JP3895543B2 - Surface wave touch panel - Google Patents

Description

[0001]
BACKGROUND OF THE INVENTION
The present invention relates to a touch panel having a function of inputting information directly from a display screen to a display device such as a liquid crystal or a personal computer CRT.
[0002]
[Prior art]
The function of the touch panel is to bring a human fingertip or other substance or the like into contact with a specific position on the surface of the touch panel and detect the contact position.
[0003]
Conventional touch panels are roughly divided into a method using a resistive film and a conductive film and a method using surface waves. First, the method using a resistive film utilizes the fact that the resistance value of the transparent conductive film changes when it comes into contact with the transparent conductive film, which can be reduced in size and thickness, and has low power consumption. However, there are problems in terms of response time, sensitivity, durability, and the like. Further, since the resistance film and the conductive film are attached to the transparent substrate, the light transmittance is remarkably lowered, and the display quality is deteriorated. On the other hand, the surface wave method utilizes the fact that the surface acoustic wave is excited on the transparent substrate and the propagation characteristic of the surface wave is changed by the medium contact. Therefore, since the light transmittance is very high, not only the display quality is not deteriorated but also the response time, sensitivity, durability and the like are excellent. As a means for exciting the surface acoustic wave, a method of indirectly exciting the transparent substrate with a wedge-shaped transducer using a bulk wave vibrator is employed. In this method, a transparent substrate is indirectly excited, and a surface acoustic wave is reflected twice by a reflection array disposed around the non-piezoelectric substrate. Therefore, the loss of surface acoustic waves is large, and it is necessary to increase the driving voltage of the transducer, and it is difficult to reduce power consumption. It has also been pointed out that it is difficult to reduce the size and thickness of the device due to the presence of a wedge-shaped transducer.
[0004]
As described above, the surface acoustic wave type touch panel is excellent in terms of light transmittance and durability, but has a significant problem in terms of downsizing, thinning, and low power consumption. It was difficult to install on mobile devices. In order to solve this problem, the piezoelectric plate on which the interdigital electrode is formed is directly fixed to the peripheral edge of the transparent substrate, compared to the surface wave excitation structure using the conventional wedge-shaped transducer, A method of propagating surface acoustic waves to the transparent electrode substrate surface has been proposed. FIG. 3 is a view for explaining the principle of position detection of the surface acoustic wave touch panel according to the present invention. In the figure, a piezoelectric plate 302 is fixedly arrayed at the peripheral edge of a transparent substrate 301 such as glass. With this arrayed piezoelectric plate 302, for example, by touching the crossing point X305 of the propagation surface wave A303 and the propagation surface wave B304 propagating on the surface of the transparent substrate 301 with a finger 306, the propagation surface wave A303 and the propagation surface wave B304 As a result, the contact position of the finger 306 can be detected. This is the detection principle of the surface wave touch panel according to the present invention.
[0005]
FIG. 4 is a detailed view of the piezoelectric plate 302 shown in FIG. In FIG. 4, a bias electrode 401 for surface wave excitation and a ground electrode 402 are formed on the surface of the piezoelectric plate 302, and both electrodes are arranged in a comb shape at the center of the surface of the piezoelectric plate 402. The portion where the bias electrode 401 and the ground electrode 402 are arranged in an interdigital shape is an effective excitation portion 403, the horizontal dimension in the figure is A dimension 404, and the vertical dimension in the figure is b dimension 405. Therefore, the area of the effective excitation portion can be defined by A · B.
[0006]
The principle and technical description of surface wave excitation by the piezoelectric plate 302 and the interdigital electrode are described in detail in Japanese Patent Application Laid-Open No. Hei 6-046496, etc., and will be omitted. The main feature of this excitation method is the wedge type. Compared to the transducer method, a simple piezoelectric plate is made into a fixed array, so that it can be reduced in size, thickness and power consumption. In addition, in the technical documents such as JP-A-6-046496 mentioned above, as a means for improving the propagation efficiency of the surface wave, it is further mentioned that the interdigital electrode side piezoelectric plate surface is fixed to the transparent substrate. Yes. Further, as a measure for further improving the propagation efficiency, it is also possible to electrically cancel the surface charge generated on the back surface of the piezoelectric plate due to the piezoelectric effect during surface wave excitation.
[0007]
[Problems to be solved by the invention]
However, this newly proposed surface-wave type touch panel has not been proposed for a practical mounting structure and electrode arrangement structure due to the particularity of the structure. The current situation is that it has not been realized.
[0008]
That is, the problem to be solved by the present invention is to provide an electrode arrangement structure and a mounting structure that can be commercialized.
[0009]
[Means for Solving the Problems]
In order to improve the surface wave propagation efficiency of the surface acoustic wave touch panel according to the present invention, the surface charge generated on the back surface of the piezoelectric plate is electrically canceled and the interdigital electrode is formed as described above. It is necessary to fix the surface. First, in order to cancel the surface charge generated on the back surface, it is necessary to form a conductive film in the region where the surface charge is generated, and secondly, the piezoelectric plate surface on which the interdigital electrode is formed is a transparent substrate. It is to stick to.
[0010]
As a means for satisfying these two requirements equally, a structure in which a side lead electrode is formed on the side surface of the piezoelectric plate is adopted. FIG. 5 is a conceptual diagram of a first example showing the electrode structure of the piezoelectric plate according to the present invention, and is a perspective view of both sides of the piezoelectric plate with the surface on which the interdigital electrode is formed as the surface. In FIG. 5, comb electrodes are formed on the surface of the piezoelectric plate 501 by both the bias electrode 502 and the ground electrode 503. The effective excitation portion 504 is limited by the comb-like electrode. Ultrasonic vibration is generated in a three-dimensional region in the piezoelectric plate determined by the effective excitation unit 504, and this ultrasonic vibration is converted into a surface wave propagating on the transparent substrate surface after the transparent substrate is fixed. The effective excitation unit 504 has a Lo dimension value 505 in the horizontal dimension and a Wo dimension value 506 in the vertical direction. Therefore, the area Se of the effective excitation unit 504 is Se = Wo × Lo.
Can be defined. Further, the ground electrode 503 is electrically connected to the first back surface terminal electrode 508 on the back surface through a ground side surface lead electrode 507 formed on the side surface of the piezoelectric plate 501. On the other hand, the bias electrode 502 is connected to the second back surface terminal electrode 509 on the back surface through a second side surface lead electrode, that is, a bias side surface electrode 510 formed on the side surface of the piezoelectric plate 501. Further, a third terminal electrode is formed on the back surface of the piezoelectric plate 501. This is the third back terminal electrode 511 in the figure. The horizontal dimension of the third back terminal electrode 511 in the figure is the L1 dimension value 512, and the vertical dimension in the figure is the W1 dimension value 513. The third back terminal electrode 511 is not electrically connected to the first back terminal electrode 508 and the second back terminal electrode 509. In FIG. 5, the L1 dimension value 512 and the W1 dimension value 513 of the third back terminal electrode 511 are set to the same values as the Lo dimension value 505 and the Wo dimension value 506 of the effective excitation portion 504 on the front surface, respectively. Therefore, the area is also equal. Further, the positional relationship between the third back terminal electrode 511 and the effective excitation portion 504 is set to the same positional relationship when projected from the thickness direction of the piezoelectric plate, as shown in the figure. In the positional relationship and the shape and size positional relationship between the third back terminal electrode 511 and the effective excitation portion 504, it is possible to cancel almost 100% of the surface charge generated on the back surface of the piezoelectric plate 501 during the previous ultrasonic excitation. As a result, the propagation efficiency of the surface wave can be improved. Further, both the L1 dimension value 512 and the W1 dimension value 513 are set to values larger than the Lo dimension value 505 and the Wo dimension value 506, and the third terminal electrode 511 is effective in the positional relationship with the effective excitation unit 504. If the positional relationship is such that the excitation unit 504 is covered, the surface charge generated on the back surface of the piezoelectric plate 501 can be canceled by almost 100%.
[0011]
In addition, since the lead electrode is formed on the side surface of the piezoelectric plate, electrical connection with the terminal electrode on the back surface becomes possible. Therefore, even if the surface on which the interdigital electrode is formed is fixed to the transparent electrode, the drive circuit and the control circuit It is also possible to take out the terminal connected to the.
[0012]
FIG. 6 is a conceptual diagram of a second example showing the electrode structure of the piezoelectric plate according to the present invention. In the figure, comb-like electrodes are formed on the surface of the piezoelectric plate 601 by both the bias electrode 602 and the ground electrode 603. The effective excitation part 604 is limited by this comb-like electrode. Ultrasonic vibration is generated in a three-dimensional region in the piezoelectric plate determined by the effective excitation unit 604, and this ultrasonic vibration is converted into a surface wave propagating on the transparent substrate surface after the transparent substrate is fixed. The effective excitation unit 604 has a Lo dimension value 605 in the horizontal direction and a Wo dimension value 606 in the vertical direction. Further, the ground electrode 603 is electrically connected to the first back terminal electrode 608 on the back surface through a ground side lead electrode 607 formed on the side surface of the piezoelectric plate 501. The first back terminal electrode 608 has an extended electrode portion 611 corresponding to the effective excitation portion 604. The lateral dimension of the extended electrode portion 611 in the figure is the L2 dimension value 612, and the longitudinal dimension value in the figure is the W2 dimension value 613.
[0013]
The L1 dimension value 612 and the W1 dimension value 613 of the extended electrode portion 611 are set to values equal to the Lo dimension value 605 and the Wo dimension value 606 of the surface effective excitation portion 604, respectively. Therefore, the area is also equal. Furthermore, the positional relationship between the extended electrode portion 611 and the effective excitation portion 604 is set to the same positional relationship when projected from the thickness direction of the piezoelectric plate, as shown in the figure. With the positional relationship and the shape dimension positional relationship between the extended electrode portion 611 and the effective excitation portion 604, it is possible to cancel almost 100% of the surface charge generated on the back surface of the piezoelectric plate 501 during the previous ultrasonic excitation. As a result, the propagation efficiency of the surface wave can be improved. Further, both the L1 dimension value 612 and the W1 dimension value 613 are set to values larger than the Lo dimension value 605 and the Wo dimension value 606, and the third terminal electrode 611 is effective in the positional relationship with the effective excitation unit 604. If the positional relationship is such that the excitation unit 604 is covered, the surface charge generated on the back surface of the piezoelectric plate 501 can be canceled by almost 100%.
[0014]
On the other hand, the bias electrode 602 is connected to the second back surface terminal electrode 609 on the back surface through a second side surface lead electrode, that is, a bias side surface electrode 610 formed on the side surface of the piezoelectric plate 601. In addition, since the lead electrode is formed on the side surface of the piezoelectric plate, electrical connection with the terminal electrode on the back surface becomes possible. Therefore, even if the surface on which the interdigital electrode is formed is fixed to the transparent electrode, the drive circuit and the control circuit It is also possible to take out the terminal connected to the.
[0015]
【Example】
A surface wave touch panel as shown in FIG. 1 can be realized by using the electrode structure of the piezoelectric plate described with reference to FIGS. FIG. 1 shows an embodiment of a fixed form of a piezoelectric plate according to the present invention. In FIG. 1, a large number of piezoelectric plates 601 described in FIG. The front surface of the piezoelectric plate 601 on which the interdigital electrode exists is fixed to the transparent substrate. In this case, since the ground side surface lead electrode 607 and the bias side surface electrode 610 are formed on the side surface of the piezoelectric plate 601 on the piezoelectric plate 601, the back surface of the piezoelectric plate 601 is the same as the ground electrode and the bias electrode, respectively. The first terminal electrode 608 and the second terminal electrode 609 which are potentials are exposed to the outside, and these electrodes are connected to the drive circuit / control circuit. In addition, the surface charge generated on the back surface of the piezoelectric plate 601 is canceled by the presence of the extended electrode portion 611 having the same potential as the ground electrode. As a result, a surface wave touch panel having very high surface wave propagation characteristics can be realized. Note that FIG. 1 is based on the piezoelectric plate having the electrode structure described in FIG. 6. However, the piezoelectric plate described in FIG. Needless to say.
[0016]
FIG. 2 shows an embodiment of a surface acoustic wave touch panel mounting structure according to the present invention. This embodiment is an embodiment based on the piezoelectric plate 601 described with reference to FIG. In the figure, a piezoelectric plate 601 is fixedly arranged in an end main change portion of the transparent substrate 101. At this time, the interdigital electrode side of the piezoelectric plate 601 is fixed to the transparent substrate, and electrode terminals to be connected to the drive circuit / control circuit are formed on the back surface side. An anisotropic conductive film 201 is pressure bonded to the exposed back surface of the piezoelectric plate 601. The anisotropic conductive film 201 is fixed to the back surface of the piezoelectric plate 601 by pressure bonding, and has a characteristic that conductivity is realized only in the thickness direction by pressure. Therefore, even after the anisotropic conductive film 201 is pressure-fixed, each terminal electrode on the back surface of the piezoelectric plate 601 is not short-circuited, and its electrical independence is maintained.
[0017]
After the anisotropic conductive film 201 is fixed, the flexible substrate 202 is fixed for the purpose of connecting to the drive circuit / control circuit. The flexible substrate 202 is formed with lead electrodes for driving the arrayed piezoelectric plates 601 in the drawing and sensing output signals, and the pressure-fixed anisotropic conductive film 201 described above. By connecting the flexible substrate 202 and the external drive / control circuit, the connection is realized.
[0018]
【The invention's effect】
By implementing the above configuration, a surface wave touch panel with extremely high surface wave propagation characteristics and low power consumption can be realized. That is, in the embodiment of FIG. 2, by forming the lead electrode on the side surface of the piezoelectric plate fixed to the transparent substrate, the piezoelectric plate surface on which the interdigital electrode is formed can be used as the fixing surface. By forming the back terminal electrode for canceling the charge generated on the back side of the plate, the propagation characteristics of the surface wave are remarkably improved. As a result, a low-power consumption surface acoustic wave touch panel can be realized. Furthermore, by adopting such an electrode structure of a piezoelectric plate, an anisotropic conductive film can be attached to the entire back surface of the piezoelectric plate, so that a very simple mounting structure can be realized. FIG. 2 is an example based on the piezoelectric plate 601 of FIG. 6 described above, but it goes without saying that the same configuration and effects are exhibited even if the piezoelectric plate 501 of FIG. 5 is used. That is.
[Brief description of the drawings]
FIG. 1 is a conceptual diagram showing an embodiment of a piezoelectric plate fixing form according to the present invention. FIG. 2 is a diagram showing an embodiment of a surface wave touch panel mounting structure according to the present invention. FIG. 4 is a conceptual diagram for explaining the position detection principle of the touch panel. FIG. 4 is a detailed diagram of the piezoelectric plate shown in FIG. 1. FIG. 5 is a conceptual diagram of a first example showing the electrode structure of the piezoelectric plate according to the present invention. Schematic diagram of second example showing electrode structure of piezoelectric plate according to the present invention
601 Piezoelectric plate 602 Bias electrode 603 Ground electrode 604 Effective excitation portion 605 Lo dimension value 606 Wo dimension value 607 Ground side surface lead electrode 608 First back surface terminal electrode 609 Second back surface terminal electrode 610 Bias side surface lead electrode 611 Expansion electrode portion 612 L2 size Value 613 W2 Dimension value 101 Transparent substrate 201 Anisotropic conductive film 202 Flexible substrate

Claims (5)

A piezoelectric plate in which interdigital electrodes are formed around a transparent substrate such as glass or plastic is fixedly disposed, and has a function of exciting a surface acoustic wave on the transparent substrate by the piezoelectric effect of this piezoelectric plate. In the structure of the surface wave touch panel that has the function of identifying the contact position by detecting the intensity change, the propagation intensity of the excitation surface wave changes when another substance contacts the transparent substrate.
Two side surface lead electrodes are formed on the side surface of the piezoelectric plate, the first side surface lead electrode is electrically connected to the bias electrode of the interdigital electrode, and the second side surface lead electrode is the ground of the interdigital electrode. together they are connected to the electrodes electrically, interdigital electrodes on the piezoelectric plate rear surface is not formed at least one or more independent rear surface terminal electrode is formed, further the backside terminal electrodes at least one is, the one A surface wave touch panel characterized by being connected to a side lead electrode. First, second, and third back surface terminal electrodes are formed on the back surface of the piezoelectric plate, and first and second side surface lead electrodes are formed on the side surfaces, and the first back surface terminal electrode is the second surface electrode. The second back terminal electrode is electrically connected to the ground electrode of the interdigital electrode on the surface of the piezoelectric plate through the side surface lead electrode, and the interdigital electrode on the surface of the piezoelectric plate is connected to the second back surface terminal electrode through the first side surface lead electrode. The third back terminal electrode is formed without being electrically connected to the first and second back terminal electrodes, and its area and effective dimension are as follows: and and equal to or more values and dimensions and area of the effective excitation portion that is determined by the interdigital electrodes of the surface, when projected in the thickness direction of the piezoelectric plate in its positional relationship, the Surface wave touch panel according to claim 1 which is or a third back surface terminal electrode in the same positional relationship and efficiency excitation portion, characterized in that a positional relationship that covers the effective excitation portion. First and second back surface terminal electrodes are formed on the back surface of the piezoelectric plate, and first and second side surface lead electrodes are formed on the side surfaces. The first back surface terminal electrode is the second side surface lead electrode. The second back-side terminal electrode is electrically connected to the ground electrode of the interdigital electrode on the surface of the piezoelectric plate via the first side surface lead electrode and the bias electrode of the interdigital electrode on the surface of the piezoelectric plate Further, the dimensional shape and area of the first back terminal electrode is a value larger than the dimensional shape and area of the effective excitation portion determined by the interdigital electrode, and in its positional relationship, when projected in the thickness direction of the piezoelectric plate, the surface wave touch panel according to claim 1, characterized in that a positional relationship that covers the effective excitation portion that is determined by the interdigital transducer.    4. The surface acoustic wave touch panel according to claim 1, wherein the surface of the piezoelectric plate for surface wave excitation on which the interdigital electrode is formed is fixed to the peripheral edge of the transparent substrate. . The surface acoustic wave drive circuit and the control circuit are electrically connected by fixing the anisotropic conductive film and the flexible substrate on the back surface of the piezoelectric plate fixedly arrayed on the peripheral edge of the transparent substrate. The surface acoustic wave touch panel according to any one of claims 1 to 4, wherein:

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