BRIEF DESCRIPTION OF THE DRAWINGS
FIG. 1 shows a nixel in an ELD of the present invention.
FIG. 2 shows a cross-section of a nixel in accordance with an exemplary embodiment of the invention.
FIG. 3 shows a flowchart of a method in accordance with an exemplary embodiment of the invention.
FIG. 4 shows a cross-section of a nixel in accordance with an exemplary embodiment of the invention.
FIG. 5 shows a flowchart of a method in accordance with an exemplary embodiment of the invention.
FIGS. 6A-6I illustrate the stages of a method in accordance with an exemplary embodiment of the invention.
FIG. 7 shows variably-shaped nixels in accordance with an exemplary embodiment of the invention.
FIG. 8 shows a flowchart of a method in accordance with an exemplary embodiment of the invention.
FIG. 9 shows a multicolor nixel in accordance with an exemplary embodiment of the invention.
FIG. 10 shows a flowchart of a method in accordance with an exemplary embodiment of the invention.
FIG. 11 shows a method in accordance with an exemplary embodiment of the invention.
FIG. 12 shows a flowchart of a method in accordance with an exemplary embodiment of the invention.
FIG. 13 shows a flowchart of a method in accordance with an exemplary embodiment of the invention.
FIG. 14 shows a flowchart of a method in accordance with an exemplary embodiment of the invention.
FIG. 15 shows a flowchart of a method in accordance with an exemplary embodiment of the invention.
FIG. 16 shows an ELD in accordance with an exemplary embodiment of the invention.
FIG. 17 shows an ELD in accordance with an exemplary embodiment of the invention.
FIG. 18 shows an apparatus in accordance with an exemplary embodiment of the invention.
FIGS. 19A-19G show a method of making an ELD in accordance with an exemplary embodiment of the invention.
FIGS. 20A-20F show a method of making an ELD in accordance with an exemplary embodiment of the invention.
FIGS. 21A-21F show an exemplary method of making an ELD in accordance with an exemplary embodiment of the invention.
FIGS. 22A-22D show a method of making an ELD in accordance with an exemplary embodiment of the invention.
FIGS. 23A-23B show a method of making an ELD in accordance with an exemplary embodiment of the invention.
DETAILED DESCRIPTION OF EXEMPLARY EMBODIMENTS
In general, the systems, methods and apparatus presented herein are directed to an individually formed modular electroluminescent element, referred to herein as a nixel, which can be combined with other nixels to form an Electroluminescent (EL) Display (ELD).
As used herein the term “module” refers to a self-contained component of a system, which has a well-defined interface to the other components. Typically something is modular if it includes or uses modules which can be interchanged as units without disassembly of the module. Design, manufacture, repair, etc. of the modules may be complex, but this is not relevant; once the module exists, since it can easily be connected to or disconnected from the system.
As used herein, the term “nixel” refers to an electroluminescent display module which is a self-contained building block for producing an electroluminescent display.
As required, specific embodiments of the invention are disclosed herein. It should be understood, however, that these are merely exemplary embodiments of the invention that can be variably practiced. Drawings are included to assist the teaching of the invention to one skilled in the art; however, they are not drawn to scale and may include features that are either exaggerated or minimized to better illustrate particular elements of the invention. Related elements may be omitted to better emphasize the novel aspects of the invention. Specific structural and functional details disclosed herein are not to be interpreted as limiting, but merely as a basis for the claims and as a representative basis for teaching one skilled in the art to variously employ the present invention.
In an exemplary embodiment, a nixel of the present invention is individually manufactured and selectively positioned on a substrate to form an ELD. Referring to the figures, wherein like numbers refer to like elements throughout, FIG. 1 shows an ELD 100 of the present invention which includes a nixel 102 in the form of a subpixel. In the exemplary embodiment shown in FIG. 2, a discrete EL apparatus, referred to herein as a nixel 102, includes a lower electrode 202, a dielectric layer in the form of a base material 204 a phosphor 206 and an upper electrode 208. As described in more detail below a nixel may include additional layers and may be formed into a variety of desired shapes.
FIG. 3 shows a flow diagram of an exemplary method of making a nixel 102. At block 302 a dielectric ceramic material 204 is formed into a chip of a desired shape, at block 304 a phosphor layer 206 is deposited on the chip; and at block 306 upper 208 and lower 202 electrodes are provided thereby forming a discrete EL apparatus. The particular EL properties of the nixel 102 can be measured by applying sufficient voltage to the upper 208 and lower 202 electrodes to generate EL in the nixel 102.
FIG. 4 shows another exemplary embodiment of a nixel 400 that includes a lower electrode layer 202, a dielectric material 204, a first charge injection layer 406, a phosphor layer 206, a second charge injection layer 410, and an upper electrode layer 208. It is contemplated, however, that either one or both charge injection layers may be eliminated.
FIG. 5 shows a flow diagram of an exemplary method 500 of the invention for making the nixel 400. FIGS. 6A-6H illustrate the various manufacturing stages described by the method 500. Referring to FIGS. 4, 5 and 6, at block 502 a dielectric base material 204 is provided. The base material 204 serves as a substrate upon which subsequent dielectric and phosphor layers can be deposited. In a preferred embodiment, the base material 204 is a ceramic dielectric composed of barium titanate, BaTiO3 (BT) or barium strontium titanate, Ba0.5Sr0.5TiO3 (BST). Barium titanate compounds are typically temperature-stable ceramics with relatively high dielectric constants that are commonly used in the manufacture of ceramic capacitors. Depending on the temperature and grain size, BST can have a peak dielectric constant of 18,000, making it an attractive dielectric choice. In an exemplary embodiment, a slurry composed of BT compound particles dissolved in a suitable solvent is carefully agitated and blended, then poured and pressurized on to a surface. Sufficient pressure is applied to form a thick and vertically homogeneous substance of a desired thickness and density. In an exemplary embodiment the BT ceramic material is formed in a sheet that is approximately 200 μm thick, commonly referred to as a green sheet prior to high temperature processing. The green sheet forms a continuous length that can be cut into a shorter length by a cutting instrument, as shown in FIG. 6A by the green BT length 602. At block 504, the green BT material can be formed into predetermined shapes and sizes. In a first embodiment, a tool is used to punch out a desired shape. By way of example and not limitation, a tool could be used to punch out an oval shape, a hexagonal shape, a triangular shape, a cylindrical shape, a mushroom shape, etc., as shown by BT shapes 604 in FIG. 6B. It is contemplated that a variety of tools may be used to form non-rectangular shapes so that nixels can be shaped in accordance with various ELD requirements and applications. Thus, the shape of the nixel of the present invention can be customized to satisfy desired mechanical attributes. For example, for flexible display applications, it may be desirable to have nixels with rounded edges without corners. As a result, an oval punch out tool may be selected to punch out ovals from the green BT material. For a second type of application, it may be desirable to have hexagonal-shaped nixels, so a hexagon punch out tool can be selected. The methods of the present invention allow the operator to design a desired punch-out shape. In a further embodiment of the invention, a laser may be used to carve a desired shape from the green ceramic material. Other instruments may also be used to define and produce a desired shape, for instance a blade or die-cut tool can be used, or molded shapes using slurry cast directly into the final shape using a mold.
After the shaping process is completed, the green BT material shapes 604 are processed. In this embodiment the shapes are sintered under monitored and controlled conditions at block 506 to produce ceramic chips 204 (FIG. 6C) of a desired density and surface smoothness to accept additional charge injection and phosphor layers. By controlling the sintering process, ceramic chips that can provide a desired dielectric result and electrical performance can be produced. In an exemplary embodiment, the ceramic chip can be sintered at temperatures ranging from 900° C. to 1200° C. for approximately 4 hours. By sintering the green BT shapes 604 prior to the deposition of charge injection and phosphor layers, and independently of the ELD support structure, concerns regarding the effects of the sintering temperatures on other materials are no longer warranted.
After the green ceramic shapes 604 have been sintered to become ceramic chips 204, charge injection, phosphor and electrode layers may be deposited. At block 508 a first charge injection layer 406 can be deposited on the ceramic chip 204 as shown in FIG. 6D. In an exemplary embodiment the charge injection layer is an alumina layer sputtered to a thickness of around 30 nm. At block 510, a phosphor layer 206 can be deposited on the first charge injection layer 406 as shown in FIG. 6E. In an exemplary embodiment, the nixel 400 is in the form of a subpixel, which is understood to produce a single color. Because the nixel 400 is single-colored, a single phosphor can be deposited as phosphor layer 206 on the first charge injection layer 406, as shown in FIG. 6E. A variety of EL phosphors may be used, including, but not limited to metal oxide phosphors and sulphide phosphors. Such metal oxide phosphors and methods of production are described in U.S. Pat. Nos. 5,725,801, 5,897,812, 5,788,882 and U.S. patent application Ser. No. 10/552,452, which patents and application are herein incorporated by reference. Metal oxide phosphors include: Zn2Si0.5Ge0.5O4:Mn, Zn2SiO4:Mn, Ga2O3:Eu and CaAl2O4:Eu. Sulfide phosphors include: SrS:Cu, ZnS:Mn, BaAl2S4:Eu, and BaAl4S7Eu. Phosphor selection may depend on many factors, including EL spectral range, required annealing temperature, and luminance values as a function of frequency and voltage. A single phosphor can be used to emit various wavelengths of light by controlling the applied signal voltages and frequencies. Alternatively, a particular phosphor can be used to emit a particular color of light. Filtering techniques can also be used to obtain a desired color.
An advantage of the present invention is the ability to make individual nixels using a variety of phosphors. For example in a first embodiment, the nixel 400 is a blue subpixel, consequently a phosphor that can produce a bright blue color is deposited as phosphor layer 206. Examples of blue-emitting phosphors that can be deposited include: BaAl2S4:Eu, which is typically annealed at 750° C., and SrS:Cu, which is typically annealed at 700° C. In a further embodiment, the nixel 400 is a green subpixel; accordingly, a green-emitting phosphor such as Zn2Si0.5Ge0.5O4:Mn, which is annealed at 800° C., is deposited on the charge injection layer 406. In yet a further embodiment, an amber subpixel is formed by depositing a layer of ZnS:Mn, while a red subpixel can be formed by depositing a layer of Ga2O3:Eu (See D. Stodilka, A. H. Kitai, Z. Huang, and K. Cook, SID'00 Digest, 2000, p. 11-13). The phosphor layer 206 can be deposited by magnetron sputtering techniques well-known in the art. In an exemplary embodiment, RF sputtering techniques using argon plasma are used to sputter a phosphor layer of approximately 7000 Å thick. In an alternative embodiment, thermal evaporation can be used to deposit a phosphor layer.
After the phosphor layer 206 has been deposited, an annealing procedure may be performed at block 512 to activate and crystallize the phosphor layer 206, as shown in FIG. 6F. As mentioned above, the temperature at which the phosphor layer 206 is annealed is dependent upon the type of phosphor material deposited. For example, BaAl2S4:Eu is annealed at 750° C. By performing the high temperature phosphor annealing process on individual nixels at this stage of the manufacturing process, previous problems and limitations related to mechanical deformation of display support structures are avoided. For example, because BaAl2S4:Eu requires annealing temperatures greater than 500° C., previous manufacturing methods employed to produce glass ELDs had difficulty using the BaAl2S4:Eu phosphor to generate blue light. By eliminating the limitations associated with the use of glass substrates, the methods of the present invention accommodate a broader array of phosphor options in the creation of ELDs. Furthermore, each nixel can be processed in accordance with its own desired characteristics.
Following the phosphor layer 206 deposition, a second charge injection layer 410 can be deposited as shown in FIG. 6G at block 514. In an exemplary embodiment, the charge injection layer 410 is composed of alumina (Al2O3). In alternative embodiments, the charge injection layer can be composed of dielectrics such as, but not limited to BaTa2O5 and SiON. The selected dielectric material can be deposited on the phosphor layer 206 by sputtering techniques to form a layer of approximately 300 Å. Although shown in the figures as comprising both a first and a second charge injection layer, a nixel of the present invention can also be made with a single charge injection layer located either above or below the phosphor layer, or no charge injection layer.
At blocks 516 and 518, upper and lower electrode layers, 208 and 202 respectively, can be formed as shown in FIGS. 6H and 6I. The upper electrode 208 can be formed using a transparent conducting material. In an exemplary embodiment, Indium Tin Oxide (ITO) containing 90% by weight of In2O3 and 10% by weight of SnO2 is sputtered to a thickness of 150 nm to form upper electrode layer 208. In an exemplary embodiment, lower electrode layer 202 is formed from a metallic substance composed of molybdenum. In a further exemplary embodiment, lower electrode layer 202 is silver or a silver alloy. Other conducting materials may also be used to form lower electrode layer 202, which is applied to the lower surface of sintered ceramic layer 204 by evaporation, sputtering or printing. Deposition of electrode layers 202 and 208 completes the nixel manufacturing process described by FIG. 5. FIG. 7 shows several exemplary embodiments of a nixel 400 of the present invention: a triangular nixel 702, a hexagonal shaped nixel 704, and an oval shaped nixel 706 are but a few of the variously shaped nixels that can be produced in accordance with the invention.
In a further exemplary embodiment of the invention, a nixel is made in the form of a multicolored EL apparatus, for example a pixel containing red, blue and green phosphors, rather than a single-colored subpixel. A method 800 of the invention for making a multicolored nixel is illustrated by the flowchart of FIG. 8. The first four blocks of the flowchart, 502, 504, 506 and 508 respectively, are the same as those shown in FIG. 5, so they will not be discussed further. After the first charge injection layer is deposited on the sintered base material at block 508 then at block 802 a first mask is positioned over the first charge injection layer to define a receiving area for a first phosphor layer. A first phosphor, for example, a red-emitting phosphor is then sputtered within the area defined by the first mask at block 804. The first mask can then be removed and a second mask positioned at block 806 so that a second phosphor, for example a blue-emitting phosphor can be deposited at block 808. At block 810, the second mask can be removed and a third mask positioned, so that a third phosphor, for example a green-emitting phosphor, can be deposited at block 812. In a preferred embodiment, the blue, red, and green phosphors are coplanar and comprise a single vertical phosphor layer of the nixel. At block 514 a second charge injection layer can be deposited on the phosphor layer. At block 814, upper and lower electrodes can be deposited as discussed above in reference to blocks 516 and 518 of method 500. Referring to FIG. 9, a multicolored nixel 900 that can be produced by method 800 is shown with a blue phosphor layer 902, a red phosphor layer 904 and a green phosphor layer 906. As mentioned earlier in the context of a single color nixel, multicolored nixels can also be produced with a single charge injection layer, multiple charge injection layers, or no charge injection layer.
Alternatively, the nixel shaping process in any of the above embodiments can be performed after deposition of charge injection, phosphor and electrode layers onto the sintered chip. This shaping may be accomplished by dicing or laser cutting, among other methods.
FIG. 10 shows an exemplary method 1000 of the invention. At block 1002 a voltage is applied to the nixel to cause electroluminescence; in an exemplary embodiment, a nixel may be provided by the methods 300, 500, or 800 as previously discussed, or by other means and an electrode provided to the upper electrode 208 and lower electrode 202 of the nixel so that a sufficient electric field is provided for EL. At block 1004, the nixel can be observed to determine its characteristics and performance. To determine nixel electrical characteristics, tests can be performed as known in the art, for example a voltage can be applied to the upper and lower electrodes as shown in FIG. 11, and the nixel response may be measured. As shown in FIG. 11 and by the method 1200 of FIG. 12, individual nixels 702, 704, and 706 can be tested for a variety of characteristics including but not limited to: testing brightness at block 1202, testing color point at block 1204, testing drive voltage at block 1206, testing sensitivity to drive voltage at block 1208, testing frequency response at block 1210, testing sensitivity to frequency at block 1212 and testing the wavelength of emitted light at block 1214. Other parameters of interest can also be tested to further characterize the nixels. These test procedures may be automated for increased efficiency.
FIG. 13 shows a further method 1300 of the invention. At block 1302 a nixel is provided; in an exemplary embodiment a nixel may be provided by the methods 300, 500 or 800 discussed above or by other means. At block 1304, the nixel can be tested to determine its characteristics as discussed above. As the nixels are tested, they can be sorted according to their characteristics and parameters at block 1306. Unsatisfactory nixels that perform below a predetermined threshold may be rejected. For example, nixels with unacceptably low brightness levels can be grouped together and discarded. Nixels that perform within an acceptable range can be retained and grouped according to their characteristics. For example, nixels with brightness levels ranging from 800 cd/m2 to 1000 cd/m2 can be put in a first group. Nixels with brightness levels from 600 cd/m2 to 800 cd/m2 can be put in a second group, and so forth, according to predetermined specifications. By sorting and rejecting individual nixels based on their characteristics, a manufacturer can improve overall ELD quality as well as production yield by using only those nixels with proven characteristics. No longer will an operator have to wait until an ELD has been completely assembled in order to test EL device performance.
Categorizing nixels and grouping them accordingly allows a manufacturer to select nixels of a particular quality or attribute for use in a particular display. Thus, nixels can be selected for an ELD based on the intended ELD application. For example, an ELD intended for a use as a portable military display may have to satisfy certain flexibility, weight and brightness requirements. Accordingly, nixels that perform well in a small, thin, flexible ELD structure can be chosen. Both mechanical and electrical attributes may be considered when selecting appropriate nixels. For example nixel shapes with rounded edges may be preferred to improve flexibility, and nixels with high luminosity values may be selected to improve visibility for the portable military display. On the other hand, for large screen ELDs intended for consumer entertainment, color quality and pixel density may be emphasized. Testing and sorting of nixels facilitates the custom design and manufacture of ELDs in response to application specifications.
Categorizing nixels also allows a manufacturer to incorporate a group of relatively homogeneous nixels in a single display. A pixel surrounded by superior pixels can be distracting to the observer, and detrimental to the overall ELD performance. However, the same pixel surrounded by pixels of generally the same quality is no longer distracting. Thus, an important factor in ELD appearance is the homogeneity of the ELD pixels. By sorting and grouping nixels according to characteristics, relatively homogenous collections of nixels are compiled. A manufacturer can then use nixels from a homogeneous group to produce an ELD.
A further advantage is the ability to label or grade a display based on the quality of the nixels included therein. For example, an ELD comprising nixels of a premium grade can be identified as a gold level display, while an ELD comprising nixels of a slightly lower grade can be identified as a silver display. In addition, by knowing the nixel characteristics, nixels that vary from the norm can be placed around the display periphery so as to be less noticeable to a viewer.
One exemplary method of producing a nixel-based ELD is shown by method 1400 in FIG. 14. At block 1402, at least one desired nixel characteristic is determined. As mentioned previously, electrical and/or mechanical attributes can be used to characterize a nixel, and can consequently be used as a basis for selecting a nixel to produce an ELD for a particular application. At block 1404, a nixel satisfying the designated one or more characteristics is selected from a quantity of nixels. Nixels can be maintained in homogeneous groups, so that a nixel satisfying the designated requirements can easily be located and retrieved. At block 1406, the retrieved nixel is incorporated into an ELD structure.
FIG. 15 shows a further method 1500 of the invention. Blocks 1302,1304, and 1306 have been described earlier in reference to method 1300, so will not be addressed again here. After the nixels have been tested and sorted, they can be positioned on an ELD support structure at block 1502, provided with electrical connections at block 1504, and encapsulated at block 1506.
Exemplary embodiments of an ELD made in accordance with the aforementioned methods are shown in FIGS. 16 and 17. FIG. 16 shows an ELD 1600 comprising a support structure 1602 and a plurality of nixels 1604, wherein the nixel 1604 may include a blue nixel 1610, a green nixel 1608, a red nixel 1606, or other colored nixel characterized by a phosphor layer that emits a particular color of light when subjected to an electric field. The nixels shown in FIG. 16 have a hexagonal shape, but could be variably shaped as discussed previously herein. As shown in FIG. 16, a red nixel 1606, green nixel 1608, and blue nixel 1610 can be placed together in a desired pattern. The support structure 1602 can be any material adapted to receive nixels and provide support for an ELD. In the exemplary embodiment shown in FIG. 17, the support structure 1602 is a flexible material such as a polymer sheet upon which a plurality of nixels 1604 are selectively positioned to form a flexible ELD 1700.
As discussed previously, nixels can be selectively arranged on a supporting material in predetermined manner to achieve a desired result, and can be selected and positioned according to electrical and/or mechanical characteristics. Furthermore, colored nixels of the present invention can be variably arranged to form color patterns. For example, for a first ELD, it may be desirable to populate an ELD with three-color nixel groups, so groups comprising a red, a blue and a green nixel can be arranged along the surface of an ELD support material. For a second ELD it may be desirable to form five-nixel color groups, in which case a green, a red, two yellow, and a blue nixel may be included. Color patterns can be customized to address consumer applications and desires. For example, it may be desirable to have an ELD composed of a plurality of color sectors. A blue sector can be made by positioning a plurality of blue nixels in a defined area of the ELD. Likewise, a green sector can be made by positioning a plurality of green nixels within a defined ELD area. The present invention provides a plethora of nixel patterning options, so that ELD performance can be optimized for a particular application. The methods of the present invention easily accommodate ELD design changes without requiring machinery to be retooled or the nixel manufacture process to be altered. New designs can be implemented simply by adjusting the nixel placement patterns.
In addition to providing color pattern flexibility, the methods of the present invention allow selective nixel placement according to nixel quality category. Referring to FIG. 18, an ELD 1800 is shown comprising a support structure 1802 and a plurality of nixels of varying quality categories that are sorted into groups having like characteristics. A first quality nixel 1806 is represented by a square with the letter A and is sorted and grouped into grouping 1804A, a second quality nixel 1808 is represented by a square with the letter B and is sorted and grouped into grouping 1804B, and a third quality category nixel 1810 is represented by a square with the letter C and is sorted and grouped into grouping 1804C. As shown in FIG. 18, first quality nixels 1806 can be used to form a homogeneous group in the center of the ELD 1800 which is typically more noticeable to a viewer than the edges of the ELD. By placing a homogeneous nixel group in the center of the display, there will be no nixel that will distract the viewer by providing a contrasting appearance relative to adjacent nixels. However, since contrasting nixels are not as obvious to a viewer when they are arranged toward the periphery of the ELD, second category nixel 1808 and third category nixel 1810 can be positioned as shown in FIG. 18, without significantly adversely affecting ELD appearance.
As discussed above, nixels may be arranged in a variety of desired patterns in accordance with desired characteristics of an ELD. Exemplary methods of incorporating nixels into an ELD will now be described. As also discussed above, when a sufficient electric field is provided to a nixel the nixel emits light. Thus, when incorporating a nixel into an ELD it is not only desirable to secure the nixel to the ELD but also to establish an electrical connection between the nixel and conductors of the ELD so that a sufficient electrical field can be generated. It should be noted that while in the following exemplary embodiments the nixels are described as being electrically connected to a plurality of orthogonal row and column conductors of a display, it is contemplated that the conductors may be provided in other arrangements and that the nixels may be incorporated into an ELD by a variety of methods.
Turning to FIGS. 19A-19G, there is shown a first exemplary method of incorporating nixels 102 into an ELD. As shown in FIG. 19A a row conductor structure 1900 is provided having a plurality of spaced apart conductors 1902 that serve as row electrodes in a completed ELD. In this example, the row conductor structure 1900 includes a flexible row conductor substrate 1904 comprising a polymer sheet. The row conductors 1902 can be gold strips provided on the surface of the conductor substrate 1904 which have a thickness of about 10 nm, a width of about 1 mm and spaced about 0.24 mm apart. The row conductors 1902 are arranged so as to provide an electrical connection with a plurality of nixels incorporated in an ELD. It is contemplated that the row conductor substrate 1904 may be made of a variety of other materials, such as nickel or aluminum. Likewise, it is contemplated that the row conductors 1902 may be made of other conductive material such as BAYTRON® conductive polymer or silver. The row conductors 1902 may be provided on the row conductor substrate 1904 by a variety of methods such as inkjet printing. Alternatively, the row conductors 1902 may comprise a conductive tape adhered to the row conductor substrate 1904 and having an adhesive surface adapted to adhere to a nixel 102.
As shown in FIGS. 19B and 20 a conductive adhesive 1906 may be provided on the row conductors 1902 so that nixels 102 may be coupled thereto. By way of example and not limitation, silver paint, conductive tape, conductive epoxy, or other conductive adhesives may be used. The adhesive 1906 may be provided in a pattern according to a desired arrangement of the nixels 102 that are to be incorporated in the display. In this embodiment, the adhesive 1906 is applied to the row conductors 1902 but it is contemplated that the adhesive 1906 could be provided on the nixels 102. The adhesive 1906 may be applied by a variety of means such as printing or depositing.
As shown in FIGS. 19C and 20B nixels 102 having a lower electrode 202 and an upper electrode 208 may be provided atop the conductive adhesive 1906 so that the lower electrode 202 of the nixels 102 contacts the conductive adhesive 1906 and the nixels 102 are coupled to the row conductors 1902 so that an electrical connection is established between the nixel lower electrode 202 and the row conductors 1902. This arrangement is shown in the panel 1908 shown in FIGS. 19D and 20C. In this exemplary embodiment, the nixels 102 are shown as generally rectangular in shape and oriented upper electrode 208 up so that the phosphor layer 206 of the nixel 102 is generally parallel to the planar row conductor 1902. This allows the emitted EL from the phosphor layer 206 to be visible through the top transparent upper electrode 208.
It is further contemplated that the nixels 102 may be arranged in desired patterns as discussed above in accordance with the particular qualities of individual nixels 102 such as quality, color point, etc. For example, nixels 102 of the present invention can be positioned on the row conductor structure 1900 by using an electronic pick and place machine (not shown), commonly used in the electronics manufacturing industry, such as the ESSEMTEC A pick-and-place machine. A typical pick-and-place machine allows placement of variably sized electronic components on variably sized substrates to produce printed circuit boards. In general, electronic components maintained on tapes, trays or sticks are selected by the pick-and-place machine and then positioned on a substrate in a computer-controlled process. The process allows specific orientation and positioning along x-y- and z-axes. Components are held in position by solder paste that is either applied to the substrate prior to component placement, or applied to the individual components during the placement process. A similar process can be used to position nixels 102 on an ELD support material. Nixels can be loaded onto reels or trays from which they can be accessed and selected by the machinery. The pick and place machine can be computer programmed to accurately position the nixels 102 on a row conductor structure 1900 or other ELD support material. As discussed above, nixels 102 can be attached to the row conductor structure 1900 by using a conductive adhesive 1906 that is either applied to the row conductor structure 1900 or to the nixels 102 themselves. In the exemplary embodiment discussed above the row conductor structure 1900 is a flexible polymer sheet and the nixels are glued thereto but the row conductor material could be any suitable conductive material. To assist the pick and place machine in properly orienting the nixels 102 it is contemplated that a nixel 102 may have a non-symmetrical shape so that the orientation of the nixel 102 can be readily determined. For example, the nixel 102 may have a protrusion located at a particular location on the nixel to assist the pick and place machine in orienting the nixel so that the upper electrode 208 of the nixel is upward to couple with a column conductor and the lower electrode 202 of the nixel 102 downward so as to couple with row conductors 1902 of an ELD.
The nixels 102 may also be placed on a row conductor structure 1900 using machinery (not shown) commonly employed in the textile industry to embellish fabrics with beads, sequins, and other decorative items. The typical machine used in the textile industry has a drum on which beads or other items are positioned. The drum is then rolled over a piece of fabric, depositing and gluing the items in a desired arrangement on the cloth or other material. Similarly, nixels 102 can be arranged and oriented on a machine drum. An adhesive 1906 such as conductive tape, glue, paint, or epoxy can be applied to the nixels 102 so that when the drum (not shown) is rolled over the row conductor structure 1900, the nixels are arranged and attached to the support in a desired arrangement.
Having coupled the nixels 102 to the row conductor structure 1900 and established electrical connection between the nixels 102 and row conductors 1902 an electrical connection may also be made between the upper electrode 208 of the nixels 102 and column conductors of a display. As shown in FIGS. 19E and 20D a conductive adhesive 1910 may be applied to the upper electrode 208 of the nixels 102. In this case, the conductive adhesive 1910 may be transparent such as transparent conductive tape so as to allow for light emission from the nixel 102 through the adhesive 1910. The conductive adhesive 1910 may be applied in a similar manner as that discussed above in connection with the conductive adhesive 1906 used for coupling the nixels 102 to the row conductors 1902.
As shown in FIGS. 19F and 20E a column conductor structure 1912 may include a column conductor substrate 1914 in the form of a flexible polymer sheet having a plurality of spaced apart column conductors 1916. The column conductors 1916 may correspond to the arrangement of the nixels 102 and the row conductors 1902 in the panel 1908 so that there is an overlap of a row conductor 1902 and column conductor 1916 at each nixel 102 so that a desired electric field may be generated at the nixels 102. The column conductor support structure 1912 may be provided atop the nixels 102 in a manner similar to that discussed above in connection with the row conductor substrate 1900 so that the column conductors 1916 are coupled to and establish an electrical connection with the upper electrodes 208 of the nixels 102 (FIG. 19F).
Preferably, the column conductors 1916 are transparent to allow for viewing of EL emitted from the nixels 102. One transparent conductor that may be used is indium tin oxide (ITO) which may be printed on the column conductor substrate 1914. In the exemplary embodiment shown in FIGS. 19E and 20D the conductive adhesive 1910 is applied to the nixels 102 but it is contemplated that a conductive adhesive may be applied to the column electrodes 1916 and/or the column conductor substrate 1914.
One advantage of using the row conductor structure 1900 and the column conductor structure 1912 is that the row conductor structure 1900 and the column conductor structure 1912 may be used to encapsulate the nixels 102. For example, the row conductor structure 1900 and column conductor structure 1912 may be vacuum sealed to provide a sealed ELD.
The intersection of the areas of any one row conductor 1902 and any one column conductor 1916 at a nixel 102 constitutes an EL pixel that may be illuminated by the generation of an electrical field at the overlap of the row 1902 and column 1916 conductors. Thus, any individual pixel in the ELD display may include one or more nixels 102. The nixels 102, row conductor structure 1900, and column conductor structure 1912 define an ELD display panel 1918. Application of an effective voltage between the two electrode layers produces an electric field above a threshold voltage to induce electroluminescence in the phosphor layer 206 of the nixels 102. Various methods can be used to address the particular nixels 102 in the display. For example, matrix addressing or some other addressing technique. It will be appreciated that the display electrodes may be provided in other arrangements. It should also be recognized that one nixel, multiple nixels, or a portion of a nixel may be subjected to an electric field (FIG. 19G) and thus define a pixel 1920 of the display (FIG. 20F).
FIGS. 21A-21F show another exemplary method of incorporating modular nixels 102 into an ELD in which nixels 102 are mechanically coupled to a support structure. As shown in FIG. 21A a nixel 102 is provided with a coupler 2102 that is adapted for coupling the nixel to a support material. In this exemplary embodiment the coupler 2102 comprises an extension 2104 having a barb 2106. The coupler 2102 may be made of ceramic and provided on the nixel by an automated punch machine.
As shown in FIG. 21 B, a row conductor structure 1900 can include a plurality of row conductors 1902, and a plurality of apertures 2108 adapted to receive the extensions 2104. As shown in FIGS. 21B-C, the nixel 102 may be forced downward toward the row conductor support structure 1900 to drive the coupler 2102 through the lower aperture 2108 so that the barb 2106 protrudes from the lower surface of the row conductor structure 1900. The barb 2106 couples the nixel 102 to the row conductor structure 1900 so that the lower electrode 202 is in contact with the row conductor 1902. In addition, the barb 2106 prevents displacement or removal of the nixel 102 from the row conductor structure 1900. As shown in FIGS. 21D-F, the column electrodes may then be provided in a similar manner to that discussed above with regard to FIGS. 20D-F.
In a further embodiment, a flexible polymer can be heated to allow the nixels 102 to be embedded to a predetermined depth in a polymer. When the polymer cools, the nixels are maintained in position, obviating the need for an adhesive. Row and column conductors may then be provided on the upper 208 and lower 202 electrodes of the nixel 102. For example, as seen in FIG. 22A, a supporting material 2202 comprising a polymer sheet may be heated so that a plurality of nixels 102 may be embedded in the supporting material 2202 in such a manner that upper 208 and lower 202 electrodes of the nixels 102 protrude from the polymer sheet 2202 (FIG. 22B). This may be accomplished using a polymer film having a thickness of about 20-50 μm. Column conductors 2204 (FIG. 22C) and row conductors 2206 (FIG. 22D) may then be deposited on the upper 208 and lower 202 electrodes of the nixel 102 by various means such as, but not limited to, printing, sputtering, and sol gel deposition. It should be noted that other methods of providing row and column electrodes may be employed and that the various techniques described herein may be used in various combinations. It is further noted that the invention is not limited to the use of flexible substrates, as other transparent materials can also be used, including glass and plastics.
Referring to FIGS. 23A and 23B, after the modular nixels 102 are incorporated into panels 1918, the panels 1918 can be aligned and joined to form a scalable ELD 2300 of desired dimensions that may then be encapsulated to protect the ELD. In an exemplary embodiment the ELD is encapsulated in a weatherproof polymer.
Thus, the present invention provides a discrete electroluminescent display module, termed a nixel, that can be individually manufactured, tested, sorted and selectively positioned to make an ELD in accordance with the invention. The modular nixels can be in the form of a single-colored subpixel, a multi-colored pixel, or a chip containing a plurality of subpixels or pixels. A substantial advantage achieved with the discrete electroluminescent display modules is that they can be tested and sorted according to electrical, optical and mechanical attributes, and selectively arranged on a substrate to produce a customized ELD for a particular application. Another advantage of the discrete electroluminescent display modules is that ELDs may be reconfigured as long as they are not permanently affixed to the supporting substrate. The present invention provides for the first time a modular ELD equivalent to the modular LED.
The methods of the invention can produce a flexible display with scalable dimensions that avoids the limitations imposed by prior art processes that employ glass to provide structure. Exemplary embodiments are included herein as examples of an invention that can be variably implemented and practiced, and as such, are not considered to be limitations, since modifications and alternative embodiments will be apparent to those skilled in the art. Thus, the invention encompasses all the embodiments and their equivalents that fall within the scope of the appended claims.
As used herein, the terms “comprises”, “comprising”, “includes” and “including” are to be construed as being inclusive and open ended, and not exclusive. Specifically, when used in this specification including claims, the terms “comprises”, “comprising”, “includes” and “including” and variations thereof mean the specified features, steps or components are included. These terms are not to be interpreted to exclude the presence of other features, steps or components.
Patent Application
20080074049
