JPH0784554A - Liquid crystal display - Google Patents

Abstract

(57) [Summary] [Object] To provide a liquid crystal display device capable of performing high-quality image display by solving the problem of display unevenness (crosstalk) on a screen by a simple and inexpensive means. [Configuration] A transmission path from the detection electrode 13 of the voltage detected from the scanning electrode 1 through the electric capacitance 12 (or electric resistance) to the operational amplifier circuit 9, that is, the wiring 14 and the detection electrode 1
The variation due to the impedance of No. 3 and the variation due to the mixing of electromagnetic noise from the outside are prevented by the guard electrode 15 and the guard electrode voltage generation circuit 16 to accurately detect the scan electrode voltage and extract the distortion voltage. By performing good feedback control, the waveform distortion of the liquid crystal drive voltage can be effectively removed, and the crosstalk of image display can be eliminated.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a liquid crystal display device.

[0002]

2. Description of the Related Art Liquid crystal display devices are widely used as information processing devices such as word processors and personal computers, and display devices such as small televisions and projection type televisions by taking advantage of features such as thinness and low power consumption. . As a liquid crystal display element in such applications,
It can be roughly divided into two types, the simple matrix type and the active matrix type.

A simple matrix type liquid crystal display device is
Since it has a simple structure including the structure of the liquid crystal display panel and can easily manufacture large-sized ones at a low manufacturing cost, it is used in a wide range of applications.

Further, the active matrix type liquid crystal display device, for example, utilizes a characteristic that a high-definition and high-contrast clear image can be displayed, and for example, a VGA (Video Grap).
It is also used as a high-definition liquid crystal display device such as a display device called hicArray) compatible display device or a CG (Computer Graphics) compatible display device.

A liquid crystal display device used for such a display device is required to have multi-digit display and high-quality display. In order to meet such demands, in recent years, the number of pixels (the number of scanning electrodes × the number of signal electrodes) of a simple matrix type liquid crystal display element represented by an STN (Super Twisted Nematic) type liquid crystal display element has significantly increased. Further, along with this, the driving frequency of the liquid crystal display element (frequency of driving voltage pulse) is also increasing.

For example, there are 200 scanning electrodes and 640 signal electrodes.
The two-valued liquid crystal display element has a time equivalent to the scanning time for one scanning electrode, that is, the minimum pulse width of the driving voltage is 60
It is as short as ~ 70μs.

In general, the liquid crystal cell for each pixel of the liquid crystal display element can be represented as a capacitor (electric capacity) in an equivalent circuit. Further, the driver IC for driving the liquid crystal display element has an output impedance, which can be generally expressed as an electric resistance by an equivalent circuit. The simple matrix type liquid crystal display device is driven by a combination of square wave pulses.
Distortion or dullness occurs in the drive voltage waveform due to the output resistance of C, the connection resistance between the driver IC and the liquid crystal display element, the drive electrode resistance of the liquid crystal display element, and the capacitance of the liquid crystal layer. The distortion and dullness of these drive voltage waveforms are
The voltage applied to the liquid crystal layer lowers or rises, which results in a positional variation in the light transmittance within the screen of the liquid crystal display element, which is a phenomenon of display unevenness called so-called crosstalk on the screen. Appear in. It can be said that the fluctuation of the liquid crystal applied voltage caused by the distortion voltage generated in the scanning electrodes is most involved in the occurrence of crosstalk in the simple matrix liquid crystal display element. Therefore, this phenomenon will be described with an example.

FIG. 8A shows an equivalent circuit in which one scanning electrode of a conventional XY simple matrix type liquid crystal display device is partially extracted. Here, C _LC is the scan electrode Y
_{n is} the capacitance 901 of the liquid crystal layer for one electrode, and R is the output resistance of the scan electrode driver, the connection resistance of the driver IC and the liquid crystal display element, and the internal resistance of the electrode itself of the scan electrode Y _n of the liquid crystal display element. Is the total electrical resistance 902.

The liquid crystal display device is usually driven by an alternating liquid crystal applied voltage. Here, it is assumed that a scan electrode driver (not shown) outputs a scan selection pulse whose polarity is inverted around the reference potential Vcom and a non-scanning selected voltage whose polarity is inverted between ± Vrev. The waveform of such a scanning voltage V2 is shown in FIG. Further, it is assumed that the signal electrode driver (not shown) outputs a signal voltage V1 having a waveform in which the polarity is inverted between ± Vrev as shown in FIG. 8B.

In this equivalent circuit, a square-wave-shaped signal voltage V1 is applied from the signal electrode driver side to the electrostatic capacitance 901 of the liquid crystal layer.
In consideration of the case where the voltage is applied to, a spike-like strain voltage V3 based on the time constant C _LC · R is generated at the connection point 903 between the liquid crystal layer (C _LC ) 901 and the total electric resistance (R) 902. The waveform of this distortion voltage V3 is shown in FIG. Since the spike-like distortion voltage V3 is generated, the liquid crystal applied voltage applied to the liquid crystal layer C _LC 901 is as shown in FIG.
As shown in (e), the waveform corresponding to the spike-like strain voltage V3 is cut off. Such a voltage change appears as uneven display on the screen, so-called crosstalk.

Further, a transparent electrode made of tin oxide or ITO (indium oxide) is generally used as a scanning electrode or a signal electrode used inside a liquid crystal display element. Such a transparent electrode has an electric resistance. Because it is relatively large,
The above-mentioned waveform rounding and distortion voltage are more remarkably generated in these electrodes.

In order to solve the above problem of display unevenness, for example, as a technique for STN type liquid crystal display element, as disclosed in JP-A-2-71718 and SID'90 Digest p.413, A method of forming a compensation voltage to be applied to the scan electrode driver based on the display data output from the signal electrode driver and appropriately changing the compensation voltage to cancel the distortion voltage at the output terminal of the scan electrode driver has been studied. ing.

However, as described above, the conventional technique does not fundamentally eliminate the influence of the connection resistance between the driver IC and the liquid crystal display element, the resistance of the driving electrode of the liquid crystal display element, and the like. Correspondingly, the distortion voltage is canceled out based on a minute compensation voltage that is set in advance. For example, in the case of a device that changes the contrast by changing the liquid crystal drive voltage or a device that expresses gradation, Since the magnitude of the distortion voltage also changes as the driving voltage changes, the initially set compensation voltage deviates from the optimum compensation value, and effective compensation is difficult. Alternatively, it may be considered to add an adjustment circuit that resets the optimum compensation voltage each time, but when incorporating a circuit that has such an adjustment circuit and performs delicate setting of the compensation voltage based on the display data. However, there is a problem that the structure of the liquid crystal drive circuit system becomes very complicated.

Regarding the problem of the internal resistance of the transparent electrode described above, from the viewpoint of making the voltage waveform uniform on the transparent electrode, the transparent electrode is formed by arranging metal wiring in parallel beside the transparent electrode. It is conceivable to reduce the apparent resistance of (1) to suppress the occurrence of distortion of the waveform of the distortion voltage and the voltage applied to the liquid crystal.

However, in such a method, there are problems that the internal structure of the liquid crystal display element including the vicinity of the transparent electrode is complicated, the manufacturing is not easy, and the manufacturing cost is high.

Further, in order to suppress the distortion of the voltage waveform and the dullness of the voltage applied to the liquid crystal, the driver IC having a very small output resistance.
However, there is a problem that development of such a special driver IC is not easy, and the use thereof is not practical because the price is expensive.

[0017]

As described above, in the conventional liquid crystal display device, the output resistance of the driver IC, the connection resistance between the driver IC and the liquid crystal display element, the driving electrode resistance of the liquid crystal display element, and the liquid crystal layer. The waveform of the liquid crystal applied voltage changes from the ideal waveform due to the distortion voltage generated due to the capacitance of the
There was a problem that occurs.

In the known technique devised against this, there is a problem that the preset compensation voltage deviates from the required optimum compensation voltage due to a disturbance such as temperature change or noise, and the apparatus is complicated or expensive. There was a problem such as becoming.

The present invention has been made to solve such a problem, and an object thereof is to solve the problem that display unevenness (crosstalk) occurs on the screen of a liquid crystal display device by a simple and inexpensive means. Another object of the present invention is to provide a liquid crystal display device capable of displaying high-quality images.

[0020]

In order to solve the above-mentioned problems, a liquid crystal display device of the present invention intersects with a scanning electrode substrate having a plurality of scanning electrodes formed thereon while maintaining a gap between the plurality of scanning electrodes. And a liquid crystal display element having a liquid crystal layer sandwiched between the scanning electrodes and the signal electrodes and a signal electrode substrate formed with a plurality of signal electrodes facing each other, and generating a scanning voltage. In a liquid crystal display device having a scan driver circuit for applying to the scan electrodes and a signal driver circuit for generating a signal voltage and applying the signal voltage to the signal electrodes, an electric capacity or an electric capacitor having one end connected to each of the plurality of scan electrodes. A resistance, a detection electrode that is connected to the electric capacitance or the other end of the electric resistance, and detects the voltage of the scan electrode in a portion to which the other end is connected, and the scan electrode with the detection electrode. A distortion voltage component is extracted from the detected voltage to be fed back to the scan electrode, and an operational amplifier circuit that suppresses the generation of the distortion voltage of the plurality of scan electrodes, one end of which is connected to the detection electrode and the other end of which is A wire that is connected to the operational amplifier circuit and transmits the voltage detected by the detection electrode to the operational amplifier circuit; and a wiring that is substantially parallel to the wire and the detection electrode along at least a part of the wire and the detection electrode. By applying a voltage to the guard electrode arranged in parallel and in a non-contact manner and the guard electrode, the impedance of the wiring and the detection electrode is controlled, and the electromagnetic noise from the outside is prevented from being mixed into the wiring and the detection electrode. And a guard electrode voltage generating circuit.

It should be noted that the return destination of the distorted voltage component extracted from the voltage detected by the detection electrode by the above-mentioned operational amplifier circuit and fed back to the scanning electrode may be the scanning electrode finally, and the scanning electrode can be fed back to the scanning electrode. Alternatively, the output of the operational amplifier circuit may be directly fed back, or the output of the operational amplifier circuit is once input to the circuit, and the distortion voltage component is superimposed on the scan voltage inside the scan voltage wiring circuit. It may be applied to the scanning electrodes and returned. However, in any case, when the distortion voltage component extracted by the operational amplifier circuit is fed back to the scan electrode, the distortion voltage of the scan electrode can be effectively suppressed so that the operational amplifier circuit It goes without saying that it is desirable to set the amplification factor and the polarity of its output to appropriate values.

Further, the above-mentioned capacitance may be formed by using the scanning electrode and the signal electrode as two electrodes facing each other and by using a liquid crystal layer as a dielectric material sandwiched between the two electrodes.

The guard electrode may be provided on either the wiring or the detection electrode, or may be provided on only one of them. Further, it may be arranged along at least a part of the wiring or the detection electrode, or may be arranged along the whole. For example, the guard electrode may be provided only in the portion where the electromagnetic interference is the largest, or may be provided in its entirety so as to protect the entire wiring and the detection electrode from the electromagnetic interference.

The guard electrode may be formed along the wiring or the detection electrode so as to cover the periphery thereof, or may be sandwiched from both sides in parallel with the wiring or the detection electrode in plan view. You may arrange two.

The voltage applied to the guard electrode by the guard electrode voltage generating circuit may be, for example, an AC voltage waveform having the same polarity as the liquid crystal applied voltage waveform, or fixed to the polarity reversal center potential of the liquid crystal applied voltage. It may be a different potential. The AC voltage waveform having the same polarity as the liquid crystal applied voltage waveform is preferable because a more effective guard action, that is, an impedance control action and a noise mixing action can be obtained.

[0026]

In the liquid crystal display device according to the present invention, a voltage is detected from a plurality of scanning electrodes by a detection electrode through an electric capacitance, and an image display such as a spike-shaped distortion voltage generated in the detected voltage of the scanning electrode is displayed. It is possible to suppress a distortion voltage or the like that is to be generated in the scan electrode by extracting a voltage change component that has an unfavorable effect on the scan electrode, that is, a distortion voltage component, by feeding back to the scan electrode by the operational amplifier circuit.

At this time, needless to say, the operational amplifier circuit is set to have a polarity (displacement direction of the output voltage) and an amplification factor that can cancel the distortion voltage generated in the scan electrodes.

Further, although an electric capacitance or an electric resistance is provided for detecting the strain voltage in the liquid crystal display element, the electrostatic capacitance component or the resistance component of the electric capacitance or the electric resistance is very small. Therefore, in order to obtain an accurate waveform of the distorted voltage component at the detection electrodes collectively from the detection capacitance or resistance, the wiring that transmits the detected voltage to the operational amplifier circuit and the input impedance of the detection electrodes must be It must be sufficiently higher than the impedance of the detection capacitance or resistance. When detecting such a high-impedance signal, it is also generally known to shield the wiring system that transmits the detected voltage to prevent voltage fluctuation due to disturbance. However, simply shielding such a wiring causes a parasitic capacitance between the wiring and the shield, and equivalently reduces the impedance of the wiring and the detection electrode. Then, such an effective reduction in the input impedance of the wiring and the detection electrode causes a fluctuation in the detected voltage. For example, the input impedance of an operational amplifier circuit formed by using a semiconductor integrated circuit decreases as the temperature rises, but the presence of parasitic capacitance emphasizes the temperature dependence of the input impedance.

Therefore, in the present invention, a guard electrode is arranged on at least a part of the wiring and the detection electrode from the electric capacitance or electric resistance for detecting the distortion voltage to the operational amplifier circuit, and the guard electrode has the same polarity as the liquid crystal drive voltage waveform. AC voltage is applied. By applying such a voltage to the guard electrode, the voltage of the detection electrode that detects the strain voltage and the wiring that transmits it becomes almost the same as the voltage of the guard electrode that is placed around it. Is eliminated, and it is electrically equivalent to the fact that only the input impedance of the operational amplifier circuit is connected to the electric capacitance or electric resistance for detecting the distorted voltage. In this way, it is possible to suppress the voltage fluctuation of the signal which is greatly affected by the impedance such as the distortion voltage generated in the scan electrodes.

Further, since the guard electrode also has the effect of an electromagnetic shield for preventing the entry of electromagnetic noise from the outside, a great effect can be obtained by removing crosstalk.

As described above, fluctuations due to the impedance of the transmission system, that is, the wiring or the detection electrode, of the voltage detected from the scanning electrode to the operational amplifier circuit via the electric capacity or the electric resistance, or the mixing of electromagnetic noise from the outside. A guard electrode and a guard electrode voltage generation circuit prevent variations due to the above conditions, so that the scan electrode voltage can be accurately detected and the distortion voltage can be extracted.

As a result, no matter what value the voltage applied from the drive voltage power supply circuit to the liquid crystal cell (liquid crystal layer) is changed, or the voltage changes depending on the temperature change or the time change of the liquid crystal layer. Even if it changes like this, or if electromagnetic noise is mixed in from the outside, the strain voltage component is always extracted accurately without suffering the adverse effects of such disturbances and the voltage fluctuations caused by the impedance of the wiring and detection electrodes. Therefore, display unevenness (crosstalk) or the like on the screen can always be effectively eliminated.

Further, according to the present invention, one feedback loop is provided in the scan electrode and the drive voltage generating circuit thereof, that is, the feedback is mainly constituted by the electric resistance or capacitance, the detection electrode, the operational amplifier circuit and the like. Since it is only necessary to form a loop, it is possible to realize a liquid crystal display device capable of displaying high-quality images very easily and inexpensively.

Alternatively, a voltage fixed to the center potential of the liquid crystal driving voltage may be applied to the guard electrode.

[0035]

Embodiments of the liquid crystal display device of the present invention will be described in detail below with reference to the drawings.

(Embodiment 1) FIG. 1 is a diagram schematically showing the structure of a liquid crystal display device according to a first embodiment of the present invention. This liquid crystal display device includes a liquid crystal display element (liquid crystal display panel) 4 in which scanning electrodes 1 and signal electrodes 2 made of a transparent electrode such as ITO are arranged in a matrix so as to face each other, and a liquid crystal layer 3 is sandwiched between the scanning electrodes 1. , And has a scan driver circuit 5 and a signal driver circuit 6 for driving it.

The scan driver circuit 5 includes a scan electrode driving section 7
And a scanning voltage power supply circuit 8 for supplying a power supply voltage thereto and an operational amplifier circuit 9 for receiving the feedback voltage and controlling the scanning voltage. The signal driver circuit 6 also includes a signal electrode driving unit 10 and a signal voltage power supply circuit 11 that supplies a power supply voltage to the signal electrode driving unit 10.

Further, in the liquid crystal display element 4, the electric capacitance 12 is provided at each end of each scanning electrode 1. These electric capacitances 12 are electrically connected at one end to the scanning electrode 1 as described above, and at the other end to the detection electrode 13 collectively, and detect the voltage of the scanning electrode 1 detected by the electric capacitance 12. They are collected together and connected to the operational amplifier circuit 9 of the scan driver circuit 5 via the wiring 14. With such an electrical structure, the distortion voltage component generated in the scan electrode 1 is extracted by the operational amplifier circuit 9 and fed back to the scan electrode 1 as a voltage for canceling the distortion voltage of the electrode 1, so that the voltage of the scan electrode 1 is It is possible to accurately and effectively eliminate the generation of the distortion voltage, regardless of how it is affected by the disturbance. This can eliminate crosstalk in the display image.

The voltage collectively detected by the detection electrode 13 is transmitted to the operational amplifier circuit 9 through the wiring 14, and the portion of the wiring 14 extending over substantially the entire length and the detection electrode 1 are detected.
A guard electrode 15 is provided in the vicinity of the connection portion between the wiring 3 and the wiring 14 in a non-contact manner along the connection portion. The guard electrode 15 is connected to the guard electrode voltage generation circuit 16. Then, the guard electrode voltage generation circuit 16 generates a voltage having the same polarity as the liquid crystal drive voltage (here, the scanning voltage) and a similar waveform, and applies the voltage to the guard electrode 15 to cause the operational amplifier circuit 9 to operate.
It operates so as to control the impedance of the wiring 14 and the detection electrode 13 up to, and removes noise from the outside. In this way, fluctuations in the detection voltage due to the impedance of the wiring 14 and the detection electrode 13 and fluctuations due to the mixing of electromagnetic noise from the outside are prevented by the guard electrode 15 and the guard electrode voltage generation circuit 16, and the scanning electrode voltage is accurately measured. Accurate extraction of the distortion voltage is performed by performing detection.

The outline of the electrical structure of the liquid crystal display device according to the present invention has been described above. Next, the specific structure and operation of the embodiment of the liquid crystal display device according to the present invention will be described in detail.

As the liquid crystal display element 4, an STN type liquid crystal display element was used. The screen size is A4 half size, and the display capacity (number of pixels) is 640 x 200 dots. The cell gap of this STN type liquid crystal display element 4 is about 7 μm, and an alignment film (not shown) made of a resin subjected to rubbing alignment treatment is provided, and liquid crystal molecules of the liquid crystal layer 3 are provided between the cell gaps of the liquid crystal display element 4. Are oriented to twist 240 °. Liquid crystal layer 3
ZLI-2293 manufactured by Merck was used as the liquid crystal composition. Further, the transparent electrodes of the scan electrode 1 and the signal electrode 2 are IT
It is formed from O. In the liquid crystal display device of the present embodiment, the optical phase compensation cell 202 is provided on the glass substrate 203 on the outward side of the liquid crystal display element in order to display black and white.
It was pasted on (a) and (b) so that black display was obtained when no voltage was applied and white display was obtained when voltage was applied. The structure of such a liquid crystal display element 4 is shown in FIG. Glass substrate 203
(B) The electric capacitance 12 is arranged at the end portion of each scanning electrode 1 provided above, as described above. This capacitance 1
2 is a detection electrode 13 and a scanning electrode which are substantially the same as the signal electrode 2 provided on the glass substrate 203 (a) so as to face the end of the scanning electrode 1 with the liquid crystal layer 3 interposed therebetween. It is formed by using the liquid crystal layer 3 sandwiched between 1 and 1 as a dielectric.

As is clear from FIG. 2, the capacitance 12 is formed by using the open end of the scanning electrode 1 and the detection electrode 13 as electrodes and the liquid crystal layer 3 sandwiched between the electrodes as a dielectric. Therefore, the liquid crystal display element 4 of the present embodiment is the detection electrode 1
The structure of the conventional liquid crystal display element need not be changed by only adding 3, and it can be manufactured extremely easily.

FIG. 3 is a block diagram showing the overall structure of the liquid crystal display device of this embodiment. A scan driver circuit 5 and a signal driver circuit 6 are connected to the scan electrodes 1 and the signal electrodes 2 in the liquid crystal display element 4, respectively. The scan driver circuit 5 generates a distortion voltage component from the scan electrode driving unit 7, a scan voltage power supply circuit 8 for supplying a power supply voltage to the scan electrode driving unit 7, and a voltage detected by the detection electrode 13 from the scan electrode 1 through the electric capacity 12. The signal driver circuit 6 has an operational amplifier circuit 9 for extracting and feeding back to the scan electrode 1, and the signal driver circuit 6 has a signal electrode drive unit 10 and a signal voltage power supply circuit 11 for supplying a power supply voltage to the signal electrode drive unit 10. There is. And the scan driver circuit 5
A guard electrode voltage generator 16 is formed inside. In FIG. 3, the scanning voltage power supply circuit 8 and the signal voltage power supply circuit 1
1 is divided and shown for easier understanding of the illustration and description, but in practice (actual circuit structure) is configured as one. This is because the structure can be simple, accurate, and inexpensive by combining them into one. In this embodiment, the circuit integrated into this one is configured as a drive voltage power supply circuit 401 as shown in FIG.

The scan electrode driver 7 receives the control signal from the scan data generating circuit 402 and outputs the output potentials of Y1 to Y200 of the scan electrode 1 to V0Y, V1, V4,
Select one from V5Y. Specifically, as shown in FIG. 3, a shift register 40 that sequentially transfers scan data is used.
3 and a switch section 404 for selecting the scanning potential when scanning is selected, that is, the scanning pulse (V0Y, V5Y) or the scanning potential (V1, V4) when not scanning is selected by this data. Receives FP (frame pulse) which determines one frame time as basic scanning data, and transfers data from outputs Y1 to Y200 based on LP (latch pulse) which determines one scanning time. In the switch unit 404, based on these transferred data, the selection potential V0Y (potential V5Y at the time of polarity reversal at the time of alternating current driving) is selected data if it is selected data, and the non-selection potential V4 (when alternating current driving is performed at the time of non-selected data) When the polarity is inverted, the potential V1) is selected and output to each scan electrode 1. In this way, for example, a scan electrode driving waveform by a general voltage averaging method as shown in FIG. 5A is obtained.

On the other hand, the signal electrode driving section 10 receives the signal from the video signal data generating circuit 405 and receives the signal electrode 2
The output potential of each of X1 to X640 of V0, V2
, V3, or V5, select and set one. Specifically, as shown in FIG. 3, a shift register 406 for sequentially transferring video signal data, a data latch 407 for temporarily storing this data, a signal selection potential (V0, V5) for designating ON display by this data, or A switch unit 4 for selecting a signal non-selection potential (V2, V3) designating OFF display
08, and the shift register 406 includes video signal data (indicated as DATA in the drawing, hereinafter referred to as DATA).
In response to this, DATA is transferred from X1 to X640 by the clock pulse CP for transferring this DATA.
The data latch 407 receives LP (latch pulse) and accumulates DATA from X1 to X640. In the switch unit 408, based on the accumulated DATA, if DATA is selected (on) data, the selection potential V5
(Or potential V0 at the time of polarity reversal during AC drive)
If non-selected data (OFF) is selected, the non-selected potential V3 (or the potential V2 at the time of polarity reversal during AC driving) is selected and output to each signal electrode 2. Thus, for example, in FIG.
A signal electrode drive waveform is obtained by a general voltage averaging method as shown in (b).

When the drive voltage is applied to each of the scanning electrode 1 and the signal electrode 2 as described above, the voltage waveform applied to the liquid crystal layer 3 has a polarity inversion as shown in FIG. With this waveform, the amplitude of the selected pulse changes according to the display contents (ON, OFF).

As is well known, the polarity inversion driving method is a driving method which is performed by using an alternating liquid crystal applied voltage in order to prevent deterioration of the liquid crystal composition due to application of a direct current voltage component to the liquid crystal layer. A reference voltage generating circuit 409 having a function of inverting the polarity in a constant cycle is added to the switch units 404 and 408 of the scan electrode driving unit 7 and the signal electrode driving unit 10 described in FIG. ), The liquid crystal applied voltage having the waveform shown in FIG. 5 is obtained by controlling the FR (polarity inversion) signal.

The drive voltage power supply circuit 401 receives the power supply voltage VDD input from the power supply and receives the liquid crystal drive voltage potentials (V0, V1, V) generally required for driving the liquid crystal display element 4.
2, V3, V4, V5, V0Y, V5Y) and output. Of these potentials, V0Y, V1, V4 and V5Y are supplied to the scan electrode driving section 7, and V0, V2, V3 and V5 are supplied to the signal electrode driving section 10, respectively.

An operational amplifier circuit 9 for controlling the distortion of the voltage of the scan electrode 1 is formed in the drive voltage power supply circuit 401, and only the distortion voltage component of the voltage detected by the detection electrode 13 is calculated. It is extracted by the amplifier circuit 9 and fed back to the scan electrode 1. The voltage detected by the detection electrode 13 passes through the wiring 14 and the buffer 410 in the drive voltage power supply circuit 401 as shown in FIG.
1 is input to the non-inverting terminal 412 side. Then, in order to extract only the distorted voltage component from the alternating-current changing detection voltage collectively detected from the scanning electrode 1 by the detecting electrode 13, it changes in synchronization with the polarity inversion signal FR and the voltage dividing circuit 4
A reference voltage Vref having an amplitude substantially equal to the amplitude of the potential of the scanning voltage output from 13 is produced, and this is subtracted from the detection voltage. The reference voltage Vref has a voltage waveform such that the potential changes in synchronization with the scanning voltage as shown in FIG.
The reference voltage Vref is input to the inverting terminal 414 of the differential amplifier 411 as a reference voltage for extracting the distortion voltage component of the scan electrode 1. The differential amplifier 411 calculates the difference between the detected voltage and the reference voltage Vref, and amplifies the difference based on the amplification factor set by the resistor 415 or the like to extract the distortion voltage component generated in the scan electrode 1. To do. Then, the extracted strain voltage component is the electric resistance R
Negative amplification factor set by 1, R2, R3, R4
Four operational amplifiers 416 (a), (b), (e),
In (f), capacitors 417 (a), (b), (c),
It is input via the capacitive coupling according to (d). Here, the four operational amplifiers 416 (a), (b), and the four operational amplifiers 416 (a), (b), which are connected via the capacitive coupling by the capacitor 417
When the input sides of (e) and (f) are electrically connected to one wiring, the potentials V0Y, V1, and V4 output from the voltage dividing circuit 413 are output.
, V5Y are short-circuited, and in order to avoid this, it is necessary to separate each from the DC voltage component.

Operational amplifiers 416 (a), (b),
(E) and (f) are potentials V0Y, V1 output from the voltage dividing circuit 413 as potentials for forming the scanning voltage waveform.
The extracted distortion voltage components are inverted and superimposed on V4 and V5Y by inverting the displacement direction and output to the switch unit 404. Then, the switch section 404 outputs the scan voltage to each scan electrode 1 as described above. In this way, the scanning voltage from which the voltage corresponding to the distortion voltage component is subtracted in advance is applied from the scanning electrode driving unit 7 to the scanning electrode 1, and the distortion voltage generated in the voltage of the scanning electrode 1 can be eliminated. Here, as the operational amplifier circuit 9 described above, in this embodiment, a differential amplifier 411 to which a detection voltage is input via a buffer 410 and a buffer 416 using an operational amplifier.
Is formed by.

The reference voltage Vref is formed by the reference voltage generating circuit 409 which is switched based on the FR signal and used as the reference voltage of the operational amplifier circuit 9 as described above, while the guard formed by using the operational amplifier. The voltage is amplified by the electrode voltage generation circuit 16 and applied to the guard electrode 15 as a voltage having the same polarity as the liquid crystal drive voltage (scanning voltage) and the same waveform. Here, for simplification of description, the reference voltage generation circuit 409 and the guard electrode voltage generation circuit 1
Although 6 and 6 are shown separately, one of them may be provided with these functions in practice.

As the guard electrode 15 and the wiring 14,
Using a wiring material similar to the wiring 14, the wiring 14 is planarly formed.
May be formed in a pattern so as to be sandwiched from both sides in a non-contact manner, or may be formed using a coaxial shielded cable. In this embodiment, the guard electrode 15 and the wiring 14 are specifically formed by a coaxial shielded cable. In this case, the outer conductor of the shield wire corresponds to the guard electrode 15,
The center conductor corresponds to the wiring 14, and the guard electrode 15 is the wiring 1.
4 will be coated so as to surround the periphery.

As described above, since the voltage of the guard electrode 15 changes in the same polarity as the scanning voltage, the parasitic capacitance of the wiring 14 sandwiched (or surrounded) by the guard electrode 15 is eliminated. It becomes equivalent, and the detected voltage from the scanning electrode 1 received by the detection electrode 13 does not fluctuate in the wiring 14 in the middle even if the ambient temperature is changed, and the impedance from the detection electrode 13 to the wiring 14 is electrically obtained. This is equivalent to directly transmitting to the operational amplifier circuit 9 as it is. Therefore, the detection voltage from the scanning electrode 1 received by the detection electrode 13 can be accurately transmitted to the operational amplifier circuit 9, and the distortion voltage can be accurately extracted.

In the liquid crystal display device according to the present invention as described above, a duty ratio of 1/200, a bias ratio of 1/13 and a frame frequency are used by using a liquid crystal driving voltage having a waveform as shown in FIG.
Display was performed by driving at 80 Hz so that the polarity was reversed every 13 lines, and the display quality was visually verified.

First, after displaying the entire screen in white, a horizontal stripe pattern of white and black is displayed in an area of vertical 150 dots × horizontal 10 dots near the center of the screen, and then the number of horizontal dots in this area is set to 5
The number was gradually increased to 00 dots, but in each case, a uniform display without crosstalk could be maintained. Also,
Although Chinese characters and alphabets were displayed continuously, the generation of strain voltage on the scan electrodes was suppressed, and a uniform display without crosstalk could be maintained. After such a test was continuously lit for 2000 hours, the same display as above was displayed, but in this case as well, a uniform display without crosstalk could be maintained.

Next, the ambient temperature of the liquid crystal display device of the present embodiment is
When the temperature was raised from 25 ° C. to 60 ° C. and the above-mentioned display was performed, it was possible to maintain a uniform display without crosstalk as in the above.

Further, the ambient temperature is 60 ° C. and the humidity is 90%.
When the display was performed under the environment of RH and the same display as described above was performed, it was possible to maintain a uniform display without crosstalk.

Although shielded cables are used as the guard electrodes 15 and the wirings 14 in the above-mentioned embodiment, a multilayer printed wiring board may be used instead.
In other words, the simplest is the so-called 3-layer pudding and wiring board.
The wiring 14 is formed on the second conductive layer in the middle of the three conductive layers.
And the guard electrodes 15 are arranged on both sides thereof. Further, the first layer and the third layer can be formed as a power supply layer and a ground layer, respectively, so as to cover the guard electrode 15 and the wiring 14 from both sides. With such a structure, the same effect as described above can be obtained.

(Embodiment 2) In the liquid crystal display device of the first embodiment, the wiring 14 is sandwiched between the guard electrodes 15 (a) and (b) as in the first embodiment, and as shown in FIG. The second guard electrodes 701 (a) and (b) were placed along the both sides of the detection electrode 13 inside the liquid crystal display element 4 along substantially the entire length. At this time, the guard electrodes 15 (a) and (b) and the second guard electrodes 701 (a) and (b) were formed as one continuous electrode although the widths were different. Then, the guard electrodes 15 (a) and (b) and the second guard electrode 701
(A) and (b) were connected to the guard electrode voltage generation circuit 16.

With such a structure, the transmission path from the detection electrode 13 to the operational amplifier circuit 9, that is, the wiring 14 is formed.
Not only that, the shield effect of the detection electrode 13 is further improved as compared with the first embodiment, crosstalk is more effectively eliminated, and good display can be realized.

(Embodiment 3) In the liquid crystal display device of the first embodiment, the input buffer 410 and the connection wirings and the like attached thereto are formed by TAB (Tape Automated Bonding) -IC8.
It was built in 01 and mounted by the TAB method. Further, the scan driver circuit 5 and the signal driver circuit 6 are replaced by a liquid crystal driver IC.
Built in 802. Then, the TAB-I of the detection electrode 13
Guard electrodes 803 (a) and (b) were formed along the vicinity of the connection portion (root portion) with C801. Then, the guard electrodes 803 (a) and 803 (b) were connected to the guard electrode voltage generation circuit 16.

Even with such a configuration, a screen without crosstalk could be displayed. FIG. 8 shows the outline of the main part of the structure of this embodiment.

A differential amplifier 41 as in the third embodiment.
1 or the like is formed in the TAB-IC 801, and the scan driver circuit 5 and the signal driver circuit 6 are formed in the liquid crystal driver IC 802 mounted by the TAB, so that at least the length of the wiring 14 up to the input buffer 410 is obtained. The length of the guard electrodes 803 (a) and (b)
Compared with the case of the above-mentioned first embodiment, it can be further largely omitted, and the structure of the liquid crystal display device can be made simple and inexpensive.

Even if the guard electrode voltage generating circuit 16 is formed in the chip of the TAB-IC 801, the same effect as described above can be obtained.

In addition to the TAB method as the mounting method, if an IC having the same circuit as the above can be mounted, for example, a chip carrier such as LCC or PLCC or a bare chip such as COG or COB. It goes without saying that various methods other than the above can be used, including the surface mounting method that can increase the mounting density such as mounting.

(Embodiment 4) In the liquid crystal display device of the first embodiment, instead of applying an alternating voltage of a waveform which changes with the same polarity as the scanning voltage waveform to the guard electrode 15, the center of the scanning voltage waveform is applied. An electric potential was applied. Even with this method, crosstalk was eliminated and good display was realized.

Besides the above, the fixed potential applied to the guard electrode 15 may be ground or a fixed potential other than the above (for example, power supply voltage). When such a fixed potential is used, the guard electrode drive circuit 16 can be simplified and the device can be made inexpensive.

(Comparative Example) The detection electrode 13 and the operational amplifier circuit 9 are removed from the liquid crystal display device of the first embodiment, and the drive voltage power supply circuit 401 is divided into a voltage dividing circuit 413 and a buffer 601 (a) as shown in FIG. , (B), (c), (d),
The drive voltage power supply circuit 600 of the conventional general structure using (e) and (f) is replaced. A liquid crystal display device having such a conventional structure was made to perform display under the same driving conditions as in the first embodiment, and the display quality was visually verified.

First, after displaying the entire screen in white, a horizontal striped pattern of black and white is displayed in an area of vertical 150 dots × horizontal 10 dots near the center of the screen, and then the number of horizontal dots in this area is set to 5
I gradually increased it to 00 dots, but when a white and black horizontal stripe pattern was displayed in an area of vertical 150 dots × horizontal 10 dots, dark crosstalk occurred in the vertical direction and the display area As the number of dots in the horizontal direction of was increased, this vertical crosstalk occurred more significantly.
In addition, new crosstalk occurs in the horizontal direction of the display,
The display quality is significantly degraded. In addition, Chinese characters and alphabets were displayed continuously, but in this case as well, remarkable crosstalk in the vertical and horizontal directions occurred, and the nonuniformity of the screen was noticeable.

Further, in the liquid crystal display device of the first embodiment, when the voltage applied to the guard electrode 15 is stopped to actually stop the function, the distortion voltage is extracted more than in the case of the first embodiment. It is considered that this is also due to inaccuracy, but unlike the case of the first embodiment, crosstalk was found on the display screen.

[0071]

As is clear from the detailed description above, the liquid crystal display device of the present invention eliminates the display unevenness caused by the waveform rounding of the liquid crystal applied voltage, and provides a uniform and good display without crosstalk. Can be realized.

[Brief description of drawings]

FIG. 1 is a diagram schematically showing a configuration of a liquid crystal display device of the present invention.

FIG. 2 is a diagram schematically showing a liquid crystal display element used in the liquid crystal display device of the present invention.

FIG. 3 is a block diagram showing an overall circuit configuration of a liquid crystal display device of the present invention.

FIG. 4 is a diagram showing a drive voltage power supply circuit of a liquid crystal display device according to the present invention.

FIG. 5 is a diagram showing a liquid crystal drive voltage waveform used in the liquid crystal display device of the present invention.

FIG. 6 is a FR signal used in the liquid crystal display device of the present invention;
The figure which shows the waveform of a reference voltage, a scanning voltage, and a guard electrode drive voltage.

FIG. 7 is a diagram schematically showing a liquid crystal display element portion of a guard electrode of the liquid crystal display device of Example 2.

8A and 8B are diagrams schematically showing a TAB of a guard electrode drive unit formed into an IC chip and a liquid crystal display element portion of the guard electrode in the liquid crystal display device of Example 3.

FIG. 9 is a diagram showing a drive voltage power supply circuit used in a liquid crystal display device of a comparative example. Force buffer

FIG. 10 is a conceptual diagram in which only one scanning electrode 1 of a conventional liquid crystal display device is extracted and expressed by an equivalent circuit and its V
The figure which shows the voltage waveform of 1, V2, and V3.

[Explanation of symbols]

DESCRIPTION OF SYMBOLS 1 ... Scan electrode, 2 ... Signal electrode, 3 ... Liquid crystal layer, 4 ... Liquid crystal display element, 5 ... Scan driver circuit, 6 ... Signal driver circuit, 7 ... Scan electrode drive part, 8 ... Scan voltage power supply circuit, 9 ...
Operational amplifier circuit, 10 ... Signal electrode drive unit, 11 ... Signal voltage power supply circuit, 12 ... Electric capacity, 13 ... Detection electrode, 14 ... Wiring, 15 ... Guard electrode, 16 ... Guard electrode voltage generation circuit, 204 ... Scan electrode voltage Detection unit, 401 ... Driving voltage power supply circuit, 409 ... Reference voltage Vref. Generation switch, 410
... buffer, 411 ... differential amplifier, 416 ... operational amplifier

Claims (1)

[Claims] 1. A scan electrode substrate on which a plurality of scan electrodes are formed, and a signal electrode substrate on which a plurality of signal electrodes are formed to face each other so as to intersect the plurality of scan electrodes while maintaining a gap therebetween. A liquid crystal display element having a liquid crystal layer sandwiched between the scan electrodes and the signal electrodes, a scan driver circuit for generating a scan voltage and applying the scan voltage to the scan electrodes,
In a liquid crystal display device having a signal driver circuit for generating a signal voltage and applying the signal voltage to the signal electrode, an electric capacitance or an electric resistance whose one end is connected to each of the plurality of scan electrodes, and an electric capacitance or an electric resistance A detection electrode that is connected to the other end and collectively detects the voltage of the scan electrode in the portion to which the other end is connected, and a distortion voltage component is extracted from the voltage detected from the scan electrode by the detection electrode. An operational amplifier circuit that feeds back to the scan electrodes and suppresses the generation of a distortion voltage of the plurality of scan electrodes; one end is connected to the detection electrode and the other end is connected to the operational amplifier circuit, and detection is performed by the detection electrode. A wiring for transmitting the generated voltage to the operational amplifier circuit, and a non-contact arrangement along at least a part of the wiring and the detection electrode substantially parallel to the wiring and the detection electrode. A guard electrode, and a guard electrode voltage generation circuit that applies a voltage to the guard electrode to control the impedance of the wiring and the detection electrode and protects the wiring and the detection electrode from external electromagnetic noise. A liquid crystal display device comprising: