JP4942729B2 - Touch panel and display device including the same - Google Patents

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, the projected capacitance (Projected Capacitive) that enables touch detection even when the front side of the touch screen with a built-in touch sensor is covered with a protective film such as a glass plate with a thickness of several millimeters. ) There is a method. 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 the touch screen in the touch panel described in Patent Document 1 below is formed by separating the insulating film from the first series of conductor elements formed in a thin dielectric film as a detection conductor for detecting capacitance. A second series of conductor elements is provided, and there is no electrical contact between the conductor 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. In addition, a thin conductor having a thickness 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. Furthermore, the touch position between the conductor elements can be interpolated based on the detected capacitance relative value of one or more conductor elements. In addition, the back-side shield surface can be eliminated by driving the unsampled conductor element through the buffer for the output of the capacitance control oscillator.

JP-A-9-511866 (page 7, line 19 to page 8, line 4, page 8, line 23 to page 9, line 6, page 13, line 12 to page 12, page 13 to line 23 to page 14, line 10, FIG. 1, FIG. 2, FIG. 6, FIG. 8)

  A relaxation oscillator can be used as the capacity control oscillator of such a touch panel. The oscillation period of the relaxation oscillator is generally determined by the charge and discharge time constants of the resistance element and the capacitive element. A part of this capacitive element is placed between the detection wiring and the user's finger (hereinafter referred to as the indicator). When the touch by the indicator occurs, according to the touch capacitance formed between the detection wiring and the indicator, A change occurs in the oscillation period of the relaxation oscillator. By detecting the amount of change in the oscillation period, the touch capacitance can be detected, and for example, the touch position detected by the adjacent detection wiring can be calculated by interpolation using the touch position between the adjacent wirings as touch coordinates.

  At that time, in order to perform high-precision interpolation of the touch coordinates, it is important to increase the capacitance detection sensitivity by the detection wiring around the touch position.

  However, when a touch is generated by the indicator, not only the detection wiring around the touch position but also the capacitance detection values of other detection wirings further away are larger than the detection values when there is no touch. That is, it has been confirmed by the discoverers that the reference value of the interpolation process fluctuates (offset occurs), and the degree of the fluctuation is in accordance with the detected wiring cross section capacitance.

  That is, if interpolation processing is performed with an offset generated in the detection values around the touch position, the interpolation processing reference changes, and there is a problem that accurate touch coordinates cannot be calculated by interpolation processing. .

  Therefore, the present invention has been made to solve such a problem, and even if an offset occurs in the detection value at the time of touch occurrence with respect to the detection value at the time when the touch has not occurred, the interpolation processing is performed. An object of the present invention is to obtain a touch panel capable of accurately calculating touch coordinates and a display device using the touch panel.

The first touch panel according to the present invention includes a touch screen having a plurality of detection lines formed in a row direction and a column direction, a switch circuit that sequentially selects the detection lines, and the detection lines selected by the switch circuit. And an indicator touched on the touch screen, a capacitance detection circuit for detecting a value corresponding to a capacitance value formed between, and a detection value detected by the capacitance detection circuit A touch position calculation circuit that calculates a position of the touch of the indicator on the touch screen, and the touch position calculation circuit is based on a detection value detected by the capacitance detection circuit. determines the the indicator of the touch presence determining means determines the presence or absence of the touch on the touch screen, and the touch existence determining means no touch of the indicator The case, from the detection value detected by the capacitance detection circuit, wherein a background calculation means for calculating a background value is the detection value when pointer touches without the said touch presence determining means instructs When determining that there is a touch of the body, a peak wiring determination unit that determines the detection wiring in which the detection value detected by the capacitance detection circuit is maximum in the row direction and the column direction, and the touch presence determination When the means determines that there is a touch of the indicator , based on the detection value of the detection wiring obtained by removing a predetermined range from the detection wiring having the maximum detection value, to the touch screen of the indicator is an increase amount from the background value generated in the detection value of said detection wire excluding the predetermined range to the touch event of the offset amount, the row and column directions An offset calculating means for calculating Re respectively, wherein when the touch existence determination means determines that the touch of the indicator is present, the detection the detection value from the detection wiring and the detection wiring becomes maximum within a predetermined range from the detection value of the wiring, based on the value obtained by subtracting said offset amount and the background value, the interpolation quantity calculation means for calculating the respective amount of interpolation in the row and column directions, the said detection value is maximized Touch position calculation means for calculating the touch position of the indicator by adding or subtracting the interpolation amount to or from the position on the touch screen corresponding to the detection wiring.

The second touch panel according to the present invention includes a touch screen having a plurality of detection lines formed in a row direction and a column direction, a switch circuit that sequentially selects the detection lines, and the switch circuit that is selected by the switch circuit. A capacitance detection circuit that detects a value corresponding to a capacitance value formed between the detection wiring and the indicator touched on the touch screen, and the capacitance detection circuit detects the capacitance. A touch position calculation circuit that calculates the position of the touch of the indicator on the touch screen based on the detection value, and the touch position calculation circuit uses the detection value detected by the capacitance detection circuit. based on the touch existence determining means determines the presence or absence of a touch to the touch screen of the indicator, and the touch existence determining means no touch of the pointer determine When, from the detection value detected by the capacitance detection circuit, and background calculation means for calculating a background value the a detection value when pointer touches no is the touch presence determining means and said Peak wiring determining means for determining the detected wiring in which the detection value detected by the capacitance detection circuit is maximized in the row direction and the column direction when it is determined that there is a touch of the indicator, and the presence or absence of the touch When the determination unit determines that there is a touch of the indicator, the touch screen of the indicator is based on the detection value of the detection wiring obtained by removing a predetermined range from the detection wiring having the maximum detection value. A first offset amount, which is an increase amount from the background value generated in the detection value of the detection wiring excluding the predetermined range when the touch is generated, is changed in the row direction. A first offset calculating means for calculating each in the fine column direction, when the touch existence determination means determines that the touch of the indicator is present, the detection value is touched in the center of the detection wire having the maximum included in the detection value of the detection wire in a predetermined range adjacent to the detection wires is, the second is the offset amount from the value obtained by subtracting said first offset amount and the background value from the detection value The second offset calculating means for calculating the offset amount in the row direction and the column direction, and the detection value that maximizes the detection value when the touch presence / absence determining means determines that the indicator touches. from the detection value of the detection wiring in a predetermined range from the wiring and the detection wiring, based on the value obtained by subtracting said background value and said first and second offset amount An interpolation amount calculating means for calculating an interpolation amount in each of the row direction and the column direction, and adding or subtracting the interpolation amount to a position on the touch screen corresponding to the detection wiring having the maximum detected value. Touch position calculation means for calculating the touch position of the indicator.

According to a first touch panel of the present invention, from the detected value, the background value, since to perform the touch coordinate calculation and offset amount generated when the touch occurs after canceled (subtracted) by pointer touch Even if the offset amount changes depending on the way (how to touch the touch panel, etc.), this can be reliably calculated and canceled, and the calculated touch coordinate accuracy can be improved.

According to a second touch panel of the present invention, from the detected value, the background value, since to perform the touch coordinate calculation and offset amount generated when the touch occurs after canceled (subtracted) by pointer touch Even if the offset amount changes depending on the way (how to touch the touch panel, etc.), this can be reliably calculated and canceled, and the calculated touch coordinate accuracy can be improved. Furthermore, each calculated offset amount contained in the detection value of the detection wires detection value is adjacent to the detection wires when a touch position in the center of the detection wire having the maximum in the row and column directions, and the background value It calculates the touch coordinates by interpolation amount calculated based on the value obtained by subtracting the offset amount. Accordingly, it is possible to improve the touch coordinate accuracy (touch resolution) by reducing the interpolation amount caused by the offset amount included in the detection wiring having the maximum detection value, and hence the error of the touch position calculation result.

<Embodiment 1>
FIG. 1 is a plan view showing a configuration of a touch screen 1 included in the touch panel according to Embodiment 1 of the present invention, and FIG. 2 is a partial perspective sectional view thereof. Hereinafter, the configuration of the touch screen 1 will be described with reference to the drawings. In the following drawings including the drawings in the case of the second embodiment, the same reference numerals used in the drawings indicate the same or corresponding components.

  As shown in FIG. 1, the touch screen 1 extends in the column direction (corresponding to the y direction in FIG. 1) and is arranged in parallel in the row direction (corresponding to the x direction in FIG. 1) at a predetermined pitch. There are provided a plurality of detection column wirings 2 and a plurality of detection row wirings 3 extending in the row direction x and arranged in parallel in the column direction y at a predetermined pitch. A predetermined number of the detection column wirings 2 are electrically connected in common by the connection wirings 4 at the upper end and the lower end, respectively, to constitute a bundle of detection column wiring groups 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 bundle of detection row wiring groups 7. 1 is composed of five (predetermined number) detection column wirings 2 and detection row wirings 3.

  Further, a predetermined number of detection column wiring groups 6 are arranged in parallel in the row direction x, and similarly, a predetermined number of detection row wiring groups 7 are arranged in parallel in the column direction y. In FIG. 1, a part of the detection column wiring group 6 and the detection row wiring group 7 (hereinafter, the detection column wiring group 6 and the detection row wiring group 7 are both referred to as a detection wiring group). However, as will be described later, in the present embodiment, the predetermined number of detection wiring groups is set to 8 systems (lines). The detection wiring group is connected to the terminal 10 by lead wires 8 and 9. In FIG. 1, when the indicator touches the touch screen 1, the detection column wiring 2 and the detection row wiring 3 (hereinafter, the detection column wiring 2 and the detection row wiring 3 are both included in the detection wiring group. A touch capacitance is formed between the indicator and the indicator. The number of detection wiring groups and the wiring pitch thereof, the number of detection wirings constituting the detection wiring group, the wiring width, and the wiring pitch are appropriately selected from the required resolution of the touch position (touch coordinate value) of the touch panel. The

  Here, if the detection wiring group is not composed of a plurality of detection wirings, but the detection wiring group is configured as a single so-called solid wiring, a large touch capacitance can be secured, but a touch panel is provided on the front surface of the display panel. When arranged and used, the detection wiring group becomes a factor that hinders the transmission of the display light, and the transmittance of the display light is reduced. Therefore, in this embodiment, the detection wiring group is configured by a plurality of detection wirings, and the area of the slit-shaped opening between the detection wirings is set large, thereby reducing the transmittance of display light. We are trying to suppress this. However, a modification in which each detection wiring group is configured as one so-called solid wiring may be applied in view of the problem of a decrease in the transmittance of display light.

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

  Note that the detection wiring may be configured using a metal wiring material such as aluminum instead of a transparent wiring using a transparent wiring material such as ITO. In this case, as described above, the detection wiring group is configured by a plurality of detection wirings, and the area of the slit-shaped opening between the detection wirings is set large, thereby allowing the transmittance for display light to be increased. Is secured.

  FIG. 3 is a diagram schematically showing the overall configuration of the touch panel in the present embodiment. 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 panel of FIG. 3 functions as a touch panel by electrically connecting the end of the detection wiring group of the touch screen 1 and the controller substrate 18 via the FPC 17. The controller board 18 is equipped with a detection processing circuit 19 that performs a calculation process of touch coordinates on the touch screen 1 of the touch position of the indicator based on the detection result of the touch capacitance. The calculated value of the touch coordinates on the touch screen 1 at the touch position of the indicator is output as detected coordinate data to an external computer (not shown) or the like.

  FIG. 4 is a block diagram showing a circuit configuration of a touch operation detection / touch coordinate calculation system in the touch panel according to the present embodiment. In this embodiment, as an example, the number of the detection column wiring groups 6 and the detection row wiring groups 7 is 8 systems each (in FIG. 4, the detection column wiring groups Wc1 to Wc8, the detection row wiring group Wr1). ~ Wr8) is described.

  4, the detection processing circuit 19 shown in FIG. 3 includes a column switch circuit 20a, a row switch circuit 20b, an oscillation circuit 21, a first count circuit 23a, a second count circuit 23b, a touch position calculation circuit 24, and a buffer circuit. 26, a clock oscillator CO, and a detection control circuit 25 for controlling the above-described components 20a, 20b, 21, 23a, 23b, 24. The detection oscillation circuit 22 includes a detection column wiring group 6, a detection row wiring group 7, a column switch circuit 20a, a row switch circuit 20b, an oscillation circuit 21, and a buffer circuit 26.

  One end (upper end in FIG. 4) of each detection wiring group 6 is connected to the column switch circuit 20a, and one end (right end in FIG. 4) of each detection row wiring group 7 is connected to the row switch circuit 20b. It is connected.

  FIG. 5 is a circuit diagram showing the configuration of the switch circuits 20a and 20b. The column switch circuit 20 a includes an analog multiplexer circuit 27 that switches the connection to 2: 1 for each wiring group of the detection column wiring group 6. Each wiring group of the detection column wiring group 6 is switched in connection with the input terminal of the oscillation circuit 21 or the output terminal of the buffer circuit 26 by the analog multiplexer circuit 27 of the column switch circuit 20a corresponding thereto. (See FIG. 4). The analog multiplexer circuit 27 may also be referred to as a switch circuit.

  Similarly, the row switch circuit 20 b includes an analog multiplexer circuit 27 that switches the connection to 2: 1 for each wiring group of the detection row wiring group 7. Each wiring group of the detection row wiring group 7 is switched in connection with the input end of the oscillation circuit 21 or the output end of the buffer circuit 26 by the analog multiplexer circuit 27 of the corresponding row switch circuit 20b.

  Thus, the analog multiplexer circuit 27 constituting the column switch circuit 20a and the row switch circuit 20b selects the connection in accordance with the instruction of the control signal output from the detection control circuit 25, and detects the column wiring for detection. The connection with the oscillation circuit 21 is sequentially switched one by one from the group 6 and the detection row wiring group 7. That is, one wiring group selected to be connected to the oscillation circuit 21 is a detection target as a selected wiring group, and the other non-selected wiring groups are connected to the output of the buffer circuit 26. Although the operation of the oscillation circuit 21 will be described later, the buffer circuit 26 buffers the charge / discharge waveform that determines the transmission cycle of the oscillation circuit 21 and applies it to the non-selected wiring group. Thereby, by making the selected wiring group and the non-selected wiring group have substantially the same potential, it is possible to reduce the influence of the coupling capacitance formed between the two wiring groups.

  In FIG. 4, the output terminal of the oscillation circuit 21 is connected to the input terminal of the first counting circuit 23a, and the transmission output signal output from the oscillation circuit 21 is input to the first counting circuit 23a. The first counting circuit 23a counts the transmission output signal output from the oscillation circuit 21 in accordance with the RESET signal output from the detection control circuit 25 and the subsequent rise timing of the ENABLE signal, and outputs the count value (count value). It outputs to the detection control circuit 25 one by one. Here, the detection control circuit 25 holds data of a predetermined count value, compares the count value input from the first count circuit 23a with the predetermined count value, and receives the input count value. At the timing when the signal becomes equal to a predetermined count value, the ENABLE signal is lowered, and the first counting circuit 23a counts the transmission output signal from the oscillation circuit 21 in accordance with the output stop timing or the falling timing of the ENABLE signal. Stop operation. That is, the first counting circuit 23a counts the transmission output signal from the first input time of the transmission output signal from the oscillation circuit 21 after RESET until the count value reaches a predetermined count value. The second counting circuit 23b, which is the subsequent stage of the first counting circuit 23a, is predetermined and output from the clock oscillator CO in accordance with the rising (output) timing of the RESET signal and ENABLE signal output from the detection control circuit 25. The counting of the pulses of the clock signal Clk having any given period is started. Then, by continuing to count the pulses of the clock signal Clk within a period until the output stop or fall timing of the ENABLE signal, the first counting circuit 23a starts counting the transmission output signal from the oscillation circuit 21. Then, the period (time) until the count value becomes the predetermined count value included in the detection control circuit 25 is counted. Then, the second counting circuit 23b outputs this period counted by the second counting circuit 23b as a “transmission period detection result” to the touch position calculation circuit 24 according to the output stop timing of the ENABLE signal. . Then, the detection control circuit 25 outputs to the touch position calculation circuit 24 a control signal that instructs to capture the transmission cycle detection result in accordance with the output stop timing of the ENABLE signal. In accordance with the input timing of this control signal, the touch position calculation circuit 24 takes in the transmission cycle detection result output from the second counting circuit 23b, and based on this transmission cycle detection result, as described later, the touch of the indicator is touched. A touch coordinate value of the position on the touch screen 1 is calculated.

  In this manner, based on the change in the oscillation cycle of the oscillation circuit 21 caused by the touch of the indicator on the touch panel, the capacitance Ctc between the detection column wiring group 6 and the indicator, and the detection row wiring. A configuration (an example of means or a measuring method for measuring the capacitances Ctc and Ctr) in which the capacitance Ctr between the group 7 and the indicator is substantially calculated in the touch position calculation circuit 24 is described. The touch panel is provided.

  FIG. 6 is a circuit diagram schematically showing the circuit configuration of the oscillation circuit 21 included in the touch panel according to the present embodiment and the connection relationship with the detection wiring group and the buffer circuit. In the present embodiment, the oscillation circuit 21 is configured using an operational amplifier circuit 30. In FIG. 6, for the sake of easy understanding, the switch circuit 20a and 20b show two detection column wiring groups 6 and the detection row wiring group 7 out of the eight systems, respectively, and the switch circuits 20a and 20b are also simplified. FIG.

  In FIG. 6, A indicates a touch position (hereinafter referred to as touch coordinates) on the detection column wiring group 6 and the detection row wiring group 7. By switching the analog multiplexer circuit 27 constituting the switch circuit 20a to the a side, the corresponding detection column wiring group 6 and the input terminal 32a of the oscillation circuit 21 are connected, and by switching to the b side, the buffer circuit 26 Connected to the output end of the. Similarly, when the analog multiplexer circuit 27 constituting the switch circuit 20b is switched to the a side, the corresponding detection row wiring group 7 and the input terminal 32a of the oscillation circuit 21 are connected and switched to the b side. It is connected to the output terminal of the buffer circuit 26.

  In this way, the analog multiplexer circuit 27 constituting the column switch circuit 20a and the row switch circuit 20b is sequentially switched to the a side in response to a command from the detection control circuit 25, thereby detecting the upper end and the detection of the detection column wiring group 6. One connection end is selected from the two connection ends, ie, the right end of the row wiring group 7, and the selected connection end is electrically connected to the inverting input end of the operational amplifier circuit 30. That is, the detection wiring group selected by the analog multiplexer circuit 27 constituting the column switch circuit 20a and the row switch circuit 20b constitutes a part of the detection feedback path 35, and this selected detection Thus, the detection oscillation circuit 22 (FIG. 4) including the wiring group for operation is configured.

  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. In this way, a so-called relaxation oscillation circuit is configured using the operational amplifier circuit 30. The oscillation circuit 21 starts from the output saturation voltage in addition to the resistor R1 and the capacitor C1, the resistance of the detection column wiring group 6 (or the resistance of the detection row wiring group 7), and the touch capacitance Ctrc (or touch capacitance Ctr). Are charged and discharged by the detection feedback path 35 constituted by Then, an oscillation output signal is output from the output terminal 33.

  With such a 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, or the indicator is in the detection row. When the touch capacitance Ctr is generated in the vicinity of the wiring group 7, the transfer characteristic of the detection feedback path 35 is changed, and the touch capacitances Ctc and Ctr are not generated (when the indicator is not touching the touch screen 1). However, the oscillation cycle of the detection oscillation circuit 22 (= the oscillation cycle of the oscillation circuit 21) increases. Then, as will be described later, the touch coordinate value on the touch screen 1 of the touch position of the indicator can be calculated by substantially detecting the touch capacitances Ctc and Ctr based on the change in the oscillation cycle. .

  Without considering a part of the detection feedback path 35 including the detection wiring group selected by the analog multiplexer circuit 27, the oscillation period Tc of the oscillation circuit 21 alone is approximately expressed by the following equation (1). Will be given to the street. The oscillation period Tc is proportional to the time constant τ of the resistor R1 and the capacitor C1.

  In the detection oscillation circuit 22 including the detection feedback path 35, when the touch capacitors Ctc and Ctr are formed by the touch of the indicator on the touch screen 1, the detection is electrically connected to the inverting input terminal of the operational amplifier circuit 30. The time constant τ is increased by the feedback path 35, and the oscillation period of the oscillation circuit 21 is also increased. This change in the oscillation period is used to detect touch capacitance, that is, to detect a touch coordinate value on the touch screen 1 at the touch position.

  Further, the charge / discharge voltage appearing at the inverting input terminal of the operational amplifier circuit 30 is input to the analog multiplexer circuit 27 via the buffer circuit 26, and the connection of the circuit is switched to the b side, whereby a non-selected wiring group. To be applied. As a result, the cross section capacitance Cc formed around the cross section (intersection) between the detection column wiring group 6 and the detection row wiring group 7 schematically shown in FIG. The applied voltage can be reduced. If the applied voltage of the cross section capacitance Cc can be ideally zero, the presence of the cross section capacitance can be ignored in the oscillation operation.

  However, due to the frequency response and output impedance of the buffer circuit 26 and the wiring resistance of the detection wiring group, the potentials of the charge / discharge voltage that determines the oscillation period of the relaxation oscillation circuit and the non-selected wiring group can be completely matched. This is difficult, and the cross-section capacitance Cc affects the oscillation period. In particular, when a touch occurs, not only the detection column wiring group 6 and the detection row wiring group 7 around the touch position but also the detection values of the other wiring groups increase simultaneously (the oscillation cycle becomes large). Phenomenon). Although this influence will be described later as an explanation of the interpolation process, an increase in the detection value from the wiring group other than the periphery of the touch position becomes an offset amount when the interpolation process is performed.

  Now, referring to FIG. 4, the output signal of the oscillation circuit 21 described above is input to the counting circuits 23a and 23b. The first counting circuit 23a in the preceding stage counts the output signal of the detection oscillation circuit 22 (= the output signal of the oscillation circuit 21) under the control of the detection control circuit 25 until the predetermined count value CP is reached (this count count). By processing, as will be described later, it is possible to smooth the influence of external noise or the like and increase the accuracy of measurement). Further, under the control of the detection control circuit 25, the period from when the first counting circuit 23a starts counting until the predetermined count value CP is reached (= (the oscillation period of the output signal of the detection oscillation circuit 22)) × (Predetermined count value CP)) is counted by the second counter circuit 23b in the subsequent stage, so that the oscillation cycle of the output signal of the detection oscillation circuit 22 is detected (the counted period is the predetermined count value CP). The value obtained by the division is the average value of the oscillation period of the output signal of the detection oscillation circuit 22).

  At this time, for example, external noise from a peripheral device such as a display device used in combination with a touch panel or random noise generated by a circuit element itself such as an analog multiplexer circuit is detected by the detection column wiring group 6, the detection When mixed in the connection path to the oscillation circuit 21 including the row wiring group 7 and the lead-out wirings 8 and 9, the oscillation frequency fluctuates, and the accuracy of the detected capacitance value decreases. On the other hand, the predetermined count value CP counted by the first counting circuit 23a is the number of integrations of the oscillation period of the oscillation circuit 21. That is, since the external noise and random noise are asynchronous with the oscillation of the oscillation circuit 21, when the predetermined count value CP is set to a large value, the influence of the external noise and the like is averaged and reduced by integration, The detection accuracy of the capacitance value is improved. However, the period until the count value of the first count circuit 23a reaches the predetermined count value CP counted by the second count circuit 23b is given by (oscillation cycle) × (predetermined count value CP). If this predetermined count value CP is set to a large value, the detection time by one detection wiring group also increases, making it difficult to satisfy the desired response time of the touch panel, and the number of detection wiring groups is large. In some cases, this trend is even more pronounced. For this reason, the predetermined count value CP is appropriately set so as to satisfy a desired response time.

  In the first embodiment, the parasitic capacitance on the detection wiring group, the lead-out wirings 8 and 9 and other circuit wirings, and the electrostatic capacitance as viewed from the input / output terminals of the switch circuit (analog multiplexer circuits 20a and 20b). , 31 are not shown for the sake of simplicity. Actually, since each circuit parameter such as a resistance value is selected in consideration of these capacitances, these capacitances do not affect the essence of the present embodiment.

  Next, the operation of detecting the touch coordinate value on the touch screen 1 at the touch position will be described with reference to FIGS. First, an operation in which detection wiring groups are sequentially connected to the oscillation circuit 21 and capacitance detection is performed by the counting circuits 23a and 23b will be described. FIG. 7 is a timing chart showing the detection / calculation operation of the touch panel in the present embodiment.

  The detection control circuit 25 outputs a control signal instructing a command to sequentially switch the eight detection column wiring groups 6 to each analog multiplexer circuit 27 constituting the column switch circuit 20a. The analog multiplexer circuit 27 selects the column wiring group to be detected from the eight detection column wiring groups 6 as shown in FIG. 7 while sequentially switching its output terminals in accordance with the control signal. Then, the upper end of the detection column wiring group 6 is connected to the connection terminal 32a of the oscillation circuit 21 in the order of Wc1, Wc2,..., Wc7, and Wc8. As a result, the upper end portion of the selected detection column wiring group 6 is connected to the inverting input end of the operational amplifier circuit 30.

  In conjunction with the switching operation of the detection target wiring group connected to the oscillation circuit 21, the first counting circuit 23 a releases the reset signal RESET from the detection control circuit 25 and outputs an enable signal output from the detection control circuit 25. When ENABLE becomes an active level (see FIG. 7), the count of the oscillation output signal of the detection oscillation circuit 22 is started, and the count is continued until a predetermined count value CP is reached. Then, the detection control circuit 25 sets the enable signal ENABLE to the inactive level when detecting that the count value output from the first count circuit 23a has reached the predetermined count value CP, and the first count circuit 23a. The counting operation is stopped.

  On the other hand, the second counting circuit 23b in the subsequent stage counts a period during which the enable signal ENABLE output from the detection control circuit 25 is at the active level based on the counting clock signal Clk. That is, the count value of the second count circuit 23b indicates a period from when the first count circuit 23a starts the count operation until the count value reaches the predetermined count value CP. Therefore, the count value CV1 of the second count circuit 23b is an averaged value obtained by integrating the oscillation period of the detection oscillation circuit 22 for a predetermined count value CP. Then, after setting the enable signal ENABLE to the inactive level, the detection control circuit 25 outputs a control signal instructing to read the count value CV1 of the second count circuit 23b to the subsequent touch position calculation circuit 24. The touch position calculation circuit 24 takes in the oscillation cycle detection result CV1 output from the second counting circuit 23b at the timing shown in FIG. 7 according to the input timing of this control signal.

  Similarly, the detection control circuit 25 outputs a control signal instructing a command to sequentially switch the eight detection row wiring groups 7 to each analog multiplexer circuit 27 constituting the row switch circuit 20b. The analog multiplexer circuit 27 selects the row wiring group to be detected from the eight detection row wiring groups 7 as shown in FIG. Then, the right end portion of the detection row wiring group 7 is connected to the connection terminal 32 a of the oscillation circuit 21 in the order of Wr 1 → Wr 2 →... → Wr 7 → Wr 8. As a result, the right end portion of the selected detection row wiring group 7 is connected to the inverting input end of the operational amplifier circuit 30.

  Similarly, the detection control circuit 25 cancels the reset signal RESET and changes the enable signal ENABLE to the active level, and the first and second counting circuits 23a and 23b relate to each detection row wiring group 7. Then, an integrated value CV1 of a predetermined count value CP times of the oscillation cycle of the detection oscillation circuit 22 is detected.

  Although details will be described later based on a flowchart, at this time, the background value Gb is subtracted from the count value CV1 of the second count circuit 23b to calculate a detection value CV2 by each wiring group. The touch position calculation circuit 24 performs touch presence / absence determination processing (touch presence / absence determination means) based on the calculated detection value CV2. The touch presence / absence determination processing is performed for each of the detection column wiring group 6 and the detection row wiring group 7, and when the detection value CV2 is equal to or greater than a predetermined threshold TL (CV2 ≧ TL), there is a touch by the indicator. Judge that Then, the touch position calculation circuit 24 calculates touch coordinates by an interpolation process described later. In FIG. 7, the column wiring group Wc4 is a column wiring group in which the detection value CV2 (the value obtained by subtracting the background value Gb from the count value CV1) is the maximum value, and the row wiring group Wr5 is the detection value CV2. Is exemplified as a row wiring group showing the maximum value.

  On the other hand, when the detection value CV2 for any of the detection column wiring groups 6 and the detection value CV2 for any of the detection column wiring groups 7 are less than a predetermined threshold TL, the touch position calculation circuit 24 Then, it is determined that there is no touch by the indicator, and the process proceeds to a background value calculation process for calculating a background detection value when there is no touch.

  Then, a series of operations of returning to the detection process by each wiring group described above is repeated through the touch coordinate calculation process or the background value calculation process. Note that the detection processing by each wiring group, the touch coordinate calculation processing, and the background value calculation processing can be partially performed in parallel.

  Next, touch coordinate calculation processing will be described. In addition to the touch presence / absence determination process (touch presence / absence determination means) described above, the touch position calculation circuit 24 includes a peak wiring determination process (peak wiring determination means), an offset amount cancellation process (offset calculation means), and an interpolation process (touch position calculation means). )have. In the peak wiring determination process, when it is determined that there is a touch in the touch presence / absence determination process, a column wiring group and a row wiring group having a maximum detection value are obtained. In the offset amount canceling process, an interpolation offset amount is obtained from the detected values excluding the peak wiring and the surrounding wiring group. In the interpolation processing, touch coordinates are calculated by interpolation processing in consideration of the interpolation offset.

  FIG. 8 is a flowchart showing a processing flow of touch presence / absence determination processing and peak wiring determination processing. Note that the detection column wiring group is also referred to as “X wiring” as wiring for detecting the x coordinate of the touch coordinates, and the detection row wiring group is “Y wiring” as wiring for detecting the y coordinate of the touch coordinates. Each of the detection column wiring group and the detection row wiring group is also simply referred to as “detection wiring” below.

  First, the respective detection wirings are sequentially connected to the oscillation circuit 21, and the period t1 in which the counting circuit 23a becomes the predetermined count value CP is measured as the count value CV1 of the counting circuit 23b (step SA1). This step shows an operation in which each wiring group described based on FIG. 6 is sequentially connected to the oscillation circuit 21 to obtain a capacitance value as a count value. Here, this is called capacity detection processing, and in the flowchart of FIG. 8, it is described including the capacity detection processing (corresponding to step SA1) preceding the peak wiring discrimination processing.

  Next, the detection value CV2 is calculated by subtracting the background count value Gb from the count value CV1 of each detection wiring (step SA2). This detection value CV2 is a value corresponding to a capacitance formed by touching or the like when a count value without touching is used as a reference. Then, it is determined whether or not there is an X wiring and a Y wiring where the detection value CV2 is equal to or greater than a preset threshold value TL (CV2 ≧ TL) (step SA3). If there is such a detection wiring, it is determined that there is a touch, and a wiring X (i) having the maximum detection value CV2 is obtained from the X wirings satisfying CV2 ≧ TL (step SA4). Similarly, the wiring Y (j) with the maximum detected value CV2 is obtained from the Y wirings satisfying CV2 ≧ TL (step SA5). After step SA5, the process proceeds to the interpolation offset amount calculation process. If the determination condition of step SA3 is not satisfied, it is determined that there is no touch, and the process proceeds to the background value calculation process (step SA6). Here, i and j indicate wiring numbers. Note that the wiring X (i) and the wiring Y (j) having the maximum detection value CV2 are referred to as peak wiring.

  FIG. 9 is a flowchart showing a background detection process for detecting the background detection value Gb shown in FIG. Here, the background detection process is performed when the determination result in step SA3 of the touch presence / absence determination process shown in FIG. 8 is No.

  In the present embodiment, the background detection process is performed every time the determination result in Step SA3 is No. If this detection time becomes a dead time for detecting capacitance from the detection wiring and affects the response time, the process shifts to the background process once every predetermined time. Otherwise, the process is bypassed. You may make it do. Since the background detection value Gb does not change steeply, there is generally no problem even if the detection interval is set wide as described above.

  The touch position calculation circuit 24 determines whether or not there is a detection wiring that satisfies the count value CV1 ≧ threshold value TLg of the second counting circuit 23b for each detection wiring (step SB1).

  When it is determined that there is a detection wiring that satisfies the count value CV1 ≧ threshold value TLg, the touch position calculation circuit 24 determines the background detection value Gb (old) set in the previous execution of the background detection process. The value Gb (old) is set as it is to the background detection value Gb (new) obtained by the current detection (step SB2).

  On the other hand, if it is determined in step SB1 that there is no detection wiring satisfying the above relationship, the touch position calculation circuit 24 detects the back detected in the previous “background detection mode” in each detection wiring. An exponential average of the ground detection value Gb (old) and the count value CV3 measured this time is calculated, and the calculated value is stored in the memory in the circuit 24 as a new background detection value Gb (new) (step) SB3). After step SB3, the process returns to the peak wiring determination process shown in FIG.

  Here, the exponential average is obtained by the following equation (2).

  In order to suppress the detection error of the background detection value and improve the accuracy of the interpolation processing, here, for example, smoothing is performed by exponential averaging. The value of α may be set as appropriate in consideration of the degree of fluctuation of the background detection value depending on the use environment. Further, the initial value of the background value may be obtained by calibration processing at the start of use of the apparatus, or a fixed value may be set in advance. Further, the first count value CV1 after the apparatus is started may be used as the initial value of the background value.

  Next, the offset amount that appears in the detection value CV2 when there is a touch will be described. FIG. 10 is a diagram illustrating how the detection value CV2 changes when the touch position is displaced vertically from the center of the wiring X (i). As in the case described later with reference to FIG. 12, the touch dimension of the finger (the dimension of the area to be touched), the wiring width (width of the wiring group), and the pitch of the wiring group are set to be substantially equal. FIG. Moreover, the case where the thickness of the transparent substrate 12 is as comparatively thin as about 0.6 mm is shown. As shown in the figure, when the touch position is displaced from the center of the wiring X (i), the detection value CV2 gradually decreases, and the amount of change is small in the vicinity of the adjacent wirings X (i−1) and X (i + 1). Become. Further, even if the touch position is further away, the detection value hardly decreases. The same applies to the Y wiring. In this way, when there is a touch, an offset occurs with respect to the background value when there is no touch, and the detection value CV2 shows a value larger than the background value even if the wiring is away from the touch position. This was confirmed by the inventors' experiments. Furthermore, it was confirmed that the offset amount increases as the cross portion capacitance generated at the cross portion between the X wiring and the Y wiring (the cross portion capacitance is schematically shown as Cc in FIG. 6).

  The reason why such an offset occurs can be considered as follows. As described above, the charge / discharge voltage that determines the oscillation cycle of the oscillation circuit 21 is applied to the non-selection detection wiring via the buffer 27, and thus, the cross section capacitance can be ignored in an ideal manner. However, the voltage applied to the cross section capacitance does not become zero due to the influence of the driving capability (response speed and output impedance) of the buffer 27, the resistance of the detection wiring, and the resistance of the lead wiring, and a certain amount of voltage remains. At this time, when a touch occurs and a touch capacitance is generated around a certain detection wiring, even when a detection wiring separated from the detection wiring is selected and connected to the oscillation circuit 21, the touch capacitance is detected via the cross section capacitance. This will cause an offset. At this time, the capacitance seen from the oscillation circuit 21 is a capacitance in which a touch capacitance and a cross portion capacitance are arranged in series. For this reason, the offset value tends to increase with the size of the cross section capacitance.

  FIG. 11 is a flowchart showing the interpolation offset amount canceling process. Here, for example, the average value of the detected values CV2 of the X wirings excluding the peak wiring X (i) and the adjacent X (i−1) and X (i + 1) (a total of three) is calculated as the offset amount Ox. (Step SC1). Similarly, the average value of the detected values CV2 of the Y wirings excluding the peak wiring Y (j) and the adjacent Y (j-1) and Y (j + 1) (a total of three) is calculated as the offset amount Oy ( Step SC2).

  Next, the offset value Ox is subtracted from each detected value CV2 of the wirings X (i-1) to X (i + 1) to be interpolated, thereby calculating an interpolated detected value CVx (step SC3). Further, the amount of offset Oy is subtracted from each detected value CV2 of the wirings Y (j-1) to Y (j + 1) to be interpolated, thereby calculating the interpolated detected value CVy (step SC4). Here, in the present embodiment, a case is considered in which interpolation processing is performed from three detection values of the peak wiring and the adjacent wiring. However, the detection values of a wide range of wiring around the peak wiring are further used. When performing the interpolation process, the offset amount is obtained as an average value of the detected values of the wirings outside this range.

  In this way, every time the peak wiring is determined in the peak wiring determination process in the previous stage, the offset amount is calculated and canceled, so the offset according to the way of touching by the indicator (how to touch the touch panel, etc.) Even if the amount changes, this can be reliably calculated and canceled.

  Next, an interpolation process performed by the touch position calculation circuit 24 will be described. Here, for simplification, it is assumed that the deviation of the count value CV2 by each detection wiring does not occur. FIG. 12 is a diagram illustrating an example of a change in the interpolation detection values CVx and CVy depending on the touch position. In FIG. 12, a reference symbol FG indicates a finger touching the touch panel. FIG. 12 shows the amount of displacement from the center position of the finger FG touched left and right in the case of X wiring and up and down in the case of Y wiring, with the centers of the peak wirings X (i) and Y (j) as the origin. The relationship between the interpolation detection values CVx and CVy with respect to (relative value) is illustrated (in the case of the wiring X (i) and Y (j), the solid line, the wiring X (i-1) and Y (j-1) The case is shown as a dotted line, and the case of wirings X (i + 1) and Y (j + 1) is shown as an alternate long and short dash line).

  FIG. 12 is a diagram in the case where the touch dimension of the finger FG (the dimension of the area to be touched), the wiring width (width of the wiring group), and the pitch of the wiring group are set to be substantially the same value p. It is. Moreover, the case where the thickness of the transparent substrate 12 is as comparatively thin as about 0.6 mm is shown. Although the touch dimension of the finger FG varies depending on the user or the degree of touch, the touch dimension of the finger FG can be considered to be about 10 mm in both width and length.

  As shown in the lower part of FIG. 12, in the wirings X (i) and Y (j), when the finger position center is displaced from the wiring center, the interpolation detection values CVx (i) and CVy (j) are obtained. When it is gradually lowered and displaced to approximately the center of the adjacent wiring center (p / 2 (p: wiring pitch)), in the case of displacement to the right or above, the adjacent wirings X (i + 1) and Y (j + 1) Is substantially the same level as the interpolation detection values CVx (i + 1) and CVy (j + 1). Also, in the case of displacement to the left or down, the detection values for interpolation CVx (i) and CVy (j) are detected by the detection values for interpolation CVx () by the adjacent wirings X (i−1) and Y (j−1). It becomes substantially the same level as i-1) and CVy (j-1). If the displacement amount becomes larger than this, the detection value for interpolation by the adjacent wiring becomes larger. Therefore, when considering the interpolation, it is considered that the touch coordinates should be interpolated with respect to the displacement amount up to p / 2. it can.

  Next, FIG. 13 is a flowchart showing the interpolation processing in the present embodiment. The interpolation process will be described with reference to FIG. The peak wiring X (i) of the X wiring obtained by the offset amount canceling process and the adjacent wiring X (i-1), X (i + 1), the peak wiring Y (j) of the Y wiring, and the adjacent wiring Y (j- 1), Y (j + 1) interpolated detection values CVx (i), CVx (i-1), CVx (i + 1), CVy (j), CVy (j-1), CVy (j + 1) The touch position calculation circuit 24 performs an interpolation process. However, here, the wiring number i is defined to increase from left to right, and the wiring number j is defined to increase from top to bottom.

  First, as a process of calculating the touch X coordinate Pxt, the touch position calculation circuit 24 determines whether the relationship between the detected values for interpolation of both wirings adjacent to the peak wiring is CVx (i + 1) ≧ CVx (i−1). This determines whether the touch position is on the left or right side of the peak X wiring X (i) (step SD1).

  When CVx (i + 1) ≧ CVx (i−1), the touch position calculation circuit 24 has the touch position (touch X coordinate Pxt) on the right side of the X coordinate Px (i) of the peak X wiring X (i). It is determined that there is an interpolation amount, and an interpolation amount ΔPx is calculated by equation (3) (step SD2). The interpolation formula will be described later.

  On the other hand, when CVx (i + 1) <CVx (i−1), the touch position calculation circuit 24 determines that the touch position (touch X coordinate Pxt) is higher than the X coordinate Px (i) of the peak X wiring X (i). It is determined that the position is on the left side, and the amount of interpolation ΔPx is calculated according to equation (4) (step SD3).

  Then, the touch position calculation circuit 24 calculates the touch X coordinate Pxt from the X coordinate Px (i) of the peak X wiring X (i) and the interpolation amount ΔPx according to Expression (5) and Expression (6) of Equation 5. Calculate (step SD4). The X coordinate Px (i) of each detection wiring i and the Y coordinate Py (j) of each detection wiring, that is, the coordinates of the center position of each detection wiring group are determined in advance according to the dimensions of the touch screen 1. If the i-th value and the j-th value of the detection wiring are specifically determined by the fixed position coordinate system, the touch position calculation circuit 24 automatically determines them.

  The touch position calculation circuit 24 holds data of this fixed position coordinate system. Therefore, when the touch position calculation circuit 24 determines the peak X wiring X (i) and the peak Y wiring Y (j) from all the detection wirings by the above-described processing, the touch position calculation circuit 24 holds the above-mentioned information. The X coordinate Px (i) of the peak X wiring X (i) and the Y coordinate Py (j) of the peak Y wiring Y (j) are calculated from the data of the position coordinate system. At the stage of using the touch panel according to the present embodiment having the touch screen 1 in combination with a display device such as a liquid crystal display device, the position coordinates are determined by the above-described fixed position coordinate system of the touch screen 1. The center position of each inspection wiring corresponds to a pixel position on the display screen of the display device, which is the number of pixels counted from the reference point with the position of the upper left corner as the reference point.

  Similarly, as a process for calculating the touch Y coordinate Pyt, the touch position calculation circuit 24 determines whether the relationship between the detected values for interpolation of both wirings adjacent to the peak wiring is CVy (j + 1) ≧ CVy (j−1). (Step SD5), it is determined whether the touch position is on the upper or lower side of the peak Y wiring Y (j).

  That is, when CVy (j + 1) ≧ CVy (j−1), the touch position calculation circuit 24 determines that the touch Y coordinate Pyt is below the Y coordinate Py (j) of the peak wiring Y (j). Then, the interpolation amount ΔPy is calculated by the equation (7) (step SD6). Here, it is assumed that the same interpolation formula is used to calculate the interpolation amount ΔPx of the touch X coordinate Pxt.

  On the other hand, when CVy (j + 1) <CVy (j−1), the touch position calculation circuit 24 determines that the touch position (touch Y coordinate Pyt) is greater than the Y coordinate Py (j) of the peak Y wiring Y (j). It is determined that the value is on the upper side, and the interpolation amount ΔPy is calculated by the equation (8) (step SD7).

  Then, the touch position calculation circuit 24 calculates the touch Y coordinate Pyt from the coordinates Py (j) of the peak Y wiring Y (j) and the interpolation amount ΔPy by the equations (9) and (10) (step SD8). ).

  Thereafter, the touch position calculation circuit 24 sends the touch coordinates (Pxt, Pyt) obtained by performing the interpolation process to the outside (step SD9), and transmits to the detection control circuit 25 that the interpolation process has been completed. As a result, the detection control circuit 25 changes the predetermined count value CV to the predetermined count value CV1, and then returns to the detection process. Each coordinate and the interpolation amount may be calculated based on the number of pixels of the display device used in combination, for example.

  Here, the interpolation formula to be used is determined by how the detection value of the peak wiring and the detection value of the adjacent wiring change with respect to the touch position. In order to simplify the processing, linear interpolation shown in Equation (11) may be used.

  However, how the detection value of the peak wiring and the detection value of the adjacent wiring change is generally nonlinear. This also depends on the distance from the detection wiring group to the touch surface (the thickness of the base substrate 12) and the touch shape.

  Therefore, for the sake of simplification, assuming that the touch shape is, for example, a square or a circle, and the touch of the indicator is considered to form a capacitance by a parallel plate between the touch part and the wiring group, The capacitance ratio is the area ratio of the portion where the touch portion faces each wiring. Therefore, the characteristic of the interpolation coefficient is as shown in the simulation result of FIG. 14, and the amount of interpolation is obtained by multiplying the value of the interpolation coefficient shown in FIG. 14 by the wiring pitch p. When the touch shape is square or rectangular, the indicator only shifts in one direction from left to right or up and down, and the characteristics of the interpolation coefficient are close to linearity, but when the touch shape is circular, First, since the amount of deviation of the indicator is small, gradually increases, and then decreases, the characteristic of the interpolation coefficient or the interpolation function f has a convex shape as shown in FIG.

  The characteristics of the interpolation coefficient shown in FIG. 14 are for the interpolation detection values CVx and CVy with the offset amount reduced. Therefore, in FIG. 14, when the ratio of the horizontal axis is 0, it is assumed that the capacitance value of one of the adjacent wirings (therefore, the detected values CVx and CVy) is 0, and the touch position of the indicator Is assumed to be at the center position of the peak wiring, and the value of the interpolation coefficient is set to 0 based on CVx and CVy with the offset amount reduced.

  Here, the touch position calculation circuit 24 determines the interpolation formula by obtaining the interpolation coefficient one by one according to the characteristic of the interpolation coefficient shown in FIG. 14, for example, and calculates the interpolation amount accordingly. Alternatively, the touch position calculation circuit 24 may provide an interpolation curve as a lookup table and calculate the interpolation amount while referring to the lookup table. FIG. 14 shows the interpolation coefficient obtained from the capacitance formed by the parallel plate of the touch part and the wiring group on the assumption that the touch shape is a square or a circle. The interpolation coefficient may be obtained by measuring the increment / decrement amount of the count value CV2 of the second counter circuit 23b while obtaining the change amount ΔCV2).

  In the present embodiment, the offset amount is calculated from the average value of the detection values of the detection wiring excluding the peak wiring and its adjacent wiring. However, the detection wiring for which the offset amount is calculated is the peak wiring. It is not necessary for all the detection wirings except the adjacent wirings. For example, the values of the adjacent wiring and the outermost detection wiring adjacent to the peak wiring may be used as representative values and obtained as an average value thereof.

  In this embodiment, smoothing is performed by exponential averaging in the background detection process, but exponential averaging is not required if there is no need for smoothing based on interpolation accuracy or the like. (Corresponding to α = 0).

  In the present embodiment, the oscillation circuit 21 is configured by connecting elements such as resistors (C1 and R1 in FIG. 5) even when the detection wiring group is not connected. This is because no detection wiring group may be connected to the inverting input terminal of the operational amplifier 30 of the oscillation circuit 21 depending on the switching timing of the first and second switch circuits 20a and 20b. This is to prevent the oscillation frequency from taking a long time when the detection wiring group is restored to the reconnected state due to a large shift. Further, when the oscillation frequency shift is small and does not cause a problem at the time of switching between the detection wiring groups connected by the analog multiplexer circuits 20a and 20b, the capacitor C1 and the resistance element R1 of the oscillation circuit 21 may be unnecessary.

  If the oscillation cycle drift of the oscillation circuit 21 itself is seen immediately after the power is turned on, the smoothness is lowered by setting α to a relatively small value immediately after the power is turned on, and α is set to a gradually larger value as time passes. Then, the smoothness may be increased.

  In the example of the present embodiment, the first counting circuit 23a counts the oscillation output signal of the oscillation circuit 21 until it reaches a predetermined count value CP, and starts counting until it reaches the predetermined count value CP. This period (time) is counted by the second counting circuit 23b, and the second counting circuit 23b outputs this period to the touch position calculation circuit 24 as an oscillation period detection result. However, instead of this configuration, the period for counting by the first counting circuit 23a is set in advance within a predetermined period (that is, the period for observing the output signal of the oscillation circuit 21 is set to a constant value). A count value counted by the first counting circuit 23a within a predetermined period may be used as an oscillation period detection result (in this case, the count of the first counting circuit 23a increases as the oscillation period T increases). The number is smaller).

  In addition, the interpolation processing is performed using the detection values of the peak wiring and the adjacent wiring. However, not only the adjacent wiring but also the detection wiring (for example, the adjacent wiring) continuous to the peak wiring and the support by the touch by the indicator. When a certain amount of touch capacitance is also formed between the two, the interpolation processing can be performed using this detection result as well.

  As described above, the touch panel in the first embodiment obtains the detection value CV2 by subtracting the background value from the count value CV1 of the counting circuit 23b, and then the offset amount generated when the touch occurs from the detection value CV2 by each detection wiring. Since touch coordinates are calculated after canceling (subtracting), even if the amount of offset changes depending on how the indicator is touched (how to touch the touch panel, etc.) It is possible to cancel, and the calculated touch coordinate accuracy can be improved.

  Further, since the offset value is calculated by averaging the detection values CV2 from the detection wiring excluding the peak detection wiring to be interpolated and the detection wiring adjacent thereto, even if there is a variation in the detection value for each detection wiring. By calculating a stable offset amount, the touch coordinate accuracy can be improved.

  Further, even when the background value when there is no touch is large, the touch coordinates are calculated by subtracting this and reducing the detection value, so that the processing load necessary for the calculation can be reduced.

  In addition, since the background value is calculated by the exponential average with the previous background value, a stable background value can be obtained even if disturbance noise or the like is mixed to cause a deviation in the detected value.

  In addition, since the interpolation amount is calculated based on the characteristic indicating the interpolation amount when the pitch of the detection wiring and the width of the indicator are substantially the same, for example, even if the indicator size (width) changes, a characteristic corresponding to the change is prepared. Thus, it is not necessary to perform a switching process or the like, and the interpolation amount can be calculated with a simple configuration.

  Further, since the characteristic of the interpolation amount with respect to the ratio of the detection wiring with the maximum detection value and the detection wiring adjacent to the detection wiring is used, the level (size) of the detection value depending on the degree of contact of the indicator with the touch panel, etc. Since the ratio between the maximum detection wiring and the detection wiring adjacent to the detection wiring does not change even if the value changes, complicated processing such as level correction is unnecessary, and the interpolation amount can be calculated with a simple configuration. Can do.

<Embodiment 2>
In the first embodiment, for example, it is considered that a capacitance is formed by a parallel plate between the touch portion by the indicator and the wiring group, and the capacitance ratio between the peak wiring and the adjacent wiring is such that the touch portion faces each capacitance. The amount of interpolation is obtained by multiplying the interpolation coefficient obtained from the relationship between the capacitance ratio and the interpolation coefficient (interpolation coefficient characteristics) shown in FIG. 14 by the wiring pitch p.

  Here, the characteristic of the interpolation coefficient described in the first embodiment is obtained under the condition that the touch dimension, the wiring width (wiring group width), and the wiring group pitch p are equal as shown in FIG. FIG. 16 is a diagram illustrating an X wiring as an example, where the touch shape is circular, the peak wiring is X (i), and the touch position is at the center of the peak wiring X (i) (a), A case where it is at a position shifted by p / 4 (b) and a case where it is in the middle of the adjacent wiring X (i + 1) are shown (c). Therefore, if the interpolation coefficient is calculated as 0, 0.25, 0.5 corresponding to each position, the calculated touch position is equal to the actual touch position and there is no error.

  However, the profile of the capacitance (touch capacitance) that is actually formed between the indicator (here circular) and the detection wiring with respect to the touch position differs from that obtained under the above conditions as shown in FIG. Arise. FIG. 17 is a diagram showing an example of a profile of the touch capacitance with respect to the touch position, where the solid line is the characteristic (a) calculated under the above conditions, and the dotted line is the touch dimension smaller than the wiring pitch (= wiring width) (b). The measured characteristics are shown for the case where the touch dimension of the alternate long and short dash line is substantially equal to the wiring pitch (c), and in the case where the touch dimension of the two-dot chain line is larger than the wiring pitch (d). The actual measurement characteristics are obtained when the transparent substrate is made of glass having a thickness of 0.7 mm and the wiring pitch is set to 7.5 mm.

  As described above, in any case, the capacitance decreases as the touch position is displaced from the center of the wiring. However, in actual measurement, the capacitance is 0 even if the touch position changes to the center of the adjacent wiring. Don't be. In other words, when the peak wiring is X (i), even if the touch position is at the center of the peak wiring X (i), the capacitance formed between the adjacent X (i + 1) and the indicator becomes zero. Don't be. If the touch dimension (in this case, the diameter of the circular indicator) is larger than the wiring pitch, of course, even if the touch position is in the center of the pitch dimension, the indicator will have a part facing the adjacent wiring. Even if it thinks, it is not 0. However, even when the touch dimension is smaller than the wiring pitch or substantially equal to the wiring pitch, a capacitance is formed between the adjacent wiring due to the spread of the electric field generated between the indicator and the detection wiring. The

  Therefore, on the condition that the touch dimension and the wiring width (wiring group width) shown in FIG. 14 are equal to the pitch p of the wiring group, using the interpolation coefficient characteristics obtained by the indicator and the detection wiring as parallel plates, When the touch position is calculated by interpolating the positions of the peak wiring and the second peak wiring, an error as shown in FIG. 18 occurs. FIG. 18 is a diagram showing an error in the touch position calculated from the interpolation coefficient characteristic, where the solid line indicates the interpolation coefficient characteristic (a), and the dotted line indicates the dash-dot line when the touch dimension is smaller than the wiring pitch (b). The second peak wiring X (i + 1) adjacent to the touch position and the peak wiring X (i) when the touch dimension is substantially equal to the wiring pitch (c) and the two-dot chain line is the touch dimension larger than the wiring pitch (d). ) And the capacitance ratio by actual measurement. Thus, the difference between the interpolation coefficient characteristic (a) and the actually measured capacitance ratio characteristics (b) to (d) appears as an error in the coordinate calculation result obtained by interpolation using the interpolation coefficient characteristic. .

  Such an error becomes a problem particularly when the demand for touch position accuracy, that is, touch position resolution is high. In this embodiment, a touch coordinate calculation method capable of reducing such an error will be described.

  FIG. 19 is a flowchart showing the interpolation offset amount canceling process of the touch coordinate calculation method according to the present embodiment. In the first embodiment, the interpolation offset amount canceling process described with reference to FIG. 11 is replaced. Since other configurations and the touch coordinate calculation processing method are the same as those in the first embodiment, detailed description thereof is omitted here. FIG. 20 is a detection characteristic diagram schematically showing an offset amount related to the interpolation offset amount canceling process. The figure shows an X wiring as an example. Here, the adjacent offset value is an offset value after canceling the offset value that appears in the adjacent wiring when the touch position is at the center of the peak wiring (corresponding to an interpolation amount of 0).

  As shown in FIG. 19, steps SCa1 to SCa2 calculate the average value of detection values CV2 excluding the peak wiring and its adjacent wirings as an offset value, and subtract from the detection values, as in the first embodiment. Thus, the first offset amount is canceled. That is, each detected value CV2 of the X wiring excluding the peak wiring X (i) and its adjacent wirings X (i-1) and X (i + 1) obtained by determining that there is a touch in the peak wiring calculation processing of the previous stage processing. Is calculated as an offset value Ox (step SCa1).

  Next, each detected value of the Y wiring excluding the peak wiring Y (j) and its adjacent wirings Y (j−1) and Y (j + 1) obtained by determining that there is a touch in the peak wiring calculation processing of the previous stage processing. The average value of CV2 is calculated as the offset value Oy (step SCa2).

  Then, correction values CVx1 (i), CVx1 (i-1), and CVx1 obtained by subtracting the offset value Ox from the detection value CV2 of the peak wiring X (i) and its adjacent wirings X (i-1) and X (i + 1). (I + 1) is calculated (step SCa3). Further, correction values CVy1 (j), CVy1 (j-1), and CVy1 obtained by subtracting the offset value Oy from the detection value CV2 of the peak wiring Y (j) and its adjacent wirings Y (j-1) and Y (j + 1). (J + 1) is calculated (step SCa4).

  Next, the offset value AOx is calculated based on the correction values CVx1 (i), CVx1 (i-1), and CVx1 (i + 1) obtained in the first offset amount cancellation process (step SCa5). A method for calculating the adjacent offset value AOx will be described later. Similarly, an offset value AOy is calculated based on the correction values CVy1 (j), CVy1 (j-1), and CVy1 (j + 1) (step SCa6).

  Then, the offset value AOx is subtracted from the correction values CVx1 (i), CVx1 (i-1), and CVx1 (i + 1), and the detection values CVx2 (i), CVx2 (i-1), and CVx2 (i + 1) for interpolation processing are obtained. Calculate (step SCa7). Similarly, correction values CVy2 (j), CVy2 (j-1), and CVy2 (j + 1) are calculated (step SCa8).

  After canceling the offset amounts (first offset amounts) Ox and Oy generated when a touch occurs by the offset amount canceling process as described above, the adjacent offset amount (first offset) appearing in the adjacent wiring when the touch position is at the center of the wiring. 2) A detection value CVx2 (i-1), CVx2 (i), CVx2 (i + 1), and touch coordinate Y for calculating the touch coordinate X are calculated by canceling the AOx and AOy. The detection values CVy2 (j−1), CVy2 (j), and CVy2 (j + 1) for interpolation processing are calculated. After that, as in the first embodiment, for example, interpolation processing is performed using the interpolation coefficient characteristics shown in FIG. 14 to calculate touch coordinates.

  As described above, the adjacent offset amounts AOx and AOy vary depending on the touch dimension. If the touch dimension at the time of use is generally fixed, it is possible to use the value obtained by actual measurement with the touch position as the center of wiring, but the actual touch dimension is the size of the indicator, for example, the finger of the user or the touch It depends on the way (touch strength, etc.). Therefore, in the present embodiment, the adjacent offset is estimated and calculated based on the total value of the detection values from the plurality of detection wirings around the peak wiring.

  FIG. 21 is a diagram showing the relationship between the touch position and the detection wiring. FIG. 21A shows the case where the touch dimension is smaller than the wiring pitch p, and FIG. 21B shows the touch dimension compared with the wiring pitch p. The large case is shown. Since the coordinates to be interpolated in the interpolation process are from the center of the peak wiring to the middle of the adjacent wiring, as can be seen from this figure, the touch dimension (width dimension for X wiring, length direction for Y wiring) Is a size substantially equal to the wiring pitch p, the touch portion faces the range of the peak wiring and the wiring adjacent to both sides thereof. That is, the total capacity generated by touch is, for example, the sum of correction detection values CVx1 (i−1), CVx1 (i), and CVx1 (i + 1) in which the offset due to touch corresponding to the wiring on both sides adjacent to the peak wiring is canceled ( X wiring) and CVy1 (j−1), CVy1 (j), and CVy1 (j + 1) total (in the case of Y wiring). Since the total capacity due to the touch can be considered to be roughly proportional to the touch dimension, for example, the touch dimension can be estimated from the total value of the detected values of a plurality of wirings adjacent to the peak wiring (here, two front and back), and the adjacent offset Can also be estimated and calculated. Here, the adjacent offset is calculated, for example, as in the following formula (12).

  Here, CV1 (ref) is CV1 (total) based on the specific touch dimension L, and g is an adjacent offset function based on the specific touch dimension L. Further, when CVx1 (i-1) + CVx1 (i) + CVx1 (i + 1) = Ax and CVy1 (j-1) + CVy1 (j) + CVy1 (j + 1) = Ay, as described above, equation (12) is It can obtain | require as following formula (13).

  The adjacent offset function has characteristics as shown in FIG. 22, for example. FIG. 23 shows an example when the transparent substrate thickness is 0.6 mm and the wiring pitch p is 7.5 mm.

  FIG. 23 shows the difference between the actual touch position based on the presence / absence of the adjacent offset (cancellation) at this time and the calculated touch position. In the figure, (a) is a circular touch having a diameter of 5 mm smaller than the wiring pitch p, (b) is a circular touch having a diameter of 7.5 mm which is the same as the wiring pitch p, and (c) is a diameter larger than the wiring pitch p. The case of a 10 mm circular touch is shown. In any case, it can be seen that the interpolation accuracy in the vicinity of the wiring center is greatly improved by performing the adjacent offset correction.

  Here, for convenience of explanation, the characteristics of the adjacent offset function shown in FIG. 22 are described so as to use the adjacent offset function (characteristic normalized by CV1 (total) based on the specific touch dimension L) based on the specific touch dimension L. However, in practice, this is not always necessary, and a characteristic for uniquely determining the adjacent offset from CV1 (total) may be used.

  In this embodiment, the adjacent offset is canceled by using the total value of the correction detection values of the peak wiring and the both adjacent wirings. In this case, the wiring range for summing the correction detection values around the peak wiring may be further expanded.

  As described above, the adjacent offset amount (second second) appearing in the adjacent wiring when the touch position is at the wiring center, based on the correction detection value obtained by canceling the offset amount (first offset amount) generated in all the wirings when the touch occurs. Interpolation processing is performed using the detected value for interpolation processing obtained by canceling the offset amount), and touch coordinates are calculated. Therefore, even if the offset amount changes depending on how the indicator is touched (such as how to touch the touch panel), this can be reliably calculated and canceled, and interpolation coordinate errors caused by the adjacent offset amount And the touch coordinate accuracy (touch resolution) can be improved.

  In addition, since the adjacent offset amount is estimated and calculated based on the total value of the corrected detection values from the peak wiring with the maximum detection value and the wiring in a predetermined range before and after that, the touch dimension changes. However, it is possible to reliably cancel the adjacent offset and improve the touch coordinate accuracy.

<Embodiment 3>
The present embodiment relates to a liquid crystal display device in which a touch panel and a liquid crystal display panel are integrated by attaching the touch screen 1 in the first embodiment to a liquid crystal display panel. FIG. 15 is a diagram showing a vertical cross-sectional configuration of the liquid crystal display device in the present embodiment. The liquid crystal display panel 41 has a color filter substrate 44 in which a color filter, a black matrix, a transparent electrode, and an alignment film are formed on a glass substrate, and a TFT (thin film transistor) that is a switching element on the glass substrate. A TFT array substrate 46, a liquid crystal layer 45 made of TN liquid crystal sandwiched between the substrates 44, 46, and a polarizing plate 48 adhered to the rear surface side of the TFT array substrate 46 by an adhesive layer 47. Further, a polarizing plate 42 is adhered to the front surface of the color filter substrate 44 by an adhesive layer 43. A backlight 49 as a light source is disposed on the back side of the liquid crystal display panel 41.

  On the other hand, the touch screen 1 according to the first embodiment is adhered to the polarizing plate 42 on the front side of the liquid crystal display panel 41 by the adhesive layer 40.

  A signal corresponding to an image to be displayed is input to the TFT array substrate 46 from an external driver circuit (not shown in FIG. 15), and accordingly, via a switching element by TFT formed for each pixel, The applied voltage of the liquid crystal layer 45 is controlled to change the alignment direction of the liquid crystal molecules. Incident light from the backlight 49 passes through the polarizing plate 48 to become linearly polarized light, and the vibration direction is bent according to the image signal to be displayed by passing through the liquid crystal layer 45 and formed on the color filter substrate 44. By passing through the color filter, the light is separated into light of the three primary colors, and further passes through the polarizing plate 42 on the front side, and becomes light having light intensity corresponding to the image signal. Further, the light passing through the polarizing plate 42 passes through the touch screen 1 on the front surface and is visually recognized by the user as display light.

  In this way, the liquid crystal display device performs a desired display by controlling the transmittance of light from the backlight 49 in accordance with the image signal. Further, the touch panel including the touch screen 1 calculates touch coordinates based on the change of the oscillation cycle and outputs the touch coordinates as in the first embodiment.

  At this time, in the touch screen 1 described in the first embodiment, the detection wiring group is configured by a plurality of detection wirings, and the area of the slit-shaped opening between the detection wirings is set to be large. Since a decrease in light transmittance is suppressed, most of the light that has passed through the polarizing plate 42 passes through the touch screen 1 and becomes display light. For this reason, even if the touch screen 1 is disposed on the front surface of the liquid crystal display panel 41, the display luminance is hardly lowered.

  Note that a liquid crystal display device can also be configured by using a liquid crystal other than the TN liquid crystal, such as an STN liquid crystal, as in this embodiment.

  In this embodiment mode, a liquid crystal display device is described as the display device. However, other types of display devices such as organic or inorganic EL display devices and PDP devices are also described in the first embodiment. A display device including a touch panel can be configured.

  As described above, according to the display device of the present embodiment, the touch screen 1 is pasted and integrated with the liquid crystal display panel 41 to constitute the display device. It can be eliminated, and the thickness of the entire apparatus can be reduced.

  Further, since the touch screen 1 and the liquid crystal display panel 41 are integrated to form a display device, the display can be caused by foreign matters such as dust mixed in the gap between the touch screen 1 and the liquid crystal display panel 41. Can prevent adverse effects.

It is the top view which showed the structure of the touch screen which the touch panel in Embodiment 1 of this invention has. It is the fragmentary perspective sectional view which showed the structure of the touch screen which the touch panel in Embodiment 1 of this invention has. 1 is an overall configuration diagram of a touch panel in Embodiment 1 of the present invention. It is the block diagram which showed the circuit structure of the touch operation | movement detection / touch coordinate calculation system of the touchscreen in Embodiment 1 of this invention. It is the circuit diagram which showed the structure of switch circuit 20a, 20b which the touchscreen in Embodiment 1 of this invention has. FIG. 3 is a circuit diagram illustrating a circuit configuration of an oscillation circuit included in the touch panel according to Embodiment 1 of the present invention and a connection relationship with a detection wiring group and a buffer circuit. 4 is a timing chart showing detection / calculation operations of the touch panel according to Embodiment 1 of the present invention. It is the flowchart which showed the touch presence / absence determination process and the peak wiring determination process of the touch panel in Embodiment 1 of this invention. It is the flowchart which showed the background detection process of the touch panel in Embodiment 1 of this invention. It is the figure which showed the change of the detected value by the detection wiring with respect to the touch position displacement of the touchscreen in Embodiment 1 of this invention. It is the flowchart which showed the interpolation offset amount cancellation process of the touch panel in Embodiment 1 of this invention. It is the figure which showed the change by the touch position of the detection value for interpolation of the touchscreen in Embodiment 1 of this invention. It is the flowchart which showed the touch coordinate calculation operation | movement by the touch panel interpolation in Embodiment 1 of this invention. It is the figure which showed the interpolation characteristic of the touchscreen in Embodiment 1 of this invention. It is the figure which showed the cross-sectional structure of the liquid crystal display device in Embodiment 3 of this invention. It is the model which showed the conditions of the touch dimension of an interpolation factor characteristic, wiring width (wiring group width), and wiring group pitch p. It is the figure which showed the example of a profile with respect to the touch position of touch capacity. It is a figure for demonstrating the error of the touch position calculated from the interpolation coefficient characteristic. It is the flowchart which showed the interpolation offset amount cancellation process of the touch coordinate calculation method in Embodiment 2 of this invention. It is the figure which showed typically the offset amount relevant to the interpolation offset amount cancellation process in Embodiment 2 of this invention. It is a schematic diagram for demonstrating the relationship between the touch position and detection wiring in Embodiment 2 of this invention. It is the figure which showed the example of the characteristic of the adjacent offset function in Embodiment 2 of this invention. It is the figure which showed an example of the difference of the actual touch position by the presence or absence of adjacent offset correction | amendment (cancellation), and the calculated touch position.

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, 20b switch circuit, 21 oscillation circuit, 23a, 23b counting circuit, 24 touch coordinate calculation Circuit, 27 analog multiplexer circuit, 40 liquid crystal display panel, Ctc, Ctr touch capacitance, Cc cross section capacitance.

Claims (15)

A touch screen having a plurality of detection wirings formed in a row direction and a column direction;
A switch circuit for sequentially selecting the detection wirings;
A capacitance detection circuit that detects a value corresponding to a capacitance value formed between the detection wiring selected by the switch circuit and the indicator touched on the touch screen;
A touch position calculation circuit that calculates a position of the touch of the indicator on the touch screen based on a detection value detected by the capacitance detection circuit;
The touch position calculation circuit includes:
Touch presence / absence determining means for determining presence / absence of touch of the indicator on the touch screen based on a detection value detected by the capacitance detection circuit;
When the touch presence / absence determining means determines that there is no touch of the indicator, a background value that is a detection value when the pointer is not touched is detected from the detection value detected by the capacitance detection circuit. Background calculating means for calculating;
Peak wiring for determining the detection wiring in which the detection value detected by the capacitance detection circuit is maximum in the row direction and the column direction when the touch presence / absence determination means determines that the indicator touch is present Discrimination means;
When the touch presence / absence determining unit determines that the indicator is touched, the detection value of the indicator is determined based on the detection value of the detection wiring excluding a predetermined range from the detection wiring having the maximum detection value . Offset calculating means for calculating an offset amount, which is an increase amount from the background value generated in the detection value of the detection wiring excluding the predetermined range when the touch screen is generated , in a row direction and a column direction, respectively; ,
When the touch existence determination means determines that the touch of the indicator is present, from the detection value of the detection wiring in a predetermined range from the detection wiring and the detection wiring the detection value becomes the maximum, the background Interpolation amount calculation means for calculating an interpolation amount in the row direction and the column direction based on a value obtained by subtracting the value and the offset amount, and
A touch position calculating unit that calculates a touch position of the indicator by adding or subtracting the interpolation amount to or from a position on the touch screen corresponding to the detection wiring having the maximum detection value. A touch screen having a plurality of detection wirings formed in a row direction and a column direction;
A switch circuit for sequentially selecting the detection wirings;
A capacitance detection circuit that detects a value corresponding to a capacitance value formed between the detection wiring selected by the switch circuit and the indicator touched on the touch screen;
A touch position calculation circuit that calculates a position of the touch of the indicator on the touch screen based on a detection value detected by the capacitance detection circuit;
The touch position calculation circuit includes:
Touch presence / absence determining means for determining presence / absence of touch of the indicator on the touch screen based on a detection value detected by the capacitance detection circuit;
When the touch presence / absence determining means determines that there is no touch of the indicator, a background value that is a detection value when the pointer is not touched is detected from the detection value detected by the capacitance detection circuit. Background calculating means for calculating;
Peak wiring for determining the detection wiring in which the detection value detected by the capacitance detection circuit is maximum in the row direction and the column direction when the touch presence / absence determination means determines that the indicator touch is present Discrimination means;
When the touch presence / absence determining unit determines that the indicator is touched, the detection value of the indicator is determined based on the detection value of the detection wiring excluding a predetermined range from the detection wiring having the maximum detection value. A first offset amount, which is an increase amount from the background value generated in the detection value of the detection wiring excluding the predetermined range when the touch screen is generated, is calculated in the row direction and the column direction, respectively. 1 offset calculating means;
When the touch presence / absence determining means determines that the indicator is touched , the detection wiring in a predetermined range adjacent to the detection wiring when the touch position is at the center of the detection wiring having the maximum detection value included in the detected value, the respectively calculated the second offset amount is the amount offset from the value obtained by subtracting said first offset amount and the background value from the detected value, the row and column directions Two offset calculation means;
When the touch existence determination means determines that the touch of the indicator is present, from the detection value of the detection wiring in a predetermined range from the detection wiring and the detection wiring the detection value becomes the maximum, the background based on the value and the first and second offset amount to the value obtained by subtracting the interpolation quantity calculation means for calculating the respective amount of interpolation in the row and column directions,
A touch position calculating unit that calculates a touch position of the indicator by adding or subtracting the interpolation amount to or from a position on the touch screen corresponding to the detection wiring having the maximum detection value. 2. The offset calculation unit of the touch position calculation circuit calculates the offset amount from an average value of the detection values of the detection wiring excluding a predetermined range from the detection wiring having the maximum detection value. touch panel. The first offset calculation means of the touch position calculation circuit calculates the first offset amount from an average value of the detection values of the detection wiring excluding a predetermined range from the detection wiring having the maximum detection value. The touch panel according to claim 2 . Second offset calculating means of the touch position calculation circuit, the detection value to calculate a second offset amount from the total value of the detected value of the detection wire in a predetermined range adjacent to the detection wire having the maximum The touch panel according to claim 2 . Said second offset calculating means of the touch position calculation circuit, the detected value of the detection values whether we said first value of the offset amount obtained by subtracting the detection wire in a predetermined range adjacent to the detection wire having the maximum The touch panel according to claim 5 , wherein the second offset amount is calculated from a total value . The interpolation quantity calculation means, and calculates an interpolation quantity with a characteristic indicative for interpolation of the pitch of the detection lines when said width of the indicator is almost identical, to claim 1 or 2 The touch panel described. The interpolation quantity calculation means, characterized in that said detection value to calculate the amount of interpolation using the characteristic indicative for interpolation quantity for the ratio of the pre-Symbol detection wire you adjacent the detection wiring and the detection wiring is maximum to touch panel of claim 7. The touch presence / absence determination unit of the touch position calculation circuit subtracts the background value from the detection value detected by the capacitance detection circuit after the background value is calculated by the background calculation unit. based on the value, it determines the presence or absence of a touch to the touch screen of the indicator, the touch panel according to claim 1 or 2. The touch presence / absence determination means of the touch position calculation circuit determines that there is a touch when a value obtained by subtracting the background value from a detection value detected by the capacitance detection circuit is equal to or greater than a first threshold value. determines that there is no touch if less than the first threshold value, the touch panel according to claim 1 or 2. The background calculation means of the touch position calculation circuit is a case where a value obtained by subtracting the background value from a detection value detected by the capacitance detection circuit is less than the first threshold value, and If less than the second threshold value, updates the value of exponential average was calculated with the background value and the detection value detected by the capacitance detecting circuit as a new said background value, claim 10 Touch panel as described in 1. The capacitance detection circuit is
The oscillation circuit has an input terminal connected to the output terminal of the switch circuit, and an oscillation cycle corresponding to a capacitance value formed between each selection detection wiring and the indicator touched on the touch screen. An oscillation circuit that outputs a signal that changes,
A first counting circuit for counting the output signal of the oscillation circuit until a predetermined count value is reached;
The period required from when the first counting circuit starts the counting operation to the predetermined count value is counted, and the oscillation period detection result obtained from the period is set as a value corresponding to the capacitance value. the touch panel according to 請 Motomeko 1 or 2; and a second counting circuit which outputs the touch position calculation circuit. The capacitance detection circuit is
Has an input connected to and output ends to the output terminal of the switching circuit, wherein the input end is connected to the selected detection wiring, the output end Ru further comprising a buffer circuit connected with the nonselected detection wire The touch panel according to claim 12. A touch panel according to any one of claims 1 to 13,
And a display panel . The display device according to claim 14 , wherein the touch screen of the touch panel is adhered to the front side of the display panel .

Images