Abstract:
A field emission display (FED) includes anode and cathode plates facing each other, having facing surfaces on which anodes and cathodes of a predetermined pattern are respectively formed, a multitude of micro tips formed on the cathode, at a predetermined spacing, an insulating layer formed on the cathode plate, surrounding and exposing the micro tips, a gate formed on the insulating layer, and spacers interposed between the anode plate and the cathode plate to maintain a predetermined spacing between the anode plate and the cathode plate, each having one end fixed in a hole formed on the anode plate.

Description:
BACKGROUND OF THE INVENTION 
     1. Field of the Invention 
     The present invention relates to a field emission display (FED), and more particularly, to a method for assembling a spacer for maintaining a constant interval between an anode plate and a cathode plate, and to an FED employing the same. 
     2. Description of the Related Art 
     Referring to a conventional field emission display (FED) of FIG. 1, an anode plate  11  and a cathode plate  12  face to each other, maintained at a constant spacing by a spacer  13 . A plurality of micro tips  14  are formed on a cathode  12   a  of the cathode plate  12 . The micro tips  14  are surrounded and exposed by an insulating layer  15 . Gates  17  are formed on the insulating layer  15 . A fluorescent film  18  is formed under an anode  11   a  of the anode plate  11 . 
     In manufacturing the FED, the spacer  13  is formed by screen-printing and curing a glass paste several times, using a mask  19 . 
     By the screen-printing method, it is known that the screen-printing and the curing must be repeated approximately 7 times to form the spacer  13  giving a spacing of approximately 200 μm between the anode plate  11  and the cathode plate  12 . The process repetitions are proportional to the spacing between the anode plate  11  and the cathode plate  12 . The screen-printing method requires repetition of screen-printing and curing and thus manufacturing spacers requires much time. Also, in the screen-printing, the glass paste may flow down, and it is difficult to increase an aspect ratio, i.e., the ratio of the height of the spacer  13  to the width thereof, to 1 or more, due to an alignment error of the screen. 
     Further, some of the electrons emitted from the micro tips  14  collide with the spacer  13  made of glass, and are dispersed. 
     SUMMARY OF THE INVENTION 
     It is an objective of the present invention to provide a method for assembling a spacer of a field emission display (FED) in which the spacer can be simply assembled between an anode plate and a cathode plate, and an aspect ratio of the spacer is 1 or more, and an FED manufactured using the same. 
     It is another objective of the present invention to provide a spacer in which the spacer supplies a repulsive force against electron beams to suppress dispersion of the electron beams and increase luminosity. 
     Accordingly, to achieve the above objective, a method for assembling a spacer of a FED including the steps of (a) forming a plurality of holes in an anode plate or a cathode plate, (b) coating an adhesive on a first end of each of a plurality of spacers of a predetermined length for maintaining the spacing between the anode plate and the cathode plate by a predetermined value, and/or in the holes, (c) inserting the first ends of the spacer respectively into the holes, and (d) curing the adhesive. 
     The step (a) may include the substeps of coating a photosensitive layer of a predetermined thickness on the anode plate or cathode plate, etching the photosensitive layer in a region where the holes are to be formed, to thereby form openings, forming holes in the anode or cathode plate exposed by the openings, using sand blasting, and removing the photosensitive layer. 
     Otherwise, the step (a) may include the steps of coating a photosensitive layer of a predetermined thickness on the anode plate or cathode plate, etching the photosensitive layer in a region where the holes are to be formed, to thereby form openings, etching the anode or cathode plate exposed by the openings to form the holes, and removing the photosensitive layer. 
     According to another aspect of the present invention, there is provided a method for assembling a spacer of a FED including the steps of (a) forming a multitude of openings where connection holes are to be formed there between, in an anode of an anode plate, (b) forming holes in the openings, smaller than the openings, in the anode plate, (c) forming a grid line in the connection holes on the anode plate for electrically connecting the holes, separated from the anode, (d) providing spacers each consisting of a glass fiber and a conductive layer coated on part of the outer surface of the glass fiber, extending from one end of the glass fiber, (e) coating metal paste for adhesion on the end of each spacer having the conductive layer, and in the holes, (f) inserting the ends of the spacers having the conductive layer respectively into the holes, and (g) curing the metal paste. 
     The FED according to another aspect of the present invention includes anode and cathode plates facing each other, having facing surfaces on which anodes and cathodes of a predetermined pattern are respectively formed, a multitude of micro tips formed on the cathode, at a predetermined spacing, an insulating layer formed on the cathode plate, surrounding and exposing the micro tips, a gate formed on the insulating layer, and spacers interposed between the anode plate and the cathode plate to maintain a predetermined spacing between the anode plate and the cathode plate, each having one end fixed in a hole formed on the anode plate. 
     The spacer comprises a glass fiber having one end fixed in the hole formed on the anode plate, and a conductive layer coated on the surface of the glass fiber to a predetermined length, to partially expose the surface of the glass fiber. 
    
    
     BRIEF DESCRIPTION OF THE DRAWINGS 
     The above objectives and advantages of the present invention will become more apparent by describing in detail a preferred embodiment thereof with reference to the attached drawings in which: 
     FIG. 1 is a sectional view of a conventional field emission display (FED); 
     FIG. 2 is a sectional view illustrating a method for manufacturing a spacer of the FED of FIG. 1; 
     FIG. 3 is a sectional view showing a FED according to the first embodiment of the present invention; 
     FIGS. 4A through 4G are sectional views illustrating a method for assembling a spacer of the FED of FIG. 3; 
     FIG. 5 is a sectional view of a FED according to a second embodiment of the present invention; 
     FIG. 6 is a sectional view of a FED according to a third embodiment of the present invention; and 
     FIGS. 7A through 7E are sectional views illustrating a method for assembling a spacer of the FED of FIG.  6 . 
    
    
     DESCRIPTION OF THE PREFERRED EMBODIMENTS 
     Referring to FIG. 3 showing a field emission display (FED)  40  according to a first embodiment of the present invention, an anode plate  21  and a cathode plate  22  face to each other, maintained at a predetermined spacing by a spacer  43 , and an anode  21   a  and a cathode  22   a  of a predetermined pattern are formed on the anode plate  21  and the cathode plate  22 , respectively. A space between the anode plate  21  and the cathode plate  22  is sealed by a sealant  45 . A fluorescent film  38  is coated on the anode  21   a  of the anode plate  21 . A plurality of micro tips  34  are formed on the cathode  22   a  of the cathode plate  22 , and the micro tips  34  are surrounded with an insulating layer  35 , with their upper portions exposed. Gates  37  are formed on the insulating layer  35 . 
     The spacer  43  is a glass bar, and is connected to the anode plate  21  by a glass paste  42  which is an adhesive. 
     A method for assembling the spacer  43  of the FED  40  will be described with reference to FIGS. 4A through 4G. 
     A plurality of holes for connecting a plurality of spacers  43  are formed on the anode plate  21  or the cathode plate  22  of FIG.  3 . That is, as shown in FIG. 4A, a photosensitive layer  25  of a predetermined thickness, for example photoresist, is formed on the anode plate  21 . Then, as shown in FIG. 4B, the photosensitive layer  25  is exposed to light and etched to form openings  23  having a size corresponding to the holes to be formed. 
     Then, the part of the anode plate  21  exposed through the openings  23  is abraded to a predetermined depth by sand blasting, as shown in FIG.  4 C. Alternatively, the part of the anode plate  21  exposed through the openings  23  may be etched. 
     Subsequently, when the photosensitive layer  25  is removed, holes  24  for connecting a spacer are completely formed as shown in FIGS. 4D and 4E. 
     As shown in FIG. 4F, an adhesive glass paste  42  is coated on one end of a glass bar used for the spacer  43 , to a predetermined thickness. Alternatively, the glass paste  42  may be appropriately poured into the hole  24  of the anode plate  21 . Preferably, both processes may be performed. It is also preferable that the glass paste  42  is injected into the hole  24  by screen-printing. Here, the glass paste  42  indicates a frit glass liquid. 
     The length of the spacer  43  is decided according to the spacing between the anode plate  21  and the cathode plate  22 . Preferably, the spacing is approximately 200 μm and the bar section is circular. 
     Subsequently, as shown in FIG. 4G, one end of each spacer  43  is inserted into a hole  24  of the anode plate  21 , to be connected thereto. At this time, the spacers  43  are aligned parallel with each other. 
     The spacers  43  inserted into the holes  24  of the anode plate  21  are annealed at a predetermined temperature, so that they are joined by curing the glass paste  42 . 
     Then, the cathode plate  22 , having the micro tips  34  of FIG. 3, is located on the other ends of the spacers  43 , and sealed with the anode plate  21 , by a sealant  45  of frit glass to have a vacuum of 10 −7  torr. 
     A FED  50  manufactured by a method according to a second embodiment of the present invention is shown in FIG.  5 . Here, like reference numerals refer to like elements. 
     According to characteristics of the present embodiment, a spacer  53  between the anode plate  21  and the cathode plate  22  is spherical. A spherical hole  54  corresponding to the shape of the spacer  53  is formed, for example, in the anode plate  21 , for connection with the spacer  53 . That is, the spherical spacer  53  is settled in the spherical hole  54  and connected by glass paste  52 . 
     The process of assembling the spacer  53  is the same as that of the first embodiment. 
     Like the first embodiment, preferably, the spacer  53  is formed of glass, and the spacing maintained by the spacer  53  between the anode plate  21  and the cathode plate  22  is approximately 200 μm. 
     A FED  60  according to a third embodiment of the present invention is shown in FIG.  6 . Like reference numerals refer to like elements. 
     Referring to FIG. 6, a spacer  63  connected to the anode plate  21  includes a cylindrical glass fiber  63   a , a conductive layer  63   b  coated on part of the outer surface of the glass fiber  63   a , and an exposed portion  63   c  uncoated with the conductive layer  63   b . The conductive layer  63   b  is formed of a conductive material such as Cr or Ti. 
     The conductive layers  63   b  of adjacent spacers  63  are electrically connected to each other by a grid line (see  21   e  of FIG.  7 C). 
     A method for assembling a spacer of the FED  60  will be described with reference to FIGS. 7A through 7E. 
     As shown in FIG. 7A, an anode  21   a  formed of an ITO layer is coated on the anode plate  21  where the spacer  63  is to be fixed. Subsequently, circular openings  21   b  and connection grooves  21   c  connecting the openings  21   b  are formed in the anode  21   a  by typical photolithography. Here, preferably, the anode plate  21  is an insulating material formed of glass. 
     As shown in FIG. 7B, holes  21   d  of a predetermined depth for connecting spacers are formed in the anode plate  21  in the openings  21   b . Here, the diameter of each  21   d  is smaller than that of each opening  21   b . As described above, the holes  21   d  are formed by the sand blast, using the photosensitive layer, or by etching. 
     Subsequently, as shown in FIG. 7C, a grid line  21   e  electrically connecting the holes  21   d  is formed between the holes  21   d . That is, the grid line  21   e  extends to the upper surface of the anode plate  21  between the holes  21   d  and preferably to the inner walls of the holes  21   d . Also, the grid line  21   e  is separated from the anode  21   a , and connected to an external circuit (not shown). The grid line  21   e  is formed of Al and Cr using a lift-off method by typical photolithography. 
     As shown in FIG. 7D, a conductive layer  63   b  is coated on at least part of the surface of the glass fiber  63   a . That is, the conductive layer  63   b  is coated from one end of the glass fiber  63   a  to a predetermined length, and other surfaces of the glass fiber  63   a  are an exposed portion  63   c  which are not coated with the conductive layer  63   b . The conductive layer  63   b  is formed by depositing a conductive material such as Cr or Ti. 
     It is also preferable that the length of the spacer  63  maintains the spacing between the anode plate  2  and cathode plate  22  at 200 μm. 
     Subsequently, as shown in FIG. 7E, a metal paste  62  for adhesion is coated in the holes  21   d  to connect the spacers  63  to the holes  21   d  of the anode plate  21 . At this time, the metal paste may be coated on one end of each spacer  63  to be connected to a hole  21   d . Preferably, the metal paste is silver paste. The metal paste ensures electrical connection of the conductive layer  63   b  to the grid line  21   e , when the spacers  63  are connected to the holes  21   d.    
     As shown in FIG. 7E, an end of the spacer  63  where the conductive layer  63   b  is formed is inserted into the hole  21   d  of the anode plate  21 , and the metal paste  62  on the inserted end is cured by annealing, to thereby fix the spacer  63 . At this time, the conductive layer  63   b  is electrically connected to the grid line  21   e  of FIG. 7C formed on the inner wall of the hole  21   d , by the metal paste  62 . 
     Subsequently, the cathode plate  22  of FIG. 6 where the micro tips  34  are formed is located on the other end of the exposed portions  63 C of the spacers  63  fixed to the anode plate  21 , and the cathode plate  22  is sealed with a sealant  45  of FIG. 6 formed of frit glass. 
     In operation of the above-described FED, if a negative (−) bias is applied to the conductive layer  63   b  through the grid line  21   e , the conductive layer  63   b  becomes a grid electrode. 
     In this state, if a predetermined positive bias is applied to the gate  37 , electrons are emitted from the micro tips  34 . At this time, the spacer  63  exerts an electric repulsive force on the emitted electrons. Thus, the electrons proceed to the fluorescent film  38  without loss caused by colliding with the spacer  63 , increasing the luminosity of the FED. 
     According to the present invention, additional spacers are bonded by a sealant to holes in an anode plate, simplifying and speeding manufacture. The spacer is formed of glass, allowing a higher aspect ratio. Also, the spacer can be used as part of the grid electrode, so that more emitted electrons reach a fluorescent film, thereby increasing the luminosity.