Electric lamp or space discharge component or device manufacturi – Process – With assembly or disassembly
Patent
1996-10-04
1999-03-02
Ramsey, Kenneth J.
Electric lamp or space discharge component or device manufacturi
Process
With assembly or disassembly
445 44, H01J 926
Patent
active
058762604
DESCRIPTION:
BRIEF SUMMARY
The present invention relates to flat display screens. It more particularly relates to the assembly of two plates constituting the bottom and the viewing surface of the screen, respectively, and between which is provided an internal gap isolated from outside.
Conventionally, a flat display screen is constituted by two external rectangular plates, for example made of glass. One plate forms the viewing surface of the screen and the other plate forms the bottom provided with emission means. These two plates are assembled with a sealing joint and are spaced one from the other. For a Field Effect Display (FED), a microtip display, or a Vacuum Fluorescent Display (VFD), the gap between the two glass plates is evacuated, whereas for a plasma display, the gap is filled with a low pressure gas.
FIG. 1 is a schematic cross-sectional view representing the conventional structure of a portion of a flat display screen with microtips and FIG. 2 is a schematic cross-sectional view representing a conventional method for assembling a microtip flat display screen.
Such microtip screens are mainly constituted by a cathode plate 1 facing an anode plate 2.
The operation and the detailed structure of an example of such a microtip screen are described in U.S. Pat. No. 4,940,916 assigned to Commissariat a l'Energie Atomique.
The cathode plate 1 is constituted, onto a glass substrate 3, of cathode conductors 4 arranged in columns. The cathode conductors 4 are coated with a resistive layer (not shown) for the homogeneity of the electronic emission. The cathode is associated with a gate 5 with interposition of an insulating layer 6 to insulate the cathode conductors 4 from gate 5. Holes are respectively formed in the gate layer 5 and in the insulating layer 6 to accommodate the microtips 7 which are formed on the resistive layer. Gate 5 is arranged in rows, the intersection of a row of gate 5 and a column cathode defines a pixel. For the sake of simplification, only a few microtips 7 are represented in FIG. 1. In practice, there are several thousand microtips 7 per pixel.
The anode plate 2 is provided with phosphors 8 deposited onto electrodes 9, which are constituted by a transparent conductive layer such as indium and tin oxide (ITO) and formed on a substrate 10.
This device uses the electric field generated between the cathode 3 and gate 5 so that electrons are extracted from microtips 7 toward suitably biased phosphors 8 of anode plate 2 crossing a vacuum gap 11.
The cathode/gate and the anode are independently formed onto the two substrates 3 and 10 to constitute cathode plate 1 and anode plate 2. The plates are assembled with a peripheral sealing joint 12 (FIG. 2). A vacuum chamber 11 is provided between the two plates 1 and 2 to enable the electrons issued from the cathode to flow toward the anode.
Plates 1 and 2 are conventionally assembled as follows.
Spacers (not shown) defining the vacuum chamber 6 are first glued over gate 5. The spacers are generally constituted by glass beads regularly distributed so that the gap 11 between plates 1 and 2 is constant.
The cathode/gate plate 1 is subjected to a thermal process under a vacuum to degas the cathode and to evaporate the glue of the spacers. The thermal process is achieved under a pressure of approximately 10.sup.-8 Pa, at a temperature of approximately 450.degree. C. for about one hour.
A similar process is applied to the anode plate 2, under a oxygen-rich atmosphere. The process causes the evaporation of the residual organic compounds included in the phosphors 8 of the anode. These organic compounds may have been used as promoters in the process of depositing the phosphors or may be pollutants resulting from subsequent processing steps.
A pumping tube 13 is placed on the free surface of cathode plate 1. Tube 13 is, for example, made of glass and is sealed at one of its opened ends in register with an aperture provided in plate 1 to form vias to gap 11. Tube 13 is subsequently used to couple a pipe 14 to make a vacuum in gap 11. Tube 13 is placed in a corner of plate 1 outsi
REFERENCES:
patent: 4018490 (1977-04-01), Berkenblit et al.
Clerc Jean-Frederic
Garcia Michel
Hamon Olivier
Pepi Richard
Pixtech SA
Ramsey Kenneth J.
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