Patent Publication Number: US-2004043138-A1

Title: Solid state lighting using compressed fluid coatings

Description:
FIELD OF THE INVENTION  
       [0001] The present invention relates generally to the field of electroluminescent lighting, and more particularly, to methods employing compressed fluid solutions and/or dispersions for depositing layers of organic electroluminescent material on substrates for use in solid state lighting applications.  
       BACKGROUND OF THE INVENTION  
       [0002] Electroluminescent (EL) materials are those that convert electrical energy into visible light. As such, these materials find application in solid state lighting because of advantages such as higher efficiency, lower power consumption, and longer lifetimes. EL materials may be inorganic or organic. Inorganic EL materials are semiconductor materials that convert electricity to light. Electrons are caused to move across a p-n junction from the n-region to the p-region and recombine with positive charges (holes). Recombination of electrons and holes results in the emission of energy in the visible wavelengths. The wavelength of emitted light is a function of the semiconductor band-gap with wider band-gaps resulting in higher frequency (or smaller wavelength) emission. Common inorganic EL materials include Aluminum Galium Arsenide (AlGaAs-Red), Aluminum Indium Galium Phosphide (AlInGaP-Yellow), Indium Galium Nitride (InGaN-Blue and Green), etc. Inorganic EL devices (or Light Emitting Diodes LEDs) are made through epitaxial crystal growth processes or through chemical vapor deposition processes. The deposited semiconductor chips are then encapsulated using plastic (epoxy) materials. Light output is a function of the semiconductor materials, manufacturing process, packaging configuration, drive current, and operating environment. Relatively long lifetimes, small size, and ruggedness make them useful in lighting applications. However, these devices are relatively rigid making them inapplicable for flexible lighting applications. In addition, they are typically point light sources making them preferred as directional light sources but less preferred for diffuse lighting applications such as general area illumination. For the latter applications, organic light emitting materials are preferred.  
       [0003] Organic light emitting devices (OLED) are classified into small molecule (SMOLED) and polymeric light emitting devices (PLED). Such materials are suitable for lighting applications because of their high processability, durability, low power consumption, wide color gamut, and wide emission angles.  
       [0004] In simplest form, an OLED is comprised of an anode for hole injection, a cathode for electron injection, and an organic or polymeric medium sandwiched between these electrodes to support charge recombination that yields emission of light. Representative of earlier organic EL devices are U.S. Pat. No. 3,172,862 to Gurnee et al, U.S. Pat. No. 3,173,050 to Gurnee, Dresner, “Double Injection Electroluminescence in Anthracene”, RCA Review, Vol. 30, pp. 322-334, 1969; U.S. Pat. No. 3,710,167 to Dresner and U.S. Pat. Nos. 4,769,292 and 4,885,211 both to Tang et al. In a basic two-layer EL device structure, described first in U.S. Pat. No. 4,356,429 to Tang, one organic layer of the EL element adjacent to the anode is specifically chosen to transport holes, therefore, it is referred to as the hole transport layer, and the other organic layer is specifically chosen to transport electrons, referred to as the electron transport layer. The interface between the two layers provides an efficient site for the recombination of the injected hole/electron pair and the resultant electroluminescence. There have also been proposed three-layer organic EL devices that contain an organic light-emitting layer (LEL) between the hole-transporting layer and electron-transporting layer, such as that disclosed by Tang et al in  J. Applied Physics,  Vol. 65, Pages 3610-3616, 1989. The light-emitting layer commonly consists of a host material doped with a guest material. Still further, there has been proposed in U.S. Pat. No. 4,769,292 to Tang et al, a four-layer EL element comprising a hole-injecting layer (HIL), a hole-transporting layer (HTL), a light-emitting layer (LEL) and an electron transport/injection layer (ETL).  
       [0005] The organic materials mentioned above are suitably deposited through sublimation, but can be deposited from a solvent with an optional binder to improve film formation. If the material is a polymer, solvent deposition is usually preferred. 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 to Spahn, 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 to Tang, et al), spatially-defined thermal dye transfer from a donor sheet (U.S. Pat. Nos. 5,851,709 to Adinolfi and 6,066,357 to Tang, et al) and inkjet methods (U.S. Pat. No. 6,066,357 to Tang, et al). In each of the above deposition techniques, however, there are drawbacks. Sublimation processes are restricted to materials that may be sublimed, excluding, for example, most polymeric materials which decompose instead of subliming. Typical solvent methods, such as spin coating, utilize solvents that are potentially harmful to health and the environment in addition to requiring subsequent solvent drying steps to eliminate residual solvents. This makes such processes difficult, slow, and expensive. In addition, uniform deposition onto non-planar surfaces, such as may be required by solid state lighting applications, is difficult, if not impossible, with the above deposition techniques.  
       [0006] Japanese Patent 09288970 A discloses a forming method for a bulb inner wall coating by constituting a supercritical fluid coating with a composition of a water suspension containing fluorescent fine particles and carbon dioxide as a supercritical fluid. However, there are many problems with this process. The use of a water suspension necessitates drying to eliminate the water present. Further, any water suspensions of OLED materials will result in extremely poor lifetimes, if there is any electroluminescence exhibited at all, because of moisture-related device contamination. The fluorescent powder is dispersed in water making it susceptible to agglomeration, settling and other mixture-related issues. Further, the spray coating processes disclosed in the patent result in highly non-uniform coatings that would make solid state devices that are substantially inferior in performance.  
       [0007] Huck et al., in WO 02/45868 A2, discloses a method of creating a pattern on a surface of a wafer using compressed carbon dioxide. The method includes dissolving or suspending a material in a solvent phase containing compressed carbon dioxide, and depositing the solution or suspension onto the surface of the wafer, the evaporation of the solvent phase leaving a patterned deposit of the material. The wafer is pre-patterned using lithography to provide the wafer with hydrophilic and hydrophobic areas. After deposition of the solution (or suspension) onto the wafer surface followed by the evaporation of the solvent phase, the material (a polymer) adheres to one of the hydrophobic and hydrophilic areas. The solution (or suspension) is deposited on the wafer surface either in the form of liquid drops or a feathered spray.  
       SUMMARY OF THE INVENTION  
       [0008] It is therefore an object of the present invention to provide a method of depositing a functional layer of material on a substrate using compressed fluids such as compressed gases, liquids or supercritical fluids.  
       [0009] It is a further object of the present invention to provide a method of depositing a layer of organic electroluminescent material on a substrate using compressed fluids based solutions and/or dispersions of organic electroluminescent materials or other functional layer materials that may be useful in electroluminescent lighting devices.  
       [0010] It is a feature of the present invention to provide a method of depositing organic thin films on a substrate using compressed fluids such as compressed gases, liquids or supercritical fluids useful in forming electroluminescent lighting devices for use in solid state lighting applications.  
       [0011] Yet another feature of the present invention is to create organic thin film coatings/deposits that are solvent-free.  
       [0012] A further feature of the present invention is to provide a method that can be used to deposit organic thin film coatings/deposits on flexible substrates.  
       [0013] It is another feature of the present invention to provide a method that can be used to deposit organic thin film coatings on substrates that are not planar.  
       [0014] Briefly stated, the foregoing and numerous other features, objects and advantages of the present invention will become readily apparent upon a review of the detailed description, claims and drawings set forth herein. These features, objects and advantages are accomplished by providing an apparatus and method of coating/depositing a functional material for solid state lighting applications. The apparatus includes a pressurized source of the compressed fluid in a thermodynamically stable or metastable mixture with a functional material. A discharge device having an inlet and an outlet is connected to the pressurized source at the inlet. The discharge device is shaped to produce a spray of functional material projected in a generally circular or elliptical pattern, although other patterns such as squares and rectangles or hexagons may also be used if desired, where the fluid is in a gaseous state at a location before or beyond the outlet of the discharge device. The shape of the spray pattern as delivered to the substrate can be modified by placing a mask between the spray nozzle and the substrate. The compressed fluid in the pressurized source can be one of a dense gas, compressed liquid, or a supercritical fluid of density greater than 0.1 g/cc.  
       [0015] The thermodynamically stable or metastable mixture includes one of the functional materials being dispersed in the fluid and/or the functional material being dissolved in the fluid.  
       [0016] The method of the present invention allows for the formation of a layer of electroluminescent material having a controlled thickness and surface uniformity. One key property of the various layers that is needed for an organic electroluminscent device is surface uniformity. Typically, a surface roughness of the order of 10 Angstroms or less is desirable for a high quality device, although surface roughnesses of up to three orders of magnitude higher than that may be adequate for some purposes and devices. 
     
    
    
     BRIEF DESCRIPTION OF THE DRAWINGS  
     [0017] In the detailed description of the preferred embodiments of the invention presented below, reference is made to the accompanying drawings, in which:  
     [0018]FIG. 1A is a schematic view of a preferred embodiment made in accordance with the present invention;  
     [0019] FIGS.  1 B- 1 G are schematic views of alternative embodiments made in accordance with the present invention;  
     [0020]FIG. 2A is a block diagram of a discharge device made in accordance with the present invention;  
     [0021] FIGS.  2 B- 2 J are cross sectional views of a nozzle portion of the device shown in FIG. 2A;  
     [0022] FIGS.  3 A- 3 D are diagrams schematically representing the operation of the present invention; and  
     [0023] FIGS.  4 A- 4 K are cross sectional views of a portion of the invention shown in FIG. 1A.  
     [0024]FIG. 5 is a cross sectional view of an OLED device.  
     [0025]FIG. 6 depicts a schematic cross-sectional view of a stacked OLED lighting structure having stacked organic EL units and having a doped organic connector in between each of the organic EL units.  
     [0026]FIG. 7 depicts a schematic cross-sectional view of another stacked OLED lighting structure illustrating some layer structures in the organic EL unit.  
     [0027]FIG. 8 depicts a schematic cross-sectional view of yet another stacked OLED lighting structure illustrating some other layer structures in the organic EL unit.  
     [0028]FIG. 9 depicts a schematic cross-sectional view of a stacked OLED illustrating a doped organic connector that includes an n-type doped organic layer and a p-type doped organic layer.  
     [0029]FIG. 10 shows a phase diagram of a typical material such as carbon dioxide. 
    
    
     DETAILED DESCRIPTION OF THE INVENTION  
     [0030] The present description will be directed in particular to elements forming part of, or cooperating more directly with, apparatus in accordance with the present invention. It is to be understood that elements not specifically shown or described may take various forms well known to those skilled in the art. Additionally, materials identified as suitable for various facets of the invention, for example, functional materials, solvents, equipment, etc. are to be treated as exemplary, and are not intended to limit the scope of the invention in any manner.  
     [0031] Referring to FIG. 1A, delivery system  10  has components,  11 ,  12 , and  13  that take chosen solvent and/or dispersant materials to a compressed gas, liquid and/or supercritical fluid state, make a solution and/or dispersion of an appropriate functional material or combination of functional materials in the chosen compressed fluid with a density greater than 0.1 g/cc, and deliver the functional materials onto a receiver  14  in a controlled manner. Functional materials can be any material that needs to be delivered to a receiver, for example electroluminescent materials, hole transport materials, electron transport materials, etc., to create a coating on the receiver by deposition and/or coating of a functional material. A receiver is any substrate that is suitable for a lighting application. Exemplary substrates include, for example, glass, silicon, polymeric materials, metals, alloys and ceramics.  
     [0032] In this context, the chosen materials taken to a compressed fluid state are gases at ambient pressure and temperature. The compressed fluid has a density that is greater than or equal to 0.1 grams per cubic centimeter. Such fluids are able to dissolve and/or disperse, and hold in solution and/or dispersion, functional solute materials of interest. Ambient conditions are preferably defined as temperature in the range from-100 to +100° C., and pressure in the range from 1×10 −8 -100 atm for this application. More preferably, ambient conditions are defined as temperature in the range from − 20  to +50° C., and pressure in the range from 1×10 −8 -10 atm  
     [0033] In FIG. 1A a schematic illustration of the delivery system  10  is shown. The delivery system  10  has a compressed fluid source  11 , a formulation reservoir  12 , and a discharge device  13  connected in fluid communication along a delivery path  16 . The delivery system  10  can also include a valve or valves  15  positioned along the delivery path  16  in order to control flow of the compressed fluid.  
     [0034] A compressed fluid carrier, contained in the compressed fluid source  11 , is any material that dissolves/solubilizes/disperses a functional material. The compressed fluid source  11  delivers the compressed fluid carrier at predetermined conditions of pressure, temperature, and flow rate as a compressed gas or a compressed liquid or supercritical fluid, all of density greater than 0.1 g/cc. Materials that are above their critical point, defined by a critical temperature and a critical pressure, are known as supercritical fluids. The critical temperature and critical pressure typically define a thermodynamic state in which a fluid or a material becomes supercritical and exhibits gas like and liquid like properties. Materials that are at sufficient temperatures and pressures below their critical point are known as compressed liquids. Materials in their compressed fluid state with a density greater than 0.1 g/cc that exist as gases at ambient conditions find application here because of their unique ability to solubilize and/or disperse functional materials of interest in the compressed fluid state.  
     [0035]FIG. 10 shows a phase diagram of a typical material such as carbon dioxide. As pressure and temperature are increased, such a material, for example, carbon dioxide, which is a gas at atmospheric pressure and room temperature, changes into a compressed fluid (either liquid or compressed gas) until a certain critical temperature and critical pressure defined by the critical point in the diagram. At temperatures and pressures above this critical point, the material is said to be in supercritical state, for example supercritical carbon dioxide. A key property of materials undergoing such changes in pressure and temperature conditions is their density, which typically increases with increasing pressure and temperature. As mentioned earlier, materials with a density greater than 0.1 gram/cubic centimeter, and the necessary pressure and temperature conditions thereof, that exist as gases as ambient conditions, find application here because of their unique ability to solubilize and/or disperse functional materials of interest.  
     [0036] Fluid carriers include, but are not limited to, carbon dioxide, nitrous oxide, ammonia, xenon, ethane, ethylene, propane, propylene, butane, isobutane, chlorotrifluoromethane, monofluoromethane, sulphur hexafluoride and mixtures thereof. Due to its characteristics, e.g. low cost, wide availability, etc., carbon dioxide is generally preferred in many applications.  
     [0037] The formulation reservoir  12  is utilized to dissolve and/or disperse functional materials in compressed gases, liquids or supercritical fluids with a density≧0.1 g/cc with or without dispersants and/or surfactants, at desired formulation conditions of temperature, pressure, volume, and concentration. The combination of functional material and compressed fluid is typically referred to as a mixture, formulation, etc.  
     [0038] The formulation reservoir  12  can be made out of any suitable materials that can safely operate at the formulation conditions. An operating range from 0.001 atmosphere (1.013×10 2  Pa) to 1000 atmospheres (1.013×10 8  Pa) in pressure and from −25° C. to 1000° C. is generally preferred. A more preferred range is from 50 to 400 atmospheres in pressure and from −20 to 100° C. Typically, the preferred materials include various grades of high-pressure stainless steel. However, it is possible to use other materials if the specific deposition application dictates less extreme conditions of temperature and/or pressure.  
     [0039] The formulation reservoir  12  should be precisely controlled with respect to the operating conditions (pressure, temperature, and volume). The solubility/dispersibility of functional materials depends upon the conditions within the formulation reservoir  12 . As such, small changes in the operating conditions within the formulation reservoir  12  can have undesired effects on functional material solubility/dispensability.  
     [0040] Additionally, any suitable surfactant and/or dispersant material that is capable of solubilizing/dispersing the functional materials in the compressed fluid for a specific application can be incorporated into the mixture of functional material and compressed fluid. Such materials include, but are not limited to, fluorinated polymers such as perfluoropolyether, siloxane compounds, polyethercarbonate, etc.  
     [0041] Referring to FIGS.  1 B- 1 D, alternative embodiments of the invention shown in FIG. 1A are described. In each of these embodiments, individual components are in fluid communication, as is appropriate, along the delivery path  16 .  
     [0042] Referring to FIGS. 1B and 1C, a pressure control mechanism  17  is positioned along the delivery path  16 . The pressure control mechanism  17  is used to create and maintain a desired pressure required for a particular application. The pressure control mechanism  17  can include a pump  18 , a valve(s)  15 , and a pressure regulator  19   a , as shown in FIG. 1B. Alternatively, the pressure control mechanism  17  can include a pump  18 , a valve(s)  15 , and a multi-stage pressure regulator  19   b , as shown in FIG. 1C. Additionally, the pressure control mechanism can include alternative combinations of pressure controlling devices, etc. For example, the pressure control mechanism  17  can include additional valve(s)  15 , actuators to regulate fluid/formulation flow, variable volume devices to change system operating pressure, etc., appropriately positioned along the delivery path  16 . Typically, the pump  18  is positioned along the delivery path  16  between the fluid source  11  and the formulation reservoir  12 . The pump  18  can be a high-pressure pump that increases and maintains system operating pressure, etc. The pressure control mechanism  17  can also include any number of monitoring devices, gauges, etc., for monitoring the pressure of the delivery system  10 .  
     [0043] A temperature control mechanism  20  is positioned along delivery path  16  in order to create and maintain a desired temperature for a particular application. The temperature control mechanism  20  is preferably positioned at the formulation reservoir  12 . The temperature control mechanism  20  can include a heater, a heater including electrical wires, a water jacket, a refrigeration coil, a combination of temperature controlling devices, etc. The temperature control mechanism can also include any number of monitoring devices, gauges, etc., for monitoring the temperature of the delivery system  10 .  
     [0044] The discharge device  13  includes a nozzle  23  positioned to provide directed delivery of the formulation towards the receiver  14 . The discharge device  13  can also include a shutter  22  to regulate the flow of the compressed fluid and functional material mixture or formulation. The shutter  22  regulates flow of the formulation in a predetermined manner (i.e. on/off or partial opening operation at desired frequency, etc.). The shutter  22  can be manually, mechanically, pneumatically, electrically or electronically actuated. Alternatively, the discharge device  13  does not have to include the shutter  22  (shown in FIG. 1C). As the mixture is under higher pressure, as compared to ambient conditions, in the delivery system  10 , the mixture will naturally move toward the region of lower pressure, the area of ambient conditions. In this sense, the delivery system is said to be self-energized.  
     [0045] The receiver  14  can be positioned on a media conveyance mechanism (not shown) that is used to control the movement of the receiver during the operation of the delivery system  10 . The media conveyance mechanism can be a drum, an x, y, z translator, any other known media conveyance mechanism, etc. The media conveyance mechanism and receiver  14  may be enclosed in or be part of an enclosure that provides control over the ambient coating/deposition conditions. For example, it may be placed in a vacuum chamber or a high-pressure chamber containing nitrogen or some other inert gas.  
     [0046] Referring to FIG. 1D, the formulation reservoir  12  can be a pressurized vessel having appropriate inlet ports  52 ,  54 ,  56  and outlet ports  58 . Inlet ports  52 ,  54 ,  56  can be used as an inlet  52  for functional material and an inlet  54  for compressed fluid. Alternatively, inlet port  56  can be used to manually add functional material to the formulation reservoir  12 . Outlet port  58  can be used as an outlet for the mixture of functional material and compressed fluid. Note that FIG. 1E depicts a nozzle  13  positioned over a moving flexible substrate  49  supported on a backing roller which is at least a portion of one example of a media conveyance mechanism  50 .  
     [0047] When automated delivery of the functional material is desired, a pump  60  is positioned along a functional material delivery path  62  between a source of functional material  64  and the formulation reservoir  12 . The pump  60  pumps a desired amount of functional material through inlet port  52  into the formulation reservoir  12 . The formulation reservoir  12  can also include additional inlet/outlet ports  59  for inserting or removing small quantities of functional material or functional material and compressed fluid mixtures.  
     [0048] Referring to FIG. 1E, the formulation reservoir  12  can include a mixing device  70  used to create the mixture of functional material and compressed fluid. Although typical, a mixing device  70  is not always necessary to make the mixture of the functional material and compressed fluid depending on the type of functional material and the type of compressed fluid. The mixing device  70  can include a mixing element  72  connected to a power/control source  74  to ensure that the functional material disperses into or forms a solution with the compressed fluid. The mixing element  72  can be an acoustic, a mechanical, and/or an electromagnetic element.  
     [0049] Referring to FIGS. 1D, 1E, and FIGS.  4 A- 4 J, the formulation reservoir  12  can also include suitable temperature control mechanisms  20  and pressure control mechanisms  17  (see FIGS. 1D and 1E) with adequate gauging instruments to detect and monitor the temperature and pressure conditions within the reservoir, as described above. For example, the formulation reservoir  12  can include a moveable piston device  76 , etc., (see FIGS.,  4 D and  4 H) to control and maintain pressure. The formulation reservoir  12  can also be equipped to provide accurate control over temperature within the reservoir. For example, the formulation reservoir  12  can include electrical heating/cooling zones  78  (see FIGS. 4C and 4G), using electrical wires  80  (see FIGS. 4D and 4H), electrical tapes, water jackets  82  (see FIGS. 4F and 41), other heating/cooling fluid jackets, refrigeration coils  84  (see FIGS. 4E and 4J), etc., to control and maintain temperature. The temperature control mechanisms  20  can be positioned within the formulation reservoir  12  or positioned outside the formulation reservoir. Additionally, the temperature control mechanisms  20  can be positioned over a portion of the formulation reservoir  12 , throughout the formulation reservoir  12 , or over the entire area of the formulation reservoir  12 .  
     [0050] Referring to FIG. 4K, the formulation reservoir  12  can also include any number of suitable high-pressure windows  86  for manual viewing or digital viewing using an appropriate fiber optics or camera set-up. The windows  86  are typically made of sapphire or quartz or other suitable materials that permit the passage of the appropriate frequencies of radiation for viewing/detection/analysis of reservoir contents (using visible, infrared, X-ray etc. viewing/detection/analysis techniques), etc.  
     [0051] The formulation reservoir  12  is made of appropriate materials of construction in order to withstand high pressures of the order of 10,000 psi or greater. Typically, stainless steel is the preferred material of construction although other high-pressure metals, metal alloys, and/or metal composites can be used.  
     [0052] Referring to FIG. 1F, in an alternative arrangement, the thermodynamically stable/metastable mixture of functional material and compressed fluid can be prepared in one formulation reservoir  12  and then transported to one or more additional formulation reservoirs which are high pressure vessels  12   a . For example, a single large formulation reservoir  12  can be suitably connected to one or more subsidiary high pressure vessels  12   a  that maintain the functional material and compressed fluid mixture at controlled temperature and pressure conditions with each subsidiary high pressure vessel  12   a  feeding one or more discharge devices  13 . Either or both reservoirs  12  and  12   a  can be equipped with the temperature control mechanism  20  and/or pressure control mechanisms  17 . The discharge devices  13  can direct the mixture towards a single receiver  14  or a plurality of receivers  14 .  
     [0053] Referring to FIG. 1G, the delivery system  10  can include ports for the injection of suitable functional material, view cells, and suitable analytical equipment such as Fourier Transform Infrared Spectroscopy, Light Scattering, UltraViolet or Visible Spectroscopy, etc. to permit monitoring of the delivery system  10  and the components of the delivery system. Additionally, the delivery system  10  can include any number of control devices  88 , microprocessors  90 , etc., used to control the delivery system  10 .  
     [0054] Although FIGS. 1A through 1G depict nozzle(s)  13  delivering a spray to a substrate in open conditions, those skilled in the art will recognize that such coating application will typically be performed in an enclosure (not shown). The enclosure allows for control of the ambient conditions therein. The ambient conditions for the enclosure include the range of temperature, pressure, and humidity. Such conditions may be maintained by an inert gas such as, for example, carbon dioxide, nitrogen, argon, circulated to the enclosure. The range of preferred humidity conditions include 0-25%, more preferred being 0-5%, even more preferred being 0-1%.  
     [0055] Referring to FIG. 2A, the discharge device  13  is described in more detail. The discharge assembly can include an on/off valve  21  that can be manually or automatically actuated to regulate the flow of the dense liquid formulation. The discharge device  13  includes a shutter device  22  which can also be a programmable valve. The shutter device  22  is capable of being controlled to turn off the flow and/or turn on the flow so that the flow of formulation occupies all or part of the available cross-section of the discharge device  13 . Additionally, the shutter device is capable of being partially opened or closed in order to adjust or regulate the flow of formulation. The discharge assembly also includes a nozzle  23 . The nozzle  23  can be provided, as necessary, with a nozzle heating module  26  and a nozzle shield gas module  27  to assist in beam collimation. The discharge device  13  also includes a stream deflector and/or catcher module  24  to assist in shaping the spray prior to the spray reaching a receiver  25 . Components  22 - 24 ,  26 , and  27  of discharge device  13  are positioned relative to delivery path  16  such that the formulation continues along delivery path  16 .  
     [0056] Alternatively, the shutter device  22  can be positioned after the nozzle heating module  26  and the nozzle shield gas module  27  or between the nozzle heating module  26  and the nozzle shield gas module  27 . Additionally, the nozzle shield gas module  27  may not be required for certain applications, as is the case with the stream deflector and catcher module  24 . Alternatively, discharge device  13  can include a stream deflector and catcher module  24  and not include the shutter device  22 . In this situation, the stream deflector and catcher module  24  can be moveably positioned along delivery path  16  and used to regulate the flow of formulation such that a continuous flow of formulation exits while still allowing for discontinuous deposition.  
     [0057] The nozzle  23  can be capable of translation in x, y, and z directions to permit suitable discontinuous and/or continuous functional material deposition on the receiver  14 . Translation of the nozzle can be achieved through manual, mechanical, pneumatic, electrical, electronic or computerized control mechanisms. Receiver  14  and/or media conveyance mechanism  50  can also be capable of translation in x, y, and z directions to permit suitable functional material deposition on the receiver  14 . Alternatively, both the receiver  14  and the nozzle  23  can be translatable in x, y, and z directions depending on the particular application.  
     [0058] In addition to translation of the nozzle  23  and/or receiver  14 , there are many configurations possible to achieve relative motion between the nozzle  23  and receiver  14 , which may be preferred for the practice of this method. For example, the receiver  14  can be flexible and releasably attached to a spinning drum to provide one axis of motion, with the nozzle translating to provide a second axis of motion. Alternatively, the receiver can be a web that is presented in front of the nozzle via rollers. Many such configurations involving translation and/or rotation of mechanical elements can be found in co-pending applications U.S. Ser. No. 10/163,326 entitled “METHOD AND APPARATUS FOR PRINTING, CLEANING, AND CALIBRATING” filed Jun. 5, 2002 in the name of Sridhar Sadasivan et al. and U.S. Ser. No. 10/051,888, entitled “METHOD AND APPARATUS FOR PRINTING AND COATING”, filed Jan. 17, 2002, in the name of Sridhar Sadasivan et al., which are hereby incorporated herein by reference. Though the remainder of this application discusses the practice of a preferred method specifically as it relates to translation mechanisms and a rigid substrate, it is not intended to limit the use of the present invention to applications of layers to rigid substrates.  
     [0059] Referring to FIGS.  2 B- 2 J, the nozzle  23  functions to direct the formulation flow towards the receiver  14 . It is also used to attenuate the final velocity with which the functional material impinges on the receiver  14 . Accordingly, nozzle geometry can vary depending on a particular application. For example, nozzle geometry can be a constant area having a predetermined shape (cylinder  28 , square  29 , triangular  30 , etc.) or variable area converging  31 , variable area diverging  38 , or variable area converging-diverging  32 , with various forms of each available through altering the angles of convergence and/or divergence. Alternatively, a combination of a constant area with a variable area, for example, a converging-diverging nozzle with a tubular extension, etc., can be used. In addition, the nozzle  23  can have a shape  33  that allows for coaxial, axisymmetric or asymmetric or any combination thereof (shown generally as shape  33 ). The shape  28 ,  29 ,  30 ,  31 ,  32 ,  33  of the nozzle  23  can assist in regulating the flow of the formulation. In a preferred embodiment of the present invention, the nozzle  23  includes a converging section or module  34 , a throat section or module  35 , and a diverging section or module  36 . The throat section or module  35  of the nozzle  23  can have a straight section or module  37 .  
     [0060] The discharge device  13  serves to direct the functional material onto the receiver  14 . The discharge device  13  or a portion of the discharge device  13  can be stationary or can swivel or raster, as needed, to provide high resolution and high precision deposition of the functional material onto the receiver  14 . Alternatively, receiver  14  can move in a predetermined way while discharge device  13  remains stationary. The shutter device  22  can also be positioned after the nozzle  23 . As such, the shutter device  22  and the nozzle  23  can be separate devices so as to position the shutter  22  before or after the nozzle  23  with independent controls for maximum deposition flexibility. Alternatively, the shutter device  22  can be integrally formed within the nozzle  23 .  
     [0061] Operation of the delivery system  10  will now be described. FIGS.  3 A- 3 D are diagrams schematically representing the operation of delivery system  10  and should not be considered as limiting the scope of the invention in any manner. A formulation  42  of functional material  40  in a compressed fluid  41  is prepared in the formulation reservoir  12 . A functional material  40 , any material of interest in solid or liquid phase, can be dispersed (as shown in FIG. 3A) and/or dissolved in a compressed fluid  41  making a mixture or formulation  42 . The functional material  40  can have various shapes and sizes depending on the type of the functional material  40  used in the formulation.  
     [0062] The compressed fluid  41 , forms a continuous phase and functional material  40  forms a dispersed and/or dissolved single phase. The formulation  42  (the functional material  40  and the compressed fluid  41 ) is maintained at a suitable temperature and a suitable pressure for the functional material  40  and the compressed fluid  41  used in a particular application. The shutter  22  is actuated to enable the ejection of a controlled quantity of the formulation  42 . The nozzle  23  delivers the spray to the substrate in a generally circular or elliptical shape.  
     [0063] The functional material  40  is controllably introduced into the formulation reservoir  12 . The compressed fluid  41  is also controllably introduced into the formulation reservoir  12 . The contents of the formulation reservoir  12  are suitably mixed using mixing device  70  to ensure intimate contact between the functional material  40  and compressed fluid  41 . As the mixing process proceeds, functional material  40  is dissolved or dispersed within the compressed fluid  41 . The process of dissolution/dispersion, including the amount of functional material  40  and the rate at which the mixing proceeds, depends upon the functional material  40  itself, the particle size and particle size distribution of the functional material  40  (if the functional material  40  is a solid), the compressed fluid  41  used, the temperature, and the pressure within the formulation reservoir  12 . When the mixing process is complete, the mixture or formulation  42  of functional material and compressed fluid is thermodynamically stable/metastable in that the functional material is dissolved or dispersed within the compressed fluid in such a fashion as to be indefinitely contained in the same state as long as the temperature and pressure within the formulation chamber are maintained constant. This state is distinguished from other physical mixtures in that there is no settling, precipitation, and/or agglomeration of functional material particles within the formulation chamber unless the thermodynamic conditions of temperature and pressure within the reservoir are changed. As such, the functional material  40  and compressed fluid  41  mixtures or formulations  42  of the present invention are said to be thermodynamically stable/metastable.  
     [0064] The functional material  40  can be a solid or a liquid. Additionally, the functional material  40  can be an organic molecule, a polymer molecule, a metallo-organic molecule, an organic nanoparticle, a polymer nanoparticle, a metallo-organic nanoparticle, an organic microparticles, a polymer micro-particle, a metallo-organic microparticle, and/or composites of these materials, etc. After suitable mixing with the compressed fluid  41  within the formulation reservoir  12 , the functional material  40  is uniformly distributed within a thermodynamically stable/metastable mixture, that can be a solution or a dispersion, with the compressed fluid  41 . This thermodynamically stable/metastable mixture or formulation  42  is controllably released from the formulation reservoir  12  through the discharge device  13 .  
     [0065] During the discharge process, the functional material  40  is precipitated from the compressed fluid  41  as the temperature and/or pressure conditions change. The precipitated functional material  44  is directed towards a receiver  14  by the discharge device  13  as a focussed and/or collimated beam. The particle size of the functional material  40  deposited on the receiver  14  is typically in the range from 1 nanometer to 1000 nanometers. The particle size distribution may be controlled to be uniform by controlling the rate of change of temperature and/or pressure in the discharge device  13 , the location of the receiver  14  relative to the discharge device  13 , and the ambient conditions outside of the discharge device  13 .  
     [0066] The delivery system  10  is also designed to appropriately change the temperature and pressure of the formulation  42  to permit a controlled precipitation and/or aggregation of the functional material  40 . As the pressure is typically stepped down in stages, the formulation  42  fluid flow is self-energized. Subsequent changes to the formulation  42  conditions (a change in pressure, a change in temperature, etc.) result in the precipitation and/or aggregation of the functional material  40  coupled with an evaporation (shown generally at 45) of the compressed fluid  41 . The resulting precipitated and/or aggregated functional material  44  deposits on the receiver  14  in a precise and accurate fashion.  
     [0067] Evaporation  45  of the compressed fluid  41  can occur in a region located outside of the discharge device  13 . Alternatively, evaporation  45  of the compressed gas, supercritical fluid and/or compressed liquid  41  can begin within the discharge device  13  and continue in the region located outside the discharge device  13 . Alternatively, evaporation  45  can occur within the discharge device  13 .  
     [0068] A spray  43  (stream, etc.) of the functional material  40  and the compressed fluid  41  is formed as the formulation  42  moves through the discharge device  13 . The receiver  14  is positioned along the path  16  such that the precipitated and/or aggregated functional material  44  is deposited on the receiver  14 . The distance of the receiver  14  from the discharge assembly is chosen such that the compressed fluid  41  evaporates from the compressed fluid state to the gas phase (shown generally at  45 ) prior to reaching the receiver  14 . Hence, there is no need for subsequent receiver-drying processes. However, there may be a need for heating for film-annealing purposes. Further, subsequent to the ejection of the formulation  42  from the nozzle  23  and the precipitation of the functional material, additional spray shaping may be achieved using external devices such as electromagnetic fields, mechanical shields, magnetic lenses, electrostatic lenses etc. Alternatively, the receiver  14  can be electrically or electrostatically charged such that the position of the functional material  40  can be controlled.  
     [0069] It is also desirable to control the velocity with which individual particles  46  of the functional material  40  are ejected from the nozzle  23 . As there is a sizable pressure drop from within the delivery system  10  to the operating environment, the pressure differential converts the potential energy of the delivery system  10  into kinetic energy that propels the functional material particles  46  onto the receiver  14 . The velocity of these particles  46  can be controlled by suitable nozzle design and control over the rate of change of operating pressure and temperature within the system. Further, subsequent to the ejection of the formulation  42  from the nozzle  23  and the precipitation of the functional material  40 , additional velocity regulation of the functional material  40  may be achieved using external devices such as electro-magnetic fields, mechanical shields, magnetic lenses, electrostatic lenses etc. Nozzle design and location relative to the receiver  14  also determine the shape of the spray of functional material  40  deposition. The actual nozzle design will depend upon the particular application addressed.  
     [0070] The nozzle  23  temperature can also be controlled. Nozzle temperature control may be controlled as required by specific applications to ensure that the nozzle opening  47  maintains the desired fluid flow characteristics. Nozzle temperature can be controlled through the nozzle-heating module  26  using a water jacket, electrical heating techniques, etc. With appropriate nozzle design, the exiting stream temperature can be controlled at a desired value by enveloping the exiting stream with a co-current annular stream of a warm or cool, inert gas, as shown in FIG. 2G.  
     [0071] The receiver  14  can be any solid including an organic, an inorganic, a metallo-organic, a metallic, an alloy, a ceramic, a synthetic and/or natural polymeric, a gel, a glass, and a composite material. The receiver  14  can be porous or non-porous. Additionally, the receiver  14  can have more than one layer. The receiver materials will be dictated by the lighting device architecture.  
     [0072] General Lighting Device Architecture  
     [0073] The present invention can be employed in most OLED device configurations. These include very simple structures comprising a single anode and cathode to more complex devices, such as passive matrix displays comprised of orthogonal arrays of anodes and cathodes to form pixels, and active-matrix displays where each pixel is controlled independently, for example, with a thin film transistor (TFT).  
     [0074] There are numerous configurations of the organic layers wherein the present invention can be successfully practiced. A typical structure is shown in FIG. 5 and is comprised of a substrate  101 , an anode layer  103 , an optional 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. Note that the substrate may alternatively be located adjacent to the cathode, or the substrate may actually constitute the anode or cathode. Also, the total combined thickness of the organic layers (OLED materials) is preferably less than 500 nm.  
     [0075] Substrate  
     [0076] The substrate  101  can either be light transmissive or opaque, depending on the intended direction of light emission. The light transmissive property is desirable for viewing the EL emission through the substrate. Transparent glass or plastic are commonly employed in such cases. For applications where the EL emission is viewed through the top electrode, the transmissive characteristic of the bottom support is immaterial, and therefore can be light transmissive, light absorbing or light reflective. Substrates for use in this case include, but are not limited to, glass, plastic, semiconductor materials, ceramics, and circuit board materials. Of course, it is necessary to provide in these device configurations a light transparent top electrode  1113 .  
     [0077] Anode  
     [0078] The conductive anode layer  103  is formed over the substrate and, when EL emission is viewed through the anode, it should be transparent or substantially transparent to the emission of interest. Common transparent anode materials used in this invention are indium-tin oxide 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 . For applications where EL emission is viewed through the top electrode, the transmissive 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 other than deposition from dense phases. Exemplary methods depositing anode materials include, for example, evaporation, sputtering, chemical vapor deposition, or electrochemical means. Anodes can also be patterned using well-known photolithographic processes.  
     [0079] Hole-Injecting Layer (HTL)  
     [0080] While not always necessary, 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 to VanSlyke, and plasma-deposited fluorocarbon polymers as described in U.S. Pat. No. 6,208,075 to Hung et al. Alternative hole-injecting materials reportedly useful in organic EL devices are described in EP 0 891 121 A1 to Inou, et al and EP 1,029,909 A1 to Kawamura, et al. The hole-injecting layer may be deposited using the method of the present invention.  
     [0081] Hole-Transporting Layer (HTL)  
     [0082] The hole-transporting layer  107  of the organic EL device 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. In 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 in U.S. Pat. Nos. 3,567,450 and 3,658,520.  
     [0083] 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 to VanSlyke and U.S. Pat. No. 5,061,569 to VanSlyke, et al. Such compounds include those represented by structural formula (C).  
                 
 
     [0084] wherein Q 1  and Q 2  are independently selected aromatic tertiary amine moieties and G is a linking group such as an arylene, cycloalkylene, or alkylene group of a carbon to carbon bond. In one embodiment, at least one of Q 1  or Q 2  contains a polycyclic fused ring structure, e.g., a naphthalene. When G is an aryl group, it is conveniently a phenylene, biphenylene, or naphthalene moiety.  
     [0085] A useful class of triarylamines satisfying structural formula (C) and containing two triarylamine moieties is represented by structural formula (D):  
                 
 
     [0086] where  
     [0087] R 1  and R 2  each independently represents a hydrogen atom, an aryl group, or an alkyl group or R 1  and R 2  together represent the atoms completing a cycloalkyl group; and  
     [0088] R 3  and R 4  each independently represents an aryl group, which is in turn substituted with a diaryl substituted amino group, as indicated by structural formula (E):  
                 
 
     [0089] wherein R 5  and R 6  are independently selected aryl groups. In one embodiment, at least one of R 5  or R 6  contains a polycyclic fused ring structure, e.g., a naphthalene.  
     [0090] Another class of aromatic tertiary amines are the tetraaryldiamines. Desirable tetraaryldiamines include two diarylamino groups, such as indicated by formula (E), linked through an arylene group. Useful tetraaryldiamines include those represented by formula (F).  
                 
 
     [0091] wherein:  
     [0092] each Ar is an independently selected arylene group, such as a phenylene or anthracene moiety,  
     [0093] n is an integer of from 1 to 4, and  
     [0094] Ar, R 7 , R 8 , and R 9  are independently selected aryl groups.  
     [0095] In a typical embodiment, at least one of Ar, R 7 , R 8 , and R 9  is a polycyclic fused ring structure, e.g., a naphthalene  
     [0096] The various alkyl, alkylene, aryl, and arylene moieties of the foregoing structural formulae (C), (D), (E), (F), can each in turn be substituted. Typical substituents include alkyl groups, alkoxy groups, aryl groups, aryloxy groups, and halogen such as fluoride, chloride, and bromide. The various alkyl and alkylene moieties typically contain from about 1 to 6 carbon atoms. The cycloalkyl moieties can contain from 3 to about 10 carbon atoms, but typically contain five, six, or seven ring carbon atoms—e.g., cyclopentyl, cyclohexyl, and cycloheptyl ring structures. The aryl and arylene moieties are usually phenyl and phenylene moieties.  
     [0097] The hole-transporting layer can be formed of a single or a mixture of aromatic tertiary amine compounds. Specifically, one may employ a triarylamine, such as a triarylamine satisfying the formula (D), in combination with a tetraaryldiamine, such as indicated by formula (F). When a triarylamine is employed in combination with a tetraaryldiamine, the latter is positioned as a layer interposed between the triarylamine and the electron injecting and transporting layer. Illustrative of useful aromatic tertiary amines are the following:  
     [0098] 1,1-Bis(4-di-p-tolylaminophenyl)cyclohexane  
     [0099] 1,1-Bis(4-di-p-tolylaminophenyl)-4-phenylcyclohexane  
     [0100] 4,4′-Bis(diphenylamino)quadriphenyl  
     [0101] Bis(4-dimethylamino-2-methylphenyl)-phenylmethane  
     [0102] N,N,N-Tri(p-tolyl)amine  
     [0103] 4-(di-p-tolylamino)-4′-[4(di-p-tolylamino)-styryl]stilbene  
     [0104] N,N,N′,N′-Tetra-p-tolyl-4-4′-diaminobiphenyl  
     [0105] N,N,N′,N′-Tetraphenyl-4,4′-diaminobiphenyl  
     [0106] N-Phenylcarbazole  
     [0107] Poly(N-vinylcarbazole), and  
     [0108] N,N′-di-1-naphthalenyl-N,N′-diphenyl-4,4′-diaminobiphenyl.  
     [0109] 4,4′-Bis[N-(1-naphthyl)-N-phenylamino]biphenyl  
     [0110] 4,4″-Bis[N-(1-naphthyl)-N-phenylamino]p-terphenyl  
     [0111] 4,4′-Bis[N-(2-naphthyl)-N-pbenylamino]biphenyl  
     [0112] 4,4′-Bis[N-(3-acenaphthenyl)-N-phlenylamino]biphenyl  
     [0113] 1,5-Bis[N-(1-naphthyl)-N-phenylamino]naphthalene  
     [0114] 4,4′-Bis[N-(9-anthryl)-N-phenylamino]biphenyl  
     [0115] 4,4″-Bis[N-(1-anthryl)-N-phenylamino]-p-terphenyl  
     [0116] 4,4′-Bis[N-(2-phenanthryl)-N-phenylamino]biphenyl  
     [0117] 4,4′-Bis[N-(8-fluoranthenyl)-N-phenylamino]biphenyl  
     [0118] 4,4′-Bis[N-(2-pyrenyl)-N-phenylamino]biphenyl  
     [0119] 4,4′-Bis[N-(2-naphthacenyl)-N-phenylamino]biphenyl  
     [0120] 4,4′-Bis[N-(2-perylenyl)-N-phenylamino]biphenyl  
     [0121] 4,4′-Bis[N-(1-coronenyl)-N-phenylamino]biphenyl  
     [0122] 2,6-Bis(di-p-tolylamino)naphthalene  
     [0123] 2,6-Bis[di-(1-naphthyl)amino]naphthalene  
     [0124] 2,6-Bis[N-(1-naphthyl)-N-(2-naphthyl)amino]naphthalene  
     [0125] N,N,N′,N′-Tetra(2-naphthyl)-4,4″-diamino-p-terphenyl  
     [0126] 4,4′-Bis {N-phenyl-N-[4-(1-naphthyl)-phenyl]amino}biphenyl  
     [0127] 4,4′-Bis[N-phenyl-N-(2-pyrenyl)amino]biphenyl  
     [0128] 2,6-Bis[N,N-di(2-naphthyl)amine]fluorene  
     [0129] 1,5-Bis[N-(1-naphthyl)-N-phenylamino]naphthalene  
     [0130] Another class of useful hole-transporting materials includes polycyclic aromatic compounds as described in U.S. Pat. No. 6,361,886 to Shi, et al. The hole-transporting layer is deposited using the method of the present invention.  
     [0131] Light-Emitting Layer (LEL)  
     [0132] As more fully described in U.S. Pat. Nos. 4,769,292 to Tang, et al and 5,935,721 to Shi, et al, 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 is deposited using the method of the present invention. 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 that supports 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.  
     [0133] 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.  
     [0134] Host and emitting molecules known to be of use include, but are not limited to, those disclosed in U.S. Pat. No. 4,768,292, 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.  
     [0135] Metal complexes of 8-hydroxyquinoline and similar derivatives (Formula G) constitute one class of useful host compounds capable of supporting electroluminescence, and are particularly suitable for light emission of wavelengths longer than 500 nm, e.g., green, yellow, orange, and red.  
                 
 
     [0136] wherein:  
     [0137] M represents a metal;  
     [0138] n is an integer of from 1 to 3; and  
     [0139] Z independently in each occurrence represents the atoms completing a nucleus having at least two fused aromatic rings.  
     [0140] From the foregoing, it is apparent that the metal can be monovalent, divalent, or trivalent metal. The metal can, for example, be an alkali metal, such as lithium, sodium, or potassium; an alkaline earth metal, such as magnesium or calcium; or an earth metal, such as boron or aluminum. Generally any monovalent, divalent, or trivalent metal known to be a useful chelating metal can be employed.  
     [0141] Z completes a heterocyclic nucleus containing at least two fused aromatic rings, at least one of which is an azole or azine ring. Additional rings, including both aliphatic and aromatic rings, can be fused with the two required rings, if required. To avoid adding molecular bulk without improving on function the number of ring atoms is usually maintained at 18 or less.  
     [0142] Illustrative of useful chelated oxinoid compounds are the following:  
     [0143] CO-1: Aluminum trisoxine [alias, tris(8-quinolinolato)aluminum(III)] 
     [0144] CO-2: Magnesium bisoxine [alias, bis(8-quinolinolato)magnesium(II)] 
     [0145] CO-3: Bis[benzo{f}-8-quinolinolato]zinc (II)  
     [0146] CO-4: Bis(2-methyl-8-quinolinolato)aluminum(III)-μ-oxo-bis(2-methyl-8-quinolinolato) aluminum(III)  
     [0147] CO-5: Indium trisoxine [alias, tris(8-quinolinolato)indium] 
     [0148] CO-6: Aluminum tris(5-methyloxine) [alias, tris(5-methyl-8-quinolinolato) aluminum(III)] 
     [0149] CO-7: Lithum oxine [alias, (8-quinolinolato)lithium(1)] 
     [0150] Derivatives of 9,10-di-(2-naphthyl)anthracene (Formula H) constitute one class of useful hosts capable of supporting electroluminescence, and are particularly suitable for light emission of wavelengths longer than 400 nm, e.g., blue, green, yellow, orange or red.  
                                                  H                                        
 
     [0151] wherein: R 1 , R 2 , R 3 , and R 4  represent one or more substituents on each ring where each substituent is individually selected from the following groups:  
     [0152] Group 1: hydrogen, or alkyl of from 1 to 24 carbon atoms;  
     [0153] Group 2: aryl or substituted aryl of from 5 to 20 carbon atoms;  
     [0154] Group 3: carbon atoms from 4 to 24 necessary to complete a fused aromatic ring of anthracenyl; pyrenyl, or perylenyl;  
     [0155] Group 4: heteroaryl or substituted heteroaryl of from 5 to 24 carbon atoms as necessary to complete a fused heteroaromatic ring of furyl, thienyl, pyridyl, quinolinyl or other heterocyclic systems;  
     [0156] Group 5: alkoxylamino, alkylamino, or arylamino of from 1 to 24 carbon atoms; and  
     [0157] Group 6: fluorine, chlorine, bromine or cyano.  
     [0158] Benzazole derivatives (Formula I) constitute another class of useful hosts capable of supporting electroluminescence, and are particularly suitable for light emission of wavelengths longer than 400 nm, e.g., blue, green, yellow, orange or red.  
                 
 
     [0159] where:  
     [0160] N is an integer of 3 to 8;  
     [0161] Z is 0, NR or S; and  
     [0162] R and R′ are individually hydrogen; alkyl of from 1 to 24 carbon atoms, for example, propyl, t-butyl, heptyl, and the like; aryl or hetero-atom substituted aryl of from 5 to 20 carbon atoms for example phenyl and naphthyl, furyl, thienyl, pyridyl, quinolinyl and other heterocyclic systems; or halo such as chloro, fluoro; or atoms necessary to complete a fused aromatic ring;  
     [0163] B is a linkage unit consisting of alkyl, aryl, substituted alkyl, or substituted aryl, which conjugately or unconjugately connects the multiple benzazoles together.  
     [0164] An example of a useful benzazole is 2, 2′,  2 ″-(1,3,5-phenylene)tris[1-phenyl-1H-benzimidazole].  
     [0165] Desirable fluorescent dopants include derivatives of anthracene, tetracene, xanthene, perylene, rubrene, coumarin, rhodamine, quinacridone, dicyanomethylenepyran compounds, thiopyran compounds, polymethine compounds, pyrilium and thiapyrilium compounds, and carbostyryl compounds. Illustrative examples of useful dopants include, but are not limited to, the following:  
                 

                 

                 
 
     [0166] Electron-Transporting Layer (ETL)  
     [0167] Preferred thin film-forming materials for use in forming the electron-transporting layer III of the organic EL devices 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 and exhibit both high levels of performance and are readily fabricated in the form of thin films. Exemplary of contemplated oxinoid compounds are those satisfying structural formula (G), previously described. The electron-transporting layer is preferably deposited using the method of the present invention.  
     [0168] Other electron-transporting materials include various butadiene derivatives as disclosed in U.S. Pat. No. 4,356,429 to Tang and various heterocyclic optical brighteners as described in U.S. Pat. No. 4,539,507 to VanSlyke. Benzazoles satisfying structural formula (I) are also useful electron transporting materials.  
     [0169] In some instances, layers  109  and  111  can optionally be collapsed into a single layer that serves the function of supporting both light emission and electron transportation.  
     [0170] Cathode  
     [0171] When light emission is through the anode, the cathode layer  113  used in this invention can be comprised of nearly any conductive material. Desirable 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 (&lt;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. 4,885,211. Another suitable class of cathode materials includes bilayers comprised of a thin layer of a low work function metal or metal salt capped with a thicker layer of conductive metal. 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 materials include, but are not limited to, those disclosed in U.S. Pat. Nos. 5,059,861 to Littman, et al, U.S. Pat. No. 5,059,862 to VanSlyke, and U.S. Pat. No. 6,140,763 to Hung, et al.  
     [0172] When light emission is viewed through the cathode, the cathode must be transparent or nearly transparent. For such applications, metals must be thin or one must use transparent conductive oxides, or a combination of these materials. Optically transparent cathodes have been described in more detail in U.S. Pat. No. 5,776,623 to Hung, et al. Cathode materials can be 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 to Tang and EP 0 732 868 to Nagayama, et al, laser ablation, and selective chemical vapor deposition.  
     [0173] Stacked Structures  
     [0174] In order to increase the luminance output, a stacked organic electroluminescent device may be fabricated, where a plurality of organic electroluminescent units may be connected using a doped organic material. In this regard, the stacked electroluminescent device comprises of an anode, a cathode, a plurality of electorluminescent units disposed between the anode and the cathode and a doped organic connector disposed between each electroluminescent unit.  
     [0175]FIG. 6 shows a stacked OLED  200  wherein the organic electroluminescent layers may be deposited by the method of the present invention. This stacked OLED has an anode  210  and a cathode  240 , at least one of which is transparent. Disposed between the anode and the cathode arc N organic EL units  220 , where N is greater than 1. These organic EL units, stacked serially to each other and to the anode and the cathode, are designated  220 . 1  to  220 .N where  220 . 1  is the first EL unit (adjacent to the anode) and  220 .N is the Nth unit (adjacent to the cathode). When N is greater than 2, there are organic EL units not adjacent to the anode or cathode, and these can be referred to as intermediate organic EL units. Disposed between any two adjacent organic EL units is a doped organic connector  230 . There are a total of N−1 doped organic connectors associated with N organic EL units and they are designated  230 . 1  to  230 .(N−1). Organic connector  230 . 1  is the doped organic connector between organic EL units  220 . 1  and  220 . 2 , and  230 .(N−1) is the doped organic connector disposed between organic EL units  220 .(N−1) and  220 .N. The stacked OLED  200  is connected to a voltage/current source  250  through electrical conductors  260 .  
     [0176] Stacked OLED  200  is operated by applying an electric potential generated by a voltage/current source  250  between a pair of contact electrodes, anode  210  and cathode  240 , such that anode  210  is at a more positive potential with respect to the cathode  240 . This externally applied electrical potential is distributed among the N organic EL units in proportion to the electrical resistance of each of these units. The electric potential across the stacked OLED causes holes (positively charged carriers) to be injected from anode  210  into the 1 st  organic EL unit  220 . 1 , and electrons (negatively charged carriers) to be injected from cathode  210  into the Nth organic EL unit  220 .N. Simultaneously, electrons and holes are generated in, and separated from, each of the doped organic connectors ( 230 . 1 - 230 .(N−1)). Electrons thus generated in, for example, doped organic connector  230 .(x−1) (1&lt;x≦N) are injected towards the anode and into the adjacent organic EL unit  220 .(x−1). Likewise, holes generated in the doped organic connector  230 .(x−1) are injected towards the cathode and into the adjacent organic EL unit  220 . x . Subsequently, these electrons and holes recombine in their corresponding organic EL units to produce light, which is observed via the transparent electrode or electrodes of the OLED.  
     [0177] The number of the organic EL units in the stacked OLED is, in principle, equal to or more than 2. Preferably, the number of the organic EL units in the stacked OLED is such that the luminance efficiency in units of cd/A is improved or maximized.  
     [0178] Device Architecture  
     [0179] Organic Electroluminescent (EL) Units  
     [0180] Each organic EL unit  220  in the stacked OLED  200  is capable of supporting hole and electron transport, and electron-hole recombination to produce light. Each organic EL unit  220  can include a single layer or a plurality of layers. Organic EL unit  220  can be formed from small molecule OLED materials or polymeric LED materials, both known in the art, or combinations thereof. There are many organic EL multilayer structures and materials known in the art that can be used as the organic EL unit of this invention. Each organic EL unit in the stacked OLED device can be the same or different from other units. Some organic EL units can be polymeric LED and other units can be small molecule OLEDs. Each organic EL unit can be selected in order to optimize performance or achieve a desired attribute, for example light transmission through the OLED stack, driving voltage, luminance efficiency, light emission color, manufacturability, device stability, and so forth.  
     [0181]FIG. 7 illustrates another useful embodiment of a stacked OLED  300  wherein the multiple organic electroluminescent layers may be deposited by the method of the present invention. In FIG. 7, there are N organic EL units  320 , each comprising HTL  323  and ETL  327 . The layer structure of this basic unit is conveniently denoted as HTL/ETL. The doped organic connectors  230  are also provided between organic EL units and function as described above. In device  300  the doped organic connectors facilitate hole injection into the HTL of one organic EL unit and electron injection into ETL of the adjacent organic EL unit. Within each organic EL unit, the transport of the hole and electron carriers is supported by the HTL and ETL, respectively. Recombination of the hole and electron carriers in the vicinity at or near the HTL/ETL interface within each organic EL unit causes light to be produced (electroluminescence). The HTL in each organic EL unit are designated  323 . 1  to  323 .N where, in this embodiment,  323 . 1  is the HTL in organic EL unit  320 . 1  adjacent to the anode, and  323 .N is the HTL in organic EL unit  320 .N adjacent to the cathode. Similarly, the ETL in each organic EL unit are designated  327 . 1  to  327 .N. The HTL in each organic EL unit can be the same or different in terms of materials used, layer thickness, method of deposition, and so forth. The properties of the HTL in the device can be individually optimized to achieve the desired performance or feature, for example, light transmission through the OLED stack, driving voltage, luminance efficiency, light emission color, manufacturability, device stability, and so forth. The same is true for the ETL. Although not necessary, it is preferable that a hole-injecting layer (HIL)  321 . 1  be provided between anode  210  and the first HTL,  323 .N. It is also preferable, but not necessary, that an electron-injecting layer (EIL)  329 .N be provided between the cathode and the last ETL,  327 .N. Both the HIL and EIL improve charge injection from the electrodes. While not shown in FIG. 7, organic EL units can optionally include a HIL between a HTL and a doped organic connector. Similarly, organic EL units can optionally include an EIL between an ETL and a doped organic connector.  
     [0182]FIG. 8 illustrates another embodiment of a stacked OLED  400 , wherein the organic EL unit  420  includes a light-emitting layer (LEL)  325  disposed between a HTL and an ETL. This unit structure is conveniently designated HTL/LEL/ETL. In this embodiment, the recombination of the hole and electron carriers and electroluminescence occurs primarily in the LEL. The LEL in each organic EL unit are designated  325 . 1  to  325 .N where, in this embodiment,  325 . 1  is the LEL in organic EL unit  420 . 1  adjacent to the anode, and  325 .N is the LEL in organic EL unit  420 .N adjacent to the cathode. The properties of the LEL in the device can be individually optimized to achieve the desired performance or feature, for example light transmission through the OLED stack, driving voltage, luminance efficiency, light emission color, manufacturability, device stability, and so forth. The description above regarding the HTL, ETL, HIL, and EIL, apply to FIG. 8 as well.  
     [0183] In order to minimize driving voltage for the stacked OLED, it is desirable to make each organic EL unit as thin as possible without compromising the electroluminescence efficiency. It is preferable that each organic EL unit is less than 500 nm thick, and more preferable that it be 2 200 nm thick. It is also preferable that each layer within the organic EL unit be 200 nm thick or less.  
     [0184] Doped Organic Connectors  
     [0185] The doped organic connectors provided between adjacent organic EL units are crucial, as this connection is needed to provide for efficient electron and hole injection into the adjacent organic EL units. Each doped organic connector of this invention includes at least one n-type (loped organic layer, or at least one p-type doped organic layer, or a combination of layers, thereof.  
     [0186] Preferably, the doped organic connector includes both an n-type doped organic layer and a p-type doped organic layer disposed adjacent to one another to form a p-n heterojunction. It is also preferred that the n-type doped organic layer is disposed towards the anode side, and the p-type doped organic layer is disposed towards the cathode side. A non-limiting example of this configuration is shown in FIG. 9, where there are two stacked organic EL units,  320 . 1  and  320 . 2 .  
     [0187] Definitions for ETL, HTL, HIL, and EIL are as defined previously. In stacked OLED  500 , n-type doped organic layer  237  is provided between ETL  327 . 1  and p-type doped organic layer  233 . The p-type doped organic layer  233  is provided between n-type doped organic layer  237  and HTL  323 . 2 . The choice of using n-type doped organic layer, or a p-type doped organic layer, or both (the p-n junction) is in part dependent on the organic materials that include the organic EL units. Each connector can be optimized to yield the best performance with a particular set of organic EL units. This includes choice of materials, layer thickness, modes of deposition, and so forth.  
     [0188] An n-type doped organic layer means that the organic layer has semi-conducting properties after doping, and the electrical current through this layer is substantially carried by the electrons. A p-type doped organic layer means that the organic layer has semi-conducting properties after doping, and the electrical current through this layer is substantially carried by the holes. A p-n heterojunction means an interfacial region (or junction) formed when a p-type layer and an n-type layer are contacted each other.  
     [0189] The n-type doped organic layer in each doped organic connector includes a host organic material and at least one n-type dopant. The host material in the n-typed doped organic layer can include a small molecule material or a polymeric material, or combinations thereof, and it is preferred that it can support electron transport. The p-type doped organic layer in each of the doped organic connector includes a host organic material and at least one p-type dopant. The host material can include a small molecule material or a polymeric material, or combinations thereof, and it is preferred that it can support hole transport. In some instances, the same host material can be used for both n-typed and p-type doped organic layers, provided that it exhibits both hole and electron transport properties set forth above. The n-type doped concentration or the p-type doped concentration is preferably in the range of 0.01-10 vol. %. The total thickness of each doped organic connector is typically less than 100 nm, and preferably in the range of about 1 to 100 nm.  
     [0190] The organic electron-transporting materials used in conventional OLED devices represent a useful class of host materials for the n-type doped organic layer. Preferred materials are metal chelated oxinoid compounds, including chelates of oxine itself (also commonly referred to as 8-quinolinol or 8-hydroxyquinoline), such as tris(8-hydroxyquinoline) aluminum. Other materials include various butadiene derivatives as disclosed by Tang (in U.S. Pat. No. 4,356,429), various hcterocyclic optical brighteners as disclosed by VanSlyke (in U.S. Pat. No. 4,539,507), triazines, hydroxyquinoline derivatives, and benzazole derivatives. Silole derivatives, such as 2,5-bis( 2 ′, 2 ″-bipridin-6-yl)-1,1-dimethyl-3,4-diphenyl silacyclopentadiene as reported by Murata et al. [Applied Physics Letters, 80, 189 (2002)], are also useful host materials.  
     [0191] The materials used as the n-type dopants in the n-type doped organic layer of the doped organic connectors include metals or metal compounds having a work function less than 4.0 eV. Particularly useful dopants include alkali metals, alkali metal compounds, alkaline earth metals, and alkaline metal compounds. The tenn “metal compounds” includes organometallic complexes, metal-organic salts, and inorganic salts, oxides and halides. Among the class of metal-containing n-type dopants, Li, Na, K, Rb, Cs, Mg, Ca, Sr, Ba, La, Ce, Sm, Eu, Tb, Dy, or Yb, and their compounds, are particularly useful. The materials used as the n-type dopants in the n-type doped organic layer of the doped organic connectors also include organic reducing agents with strong clcctron-donating properties. By “strong electron-donating properties” it is meant that the organic dopant should be able to donate at least some electronic charge to the host to form a charge-transfer complex with the host. Non-limiting examples of organic molecules include bis(ethylenedithio)-tetrathiafulvalene (BEDT-TTF), tetrathiafulvalene (TTF), and their derivatives. In the case of polymeric hosts, the dopant can be any of the above or also a material molecularly dispersed or copolymerized with the host as a minor component.  
     [0192] The hole-transporting materials used in conventional OLED devices represent a useful class of host materials for the p-type doped organic layer. Preferred materials include aromatic tertiary amines having 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. Other suitable triarylamines substituted with one or more vinyl radicals and/or comprising at least one active hydrogen-containing group are disclosed by Brantley et al. (U.S. Pat. Nos. 3,567,450 and 3,658,520). A more preferred class of aromatic tertiary amines are those which include at least two aromatic tertiary amine moieties as described by VanSlyke (U.S. Pat. Nos. 4,720,432 and 5,061,569). Non-limiting examples include as N,N′-di(naphthalene-1-yl)-N,N′-diphenyl-benzidine (NPB) and N,N′-diphenyl-N,N′-bis(3-methylphenyl)-1,1-biphenyl-4,4′-diamine (TPD), and N,N,N′,N′-tetranaphthyl-benzidine (TNB).  
     [0193] The materials used as the p-type dopants in the p-type doped organic layer of the doped organic connectors are oxidizing agents with strong electron-withdrawing properties. By “strong electron-withdrawing properties” we mean that the organic dopant should be able to accept some electronic charge from the host to form a charge-transfer complex with the host. Some non-limiting examples include organic compounds such as 2,3,5,6-tetrafluoro-7,7,8,8-tetracyanoquinodimethane (F 4 -TCNQ) and other derivatives of TCNQ, and inorganic oxidizing agents such as iodine, FeCl3, SbCl5, and some other metal chlorides. In the case of polymeric hosts, the dopant can be any of the above or also a material molecularly dispersed or copolymerized with the host as a minor component.  
     [0194] Examples of materials that can be used as host for either the n-type or p-type doped organic layers include, but are not limited to: various anthracene derivatives as described in Formula F below and in U.S. Pat. No. 5,972,247 to Shi, et al, certain carbazole derivatives, such as 4,4-bis(9-dicarbazolyl)-biphenyl (CBP); and distyrylarylene derivatives such as 4,4′-bis(2,2′-diphenyl vinyl)-1,1′-biphenyl and as described in U.S. Pat. No. 5,121,029 to Hosakawa, et al.  
     [0195] The materials used for fabricating the doped organic connectors of this invention are substantially transparent to emitting light.  
     [0196] Encapsulation  
     [0197] Most OLED devices are sensitive to moisture and/or oxygen and must therefore be encapsulated in a hermetic enclosure that includes an oxygen and moisture impenetrable substrate and cover member that are sealed in a dry, inert, atmosphere such as nitrogen or argon. A desiccant such as alumina, bauxite, calcium sulfate, clays, silica gel, zeolites, alkaline metal oxides, alkaline earth metal oxides, sulfates, or metal halides and perchlorates may be used to dry the process chamber atmosphere and may be included in the enclosure as described in U.S. Pat. No. 6,226,890 to Boroson, et al. The cover member may be directly deposited over the cathode structure of the OLED device or may consist of a separate element that is bonded to the substrate subsequent to deposition of the EL layers. Hermetic bonding of the substrate and cover member may be accomplished by a variety of means, e.g., direct bonding, represented by surface activation methods and electrostatic or anodic bonding and indirect bonding whcre an intermediate material is introduced between the substrate and cover member as a bonding agent. Suitable intermediate materials include organic bonding agents such as epoxy compounds that may be filled with micro glass beads, particles or rods, and inorganic bonding agents such as low melting temperature glasses and metallic alloys. An inorganic seal material is preferable to minimize oxygen and moisture permeability and may obviate the need to add a desiccant if the seal is performed under the same dry, inert conditions as the EL layer coating deposition process. A coating such as indium tin oxide, nickel or gold on the substrate and cover member may be used to facilitate adhesion of the bonding agent to the substrate. Ribbons, wires, powders, pastes and preforms of organic and inorganic bonding agents may be dispensed on the substrate perimeter as required. The bonding agent may advantageously be deposited in a precisely controlled manner through the use of ink-jet technologies that propel drops of bonding agent onto a substrate to form discrete drops or continuous traces. The sealing process must not generate damaging by-products from, for example, dissociated gases and is constrained by the temperature limitations of the EL coatings unless it is possible to limit these effects to the seal area.  
     [0198] Electrical Considerations  
     [0199] An electrical potential must be developed across the thickness of the EL coatings in order for them to emit light. The intensity of the emitted light is related to the local voltage potential so the transparent, electrically conductive layers acting as the anode or cathode must be sufficiently conductive, and have an adequate number of connection points to maintain a substantially constant voltage across their active area. A number of electrical edge connection locations in parallel may be required on either or both the anode and cathode to achieve the required voltage uniformity across the panel. It may further be required to create narrow, opaque bus structures on the face of the panels that are barely visible at normal viewing distances. The purpose of this bus is to maintain a reasonably constant voltage over the anode area. The bus may consist of aluminum that is deposited in a grid pattern having narrow traces that cover perhaps 10% of the anode area. The use of this bus structure reduces the requirement on the ITO layer that it have low electrical resistance. This in turn reduces the required ITO thickness and thereby improves the optical transmission efficiency of the anode area not obstructed by the bus structure.  
     [0200] Extraction Efficiency  
     [0201] Refractive index differences between the EL layers, ITO, substrate and air cause as much as 80% of generated light to reflect off the interfaces and be trapped and attenuated in the structure. Only light that is emitted at sufficiently small angles to the substrate normal will escape as useable light. It is therefore desirable to minimize the number of optical transmission layers having different optical indices or to match the indices of the layers. Additionally, it is advantageous to incorporate light piping and scattering structures that are dispersed according to their function in the appropriate coatings to redirect internally reflected light out through the substrate [Yamasaki, T., et. al.,  Appl. Phys. Lett.,  76, 1243 (2000)]. A complimentary approach is to pattern surface features on one or both sides of the emitting-side substrate that effectively increases the critical escape angle [Schnitzer, I., Yablonovitch, E.,  Appl. Phys. Lett.,  63, 2174 (1993)], [Lupton, J. M., et. al., Appl. Phys. Lett. 77, 3340 (2000)].  
     [0202] Mechanical Protection  
     [0203] A plastic laminate may advantageously be applied over a thin glass substrate to increase its shock resistance and durability and may also be advantageously applied over a thin aluminum or glass cover member for the same reasons. This laminate may be patterned so as to serve as a light diffuser and may advantageously include a featured surface in the form of a hemispherical lens array to again improve the light extraction efficiency [Madigan, C., et. al.,  Appl. Phys. Lett.,  76, 1650 (2000)]. Finally, a frame structure is envisioned that supports, protects and provides rigidity to the light panel and additionally provides a convenient and rugged means of making electrical contact.  
     [0204] The entire contents of the patents and other publications referred to in this specification are incorporated herein by reference.  
     [0205] 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                                                 10   Delivery System            11   Compressed Fluid Source            12   Formulation Reservoir            12a   High-pressure Vessels            13   Discharge Device            14   Receiver            15   Valve(s)            16   Delivery Path            17   Pressure Control Mechanism            18   Pump            19a   Pressure Regulator            19b   Multi-stage Pressure               Regulator            20   Temperature Control               Mechanism            21   On/Off Valve            22   Shutter            23   Nozzle            24   Stream Deflector/Catcher               Module            25   Receiver            26   Nozzle Heating Element            27   Nozzle Shield Gas Module            28   Cylinder            29   Square            30   Triangle            31   Variable Area Converging            32   Variable Area Converging-               Diverging            33   Shape            34   Converging Section or               Module            35   Throat Section or Module            36   Diverging section or Module            37   Straight section or Module            38   Variable Area Diverging            40   Functional Material            41   Compressed Fluid            42   Formulation            43   Spray            44   Functional Material            45   Evaporation            46   Individual Particles            47   Nozzle Opening            49   Flexible Substrate            50   Media Conveyance               Mechanim            52   Inlet Ports            54   Inlet Ports            56   Inlet Ports            58   Outlet Ports            59   Inlet/Outlet Ports            60   Pump            62   Delivery Path            64   Functional Material            70   Mixing Device            72   Mixing Element            74   Power/Control source            76   Moveable Piston Device            78   Heating/Cooling Zones            80   Electrical Wires            82   Electrical Tapes, Water               Jackets            84   Refrigeration Coils            86   High-pressure Widows            88   Control Device            90   Microprocessors           101   Substrate           103   Anode           105   Hole-Injecting layer (HIL)           107   Hole-Transporting layer               (HTL)           109   Light-Emitting layer (LEL)           111   Electron-Transporting layer               (ETL)           113   Cathode           200   Stacked OLED           210   Anode           220   Cathode           220.1   EL Unit           220.2   EL Unit           220.N   EL Unit           220(N-1)   EL Unit           230   Doped Organic Connector           230.1   Organic Connector           230.2   Organic Connector           230(N-1)   Doped Organic Connector           233   Doped Organic Layer           237   Doped Organic Layer           240   Cathode           250   Voltage/Current Source           260   Electrical Conductors           300   Stacked OLED           320   N Organic EL Units           320.1   EL Unit           320.2   EL Unit           320.N   El Unit           321.1   Hole Injection Layer           323   HTL           323.1   HTL in Organic EL Unit           323.2   HTL           323.N   HTL in Organic EL Unit           325   Light Emitting Layer           325.1   LEL           325.N   LEL           327   ETL           327.1   ETL in Organic EL Unit           327.N   ETL in Organic EL Unit           329.N   Electron-Injecting Layer           400   Stacked OLED           420   EL Unit           420.1   EL Unit           420.N   EL Unit           500   Stacked OLED