EP0789930B1

EP0789930B1 - Field emitter display

Info

Publication number: EP0789930B1
Application number: EP95938760A
Authority: EP
Inventors: Akintunde I. Akinwande
Original assignee: Honeywell Inc
Current assignee: Honeywell Inc
Priority date: 1994-10-31
Filing date: 1995-10-20
Publication date: 2001-08-29
Anticipated expiration: 2015-10-20
Also published as: WO1996013848A1; JPH10508147A; DE69522465D1; DE69522465T2; CA2201473A1; EP0789930A1

Description

BACKGROUND OF THE INVENTION

The present invention pertains to displays, and particularly to avionics displays. More particularly, the invention pertains to a flat panel display having high resolution and brightness with low power consumption.
A display from which the preamble of claim 1 departs is known from EP-A-0681311.
No available electronic display meets the above-noted characteristics needed for a modern avionics display. The cathode ray tube (CRT) has a high luminous efficiency, superior contrast ratios and excellent viewing angles. However, two deficiencies of the CRT are the bulk of the electron gun and large power usage by the deflection amplifiers. There has been much effort expended over the years to develop a flat CRT. Two approaches in the development involved, first, folding the electron gun around to be in parallel with the tube face; and second, producing an electron beam for each pixel by means of an areal cathode and a grid system. Of these approaches, the first one was implemented in the SONY WATCHMAN and the second one was used in a vacuum fluorescent display (VFD) of ISE. These were the only commercial successes of such approaches.
Others have demonstrated the use of a cone field emitter array (CFEA) as the areal cathode. However, both VFD and the CFEA device do not use high luminous efficiency phosphors from which one can obtain from cathodluminescence by employing a high voltage anode circuit. The CFEA device cannot use a high voltage anode because of reliability problems due to field forming of the emitter tip and emitter erosion by particles desorbed, from surfaces by electrons.
A device is needed that retains the advantages of cathodluminescence such as high brightness, high luminous efficiency and good angular viewability, but has the features of compact thinness, random addressability and low power consumption.

SUMMARY OF THE INVENTION

The present invention provides all of the above-mentioned features desired in a display. It is a thin-film-edge field emitter array (FEA) display according to claim 1 that has a two-dimensional array of matrix addressable thin-film-edge field emitters as electron sources for a cathodoluminescent screen. The advantages of the present invention over previous FEA displays are that the radius of curvature of the emitter is determined by film deposition resulting in better uniformity and higher current densities, the capacitor and series resistor for current bias is easier to implement, the fabrication process is based on integrated circuit (IC) and micromachining processes that lead to lower cost manufacturing, emitter burnout is eliminated by using an on-chip focusing electrode which provides for higher reliability and yield, and higher luminous efficiency results because of the use of high voltage phosphors.
Other advantages of this invention are high brightness and high contrast because electron emission current increases exponentially with increasing voltage, leading to high brightness, large dynamic range and high transconductance with the use of thin-film-edge emitters and high-voltage phosphors. Also there is high-yield manufacturing since each pixel consists of more than 100 emitting edges leading to a high degree of redundancy. Only a current density of < 5µA/cm² is required for a brightness of 1000 fL, assuming a screen voltage of 15 kilovolts and luminous efficiency of 20 lumen/watt. Current equalization resistive elements prevent a single failure from pulling the pixel or line/row of pixels low, leading to a defect-tolerant flat-panel display fabrication process. The edge emitter does not suffer from the deleterious effects of field forming and particle induced desorbtion emitter erosion. Hence the device can use high-voltage phosphors without any reliability problems. This allows the use of more efficient phosphors and consequently lower power operation for the same brightness and permits high-resolution proximity focusing. High-voltage phosphors have long lifetimes because they require less current, and high luminous efficiency phosphors lead to low power consumption.

BRIEF DESCRIPTION OF THE DRAWING

Figure 1 shows a basic comb-tooth edge field emitter.
Figures 2a and 2b illustrate emitter edges.
Figure 3 shows a perspective of an emitter.
Figures 4 and 5 show views of another kind of emitter.
Figure 6 is a side cutaway view of an emitter.
Figure 7 is a cross-section view from figure 6.
Figures 8a-c show three comb structures of an emitter.
Figure 9 reveals an array layout of emitters.
Figure 10 is a cross-section of a thin-film-edge emitter used in a flat panel display.
Figure 11 shows the place of the field emitter in a display.
Figure 12 is a portion of the structure of a display having field emitters.
Figure 13 is a perspective view of a field emitter microstructure.
Figure 14 is a flow chart for fabrication of a field emitter array display.
Figure 15 illustrates a laminated emitter structure.
Figure 16 shows a dual control electrode emitter structure for a display.
Figure 17 shows a single control electrode emitter structure for a display.
Figure 18 reveals a planar thin film edge field emitter for a display, having the phosphor layer on the same substrate as the field emitter.

DESCRIPTION OF THE SPECIFIC EMBODIMENT

Figure 1 shows the basic comb-tooth edge field emitter 20. Emitter 20 has a lead-in conductor 1, is in electrical connection with an outside voltage source, and is in contact with an emitter structure 3, through a resistive element 5, and a conductive element 6 at electrical contact 2. Lead-in conductor 1 preferably physically contacts only resistive element 5.
Emitter edge 4 of emitter structure 3 is segmented into a plurality of comb-like elements e₁ ... e_n. The segmentation of the emitter edge serves to isolate burn-out problems. Localizing the edge length will prevent spreading of the burn-out and confine the problem to its originating comb element.
A resistive film 5, typically but not limited to tantalum nitride or a polysilicon, is formed through thin film construction techniques to be in contact with emitter structure 3 so that the resistance applied is in series with emitter edge 4. The resistive film serves to limit excessive direct current (D.C.) emission currents to the emitter edge from sharp points or uncontrollable discharges from stray capacitance.
A conductive film 6 and an insulator 11, which may be an oxide or nitride, is also obtained through thin film techniques layered above resistive film 5 such that the elements are in parallel with each other. Together, resistive film 5, insulator 11, and conductive film 6 serve as a capacitor which provides a high frequency bypass for alternating current (A.C.) through lead-in conductor 1. The capacitor enables amplification of high frequency signals as if the current limiting load line were due to a very small resistor, thus greatly increasing the gain of the amplifier. This is so because the D.C. current is limited in its ability to damage the emitter by the resistor; and because the bypass capacitor provides another way for the high frequency signal to pass the emitter.
Figures 2a and 2b illustrate two emitter edges 61 and 62, respectively, with arrows suggesting electron flow at the edge of each. The ridged edge 62 type is presently preferred because the comers of edge 61 are likely to cause concentration of electron emission and begin failure.
Figure 3 shows a perspective view of the emitter illustrated in figure 1. The structure shown at item 7 serves as a support layer. Also visible in this view is insulating substrate layer 12, and upper and lower control electrodes 8 and 9. A control electrode acts as a lateral gate which controls the current flow between anode 10 and electron-emitting cathode 4.
Figures 4 and 5 show plan and perspective views, respectively, of a second kind of emitter. In this configuration, the entire emitter structure is segmented into comb-like elements 4. Each comb-like element e₁ ... e_n has an individual resistor element 5 connecting it to conductor contact 2.
The arrangement of the second configuration enables a larger total current to be drawn without burning out the individual comb elements. The first configuration shown in figures 1 and 3, enables a lesser amount of total current to be drawn than the second configuration (assuming the two were of the same size), but has a more effective capacitive coupling because of the larger area of the resistive film.
Figure 6 shows a side cutaway view which could represent either one of the two configurations of the emitter. Also shown in figure 6 is dielectric material 11, between conductive element 6 and resistive element 5, as well as insulating substrate 12 upon which the emitter is constructed.
Figure 7 is a detailed side view taken at line 7-7 of figure 6. From the top, there is a support layer 15 (preferably nitride, though other well known support layers with similar electrical characteristics could be used). Upper control electrode 8 (preferably TiW, around 250 nm (2500 angstroms), though other metals or conductive materials could be used), an upper sacrificed layer 16 (preferably SiO₂; about 300 nm (3000 angstroms), although other supporting materials of similar electrical qualities could be substituted); the emitter surrounded by two support layers, i.e., the support layers are nitride 11a and 11b of about 200 nm (2000 angstroms) in thickness and the emitter e, a 30 nm (300 angstrom) layer of TiW, although substitute materials may be used as in the similar above layers). Below this, is another "lower" sacrifice layer 17, similar in makeup and thickness to upper sacrifice layer 16 and lower electrode 9, about 100 nm (1000 angstroms) of TiW. The whole structure is supported by another support layer 11 (of about 100 nm (1000 angstroms)) and laid down upon SiO₂ wafer 12 (again, here too, substitutes such as crystalline silicon could be substituted, for instance. Most reasonable substitute materials will occur easily to one of ordinary skill in these arts.).
Figures 8a, 8b and 8c illustrate three alternatives for comb structure 4 combined with resistor elements 2. Figure 8d is a side cross-section view of element e of the configuration shown in figure 8b.
Figure 9 shows a piece 40 of an array employing emitters 41, 42, 43, and 44, and resistor elements 2a, 2b and 2c. Control electrode wires 50, 52 and 54 (metalization or other current carrying structures) and lines 63 and 65 are connected at junctions 51 and 53, respectively, to turn on emitter 41.
Figure 10 is a diagram that reveals further details of a thin-film-edge emitter 70 that is used in an FEA flat panel display. On a substrate 71 is a nitride layer 72 of about 250 nm (2500 angstroms). Formed on layer 72 is a gate electrode 73 which is of about 100 nm (1000 angstroms) thick of TiW. Formed on layer 72 is a 350 nm (3500 angstrom) layer 74 of oxide. Found on oxide layer 74 is a 150 nm (1500 angstrom) layer 75 of nitride which is used to support 20 to 30 nm (200 to 300 angstroms) of TiW as emitter edge layer 76. A 150 nm (1500 angstrom) nitride layer 77 is formed on emitter edge layer 76. Nitride layers 75 and 77 provide structural support for emitter layer 76. Formed on layer 77 is a 350 nm (3500 angstrom) layer 79 of silicon dioxide. Gate electrode 80 of about 250 nm (2500 angstroms) of TiW is formed on a portion of oxide layer 79. A 250 nm (2500 angstrom)layer 81 is formed on gate electrode 80 and oxide layer 79.
The edges of gate electrodes 73 and 80, and nitride layers 72, 75, 77 and 81 are approximately aligned with the emitting edge of emitter edge layer 76. A via is etched in layers 77, 79 and 81 for forming emitter control via resistive metal 78, which is effectively a resistor in connected in series with emitter edge 76. Metal 78 is TaN. Oxide layers 74 and 79 are etched back about 0.5 micron from the emitting edge of emitter edge layer 76. Also formed on substrate 71 is nitride layer 82 of about 250 nm (2500 angstroms) that is apart from the emitter edge wafer 70. Formed on layer 82 is anode 83 having about 0.5 micron layer of TiW. The metal of items 73, 76, 80 and 83 may be other than TiW but needs to have a similar work function so as to prevent electrochemical reactions that would occur between such items composed of different metals. Anode 83 functions as a focusing electrode for the electrons emitted from emitter edge 76. Anode 83 is adjustable in distance about 1.5 to 4 microns from edge 76, to effect optimum focusing.
Emitters 70 may be formed as a comb tooth emitter having a plurality of teeth as assemblies 20 and 21 shown in figures 3 and 5, respectively. The number of teeth of the emitter is not critical but a preferred number for a display may be four as field emitter 84 of figure 11 has. Each emitter tooth has a width 85 of about 4 microns wide. Emitter 84 has dimension 87 of about 30 microns, and is one of the emitters that compose pixel 88 which has a dimension 89 of 100 to 300 microns on each side. A two dimensional array of pixels 88 compose a matrixed addressable pixel array 90, having a dimension 91 determined by resolution and pixel size. The numbers of emitters 84 in a pixel 88 and of pixels 88 in array 90 are a matter of design choice.
Figure 12 shows a portion of the structure of display 100, having field emitters 84 situated on substrate 71. Column address conducting strip 92 and row address conducting strip 93 select the particular pixel 88 to be turned on to emit electrons which go to an out-of-plane screen 97. Strip 92 is connected to the gate of field emitter 84 and strip 93 is connected to the resistor/emitter of field emitter 84. Screen 94 is composed of a glass plate or substrate 95. A phosphor layer 96 is formed on glass plate or substrate 95 and a tin aluminum (Al) layer 97, transparent to beams 98 of electrons but conductive of electric signals, is formed on phosphor layer 96. Layer 97 is connected to a positive terminal of a voltage source that has the other negative terminal connected to the respective emitters 84. Electron emissions 98 impinge phosphor layer 96 as they go through anode 97. As phosphor layer 96 is impinged by emitted electrons 98, layer 96 emits photons in the area which is impinged by emissions or electrons 98, resulting in a visible indication of light to an observer. Alternatively, layer 96 may be an indium tin oxide (ITO) film, which is conductive of electric signals but transparent to light, formed on glass plate or substrate 95; and layer 97 may be phosphor formed on layer 96 which is connected to a positive terminal of a voltage source that has the other negative terminal connected to the respective emitters 84. Film or layer 96 is the anode for collecting electron emissions 98 of emitters 84. Electron emissions 98 impinge phosphor layer 97 as they go to anode 96. As phosphor layer 97 is impinged by emitted electrons 98, layer 97 emits photons in the area which is impinged by emissions or electrons 98, resulting in a visible indication of light to an observer. On glass plate is coated an antireflective film 111 for enhanced viewing. Screen 94 is supported parallel to substrate 71 by dielectric spacer 99 at a distance of between 200 and 10,000 microns between screen 94 and substrate 71.
In figure 13 is a configuration of a vacuum microelectronic field emitter microstructure 101. A thin-film-edge emitter 102 is sandwiched between control electrodes 103 and 104. Electrons are emitted laterally from emitter 102 and are collected at anode 105 a few microns away from emitter 102. Structure 101 is fabricated with a process which combines silicon integrated circuit (IC) patterning techniques with surface micromachining, as is outlined as a simplified process in figure 14.
Field emitter structure 84 of display 100 in figure 12 is similar to structure 101 in figure 13. However, anode 105 of structure 101 would be a focusing electrode. Emitter edge 102 of structure 101 is split into comb elements 106 and each emitter comb element or finger 106 is connected individually to a current equalization resistive layer or element 107. Resistive element 107 prevents electromigration and burnout of emitting edge 102 by limiting the D.C. current in each finger 106. Thin-film edge emitter structure 102 having comb resistors 107 for fingers 106, permits individual bias for each emitter thereby preventing a few shorts from pulling the line voltage down. Lateral series resistor 107 is not sensitive to slight fabrication process variations. Thin-film-edge emitter 102 has low intrinsic capacitance. Series resistor 107 of fingers can be bypassed at the appropriate frequencies by a bypass capacitor 108 to allow fast emitter 101 response times.
Emitter edge 102 fingers 106 need to be thin (i.e. <20 nm (<200 angstroms)) to attain the high electric fields for low-voltage emission. The ideal emitter structure is a tapered lateral emitter having a very thin emitting edge, which is difficult to achieve in a thin-film-edge emitter form. Figure 15 shows a compromise laminated emitter structure 109 that combines the advantages of the thin-film-edge sharpness with the current carrying capability of a thick film. The operating gate voltage is kept reasonably low by using a low workfunction emitter composed of LaB6, CeB6, C5-implanted W1 or Cs-implanted TiW.
Several field emitter structures, based on the thin-film-edge emitter, are suitable for displays. One is a dual control electrode structure 110 in Figure 16, which resembles a vacuum transistor used for RF amplification. Emitter 112 is symmetrically placed between an upper control electrode 113 above emitter 112 and a lower control electrode 114 situated on substrate 118 below emitter 112. Electrodes 113 and 114 are electron emission 116 intensity controlling gates. Electrodes 113 and 114 are each spaced at 0.5 microns apart from emitter 112. The anode of a vacuum transistor is used as a focusing electrode 115, situated on substrate 118, which is biased between a minus 20 and minus 50 volts, typically at a minus 35 volts, with respect to emitter 112. Electrode 115 is about 4 microns from emitter 112. Emitter 112 is set at zero volts and control electrodes 113 and 114 are set at about a plus 100 volts. The negative bias on electrode 115 turn electrons 116 form a lateral direction to a vertical direction toward screen 117. Screen 117 has a glass plate 119 with an ITO layer 120 formed on it. ITO layer 120 is connected as an anode or collector for electrons 116. Formed on ITO layer 120 is a layer of phosphor 121. Phosphor layer 121 is about 2,500 microns in distance from parallel substrate 118. Collector 120 is biased at a positive 20,000 volts (i.e., at a field of 8 volts per micron). The electron energy spread of emission 116 is about 0.1 electron volt (eV) and the emission angle is ± 45 degrees.
Another display field emitter structure is the single control electrode configuration 122 shown in figure 17. Configuration 122 has the same items, physical dimensions, voltage requirements, and operational characteristics as configuration 110 of figure 16. The only distinction is that there is no lower electrode or gate 114 in configuration 122. The position and height of focus electrode 115 has an effect on the collimation of electrons 116. The best position for electrode 115 is below emitter 112 for configuration 110 and is at the same level as upper control gate 113 for configuration 122. The electrons seem to be better collimated in configuration 122. Both configurations 110 and 122 are little susceptible to emitter 112 erosion by energetic particles desorbed by electron 116 bombardment of phosphor screen 121.

The performance specifications of a small FEA display are shown in the following table.

Full color	8 bits/color
Resolution	160 dpi
Brightness	300 fL
Contrast ratio	> 100:1
Dimmability	2000:1
Frame rate	60 Hz
Pixel size	200 µm x 150 µm
Anode/Emitter spacing	1000 - 2500 µm
Gate/Emitter spacing	0.5 µm
Anode/Emitter voltage	20,000 V
Gate/Emitter voltage	100 V
Luminance (brightness)	7000 cd/m^-
Filter transmittance	0.1
Intrinsic contrast	300:1
Response time	< 5 ms
Viewing angle	± 90°

In this example, there is a brightness (luminance) of 700 cd/m² (approximately 210 fL) with the contrast enhancement filter. If the transmittance of the contrast enhancement filter T is 0.1, this translates into a brightness (luminance) L of 7000 cd/m² at the emitting source. For a Lambertian surface producing directionally uniform luminance, the luminous exitance M is given by M = π L The total luminous flux F_v through each pixel is thus Fv = ∫M dA = MA = πLA where A is the area. For a pixel size of 200 µm x 150 µm, A = 3 x 10⁴ µm² = 3 x 10^-8 m², Fv = 6.60 x 10-4 lumen The spectral luminous efficacy k(l) at wavelength of l is given by k(l) = Fvl Fel where F_vl is the spectral luminous energy flux and F_el is the spectral radiant energy flux Fvl = -Fv _l Fel = _Fe _l and where F_e is the total radiant flux. The total luminous efficacy is given by K
With K = 25 lm/W, then the radiant flux is Fe = 0.026 mW For a display operated at an anode voltage V_a = 20,000 volts, then the anode current per pixel is given by Ia = Fe Va = 1.32 nA/pixel
Phosphor layer 121 acts as the anode and may be deposited on the glass. This may be followed by a thin layer 120 of Al which is a conducting layer and also acts as a reflector. In operation, the emitted electrons travel to anode 121, causing luminous emission when they impinge on phosphor screen 121. High-voltage phosphors are much better than low-voltage phosphors because the brightness is proportional to the accelerating voltage and the current density, and phosphor lifetime is inversely proportional to the deposited charge density. The following table compares the characteristics of low- and high-voltage cathodoluminescent phosphors.
In figure 12. the phosphor screen is part of individual edge emitter array 84. Array 100 may emit one of several colors, depending on the kind of phosphor 97 that screen 94 has. The above table gives examples of materials used for attaining red, green and blue light emitting phosphors. Pixel 88 of an array of field emitters 84, along with a phosphor screen 94 like that of figure 12, may be designed to emit red. green or blue light, even light of another color with the appropriate phosphor. Thus, red. green and blue pixels can be placed in matrixed addressable pixel array 90. for obtaining a full color field emitter display. The pixel layout, for instance, may be that each pixel of a given color is bordered by pixels of the other colors. Examples of color pixel formats. for three and four color matrix arrays, are set forth in the related art, such as a United States patent, number 4,800,375, by Louis Silverstein et al., issued January 24, 1989, and entitled "Four Color Repetitive Sequence Matrix Array for Flat Panel Displays."
If the required luminance (brightness) of the flat-panel display with a contrast enhancement filter is L, then for a Lambertian (diffuse) surface, the luminous exitance M is given by M = π L . If the filter transmittance is T, then the actual luminous exitance M_o is given by Mo = MT = πLT . and the luminous flux Φ_v is given by Φv = MoA = πLAT . For a 12.7cm x 12.7cm avionics display, the area A = 161.3 cm² = 1.613 x 10^-2 m². If the luminous exitance L = 200 fL ^a 700 cd/m² and the filter transmittance T @ 0.3, then M_o @ 7300 cd/m² and the luminous flux Φ_v is given by Φv = MoA @ 120 lm. For a phosphor with luminous efficacy of K and anode voltage V_a, the current density required is J = Φ v KAVa . The phosphor lifetime t is determined by the total charge density QL deposited; QL = Jt, and τ = QL J = QLKAVa Φ v . Typically Q_L = 10⁶ Coulomb/m² t = 2.688 x 102 KVa sec. For low-voltage phosphors, K = 2 lm/W and V_a = 200 V, thus t = 15 h (2 days at 8 h/day). For high-voltage phosphors, K = 25 lm/W and V_a = 20,000 V, thus t = 37,500 h (≥10 years at 8 h/day).
For lifetime considerations, high-voltage phosphors are better than low voltage phosphors. An issue that needs to be addressed is the breakdown of dielectric spacers due to the high anode voltages. However, dielectric breakdown should not be an issue since at 20,000 volts, the electric field of dielectric spacers 99 (in figure 12) is below 10⁵ V/cm.
A third display field emitter structure is an on-chip phosphor screen configuration 124 in figure 18. Configuration 124 is a derivative of configuration 110. A trench 125, between 1.0 to 2.5 microns deep, is etched (with micromachining) in substrate 118 in the area of former focusing electrode 115. An anode 123 is deposited in trench 125. After the anode 123 deposition, a phosphor layer 127 is defined by e-beam evaporation and lift-off. Electrons 126 go from emitter 112 towards phosphor screen 127 and anode 123, to emit photons for viewing. Laterally, anode 123 is between 2 to 10 microns from the nearest edge of emitter 112. The anode 123 voltage is equal to or greater than positive 500 volts relative to emitter 112 which is at a zero voltage. Upper control gate 113 and lower control gate 114 are at 100 volts and situated similarly relative to emitter 112 as in configuration 110 of figure 16.

Claims

A display comprising an array (20) of field emitters having a thin-film edge comprising:

a substrate (12);

a plurality of field emitters (41 - 44) situated on said substrate, the emitters arranged on said substrate in rows and columns, each emitter having first and second terminals; a plurality of row address conductors (50 - 54) connected to the first terminals of said plurality of emitters;

a plurality of column address conductors (63, 65) connected to the second terminals of said plurality of emitters; and

a phosphor screen (96) at a distance from said substrate (12); and

wherein:

excitation of each emitter is effected by an application of a signal to a row address conductor and a column address conductor connected to the emitter; and

excitation of each emitter results in emission of electrons to said phosphor screen resulting in emission of photons from said phosphor screen;

a cathode (4) connected to the first terminal;

an anode (10) connected to the second terminal; and

a first control electrode (8); and

wherein:

said phosphor screen (96) is situated on the anode of said emitter; and

said field emitter further comprises a comb emitter structure (3, 4),

characterized in that

a resistive element (5) is inserted and connected in series between the cathode and the first terminal, for limiting current to the cathode; and

a capacitive element (5, 6, 11) is connected in parallel with the resistive element.
The display of Claim 1, wherein each emitter further comprises a second control electrode (9).
The display of Claim 2, wherein said phosphor screen (96) comprises:

a glass sheet (95);

a layer of phosphor (96) formed on the glass sheet; and

a metal film (97) formed on the layer of phosphor film.
The display of claim 2, wherein said phosphor screen (96) comprises:

a glass sheet (95);

a metal film (97) formed on the glass sheet; and

a layer of phosphor (96) formed on the metal film.
The display of claim 3, further comprising at least one dielectric spacer (99) for supporting said phosphor screen (96) relative to said substrate (71).
The display of one of claims 1 to 5 comprising:

a plurality of pixels (88), wherein each pixel comprises at least one field emitter (84), each pixel having first and second terminals;

a plurality of row address conductors (93) connected to the first terminals of said plurality of pixels; and

a plurality of column address conductors (92) connected to the second terminals of said plurality of pixels.
The display of Claim 6, wherein said plurality of pixels comprises:

a first group of pixels having the capability of emitting light of a first color;

a second group of pixels having the capability of emitting light of a second color; and

a third group of pixels having the capability of emitting light of a third color.
The display of Claim 7, wherein said plurality of pixels are arranged on the display such that each pixel of one group of pixels is proximate to pixels of the other two groups of pixels.
The display of Claim 8, wherein:

the phosphor screen of each pixel of the first group of pixels, has a first kind of phosphor for causing emitted light to be of the first color;

the phosphor screen of each pixel of the second group of pixels has a second kind of phosphor for causing emitted light to be of the second color; and

the phosphor screen of each pixel of the third group of pixels has a third kind of phosphor for causing emitted light to be of the third color.