Partially conjugated polymers with spiro centers and their...

Details Partially conjugated polymers with spiro centers and their... Partially conjugated polymers with spiro centers and their...

1998-08-21

2002-03-26

Yamnitzky, Marie (Department: 1774)

Stock material or miscellaneous articles

Composite

Of inorganic material

C428S917000, C313S504000, C257S040000, C252S301350, C528S397000, C528S403000, C528S412000, C528S423000

Reexamination Certificate

active

06361884

ABSTRACT:

There is a great industrial need for large-area, solid-state light sources for a number of applications, predominantly in the field of display elements, VDU technology and lighting engineering. The demands made of these light sources can at present not be met fully satisfactorily by any of the existing technologies.
As alternatives to conventional display and lighting elements, e.g. incandescent lamps, gas discharge lamps and non-self-illuminating liquid crystal display elements, use has for some time been made of electroluminescence (EL) materials and devices, e.g. light emitting diodes (LEDs).
DE-A 25 45 784 (corresponds to U.S. Pat. No. 3,995,299) describes an electroluminescence device having a radiation source which comprises a layer of an amorphous or predominantly amorphous polymer material having appreciable electrical charge mobility and a low ionization potential, a strong electron donor, a strong electron acceptor and preferably at least one luminescent additive; electrical connections via which an electric current can be passed through the thickness of the layer for exciting radiation therefrom are provided.
Polymer materials which have been used are both conjugated polymers such as poly(p-phenylene-vinylene) (see, for example, WO-A 90/13148) and non-conjugated polymers (see, for example, I. Sokolik et al., J. Appl. Phys. 1993, 74, 3584); conjugated materials generally have the advantage of a higher charge carrier mobility and thus better efficiency and lower operating voltages. In addition, the thermal stability of the last-named polymers is not at all satisfactory. This type of polymer also leads to broad emission bands, which is equivalent to low color purity.
Apart from devices based on polymers, electroluminescence devices based on low molecular weight organic compounds have also been known for some time. EP-A-0 676 461 describes such devices comprising spiro compounds as electroluminescence materials.
Although good results have been achieved using these materials, the property profile of such compounds is still quite capable of improvement.
Since, in addition, the development of electroluminescence materials, in particular those based on polymers, can in no way be regarded as having been concluded, the manufacturers of lighting and display devices are interested in a wide variety of electroluminescence materials for such devices.
This is due, inter alia, to the fact that only the interaction of the electroluminescence materials with the further components of the devices allows conclusions to be drawn as to the quality of the electroluminescence material.
It is therefore an object of the present invention to provide new electroluminescence materials which, when used in lighting or display devices, are capable of improving the property profile of these devices.
It has now surprisingly been found that certain partially conjugated polymers having spiro centers are particularly suitable as electroluminescence materials and, in particular, have excellent processability.
The invention accordingly provides a partially conjugated polymer comprising repeating units of the formula (I),
where the symbols have the following meanings:
A are identical or different and are each from zero to eight identical or different arylene and/or heteroarylene and/or vinylene and/or acetylene groups which, like the spirobifluorene framework, may be substituted or unsubstituted.
The polymers of the invention preferably comprise from 2 to 1000, particularly preferably from 2 to 100, in particular from 2 to 40, repeating units of the formula (I).
The polymers of the invention preferably consist of repeating units of the formula (I).
Preference is given to homopolymers, but likewise to copolymers, i.e. polymers in which the group A in the individual repeating units has different meanings or the spirobifluorene framework is substituted differently. Such copolymers preferably comprise from 2 to 5 different monomers, particularly preferably 2 or 3.
Such copolymers which have further structural units in addition to structural units of the formula (I) preferably comprise at least 50% by weight of structural elements of the formula (I).
The arylene or heteroarylene units are generally aromatic systems having from 2 to 20 carbon atoms.
Preferred substituents are straight-chain, cyclic or branched alkyl, alkoxy or ester groups having from 1 to 22 carbon atoms, aryl and/or aryloxy groups preferably having from 2 to 20 carbon atoms, preferably phenyl and/or phenyloxy groups, where the aromatic may bear C
1
-C
22
-alkyl, C
1
-C
22
-alkoxy, Br, Cl, F, CN, CO
2
R, SO
3
R and/or P(O)(OR)
2
as substituents, Br, Cl, F, CN, CO
2
R, SO
3
R, P(O)(OR)
2
and CF
3
. Here, R is H or a straight-chain or branched alkyl group having from 1 to 22 carbon atoms or a singly charged cation, preferably alkali metal such as Na or K, or a tetraalkylammonium group such as N(butyl)
4
.
The aryl and heteroaryl groups in the group A preferably have zero, one or two substituents. The individual six-membered rings of the spirobifluorene preferably have zero or one substituent.
The group A preferably consists of from 1 to 6, particularly preferably from 2 to 4, of the abovementioned groups.
The polymers of the invention display, in particular, a high color purity of the emission, good film-forming properties and good solubility in at least one organic solvent having a boiling point of from 30 to 300° C.
For the purposes of the invention, a polymer is a compound whose electroluminescence spectrum remains essentially unchanged on adding further repeating units.
Preference is furthermore given to polymers in which the group A in the formula (I) comprises the following molecular building blocks:
where
S
1
, S
2
, S
3
and S
4
are identical or different and are H or the above-described preferred substituents;
X, Y are identical or different and are CS
1
, N;
Z are identical or different and are —O—, —S—, —NS
1
—, —CS
1
S
2
—, —CS
1
═CS
1
—, —CS
1
═N—,
where S
1
, S
2
are H or the above-described preferred substituents.
Particular preference is given to polymers in which the group A in the formula (I) has the following meanings:
S
1
and S
2
are as defined above and can also be H.
X, Y are identical or different and are CS
1
, N;
Z are identical or different and are —O—, —S—, —NS
1
—, —CS
1
S
2
—, —CS
1
═CS
1
—, —CS
1
═N—.
Very particular preference is given to polymers which have the following structure:
where X has the following meanings:
chemical bond
and
S
1
and S
2
are as defined above and can also be H;
n is a natural number from 2 to 1000.
Such polymers are particularly well suited to achieving a blue electroluminescence.
The polymers of the invention can be prepared by literature methods known per se as are described in standard works on organic synthesis, e.g. Houben-Weyl, Methoden der Organischen Chemie, Georg-Thieme-Verlag, Stuttgart or J. March, Advanced Organic Chemistry, Fourth Ed., John Wiley & Sons, New York 1992.
The preparation is carried out under reaction conditions which are known and suitable for the reactions mentioned. It is also possible to make use of variants which are known per se and are not mentioned more specifically here.
Starting compounds used for the preparation of the polymers of the invention are, in general, monomers which have a 9,9′-spirobifluorene center and in the 2,2′ positions bear substituents which make a polymerization reaction possible and, if desired, in any other positions may bear further substituents which do not interfere with this reaction.
Methods of synthesizing these monomers are preferably based on the synthesis of 9,9′-spirobifluorene, which is described in the abovementioned literature references, and on further substitution reactions on this basic molecule which are generally customary and can be carried out without problems by those skilled in the art.
Less preferred, but naturally also possible, is building up spirobifluorene derivatives which are already appropriately functionalized, starting from appropriately substituted

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