KR20110081474A - Single layer touch screen device with high precision and decision method of sensing position - Google Patents

Abstract

PURPOSE: A monolayer touch screen device with high precision and a location decision method are provided to decide a touch location on an X axis more precisely. CONSTITUTION: A plurality of signal electrodes are formed in a touch screen panel(100). A driving unit(220) applies a voltage having different waveforms to both ends of the signal electrode. A sensing unit(230) measures a charge quantity accumulated by an object touching the signal electrode. A signal processing unit(240) standardizes the charge quantity and decides a touch location.

Description

Single Layer Touch Screen Device with High Precision and Decision Method of Sensing Position}

The present invention relates to a structure and a positioning method of a single layer capacitive touch screen device with minimal operation error.

The touch screen panel is simple to input, so it is often used in mobile phones and monitors. Since the capacitive type can be made as a single layer without an air layer inside, it is expected to be used in mobile phones in the future because of the low transmittance loss. 1 is a plan view of a conventional single layer capacitive touch screen panel. Such a structure is mentioned in detail in Korean Patent Publication No. 10-2009-0048770. In the conventional single layer capacitive touch screen device, two electrodes are paired and detected. The left electrode 132 has a narrow width in the horizontal direction (X axis) of the screen, and the right electrode 131 has a large width. The left and right electrodes are made of a transparent and electrically conductive material such as ITO. The substrate 110 is usually a transparent plastic material. The left electrode and the right electrode are connected to an external sensing circuit by the outer electrode 141. The outer electrode 141 and the uniform electrode 142 make silver paste by screen printing. Uniform electrodes reduce the contact resistance between the outer and left electrodes and between the outer and right electrodes. A plurality of pairs consisting of one left electrode and one right electrode are formed in the vertical axis direction (Y axis).

2 is a cross-sectional view of a conventional single layer capacitive touch screen. The finger 300 on the glass cover 120 acts as a grounded electrode. There is a constant capacitance between the bottom electrode (left electrode, right electrode), the glass cover and the contact surface of the finger. Let A (L) be the area where the finger and the left electrode overlap, A (R) be the area where the right electrode and the finger overlap, and let d and ε be the thickness and dielectric constant of the glass cover, respectively. The capacitance C _L formed by the left electrode 132 and the finger and the capacitance C _R formed by the right electrode 131 and the finger are as follows.

3 is a view illustrating a conventional capacitive type projection of the finger 300 on the left electrode 132 and the right electrode 131. It is assumed that the finger 300 is rectangular as in Fig. 3A. The capacitance is generated in the area where the left electrode and the finger are in contact with each other, and the capacitance is generated in the area where the finger is in contact with each other. The capacitance is proportional to the area where the finger and the electrode are in contact. If the finger is placed in the center of the X axis, the capacitance formed at the left electrode and the right electrode is the same. The smaller the finger is to the left, the smaller the capacitance. If the length of the left electrode and the right electrode is X _O , the X-axis position where the finger is placed can be obtained by the following equation.

In the conventional single layer capacitive touch screen device, the X-axis position of the finger is determined according to the area ratio of the left electrode and the right electrode in the area where the finger contacts. If the finger has a rectangular shape as shown in Fig. 3A and is larger than the width of the electrode, the X-axis positioning degree is high. However, since the shape of the finger is elliptical, as shown in FIG. In addition, when the finger is smaller than the electrode width like a child, as shown in (c) and (d) of FIG. In order to compensate for this problem, in Patent Document 10-2009-0082965, the left and right electrodes are divided into two as shown in FIG. Enhanced linearity. However, the structure of the left and right electrodes are in contact with each other, so many disconnections and short circuits occur, resulting in poor productivity.

In the present invention, the accuracy of determining the X-axis position is increased by normalizing the amount of charged charge while alternately changing the voltage across the signal electrode. That is, it describes a method of finding the structure and location information of a single-layer touch screen panel that accurately determines the X-axis position regardless of the size and shape of the contact area of the finger.

In the capacitance method of the present invention, the signal electrodes are arranged side by side on the same plane, and different voltage waveforms are applied to both ends of the signal electrodes, thereby varying the voltage applied to the signal electrodes according to the X-axis position. In the present invention, since the amount of electric charge induced varies depending on the area of the finger, the voltage waveform across the signal electrode is changed, and the coordinates are determined by normalizing the change in capacitance according to the size of the finger.

Since the touch screen of the present invention is simple in structure, it is low in cost and more precisely determines the X-axis position. In addition, since the transmittance loss can be reduced by being integrated on the color filter substrate of the TFT LCD, the touch function can be realized while maintaining the characteristics of the display device having a bright screen.

1 is a plan view of a conventional single layer capacitive touch screen panel.
2 is a cross-sectional view of a conventional single layer capacitance method.
3 is an explanatory diagram of a conventional capacitance method.
5 is a plan view of a capacitive touch screen panel of the present invention.
6 is a cross-sectional view of the touch screen panel of the present invention.
Figure 7 shows the voltage distribution in the signal electrode of the present invention.
8 is an equivalent circuit diagram of a touch screen panel of the present invention.
9 is a configuration diagram of a touch screen device.
10 is a configuration diagram of a detector and a signal processor.
11 is a timing chart of the detection method of the present invention.
12 is a flow chart for determining the location of the present invention.
13 is a cross-sectional view of the TFT LCD to which the touch screen device of the present invention is applied.

The touch screen panel according to the present invention has a structure in which a plurality of signal electrodes 111 are parallel to the horizontal axis (X axis). 5 is a plan view of a capacitive touch screen panel of the present invention. The signal electrode 111 is made of a transparent and electrically conductive material such as ITO. The substrate 110 is a transparent plastic material. The signal electrode 111 is connected to the driving module 200 by the outer electrode 141. The outer electrode and the uniform electrode 142 are made by screen printing silver paste. Silver paste has much lower sheet resistance than signal electrodes. The uniform electrode reduces contact resistance between the outer electrode 141 and the signal electrode 111. The signal electrode 111 has a sheet resistance of 100 Ω / cm 2 or more. The total resistance of the outer electrode is made less than 0.1 kΩ. On the other hand, the resistance to both ends of the signal electrode is made larger to see 10kΩ. The resistance of the outer electrode is made less than about 1% of the resistance of the signal electrode. In this case, if voltage is applied to the outer electrodes at both ends of the signal electrode, the voltage attenuation caused by the outer electrode resistance can be ignored. The outer electrodes connected to both ends of the signal electrode are symmetrical with each other.

6 is a cross-sectional view of the touch screen panel 100 of the present invention. The touch screen panel used in the mobile phone and the monitor is coupled to the display element, the shielding electrode 112 prevents disturbance caused by electromagnetic waves coming from the driving unit of the display element. The shielding electrode is made of a transparent electrode such as ITO through which light is transmitted and grounded. The finger 300 on the glass cover 120 acts as a grounded electrode. A constant capacitance occurs on the contact surface between the signal electrode 111, the glass cover 120, and the finger. When the overlapping area between the finger and the signal electrode 111 is A, and the thickness and dielectric constant of the glass cover are d and ε, respectively, the change in capacitance (ΔC) generated when the finger is in contact is as follows.

Figure 7 shows the voltage distribution in the signal electrode of the present invention. As shown in FIG. 7A, the left uniform electrode 143 which is the X-axis origin is connected to the ground. The voltage waveform V (t) is applied to the right uniform electrode 142. V (t) is applied to the outer electrode, but because the resistance of the outer electrode is lower than that of the signal electrode, it is considered that there is no voltage drop at the outer electrode. FIG. 7B is an equivalent circuit of the signal electrode in the state shown in FIG. 7A. A resistor is a circuit connected in series. In such an equivalent circuit, the voltage waveform at an arbitrary point x in the X-axis is as follows.

Information about the X-axis position is contained in the amplitude of the voltage waveform. As the X-axis position increases, the amplitude increases as shown in FIG. In the present invention, the amplitude of the voltage waveform applied to the signal electrode is varied according to the X-axis position, and the X-axis position information is extracted through normalization. When a finger touches x, which is an arbitrary point on the signal electrode X axis, the capacitance ΔC increases with the signal electrode, whereby the charge Q by the finger accumulates in the signal electrode with time as shown in the following equation.

8 is an equivalent circuit diagram of a touch screen panel of the present invention. (A) is the equivalent circuit when the maximum voltage waveform is applied to the left uniform electrode which is the X-axis origin, and the right uniform electrode is grounded. (B) grounds the left uniform electrode, the X-axis origin, and the right uniform electrode is the equivalent circuit when the maximum voltage waveform is applied. (C) is an equivalent circuit when the maximum voltage waveform is applied to both the left and right uniform electrodes. (D) is an equivalent circuit when both the left and right uniform electrodes are grounded. If the total resistance of the signal electrode between the left and right uniform electrodes is R and the X-axis length of the signal electrode is X ₀ , the resistance R _a from the origin to any point x and the right uniform electrode at any point x The resistance R _{b to} is as follows.

In the equivalent circuits of (a), (b), (c), and (d) of FIG. 8, the voltages V (+), V (-), V (+,-), V at any point x in the X-axis. (0,0) is as below.

In the equivalent circuits of (a), (b), (c), and (d) of FIG. 8, the charges accumulated in the capacitance ΔC of the finger and the signal electrode at an arbitrary point x on the X-axis are Q (+), Q (-), Q (+,-), and Q (0,0) are as follows.

The information on the x value can be simply obtained from the following equation.

Q (+) and Q (-) are measured, and the sum of these values and the Q (+,-) value can be compared to verify the reliability of the current measurement. Q (0,0) is the offset value of the measurement system.

If the impedance Z due to the total capacitance C across the signal electrode is very large compared to the resistance R of the signal electrode, the voltage division of the driving electrode can ignore the influence of the capacitance of the touch panel. If the frequency of the voltage waveform across the signal electrode is f, the following condition must be satisfied.

If the driving frequency is 10KHz and the capacitance C is 20pF, the impedance is about 10MΩ, so that the resistance between both ends of the signal electrode is less than 100kΩ.

9 is a configuration diagram of a touch screen device of the present invention. The touch screen device is largely comprised of the touch screen panel 100 and the driving module 200. The drive module consists of one or several ICs. The driving module includes a control unit 210 in charge of overall control, a driving unit 220 for applying a voltage waveform to the signal electrode of the touch screen panel, and a sensing unit 230 for sensing the amount of charge accumulated in the signal electrode of the touch screen panel. It is composed of a signal processor 240 for processing the signal to switch to the X, Y coordinate. The signal processor may perform its function in an external system. When voltage is applied from the driver to the signal electrode, the sensing unit and the signal electrode are electrically disconnected, and when detecting a signal, the driver and the signal electrode are electrically disconnected. The signal electrode is connected to the sensing unit 230 of the driving module of FIG. 10. The sensing unit is composed of an (n × 1) multiplex 231 for sequentially selecting the sensing electrodes and an integrating circuit 232 for collecting charges and converting them into voltages. The charge ΔQ generated by finger contact is collected at C _S connected to the operational amplifier OP Amp. The voltage outputted from OP Amp (V ₀ ) is as below.

When R _S (Reset switch) is connected, the electric charge accumulated in C _S is discharged and initialized. There is only one ADC (Analogy Digital Convert) that reads the integrator and the output voltage V ₀ , and the signal electrodes are read alternately using the multiplex 231 one by one. The digital value of the output voltage is calculated as position coordinates by DSP (Digital Signal Processing). The signal processor 240 may be inside the driving module 200 as shown in FIG. 9 or may be placed in an external system.

11 is a timing chart of the detection method of the present invention. D (+) is the voltage waveform applied to the left of the signal electrode. D (-) is the voltage waveform on the right side of the signal electrode. Waveforms are simultaneously applied to all signal electrodes. The amount of charge induced in the first signal electrode is measured in synchronization with the VS signal. First, the reset switch of the integrating circuit of OP Amp is operated to erase the charge accumulated in C _S , and then the first signal electrode S (0) is connected to the integrating circuit to measure the charge by changing the voltage. When the first signal has been read, the reset switch is operated to erase the charge accumulated in C _S , and then the second signal electrode S (1) is connected to the integrating circuit and the charge is converted into a voltage. This process is performed up to the last signal electrode S (n). The charge accumulated on the nth signal electrode is called Q (n, +). Then, during the frame, the voltages are swapped with each other, and the same process is repeated to measure the charge. The charge accumulated on the nth signal electrode is called Q (n,-). In the verification frame, V voltage is applied to both ends of the signal electrode and the amount of charge is measured. The charge accumulated on the nth signal electrode is called Q (n, +,-). In the offset (off set) frame, 0V is applied to both ends of the signal electrode and the amount of charge is measured. It is a value that contains the noise generated from the outside during signal transmission or the offset voltage from other sensors. The charge accumulated on the nth signal electrode is called Q (n, 0,0).

     The output signal is calculated as a coordinate value touched by DSP (Digital Signal Processing). The DSP removes each signal electrode offset, and then calculates x (n) corresponding to the X-axis coordinates of each signal electrode using this value.

값과

을 비교하여 차이가 클 경우에는 에러처리루틴으로 제어를 넘길 수 있다.
Also

Value and

If the difference is large, control can be transferred to the error handling routine.

12 is a flow chart for determining the position of the touch screen panel of the present invention. When the touch screen panel is operated, the driving unit applies a waveform to the driving electrode and performs initial calibration measurement. The calibration measurement measures the charge accumulated in the sensing electrode, i.e., the parasitic capacitance, without finger contact. This value is due to the parasitic capacitance C ₀ between the signal and shielding electrodes in the absence of fingers or other contacts. The correction measurement value measured in the + frame at the i-th signal electrode is called Q ₀ (+, i), and the correction measurement value measured in the -frame at the i-th signal electrode is called Q ₀ (-, i). In the calibrated measurement, there was no difference between the measured values at + frame and-frame. If the difference in the amount of charge in the + frame and the-frame is small, the calibration measurement is completed. Measure + frame, -frame, verification frame, offset frame and verify that the measurement is done properly. Compare the plus and minus frame readings with those from the verification frame and measure again if they deviate from the tolerance. By determining the signal electrode that is maximized by adding the + frame and-frame measurement values, the position information on the Y axis can be obtained. Subsequently, the X-axis position information is obtained through the standardization process of the signal electrode that is maximized.

Since the height of the finger of the contacting surface is approximately 1 cm, the width of the electrode is made about 1 cm. If the width of the electrode is too small, there is little change in capacitance caused by the finger. The thickness of the glass cover is within 1 mm. The width of the transparent electrode is determined from the thickness of the glass cover and the area of the finger, with the width of the signal electrode between 4 mm and 10 mm.

The most widely used field of touch screen panel is a mobile phone, and TFT LCD is widely used as a display device of the mobile phone. A touch screen panel as shown in FIG. 6 is attached on the TFT LCD. By integrating the touch screen panel on the TFT LCD glass substrate, it is possible to realize a bright screen by reducing defects and light loss in assembly. In addition, the common electrode of the TFT LCD as well as the substrate can be shared as the shielding electrode, thereby reducing the material cost. 13 is a cross-sectional view of the touch screen panel of the present invention integrated with a TFT LCD. The liquid crystal layer 430 is formed between the TFT substrate 410 and the color filter substrate 420. The color filter substrate 422 and the common electrode 421 are formed on the color filter substrate facing the TFT substrate. The color filter is composed of red (R), green (G), and blue (B) as unit elements. In FIG. 13, the polarizer is attached to the TFT substrate, and the analyzer is attached to the touch screen signal electrode. In FIG. 13, the polarizer and the analyzer are omitted. A signal electrode 423 is first formed on the color filter glass substrate 420, and then a color filter layer and a common electrode are formed on the glass substrate behind the touch panel electrode. That is, in the process of making color filters, a touch screen panel can be made at the same time.

100: touch screen panel of the present invention 100 ': conventional touch screen panel
110 substrate 111 signal electrode 112 shielding electrode
120: glass cover 131, 132: right electrode, left electrode
141: outer electrode 142: uniform electrode
200: drive module
210: controller 220: driver 230: detector 240: signal processor
300: finger (contact object)
400: TFT LCD Panel
410 TFT substrate 420 color filter substrate 421 common electrode
423: signal electrode 430: liquid crystal layer

Claims (7)

A touch screen panel 100 in which a plurality of signal electrodes 111 are formed in parallel with each other;
A driver 220 which applies a voltage having a different waveform to both ends of the signal electrode 111;
A detector 230 measuring the amount of charge accumulated by the object 300 in contact with the signal electrode 111;
And a signal processor 240 for determining a position by normalizing the charge amount. The driving module 200 of claim 1, further comprising: a driving module 200 measuring the amount of charge by applying two voltage waveforms having different waveforms on both ends of the signal electrode 111, and changing the two voltage waveforms across the signal electrode. Touch screen device. The touch screen device as set forth in claim 2, further comprising a signal processor (240) which obtains a sum of the two charges and undergoes a standardization process. The touch screen device as claimed in claim 2, further comprising a drive module (200) for entering a measurement procedure for verifying a measurement error. 4. The touch screen device according to claim 3, wherein the transparent signal electrode (111) comprises a touch screen panel (100) provided on the color filter substrate (420) of the liquid crystal display device. Detecting an amount of charge accumulated in the signal electrode by applying a voltage having a different waveform to both ends of the signal electrode in a state where there is no contact with the object;
Detecting an amount of charge accumulated in the signal electrode while applying a voltage having a different waveform to both ends of the signal electrode while there is an object in contact;
Detecting the amount of charge accumulated in the signal electrode by changing a different voltage between the waveforms across the signal electrode;
Erasing the amount of charge in the absence of an object;
Touch screen position measurement method to determine the position of the object through the standardization process. The method of claim 6, further comprising verifying accuracy of measurement by applying a verification waveform across the signal electrode.

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