U.S. patent application number 10/948013 was filed with the patent office on 2006-03-23 for protected polymeric film.
This patent application is currently assigned to 3m Innovative Properties Company. Invention is credited to Fred B. McCormick, Manoj Nirmal, George V. Tiers.
Application Number | 20060063015 10/948013 |
Document ID | / |
Family ID | 35482298 |
Filed Date | 2006-03-23 |
United States Patent
Application |
20060063015 |
Kind Code |
A1 |
McCormick; Fred B. ; et
al. |
March 23, 2006 |
Protected polymeric film
Abstract
A protected polymeric film comprises a polymeric film substrate
having a first major surface and a second major surface opposite
the first major surface, and a protective structure provided on at
least the first major surface of the substrate, wherein the
protective structure comprises a layer of boron oxide and an
inorganic barrier layer. A protective structure may also be
provided on the second major surface of the substrate. Organic
electronic components may be formed on or attached to the protected
polymeric films.
Inventors: |
McCormick; Fred B.;
(Maplewood, MN) ; Nirmal; Manoj; (St. Paul,
MN) ; Tiers; George V.; (St. Paul, MN) |
Correspondence
Address: |
3M INNOVATIVE PROPERTIES COMPANY
PO BOX 33427
ST. PAUL
MN
55133-3427
US
|
Assignee: |
3m Innovative Properties
Company
|
Family ID: |
35482298 |
Appl. No.: |
10/948013 |
Filed: |
September 23, 2004 |
Current U.S.
Class: |
428/457 ;
428/480; 428/698; 428/702; 428/704 |
Current CPC
Class: |
H01L 51/5253 20130101;
C23C 14/08 20130101; Y10T 428/31786 20150401; H01L 51/5256
20130101; Y10T 428/31667 20150401; Y10T 428/31681 20150401; H01L
51/5259 20130101; H01L 51/0096 20130101; Y10T 428/249983 20150401;
Y10T 428/31678 20150401; Y02E 10/549 20130101 |
Class at
Publication: |
428/457 ;
428/704; 428/702; 428/698; 428/480 |
International
Class: |
B32B 9/04 20060101
B32B009/04; B32B 15/04 20060101 B32B015/04; B32B 27/36 20060101
B32B027/36 |
Claims
1. A protected polymeric film comprising: a) a polymeric film
substrate having a first major surface and a second major surface
opposite the first major surface; and b) a protective structure
provided on at least the first major surface of the substrate,
wherein the protective structure comprises a layer of boron oxide
and an inorganic barrier layer.
2. A protected polymeric film according to claim 1, having low
moisture permeability.
3. A protected polymeric film according to claim 1, wherein the
layer of boron oxide is disposed on the first major surface of the
substrate, and the inorganic barrier layer is disposed over the
layer of boron oxide.
4. A protected polymeric film according to claim 3, wherein there
is no intervening layer between the boron oxide layer and the
inorganic barrier layer.
5. A protected polymeric film according to claim 4, wherein the
inorganic barrier layer is a multilayer construction.
6. A protected polymeric film according to claim 1, wherein the
inorganic barrier layer is selected from the group consisting of
metals, metal oxides, metal nitrides, metal carbides, metal
oxynitrides, metal oxyborides, metal oxycarbides, and combinations
thereof.
7. A protected polymeric film according to claim 6, wherein the
inorganic barrier layer comprises silicon oxide.
8. A protected polymeric film according to claim 1, wherein the
layer of boron oxide is disposed on the first major surface of the
substrate, and the inorganic barrier layer is disposed over the
layer of boron oxide and cooperates with the first major surface of
the substrate to encapsulate the layer of boron oxide.
9. A protected polymeric film according to claim 1, wherein the
inorganic barrier layer is disposed on the first major surface of
the substrate, and the layer of boron oxide is disposed over the
inorganic barrier layer.
10. A protected polymeric film according to claim 9, wherein there
is no intervening layer between the boron oxide layer and the
inorganic barrier layer.
11. A protected polymeric film according to claim 10, wherein the
inorganic barrier layer is a multilayer construction.
12. A protected polymeric film according to claim 1, further
comprising a buffer layer.
13. A protected polymeric film according to claim 12, wherein the
inorganic barrier layer is disposed on the first major surface of
the substrate, the layer of boron oxide is disposed over the
inorganic barrier layer, and the buffer layer is disposed over the
layer of boron oxide.
14. A protected polymeric film according to claim 13, wherein there
is no intervening layer between the boron oxide layer and the
inorganic barrier layer, and there is no intervening layer between
the boron oxide layer and the buffer layer.
15. A protected polymeric film according to claim 13, wherein the
buffer layer comprises an organometallic compound or a chelate
compound.
16. A protected polymeric film according to claim 1, wherein the
protective structure further comprises a second inorganic barrier
layer.
17. A protected polymeric film according to claim 16, wherein the
inorganic barrier layer is disposed on the first major surface of
the substrate, the layer of boron oxide is disposed over the
inorganic barrier layer, and the second inorganic barrier layer is
disposed over the layer of boron oxide.
18. A protected polymeric film according to claim 17, wherein the
layer of boron oxide is encapsulated between the two inorganic
barrier layers.
19. A protected polymeric film according to claim 17, wherein there
is no intervening layer between the layer of boron oxide and the
inorganic barrier layer, and there is no intervening layer between
the layer of boron oxide, and the second inorganic barrier
layer.
20. A protected polymeric film according to claim 1, wherein the
inorganic barrier layer is a multilayer construction.
21. A protected polymeric film according to claim 20, wherein the
inorganic barrier layer comprises alternating polymeric and
inorganic layers.
22. A protected polymeric film according to claim 1, further
comprising a second protective structure, wherein the second
protective structure is provided on the second major surface of the
substrate and comprises a layer of boron oxide and an inorganic
barrier layer.
23. A protected polymeric film according to claim 22, where, in the
second protective structure, the layer of boron oxide is disposed
on the first major surface of the substrate, and the inorganic
barrier layer is disposed over the layer of boron oxide.
24. A protected polymeric film according to claim 1, having a
moisture permeation rate that does not exceed 5.times.10.sup.-4
g/m.sup.2/day.
25. A protected polymeric film according to claim 24, having a
moisture permeation rate that does not exceed 1.times.10.sup.-6
g/m.sup.2/day.
26. A protected polymeric film comprising: a) a polyester film
having a first major surface and a second major surface opposite
the first major surface; and b) a layer of boron oxide on the first
major surface of the polyester film and a layer of an inorganic
oxide, other than boron oxide, on the layer of boron oxide, with no
intervening layer between the layer of boron oxide and the layer of
inorganic oxide.
27. A protected organic electroluminescent device comprising: a) a
polymeric film substrate having a first major surface, a second
major surface opposite the first major surface, and a protective
structure on the first major surface of the substrate, the
protective structure comprising a layer of boron oxide and an
inorganic barrier layer; b) an electroluminescent assembly
comprising a first electrode, a second electrode, and a light
emitting structure disposed between the first and second
electrodes, wherein the electroluminescent assembly is disposed (i)
on the first major surface of the substrate and either under or
over the protective structure, or (ii) on the second major surface
of the substrate.
28. A protected organic electroluminescent device according to
claim 27, wherein the electroluminescent assembly is disposed on
the second major surface of the substrate.
29. A protected organic electroluminescent device according to
claim 27, wherein the electroluminescent assembly is disposed on
the first major surface of the substrate and over the protective
structure.
30. A protected organic electroluminescent device according to
claim 27, wherein the electroluminescent assembly is disposed on
the first major surface of the substrate and under the protective
structure.
31. A protected organic electroluminescent device according to
claim 27, wherein the inorganic barrier layer is disposed on the
first major surface of the substrate and the boron oxide layer is
disposed on the inorganic barrier layer.
32. A protected organic electroluminescent device according to
claim 27, wherein the layer of boron oxide is disposed on the first
major surface of the substrate and the inorganic barrier layer is
disposed on the layer of boron oxide.
33. A method for reducing the transmission of moisture by a
polymeric film otherwise able to transmit moisture, the method
comprising the steps: a) providing a polymeric film having a first
major surface and a second major surface opposite the first major
surface; b) applying to at least the first major surface of the
polymeric film a protective structure comprising a layer of boron
oxide and an inorganic barrier layer to reduce the ability of the
polymeric film to transmit moisture.
Description
TECHNICAL FIELD
[0001] This invention relates to protected polymeric films and,
more particularly, to polymeric films that have a reduced tendency
to transmit moisture. This invention also relates to articles that
incorporate such protected polymeric films.
BACKGROUND
[0002] Polymeric films tend to transmit moisture (e.g., water
vapor), which can be undesirable if the transmission of moisture is
detrimental to components that are secured to or subsequently
formed on the film. As one example, organic electroluminescent
devices may suffer reduced output or premature failure when exposed
to moisture. Techniques have been developed to encapsulate and
prolong the life of such devices, which may be sufficient if the
device is formed on a glass substrate that is impermeable to
moisture. Increasingly, however, it is desirable to form such
devices on a polymeric film, but such films tend to inherently
transmit moisture. A protected polymeric film that exhibited low
permeability to moisture would be especially useful, but despite
intense industrial effort to develop such a film, only limited
success has been attained so far.
SUMMARY OF THE INVENTION
[0003] In one aspect, the present invention provides a protected
polymeric film comprising a polymeric film substrate having a first
major surface and a second major surface opposite the first major
surface, and a protective structure that is provided on at least
the first major surface of the substrate. The protective structure
comprises a layer of boron oxide and an inorganic barrier layer.
The layer of boron oxide may be disposed on the first major surface
of the substrate with the inorganic barrier layer disposed over the
layer of boron oxide. Alternatively, the inorganic barrier layer
may be disposed on the first major surface of the substrate with
the layer of boron oxide disposed over the inorganic barrier layer.
A second protective structure (also comprising a layer of boron
oxide and an inorganic barrier layer) may be provided on the second
major surface of the substrate. The expressions "disposed on" and
"disposed over" are not meant to suggest that direct, intimate
contact is required between the layers that are in this
relationship, but instead are relative terms of position.
[0004] In some embodiments, the inorganic barrier layer cooperates
with the first major surface of the substrate to encapsulate the
layer of boron oxide. In other embodiments, the protective
structure further comprises a second inorganic barrier layer. The
layer of boron oxide may then be disposed between, and optionally
be encapsulated by, the two inorganic barrier layers.
[0005] The inorganic barrier layer preferably comprises an
inorganic oxide, boride, nitride, carbide, oxynitride, oxyboride,
or oxycarbide, such as silicon oxides, nitrides or carbides;
diamond-like carbon layers; and metals such as silicon, aluminum or
combinations thereof. Specific examples include silicon oxide
(monoxide or dioxide), silicon nitride, aluminum oxide or silicon
aluminum oxide. The inorganic barrier layer may be a multilayer
construction comprising, for example, alternating polymeric and
inorganic layers. In some instances, the inorganic barrier layer
has low moisture permeability.
[0006] Protected polymeric films according to the invention may
further, and optionally, comprise a buffer layer such as an
organometallic compound or a chelate compound. In these
embodiments, the inorganic barrier layer may be disposed on the
first major surface of the substrate, the layer of boron oxide may
be disposed over the inorganic barrier layer, and the buffer layer
may be disposed over the layer of boron oxide.
[0007] The protective structures reduce the inherent, but
potentially undesirable, tendency of polymeric films to transmit
moisture. As a result, the protected polymeric films of the
invention provide a good support on which an electroluminescent
assembly (e.g., comprising a first electrode, a second electrode,
and a light emitting structure disposed between the first and
second electrodes) may be subsequently formed or attached. The
electroluminescent assembly may be disposed on the surface of the
polymeric film carrying the protective structure (either underneath
it or over it), or on the opposite surface of the polymeric
film.
[0008] In another aspect, the present invention provides a method
for reducing the transmission of moisture by a polymeric film by
applying a protective structure, such as those described above, to
at least a first major surface of the polymeric film.
BRIEF DESCRIPTION OF THE DRAWINGS
[0009] The invention will be more fully appreciated with reference
to the following non-limiting and not-to-scale drawings in which
the same reference symbols designate like or analogous components
throughout and in which:
[0010] FIG. 1 is a schematic sectional view of a first embodiment
of a protected polymeric film according to the invention;
[0011] FIG. 2 is a schematic sectional view of a second embodiment
of a protected polymeric film according to the invention;
[0012] FIG. 3 is a schematic sectional view of a third embodiment
of a protected polymeric film according to the invention;
[0013] FIG. 4 is a schematic sectional view of a fourth embodiment
of a protected polymeric film according to the invention;
[0014] FIG. 5 is a schematic sectional view of a fifth embodiment
of a protected polymeric film according to the invention; and
[0015] FIG. 6 is a schematic sectional view of a sixth embodiment
of a protected polymeric film according to the invention.
DETAILED DESCRIPTION
[0016] Broadly, and in one aspect, the invention provides a
protected polymeric film comprising a polymeric film substrate
having a first major surface and a second major surface opposite
the first major surface, and a protective structure that is
provided on at least the first major surface of the substrate. The
protective structure comprises a layer of boron oxide and an
inorganic barrier layer. Other layers may be optionally included in
the protective structure, on the polymeric film substrate, or
both.
[0017] The protected polymeric films of the invention can be used
to inhibit the transmission of moisture in a variety of
applications. They are especially useful as substrates for use with
organic electronic devices such as organic electroluminescent
devices, organic transistors, liquid crystal displays, and other
electronic components.
[0018] Broadly, a "protected polymeric film" refers to a polymeric
film substrate that has been provided with a protective structure
as described herein, and a "protective structure" refers to the
layer of boron oxide and the inorganic barrier layer that have been
provided on the polymeric film substrate. Polymeric film substrates
tend to transmit, or otherwise be permeable to moisture, which is
undesirable if the transmission of moisture by the substrate is
detrimental to components that are secured to or subsequently
formed on the substrate.
[0019] Thus, a "protected polymeric film" more specifically refers
to a polymeric film substrate that has a reduced ability to
transmit moisture relative to the same polymeric film substrate
that does not have the protective structure. Similarly, a
"protective structure" more specifically refers to a layered
assembly comprising the layer of boron oxide and the inorganic
barrier layer, and which reduces the undesirable, but inherent,
tendency of a polymeric film to transmit moisture relative to the
same polymeric film that does not have the protective structure.
The protective structure is preferably adapted to reduce, often
substantially, the inherent tendency of a polymeric film to
transmit moisture through the surface(s) to which the protective
structure has been applied.
[0020] Preferably, the protective structure results in protected
polymeric films that have sufficiently low moisture permeability to
make them useful for encapsulating at least the anode, cathode and
organic electronic layers of organic electronic devices.
"Encapsulating" means surrounding or enclosing the exposed moisture
sensitive surfaces of these layers. Organic electronic devices
typically require protection from moisture in excess of the levels
that can be measured by commercially available equipment such as
that provided by MOCON (Modem Controls, Minneapolis, Minn.). While
MOCON equipment is typically capable of measuring moisture
permeation rates as low as 5.times.10.sup.-4 grams/square meter/day
(g/m.sup.2/day), permeation rates as low as 1.times.10.sup.-6
g/m.sup.2/day have been described as a desirable target.
Accordingly, "low moisture permeability" more preferably means a
moisture permeation rate of less than 5.times.10.sup.-4
g/m.sup.2/day, more preferably less than 1.times.10.sup.-5
g/m.sup.2/day, even more preferably less than 1.times.10.sup.-6
g/m.sup.2/day as measured pursuant to ASTM Test Method F-1249.
[0021] Turning now to the drawings, FIG. 1 shows a protected
polymeric film 10 comprising a polymeric film substrate 12 having a
first major surface 12a and a second major surface 12b opposite the
first major surface 12a. A protective structure 14 is provided on
at least the first major surface 12a of substrate 12. Protective
structure 14 comprises a layer of boron oxide 16 and an inorganic
barrier layer 18. Preferably, there are no intervening layers
between substrate 12 and protective structure 14 as this could
impair the ability of the protective structure to reduce the
transmission of moisture through the substrate. Similarly, it is
preferred that there be no intervening layers between boron oxide
layer 16 and inorganic barrier layer 18 as this too could impair
the ability of protective structure 14 to reduce the transmission
of moisture by substrate 12.
[0022] FIG. 1 illustrates boron oxide layer 16 as being
intermediate substrate 12 and inorganic barrier layer 18; however,
the relative position of these two layers could be reversed such
that inorganic barrier layer 18 is intermediate substrate 12 and
boron oxide layer 16. Preferred are those constructions in which
the inorganic barrier layer and the boron oxide layer are arranged
such that encroaching moisture encounters the inorganic barrier
layer before encountering the boron oxide layer.
[0023] Substrate 12 is a polymeric film. By "film" is meant a
material having length and width dimensions that are substantially
greater than the material's thickness. Included within the concept
of a "film" are a tape, a ribbon and a roll, which generally
describe a material that also has a length dimension that is
substantially greater than its width, the width also being
substantially greater than the thickness. Such materials are often
provided with a central core about which the material is wrapped in
multiple windings so as to facilitate processing steps during which
the protective structure is applied to the substrate (e.g., in
roll-to-roll production), additional manufacturing operations, or
post-processing handling, storage and shipping. Also included
within the concept of a "film" is a sheet, page or panel, which
generally describe a material that has length and width dimensions
that are more nearly equal. Such materials are often handled in a
stack of multiple individual layers that facilitate processing
steps during which the protective structure is applied to the
substrate in a sheet-fed or a similar sheeting type operation.
[0024] The term "polymeric" refers to homopolymers and copolymers,
as well as homopolymers or copolymers that may be formed in a
miscible blend, for example, by coextrusion or by reaction,
including, e.g., transesterification. The term "copolymer"
describes materials that are derived from two or more different
monomeric units and includes random, block and graft copolymers.
Polymers suitable for providing substrate 12 may be any of a number
of known polymers such as thermoset (crosslinked), thermosettable
(crosslinkable), or thermoplastic polymers that are capable of
being formed into a film, including acrylates (including
methacrylates such as polymethylmethacrylate), polyols (including
polyvinyl alcohols), epoxy resins, silanes, siloxanes (with all
types of variants thereof), polyvinyl pyrrolidones, polyimides,
polyamides, poly (phenylene sulphide), polysulfones,
phenol-formaldehyde resins, cellulose ethers and esters (for
example, cellulose acetate, cellulose acetate butyrate, etc.),
nitrocelluloses, polyurethanes, polyesters (for example, poly
(ethylene terephthalate), poly (ethylene naphthalate)),
polycarbonates, polyolefins (for example, polyethylene,
polypropylene, polychloroprene, polyisobutylene,
polytetrafluoroethylene, polychlorotrifluoroethylene, poly
(p-chlorostyrene), polyvinylidene fluoride, polyvinylchloride,
polystyrene, poly .alpha.-methyl styrene, etc.), phenolic resins
(for example, novolak and resole resins), polyvinylacetates,
styrene/acrylonitriles, styrene/maleic anhydrides,
polyoxymethylenes, polyvinylnaphthalenes, polyetheretherketones,
polyaryletherketones, fluoropolymers, polyarylates, polyphenylene
oxides, polyetherimides, polyarylsulfones, polyethersulfones,
polyamideimides, and polyphthalamides.
[0025] For some applications it may be desirable for substrate 12
to have a visible light transmission, for example a transmission of
at least about 70%, at a visible light wavelength of interest. In
other applications it may be desirable for the substrate to be
oriented, biaxially oriented and/or heat-stabilized. In some cases,
it may be desirable for substrate 12 to be flexible, by which it is
meant that substrate 12 can be wrapped about a core to produce a
roll having multiple windings as described above. The thickness of
substrate 12 is largely dictated by the intended application for
the protected polymeric film, but for many uses a thickness of
about 0.01 to 1 mm, more preferably about 0.05 to 0.25 mm is quite
useful.
[0026] With continued reference to FIG. 1, protective structure 14
comprises a layer of boron oxide 16 and an inorganic barrier layer
18. Several advantages are associated with using boron oxide in the
present invention, although it will be understood that not every
advantage will necessarily be reflected in each application that
incorporates the protected polymeric films of the invention. Boron
oxide may be deposited on or otherwise applied to the polymeric
film substrate as an optically clear or transparent glass-like
material, which may be advantageous for applications where this
layer needs to be transmissive to light such as in an organic
electroluminescent device. In addition, the boron oxide layer may
reduce the inherent tendency of a polymeric film substrate to
transmit moisture, whether emanating from the ambient environment
or from components formed on or attached to the substrate.
[0027] While not wishing to be bound by a particular theory, it is
believed that the boron oxide functions as a desiccant, scavenging
moisture by reacting with it to yield boric acid, a relatively weak
acid the solid form of which is not likely to be detrimental to
many of the components that may be formed on or attached to the
substrate. This can be represented by the reaction of one molecule
of boron oxide with three molecules of water,
B.sub.2O.sub.3+3H.sub.2O.fwdarw.2B(OH).sub.3. Additional reaction
products in the form of evolved gasses or liquids are not
liberated.
[0028] Boron oxide also offers certain processing advantages that
may be desirable depending upon the application. For example, boron
oxide may be applied to the polymeric film substrate by several
techniques including sputtering, chemical vapor deposition,
electron beam deposition, and thermal evaporation (e.g., vapor
deposition). Vapor deposition is a preferred method when the target
surface is susceptible to damage from more energetic application
methods such as sputtering. Desirably, boron oxide can be vapor
deposited at an acceptable rate under moderate conditions (e.g.,
deposition rates of about 10 to 50 .ANG./sec may be achieved under
a vapor pressure of about 10.sup.-6 to 10.sup.-4 Torr), without
showing signs of decomposition (e.g., discoloration of the source
material).
[0029] Boron oxide layer 16 is provided on that portion of
polymeric film substrate 12 that is intended to be protected
against moisture transmission and will be determined by the
individual application. The thickness of boron oxide layer 16 will
also vary substantially depending upon the nature of the
application for protected polymeric film 10, moisture conditions to
which the protected polymeric film is likely to be exposed during
use, other layers present in protective structure 14, requirements
for optical transparency and mechanical flexibility of the
protected polymeric film, cost, etc. As layer thickness increases,
resistance to moisture transmission will increase, but perhaps at
the expense of reduced transparency, reduced flexibility, and
increased cost. Within these guidelines boron oxide layer 16 is
provided at an effective thickness, by which is meant a thickness
sufficient to reduce the undesirable, but inherent, tendency of a
polymeric film to transmit moisture relative to the same polymeric
film that does not have the boron oxide layer. More specifically,
the boron oxide layer is preferably provided at a thickness of
about 50 .ANG. to 10,000 .ANG., more preferably about 500 .ANG. to
5,000 .ANG., and even more preferably about 3,000 .ANG. to 5,000
.ANG..
[0030] Still referring to FIG. 1, protective structure 14 also
comprises inorganic barrier layer 18, which cooperates with boron
oxide layer 16 to protect polymeric film substrate 12. Inorganic
barrier layer 18 may provide protection against exposure to
moisture, oxygen, and heat and/or mechanical impact, although it is
most often included as a moisture and/or oxygen barrier. In this
capacity, it is preferred that inorganic barrier layer 18 be
selected to result in a polymeric film having low moisture
permeability. It is also preferred that inorganic barrier layer 18
not be reactive with boron oxide layer 16, polymeric film substrate
12, other layers adjacent to the inorganic barrier layer, and any
components formed on or attached to the polymeric film substrate.
In certain applications it may be desirable for inorganic barrier
layer 18 to be deposited or otherwise applied as an optically clear
or transparent material, which may be advantageous for applications
where this layer needs to be transmissive to light such as in an
organic electroluminescent device.
[0031] A variety of materials may be employed as the inorganic
barrier layer. Preferred inorganic barrier layer materials include
metals, metal oxides, metal nitrides, metal carbides, metal
oxynitrides, metal oxyborides, metal oxycarbides, 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, tantalum oxide, zirconium oxide, niobium
oxide, boron carbide, tungsten carbide, silicon carbide, aluminum
nitride, silicon nitride, boron nitride, aluminum oxynitride,
silicon oxynitride, silicon oxycarbide, 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.
[0032] The inorganic barrier layer may be applied or 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. Materials suitable for inorganic barrier
layer 18 depend partly on the protective function that it is
intended to play, but glass and inorganic oxides (e.g., oxides of
silicon, aluminum or combinations thereof, such as silicon
monoxide, silicon dioxide, aluminum oxide or silicon aluminum
oxide) are quite useful. Further examples of inorganic barrier
layers useful in this invention include materials fabricated using
Plasma Enhanced Chemical Vapor Deposition (PE-CVD), such as those
described in U.S. Pat. No. 6,696,157 (David).
[0033] In another embodiment, inorganic barrier layer 18 may be
provided by a multilayer construction comprising, for example,
alternating polymeric and inorganic layers. The inorganic layers
may be provided by any of the materials noted above for the
inorganic barrier layer, and the polymeric layers may be, for
example, (meth)acrylates, polyesters, fluorinated polymers,
parylenes, cyclotenes, or polyalkylenes. Multilayer constructions
may be prepared by way of a "PML" (i.e., polymer multilayer)
process, or other techniques in which the layers are applied, as
appropriate, by sputtering, spin-coating, thermal evaporation,
chemical vapor deposition, etc. Suitable examples of multilayer
constructions are described in, for example, U.S. Pat. No.
5,440,446 (Shaw), U.S. Pat. No. 6,497,598 (Affinito), European
Patent Publication No. 0 777 280 A2 (Motorola), WO 01/89006 Al
(Battelle Memorial Institute), and U.S. Patent Publication No.
2002/0068143 (Silvernail, et al.).
[0034] The thickness of inorganic barrier layer 18 will also vary
substantially depending upon the nature of the application for
protected polymeric film 10, moisture/air conditions to which the
protected polymeric film is likely to be exposed during use, other
layers present in protective structure 14, requirements for optical
transparency and mechanical flexibility of the protected polymeric
film, cost, etc. As layer thickness increases, resistance to
moisture transmission will increase, but perhaps at the expense of
reduced transparency, reduced flexibility, and increased cost.
Within these guidelines inorganic barrier layer 18 is provided at
an effective thickness, by which is meant a thickness sufficient to
increase the ability of the polymeric film to resist transmission
of moisture, resist thermal and/or mechanical impact, etc. relative
to the same polymeric film that does not have a protective
structure that includes the inorganic barrier layer. More
specifically, the inorganic barrier layer is preferably provided at
a thickness of about 0.5 .mu.m to 70 .mu.m, more preferably about
1.5 .mu.m to 40 .mu.m, and even more preferably about 3.5 .mu.m to
30 .mu.m.
[0035] The embodiment of protected polymeric film 10 shown in FIG.
1, where boron oxide layer 16 is intermediate inorganic barrier
layer 18 and polymeric film substrate 12 (i.e., encroaching
moisture encounters the inorganic barrier layer before encountering
the boron oxide layer), offers certain advantages. This arrangement
permits boron oxide layer 16 to be deposited in an essentially
continuous layer, but without the need to rigorously avoid forming
pinholes and other similar defects that frequently accompany vapor
deposition and other processes because inorganic barrier layer 18
also resists moisture transmission and is the layer that first
encounters encroaching moisture (relative to the boron oxide
layer). This arrangement also permits boron oxide layer 16 to
provide a "last line of defense" in reducing moisture transmission
by polymeric film substrate 12.
[0036] Turning now to FIG. 2, another embodiment of a protected
polymeric film 10 is illustrated which is similar to the embodiment
of FIG. 1, but offering the further advantage that inorganic
barrier layer 18 encapsulates or seals lateral side edges 16a and
16b of boron oxide layer 16 so as to additionally protect this
layer from being exposed to moisture at its edges. This embodiment
may be particularly useful in higher moisture environments or where
the boron oxide layer 16 is to be made available to only resist the
transmission of moisture that has penetrated inorganic barrier
layer 18.
[0037] The embodiment of FIG. 3 is similar to the embodiment of
FIG. 1 but further comprises a second inorganic barrier layer 20
that is disposed between boron oxide layer 16 and polymeric film
substrate 12. Second inorganic barrier layer 20 is similar to
inorganic barrier layer 18, and the foregoing discussion of
inorganic barrier layer 18 is applicable to second inorganic
barrier layer 20. The embodiment of FIG. 3 offers the additional
advantage of giving enhanced protection to polymeric film substrate
12 as a result of second inorganic barrier layer 20. The embodiment
of FIG. 4 is similar to the embodiment of FIG. 2 but further
comprises a second inorganic barrier layer 20 like that shown in
FIG. 3. Thus, in FIG. 4, inorganic barrier layers 18 and 20
cooperate to encapsulate or seal boron oxide layer 16 so as to
additionally protect this layer from being exposed to moisture at
its edges.
[0038] Turning now to FIG. 5, another embodiment of a protected
polymeric film 10 is presented which is similar to the embodiment
shown in FIG. 1 but further comprising an optional buffer layer 22.
A buffer layer refers to a layer that separates the protective
structure from components or other layers that are secured to or
subsequently formed on the substrate, such components or layers
being generically represented by reference numeral 24 in FIG. 5.
The buffer layer may provide a wide variety of possible functions,
depending upon the use to which the protected polymeric film is
put. For example, the buffer layer may provide a smooth surface on
which components or other layers may be secured or subsequently
formed. It may provide an anchoring or priming layer that improves
the adhesion of subsequently formed or secured components or
layers. The buffer layer may protect any subsequently formed or
secured components or layers from reaction with the inorganic
barrier layer or the boron oxide layer. The buffer layer may
perform an optical function, and may be electrically active.
[0039] The buffer layer may be formed from a wide variety of
materials, both organic and inorganic, and the actual selection
will be influenced by the particular function or functions that the
buffer layer is intended to serve. For example, if electronic
components, or layers that form a portion of an electronic
component, will be formed on or secured to the polymeric film
substrate, materials that are not oxidizing agents, not
hygroscopic, not acidic, and that are non-reactive with the
electronic components or layers might be preferred.
[0040] In one application, protected polymeric films according to
the invention are useful as substrates for supporting organic
electronic components, including organic electroluminescent devices
(e.g., organic light emitting diodes), etc. In this instance, the
buffer layer may be formed of materials used to provide any of the
electrically active layers in such components, such as copper
phthalocyanine (CuPc),
4,4',4''-tris(N-3-methylphenyl-N-phenylamino)triphenylamine
(MTDATA), N,N'-bis(3-naphthalen-2-yl)-N,N'-bis(phenyl)benzidine
(NPD), tris(8-hydroxyquinoline) aluminum (ALQ), gold, silicon
monoxide, etc.
[0041] The thickness of the buffer layer also depends on the
function that the buffer layer is intended to serve, but
thicknesses in the range of about 500 .ANG. to 2,000 .ANG. have
generally been found to be useful.
[0042] FIG. 6 illustrates an embodiment in which both first major
surface 12a and second major surface 12b of polymeric film
substrate 12 have been provided with a protective structure 14
comprising a layer of boron oxide 16 and an inorganic barrier layer
18. The embodiment of FIG. 6 further includes a second inorganic
barrier layer 20 associated with each protective structure,
although it will be understood that the second inorganic barrier
layer is optional and may be excluded from one or both protective
structures. Similarly, while FIG. 6 shows each layer of boron oxide
16 as having been encapsulated by the inorganic barrier layers,
this is only optional.
[0043] Though not shown in the drawings, various functional layers
or coatings can be added to the protected polymeric films of the
invention to alter or improve their physical or chemical
properties, particularly at the surface of the film. Such layers or
coatings may include, for example, visible light-transmissive
conductive layers or electrodes (e.g., of indium tin oxide);
antistatic coatings or films; flame retardants; UV stabilizers;
abrasion resistant or hardcoat materials; optical coatings or
filters; anti-fogging materials; magnetic or magneto-optic coatings
or films; photographic emulsions; prismatic films; holographic
films or images; adhesives such as pressure sensitive adhesives or
hot melt adhesives; primers to promote adhesion to adjacent layers;
and low adhesion backsize materials for use when the barrier
assembly is to be used in adhesive roll form. These functional
components can be incorporated into one or more of the outermost
layers of the barrier assembly or can be applied as a separate film
or coating.
[0044] The invention will now be described with reference to the
following non-limiting examples, in which all parts and percentages
are by weight unless otherwise indicated.
EXAMPLES
[0045] Unless otherwise indicated, the following abbreviations are
used in the examples. TABLE-US-00001 Abbrevi- ation Description
B.sub.2O.sub.3 Boron oxide, 99.9995%, 200 ppm H.sub.2O, available
from Alfa Aesar, Ward Hill, MA as stock# 11160 FTCNQ
Tetrafluoro-tetracyanoquinodimethane available from Tokyo Kasei
Kogyo Co., Tokyo, Japan Al Puratronic aluminum shots, 99.999%,
available from Alfa Aesar, Ward Hill, MA AlQ
Tris(8-hydroxyquinoline) aluminum available from H. W. Sands Corp,
Jupiter, FL C545T Coumarin available from Eastman Kodak Co.,
Rochester, NY as Coumarin 545T SR399 Dipentaaerithritol penta
acrylate available from Sartomer Company, Exton, PA as SR339
.beta.-CEA .beta.-carboxyethyl acrylate available from UCB Radcure
Inc., N. Augusta, SC, as BCEA EHPE3150 Alicyclic epoxy resin
available from Daicel Chemical Industries, Fort Lee, NJ, as
Polyester EHPE3150 Ebecryl Epoxy novolac acrylate available from
UCB Radcure 629 Inc., N. Augusta, SC, as Ebecryl 629 Irgacure
1-hydroxycyclohexyl phenyl ketone available from 184 Ciba Specialty
Chemicals Corporation, Tarrytown, NY, as Irgacure 184 UVI-6974
Triarylsulfonium hexafluoroantimonate available from Ciba Specialty
Chemicals Corporation, Tarrytown, NY, as Cyracure UVI-6974 LiF
Lithium fluoride, 99.85%, available from Alfa Aesar, Ward Hill, MA
as product number 36359 MTDATA
4,4',4''-tris(N-3-methylphenyl-N-phenylamino)tri- phenylamine,
sublimed, available from H. W. Sands Corp., Jupiter, FL, as product
number OSA3939 NPD
N,N'-bis(3-naphthalen-2-yl)-N,N'-bis(phenyl)benzidine available
from H. W. Sands Corp, Jupiter, FL ITO Indium tin oxide Fusion D A
UV lamp available from Fusion UV Systems, UV Lamp Gaithersburg, MD,
under the trade designation F600 Fusion D UV Lamp Fusion H A UV
lamp available from Fusion UV Systems, UV Lamp Gaithersburg, MD,
under the trade designation F600 Fusion H UV Lamp SiAlO Silicon
aluminum oxide OLED Organic light-emitting diode MEK Methyl ethyl
ketone PET Polyethylene terephthalate CAG150 A microgravure coater
available from Yasui Seiki Co. (USA), Bloomington, IN, as Model CAG
150 and fitted with a 110R knurl Ag Silver (target available from
Arconium, Providence RI) Thermo- A hot melt adhesive film available
from 3M Company, bond St. Paul, MN, as Thermo-bond 845-EG with a
thickness 845-EG-2.5 of 2.5 mils HSPE A PET film available from
Teijin Corp., Japan, as HSPE 100 (thickness = 100 microns) or HSPE
50 (thickness = 50 microns) 8141 An optically clear thin film
laminating adhesive Adhesive available from 3M Company, St. Paul,
MN as 3M 8141
[0046] Any materials for which a source has not been identified in
the examples or in the foregoing table may be obtained from Aldrich
Chemical Company, Milwaukee, Wis.
Example 1
[0047] An OLED device incorporating a protected polymeric film
according to the invention was prepared in Example 1. A UV-curable
solution was prepared by combining 80 grams Ebecryl 629, 20 grams
SR399, and 2 grams Irgacurel 84 that had been dissolved in 1000
grams of MEK. The resulting solution was coated onto a roll of 6.5
inch wide HSPE 100 PET film substrate using a CAG 150 microgravure
coater operating at 20 ft/min. The coating was subsequently in-line
dried at 70.degree. C. and then cured under a nitrogen atmosphere
with a Fusion D UV Lamp operating at 100% power. This resulted in a
transparent PET film substrate having an approximately 0.7 .mu.m
thick transparent coating thereon.
[0048] A polymer web mask commercially available from 3M Company
under the trade designation Scotchpak 1220 was die cut and then
thermally laminated to the coated surface of the PET film substrate
using a roll-to-roll laminator. An approximately 35 nm thick layer
of ITO, followed by an approximately 10 nm thick layer of Ag,
followed by another approximately 35 nm thick layer of ITO were
sequentially deposited on the coated surface of the PET film
substrate using a DC sputtering process employing a pressure of 1
mTorr, 1 kW of power, and argon and oxygen flow rates of 150 sccm
and 6 sccm, respectively, for coating the ITO, and an argon flow
rate of 150 sccm for coating the Ag. These coating conditions
resulted in a sheet resistance of 10 ohms/square. The ITO layers
served as anodes and as robust contacts for the cathodes for the
subsequently formed OLED devices.
[0049] The polymer mask was then peeled off resulting in a
conductive pattern on the PET film substrate. A sample of the
conductive patterned substrate measuring 50 mm.times.50 mm was cut
from the roll and contained four pixels each measuring 0.25
cm.sup.2. The sample was ultrasonically cleaned by sonication in a
warm (about 110.degree. F.) detergent solution (Deconex 12 NS,
Borer Chemie, Zuchwil, Switzerland) for about 5 minutes, rinsing in
warm (about 110.degree. F.) deionized water for about 10 min, and
drying in a nitrogen purged oven for at least 4 hours. The
ITO/Ag/ITO surface was then plasma treated for 2 minutes at a
pressure of 300 mTorr, oxygen flow rate of 500 sccm, and RF power
of 400 watts in a plasma treater commercially available from AST,
Inc., Billerica, Mass., under the trade designation Model PS
500.
[0050] A hole-injecting layer (MTDATA:FTCNQ (2.8% doping)) was
vapor deposited at a rate of 1.8 .ANG./s to a thickness of 3,000
.ANG. on top of the conductive pattern on the PET film substrate. A
green emitting OLED stack was then vapor deposited on top of the
hole-injecting layer using thermal evaporation in a vacuum chamber
at about 5.times.10.sup.-6 Torr. More specifically, the OLED stack
was provided by the following sequential depositions over the
hole-injecting layer: NPD (400 .ANG., 1 .ANG./s)/AlQ:C545T(1%
doping, 300 .ANG., 1 .ANG./s)/AlQ(200 .ANG., 1 .ANG./s)/LiF(7
.ANG., 0.5 .ANG./s)/Al(2500 .ANG., 25 .ANG./s).
[0051] The OLED devices were then encapsulated by depositing 3,000
.ANG. of B.sub.2O.sub.3 on top of the device structure layers using
thermal evaporation (about 3-5 .ANG./s) from a tungsten dimple
source (S8A-0.010W, R. D. Mathis, Signal Hill, Calif.) A 2 mil
thick protective copper foil was then thermally laminated at a
temperature of approximately 80.degree. C. using a hand-operated
rubber roller on top of the B.sub.2O.sub.3 layer and with
Thermo-bond 845-EG-2.5. The copper foil was large enough to
encapsulate the emitting areas of the four pixels, but the edges of
the PET film substrate remained exposed to provide a point for
electrical contact. For convenience, this is referred as "OLED
Device A." Device efficiencies for OLED Device A were measured
using a photo-optically corrected silicon photodiode (UDT Sensors,
Hawthorne, Calif.).
[0052] The effect on device efficiency of incorporating a protected
polymeric film according to the invention into OLED Device A was
then assessed.
[0053] A 3,000 .ANG. thick layer of B.sub.2O.sub.3 was deposited on
the surface of the PET film substrate opposite the surface on which
the device structure had been deposited and using the deposition
conditions described above for the previously applied
B.sub.2O.sub.3 layer.
[0054] A multilayer inorganic barrier layer was then prepared by
laminating a pair of multilayer assemblies in face-to-face fashion
with an optical adhesive. Each assembly comprised six alternating
layers of polymer and inorganic material formed on a PET base. When
completed, the laminated multilayer inorganic barrier had the
following construction: PET base/Polymer 1/SiAlO/Polymer
2/SiAlO/Polymer 2/SiAlO/Optical Adhesive/SiAlO/Polymer
2/SiAlO/Polymer 2/SiAlO/Polymer 1/PET base. Each assembly was
formed as described in the following paragraphs.
[0055] PET base+Polymer 1 ("Layer 1"). HSPE 50 PET base film was
coated with a UV-curable solution that was prepared by mixing 145.5
grams Ebecryl 629, 37.5 grams .beta.-CEA, and 9.03 grams Irgacure
184 that had been dissolved in 972 grams MEK using a CAG-150
microgravure coater operating at 6.1 m/min. The coating was cured
using a Fusion H UV Lamp running at 100% power to provide Polymer
1.
[0056] SiAlO Layer ("Layer 2"). The PET base film coated with
Polymer 1 (i.e., Layer 1) was then loaded into a roll-to-roll
sputter coater and the deposition chamber was pumped down to a
pressure of 2.times.10.sup.-6 Torr. A 60 nm thick SiAlO inorganic
oxide layer was deposited atop Polymer 1 by reactively sputtering a
Si-Al target (90%-10% Si--Al target commercially available from
Academy Precision Materials, Albuquerque, N.M.) using 2 kW and
600V, a gas mixture containing 51 sccm argon and 30 sccm oxygen at
a pressure of 1 mTorr, and a web speed of 0.43 m/min.
[0057] Polymer 2 ("Layer 3"). Using the conditions described for
the application and curing of Polymer 1 but with the CAG 150
microgravure coater operating at a speed of 4.6 m/min, the
previously applied SiAlO layer was overcoated with a UV-curable
solution that was prepared by combining 2.25 grams UVI-6974, 42.75
grams EHPE3150 in 405 grams MEK, and then cured to provide Polymer
2.
[0058] Using the same conditions as for Layer 2 and Layer 3,
respectively, a second SiAlO layer was deposited atop Layer 3 to
form Layer 4, a second layer of Polymer 2 was coated atop Layer 4
to form Layer 5, and a third layer of SiAlO was deposited atop
Layer 5 to form Layer 6, thereby providing an assembly having a PET
base/Polymer 1/SiAlO/Polymer 2/SiAlO/Polymer 2/SiAlO
configuration.
[0059] The resulting assembly was split into two rolls and
laminated together in face-to-face fashion using 8141 Adhesive and
a two-roll laminator to form a multilayer inorganic barrier.
[0060] The multilayer inorganic barrier was then laminated to the
exposed B.sub.2O.sub.3 layer with 8141 Adhesive thereby completing
the incorporation of a protected polymeric film into OLED device A.
Device efficiencies were measured again and using the same
procedure as employed previously. Incorporating a protected
polymeric film according to the invention into OLED Device A did
not significantly change the efficiency of the resulting
device.
Example 2
[0061] An OLED device incorporating a protected polymeric film
according to the invention was prepared in Example 2. Additional
samples of OLED Device A from Example 1 were prepared and the
copper foil was edge sealed using a thin bead of epoxy (Araldite
2014 available from Huntsman LLC, Advanced Materials Division,
Vantico, East Lansing, Mich.). The epoxy was allowed to cure to
hardness over 12 hours in a N.sub.2 atmosphere at room temperature.
For convenience, this is referred to as "OLED Device B."
[0062] An inorganic barrier layer was then prepared according to
the following procedure. A UV-curable polymer solution was prepared
by combining 2.25 grams UVI-6974 with 42.75 grams EHPE3150 in 405
grams MEK. The resulting solution was coated onto a 6.5 inch wide,
100 micron thick fluorine polyester film commercially available
from Ferrania Imaging Technologies, Italy, under the trade
designation Arylite using a CAG 150 microgravure coater operating
at a speed of 15 ft/min. The coating was subsequently in-line dried
at 70.degree. C. and then cured under a nitrogen atmosphere with a
Fusion D UV Lamp operating at 100% power. This resulted in a
transparent film having an approximately 0.7 .mu.m thick
transparent coating thereon.
[0063] The coated film was loaded into a sputter coater and the
deposition chamber was pumped down to a pressure of
2.times.10.sup.-6 Torr. A 60 nm thick SiAlO inorganic oxide layer
was deposited using 370 W and 375 V, a gas mixture containing 20
sccm argon and 18 sccm oxygen at a pressure of 6 mTorr, and a web
speed of 7 inches/minute. A 90/10 target of Si/Al available from
Applied Precision Materials, Albuquerque, N.M. was used as the
target material.
[0064] Inorganic barrier layers were then incorporated into
previously prepared samples of OLED Device B to form, respectively,
OLED Device B1 and OLED Device B2.
[0065] OLED Device B1 was prepared by depositing a 3,000 .ANG.
thick layer of B.sub.2O.sub.3 on the surface of the PET film
substrate opposite the surface on which the device structure had
been built. The B.sub.2O.sub.3 was deposited using thermal
evaporation (.about.3-5 .ANG./second) from a tungsten dimple source
(S8A-0.010W, R.D. Mathis, Signal Hill, Calif.). The previously
prepared inorganic barrier layer was then laminated over the
exposed B.sub.2O.sub.3 layer using 8141 Adhesive and a two-roll
laminator to complete OLED Device B1.
[0066] OLED Device B2 was prepared by laminating the previously
prepared inorganic barrier layer to the "front side" surface of the
PET film substrate (i.e., the surface opposite the surface on which
the device structure had been build) by using 8141 Adhesive and a
roll-to-roll laminator. Thus, OLED Device B2 differed from OLED
Device B1 in that it lacked the B.sub.2O.sub.3 layer used on the
front side of OLED Device B1.
[0067] The samples (OLED Device B1 and OLED Device B2) were stored
under ambient conditions. Photographs of the lit devices (i.e.,
OLED Device B1 and OLED Device B2) were taken periodically to
compare dark spot growth. Samples of OLED Device B2 (i.e., without
B.sub.2O.sub.3 on the front side) showed significantly more dark
spot growth over time than samples of OLED Device B1 having the
B.sub.2O.sub.3 layer on the front side.
[0068] The invention is amenable to various modifications and
alternative forms, specifics thereof having been shown by way of
example in the foregoing drawings and description. It will be
understood, however, that the invention is not limited to these
particular embodiments. On the contrary, the intention is to cover
all modifications, equivalents and alternatives falling within the
spirit and scope of the invention, which is defined by the appended
claims. Various modifications and equivalent processes, as well as
numerous structures to which the present invention may be
applicable, will be readily apparent to those of skill in the art
to which the present invention is directed.
* * * * *