JP2002014771A - Insulation method for capacitively-coupled touch panel - Google Patents

Abstract

PROBLEM TO BE SOLVED: To make the insulation of a touch panel whose surface is covered with a thin protective layer (insulating layer) electrically safe. SOLUTION: An isolator, a capacitor which becomes an impedance of an insulator at a power frequency, a coupling coil (mutual inductance), A
Install an insulation transformer for C power supply.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a capacitive coupling type touch panel device and a system using the same, and more particularly, to a method of insulating a capacitive coupling type touch panel having a thin protective layer on its surface.

[0002]

2. Description of the Related Art Conventionally, a capacitively-coupled touch panel which has been put to practical use is intended to practically eliminate the "palm effect" (described in paragraph 0003) in the case of a type in which a uniform sheet resistor is used over the entire effective surface of the panel. The thickness of the protective layer (also serving as an insulating effect) on the panel surface was set to an extremely thin thickness of 1 μm or less. Also,
In other types (such as matrix electrodes), the thickness of the insulating layer on the panel surface is set to 0.4 mm or less in order to strongly detect capacitive coupling with a finger.

The "palm effect" will be described with reference to FIG. This touch panel 42 is an example of a capacitive coupling type in which a 0.4 mm glass insulating layer is provided on the panel surface for electrical safety. FIG. 5 shows a state when a finger 41 touches the panel surface 43. I have. Even if the operator intends to touch the point P1 with the finger 41, the coupling capacitance is actually between the other fingers and P2 and P3 in addition to between the point P1 and the tip of the finger 41, and between the palm and P4. Also, as shown in FIG. These extra coupling capacitances are actually distributed around P2, P3 and P4. The position recognized by the touch panel device is (the coupling capacity between the point P1 and the fingertip is 10p
The Pm point, which is one point obtained by weighting and averaging these points (because only the F-th position is reached), is calculated.

Therefore, a point shifted mainly in the palm direction is detected rather than a touch point that the operator is conscious of. This shift phenomenon is referred to as “palm effect” in the present application. Here, as the insulating layer on the panel surface becomes thinner, the capacitive coupling between the tip of the finger 41 and the point P1 becomes stronger, and Pm
The point approaches the point P1. For this reason, those currently in practical use have an extremely thin surface film thickness as described above.

[0005]

SUMMARY OF THE INVENTION Commercial AC 100-20
In a touch panel device supplied with power from 0 V, a power component leaks more or less into a circuit via a power transformer, via electromagnetic coupling, or via a power noise filter (especially using a capacitor). This is transmitted to the sheet resistance of the touch panel or the matrix electrode. In the case of AC 200 to 250 V, the thickness of the insulator safe for the human body is said to be about 0.4 mm, and it cannot be said that the thickness of the protective layer (insulating layer) on the panel surface is sufficiently safe.

[0006]

Means for Solving the Problems An isolator, a capacitor which becomes an impedance of an insulator at a power supply frequency, a coupling coil (mutual inductance), an insulation transformer for an AC power supply, and the like are arranged between the touch panel and the power supply.

[0007]

The isolator and the coupling coil transmit the signal frequency component but block the power supply frequency component and the DC component. In addition, the capacitor has a value that can be regarded as an insulator at the AC power supply frequency and at the DC power supply frequency as a signal coupling capacitor. The insulating transformer of the AC power supply is insulated between the primary winding and the secondary winding from both AC and DC. Therefore, the AC power supply frequency component and D
The touch panel and the power supply are insulated from the C component at an arbitrary voltage.

[0008]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS The present invention is applied to a touch panel device of a type using a uniform surface resistor over the entire effective surface of a touch panel, a system using the same, and other types (matrix panel electrodes, etc.). Is effective for AC and DC power supplies. In addition, not only in the case of detecting the touch position, but also in the case of a touch panel having only a switch function of detecting proximity or contact of a finger, the insulation method of the present invention is effectively implemented for AC and DC power supplies.

[0009]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS The details of the present invention will be described below with reference to the accompanying drawings. FIG. 1, which is the first embodiment, is an explanatory diagram of a method of insulating a touch panel device as a single block including a panel section and a part of an active circuit. The touch panel 2 has a low resistance peripheral electrode provided around a uniform sheet resistor, and the panel surface is covered with a protective film (1 μm or less, an insulating film for low voltage). Therefore, this touch panel 2 is a capacitive coupling type finger panel 2 of the human body 1.
FIG. 4 is a sensor panel for detecting a two-dimensional touch position on the touch panel.

The touch panel 2 and the signal processing circuit 6 are connected via connection cords 4,..., 4 and switches 5,. The oscillator 8 causes the sheet resistor of the touch panel 2 to oscillate in voltage via the signal coupling capacitor 7. The human body 1 has a grounding effect,
A signal current flows between the finger of the human body 1 and the panel 2 via capacitive coupling. The touch position is calculated by measuring a current value detected from each point around the touch panel 2. Since the signal processing circuit 6 also includes an active circuit, a relatively simple and accurate signal can be detected. For a detailed description of these operations, refer to Japanese Patent Application Laid-Open No. 11-304942, Japanese Patent Application No. 11-216672, and the like.

The signal processing circuit 6 and the main control circuit 10 are connected via an isolator 9 to transmit necessary signal components but block (insulate) power supply frequency components. The insulation of the capacitor 7 will be described. AC10
It is said that an impedance of 1 MΩ or more is a measure of the safe insulation of the human body from 0 to 200 V. At the power supply frequency (60 Hz), the impedance of 1 MΩ is about 2500 pF for the capacitor. In many cases, the power supply noise filter divides the power supply voltage by half and transmits it to its ground circuit. In this case, about 500
5000 pF, which results in an impedance of kΩ, may be sufficient. In this embodiment, the signal coupling capacitor 7
The value of (insulating capacitor for the power supply) is set to 2200 pF. Signal frequency (frequency of oscillator 8) is 200k
Above 200 Hz the impedance at 2200 pF is 37
0 Ω or less, and sufficiently transmit signals. As mentioned above,
The block indicated by reference numeral 3 is insulated from other circuits at the power supply frequency. That is, the touch panel 2 is insulated from the power supply.

When a capacitor is used as a part of the isolator 9, the total capacity of the capacitor and the capacitor 7 is 50.
If it is not more than 00 pF, the above-mentioned insulating property is obtained. Even when the electrode structure of the touch panel is a matrix or another structure, the above-described insulating method can be similarly used. Furthermore,
The above-described insulating method can be similarly used not only in the case of detecting the touch position in two dimensions but also in the case of detecting it in one dimension or a touch panel having only a switch function of detecting proximity or contact of a finger.

Next, a second embodiment will be described. FIG.
FIG. 4 is an explanatory diagram of a method of insulating the panel unit 11 from a power supply by a capacitor. The touch panel 12 is connected to the control unit 15 via connection cords 13,..., 13 and signal coupling capacitors 14,. If the total capacitance of the capacitors 14,...
Are insulated from the power supply. But here is something to note. In the case of a two-dimensional touch panel using a uniform surface resistor, if the combined impedance of the signal coupling capacitor 14 and the input impedance of the control unit 15 is about 10Ω or more, a touch detection position error (error toward the center) becomes large. It is becoming. Therefore, there is a lower limit on the signal frequency. In this embodiment (connection code 1
3,..., And 13), almost good touch detection positions were obtained at a signal frequency of 10 MHz or more. For a touch panel having only a switch function of detecting proximity or contact of a finger, almost satisfactory detection was obtained at a signal frequency of 100 kHz or more.

Next, a third embodiment will be described. FIG. 3 shows the coupling coils 24,.
FIG. 5 is an explanatory diagram of a method of insulating the panel unit 21 from a power supply by using FIG. Here, the coupling coils 24,.
24 functions as an isolator. The signal output of the oscillator 27 is composed of a capacitor 25, a coupling coil 24,.
The touch panel 22 is subjected to voltage oscillation via the primary coil 4 and the connection cords 23,..., 23. Capacitor 2
Reference numeral 5 is a signal coupling capacitor and an insulating capacitor for a power supply, which are the same as those in the first embodiment, and functioned effectively at a signal frequency of 200 kHz or more. Since the panel unit 21 is insulated from the power supply, the touch panel 22 is naturally insulated from the power supply. It should be noted here that the coupling coil 24,.
, 24, while ensuring the withstand voltage between the primary and secondary windings, increasing the coupling coefficient, and accurately adjusting the input impedance as viewed from the primary side to about 10Ω or less at the signal frequency. In the case of a touch panel having only a switch function of detecting proximity or contact of a finger, it goes without saying that only one coupling coil 24 is required.

Next, a fourth embodiment will be described. FIG. 4 is a diagram illustrating a method of insulating the entire system including the touch panel device from an AC power supply by using an insulating transformer. In the present embodiment, the total system 30 including the touch panel device including the touch panel 31 and the control unit 32 and the system main body 33 such as a personal computer is integrated and is isolated from the AC power supply by the insulating transformer 34. is there. The thing to note here is that
Since the insulating transformer 34 blocks (insulates) even the signal frequency, and since it is difficult to obtain a strong grounding effect in the system body 33 such as a personal computer, the touch panel 31
And the signal current flowing between the fingers greatly decreases, and stable touch detection becomes difficult. In this embodiment, the signal frequency is set to 300
When the frequency was set to kHz or higher, the grounding effect of the system body and the human body was enhanced, and good touch detection was obtained. For details on the body circuit ground and the effect of grounding the human body, see Japanese Patent Application No. 10-32.
See No. 1508 and the like.

For good touch detection even at a lower signal frequency, the AC power supply (one side) and the system circuit ground may be connected via a capacitor of 2500 pF or less (not shown). This can be achieved even if the stray capacitance of the insulating transformer 34 is increased. 2500 pF or less is because 100% of the AC power supply voltage is applied to this capacitor.

[0017]

According to the method of the present invention, safe insulation can be provided with almost no decrease in touch detection performance, no matter how thin the protective film (insulating film) on the touch panel surface.

[Brief description of the drawings]

FIG. 1 is an explanatory view of a method of insulating a touch panel device as a single block, including a panel portion and a part of an active circuit.

FIG. 2 is an explanatory view of a method of insulating a panel unit from a power supply by a capacitor.

FIG. 3 is a diagram illustrating a method of insulating a panel unit from a power supply by a coupling coil and a capacitor.

FIG. 4 is an explanatory diagram of a method of insulating an entire system including a touch panel device from an AC power supply by using an insulating transformer.

FIG. 5: Heat 0.4 mm on the surface for electrical safety
Explanatory drawing of the "palm effect" in a capacitively-coupled touch panel provided with the above insulating layer

[Explanation of symbols]

Reference Signs List 1 human body 2 touch panel 3 block insulated from power supply up to 60 Hz 4 connection cord 5 switch 6 signal processing circuit 7 insulation capacitor (signal coupling capacitor) for power supply 8 oscillator 9 isolator 10 main control circuit of touch panel device 11 power supply 12 Insulated capacitor (signal coupling capacitor) for power supply 15 Control unit of touch panel device 21 Panel part insulated from power supply by coil and capacitor 22 Touch panel 23 Connection code 24 Coupling Coil 25 Capacitor 26 Control unit 27 Oscillator 30 Total system insulated from power supply 31 Touch panel 32 Control unit of touch panel device 33 System body such as personal computer 34 Insulation Nsu

Claims (5)

[Claims] 1. A method for insulating a capacitively-coupled touch panel having a thin-film protective layer on its surface from a power supply, comprising: providing an insulating block including the touch panel and an active circuit; And isolating the touch panel from the power supply by isolating the power supply with an isolator and a signal coupling capacitor having a total of 5000 pF or less. 2. A method for insulating a capacitively coupled touch panel having a thin-film protective layer on its surface from a power supply, wherein the touch panel and a control unit are connected via a signal coupling capacitor of 5000 pF or less in total. And insulating the touch panel from the power supply. 3. A method for insulating a capacitively-coupled touch panel having a thin-film protective layer on its surface from a power supply, comprising:
The touch panel is insulated from the power supply by connecting to a signal coupling capacitor of 00 pF or less via a primary winding of a coupling coil and connecting a secondary winding of the coupling coil to the control unit. Insulation method in a capacitively-coupled touch panel. 4. A method of insulating a capacitively-coupled touch panel having a thin-film protective layer on its surface from an AC power supply,
By using a signal frequency of 300 kHz or more, the touch panel is isolated from the AC power supply by supplying the AC power to a touch panel device including the touch panel and a system body such as a personal computer via an isolation transformer. Insulation method for a capacitively coupled touch panel. 5. An insulating method for an AC power supply of a capacitively-coupled touch panel provided with a thin protective layer on the surface, the method comprising:
The AC power is supplied to a touch panel device including the touch panel and a system body such as a personal computer through an insulating transformer, and the circuit ground of the system body is connected to the A ground.
A method for insulating a capacitively-coupled touch panel, wherein the touch panel is insulated from the AC power supply by connecting to the C power supply via a capacitor of 2500 pF or less.