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
  • H01J29/02—Electrodes; Screens; Mounting, supporting, spacing or insulating thereof
  • H01J29/028—Mounting or supporting arrangements for flat panel cathode ray tubes, e.g. spacers particularly relating to electrodes
• • 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
  • H01J31/00—Cathode ray tubes; Electron beam tubes
  • H01J31/08—Cathode ray tubes; Electron beam tubes having a screen on or from which an image or pattern is formed, picked up, converted, or stored
  • H01J31/10—Image or pattern display tubes, i.e. having electrical input and optical output; Flying-spot tubes for scanning purposes
  • H01J31/12—Image or pattern display tubes, i.e. having electrical input and optical output; Flying-spot tubes for scanning purposes with luminescent screen
  • H01J31/123—Flat display tubes
  • H01J31/125—Flat display tubes provided with control means permitting the electron beam to reach selected parts of the screen, e.g. digital selection
  • H01J31/127—Flat display tubes provided with control means permitting the electron beam to reach selected parts of the screen, e.g. digital selection using large area or array sources, i.e. essentially a source for each pixel group
• • H—ELECTRICITY
  • H01—ELECTRIC ELEMENTS
  • H01J—ELECTRIC DISCHARGE TUBES OR DISCHARGE LAMPS
  • H01J2201/00—Electrodes common to discharge tubes
  • H01J2201/30—Cold cathodes
  • H01J2201/304—Field emission cathodes
• • H—ELECTRICITY
  • H01—ELECTRIC ELEMENTS
  • H01J—ELECTRIC DISCHARGE TUBES OR DISCHARGE LAMPS
  • H01J2329/00—Electron emission display panels, e.g. field emission display panels
  • H01J2329/86—Vessels
  • H01J2329/8625—Spacing members

Definitions

• the present invention relates to a flat display screen. It applies more particularly to a flat screen of the type comprising a microtip cathode of electronic bombardment of an anode carrying phosphor elements. This type of screen is commonly called a micro-tip screen.
• FIG. 1 represents the functional structure of a flat screen with microtips of the type to which the invention relates.
• a microtip screen is essentially constituted by a cathode 1 with microtips 2 and a grid 3 for view of holes 4 corresponding to the locations of the microtips 2.
• the cathode 1 is placed opposite a cathode-ray anode.
• nescente 5 including a glass substrate 6 constitutes the screen surface.
• the cathode 1 is organized in columns and is made up, on a substrate 10 for example of glass, of conductors cathode organized in mesh from a conductive layer.
• the microtips 2 are produced on a resistive layer 11 deposited on the cathode conductors and are available inside the meshes defined by the cathode conductors.
• FIG. 1 partially represents the interior of a mesh, the cathode conductors do not appear in this figure.
• the cathode 1 is associated with the grid 3 which is it organized in lines, an insulating layer (not shown) being interposed between the cathode conductors and the grid 3.
• the intersection of a line of the grid 3 and a column of cathode 1 defines a pixel.
• This device uses the electric field created between the cathode 1 and the grid 3 so that electrons are extracted from the microtips 2 towards phosphor elements 7 of the anode 5.
• the anode 5 is provided with strips alternating phosphor elements 7, each corresponding to a color (Blue, Red, Green). The strips are separated from each other by an insulator 8.
• the phosphor elements 7 are deposited on electrodes 9, made up of corresponding strips of a transparent conductive layer such as indium tin oxide ( ITO).
• the sets of blue, red and green bands are alternately polarized with respect to the cathode 1, so that the electrons extracted from the micro-tips 2 of a pixel of the cathode / grid are alternately directed towards the phosphor elements 7 opposite each of the colors.
• the assembly of the two substrates, or plates, 6 and 10 respectively supporting the anode 5 and the cathode 1 is effec ⁇ killed with care of an empty space 12 for circulation of the electrons emitted by the cathode 1.
• the anode-cathode voltage is directly related to the brightness of the screen.
• the more we seek to reduce the shadow areas due to the spacers by reducing their diameter the more we must reduce the anode-cathode voltage, and the more we reduce the brightness of the screen.
• the diameter of the balls is limited to approximately 200 ⁇ in order not to create shadow zones, the anode-cathode voltage is then limited to approximately 500 to 1000 V.
• the present invention aims to overcome these drawbacks by proposing a microtip screen which can operate under high anode-cathode voltage.
• the present invention provides a flat display screen of the type comprising an electron bombardment microtip cathode associated with a grid, an anode carrying phosphor elements, and a inter-electrode space, screen which further comprises an insulating plate for defining said space associated with means for keeping this plate away from the anode, said plate being provided with holes in line with microtip zones.
• said means for keeping the plate at a distance are constituted by balls distributed between the plate and the anode.
• said means for keeping the plate at a distance are formed by bosses which the plate has on its face opposite the anode.
• said plate also comprises, outside the useful surface of the screen, a light for receiving an element for trapping impurities.
• said plate is coated, on the anode side, with a conductive layer.
• said conductive layer is reflective towards the anode.
• said conductive layer is made of a material for trapping impurities.
• said plate is made of glass, and the holes are obtained by photofor ⁇ mage.
• said plate has a thickness of given value between
• the means for keeping the plate away from the anode have a thickness of given value between 0.05 and 0.2 m.
• FIG. 1 is intended to state the state of the art and the problem posed;
• FIG. 2 represents a perspective view of an embodiment of a spacer according to the invention;
• Figure 3 shows schematically and in section, a flat display screen according to the invention.
• the representations of the figures are not to scale and the same elements have been designated in the different figures by the same references.
• the essential characteristic of the present invention is to propose a spacer whose structure does not harm the path of the electrons emitted by the cathode and whose thickness is without effect on the regularity of light emission of the screen.
• the invention foresees a spacer 13 in the form of an insulating plate of regular thickness and whose surface is substantially the same as that of the cathode and the anode of the screen.
• This plate 13 is provided with holes 14 at the right of each pixel defined by the intersection of a line of the grid and a column of the cathode, or at the right of each sub-pixel defined by the interior of 'a mesh of cathode conductors.
• this plate 13 is associated with means for keeping it at a distance from the anode 5.
• These means consist for example of balls 20 of small diameter, distributed between the plate 13 and the anode 5 as shown in FIG. 3, or bosses formed directly on the surface of the plate 13 which is opposite the anode 5.
• These bosses will preferably have a shape such that their contact surface with the anode 5 is as small as possible.
• these bosses could be spherical or pointed towards the anode 5.
• the association of the plate 13 provided with the holes 14 and of these means of remote maintenance makes it possible to benefit both from the absence of an obstacle for the electrons emitted by the microtips 2 of the cathode 1 and d '' a large inter-electrode space.
• the plate 13 is for example made of glass and the holes 14 can for example be made by photoforming.
• the holes 14 may be circular, square, or the like. However, care should be taken that the size of the holes 4 and the periodicity of the pattern of their distribution in the plate 13 are such that no moiré phenomenon can be observed from the surface of the screen. To do this, it will be ensured that the surface of a sub-pixel, or of a pixel depending on the embodiment chosen, can fit into a hole 14. Preferably, the size of a hole 14 will be slightly larger than the size of a pixel, or of a sub-pixel, to take account of any slight misalignment when positioning the plate 13 on the grid 3.
• the plate 13 is during the assembly of the screen, placed on the grid 3, the holes 14 of the plate 13 being perpendicular to the intersections between the lines 15 of the grid 3 and the columns 16 of the cathode 1 or in line with the meshes of the cathode conductors.
• the lumino ⁇ phorous elements are represented by a layer designated by the reference 7 and the anode conductors by a layer designated by the reference 9. On the anode 5 side, this representation could match the structure of a monochrome screen.
• the plates 6 and 10 are assembled in a conventional manner by means of a sealing joint 18.
• This joint 18 may for example consist of a bead of fusible glass.
• the plate 10 is conventionally provided, outside its useful surface, with a pumping tube 19 opening into the space 12 from the external face of the plate 10.
• This pumping tube 19 is closed at its free end once a vacuum has been created in the space 12.
• the means for holding the plate 13 away from the anode 5 (for example the balls 20) allow a communication between the holes 14 and the pumping tube 19.
• the thickness of these distance holding means is for example a given value between 0.05 and 0.2 mm.
• the invention therefore allows the thickness of the empty space 12 to be fixed at a value such that it allows the cathode and the anode to be supplied with a much greater potential difference. This improves the brightness of the screen.
• the thickness of the plate 13 is for example a given value between 0.2 and 2 mm.
• a thickness of 1 mm for the plate 13 associated with balls 20 with a diameter of about 0.2 mm allows, without the risk of electric arcing, an anode tension cathode of approximately 10,000 V.
• the diameter of the holes 14 of the plate 13 depends on the size of the pixels or sub-pixels, it is for example of a given value between 60 and 300 ⁇ m.
• the pitch between two holes 14 of the plate 13 is for example of a given value of about 100 ⁇ m.
• the plate 13 is, according to a preferred embodiment, metallized on its surface opposite the anode 5 to create a reflecting surface 21 which further improves the brightness of the screen by referring to the phosphor elements 7, the light they emit towards the inside of the screen.
• a metallization 21 makes it possible to refocus the electrons emitted by cathode 1 and thus optimize the brightness and the contrast of proximity of the screen, the metalli ⁇ cation 21 playing the role of a focusing grid.
• Another advantage of the invention is that it makes it possible to use, for the anode 5, so-called high-voltage phosphor elements 7.
• the anode conductors which are classi ⁇ cally formed of a transparent material between the plate 6 and the phosphor elements 7 can now be formed, by a very thin aluminum film affixed to the luminescent elements 7, space side. vacuum 12.
• the power of the electrons emitted under high anode-cathode voltage allows them to pass through this thin aluminum film. This has the effect of increasing the brightness of the screen while increasing the contrast of proximity.
• the increase made possible in the thickness of the inter-electrode space 12 leads to a particularly advantageous secondary effect.
• the constituent layers of the electrodes and the sealing joint 18 tend to degas during the operation of the screen. Such degassing is harmful and it is necessary to provide, in communication with the vacuum space 12, an element for trapping impurities, or degasser, commonly called a getter.
• This getter is conventionally placed in the pumping tube 19 before it is closed.
• a drawback which results therefrom is that this tube 19 constitutes a significant projection, perpendicular to the bottom of the screen while an attempt is made to produce a flat screen of the smallest possible size.
• the volume of the getter influences the life of the screen. The larger the getter, the longer the screen will have a lifespan, but the longer the length of the tube 19 must be to accommodate this getter.
• the invention makes it possible to reduce the overall size of the screen by allowing the length of the pumping tube 19 to be reduced to a minimum length.
• This minimum length is linked to the constraints of closing the tube 19 by melting the glass of which it is made, for example. Indeed, this closure must be carried out far enough from the plates 6 and 10 so as not to damage them.
• a tube 19 with a length of about 6 mm is sufficient to allow the end of the tube 19 to be closed with conventional methods without damaging the plates 6 and 10.
• the getter according to the invention can be housed in different places.
• the plate 13 is pour ⁇ view, in the vicinity of an edge of the screen, of a light 22 for receiving a getter 23.
• the useful volume of the getter 23 is then greater and the he increase of its external surface increases its degassing capacity.
• the thicknesses of the various constituents of a screen according to the invention are as follows.
• the plates 6 and 10 each have a thickness of approximately 1 mm.
• the thickness of the layer of anode conductors 9 is approximately 0.1 ⁇ m and that of the phosphor elements 7 is between 4 and 10 ⁇ m.
• the thickness of the columns 16 is of the order of 0.4 to 0.8 ⁇ m
• the thickness of the insulating layer 24 between the cathode 1 and the grid 3 is approximately 1.3 ⁇ m and the thickness of the grid 3 is of the order from 0.2 to 0.4 ⁇ m.
• the thickness of the plate 13 is between 0.2 and 2 mm depending on the operating anode-cathode voltage of the screen. If the metallization layer 21 plays the role of getter, its thickness is for example around 50 ⁇ m.
• the diameter of the beads is approximately 50 ⁇ m.
• each of the constituents described for the layers may be replaced by one or more constituents having the same characteristics and / or fulfilling the same function.
• the dimensional indications given by way of example may be modified as a function of the characteristics sought for the screen, of the materials used, or others.
• the thickness of the plate 13 depends on the operating anode-cathode voltage of the screen, and the diameter as well as the pitch of the holes 14 depend on the size of the pixels or sub-pixels of the screen.
• the choice of the height of the means for keeping the plate 13 of the anode 5 at a distance depends in particular on the pitch of the holes 14.
• These means for maintaining distance can be other than balls, for example example of studs, cylindrical columns, etc. It is also possible to provide means for maintaining distance from the cathode side.

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• Cathode-Ray Tubes And Fluorescent Screens For Display (AREA)

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Publications (2)

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• 1994
  • 1994-08-24 FR FR9410390A patent/FR2724041B1/fr not_active Expired - Fee Related
• 1995
  • 1995-08-23 EP EP95928531A patent/EP0724771B1/de not_active Expired - Lifetime
  • 1995-08-23 US US08/633,738 patent/US5786660A/en not_active Expired - Fee Related
  • 1995-08-23 DE DE69523556T patent/DE69523556T2/de not_active Expired - Fee Related
  • 1995-08-23 JP JP8507828A patent/JPH09504642A/ja active Pending
  • 1995-08-23 WO PCT/FR1995/001105 patent/WO1996006450A1/fr active IP Right Grant

Non-Patent Citations (1)

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