STRUCTURE OF ELECTRONIC CANYON CATHEDRAL FOR CATHODE RAY PIPE BACKGROUND OF THE INVENTION The present invention relates to a cathode structure of an electron gun for a cathode ray tube (CRT) and more particularly to a cathode ray tube. which adopts a field emission device. A directly or indirectly heated cathode is used as a source of thermonion emission in the CRT (cathode ray tube) of existing monitors and televisions. Since the thermionic emission material of the conventional cathode structure is heated by a special heating source to emit thermions (charged particle emitted by a hot body) certain inherent problems arise. First, the normal period for emitting the thermoions is relatively long because the thermionic emission material is heated after the support elements are heated to hold the thermionic emission material with the heat generated by a heating source. Therefore, the time required to form an image on the cathode ray tube is increased, for example up to 8 to 9 seconds. Second, there is a phenomenon of thermal deviation due to the thermal expansion of the support element to hold the thermionic emission material. REF: 25158 Thirdly, an energy consumption of between 2 and 4 Watts is required to heat the thermionic emission material. To overcome the aforementioned problems, a cathode structure adopting a field emission device has been devised. With reference to Figure 1, the cathode structure comprises an electrode element 11, an insulating element 12 combined with the electrode element 11 and a cell 20 installed on the insulating element 12 and having field emission devices. As shown in Figures 2 and 3, the cell 20 comprises a substrate 21 and three cathode layers 22 formed in a predetermined configuration on the substrate 21. A plurality of metal tips 23 for emitting electron beams corresponding to the signals of the green, red and blue are formed on layer 22 of the cathode. Each of the metal tips 23 are insulated from one another by an insulating layer 24 having holes 24a and a layer 25 of the gate electrode, which has gates 25a through which the metal tips 23 are exposed, formed on top of them. of the insulating layer 24. In the operation of the conventional cathode structure as constituted above, the amount of electrons emitted from the metal tips 23 is controlled by applying negative or zero voltages to the cathode layer 22 and a positive voltage to the cathode layer 22. the layer 25 of the gate electrode. Also, since the layer 25 of the gate electrode is formed on the total surfaces of the substrate 21, the control signal is distorted by the capacitance between the layer 25 of the gate electrode and the cathode layer 22.
BRIEF DESCRIPTION OF THE INVENTION In order to solve the above problems, it is an object of the present invention to provide a cathode structure of an electron gun for a cathode ray tube (CRT) in which the distortion of a control signal to control a beam The electrons emitted from the metal tips can be prevented by reducing the capacitance between a gate electrode and a cathode electrode. Therefore, to achieve the above object, a cathode structure of an electron gun for a cathode ray tube (CRT) comprising a substrate is provided; cathode electrode layers formed on the substrate, spaced at predetermined intervals; a plurality of metal tips for emitting electrons, formed on the upper surface of the cathode electrode layer; an insulating layer formed on the cathode electrode layer and the substrate to isolate each of the metal tips from each other; a first layer of the gate electrode formed on top of the insulating layer where the metal tips are formed and which have gates through which the metal tips are exposed; and a second layer of the gate electrode formed on top of the insulating layer, which extends hopzontally from the first layer of the gate electrode and divided into several parts of a space therebetween. Also, it is preferable that a conductive portion of the cathode connected to the cathode electrode layer is formed between the insulating layer where the space is located.
BRIEF DESCRIPTION OF THE DRAWINGS The above objects and advantages of the present invention will become more apparent when describing in detail a preferred embodiment thereof with reference to the accompanying drawings in which: Figure 1 is an exploded perspective view illustrating a conventional cathode structure of an electron gun for a cathode ray tube (CRT); Figure 2 is a plan view illustrating a cell of the cathode structure of an electron gun for the cathode ray tube shown in Figure 1; Figure 3 is a sectional view taken along the line lll- Ill of Figure 2; Figure 4 is a plan view illustrating a cell of a cathode structure of an electron gun for a cathode ray tube according to the present invention; Figure 5 is a sectional view taken along the line V-V of Figure 4; and Figure 6 is a sectional view taken along the line VI-V1 of Figure 4.
DETAILED DESCRIPTION OF THE INVENTION Figures 4 to 6 show an embodiment of the cathode structure of an electron gun for a cathode ray tube according to the present invention. With reference to the drawings, the cathode structure includes a substrate 51, three layers 52 of the cathode electrode formed on the substrate 51 spaced apart from one another at predetermined intervals and a plurality of metal tips 53 formed on the electrode layer 52 of the cathode. cathode to emit electrons. In it, the conductive portions 52a of the cathode extend laterally from the layer 52 of the cathode electrode. An insulating layer 54 having holes 54a is formed on the substrate 51 on which the layer 52 of the cathode electrode is formed, such that the insulating layer 54 insulates each metal tip 53. Also, a first layer 56 of the gate electrode, having gates 56a formed to expose the metal tips 53 therethrough and a second layer 57 of the gate electrode extending laterally from the first layer 56 of the gate electrode , are formed on top of the insulating layer 54. The second layer 57 of the gate electrode is divided into several parts by a space 60 through which the insulating layer 54 is exposed. The conductive portion 52a of the cathode is formed between the lower surface of the insulating layer 54 where the space 60 and the upper surface of the substrate 51 are located as shown in Figure 6. In the operation of the cathode structure of a cannon of electrons for a cathode ray tube (CRT) according to the present invention as constituted above, a predetermined voltage or a potential that is zero with respect to earth is applied to each layer 52 of the cathode electrode and a positive voltage to the first and second layers 56 and 57 of the gate electrode, to thereby control the amount of electrons emitted from the metal tips 53. According to the present invention, the second layer 57 of the gate electrode is divided into several parts and there is a space in the second electrode layer on the layer 52 of the cathode electrode and the conductive portion 52a of the cathode, in such a way that the capacitance of the gate electrode layer can be reduced. In particular, because the layer 52 of the cathode electrode is not formed on the lower surface of the insulating layer 54, an electron charge can be prevented from accumulating, thereby reducing the capacitance. The reduction in the capacitance of the gate electrode prevents the distortion of the control signal to control the electron beam generated from the metal tips. It will be noted that the present invention is not limited to the preferred embodiment described above and it is clear that variations and modifications can be made by those skilled in the art within the spirit and scope of the present invention defined in the appended claims. It is noted that in relation to this date, the best method known by the applicant to carry out the aforementioned invention, is the conventional one for the manufacture of the objects to which it relates. Having described the invention as above, property is claimed as contained in the following