Aryl-substituted poly-p-arylenevinylenes

Details Aryl-substituted poly-p-arylenevinylenes Aryl-substituted poly-p-arylenevinylenes

2001-02-22

2004-06-01

Yamnitzky, Marie (Department: 1774)

Stock material or miscellaneous articles

Composite

Of inorganic material

C428S917000, C313S504000, C257S040000, C528S086000, C526S293000, C526S294000, C526S296000

Reexamination Certificate

active

06743525

ABSTRACT:

The invention relates to aryl-substituted poly-p-arylenevinylenes, the use thereof in organic electroluminescent devices and organic electroluminescent devices comprising such aryl-substituted poly-p-arylenevinylenes.
Aryl-substituted poly-p-arylenevinylenes of the type mentioned in the opening paragraph and electroluminescent (EL) devices, polymer electroluminescent devices for short, comprising such polymers are disclosed in the international patent application WO 99/21936. Dependent on the particular structure, the polymers disclosed therein are capable of light emission in the green to red range of the visible spectrum. The color of light emission does not shift when a polymer EL device comprising the known polymer is stored at elevated ambient temperatures for an extended period of time. Furthermore, the polymer EL devices comprising these polymers have a service life exceeding 1500 to 5000 h when driven at a brightness of 20 Cd/m
2
. For many purposes however, a brightness of 20 Cd/m
2
is too low and a brightness of at least 100 to 200 Cd/m
2
is required. This is for example the case in a matrix display device which is driven in a time-multiplexed manner. Although the brightness of an EL device can be simply increased by increasing the voltage at which it is driven increasing the brightness generally leads, as is well-known in the art, to a substantial reduction in service life. A further substantial reduction in service life is generally observed when a polymer EL device is driven at elevated ambient temperatures such as 70 to 80° C. However, satisfactory operation of the devices at those elevated temperatures for an extended period of time is a prerequisite for many applications. Such applications include display devices for automotive applications and mobile phones.
It is an object of the invention to provide, inter alia, aryl-substituted poly-p-arylenevinylenes which, when used in an organic EL device, render the EL device capable of providing a satisfactory service life when driven at an initial brightness of at least 100 or better still, at least 200 Cd/m
2
. More in particular the EL device should be capable of providing a satisfactory service life even in the case where the EL device is driven at elevated ambient temperatures of 70 to 80° C.
In accordance with the invention, this objective is achieved by aryl-substituted poly-p-arylenevinylenes comprising a repeating unit of the formula (C1),
in which one or more of the unsubstituted aromatic carbon atoms may be replaced by nitrogen atoms, —OC
m
and —OC
n
are alkoxy groups, m and n are integers from 2 to 6 with m+n=8, p is 0, 1, 2 or 3 and in which R is CN, Cl, F, CF
3
, NO
2
, or SO
3
Z wherein Z is a monovalent cation such as Na
+
, or in which R is —XR
1
wherein the unit —X— represents a single bond, —O—, —S—, —CO—, —COO—, —OCO—, —SO—, —SO
2
—, —N(R
2
)— or —N(R
2
)CO—, and wherein R
1
and R
2
are the same or different and constitute a straight-chain branched or cyclic C
1
-C
20
alkyl group or together an C
1
-C
20
alkylene group, in which C
1
-C
20
alkyl or C
1
-C
20
alkylene group one or more hydrogens are optionally substituted by F or a C
4
-C
12
aryl group and/or one or more non-adjacent —CH
2
— units are optionally substituted by C
4
-C
12
arylene, —O—, —S—, —CO—, —COO—, —OCO—, —SO—, —SO
2
—, —N(R
3
)— or —N(R
3
)CO— where R
3
is C
1
-C
20
alkyl, or in which R is a C
4
-C
12
aryl group which may or may not be substituted.
As a typical example, an organic EL device comprising a yellow to green light emitting polymer in accordance with the invention as electroluminescent material is capable of providing a service life of at least 45 to 200 h when subjected to an accelerated service life test which involves driving the device at a constant current, at an initial brightness of 200 Cd/m
2
and at an ambient temperature of 80° C.
An EL device comprising a red to orange light emitting polymer in accordance with the invention as electroluminescent material in an organic EL device is at least capable of providing a service life of at least 800 to 1200 h when subjected to an accelerated service life test which involves driving the device at a constant current, at an initial brightness of 100 Cd/m
2
and at an ambient temperature of 70° C.
In the context of the invention, the service life is defined as the time at which the brightness is reduced to half its initial value while driving the device at a constant current. Evidently, such a device is also capable of operating that long at a constant brightness of at least half said initial brightness.
In the context of the invention, the term organic includes polymeric whereas the term polymer and affixes derived therefrom, includes homopolymer, copolymer, terpolymer and higher homologues as well as oligomer.
In WO 98/271376, EL polymers similar to the polymers of WO 99/21936 are disclosed.
Preferably, the polymers in accordance with the invention are used as electroluminescent polymers. Alternatively, they may be suitably used as photoluminescent, charge-injecting and/or charge-transporting polymers. In case of an EL device comprising a single organic layer comprising the polymer in accordance with the invention, the polymer serves as charge-injecting charge-transport and electroluminescent polymer at the same time.
Referring to formula (C1), p is preferably 0 or 1 and R, if present, is located at a 5-position of the phenylene ring.
If the polymer is to emit green or more greenish light p is preferably 0 and R, if present, selected to be a C
1
-C
20
alkyl group of the type defined above.
If the polymer is to emit yellow or more yellowish light the R is preferably selected to be a C
1
-C
20
alkoxy group of the type defined above. Preferred alkoxy groups are OC
4
, in particular 2-methylpropyloxy, and OC
10
, in particular 3,7-dimethyloctyloxy. Even more preferred is methoxy.
Preferred embodiments of the polymers in accordance with the invention are claimed in claims 2 to 4.
In another preferred embodiment, the polymer is characterized in that the proportion of repeating units which are repeating units of formula (C1) is at least 0.95. The benefit in terms of service life to be had by using the polymers in accordance with the invention is optimized if the proportion of repeating units of formula (C1) is as large as possible. Preferred is a proportion of at least 0.95 because then the emission spectrum of the copolymer or higher homologue substantially coincides with that of the homopolymer of repeating units according to formula (C1).
In yet another preferred embodiment, the polymer is characterized in that the proportion of repeating units which are repeating units of formula C1 is less than 0.95. In order to widen the range of properties available within the class of polymers in accordance with the invention, which may for example be advantageous if the emission spectrum of the polymer is to be adapted to suit the needs for a particular application, a plurality of different repeating units is preferably used thus obtaining copolymers, terpolymers and higher homologues. In order to substantially retain the service life enhancing property of the polymers comprising the repeating unit of the formula (C1), the proportion should be preferably at least 0.35.
In a particular embodiment, the polymer in accordance with the invention has, apart from the repeating unit of formula (C1) at least one further type of 1,4-phenylenevinylene repeating unit. Use of copolymers, terpolymers etc. of 1,4-phenylenevinylene repeating units in EL devices is attractive since they combine a high luminescence efficiency with good electron- and hole-transporting and injecting properties. Moreover they can be processed in a simple manner from solution.
If the polymer comprises a plurality of repeating units thus obtaining copolymers, terpolymers and the like it is most preferred that each of said units is a repeating unit of the formula (C1) or preferred embodiments thereof.
In accordance with WO 99/21936, in order to reduce red shift the further 1,4-phenylenevin

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