Display device with touch panel
View Patent ↗Provided is a display device with a touch panel having the cost thereof reduced without a decrease in the transmittance ratio of light. A substrate has a planar transparent conductive film formed on an observer side thereof. The transparent conductive film is used as a transparent electrode of an electrostatic capacitance coupling type touch panel. A position detection pulsating voltage production circuit that inputs a pulsating voltage for position detection, and a coordinate position arithmetic circuit that computes a touched position on the transparent conductive film touched with an observer's finger are included. The transparent conductive film is shaped to have four corners. The position detection pulsating voltage generation circuit applies the position detection pulsating voltage to each of the four corners of the transparent conductive film at different timings. When the position detection pulsating voltage is applied to one of the four corners of the transparent conductive film, the coordinate position arithmetic circuit computes the touched position on the transparent conductive film, which is touched with the observer's finger, on the basis of a voltage outputted through the corner diagonally opposite to the corner to which the pulsating voltage is applied.
1. A display device with a touch panel including a substrate that has a planar transparent conductive film formed on the surface thereof on an observer side, the transparent conductive film being used as a transparent electrode of an electrostatic capacitance coupling type touch panel, comprising:
a position detection pulsating voltage production circuit that produces a pulsating voltage for position detection; and
a coordinate position arithmetic circuit that computes a touched position on the transparent conductive film, wherein:
the transparent conductive film is shaped to have four corners;
the position detection pulsating voltage production circuit applies the pulsating voltage for position detection to each of the four corners of the transparent conductive film at different timings; and
when the pulsating voltage for position detection is applied to one of the four corners of the transparent conductive film, the coordinate position arithmetic circuit computes the touched position on the transparent conductive film on the basis of a rise time of a voltage outputted through a corner diagonally opposite to the one of the four corners to which the pulsating voltage is applied.
2. The display device with a touch panel according to claim 1 , wherein:
assuming that one pair of diagonal corners of the transparent conductive film includes corners A and B and the other pair of diagonal corners thereof includes corners C and D, the coordinate position arithmetic circuit computes the touched position on the transparent conductive film on the basis of the time difference A-B between the time A during which when the pulsating voltage for position detection is applied to the corner A of the transparent conductive film, the voltage outputted through the corner B is retained at a predetermined voltage, and the time B during which when the pulsating voltage for position detection is applied to the corner B of the transparent conductive film, the voltage outputted through the corner A is retained at a predetermined voltage, and the time difference C-D between the time C during which when the pulsating voltage for position detection is applied to the corner C of the transparent conductive film, the voltage outputted through the corner D is retained at the predetermined voltage, and the time D during which when the pulsating voltage for position detection is applied to the corner D of the transparent conductive film, the voltage outputted through the corner C is retained at the predetermined voltage.
3. The display device with a touch panel according to claim 2 , wherein:
the pulsating voltage for position detection applied to the corner A or C of the transparent conductive film is a pulsating voltage that varies from a first voltage level to a second voltage level; and
the pulsating voltage for position detection applied to the corner B or D of the transparent conductive film is a pulsating voltage that varies from the second voltage level to the first voltage level.
4. The display device with a touch panel according to claim 2 , wherein:
the coordinate position arithmetic circuit includes an integration circuit;
the integration circuit integrates the predetermined current during the time A or C, releases the predetermined current during the time B or D, and thus outputs a voltage associated with the time difference A-B or C-D.
5. The display device with a touch panel according to claim 4 , wherein the integration circuit includes an integration circuit A that integrates the predetermined current during the time A and releases the predetermined current during the time B, and wherein the integration circuit A integrates the predetermined current during the time C and releases the predetermined current during the time D.
6. The display device with a touch panel according to claim 4 , wherein:
the position detection pulsating voltage production circuit applies the pulsating voltage for position detection to each of the four corners a plurality of times;
the integration circuit outputs a voltage obtained by adding up voltages associated with time differences A-B or C-D calculated by applying the pulsating voltage for position detection to each of the four corners a plurality of times.
7. The display device with a touch panel according to claim 4 , wherein the coordinate position arithmetic circuit includes an A/D conversion circuit connected on a stage succeeding the integration circuit.
8. The display device with a touch panel according to claim 1 , wherein the display device is an IPS type liquid crystal display device.
9. The display device with a touch panel according to claim 8 , further comprising a conductive polarizer disposed on the transparent conductive film.