Abstrict A polymeric substrate for a moisture-sensitive electronic device
includes a polymeric support having a top and bottom surface, and
a desiccant layer disposed over at least a portion of the top or
bottom surface of the polymeric support, or both.
Claims 1. A polymeric substrate for a moisture-sensitive electronic device
comprising: a) a polymeric support having a top and bottom surface;
and b) a desiccant layer disposed over at least a portion of the
top or bottom surface of the polymeric support, or both.
2. The polymeric substrate of claim 1 further including an inorganic
barrier layer disposed over the desiccating layer or between the
desiccating layer and the polymeric support.
3. The polymeric substrate of claim 1 wherein the desiccant layer
is further provided over at least a portion of side surfaces of
the polymeric support.
4. The polymeric substrate of claim 2 wherein the desiccant layer
is further provided over at least a portion of side surfaces of
the polymeric support.
5. A polymeric substrate for a moisture-sensitive electronic device
comprising: a) a polymeric support having a top and bottom surface;
and b) a host and a desiccant molecularly dispersed in such host
defining a desiccating film that is disposed over at least a portion
of the top or bottom surface of the polymeric support, or both.
6. The polymeric substrate of claim 5 further including an inorganic
barrier layer disposed over the desiccating film or between the
desiccating film and the polymeric support.
7. The polymeric substrate of claim 5 wherein the desiccating film
is further provided over at least a portion of side surfaces of
the polymeric support.
8. The polymeric substrate of claim 6 wherein the desiccating film
is further provided over at least a portion of side surfaces of
the polymeric support.
9. A polymeric substrate for a moisture-sensitive electronic device
comprising: a) a polymeric support having a top and bottom surface;
and b) a plurality of alternating layer structures formed over the
top or bottom surfaces of the polymeric support, or both, wherein
such alternating layer structure includes: i) a desiccant layer;
and ii) an inorganic barrier layer provided over the desiccant layer.
10. A polymeric substrate for a moisture-sensitive electronic device
comprising: a) a polymeric support having a top and bottom surface;
and b) a plurality of alternating layer structures formed over the
top or bottom surfaces of the polymeric support, or both, wherein
such alternating layer structure includes: i) a host and a desiccant
molecularly dispersed in such host defining a desiccating film;
and ii) an inorganic barrier layer provided over the desiccating
film.
11. A polymeric substrate for a moisture-sensitive electronic device
comprising: a) a polymeric support having a top and bottom surface;
and b) a patterned desiccant layer disposed over the top or bottom
surface of the polymeric support, or both.
12. The polymeric substrate of claim 111 wherein the patterned
desiccant layer is discontinuous.
13. The polymeric substrate of claim 11 wherein the desiccant layer
is a desiccating film having a host and desiccant molecularly dispersed
in such host.
14. The polymeric substrate of claim 12 wherein the desiccant layer
is a desiccating film having a host and desiccant molecularly dispersed
in such host.
15. The polymeric substrate of claim 11 further including an inorganic
barrier layer disposed over the desiccant layer or between the desiccant
layer and the polymeric support.
16. The polymeric substrate of claim 12 further including an inorganic
barrier layer disposed over the desiccant layer or between the desiccant
layer and the polymeric support.
Description CROSS REFERENCE TO RELATED APPLICATIONS
[0002] The present invention relates to polymeric substrates for
moisture-sensitive electronic devices.
BACKGROUND OF THE INVENTION
[0003] It is desirable to use a polymeric substrate for various
electronic devices in order to make them flexible. Such devices
include organic light-emitting diode (OLED) displays, LCD displays,
photovoltaics, and sensors. However, many such devices are sensitive
to moisture and polymeric substrates typically have high Water permeability.
To address this problem, it has been proposed to coat moisture barrier
layers over the polymeric substrates, for example, for use with
flexible OLEDs. However, it is still very difficult to avoid defects
that permit moisture into the electronic device. There is a continuing
need to improve the moisture protection of electronic devices on
polymeric substrates.
SUMMARY OF THE INVENTION
[0004] It is therefore an object of the present invention to provide
an effective way of preventing moisture from degrading the performance
of an electronic device on a polymeric substrate.
[0005] This object is achieved by a polymeric substrate for a moisture-sensitive
electronic device comprising:
[0006] a) a polymeric support having a top and bottom surface;
and
[0007] b) a desiccant layer disposed over at least a portion of
the top or bottom surface of the polymeric support, or both.
ADVANTAGES
[0008] The invention provides an electronic device on a polymeric
substrate that is better protected from moisture, thereby achieving
longer lifetime and excellent device performance. The invention
further provides a way for protecting a flexible OLED device without
negatively impacting the light transmission characteristics of the
polymeric support.
BRIEF DESCRIPTION OF THE DRAWINGS
[0009] FIG. 1 is a cross-sectional view of an OLED device;
[0010] FIG. 2A is a cross-sectional view of a polymeric substrate
of this invention;
[0011] FIG. 2B is a cross-sectional view of another polymeric substrate
of this invention;
[0012] FIG. 2C is a cross-sectional view of yet another polymeric
substrate of this invention;
[0013] FIG. 2D is a cross-sectional view of still another polymeric
substrate of this invention;
[0014] FIG. 3 is a cross-sectional view of another polymeric substrate
of this invention;
[0015] FIG. 4 is a cross-sectional view of another polymeric substrate
of this invention;
[0016] FIG. 5 is a plan view of an OLED having first electrode
and contact pads provided over a polymeric substrate of this invention;
[0017] FIG. 6 shows the OLED of FIG. 5 after deposition of a patterned
insulator layer;
[0018] FIG. 7A is a plan view of the OLED from FIG. 6 after deposition
of the organic EL media and second electrode;
[0019] FIG. 7B is a cross-sectional view of the OLED device of
FIG. 7A taken along lines 7B-B;
[0020] FIG. 8 is a cross-sectional view of the OLED device of FIG.
7 with various other functional layers for encapsulation;
[0021] FIG. 9A is a plan view of a polymeric substrate of this
invention with a patterned desiccant layer;
[0022] FIG. 9B is a cross-sectional view of the polymeric substrate
of FIG. 9 taken along lines 9A-A;
[0023] FIG. 10 is a cross-sectional view of an OLED device using
the polymeric substrate of FIG. 9A; and
[0024] FIG. 11 is a cross-sectional view of a polymeric substrate
of this invention with multiple layers of patterned desiccant.
DETAILED DESCRIPTION OF THE INVENTION
[0025] The present invention can be used with any electronic device
having a polymeric support and requiring moisture protection. In
particular, this invention is suitable for flexible OLED devices
provided on a polymeric support. The features of a typical OLED
device will now be discussed.
General OLED Device Architecture
[0026] The present invention can be employed in most OLED device
configurations. These include very simple structures comprising
a single anode and cathode to more complex devices, such as passive
matrix displays comprised of orthogonal arrays of anodes and cathodes
to form pixels, and active-matrix displays where each pixel is controlled
independently, for example, with thin film transistors (TFTs).
[0027] There are numerous configurations of the organic layers
wherein the present invention can be successfully practiced. A schematic
of a pixel area of the device, not to scale, is shown in FIG. 1.
It includes a substrate 101 an anode 103 a hole-injecting layer
105 a hole-transporting layer 107 a light-emitting layer 109
an electron-transporting layer 111 and a cathode 113. The substrate
of this invention includes a polymeric support. These layers are
described in more detail below. Note that the cathode can alternatively
be located adjacent to the substrate. The organic layers between
the anode and cathode are conveniently referred to as the organic
EL element or organic EL media. The total combined thickness of
the organic layers is preferably less than 500 nm.
[0028] The anode and cathode of the OLED are connected to a voltage/current
source 150 through electrical conductors 160. The OLED is operated
by applying a potential between the anode and cathode such that
the anode is at a more positive potential than the cathode. Holes
are injected into the organic EL element from the anode and electrons
are injected into the organic EL element at the anode. Enhanced
device stability can sometimes be achieved when the OLED is operated
in an alternating current (AC) mode where, for some time period
in the cycle, the potential bias is reversed and no current flows.
An example of an AC driven OLED is described in U.S. Pat. No. 5552678.
Anode
[0029] When EL emission is viewed through anode 103 the anode
should be transparent or substantially transparent to the emission
of interest. Common transparent anode materials used in this invention
are indium-tin oxide (ITO), indium-zinc oxide (IZO), and tin oxide,
but other metal oxides can work including, but not limited to, aluminum-
or indium-doped zinc oxide, magnesium-indium oxide, and nickel-tungsten
oxide. In addition to these oxides, metal nitrides, such as gallium
nitride, and metal selenides, such as zinc selenide, and metal sulfides,
such as zinc sulfide, can be used as the anode. For applications
where EL emission is viewed only through the cathode electrode,
the transmissive characteristics of anode are immaterial and any
conductive material can be used, transparent, opaque, or reflective.
Example conductors for this application include, but are not limited
to, gold, iridium, molybdenum, palladium, and platinum. Typical
anode materials, transmissive or otherwise, have a work function
of 4.1 eV or greater. Desired anode materials are commonly deposited
by any suitable means such as evaporation, sputtering, chemical
vapor deposition, or electrochemical means. Anodes can be patterned
using well known photolithographic processes. Optionally, anodes
can be polished prior to application of other layers to reduce surface
roughness so as to reduce shorts or enhance reflectivity.
Hole-Injecting Layer (HIL)
[0030] It is often useful to provide a hole-injecting layer 105
between anode 103 and hole-transporting layer 107. The hole-injecting
material can serve to improve the film formation property of subsequent
organic layers and to facilitate injection of holes into the hole-transporting
layer. Suitable materials for use in the hole-injecting layer include,
but are not limited to, porphyrinic compounds as described in U.S.
Pat. No. 4720432 plasma-deposited fluorocarbon polymers as described
in U.S. Pat. Nos. 6127004 6208075 and 6208077 some aromatic
amines, for example, m-MTDATA (44',4''-tris[(3-methylphenyl)-phenylamino]triphenylamine),
and inorganic oxides including vanadium oxide (VOx), molybdenum
oxide (MoOx), and nickel oxide (NiOx). Alternative hole-injecting
materials reportedly useful in organic EL devices are described
in EP 0 891 121 A1 and EP 1 029 909 A1.
Hole-Transporting Layer (HTL)
[0031] The hole-transporting layer 107 contains at least one hole-transporting
compound such as an aromatic tertiary amine, where the latter is
understood to be a compound containing at least one trivalent nitrogen
atom that is bonded only to carbon atoms, at least one of which
is a member of an aromatic ring. In one form the aromatic tertiary
amine can be an arylamine, such as a monoarylamine, diarylamine,
triarylamine, or a polymeric arylamine. Exemplary monomeric triarylamines
are illustrated by Klupfel, et al. U.S. Pat. No. 3180730. Other
suitable triarylamines substituted with one or more vinyl radicals
and/or comprising at least one active hydrogen containing group
are disclosed by Brantley, et al. U.S. Pat. Nos. 3567450 and 3658520.
[0032] A more preferred class of aromatic tertiary amines are those
which include at least two aromatic tertiary amine moieties as described
in U.S. Pat. Nos. 4720432 and 5061569. The hole-transporting
layer can be formed of a single or a mixture of aromatic tertiary
amine compounds. Illustrative of useful aromatic tertiary amines
are the following: [0033] 11-Bis(4-di-p-tolylaminophenyl)cyclohexane;
[0034] 11-Bis(4-di-p-tolylaminophenyl)-4-phenylcyclohexane; [0035]
N,N,N',N'-tetraphenyl-44'''-diamino-11':4', 1'':4'', 1'''-quaterphenyl;
[0036] Bis(4-dimethylamino-2-methylphenyl)phenylmethane; [0037]
14-bis[2-[4-[N,N-di(p-toly)amino]phenyl]vinyl]benzene (BDTAPVB);
[0038] N,N,N',N'-Tetra-p-tolyl-44'-diaminobiphenyl; [0039] N,N,N',N'-Tetraphenyl-44'-diaminobiphenyl;
[0040] N,N,N',N'-tetra-1-naphthyl-44'-diaminobiphenyl; [0041] N,N,N',N'-tetra-2-naphthyl-44'-diaminobiphenyl;
[0042] N-Phenylcarbazole; [0043] 44'-Bis[N-(1-naphthyl)-N-phenylamino]biphenyl
(NPB); [0044] 44'-Bis[N-(1-naphthyl)-N-(2-naphthyl)amino]biphenyl
(TNB); [0045] 44'-Bis[N-(1-naphthyl)-N-phenylamino].sub.p-terphenyl;
[0046] 44'-Bis[N-(2-naphthyl)-N-phenylamino]biphenyl; [0047] 44'-Bis[N-(3-acenaphthenyl)-N-phenylamino]biphenyl;
[0048] 15-Bis[N-(1-naphthyl)-N-phenylamino]naphthalene; [0049]
44'-Bis[N-(9-anthryl)-N-phenylamino]biphenyl; [0050] 44'-Bis[N-(1-anthryl)-N-phenylamino]-p-terphenyl;
[0051] 44'-Bis[N-(2-phenanthryl)-N-phenylamino]biphenyl; [0052]
44'-Bis[N-(8-fluoranthenyl)-N-phenylamino]biphenyl; [0053] 44'-Bis[N-(2-pyrenyl)-N-phenylamino]biphenyl;
[0054] 44'-Bis[N-(2-naphthacenyl)-N-phenylamino]biphenyl; [0055]
44'-Bis[N-(2-perylenyl)-N-phenylamino]biphenyl; [0056] 44'-Bis[N-(1-coronenyl)-N-phenylamino]biphenyl;
[0057] 26-Bis(di-p-tolylamino)naphthalene; [0058] 26-Bis[di-(1-naphthyl)amino]naphthalene;
[0059] 26-Bis[N-(1-naphthyl)-N-(2-naphthyl)amino]naphthalene; [0060]
N,N,N',N'-Tetra(2-naphthyl)-44''-diamino-p-terphenyl; [0061] 44'-Bis
{N-phenyl-N-[4-(1-naphthyl)-phenyl]amino}biphenyl; [0062] 26-Bis[N,N-di(2-naphthyl)amino]fluorene;
[0063] 44',4''-tris[(3-methylphenyl)phenylamino]triphenylamine
(MTDATA); and [0064] 44'-Bis[N-(3-methylphenyl)-N-phenylamino]biphenyl
(TPD).
[0065] Another class of useful hole-transporting materials includes
polycyclic aromatic compounds as described in EP 1 009 041. Some
hole-injecting materials described in EP 0 891 121 A1 and EP 1 029
909 A1 can also make useful hole-transporting materials. In addition,
polymeric hole-transporting materials can be used including poly(N-vinylcarbazole)
(PVK), polythiophenes, polypyrrole, polyaniline, and copolymers
including poly(34-ethylenedioxythio-phene)/poly(4-styrenesulfonate),
also called PEDOT/PSS.
Light-Emitting Layer (LEL)
[0066] As more fully described in U.S. Pat. Nos. 4769292 and
5935721 each of the light-emitting layers (LEL) of the organic
EL element include a luminescent fluorescent or phosphorescent material
where electroluminescence is produced as a result of electron-hole
pair recombination in this region. The light-emitting layer can
be comprised of a single material, but more commonly contains a
host material doped with a guest emitting material, or materials
where light emission comes primarily from the emitting materials
and can be of any color. This guest emitting material is often referred
to as a light-emitting dopant. The host materials in the light-emitting
layer can be an electron-transporting material, as defined below,
a hole-transporting material, as defined above, or another material
or combination of materials that support hole-electron recombination.
The emitting material is typically chosen from highly fluorescent
dyes and phosphorescent compounds, e.g., transition metal complexes
as described in WO 98/55561 WO 00/18851 WO 00/57676 and WO 00/70655.
Emitting materials are typically incorporated at 0.01 to 10% by
weight of the host material.
[0067] The host and emitting materials can be small nonpolymeric
molecules or polymeric materials including polyfluorenes and polyvinylarylenes,
e.g., poly(p-phenylenevinylene), PPV. In the case of polymers, small
molecule emitting materials can be molecularly dispersed into a
polymeric host, or the emitting materials can be added by copolymerizing
a minor constituent into a host polymer.
[0068] An important relationship for choosing an emitting material
is a comparison of the bandgap potential, which is defined as the
energy difference between the highest occupied molecular orbital
and the lowest unoccupied molecular orbital of the molecule. For
efficient energy transfer from the host to the emitting material,
a necessary condition is that the band gap of the dopant is smaller
than that of the host material. For phosphorescent emitters (including
materials that emit from a triplet excited state, i.e., so-called
"triplet emitters") it is also important that the host
triplet energy level of the host be high enough to enable energy
transfer from host to emitting material.
[0069] Host and emitting materials known to be of use include,
but are not limited to, those disclosed in U.S. Pat. Nos. 4768292
5141671 5150006 5151629 5405709 5484922 5593788
5645948 5683823 5755999 5928802 5935720 5935721
6020078 6475648 6534199 6661023 U.S. Patent Application
Publications 2002/0127427 A1 2003/0198829 A1 2003/0203234 A1
2003/0224202 A1 and 2004/0001969 A1 the disclosures of which are
herein incorporated by reference.
[0070] Metal complexes of 8-hydroxyquinoline (oxine) and similar
derivatives constitute one class of useful host compounds capable
of supporting electroluminescence. Illustrative of useful chelated
oxinoid compounds are the following: [0071] CO-1: Aluminum trisoxine
[alias, tris(8-quinolinolato)aluminum(III)]; [0072] CO-2: Magnesium
bisoxine [alias, bis(8-quinolinolato)magnesium(II)]; [0073] CO-3:
Bis[benzo{f}-8-quinolinolato]zinc (II); [0074] CO-4: Bis(2-methyl-8-quinolinolato)aluminum(III)-.mu.-oxo-bis(2-methyl-8-quinol-
inolato) aluminum(III); [0075] CO-5: Indium trisoxine [alias, tris(8-quinolinolato)indium];
[0076] CO-6: Aluminum tris(5-methyloxine) [alias, tris(5-methyl-8-quinolinolato)
aluminum(III)]; [0077] CO-7: Lithium oxine [alias, (8-quinolinolato)lithium(I)];
[0078] CO-8: Gallium oxine [alias, tris(8-quinolinolato)gallium(III)];
and [0079] CO-9: Zirconium oxine [alias, tetra(8-quinolinolato)zirconium(IV)].
[0080] Another class of useful host materials includes derivatives
of anthracene, such as those described in WO 2004018587 U.S. Pat.
Nos. 5935721 5972247 6465115 6534199 6713192 U.S.
Patent Application Publications 2002/0048687 A1 and 2003/0072966
A1 the disclosures of which are herein incorporated by reference.
Some examples include derivatives of 910-dinaphthylanthracene derivatives
and 9-naphthyl-10-phenylanthracene. Other useful classes of host
materials include distyrylarylene derivatives as described in U.S.
Pat. No. 5121029 and benzazole derivatives, for example, 2 2',
2''-(135-phenylene)tris[1-phenyl-1H-benzimidazole].
[0081] Desirable host materials are capable of forming a continuous
film. The light-emitting layer can contain more than one host material
in order to improve the device's film morphology, electrical properties,
light emission efficiency, and lifetime. Mixtures of electron-transporting
and hole-transporting materials are known as useful hosts. In addition,
mixtures of the above listed host materials with hole-transporting
or electron-transporting materials can make suitable hosts.
[0082] Useful fluorescent dopants include, but are not limited
to, derivatives of anthracene, tetracene, xanthene, perylene, rubrene,
coumarin, rhodamine, and quinacridone, dicyanomethylenepyran compounds,
thiopyran compounds, polymethine compounds, pyrilium and thiapyrilium
compounds, fluorene derivatives, periflanthene derivatives, indenoperylene
derivatives, bis(azinyl)amine boron compounds, bis(azinyl)methane
compounds, derivatives of distryrylbenzene and distyrylbiphenyl,
and carbostyryl compounds. Among derivatives of distyrylbenzene,
particularly useful are those substituted with diarylamino groups,
informally known as distyrylamines.
[0083] Suitable host materials for phosphorescent emitters (including
materials that emit from a triplet excited state, i.e., so-called
"triplet emitters") should be selected so that the triplet
exciton can be transferred efficiently from the host material to
the phosphorescent material. For this transfer to occur, it is a
highly desirable condition that the excited state energy of the
phosphorescent material be lower than the difference in energy between
the lowest triplet state and the ground state of the host. However,
the band gap of the host should not be chosen so large as to cause
an unacceptable increase in the drive voltage of the OLED. Suitable
host materials are described in WO 00/70655 A2 WO 01/39234 A2
WO 01/93642 A1 WO 02/074015 A2 WO 02/15645 A1 and U.S. Patent
Application Publication 2002/0117662 A1 the disclosure of which
is herein incorporated by reference. Suitable hosts include certain
aryl amines, triazoles, indoles, and carbazole compounds. Examples
of desirable hosts are 44'-N,N'-dicarbazole-biphenyl (CBP), 22'-dimethyl-44'-N,N'-dicarbazole-biphenyl,
m-(N,N'-dicarbazole)benzene, and poly(N-vinylcarbazole), including
their derivatives.
[0084] Examples of useful phosphorescent materials that can be
used in light-emitting layers of this invention include, but are
not limited to, those described in WO 00/57676 WO 00/70655 WO
01/41512 A1 WO 02/15645 A1 WO 01/93642 A1 WO 01/39234 A2 WO
02/071813 A1 WO 02/074015 A2 U.S. Pat. Nos. 6451455 6458475
6573651 6413656 6515298 6451415 6097147 EP 1 239
526 A2 EP 1 238 981 A2 EP 1 244 155 A2 JP 2003059667A, JP 2003073665A,
JP 2003073387A, JP 2003 073388A, U.S. Patent Application Publications
2003/0124381 A1 2003/0059646 A1 2003/0054198 A1 2003/0017361
A1 2003/0072964 A1 2003/0068528 A1 2002/0100906 A1 2003/068526
A1 2003/0068535 A1 2003/0141809 A1 2003/0040627 A1 2002/0197511
A1 and 2002/0121638 A1 the disclosures of which are herein incorporated
by reference.
Electron-Transporting Layer (ETL)
[0085] Preferred thin film-forming materials for use in forming
the electron-transporting layer 111 of the organic EL elements of
this invention are metal chelated oxinoid compounds, including chelates
of oxine itself (also commonly referred to as 8-quinolinol or 8-hydroxyquinoline).
Such compounds help to inject and transport electrons, exhibit high
levels of performance, and are readily fabricated in the form of
thin films. Exemplary oxinoid compounds were listed previously.
[0086] Other electron-transporting materials include various butadiene
derivatives as disclosed in U.S. Pat. No. 4356429 and various
heterocyclic optical brighteners as described in U.S. Pat. No. 4539507.
Benzazoles and triazines are also useful electron-transporting materials.
Cathode
[0087] When light emission is viewed solely through the anode,
the cathode 113 used in this invention can be comprised of nearly
any conductive material. Desirable materials have effective film-forming
properties to ensure effective contact with the underlying organic
layer, promote electron injection at low voltage, and have effective
stability. Useful cathode materials often contain a low work function
metal (<4.0 eV) or metal alloy. One preferred cathode material
is comprised of a Mg:Ag alloy wherein the percentage of silver is
in the range of 1 to 20%, as described in U.S. Pat. No. 4885221.
Another suitable class of cathode materials includes bilayers comprising
a thin electron-injection layer (EIL) in contact with the organic
layer (e.g., ETL), which is capped with a thicker layer of a conductive
metal. Here, the EIL preferably includes a low work function metal
or metal salt, and if so, the thicker capping layer does not need
to have a low work function. One such cathode is comprised of a
thin layer of LiF followed by a thicker layer of Al as described
in U.S. Pat. No. 5677572. Other useful cathode material sets include,
but are not limited to, those disclosed in U.S. Pat. Nos. 5059861
5059862 and 6140763.
[0088] A metal-doped organic layer can be used as an electron-injecting
layer. Such a layer contains an organic electron-transporting material
and a low work-function metal (<4.0 eV). For example, Kido, et
al. reported in "Bright Organic Electroluminescent Devices
Having a Metal-Doped Electron-Injecting Layer", Applied Physics
Letters, 73 2866 (1998) and disclosed in U.S. Pat. No. 6013384
that an OLED can be fabricated containing a low work-function metal-doped
electron-injecting layer adjacent to a cathode. Suitable metals
for the metal-doped organic layer include alkali metals (e.g. lithium,
sodium), alkaline earth metals (e.g. barium, magnesium, calcium),
or metals from the lanthanide group (e.g. lanthanum, neodymium,
lutetium), or combinations thereof. The concentration of the low
work-function metal in the metal-doped organic layer is in the range
of from 0.1% to 30% by volume. Preferably, the concentration of
the low work-function metal in the metal-doped organic layer is
in the range of from 0.2% to 10% by volume. Preferably, the low
work-function metal is provided in a mole ratio in a range of from
1:1 with the organic electron transporting material.
[0089] When light emission is viewed through the cathode, the cathode
should be transparent or nearly transparent. For such applications,
metals should be thin or one should use transparent conductive oxides,
or include these materials. Optically transparent cathodes have
been described in more detail in U.S. Pat. Nos. 4885211 5247190
5703436 5608287 5837391 5677572 5776622 5776623
5714838 5969474 5739545 5981306 6137223 6140763
6172459 6278236 6284393 JP 3234963 and EP 1 076 368.
Cathode materials are typically deposited by evaporation, sputtering,
or chemical vapor deposition. When needed, patterning can be achieved
through many well known methods including, but not limited to, through-mask
deposition, integral shadow masking, for example, as described in
U.S. Pat. No. 5276380 and EP 0 732 868 laser ablation, and selective
chemical vapor deposition.
Other Common Organic Layers and Device Architecture
[0090] In some instances, layers 109 and 111 can optionally be
collapsed into a single layer that serves the function of supporting
both light emission and electron transportation. It also known in
the art that emitting dopants can be added to the hole-transporting
layer, which can serve as a host. Multiple dopants can be added
to one or more layers in order to produce a white-emitting OLED,
for example, by combining blue- and yellow-emitting materials, cyan-
and red-emitting materials, or red-, green-, and blue-emitting materials.
White-emitting devices are described, for example, in EP 1 187 235
EP 1 182 244 U.S. Pat. Nos. 5683823 5503910 5405709 5283132
6627333 U.S. Patent Application Publications 2002/0186214 A1
2002/0025419 A1 and 2004/0009367 A1 the disclosures of which are
herein incorporated by reference.
[0091] Additional layers such as exciton, electron and hole-blocking
layers as taught in the art can be employed in devices of this invention.
Hole-blocking layers are commonly used to improve efficiency of
phosphorescent emitter devices, for example, as in WO 00/70655A2
WO 01/93642A1 U.S. Patent Application Publications 2003/0068528
A1 2003/0175553 A1 and 2002/0015859 A1 the disclosures of which
are herein incorporated by reference.
[0092] This invention can be used in so-called stacked device architecture,
for example, as taught in U.S. Pat. Nos. 5703436 6337492 6717358
and U.S. Patent Application Publication 2003/0170491 A1 the disclosure
of which is herein incorporated by reference.
Deposition of Organic Layers
[0093] The organic materials mentioned above are suitably deposited
through a vapor phase method such as sublimation, but can be deposited
from a fluid, for example, from a solvent with an optional binder
to improve film formation. If the material is a polymer, solvent
deposition is useful, but other methods can be used, such as sputtering,
chemical vapor deposition, or thermal transfer from a donor sheet.
The material to be deposited by sublimation can be vaporized from
a sublimation "boat" often comprised of a tantalum material,
e.g., as described in U.S. Pat. No. 6237529 or can be first coated
onto a donor sheet and then sublimed in closer proximity to the
substrate. Layers with a mixture of materials can use separate sublimation
boats or the materials can be premixed and coated from a single
boat or donor sheet. Patterned deposition can be achieved using
shadow masks, integral shadow masks (U.S. Pat. No. 5294870), spatially-defined
thermal dye transfer from a donor sheet (U.S. Pat. Nos. 5688551
5851709 and 6066357), and inkjet method (U.S. Pat. No. 6066357).
Optical Optimization
[0094] OLED devices of this invention can employ various well known
optical effects in order to enhance its properties if desired. This
includes optimizing layer thicknesses to yield maximum light transmission,
providing dielectric mirror structures, replacing reflective electrodes
with light-absorbing electrodes, providing anti-glare or anti-reflection
coatings over the display, providing a polarizing medium over the
display, or providing colored, neutral density, or color conversion
filters in functional relationship with the light-emitting areas
of the display. Filters, polarizers, and anti-glare or anti-reflection
coatings can also be provided over a cover or as part of a cover.
[0095] The OLED device can have a microcavity structure. In one
useful example, one of the metallic electrodes is essentially opaque
and reflective; the other one is reflective and semitransparent.
The reflective electrode is preferably selected from Au, Ag, Mg,
Ca, or alloys thereof. Because of the presence of the two reflecting
metal electrodes, the device has a microcavity structure. The strong
optical interference in this structure results in a resonance condition.
Emission near the resonance wavelength is enhanced and emission
away from the resonance wavelength is depressed. The optical path
length can be tuned by selecting the thickness of the organic layers
or by placing a transparent optical spacer between the electrodes.
For example, an OLED device of this invention can have ITO spacer
layer placed between a reflective anode and the organic EL media,
with a semitransparent cathode over the organic EL media.
Encapsulation
[0096] As stated, OLED devices are sensitive to moisture or oxygen,
or both, so they are commonly sealed in an inert atmosphere such
as nitrogen or argon. In sealing an OLED device in an inert environment,
a protective cover can be attached using an organic adhesive, a
metal solder, or a low melting temperature glass. Because polymeric
support materials are typically sensitive to heat, organic adhesives
are preferred. In addition, if the device is flexible, the cover
should also flex. A desiccant can be provided within the sealed
space. Various desiccants can be used including, for example, alkali
and alkaline metals, alumina, bauxite, calcium sulfate, clays, silica
gel, zeolites, alkaline metal oxides, alkaline earth metal oxides,
sulfates, or metal halides and perchlorates. Desiccating films having
a host and a molecularly dispersed desiccant material can also be
used, such films are discussed below. In addition, the desiccant
can be used in combination with barrier layers such as SiOx, Teflon,
and alternating inorganic/polymeric layers as known in the art.
Barrier layers can be provided over the OLED, between the OLED and
a flexible support, or both.
[0097] Some nonlimiting examples of inorganic barrier layer materials
include metal oxides such as silicon oxides and aluminum oxides,
and metal nitrides such as silicon nitride. Metal oxynitrides are
also useful. Suitable examples of inorganic barrier layer materials
include aluminum oxide, silicon dioxide, silicon nitride, silicon
oxynitride, and diamond-like carbon. In some circumstances it is
useful if the inorganic barrier layer material can be electronically
conductive, such as a conductive metal oxide, a metal or metal alloy.
In this case, the conductive inorganic barrier layer can carry current
to one or more device electrodes, serve as the electrode, or provide
a way for discharging static electricity. Metals such as Al, Ag,
Au, Mo, Cr, Pd, or Cu, or alloys containing these metals can be
useful inorganic barrier layers. Multiple layers of metal can be
used to fabricate a conductive inorganic barrier layer. Where unwanted
shorting can occur, conductive barrier layers should not be used,
or they should be patterned, e.g., with a shadow mask, such that
they do not cause shorting. The inorganic barrier layer is typically
provided in a thickness of ten to several hundreds of nanometers.
[0098] Useful techniques of forming layers of inorganic barrier
layer material from a vapor phase include, but are not limited to,
thermal physical vapor deposition, sputter deposition, electron
beam deposition, chemical vapor deposition (CVD), plasma-enhanced
chemical vapor deposition, laser-induced chemical vapor deposition,
and atomic layer deposition (ALD). CVD and ALD are particularly
useful. In some instances, said materials can be deposited from
a solution or another fluidized matrix, e.g., from a super critical
solution of CO.sub.2. Care should be taken to choose a solvent or
fluid matrix does not negatively affect the performance of the device.
Patterning of said materials can be achieved through many ways including,
but not limited to, photolithography, lift-off techniques, laser
ablation, and more preferably, through shadow mask technology.
[0099] The organic barrier layer material can be monomeric or polymeric,
and can be deposited using vapor deposition or from solution. If
cast from solution, it is important that the deposition solution
does not negatively affect the OLED device.
[0100] Conveniently, the organic barrier layer is made of a polymeric
materials such as parylene materials, which can be deposited from
a vapor phase to provide a polymer layer having excellent adhesion
to, and step coverage over, topological features of the OLED devices,
including defects such as particulate defects. The organic barrier
layer is typically formed in a thickness range of from 0.01 to 5
micrometer. However, by their very nature, the organic materials
in the organic barrier layer exhibit more moisture permeability
than a layer formed of an inorganic dielectric material or a layer
formed of a metal. Thus, it is often desirable to encase the organic
barrier layer with an inorganic material.
EMBODIMENTS
[0101] Turning now to FIG. 2A, a cross-sectional view of one embodiment
of this invention is shown. Here, where the desiccant layer 304
is provided as a layer over a first surface of a polymeric support
302 that is to be used as a substrate for an electronic device such
as an OLED. The polymeric support 302 can be flexible. Some nonlimiting
examples of useful polymeric support materials include polyolefins,
for example, polyethylene and polypropylene; polyesters; polyarylates,
polyacrylates, polyethyleneterephthalate; polyethylenenaphthalate;
polystyrene; polyamides; polyimides; polyethersulfonate, and polyorganosilicones,
as well as other transparent polymers and copolymers including other
high T.sub.g polymers.
[0102] As shown in FIG. 2B and FIG. 2C, desiccant layer 304 can
be provided on other surfaces of the support, alone or in combination.
Desiccant layer 304B is provided on a second surface that is opposite
the first surface (i.e., opposite the side where the electronic
device is fabricated), and desiccant layer 304C is provided on the
edges of the polymeric support. Desiccant layers 304 304B, and
304C can be the same or different, but are conveniently the same.
If light is transmitted through the support, the desiccant should
be light transmissive. As shown in FIG. 2D, desiccant can be provided
on all sides of the polymeric support 302. Although not shown, a
barrier layer can be provided over desiccant layers 304 304B, and
304C.
[0103] Various materials can be used for desiccant layer 304 (for
the purposes of discussion, this includes 304B and 304C) including,
for example, alkali and alkaline metals, alumina, bauxite, calcium
sulfate, clays, silica gel, zeolites, alkaline metal oxides, alkaline
earth metal oxides, sulfates, or metal halides and perchlorates.
Preferably, desiccant layer 304 includes a metal complex selected
from formulas I, IV, V, VI, and VII below. Advantageously, desiccant
layer 304 is a light transmissive desiccating film having a host
and a molecularly dispersed desiccant material provided within the
host. A "molecularly dispersed desiccant" is a water reactive
molecule or a water reactive functional group provided within an
inert "host" so that such reactive molecule or group is
diluted relative to a pure film of the desiccant. Molecularly dispersed
desiccants are discussed in more detail below. An advantage of providing
the molecularly dispersed desiccant within a host is that this reduces
the formation of aggregates or particles, especially if the desiccant
is a metal complex or organometallic material. One common byproduct
of the reaction of water with such metal-containing materials is
the formation of metal oxides that are prone to aggregate and form
small particles. Such aggregates and particles can absorb or scatter
light. This is undesirable when light is emitted through the desiccant.
[0104] One class of useful desiccant material includes a Lewis
acid organometallic structure that, when it reacts with water, forms
a carbon-hydrogen bond but does not form an alcohol. Alcohols can
adversely affect the performance of an OLED device if they are permitted
to diffuse into the OLED device. This class of material limits this
concern. In one preferred embodiment, the Lewis acid has the structure
shown in Formula (I) R.sup.1.sub.n-M-R.sup.2.sub.m (I) wherein:
[0105] M is a metal;
[0106] R.sup.1 is an organic substituent wherein at least one carbon
is directly bonded to the metal;
[0107] R.sup.2 is a silyl oxide substituent wherein the oxygen
is directly bonded to the metal, or an amide substituent having
a nitrogen directly bonded to the metal; and
[0108] n=1 2 3 or 4 and m=0 1 2 or 3 and are selected to
fulfill the coordination requirements of M so that Formula I is
neutral in charge.
[0109] Metals selected from Group IIB, IIIA, IIIB, or IVB, or first
row transition metals are useful in present invention. Preferably,
they are Al, Zn, Ti, Mg, or B.
[0110] When more than one R.sup.1 substituent is used, the R.sup.1
substituents can be the same or different from each other. Likewise,
when more than one R.sup.2 substituent is used, the R.sup.2 substituents
can be the same or different from each other.
[0111] Some useful examples of organic substituents that can be
used as R.sup.1 include alkyl, alkenyl, aryl, and heteroaryl compounds
where a saturated or unsaturated carbon is bonded to the metal.
These compounds can be further substituted with alkyl, alkenyl,
aryl, heteroaryl, halogen, cyano, ether, ester, or tertiary amine
groups, or combinations thereof. Some nonlimiting examples of R.sup.1
methyl, ethyl, n-propyl, n-butyl, n-pentyl, n-hexyl, n-heptyl, n-octyl,
i-propyl, t-butyl, cyclohexyl, tetradecyl, octadecyl, benzyl, phenyl,
and pyridyl. In addition, R.sup.1 can be part of an oligomeric or
polymeric system. For example, R.sup.1 can be a part of a polystyrene,
polybutadiene, polymethacrylate, polysiloxane, or polyfluorene structure.
[0112] Silyl oxides with the following Formula II can be selected
as R.sup.2 for the present invention: wherein R.sup.3 through R.sup.6
are organic substituents and p is an integer from 0 to 1000. Some
organic substituents useful for R.sup.3 through R.sup.6 include
alkyl, alkenyl, aryl, and heteroaryl compounds, which can be further
substituted with alkyl, alkenyl, aryl, heteroaryl, halogen, cyano,
ether, ester, or tertiary amine groups, or combinations thereof.
Preferably R.sup.3 through R.sup.6 are alkyl or aryl groups.
[0113] Amides with the following Formula III can be selected as
R.sup.2 for the present invention: wherein R.sup.8 and R.sup.9 are
organic substituents. Some organic substituents useful for R.sup.8
and R.sup.9 include alkyl, alkenyl, aryl, and heteroaryl compounds,
which can be further substituted with alkyl, alkenyl, aryl, heteroaryl,
halogen, cyano, ether, ester, or tertiary amine groups, or combinations
thereof. R.sup.8 and R.sup.9 can be joined to form a ring system.
R.sup.8 or R.sup.9 or both can be part of an oligomeric or polymeric
system. For example, R.sup.8 or R.sup.9 can be a part of a polystyrene,
polybutadiene, polymethacrylate, polysiloxane, or polyfluorene structure.
[0114] Although not shown in Formula I, there can be additional,
non charge-bearing moieties weakly or strongly coordinated to the
metal center. For example, there can be solvent molecules coordinated
to the metal center in addition to R.sup.1.
[0115] Examples of useful desiccant materials for practicing this
invention include, but are not limited to, Al(C.sub.2H.sub.5).sub.3
Al(C.sub.4H.sub.9).sub.3 B(C.sub.4H.sub.9).sub.3 Zn(C.sub.4H.sub.9).sub.2
Al(t-butyl).sub.3 Ti(t-butyl).sub.4 Mg(t-butyl).sub.2 Al(C.sub.4H.sub.9).sub.2(N(C.sub.6H.sub.5).sub.2),
Al(C.sub.4H.sub.9)(N(C.sub.6H.sub.5).sub.2).sub.2 and the structures
shown below:
[0116] Equations 1-3 show how these moisture-absorbing materials
react with water, using various examples of R.sup.1 and R.sup.2
formula I wherein M is aluminum. For example: Al(C.sub.4H.sub.9).sub.3+3H.sub.2O.fwdarw.3C.sub.4H.sub.10+Al(OH).sub.3
(1) Al(C.sub.4H.sub.9)((OSi(CH.sub.3).sub.2).sub.50C.sub.2H.sub.5).sub.2+-
3H.sub.2O.fwdarw.C.sub.4H.sub.10+2Si(OH)(CH.sub.3).sub.2).sub.50C.sub.2H.s-
ub.5+Al(OH).sub.3 (2) Al(C.sub.4H.sub.9).sub.2(N(C.sub.6H.sub.5).sub.2)+3H.sub.2O.fwdarw.2C.sub-
.4H.sub.10+2NH(C.sub.6H.sub.5).sub.2+Al(OH).sub.3 (3).
[0117] As can be seen, R.sup.1 of all compounds reacts with water
to form a carbon-hydrogen bond. In the case of R.sup.2 the reaction
with water forms a silyl oxygen-hydrogen bond or a nitrogen-hydrogen
bond. None of these substituents form harmful alcohol species. The
reaction products are also substantially transparent to visible
light. In some instances, it can be advantageous to avoid the build
up gaseous byproducts. When this is desired, R.sup.1 and R.sup.2
should be selected to have 6 or more carbon atoms so that their
reaction products with water have a low vapor pressure at temperatures
less than 50.degree. C.
[0118] Methods for synthesizing the Lewis acid organometallic desiccant
of this invention can be found in Salt Effects in Organic and Organometallic
Chemistry, VCH Publishers, Inc, New York, 1992.
[0119] Another useful moisture absorbing material of this invention
includes a reactive salt of a negatively charged organometallic
complex that, when it reacts with water, forms a carbon-hydrogen
bond but does not form an alcohol.
[0120] In a preferred embodiment, the reactive salt has the structure
shown in Formula (IV) (A.sup.+b).sub.c[M(R.sup.1).sub.n(R.sup.2).sub.m(X).sub.l].sup.-q
(IV) wherein:
[0121] A is a cation having charge b;
[0122] M is a metal;
[0123] R.sup.1 is an organic substituent wherein at least one carbon
is directly bonded to the metal;
[0124] R.sup.2 is a silyl oxide wherein the oxygen is directly
bonded to the metal, or an amide having a nitrogen directly bonded
to the metal;
[0125] X is an anionic substituent having a pKa <7;
[0126] l=1 or 2;
[0127] n=1 2 3 or 4;
[0128] m=0 1 2 or 3;
[0129] q=is the charge of the anionic organometallic complex and
is 1 or 2; and
[0130] b=q/c.
[0131] Metals selected from Group IIB, IIIA, IIIB, or IVB, or first
row transition metals are useful in present invention, preferably
Al, Zn, Ti, Mg, or B.
[0132] When more than one R.sup.1 substituent is used, the R.sup.1
substituents can be the same or different from each other. Likewise,
when more than one R.sup.2 or X substituent is used, the R.sup.2
or X substituents can be the same or different from each other.
[0133] Some useful examples of R.sup.1 and R.sup.2 are those previously
described in relation to Formula I.
[0134] The substituent X can be an inorganic anionic material such
as fluoride, chloride, bromide, iodide, nitrate, sulfate, tetrafluoroborate,
hexafluorophosphate, or perchlorate. Alternatively, X can be an
organic anionic material including a carboxylate, a sulfonate, or
a phosphonate. When X is organic, it can be part of an oligomeric
or polymeric system. Some examples of organic materials suitable
for X include acetate, formate, succinate, toluenesulfonate, and
polystyrenesulfonate.
[0135] The cation A can be a positively charged metal ion such
as an alkali, alkaline, or alkaline earth metal. Cation A can be
a positively charged metal complex, for example, a complex of an
alkali, alkaline, or alkaline earth metal with a crown ether, an
alkylpolyamine, or the like. Alternatively, cation A can be a positively
charged organic compound. Preferred positively charged organic compounds
include those that contain nitrogen or phosphorous. Some examples
of positively charged organic compounds suitable as cation A include
tetraalkylammonium, alkylpyridinium, and tetraalkylphosphonium compounds.
When cation A is a positively charged metal complex or organic compound,
it can be part of an oligomeric or polymeric system such as a polyvinylpyridinium
system.
[0136] Although not shown in Formula IV, there can be additional,
non charge-bearing moieties weakly or strongly coordinated to the
metal center. For example, there can be solvent molecules coordinated
to the metal center in addition to R.sup.1 and X.
[0137] A few nonlimiting examples of useful desiccant materials
for practicing this invention include K[Al(C.sub.2H.sub.5).sub.3F],
[N(CH.sub.3).sub.4][Al(C.sub.4H.sub.9).sub.3Cl], [N(C.sub.4H.sub.9).sub.4][B(C.sub.5H.sub.5).sub.3F],
[N-t-butylpyridinium][B(C.sub.5H.sub.5).sub.3(OC(.dbd.O)--C.sub.5H.sub.5)-
], Li.sub.2[Zn(C.sub.4H.sub.9).sub.2Cl], and K[(i-Bu).sub.3Al--F--Al(i-Bu).sub.3].
[0138] Equation 4 shows one example of how these moisture-absorbing
materials react with water K[Al(C.sub.2H.sub.5).sub.3F]+3H.sub.2O.fwdarw.3C.sub.2H.sub.5+Al(OH).sub.-
3+KF (4).
[0139] As can be seen, R.sup.1 reacts with water to form a carbon-hydrogen
bond. In the case of R.sup.2 (not shown) the reaction with water
forms a silyl oxygen-hydrogen bond or a nitrogen-hydrogen bond.
None of these substituents form harmful alcohol species. The reaction
products are also substantially transparent to visible light. In
some instances, it can be advantageous to avoid the build up gaseous
byproducts. When this is desired, R.sup.1 and R.sup.2 should be
selected to have 6 or more carbon atoms so that their reaction products
with water have a low vapor pressure at temperatures less than 50.degree.
C.
[0140] The reactive salt can be synthesized by reacting the corresponding
Lewis acid organometallic complex [M(R.sup.1).sub.n(R.sup.2).sub.m].sup.0
with the a salt of X, e.g., (A.sup.+b).sub.cX. Methods for synthesizing
the Lewis acid organometallic desiccant of this invention can be
found in Salt Effects in Organic and Organometallic Chemistry, VCH
Publishers, Inc, New York, 1992.
[0141] Another useful set of desiccant materials includes those
defined by Formula V
[0142] In Formula V, R.sub.10 is one selected from the group including
alkyl group, alkenyl group, aryl group, cycloalkyl group, heterocyclic
group and acyl group having at least one carbon atom, M is a trivalent
metal atom, and n is an integer of two to four.
[0143] Another useful set of desiccant materials includes those
defined by Formula VI
[0144] In Formula VI, each of R.sub.11 R.sub.12 R.sub.13 R.sub.14
and R.sub.15 is one selected from the group including alkyl group,
alkenyl group, aryl group, cycloalkyl group, heterocyclic group
and acyl group having at least one carbon atom, and M is a trivalent
metal atom.
[0145] Another useful set of desiccant materials includes those
defined by Formula VII
[0146] In Formula VI, each of R.sub.11 R.sub.12 R.sub.13 R.sub.14
and R.sub.15 is one selected from the group including alkyl group,
alkenyl group, aryl group, cycloalkyl group, heterocyclic group
and acyl group having at least one carbon atom, and M is a tetravalent
metal atom.
[0147] Although the materials defined in Formulas V-VII form alcohols
when they react with water, they can be useful in this invention
if proper precautions are taken. For example, a barrier layer between
the desiccant and the OLED can be useful to stop diffusion of the
alcohol. The R groups can be selected so that they are large enough
to prevent any significant diffusion. Also, they might be part of
a polymeric backbone that cannot diffuse. In addition, not all electronic
devices are as sensitive to alcohols as an OLED device.
[0148] The desiccating film host can be any number of inert materials
that serves to dilute the desiccant material in order to reduce
aggregation and particle formation that would normally occur for
the pure desiccant material. The host can be organic or inorganic,
but preferably is organic.
[0149] The desiccant can be provided on the polymeric support 302
in numerous ways, depending on the material. They can be deposited
by thermal vapor deposition to form a film of the desiccant. The
film thickness is not limited, but it is believed that a thickness
range of from 0.05 microns to 500 microns is suitable, depending
on the application and the required of water absorption capacity.
In the case of a molecularly dispersed desiccant, the desiccant
and the host can be codeposited by thermal vapor deposition.
[0150] In some cases, the desiccant material(s), including the
option of using a molecularly dispersed desiccant within a host,
can be dissolved or suspended in an organic solvent such as acetates,
ketones, cyclohexanes and provided over the polymeric support, for
example, by spin coating, dip coating, curtain coating, ink jet
deposition, and the like. When particulate desiccant materials are
used, they can be coated along with a polymer binder. In the case
of molecularly dispersed desiccants or particulate desiccants, the
desiccating film host or binder can comprise inert polymeric matrix,
for example poly(butyl methacrylate), which can be cast from an
organic solvent such acetates, ketones, or cyclohexanes or mixtures
thereof. A typical loading of desiccant relative to the polymer
host is 0.05 to 50% by weight. Other polymers that can be used as
a desiccating film host include, but are not limited to, polymethacrylates,
polysiloxanes, poly vinylacetate, polystyrenes, polyacrylates, polybutadiene,
or cycoloefine polymers. When the desiccating film host is a polymer
or oligomer, the desiccant material can be covalently or ionically
bound to the host so long as the desiccant moieties are molecularly
dispersed relative to each other. The desiccant can be part of a
pendant group or incorporated into the backbone of the host polymer.
[0151] The desiccant can also be molecularly dispersed into a polymer
host without the presence of solvent by heating the polymer to reduce
its viscosity, and mixing in the desiccant.
Flexible Support/Barrier/Desiccant/Barrier
[0152] It is particularly advantageous to use the desiccant in
combination with barrier layers. It will be understood that multiple
desiccant layers can be used interspersed between barrier layers.
A barrier layer can be provided between the polymeric support and
the desiccant, over the desiccant, or both. All of these layers
provide a flexible substrate. Turning now to FIG. 3 a first barrier
layer 306 is provided over the polymeric support 302. Desiccant
layer 304 is provided over the first barrier layer 306 and a second
barrier layer 308 is provided over the desiccant layer 304 and first
barrier layer 306. As described previously, the first and second
barrier layers can each be a single layer or a plurality of sublayers,
for example, alternating inorganic/organic sublayers.
[0153] In another embodiment of a flexible substrate, FIG. 4 shows
a first barrier layer 306 provided over the polymeric support 302.
Desiccant layer 304 is patterned over the first barrier layer 306
and a second barrier layer 308 is provided over the desiccant layer
304 and over the first barrier layer 306. Desiccant layer 304 has
a smaller area than the first or second barrier layers, 306 and
308 respectively. Polymeric support 302 first barrier layer 306
desiccant layer 304 and second barrier layer 308 are collectively
referred to as polymeric substrate 310. The advantage of this embodiment
is that there is less chance of delamination of the second barrier
layer that can be caused by high levels of moisture reacting with
the desiccant near the edges of the support. In many device embodiments,
the edges of the flexible support are exposed to ambient. Even if
no delamination occurs, the desiccant layer 304 can be quickly consumed
if the edges are directly exposed to the ambient. In FIG. 4 the
desiccant layer 304 is encased between two barrier layers. Although
the desiccant can rapidly capture moisture that can penetrate through
minor defects in either barrier layer, it will not be consumed quickly
because there is no edge moisture path available from the ambient.
OLED Device Fabrication
[0154] FIGS. 5-7 illustrate various stages of the fabrication of
an OLED device 200A. Turning first to FIG. 5 a top view of an OLED
polymeric substrate 310 is shown. A predetermined seal area 210
is represented by the space between the dotted lines in FIG. 2.
The inner dotted line further represents the sealed region of the
OLED device. Over OLED polymeric substrate 310 are provided a first
electrode 204 a first electrical contact pad 208 and a first electrical
interconnect line 206 that provides an electrical connection between
the first electrode 204 and the first electrical contact pad 208.
The first electrical interconnect line 206 extends through the seal
area. As discussed previously, the first electrode 204 can be the
anode or cathode, and can be any number of well known conductive
materials, as discussed above. The conductive material used for
each of the first electrode 204 the first electrical interconnect
line 206 and the first electrical contact pad 208 can be the same
or different. In addition, each of the first electrode 204 the
first electrical interconnect line 206 and the first electrical
contact pad 208 can contain two or more layers of different conductive
materials.
[0155] A second interconnect line 216 and a second contact pad
218 are provided over the OLED polymeric substrate 310 to provide
a way for making electrical contact to a second electrode that is
formed in a later step. The conductive material used for the second
contact pad 218 and second interconnect line 216 can be the same
or different, and can also be the same or different from the material(s)
used as the first electrical contact pad 208 and first electrical
interconnect line 206.
[0156] The conductive materials for forming the first electrode
204 the first and second interconnect lines, and the first and
second contact pads can be deposited by vacuum methods such as thermal
physical vapor deposition, sputter deposition, plasma-enhanced chemical
vapor deposition, electron-beam assisted vapor deposition, and other
methods known in the art. In addition, so-called "wet"
chemical processes can be used such as electroless and electrolytic
plating. The first electrode 204 the first electrical interconnect
line 206 the first electrical contact pad 208 the second interconnect
line 216 and the second contact pad 218 can be provided in the same
patterning step or different patterning steps. Patterning can be
achieved by deposition through a shadow mask, photolithographic
methods, laser ablation, selective electroless plating, electrochemical
etching, and other well known patterning techniques.
[0157] The second first electrode 204 interconnect lines 206 and
216 and contact pads 208 and 218 are made from aluminum. Although
the first electrode can be transparent, in this arrangement, the
first electrode functions as the anode and is reflective and opaque.
In order to provide a high work function surface for effective hole
injection, a layer of indium-doped tin oxide (ITO) is provided over
the anode (not shown). The second contact pad 218 and second interconnect
line 216 are made from aluminum in this embodiment.
[0158] Turning now to FIG. 6 an insulation layer 244 is provided
in a pattern over the OLED polymeric substrate 310. The insulation
layer 244 extends over a portion of the first electrode 204 and
over at least a portion of the first and second interconnects, 206
and 216. A via 246 is provided over the second interconnect line
216 that is located inside the sealed region. The insulation layer
244 does not extend through the predetermined seal area 210 in this
embodiment.
[0159] The insulation layer 244 can be any number of organic or
inorganic materials provided that the material has low electrical
conductivity and provides effective adhesion with the surfaces over
which it is applied. The insulation layer 244 acts to reduce shorting
that can occur between first and second electrodes, and can provide
planarization. Insulation layer 244 is typically provided in a thickness
of from a few nanometers to a few microns. Many of the same materials
and deposition methods can be used to form the insulation layer
244 as described above for barrier layer materials.
[0160] Some examples of organic materials that are useful for the
insulation layer 244 include polyimides, parylene, and acrylate-based
photoresist materials. Some examples of inorganic materials that
are useful for the insulation layer 244 include metal oxides such
as silicon oxides and aluminum oxides, and metal nitrides such as
silicon nitride and ceramic composites. In addition, the materials
can be provided from a solution, such as a sol-gel.
[0161] As shown in FIG. 7A, the organic EL media layer 212 and
second electrode 214 are then deposited to make OLED device 200A.
To illustrate the layer order, the lower right corner of first electrode
area is pictorially cut away to show the first electrode 204. A
cross-sectional view taken along lines 7B-B is shown in FIG. 7B.
Note that the detailed layer structure of polymeric substrate 310
is not shown. In this arrangement, the second electrode is the cathode
and is semitransparent. It is made from a thin layer of Li (e.g.,
1 nm) in contact with the organic EL media, a thin layer of Al (e.g.,
10 nm) over the lithium, and a thicker layer of ITO (e.g. 100 nm)
over the Al. The cathode makes contact to the second interconnect
line 216 in the via.
[0162] To illustrate the layer order, the lower right corner of
first electrode area is pictorially cut away to show the first electrode
204. The organic EL media layer 212 is described in more detail
below, but it can contain one or several layers of different materials.
The organic EL media layer 212 is provided over the entire first
electrode 204 and over a portion of the insulation layer 244. The
organic EL media layer does not extend into the via 246 or through
the predetermined seal area 210. The second electrode 214 is patterned
over the first electrode and into the via 246 but does not contact
the first electrical interconnect line 206. The light-emitting area
(pixel) is defined by the area of overlap of the first electrode
204 with the second electrode 214 wherein there is organic EL media
sandwiched there between. Because the first electrode is reflective
and opaque, and the second electrode is semitransparent, this light
will emit in a direction away from polymeric substrate 310. This
is referred to as a "top-emitting" OLED. The present invention
can also work with a bottom emitting OLED where light is transmitted
through the substrate so long as the layers of polymeric substrate
310 are transmissive to light.
[0163] The second electrode 214 can be deposited and patterned
using methods previously described.
[0164] Turning now to FIG. 8 a top-emitting, encapsulated OLED
device 200 is shown. In this arrangement, an optional first barrier
layer 271 is provided over the OLED device. As described previously,
the barrier layer can be a single layer or a plurality of sublayers,
for example, alternating inorganic/organic sublayers. An optional
light transmissive desiccating film 262 is provided over first barrier
layer 271. In addition to producing an additional barrier to moisture
penetration, first barrier layer 271 can protect the OLED from solvents
or chemical reactions associated with the light transmissive desiccating
film. An optional second barrier layer 272 has been provided over
light transmissive desiccating film 262. Over the second barrier
layer 272 an optional polymer buffer layer 242 provided.
[0165] When light is taken out through the cover, the polymer buffer
layer is selected to be transparent or nearly transparent, and having
this layer between the cathode and the cover can improve optical
out-coupling. The polymer buffer layer 242 can be any number of
materials including UV or heat cured epoxy resin, acrylates, or
pressure sensitive adhesive. An example of a useful UV-curable epoxy
resin is Optocast 3505 from Electronic Materials Inc. An example
of useful pressure sensitive adhesive is Optically Clear Laminating
Adhesive 8142 from 3M. The polymer buffer layer 242 can also serve
a dual role as the light transmissive desiccating film.
[0166] An optional cover 323 is provided having deposited thereon
a seal material 224 in a pattern corresponding to the predetermined
seal area 210. It is useful in many instances that the cover 323
be flexible. The polymer buffer layer 242 does not have to be deposited
onto the OLED device, but can be provided on the cover 323 along
with seal material 224. Alternatively, the polymer buffer layer
material can also serve as the seal material. The cover 323 with
the patterned seal material 224 is provided over the OLED device
200A in alignment with the predetermined seal area 210. Pressure
is applied between the polymeric support 302 and the cover 323 while
the seal material is cured or fused. The sealing step is preferably
done under inert conditions such as under vacuum or under a dry
nitrogen or argon atmosphere. The cover can be made from glass,
metal, a ceramic, a polymer or a composite. In this arrangement,
it should be light transmissive, but it does not have to be such
if light is transmitted through the first electrode. Preferably,
if a polymer cover is used, it is provided with a moisture barrier
layer(s) adjacent to the interface with the seal material.
[0167] The seal material 224 can be an organic adhesive such as
UV or heat cured epoxy resin, acrylates, or pressure sensitive adhesive.
Alternatively, the seal material can be a glass frit seal material
or a metal solder. However, because such materials typically require
high temperatures for sealing, organic seal materials are preferred.
[0168] The first barrier layer 306 can be conductive (e.g., aluminum),
so long as the second barrier layer 308 is not. This is to prevent
shorting between the first and second electrodes. A bottom-emitting
structure can also be made so long as the polymeric substrate 310
is substantially transparent to light.
Polymeric Support with Patterned Desiccant
[0169] As shown in FIG. 8 the area of desiccant 306 is sized to
accommodate the particular device for which it is intended. However,
in some manufacturing settings it is desirable that the flexible
substrate has more versatility. That is, it is advantageous to use
the same flexible substrate for multiple purposes or differently
sized devices, and avoid the potential problems of ambient moisture
at the edges of the flexible substrate.
[0170] Turning to FIG. 9A, a plan view of a polymeric support 302
over which patterned desiccant layer 305 has been provided in a
discontinuous pattern of island-like regions. The lower left corner
has been cut away to show more clearly the layer structure. As in
FIG. 4 the patterned desiccant layer 305 is provided between first
and second barrier layers 306 and 308. A cross-sectional view is
shown in FIG. 9B taken along lines 9A-A. The assembly is polymeric
substrate 311. The discontinuous desiccant reduces the potential
for delamination of the second barrier layer 308 and avoids the
rapid consumption of desiccant associated with moisture penetration
from the edges. These advantages are maintained regardless of how
the polymeric substrate 311 is cut.
[0171] Patterning of the desiccant in island-like regions can be
done by shadow masking if the desiccant is vapor deposited. For
solution applied desiccant, patterning methods include, but are
not limited to, contact printing, screen printing, ink jet, and
photolithography. Thermal transfer from a donor element can be used.
Patterned surface modification of the substrate to affect wetting
and/or adhesion properties of the desiccant to the substrate can
be used. Physical surface features in the substrate, e.g., patterned
wells, can be used to produce sites where the desiccant will deposit.
[0172] Turning now to FIG. 10 an OLED display is shown using the
substrate from FIG. 9B. It is fabricated in a manner entirely analogous
to that shown in FIG. 8 except that polymeric substrate 310 has
been replaced with polymeric substrate 311. Patterned desiccant
layer 305 provides an excellent moisture trap for water vapor that
permeates the flexible support 302 and defects in first barrier
layer 306. Light transmissive desiccating film 262 provides an excellent
moisture trap for water vapor that can be trapped in the sealed
area or that permeates the seal material 224.
[0173] Turning to FIG. 11 a cross-sectional view of another embodiment
of this invention. Polymeric substrate 312 is analogous to polymeric
substrate 311 from FIG. 9B, except that an additional layer of patterned
desiccant layer 315 and third barrier layer 318 are provided. The
materials used for these features can be the same as or different
from the materials used for patterned desiccant layer 305 and second
barrier layer 308. The location of patterned desiccant layer 315
is staggered relative to the patterned desiccant layer 305 in order
to provide additional protection to the electronic device that is
formed over polymeric substrate 312.
[0174] The invention has been described in detail with particular
reference to certain preferred embodiments thereof, but it will
be understood that variations and modifications can be effected
within the spirit and scope of the invention.
PARTS LIST
[0175] 101 substrate [0176] 103 anode [0177] 105 hole-injecting
layer [0178] 107 hole-transporting layer [0179] 109 light-emitting
layer [0180] 111 electron-transporting layer [0181] 113 cathode
[0182] 150 voltage/current source [0183] 160 electrical conductors
[0184] 200 encapsulated OLED device [0185] 200A OLED device [0186]
204 first electrode [0187] 206 first electrical interconnect line
[0188] 208 first electrical contact pad [0189] 210 seal area [0190]
212 organic EL media layer [0191] 214 second electrode [0192] 216
second interconnect line [0193] 218 second contact pad [0194] 224
seal material [0195] 242 polymer buffer layer [0196] 244 insulation
layer [0197] 246 via [0198] 262 light transmissive desiccating film
[0199] 271 first barrier layer [0200] 272 second barrier layer [0201]
302 polymeric support [0202] 304 desiccant layer [0203] 304B desiccant
layer [0204] 304C desiccant layer [0205] 305 patterned desiccant
layer [0206] 306 first barrier layer [0207] 308 second barrier layer
[0208] 310 polymeric substrate [0209] 311 polymeric substrate [0210]
312 polymeric substrate [0211] 315 patterned desiccant layer [0212]
318 third barrier layer [0213] 323 cover |