Abstract:
A high resolution field emission display includes a faceplate and a baseplate. The faceplate includes a transparent viewing layer, a transparent conductive layer formed on the transparent viewing layer and intersecting stripes of light-absorbing, opaque insulating material formed on the transparent conductive layer. The insulating material defines openings less than one hundred microns wide between the intersecting stripes. The faceplate also includes a plurality of localized regions of cathodoluminescent material, each formed in one of the openings. The cathodoluminescent material includes a metal oxide providing reduced resistivity in the cathodoluminescent material. Significantly, the reduced resistivity of the cathodoluminescent material together with the focusing effect of the insulating material provide increased acuity in luminous images formed on the faceplate. The baseplate includes a substrate, an emitter formed on the substrate and a dielectric layer formed on the substrate and having an opening formed about the emitter. The baseplate also includes a conductive extraction grid formed on the dielectric layer and having an opening formed about the emitter.

Description:
STATEMENT OF GOVERNMENT INTEREST  
       [0001] This invention was made with government support under Contract No. DABT63-93-C-0025 awarded by Advanced Research Projects Agency (ARPA). The government has certain rights in this invention. 
     
    
     
       TECHNICAL FIELD  
         [0002]    This invention relates in general to visual displays for electronic devices and in particular to improved focusing apparatus and techniques for field emission displays.  
         BACKGROUND OF THE INVENTION  
         [0003]    [0003]FIG. 1 is a simplified cross-sectional view of a portion of a field emission display  10  including a faceplate  20  and a baseplate  21 , in accordance with the prior art. FIG. 1 is not drawn to scale. The faceplate  20  includes a transparent viewing screen  22 , a transparent conductive layer  24  and a cathodoluminescent layer  26 . The transparent viewing screen  22  supports the layers  24  and  26 , acts as a viewing surface and as a wall for a hermetically sealed package formed between the viewing screen  22  and the baseplate  21 . The viewing screen  22  may be formed from glass. The transparent conductive layer  24  may be formed from indium tin oxide. The cathodoluminescent layer  26  may be segmented into localized portions. In a conventional monochrome display  10 , each localized portion of the cathodoluminescent layer  26  forms one pixel of the monochrome display  10 . Also, in a conventional color display  10 , each localized portion of the cathodoluminescent layer  26  forms a green, red or blue sub-pixel of the color display  10 . Materials useful as cathodoluminescent materials in the cathodoluminescent layer  26  include Y 2 O 3 :Eu (red, phosphor P-56), Y 3 (Al, Ga) 5 O 12 :Th (green, phosphor P-53) and Y 2 (SiO 5 ):Ce (blue, phosphor P-47) available from Osram Sylvania of Towanda PA or from Nichia of Japan.  
           [0004]    The baseplate  21  includes emitters  30  formed on a planar surface of a substrate  32 , which may include semiconductor materials. The substrate  32  is coated with a dielectric layer  34 . In one embodiment, this is effected by deposition of silicon dioxide via a conventional TEOS process. The dielectric layer  34  is formed to have a thickness that is approximately equal to or just less than a height of the emitters  30 . This thickness is on the order of 0.4 microns, although greater or lesser thicknesses may be employed. A conductive extraction grid  38  is formed on the dielectric layer  34 . The extraction grid  38  may be formed, for example, as a thin layer of polysilicon. The radius of an opening  40  created in the extraction grid  38 , which is also approximately the separation of the extraction grid  38  from the tip of the emitter  30 , is about 0.4 microns, although larger or smaller openings  40  may also be employed.  
           [0005]    In operation, the extraction grid  38  is biased to a voltage on the order of 100 volts, although higher or lower voltages may be used, while the substrate  32  is maintained at a voltage of about zero volts. Intense electrical fields between the emitter  30  and the extraction grid  38  cause field emission of electrons from the emitter  30  in response to the voltages impressed on the extraction grid  38  and emitter  30 .  
           [0006]    A larger positive voltage, also known as an anode voltage V A , ranging up to as much as 5,000 volts or more but often 2,500 volts or less, is applied to the faceplate  20  via the transparent conductive layer  24 . The electrons emitted from the emitter  30  are accelerated to the faceplate  20  by the anode voltage V A  and strike the cathodoluminescent layer  26 . This causes light emission in selected areas, i.e., those areas adjacent to where the emitters  30  are emitting electrons, and forms luminous images such as text, pictures and the like.  
           [0007]    When the emitters  30  emit electrons, the resultant beam of electrons spreads as the electrons travel from the emitter  30  towards the faceplate  20 . When the electron emissions associated with a first localized portion of the cathodoluminescent layer  26  also impact on a second localized portion of the cathodoluminescent layer  26 , both the first and second localized portions of the cathodoluminescent layer  26  emit light. As a result, the first pixel or sub-pixel uniquely associated with the first localized portion of the cathodoluminescent layer  26  correctly turns on, and at least a portion of a second pixel or sub-pixel uniquely associated with the second localized portion of the cathodoluminescent layer  26  incorrectly turns on. In a color field emission display  10 , this can cause purple light to be emitted from a blue sub-pixel and a red sub-pixel together when only red light from the red sub-pixel was desired. This is problematic because it degrades the image formed on the faceplate  20  of the field emission display  10 .  
           [0008]    In a monochrome field emission display  10 , color distortion does not occur, but the resolution of the image formed on the faceplate  20  is reduced by this spreading of the electron beams from the emitters  30 . This is exacerbated in either type of field emission display  10  as the resolution of the field emission display  10  is increased by crowding pixels or sub-pixels more closely together.  
           [0009]    A second problem that may occur is that the entire emitted beam of electrons may travel at an angle to the path that they were intended to take, i.e., form a tilted beam of electrons. This may occur because of electrostatic effects involving interactions with other pixels. Alternatively, variations in shapes of tips of the emitters  30  or in extraction grid  38  geometry resulting from normal manufacturing variability may result in some electron beams being tilted relative to others. As a result, more than one pixel may be impacted by an electron beam intended to result in light emission from only a single pixel.  
           [0010]    These problems may be referred to as bleedover. The likelihood of bleedover is increased by any misalignment between the localized portions of the cathodoluminescent layer  26  and their associated sets of emitters  30 . Additionally, as the current from any one of the emitters  30  is increased, the problem of bleedover increases.  
           [0011]    In some applications, a small field emission display  10  is intended to be viewed through magnifying optics, such as lenses or magnifying reflectors. These applications require a high resolution field emission display  10 . High resolution field emission displays  10  use fewer emitters  30  per pixel or sub-pixel. This arises for several reasons, one of which is that a smaller pixel or sub-pixel subtends a smaller area in which the emitters  30  can be provided. As a result, each emitter  30  in a high resolution field emission display  10  has a greater influence on the light emitted from the pixel or sub-pixel associated with it. This increases the need to be able to control electron emissions and the spread of electron emissions from each emitter  30 .  
           [0012]    In conventional field emission displays  10 , attempts have been made to alleviate bleedover in several ways. The anode voltage V A  applied to the transparent conductive layer  24  of the conventional field emission display  10  is a relatively high voltage, such as 1,000 volts or more, so that the electrons emitted from the emitters  30  are strongly accelerated to the faceplate  20 . As a result, the electron emissions spread out less as they travel from the emitters  30  to the faceplate  20 . The gap between the faceplate  20  and the baseplate  21  of the conventional field emission display  10  is relatively small (ca. one thousandth of an inch or twenty-five microns per 100 volts of anode voltage V A ), again reducing opportunity for spreading of the emitted electrons.  
           [0013]    Some solutions that have been tried for reducing bleedover either increase the anode voltage V A  applied to the transparent conductive layer  24  or decrease the spacing between the faceplate  20  and the baseplate  21  in order to reduce spreading of the electron emissions. However, it has been found that these are impractical solutions because the anode voltage V A  applied between the transparent conductive layer  24  and the baseplate  21  may cause arcing when either of these solutions is attempted.  
           [0014]    Another way in which bleedover is reduced in conventional field emission displays  10  is by spacing the localized portions of the cathodoluminescent layer  26  relatively far apart. This is possible because of the relatively low display resolution provided by conventional field emission displays  10 . As a result, the electron emissions impact the correct localized portion of the cathodoluminescent layer  26 . However, as the resolution of images displayed by field emission displays  10  increases, the localized portions of the cathodoluminescent layer  26  are necessarily crowded closer together. As a result, bleedover may occur.  
           [0015]    One solution that has been employed in conventional cathode ray tubes is to metalize the back surface of the cathodoluminescent layer  26 . However, in field emission displays  10 , this technique would require an increase of several hundred percent in the anode voltage V A  in order to achieve the same luminosity. However, an increase of anode voltage V A  in field emission displays  10  requires an increased separation between the faceplate  20  and the baseplate  21 . As a result, the electron beam from each emitter  30  spreads out even more in traveling from the emitter  30  to the faceplate  20 . Additionally, the increased anode voltage V A  itself is objectionable from the perspectives of power consumption and circuit complexity.  
           [0016]    One approach to controlling the spatial spread of electrons emitted from a group of the emitters  30  is to surround the area emitting the electrons with a focusing electrode (not shown). This allows increased control over the spatial distribution of the emitted electrons via control of the voltage applied to the focusing electrode, which in turn provides increased resolution for the resulting image. One such approach, where each focusing element serves many emitters, is described in U.S. Pat. No. 5,528,103, entitled “Field Emitter With Focusing Ridges Situated To Sides Of Gate,” issued to Spindt et al.  
           [0017]    Disadvantages to the prior art approaches include the need for another voltage source for the focusing electrode and problems due to variations in turn-on voltage from one emitter  30  to another. When a group of emitters  30  are all affected by a single focusing electrode, some of the emitters  30  may exhibit a turn-on voltage that differs from that exhibited by other emitters  30 . The effect that the focusing electrode has on the electrons emitted from each of these emitters  30  will differ. Additionally, some of the current through the emitters  30  will be collected by the focusing electrode. This complicates the relationship between the current through the emitter  30  and the amount of light that is generated at the faceplate  20  because some of the current through the emitter  30  is diverted en route to the faceplate  20  by the focusing electrode. Further, the effects of the focusing electrode may be different for emitters  30  that are closer to the focusing electrode than for emitters  30  that are farther away from the focusing electrode. The lack of control over the amount of light emitted in response to a known emitter current results in poorer imaging characteristics for the display  10 .  
           [0018]    In magnified, high resolution field emission displays  10 , each pixel must be able to provide higher light output because the intensity of the illumination when it reaches the eye of the viewer is reduced in proportion to the magnification needed in order to view it. As a result, the current density in each pixel is increased relative to larger field emission displays  10 . As discussed in “Resistivity Effect of ZnGa 2 O 4 :Mn Phosphor Screen on Cathodoluminescence Characteristics of Field Emission Display” by S. S. Kim et al., J. Vac. Sci. Technol. B 16(4), July August 1998, resistance in the cathodoluminescent layer  26  itself can significantly affect luminance through several mechanisms, as is explained below in more detail.  
           [0019]    A first mechanism is due to a voltage drop occurring in the cathodoluminescent layer  26 . Most cathodoluminescent materials are formed from metal oxides or sulfides having resistivities ρ on the order of 10 10  Ω-cm. An exception is ZnO:Zn, which has a resistivity on the order of 10 6  Ω-cm, but which is poorly suited for use in color field emission displays  10 . The materials used to form the cathodoluminescent layer  26  typically are powdered and have particle sizes on the order of two microns or less. In order to provide a reasonably uniform cathodoluminescent layer  26 , it is necessary to deposit a cathodoluminescent layer  26  that is three or more particles thick, or six to ten microns thick.  
           [0020]    Electrons incident on the cathodoluminescent layer  26  typically only excite fifteen to thirty Angstroms of that portion of the cathodoluminescent layer  26  that is closest to the emitters  30 . Although the cathodoluminescent layer  26  is formed on the transparent conductive layer  24 , which is typically indium tin oxide having a sheet resistivity of about 25 Ω/□, the voltage drop through the cathodoluminescent layer  26  can amount to a significant percentage of the anode voltage V A  applied to the transparent conductive layer  24 . In some experiments using low anode voltages V A  in vacuum fluorescent displays, the anode voltage V A  is reduced by as much as seventy percent or more from one side of the cathodoluminescent layer  26  to the other, thereby reducing the electron-attracting effect of the anode voltage V A  substantially. As a result, the number of electrons arriving in the pixel per unit time is reduced, reducing pixel luminosity.  
           [0021]    A second mechanism in which the resistance of the cathodoluminescent layer  26  affects pixel luminosity involves localized heating of the cathodoluminescent layer  26  due to the increased current through the cathodoluminescent layer  26 . The localized heating reduces the efficiency of the cathodoluminescent layer  26 . This phenomenon is known as “thermal quenching” of the cathodoluminescent materials making up the cathodoluminescent layer  26 . As a result, the luminosity per incident electron decreases, providing a darker pixel than is needed. Useful lifetime of the cathodoluminescent layer  26 , and hence of the display  10  incorporating the cathodoluminescent layer  26 , may also be reduced.  
           [0022]    All of these effects tend to degrade linearity of the relationship between current through the emitter  30  and luminosity of the pixel associated with the emitter  30 . A linear relationship between these two quantities greatly simplifies useful and effective operation of field emission displays  10 .  
           [0023]    There is therefore a need for a way to increase the linearity of the relationship between pixel luminosity and emitter current to provide robust field emission displays, and especially high resolution field emission displays, without significantly increasing fabrication complexity for such displays.  
         SUMMARY OF THE INVENTION  
         [0024]    In accordance with one aspect of the invention, a field emission display includes a faceplate having a transparent viewing layer, a transparent conductive layer formed on the transparent viewing layer and a grille of lightabsorbing, opaque insulating material formed on the transparent conductive layer and defining openings within the grille. The light absorption and opacity of the grille increases the contrast of the faceplate. The faceplate also includes a plurality of pixels formed of cathodoluminescent material. Each pixel is formed in one of the openings. The cathodoluminescent material includes a noncathodoluminescent material providing reduced resistivity in the cathodoluminescent material.  
           [0025]    Significantly, the light-absorbing, opaque insulating material charges electrostatically in direct response to bleedover of electrons from any one pixel or sub-pixel. As a result, localized electrostatic fields provide enhanced focusing performance together with reduced circuit complexity compared to prior art approaches. Additionally, the noncathodoluminescent material results in more accurate control of voltages accelerating electrons towards the cathodoluminescent material. This, in turn, results in superior display performance, especially for high resolution field emission displays. 
       
    
    
     BRIEF DESCRIPTION OF THE DRAWINGS  
       [0026]    [0026]FIG. 1 is a simplified cross-sectional view of a portion of a field emission display according to the prior art.  
         [0027]    [0027]FIG. 2 is a simplified cross-sectional view of a faceplate at one stage in fabrication, in accordance with an embodiment of the present invention.  
         [0028]    [0028]FIG. 3 is a simplified cross-sectional view of the faceplate of FIG. 2 at a later stage in fabrication, in accordance with embodiments of the present invention.  
         [0029]    [0029]FIG. 4 is a simplified cross-sectional view of the faceplate of FIG. 3 at a later stage in fabrication, in accordance with an embodiment of the present invention.  
         [0030]    [0030]FIG. 5 is a simplified and magnified cross-sectional view of the faceplate of FIG. 4, showing details of the cathodoluminescent layer, in accordance with an embodiment of the present invention.  
         [0031]    [0031]FIG. 6 is a simplified block diagram of a computer including a field emission display using the faceplate of FIG. 5, in accordance with an embodiment of the present invention. 
     
    
     DETAILED DESCRIPTION OF THE INVENTION  
       [0032]    [0032]FIG. 2 is a simplified cross-sectional view of a faceplate  20 ′ at one stage in fabrication, in accordance with an embodiment of the present invention. The faceplate  20 ′ includes the transparent viewing screen  22  and the transparent conductive layer  24 . In one embodiment, the transparent conductive layer  24  is a layer of indium tin oxide formed by sputtering. The transparent conductive layer  24  typically has a thickness of 150 to 200 nanometers, an optical transmissivity in excess of 90% to 95% and a sheet resistivity of about 25 Ω/□.  
         [0033]    The faceplate  20 ′ is coated with a photoresist  42  that is compatible with electrophoretic deposition. The photoresist  42  is conventionally masked, exposed to light of appropriate wavelength and intensity and is then developed to provide elongated openings  44  in the photoresist  42 . Although not shown in FIG. 2, spaced-apart elongated openings are also formed perpendicular to the openings  44  to form a grid pattern. The openings may be of any shape and may be arranged in any pattern with respect to one another.  
         [0034]    For example, polyvinyl alcohol and an ammonium dichromate sensitizer can be used to form photoresist  42  that is compatible with isopropyl alcohol as a carrier medium during electrophoretic deposition. This photoresist  42  does not conduct electricity. As a result, electrophoresis may be used to selectively deposit particles from a colloidal suspension (not shown in FIG. 2) into the openings  44  using the transparent conductive layer  24  as one electrode in a conventional electrophoretic deposition process.  
         [0035]    [0035]FIG. 3 is a simplified cross-sectional view of the faceplate  20 ′ of FIG. 2 at a later stage in fabrication, in accordance with an embodiment of the present invention. In one embodiment of the faceplate  20 ′, an insulating, opaque and light-absorbing material is deposited in the openings  44 , and the resist  42  is then removed, thereby leaving a grille  46  formed on the conductive layer  24 . In one embodiment, the grille  46  is formed by electrophoretic deposition of materials such as cobalt oxide, manganese oxide or chromium oxide through the grille pattern formed in the photoresist  42  of FIG. 2. In one embodiment, the grille  46  has a thickness of five to ten microns.  
         [0036]    Hydrated nitrates of lanthanum, cerium, indium or aluminum may be added to the isopropyl alcohol as electrolytes to provide conductivity during the electrophoretic deposition of the grille  46 . In one embodiment, these electrolytes also act as a binding agent in the grille  46 , lending robustness to the grille  46  and binding the grille  46  to the transparent conductive layer  24 , after suitable treatment. In some embodiments, following electrophoretic deposition of the grille  46 , the photoresist layer  42 , the grille  46  and the transparent layers  22  and  24  are baked in atmosphere at a temperature of about 400° C. for fifteen to thirty minutes to dry the grille  46  and to decompose the photoresist layer  42 . Alternatively, plasma ashing in an oxygen-bearing plasma may be used to strip the photoresist layer  42 . In some embodiments, the grille  46  is five to ten microns thick and defines openings  48  having a width  50  that is about twenty five microns on a side or larger. Each of the openings  48  form individual pixels at a later stage in fabrication. In some embodiments, the grille  46  includes openings having a width that is less than one hundred microns.  
         [0037]    In another embodiment, the grille  46  is formed by conventional sputtering of a layer of material such as cobalt oxide, manganese oxide or chromium oxide on the transparent conductive layer  24 . Photoresist is then applied over the sputtered layer and patterned to form an etch mask. Following etching of the sputtered layer but not the transparent conductor, the photoresist is stripped, forming the grille  46 .  
         [0038]    [0038]FIG. 4 is a simplified cross-sectional view of the faceplate  20 ′ of FIG. 3 at a later stage in fabrication, in accordance with embodiments of the present invention. Following formation of the grille  46 , cathodoluminescent layers  26  are sequentially deposited through photoresist masking layers via conventional electrophoresis into selected openings  48  to form pixels or sub-pixels  52 . For example, a first sub-pixel  52   a  may include Y 2 O 3 :Eu cathodoluminescent material  26  to emit red light when bombarded by electrons. An adjacent sub-pixel  52   b  may include Y 3 (Al, Ga) 5 O 12 :Tb cathodoluminescent material  26  to emit green light when bombarded by electrons. Another adjacent sub-pixel  52   c  may include Y 2 (SiO 5 ):Ce cathodoluminescent material  26  to emit blue light when bombarded by electrons. In color displays  10 , each sub-pixel  52  of one color will have nearest neighbors including sub-pixels  52  of each of the other two colors used in the display  10 .  
         [0039]    [0039]FIG. 5 is a magnified cross-sectional view of the faceplate  20 ′ of FIG. 4, showing details of the cathodoluminescent layer  26 , in accordance with embodiments of the present invention. The material forming the cathodoluminescent layer  26  includes a mixture of particles  54  of powdered conductive material and particles  56  of cathodoluminescent material. The conductive particles  54  are provided to reduce the resistivity ρ in the cathodoluminescent layer  26 . For clarity of illustration and ease of understanding, the particles  54  of powdered conductive material are illustrated as being round dots, while the particles  56  of cathodoluminescent material are illustrated as being irregular, however, it will be understood that these shapes are for purposes of illustration only.  
         [0040]    In some embodiments, the particles  54  of powdered conductive material are formed from powdered metal oxides. As used herein, the term “metal oxide” refers to metal oxides that do not exhibit significant cathodoluminescent activity in response to electron bombardment, while the term “cathodoluminescent material” refers to compounds, that may include combinations of metal atoms and oxygen, exhibiting light emission in response to bombardment by electrons.  
         [0041]    In one embodiment, the cathodoluminescent layers  26  forming the pixels  52  of FIG. 4 are deposited by conventional electrophoresis using mixtures of particles  56  of powdered cathodoluminescent materials and particles  54  of powdered metal oxides such as indium oxide, tin oxide, tungsten trioxide and vanadium pentoxide. In one embodiment, the particles  56  forming the powdered cathodoluminescent materials have a diameter of two microns or less. In one embodiment, the particles  54  forming the powdered conductive materials have diameters that are less than one-half micron in diameter. In one embodiment, the particles  54  forming the powdered metal oxides have diameters that are no more than one-fourth of the average diameter of the particles  56  forming the powdered cathodoluminescent materials. In one embodiment, the powdered metal oxides form between 0.1 and five weight percent of the combination of the powdered cathodoluminescent particles  56  and the powdered metal oxide particles  54  forming the cathodoluminescent layer  26 .  
         [0042]    The difference between the sizes of the metal oxide particles  54  and the cathodoluminescent particles  56  allow the metal oxide particles  54  to pack into interstices between the cathodoluminescent particles  56 . In one embodiment, the metal oxide particles  54  reduce the resistivity ρ of the composite cathodoluminescent layer  26  to less than 10 9  Ω-cm. As a result, a voltage V P  that would otherwise develop across the cathodoluminescent layer  26  in response to current through the cathodoluminescent layer  26  is reduced. The voltage V P  tends to reduce the anode voltage V A  applied to the transparent conductive layer  24  as manifested on the side of the cathodoluminescent layer  26  that is facing the emitters  30 , causing electrons from the emitters  30  to be less strongly attracted to the cathodoluminescent layer  26 .  
         [0043]    In operation, embodiments of the faceplate  20 ′ of the present invention provide several advantages, especially for very high resolution field emission displays  10  of the type intended to be viewed through magnifing optics. The insulating grille  46  between the conductive transparent layer  24  and the emitters  30  causes electrons that miss the openings  48  (FIG. 3) defining pixels  52  (FIG. 4) to electrically charge localized portions of the grille  46 . The degree of localized charging is related to the number of electrons that miss the intended pixel  52 , and the location of the localized charging is coincident with locations at which that portion of the incident electron beam is missing the intended pixel  52 . A localized electrostatic field is thus provided, focusing the electron beam back towards the intended pixel  52 . As a result, the insulating grille  46  provides a self-focusing mechanism that is related to the proportion of the electron beam that is missing the intended pixel  52 .  
         [0044]    Combining the focusing effect of the grille  46  with the resistivity reduction of the particles  54  of metal oxide provides more accurately defined electron bombardment of the pixels  52 . This more accurate control of electron bombardment both increases the luminosity of the pixels  52  by increasing the effect of the anode voltage V A  and increases the optical contrast between the illuminated pixels  52  and surrounding areas. Significantly, the luminosity, contrast and acuity of images formed on small displays  10  that are intended to be viewed through magnifying optics are improved.  
         [0045]    Additional advantages of embodiments of the present invention include not requiring a conductive focusing electrode (not shown) to be formed on an intervening insulator (not shown) formed on the transparent conductive layer  24 . Displays requiring such focusing electrodes risk catastrophic failure when the focusing electrode forms an electrical arc through the intervening insulator, or across the surface of the insulator to one or more pixels  52 . Fabrication of the faceplate  20  is more complex because additional lithographic steps are required in order to define the intervening insulator and to define the focusing electrode. Further, no focusing electrode power supply (not shown) is required if there is no focusing electrode, simplifying design and production requirements for the display  10 .  
         [0046]    Moreover, combining the metal oxide particles  54  with the cathodoluminescent particles  56  provides reduced resistivity ρ in the cathodoluminescent layer  26 . As a result, the amount of electrical power that is dissipated in the cathodoluminescent layer  26  is reduced, thereby reducing resistive heating of the cathodoluminescent layer  26 . Thermal quenching of the cathodoluminescent layer  26  is reduced, increasing both light output from the display  10  and useful life of the faceplate  20 ′. These factors are particularly significant in high resolution displays  10 .  
         [0047]    It will be appreciated that the faceplate  20 ′ that has been described includes what is known as a “blanket” anode, i.e., the transparent conductive layer  24  is not segregated into electrically distinct areas. Advantages to the blanket anode formed by the transparent conductive layer  24  include not having to switch anode voltages V A , not having to cope with electrical noise resulting from switching high anode voltages V A  and being able to simultaneously activate red  52   a , green  52   b  and blue  52   c  pixels by switching voltages coupled to the extraction grid  38  and the emitters  30  associated with the pixels  52   a ,  52   b  and  52   c.    
         [0048]    The grille  46  used in embodiments of the present invention is also useful in color sequencing field emission displays  10 . Color sequencing displays  10  electrically separate the portions of the transparent conductive layer  24  for each of the colors to be displayed. The anode voltage V A  is first switched to allow the red pixels  52   a  to be operated, then the anode voltage V A  is switched to allow the green pixels  52   b  to be operated and then the anode voltage V A  is switched to allow the blue pixels  52   c  to be operated. As a result, color sequencing displays  10  require three times as high a switching speed for a given frame rate as do displays  10  using transparent conductive layers  24  formed into blanket anodes.  
         [0049]    [0049]FIG. 6 is a simplified block diagram of a portion of a computer  60  including the field emission display  10  of FIG. 1 together with the faceplate  20 ′ as described with reference to FIGS. 2 through 5 and associated text. The computer  60  includes a central processing unit  62  coupled via a bus  64  to a memory  66 , function circuitry  68 , a user input interface  70  and the field emission display  10  including the faceplate  20 ′ according to the embodiments of the present invention. The memory  66  may or may not include a memory management module (not shown), but preferably includes both a ROM for storing instructions providing an operating system and a read-write memory for temporary storage of data. The processor  62  operates on data from the memory  66  in response to input data from the user input interface  70  and displays results on the field emission display  10 . The processor  62  also stores data in the readwrite portion of the memory  66 . Examples of systems where the computer  60  finds application include personal/portable computers, camcorders, televisions, automobile electronic systems, microwave ovens and other home and industrial appliances.  
         [0050]    Field emission displays  10  for such applications provide significant advantages over other types of displays, including reduced power consumption, improved range of viewing angles, better performance over a wider range of ambient lighting conditions and temperatures and higher speed with which the display can respond. Field emission displays find application in most devices where, for example, liquid crystal displays find application.  
         [0051]    Although the present invention has been described with reference to a preferred embodiment, the invention is not limited to this preferred embodiment. Rather, the invention is limited only by the appended claims, which include within their scope all equivalent devices or methods which operate according to the principles of the invention as described.