JP2005084982A - Electrostatic capacitance type touch panel device - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide an electrostatic capacitance type touch panel device for an input system, while varying a two-way switching mechanism, reducing the number of part items, and at the same time making free layout of switches possible. <P>SOLUTION: A capacitance type touch panel device comprises a touch panel, where an electrode sheet made of the expanded PET film of a panel part with a nontransparent switch electrode printed thereon is affixed to an acrylic or glass plate with a transparent adhesive; a computing circuit for measuring changes in the capacitance of each switch of the touch panel, when a conducting member is in contact with each switch and when it is not; and a control board with a nonvolatile memory mounted thereon for storing the changes. <P>COPYRIGHT: (C)2005,JPO&NCIPI

Description

  The present invention relates to a touch panel device that employs a capacitive coupling method as an input method.

Conventionally, a resistive touch panel is often mounted on an input unit of a monitor with a touch panel. As shown in Fig. 1, a typical resistive film type touch panel was formed by depositing ITO transparent electrodes on the surface of both the glass plate and PET film, facing each other with a spacer in between, and pressing with a finger It is a mechanism that can be input with.
However, as shown in FIG. 2, the monitor with a touch panel has a function key at the bottom of the display device to change the display state (brightness and contrast), and a mechanical switch such as a tact switch is used. In order to adjust the brightness and contrast with the touch panel, there are cases where the operation cannot be performed depending on the display state, and a method in which another switch such as a tact switch can be provided and changed is adopted. Therefore, the function key section requires a switch mechanism different from the touch panel.

JP 09-244810 A

  Therefore, in the conventional system, the switch mechanism is configured by two systems of a touch panel and a mechanical switch, and accordingly, two types of control circuits are required. Further, depending on the use environment, there is a device in which fixed item selection switches registered in advance on both sides of the display device (liquid crystal panel or CRT display) are mounted. In that case, the mechanical switch is difficult to use because there are many restrictions on the shape, height and arrangement of the switch. Accordingly, an object of the present invention is to adopt a capacitive touch panel device as an input method, change the two-type switch mechanism, reduce the number of parts, and at the same time, allow a free layout of switches.

An electrostatic capacitance type touch panel is a touch panel in which a PET film of a panel portion is expanded and an electrode sheet on which an opaque switch electrode is printed is attached to an acrylic plate or a glass plate. Capacitance type touch panel device comprising a control circuit equipped with an arithmetic circuit for measuring the amount of change in capacitance of the switch in a contact state and a non-contact state, and a non-volatile memory for storing the amount of change when the conductive member to be capacitively coupled It is.
In the present specification, description will be made using a human finger as the conductive member.

  According to the present invention, in the switch configuration of the monitor with a touch panel, the double structure of the touch panel and the tact switch is eliminated, and further, there is no mechanical switch with a movable part, so there is no malfunction due to secular change or poor contact and high reliability. A touch panel can be realized. In addition, there is no switch protrusion on the surface, the switch shape can be expressed with a sticker, the fixed items can be changed easily, and low cost can be realized.

The present invention comprises a panel unit and a control unit as shown in the system configuration diagram of FIG. The panel part creates an extended electrode sheet (FIG. 5) in which an ITO transparent electrode and a silver paste electrode are printed on a PET film, and the electrode sheet is applied to a glass plate or an acrylic plate (dielectric) using a transparent adhesive. It has a pasted structure. (FIG. 6).
The extended electrode sheet structure is composed of a switch electrode and an opaque switch electrode. The transparent switch electrode and the opaque switch electrode are formed in a circle or quadrangle that can hide a human finger, and the GND pattern is applied to the periphery of the panel to reduce noise and stabilize the signal level. A structural diagram of the extended electrode sheet is shown in FIG. The connection terminals are formed in a two-layer structure in which the first layer on the PET film is printed with silver paste and the second layer is printed with carbon for protecting the connection terminals.
The lead pattern 1 and the transparent switch electrode are printed with the ITO transparent electrode so that the display from below can be seen in the display area. Since the lead pattern 2 and the opaque switch electrode are non-display areas, they need not be transparent and are printed with a silver paste having a low resistance value.
The control unit includes an analog switch type multiplexer for switching switch electrodes (hereinafter referred to as a switch electrode together with a transparent switch electrode and an opaque switch electrode) in order, and an oscillation circuit capable of changing the frequency. A non-volatile memory for storing threshold data and a CPU with an input capture function capable of measuring the width of the waveform are included.
The operation principle of this capacitive touch panel will be described with reference to FIG. First, in order to connect the switch electrode designated by the program and the oscillation circuit in the block diagram of FIG. 9, a control signal is output from the I / O terminal of the CPU to the switch electrode switching circuit. This switch electrode switching circuit connects the switch electrode and the oscillation circuit when the control signal “1” (digitally high level) is output from the I / O terminal of the CPU, and the control signal “0” (digitally). If a low level is output, the switch electrode has a function of connecting to the GND signal.
Next, a procedure until a switch is specified will be described using an actual touch panel monitor incorporating a capacitive touch panel. The following two points are implemented to define the On / Off level of each switch. First, in a non-contact state where the finger does not touch the panel, the CPU outputs a control signal from the I / O terminal according to the program, up to switches T1 to F3 (T1 to T9, S1 to S6, F1 to F3 in this order). The oscillation frequency is measured, and the transmission frequency in each switch-off state is stored in a nonvolatile memory connected to the CPU. Next, one finger is placed on the panel, and the frequency is similarly measured from the switches T1 to F3, and the transmission frequency of each switch On state is stored in the nonvolatile memory. With this measurement, the On / Off level can be determined even with switches having different capacitance changes, and On / Off can be determined without erroneous recognition.
When a human finger actually approaches the switch electrode, the capacitance of the switch electrode increases. Humans are originally conductors having a capacitance of about 100 pF, and when a human finger as a conductor approaches the switch electrode, an electrostatic induction phenomenon occurs and the capacitance increases. The oscillation circuit detects a change in the increased capacitance, and the transmission frequency changes following the increase in the capacitance.
The control unit measures the oscillation frequency using an input capture function built in the CPU. The CPU controls the changeover switch circuit from the I / O terminal and measures the transmission frequency in order from the switches T1 to F3. When the transmission frequency measured this time is compared with the transmission frequency at the time of On / Off of each switch stored in the non-volatile memory first, only the switch approaching the finger decreases the frequency.
Based on this principle, it is possible to determine which switch electrode a human finger touches, and since the switch function and location can be determined, a capacitive touch panel can be realized.

  Hereinafter, an embodiment of the present invention will be described with reference to the drawings. The switch switching circuit will be described with reference to FIG. When the switch electrode T1 and the oscillation circuit 1 are connected, "1" is output from the I / O terminal 3 of the CPU 2 to the control signal, and "0" is output to the control signal from the other switch electrodes T2 to F3. In this state, the switch electrode switching circuit 4 connects the switch electrode T1 and the oscillation circuit, and the switch electrodes T2 to F3 are connected to GND.

  Next, the oscillation circuit of FIG. 10 is a C-MOS type timer IC that is very common in TLC555. The calculation formula of the oscillation frequency is presented from the manufacturer's data sheet, and can be obtained by substituting a constant at f = 1.44 / (R1 + 2 × R2) × C1. In this case, since an oscillation frequency of about 100 kHz that can be measured by a general CPU is convenient, a circuit that oscillates in a multivibrator mode with resistors R1 = 1 kΩ, R2 = 68 kΩ, and C1 = 100 pF is configured. Next, a capacitor C2 connected by a dotted line represents an equivalent capacitance capacitor corresponding to a change in capacitance when a finger touches the switch electrode. When touching with one finger, the capacitance increases by about 0.1 pF and with two fingers, the capacitance increases by about 0.2 pF. The capacitor C3 is a capacitor for stabilizing the transmission.

Now, the frequency change when the finger touches the function key switch F1 on the touch panel monitor shown in FIG. 11 will be described.
・ Oscillation frequency when finger is not touching F1 switch ・ C = 100pF (C1)
・ Frequency about 100.1 kHz ・ Oscillation frequency when F1 switch is touched with a finger ・ C = 100.1 pF (parallel connection C1 + C2)
-Frequency about 100 kHz When the switch F1 was touched with a finger, the oscillation frequency decreased because electrostatic induction occurred between the switch electrode and the finger and the capacitance increased.
As a result, the capacitance of the capacitor that determines the frequency of the timer IC of the TLC 555 is increased, so that the oscillation frequency is reduced by 100 Hz as shown in FIG.
Applying this principle, the oscillation frequency displacement shown in FIG. 9 is constantly monitored for each switch by the input capture function counter built in the CPU, and it is defined that the touch is when the frequency is reduced by 70 Hz or more. The function key F1 can be specified.

  Since the function key F1 can be specified, if the extension electrode sheet is attached to the casing as shown in the lower diagram of FIG. 10 and the display sticker for specifying the switch location is attached to the casing surface, An electrostatic coupling type touch panel monitor without a switch can be realized.

    Applying the above principle, we will apply it to a system that can use the touch panel widely for visually handicapped persons by adding braille to the membrane switch to the function key and fixed key part. As a specific method, in the structure shown in FIG. 13, the transmission frequency in a non-contact state on the switch, the transmission frequency in a state where a finger is placed on the braille and slid left and right, and the membrane switch is pushed in the state shown in the lower diagram of FIG. If the state of the three transmission frequencies is stored in a non-volatile memory and the amount of change is compared, the oscillation frequency changes depending on how the membrane switch is pressed, so it is possible to determine On / Off. A capacitive touch panel equipped with a Braille input function can be realized by clicking the membrane switch of the visually impaired and the amount of change in frequency.

    A built-in click dome (made of metal) to give a stronger click feeling to the membrane switch, or a deep depression feeling by adding a dent to the housing can be stored in the non-volatile memory and the amount of change compared. This is possible.

    Next, not only the flat panel but also the ITO transparent electrode shown in FIG. Since it is formed in a film shape, it can be attached to a curved surface, and a capacitive curved surface switch can be realized.

Structure diagram of a resistive film type touch panel. General monitor with touch panel. The structure diagram of a transparent electrode sheet. The structure diagram of a capacitive touch panel. Extended electrode sheet structure drawing. Capacitance type expansion touch panel block diagram. The system block diagram of an electrostatic capacitance type touch panel. Expansion electrode sheet block diagram. Capacitance type touch panel control circuit block diagram. Monitor with capacitive touch panel. Equivalent circuit of transmission circuit. Change in transmission frequency. Capacitance type braille input switch. Capacitance type phase switch.

Explanation of symbols

1 Transmission circuit
2 CPU
3 I / O terminal 4 Switch electrode switching circuit

Claims (4)

An electrostatic capacitance type touch panel is a touch panel in which a PET film of a panel portion is expanded and an electrode sheet on which an opaque switch electrode is printed is attached to an acrylic plate or a glass plate. The conductive member to be capacitively coupled includes a control circuit on which an arithmetic circuit for measuring the capacitance change amount of the switch in a contact state and a non-contact state and a non-volatile memory for storing the change amount are mounted. Capacitive touch panel device. The capacitive touch panel device according to claim 1, wherein the capacitive touch panel switch is built in a monitor with a touch panel. The capacitive touch panel device according to claim 1, wherein the switch of the touch panel is affixed with a sheet provided with braille at a portion where the conductive member contacts. The capacitive touch panel device according to any one of claims 1 to 3, wherein the electrode sheet is made of a film and can be arranged on a curved surface.

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