U.S. patent application number 12/347790 was filed with the patent office on 2009-07-02 for polymer.
This patent application is currently assigned to CAMBRIDGE DISPLAY TECHNOLOGY LIMITED. Invention is credited to Jeremy Burroughes, Clare Foden, Richard Friend.
Application Number | 20090167170 12/347790 |
Document ID | / |
Family ID | 9947307 |
Filed Date | 2009-07-02 |
United States Patent
Application |
20090167170 |
Kind Code |
A1 |
Burroughes; Jeremy ; et
al. |
July 2, 2009 |
Polymer
Abstract
A polymer formed from optionally substituted first repeat units
of formula (I) wherein Ar is selected from (a) aromatic hydrocarbon
substituted with at least one electron withdrawing group or
electron withdrawing heteroaryl. The polymers have application in
electroluminescent devices.
Inventors: |
Burroughes; Jeremy;
(Cambridge, GB) ; Friend; Richard; (Cambridge,
GB) ; Foden; Clare; (Cambridge, GB) |
Correspondence
Address: |
MARSHALL, GERSTEIN & BORUN LLP
233 SOUTH WACKER DRIVE, 6300 SEARS TOWER
CHICAGO
IL
60606-6357
US
|
Assignee: |
CAMBRIDGE DISPLAY TECHNOLOGY
LIMITED
Cambridgeshire
GB
|
Family ID: |
9947307 |
Appl. No.: |
12/347790 |
Filed: |
December 31, 2008 |
Related U.S. Patent Documents
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Application
Number |
Filing Date |
Patent Number |
|
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10533989 |
Feb 13, 2006 |
7494720 |
|
|
PCT/GB2003/004753 |
Nov 4, 2003 |
|
|
|
12347790 |
|
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|
Current U.S.
Class: |
313/504 ;
528/377; 548/134 |
Current CPC
Class: |
C08G 2261/149 20130101;
C08G 2261/146 20130101; H01L 51/0059 20130101; Y10S 428/917
20130101; H01L 51/0043 20130101; H01L 51/50 20130101; C08G 2261/148
20130101; C08G 61/02 20130101; C09K 2211/1416 20130101; C09K
2211/1425 20130101; C09K 2211/1433 20130101; H01L 51/0039 20130101;
C08G 2261/514 20130101; C09K 11/06 20130101; H05B 33/14 20130101;
C08G 2261/124 20130101; C08G 2261/5222 20130101 |
Class at
Publication: |
313/504 ;
528/377; 548/134 |
International
Class: |
H01J 1/63 20060101
H01J001/63; C08G 75/32 20060101 C08G075/32; C07D 285/10 20060101
C07D285/10 |
Foreign Application Data
Date |
Code |
Application Number |
Nov 6, 2002 |
GB |
GB0225869.7 |
Claims
1. A polymer comprising optionally substituted first repeat units
of formula (I): ##STR00025## wherein Ar is electron withdrawing
heteroaryl.
2. A polymer according to claim 1 comprising repeat units of
formula (II): ##STR00026## wherein each Ar is electron withdrawing
heteroaryl.
3. A polymer according to claim 1 wherein Ar is selected from the
group consisting of optionally substituted pyridines and optionally
substituted triazines.
4. A polymer according to claim 1 comprising a second repeat
unit.
5. A polymer according to claim 4 wherein the second repeat unit is
selected from the group consisting of triarylamines and
heteroaromatics.
6. A polymer according to claim 1 that is capable of transporting
electrons.
7. A polymer according to claim 6 that comprises at least one
segment capable of at least one of hole transport and hole
emission.
8. An optical device comprising a polymer according to claim 1.
9. An optical device according to claim 8 that is an
electroluminescent device.
10. An electroluminescent device comprising: a first electrode for
injecting charge carriers of a first type; a second electrode for
injecting charge carriers of a second type; and an emissive layer
comprising a polymer according to claim 1 between the first and
second electrodes.
11. A monomer comprising an optionally substituted compound of
formula (IV): ##STR00027## wherein each P independently represents
a polymerizable group and Ar is electron withdrawing
heteroaryl.
12. A monomer according to claim 11 comprising an optionally
substituted compound of formula (V): ##STR00028## wherein each P
independently represents a polymerizable group and each Ar is
electron withdrawing heteroaryl.
13. A monomer according to claim 12 wherein each P is independently
selected from the group consisting of reactive boron derivative
groups and reactive halide functional groups.
14. A monomer according to claim 13, wherein at least one P is a
reactive boron derivative group selected from the group consisting
of boronic acid groups, boronic ester groups, and borane
groups.
15. A process for preparing a polymer comprising a step of reacting
a first monomer as defined in claim 12 with a second monomer that
may be the same or different from the first monomer under
conditions so as to polymerize the monomers.
16. A process for preparing a polymer according to claim 15 which
comprises polymerizing in a reaction mixture: (a) a monomer
according to claim 12 wherein each P is a reactive boron derivative
group selected from the group consisting of boronic acid groups,
boronic ester groups, and borane groups, and an aromatic monomer
having at least two reactive halide functional groups; or (b) a
monomer according to claim 12 wherein each P is a reactive halide
functional group, and an aromatic monomer having at least two
reactive boron derivative groups selected from the group consisting
of boronic acid groups, boronic ester groups, and borane groups; or
(c) a monomer according to claim 12 wherein one P is a reactive
halide functional group and one P is a reactive boron derivative
group selected from boronic acid groups, boronic ester groups, and
borane groups, wherein the reaction mixture comprises a catalytic
amount of a catalyst suitable for catalyzing the polymerization of
the aromatic monomers, and a base in an amount sufficient to
convert the reactive boron derivative functional groups into
boronate anionic groups.
Description
CROSS-REFERENCE TO RELATED APPLICATIONS
[0001] This is a continuation of U.S. patent application Ser. No.
10/533,989, which is the U.S. national phase of International
Application No. PCT/GB03/004753 filed Nov. 4, 2003, the entire
disclosures of which are incorporated herein by reference.
FIELD OF THE INVENTION
[0002] This invention relates to semiconductive polymers, their
synthesis and use in optical devices.
BACKGROUND OF THE INVENTION
[0003] Electroactive polymers are now frequently used in a number
of optical devices such as in polymeric light emitting diodes
("PLEDs") as disclosed in WO 90/13148, photovoltaic devices as
disclosed in WO 96/16449 and photodetectors as disclosed in U.S.
Pat. No. 5,523,555.
[0004] A typical PLED comprises an organic electroluminescent layer
located between an anode and a cathode. In operation, holes are
injected into the device through the anode and electrons are
injected into the device through the cathode. Holes enter the
highest occupied molecular orbital ("HOMO") of the
electroluminescent polymer and electrons enter the lowest
unoccupied molecular orbital ("LUMO") and then combine to form an
exciton which undergoes radiative decay to give light. The color of
light emitted from the electroluminescent polymer depends on its
HOMO-LUMO bandgap.
[0005] An electron transport material is commonly used to assist in
transport of electrons from the cathode to the LUMO of the
electroluminescent polymer and thus increase device efficiency.
Suitable electron transport materials are those having a LUMO level
falling between the LUMO level of the electroluminescent polymer
and the workfunction of the cathode. Similarly, a hole transporting
material having a HOMO level failing between the workfunction of
the anode and the HOMO level of the emissive material is commonly
used. For example, WO 99/48160 discloses a blend of a hole
transporting polymer, an electron transporting polymer and an
electroluminescent polymer. Alternatively, the electron
transporting functionality and the emissive functionality may be
provided by different blocks of a block copolymer as disclosed in
WO 00/55927.
[0006] A focus in the field of PLEDs has been the development of
full color displays for which red, green and blue
electroluminescent polymers are required--see for example Synthetic
Metals 111-112 (2000), 125-128. To this end, a large body of work
has been reported in the development of electroluminescent polymers
for each of these three colors with red, green and blue emission as
defined by PAL standard 1931 CIE co-ordinates.
[0007] A difficulty encountered with blue electroluminescent
polymers is that their lifetime (i.e. the time taken for brightness
to halve from a given starting brightness at fixed current) tends
to be shorter than that of corresponding red or green materials.
One of the factors that has been proposed as contributing to the
more rapid degradation of blue materials is that their LUMO levels,
and consequently the energy level of the charged state following
injection of an electron into the LUMO, tends to be less deep than
those of corresponding red or green materials. It is therefore
possible that materials comprising these lower electron affinities
are less electrochemically stable and therefore more prone to
degradation.
[0008] For simplicity, a full color display will preferably have
the same cathode material for all three electroluminescent
materials. This results in the further problem that the energy gap
between the LUMO and the workfunction of the cathode for a typical
blue electroluminescent polymer is greater than that for a typical
red or green electroluminescent polymer. This may contribute to
lower efficiency.
[0009] Clearly, assisted electron injection into blue
electroluminescent polymers is desirable, however the choice of
electron transporting material is constrained by the fact that the
emissive material is generally that with the smallest bandgap. This
limitation is particularly restrictive in the case of blue
electroluminescent polymers since the bandgap required for blue
emission is the largest of red, green and blue.
[0010] Chains of fluorene repeat units, such as homopolymers or
block copolymers comprising dialkylfluorene repeat units, may be
used as electron transporting materials. In addition to their
electron transporting properties, polyfluorenes have the advantages
of being soluble in conventional organic solvents and have good
film forming properties. Furthermore, fluorene monomers are
amenable to Yamamoto polymerization or Suzuki polymerization which
enables a high degree of control over the regioregularity of the
resultant polymer.
[0011] One example of a polyfluorene based polymer is a blue
electroluminescent polymer of formula (a) disclosed in WO
00/55927:
##STR00001##
wherein w+x+y=1, w<0.5, 0.ltoreq.x+y.ltoreq.0.5 and n<2.
[0012] In this polymer, chains of dioctylfluorene, denoted as F8,
function as the electron transport material; the triphenylamine
denoted as TFB functions as the hole transport material and the
bis(diphenylamino)benzene derivative denoted as PFB functions as
the emissive material.
[0013] WO 94/29883 discloses use of electron withdrawing groups,
particularly nitrile groups, as substituents on electroluminescent
polymers for the purpose of reducing the barrier to electron
injection between a high workfunction electrode and the
electroluminescent polymer. This document only teaches use of such
substituents on poly(arylene vinylenes).
J. Poly. Sci. Part A: Polym. Chem. Vol. 39 (2001) discloses a
polymer of repeat units of formula (b):
##STR00002##
[0014] This disclosure describes use of fluorinated sidechains as a
means of decreasing interchain interactions that have been reported
to cause aggregation of polyfluorenes and contains no discussion of
using such electron deficient substituents as a means to increase
electron affinity. This polymer is disclosed as showing no
photoluminescence.
[0015] There are disclosures of diphenylfluorenes wherein the
phenyl group carries substituents, however these substituents are
electron donating as measured by their Hammett sigma constants. For
example, WO 00/22026 discloses a homopolymer having a repeat unit
of formula (c):
##STR00003##
[0016] Also disclosed in this document are copolymers of (c) with
dialkylfluorene repeat units and with triarylamine repeat units.
Asymmetric substitution of the 9-position of fluorene is described
for the purpose of avoiding polymer aggregation; this document
contains no teaching of 9-substituents used for the purpose of
enhanced electron injection of the fluorene backbone. Similarly, WO
99/20675 discloses a 1:1 copolymer of 9,9-di-n-octylfluorene and
9,9-di(4-methoxyphenyl)fluorene and WO 01/62822 discloses a
polyfluorene with triarylamine 9-substituents.
[0017] JP 10095972 discloses a molecule of formula (e):
##STR00004##
[0018] This is disclosed as an emissive material of the type known
as "small molecules" rather than polymers as described
hereinbefore. This molecule is used in conjunction with a separate,
electron transporting molecule. The use of fluorine substituents on
the phenyl ring is not described for the purpose of increasing
electron affinity of the fluorene ring; fluorine substituents are
merely one of a large number of possible substituents for the
phenyl ring disclosed in this document.
[0019] It is an object of the invention to provide a high electron
affinity material that is capable of functioning as an electron
transport material for a blue electroluminescent material. For the
reasons explained above, such a material would also be capable of
functioning as an electron transport material for a red or green
material. Furthermore, such material may, as a result of its large
HOMO-LUMO bandgap, be used as a blue electroluminescent
material.
SUMMARY OF THE INVENTION
[0020] According to the invention, improved electron injection, and
therefore improved PLED performance, may be accomplished by
increasing the electron affinity of known polyfluorenes.
[0021] Accordingly, in a first aspect the invention provides a
polymer comprising optionally substituted first repeat units of
formula (I):
##STR00005##
[0022] wherein Ar is selected from: [0023] (a) aromatic hydrocarbon
substituted with at least one electron withdrawing group or [0024]
(b) electron withdrawing heteroaryl.
[0025] Preferably, the polymer comprises repeat units of formula
(II):
##STR00006##
[0026] wherein each Ar is independently selected from: [0027] (a)
aromatic hydrocarbon substituted with at least one electron
withdrawing group or [0028] (b) electron withdrawing
heteroaryl.
[0029] Preferred Ar groups according to (a) are independently
selected from units of formula (III):
##STR00007##
[0030] wherein n is from 1-3 and R.sub.1-R.sub.5 are independently
selected from: [0031] hydrogen; [0032] solubilizing groups selected
from alkyl, alkoxy, arylalkyl and heteroarylalkyl; and [0033]
electron withdrawing groups
[0034] such that at least one of R.sub.1-R.sub.5 is an electron
withdrawing group. Most preferably n=1, i.e. Ar is phenyl.
[0035] Another preferred set of Ar groups according to (a) are
fused aromatic hydrocarbons such as naphthalene and anthracene.
[0036] Preferably, the electron withdrawing group is selected from:
groups comprising fluorine, cyano, nitro, carboxyl, amides,
ketones, phosphinoyl, phosphonates, sulfones and esters. More
preferably, the at least one electron withdrawing group is selected
from fluorine atoms, fluoroalkyl, fluoroaryl and
fluoroheteroaryl.
[0037] Preferred electron withdrawing heteroaryls according to (b)
are optionally substituted N-containing heteroaryls, in particular
optionally substituted pyridines, most particularly pyridine-4-yl;
pyrazines; pyrimidines; pyridazines; triazines, most particularly
1,3,5-triazine-2-yl and oxadiazoles. The electron withdrawing
heteroaryl may be substituted with electron withdrawing groups as
outlined above to further increase its electron withdrawing
effect.
[0038] Preferably, the polymer according to the invention comprises
a second repeat unit. More preferably the second repeat unit is
selected from triarylamines and heteroaromatics.
[0039] Preferably, the polymer according to the invention is
capable of transporting electrons. In addition, the polymer
preferably has at least one segment capable of hole transport
and/or emission. Two or more functions of hole transport, electron
transport and emission may be provided by the same segment. In
particular, a single segment may function as both an electron
transporter and an emitter.
[0040] In a second aspect, the invention provides an optical
device, preferably an electroluminescent device, comprising a
polymer as described above.
[0041] In one embodiment of the second aspect is provided an
electroluminescent device comprising: [0042] a first electrode for
injecting charge carriers of a first type; [0043] a second
electrode for injecting charge carriers of a second type; and
[0044] an emissive layer comprising a polymer according to the
first aspect of the invention between the first and second
electrodes.
[0045] The emissive material within the emissive layer may be the
polymer according to the first aspect of the invention or another
material, preferably another polymer, blended with the polymer
according to the first aspect of the invention. Preferably, the
polymer according to the first aspect of the invention is capable
of transporting electrons in this device.
[0046] In a third aspect, the invention provides a monomer
comprising an optionally substituted compound of formula (IV):
##STR00008##
[0047] wherein each P independently represents a polymerizable
group and Ar is as defined above.
[0048] Preferably, the monomer comprises an optionally substituted
compound of formula (V):
##STR00009##
[0049] Preferably, each P is independently selected from a reactive
boron derivative group selected from a boronic acid group, a
boronic ester group and a borane group and a reactive halide
group.
[0050] In a fourth aspect, the invention provides a process for
preparing a polymer comprising a step of reacting a first monomer
as described above with a second monomer that may be the same or
different from the first monomer under conditions so as to
polymerize the monomers.
[0051] Preferably, the process comprises polymerizing in a reaction
mixture: [0052] (a) a monomer according to the third aspect of the
invention wherein each P is a reactive boron derivative group
selected from a boronic acid group, a boronic ester group and a
borane group, and an aromatic monomer having at least two reactive
halide functional groups; or [0053] (b) a monomer according to the
third aspect of the invention wherein each P is a reactive halide
functional group, and an aromatic monomer having at least two
reactive boron derivative groups selected from boronic acid groups,
boronic ester groups and borane groups; or [0054] (c) a monomer
according to the third aspect of the invention wherein one P is a
reactive halide functional group and one P is a reactive boron
derivative group selected from a boronic acid group, a boronic
ester group and a borane group,
[0055] wherein the reaction mixture comprises a catalytic amount of
a catalyst suitable for catalyzing the polymerization of the
aromatic monomers, and a base in an amount sufficient to convert
the reactive boron derivative groups into boronate anionic
groups.
[0056] The inventors have found that polymers according to the
invention function effectively as electron transporting materials
for red, green or blue electroluminescent polymers without
adversely affecting device properties as has been found for systems
having aliphatic electron withdrawing 9-substituents such as
perfluoroalkyl.
DETAILED DESCRIPTION OF THE INVENTION
[0057] The polymers prepared using monomers according to the
invention may be homopolymers or copolymers. A wide range of
co-monomers for polymerization with the monomers of the invention
will be apparent to the skilled person. Examples of comonomers
include triarylamines as disclosed in, for example, WO 99/54385 and
heteroaryl units as disclosed in, for example, WO 00/46321 and WO
00/55927.
[0058] Particularly preferred triarylamine repeat units for such
copolymers include units of formulae 1-6:
##STR00010##
[0059] X and Y may be the same or different and are substituent
groups. A, B, C and D may be the same or different and are
substituent groups. It is preferred that one or more of X, Y, A, B,
C and D is independently selected from the group consisting of
alkyl, aryl, perfluoroalkyl, thioalkyl, cyano, alkoxy, heteroaryl,
alkylaryl and arylalkyl groups. One or more of X, Y, A, B, C and D
also may be hydrogen. It is preferred that one or more of X, Y, A,
B, C and D is independently an unsubstituted, isobutyl group, an
n-alkyl, an n-alkoxy or a trifluoromethyl group because they are
suitable for helping to select the HOMO level and/or for improving
solubility of the polymer.
[0060] Particularly preferred heteroaryl repeat units for such
copolymers include units of formulae 7-21:
##STR00011##
[0061] wherein R.sub.6 and R.sub.7 are the same or different and
are each independently a substituent group. Preferably, one or both
of R.sub.6 and R.sub.7 may be selected from hydrogen, alkyl, aryl,
perfluoroalkyl, thioalkyl, cyano, alkoxy, heteroaryl, alkylaryl, or
arylalkyl. These groups are preferred for the same reasons as
discussed in relation to X, Y, A, B, C and D above. Preferably, for
ease of manufacture, R.sub.6 and R.sub.7 are the same. More
preferably, they are the same and are each a phenyl group.
##STR00012## ##STR00013##
[0062] Electron withdrawing groups/heteroaryls suitable for
monomers and repeat units of formula (I) according to the invention
will be apparent to the skilled person. In particular, those
substituents/heteroaryls having a positive Hammett sigma constant
may be suitable. The electron withdrawing groups/heteroaryls should
preferably be selected to avoid interference with the
polymerization of the monomer, e.g. by steric hindrance.
[0063] Electron withdrawing groups Ar according to (a) or (b) may
be provided with solubilizing groups. Particularly preferred as
solubilizing groups are optionally substituted, branched or linear
C.sub.1-20 alkyl or alkoxy, more preferably C.sub.4-10 alkyl.
[0064] The polymer according to the invention may be a homopolymer
or a copolymer. Where it is a copolymer, it may be a 1:1 copolymer,
random or block copolymer. A block copolymer according to the
invention may comprise at least two regions selected from: [0065] a
hole transporting region [0066] an electron transporting region
[0067] an emissive region.
[0068] The functions of charge transport and emission may be
provided by a range of moieties which will be apparent to the
skilled person, as described in, for example, WO 00/55927 or U.S.
Pat. No. 6,353,083.
[0069] Preferred methods for polymerization of the monomers
according to the invention are Suzuki polymerization as described
in, for example, WO 00/53656 and Yamamoto polymerization as
described in, for example, T. Yamamoto, "Electrically Conducting
And Thermally Stable .pi.-Conjugated Poly(arylene)s Prepared by
Organometallic Processes", Progress in Polymer Science 1993, 17,
1153-1205.
EXAMPLES
Monomer Examples
[0070] Monomers according to the invention may be prepared in
accordance with the following scheme:
##STR00014##
Modelled Examples
[0071] The effect of appending various groups to the phenyl rings
of 9,9-diphenylfluorene repeat unit HOMO and LUMO levels was
calculated using AM1 from the AMPAC software package (1) and ZINDO
calculations from the Gaussian software package (2).
[0072] 1) AM1 in Ampac program package [0073] Ampac 5.0 User's
Manual, .COPYRGT. 1994 Semichem, 7128 Summit, Shawnee, Kans.
66216
[0074] 2) ZINDO from Gaussian software: [0075] Gaussian 98,
Revision A.9, [0076] M. J. Frisch, G. W. Trucks, H. B. Schlegel, G.
E. Scuseria, [0077] M. A. Robb, J. R. Cheeseman, V. G. Zakrzewski,
J. A. Montgomery, Jr., [0078] R. E. Stratmann, J. C. Burant, S.
Dapprich, J. M. Millam, [0079] A. D. Daniels, K. N. Kudin, M. C.
Strain, O. Farkas, J. Tomasi, [0080] V. Barone, M. Cossi, R. Cammi,
B. Mennucci, C. Pomelli, C. Adamo, [0081] S. Clifford, J.
Ochterski, G. A. Petersson, P. Y. Ayala, Q. Cui, [0082] K.
Morokuma, D. K. Malick, A. D. Rabuck, K. Raghavachari, [0083] J. B.
Foresman, J. Cioslowski, J. V. Ortiz, A. G. Baboul, [0084] B. B.
Stefanov, G. Liu, A. Liashenko, P. Piskorz, I. Komaromi, [0085] R.
Gomperts, R. L. Martin, D. J. Fox, T. Keith, M. A. Al-Laham, [0086]
C. Y. Peng, A. Nanayakkara, M. Challacombe, P. M. W. Gill, [0087]
B. Johnson, W. Chen, M. W. Wong, J. L. Andres, C. Gonzalez, [0088]
M. Head-Gordon, E. S. Replogle, and J. A. Pople, [0089] Gaussian,
Inc., Pittsburgh Pa., 1998.
[0090] The results are summarized in the table below:
TABLE-US-00001 HOMO LUMO Structure Name (eV) (eV) ##STR00015## F8
-7.84 0.04 ##STR00016## dpf -7.79 -0.06 ##STR00017## pdpf -8.16
-0.40 ##STR00018## mdpf -8.08 -0.30 ##STR00019## dmdpf -8.36 -0.72
##STR00020## fldpf -8.25 -1.10 ##STR00021## C1dpf -7.70 -0.01
##STR00022## C8dpf -7.68 0.00 ##STR00023## hadpf -7.69 0.04
[0091] As can be seen from these examples, replacement of octyl
with phenyl has a relatively small effect on LUMO level, however a
significant change is only effected by substitution by electron
withdrawing groups such as fluorine or perfluoroalkyl. By
comparison with unsubstituted diphenylfluorene, it can be seen that
alkoxy groups substituted in the para position, as per the prior
art, are not predicted to show any electron withdrawing character.
This is consistent with known electron withdrawing properties of
such substituents, in particular their negative Hammett sigma
constants.
Polymer Examples
[0092] Polymers according to the invention having formula P1 were
prepared by Suzuki polymerization in accordance with the process
described in WO 00/53656, by reaction of the following monomers in
the ratios set out in the table below: [0093]
2,7-dioxalaborane-9,9-di-(n-octyl)fluorene [0094]
2,7-dioxalaborane-9,9-di-(4-trifluoromethylphenyl)fluorene [0095]
N,N-di(4-bromophenyl)-N-(4-sec-butylphenyl)amine (to produce the
"TFB" repeat unit shown below) [0096]
Di[N-(4-bromophenyl)-N-(4-n-butylphenyl)]-phenylene-1,4-diamine (to
produce the "PFB" repeat unit shown below)
##STR00024##
[0096] wherein w+x+y+z=1, w+z<0.5, 0.ltoreq.x+y.ltoreq.0.5,
z>0 and n<2
[0097] Particular embodiments are as follows:
TABLE-US-00002 Example w x y z 1 50 10 10 30 2 50 0 10 40 3 0 0 50
50 4 0 0 0 100 5 50 0 0 50
[0098] Where TFB and PFB are present, as in example 1, the polymer
may function as a blue electroluminescent polymer as described in
WO 00/55927.
[0099] Where TFB is present and PFB is absent the polymer may be a
block copolymer with hole and electron transporting segments
(example 2) or a 1:1 regioregular hole transporting copolymer
(example 3). It may also show blue electroluminescence.
[0100] Where TFB and PFB are absent, the polymer may be used as an
electron transporting polymer for a red, green or blue
electroluminescent material (examples 4 and 5).
Device Example
[0101] A device according to the invention was prepared as
follows:
[0102] 1) Depositing poly(ethylenedioxythiophene)/polystyrene
sulfonate (PEDT/PSS), available from Bayer.RTM. as Baytron P.RTM.,
by spin coating onto an indium tin oxide anode supported on a glass
substrate (available from Applied Films, Colorado, USA).
[0103] 2) Depositing polymer P1 onto the PEDT/PSS by spin coating
from xylene solution having a concentration of 2% w/v.
[0104] 3) Depositing a cathode comprising a first layer of calcium
and a second layer of aluminium by evaporation onto the polymer
P1.
[0105] Although the present invention has been described in terms
of specific exemplary embodiments, it will be appreciated that
various modifications, alterations and/or combinations of features
disclosed herein will be apparent to those skilled in the art
without departing from the spirit and scope of the invention as set
forth in the following claims.
* * * * *