Patent Publication Number: US-2007096660-A1

Title: Display device

Description:
BACKGROUND OF THE INVENTION  
      1. Field of the Invention  
      The invention relates to electron emitting devices employable by devices, e.g., display devices and flat lamps, which allow the devices to operate at reduced driving voltages and/or have improved luminous efficiency.  
      2. Description of the Related Art  
      Flat panel display devices, e.g., plasma display panels (PDPs), liquid crystal displays (LCDs), are being used in lieu of conventional cathode ray tubes. In PDPs, a discharge gas may be filled between two substrates on which a plurality of electrodes may be formed. When a discharge voltage is applied to the discharge gas to generate ultraviolet (UV) light, which in turn excite phosphor layers formed in a predetermined pattern, thereby emitting visible light and displaying a desired image on the PDP.  
      PDPs generally include a noble gas, such as Xe, Ne. In conventional PDPs, when a predetermined voltage is applied across electrodes of the PDP, the noble gas may be ionized into a plasma state, i.e., plasma discharge, and UV light may be emitted. The excited Xe gas may be stabilized when releasing photons of light energy, i.e., while generating UV light.  
      In order to display images in the conventional plasma display panel, a relatively high amount energy is required for ionizing the discharge gas, and thus, a high driving voltage is applied. However, plasma display panels generally have a relatively low luminous efficiency. Similarly, flat panel lamps employing conventional plasma cell structures to emit light also generally require a relatively high driving voltage, and have a relatively low luminous efficiency.  
     SUMMARY OF THE INVENTION  
      The invention is therefore directed to electron emitting devices employable in device, e.g., display devices and flat lamps, which substantially overcome one or more of the problems due to limitations and disadvantages of the related art.  
      It is therefore a feature of embodiments of the invention to provide electron emitting devices, which can reduce a driving voltage of a device, e.g., display devices and/or flat lamps, employing such electron emitting devices.  
      It is therefore another feature of embodiments of the invention to provide electron emitting devices, which can increase a luminous efficiency of a device, e.g., display devices and/or flat lamps, employing such electron emitting devices.  
      At least one of the above and other features and advantages of the present invention may be realized by providing a device, including a first substrate and a second substrate facing each other, and including a plurality of cells defined between the first and second substrates, an electron accelerating and emitting unit, disposed between the first and second substrates, for accelerating and emitting electrons, a gas including N 2  within the cell, the gas capable of being excited by the electrons emitted by the electron accelerating and emitting unit to generate ultraviolet light, and a light emitting layer disposed on an outer surface of one of the first and second substrates, the light emitting layer capable of being excited by the ultraviolet light to generate visible light.  
      The electrons emitted from the electron accelerating and emitting unit may have an energy level that is larger than an energy level required to excite the gas in the cell, and smaller than an energy level required to ionize the gas. For example, the electrons may have an energy level at or within a range of about 11 eV to about 16 eV.  
      The electron accelerating and emitting unit may include a plurality of first electrodes and second electrodes disposed between the first and second substrate, and an electron accelerating layer capable of emitting the electrons to a respective cell when voltages are applied to the first and second electrodes.  
      The first electrode and the second electrode may be disposed on different surfaces of the respective cell. The first and second electrodes may be disposed on opposing surfaces of the first substrate and the second substrate. One of the first and second electrodes may be disposed on one of the first substrate and the second substrate, and the other of the first and second electrodes may be disposed on a sidewall surface of respective cells. The first and second electrodes may be disposed on both sides of respective cells.  
      A third electrode may be formed on the first electrode. Voltages applied to the first electrode, the second electrode, and the third electrode are V 1 , V 2 , and V 3 , respectively, the voltages V 1 , V 2 , and V 3  may satisfy a relationship of V 1 &lt;V 3 ≦V 2 . At least one of the second electrode and the third electrode may have a mesh structure.  
      The first electron accelerating layer may include oxidized porous silicon.  
      The device may include second electron accelerating layers on the second electrode, and accelerating and emitting electrons that excite the gas into the cell when the voltages are applied to the first and second electrodes. The first electrode and the second electrode may be driven by alternating current (AC) voltages. Third electrodes may be on the first electron accelerating layers, and fourth electrodes formed on the second electron accelerating layers. The third and fourth electrodes have mesh structures. The first and second electron accelerating layers may include oxidized porous silicon.  
      The first electrodes and the second electrodes may extend in directions crossing each other. The first electrodes and the second electrodes may extend parallel to each other, and the electron emitting device may further include a plurality of address electrodes extending in a direction crossing a direction along which the first and second electrodes extend.  
      The device may include a dielectric layer covering the address electrodes. 
    
    
     BRIEF DESCRIPTION OF THE DRAWINGS  
      The above and other features and advantages of the invention will become more apparent to those of ordinary skill in the art by describing in detail exemplary embodiments thereof with reference to the attached drawings in which:  
       FIG. 1  illustrates a schematic of a cross-sectional view of a first exemplary embodiment of an electron emitting device;  
       FIG. 2  illustrates a graph of an energy level of N 2 , which may be employed as a gas in embodiments of the invention;  
       FIG. 3  illustrates a spectrum of UV light generated by excited species in nitrogen;  
       FIG. 4  illustrates a graph of transmittances of the UV light through a first glass substrate and a second glass substrate according to wavelengths of the UV light;  
       FIGS. 5A through 5D  illustrate waveforms of voltages that may be applied to the electrodes of the electron emitting device of  FIG. 1 ;  
       FIG. 6  illustrates a schematic of a cross-sectional view of a second exemplary embodiment of an electron emitting device;  
       FIG. 7  illustrates a schematic of a cross-sectional view of a third exemplary embodiment of an electron emitting device;  
       FIGS. 8A and 8B  illustrate waveforms of voltages that may be applied to electrodes of the electron emitting device of  FIG. 7 ;  
       FIG. 9  illustrates a schematic of a cross-sectional view of a fourth exemplary embodiment of an electron emitting device;  
       FIG. 10  illustrates a schematic of cross-sectional view of a fifth exemplary embodiment of an electron emitting device;  
       FIG. 11  illustrates a schematic of a cross-sectional view of a sixth exemplary embodiment of an electron emitting device; and  
       FIG. 12  illustrates a schematic of a cross-sectional view of a seventh exemplary embodiment of an electron emitting device.  
    
    
     DETAILED DESCRIPTION OF THE INVENTION  
      Korean Patent Application No. 10-2005-0105058, filed on Nov. 3, 2005, in the Korean Intellectual Property Office, and entitled: “Display Device,” is incorporated by reference herein in its entirety.  
      The invention will now be described more fully hereinafter with reference to the accompanying drawings, in which exemplary embodiments of the invention are illustrated. The invention may, however, be embodied in different forms and should not be construed as limited to the embodiments set forth herein. Rather, these embodiments are provided so that this disclosure will be thorough and complete, and will fully convey the scope of the invention to those skilled in the art.  
      In the figures, the dimensions of layers and regions may be exaggerated for clarity of illustration. It will also be understood that when a layer or element is referred to as being “on” another layer or substrate, it can be directly on the other layer or substrate, or intervening layers may also be present. Further, it will be understood that when a layer is referred to as being “under” another layer, it can be directly under, and one or more intervening layers may also be present. In addition, it will also be understood that when a layer is referred to as being “between” two layers, it can be the only layer between the two layers, or one or more intervening layers may also be present. Like reference numerals refer to like elements throughout.  
      Various exemplary embodiments of electron emitting devices employing one or more aspects of the invention will be described below. Electron emitting devices may have various structures. For example, an electron emission structure used in a general side conduction electron emitter display (SED) may be employed and/or an electron emission structure using a metal insulator metal (MIM) may be employed. The invention is not limited to these examples.  
      One or more electron emitting devices may be employed in, e.g., as a display panel, e.g., PDP, or a backlight unit for a display panel, e.g., LCD. For example, as a display panel a plurality of electron emitting devices employing one more aspects of the invention may be arranged in, e.g., a matrix form, and an image(s) may be realized thereon by controlling voltages applied to electrodes thereof. Similarly, a plurality of such electron emitting devices may be arranged adjacent to each other so as to emit light to, e.g., an LCD.  
       FIG. 1  illustrates a schematic of a cross-sectional view of a first exemplary embodiment of an electron emitting device  100 .  
      Referring to  FIG. 1 , the electron emitting device  100  may include a first substrate  110 , a second substrate  120 , a plurality of barrier ribs  113 , a cell(s)  114 , a first electrode  131 , a second electrode  132 , a third electrode  133 , and an electron accelerating layer  140 . The electron emitting device  100  may emit electrons into the cell  114 . The electron emitting device  100  will be described in detail below.  
      The first substrate  110  and the second substrate  120  may face each other with a predetermined interval therebetween. The first substrate  110  and the second substrate  120  may have a high transmittance for visible light, and may be colored to improve bright room contrast. For example, the first substrate  110  and the second substrate  120  may be formed of, e.g., glass. Embodiments of the invention are not limited to such a structure. For example, in other embodiments of the invention, the first substrate  110  and the second substrate  120  may include plastic, and may have flexible structure.  
      The plurality of barrier ribs  113  may be formed between the first substrate  110  and the second substrate  120 . The barrier ribs  113 , together with the first and second substrates  110 ,  120 , may define the plurality of cells  114  in a space between the first substrate  110  and the second substrate  120 . The barrier ribs  113  may reduce and/or prevent electrical and optical cross talk from occurring between the cells  114 .  
      Display devices employing the electron emitting device  100  may include a plurality of light emitting layers  115 . The light emitting layers  115  may be disposed on an outer surface of the second substrate  120 . A unit pixel (not shown) of the display device may include one light emitting layer  115  capable of producing a primary color, e.g., a red light emitting layer, a blue light emitting layer, and a green light emitting layer. Each of the cells  114  may be associated with one of the light emitting layers  115 . For example, each of the cells  114  may be associated one of the red, green or blue light emitting layers  115 . For example, the red light emitting layer may be formed on a portion of the outer surface of the second substrate  120 , which corresponds to a red cell, the green light emitting layer may be formed on a portion of the outer surface of the second substrate  120 , which corresponds to a green cell, and the blue light emitting layer may be formed on a portion of the outer surface of the second substrate  120 , which corresponds to a blue cell.  
      In the description of exemplary embodiments herein, the light emitting layer  115  may correspond to a material layer that generates visible light in response to UV light. In embodiments of the invention, the light emitting layer  115  may include quantum dots.  
      A gas including N 2  may fill the cells  114 . If the gas is N 2 , the gas may generate UV light having long wavelengths. However, the invention is not limited to a gas including N 2 . For example, the gas may include various kinds of gases such as Xe. In the following description, the gas refers to a gas that is excited by external energy, .e.g., accelerated electrons, to generate the UV light. Also, the gas employed in one or more aspects of the invention may be employed as the discharge gas.  
      The first electrode  131  may be formed in each of the cells  114  on the first substrate  110 . The second electrode  132  may be formed in each cell  114  on a lower surface of the second substrate  120 , and may extend along a direction of crossing a direction along which the first electrode  131  extends. The first and second electrodes  131  and  132  may be a cathode and an anode, respectively. The second electrode  132  may include a transparent conductive material, e.g., an indium tin oxide (ITO). In addition, a dielectric layer (not shown) may be formed on the second electrode  132 .  
      The electron accelerating layer  140  may be formed on the first electrode  131 . The third electrode  133 , e.g., a grid electrode, may be formed on the electron accelerating layer  140 . The electron accelerating layer  140  may be formed of any material that can accelerate the electrons, and may include, e.g., oxidized porous silicon. More particularly, the oxidized porous silicon may be, e.g., oxidized porous poly silicon and/or oxidized porous amorphous silicon.  
      The electron accelerating layer  140  may include, e.g., carbon nanotube and/or boron nitride bamboo shoot (BNBS). The BNBS may include an sp 3  bonding 5H-BN, which is a material developed by National Institute for Material Science (NIMS) of Japan and was made public in March, 2004. BNBS is very hard and has a very stable structure. BNBS is harder than any other material, except for diamond. In addition, BNBS is transparent at or in a wavelength range of about 380 nm to about 780 nm, which is the visible light region, and BNBS has negative electron affinity. Therefore, the electron emitting property of the BNBS is very high (Handbook of refractory carbides and nitrides, Hugh O. Pierson, Noyes Publication, Table 13.6 P236, 1996).  
      A brief description of an operation of the electron emitting units  100  will be described below. When predetermined voltages are respectively applied to the first electrode  131  and the third electrode  133  (and/or the second electrode  132 ), the electron accelerating layer  140  may accelerate the electrons induced from the first electrode  131  and may emit the electrons into the cell  114  through the third electrode  133 . In the first exemplary embodiment, the electrons may be emitted as E-beams. The E-beams emitted into the cell  114  may excite the gas, and the excited gas may generate the UV light, while the gas may be stabilizing. The UV light may transmit through the second substrate  120 , before exciting the light emitting layer  115  to generate the visible light for realizing an image(s) on the display device employing the electron acceleration and emission unit  100 .  
      The E-beam may have an energy level that is larger than an energy level required to excite N 2  and smaller than an energy level required to ionize the gas. Therefore, voltages, having an electron energy, which may be optimized for exciting the gas using the E-beams, may be applied to the first electrode  131 , the third electrode  133 , and/or the second electrode  132 .  
       FIG. 2  illustrates a graph of an energy level of N 2 , which may be a source for generating UV light. Referring to  FIG. 2 , 16 eV is required to ionize N 2 , and 11 eV or more of energy is required to excite N 2 .  FIG. 3  illustrates a second positive band spectrum of the UV light that may be generated by excited species in N 2 . Referring to  FIG. 3 , the excited N 2  has peaks at 337 nm, 358 nm, and 381 nm, while stabilizing. Accordingly, the energy of the E-beam that may be emitted into the cell  114  by the electron accelerating layer  140  may be at or in a range of about 11 eV to about 16 eV in order to excite N 2 .  
       FIG. 4  illustrates a graph of transmittances of UV light according to the wavelengths of the UV light when the UV light is transmitted through first and second glass substrates. The first glass substrate may be transparent glass substrate, and may have a thickness of 2.8 mm. The second glass substrate may be formed on an inner surface of the first glass substrate in a predetermined pattern and may be formed of ITO. In addition, first curve f 1  in  FIG. 4  denotes the transmittance of the UV light transmitting the first glass substrate, and second curve f 2  of  FIG. 4  denotes the transmittance of the UV light transmitting the second glass substrate.  
      For example, in a case where the UV light has wavelengths of 337 nm, 358 nm, and 381 nm, the transmittances of the UV light through the second glass substrate are about 31%, 66%, and 73%, respectively. That is, the UV light generated by N 2  gas in the cells  114  can sufficiently excite the light emitting layers  115  formed on the second substrate  120 .  
       FIGS. 5A through 5D  illustrate waveforms of voltages that may be applied to the electrodes of the electron emitting device of  FIG. 1 .  
      Referring to  FIG. 5A , pulse type voltages may be respectively applied to the first, second, and third electrodes  131 ,  132 , and  133 . Assuming that the voltages applied to the first, second, and third electrodes  131 ,  132 , and  133  are V 1 , V 2 , and V 3 , respectively, the voltages may satisfy a relationship of V 1 &lt;V 3 &lt;V 2 . When the voltages are applied to the electrodes  131 ,  132 , and  133 , the E-beams (E-beam) may be emitted into the cells  114  by the electron accelerating layer  140 . The E-beams (E-beam) may be accelerated toward the second electrode  132  by the voltages applied to the third and second electrodes  133  and  132 , and the gas may be excited. The gas may be discharged by controlling the voltage applied to the second electrode  132 . In embodiments of the invention, the second electrode  132  may be grounded, as shown in  FIG. 5B . In such embodiments, the electrons reaching the second electrode  132  may escape outside of the cell  114 .  
      Referring to  FIG. 5C , assuming that the voltages applied to the first, second, and third electrodes  131 ,  132 , and  133  are V 1 , V 2 , and V 3 , in embodiments of the invention, the voltages may be set to satisfy a relationship of V 1 &lt;V 3 =V 2 . When the voltages V 1 , V 2 , V 3  are applied to the electrodes  131 ,  132 ,  133 , the E-beam (E-beam) may be emitted into the cells  114  through the electron accelerating layer  140  by the voltages V 1 , V 3  applied to the first and third electrodes  131  and  133 , and the gas may be excited by the E-beam (E-beam). The second and third electrodes  132  and  133  may be grounded, as shown in  FIG. 5D . In this case, the electrons reaching the second electrode  132  may escape to the outside of the cell  114 .  
      In the following description of other exemplary embodiments, in general, only differences from the first exemplary embodiment of the electron emitting device described above will be described.  
       FIG. 6  illustrates a schematic of a cross-sectional view of a second exemplary embodiment of an electron emitting device  100 ′. The electron emitting device  100 ′ substantially corresponds to the electron emitting device  100  illustrated in  FIG. 1 , but for employing a second electrode  132 ′ and a third electrode  133 ′ in lieu of the first electrode  132  and third electrode  133 . Referring to  FIG. 6 , the second electrode  132 ′ may be formed as a mesh so that visible light generated in the cell  114  may be transmitted therethrough. In such embodiments, the third electrode  133 ′ may also be formed as a mesh so that the electrons accelerated by the electron accelerating layer  140  may be easily emitted into the cell(s)  114 .  
       FIG. 7  illustrates a schematic of a cross-sectional view of a third exemplary embodiment of an electron emitting device  200 .  
      Referring to  FIG. 7 , the electron emitting device  200  may include a first substrate  210 , a second substrate  220 , a first electrode  231 , a second electrode  232 , a third electrode  233 , a fourth electrode  234 , a plurality of barrier ribs  213 , a cell  214 , a first electron adjusting layer  241 , and a second electron adjusting layer  242 .  
      The first substrate  210  and the second substrate  220  may extend parallel to each other with a predetermined distance therebetween. The plurality of barrier ribs  213  may be arranged in a space between the first and second substrates  210  and  220 , and together with the first and second substrates  210 ,  220  may define the cell(s)  214  between the first and second substrates  210  and  220 . A gas including N 2  may be filled in the cells  214 . If the gas is N 2 , the gas may generate UV light having a long wavelength.  
      The first electrode  231  may be formed in each cell(s)  214  on the first substrate  210 . The second electrode  232  may be formed in each of the cells  214  on a lower surface of the second substrate  220 , and the second electrode  232  may extend along a direction of crossing a direction along which the first electrode  231  extends. The first electron accelerating layer  241  and the second electron accelerating layer  242  may be formed on the first and second electrodes  231  and  232 , respectively. The third electrode  233  and the fourth electrode  234  may be formed on the first and second electron accelerating layers  241  and  242 , respectively.  
      The third electrode  233  and the fourth electrode  234  may be grid electrodes. The first and second electron accelerating layers  241  and  242  may include any material that may accelerate the electrons, and may include oxidized porous silicon. The oxidized porous silicon may be, e.g., oxidized porous poly silicon and/or oxidized porous amorphous silicon. The first and second electron accelerating layers  241  and  242  may include carbon nanotube and/or BNBS.  
      When predetermined voltages are applied to the first electrode  231 , the third electrode  233 , and/or the second electrode  232 , the first electron accelerating layer  241  may accelerate the electrons induced from the first electrode  231  to emit a first electron beam (E 1 -beam) into the cell  214  through the third electrode  233 . When predetermined voltages are applied to the second electrode  232 , the fourth electrode  234 , and/or the first electrode  231 , the second electron accelerating layer  242  may accelerate the electrons induced from the second electrode  232  to emit a second electron beam (E 2 -beam) into the cell  214  through the fourth electrode  234 .  
      The first and second electron beams (E 1 -beam, E 2 -beam) may be alternately emitted into the cell  214  because an alternating current (AC) voltage may be applied between the first and second electrodes  231  and  232 . Each of the first and second electron beams (E 1 -beam, E 2 -beam) may excite the gas, and the excited gas may generate the UV light that may excite the light emitting layer  215 , while the gas itself is stabilizing. Therefore, energy levels of the first and second electron beams (E 1 -beam, E 2 -beam) may be larger than the energy level required to excite the gas, and smaller than the energy level required to ionize the gas, as described above. As discussed above, the energy levels of the first and second electron beams (E 1 -beam, E 2 -beam) may be at or in a range of about 11 eV to about 16 eV.  
      The second and fourth electrodes  232  and  234  may include a transparent conductive material, e.g., ITO, so that the visible light may be transmit through the second and fourth electrodes  232  and  234 . The third and fourth electrodes  233  and  234  may be formed as meshes so that the electrons accelerated by the first and second electron accelerating layers  241  and  242  may be relatively easily emitted into the cell(s)  214 . One of the first substrate  210  and the second substrate  220  may further include one or more electrodes (not shown).  
      In embodiments of the invention employing the electron emitting device  200 , voltages illustrated in  FIGS. 8A and 8B  and described below, may be applied to the electrodes of the electron emitting device  200 .  
      Display devices employing the electron emitting device  200  may include a plurality of light emitting layers  215  and multiple ones of the cells  214 . The light emitting layer  215 , e.g., red, green, or blue light emitting layer, corresponding to each of the cells  214 , e.g., red, green or blue cell, may be arranged on a corresponding portion of an outer surface of the second substrate  220 .  
       FIGS. 8A and 8B  illustrate waveforms of voltages that may be applied to electrodes of the electron emitting device  200  illustrated in  FIG. 7 .  
      Referring to  FIG. 8A , pulse type voltages may be applied to the first, second, third, and fourth electrodes  231 ,  232 ,  233 , and  234 , respectively. Assuming that the voltages applied to the first, second, third, and fourth electrodes  231 ,  232 ,  233 , and  234  are V 1 , V 2 , V 3 , and V 4 , the voltages may satisfy relationships of V 1 &lt;V 3  and V 2 &lt;V 4 . When the voltages V 1 , V 2 , V 3 , V 4  are applied to the electrodes  231 ,  232 ,  233 ,  234 , the first electron beam (E 1 -beam) may be emitted into the cell  214  through the first electron accelerating layer  241  as a result of the voltages V 1 . V 3  and/or V 2  that may be respectively applied to the first electrode  231 , the third electrode  233 , and/or the second electrode  232 . The second electron beam (E 2 -beam) may be emitted into the cell  214  through the second electron accelerating layer  242  by the voltages V 2 , V 4  and/or V 1  that may be respectively applied to the second electrode  232 , the fourth electrode  234 , and/or the first electrode  231 . Because an AC voltage may be applied between the first electrode  231  and the second electrode  232 , the first and second electron beams (E 1 -beam, E 2 -beam) may be alternately into the cell  213  and excite the gas. As illustrated in  FIG. 8B , the third and fourth electrodes  233  and  234  may be grounded.  
       FIG. 9  illustrates a schematic of a cross-sectional view of a fourth exemplary embodiment of an electron emitting device  300 .  
      Referring to  FIG. 9 , the electron emitting device  300  may include a first substrate  310 , a second substrate  320 , pairs of first electrodes  331  and second electrodes  332 , third electrodes  333 , fourth electrodes  334 , a cell(s)  314 , first and second electron accelerating layers  341 ,  342 , and a dielectric layer  312 . The electron emitting device  300  may also include an address electrode  311 . The first substrate  310  and the second substrate  320  may face each other with a predetermined space therebetween.  
      One or more of the cell(s)  314  may be defined in the space between the first and second substrates  310 ,  320 . The respective address electrodes  311  may be formed on the first substrate  310 , and the address electrodes  311  may be embedded in the dielectric layer  312 . A gas including N 2  may be filled in the cells  314 . If the gas is N 2 , the gas may generate UV light having a long wavelength.  
      The pair of first and second electrodes  331  and  332  may be formed in each cell  314  between the first and second substrates  310  and  320 . The first and second electrodes  331  and  332  may be respectively disposed on opposing sides of the cell  314  extending between the first and second substrates  310 ,  320 . The first electron accelerating layer  341  and the second electron accelerating layer  342  may be formed on inner surfaces of the first and second electrodes  331  and  332 . The third electrode  333  and the fourth electrode  334  may be formed on the first and second electron accelerating layers  341  and  342 .  
      The first and second electron accelerating layers  341  and  342  may include any material that may accelerate the electrons, and may include oxidized porous silicon. The oxidized porous silicon may be, e.g., oxidized porous poly silicon or oxidized porous amorphous silicon. The first and second electron accelerating layers  341  and  342  may include carbon nanotube and/or BNBS.  
      The third and fourth electrodes  333  and  334  may be formed as meshes so that the electrons accelerated by the first and second electron accelerating layers  341  and  342  may be relatively easily emitted into the cells  314 . The first and second electron accelerating layers  341  and  342  may define the space between the first and second substrates  310  and  320 , and thus, together with the first and second substrates  310 ,  320  may define the cell(s)  314 . A plurality of barrier ribs (not shown) may be formed between the first and second substrates  310  and  320  to define the space between the first and second substrates  310  and  320  and form the cells  314 .  
      The first electron accelerating layer  341  may emit a first electron beam (E 1 -beam) into the cell  314  when predetermined voltages are respectively applied to the first electrode  331 , the third electrode  333 , and/or the second electrode  332 . The second electron accelerating layer  342  may emit a second electron beam (E 2 -beam) into the cell  314  when the predetermined voltages are respectively applied to the second electrode  332 , the fourth electrode  334 , and/or the first electrode  331 . The first and second electron beams (E 1 -beam, E 2 -beam) may be alternately emitted into the cell  314  because an AC voltage may be applied between the first electrode  331  and the second electrode  332 .  
      Each of the first and second electron beams (E 1 -beam, E 2 -beam) may excite the gas, and the excited gas may generate the UV light that may excite the light emitting layer  314 , while the gas itself is stabilized. As discussed above, energy levels of the first and second electron beams (E 1 -beam, E 2 -beam) may be larger than the energy level required to excite the gas, and may be smaller than the energy level required to ionize the gas. More particularly, as described above, the energy levels of the first and second electron beams (E 1 -beam, E 2 -beam) may be at or in a range of about 11 eV to about 16 eV.  
      Display devices employing the electron emitting device  300  may include multiple ones of the cells  314 , and a plurality of light emitting layers  315 . The light emitting layers  315  may be disposed on a corresponding outer surface of the second substrate  320 . A unit pixel (not shown) of the display device may include one light emitting layer  315  capable of producing a primary color, e.g. a red light emitting layer, a blue light emitting layer, and a green light emitting layer. Each of the cells  314  may be associated with one of the light emitting layers  315 .  
      In embodiments of the invention employing the electron emitting device  300 , the voltages illustrated in  FIGS. 8A and 8B  and described above, may be applied to the electrodes of the electron emitting device  300 .  
       FIG. 10  illustrates a schematic of cross-sectional view of a fifth exemplary embodiment of an electron emitting device  400 .  
      Referring to  FIG. 10 , the electron emitting device  400  may include a first substrate  410 , a second substrate  420 , a first electrode  431 , a second electrode  432 , a third electrode  433 , a plurality of barrier ribs  413 , a cell  414 , a first electron accelerating layer  441 , and a second electron accelerating layer  442 . The electron emitting device  400  may also include an address electrode  411 . The first substrate  410  and the second substrate  420  may be arranged parallel to each with a predetermined space therebetween. The plurality of barrier ribs  413  may be arranged between the first substrate  410  and the second substrate  420 . Together with the first substrate  410  and the second substrate  420 , the plurality of barrier ribs  413  may define the cell(s)  414  between the first and second substrates  410  and  420 .  
      A gas including N 2  may be filled in the cells  414 . If the gas is N 2 , the gas may generate UV light having a long wavelength.  
      The address electrode  411  may be formed on the first substrate  410 , and the address electrode  411  may be covered by a dielectric layer  412 . The pair of the first electrode  431  and the second electrode  432  may be formed at each cell  414  on a lower surface of the second substrate  420 . The first and second electrodes  431  and  432  may be formed in a direction crossing a direction along which the address electrode  411  extends.  
      In addition, the first electron accelerating layer  441  and the second electron accelerating layer  442  may be formed on lower surfaces of the first and second electrodes  431  and  432 . The third electrode  433  and the fourth electrode  434  may be formed on lower surfaces of the first and second electron accelerating layer  441  and  442 . The first and second electron accelerating layer  441  and  442  may include any material that can accelerate the electrons, and may include oxidized porous silicon. The oxidized porous silicon may be, e.g., oxidized porous poly silicon or oxidized porous amorphous silicon. In addition, the first and second electron accelerating layers  441  and  442 , and/or may include carbon nanotube or BNBS.  
      When predetermined voltages are applied to the first electrode  431 , the third electrode  433 , and/or the second electrode  432 , the first electron accelerating layer  441  may emit a first electron beam (E 1 -beam) into the cell  414 . When predetermined voltages are applied to the second electrode  431 , the fourth electrode  434 , and/or the first electrode  431 , the second electron accelerating layer  442  may emit a second electron beam (E 2 -beam) into the cell  414 . The first and second electron beams (E 1 -beam, E 2 -beam) may be alternately emitted into the cell  414  because the AC voltage may be applied between the first and second electrodes  431  and  432 .  
      Each of the first and second electron beams (E 1 -beam, E 2 -beam) may excite the gas, and the excited gas may generate the UV light that excites the light emitting layer  415 , while the gas itself is stabilizing. Therefore, as discussed above, the energy levels of the first and second electron beams (E 1 -beam, E 2 -beam) may be larger than the energy level required to excite the gas, and smaller than the energy level required to ionise the gas. More particularly, as described above, the energy levels of the first and second electron beams (E 1 -beam, E 2 -beam) may be at or in a range of about 11 eV to about 16 eV.  
      The first, second, third, and fourth electrodes  431 ,  432 ,  433 , and  434  may include a transparent conductive material, e.g., ITO, so that the visible light may be transmitted through the first, second, third and/or fourth electrodes  431 ,  432 ,  433 ,  434 . The third and fourth electrodes  433  and  434  may be formed as meshes so that the electrons accelerated by the first and second electron accelerating layers  441  and  442  may be relatively easily emitted into the cells  414 .  
      In embodiments of the invention employing the electron emitting device  400 , the voltages illustrated in  FIGS. 8A and 8B  and described above, may be applied to the electrodes of the electron emitting device  400 .  
      Display devices employing the electron emitting device  400  may include multiple ones of the cells  414 , and a plurality of light emitting layers  415 . The light emitting layers  415  may be disposed on a corresponding outer surface of the second substrate  420 . A unit pixel (not shown) of the display device may include one light emitting layer  415  capable of producing a primary color, e.g. a red light emitting layer, a blue light emitting layer, and a green light emitting layer. Each of the cells  414  may be associated with one of the light emitting layers  415 .  
       FIG. 11  illustrates a schematic of a cross-sectional view of a sixth exemplary embodiment of an electron emitting device  500 .  
      Referring to  FIG. 11 , the electron emitting device  500  may include a first substrate  510 , a second substrate  520 , a cell  514 , a first electrode  531 , a pair of second electrodes  532 , a first electron accelerating layer  541 , and a second electron accelerating layer  542 . The first substrate  510  and the second substrate  520  may be arranged parallel to each with a predetermined space therebetween. The cell(s)  514  may be defined in the space between the first and second substrates  510 ,  520 . A gas including N 2  may fill the cell(s)  514 . If the gas is N 2 , the gas may generate UV light having a long wavelength.  
      The first electrode  531  and the pair of second electrodes  532  may be formed in each of the cells  514  between the first and second substrates  510 ,  520 . The first electrode  531  may be disposed on an upper surface of the first substrate  510 , and the second electrodes may be disposed on both sides of the cell  514 . The first electrode  531  may extend along a direction that crosses a direction along which the second electrodes  532  extend.  
      A first electron accelerating layer  541  and a second electron accelerating layer  542  may be formed on inner surfaces of the first and second electrodes  531  and  532 . A third electrode  533  and a fourth electrode  534  may be formed on the first and second electron accelerating layers  541  and  542 . The first and second electron accelerating layers  541  and  542  may include any material that may accelerate the electrons, and may include oxidized porous silicon. The oxidized porous silicon may be, e.g., oxidized porous poly silicon and/or oxidized porous amorphous silicon. The first and second electron accelerating layers  541  and  542  may include carbon nanotube and/or BNBS.  
      When predetermined voltages are applied to the first electrode  531 , the third electrode  533  and/or the second electrode  532 , the first electron accelerating layer  541  may emit a first electron beam (E 1 -beam) into the cell  514 . When predetermined voltages are applied to the second electrode  532 , the fourth electrode  534 , and/or the first electrode  531 , the second electron accelerating layer  542  may emit a second electron beam (E 2 -beam) into the cell  514 . The first and second electron beams (E 1 -beam, E 2 -beam) may be alternately emitted into the cell  514  because the AC voltage may be applied between the first and second electrodes  531  and  532 . Each of the first and second electron beams (E 1 -beam, E 2 -beam) may excite the gas, and the excited gas may generate the UV light that excites the light emitting layer  515 , while the gas itself is stabilizing. As discussed above, the energy levels of the first and second electron beams (E 1 -beam, E 2 -beam) may be larger than the energy level required to excite the gas, and smaller than the energy level required to ionise the gas. More particularly, as discussed above, the energy levels of the first and second electron beams (E 1 -beam, E 2 -beam) may be at or in a range of about 11 eV to about 16 eV.  
      The third and fourth electrodes  533  and  534  may be formed as meshes so that the electrons accelerated by the first and second electron accelerating layers  541  and  542  may be easily emitted into the cell  514 . The second electron accelerating layers  542  may define the space between the first and second substrates  510  and  520 , and thus, together with the first and second substrates  510 ,  520  may define the cells  514 . A plurality of barrier ribs (not shown) may be formed between the first and second substrates  510  and  520  to define the space between the first and second substrates  510 ,  520  and to form the cells  514  may be further disposed between the first and second substrates  510  and  520 .  
      In embodiments of the invention employing the electron emitting device  500 , the voltages illustrated in  FIGS. 8A and 8B  and described above, may be applied to the electrodes of the electron emitting device  500 .  
      Display devices employing the electron emitting device  500  may include multiple ones of the cells  514 , and a plurality of light emitting layers  515 . The light emitting layers  515  may be disposed on a corresponding outer surface of the second substrate  520 . A unit pixel (not shown) of the display device may include one light emitting layer  515  capable of producing a primary color, e.g. a red light emitting layer, a blue light emitting layer, and a green light emitting layer. Each of the cells  514  may be associated with one of the light emitting layers  515 .  
      The display device according to the invention can be applied to a flat panel lamp that is mainly used as a back light unit of a liquid crystal display (LCD).  
       FIG. 12  illustrates a schematic of a cross-sectional view of a seventh exemplary embodiment of an electron emitting device.  
      Referring to  FIG. 12 , a first substrate  610 , a second substrate  620 , a cell  614 , spacers  613 , a first electrode  631 , a second electrode  632 , a third electrode  633 , and an electron accelerating layer  640 . The first substrate  610  and the second substrate  620  may be arranged parallel to each other with a predetermined distance therebetween. The first and second substrates  610  and  620  may be, e.g., glass substrates. The spacers  613  may be formed between the first and second substrates  610  and  620 , and together with the first and second substrates  610 ,  620  may define the cell(s)  614 .  
      A gas including N 2  may be filled in the cells  614 . If the gas is N 2 , the gas may generate UV light having long wavelengths.  
      The first electrode  631  corresponding to the cell(s)  614  may be formed on an upper surface of the first substrate  610 , and the second electrode  632  corresponding to cell(s)  614  may be formed on a lower surface of the second substrate  620  parallel to the first electrode  631 . The first and second electrodes  631  and  632  may be a cathode and an anode, respectively. The second electrode  632  may be formed of a transparent conductive material, e.g., ITO, so that the visible light may transmit the second electrode  632 . In embodiments of the invention, the second electrode  632  may be formed as a mesh. The electron accelerating layer  640  may be formed on the upper surface of the first electrode  631 , and the third electrode  633  may be formed on the electron accelerating layer  640 . The electron accelerating layer  640  may include any material that may accelerate the electrons, and may include, e.g., oxidized porous silicon. The oxidized porous silicon may be, e.g., oxidized porous poly silicon and/or oxidized porous amorphous silicon. The electron accelerating layers  640  may include, e.g., carbon nanotube or BNBS.  
      When predetermined voltages are applied to the first electrode  631 , the third electrode  633 , and/or the second electrode  632 , the electron accelerating layer  640  may accelerate the electrons induced from the first electrode  631  to emit electron beam (E-beam) into the cell  614  through the third electrode  633 . The electron beam (E-beam) emitted into the cell  614  may excite the gas in the cell  614 , and the excited gas may generate UV light while the gas is stabilizing. The UV light may excite the light emitting layer  615  to generate visible light. The third electrode  633  may be formed as a mesh so that the electrons accelerated by the electron accelerating layer  649  may be emitted into the cell  614 .  
      As described above, the energy level of the electron beam (E-beam) may be larger than the energy level required to excite the gas, and smaller than the energy level required to ionize the gas. More particularly, as described above, the energy level of the electron beam (E-beam) may be at and/or in a range of about 11 eV to about 16 eV.  
      In embodiments of the invention employing the electron emitting device  600 , the voltages illustrated in  FIGS. 8A and 8B  and described above, may be applied to the electrodes of the electron emitting device  600 .  
      Display devices employing the electron emitting device  600  may include multiple ones of the cells  614 , and a plurality of light emitting layers  615 . The light emitting layers  615  may be disposed on a corresponding outer surface of the second substrate  620 . A unit pixel (not shown) of the display device may include one light emitting layer  615  capable of producing a primary color, e.g. a red light emitting layer, a blue light emitting layer, and a green light emitting layer. Each of the cells  614  may be associated with one of the light emitting layers  615 .  
      Embodiments of the invention provide electron emitting devices that may be capable of emitting light for displaying images on a display device without needing to ionize a gas housed in cell(s) of the display device. That is, embodiments of the invention may provide electron emitting devices that may be capable of emitting light for displaying images on the display device while only exciting the light emitting material/gas housed in the cell(s). Therefore, embodiments of the invention may enable the driving voltage of a device, e.g., display device or flat lamp, employing such an electron emitting device to be lowered, while improving brightness and luminous efficiency of the device.  
      Embodiments of the invention may employ N 2  gas, as the gas that may fill the cell(s). Thus, embodiments of the invention enable costs for manufacturing, e.g., a display device, and/or a flat lamp, to be reduced and a manufacturing method thereof to be simplified.  
      Embodiments of the invention may enable UV light having long wavelength(s) to be generated, and thus, a transport efficiency of the UV light and the efficiency of the respective light emitting material may be improved, and the display process may be performed with high efficiency. For example, if UV light having a wavelength of 330 nm or longer is used to excite the gas, a stokes efficiency of the light emitting material may be about two times higher than that of using the UV light having a wavelength of 147 nm. Also, transmittance of the UV light through the first and second substrates may be improved.  
      Exemplary embodiments of the invention have been disclosed herein, and although specific terms are employed, they are used and are to be interpreted in a generic and descriptive sense only and not for purpose of limitation. Accordingly, it will be understood by those of ordinary skill in the art that various changes in form and details may be made without departing from the spirit and scope of the invention as set forth in the following claims.