US 3840858 A
Description (OCR text may contain errors)
United States Patent [191 Usui [451 Oct. 8, 1974 1 ALPHA-NUMERICAL DISPLAY DEVICE  Inventor: Setsuo Usui, Kanagawa-ken, Japan  Assignee: Sony Corporation, Tokyo, Japan  Filed: Jan. 3, 1973  Appl. No.1 320,720
 Foreign Application Priority Data Primary Examiner-Harold l. Pitts Attorney, Agent, or Firm-Hill, Gross, Simpson, Van Santen, SteadmamChiara & Simpson  ABSTRACT An alpha-numerical display device comprising a plurality of light emitting diodes mounted in a prearranged design on a surface of a transparent plate whose diode mounting surface side has formed thereon a plurality of conductive strips between which a layer of opaque insulating material is formed except for windows in which the diodes are located. An insulating layer covers the opaque layer and the conductive strips. Bridging strips are formed in a layer overlying the insulating layer which connect the electrodes of the diodes to their associated conductive strips for energization. Each bridging strip extends at one end down through a window in the insulating layer adjacent an associated diode electrode into electrical contact therewith and the other end extends down through another window into electrical contact with its associated conductive strip. A reflective layer may be employed above the back side of the diode and spaced therefrom to cause the bulk of the light emitted from the diode to be transmitted through the ductive strips so that while isolated from each other they still cover a very large percentage of the surface of the transparent mounting plate.
14 Claims, 16 Drawing Figures PATENTED BET 1 74 3.840.858 SHEET 20F 4 PATENTEBUBI 8:914
SHEET 3 0f 4 PAIENTEDBBT 81w 3 840 858 sum nor 4 I ALPHA-NUMERICAL DISPLAY DEVICE CROSS-REFERENCES TO RELATED APPLICATION This application is related to co-pending application Ser. No. 384,232, filed July 31, 1973, entitled AL- PHA-NUMERIC CHARACTER DISPLAY DEVICE AND METHOD, WHOSE CHARACTERS ARE FORMED OF LIGHT EMITTING DIODES," assigned to the assignee of the present application and in which the inventor is Setsuo Usui.
BACKGROUND OF THE INVENTION Alpha-numerical display devices have now come into rather extensive use. As the term is used, an alphanumerical display refers to a grouping of individual segments which form a numeral, a letter or some other sign. Typically such devices are formed in a glass envelope containing an ionizable gas with the segments formed as cathode elements and with one or more anodes associated with a group of cathodes'to cause the segments to glow. One disadvantage of this type of device lies in the fact that it is difficult to get a sharp narrow line for each segment of the display.
Light emitting diodes are known. The emitted light from such a diode comes from hole-electron recombinations. In a solid-state light-emitting diode the supply of higher energy electrons is provided by forward biasing the diode, thus injecting electrons into the n region (and holes into the p region). The injected holes and electrons then recombine with the majority carriers near the junction. The recombination radiation is then emitted in all directions.
Heretofore, one form of light emitting diode which has been used is as shown in FIG. 16 with one ohmic contact formed on one whole surface of the diode and other ohmic contact partially covering the surface of the diode. In such an arrangement, the utilized light is l numerical display devices, and one such structure is disclosed in Electronics, May
ll, 1970, pages 88 to SUMMARY OF THE INVENTION The present invention employs a plurality of light emitting diodes mounted on edge on a transparent insulating plate arranged in a desired design with each diode forming a segment of the design. Conductive leads to the ohmic contacts of the diodes are formed either directly on the transparent plate or on an opaque layer overlying one surface of the plate, there being a window provided through the opaque layer for each diode. An insulating layer covers the conductive leads. 1r shape bridge connections have their legs extending through the insulating layer to connect an ohmic contact with its associated lead. A further protective layer then covers the upper surface of the assembly. Preferably, a reflective sheet is formed in the assembly above the diode edge opposite the window through which light is emitted. If a visible indication is desired from both sides, the reflective sheet may be omitted and a window formed through the assembly above the upper edge of the diode.
In an alpha-numerical display device of the present invention the width of the light emitting diodes determines the width of the lines defining the segments of the design. This enables an extremely fine line pattern to be obtained.
It is an object of the present invention to provide a novel alpha-numerical display device employing a light-emitting diode for each segment of the display.
It is a further object of the present invention to provide an alpha-numerical display device employing light-emitting diodes having a novel integrated circuit connecting the ohmic contacts of the various diodes.
It is still another object of the present invention to provide a novel alpha-numerical display device employing a fine line light source for each indicating line of the device.
It is another and further object of the present inven-' tion to provide a novel alpha-numerical display device having a high degree of brightness.
A still further object of this invention is to provide a novel alpha-numerical display device which is economical to manufacture and which is rugged and reliable in use.
Another object of the present invention is to provide a novel alpha-numerical display device which provides an indication on both sides.
BRIEF DESCRIPTION OF THE DRAWINGS FIG. 1 is an isometric diagrammatic view of a light emitting diode as employed in the present invention.
FIG. 2 is a plan view of the upper surface of the transparent plate after the conductive leads have been formed thereon.
FIGS. 3, 4, 6, 7, 9, 10 and 11 show in a sequence of diagrammatic .sectional views the formation of an alpha-numerical display device embodying a preferred form of the present invention.
FIG. 5 is a plan view of the transparent plate, the conductive leads and an insulating layer after the latter has been laid down on the former.
FIG. 8 is a diagrammatic plan view showing the location of the rr-shape jumpers of the assembly.
FIG. 12 is a diagrammatic plan view of the under (front) surface of one unit of an alpha-numerical display device.
FIG. 13 is a diagrammatic plan view similar to FIG. 2 but showing a modified type of conductive leads.
FIG. 14 is a diagrammatic plan view similar to FIG. 5 showing the insulating layer arrangement of the modified form.
FIG. 15 diagrammatically shows how the conductive strips are electrically connected to the ohmic contacts of the light-emitting diodes.
FIG. 16 is a diagrammatic illustration of one form of light emitting diode.
DESCRIPTION OF THE PREFERRED EMBODIMENTS Referring to FIG. 1 of the drawings, there is shown therein a light-emitting diode .1 having a P-N junction formed between a P-type region 2 and an N-type region 3. This diode is preferably made, for example, of gallium phosphide, silicon carbide or gallium nitride. The diode 1 is preferably made by cutting a semiconductor wafer with a diamond saw. Ohmic contacts 4 and 5 are and forms of the conductive strips 6.
3 formed on the P-type and N-type regions 2 and 3 respectively.
By way of example, and not by way of limitation, it
has been found that the following dimensions for the diode are particularly effective. The thickness dimension a of the P-type region is preferably 50 to 100 microns with 80 microns being particularly suitable. The
thickness dimension b of the N-type region is preferably between 200 and 300 microns with 250 microns being particularly suitable. The maximum'thickness di- .mensions c and d of the ohmic contacts are preferably of the'order of 1,000 Angs'troms. The length dimension e of the light emitting diode is preferably approximately 2 milimeters. The width dimension f is preferably approximately 50 to l microns.
To understand the structure of the alpha-numerical I display device of the present invention, the progressive steps of forming a preferred embodiment thereof are shown in FIGS. 2 to 11, inclusive. As shown in FIGS.
face of the device. On the back or upper surface of this glass plate 7 a plurality of conducting strips 6 are formed as shown in'FlG. 2. These strips 6 will provide sensitive resins are disclosed in detail in co-pending application, Ser. No. 227,444, filed Feb. 18, 1972 by the same inventoL One of the mask windows 9 is u'sedfor indicating a decimal point and the others are used for a numeric indication. The layer 11 is formed by'first to form a protectivemask 16 for sand-blasting and having a plurality of windows 17 as shown in FIG. 7.
Thereafter, a conductive resin layer 18 is formed on the protective mask 16 and into the windows 17. As will hereafter be apparent, this conductive resin layer 18 provides the jumper connections between the ohmic contacts of the light emitting diodes l and the conductive strips 6 and may be conveniently thought of as being 11' shaped.
The conductive resin layer 18 may be formed by coating a resin such as OI- MEX AG (Trade name of Pransene Co. Institute) or EPOTEK I-I-3l (Trade name) and heating at approximately 100C for 'about3 2 and 3, a transparent glass plate 7 provides the front;
On the conductive layer 18 a protectivemask layer 19 is formed selectively as shown in FIG. 8. The protective mask layer 19 may be formed by coating a photo sensitive resin such as SONNE KPM 1027, then exposing it through a mask having a predetermined patv tern, and developing it. In order to provide the desired 1r shaped jumpers, the conductive resin layer 18 is selectively removed by sand-blasting as indicated by the arrowsinFIG. 9. i
A protective layer '20 is formed on the protective mask layers 16and 19 to obtain a flat back (upper) surface as shown in FIG. 10. The protective layer 20 may be formed by coating aphoto sensitive resin such as SONNE KPM 1027 and exposing it.
A protective plate 21- made by the same material as insulating plate 7 is adhered to theprotective' layer 20 by an adhesive 22. A metal layer 23 may beformed on an inner surface of the-layer 21 so that light from the I the trade name "fsONNE RPM 1027" and SONNE I KPM'10I8. which is colored by a dye so as to be opaque to light from thelightemitting diode. Photo laying down a layer 10 of a photo sensitive resin such 1 as SONNE KPM 1027. as shown in FIG. .3. This photo sensitive resin may be colored by a dye to be opaque to light from the diode; The photo sensitive resin 10 is selectively exposed to light through an optical mask not shown) having aipredeterminedpattern the insulating layer 11 as shown in FIGS. 4 andS.
This insulating layer 11 has eight positioning windows 12 (FIG. 5) for receivingand holding the light emitting diode therein and a plurality of Ieadconnecting windows '13 located above predetermined portions A photosensitiveresin 14, such as SONNE KPM I027 is poured into the positioning windows 12 and the light emitting diodes 1 are positioned therein by exposing the resin 14 to light through mask windows 9 and developing it to remove excess resin. The photo sensitive'resin 14 may include a transparent powder for diffusinglight from the diode 1. Such a transparent powder may be selected from acrylic resin, glass, silica or pigmentpowders which are transparent to light from the diode l but having a different refractive index from that of the photo sensitive resin 14. A photo sensitive resin 15 is coatedas shown in FIG. 6, and isthen selectively removed by exposing and developing processes diode, l effectively emits rto the outside through the window 9 andthe insulating plate. 7 as shown in FIG. I
l l". FIG..12 shows a front view of: the insulating alphanumerical display device 24 of this invention. The P-N junctions of the diodes'tl are faced 'on the insulating plate 7 so that light from the P-N junctions effectively emits to the outside through the plate 7. It will be appreciated that the maximum width of the numerical segments is determined by the thickness of the semiconductor wafer producing the lightemitting idiodes. For this reason, the width of the'alpha-numerical display segment is freely selectable to provide a semicon,-. ductor wafer of various thicknesseswithout difficulty of coating or slicing. i I
' FIGS. 13 to 15 show a modified form invention. Referring first to FIG. 13, a plurality of conductive strips 31 are laid'down'on a transparent glass plate 32by selective disposition. In this embodiment the conductive strips 31 are formed wider than the con- I ductive stripsshown in" FIG. 2 so that these conductive strips 31 themselves may be: used as a mask for preventing unwanted light frottrthelight emitting diodes.
Thereafter, an insulating layer 33 (FIG. '14) which has been colored by a blue dye is formed on the glass plate 32. This insulating layer 33 has four windows 34 which are positioning portions for the light emitting diodes 35. Nine ofthese light emitting diodes having the same construction as shownin FIG. 1' are'securedto the glass plate 32 by an adhesive or a photo sensitive resin exposed from the glass plate side. This particular process is not essential to this invention, but is useful to prevent I the P-N junctions from having a conductive resinflow ing between thediodes 35 and the plate 32. The N 1 of the present I junctions of the diodes 35 are positioned perpendicular to the plane of the glass plate 32.
Thereafter, a conductive resin or a silver paint is poured into the windows 34 and heated to form conductive layers 36 for electrically connecting the ohmic contacts of the diodes 35 to the conductive strips 31 respectively so that an alpha-numerical display device 37 is obtained (FIG.
The alpha-numerical display device 37 may be coated with a protective resin to prevent deterioration of the diodes 35.
In the preferred embodiments, an indication is viewed through the transparent insulating plate 7 or 32 but it should be noted that it is possible to have light also emitted from the back side provided a window is left on the back side from the light emitting diode outwardly to the rear.
The insulating plate 7 or 32 may be colored and may be transparent only to light from the diode so that the contrast for indication is improved.
I claim as my invention:
1. An alpha-numerical display device comprising a transparent insulating plate having a plurality of light emitting diodes mounted thereon with their P-N junctions disposed perpendicular to the plane of said plate and arranged in an array for alpha-numerical display, and means for selectively forwardly biasing different ones of said light emitting diodes, a plurality of conducting strips are formed on the same surface of said transparent insulating plate as said diodes and in which a first insulating layer is formed on said plate between said strips except for a window therethrough opposite each light emitting diode and light is emitted from said diode in a direction parallel to said P-N junction.
2. An alpha-numerical display device according to claim 1, in which a second insulating layer is formed over said conducting strips and said first insulating layer and conductive jumpers formed on said second insulating layer and extending down therethrough and each having two terminal arms, one of which is connected to one side of said diode and the other to a conductive strip.
3. An alpha-numerical display device according to claim 1, in which said first insulating layer is opaque.
4. An alpha-numerical display device comprising a transparent insulating plate having a plurality of light emitting diodes mounted thereon with their P-N junctions disposed perpendicular to the plane of said plate and arranged in an array for alpha-numerical display, and means for selectively forwardly biasing different ones of said light emitting diodes, in which said means for forwardly biasing includes a plurality of conducting strips mounted 'on the same surface of said transparent insulating plate as said light emitting diodes, an insulating layer substantially covering nearly all of the area between said conducting strips, whereby said insulating layer and strips act as an opaque mask and light emitted from said diodes in a direction parallel to said P-N junctions.
5. An alpha-numerical display device comprising a transparent insulating plate, a plurality of light emitting diodes mounted in a pre-arranged design on one surface of said plate and having P-N junctions normal to said plate, a plurality of conductive strips formed on said plate on the same side that said diodes are mounted, a first layer of opaque insulating material,
through said second insulating layer into contact with one of said conductive strips and light emitted from said diodes in a direction parallel to said P-N junctions.
6. An alpha-numerical display device according to claim 5, in which a protective insulating layer covers the assembly over the side opposite said transparent insulating plate.
7. An alpha-numerical display device according to claim 5 having a reflecting member for each of said diodes mounted above and spaced from said diodes to reflect light through said window.
8. An alpha-numerical display device according to claim 5, in which a second window is provided on the back side of the array for each of said diodes, whereby when light is emitted from said diodes it may be seen from both sides of the display device.
9. An alpha-numerical display device according to claim 2, in which said conducting strips extend out beyond at least one edge of said second insulating layer to provide terminal connections for said conducting strips.
10. A light emitting device comprising an insulating plate, at least two conductive layers formed on said plate, an insulating layer formed on said plate and having at least one window, a light emitting diode positioned in said window, said light emitting diode having two electrodes and a P-N junction perpendicular to a plane of said insulating plate, and means for connecting said electrodes to said conductive layers respectively.
11. A light emitting device according to claim 10, wherein said insulating plate is transparent to light from said light emitting diode.
12. A light emitting device according to claim 10, wherein said connecting means are conductive resin layers formed between said electrodes and said conductive layers respectively.
13. A light emitting device according to claim 10, wherein said window of said insulating layer has a portion for positioning said light emitting diode and a portion for receiving said connecting means.
14. A light emitting device comprising an insulating plate, a plurality of conductive layers formed on said insulating plate, an insulating layer formed at least on said insulating plate and having a plurality of windows, a plurality of light emitting diodes positioned in said windows respectively with P-N- junctions normal to said plate, said insulating layer absorbing at least light from said light emitting diode, said light emitting diodes having two electrodes and a junction perpendicular to a plane of said insulating plate, and means for connecting said electrodes to said conductive layer, respectively.