Patent Publication Number: US-5834891-A

Title: Spacers, spacer units, image display panels and methods for making and using the same

Description:
CROSS REFERENCE TO RELATED APPLICATION 
     This patent application is related to copending U.S. patent application Ser. No. 08/665,713 filed Jun. 18, 1996 of Bruce E. Novich entitled &#34;SPACER UNITS, IMAGE DISPLAY PANELS AND METHODS FOR MAKING AND USING THE SAME&#34;, filed concurrently with the present patent application. 
     FIELD OF THE INVENTION 
     The present invention relates generally to image display panels and, more particularly, to spacers and spacer units for aligning emitters and displays of image display panels, image display panels including the same, and methods for making and using the same. 
     BACKGROUND OF THE INVENTION 
     The demand for inexpensive, compact, lightweight and power efficient image display panels which provide color, contrast, brightness and resolution comparable to conventional cathode ray tube (&#34;CRT&#34;) technology is increasing. Flat panel image display (&#34;FPD&#34;) is desirable in applications such as portable computers and flat screen television, in which the significant physical depth of conventional CRT technology is a disadvantage. 
     Known flat panel image display devices include passive or active matrix liquid crystal displays (&#34;LCD&#34;), electroluminescent displays (&#34;EL&#34;), gas plasma displays and field emission displays (&#34;FED&#34;). The trend in FPD technology is to provide improved image resolution, faster data-to-image transfer, lighter weight, lower energy consumption and higher brightness. The combination of these trends has posed significant challenges for cost effective manufacture of flat panel displays. 
     Each of the various types of image displays described above typically include an emitter panel and opposed display panel. These panels must be insulated from each other to prevent an electrical breakdown. Uniform alignment and separation between the panels is necessary to provide low distortion, high brightness and uniform resolution. The problem of maintaining alignment and separation between the panels is exacerbated in image displays in which the interior of the display is maintained under vacuum, such as in field emission displays. A high aspect ratio spacer is needed to maintain accurate and precise separation between the emitter panel and the display panel without interfering with the transmission of energy such as electrons between the same, which can cause optical defects. As used herein, the term &#34;aspect ratio&#34; means the ratio of the spacer thickness to its width. A non-limiting example of a suitable aspect ratio for a spacer for use in a FPD is about 1000 micrometers (μm) to about 50 μm or about 20:1. 
     U.S. Pat. Nos. 4,099,082 and 4,183,125 disclose cellular spacer-supports for a luminescent display panel. The spacer-support comprises a stack of mutually registered open lattices of tensioned, highly flexible insulative filaments (such as glass filaments) which define an array of narrow transverse openings to permit the unattenuated passage of energy therethrough (column 4, lines 59-63). The filaments are tensed into the desired configuration by stringing upon the pins of a frame (column 6, lines 3-7). The stack of filaments is coated with a cement such as glass cement (column 6, lines 33-36), potassium silicate, sodium silicate or glass cladding (col. 8, lines 13-16); cured in an oven (column 6, lines 59-62); and the edges of the spacer are trimmed (column 7, lines 20-22). However, it can be difficult to align the lattice openings of such a spacer with the corresponding pixel groups, maintain the lattice flat and parallel between the emitter and display panels to prevent fiber cracking during the FPD assembly process and to prevent cement from contaminating the interior components of the panel. 
     Misalignment of the spacer unit within the FPD can cause serious visual defects in the display and, in vacuum displays, can result in poor sealing leading to hermeticity failure. A high aspect ratio spacer unit is needed which is dimensionally stable, self-leveling, preferably free of loose particulate materials which can contaminate interior components, resistant to thermal cycling, inexpensive to manufacture and install in an image display panel, easily modified for including additional components such as electrodes, and essentially self-aligning when installed between an emitter panel and a display panel. A spacer unit which is self-leveling and self-aligning is highly desirable to reduce cost and waste during FPD assembly. 
     SUMMARY OF THE INVENTION 
     The present invention provides a spacer unit, comprising: (a) a spacer for separating and aligning an emitter and a display of an image display is panel, the spacer comprising an assembly having a first side and a second side, the assembly comprising: (1) a first layer having a first side and a second side and comprising a plurality of generally parallel, spaced apart fibers; and (2) a second layer having a first side and a second side and comprising a plurality of generally parallel, spaced apart fibers, the second side of the first layer being adjacent to the first side of the second layer, the fibers of the first layer being positioned to form a plurality of intersections with the fibers of the second layer, at least one fiber, selected from the group consisting of the fibers of the first layer and the fibers of the second layer, having a bonding agent applied thereto at an intersection with a corresponding fiber to bond the fiber with the corresponding fiber at the intersection thereof, the assembly having a plurality of passageways between the fibers of the first layer, the fibers of the second layer and the intersections, the passageways being generally perpendicular to the fibers of the first layer and the fibers of the second layer, such that when the assembly is positioned between an emitter and a display of an image display panel at least one of the passageways permits the passage of energy therethrough between the emitter and the display; and (b) a sealing frame positioned about and engaging at least a portion of a periphery of the spacer, the sealing frame having a first end for being positioned adjacent to a portion of the emitter and a second end for being positioned adjacent to a portion of the display, the sealing frame comprising a deformable sealing material, such that when (i) the sealing frame and spacer are positioned between the emitter and the display; (ii) the first end of the sealing material is deformed and positioned adjacent a portion of the emitter; and (iii) the second end of the sealing material is deformed and positioned adjacent a portion of the display, the sealing material provides an essentially sealed region between the spacer, the emitter and the display. 
     The present invention provides a spacer unit, comprising: (a) a spacer for separating and aligning an emitter and a display of an image display panel, the spacer comprising an assembly having a first side and a second side, the assembly comprising: (1) a first layer having a first side and a second side and comprising a plurality of generally parallel, spaced apart fibers; and (2) a second layer having a first side and a second side and comprising a plurality of generally parallel, spaced apart fibers, the second side of the first layer being adjacent to the first side of the second layer, the fibers of the first layer being positioned to form a plurality of intersections with the fibers of the second layer, at least one fiber, selected from the group consisting of the fibers of the first layer and the fibers of the second layer, having a bonding agent applied thereto at an intersection with a corresponding fiber to bond the fiber with the corresponding fiber at the intersection thereof, the assembly having a plurality of passageways between the fibers of the first layer, the fibers of the second layer and the intersections, the passageways being generally perpendicular to the fibers of the first layer and the fibers of the second layer, such that when the assembly is positioned between an emitter and a display of an image display panel at least one of the passageways permits the passage of energy therethrough between the emitter and the display; and (b) a sealing frame positioned about and engaging at least a portion of a periphery of the spacer, the sealing frame having a first end for being positioned adjacent to a portion of the emitter and a second end for being positioned adjacent to a portion of the display, the sealing frame comprising a sealing material having a predetermined deformation temperature which is less than a predetermined deformation temperature of a component of the image display panel selected from the group consisting of the emitter, the display and the spacer, such that when (i) the sealing frame and the spacer are positioned between the emitter and the display and (ii) the sealing material is heated to a temperature greater than the predetermined deformation temperature of the sealing material but less than the predetermined deformation temperature of the component of the image display panel, the sealing material provides an essentially sealed region between the spacer, the emitter and the display. 
     Another aspect of the present invention is an image display panel comprising: (a) an emitter; (b) a display; and (c) the above spacer unit positioned therebetween. 
     Yet another aspect of the present invention is a method for making an image display panel, comprising the steps of: (a) positioning the above spacer unit between an emitter and a display; and (b) heating the spacer unit under vacuum to deform at least a portion of the sealing material to bond the sealing frame between the emitter and display and form a substantially evacuated region therebetween. 
     Another aspect of the present invention is a method for making an image display panel, comprising the steps of: (a) positioning the above spacer unit between an emitter and a display; (b) heating the spacer unit to deform at least a portion of the sealing material to bond the sealing frame between the emitter and display and form an evacuatable region therebetween; and (c) at least partially evacuating the evacuatable region of the image display panel. 
     Another aspect of the present invention is a method for aligning an emitter substrate with a display, comprising the steps of: (a) positioning the above spacer unit between an emitter and a display; and (b) heating the spacer unit to deform at least a portion of the sealing material to bond the sealing frame between the emitter and display to align the emitter and display and form an evacuatable region therebetween. 
     Another aspect of the present invention is a spacer for separating an emitter, from a display of an image display panel, comprising: an assembly having a first side and a second side, the assembly comprising: (a) a first layer having a first side and a second side and comprising a plurality of generally parallel, spaced apart fibers; and (b) a second layer having a first side and a second side and comprising a plurality of generally parallel, spaced apart fibers, the second side of the first layer being adjacent to the first side of the second layer, the fibers of the first layer being positioned to form a plurality of intersections with the fibers of the second layer, at least one of the fibers of the first layer and the fibers of the second layer having a fiber protectorant, comprising a curable functional organo silane, applied to at least a portion thereof in a region of at least one of the plurality of intersections for inhibiting abrasion of the fibers at the intersections thereof, the assembly having a plurality of passageways between the fibers of the first layer, the fibers of the second layer and the intersections, the passageways being generally perpendicular to the fibers of the first layer and the fibers of the second layer, such that when the assembly is positioned between an emitter and a display of an image display panel, at least one of the passageways permits the passage of energy therethrough between the emitter and the display. 
     Another aspect of the present invention is a spacer for separating an emitter from a display of an image display panel, comprising: an assembly having a first side and a second side, the assembly comprising: (a) a first layer having a first side and a second side and comprising a plurality of generally parallel, spaced apart fibers; and (b) a second layer having a first side and a second side and comprising a plurality of generally parallel, spaced apart fibers, the second side of the first layer being adjacent to the first side of the second layer, the fibers of the first layer being positioned to form a plurality of intersections with the fibers of the second layer, at least one of the fibers of the first layer and the fibers of the second layer having a fiber protectorant, comprising a curable functional organo titanate, applied to at least a portion thereof in a region of at least one of the plurality of intersections for inhibiting abrasion of the fibers at the intersections thereof, the assembly having a plurality of passageways between the fibers of the first is layer, the fibers of the second layer and the intersections, the passageways being generally perpendicular to the fibers of the first layer and the fibers of the second layer, such that when the assembly is positioned between an emitter and a display of an image display panel, at least one of the passageways permits the passage of energy therethrough between the emitter and the display. 
     Yet another aspect of the present invention is a spacer for separating an emitter from a display of an image display panel, comprising: an assembly having a first side and a second side, the assembly comprising. (a) a first layer having a first side and a second side and comprising a plurality of generally parallel, spaced apart fibers; and (b) a second layer having a first side and a second side and comprising a plurality of generally parallel, spaced apart fibers, the second side of the first layer being adjacent to the first side of the second layer, the fibers of the first layer being positioned to form a plurality of intersections with the fibers of the second layer, at least one of the fibers of the first layer and the fibers of the second layer having a fiber protectorant, comprising a curable functional organo zirconate, applied to at least a portion thereof in a region of at least one of the plurality of intersections for inhibiting abrasion of the fibers at the intersections thereof, the assembly having a plurality of passageways between the fibers of the first layer, the fibers of the second layer and the intersections, the passageways being generally perpendicular to the fibers of the first layer and the fibers of the second layer, such that when the assembly is positioned between an emitter and a display of an image display panel, at least one of the passageways permits the passage of energy therethrough between the emitter and the display. 
    
    
     BRIEF DESCRIPTION OF THE DRAWINGS 
     The foregoing summary, as well as the following detailed description of the preferred embodiments, will be better understood when read in conjunction with the appended drawings. In the drawings: 
     FIG. 1 is a schematic perspective view of an image display panel according to the present invention; 
     FIG. 2 is a cross-sectional view of the image display panel of FIG. 1, taken along lines 2--2 of FIG. 1; 
     FIG. 3 is an enlarged perspective view of a portion of a spacer for an image display panel according to the present invention; 
     FIG. 4 is an enlarged perspective view of a portion of an alternative embodiment of a spacer according to the present invention; 
     FIG. 5 is an enlarged perspective view of a portion of another alternative embodiment of a spacer according to the present invention; 
     FIG. 6 is an enlarged perspective view of a portion of another alternative embodiment of a spacer having electrodes according to the present invention; 
     FIG. 7 is an enlarged top plan view of a spacer unit according to the present invention; 
     FIG. 8 is a cross-sectional view of the spacer unit of FIG. 7 taken along lines 8--8 of FIG. 7; 
     FIG. 9 is an enlarged perspective view of a mandrel for making a spacer and/or spacer unit according to the present invention; 
     FIG. 10 is an enlarged perspective view of the mandrel of FIG. 9 having a plurality of fibers wound thereon according to the present invention; 
     FIG. 11 is an enlarged perspective view of the mandrel of FIG. 10 having a plurality of fibers wound thereon and a frame according to the present invention; and 
     FIG. 12 is a cross-sectional view of the mandrel of FIG. 11, taken along lines 12--12 of FIG. 11. 
    
    
     DETAILED DESCRIPTION OF THE INVENTION 
     The present invention includes an image display panel 10, shown in FIGS. 1 and 2. The present invention is useful for a wide variety of image display panels in which individual imaging elements or groups of imaging elements, such as a pixel 12, are formed from a portion 14 of an emitter 16 and a corresponding portion 18 of a display 20, as shown in FIG. 2. 
     Flat panel displays utilize an addressing scheme to access and configure individual imaging elements or pixels 12 to display information sent from a computer (not shown) or other device to the image display panel 10. Methods and apparatus for transmitting information from a computer or other transmitting device to an image display panel are well known to those skilled in the art and further discussion thereof is not believed to be necessary in view of the present disclosure. 
     Non-limiting examples of image display panels for which the present invention is useful include passive or active matrix liquid crystal displays (LCDs), electroluminescent displays, gas plasma displays and field emission displays. 
     Passive matrix addressed LCDs use liquid crystal material to provide the display. Passive LCDs generally have poor contrast, a limited range of viewing angles, and high power consumption for color panels. Active matrix addressed LCDs can have, for example, an array of diodes, thin film transistors -TFTs) or metal-insulator-metal (MIM) devices. 
     In a gas plasma display, individual display elements or groups of elements are formed in discrete cells which are bounded by intersections of adjacent row and column electrodes. Gas in the region of energized intersecting row and column electrodes is ignited to produce illumination in the corresponding region of the display. 
     An important aspect of the present invention is the spacer unit, which will be discussed in detail below. To better understand this important aspect of the invention, the environment or image display panel in which such a spacer unit is useful will first be discussed. 
     The preferred image display panel 10 of the present invention is a FED or field emission display 22, shown in FIGS. 1 and 2. The shape of the image display panel 10 can be generally rectangular, square, circular, or any shape desired. Referring to FIG. 1, the overall length 24 of the image display panel 10 can be about 0.005 to about 1 meter, and is preferably about 0.1 to about 0.5 meters. The overall width 26 of the image display panel 10 can be about 0.005 to about 1 meter, and is preferably about 0.01 to about 0.5 meters. The overall thickness 28 of the image display panel can be about 0.1 to about 10 millimeters (mm), and is preferably about 1 to about 4 mm. One skilled in the art would understand that the physical dimensions of the image display panel 10 can be greater or less than the dimensions given above depending upon the desired application. 
     As shown in FIG. 2, the field emission display 22 includes an emitter 16. The emitter 16 includes an electrically insulative substrate 30 which can be formed from an electrically insulating material such as glass or a polymeric material. Non-limiting examples of suitable glass materials include silicate-based glass materials such as soda lime silicate glass and alkaline earth aluminoborosilicate glass. Suitable glass materials include Corning 1737 and 7059 glasses which are commercially available from Corning Glass Works of Corning, N.Y. and Nippon Electric BLC Glass of Nippon Electric, Japan. A detailed explanation of such glass materials is not believed to be necessary for purposes of this application, however, a further discussion of such glass materials is set forth in Moffat, MRS Bulletin, Vol. 21, No. 3, Mar. 1996 at pages 31-34, which is hereby incorporated by reference. Optically transparent polycarbonate can be used as an emitter substrate in FPDs which are not subjected to a high internal sealing vacuum. Preferably, the insulative substrate 30 is generally flat, although the interior surface 32 of the insulative substrate 30 can have ridges, protrusions or irregularities, as desired. 
     The dimensions of the insulative substrate 30 can vary based upon such factors as the desired length 24 and width 26 of the image display panel 10 and selection of the insulating material. Referring to FIGS. 1 and 2, preferably the length 34 and width 36 of the insulative substrate 30 are generally equal to the length 24 and width 26 of the image display panel 10, although the length 34 and width 36 of the insulative substrate 30 can be greater than or less than the length 24 and width 26 of the image display panel 10, if desired. The length 34 of the insulative substrate 30 can be about 0.005 to about 1 meter, and is preferably about 0.01 to about 0.5 meters. The width 36 of the insulative substrate 30 can be about 0.005 to about 1 meter, and is preferably about 0.01 to about 0.5 meters. The thickness 38 of the insulative substrate 30 can be about 0.1 to about 10 millimeters (mm), and is preferably about 0.5 to about 2 mm. 
     The insulative substrate 30 has on at least a portion 40 of its interior surface 32 a conductive layer 42, shown in FIG. 2, preferably comprising a plurality of row conductors 44 and a plurality of column conductors 46, shown in FIG. 1. The conductors 44, 46 can be formed from thin film conductive materials, such as indium-tin oxide (&#34;ITO&#34;). Typically, suitable indium-tin oxide has a resistivity of about 5Ω/square inch. The conductors 44, 46 can be formed upon the interior surface 32 of the insulative substrate 30 by a method such as for example chemical vapor deposition (CVD). Other methods for forming the conductive layer 42 are well known to those skilled in the art and further discussion thereof is not believed to be necessary in view of the present disclosure. 
     Referring now to FIG. 1 to discuss the general overall dimensions of suitable conductors, the length 48 of the row conductors 44 can be generally equal to the width 36 of the insulative substrate 30 and the length 50 of the column conductors 46 can be generally equal to the length 34 of the insulative substrate 30, although the lengths 48, 50 can vary as desired. The thickness 54 of the conductors 44, 46 is preferably the minimum needed to reliably conduct energy to the emitter tips 56, and can be about 300 nanometers to about 500 nanometers. 
     Preferably, in a field emission display such as is shown in FIGS. 1 and 2, an emitter tip 56 or cathode (field emission site) is positioned at each of the intersections 58 of the respective conductors 44, 46. Each intersection of a row conductor 44 and column conductor 46 corresponds to a pixel 12 or portion of a pixel. The emitter tip 56 can be formed upon the intersection 58 from a semiconductive material such as silicon, tungsten or diamond by any method known to those skilled in the art. Non-limiting examples of suitable diamond emitters are disclosed in Jaskie, Materials Bulletin, Vol. 21, No. 3 (March 1996) at pages 59-64, which is hereby incorporated by reference. Examples of suitable tungsten emitters are disclosed in Cathey, Information Display, No. 10, pages 16-20 (1995), which is hereby incorporated by reference. 
     The emitter tip 56 is preferably conically shaped, although the emitter tip 56 can be pyramidal or any shape having a point 57 for directing a stream of charged particles or energy 68 toward the display 20. The dimensions of suitable emitter tips 56 are well known to those skilled in the art and further discussion thereof is not believed to be necessary. The emitter tips 56 can be positioned at a distance 65 of about 3 to about 5 micrometers from each other, for example. 
     As shown in FIG. 2, when energy is supplied to the intersection 58 of a row conductor 44 and a column conductor 46 from an energy source 66, the energy is conducted to the corresponding emitter tip 56 which emits energy 68, such as electrons. The energy is accelerated towards the oppositely charged display 20 to provide an image (not shown) on the display 20. Selective energizing of the conductors 44, 46 is controlled by a controller (not shown), such as an analog controller which varies the intensity of the color of the display 20 by varying the voltage applied to the conductors 44, 46. 
     The portion 70 of the conductors 44, 46 surrounding the emitter tips 56 is preferably coated with or in facing engagement with an insulative layer 72, which can be formed from an electrically insulating material such as glass or a polymeric material by any method well known to those skilled in the art. The thickness of the insulative layer 72 can vary based upon such factors as the insulating material selected and the voltage to be imparted to the conductors 44, 46. The insulative layer 72 inhibits stray particles such as energy 68 emitted from adjacent emitter tips 56 from migrating to adjacent display areas causing picture distortion. 
     In the preferred field emission display shown in FIG. 2, the emitter 16 includes a conductive layer or gate electrode 76 (a low potential anode gate structure) positioned upon the insulative layer 72 surrounding the emitter tips 56. One skilled in the art would understand that a gate electrode may not be required in other types of displays. The gate 76 includes a plurality of apertures 84 through which respective emitter tips 56 are positioned. The point 57 of the emitter tip 56 is preferably generally level with the surface 78 of the gate electrode 76. When a voltage differential is applied from the energy source 66 between the cathode and gate 76, a stream of energy is emitted toward the display 20. Suitable materials, dimensions and methods for forming the gate 76 are well known to those skilled in the art. 
     As discussed above, the image display panel 10 also comprises a display 20 or anode, shown in FIGS. 1 and 2. The image display panel 10 is preferably essentially free and more preferably completely free of any insulating or glass panels between the emitter tips 56 and the display 20. 
     The display 20 includes a transparent, electrically insulative substrate 86 which can be formed from an electrically insulating material such as glass is or a polymeric material. The insulative substrate 86 can be formed from such materials as are discussed above for forming the insulative substrate 30. Preferably, the insulative substrate 86 is generally flat, although the interior surface 88 of the insulative substrate 86 can have ridges, protrusions or irregularities, as desired. 
     Preferably, the length 90 and width 92 of the insulative substrate 86 are generally equal to the length 24 and width 26 of the image display panel 10 and/or emitter 16, although the length 90 and width 92 of the insulative substrate 86 can be greater than or less than the length 24 and width 26 of the image display panel 10, if desired. The length 90 of the insulative substrate 86 can be about 0.005 to about 1 meter, and is preferably about 0.01 to about 0.5 meters. The width 92 of the insulative substrate 86 can be about 0.005 to about 1 meter, and is preferably about 0.01 to about 0.05 meters. The thickness 94 of the insulative substrate 86 can be about 0.1 to about 10 millimeters (mm), and is preferably about 0.5 to about 2 mm. 
     As shown in FIG. 2, the insulative substrate 86 has on at least a portion 96 of its interior surface 88 an electrically conductive layer 98 preferably comprising a plurality of row conductors 100 and a plurality of column conductors 102, shown in FIG. 1. The conductors 100, 102 can be formed from a conductive material, such as indium-tin oxide, by any method well known to those skilled in the art such as chemical vapor deposition (CVD) mentioned above. 
     Referring now to FIG. 1, the length 104 of the row conductors 100 can be generally equal to the width 92 of the insulative substrate 86 and the length 106 of the column conductors 102 can be generally equal to the length 90 of the insulative substrate 86, although the lengths 104, 106 can vary as desired. 
     As shown in FIG. 2, the conductive layer 98 has on an interior surface 108 thereof a luminescent material 110 which emits radiation upon some form of excitation, for example by contact with energy 68. Although not believed to be necessary herein, a detailed discussion of luminescent materials can be found in 1 Van Nostrand&#39;s Scientific Encyclopedia, page 1737 (7th Ed. 1989), which is hereby incorporated by reference. Briefly, the luminescence process involves absorption of energy, excitation of the luminescent material and emission of energy, typically by visible radiation. 
     As discussed in Van Nostrand&#39;s, above, non-limiting examples of suitable luminescent materials 110 include photoluminescents which are excited by photons, electroluminescents which are excited by electric fields and cathodoluminescents which are excited by cathode rays. The luminescent material 110 can be applied to the conductive layer 98 by electrophoretic deposition or any other method well known to those skilled in the art. 
     The luminescent material 110 luminesces in one of three predetermined primary colors--red, blue or green--upon excitation provided by energy 68 received from the emitter 16. Energy from the luminescent material 110 is transferred to the conductive layer 98 to complete the circuit to the energy source 66. 
     The luminescent materials typically used in FEDs are similar to those used in CRTs. Non-limiting examples of suitable luminescent materials 110 are: Y 2  O 3  --Eu for red color; Y 3  (Al, Ga) 5  O 12  --Tb for green; Y 2  SiO 5  --Ce for blue; and Y 2  O 2  S--Tb, Sm for white. 
     As shown in FIG. 2, the average distance 112 between the emitter 16 and the display 20 can be about 200 micrometers. One skilled in the art would understand that this distance can vary based upon such factors as the materials from which the components are formed, the desired intensity of the energized luminescent material and the overall desired dimensions of the image display panel. The voltage differential between the emitter 16 and display 20 can be about 300 to about 1000 volts. 
     An important aspect of the present invention is a spacer unit 114 (shown in FIGS. 7 and 8) which provides the image display panel 10 with mechanical support against atmospheric and other externally applied pressure on the emitter 16 and display 20, as well as to align the emitter 16 and display 20. The spacer unit 114 comprises a spacer 116 (best shown in FIG. 3) for separating and aligning the emitter 16 and display 20. The spacer 116 is preferably electrically insulative, although the spacer 116 can be semi-conductive or conductive, if desired. The spacer 116 preferably is inexpensive, stable under electron bombardment, capable of withstanding baking temperatures of greater than about 550° C., resistant to thermal cycling, dimensionally accurate so as not to visibly interfere with the operation of the image display panel and easy to assemble, transport and implement. Preferably, the spacer 116 has a high aspect ratio, preferably about 2:1 to about 100:1, and more preferably about 20:1. 
     Referring to FIGS. 2 and 3, the spacer 116 comprises one or more assemblies 118, each assembly 118 having a first side 120 and a second side 122. Referring now to FIG. 2, the first side 120 of the assembly 118 is adjacent to the emitter 16 and the second side 122 of the assembly 118 is adjacent to the display. Preferably, in a field emission display, the first side 120 of the assembly 118 is in contact or facing engagement with the surface 78 of the gate electrode 76 of the emitter 16. Also, the second side 122 of the assembly 118 is preferably in facing engagement with the luminescent material 110 or conductive layer 98 of the display 20. The first side 120 and second side 122 of the assembly 118 are preferably generally parallel, however the first side 120 and second side 122 can be positioned at an angle, if desired. Alternatively, the first side 120 or second side 122 can be positioned adjacent to a first side 121 or second side 123 of another assembly 119, as shown in FIG. 3. 
     The length 124 of the assembly 118 is preferably slightly less than the overall length 24 of the image display panel 10. The length 124 of the assembly 118 can be about 0.005 to about 1 meter, and is preferably about 0.01 to about 0.5 meters. The width 126 of the assembly 118 is preferably slightly less than the overall width 26 of the image display panel 10. The width 126 of the assembly 118 can be about 0.005 to about 1 meter, and is preferably about 0.01 to about 0.5 meters. The thickness 128 of the assembly 118 can be about 1 to about 10 millimeters, and is preferably about 0.4 to about 1 millimeters. 
     As shown in FIG. 3, the assembly 118 comprises one or more first layers 130, each first layer 130 having a first side 132 and a second side 134. The first layer 130 comprises a plurality of generally parallel, spaced-apart fibers 136. As used herein, the term &#34;fibers&#34; means an individual or a bundle of fibers, filaments, strands, threads, rods, ribbons and combinations thereof. The term &#34;strand&#34; as used herein refers to a plurality of individual filaments 137. 
     The fibers 136 are preferably electrically insulative. Also, the fibers 136 preferably have high compressive strength, sufficient ductility to withstand processing and assembly, and are substantially free of outgassing tendencies at vacuum pressures typically used to assemble the spacer unit 114 (and are therefore preferably inorganic). 
     The fibers 136 are preferably generally cylindrical as shown in FIG. 3, although the fibers 136 can have any shape desired, such as triangular, square and rectangular in cross section. The surfaces 139 of the fibers 136 are preferably generally smooth, although the surfaces 139 can have irregularities such as protrusions or indentations. 
     The number of generally spaced apart fibers 136 can be 2 to as many as desired, although preferably the number of fibers 136 is 2 to about 100, and more preferably about 25 to about 50. 
     The mean average diameter 141 of each of the fibers 136 (individual or bundle) can be about 5 to about 1000 micrometers, and preferably is about 25 to about 100 micrometers. Fibers 136 of different diameters can be used, if desired. The number of individual filaments 137 in each of the fibers 136 (if each fiber contains a plurality of individual filaments 137) can be one to about 10,000 fibers, and is preferably about 100 to about 1,000 fibers. The spacing 143 between each of the plurality of fibers 136 is about 0.02 to about 50 millimeters, and is preferably about 0.2 to about 30 millimeters. 
     The fibers 136 of the first layer 130 can be formed from natural materials, man-made materials or combinations thereof which have a deformation or melting temperature which is greater than the processing, assembly and use temperatures to which the image display panel 10 will be subjected. Fibers 136 useful in the present invention are discussed at length in the Encyclopedia of Polymer Science and Technology, Vol. 6 (1967) at pages 505-712, which is hereby incorporated by reference. 
     Suitable man-made fibers can be formed from a fibrous or fiberizable material prepared from inorganic substances, natural organic polymers or synthetic organic polymers, as discussed in the Encyclopedia of Polymer Science and Technology, Vol. 6 at 506-507. As used herein, the term &#34;fiberizable&#34; means a material capable of being formed into a generally continuous filament, fiber, strand or yarn. 
     Suitable inorganic fibers are discussed in the Encyclopedia of Polymer Science and Technology, Vol. 6 at 610-690 and include ceramics, minerals, polycrystalline and carbon or graphite fibers. Non-limiting examples of suitable ceramics include glass, basalt, alumina, alumina-silica, mullite and silicon carbide. Non-limiting examples of suitable minerals include rock wool, wollastinite and sapphire. Also useful in the present invention are metallic fibers such as aluminum, steel and copper which are coated with an insulative coating and metallic fibers which are non-conducting or poorly conducting. For more information on suitable metallic fibers, see Encyclopedia of Polymer Science and Technology, Vol. 6 at 569-570. 
     The preferred fibers for use in the present invention are glass fibers, a class of fibers generally accepted to be based upon oxide compositions such as silicates selectively modified with other oxide and non-oxide compositions. Useful glass fibers can be formed from any type of fiberizable glass composition known to those skilled in the art, and include those prepared from fiberizable glass compositions such as &#34;E-glass&#34;, &#34;A-glass&#34;, &#34;C-glass&#34;, &#34;D-glass&#34;, &#34;R-glass&#34;, &#34;S-glass&#34;, and E-glass derivatives that are fluorine-free and/or boron-free. Such compositions and methods of making glass filaments therefrom are well known to those skilled in the art and further discussion thereof is not believed to be necessary in view of the present disclosure. If additional information is needed, such glass compositions and fiberization methods are disclosed in K. Loewenstein, &#34;The Manufacturing Technology of Glass Fibres&#34;, (3d Ed. 1993) at pages 30-44, 47-60, 115-122 and 126-135, which are hereby incorporated by reference. 
     Preferred glass fibers have the filament designations D900, D450 and E225, which are well understood by those skilled in the art. For a detailed explanation of the meanings of these filament designations, see Loewenstein (3d Ed.) at pages 25-27, which is hereby incorporated by reference. 
     It is understood that combinations of any of the above fibers can be used in the spacer 116, spacer unit 114 and image display panel 10 of the present invention, if desired. 
     The present invention will now be discussed generally with reference to the preferred glass fibers, although one skilled in the art would understand that any of the fibers discussed above are also useful in the present invention. 
     Preferably, one or more coating compositions are present on at least a portion of the surface 139 of the glass fibers 136 to protect the surface from abrasion during processing and assembly of the spacer. Non-limiting examples of suitable coating compositions include sizing compositions and secondary coating compositions. As used herein, the terms &#34;size&#34;, &#34;sized&#34; or &#34;sizing&#34; refer to the aqueous or non-aqueous composition applied to the filaments immediately after formation of the glass fibers. The term &#34;secondary coating&#34; refers to a coating composition applied secondarily to one or a plurality of strands of glass fibers after the sizing composition is applied, and preferably at least partially dried. 
     Typical sizing compositions can include as components film-formers, lubricants, waxes, coupling agents, emulsifiers, antioxidants, ultraviolet light stabilizers, colorants, antistatic agents and water, to name a few. Non-limiting examples of suitable sizing compositions are disclosed in Loewenstein (3d Ed.) at pages 237-289 and U.S. Pat. Nos. 4,390,647 and 4,795,678, each of which is hereby incorporated by reference. 
     Preferred sizing compositions for use herein are those typically used for textile applications which generally include starch as the film former, wax and non-ionic lubricant components. Useful starches include those prepared from potatoes, corn, wheat, waxy maize, sago, rice, milo and mixtures thereof. Non-limiting examples of useful starches include Kollotex 1250 (a low viscosity, low amylose potato-based starch etherified with ethylene oxide which is commercially available from AVEBE of the Netherlands), National 1554 (a high viscosity, low amylose crosslinked potato starch), Hi-Set 369 (a low viscosity propylene oxide modified corn starch having an amylose/amylopectin ratio of about 55/45), Hylon and Nabond high viscosity starches (which are commercially available from National Starch and Chemical Corp. of Bridgewater, N.J.), and Amaizo starches which are commercially available from American Maize Products Company of Hammond, Ind. 
     The wax component of the sizing composition can include one or more aqueous soluble, emulsifiable or dispersible waxes. Examples of such waxes include vegetable, animal, mineral, synthetic or petroleum waxes. Useful petroleum-derived microcrystalline waxes are commercially available from Petrolite Corp. of Tulsa, Okla. and Michelman, Inc. of Cincinnati, Ohio. 
     Non-limiting examples of useful non-ionic lubricants include vegetable oils and hydrogenated vegetable oils, such as cottonseed oil, corn oil and soybean oil (Eclipse 102 hydrogenated soybean oil which is commercially available from Van den Bergh Foods Company of Lisle, Ill.); trimethylolpropane triesters; pentaerythritol tetraesters; derivatives and mixtures thereof. 
     The sizing can be applied in many ways, for example by contacting the filaments with a static or dynamic applicator, such as a roller or belt applicator, spraying or other means. See Loewenstein (3d Ed.) at pages 165-172, which is hereby incorporated by reference. 
     The sized fibers are preferably dried at room temperature or at elevated temperatures. Drying of glass fiber forming packages or cakes is discussed in detail in Loewenstein (3d Ed.) at pages 219-222, which are hereby incorporated by reference. For example, the forming package can be dried in an oven at a temperature of about 104° C. (220° F.) to about 160° C. (320° F.) for about 10 to about 24 hours to produce glass fiber strands having a dried residue of the composition thereon. The temperature and time for drying the glass fibers will depend upon such variables as the percentage of solids in the sizing composition, components of the sizing composition and type of glass fiber. The sizing is typically present on the fibers in an amount between about 0.1 percent and about 5 percent by weight after drying. 
     Suitable ovens or dryers for drying glass fibers are well known to those skilled in the art. The dryer removes excess moisture from the fibers 136 and, if present, cures any curable sizing or secondary coating composition components. 
     After drying, the sized glass strands can be gathered together into bundles of generally parallel fibers (roving), twisted into a yarn or woven into a cloth. The strands can be twisted by any conventional twisting technique known to those skilled in the art, for example by using twist frames. Generally, twist is imparted to the strand by feeding the strand to a bobbin rotating at a speed which would enable the strand to be wound onto the bobbin at a faster rate than the rate at which the strand is supplied to the bobbin. Generally, the strand is threaded through an eye located on a ring which traverses the length of the bobbin to impart twist to the strand, typically about 0.5 to about 4 turns per inch. Fabric can be woven using any conventional loom, such as a shuttle loom, air jet loom, rapier loom or other weaving machine. 
     The roving or twisted glass fibers are generally further treated with a secondary coating or bonding composition 145 which is different from the sizing composition. The bonding composition 145 is any material which secures or adheres intersecting portions of the fibers 136 of the first layer 130 with the fibers 138 of the second layer 140, which will be discussed in detail below. 
     The bonding composition 145 is an adhesive or curable composition which can be selected from coupling agents, cementitious materials or glues, gels (such as sol-gels), cross-linking agents and combinations thereof. 
     The term &#34;adhesive&#34; as used herein means any substance, inorganic or organic, natural or synthetic, that is capable of bonding other substances together by surface attachment. See Hawley&#39;s Condensed Chemical Dictionary at page 23 (12th Ed. 1993), which is hereby incorporated by reference. As used herein, the term &#34;curable&#34; means that (1) the components of the bonding composition are capable of being at least partially dried by air and/or heat; and/or (2) the components of the bonding composition and/or glass fibers are capable of being crosslinked to each other to change the physical properties of the components. See Hawley&#39;s Condensed Chemical Dictionary at page 331 (12th Ed. 1993), which is hereby incorporated by reference. The bonding composition 145 can be cured by heating to a predetermined bonding temperature which is a characteristic of the material selected, radiation and/or by a cross-linking agent. 
     As used herein, the term &#34;sol-gel&#34; means a suspension of small colloidal particles formed in a solution which are linked together into chains and three-dimensional networks that fill the liquid phase as a gel. L. Hench et al. (Ed.), Science of Ceramic Chemical Processing, (1986) at page 5, which is hereby incorporated by reference. The phrase &#34;cross-linking agent&#34; as used herein means an agent which attaches two chains of polymer molecules by bridges, composed of either an element, a group or a compound, which join certain carbon atoms of the chains by primary chemical bonds. See Hawley&#39;s Condensed Chemical Dictionary at page 325 (12th Ed. 1993), which is hereby incorporated by reference. 
     The bonding composition 145 can additionally include one or more components of a conventional sizing composition, discussed above, if desired. The bonding composition 145 can be applied to the fibers 136 and/or 138 neat or with a solvent or carrier such as water. Alternatively, the bonding composition 145 can be a glass cladding which has a deformation or melting temperature which is less than the deformation or melting temperature of the fibers 136, 138. 
     Preferably, the bonding composition 145 includes a coupling agent such as a functional organo silane coupling agent, transition metal coupling agent, phosphonate coupling agent, amino-containing Werner coupling agent and mixtures thereof. Such coupling agents can lubricate the fibers prior to curing to inhibit and protect the fibers from abrasion. These coupling agents typically have dual functionality. Each metal or silicon atom has attached to it one or more groups which can react or compatibilize with the fiber or glass surface, the components of the sizing composition, the other components of the bonding composition, if any, and/or by condensation with other, if any, hydrolyzable groups of the bonding composition. As used herein, the term &#34;compatibilize&#34; means that the groups are chemically attracted, but not bonded, to the fiber or glass surface, the components of the sizing composition and/or the other components of the bonding composition, for example by polar, wetting or solvation forces. Examples of hydrolyzable groups include: ##STR1## the monohydroxy and/or cyclic C 2  -C 3  residue of a 1,2- or 1,3 glycol, wherein R 1  is C 1  -C 3  alkyl; R 2  is H or C 1  -C 4  alkyl; R 3  and R 4  are independently selected from H 1 , C 1  -C 4  alkyl or C 6  -C 8  aryl; and R 5  is C 4  -C 7  alkylene. Examples of suitable compatibilizing or functional groups include epoxy, glycidoxy, mercapto, cyano, allyl, alkyl, urethano, halo, isocyanato, ureido, imidazolinyl, vinyl, acrylato, methacrylato, amino or polyamino groups. 
     Functional organo silane coupling agents are preferred for use in the present invention. Examples of suitable functional organo silane coupling agents include 3-aminopropyldimethylethoxysilane, gamma-aminopropyltriethoxysilane, gamma-aminopropyltrimethoxysilane, beta-aminoethyltriethoxysilane, N-beta-aminoethyl-aminopropyltrimethoxysilane, gamma-isocyanatopropyltriethoxysilane, vinyl-trimethoxysilane, vinyl-triethoxysilane, allyl-trimethoxysilane, mercaptopropyltrimethoxysilane, mercaptopropyltriethoxysilane, glycidoxypropyltriethoxysilane, glycidoxypropyltrimethoxysilane, 4,5-epoxycyclohexyl-ethyltrimethoxysilane, ureidopropyltrimethoxysilane, ureidopropyltriethoxysilane, chloropropyltrimethoxysilane, and chloropropyltriethoxysilane. 
     Non-limiting examples of useful functional organo silane coupling agents include epoxy (A-187 gamma-glycidoxypropyltrimethoxysilane), methacrylate (A-174 gamma-methacryloxypropyltrimethoxysilane) and amino (A-1100 gamma-aminopropyltriethoxysilane) silane coupling agents, each of which are commercially available from OSi Specialties, Inc. of Tarrytown, N.Y. Preferred organo silane coupling agents include bis silanes such as bis(trimethoxysilylpropyl) amine, which are commercially available from OSi Specialties, Inc. The organo silane coupling agent based bonding composition can be at least partially hydrolyzed with water prior to application to the fiber, preferably at about a 1:1 stoichiometric ratio or, if desired, applied in unhydrolyzed form. 
     Preferably, the bonding composition 145 is essentially free of any reactive metallic materials such as sodium or potassium when the bonding composition 145 includes an organo silane coupling agent. 
     Suitable transition metal coupling agents include titanium, zirconium and chromium coupling agents. Non-limiting examples of suitable titanate coupling agents include titanate complexes such as Ken-React KR-44, KR-34 and KR-38; suitable zirconate coupling agents include Ken React NZ-97 and LZ-38, all of which are commercially available from Kenrich Petrochemical Company. Suitable chromium complexes include Volan which is commercially available from E.I. duPont de Nemours of Wilmington, Del. The amino-containing Werner-type coupling agents are complex compounds in which a trivalent nuclear atom such as chromium is coordinated with an organic acid having amino functionality. Other metal chelate and coordinate type coupling agents known to those skilled in the art can be used herein. 
     The amount of coupling agent can be 0 to about 100 weight percent of the bonding composition on a total solids basis, and is preferably about 10 to about 80 weight percent. 
     Non-limiting examples of cementitious materials useful in the present invention include cements such as devitrifying and non-devitrifying glass frits which are commercially available from SEM-COM Co., Inc. of Toledo, Ohio or Ferro Corporation of Cleveland, Ohio. Other cementitious materials useful in the present invention include silicates, such as sodium silicate or potassium silicate, and silicones. The amount of cementitious material in the bonding composition can be 0 to about 100 weight percent of the bonding composition on a total solids basis, and is preferably about 10 to about 60 weight percent. 
     Non-limiting examples of sol-gels useful in the present invention include partially or fully hydrolyzed organo functional silanes such as HYDROSIL® products which are commercially available from Huls America of Piscataway, N.J. Alternatively, the sol-gel can be the reaction product of tetraorthosilicate (TEOS) with pH adjusted water. The amount of gel in the bonding composition can be 0 to about 100 weight percent of the bonding composition on a total solids basis, and is preferably about 1 to about 5 weight percent. 
     Non-limiting examples of cross-linking agents useful in the present invention include melamine formaldehyde, blocked isocyanates such as Baybond XW 116 or XP 7055, epoxy crosslinkers such as Witcobond XW by Witco Corp., and polyesters such as Baybond XP-7044 or 7056, which are commercially available from Bayer of Pittsburgh, Pa. The amount of cross-linking agent in the bonding composition can be 0 to about 100 weight percent of the bonding composition on a total solids basis, and is preferably about 10 to about 60 weight percent. 
     The bonding agent can include a conductive dopant for dissipating any static charge formed during assembly of the FPD to ground. A non-limiting example of a suitable dopant is carbon black. 
     The bonding composition is applied to at least a portion 147 of the is surface 139 of the fibers 136 of the first layer 130 and/or the fibers 138 of the second layer 140 in an amount effective to coat or impregnate at least the portion 147 of the fibers 136,138. The bonding composition can be conventionally applied by dipping the fibers 136 and/or 138 in a bath containing the composition, by spraying the composition upon the fibers or by contacting the fibers with a static or dynamic applicator such as a roller or belt applicator, for example. The coated fibers can be passed through a die to remove excess bonding composition from the fibers and/or dried as discussed above for a time sufficient to at least partially dry or cure the bonding composition. 
     As shown in FIG. 3, the assembly 118 also includes one or more second layers 140, each second layer having a first side 142 and a second side 144. The second layer 140 comprises a plurality of generally parallel, spaced-apart fibers 138, which can be the same or different from the fibers 136 of the first layer 130. Suitable materials for fibers 138 are the same as those discussed above for the fibers 136 of the first layer 130. The fibers 138 of the second layer 140 can also have similar physical characteristics and dimensions as the fibers 136 of the first layer 130. Also, the fibers 138 of the second layer 140 can be coated with the bonding composition discussed above in lieu of or in addition to the coating of the bonding composition upon the first layer 130 of fibers 136. 
     The second side 134 of the first layer 130 is adjacent to and preferably in facing engagement with the first side 142 of the second layer 140. The fibers 136 of the first layer 130 are positioned to form a plurality of intersections 146 with the fibers 138 of the second layer 140, for example by positioning the fibers 136, 138 at an angle ranging from about 10 to about 170 degrees (preferably about 90 degrees as shown in FIG. 3) or by weaving the fibers 136, 138 as shown in FIG. 5. The fibers 136 of the first layer 130 are bonded to the corresponding fibers 138 of the second layer 140 at the intersections 146 thereof by the bonding composition 145 discussed above. 
     The amount of the bonding composition 145 applied to the fiber(s) 136, 138 can be about 1 to about 200 weight percent based upon the weight of the fiber, and preferably is about 5 to about 10 weight percent. 
     As shown in FIG. 4, the assembly 118 can include additional layers 149 which intersect the first and second layers 130, 140 at an angle ranging from about 10 to about 170 degrees. The assembly 118 can also include one or more electrodes 151, shown in FIG. 6. The electrodes 151 can be formed from a metallic material and can be for example, wire, foil and/or mesh. The electrodes 151 can be positioned by stacking or weaving within the assembly 118. 
     The assembly 118 has a plurality of passageways 148, best shown in FIGS. 2 and 3. Each passageway 148 is bounded by the adjacent fibers 136 of the first layer 130, the adjacent fibers 138 of the second layer 140 and the corresponding intersections 146. The passageways 148 are generally perpendicular to the fibers 136 of the first layer 130 and the fibers 138 of the second layer 140, such that when the assembly 118 is positioned between the emitter 16 and the display 20 of the image display panel 10 as shown in FIG. 2, the passageways 148 permit the passage of energy 68 or other particles therethrough between the emitter 16 and the display 20. In the preferred embodiment (a field emission display) shown in FIG. 2, each emitter tip 56 is positioned at an end 150 of a respective passageway 118 spaced apart from the display 20. 
     The shape of the passageway 148 is determined by the configuration of the fibers 136, 138 in the assembly 118. For example, for the configuration shown in FIG. 3, the passageways 148 are generally square. Alternatively, the passageways 148 can be triangular as shown in FIG. 4, rectangular or octagonal, for example. The depth 152 of the passageway 148 is preferably generally equal to the thickness 128 of the assembly 118. The passageways 148 have a high aspect ratio, generally about 20 to about 1, i.e., the ratio of the depth 152 of the passageway 148 to the width 156 of the fibers 136 or 138. 
     Referring now to FIGS. 7 and 8, the spacer unit 114 includes a sealing frame 158 positioned about and engaging at least a portion 160 of a periphery or third side 162 of the spacer 116. The spacer 116 can include one or more sides 162, as desired. As shown in FIG. 1, for example, the spacer 616 has four sides 162. 
     The sealing frame 158 has a first end 164 and a second end 166. The first end 164 of the sealing frame 158 is positioned adjacent to and preferably engages a portion 168 of the emitter 16. The second end 166 of the sealing frame 158 is positioned adjacent to and preferably engages a portion 170 of the display 20. 
     The width 178 and length 179 of the sealing frame 158 are preferably slightly greater than the larger of the corresponding lengths and widths of the other components of the image display panel 10, such as the emitter 16, display 20 and spacer 116 components, such that the emitters 16 can be hermetically sealed between the interior 176 of the sealing frame 158, the emitter substrate 30 and the display substrate 86. The width of the sealing frame can be about 0.005 to about 1 meter. The length 179 of the sealing frame can be about 0.005 to about 1 meter. 
     The height 180 of the sealing frame is preferably generally greater than the thickness 128 of the spacer 116, and preferably corresponds generally to the distance between the emitter substrate 30 and display substrate 86. The height 180 of the sealing frame can be about 0.01 to about 10 millimeters, and is preferably about 0.254 mm (0.010 inches) to about 6.35 mm (0.250 inches). The thickness 183 of the sealing frame 158 can be about 0.3 to about 10 millimeters, and is preferably about 0.5 to about 1 millimeter. The height 180 and thickness 183 of the sealing frame 158 should not influence the spacing between the emitter 16 and the display 20 which is maintained by the spacer 116. 
     The sealing frame 158 comprises a deformable sealing material 172. As used herein, the terms &#34;deformation&#34; and &#34;deformable&#34; mean that the sealing material 172 softens or deforms upon exposure to an external agent, for example heat, radiation and/or a chemical agent, such as a cross-linking agent as discussed above or a reaction promoter, and resolidifies or hardens upon removal or consumption of the external agent to a hardness sufficient to resist the external forces or pressure in the environment to which the image display panel 10 is to be subjected. 
     Preferably, the sealing material 172 is heat deformable and has a predetermined deformation temperature which is less than a predetermined deformation temperature of the other components of the image display panel 10, such as the emitter 16, display 20 and spacer 116. 
     The sealing material 172 can be, for example, any organic or inorganic cement, and is preferably a devitrifying or vitrifying glass frit, such as SCB-2 lead silicate glass having a deformation temperature or softening point of about 450° C. which is commercially available from SEM-COM Co., Inc. Another example of a suitable sealing material 172 is SCA-5 glass having a deformation temperature or softening point of about 730° C., which is also commercially available from SEM-COM Co., Inc. 
     Preferably the deformation temperature of the sealing material 172 is about 300° C. to about 750  C., and more preferably about 450° C. to about 525  C. The deformation temperature of the sealing material 172 depends upon the material selected. The deformation temperatures of the other components of the image display panel 10, such as the emitter 16, display 20 and spacer 116, are preferably greater than the deformation temperature of the sealing material 172 or greater than about 550° C. to minimize distortion of the components. Alternatively, the sealing material can be a cement such as potassium silicate or sodium silicate or a coupling agent such as are discussed in detail above, for example a functional organo silane coupling agent. 
     Pressure can also be applied to the sealing material 172 prior, during or subsequent to heating to consolidate and further strengthen the spacer unit 114. A non-limiting example of a suitable apparatus for applying pressure to the sealing material is a heated lamination press, such as is commercially available from Tetrahedron Corporation of San Diego, Calif. The pressure applied to the sealing material 172 depends upon such factors as the type of sealing material and temperature and time of heating the sealing material. 
     The amount of sealing material 172 applied to the emitter 16 and display 20 can vary based upon such factors as the particular sealing material selected, the desired resistance of the sealing frame 158 to distortion from pressure, which depends in part upon the thickness 183 of the sealing frame 158 (discussed above), and other forces to which the image display panel 10 will be subjected. For example, the amount of sealing material 172 can be about 1 to about 1000 grams. 
     When the sealing frame 158 and spacer 116 are positioned between the emitter 16 and the display 20 and the sealing material 172 is heated to a predetermined temperature greater than the predetermined deformation temperature of the sealing material 172 but less than the predetermined deformation temperature of the other components of the image display panel 10, such as the emitter 16, display 20 and spacer 116, the sealing material 172 provides an essentially sealed region 174 between the emitter 16 and the display 20 which encloses the spacer 116 and interior components of the image display panel 10, such as the emitter tips 56. 
     As used herein, the phrase &#34;essentially sealed region&#34; means that the space between the emitter 16 and the display 20 is generally greater than about 90 percent by area sealed by the frame 158 around the periphery 162 of the image display panel 10, and preferably is fully or hermetically sealed if the process is conducted under a vacuum. If the image display panel 10 is not assembled under vacuum, the unsealed portion can be used to evacuate the interior 176 of the image display panel 10. Alternatively, a small aperture can be present in the emitter 16 and/or display 20 through which the interior 176 of the image display panel 10 can be evacuated. 
     Preferably, for a field emission display, the vacuum pressure in the interior 176 of the image display panel 10 is less than about 10 -5  torr, and more preferably less than about 10 -6  torr. The interior 176 of the sealed region 174 which is under vacuum contains an inert gas, such as argon. 
     Preferably, the sealing unit 114 is self-leveling when positioned between the emitter 16 and display 20 and the sealing material 172 is heated to the predetermined deformation temperature of the sealing material, i.e., the sealing material 172 deforms such that the first side 120 of the spacer assembly 118 is adjacent to or engages the emitter 16 and the second side 122 of the spacer assembly 118 is adjacent to or engages the display 20. The spacer 116 preferably is self-aligned by alignment of the sealing unit 114 with the emitter 16 and display 20. 
     While the spacer and spacer unit of the present invention have been discussed in detail with regard to use in a field emission display, one skilled in the art would understand that the spacer and spacer unit of the present invention are also useful in other image display panels, such as liquid crystal displays, electroluminescent displays and gas plasma displays. Methods for using the spacer and spacer unit of the present invention with these and other types of image display panels would be understood by one skilled in the art in view of the above disclosure and further discussion thereof is not believed to be necessary. For example, in a gas plasma display panel the passageways of the spacer are aligned with the emitter and display elements. 
     A method for making a spacer and a spacer unit according to the present invention will now be discussed. One skilled in the art would understand that other methods can be used for making the above spacer and spacer unit. 
     As shown in FIG. 9, a mandrel 200 for filament winding a spacer 116 and spacer unit 114 according to the present invention is provided. The mandrel 200 includes a base 202. The base 202 has a top 204, bottom 206 (shown in FIG. 12) and four sides 208 therebetween. One skilled in the art would understand that the number of sides can vary, for example from 3 which provides triangular passageways to 8 which provides octagonal passageways, to provide spacers 116 of different configurations. 
     The base 202 of the mandrel 200 can be formed from any rigid material or combination of rigid materials which resist deformation during winding and any subsequent heating or curing steps for the spacer and spacer unit. Suitable materials for the base 202 include ceramics such as silicon and alumina, metals such as aluminum and steel, polymers which resist deformation such as DELRIN® acetal, which is commercially available from duPont, graphite and combinations thereof. 
     Referring to FIG. 9, the top 204 and the upper portion 210 of the sides 208 include a plurality of slots 212 for receiving the fibers 136, 138 therein during filament winding of the spacer 116. The diameter of the slots 212 corresponds generally to and is preferably slightly larger than the diameter of the fibers 136, 138. The diameter of the slots 212 permits the fibers 136, 138 to be stacked generally perpendicularly to the sides 208, as shown in FIGS. 10 and 12. The diameter of the slots 212 can be about 5 to about 200 micrometers, and is preferably about 15 to about 80 micrometers. 
     The depth 213 of the slots 212 can vary, but preferably corresponds generally to the desired height of the spacer 116 and can be about one-fifth to about one-half of the height 218 of the mandrel 200. The slots 212 preferably traverse the entire width of the top 204 of the mandrel 200, as shown in FIG. 9. 
     The distance 211 between the slots 212, shown in FIG. 9, corresponds to the desired spacing between pixels 12, pixel groups, emitter tips 56 or emitter tip groups. The distance 211 can be about 0.5 to about 10 millimeters, and is preferably about 4 millimeters. The number of slots 212 corresponds to the number of fibers 136, 138, respectively, which corresponds to the line and space pitch of the selected flat panel display design and type. 
     Referring to FIG. 10, the mandrel 200 has a length 214 which is generally greater than the length 124 of the assembly 118. The length 214 of the mandrel can be any size which corresponds generally to the length of the image display panel 10. The width 216 of the mandrel is generally greater than the width 126 of the assembly 118 to provide an edge for trimming. The width 216 of the mandrel 200 can be any size which corresponds generally to the width of the image display panel 10. The thickness 218 of the mandrel 200 is generally equal to the thickness 128 of the assembly 118 and corresponds to the desired spacing between the emitter 16 and the display 20. 
     As shown in FIG. 9, the mandrel 200 includes a groove 220 having a bottom 222 and opposed, generally parallel walls 224 extending therefrom. The groove 220 receives the fibers 136, 138 and the sealing material 172 (as shown in FIGS. 11 and 12). The depth 226 of the groove 220 corresponds generally to the desired height 180 of the sealing frame 158 and can be about one-third to about two-thirds of the height 218 of the mandrel 200. The width 228 of the groove 220 can be about 0.2 to about 1.5 millimeters. 
     Referring now to FIG. 12, the mandrel 200 preferably has a recess 230 in the top 204 for receiving and retaining a removable insert 232. The insert 232 can be removed from the recess 230 to facilitate removal of the wound spacer 116 or spacer unit 114 therefrom. The recess 230 preferably includes one or more apertures 236 (shown in phantom in FIG. 9) therethrough for facilitating removal of the insert 232. Preferably, the recess 230 is about 50 to about 75 percent of the height 218 of the mandrel 200. 
     The insert 232 is preferably generally rectangular or square and can be formed from graphite or any suitable rigid material such as the materials described above for the base 202. As shown in FIG. 9, the insert 232 has a length 238, a width 240 and a height 242 of about 80 to about 100 percent of the desired size of the display area. The insert 232 dimensions are selected to ensure that the fiber spacing to be placed in the active display area will be maintained at the desired pitch during spacer manufacturing. The insert 232 has a top portion 244 having a plurality of slots 246 for aligning the fibers 136, 138. The depth 248, diameter 250 and distance 252 between the slots 246 is preferably generally equal to the depth 213, diameter and distance 211 between the slots 212 in the base 202 of the mandrel 200. 
     The recess 230 can also receive removable precision alignment members 234 for aligning the fibers 136,138 in the insert 232. The alignment members 234 can be formed from any rigid material such as are discussed above for the base 202, however preferred materials are those which can be machined to precise tolerances of about ±25 micrometers. Non-limiting examples of such materials include silicon and DELRIN®. 
     The alignment members 234 are preferably rod-shape as shown in FIGS. 9-13 and are positioned between the recess 230 and the insert 232 The alignment members 234 have in a top portion 254 thereof a plurality of slots 258 for receiving and aligning the fibers 136, 138, as shown in FIG. 9. The depth and diameter of the slots 258 in the alignment members 234 are preferably less than the depth 248 and diameter 250 of the slots 246 in the insert 232. The depth of the slots 258 in the alignment members 234 is generally greater than the desired thickness 128 of the spacer 116. The diameter of the slots 258 in the alignment members 234 is generally slightly greater than the diameter of the fibers 136, 138. The distance 256 between the slots 258 is generally equal to the distance 211 between the slots 212 in the base 202 of the mandrel 200, and is preferably equal to the desired pitch for the spacer assembly 118. 
     The mandrel 200 can be positioned in any suitable filament winding machine, such as those which are commercially available from McLean-Anderson of Milwaukee, Wis., and the fibers 136 and 138 wound about the mandrel in any pattern as desired. For example, the first and second layers 130,140 can be wound in alternating fashion or in any order desired. 
     Alternatively, the fibers 136 and 138 can be interwoven using looms such as are commercially available from Tsudakoma of Kanazawa, Japan and Sulzer-Ruti of Zurich, Switzerland. 
     A spacer 116 and spacer unit 114 according to the present invention can be formed by the following method. As shown in FIG. 9, the insert 232 and alignment members 234 are positioned within the recess 230 of the base 202 of the mandrel 200. Fibers 136 are wound about the mandrel 200 through the slots 212, 246 and 258 to form a first layer 130. Next, fibers 138 are wound generally perpendicularly to the fibers 136 about the mandrel 200 through the slots 212, 246 and 258 to form a second layer 140. Alternating first layers 130 and second layers 140 are wound about the mandrel 200 to form the assembly 118 of the spacer 116 to the desired height which corresponds to the distance desired to be maintained between the emitter 16 and the display 20. 
     The fibers 136 and/or 138 can be coated with the bonding composition prior to winding or the wound assembly 118 can be coated by spraying or immersing the assembly in the bonding composition, as discussed above. 
     The assembly 118 and mandrel 200 can be heated at a temperature and for a time sufficient to cure the curable components of the bonding composition. For example, for an aqueous suspension of the bonding composition having about 80 weight percent solids containing bis(trimethyloxysilylpropyl) amine applied to glass fibers, the assembly 118 and mandrel 200 can be heated at a temperature of about 500° C. for about one (1) hour to substantially cure the bonding composition and bond the fibers 136, 138 together in a substantially rigid assembly 118. The assembly 118 and mandrel 200 are cooled to ambient temperature (about 25° C.). The assembly 118 can be removed from the mandrel 200 by severing the fibers 136, 138 along the sides 208 or bottom 206 of the mandrel 200 and applying pressure to the bottom of the insert 232 through the apertures 236 in the mandrel 200 to unseat and remove the insert 232 and alignment members 234 from the recess 230. 
     Alternatively, to form a spacer unit 114 according to the present invention, prior to removing the spacer 116 from the mandrel 200, the sealing material 172 can be positioned within the groove 220 of the mandrel 200. A release agent, such as graphite, can be used to coat the groove 220 prior to positioning the sealing material 172 therein. 
     The bonding composition can be cured prior to or during heating of the spacer unit 114 to mold the sealing material 172 about the fibers 136, 138 in the groove 220. Heat or a curing agent can be applied to the sealing material 172, and preferably also to the mandrel 200 and assembly 118, to deform the sealing material 172 and cause the sealing material 172 to substantially encapsulate the fibers 136, 138 in the groove 220. The predetermined temperature to which the sealing material 172 is heated is greater than the predetermined deformation temperature of the sealing material 172. 
     For example, if the sealing material 172 is SCB-2 glass which is commercially available from SEM-COM Corporation of Toledo, Ohio, the sealing material 172 can be deformed by heating to a temperature of about 450° C. for about 30 minutes. The spacer unit 114 can be heated under pressure, for example by using a heated lamination press as discussed above. One skilled in the art would understand that the temperature and time for deforming or curing the sealing material 172 can vary based upon such factors as the material selected for use and the amount of material used. 
     After heating, the spacer unit 114 can be cooled to ambient temperature (about 25° C.) to permit resolidification of the sealing material 172 about the fibers 136, 138 to form a generally rigid spacer unit 114. The spacer unit 114 can be removed from the mandrel 200 as discussed above. 
     The present invention also includes a method for aligning an emitter substrate with a display. Preferably, the method is carried out in an inert gas vacuum, i.e., at a pressure less than about 760 torr using an inert gas such as is discussed above. 
     The method includes positioning the spacer unit 114 between an emitter 16 and a display 20 to align selected emitter elements with corresponding display elements to permit energy or other particles to flow from the emitter 16 through the corresponding passageways 148 of the spacer 116 to the corresponding portion of the display 20. For example, in a field emission display, the spacer unit is positioned to align the emitter tips 56 with the corresponding passageways 148 and corresponding portions of the display 20. 
     The spacer unit 114 can be bonded first to either the emitter 16 or display 20, or it can be essentially simultaneously bonded to both to form the image display panel 10. 
     The spacer unit 114, and preferably the entire image display panel 10, is heated to a predetermined temperature sufficient to deform the sealing material 172 to bond the sealing frame 158 between the emitter 16 and is display 20 to align the emitter 16 and display 20, but less than the predetermined temperature at which the other components of the image display panel 10 deform, for example the emitter 16, the display 20 and the spacer 116. For example, for SCB-2 glass sealing material, the spacer unit can be heated to a temperature of about 400° C. to about 550 C. for about 0.2 to about 0.5 hours to deform the sealing material yet not deform the emitter 16, the display 20 and the spacer 116, which are composed of materials having higher deformation temperatures. The image display panel 10 is then cooled to ambient temperature (about 25° C.). 
     The image display panel 10 can be installed in a display device, such as a computer (not shown) or television (not shown). The image display panel 10 can be connected to the energy source 66 prior or subsequent to installation. 
     An image display panel can be made using the above method either by assembling the above components of the image display panel in an inert gas vacuum as discussed above or by assembling the components at atmospheric pressure (about 760 torr) and evacuating the evacuatable or interior region formed between the emitter 16 and display 20 and bounded by the spacer unit 114 to a predetermined vacuum pressure, examples of which are given above. 
     The present invention will now be illustrated by the following specific, non-limiting example. 
     EXAMPLE 
     A spacer unit according to the present invention was fabricated from #633 D-450 E-type fiber glass strand with a twist of 1 turn per inch, which is commercially available from PPG Industries, Inc. of Pittsburgh, Pa. The #633 fiber glass strand has a sizing composition applied thereto comprising starch, oil, emulsifier, cationic lubricants, epoxy silane and polyethylene glycol. The average diameter of each strand was about 0.05 mm (0.002 inches). The line width (distance from the centerline) of each strand was about 0.05 mm (0.002 inches) and the spacing (line pitch) between the strands was about 4.62 mm (0.182 inches). 
     The spacer was formed by wrapping the strand about a graphite mandrel, such as is discussed in detail above, having five slots across the length of the mandrel and five slots across the width of the mandrel, the slots intersecting at about 90 degree angles. The graphite material from which the mandrel was fabricated is commercially available from POCO Graphite Corporation of Texas. The width of each slot was about 0.203 mm (0.008 inches) and the depth of each slot was about 0.762 mm (0.030 inches). 
     Silicon rod-shaped precision alignment members, such as are discussed above, were positioned in the recess of the mandrel. The width of each slot in the alignment members was about 0.05 mm (0.002 inches) and the depth of each slot was about 0.762 mm (0.030 inches). The spacing (line pitch) between the strands was about 4.62 mm (0.182 inches). 
     A conventional graphite mold release well known to those skilled in the art was applied to the graphite mandrel to facilitate release of the spacer and spacer unit after heating. 
     Ten layers of strand, the strands of each layer alternating at about 90 degree angles, were successively wound about the slots of the mandrel and alignment members as discussed in detail above. After winding, the mandrel with the strands wound thereon was dipped into a bath of bonding composition of bis(trimethoxysilylpropyl) amine to coat the strands. The coated strands were dried at room temperature (about 25° C). 
     After drying, SCB-2 glass frit sealing material was poured into the groove of the mandrel (groove 220 shown in FIGS. 11 and 12) to encapsulate the glass fiber strands. The thickness of the groove was about 2.54 mm (0.100 inches). The mandrel with the bonded strands and sealing material was placed in an air oven at a temperature of about 450° C. for 30 minutes. The mandrel and sealing unit were withdrawn from the oven and cooled to room temperature. The spacer unit and mandrel were separated as discussed in detail above. 
     The present invention provides a spacer, spacer unit, image display panel and methods for making and using the same which provide dimensionally stable particle passageways between an emitter and a display, are resistant to thermal cycling, inexpensive to manufacture and install in an image display panel, easily modified to include additional components such as electrodes, and are essentially self-leveling and self-aligning when installed between an emitter panel and a display panel. 
     It will be appreciated by those skilled in the art that changes could be made to the embodiments described above without departing from the broad inventive concept thereof. It is understood, therefore, that this invention is not limited to the particular embodiments disclosed, but it is intended to cover modifications which are within the spirit and scope of the invention, as defined by the appended claims.