U.S. patent application number 09/328069 was filed with the patent office on 2002-04-18 for 09283192electroluminescent devices using blend systems.
Invention is credited to ELSCHNER, ANDREAS, THORN-CSANYI, EMMA, WEHRMANN, ROLF.
Application Number | 20020045060 09/328069 |
Document ID | / |
Family ID | 26046704 |
Filed Date | 2002-04-18 |
United States Patent
Application |
20020045060 |
Kind Code |
A1 |
WEHRMANN, ROLF ; et
al. |
April 18, 2002 |
09283192ELECTROLUMINESCENT DEVICES USING BLEND SYSTEMS
Abstract
An electroluminescent device comprising an oligomer of
substituted p-divinylbenzene is disclosed. The oligomer has the
general formula (I) 1 in which R.sup.1 and R.sup.2 independently
denote a member selected from the group consisting of hydrogen,
linear alkyl containing 1 to 12 carbon atoms, linear alkoxy
containing 1 to 12 carbon atoms, branched alkyl containing 3 to 12
carbon atoms, branched alkoxy containing 3 to 12 carbon atoms and
cycloalkyl containing 4 to 10 carbon atoms with the proviso that
R.sup.1 and R.sup.2 may not both be hydrogen, R.sup.3 and R.sup.4
independently denote hydrogen, C.sub.1-C.sub.6-alkyl, CN or
halogen, R.sup.5, R.sup.6 R.sup.7 and R.sup.8 independently denote
any desired radicals, and n is 2 to 20.
Inventors: |
WEHRMANN, ROLF; (KREFELD,
DE) ; ELSCHNER, ANDREAS; (MUHLHEIM, DE) ;
THORN-CSANYI, EMMA; (HAMBURG, DE) |
Correspondence
Address: |
BAYER CORPORATION
PATENT DEPARTMENT
100 BAYER ROAD
PITTSBURHG
PA
152059741
|
Family ID: |
26046704 |
Appl. No.: |
09/328069 |
Filed: |
June 8, 1999 |
Current U.S.
Class: |
428/690 ;
428/917 |
Current CPC
Class: |
H01L 51/0042 20130101;
H01L 51/0081 20130101; C09K 11/06 20130101; H01L 51/0038 20130101;
C08G 61/02 20130101; H05B 33/14 20130101; H01L 2251/308 20130101;
H01L 51/5012 20130101; Y10S 428/917 20130101; H01L 51/0037
20130101 |
Class at
Publication: |
428/690 ;
428/917 |
International
Class: |
B32B 009/00; H01J
001/62 |
Claims
What is claimed is:
1. An electroluminescent device, comprising an oligomer of
substituted p-divinylbenzene of the general formula (I) 4in which
R.sup.1 and R.sup.2 independently denote a member selected from the
group consisting of hydrogen, linear alkyl containing 1 to 12
carbon atoms, linear alkoxy containing 1 to 12 carbon atoms,
branched alkyl containing 3 to 12 carbon atoms, branched alkoxy
containing 3 to 12 carbon atoms and cycloalkyl containing 4 to 10
carbon atoms with the proviso that R.sup.1 and R.sup.2 may not both
be hydrogen, R.sup.3 and R.sup.4 independently denote hydrogen,
C.sub.1-C.sub.6-alkyl, CN or halogen, R.sup.5, R.sup.6 R.sup.7 and
R.sup.8 independently denote any desired radicals, and n is 2 to
20.
2. The electroluminescent device of claim 1, wherein R.sup.5 and
R.sup.7 independently denote hydrogen or alkyl and R.sup.6 and
R.sup.8 independently denote alkyl or aryl radicals.
3. The electroluminescent device of claim 2, wherein R.sup.5 and
R.sup.7 independently denote C.sub.1-C.sub.4-alkyl.
4. The electroluminescent device of claim 3, wherein R.sup.5 and
R.sup.7 denote methyl groups.
5. The electroluminescent device of claim 2 wherein R.sup.6 and
R.sup.8 independently denote C.sub.1-C.sub.6-alkyl or phenyl.
6. The electroluminescent device of claim 5 wherein alkyl and
phenyl radicals contain at least one functional groups selected
from the group consisting of --OH, --CN, --CHO and Br.
7. The electroluminescent device of claim 1 further comprising a
binder B.
8. The electroluminescent device of claim 7 wherein binder B is
selected from the group consisting of polycarbonate, polyester
carbonate, copolymer of styrene, polysulfone, polymer based on
vinyl-group containing monomers, polyolefin and phenoxy resin.
9. The electroluminescent device comprising the reaction product of
an oligomer of substituted p-divinylbenzene of the general formula
(I) 5in which R.sup.1 and R.sup.2 independently denote a member
selected from the group consisting of hydrogen, linear alkyl
containing 1 to 12 carbon atoms, linear alkoxy containing 1 to 12
carbon atoms, branched alkyl containing 3 to 12 carbon atoms,
branched alkoxy containing 3 to 12 carbon atoms and cycloalkyl
containing 4 to 10 carbon atoms with the proviso that R.sup.1 and
R.sup.2 may not both be hydrogen, R.sup.3 and R.sup.4 independently
denote hydrogen, C.sub.1-C.sub.6-alkyl, CN or halogen, R.sup.5and
R.sup.7independently denote hydrogen or alkyl, R.sup.6 and R.sup.8
independently denote alkyl or aryl radicals. and n is 2 to 20, with
at least one polymeric resin containing double bonds.
10. The electroluminescent device of claim 9 wherein said polymeric
resin is a member selected from the group consisting of
polybutadiene and polyoctamer.
Description
[0001] An electroluminescent (EL) device is characterized in that
it emits light when an electrical voltage is applied and current
flows. Such devices have long been known in engineering as
"light-emitting diodes" (LEDs). The emission of light is due to the
fact that positive charges ("holes") and negative charges
("electrons") recombine with the emission of light.
[0002] In the development of light-emitting components for
electronics or photonics, use is mainly made at present of
inorganic semiconductors, such as gallium arsenide. Punctiform
indicating elements can be produced on the basis of such
substances. Large-area devices are not possible.
[0003] In addition to semiconductor light-emitting diodes,
electroluminescent devices based on vapour-deposited
low-molecular-weight organic compounds are known (U.S. Pat. No.
4,539,507, U.S. Pat. No. 4,769,262, U.S. Pat. No. 5,077,142, EP-A
406 762, EP-A 278 758, EP-A 278 757).
[0004] Furthermore, polymers, such as poly(p-phenylenes) and
poly(p-phenylenevinylenes) (PPV) are described as
electroluminescent polymers: G. Leising et al., Adv. Mater. 4
(1992) No. 1; Friend et al., J Chem. Soc., Chem. Commun. 32 (1992);
Saito et al., Polymer, 1990, Vol. 31, 1137; Friend et al., Physical
Review B, Vol. 42, No. 18, 11670 or WO 90/13148. Further examples
of PPV in electroluminescent indicators are described in EP-A 443
861, WO-A-9203490 and 92003491.
[0005] EP-A 0 294 061 discloses an optical modulator based on
polyacetylene.
[0006] Heeger et al. have proposed soluble, conjugated PPV
derivatives for producing flexible polymeric LEDs (WO
92/16023).
[0007] Polymer blends of various compositions are likewise known:
M. Stolka et al., Pure & Appl. Chem., Vol. 67, No. 1, pp
175-182, 1995; H. Bassler et al., Adv. Mater. 1995, 7, No. 6, 551;
K. Nagai et al., Appl. Phys. Lett. 67 (16), 1995, 2281; EP-A 532
798.
[0008] As a rule, the organic EL devices contain one or more layers
of organic charge transport compounds. The basic structure of the
layer sequence is as follows:
[0009] 1 Carrier, substrate
[0010] 2 Base electrode
[0011] 3 Hole-injecting layer
[0012] 4 Hole-transporting layer
[0013] 5 Light-emitting layer
[0014] 6 Electron-transporting layer
[0015] 7 Electron-injecting layer
[0016] 8 Top electrode
[0017] 9 Contacts
[0018] 10 Packaging, encapsulation.
[0019] The layers 3 to 7 are the electroluminescent element.
[0020] This structure is the most general case and can be
simplified by omitting individual layers so that one layer assumes
a plurality of tasks. In the simplest case, an EL device comprises
two electrodes between which an organic layer is situated which
fulfils all the functions, including the emission of light. Such
systems are described, for example, in Application WO 90/13148 on
the basis of poly(p-phenylene-vinylene).
[0021] Multilayer systems can be constructed by vapour-deposition
processes in which the layers are applied successively from the gas
phase or by pouring methods. Because of the higher processing
speed, pouring methods are preferred. However, in certain cases,
the process of partially dissolving a layer already applied may
present a difficulty in depositing the next layer on top.
[0022] The object of the present invention is to provide
electroluminescent devices having high luminous density, the
mixture to be applied being pourable, i.e. capable of being applied
from solution.
[0023] It was found that electroluminescent devices containing
material A or a blend of material A with polymeric binder B,
mentioned below fulfil these requirements. In the following, the
term zone is also to be equated with layer.
[0024] The present invention therefore relates to
electroluminescent devices containing, as electroluminescent
material A, at least one oligomer of substituted p-divinylbenzene
having the general formula (I) 2
[0025] in which
[0026] R.sup.1 and R.sup.2 independently represent hydrogen, or
linear alkyl or alkoxy containing 1 to 12 carbon atoms, preferably
1 to 8 carbon atoms, or branched alkyl or alkoxy containing 3 to
12, preferably 3 to 8 carbon atoms, or cycloalkyl containing 4 to
10, preferably 5 or 6 carbon atoms, with the proviso that
[0027] R.sup.1 and R.sup.2 may not both by hydrogen,
[0028] R.sup.3 and R.sup.4 are identical or different and represent
hydrogen, C.sub.1-C.sub.6-alkyl (preferably methyl or ethyl), CN or
halogen (preferably fluorine, chlorine or 5 bromine),
[0029] R.sup.5, R.sup.6 R.sup.7 and R.sup.8 are identical or
different and may be any desired radicals, inter alia, radicals
suitable for coupling oligomers to other oligomers/polymers, n is
an integer from 2 to 20, preferably 2 to 15 and particularly
preferably 2 to 10,
[0030] R.sup.5 and R.sup.7 represent independently of one another,
preferably hydrogen or alkyl, in particular Cl-C.sub.4-alkyl, very
particularly preferably methyl,
[0031] R.sup.6 and R.sup.8 represent, independently of one another,
preferably alkyl or aryl radical, in particular
C.sub.1-C.sub.6-alkyl or phenyl. The alkyl and phenyl radicals may
contain one or more functional groups, such as, for example, --OH,
--CN, --CHO or Br.
[0032] With suitable substitution, the oligomers of substituted
divinylbenzene may also be incorporated, for example, in polymers
as discussed below, by means of functional groups. In this
connection, it is possible to produce both main-chain and
side-chain polymers containing low-molecular-weight compounds.
[0033] The oligomers may be coupled to polymers containing double
bonds, for example unsaturated polymers, such as polybutadiene and
polyoctamer by metathetic incorporation (cross-metathesis reaction
of the oligomers and an unsaturated polymer).
[0034] The electroluminescent device is made up of an anode, an
electroluminescent element and a cathode, at least one of the two
electrodes being transparent or semi transparent in the visible
spectral range. The electroluminescent element contains:
[0035] A hole-injecting zone, a hole-transporting zone, an
electroluminescent zone, an electron-transporting zone and/or an
electron-injecting zone, characterized in that the
electroluminescent element optionally contains a functionalized
compound from the group comprising the hole-transporting materials,
a luminescent material A and, optionally, electron-transporting
materials, at least one zone being present, individual zones being
omitted and the joined zone(s) taking over a multiplicity of
tasks.
[0036] A zone can take over a multiplicity of tasks, i.e., a zone
may contain, for example, hole-injecting, hole-transporting,
electroluminescent, electron-injecting and/or electron-transporting
substances.
[0037] The electroluminescent element may furthermore contain one
or more transparent polymeric binders B.
[0038] An additional embodiment of the invention relates to the
device comprising the product of reaction of the oligomer of
formula (I) and a polymeric resin containing double bonds, for
example unsaturated polymers, such as polybutadiene or
polyoctamer.
[0039] The oligomers of substituted p-divinylbenzene may be
produced by known methods, for example by metathesis reactions,
which are described in Macromol. Rapid Commun., 16 (1995),149 (cf.
also Examples).
[0040] The products are soluble in common solvents. They can be
processed to form transparent films which, depending on the value
of n and/or the choice of substituents on the phenyl ring, exhibit
different photoluminescents. By varying n and/or the choice of the
substituents, the wavelength (color) of the emitted light can
therefore be systematically adjusted.
[0041] The binder B represents polymers and/or copolymers, such as,
for example, polycarbonates, polyester carbonates, copolymers of
styrenes, such as SAN or styrene acrylates, polysulfones, polymers
based on vinyl-group-containing monomers, such as, for example,
poly(meth)acrylates, polyvinylpyrrolidone, polyvinylcarbazole,
vinyl-acetate and vinyl-alcohol polymers and copolymers,
polyolefins, cyclic olefin copolymers, phenoxy resins, etc.
Mixtures of different polymers can also be used. The polymeric
binders B have molecular weights of from 10,000 to 200,000 g/mol.,
are soluble and film-forming and are transparent in the visible
spectral range. They are described, for example, in Encyclopedia of
Polymer Science and Engineering, 2nd ed., A. Wiley-Interscience
Publication. The electroluminescent material A may be dispersed in
the transparent binders B. The concentration ratios are variable as
desired. Binder B is normally used in an amount of up to 95,
preferably up to 80%, based on the total weight of A and B.
[0042] To produce the layer, the components A) and, optionally, B)
are dissolved in a suitable solvent, such as chloroform and are
applied to a suitable substrate by pouring, doctor-blading or
spin-coating. Suitable substrates include glass or a plastics
material which is provided with a transparent electrode. A sheet of
polycarbonate, polyester, such as polyethylene terephthalate or
polyethylene naphthalate, polysulfone or polyimide may be used as
plastics material.
[0043] Suitable as transparent or semi transparent electrodes
are:
[0044] a) metal oxides, for example indium/tin oxide (ITO), tin
oxide (NESA) zinc oxide, doped tin oxide, doped zinc oxide,
etc.,
[0045] b) semi-transparent metal films, for example, Au, Pt, Ag,
Cu, etc.,
[0046] c) conductive polymer films, such as polyanilines,
polythiophenes, etc.
[0047] The metal oxide film electrodes and the semi-transparent
metal-film electrodes are applied by procedures such as vapor
deposition, sputtering, platinum, coating, etc., in thin layer. The
conductive polymer films are applied by procedures such as
spin-coating, casting, doctor-blading, etc., from solution.
[0048] The thickness of the electrode is at least 3 nanometers
(nm), preferably 10 nm to 500 nm.
[0049] The electroluminescent layer is applied directly as a thin
film to the electrode or to an optionally present
charge-transporting layer. The thicknesses of the film is 10 to 500
nm, preferably 20 to 400 nm, particularly preferably 50 to 250
nm.
[0050] A further charge-transporting layer may be inserted on the
electroluminescent layer before a counterelectrode is applied.
[0051] An assembly of suitable charge-transporting interlayers
which may be hole-conducting and/or electron-conducting materials
which may be present in polymeric or low-molecular-weight form,
optionally as a blend, is disclosed in EP-A 532 798, incorporated
herein by reference. Particularly suitable are specially
substituted polythiophene which have hole-transporting properties.
They are described, for example, in EP-A 686 662 incorporated
herein by reference.
[0052] The content of low-molecular-weight hole conductor in a
polymer binder can be varied in the range from 2 to 97%;
preferably, 5 to 95%, particularly preferably 10 to 90%, in
particular 10 to 85% relative to the weight of the polymeric binder
and hole conductor. The hole-injecting or hole-conducting zones can
be deposited by various methods.
[0053] Film-forming hole conductors can also be used in pure form
(100%). Optionally, the hole-injecting or hole-conducting zone may
also contain proportions of an electroluminescent substance.
[0054] Blends which are composed exclusively of oligomers of
substituted divinylbenzene may be vapor-deposited; soluble and
film-forming blends, which may also contain (not necessarily) a
binder B) in addition to low-molecular-weight compounds, may be
deposited from a solution, for example, by means of spin-coating,
pouring or doctor-blading.
[0055] It is also possible to apply emitting and/or
electron-conducting substances in a separate layer to the
hole-conducting layer containing the component A. In this
connection, an emitting substance may also be added (as "dopant")
to the layer containing the compound A and an electron-conducting
substance additionally applied. An electroluminescent substance may
also be added to the electron-injecting or electron-conducting
layer.
[0056] On the other hand, the electroluminescent materials A) may
themselves also be used as dopants in electroluminescent
devices.
[0057] The content of low-molecular-weight electron conductors in
the polymeric binder can be varied in the range from 2 to 95%,
preferably, 5 to 90%, particularly preferably 10 to 85% relative to
the total weight of electron conductor and binder. Film-forming
electron conductors may also be used in pure form (100%).
[0058] The counterelectrode is composed of a conductive substance,
which may be transparent. Preferably, metals, for example Al, Au,
Ag, Mg, In, etc. or alloys and oxides of the later which can be
applied by procedures such as vapor deposition, sputtering or
platinum coating, are suitable.
[0059] The device according to the invention is brought into
contact with the two electrodes by two electrical leads (for
example, metal wires).
[0060] When a direct voltage in the range from 0.1 to 100 volts is
applied, the devices emit light of a wavelength from 200 to 2000
.mu.m. They exhibit photoluminescence in the range from 200 to 2000
nm.
[0061] The devices according to the invention are suitable for
producing units for the purpose of illumination and for the purpose
of displaying information.
Guidelines
[0062] 1. Metathetic preparation of ring-substitution
p-phenylenevinylene oligomers (and polymers)
[0063] Starting from a 2,5-ring-substituted
1,4-(bis-1-alkenyl)benzene, such as, for example,
1,4-divinylbenzene, 1,4-di(1-propenyl)benzene,
1,4-di(1-isobutenyl)benzene etc. and adding a metathesis-active
catalyst, such as, for example,
Mo(NAr.sup.Me2)(CHCMe.sub.2Ph)[OCMe(CF.sub.3).sub.2- ].sub.2,
oligomerization (metathetic polycondensation) is carried out by
cleaving and removing a low-molecular-weight monoolefin, such as,
for example, ethene, 2-butene, 3-hexene, etc. Scheme 1 shows the
reaction equation for the metathetic conversion of
2,5-disubstituted 1,4-divinylbenzenze.
[0064] Mo(NAr.sup.Me2)(CHCMe.sub.2Ph)[OCMe(CF.sub.3).sub.2].sub.2:
The synthesis is carried out according to the literature
specification of R. R. Schrock, J. S. Murdzek, G. C. Bazan, J.
Robbins, M. DiMare, M. O'Regan, J. Chem, Soc., 112 (1990), 3875.
3
[0065] R.sup.1 and R.sup.2 independently are hydrogen, alkyl or
alkoxy substituents, and n is 2 to 20.
[0066] The polycondensation reactions are carried out under an
inert gas stream, argon being used, from which oxygen traces and
water traces and water traces are removed (<10.sup.-5% by
volume) by means of an "Oxisorb.sup.R" miniature absorber (supplied
by Messer-Grie.beta.heim, Duisburg, Germany). A schlenk tube or a
flask provided with inert gas and vacuum connections (standard
Schlenk technique) is used as reaction vessel.
[0067] Before use, the glassware is baked out for approximately 4
hours under a mercury-diffusion-pump vacuum and then filled with
argon.
[0068] The solvents toluene, decalin, cyclohexane, hexane, pentane
are refluxed for 2 to 3 days over lithium alanate and distilled off
under argon. 0.5 ml of n-butyllithium are then added to 250 ml of
solvent, subjected to a plurality of freezing/thawing cycles until
vacuum constancy is reached (mercury-diffusion-pump vacuum) and
condensed over into a stock vessel.
[0069] The polycondensation of dibutyl-, diheptyl- or
didecyl-substituted divinylbenzenes and the protection (cross
metathesis) of the alkyl-substituted p-divinylbenzene oligomers are
carried out at room temperature. The conversion of dicyclohexyl- or
diheptyloxy-substituted p-divinylbenzenes is carried out at an
elevated temperature of 50.degree. C. and up to 80.degree. C.
EXAMPLES
[0070] Synthesis of Oligomers of 2,5-heptyl-substituted
1,4-divinylbenzene
[0071] a) Preparation of Oligomers Having Narrow Dispersity
[0072] 68 mg (208 .mu.mol) of 2,5-diheptyl-1,4-divinylbenzene are
introduced as a solid into a Schlenk tube provided with protective
gas and vacuum connections and the reaction is started by rapidly
adding the catalyst solution (0.5 ml of a toluene solution of
Mo(NAr)(CHAr')[OC(CH.sub.3)(CF.sub.3).sub.2].sub.2) with the
concentration of C=6.7 mmol./l. The polycondensation is carried out
in sealed equipment at reduced pressure with constant stirring.
Ethene is removed by repeatedly applying a reduced pressure for a
short time to the reaction flask (approximately 3 times in the
first hour, then about every 6 hours) to shift the equilibrium of
the reaction to the polycondensate side.
[0073] After a reaction time of 24 hours, the experiment is
terminated by adding propanal. Propanal makes possible the defined
termination of the metathesis reaction by means of a reaction
analogous to the Wittig reaction. The reaction mixture. is taken up
in 30 ml of toluene and then filtered. The product is obtained by
precipitation in 100 ml of methanol after filtration, drying and
extraction by means of chloroform.
[0074] The product isolated exhibits a narrow molecular-weight
distribution (GPC). The chain length was 10 to 11 (.sup.1H-NMR;
n=number of .alpha.-methylene protons/number of vinyl protons),
[0075] .sup.1H-NMR (100 MHz, CDCl.sub.3)
[0076] .delta. (ppm)=7.43 (Ar--H); 7.23 (Ar--CH.dbd.CH--Ar,
trans-vinylene); 6.97 (Ar--CH.dbd.CH.sub.2); 5.67 (trans-vinyl
terminal group proton); 5.26 (cis-vinyl terminal group proton);
2.75 (.alpha.-CH.sub.2); 1.10-1.70 (.beta.-.xi.-CH.sub.2), 0.89
-CH.sub.3
[0077] UV/V is (in THF)
[0078] .lambda. (nm)=395
[0079] b) Preparation of Oligomers with Wide Molecular-weight
Distribution
[0080] 2 g (6.12 mmol) of 2,5-diheptyl-1,4-divinylbenzene are dried
for several hours in a mercury diffusion-pump vacuum in a flask
provided with inert gas and vacuum connections. Then 50 ml of
pentane and 0.123 mmol of catalyst dissolved in 17 ml of pentane
(c=7.22 mmol/l) are added. After applying a slight vacuum, the
reaction mixture is stirred for 24 hours at room temperature under
an inert gas atmosphere. After adding 3 ml of propionaldehyde, the
solvent is removed using a rotary evaporator, the crude product is
taken up in toluene and the higher-molecular-weight oligomer
fraction is precipitated by adding double the volume of methanol.
This product is filtered off, predried in an oil-pump vacuum
(=10.sup.-2 bar) for 10 hours and then dried for a further 10 hours
in a mercury diffusion-pump vacuum. 1.05 g (56%) of oligomer having
a mean degree of polymerization of 6 to 7 are obtained as a green,
fluorescent solid.
[0081] Product Characterization:
[0082] .sup.1H-NMR (CDCl.sub.3, 100 MHz)
[0083] .delta. (ppm)=7.42 (Ar--H); 7.23 (Ar--CH.dbd.CH--Ar,
trans-vinylene); 6.95 (Ar--CH.dbd.CH.sub.2); 5.67 (trans-vinyl
terminal group proton); 5.27 (cis-vinyl terminal group proton);
2.76 (.alpha.-CH.sub.2); 1.10-1.70 (.beta.-.xi.-CH.sub.2); 0.88
--CH.sub.3
[0084] UV/V is (in THF)
[0085] .lambda. (nm)=390 (.pi.-.pi.*)
[0086] c) Protection of the oligomers prepared; cross-metathesis
with trans-3-hexene, i.e. for example: R.sub.5 and R.sub.7=H and
R.sub.6 and R.sub.8=ethyl.
[0087] The cross-metathesis experiments are carried out in the
solvent toluene. The substituted divinylbenzene oligomers prepared
in hexane are used.
[0088] Catalyst: oligomer: trans-3-hexene=1:10:300, the catalyst
concentration is 1 mmol/l.
[0089] The reaction is carried out at room temperature and
terminated after one day by adding propanal. Solvents and volatile
substances are removed by means of oil-pump vacuum. Then the
residue is taken up in toluene and the solution is added dropwise
to a precipitation bath (methanol) via a paper filter. The product
is extracted by means of a Buchner funnel and adhering solvent
residues are removed in a mercury diffusion-pump vacuum.
[0090] The working-up was identical to that of the unprotected
substituted divinylbenzene oligomers.
[0091] The protection of the terminal vinyl double bonds proceeds
quantitatively and highly selectively. The product is characterized
by .sup.1H-NMR, UV/Vis-IR, DSC and GPC analyses, and, in the case
of the protected monomer (n=1), additionally with the aid of gas
chromatography.
[0092] 2. Structure of the Electroluminescent Devices
[0093] In the examples described below, a glass plate (Baltracon
255 supplied by Balzers) is used which is coated with ITO
(indium-tin oxide) and which is additionally provided with an
approximately 30 to 50 nm thick layer of polyethylene
dioxythiophene (PEDT)/polystyrene sulfonate (PSS)--Baytron.RTM.
from Bayer AG, Leverkusen, Germany--on the ITO surface. The
2,5-diheptyl-1,4-divinylbenzenze with n=6-7, terminal group:
CH--CH.sub.2--CH.sub.3, i.e. R.sub.5 and R.sub.7=H and R.sub.6 and
R.sub.8=ethyl, is used as electroluminescent material.
[0094] a) A 1.5% solution composed of polyvinylcarbazole
(PVK)-Luvican EP from BASF AG, Ludwigshafen, Germany and
2,5-diheptyl-1,4-divinylbenzene oligomer (n=6=7), at a weight ratio
of 1: 1, in chloroform is spread over an ITO/PEDT/PVK substrate on
a commercial spin coater at a rotational speed of 400 min.sup.-1.
The layer thickness is 100 nm. Aluminum is vapor-deposited as
counterelectrode.
[0095] After contacting and applying an electrical field, the
device exhibits visually perceptible electroluminescence in the
blue spectral region at about 6 V.
[0096] b) The structure described under a) is extended by
vapor-depositing a 30 nm thick layer of aluminum oxine (Alq.sub.3)
on the layer of PVK.
[0097] After making contact and applying an electrical field, the
device exhibits visually perceptible electroluminescence in the
green spectral range at about 6 V.
[0098] c) The structure is analogous to b) with the difference that
PVK is replaced by polystyrene.
[0099] After making contact and applying an electrical field, the
device exhibits visually perceptible electroluminescence in the
green spectral range from about 6 V.
* * * * *