JP2002342027A - Display device with touch sensing function - Google Patents

Abstract

PROBLEM TO BE SOLVED: To prevent the quality of display information displayed on a display device from being degraded by the remarkable lowering of the transmissivity of light due to the increase of the total thickness of a system and the presence of the transparent electrode of a touch panel in the case of the combination of the display device and the touch panel. SOLUTION: By fixing, arraying and arranging a piezoelectric plate where an interdigital electrode is formed at the peripheral end part of a transparent substrate, a surface acoustic wave exciting function is provided on the substrate. Further, the propagation speed of excited surface acoustic waves is changed by the contact of a fingertip or the other material on the transparent substrate and a touch sensing function capable of specifying a contact position by detecting the strength change is added.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a liquid crystal display and a personal computer CR.
Display devices such as T

[0002]

2. Description of the Related Art In recent years, a display device using a liquid crystal element has been indispensable for the development of portable equipment represented by a portable telephone. A conventional display device using liquid crystal (hereinafter simply referred to as a display device for the sake of simplicity) has a function of unilaterally displaying characters, numerals, figures, and the like to a human or the outside world. In order to solve this problem, a touch panel has been devised that has a function of allowing a person to make a decision based on display information displaced from a display device and inputting the result to a portable device, that is, a touch sensing function. In this touch panel, a medium such as a human fingertip or another substance is brought into contact with a specific position on the surface of the touch panel, and the contact position is detected. The touch panel and the display device are assembled as independent devices due to their mechanism, and are set at the same location when the final product such as a portable device is manufactured. FIG.
It is a conceptual diagram which shows the basic structure of the conventional display apparatus and a touch panel, and its set structure. In the figure, the liquid crystal element 303
Are sandwiched between two substrates, that is, a display device upper transparent substrate 301 and a display device lower substrate 302. A liquid crystal gap guide plate 305 is provided to maintain a space (gap) for confining the liquid crystal element 303, and is fixed to both the display device upper transparent substrate 301 and the display device lower substrate 302. A polarizing plate 304 is fixed to the outer surface of the upper transparent substrate 301 of the display device. The above is a conceptual diagram of the basic structure of the display device. At this time, as a material of the upper transparent substrate 301 of the display device, a transparent material such as glass and transparent plastic is used. A display unit 306 shown in the figure is a display unit of the display device, and characters, numerals, figures, and the like are displayed in this area. The basic structure of the touch panel includes a touch panel upper transparent substrate 307, a touch panel lower transparent substrate 308, and a touch panel gap guide plate 310. The touch panel upper transparent substrate 307 and the touch panel lower transparent substrate 3
08, a transparent electrode 309 is formed inside the transparent substrates. Also, in order to form a set structure with the display device, a support plate 3
11 is fixed. The upper and lower transparent substrates 307 and 308 of the touch panel are made of a transparent material such as glass and transparent plastic, like the upper transparent substrate 301 of the display device in the figure. These two devices are set in the direction of the arrow shown in the figure.

[0003]

The setting of such a display device and a touch panel device as a set has been a serious problem in recent years, particularly in information portable equipment, which is increasingly required to be thinner and smaller. The problem is first
In addition, since the touch panel is further set on the upper portion of the display device to be set, the total thickness of the system is significantly increased. Second, due to the presence of the transparent electrode formed on the transparent substrate of the touch panel, Light transmittance is significantly reduced, and as a result, the quality of display information displayed on the display device is reduced. Therefore, it has been difficult to mount it on a portable device that has been remarkably developed in recent years. That is, the problem to be solved by the present invention is that the problem caused by setting a touch panel and a display device as described above is considered. There is a fundamental solution.

[0004]

FIG. 4 shows the concept of the principle of touch sensing according to the present invention. This sensing principle is a method in which a surface acoustic wave is propagated to the surface of a transparent electrode substrate by fixing and arraying a piezoelectric plate on which interdigital electrodes are formed directly on the peripheral end of a transparent substrate. In the figure, a piezoelectric plate 402 is fixedly arrayed at a peripheral end of a transparent substrate 401 such as glass. By touching the intersection X405 of the propagation surface wave A403 and the propagation surface wave B404 propagating on the surface of the transparent substrate 401 with the finger 406 or the like by the arrayed piezoelectric plates 402, the propagation surface wave A403 and the propagation surface wave B404 Are disturbed, and as a result, the contact position of the finger 406 can be detected.

FIG. 5 is a detailed view of the piezoelectric plate 402 shown in FIG. In FIG. 5, a bias electrode 501 and a ground electrode 502 for exciting a surface wave are formed on the surface of a piezoelectric plate 402, and both electrodes are arranged in an interdigital shape at the center of the surface of the piezoelectric plate 402.

This portion is an interdigital electrode portion 503, and a surface wave is excited on the transparent substrate shown in FIG. 4 at the interdigital electrode portion 503. The principle and technical description of the surface wave excitation by the piezoelectric plate 402 and the interdigital electrodes are omitted in detail because they are described in detail in JP-A-6-046496, etc. Compared to the touch sensing method using electrodes, the transparent electrode does not lower the transmittance of transmitted light, and it is a method of simply fixing the piezoelectric plate to the transparent substrate, which makes it possible to reduce the size of the device. Has characteristics. Further, by making the thickness of the piezoelectric plate smaller than the thickness of the transparent substrate, the displacement distribution of the excitation surface wave can be localized near the transparent substrate surface. In addition,
The polarization direction of the piezoelectric plate on which the interdigital electrodes described in FIGS. 4 and 5 are equal to the direction perpendicular to the plate surface on which the interdigital electrodes are formed.

By using a new touch sensing technology using surface waves, a piezoelectric plate is arrayed on a transparent substrate of a display device in contrast to a conventional configuration method in which a touch panel and a display device that are separately configured are set. Then, by exciting the surface waves, a display element having a touch sensing function on a transparent substrate, that is, a display device with a touch sensing function can be proposed.

[0008]

FIG. 1 shows an embodiment of a display device with a touch sensing function according to the present invention. The dimension value of the plate thickness 102 of the piezoelectric plate 101 having a polarization axis in the direction perpendicular to the plate surface and further having comb electrodes formed on the plate surface is d1. The piezoelectric plate 101 is fixedly arrayed around the outer surface edge of the upper transparent substrate 103 of the display device. At this time, the dimension value of the thickness 104 of the upper transparent substrate 103 of the display device is t1, and the following inequality (1) is established with respect to the dimension value d1 of the thickness 102 of the piezoelectric plate 101.

T1> d1 (1) At this time, the upper transparent substrate 103 of the display device shown in the figure is made of a material such as glass and transparent plastic. Further, a polarizing plate 112 is fixed to the entire outer surface of the upper transparent substrate 103 of the display device. therefore,
The polarizing plate 112 also exists as an intermediate layer at the fixed interface between the piezoelectric plate 101 and the upper transparent substrate 103 of the display device. The thickness of the polarizing plate 112 is very thin and can be ignored compared to the thickness d1 of the piezoelectric plate 101 and the thickness t1 of the upper transparent substrate 103 for display. Further, a liquid crystal element 106 is interposed in a gap between the display device upper transparent substrate 103 and the display device lower substrate 105. There is a liquid crystal gap guide plate 107 to maintain this gap.

An anisotropic conductive film 10 is formed on the surface of the piezoelectric plate 101.
8 are fixed, and a flexible substrate 109 is further connected via the anisotropic conductive film 108. Piezoelectric plate 1
The bias electrode and the ground electrode of the IDT formed on the anisotropic conductive film 108 and the flexible substrate 1
09, the externally provided surface wave drive circuit 110
And a touch sensing detection circuit 111. The surface acoustic wave 113 excited by the surface acoustic wave drive circuit 110 propagates through the display section 114 of the upper transparent substrate 103 of the display device. Since the displacement distribution of the excitation surface wave 113 is localized on the surface of the display unit 114 under the conditions defined by the above-described expression (1), the display device upper transparent substrate 103 and the display device upper transparent Substrate 10
The liquid crystal element 106 existing in the gap of No. 5 is not affected. When the propagation intensity of the excitation surface wave 213 changes due to touch sensing on the display unit 114, the change in intensity can be detected by the touch sensing detection circuit 211.

FIG. 2 shows another embodiment of the display device with a touch sensing function according to the present invention. The dimension value of the plate thickness 202 of the piezoelectric plate 201 having a polarization axis in the direction perpendicular to the plate surface and further having the comb-shaped electrodes formed on the plate surface is d2. The piezoelectric plate 202 is directly fixedly arrayed around the outer surface edge of the upper transparent substrate 203 of the display device without the interposition of the polarizing plate 212. At this time, the dimension value of the thickness 204 of the upper transparent substrate 203 of the display device is t2, and the following inequality (2) is established with respect to the dimension value d2 of the thickness 202 of the piezoelectric plate 201.

T2> d2 (2) At this time, the upper transparent substrate 203 of the display device is made of a material such as glass and transparent plastic. Further, the polarizing plate 212 is fixed to only the portion where the piezoelectric plates 201 are not fixedly arrayed, that is, only the display portion 214, on the outer surface of the upper transparent substrate 203 of the display device. The thickness of the polarizing plate 212 is very small,
01 and the thickness t of the display device upper transparent substrate 203.
The thickness is negligible compared to 2. A liquid crystal element 206 is interposed in a gap between the display device upper transparent substrate 203 and the display device lower substrate 205, and a liquid crystal gap guide plate 207 is provided to maintain the gap.
An anisotropic conductive film 208 is fixed on the surface of the piezoelectric plate 201, and a flexible substrate 209 is connected via the anisotropic conductive film 208. The bias electrode and the ground electrode of the interdigital transducer formed on the piezoelectric plate 201 are connected to the surface wave drive circuit 210 and the touch sensing detection circuit 211 by the anisotropic conductive film 208 and the flexible substrate 209. In addition, this surface wave drive circuit 2
10 and the touch sensing circuit 211 are provided on the outer surface of the display device lower substrate 205. The excitation surface waves 213 excited by the surface acoustic wave drive circuit 210 propagate through the display section 214 of the upper transparent substrate 203 of the display device. Since the displacement distribution of the excitation surface wave 213 is localized on the surface of the display unit 214 under the conditions defined by the above-mentioned equation (2), the display device upper transparent substrate 203 and the display device upper transparent It does not affect the liquid crystal element 206 existing in the gap of the substrate 205. When the propagation intensity of the excitation surface wave 213 changes due to the touch sensing on the display unit 214, the change in the intensity can be detected by the touch sensing detection circuit 211.

[0013]

According to the structure shown in FIG. 1 in which the piezoelectric plate on which the interdigital electrodes are formed is fixedly arrayed around the edge of the transparent substrate, a surface wave is generated on the upper transparent substrate of the display device. It can be propagated. Furthermore, by setting the thickness of the piezoelectric plate to be fixedly arrayed to be smaller than the thickness of the upper transparent substrate, it becomes possible to localize the excitation surface wave near the surface of the upper transparent electrode, thereby affecting the liquid crystal element. Without giving it, it is possible to perform touch sensing by directly touching the display unit of the display device, and the problem that the total thickness of the system described above is significantly increased can be solved. In addition, since the transparent electrode does not exist in the display portion of the upper transparent substrate, the problem of deterioration in light transmittance can be solved. Therefore, compared to the conventional configuration system, the quality can be improved and the size can be reduced.

When the configuration shown in FIG. 2 is employed, the piezoelectric plate and the upper transparent substrate are directly fixedly arrayed without interposing a polarizing plate, so that it is possible to improve the propagation characteristics of the excitation surface wave in the display section. Further, since the driving circuit and the sensing circuit are installed outside the lower substrate, the system can be further compacted.

[Brief description of the drawings]

FIG. 1 is a view showing an embodiment according to the present invention, and is an example of a display device in which a touch panel function is added on a transparent substrate.

FIG. 2 is a view showing another embodiment according to the present invention, and is an example of a display device in which a surface acoustic wave drive circuit and a position detection circuit are installed outside a lower substrate;

FIG. 3 is a conceptual diagram showing a basic structure and a set structure of a conventional display device and a touch panel.

FIG. 4 is a conceptual diagram illustrating the principle of touch sensing according to the present invention.

FIG. 5 is a conceptual diagram for explaining in detail a piezoelectric plate for surface wave excitation according to the present invention.

[Explanation of symbols]

 201: piezoelectric plate 202: piezoelectric plate thickness d2 203: display device upper transparent substrate 204: display device upper transparent substrate thickness t2 205: display device lower substrate 206: liquid crystal element 207: liquid crystal gap guide plate 208: anisotropic conductive Film 209: Flexible substrate 210: Surface wave drive circuit 211: Touch sensing drive circuit 212: Polarizer 213: Excitation surface wave 214: Display unit

 ──────────────────────────────────────────────────続 き Continuing on the front page (72) Inventor Hideki Kitajima 1-8-1 Nakase, Mihama-ku, Chiba-shi, Chiba Inside of SII RRD Center Co., Ltd. (72) Inventor Takashi Sarada 1 Nakase, Mihama-ku, Chiba-shi, Chiba 8-8 chome S.I.R.D. Center (72) Inventor Masataka Shinogi 1-8-8 Nakase, Mihama-ku, Chiba-shi, Chiba Seiko Instruments Inc. (72) Inventor Koji Toda Futaba, Yokosuka-shi, Kanagawa 1-49-18 Toda Kojinai F-term (reference) 2H089 HA18 HA40 QA02 QA05 QA11 QA12 QA13 5B087 AB04 AB07 AE09 CC02 CC11 CC25 5G435 AA03 AA18 BB12 BB15 EE47 LL08

Claims (4)

[Claims] A liquid crystal element is sandwiched between two substrates, and at least one of the two substrates has a basic structure such that the substrate is a transparent substrate of glass, plastic, or the like. Take off the fixed polarizing plate,
In a liquid crystal display device for displaying characters, numerals, figures, and the like in the external world, a piezoelectric substrate having a polarization direction parallel to a thickness direction at a peripheral end of an outer surface of the transparent substrate, and an interdigital electrode formed on the surface. The plate is arranged in a fixed array, and has a function of exciting surface acoustic waves on the transparent substrate by the piezoelectric effect of the piezoelectric plate.Furthermore, when the fingertip or another substance comes into contact with the transparent substrate, the plate is excited. The display device is characterized in that the propagation strength of the surface acoustic wave changes and a function of detecting a change in the strength to specify a contact position, that is, a so-called touch sensing function is added. A piezoelectric plate with interdigital electrodes is fixedly arranged around a transparent substrate such as glass or plastic, and has the function of exciting surface acoustic waves on the transparent substrate by the piezoelectric effect of this piezoelectric plate. Or, when another substance comes into contact with the transparent substrate, the propagation intensity of the excited surface acoustic wave changes, and the structure of the surface acoustic wave touch panel having a function of specifying the contact position by detecting the change in the intensity is detected. In the above, the piezoelectric plate is fixedly arranged on a transparent substrate with the surface on which the interdigital electrodes are formed facing downward, and two side surface lead electrodes are formed on the side surface of the piezoelectric plate, The second side lead electrode is electrically connected to the interdigital electrode bias electrode, and the second side lead electrode is electrically connected to the interdigital electrode ground electrode. At least one or more independent back terminal electrodes are formed on the back surface of the unformed piezoelectric plate, and at least one of the back terminal electrodes is connected to one side lead electrode. Surface wave touch panel. 2. The display device according to claim 1, wherein the thickness of the transparent substrate is larger than the thickness of the piezoelectric substrate on which the interdigital electrodes are formed. 3. A surface wave driving circuit and a sensing circuit by fixing an anisotropic conductive film or a flexible substrate on the surface of the piezoelectric plate fixedly arrayed at a peripheral end on the transparent substrate. The display device according to claim 1, wherein the display device is electrically connected to the display device. 4. The surface wave drive circuit and the sensing circuit,
The display device according to any one of claims 1 to 3, wherein the display device is provided outside a rear surface of a second substrate constituting the display device.