Visual display

Details Visual display Visual display

2000-03-31

2003-11-04

Patel, Vip (Department: 2879)

Electric lamp and discharge devices

With luminescent solid or liquid material

Vacuum-type tube

C313S491000

Reexamination Certificate

active

06642648

ABSTRACT:

FIELD OF THE INVENTION
The present invention relates to a visual display, particularly though not exclusively for use with data processing apparatus.
BACKGROUND OF THE INVENTION
Visual displays for data processing apparatus, such as computers, are normally of the cathode ray tube type. These generally have a depth of the order of their size dimension, which conventionally is their corner to corner or diagonal dimension. This depth can render them inconvenient in use. Recently, laptop computers have become increasingly widely used. These incorporate a “flat” screen display, usually of the liquid crystal type.
Proposals have been made to provide displays having flat screen cathode ray tubes. These are known as Spindt cathodes, after the inventor of U.S. Pat. No. 3,755,704. In this specification, they are referred to as field emission devices.
OBJECT OF THE INVENTION
The object of the present invention is to provide an improved “flat” screen field emission visual display and an emission device for the display.
The Invention
According to a first aspect of the invention there is provided a field effect emission device for a visual display comprising:
a substrate and
an emission layer on one face of the substrate, the emission layer having:
a multiplicity of emitters and gates, arranged as an array of emission pixels and
conductive connections in the emission layer to the emitters and the gates;
the substrate having:
conductive vias provided through the substrate or at least a front layer thereof to at least some of the said conductive connections in the emission layer for electrical connection to their emitters and gates.
We envisage that normally all of the conductive connections in the emission layer will have respective vias.
Provision of the conductive vias to the conductive connections in the emission layer provides direct contact to the connections and thus to the emitters and the gates. This has advantages in terms of the real time response of the emitters and gates to control signals. In other words, it provides for fast switching of the emitters and gates and thus sharp video characteristics.
Normally, the conductive connections will be emitter and gate lines to which the vias connect directly.
In preferred embodiments, each of the emitter and gate lines has a plurality of vias connected to it.
Whilst it is envisaged that some of the vias may connect to their lines at their ends; preferably the vias are provided within the body of emitters or the gates, that is with emitters or gates positioned on the lines to both sides of the position of the vias.
In accordance with an important feature of the invention, the drivers are mounted on the back face (the face opposite from the emitter face) of the substrate. Again, in combination with the vias through the substrate this enhances emission response.
It is envisaged that the substrate can have a single layer, with electrical connection tracks and preferably driver contact pads provided on its face opposite from the emission layer.
Normally, the substrate has at least one substrate layer additional to the front substrate layer,
the or each said additional substrate layer having conductive vias therethrough,
electrical interconnection tracks being provided at the interface(s) between the or each adjacent pair of substrate layers for electrical interconnection of the vias of the pair(s) of adjacent layers and
electrical connection tracks and preferably driver contact pads being provided on an outer face of a back one of the additional substrate layer(s) opposite from the front substrate layer.
This arrangement provides that the pitch of the gate and emitter lines can be progressively fanned out for connection to drivers.
Additionally, the field emission device will usually include at least one intermediate, additional substrate layer between the front and the back substrate layers.
The electrical interconnection tracks provided at the interface(s) between the or each adjacent pair of substrate layers can be provided on one only of the respective substrate layers at the interface(s), inter-layer contact being between vias of one layer and tracks of the other layer. Alternatively, the electrical interconnection tracks can be provided on both of the respective substrate layers at the interface(s), inter-layer contact being between tracks of one layer and tracks of the other layer.
Preferably, no gate line nor emitter line connection via is coincident, from the front substrate layer to the next, with a via in the next substrate layer
Preferably, the gate line and emitter line vias are arranged in at least the substrate layer having the emission layer in an array of aligned series of vias in two alternate orientations, both orientations being offset with respect to the emitter and gate line directions within the array, all the series are parallel to one or other of the orientations. The array of aligned series of vias can be a zig zag array with gaps between the zigs and the zags. In one particular arrangement, one of the alternate orientations is equal to the orientation of the aligned series, and alternate series of vias are not only parallel but themselves aligned.
The substrate is preferably of ceramic, conveniently of alumina to provide compatibility of thermal expansion with other components of the visual display, particularly a face plate. The vias are apertures in the substrate layers, which are filled with sintered metallic material.
At least some of the electrically conductive connections, lines, connection tracks and interconnection tracks are locally recessed into the material of the substrate layer(s). In particular, the emitter lines are preferably flush on their emission sides with the emission side of the substrate, with a planar dielectric layer separating the emission lines and the gates lines. Normally, a resistive layer will be provided on the emitter line side of the dielectric layer.
In one embodiment, the substrate includes additional vias and conductive tracks for providing electric connection through the substrate for phosphor excitation lines.
In accordance with a further preferred feature, the back face of the substrate has a peripheral metallic stripe for solder connection of the device into the visual display.
Further, power and signal supply tracks are preferably provided on the back surface of the back layer for powering the drivers and providing control signals to them.
Normally, the gates are circular apertures in the gate line stripes, with the emitters being pointed features projecting towards the gate apertures through voids in the dielectric layer.
According to a second aspect of the invention there is provided a visual display comprising:
a field emission device of the first aspect;
a glass face plate incorporating phosphor material selectively excitable by the emission device pixels; and
fused sealing material peripherally sealing the face plate to the emission device, whereby the face plate is parallelly spaced from the emission layer of the emission device and the space therebetween is evacuated.
It can be envisaged that the sealing material is interposed directly between the face plate and the emission device. However, it is preferred that the sealing material is provided on a wall interposed between the face plate and the emission device.
In the preferred embodiments, the visual display includes a carrier attached to the face of the emission device opposite from its emission layer.
The preferred arrangement is that the fused sealing material is provided on a peripheral wall which is sealed to the carrier and extends from it to the face plate or which forms one limb of the carrier which is of L-shaped cross-section and extends towards the face plate, the face plate being sealed to the wall by the fused sealing material and the emission device being sealingly attached to the carrier at the face of the emission device opposite from its emission layer.
Whilst the emission device may be secured to the carrier by means of adhesive, in the preferred embodiments, the device is soldered to the carrier.

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