KR20170026069A - Touch force sensing apparatus - Google Patents

Abstract

According to an embodiment, a plurality of electrodes for touch detection; One or more pressure sensors for touch pressure detection; At least one signal wiring and a ground wiring connected to each of the pressure sensors; And a shield wiring disposed between the signal wiring and the ground wiring, the shield wiring being controlled coincident with the signal wiring.

Description

TOUCH FORCE SENSING APPARATUS

The present invention relates to a touch pressure detecting device, and more particularly, to a touch pressure detecting device in which a phenomenon of parasitic capacitance formed in a connection path between a pressure sensor and a driving circuit is eliminated.

BACKGROUND ART A touch panel is an input device mounted on a surface of a display to convert a physical contact of a user's finger into an electrical signal to operate the product. The touch panel can be widely applied to various display devices. In recent years, It is growing rapidly.

Such a touch panel can be classified into a resistive type, a capacitive type, an ultrasonic type (SAW), and an infrared type (IR) according to the operation principle.

Among them, the conventional capacitance type touch panel basically includes a substrate, a metal wiring layer, and a pattern layer. The pattern layer is composed of a plurality of pattern electrodes (touch patterns), and each pattern electrode generates an electrical signal corresponding to external physical contact. Then, the generated electrical signal is transmitted to the control unit of the product through the metal wires connected to the pattern electrode to operate the product.

In recent years, various types of applications having various functions in smart phones, smart TVs, and the like have emerged, so that demand for various touch methods in touch panels is increasing rapidly.

Therefore, there is a demand for a technique for judging various characteristics of the touch, specifically, the touch pressure, and performing an operation based thereon, instead of simply determining the touch position.

An object of the present invention is to eliminate an impedance difference in a plurality of pressure sensors for touch pressure detection.

Another object of the present invention is to eliminate the parasitic capacitance which can be formed in the connection path between the pressure sensor and the driving circuit.

According to an aspect of the present invention, there is provided a touch sensing apparatus including: a plurality of electrodes for touch detection; One or more pressure sensors for touch pressure detection; At least one signal wiring and a ground wiring connected to each of the pressure sensors; And a shield wiring disposed between the signal wiring and the ground wiring, the shield wiring being controlled coincident with the signal wiring.

According to the present invention, impedance differences in a plurality of pressure sensors for touch pressure detection can be eliminated.

Further, according to the present invention, the parasitic capacitance which can be formed in the connection path between the pressure sensor and the driving circuit is eliminated.

FIG. 1 is a view showing a configuration of a display device capable of touch pressure detection according to an embodiment of the present invention.
2 is a view showing only a pressure sensor in a display device capable of touch pressure detection according to an embodiment of the present invention.
3 is a circuit diagram showing an impedance formed on a pressure sensor according to an embodiment of the present invention as an equivalent circuit.
4 is a diagram schematically showing an arrangement of shield wirings according to an embodiment of the present invention.
5 is a view showing a configuration of a touch pressure detecting device according to an embodiment of the present invention.

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS Hereinafter, the present invention will be described with reference to the accompanying drawings. The present invention may, however, be embodied in many different forms and should not be construed as limited to the embodiments set forth herein. In order to clearly illustrate the present invention, parts not related to the description are omitted, and similar parts are denoted by like reference characters throughout the specification.

Throughout the specification, when a part is referred to as being "connected" to another part, it includes not only "directly connected" but also "indirectly connected" . Also, when an element is referred to as "comprising ", it means that it can include other elements, not excluding other elements unless specifically stated otherwise.

Hereinafter, embodiments of the present invention will be described in detail with reference to the accompanying drawings.

1 is a view showing a schematic configuration of a touch pressure detecting device according to an embodiment of the present invention.

Referring to FIG. 1, a display device including a touch pressure detecting device according to an embodiment includes a glass substrate 100, a black matrix 200 formed under the glass substrate 100, And a transparent electrode layer 300 formed thereon. The transparent electrode layer 300 is provided with a plurality of electrodes for detecting a touch on the upper surface of the glass substrate 100.

At least a part of the edge of the transparent electrode layer 300 is provided with a plurality of pressure sensors 310 for sensing the pressure of the touch generated on the upper surface of the glass substrate 100.

The process of improving the display device will now be described.

First, a black matrix 200 is formed on a glass substrate 100 by a printing method or a sputtering method, and then a transparent electrode layer 300 is formed on the entire surface by a sputtering method.

Thereafter, an electrode for touch detection and an electrode pattern for pressure detection are formed in the transparent electrode layer 300 through a wet etching, a dry etching, or a laser method. The electrode pattern for pressure detection becomes a part of the pressure sensor 310. That is, a portion of the transparent electrode layer 300 functions as the first electrode 311 of the pressure sensor 310.

A piezoelectric material 312 is printed and formed on the first electrode 311 of the pressure sensor 310. A printed layer such as a carbon layer may be further formed between the black matrix 200 and the piezoelectric material 312 when necessary.

A second electrode 313 is formed on the piezoelectric material 312 so as to face the first electrode 311 and an insulating layer is formed on the piezoelectric material 312 as a protective layer 314 for protecting the internal electrodes.

2 is a plan view showing only the pressure sensor 310 shown in FIG.

Referring to FIG. 2, four pressure sensors 310 are disposed near four corners of the display device.

The four pressure sensors 310 are all connected to the driving circuit 400 via the signal line 320. [ The length of the signal wiring 320 extending from the pressure sensor 310 disposed adjacent to the driving circuit 400 and the length of the signal wiring 320 extending from the pressure sensor 310 arranged at a distance from the driving circuit 400 The lengths of the first electrode 320 and the second electrode 320 are different. In addition, the impedance varies depending on the length of the signal line 320 connected to each pressure sensor 310.

In FIG. 2, the pressure sensor 310 located at the upper right of the drawing is connected to the driving circuit 400 as an equivalent circuit, which is the same as the circuit diagram of FIG.

Since the pressure sensor 310 operates on the principle that the resistance value changes according to the touch pressure, it can be expressed as a variable resistance.

A signal wiring 320 and a ground wiring 330 are connected to the pressure sensor 310. A parasitic capacitance Cp is formed in the signal wiring 320 and the ground wiring 330. This parasitic capacitance Cp is formed together with a large resistance R when formed of a transparent electrode having a sheet resistance value. As the length of the signal wiring 320 becomes longer, more parasitic capacitance Cp and resistance R are formed.

3, if the parasitic capacitance Cp connected in parallel is extremely large, even if the resistance value of the pressure sensor 310 changes due to the touch pressure, the resistance R and the parasitic capacitance Cp The charge charged in the parasitic capacitance Cp is guided to the pressure sensor 310 side instead of the drive circuit 400 direction. Therefore, at the stage of the driving circuit 400, the resistance change value of the pressure sensor 310 can not be detected properly or it takes a very long time to detect it.

In order to solve this problem, the embodiment of the present invention disposes the shield wiring 340 between the signal wiring 320 connected to the pressure sensor 310 and the ground wiring 330, as shown in FIG.

When there are two conductors, the amount of charge charged between both conductors can be defined as Q = CV. At this time, when the potential difference between both conductors is 0V, the amount of charge charged between the two conductors is eliminated, and the capacitance can also be removed.

Therefore, in the embodiment, the potential of the signal wiring 320 is applied to the shield wiring 340 so that the potential difference between the signal wiring 320 and the shield wiring 340 is brought close to 0 V, The parasitic capacitance Cp (see FIG. 3) can be made zero.

According to this, the amount of change in the resistance value in the pressure sensor 310 can be accurately transmitted to the driving circuit 400 side.

5 is a view showing a structure of a pressure sensor to which a shield wiring according to an embodiment of the present invention is applied.

Referring to FIG. 5, it can be seen that the shield wiring 340 is disposed between the signal wiring 320 connected to each pressure sensor 310 and the ground wiring 330. This arrangement effectively prevents the parasitic capacitance from being formed in the signal line 320 by controlling the potentials of the signal line 320 and the shield line 340 to coincide with each other. The resistance change value in the pressure sensor 310 can be accurately transmitted to the driving circuit side irrespective of the distance between the electrodes.

It will be understood by those skilled in the art that the foregoing description of the present invention is for illustrative purposes only and that those of ordinary skill in the art can readily understand that various changes and modifications may be made without departing from the spirit or essential characteristics of the present invention. will be. It is therefore to be understood that the above-described embodiments are illustrative in all aspects and not restrictive. For example, each component described as a single entity may be distributed and implemented, and components described as being distributed may also be implemented in a combined form.

The scope of the present invention is defined by the appended claims, and all changes or modifications derived from the meaning and scope of the claims and their equivalents should be construed as being included within the scope of the present invention.

Claims (1)

A plurality of electrodes for touch detection;
One or more pressure sensors for touch pressure detection;
At least one signal wiring and a ground wiring connected to each of the pressure sensors; And
And a shield wiring which is disposed between the signal wiring and the ground wiring and which is controlled to coincide with the signal wiring.

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