U.S. patent application number 11/860143 was filed with the patent office on 2008-03-06 for phototherapy bandage.
This patent application is currently assigned to University of Florida Research Foundation, Inc.. Invention is credited to James Boncella, PAUL H. Holloway, Gary McGuire, John Reynolds, Kirk S. Schanze, Olga A. Shenderova.
Application Number | 20080058689 11/860143 |
Document ID | / |
Family ID | 32507883 |
Filed Date | 2008-03-06 |
United States Patent
Application |
20080058689 |
Kind Code |
A1 |
Holloway; PAUL H. ; et
al. |
March 6, 2008 |
PHOTOTHERAPY BANDAGE
Abstract
A phototherapy bandage capable of providing radiation to a
localized area of a patient for accelerating would healing and pain
relief, photodynamic therapy, and for aesthetic applications. The
phototherapy bandage may include a flexible light source that is
continuous across the bandage for providing a selected light, such
as a visible light, a near-infrared light, or other light, having
substantially similar intensity across the bandage. The bandage may
also be flexible and capable of being attached to a patient without
interfering with the patient's daily routine. The phototherapy
bandage may easily conform to the curves of a patient and may come
in a variety of exterior shapes and sizes.
Inventors: |
Holloway; PAUL H.;
(Gainesville, FL) ; McGuire; Gary; (Chapel Hill,
NC) ; Shenderova; Olga A.; (Raleigh, NC) ;
Reynolds; John; (Gainesville, FL) ; Schanze; Kirk
S.; (Gainesville, FL) ; Boncella; James;
(Gainesville, FL) |
Correspondence
Address: |
AKERMAN SENTERFITT
P.O. BOX 3188
WEST PALM BEACH
FL
33402-3188
US
|
Assignee: |
University of Florida Research
Foundation, Inc.
Gainesville
FL
32611
International Technology Center
Raleigh
NC
27617
|
Family ID: |
32507883 |
Appl. No.: |
11/860143 |
Filed: |
September 24, 2007 |
Related U.S. Patent Documents
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Application
Number |
Filing Date |
Patent Number |
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10732086 |
Dec 10, 2003 |
7304201 |
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11860143 |
Sep 24, 2007 |
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10170942 |
Jun 12, 2002 |
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10732086 |
Dec 10, 2003 |
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60432284 |
Dec 10, 2002 |
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Current U.S.
Class: |
602/42 ;
607/88 |
Current CPC
Class: |
A61N 5/0616 20130101;
A61N 5/062 20130101; A61N 2005/0653 20130101; A61N 2005/0645
20130101; A61N 2005/065 20130101; A61F 15/00 20130101 |
Class at
Publication: |
602/042 ;
607/088 |
International
Class: |
A61N 5/06 20060101
A61N005/06; A61F 13/00 20060101 A61F013/00 |
Claims
1. A phototherapeutic bandage, comprising: a base formed from a
flexible substrate; a thin film flexible electroluminescent source
coupled to the base and extending continuously across at least a
portion of the base for emitting radiation to a target area on a
patient; and wherein the bandage is capable of conforming to a
surface area of the target area.
2. The phototherapeutic bandage of claim 1, further comprising an
adhesive layer having a first and second side, wherein the first
side of the adhesive layer is attached to the base and the second
side is for fastening said bandage to a target area on a
patient.
3. The phototherapeutic bandage of claim 1, wherein said
electroluminescent source is a single continuous film having an
area which substantially covers the base and said continuous film
area is adapted to emit substantially uniform radiation across the
base.
4. The phototherapeutic bandage of claim 1, further comprising an
optically transparent moisture barrier layer over the
electroluminescent source.
5. The phototherapeutic bandage of claim 1, wherein said
electroluminescent source is an inorganic electroluminescent source
and comprises an electroluminescent layer positioned between two
transparent insulators, wherein the two transparent insulators are
positioned between two electrodes.
6. The phototherapeutic bandage of claim 5, wherein the two
transparent insulators are selected from the group consisting of
ZnS, SrS, ZnGa.sub.2O.sub.4, ZnSiO.sub.4, CaSSe, CaS, and silicon
oxynitride.
7. The phototherapeutic bandage of claim 5, wherein the two
transparent insulators are selected from the group consisting of
ATO and barium tantalate.
8. The phototherapeutic bandage of claim 5, wherein the
electroluminescent layer is selected from the group consisting of
Mn, Cu, Ce, Nd, Sm, Eu, Tb, Tm, Er, and Nd and as sulfides, halide
compounds and complexes such as oxy-compounds.
9. The phototherapeutic bandage of claim 5, wherein the
electroluminescent layer is selected from the group consisting of
Ag in SrS, and Cu with Ag in SrS for a blue EL phosphor.
10. The phototherapeutic bandage of claim 5, wherein the two
electrodes are selected from the group consisting of aluminum,
indium tin oxide and nickel-cobalt spinel oxide.
11. The phototherapeutic bandage of claim 5, wherein the
electroluminescent layer is pixilated and capable of producing
radiation in a plurality of narrowband wavelengths.
12. The phototherapeutic bandage of claim 5, wherein said inorganic
electroluminescent source comprises zinc sulfide doped with at
least one lanthanide.
13. The phototherapeutic bandage of claim 1, wherein said
electroluminescent source is an organic electroluminescent source
and comprises an electroluminescent layer positioned between two
electron injection layers, wherein the two electron injection
layers are positioned between two electrodes.
14. The phototherapeutic bandage of claim 1, wherein said
electroluminescent source is formed from a luminescent polymer and
a metal containing compound, wherein the metal containing compound
comprises a metal-ligand complex, wherein the adsorption spectrum
of the metal-ligand complex at least partially overlaps with the
emission spectrum of the luminescent polymer such that when the
luminescent polymer becomes electronically excited, energy is
transformed from the luminescent polymer to the metal-ligand
complex, wherein at least a portion of the energy transferred from
the luminescent polymer to the metal-ligand complex is emitted by
the metal-ligand complex as near-infrared radiation.
15. A phototherapeutic bandage, comprising: a base formed from a
flexible substrate; an adhesive layer having a first and second
side, wherein the first side of the adhesive layer is attached to
the base and the second side is for fastening said bandage to a
target area on a patient; a single, continuous, thin film, flexible
electroluminescent source coupled to the base and extending
continuously across at least a portion of the base for emitting
radiation to the target area on a patient; wherein the bandage is
capable of conforming to a surface area of a body to be treated;
and wherein the electroluminescent source is capable of producing
near-infrared light.
16. The phototherapeutic bandage of claim 15, further comprising an
optically transparent moisture barrier layer over the
electroluminescent source.
17. The phototherapeutic bandage of claim 15, wherein said
electroluminescent source is an inorganic electroluminescent source
and comprises an electroluminescent layer positioned between two
transparent insulators, wherein the two transparent insulators are
positioned between two electrodes.
18. The phototherapeutic bandage of claim 17, wherein the
electroluminescent layer is selected from the group consisting of
ZnS, SrS, ZnGa.sub.2O.sub.4, ZnSiO.sub.4, CaSSe, and CaS.
19. The phototherapeutic bandage of claim 15, wherein said
electroluminescent source is an organic electroluminescent source
and comprises an electroluminescent layer positioned between two
electron injection layers, wherein the two electron injection
layers are positioned between two electrodes.
20. The phototherapeutic bandage of claim 15, wherein said
electroluminescent source is formed from a luminescent polymer and
a metal containing compound, wherein the metal containing compound
comprises a metal-ligand complex, wherein the adsorption spectrum
of the metal-ligand complex at least partially overlaps with the
emission spectrum of the luminescent polymer such that when the
luminescent polymer becomes electronically excited, energy is
transformed from the luminescent polymer to the metal-ligand
complex, wherein at least a portion of the energy transferred from
the luminescent polymer to the metal-ligand complex is emitted by
the metal-ligand complex as near-infrared radiation.
Description
CROSS-REFERENCE TO RELATED APPLICATION
[0001] This is a continuation application of U.S. application Ser.
No. 10/732,086, filed Dec. 10, 2003, which is a
continuation-in-part of U.S. application Ser. No. 10/170,942, filed
Jun. 12, 2002, and which claims the priority benefit of U.S.
Provisional Application No. 60/432,284, filed Dec. 10, 2002.
FIELD OF THE INVENTION
[0002] The invention is directed generally to phototherapy, and
more particularly, to methods and devices for administering
radiation to a targeted site on a patient.
BACKGROUND
[0003] Phototherapy is the therapeutic use of light that has been
recognized as an effective method of treating wounds and reducing
pain in humans. External phototherapy has been effective in
treating various medical conditions, such as, but not limited to,
bulimia nervosa, herpes, psoriasis, seasonal affective disorder,
sleep disorders, acne, skin cancer, hyperbilirubinemia in infants,
and other conditions. Phototherapy is typically administered to a
patient using a light source consisting of either a bank of lights,
referred to as a light bank, or a fiber optic light source. Some of
the first phototherapy light sources included light banks
positioned over incubators or open bassinets, or under hoods or
transparent supports. Typically, the light sources used in
phototherapy consist of fluorescent tubes, metal halide lamps, or
light-emitting diodes (LEDs).
[0004] While light sources having light banks are still being used,
such devices are not without their disadvantages. For instance,
phototherapy devices using light banks require that patients wear
eye protection that is often uncomfortable. These devices also
require that patients remain relative stationary while receiving
treatment. Furthermore, these devices are typically large and
immobile, which thus, require patients to visit the locations of
the light sources each time a dosage is needed. Light sources using
light banks are disadvantageous for at least these reasons.
[0005] Fiber optic light sources were developed as a substitute for
phototherapy devices containing light banks but have not eliminated
all of the drawbacks associated with these devices. For instance,
while the fiber optic lights are more mobile than light bank
devices, the fiber optic lights typically deliver lower overall
amounts of light than the light banks. Additionally, fiber optic
lights are often used in conjunction with fiber optic mats having
specific geometries. Often times, the geometries of the fiber optic
mats are compromised when forces are placed on the fiber optic mats
in order to place the fiber optic mats in contact with patients'
skin surfaces. This undesirably results in greater light intensity
being concentrated near the light source than at other portions of
the fiber optic mat.
[0006] LEDs are typically used as light sources for phototherapy.
For instance, U.S. Pat. Nos. 6,290,713 and 6,096,066 describe
flexible mats having a plurality of LEDs positioned in arrays that
are coupled to a plurality of conductive traces for emitting light.
The LEDs are point sources that do not emit light over a broad
area, but rather over a narrow area. Light produced by the LEDs is
diffused and made more uniform by placing diffusers in the mats
near the LEDs. Without the diffusers, the arrays of LEDs are simply
collections of point sources. Because diffusers are used, the LEDs
cannot be placed in contact with a surface. Instead, the thickness
of the diffuser limits the proximity with which the LEDs may be
positioned proximate to a surface. Thus, the amount of light that
an LED emits is not the same amount of light that reaches the
surface because a portion of the light produced by the LED is lost
when the LED is not placed in contact with a surface.
[0007] LEDs produce a single wavelength of light. If more than one
wavelength of light is required, more than one type of LED must be
used. In order to operate the LEDs, the mats contain numerous
conductors to provide power to each LED individually. These
conductors significantly add to the overall weight and complexity
of the mats.
[0008] The mats are made even more complex with the addition of
channels for dissipating heat. Use of the plurality of LEDs in such
close proximity to each other produces high amounts of heat that
can pose potentially dangerous conditions. This heat is typically
vented from the devices using channels between the LEDs. While the
channels do allow a portion of the heat produced by the LEDs to be
vented from the mat, not all of the heat generated is removed.
[0009] Thus, a need exists for a phototherapy device that delivers
light in a more efficient manner while retaining the advantages of
a flexible mat.
SUMMARY OF THE INVENTION
[0010] According to one aspect of this invention, the phototherapy
bandage is a self-contained device that is formed from a base and
at least one light source for emitting radiation and directing it
toward a targeted location on a patient, which is defined to be a
human or an animal. In at least one embodiment, the phototherapy
bandage is flexible and capable of conforming to a patient, and
more specifically, is capable of being coupled to an exterior skin
surface of a patient. In one embodiment, the light source may be an
electroluminescent (EL) device, which may be an organic or
inorganic electroluminescent device.
[0011] The EL device may be capable of emitting radiation at
different wavelengths, such as all wavelengths forming visible
light, including red light, near-infrared radiation (NIR or
near-IR), and mid-infrared radiation. The EL device is capable of
providing illumination within a limited wavelength range to a
target area from one to tens of square centimeters. The EL light
source can be tailored to emit wavelengths from visible light to
near-infrared light by co-doping or by using multilayered EL
structures. A single EL light source can be used to treat a range
of conditions and can be fabricated to control flux and dose.
[0012] The EL light source may be coupled to the base using any
connection mechanism, and in one embodiment, the base may be
coupled to at least one light source using an adhesive. The
adhesive may also be used to couple the phototherapy bandage to a
patient. The base may also include a moisture barrier for
preventing moisture from contacting the light source.
[0013] The phototherapy bandage may also include one or more
batteries, which may or may not be rechargeable, for powering the
light source. The phototherapy bandage may further have one or more
microprocessors for controlling operation of the light source. The
microprocessor may operate the light source continuously or
intermittently depending on a variety of factors. The phototherapy
bandage may further include a moisture barrier positioned on the
light source to prevent the light source, the microprocessor, and
the battery from contacting a fluid. The phototherapy bandage may
be used for aesthetic applications and for photodynamic
therapy.
[0014] An advantage of this invention is that the phototherapy
bandage is flexible and capable of being attached to a patient to
accelerate wound healing and providing pain relief without
interfering with the patient's daily activities.
[0015] Another advantage of this invention is that the light source
is capable of being extended across the healing area of the bandage
so that when used the selected wavelength of light, which may be,
visible light, near-IR light, or longer wavelength IR light, may be
emitted in a relatively uniform manner towards the intended healing
surface.
[0016] Another advantage of this invention is that the phototherapy
bandage is a self-contained device that is easy to carry and
wear.
[0017] Yet another advantage of this invention is that the
phototherapy bandage may be self-applied by the patient.
[0018] Another advantage of this invention is that the phototherapy
bandage is portable and is relatively small, which enables the
bandage to be packed in various hand bags, backpacks, hiking
equipment, luggage and other storage devices.
[0019] Still another advantage of this invention is that the
phototherapy bandage may be contained in a moisture resistant
package and applied to a patient when necessary.
[0020] Another advantage of this invention is that the phototherapy
bandage may be used for a relatively long duration when used with
rechargeable batteries.
[0021] Yet another advantage of this invention is that the EL
source is capable of emitting both visible and NIR wavelengths.
[0022] Another advantage of this invention is that the EL source
can emit multiple NIR wavelengths at wavelengths that are known to
have therapeutic benefits in wound healing and pain relief.
[0023] Still another advantage of this invention is that the EL
source may be formed from one or more layers or pixels that allow
sequential or simultaneous emission of light at different
wavelengths.
[0024] Another advantage of this invention is that the EL source is
capable of operating at or below freezing temperatures.
[0025] Yet another advantage of this invention is that the EL
source may be operated using low voltage.
[0026] Another advantage of this invention is that the EL source is
capable of emitting a uniform emission without use of
diffusers.
[0027] Another advantage of this invention is that the EL source is
rugged and capable of absorbing the stresses commonly placed on a
bandage.
[0028] These and other features and advantages of the present
invention will become apparent after review of the following
drawings and detailed description of the disclosed embodiments.
BRIEF DESCRIPTION OF THE DRAWINGS
[0029] The accompanying drawings, which are incorporated in and
form a part of the specification, illustrate preferred embodiments
of the presently disclosed invention(s) and, together with the
description, disclose the principles of the invention(s). These
several illustrative figures include the following:
[0030] FIG. 1 is an artistic rendering of an exemplary embodiment
of a phototherapy bandage;
[0031] FIG. 2 is a schematic diagram of a side view of a
phototherapy bandage of this invention;
[0032] FIG. 3 is a schematic diagram of the chemical structure of
MEH-PPV;
[0033] FIG. 4 is a schematic diagram of the chemical structure for
Ln(TPP)acac;
[0034] FIG. 5 shows an EL spectrum of MEH-PPV doped with 5 mol %
Yb(TPP)acac measured at 9V and of MEH-PPV doped with 5 mol %
Er(TPP)acac at 13V;
[0035] FIG. 6 is a cross-sectional view of a thin film
electroluminescent light source;
[0036] FIG. 7 is a cross sectional view of another thin film
electroluminescent light source;
[0037] FIG. 8 is an exemplary pixel pattern for a first TFEL panel
consistent with certain embodiments of the present invention;
and
[0038] FIG. 9 is an exemplary pixel pattern for a second TFEL panel
consistent with certain embodiments of the present invention.
DETAILED DESCRIPTION
[0039] The phototherapy bandage 10 of this invention is capable of
providing radiation to a localized area of a patient, who may be a
human or animal, for accelerating wound healing and pain relief. In
addition, phototherapy bandage 10 may also be used for photodynamic
therapy and for aesthetic applications. In one embodiment,
phototherapy bandage 10 is flexible and capable of being attached
to a patient without interfering with the patient's daily routine.
Phototherapy bandage 10 may easily conform to the curves of a
patient and may come in a variety of exterior shapes and sizes.
[0040] The term "phototherapy", as used herein is intended to
embrace both phototherapy and photodynamic therapy. The term
"infrared" as used herein is intended to encompass the range of
light spectrum above approximately 650 nm and includes regions
often termed "near-infrared" and includes "mid-infrared."
"Transparency" as used herein is defined as passing a substantial
portion of light at a wavelength of interest, while "reflectivity"
is similarly defined as reflective of a substantial portion of
light at a wavelength of interest. The term Thin Film
Electroluminescence (TFEL) as used herein should be interpreted to
mean electroluminescent (EL) devices that are made of stacked
layers that are substantially planar in that the thickness of their
essential light creation components is much smaller than their
other dimensions. This term is intended to embrace inorganic high
field EL devices as well as organic light emitting devices (OLEDs)
(whether a dopant is used in the active layer or not), which can be
made with major dimensions ranging from millimeters to several
inches and beyond. The term TFEL specifically excludes conventional
inorganic semiconductor laser and conventional inorganic
semiconductor diode devices such as LEDs and LDs (which may broadly
fall within certain definitions of EL sources). The term TFEL also
clearly specifically excludes incandescent lamps, fluorescent lamps
and electric arcs. The term EL as used herein, is generally
intended to mean TFEL. The term "dopant" as used herein can mean a
dopant atom (generally a metal) as well as metal complexes and
metal-organic compounds used as an impurity within the active layer
of a TFEL device. Some of the organic-based TFEL active layers may
not contain dopants. The term LED as used herein is intended to
mean conventional inorganic (e.g., doped compound semiconductor
based) semiconductor light emitting diodes. The term "OLED" is
intended to exclude such conventional inorganic semiconductor LEDs,
even though an OLED is often referred to as a type of organic based
light emitting diode.
[0041] In one embodiment, as shown in FIGS. 1 and 2, phototherapy
bandage 10 is composed of one or more flexible light sources 12
that are coupled to a base 14. In at least one embodiment, a single
light source 12 may be employed. Phototherapy bandage 10 may
further include an adhesive 16 coupled to base 14 for attaching
phototherapy bandage 10 to a patient. Phototherapy bandage 10 may
also include a battery 18 and a microprocessor 20 that may control
light source 12. Battery 18 may be coupled to microprocessor 20
using any conventional devices, such as, but not limited to, one or
more insulated electrically conductive wires. Battery 18 may be a
conventional battery that is rechargeable or not and sized
proportionally to be attached to base 14, as shown in FIG. 2.
Battery 18 may be flexible and may have a thickness of about 0.5 mm
with 1.5 volts at 2.5 m Ah/cm.sup.2. Multiple batteries may be used
to achieve the desired voltage. Microprocessor 20 may be
programmable and capable of controlling the operation of light
source 12 in many ways. Microprocessor 20 may be integrated with a
panel to select or set the optical protocols, which will allow
different doses, frequencies and times of exposure.
[0042] In one or more embodiments, light source 12 may be a light
source that is itself flexible and capable of emitting light in a
substantially similar intensity across the bandage 10. For
instance, the light source 12 may be, but is not limited to being,
an electroluminescent device (EL) spread across a substantial
portion of the base 14. The light source 12 may include only two
electrodes that need to be connected to a battery 18, rather than
the plurality of conductors used with arrays of LEDs. This minimal
number of conductors used in this invention reduces manufacturing
costs and complexity of the bandage 12 and enhances its
reliability. In one embodiment, the light source 12 may be a thin
film EL (TFEL) device. The EL light source 12 may be capable of
emitting light at both visible and NIR wavelengths. In addition,
light source 12 may be capable of emitting radiation substantially
uniformly over a targeted area of a patient without the use of
diffusers. The EL device may be configured to emit a single
wavelength or multiple wavelengths of light. The EL device may have
one or more layers capable of being activated separately or
together and have compositions that produce two or more different
emissions. The two or more layers may be turn on separately or
simultaneously.
[0043] The EL device forming light source 12 may be an inorganic
electroluminescent light source, as described in more detail below.
For instance, the EL device may be formed from zinc sulfide doped
with one or more lanthanide elements, such as, but not limited to,
neodymium, samarium, terbium, dysprosium, holmium, erbium, thulium,
and ytterbium. The inorganic EL may include a thin layer of zinc
sulfide doped with a lanthanide sandwiched between two insulator
films. The lanthanide concentration may be between about 0.1% and
about 2.0%, and the two insulator films may be made of silicon
oxynitride. The inorganic EL may include a reflecting electrode on
a back surface of the device and a transparent electrode on the
front surface of the device. The El device forming light source 12
may also be an organic light source such as, but not limited to,
the light sources described in more detail below.
[0044] Base 14 may be configured to be attached to a patient and
conform to the contours of the patient's outer skin surface or
other surface. In another embodiment, base 14 is configured to be
placed in close proximity to a patient, but not in contact with the
patient. Base 14 may be any flexible material that is capable of
conforming to the exterior shape of human and animal bodies and may
include, but is not limited to, biocompatible polymers or plastics.
Base 14 also forms an illuminating surface from which radiation
leaves phototherapy bandage 10.
[0045] Phototherapy bandage 10 may include one or more barriers 15
attached to the top portion of base 14. Barrier 15 may prevent
moisture from contacting battery 18 and microprocessor 20. In
addition, barrier 15 may be reflective so that light produced by
light source 12 is reflected and does not pass through barrier
15.
[0046] Adhesive 16 may be coupled to one or more sides of base 14.
Adhesive 16 may be applied intermittingly or may be applied to
cover an entire side of base 14. In one embodiment, adhesive 16 is
applied in strips to base 14. Adhesive 16 may be any conventional
adhesive and preferably has sufficient strength to keep
phototherapy bandage 10 in contact with a patient while not having
too much strength such that phototherapy bandage 10 cannot be
removed from the patient. As shown in FIG. 2, adhesive 16 may be
located between base 14 and light source 12.
[0047] Phototherapy bandage 10 may include a barrier 22 coupled to
light source 12 for preventing moisture from contacting light
source 12. Barrier 22 may be photon transparent. Phototherapy
bandage 10 may include wound dressing 24 coupled to a bottom
surface of the bandage 10. Wound dressing 24 may also be photon
transparent and sterile.
[0048] Phototherapy bandage 10 may be coupled to a patient by
another person or may be self-administered by the patient. In
addition, phototherapy bandage 10 may be stored in a moisture
resistant package that may be easily packaged together with a first
aid kit or packaged separately for outdoorsmen and others.
[0049] During use, phototherapy bandage 10 is coupled to a surface
of a patient. The patient may attach phototherapy bandage 10 to
himself or herself, or phototherapy bandage may be attached by
someone else. The phototherapy bandage 10 may be coupled to the
wound site for any amount of time depending on whether the bandage
is being used for pain relief or tissue healing. In one embodiment,
phototherapy bandage 10 is attached to a skin surface from three to
ten days. While phototherapy bandage 10 is attached to a patient,
the bandage may emit light continuously or intermittently, or both.
The therapy process may be controlled by microprocessor 20.
Electroluminescent Light Sources
[0050] The light source may be formed from electroluminescent
materials capable of producing visible light, near-infrared
(near-IR) radiation, and longer wavelength radiation, such as
mid-infrared radiation. In at least one embodiment, the
electroluminescent materials may be formed from a luminescent
polymer and a metal containing compound where the metal containing
compound incorporates a metal-ligand complex such that the
absorption spectrum of the metal-ligand complex at least partially
overlaps with the emission spectrum of the luminescent polymer. As
the absorption spectrum of the metal-ligand complex at least
partially overlaps with the emission spectrum of the luminescent
polymer when the luminescent polymer becomes electronically
excited, energy can be transferred from the luminescent polymer to
the metal-ligand complex. At least a portion of the energy
transferred from the luminescent polymer to the metal-ligand
complex can then be emitted by the metal-ligand complex as
near-infrared radiation. Conjugated polymers that are luminescent
can be utilized.
[0051] In one embodiment, where the electroluminescent material may
be a luminescent polymer and a metal-containing compound where the
metal-containing compound incorporates a metal-ligand complex, the
absorption spectrum of the ligand of the metal-ligand complex at
least partially overlaps with the emission spectrum of the
luminescent polymer such that when the luminescent polymer becomes
electronically excited, energy is transferred from the luminescent
polymer to the ligand. Energy can then be transferred from the
ligand to the metal by sensitization. The energy transferred to the
metal by sensitation may then be emitted as near-IR radiation or
other radiation.
[0052] The energy transferred from the luminescent polymer to the
metal-ligand complex or from the luminescent polymer to the ligand
can be transferred by one or more mechanisms including, but not
limited to, Forster transfer and/or Dexter transfer. The
luminescent polymer can become electronically excited upon the
creation of excitons in the luminescent polymer by, for example,
the application of an electric current through the luminescent
polymer and/or exposing the luminescent polymer to photons. Once
created, the excitons within the luminescent polymer can be mobile
within the luminescent polymer. At least a portion of these mobile
excitons may then be trapped by the metal, or metal-ligand complex,
within the luminescent polymer.
[0053] In another embodiment, the metal-containing compound can be
a metal organic compound. In at least one embodiment, the
metal-containing compound may include a lanthanide as the metal.
The metal-containing compound that includes a lanthanide may also
include one or more ligands, which may be, but is not limited to
being, a macrocyclic chelator, which is strongly light absorbing.
The metal compounds that may be used are metals that include
lanthanides such as, but not limited to, Yb.sup.+3, Dy, Nd, Ho, Pr,
Er.sup.+3, or Tm, sulfides, and halide compounds and complexes such
as oxy-compounds. The metal compounds may also be oxomolybdenum(IV)
complexes, such as [MoOCL(CN-t-Bu).sub.4].sup.+ and related
compounds, or Pt-Pd stacked complex such as [Pt(NC-R).sub.4.sup.2-]
and related compounds.
[0054] Ligands that may be utilized may include, but are not
limited to, the entire family of light absorbing organic compounds
that are known to bind to metal ions by chelation, coordinate
covalent bonding, or other binding mechanisms. Specific examples
include (1) tetraaryl porphyrins, wherein the aryl group may, or
may not, be substituted with alkyl, alkyl ether, oligoether, alkyl
sulfonate, alkyl amine, and/or other substituent groups or atoms,
such as 5, 10, 15, 20-tetraphenylporphyrin, (2) octaalkyl
porphyrins including octaethyl porphyrin, (3) chlorophyls,
bacteriochlorophyls, chlorins, and other naturally and unnaturally
occurring tetrapyrroler macrocycles, (4) texaphyins and related
substituted and unsubstituted pentapyrrole macrocycles, (5)
phthalocyanines, naphthophthalocyanines, and other
structurally-related substituted and unsubstituted
phthalocyanines.
[0055] Polymers that may be utilized may include, but are not
limited to, the entire family of conjugated polymers including (1)
those that are fully conjugated, (2) those that include broken
links of conjugation, and (3) those that incorporate copolymers of
either block or random nature. The polymers and copolymers may have
structures that include backbone, side chains, graft, branch,
hyperbranched, and/or dendritic. Examples of conjugated polymers
that may be used, include, but are not limited to: [0056] 1.
Poly(arylenes) include polyphenylenes, polyfluorenes, and
polyanthracenes. Hydrocarbon aromatic polymers that have high
efficiency of light emission may also be used. [0057] 2.
Poly(arylene vinylene)s including aromatic hydrocarbon arylenes
such as poly(phenylene vinylene), poly(anthracenylene vinylene) and
other aryl linked vinylene-based polymers. Hydrocarbon
vinylene-based polymers that have a high efficiency of light
emission may also be used. Poly(arylene vinylene)s where the
arylene unit is heterocyclic in nature, including poly(thienylene
vinylene) and/or poly(pyridine vinylene), known for their
red-shifted luminescence relative to PPV's and
oxadiazole-containing polymers, known for their enhanced electron
transport carrying capabilities.
[0058] 3. Poly(heterocycle)s including poly(thiophene)s, known for
their enhanced hole transporting capabilities and poly(furans).
All of the polymer families can be functionalized to provide
processability through solubility and fusibility. Substituent
groups include but are not limited to alkyl, alkyl ether,
oligoether, alkyl sulfonate, alkyl amine, and other groups.
[0059] Near-IR photoluminescence (PL) and/or electroluminescence
(EL) can be achieved from blends of MEH-PPV with Yb(TPP)acac and/or
Er(TPP)acac. FIG. 3 shows the structure for MEH-PPV and FIG. 4
shows the structure for Ln(TPP)acac, where Ln=Yb.sup.3+, TPP=5, 10,
15, 20-tetraphenylporphyrin, and acac=acetylacetonate. These
materials may involve sensitization of a lanthanide-TPP complex by
a conjugated polymer, which can lead to the narrow bandwidth
emission derived from, for example,
Yb.sup.2F.sub.7/2.fwdarw..sup.2F.sub.7/2 (977 nm) and/or
Er.sup.4I.sub.15/2.fwdarw.I.sub.15/2 (1560 nm) transitions. A
variety of lanthanides may be used to provide tunable PL and EL
throughout the near-IR region. For instance, Yb- and Er-TPP(acac)
complexes can provide emission at 977 nm and 1560 nm,
respectively.
[0060] The efficiency of the luminescence from lanthanides may be
increased by complexing the ions with a ligand-chromophore that can
serve to more efficiently harvest the energy and sensitize the
lanthanide's emission, for example, by exchanging energy transfer
from the ligand-based triplet state. The TPP ligand has a high
degree of spectral overlap of its Q-absorption bands with the
MEH-PPV fluorescence allowing, for example, highly efficient
Forster energy transfer. Due to the excellent spectral overlap,
addition of Yb(TPP)acac or Er(TPP)acac to MEH-PPV can lead to
efficient quenching of the fluorescence from the conjugated polymer
host. Furthermore, in lanthanide porphyrin complexes, intersystem
crossing to the triplet state can occur with high efficiency, which
may approach 100% in some embodiments. The ligand can also act as
an effective sensitizer to produce the spin-forbidden, luminescent
F-states of the lanthanide ions.
[0061] The electroluminescence material may be formed from a 100 nm
thick spin-coated film produced by blending Yb(TPP)acac or
Er(TPP)acac with MEH-PPV. FIG. 5 illustrates the photoluminescence
of neat MEH-PPV (.about.) and MEH-PPV doped with 2 mol %
Yb(TPP)acac (-)based on polymer repeat unit), upon excitation at
350 nm. The spectrum of the blend is plotted on the same absolute
scale as that of the neat polymer, with the y-scale of the inset
expended by a factor of 100. The MEH-PPV fluorescence that appears
at 589 nm is quenched approximately 98% when Yb(TPP)acac is
present. Quenching of the visible emission may be accompanied by
the appearance of the Yb emission at 977 nm in the near-IR. An
excitation spectrum for the 977 nm emission shows a strong band
that id due to the visible absorption of the host polymer,
demonstrating its role as a sensitizer. Analogous results can be
observed when Er(TPP)acac is blended into MEH-PPV, with the near-IR
emission appearing at 1560 nm.
[0062] In at least one embodiment, the near-IR electroluminescent
light source may be formed from an indium-tin-oxide (ITO) glass
coated with PEDOT/PSS (Bayer Baytrom P VP A1 4083) as a hole
transport layer. The MEH-PPV:Ln(TPP)acac blend may be spin coated
from solution (1% wt of the polymer in toluene) and the resulting
film vacuum dried from 12 hours (1.times.10.sup.-6 torr) at room
temperature. Calcium (50 .ANG.) followed by A1 (1500 .ANG.) layers
may then be thermally evaporated at 1.times.10.sup.-6 Torr without
breaking the vacuum between the metal depositions. After
deposition, the light source may be encapsulated with epoxy to
minimize exposure to oxygen and moisture.
[0063] The light source 12 may also be a light source for
phototherapy or photodynamic therapy that can be positioned in
close proximity to or in direct contact with the tissue or skin of
the patient. In certain embodiments consistent with the present
invention, the light source has a thin, lightweight TFEL panel
designed to provide uniform illumination over the area to be
treated without the use of diffusers that would attenuate a portion
of the light output. A single illuminating unit can be used as a
TFEL panel requiring only two electrodes with two electrical
connections, and can be made as large as several inches by several
inches or even several feet by several feet. The light source may
be operated in a range of power and frequency that does not
generate excessive heat so that the light source surface may be
used in contact with a patient's skin without discomfort and
without need for the use of a cooling mechanism. The light source
can be designed to emit light with wavelengths ranging from the
visible to the infrared range. Selection of the appropriate
wavelength allows the optimization of the light source for specific
treatments.
[0064] As shown in FIG. 6, an exemplary TFEL panel and associated
circuitry consistent with certain embodiments of the present
invention is illustrated as 100. For purposes of the current
discussion, start by assuming that this is an inorganic high field
EL device. In this simple embodiment, a thin film
electroluminescent panel is fabricated by sandwiching an inorganic
electroluminescent layer 104 between two transparent insulators 108
and 112, which are further sandwiched between a pair of electrodes
116 and 120. The seal material (glass or polymer) 122 covers the
light emitting portion of the device and protects the user from the
high voltage used to generate the light. In one embodiment, the
layer 122 also serves as a substrate for the growth of thin films
of the materials composing the TFEL panel. When layer 122 serves
only as a seal material, the substrate supporting the thin films
can be placed beneath the bottom electrode 120. This produces a
single illuminating unit requiring only two electrodes that can be
as large as several inches by several inches and even several feet
by several feet.
[0065] In this exemplary embodiment, an active inorganic
electroluminescent layer 104 generates light by impact excitation
of a light-emitting center (called the activator or dopant),
embedded in a host material, by high-energy electrons. Since the
electrons gain their energy from an electric field (1-2 MV/cm),
this type of EL is often called high field electroluminescence
(HFEL). A host matrix with an activator in this embodiment can be
in the form of inorganic thin film or powder doped with a metal ion
(ions) or metal complex (complexes). In general, the host material
has a band gap large enough to emit light without absorption as
well as to provide a medium for the efficient transport of high
energy electrons. Examples of the inorganic host matrix forming the
electroluminescent layer include, but are not limited to, ZnS, SrS,
ZnGa.sub.2O.sub.4, ZnSiO.sub.4, CaSSe, CaS and others. Examples of
active centers incorporated in the EL phosphor material include,
but are not limited to: Mn, Cu, rare earth elements (such as Ce,
Nd, Sm, Eu, Tb, Tm, Er, Nd and others), and their complexes (TbOF
and others). The electroluminescent layer 104 may be formed from
ZnS, SrS, or an oxide layer doped with the above-identified EL
phosphor material.
[0066] To enhance the efficiency and shift the peak emission
wavelength, co-doping can be also used (for example, Ag in SrS:Cu
with Ag in SrS for a blue EL phosphor). The insulators 108 (for
example, ATO, which is a mixture of TiO.sub.2 and Al.sub.2O.sub.3)
and 112 (for example, barium tantalate, which is BaTa.sub.2O.sub.4)
on either side of the active layer limit the maximum current to the
capacitive charging and discharging displacement current level. The
insulators 108, 122 may also be formed from silicon oxynitride
Electrodes sandwiching the insulator and EL layers form a basic
capacitive structure. Electrode 116 is a transparent conductive
electrode such as, for example, an Indium Tin Oxide (ITO) electrode
or aluminum, that permits light of a certain wavelength range to
pass. Alternate electrode materials, such as nickel-cobalt spinel
oxide, may be used to extend the range of transparency further into
the IR range.
[0067] Electrode 120 is preferably somewhat reflective (for
example, Al) so that light that is incident on electrode 120 will
reflect back through electrode 116. In certain embodiments
consistent with the present invention, the electrode closer to the
area to be treated by the TFEL light source is transparent while
the second electrode serves as a reflector. Light emitted in the
phosphor layer is uniform in all directions. The reflecting
electrode serves to reflect light generated in the phosphor layer
emitted in that direction as well as any light reflected from the
patient's skin not absorbed by the other layers in the TFEL
structure. Due to the reflective properties of the electrode, the
overall light source efficiency is improved. The highest luminance
reported in flat panel display industry for TFEL panel (pixelated)
with inorganic emission layer in the visible region of light
spectrum currently is >1000 cd/m.sup.2 (>1 mW/cm.sup.2).
[0068] A typical thickness of the TFEL panel, not counting a
substrate, is about 1.5 mm. A typical thickness of a glass or
polymer substrate in an EL device is about 1 mm. Thus the
illuminating panel can be made to be very light and compact. This
structure can be extended in width to produce a TFEL panel that is
large in area and somewhat planar with a very thin cross section.
Yet wiring to such a device may remain as simple as a two-wire
connection.
[0069] In another embodiment, the active layer of the TFEL is an
organic-based material. Organic-based electroluminescent light
(OEL) sources have been under development for several years and may
be particularly attractive for PT applications because of their
very simple fabrication techniques (for example, spin on coating of
organic material), high brightness emission in the visible and IR
part of the spectrum and low operational voltage. The high
brightness makes OEL displays attractive as a source of radiation
and the low voltage operation allows the OEL sources to be battery
powered, which enhances their portability and ease of use in the
field.
[0070] FIG. 6 can also represent the structure of an OEL. In this
case, the active layer 104 is an organic material as will be
described later. The electrodes 116 and 120 are similar or
identical in structure to that of the inorganic HFEL source
previously described. Instead of insulating layers 108 and 112, the
OEL often uses an electron/(or hole) injection/(or blocking) layer
that is similarly located. Additionally, the organic material
forming the active layer may be made up of multiple layers and may
or may not have a dopant.
[0071] Currently, the typical luminance of OEL sources is between
several hundred cd/m.sup.2 to several thousand cd/m.sup.2. However,
luminance as large as slightly less than 40000 cd/m.sup.2
(corresponding to about 40 mW/cm.sup.2) in the region of visible
light has been observed. A large variety of polymers, copolymers
and their derivatives have been demonstrated within last the decade
to posses EL properties. The configuration of such polymer-based
devices may have a simple single layer, bilayers, or blends of
polymers used to enhance efficiency, tune the emission wavelength
or even provide devices that emit light of different colors simply
by changing the driving voltage. In the last case, as an example, a
blend of two polythiophene-based polymers can be cited, which
posses two different bandgaps and thus different emission colors
and different turn-on voltages. As described above, a typical
single layer polymer organic TFEL is constructed by sandwiching a
thin layer of luminescent conjugated polymer between an anode and
cathode, where one electrode is transparent. Organic materials can
be also be made up of emitting metal containing organic compounds
(for example, aluminum, tris(8-hydroxyquinoline, and conjugated
polymers)) incorporated into the polymer host matrix also have been
employed as OEL materials for generating visible light. When
containing rare earth ions, emission from metal containing organic
compounds often exhibit sharp peaks in both visible and NIR
spectral regions. Relatively recently, organolanthanide phosphors
have been demonstrated to give high enough brightness and
efficiency to underline their potential for use in OEL devices.
Organic TFEL devices are sometimes referred to as an OLED.
[0072] In one embodiment consistent with the present invention,
organic-based TFEL panel 100 has a layer 122 that forms a
supporting substrate (glass or polymer) and that also serves as a
sealing material protecting the organic material from degradation,
a transparent conducting electrode 116 (such as, for example, ITO),
a hole transport conducting polymer layer 108 (such as, for example
PEDOT-PSS), the active light emitting layer 104, and the top
electrode structure in the form of a calcium layer 112 and aluminum
layer 120, where Ca and Al can be substituted by other conductive
materials with relatively low work function. The emitting layer can
be, for example, made of blends of MEH-PPV or PPP-OR11 with
lanthanide-TPP complexes, where lanthanide can be Yb (peak emission
at 977 nm), Er (1560 nm) and others.
[0073] In another embodiment, the OEL device emitting red light
(612 nm peak) can have the following layers: glass (polymer)
substrate/ITO/Eu(TTFA)3(phen):PBD:PVK/BCP/Ca/Al. In this
embodiment, a new functional layer-BCP, is incorporated as a
hole-blocking layer substantially improving brightness and
efficiency. In general, in addition to the layers of materials
described above, additional layers for OEL device can be
incorporated, such as electron or hole injection or blocking
layers. Other configurations are also possible without departing
from the present invention.
[0074] In both inorganic and organic-based TFEL devices, a single
emitting unit driven by two electrodes can be substantially large
due to much lower current generated in these structures as compared
to semiconductor LEDs. A single illuminating unit requires only two
electrodes but can be as large as several inches by several inches
and even several feet by several feet. The current within high
field inorganic EL and OELs range from several mA/cm.sup.2 to about
100 mA/cm.sup.2, while for semiconductor LEDs it is about 100
A/cm.sup.2.
[0075] Light is generated in inorganic TFEL device 100 by
application of an AC voltage across electrodes 116 and 120 of
sufficient magnitude to cause emission of light by the active layer
104. DC could be used but at the expense of higher current drain.
Electrical charge is injected into the active layer, by application
of voltage across the electrodes, exciting the dopant atoms.
Relaxation of the dopant atoms back to the ground state results in
the emission of photons characteristic of the dopant atom and the
phosphor host. The wavelength of the light emitted is determined by
the dopant or dopants in the active layer. Each dopant used in the
TFEL panel will exhibit a unique spectral output characteristic of
that dopant. Often, if a single dopant is used, light will be
emitted predominantly at a single wavelength, but often a single
dopant will also result in multiple dominant lines in the output
frequency spectrum. Multiple dopants, such as, but not limited to
three, can be effectively used to generate light at multiple
wavelengths or spectra.
[0076] Inorganic TFEL devices have been optimized for emission in
the visible wavelength range specifically for display applications
using, for example dopants such as copper to produce blue emission
and manganese to produce amber emission. Doping the phosphor layer
with a rare-earth element, a strong EL emission band produces light
in the infrared range accompanied in many cases by some level of
emission in the visible range. The selection of the appropriate
dopant allows the characteristic EL emission to be changed to
wavelengths ranging from the visible to the infrared. The spectrum
can also be modified somewhat by annealing. The emission is
determined by the specific dopant used. The use of two or more
dopants can produce multiple characteristic emission lines. The
wavelengths may be chosen to match the portions of the
electromagnetic spectrum known to have therapeutic benefit in
phototherapy, or to activate the photoreactive agent in
photodynamic therapy. Some illustrative dominant wavelengths
associated with several dopants are given by Table 1 below. This
listing should not be considered exhaustive or limiting, but merely
illustrative of the ability to produce EL emissions in the range of
wavelengths that are useful for phototherapy applications.
TABLE-US-00001 TABLE 1 INORGANIC AND DOMINANT LIGHT ORGANIC EL
MATERIAL WAVELENGTHS EMITTED (MATRIX:DOPANT) FROM EL SOURCE ZnS:Tm
(Thulium) 480 nm and 800 nm ZnS:Nd (Neodymium) 890 nm ZnS:Er
(Erbium) 550, 660 and 980 nm ZnS:Mn 580 nm (yellow) SrS:Cu 475 nm
(green/blue) (SrS:Cu, Ag) (430 nm) (blue) SrS:Ce 510-550 nm double
peaked Eu(TTFA).sub.3(phen):PBD:PVK 612 nm (red)
Yb(TPP)acac:MEH-PPV 977 nm
[0077] Light emitted from a TFEL source such as described herein is
generally not a pure light at any given wavelength. Rather, the
light source produces a spectrum of light that frequently exhibits
sharp peaks in intensity at one or more wavelengths. The
approximate wavelength of the dominant intensity peaks are listed
in the table above for the exemplary dopants listed. Uniform light
intensity over the entire light source surface area is achieved
with uniform dopant distribution and film thicknesses in the TFEL
panel, parameters readily controlled during the manufacturing
process.
[0078] In the phototherapy device 100 of FIG. 6, a variable voltage
source 126 supplies AC voltage to the TFEL panel electrodes 116 and
120 to induce emission of light. In this embodiment, the variable
voltage source supplies a voltage under control of microprocessor
130. The microcontroller may control any one or more desired
parameters of the AC voltage including, but not limited to, voltage
level, frequency and modulation characteristics to control the
light output from the TFEL panel. The desired output level and
other parameters can be controlled by user input to a control panel
134 operating as a user interface providing I/O functions to the
microprocessor 130. Such parameters may be directly controlled in
some embodiments or controlled as a function of treatment
selections made at the control panel without knowledge of the
actual physical parameters being influenced.
[0079] In the embodiment illustrated, if multiple dopants are used
and uniformly distributed, then light is emitted at multiple
frequencies at a variable intensity level and time that is
controllable by microprocessor 130 which acts as a controller upon
appropriate receipt of user input at control panel 134. According
to this design, the TFEL source can be manufactured and operated as
a single light source with the entire panel uniformly activated.
One or more conductive elements is attached to both the top and
bottom electrode of the TFEL panel and connected to a suitable
power source such as source 126. This simple design results in a
reliable TFEL light source since there are minimal components and
minimal connections, and produces a device that is light in weight
with low heat generation and low current drain. In this embodiment,
all available spectra of light from the TFEL panel are produced
whenever an appropriate voltage is applied to the panel. For
inorganic TFEL, a relatively high voltage (about 200V) may be
required to produce light emissions. In this case, the voltage
source 126 may incorporate a voltage converter to appropriately
boost the voltage to required levels. However, it should be noted
that high voltage does not imply limitations on portability. In
addition, TFEL displays have superb shock resistance and can
normally operate at -25.degree. C. to +65.degree. C.
[0080] In an alternative embodiment, as illustrated in FIG. 7, a
phototherapy device 200 is illustrated in which multiple light
spectra are individually selectable. In this embodiment, two or
more TFEL panels are stacked to provide the user with the ability
to individually address each panel and thus select one of two
wavelengths, or sets of wavelengths, for the phototherapy treatment
protocol. For an inorganic TFEL, the first panel structure is
similar to that of FIG. 6 in which the active layer 104, surrounded
by insulators 108 and 112 are positioned between transparent
electrode 116 and electrode 120 (Electrode 120 is preferably
reflective at the wavelengths of interest.). A second TFEL panel is
fabricated by positioning a second active layer 204 between two
transparent insulators 208 and 212. The two transparent insulators
208 and 212 are in turn positioned between a pair of transparent
electrodes 216 and 220. Electrode 220 is then coupled to electrode
116 using a transparent insulating glue or tape 224 or other
mechanism to hold the two panels together. In another embodiment, a
single electrode may be substituted for electrodes 220 and 116 by
appropriate modification of the outputs from the variable voltage
source. In an organic TFEL embodiment, the structural changes
discussed in connection with FIG. 6 can be applied equally to the
structure of FIG. 7 to achieve a multiple layer organic active
layer TFEL.
[0081] In this embodiment, variable voltage source 226 supplies
voltage across electrodes 116 and 120 and across electrodes 216 and
220. The device is again isolated from the user's skin by a seal
layer 122. Thus, the light emission from the top panel and the
bottom panel can be independently selected by selective application
of voltage to the two stacked TFEL panels. Due to having to pass
through the upper TFEL panel, emissions from the lower TFEL panel
will be slightly attenuated compared to those from the upper TFEL
panel, and this should be accounted for in development of treatment
protocols. Since the thickness of each EL panel can be about 1 mm,
the attenuation is generally low (about 10%). The output, as in
device 100, is selected by controlling the variable voltage source
226 by microprocessor 230, operating under control of a computer
program with the user input selected via control panel 234. Due to
the low current consumption of the TFEL panel, this apparatus (as
well as apparatus 100) may be readily battery powered by battery
240. Battery 240 can either be replaceable batteries or may be a
rechargeable battery that can be charged by battery charging
circuit 244. This circuit may also incorporate voltage regulators
and voltage converters (for inorganic TFEL) and other peripheral
circuitry as will be clear to those skilled in the art to assure
uniformity of voltage, etc.
[0082] An alternate embodiment involves producing a patterned array
of TFEL pixels in order to produce multiple characteristic emission
lines. Some of the pixels are designed to emit one wavelength or
spectrum while others are designed to produce an alternate
wavelength or spectrum by doping the phosphor used to generate the
two types of pixels with different dopants. the pixels can be
interconnected so that all the pixels of one type can be activated
simultaneously. The two, or more, pixel types could be switched on
separately to generate emission characteristic of the activated
pixels or rapidly switched on and off sequentially producing both
types of emission.
[0083] FIG. 8 illustrates one embodiment that uses arrays of pixels
in a prescribed pattern to produce multiple spectra of light
emissions. In this embodiment, a checkerboard pattern is used with
alternating segments of doped electroluminescent material being
doped with two different dopants. For example, a first dopant can
be used to dope segments 702 (represented by the white squares),
while a second dopant can be used to dope segments 706 (represented
by the hashed squares) in the same manner used to create pixels in
a video display. In a case of organic TFEL based on light emitting
polymers which do not require dopants, these segments can be made
of different types of light emitting polymers. Electrodes are
fabricated so that each of the segments 702 can be collectively
addressed (again in a manner similar to that used in video
displays, except that all pixels associated with each spectrum can
be addressed simultaneously) and each of the segments 706 can be
collectively addressed. The user can then address segments 702 with
appropriate drive voltage to produce light at the wavelength
associated with the dopant used in the segments associated with
702. The user can separately or simultaneously address the segments
706 associated with the second dopant to produce light having
different spectral characteristics. As the segments are made small
and smaller, the light from the panel becomes more uniform, but the
panel becomes somewhat more complex and expensive to manufacture.
Similarly, depending on applications, a TFEL panel with only one
dopant can also be pixilated. The pixel size can range from several
mm to several inches.
[0084] A somewhat simpler structure is illustrated in FIG. 9 in
which alternating segments of the panel with first and second
dopants are fabricated in successive columns. Thus, a column 802
has the first dopant and the column 806 has the second dopant.
Again, the complexity of manufacture increases as the columns are
made smaller, but the uniformity of the output becomes better. Of
course, those skilled in the art will appreciate that other
arrangements of doped segments of the panel can be devised, and
that the present invention is not limited to two such dopants.
Moreover, multiple dopants can be used for each of the segments of
the panel and multiple layers can be used with these embodiments
without departing from the present invention.
[0085] In addition to the embodiments described in connection with
FIGS. 8 AND 9, multiple layers (similar to the embodiment shown in
FIG. 7) can be used to generate the pixels with an upper layer
contributing to a first spectrum and the lower layer contributing
to the second layer with the pixels alternating with one another as
in FIGS. 8 and 9 to provide the user with the option of selection
of either of the two spectra.
[0086] As previously noted, a further aspect of the present
invention is the ability to bring the light source 12, the TFEL
panel, in direct contact with the skin without the necessity of a
cooling device. Other light sources, such as LEDs, exhibit higher
power dissipation than TFEL devices. LEDs often produce a
significant amount of heat and may require a cooling mechanism. The
TFEL light source 12 may feel warm when in contact with the skin
under normal operating conditions, but does not produce enough heat
to require supplemental cooling. The TFEL light source 12 can be
comfortably and safely used for extended periods of time.
[0087] The foregoing is provided for purposes of illustrating,
explaining, and describing embodiments of this invention.
Modifications and adaptations to these embodiments will be apparent
to those skilled in the art and may be made without departing from
the scope or spirit of this invention.
* * * * *