NEW ORGANIC COMPOUND AND ORGANIC LIGHT EMITTING DEVICE USING
THE SAME
Technical Field
The present invention relates to a new organic compound
and an organic light emitting device using the same.
Background Art
In general, the so-called "organic light emitting"
phenomenon (organic electroluminescence) refers to a
phenomenon in which electric energy is transformed into light
energy by means of an organic substance. Particularly, when
an organic film is disposed between an anode and a cathode
and then electric potential is applied between both
electrodes, holes and electrons are injected into the organic
film from the anode and the cathode, respectively. When the
holes and; electrons injected as described above are
recombined, excitons are formed. Further, when the exitons
drop to a ground state, lights are emitted.
In addition to the above-described organic light
emitting mechanism in which light emission is made by
recombining of charges injected from both electrodes, there
is another mechanism in which holes and electrons are not
injected from external electrodes but are generated by an
amphoteric charge-generating layer under the application of
alternating current voltage, as in the case of a conventional
inorganic thin film light emitting device, and the holes and
electrons move to an organic thin film layer, resulting in
light emission (Appl. Phys. Lett., 85(12), 2382-2384).
Since POPE, KALLMAN, et al. found electro-luminescence
in anthracene single crystal in 1963, active research and
development into OLEDs (Organic Light Emitting Devices) have
been made up to now. Recently, organic light emitting devices
have been used in flat panel display devices, lighting
devices, etc. Such organic light emitting devices have been
developed so rapidly that performance as display devices is
remarkably improved and various applied products are
developed.
In order to manufacture more efficient organic light
emitting devices, many attempts have been made to manufacture
an organic film in the device in the form of a multilayer
structure instead of a monolayer structure. Most of currently
used organic light emitting devices have a structure in which
an organic film and electrodes are deposited. The organic
film generally has a multilayer structure including a hole
injection layer, hole transport layer, light emitting layer,
electron transport layer and an electron injection layer.
It is knbwn. that OLEDs are characterized by' high
brightness, high efficiency, low drive voltage, color
changeability, low cost, etc. However, in order to have such
characteristics, each layer forming an organic film in a
device (for example, a hole injection layer, hole transport
layer, light emitting layer, electron transport layer and
electron injection layer) must be formed of more stable and
efficient materials.
A method of doping a light emitting host with a
fluorescent compound so as to increase the light emitting
efficiency of a multilayer-structured OLED was disclosed.
Particularly, according to Tang, et al. (J. Appl. Phys. Vol.
65 (1989) , p. 3610) , light emitting efficiency can be
improved by mixing a fluorescent compound having a high
quantum efficiency (for example, coumarin pigments or pyran
derivatives) in a small amount with a light emitting host, in
this case, light having a desired wavelength can be obtained
depending on the type of the fluorescent compound. However,
when Alq3 is used as electron transport material and drive
voltage is increased to obtain high brightness, green light
emission based on Alq3 may be observed in addition to light
emission based on the doped fluorescent compound. This is
problematic in terms of color purity, particularly when the
color of light to be emitted is blue. It is known that such a
problem results from a narrow band gap between the HOMO
(highest occupied molecular orbital) and the LOMO (lowest
unoccupied molecular orbital) of Alq3. Such a narrow band gap
results in exciton diffusion from a light emitting layer to
Alq3, thereby causing light emission based on Alq3.
The use of hole block material has been reported as
another method for increasing light emitting efficiency of
OLEDs, wherein the hole block material includes 3-(4-
biphenylyl) -4-phenyl-5- (4-tert-butylphenyl) -1,2, 4-triazole
(TAZ), bathocuproine (BCP), etc. (Jpn. J. App. Phys. Part 2,
1993, 32, L917). However, the above-mentioned materials 3how
poor durability and have a serious problem of deterioration
of a device, particularly when the device is subjected to
continuous light emission while being stored at high
temperature. Moreover, there are additional problems in that
the above-mentioned materials should be provided as a layer
separated from a light emitting layer, and that drive voltage
increases due to a large band gap between the HOMO and the
LUMO when the materials are used.
Therefore, in order to overcome the problems occurring
in the prior art and to further improve characteristics of;
OLEDs, it. is necessary to develop more stable and efficient
materials that may be used in OLEDs.
Brief Description of the Drawings
FIGs. 1 to 5 are schematic views each illustrating the
structure of an organic light emitting device (OLED) that may
be applied to the present invention, wherein reference
numeral 101 is a substrate, 102 is an anode, 103 is a hole
injection layer, 104 is a hole transport layer, 105 is a
light emitting layer, 108 is a hole block layer, 106 is an
electron transport layer and 107 ±3 a cathode 107.
FIG. 6 is a graph showing the current-voltage
relationship of the OLED according to Example 1 and that of
the OLED according to Comparative Example 1.
Disclosure of the Invention
It is an object of the present invention to improve
durability and/or efficiency of an organic light emitting
device by an organic substance capable of carrying out at
least one function selected from the group consisting of hole
injection, hole transport, hole block, light emitting,
electron transport, electron injection, and buffering between
an anode and a hole injection layer, wherein the organic
substance is designed by using a cyclic trimer core structure
represented by the following formula 1.
According to an aspect of the present invention, there
is provided a compound represented by formula 1:
[Formula 1)
wherein
A is B or N;
X is N or CRo, wherein Ro is selected from the group
consisting of a hydrogen atom (H) , halogen atom, nitrile
group (CN), nitro group (NO2) , formyl group, acetyl group,
benzoyl group, amide group, styryl group, acetylene group,
quinoline group, quinazoline group, phenanthroline group,
cuproine group, anthraquinone group, benzoquinone group,
quinone group, acridine group, substituted or non-substituted
alkyl group, substituted or non-substituted aryl group,
substituted or non-substituted aralkyl group, substituted or
non-substituted arylamine group, substituted or non-
substituted alkylamine group, substituted or non-sub3tituted
aralkylamine group, and substituted or non-substituted
heterocyclic group; and
each of Y, Y' and Y" represents a substituted or non-
substituted aromatic heterocycle that includes a 5-membered
aromatic heterocycle containing A and X as ring members or a
6-membered aromatic heterocycle containing A and X as ring
members, wherein Y, Y' and Y" are identical or different.
The number of substituents present in Y, Y' and Y" is
at least one and the substituents are identical or different,
each substituent being selected from the group consisting of
a halogen atom, nitrile group (CN), nitro group (NO2) , formyl
group, acetyl group, benzoyl group, amide group, styryl
group, acetyelene group, quinoline group, quinazoline group,
phenanthroline group, cuproine group, anthraquinone group,
benzoquinone group, quinone group, acridine group,
substituted or non-substituted alkyl group, substituted or
non-substituted aryl group, substituted or non-substituted
aralkyl group, substituted or non-substituted arylamine
group, substituted or non-substituted alkylamine group,
substituted or non-substituted aralkylamine group, and
substituted or non-substituted heterocyclic group, wherein in
some cases two substituents adjacent to each other may form a
fused ring together.
According to another aspect of the present invention,
there is provided an organic light emitting device including
a first electrode, an organic film having one or more layers
and a second electrode, laminated successively, wherein at
least one layer of the organic film includes at least one
compound represented by formula 1.
Hereinafter, the present invention will be explained in
detail.
The present invention provides a compound represented
by formula 1.
The compound represented by formula 1 is an organic
substance including a cyclic t rimer core structure. The
compound is capable of carrying out at least one function
selected from the group consisting of hole injection, hole
transport, hole block, light emitting, electron transport,
electron injection, and buffering between an anode and a hole
injection layer, depending on the type of each unit forming
the trimer or substituents in each unit. Particularly, the
function of buffering between an anode and a hole injection
layer is required when interfaceal contact between them is
poor, or when direct hole injection into a hole injection
layer is not made properly. Many compounds are known to carry
out at least one function selected from the group consisting
of hole injection, hole transport, hole block, light
emitting, electron transport, electron injection, and
buffering between an anode and a hole injection layer. Most
of them generally include a substituted or non-substituted
aromatic or heteroaromatic group.
Meanwhile, all kinds of compounds capable of carrying
out at least one function selected from the group consisting
of hole injection, hole transport, hole block, light
emitting, electron transport, electron injection, and
buffering between an anode and a hole injection layer can be
prepared by varying the type of each trimer-forming unit or
substituents present in each unit from the organic substance
represented by the above formula 1 including a cyclic trimer
core structure. Heretofore, it has not been known that all
kinds of compounds capable of carrying out at least one
function needed for a desired organic light emitting device
can be prepared by varying the type of each unit or
substituents from one basic structure.
Organic substances that function as hole injection
materials are compounds facilitating hole injection from an
anode. Preferably, such compounds have ionization potential
suitable for hole injection from an anode, high interfacial
adhesion to an anode, non-absorbability in the visible light
range, etc. Particular examples of units or substituents
capable of performing a function of a hole injection include
organic substances of metal porphyrin, oligothiophen,
arylamine series, organic substances of hexanitrile
hexaazatriphenylene, quinacridone series, organic substances
of perylene series, conductive polymers based on
anthraquinone, polyaniline, and polythiophene or polymers
such as dopants, but are not limited thereto.
Organic substances that function as hole transport
materials preferably have high hole mobility and high LUMO
energy level for electron blocking. Particular examples of
units or substituents capable of performing a function of a
hole transport may include organic substances of arylamine
series, conductive polymers and block copolymers having both
conjugated portions and non-conjugated portions, but are not
limited thereto. Particular examples thereof include
triarylamine derivatives, amines having a bulky aromatic
group, starburst aromatic amines, spirof luorene.-containing
amines, crossl inked amines and anthracene-based compounds.
Organic substances that function as electron transport
materials are those having an electron withdrawing group.
Units or substituents capable of performing a function of an
electron transport may include compounds containing a
functional group capable of withdrawing electrons by
resonance (for example cyano, oxadiazole or triazole group).
Particular exmples thereof include 8-hydroxyquinolone-Al
complex; complexes including Alq3; organic radical compounds;
and hydroxy- flavone-meta1 complexes, but are not limited
thereto.
Organic substances that function as light emitting
materials are those having moieties capable of emitting light
by accepting and recombining holes and electrons and may
include fluorescent materials and phosphorescent materials.
Particular examples of units or substituents capable of
performing a function of a light emitting include 8-
hydroxyquinoline aluminum complex (Alq3) ; compounds of
carbazole series; dimerized styryl compounds; BAlq3; 10-
hydroxybenzoquinoline-metal compounds; compounds of
benzoxazole, benzthiazole and benzimidazole series; polymers
based on poly(p-phenylenevinylene) series; polymers based on
poly-phenylenevinylene (PPV); spiro compounds; and compounds
of polyfluorene, rubrene and anthracene series, but are not
limited thereto.
Meanwhile, an organic substance designed by using the
cyclic trimer core structure represented by formula 1 has a
molecular weight higher than that, of each monomer forming the
trimer. Accordingly, it has high thermal stability, thereby
improving durability of an OLED including an organic film
formed by using the same. Additionally, when a moriomeric
organic substance used in a light emitting layer is
trimerized, the resultant molecular weight increases
accordingly, and thus it is possible to obtain an organic
substance having a long wavelength shifted from a short
wavelength (for example, from blue to red) . Further, the
compound represented by formula 1 having a trimerized
structure provides a suitable band gap between the HOMO and
the LUMO and energy value compared to each monomer forming
the trimer, thereby reducing drive voltage.
Additionally, in the cyclic trimer core structure
represented by formula 1, the saturated 6-membered ring
having three heteroatoms (A) forms a non-planar (for example.
chair-like) structure like the structure of cyclohexane,
contrary to a flat aromatic ring. Therefore' three units'
i-e.,that . . . ,
are bonded symmetrically to
the 6-membered ring form a non-planar propeller-like
structure in which they are distorted symmetrically to one
another, so that steric hindrance among the three units can
be reduced. Further, if each of the units (generally,
substituted or non-substituted aromatic compounds) forming
the trimer is present as a monomer, the aromatic compounds
are laminated together in the form of a flat plane and thus
permit intermolecular interaction. However, if monomers are
trimerized into the core structure represented by formula 1,
their amorphous characteristics can be exerted more.
Therefore, it is possible to prevent the breakdown of a
device caused by crystallization resulting from the Joule
heat generated during- the operation of an OLED. Further, the
cyclic trimer core structure represented by formula 1 has
three units bonded symmetrically to the non-planar 6-membered
ring and thus it is possible to design organic substances
having structures that are not excessively planar but
ordered. The above-described characteristics are useful for
an organic substance used in a hole transport layer or
electron transport layer.
The cyclic trimer represented by formula 1 does not
permit extension of conjugation among units because of the
saturated 6-membered ring, and thus each unit can function
independently from each other. Therefore, it is possible to
contemplate each unit individually and to facilitate
One example of the compound represented by formula 1 is
a compound represented by the following formula 2:
[Formula 2]
wherein
A and X are the same as defined above with regard to
formula 1; and
Rl to R6 are identical or different and each is
selected from the group consisting of a hydrogen atom (H) ,
halogen atom, nitrile group (CN), nitro group (NO2) , formyl
group, acetyl group, benzoyl group, amide group, styryl
group, acetylene group, quinoline group, quinazoline group,
phenanthroline group, cuproine group, anthraquinone group,
benzoquinone group, quinone group, acridine group,
substituted or non-substituted alkyl group, substituted or
non-substituted aryl group, substituted or non-substituted
aralkyl group, substituted or non-substituted arylamine
group, substituted or non-substituted alkylamine group,
substituted or non-substituted aralkylamine group, and
substituted or non-3ubstituted heterocyclic group, wherein in
some cases Rl and R2, R3 and R4, and R5 and R6 may form a
fused ring with each other.
Another example of the compound represented by formula
1 is a compound represented by the following formula 3:
[Formula 3]
wherein
A and X are the same as defined above with regard to
formula 1; and
Rl to R18 are identical or different and have the same
meanings as Rl to R6 in the above formula 2, wherein in some
cases each of Rl to R18 may form a fused ring together with a
substituent adjacent thereto.
Non-limitative examples of the substituents in formulae
1-3 (for example Ro to R18) will be described hereinafter.
Halogen atoms include a fluorine (F), chlorine (CI),
bromine (Br) and iodine (I) atoms.
Alkyl groups preferably have 1 to 20 of carbon atoms
(C1-C20) and include linear alkyl groups such as methyl,
ethyl, propyl, hexyl, etc., and branched alkyl groups such as
isopropyl, tert-butyl, etc.
Aryl groups include monocyclic aromatic cycles such as
phenyl, etc., and multicyclic aromatic cycles such as
naphthyl, anthryl, pyrene, perylene, etc.
Aralkyl groups include C1-C20 alkyl groups substituted
with aromatic hydrocarbons such as phenyl, biphenyl,
naphthyl, terphenyl, anthryl, pyrene, perylene, etc.
Arylamine groups include amine groups substituted with
aromatic hydrocarbons such as phenyl, biphenyl, naphthyl,
terphenyl, anthryl, pyrene, perylene, etc.
Alkylamine groups include amine groups substituted with
C1-C20 aliphatic hydrocarbons.
Aralkylamine groups include amine groups substituted
with aromatic hydrocarbons such as phenyl, biphenyl,
naphthyl, terphenyl, anthryl, pyrene, perylene, etc., and Cl-
C20 aliphatic hydrocarbons.
Heterocyclic groups include pyrrolyl, thienyl, indole,
oxazole, imidazole, thiazole, pyridyl, pyrimidine,
piperazine, thiophene, furan, pyridazinyl, etc.
In formulae 2 and 3, fused rings formed by each of Rl
to R18 with a substituent adjacent thereto include pyrrole,
furan, thiophene, indole, oxazole, imidazole, thiazole,
pyridine, pyrizine, benzene, naphthalene, pyrazine,
quinoline, quinazoline, phenanthroline, cuproine,
anthraquinone, benzoquinone, quinone, acridine, etc.
Further, each of substituted alkyl, aryl, aralkyl,
arylaminej alkylamine, aralkylamine and heterocyclic groups
in Ro to R18 may have one or more substituents selected from
the group consisting of a halogen atom including fluorine,
chlorine, bromine and iodine, nitrile, nitro, formyl, acetyl,
arylamine, alkylamine, aralkylamine, benzoyl, amide, styryl,
acetylene, phenyl, naphathyl, anthryl, pyrene, perylene,
pyridyl, pyridazyl, pyrrolyl, imidazolyl, quinolyl, anthrone,
acridone, acridine, etc.
Particular examples of the compound represented by
formula 1 include the compounds represented by formulae 1-1
to 1-46, but are not limited thereto:
[Formula 1-1J
Additionally, the compound represented by formula 1
(for example, compound represented by formulae 1-1 or 1-35)
can be used as a phosphorescence host, which may be used
together with a phosphorescence dopant, in an organic
phosphorescence light emitting device.
Meanwhile, as can be seen from the following Example 1,
the compound represented by formula 1-1 is a substance that
functions as an electron injection/ transport material.
Further, it can be seen indirectly that the compound
represented by formula 1-1 is an n-type substance. Therefore,
it can be seen that compounds having the compound represented
by formula 1-1 as a core also function as electron
injection/transport materials. Each monomer (benzimidazole)
forming the trimeric compound represented by formula 1-1
cannot be applied to an organic film in an OLED by itself,
because the band gap between the HOMO and the LUMO is large,
it has no electron mobility and it has such a small molecular
weight as to be sublimated easily. However, when a cyclic
trimer represented by formula 1 is formed from such a
monomer, it is possible to increase the molecular weight, to
reduce the band gap between the HOMO and the LUMO and to
impart electron mobility. Accordingly, even if a compound
cannot function as a material for hole injection, hole
transport, hole block, light emitting, electron transport,
electron injection, and buffering between an anode and a hole
injection layer, or the like, it is possible to cause the
compound to have the above-described functions by forming a
cyclic trimer represented by formula 1 from the compound as a
monomer.
Meanwhile, the organic substance represented by formula
1-12 has a core represented by formula 1-1 having n-type
characteristics and arylamine substituents imparting p-type
characteristics, and thus can function as a hole transport
material, as can be seen from the following Example 2.
Therefore, compounds having a core represented by formula 1
can provide materials having p-type characteristics, n-type
characteristics or amphoteric characteristics depending on
the characteristics of substituents. Further, such
characteristics depending on substituents determine an
organic layer in an OLED that a compound represented by
formula 1 can be used.
The compound represented by formula 1 can be prepared
by using the following starting materials:
Particularly, non-limitative examples of the starting
materials include the following compounds:
wherein A, X and Rl to R6 as substituents for Y, Y' and
Y" are the same as defined above with regard to formula 1, 2
or 3; and Z is a halogen atom. Particularly, 2 may be
selected from the group consisting of F, CI, Br and I.
According to the present invention, compounds
represented by formula 1 may be prepared by trimerizing the
starting materials and optionally introducing substituents to
the resultant trimeric compounds if necessary. Trimerization
or substituent introduction may be performed by using any
conventional methods known to one skilled in the art.
Further, solvents may be used in synthetic routes, if
desired. For example, a desired trimer compound can be
prepared by heating at least one compound selected from the
above starting materials to 200-300 T£. Preparation of trimer
compounds will be explained in detail through the following
Preparation Examples. However, it is to be understood that
methods described in the following Preparation Examples can
be modified by one skilled in the art in order to prepare
compounds according to the present invention.
The present invention also provides an organic light
emitting device (OLED) including a first electrode, an
organic film having one or more layers and a second
electrode, laminated successively, wherein at least one layer
of the organic film contains at least one compound
represented by formula 1.
In the OLED according to the present invention, the
organic film containing the compound represented by formula 1
may be formed by using a vacuum deposition method or a
solution coating method. Particular examples of the solution
coating method include spin coating, dip coating, doctor
blade coating, ink-jet printing or heat transfer method, but
are not limited thereto.
The organic film containing the compound represented by
formula 1 may have a thickness of 10 (m or less, preferably
0.5 iaa or less, and more preferably 0.001-0.5 f/m.
The compound represented by formula 1 may be used
together with other known materials that function as
materials for hole injection, hole transport, light emitting,
electron transport or electron injection (if necessary).
The OLED according to the present invention may have a
structure having an organic film including a hole injection
layer, a hole transport layer, a light emitting layer, an
electron transport layer, an electron injection layer and a
buffering layer disposed between an anode and the hole
injection layer. However, the structure of OLED is not
limited thereto and the number of layers included in the
organic film may be reduced.
According to the invention, organic light emitting
devices (OLED) may have structures as shown in FIGs. 1 to 5,
but the embodiments shown in the figures are not limitative.
FIG. 1 shows an OLED having a structure in which an
anode 102, a light emitting layer 105 and a cathode 107 are
laminated successively on a substrate 101.
FIG. 2 shows an OLED having a structure in which an
anode 102, a hole transport/light emitting layer 105, a light
emitting/electron . transport layer 106 and a cathode 107 are
laminated successively on a substrate 101.
FIG. 3 shows^ an OLED having a structure in which, an
,anode 102, a hole transport layer 104, a light emitting--layer
105, an electron transport layer 106 and a cathode 107 are
laminated successively on a substrate 101.
FIG. 4 shows an OLED having a structure in which an
anode 102, a hole injection layer 103, a hole transport layer
104, a light emitting layer 105, an electron transport layer
106 and a cathode 107 are laminated successively on a
substrate 101.
FIG. 5 shows an OLED having a structure in which an
anode 102, a hole injection layer 103, a hole transport layer
104, a light emitting layer 105, a hole block layer 108, an
electron transport layer 106 and a cathode 107 are laminated
successively on a substrate 101.
molecular designs. For example, each unit can be derived front
a monomer having a function different from each other.
Additionally, when a monomeric organic substance used in a
light emitting layer is trimorized into a cyclic form at
meta-positions as depicted in formula 1, its molecular weight
increases followed by a wavelength shift to a long
wavelength. In this case, the saturated 6-membered ring
prevents further extension of conjugation, and thus can
reduce a shift range compared to a linear polymer obtained
from the monomer.
In formula 1, A is preferably a nitrogen atom (N) .
In formula 1, X is preferably a nitrogen atom (N) .
In formula 1, when substituents attached to Y, Y' and
Y" include an alky.I group, the length of the alkyl group does
not significantly affect the compound of formula 1 in
carrying out at least one tunct. ion selected irom the group
consisting of hole injection, hole transport, hole block,
light emitting, electron transport, electron injection, and
buffering between an anode and a hole injection layer. Light
absorption or emission in an electronic device can be
affected by the conjugation length of a functional compound.
Because the length of an alkyl group included in the compound
does not affect the conjugation length of the compound, it
has no direct effect on the wavelength of the compound or on
characteristics of a device. However, the length of an alkyl
group may affect the selection of a method of applying the
compound to an OLED (for example, a vacuum deposition method
or a solution coating method) . Therefore, there is no
Materials for cathode 107 may include metals such as
magnesium, calcium, sodium, potassium, titanium, indium,
yttrium, lithium, gadolinium, aluminum, silver, tin and lead
or alloys thereof; and multi-layered materials such as LiF/Al
or LiOz/Al, but are not limited thereto.
Advanced Effect
According to the present invention, it is possible to
provide an organic substance capable of carrying out at least
one function selected from the group consisting of hole
injection, hole transport, hole block, light emitting,
electron transport, electron injection, and buffering between
an anode and a hole injection layer through molecular designs
using a cyclic trimer core structure represented by formula
1. Further, it is possible to improve durability and/or
efficiency of an organic light emitting device by using the
organic substance in an organic film of the device.
Mode for Carrying Out: the Invention
Hereinafter, the present invention will be explained in
more detail through Preparation Examples 1-6, Examples 1 and
2, and Comparative Examples 1 and 2. It is to be understood
that the following examples are illustrative only and the
present invention is not limited thereto.
Preparation Example 1
Synthesis of compounds of formula 1-1 (Trimerization of
2-chlorobenzimida2ole)
[Formula 1-1]
5 g (0.0327 mole) of 2-chlorobenzimidazole as a
starting material was introduced into a 50 mL long-necked
flask and the flask was immersed in an oil bath preheated to
195*0. Hereupon, the starting material was dissolved and
transformed back into a solid state immediately, while
generating hydrogen chloride gas. When the gas stopped
bubbling, the reaction mixture was cooled to room temperature
and the resultant solid compound was recrystallized with
nitrobenzene. Then, the product was filtered, washed with
ethanol and ether in turn then dried under vacuum to obtain
the compound represented by formula 1-1 as a white solid (2.5
g, yield 50%).
The analysis results for the compound are as follows:
m.p. 391-393*C; lH NMR (500MHz, DMSO-d6) 8.51 (d, 3H) , 7.96
(d, 3H), 7.59 (m, 6H) ; MS [M+l] 348
Propagation Example 2
Synthesis of compound of formula 1-5(Trimerization of
l-iodo-2-chloro-4,5-dicyanoimidazole)
10 g (0.036 mole) of l-iodo-2-chloro-4,5-
dicyanoimidazole as a starting material was introduced into a
50 mL long-necked flask, equipped with a sublimation device.
Then, the flask was purged with nitrogen continuously two
times under vacuum and immersed in an oil bath preheated to
220-240"C. After maintaining the above temperature for 5
hours, I2 and TCI as halogen decomposition products were
formed on a cold finger. After cooling back to room
temperature, the flask was purged with nitrogen under vacuum.
The resultant brown solid was pulverized and 10% Na2S203 (40
mL) was added thereto. Then, the mixture was stirred for 30
minutes at room temperature and then filtered (three times) .
The filtered solid was washed with water repeatedly and then
dried under vacuum to obtain the compound represented by
formula 1-5 as a yellowish brown solid (2.92 g, yield 70%).
The analysis results for the compound were as follows:
purity 99.6%; m.p. >400"C; UC NMR (400 MHz, DMSO-dg , ppm)
135.0, 123.2, 110.3, 106.5, 106.2
Preparation Examplo 3
Synthesis of compound of formula 1-6 (Trimerization of
4,5-diphenylimidazole)
[Formula 1-6J
2.0 g (0.0091 mole) of 4,5-diphenylimidazole as a
starting material, 0.01 g of dichloropalladium, 0.3 g of
sulfur, 0.1 mL of phenylthioether and 10 mL of phenylether
were introduced into a 50 ml, round-bottom flask equipped with
a condenser. The reaction mixture was reacted under reflux
and then cooled. Then, 50 mL of ether was added thereto to
form precipitate. The precipitate was removed by using a
depressurized filter and then the filtrate was distilled
under reduced pressure to remove all solvents therefrom.
Then, the resultant product was dissolved into 10 mL of
dioxane at 90-100"C and 15 mL of acetic acid was added thereto
to perform recrystallization. The resultant product was
filtered by using a depressurized filter to obtain a dark
gray solid. The dark gray solid was purified by sublimation
to obtain the compound represented by formula 1-6 as a
greenish white solid (0.6 g, yield 30%).
The analysis results for the compound were as follows:
purity 99.6%; m.p. 361-363*0; XH NMR (400 MHz, DMSO-cfe) 7.60 -
7.64 (m, 5H), 7.23 -7.16 (m, 5H) ; MS [M+l]* 655, [M]" 654
Preparation Exanpl* 4
Synthesis of compound of formula 1-12
(1) Synthesis of compound of formula 4a
To a mixture containing 2-chlorobenzinvidazole (0.763 g,
5 nmol) as a starting material dissolved in 25 roL of
methanol, bromine/raethanol solution (0.26 mL/5 roL) was
gradually added dropwise. Then, the reaction mixture was
stirred for 5 hours at room temperature. After checking a
reaction degree by HPLC, 25 mL of water was added and the
mixture was stirred for 18 hours at room temperature. The
resultant precipitate was filtered and washed with cold water
repeatedly until it became neutral. Then, the resultant
product was recrystallized with methanol/water (1:1) solution
to obtain the compound of formula 4a as a white solid (0.6 g,
yield 52.0%).
The analysis results for the compound were as follows:
m.p. 228-230"C; Hi NMR (400 MHz, DMSO-d«) 7.73 (s, 1H), 7.49 -
7.47 (d, 1H), 7.39-7.36 (d, 1H); MS [M+l]* 231
(2) Synthesis of compound of formula 4b (Trimerization
of 5-bromo-2-chlorobenzimidazole)
1.1 g (4.7 mmole) of 5-bromo-2-chlorobenzinu.dazole as a
starting material was introduced into a 50 mL long-necked
flask and was immersed in an oil bath preheated to 230*0.
Hereupon, the starting material was dissolved and transformed
back into a solid state immediately, while generating
hydrogen chloride gas. When the gas stopped bubbling, the
reaction mixture was cooled to room temperature and the
resultant solid compound was recrystallized with
nitrobenzene. Then, the product was filtered, washed with
ethanol and ether in turn and then dried under vacuum to
obtain the compound represented by formula 4b as a pale
yellow solid (0.43 g, yield 47%).
The analysis results for the compound are as follows:
m.p. 354*C; MS [M+1J 583(isomer)
(3) Synthesis of compound of formula 1-12
To a 50 mL round-bottom flask equipped with a
condenser, sequentially added were a mixed solution
containing 10 mL of mesitylene and the compound of formula 4b
<0.4 g, 0.68 mmol), 50 mg of Pd2(dba)3 (0.005 mmol) , 17 mg of
P(t-Bu)3 (0.081 mmol), and 0.28 g of Na(t-OBu) (3 mmol). The
reaction mixture was reacted for 5 hours at 120*C. After the
reaction mixture was cooled to room temperature, 20 mL of
toluene and 30 mL of water were added thereto to perform
phase separation. The organic layer obtained from the
preceding step was dried over MgS04 and the dried product was
distilled under reduced pressure to remove all solvents
therefrom. The product was separated by column chromatography
and then washed with ethanol to obtain the compound of
formula 1-12 as a white solid (200 mg, yield 30%) .
The analysis results for the compound were as follows:
m.p. 2l 350*0; JH NMR(500MHz, DMSO-d6) 8.27-8.15 (m, 1H) , 8.09-
7.74 (m, 3H), 7.63-7.16 (m, 8H) , 6.97-6.86 (m, 3H); MS [M+1J
1000
Preparation Example 5
Synthesis o£ compound of formula 1-4 6
(1) Synthesis of compound of formula 5b (2-
chloroperimidine)
Purified 1, 8-diaminonaphthalene (1.7 g, 10.7 mmol) was
introduced into 30 mL of diluted hydrochloric acid solution
(0.5N) and heated to be completely dissolved. After 10 mL of
aqueous sodium cyanide solution (0.7 g, 10.7 mmol) was
gradually added thereto, red precipitate was formed. The red
precipitate was heated for 1 hour and cooled. Then, the
resultant precipitate was filtered, washed with ether and
then dried under vacuum to obtain 2-perimidinone (5a) as a
pale reddish white solid (1.12 g, 6.1 mmol, yield 57%). The
resultant solid was added to 10 mL of phosphorous oxychloride
(POCI3) and refluxed for 3 hours by heating. Then, excessive
amount of phosphorous oxychloride was removed by vacuum
distillation. The residue was dispersed in water and
neutralized with 2N aqueous ammonia to form yellow
precipitate. The precipitate was filtered and the filtrate
was precipitated again by using THF and hexane as solvents.
Then, the solution was filtered again and the filtered
product was dried under vacuum to obtain 2-chloroperimidine
as a light yellow solid (0.6 g, 2.9 mmol, yield 50%).
The analysis results for the above compounds were as
follows:
2-perimidinone (5a): lH NMR (400 MHz, DMSO-d6) , 10.06 (s,
2H), 7.21 (t, J - 7.6 Hz, 2H), 7.10 (d, J = 8.4 Hz, 2H), 6.51
(d, J - 7.6 Hz, 2H)
2-chloroperimidine (5b): *H NMR (400 MHz, DMSO-d6),
11.35 (s, 1H) , 7.20-7.08 (m, 4H) , 6.60 (d, J" 6.4 Hz, 1H) ,
6.38 (d, J = 6.8 Hz, 1H)
(2) Synthesis of compound of formula 1-46
2-chloroperimidine (0.73 g, 3.6. mmol) was introduced
into a flask equipped with a mechanical stirrer under
nitrogen atmosphere and heated to 210T^ to dissolve it. After
stirring for 10 minutes, the mixture turned dark red. About
20 mL of nitrobenzene was added thereto, and the mixture was
stirred for about 1 hour, cooled and filtered to separate
precipitate. The filtered product was washed sufficiently
with nitrobenzene, saturated sodium carbonate solution,
water, ethanol and THF, in turn, and then was dried under
vacuum to obtain 0.57 g of the compound represented by
formula 1-46 as a red solid (yield 32%).
The analysis results for the compound were as follows:
lH NMR (400 MHz, DMSO-ck) , 7.52" 7.28 (m, 12H) , 6.94-6.80 (m,
6H); MS (M+HC1+H) 535
Example 1
(Manufacture of organic liqht emitting device)
A glass substrate on which a thin film of ITO (indium
tin oxide) was coated to a thickness of 1500A was immersed in
distilled water containing a detergent to wash the substrate
with ultrasonic waves for 30 minutes. Next, washing with
ultrasonic waves was repeated for 10 minutes and two times by
using distilled water. The detergent was a product
commercially available from E'isher Co. The distilled water
has been filtered previously by using a filter commercially
available from Millipore Co. After the completion of washing
with distilled water, washing with ultrasonic waves was
carried out by using solvents such as isopropyl alcohol,
acetone and methanol, in turn. The resultant product was
dried and transferred to a plasma cleaner. Then, the
substrate was cleaned for 5 minutes by using nitrogen plasma
and transferred to a vacuum deposition device.
On the ITO transparent electrode prepared as described
above, hexanitrile hexaazatriphenylene represented by the
following formula 4 was coated to a thickness of 500A by
thermal vacuum deposition, thereby forming a hole injection
layer. Next, NPB as a hole transport material was coated
thereon to a thickness of 4 00 A by vacuum deposition.
Additionally, a light emitting compound (Alq3) represented by
the following formula 5 was coated thereon to a thickness of
300A by vacuum deposition to form a light emitting layer. On
the light emitting layer, the compound represented by formula
1-1 was coated to a thickness of 200A by vacuum deposition to
form an electron injection/transport layer. Next, on the
electron injection/transport layer, lithium fluoride (LiF)
and aluminum were sequentially vacuum-deposited to a
thickness of 10A and 2500A, respectively, to form a cathode.
In the above process, deposition rate of each organic
substance was maintained at 1 A/sec and deposition rates of
lithium fluoride and aluminum were maintained at 0.2 A/sec
and 3-7 A/sec, respectively.
[Formula 4]
The resultant organic light emitting device showed a
drive voltage of 3.57V at a forward current density of 10
mA/cm2. Further, specific green spectrum of Alq3 was observed
with x«3.94 and y=0.56 based on the 1931 CIE color
coordinate. Such light emitting operation of the device at
the above drive voltage indicates that the compound of
formula 1-1 contained in the layer disposed between the light
emitting layer and the cathode can function as an electron
injection/transport material.
Comparative Example 1
Example 1 was repeated to manufacture an organic light
emitting device, except that Alq3, a conventional compound
useful for electron injection and transport was coated on the
light emitting layer to a thickness of 200A by vacuum
deposition, instead of the compound of formula 1-1, to form
an electron injection/transport layer.
The resultant organic light emitting device showed a
drive voltage of 4.12V at a forward current density of 10
mA/cm2. Further, specific green spectrum of Alq3 was observed
with x^0.34 and y*=0.56 based on the 1931 CIE color
coordinate.
The following Table 1 shows the results of variations
in drive voltage depending on currents for the organic light
emitting devices obtained from Example 1 and Comparative
Example 1.
[Table 1]
As can be seen from Table 1, when an electron
injection/transport layer for an organic light emitting
device is formed by using the compound of formula 1-1, the
drive voltage can be reduced under the same current density,
compared to an organic light emitting device using AJLq3 that
is a conventional material functioning as an electron
injection/transport layer.
Example 2
On the ITO transparent electrode prepared as described
in Example 1, hexanitrile hexauzatriphenylene represented by
formula 4 was coated to a thickness of 500A by thermal vacuum
deposition, thereby forming a hole injection layer. Next, the
compound of formula 1-12 obtained from Preparation Example 4,
as a hole transport material, was coated thereon to a
thickness of 200A by vacuum deposition. Additionally, a light
emitting compound (Alq3) represented by formula 5 was coated
thereon to a thickness of 300A by vacuum deposition to form a
light emitting layer. On the light emitting layer, the
compound represented by the following formula 6 was coated to
a thickness of 200A by vacuum deposition to form an electron
injection/transport layer. Next, on the electron
injection/transport layer, lithium fluoride (LiF) and
aluminum were sequentially vacuum-deposited to a thickness of
10A and 2500A, respectively, to form a cathode. In the above
process, deposition rate of each organic substance was
maintained at 1 A/sec and deposition rates of lithium
fluoride and aluminum were maintained at 0.2 A/sec and 3-7
A/sec, respectively.
(Formula 6]
The resultant organic light emitting device showed a
light emitting efficiency of 460 cd/cm2 at a forward current
density of 100 mA/cm2. Further, specific green spectrum of
Alq3 was observed with x=0.32 and y=0.56 based on the 1931
CIE color coordinate. Such light emitting operation of the
device at the above drive voltage indicates that the compound
of formula 1-12 contained in the layer disposed between the
hole injection layer and the light emitting layer can
function as a hole transport material.
Corapara'tive Example 2
Example 2 was repeated to manufacture an organic light
emitting device, except that NPB, a conventional compound
useful for hole transport was coated on the hole injection
layer to a thickness of 200A by vacuum deposition, instead of
the compound of formula 1-12, to form a hole transport layer.
The resultant organic light emitting device showed a
light emitting efficiency of 340 cd/cmz at a forward current
density . of 100 ..iBA/cxn2. Further, specific green spectrum of
Alq3 was observed with x=0.32 and y=0.56 based on the 1931
CIE color coordinate.
As can be seen from Example 2 and Comparative Example
2, when an organic light emitting device includes the
compound represented by formula 1-12 in a hole transport
layer, the light emitting efficiency can be improved under
the same current density, compared to an organic light
emitting device including NPB in a hole transport layer.
While this invention has been described in connection
with what is presently considered to be the most practical
and preferred embodiment, it is to be understood that the
invention is not limited to the disclosed embodiment and the
drawings. On the contrary, it is intended to cover various
modifications and variations within the spirit and scope of
the appended claims.
WE CLAIM:
1. An organic light emitting device comprising a first electrode, an organic film having one or
more layers and a second electrode, laminated successively, wherein said at least one layer of the
organic film has at least one compound represented by Formula 1:
wherein A is B or N; X is N or CR0, wherein R0 is selected from the group consisting of a
hydrogen atom (H), halogen atom, nitrile group (CN), nitro group (N02), formyl group, acetyl group,
benzoyl group, amide group, styryl group, acetylene group, quinoline group, quinazoline group,
phenanthroline group, cuproine group, anthraquinone group, benzoquinone group, quinone group,
acridine group, substituted or non-substituted alkyl group, substituted or non-substituted aryl group,
substituted or non-substituted aralkyl group, substituted or non-substituted arylamine group, substituted
or non-substituted alkylamine group, substituted or non-substituted aralkylamine group, and substituted
or non-substituted heterocyclic group; and wherein
alkyl groups have 1 to 20 of carbon atoms and represent linear alkyl groups or branched alkyl
groups,
aryl groups represent monocyclic aromatic cycles or multicyclic aromatic cycles,
aralkyl groups represent C1-C20 alkyl groups substituted with aromatic hydrocarbons,
arylamine groups represent amine groups substituted with aromatic hydrocarbons,
arkylamine groups represent amine groups substituted with C1-C20 aliphatic hydrocarbons,
aralkylamine groups represent amine groups substituted with aromatic hydrocarbons or Cl-
C20 aliphatic hydrocarbons, and
heterocyclic groups are selected from the group consisting of pyrrolyl, thienyl, indole,
oxazole, imidazole, thiazole, pyridyl, pyrimidine, piperazine, thiophene, furan, and pyridazinyl; and
wherein each of Y, Y' and Y" represents a substituted or non-substituted aromatic heterocycle
that includes a 5-membered aromatic heterocycle containing A and X as ring members or a 6-
membered aromatic heterocycle containing A and X as ring members, wherein Y, Y' and Y" are
identical or different.
2. The organic light emitting device as claimed in claim 1, wherein each of Y, Y' and Y" is
substituted with one or more identical or different substituents selected from the group consisting of a
halogen atom, nitrile group (CN), nitro group (N02), formyl group, acetyl group, benzoyl group, amide
group, styryl group, acetylene group, quinoline group, quinazoline group, phenanthroline group,
cuproine group, anthraquinone group, benzoquinone group, quinone group, acridine group, substituted
or non-substituted alkyl group, substituted or non-substituted aryl group, substituted or non-substituted
aralkyl group, substituted or non-substituted arylamine group, substituted or non-substituted alkylamine
group, substituted or non-substituted aralkylamine group, and substituted or non-substituted
heterocyclic group, wherein two substituents adjacent to each other are not fused or form a fused ring
together.
3. The organic light emitting device as claimed in claim 1, wherein the compound is
represented by formula 2:
wherein A and X are the same as defined in claim 1; and
Rl to R6 are identical or different and each is selected from the group consisting of a
hydrogen atom (H), halogen atom, nitrile group (CN), nitro group (N02), formyl group, acetyl group,
benzoyl group, amide group, styryl group, acetylene group, quinoline group, quinazoline group,
phenanthroline group, cuproine group, anthraquinone group, benzoquinone group, quinone group,
acridine group, substituted or non-substituted alkyl group, substituted or non-substituted aryl group,
substituted or non-substituted aralkyl group, substituted or non-substituted arylamine group, substituted
or non-substituted alkylamine group, substituted or non-substituted aralkylamine group, and substituted
or non-substituted heterocyclic group, wherein Rl and R2, R3 and R4, and R5 and R6 optionally form
a fused ring with each other.
4. The organic light emitting device as claimed in claim 1, wherein the compound is
represented by formula 3:
[Formula 3]
wherein A and X are the same as defined in claim 1; and
Rl to R18 are identical or different and each is selected from the group consisting of a
hydrogen atom (H), halogen atom, nitrile group (CN), nitro group (NO2), formyl group, acetyl group,
benzoyl group, amide group, styryl group, acetylene group, quinoline group, quinazoline group,
phenanthroline group, cuproine group, anthraquinone group, benzoquinone group, quinone group,
acridine group, substituted or non-substituted alkyl group, substituted or non-substituted aryl group,
substituted or non-substituted aralkyl group, substituted or non-substituted arylamine group, substituted
or non-substituted alkylamine group, substituted or non-substituted aralkylamine group, and substituted
or non-substituted heterocyclic group, wherein each of Rl to R18 optionally form a fused ring together
with a substituent adjacent thereto.
5. The organic light emitting device as claimed in claim 1, wherein the compound is selected
from the group consisting of compounds represented by formulae 1-1 to 1-18 and 1-20 to 1-46:
[Formula 1-1]

Disclosed is a compound represented
by formula 1; wherein each of A, X, Y. Y, and Y, has the same meaning as described herein. When used in an organic light emitting device; the compound represented by formula 1 has at least one function selected from the group consisting of hole injection, hole transport, light mitting, election transport, electron injection, etc, depending on the type of each onit forming the trimer or substitutents in each unit. An organic light emitting device is also disclosed. The organic light emitting device includes a first electrode, an organic having one or more layers and a second electrode, laminated successively, wherein at least one layer of the organic film includes at least one compound represented by formula 1.