JPH07294871A - Liquid crystal display device - Google Patents

Abstract

PURPOSE:To provide a liquid crystal display device displaying a high quality image by resolving a problem that an unevermess (cross talk) is generated on a screen in the liquid crystal display device with a simple and low cost means and especially eliminating the display unevermess of the screen in a vertical fly-back period. CONSTITUTION:This device is provided with an interruption switch 305 controlling outputs of operational amplifier circuits 11 and a control circuit 12 making the interruption switch 305 be in an OFF-state during the vertical fly-back period by controlling the operation of the interruption switch 305. The generation of the crosstalk of the screen caused by turbulance like noise of negative feedback control operations in the vertical fly-back period is eliminated by allowing the negative feedback operations of operational amplifier circuits 11 to be stopped during the vertical fly-back period by using the interruption switch 305.

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. 7A 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
03 outputs the scanning voltage 0. Also,
The signal driver circuit 604 has a ±
It is assumed that a signal voltage having a waveform in which the polarity is inverted between V _x is output.

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. 7D. 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 according to the present invention comprises a scanning electrode substrate having a plurality of scanning electrodes formed thereon, and a plurality of signals so as to intersect the scanning electrodes. A signal electrode substrate in which electrodes are formed so that the signal electrodes and the scanning electrodes are opposed to each other with a gap maintained, and a liquid crystal layer sealed and sandwiched around the gap to surround the periphery thereof are provided. A liquid crystal display panel, a drive voltage generation circuit that outputs a plurality of potentials for generating a scan voltage, and one potential selected from a plurality of potentials output from the drive voltage generation circuit and applied to the scan electrodes. And a scan driver circuit that forms a scan voltage by the operation of the select switch circuit and applies the scan voltage to each of the plurality of scan electrodes, and a signal to each of the plurality of signal electrodes. A signal driver circuit for applying a voltage, a voltage detection unit composed of a plurality of electric capacitors or a plurality of electric resistances each having one end connected to each of the plurality of scan electrodes, and a plurality of electric capacitors or a plurality of electric capacitances of the voltage detection unit. An operational amplifier circuit in which the other end of the electric resistance is electrically connected to an input end all together, and a voltage input to the input end is amplified and polarity in a direction to reduce distortion of the voltage of the scan electrode. An operational amplifier circuit that inverts and outputs from the output terminal, and synthesizes with a potential output from the drive voltage generation circuit, a switching switch circuit that controls ON / OFF of the output of the operational amplifier circuit, and the switching switch circuit. A control circuit for controlling the operation of the scan driver circuit, wherein the disconnection switch circuit is turned off during a vertical blanking period of the scan driver circuit, and the connection is switched during a frame period of the scan driver circuit. Is characterized by comprising a control circuit for the switching circuit to the ON state, the.

Further, a scan electrode substrate having a plurality of scan electrodes formed thereon, and a plurality of signal electrodes formed so as to intersect with the scan electrodes and the signal electrodes and the scan electrodes face each other with a gap maintained. Liquid crystal display panel having a signal electrode substrate arranged in such a manner and a liquid crystal layer sealed and sandwiched around the gap, and driving voltage generation for outputting a plurality of potentials for generating a scanning voltage And a selection switch circuit that selects one potential from a plurality of potentials output from the drive voltage generation circuit and applies the potential to the scan electrode, and the scan voltage is formed by the operation of the selection switch circuit. A scan driver circuit for applying the scan voltage to each of the plurality of scan electrodes, a signal driver circuit for applying a signal voltage to each of the plurality of signal electrodes, and the signal driver circuit on the signal electrode substrate. A voltage detection electrode formed in parallel with the signal electrode, the scanning electrode being arranged opposite to a portion different from the input end portion to which the scanning voltage is applied, while maintaining a gap. A voltage detection electrode for detecting the voltage of the scanning electrode via the liquid crystal layer and the voltage detection electrode connected to an input end, and the voltage detected from the voltage detection electrode is input to the input end. An amplification operation circuit, which amplifies the input voltage in a direction to reduce the distortion of the voltage of the scan electrode, inverts the polarity, outputs the amplified voltage, and outputs the output voltage from the drive voltage generation circuit. An operational amplifier circuit, a switching switch circuit that controls on / off of a combined operation of the output of the operational amplifier circuit and the potential output from the drive voltage generation circuit, and a control circuit that controls the operation of the switching switch circuit. A control circuit that turns off the interrupt switch circuit during a vertical blanking period of the scan driver circuit and turns on the interrupt switch circuit during a frame period of the scan driver circuit; It is characterized by having.

As a more specific configuration of the operational amplifier circuit described above, for example, a circuit structure such as the one shown below can be preferably used.

That is, one buffer (buffer amplifier), to which the voltage detected by the voltage detection electrode and output from this voltage detection electrode is input, and the voltage input via this buffer are supplied to the scanning electrode. A circuit structure formed by combining a plurality of operational amplifier elements, which are amplified in a direction of reducing the distortion voltage component and are combined with the respective potentials output from the drive voltage generation circuit and output, can be preferably used. . Alternatively, one operational amplifier element to which the voltage detected by the voltage detection electrode is input, which amplifies and outputs the input voltage in the direction of reducing the distortion voltage component of the scan electrode, A circuit structure formed by combining a voltage output from one operational amplifier element and a plurality of adder circuits that combine and output the respective potentials output from the drive voltage generation circuit can be preferably used. .

Alternatively, in addition to the circuit structure illustrated above, if the operational amplifier circuit has a function of amplifying in the direction of reducing the voltage distortion of the scan electrode and inverting the polarity and outputting the amplified voltage, It goes without saying that it is possible to use circuit structures other than the three examples.

As the operational amplifier element, for example, an inverting amplifier can be used. Then, as described above, it is desirable that the amplification factor of the operational amplifier element is set to an amplification factor for amplifying the distortion voltage component of the voltage scanning electrode detected by the voltage detection electrode in the direction of reducing it. The specific preferable value of this amplification factor is determined depending on the dielectric constant of the liquid crystal layer of each liquid crystal display device, the electrical resistance of the scan electrodes, the signal electrodes, the voltage detection electrodes, etc., the internal resistance of the scan driver circuit, etc. . Therefore, the optimum value may be appropriately obtained for each specification of each liquid crystal display device, and the amplification factor of the operational amplifier element may be set to the optimum value for each specification.

Needless to say, the scan voltage output from the scan driver circuit is a voltage formed by combining a scan non-selection voltage and a 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.

[0027]

In the liquid crystal display device according to the present invention, the voltage detected from the scanning electrode by the voltage detecting means such as the voltage detecting electrode is amplified and polarity-inverted by the operational amplifier circuit, and the amplified voltage is output from the operational amplifier circuit. It is possible to cancel the strain voltage generated in the scan electrode by synthesizing into a potential to be applied and finally negatively feeding back to the voltage of the scan electrode. Here, the operational amplifier circuit should be 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. Needless to say.

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-shaped distortion voltage generated in the voltage of the scan electrode,
By taking out the distorted voltage components from the plurality of scan electrodes collectively and feeding back the distorted voltage components to the scan electrodes negatively, it is possible to suppress the distorted voltage to be generated in the scan electrodes. Therefore, even if the magnitude of the liquid crystal applied voltage such as the scanning voltage and the signal voltage is changed to any value, the stable crosstalk removing effect can be obtained by a simple means.

Further, according to the present invention, it is possible to eliminate the display unevenness of the image during the vertical blanking period which is derived from the negative feedback control.

That is, in a practical liquid crystal display device, generally, in addition to the frame period directly involved in image display, it is not directly involved in image display between one frame period and the next frame period. A vertical blanking period is provided. The liquid crystal applied voltage applied to the liquid crystal layer changes abruptly when shifting from one frame period to the vertical blanking period or shifting from the vertical blanking period to the next frame period. Then, the abrupt change of the liquid crystal applied voltage is detected by the voltage detecting means, and the detected voltage is negatively fed back to the scan electrode through the operational amplifier circuit as noise. Generally, a signal voltage for displaying an image is not applied to the liquid crystal layer during the vertical blanking period. For this reason, during the vertical blanking period, only the voltage negatively fed back as noise is particularly emphasized and applied to the liquid crystal layer. To be seen. This crosstalk is visually recognized by the eyes of the screen viewer while overlapping with the image of the next frame. As a result, the eyes of the screen viewer will perceive it as if crosstalk occurred in the image during the frame period. The present inventors have confirmed that crosstalk is remarkably visually recognized in a display image of an actual liquid crystal display device due to such a phenomenon.

Therefore, in order to eliminate such a display defect visually recognized as crosstalk on the screen during the vertical blanking period, in the present invention, a disconnect switch circuit for controlling the output of the operational amplifier circuit is used. , And a control circuit for controlling the operation of the interrupting switch circuit to turn off the interrupting switch circuit during the vertical blanking period. By using such a disconnect switch circuit, by stopping the negative feedback control described above during the vertical blanking period, the crossing of the screen caused by the noise-like disturbance of the negative feedback control operation during the vertical blanking period. It is possible to eliminate the occurrence of talk.

Thus, according to the present invention, it is possible to eliminate the occurrence of crosstalk on the screen of the liquid crystal display device during the frame period and the vertical blanking period. As a result, it is possible to provide a liquid crystal display device that displays a high-quality image.

[0033]

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

FIG. 1 is a diagram schematically showing the structure of a liquid crystal display device according to an embodiment of the present invention. In this liquid crystal display device, a scanning electrode 1 and a signal electrode 2 made of a transparent electrode such as ITO are opposed to each other in a matrix shape with a gap, and a liquid crystal layer 3 is sandwiched in the gap (liquid crystal display element). A display panel) 4, a scan driver circuit 5 and a signal driver circuit 6 for driving the liquid crystal display element 4,
It has a power supply circuit 7 as a drive voltage generation circuit for supplying a power supply voltage to the scan driver circuit 5 and the signal driver circuit 6. Note that, in FIG. 1, the liquid crystal layer 3 is not represented by using diagonal lines or the like for simplification of the drawing. However, actually, the liquid crystal layer 3 exists in the portions indicated by reference numerals 3 and 10 in the drawing.

Inside the liquid crystal display element 4, one voltage detecting electrode 9 is formed on the signal electrode substrate 8 in parallel with the end of the column of the signal electrodes 2. This voltage detection electrode 9
Are arranged so as to face all the scanning electrodes 1 with the liquid crystal layer 3 in between. The voltage detection electrode 9 supplies the voltage of all the scanning electrodes 1 in the liquid crystal display element 4 to the liquid crystal layer 3
To detect through. 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 capacitance 10 and detects the voltage on the scanning electrode 1 through the capacitive coupling by the electric capacitance 10.

The operational amplifier circuit 11 is connected to the output terminal of the voltage detection electrode 9. This operational amplifier circuit 11
Outputs the voltage detected by the voltage detection electrode 9 after amplifying and reversing the polarity in the direction of effectively eliminating the distorted voltage component generated in the scan electrode 1. Then, the output is combined with each potential output from the power supply circuit 7.

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 a constant determined by various conditions for each design of each liquid crystal display device, such as the electrical characteristics of the liquid crystal composition used for the liquid crystal display element 4 and the internal resistance of the signal driver circuit and the scan driver circuit. is there. 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 also:
Suitable values are determined as different values for each design of each liquid crystal display device. Therefore, it is practically impossible to specifically limit the value of the amplification factor K of the operational amplifier circuit 11. Therefore,
The value for each liquid crystal display device may be substituted into the above equation to appropriately calculate a suitable amplification factor K. Incidentally, in the present embodiment, the value of the amplification factor of the operational amplifier circuit 11 is K =
Set to 10.

The specific circuit structure of the operational amplifier circuit 11 is, as shown in FIG. 2 (and FIG. 1), a buffer amplifier 301a, a differential amplifier 301b, and an inverting amplifier 302.
It is formed of a, b, and c.

The buffer amplifier 301a is used as a so-called buffer for preventing an electric influence from going back to the preceding stage. The voltage detected by the voltage detection electrode 9 passes through the buffer amplifier 301a and the differential amplifier 301.
Input to b. In the differential amplifier 301b, the voltage of the scan pulse is subtracted from the voltage detected by the voltage detection electrode 9, and the strain voltage generated in the scan electrode 1 is extracted and output. This extracted voltage is output to each inverting amplifier 302.
Input to a, b, and c, respectively. Then, the inverting amplifiers 302a, 302b, 302c amplify and invert the polarity of the voltage detected by the voltage detection electrode 9 in the direction of reducing the distortion voltage component of the scan electrode, and respectively output the respective potentials output from the power supply circuit 7. To synthesize. That is, the inverting amplifier 302a synthesizes the voltage detected and amplified / inverted by the voltage detection electrode 9 and the potential V _Y output from the power supply circuit 7. In addition, the inverting amplifier 3
02b synthesizes the voltage detected by the voltage detection electrode 9, amplified and inverted, and the potential V _com output from the power supply circuit 7.
The inverting amplifier 302a synthesizes the voltage detected and amplified / inverted by the voltage detection electrode 9 and the potential V _Y output from the power supply circuit 7. Then, the inverting amplifiers 302a, 302b, 302c respectively output the combined voltage to the scan driver circuit 5.

The potentials ± V _x for producing the signal voltage among the outputs of the power supply circuit are respectively output buffer amplifier 30.
It is output to the signal driver circuit 6 via 3a and 3b.

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 304a, b, c, d as shown in FIG.

As described above, in the liquid crystal display device of the present invention, the voltage including the distortion voltage component on the scanning electrode 1 is taken out, and the voltage is inverted and amplified in the direction of canceling the voltage with respect to the distortion voltage component. It is returned to the scanning 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. The voltage detection electrode 9 extracts a voltage including a distortion voltage component from the scan electrode 1 itself, regardless of whether it is attenuated toward the open end or is affected by any other disturbance. Are calculated and amplified in step S3, combined with the output potential of the power supply circuit 7, and fed back to the scan electrode 1 itself via the scan driver circuit 5. As a result, the distortion voltage component of the scan electrode 1 can be effectively eliminated during the frame period. As a result, the above-described structure can eliminate crosstalk in the display image during the frame period.

Further, the liquid crystal display device of the present invention is
An interrupt switch 305 for stopping the operation of the operational amplifier circuit 11 during the vertical blanking period, and an interrupt switch 305.
And a control circuit 12 for controlling the.

In a liquid crystal display device which is generally used for practical use, in addition to the frame period directly involved in image display, it is directly involved in image display between one frame period and the next frame period. There is a vertical blanking period. The liquid crystal applied voltage applied to the liquid crystal layer 3 changes abruptly when shifting from one frame period to the vertical blanking period or shifting from the vertical blanking period to the next frame period. Then, the abrupt change of the voltage applied to the liquid crystal is detected by the voltage detection electrode 9 through the electric capacity 10 of the liquid crystal layer 3, and the detected voltage passes through the operational amplifier circuit 11 and causes noise to the scanning electrode 1. Will be negatively fed back. In general, the signal voltage for displaying an image is not applied to the liquid crystal layer 3 during the vertical blanking period. Therefore, the distortion voltage due to the change in the signal voltage during the vertical blanking period does not occur as significantly on the scan electrode 1 as during the frame period. Therefore, during the vertical blanking period, the voltage detection electrode 9 and the operational amplifier circuit 11 have almost no effect on the negative feedback control for the voltage of the scan electrode. Rather, only the voltage negatively fed back in a noise manner during the vertical retrace period by the voltage detection electrode 9 and the operational amplifier circuit 11 is particularly emphasized and applied to the liquid crystal layer. As a result, it is visually recognized that crosstalk rather occurs on the screen during the vertical blanking period. That is, noise-induced crosstalk on the screen during the vertical blanking period is visually recognized as overlapping with the image of the next frame. In this way, the eyes of the screen viewer recognize the image as if crosstalk occurs in the image during the frame period. The present inventors have confirmed that crosstalk is remarkably visually recognized in a display image of an actual liquid crystal display device due to the above phenomenon.

Therefore, in order to eliminate such a display defect visually recognized as crosstalk on the screen during the vertical blanking period, the output of the operational amplifier circuit 11 is controlled in the liquid crystal display device of the present invention. The interrupt switch 305 and the control circuit 1 which controls the operation of the interrupt switch 305 and turns off the interrupt switch 305 during the vertical blanking period.
2 is provided.

In the present embodiment, the connection / disconnection switch 305 is connected to the output terminal of the differential amplifier 301b and each inverting amplifier 302a.
It is inserted between b and c. Then, under the control of the control circuit 12, in synchronization with the scan driver circuit 5, the disconnection switch 305 is turned off during the vertical blanking period and is turned on during the frame period.

By using such a disconnecting switch 305,
By canceling the output of the operational amplifier circuit 11 during the vertical blanking period, the crosstalk generated on the screen due to the noise-like disturbance of the negative feedback control during the vertical blanking period is eliminated. .

The control circuit 12 controls the operation of the interrupt switch 305 based on the scan control signal (FP) and the latch pulse (LP) which are also used in the scan driver circuit 5.

As described above, according to the present invention, the occurrence of crosstalk on the screen of the liquid crystal display device can be eliminated during the frame period and the vertical blanking period. As a result, it is possible to provide a liquid crystal display device that displays a high-quality image.

The above has outlined the structure and operation of the liquid crystal display device according to the present invention. Next, the liquid crystal display element 4, the scan driver circuit 5, the signal driver circuit 6, the power supply circuit 7, the interruption switch 305, and the control circuit 12 in the liquid crystal display device according to the first embodiment of the present invention will be described more specifically. The detailed structure and operation will be described.

In this embodiment, the liquid crystal display element 4 is an STN type liquid crystal display element as shown in FIG.
The screen size is A4 and the display capacity (number of pixels) is 240 x
It is 640 dots. The STN type liquid crystal display element 4 has a cell gap of about 7 μm and is provided with an alignment film (not shown) made of a resin subjected to a rubbing alignment treatment, and the liquid crystal of the liquid crystal layer 3 is provided between the cell gaps of the liquid crystal display element 4. The molecules are oriented so that they twist by 240 °. As the liquid crystal composition of the liquid crystal layer 3, ZLI-2293 manufactured by Merck Ltd. was used. The scanning electrode 1, the signal electrode 2, and the voltage detection electrode 9 are formed using ITO (an indium and tin oxide compound) as a material.

In order to realize black and white display on the surface of the signal electrode substrate 8 of the liquid crystal display element 4 on the outward side of the glass substrate 13 and on the surface of the scanning electrode substrate 14 on the outward side of the glass substrate 15. 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 inner surface of the glass substrate 13 on the signal electrode substrate 8 side. The voltage detection electrode 9 is formed at the right end of the column of the signal electrodes 2 in the figure in the form of an elongated strip substantially parallel to the signal electrodes 2. The voltage detection electrode 9 is provided in the liquid crystal display element 4 as follows.
It is arranged so as to traverse all the scanning electrodes 1, and faces the scanning electrodes 1 via the liquid crystal layer 3. 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 face each other.
It is used as a sheet of electrode. In other words, by using the open end portion of the scanning electrode 1, the voltage detection electrode 9, and the liquid crystal layer 3 sandwiched by these two electrodes from the upper and lower surfaces,
The electric capacity 10 is formed.

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 gives a power supply voltage to the scan driver circuit 5 and the signal driver circuit 6, respectively. Then, the operational amplifier circuit 11, the intermittent switch 305, and the control circuit 12
Is actually formed on the circuit board on which the power supply circuit 7 is formed, as shown in FIG. This is to simplify the actual wiring pattern on the circuit board. However, it goes without saying that the specific circuit configuration is not necessarily limited to only incorporating the operational amplifier circuit 11 and the like on the circuit board of the power supply circuit 7 as in this embodiment. For example, when the power supply circuit 7 is formed by an IC itself, the operational amplifier circuit 11 and the like may be added to the outside of the power supply circuit 7 by so-called external attachment. In addition to this, as an actual circuit structure, the operational amplifier circuit 1 described above is used.
Since various variations are conceivable as long as the circuits satisfy the functions of the control circuit 1, the control circuit 12, and the like, this embodiment has shown the simple and compact structure as described above as an example.

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; scan control signal) that determines one frame period as basic scan data, it becomes LP (latch pulse) that determines one scan time. Based on this, the scan data from the outputs Y1 to Y240 are transferred line-sequentially to the 240 register elements provided in the shift register 17.

Inside the switch section 18, switch elements are connected in rows, 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 selects a potential corresponding to the image data from the potentials (+ V _x , -V _x ) output from the power supply circuit 7. Then, a signal voltage is applied to each of the 640 signal electrodes 2 of X1 to X640. That is, the signal driver circuit 6
As shown in FIG. 3, a shift register 19 in which register elements for transferring image data in a line-sequential manner are arranged in a row, and the image data transferred in a line-sequential manner to the register elements of the shift register 19 are arranged at predetermined timings. The main part is formed of a data latch 20 for holding in a parallel state, and a switch section 21 for selecting a potential to be output by betting a signal voltage based on the image data held in a parallel state by the data latch 20. Has been done.

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

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 the electric resistances 304a, b, c, d 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. Here, + V _Y is input to the non-inverting terminal of the inverting amplifier 302a. Then, in the inverting amplifier 302a,
+ V _Y is combined with the voltage detected by the voltage detection electrode 9 and then supplied to the scan driver circuit 5. Also, -V _Y is input to the non-inverting terminal of the inverting amplifier 302c. And in inverting amplifier 302c, -V _Y voltage detecting electrodes 9
It is supplied to the scan driver circuit 5 after being combined with the voltage detected from. Further, V _com is input to the non-inverting terminal of the inverting amplifier 302b, and after being combined with the voltage detected from the voltage detection electrode 9, it is supplied to the scan driver circuit 5.

Further, + V _x and -V _x are supplied to the signal driver circuit 6 via the output buffer amplifiers 303a and 303b, respectively.

Then, the scan driver circuit 5 includes the scan electrodes 1
On the other hand, the scanning voltage having the waveform as shown in the example in FIG. 5 is applied. Further, the signal driver circuit 6 applies a signal voltage having a waveform as shown in the example in FIG. 5 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 liquid crystal layer 3 sandwiched at the intersection of the scanning electrode 1 and the signal electrode 2. The voltage waveform applied to is a waveform as an example shown in FIG.

In other words, 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).

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. The switch section 18 in the scan driver circuit 5 and the switch section 21 in the signal driver circuit 6 described above are controlled by a polarity inversion signal (FR) and are formed to invert the polarity at a constant cycle. As for this structure, a general structure for performing polarity reversal is used. That is, in the switch unit 18, 1
When scanning is selected for each frame, the polarity of voltage is + V _Y
And -V _Y are changed alternately. At this time, the scanning non-selection voltage V _com is an intermediate voltage between + V _Y and −V _Y.
In other words, with the voltage V _com at the time of non-selection of scanning as the center, + V
_The waveform is such that _Y and -V _Y appear with their polarities alternately inverted for each frame.

Here, induced by the change in the signal voltage of the signal electrode 2 facing the scanning electrode 1 through the liquid crystal layer 3, a distortion voltage component is generated in the voltage of the scanning electrode 1.

[0068] During the scanning non-selection period, as described above, the scanning non-selection voltage V _{co m} is applied to the scanning electrode 1. This V _com is a flat waveform 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 liquid crystal display device of the present invention,
The voltage detection electrode 9 detects the voltage of the scan electrode 1 including the above-mentioned distortion voltage component from the scan electrode 1 itself through the liquid crystal layer 3. The single voltage detection electrode 9 is arranged to face all the scanning electrodes 1 with the liquid crystal layer 3 interposed therebetween. Therefore, this one voltage detection electrode 9 is used for all the scanning electrodes 1.
The voltage that averages the voltage of is detected. The voltage detected by the voltage detection electrode 9 is input to the operational amplifier circuit 11.

The operational amplifier circuit 11 amplifies and inverts 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, when a voltage including a distortion voltage having a displacement in the + direction with reference to V _com is detected by the scanning electrode 1 to the voltage detection electrode 9, the detected voltage has a distortion voltage component in the operational amplifier circuit 11. The extracted voltage is inverted and amplified, and becomes a voltage including a voltage having a waveform similar to the waveform of the distorted voltage component of the scan electrode 1 and having an amplitude in the − direction with reference to V _com . The voltages thus inverted and amplified in the operational amplifier circuit 11 are combined with + V _Y , V _com , and −V _Y output from the power supply circuit 7 inside the operational amplifier circuit 11. Then, it is output from the operational amplifier circuit 11 to the scan driver circuit 5. Then, this voltage is finally fed back to the scan electrode 1 via the scan driver circuit 5.

In this embodiment, as the operational amplifier circuit 11, a differential amplifier is used to extract the distortion voltage component. The voltage from the voltage detection electrode 9 is input to the non-inverting input terminal side of the differential amplifier 301b, while the voltage (signal) that does not include distortion is input to the inverting input terminal side. Then, the distortion voltage is extracted by taking the difference between the two in the differential amplifier. At this time, the voltage (signal) not including the distortion was obtained by switching the two DC potentials using the polarity inversion signal FR. This is shown as a switch circuit 306 in FIG. This switch circuit 306 causes two potentials of + V _x and −V _x to be FR.
Switching based on the signal. In this way, it is possible to accurately detect the distortion voltage by the differential amplifier 301b using the voltage without distortion.

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 can be effectively canceled by negative feedback control. As a result, it is possible to remove unevenness in density (crosstalk) in the display screen of the liquid crystal display device and maintain good image display.

Then, in order to eliminate a display defect visually recognized as crosstalk on the screen during the vertical blanking period, a disconnection switch 305 which controls the output of the operational amplifier circuit 11 is eliminated.
In the present embodiment, the control circuit 12 for controlling the operation of the interruption switch 305 and turning the interruption switch 305 off during the vertical blanking period is formed.
The interrupt switch 305 is inserted between the output terminal of the differential amplifier 301b and each of the inverting amplifiers 302a, 302b, 302c.
Then, under the control of the control circuit 12, in synchronization with the scan driver circuit 5, the intermittent switch 30 is operated during the vertical blanking period.
5 is turned off and is turned on during the frame period. The connection / disconnection switch 305 itself may be any switch that can perform a simple connecting / disconnecting operation. That is, as the disconnecting switch 305, for example, an FET
Elements and analog switches can be used.

By using such a connecting / disconnecting switch 305,
By canceling the output of the operational amplifier circuit 11 during the vertical blanking period, the crosstalk generated on the screen due to the noise-like disturbance of the negative feedback control during the vertical blanking period is eliminated. To do.

Then, the control circuit 12 controls the operation of the interrupt switch 305 based on the scan control signal (FP) and the latch pulse (LP) which are also used in the scan driver circuit 5. The circuit structure of the control circuit 12 is formed as a counter circuit in this embodiment.

FIG. 6 is a timing chart showing the operation timings of the control circuit 12 and the interruption switch 305, the scanning control signal (FP) and the latch pulse (LP). When the control circuit 12 including a counter circuit detects the start of one frame based on the scanning control signal (FP), it counts from the latch pulse (LP) from that point. When the 241st pulse of the latch pulse (LP) is counted, it is continuously interrupted in the vertical blanking period from this time to the 245th latch pulse (that is, the falling edge of the FP pulse of the next frame). A control signal for turning off the switch 305 is generated. This operation is performed for each vertical blanking period, and the disconnection switch 305 is turned off for each vertical blanking period. on the other hand,
In each frame period, a control signal for turning on the intermittent switch 305 is generated.

In this embodiment, the number of scanning lines is 2
Since the case of a liquid crystal display device in which 40 lines are driven under a drive condition of 1/244 duty is described as an example, the vertical blanking period is the period for four scanning lines as described above. However, it goes without saying that the application of the technique of the present invention is not limited to only one example of such driving conditions. The present invention can be applied to a liquid crystal display device using other driving conditions. In that case, the detection timing of the vertical blanking period in the control circuit 12 may be appropriately changed according to the number of scanning lines and the number of LP pulses in the vertical blanking period for each liquid crystal display device. For example, when the number of scanning lines is 480 and the liquid crystal display device has a vertical blanking period of 8 scanning lines, counting is started by using FP as a trigger, and 481 to 488 pulses are vertically returned. The control circuit 12 may be set so as to detect as a line period and generate a control signal for turning off the interruption switch 305 during that period.

In the liquid crystal display device of the first embodiment according to the present invention as described above, a duty ratio of 1/244 and a bias ratio are used by using a liquid crystal drive voltage having a waveform as shown in FIG.
Display was performed by driving at a frame frequency of 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.

Further, no matter what kind of display data the signal voltage corresponding to is applied to the 240th scanning selection period of a frame and the 1st scanning selection period of the next frame, a display defect such as crosstalk occurs on the screen. There wasn't.

Furthermore, the state of the screen was confirmed by variously changing the display data corresponding to the 241st to 244th scanning periods corresponding to the vertical blanking period. That is, the signal voltage during the vertical blanking period was changed variously, and the image display states before and after the vertical blanking period were examined. As a result, no display failure such as crosstalk occurred on the screen. In particular,
The state of the screen during the vertical blanking period was confirmed, but there was no display disorder on the screen that would cause screen crosstalk.

Further, although Chinese characters and alphabets were continuously displayed, the generation of the distortion voltage in the scanning electrodes was suppressed and the uniform display without crosstalk could be maintained. From such an experimental result, the liquid crystal display device of the present invention has a problem of occurrence of display unevenness (crosstalk) on the screen.
We have confirmed that high-quality image display can be achieved by solving by simple and inexpensive means.

(Comparative Example to the Above Example) A liquid crystal display device having a structure in which the interrupt switch 305 and the control circuit 12 were removed from the liquid crystal display device of the above example was prepared.
That is, although the operational amplifier circuit 11 having the negative feedback control function and the voltage detection electrode 9 are provided, the disconnection switch 305 and the control circuit 12 for canceling the operational amplifier circuit 11 during the vertical retrace period are not provided. A display device was prepared. Then, this liquid crystal display device was caused to perform display under the same driving conditions as those in the above-mentioned examples, and the display quality was visually confirmed.

That is, after the entire screen is displayed 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 the number of horizontal dots in this area is up to 500 dots. It gradually increased. as a result,
In either case, the negative feedback control was effectively performed on the screen during the frame period, and a uniform display without crosstalk could be maintained.

However, the display data corresponding to the 240th and 241st to 244th scanning periods corresponding to the vertical blanking period are greatly increased from the display data in the frame period directly related to the image display before and after that. Various changes, such as changing. As a result, the voltage applied to the liquid crystal changed during the vertical blanking period, crosstalk occurred on the screen, the nonuniformity of the screen was conspicuous, and the display quality was significantly deteriorated.

[0086]

As is clear from the detailed description above, according to the present invention, the problem of display unevenness (crosstalk) on the screen of a liquid crystal display device can be solved by a simple and inexpensive means. it can. Further, in the present invention, it is possible to eliminate the display unevenness (crosstalk) of the screen that has been conventionally generated due to the voltage fluctuation during the vertical blanking period. As a result, 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 according to the present invention.

FIG. 2 is a diagram showing a structure of a power supply circuit and an operational amplifier circuit of a liquid crystal display device according to the present invention.

FIG. 3 is a diagram showing an overall circuit structure of a liquid crystal display device according to the present invention.

FIG. 4 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 according to the present invention.

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

FIG. 6 is a timing chart showing operation timings of the control circuit 12 and the interrupt switch 305 of the liquid crystal display device according to the present invention, and a scan control signal (FP) and a latch pulse (LP).

FIG. 7 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 ... Control circuit 305 ... Interruption switch

Claims (2)

[Claims] 1. A scanning electrode substrate having a plurality of scanning electrodes formed thereon, and a plurality of signal electrodes formed so as to intersect with the scanning electrodes, and the signal electrodes and the scanning electrodes face each other with a gap maintained. Liquid crystal display panel having a signal electrode substrate arranged in such a manner and a liquid crystal layer sealed and sandwiched around the gap, and driving voltage generation for outputting a plurality of potentials for generating a scanning voltage And a selection switch circuit that selects one potential from a plurality of potentials output from the drive voltage generation circuit and applies the selected potential to the scan electrode. The scan voltage is formed by the operation of the selection switch circuit. Then, a scan driver circuit that applies the scan voltage to each of the plurality of scan electrodes, a signal driver circuit that applies a signal voltage to each of the plurality of signal electrodes, and each of the plurality of scan electrodes A voltage detection unit having a plurality of electric capacities or a plurality of electric resistances, each of which is connected at one end, and the other ends of the plurality of electric capacities or a plurality of electric resistances of the voltage detection unit are electrically connected together to the input end. In the operational amplifier circuit, the voltage input to the input terminal is amplified and polarity-inverted in a direction to reduce the distortion of the voltage of the scan electrode and output from the output terminal, and the output of the drive voltage generation circuit is output. An operational amplifier circuit for synthesizing the potential of the operational amplifier circuit, a switching switch circuit for controlling ON / OFF of the output of the operational amplifier circuit, and a control circuit for controlling the operation of the switching switch circuit. A liquid crystal display device, comprising: a control circuit for turning off the intermittent switch circuit during a frame period and turning on the intermittent switch circuit during a frame period. 2. A scan electrode substrate having a plurality of scan electrodes formed thereon, and a plurality of signal electrodes formed so as to intersect with the respective scan electrodes, and the signal electrodes and the scan electrodes face each other with a gap maintained. Liquid crystal display panel having a signal electrode substrate arranged in such a manner and a liquid crystal layer sealed and sandwiched around the gap, and driving voltage generation for outputting a plurality of potentials for generating a scanning voltage And a selection switch circuit that selects one potential from a plurality of potentials output from the drive voltage generation circuit and applies the selected potential to the scan electrode. The scan voltage is formed by the operation of the selection switch circuit. A scan driver circuit for applying the scan voltage to each of the plurality of scan electrodes, a signal driver circuit for applying a signal voltage to each of the plurality of signal electrodes, and the signal driver circuit on the signal electrode substrate. A voltage detection electrode formed in parallel with the electrode, and is arranged so as to be opposed to a portion of each scanning electrode different from the input end portion to which the scanning voltage is applied, while maintaining a gap. A voltage detection electrode for detecting the voltage of the scan electrode via the liquid crystal layer, and an amplifier in which the voltage detection electrode is connected to an input end and the voltage detected from the voltage detection electrode is input to the input end An arithmetic circuit that amplifies the input voltage in a direction to reduce distortion of the voltage of the scan electrode, inverts the polarity, outputs the amplified voltage, and outputs the output voltage from the drive voltage generating circuit. An amplifier circuit, a switching switch circuit for controlling on / off of a combined operation of the output of the operational amplifier circuit and the potential output by the drive voltage generation circuit, and a control circuit for controlling the operation of the switching switch circuit And a control circuit for turning off the interruption switch circuit during a vertical blanking period and turning on the interruption switch circuit during a frame period. apparatus.