Organic compounds -- part of the class 532-570 series – Organic compounds – Sulfur containing
Reexamination Certificate
2001-04-10
2004-08-31
Badio, Barbara P. (Department: 1616)
Organic compounds -- part of the class 532-570 series
Organic compounds
Sulfur containing
C568S642000, C564S305000
Reexamination Certificate
active
06784322
ABSTRACT:
STATEMENT AS TO RIGHTS TO INVENTIONS MADE UNDER FEDERALLY SPONSORED RESEARCH AND DEVELOPMENT
Not applicable
BACKGROUND OF THE INVENTION
Organic light emitting devices (OLEDs) are comprised of several thin layers of organic materials. These layers can be made to electroluminesce by applying a voltage across the device, and with sufficient brightness, range of color and operating lifetimes can be a practical alternative to LCD-based full color flat-panel displays. By placing red (R), green (G), and blue (B) emitting organic materials in a vertically stacked geometry with other transparent thin organic films, a new OLED display pixel is achieved which can be fabricated simply and provide a cost effective display panel.
In general, these OLED devices rely on a common mechanism leading to optical emission. Typically, this mechanism is based upon the radiative recombination of a trapped charge. Specifically, OLEDs will contain at least two thin organic layers separating the anode and cathode of the device. The material of one of these layers is specifically chosen based on the material's ability to transport holes, a “hole transporting layer” (HTL), and the material of the other layer is specifically selected according to its ability to transport electrons, an “electron transporting layer” (ETL). With such a construction, the device can be viewed as a diode with a forward bias when the potential applied to the anode is higher than the potential applied to the cathode. Under these bias conditions, the anode injects holes (positive charge carriers) into the hole transporting layer, while the cathode injects electrons into the electron transporting layer. The portion of the luminescent medium adjacent to the anode thus forms a hole injecting and transporting zone while the portion of the luminescent medium adjacent to the cathode forms an electron injecting and transporting zone. The injected holes and electrons each migrate toward the oppositely charged electrode. When an electron and hole localize on the same molecule, a Frenkel exciton is formed. Recombination of this short-lived state may be visualized as an electron dropping from its conduction potential to a valence band, with relaxation occurring, under certain conditions, preferentially via a photoemissive mechanism. Under this view of the mechanism of operation of typical thin-layer organic devices, the electroluminescent layer comprises a luminescence zone receiving mobile charge carriers (electrons and holes) from each electrode.
The materials that function as the electron transporting layer of the OLED are frequently the same materials that are incorporated into the OLED to produce the electroluminescent emission. Such devices in which the electron transporting layer functions as the emissive layer are referred to as having a single heterostructure. Alternatively, the electroluminescent material may be present in a separate emissive layer between the hole transporting layer and the electron transporting layer in what is referred to as a double heterostructure.
In addition to emissive materials that are present as the predominant component in the electron transporting layer, and that function both as the electron transporting material as well as the emissive material, the emissive material may itself be present in relatively low concentrations as a dopant in the electron transporting layer. Whenever a dopant is present, the predominant material in the electron transporting layer may be referred to as a host material. Materials that are present as host and dopant are selected so as to have a high level of energy transfer from the host to the dopant material. In addition, these materials need to be capable of producing acceptable electrical properties for the OLED. Furthermore, such host and dopant materials are preferably capable of being incorporated into the OLED using starting materials that can be readily incorporated into the OLED by using convenient fabrication techniques, in particular, by using vacuum-deposition techniques.
It is desirable for OLEDs to be fabricated using materials that provide electroluminescent emission in a relatively narrow band centered near selected spectral regions, which correspond to one of the three primary colors, red, green and blue so that they may be used as a colored layer in an OLED or stacked OLED. Additionally, the compounds should come from a class of compounds in which the emission may be varied by selectively varying the substituents or by modifying the structure of a base compound that produces emission from a charge transfer transition. Still further, the compounds should be capable of being readily deposited as a thin layer using vapor-phase or vacuum deposition techniques so that the compound can be readily incorporated into an OLED that is prepared entirely from, for example, vacuum-deposited organic materials. Still other considerations for new OEL materials involves considerations of environmental stability, cycle life and ease of fabrication. In order to ensure environmental stability and long cycle life, the organic phosphors should be as inert to unwanted chemical and electrochemical reactions as possible.
A candidate structure in terms of stability would be polyparaphenylene (PPP), a polymer composed of a sequence of linearly connected benzene rings. PPP has excellent stability and luminescence properties, but is neither soluble in organic solvents nor volatile. As a result, PPP cannot be deposited as a thin film on a substrate surface to allow fabrication of a useful display device.
What is needed in the art are new polyparaphenylene materials that have suitable solubility and or deposition properties and further have the desired luminescence properties. Surprisingly, the present invention provides such compounds.
SUMMARY OF THE INVENTION
In one aspect, the present invention provides an oligomeric para-phenylene compound having the formula:
R
1
—(Ar
i
)
n
—R
2
wherein the subscript n is an integer of from 5 to 15; the superscript i is an integer of from 1 to n and denotes the position downstream from R
1
; each Ar
i
is a substituted or unsubstituted aryl group; R
1
and R
2
are each substituents that increase the solubility of the para-phenylene compound in nonpolar organic solvents relative to the solubility of the corresponding compound wherein R
1
and R
2
are hydrogen; with the proviso that the Ar
i
groups are linked together in a 1,4-paraphenylene manner.
Preferably the substituents R
1
and R
2
each independently have the formula:
R
3
—(Ar
j
)
m
—
wherein the subscript m is an integer of from 1 to 5; the superscript j is an integer of from 1 to m and denotes the position of each Ar
j
away from R
3
. Each Ar
j
is selected from:
a) a 1,4-phenylene group having the formula:
wherein each R
4
is independently selected from H, substituted or unsubstituted (C
1
-C
12
)alkyl, substituted or unsubstituted (C
1
-C
12
)alkoxy, substituted or unsubstituted (C
1
-C
12
)alkylamino, substituted or unsubstituted (C
1
-C
12
)alkylthio, substituted or unsubstituted di(C
1
-C
12
) alkylamino, substituted or unsubstituted arylamino, substituted or unsubstituted diarylamino and halogen, with the proviso that at least two of the four R
4
substituents are independently selected from substituted or unsubstituted (C
1
-C
12
)alkyl and substituted or unsubstituted (C
1
-C
12
)alkoxy, and
b) an aryl biradical selected from 1,4-naphthylene, 1,4-anthrylene, 9,10-anthrylene, 5,6,7,8-tetrahydronaphth-1,4-ylene, 9,9′,10,10′-tetra(C
1
-C
12
)alkyl-9,10-dihydroanthr-1,4-ylene, 9,9′10,10′-tetraaryl-9,10-dihydroanthr-1,4-ylene, 9,9′10,10′-tetra(C
1
-C
12
)alkyl-9,10-dihydroanthr-2,6-ylene, and 9,9′10,10′-tetraaryl-9,10-dihydroanthr-1,4-ylene; and R
3
is selected from H, substituted or unsubstituted (C
1
-C
12
)alkyl, substituted or unsubstituted (C
1
-C
12
)alkoxy, substituted or unsubstituted (C
1
-C
12
)alkylamino, substituted or unsubstituted (C
1
-C
12
)alkylthio, substituted or unsubstituted di(C
1
-C
12
)alkylamino, substituted
Badio Barbara P.
Honeywell International , Inc.
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