U.S. patent application number 13/545297 was filed with the patent office on 2012-11-01 for moisture barrier coatings for organic light emitting diode devices.
This patent application is currently assigned to 3M Innovative Properties Company. Invention is credited to Moses M. David, Fred B. McCormick, Mark A. Roehrig.
Application Number | 20120273976 13/545297 |
Document ID | / |
Family ID | 39493283 |
Filed Date | 2012-11-01 |
United States Patent
Application |
20120273976 |
Kind Code |
A1 |
David; Moses M. ; et
al. |
November 1, 2012 |
MOISTURE BARRIER COATINGS FOR ORGANIC LIGHT EMITTING DIODE
DEVICES
Abstract
A process for fabricating an amorphous diamond-like film layer
for protection of a moisture or oxygen sensitive electronic device
is described. The process includes forming a plasma from silicone
oil, depositing an amorphous diamond-like film layer from the
plasma, and combining the amorphous diamond-like film layer with a
moisture or oxygen sensitive electronic device to form a protected
electronic device. Articles including the amorphous diamond-like
film layer on an organic electronic device are also disclosed.
Inventors: |
David; Moses M.; (Woodbury,
MN) ; McCormick; Fred B.; (Maplewood, MN) ;
Roehrig; Mark A.; (Stillwater, MN) |
Assignee: |
3M Innovative Properties
Company
|
Family ID: |
39493283 |
Appl. No.: |
13/545297 |
Filed: |
July 10, 2012 |
Related U.S. Patent Documents
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Application
Number |
Filing Date |
Patent Number |
|
|
11677327 |
Feb 21, 2007 |
8241713 |
|
|
13545297 |
|
|
|
|
Current U.S.
Class: |
257/790 ;
118/723E; 257/40; 257/E51.002 |
Current CPC
Class: |
H01L 51/524 20130101;
H01L 51/5237 20130101; H01L 2224/48472 20130101; H01L 2251/5338
20130101; H01L 2924/00 20130101; H01L 2924/12044 20130101; H01L
2924/12044 20130101; H01L 51/5253 20130101 |
Class at
Publication: |
257/790 ;
118/723.E; 257/40; 257/E51.002 |
International
Class: |
H01L 23/29 20060101
H01L023/29; C23C 16/505 20060101 C23C016/505 |
Claims
1. An article comprising; an organic electronic device; an
amorphous diamond-like film layer adjacent to the organic
electronic device, wherein the amorphous diamond-like film layer
comprises a siloxane moiety and having a thickness of greater than
1000 Angstroms.
2. An article according to claim 1, wherein the amorphous
diamond-like film encapsulates the organic electronic device.
3. An article according to claim 1, wherein the amorphous
diamond-like film layer has a thickness in a range from 1000 to
10000 nanometers.
4. An article according to claim 1, wherein the organic electronic
device comprises an organic light emitting diode, a photovoltaic
article, or a thin-film transistor.
5. An article according to claim 1, further comprising a polymer or
metallic layer disposed on the amorphous diamond-like film layer or
between the amorphous diamond-like film layer and the organic
electronic device.
6. An article according to claim 1, further comprising a polymer or
metallic layer disposed on the amorphous diamond-like film layer,
and a second polymer or metallic layer disposed between the organic
electronic device and the amorphous diamond-like film layer.
7. An article according to claim 1, wherein the organic electronic
device is a component of a display, signage, or lighting element of
the article.
8. An article according to claim 1, wherein the organic electronic
device is a component of a cell phone, MP3 player, PDA, television,
DVD player, luminare, sign, billboard, or LCD.
9. A plasma deposition apparatus comprising; a vacuum chamber
comprising a powered electrode and an counter electrode; a radio
frequency power source in electrical connection with the powered
electrode through an impedance matching network; and a silicone oil
source in fluid communication with the vacuum chamber.
10. An apparatus according to claim 9, further comprising a silane
source in fluid communication with the vacuum chamber and a process
gas source in fluid communication with the vacuum chamber.
11. An apparatus according to claim 10, wherein the silicone oil
source comprises silicone oil disposed on a carbon cloth and a
power source in electrical connection with the carbon cloth.
12. An apparatus according to claim 9, wherein the silicone oil
source is disposed within the vacuum chamber.
13. An apparatus according to claim 12, wherein the silicone oil
source is shielded with a Faraday cage.
14. An organic electronic device fabrication system comprising the
plasma deposition apparatus according to claim 9.
Description
CROSS REFERENCE TO RELATED APPLICATIONS
[0001] This application is a divisional of U.S. application Ser.
No. 11/677,327, filed Feb. 21, 2007, now allowed, the disclosure of
which is incorporated by reference in its entirety herein.
FIELD
[0002] The present invention relates to barrier coatings for
protection of moisture and/or oxygen sensitive electronic devices
such as an organic light emitting diode device.
BACKGROUND
[0003] Organic light emitting diode (OLED) devices can suffer
reduced output or premature failure when exposed to water vapor
and/or oxygen. Metals and glasses have been used to encapsulate and
prolong the life of OLED devices, but metals typically lack
transparency and glass lacks flexibility. Efforts are underway to
find alternative encapsulation materials for OLEDs and other
electronic devices. Examples of various types of vacuum processes
are described in the patent and technical literature for the
formation of barrier coatings. These methods span the range of
e-beam evaporation, thermal evaporation, electron-cyclotron
resonance plasma-enhanced chemical vapor deposition (PECVD),
magnetically enhanced PECVD, reactive sputtering, and others.
[0004] A need exists for improved encapsulation of organic
electronic devices, such as OLEDs, organic photovoltaic devices
(OPVs), and organic transistors, and inorganic electronic devices,
such as thin film transistors (including those made using zinc
oxide (ZnO), amorphous silicon (a-Si), and low temperature
polysilicon (LTPSi)).
BRIEF SUMMARY
[0005] This disclosure describes an amorphous diamond-like film or
coating formed via ion enhanced plasma chemical vapor deposition
utilizing silicone oil and an optional silane source to form the
plasma. The amorphous diamond-like film forms a moisture or oxygen
barrier on a moisture or oxygen sensitive article.
[0006] In one embodiment, a process for fabricating an amorphous
diamond-like film layer for protection of a moisture or oxygen
sensitive electronic device is described. The process includes
forming a plasma from silicone oil, depositing an amorphous
diamond-like film layer from the plasma, and combining the
amorphous diamond-like film layer with a moisture or oxygen
sensitive electronic device to form a protected electronic
device.
[0007] In another embodiment, an article includes an organic
electronic device and an amorphous diamond-like film layer adjacent
to the organic electronic device. The amorphous diamond-like film
layer includes siloxane moiety and has a thickness of greater than
1000 Angstroms.
[0008] In a further embodiment, a plasma deposition apparatus
includes a vacuum chamber having a powered electrode and a counter
electrode, a radio frequency power source in electrical connection
with the powered electrode through an impedance matching network,
and a silicone oil source in fluid communication with the vacuum
chamber.
[0009] In another embodiment, a process for fabricating an
amorphous diamond-like film layer on a substrate includes forming a
radio frequency plasma from silicone oil, and depositing an
amorphous diamond-like film layer from the plasma onto a
substrate.
BRIEF DESCRIPTION OF THE DRAWINGS
[0010] The disclosure may be more completely understood in the
following detailed description of various embodiments of the
invention in connection with the accompanying drawings, in
which:
[0011] FIG. 1 is a schematic view of a barrier assembly;
[0012] FIG. 2 is a schematic view of a barrier assembly having
multiple layers made from alternating amorphous diamond-like layers
and polymer layers;
[0013] FIG. 3 is a schematic view of a laminated barrier assembly
having multiple layers made from polymers;
[0014] FIGS. 4A-4C are diagrams of first embodiments of OLED
devices encapsulated with amorphous diamond-like coatings;
[0015] FIGS. 5A-5C are diagrams of second embodiments of OLED
devices encapsulated with amorphous diamond-like coatings;
[0016] FIGS. 6A-6C are diagrams of third embodiments of OLED
devices encapsulated with amorphous diamond-like coatings;
[0017] FIG. 7 is a diagram of a plasma deposition system for
applying amorphous diamond-like coatings; and
[0018] FIG. 8 is a schematic diagram of a sample mounting for
amorphous diamond-like coating deposition.
DETAILED DESCRIPTION
[0019] An ion enhanced plasma chemical vapor deposition process
utilizing a plasma formed from silicone oil and an optional silane
source can be used that leads to flexible amorphous diamond-like
film layers or coatings having superior moisture vapor barrier
performance. Excellent barrier performance can be achieved from
these barrier films formed on a substrate in intimate contact with
an electrode utilizing radio frequency (RF) plasma conditions. The
moisture vapor transmission rates (MVTRs) of these barrier coatings
deposited using this process were less than 0.015 g/m.sup.2 day
measured using ASTM F-1219 at 50 degrees centigrade. Barrier
coatings at least 1000 Angstroms (100 nm) thick deposited under
high self-bias and low pressures (approximately 5-20 mTorr) result
in superior low moisture vapor transmission rates.
[0020] The amorphous diamond-like film layers or coatings are
deposited on an electrode powered using an RF source operating at
least 0.1 W/cm.sup.2 of forward power. The vacuum chamber is
configured such that these operating conditions result in a very
high (>500 V) negative potential on the electrode. As a result
of ion bombardment from having high substrate bias (e.g., ion
enhanced), the coating formed has very low free volume. The
electrode can be water cooled, as desired. In many embodiments, a
siloxane source such as vaporized silicone oil is introduced in
quantities such that the resulting plasma formed coatings are
flexible. These coatings have high optical transmission. Any
additional useful process gases, such as oxygen, nitrogen and/or
ammonia for example, can be used with the siloxane and optional
silane to assist in maintaining the plasma and to modify the
properties of the amorphous diamond-like film layers or coatings.
Combinations of additional process gases can be employed, as
desired.
[0021] The amorphous diamond-like film layers or coatings may be
used for various types of electronic device (e.g., organic
electronic device) applications, for example, organic
electroluminescent thin films, photovoltaic devices, thin-film
transistors, and other such devices. Electronic device articles
having the amorphous diamond-like film layers or coatings may be
used in the fabrication of flexible electronic devices such as
OLEDs used as a component in displays, solid state lighting or
signage; organic transistors; organic (OPVs), silicon and ternary
photovoltaics; liquid crystal displays (LCD), and other lighting
devices. A partial listing of useful articles of manufacture that
can utilize the protected electronic device articles described
herein includes cell phones, MP3 players, PDAs, televisions, DVD
players, luminares, POP signs, billboards, LCDs, and the like.
[0022] These amorphous diamond-like film layers or coatings can be
used to encapsulate the electronic devices directly, and the
amorphous diamond-like film layers or film can be used as a cover
for encapsulating the electronic devices. Due to the superior
barrier performance of the amorphous diamond-like film layers or
coatings produced using the described ion enhanced plasma chemical
vapor deposition conditions, such devices can be produced at a
lower cost with better performance.
[0023] The term "polymer" refers to homopolymers and copolymers, as
well as homopolymers or copolymers that may be formed in a miscible
blend, e.g., by coextrusion or by reaction, including, e.g.,
transesterification. The term "polymer" also includes plasma
deposited polymers. The term "copolymer" includes both random and
block copolymers. The term "curable polymer" includes both
crosslinked and uncrosslinked polymers. The term "crosslinked"
polymer refers to a polymer whose polymer chains are joined
together by covalent chemical bonds, usually via crosslinking
molecules or groups, to form a network polymer. A crosslinked
polymer is generally characterized by insolubility, but may be
swellable in the presence of an appropriate solvent.
[0024] The term a "visible light-transmissive" support, layer,
assembly or device means that the support, layer, assembly or
device has an average transmission over the visible portion of the
spectrum, Tvis, of at least about 20%, measured along the normal
axis.
[0025] The term "amorphous diamond-like film" refers to
substantially (i.e., greater than 95%) or completely amorphous
glass including silicone, and optionally including one or more
additional components selected from the group including carbon,
hydrogen, nitrogen, oxygen, fluorine, sulfur, titanium, and copper.
Other elements may be present in certain embodiments. The amorphous
diamond-like films may contain clustering of atoms to give it a
short-range order but are essentially void of medium and long range
ordering that lead to micro or macro crystallinity which can
adversely scatter radiation having wavelengths of from 180
nanometers (nm) to 800 nm.
[0026] As used herein, "comprising" and "including" are used in an
open-ended fashion, and thus should be interpreted to mean
"including, but not limited to . . . ".
[0027] Unless otherwise indicated, all numbers expressing feature
sizes, amounts, and physical properties used in the specification
and claims are to be understood as being modified in all instances
by the term "about." Accordingly, unless indicated to the contrary,
the numerical parameters set forth in the foregoing specification
and attached claims are approximations that can vary depending upon
the desired properties sought to be obtained by those skilled in
the art utilizing the teachings disclosed herein.
[0028] The recitation of numerical ranges by endpoints includes all
numbers subsumed within that range (e.g. 1 to 5 includes 1, 1.5, 2,
2.75, 3, 3.80, 4, and 5) and any range within that range.
[0029] As used in this specification and the appended claims, the
singular forms "a", "an", and "the" encompass embodiments having
plural referents, unless the content clearly dictates otherwise. As
used in this specification and the appended claims, the term "or"
is generally employed in its sense including "and/or" unless the
content clearly dictates otherwise.
[0030] Silicone, silicone oil, or siloxanes are used
interchangeably and refer to oligomeric and higher molecular weight
molecules having a structural unit R.sub.2SiO in which R is
independently selected from hydrogen, (C.sub.1-C.sub.8)alkyl,
(C.sub.5-C.sub.18)aryl, (C.sub.6-C.sub.26)arylalkyl, or
(C.sub.6-C.sub.26)alkylaryl. These can also be referred to as
polyorganosiloxanes and include chains of alternating silicon and
oxygen atoms (--O--Si--O--Si--O--) with the free valences of the
silicon atoms joined usually to R groups, but may also be joined
(crosslinked) to oxygen atoms and silicon atoms of a second chain,
forming an extended network (high MW).
[0031] FIG. 1 is a schematic view of a barrier assembly having an
amorphous diamond-like film, layer, or coating 100 to reduce or
prevent substantial transfer of moisture and/or oxygen, or other
contaminants, to an underlying substrate or electronic device 102.
The assembly can represent any type of substrate or electronic
device requiring or benefiting from protection from moisture and/or
oxygen, such as the moisture and/or oxygen sensitive examples
provided above. For certain types of electronic or display devices,
for example, oxygen and/or moisture can severely degrade their
performance or lifetime, and thus the coating 100 can provide
significant advantages in device performance.
[0032] In some embodiments, the amorphous diamond-like film, layer,
or coating 100 is deposited onto one or both sides of a flexible
film 102. The flexible film 102 can be formed of any useful
material such as polymeric and/or metallic materials. In some of
these embodiments, an electronic device is formed or disposed on or
adjacent to either, the amorphous diamond-like film 100, or onto
the flexible film 102.
[0033] While the electronic device or flexible film 102 is
illustrated as a planar element, it is understood that the
electronic device or flexible film 102 can have any shape. In many
embodiments, the electronic device or flexible film 102 includes a
non-planar or structured surface having a surface topography. This
disclosure allows a generally uniform layer of barrier coating to
be disposed on the structured surface on both horizontal and
vertical surfaces that form the surface topography. The amorphous
diamond-like film 100 can be any useful thickness. In many
embodiments, the an amorphous diamond-like film 100 can have a
thickness of greater than 500 Angstroms, or greater than 1,000
Angstroms. In many embodiments, the an amorphous diamond-like film
100 can have a thickness in a range from 1,000 to 50,000 Angstroms,
or from 1,000 to 25,000 Angstroms, or from 1,000 to 10,000
Angstroms.
[0034] In some embodiments, the an amorphous diamond-like film 100
includes one or more amorphous diamond-like film layers or an
amorphous diamond-like film layer formed by changing or pulsing the
process gases that form the plasma for depositing the amorphous
diamond-like film layer 100. For example, a base layer of a first
amorphous diamond-like film can be formed an then a second layer of
a second amorphous diamond-like film can be formed on the first
layer, where the first layer has a different composition than the
second layer. In some embodiments, a first amorphous diamond-like
film layer is formed from a silicone oil plasma and then a second
amorphous diamond-like film layer is formed from a silicone oil and
silane plasma. In other embodiments, two or more amorphous
diamond-like films layers of alternating composition are formed to
create the amorphous diamond-like film 100.
[0035] One aspect of this disclosure is that the substrates for
deposition of the amorphous diamond-like film from the plasma are
subject to intense ion bombardment during the deposition process.
As a result of this ion bombardment, the resulting film is
densified and its density can be controlled by the degree of ion
bombardment. Furthermore, the ion bombardment leads to better
coverage of the depositing amorphous diamond-like film over surface
features or the topography of the substrate. In many embodiments,
it is important to conformally deposit amorphous diamond-like film
over the surface topography, particularly over steps and defect
sites on the substrate. In the presence of the ion bombardment, the
surface mobility of the depositing species is improved, leading to
improved step coverage and coverage over any defects which might be
present on the surface of the substrate.
[0036] Ion bombardment is achieved in this disclosure by means of
an asymmetric electrode system with the articles for deposition
placed on the powered electrode (as described below). The
asymmetric attribute is obtained by making the powered electrode of
smaller area when compared to the grounded chamber wall. The
negative DC self-bias voltages achieved at the operating pressure
of 1-100 mTorr are in the range of 100-1500 volts. The presence of
this voltage causes the positive ions in the plasma to be
accelerated towards the substrate surface, leading to intense ion
bombardment of the substrate surface.
[0037] A surprising attribute of this disclosure is that the
electronic devices (e.g., organic light emitting devices) are not
damaged by the presence of a large negative DC self-bias voltage of
several hundred volts which leads to intense ion bombardment. In
the case of fabrication of other microelectronic devices,
particular care is taken to prevent the devices from getting
damaged by the ion bombardment. Not only is it surprising that the
organic electronic devices are not damaged by the ion bombardment
but this ion-bombardment was found to be provide improved moisture
barrier performance of the amorphous diamond-like film.
[0038] FIG. 2 is a schematic view of a laminated barrier assembly
110 having multiple layers made from alternating amorphous
diamond-like film layers 116, 120 and polymer layers 114, 118
protecting an underlying substrate or electronic device 112. FIG. 3
is a schematic view of a laminated barrier assembly 130 having
multiple layers made from alternating different types of polymer
layers, for example alternating polymer layers 136, 140 and polymer
layers 134, 138 protecting an underlying substrate or electronic
device 132. In this example, layers 136 and 140 are composed of a
first type of polymer, and layers 134 and 138 are composed of a
second type of polymer different from the first type of polymer.
Any highly crosslinked polymers may be used for the layers,
examples of which are provided below. An amorphous diamond-like
film can be disposed on the assembly 130. Each group of different
polymers (e.g., 134 and 136), or combinations of polymers including
amorphous diamond-like film (e.g., 114 and 116), are referred to as
a dyad, and the assembly can include any number of dyads. It can
also include various types of optional layers between the dyads,
examples of which are provided below.
[0039] Assemblies 110 and 130 can include any number of alternating
or other layers. Adding more layers may improve the lifetime of the
assemblies by increasing their imperviousness to oxygen, moisture,
or other contaminants. Use of more or multiple layers may also help
cover or encapsulate defects within the layers. The number of
layers can be selected, based upon particular implementations or
other factors.
[0040] Substrates having moisture or oxygen barrier coatings can
include any type of substrate material for use in making an
electronic device. The substrate can be rigid, for example by using
glass or other materials. The substrate can also be curved or
flexible, for example by using plastics, metals, or other
materials. The substrate can be of any desired shape, and it can be
transparent or opaque. In many embodiments, electronic device
substrates are flexible plastic materials including thermoplastic
films such as polyesters (e.g., PET), polyacrylates (e.g.,
polymethyl methacrylate), polycarbonates, polypropylenes, high or
low density polyethylenes, polyethylene naphthalates, polysulfones,
polyether sulfones, polyurethanes, polyamides, polyvinyl butyral,
polyvinyl chloride, polyvinylidene difluoride and polyethylene
sulfide, and thermoset films such as cellulose derivatives,
polyimide, polyimide benzoxazole, and poly benzoxazole.
[0041] Other suitable materials for the substrate include
chlorotrifluoroethylene-vinylidene fluoride copolymer (CTFE/VDF),
ethylene-chlorotrifluoroethylene copolymer (ECTFE),
ethylene-tetrafluoroethylene copolymer (ETFE), fluorinated
ethylene-propylene copolymer (FEP), polychlorotrifluoroethylene
(PCTFE), perfluoroalkyl-tetrafluoroethylene copolymer (PFA),
polytetrafluoroethylene (PTFE), polyvinylidene fluoride (PVDF),
polyvinyl fluoride (PVF), tetrafluoroethylene-hexafluoropropylene
copolymer (TFE/HFP),
tetrafluoroethylene-hexafluoropropylene-vinylidene fluoride
terpolymer (THV), polychlorotrifluoroethylene (PCTFE),
hexafluoropropylene-vinylidene fluoride copolymer (HFP/VDF),
tetrafluoroethylene-propylene copolymer (TFE/P), and
tetrafluoroethylene-perfluoromethylether copolymer (TFE/PFMe).
[0042] Other suitable materials for the substrate include metals
and metal alloys. Examples of metals for the substrate include
copper, silver, nickel, chromium, tin, gold, indium, iron, zinc,
and aluminum. Examples of metal alloys for the substrate include
alloys of these listed metals. Another particularly suitable
material for the substrate is steel. The metals and metal alloys
can be implemented with foils for flexible devices, for example.
The metal or metal alloy substrates can include additional
materials such as a metal coating on a polymer film.
[0043] Alternative substrates include materials having a high glass
transition temperature (Tg) barrier, preferably being
heat-stabilized, using heat setting, annealing under tension, or
other techniques that will discourage shrinkage up to at least the
heat stabilization temperature when the support is not constrained.
If the support has not been heat stabilized, then it preferably has
a Tg greater than that of polymethyl methacrylate (PMMA, Tg=105
degrees centigrade). More preferably the support has a Tg of at
least about 110 degrees centigrade, or at least about 120 degrees
centigrade, or at least about 128 degrees centigrade. In addition
to heat-stabilized polyethylene terephthalate (HSPET), other
preferred supports include other heat-stabilized high Tg
polyesters, PMMA, styrene/acrylonitrile (SAN, Tg=110 degrees
centigrade), styrene/maleic anhydride (SMA, Tg=115 degrees
centigrade), polyethylene naphthalate (PEN, Tg=about 120 degrees
centigrade), polyoxymethylene (POM, Tg=about 125 degrees
centigrade), polyvinylnaphthalene (PVN, Tg=about 135 degrees
centigrade), polyetheretherketone (PEEK, Tg=about 145 degrees
centigrade), polyaryletherketone (PAEK, Tg=145 degrees centigrade),
high Tg fluoropolymers (e.g., DYNEON.TM. HTE terpolymer of
hexafluoropropylene, tetrafluoroethylene, and ethylene, Tg=about
149 degrees centigrade), polycarbonate (PC, Tg=about 150 degrees
centigrade), poly alpha-methyl styrene (Tg=about 175 degrees
centigrade), polyarylate (PAR, Tg=325 degrees centigrade) fluorene
polyester (FPE, Tg=325 degrees centigrade), polynorborene (PCO,
Tg=330 degrees centigrade), polysulfone (PSul, Tg=about 195 degrees
centigrade), polyphenylene oxide (PPO, Tg=about 200 degrees
centigrade), polyetherimide (PEI, Tg=about 218 degrees centigrade),
polyarylsulfone (PAS, Tg=220 degrees centigrade), poly ether
sulfone (PES, Tg=about 225 degrees centigrade), polyamideimide
(PAI, Tg=about 275 degrees centigrade), polyimide (Tg=about 300
degrees centigrade) and polyphthalamide (heat deflection temp of
120 degrees centigrade). For applications where material costs are
important, supports made of HSPET and PEN are especially preferred.
For applications where barrier performance is paramount, supports
made of more expensive materials may be employed. In many
embodiments, the electronic device substrate has a thickness of
about 0.01 millimeters (mm) to about 1 mm, or about 0.05 mm to
about 0.25 mm.
[0044] Amorphous diamond-like film is an amorphous carbon system
including a substantial quantity of carbon, silicon or silicone and
oxygen that exhibits diamond-like properties. In these films, on a
hydrogen-free basis, there is at least 5% carbon, a substantial
amount of silicon (typically at least 25%) and no more than 50%
oxygen. The unique combination of a fairly high amount of silicon
with a significant amount of oxygen and a substantial amount of
carbon makes these films highly transparent and flexible (unlike
glass).
[0045] Amorphous diamond-like thin films may have a variety of
light transmissive properties. Depending upon the composition, the
amorphous diamond-like films may have increased transmissive
properties at various frequencies. However, in specific
implementations the amorphous diamond-like film (when approximately
one micrometer thick) is at least 70% transmissive to radiation at
substantially all wavelengths from about 250 nm to about 800 nm and
more preferably from about 400 nm to about 800 nm. The extinction
coefficient of amorphous diamond-like film is as follows: 70%
transmission for a one micrometer thick film corresponds to an
extinction coefficient (k) of less than 0.02 in the visible
wavelength range between 400 nm and 800 nm.
[0046] Diamond-like films, having significantly different
properties from the amorphous diamond-like film of the present
disclosure due to the arrangement and intermolecular bonds of
carbon atoms in the specific material, have previously been
described. The type and amount of intermolecular bonds are
determined by infrared (IR) and nuclear magnetic resonance (NMR)
spectra. Carbon deposits contain substantially two types of
carbon-carbon bonds: trigonal graphite bonds (sp2) and tetrahedral
diamond bonds (sp3). Diamond is composed of virtually all
tetrahedral bonds, while diamond-like films are composed of
approximately 50% to 90% tetrahedral bonds, and graphite is
composed of virtually all trigonal bonds.
[0047] The crystallinity and the nature of the bonding of the
carbon system determine the physical and chemical properties of the
deposit. Diamond is crystalline whereas the diamond-like film is a
non-crystalline glassy amorphous material, as determined by x-ray
diffraction. Diamond is essentially pure carbon, whereas
diamond-like film contains a substantial amount of non-carbon
components, including silicon.
[0048] Diamond has the highest packing density, or gram atom
density (GAD) of any material at ambient pressure. Its GAD is 0.28
gram atoms/cc. Amorphous diamond-like films have a GAD ranging from
about 0.20 to 0.28 gram atoms/cc. In contrast, graphite has a GAD
of 0.18 gram atoms/cc. The high packing density of diamond-like
film affords excellent resistance to diffusion of liquid or gaseous
materials. Gram atom density is calculated from measurements of the
weight and thickness of a material. The term "gram atom" refers to
the atomic weight of a material expressed in grams.
[0049] Amorphous diamond-like film is diamond-like because, in
addition to the foregoing physical properties that are similar to
diamond, it has many of the desirable performance properties of
diamond such as extreme hardness (typically 1000 to 2000
kg/mm.sup.2), high electrical resistivity (often 109 to 1013
ohm-cm), a low coefficient of friction (for example, 0.1), and
optical transparency over a wide range of wavelengths (a typical
extinction coefficient of about between 0.01 and 0.02 in the 400 nm
to 800 nm range).
[0050] Diamond films also have some properties which, in many
applications, make them less beneficial than amorphous diamond-like
films. Diamond films usually have grain structures, as determined
by electron microscopy. The grain boundaries are a path for
chemical attack and degradation of the substrates, and also cause
scattering of actinic radiation. Amorphous diamond-like film does
not have a grain structure, as determined by electron microscopy,
and is thus well suited to applications wherein actinic radiation
will pass through the film. The polycrystalline structure of
diamond films causes light scattering from the grain
boundaries.
[0051] In creating an amorphous diamond-like film, various
additional components can be incorporated into the basic SiOCH
composition. These additional components can be used to alter and
enhance the properties that the amorphous diamond-like film imparts
to the electronic device substrate. For example, it may be
desirable to further enhance the barrier and surface
properties.
[0052] The additional components may include one or more of
hydrogen (if not already incorporated), nitrogen, fluorine, sulfur,
titanium, or copper. Other additional components may also be of
benefit. The addition of hydrogen promotes the formation of
tetrahedral bonds. The addition of fluorine is particularly useful
in enhancing barrier and surface properties of the amorphous
diamond-like film, including the ability to be dispersed in an
incompatible matrix. The addition of nitrogen may be used to
enhance resistance to oxidation and to increase electrical
conductivity. The addition of sulfur can enhance adhesion. The
addition of titanium tends to enhance adhesion as well as diffusion
and barrier properties.
[0053] These amorphous diamond-like materials may be considered as
a form of plasma polymers, which can be deposited on the assembly
using, for example, a vapor source. The term "plasma polymer" is
applied to a class of materials synthesized from a plasma by using
precursor monomers and/or oligomers in the gas phase at low
temperatures. Precursor molecules are broken down by energetic
electrons present in the plasma to form free radical species. These
free radical species react at the substrate surface and lead to
polymeric thin film growth. Due to the non-specificity of the
reaction processes in both the gas phase and the substrate, the
resulting polymer films are highly cross-linked and amorphous in
nature.
[0054] Typically, these plasma polymers have an organic nature to
them due to the presence of hydrocarbon and carbonaceous functional
groups such as CH.sub.3, CH.sub.2, CH, Si--C, Si--CH.sub.3, Al--C,
Si--O--CH.sub.3, Si--O--Si, etc. The presence of these functional
groups may be ascertained by analytical techniques such as IR,
nuclear magnetic resonance (NMR) and secondary ion mass (SIMS)
spectroscopies. The carbon content in the film may be quantified by
electron spectroscopy for chemical analysis (ESCA).
[0055] Not all plasma deposition processes lead to plasma polymers.
Inorganic thin films are frequently deposited by plasma enhanced
chemical vapor deposition at elevated substrate temperatures to
produce thin inorganic films such as amorphous silicon, silicon
oxide, silicon nitride, aluminum nitride, etc. Lower temperature
processes may be used with inorganic precursors such as silane
(SiH.sub.4) and ammonia (NH.sub.3). In some cases, the organic
component present in the precursors is removed in the plasma by
feeding the precursor mixture with an excess flow of oxygen.
Silicon rich films are produced from tetramethyldisiloxane
(TMDSO)-oxygen mixtures where the oxygen flow rate is ten times
that of the TMDSO flow. Films produced in these cases have an
oxygen to silicon ratio of about 2, which is near that of silicon
dioxide.
[0056] The amorphous diamond-like film layer of this disclosure is
differentiated from other inorganic plasma deposited thin films by
the oxygen to silicon ratio in the films and by the amount of
carbon and siloxane character present in the films. When a surface
analytic technique such as ESCA is used for the analysis, the
elemental atomic composition of the film may be obtained on a
hydrogen-free basis. Amorphous diamond-like film films of the
present disclosure are substantially sub-stoichiometric in their
inorganic component and substantially carbon-rich, depicting their
organic nature. In films containing silicon for example, the oxygen
to silicon ratio is preferably below 1.8 (silicon dioxide has a
ratio of 2.0), or below 1.5 as in the case of amorphous
diamond-like film, and the carbon content is in a range from about
5 to 50%. Furthermore, the organic siloxane structure (i.e.,
siloxane moiety) of the films may be detected by IR spectra of the
film with the presence of Si--O--Si groups by secondary ion mass
spectroscopy (SIMS).
[0057] One advantage of amorphous diamond-like film coatings or
films that include siloxane is their resistance to cracking in
comparison to other films. Amorphous diamond-like film coatings are
inherently resistant to cracking either under applied stress or
inherent stresses arising from manufacture of the film. In addition
amorphous diamond-like film can be formed at greater thicknesses
than other plasma barrier films, such as, for example, from 1000 to
25000 Angstroms.
[0058] The polymer layers used in the multilayer stack of the
barrier assemblies are preferably crosslinkable. The crosslinked
polymeric layer lies atop the substrate or other layers, and it can
be formed from a variety of materials. Preferably the polymeric
layer is crosslinked in-situ atop the underlying layer. If desired,
the polymeric layer can be applied using conventional coating
methods such as roll coating (e.g., gravure roll coating) or spray
coating (e.g., electrostatic spray coating), then crosslinked
using, for example, ultraviolet (UV) radiation. Most preferably the
polymeric layer is formed by flash evaporation, vapor deposition
and crosslinking of a monomer as described in the present
specification. Volatilizable (meth)acrylate monomers are preferred
for use in such a process, with volatilizable acrylate monomers
being especially preferred. Preferred (meth)acrylates have a
molecular weight in the range of about 150 to about 600, or about
200 to about 400. Other preferred (meth)acrylates have a value of
the ratio of the molecular weight to the number of acrylate
functional groups per molecule in the range of about 150 to about
600 g/mole/(meth)acrylate group, or about 200 to about 400
g/mole/(meth)acrylate group. Fluorinated (meth)acrylates can be
used at higher molecular weight ranges or ratios, e.g., about 400
to about 3000 molecular weight or about 400 to about 3000
g/mole/(meth)acrylate group. Coating efficiency can be improved by
cooling the support. Particularly preferred monomers include
multifunctional (meth)acrylates, used alone or in combination with
other multifunctional or monofunctional (meth)acrylates, such as
hexanediol diacrylate, ethoxyethyl acrylate, phenoxyethyl acrylate,
cyanoethyl (mono)acrylate, isobornyl acrylate, isobornyl
methacrylate, octadecyl acrylate, isodecyl acrylate, lauryl
acrylate, beta-carboxyethyl acrylate, tetrahydrofurfuryl acrylate,
dinitrile acrylate, pentafluorophenyl acrylate, nitrophenyl
acrylate, 2-phenoxyethyl acrylate, 2-phenoxyethyl methacrylate,
2,2,2-trifluoromethyl(meth)acrylate, diethylene glycol diacrylate,
triethylene glycol diacrylate, triethylene glycol dimethacrylate,
tripropylene glycol diacrylate, tetraethylene glycol diacrylate,
neopentyl glycol diacrylate, propoxylated neopentyl glycol
diacrylate, polyethylene glycol diacrylate, tetraethylene glycol
diacrylate, bisphenol A epoxy diacrylate, 1,6-hexanediol
dimethacrylate, trimethylol propane triacrylate, ethoxylated
trimethylol propane triacrylate, propylated trimethylol propane
triacrylate, tris(2-hydroxyethyl)isocyanurate triacrylate,
pentaerythritol triacrylate, phenylthioethyl acrylate,
naphthloxyethyl acrylate, IRR-214 cyclic diacrylate from CYTEC
INDUSTRIES, INC., epoxy acrylate RDX80095 from Rad-Cure
Corporation, and mixtures thereof. A variety of other curable
materials can be included in the crosslinked polymeric layer, e.g.,
vinyl ethers, vinyl naphthylene, acrylonitrile, and mixtures
thereof.
[0059] Alternative materials for the polymer layers include
materials having a Tg greater than or equal to that of HSPET. A
variety of alternative polymer materials can be employed.
Volatilizable monomers that form suitably high Tg polymers are
especially preferred. Preferably the alternative polymer layer has
a Tg greater than that of PMMA, more preferably a Tg of at least
about 110 degrees centigrade, yet more preferably at least about
150 degrees centigrade, and most preferably at least about 200
degrees centigrade. Especially preferred monomers that can be used
to form this layer include urethane acrylates (e.g., CN-968,
Tg=about 84 degrees centigrade and CN-983, Tg=about 90 degrees
centigrade, both commercially available from Sartomer Co.),
isobornyl acrylate (e.g., SR-506, commercially available from
Sartomer Co., Tg=about 88 degrees centigrade), dipentaerythritol
pentaacrylates (e.g., SR-399, commercially available from Sartomer
Co., Tg=about 90 degrees centigrade), epoxy acrylates blended with
styrene (e.g., CN-120S80, commercially available from Sartomer Co.,
Tg=about 95 degrees centigrade), di-trimethylolpropane
tetraacrylates (e.g., SR-355, commercially available from Sartomer
Co., Tg=about 98 degrees centigrade), diethylene glycol diacrylates
(e.g., SR-230, commercially available from Sartomer Co., Tg=about
100 degrees centigrade), 1,3-butylene glycol diacrylate (e.g.,
SR-212, commercially available from Sartomer Co., Tg=about 101
degrees centigrade), pentaacrylate esters (e.g., SR-9041,
commercially available from Sartomer Co., Tg=about 102 degrees
centigrade), pentaerythritol tetraacrylates (e.g., SR-295,
commercially available from Sartomer Co., Tg=about 103 degrees
centigrade), pentaerythritol triacrylates (e.g., SR-444,
commercially available from Sartomer Co., Tg=about 103 degrees
centigrade), ethoxylated (3) trimethylolpropane triacrylates (e.g.,
SR-454, commercially available from Sartomer Co., Tg=about 103
degrees centigrade), ethoxylated (3) trimethylolpropane
triacrylates (e.g., SR-454HP, commercially available from Sartomer
Co., Tg=about 103 degrees centigrade), alkoxylated trifunctional
acrylate esters (e.g., SR-9008, commercially available from
Sartomer Co., Tg=about 103 degrees centigrade), dipropylene glycol
diacrylates (e.g., SR-508, commercially available from Sartomer
Co., Tg=about 104 degrees centigrade), neopentyl glycol diacrylates
(e.g., SR-247, commercially available from Sartomer Co., Tg=about
107 degrees centigrade), ethoxylated (4) bisphenol a
dimethacrylates (e.g., CD-450, commercially available from Sartomer
Co., Tg=about 108 degrees centigrade), cyclohexane dimethanol
diacrylate esters (e.g., CD-406, commercially available from
Sartomer Co., Tg=about 110 degrees centigrade), isobornyl
methacrylate (e.g., SR-423, commercially available from Sartomer
Co., Tg=about 110 degrees centigrade), cyclic diacrylates (e.g.,
IRR-214, commercially available from Cytec Industries, Inc.,
Tg=about 208 degrees centigrade) and tris(2-hydroxy
ethyl)isocyanurate triacrylate (e.g., SR-368, commercially
available from Sartomer Co., Tg=about 272 degrees centigrade),
acrylates of the foregoing methacrylates and methacrylates of the
foregoing acrylates.
[0060] Optional layers can include "getter" or "desiccant" layers
functionally incorporated within or adjacent to the barrier
coating; examples of such layers are described in U.S. Patent
Publication Nos. 2006-0063015 and 2006-0061272, which are
incorporated herein by reference as if fully set forth. Getter
layers include layers with materials that absorb or deactivate
oxygen, and desiccant layers include layers with materials that
absorb or deactivate water.
[0061] Optional layers can include encapsulating films, for example
barrier layers, optical films, or structured films. The optical
film can include, for example, a light extracting film, a diffuser,
or a polarizer. The structured film can include films having
microstructured (micron-scaled) features such as prisms, grooves,
or lenslets.
[0062] In some embodiments, the barrier layers include one or more
inorganic barrier layers. The inorganic barrier layers, when
multiple such layers are used, do not have to be the same. A
variety of inorganic barrier materials can be employed. Preferred
inorganic barrier materials include metal oxides, metal nitrides,
metal carbides, metal oxynitrides, metal oxyborides, and
combinations thereof, e.g., silicon oxides such as silica, aluminum
oxides such as alumina, titanium oxides such as titania, indium
oxides, tin oxides, indium tin oxide ("ITO"), tantalum oxide,
zirconium oxide, niobium oxide, boron carbide, tungsten carbide,
silicon carbide, aluminum nitride, silicon nitride, boron nitride,
aluminum oxynitride, silicon oxynitride, boron oxynitride,
zirconium oxyboride, titanium oxyboride, and combinations thereof.
Indium tin oxide, silicon oxide, aluminum oxide and combinations
thereof are especially preferred inorganic barrier materials. ITO
is an example of a special class of ceramic materials that can
become electrically conducting with the proper selection of the
relative proportions of each elemental constituent.
[0063] The inorganic barrier layers, when incorporated into the
assembly, preferably are formed using techniques employed in the
film metallizing art such as sputtering (e.g., cathode or planar
magnetron sputtering), evaporation (e.g., resistive or electron
beam evaporation), chemical vapor deposition, plating and the like.
Most preferably the inorganic barrier layers are formed using
sputtering, e.g., reactive sputtering. Alternatively, they can be
formed atomic layer deposition, which can help to seal pin holes in
the barrier coatings.
[0064] Enhanced barrier properties have been observed when the
inorganic layer is formed by a high energy deposition technique
such as sputtering compared to lower energy techniques such as
conventional chemical vapor deposition processes. Without being
bound by theory, it is believed that the enhanced properties are
due to the condensing species arriving at the substrate with
greater kinetic energy, leading to a lower void fraction as a
result of compaction. The smoothness and continuity of each
inorganic barrier layer and its adhesion to the underlying layer
can be enhanced by pretreatments (e.g., plasma pretreatment) such
as those described above.
[0065] The barrier assemblies can also have a protective polymer
topcoat layer. If desired, the topcoat polymer layer can be applied
using conventional coating methods such as roll coating (e.g.,
gravure roll coating), spray coating (e.g., electrostatic spray
coating), or plasma deposition. A pretreatment (e.g., plasma
pretreatment) may be used prior to formation of the topcoat polymer
layer. The desired chemical composition and thickness of the
topcoat polymer layer will depend in part on the nature and surface
topography of the underlying layer(s), the hazards to which the
barrier assembly might be exposed, and applicable device
requirements. The topcoat polymer layer thickness preferably is
sufficient to provide a smooth, defect-free surface that will
protect the underlying layers from ordinary hazards.
[0066] The polymer layers can be formed by applying a layer of a
monomer or oligomer to the substrate and crosslinking the layer to
form the polymer in situ, e.g., by flash evaporation and vapor
deposition of a radiation-crosslinkable monomer, followed by
crosslinking using, for example, an electron beam apparatus, UV
light source, electrical discharge apparatus or other suitable
device. Coating efficiency can be improved by cooling the support.
The monomer or oligomer can also be applied to the substrate using
conventional coating methods such as roll coating (e.g., gravure
roll coating), spray coating (e.g., electrostatic spray coating),
or plasma deposition, then crosslinked as set out above. The
polymer layers can also be formed by applying a layer containing an
oligomer or polymer in solvent and drying the thus-applied layer to
remove the solvent. More preferably, the polymer layers are formed
by flash evaporation and vapor deposition followed by crosslinking
in-situ.
[0067] A roll-to-roll manufacture (web process) to make barrier
assemblies is described in U.S. Pat. No. 5,888,594, incorporated
herein by reference. In addition to a web process, barrier
assemblies can be made in a batch process such as those described
below in the Examples.
[0068] Organic electronic devices such as OLED devices, OPVs, and
organic transistors are often sensitive to oxygen and moisture
present in the ambient atmosphere. Embodiments of the present
disclosure include the use of an ion enhanced plasma chemical vapor
deposition process that leads to amorphous diamond-like coatings
having superior moisture vapor barrier performance. In one
particular embodiment, amorphous diamond-like barrier coatings are
deposited directly onto a bare OLED device with at least no
substantial degradation of device performance induced by the
deposition process. In a second embodiment, barrier coatings are
deposited directly onto an OLED device previously encapsulated with
a protective film (e.g., polymer film) that is in intimate contact
with the OLED structure with at least no substantial degradation of
device performance induced by the deposition process. In a third
embodiment, barrier coatings are deposited directly onto an OLED
device previously encapsulated with a protective film (e.g.,
polymer film) that is not in intimate contact with the OLED
structure with at least no substantial degradation of device
performance induced by the deposition process. In further
embodiments, the barrier coatings can also be applied to the
surface of the device substrate opposite that which carries the
device. In other embodiments, amorphous diamond-like coatings are
deposited on a substrate and an organic electronic device is formed
or deposited on either side of the amorphous diamond-like coated
substrate and then a barrier film is formed or laminated onto the
organic electronic device, where the barrier film is an amorphous
diamond-like coatings, a polymer barrier layer, or a combination of
one or more amorphous diamond-like layers and polymer layers. Any
combination of these embodiments is also contemplated.
[0069] An OLED is typically a thin film structure formed on a
substrate such as glass or transparent plastic. A light-emitting
layer of an organic electroluminescent (EL) material and optional
adjacent semiconductor layers are located between a cathode and an
anode. The EL material can be sandwiched or interdigitated, for
example, between the cathode and anode. As an alternative to a
conventional OLED device, a light-emitting electrochemical cell may
be used, an example of which is described in U.S. Pat. No.
5,682,043, which is incorporated herein by reference. The
semiconductor layers may be either hole injection (positive charge)
or electron injection (negative charge) layers and also comprise
organic materials. The material for the light-emitting layer may be
selected from many organic EL materials. The light emitting organic
layer may itself include multiple sublayers, each including a
different organic EL material. Examples of the organic EL materials
include the following: vapor deposited small molecule materials;
and solution coated light emitting polymers and small molecules
applied by spin coating, inkjet printing, or screen printing. The
organic EL material can be transferred to a receptor by laser
induced thermal imaging (LITI) to make a LITI patterned device. The
OLED devices can include passive matrix OLEDs or active matrix
OLEDs. The devices can also include other components for use in
driving them such as conductive leads and antennas.
[0070] FIGS. 4A-4C, 5A-5C, and 6A-6C show diagrams of various
exemplary embodiments of barrier assemblies. FIG. 4A illustrates a
device having, with the construction shown, organics 302, a cathode
304, amorphous diamond-like film 306, an anode and lead 308, a
substrate 310, and a cathode lead 312. FIG. 4B illustrates a device
having, with the construction shown, organics 314, a cathode 316,
amorphous diamond-like film 318, an anode and lead 320, a substrate
322, and a cathode lead 324. FIG. 4C illustrates a device having,
with the construction shown, organics 326, a cathode 328, amorphous
diamond-like film 330, an anode and lead 332, a substrate 334, a
cathode lead 336, and contact vias 338. The vias can provide for
electrical connection to the cathode and anode leads or other
electrodes using, for example, vias conductive adhesives, silver
ink, or soldering.
[0071] FIG. 5A illustrates a device having, with the construction
shown, organics 340, an adhesive 342, a cathode 344, a cover film
346, amorphous diamond-like film 348, an anode and lead 350, a
substrate 352, and a cathode lead 354. FIG. 5B illustrates a device
having, with the construction shown, organics 356, an adhesive 358,
a cathode 360, a cover film 362, amorphous diamond-like film 364,
an anode and lead 366, a substrate 368, and a cathode lead 370.
FIG. 5C illustrates a device having, with the construction shown,
organics 372, an adhesive 374, a cathode 376, a cover film 378,
amorphous diamond-like film 380, an anode and lead 382, a substrate
384, a cathode lead 386, and contact vias 388.
[0072] FIG. 6A illustrates a device having, with the construction
shown, organics 390, an open space 392, cathode 394, cover film
396, amorphous diamond-like film 398, an anode and lead 400, a
substrate 402, an adhesive 404, and a cathode lead 406. FIG. 6B
illustrates a device having, with the construction shown, organics
408, an open space 410, a cathode 412, a cover film 414, amorphous
diamond-like film 416, an anode and lead 418, a substrate 420, an
adhesive 422, and a cathode lead 424. FIG. 6C illustrates a device
having, with the construction shown, organics 426, an open space
428, a cathode 430, a cover film 432, amorphous diamond-like film
434, contact vias 436, an anode and lead 438, a substrate 440, an
adhesive 442, and a cathode lead 444.
[0073] In FIGS. 4A-4C, 5A-5C, and 6A-6C, the recited elements can
be implemented with, for example, the following: the organics can
include an OLED or any organic electronic device; the electronic
device substrates can include any of those substrate materials
identified above including flexible or rigid materials; the anode,
cathode, and contact vias (or other types of electrodes such as a
source, drain, and gate for a transistor) can include a metal or
any conductive element; the adhesive can include any material
capable of adhering together two or more components such as an
optical adhesive; the cover film can include any material such as a
polymer layer or a film such as PET as previously described for
substrates and rigid materials such as glass and metal; and the
amorphous diamond-like film can include a film of the amorphous
diamond-like film as described above or other amorphous
diamond-like film. Also, the encapsulating or protective layers of
the devices shown in FIGS. 6A-6C, 7A-7C, and 8A-8C can be repeated
to form any number of dyads, and the devices can alternatively
include additional layers such as those identified above.
[0074] In lieu of contact vias, electrical contacts may be made by
interleaving conductive paths between layers of encapsulating
films. Such a contact can be formed by first coating through, for
example, a shadow mask a substantial portion, typically more than
one half, of the organic electronic device with a thin film
encapsulant such that a portion of a device electrode remains
exposed. A conductive film, such as a metal or transparent
conductive oxide, is then deposited through a different mask such
that contact is made with the exposed electrode and a portion of
the conductive film is disposed on the initial encapsulation film.
A second encapsulation film is then deposited such that the exposed
portion of the device is covered as well as a portion of the first
encapsulation film and conductive film. The end result is an
organic electronic device covered by a thin film encapsulant and a
conductive path from an electrode to the exterior of the
device.
[0075] This type of encapsulation may be particularly useful for
direct-drive OLED solid state lighting and signage applications as
minimal patterning of the bottom electrode is required. Multiple
layers with interleaved conductors may be deposited, and conductive
paths to multiple electrodes on a single substrate may be
established. The thin film encapsulants may include DLF, sputtered
oxides, plasma polymerized films, thermally deposited materials
such as SiO and GeO, and polymer/barrier multilayers.
[0076] It is also possible to combine the various embodiments of
the present disclosure. For example, an OLED device can be directly
encapsulated with amorphous diamond-like film as illustrated in the
embodiments shown in FIGS. 4A-4C, followed by lamination of a
protective film and a second layer of amorphous diamond-like film;
in essence, this combines embodiments shown in FIGS. 4A-4C and
5A-5C.
[0077] The barrier coatings of embodiments of the present invention
provide for several advantageous characteristics. The barrier
coatings are hard and abrasion resistant, provide improved moisture
and/or oxygen protection, may be single layers or multiple layers,
have good optical properties, and can provide a way to edge-seal
adhesive bond lines as illustrated in FIGS. 4C, 5C, and 6C. The
barrier coatings may be applied to flexible and rigid devices or
substrates.
[0078] Direct encapsulation of OLEDs provides for a process that
can be carried out at high speed. The amorphous diamond-like film
deposition process is rapid; 60 .ANG./second deposition rates have
been shown and higher rates are possible. The amorphous
diamond-like film deposition process may provide for single layer
direct encapsulation, although multilayers may be desirable in some
cases. The ion enhanced plasma deposition process, as described
above and in the Examples, does not damage the OLED device layers.
It has been found that the use of silicone oil reduces stresses
found in prior deposited diamond like films. Stresses in the
diamond-like film coatings can cause delamination of the OLED
device architecture or topography in some instances. In particular,
the formation of at least one amorphous diamond-like layer
utilizing only siloxane as the carbon source resulted in
significantly reduced stresses in the final encapsulated organic
electronic devices such that delamination or cracks in the final
encapsulated organic electronic devices were not detected. Any
remaining stresses, if present, in the amorphous diamond-like
coatings described herein can be eliminated, if desired, by placing
protective and/or stress relieving coatings on top of the OLED
prior to the amorphous diamond-like film encapsulation. Protective
coatings could include, for example, metal films or ceramic films
such as silicon monoxide or boron oxide. Boron oxide would also
serve as a desiccant layer. Metallic protective films may require
an insulating underlayer to avoid undesirable electrical shorting
between individual emissive areas on a device. Stress relieving
coatings can also include organic coatings on top of the OLED prior
to amorphous diamond-like film encapsulation.
[0079] One method of applying stress reducing coatings includes
depositing layers of deformable materials over top of the OLED
prior to amorphous diamond-like film deposition. For example,
copper phthalocyanine, or organic glass-like materials can be vapor
deposited in vacuum from heated crucibles as the last step in the
OLED device fabrication process. Stresses in the subsequent
amorphous diamond-like film layers can be relieved by relaxation,
deformation, or delamination of these layers, thereby preventing
delamination of the OLED device layers.
[0080] Another method of applying protective and/or stress
relieving coatings includes adhesively laminating a cover film onto
the OLED. The cover film could be a transfer adhesive layer, such
as a Thermobond.TM. hot melt adhesive or it could be PET, PEN, or
the like, or a barrier film such as ultrabarrier film coated with
an adhesive layer. An example of an embodiment having strain relief
includes the construction shown in FIG. 5A without the cover film
346. Ultrabarrier films include multilayer films made, for example,
by vacuum deposition of two inorganic dielectric materials
sequentially in a multitude of layers on a glass or other suitable
substrate, or alternating layers of inorganic materials and organic
polymers, as described in U.S. Pat. Nos. 5,440,446; 5,877,895; and
6,010,751, all of which are incorporated herein by reference.
[0081] Bare adhesive or PET and PEN film layers may provide
sufficient protection to allow an OLED device to be transferred
under ambient conditions to a amorphous diamond-like film
encapsulation tool. Ultrabarrier films may provide sufficient
encapsulation to enable long device lifetimes. Depositing amorphous
diamond-like film coatings over top of the encapsulation film seals
the edges of the adhesive bond lines as well as provides an
additional barrier coating on the surface of the encapsulating
film. Substrates can also include non-barrier substrate materials,
in which case the amorphous diamond-like film can also be used to
encapsulate the substrate as shown in FIGS. 4B, 4C, 5B, 5C, 6B, and
6C.
[0082] A further advantage of the amorphous diamond-like film
deposition process is that it has been demonstrated in a
roll-to-roll format. Thus, the amorphous diamond-like film
encapsulation method, including the use of protective stress
relief, and/or cover film layers, is well suited to an OLED web
manufacturing process. The process may be used on both top emitting
and bottom emitting OLED device architectures.
[0083] Embodiments of the present invention will now be described
with reference to the following non-limiting examples.
EXAMPLES
Example 1
[0084] As shown in FIG. 7, a plasma deposition system 450 was used
for the deposition of the amorphous diamond-like film onto devices
456. System 450 includes an aluminum vacuum chamber 452 containing
a 12''.times.12'' bottom electrode with the chamber walls acting as
the counter-electrode. The spacing between the powered electrode
and the grounded electrode is three inches. Because of the larger
surface area of the counter-electrode, the system may be considered
to be asymmetric, resulting in a large sheath potential at the
powered electrode on which the substrates to be coated are placed.
The chamber is pumped by a pumping system 454, which comprises a
turbomolecular pump (Pfeiffer Model No. TPH510) backed by a
mechanical pump (Edwards Model No. 80). A gate valve serves to
isolate the chamber from the pumping system when the chamber is
vented.
[0085] Process gases 455 and 457 are metered through mass flow
controllers (Brooks Model No. 5850 S) and blended in a manifold
before they are introduced into the chamber through gun-drilled
holes 451 and 453 parallel to the electrode and linked into the
chamber by a multitude of smaller (0.060'' diameter) holes spaced
one inch apart. Siloxane source (i.e., silicone oil) 460 vapor 465
is provided into the vacuum chamber through any useful means. In
one embodiment, silicone oil is 460 disposed on graphite or carbon
cloth in electrical connection to a power source and is vaporized
(by heating the carbon cloth via passing current through the carbon
cloth) within the vacuum chamber while being shielded from the
plasma with a Faraday cage.
[0086] Pneumatic valves serve to isolate the flow controllers from
the gas/vapor supply lines. The process gases, oxygen 455
(ultrahigh purity 99.99%, from Scott Specialty Gases) and
tetramethylsilane 457 (TMS NMR grade, 99.9%, from Sigma Aldrich)
are stored remotely in gas cabinets and piped to the mass flow
controllers by 0.25'' (diameter) stainless steel gas lines. The
typical base pressure in the chamber is below 1.times.10-5 Torr
based on the size and type of the pumping system. Pressure in the
chamber is measured by a 0.1 Torr capacitance manometer (type 390
from MKS Instruments).
[0087] The plasma is powered by a 13.56 MHz radio frequency power
supply (Advanced Energy, Model RFPP-RF10S) through an impedance
matching network (Advanced Energy, Model RFPP-AM20). The AM-20
impedance network was modified by changing the load coil and the
shunt capacitance to suit the plasma system constructed. The
impedance matching network serves to automatically tune the plasma
load to the 50 ohm impedance of the power supply to maximize power
coupling. Under typical conditions, the reflected power is less
than 2% of the incident power.
[0088] Bottom emitting glass OLEDs containing four independently
addressable 5 mm.times.5 mm pixels were fabricated on patterned ITO
coated glass (20 Ohm/sq, available from Midwest Micro-Devices LLC,
Toledo Ohio) substrates by conventional thermal vapor deposition
through shadow masks in a bell jar evaporator evacuated to
5.times.10-6 torr. The OLED device layers deposited on top of the
patterned ITO anodes were (in order of deposition):/NPD (400 .ANG.
at 1 .ANG./s)/AlQ doped with C545T (1% doping, 300 .ANG. at 1
.ANG./s)/AlQ (200 .ANG. at 1 .ANG./s)/LiF (7 .ANG. at 0.5
.ANG./s)/Al (2500 .ANG. at 25 .ANG./s).
[0089] An unencapsulated glass four pixel bottom emitting green
OLED device was placed in the plasma deposition chamber batch
coater described above and shown in FIG. 7 (OLED coated side facing
up) and held to the electrode with strips of 3M Scotch.TM. 811
removable tape along each edge of the device as shown in FIG. 8.
The schematic illustrates, with the construction shown in FIG. 8,
tape 462, 464, an ITO cathode pad 466, a cathode 468, an organic
electronic device 470, an ITO anode 472, a device substrate 474,
and an amorphous diamond-like film layer 476. The tape (462 and
464) prevents device movement during amorphous diamond-like film
deposition and serves as a mask to prevent amorphous diamond-like
film deposition over portions of the ITO cathode and anode leads,
thereby allowing for electrical contact after encapsulation.
[0090] The system, the device shown in FIG. 8 in the chamber shown
in FIG. 7, was pumped to base pressure (below about
1.times.10.sup.-3 Torr) and oxygen gas was introduced at a flow
rate of 150 sccm which produced a pressure of about 7 to 8 mTorr.
The sample (device) surface was primed by a 10 second exposure to
oxygen plasma (1000 watt RF power). With the plasma still ignited,
a 1.7A current was applied to the graphite heating cloths which
vaporized a 0.6 g sample of silicone oil (DMS-S12, Gelest, Inc.
Morrisville, Pa.), that was placed onto the carbon cloths
previously, into the RF plasma. Without extinguishing the plasma
and after a 5 to 10 second delay, tetramethylsilane gas was
introduced (50 sccm) while maintaining the oxygen flow at 150 sccm
and 1.7A current flow through the carbon cloths for 2 minutes. This
produced approximately 1000 nm thick amorphous diamond-like film on
top of and around the OLED device. After removal from the plasma
chamber, a nearly colorless and optically uniform amorphous
diamond-like film could be seen on the top surface of the device
when viewing the device from an angle. Other than this film, the
OLED device was visibly unchanged by the deposition process.
Operational characteristics of voltage and brightness for the
amorphous diamond-like film encapsulated device were compared to an
OLED device that was left bare and no noticible difference was
measured between the amorphous diamond-like film encapsulated and
bare OLED devices.
Example 2
[0091] The same apparatus and procedure described in Example 1 was
used to make an encapsulation layer on a second 4 pixel OLED
device. However, the flow of TMS was set to zero which resulted in
a silicone only amorphous diamond-like film encapsulation film.
After removal from the plasma chamber, a nearly colorless optically
uniform diamond-like film could be seen on the top surface of the
device when viewing the device from an angle. Other than this film,
the OLED device was visibly unchanged by the deposition process.
When compared to a bare unencapsulated control device, no noticible
difference in performance was measured.
Example 3
[0092] The same apparatus and procedure described in Example 1 was
used to make an encapsulation layer on a second 4 pixel OLED device
with a 225 sccm flow of anhydrous ammonia instead of oxygen. This
produced a nitride amorphous diamond-like film over and around the
OLED device. After removal from the plasma chamber, a nearly
colorless optically uniform diamond-like film could be seen on the
top surface of the device when viewing the device from an angle.
Other than this film, the OLED device was visibly unchanged by the
deposition process. When compared to a bare unencapsulated control
device, no noticible difference in performance was measured.
Example 4
[0093] An OLED device that was left bare, that is, no attempt was
made to protect the OLED device from the environment, was operated
continuously at 8V and left out in ambient conditions of a
laboratory. After approximately 24 hours the device was completely
dead. Simultaneously, the encapsulated device from Example 1 was
also continuously operated at 8V and left out in ambient laboratory
conditions. The device remained operational after more than 1000
hours of continuous operation.
Example 5
[0094] Transmission infrared spectra were measured from germainium
wafers (source) that had amorphous diamond-like film coatings
deposited onto them following the same process and material steps
illustrated in Examples 1, 2, and 3. In Examples 1 and 2 the
infrared transmission spectra yielded strong absorbances in the
1050 cm-1 to 1070 cm-1 range indicating the presence of Si--O
bonding. Two additional absorbencies were measured in the 830 cm-1
to 880 cm-1 range indicating the presence of silicone
--Si(CH3)2-O--Si(CH3)2O--) bonding. When compared to examples 1 and
2, the infrared measurements for Example 3 (DLF films made with
anhydrous ammonia) showed substantial variation; there was a large
reduction in absorbance in the Si--O band (1050 cm-1 to 1070 cm-1)
and the disappearance of the absorbencies in the silicone band (830
cm-1 to 880 cm-1) indicating that the oxygen was replaced with
nitrogen in the amorphous diamond-like film.
Example 6
[0095] A four pixel OLED device was encapsulated by the same
process steps and materials described in Example 1 and was further
encapsulated by a PEN film (0.005 inches thick, Dupont Teijin
Films) coated on both sides with multilayer barrier coatings. The
additional encapsulation was made by laminating the barrier film
with a pressure sensitive adhesive (ARclear.RTM. 90537, Adhesives
Research Inc., Glen Rock, Pa.) directly to the amorphous
diamond-like film layer of the amorphous diamond-like film
encapsulated OLED device. No difference in device performance was
measured when compared to bare, un-encapsulated control device.
[0096] Thus, embodiments of the MOISTURE BARRIER COATINGS FOR
ORGANIC LIGHT EMITTING DIODE DEVICES are disclosed. One skilled in
the art will appreciate that the present invention can be practiced
with embodiments other than those disclosed. The disclosed
embodiments are presented for purposes of illustration and not
limitation, and the present invention is limited only by the claims
that follow.
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