JPH08328739A - Display device provided with coordinate detection function - Google Patents

Abstract

PURPOSE: To provide a display device provided with a coordinate detection function using the LCD of a TFT type for which sure coordinate detection is guaranteed without causing the substantial rise of a cost. CONSTITUTION: On the side of a display surface from plural gate electrodes 43 and source electrodes 43b provided so as to control a transistor for display- driving picture elements and disposed respectively in parallel in different directions so as to be orthogonally crossed to each other, an LCD display panel provided with a counter electrode 47 opposite to a driving electrode driven by the transistor and connected to the plural picture elements in common is provided. A voltage successively applied to the gate electrodes 43a and the source electrodes 43b is detected through capacitance between the electrodes 43a and 43b by a pen 12 for instructing an optional position and a coordinate indicated by the pen 12 is decided based on the timing of the detection. Plural holes 53 are provided on the counter electrode 47.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a display device having a coordinate detecting function, which is provided with a coordinate detecting function.

[0002]

2. Description of the Related Art An integrated input display device in which a tablet which is a coordinate input device and a display device are superposed on each other is a display input device of an information processing device such as an electronic notebook, a pen input word processor, a pen input personal computer and a pen input terminal. Is used as. The integrated input / display device is excellent in operability because the input position (coordinates) of information and the display position coincide with each other.

Integrated input and display devices are typically LCDs.
It is configured by superimposing a transparent tablet (a coordinate input device using a pen as a position indicating means) on the display surface of the (liquid crystal display), or by laying an opaque tablet under the LCD. That is, in the usual configuration, a tablet is required in addition to the LCD.

On the other hand, if the tablet function can be realized by using the electrodes of the dot matrix LCD as they are, a dedicated tablet becomes unnecessary, so that the cost can be reduced and the weight of the device can be reduced.

Such a display device with a coordinate detection function using the electrodes of the LCD for coordinate detection is conventionally realized by operating according to a timing chart as shown in FIG. Note that the display device with coordinate detection function described below uses an STN-type LCD.

When performing coordinate detection using the electrodes of the LCD, the operation time of one frame period of the LCD is divided into a display period and a coordinate detection period, and a general LCD is used during the display period.
In the coordinate detection period, the coordinate detection voltage is sequentially applied to the vertical and horizontal electrodes of the LCD, and the voltage is detected through the capacitance between the pen and the electrode to detect the X and Y coordinates. To measure.

In the coordinate detection period, first, L shown in FIG.
A voltage is sequentially applied to the vertical electrodes (for X coordinate measurement) of the CD (X measurement period). When the pen is used to press on the coordinate detection surface (display screen), when a voltage is applied to the lateral electrode immediately below the pen tip, as shown in FIG. Due to the stray capacitance, a pulse voltage is generated on the sensor (metal rod) of the pen tip as shown in FIG. By measuring the time (Tx) from the start of X-coordinate measurement to the detection of this pulsed voltage, the X-coordinate of the pen tip corresponding to Tx can be detected.

Subsequently, the Y coordinate is similarly measured (Y
During the measurement period), the time (Ty) from the start of Y coordinate measurement to the detection of the pulsed voltage is measured to detect the Y coordinate of the pen tip according to Ty. In this way, one point (X coordinate, Y coordinate) on the coordinate detection surface designated by the pen is obtained.

Even if one frame period is divided into the display period and the coordinate detection period as described above, the pulse width of the voltage applied to the electrode during the coordinate detection period is short, so that the voltage is applied to the electrode during the coordinate detection period. Has almost no effect on the display.

The signal detected by the pen is processed through the circuit shown in FIG. The potential of the voltage detected by the pen is first amplified by an amplifier provided inside the pen. The signal output from the pen is amplified by the amplifier of the analog processing circuit and then filtered by the low pass filter (LPF). In addition, the comparator detects if the level exceeds the threshold level,
A pulse signal is generated. By measuring the time until the pulsed voltage (pulse rising) is detected, the coordinates of the pen tip can be known.

The display device with the coordinate detection function described above is S
Although it is realized by using a TN type LCD, in recent years, a structure realized by using a TFT type LCD has been considered.

To realize a display device with a coordinate detection function using a TFT type LCD, it is basically the same as the case of using an STN type LCD, but a TFT type LC is used.
Due to the structure of D, it is necessary to change the special operation and the LCD structure itself.

A method for realizing a display device with a coordinate detection function using a TFT type LCD will be described below.
FIG. 15 shows the structure of a general TFT type LCD. As shown in FIG. 15, the TFT-type LCD has a polarizing plate, a polarizing plate, a
Glass substrate, electrode (transistor) and drive electrode (IT
O), liquid crystal, counter electrode (ITO), color filter,
A glass substrate and a polarizing plate are laminated in this order.

The operation period of the LCD is the STN shown in FIG.
Similar to the LCD of the system, it is divided into a display period and a coordinate detection period, and a screen display operation is performed during the display period and coordinate detection is performed during the coordinate detection period. The display detection period is divided into an X coordinate detection period and a Y coordinate period, and the X electrode (source electrode) and the Y electrode (gate electrode) are sequentially applied with voltage.

In order to prevent the display image from being affected, it is necessary to apply a voltage that does not turn on the transistor connected to each electrode in order to prevent the display image from being affected.

Even when a TFT type LCD is used, ST
Similar to the case of using the N-type LCD, a signal indicating the position of the pen tip is detected via the capacitance between each electrode to which a voltage is applied and the pen. The signal detected by the pen is processed by an analog processing circuit as shown in FIG. 14, and each coordinate value is determined by the signal detection timing. Specifically, the time from the voltage application start time of each electrode to the signal detection is measured, and each coordinate value is determined by the measured value.

[0017]

However, the conventional TF
As shown in FIG. 15, the T-type LCD has a structure in which the counter electrode is located above the layer in which the transistor and the electrode are arranged, that is, between the electrode and the pen for detecting coordinates. . Since the counter electrode in the conventional TFT type LCD is a solid electrode over the entire surface, it shields the electrostatic capacitance from the X and Y electrodes to which a voltage is applied. Therefore, the pen may not be able to obtain a sufficient signal for coordinate detection, and a stable coordinate detection operation cannot be guaranteed.

On the other hand, in the conventional case, a TFT type LCD is used.
However, the structure shown in FIG. 16 has been considered in which a sufficient signal for coordinate detection can be detected by the pen. The TFT type LCD shown in FIG. 16 has a polarizing plate, a glass substrate, a color filter, a counter electrode, a liquid crystal body, an electrode (transistor) and a driving electrode, a glass substrate, and a polarized light from the side that radiates white light (such as a backlight). The plates are sequentially stacked. That is, contrary to the structure shown in FIG. 15, by arranging the counter electrode below the X and Y electrodes, the detection level by the pen is increased to enable coordinate detection.

However, the TFT having the structure shown in FIG.
The LCD of the type has a lower display quality than the LCD of the structure shown in FIG. Therefore, it is inconvenient to reduce the performance of the display, which is the main function, for detecting the coordinates, and it has been difficult to actually use the structure shown in FIG.

In addition, currently manufactured TFTs are generally manufactured.
Since the LCD of the system adopts the structure shown in FIG. 15, it is necessary to redesign the TFT module to adopt the structure shown in FIG. 16 in which the counter electrode is on the lower side of the display screen. . Therefore, the manufacturing process of the LCD currently being manufactured also has to be changed in order to realize the display device with the coordinate detection function. This will lead to a significant increase in cost.

The present invention has been made in consideration of the above-mentioned circumstances, and a display device with a coordinate detection function using a TFT type LCD in which reliable coordinate detection is guaranteed without causing a large increase in cost. The purpose is to provide.

[0022]

According to the present invention, there are provided a plurality of gate electrodes arranged in parallel in different directions so as to be orthogonal to each other, which are provided for controlling an active element for driving a display of a pixel. A panel is provided on the display surface side of the source electrode, the counter electrode being commonly connected to a plurality of pixels facing the drive electrode driven by the active element. The panel is sequentially applied to the gate electrode and the source electrode. With the coordinate detection function, the detected voltage is detected by the position indicating means for indicating an arbitrary position via the capacitance between the electrodes and the coordinates indicated by the position indicating means are determined based on the timing of the detection. In the display device, a plurality of holes are provided in the counter electrode.

Further, the plurality of holes provided in the counter electrode are characterized in that they are provided at equal intervals and have the same shape and size. Further, the hole provided in the counter electrode is provided so as to correspond to a position where the gate electrode and the source electrode intersect with each other.

Further, the panel is characterized in that a black matrix is arranged, and the holes provided in the counter electrode are provided corresponding to positions where the black matrix is not arranged.

Further, the counter electrode is composed of a plurality of electrodes arranged in parallel with a direction in which the gate electrode or the source electrode is arranged. Further, the plurality of electrodes are arranged at positions that do not overlap with the gate electrodes or the source electrodes that are arranged in parallel. Also, each of the plurality of electrodes,
It is characterized by the same width as the pixel.

[0026]

According to this structure, the plurality of holes provided in the counter electrode reduce the shielding effect of the counter electrode on the capacitance, and the position of the gate electrode or the source electrode can be reduced when the voltage is applied to the gate electrode or the source electrode. It is possible to raise the signal level for detecting the coordinate position detected by the pointing means (pen).

Further, a plurality of holes provided in the counter electrode are
By providing the same shape and the same size at equal intervals, it is possible to detect signals under the same conditions regardless of the position of the pen on the panel.

Further, by providing a hole at a position where the gate electrode and the source electrode to which a voltage is applied for coordinate detection intersect, the shield effect of the electrostatic capacitance by the counter electrode can be more effectively reduced.

Further, in the case of a panel structure in which a black matrix is provided depending on the positions where the active elements (transistors) and the electrodes are arranged, the black matrix has a function of shielding the electrostatic capacitance. By providing a hole in the counter electrode corresponding to the position where the black matrix is not arranged, it is possible to effectively reduce the shielding effect of the electrostatic capacitance by the counter electrode.

Further, by arranging the counter electrodes by arranging a plurality of electrodes in parallel, it is possible to reduce the shield effect of the electrostatic capacitance by the counter electrodes by the distance secured between the electrodes.
Further, by providing a plurality of electrodes forming the counter electrode at positions that do not overlap the gate electrode or the source electrode to which voltage is applied for coordinate detection, it is possible to more effectively reduce the shield effect of electrostatic capacitance by the counter electrode. Can be achieved.

[0031]

Embodiments of the present invention will be described below with reference to the drawings. FIG. 1 is a block diagram showing the configuration of a display device with a coordinate detection function according to this embodiment. As shown in Figure 1,
The display device with the coordinate detection function includes an LCD display panel 10,
Pen 12, vertical electrode upper drive circuit 14a, vertical electrode lower drive circuit 14b, horizontal electrode drive circuit 16, analog processing circuit 20, tablet control circuit 22, and LCD.
It is configured by the control device 24. The display device with the coordinate detection function is connected to the information processing device 30 and operates by providing a display period and a coordinate detection period, and is used for displaying the processing content of the information processing device 30 and inputting data.

The LCD display panel 10 is a panel for displaying and inputting coordinate data, and is shown in FIG. 2 (and FIG. 1).
As shown in 5), each part is laminated.
That is, the polarizing plate 40, the glass substrate 41, the electrode 43 (transistor 44 (not shown)) and the drive electrode 45 (ITO), from the side that emits white light (backlight or the like).
A liquid crystal body 46, a counter electrode 47 (ITO), a color filter 48, a glass substrate 50, and a polarizing plate 51 are laminated in this order.

On the LCD display panel 10, electrodes 43 (gate electrodes 43a, 43a,
A source electrode 43b) is provided. Gate electrode 43
The a and the source electrode 43b are arranged in directions orthogonal to each other, and are used as electrodes for coordinate detection during the coordinate detection period. In this embodiment, the gate electrode 43a is used as a Y electrode (horizontal electrode) for detecting the Y coordinate, and the source electrode 43b is used as an X electrode (vertical electrode) for detecting the X coordinate.

The pen 12 is a position pointing device used to detect a potential via a capacitance between the electrode 43 and the electrode 43 when the pen 12 is applied to the electrode arranged on the LCD display panel 10.

The vertical electrode upper drive circuit 14a and the vertical electrode lower drive circuit 14b are L under the control of the tablet controller 22 in accordance with the display period or the coordinate detection period.
The source electrode 4 vertically arranged on the CD display panel 10.
A voltage is sequentially applied to each electrode of 3b (X electrode).

Under the control of the tablet controller 22, the lateral electrode drive circuit 16 has a gate electrode 43a (Y electrode) arranged in the lateral direction on the LCD display panel 10 in accordance with the display period or the coordinate detection period. The voltage is sequentially applied to each of the electrodes.

The analog processing circuit 20 processes a signal detected by the pen 12, and as shown in FIG. 14, is composed of an amplifier also serving as a low pass filter (LPF) and a comparator circuit.

Under the control of the LCD control device 24 and the information processing device 22, the tablet control circuit 22 has a vertical electrode upper drive circuit 14a, a vertical electrode lower drive circuit 14b, and a horizontal electrode for display or coordinate detection. Drive circuit 1
6, drive control, and determination of X and Y coordinate values based on the voltage detection timing from the analog processing circuit 20.

The LCD control unit 24 controls the tablet control unit 22, reads the display data from the information processing unit 30, and sends a coordinate display signal for driving the electrodes to the tablet control unit 22.

The information processing device 30 includes the LCD display panel 1
Display data indicating the content to be displayed on 0 is sent to the LCD display device 24, and the data of the coordinates indicated by the pen tip of the pen 12 is input from the tablet control device 22.

Also in this embodiment, the display device with the coordinate detecting function is realized by operating according to the timing chart as shown in FIG. Next, the first embodiment will be described. The counter electrode of the first embodiment is provided with a large number of holes as shown in FIG. That is, in the first embodiment, by providing a large number of holes 53 in the counter electrode, as shown in FIG. 4, the shield effect of the counter electrode 47 is reduced and a sufficient signal for detecting coordinates by the pen 12 is obtained. It allows you to do things.

The hole 53 provided in the counter electrode 47 is TF
Due to the structure of the T-type LCD, there is no problem in size, and a circular shape having the same size or a shape close to a circular shape is used. Also,
As shown in FIG. 3, the signals detected by the pen 12 are arranged at equal intervals so that the signals are detected at an equal level regardless of the position of the pen tip on the LCD display panel 10. Further, as shown in FIG. 5, by providing each hole at a position right above the intersection of the gate electrode 43a (Y electrode) and the source electrode 43b (X electrode), the shielding effect is further reduced. It is possible to realize highly accurate coordinate detection (when there is no black matrix 49).

By the way, in the TFT type LCD, a thin portion called a black matrix 49 is used because the display quality is deteriorated due to a portion (transistor 44, source electrode 43b, gate electrode 43a) around the pixel electrode where the display cannot be controlled. As shown in FIG. 2, there is one in which a metal film is arranged on each electrode 43 and the transistor 44.

For example, if each hole 53 is provided at a position just above the intersection of the gate electrode 43a (Y electrode) and the source electrode 43b (X electrode) as described above, in the case where the holes 53 overlap the black matrix 49. Is the counter electrode 47
Although the shielding effect of the counter electrode 47 is lowered by the holes provided in the black matrix 49,
In order to shield the capacitance from 3, the pen 12
Will lower the detection potential.

Therefore, in this case, as shown in FIG. 6, the holes 53 provided in the counter electrode 47 are provided so as not to overlap the position of the black matrix 49 and at even intervals. This allows the black matrix 49
Since the shield effect can be reduced without being affected by, it is possible to realize highly accurate coordinate detection.

Next, the second embodiment will be described. Second
The counter electrode 47 of the embodiment is not a solid electrode over the entire surface, but as shown in FIG. 7, a plurality of plate rod-shaped electrodes 55 are arranged in parallel in a horizontal direction or a vertical direction at a predetermined interval, and each electrode thereof is arranged. It is configured by connecting 55 to the liquid crystal body 46. That is, in the second embodiment, by arranging the plurality of electrodes 55 in parallel at intervals, as shown in FIG. 8, the shield effect of the counter electrode 47 is reduced, and the coordinates of the pen 12 are detected. This is to make it possible to obtain a sufficient signal.

In order to increase the detection level of the signal detected by the pen 12, the gate electrode 43a (or the source electrode 43b may be provided) between the adjacent electrodes 55 as shown in FIG. It can be realized by arranging so as to be positioned.

Further, each electrode 55 (counter electrode 47) shields the electrostatic capacitance from the gate electrode 43a and the source electrode 43b, so that the electrode width is preferably narrow. However, since the counter electrode 47 is the electrode 55 connected to one side surface of the liquid crystal cell for each pixel, it is necessary to have a width equal to or larger than the width of each liquid crystal cell. Therefore, the width of each electrode 55 forming the counter electrode 47 is set to be the same as or approximately the same as the width of the liquid crystal cell as shown in FIG. As a result, the shield effect of the counter electrode 47 can be reduced without affecting the display performance, so that highly accurate coordinate detection can be realized.

Although the TFT type LCD has been described as an example in the above embodiment, another LCD or another LCD having a similar structure in which the counter electrode 47 is provided on the display screen side is used. It is possible to apply to the flat panel display of.

[0050]

As described above in detail, according to the present invention, the shield effect of the counter electrode located between the electrode to which the voltage is applied during the coordinate detection period and the pen for coordinate detection is reduced. Since a signal level for reliable coordinate detection can be obtained with the structure of a general TFT type LCD, a TFT type LCD that ensures reliable coordinate detection without causing a significant increase in cost can be obtained. It is possible to provide the display device having the coordinate detection function used.

[Brief description of drawings]

FIG. 1 is a block diagram showing the configuration of a display device with a coordinate detection function according to an embodiment of the present invention.

FIG. 2 is a sectional view for explaining the structure of the LCD display panel 10 in the present embodiment.

FIG. 3 is a diagram for explaining the structure of a counter electrode in the first embodiment.

FIG. 4 is a diagram for explaining an operation effect when performing coordinate detection in the first embodiment.

FIG. 5 is a diagram for specifically explaining the structure of the counter electrode in the first embodiment.

FIG. 6 is a diagram for specifically explaining the structure in the case where there is a black matrix of the counter electrode in the first embodiment.

FIG. 7 is a diagram for explaining the structure of a counter electrode in the second embodiment.

FIG. 8 is a diagram for explaining an operation effect when performing coordinate detection in the second embodiment.

FIG. 9 is a diagram for specifically explaining the structure of the counter electrode in the second embodiment.

FIG. 10 is a diagram for specifically explaining another structure of the counter electrode in the second embodiment.

FIG. 11 is a timing chart for explaining the operation of the display device with the coordinate detection function.

FIG. 12 is a diagram showing electrodes arranged on an LCD.

FIG. 13 is a diagram for explaining potential detection by a pen.

FIG. 14 is a diagram for explaining processing of a signal detected by a pen.

FIG. 15 is a diagram showing a structure of a general TFT type LCD.

FIG. 16 is a diagram showing the structure of another conventional TFT type LCD.

[Explanation of symbols]

10 ... LCD display panel, 12 ... Pen, 14a ... Vertical electrode upper drive circuit, 14b ... Vertical electrode lower drive circuit,
16 ... Lateral electrode drive circuit, 20 ... Analog processing circuit,
22 ... Tablet control device, 24 ... LCD control circuit, 3
0 ... Information processing device, 40, 51 ... Polarizing plate, 41, 50 ...
Glass substrate, 43 ... Electrode, 43a ... Gate electrode, 43b
... source electrode, 44 ... transistor, 45 ... driving electrode,
46 ... Liquid crystal body, 47 ... Counter electrode, 48 ... Color filter, 49 ... Black matrix, 53 ... Hole, 55 ... Electrode.

Claims (7)

[Claims] 1. A display surface side of a plurality of gate electrodes and source electrodes, which are provided in order to control an active element for driving a pixel to display, and are arranged in parallel in different directions so as to be orthogonal to each other, It has a panel provided with a counter electrode commonly connected to a plurality of pixels facing a drive electrode driven by the active element, and a voltage applied sequentially to the gate electrode and the source electrode is set at an arbitrary position. In a display device with a coordinate detection function, which detects by a position indicating means for indicating via a capacitance between the position indicating means and the coordinates indicated by the position indicating means based on the timing of the detection, the counter electrode is A display device with a coordinate detection function, which is provided with a plurality of holes. 2. The plurality of holes provided in the counter electrode,
The display device with a coordinate detection function according to claim 1, wherein the display device has the same shape and size at equal intervals. 3. The display device with a coordinate detection function according to claim 1, wherein the hole provided in the counter electrode is provided at a position where the gate electrode and the source electrode intersect with each other. 4. The panel is provided with a black matrix, and the holes provided in the counter electrode are provided at positions where the black matrix is not provided. A display device with the described coordinate detection function. 5. The coordinate detection function according to claim 1, wherein the counter electrode is composed of a plurality of electrodes arranged in parallel with a direction in which the gate electrode or the source electrode is arranged. Display device. 6. The display with a coordinate detection function according to claim 5, wherein the plurality of electrodes are arranged at positions that do not overlap with the gate electrodes or the source electrodes which are arranged in parallel. apparatus. 7. The display device with coordinate detection function according to claim 5, wherein each of the plurality of electrodes has the same width as a pixel.