1-21b (99.99%)/ 3-14b (99.99%) 402 Present (99.99%) 2-25b (99.99%)
invention
[0287] As is clear from Table 2, the organic EL element of the
present invention exhibits longer light emission lifetime in
comparison to the organic EL elements in Comparative example.
Example 3
Preparation of Organic EL Element 3-1
Preparation of White-Illuminating Device
[0288] Organic EL element 3-1 was prepared similarly to preparation
of organic EL element 1-1, except that 30 mg of dopant compound
Ir-1 contained in a light emission layer was replaced by 9 mg of
Ir-1, 9 mg of Ir-9 and 12 mg of Ir-14 in preparation of organic EL
element 1-5 in Example 1.
[0289] When electricity was applied to this element, while light
was obtained, and it was confirmed that the element was usable as
an illuminating device.
Example 4
Synthesis of Compound 5-1a
Comparative Organic Electroluminescent Element Material
##STR00030##
[0291] In 200 mL of toluene, dissolved were 15.0 g of compound
5-1-1 (HPLC purity of 99.65%) and 18.0 g of compound 5-1-2 (HPLC
purity of 99.82%), followed by addition of 1.0 g of Aliquat 336 and
30 mL of a 2 mol/L sodium hydrogen carbonate solution under
nitrogen atmosphere.
[0292] After vigorously stirring this mixture, and heating it via
reflow for 20 hours, 1 g of bromobenzene was added, followed by
heating for 5 hours. This reaction solution was cooled to
60.degree. C., and slowly added in a mixed solution of 3 L of
methanol and 300 mL of pure water while stirring.
[0293] A precipitate was filtrated and repeatedly washed with
methanol and pure water, and subsequently dried in a vacuum oven at
60.degree. C. for 10 hours to obtain 19.0 g of compound 5-1a as a
comparative organic electroluminescent element material. Spectral
characteristics of compound 5-1a coincided with those of compound
5-1.
Synthesis of Compound 5-1b
Organic Electroluminescent Element Material of the Present
Invention
[0294] Nineteen grams of compound 5-1b as an organic
electroluminescent element material of the present invention were
prepared similarly to synthesis of compound 5-1a as a comparative
organic electroluminescent element material, except that employed
were 5-1-1 (HPLC purity of 99.99%) and 5-1-2 (HPLC purity of
99.99%) each as a high purity monomer having an impurity content of
1000 ppm or less.
Preparation of Organic EL Element 5-1
Comparative Example
[0295] A substrate (NA45, produced by NH Techno Glass Corp.),
prepared by forming a 150 nm thick ITO (indium tin oxide) film as
an anode on a glass plate, was subjected to patterning, and a
transparent supporting substrate provided with this ITO transparent
electrode was cleaned with isopropyl alcohol via ultrasonic waves,
followed by being dried employing dry nitrogen gas and being
cleaned for 5 minutes employing UV ozone.
[0296] This substrate was moved in nitrogen atmosphere, and a
solution in which 60 mg of compound 5-1a as a comparative organic
EL element material were dissolved in 6 mL of toluene was coated by
a spin coating method to form a film at 1,000 rpm for 30 seconds,
followed by drying in vacuum at 150.degree. C. for one hour to form
a hole transport layer having a film thickness of 30 nm.
[0297] Subsequently, a solution in which 60 mg of H1 and 6.0 mg of
Ir-12 were dissolved in 6 mL of toluene was coated on the hole
transport layer by a spin coating method to form a film at 1,000
rpm for 30 seconds, followed by heating in vacuum at 150.degree. C.
for one hour to obtain a light emission layer having a film
thickness of 40 nm.
[0298] Further, a solution in which 20 mg were dissolved in 6 mL of
butanol was coated by a spin coating method to form a film at 1,000
rpm for 30 seconds, followed by heating in vacuum at 150.degree. C.
for one hour to obtain the first electron transport layer having a
film thickness of 20 nm.
[0299] Next, this substrate was fixed on a substrate holder in a
vacuum evaporator, and inside the vacuum evaporator, 200 mg of
Alq.sub.3 were charged in a molybdenum resistance heating boat.
After depressurizing the vacuum chamber to 4.times.10.sup.-4 Pa,
the foregoing heating boat in which Alq.sub.3 was charged was
heated via electricity application to conduct evaporation on the
foregoing first electron transport layer at a deposition rate of
0.1 nm/sec to form the second electron transport layer having a
film thickness of 40 nm.
[0300] In addition, the substrate temperature during evaporation
was room temperature. Subsequently, lithium fluoride and aluminum
were deposited so as to give thicknesses of 0.5 nm and 110 nm,
respectively to form a cathode. Thus, organic EL element 5-1
(Comparative example) was Prepared.
Preparation of Organic EL Element 5-2
The Present Invention
[0301] Organic EL element 5-2 was prepared similarly to preparation
of organic EL element 5-2, except that compound 5-1a as a
comparative organic EL element material was replaced by compound
5-1b as an organic electroluminescent element material of the
present invention.
<<Evaluation of Organic EL Element>>
[0302] As to evaluations of the resulting organic EL elements 5-1
and 5-2, the evaluations were made by the same method as used in
Example 1. The values of externally taking-out quantum efficiency
and light emission lifetime are represented by the relative values
when those of organic EL element 5-1 each is set to 100.
[0303] The obtained results are shown below.
TABLE-US-00003 Hole Externally Light Organic EL transport
taking-out emission element No. material quantum efficiency
lifetime Remarks 5-1 5-1a 100 100 Comparative example 5-2 5-1b 102
321 Present invention
[0304] As is clear from the above-described, it is to be understood
that organic EL element 5-2 prepared with 5-1b as an organic EL
element material of the present invention exhibits drastically
longer light emission lifetime in comparison to organic EL element
5-1 as a comparative example.
* * * * *