Patent Publication Number: US-7583017-B2

Title: Electron emission display

Description:
CROSS-REFERENCE TO RELATED APPLICATION 
   This application claims priority to and the benefit of Korean Patent Application No. 10-2005-0100658, filed on Oct. 25, 2005, in the Korean Intellectual Property Office, the entire content of which is incorporated herein by reference. 
   BACKGROUND OF THE INVENTION 
   1. Field of the Invention 
   The present invention relates to an electron emission display, and more particularly, to an electron emission display having a structure for applying voltage to an anode electrode for accelerating an electron beam. 
   2. Description of Related Art 
   In general, electron emission elements can be classified into those using hot cathodes as an electron emission source and those using cold cathodes as the electron emission source. 
   There are several types of cold cathode electron emission elements, including Field Emitter Array (FEA) elements, Surface Conduction Emitter (SCE) elements, Metal-Insulator-Metal (MIM) elements, and Metal-Insulator-Semiconductor (MIS) elements. 
   A conventional electron emission display includes an array of electron emission elements arranged on a first substrate and a light emission unit arranged on a second substrate. The light emission unit includes phosphor layers and an anode electrode. The electron emission display further includes electron emission regions arranged on the first substrate and driving electrodes arranged on the first substrate to control electron emission from the electron emission regions. The anode electrode arranged on the second substrate causes electrons emitted from the electron emission regions to be effectively accelerated toward the phosphor layers. Accordingly, the electrons emitted from the electron emission regions excite the phosphor layers to display an image. 
   The anode electrode receives a direct current voltage of, for example, hundreds to thousands of positive volts that can accelerate the electrons emitted from the first substrate to the second substrate. The voltage is applied from an input terminal. The input terminal extends from the anode electrode to an edge of the second substrate and has a portion arranged outside of a vacuum envelope (or chamber) formed by the first substrate and the second substrate. 
   Therefore, the second substrate must be provided with a portion on which the input terminal will be arranged. In the conventional electron emission display, one edge of the second substrate protrudes to provide the portion on which the input terminal will be arranged. 
   As described above, in order to apply the voltage to the anode electrode, the second substrate includes the protruding portion which extends past an opposite edge of the first substrate. Therefore, the protruding portion increases the overall size of the display. However, the protruding portion is a non-effective area in that an image is not displayed at the protruding portion, and therefore increases an amount of dead space. 
   The input terminal may be arranged on the first substrate in order to reduce the amount of dead space. However, when the input terminal is arranged on the first substrate, one or more extra holes must be formed on the first substrate to connect the input terminal with the anode electrode. 
   SUMMARY OF THE INVENTION 
   An aspect of the present invention provides an electron emission display in which an area of a space occupied by an input terminal of an anode electrode is reduced, thereby reducing an area of unnecessary space not used to display an image. 
   In an embodiment of the present invention, an electron emission display includes a first substrate and a second substrate facing the first substrate. An electron emission unit is arranged on the first substrate. A light emission unit is arranged on the second substrate, the light emission unit having an anode electrode for accelerating an electron beam emitted from the electron emission unit. A sealing member is adapted to seal an exhaust hole of the first substrate. A voltage supply unit is adapted to apply an anode voltage to the anode electrode via the sealing member. 
   The voltage supply unit may include a connecting member for electrically connecting the sealing member to the anode electrode and a supply member connected to the sealing member to supply the anode voltage to the sealing member. 
   The connecting member may include a lead line. 
   The connecting member may be connected with the anode electrode by a first electrically conductive adhesive layer, and the connecting member may be connected with the sealing member by a second electrically conductive adhesive layer. 
   The connecting member may be an electrically conductive elastic body. The electrically conductive elastic body may be a coil spring or a leaf spring having a bent centerline. 
   The supply unit may include a lead line connected with the sealing member and arranged on the first substrate. 
   The lead line may be connected with the sealing member by an electrically conductive adhesive layer. 
   The sealing member may be formed of an electrically conductive material, metal, or a metal alloy. 
   The sealing member may be configured to have a hemispherical shape or a substantially flat shape. 
   The sealing member may be coupled to the first substrate by a frit deposited on a periphery of the sealing member. 
   The sealing member may be darkened by a heat treatment. 
   The electron emission unit may include an electron emission region, a plurality of cathode electrodes, and a plurality of gate electrodes arranged to cross the cathode electrodes. The cathode electrodes and the gate electrodes may be insulated from each other and adapted to control the electron emission region. The light emission unit may include a plurality of phosphor layers and a black layer arranged between at least two of the phosphor layers. 
   The electron emission region may include a material selected from the group consisting of carbon nanotubes, graphite, graphite nanofibers, diamonds, diamond-like carbon, fullerene (C 60 ), silicon nanowires, and combinations thereof. 

   
     BRIEF DESCRIPTION OF THE DRAWINGS 
     The accompanying drawings, together with the specification, illustrate exemplary embodiments of the present invention, and, together with the description, serve to explain the principles of the present invention. 
       FIG. 1  is a partial sectional view of an electron emission display according to an embodiment of the present invention. 
       FIG. 2  is a partial exploded perspective view of the electron emission display shown in  FIG. 1 . 
       FIG. 3  is a perspective view of a sealing member and a second lead line shown in  FIG. 1 . 
       FIG. 4  is a partial sectional view of an electron emission display according to another embodiment of the present invention. 
       FIG. 5  is a partial sectional view of an electron emission display according to another embodiment of the present invention. 
       FIG. 6  is a flowchart illustrating a method of manufacturing an electron emission display according to an embodiment of the present invention. 
   

   DETAILED DESCRIPTION 
   In the following detailed description, only certain exemplary embodiments of the present invention are shown and described, by way of illustration. As those skilled in the art would recognize, the described exemplary embodiments may be modified in various ways, all without departing from the spirit or scope of the present invention. Accordingly, the drawings and description are to be regarded as illustrative in nature, and not restrictive. 
     FIG. 1  is a partial sectional view of an electron emission display according to an embodiment of the present invention,  FIG. 2  is a partial exploded perspective view of the electron emission display according to the embodiment of the present invention, and  FIG. 3  is a perspective view of a sealing member and a second lead line according to the embodiment of the present invention. 
   Referring to  FIGS. 1 and 2 , an electron emission display  1  according to an embodiment of the present invention includes a first substrate  2  and a second substrate  4  facing the first substrate  2 . The first substrate  2  and the second substrate  4  are spaced apart from each other by a certain (or predetermined) distance therebetween. A frame  6  is arranged at respective peripheries (or peripheral regions) of the first substrate  2  and the second substrate  4  to form an enclosed space. Therefore, the first substrate  2 , the second substrate  4 , and the frame  6  form a vacuum envelope (or chamber). 
   An electron emission unit  8  including an array of electron emission elements is arranged on the first substrate  2  to form an electron emission device  9 . A light emission unit  10  is arranged on the second substrate  4 . The electron emission device  9  is combined with the light emission unit  10  to make the electron emission display  1 . 
   In  FIGS. 1 and 2 , the electron emission display  1  is shown as having an array of FEA elements. 
   The electron emission unit  8  includes a plurality of electron emission regions  12  arranged on the first substrate  2  and drive electrodes for controlling electron emission of the electron emission regions  12 . The drive electrodes include cathode electrodes  14 , gate electrodes  16 , and a focusing electrode  18 . 
   The cathode electrodes  14  are arranged in a striped pattern to extend along a first direction (e.g., along a y-axis in  FIG. 1 ), and a first insulation layer  20  is arranged on the first substrate  2  to fully cover the cathode electrodes  14 . The gate electrodes  16  are arranged on the first insulation layer  20  in a striped pattern to extend along a second direction (e.g., along an x-axis in  FIG. 1 ) to cross the cathode electrodes  14  at right angles. 
   Regions at where the cathode electrodes  14  are crossed by the gate electrodes  16  define pixel regions. Each pixel region corresponds to one or more of the electron emission regions  12 . Openings  201  and  161  corresponding to the electron emission regions  12  are respectively arranged on the first insulation layer  20  and the gate electrodes  16  to expose the electron emission regions  12 . The electron emission regions  12  are formed of a material that emits electrons when an electric field is applied thereto in a vacuum atmosphere. By way of example, the material may be a carbonaceous material and/or a nanometer-sized material. For example, the electron emission regions  12  can be formed of carbon nanotubes, graphite, graphite nanofibers, diamonds, diamond-like carbon, C 60 , silicon nanowires, and/or combinations thereof. Alternatively, the electron emission regions  12  may be formed of a molybdenum-based material and/or a silicon-based material. In this alternative situation, the electron emission regions may be formed to have a pointed-tip structure. 
   Either the cathode electrodes  14  or the gate electrodes  16  serve as scan electrodes for receiving a scan drive voltage (or voltages), and the other electrodes function as data electrodes for receiving a data drive voltage (or voltages). Electric fields are formed around the electron emission regions  12  where a voltage difference between the cathode electrodes  14  and the gate electrodes  16  is equal to or higher than a threshold value. Electrons are then emitted from the electron emission regions  12 . 
   An embodiment in which the gate electrodes  16  are arranged above the cathode electrodes  14  with the first insulation layer  20  arranged therebetween is illustrated (see, for example,  FIGS. 1 and 2 ). However, embodiments of the present invention are not limited to this embodiment. That is, the cathode electrodes  14  may be arranged above the gate electrodes  16 . Accordingly, the electron emission regions may be arranged on the first insulation layer to contact a surface of the cathode electrodes. 
   A second insulation layer  22  is arranged on the first insulation layer  20  to cover the gate electrodes  16 , and the focusing electrode  18  is arranged on the second insulation layer  22 . Openings  181  and  221  are respectively arranged on the focusing electrode  18  and the second insulation layer  22  to expose the electron emission regions  12 . One of the openings  221  and a corresponding opening of the openings  181  may correspond to one of the pixel regions. 
   Describing the light emission unit  10  in more detail, phosphor layers  24  and black layers  26  for enhancing a contrast of a displayed image are arranged on a surface of the second substrate  4  facing the first substrate  2  (e.g., one of the black layers  26  is arranged between at least two of the of the phosphor layers  24 ). An anode electrode  28  is arranged on the phosphor layers  24  and the black layers  26 . 
   The anode electrode  28  heightens a screen luminance by accelerating electron beams and reflecting visible light rays radiated from the phosphor layers  24  to the first substrate  2  back toward the second substrate  4 . 
   The anode electrode  28  may be a metal layer formed, by way of example, of aluminum. Alternatively, the anode electrode may be a transparent conductive layer formed, by way of example, of indium tin oxide (ITO). In this alternative situation, the anode electrode is arranged on respective surfaces of the phosphor layers  24  and the black layers  26 , which face the second substrate  4 . 
   An exhaust hole  30  (see, for example,  FIG. 1 ) is arranged on the first substrate  2  to exhaust (or evacuate) air from inside the vacuum envelope, and the exhaust hole  30  is sealed with a sealing member  34  after an evacuation process is performed. 
   A voltage supply unit  50  is arranged on the first substrate  2 . The voltage supply unit  50  applies a drive voltage to the anode electrode  28  from an electric power source arranged outside of the vacuum envelope. 
   As shown in  FIG. 1 , the voltage supply unit  50  includes a connecting member  51  and a supply member  53 . The connecting member  51  electrically interconnects the anode electrode  28  and the sealing member  34 , and the supply member  53  provides the drive voltage to the sealing member  34 . 
   The supply member  53  may include a first lead line  32 , and the connecting member  51  may include a second lead line  36 . 
   One end of the first lead line  32  is connected with the external electric power source, and the sealing member  34  is connected with the first lead line  32  at an opposite end of the first lead line  32 . The first lead line  32  may contact the sealing member  34  over a relatively large contact area in order to reduce a level of contact resistance. A first electrically conductive adhesive layer  33   a  may be arranged between the sealing member  34  and the first lead line  32  to enhance an adhesive force between the sealing member  34  and the first lead line  32 , and the first electrically conductive adhesive layer  33   a  may be formed of an electrically conductive adhesive to allow a current generated by the drive voltage to flow through the first electrically conductive adhesive layer  33   a.    
   The sealing member  34  may be coupled to the first substrate  2  via a frit  38 , and the frit  38  may be arranged on a periphery (or peripheral region) of the sealing member  34  so as not to hinder a coupling between the second lead line  36  and the sealing member  34 . After the sealing member  34  is coupled with the second lead line  36 , the sealing member  34  may be darkened by a heat treatment at a temperature of about 950° C. The heat treatment of the sealing member  34  creates an oxidized layer, of a material such as Cr 2 O x , on a surface of the sealing member  34 , thereby reinforcing the coupling (or bond) between the frit  38  and the sealing member  34 . The reinforced coupling (or bond) between the frit  38  and the sealing member  34  reduces a risk of or prevents an occurrence of a vacuum leak more effectively. 
   As shown in  FIG. 3 , the sealing member  34  may be configured to have a hemispherical shape. However, embodiments of the present invention are not limited to this case. By way of example, the sealing member  34  may be configured to have a substantially flat shape, and a top surface of the sealing member may be circular or polygonal in shape. The sealing member  34  may be formed of a conductive material, such as metal or a metal alloy, in order to allow a current to flow through the sealing member  34 . 
   As shown in  FIG. 1 , the anode electrode  28  and the sealing member  34  are interconnected by the second lead line  36 . The second lead line  36  is coupled with the sealing member  34  over a first contact surface  360 , and the second lead line  36  is coupled with the anode electrode  28  over a second contact surface  362 . Each of the first contact surface  360  and the second contact surface  362  may be configured in order to reduce respective levels of contact resistance. A second electrically conductive adhesive layer  33   b  may be arranged between the sealing member  34  and the second lead line  36  at the first contact surface  360 . A third electrically conductive adhesive layer  33   c  may be arranged between the anode electrode  28  and the second lead line  36  at the second contact surface  362 . Silver (Ag) paste may be used to form the second electrically conductive adhesive layer  33   b  and the third electrically conductive adhesive layer  33   c.    
   The first lead line  32  and the second lead line  36  may be formed of any of a variety of conductive materials such as Cr, Al, Ag, ITO, or combinations thereof. 
   The drive voltage is applied from the external electric power source to the anode electrode  28  in the following order: from the external electric power source to the first lead line  32 , then to the first electrically conductive adhesive layer  33   a , then to the sealing member  34 , then to the second electrically conductive adhesive layer  33   b , then to the second lead line  36 , then to the third electrically conductive adhesive layer  33   c , and then to the anode electrode  28 . 
   Because the drive voltage is applied to the anode electrode  28  via the sealing member  34 , there is no need to extend the second lead line  36 , which effectively connects the anode electrode to the external electric power source, outside of the vacuum envelope and through the sealing member  34  used for sealing the exhaust hole  30  on the first substrate  2 . 
   Therefore, a risk of leakage from inside the vacuum envelope of the electron emission display  1  can be reduced. 
   In a further embodiment, the anode electrode  28  can be connected to the external electric power source via the exhaust hole  30 , which is already formed to exhaust internal gas out from the vacuum envelope, without using any additional holes. Therefore, a manufacturing process can be simplified. 
   A plurality of spacers  40  may be arranged between the first substrate  2  and the second substrate  4  to uniformly maintain a certain (or predetermined) gap between the first substrate  2  and the second substrate  4  to counter an application of an external force. The spacers  40  may be configured to have a shape of a cylindrical post (e.g., a post having a circular cross section) or a rectangular post (e.g. a post having a rectangular cross section). 
     FIGS. 4 and 5  are partial sectional views of electron emission displays according to other embodiments of the present invention. 
   Electron emission displays of these other embodiments are substantially identical to that of the foregoing embodiment with the exception of the connection member of the voltage supply unit. Therefore, the same reference numbers will be used to refer to corresponding elements of the foregoing embodiment, and only the connection member will be described in more detail below. 
   Referring first to  FIG. 4 , a connecting member  51 ′ may be formed by a coil spring. Alternatively, as shown in  FIG. 5 , a connecting member  51 ″ may be formed by a leaf spring having a bent centerline. 
   However, embodiments of the present invention are not limited to the examples described above. That is, any of various suitable electrically conductive elastic structures can be used to form the connecting member. 
   When the connecting members  51 ′ and  51 ″ are formed of an electrically conductive elastic structure as described above, the connecting members  51 ′,  51 ″ can better elastically absorb shock energy originating from inside or outside of the vacuum envelope, as compared to an electron emission display not including the respective structure(s) shown in  FIG. 4  and/or  FIG. 5 . Therefore, when either one of the connecting members  51 ′ and  51 ″ is coupled to the anode electrode  28  and the sealing member  34 , the either one of the connecting members  51 ′ and  51 ″ prevents or restrains movements of the anode electrode  28  and the sealing member  34  away from their respective positions caused by shock energy. 
   In the embodiments of the present invention described, an electron emission display has an array of FEA elements. However, embodiments of the present invention are not limited to this situation. For example, embodiments of the present invention can also be applied to an electron emission display having an array of SCE elements, MIM elements, and/or MIS elements. 
     FIG. 6  is a flowchart illustrating a method of manufacturing an electron emission display according to an embodiment of the present invention. The electron emission display shown in  FIG. 1  is used to describe the method shown in  FIG. 6 . 
   Referring to  FIG. 6 , a method of manufacturing the electron emission display includes performing an anode preparation process S 10 , performing a cathode preparation process S 30 , and performing a seal member preparation process S 50 . 
   In the anode preparation process S 10 , a seal frit is deposited on the periphery (or peripheral region) of the second substrate  4  on which the light emission unit  10  is coupled with the second lead line  36  (S 11 ), and the seal frit is fired at a temperature within a range from about 400 to about 500° C. (S 13 ). Then, the frame  6  is arranged on the seal frit (S 15 ), fired at a temperature within a range from about 400 to about 500° C., and adhered to the second substrate  4  (S 17 ). 
   In the cathode preparation process S 30 , the exhaust hole  30  is formed on the first substrate  2  on which the electron emission unit  8  is arranged. 
   In the sealing member preparation process S 50 , the sealing member  34  is arranged (S 51 ) and darkened through a heat treatment process (S 53 ). Then, a seal frit  38  is deposited and fired around the exhaust hole  30  of the first substrate  2  (e.g. at a temperature within a range from about 400 to about 500° C.) (S 55 ). The heat treatment process may be conducted by hydrogen-wet heat treatment at a temperature within a range from about 900 to about 1000° C. (S 57 ). Next, the anode electrode  28  is connected to one end of the second lead line  36  via the third electrically conductive adhesive layer  33   c  (S 57 ). 
   After the above processes are performed, a seal frit is deposited on one end of the frame  6 , the one end not being coupled to the second substrate  4 , and the first substrate  2  and the second substrate  4  are joined by the frame  6  (S 70 ). Alternatively, the seal frit may be deposited on the first substrate  2  rather than on the frame  6 . 
   Then, the vacuum envelope composed of the first substrate  2 , the second substrate  4 , and the frame  6  is fired, by way of example, at a temperature within a range from about 400 to about 500° C. Here, the opposite end of the second lead line  36  (that is, the portion of the connection member  51  connected to the second substrate  4 ) extends through the exhaust hole  30 . 
   Then, internal air is exhausted out from the vacuum envelope through the exhaust hole  30  (S 110 ). 
   Then, the sealing member  34  is connected with the second lead line  36  via the second electrically conductive adhesive layer  33   b  and, at substantially the same time, the sealing member  34  is adhered to the first substrate  2  via the frit  38  in order to seal the exhaust hole  30 . Then, the sealing member  34  is heated, by way of example, at a temperature within a range from about 350 to about 450° C. (S 130 ) so that the vacuum envelope is properly sealed by the sealing member  34  (S 150 ). 
   Then, when the drive voltage is applied to the first lead line  32  (S 170 ), the drive voltage is applied to the anode electrode  28  via the following sequence: from the first lead line  32  to the first electrically conductive adhesive layer  33   a , then to the sealing member  34 , then to the second electrically conductive adhesive layer  33   b , then to the second lead line  36 , then to the third electrically conductive adhesive layer  33   c , and then to the anode electrode  28 . 
   According to embodiments of the present invention, in the electron emission display  1 , the drive voltage is applied to the anode electrode  28  via the sealing member  34 . Therefore, space occupied by the input terminal is minimized without forming an additional hole for extending the second lead line  36  from the anode electrode  28  to the external electric power source. Also, because the frit  8  arranged on the sealing member  34  and the second electrically conductive adhesive layer  33   b  do not overlap with each other, a tight sealing of the vacuum envelope can be ensured. 
   While the present invention has been described in connection with certain exemplary embodiments, it is to be understood that the invention is not limited to the disclosed embodiments, but, on the contrary, is intended to cover various modifications and equivalent arrangements included within the spirit and scope of the appended claims, and equivalents thereof.