JP2010117955A - Display - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a display with a capacitance coupling system touch panel for precisely detecting touch position coordinates by simple circuit configurations. <P>SOLUTION: A capacitance coupling system touch panel includes: a plurality of X electrodes; and a plurality of Y electrodes crossing the X electrodes, and the X electrodes and Y electrodes are provided with overlapped crossing sections and an electrode section formed between the two crossing sections, and a coordinate position detection circuit includes: a reference clock generation circuit for generating a reference clock; a switch circuit for connecting an oscillating circuit with both the ends of each of the plurality of X electrodes and the plurality of Y electrodes; and an arithmetic circuit for calculating the touch position of the finger of an observer to the capacitance coupling system touch panel according to a difference between the oscillation frequency of a ring oscillator configured of each of the plurality of X electrodes and the plurality of Y electrodes and the oscillating circuit and the frequency of the reference clock. <P>COPYRIGHT: (C)2010,JPO&INPIT

Description

  The present invention relates to a display device with a touch panel, and more particularly to a technique effective when applied to a display device with a touch panel including a capacitively coupled touch panel.

In recent years, touch screen technology supporting a “human friendly” graphical user interface has become important in the spread of mobile devices.
As this touch panel technology, a capacitive coupling type touch panel is known, and a general capacitive coupling type touch panel is provided with a touch panel substrate in which a conductive coating (transparent conductive film) is applied on the surface of a glass substrate. The position is detected by touching the finger here.
There is also known a liquid crystal display panel with a touch panel that performs an operation corresponding to a menu by attaching the touch panel substrate to the surface of the liquid crystal display panel and touching a menu screen displayed on the liquid crystal display panel with a finger. (See Patent Document 1 below)

As prior art documents related to the invention of the present application, there are the following.
JP 2006-146895 A

In the liquid crystal display panel with a touch panel described in Patent Document 1 described above, an AC signal is applied from the four corners of the touch panel coated with a transparent conductive film, and the current flowing through the finger touching the touch panel is detected to detect coordinates. The current is detected by detecting the voltage across the current detection resistor installed at the four corners of the touch panel and converting it to a current.
However, the liquid crystal display panel with a touch panel described in Patent Document 1 described above has the following problems.
(1) In order to secure the current flowing through the finger touching the touch panel, it is necessary to increase the thickness of the transparent conductive film to reduce the resistance. Therefore, the transmittance of the touch panel is lowered.
(2) Four sets of circuits are required corresponding to the four corners. That is, the circuit configuration is complicated because four sets of each of the current detection circuit, noise filter, and sample hold are required.
The present invention has been made to solve the above-described problems of the prior art, and an object of the present invention is to provide a capacitive coupling system that can accurately detect touch position coordinates with a simple circuit configuration. The object is to provide a display device with a touch panel.
The above and other objects and novel features of the present invention will become apparent from the description of this specification and the accompanying drawings.

Of the inventions disclosed in this application, the outline of typical ones will be briefly described as follows.
(1) a display panel, a capacitive coupling type touch panel disposed on the display panel, and a coordinate position detection circuit for calculating a touch position of an observer's finger on the capacitive coupling type touch panel; The capacitively coupled touch panel includes a plurality of X electrodes and a plurality of Y electrodes that intersect the X electrodes, and the X electrodes and the Y electrodes overlap each other; The coordinate position detection circuit includes a reference clock generation circuit that generates a reference clock, and a plurality of X electrodes and a plurality of Y electrodes. A switching circuit for connecting an oscillation circuit at both ends, an oscillation frequency of a ring oscillator composed of each of the plurality of X electrodes and the plurality of Y electrodes and the oscillation circuit, and the reference clock And an arithmetic circuit for calculating a touch position on the touch panel of the electrostatic capacitive coupling method of a finger of the observer in accordance with the difference between the frequency.
(2) In (1), the coordinate position detection circuit includes a phase frequency comparator that compares the output of the ring oscillator and the reference clock, and the phase frequency comparator includes an oscillation frequency of the ring oscillator. However, when the frequency is lower than the frequency of the reference clock, an output signal is output, and the period of the output signal is longer as the difference between the oscillation frequency of the ring oscillator and the frequency of the reference clock is larger.
(3) In (2), the counter includes a counter that counts the period of the output signal output from the phase frequency comparator, and the switch circuit includes a plurality of X electrodes and a plurality of Y electrodes. Oscillation circuits are sequentially connected to both ends, and the arithmetic circuit determines the center of gravity in the Y direction of the capacitive coupling type touch panel based on the histogram of count values for each of the plurality of X electrodes, and each of the plurality of Y electrodes. Based on the histogram of the count values, the center of gravity of the capacitive coupling type touch panel in the X direction is obtained, and the touch position of the observer's finger on the capacitive coupling type touch panel is calculated.

(4) In (1), a front panel is provided so as to overlap the capacitively coupled touch panel.
(5) In (4), a recess is formed in the front panel, and the capacitively coupled touch panel is accommodated in the recess.
(6) In (1), the area of the electrode part of the Y electrode is smaller than the area of the electrode part of the X electrode, and a dummy electrode is formed in the vicinity of the electrode part of the X electrode or Y electrode.
(7) In (1), the electrode part of the X electrode and the electrode part of the Y electrode are formed in the same layer.
(8) In (1), the display panel has a long side and a short side, the Y electrode is formed along the long side, and the X electrode is formed along the short side. .
(9) In (1), the capacitively coupled touch panel includes a plurality of X electrode signal wirings connected to both ends of each of the plurality of X electrodes, and each of the plurality of Y electrodes. A plurality of Y electrode signal wirings connected to both ends, and a plurality of X electrode signal wirings and a flexible substrate connected to the plurality of Y electrode signal wirings at connection portions.
(10) In (1), the coordinate position detection circuit is connected to each of the plurality of X electrodes and the plurality of Y electrodes via the flexible substrate.

The effects obtained by the representative ones of the inventions disclosed in the present application will be briefly described as follows.
According to the present invention, it is possible to provide a capacitively coupled display device with a touch panel that can accurately detect touch position coordinates with a simple circuit configuration.

Hereinafter, embodiments of the present invention will be described in detail with reference to the drawings.
In all the drawings for explaining the embodiments, parts having the same functions are given the same reference numerals, and repeated explanation thereof is omitted.
In this embodiment, a liquid crystal display panel will be described as an example of a display panel. The display panel is not limited to a liquid crystal display panel as long as it can use a touch panel, and an organic light-emitting diode element or a surface conduction electron-emitting element can also be used.
FIG. 1 is a plan view showing a schematic configuration of a display device with a touch panel according to an embodiment of the present invention. 2 is a cross-sectional view showing a cross-sectional structure taken along the line AA ′ of FIG.
As shown in FIGS. 1 and 2, the display device 300 of the present embodiment includes a liquid crystal display panel 600, a capacitively coupled touch panel 400 disposed on the surface of the liquid crystal display panel 600 on the viewer side, A backlight 700 is provided below the surface of the liquid crystal display panel 600 opposite to the viewer side. As the liquid crystal display panel 600, for example, a liquid crystal display panel of an IPS method, a TN method, a VA method, or the like is used.
The liquid crystal display panel 600 is formed by bonding two substrates 620 and 630 arranged to face each other, and polarizing plates 601 and 602 are provided outside the two substrates. Further, the liquid crystal display panel 600 and the touch panel 400 are joined by a first adhesive 501 made of a resin / adhesive film or the like.
Further, a front protective plate (also called a front window or front panel) 12 made of acrylic resin or glass is bonded to the outside of the touch panel 400 by a second adhesive material 502 made of a resin / adhesive film or the like.
The front protective plate 12 is provided with a recess 612, and the thickness of the front protective plate 12 is thin in a region overlapping the touch panel 400 and thick in the peripheral portion. Thus, in this embodiment, the detection sensitivity is increased and the strength of the front protective plate 12 is ensured.
A transparent conductive layer 603 made of ITO is provided on the liquid crystal display panel side of the touch panel 400. The transparent conductive layer 603 is formed for the purpose of shielding a signal generated in the liquid crystal display panel 600.

The liquid crystal display panel 600 is provided with a large number of electrodes, and a voltage is applied to the electrodes as signals at various timings. The change in voltage in the liquid crystal display panel 600 becomes noise for the electrodes provided on the capacitively coupled touch panel 400.
Therefore, it is necessary to electrically shield the touch panel 400 from the liquid crystal display panel 600, and the transparent conductive layer 603 is provided as a shield electrode. In order to function as a shield electrode, a constant voltage is supplied to the transparent conductive layer 603 from the flexible printed circuit board 71 or the like, for example, a ground potential.
The flexible printed circuit board 71 is connected to a connection terminal (not shown) formed on the surface (hereinafter referred to as the front surface) on which the electrodes of the touch panel 400 are formed, but the surface on which the transparent conductive layer 603 is provided (hereinafter referred to as the back surface). A conductive member 80 is provided to supply a voltage such as a ground potential.
Note that the transparent conductive layer 603 desirably has a sheet resistance value of 150 to 200 Ω / □, which is about the same as that of an electrode provided on the touch panel 400, in order to suppress the influence of noise. The resistance value of the transparent conductive layer 603 made of ITO is known to be related to the size of the crystal grains, but crystallization can be achieved by setting the heat treatment temperature at the time of forming the transparent conductive layer 603 to 200 ° C. or higher. It is possible to advance the sheet resistance value to 150 to 200Ω / □.
Further, a transparent conductive layer 603 having a lower resistance can be used. For example, by setting the heat treatment temperature to 450 ° C. and sufficiently crystallizing the transparent conductive layer 603, the sheet resistance value can be set to 30 to 40Ω / □.

If the transparent conductive layer 603 for shielding is comparable to or lower in resistance than the electrode provided on the touch panel 400, the effect of suppressing noise is improved.
The flexible printed circuit board 71 is connected to a touch panel control circuit (not shown), and detection of an input position and the like are controlled by the touch panel control circuit. The electrodes provided on the front surface of the touch panel 400 and the touch panel control circuit are electrically connected via the flexible printed circuit board 71. In addition, an arbitrary voltage such as a ground potential is supplied to the transparent conductive layer 603 provided on the back surface via the flexible printed circuit board 71.
Since the flexible printed circuit board 71 is connected to an input terminal provided on the front surface of the touch panel 400, it is necessary to provide a wiring from the input terminal to the transparent conductive layer 603 provided on the back surface to be electrically connected. Therefore, a back connection pad is provided in line with the input terminal, and the back connection pad and the transparent conductive layer 603 on the back are connected by the conductive member 80. Details of the back surface connection pad will be described later.
As shown in FIG. 2, in this embodiment, the spacer 30 is inserted between the substrate 620 and the touch panel 400.
In the hybrid structure in which the touch panel 400 and the front window 12 are combined with the liquid crystal display panel 600, there is a problem that the glass strength of the substrate 620 of the liquid crystal display panel 600 is weak.
In the substrate 620, a region where the drive circuit 50 is mounted protrudes from the other substrate 630 and has a single plate shape. There is a case where the substrate 620 is damaged in the mounting area of the drive circuit 50. Therefore, the spacer 30 is inserted between the substrate 620 and the touch panel 400 to improve the strength.

Next, the liquid crystal display panel 600 will be described with reference to FIG. FIG. 3 is a block diagram showing a basic configuration of the liquid crystal display panel 600. However, in FIG. 3, the touch panel 400 is omitted for explaining the liquid crystal display panel 600.
As described above, the liquid crystal display device includes the liquid crystal display panel 600, the drive circuit 50, the flexible printed circuit board 72, and the backlight 700. A drive circuit 50 is provided on one side of the liquid crystal display panel 600, and various signals are supplied to the liquid crystal display panel 600 by the drive circuit 50. The liquid crystal display panel 600 is electrically connected to a flexible printed circuit board 72 for supplying an external signal to the drive circuit 50.
The liquid crystal display panel 600 includes a substrate 620 (hereinafter also referred to as a TFT substrate) on which a thin film transistor 610, a pixel electrode 611, a counter electrode (common electrode) 615 and the like are formed, and a substrate 630 (hereinafter referred to as a filter) on which a color filter and the like are formed. Are also stacked with a predetermined gap therebetween, and both substrates are bonded together by a sealing material (not shown) provided in the shape of a frame in the vicinity of the peripheral edge between the two substrates. A liquid crystal composition is sealed and sealed, and polarizing plates 601 and 602 (see FIG. 2) are attached to the outside of both substrates, and a flexible printed circuit board 72 is connected to the TFT substrate 620.
Note that this embodiment similarly applies to a so-called horizontal electric field type liquid crystal display panel in which the counter electrode 615 is provided on the TFT substrate 620 and to a so-called vertical electric field type liquid crystal display panel in which the counter electrode 615 is provided on the filter substrate 630. Applied.

In FIG. 3, a scanning signal line (also referred to as a gate signal line) 621 extending in the x direction and arranged in parallel in the y direction, and a video signal line extending in the y direction and arranged in parallel in the x direction (in FIG. 3). 622), and a pixel portion 608 is formed in a region surrounded by the scanning signal line 621 and the drain signal line 622.
Note that although the liquid crystal display panel 600 includes a large number of pixel portions 608 in a matrix, only one pixel portion 608 is shown in FIG. 3 for easy understanding. The pixel portions 608 arranged in a matrix form a display region 609, and each pixel portion 608 plays a role of a pixel of a display image and displays an image in the display region 609.
The thin film transistor 610 of each pixel portion 608 has a source connected to the pixel electrode 611, a drain connected to the video signal line 622, and a gate connected to the scanning signal line 621. The thin film transistor 610 functions as a switch for supplying a display voltage (gradation voltage) to the pixel electrode 611.
Note that although the names of the source and the drain may be reversed due to a bias relationship, the one connected to the video signal line 622 is referred to as a drain here. Further, a liquid crystal capacitor is formed between the pixel electrode 611 and the counter electrode 615.
The drive circuit 50 is disposed on a transparent insulating substrate (glass substrate, resin substrate, etc.) constituting the TFT substrate 620. The drive circuit 50 is connected to the scanning signal line 621, the video signal line 622, and the counter electrode signal line 625.

A flexible printed circuit board 72 is connected to the TFT substrate 620. The flexible printed circuit board 72 is provided with a connector 640. The connector 640 is connected to an external signal line and receives an external signal. A wiring 631 is provided between the connector 640 and the drive circuit 50, and an external signal is input to the drive circuit 50.
The flexible printed circuit board 72 supplies a constant voltage to the backlight 700. The backlight 700 is used as a light source for the liquid crystal display device 600. Note that the backlight 700 is provided on the back surface or the front surface of the liquid crystal display panel 600, but in FIG. 3, the backlight 700 is displayed side by side with the liquid crystal display panel 600 for the sake of simplicity.
A control signal sent from a control device (not shown) provided outside the liquid crystal display panel 600 and a power supply voltage supplied from an external power supply circuit (not shown) are driven via the connector 640 and the wiring 631. Input to the circuit 50.
Signals input to the driving circuit 50 from the outside are control signals such as a clock signal, a display timing signal, a horizontal synchronizing signal, a vertical synchronizing signal, display data (R, G, B), and a display mode control command. The drive circuit 50 drives the liquid crystal display panel 600 based on the input signal.
The drive circuit 50 is composed of a one-chip semiconductor integrated circuit (LSI), and outputs a scanning signal output circuit to the scanning signal line 621, a video signal output circuit to the video signal line 622, and a counter electrode signal line 625. And an output circuit for outputting a common electrode voltage (common voltage).

The driving circuit 50 sequentially supplies a “High” level selection voltage (scanning signal) to each scanning signal line 621 of the liquid crystal display panel 600 every horizontal scanning time based on a reference clock generated inside. Accordingly, the plurality of thin film transistors 610 connected to each scanning signal line 621 of the liquid crystal display panel 1 electrically conducts the video signal line 622 and the pixel electrode 611 during one horizontal scanning period.
Further, the driving circuit 50 outputs a gradation voltage corresponding to the gradation to be displayed by the pixel to the video signal line 622. When the thin film transistor 610 is turned on (conductive), a gradation voltage (video signal) is supplied from the video signal line 622 to the pixel electrode 611. After that, when the thin film transistor 610 is turned off, the gradation voltage based on the image to be displayed by the pixel is held in the pixel electrode 611.
A constant counter electrode voltage is applied to the counter electrode 615, and the liquid crystal display panel 600 changes the orientation direction of the liquid crystal molecules sandwiched between the pixel electrode 611 and the counter electrode 615 due to the potential difference between the pixel electrode 611 and the counter electrode 615. An image is displayed by changing the transmittance or reflectance of the image.
In addition, the drive circuit 50 performs common inversion driving for outputting a counter electrode voltage whose polarity is inverted every certain period to the counter electrode signal line 625 in order to perform AC driving.
As described above, a change in a signal for driving the liquid crystal panel 600 is detected by the touch panel 400 as noise. Therefore, it was necessary to take measures. In particular, the touch panel 400 has a property of prompting the user to input based on an image displayed on the liquid crystal panel 600, and needs to be provided so as to overlap with a display device such as the liquid crystal panel 600. It is strongly influenced by the noise generated by the device.

Next, FIG. 4 shows a schematic diagram of the touch panel 400. This embodiment shows a case where the touch panel 400 is used vertically. Note that the outer shape of the touch panel used to overlap the display panel is substantially the same as that of the display panel. The display panel is generally rectangular, and generally, either the X direction or the Y direction is long.
In FIG. 4, it is assumed that the liquid crystal display panel 600 used to overlap the touch panel 400 also has a vertically long shape.
Touch panel 400 uses glass substrate 5 as a transparent substrate, touch panel electrodes 1 and 2, connection terminal 7, and touch panel electrodes 1 and 2 on one surface (also referred to as the front surface) of glass substrate 5. Wiring 6 up to 7 and a back surface connection pad 81 are arranged. At least the intersecting portion of the two kinds of electrodes arranged so as to be orthogonal is separated by an insulating film. It is also possible to use a transparent resin substrate instead of the glass substrate 5.
The touch panel electrodes 1 and 2 are formed of a transparent conductive film made of ITO, and an electrode extending in the vertical direction (Y direction in the figure) and arranged in parallel in the horizontal direction (X direction) is referred to as a Y electrode 1. An electrode extending in the horizontal direction (X direction) so as to cross the Y electrode 1 and formed in parallel in the vertical direction (Y direction) is referred to as an X electrode 2. A change in electrostatic capacitance of the Y electrode 1 and the X electrode 2 is detected, and the touched position is calculated. A detectable area inside the dotted line indicated by reference numeral 3 is called an input area.
An oscillation circuit described later is connected to both ends of the Y electrode 1 and the X electrode 2 provided on the touch panel 400. Therefore, the wiring 6 is formed on the outer periphery of the input area 3 and connected to the connection terminal 7 formed in parallel with one side of the touch panel 400. A back surface connection pad 81 is provided along with the connection terminal 7 and is electrically connected to a transparent conductive layer 603 provided on the back surface of the glass substrate 5 via a conductive member 80 described later.
In addition to the connection terminal 7, a back connection terminal 82 and a dummy connection terminal 83 are provided. Further, the back connection pad 81 is formed to have a larger area than the connection terminal 7, and the connection work of the conductive member 80 is facilitated. Further, by providing the dummy connection terminal 83, it is possible to prevent a short circuit between the terminals. Reference numeral 84 denotes a wiring for electrically connecting the back surface connection terminal 82 and the back surface connection pad 81 and can be formed in the same process as the other wiring 6.

Next, each Y electrode 1 and X electrode 2 will be described. Both the Y electrode 1 and the X electrode 2 are narrow at the intersections 1a and 2a, and are wide at the electrode parts 1b and 2b sandwiched between the two intersections 1a or 2a. The electrode portions 1b and 2b sandwiched between the intersecting portions 1a or 2a are also referred to as individual electrodes.
In FIG. 4, the width of the individual electrode 1b of the Y electrode 1 of the touch panel 400 is decreased. That is, the area of the Y electrode 1 is reduced to correspond to the ratio of the number of individual electrodes 2b of the X electrode 2 to the number of individual electrodes 1b of the Y electrode 1, and the individual electrode 1a and the floating potential electrode (Dummy electrode) 4 is separated.
Therefore, the area of the Y electrode 1 whose electrode area has been increased according to the vertically long shape is reduced to make the capacitance on one line substantially equal to that of the X electrode 2, and due to fluctuations in the signal voltage generated from the liquid crystal display panel 600. Noise was made equal between the Y electrode 1 and the X electrode 2.
As described above, the transparent conductive layer 603 is provided on the back surface of the touch panel 400 to suppress the influence of noise from the liquid crystal display panel 600. However, even when the transparent conductive layer 603 is provided, the influence of noise from the liquid crystal display panel 600 may become a problem.
In the prior art, the individual electrodes on each line in the X direction and the Y direction have the same size, but the length of one line differs between the electrodes in the X direction and the electrodes in the Y direction. Different. Therefore, the capacity of one line differs between the X direction and the Y direction. For example, in the case of a vertically long touch panel, the capacity of one line of the Y electrode arranged parallel to the Y direction is larger than the capacity of one line of the X electrode arranged parallel to the X direction.
Therefore, in the conventional touch panel in which the capacitance on one electrode line is different between the X direction and the Y direction, the noise intensity is different between the X direction and the Y direction. That is, in the conventional touch panel, the S / N ratio differs between the X direction and the Y direction. Due to the difference in S / N ratio, there is a problem that the detection sensitivity of the entire touch panel is defined by the lower S / N ratio.
In this embodiment, it is possible to solve the above problems and provide an input device having a large S / N ratio and good detection sensitivity. When the area is reduced by dividing the individual electrode 1b and the floating electrode 4 is formed, the ground capacity can be reduced, so that the noise level can be lowered.

In the electrode shown in FIG. 4, when the floating electrode 4 is not disposed, the interval 8 between the adjacent Y electrode 1 and X electrode 2 becomes wide. As described above, the Y electrode 1 and the X electrode 2 are formed of a transparent conductive film. In this interval 8, an insulating film and a glass substrate are formed, and there is no transparent conductive film. With respect to the transmittance, the reflectance, and the chromaticity of the reflected light, a difference occurs between the portion where the transparent conductive film is present and the portion where the transparent conductive film is not present, so that the interval 8 is visible to the naked eye, thereby reducing the quality of the displayed image.
In our study, when the interval 8 is 30 μm, the interval appears thin, and when it is 20 μm, it is almost invisible. Also, the result was invisible at 10 μm. As the interval 8 is narrowed, the capacitance between the Y electrode 1 and the X electrode 2 adjacent to each other via the floating electrode 4 increases. In addition, by narrowing the interval 8, the defect that the Y electrode 1 or the X electrode 2 and the floating electrode 4 are short-circuited due to pattern formation abnormality due to adhesion of foreign matters during the process increases.
When the floating electrode 4 adjacent to the individual electrode 1b of the Y electrode 1 is short-circuited, the ground capacity for the corresponding one line of the Y electrode increases, noise increases, and the detection sensitivity decreases. The floating electrode 4 is divided into four parts as shown in FIG. 4 in order to reduce the increased capacitance when short-circuited. When more finely subdivided, the concern about short-circuit defects is reduced, but since there are more areas without transparent conductive film in the corresponding area, there is a concern that differences in transmittance, reflectance, and chromaticity with adjacent electrodes may occur and increase. is there. Therefore, as described above, the floating electrode 4 is divided into four parts, and the distance between the electrodes is set to about 20 μm narrower than 30 μm.
In this embodiment, the case where the liquid crystal display panel 600 is used while being stacked on the vertically long liquid crystal display panel 600 is shown, but the effect of the present invention is not changed even when the liquid crystal display apparatus is stacked horizontally or on another type of image display apparatus. Further, the number of divisions of the floating electrode is not limited to four divisions.

Next, the coordinate position detection method in the touch panel 400 of the present embodiment will be described with reference to FIG.
In this embodiment, one of the plurality of Y electrodes 1 and the plurality of X electrodes 2 is selected, and the selected electrode and the oscillation circuit RIO constitute a ring oscillator. In this ring oscillator, since the frequency of the output clock decreases depending on the resistance of the electrode and the time constant consisting of the additional capacitance due to finger touch, information on the finger touch can be obtained by detecting this decrease in oscillation frequency. it can. Here, the oscillation circuit RIO is composed of an odd number of inverters.
As shown in FIG. 7, the detection of a decrease in the oscillation frequency of the ring oscillator is performed by generating a reference clock in advance by the reference clock generation circuit BAO, and using this phase clock and the output clock of the ring oscillator as the phase frequency comparator PFD. Use and compare. Note that the phase frequency comparator PFD can be configured by, for example, an exclusive OR circuit.
As shown in FIGS. 6 and 8, the frequency f _{0 of the} reference clock is lower than the oscillation frequency f ₁ of the output clock of the ring oscillator when there is no finger touch, and the output of the ring oscillator when there is a finger touch. It is set higher than the oscillation frequency f _{2 of the} clock.
As shown in FIG. 9, the phase frequency comparator PFD compares the frequency f _{0 of the} reference clock with the oscillation frequency f of the output clock of the ring oscillator, and the output frequency of the ring oscillator is higher than the frequency f _{0 of the} reference clock. When the oscillation frequency f is high, there is no finger touch, so a low level signal pulse is output.
On the other hand, when the oscillation frequency f of the output clock of the ring oscillator is lower than the frequency f _{0 of the} reference clock, there is a finger touch, so that a signal pulse that becomes a high level is output according to the detected capacitance.

The signal pulse output from the phase frequency comparator PFD becomes a signal pulse having a high pulse width with an increase in the degree of decrease in the oscillation frequency of the ring oscillator due to finger touch. Therefore, during the high level period, the counter CNT By measuring the clock CK, the indirectly detected capacitance value can be obtained.
The phase frequency comparator PFD performs the above-described series of detection processing on each of the plurality of Y electrodes 1 and the plurality of X electrodes 2 in order, and the distribution of the capacitance due to the finger touch detected by each electrode is counter CNT Can be obtained as a histogram of the count values.
The arithmetic circuit EZA calculates the center of gravity of the touch panel 400 in the X direction and the Y direction from the obtained count value histogram, and calculates the finger touch coordinates.
The oscillation frequency of the output clock of the ring oscillator is determined by an additional capacitance due to finger touch on the touch panel 400 and a time constant composed of resistances at both ends of each of the Y electrode 1 and the X electrode 2. Therefore, the transparent conductive film forming each electrode of the Y electrode 1 and the X electrode 2 may be thinned to increase the resistance value. Thereby, the transmittance of the touch panel 400 can be improved.
An example of a configuration for sequentially performing the above-described series of detection processes on each of the plurality of X electrodes 2 is shown in FIG.
In FIG. 10, both ends of the plurality of X electrodes 2 are grounded via the switch element SW and connected to the oscillation circuit RIO via the gate circuit TG. Then, by sequentially inputting a low level selection voltage to each of the terminals TA1 to TA7, one of the plurality of X electrodes 2 is selected, and both ends of the selected electrode are connected to the oscillation circuit RIO. . When no electrode is selected, a high level selection voltage is input to each of the terminals TA1 to TA7 to turn on the switch element SW and connect both ends of the unselected electrode to the ground potential.
Note that the oscillation circuit RIO, the phase frequency comparator PFD, the arithmetic circuit EZA, the reference clock generation circuit BAO, the counter CNT, the switch element SW, and the gate circuit TG shown in FIG. 10 are the touch panel control circuit (not shown). Z).

Next, the front protective plate 12 will be described with reference to FIG. FIG. 11 is a schematic perspective view of the front protective plate 12 as viewed from the touch panel 400 side. A recess 612 is formed in the front protective plate 12 so that the touch panel 400 can be accommodated. Further, the peripheral portion 614 is formed thicker than the concave portion 612, and the peripheral portion 614 ensures sufficient strength. Further, a groove 613 is formed in a part of the peripheral portion 614 so that the flexible printed circuit board 71 can extend outward from the recess 614.
The recess 612 provided in the front protective plate 12 can be formed by cutting the front protective plate 12. In addition, the thicker the peripheral portion 614 of the front protective plate 12 fixed to the housing or the like, the stronger the strength of dropping the device, etc., 0.7 mm to 1.0 mm for acrylic, 0.5 mm to 1.0 mm for glass Is desirable.
However, for the touch panel 400, it is desirable that the thickness of the concave portion 614 is 0.5 mm or less in the case of acrylic, because the sensitivity when operating with a finger is lowered if the material attached on the operation surface is thick. In this case, 0.8 mm or less is desirable.

Next, FIG. 12 shows how the transparent conductive layer 603 and the back surface connection pad 81 are connected. 12A is a schematic plan view of the touch panel 400, and FIG. 12B is a schematic side view thereof. In FIG. 12, the connection between the transparent conductive layer 603 and the back surface connection pad 81 is illustrated in a simplified manner. In the touch panel 400, the input area 3 is formed on the front surface of the glass substrate 5. Further, a back connection terminal 82 is formed on the front surface, and the back connection terminal 82 is connected to a flexible printed circuit board 71 (not shown). The connection between the back connection terminal 82 and the back connection pad 81 is connected via a wiring 84. The wiring 84 is formed integrally with the back surface connection terminal 82 and the back surface connection pad 81.
The back surface connection pad 81 and the transparent conductive layer 603 are connected as a conductive member 80 via a conductive tape (hereinafter, the conductive tape is also indicated by reference numeral 80). The conductive tape 80 has a wiring formed of a copper foil on a resinous base material, and an anisotropic conductive film including conductive beads having a particle diameter of 4 μm is attached to one side of the copper foil. One end of the conductive tape 80 is attached to the back surface connection pad 81 and the other end is attached to the transparent conductive layer 603. After pasting, the conductive tape 80 is heat-bonded by hot tweezers or the like. In FIG. 12, the conductive tape 80 is connected at two places on the left and right sides of the side of the touch panel 400 where the connection terminals 7 are provided.
The cost can be reduced by using a conductive tape 80 that is less expensive than a flexible printed circuit board and heat-pressing it with hot tweezers, which is a general tool. Further, in the work using hot tweezers, it is not necessary to turn the touch panel 400 upside down when pressing the back surface, and the possibility of damaging or soiling the electrode surface of the touch panel 400 can be reduced.

Next, the manufacturing method of the touch panel by this invention is demonstrated using FIGS. 13-17. FIG. 4A is a schematic cross-sectional view of each process step along the line BB ′ in FIG. Similarly, a schematic cross-sectional view of each process step along the line CC ′ in FIG. 4 is shown in FIG.
First, the first step will be described with reference to FIG. In the step shown in FIG. 13, after a first ITO film (Indium Tin Oxide) is formed on the glass substrate 5 to a thickness of about 15 nm, a silver alloy is formed to a thickness of about 200 nm.
A resist pattern is formed by a photolithography process, and the silver alloy film is patterned. Next, the resist is peeled and removed, a resist pattern is formed by a photolithography process, and the first ITO film is patterned.
Thereafter, the resist is peeled off and a patterned ITO film 14 and silver alloy film 15 are formed as shown in FIG.
Since the silver alloy film 15 is opaque, in order to avoid being visually recognized, the silver alloy film 15 is removed from a portion of the liquid crystal display panel 600 to be overlapped later, and the silver alloy film 15 is formed only on the peripheral wiring pattern 6. .
Next, a 2nd process is demonstrated using FIG. A photosensitive interlayer insulating film 16 is applied on a substrate on which a pattern of the first ITO film 14 and the silver alloy film 15 is formed, and is patterned by a photolithography technique. As the interlayer insulating film 16, it is desirable to apply a film having SiO ₂ as a main component to a thickness of 1 μm or more. As shown in FIG. 14B, a contact hole 17 is provided in the peripheral portion. Further, the interlayer insulating film pattern 16 is removed from the connection portion 7 used for connection to the external drive circuit.

Next, a 3rd process is demonstrated using FIG. A second ITO film is formed to a thickness of about 30 nm, a resist pattern is formed by a photolithography process, and the second ITO film is patterned. Thereafter, the resist is peeled off and a second ITO film 18 is formed as shown in FIG.
Next, a 4th process is demonstrated using FIG. The same film as the insulating film used in the second step is applied again on the substrate as the uppermost protective film 19. A pattern is formed on the uppermost protective film 19 by a photolithography process.
Next, the fifth step will be described with reference to FIG. In the fifth step, an ITO film is formed as the transparent conductive layer 603 on the back surface of the glass substrate 5. At this time, a mask is formed on the periphery of the front surface of the glass substrate 5. When forming the ITO film on the back surface, there is a risk that the ITO will go around the edge of the glass substrate 5 and adhere to the front surface side. Therefore, it is necessary to protect the peripheral part of the front surface of the glass substrate 5 with a mask. The touch panel 400 is formed through the above steps.
In addition, as a transparent conductive layer 603 formed on the back surface of the glass substrate 5, instead of the ITO film, a conductive and transparent material such as a PET film with ITO may be used.

Next, a modification of the touch panel according to the embodiment of the present invention will be described with reference to FIGS. 18 is a plan view showing a schematic configuration of a modified example of the touch panel according to the embodiment of the present invention. FIG. 19 is a cross-sectional view showing a cross-sectional structure taken along line AA ′ of FIG. FIG. 19 is a cross-sectional view showing a cross-sectional structure along the line BB ′ in FIG. 18.
Also in the touch panel 400 illustrated in FIG. 18, the touch panel 400 extends in the first direction (for example, the X direction) and is arranged in parallel at a predetermined arrangement pitch in the second direction (for example, the Y direction) that intersects the first direction. A plurality of X electrodes 2 and a plurality of Y electrodes 1 extending in the second direction crossing the X electrodes 2 and arranged in parallel in the first direction at a predetermined arrangement pitch. Yes.
Each of the plurality of X electrodes 2 includes an intersecting portion 2a and an electrode portion 2b having a width wider than the width of the intersecting portion 2a. Each of the plurality of X electrodes 2 is disposed on the surface of the glass substrate 5 on the viewer side. The plurality of X electrodes 2 are covered with an interlayer insulating film 16 and an uppermost protective film 19 formed thereon. Instead of the glass substrate 5, for example, a transparent insulating substrate may be used.
Each of the plurality of Y electrodes 1 includes an intersecting portion 1a and an electrode portion 1b having a width wider than the width of the intersecting portion 1a. Each electrode portion 1 b of the plurality of Y electrodes 1 is formed in the same layer as the X electrode 2 and separated from the X electrode 2. That is, each electrode portion 1 b of the plurality of Y electrodes 1 is arranged on the surface of the glass substrate 5 on the viewer side, like the X electrode 2. The electrode portions 1b of the plurality of Y electrodes 1 are covered with an interlayer insulating film 16 and an uppermost protective film 19 formed thereon.
Each intersecting portion 1a of the plurality of Y electrodes 1 is disposed on an interlayer insulating film 16 formed on the surface of the observer side of the glass substrate 5, and is covered with an uppermost protective film 19 formed thereon. ing.
The intersecting portion 1a of the Y electrode 1 intersects the intersecting portion 2a of the X electrode 2 in a planar manner, and a contact hole 17a formed in the interlayer insulating film 16 in two adjacent electrode portions 1b across the intersecting portion 2a. Are electrically and mechanically connected to each other.
The touch panel 400 has a central region in which the plurality of electrodes 1Y and 1X are disposed, and a peripheral region disposed around the central region. In the peripheral region of the touch panel 400, as shown in FIG. 15, a plurality of peripheral wirings 6 electrically connected to each of the plurality of electrodes 1Y and the plurality of X electrodes 2 are arranged. The Y electrode 1 and the X electrode 2 are made of, for example, ITO (Indium Tin Oxide).

Next, a method for manufacturing touch panel 400 shown in FIG. 18 will be described.
First, a first ITO film (Indium Tin Oxide) is formed on the surface of the observer side of the glass substrate 5, and then a silver alloy film is formed.
Next, a resist pattern is formed by a photolithography process, and the silver alloy film is patterned. Next, the resist is peeled and removed, a resist pattern is formed by a photolithography process, and the first ITO film is patterned.
Thereafter, the resist is stripped and removed, and the patterned electrode portion 1b of the Y electrode, the crossing portion 1a and the electrode portion 1b of the X electrode 2, and the peripheral wiring 6 are formed as shown in FIG.
Next, a photosensitive interlayer insulating film 16 is applied on the substrate on which the electrode portion 1b of the Y electrode, the crossing portion 1a and the electrode portion 1b of the X electrode 2 and the peripheral wiring 6 are formed, and patterning is performed by a photolithography technique. . Here, a contact hole 17 is provided in the interlayer insulating film 16. Further, the interlayer insulating film 16 is removed from the connection portion 7 used for connection with the external drive circuit.
Next, a second ITO film is formed on the glass substrate 5, a resist pattern is formed by a photolithography process, and the second ITO film is patterned. Thereafter, the resist is peeled and removed to form an intersection 1a of the Y electrodes 1 as shown in FIG. In this step, the intersecting portion 1 a of the Y electrode 1 is connected to the electrode portion 1 b of the Y electrode 1 through ITO in the contact hole 17.
Next, the same film as the insulating film used in the previous step is applied again on the substrate as the uppermost protective film 19. A pattern is formed on the uppermost protective film 19 by a photolithography process.
Finally, an ITO film is formed as the transparent conductive layer 603 on the back surface of the glass substrate 5.

18 to 20, the example in which the electrode portion 1b of the Y electrode 1, the intersecting portion 2a of the X electrode 2, the electrode portion 2b, and the peripheral wiring 6 are formed in the same layer on the glass substrate 5 has been described. The electrode portion 1b of the Y electrode 1, the crossing portion 2a of the X electrode 2 and the electrode portion 2b are formed on the interlayer insulating film 16,
The intersecting portion 1 a of the Y electrode 1 and the peripheral wiring 6 may be formed on the glass substrate 5.
Further, in FIG. 18 to FIG. 20, since the number of electrode portions 1b of the Y electrode 1 and the number of electrode portions 2b of the X electrode 2 are the same, the widths of the respective electrode portions (1b, 2b) are the same. When the number of electrode portions 1b of the Y electrode 1 and the number of electrode portions 2b of the X electrode 2 are different, for example, when the number of electrode portions 1b of the Y electrode 1 is larger than the number of electrode portions 2b of the X electrode 2, FIG. As shown, the width of the electrode portion 1b of the Y electrode 1 may be reduced. That is, the area of the Y electrode 1 is reduced to correspond to the ratio of the number of individual electrodes 2b of the X electrode 2 to the number of individual electrodes 1b of the Y electrode 1, and the individual electrode 1a and the floating potential electrode (dummy electrode) 4 may be separated.
As described above, according to the present embodiment, it is possible to produce a touch panel excellent in detection sensitivity in the capacitive coupling input device for a display device for image information and character information.
Note that the present invention is not limited to the shape of the input detection area and the shape of the individual electrodes. In the embodiment, the electrodes in the X direction and the Y direction that are orthogonal to each other are described. However, if the purpose is to improve the S / N ratio between the electrode lines used to detect the input position, the electrodes intersect diagonally. It is also effective for capacitance between electrodes having different lengths.
As mentioned above, the invention made by the present inventor has been specifically described based on the above embodiments. However, the present invention is not limited to the above embodiments, and various modifications can be made without departing from the scope of the invention. Of course.

It is a top view which shows schematic structure of the display apparatus with a touchscreen of the Example of this invention. FIG. 2 is a cross-sectional view showing a cross-sectional structure taken along the line A-A ′ of FIG. 1. It is a block diagram which shows the basic composition of the liquid crystal display panel of the Example of this invention. It is a top view which shows schematic structure of the touchscreen of the Example of this invention. It is a figure for demonstrating the coordinate position detection method of the touchscreen of the Example of this invention. It is a figure which shows the circuit structure of the coordinate position detection part of the touchscreen of the Example of this invention. It is a figure which shows the oscillation frequency of the output clock of a ring oscillator at the time of the finger touch in the touch panel of the Example of this invention, and when there is no finger touch. It is a figure which shows the oscillation frequency of the output clock of a ring oscillator at the time of the finger touch in the touch panel of the Example of this invention, and when there is no finger touch. It is a figure for demonstrating the output pulse of the phase frequency comparator at the time of finger touch in the touch panel of the Example of this invention, and when there is no finger touch. It is a figure for demonstrating an example for connecting the X electrode and Y electrode to an oscillation circuit sequentially in the touchscreen of the Example of this invention. It is a perspective view which shows schematic structure of the front panel of the Example of this invention. It is the top view and sectional drawing which show schematic structure of the touchscreen of the Example of this invention. It is sectional drawing for demonstrating the 1st process of the manufacturing method of the touchscreen of the Example of this invention. It is sectional drawing for demonstrating the 2nd process of the manufacturing method of the touchscreen of the Example of this invention. It is sectional drawing for demonstrating the 3rd process of the manufacturing method of the touchscreen of the Example of this invention. It is sectional drawing for demonstrating the 4th process of the manufacturing method of the touchscreen of the Example of this invention. It is sectional drawing for demonstrating the 5th process of the touchscreen manufacturing method of the Example of this invention. It is a top view which shows schematic structure of the modification of the touchscreen of the Example of this invention. It is sectional drawing which shows the cross-sectional structure along the A-A 'line | wire of FIG. It is sectional drawing which shows the cross-section along a B-B 'line | wire of FIG.

Explanation of symbols

DESCRIPTION OF SYMBOLS 1 Y electrode 1a, 2a Crossing part 1b, 2b Electrode part 2 X electrode 3 Input area 4 Floating electrode 5 Glass substrate 6 Wiring 7 Connection terminal 8 Space | interval 12 Front protective plate 14 1st ITO film 15 Silver alloy film 16 Interlayer Insulating film 17 Contact hole 18 Second ITO film 19 Uppermost protective film 30 Spacer 50 Drive circuit 71, 72 Flexible printed circuit board 80 Conductive member 81 Back connection pad 82 Back connection terminal 83 Dummy connection terminal 84 Wiring 300 Display device 400 Touch panel 501 First adhesive material 502 Second adhesive material 600 Liquid crystal display panel 601 602 Polarizing plate 603 Transparent conductive layer 608 Pixel portion 609 Display region 610 Thin film transistor 611 Pixel electrode 612 Recess 613 Groove 614 Peripheral portion 615 Counter electrode (common electrode)
620, 630 Substrate 621 Scanning signal line (gate signal line)
622 Video signal line (drain signal line)
625 Counter electrode signal line 631 Wiring 640 Connector 700 Backlight,
RIO oscillation circuit BAO reference clock generation circuit PFD phase frequency comparator CNT counter EZA arithmetic circuit SW switch element TG gate circuit

Claims (10)

A display panel;
A capacitively coupled touch panel disposed over the display panel;
A coordinate position detection circuit that calculates the touch position of the finger of the observer to the capacitive coupling type touch panel,
The capacitive coupling type touch panel includes a plurality of X electrodes and a plurality of Y electrodes intersecting with the X electrodes,
The X electrode and the Y electrode have an intersecting portion overlapping each other and an electrode portion formed between the two intersecting portions,
The coordinate position detection circuit includes a reference clock generation circuit that generates a reference clock;
A switch circuit for connecting an oscillation circuit to both ends of each of the plurality of X electrodes and the plurality of Y electrodes;
According to the difference between the oscillation frequency of the ring oscillator composed of the electrodes of the plurality of X electrodes and the plurality of Y electrodes and the oscillation circuit, and the frequency of the reference clock, A display device comprising: an arithmetic circuit that calculates a touch position on a capacitive coupling touch panel. The coordinate position detection circuit includes a phase frequency comparator that compares the output of the ring oscillator and the reference clock,
The phase frequency comparator outputs an output signal when the oscillation frequency of the ring oscillator is lower than the frequency of the reference clock,
The display device according to claim 1, wherein a period of the output signal is longer as a difference between an oscillation frequency of the ring oscillator and a frequency of the reference clock is larger. A counter that counts a period of an output signal output from the phase frequency comparator;
The switch circuit sequentially connects an oscillation circuit to both ends of each of the plurality of X electrodes and the plurality of Y electrodes,
The arithmetic circuit is based on a histogram of count values for the plurality of X electrodes based on a histogram of the Y direction of the capacitive coupling type touch panel and a count value histogram for the plurality of Y electrodes. The display device according to claim 2, wherein a center of gravity of the coupling type touch panel in the X direction is obtained, and a touch position of the observer's finger on the capacitive coupling type touch panel is calculated.   The display device according to claim 1, further comprising a front panel disposed on the capacitively coupled touch panel.   The display device according to claim 4, wherein a recess is formed in the front panel, and the capacitively coupled touch panel is accommodated in the recess.   The area of the electrode part of the Y electrode is smaller than the area of the electrode part of the X electrode, and a dummy electrode is formed in the vicinity of the electrode part of the X electrode or the Y electrode. Display device.   The display device according to claim 1, wherein the electrode portion of the X electrode and the electrode portion of the Y electrode are formed in the same layer. The display panel has a long side and a short side,
The Y electrode is formed along the long side,
The display device according to claim 1, wherein the X electrode is formed along the short side. The capacitively coupled touch panel includes a plurality of X electrode signal wirings connected to both ends of each of the plurality of X electrodes,
A plurality of Y electrode signal wirings connected to both ends of each of the plurality of Y electrodes;
The display device according to claim 1, further comprising: a flexible substrate connected to the plurality of X electrode signal lines and the plurality of Y electrode signal lines at a connection portion.   The display device according to claim 1, wherein the coordinate position detection circuit is connected to each of the plurality of X electrodes and the plurality of Y electrodes via the flexible substrate.

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