U.S. patent application number 10/126585 was filed with the patent office on 2003-03-06 for compound for red organic el device and organic el device using the same.
This patent application is currently assigned to LG Electronics Inc.. Invention is credited to Kim, Dong-Uk, Tak, Yoon-Heung.
Application Number | 20030044644 10/126585 |
Document ID | / |
Family ID | 19536959 |
Filed Date | 2003-03-06 |
United States Patent
Application |
20030044644 |
Kind Code |
A1 |
Kim, Dong-Uk ; et
al. |
March 6, 2003 |
Compound for red organic EL device and organic EL device using the
same
Abstract
Compound for a red organic EL device and an organic EL device
using the same, which can improve an luminance efficiency, an
emitting light color and a device stability, the compound of the
following structural formula: 1 1) Wherein G1 and G2 are identical
or different electron withdrawing groups except a case when both of
G1 and G2 are cyano groups, or G1 and G2 are electron withdrawing
groups interconnected with a molecular chain to form a cyclic
compound or a heterocyclic compound; 2) And, wherein the R1 or the
R2 is any one selected from a substituted or unsubstituted alkyl
group (with 1.about.5 carbons), a substituted or unsubstituted aryl
group and --CH.dbd.CH-A1, the chemical formula A1 being a
4-dialklyamino-phenyl, a 4-dialkylamino-2-alkoxyphenyl, a
julolidine, an 8-alkoxy julolidine, a diphenylaminophenyl, a
diphenylaminophenyl having an alkyl group substituted therein, or a
diphenylaminophenyl having an alkoxy group substituted therein
where the alkyl or the alkoxy has 1.about.5 carbons; 3) And,
wherein X is O, N, Se or S.
Inventors: |
Kim, Dong-Uk; (Seoul,
KR) ; Tak, Yoon-Heung; (Yongin-si, KR) |
Correspondence
Address: |
FLESHNER & KIM, LLP
P.O. Box 221200
Chantilly
VA
20153-1200
US
|
Assignee: |
LG Electronics Inc.
|
Family ID: |
19536959 |
Appl. No.: |
10/126585 |
Filed: |
April 22, 2002 |
Related U.S. Patent Documents
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Application
Number |
Filing Date |
Patent Number |
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10126585 |
Apr 22, 2002 |
|
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09298838 |
Apr 26, 1999 |
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6451456 |
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Current U.S.
Class: |
428/690 ;
252/301.16; 313/504; 428/917 |
Current CPC
Class: |
H01L 51/5012 20130101;
H01L 51/0065 20130101; Y10S 428/917 20130101; H01L 51/0051
20130101; H01L 51/0067 20130101; H01L 51/0081 20130101; C09K 11/06
20130101 |
Class at
Publication: |
428/690 ;
428/917; 313/504; 252/301.16 |
International
Class: |
H05B 033/14; C09K
011/06 |
Foreign Application Data
Date |
Code |
Application Number |
Apr 30, 1998 |
KR |
15694/1998 |
Claims
What is claimed is:
1. A compound of the following structural formula: 71) Wherein G1
and G2 are identical or different electron withdrawing groups
except a case when both of G1 and G2 are cyano groups, or G1 and G2
are electron withdrawing groups interconnected with a molecular
chain to form a cyclic compound or a heterocyclic compound; 2) And,
wherein the R1 or the R2 is any one selected from a substituted or
unsubstituted alkyl group (with 1.about.5 carbons), a substituted
or unsubstituted aryl group and --CH.dbd.CH-A1, the chemical
formula A1 being a 4-dialklyamino-phenyl, a
4-dialkylamino-2-alkoxyphenyl, a julolidine, an 8-alkoxy
julolidine, a diphenylaminophenyl, a diphenylaminophenyl having an
alkyl group substituted therein, or a diphenylaminophenyl having an
alkoxy group substituted therein where the all or the alkoxy has
1.about.5 carbons; 3) And, wherein X is O, N, Se or S.
2. A compound as claimed in claim 1, wherein the identical or
different electron withdrawing groups of G1 and G2 except a case
when both of G1 and G2 are cyano groups are materials selected
independently from each other from cyano, acyl, alkylcabonyl,
alkoxycarbonyl, nitroaryl, cyanoaryl, alkylsulfonyl, fluorsulfonyl,
nitro, oxadiazoyl, thiadiazoyl, triazoyl, N-substituted triazoyl,
benzoxazoyl, benzodiazoyl, or benzothiazoyl.
3. A compound as claimed in claim 1, wherein the electron
withdrawing groups of G1 and G2 interconnected with a molecular
chain to form a cyclic compound or a heterocyclic compound are
materials selected from 1,3-indandione, 1,3-cyclohexanedione,
5,5-dimethyl-1,3-cyclohexanedione, 1,3-dioxane-4,6-dione,
2-isoxanzoline-5-one, 2-thiobarbituric acid, barbituric acid,
1,3-dialkyl-2-thiobarbituric acid, 1,3-dialkyl-barbituric acid,
pyrazolinone, isoxazolinone, oxindole,
2,4,6-triketohexahydropyrimidine, 2-thio-2,4-thiazolidinedinone,
thianaphthenone, 2-thio-2,5-thiazolidinedione,
2,4-thiazolidinedione, thiazolidinone, 4-thiazolinone,
1-amino-2-oxazolin-4-one, 2,4-imidazolidinedione,
2-thio-2,4-imidazolidinedione, 2-imidazolin-5-one and
furan-5-one.
4. A compound as claimed in claim 1, wherein 1,3-indandione which
is the electron withdrawing groups of G1 and G2 interconnected with
a molecular chain has one or more than one selected from a
substituted or unsubstituted alkyl group (with 1.about.15 carbons),
a alkoxy group(with 1.about.15 carbons), a substituted or
unsubstituted aryl group, a halogen group, an alkylsulfuric
group(the alkyl with 1.about.15 carbons), an arylsulfuric group, an
alkylamino group (the alkyl with 1.about.15 carbons), an arylamino
group, and a cyano group, substituted therein.
5. A compound as claimed in claim 1, wherein the G1 and G2 are an
1,3-indandione which is electron withdrawing groups interconnected
with a molecular chain, the R1 is a methyl group, and the R2 is
--CH.dbd.CH-A1, where the A1 is 4-dimethylamino-phenyl.
6. A compound as claimed in claim 1, wherein the G1 and G2 are an
1,3-dimethyl-barbituric acid which is electron withdrawing groups
interconnected with a molecular chain, the R1 is a methyl group,
and the R2 is --CH.dbd.CH-A1, where the A1 is
4-dimethylamino-phenyl.
7. An organic electroluminescence(EL) device having a first
electrode, a second electrode and a stack of a plurality of organic
layers, the device comprising a light emitting layer of a compound
with the following structural formula: 81) Wherein G1 and G2 are
identical or different electron withdrawing groups except a case
when both of G1 and G2 are cyano groups. or G1 and G2 are electron
withdrawing groups interconnected with a molecular chain to form a
cyclic compound or a heterocyclic compound; 2) And, wherein the R1
or the R2 is any one selected from a substituted or unsubstituted
alkyl group (with 1.about.5 carbons), a substituted or
unsubstituted aryl group and --CH.dbd.CH-A1, the chemical formula
A1 being a 4-dialklyamino-phenyl, a 4-dialkylamino-2-alkoxyphenyl-
, a julolidine, an 8-alkoxy julolidine, a diphenylaminophenyl, a
diphenylaminophenyl having an alkyl group substituted therein, or a
diphenylaminophenyl having an alkoxy group substituted therein
where the alkyl or the alkoxy has 1.about.5 carbons; 3) And,
wherein X is O, N, Se or S.
8. A compound as claimed in claim 7, wherein the identical or
different electron withdrawing groups of G1 and G2 except a case
when both of G1 and G2 are cyano groups are materials selected
independently from each other from cyano, acyl, alkylcabonyl,
alkoxycarbonyl, nitroaryl, cyanoaryl, alkylsulfonyl, fluorsulfonyl,
nitro, oxadiazoyl, thiadiazoyl, triazoyl, N-substituted triazoyl,
benzoxazoyl, benzodiazoyl, or benzothiazoyl.
9. A compound as claimed in claim 7, wherein the electron
withdrawing groups of G1 and G2 interconnected with a molecular
chain are materials selected from 1,3-indandione,
1,3-cyclohexanedione, 5,5-dimethyl-1,3-cyclohexanedione,
1,3-dioxane-4,6-dione, 2-isoxanzoline-5-one, 2-thiobarbituric acid,
barbituric acid, 1,3-dialkyl-2-thiobarbituric acid,
1,3-dialkyl-barbituric acid, pyrazolinone, isoxazolinone, oxindole,
2,4,6-triketohexahydropyrimidine, 2-thio-2,4-thiazolidinedinone,
thianaphthenone, 2-thio-2,5-thiazolidinedi- one,
2,4-thiazolidinedione, thiazolidinone, 4-thiazolinone,
1-amino-2-oxazolin-4-one, 2,4-imidazolidinedione,
2-thio-2,4-imidazolidin- edione, 2-imidazolin-5-one and
furan-5-one.
10. A compound as claimed in claim 9, wherein 1,3-indandione which
is the electron withdrawing groups of G1 and G2 interconnected with
a molecular chain has one or more than one selected from a
substituted or unsubstituted alkyl group (with 1.about.15 carbons),
a alkoxy group(with 1.about.15 carbons), a substituted or
unsubstituted aryl group, a halogen group, an alkylsulfuric
group(the alkyl with 1.about.15 carbons), an arylsulfuric group, an
alkylamino group (the alkyl with 1.about.15 carbons), an arylamino
group, and a cyano group, substituted therein.
11. A compound as claimed in claim 7, wherein the G1 and G2 are an
1,3-indandione which is electron withdrawing groups interconnected
with a molecular chain, the R1 is a methyl group, and the R2 is
--CH.dbd.CH-A1, where the A1 is 4-dimethylamino-phenyl.
12. A compound as claimed in claim 7, wherein the G1 and G2 are an
1,3-dimethyl-barbituric acid which is electron withdrawing groups
interconnected with a molecular chain, the R1 is a methyl group,
and the R2 is --CH.dbd.CH-A1, where the A1 is
4-dimethylamino-phenyl.
13. An organic electroluminescence(EL) device having a first
electrode, a second electrode, and a stack of a plurality of
organic layers, the device comprising a light emitting layer doped
with a compound with the following structural formula: 91) Wherein
G1 and G2 are identical or different electron withdrawing groups
except a case when both of G1 and G2 are cyano groups, or G1 and G2
are electron withdrawing groups interconnected with a molecular
chain to form a cyclic compound or a heterocyclic compound; 2) And,
wherein the R1 or the R2 is any one selected from a substituted or
unsubstituted alkyl group (with 1.about.5 carbons), a substituted
or unsubstituted aryl group and --CH.dbd.CH-A1, the chemical
formula A1 being a 4-dialklyamino-phenyl, a
4-dialkylamino-2-alkoxyphenyl, a julolidine, an 8-alkoxy
julolidine, a diphenylaminophenyl, a diphenylaminophenyl having an
alkyl group substituted therein, or a diphenylaminophenyl having an
alkoxy group substituted therein where the alkyl or the alkoxy has
1.about.5 carbons; 3) And, wherein X is O, N, Se or S.
14. A compound as claimed in claim 13, wherein the identical or
different electron withdrawing groups of G1 and G2 except a case
when both of G1 and G2 are cyano groups are materials selected
independently from each other from cyano, acyl, alkylcabonyl,
alkoxycarbonyl, nitroaryl, cyanoaryl, alkylsulfonyl, fluorsulfonyl,
nitro, oxadiazoyl, thiadiazoyl, triazoyl, N-substituted triazoyl,
benzoxazoyl, benzodiazoyl, or benzothiazoyl.
15. A compound as claimed in claim 13, wherein the electron
withdrawing groups of G1 and G2 interconnected with a molecular
chain are materials selected from 1,3-indandione,
1,3-cyclohexanedione, 5,5-dimethyl-1,3-cyclohexanedione,
1,3-dioxane-4,6-dione, 2-isoxanzoline-5-one, 2-thiobarbituric acid,
barbituric acid, 1,3 -dialkyl-2-thiobarbituric acid,
1,3-dialkyl-barbituric acid, pyrazolinone, isoxazolinone, oxindole,
2,4,6-triketohexahydropyrimidine, 2-thio-2,4-thiazolidinone,
thianapthenone, 2-thio-2,5-thiazolidinedione,
2,4-thiazolidinedione, thiazolidinone, 4-thiazolinone,
1-amino-2-oxazolin4-one, 2,4-imidazolidinedione,
2-thio-2,4-imidazolidine- dione, 2-imidazolin-5-one and
furan-5-one.
16. A compound as claimed in claim 15, wherein 1,3-indandione which
is the electron withdrawing groups of G1 and G2 interconnected with
a molecular chain has one or more than one selected from a
substituted or unsubstituted alkyl group (with 1.about.15 carbons),
a alkoxy group(with 1.about.15 carbons), a substituted or
unsubstituted aryl group, a halogen group, an alkylsulfuric
group(the alkyl with 1.about.15 carbons), an arylsulfuric group, an
alkylamino group (the alkyl with 1.about.15 carbons), an arylamino
group, and a cyano group, substituted therein.
17. A compound as claimed in claim 13, wherein the G1 and G2 are an
1,3-indandione which is electron withdrawing groups interconnected
with a molecular chain, the R1 is a methyl group, and the R2 is
--CH.dbd.CH-A1, where the A1 is 4-dimethylamino-phenyl.
18. A compound as claimed in claim 13, wherein the G1 and G2 are an
1,3dimethyl-barbituric acid which is electron withdrawing groups
interconnected with a molecular chain, the R1 is a methyl group,
and the R2 is --CH.dbd.CH-A1, where the A1 is
4-dimethylamino-phenyl.
Description
BACKGROUND OF THE INVENTION
[0001] 1. Field of the Invention
[0002] The present invention relates to a display, and more
particularly, to a material for a red organic
electroluminescence(EL) device and an organic EL device using the
same.
[0003] 2. Background of the Related Art
[0004] As sizes of displays become the larger, demand for a flat
display which occupy less spaces increase, as one of which there is
the electroluminescence device. There are an inorganic
electroluminescence device and an organic electroluminescence
device depending on materials used therein. The inorganic
electroluminescence device is provided with a light emitting unit
to which a high electric field is applied for accelerating
electrons, so that the electrons collide onto and excite a
luminescent center therein to emit a light. And, the organic
electroluminescence device is provided with an electron injection
electrode(cathode) and a hole injection electrode(anode) from which
electrons and holes are injected into the light emitting unit, so
that the injected electrons and the holes are coupled into exciton,
to emit a light when the exciton drops from an exited state to a
ground state. While the inorganic electroluminescence device that
requires a strong electric field due to the above operation
principle requires a relatively high driving voltage of approx.
100.about.200V, because the organic electroluminescence device has
an advantage in that it is operable at a low voltage of
5.about.20V, there have been active studies on the organic
electroluminescence device. Besides, as the organic
electroluminescence device has excellent characteristics, such as a
wide angle of view, a fast response speed and a high contrast so
on, the organic electroluminescence device can be used as a pixel
of a graphic display, or a TV image display or a surface light
source, and as the organic electroluminescence device is thin and
light and has a good sense of color, the organic
electroluminescence device is suitable for a flat display of the
next generation.
[0005] A structure of a related art organic electroluminescence
device will be explained.
[0006] The related art organic electroluminescence device is
provided with a first electrode formed on a transparent substrate,
a hole injection and transport layer formed on the first electrode,
a light emitting layer formed on the hole injection and transport
layer, an electron injection and transport layer formed on the
light emitting layer, and a second electrode formed on the electron
injection and transport layer. Considering the operation of
electroluminescence devices as consisting of two processes, firstly
formation of the exciton(pair of electron-hole) and secondly its
decay, the former involves i)carrier injection, ii)carrier
transport and iii)carrier recombination, while the latter
encompasses a competition between radiative and non-radiative decay
channels. Since the disclosure of the organic electroluminescence
device by Kodak in 1987, many researchers in the world from Japan,
the U.K., and the U.S.A. and etc., participate in the practical
application and development of the organic electroluminescence
device. Currently, though many studies are undervay for materials
of the organic EL device, the following materials are in general
used as the organic EL device.
[0007] The hole transport layer is formed of triphenylamine
derivatives, such as
N,N'-diphenyl-N,N'-bis(3-methylphenyl)-(1,1'-biphenyl)-4,4'-diami-
ne(TPD) or
N,N'-dinaphthyl-N,N'-phenyl-(1,1'-biphenyl)-4,4'-diamine(NPD). And,
the electron transport layer is in general formed of alkyl metal
complex, such as tris(8-hydroxy quinolate) aluminum(Alq.sub.3). The
organic light emitting layer is formed of Alq.sub.3 as base with
dopant of organic EL dyes for adjusting color of lights. In the
meantime, a red EL device, a green EL device and a blue EL device
are required for realization of a fall color display, wherein
coumarine 6 or quinacridone derivatives are used as dopants in a
case of the green EL device, and
DCM(4-dicyanomethylene-2-p-dimethylaminostyryl-6-methyl4H-pyran)
derivatives are used as dopants in a case of the red EL device.
[0008] However, the related art organic EL device has the following
problems.
[0009] It is known that a stability of the green EL device has
reached to a practicable level. However, in the cases of the blue
EL device and the red EL device, colors of emitted lights and
stabilities are not reached to practicable levels and luminance
efficiencies are also not reached to a satisfactory level.
SUMMARY OF THE INVENTION
[0010] Accordingly, the present invention is directed to a material
for a red organic EL device and an organic EL device using the same
that substantially obviates one or more of the problems due to
limitations and disadvantages of the related art.
[0011] An object of the present invention is to provide a material
for a red organic EL device and an organic EL device using the
same, which can improve an luminance efficiency, an emitting light
color and a device stability.
[0012] Additional features and advantages of the invention will be
set forth in the description which follows, and in part will be
apparent from the description, or may be learned by practice of the
invention. The objectives and other advantages of the invention
will be realized and attained by the structure particularly pointed
out in the written description and claims hereof as well as the
appended drawings.
[0013] To achieve these and other advantages and in accordance with
the purpose of the present invention, as embodied and broadly
described, there is provided the compound of the following
structural formula: 2
[0014] 1) Wherein G1 and G2 are identical or different electron
withdrawing groups except a case when both of G1 and G2 are cyano
groups, or G1 and G2 are electron withdrawing groups interconnected
with a molecular chain to form a cyclic compound or a heterocyclic
compound;
[0015] 2) And, wherein the R1or the R2 is any one selected from a
substituted or unsubstituted alkyl group (with 1.about.5 carbons),
a substituted or unsubstituted aryl group and --CH.dbd.CH-A1, the
chemical formula A1 being a 4-dialklyamino-phenyl, a
4-dialkylamino-2-alkoxyphenyl- , a julolidine, an 8-alkoxy
julolidine, a diphenylaminophenyl, a diphenylaminophenyl having an
alkyl group substituted therein, or a diphenylaminophenyl having an
alkoxy group substituted therein where the alkyl or the alkoxy has
1.about.5 carbons;
[0016] 3) And, wherein X is O, N, Se or S.
[0017] In another aspect of the present invention, there is
provided an organic electroluminescence device having a first
electrode, a second electrode and a stack of a plurality of organic
layers, including a light emitting layer of a compound with the
aforementioned structural formula.
[0018] In further aspect of the present invention, there is
provided an organic electroluminescence device having a first
electrode, a second electrode and a stack of a plurality of organic
layers, including a light emitting layer doped with a compound with
the aforementioned structural formula.
[0019] It is to be understood that both the foregoing general
description and the following detailed description are exemplary
and explanatory and are intended to provide further explanation of
the invention as claimed.
BRIEF DESCRIPTION OF THE DRAWINGS
[0020] The accompanying drawings, which are included to provide a
further understanding of the invention and are incorporated in and
constitute a part of this specification, illustrate embodiments of
the invention and together with the description serve to explain
the principles of the invention:
[0021] In the drawings:
[0022] FIG. 1 illustrates a section showing an organic EL device
having a material in accordance with a preferred embodiment of the
present invention applied thereto;
[0023] FIG. 2 illustrates a graph showing IV-characteristics of the
organic EL device having
4-(1',3'-indandione)-2-p-dimethylaminostyryl-6-m- ethyl-4H-pyran of
the present invention and DCM-2 of the related art applied thereto,
respectively;
[0024] FIG. 3 illustrates a graph showing current densities of the
organic EL devices having
4-(1',3'-indandione)-2-p-dimethylaminostyryl-6-methyl-4- H-pyran of
the present invention DCM-2 of the related art applied thereto,
respectively;
[0025] FIG. 4 illustrates a graph showing current
density-brightness of the organic EL devices having
4-(1',3'-indandione)-2-p-dimethylaminostyry- l-6-methyl-4H-pyran of
the present invention and DCM-2 of the related art applied thereto,
respectively;
[0026] FIG. 5 illustrates a graph showing spectrums of the organic
EL devices having
4-(1',3'-indandione)-2-p-dimethylaminostyryl-6-methyl-4H-p- yran of
the present invention and DCM-2 of the related art applied thereto,
respectively; and
[0027] FIG. 6 illustrates a graph showing lifetimes of the organic
EL devices having
4-(1',3'-indandione)-2-p-dimethylaminostyryl-6-methyl-4H-p- yran of
the present invention and DCM-2 of the related art applied thereto,
respectively.
DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENT
[0028] The present invention suggests to modify a structure of
DCM(4-dicyanomethylene-2-p-dimethylaminostyryl-6-methyl-4H-pyran),
i.e., to modify electron withdrawing group and electron donating
group, to provide a compound of the following formula 3
[0029] 1) Wherein, G1 and G2 are identical or different electron
withdrawing groups except a case when both of G1 and G2 are cyano
groups, or electron withdrawing groups interconnected with a
molecular chain to form a cyclic compound or a heterocyclic
compound. The identical or different electron withdrawing groups of
G1 and G2 except a case when both of G1 and G2 are cyano groups are
preferably materials selected independently from cyano, acyl,
alkylcabonyl, alkoxycarbonyl, nitroaryl, cyanoaryl, alkylsulfonyl,
fluorsulfonyl, nitro, oxadiazoyl, thiadiazoyl, triazoyl,
N-substituted triazoyl, benzoxazoyl, benzodiazoyl, orbenzothiazoyl.
And, the electron withdrawing groups of G1 and G2 interconnected
with a molecular chain to form a cyclic compound or a heterocyclic
compound are preferably materials selected from 1,3-indandione,
1,3-cyclohexanedione, 5,5-dimethyl-1,3-cyclohexanedione,
1,3-dioxane-4,6-dione, 2-isoxanzoline-5-one,2-thiobarbituric acid,
barbituric acid, 1,3-dialkyl-2-thiobarbituric acid,
1,3-dialkyl-barbituric acid, pyrazolinone, isoxazolinone, oxindole,
2,4,6-triketohexahydropyrimidine, 2-thio-2,4-thiazolidinedinone,
thianaphthenone, 2-thio-2,5-thiazolidinedione,
2,4-thiazolidinedione, thiazolidinone, 4-thiazolinone,
1-amino-2-oxazolin-4-one, 2,4-imidazolidinedione,
2-thio-2,4-imidazolidinedione, 2-imidazolin-5-one and furan-5-one.
The electron withdrawing groups of G1 and G2 interconnected with a
molecular chain to form a cyclic compound or a heterocyclic
compound are more preferably materials selected from the following
structural formulae. 4
[0030] Where, R in the structural formulae of the electron
withdrawing groups is an alkyl group with 1.about.5 carbons or
hydrogen. And, 1,3-indandione which is the electron withdrawing
groups of G1 and G2 interconnected with a molecular chain may have
one or more than one selected from a substituted or unsubstituted
alkyl group(with 1.about.15 carbons), a alkoxy group(with
1.about.15 carbons), a substituted or unsubstituted aryl group, a
halogen group, an alkylsulfuric group(the alkyl with 1.about.15
carbons), an arylsulfuric group, an alkylamino group (the alkyl
with 1.about.15 carbons), an arylamino group, and a cyano group,
substituted therein. The substituted 1,3-indandione has the
following structural formula, where R and R' is the foregoing
substituted group 5
[0031] 2) And, wherein the R1 or the R2 is any one selected from a
substituted or unsubstituted alkyl group (with 1.about.5 carbons),
a substituted or unsubstituted aryl group and --CH.dbd.CH-A1. The
chemical formula A1 is a 4-dialklyamino-phenyl, a
4-dialkylamino-2-alkoxyphenyl, ajulolidine, an 8-alkoxy julolidine,
a diphenylaminophenyl, a diphenylaminophenyl having an alkyl group
substituted therein, or a diphenylaminophenyl having an alkyl group
substituted therein where the alkyl or the alkoxy has 1.about.5
carbons. The A1 is preferably selected from the following
substituents. 6
[0032] Where, R in above structural formulae is an alkyl group with
1.about.5 hydrogens or carbons, and R' is a hydrogen or methyl
group.
[0033] 3) And, wherein X is O, N, Se or S. In this instance, the
nitrogen atom may have a substituted or unsubstituted alkyl group,
a substituted or unsubstituted aryl group, aralkyl, cycloalkyl,
alkenyl, hydroxy, alkoxy, aryloxy, or halogen, substituted
therewith.
[0034] The compound of the present invention for organic EL device
may be used as a material for forming a light emitting layer or as
a dopant to be doped in the light emitting layer. When the compound
is used as the dopant, the compound of the present invention is
vacuum deposited on Alq.sub.3 and the like as a base in a mass
ratio of 0.0001-50% to Alq.sub.3, to form the light emitting
layer.
EXAMPLES
[0035] The present invention and advantages thereof will be further
explained in detail by way of examples.
Synthesis
Example 1
Synthesis of 4-(1',3'-indandione)-2,6-dimethyl-4H-pyran
[0036] As one of compounds of the present invention, there is
4-(1',3'-indandione)-2-p-dimethylaminostyryl-6-methyl-4H-pyran(called
"Rd-1") having one electron withdrawing group of 1,3-indandione and
one electron donating group of tertiary amine.
[0037] The Rd-1 may be prepared according to the following
process.
[0038] 2,6-dimethyl-.gamma.-pyran 0.85 g and 1,3-indandione 1 g are
dissolved in acetic anhydride solvent 20 ml and make reaction at a
reflux temperature for 24 hours, to obtain
4-(1',3'-indandione)-2,6-dimethyl-4H-- pyran 0.9 g. Instead of the
acetic anhydirde, other solvents may be used. Both the prepared
intermediate compound 4-(1', 3'-indandione)-2,6-dimethy- l4H-pyran
0.5 g and p-dimethylaminobenzaldehyde 0.38 g are dissolved in 10ml
ethanol solvent, 0.3 ml piperidine is dropped thereto, left for 24
hours at 90.degree. C. for reaction, to obtain 0.2 g of
4-(1',3'-indandione)-2-p-dimethylaminostyryl-6-methyl-4H-pyran,
i.e., "Rd-1". In this instance, other polar solvents including
alcohol solvent may be used instead of the ethanol solvent, and
other base may be used instead of the piperidine. The prepared
compound is dark violent colored solid. A molecular structure of
the Rd-1 is known by NMR and elementary analysis. NMR(CDCl.sub.3);
N--(CH.sub.3).sub.2 (2.16ppm, s, 6H), --CH.sub.3(3.04ppm, s, 3H),
aromatic and vinylic H(6.50-8.50 ppm, m, 12H). Elementary analysis:
actual measurement: C(80.6%), H(6.2%), N(3.7%), calculation;
C(78.3%), H(5.5%), N(3.7%).
[0039] Vacuum sublimation may be used to refine the prepared Rd-1
for use in the organic EL device. The 1,3 indandione group and the
amino group in the Rd-1, with opposite properties, interact to each
other through a covalent bond, to provide a quantum efficiency
better than the related art DCM derivatives and light emission
peaks of which a color purity of emitted light in a red wavelength
band is improved.
Example 2
Synthesis of 4-(dimethylbarbituric
acidic)-2-p-dimethylaminostyryl-6-methy- l4H-pyran
[0040] As another embodiment of the present invention,
4-(dimethylbarbituric
acidic)-2-p-dimethylaminostyryl-6-methyl-4H-pyran having one
electron withdrawing group of 1,3-dimethyl-barbituric acid and one
electron donating group of tertiary amine is prepared, wherein the
1,3-dimethyl-barbituric acid and the tertiary amine, with opposite
properties, interact to each other through a covalent bond, to
provide a quantum efficiency better than the related art DCM
derivatives and light emission peaks of which a color purity of
emitted light in a red wavelength band is improved.
[0041] The above compound may be prepared according to the
following process.
[0042] Both 5.3 g of 2,6-dimethyl-.gamma.-pyran and 5.3 g of
dimethyl barbituric acid are dissolved in 50 ml acetic anhydride
solvent, left for 5 min. at 25.degree. C.about.reflux temperature
for reaction, to obtain 4-(dimethylbarbituric
acidic)-2,6-dimethyl-4H-pyran. Both the prepared
4-(dimethylbarbituric acidic)-2,6-dimethyl4H-pyran 0.3 g and
p-dimethylaminobenzaldehyde 0.17 g are dissolved in ethanol solvent
15 ml, and piperidine 0.3 ml is dropped thereto, and left for
reaction for more than 5 min. at 25.degree. C..about.reflux
temperature, to obtain 4-(dimethylbarbituric
acidic)-2-p-dimethylaminostyryl-6-methyl-4H-pyran 0.7 g. The
prepared compound is dark violet colored solid. A molecular
structure of the compound is known by NMR and elementary analysis.
NMR(CDCl3); N--(CH.sub.3).sub.2 (2.18ppm, s, 6H), C--CH.sub.3 (3.04
ppm, s, 3H), CON--CH.sub.3 (3.05ppm, s, 3H), CON--CH.sub.3
(3.40ppm, s, 3H), aromatic and vinylic H (6.50.about.9.00ppm, m,
8H). Elementary analysis: actual measurement; C(70.3%), H(6.7%) and
N(11.2%), calculation; C(67.2%), H(5.9%) and N(10.7%).
[0043] Other compounds not explained herein may be prepared by
similar processes.
Fabrication and Performance of EL Device
Example 3
The Steps of Fabrication
[0044] One embodiment organic EL device having the compound of the
present invention applied thereto may be fabricated according to
the following steps.
[0045] (1) A first electrode is formed on a transparent substrate
to a thickness of approx. 100 nm.
[0046] (2) A hole injection layer of copper phthalocyanine(CuPc) is
formed on the first electrode to a thickness of approx. 10
nm.about.20 nm.
[0047] (3) A hole transport layer of
N,N'-dinaphthyl-N,N'-phenyl-(1,1'-bip- henyl)-4,4'-diamine (NPD) is
formed on the hole injection layer to a thickness of approx. 30
nm.about.50 nm.
[0048] (4) An organic Light emitting layer of
tris(8-hydroxy-quinolate) aluminum(Alq.sub.3) is deposited on the
hole transport layer to a thickness of approx. 40 nm.about.60 nm
and approx. 1% of dopant is added thereto.
[0049] (5) An electron injection layer of an alkali metal or alkali
earth metal compound is formed on the organic Light emitting layer
having the dopant deposited or not deposited thereon. And,
[0050] (6) A second electrode is formed on the electron injection
layer to a thickness of approx. 100 nm.about.200 nm. A layer of
Li.sub.2O may be formed between the electron injection layer and
the second electrode.
Example 4
EL Device with Rd-1 Doped Alq.sub.3 Light Emitting Layer
[0051] An organic EL device is fabricated as shown in FIG. 1. That
is, the organic EL device shown in FIG. 1 includes a transparent
substrate 1/a first electrode 3/a hole injection layer 5/a hole
transport layer 7/a light emitting layer 9/an electron transport
layer 11/an electron injection layer 13/a second electrode 15. The
light emitting layer 9 is formed of Alq.sub.3 doped with 1% Rd-1.
For comparison to the aforementioned organic EL device of the
present invention, an identical EL device doped with 1% DCM-2 of
the related art, instead of 1% Rd-1 of the present invention, is
fabricated.
Example 5
Performance of EL Device with Rd-1 Doped Light Emitting Layer
[0052] The experiments results of which are shown in FIGS.
2.about.6 are on organic EL devices of Alq3 doped with 1% DCM-2 and
1% Rd-1, respectively.
[0053] FIG. 2 illustrates a graph showing IV-characteristics of the
organic EL device having
4-(1',3'-indandione)-2-p-dimethylaminostyryl-6-m-
ethyl-4H-pyran(Rd-1) of the present invention and DCM-2 of the
related art applied thereto respectively, wherefrom general
characteristics of the organic EL devices can be known. From FIG.
2, it can be known that the IV-curves of the organic EL devices
having DCM-2 and Rd-1 applied thereto respectively are typical
diode IV-curves.
[0054] This can be clearly known from FIG. 2 which illustrates
current density curves of the two materials. That is, the devices
emit no lights in a negative voltage region, and have 5V of turn on
voltages and almost identical current densities. X-axis in FIG. 3
denotes electric fields, and Y-axis denotes current densities. The
electric field means a voltage on the device divided by a thickness
of the device. It can be known from FIG. 3 that the organic EL
devices having DCM-2 and Rd-1 applied thereto respectively have
almost identical current densities at a high field over
6.times.10.sup.6 V/cm.sup.2 and the organic EL device having Rd-1
applied thereto has a current density slightly lower than the
organic EL device having DCM-2 applied thereto at a low field.
[0055] FIG. 4 illustrates a graph showing current
density-brightness of the organic EL devices having
4-(1',3'-indandione)-2-p-dimethylaminostyry- l-6-methyl4H-pyran) of
the present invention and DCM-2 of the related art applied thereto
respectively, wherefrom it can be known that the organic EL device
having DCM-2 applied thereto has a brightness of approx. 2500
cd/m.sup.2 at a current density of 1A and the organic EL device
having Rd-1 applied thereto has a brightness of approx. 7000
cd/m.sup.2 at the same current density. The brightnesses were
results of measurements on one pixel smith an area of 9 mm.sup.2 by
a calibrated spectrascan PR650.
[0056] FIG. 5 illustrates a graph showing spectra of the organic EL
devices having
4-(1',3'-indandione)-2-p-dimethylaminostyryl-6-methyl-4H-p-
yran(Rd-1) of the present invention and DCM-2 of the related art
applied thereto respectively, wherefrom it can be known that the
organic EL device having DCM-2 applied thereto has a
wavelength(.lambda..sub.MAX) of a light emitted therefrom of 630 nm
and the organic EL device having Rd-1 applied thereto has a
wavelength of a light emitted therefrom of 650 nm, shifted further
toward red color than the case of DCM-2 by approx. 20 nm. It is
assumed that this is caused by the stronger electron attraction of
indandione in Rd-1 than cyano in DCM-2, that drops a conduction
band of Rd-1 to be lower than the DCM-2 and, in turn, makes an
internal blocking barrier, which is formed by the conduction band
of a substance and holds electrons to stay within an internal
boundary, of Rd-1 greater, to accumulate more electrons therein to
provide a greater probability of hole-electron coupling compared to
DCM-2, thereby improving a brightness of Rd-1 and shifting a
wavelength of a light emitted from the Rd-1 toward a red wavelength
by approx. 20 nm than DCM-2 due to such a band gap. And, in view of
structures, because the substituent of Rd-1 is more
three-dimensional and larger than DCM-2, the device with Rd-1 has a
longer lifetime.
[0057] FIG. 6 illustrates a graph showing lifetimes of the organic
EL devices having
4-(1',3'-indandione)-2-p-dimethylaminostyryl-6-methyl-4H-p-
yran(Rd-1) of the present invention and DCM-2 of the related art
applied thereto respectively, tested and measured under the same
conditions. The test condition is as follows; A sample driving
condition is 70 frames/sec, a duty cycle is {fraction (1/40)}, a
forward bias is 14V with a pulse width of 350 .mu.s, a reverse bias
is -12V with a pulse width of 44 .mu.s. And, a reverse condition is
1 Hz at a position of a middle of a frame pulse. An operating
lifetime is taken as a time period in which an initial brightness
drops by half at a room temperature. As a result of the
measurements, the operating lifetime of Rd-1 is longer by approx.
700 hours than DCM-2.
[0058] Summarizing all the results of measurements, it can be known
that the compounds of the present invention is more suitable to a
red organic EL device than the DCM of the related art in view of
performance and structure, which can be summarized as follows.
[0059] Because the compounds of the present invention for an
organic EL device have light emission peaks more shifted toward a
red wavelength band than DCM group, such as DCM-1 or DCM-2 used as
a red light emission material in the related art, an improved color
purity can be provided. That is, the organic EL device having the
compounds of the present invention applied thereto have light
emission peaks closer to a red wavelength band, which difference
provides significantly better color purity in red light and a
higher light emission efficiency than the related art DCM.
Moreover, the compounds of the present invention provide a longer
lifetime of the organic EL device when the compounds are applied
thereto.
[0060] It will be apparent to those skilled in the art that various
modifications and variations can be made in the material for a red
organic EL device and the organic EL device using the same of the
present invention without departing from the spirit or scope of the
invention. Thus, it is intended that the present invention cover
the modifications and variations of this invention provided they
come within the scope of the appended claims and their
equivalents.
* * * * *