US3385992A - Electroluminescent display panel with rod-like electrodes embedded in phosphor - Google Patents

Description

May 28, 1968 A. z. CHABERSKI 3,385,992

ELECTRLUMINESCENT DISPLAY PANEL WITH ROD-LIKE ELECTRODES EMBEDDED IN PHOSPHOR med Feb. 17, 1967 ALEKSANDER Z. CHABERSKI.

ATTORNEY INVENTOR` United States Patent O ELECTROLUMINESCENT DISPLAY PANEL WITH ROD-LIKE ELECTRGDES EMBED- DED IN PHOSPHOR Alelrsander Z. Chaberski, Buffalo, NX., signor of fifty percent to Carl Di Pietro, East Aurora, NX. Filed Feb. I7, 1967, Ser. No. 616,967 5 (lairnso (Cl. S13- 108) ABSTRACT 0F THE DISCLOSURE A rectangular dielectric substrate, a sheet of electroluminescent phosphor overlying the substrate, a plurality of transversely extending conductors having a plurality of rod-shaped electrodes embedded in the phosphor, a plurality of longitudinally extending conductors having a plurality of rod-shaped electrodes embedded in the phosphor, a set of horizontal photosensitive elements each one of which being connected to a separate one of the transverse conductors, a set of vertical photosensitive elements each one of which being connected to a separate one of the longitudinal conductors, and vibrating mirror scanners associated with each set of photosensitive elements.

Bzrckgrou'nd of the invenlion The present invention relates to television displays and, more particularly, to an improved solid-state electroluminescent television display apparatus.

Electrolurninescent displays currently in use generally comprise a plurality of coplanar spaced horizontal grid electrodes and a plurality of spaced coplanar vertical grid electrodes. The vertical and horizontal electrodes occupy separate planes so that a layer of electrolurninescent material can be sandwiched therebetween.

Generally, one or both sets of the electrode grids must be transparent in order that the radiations from electroluminescent material in between can be seen. The electroluminescent material glows according to the principles of electroluminescence when a sufficient potential exists between the horizontal and vertical electrodes; the radiation being most intense at the intersection point of the grids, whereat the actual intensity will be a function of the strength of the exciting signal. Various types of scanning structures have been proposed functioning to permit each of the electrode intersections to be energized in sequence according to the strength of a synchronized video signal from the television receiver` The foregoing types of display screens have not been capable of developing a very intense image. This has been due, inter alia, to the fact that the light from the electroluminescent phosphor in passing through the transparent electrodes losses intensity as a consequence of absorption thereof by the electrodes.

Moreover, transparent electrodes are more costly to produce than opaque electrodes.

In addition, since the phosphor is not exposed but sandwiched between the electrodes, replacement thereof is difficult, if not impossible.

Summary of the invention The foregoing and other disadvantages are overcome by the apparatus according to the present invention by the provision of a sheet of electrolurninescent material; a plurality of spaced electrodes embedded irr the electroluminescent material, and defining a plurality of transversely extending columns and longitudinally extending rows; means electrically connecting each of the electrodes in any column in series with every other electrode in that column; means electrically connecting each of the electrodes in any row in series with every other electrode in 3,385,9@2 Patented May 2S, 1968 ICC that row; and means for developing a potential difference between particular column and row electrodes.

In addition to the display screen, the present invention contemplates horizontal and vertical scanning means in the form of oscillating mirrors that function to direct visible light beams sequentially across adjacent horizontal and vertical photosensitive elements; thereby permitting a video signal to energize the electroluniinescent phosphor adjacent the intersection of the horizontal and vertical coordinates of the photosensitive elements.

According to the present invention, these energized electrodes are characterized by generally pin or rod-shaped opaque members, the axis of which are perpendicular to the plane of the display panel, and each elemental picture area is defined by a generally diamond-shaped surface area of the phosphor the four corners of which cornprise four of the electrodes.

ln this manner the radiations from the.` glowing phosphor are exposed directly to the eye of the viewer and are more intense than prior art constructions utilizing transparent electrodes,

In addition to presenting a display apparatus that is simple to construct, the present invention provides in such construction a novel arrangement in which the phosphor can easily be removed and replaced.

Other advantages and unique features of the present invention become apparent from that which follows.

Brief description of Ille drawing For a fuller understanding ofthe present: invention, both as to its organization and method of operation, reference should now be had to the following description of the saine taken in conjunction with the accompanying drawings wherein:

FIGURE 1 is a fragmentary pictorial schematic representation of the improved display apparatus according to the present invention with parts thereof illustrated in broken-away section;

FIGURE 2 is a sectional view taken along line 2-2 of FIGURE 1; and

FIGURE 3 is an equivalent circuit `diagram of one elemental picture area according to the present invention.

Description of the preferred embodiment Referring now to the drawings and, more particularly, to FIGURE 1, the display screen or panel generally depicted Kby numeral 10 is illustrated as comprising a substantially rectangular substrate 12, which may be fabricated of any suitable dielectric material such as glass, for example. A sheet or layer 14 of suitable electroluminescent material, such as phosphor, overlies and is coextensive with the substrate 12 in contacting relation therewith.

Extending transversely of substrate 12 and embedded therein are a plurality of spaced vertical conductors, fabricated of a suitable metal, depicted by the numerals 18a, 18h, 18 181. A plurality of spaced similar horizontal conductors 26a, 20h, 200 20 are embedded in substrate 12 extending longitudinally thereof. As illustrated more clearly in FIGURE 2 the vertical conductors are spaced Ibelow the horizontal conductors, and are not in contact therewith. Alternatively, the horizontal conductors can be -below the vertical conductors. The conductors are preferably set into position while the substrate is still in the molten or fluid state.

Integral with or suitably affixed to each of the horizontal and vertical conductors are a plurality of metallic electrodes depicted generally by the numeral 22. The electrodes 22C that are fixed to the vertical conductors 18H, 18h, 18 18H define a plurality of equally spaced columns, whereas the electrodes 22R that. are fixed to the horizontal conductors define a plurality of equally spaced rows. As illustrated, except for the conductors at the extremities of the display screen, the intersection center of any horizontal and vertical conductor is equally spaced from each of four electrodes, two from each conductor. In this manner these electrodes are located at the corners of a generally diamond-shaped surface area of the phosphor. Also as shown, the rod-shaped electrodes 22 are each dimensionally larger along an axis perpendicular to the central plane of screen than along an axis that is parallel thereto, whereas said screen is dirnensionally smaller along an axis perpendicular to said central plane than along an axis parallel thereto. Each of the electrodes 22 projects perpendicularly from the surface of its respective conductor, passes through the substrate 12 and is embedded into the electroluminescent sheet 14 terminating, preferably, flush with the top surface thereof. Although the electrodes are shown as comprising cylindrically shaped rods or pins, it is contemplated that other suitable cross-sectional shapes would suflice. Each of the conductors electrically connects each of the electrodes associated therewith in series with every other electrode associated with that particular conductor, as shown.

A horizontal terminal conducting strip 24 is located adjacent the transversely extending conductors 18, and a similar terminal strip 26 is located adjacent the longitudinally extending conductors 20. Projecting from the strip 24 are a plurality of photosensitive elements 20a, 23h, 28C 28 severally connected to the several conductors 18e, 18h, 18C 18u. Similarly, a plurality of photosensitive elements 30a, 30D, 30c 30 project from terminal 25 and are severally electrically connected to the conductors 20a, 20h, 20C 2011. These photosensitive elements may be photoresistors, as cadmium sulphide for example, that exhibit a very high dark resistance that becomes almost zero when exposed to light.

Located directly above the photosensitive elements that are associated with terminal 24 is a scanner 32, which may be a light reecting mirror or other suitable means, having a reflecting surface 34. An oscillating motor 36 or the like is mechanically coupled to scanner 32 via line 38 for imparting an oscillating vibratory motion thereto. A light collimator 40 is adapted to direct a beam of light c from a suitable source 42 to the reflecting surface 34. Adjacent collimator 40 is a shutter mechanism 44 driven mechanically by a motor 46 via line d8. As will become apparent hereinbelow, the shutter functions to cause beam c to scan the photoresistors in one direction only.

There is similarly provided a scanner 52 having a refleeting surface 54 located above the photosensitive elements associated with terminal 26. A second oscillating motor 56 is mechanically coupled to member 52 via line 58. A second collimator 60 is adapted to direct a beam of light d from light source 62 to the reflecting surface 54. Similarly, a second shutter 64 is provided to allow the beam d to scan the photoresistors in one direction only. A motor `titi is provided to drive shutter 64 via line 60.

A television receiver has leads 72, '74 therefrom connected respectively to the terminals 24 and 26 for delivering a video signal thereto. The motors 36 and 46 are synchronized Aby a horizontal synchronization signal from receiver 70 via line 76; whereas the motors 56 and 66 are synchronized by a vertical synchronization signal from receiver 70 via line 7.8, as is conventional television practice.

Considering the operation of the hereinabove described apparatus, when the light beam c is directed by scanner 32 on a particular photoresistor, say 28h, that resistor becomes highly conductive to connect the terminal strip 24 with its associated transverse conductor, 180 in this instance. Similarly, when the light beam d is directed by scanner 52 on to a particular photoresistor, say 30, that resistor becomes highly conductive thereby connecting the terminal strip 26 with a corresponding longitudinal conductor, 20 in this example. The video signal from receiver 70 will, in this instance, appear across the four electrodes in the vicinity of the intersection of the conductors 18b and 20C, illustrated schematically by the dotted lines e, f, g, and l1 in FIGURE l. The phosphor layer within the diamond-shaped surface area e, f, g, and h defined by the four electrodes will radiate with an intensity that is a function of the video signal appearing across the electrodes. It is this diamond-shaped glowing area that constitutes an elemental picture area of the television display screen. It is therefore readily apparent that the section of the screen shown in FIGURE 1 is greatly enlarged, for clarity. Y

The equivalent circuit of the four electrodes that coact to define a single picture element, and the electroluminescent phosphor within the diamond-shaped surface area e, f, g and h is illustrated schematically in FIGURE 3. Here the photosensitive element is represented by a resistor and a shunting switch 101. Each of the four pairs of cooperating electrodes are depicted as capacitive elements 102, 103, 104 and 105, with the phosphor P depicted as occupying the space therebetween. The video signal appears across terminals 106 and 107. When the scanning beam falls upon a photosensitive element, equivalent to the closing of switch 1101, the full video signal is permitted to appear across the four parallel capacitors 102, 103, 104 and 105, causing the electroluminescent phosphor therebetween to glow with an intensity that is a function of the strength of the video signal.

It is important to note that the light emitted from the diamond-shaped phosphor spot does not have to pass through transparent conductors, and consequently the intensity of the glow will be greater than prior devices utilizing transparent electrodes. Thus, the effective area of light emission is greatly increased.

In addition, since the electroluminescent phosphor is exposed the layer can be easily dissolved and replaced under the application of acetone or some similar material. This characteristic is extremely advantageous in that, as is known, the electroluminescent phosphors only have limited lifetimes.

To further increase the intensity of the glowing diamond-shaped spot the top surface of substrate 12 can be coated with a mirror-like reflecting surface at 13.

Where the display screen 10 is to be employed in the production of a television picture of the type havinga 525 line horizontal sweep with 700 increments along each horizontal sweep, that is 525 vertical by 700 horizontal increments (for optimum resolution) or an aggregate of 367,500 picture elements; as is conventional, the ratio of the width of the display to the height thereof is 4:3. According to the present invention it takes four electrodes to make up therebetween one generally diamond-shaped picture element; however, as illustrated, since each electrode contributes to four picture elements, the total number of electrodes corresponds to the total number of picture elements. Thus, a screen with 367,500 electrodes would achieve the best resolution according to present convention; however, satisfactory resolution can be obtained with under 200,000 electrodes. Of course, the actual spacing between the electrodes will depend on the overall size of the screen and also, the acuity requirements.

It is obvious that three of the screens according to the present invention could be combined with the proper phosphors for the production of a color display.

Although the foregoing description contemplated the use of vibrating mirrors as scanning means, this was intended by way of example and not limitation; other suitable mechanisms can be employed.

A preferred embodiment has been illustrated and described; other Variations and modifications will occur to those skilled in the art without departing from the spirit of the invention, which is to be limited only by the scope of the appended claims.

I claim:

1. An electroluminescent display apparatus of the character described, comprising;

(a) a sheet of electroluminescent material,

(b) a plurality of spaced electrodes embedded in said sheet dening a plurality of transversely extending columns and a separate plurality of longitudinally extending rows, each of said electrodes projecting through one and the same side of said sheet of electrolurninescent material,

(c) rst means comprising a plurality of spaced longitudinal conductors electrically connecting each of the electrodes in any column in series with every other electrode in that column,

(d) second means comprising a plurality of spaced longitudinal conductors electrically connecting each of the electrodes in any row in series with every other electrode in that row, and

(e) means for energizing predetermined ones of said spaced transverse and longitudinal conductors.

2. The apparatus according to claim 1, wherein;

(f) said conductors are located in separate planes on the same side of said sheet of electroluminescent material.

3. The apparatus according to claim 2, wherein;

(g) the intersection of any one of said transverse and longitudinal conductors is substantially equally spaced from four of said electrodes, two of which are xed to said one transverse conductor and two of which are Xed to said one longitudinal conductor.

4. The apparatus according to claim 1 wherein there is further provided;

(f) horizontal photosensitive elements attached electrically -to each of said transverse conductors,

(g) vertical photosensitive elements attached electrically to each of said longitudinal conductors, and

(h) scanning means for each of said horizontal and vertical photosensitive elements,

(i) said scanning means comprising a horizontal oscillating light reec-ting surface, and

(j) a vertical oscillating light reecting surface.

5. The apparatus according to claim 1, wherein;

(f) each of said electrodes comprises a generally rodshaped member.

References Cited UNITED STATES PATENTS 2,848,637 8/1958 Mager. 2,858,480 10/ 1958 Shadowitz. 2,967,972 1/1961 De Haan. 3,023,338 2/ 1962 Cerulli. 3,2905 37 12/ 1966 Logan. 3,312,825 4/ 1967 Robinson.

ROBERT SEGAL, Primary Examiner.

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