U.S. patent application number 11/383504 was filed with the patent office on 2006-09-07 for lighting apparatus with flexible oled area illumination light source and fixture.
Invention is credited to Ronald S. Cok.
Application Number | 20060197456 11/383504 |
Document ID | / |
Family ID | 29419622 |
Filed Date | 2006-09-07 |
United States Patent
Application |
20060197456 |
Kind Code |
A1 |
Cok; Ronald S. |
September 7, 2006 |
LIGHTING APPARATUS WITH FLEXIBLE OLED AREA ILLUMINATION LIGHT
SOURCE AND FIXTURE
Abstract
Lighting apparatus includes a solid-state area illumination
light source, having: a planar flexible substrate, a flexible
organic light emitting diode (OLED) layer deposited on the flexible
substrate, the organic light emitting diode layer including first
and second electrodes for providing electrical power to the OLED
layer, a flexible encapsulating cover covering the OLED layer, and
first and second conductors electrically connected to the first and
second electrodes, and extending beyond the encapsulating cover for
making electrical contact to the first and second electrodes by an
external power source, whereby the light source may be stored in a
space saving planar configuration; and a lighting fixture for
removably receiving and holding the light source in a curved 3
dimensional configuration, the lighting fixture including a support
for holding the light source in the curved configuration and
contacts for providing electrical contact between said first and
second conductors and an external power source.
Inventors: |
Cok; Ronald S.; (Rochester,
NY) |
Correspondence
Address: |
Paul A. Leipold;Patent Legal Staff
Eastman Kodak Company
343 State Street
Rochester
NY
14650-2201
US
|
Family ID: |
29419622 |
Appl. No.: |
11/383504 |
Filed: |
May 16, 2006 |
Related U.S. Patent Documents
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Application
Number |
Filing Date |
Patent Number |
|
|
10776749 |
Feb 11, 2004 |
7075226 |
|
|
11383504 |
May 16, 2006 |
|
|
|
10156396 |
May 28, 2002 |
6771021 |
|
|
10776749 |
Feb 11, 2004 |
|
|
|
Current U.S.
Class: |
315/56 |
Current CPC
Class: |
Y02B 20/36 20130101;
H01R 12/721 20130101; F21S 6/004 20130101; Y02B 20/30 20130101;
H01L 2251/5338 20130101; F21S 8/04 20130101; H01L 2251/5361
20130101; F21V 19/0005 20130101; F21Y 2115/15 20160801; F21S 6/002
20130101; F21Y 2105/00 20130101; H01L 51/524 20130101; F21K 9/232
20160801; F21S 6/00 20130101; F21V 3/00 20130101; F21S 6/005
20130101 |
Class at
Publication: |
315/056 |
International
Class: |
H01J 13/46 20060101
H01J013/46 |
Claims
1. A lighting fixture for removably receiving and holding a
flexible planar light source in a curved three-dimensional
configuration, the light source including first and second
electrical conductors, comprising: a) a support for holding the
flexible planar light source in the curved configuration; and b)
contacts for providing electrical contact between said first and
second conductors and an external power source.
2. The lighting fixture claimed in claim 1, wherein the curved
configuration is cylindrical, spiral, or pyramidal.
3. The lighting fixture claimed in claim 1, wherein the external
power source is a standard power source.
4. The lighting fixture claimed in claim 2, wherein the standard
power is selected from the group consisting of 110 volt AC, 220
volt AC, 24 volt DC, 12 volt DC, and 6 volt DC.
5. The lighting fixture claimed claim 1, further comprising a
transparent or translucent housing surrounding the light
source.
6. The lighting fixture claimed in claim 1, further comprising a
base adapted to be received by and make electrical contact with a
standard electrical outlet.
7. The lighting fixture claimed in claim 1, further comprising a
converter connected to the first and second conductors for
converting power from the external power source to a form useable
by the planar light source.
8. The lighting fixture claimed in claim 7, wherein the converter
converts AC line voltage to a voltage useable by the planar light
source.
9. The lighting fixture claimed in claim 1, further comprising a
reflector for directing light from the light source.
10. The lighting fixture claimed in claim 1, wherein the lighting
fixture is a ceiling lamp.
11. The lighting fixture claimed in claim 1, wherein the lighting
fixture is a table lamp.
12. The lighting fixture claimed in claim 1, wherein the lighting
fixture is a floor lamp.
13. The lighting fixture claimed in claim 1, wherein the planar
light source has a rectangular shape and the support includes
clamps for holding two edges of the light source to bow the light
source into a cylindrical configuration.
14. The lighting fixture claimed in claim 13, wherein the contacts
are located in the clamps.
15. The lighting fixture claimed in claim 1 wherein the planar
light source has an elongated rectangular shape and the support
includes a frame and clamps for holding the planar light source in
a spiral configuration about the frame.
16. The lighting fixture claimed in claim 15, wherein the contacts
are located in the clamps.
17. The lighting fixture claimed in claim 1, wherein the planar
light source has the shape of a ring segment, and the support
includes clamps for holding the light source in a conical
configuration.
18. The lighting fixture claimed in claim 17, wherein the contacts
are located in the clamps.
Description
CROSS REFERENCE TO RELATED APPLICATIONS
[0001] This application is a divisional of application Ser. No.
10/776,749, filed Feb. 11, 2004, which is a divisional of
application Ser. No. 10/156,396, filed May 28, 2002.
FIELD OF THE INVENTION
[0002] The present invention relates to the use of organic light
emitting diodes for area illumination.
BACKGROUND OF THE INVENTION
[0003] Solid-state lighting devices made of light emitting diodes
are increasingly useful for applications requiring robustness and
long-life. For example, solid-state LEDs are found today in
automotive applications. These devices are typically formed by
combining multiple, small LED devices providing a point light
source into a single module together with glass lenses suitably
designed to control the light as is desired for a particular
application (see, for example WO99/57945, published Nov. 11, 1999).
These multiple devices are expensive and complex to manufacture and
integrate into single area illumination devices. Moreover, LED
devices provide point sources of light that are not preferred for
area illumination.
[0004] Conventional illumination devices such as incandescent or
fluorescent light bulbs are bulky, fragile, and problematic to
handle and ship. Although the bulbs are filled with gas, the glass
tubes are easily broken and occupy substantial space, especially in
comparison to the actual light emitting area or material of the
device. The bulbs must be carefully packed and require a large
volume for shipping.
[0005] Existing solid-state lighting elements may be planar and
hence easy and cost-effective to ship but do not address the need
for lighting elements that have a variety of conventional
three-dimensional shapes as found, for example, in light bulbs for
decorative lighting. It is also useful if a lighting device is
readily and safely replaced by consumers at minimal cost.
[0006] There is a need therefore for an improved, replaceable OLED
area illumination device having a simple construction using a
single substrate, is compatible with the existing lighting
infrastructure, is efficient to ship, and provides a variety of
three-dimensional shapes.
SUMMARY OF THE INVENTION
[0007] The need is met by providing lighting apparatus that
includes a solid-state area illumination light source, having: a
planar flexible substrate, a flexible organic light emitting diode
(OLED) layer deposited on the flexible substrate, the organic light
emitting diode layer including first and second electrodes for
providing electrical power to the OLED layer, a flexible
encapsulating cover covering the OLED layer, and first and second
conductors electrically connected to the first and second
electrodes, and extending beyond the encapsulating cover for making
electrical contact to the first and second electrodes by an
external power source, whereby the light source may be stored in a
space saving planar configuration; and a lighting fixture for
removably receiving and holding the light source in a curved 3
dimensional configuration, the lighting fixture including a support
for holding the light source in the curved configuration and
contacts for providing electrical contact between said first and
second conductors and an external power source.
ADVANTAGES
[0008] The present invention has the advantage of providing a
lighting apparatus having a light source that can be stored
efficiently in a planar configuration, thereby saving considerable
storage space. Another advantage is that the planar flexible light
sources are not fragile and can be packaged in thin, unpadded
packaging.
BRIEF DESCRIPTION OF THE DRAWINGS
[0009] FIG. 1 illustrates a partial cross section of a prior art
conventional OLED illumination device;
[0010] FIG. 2 is a perspective view of a flexible area illumination
light source, including a detail of the layer structure, according
to one embodiment of the present invention;
[0011] FIG. 3 is a perspective view of the flexible light source of
FIG. 2 shown in a curved configuration;
[0012] FIG. 4 is a perspective view of a lighting fixture for
holding the light source of FIG. 3 in its curved configuration;
[0013] FIG. 5 is a top view of the lighting fixture and light
source showing clips for holding the light source in the curved
configuration;
[0014] FIG. 6 is a perspective view of a light source and lighting
fixture according to an alternative embodiment of the present
invention;
[0015] FIG. 7 is a perspective view of an alternative embodiment of
a light source useable according to the present invention;
[0016] FIG. 8 is a perspective view of a further alternative
embodiment of a light source useable according to the present
invention;
[0017] FIG. 9 is a perspective view of a lighting fixture holding a
plurality of flexible light sources according to a further
alternative embodiment of the present invention;
[0018] FIG. 10 is a perspective view of a light source held in a
spiral configuration according to the present invention;
[0019] FIG. 11 is a perspective view of a light source held in a
conical configuration according to the present invention;
[0020] FIG. 12 is a perspective view of a light source and lighting
fixture having a standard base.
[0021] FIG. 13 is a perspective view of lighting apparatus
according to the present invention including a light transmissive
housing according to one embodiment of the present invention;
[0022] FIG. 14 is a perspective view of a stack of flexible light
sources according to the present invention; and
[0023] FIG. 15 is a cross sectional view of an OLED light source as
known in the prior art.
[0024] It will be understood that the figures are not to scale
since the individual layers are too thin and the thickness
differences of various layers too great to permit depiction to
scale.
DETAILED DESCRIPTION OF THE INVENTION
[0025] FIG. 1 is a schematic diagram of a prior art OLED light
source 10 including an organic light emitting layer 12 disposed
between two electrodes, e.g. a cathode 14 and an anode 16. The
organic light emitting layer 12 emits light upon application of a
voltage from a power source 18 across the electrodes. The OLED
light source 10 typically includes a substrate 20 such as glass or
plastic. It will be understood that the relative locations of the
anode 16 and cathode 14 may be reversed with respect to the
substrate. The term OLED light source refers to the combination of
the organic light emitting layer 12, the cathode 14, the anode 16,
and other layers described below.
[0026] Referring to FIG. 2, a solid-state area illumination light
source, includes a planar flexible substrate 20, a flexible organic
light emitting diode (OLED) layer 12 deposited on the flexible
substrate, the organic light emitting diode layer including first
and second electrodes 14 and 16 for providing electrical power to
the OLED layer, a flexible encapsulating cover 30 covering the OLED
layer, first and second conductors 24 and 26 electrically connected
to the first and second electrodes, and extending beyond the
encapsulating cover 30 for making electrical contact to the first
and second electrodes 14 and 16 by an external power source,
whereby the light source may be stored in a space saving planar
configuration. The encapsulating cover may be a coated layer or an
additional layer of material affixed over the OLED layers and
sealed at the edges of the devices. Light may be emitted either
through the substrate or the cover, or both, if they are
transparent. The OLED layers themselves are continuous over the
substrate to form a single contiguous light-emitting area. As shown
in FIG. 3, the flexible substrate 20 can be curved into a three
dimensional form and, as shown in FIG. 4, inserted into an aperture
36 in a lighting fixture 34 for removably receiving and holding the
light source 10 in a curved three-dimensional configuration. The
lighting fixture includes a support 38 having clips 39 for holding
the light source in the curved configuration, and contacts 40
within the aperture 36 for providing electrical contact between the
first and second conductors and an external power source.
[0027] The support 38 may be transparent. In one embodiment of the
present invention, the flexible substrate 20 can define a tab
portion 21 that may include an orientation feature such as step 28
to insure that the light source is inserted in the fixture in the
correct orientation. The tab portion 21 can be inserted into the
aperture 36 of the fixture 34 and the light source 10 shaped around
the support 38. Alternatively, additional contacts may be included
in the aperture or on either side of the flexible substrate using
conductive vias to provide electrical contact with the conductors
regardless of the orientation in which the tab is inserted (not
shown).
[0028] The flexible substrate 20 may be fastened to the support 38
with, for example, an adhesive, hook loop fasteners, or a
mechanical restraint such as a clip or detent. In applications
where it is not required to emit light from both sides of the
substrate, one or more of the substrate, cover, anode, or cathode
may be opaque or reflective. The light source 10 may be physically
inserted into or removed from the fixture by pushing or pulling the
substrate 20 into or out of the aperture 36.
[0029] FIG. 5 shows a top view of the support 38 with clips 39 for
holding edges of the light source 10. To install the light source
10 in fixture 34, the tab portion 21 is first inserted into the
aperture 36. Next, the light source 10 is wrapped around the
support 38 and the edges of the flexible light source 10 are
inserted under clips 39 as shown by arrow A.
[0030] Referring to FIG. 6, in another embodiment, the flexible
substrate 20 may define two tabs 21 and 22. The first and second
conductors 24 and 26 are each located on a respective tab portion
and structured to fit into complementary apertures 36 and 36' in a
fixture 34. The fixture 34 includes one or more fins 41 for
supporting the flexible light source 10.
[0031] Referring to FIG. 7 in a further embodiment, the substrate
20 does not define a physical protrusion but includes first and
second conductors 24 and 26 located on an edge of the substrate 20.
FIG. 8 illustrates an alternative arrangement wherein the first and
second conductors 24 and 26 are at opposite edges of the substrate
20. In the embodiments shown in FIGS. 7 and 8, the apertures in the
lighting fixture are wide enough to receive the entire edge of the
substrate. Alternatively, the support can include clamps for
holding two or more edges of the light source to bow the light
source into a three-dimensional configuration, for example a
cylindrical configuration. The contacts in the lighting fixture may
be located in the clamps. A wide variety of other configurations
are readily designed, including rings or conical sections.
[0032] Referring to FIG. 9, an alternative fixture and support are
shown wherein two light sources 10 are held in a common fixture 34.
The half cylinder configurations shown in FIGS. 6 and 9 are useful,
for example, for under-shelf lighting.
[0033] FIG. 10 illustrates another embodiment wherein the body of
the light source 10 has an elongated rectangular shape and is held
in a spiral configuration by the fixture 34. Clips 39 are provided
at both ends of the spiral for holding the light source. FIG. 11
shows an embodiment wherein the light source 10 is held in the
shape of a cone by fixture 34.
[0034] Referring to FIG. 4, the lighting fixture 34 can be adapted
to connect the OLED light source 10 to an external power source
(such as a standard household electrical grid, not shown). The
fixture 34 may include power-conditioning circuitry 50 to convert
the electrical power from the external power source to a form
suitable for powering the OLED light source 10. For example, the
OLED light source 10 may require a rectified voltage with a
particular waveform and magnitude; the power conditioning circuitry
can provide the particular waveform using conventional power
control circuitry. The particular waveform may periodically reverse
bias the light emitting organic materials to prolong the life time
of the OLED materials. The fixture may also include a switch (not
shown) for controlling the power to the light source.
[0035] The brightness of the light source 10 may be controlled by
varying the power provided to the OLED. In particular, pulse-width
modulation schemes well known in the art may be employed (see for
example, EP1094436A2, published Apr. 25, 2001) and implemented by
the power conditioning circuitry 50. Alternatively, the amount of
power provided to the light emitting area may be reduced, for
example by reducing the voltage or limiting the current supplied to
the OLED. A brightness control switch may be integrated into the
socket, for example with variable resistance switch formed. The
power source may be standard 110 volt AC as found in North America,
220 volt AC as found in Europe, or other standard power
configurations such as 24-, 12-, or 6-volt DC.
[0036] The OLED light source 10 can be provided as a standard
element and fixtures 34 customized to markets with differing power
systems. OLED light sources 10 may be provided with different
shapes or other attributes useful in specific applications and may
be employed with a common socket, thereby decreasing costs and
improving usefulness of the lighting apparatus.
[0037] Referring to FIG. 12, the lighting fixture 34 may include a
support portion 38 and a standard light bulb base 44 such as a US
standard screw type lamp base as shown in FIG. 12, or a pin-type
base (not shown). A wide variety of standard lamp bases are known
in the prior art and may be used with the fixture of the present
invention.
[0038] Referring to FIG. 13, a transparent or translucent screen or
housing 52 may be provided around the OLED light source 10 to
diffuse the light and provide additional physical protection and
cosmetic appeal. The housing may take a variety of shapes, for
example the shape of a standard light bulb.
[0039] Referring to FIG. 14, the flexible light sources 10 may be
stacked and packed in a planar configuration for compact storage
and shipment. This compact packing arrangement significantly
reduces the packing volume necessary for traditional bulbs and
provides a robust, sturdy means for storing, transporting, and
stocking the lighting light sources 10.
[0040] The present invention may be employed in a wide variety of
conventional applications, for example in a table-top lamp,
floor-lamp, ceiling lamp, or chandelier. The present invention may
also be employed in portable illumination devices using DC power
sources.
[0041] In a preferred embodiment, the Organic Light Emitting Diode
layers (OLED layers) are composed of small molecule OLEDs as
disclosed in but not limited to U.S. Pat. No. 4,769,292, issued
Sep. 6, 1988 to Tang et al., and U.S. Pat. No. 5,061,569, issued
Oct. 29, 1991 to VanSlyke et al.
OLED Element Architecture
[0042] There are numerous configurations of OLED elements wherein
the present invention can be successfully practiced. A typical,
non-limiting structure is shown in FIG. 15 and is comprised of an
anode layer 103, a hole-injecting layer 105, a hole-transporting
layer 107, a light-emitting layer 109, an electron-transporting
layer 111, and a cathode layer 113. These layers are described in
detail below. The total combined thickness of the organic layers is
preferably less than 500 nm. A voltage/current source 250 is
required to energize the OLED element and conductive wiring 260 is
required to make electrical contact to the anode and cathode. The
TFT layers and associated wiring serve these functions.
Substrate
[0043] Substrate 20 is preferably light transmissive but may also
be opaque. Substrates for use in this case include, but are not
limited to, very thin glass and plastics.
Anode
[0044] The anode layer 103 is preferably transparent or
substantially transparent to the light emitted by the OLED
layer(s). Common transparent anode materials used in this invention
are indium-tin oxide (ITO), indium-zinc oxide (IZO) and tin oxide,
but other metal oxides can work including, but not limited to,
aluminum- or indium-doped zinc oxide, magnesium-indium oxide, and
nickel-tungsten oxide. In addition to these oxides, metal nitrides,
such as gallium nitride, and metal selenides, such as zinc
selenide, and metal sulfides, such as zinc sulfide, can be used in
layer 103. When the anode is not transparent, the light
transmitting characteristics of layer 103 are immaterial and any
conductive material can be used, transparent, opaque or reflective.
Example conductors for this application include, but are not
limited to, gold, iridium, molybdenum, palladium, and platinum.
Typical anode materials, transmissive or otherwise, have a work
function of 4.1 eV or greater. Desired anode materials are commonly
deposited by any suitable means such as evaporation, sputtering,
chemical vapor deposition, or electrochemical means. Anodes can be
patterned using well-known photolithographic processes.
Hole-Injecting Layer (HIL)
[0045] It is often useful that a hole-injecting layer 105 be
provided between anode 103 and hole-transporting layer 107. The
hole-injecting material can serve to improve the film formation
property of subsequent organic layers and to facilitate injection
of holes into the hole-transporting layer. Suitable materials for
use in the hole-injecting layer include, but are not limited to,
porphyrinic compounds as described in U.S. Pat. No. 4,720,432, and
plasma-deposited fluorocarbon polymers as described in U.S. Pat.
No. 6,208,075. Alternative hole-injecting materials reportedly
useful in organic EL devices are described in EP 0 891 121 A1 and
EP 1 029 909 A1.
Hole-Transporting Layer (HTL)
[0046] The hole-transporting layer 107 contains at least one
hole-transporting compound such as an aromatic tertiary amine,
where the latter is understood to be a compound containing at least
one trivalent nitrogen atom that is bonded only to carbon atoms, at
least one of which is a member of an aromatic ring. In one form the
aromatic tertiary amine can be an arylamine, such as a
monoarylamine, diarylamine, triarylamine, or a polymeric arylamine.
Exemplary monomeric triarylamines are illustrated by Klupfel et al.
U.S. Pat. No. 3,180,730. Other suitable triarylamines substituted
with one or more vinyl radicals and/or comprising at least one
active hydrogen containing group are disclosed by Brantley et al
U.S. Pat. No. 3,567,450 and U.S. Pat. No. 3,658,520. A more
preferred class of aromatic tertiary amines are those which include
at least two aromatic tertiary amine moieties as described in U.S.
Pat. No. 4,720,432 and U.S. Pat. No. 5,061,569. Illustrative of
useful aromatic tertiary amines include, but are not limited to,
the following:
[0047] 1,1-Bis(4-di-p-tolylaminophenyl)cyclohexane
[0048] 1,1-Bis(4-di-p-tolylaminophenyl)-4-phenylcyclohexane
[0049] 4,4'-Bis(diphenylamino)quadriphenyl
[0050] Bis(4-dimethylamino-2-methylphenyl)-phenylmethane
[0051] N,N,N-Tri(p-tolyl)amine
[0052]
4-(di-p-tolylamino)-4'-[4(di-p-tolylamino)-styryl]stilbene
[0053] N,N,N',N'-Tetra-p-tolyl-4-4'-diaminobiphenyl
[0054] N,N,N',N'-Tetraphenyl-4,4'-diaminobiphenyl
[0055] N,N,N',N'-tetra-1-naphthyl-4,4'-diaminobiphenyl
[0056] N,N,N',N'-tetra-2-naphthyl-4,4'-diaminobiphenyl
[0057] N-Phenylcarbazole
[0058] 4,4'-Bis[N-(1-naphthyl)-N-phenylamino]biphenyl
[0059] 4,4'-Bis[N-(1-naphthyl)-N-(2-naphthyl)amino]biphenyl
[0060] 4,4''-Bis[N-(1-naphthyl)-N-phenylamino]p-terphenyl
[0061] 4,4'-Bis[N-(2-naphthyl)-N-phenylamino]biphenyl
[0062] 4,4'-Bis[N-(3-acenaphthenyl)-N-phenylamino]biphenyl
[0063] 1,5-Bis[N-(1-naphthyl)-N-phenylamino]naphthalene
[0064] 4,4'-Bis[N-(9-anthryl)-N-phenylamino]biphenyl
[0065] 4,4''-Bis[N-(1-anthryl)-N-phenylamino]-p-terphenyl
[0066] 4,4'-Bis [N-(2-phenanthryl)-N-phenylamino]biphenyl
[0067] 4,4'-Bis[N-(8-fluoranthenyl)-N-phenylamino]biphenyl
[0068] 4,4'-Bis[N-(2-pyrenyl)-N-phenylamino]biphenyl
[0069] 4,4'-Bis[N-(2-naphthacenyl)-N-phenylamino]biphenyl
[0070] 4,4'-Bis[N-(2-perylenyl)-N-phenylamino]biphenyl
[0071] 4,4'-Bis[N-(1-coronenyl)-N-phenylamino]biphenyl
[0072] 2,6-Bis(di-p-tolylamino)naphthalene
[0073] 2,6-Bis[di-(1-naphthyl)amino]naphthalene
[0074] 2,6-Bis[N-(1-naphthyl)-N-(2-naphthyl)amino]naphthalene
[0075] N,N,N',N'-Tetra(2-naphthyl)-4,4''-diamino-p-terphenyl
[0076] 4,4'-Bis
{N-phenyl-N-[4-(1-naphthyl)-phenyl]amino}biphenyl
[0077] 4,4'-Bis[N-phenyl-N-(2-pyrenyl)amino]biphenyl
[0078] 2,6-Bis[N,N-di(2-naphthyl)amine]fluorene
[0079] 1,5-Bis[N-(1-naphthyl)-N-phenylamino]naphthalene
[0080] Another class of useful hole-transporting materials includes
polycyclic aromatic compounds as described in EP 1 009 041. In
addition, polymeric hole-transporting materials can be used such as
poly(N-vinylcarbazole) (PVK), polythiophenes, polypyrrole,
polyaniline, and copolymers such as
poly(3,4-ethylenedioxythiophene)/poly(4-styrenesulfonate) also
called PEDOT/PSS.
Light-Emitting Layer (LEL)
[0081] As more fully described in U.S. Pat. Nos. 4,769,292 and
5,935,721, the light-emitting layer (LEL) 109 of the organic EL
element comprises a luminescent or fluorescent material where
electroluminescence is produced as a result of electron-hole pair
recombination in this region. The light-emitting layer can be
comprised of a single material, but more commonly consists of a
host material doped with a guest compound or compounds where light
emission comes primarily from the dopant and can be of any color.
The host materials in the light-emitting layer can be an
electron-transporting material, as defined below, a
hole-transporting material, as defined above, or another material
or combination of materials that support hole-electron
recombination. The dopant is usually chosen from highly fluorescent
dyes, but phosphorescent compounds, e.g., transition metal
complexes as described in WO 98/55561, WO 00/18851, WO 00/57676,
and WO 00/70655 are also useful. Dopants are typically coated as
0.01 to 10% by weight into the host material. Iridium complexes of
phenylpyridine and its derivatives are particularly useful
luminescent dopants. Polymeric materials such as polyfluorenes and
polyvinylarylenes (e.g., poly(p-phenylenevinylene), PPV) can also
be used as the host material. In this case, small molecule dopants
can be molecularly dispersed into the polymeric host, or the dopant
could be added by copolymerizing a minor constituent into the host
polymer.
[0082] An important relationship for choosing a dye as a dopant is
a comparison of the bandgap potential which is defined as the
energy difference between the highest occupied molecular orbital
and the lowest unoccupied molecular orbital of the molecule. For
efficient energy transfer from the host to the dopant molecule, a
necessary condition is that the band gap of the dopant is smaller
than that of the host material.
[0083] Host and emitting molecules known to be of use include, but
are not limited to, those disclosed in U.S. Pat. No. 4,769,292,
U.S. Pat. No. 5,141,671, U.S. Pat. No. 5,150,006, U.S. Pat. No.
5,151,629, U.S. Pat. No. 5,405,709, U.S. Pat. No. 5,484,922, U.S.
Pat. No. 5,593,788, U.S. Pat. No. 5,645,948, U.S. Pat. No.
5,683,823, U.S. Pat. No. 5,755,999, U.S. Pat. NO. 5,928,802, U.S.
Pat. No. 5,935,720, U.S. Pat. No. 5,935,721, and U.S. Pat. No.
6,020,078.
[0084] Metal complexes of 8-hydroxyquinoline and similar oxine
derivatives constitute one class of useful host compounds capable
of supporting electroluminescence, and are particularly suitable.
Illustrative of useful chelated oxinoid compounds are the
following: [0085] CO-1: Aluminum trisoxine [alias,
tris(8-quinolinolato)aluminum(III)] [0086] CO-2: Magnesium bisoxine
[alias, bis(8-quinolinolato)magnesium(II)] [0087] CO-3:
Bis[benzo{f}-8-quinolinolato]zinc (II) [0088] CO-4:
Bis(2-methyl-8-quinolinolato)aluminum(III)-.mu.-oxo-bis(2-methyl-8-quinol-
inolato)aluminum(III) [0089] CO-5: Indium trisoxine [alias,
tris(8-quinolinolato)indium] [0090] CO-6: Aluminum
tris(5-methyloxine) [alias,
tris(5-methyl-8-quinolinolato)aluminum(III)] [0091] CO-7: Lithium
oxine [alias, (8-quinolinolato)lithium(I)] [0092] CO-8: Gallium
oxine [alias, tris(8-quinolinolato)gallium(III)] [0093] CO-9:
Zirconium oxine [alias, tetra(8-quinolinolato)zirconium(IV)]
[0094] Other classes of useful host materials include, but are not
limited to: derivatives of anthracene, such as
9,10-di-(2-naphthyl)anthracene and derivatives thereof,
distyrylarylene derivatives as described in U.S. Pat. No.
5,121,029, and benzazole derivatives, for example,
2,2',2''-(1,3,5-phenylene)tris[1-phenyl-1H-benzimidazole].
[0095] Useful fluorescent dopants include, but are not limited to,
derivatives of anthracene, tetracene, xanthene, perylene, rubrene,
coumarin, rhodamine, quinacridone, dicyanomethylenepyran compounds,
thiopyran compounds, polymethine compounds, pyrilium and
thiapyrilium compounds, fluorene derivatives, periflanthene
derivatives and carbostyryl compounds.
Electron-Transporting Layer (ETL)
[0096] Preferred thin film-forming materials for use in forming the
electron-transporting layer 111 of the organic EL elements of this
invention are metal chelated oxinoid compounds, including chelates
of oxine itself (also commonly referred to as 8-quinolinol or
8-hydroxyquinoline). Such compounds help to inject and transport
electrons, exhibit high levels of performance, and are readily
fabricated in the form of thin films. Exemplary oxinoid compounds
were listed previously.
[0097] Other electron-transporting materials include various
butadiene derivatives as disclosed in U.S. Pat. No. 4,356,429 and
various heterocyclic optical brighteners as described in U.S. Pat.
No. 4,539,507. Benzazoles and triazines are also useful
electron-transporting materials.
[0098] In some instances, layers 111 and 109 can optionally be
collapsed into a single layer that serves the function of
supporting both light emission and electron transport. These layers
can be collapsed in both small molecule OLED systems and in
polymeric OLED systems. For example, in polymeric systems, it is
common to employ a hole-transporting layer such as PEDOT-PSS with a
polymeric light-emitting layer such as PPV. In this system, PPV
serves the function of supporting both light emission and electron
transport.
Cathode
[0099] Preferably, the cathode 113 is transparent and can comprise
nearly any conductive transparent material. Alternatively, the
cathode 113 may be opaque or reflective. Suitable cathode materials
have good film-forming properties to ensure good contact with the
underlying organic layer, promote electron injection at low
voltage, and have good stability. Useful cathode materials often
contain a low work function metal (<4.0 eV) or metal alloy. One
preferred cathode material is comprised of a Mg:Ag alloy wherein
the percentage of silver is in the range of 1 to 20%, as described
in U.S. Pat. No. 4,885,221. Another suitable class of cathode
materials includes bilayers comprising a thin electron-injection
layer (EIL) and a thicker layer of conductive metal. The EIL is
situated between the cathode and the organic layer (e.g., ETL).
Here, the EIL preferably includes a low work function metal or
metal salt, and if so, the thicker conductor layer does not need to
have a low work function. One such cathode is comprised of a thin
layer of LiF followed by a thicker layer of Al as described in U.S.
Pat. No. 5,677,572. Other useful cathode material sets include, but
are not limited to, those disclosed in U.S. Pat. Nos. 5,059,861;
5,059,862, and 6,140,763.
[0100] When cathode layer 113 is transparent or nearly transparent,
metals must be thin or transparent conductive oxides, or a
combination of these materials. Optically transparent cathodes have
been described in more detail in U.S. Pat. No. 4,885,211, U.S. Pat.
No. 5,247,190, JP 3,234,963, U.S. Pat. NO. 5,703,436, U.S. Pat. No.
5,608,287, U.S. Pat. No. 5,837,391, U.S. Pat. No. 5,677,572, U.S.
Pat. No. 5,776,622, U.S. Pat. No. 5,776,623, U.S. Pat. No.
5,714,838, U.S. Pat. No. 5,969,474, U.S. Pat. No. 5,739,545, U.S.
Pat. No. 5,981,306, U.S. Pat. No. 6,137,223, U.S. Pat. No.
6,140,763, U.S. Pat. No. 6,172,459, EP 1 076 368, and U.S. Pat. No.
6,278,236. Cathode materials are typically deposited by
evaporation, sputtering, or chemical vapor deposition. When needed,
patterning can be achieved through many well known methods
including, but not limited to, through-mask deposition, integral
shadow masking as described in U.S. Pat. No. 5,276,380 and EP 0 732
868, laser ablation, and selective chemical vapor deposition.
Deposition of Organic Layers
[0101] The organic materials mentioned above are suitably deposited
through a vapor-phase method such as sublimation, but can be
deposited from a fluid, for example, from a solvent with an
optional binder to improve film formation. If the material is a
polymer, solvent deposition is useful but other methods can be
used, such as sputtering or thermal transfer from a donor sheet.
The material to be deposited by sublimation can be vaporized from a
sublimator "boat" often comprised of a tantalum material, e.g., as
described in U.S. Pat. No. 6,237,529, or can be first coated onto a
donor sheet and then sublimed in closer proximity to the substrate.
Layers with a mixture of materials can utilize separate sublimator
boats or the materials can be pre-mixed and coated from a single
boat or donor sheet. Patterned deposition can be achieved using
shadow masks, integral shadow masks (U.S. Pat. No. 5,294,870),
spatially-defined thermal dye transfer from a donor sheet (U.S.
Pat. Nos. 5,851,709 and 6,066,357) and inkjet method (U.S. Pat. No.
6,066,357). While all organic layers may be patterned, it is most
common that only the layer emitting light is patterned, and the
other layers may be uniformly deposited over the entire device.
Optical Optimization
[0102] OLED layers used with this invention can employ various
well-known optical effects in order to enhance its properties if
desired. This includes optimizing layer thicknesses to yield
maximum light transmission, providing dielectric mirror structures,
replacing reflective electrodes with light-absorbing electrodes,
providing anti-glare or anti-reflection coatings over the device,
providing a polarizing medium over the device, or providing
colored, neutral density, or color conversion filters over the
device. Filters, polarizers, and anti-glare or anti-reflection
coatings may be specifically provided over the cover or as part of
the cover.
[0103] The invention has been described in detail with particular
reference to certain preferred embodiments thereof, but it will be
understood that variations and modifications can be effected within
the spirit and scope of the invention.
PARTS LIST
[0104] 10 OLED light source [0105] 12 organic light emitting layer
[0106] 14 cathode [0107] 16 anode [0108] 18 power source [0109] 20
substrate [0110] 21 tab portion of substrate [0111] 22 tab portion
of substrate [0112] 30 encapsulating cover [0113] 24 first
conductor [0114] 26 second conductor [0115] 28 step [0116] 34
lighting fixture [0117] 36 aperture [0118] 36' aperture [0119] 38
support [0120] 39 clip [0121] 40 contact [0122] 41 light source
support fin [0123] 44 standard lamp base [0124] 50 power
conditioning circuitry [0125] 52 light transmissive housing [0126]
103 anode [0127] 105 hole-injecting layer [0128] 107
hole-transporting layer [0129] 109 light-emitting layer [0130] 111
electron-transporting layer [0131] 113 cathode layer [0132] 250
voltage/current source [0133] 260 conductive wiring
* * * * *