KR100226812B1 - position detecting LCD - Google Patents

Abstract

The present invention relates to a position detection liquid crystal display device, wherein the position detection means is used as an ITO, and an AC signal having a DC level is supplied to the drive signal applying unit through an AC signal generator, a DC signal generator, an analog ether unit, and a panel applying unit. By applying it simultaneously, the dual AC signal is applied as a drive signal for position detection, and the DC signal is applied as a VCOM signal by using an analog switch and a capacitor. The exact position detection of the stylus can be detected without distortion of the potential distribution due to the position detection. This is possible and is intended to improve the image quality of the liquid crystal display.

Description

Position detecting LCD

BACKGROUND OF THE INVENTION 1. Field of the Invention [0001] The present invention relates to a position sensing liquid crystal display (PSLCD), and more particularly, to a position detecting liquid crystal display suitable for eliminating the interference between the black matrix and the ITO for the common electrode and simplifying the manufacturing process.

In general, the position detection liquid crystal display device uses a position detection element in a conventional LCD, but the technology of using the black matrix of the LCD as the position detection element has been improved.

1A to 1B are views for explaining a position detection liquid crystal display device using the black matrix of the LCD as the position detection element.

As shown in FIG. 1A, a driving AC signal for position detection was applied to four corners of the position detection device to detect the position of the stylus (electronic pen).

That is, 5V driving AC signals are applied to the reference numerals 1 and 4, and the potential distribution is generated in the vertical axis direction by connecting the ground terminals to the reference numerals 2 and 3.

5V driving AC signals were applied to the reference numerals 1 and 2, and the ground terminals were connected to the reference numerals 3 and 4 to generate the potential distribution in the horizontal axis direction.

As such, the driving AC signal and the ground signal are alternately applied to detect the position of the stylus or the electronic pen.

Here, reference numeral 5 is a grid composed of black matrices formed in the X-axis and Y-axis directions, respectively.

In this case, in order for the potential to be linearly distributed in the grid, the resistance along the path through which the signal flows should be compensated.

FIG. 1B illustrates an equipotential holding resistor and an equipotential compensating resistor outside the grid area arranged and arranged on the X and Y axes.

As shown in FIG. 1B, the X-axis and Y-axis grids are not formed every pixel, but are formed by skipping a plurality of pixels.

When the driving signal is applied at the four corners, the potentials at each point (reference numerals 14a, 14b, 14c) of the first grid input unit (reference numeral 14) to which the driving signal is input appear different.

Therefore, as shown in FIG. 1B, the equipotential holding resistor 15 and the equipotential compensating resistor 16 are formed outside the grid area.

However, in the position detection liquid crystal display, an overcoat (not shown) layer is formed on the black matrix layer used as the grid as the position detection element, and the ITO for the common electrode VCOM is formed thereon.

Therefore, since the overcoat layer, which is a dielectric material, exists between the conductive black matrix and the ITO, a capacitor is formed.

2 is a cross-sectional view of a position detection liquid crystal display device showing that such a capacitor is formed.

As shown in FIG. 2, a black matrix 22 is formed on the upper plate glass 21 and electrically connected to the black matrix 22 to form an equipotential compensation resistor 23, and electrically connected to the equipotential compensation resistor 23. An equipotential holding resistor 24 is formed to be connected.

R, G, and B color filter layers 25 are formed between the black matrices 22.

In addition, an overcoat layer 26 is formed on the front surface of the color filter layer 25 and the equipotential holding resistor 24, and an ITO 27 is formed on the overcoat layer 26.

Accordingly, as described above, a capacitor coupling phenomenon occurs between the conductive equipotential sustaining resistor 24, the equipotential compensating resistor 23, and the black matrix 22 and the ITO 27.

This capacitor coupling phenomenon makes the position signal detected by the stylus (or electronic pen) very small, and thus the noise increases so much that accurate position detection is impossible.

3 is a diagram illustrating the degree of influence of the ITO and the black matrix on the stylus.

Reference numeral 31 denotes the coupling by the black matrix 22 and reference numeral 33 denotes the coupling by the ITO 27.

Here, the coupling degree increases as the capacitance increases, and comparing the capacitance from the ITO 27 to the stylus and the capacitance from the black matrix 22 to the stylus shows which effect is greater.

That is, as shown in FIG. 3, when the thickness of the top glass 21 is dO, the thickness of the overcoat layer 26 is dOC, and the thickness of the color filter layer 25 is dCF, the thickness and area Lbm, Comparing the magnitude of the capacitance using Lpixel), it can be seen that the capacitance between the ITO 27 and the stylus is greater than the capacitance between the black matrix 22 and the stylus.

Furthermore, although only the influence in unit pixels is considered in FIG. 3, the influence becomes even greater when considering the black matrix and the black matrix used as the actual grid.

4 is a diagram for showing the influence between black matrices.

Reference numeral 41 in FIG. 4 denotes a Y-axis grid and reference numeral 42 denotes an X-axis grid.

Reference numeral 41a denotes a black matrix used as the Y-axis grid and reference numeral 42a denotes a black matrix used as the X-axis grid.

In the black matrix structure, the Y-axis grid formed by the black matrix of reference numeral 41a is formed for each of a plurality of pixels in the horizontal direction, and the X-axis grid formed by the black matrix of the reference numeral 42a is formed in the plurality of vertical directions. It is formed per pixel.

Thus, the black matrix in between has a signal that is induced in the ITO (not shown in the figure but formed across the entire surface of the black matrix).

As a result, the capacitance between the ITO and the stylus becomes much larger than when only the unit pixel is considered.

The conventional position detection liquid crystal display device has the following problems.

Noise is generated due to the capacitance appearing between the black matrix and the ITO for the common electrode, and this noise causes the stylus to not accurately detect the position.

SUMMARY OF THE INVENTION An object of the present invention for solving the above problems is to provide a position detection liquid crystal display device which is capable of accurate position detection and simplifies the process by eliminating mutual interference between the black matrix and the ITO by using the common electrode itself as a position sensing grid. It is.

1A is a diagram illustrating an X and Y axis grid according to a conventional position detection liquid crystal display device.

1B is a plan view of a top plate according to a conventional position detection liquid crystal display device;

2 is a cross-sectional view of a top plate according to a conventional position detection liquid crystal display device;

3 is a view showing the degree of influence of the ITO and the black matrix on the stylus according to the prior art

4 shows an arrangement of a black matrix according to the prior art.

5 is a conceptual diagram illustrating a position detection liquid crystal display device according to the present invention.

6 is a diagram illustrating the magnitude of voltage when a voltage is applied using the concept of FIG. 5;

7 is a plan view of a top plate according to a first embodiment of the present invention;

8 is a plan view of a top plate according to a second embodiment of the present invention;

9 is a detailed configuration diagram of a driving signal applying unit according to the present invention;

10 is a detailed circuit diagram according to FIG.

Figure 11a is a detailed configuration diagram of the panel applying unit according to the present invention

11B is a timing diagram of a switch control signal according to the present invention.

12A is a view showing another embodiment of the panel applying unit according to the present invention

12B is a timing diagram of the switch control signal according to FIG. 12A.

13 is a conceptual diagram illustrating a driving signal applying unit according to another embodiment of the present invention.

14 is a view showing another embodiment of the panel applying unit according to FIG.

15A is a timing diagram of a switch control signal according to FIG. 14.

15B to 15C are waveform diagrams of a driving signal and a VCOM signal according to FIG. 14.

Explanation of symbols for main parts of the drawings

72a, 72b, 72c, 72d: driving signal applying unit 75: ITO

91: AC signal generator 92: Analog Ether section

93: DC generating part 94: Panel applying part

110a: analog switch 110b: amplifier

The position detection liquid crystal display device of the present invention for achieving the above object is a liquid crystal display device having an ITO used as a common electrode and a position detection element, and an equipotential compensation resistance and an equipotential holding resistance formed in the periphery of the ITO, and the DC to the ITO; And a driving signal applying unit for applying an AC signal including a level, and a stylus for detecting an AC signal according to the position of the ITO and detecting its position.

First, Japanese Patent Laid-Open No. 7-36017 proposes a technique using a common electrode as a position sensing means in an active matrix liquid crystal display device.

The technique described in Japanese Patent Laid-Open No. 7-36017 is configured to be orthogonal to each other via an insulating film in disposing the ITO for the common electrode.

However, in the above technique, an insulation is interposed between ITOs formed to be orthogonal to each other, and the process is complicated by interposing an insulation. As the insulating material is interposed, the width of the liquid crystal panel increases by that much.

The present invention is improved to this problem, in the use of ITO instead of the black matrix for the position detection, because the insulator is not used to simplify the manufacturing process and to minimize the width of the liquid crystal panel.

And to solve the above-mentioned problems of the prior art.

Hereinafter, the position detection liquid crystal display of the present invention will be described with reference to the accompanying drawings.

5 is a conceptual diagram for explaining a position detection liquid crystal display device according to the present invention.

As shown in FIG. 5, a plurality of resistors are connected in series to an input terminal for inputting a driving signal to the position detection device, and a capacitor is connected in series at the far end.

When an AC sine wave having a DC level is applied to the input terminal, the magnitude of the detected voltage is different between the resistors.

FIG. 6 is a graph showing the magnitudes of voltages that are different between resistors when a sine wave is applied after the configuration as shown in FIG. 5.

As shown in FIG. 5, when an AC sine wave having a DC level applied through an input terminal passes through the resistance element, a voltage drop corresponding to the magnitude of the resistance occurs.

When the voltage drop AC sine wave passes through the resistance element again and repeats this process, the signal applied to the resistance element in front of the capacitor is the amplitude of the AC component in the AC sine wave having the first applied DC level. ) Only decreases, and the DC level remains unchanged.

Therefore, only the signal of the DC component is present at the input of the capacitor shown in FIG.

Using this principle, when the AC sine wave having the above DC level is applied as the VCOM signal applied to the ITO of the LCD, that is, the common electrode, and the dot inversion method is applied, the DC component is the VCOM voltage. The component can be used as a driving signal for position detection applied to the existing black matrix.

At this time, the signal of VCOM may vibrate with AC and affect the capacitance of the liquid crystal, but it can be solved by making the vibration frequency of AC very large than the response frequency of the liquid crystal.

That is, VCOM is influenced by one side of the capacitor of the liquid crystal, that is, the average value of the AC component (which is a signal of the DC component).

In this case, the AC sine wave having the DC level may be generated by adding a signal of a DC component for position detection to an existing VCOM signal.

7 is a plan view of a top plate and a driving signal applying unit according to the first embodiment of the position detection liquid crystal display device of the present invention.

According to the first embodiment of the present invention, in the position detecting liquid crystal display device using the position detecting means as the ITO, the driving signal applying unit (72a, 72b, 72c, 72d) consisting of a capacitor and a switching element and the driving signal application A drive signal output from the sections 72a, 72b, 72c, 72d is connected to an equipotential holding resistor 73 for applying an even potential to the position detecting means and the equipotential holding resistor 73 so that the drive signal is detected. It is composed of an equipotential compensation resistor 74 which compensates the resistance value to achieve an equipotential when applied to each grid of means.

Here, the driving signal applying unit 72 is formed at four corners of the upper plate glass, respectively, and is composed of switching elements and capacitors formed at the front end of the equipotential sustaining resistor 73 as shown in FIG.

The switching elements of the driving signal applying units 72a, 72b, 72c, and 72d selectively output to the upper plate according to the switch control signal among the driving signal and the ground signal to be applied.

The ITO 75 is made of one flat plate.

Operation of the position detection liquid crystal display according to the first embodiment of the present invention configured as described above is as follows.

As shown in FIGS. 5 and 7, the first switch 75a and the third switch 75c of the first and second driving signal applying units 72a and 72b of the driving signal applying units located at the four corners of the upper plate are disposed. When the sixth and eighth switches 75f and 75h of the third and fourth driving signal applying units 72c and 72d are turned on, the first and third switches 75a and 75c are turned on. The signal shown in FIG. 5 (that is, an AC sine wave having a DC level) is applied.

That is, when an AC signal having a DC offset is applied, the DC offset remains as it is and forms a voltage distribution in which only the peak-to-peak voltage of the AC signal decreases in the Y-axis direction.

The driving signal is applied through the process of applying four driving signals as in the conventional position detection liquid crystal display.

In the input drive signal (AC sine wave having a DC level), an AC signal is applied to the upper plate as a drive signal, and a DC signal that cannot escape through the capacitors of the drive signal applying units is used as a VCOM signal.

8 is a plan view and a driving signal applying unit of the upper plate of the position detection liquid crystal display according to the second embodiment of the present invention.

According to the second embodiment of the present invention, the ITO used as the position detecting means is patterned in the shape of a mesh rather than one flat plate.

As shown in FIG. 8, the second embodiment of the present invention is located at four corners of the upper plate glass, and includes a driving signal applying unit 82 consisting of a capacitor and a switching element, an equipotential holding resistor 83, and an equipotential compensating resistor 84. And an X-axis grid 85a and a Y-axis grid 85b electrically connected to the equipotential compensation resistor 84 and patterned in the X-axis and Y-axis directions.

Here, the grids 85a and 85b are composed of ITO, and reference numeral 25 denotes the width of the data line and reference numeral 26 denotes the width of the gate line.

The widths of the X and Y axis grids 85a and 85b are equal to the sum of the widths of the plurality of pixels.

As such, the patterning of the grids 85a and 85b equals the sum of the widths of several pixels. The smaller the width of the patterned ITO is, the larger the resistance becomes, so that the potential of VCOM is positioned at the position. It can vary a lot, because it seriously affects the quality of LCD.

As in the second embodiment of the present invention, when the ITO used as the position detecting means is formed by patterning a mesh, it has a higher resistance value than the case of one flat plate, so that the potential distribution is distinct.

9 is a detailed block diagram of a driving signal applying unit according to the position detection liquid crystal display device of the present invention.

As shown in FIG. 9, it comprises an AC signal generator 91, an analog ether unit 92, a DC generator 93, and a panel applying unit 94. As shown in FIG.

Here, the AC signal generator 91 generates and outputs a sine wave, which is a position detection driving signal for coupling with the stylus, and the analog ether 92 is connected to the common electrode ITO of the LCD used as the position detection means. Apply an AC signal with a DC offset.

In addition, the DC generator 93 generates DC applied to the ITO for the common electrode. The panel applying unit 94 receives the output of the analog ether unit 92 and selectively outputs it to the ITO of the upper plate.

Hereinafter, the configuration block of FIG. 9 will be described in detail.

FIG. 10 is a circuit diagram illustrating a DC generator and an analog adder of FIG. 9.

As shown in FIG. 10, a DC generator 93 for generating and outputting a DC signal for VCOM using a voltage divider connected in series with a plurality of resistors R1, R2, and R3 detects the position of the stylesus. Analog signal output unit consisting of an output signal of the AC signal generator 91 for outputting a drive AC signal for the operation, and the OP amplifier 100, the output signal of the DC generator 93 is input to the non-inverting input terminal ( 92).

Herein, resistance elements R6 and R5 are formed between the output terminal of the AC signal generator 91 and the output terminal of the DC generator 93 and the non-inverting input terminal of the OP amplifier 100, respectively.

A capacitor C1 is formed between the output terminal of the DC generator 93 and the resistance element R5.

As described above, the analog ether unit 92 configured as described above outputs an AC sine wave having a DC level to the ITO which serves as a position detecting means and at the same time serves as a common electrode of the LCD.

The AC sine wave signal having the DC level output from the analog ether unit 92 is input to the panel applying unit 94. The panel applying unit 94 will be described in detail below.

11A is a detailed configuration diagram of the panel applying unit according to the present invention.

The panel applying unit according to the present invention is largely composed of an analog switch unit 110a and an amplifier unit 110b as shown in FIG. 11A.

Here, the analog switch unit 110a receives the output signal and the ground signal of the analog ether unit 92 and receives the output signal and the ground signal of the analog ether unit 92 by the switch control signals SC1 to SC4. Optionally output

The amplification unit 110b includes a non-inverting voltage follower.

The operation description of the panel applying unit is as follows.

11B is a timing diagram of a switch control signal for controlling the analog switch.

In general, in the position detection liquid crystal display, a driving signal is applied at four corners of the top plate.

As described above, which of the driving signals is applied to the four corners and which of the driving signals is to be applied is also determined by the output signal of the panel applying unit.

As shown in FIG. 11A, the output signal of the analog ether unit 92 is applied to eight analog switches and four of the switches, and a ground signal is applied to the remaining four analog switches.

At this time, the output signal and the ground signal of the analog ether unit 92 selected according to the switch control signal for controlling the on / off state of the analog switches are applied to the non-inverting input terminal of the amplifying unit ().

As shown in FIG. 11B, initially, SC1 and SC2 remain high among the switch control signals SC1 to SC4, and the SC3 becomes high as soon as the SC1 becomes low. .

At this time, the first and eighth switches 111a and 111h of the eight analog switches are turned on so that the output signal and the ground signal of the analog ether unit 92 are first turned on through the switches. It is input to the amplifier 112a.

In addition, the second and seventh switches 111b and 111g of the analog switch unit 110a are turned on by the switch control signal SC2, and the output signal and the ground signal of the analog ether unit 92 transmitted through these switches are the amplification unit. It is input to the fourth amplifier 112d of 110b.

In this case, the switch control signals SC3 and SC4 are sequentially applied to the position detecting means through the same operation as described above.

As such, when the driving signal is selectively applied to the top glass through the first, second, third, and fourth amplifiers 112a, 112b, 112c, and 112d, the driving signal serves as position detection and VCOM.

12A is a circuit diagram according to another embodiment of the panel applying unit of the present invention.

It consists of two groups of analog switches 120a and 120b for selectively outputting the output signal of the analog ether unit 92 by the switch control signals SC11 and SC14 and the inverted switch control signal.

An inverter was used to invert the switch control signal.

The operation description according to another embodiment of the panel applying unit of the present invention configured as described above is similar to the operation of the panel applying unit described above.

That is, when the switch control signal becomes high, one group of analog switches 120a of the two groups of analog switches 120a and 120b is turned on and the other group of analog switches 120b pass through the inverter. One switch control signal goes low, so it is not turned on.

On the contrary, when the switch control signal is turned low, the group 1 analog switches 120a are turned off and the group 1 analog switches 120b are turned on.

The signals passing through the selectively turned-on analog switches are selectively applied to the four corner portions of the top plate to serve as driving signals and VCOM signals for position detection.

12B is a timing diagram of the switch control signal. When the switch control signals SC11 and SC12 are high signals, the corresponding group of analog switches 121a and 121b are turned on and simultaneously pass through the inverter. Since SC11 and SC12 become low signals, the two groups of analog switches 121g and 121h are turned off.

Subsequently, as soon as the switch control signal SC11 is changed to a low signal, another switch control signal SC13 is changed to a high signal, and the group 1 analog switch 121c is turned on.

At this time, since the SC11 becomes the low signal, the corresponding group 1 analog switch 121a is turned off and at the same time the group 2 analog switch 121h is turned on.

As described above, the driving signal and the VCOM signal are selectively applied at four corners of the top glass through a process in which the analog switch is sequentially turned on / off.

13 illustrates another embodiment of the driving signal applying unit according to the present invention.

As shown in FIG. 13, the driving signal applying unit according to another embodiment includes a resistor instead of a switching device and a capacitor.

Accordingly, when the driving signal is applied in the X-axis direction, the first and third driving signal applying units 130a and 130c apply an AC signal having a DC offset and the remaining second and fourth driving signal applying units 130b, 130d) applies only a DC signal.

When the driving signal is applied in this way, a voltage drop occurs in the X-axis direction.

At this time, the DC signal remains unchanged, but only the peak-to-peak voltage of the AC signal having the DC offset is reduced.

The circuit diagram for making a signal input to the top glass in this way is shown in FIG.

14 is a circuit diagram according to another embodiment of the driving signal applying unit shown in FIG. 13, which is similar to the circuit diagram shown in FIG. 10.

However, the switching element 140 is further configured between the resistance element R6 configured between the output terminal of the AC signal generator 91 and the non-inverting input terminal.

The AC signal is selectively applied to the panel applying unit 94 through a switch control signal for controlling the switching element 140.

That is, in the case where two switch control signals among the switch control signals SCa, SCb, SCc, and SCd are made high signals and the remaining two switch control signals are made low signals, for example, two switch control signals SCa, If SCb, is a high signal and the remaining two switch control signals SCc, SCd are low signals, the signal output from the first and third drive signal applying units 130a and 130c to the top glass is DC, as shown in FIG. It becomes an AC signal with an offset.

The signal output from the second and fourth driving signal applying units 130b and 130d to the upper glass is a DC signal.

15A is a timing diagram of the switch control signal as described above, and FIGS. 15B to 15C are signal waveforms according to timing of the switch control signal.

As shown in Fig. 15A, when the switch control signals SCa and SCb are high signals, the other switch control signals SCc and SCd become low signals.

At this time, as shown in the drawing, the waveform shown in FIG. 15B is applied through the first and third driving signal applying units 130a and 130c shown in FIG. 13 and the second and fourth driving signal applying units The waveform applied through 130b and 130d becomes a waveform as shown in FIG. 16C.

As a result, an AC signal having a DC level is applied to the drive signal applying unit to which the drive signal for position detection is applied, and a pure DC signal is applied to the other side.

Of course, the application of the AC or DC signal input to the upper plate glass through the driving signal applying unit is made after determining which of the four driving signal applying units applies the AC signal and which one applies the DC signal.

As described above, the position detection liquid crystal display device of the present invention has the following effects.

First, since the ITO for the common electrode is patterned to be orthogonal to one another or used as a position detecting means, the signal interference between the black matrix and the ITO is eliminated, so that accurate position detection by the stylus is possible.

Second, in patterning the ITOs used as the position detecting means to be orthogonal to each other, the width of the panel can be reduced since no insulating film is interposed therebetween.

Third, since the AC signal having the DC level is used as the drive signal and the VCOM signal for position detection, the circuit configuration is simplified.

Claims (15)

A liquid crystal display device having an ITO used as a common electrode and a position detecting element, and an equipotential compensation resistance and an equipotential holding resistance formed around the ITO; A drive signal applying unit for applying an AC signal including a DC level to the ITO; And a stylus for detecting an AC signal generated by the ITO to detect its own position coordinates. 2. The position detection liquid crystal display device according to claim 1, wherein the signal of the DC level among the AC signals including the DC level is used as a VCOM signal and the AC signal is used as a drive signal for detecting the position of the stylus. The liquid crystal display of claim 1, wherein the ITO comprises an X axis and an Y axis. delete 4. The position detection liquid crystal display device according to claim 3, wherein an insulating layer is not interposed between the ITO arranged on the X axis and the Y axis. The method of claim 1, The drive signal applying unit is an AC signal generator for generating a drive signal for position detection; A DC generator for generating a VCOM signal, An analog ether unit which inputs the analog signal output from the AC signal generator and the DC generator and outputs the sum signal; And a panel applying unit for selectively combining the output signal and the ground signal of the analog ether unit and outputting the ground signal through an amplifier. 7. The liquid crystal display of claim 6, wherein the DC generator comprises a voltage divider made of a resistance element. The apparatus of claim 6, wherein the panel applying unit comprises: a plurality of analog switches for selectively switching the output signal and the ground signal of the analog ether unit by a control signal; And an amplifier for amplifying the signals outputted through the plurality of analog switches. The liquid crystal display of claim 8, wherein the amplifier comprises a voltage follower. The method of claim 6, The panel applying unit receives a switch control signal as it is and a first analog switch unit for determining an operation state; And a second analog switch unit in which an operation state is determined according to a signal inverting the switch control signal. 12. The position detection liquid crystal display device according to claim 10, wherein an inverter is used to invert the switch control signal. delete delete delete The position detection liquid crystal display device according to claim 1, wherein the frequency of the AC signal is larger than the response frequency of the liquid crystal.

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