Fluorene-containing polymers and electroluminescent devices...

Details Fluorene-containing polymers and electroluminescent devices... Fluorene-containing polymers and electroluminescent devices...

2001-03-15

2003-08-12

Yamnitzky, Marie (Department: 1774)

Stock material or miscellaneous articles

Composite

Of inorganic material

C428S917000, C428S704000, C313S504000, C257S040000, C257S094000

Reexamination Certificate

active

06605373

ABSTRACT:

BACKGROUND OF THE INVENTION
Polymers containing conjugated groups are known to be useful as materials for preparing organic based light-emitting diodes. However, their light output at low drive voltage and efficiency are less than desirable for certain applications. Thus, there is a need for devices with improved efficiency and a need for devices that can provide high brightness at low drive voltage.
SUMMARY OF THE INVENTION
In one aspect, this invention is a copolymer comprising 10-90 percent by weight of groups of Formula (I):
and from 10-90 percent by weight of groups selected from Formulas (II), (III), and (IV):
and mixtures thereof; wherein R
1
is independently in each occurrence H, C
1
-C
20
hydrocarbyl or C
1
-C
20
hydrocarbyl containing one or more S, N, O, P or Si atoms, C
4
-C
16
hydrocarbyl carbonyloxy, C
4
-C
16
aryl(trialkylsiloxy) or both R
1
may form with the 9-carbon on the fluorene ring a C
5
-C
20
cycloaliphatic structure or a C
4
-C
20
cycloaliphatic structure containing one or more heteroatoms of S, N, or O;
R
2
is independently in each occurrence C
1
-C
20
hydrocarbyl, C
1
-C
20
hydrocarbyloxy, C
1
-C
20
thioether, C
1
-C
20
hydrocarbylcarbonyloxy or cyano;
R
3
is independently in each occurrence carboxyl, C
1
-C
20
alkyl, C
1
-C
20
alkoxy or a group of the formula —CO
2
R
4
wherein R
4
is a C
1
-C
20
alkyl; and
a and b are independently in each occurrence an integer from 0 to 3.
In a second aspect, this invention is a composition comprising (a) 1-99 percent by weight of the copolymer of the first aspect of the invention, and (b) 99-1 percent by weight of at least one polymer containing groups of Formula (I) and, optionally, conjugated groups other than those of Formulas (II), (III), and (IV).
In a third aspect, this invention is an electroluminescent (EL) device comprising at least one organic film, at least one of which is a light-emitting organic film, arranged between an anode material and a cathode material such that under an applied voltage, holes are injected from the anode material into the organic film adjacent to the anode material and electrons are injected from the cathode material into the organic film adjacent to the cathode material when the device is forward biased, resulting in light emission from the light-emitting organic film; wherein at least one layer comprises the copolymer of the first aspect of the invention.
The copolymers of the invention, when used as a light-emitting and/or hole-transport layer in an electroluminescent device, provide a device with higher efficiency and higher brightness at low drive voltages than a corresponding device without a copolymer of this invention. Efficiency is expressed as lumens/watt (Lm/W). These and other advantages of the invention will be apparent from the description which follows.
DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS
The term “conjugated groups” as used herein refers to moieties containing double bonds, triple bonds and/or aromatic rings. The incorporation of such groups into a polymer may be used to modify its light absorption, ionization potential, and/or electronic properties. “Hydrocarbyl” as used herein means any organic moiety containing only hydrogen and carbon unless specified otherwise, and may include aromatic, aliphatic, cycloaliphatic and moieties containing two or more of aliphatic, cycloaliphatic and aromatic moieties.
In the above formulas, R
1
is preferably H, C
1
-C
12
alkyl, C
6
-C
10
aryl or alkyl-substituted aryl, C
4
-C
16
hydrocarbylcarbonyloxy, (C
9
-C
16
aryl)trialkylsiloxy, a poly(alkyleneoxy) group having a terminal hydroxy, C
1
-C
10
hydrocarbyloxy, or a group of the formula: —(CH
2
)
b
CO
2
R
6
, —(CH
2
)
b
SO
3
R
6
, —(CH
2
)
b
N(R
1
)
2
, —(CH
2
)
b
N
+
(R
1
)
3
, or —(CH
2
)
b
—CN, wherein R
6
is a C
1
-C
6
hydrocarbyl, H, Li
+
, Na
+
, or K
+
, and b is as defined above. In the embodiment where the two R
1
form a ring structure with the 9-carbon atom of the fluorene ring, the ring structure formed is preferably a C
5
-C
20
cycloaliphatic structure or a C
1
-C
20
cycloaliphatic structure containing one or more heteroatoms of S, N, or O; even more preferably a C
5
-C
10
aliphatic ring or a C
4
-C
10
aliphatic ring containing one or more of S or O; and most preferably a C
5
-C
10
cycloalkyl or C
4
-C
10
cycloalkyl containing oxygen.
The fluorene groups in Formula (I) above may further be substituted at the 3-, 4-, 5- or 6-positions with substituents (R
2
) which do not adversely affect the formation of oligomers or polymers from the corresponding monomers, nor the subsequent processing of the oligomers or polymers for their intended uses. Preferably, R
2
is C
1
-C
4
alkoxy, phenoxy, C
1
-C
4
alkyl, phenyl or cyano. However, “a” is preferably 0.
The groups of Formula (I) are preferably present in the copolymer in an amount, based on the weight of the copolymer, of at least 10 percent, more preferably at least 20 percent, most preferably at least 50 percent; but preferably no greater than 99 percent, more preferably no greater than 85 percent, and most preferably no greater than 75 percent. The groups of Formulas (II), (III), and (IV) are preferably present in the copolymer in an amount, based on the weight of the copolymer, of at least 5 percent, more preferably at least 10 percent, most preferably at least 20 percent; but preferably no greater than 95 percent, more preferably no greater than 85 percent, and most preferably no greater than 75 percent.
The polymers and blends of the invention demonstrate strong photoluminescence in dilute solutions or in the solid state. When such materials are exposed to a light of a wavelength of 300-700 nanometers (nm), the materials emit light of wavelengths in the region of 400-800 nm. More preferably, such materials absorb light of wavelengths of from 350-400 nm and emit light of wavelengths in the region of 400-650 nm. The polymers and blends of the invention are readily soluble in common organic solvents. They are processible into thin films or coatings by conventional techniques.
The fluorene oligomers or polymers of this invention preferably have a weight average molecular weight of 1000 Daltons or greater, more preferably 5000 Daltons or greater, even more preferably 10,000 Daltons or greater, even more preferably 15,000 Daltons or greater and most preferably 20,000 Daltons or greater; preferably 1,000,000 Daltons or less, more preferably 500,000 Daltons or less and most preferably 200,000 Daltons or less. Molecular weights are determined according to gel permeation chromatography using polystyrene standards. The degree of polymerization of the polymers of the invention is preferably at least 3.
Preferably, the copolymers of the invention demonstrate a polydispersity (Mw/Mn) of 5 or less, more preferably 4 or less, even more preferably 3 or less, even more preferably 2.5 or less and most preferably 2.0 or less.
Preferably, the copolymer of the first aspect of the invention has one of the following structures:
wherein n is a number greater than 3.
Processes for Preparing Polymers
The polymers containing groups of Formulas (I)-(IV) may be prepared by any suitable process, but are preferably prepared by one of the processes described below. The condensation reaction of an aromatic boronate and a bromide, commonly referred to as the “Suzuki reaction”, is described in N. Miyaua and A. Suzuki,
Chemical Reviews
, Vol. 95, pp. 457-2483 (1995). This reaction can be applied to prepare high molecular weight polymers and copolymers. To prepare polymers, a dibromide having an internal group selected from Formulas (I)-(IV), or mixtures thereof, is reacted with an equimolar amount of diboronic acid or diboronate having an internal group selected from Formulas (I)-(IV), or mixtures thereof, under the catalytic action of Pd and triphenylphosphine. The reaction is typically conducted at about 70° C. to 120° C. in an aromatic hydrocarbon solvent such as toluene. Other solvents such as dimethylformamide and tetrahydrofuran can also be used alone, or in mixtures with,

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