U.S. patent application number 14/343530 was filed with the patent office on 2014-08-14 for organic electroluminescent device.
This patent application is currently assigned to HODOGAYA CHEMICAL CO., LTD.. The applicant listed for this patent is Shuichi Hayashi, Shigeru Kusano, Norimasa Yokoyama. Invention is credited to Shuichi Hayashi, Shigeru Kusano, Norimasa Yokoyama.
Application Number | 20140225100 14/343530 |
Document ID | / |
Family ID | 47882880 |
Filed Date | 2014-08-14 |
United States Patent
Application |
20140225100 |
Kind Code |
A1 |
Yokoyama; Norimasa ; et
al. |
August 14, 2014 |
ORGANIC ELECTROLUMINESCENT DEVICE
Abstract
An organic electroluminescent device having a capping layer
composed of material having a high refractive index, excelling in
thin film stability and durability and having no absorption in the
respective wavelength ranges of blue, green, and red is provided to
improve device characteristics of the organic electroluminescent
device, particularly to greatly improve light extraction
efficiency. The organic electroluminescent device has at least an
anode electrode, a hole transport layer, a light emitting layer, an
electron transport layer, a cathode electrode, and the capping
layer in this order, wherein the capping layer contains an
arylamine compound (X) having a structure in which two
triphenylamine structures are joined within a molecule via a single
bond or a divalent group that does not contain a heteroatom.
Inventors: |
Yokoyama; Norimasa; (Tokyo,
JP) ; Hayashi; Shuichi; (Tokyo, JP) ; Kusano;
Shigeru; (Tsukuba-shi, JP) |
|
Applicant: |
Name |
City |
State |
Country |
Type |
Yokoyama; Norimasa
Hayashi; Shuichi
Kusano; Shigeru |
Tokyo
Tokyo
Tsukuba-shi |
|
JP
JP
JP |
|
|
Assignee: |
HODOGAYA CHEMICAL CO., LTD.
Tokyo
JP
|
Family ID: |
47882880 |
Appl. No.: |
14/343530 |
Filed: |
September 6, 2012 |
PCT Filed: |
September 6, 2012 |
PCT NO: |
PCT/JP2012/005665 |
371 Date: |
March 7, 2014 |
Current U.S.
Class: |
257/40 |
Current CPC
Class: |
H01L 51/0058 20130101;
H01L 51/0061 20130101; H01L 51/0074 20130101; C07C 211/54 20130101;
C07D 209/88 20130101; C09B 57/008 20130101; H01L 51/005 20130101;
C07D 333/76 20130101; C07D 213/38 20130101; H01L 51/0059 20130101;
H01L 51/5253 20130101; H01L 51/0067 20130101; C07C 211/58 20130101;
H01L 51/0052 20130101; H01L 51/006 20130101; H01L 51/5056 20130101;
H01L 51/5275 20130101; H01L 51/0072 20130101 |
Class at
Publication: |
257/40 |
International
Class: |
H01L 51/00 20060101
H01L051/00; H01L 51/52 20060101 H01L051/52 |
Foreign Application Data
Date |
Code |
Application Number |
Sep 12, 2011 |
JP |
2011-198221 |
Claims
1. An organic electroluminescent device comprising at least an
anode electrode, a hole transport layer, a light emitting layer, an
electron transport layer, a cathode electrode, and a capping layer
in this order, wherein the capping layer comprises an arylamine
compound (X) having a structure in which two triphenylamine
structures are joined within a molecule via a single bond or a
divalent group that does not contain a heteroatom.
2. The organic electroluminescent device according to claim 1,
wherein the arylamine compound (X) having a structure in which two
triphenylamine structures are joined within a molecule via a single
bond or a divalent group that does not contain a heteroatom is an
arylamine compound (X') represented by the following general
formula (1): ##STR00024## wherein R.sub.1 to R.sub.28 may be the
same or different, and each represents a hydrogen atom, a deuterium
atom, a fluorine atom, a chlorine atom, cyano, trifluoromethyl,
nitro, linear or branched alkyl of 1 to 6 carbon atoms that may
have a substituent, linear or branched alkenyl of 2 to 6 carbon
atoms that may have a substituent, cycloalkyl of 5 to 10 carbon
atoms that may have a substituent, linear or branched alkyloxy of 1
to 6 carbon atoms that may have a substituent, cycloalkyloxy of 5
to 10 carbon atoms that may have a substituent, a substituted or
unsubstituted aromatic hydrocarbon group, a substituted or
unsubstituted aromatic heterocyclic group, a substituted or
unsubstituted condensed polycyclic aromatic group, or substituted
or unsubstituted aryloxy, where these substituents may bind to each
other to form a ring when a plurality of these substituents bind to
the same benzene ring; R.sub.1 to R.sub.10 and R.sub.19 to R.sub.28
may form rings by binding to benzene rings to which the respective
groups bind; and A represents a divalent group represented by the
following structural formulae (B) to (F), or a single bond, where
when A is a single bond, at least one of R.sub.1 to R.sub.28 is a
substituted or unsubstituted aromatic hydrocarbon group,
##STR00025## wherein R.sub.29 to R.sub.32 may be the same or
different, and each represents a hydrogen atom, a deuterium atom, a
fluorine atom, a chlorine atom, cyano, trifluoromethyl, linear or
branched alkyl of 1 to 6 carbon atoms, linear or branched alkenyl
of 2 to 6 carbon atoms, a substituted or unsubstituted aromatic
hydrocarbon group, a substituted or unsubstituted aromatic
heterocyclic group, or a substituted or unsubstituted condensed
polycyclic aromatic group, where these substituents may bind to
each other to form a ring when a plurality of these substituents
bind to the same benzene ring; and n is an integer of 1 to 3, where
when a plurality of each of R.sub.29 to R.sub.32 are present (when
n is 2 or 3), R.sub.29 to R.sub.32 may be the same or different,
##STR00026## wherein R.sub.33 to R.sub.42 may be the same or
different, and each represents a hydrogen atom, a deuterium atom, a
fluorine atom, a chlorine atom, cyano, trifluoromethyl, linear or
branched alkyl of 1 to 6 carbon atoms, linear or branched alkenyl
of 2 to 6 carbon atoms, a substituted or unsubstituted aromatic
hydrocarbon group, a substituted or unsubstituted aromatic
heterocyclic group, or a substituted or unsubstituted condensed
polycyclic aromatic group, where these substituents may bind to
each other to form a ring, ##STR00027## wherein R.sub.43 to
R.sub.50 may be the same or different, and each represents a
hydrogen atom, a deuterium atom, a fluorine atom, a chlorine atom,
cyano, trifluoromethyl, linear or branched alkyl of 1 to 6 carbon
atoms, linear or branched alkenyl of 2 to 6 carbon atoms, a
substituted or unsubstituted aromatic hydrocarbon group, a
substituted or unsubstituted aromatic heterocyclic group, or a
substituted or unsubstituted condensed polycyclic aromatic group,
where these substituents may bind to each other to form a ring,
##STR00028## wherein R.sub.51 to R.sub.55 may be the same or
different, and each represents a hydrogen atom, a deuterium atom, a
fluorine atom, a chlorine atom, cyano, trifluoromethyl, linear or
branched alkyl of 1 to 6 carbon atoms, linear or branched alkenyl
of 2 to 6 carbon atoms, a substituted or unsubstituted aromatic
hydrocarbon group, a substituted or unsubstituted aromatic
heterocyclic group, or a substituted or unsubstituted condensed
polycyclic aromatic group, where these substituents may bind to
each other to form a ring.
3. The organic electroluminescent device according to claim 2,
wherein A is a divalent group represented by the structural formula
(B) in the general formula (1).
4. The organic electroluminescent device according to claim 3,
wherein A is a divalent group represented by the structural formula
(B), and n is 1 in the general formula (1).
5. The organic electroluminescent device according to claim 2,
wherein A is a single bond in the general formula (1).
6. The organic electroluminescent device according to claim 2,
wherein A is a divalent group represented by the structural formula
(D) in the general formula (1).
7. The organic electroluminescent device according to claim 1,
wherein the thickness of the capping layer is within a range of 30
nm to 120 nm.
8. The organic electroluminescent device according to claim 1,
wherein the refractive index of the capping layer is 1.75 or more
when the wavelength of light that transmits the capping layer is
within a range of 530 nm to 750 nm.
9. The organic electroluminescent device according to claim 2,
wherein the thickness of the capping layer is within a range of 30
nm to 120 nm.
10. The organic electroluminescent device according to claim 3,
wherein the thickness of the capping layer is within a range of 30
nm to 120 nm.
11. The organic electroluminescent device according to claim 4,
wherein the thickness of the capping layer is within a range of 30
nm to 120 nm.
12. The organic electroluminescent device according to claim 5,
wherein the thickness of the capping layer is within a range of 30
nm to 120 nm.
13. The organic electroluminescent device according to claim 6,
wherein the thickness of the capping layer is within a range of 30
nm to 120 nm.
14. The organic electroluminescent device according to claim 2,
wherein the refractive index of the capping layer is 1.75 or more
when the wavelength of light that transmits the capping layer is
within a range of 530 nm to 750 nm.
15. The organic electroluminescent device according to claim 3,
wherein the refractive index of the capping layer is 1.75 or more
when the wavelength of light that transmits the capping layer is
within a range of 530 nm to 750 nm.
16. The organic electroluminescent device according to claim 4,
wherein the refractive index of the capping layer is 1.75 or more
when the wavelength of light that transmits the capping layer is
within a range of 530 nm to 750 nm.
17. The organic electroluminescent device according to claim 5,
wherein the refractive index of the capping layer is 1.75 or more
when the wavelength of light that transmits the capping layer is
within a range of 530 nm to 750 nm.
18. The organic electroluminescent device according to claim 6,
wherein the refractive index of the capping layer is 1.75 or more
when the wavelength of light that transmits the capping layer is
within a range of 530 nm to 750 nm.
19. The organic electroluminescent device according to claim 7,
wherein the refractive index of the capping layer is 1.75 or more
when the wavelength of light that transmits the capping layer is
within a range of 530 nm to 750 nm.
20. The organic electroluminescent device according to claim 9,
wherein the refractive index of the capping layer is 1.75 or more
when the wavelength of light that transmits the capping layer is
within a range of 530 nm to 750 nm.
Description
TECHNICAL FIELD
[0001] The present invention relates to an organic
electroluminescent device (hereinafter referred to as an organic EL
device) which is a preferred self-luminous device for various
display devices. Specifically, this invention relates to an organic
EL device using a specific arylamine derivative, particularly an
organic EL device greatly improved in light extraction
efficiency.
BACKGROUND ART
[0002] The organic EL device is a self-luminous device and has been
actively studied for their brighter, superior visibility and the
ability to display clearer images in comparison with liquid crystal
devices.
[0003] In 1987, C. W. Tang and colleagues at Eastman Kodak
developed a laminated structure device using materials assigned
with different roles, realizing practical applications of an
organic EL device with organic materials. These researchers
laminated an electron-transporting phosphor and a hole-transporting
organic substance, and injected both charges into a phosphor layer
to cause emission in order to obtain a high luminance of 1,000
cd/m.sup.2 or more at a voltage of 10 V or less (refer to Patent
Documents 1 and 2, for example).
[0004] To date, various improvements have been made for practical
applications of the organic EL device. Various roles of the
laminated structure are further subdivided to provide an
electroluminescence device that includes an anode, a hole injection
layer, a hole transport layer, a light emitting layer, an electron
transport layer, an electron injection layer, and a cathode
successively formed on a substrate, wherein high efficiency and
durability are achieved by a light emitting device of bottom
emission structure that emits light from the bottom (refer to
Non-Patent Document. 1, for example).
[0005] Light emitting devices of op emission structure that emit
light from die top using metal with a high work function as an
anode have been used in recent years. Unlike the light emitting
device of bottom emission structure restricted in the area of a
light emitting part by a pixel circuit, the light emitting device
of top emission structure has an advantage of having a wide light
emitting part. In the light emitting device of top emission
structure, a semitransparent electrode of LiF/Al/Ag (refer to
Non-patent document 2, for example), Ca/Mg (refer to Non-patent
document 3, for example), LiF/MgAg, or the like is used as a
cathode.
[0006] In such a light emitting device, when light emitted in a
light emitting layer is incident on the other film, if the light is
incident at a certain angle or more, the light is totally reflected
on an interface between the light emitting layer and the other
film. Consequently, only a part of the emitted light has been used.
In recent years, a light emitting device provided with a "capping
layer" with a high refractive index, on the outside of a
semitransparent electrode with a low refractive index has been
proposed to improve light extraction efficiency (refer to
Non-patent documents 2 and 3, for example).
[0007] The capping layer in the light emitting device of top
emission structure has an effect that the light emitting device
using Ir(ppy).sub.3 as a light emitting material has a current
efficiency of 38 cd/A in the case of having no capping layer, while
a light emitting device using ZnSe with a film thickness of 60 nm
as the capping layer has a current efficiency of 64 cd/A, that the
efficiency improvement of about 1.7 times is recognized. It is also
indicated that the maximum point of transmittance of the
semitransparent electrode and the capping layer does not
necessarily coincide with the maximum point of efficiency, and it
is indicated that the maximum point of light extraction efficiency
is determined by an interference effect (refer to Non-patent
document for example).
[0008] The use of a metal mask of high definition is proposed for
the formation of the capping layer. However, in such a metal mask,
there has been a problem of worsening alignment accuracy due to
distortion caused by heat. That is, ZnSe has a high melting point
of 1,100.degree. C. or higher (refer to Non-patent document 3, for
example), and vapor deposition in an accurate position is impeded
in the mask of high definition. Many inorganic substances have high
vapor deposition temperatures and are unsuitable for the use of the
mask of high definition, and there is a possibility of damaging the
light emitting device itself. Further, since the light emitting
device is damaged in film formation by a sputtering method, the
capping layer containing an inorganic substance as a constitutive
material cannot be used.
[0009] In the case of using tris(8-hydroxyquinoline)) aluminum
(hereinafter, referred to as "Alq.sub.3") as the capping layer for
adjusting a refractive index (refer to Non-patent document 2, for
example), although Alq.sub.3 is known as an organic EL material
generally used as a green light emitting material or an electron
transport material, it has weak absorption in the vicinity of 450
nm used for a blue light emitting device. In consequence, there has
been a problem of causing a decrease in color purity and a decrease
in light extraction efficiency in the case of the blue light
emitting device.
[0010] A material having a high refractive index and excelling in
thin film stability and durability is demanded as a material for
the capping layer to improve device characteristics of the organic
EL device, particularly to greatly improve light extraction
efficiency.
CITATION LIST
Patent Documents
[0011] Patent Document 1: JP-A-8-48656 [0012] Patent Document 2:
Japanese Patent No. 3194657 [0013] Patent Document 3: JP-A-7-126615
[0014] Patent Document 4: JP-A-8-48656 [0015] Patent Document 5:
JP-2005-108804
Non-Patent Documents
[0015] [0016] Non-Patent Document 1: The Japan Society of Applied
Physics, 9th Lecture Preprints, op. 55 to 61 (2001) [0017]
Non-Patent Document 2: Appl. Phys, Lett., 78, 544 (2001) [0018]
Non-Patent Document 3: Appl. Phys. Lett., 82, 466 (2003)
SUMMARY OF THE INVENTION
Problems to be Solved by the Invention
[0019] An object of the present invention is to provide an organic
EL device having a capping layer composed of a material having a
high refractive index, excelling in thin film stability and
durability and having no absorption in the respective wavelength
regions of blue, green and red colors to improve device
characteristics of the organic EL device, particularly to greatly
improve light extraction efficiency.
[0020] Physical properties of the material of the capping layer
suitable for the present invention include (1) a high refractive
index, (2) vapor deposition ability without causing thermal
decomposition, (3) a stable thin film state, and (4) a high glass
transition temperature. Physical properties of the device suitable
for the present invention include (1) high light extraction
efficiency, (2) no decrease in color purity, (3) light transmission
without changes with the lapse of time, and (4) a lona life.
Means for Solving the Problems
[0021] In order to achieve the above objects, the present inventors
noted that an arylamine-based material excels in thin film
stability and durability, selected a specific arylamine compound
with a high refractive index, produced an organic EL device using
the specific arylamine compound as a material for composing a
capping layer, and completed the present invention after thorough
evaluations of the device characteristics.
[0022] Specifically, the following organic EL device is provided
according to the present invention.
[0023] 1) An organic EL device including at least an anode
electrode, a hole transport layer, a light emitting layer, an
electron transport layer, a cathode electrode and a capping layer
in this order, wherein the capping layer includes an arylamine
compound (X) having a structure in which two triphenylamine
structures are joined within molecule via a single bond or a
divalent group that does not contain a heteroatom.
[0024] 2) The organic EL device of 1), wherein the arylamine
compound (X) having a structure in which two triphenylamine
structures are joined within a molecule via a single bond or a
divalent group that does not contain a heteroatom is an arylamine
compound (X') represented by the following general formula (1).
##STR00001##
[0025] In the formula, R.sub.1 to R.sub.28 may be the same or
different, and each represents a hydrogen atom, a deuterium atom, a
fluorine atom, a chlorine atom, cyano, trifluoromethyl, nitro,
linear or branched alkyl of 1 to 6 carbon atoms that may have a
substituent, linear or branched alkenyl of 2 to 6 carbon atoms that
may have a substituent, cycloalkyl of 5 to 10 carbon atoms that may
have a substituent, linear or branched alkyloxy of 1 to 6 carbon
atoms that may have a substituent, cycloalkyloxy of to 10 carbon
atoms that may have a substituent, a substituted or unsubstituted
aromatic hydrocarbon group, a substituted or unsubstituted aromatic
heterocyclic: group, a substituted or unsubstituted condensed
polycyclic aromatic group, or substituted or unsubstituted aryloxy.
These substituents may bind to each other to form a ring when a
plurality of these substituents bind to the same benzene ring, and
R.sub.1 to R.sub.10 and R.sub.19 to R.sub.28 may form rings by
binding to benzene rings to which the respective groups bind. A
represents a divalent group represented by the following structural
formulae (B) to (F), or a single bond, where when A is a single
bond, at least one of R.sub.1 to R.sub.a is a substituted or
unsubstituted aromatic hydrocarbon group.
##STR00002##
[0026] In the formula, R.sub.29 to R.sub.32 may be the same or
different, and each represents a hydrogen atom, a deuterium atom, a
fluorine atom, a chlorine atom, cyano, trifluoromethyl, linear or
branched alkyl of 1 to 6 carbon atoms, linear or branched alkenyl
of 2 to 6 carbon atoms, a substituted or unsubstituted aromatic
hydrocarbon group, a substituted or unsubstituted aromatic
heterocyclic group, or a substituted or unsubstituted condensed
polycyclic aromatic group. These substituents may bind to each
other to form a ring when a plurality of these substituents bind to
the same benzene ring, and n is an integer of 1 to 3. When a
plurality of each of R.sub.29 to R.sub.32 are present (when n is 2
or 3), R.sub.29 to R.sub.32 may be the same or different.
##STR00003##
[0027] In the formula, R.sub.33 to R.sub.42 may be the same or
different, and each represents a hydrogen atom, a deuterium atom, a
fluorine atom, a chlorine atom, cyano, trifluoromethyl, linear or
branched alkyl of 1 to 6 carbon atoms, linear or branched alkenyl
of 2 to 6 carbon atoms, a substituted or unsubstituted aromatic
hydrocarbon group, a substituted or unsubstituted aromatic
heterocyclic group, or a substituted or unsubstituted condensed
polycyclic aromatic group. These substituents may bind to each
other to form a ring.
##STR00004##
[0028] In the formula, R.sub.43 to R.sub.50 may be the same or
different, and each represents a hydrogen atom, a deuterium atom, a
fluorine atom, a chlorine atom, cyano, trifluoromethyl, linear or
branched alkyl of 1 to 6 carbon atoms, linear or branched alkenyl
of 2 to 6 carbon atoms, a substituted or unsubstituted aromatic
hydrocarbon group, a substituted or unsubstituted aromatic
heterocyclic group, or a substituted or unsubstituted condensed
polycyclic aromatic group. These substituents may bind to each
other to form a ring.
##STR00005##
[0029] In the formula, R.sub.51 to R.sub.5s may be the same or
different, and each represents a hydrogen atom, a deuterium atom, a
fluorine atom, a chlorine atom, cyano, trifluoromethyl, linear or
branched alkyl of 1 to 6 carbon atoms, linear or branched alkenyl
of 2 to 6 carbon atoms, a substituted or unsubstituted aromatic
hydrocarbon group, a substituted or unsubstituted aromatic
heterocyclic group, or a substituted or unsubstituted condensed
polycyclic aromatic group. These substituents may bind to each
other to form a ring.
[0030] 3) The organic EL device of 2), wherein the A is a divalent
group represented by the structural formula (B).
[0031] 4) The organic EL device of 3), wherein the A is a divalent
group represented by the structural formula (B), and n is 1.
[0032] 5) The organic EL device of 2), wherein the A is a single
bond.
[0033] 6) The organic EL device of 2), wherein the A is a divalent
group represented by the structural formula (D).
[0034] 7) The organic EL device of 1) to 6), wherein the thickness
of the capping layer is within a range of 30 nm to 120 nm.
[0035] 8) The organic EL device of any one of 1) to 7), wherein the
refractive index of the capping layer is 1.75 or more when the
wavelength of light that transmits the capping layer is within a
range of 530 nm to 750 nm.
[0036] Specific examples of the "linear or branched alkyl of 1 to 6
carbon atoms", "cycloalkyl of 5 to 10 carbon atoms", or "linear or
branched alkenyl of 2 to 6 carbon atoms" in the "linear or branched
alkyl of 1 to 6 carbon atoms that may have a substituent",
"cycloalkyl of 5 to 10 carbon atoms that may have a substituent",
or "linear or branched alkenyl of 2 to 6 carbon atoms that may have
a substituent" represented by R.sub.1 to R.sub.28 in the general
formula (1) include methyl, ethyl, n-propyl, isopropyl, n-butyl,
isobutyl, tert-butyl, n-pentyl, isopentyl, neopentyl, n-hexyl,
cyclopentyl, cyclohexyl, 1-adamantyl, 2-adamantyl, vinyl, allyl,
isopropenyl, and 2-butenyl. These substituents may bind to each
other to form a ring. R.sub.1 to R.sub.10 and R.sub.19 to R.sub.28
may form rings by binding to benzene rings to which the respective
groups bind, via a single bond, substituted or unsubstituted
methylene, an oxygen atom, a sulfur atom, or N--Ar. "N" in "N--Ar"
represents a nitrogen atom, and "Ar" represents a "substituted or
unsubstituted aromatic hydrocarbon group", a "substituted or
unsubstituted aromatic heterocyclic group", or a "substituted or
unsubstituted condensed polycyclic aromatic group", and can be the
same groups exemplified as the aromatic hydrocarbon group, the
aromatic heterocyclic group or the condensed polycyclic aromatic
group in R.sub.1 to R.sub.28 below. Substituents that these groups
may have can be the same substituents exemplified for the same
groups in R.sub.1 to R.sub.2e below.
[0037] Specific examples of the "substituent" in the "linear or
branched alkyl of 1 to 6 carbon atoms that has a substituent", the
"cycloalkyl of 5 to 10 carbon atoms that has a substituent", or the
"linear or branched alkenyl of 2 to 6 carbon atoms that has a
substituent" represented by R.sub.1 to R.sub.28 in the general
formula (1) include a deuterium atom; trifluoromethyl; cyano;
nitro; halogen atoms such as a fluorine atom, a chlorine atom, a
bromine atom, and an iodine atom; linear or branched alkyls of 1 to
6 carbon atoms such as methyl, ethyl, n-propyl, isopropyl, n-butyl,
isobutyl, tert-butyl, n-pentyl, isopentyl, neopentyl, and n-hexyl;
linear or branched alkyloxys of 1 to 6 carbon atoms such as
methyloxy, ethyloxy, and propyloxy; alkenyls such as allyl;
aralkyls such as benzyl, naphthylmethyl, and phenethyl; aryloxys
such as phenyloxy and tolyloxy; arylalkyloxys such as benzyloxy and
phenethyloxy; aromatic hydrocarbon groups or condensed polycyclic
aromatic groups such as phenyl, biphenylyl, terphenylyl, naphthyl,
anthracenyl, phenanthryl, fluorenyl, indenyl, pyrenyl, perylenyl,
fluoranthenyl, and triphenylenyl; aromatic heterocyclic groups such
as pyridyl, furanyl, pyranyl, thienyl, pyrrolyl, quinolyl,
isoquinolyl, benzofuranyl, benzothienyl, indolyl, carbazolyl,
benzooxazolyl, benzothiazolyl, quinoxalyl, benzoimidazolyl,
pyrazolyl, dibenzofuranyl, dibenzothienyl, and carbolinyl;
arylvinyls such as styryl and naphthylvinyl; acyls such as acetyl
and benzoyl; dialkylamino groups such as dimethylamino and
diethylamino; disubstituted amino groups such as diphenylamino and
dinaphthylamino, substituted with aromatic hydrocarbon groups or
condensed polycyclic aromatic groups; diaralkylamino groups such as
dibenzylamino and diphenethylamino; disubstituted amino groups such
as dipyridylamino and dithienylamino, substituted with aromatic
heterocyclic groups; dialkenylamino groups such as diallylamino;
and disubstituted amino groups substituted with a substituent
selected from alkyl, an aromatic hydrocarbon group, a condensed
polycyclic aromatic group, aralkyl, an aromatic heterocyclic group,
and alkenyl. These substituents may be further substituted with
other substituents.
[0038] Specific examples of the "linear or branched alkyloxy of 1
to 6 carbon atoms" or the "cycloalkyloxy of 5 to 10 carbon atoms"
in the "linear or branched alkyloxy of 1 to 6 carbon atoms that may
have a substituent" or the "cycloalkyloxy of 5 to 10 carbon atoms
that may have a substituent" represented by R.sub.1 to R.sub.2e in
the general formula (1) include methyloxy, ethyloxy, n-propyloxy,
isopropyloxy, n-butyloxy, tert-butyloxy, n-pentyloxy, n-hexyloxy,
cyclopentyloxy, cyclohexyloxy, cycloheptyloxy, cyclooctyloxy,
1-adamantyloxy, and 2-adamantyloxy. These substituents may bind to
each other to form a ring. R.sub.1 to R.sub.10 and R.sub.19 to
R.sub.2e may form rings by binding to benzene rings to which the
respective groups bind, via a single bond, substituted or
unsubstituted methylene, an oxygen atom, a sulfur atom, or N--Ar.
"N" in "N--Ar" represents a nitrogen atom, and "Ar" represents a
"substituted or unsubstituted aromatic hydrocarbon group", a
"substituted or unsubstituted aromatic heterocyclic group", or a
"substituted or unsubstituted condensed polycyclic aromatic group",
and can be the same groups exemplified as the aromatic hydrocarbon
group, the aromatic heterocyclic group or the condensed polycyclic
aromatic group in R.sub.1 to R.sub.28 below. Substituents that
these groups may have can be the same substituents exemplified for
the same groups in R.sub.1 to R.sub.28 below.
[0039] Specific examples of the "substituent" in the "linear or
branched alkyloxy of 1 to 6 carbon atoms that has a substituent" or
the "cycloalkyloxy of 5 to 10 carbon atoms that has a substituent"
represented by R.sub.1 to R.sub.28 in the general formula (1)
include a deuterium atom; trifluoromethyl; cyano; nitro; halogen
atoms such as a fluorine atom, a chlorine atom, a bromine atom, and
an iodine atom; linear or branched alkyls of 1 to 6 carbon atoms
such as methyl, ethyl, n-propyl, isopropyl, n-butyl, isobutyl,
tert-butyl, n-pentyl, isopentyl, neopentyl, n-hexyl; linear or
branched alkyloxys of 1 to 6 carbon atoms such as methyloxy,
ethyloxy, and propyloxy; alkenyls such as allyl; aralkyls such as
benzyl, naphthylmethyl, and phenethyl; aryloxys such as phenyloxy
and tolyloxy; arylalkyloxys such as benzyloxy and phenethyloxy;
aromatic hydrocarbon groups or condensed polycyclic aromatic groups
such as phenyl, biphenylyl, terphenylyl, naphthyl, anthracenyl,
phenanthryl, fluorenyl, indenyl, pyrenyl, perylenyl, fluoranthenyl,
and triphenylenyl; aromatic heterocyclic groups such as pyridyl,
furanyl, pyranyl, thienyl, pyrrolyl, quinolyl, isoquinolyl,
benzofuranyl, benzothienyl, indolyl, carbazolyl, benzooxazolyl,
benzothiazolyl, quinoxalyl, benzoimidazolyl, pyrazolyl,
dibenzofuranyl, dibenzothienyl, and carbolinyl; arylvinyls such as
styryl and naphthylvinyl; acyls such as acetyl and benzoyl;
dialkylamino groups such as dimethylamino and diethylamino;
disubstituted amino groups such as diphenylamino and
dinaphthylamino, substituted with aromatic hydrocarbon groups or
condensed polycyclic aromatic groups; diaralkylamino groups such as
dibenzylamino and diphenethylamino; disubstituted amino groups such
as dipyridylamino and dithienylamino, substituted with aromatic
heterocyclic groups; dialkenylamino groups such as diallylamino;
and disubstituted amino groups substituted with a substituent
selected from alkyl, an aromatic hydrocarbon group, a condensed
polycyclic aromatic group, aralkyl, an aromatic heterocyclic group,
and alkenyl. These substituents may be further substituted with
other substituents.
[0040] Specific examples of the "aromatic hydrocarbon group", the
"aromatic heterocyclic group", or the "condensed polycyclic
aromatic group" in the "substituted or unsubstituted aromatic
hydrocarbon group", the "substituted or unsubstituted aromatic
heterocyclic group", or the "substituted or unsubstituted condensed
polycyclic aromatic group" represented by R.sub.1 to R.sub.2e in
the general formula (1) include phenyl, biphenylyl, terphenylyl,
naphthyl, anthryl, phenanthryl, fluorenyl, indenyl, pyrenyl,
perylenyl, fluoranthenyl, triphenylenyl, pyridyl, furanyl, pyranyl,
thienyl, quinolyl, isoquinolyl, benzofuranyl, benzothienyl,
indolyl, carbazolyl, benzooxazclyl, benzothiazolyl, quinoxalyl,
benzoimidazolyl, pyrazolyl, dibenzofuranyl, dibenzothienyl, and
carbolinyl. These substituents may bind to each other to form a
ring. R.sub.1 to R.sub.10 and R.sub.19 to R.sub.28 may form rings
by binding to benzene rings to which the respective groups bind,
via a single bond, substituted or unsubstituted methylene, an
oxygen atom, a sulfur atom, or N--Ar. "N" in "N--Ar" represents a
nitrogen atom, and "Ar" represents a "substituted or unsubstituted
aromatic hydrocarbon group", a "substituted or unsubstituted
aromatic heterocyclic group", or a "substituted or unsubstituted
condensed polycyclic aromatic group", and can be the same groups as
exemplified above. Substituents that these groups may have can be
the same substituents as exemplified below.
[0041] Specific examples of the "substituent" in the "substituted
aromatic hydrocarbon group", the "substituted aromatic heterocyclic
group", or the "substituted condensed polycyclic aromatic group"
represented by R.sub.1 to R.sub.28 in general formula (1) include a
deuterium atom; cyano; trifluoromethyl; nitro; halogen atoms such
as a fluorine atom, a chlorine atom, a bromine atom, and an iodine
atom; linear or branched alkyls of 1 to 6 carbon atoms such as
methyl, ethyl, n-propyl, isopropyl, n-butyl, isobutyl, tert-butyl,
n-pentyl, isopentyl, neopentyl, and n-hexyl; cycloalkyls of 5 to 10
carbon atoms such as cyclopentyl and cyclohexyl; linear or branched
alkenyls of 2 to 6 carbon atoms such as vinyl, allyl, 2-butenyl,
and 1-hexenyl; linear or branched alkyloxys of 1 to 6 carbon atoms
such as methyloxy, ethyloxy, and propyloxy; cycloalkyloxys of 5 to
10 carbon atoms such as cyclopentyloxy and cyclohexyloxy; aralkyls
such as benzyl, naphthylmethyl, and phenethyl; aryloxys such as
phenyloxy, tolyloxy, biphenylyloxy, terphenylyloxy, naphthyloxy,
anthryloxy, phenanthryloxy, fluorenyloxy, indenyloxy, pyrenyloxy,
and perylenyloxy; arylalkyloxys such as benzyloxy and phenethyloxy;
aromatic hydrocarbon groups or condensed polycyclic aromatic groups
such as phenyl, biphenylyl, terphenylyl, naphthyl, anthracenyl,
phenanthryl, fluorenyl, indenyl, pyrenyl, perylenyl, fluoranthenyl,
and triphenylenyl; aromatic heterocyclic groups such as pyridyl,
furanyl, pyranyl, thienyl, pyrrolyl, quinolyl, isoquinolyl,
benzofuranyl, benzothienyl, indolyl, carbazolyl, benzooxazolyl,
benzothiazolyl, quinoxalyl, benzoimidazolyl, pyrazolyl,
dibenzofuranyl, dibenzothienyl, and carbolinyl; aryivinyls such as
styryl and naphthylvinyl; acyls such as acetyl and benzoyl;
dialkylamino groups such as dimethylamino and diethylamino;
disubstituted amino groups such as diphenylamino and
dinaphthylamino, substituted with aromatic hydrocarbon groups or
condensed polycyclic aromatic groups; diaralkylamino groups such as
dibenzylamino and diphenethylamino; disubstituted amino groups such
as dipyridylamino and dithienylamino, substituted with aromatic
heterocyclic groups; dialkenylamino groups such as diallylamino;
and disubstituted amino groups substituted with a substituent
selected from alkyl, an aromatic hydrocarbon group, a condensed
polycyclic aromatic group, aralkyl, an aromatic heterocyclic group,
and alkenyl. These substituents may be further substituted with
other substituents.
[0042] Specific examples of the "aryloxy" in the "substituted or
unsubstituted aryloxy" represented by R.sub.1 to R.sub.28 in
general formula (1) include phenyloxy, tolyloxy, biphenylyloxy,
terphenylyloxy, naphthyloxy, anthryloxy, phenanthryloxy,
fluorenyloxy, indenyloxy, pyrenyloxy, and perylenyloxy. These
substituents may bind to each other to form a ring. R.sub.1 to
R.sub.10 and R.sub.19 to R.sub.28 may form rings by binding to
benzene rings to which the respective groups bind, via a single
bond, substituted or unsubstituted methylene, an oxygen atom, a
sulfur atom, or N--Ar. "N" in "N--Ar" represents a nitrogen atom,
and "Ar" represents a "substituted or unsubstituted aromatic
hydrocarbon group", a "substituted or unsubstituted aromatic
heterocyclic group", or a "substituted or unsubstituted condensed
polycyclic aromatic group", and can be the same groups exemplified
as the aromatic hydrocarbon group, the aromatic heterocyclic group
or the condensed polycyclic aromatic group in R.sub.1 to R.sub.28
above. Substituents that these groups may have can be the same
substituents exemplified for the same groups in R.sub.1 to R.sub.28
above.
[0043] Specific examples of the "substituent" in the "substituted
aryloxy" represented by R.sub.1 to R.sub.2e in general formula (1)
include a deuterium atom; cyano; trifluoromethyl; nitro; halogen
atoms such as a fluorine atom, a chlorine atom, a bromine atom, and
an iodine atom; linear or branched alkyls of 1 to 6 carbon atoms
such as methyl, ethyl, n-propyl, isopropyl, n-butyl, isobutyl,
tert-butyl, n-pentyl, isopentyl, neopentyl, and n-hexyl;
cycloalkyls of 5 to 10 carbon atoms such as cyclopentyl and
cyclohexyl; linear or branched alkenyls of 2 to 6 carbon atoms such
as vinyl, allyl, 2-butenyl, and 1-hexenyl; linear or branched
alkyloxys of 1 to 6 carbon atoms such as methyloxy, ethyloxy, and
propyloxy; cycloalkyloxys of 5 to 10 carbon atoms such as
cyclopentyloxy and cyclohexyloxy; aralkyls such as benzyl,
naphthylmethyl, and phenethyl; aryloxys such as phenyloxy,
tolyloxy, biphenylyloxy, terphenylyloxy, naphthyloxy, anthryloxy,
phenanthryloxy, fluorenyloxy, indenyloxy, pyrenyloxy, and
perylenyloxy; arylalkyloxys such as benzyloxy and phenethyloxy;
aromatic hydrocarbon groups or condensed polycyclic aromatic groups
such as phenyl, biphenylyl, terphenylyl, naphthyl, anthracenyl,
phenanthryl, fluorenyl, indenyl, pyrenyl, perylenyl, fluoranthenyl,
and triphenylenyl; aromatic heterocyclic groups such as pyridyl,
furanyl, pyranyl, thienyl, pyrrolyl, quinolyl, isoquinolyl,
benzofuranyl, benzothienyl, indolyl, carbazolyl, benzooxazolyl,
benzothiazolyl, quinoxalyl, benzoimidazolyl, pyrazolyl,
dibenzofuranyl, dibenzothienyl, and carbolinyl; arylvinyls such as
styryl and naphthylvinyl; acyls such as acetyl and benzoyl;
dialkylamino groups such as dimethylamino and diethylamino;
disubstituted amino groups such as diphenylamino and
dinaphthylamino, substituted with aromatic hydrocarbon groups or
condensed polycyclic aromatic groups; diaralkylamino groups such as
dibenzylamino and diphenethylamino; disubstituted amino groups such
as dipyridylamino and dithienylamino, substituted with aromatic
heterocyclic groups; dialkenylamino groups such as diallylamino;
and disubstituted amino groups substituted with a substituent
selected from alkyl, an aromatic hydrocarbon group, a condensed
polycyclic aromatic group, aralkyl, an aromatic heterocyclic group,
and alkenyl. These substituents may be further substituted with
other substituents.
[0044] Specific examples of the "linear or branched alkyls of 1 to
6 carbon atoms" or the "linear or branched alkenyls of 2 to 6
carbon atoms" represented by R.sub.29 to R.sub.55 in structural
formulae (B) to (D) and (F), corresponding to A in general formula
(1), include methyl, ethyl, n-propyl, isopropyl, n-butyl, isobutyl,
tert-butyl, n-pentyl, isopentyl, neopentyl, n-hexyl, vinyl, allyl,
isopropenyl, and 2-butenyl. These substituents may form a ring by
binding to each other via a single bond, substituted or
unsubstituted methylene, an oxygen atom, or a sulfur atom. In the
case of forming the ring, it is preferable that the substituents
bind to each other via a single bond or dimethylmethylene to form
the ring.
[0045] Specific examples of the "aromatic hydrocarbon group", the
"aromatic heterocyclic group", or the "condensed polycyclic
aromatic group" in the "substituted or unsubstituted aromatic
hydrocarbon group", the "substituted or unsubstituted aromatic
heterocyclic group", or the "substituted or unsubstituted condensed
polycyclic aromatic group" represented by R.sub.29 to R.sub.55 in
structural formulae (B) to (D) and (F), corresponding to A in
general formula (1), include phenyl, biphenylyl, terphenylyl,
tetrakisphenyl, styryl, naphthyl, anthryl, acenaphthenyl,
fluorenyl, phenanthryl, indenyl, pyrenyl, pyridyl, pyrimidyl,
furanyl, pyrrolyl, thienyl, quinolyl, isoquinolyl, benzofuranyl,
benzothienyl, indolyl, carbazolyl, benzooxazolyl, benzothiazolyl,
quinoxalyl, benzoimidazolyl, pyrazolyl, dibenzofuranyl,
dibenzothienyl, naphthyridinyl, phenanthrolinyl, and acridinyl.
These substituents may form a ring by binding to each other via a
single bond, substituted or unsubstituted methylene, an oxygen
atom, or a sulfur atom when a plurality of these substituents bind
to the same benzene ring. In the case of forming the ring, it is
preferable that the substituents bind to each other via a single
bond or dimethylmethylene to form the ring.
[0046] Specific examples of the "substituent" in the "substituted
aromatic hydrocarbon group", "substituted aromatic heterocyclic
group", or "substituted condensed polycyclic aromatic group"
represented by R.sub.29 to R.sub.55 in structural formulae (B) to
(D) and (F), corresponding to A in general formula (1), include a
deuterium atom, a fluorine atom, a chlorine atom, trifluoromethyl,
linear or branched alkyl of 1 to 6 carbon atoms, phenyl,
biphenylyl, terphenylyl, tetrakisphenyl, styryl, naphthyl,
fluorenyl, phenanthryl, indenyl, and pyrenyl. These substituents
may be further substituted. These substituents may form a ring by
binding to each other via a single bond, substituted or
unsubstituted methylene, an oxygen atom, or a sulfur atom. In the
case of forming the ring, it is preferable that the substituents
bind to each other via a single bond or dimethylmethylene to form
the ring.
[0047] The arylamine compound (X) having a structure in which two
triphenylamine structures are joined within a molecule via a single
bond or a divalent group that does not contain a heteroatom, for
use in the organic EL device of the present invention, can be used
as a constitutive material of a hole injection layer, a hole
transport layer, a light emitting layer, an electron blocking
layer, or a capping layer of an organic EL device.
[0048] In the organic EL device of the present invention, the
thickness of the capping layer is preferably in a range of 30 nm to
120 nm, further preferably in a range of 40 nm to 80 nm.
[0049] In the organic EL device of the present invention, the
refractive index of the capping layer when the wavelength of light
transmitted through the capping layer is within a range of 530 nm
to 750 nm, is preferably 1.75 or more, further preferably 1.80 or
more.
[0050] In the organic EL device of the present invention, the
capping layer may be prepared by laminating two or more kinds of
different constitutive materials.
Effects of the Invention
[0051] The organic EL device of the present invention can be
greatly improved in light extraction efficiency because of having
the capping layer that is provided outside the transparent or
semitransparent electrode and that has a refractive index higher
than that of the semitransparent electrode. Since a specific
arylamine compound having a structure in which two triphenylamine
structures are joined within a molecule via a single bond or a
divalent group that does not contain a heteroatom, is used for the
capping layer, a film can be formed at a temperature of 400.degree.
C. or lower to prevent the damage of a light emitting device.
Further, a high-definition mask is used to optimize the extraction
efficiency of light of each color, and the organic EL device can be
suitably applied to a full-color display to permit the display of a
clear, light image with high color purity.
[0052] In the organic EL device of the present invention, since a
material for the organic EL device having a high refractive index
and excelling in thin film stability and durability is used as the
material for the capping layer, light extraction efficiency can be
greatly improved in comparison with conventional organic EL
devices. Further, the organic EL device of high efficiency with a
long life can be achieved.
BRIEF DESCRIPTION OF THE DRAWINGS
[0053] FIG. 1 is a diagram illustrating the configuration of the
organic EL devices of Examples 3 to 10 and Comparative Example
1.
MODE FOR CARRYING OUT THE INVENTION
[0054] The arylamine compound having a structure in which two
triphenylamine structures are joined within a molecule via a single
bond or a divalent group that does not contain a heteroatom,
represented by the general formula (1) and suitably used for the
organic EL device of the present invention, may be synthesized by a
known method (refer to Patent documents 3 to 5, for example).
[0055] The following presents specific examples of particularly
preferred compounds among the arylamine compounds (X') each having
a structure in which two triphenylamine structures are joined
within a molecule via a single bond or a divalent group that does
not contain a heteroatom, represented by the general formula (1)
and suitably used for the organic EL device of the present
invention. The present invention, however, is not restricted to
these compounds.
##STR00006## ##STR00007## ##STR00008## ##STR00009## ##STR00010##
##STR00011## ##STR00012## ##STR00013## ##STR00014## ##STR00015##
##STR00016## ##STR00017## ##STR00018## ##STR00019##
##STR00020##
[0056] The following presents specific examples of preferred
compounds in addition to the arylamine compounds (X') each having a
structure in which two triphenylamine structures are joined within
a molecule via a single bond or a divalent group that does not
contain a heteroatom, represented by the general formula (1) in the
arylamine compounds (X) each having a structure in which two
triphenylamine structures are joined within a molecule via a single
bond or a divalent group that does not contain a heteroatom,
suitably used for the organic EL device of the present invention.
The present invention, however, is not restricted to these
compounds.
##STR00021##
[0057] These compounds were purified by methods such as column
chromatography, adsorption using silica gel, activated carbon,
activated clay, or the like, and recrystallization or
crystallization using a solvent, and purified by sublimation or the
like in the end. Melting points, glass transition points (Tg), and
refractive indexes were measured as physical values. The melting
point can be used as an index of vapor deposition property, the
glass transition point (Tg) as an index of stability in a thin film
state, and the refractive index as an index in regard to the
improvement of light extraction efficiency.
[0058] The melting points and the glass transition points (Tg) were
measured using powder, with a high-sensitive differential scanning
calorimeter (DSC3100S made by Bruker AXS).
[0059] For the measurement of the refractive indexes, a thin film
of 60 nm was fabricated on a silicon substrate, and a compact
high-speed spectroscopic ellipsometer (UNECS-2000 made by Ulvac,
Inc.) was used.
[0060] The organic EL device of the present invention may have a
structure including an anode made of metal, a hole transport layer,
a light emitting layer, an electron transport layer, a
semitransparent cathode, and a capping layer successively formed on
a glass substrate in a light emitting device of top emission
structure, optionally with a hole injection layer between the anode
and the hole transport layer, an electron blocking layer between
the hole transport layer and the light emitting layer, a hole
blocking layer between the light emitting layer and the electron
transport layer, and an electron injection layer between the
electron transport layer and the cathode. Some of the organic
layers in this multilayer structure may be omitted or combined. For
example, the organic EL device may be configured to combine the
hole transport layer with the electron blocking layer and to
combine the electron transport layer with the hole blocking layer.
The total of film thickness of the respective layers of the organic
EL device is preferably about 200 nm to 750 nm, further preferably
about 350 nm to 600 nm. The film thickness of the capping layer is
preferably 30 nm to 120 nm, for example, and further preferably 40
nm to 80 nm. In this case, excellent light extraction efficiency
can be obtained. The film thickness of the capping layer may be
suitably changed according to the kind of a light emitting material
used for the light emitting device, the thickness of the organic EL
device excluding the capping layer, and the like.
[0061] An electrode material with a large work function such as ITO
or gold is used for the anode of the organic EL device of the
present invention.
[0062] The hole injection layer of the organic EL device of the
present invention may be made of materials, the examples of which
include an arylamine compound having a structure in which three or
more triphenylamine structures are joined within a molecule via a
single bond or a divalent group that does not contain a heteroatom,
such as starburst-type triphenylamine derivatives and various
triphenylamine tetramers; porphyrin compounds represented by copper
phthalocyanine; accepting heterocyclic compounds such as hexacyano
azatriphenylene; and coating-type polymer materials. These
materials may be individually formed into films, or may be used as
a single layer formed into a film as a mixture with other
materials, or may be formed into a laminated structure of
individually formed layers, a laminated structure of mixedly formed
layers, or a laminated structure of the individually formed layer
and the mixedly formed layer. These materials may be formed into a
thin film by a vapor deposition method or other known methods such
as a spin coating method and an inkjet method.
[0063] Preferred examples of material used for the hole transport
layer of the organic EL device of the present invention include
N,N'-diphenyl-N,N'-di(m-tolyl)benzidine (hereinafter referred to as
TPD), N,N'-diphenyl-N,N'-di(.alpha.-naphthyl)benzidine (hereinafter
referred to as NPD), 1,1-bis[4-(di-4-tolylamino)phenyl]cyclohexane
(hereinafter referred to as TAPC), particularly an arylamine
compound having a structure in which two triphenylamine structures
are joined within a molecule via a single bond or a divalent group
that does not contain a heteroatom, represented by the general
formula (1), such as N,N,N',N'-tetrabiphenylylbenzidine, and an
arylamine compound having a structure in which three or more
triphenylamine structures are joined within a molecule via a single
bond or a divalent group that does not contain a heteroatom, such
as various triphenylamine trimers and tetramers. These materials
may be individually formed into films, or may be used as a single
layer formed into a film as a mixture with other materials, or may
be formed into a laminated structure of individually formed layers,
a laminated structure of mixedly formed layers, or a laminated
structure of the individually formed layer and the mixedly formed
layer. These materials may be formed into a thin film by a vapor
deposition method or other known methods such as a spin coating
method and an inkjet method.
[0064] Material used for the hole injection layer or the hole
transport layer may be obtained by p-doping trisbromophenylamine
hexachloroantimony or the like into the material commonly used for
these layers, or may be, for example, polymer compounds each having
a TPD structure as a part of the compound structure.
[0065] Examples of material used for the electron blocking layer of
the organic EL device of the present invention can be compounds
having an electron blocking effect, including carbazole derivatives
such as 4,4',4''-tri(N-carbazolyl)triphenylamine (hereinafter
referred to as TCTA), 9,9-bis[4-(carbazol-9-yl)phenyl]fluorene,
1,3-bis(carbazol-9-yl)benzene (hereinafter referred to as mCP), and
2,2-bis(4-carbazol-9-ylphenyl)adamantane (hereinafter referred to
as Ad-Cz); and compounds having a triphenylsilyl group and a
triarylamine structure, as represented by
9-[4-(carbazol-9-yl)phenyl]-9-[4-(triphenylsilyl)phenyl]-9H-fluorene.
These materials may be individually formed into films, or may be
used as a single layer formed into a film as a mixture with other
materials, or may be formed into a laminated structure of
individually formed layers, a laminated structure of mixedly formed
layers, or a laminated structure of the individually formed layer
and the mixedly formed layer. These materials may be formed into a
thin film by a vapor deposition method or other known methods such
as a spin coating method and an inkjet method.
[0066] Examples of material used for the light emitting layer of
the organic EL device of the present invention can be quinolinol
derivative metal complexes such as Alq.sub.3, various metal
complexes, anthracene derivatives, bis(styryl)benzene derivatives,
pyrene derivatives, oxazole derivatives, and polyparaphenylene
vinylene derivatives. The light emitting layer may include a host
material and a dopant material. Examples of the host material can
be thiazole derivatives, benzimidazole derivatives, and polydialkyl
fluorene derivatives, in addition to the above light-emitting
materials. Examples of the dopant material can be quinacridone,
coumarin, rubrene, perylene, derivatives thereof, benzopyran
derivatives, rhodamine derivatives, and aminostyryl derivatives.
These materials may be individually formed into films, or may be
used as a single layer formed into a film as a mixture with other
materials, or may be formed into a laminated structure of
individually formed layers, a laminated structure of mixedly formed
layers, or a laminated structure of the individually formed layer
and the mixedly formed layer.
[0067] The light-emitting material may be a phosphorescent
light-emitting material. Phosphorescent materials as metal
complexes of metals such as iridium and platinum may be used as the
phosphorescent light-emitting material. Examples of the
phosphorescent materials can be green phosphorescent materials such
as Ir(ppy).sub.3, blue phosphorescent materials such as FIrpic and
FIr6, and red phosphorescent materials such as Btp.sub.2Ir(acac).
As the host materials, examples of hole injecting and transporting
host materials can be carbazole derivatives such as
4,4'-di(N-carbazolyl)biphenyl (hereinafter referred to as CBP),
TCTA, and mCP, and examples of electron transporting host materials
can be p-bis(triphenylsilyl)benzene (hereinafter referred to as
UGH2) and
2,2',2''-(1,3,5-phenylene)-tris(1-phenyl-1H-benzimidazole)
(hereinafter referred to as TPBI) to produce a high-performance
organic EL device.
[0068] In order to avoid concentration quenching, it is preferable
to dope the host material with the phosphorescent light-emitting
material by co-evaporation in a range of 1 to 30 weight percent to
the whole light emitting layer.
[0069] These materials may be formed into a thin film by using a
vapor deposition method or other known methods such as a spin
coating method and an inkjet method.
[0070] The hole blocking layer of the organic EL device of the
present invention may be formed by using hole blocking compounds
such as metal complexes of phenanthroline derivatives, e.g.
bathocuproin (hereinafter referred to as BCP), metal complexes of
quinolinol derivatives, e.g. aluminum(III)
bis(2-methyl-8-quinclinate)-4-phenylphenolate (hereinafter referred
to as BAlq), various rare earth complexes, triazole derivatives,
triazine derivatives, and oxadiazole derivatives. These materials
may also serve as the material of the electron transport layer.
These materials may be individually formed into films, or may be
used as a single layer formed into a film as a mixture with other
materials, or may be formed into a laminated structure of
individually formed layers, a laminated structure of mixedly formed
layers, or a laminated structure of the individually formed layer
and the mixedly formed layer. These materials may be formed into a
thin film by a vapor deposition method or other known methods such
as a spin coating method and an inkjet method.
[0071] The electron transport layer of the organic EL device of the
present invention may be formed by using metal complexes of
quinolinol derivatives such as Alq.sub.3 and BAlq, various metal
complexes, triazole derivatives, triazine derivatives, oxadiazole
derivatives, thiadiazole derivatives, pyridoindole derivatives,
carbodiimide derivatives, quinoxaline derivatives, phenanthroline
derivatives, and silole derivatives. These materials may be
individually formed into films, or may be used as a single layer
formed into a film as a mixture with other materials, or may be
formed into a laminated structure of individually formed layers, a
laminated structure of mixedly formed layers, or a laminated
structure of the individually formed layer and the mixedly formed
layer. These materials may be formed into a thin film by a vapor
deposition method or other known methods such as a spin coating
method and an inkjet method.
[0072] The electron injection layer of the organic EL device of the
present invention may be formed by using alkali metal salts such as
lithium fluoride and cesium fluoride; alkaline earth metal salts
such as magnesium fluoride; and metal oxides such as aluminum
oxide. However, the electron injection layer may be omitted in the
preferred selection of the electron transport layer and the
cathode.
[0073] The electron injection layer or the electron transport layer
may be one obtained by the N-doping of metals such as cesium in the
materials commonly used for these layers.
[0074] The semitransparent cathode of the organic EL device of the
present invention may be made of an electrode material having a low
work function such as aluminum; an alloy having an even lower work
function such as a magnesium-silver alloy, a magnesium-calcium
alloy, a magnesium-indium alloy, or an aluminum-magnesium alloy; or
ITO or EZO as an electrode material.
[0075] The capping layer of the organic EL device of the present
invention is preferably made of an arylamine compound having a
structure in which two triphenylamine structures are joined within
a molecule via a single bond or a divalent group that does not
contain a heteroatom, represented by the general formula (1), such
as N,N,N',N'-tetrabiphenylylbenzidine. These materials may be
individually formed into films, or may be used as a single layer
formed into a film as a mixture with other materials, or may be
formed into a laminated structure of individually formed layers, a
laminated structure of mixedly formed layers, or a laminated
structure of the individually formed layer and the mixedly formed
layer. These materials may be formed into a thin film by a vapor
deposition method or other known methods such as a spin coating
method and an inkjet method.
[0076] FIG. 1 shows the organic EL device of top emission
structure. The present invention, however, is not restricted to the
organic EL device of top emission structure but is also applicable
to an organic EL device of bottom emission structure and an organic
EL device of dual emission structure that emits light from both top
and bottom directions. In these cases, an electrode present in a
direction to extract light from a light emitting device to the
exterior is required to be transparent or semitransparent.
[0077] It is preferable that the refractive index of the material
that composes the capping layer is larger than that of an adjacent
electrode. That is, light extraction efficiency in the organic EL
device is improved by the capping layer. Its effect, however, is
valid because the effect of light interference is larger when the
reflectance at an interface between the capping layer and material
in contact with the capping layer is larger. Consequently, the
refractive index of the material that composes the capping layer is
preferably larger than that of the adjacent electrode, and the
refractive index is required to be 1.70 or more, further preferably
1.75 or more, and particularly preferably 1.80 or more.
[0078] The following describes an embodiment of the present
invention in more detail based on Examples. The present invention,
however, is not restricted to the following Examples.
Example 1
[0079] The melting points and the glass transition points of the
compounds of the present invention were determined using a
high-sensitive differential scanning calorimeter (DSC 3100S made by
Bruker AXS).
TABLE-US-00001 Glass Melting transition point point Exemplified
Compound (1-1) 265.degree. C. 132.degree. C. Exemplified Compound
(1-13) 216.degree. C. 103.degree. C. Exemplified Compound (1-14)
218.degree. C. 160.degree. C. Exemplified Compound (1-17)
273.degree. C. 108.degree. C. Exemplified Compound (1-18)
266.degree. C. 106.degree. C. Exemplified Compound (1-27)
258.degree. C. 126.degree. C. Exemplified Compound (1-32)
153.degree. C. 107.degree. C. Exemplified Compound (1-33)
210.degree. C. 113.degree. C. Exemplified Compound (1-36)
160.degree. C. 125.degree. C. Exemplified Compound (1-37)
168.degree. C. 144.degree. C. Exemplified Compound (1-46)
251.degree. C. 128.degree. C.
[0080] The compounds of the present invention have the glass
transition points of 100.degree. C. or higher. This indicates that
the compounds of the present invention have a stable thin-film
state.
Example 2
[0081] A vapor-deposited film with a film thickness of 60 nm was
fabricated on a silicon substrate using the compounds of the
present invention, and the refractive indexes of 633 nm were
measured using the compact high-speed spectroscopic ellipsometer
(UNECS-2000 made by Ulvac, Inc.).
TABLE-US-00002 Refractive Index Exemplified Compound (1-1) 1.81
Exemplified Compound (1-13) 1.78 Exemplified Compound (1-14) 1.76
Exemplified Compound (1-17) 1.79 Exemplified Compound (1-18) 1.88
Exemplified Compound (1-27) 1.82 Exemplified Compound (1-32) 1.80
Exemplified Compound (1-33) 1.89 Exemplified Compound (1-36) 1.76
Exemplified Compound (1-37) 1.85 Exemplified Compound (1-42) 1.76
Exemplified Compound (1-46) 1.78 Comparative Compound (Alq.sub.3)
1.70
[0082] The compounds of the present invention thus pave values
larger than the refractive index 1.70 of Comparative Compound
(Alq.sub.3), and large improvement of light extraction efficiency
in an organic EL device can be expected.
Example 3
[0083] The organic EL device was fabricated by vapor-depositing a
hole injection layer 3, a hole transport layer 4, a light emitting
layer 5, an electron transport layer 6, an electron injection layer
7, a cathode 8 and a capping layer 9 in this order on a glass
substrate 1 on which a reflecting ITO electrode was formed as a
metal anode 2 beforehand as shown in FIG. 1.
[0084] Specifically, the glass substrate 1 having ITO (thickness
150 nm) formed thereon was subjected to ultrasonic washing in
isopropyl alcohol for 20 minutes and then dried for 10 minutes on a
hot plate heated to 250.degree. C. After UV ozone treatment for 2
minutes, the glass substrate with ITO was installed in a vacuum
vapor deposition apparatus, and the pressure was reduced to 0.001
Pa or lower. This was followed by formation of the hole injection
layer 3 by forming Compound 2 of the structural formula below to
cover the metal anode 2 in a film thickness of 60 nm at a vapor
deposition rate of 6 nm/min. The hole transport layer 4 was then
formed on the hole injection layer 3 by forming Exemplified
Compound (1-13) of the structural formula above in a film thickness
of 40 nm at a vapor deposition rate of 6 nm/min. The light emitting
layer 5 was formed on the hole transport layer 4 in a film
thickness of 30 nm by dual vapor deposition of Compound 3 of the
structural formula below and Compound 4 of the structural formula
below at a vapor deposition rate ratio of Compound 3:Compound
4=5:95'. The electron transport layer 6 was formed on the light
emitting layer 5 by forming Compound 5 of the structural formula
below in a film thickness of 30 nm at a vapor deposition rate of 6
nm/min. The electron injection layer 7 was formed on the electron
transport layer 6 by forming lithium fluoride in a film thickness
of 0.5 nm at a vapor deposition rate of 0.6 nm/min. The cathode 8
was formed on the electron injection layer 7 by forming a magnesium
silver alloy in a film thickness of 10 nm. Finally, Exemplified
Compound (1-13) was formed as the capping layer 9 in a film
thickness of 60 nm at a vapor deposition rate of 6 nm/min. The
characteristics of the thus fabricated organic EL device were
measured in the atmosphere at an ordinary temperature.
[0085] Table 1 summarizes the results of emission characteristics
measurements performed by applying DC voltage to the fabricated
organic EL device.
##STR00022## ##STR00023##
Example 4
[0086] An organic EL device was fabricated under the same
conditions used in Example 3, except that the capping layer 9 was
formed by forming Exemplified Compound (1-17) in a thickness of 60
nm, instead of using Exemplified Compound (1-13). The
characteristics of the fabricated organic EL device were measured
in the atmosphere at an ordinary temperature. Table 1 summarizes
the results of the emission characteristics measurements performed
by applying DC voltage to the fabricated organic EL device.
Example 5
[0087] An organic EL device was fabricated under the same
conditions used in Example 3, except that the capping layer 9 was
formed by forming Exemplified Compound (1-18) in a thickness of 60
nm, instead of using Exemplified Compound (1-13). The
characteristics of the fabricated organic EL device were measured
in the atmosphere at an ordinary temperature. Table 1 summarizes
the results of the emission characteristics measurements performed
by applying DC voltage to the fabricated organic EL device.
Example 6
[0088] An organic EL device was fabricated under the same
conditions used in Example 3, except that the capping layer 9 was
formed by forming Exemplified Compound (1-27) in a thickness of 60
nm, instead of using Exemplified Compound (1-13). The
characteristics of the fabricated organic EL device were measured
in the atmosphere at an ordinary temperature. Table 1 summarizes
the results of the emission characteristics measurements performed
by applying DC voltage to the fabricated organic EL device.
Example 7
[0089] An organic EL device was fabricated under the same
conditions used in Example 3, except that the capping layer 9 was
formed by forming Exemplified Compound (1-32) in a thickness of 60
nm, instead of using Exemplified Compound (1-13). The
characteristics of the fabricated organic EL device were measured
in the atmosphere at an ordinary temperature. Table 1 summarizes
the results of the emission characteristics measurements performed
by applying DC voltage to the fabricated organic EL device.
Example 8
[0090] An organic EL device was fabricated under the same
conditions used in Example 3, except that the capping layer 9 was
formed by forming Exemplified Compound (1-33) in a thickness of 60
nm, instead of using Exemplified Compound (1-13). The
characteristics of the fabricated organic EL device were measured
in the atmosphere at an ordinary temperature. Table 1 summarizes
the results of the emission characteristics measurements performed
by applying DC voltage to the fabricated organic EL device.
Example 9
[0091] An organic EL device was fabricated under the same
conditions used in Example 3, except that the capping layer 9 was
formed by forming Exemplified Compound (1-36) in a thickness of 60
nm, instead of using Exemplified Compound (1-13). The
characteristics of the fabricated organic EL device were measured
in the atmosphere at an ordinary temperature. Table 1 summarizes
the results of the emission characteristics measurements performed
by applying DC voltage to the fabricated organic EL device.
Example 10
[0092] An organic EL device was fabricated under the same
conditions used in Example 3, except that the capping layer 9 was
formed by forming Exemplified Compound (1-37) in a thickness of 60
nm, instead of using Exemplified Compound (1-13). The
characteristics of the fabricated organic EL device were measured
in the atmosphere at an ordinary temperature. Table 1 summarizes
the results of the emission characteristics measurements performed
by applying DC voltage to the fabricated organic EL device.
Comparative Example 1
[0093] An organic EL device was fabricated under the same
conditions used in Example 3, except that the capping layer 9 was
formed by forming Alq.sub.3 in a thickness of 60 nm, instead of
using Exemplified Compound (1-13). The characteristics of the
fabricated organic EL device were measured in the atmosphere at an
ordinary temperature. Table 1 summarizes the results of the
emission characteristics measurements performed by applying DC
voltage to the fabricated organic EL device.
TABLE-US-00003 TABLE 1 Current Power External Luminance efficiency
efficiency quantum Voltage [V] [cd/m.sup.2] [cd/A] [lm/W]
efficiency [%] (@10 mA/cm.sup.2) (@10 mA/cm.sup.2) (@10
mA/cm.sup.2) (@10 mA/cm.sup.2) (@10 mA/cm.sup.2) Ex. 3 Exemplified
4.17 538 5.38 4.05 10.94 Compound (1-13) Ex. 4 Exemplified 4.11 504
5.04 3.85 10.45 Compound (1-17) Ex. 5 Exemplified 4.13 526 5.26
4.00 10.82 Compound (1-18) Ex. 6 Exemplified 4.18 507 5.07 3.81
10.35 Compound (1-27) Ex. 7 Exemplified 4.12 541 5.41 4.12 11.10
Compound (1-32) Ex. 8 Exemplified 4.16 531 5.31 4.00 10.81 Compound
(1-33) Ex. 9 Exemplified 4.14 506 5.06 3.83 10.40 Compound (1-36)
Ex. 10 Exemplified 4.11 528 5.28 4.03 10.89 Compound (1-37) Com.
Alq.sub.3 4.15 496 4.96 3.75 10.20 Ex. 1
[0094] As shown in Table 1, the driving voltage at a current
density of 10 mA/cm.sup.2 in Examples 3 to 10 was substantially
equivalent to that in Comparative Example 1 using Alq.sub.3, while
luminance, current efficiency and power efficiency were all
improved. Further, a great improvement in external quantum
efficiency could be confirmed. This indicates that light extraction
efficiency can be greatly improved by containing, in the capping
layer, a material having a high refractive index and suitably used
for the organic EL device of the present invention.
INDUSTRIAL APPLICABILITY
[0095] As demonstrated above, the arylamine compound having a
structure in which two triphenylamine structures are joined within
a molecule via a single bond or a divalent group that does not
contain a heteroatom, suitably used for the organic EL device of
the present invention, excels as the compound for the organic EL
device because of having a high refractive index, attaining a great
improvement in light extraction efficiency and having a stable
thin-film state. High efficiency can be obtained, and durability
can be improved by fabricating the organic EL device using this
compound. The use of this compound having no absorption in the
respective wavelength ranges of blue, green, and red is
particularly suitable in the case of displaying a clear, light
image with high color purity. For example, development to
application of domestic electrical appliances and illumination can
be achieved.
DESCRIPTION OF REFERENCE NUMERAL
[0096] 1 Glass substrate [0097] 2 Metal anode [0098] 3 Hole
injection layer [0099] 4 Hole transport layer [0100] 5 Light
emitting layer [0101] 6 Electron transport layer [0102] 7 Electron
injection layer [0103] 8 Cathode [0104] 9 Capping layer
* * * * *