JP2009042974A - Touch panel, and display apparatus with the same - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To obtain a touch panel capable of accurately detecting a touch position even if an oscillation frequency is deviated in accordance with the separation of the touch position from one end of a detecting wire when the resistance of the detecting wire is high. <P>SOLUTION: One end or another end of the detecting wire is selected and successively connected to an oscillation circuit 21, an oscillation frequency of a signal output from the oscillation circuit 21 is counted in counting circuits 23a, 23b, and on the basis of both oscillation frequencies obtained when one end or the other end of the detecting wire to the oscillation circuit 21, a touch position calculation circuit 24 calculates a touch position, so that the touch position can be accurately calculated by suppressing a deviation of the oscillation frequency. <P>COPYRIGHT: (C)2009,JPO&INPIT

Description

  The present invention relates to a touch panel and a display device including the touch panel.

  A touch panel that detects a touch by a finger and identifies its position coordinate is attracting attention as one of the excellent user interface means, and various types of touch panels such as a resistive film type and a capacitance type have been commercialized. ing.

  As one of the capacitance methods, there is a PCT (Projected Capacitive Touchscreen) method that enables touch detection even when the front side of a touch screen with a built-in touch sensor is covered with a protective plate such as a glass plate with a thickness of several millimeters. is there. This method has advantages such as the fact that the protective plate can be arranged on the front surface, so that it is excellent in robustness, can detect touch even when wearing gloves, and has a long life because there is no moving part.

  For example, the configuration of a touch screen of a touch panel using the PCT method described in Patent Document 1 below includes a first series of conductor elements formed on a thin dielectric film and an insulating film as a detection conductor for detecting capacitance. A second series of conductive elements formed at intervals are provided, and there is no electrical contact between the conductive elements, and a plurality of intersections are formed. The most suitable material for the conductor element is a metal material such as silver. Moreover, the visibility becomes a problem on display, and indium oxide is used when the visibility is lowered. Further, a thin electric wire of 10 to 20 μm can be used instead of the conductor element.

  The conductor element for detecting the electrostatic capacitance is connected to the capacitance control oscillator via an output line and a multiplexer. The output is counted by a divider and used as capacity detection data.

JP-T-9-51186 (page 7, line 19 to page 8, line 4, page 8, line 23 to page 9, line 6, page 13, line 12 to line 12, FIG. 1, FIG. 2, FIG. 8)

  A relaxation oscillator can be used as the capacity control oscillator of such a touch panel. In the relaxation oscillator, the oscillation period is generally determined by the charge / discharge time constants of the resistance element and the capacitive element. A part of this capacitive element is formed between the detection wiring and the user's finger (hereinafter referred to as the indicator). The capacitance of the relaxation oscillator is determined according to the touch capacitance formed between the detection wiring and the indicator when a touch by the indicator occurs. A change occurs in the oscillation period. By detecting the amount of change in the oscillation period, it is possible to detect the touch capacitance and determine the presence or absence of the touch and its position (hereinafter referred to as the touch position).

  In order to reduce the visibility of the detection wiring, for example, when a transparent wiring material such as ITO (Indium Tin Oxide) is used, the resistance of the detection wiring is higher than that of a highly conductive metal material such as silver or copper. . In this case, as the touch position moves away from the detection end, the resistance of the detection wiring becomes extremely high, so that the amount of change in the oscillation period due to the touch capacitance is small, especially large (about 10 inches or more here). Since it is difficult to detect the touch capacitance in the touch panel, there is a problem that the touch position cannot be accurately detected.

  In order to reduce the resistance of the detection wiring, it is conceivable to increase the width of the detection wiring. However, since the touch panel is mounted on the front surface of the display device, in order to suppress the decrease in the transmittance of the display light, for example, Even if a transparent wiring material is used for the detection wiring, the width of the detection wiring is limited. In addition, if the width of the detection wiring is increased, the detection resolution of the touch position becomes coarse.

  The present invention has been made to solve such a problem, and an object of the present invention is to provide a touch panel that can reliably detect a touch capacitance and determine a touch position even when the resistance of a detection wiring is large. To do.

  Moreover, even if the detection wiring is formed using a high-resistance transparent wiring material, it is possible to obtain a touch panel that can suppress a decrease in the transmittance of display light without increasing the width of the detection wiring more than necessary. Objective.

  The touch panel according to the present invention has a plurality of detection wirings formed in a matrix direction, and sequentially selects a touch screen to be touched by an indicator and the detection wiring, and the selected detection wirings A switch circuit that sequentially selects one of the connection ends of the one end and the other end, and is connected to the detection wiring via the connection end selected by the switch circuit, and between the indicator and the detection wiring An oscillation circuit whose oscillation cycle changes according to the capacitance formed in the circuit, and the oscillation cycle when one end of the detection wiring is connected to the oscillation circuit and the oscillation circuit when the other end is connected to the oscillation circuit A touch position calculation circuit that sequentially obtains the detection result of the detection wiring based on both of the oscillation cycles and calculates the touch position of the indicator based on the detection results of the plurality of detection wirings.

  Even if the resistance of the detection wiring is large, the touch position is calculated based on the oscillation cycle when both ends of the detection wiring are connected, so only one end of the detection wiring oscillates. When the circuit is connected to the circuit, the deviation of the oscillation cycle that occurs as the touch position goes to the other end can be suppressed, and the touch position can be calculated accurately.

  In addition, since the touch position can be accurately calculated even when the resistance of the detection wiring is large, even if the detection wiring is formed using a high-resistance transparent wiring material, the wiring width is not increased more than necessary. There is an effect that a decrease in the transmittance of the display light can be suppressed.

Embodiment 1 FIG.
FIG. 1 is a plan view showing a configuration of a touch screen in a touch panel according to Embodiment 1 of the present invention, and FIG. 2 is a partial perspective sectional view thereof. The configuration will be described below with reference to the drawings. In the following embodiments, the same reference numerals as those in FIG. 1 denote the same or corresponding components in the drawings.

  As shown in FIG. 1, the touch screen 1 includes detection column wirings 2 extending in the column direction (y direction in FIG. 1) and arranged in parallel at a predetermined pitch, and the row direction (x direction in FIG. 1). The detection row wirings 3 extending in parallel to each other at a predetermined pitch are provided. A predetermined number of the detection column wirings 2 are electrically connected in common by the connection wiring 4 at the upper end and the lower end, respectively, and constitute a detection column wiring group 6. Similarly, the predetermined number of detection row wirings 3 are electrically connected in common by the connection wiring 5 at the left end and the right end, respectively, and constitute a detection row wiring group 7. FIG. 1 shows an example in which the predetermined number is five. Furthermore, a predetermined number of detection column wiring groups 6 are arranged in parallel, and a predetermined number of detection row wiring groups 7 are also arranged in parallel. In FIG. 1, the detection column wiring group 6 and the detection row wiring group 7 (hereinafter referred to as the detection wiring group) are partially omitted. The number of each is 8 systems (books). The detection wiring group is connected to the terminal 10 by lead-out wirings 8a, 8b, 9a, 9b. When the indicator touches the touch screen 1, a touch capacitance is formed between the detection column wiring 2 and the detection row wiring 3 (hereinafter referred to as detection wiring) constituting the detection wiring group and the indicator. The The number and wiring pitch of the detection wiring groups, and the number, wiring width and wiring pitch of the detection wirings constituting these detection wiring groups can be appropriately selected from the required resolution of the touch position of the touch panel.

  Here, if the detection wiring group is not composed of a plurality of detection wirings but a single so-called solid wiring, a large touch capacitance can be secured, but the area of the slit-shaped opening between the detection wirings is small. Therefore, when the touch panel 1 is arranged and used on the front surface of the display panel, the transmission of the display light is prevented and the transmittance of the display light is reduced. Therefore, in the first embodiment, the detection wiring group is constituted by a plurality of detection wirings, and the area of the slit-shaped opening between the detection wirings is increased, thereby reducing the transmittance of the display light. Suppressed.

  The layer configuration of the touch screen 1 will be described with reference to FIG. The upper surface is a transparent substrate (hereinafter referred to as a base substrate 12) made of transparent glass or resin, and the detection column wiring 2 made of a transparent wiring material such as ITO is formed on the back surface of the base substrate 12. A transparent interlayer insulating film 13 such as SiN (silicon nitride) is formed thereunder, and the detection row wiring 3 made of a transparent wiring material is formed on the back surface thereof. Further, a transparent protective film 14 such as SiN is formed below the interlayer insulating film 13. The positions of the detection column wiring 2 and the detection row wiring 3 are reversed, the detection row wiring 3 is formed on the back surface of the base substrate 12, and the detection column wiring 2 is formed on the back surface of the interlayer insulating film 13. Also good.

  FIG. 3 is an overall configuration diagram of the touch panel according to Embodiment 1 of the present invention. A terminal of an FPC (Flexible Printed Circuit) 17 is mounted on the terminal 10 of the touch screen 1 (not shown in FIG. 3; see FIG. 1) by using an ACF (Anisotropic Conductive Film) or the like. The end of the detection wiring group and the controller board 18 are electrically connected to function as a touch panel. The controller board 18 is equipped with a detection processing circuit 19 that performs processing for calculating the touch position of the indicator based on the detection result of the touch capacitance. The touch position calculated by the detection processing circuit 19 is externally detected. Output to a computer.

  FIG. 4 shows a block diagram of a touch position calculation operation on the touch panel according to the first embodiment of the present invention. In the first embodiment, a case will be described where the number of detection column wiring groups 6 and detection row wiring groups 7 are each configured as eight systems (Wc1 to Wc8, Wr1 to Wr8 in FIG. 4).

  The detection processing circuit 19 (not shown in FIG. 4, see FIG. 3) includes a first switch circuit (hereinafter referred to as analog multiplexer circuits 20a, 20b, 20c, and 20d), an oscillation circuit 21, and a counting circuit. 23a, 23b, a touch position calculation circuit 24, and a detection control circuit 25. Further, in the detection processing circuit 19, the counting circuits 23 a and 23 b, the touch position calculation circuit 24, and the detection control circuit 25 are referred to as a touch position calculation circuit 26, and the touch position calculation of the indicator is calculated based on the oscillation output signal output from the oscillation circuit 21. It is carried out. The detection oscillation circuit 22 includes a detection column wiring group 6, a detection row wiring group 7, analog multiplexer circuits 20 a, 20 b, 20 c and 20 d, and an oscillation circuit 21.

  One end (upper end in FIG. 4) of each detection column wiring group 6 is switched to 8: 1 analog multiplexer circuit 20a, and the other end (lower end in FIG. 4) is switched to 8: 1. It is connected to the multiplexer circuit 20b. Similarly, one end (the left end in FIG. 4) of each detection row wiring group 7 is set to the analog multiplexer circuit 20c for switching to 8: 1, and the other end (the right end in FIG. 4) is set to 8: 1. The analog multiplexer circuit 20d to be switched is connected. The analog multiplexer circuits 20 a, 20 b, 20 c and 20 d are connected to the oscillation circuit 21. Here, the analog multiplexer circuits 20a, 20b, 20c, and 20d are selected to be connected according to an instruction from the detection control circuit 25, and the connection between the detection wiring group and the oscillation circuit 21 is sequentially switched one by one.

  The oscillation circuit 21 is connected to the counting circuit 23a, and an oscillation output signal output from the oscillation circuit 21 is input to the counting circuit 23a. The counting circuits 23a and 23b count the oscillation output signal output from the oscillation circuit 21 until a predetermined count value is obtained, and obtain a period (time) from the start of counting to the predetermined count value. The oscillation cycle detection result is output to the touch position calculation circuit 24. Based on this oscillation cycle detection result, the touch position calculation circuit 24 calculates the touch position. The oscillation circuit 21, the counting circuits 23a and 23b, and the touch position calculation circuit 24 are connected to the detection control circuit 25, respectively. As described above, in accordance with the change in the oscillation cycle of the oscillation circuit 21, the electrostatic capacitance Ctc between the detection column wiring group 6 and the indicator and the electrostatic capacitance between the detection row wiring group 7 and the indicator. The capacity Ctr is calculated.

  FIG. 5 is a circuit diagram showing the connection between the circuit configuration of the oscillation circuit 21 and the detection wiring group in the touch panel according to Embodiment 1 of the present invention. In the first embodiment, the oscillation circuit 21 is configured using an operational amplifier circuit 30 and includes a second switch circuit (hereinafter referred to as an analog multiplexer circuit 31) that switches the connection to 4: 1. . The analog multiplexer circuits 20a to 20d and 31 are collectively referred to as switch circuits.

  In FIG. 5, only one detection column wiring group 6 and detection row wiring group 7 selected from eight systems by the analog multiplexer circuits 20a to 20d are shown, and the analog multiplexer is also shown. The circuits 20a to 20d are omitted. In FIG. 5, A indicates the touch position on the detection column wiring group 6 (hereinafter referred to as touch column coordinates), and B indicates the touch position on the detection row wiring group 7 (hereinafter referred to as touch row coordinates). Show. The detection column wiring group 6 selected by the analog multiplexer circuits 20a to 20b has a connection terminal 32a on the upper end Ta side, a connection terminal 32b on the lower end Tb side, and a detection selected by the analog multiplexer circuits 20c to 20d. The left end Tc side of the row wiring group 7 is connected to the connection terminal 32c, and the right end Td side is connected to the connection terminal 32d. The analog multiplexer circuit 31 selects one connection end from the four connection ends of the upper end Ta and the lower end Tb of the detection column wiring group 6 and the left end Tc and the right end Td of the detection row wiring group 7 to select an operational amplifier circuit. It connects to the inverting input terminal of 30.

  A resistor Ra is connected between the non-inverting input terminal of the operational amplifier circuit 30 and the ground, and a resistor Rb is connected between the non-inverting input terminal and the output terminal. A capacitor C1 is connected between the inverting input terminal of the operational amplifier circuit 30 and the ground, and a resistor R1 is connected between the inverting input terminal and the output terminal. The so-called relaxation oscillation circuit is configured using the operational amplifier circuit 30 in this way. The oscillation circuit 21 detects from the output saturation voltage a resistor R1 and a capacitor C1, a resistor of the detection column wiring group 6 (or a resistance of the detection row wiring group 7), and a touch capacitor Ctc (or Ctr). Oscillation occurs when charging / discharging is performed by the feedback path 35. An oscillation output signal is output from the output terminal 33.

  When the connection of the analog multiplexer circuit 31 is switched according to the instruction of the detection control circuit 25 input from the terminal 34, the connection between the connection terminals 32a to 32d and the inverting input terminal of the operational amplifier circuit 30 is switched. By switching the switch circuit, any one of the four connection ends of the upper end Ta and the lower end Tb of the detection column wiring group 6 and the left end Tc and right end Td of the detection row wiring group 7 is connected to the inverting input end of the operational amplifier circuit 30. Electrically connected. That is, the detection wiring group selected by the switch circuit constitutes a part of the detection feedback path 35, thereby forming the detection oscillation circuit 22 including the detection feedback path 35. When each of the analog multiplexer circuits 20a to 20d has an enable function for prohibiting conduction with any input, the analog multiplexer circuit 31 is not necessary.

  With this configuration, when the indicator touches the touch screen 1, the indicator is brought close to the detection column wiring group 6 to generate a touch capacitance Ctc, and is brought close to the detection row wiring group 7. When the touch capacitance Ctr is generated, the transfer characteristic of the detection feedback path 35 changes, and the detection oscillation circuit 22 is more effective than when the touch capacitances Ctc and Ctr are not generated (when the indicator is not touching the touch screen 1). Oscillation period (= oscillation period of the oscillation circuit 21) increases. The touch capacitances Ctc and Ctr can be detected from the change in the oscillation period, and the touch position can be calculated.

The oscillation period Tc of the oscillation circuit 21 alone without the detection feedback path 35 is approximately as shown by the following equation (1), and is proportional to the time constant τ of the resistor R1 and the capacitor C1.
Tc = 2τ · ln ((1 + k) / (1-k)) (1)
In addition, τ = R1 · C1
k = Ra / (Ra + Rb)
(R1, C1, Ra, and Rb indicate the resistance value and capacitance value of each element.)
In the detection oscillating circuit 22 including the detection feedback path 35, when the touch capacitors Ctc and Ctr are formed by touching the indicator, the detection feedback path 35 electrically connected to the inverting input terminal of the operational amplifier circuit 30 causes the above-described operation. The time constant τ increases and the oscillation period also increases. This change is used for touch capacitance detection, that is, touch position detection. However, as will be described later, even if the touch capacitances Ctc and Ctr are generated, the resistance of the detection wiring group exists in series with the touch capacitances Ctc and Ctr. The degree of change in the touch angle decreases, and the detection sensitivity of the touch capacitors Ctc and Ctr, that is, the touch position detection sensitivity decreases.

  Here, the oscillation period of the output signal of the detection oscillation circuit 22 is counted until the output signal of the detection oscillation circuit 22 (= the output signal of the oscillation circuit 21) reaches a predetermined count value by the subsequent counting circuit 23a. Further, the period from when the counting circuit 23a starts counting until it reaches a predetermined count value is detected by counting with the subsequent counting circuit 23b.

  In the first embodiment, the parasitic capacitances of the detection wiring and lead-out wirings 8a, 8b, 9a, and 9b and other circuit wirings and the electrostatic capacitance as viewed from the input / output terminals of the switch circuit (analog multiplexer circuit 20a to (Capacitance inside 20d, 31) is omitted for simplicity. Actually, it is necessary to select each circuit parameter such as a resistance value in consideration of these capacitances, but this does not affect the essence of the first embodiment.

  Next, the operation for detecting the touch position will be described with reference to FIGS. FIG. 6 is an explanatory diagram showing the operation of the counting circuits 23a and 23b in the touch panel according to the first embodiment of the present invention. First, the connection of the analog multiplexer circuit 31 of the oscillation circuit 21 is switched to the a side in FIG. 5, and the detection target is the detection column wiring group 6 and the connection end is the upper end Ta as shown in FIG. 6 (a). . Next, a control signal is input from the detection control circuit 25 to the terminal 34, and the analog multiplexer circuit 20a is sequentially switched and detected from the eight detection column wiring groups 6 as shown in FIG. 6B. A target wiring group is selected and connected to the oscillation circuit 21 in the order of Wc1, Wc2,..., Wc7, and Wc8. At this time, the upper end Ta of the selected detection column wiring group 6 is connected to the inverting input terminal of the operational amplifier circuit 30 (hereinafter, this state is referred to as connection relation 1).

  In conjunction with the switching operation of the detection target and connection end connected to the oscillation circuit 21, the counting circuit 23 a is when the reset signal RESET from the detection control circuit 25 is released and the enable signal ENABLE becomes an active level. (See FIGS. 6C and 6D), the counting of the oscillation output signal of the detection oscillation circuit 22 is started and counted until a predetermined count value is reached. When the predetermined count value is reached, the detection control circuit 25 sets the enable signal ENABLE to an inactive level and stops the counting of the counting circuit 23a.

  On the other hand, the counter circuit 23b in the subsequent stage counts a period during which the enable signal ENABLE is at the active level based on the counting clock signal Clk. That is, the count value of the count circuit 23b indicates a period from when the count circuit 23a starts counting until it reaches a predetermined count value. The count value of the counting circuit 23b is proportional to the oscillation period of the detection oscillation circuit 22 (a predetermined count value multiple of the oscillation period of the detection oscillation circuit 22). The oscillation period is counted. Then, the subsequent touch position calculation circuit 24 captures the oscillation cycle detection result output from the counting circuit 23b at the timing shown in FIG.

  Subsequently, the connection of the analog multiplexer circuit 31 of the oscillation circuit 21 is switched to the b side in FIG. 5, the detection target is the detection column wiring group 6, and the connection end is the lower end Tb (hereinafter, this state is referred to as connection relationship 2. In the same manner as described above, the oscillation cycle of the detection oscillation circuit 22 is detected in the counting circuits 23a and 23b.

  Next, the connection of the analog multiplexer circuit 31 of the oscillation circuit 21 is switched to the c side in FIG. 5, the detection target is the detection row wiring group 7, and the connection end is the left end Tc (hereinafter this state is referred to as connection relationship 3. The oscillation cycle of the detection oscillation circuit 22 is detected by the counting circuits 23a and 23b. Further, the connection of the analog multiplexer circuit 31 of the oscillation circuit 21 is switched to the d side in FIG. 5, the detection target is the detection row wiring group 7, and the connection end is the right end Td (hereinafter this state is referred to as connection relationship 4). ) The oscillation cycle of the detection oscillation circuit 22 is detected by the counting circuits 23a and 23b. In FIG. 6, (c) to (e) are omitted when the detection target is the detection row wiring group 7, but (c) to (e) when the detection target is the detection column wiring group 6. It is the same timing as e).

  FIG. 7 is a characteristic diagram showing the deviation of the oscillation period in the touch panel according to Embodiment 1 of the present invention. The horizontal axis represents the ratio of the resistance from the upper end Ta to the touch column coordinate A with respect to the total resistance of the detection column wiring group 6 (or the ratio of the resistance from the left end Tc to the touch row coordinate B with respect to the total resistance of the detection row wiring group 7. The vertical axis represents the relative value to the oscillation period of the detection oscillation circuit 22 when the touch row coordinate A is the center of the detection column wiring group 6 (or the touch row coordinate B is the detection row wiring group). 7 is a relative value with respect to the oscillation period of the oscillation circuit 22 for detection when the center is 7). In FIG. 7, the oscillation period in connection relations 1 and 3 is indicated by a solid line, and the oscillation period in connection relations 2 and 4 is indicated by a broken line. Moreover, the average value of the connection relations 1 and 2 and the average value of the connection relations 3 and 4 are indicated by a one-dot chain line. In FIG. 7, as an example, the wiring resistance of the detection column wiring group 6 and the detection row wiring group 7 (resistance of the entire detection wiring group) is 12 kΩ, R1 is 5 kΩ, Ra and Rb are 10 kΩ, and C1 is A case where 200 pF and touch capacitances Ctc and Ctr are 5 pF is shown.

  Here, the deviation of the oscillation period in the detection column wiring group 6 will be described as an example, but the detection row wiring group 7 can be similarly considered. As shown in FIG. 5, the resistance values from the upper end Ta and the lower end Tb of the detection column wiring group 6 to the touch column coordinate A are Rc1 and Rc2, respectively. The resistance ratio Rc1 / (Rc1 + Rc2) from the upper end Ta to the touch column coordinate A with respect to the wiring resistance of the detection column wiring group 6 to be detected, in other words, the touch column coordinates from the upper end Ta to the entire length of the detection column wiring group 6 to be detected. According to the ratio of the distance to A, that is, the touch column coordinate A with respect to the detection column wiring group 6 to be detected, even if the touch capacitance Ctc is fixed, it can be seen that the oscillation cycle differs as shown by the solid line in FIG. . When the upper end Ta side is connected to the oscillation circuit 21, the greater the resistance ratio (the lower the touch row coordinate A is), the smaller the oscillation period (solid line in FIG. 7), and the lower end Tb side is connected to the oscillation circuit 21. In the case of connection, the oscillation period becomes smaller (the broken line in FIG. 7) as the resistance ratio becomes smaller (the touch row coordinate A goes up). This is because when the wiring resistance of the detection column wiring group 6 is large, the transfer characteristic of the detection feedback path 35 determined from Rc1, Ctc, R1, and C1 changes due to the change of the touch column coordinate A.

  Originally, when the touch capacitor Ctc is formed between the detection column wiring group 6 and the indicator, the oscillation cycle becomes longer than when the indicator is not touched, and this change detects the touch by the indicator. The However, when the wiring resistance of the detection column wiring group 6 is large, when only one end of the detection column wiring group 6 is connected to the oscillation circuit 21 as a connection end, the touch column coordinate A is changed from the connection end to the other end. As the distance increases, the oscillation period of the detection oscillation circuit 22 decreases, and the detection sensitivity of the touch capacitance decreases. Therefore, in the first embodiment, the oscillation cycle when the upper end Ta and the lower end Tb are connected to the oscillation circuit 21 is averaged by the touch position calculation circuit 24, and the oscillation cycle deviation by the touch column coordinate A, that is, The deviation of the detection sensitivity of the touch capacitance is reduced (the dashed line in FIG. 7).

The touch position calculation circuit 24 holds a detection result average value obtained by averaging the oscillation cycle detection results output from the counting circuit 23b when the upper end Ta and the lower end Tb of the detection column wiring group 6 are sequentially connected to the oscillation circuit 21, respectively. To do. The last detection column wire group 6 scans detected were detected result an average value D _n (t-1) and the detection result detected by the current scan average value D _n (t) the difference between E _n (t) Is calculated. Here, n is a detection column wiring number (hereinafter referred to as a column address), and t is a scan number. It is determined that there is a touch position in the vicinity of the maximum detection column wiring group 6 from the detection column wiring group 6 in which the difference value E _n (t) is a predetermined value or more, and the column address n is set to the column address n. The touch column coordinate A is assumed.

Similarly, the touch position calculation circuit 24 averages the oscillation period detection results output from the counting circuit 23b when the left end Tc and the right end Td of the detection row wiring group 7 are sequentially connected to the oscillation circuit 21, respectively. Holds the average value. The last detection row wire group 7 Scan and detected detection result the mean value D _m (t-1) and the detection result detected by the current scan average value D _m (t) the difference between E _m (t) Is calculated. Here, m is a detection row wiring number (hereinafter referred to as a row address), and t is a scan number. It is determined that there is a touch position in the vicinity of the maximum detection row wiring group 7 from the detection row wiring group 7 in which the difference value E _m (t) is equal to or greater than a predetermined value, and the row address m is set as the row address m. The touch row coordinate B is assumed. Then, the touch position is determined by the touch column coordinates A and the touch row coordinates B obtained by the detection column wiring group 6 and the detection row wiring group 7 arranged in a vertical and horizontal matrix.

Furthermore, the difference value E _n-1 of the detection result average value of the detection column wire group 6 difference value E _n (t) is adjacent to the detection column wire group 6 becomes maximum (the column address n-1 and n + 1) If interpolation processing is performed using (t) and E _{n + 1} (t), more detailed touch row coordinates A can be calculated. Similarly, the difference value of the detection result average value in detection row wire group 7 the difference value E _m (t) is adjacent to the detection row wire group 7 having the maximum (row address m-1 and _m + 1) E _m- If interpolation processing is performed using ₁ (t) and E _{m + 1} (t), more detailed touch row coordinates B can be calculated. Thus, when a slit-shaped opening between detection wiring groups is touched, the touch position is not approximated by the number (column address and row address) of the detection wiring group closest to the touch position. In addition, it can be expressed by column coordinates and row coordinates between the detection wiring groups, which are accurate positions actually touched, and a more detailed touch position can be calculated.

  As described above, since the electrostatic capacitance formed between the indicator and the detection wiring group by the touch of the indicator is detected as the oscillation cycle of the detection oscillation circuit 22, the subsequent stage of the detection oscillation circuit 22 is a digital circuit. Since an analog circuit such as an A / D converter can be eliminated in the subsequent stage, the circuit configuration is simplified. Further, in order to increase the detection sensitivity of the touch capacitance, that is, the detection sensitivity of the oscillation period output from the detection oscillation circuit 22, the counting time of the counting circuits 23a and 23b may be increased, and the sensitivity is increased by the A / D converter. It is easier to handle than the case.

  In the first embodiment, the oscillation circuit 21 is configured by connecting elements (C1 and R1) such as resistors even when the detection wiring group is not connected. Depending on the switching timing of the switch circuit, any detection wiring group may not be connected to the oscillation circuit 21. At this time, the oscillation cycle is greatly shifted, and the detection wiring group is reconnected. This is to prevent the oscillation frequency from taking a long time when returning. Further, when the oscillation frequency shift is small and does not cause a problem at the time of switching of the detection wiring groups connected by the analog multiplexer circuits 20a to 20d, C1 and R1 of the oscillation circuit 21 may be unnecessary.

  In the first embodiment, the detection oscillation circuit 22 including the detection wiring group is configured by the operational amplifier circuit 30. However, the same configuration can be achieved by using other types of amplifier circuits such as an inverter circuit. It is. Furthermore, a multivibrator circuit using an RS flip-flop can be used.

  In the touch position calculation circuit 24 described above, the touch column coordinates A of the detection column wiring group 6 are calculated based on the average value of the oscillation cycle detection results when the upper end Ta and the lower end Tb are connected to the oscillation circuit 21. However, in order to correct the deviation of the oscillation period when each of the upper end Ta and the lower end Tb is connected to the oscillation circuit 21, the difference or ratio of the respective oscillation period detection results is obtained and detected based on this result. The touch column coordinate A of the column wiring group 6 may be calculated. Note that the touch line coordinates B can be calculated in the same manner, and the touch position can be calculated.

  In the first embodiment, the touch position is calculated using a detection wiring group composed of a plurality of detection wirings, but the same processing is performed for each detection wiring instead of the detection wiring group. The touch position may be calculated by performing.

  The touch panel according to the first embodiment calculates the touch position based on both oscillation cycles when one end and the other end of the detection wiring are connected even when the resistance of the detection wiring is large. When only one end of the detection wiring is connected to the oscillation circuit, it is possible to suppress the deviation of the oscillation cycle that occurs as the touch position goes to the other end, and the touch position can be calculated accurately.

  In addition, since the touch position can be accurately calculated even when the resistance of the detection wiring is large, even if the detection wiring is formed using a high-resistance transparent wiring material, the wiring width is not increased more than necessary. There is an effect that a decrease in the transmittance of the display light can be suppressed.

  Furthermore, since the oscillation circuit of the oscillation circuit is counted and the touch capacitance is detected, the subsequent stage of the oscillation circuit can be constituted by a digital circuit, and the touch panel can be realized with a simple configuration.

Embodiment 2. FIG.
In the first embodiment, scanning is performed while sequentially switching the detection target (detection wiring group) connected to the oscillation circuit 21 and the connection end, and the touch position is calculated from the detection result. For example, the detection column wiring By taking the ratio of the oscillation cycle detection results when the upper end Ta and the lower end Tb of the group 6 are connected, the approximate touch row coordinates when a touch occurs can be estimated. In the second embodiment, a touch panel configured to determine the scan priority of the detection row wiring group 7 using this will be described. Since the configuration is the same as that of the first embodiment, the description is omitted and only the operation is described.

  FIG. 8 is an explanatory diagram of the touch position calculation operation of the touch panel according to the second embodiment of the present invention. In FIG. 8, A shows the touch column coordinates as in FIG. First, in the same way as in the first embodiment, the touch position calculation circuit 24 uses the oscillation cycle detection result obtained by connecting the upper end Ta and the lower end Tb of the detection column wiring group 6 to the oscillation circuit 21 to detect the vicinity of the touch position. A column address (n = 2 in FIG. 8) is calculated and set as the touch column coordinate A. Further, the ratio of the detection column wiring group 6 (Wc2 in FIG. 8) in the vicinity of the touch position (oscillation cycle detection result when connected at the upper end) / (oscillation cycle detection result when connected at the lower end) (hereinafter referred to as a ratio between both ends). ) To estimate the approximate touch row coordinates based on the characteristics shown in FIG. It is estimated that the larger the ratio of both ends, the more approximate the touch row coordinates are on the upper end Ta side. For example, FIG. 8 shows an example in which it is estimated that the approximate touch row coordinate is the row address m = 4 based on the both-end ratio. Then, the detection row wiring group 7 (Wr3 to Wr5 in FIG. 8) in the vicinity of the approximate touch row coordinates is preferentially connected to the oscillation circuit 21 to obtain the touch row coordinates B (not shown in FIG. 8). As for the priority connection of the detection row wiring group 7, the touch position calculation circuit 24 outputs an instruction signal to the detection control circuit 25, and the detection control circuit 25 controls the analog multiplexer circuits 20a to 20d and 31. Done.

  The method of calculating the touch row coordinate B is almost the same as in the first embodiment, but in the first embodiment, all the row wiring groups for detection Wr1 to Wr8 are scanned. The difference is that only the detection row wiring group 7 of the three systems Wr3 to Wr5 is scanned to obtain the touch row coordinate B. As a result, it is possible to reduce the time required for detecting the touch capacitance, that is, detecting the touch position, compared to scanning all of the detection row wiring groups 7 as in the first embodiment. When the difference value of the detection result average values of the detection row wiring group 7 in the vicinity of the estimated approximate touch row coordinates is equal to or less than a predetermined value, the remaining detection row wiring groups 7 (Wr1, Wr2, Wr6 to Wr8). ) To obtain the touch row coordinate B. Thus, by obtaining the touch column coordinates A and the touch row coordinates B, the touch position can be determined.

  In the above description, the touch row coordinates B are obtained after obtaining the touch column coordinates A, but this order may be reversed. The touch row coordinate B is calculated from the oscillation cycle detection result when the left end Tc and the right end Td of the detection row wiring group 7 are connected, and further (oscillation cycle detection result at the left end connection) / (oscillation at the right end connection) The approximate touch column coordinates can be estimated from the ratio of the period detection results), the detection column wiring group 6 in the vicinity thereof can be preferentially connected to obtain the touch column coordinates A, and the touch position can be determined.

  According to the second embodiment, scanning is performed by calculating approximate touch row coordinates (or approximate touch column coordinates) based on a ratio of oscillation cycles when one end and the other end of the detection wiring are connected. There is an effect that the time for calculating the touch position can be shortened by limiting the wiring.

Embodiment 3 FIG.
In Embodiment 3, a liquid crystal display device integrated by attaching the touch screen 1 in Embodiment 1 or 2 to a liquid crystal display panel will be described.

  FIG. 9 is a cross-sectional configuration diagram of a liquid crystal display device according to Embodiment 3 of the present invention. The liquid crystal display panel 40 includes a color filter substrate 42 in which a color filter, a black matrix, a transparent electrode, and an alignment film are formed on a glass substrate, a TFT array substrate 44 in which TFTs that are switching elements are formed on the glass substrate, A liquid crystal layer 43 made of TN liquid crystal sandwiched between them, an adhesive layer 45 on the rear surface side of the TFT array substrate 44, and a polarizing plate 46 adhered to the TFT array substrate 44 by the adhesive layer 45 are provided.

  A backlight 47 as a light source is disposed on the back side of the liquid crystal display panel 40. On the other hand, on the front side of the liquid crystal display panel 40, the touch screen 1 described in the first or second embodiment is adhered to the color filter substrate 42 by the adhesive layer 41.

  A signal corresponding to an image to be displayed is input to the TFT array substrate 44 from an external driver circuit (not shown in FIG. 9), and a liquid crystal layer is connected via a switching element formed by TFTs corresponding to each pixel. The applied voltage of 43 is controlled to change the alignment direction of the liquid crystal molecules. Incident light from the backlight 47 passes through the polarizing plate 46 to become linearly polarized light, and passes through the liquid crystal layer 43 so that the vibration direction is bent according to the image signal to be displayed, and the color generated on the color filter substrate 42. By passing through the filter, it is separated into the three primary colors and passes through the touch screen 1 having a polarization function. In this way, the liquid crystal display device performs a desired display by controlling the transmittance of light from the backlight 47 in accordance with the image signal. In addition, the touch panel including the touch screen 1 calculates the touch position based on the change of the oscillation cycle and outputs the result as in the first or second embodiment.

  Note that a liquid crystal display device can also be configured in the same manner as in this embodiment even when a liquid crystal other than a TN liquid crystal such as an STN liquid crystal is used. In addition, although the liquid crystal display device has been described in the present embodiment, other types of display devices such as an organic EL display device and a PDP can be similarly configured.

  According to the third embodiment, since the touch screen is bonded and integrated with the liquid crystal display panel, the touch screen holding mechanism which has been conventionally required can be eliminated, and the entire apparatus can be thinned. It becomes.

  Furthermore, since the touch screen and the liquid crystal display panel are integrated, it is possible to prevent an adverse effect on the display caused by dust or the like entering the gap between the touch screen and the liquid crystal display panel.

It is a top view which shows the structure of the touch screen in the touchscreen by Embodiment 1 of this invention. It is a fragmentary perspective sectional view which shows the structure of the touch screen in the touchscreen by Embodiment 1 of this invention. 1 is an overall configuration diagram of a touch panel according to Embodiment 1 of the present invention. It is a block diagram of the touch position calculation operation in the touch panel by Embodiment 1 of this invention. It is a circuit diagram which shows the connection of the circuit structure of the oscillation circuit 21 and the detection wiring group in the touchscreen by Embodiment 1 of this invention. It is explanatory drawing which shows operation | movement of the counting circuits 23a and 23b in the touch panel by Embodiment 1 of this invention. It is a characteristic view which shows the deviation of the oscillation period in the touchscreen by Embodiment 1 of this invention. It is explanatory drawing of the touch position calculation operation | movement of the touchscreen by Embodiment 2 of this invention. It is a cross-sectional block diagram of the liquid crystal display device by Embodiment 3 of this invention.

Explanation of symbols

DESCRIPTION OF SYMBOLS 1 Touch screen, 2 detection column wiring, 3 detection row wiring, 6 detection column wiring group, 7 detection row wiring group, 20a-20d, 31 analog multiplexer circuit,
21 oscillation circuit, 26 touch position calculation circuit, 40 liquid crystal display panel,
Ctc, Ctr Touch capacitance.

Claims (8)

A touch screen having a plurality of detection wires formed in a matrix direction and touched by an indicator;
A switch circuit that sequentially selects the detection wirings and sequentially selects one of the connection ends of the selected detection wirings;
An oscillation circuit that is connected to the detection wiring via the connection end selected by the switch circuit, and whose oscillation cycle changes according to a capacitance formed between the indicator and the detection wiring; ,
Obtaining detection results of the detection wiring sequentially based on both the oscillation period when one end of the detection wiring is connected to the oscillation circuit and the oscillation period when the other end is connected to the oscillation circuit, A touch position calculation circuit that calculates a touch position of the indicator based on the detection result of the detection wiring;
Touch panel equipped with.   2. The touch position calculation circuit obtains a detection result of the detection wiring by averaging an oscillation period when one end of the detection wiring is connected and an oscillation period when the other end is connected. The touch panel described.   When either the row direction or the column direction is the first direction and the other is the second direction, the touch position calculation circuit calculates the touch position of the detection wiring in the first direction, and the first direction The approximate touch position in the second direction is estimated according to the ratio of the oscillation cycle when one end and the other end of the detection wiring in the direction are connected, and for the detection wiring in the second direction, 2. The touch panel according to claim 1, wherein the switch circuit is controlled so that the detection wiring in the vicinity of the approximate touch position is preferentially connected to the oscillation circuit. A group of detection wires in which a predetermined number of detection wires are connected in parallel;
A touch screen having a plurality of the detection wiring groups formed in a matrix direction and touched by an indicator;
A switch circuit that sequentially selects the detection wiring group and sequentially selects either one of the connection ends of the selected detection wiring group or the other end;
Oscillation that is connected to the detection wiring group via the connection end selected by the switch circuit, and whose oscillation cycle changes according to the capacitance formed between the indicator and the detection wiring group Circuit,
The detection results of the detection wiring group are sequentially obtained based on both the oscillation period when one end of the detection wiring group is connected to the oscillation circuit and the oscillation period when the other end is connected to the oscillation circuit. A touch position calculation circuit that calculates a touch position of the indicator based on the detection results of the plurality of detection wiring groups;
Touch panel equipped with.   The touch position calculation circuit obtains a detection result of the detection wiring group by averaging an oscillation period when one end of the detection wiring group is connected and an oscillation period when the other end is connected. Item 4. The touch panel according to item 4.   When either the row direction or the column direction is the first direction and the other is the second direction, the touch position calculation circuit calculates the touch position of the detection wiring group in the first direction, and the first direction The approximate touch position in the second direction is estimated according to the ratio of the oscillation cycles when one end and the other end of the detection wiring group in one direction are connected, and the detection wiring group in the second direction 5. The touch panel according to claim 4, wherein the switch circuit is controlled so that the detection wiring group in the vicinity of the approximate touch position is preferentially connected to the oscillation circuit.   A display device comprising the touch panel according to claim 1 and a liquid crystal display panel.   8. The display device according to claim 7, wherein the touch screen is adhered to the front side of the liquid crystal display panel.

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