Classifications

• • H—ELECTRICITY
  • H01—ELECTRIC ELEMENTS
  • H01J—ELECTRIC DISCHARGE TUBES OR DISCHARGE LAMPS
  • H01J29/00—Details of cathode-ray tubes or of electron-beam tubes of the types covered by group H01J31/00
  • H01J29/94—Selection of substances for gas fillings; Means for obtaining or maintaining the desired pressure within the tube, e.g. by gettering
• • H—ELECTRICITY
  • H01—ELECTRIC ELEMENTS
  • H01J—ELECTRIC DISCHARGE TUBES OR DISCHARGE LAMPS
  • H01J9/00—Apparatus or processes specially adapted for the manufacture, installation, removal, maintenance of electric discharge tubes, discharge lamps, or parts thereof; Recovery of material from discharge tubes or lamps
  • H01J9/38—Exhausting, degassing, filling, or cleaning vessels
  • H01J9/395—Filling vessels
• • H—ELECTRICITY
  • H01—ELECTRIC ELEMENTS
  • H01J—ELECTRIC DISCHARGE TUBES OR DISCHARGE LAMPS
  • H01J2329/00—Electron emission display panels, e.g. field emission display panels

Definitions

• the present invention relates generally to a device using a source of field effect electrons (for example microtips) and more particularly to a field emission device for example a flat screen display by cathodoluminescence excited by field emission , or cold emission, using microtips. It also relates to the manufacture of such a device.
• a source of field effect electrons for example microtips
• a field emission device for example a flat screen display by cathodoluminescence excited by field emission , or cold emission, using microtips. It also relates to the manufacture of such a device.
• the invention relates to the constitution of a reducing atmosphere inside the device in order to combat the oxidation of the microtips (or other electron emitting elements) during the operation of this device. .
• Microtip screens are flat cathode ray tubes that operate under vacuum. These screens include a cathode (formed in particular of cathode conductors, grids and microtips) and an anode (formed of conductors and phosphors).
• a cathode formed in particular of cathode conductors, grids and microtips
• an anode formed of conductors and phosphors.
• a getter is used, as is done for conventional cathode ray tubes.
• a getter is an element which, when activated under vacuum by heating, is capable of fixing the gases desorbed by the device and maintain the vacuum level necessary for the proper functioning of it.
• Figure 1 is a partial view, in cross section, of a microtip screen 1 according to the prior art. It includes two glass slides 2 and 3 placed facing each other. The blades 2 and 3 are sealed on their periphery by means of a glass paste 4 with low melting point.
• the blade 3 supports, on its internal part on the screen, the cathode which is made up of microtips 5 preferably formed on a resistive layer, such as a silicon layer 6 deposited on cathode conductors 14, and of electrodes. grid 7 separated from the resistive layer 6 by a layer 8 of dielectric material.
• the blade 2 supports, on its internal part on the screen, the anode which consists of one or more conductive layers 9 supporting one or more phosphors 10.
• a space 11 isolated from outside This space 11 is maintained under vacuum.
• the vacuum was obtained by means of a queusot 12 provided in the blade 3.
• the queusot 12 is initially opened and connected to a vacuum pump. It also allows the introduction of one or more getters such as the getter 13. Once the vacuum is achieved, the queusot 12 is closed as shown in FIG. 1.
• the lifespan of these devices depends, among other things, on that of the cathodes which is linked to the fall in the electron current as a function of time. This lifetime of the cathodes depends very much on the quantity and the nature of the residual gases present in the closed structure constituting the screen.
• the electron bombardment of the anode produces gases by a very dependent degassing effect. of the nature of the phosphors that the anode includes. It is now well demonstrated that the drop in the electron current emitted by the cathode is essentially caused by oxidation of the emissive material constituting the microtips. This oxidation caused by the desorbed gases is particularly evident when the microtips are made of molybdenum.
• a material sensitive to oxidation such as molybdenum
• This third approach is particularly interesting because it makes it possible to use molybdenum as an emissive material while retaining numerous possibilities of choice among phosphors.
• Document FR-A-2 755 295 describes an improvement to this process to remedy the loss of hydrogen during the assembly phase of the screen.
• Getters capable of maintaining a sufficient hydrogen pressure are specific and have a relatively low pumping capacity with respect to the other oxidizing gases.
• the amount of getter introduce is high (approximately 0.5 g for a 5 inch screen), which can pose cost problems and congestion, especially in the field of] _0 large screens.
• the quantity of hydrogen that must first adsorb the getter is quite considerable (1333 cmN Pa to 13330 cmN Pa, or 10 to 100 cm 3. Torr per gram of getter) which, taking into account the volume of - j _5 the screen, may cause the manufacturer to assemble the screen under hydrogen pressure close to the atmosphere.
• the reducing gas is under a pressure between 10 ⁇ 8 mbar and 10 "3 mbar and, preferably, under a pressure between 10 ⁇ 8 mbar and 10 "" 5 mbar.
• the gas of formula N x H y is NH 3-
• the device may further comprise one or more getters in communication with the internal space of the device.
• the closed structure may consist of a first blade supporting a microtip cathode on its face internal to the structure, a second blade placed opposite the first blade and supporting an anode on its face internal to the structure, and means for sealing the first blade to the second blade around their periphery.
• Luminophores can also be distributed over the anode. It is for example a flat display screen.
• a second object of the invention consists of a method of manufacturing such a device, comprising the following steps:
• a third object of the invention consists of another method of manufacturing such a device, comprising the following steps:
• connection of the pumping pipe to an apparatus comprising means for creating a vacuum and means for injecting said reducing gas;
• the assembly step takes place under vacuum or under a controlled atmosphere, by heating to the action temperature of the sealing means.
• the device is brought back to ambient temperature and is put into operation for a determined period before the completion of the other stages.
• the methods may further comprise the following steps:
• a fourth object of the invention consists of an apparatus for implementing these two methods, comprising:
• the intermediate means may include a gas tank communicating with said
• the intermediate means can simply comprise a valve.
• a fifth object of the invention consists of another method of manufacturing such a device, comprising the following steps:
• a sixth object of the invention consists of yet another method of manufacturing such a device, comprising the following steps:
• the device comprising sealing means acting hot, a hole provided in the device being intended to put in communication the internal space of the closed structure and the interior of the sealed enclosure;
• a seventh object of the invention consists of an apparatus for implementing these latter two methods, comprising:
• a sealed enclosure capable of receiving said device
• this apparatus may further comprise means for producing a controlled atmosphere communicating with the interior of the enclosure by means of a third valve connected to means for producing the controlled atmosphere, for example a bottle of appropriate gas.
• FIG. 1, already described, is a partial view in schematic cross-section of a microtip display screen according to the prior art
• FIG. 2 is a schematic view of a first device for implementing a method of manufacturing a device according to the present invention
• FIG. 3 is a schematic view of a second device for the implementation of another method of manufacturing a device according to the present invention.
• the particular choice of the gas N x H y , or of a gaseous mixture based on N x H y makes it possible both to combat the oxidation of the emissive material from the electron emitting source while avoiding deposits on the emissive material. Indeed, the possible decomposition of this gas takes place in gaseous form unlike other types of reducing gases (CH, H 2 S for example).
• getters that will eventually _ Q used include those sold by SAES GETTERS SpA, for example:
• the zirconium-iron getter which can be activated at low temperature (around 400 ° C), referenced under the registered trademark ST 122. 0
• the sealing wall 22 of the two blades of the device consists of a glass with a low melting point called "fried glass".
• the device 20 is then placed in a zone 30 of the apparatus shown in FIG. 2 allowing it to be steamed.
• the pipe 21 is connected to a pipe 41 which makes it possible to connect it to a vacuum pump 42 of the turbomolecular type via a pipe 43 fitted with a valve 44 on the one hand and to the outlet orifice of a gas tank 45, of known volume (for example 0.7 pounds), via a pipe 46 fitted with a valve 47 on the other hand.
• a bottle of NH 3 48 is connected to the inlet port of the reservoir 45 via a pipe 49 fitted with a valve 50.
• This valve 50 is a needle valve which makes it possible to easily regulate the flow rate.
• the apparatus thus constituted also comprises a gauge 51, making it possible to measure the pressure of the gas contained in the tank 45, and a gauge 52 making it possible to measure the pressure at the outlet of the screen 20.
• the screen 20 and the tank 45 are evacuated, the valves 44 and 47 being open and the valve 50 being closed, thanks to the vacuum pump 42.
• the screen 20 is then steamed at 360 ° C for 16 hours. After cooling to room temperature, the screen 20 is operated for 20 hours. After stopping this operating phase which allowed the degassing of the phosphors, the getter 23 (or the getters) is activated by radiofrequency heating at a temperature of 800 ° C. for 4 minutes.
• the reservoir 45 is then isolated by closing the valve 47. Ammonia is introduced into the reservoir 45.
• the screen 20 is then isolated from the vacuum pump 42 by closing the valve 44.
• the valve 47 is then opened and the ammonia is introduced into the screen 20 at an equilibrium pressure which depends on the quantity introduced. in tank 45 and that is preferably between 10 "8 and 10 -5 mbar.
• the screen 20 can then be separated from the device by closing the shank 21.
• NH 3 can be introduced into the screen in dynamic regime.
• a partial pressure of NH 3 is regulated by the valve 50, the valves 44 and 47 being open.
• the partial pressure of NH 3 is preferably between 10 ⁇ 8 and 10 ⁇ 5 mbar.
• the screen After a dynamic scanning period of a few minutes to a few tens of minutes, the screen is separated from the device by closing the window.
• the assembly of the screen can be of the integral type, which means that the screen is degassed and then sealed under vacuum or under a controlled atmosphere.
• the process is such that after sealing it remains under vacuum, or under a controlled atmosphere, by difference from the previous case (examples 1 and 2) for which, after sealing, the screen is returned to atmospheric pressure and then pumped again and steamed.
• the various elements of the screen are positioned under vacuum and then baked at a temperature of the order of 300 to 450 ° C. for one or many hours.
• the getters can be positioned either inside the screen, or in a protuberance of the closed queusot type or getter box.
• the anode can be pressed against the cathode or kept at a certain distance from the cathode. In the latter case, the degassing is more effective.
• the apparatus of FIG. 3 also includes a turbomolecular vacuum pump 62 which communicates with the interior of the enclosure 60 by means of a pipe 63 equipped with a valve 64.
• a bottle of NH 3 65 communicates with the interior of the enclosure 60 thanks to a pipe 66 equipped with a valve 67.
• a gauge 68 makes it possible to measure the pressure prevailing in the sealed enclosure 60.
• a pipe 71 equipped with a valve 72 also makes it possible to communicate the interior of the enclosure 60 with a bottle 73 in the case where one wishes to place the interior of the enclosure under a controlled atmosphere.
• a NH 3 pressure of between 10 ⁇ 8 and 10 "3 mbar is introduced into the enclosure 60 containing the screen.
• the anode and cathode plates are brought into contact via the sealing glass, if they were not already, and the screen is sealed under the pressure of NH 3 previously established at a temperature between 450 ° C and 500 ° C.
• getter Depending on the type of getter used, it must or may not be “flashed” or activated after closing and returning to room temperature. He can be advantageous to use a getter of the type ST 122 which can be activated during the assembly phase.
• Example 4 According to a variant of the embodiment described in Example 3, one of the elements of the screen (cathode plate, anode plate, getter box) has a hole, with a diameter of the order of a millimeter or a few millimeters, which allows communication between the interior of the screen and the interior of the watertight enclosure 60.
• Example 3 the various elements of the screen are positioned under vacuum and then steamed.
• the sealing phase can be done here under a controlled atmosphere, which is advantageous when using a glass of the borosilicate type for the screen blades, the enclosure being pumped back after the assembly of the screen.
• This embodiment can be advantageous even when the sealing is carried out under vacuum because all the products degassed inside the screen during the sealing are evacuated, which makes it possible to have a better vacuum inside the screen.
• an NH 3 pressure of some 10 8 to 10 ⁇ 3 mbar is introduced into the enclosure and consequently into the screen.
• the communication hole between the screen and the enclosure is then filled in by any appropriate means.

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• Engineering & Computer Science (AREA)
• Manufacturing & Machinery (AREA)
• Manufacture Of Electron Tubes, Discharge Lamp Vessels, Lead-In Wires, And The Like (AREA)
• Cathode-Ray Tubes And Fluorescent Screens For Display (AREA)
• Compressors, Vaccum Pumps And Other Relevant Systems (AREA)

Applications Claiming Priority (3)

Publications (2)

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ID=9544950

Family Applications (1)

Country Status (6)

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Family Cites Families (12)

• 1999
  • 1999-04-28 FR FR9905361A patent/FR2793068B1/fr not_active Expired - Fee Related
• 2000
  • 2000-04-26 WO PCT/FR2000/001101 patent/WO2000067285A1/fr active IP Right Grant
  • 2000-04-26 JP JP2000616037A patent/JP2003500792A/ja not_active Withdrawn
  • 2000-04-26 EP EP00922750A patent/EP1173877B1/de not_active Expired - Lifetime
  • 2000-04-26 DE DE60020959T patent/DE60020959T2/de not_active Expired - Fee Related
  • 2000-04-26 US US09/959,391 patent/US6888294B1/en not_active Expired - Fee Related

Non-Patent Citations (1)

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