Touch sensor using capacitance detection and liquid crystal display having the same

A liquid crystal display comprising:

• a liquid crystal display panel that comprises a plurality of pixels to display an image;
• a touch sensor disposed within the liquid crystal display panel to detect a touch event;
• a coordinate detection circuit connected to the touch sensor to detect coordinates of a point at which a touch event occurs;
• and
• a driver that drives the liquid crystal display panel based on the coordinates,
• wherein the touch sensor comprises:
• a plurality of x-axis read-out lines;
• a plurality of y-axis read-out lines crossing the x-axis read-out lines, wherein the x-axis read-out lines are insulated from the y-axis read-out lines;
• and
• a plurality of sensor units provided in a plurality of regions defined by the x-axis read-out lines and the y-axis read-out lines,
• wherein each sensor unit comprises:
• a reset unit having a first transistor, wherein the first transistor comprising a control terminal receiving a first control signal, an input terminal receiving a first reset signal and an output terminal outputting the first reset signal based on the first control signal;
• a capacitance detector having a liquid crystal capacitor that changes the first reset signal based on a variation of a cell gap of the liquid crystal display panel caused by a touch event, wherein the output terminal of the first transistor is directly connected to a first electrode of the liquid crystal capacitor;
• a first output unit having a second transistor that changes an electric potential of a corresponding x-axis read-out line in response to the first reset signal changed in the liquid crystal capacitor;
• a second output unit having a third transistor that changes an electric potential of a corresponding y-axis read-out line in response to the first reset signal changed in the liquid crystal capacitor;
• and
• a line reset unit comprising:
• a fourth transistor comprising a control terminal receiving the first control signal, an input terminal directly receiving a second reset signal, and an output terminal directly connected to one of the x-axis and y-axis read out lines;
• and
• a first capacitor connected in parallel with the fourth transistor between the input and output terminals,
• wherein the first capacitor having a capacitance greater than that of the liquid crystal capacitor.

A liquid crystal display comprising:

• a liquid crystal display panel that comprises a plurality of pixels to display an image;
• a touch sensor disposed within the liquid crystal display panel to detect a touch event;
• a coordinate detection circuit connected to the touch sensor to detect coordinates of a point at which a touch event occurs;
• and
• a driver that drives the liquid crystal display panel based on the coordinates,
• wherein the touch sensor comprises:
• a plurality of x-axis read-out lines;
• a plurality of y-axis read-out lines crossing the x-axis read-out lines,
• wherein the x- axis read-out lines are insulated from the y-axis read-out lines;
• and
• a plurality of sensor units provided in a plurality of regions defined by the x-axis read-out lines and the y-axis read-out lines,
• wherein each sensor unit comprises:
• a reset unit having a first transistor, wherein the first transistor comprising a control terminal receiving a first control signal, an input terminal receiving a first reset signal and an output terminal outputting the first reset signal based on the first control signal;
• a capacitance detector having a liquid crystal capacitor that changes the first reset signal based on a variation of a cell gap of the liquid crystal display panel caused by a touch event, wherein the output terminal of the first transistor is directly connected to a first electrode of the liquid crystal capacitor;
• a first output unit having a second transistor that changes an electric potential of a corresponding x-axis read-out line in response to the first reset signal changed in the liquid crystal capacitor;
• a second output unit having a third transistor that changes an electric potential of a corresponding y-axis read-out line in response to the first reset signal changed in the liquid crystal capacitor;
• and
• a line reset unit comprising:
• a fourth transistor comprising a control terminal receiving the first control signal, an input terminal directly receiving a second reset signal, and an output terminal directly connected to one of the x-axis and y-axis read out lines;
• and
• a first capacitor connected in parallel with the fourth transistor between the input and output terminals,
• wherein the coordinate detection circuit comprises:
• an x-axis comparator that is connected to the x-axis read-out lines, and compares signals output from the x-axis read-out lines with a preset reference signal to output a first comparative signal;
• a y-axis comparator that is connected to the y-axis read-out lines, and compares signals output from the y-axis read-out lines with the preset reference signal to output a second comparative signal;
• and
• a coordinate generator that generates coordinates of a point, at which the touch event occurs, based on the first and second comparative signals.