Organic light emitting displays and new fluorescent compounds

Details Organic light emitting displays and new fluorescent compounds Organic light emitting displays and new fluorescent compounds

2001-03-06

2003-09-30

Yamnitzky, Marie (Department: 1774)

Compositions

Organic luminescent material containing compositions

C252S301350, C428S690000, C428S917000, C313S504000, C549S283000, C549S288000, C548S305100

Reexamination Certificate

active

06627111

ABSTRACT:

TECHNICAL FIELD
The present invention relates to organic light emitting displays (OLED) and more particularly to organic light emitting displays comprising fluorescent dyes having an amine moiety substituted with two aryl groups in the emitting layer. Organic light emitting displays of the present invention exhibit increased fluorescent efficiency.
The present invention also relates to new fluorescent compounds having amine moiety substituted with two aryl groups which are useful in the organic light emitting displays, as well as for other purposes such as laser dyes, fluorescent probes in biological systems and in electro-optical applications.
BACKGROUND OF INVENTION
An electric display device is an electronic device for visually transmitting information from a machine to a person, thereby acting as an interface. Among the more promising emerging display technologies is the organic light emitting display (OLED).
One of the simpler routes to full-color organic light emitting diode (OLED) displays uses thin films containing fluorescent dyes to down-convert blue emitted light to green and red. These fluorescent materials need to have high absorbance in the blue wavelengths, high fluorescence efficiencies in the green or red wavelengths and be photo-oxidatively stable. These color-conversion materials must be patterned to match the size of the sub-pixels in the display.
At present, many of the known fluorescent materials have the correct color spectra but suffer from photo-degradation and low fluorescence quantum yields and furthermore are too basic to be incorporated into a directly patternable manufacturing process. Some fluorescent dyes have strongly pH-dependent absorption and fluorescence characteristics. This puts limits on the pH range of the medium in which the fluorophore is useful. This pH sensitivity is due to the reconfiguration of the fluorophores that occurs upon protonation. For example, current fluorophores containing dialkylamine groups are subject to protonation in the presence of acid.
One particular problem found with pH-sensitive fluorescent dyes is in their use in color-conversion materials. In the case of small pixels (2-50 microns in width) found in micro- and compact displays, the ability to use a photopatternable material as the matrix for the fluorescent dyes would be a very attractive patterning scheme. Unfortunately, the most commonly used fluorescent dyes contain primary or alkyl substituted amines as part of the chromophore. These pH-sensitive amines are incompatible with the chemistry of most modern photoresists, in particular the acid generated during exposure protonates the dialkylamine, bleaches the fluorescent dye, and renders the color-converter useless. Many current lithographic processes employ acid catalyzed chemically amplified photoresists. Accordingly, there exists a need to provide for improved fluorescent materials.
SUMMARY OF INVENTION
The present invention provides fluorescent materials which do not suffer from the above problems and disadvantages and consequently are more suitable for use in OLED systems. Fluorescent materials of the present invention exhibit enhanced fluorescence efficiency and photo-oxidative stability, and are relatively insensitive to pH.
Fluorescent materials used in the present invention, being relatively pH-insensitive, are capable of surviving photopatterning processes involving photo-acid generators. Accordingly, simpler direct routes to photolithographically patterned color-converters can be used.
It has surprisingly been found according to the present invention that amine fluorescent compounds having an amine moiety substituted with two aryl groups have much higher fluorescence efficiency than their alkyl substituted analogs, making the color-conversion films more efficient as well. Photo-oxidative stability is another unexpected feature of the compounds employed pursuant to the present invention.
Accordingly, the present invention relates to an organic light emitting display which comprises a hole transporting/anode layer, an electron transporting/cathode layer and an emitting layer located intermittent the anode layer and cathode layer. The emitting layer comprises a fluorescent dye having at least one amine moiety substituted with two aryl groups.
A further aspect of the present invention relates to fluorescent compounds selected from the group consisting of
wherein each R individually is selected from the group consisting of H, alkyl, substituted alkyl, aryl, substituted aryl, halogen, carboxylic acid and derivatives thereof, hydroxy, alkoxy, aryloxy, nitro, sulfonic acid and derivatives; substituted and unsubstituted heterocyclic. The various R groups can be the same or different from each other.
Each Ar individually is an aryl or substituted aryl group.
A still further aspect of the present invention relates to compositions containing polymeric resist and a fluorescent dye having an amine moiety substituted with two aryl groups.
Still other objects and advantages of the present invention will become readily apparent by those skilled in the art from the following detailed description, wherein it is shown and described preferred embodiments of the invention, simply by way of illustration of the best mode contemplated of carrying out the invention. As will be realized the invention is capable of other and different embodiments, and its several details are capable of modifications in various obvious respects, without departing from the invention. Accordingly, the description is to be regarded as illustrative in nature and not as restrictive.
BEST AND VARIOUS MODES FOR CARRYING OUT INVENTION
The compounds employed according to the present invention are fluorescent dyes that have at least one amine moiety substituted with two aryl groups. The preferred aryl substituent is phenyl. Examples of other suitable aryl groups are naphthyl, anthracyl, dinaphthyl, ditoluyl, bis(p-methylphenyl), dianthracenyl, mixed aryl groups such as phenylnaphthyl and phenyltoluyl, and substituted aryl groups such as toluyl.
The fluorescent dyes can be used as an emitting layer in light emitting displays. Pixels of the fluorescent dyes can be fabricated by any of the well known techniques such as use of photoresists for photolithographic patterning, ink jet printing and evaporation through a shadow mask.
The organic light emitting displays further include a hole transporting/anode layer and an electron transporting/cathode layer. Materials for these layers are well known and need not be described herein. Examples of such can be found in U.S. Pat. Nos. 5,126,214, 5,294,870, 5,705,285 and EP 892 589 A1, disclosures of which are incorporated herein by reference.
Examples of some preferred compounds employed in the present invention are represented by the following formulae
analog of DCM
wherein each R individually is selected from the group consisting of H, alkyl, substituted alkyl, aryl, substituted aryl, cycloalkyl, halogen, carboxylic acid and derivatives thereof, hydroxy, alkoxy, aryloxy, nitro, sulfonic acid and derivatives thereof, substituted and unsubstituted heterocyclic; and each Ar individually is an aryl or substituted aryl.
Listed below are definitions of various terms used to describe this invention. These definitions apply to the terms as they are used throughout this specification, unless otherwise limited in specific instances, either individually or as part of a larger group.
The term “alkyl” refers to straight or branched chain unsubstituted hydrocarbon groups of 1 to 20 carbon atoms, preferably 1 to 8 carbon atoms, and more preferably unsubstituted alkyl groups of 1 to 4 carbon atoms.
The term “substituted alkyl” typically refers to an alkyl group substituted by, for example, one to four substituents, such as halo, trifluoromethyl, trifluoromethoxy, hydroxy, thiol, alkylsulfonyl, arylsulfonyl, aralkylsulfonyl, sulfonamido (e.g. SO
2
NH
2
), substituted sulfonamido, nitro, cyano, carboxy, carbamyl (e.g. CONH
2
) substituted carbamyl (e.g. CONH alkyl, CONH aryl, CONH aralkyl or cases where there are two substitu

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