JPH10124256A - Display integrated type tablet device - Google Patents

Abstract

PROBLEM TO BE SOLVED: To increase coordinate detection precision and prevent misdetection by setting the pulse width of a pulse signal for Y-coordinate detection to larger than a time constant determined according to specific conditions. SOLUTION: A row electrode driving circuit 2 is equipped with a shift register 21 and outputs shift data (s) from Q1 to Q6 while transferring it in sequence with a clock ck1 to supply a row electrode scanning signal to a display panel. Further, pulses PY for coordinate detection are inserted with ck2, and consequently the Y coordinate of an electronic pen 6 is detected in a display period. At this time, the pulse width of the pulses PY for coordinate detection is set by a 2nd pulse width setting circuit to larger than the time constant determined by the resistance and electrostatic capacity from the start end to the terminal of a row electrode. Consequently, the pulses PY for coordinate detection reach a reference value almost needed for coordinate detection even at the right end of a display panel, so coordinate detection becomes possible over the entire display panel with high precision.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a display-integrated tablet device used for inputting characters, graphics, and the like to information equipment, word processors, and the like.

[0002]

2. Description of the Related Art There has been proposed a method of inputting handwritten characters and the like with a pen on a display panel. As a method therefor, there is a method of stacking the display panel and the tablet panel, or a method of sharing the display panel and the tablet panel.

As shown in FIG. 9, a tablet panel 101 and a display panel 1 of a pressure-sensitive system, an electromagnetic induction system, or the like are used.
The electronic pen 103 is used for handwriting input in a structure in which the 02 is superimposed, and has been mounted on various information devices, but has problems such as reduction in size, weight, and price.

On the other hand, in the latter, as shown in FIG. 7, a row electrode drive circuit 2, a column electrode drive circuit 3 of a display panel 1 and their respective electrodes are used for not only display but also a drive circuit for scanning by pen input. It is commonly used as a detection electrode, and is disclosed in detail, for example, in Japanese Patent Application Laid-Open No. 6-314166. This display-integrated tablet device has a display panel with T
An FT display panel can be used, and in the following description,
A case of an active matrix type liquid crystal display panel using TFTs as switching elements will be described.

In FIG. 7, a display control circuit 4 for generating a display data signal and a Y coordinate detection data signal and a detection control circuit 5 for generating an X coordinate detection data signal are switched by a switching circuit 8 under the control of a control circuit 9. Display panel 1
And the coordinate detection circuit 7 obtains each coordinate from the voltage induced in the electronic pen 6. A column electrode S ₁ for driving the source of each TFT 11 during the display period of the display panel ₁
Row electrodes G ₁ ~G ₆ for driving to S ₆ and the gate, each T
While a display control signal for driving the FT 11 is applied, it also serves as a scanning electrode for detecting coordinates of the electronic pen 6. The row electrode driving circuit 2 and the column electrode driving circuit 3 also serve as driving circuits for displaying and detecting coordinates of the electronic pen 6.

[0006] As shown in FIG. 10, the electronic pen 6 has a detection electrode 108 for detecting coordinates at the tip, and makes the electronic pen 6 approach a protection panel 105 installed on the display panel 1. And the scan electrode 109 (column electrode and row electrode) of the display panel 1 and the pen code 1 via the pen substrate 106 including an amplification unit for amplifying the detected signal.
07 to the outside. The protection panel 105 protects the surface of the display panel 1 and improves the slidability of the electronic pen 6.

Next, the operation of the display-integrated tablet device will be described with reference to FIGS.

FIG. 6 shows the overall operation timing of display and detection of the display-integrated tablet device. Here, by operating the row electrode driving circuit 2 and the column electrode driving circuit 3 of the display panel 1 in a display period (shared with the Y coordinate detection period) and an X coordinate detection period, one display panel 1 is obtained. Is used to detect the coordinates of the electronic pen 6. The X coordinate detection period corresponds to a vertical blanking period in a CRT display. During this period, a scanning voltage for coordinate detection is sequentially applied to the column electrodes. When a scanning voltage is applied to the column electrode directly below the electronic pen 6 by this scanning, the detection voltage induced at the detection electrode of the electronic pen 6 indicates a peak value. X in the detection circuit 7
This is for obtaining coordinates.

FIG. 5 shows the detailed operation timing for explaining the detection of the Y coordinate. Here, the detection of the Y coordinate is performed during this period by using scanning for displaying the row electrodes during the display period. The pulse of the shift data signal s is shifted in synchronization with the first clock signal ck1 to generate the image display pulse PT in the row electrode scanning signals ga1 to ga6.
Further, the pulse PT for image display is made low only during the period of the second clock signal ck2 to generate the pulse PT for coordinate detection. A row electrode scanning signal for the row electrode scanning signal ga1~ga6 display and Y coordinate detection, output from the row electrode driving circuit 2 in FIG. 7, each via a row electrode G ₁ ~G ₆ TFT1
While being supplied to one gate, the information supplied from the column electrode drive circuit 3 to the source of the TFT 11 via the column electrodes S _{1 to} S ₆ is displayed. This row electrode scanning signal is characterized in that a coordinate detection pulse PY is provided near the center of the image display pulse PT.

When the electronic pen 6 comes into contact during this display period, a voltage as shown by Pd in FIG. 5 is induced in the electronic pen 6 by electrostatic coupling with the row electrodes of the display panel 1. A minute voltage such as Yd is also induced in this voltage by the coordinate detection pulse PY. 5 includes a spike-like voltage Ys having a larger amplitude than Yd, which is a voltage induced on the detection electrode of the electronic pen 6 by the signal COM of FIG. The signal COM is a voltage applied to the counter electrode 14 in FIG. 7 for preventing deterioration of the liquid crystal and the like.

From the Pd induced by the electronic pen 6 during the display period, only Yd caused by the coordinate detection pulse PY is
The coordinate detection circuit 7 extracts the sampling signal Sg and extracts it as Pds in FIG. Pds1 is obtained by reducing the time axis of Pds, the dotted line shows an envelope, and Pds1 is obtained when the image display pulse PT is applied to the row electrode immediately below the tip position of the electronic pen 6 placed on the display panel 1. The envelope shows the peak value. That is, when the electronic pen 2 is placed on the row electrode G2, Pds1 corresponding to the coordinate detection pulse PY of the row electrode scanning signal ga2 shows a peak as shown in FIG.

Further, Pds2 is obtained by obtaining an envelope waveform of the signal component Pds1 by a peak value follower circuit and a low-pass filter circuit and inverting the polarity, and further binarizes the signal component Pds1 by using Vt as a reference voltage. Thus, the detection pulse Pds3 is obtained.
Further, at the start of scanning, for example, the time T from when the shift data signal s rises to when the envelope waveform Pds2 shows a peak value is obtained by measuring the rising and falling of the Pds3 with a counter or the like to obtain the Y coordinate. .

Actually, Pds2 is delayed from Pds1 by a low-pass filter circuit or a peak value follower circuit, but the amount is very small. Since the amount is constant, if the high detection accuracy is required, the delay amount is corrected. Calculate the coordinates.

[0014]

The display-integrated tablet device is useful for reducing the size, weight, and price of an information device having a pen input function by sharing and integrating the display panel and the tablet panel. It is.

In the display integrated type tablet device, FIG.
The X coordinate detection period is provided separately from the display period as described above, and the X coordinate is detected by sequentially applying the coordinate detection scanning pulse to the column electrode during this period. Therefore, the operation during the X coordinate detection period is independent irrespective of the display, and the scanning pulse width and speed for detection can be freely set within a predetermined range. There are few issues regarding

However, when the Y-coordinate of the electronic pen 6 is detected on the display panel 1 of the display-integrated tablet device, the Y-coordinate of the electronic pen 6 is detected with high accuracy in an environment with little noise. In an environment where there is a lot of noise radiated from other electric devices, the accuracy of coordinate detection may be reduced.

Further, when the noise is examined in detail, the accuracy of the coordinate detection is not reduced in the entire area of the display panel 1 but in the area close to the row electrode driving circuit 2, that is, in the display panel 1 shown in FIG. At the left end, the coordinates can be detected with high accuracy. However, as the distance from the right end of FIG. 7, that is, the distance from the row electrode drive circuit 2 increases, the detection accuracy of the Y coordinate of the electronic pen decreases. did.
(Hereinafter, the right and left ends will be described with reference to the arrangement in FIG. 7). Here, the coordinate detection accuracy indicates that, when the electronic pen 6 is placed on the input surface of the display panel 1, the position of the tip of the electronic pen 6 and the detected coordinates are different from each other by several pixels.
Is a phenomenon in which coordinate detection has nothing to do with the position.

Next, as a result of a detailed investigation and analysis of the causes of the coordinate detection accuracy and the erroneous detection by the inventors, it was found that there were two causes. First, the first cause will be described.

The cause of the decrease in the coordinate detection accuracy on the right side of the display panel 1 is that each row electrode driving circuit 2 causes each T
Under the influence of the distribution of the electric resistance and the capacitance of the row electrode that supplies the image display pulse PT to the gate of the FT 11, the waveform of the coordinate detection pulse PY is sequentially supplied while supplying the gate pulse to the gate of each TFT 11. It has been found that deterioration (rising and falling of the pulse increases) during transmission through the row electrode.

FIG. 4 shows the distribution of the resistance and capacitance of an arbitrary n-th row electrode Gn connected to the output terminal of the row electrode drive circuit 2 in FIG. Gni of the row electrode Gn is an input terminal of the row electrode drive circuit 2 (the left end of the display panel 1 in FIG. 7). Gnr indicates the end of the same row electrode as Gni (the right end of the display panel 1 in FIG. 7). In the meantime, as shown in FIG. 4, the distribution between the other electrodes G'nr and G'ni is as shown in FIG. Forming a distribution circuit comprising a resistance r and a distribution capacitance c,
The row electrode scanning signal gan is supplied to the gate of each TFT 11 of the display panel 1.

Generally, the row electrode is formed of a metal having a relatively low specific resistance such as aluminum on a substrate such as glass.
7. The thickness of the electrode is as thin as several thousand angstroms and the electrode width is several tens of microns, so that the resistance value as an electrode is high.
For a 4-inch display panel, the input terminal Gni and the terminal G
The total resistance R between nr reaches the order of 3.0 to 3.5 kΩ.

The capacitance is the total capacitance between the row electrodes, the counter electrode 14, the other electrodes such as the column electrodes, and is determined by the electrode structure and the thickness of the liquid crystal layer. In the display panel, the terminal G where the row electrode drive circuit 2 is separated
The total capacitance C between nr and G'nr can be as high as 450 pF.

Therefore, the row electrode driving circuit 2 generates
An image display pulse PT including a coordinate detection pulse PY such as gai shown in (1) (when the scanning voltage with respect to the reference voltage is V
When s) is supplied from the input terminal Gni of the row electrode, the row electrode scanning signal ga at the left end of the display panel 1 close to the row electrode drive circuit 2 has a scanning voltage and waveform similar to gal shown in FIG. The signal voltage is almost the same as the input terminal gai.

However, as transmitted to the right side, the scanning voltage on the row electrode gradually decreases due to the distributed resistance r and the distributed capacitance c,
In the vicinity of the center of the display panel 1, gac shown in FIG. 3B is obtained. At the right end of the display panel 1, ga shown in FIG.
r. The peak value of the coordinate detection pulse PY in the negative direction, which should be Vs, is Vs at the left end and αc at the center.
Vs, and gradually lowers to αrVs at the right end (1> αc
> Αr). This is because the coordinate detection pulse PY is approximately Ep.
y = Vs exp (−t / RC)
Is smaller than Epyr ≒ 0 within the period of the pulse width tc.

On the other hand, the coordinates of the electronic pen 6 are electrostatically charged by a coordinate detection pulse PY applied to the row electrode.
Is detected from the voltage induced on the detection electrode. Therefore, when the electronic pen 6 is located at the left end of the screen, FIG.
3D, the detection electrode 108 of the electronic pen 6 receives Yd of FIG.
An induced voltage having a peak value Vd as shown in FIG.

However, at the right end of the display panel 1, since the peak value of the coordinate detection pulse PYr is reduced to αrVs as shown by gar in FIG. 3B, the electronic pen 6 is moved to the right end of the display panel 1. When it is placed, the voltage induced on the detection electrode 108 of the electronic pen 6 decreases to αrVd as indicated by Ydr in FIG.

Here, the detection voltages Ydl, Y in FIG.
dc and Ydr indicate detection waveforms when the input impedance of the detection electrode of the electronic pen is sufficiently high and the characteristics of the circuit system are set to ideal values in order to facilitate understanding of the description. Coordinate detection pulse PY applied to the electrode
Although the same waveform is shown, the waveform is actually distorted.

As the voltage induced on the detection electrode 108 of the electronic pen 6, only the induced voltage Yd by the coordinate detection pulse PY is extracted by the sampling signal Sg in FIG. However, the peak value is, as is clear from the above description, the electronic pen 6
Is high at the left end of the display panel 1,
Is low at the right end of the display panel. That is, the peak value Vpd of Pds1 in FIG. 5 is lower when the electronic pen 6 is placed on the right end of the display panel 1 than when the electronic pen 6 is placed on the left end of the display panel 1. Further, similarly, the envelope voltage Pds2 obtained based on Pds1 becomes a low value when the electronic pen 6 is placed at the right end of the display panel 1.

Therefore, when the electronic pen 6 is placed at the right end of the display panel 1, the signal component is reduced, the noise component becomes relatively large, and the coordinates become larger than when the electronic pen 6 is placed at the left end of the display panel 1. It was found that this was one of the causes of the decrease in detection accuracy.

Further, when this phenomenon is remarkable, the peak value of the detection voltage may not reach the reference voltage Vt in FIG. 5, and in this case, the detection pulse Pds3 is not output from the comparator, so that the detection pulse Pds3 does not correspond to the Y coordinate. Instead, a value completely different from the position of the electronic pen 6 is output as an erroneous detection signal.

Next, the second cause will be described. In the above description, the peak value of the coordinate detection pulse PY decreases at the right end of the display panel 1 due to the distributed resistance r and the distributed capacitance c of the row electrode, so that the coordinates when the electronic pen 6 is placed at the right end of the display panel 1 It was stated that the detection accuracy was reduced.

However, the rise and fall times of the coordinate detection pulse PY become longer due to the distributed resistance r and the distributed capacitance c of the row electrodes. That is, as shown in PYc at the center and PYr at the right end in FIG. 3B, the voltage width increases toward the right end of the display panel 1 and the coordinate detection pulse P in FIG.
It extends from the voltage width of Y.

As a result, when the electronic pen 6 is placed at the right end of the display panel 1, the voltage induced on the electronic pen 6 also changes as shown in FIG.
(3) As shown in Ydr, the waveform becomes smoother with longer rise and fall times toward the right end.
The signal voltage has a wide width with a tail trailing behind the rise time of PY.

Therefore, as shown in FIG. 3D, when the detection signal is extracted by the sampling signal Sgc having the same pulse width tc at the same timing as the coordinate detection pulse PY, Ysc and Ysr in FIG. As shown in the figure, not only the peak value becomes lower than Ysl, but also the tail portion indicated by oblique lines is removed. When the envelope signal is obtained from the detection signal from which the tail portion has been removed through a low-pass filter, there is a portion that cannot be extracted.
The peak value of the detection signal Pds1 shown in FIG. 5 becomes a lower value than when the electronic pen 6 is placed at the left end of the display screen. As a result, it has been found that the noise component relative to the signal becomes relatively large similarly to the first cause, which further reduces the coordinate detection accuracy and causes the occurrence of erroneous detection.

An object of the present invention is to provide a display-integrated tablet device with improved coordinate detection accuracy and no erroneous detection in view of the above problems.

[0036]

According to a first aspect of the present invention, there is provided a display-integrated tablet device, comprising: a display panel having a display portion corresponding to an intersection of two electrodes where a plurality of row electrodes and a plurality of column electrodes intersect; An electronic pen that electrostatically couples with the row electrode and the column electrode; a row electrode driving unit that applies a predetermined signal to the row electrode; a column electrode driving unit that applies a predetermined signal to the column electrode; A row electrode drive control means for controlling the row electrode drive means to sequentially apply a display pulse signal and a Y coordinate detection pulse signal set in the display pulse signal to the row electrodes during the period; A column electrode drive control means for controlling the column electrode drive means to sequentially apply an X coordinate detection pulse signal to the column electrodes; and a detection voltage induced on the electronic pen by the Y coordinate detection pulse signal. Y position of the above electronic pen And a coordinate detecting means for detecting an X coordinate of the electronic pen based on a detection voltage induced on the electronic pen by an X coordinate detecting pulse signal. The pulse width of the use pulse signal is set to a value larger than a time constant τ determined by the resistance and the capacitance from the start to the end of the row electrode to which the Y coordinate detection pulse signal is applied.

According to a second aspect of the present invention, there is provided a display-integrated tablet device, comprising: a display panel having a display section corresponding to an intersection of two electrodes where a plurality of row electrodes and a plurality of column electrodes intersect; An electronic pen that electrostatically couples with a column electrode; a row electrode driving unit that applies a predetermined signal to the row electrode; a column electrode driving unit that applies a predetermined signal to the column electrode; A row electrode drive control means for controlling a drive means to sequentially apply a display pulse signal and a Y coordinate detection pulse signal set in the display pulse signal to the row electrodes; Control means X
A column electrode drive control means for sequentially applying a coordinate detection pulse signal to the column electrodes; and a Y-coordinate of the electronic pen based on a detection voltage induced in the electronic pen by the Y coordinate detection pulse signal.
A display integrated tablet device comprising: a coordinate detection means for detecting the coordinates and detecting an X coordinate of the electronic pen based on a detection voltage induced on the electronic pen by a pulse signal for X coordinate detection. Gate means for extracting a detection voltage induced in the electronic pen by the detection pulse signal within a range of a gate pulse width of the gate pulse signal, wherein the gate pulse width is determined by a pulse width of the Y coordinate detection pulse signal and an extension period. The extension period is set to a value larger than a time constant τ determined by the resistance and the capacitance from the start to the end of the row electrode to which the Y coordinate detection pulse signal is applied.

According to a third aspect of the present invention, there is provided a display-integrated tablet device, comprising: a display panel having a display section corresponding to an intersection of two electrodes where a plurality of row electrodes and a plurality of column electrodes intersect; An electronic pen electrostatically coupled to a column electrode; a row electrode driving unit for applying a predetermined signal to the row electrode; a column electrode driving unit for applying a predetermined signal to the column electrode; and a row electrode for a display period. A row electrode drive control means for controlling a drive means to sequentially apply a display pulse signal and a Y coordinate detection pulse signal set in the display pulse signal to the row electrodes; Control means X
A column electrode drive control means for sequentially applying a coordinate detection pulse signal to the column electrodes; and a Y-coordinate of the electronic pen based on a detection voltage induced in the electronic pen by the Y coordinate detection pulse signal.
A display integrated tablet device comprising: a coordinate detecting means for detecting the coordinates and detecting the X coordinate of the electronic pen based on a detection voltage induced on the electronic pen by the X coordinate detecting pulse signal; Gate means for extracting a detection voltage induced in the electronic pen by the detection pulse signal within a range of a gate pulse width of the gate pulse signal, wherein the gate pulse width is determined by a pulse width of the Y coordinate detection pulse signal and an extension period. The extension period is set to a value larger than a time constant τ determined by the resistance and capacitance from the start to the end of the row electrode to which the Y coordinate detection pulse signal is applied, and The pulse width of the pulse signal is larger than the time constant τ determined by the resistance and capacitance from the start to the end of the row electrode to which the Y coordinate detection pulse signal is applied. It is characterized in that it is set to a low value.

According to a fourth aspect of the present invention, there is provided a display-integrated tablet device according to any one of the first to third aspects, wherein the Y-coordinate detection pulse signal and the gate pulse signal are generated from the same pulse source. It is characterized by being performed.

According to a fifth aspect of the present invention, there is provided a display-integrated tablet device according to any one of the first to third aspects, wherein the pulse width of the Y-coordinate detection pulse signal ranges from τ to 5τ. There is a feature.

According to a sixth aspect of the present invention, there is provided a display-integrated tablet device according to any one of the first to third aspects, wherein the extension period is in a range from τ to 5τ. .

[0042]

DESCRIPTION OF THE PREFERRED EMBODIMENTS The device configuration of the present invention can use a conventional display-integrated tablet device, and its basic operation is the same. In the present invention, the setting of the pulse widths of the coordinate detection pulse PY and the sampling pulse Sg is different from the conventional one.

That is, in the first embodiment of the present invention, the pulse width of the coordinate detection pulse PY is adjusted to include the resistance R of the entire length of one predetermined row electrode, the row electrode, the column electrode S, the counter electrode 14 and the like. The characteristic is that the time constant τ = RC determined by the capacitance C with the other electrode is set to a value larger than RC. As a result, even at the right end of the display panel 1, since the coordinate detection pulse PY almost reaches the reference value required for coordinate detection, coordinate detection can be performed with high accuracy over the entire display panel.

According to the second aspect of the present invention, the pulse width of the sampling pulse Sg for extracting the detection voltage induced in the electronic pen 6 by the coordinate detection pulse PY is supplied from the row electrode driving circuit 2 for the coordinate detection. It includes the pulse width of the pulse PY and extends the time from the end (rising) of the coordinate detection pulse PY. The extension time is determined by a time constant τ = RC determined by the resistance R of the entire length of one row electrode and the capacitance C between the row electrode and all other electrodes including the column electrode S and the counter electrode 14 and the like. The feature is that it is set to a large value.

The pulse width of the sampling pulse is
In order to include the pulse width of the coordinate detection pulse PY, it is preferable to generate the sampling pulse Sg in synchronization with the first clock signal ck1 or the second clock signal ck2.

Further, the combined use of the first and second embodiments of the present invention is more effective in preventing erroneous detection and improving the accuracy of coordinate detection.

[0047]

In the first embodiment, as a means for increasing the peak value of the coordinate detection pulse PY of FIG. 3B, the pulse width tc of the coordinate detection pulse PY of FIG. By setting a large value, highly accurate coordinate detection is performed in the entire screen. That is, the coordinate detection pulse PY
Is the resistance from the input terminal of the row electrode drive circuit 2 to the gate of the TFT connected to the last stage of the row electrode, that is, the total resistance between Gni and Gnr in FIG. Is set to a value greater than the time constant τ = RC. Note that it is difficult to define τ because it is a distribution constant composed of the distribution resistance r and the distribution capacitance c. However, in a very approximate analysis at the right end of the display panel 1, the resistance R and the capacitance C Is sufficient.

FIG. 2 shows a coordinate detection pulse and a waveform diagram for explaining the operation. gaiw is obtained by expanding the pulse width tc of the coordinate detection pulse PY to tcw, and changing the pulse width tcw of the coordinate detection pulse PYw to the time constant τ (τ = τ).
RC). According to experimental results, this value is most preferably selected to be about 2 to 3τ. tcw
Is ck2 in FIG. 1 and its generation is the same as in the prior art, but will be described later.

In an actual 8.4-inch display panel, R is about 3.3 kΩ and C is about 450 pF. In this case, τ ≒ 1.5 μS. In this panel, the pulse width tcw was set to 2.5 μS. In this state, the ratio of the peak value of the detected voltage when the electronic pen 6 was placed at the left end of the display panel 1 to the right end was about 0.9. It has been confirmed that there is almost no problem in practical use.

As described above, the pulse width tcw is preferably larger than τ in consideration of the coordinate detection accuracy, but the larger the pulse width tcw is, the better, and there are restrictions. This is because, as described above, in the display-integrated type tablet device, since the coordinate detection pulse PYw is inserted in the image display pulse PT of the row electrode scanning signal, the gate of the TFT 11 of the display panel 1 is turned off. O
During the N period, the pulse width becomes shorter by the pulse width tcw, the supply time of the display data supplied from the column electrode driving circuit 3 to the source of the TFT 11 via the electrodes S _{1 to} S ₆ becomes shorter, and the picture element connected to the drain becomes smaller. Since the amount of charge for charging the electrode 12 decreases and the display quality deteriorates, it is desirable to set the pulse width tcw of the coordinate detection pulse PYw to a value as small as possible in order to obtain high-quality display.

As described above, in practical use, the pulse width must be set so that both can be compromised. However, according to experimental results, the upper limit of the pulse width tcw is 5τ, and the viewpoint of coordinate detection accuracy and reliability are taken into consideration. Is a sufficient value,
If it is larger than this, the display quality may decrease.
Specifically, for example, the number of row electrodes of the display panel 1 is 480.
Here, when the number of display frames per second is 60 frames / sec, the pulse width of the image display pulse PT of the row electrode scanning signal including the coordinate detection pulse PYw is about 31 μS, and the pulse width tcw of the coordinate detection pulse PYw. Is set to 5τ, the period during which the gate of the TFT 11 of the image display pulse PT is turned on is reduced to 21 μS.

Therefore, the range of the pulse width tcw of the coordinate detection pulse PYw is preferably set to τ <tcw <5τ. Practically, if it is selected to be about 2 to 3τ, there is no problem in detecting coordinates with the electronic pen, and there is no problem in terms of display quality at all.

As means for preventing the deterioration of display quality due to the above factors while widening the pulse width tcw, the TFT 1
The transconductance gm of 1 (gm = ∂Id / ∂Eg:
It is also effective to design the TFT structure so as to increase Id = drain current, Eg = gate voltage, and charge the pixel electrode 12 connected to the drain with a sufficient amount of charge even if the gate application time is short. . In this case, the shape of the TFT becomes slightly larger and the pixel electrode 12 becomes smaller accordingly, so that the contrast of the display screen decreases.

Next, a second embodiment applied to a sampling signal will be described with reference to FIG. In the following description, a description will be given of a form used together with the first embodiment, that is, a form in which the pulse width of the coordinate detection pulse PYw is set to a pulse width tcw larger than τ. Note that it is desirable to use the first embodiment and the second embodiment together, but it is not limited to this, and it goes without saying that the first embodiment and the second embodiment can be implemented independently.

Gaiw in FIG. 2 is the same as in the first embodiment, and is a coordinate detection pulse PYw supplied from the row electrode drive circuit 2 to the row electrodes. The pulse width tcw is set to be larger than the time constant τ. And the peak value is Vs.

The garw in FIG. 2 is a coordinate detection pulse PY.
display panel 1 when w is supplied from row electrode drive circuit 2
Is the row electrode scanning signal at the right end of the graph, and both the fall time and the rise time are increased by the resistance R and the capacitance C of the row electrode. However, since the pulse width tcw is set in advance to be larger than the time constant τ, the peak value of PYw reaches almost Vs.

Ydrw in FIG. 2 is near the coordinate detection pulse PYw of the detection voltage induced in the electronic pen 6 due to electrostatic induction from the row electrode when the electronic pen 6 is placed at the right end of the display panel 1. Only the corresponding waveform is taken out and illustrated, and the induced voltage component Ys by COM is omitted.

Sgw in FIG. 2 is a coordinate detection pulse PYw.
Is a sampling signal for extracting a component due to
aiw, which completely includes the coordinate detection pulse PYw, and which is longer than the falling time of the coordinate detection pulse PYw by tce
Just extended. The extension time tce is a time constant τ = R determined by the resistance R and the capacitance C of the row electrode.
It is set larger than C. Sampling pulse Sgw
Will be described later as Sg in FIG.

In FIG. 2, Ysrw represents the detection voltage Ydrw induced by the electronic pen 6 due to the electrostatic induction from the row electrode when the electronic pen 6 is placed at the right end of the display panel 1, and the pulse width of the sampling signal Sgw. Since the pulse width of the sampling pulse sgw is set wide as described above with the signal voltage sampled by the above, most of the induced voltage is extracted only by cutting off a part of the end of the rising portion very slightly. Therefore, even when the electronic pen 6 is placed at the right end of the display panel 1, the coordinate detection accuracy does not decrease.

As described above, the extension time tce is preferably at least larger than τ from the viewpoint of the coordinate detection accuracy. However, the longer time tce is not necessarily better, and there is an upper limit. That is, the extension time tc
e must not exceed the time tp from the rise of the coordinate detection pulse PYw to the fall of the image display pulse PT shown in FIG. Because the component of the induced voltage Ys of the detection voltage due to the COM voltage having a large amplitude is included in the detection voltage when it exceeds tp, and this component does not include the position information of the electronic pen 6 at all. Since the accuracy decreases, it is necessary to set τ <tce <tp.

The range of the extension time tce is τ <tc
It is preferable to set e <5τ. Practically 2-3τ
If it is selected to the extent, there is no problem in detecting coordinates with the electronic pen, and there is no practical problem in terms of display quality. In addition,
The extension time tce is preferably set longer than the pulse width tcw of the first embodiment.

Next, a block diagram for generating control signals for realizing the first and second embodiments and the operation thereof will be described with reference to FIG.

The row electrode drive circuit 2 has a shift register 21 and outputs the shift data s from Q _{1 to} Q ₆ while sequentially transferring the shift data s by the clock ck1. In addition, the output outputs the row electrode scanning signal ga1~ga6 obtained via the 3AND circuit 24 according to the inverted signal of the clock ck1 and ck2, the row electrode scanning signal in FIG. 5 to the row electrodes G ₁ ~G ₆ of the display panel 1 To display by the same operation as the conventional display-integrated tablet device, and inserts a coordinate detection pulse PY by ck2, thereby detecting the Y coordinate of the electronic pen 6 during the display period.

Sampling pulse sg, clock ck
2 and the clock ck1 divide the frequency of the reference pulse generated by the fundamental frequency generation circuit 31 by the frequency down-converting circuit 32 to generate a reference clock of frequency fd.
The phase and pulse width are set to predetermined values by the third delay circuits 25, 27, 29 and the first, second, and third pulse width setting circuits 26, 28, 30, respectively. In this case, all three types of pulses sg, ck1, and ck2 have independent delay circuits and pulse width setting circuits, but may be omitted or shared. For example, the frequency fd of the reference clock output from the frequency down converter 32 is
The pulse width setting circuit 26 may be omitted and replaced with ck1.
Further, the second delay circuit 27 and the third delay circuit 29 are shared,
Only the pulse width may be changed.

The sampling pulse sg output from the third pulse width setting circuit 30 samples the detection signal Pd of each electronic pen in FIG. 5 by the gate circuit 34 to the induced voltage Yd including the position information of the electronic pen 6.

The pulse width set by the second pulse width setting circuit 28 determines the pulse width of tcw in FIG. 2, and is larger than the time constant τ determined by the resistance R and the capacitance C of the row electrode. Is set.

The pulse width set by the third pulse width setting circuit 30 includes ck2 output from the second pulse width setting circuit 28, and the resistance R and the capacitance C of the row electrode are determined by the fall time of ck2. Is set longer by an extension time tce larger than the time constant τ determined by

The electronic pen 6 has the same structure as that of FIG.
The detection signal amplifying circuit 33 includes the amplifying circuit of the pen board 106 shown in FIG. 10. The pds1 in FIG. 5 is extracted from the detected voltage of the electronic pen 6.

The envelope shaping circuit 35 obtains the envelope of pds1 or a waveform close thereto, and is composed of a peak value follower circuit and a low-pass filter circuit, and the waveform shown by Pds2 in FIG. 5 is obtained. After that, it is compared with the reference voltage Vt by the comparator of the binarization circuit 36, and is converted into a binarized signal of Pds3 in FIG.

The frequency fc of the counter pulse output from the frequency down converter 32 has a peak in the envelope obtained by pds extracted from the detection voltage of the electronic pen 6 in FIG. 5 from the reference time (for example, the shift data signal s). Is a clock pulse for measuring the time T up to the Y-coordinate of the electronic pen 6 by measuring the time T with a counter or the like, and is set to a value higher than the frequency fd and is selected to be about 2 to 4 times the frequency fd. Usually, but especially shift register 2
It does not have to be an integral multiple of one reference clock fd. The counter value measured by the counter circuit 37 in this way is further subjected to a correction process by the correction circuit 38 or a computer to make it coincide with the coordinate system on the panel.

In the above description, the case of the liquid crystal display panel using the TFT shown in FIG. 7 has been described. However, the display panel is not limited to this, and the duty type liquid crystal display as shown in FIG. Can also be applied to panels.

That is, in FIG. 8, the basic structure is the same, although there is no display member and no switching element interposed between the row electrode and the column electrode. The row electrodes and the column electrodes are the display electrodes and also signal transmission paths from the respective drive circuits to the display picture elements, and the intersection area between the two electrodes is the display picture element. The display is performed by simultaneously applying display data to each column electrode from the column electrode drive circuit 3 and applying the information to the row electrode of the row to be displayed, thereby displaying the row, and sequentially changing the displayed row. It is. Therefore, the row electrode scanning signal is
As in the case of the TFT, the Y coordinate of the electronic pen 6 can be detected by applying the scanning signal including the coordinate detection pulse PY in the same manner as the row electrode scanning signal. Further, similarly, the present invention can be applied to an EL panel. As in the above-described embodiment, the constraint that the pulse width of the coordinate detection pulse PY and the pulse width of the sampling pulse are determined by the resistance and the capacitance of the row electrode. With the addition, highly accurate detection is possible even in this type of display panel.

[0073]

According to the present invention, it is possible to provide a display-integrated tablet device capable of detecting coordinates with high accuracy over the entire display screen while maintaining the display quality.

[Brief description of the drawings]

FIG. 1 is a configuration diagram of a row electrode drive circuit of a display-integrated tablet device of the present invention.

FIG. 2 is a waveform diagram for explaining a coordinate detection operation according to the present invention.

3A and 3B are a waveform diagram of a voltage applied to a row electrode and a waveform diagram of a detected voltage for explaining a conventional problem.

FIG. 4 is an equivalent circuit diagram of a row electrode of the row electrode drive circuit.

FIG. 5 is a time chart showing a Y coordinate detection operation according to the related art and the present invention.

FIG. 6 is a diagram showing the overall operation timing of a display period and a coordinate detection period according to the related art and the present invention.

FIG. 7 is a block diagram of a display-integrated tablet device using a TFT liquid crystal display panel.

FIG. 8 is a block diagram of a display-integrated tablet device using an STN liquid crystal display panel.

FIG. 9 is an explanatory diagram of a conventional tablet device.

FIG. 10 is a view showing the structure of an electronic pen according to the related art and the present invention.

[Description of Signs] 1 display panel 2 row electrode drive circuit 3 column electrode drive circuit 4 display control circuit 5 detection control circuit 6 electronic pen 7 coordinate detection circuit 8 switching circuit 9 control circuit

 ──────────────────────────────────────────────────続 き Continued on the front page (72) Inventor Kiyohiro Nozaki 22-22, Nagaikecho, Abeno-ku, Osaka-shi, Osaka Inside Sharp Corporation (72) Inventor Hitoshi Nono 22-22, Nagaikecho, Abeno-ku, Osaka-shi, Osaka Sharp Inside the company

Claims (6)

[Claims] A display panel provided with a display portion corresponding to an intersection of the two electrodes where a plurality of row electrodes and a plurality of column electrodes intersect; an electronic pen electrostatically coupled to the row electrode and the column electrode; A row electrode driving unit that applies a predetermined signal to the row electrode, a column electrode driving unit that applies a predetermined signal to the column electrode, and a display pulse signal by controlling the row electrode driving unit during a display period. A row electrode drive control means for sequentially applying the Y coordinate detection pulse signal set in the display pulse signal to the row electrodes, and an X coordinate detection pulse signal by controlling the column electrode drive means during the coordinate detection period And a column electrode drive control means for sequentially applying to the column electrodes, a Y coordinate of the electronic pen is detected based on a detection voltage induced in the electronic pen by the Y coordinate detection pulse signal, while an X coordinate detection pulse signal is detected. With the above electronic pen In a display-integrated tablet device comprising: a coordinate detection means for detecting the X coordinate of the electronic pen based on the induced detection voltage, the pulse width of the Y coordinate detection pulse signal is determined by applying the Y coordinate detection pulse signal. A display-integrated tablet device, wherein the value is set to a value larger than a time constant τ determined by a resistance and a capacitance from a start end to an end of a row electrode. 2. A display panel comprising a display unit corresponding to an intersection of two electrodes where a plurality of row electrodes and a plurality of column electrodes intersect, an electronic pen electrostatically coupled to the row electrodes and the column electrodes, A row electrode driving unit that applies a predetermined signal to the row electrode, a column electrode driving unit that applies a predetermined signal to the column electrode, and a display pulse signal by controlling the row electrode driving unit during a display period. A row electrode drive control means for sequentially applying the Y coordinate detection pulse signal set in the display pulse signal to the row electrodes, and an X coordinate detection pulse signal by controlling the column electrode drive means during the coordinate detection period And a column electrode drive control means for sequentially applying to the column electrodes, a Y coordinate of the electronic pen is detected based on a detection voltage induced in the electronic pen by the Y coordinate detection pulse signal, while an X coordinate detection pulse signal is detected. With the above electronic pen A display integrated tablet device having coordinate detection means for detecting the X coordinate of the electronic pen based on the induced detection voltage, wherein a gate voltage is applied to the detection voltage induced in the electronic pen by a Y coordinate detection pulse signal. A gate means for extracting the signal within a range of a gate pulse width of the signal, wherein the gate pulse width includes a pulse width of the Y coordinate detection pulse signal and an extension period, and the Y coordinate detection pulse signal is applied during the extension period. A display-integrated tablet device, wherein the value is set to a value larger than a time constant τ determined by a resistance and a capacitance from a start end to an end of a row electrode. 3. A display panel having a display unit corresponding to an intersection of two electrodes where a plurality of row electrodes and a plurality of column electrodes intersect, an electronic pen electrostatically coupled to the row electrodes and the column electrodes, A row electrode driving unit that applies a predetermined signal to the row electrode, a column electrode driving unit that applies a predetermined signal to the column electrode, and a display pulse signal by controlling the row electrode driving unit during a display period. A row electrode drive control means for sequentially applying the Y coordinate detection pulse signal set in the display pulse signal to the row electrodes, and an X coordinate detection pulse signal by controlling the column electrode drive means during the coordinate detection period And a column electrode drive control means for sequentially applying to the column electrodes, a Y coordinate of the electronic pen is detected based on a detection voltage induced in the electronic pen by the Y coordinate detection pulse signal, while an X coordinate detection pulse signal is detected. With the above electronic pen A display integrated tablet device having coordinate detection means for detecting the X coordinate of the electronic pen based on the induced detection voltage, wherein a gate voltage is applied to the detection voltage induced in the electronic pen by a Y coordinate detection pulse signal. A gate means for extracting the signal within a range of a gate pulse width of the signal, wherein the gate pulse width includes a pulse width of the Y coordinate detection pulse signal and an extension period, and the Y coordinate detection pulse signal is applied during the extension period. Is set to a value larger than the time constant τ determined by the resistance and the capacitance from the start end to the end of the row electrode, and the pulse width of the Y coordinate detection pulse signal is applied to the Y coordinate detection pulse signal. A display-integrated tablet device, wherein the value is set to a value larger than a time constant τ determined by a resistance and a capacitance from a start end to an end of a row electrode. 4. The display integrated tablet device according to claim 1, wherein the Y-coordinate detection pulse signal and the gate pulse signal are generated from the same pulse source. 5. The pulse width of the Y-coordinate detection pulse signal is:
4. The display-integrated tablet device according to claim 1, wherein the tablet device has a range of τ to 5τ. 6. The display-integrated tablet device according to claim 1, wherein the extension period ranges from τ to 5τ.