JPH07281151A - Liquid crystal display device - Google Patents

Abstract

PURPOSE:To provide a liquid crystal display device capable of dissolving the occurrence of display unevenness (cross talk) in a picture in the liquid crystal display device by a simple and inexpensive means and performing a high definition image display. CONSTITUTION:A distortion voltage occurring on a scanning electrode l and a voltage drop phenomenon occurring in the longitudinal direction of the scanning electrode 1 are canceled by amplifying and polarity-inverting the voltage detected from the opened end part of the scanning electrode 1 by a voltage detection means such as a voltage detection electrode 9 through a liquid crystal layer 3 by an operational amplifier circuit 11, and feeding back it to the input end part of the scanning electrode 1 by a voltage application means such as a voltage application electrode 12 through the liquid crystal layer 3.

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. Above all, the simple matrix type liquid crystal display device has a wide range of applications because it has a simple structure including the structure of the liquid crystal display element (liquid crystal display panel) and can easily manufacture large-sized ones at a low manufacturing cost. It is used.

Such a simple matrix type liquid crystal display device is required to have a multi-digit display, that is, a multi-pixel display screen and a high-quality display performance. 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, 240 scanning electrodes and 640 signal electrodes
In the case of a binary liquid crystal display element of about this number, the time corresponding to the scanning time for one scanning electrode, that is, the minimum pulse width of the drive voltage is as short as about 60 to 70 μs. .

In general, the liquid crystal cell for each pixel of the liquid crystal display element can be expressed as a capacitor, that is, an 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. A simple matrix type liquid crystal display device is driven by a combination of square wave pulses. At this time, the output resistance of the driver IC, the connection resistance between the driver IC and the liquid crystal display element, the internal resistance (R) of the driving electrodes of the liquid crystal display element, and the electrostatic capacitance (C _LC ) of the liquid crystal layer parasitically occur. Distortion or dullness occurs in the waveform of the drive voltage due to the differentiating circuit formed in.

The distortion or dullness of the waveform of the driving voltage causes a decrease or increase in the voltage applied to the liquid crystal layer, which results in a positional variation of the light transmittance within the screen of the liquid crystal display element, so-called. The phenomenon of uneven display called crosstalk appears on the screen.

In the simple matrix type liquid crystal display element, the distortion voltage generated in the voltage of the scanning electrode is most involved in the occurrence of crosstalk. Therefore, a phenomenon in which a distortion voltage occurs in the scan electrode will be described with reference to a typical example.

FIG. 6A 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 (so-called liquid crystal capacitance) 601 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 scan electrode Y _n of the liquid crystal display element. The total electrical resistance 602 is the internal resistance of the electrode itself.

The liquid crystal display device is usually driven by an alternating liquid crystal applied voltage. Here, the scan driver circuit 6
It is assumed that 03 outputs a scanning voltage having a scanning pulse having a waveform of amplitude ± V _Y whose polarity is inverted every frame. Further, it is assumed that the signal driver circuit 604 outputs a signal voltage having a waveform in which the polarity is inverted between ± V _x as shown in FIG. 6B.

In this equivalent circuit, consider a case where a square wave signal voltage is applied to the electrostatic capacitance (C _LC ) 601 of the liquid crystal layer from the signal driver circuit 604 side. The capacitance 601 of the liquid crystal layer, to a connection point 605 between the electric resistance (R) 602 of the sum, spike distortion based on the constant C _LC · R when differentiating circuit formed by the C _LC and R Voltage V _n
Occurs. The waveform of this distortion voltage V _n is shown in FIG. Since such a spiked distortion voltage V _n is generated in the voltage of the scan electrode, the liquid crystal applied voltage applied to the electrostatic capacitance 601 of the liquid crystal layer is a spiked distortion voltage as shown in FIG. 6D. The waveform is such that the voltage corresponding to V _n has been scraped. Due to such a change in voltage, uneven display, that is, so-called crosstalk appears on the screen.

Further, tin oxide and ITO (indium-based) are used for the scanning electrodes and signal electrodes used inside the liquid crystal display element.
A transparent electrode made of a tin oxide compound) is generally used. Such a transparent electrode has a relatively high electric resistance.
Therefore, since the above-mentioned R is present in these electrodes in a larger value, the distortion voltage and the waveform blunting caused by the above-mentioned C _LC · R are more significantly generated in the scan 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 driver circuit based on the display data output from the signal electrode driver and appropriately changing the compensation voltage to cancel the distortion component of the voltage of the scan electrode has been studied. There is.

However, in such a conventional technique, the scan driver circuit 603 and the signal driver circuit 6 are provided.
The effect of the internal resistance of the liquid crystal driver IC actually used as 04, the connection resistance between the liquid crystal driver IC and the liquid crystal display element, the resistance of each scanning electrode of the liquid crystal display element, the resistance of the signal electrode, etc. is fundamentally eliminated. I'm not. The distortion voltage on the scan electrodes as described above is canceled based on the minute compensation voltage set in advance corresponding to the display data.

Therefore, for example, in the case of a device that changes the contrast by changing the liquid crystal driving voltage or a device that performs gradation expression, the magnitude of the distortion voltage also changes with the change of the liquid crystal driving voltage, so that actual compensation is not possible. The required voltage deviates from the initially set compensation voltage value.
Therefore, there is a problem that effective compensation is difficult. Alternatively, it is also considered to add an adjusting circuit or the like that resets the optimum compensation voltage each time. However, when incorporating a circuit having such an adjusting circuit and performing delicate setting of the compensation voltage based on the display data, there is a problem that the structure of the liquid crystal drive circuit system becomes very complicated.

Regarding the problem of the electric resistance of the transparent electrode generally used for the scanning electrode, it is considered to reduce the apparent resistance of the scanning electrode by arranging metal wiring in parallel beside the scanning electrode. To be As a result, it is possible to suppress the generation of distortion of the waveform of the distortion voltage or the voltage applied to the liquid crystal.

However, in such a method, the internal structure of the liquid crystal display element including the vicinity of the scanning electrode becomes complicated, and the production of fine fine metal wiring is not easy, and the production cost is high. There is a problem of becoming.

It is also possible to use a driver IC having an extremely small output resistance in order to suppress the distortion of the voltage waveform and the dullness of the voltage applied to the liquid crystal, but it is not easy to develop and put into practical use such a special driver IC. , This is also impractical.

[0018]

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 internal resistance of the scan electrode of the liquid crystal display element, etc. The distortion voltage generated in the scanning electrodes due to the electric resistance and the capacitance of the liquid crystal layer causes the waveform of the liquid crystal applied voltage to change from the ideal (preferably designed) waveform in the liquid crystal driving theory, and There is a problem that display unevenness (that is, crosstalk) occurs. In the known technology proposed as a solution to this, there is a problem in that the preset compensation voltage deviates from the optimum compensation voltage necessary for eliminating the distortion voltage due to changes in the display image condition and environment. However, there is a problem that the device becomes complicated and the cost becomes high.

The present invention has been made to solve such a problem, and an object thereof is to solve the problem of occurrence of display unevenness (crosstalk) on a screen in 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 high-quality image display.

[0020]

In order to solve the above-mentioned problems, a liquid crystal display device of the present invention comprises a scanning electrode substrate having a plurality of scanning electrodes formed thereon, and a plurality of signals in a direction intersecting with the respective scanning electrodes. A signal electrode substrate in which electrodes are formed and the signal electrodes and the scanning electrodes are opposed to each other with a gap maintained between them, a liquid crystal layer whose periphery is sealed and sandwiched by the gap, A scan driver circuit for applying a scan voltage to a scan electrode, a signal driver circuit for applying a signal voltage to each of the signal electrodes, and a voltage detection means formed on the signal electrode substrate, wherein Voltage detection means for detecting the voltage of the open end portion on the opposite side of the input end portion to which the scanning voltage is applied, through an electric capacitance or an electric resistance,
Computation amplification means for amplifying and reversing the polarity of the voltage detected by the voltage detection means, and voltage application means formed on the signal electrode substrate, wherein the voltage output from the computation amplification means is converted into electric capacity or electric capacity. And a voltage applying unit that applies a voltage to the input end portion of each scan electrode via a resistor.

Further, a scanning electrode substrate having a plurality of scanning electrodes formed thereon, and a plurality of signal electrodes formed in a direction intersecting the scanning electrodes, and the signal electrodes and the scanning electrodes face each other with a gap maintained. A signal electrode substrate arranged in such a manner, a liquid crystal layer sealed and sandwiched around the gap, and a scan driver circuit for applying a scan voltage to each scan electrode,
A signal driver circuit for applying a signal voltage to each signal electrode, and a voltage detection electrode formed in parallel with the signal electrode on the signal electrode substrate, wherein the scanning voltage of each scanning electrode is applied. A voltage detection electrode, which is arranged to face an open end portion opposite to the input end portion, detects the voltage of the open end portion of the scanning electrode via the liquid crystal layer, and the voltage detection electrode. An operational amplifier circuit for amplifying and reversing the polarity of the generated voltage, and a voltage application electrode formed on the signal electrode substrate in parallel with the signal electrode, to which the scanning voltage of each scanning electrode is applied A voltage applying electrode that is arranged to face the end portion and that applies a voltage output from the operational amplifier circuit to the input end portion of each of the scanning electrodes via the liquid crystal layer. as a feature That.

Further, a scan electrode substrate having a plurality of scan electrodes formed thereon, and a plurality of signal electrodes formed in a direction intersecting with the scan electrodes face each other with a gap maintained therebetween. A signal electrode substrate arranged in such a manner, a liquid crystal layer sealed and sandwiched around the gap, and a scan driver circuit for applying a scan voltage to each scan electrode,
A signal driver circuit for applying a signal voltage to each of the signal electrodes, and a voltage detection unit formed on the signal electrode substrate, wherein the voltage of an input end portion to which the scanning voltage of each of the scanning electrodes is applied is electrically supplied. Voltage detection means for detecting via a capacitance or electric resistance, operational amplification means for amplifying and inverting the polarity of the voltage detected by the voltage detection means, and voltage application means formed on the signal electrode substrate, It is characterized by further comprising voltage applying means for applying the voltage output from the operational amplifying means to an open end portion of each scan electrode opposite to the input end portion via an electric capacitance or an electric resistance. .

Further, a scan electrode substrate having a plurality of scan electrodes formed thereon, and a plurality of signal electrodes formed in a direction intersecting with the scan electrodes face each other with a gap maintained therebetween. A signal electrode substrate arranged in such a manner, a liquid crystal layer sealed and sandwiched around the gap, and a scan driver circuit for applying a scan voltage to each scan electrode,
A signal driver circuit for applying a signal voltage to each signal electrode, and a voltage detection electrode formed in parallel with the signal electrode on the signal electrode substrate, wherein the scanning voltage of each scanning electrode is applied. A voltage detection electrode that is arranged to face the input end portion, and that detects the voltage of the input end portion to which the scanning voltage of each of the scanning electrodes is applied via the liquid crystal layer; and the voltage detection electrode. An operational amplifier circuit for amplifying and reversing the polarity of the detected voltage, and a voltage application electrode formed on the signal electrode substrate, the side being opposite to the input end portion of each scanning electrode to which the scanning voltage is applied. And a voltage applying electrode that is arranged to face the open end portion of the scanning electrode and applies the voltage output from the operational amplifier circuit to the open end portion of each of the scan electrodes via the liquid crystal layer. Special It is set to.

In addition to the case where one end of the scan electrode is connected to the scan driver circuit as an input end as described above, for example, a drive circuit is connected to both ends of each scan electrode as an input end, The present invention can also be applied to a liquid crystal display device having a structure in which the scanning electrodes are driven from both ends (scanning voltage is applied to the scanning electrodes). In the case of such a liquid crystal display device driven at both ends, since the "open end" of the scan electrode as described above cannot be discriminated, for example, the part farthest from the input end, that is, the central part of each scan electrode is The voltage detecting means, the voltage applying means, or the like may be formed in this portion by regarding it as the open end.

Needless to say, the scan voltage output from the scan driver circuit is a voltage formed by a combination of the scan non-selection voltage and the scan selection voltage (so-called scan pulse). More specifically, as the polarity reversal method, even when the scanning non-selection voltage is constant and only the scanning selection voltage (scanning pulse) inverts the polarity with the scanning non-selection voltage as the central voltage, or Even when both the scanning selection voltage and the scanning non-selection voltage are both inverted around the center voltage of
The present invention can be applied to either case.

[0026]

In the liquid crystal display device according to the present invention, the voltage detected by the voltage detecting means such as the voltage detecting electrode from the input end portion (or open end portion) of the scan electrode via the electric capacitance is detected by the operational amplifier circuit. Amplification and polarity inversion are performed, and this is fed back to the open end portion (or input end portion) of the scan electrode via a capacitance by a voltage applying means such as a voltage applying electrode, so that the strain voltage generated in the scan electrode is reduced. Can be canceled. It goes without saying that the operational amplifier circuit is set so as to amplify and polarize the input voltage in such a direction as to effectively cancel the distortion voltage generated in the scan electrodes and output the amplified voltage. .

As described above, the voltage of the scan electrode including the distortion voltage component which has an unfavorable influence on the image display, such as the spike-like distortion voltage generated in the voltage of the scan electrode,
By taking out collectively from a plurality of scan electrodes and feeding back this strain voltage component to the scan electrodes, it is possible to suppress the strain voltage that is about to occur in the scan electrodes.

Therefore, no matter how the magnitude of the liquid crystal applied voltage such as the scanning voltage or the signal voltage is changed, or how the liquid crystal applied voltage changes due to the temperature change or the change over time of the liquid crystal layer. Also, it is possible to obtain a stable crosstalk removing effect without fluctuations in operating characteristics by a simple means.

Moreover, according to the present invention, the voltage state of the scan electrode is feedback-controlled from the voltage input end portion of the scan electrode to the open end portion (or in the opposite direction). Therefore, the gradient voltage attenuation that occurs from the input end portion to the open end portion of the scan electrode due to the internal resistance of the scan electrode can be eliminated by the feedback control according to the present invention.

As described above, according to the present invention, it is possible to eliminate the voltage attenuation inside the scan electrodes and to eliminate the variation in the brightness on the display screen caused by the voltage attenuation.

[0031]

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

In this liquid crystal display device, the scanning electrodes 1 and the signal electrodes 2 made of a transparent electrode such as ITO are arranged to face each other in a matrix with a gap, and the liquid crystal layer 3 is sandwiched in the gap. An element (liquid crystal display panel) 4, a scan driver circuit 5 and a signal driver circuit 6 for driving the liquid crystal display element 4, and these scan driver circuits 5
And a power supply circuit 7 for supplying a power supply voltage to the signal driver circuit 6.

Inside the liquid crystal display element 4, one voltage detection electrode 9 is formed on the signal electrode substrate 8 in parallel with the end of the column of the signal electrode 2. This voltage detection electrode 9
Are arranged so as to face the open end portion opposite to the input end portion to which the scan voltage of all the scan electrodes 1 is applied, with the liquid crystal layer 3 interposed therebetween. The voltage detecting electrode 9 detects the voltage of the open end portion on the opposite side of the input end portion to which the scan voltage of all the scan electrodes 1 is applied in the liquid crystal display element 4.
Detection is performed via the liquid crystal layer 3. Here, the liquid crystal layer 3 is used as an electric capacity. That is, the voltage detection electrode 9 uses the liquid crystal layer 3 as the electric capacity 10a, and uses the electric capacity 10a.
The voltage on the scan electrode 1 is detected via the capacitive coupling by a.

The operational amplifier circuit 11 is connected to the output terminal of the voltage detection electrode 9. This operational amplifier circuit 11
Causes the voltage detected by the voltage detection electrode 9 to be amplified and polarity-reversed in such a direction as to effectively eliminate the distorted voltage component generated in the scan electrode 1.

Here, the amplification factor of the output voltage with respect to the input voltage of the operational amplifier circuit 11 is K, and the electric capacity (liquid crystal capacity) of the liquid crystal layer 3 sandwiched between the scanning electrode 1 and the signal electrode 2 is C.
_Letting R _{ITO be} the electric resistance of the transparent conductive film (ITO) forming the _LC and the scanning electrode 1, etc., the amplification factor K of the operational amplifier circuit 11 is K.
Can be set to a suitable value based on the following equation: K = A (C _LC × R _ITO ), where A is a constant.

Here, the constant A in the above equation is the liquid crystal display element 4
It is a constant that is determined by the combination of various conditions for each design of each liquid crystal display device, such as the electrical characteristics of the liquid crystal composition used in, the internal resistance of the signal driver circuit and the scan driver circuit.
Therefore, since the constant A has a different value for each liquid crystal display device having a different design, the amplification factor K of the operational amplifier circuit 11 determined by the above equation is a different value suitable for each design of each liquid crystal display device. Determined. Therefore, the operational amplifier circuit 1
It is practically impossible to specifically limit the value of the amplification factor K of 1. Therefore, a value for each liquid crystal display device may be substituted into the above equation to appropriately calculate a suitable amplification factor K. In this embodiment, the value of the amplification factor of the operational amplifier circuit 11 is set to K = 10.

The inside of the liquid crystal display element 4 is shown in FIG.
As shown in FIG. 1, one voltage application electrode 12 is formed in parallel on the signal electrode substrate 8 at the end of the column of the signal electrodes 2.
The voltage applying electrode 12 is arranged so as to face the input end portions of all the scanning electrodes 1 to which the scanning voltage is applied, with the liquid crystal layer 3 in between. The voltage applying electrode 12 is
The voltage output from the operational amplifier circuit 11 is applied to the liquid crystal layer 3
Is applied to the input end portions of all the scan electrodes 1 via. Here, the liquid crystal layer 3 is used as the electric capacity 10b. That is, the voltage application electrode 12 applies the voltage output from the operational amplifier circuit 11 onto the scan electrode 1 via the capacitive coupling by the electric capacitance 10b.

In the present invention, with the structure as described above, the voltage including the distorted voltage component on the scanning electrode 1 is taken out, the polarity is inverted and amplified in the direction of canceling the voltage with respect to the distorted voltage component, and scanning is performed. It is returned to the electrode 1. In such feedback control, even if the voltage of the scan electrode 1 fluctuates due to the change in the signal voltage on the signal electrode 2 side, the voltage of the scan electrode 1 is changed from the input end portion by the internal resistance of the scan electrode 1 itself. Whether it decays to the open end or is subject to fluctuations due to any other disturbance, the scan electrode 1
Since the voltage including the distortion voltage component is extracted from itself and fed back to the scan electrode 1 itself, the distortion voltage component of the scan electrode 1 can always be effectively eliminated. As a result, the technique of the present invention can eliminate crosstalk in the display image.

The above has outlined the structure and operation of the liquid crystal display device according to the present invention. Next, more specific structures and operations of the liquid crystal display element 4, the scan driver circuit 5, the signal driver circuit 6, and the power supply circuit 7 in the liquid crystal display device according to the first embodiment of the present invention will be described.

In this example, an STN type liquid crystal display element was used as the liquid crystal display element 4. The screen size is A4, and the display capacity (number of pixels) is 240 x 640 dots. The cell gap of this STN type liquid crystal display element 4 is about
An alignment film (not shown) made of resin having a thickness of 7 μm and subjected to a rubbing alignment treatment is provided, and the liquid crystal molecules of the liquid crystal layer 3 are aligned so as to be twisted by 240 ° between the cell gaps of the liquid crystal display element 4. As the liquid crystal composition of the liquid crystal layer 3, ZLI-2293 manufactured by Merck Ltd. was used. Further, the scanning electrode 1, the signal electrode 2, the voltage detection electrode 9 and the voltage application electrode 12 are made of ITO.
(Indium and tin oxide compound) is used as a material.

Then, on the surface of the signal electrode substrate 8 of the liquid crystal display element 4 facing outward of the glass substrate 13 and on the surface of the scanning electrode substrate 14 facing outward of the glass substrate 15, black and white display is realized. An optical phase compensation cell (not shown) is attached. With such a structure, the liquid crystal display device of the present embodiment displays black when no voltage is applied and white when a voltage is applied.

The voltage detection electrode 9 is formed on the inward surface of the glass substrate 13 on the signal electrode substrate 8 side at the right end of the row of signal electrodes 2 in the figure in the form of an elongated strip substantially parallel to the signal electrodes 2. ing. The voltage detection electrode 9 is arranged in the liquid crystal display element 4 so as to cross the open end portions of all the scanning electrodes 1, and the liquid crystal layer 3 is interposed between the open end portions of the scan electrodes 1. Face to face. At this time, the liquid crystal layer 3
Is used as a dielectric, and the open end portion of the scanning electrode 1 and the voltage detection electrode 9 are used as two electrodes facing each other. That is, by using the open end portion of the scan electrode 1, the voltage detection electrode 9, and the liquid crystal layer 3 sandwiched between these two electrodes from the upper and lower surfaces, the capacitance 10
That is, a is formed.

On the other hand, the voltage application electrode 12 is formed on the signal electrode substrate 8 on the inward surface of the glass substrate 13.
Is formed in an elongated strip shape substantially parallel to the signal electrode 2 at the left end of the column of FIG. The voltage detecting electrode 9 is arranged in the liquid crystal display element 4 so as to cross the input end portions of all the scanning electrodes 1, and the liquid crystal layer 3 is interposed between the input end portions of the scanning electrodes 1. Face to face. At this time, the liquid crystal layer 3 is used as a dielectric, and the input end portion of the scanning electrode 1 and the voltage applying electrode 12 are used as electrodes facing each other. That is, the input end portion of the scan electrode 1, the voltage application electrode 12, and the liquid crystal layer 3 sandwiched by these two electrodes from the upper and lower surfaces are used to form the electric capacitance 10b.

FIG. 3 is a block diagram showing the overall structure of the liquid crystal display device of this embodiment. Each scan electrode 1 in the liquid crystal display element 4 is connected to the scan driver circuit 5. Further, each signal electrode 2 is connected to the signal driver circuit 6. Then, the power supply circuit 7 supplies a power supply voltage to the scan driver circuit 5 and the signal driver circuit 6, respectively.

In the scan driver circuit 5, the scan control signal (F
P), the potential (+ V _Y , −, which is output from the power supply circuit 7
A potential corresponding to the scanning voltage control signal is selected from V _Y , V _com , + V _x , and −V _x ) and applied to each of the 240 scanning electrodes 1 of Y1 to Y240. More specifically, as shown in FIG. 3, a shift register 17 that sequentially transfers a scan control signal internally, and a scan pulse (+ V _Y , -V _Y ) which is controlled by the shift register 17 and is selected for scanning.
_{Alternatively} , the main part of the scan driver circuit 5 is constituted by the switch section 18 for selecting the scan potential (V _com ) when the non-scan is selected.

In the scan driver circuit 5, when the shift register 17 receives FP (frame pulse) that determines one frame period as basic scan data, it outputs Y based on LP (latch pulse) that determines one scan time.
Scan data from 1 to Y240 in the shift register 1
Data is transferred line-sequentially to 240 register elements provided inside 7.

Inside the switch section 18, there are arranged in series switch elements, one for each of the 240 scanning electrodes 1. Each of the switch elements is also connected to each of the 240 register elements provided inside the shift register 17, and the scan data transferred to the register elements inside the shift register 17 line-sequentially. The switching operation is performed based on That is, each switch element of the switch unit 18 selects the potentials + V _Y and −V _Y and outputs them to the scan electrode 1 when the scan data input from the register elements connected to each is “select” data. . In the case of “non-selected” data, the potential V _com is selected and output to the scan electrode 1. Thus, for example, in FIG.
A scan voltage waveform (so-called scan electrode drive waveform) based on a general voltage averaging method as shown in (a) is applied from the scan driver circuit 5 to the scan electrode 1. On the other hand, the signal driver circuit 6 receives the image data input from the drive data generation circuit 16 and outputs the potentials (+ V _Y , −V _Y , V _com , + V _x , −V _x ) output from the power supply circuit 7. Select the potential corresponding to the image data from among X1 to X640
A signal voltage is applied to each of the 640 signal electrodes 2.
That is, as shown in FIG. 3, the signal driver circuit 6 includes a shift register 19 in which register elements for transferring image data line-sequentially are arranged in a row, and image data transferred line-sequentially to the register elements of the shift register 19. Is held in parallel at a predetermined timing, and a switch section 21 for selecting a potential to be output by betting a signal voltage based on the image data held in parallel by the data latch 20. Its main part is formed.

The shift register 19 uses the image data (see FIG. 3).
It is shown as DATA inside. In the text below, "D
ATA ”), the timing is controlled based on the clock pulse (CP) for transferring the DATA, and the DATA corresponding to all the signal electrodes 2 (X1 to X640) are line-sequentially registered in each register. Transfer to the element. Then, the data latch 20 outputs a latch pulse (LP).
In response to this, DATA corresponding to all the signal electrodes 2 from X1 to X640 is held in parallel. Then, the switch unit 21 selects the potential + V _x when DATA is the selected (ON) data and the scanning voltage is −V _Y , based on the DATA held in the data latch 20 as data in a parallel state, and DATA is When the scanning voltage is + V _{Y in} the selection (on) data, the potential −V _x is selected. Alternatively, when DATA is unselected data (OFF), the reverse selection is performed as compared with the case where DATA is selected (ON) data. That is, when the scanning voltage is −V _Y , the potential −V _x
When the scanning voltage is + V _Y , the potential + V _x is selected.

In this way, the signal driver circuit 6 applies to each signal electrode 2 a signal electrode drive voltage, that is, a signal voltage having a waveform based on the voltage averaging method as shown in FIG. 5B, for example.

The power supply circuit 7 has the potentials (+ V _Y , -V _Y , V _com , + V _x , necessary to drive the liquid crystal display element 4).
-V _x ) is output. The power supply circuit 7 is composed of a voltage dividing circuit using electric resistances 301, 302, 303, 304 as shown in FIG.

Of the potentials output from the power supply circuit 7, + V _Y , -V _Y and V _com are supplied to the scan driver circuit 5. Further, + V _x and −V _x are supplied to the signal driver circuit 6. Using these supplied potentials, the scan driver circuit 5 applies the scan voltage having the above waveform to the scan electrode 1. Further, the signal driver circuit 6 applies the signal voltage having the above waveform to the signal electrode 2.

In this way, when the scanning voltage is applied to the scanning electrode 1 and the signal voltage is applied to the signal electrode 2,
The voltage waveform applied to the liquid crystal layer 3 sandwiched at the intersection of the scanning electrode 1 and the signal electrode 2 has a waveform as shown in FIG. That is, in the present embodiment, the waveform is such that the polarity is inverted for each frame, and the amplitude of the selection pulse changes according to the display content (ON, OFF).
The polarity reversal driving method is a well-known driving method that 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. Switch unit 18 in the scan driver circuit 5 described above
The switch section 21 in the signal driver circuit 6 is formed so as to be inverted by a constant cycle under the control of the polarity inversion signal (FR). As for this structure, a general structure for performing polarity reversal is used. That is, in the switch section 18, the polarities of the scan selection voltages selected for each frame are alternately changed to + V _Y and −V _Y. At this time, scanning non-selection voltage V _com
Is an intermediate voltage between + V _Y and −V _Y.

Then, induced by the change in the signal voltage of the signal electrode 2 facing the scan electrode 1 through the liquid crystal layer 3, a distortion voltage component is generated in the voltage of the scan electrode 1. For example, the scan non-selection voltage V _com is applied to the scan electrode 1 during the scan non-selection period. This V _com is a flat waveform voltage over most of one frame except the scan selection period. While the V _com is being applied to the scan electrode 1, a change in the signal voltage of the signal electrode 2 exerts an inductive effect on the signal electrode 1 via the liquid crystal layer 3. As a result, a distorted voltage component is generated in the voltage of the scan electrode 1 during the scan non-selection period, which should have an originally flat waveform. A typical waveform of this distortion voltage component is a spike-wave-shaped distortion caused by a differential circuit parasitically formed by the liquid crystal capacitance C _LC of the liquid crystal layer 3 and the internal resistance R _ITO of the scan electrode 1. Voltage.

Therefore, in the present invention, the voltage detection electrode 9
Is the voltage of the scan electrode 1 including the above-mentioned distortion voltage component,
Detection is performed from the scanning electrode 1 itself through the liquid crystal layer 3. The single voltage detection electrode 9 is arranged to face the open end portions of all the scanning electrodes 1 with the liquid crystal layer 3 interposed therebetween. Therefore, one voltage detection electrode 9 detects a voltage obtained by averaging the voltages of all the scan electrodes 1.

The operational amplifier circuit 11 amplifies and reverses the voltage input from the voltage detection electrode 9 in such a direction as to effectively eliminate the distorted voltage component that is about to occur in the scan electrode 1. For example, V on the open end of scan electrode 1
voltage containing a distortion voltage having a displacement of + direction relative to the _com can be polarity inverted by the operational amplifier circuit 11, V _{co m}
Is a voltage having an amplitude in the negative direction with respect to the reference voltage, which is similar to the spike-shaped waveform of the original distortion voltage, and is amplified to a voltage including a voltage whose amplitude is amplified.
Then, the operation-amplified voltage is sent from the operation-amplifying circuit 11 to the voltage application electrode 12. Then, the voltage is applied to the input end of the scan electrode 1 by the voltage applying electrode 12.
In addition, as for the voltage drop from the input end to the open end of the scan electrode 1, that is, the voltage drop component, the voltage drop component of the scan electrode 1 is extracted from the scan electrode 1 itself and polarity-inverted to scan as in the case of eliminating the distortion. It is returned to the electrode 1 itself.

As described above, in the liquid crystal display device of the present invention, the distortion voltage component generated in the voltage on the scan electrode 1 is effectively canceled, and the voltage drop in the longitudinal direction of the scan electrode 1 is compensated, so that the distortion occurs. It is possible to eliminate unevenness in display (crosstalk) on the display screen due to a voltage component or a voltage drop, and maintain good image display.

Here, the operational amplifier circuit 11 of this embodiment is
In this embodiment, it is formed by using an operational amplifier element 25 having an inverting terminal 22, a non-inverting terminal (positive terminal) 23, and an output terminal 24. The amplification factor of the operational amplification element (amplification element) 25 is set by an electric resistance 26 connected between the inverting terminal 22 and the output terminal 24 and an electric resistance connected between the inverting terminal and the buffer. Needless to say. A buffer 27 is connected immediately before the inverting terminal 22 of the operational amplifier element.

However, the circuit or the circuit element forming the operational amplifier circuit 11 according to the present invention is not limited to the operational amplifier element as shown in the above embodiment. Any circuit element or circuit that has a function of amplifying the input voltage with a predetermined amplification factor and outputting the polarity after inverting the polarity can be suitably used as the operational amplifier circuit 11 according to the present invention.

In the liquid crystal display device of the first embodiment according to the present invention as described above, a duty ratio of 1/240 and a bias ratio are used by using a liquid crystal drive voltage having a waveform as shown in FIG.
A display was performed by driving so that the polarity was reversed every 13 lines at 1/13 and a frame frequency of 80 Hz, and the display quality was visually confirmed.

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.

From such experimental results, we have confirmed that the liquid crystal display device of the present invention has a high display quality, excellent durability, and high reliability.

(Comparative Example to First Example) The voltage detecting electrode 9, the operational amplifier circuit 11, and the voltage applying electrode 12, which are the main parts of the technique according to the present invention, are removed from the liquid crystal display device of the first example. A liquid crystal display device having the above structure is prepared, and a liquid crystal display device having a conventional structure in which a total of 153600 pixels are formed by the number of scanning electrodes 240 × the number of signal electrodes 640, and the same driving conditions as those in the first embodiment are used. A display was performed and the display quality was visually confirmed.

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
Although the number of dots was gradually increased to 00 dots, crosstalk darker than the surroundings occurred in the vertical direction, and the display quality was 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. In particular, the display unevenness which is clearly caused by the voltage drop phenomenon was conspicuous in the longitudinal direction of the scan electrode, that is, from the input end portion to the output end portion of the scan electrode.

(Embodiment 2) FIG. 4 is a diagram showing a liquid crystal display device according to a second embodiment of the present invention. In the liquid crystal display device of the second embodiment, the arrangement of the voltage detection electrode 9 and the voltage application electrode 12 in the liquid crystal display device of the first embodiment is reversed. That is, the voltage detection electrode 9 is connected to the scanning electrode 1
The voltage applying electrode 12 is arranged at the input end portion of the scanning electrode 1
It is located at the open end of the. In the liquid crystal display device of the second embodiment having such a structure, similarly to the liquid crystal display device of the first embodiment, the distortion voltage component is effectively canceled and the distortion voltage component and the voltage drop are eliminated. It is possible to remove unevenness in display density (crosstalk) on the display screen, which is caused, and maintain good image display.

The liquid crystal display device of the second embodiment according to the present invention was driven to display on the liquid crystal screen. At this time, the duty ratio of 1/240 and the bias ratio are set by using the liquid crystal drive voltage having the waveform as shown in FIG.
The liquid crystal display device of the second embodiment was driven so that the polarity was inverted every 13 lines at 1/13 and a frame frequency of 80 Hz. Then, the quality of the displayed image was visually confirmed.

As a result, similarly to the liquid crystal display device of the first embodiment, the liquid crystal display device of the second embodiment can realize a high-quality image display and has a high durability and a high reliability. We actually confirmed that it was a device.

[0068]

As has been clearly described in the above detailed description, according to the present invention, the problem of display unevenness (crosstalk) on the screen of a liquid crystal display device is solved by a simple and inexpensive means, A liquid crystal display device that displays a high-quality image can be provided.

[Brief description of drawings]

FIG. 1 is a diagram showing an outline of a liquid crystal display device of a first embodiment.

FIG. 2 is a schematic plan view (a) and a sectional view (b) showing a structure of a liquid crystal display element used in the liquid crystal display device of the first embodiment.

FIG. 3 is a diagram showing the structure of the liquid crystal display device of the first embodiment.

FIG. 4 is a diagram showing a structure of a liquid crystal display device according to a second embodiment.

FIG. 5 is a diagram showing drive voltage waveforms used in the liquid crystal display devices of the first and second embodiments.

FIG. 6 is a diagram showing a distortion voltage component generated in a voltage of a scanning electrode of a conventional liquid crystal display device.

[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 ... Power supply circuit 8 ... Scan electrode substrate 9 ... Voltage detection electrode 10 ... Electric capacity 11 ... Operation amplification circuit 12 ... Voltage application electrode

Claims (4)

[Claims] 1. A scan electrode substrate having a plurality of scan electrodes formed thereon, and a plurality of signal electrodes formed in a direction intersecting with the scan electrodes, the signal electrodes and the scan electrodes being opposed to each other with a gap maintained therebetween. Signal electrode substrate arranged in such a manner, a liquid crystal layer sealed and sandwiched around the gap, a scan driver circuit for applying a scan voltage to each of the scan electrodes, and a signal voltage to each of the signal electrodes. And a voltage detection unit formed on the signal electrode substrate for applying a voltage to an open end portion of the scan electrode on the opposite side of the input end portion to which the scan voltage is applied. Voltage detection means for detecting via electric capacitance or electric resistance, operational amplification means for amplifying and inverting the polarity of the voltage detected by the voltage detection means, and voltage application means formed on the signal electrode substrate. , A liquid crystal display device; and a voltage applying means for applying to the input end portion of said scanning electrodes via an electrical capacitance or the electrical resistance the voltage output from the serial operational amplifier means. 2. A scan electrode substrate having a plurality of scan electrodes formed thereon, and a plurality of signal electrodes formed in a direction intersecting with the scan electrodes, and the signal electrodes and the scan electrodes face each other with a gap maintained therebetween. Signal electrode substrate arranged in such a manner, a liquid crystal layer sealed and sandwiched around the gap, a scan driver circuit for applying a scan voltage to each of the scan electrodes, and a signal voltage to each of the signal electrodes. And a voltage detection electrode formed in parallel with the signal electrode on the signal electrode substrate, the side being opposite to the input end portion to which the scanning voltage of each scanning electrode is applied. A voltage detection electrode that is arranged to face the open end portion of the scanning electrode and that detects the voltage of the open end portion of the scan electrode via the liquid crystal layer; and a voltage detected by the voltage detection electrode is amplified and Calculation to invert the polarity An amplifier circuit and a voltage applying electrode formed in parallel with the signal electrode on the signal electrode substrate, the voltage applying electrode being arranged to face an input end portion of each scanning electrode to which the scanning voltage is applied. And a voltage applying electrode for applying the voltage output from the operational amplifier circuit to the input end portion of each scanning electrode via the liquid crystal layer. 3. A scan electrode substrate having a plurality of scan electrodes formed thereon, and a plurality of signal electrodes formed in a direction intersecting the scan electrodes, and the signal electrodes and the scan electrodes face each other with a gap maintained. Signal electrode substrate arranged in such a manner, a liquid crystal layer sealed and sandwiched around the gap, a scan driver circuit for applying a scan voltage to each of the scan electrodes, and a signal voltage to each of the signal electrodes. And a voltage detection unit formed on the signal electrode substrate, wherein a voltage of an input end portion to which the scanning voltage of each of the scanning electrodes is applied is transferred via an electric capacity or an electric resistance. Voltage detection means for detecting, operational amplification means for amplifying and inverting the polarity of the voltage detected by the voltage detection means, and voltage application means formed on the signal electrode substrate. A liquid crystal display device; and a voltage applying means for applying to the open end portion opposite to the been the input end portion of said scanning electrodes via an electrical capacitance or electrical resistance voltage. 4. A scan electrode substrate having a plurality of scan electrodes formed thereon, and a plurality of signal electrodes formed in a direction intersecting with the scan electrodes, and the signal electrodes and the scan electrodes oppose each other with a gap maintained therebetween. Signal electrode substrate arranged in such a manner, a liquid crystal layer sealed and sandwiched around the gap, a scan driver circuit for applying a scan voltage to each of the scan electrodes, and a signal voltage to each of the signal electrodes. And a voltage detection electrode formed in parallel with the signal electrode on the signal electrode substrate, the signal driver circuit facing the input end portion to which the scanning voltage of each scanning electrode is applied. And a voltage detection electrode for detecting the voltage of the input end portion to which the scanning voltage of each of the scanning electrodes is applied via the liquid crystal layer, and amplifying the voltage detected by the voltage detection electrode. Reverse polarity An operational amplifier circuit and a voltage application electrode formed on the signal electrode substrate, facing the open end portion of each scan electrode opposite to the input end portion to which the scan voltage is applied. A liquid crystal display device, comprising: a voltage applying electrode which is arranged and applies a voltage output from the operational amplifier circuit to the open end portion of each scanning electrode via the liquid crystal layer.