ELECTROSTATIC CAPACITY TYPE TOUCH SENSOR

• US 20120001869A1
• Filed: 07/01/2011
• Published: 01/05/2012
• Est. Priority Date: 07/01/2010
• Status: Active Grant

• Current Assignee: Semiconductor Components Industries LLC (ON Semiconductor Corporation)
• Original Assignee: Semiconductor Components Industries LLC (ON Semiconductor Corporation)
• Inventors: OTAGAKI, Takayasu, ITO, Hiroya, ICHIKAWA, Atsuhiro, HASEGAWA, Kazuhiro
• Granted Patent: US 8,619,058 B2
• Time in Patent Office: Days
• US Class Current: 345/174
• CPC Class Codes: G06F 3/03547 Touch pads, in which fingers can move on a surface
• CPC Class Codes: G06F 3/044 by capacitive means
• CPC Class Codes: G06F 3/0443 using a single layer of sensing electrodes
• CPC Class Codes: G06F 3/0448 Details of the electrode shape, e.g. for enhancing the detection of touches, for generating specific electric field shapes, for enhancing display quality
• CPC Class Codes: H03K 17/962 Capacitive touch switches
• CPC Class Codes: H03K 2017/9602 characterised by the type or shape of the sensing electrodes

Abstract

There is offered an electrostatic capacity type touch sensor capable of detecting a large number of touch positions with high accuracy. The electrostatic capacity type touch sensor is composed of a touch panel and a signal processing circuit. The touch panel is structured to include first through fourth detection electrodes, first and second common electric potential lines, a common electric potential wiring, a common electric potential terminal and first through fourth output terminals disposed on an insulating substrate. The signal processing circuit is structured to include a clock generator, a selection circuit, a charge amplifier, an A/D converter and an arithmetic unit. The charge amplifier detects a change in capacitance induced by that a finger of an operator touches the first through fourth detection electrodes.

Claims

1. An electrostatic capacity type touch sensor, comprising:

a substrate;

a first common electric potential line disposed on the substrate;

a second common electric potential line disposed on the substrate, the second common electric potential line surrounding the first common electric potential line;

first and second detection electrodes disposed in a region interposed between the first and second common electric potential lines and being axisymmetrical with respect to a Y axis, the Y axis intersecting a common center of the first and second common electric potential lines;

third and fourth detection electrodes disposed in the region and being axisymmetrical with respect to an X axis, the X axis intersecting the common center and being orthogonal to the Y axis; and

a charge amplifier generating a first output voltage and a second output voltage, the first output voltage being proportional to a capacitance difference between a capacitance of a first capacitor formed between the first detection electrode and the first and second common electric potential lines and a capacitance of a second capacitor formed between the second detection electrode and the first and second common electric potential lines, the second output voltage being proportional to a capacitance difference between a capacitance of a third capacitor formed between the third detection electrode and the first and second common electric potential lines and a capacitance of a fourth capacitor formed between the fourth detection electrode and the first and second common electric potential lines.

2. The electrostatic capacity type touch sensor of claim 1, wherein the first common electric potential line is disposed on a circumference of a first circle with a first radius, and the second common electric potential line is disposed on a circumference of a second circle with a second radius, the second radius being larger than the first radius, and wherein a boundary region between the first detection electrode and the third detection electrode is set so that an area of the first detection electrode included in a sector form of the second circle and an area of the third detection electrode included in the sector form vary linearly as the sector form rotates.

3. The electrostatic capacity type touch sensor of claim 2, wherein the boundary region between the first detection electrode and the third detection electrode is set so that the area of the first detection electrode included in the sector form linearly decreases and the area of the third detection electrode included in the sector form linearly increases as the sector form rotates.

4. The electrostatic capacity type touch sensor of claim 2, wherein X and Y coordinates of a point on a center line of the boundary region in a first quadrant of an X-Y coordinate system are represented by following equations:

X=(R+W×

n/90°

)×

cos(π

×

n/180°

)

Y=(R+W×

n/90°

)×

sin(π

×

n/180°

)

where R denotes the first radius, R+W denotes the second radius, and n varies from 0°

to 90°

.

5. The electrostatic capacity type touch sensor of claim 1, further comprising an arithmetic unit detecting a touch position on the region interposed between the first and second common electric potential lines based on calculation of tan⁻

1(V1/V2), where V1 denotes the first output voltage and V2 denotes the second output voltage.

6. The electrostatic capacity type touch sensor of claim 1, wherein the first common electric potential line is disposed on a circumference of a first ellipse and the second common electric potential line is disposed on a circumference of a second ellipse, the second ellipse being larger than the first ellipse.

7. An electrostatic capacity type touch sensor, comprising:

a substrate;

a first common electric potential line disposed on the substrate;

a second common electric potential line disposed on the substrate adjacent the first common electric potential line;

first, second, third and fourth detection electrodes disposed in a region interposed between the first common electric potential line and the second common electric potential line; and

a charge amplifier generating a first output voltage and a second output voltage, the first output voltage being proportional to a capacitance difference between a capacitance of a first capacitor formed between the first detection electrode and the first and second common electric potential lines and a capacitance of a second capacitor formed between the second detection electrode and the first and second common electric potential lines, the second output voltage being proportional to a capacitance difference between a capacitance of a third capacitor formed between the third detection electrode and the first and second common electric potential lines and a capacitance of a fourth capacitor formed between the fourth detection electrode and the first and second common electric potential lines,

wherein the first common electric potential line is disposed on a circumference of a first arc with a first radius and the second common electric potential line is disposed on a circumference of a second arc with a second radius, the first and second arcs sharing a common center and the second radius being larger than the first radius, and wherein a boundary region between the first detection electrode and the third detection electrode is set so that an area of the first detection electrode included in a sector form of the second arc having a predetermined center angle decreases as the sector form rotates and an area of the third detection electrode included in the sector form increases as the sector form rotates.