Light emitting display panels
US 3258644 A
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J. A. RAJCHMAN 5 Sheets-Sheet 1 LIGHT EMITTING DISPLAY PANELS ArraiA/Ef June 28, 1966 J. A. RAJCHMAN 3,258,644
LIGHT EMITTING DISPLAY PANELS INVENTOR. 1 f4. AJc'f/M A/ Arran/Y June 28, 1966 J. A. RAJcl-IMAN LIGHT EMITTING DISPLAY PANELS 5 Sheets-Sheet 3 Filed Feb. 26, 1965 ZIK/i005 46 M Ww Mn wwf/cme idw W J A ,H r M y l H MM y /H Hf l /b l H, M Nys Mr f 5 Mc 4 MW ,0, VA 0M ,f
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LIGHT EMITTING DISPLAY PANELS Filed Feb. 26, 1963 5 Sheets-Sheet 4 (5054/ (0W d/ ROW EUW ,60W ,60W
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LIGHT EMITTING DISPLAY PANELS Filed Feb. 26, 1965 5 Sheets-Sheet 5 IN VEN TOR. J /v ,4. Pfiff/M4N United States Patent O 3,258,644 LIGHT EMITTING DISPLAY PANELS Jan A. Rajchman, Princeton, NJ., assignor to Radio Corporation of America, a corporation of Delaware Filed Feb. 26, 1963, Ser. No. 261,160 10 Claims. (Cl. 315-55) This invention relates to light emitting panels and particularly to ferroelectric, electroluminescent panel type displays.
The light emitting panels of the invention comprise a plurality of planar rows, each row including light emitting means and control elements for the light emitting means. The light emitting means of each row extends along the length thereof and is arranged along one edge of the width dimension of the row. The rows are assembled one over another with portions of the planar surfaces thereof in contact but with the light emitting means of each row visible. In one embodiment of the invention, the rows are placed one over the other Venetian blind fashion with the light emitting means appearing as the non-overlapped portions of the Venetian blinds. In another embodiment of the invention, the light emitting means extends only along the narrow edge of each row. Here, the rows of elements are placed in contact with one another along their entire planar surfaces and with the narrow edges thereof aligned and serving as the display. The row conductors for the panel elements are built into each row and extend in the row direction. The column conductors for the panel extend at right angles to the row conductors and engage the columns of control elements.
The invention is discussed in greater detail below and is described in the following drawings of which:
The FIG. 1 is a block and schematic circuit diagram of a known so called live element transcharger;
FIG. 2 is a cross-sectional view of a row of transcharger electroluminescent display elements according to the present invention;
FIGS. 3a-3d are sections through FIG. 2;
FIG. 4 is an exploded view of a display element of the present invention;
FIG. 5 is a cross-sectional view of an electroluminescent display panel according to the present invention;
FIGS. 6 and 7 are sections taken through FIG. 5;
FIG. 8 is a perspective view, partially in cross-section, of a row of elements according to another embodiment of the present invention;
FIG. 9 is a cross-sectional view of a modified electroluminescent display panel construction; and
FIG. l0 is a cross-sectional view of a modified form of transcharger-electroluminescent display element construction.
The so called live element transcharger of FIG. l is discussed in detail in co-pending application Serial No. 195,453, liled May 17, 1962, by E. Fatuzzo, and assigned to the same .assignee as the present invention. Although the circuit shown in FIG. 2 includes six ferroelectric capacitor elements 1l), 12, 14, 16, 18 and 20, the elements 14 and 16, which serve `as coupling elements, are the functional equivalent of a single element. Therefore, the term live element transcharger is used both here and in cases in which l, 3 or any larger nurnber of coupling capacitors are employed. An electroluminescent element 22 and alternating current source 24 are connected to the ferroelectric capacitors 10 and 12. A column pulse source 26 is connected to ferroelectric element 18 and row pulse source 28 is connected to ferroelectric capacitor 20.
In the operation of the transcharger of FIG. l, ferroelectric capacitors and 12 are initially polarized in opposite directions. So polarized, they offer a high impedance to the alternating voltage of source 24 and the electroluminescent element 22 does not produce light. The capacitors I8 and 20 are initially polarized in the same direction. Therefore, if a single pulse, such as the pulse from source 26 or, alternatively, a pulse from source 28, is applied to the circuit it does not unblock the circuit 24, 22, 12, 10. Instead, the pulse from source 28 sees a low impedance path through capacitors 18 and 2i?. Similarly, the pulse from sour-ce 26 sees a low impedance path through the same two capacitors. However, if coincident pulses are applied from sources 26 and 23 they pass through coupling capacitors 14 and 16 and change (fully or partially) the polarization of one of the elements 11B and 12. When this occurs, the polarization of capacitors lll and 12 is in the same direction so that they offer a low impedance to the alternating voltage from source 24. Therefore, the source voltage builds up across the electroluminescent element 22 and the latter produces light.
To re-establish the circuit to its initial operating condition, a reset pulse from a source (not shown) is applied through one of the capacitors such as 18 to the circuit including capacitors 12, It). The reset pulse switches the :polarity of one of the capacitors It) and 12 4to a condition such that it is opposite the polarity of the other one of the capacitors 10 and 12. This causes circuit 10, 12, 22 again to be blocked, and the electroluminescent element goes out.
In a large electroluminescent panel, thousands of the transchargers such as shown in FIG. 1, each with its electroluminescent element, may be used. In a specific example discussed later, the panel includes 367,560 transchargers. These transchargers can be fabricated indi- Ividually and then interconnected to produce an array of such elements. On the other hand, one may make `all of the transchargers (and their associated electroluminescent elements) in a single step. It is preferred, however, to make a row of transchargers (and their associated electroluminescent elements) at a time and then to assemble the rows to make up the entire panel. Construction by rows has the advantage of saving labor over fabricating individual elements for interconnection. Construction .by rows also reduces the risk of failure of an entire panel after assembly, if the rows are tested individually before assembly. The individual rows can be made on a stilf backing material or, as an alternative can be made up as a continuous roll on a llexible strip such as Mylar. When made according to the latter method, a row of the elements consists of a length taken from the entire roll.
A cross-sectional view of a row of transcharger-electrolurninescent elements embodying the presen-t invention is shown in FIG. 2. The exploded perspective view of FIG. 4 should also be referred to. The bottom layer consists of transparent insulating material 39 such as glass in the case of an inflexible row of such elements or Mylar in a e-ase in which a continuous roll of transchargers is to be made. A conductive strip 32 is printed or otherwise fabricated onto the insulator 30 along the left-hand edge thereof. The conductor employed may be silver, gold, or the like. Next to and in contact with this conductor 32 is transparent conductor 34 such as a very thin layer of evaporated -aluminum or a layer of tin-oxide material known as tic. In intimate contact with this layer is a layer of electroluminescent material 36. Both the electroluminescent material and the transparent conductor 34 `are in contact with conductor 32.
'I'.he spaced, rectangularly shaped elements i0 and 42, located on the insulator 30, are electrodes. They are conductors and may be printed, silk screened, or otherwise formed on the insulator 30. The ferroelectric material is the next layer as shown at 44. The nal layer consists of electrodes 46, 48 and 50 as well as conductors 52 and 54 which are themselves electrodes.
The various layers making up the row of transchargerelectroluminescent elements are shown in greater detail in FIGS. S11-3d. Elements corresponding in structure and function to the elements of FIG. 2 have similar reference numerals applied. The correspondence between the circuit elements of FIG. 1 and the circuit elements of FIG. 2 is also indicated by similar reference numerals and the dashed ovals in FIG. 2.
The fabrication of the rows of transcharger elements into a panel type of display is shown in FIGS. 5, 6 and 7. The rows of elements (all identical to the one of FIGS. 2, 3 and 4) are placed one over another in Venetian blind fashion between two plates 60 and 62. Plate 60, made of an insulating material such as glass, has column conductors 64 printed thereon which engage the portions 50b (see FIGS. 2 and 7) of the electrode 50 located at the bottoms of the rows. The electroluminescent material is visible through the transparent conductive coating 34 (FIG. 2) the transparent backing layer 30 (FIG. 2) and the glass plate 62. The details of the various layers ymaking up the transcharger of FIG. 5 are not shown in FIG. 5 but the electroluminescent material is indicated schematically by dots.
In the electroluminescent panel of FIG. 5 perhaps 1/3 of each row of transcharger electroluminescent elements is viewing area, that is, contains electroluminescent material. If it is desired to improve the definition of the display, a smaller width of electroluminescent material may be employed in which case t-he portion of the Venetian blind construction exposed to the viewer would Ibe smaller. When constructed in this manner, the portion 50a of the electrode 50 in one row of elements engage the portions 50b of electrode 50 of the immediately adjacent row of elements. Constructed in this way, the column conductors 64 are not necessary since the contacts S themselves act as the column conductors.
As already mentioned, the backing material for the electroluminescent transcharger elements may be llexible or may be stiff. In the case of flexible elements, the drawing of FIG. is considerably out of scale, as the thickness of the glass supports 60 and 62 is much much greater than that of the respective rows of transcharger electroluminescent elements. In the case of .a panel made up of rigid rows of elements using a backing such as glass, it may be desirable to key the glass plates 60 and 62 to effect the proper spacing lbetween elements. This may be done, for example, by forming the upper surface of glass plate 62 (and, if desired, the lower surface of plate 60) with sawtooth slots which engage the corners of the rows of the transcharger electroluminescent elements holding them in position and assuring the proper spacing between the elements. This alternative construction is shown, in part, in FIG. 9.
A view of the front of the electroluminescent panel, showing the electroluminescent material, as seen by the viewer, appears, in part, in FIG. 6. The back of the electroluminescent panel, showing the column conductors appears, in part, in FIG. 7.
The electronics associated with the electroluminescent panel is not part of the present invention and is not shown. In general, the column and row decoders (for selecting a desired panel location) may be similar to those employed in coincident current memories. In a preferred way of operating the system, a memory may be employed for accumulating and temporarily storing an entire row of information. This row of information is applied to the panel a row at a time to permit higher speed operation.
An alternative form of construction is shown in FIG. 8. Here, the electroluminescent layer 36 occurs at one edge of the display. The conductors 82 which make contact with the electrodes 46' extend behind the electroluminescent layer. Accordingly, when a transcharger element is actuated, the area of the electroluminescent layer, located directly over the conductor 82 of that transcharger, lights up. The operation of the row of FIG. 8 is similar to that of the embodiment of FIGS. 2-6, and the same reference numerals primed have been applied t0 similar elements.
In the electroluminescent display panels of the invention, the electroluminescent material takes up only a small part of the area of the transcharger electroluminescent element. For example, the transcharger insulator material 30 which may be glass or Mylar may have a width of 1/2 or 1A inch and the width of the strip of electroluminescent material may then be the order of 1/10 to 2/10 inch. However, by means of the Venetian blind construction or the on edge construction of FIG. 8, relatively small picture elements can be obtained without obstructing the picture with the much larger area taken up by the ferroelectric capacitor elements. Accordingly, the display panel of the invention can provide a picture with high resolution, requiring relatively small picture elements, but without the complication of extreme microminiaturization. For example, using an electroluminescent layer having a width of V10 inch, one can obtain a picture display of standard television type by using 525 such lines. The display would be roughly 521/2 inches in height (525 lines) and 7() inches in width (here the width of the picture element together with the spacing to the next element is assumed to be J/10 inch and the total number of elements per row is assumed to be 700 Tthe transcharger electroluminescent elements are shown to have two coupling elements (ferroelectric capacitors 14 and 16 of FIG. 1). However, if desired, 3 to 9 such coupling elements may be used instead as discussed in the above-mentioned co-pending application. The greater the number of coupling elements, the greater the degree of isolation between circuits 18, 20 and 10, 12, 22. The construction method is quite isimilar to that already described. To illustrate, FIG. 10 shows a transchargerelectroluminescent element having four coupling capacitors 14, 14a, 14b and 16.
Many different materials are possible for the transcharger -ferroelectric elements of the invention. Tthe ferroelectric material, for example, may be single crystal material, ceramic material, or -crystallite material in a binder. The single crystal material, in general, is suitable only for mounting on an inflexible backing such as glass. A typical crystal which may be employed is triglycene sulfate which may be cut or grown into the desired shape. Typical ceramic lmaterials include barium titanate, lead zirconate, lead 4titanate, lead stannate and solid solutions in various percentages of the last three materials mentioned. These may be made into long thin at sheets in various ways as, for example, by hot pressing, sintering or doctor blading. These are relatively inflexible and are suited for use on a stiff backing material. However, a polycrystalline form of saltpeter (KNO3), as described on the inside cover of `the February 1963 issue of International IScience and Technology, may be employed on a flexible substrate. An example of a crystallite in a binder is antimony sulfur iodine (SbSI). This material grows in the shape of thin rods. It may be ground up to very small individual rods, placed on a Mylar strip ina suitable binder and oriented in a desired direction by the application of a strong electric eld.
Another way of using a ferroelectric on a flexible substrate is to store the green doctor bladed ferroelectric on the roll of elements so that the tape retains its flexibility. When the tape -on the roll is cut up into lengths to provide the rows of the display, and the rows are assembled to form the entire panel, the ferroelectric may be fired. However, this requires that the exible backing material be of a sufficiently high melting temperature and/or the green ferrite of suiciently low ring temperature that the backing material does not melt in the process.
With respect to the transparent conductor, here too many different materials are possible. Tic (tin oxide powder which is tired at a relatively high temperature) has already been mentioned. Another possibility is to evaporate a thin layer of copper followed by a slightly thicker layer of gold. Mixes of gold and bismuth in very thin layers are also transparent and suitable.
The electroluminescent powder may be laid down by standard techniques. It may be placed in a suitable binder and sprayed on with a gun. Alternatively, it may be doctor bladed onto the backing layer.
An important advantage of fabricating the lines of the panel on a length of tape as discussed above is that Ithe fabrication technique can be automated. For example, the printing, silk screening and/or other means for applying the various elements making up the tape can be automatic. In addition, the tape can be tested automatically so that portions there-of found to be defective can be appropriately marked or even cut out of the roll.
The example chosen to illustrate the invention is an electroluminescent panel type display. As employed here, the term display implies some sort of picture such as a television picture or a chart of some kind such as may be employed, for example, to show positions of aircraft or market quotations. In the display chosen to illustrate the present invention, the control elements for turning the individual elements of the display on and off are transchargers. It should be appreciated that the invention is applicable -to any type of light emitting panel and it should also be appreciated that the control circiut need not be a 5 element transcharger and, in fact, need not even include ferroelectric elements. An example of a light emitting panel, actually a memory, in which the presence or absence of light is indicative of the value of the binary bit stored at a particular location, which may be fabricated line-by-line in the manner discussed in the present application may be found in Briggs Patent No. 3,046,529, issued July 24, 1962. The various lines making up the memory may be arranged Venetian blind fashion, as in one embodiment of the system discussed in detail herein, or on end fashion, as in the embodiment of FIG. 8. The system of the Briggs patent employs ferroelectric elements for storage of binary information. However, it does not use transchargers.
What is claimed is:
1. A light emitting panel comprising, a plurality of rows of elements, said rows being arranged side-by-side and abutting one another, each row including light emitting means along the length of the row and arranged along the one edge of the width dimension of the row, and control elements occupying a portion of the remainder of each row, the rows being arranged with the planar surfaces thereof in contact and with the light emitting means of each row at least partially visible and lying immediately adjacent to the light emitting means of the next adjacent row, whereby control elements are hidden from view by said light emitting means.
2. A light emitting panel comprising, a plurality of planar rows of elements, said rows being arranged sideby-side and abutting one another, each row including light emitting means along the length of the row and arranged along one edge of the width dimension of the row, and control elements occupying a portion of the remainder of each row, the rows being arranged Venetian-blind fashion with the major portions of the planar surfaces thereof in contact, and with the light emitting means of each row visible and lying immediately adjacent t-o the light emitting means of the next adjacent row, and with the light emitting means of each row lying over control elements of the next adjacent row.
3. A light emitting panel comprising, a plurality of planar rows of elements, each row including an electroluminescent light emitting layer extending along the length of the Irow and arranged along one edge of the width dimension of the row, and ferroelectric control elements occupying the major portion of the remainder of each row, the rows being arranged one over the other with portions of the planar surfaces thereof beneath which the ferroelectric control elements are located in contact and thereby hidden from view and with the electroluminescent light emitting layer of each row visible.
4. A solid state light emitting panel comprising, in combination, a plurality of planar rows of elements, each row including light emitting means extending along the length of the row along an edge of the row, and control elements f-or the light emitting means occupying at least the major portion of the remainder of each row, the planar elements being arranged, Venetian-blind fashion, one over the other, over at least a`major portion of the planar surfaces thereof so that the control elements are not visible but with the light emitting means of each row visible.
5. An improved construction for a panel type display comprising a plurality of planar rows of elements, each row including an electroluminescent light emitting layer extending along the length of the row and arranged along one edge of the width dimension of the row, and ferroelectric control elements -occupying the major portion of the remainder of each row, the rows being arranged, Venetian-blind fashion, one over the other with the major portions of the planar surfaces thereof beneath which the ferroelectric control elements are located in contact and thereby hidden from view and with the electroluminescent light emitting layer of each row visible.
6. An improved construction for a panel type display comprising,
a plurality of planar rows of elements, each row including an electroluminescent light emitting layer extending along the length of the row and arranged along one edge of the width dimension of the row and ferroelectric control elements occupying the major portion of the remainder of each row, the rows being arranged one over the other with at least the major portions of the planar surfaces thereof beneath which the ferroelectric control elements are located in contact and thereby hidden from view and with the electroluminescent light emitting layer of each -row visible;
row conductors for the ferroelectric control elements located in each row and extending in the length dimension thereof; and
column conductors for the ferroelectric contr-ol elements extending in a direction parallel to the plane of the light emitting layers and perpendicular to the length dimensions of the rows, and in contact with the respective columns of control elements.
7. A transcharger electroluminescent element cornprising, in combination,
a transparent insulating substrate;
a rst group of spaced electrodes formed on the substrate;
a transparent conductor layer located on the substrate;
a layer of electroluminescent material located on the transparent conductor layer;
a layer of ferroelectric material located on the rst group of spaced electrodes; and
a second group of spaced electrodes located over the ferroelectric material, one of said second electrodes being located over both the ferroelectric material and the electroluminescent material, said rst and second groups of electrodes together with the ferroelectric material providing a five element transcharger, and the overlapping one of the second electrodes, the electroluminescent layer and the transparent conductor together providing a light emitting element which is visible through the substrate.
8. A transcharger electroluminescent element cornprising, in combination,
a transparent insulating substrate;
a first group of three aligned spaced electrodes formed on the substrate;
a transparent conductor layer located on the substrate;
a layer of electroluminescent material located on the transparent conductor layer;
a layer of ferroelectric material located on the lrst group of electrodes;
a second group of ve aligned, spaced electrodes located over the ferroelectric material and the first electrodes, one of said second electrodes being located over both the ferroelectric material and the electroluminescent material, said second group vof electrodes being spaced with respect to the first group of electrodes to provide the 6 ferroelectric capacitors of a transcharger, and the overlapping one of the second electrodes, the electroluminescent layer, and lthe transparent conductor together providing a light emitlting element which is visible through the substrate.
9. A row of transcharger electroluminescent elements comprising, in combination,
a length of insulating substrate;
a transparent electrode on one surface, the substrate extending along one edge of the substrate;
rst spaced electrodes extending parallel to the transparent electrode and aligned with one another in lboth the length and width dimensions of the substrate;
an electroluminescent layer on the transparent elec trode extending along the length of the transparent electrode;
a ferroelectric layer covering the first spaced electrodes;
a group of second spaced electrodes, each lying partially on the ferroelectric layer and partially on `the electroluminescent layer, said group of second electrodes extending in a direction parallel to the length dimension of the substrate;
a rst continuous conductor on the ferroelectric layer,
spaced from the second spaced electrodes and extending parallel to the length dimension of the substrate, said conductor serving as a connection to which a power supply voltage for the electroluminescent layer may be applied;
a third group of spaced electrodes, each lying over the ferroelectric layer, said third group of electrodes extending in a direction parallel to the length dimension of the substrate;
a second continuous conductor on the ferroelectric layer, extending parallel to the rst conductor, spaced from the `third electrodes and lying on the side thereof opposite from the second conductor, said second conductor serving as a row connection for the ferroelectric capacitors formed between the rst electrodes on one hand, and the second electrodes, third electrodes, and first and second conductors, on the other hand; and
a fourth group of spaced electrodes, each lying over the ferroelectric layer and on the opposite side of the second conductor than the third group of electrodes, said fourth group of electrodes extending in a direction parallel to the second conductor and serving as the column connections to the abovementioned ferroelectric capacitors.
10. An array including a plurality of discrete rows 30 that each row, except the first, covers all except the light emitting elements of the adjacent row of elements.
References Cited by the Examiner UNITED STATES PATENTS 5/1959 Anderson et al. 313-108 X 12/1959 Sack 315-169 GEORGE N. WESTBY, Primary Examiner. 40 R. JUDD, Assistant Examiner.