Electricity: electrical systems and devices – Electrostatic capacitors – Variable
Patent
1992-08-18
1995-07-11
Reynolds, Bruce A.
Electricity: electrical systems and devices
Electrostatic capacitors
Variable
4004791, 345173, H01G 700
Patent
active
054326710
DESCRIPTION:
BRIEF SUMMARY
BACKGROUND OF THE INVENTION
The present invention relates to a device forming a touch screen of the capacitive type intended in particular to cover a visualizing screen of a visualizing display unit such for example as a cathode ray tube.
One knows such devices comprising a plate-shaped transparent dielectric substrate such as glass the front face of which opposite to the visualizing screen comprises a certain number of electrically conducting electrodes insulated from each other so as to form a matrix of keys. These electrodes forming keys are connected to an electronic circuit accommodated in the visualizing unit through the medium of conducting wires deposited on the front face of the substrate and terminating into two rows of contact points spaced from the lower and upper edges, respectively, of the substrate. The conducting wires for the connection of the internal electrodes of the matrix to the electronic circuit are disposed in the spaces between adjacent electrodes. The electrodes and the wires are generally made from indium and tin oxide. When an operator is putting a finger upon one of the electrodes forming keys there occurs a capacity variation influencing the natural frequency of an oscillator associated with this key forming a part of the electronic circuit.
These known devices exhibit the following inconveniences: of the electrodes forming keys and of the conducting tracks which for the latter may result in an interruption of their continuity. This wear causes failures of the key-forming electrodes and of the tracks involved. This failure occurs pursuant to scratches of the front face of the touch screen which may also interrupt the continuity of the tracks; direct touching of the connecting tracks instead of the electrodes forming keys in particular in the case where these electrodes are of relatively small dimensions; with the electrodes forming keys by electrostatic discharges upon the screen is to be feared.
Some known devices provide the deposit of an insulating protective layer of SiO.sub.2 or the like upon the front face of the touch screen but this layer is of a thickness limited by the present technique and is wearing out relatively quick so that the inconveniences mentioned hereinabove are found again.
SUMMARY OF THE INVENTION
The present invention proposes a device forming a touch screen of the capacitive type allowing to eliminate the inconveniences hereabove.
Therefore, the device according to the invention is characterized in that it comprises a first group of electrically conducting, transparent electrodes insulated from each other, not exposed to the outside and to be connected to an electronic circuit for the capacity variation detection and a second group of electrically conducting, transparent, free electrodes insulated from one another to form front keys and separated from the first group by a dielectric, the electrodes of the second group being superimposed to the electrodes of the first group while facing each other so as to form pairs of capacitors the capacity of each one of which varies when a body forming a mass reference frame such as a finger of an operator is put upon a front key.
According to an embodiment the electrodes of the first group are provided upon the rear face of a plate-shaped substrate of a transparent dielectric material such as glass and the electrodes forming keys of the second group are provided on the front face of the substrate.
According to another embodiment the electrodes of the first group are provided on the front face of a first plate-shaped substrate of a transparent dielectric material such as glass and the electrodes forming keys of the second group are provided on the front face of a second plate-shaped substrate of a transparent dielectric material fastened for example by sticking onto the front face of the first substrate.
According to a characteristic of the invention the first and second groups of electrodes form two matrices with columns and rows, respectively, and the electrodes of the first group are connected by very fine
REFERENCES:
patent: 3696409 (1972-10-01), Braaten
patent: 4090092 (1978-05-01), Serrano
patent: 4123631 (1978-10-01), Lewis
patent: 4161766 (1979-07-01), Castleberry et al.
patent: 4205418 (1980-06-01), Przybylek
patent: 4290052 (1981-09-01), Eichelberger et al.
patent: 4394643 (1983-07-01), Williams
patent: 4561002 (1985-12-01), Chiu
patent: 4595913 (1986-06-01), Aubochon
patent: 4614937 (1986-09-01), Poujois
patent: 4924222 (1990-08-01), Antikidis
Mors Composants
Reynolds Bruce A.
Switzer Michael D.
LandOfFree
Device forming tactile screen of the capacitive type does not yet have a rating. At this time, there are no reviews or comments for this patent.
If you have personal experience with Device forming tactile screen of the capacitive type, we encourage you to share that experience with our LandOfFree.com community. Your opinion is very important and Device forming tactile screen of the capacitive type will most certainly appreciate the feedback.
Profile ID: LFUS-PAI-O-507905