Electric lamp and discharge devices – With luminescent solid or liquid material – Vacuum-type tube
Patent
1996-07-29
1998-07-28
Patel, Nimeshkumar D.
Electric lamp and discharge devices
With luminescent solid or liquid material
Vacuum-type tube
313496, 313336, H01J 3112, H01J 2982
Patent
active
057866600
DESCRIPTION:
BRIEF SUMMARY
BACKGROUND OF THE INVENTION
1. Field of the Invention
The present invention relates to the fabrication of a flat display screen. It more particularly applies to a flat display screen comprising a cathode including microtips for electronically bombarding an anode including phosphor elements. This type of screen is commonly called a microtip screen.
2. Discussion of the Related Art
FIG. 1 represents the structure of a flat microtip screen with microtips of the type used according to the invention.
Such microtip screens are mainly constituted by a cathode 1 including microtips 2 and by a gate 3 provided with holes 4 corresponding to the positions of the microtips 2. Cathode 1 is disposed so as to face a cathodoluminescent anode 5, formed on a glass substrate 6 that constitutes the screen surface.
The operation and the detailed structure of such a microtip screen are described in U.S. Pat. No. 4,940,916 assigned to Commissariat a l'Energie Atomique.
The cathode 1 is disposed in columns and is constituted, onto a glass substrate 10, of cathode conductors arranged in meshes from a conductive layer. The microtips 2 are disposed onto a resistive layer 11 that is deposited onto the cathode conductors and are disposed inside meshes defined by the cathode conductors. FIG. 1 partially represents the inside of a mesh, without the cathode conductors. The cathode 1 is associated with the gate 3 which is arranged in rows, an insulating layer (not shown) being interposed between the cathode conductors and gate 3. The intersection of a row of gate 3 with a column of cathode 1 defines a pixel.
This device uses the electric field generated between the cathode 1 and gate 3 so that electrons are transferred from microtips 2 toward phosphor elements 7 of anode 5. In color screens, the anode 5 is provided with alternate phosphor strips 7, each strip corresponding to a color (red, green, blue). The strips are separated one from the other by an insulating material 8. The phosphor elements 7 are deposited onto electrodes 9, which are constituted by corresponding strips of a transparent conductive layer such as indium and tin oxide (ITO). The groups of red, green, blue strips are alternatively biased with respect to cathode 1 so that the electrons extracted from the microtips 2 of one pixel of the cathode/gate are alternatively directed toward the facing phosphor elements 7 of each color.
The assembly of the two substrates, or plates, 6 and 10, supporting anode 5 and cathode 1, respectively, provides an internal space 12 where the electrons emitted by cathode 1 flow.
A problem encountered lies in the formation of the space 12, because the distance between cathode 1 and anode 5 must be constant so that the brightness of the screen is regular over its whole surface.
For this purpose beads (not shown), for example made of glass and regularly distributed between gate 3 and anode 5, are conventional used. However a drawback of using beads distributed over the whole useful surface of the screen is that they constitute obstacles to the path of the electrons emitted by microtips 2. These obstacles cause shadow areas on the screen because the phosphor elements 7 facing them cannot receive electrons. Even though the spherical shape limits this effect by decreasing the contact surface between the spacer and a phosphor element 7, this is only true for small-diameter beads.
Indeed, the larger the diameter of the beads, the more visible these beads are on the screen surface by generating shadow areas. This requires the use of small-diameter beads, which limits the thickness of the vacuum space 12 and therefore the distance between anode 5 and cathode 1. The smaller the distance between anode 5 and cathode 1, the lower the anode-cathode voltage must be to prevent the formation of electric arcs which would destroy the screen. However, the anode-cathode voltage is directly related to the screen's brightness. Thus, when one wishes to reduce the shadow areas due to the spacers by decreasing the diameter of the spacers, the anode-cathode voltage must b
REFERENCES:
patent: 5504387 (1996-04-01), Hamagishi et al.
patent: 5541473 (1996-07-01), Duboc, Jr. et al.
patent: 5543684 (1996-08-01), Kumar et al.
patent: 5587623 (1996-12-01), Jones
Patel Nimeshkumar D.
Pixtech S.A.
LandOfFree
Flat display screen with a high inter-electrode voltage does not yet have a rating. At this time, there are no reviews or comments for this patent.
If you have personal experience with Flat display screen with a high inter-electrode voltage, we encourage you to share that experience with our LandOfFree.com community. Your opinion is very important and Flat display screen with a high inter-electrode voltage will most certainly appreciate the feedback.
Profile ID: LFUS-PAI-O-25519