Abstract:
The present invention relates to a field emission device and an electrode structure thereof, comprising a starting base and a curved extending part formed on a surface of various shaped or dimensional structure. Therefore, the applied device and range is increased. The curved extending part is also for reducing the number of the contact point, as to simplify the procedure to design the peripheral circuit. Besides, a resisting section can be formed on the starting base. The resisting value of the resisting section is designed to provide various lighting effects.

Description:
RELATED APPLICATIONS 
       [0001]    The present application is based on, and claims priority from, Taiwan Application Number 096125373, filed Jul. 12, 2007, the disclosure of which is hereby incorporated by reference herein in its entirety. 
       BACKGROUND OF THE INVENTION 
       [0002]    1. Field of the Invention 
         [0003]    The present invention relates to a field emission device and an electrode structure thereof and, more particularly, to a field emission device and an electrode structure thereof suitable for displaying or illuminating. 
         [0004]    2. Description of Related Art 
         [0005]    In current light-emitting devices, a field emission device is favored due to its stable structure and uniform luminance. The field emission device can apply to various electric structures, such as a lamp, a display device, or a back light module. 
         [0006]    The luminance mechanism of the field emission device is that an electric potential is applied to the gate electrode to draw electrons out of the cathode, and the electrons are attracted and accelerated by the electric potential at the anode to bombard the fluorescence material coated on the anode so that the fluorescence material, absorbing partial energy of the electrons, is excited to generate light. 
         [0007]    Conventionally, cathodes of a field emission device are formed into the shape of plural separated bars consisting of an electron source material on a cathode base, and gate electrodes consisting of a conductive material is formed into the shape of plural bars at the periphery of the cathodes. Therefore, a driving circuit can transmit different driving signals to each cathode and gate electrode individually for controlling their electric potentials, such that the cathodes can emit electrons and a fluorescence material can generates light. Unfortunately, since the electron sources or the gate electrodes are plural and separated the number of electric contacts is increased so as to complicate the driving circuit. This problem is a large obstacle to the manufacturing of a field emission device. 
       SUMMARY OF THE INVENTION 
       [0008]    The object of the present invention is to provide an electrode structure of a field emission device for decreasing electric contacts so that the circuit design can be simplified. 
         [0009]    Another object of the present invention is to provide an electrode structure of a field emission device suitable for being applied to various shapes of surfaces or stereo-structures. 
         [0010]    The other object of the present invention is to provide an electrode structure of a field emission device for improving the illumination uniformity of the field emission device. 
         [0011]    To achieve the objects, an electrode structure of a field emission device of the present invention includes a starting base and at least one extending part. The extending part connects to the starting base, and the extending part is winding-shaped. 
         [0012]    To achieve the objects, a field emission device of the present invention includes an anode and a cathode. The cathode is disposed corresponding to the anode. The cathode comprises a starting base and at least one extending part, wherein the extending part connecting to the starting base is winding-shaped. 
         [0013]    When electric potentials of reverse parity are individually applied to the anode and the cathode of the field emission device, electrons emitted from the cathode to the anode. However, the field emission device comprising a fluorescence material is preferred because the fluorescence material illuminates light as the electrons bombard the fluorescence material. Moreover, the field emission device can further comprises a gate electrode disposed at the periphery of the cathode. The electric potential applied to the gate electrode controls whether the electrons emit from the cathode or not. Also, the gate electrode can comprises a starting base and an extending part, wherein the extending part connecting to the starting base is winding-shaped. 
         [0014]    The electrode structure can be an electron source or a gate electrode. In addition, the electrode structure can be formed on various shapes of a surface or a surface of a stereo-structure, such as a plane surface in the shape of a circle, an ellipse or a polygon, or a surface of a stereo-structure in the shape of a sphere, a hemisphere or a cylinder. Hence, the winding-shaped extending part can reduce the number of the electric contacts so as to simplify the design of the peripheral circuit. 
         [0015]    The electrode structure can be made of any conventional material. Preferably, the electrode structure is made of an electron source material or a conductive material. The electron source material can be any material with low work function, such as silicon, metal or carbonic material. Preferably, the electron source material is polysilicon, molybdenum, niobium, wolfram, diamond film, carbon nanotube or graphite. The conductive material can be metal, such as silver or gold. 
         [0016]    The shape of the starting base is not limited. Preferably, the starting base is in the shape of a bar. The shape of the extending part is not limited. Preferably, the extending part is in the shape of an arc, a circle or a spiral, such as circular spiral or polygon spiral. The number of the extending parts is not limited. Preferably, the number of the extending parts is more than one. 
         [0017]    As the electrode structure is functioning as a cathode, the electrode structure emits electrons under an electric field. As the electrode structure is functioning as a gate electrode, a positive potential is applied to its starting base. In addition, the starting base of the gate electrode can further comprises a resistance disposed between two extending parts of the gate electrode. Preferably, the resistance is made of a material with low resistance value. Therefore, the decrease of the electric potential caused by the increase of the transmitting path at two extending parts can be compensated, and the illumination uniformity of the field emission device is improved. 
         [0018]    The field emission device of the present invention comprising at least one winding-shaped extending part or plural extending parts connected to each other can be formed on a plan surface, a curved surface or a surface of a stereo-structure. Accordingly, the number of the electric contacts is reduced so as to simplify the design of the circuit. In addition, each part of the electrode structure can further comprises a resistance with different resistance value for compensating the decrease of the electric potentials at each part of the electrode structure so that the illumination uniformity of the field emission device can be improved. 
         [0019]    Still other objects and advantages of the present invention will become readily apparent to those skilled in the art from the following detailed description, wherein the preferred embodiments of the invention are shown and described, simply by way of illustration of the best mode contemplated of carrying out the invention. As will be realized, the invention is capable of other and different embodiments, and its several details are capable of modifications in various obvious aspects, all without departing from the invention. Accordingly, the drawings and description thereof are to be regarded as illustrative in nature, and not as restrictive. 
     
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
         [0020]    The present invention is illustrated by way of example, and not by limitation, in the figures of the accompanying drawings, wherein elements having the same reference numeral designations represent like elements throughout and wherein: 
           [0021]      FIG. 1  is a schematic drawing of the field emission device according to a preferred embodiment of the present invention; 
           [0022]      FIG. 2  is a schematic drawing of the cathode of the field emission device according to a preferred embodiment of the present invention; 
           [0023]      FIG. 3  is a schematic drawing the cathode according to another preferred embodiment of the present invention; 
           [0024]      FIG. 4  is a schematic drawing the cathode according to the other preferred embodiment of the present invention; 
           [0025]      FIG. 5  is a schematic drawing the cathode according to the other preferred embodiment of the present invention; and 
           [0026]      FIG. 6  is a schematic drawing the cathode according to the other preferred embodiment of the present invention. 
       
    
    
     DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENT 
       [0027]    With reference to  FIG. 1  and  FIG. 2 ,  FIG. 1  shows a schematic drawing of a field emission device according to the first preferred embodiment of the present invention, and  FIG. 2  shows a schematic drawing of the cathode of this embodiment. As shown in  FIG. 1  and  FIG. 2 , field emission device  1  comprises an anode  11  and a cathode  12  corresponding to the anode  11 . In this embodiment, the anode  11  made of a transparent conducting-material, indium-tin oxide (ITO), is applied with a positive potential. A fluorescence material radiating visible light is coated on the anode  11 . Moreover, the space between the anode  11  and the cathode  12  is at a low-pressure environment near a vacuum such that the pollution of and the damage to the anode  11  and the cathode  12  caused by impurities can be prevented. In this embodiment, the pressure of the space is maintained below 10 −6  torr. 
         [0028]    The cathode  12  comprises a substrate  121 , an electron source  122  and a gate electrode  123 , wherein the electron source  122  and the gate electrode  123  is formed on the substrate  121 , and the electron source  122  is located corresponding to the anode  11 . In this embodiment, the substrate  121  is a glass substrate. The electron source  122  is made of an electron source material. Precisely, the electron source  122  of this embodiment is made of carbon nanotube (CNT). In addition, the gate electrode  123  made of conducting-material is disposed at the periphery of the electron source  122 . In this embodiment, the gate electrode  123  is formed by screen-printing metal slurry on a surface of the substrate  121 . 
         [0029]    The electron source  122  comprises a starting base  1221  and an extending part  1222  connecting to the starting base  1221 . In this embodiment, the starting base  1221  of the electron source  122  is in the shape of a bar. Most importantly, the extending part  1222  is winding-shaped. In this embodiment, the extending part  1222  is in the shape of a circular spiral. Also, the shape of the gate electrode  123  is a combination of a bar and a circular spiral. The extremities of the electron source  122  and the gate electrode  123 , i.e. the electric contact A of the starting base  1221  of the electron source  122 , the electric contact B of the extending part  1222  of the electron source  122 , the electric contact A of the gate electrode  123  and the electric contact B of the gate electrode  123 , electrically connects to a driving circuit (not shown) through circuit  124 A,  124 B,  125 A and  125 B. Hence, the driving circuit, connecting to the electric contacts A and B through the circuit  124 A,  124 B,  125 A and  125 B that passing through the cathode  12 , can control the electric potential of the electron source  122  and the gate electrode  123 . As the electric potential of the anode  11  is positive and the electric potential of the electron source  122  is zero, negative, or below the electric potential of the anode  11 , the potential deference between the anode  11  and the electron source  122  is large enough for the electron source  122  to emit electrons toward the anode  11 , such that the fluorescence material  111  illuminates light. On the other hand, the electron source  122  emits no electrons as the electric potential of the electron source  122  is high and the potential deference between the anode  11  and the electron source  122  is not large enough for the electron source  122  to emit electrons, such that fluorescence material  111  illuminates no light. In addition, the gate electrode  123  is used to reduce the electric potential of the gate electrode  123  for improving illumination uniformity. In this embodiment, the effect of controlling luminance as mentioned above can be achieved when the electron source  122 , as well as gate electrode  123 , connects to the driving circuit through two electric contacts A and B. Therefore, the design of the driving circuit can be simplified. 
         [0030]      FIG. 3  shows the schematic drawing of the cathode according to the second preferred embodiment of the present invention. As shown in  FIG. 3 , it can tell several differences between the cathode of this embodiment and the first preferred embodiment. Firstly, in this embodiment, each of the extending part  1222  of the electron source  122 , formed on the square cathode  12 , is in the shape of a quadrilateral spiral. The extending parts  1222 &#39;s number is four and they are arranged in a matrix. Secondly, at least one gate electrode  123  is formed at two sides of the periphery of the electron source  122  for increasing the electric field. Thirdly, the driving circuit (not shown) electrically connecting to the electron source  122  and the gate electrode  123  controls four electron sources  122  to emit electrons at different time alternately or at the same time so that various illumination effect can be achieved. 
         [0031]      FIG. 4  shows the schematic drawing of the cathode  12  according to the third preferred embodiment of the present invention. In this embodiment, the cathode  12  comprises a substrate  121 , an electron source  122  and a gate electrode  123 . As shown in  FIG. 4 , it can tell several differences between the cathode of this embodiment and the first preferred embodiment. Firstly, there are plural extending parts  1223 ,  1224  and  1225  connects to the starting base  1221  of the electron source  122 , and the shapes of these extending parts  1223 ,  1224  and  1225  are arcs or circles. Secondly, the gate electrode  123  comprises a starting base  1231  and plural extending parts  1232  and  1233 , and the shapes of these extending parts  1232  and  1233  are arcs. Thirdly, a resistance  1234  is formed between the extending parts  1232  and  1233  of the gate electrode  123 . The resistance  1234  is made of a material with low resistance value. In this embodiment, the resistance  1234  is manufactured using ruthenium oxide by screen-printing. Also, the resistance  1234 , as shown in  FIG. 4 , can be manufactured using other resistance material by other method, such as inkjet-printing, vapor deposition, or sputtering. Accordingly, the decrease of the electric potential caused by the increase of the transmitting path of circuits can be compensated so that the electric potentials of the extending part  1232  and the extending part  1233  are getting closer. Therefore, the electric field applied to the extending parts  1223 ,  1224  and  1225  of the electron source  122  is similar, and the illumination uniformity of the field emission device is improved. Moreover, the resistance value of the resistance  1234  can be modified depending on the desired illumination effect. For instance, the modification of the resistance value of the resistance  1234  can cause the extending part  1232  and the extending part  1233  of the electron source  122  to have different electric potentials. Hence, this electron source  122  is suitable to be used in a field emission device with gradient illuminating-light. 
         [0032]      FIG. 5  shows the schematic drawing of the field emission device according to the fourth preferred embodiment of the present invention. As shown in  FIG. 5 , the difference between this embodiment and the first preferred embodiment is that the electron source  122  and the gate electrode  123  are formed on the surface of a sphere. In other words, the substrate  121  of the cathode  12  is a sphere.  FIG. 6  shows the schematic drawing of the field emission device according to the fifth preferred embodiment of the present invention. 
         [0033]    As shown in  FIG. 6 , the difference between this embodiment and the fifth preferred embodiment is that the electron source  122  and the gate electrode  123  are formed on the surface of a sphere. In other words, the substrate  121  of the cathode  12  is a cylinder substrate  121 . Accordingly, the electrode structure of the present invention can be formed on various shapes of surface and stereo-structure. 
         [0034]    To sum up, the field emission device, as well as the electrode structure thereof, of the present invention comprises a starting base and a winding-shaped extending part. Therefore, the electrode structure can be formed on various shapes of surface and stereo-structure so that its application scope is increased. In addition, the winding-shaped extending part can decrease the number of electric contacts. Accordingly, the design of the peripheral circuit can be simplified and put into practice easily. Moreover, the starting base can further comprise a resistance. Through the modification of the resistance value, different illumination effect can be achieved. 
         [0035]    Although the present invention has been explained in relation to its preferred embodiment, it is to be understood that many other possible modifications and variations can be made without departing from the scope of the invention as hereinafter claimed. 
         [0036]    It will be readily seen by one of ordinary skill in the art that the present invention fulfils all of the objects set forth above. After reading the foregoing specification, one of ordinary skill in the art will be able to affect various changes, substitutions of equivalents and various aspects of the invention as broadly disclosed herein. It is therefore intended that the protection granted hereon be limited only by definition contained in the appended claims and equivalents thereof.