Abstract:
Electroluminescent (EL) displays, media, and members, and methods associated therewith. One such display includes an EL material, conductor layers, and a reflective image formed by a pattern of imaging substance applied adjacent at least one of the conductor layers. The EL material is between at least two of the conductor layers, and at least one of the conductor layers is applied adjacent the EL material in a pattern to form a conductive image. Upon application of an operational potential to the at least two of the conductor layers having the EL material therebetween, the display can be illuminated in an area corresponding to the conductive image.

Description:
FIELD OF THE DISCLOSURE 
   The disclosure is directed to electroluminescent (EL) displays and methods to produce such displays. In particular, in one embodiment, the disclosure is directed to EL displays fabricated using micro-fluid ejection methods. 
   BACKGROUND AND SUMMARY 
   A variety of displays are used to attract the attention of consumers. Illumination of these displays is often provided by incandescent or fluorescent lighting systems which are expensive to construct and operate. 
   In order to provide lower cost illumination of displays (which, as used herein, also includes signs, billboards, other types of signage and the like), newer, lower cost illumination devices may be used. For example, one type of display device in use today uses electroluminescence (EL) technology to emit light, thereby featuring an image. Illumination of the display device is accomplished by placing alternating electric fields across a layer of electroluminescent material that is sandwiched between a transparent conductor layer and a second conductor layer usually with an intervening dielectric to prevent voltage breakdown. 
   A translucent substrate containing an image printable layer may be applied to an electroluminescent substrate containing the electroluminescent material and an image may be printed on the image printable layer. Upon activation of the electroluminescent material, the image is illuminated. Construction of one such electroluminescent media is described for example in U.S. Publication No. 2002/0090495, the disclosure of which is incorporated herein by reference. 
   Conventional electroluminescent displays are typically highly customized. Hence, everything from the display device to any related driving electronics is unique to a particular end use of the display. Thus, the user&#39;s ability to implement changes to the display is limited and changes or alterations of the display may be extremely costly. 
   Another disadvantage of conventional electroluminescent displays is that such displays usually require illumination of the entire electroluminescent media at one time. Accordingly, it is difficult to provide displays with selective illumination or displays having the appearance of motion. Accordingly, there remains a need for improved electroluminescent display systems. 
   With regard to the foregoing needs, an exemplary embodiment of the disclosure provides a display including an electroluminescent (EL) material, conductor layers, and a reflective image formed by a pattern of imaging substance applied adjacent at least one of the conductor layers. The EL material is between at least two of the conductor layers, and at least one of the conductor layers is applied adjacent the EL material in a pattern to form a conductive image. Upon application of an operational potential to the at least two of the conductor layers having the EL material therebetween, the display can be illuminated in an area corresponding to the conductive image. 
   Another exemplary embodiment of the disclosure provides a method for making a display comprising an electroluminescent (EL) material and conductor layers, wherein the EL material is between at least two of the conductor layers. The method involves applying imaging substance in a pattern adjacent at least one of the conductor layers to form a reflective image. At least one of the conductor layers is applied adjacent the EL material in a pattern to form a conductive image. Upon application of an operational potential to the at least two of the conductor layers having the EL material therebetween, the display can be illuminated in an area corresponding to the conductive image. 
   An advantage of at least some of the foregoing embodiments is that customized displays using EL materials may be made at a customer&#39;s site using relatively inexpensive imaging apparatus, such as printers. Since designs may be created quickly on a computer and printed with relative ease on a second substrate such as paper, such displays may be fabricated quickly and at less cost than with slower depositing techniques that require blanket EL layers. Hence, the embodiments described herein may provide displays and signage that enable a wider range of design features and improved interchangeability of the displays. 

   
     BRIEF DESCRIPTION OF THE DRAWINGS 
     Further advantages of the exemplary embodiments may become apparent by reference to the detailed description when considered in conjunction with the elements through the several views, and wherein: 
       FIG. 1A  is a cross-sectional view, not to scale, of an electroluminescent (EL) display according to the disclosure; 
       FIG. 1B  is a plan view, not to scale, of an electroluminescent (EL) display according to the disclosure; 
       FIG. 2  is a cross-sectional view, not to scale, of a first member (including an electroluminescent (EL) substrate, an adhesion layer, a translucent image receiving layer, and an image) and a second member (including a second substrate and an electrode layer) according to the disclosure; 
       FIG. 3  is a cross-sectional view, not to scale, of a first member of an electroluminescent (EL) display according to the disclosure. 
       FIG. 4  is a flow diagram depicting the steps of a method to fabricate an EL display according to the disclosure; and 
       FIG. 5  is a cross-sectional view, not to scale, of a first member (including an electroluminescent (EL) substrate, a removable liner layer, an adhesive layer, a translucent image receiving layer, and an image) and a second member (including a second substrate and an electrode layer) according to the disclosure. 
   

   DETAILED DESCRIPTION OF EXEMPLARY EMBODIMENTS 
   As described in more detail below, embodiments of the disclosure provide a system and method for providing improved EL displays. A pattern(s) may be printed on an EL substrate to provide, for example, a customized display that is attachable to a second substrate. Conductive material may be printed in a pattern(s) on a second substrate to form a conductive image. The second substrate may be attached to the EL substrate, thereby creating an EL display that may be selectively illuminated by the introduction of an electric current to the pattern of conductive material. 
   With reference to  FIG. 1 , there is provided a cross-sectional view, not to scale, of a display  10  including a substrate  12 . In this embodiment, the substrate  12  is an EL substrate. Current commercially available EL substrates  12  typically include an insulative or dielectric layer  14 , an EL material layer  16 , a translucent conductor layer  18 , and a translucent protective layer  20 . It is conceivable that EL substrates  12  could reduce the number of these layers by incorporating some or all of these functions in the EL material itself, for example. Furthermore, some applications may not require one or more of these layers. For example, in some disposable applications, the protective layer  20  may not be needed. 
   Although it may not be necessary for some current or future printing techniques and/or EL substrates, an image receiving layer  22  may be applied to the translucent protective layer  20  to provide a suitable surface for receiving a reflective image  24 . The image  24  can be printed on to a first surface  26  of the image receiving layer  22 . An adhesion layer  28  can be applied to a second surface  30  of layer  14 . A plan view of the display  10  with an image  24  is shown in  FIG. 1B . 
   Layers  14 ,  16 ,  18 ,  20 ,  22 , and  28  comprise a first medium  34  on which the image  24  is applied to form a first member  32  (shown separately in  FIG. 2 ). The image  24  may be provided by a pattern of applied imaging substance such as, for example, monochrome or color inks. Such a substance may be applied to the image receiving layer  22  using, for example, screen printing, rotogravure printing, flexographic printing, lithographic printing, laser printing, ink jet printing, and the like. More flexibility in applying an image to the image receiving layer  22  may be provided by ink jet printing as described in U.S. Publication No. 2002/0090495. 
   The first medium  34  has an overall thickness ranging from about 0.1 to about 0.6 millimeters. The insulative or dielectric layer  14  typically has a thickness ranging from about 20 to about 200 micrometers, and may be provided by a material selected from tantalum oxide, aluminum oxide, alumina, aluminosilicates, borosilicate glass, an alkali metal aluminosilicate hydrate, polyester films, polyimide films, polyamide films, polycarbonate films, poly(phenylene oxide films, poly(phenylene sulfide) films, poly(vinyl chloride) films, poly(chlorotrifluoroethylene) films, poly(p-phenyleneethylene) films, polystyrene films, polyethylene films, polypropylene films, poly(tetrafluoroethylene) films, and the like. A particularly suitable layer  14  might comprise a fluoropolymer material, such as a poly(tetrafluoretheylene), loaded with an alkaline earth metal titanate (or, e.g., barium titanate or strontium titanate). 
   The EL layer  16  may include organic and/or inorganic EL materials. Inorganic materials typically provide brighter luminous characteristics and may be selected from terbium-doped zinc sulfide (ZnS:Tb), manganese-doped zinc sulfide (ZnS:Mn), cerium-doped yttrium aluminum garnet (YAG:Ce), copper-doped zinc selenium sulfide (ZnSeS:Cu), europium-doped strontium barium silicon oxide (SrBaSiO4:Eu), cerium-doped strontium sulfide (SrS:Ce), copper-doped strontium sulfide (SrS:Cu), copper and silver-doped strontium sulfide (SrS:Cu,Ag), and the like. The thickness of the EL layer  16  may range from about 100 nanometers to about 5 microns. 
   The conductor layer  18  of the EL substrate  12  is typically made of a translucent conductive material such as indium tin oxide (ITO), zinc oxide, aluminum- or boron-doped zinc oxide, cadmium sulfide, cadmium oxide, tin oxide, and Fluorine-doped tin oxide. The conductor layer  18  typically has a thickness ranging from about 50 to about 10,000 Angstroms. 
   A protective transparent or translucent protective layer  20  is applied to the translucent conductor layer  18 . The translucent protective layer  20  may be selected from polyethylene terephthalate, polybutylene &gt;terephthalate, polycarbonate, and the like. The thickness of the protective layer  20  may range from about 20 to about 150 micrometers). 
   The EL substrate  12  is relatively thin and ideally flexible so that it can be easily handled in an imaging apparatus, such as an ink jet printer. Overall, the thickness of the EL substrate  12  ranges from about 0.1 to about 0.5 millimeters EL substrates  12  as described above are commercially available from BKL, Inc. of King of Prussia, Pa., Luminescent Systems, Inc. of Lebanon, N.H., and Edmund Optics, Inc. of Barrington, N.J. 
   As previously mentioned, an image receiving layer  22 , such as an ink receptive layer, can be applied adjacent (e.g., to) the protective layer  20  of the EL substrate  12 . The image receiving layer  22  may be provided by a wide variety of micro-porous organic or inorganic materials that are, for example, compatible with the ink applied to form the image  24 . One such image receiving layer  22  is a layer of fumed silica in a binder. The thickness of the image receiving layer  22  may range from about 1 to about 40 micrometers. 
   The image receiving layer  22  may be applied to the protective layer  20  by a wide variety of coating techniques, including but not limited to, roll coating, doctor blade coating, spray coating, dipping, screen coating, and the like. However, in order to minimize the cost of the EL display  10 , the image receiving layer  22  may be applied by a micro-fluid ejection device in the same pattern as the image  24 , since the image  24  may not be applied to the entire area of the EL substrate  12  as shown in  FIG. 1B . 
   A second medium  36  is provided, such as one comprising a second substrate  38 . Another conductor layer, such as electrode layer  40 , may be applied in a pattern to form a conductive image on the second substrate  38  by a wide variety of printing techniques including, but not limited to, screen printing, rotogravure printing, flexographic printing, lithographic printing, and ink jet printing. The electrode layer  40  may also be, for example, a single conductive layer (e.g., where conductor layer  18  is applied adjacent the EL material layer in a pattern). Conductive inks that may be used to provide the electrode layer  40 , include, but are not limited to inks containing copper, silver, or carbon particles. In order to provide increased flexibility for design and operation of the EL display  10 , a conductive ink may be applied by a micro-fluid ejection device to provide the selective conductor pattern for the electrode layer  40 : In an alternative embodiment, the electrode layer  40  might be applied directly onto surface  30  of EL substrate  12  (adhesion layer  28  therefore being unnecessary). 
   The thickness of the electrode layer  40  may range from about 0.5 to about 5 micrometers. The second medium  36  having an electrode layer  40  formed thereon may be viewed as constituting a second member  42 , shown separated from first member  32  in  FIG. 2 . With reference back to  FIG. 1 , the second member  42  can be attached to the first member  32  adjacent a third surface  44  of the adhesion layer  28  to form the EL display  10 . 
   The second substrate  38  for supporting the electrode layer  40  can be made of paper ranging in thickness from about 0.5 to about 2 mils (or about 15 to about 50 micrometers). The second substrate  38  may, however, consist of other materials such as coated paper, PET, polycarbonate films, polyamide films, polystyrene films, polypropylene films, and the like. 
   The EL display  10  will illuminate in areas  48  where the electrode layer  40  has been deposited (corresponding to the conductive image) when an operational potential is applied between conductor layer  18  and the electrode layer  40 . The electrode layer  40  may be further subdivided into more than one sublayer such as a conductor layer, contact pads, and a trace layer connecting the conductor layer to the contact pads, or may constitute a single layer including any necessary electrical traces and contact pads. 
   A viewer, looking at the EL display  10  ( FIG. 1 ) in the direction of arrow  46 , may see illuminated areas (designated one-dimensionally by block  48 ) corresponding to areas where the electrode layer  40  has been applied to the second substrate  38 . A viewer, looking at the EL display apparatus  10  in the direction of arrow  46 , may also see reflective image areas (designated one-dimensionally by block  50 ) corresponding to areas where the image  24  was applied to the image receiving layer  22 . The illuminated areas  48  and the reflective image areas  50  may or may not overlap with one another. 
   One embodiment of the present invention shown in  FIG. 3  includes an electroluminescent (EL) display first member  132 . The first member  132  includes an EL substrate  112 . As mentioned in the previous embodiment with reference to EL substrate  12  in  FIG. 1 , the EL substrate  112  shown in  FIG. 3  typically includes an insulative or dielectric layer  114 , an EL material layer  116 , a translucent conductor layer  118 , and a translucent protective layer  120 . An image receiving layer  122  may be applied to the translucent protective layer  120  to provide a suitable surface for receiving an image  124 . The image  124  may be printed onto a first surface  126  of the image receiving layer  122 . An adhesion layer  128  can be applied to a second surface  130  of the insulative layer  114 . 
   In this embodiment, the adhesion layer  128  includes at least two sub-layers including a removable liner layer  128 A and an adhesive layer  128 B. The adhesive layer  128 B has a thickness ranging from about 7 to about 75 micrometers, and should remain substantially attached to the second surface  130  of the insulative layer  114  if and when the removable liner layer  128 A is removed. The adhesive layer  128 B can be used to attach the first member  132  to an electrical conductive member such as one formed on a second medium (e.g., medium  36  shown in  FIG. 1A  or medium  236  shown in  FIG. 5 ). The identity of and physical properties of the materials that make up the first member  132  can be similar to those described above with reference to the first member  32  as shown in  FIG. 2 . Therefore, the properties and characteristics of first member  132  will not be repeated here. 
   Yet another embodiment of the invention includes a method to fabricate an is EL display such as EL display  10 .  FIG. 4  provides a flow chart summarizing the steps of one method described herein.  FIG. 5  illustrates fabrication of an EL display according to the flow chart provided in  FIG. 4  and the following description. The first step  140  in  FIG. 4  includes providing a first medium  234 , such as one similar to the first medium  34  described above. As shown in step  142 , a reflective image  224 , such as one similar to image  24  described above, can be printed onto the first medium  234 , such as through the use of micro-fluid ejection printing technology. Step  144  of the process includes removing a removable liner layer  228 A, such as one similar to removable liner layer  128 A discussed above. If a removable liner is not present, step  144  may be skipped. 
   Step  146  includes providing a second medium  236 , such as one similar to second medium  36  shown in  FIG. 1A . At least one conductor layer  240  is then printed onto the second medium  236  as shown in step  148 . As discussed in previous embodiments, the conductor layer  240  may be further subdivided into more than one sublayer, such as a conductor layer, contact pads, and a trace layer connecting the conductor layer to the contact pads, or may constitute a single layer including any necessary electrical traces and contact pads. If the conductor layer  240  is further subdivided into more than one layer, additional printing steps such as step  150  may be necessary to apply the additional layer or layers. As shown in step  152 , the first medium  234  and the second medium  236  may be combined (e.g., attached to one another, as by an adhesive layer  228  similar to adhesion layer  28  ( FIG. 1A ) or adhesive layer  128 B ( FIG. 3 )). It should be understood that the first set of steps (steps  140 ,  142 , and  144 ) and the second set of steps ( 146 ,  148 , and  150 ) may occur simultaneously or in different orders. 
   Having described various aspects and embodiments herein and several advantages thereof, it will be recognized by those of ordinary skill that the disclosed embodiments are susceptible to various modifications, substitutions and revisions within the spirit and scope of the appended claims.