WO2002020694A1

WO2002020694A1 - Low molecular chromophore compounds and electroluminescence display device comprising the same

Info

Publication number: WO2002020694A1
Application number: PCT/KR2001/001485
Authority: WO
Inventors: Jong-Wook Park
Original assignee: Vistorm Co., Ltd.
Priority date: 2000-09-06
Filing date: 2001-08-31
Publication date: 2002-03-14
Also published as: KR20010044090A; AU2001282664A1; KR20020020204A; KR100351234B1

Abstract

The present invention relates to low molecular chromophore compounds applicable to any one of electroluminescent layer, hole transport layer or electron transport layer of electroluminescence display device. Low molecular chromophore compounds for electroluminescence display device of the present invention comprise carbazole (CVZ) as electron donor part and chromophore, and a stilbene group capable of controlling luminescence area. Furthermore, in order to enhance luminescence efficiency, low molecular chromophore compounds of the present invention may be used along with at least one dopant such as dicarbazolyl azobenzene (DCAB), fluorenyl diacetylene, perylene, carbazole and derivatives thereof, coumarine compounds and 4-(dicyanomethylene)-2-methyl-6-(1,1,7,7-tetramethyljulodinyl-9-enyl)-4H-pyran.

Description

LOW MOLECULAR CHROMOPHORE COMPOUNDS AND

ELECTROLUMINESCENCE DISPLAY DEVICE COMPRISING THE SAME

BACKGROUND OF THE INVENTION

(a) Field of the Invention

The present invention relates to chromophore compounds for

electroluminescence display device and organic electroluminescence display

device comprising the same, more particularly, to low molecular chromophore

compounds applicable to any one of electroluminescent layer (EML), electron

transport layer (ETL) or hole transport layer (HTL) of organic

electroluminescence display device, and highly efficient organic

electroluminescence display device comprising the same.

(b) Description of the Related Art

Recently, as the development of information and communication

industry is accelerated, higher performance display devices are required.

Such display devices may be classified into luminescence type and non-

luminescence type. For the former device, Cathode Ray Tube (CRT),

Electroluminescence Display (ELD), Light Emitting Diode (LED), Plasma

Display Panel (PDP), etc. are exemplified. For the latter device, Liquid

Crystal Display (LCD), etc. are exemplified.

The luminescence type and non-luminescence type display devices

have basic performance such as working voltage, consumption power, brightness, contrast, response time, lifetime and color display, etc. However,

liquid crystal display devices which have largely been used until now have

problems in terms of response time, contrast and viewing angle among the

basic performance described above. Displays using luminescence diode

are expected as next generation display device which solves the problems of

liquid crystal display since they have short response time, and do not require

backlight due to having self-luminescence properties and have improved

brightness etc.

Electroluminescence diode has difficulties in application to large area

electroluminescence display device because inorganic material with

crystalline form is mainly used. Furthermore, in case of

electroluminescence display device using inorganic material, there are

disadvantages that more than 200 V of driving voltage is required and it is

expensive. Active research on electroluminescence display device

comprising the organic material has been undertaken since Eastman Kodak

Company disclosed a device made from material having π-conjugated

structure in 1987. In case of organic material, there are advantages that

synthetic pathway is relatively simpler and various forms of materials are

synthesized, and thus color tuning is possible. On the contrary, the organic

material has disadvantages that crystallization by heat occurs due to low

mechanical strength.

Organic materials used in electroluminescence display device are classified into low molecular organic materials and high molecular organic

materials. For low molecular organic materials, diamine, diamine

derivatives such as N,N'-bis-(4-methylphenyl)-N,N'-bis(phenyl)benzidine

(TPD), etc., derivatives of perylene tetracarboxylic acid, oxadiazole

derivatives, 1 ,1 ,4,4-tetraphenyl-1 ,3-butadiene (TPB), etc. are exemplified.

In case of organic electroluminescence display device, evaporation

method is used for producing thin film. When applying low molecular

compounds, more uniform thin film can be obtained than when applying high

molecular compounds, and thus brightness and luminescence efficiency of

the device are more improved.

SUMMARY OF THE INVENTION

The object of the present invention is to provide low molecular

chromophore compounds for electroluminescence display device, which can

be applied to any one of electroluminescent layer, hole transport layer or

electron transport layer of electroluminescence display device.

Another object of the present invention is to provide a

electroluminescence display device having a low driving voltage, various

color developments, and short response time.

The present invention provides to achieve the objects as described

above, low molecular chromophore compounds in which carbazole (CVZ),

carbazole derivatives or analogs of aromatic amines as electron donor part

are located at both sides of the compounds and a stilbene group capable of controlling luminescence area is located at the center of the compounds.

The present invention also provides electroluminescence display

device in which said low molecular chromophore compounds are applied to

any one of electroluminescent layer, hole transport layer or electron

transport layer.

BRIEF DESCRIPTION OF THE DRAWINGS

Fig. 1 shows proton nuclear magnetic resonance spectrum (¹H-NMR)

spectrum to 4,4'-dicarbazolyl stilbene (DCS) prepared according to Example

1 of the present invention.

Fig. 2 is a schematic sectional view of organic electroluminescence

display device according to the present invention.

Fig. 3 shows photoluminescence (PL) spectrum of 4,4'-dicarbazolyl

stilbene.

Fig. 4 shows EL spectrum of electroluminescence diode comprising

ITO anode, buffer layer, 4,4'-dicarbazolyl stilbene electroluminescent layer,

LiF layer and Al cathode (ITO/PEDOT/DCS/LIF/AI) which is manufactured

according to Example 4 of the present invention.

Fig. 5 shows current-voltage (l-V) characteristic of

electroluminescence diode comprising ITO anode, buffer layer, 4,4'-

dicarbazolyl stilbene electroluminescent layer, LiF layer and Al cathode

(ITO/PEDOT/DCS/LIF/AI) which is manufactured according to Example 4 of

the present invention. Fig. 6 shows EL spectrum of electroluminescence diode comprising

ITO anode, buffer layer, electroluminescent layer comprising 4,4'-dicarbazolyl

stilbene doped with dicarbazolyl azobenzene, LiF layer and Al cathode

(ITO/PEDOT/DCS-DCAB/LIF/AI) which is manufactured according to

Example 5 of the present invention.

Fig. 7 shows EL spectrum of electroluminescence diode comprising

ITO anode, buffer layer, electroluminescent layer comprising 4, 4' -dicarbazolyl

stilbene doped with fluorenyl diacetylene, LiF layer and Al cathode

(ITO/PEDOT/DCS-FDA/LIF/AI) which is manufactured according to Example

6 of the present invention.

Fig. 8 shows EL spectrum of electroluminescence diode comprising

ITO anode, buffer layer, electroluminescent layer comprising 4,4'-dicarbazolyl

stilbene doped with cabazole, LiF layer and Al cathode (ITO/PEDOT/DCS-

CVZ/LIF/AI) which manufactured according to Example 8 of the present

invention.

DETAILED DESCRIPTION OF THE PRESENT INVENTION

Low molecular chromophore compounds of the present invention are

organic compounds applicable to any one of electroluminescent layer, hole

transport layer or electron transport layer of electroluminescence display

device. Said compounds comprise carbazole (CVZ), carbazole derivatives

or aromatic amine-based analogs as electron donor part, and a stilbene

group capable of controlling luminescence area. The compounds have carbazole-stilbene-carbazole structure where carbazole (CVZ), carbazole

derivatives or aromatic amine-based analogs are located at both sides of the

compounds and a stilbene group is located at the center of the compounds.

Specific examples of these compounds are 4,4'-dicarbazolyl stilbene (DCS)

or substituted 4,4'-dicarbazolyl stilbene derivatives at its carbazole group

represented as the formula (1):

(1) wherein, R₁₅ R₂, R3 and R are independently selected from the group

consisting of hydrogen, Ci to C₁₂ aliphatic alkyl group, branched alkyl group,

C₅ to C₂ cyclic alkyl group, C₄ to C₁₄ aromatic group, and the aromatic group

has at least one substituent selected from the group consisting of halogen

such as F, Cl, Br and I, R'₃Si (R' is Ci to C1₂ alkyl group), Ci to C₁₂ alkoxy,

aliphatic amine and aromatic amine. Substituents of said chromophore

compounds may be selected to obtain desirable properties such as

crystallization degree, thermal stability, solubility, etc.

Furthermore, for low molecular chromophore compound of the

present invention, compounds having structure where aromatic amine-based analogs instead of carbazole as electron donor part are located at both sides

of the compounds and a stilbene group capable of controlling luminescence

area is located at the center of the compounds may be used. The aromatic

amine-based analogs are functional groups selected from the group

consisting of formulas (2) to (15). These may be symmetrically or

asymmetrically linked to the stilbene group at ortho, meta, or para positions.

(2) wherein, R₅ and R₆ are independently hydrogen or Ci to C₆ alkyl

group, and m and n are an integer of 0 to 6.

(3)

(4)

(5)

(6)

(7) wherein, R₇ and R₈ are independently selected from the group

consisting of hydrogen, halogen selected from the group consisting of F, Cl,

Br and I, preferably F, Ci to C₁₂, preferably Ci to C₆ alkyl group, Ci to Cι₂,

preferably Ci to C₆ alkoxy group, C₆ to C₃o, preferably C₆ to Cι₈ aryl group,

and C₆ to C₃o, preferably C₆ to Cι₈ aryloxy group.

(8) wherein, m and n are an integer of 0 to 6.

(9) wherein, m and n are an integer of 0 to 6.

wherein, m and n are an integer of 0 to 6.

(11) wherein, m and n are an integer of 0 to 6.

(12)

wherein, R₉ and R- are independently C₆ to C30, preferably C₆ to Cι₈

aryl group, more preferably phenyl group, and m and n are an integer of 0 to

6.

(13)

wherein, m and n are an integer of 1 to 6.

(14)

wherein, R-n is selected from the group consisting of hydrogen,

halogen selected from the group consisting of F, Cl, Br and I, preferably F, Ci

to C₁₂, preferably C-i to C₆ alkyl group, C-_\ to C₁₂, preferably Ci to C₆ alkoxy

group, C₆ to C30, preferably C₆ to C-|₈ aryl group, and C₆ to C₃₀, preferably C₆

to C₁₈ aryloxy group.

At least one hydrogen which exists in the aromatic ring of the

aromatic amine-based analogs of the formulas (2) to (15) may be substituted

with functional groups selected from the group consisting of halogen selected

from the group consisting of F, Cl, Br and I, preferably F, Ci to Cι₂, preferably

Ci to C₆ alkyl group, Ci to Cι₂, preferably C-i to C₆ alkoxy group, Ci to Cι₂,

preferably Ci to C₆ haloalkyl group, preferably fluoroalkyl, C₆ to C₃₀,

preferably C₆ to Cι₈ aryl group, and C₆ to C₃o, preferably C₆ to Cι₈ aryloxy

group. The preferred example with the functional groups is a substituent of

the formula (6) as described above having the following formula (16):

(16)

wherein, Rι₂ is Ci to Cι₂, preferably Ci to C₆ haloalkyl, preferably CF₃,

and R13 is hydrogen, Ci to Cι₂, preferably Ci to C₆ alkyl group, Ci to Cι₂,

preferably C-i to C₆ alkoxy group, C₆ to C₃₀, preferably C₆ to C₁₈ aryl group or

C₆ to C-30, preferably C₆ to C₁₈ aryloxy group.

Low molecular chromophore compounds of the present invention may

be used with dopants such as organic compounds having conjugated double

bonds. Said dopants are organic compounds having conjugated double

bonds and materials which have a smaller energy gap than the doped

material, and thus less maximum wavelength value than the doped material, and good energy transfer and chromophore property. For said dopants, at

least one compound selected from the group consisting of dicarbazolyl

azobenzene (DCAB), fluorenyl diacetylene (FDA), perylene, carbazole,

carbazole derivatives, coumarine compounds and 4-(dicyanomethylene)-2-

methyl-6-(1 ,1 ,7,7-tetramethyljulodinyl-9-enyl)-4H-pyran (DCJT) may be used.

The dicarbazolyl azobenzene (DCAB) has the formula (17):

(17)

The fluorenyl diacetylene (FDA) has the formula (18):

(18)

wherein, Ru and R15 are independently selected from the group

consisting of hydrogen, Ci to C-io alkyl group, C₅ to C aromatic ring, C₅ to

C₂₄ cycloalkane, and acetyl group.

The perylene has the formula (19).

(19)

The 4-(dicyanomethylene)-2-methyl-6-(1 ,1 ,7,7-tetramethyljulodinyl-9-

enyl)-4H-pyran has the formula (20):

(20)

For said coumarines compounds, coumarine 6 (manufactured by

exciton corp.) having the formula (21) may be preferably used:

(21)

Said dopants may have more than one substituent to obtain desirable

properties such as crystallization degree, thermal stability, solubility, etc.

Dicarbazolyl azobenzene (DCAB), fluorenyl diacetylene (FDA),

perylene, carbazole and carbazole derivatives serve as blue dopants,

coumarines compounds as green dopants, and 4-(dicyanomethylene)-2- methyl-6-(1 ,1 ,7,7-tetramethyljulodinyl-9-enyl)-4H-pyran serves as red dopant.

A combination of more than one dopant may be used.

The amount of said dopants is preferably 0.1 to 30 % by weight, more

preferably 5 to 30 % by weight, most preferably 5 to 10 % by weight, based

on the amount of low molecular chromophore compounds.

The electroluminescent layer of the present invention can be formed

by standard methods including, but not limited to, physical vapor deposition

methods, sputtering, spin-coating, or solution casting.

According to the first preferred embodiment, a process for

synthesizing 4,4'-dicarbazolyl stilbene (DCS) of the formula (1) is provided.

The synthesizing comprises: a) preparing 4-carbazolyl benzaldehyde by

reacting carbazole with 4-fluorbenzaldehyde under the presence of

potassium carbonate/dimethylformamide; and b) synthesizing 4,4'-

dicarbazolyl stilbene by reacting 4-fluorbenzaldehyde in tetrahydrofuran

solvent under the presence of tetrachlorotitanium and zinc metal, as shown in

the scheme shown below:

According to the second preferred embodiment, 4,4'-dicarbazolyl

stilbene may be synthesized through a synthetic method, which comprises a)

reacting n-alkyllithium with 1 ,2-dichloroethylene under solvent, followed by

adding tri(n-butyl)tin halide to obtain the resulting reactant; b) adding

azobisisobutylonitrile (AIBN) as initiator and tri(n-butyl)tin hydride to the

reactant of the a) step, thereby preparing trans-1 ,2-bis(tri-n-

butylstannyl)ethylene; c) dissolving tris(dibenzylidene acetone)dipalladium,

diphenylphosphinoferrocene, NaO-t-butyl and 1 ,4-dibromobenzene in solvent,

followed by reacting with carbazole to prepare 1 -(9-N-carbazolyl)-4-

bromobenzene; and d) dissolving trans-1 , 2-bis(tri-n-butylstannyl) ethylene

prepared in the b) step and 1 -(9-N-carbazolyl)-4-bromobenzene prepared in

the c) step in solvent, followed by reacting with

tetra(triphenylphosphine)palladium (Pd(PPh₃)₄) to prepare 4,4'-dicarbazolyl

stilbene.

According to the third preferred embodiment, which utilizes Ullmann

coupling reaction, 4,4'-dicarbazolyl stilbene may be prepared by dissolving

4,4-dibromostilbene, carbazole, activated Cu, potassium carbonate, and 18- crown-6 in organic solvent, followed by reacting for 2 to 3 days.

The low molecular chromophore compounds according to the present

invention are applied between anode made from ITO (indium tin oxide)

having a large work function, which injects holes, and cathode made from

metals having various work function, such as aluminum,

lithiumfluoride/aluminum, copper, silver, calcium, gold, magnesium, etc., an

alloy of magnesium and silver, and an alloy of aluminum and lithium, which

injects electrons.

Examples

^' Hereinafter, the preferred embodiments of the present invention will be

described. However, these are presented only for better understanding of

the present invention, and the present invention is not limited thereto.

Example 1

Method for synthesizing 4,4'-bis[carbazolyl-(9)l-stilbene (1)

10 g (60 mmol) of carbazole (product of Aldrich corp.) and 7.425 g

(60 mmol) of 4-fluorobenzaldehyde (product of Aldrich corp.) were placed

into 100 mi of flask, and then, to this mixture was added 16.5 g of two-fold

equivalent of potassium carbonate, followed by agitating the mixture with

refluxing under dimethylformamide solvent. Whether the reaction is

completed or not was examined by tin layer chromatography (TLC), and then,

the resultant product was separated by column chromatography, and

produced 4-carbazolyl benzaldehyde was agitated with refluxing for 6 hours in tetrahydrofuran solvent dried under the presence of two-fold equivalent of

tetrachlorotitanium and two-fold equivalent of zinc metal. The resultant

product was purified using column chromatography, and then, crystal was

extracted from toluene to obtain pure 4,4'-bis[dicarbazolyl-(9)]-stilbene (DCS).

The yield of the final product was more than 80% and very stabilized form

was observed.

Example 2

Method for synthesizing 4,4'-bis|carbazolyl-(9)1-stilbene (2)

(1 ) Synthesis of trans-1 ,2-bis(tri-n-butylstannyl)ethylene

Into 100 m£ of schlenk flask were placed 1 ,2-dichloroethylene 3.2 mϋ

(41.7 mmol) and about 40 ml of dried THF, and then, was cooled at the

temperature of -78 ^°C , followed by slowly adding 1.6 M of n-butyllithium (n-

BuLi) 51.5 mi (82.4 mmol) in dropwise. The solution was light pink in color.

After adding n-butyl lithium, the solution was left to ambient temperature.

After about 1 hour, the temperature was decreased again to -78 ^°C, and then,

tri(n-butyl)tin chloride 11.18 ml (41.2 mmol) was added to the solution,

followed by stirring for 1 hour, and then, about 1 cc of methyl iodide was

added to the solution, followed by additional stirring for 1 hour. The solution

was vacuum-evaporated at 100 to 150 ^°C, at a pressure of about 0.01 torr,

and to the resultant compound 12.81 g (36.3 mmol) were added tri(n-butyl)tin

hydride 21.3 g (73.2 mmol) and azobisisobutylronitrile (AIBN) 0.13 g, and

then, the mixture was stirred for about 4 hours at about 90 "C, followed by vacuum-evaporation to separate the final compound. The yield was 70 %.

(2) Synthesis of 1-(9-N-carbazolyl)-4-bromobenzene

Tris(dibenzylidenacetone)dipalladium (Pd₂(DBA)₃) 0.054 g (0.015

equivalent), diphenylphosphinoferrocene (DPPF) 0.049 g (0.0225 equivalent),

NaO-t-Bu 0.57 g (1.5 equivalents) and 1 ,4-dibromobenzene 2.8 g (3

equivalents) were dissolved in toluene 40 to 50 ml, followed by stirring for 20

to 30 minutes and then, at near 100 ^°C, carbazole 0.66 g (1 equivalent) was

put into the solution. The reaction was conducted for 2 to 3 days under

refluxing condition. All reagents were transferred in nitrogen atmosphere.

The reaction was monitored by TLC, and when all carbazole disappeared,

the reaction solution was cooled and was dispersed in a large amount of

MeOH, and then, the resultant product was filtrated and dried, and purified by

silica-gel chromatography.

(3) Synthesis of [4,4'-bis[carbazolyl-(9)]-stilbene]

1-(9-N-carbazolyl)-4-bromobenzene 2 equivalents and trans-1 ,2-

bis(tri-n-butylstannyl) ethylene 1 equivalent were dissolved in toluene, and

then, 3 mol% of Pd(PPh₃)₄were added, followed by degassing the reactant

mixture. The reaction was conducted for about 1 to 2 days under mild

refluxing condition. All reagents were transferred in nitrogen atmosphere.

The reaction was monitored by TLC, and when all carbazole disappeared,

the reaction solution was cooled and was dispersed in a large amount of

MeOH, and then, the resultant product was filtrated and dried, and purified by silica-gel chromatography.

Example 3

Method for synthesizing 4,4'-bisrcarbazolyl-(9)1-stilbene (3)

The synthesis was achieved by way of Ullmann coupling reaction.

4,4-dibromostilbene 0.0312 mol, carbazole 0.0625 mol, activated Cu

0.0625 mol, potassium carbonate 0.0248 mmol, and 18-crown-6 1.88 mmol

were dissolved in about 300 to 400 ml of 1 ,2-dichlorobenzene, followed by

reacting the mixture at 180 ^°C for 2 to 3 days. All reagents were

transferred in nitrogen atmosphere. The reaction was monitored by TLC,

and the product was dried, and purified by silica-gel chromatography.

The structure of chromophore compound

In order to confirm the structure of 4,4'-dicarbazolyl stilbene (DCS),

¹H-NMR spectrum was measured to be shown in Fig. 1. The results of

element analysis measurement are as follows.

Elemental analysis of C₃₈H₂₆N₂: theoretical values C, 89.41 ; H, 5.1 ; N,

5.49 : measured values C, 89.38; H, 5.11 ; N, 5.51

Construction of electroluminescence display device

Example 4

Fig. 2 shows the sectional structure of electroluminescence display

device, where ITO anode 1 is formed on glass substrate and buffer layer 2

exists to compensate the surface of ITO layer and help the injection and flow

of holes. The suitable materials such as plastic, quartz, ceramic, and silicon may be used instead of glass. Materials used as buffer are exemplified by

high molecular materials such as doped polyaniline (PANI) and doped

polyethylenedeoxythiopene (PEDOT), and low molecular materials such as

alpha-CuPc. A thin film having thickness from 20 nm to 150 nm was

formed by spin coating PANI and PEDOT. Alternatively, a thin film having

thickness from 20 nm to 100 nm might be formed by vacuum-deposition of

alpha-CuPc. A hole transport layer (HTL) 3 with thickness of 20 nm to 100

nm may be formed with TPD or TPD derivatives on the buffer layer. 4,4'-

dicarbazolyl stilbene (DCS) prepared according to Example 1 was vaccum-

deposited with the velocity of 0.5 A/sec, under the vacuum condition of 1 x

10^"6 torr, onto ITO/buffer layer or ITO/buffer/hole transport layer (HTL),

forming electroluminescent layer 4 having area of 4 mn and thickness of 300

to 1000 A. Electron transport layer (ETL) 5 with thickness of 5 nm to 80

nm may be formed with Alq₃ or Bu-PBD on the electroluminescent layer.

Then, LiF layer 6 with thickness of 0.5 nm which helps the injection of

electron was formed thereon using vacuum-deposition, and aluminum

cathode 7 with thickness of >100 nm was vacuum-deposited to manufacture

a electroluminescence diode. In deposition, the thickness and growth

velocity of the film were controlled by utilizing a monitor of film thickness. As

a result of examination with optical microscope and electron microscope,

electroluminescent layer of chromophore compounds showed excellent film

surface properties. Example 5

A luminescence diode was manufactured by the same method as

Example 4, except that, in forming electroluminescent layer of a

luminescence diode, DCS-DCAB electroluminescent layer was manufactured

by deposition of 4'-dicarbazolyl stilbene (DCS) along with 5 % by weight of

dicarbazolyl azobenzene (DCAB) based on the weight of DCS.

Example 6

A luminescence diode was manufactured by the same method as

Example 4, except that, in forming electroluminescent layer of luminescence

diode, DCS-FDA luminescence layer was manufactured by deposition of 4'-

dicarbazolyl stilbene (DCS) along with 5 % by weight of fluorenyl diacetylene

(FDA) based on the weight of DCS.^"

Example 7

A luminescence diode was manufactured by the same method as

Example 4, except that, in forming electroluminescent layer of luminescence

diode, DCS-perylene luminescence layer was manufactured by deposition of

4'-dicarbazolyl stilbene (DCS) along with 5 % by weight of perylene based on

the weight of DCS.

Example 8

A luminescence diode was manufactured by the same method as

Example 4, except that, in forming electroluminescent layer of luminescence

diode, DCS-CVZ luminescence layer was manufactured by deposition of 4'- dicarbazolyl stilbene (DCS) along with 5 % by weight of carbazole based on

the weight of DCS.

Measurements of the properties of electroluminescence display

PL spectrum of 4,4'-dicarbazolyl stilbene was shown in Fig. 3 and EL

spectrum of the electroluminescence diode manufactured according to

Example 4 as described above was shown in Fig. 4. According to UV-vis

spectrum, an absorption band at 380 nm was shown, and this band seems to

be a result of π→π* transition of conjugated double bond. According to PL

and EL spectra, in case that excitation wavelength was 380 nm, maximum

wavelength of luminescence color was 423 nm, showing a wavelength of

blue color in a series of deep blue. This corresponds to 2.93 eV of quantum

energy.

Furthermore, to the luminescence diode of Example 4 was applied an

electric field, and l-V characteristic was measured. I-V characteristic of

luminescence diode (ITO/PEDOT/DCS/LiF/AI) in which the compound of

Example 1 was applied to electroluminescent layer (600 A) was measured

to be shown in Fig. 5. In the curve of Fig. 5, typical l-V characteristics of

diode were shown. Turn-on voltage was 4 V, and maximum brightness was

7,000 cd/m². These measurement results indicated that turn-on voltage was

lower and higher brightness was shown than those of the conventional

chromophore compounds.

EL spectrum of ITO/PEDOT/DCS-DCAB/LiF/AI luminescence diode in which electroluminescent layer was formed by deposition of DCS

chromophore compounds together with dicarbazolyl azobenzene (DCAB)

dopant was shown in Fig. 6. EL spectrum of ITO/PEDOT/DCS-FDA/LiF/AI

luminescence diode of Example 6, in which fluorenyl diacetylene (FDA) was

used as dopant, was shown in Fig. 7. EL spectrum of ITO/PEDOT/DCS-

FDA/LiF/AI luminescence diode of Example 8, in which carbazole was used

as dopant, was shown in Fig. 8. These devices showed a high increase of

brightness to the extent of about 10,000 to 20,000 cd/m² in maximum

brightness, thereby indicating that the chromophore compounds of the

present invention can be applied to multiple layer EL display device with high

efficiency.

Comparative Example 1

Conventional 1 ,1 ,4,4-tetraphenyl-1 ,3-butadiene (TPB) as low

molecular chromophore compound was placed between ITO anode and Al

cathode, and an electric field was applied thereto, measuring luminescence

diode properties. Maximum wavelength of luminescence color was 460 nm,

showing blue color wavelength, and, in case that electroluminescent layer

was manufactured to have thickness of 600 A, the turn-on voltage was 10 V

and the brightness was 5000 cd/m'.

Organic compounds for electroluminescence display device of the

present invention comprise carbazole as electron donor part, and stilbene

group capable of controlling luminescence area, which can be applicable to any one of electroluminescent layer, hole transport layer, and electron

transport layer. In case that said low molecular chromophore compounds

are applied, electroluminescence display device emitting blue color can be

driven at low voltage. Furthermore, dopants which are organic compounds

with conjugated double bonds and doping materials having a smaller energy

gap than the doped materials, and thus, less maximum wavelength value

than the doped materials, and good energy transfer and chromophore

property, are used along with the chromophore compounds to make various

color realization at low energy possible, and to improve the brightness and

luminescence efficiency.

The simple modifications and changes of the present invention may be

made by those skilled in the art, without departing from the scope of the

invention.

Claims

WHAT IS CLAIMED IS:

1. A low molecular chromophore compound for electroluminescence

display device, comprising carbazole (CVZ), carbazole derivatives or

aromatic amine-based analogs as electron donor part are located at both

sides of the compound, and a stilbene group capable of controlling

luminescent area is located at the center of the compound.

2. The low molecular chromophore compound for

electroluminescence display device according to claim 1 , the compound is

represented by the formula (1):

(1) wherein Rt, R₂, R₃ and R₄are independently selected from the group

consisting of H, Ci to C₁₂ aliphatic alkyl group, branched chain alkyl group, C₅

to C₂₄ cyclic alkyl group, C₄ to Cι₄ aromatic group, and said aromatic group

have at least one substituent selected from the group consisting of halogen

selected from the group consisting of more than one of F, Cl, Br and I, R'sSi

(R' is Ci to Cι₂ alkyl group), Ci to Cι₂ alkoxy, aliphatic amine and aromatic amine.

3. The low molecular chromophore compound for

electroluminescence display device according to claim 1 , wherein said

aromatic amine-based analogs of said chromophore compound are at least

one functional group selected from the group consisting of formulas (2) to

(15):

(2) wherein, R₅ and R₆ are independently hydrogen, or Ci to C₆ alkyl

group, and m and n are an integer of 0 to 6;

(3);

(4);

(5);

(6);

(7)

wherein, R₇ and R₈ are independently selected from the group

consisting of hydrogen, halogen selected from the group consisting of F, Cl,

Br and I, Ci to Cι₂ alkyl group, Ci to C₁₂ alkoxy group, C₆ to C₃o aryl group,

and C₆ to C₃o aryloxy group;

(8) wherein, m and n are an integer of 0 to 6;

(9) wherein, m and n are an integer of 0 to 6;

(10)

wherein, m and n are an integer of 0 to 6;

(11) wherein, m and n are an integer of 0 to 6;

(12)

wherein, R₉ and Rio are independently C₆ to C₃o aryl group, and m

and n are an integer of 0 to 6;

(13)

wherein, m and n are an integer of 1 to 6;

(14)

wherein, Rn is selected from the group consisting of hydrogen,

halogen selected from the group consisting of F, Cl, Br and I, Ci to Cι₂ alkyl

group, Ci to C₁₂ alkoxy group, C₆ to C₃₀ aryl group, and C₆ to C30 aryloxy

group; and

(15)

4. The low molecular chromophore compound for

electroluminescence display device according to claim 3, wherein aromatic

ring of said aromatic amine-based analogs having the formulas (2) to (15)

has at least one substituent selected from the group consisting of halogen

selected from the group consisting of F, Cl, Br and I, Ci to C₁₂ alkyl group, Ci

to C-i₂ alkoxy group, Ci to C₁₂ haloalkyl group, C₆ to C30 aryl group, and C₆ to

C30 aryloxy group.

5. The low molecular chromophore compound for

electroluminescence display device according to claim 4, wherein aromatic ring of said aromatic amine-based analogs having the formula (2) to (15) has

at least one substituent selected from the group consisting of F, Ci to C₆ alkyl

group, Ci to C₆ alkoxy group, C to C₆ fluoroalkyl group, C₆ to Cι₈ aryl group,

and C₆ to Cι₈ aryloxy group.

6. The low molecular chromophore compound for

electroluminescence display device according to claim 4, said aromatic

amine-based analogs have the formula (16):

(16)

wherein, R ₂ is Ci to Cι₂ haloalkyl, and R₁3 is hydrogen, Ci to Cι₂

alkyl group, Ci to Cι₂ alkoxy group, C₆ to C₃₀ aryl group or C₆ to C₃₀ aryloxy

group.

7. The low molecular chromophore compound for

electroluminescence display device according to claim 6, wherein R₁₂ is CF₃

and R₁3 is hydrogen, Ci to C₆ alkyl group, Ci to C₆ alkoxy group, C& to Cι₈

aryl group or C₆ to C-ie aryloxy group.

8. The low molecular chromophore compound for

electroluminescence display device according to claim 3, wherein said

aromatic amine-based analogs are symmetrically or asymmetrically linked to

a stilbene group.

9. An organic electroluminescence display device comprising low

molecular chromophore compound according to claim 1 applied to at least

one of electroluminescent layer, hole transport layer and electron transport

layer.

10. An organic electroluminescence display device comprising low

molecular chromophore compound according to claim 2 applied to at least

one of electroluminescent layer, hole transport layer and electron transport

layer.

11. An organic electroluminescence display device comprising low

molecular chromophore compound according to claim 3 applied to at least

one of electroluminescent layer, hole transport layer and electron transport

layer.

12. An organic electroluminescence display device comprising low

molecular chromophore compound according to claim 4 applied to at least

one of electroluminescent layer, hole transport layer and electron transport

layer.

13. An organic electroluminescence display device comprising low

molecular chromophore compound according to claim 5 applied to at least

one of electroluminescent layer, hole transport layer and electron transport

layer.

14. An organic electroluminescence display device comprising low

molecular chromophore compound according to claim 6 applied to at least one of electroluminescent layer, hole transport layer and electron transport

layer.

15. An organic electroluminescence display device comprising a low

molecular chromophore compound according to claim 1 and dopant which is

organic compounds having conjugated double bonds, a smaller energy gap

than the doped material, and thus less maximum wavelength value than the

doped material, and good energy transfer and chromophore property.

16. The organic electroluminescence display device according to

claim 15, wherein said dopant is at least one compound selected from the

group consisting of dicarbazolyl azobenzene (DCAB) of the formula (17),

fluorenyl diacetylene (FDA) of the formula (18), perylene of the formula (19),

carbazole, carbazole derivatives, coumarine compounds and 4-

(dicyanomethylene)-2-methyl-6-(1 ,1 ,7,7-tetramethyljulodinyl-9-enyl)-4H-pyran

of the formula (20):

(17)

wherein, R ₄ and R₁₅ are independently selected from the group

consisting of hydrogen, Ci to C10 alkyl group, C₅ to C₂₄ aromatic ring, C₅ to

C₂ cycloalkane, and acetyl group,

(19)

(20)

17. The organic electroluminescence display device according to

claim 15, wherein the amount of said dopant is 0.1 to 30 % by weight based

on the chromophore compound.

18. An organic electroluminescence display device comprising a low

molecular chromophore compound according to claim 3 and dopant which is

organic compounds having conjugated double bonds, a smaller energy gap

than the doped material, and thus less maximum wavelength value than the doped material, and good energy transfer and chromophore property.

19. The organic electroluminescence display device according to

claim 18, wherein said dopant is at least one compound compound selected

from the group consisting of dicarbazolyl azobenzene (DCAB) of the formula

(17), fluorenyl diacetylene (FDA) of the formula (18), perylene of the formula

(19), carbazole, carbazole derivatives, coumarine compounds and 4-

(dicyanomethylene)-2-methyl-6-(1 ,1 ,7,7-tetramethyljulodinyl-9-enyl)-4H-pyran

of the formula (20):

(17)

(18)

wherein, R₁₄ and R ₅ are independently selected from the group

consisting of H, Ci to Cio alkyl group, C₅ to C₂₄ aromatic ring, C₅ to C₂

cycloalkane, and acetyl group,

(19)

(20)

^'20. The organic electroluminescence display device according to

claim 18, wherein the amount of said dopant is 0.1 to 30 % by weight based

on the chromophore compound.

21. An organic electroluminescence display device comprising 4,4'-

dicarbazolyl stilbene, and carbazole or carbazole derivatives dopant.

23. A method for preparing a low molecular chromophore

compound for organic electroluminescence display device, comprising:

a) preparing 4-carbazolyl benzaldehyde by reacting carbazole with 4-

fluorbenzaldehyde under the presence of potassium carbonate/

dimethylformamide; and

b) synthesizing 4,4'-dicarbazolyl stilbene by reacting 4-

fluorbenzaldehyde in tetrahydrofuran solvent under the presence of

tetrachlorotitanium and zinc metal.

24. A method for preparing a low molecular chromophore compound for organic electroluminescence display device, comprising:

a) reacting n-alkyllithium with 1 ,2-dichloroethylene under solvent,

followed by adding tri(n-butyl)tin halide to obtain the resulting

reactant;

b) adding azobisisobutylonitrile (AIBN) as initiator and tri(n-butyl)tin

hydride to the reactant of the a) step, thereby preparing trans-1 ,2-

bis(tri-n-butylstannyl) ethylene;

c) dissolving tris(dibenzylideneacetone)dipalladium,

diphenylphosphinoferrocene, NaO-t-butyl and 1 ,4-dibromobenzene

in solvent, followed by reacting with carbazole to prepare 1-(9-N-

carbazolyl)-4-bromobenzene; and

d) dissolving trans-1 ,2-bis(tri-n-butylstannyl) ethylene prepared in the

b) step and 1 -(9-N-carbazolyl)-4-bromobenzene prepared in the c)

step in solvent, followed by reacting with

tetra(triphenylphosphine)palladium (Pd(PPh₃)₄) to prepare 4,4'-

dicarbazolyl stilbene.

25. A method for preparing a low molecular chromophore

compound for organic electroluminescence display device, comprising

preparing 4,4'-dicarbazolyl stilbene by reacting 4,4-dibromostilbene,

carbazole, activated Cu, potassium carbonate and 18-crown-6 under organic

solvent.