JPH056149A - Driving method of liquid crystal display device - Google Patents

Abstract

(57) [Abstract] [Purpose] Multi-level gradation display is performed without using multi-level voltage level drive signals, and moreover, fluctuations in transmittance due to the influence of image data applied to other pixels are suppressed. By reducing the number, it is possible to obtain a display with a correct gradation according to the image data. [Structure] Between the drive signal input terminal of the active element 2 composed of a diode and the counter electrode 4, during the selection period T _S , selection of either positive or negative polarity having a pulse of a width or number according to image data. In the non-selection period T _{O in} which a voltage is applied to select another pixel, the potential changes in a cycle shorter than the selection period, and the scanning signal S _S supplied to one of the signal line 3 and the counter electrode 4 is supplied. A voltage having a waveform in which the areas of the positive side and the negative side are substantially equal to each other with the non-selection potential V _C2 as the center is applied.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a method of driving an active matrix liquid crystal display device having a non-linear resistance element as an active element.

[0002]

2. Description of the Related Art As an active matrix liquid crystal display element used for a display device such as a television set or a personal computer, there is one using a non-linear resistance element as an active element.

An active matrix liquid crystal display element using this non-linear resistance element as an active element has pixel electrodes arranged in a row direction and a column direction on one of a pair of transparent substrates facing each other with a liquid crystal layer interposed therebetween. And an active element composed of a non-linear resistance element connected to each of these pixel electrodes, and a signal line for supplying a drive signal to this active element, and a counter electrode facing the pixel electrode is provided on the other substrate. In the liquid crystal display element having the configuration provided, a scanning signal is supplied to one of the signal line and the counter electrode, and a data signal is supplied to the other, so that the pixel electrode and the counter electrode and the liquid crystal therebetween are provided. The plurality of pixels formed by are sequentially selected and driven in time division.

The non-linear resistance element used as the active element of the active matrix liquid crystal display element is MI.
An element having an M structure (metal-insulating film-metal laminated structure) (hereinafter,
MIM)) and an element having a semiconductor such as a thin film diode, and the active element formed of a thin film diode includes one called a diode ring and one called a back-to-back.

However, in the active matrix liquid crystal display element using the MIM as an active element, the inter-electrode voltage of the pixel (the pixel electrode and the counter electrode is different from the selection voltage applied between the drive signal input end of the MIM and the counter electrode). It has a problem of poor followability.

That is, in the active matrix liquid crystal display element using the MIM as an active element, a current flows through the MIM in response to a drive signal supplied from a signal line, and the current causes a charge to be accumulated between both electrodes of the pixel, A voltage according to the accumulated charges is applied to the liquid crystal, but the MIM
Has a slow current-voltage characteristic, and a sufficient current does not flow, so that the rate of increase of the voltage between both electrodes is slow. Therefore, since the inter-electrode voltage of the pixel cannot be increased within the limited selection period, the inter-electrode voltage of the pixel follows the selection voltage applied between the input terminal of the MIM and the counter electrode. It does not change.

This is because the current flowing through the MIM is a tunnel current based on the tunnel effect, and the element area of the MIM used as an active element of the liquid crystal display element is limited, so that it is difficult to increase the tunnel current. Because.

Therefore, it is necessary to drive the liquid crystal display element using the MIM as an active element at a considerably high voltage (especially, in the case of high time division driving, the selection period becomes short, so that a higher voltage is required. Therefore, the power consumption is large, and the drive circuit for generating the drive signal of high voltage is required to have a high breakdown voltage, so that it is difficult to integrate the drive circuit.

Further, since the liquid crystal display element using the MIM as the active element has a slow current-voltage characteristic of the MIM as described above, the selection voltage applied between the input terminal of the active element and the counter electrode is large. The change width of the voltage between the electrodes of the pixel with respect to the change of is small, and in order to perform gradation display that changes the degree of brightness of the pixel, it is necessary to change the voltage value of the selection voltage with an extremely large width. The key display was also difficult.

On the other hand, a non-linear resistance element having a semiconductor, for example, an active matrix liquid crystal display element using a thin film diode as an active element, has a current-
Since the voltage characteristic is abrupt, it can be driven at a relatively low voltage, and gradation display is also possible. The gradation display of the active matrix liquid crystal display element is conventionally performed by a driving method called voltage modulation.

This driving method by voltage modulation is a method of controlling the voltage value of the selection voltage according to the image data, and the voltage value according to the image data is applied between the input terminal of the active element and the counter electrode during the selection period. When the selection voltage is applied, electric charges are accumulated between both electrodes of the pixel during this selection period, the voltage between the electrodes rises to a voltage value according to the image data, and the liquid crystal of the pixel responds to the above image data. A voltage is applied.

[0012]

However, since the above-described conventional driving method performs gradation display by controlling the voltage value of the selection voltage according to the image data, the number of display gradations is used as the driving signal. Therefore, there is a problem in that the driving circuit becomes complicated as the number of display gradations increases, so that a power supply circuit that outputs a voltage of a multi-step voltage level is required as the number of display gradations increases.

Moreover, in the conventional driving method, the voltage accumulated in the pixel during the selection period fluctuates due to the influence of the image data for driving the other pixels in the same column during the non-selection period. There is a problem that the light transmittance of the pixel changes.

This is because the active element has a capacitance, and an active element composed of a non-linear resistance element having a semiconductor such as a thin film diode is much smaller than the capacitance which the MIM has, but it is conductive. There is some capacitance between the bodies (between the upper and lower electrodes in a thin film diode).

Therefore, the pixel and the active element in the active matrix liquid crystal display element have a capacitance (hereinafter, referred to as a pixel) which is formed by the pixel electrode and the counter electrode and the liquid crystal between them when the active element is in the ON state. This is represented by an equivalent circuit in which C _LC and an active element are connected in series, and when the active element is turned off, the pixel capacity C _LC and the capacity of the active element (hereinafter referred to as element capacity)
It is represented by an equivalent circuit in which C _D is connected in series.

Therefore, the inter-electrode voltage V _LC of the pixel is the current-voltage of the active element up to the voltage applied between the input terminal of the active element and the counter electrode during the selection period when the active element is on. The active element rises in a rising curve according to the characteristics and the charging characteristic of the pixel capacitance C _LC , but when the selection period elapses into the non-selection period, the applied voltage drops to the non-selection voltage, and the active element is turned off. Acts as a capacity,
The amount of decrease in the voltage between the input terminal of the active element and the counter electrode (the voltage difference between the selected voltage and the non-selected voltage) is the pixel capacitance C _LC and the element capacitance C _{D of the} active element that are connected in series. In addition, the voltage is divided at a ratio opposite to the capacity ratio.

Therefore, the voltage held in the pixel capacitance C _LC in the non-selection period is changed from the voltage charged in the selection period to the voltage between the input terminal of the active element and the counter electrode in the non-selection period. Of the voltage drop amount, the value is reduced by the divided voltage amount to the pixel capacitance C _LC .

Due to its responsiveness, the liquid crystal between both electrodes of the pixel does not operate at the voltage applied during the extremely short selection period, and the inter-electrode voltage of the pixel (holding the pixel capacitance C _LC during the non-selection period). Therefore, if the inter-electrode voltage V _LC drops significantly during the non-selection period, the effective voltage for operating the liquid crystal becomes low.

Therefore, in the above active matrix liquid crystal display element, between the input end of the active element and the counter electrode,
The pixel is driven by applying a voltage that allows for the decrease in the inter-electrode voltage of the pixel in the non-selection period. If the selection voltage with such a voltage value is applied, the selection period ends and the non-selection is completed. Since the inter-electrode voltage V _LC of the pixel at the time becomes the voltage value according to the image data, the transmittance of the pixel can be set to the gradation according to the image data.

However, the active matrix liquid crystal display element is driven in a time division manner by supplying a scanning signal to one of the signal line for supplying a driving signal to the active element and the counter electrode and supplying a data signal to the other. , The image data for driving other pixels in the same column is applied together with the data signal to the input terminal of the counter electrode or the active element of the pixel which has entered the non-selection period after the selection period, and therefore the non-selection period The voltage between the input terminal of the active element of the inside pixel and the counter electrode fluctuates.

When the voltage between the input terminal of the active element and the counter electrode changes in this way, the voltage between the electrodes of the pixel, that is, the holding voltage of the pixel capacitance C _LC changes. The change in the holding voltage of the pixel capacitance C _LC is similar to the change in the voltage when the selection period is changed to the non-selection period, and the variation amount of the voltage between the input terminal of the active element and the counter electrode is changed to the pixel capacitance C _LC. And element capacitance C _D
The pixel capacitance C of the voltage divided at a ratio opposite to the capacitance ratio with
_It is the voltage divided by _LC .

Since the liquid crystal between both electrodes of the pixel operates according to the voltage between the electrodes of the pixel (the holding voltage of the pixel capacitance C _LC ) in the non-selection period as described above, as described above. When the holding voltage of the inside pixel capacitance C _LC changes due to the influence of the image data for driving other pixels, the transmittance of the pixel changes accordingly, and the display of the correct gradation according to the image data can be obtained. Disappear.

The present invention is directed to a method of driving an active matrix liquid crystal display device using an active element composed of a non-linear resistance element having a semiconductor.
It is possible to perform multi-gradation gray scale display without using multi-level voltage level drive signals, and reduce fluctuations in transmittance due to the influence of image data for driving other pixels, It is an object of the present invention to provide a driving method capable of obtaining a display with a correct gradation according to image data.

[0024]

According to the driving method of the present invention, a positive or negative pulse having a width or a number of pulses corresponding to image data is provided between the drive signal input terminal of the active element and the counter electrode during the selection period. In a non-selection period in which a selection voltage of one polarity is applied and another pixel is selected, the potential changes in a cycle shorter than the selection period and a scanning signal supplied to one of the signal line and the counter electrode. It is characterized in that a voltage having a waveform in which the areas on the positive side and the negative side are substantially equal to each other with respect to the potential in the non-selection period is applied.

In this driving method, for example, one of the signal line and the counter electrode is kept at a positive or negative potential during the selection period, and is positive or negative during the non-selection period, and the selection is performed. A scanning signal that keeps a potential lower than the potential during the period is supplied, and on the other hand, a positive side and a negative side with respect to the reference potential are provided with a pulse having a width or number of pulses according to image data and a selection period divided into a plurality Can be implemented by supplying a data signal whose potential changes with an amplitude approximately equal to.

[0026]

That is, according to the present invention, a liquid crystal display element using an active element composed of a non-linear resistance element having a semiconductor is driven by a modulation system according to a pulse width or a pulse number, and is composed of a non-linear resistance element having a semiconductor. Since the active element has a rapid current-voltage characteristic and high responsiveness, charge is rapidly accumulated between the pixel electrode and the counter electrode, so that a voltage is applied between both electrodes. The rising speed of the voltage between both electrodes with respect to time is fast.

Therefore, the voltage applied between the pixel electrode and the counter electrode changes according to the pulse width or the number of pulses of the selection voltage applied between the drive signal input terminal of the active element and the counter electrode. .

Therefore, if the selection voltage pulse width or the number of pulses is controlled according to the image data, the voltage applied between the pixel electrode and the counter electrode can be changed to control the transmittance of the pixel. it can.

In the present invention, the liquid crystal display element using the semiconductor active element is driven not by the conventional voltage modulation method but by the modulation method based on the pulse width or the number of pulses. It is possible to cause the liquid crystal display element to perform multi-gradation gradation display without using multi-level voltage level drive signals.

In addition, in the present invention, a selection voltage having either a positive or negative polarity of the pulse width or the number of pulses according to the image data is provided between the drive signal input terminal of the active element and the counter electrode during the selection period. A waveform in which the potential changes in a cycle shorter than the selection period during the non-selection period in which the applied voltage is applied and other pixels are selected, and the areas on the positive side and the negative side of the potential of the scanning signal in the non-selection period are substantially equal to each other. Since the voltage of 1 is applied, there is almost no change in the transmittance of the pixel during the non-selection period.

That is, the inter-electrode voltage of the pixel during the non-selection period fluctuates every moment under the influence of the image data for driving the other pixels. If the voltage applied to the counter electrode is a voltage having the above waveform, the variation in the voltage between the electrodes of the pixel is
The fluctuation amount of the voltage to the positive side and the fluctuation amount of the voltage to the negative side around the potential of the scanning signal in the non-selection period become almost equal fluctuations, and the effective value of the inter-electrode voltage of the pixel (holding Voltage) hardly changes.

Therefore, since the holding voltage of the pixel does not change during the non-selection period, the transmissivity of the pixel becomes the transmissivity corresponding to the voltage accumulated between the electrodes of the pixel according to the selection voltage applied during the selection period. To be kept. Therefore, it is possible to obtain the display of the correct gradation according to the image data.

[0033]

【Example】

(First Embodiment) Hereinafter, a first embodiment of the present invention will be described with reference to FIGS.
This will be described with reference to FIG.

First, the structure of an active matrix liquid crystal display element driven by the driving method of this embodiment will be described. FIG. 5 is a plan view of a part of the liquid crystal display element. Here, a nonlinear resistance element having a semiconductor is shown. The active element composed of a diode ring composed of a thin film diode is shown.

This liquid crystal display element includes a pair of transparent substrates (both not shown) facing each other with a liquid crystal layer interposed therebetween, and a plurality of pixel electrodes 1 arranged in the row and column directions on one substrate. , An active element 2 connected to each of these pixel electrodes, and a signal line 3 for supplying a drive signal to the active element 2.
And the counter electrode 4 facing the pixel electrode 1 is provided on the other substrate.

The active element 2 is a so-called diode ring in which the same number of thin film diodes 5 and 6 are connected in parallel in opposite directions, one end of which is connected to the pixel electrode 1 and the other end of which is connected to the signal line 3. Has been done.

Although FIG. 5 shows one thin film diode 5 and one thin film diode 6 which form a diode ring, the forward circuit and the reverse circuit of this diode ring generally include a plurality of thin film diodes. It is configured by connecting in series.

The signal line 3 is provided for each active element group arranged in the row direction (horizontal direction in the drawing), and the semiconductor active element 2 is connected to the signal line 3 for each row. Further, the counter electrode 4 is provided for each pixel electrode group arranged in the column direction (vertical direction in the drawing), and each counter electrode 4 faces the pixel electrode 1 of each column via a liquid crystal (not shown). . Each pixel of this liquid crystal display element is formed by the pixel electrode 1, the counter electrode 4 and the liquid crystal between them.

FIG. 6 is an equivalent circuit diagram of one pixel display element of the liquid crystal display element. Since the pixel formed by the pixel electrode 1, the counter electrode 4 and the liquid crystal between them is equivalent to a capacitor, As shown in FIG. 6A, a pixel display element including a pixel and an active element 2 has a capacitance (hereinafter, referred to as pixel capacitance) C _{LC of the} pixel and an active element 2 including a diode ring connected in series. It is represented by a connected equivalent circuit.

Further, the thin film diodes 5 and 6 forming the diode ring which is the active element 2 have a pair of electrodes opposed to each other with the semiconductor layer having the P-I-N junction structure sandwiched therebetween. 5 and 6 have a capacitance, so that the active element 2 also has the above-mentioned thin film diode 5,
It has a capacity equivalent to the sum of the capacities of 6. For this reason,
The equivalent circuit is represented by a series connection circuit of the pixel capacitance C _CL and the capacitance of the active element 2 (hereinafter, referred to as element capacitance) C _D as shown in FIG. 6B when the diode ring is off. Be done.

This liquid crystal display element is driven for display by supplying a drive signal to each signal line 3 and each counter electrode 4. In this display drive, for example, a sequential scanning signal is applied to each signal line 3. The counter electrode 4 is supplied and synchronized with this.
Data signal is supplied to each pixel to sequentially select each pixel by time division driving.

This driving method will be described. FIG. 1 is a waveform diagram of the driving signal. FIG. 1A shows the waveform of the scanning signal S _S supplied to the signal line 3 in the first row, and FIG. 6C shows a waveform of the data signal S _D supplied to the counter electrode 4 of FIG. 6, where (c) is between the drive signal input end (connection end with the signal line 3) of the active element 2 and the counter electrode 4 (a in FIG. 6). The waveform of the voltage Va-c applied between the point and the point c) is shown. In FIG. 1, T _S represents one field T _F in the number of pixel rows (number of signal lines)
It is a selection period divided according to.

The scanning signal S _S becomes the selection potential V _C1 during the selection period T _S , and the non-selection potential V _C2 during the non-selection period T _O.
And the polarity is inverted between the positive side and the negative side around the reference potential V _{G in the} cycle corresponding to one field T _F. It said selection potential V _C1 is the potential difference is higher than the threshold voltage of the active element (diode rings) second potential between the reference potential V _G, the non-selection potential V _C2 is the potential difference between the reference potential V _G is active The potential is lower than the threshold voltage of the element 2.

The data signal S _D is a signal having a data pulse having a width corresponding to image data supplied from the outside in synchronization with the selection period of the pixels in each row, and the data signal S _D is for each row. Selection period T for each pixel selection period
A cycle in which _S is evenly divided, for example, the selection period T _S is 2
The potential changes to the positive side and the negative side with respect to the reference potential V _G in an equally divided cycle.

[0045] That is, the data signal S _D is a signal having a data pulse width corresponding to the image data every half period 1 / 2T _S selection period T _S, the first half of the selection period T _S And the data pulse in the latter half of the selection period T _S are pulses having polarities opposite to each other with respect to the reference potential V _G. Further, the data pulses in the first half and the second half of one selection period T _S are pulses according to the same image data,
Therefore, the pulses on the positive side and the negative side have the same width and the absolute value of the potential V _S is also equal. The data pulse (pulse on the positive side and the pulse on the negative side) for each selection period T _S is
The absolute value of the potential V _S is the same, and only the pulse width changes according to the image data supplied in each selection period T _S.

That is, in the data signal S _D , the waveform of each waveform for each selection period T _S is the area of the waveform on the positive side with the reference potential V _G as the center (the area of the region shaded to the right in FIG. 1). The signal A1 and the area of the waveform on the negative side (the area of the region shaded in the lower right in FIG. 1) B1 are substantially equal in waveform.

The data signal S _D shown in FIG. 1 has a pulse width (width of the data pulse on the positive side and the negative side) of the selection period T _S1 of the pixels in the first row is 1/10 of the selection period. The pulse width of the selection period T _S2 of the pixels of the second row is 4/10 of the selection period, and the pulse width of the selection period T _S3 of the pixels of the third row is the signal of 3/10 of the selection period. _D selection periods T _S1 , T _S2 ,
T _S3 ... each of the pulse width in accordance with the image data, the selection period T _S 0/10 (no pulse) 5/10 (the selection period T _S 1/2
The full width of) changes.

When the scanning signal S _S and the data signal S _D having such waveforms are supplied to the signal line 3 and the counter electrode 4, the drive signal input terminal of the active element 2 connected to the signal line 3 (hereinafter, A voltage (scanning signal S _S and data signal S _D) having a waveform obtained by combining the scanning signal S _S and the data signal S _D as shown in FIG. 1C between the counter electrode 4 and the input electrode). Voltage Va-c corresponding to the potential difference between

The voltage Va-c applied between the input terminal of the active element 2 and the counter electrode 4 has a positive or negative polarity having a pulse width corresponding to the image data during the selection period T _S. Is a voltage of which the potential changes in a cycle of ½ of the selection period T _{S in} the non-selection period T _O in which another pixel in the same column is selected.

That is, of the voltage Va-c, the selection voltage applied during the selection period T _S is the data signal S _D.
Is 0, it is the same as the selection potential V _C1 of the scanning signal S _S , and when the potential of the data signal S _D becomes the potential of the data pulse, the selection potential V _C1 of the scanning signal S _S becomes Voltage V _C1 + V with potential V _S or −V _S superimposed
_S or V _C1 −V _S.

The selection voltage (hereinafter referred to as the reference selection voltage) V _C1 when the potential of the data signal S _D is 0 is the threshold voltage of the thin film diodes 5 and 6 of the diode ring which is the active element 2. Higher voltage. Further, the selection voltage V _C1 + V _S when the potential of the data signal S _D becomes the potential V _S of the data pulse on the positive side with respect to the reference potential V _G is higher than the reference selection voltage V _C1 . Select voltage V _C1 −V _S when the potential of the data signal S _D becomes the potential −V _S of the data pulse on the negative side with respect to the reference potential V _G
Is a high voltage lower than the reference selection voltage V _C1 .

The voltage applied between the input terminal of the active element 2 and the counter electrode 4 during the non-selection period T _O (hereinafter referred to as non-selection voltage) drives other pixels in the same column. Is a voltage in which the data pulse corresponding to the image data is superimposed on the scanning signal S _S , and this non-selection voltage is the same as the non-selection potential V _C2 of the scanning signal S _S when the potential of the data signal S _D is 0. However, when the potential of the data signal S _D becomes the potential of the data pulse, the voltage V _C2 + V in which the potential V _S or −V _S of the data pulse is superimposed on the non-select potential V _C2 of the scanning signal S _S
S or V _C2- V _S.

The voltages V _C2 + V _S and V _C2 -V _S are both lower than the reference selection voltage V _C1 of the selection voltage applied during the selection period T _S , and the scanning signal S _S is not selected. voltage V _C2 + V _S to which the data pulse voltage V _S of the positive side is superimposed on reference potential V _G to the potential V _C2, the scanning signal S _S negative data the selection potential V _C1 with respect to the reference potential V _G of The voltage is lower than the superimposed voltage V _C1 −V _{S of the} pulse potential −V _S.

That is, the non-selection voltage is a voltage in which a positive side data pulse and a negative side data pulse corresponding to image data for driving other pixels in the same column are superposed, In S _D , the waveform for each selection period T _S is the area A1 of the waveform on the positive side with the reference potential V _G as the center.
And the area B1 of the waveform on the negative side are substantially equal to each other, the non-selection voltage is equal to the area A2 of the waveform on the positive side centering on the non-selection potential V _C2 of the scanning signal S _S and the area on the negative side. The voltage is approximately equal to the area B2 of the waveform.

Then, the input end of the active element 2 and the counter electrode 4
When the selection voltage is applied between and, the voltage is applied between the pixel electrode 1 connected to the active element 2 and the counter electrode 4. That is, in FIG. 6, when a selection voltage is applied between a and c, the potential difference between both ends of the active element 2 composed of a diode ring becomes higher than its threshold voltage, the active element 2 is turned on, and the pixel electrode An electric current flows in 1 and a voltage is applied between bc (between the pixel electrode 1 and the counter electrode 4).

As described above, when the voltage is applied between b and c, the charging of the pixel capacitance C _LC formed by the pixel electrode 1, the counter electrode 4 and the liquid crystal between them is started. The charging of the pixel capacitance C _LC is continued during the selection period T _S.

When the selection period T _S elapses and the non-selection period T _O is reached, at this time, the charging of the pixel capacitance C _LC progresses and the charging voltage becomes high.
_{Since the} voltage applied to _{O from} the signal line 3 to the input terminal of the active element 2 becomes low, the potential difference between both ends of the active element 2 becomes small, the active element 2 is turned off, and the charging of the pixel capacitance C _LC is stopped. To do.

In this case, when the active element 2 is turned off, the active element 2 acts as a capacitor, and therefore, FIG.
A-c voltage (voltage between the input terminal of the active element 2 and the counter electrode 4) Va-c at (a difference between the voltage in the selection period T _{S and} the voltage in the non-selection period T _O ) Is the pixel capacitance C _LC and the element capacitance C of the active element 2 which are connected in series with each other.
_The voltage is divided into _D and the ratio opposite to the capacity ratio.

Therefore, the voltage held in the pixel capacitance C _LC during the non-selection period T _O is the pixel capacitance out of the decrease in the a-c voltage Va-c from the voltage charged during the selection period T _S. The voltage is reduced by the partial pressure value to C _LC .

The liquid crystal is composed of the pixel electrode 1 and the counter electrode 4
It operates by the voltage between and. Due to its responsiveness, the liquid crystal does not operate even when a high electric field is applied during the extremely short selection period T _S , but operates in response to the holding voltage of the pixel capacitance C _LC during the non-selection period T _O.

Since the pixel capacitance C _LC is in the voltage holding state during the non-selection period T _O , the voltage between the pixel electrode 1 and the counter electrode 4 is kept at the holding voltage of the pixel capacitance C _LC . liquid crystal during non-selection period T _O retains its operating state.

However, since the counter electrode 4 is supplied with the data signal S _D having a waveform as shown in FIG. 1B having image data for driving the pixels of each row, the selection period T
Image data for driving other pixels in the same column is applied together with the data signal S _D to the counter electrode 4 of the pixel which has been in the non-selected state after passing _S, and the potential of the counter electrode 4 changes. However, as a result, the voltage Va-c between a and c changes and the voltage between the electrodes of the pixel changes. This a-c voltage Va-c
Change in the inter-electrode voltage of the pixel due to variations in, like the voltage change when changes to the non-selection period T _O from the selection period T _S described above, the pixel capacitance variation of a-c voltage Va-c C _LC Of the voltage divided by the ratio opposite to the capacitance ratio of the element capacitance C _D to the pixel capacitance C _LC .

However, in this driving method, the non-selection period T
_The non-selection voltage applied between the input terminal of the active element 2 and the counter electrode 4 in _O is divided into the area A2 of the waveform on the positive side and the area B2 of the waveform on the negative side with respect to the reference potential V _G. Since the voltages are substantially equal to each other, the fluctuation of the voltage Va-c between a and c due to the influence of the image data for driving the other pixels is caused by the scanning signal S.
The fluctuation amount to the positive side and the fluctuation amount to the negative side are substantially equal to each other with the non-selection potential V _C2 of _S as the center. Therefore, the holding voltage of the pixel, which is the effective value during the non-selected period, does not change.

Further, when the next selection period T _S comes, at this time, the selection voltage having the opposite polarity to that of the previous selection period T _S is shown in FIG.
Is applied between a and c, the potential difference across the active element 2 becomes higher than its threshold voltage, the active element 2 is turned on, and the pixel capacitance C _LC is charged to the opposite polarity. The following is
It is similar to the above operation. Next, gradation display by the above driving method will be described.

2 to 4 show the waveform of the voltage Va-c applied between the input terminal of the active element 2 and the counter electrode 4 and the voltage Vb applied between the pixel electrode 1 and the counter electrode 4. Shows the relationship with -c.

[0066] Figure 2 is located in the state when the data pulse width of the positive and negative sides of the data signal S _D is applied during the selection period T _S is 0/10 (no pulse) of each selection period T _S ,
At this time, a selection voltage having a waveform as shown in (a) is applied between the input terminal of the active element 2 and the counter electrode 4.

When the selection voltage having such a waveform is applied between the input terminal of the active element 2 and the counter electrode 4, the pixel electrode 1
The voltage Vb-c applied between the counter electrode 4 and the counter electrode 4 rises with a rising curve corresponding to the reference selection voltage V _C1 over the entire selection period T _S , as shown in FIG. 2B.

Then, when the selection period T _S elapses and the non-selection period T _O is reached and the active element 2 is turned off, the pixel capacitance C _LC
Of the voltage charged during the selection period T _S from the voltage a−
Of the decrease in the inter-c voltage Va-c, the voltage V1 is reduced by the voltage divided by the pixel capacitance C _LC in the ratio opposite to the capacitance ratio of the pixel capacitance C _LC and the element capacitance C _D , and this voltage V1 Becomes a holding voltage between the pixel electrode 1 and the counter electrode 4.

The degree of the voltage drop of the pixel capacitance C _LC when the non-selection period T _O after the selection period T _S has elapsed is as follows.
Since it depends on the capacitance ratio between the pixel capacitance C _LC and the element capacitance C _D , if the capacitance value of the element capacitance C _D is reduced to about 1/10 of the pixel capacitance C _LC , the above voltage drop can be suppressed. it can.

[0070] FIG. 3 is a state when the data pulse width of the positive and negative sides of the data signal S _D is applied during the selection period T _S is one-tenth of each selection period T _S, the At this time, between the input terminal of the active element 2 and the counter electrode 4,
A selection voltage having a waveform as shown in (a) is applied.

In the waveform of the selection voltage, the data signal S _D supplied to the counter electrode has a data pulse of the potential V _D having the same polarity as the scanning signal S _{S at} the end of the first half of the selection period T _S. a waveform when a signal having the data pulses in the second half of the end to the scan signal S _S and the opposite polarity of the potential -V _D selection period T _S, therefore, the input end of the active element 2 in the first half of the selection period T _S selection voltage applied between the counter electrode 4 and is subjected to end from the initial of the first half period a reference selection voltage V _C1 is the low pulse superimposing voltage V _C1 -V _S than the reference selection voltage V _C1 at the end Become. The selection voltage applied between the input terminal of the active element 2 and the counter electrode 4 in the latter half of the selection period T _S is the reference selection voltage V _C1 from the beginning to the end of this latter half period, and at the end, The pulse superposition voltage V _C1 + V _S , which is higher than the reference selection voltage V _C1 , is obtained.

When the selection voltage having such a waveform is applied between the input terminal of the active element 2 and the counter electrode 4, the pixel electrode 1
The voltage Vb-c applied between the counter electrode 4 and the counter electrode 4 is a rising curve corresponding to the reference selection voltage V _C1 from the beginning to the end of the first half of the selection period T _S , as shown in FIG. 3B. Rising, at the end of the first half, the low voltage pulse superposition voltage V
With rises at the rising curve corresponding to _C1 -V _S, the rise in the rising curve in accordance with the reference selection voltage V _C1 again from the second half of and early termination of the selection period T _S, in this latter half of the final, pulse superimposing the high voltage Voltage V _C1 +
It rises rapidly with the application of V _S.

When the non-selection period T _O is reached after the selection period T _S has elapsed, the voltage of the pixel capacitance C _LC becomes the voltage V2 lowered at a constant rate, and this voltage V2 is changed to the pixel electrode 1 and the counter electrode. The holding voltage is between 4 and 4.

[0074] Figure 4 is 1/2 of the total width of 5/10 (the selection period T _S of each data pulse widths of positive and negative of the data signal S _D is applied during the selection period T _S is the selection period T _S ) Is the maximum width, and at this time, a selection voltage having a waveform as shown in (a) is applied between the input end of the active element 2 and the counter electrode 4.

The waveform of the selection voltage is the same as the counter electrode 4
The data signal supplied S _D to the have a data pulse of the scanning signal S _S of the same polarity as the potential V _D in the first half of the selection period T _S, the scanning signal S _S and the opposite polarity of the potential in the second half of the selection period T _S The waveform is a signal having a -V _D data pulse. Therefore, the selection voltage applied between the input terminal of the active element 2 and the counter electrode 4 in the first half of the selection period T _S is the reference voltage. Pulse superposition voltage V _C1 −V lower than the selection voltage V _C1
The selection voltage applied between the input terminal of the active element 2 and the counter electrode 4 in the latter half of the selection period T _S is the pulse superposition voltage V _C1 + V _S higher than the reference selection voltage V _C1. .

When the selection voltage having such a waveform is applied between the input terminal of the active element 2 and the counter electrode 4, the pixel electrode 1
As shown in FIG. 4B, the voltage Vb-c applied between the counter electrode 4 and the counter electrode 4 becomes a low voltage pulse superposition voltage V _C1 −V _S in the first half of the selection period T _S. The rising edge corresponds to the rising curve, and the latter half of the selection period T _S rises rapidly with the rising curve corresponding to the high-voltage pulse superimposed voltage V _C1 + V _S throughout the entire period.

Further, when the selection period T _S has elapsed and the non-selection period T _O has come, the voltage of the pixel capacitance C _LC becomes the voltage V3 lowered at a constant rate, and this voltage V3 is the pixel electrode 1 and the counter electrode 4. It becomes the holding voltage between and.

2 to 4, the voltage Vb− applied between the pixel electrode 1 and the counter electrode 4 during the selection period T _S.
The peak value of c (the voltage value at the end of the selection period T _S ) is the selection voltage applied between the input terminal of the active element 2 and the counter electrode 4, and the current-voltage characteristic of the diode ring which is the active element 2. And the time for which the selection voltage is applied (selection period) T _S.

That is, the voltage Vb-c applied between the pixel electrode 1 and the counter electrode 4 during the selection period T _S is the voltage Va applied between the input terminal of the active element 2 and the counter electrode 4. -c
According to the selected voltage value of the active element 2 rises with a rising curve determined by the current-voltage characteristics of the active element 2, and the selection period T
_{When S} has passed and the selection voltage is no longer applied, the rise stops.

Then, the input terminal of the active element 2 and the counter electrode 4
The selection voltage applied between and is the reference selection voltage V _C1 ,
Pulse superposition voltage V _C1 −V lower than this reference selection voltage V _C1
S and pulse superposition voltage V _C1 + higher than the reference selection voltage V _C1
Since a three-level voltage of the V _S, the voltage Vb-c which is applied between the pixel electrode 1 and the counter electrode 4, when the reference selection voltage V _C1 is applied according to the voltage V _C1 Pulse rise voltage V _C1
When −V _S is applied, it rises with a gentler rising curve than when the reference selection voltage V _C1 is applied, and when the high voltage pulse superposition voltage V _C1 + V _S is applied, the reference selection voltage V _C1 is applied.
It rises with a steeper rising curve than when _C1 is applied.

Further, these applied voltages V _C1 , V _C1 −V _S ,
The rising amount of the voltage Vb-c with respect to V _C1 + V _S is
In order to correspond to the application time of each of the voltages V _C1 , V _C1 −V _S , and V _C1 + V _S , the peak value of the voltage Vb-c is the application time of the reference selection voltage V _{C1 in} the selection period T _S and the superimposed voltage. V _C1 + V
It changes according to the ratio with the application time of _S.

Therefore, the voltage held in the pixel capacitor C _CL when the selection period T _S has passed and the non-selection period T _O has elapsed (from the voltage charged during the selection period T _S to the voltage between a and c) Vb-c, which is a voltage reduced by the divided voltage value to the pixel element capacitance C _LC of the decrease amount of the
It depends on the data pulse width of the selection voltage applied between and.

For example, when the selection voltage is a voltage with a data pulse width of 0 (no pulse) as shown in FIG. 2, the voltage Vb-c held in the pixel capacitance C _CL is within the control range. of becomes the lowest voltage V1, if the selected voltage is a voltage having a data pulse of the maximum width as shown in FIG. 4, the voltage Vb-c to be held in the pixel capacitor C _CL, the highest among the control range The voltage becomes V3.

When the selection voltage is a voltage having data pulses in the first half and the second half of the selection period T _S as shown in FIG. 3, the voltage V held in the pixel capacitor C _CL is
bc is the voltage V2 between the minimum and maximum of its control range.
This voltage V2 changes according to the data pulse width of the selection voltage.

The selection voltage (V
ac voltage during the selection period T _S of) is a waveform the first half of the end and the data pulse in the second half of the end are superposed selection period T _S, the selection voltage, the initial first and second halves of the selection period T _S Alternatively, it may have a waveform in which pulses are superimposed in the middle period, and in that case also, the voltage Vb-c applied between the pixel electrode 1 and the counter electrode 4 is this voltage during the application of the reference selection voltage V _C1. rises at the rising curve corresponding to V _C1, pulse superimposing voltage _{V C1 -V S, V C1 +} V this respective voltage during application of _S V _C1 -V _S, for rises at the rising curve corresponding to V _C1 + V _S, the pixel The voltage Vb- held in the capacitor C _CL
c has a value corresponding to the data pulse width of the selection voltage.

On the other hand, the rising angle of the liquid crystal depends on the pixel electrode 1
It varies depending on the value of the voltage (holding voltage of the pixel capacitance C _LC ) Vb-c applied between the counter electrode 4 and the counter electrode 4, and the transmittance of the pixel changes according to the rising angle of the liquid crystal.

Therefore, as described above, the selection period T _S
A selective voltage having a pulse width corresponding to image data is applied between the input terminal of the active element 2 and the counter electrode 4 to activate the active element 2
If a voltage having a value corresponding to the data pulse width of the selection voltage is applied between the pixel electrode 1 and the counter electrode 4 connected to
It is possible to realize gradation display by controlling the transmittance of the pixels.

Next, the number of gradations in the gradation display will be described. With respect to the number of gradations, the number of gradations of the voltage Vb-c charged to the pixel capacitor C _CL during the limited selection period T _S is set. It depends on whether you can choose.

Then, as described above, the data pulse width of the selection voltage applied between the input terminal of the active element 2 and the counter electrode 4 is changed to control the voltage applied between the pixel electrode 1 and the counter electrode 4. In the gradation display by the pulse width modulation, the pixel electrode 1 and the counter electrode 4 corresponding to the data pulse width of the selection voltage are
The change in the applied voltage between the active element 2 and the liquid crystal display element is determined by the current-voltage characteristic of the active element. However, in the liquid crystal display element using the active element 2 including the diode ring, the current-voltage characteristic of the active element 2 is sharp. In addition, since the responsiveness is high, the applied voltage between the pixel electrode 1 and the counter electrode 4 can be greatly changed.

FIG. 7 shows the current-voltage characteristics of the diode ring, which is the active element 2 of the liquid crystal display element, in comparison with the current-voltage characteristics of the MIM utilizing the tunnel effect. , The diode ring is MI
Compared with M, the current-voltage characteristics are rapid and the response is high.

Therefore, the above-mentioned liquid crystal display element using the diode ring as the active element 2 does not need to have a high applied voltage unlike the liquid crystal display element having the MIM as an active element, and gradation display by high time division drive is possible. Is possible.

The current-voltage characteristics of the diode ring can be arbitrarily selected by changing the film thickness of the I-type semiconductor layer of the thin film diodes 5 and 6, and between a and b in FIG. 6A. The current-voltage characteristics can be arbitrarily selected by changing the number of the thin film diodes 5 and 6 of FIG.

That is, the current-voltage characteristics of the diode ring become steeper as the film thickness of the I-type semiconductor layer of the thin film diodes 5 and 6 becomes thinner, and the thin film diodes of the forward circuit and the reverse circuit of the diode ring are formed. The smaller the number, the more rapid.

FIG. 8 shows an input terminal of the active element 2 and the counter electrode 4 of a liquid crystal display element having a diode ring as the active element 2.
And (a) is a charging characteristic diagram of the pixel capacitance C _LC with respect to a voltage Va-c applied between the pixel capacitance and the liquid crystal display element using a diode ring having a general current-voltage characteristic. The characteristic, (b), shows the pixel capacitance charging characteristic of the liquid crystal display element using the diode ring having a more rapid current-voltage characteristic.

The pixel capacitance charging characteristic shown in FIG.
About 40μ charging voltage of the pixel capacitor C _LC at the charging time in seconds is characteristic reaches a peak, the liquid crystal display device having the pixel capacitor charge characteristics, bisecting the time about 40μ sec (select the selection period T _S The period T _S is suitable for high time division driving with a time division number of about 80 μsec.

Therefore, gradation display of this liquid crystal display element may be performed by controlling the pulse width of the selection voltage within the range of 0 to about 40 μsec. For example, between the pixel electrode 1 and the counter electrode 4. In the case of a negative display type liquid crystal display element in which a pixel transmits light when a voltage is applied, the gradation of the display pixel becomes darkest when a selection voltage with a pulse width of 0 (no pulse) is applied. When the selection voltage with a pulse width of about 40 μsec is applied, the brightness becomes maximum, and when the selection voltage with a pulse width within the range of 0 to about 40 μsec is applied, the brightness becomes according to the pulse width.

As described above, the number of display gradations depends on how many steps the voltage Vb-c that charges the pixel capacitance C _CL can be selected during the selection period T _S , but the gradation difference is clear. In order to obtain a high gradation display, it is necessary to make the difference in the charging voltage Vb-c of the pixel capacitance C _CL , that is, the difference in the voltage applied between the pixel electrode 1 and the counter electrode 4 large to some extent.

For this reason, the pulse width of the selection voltage is the voltage V of the voltage difference that produces a clear gradation difference in the pixel capacitance C _LC.
Although it is necessary to control the width difference so that bc can be charged, the rising curve of the voltage Vb-c charged in the pixel capacitance C _LC is assumed to have a constant current-voltage characteristic of the active element 2. Since the voltage Va-c applied between the input terminal of the active element 2 and the counter electrode 4 is determined, the applied voltage Va-c is increased to some extent to make the rising curve of the charging voltage Vb-c steep. By doing so, even if the pulse width difference of the selection voltage is relatively small, the pixel capacitance C _LC can be charged with the voltage Vb-c having a sufficient voltage difference.

When the applied voltage Va-c is increased,
During the selection period T _S , the range of the voltage Vb-c charged in the pixel capacitor C _CL becomes large according to the pulse width of the selection voltage. If the range of the charged voltage Vb-c is large, the pixel electrode 1
The number of steps of the voltage applied between the counter electrode 4 and the counter electrode 4 can be increased.

Therefore, if the voltage value of the selection voltage is set high to some extent, the number of pulse widths of the selection voltage can be increased to perform multi-step gradation display. In addition,
The voltage value of the selection voltage may be a voltage considerably lower than the voltage required to cause the liquid crystal display element using the MIM as an active element to perform gradation display. This also applies to the liquid crystal display element having the pixel capacitance charging characteristic shown in FIG.

Further, the pixel capacitance charging characteristic shown in FIG. 8B is a characteristic in which the charging voltage of the pixel capacitance C _LC reaches a peak in a charging time of 10 to 15 μsec, and a liquid crystal having this pixel capacitance charging characteristic. The display element is divided into two equal parts of the selection period T _S.
The number of display gray scales is much larger than that of the liquid crystal display element having the pixel capacitance charging characteristic shown in FIG. 10A because it can be made very short, 10 to 15 μsec (selection period T _S is 20 to 30 μsec). The time-division driving can be performed by the time-division number.

Since the above-mentioned driving method drives the liquid crystal display element in which the diode ring is the active element 2 by the pulse width modulation method, the voltage modulation conventionally used as the driving method of the above-mentioned liquid crystal display element. Unlike the system, it is not necessary to use a drive signal of multiple voltage levels, and therefore the drive circuit having a simple structure can cause the liquid crystal display element to perform multi-tone gradation display.

On the other hand, in the non-selection period T _O , the scanning signal S _S supplied to the signal line 3 becomes the non-selection potential V _C2 , but the counter electrode 4 has image data for each selection period of the pixels in each row. Since the data signal S _D whose pulse width changes according to the voltage is supplied, the voltage Va− between the input terminal of the active element 2 and the counter electrode 4 is
c is in the non-selection period T _O, varies depending on the image data for driving the other pixels in the same column.

[0104] Therefore, the inter-electrode voltage of the pixel in the non-selection period T _O is similar to the voltage fluctuation when it becomes non-selection period T _O from the selection period T _S as described above, the a-c voltage Va is divided into the pixel capacitance C _LC of the pixel capacitor partial pressure value (pixel capacitance C _LC and the element capacitance C _D and the divided by the voltage at a ratio of the volume ratio and opposite to C _LC of the fluctuation Voltage).

[0105] That is, the pixels in the non-selection period T _O is
Figure 2, such as the non-selection period T _O of the waveform at Figure 4 (b), from the voltage value (the voltage applied during the selection period T _S of the inter-electrode voltage V _LC when the selection period T _S is completed , A voltage value reduced by the divided voltage value to the pixel capacitance C _{LC in} the decrease amount of the voltage ac between a and c in the non-selection period T _O ) V1,
Variation in V2 and V3 due to the influence of image data for driving other pixels (variation _divided into pixel capacitance C _LC )
The non-selection voltage with is superimposed is applied.

However, in the above driving method, as shown in FIG. 1, the scanning signal S _S supplied to the signal line 3 is kept at the selection potential V _C1 of either positive or negative polarity during the selection period T _S , During the non-selection period T _O , the data signal S _D supplied to the counter electrode 4 is set as a signal that holds the non-selection potential V _C2 which is either positive or negative and is lower than the selection potential V _C1 potential during the selection period T _S. A signal having a pulse having a width corresponding to image data and having a potential that changes with an amplitude substantially equal to the positive side and the negative side with respect to the reference potential V _G in a cycle that divides the selection period T _S into two, that is, the reference potential. Since the area A1 of the positive side waveform and the area B1 of the negative side waveform are substantially equal to each other with V _G as the center, a signal between the input end of the active element 2 and the counter electrode 4 is generated during the non-selection period T _O. voltage applied to, as described above, a non-selection scanning signal S _S potentials V _C2 A voltage approximately equal waveform and the area B2 of the waveform of the positive side of the area A2 and the negative waveform as the center.

[0107] Thus, the non-selection voltage applied between the pixel during non-selection period T _O electrodes, as shown in (b) of FIGS. 2-4, 1/2 of the period of the selection period T _S Then, when the selection period T _S ends, the voltage value of the inter-electrode voltage V _LC (hereinafter referred to as the reference holding voltage) V1, V2, and V3 is substantially the same amplitude on the positive side and the negative side (other pixels). Is a voltage whose voltage value changes with the amplitude of the fluctuation due to the influence of the image data for driving. That is, the non-selection voltage applied between the electrodes of the pixel during the non-selection period T _O is the area A of the waveform on the positive side with the reference holding voltages V1, V2, V3 as the center.
3 and the area B3 of the waveform on the negative side are almost equal.

For this reason, the amount of change in the non-selection voltage applied between the electrodes of the pixels during the non-selection period T _O is approximately equal to the amount of change in the negative side, and therefore the positive side and the negative side are the same. Since the fluctuations in the voltages are canceled by each other, the effective value of the inter-electrode voltage of the pixel in the non-selection period T _O , that is, the holding voltage is maintained at the reference holding voltages V1, V2, and V3 and hardly changes.

If the effective value of the inter-electrode voltage during the non-selection period T _O hardly changes, the voltage-transmittance characteristic of the pixel during the non-selection period T _O also hardly changes, so that the pixel transmittance is , The voltage values V1 and V2 accumulated in the pixel capacitance C _LC according to the pulse width of the selection voltage applied in the selection period T _S
, V3, the transmissivity corresponding to V3 is maintained, so that the transmissivity of the pixel hardly changes during the non-selection period T _O.
Therefore, it is possible to obtain the display of the correct gradation according to the image data.

That is, FIG. 9 shows the pulse width-transmittance characteristics of one pixel when the active matrix liquid crystal display element having the above-mentioned structure is time-division driven by the driving method of the above-mentioned embodiment, and the solid line shows Among the pixels in one column corresponding to one counter electrode 4, all the other pixels except the measurement pixel are controlled to be in the transmissive state (state in which the selection voltage is not applied), the broken line indicates When all the pixels other than the measurement pixel among the pixels in one column are controlled to be in the non-transmissive state (a state in which a selection voltage having a maximum pulse width corresponding to half the entire width of the selection period is applied) It is a characteristic.

As is clear from FIG. 9, the pulse width-transmittance characteristics under the above two conditions are very similar,
The fluctuation range of the transmittance, which varies depending on the driving state of other pixels in the same column, is within about 5%.

Therefore, the pulse width-transmittance characteristic is hardly influenced by the driving states of the other pixels, and therefore the transmittance of the pixel depends on the pulse width of the selection voltage applied in the selection period T _S. It can be controlled correctly.

[0113] Moreover, in the driving method of the above embodiment, the data signal S _D but is a signal having a data pulse of the positive and negative sides with respect to the waveform reference potential V _G of the selection period, the selection period T _S The selection voltage applied between the input terminal of the active element 2 and the counter electrode 4 is a voltage obtained by superimposing any data pulse on the positive side or the negative side with respect to the non-selection potential V _C2 of the scanning signal S _S. Since the voltage has either positive or negative polarity, the charge of one polarity is accumulated between the pixel electrode 1 and the counter electrode 4 during the selection period T _S.

That is, the charge between the electrodes of the pixel is carried out by making full use of the selection period, and therefore the charge time between the electrodes of the pixel can be sufficiently taken.
The voltage applied between the electrodes of the pixel can be made sufficiently high without being affected by the ability of the active element (the ability to pass a current).

In the conventional driving method, the pixel voltage −
Since the driving state of other pixels greatly affects the transmittance characteristics, in order to reduce the fluctuation of the voltage-transmittance characteristics, the element capacitance of the active element relative to the pixel capacitance is made considerably small, and other pixels are driven. Among the fluctuations of the applied voltage between the input terminal of the active element and the counter electrode due to the image data, it is necessary to extremely reduce the voltage divided by the pixel capacitance.

Therefore, in the conventional liquid crystal display element using the diode ring as an active element, the diodes forming the diode ring are formed in the smallest possible element area to reduce the capacitance, or the forward direction of the diode ring is used. The circuit and the reverse circuit are each configured by connecting a plurality of diodes in series to reduce the capacitance of the diode ring.

However, in order to reduce the element area of the diode as described above, highly precise patterning is required in the manufacturing thereof, and the number of diodes constituting the forward and reverse circuits of the diode ring is increased. Therefore, the area occupied by the diode ring becomes large, and the area of the pixel electrode is restricted accordingly.

On the other hand, in the driving method of the above-described embodiment, as described above, the fluctuation amount of the non-selection voltage to the positive side and the fluctuation amount to the negative side are canceled each other. The voltage fluctuations can be large to some extent, and thus
Of the variation of the applied voltage between the input terminal of the active element 2 and the counter electrode 4, it is not necessary to extremely reduce the voltage divided by the pixel capacitance C _LC .

Therefore, the ratio of the element capacitance C _D to the pixel capacitance C _LC is such that the voltage drop due to the capacitance ratio partial pressure when the selection period T _{S changes} to the non-selection period T _O can be suppressed within a certain range ( For example, about 1/10).

Therefore, according to the driving method of the above-described embodiment, the diodes constituting the diode ring can be formed in a relatively large element area, so that the diode ring can be easily manufactured without the need for highly precise patterning. In addition, the number of diodes forming the forward and reverse circuits of the diode ring is reduced, the area occupied by the diode ring is reduced, and the area of the pixel electrode is correspondingly increased to increase the aperture ratio of the liquid crystal display element. Can be higher.

In the above embodiment, the data signal is a signal whose potential changes to the positive side and the negative side with respect to the reference potential V _G in a cycle that divides the selection period T _S into two equal parts. If the signal changes in potential to the positive side and the negative side with respect to the reference potential V _G in a cycle in which the selection period T _S is divided into a plurality of periods,
The signal may have any waveform, in short, between the input end of the active element 2 and the counter electrode 4, during the selection period T _S , either positive or negative polarity having a pulse having a width corresponding to the image data. Is applied to the non-selection period T _O and the selection period T
_It suffices that the potential changes in a cycle shorter than _S and that a voltage having a waveform in which the positive side area and the negative side area of the scanning signal S _S are substantially equal to each other around the non-selection potential V _C2 is applied. (Second Embodiment) Next, a second embodiment of the present invention will be described with reference to FIG.
~ It demonstrates with reference to FIG. Note that the description of the items overlapping with those of the first embodiment described above will be omitted.

The driving method of this embodiment will be described with reference to FIG.
0 is a waveform diagram of a drive signal, and (a) is a scanning signal S supplied to the signal line 3 in the first row of the liquid crystal display element shown in FIG. 7.
The waveform of _S , (b) shows the waveform of the data signal S _D supplied to one counter electrode 4, and (c) shows the drive signal input end of the active element 2 (the connection end with the signal line 3) and the counter electrode. 4 applied (between points a and c in FIG. 6) Va-c
Shows the waveform of.

The scanning signal S _S is the same signal as in the first embodiment, and becomes the selection potential V _C1 during the selection period T _S and the non-selection potential V _C2 during the non-selection period T _O , and the one field T _F. The polarity is inverted every time.

On the other hand, the data signal S _D is a signal having a number of data pulses corresponding to the image data supplied from the outside in synchronization with the selection period of the pixels in each row, and the data signal S _D is for each row. Selection period T for each pixel selection period
It is a signal in which the potential changes with an equal amplitude on the positive side and the negative side with respect to the reference potential V _G in a cycle in which _S is evenly divided. In the figure, the number of divisions of the selection period T _S is divided into 10 equal parts in order to make the waveform easy to see, but the number of divisions of the selection period T _S is, for example, several tens, and the width of the data pulse is , The width of one divided period of the selection period T _S is the same.

The number of data pulses of the positive side potential V _S and the number of data pulses of the negative side potential −V _S in each selection period of the data signal S _D are the numbers corresponding to the same image data. Therefore, the number of data pulses on the positive side and the number of data pulses on the negative side for each selection period are the same, and the potential V _S thereof is
Are equal in absolute value.

That is, the data signal S _D is a signal whose waveform in each selection period T _S is such that the area of the positive side waveform and the area of the negative side waveform about the reference potential V _G are substantially equal. Is.

The data signal S _D shown in FIG.
The number of pulses on the positive and negative sides in the selection period T _S1 for the pixels in the first row is 1, respectively, and the number of pulses on the positive and negative sides in the selection period T _S2 for the pixels in the second row are 4 and 3, respectively. The number of pulses on the positive side and the number of pulses on the negative side in the selection period T _S3 of the pixel are 2 respectively, and each selection period T of the data signal S _D
The number of positive and negative data pulses for each _S1 , T _S2 , T _S3, ...
Depending on the image data, it varies in the range of 0 (no pulse) to n (the maximum allowable number of pulses that can be applied during the selection period T _S determined by the pulse width).

When the scanning signal S _S and the data signal S _D having such waveforms are supplied to the signal line 3 and the counter electrode 4, the input terminal of the active element 2 connected to the signal line 3 and the counter electrode 4 are connected.
, A voltage Va-c having a waveform obtained by combining the scanning signal S _S and the data signal S _D as shown in FIG. 10C is applied.

Of the voltage Va-c applied between the input terminal of the active element 2 and the counter electrode 4, the selection voltage applied during the selection period T _S is 0 when the potential of the data signal S _D is 0. Is the same as the selection potential V _C1 of the scanning signal S _S ,
When the potential of the data signal S _D becomes the potential of the data pulse,
Scanning signal S _S of the selection potential V _C1 to the data pulse potential V _S or the voltage V _C1 to -V _S is superimposed + V _S or V _C1
It becomes -V _S. In addition, each of the voltages V _C1 , V _C1 −V _S , V
The value of _C1 + V _S is the same as in the first embodiment.

The non-selection voltage applied between the input terminal of the active element 2 and the counter electrode 4 during the non-selection period T _O depends on the image data for driving the other pixels in the same column. The data pulse is a voltage superimposed on the scanning signal S _S , and this non-selection voltage is the same as the non-selection potential V _C2 of the scanning signal S _S when the potential of the data signal S _D is 0. When the potential of S _D becomes the potential of the data pulse, it becomes the voltage V _C2 + V _S or V _C2 −V _S in which the potential V _S or −V _S of the data pulse is superimposed on the non-select potential V _C2 of the scanning signal S _S. The values of the voltages V _C2 , V _C2 −V _S , and V _C2 + V _S are also the same as those in the first embodiment.

That is, the non-selection voltage is a voltage in which the positive side data pulse and the negative side data pulse corresponding to the image data for driving the other pixels in the same column are superposed. The voltage is the non-selection potential V _C2 of the scanning signal S _S.
The area of the waveform on the positive side and the area of the waveform on the negative side are substantially equal to each other.

Then, the input end of the active element 2 and the counter electrode 4
When a selection voltage is applied between the pixel electrode 1 and the counter electrode 4, the voltage is applied between the pixel electrode 1 connected to the active element 2 and the counter electrode 4.
The charging of the pixel capacitance C _LC formed by the pixel electrode 1, the counter electrode 4 and the liquid crystal between them is started.

Further, after the selection period T _S has passed and the non-selection period T _O has been reached, the voltage between the input terminal of the active element 2 and the counter electrode 4, that is, the voltage Va-c between a and c in FIG. When lowered, the charging stop to the pixel capacitance C _LC active element 2 is turned off, the voltage of the pixel capacitor C _LC is the voltage during the selection period T _S, decrement of a-c voltage Va-c Pixel capacity C _LC
Divided value to (the pixel capacitance C _LC and the element capacitance C _{D of the} active element 2
In addition, the voltage is reduced by the voltage divided by the pixel capacitance C _LC of the voltage divided in the ratio opposite to the capacitance ratio. The gradation display by the driving method of this embodiment is also basically performed in the same manner as in the first embodiment described above.

That is, FIGS. 11 to 13 show the active element 2
3 shows the relationship between the waveform of the voltage Va-c applied between the input terminal of the pixel electrode 1 and the counter electrode 4 and the voltage Vb-c applied between the pixel electrode 1 and the counter electrode 4.

In FIG. 11, the number of data pulses on the positive side and the negative side of the data signal S _D applied during the selection period T _S is 0 respectively.
This is a state when there is no pulse, (a) is the waveform of the selection voltage applied between the input terminal of the active element 2 and the counter electrode 4, and (b) is the pixel electrode 1 and the counter electrode 4. It is a waveform of the voltage Vb-c applied during the period.

In FIG. 12, the number of data pulses on the positive side and the negative side of the data signal S _D applied during the selection period T _S is 1 each.
(A) is a waveform of the selection voltage applied between the input end of the active element 2 and the counter electrode 4,
(B) is a waveform of the voltage Vb-c applied between the pixel electrode 1 and the counter electrode 4.

FIG. 13 shows a state in which the number of data pulses on the positive side and the number of data pulses on the negative side of the data signal S _D applied in the selection period T _S are the maximum allowable number of pulses n, respectively. 2 shows the waveform of the selection voltage applied between the input terminal of 2 and the counter electrode 4, and (b) shows the waveform of the voltage Vb-c applied between the pixel electrode 1 and the counter electrode 4.

Also in the driving method of this embodiment, the voltage Vb-c applied between the pixel electrode 1 and the counter electrode 4 is selected between the input terminal of the active element 2 and the counter electrode 4. When the voltage is the reference selection voltage V _C1 , it rises with a rising curve corresponding to this voltage V _C1, and when the selection voltage becomes the pulse superposition voltage V _C1 −V _S lower than the reference selection voltage V _{C1, the} reference selection The voltage rises with a gentler rising curve than when the voltage V _C1 is applied, and rises with a steep angle rising curve when the selection voltage becomes the voltage voltage V _C1 + V _S of the high voltage pulse. The voltage Vb-c applied between the pixel electrode 1 and the counter electrode 4 is different depending on the number of data pulses of the selection voltage. ) Standing like a staircase Want.

Therefore, the voltage held in the pixel capacitor C _CL when the selection period T _S has elapsed and the non-selection period T _O has elapsed (from the voltage charged during the selection period T _S to the voltage between a and c) Vb-c, which is a voltage reduced by the divided voltage value to the pixel capacitance C _CL among the decrease amount of V.sub.CL) depends on the number of data pulses of the selection voltage applied between the input terminal of the active element 2 and the counter electrode 4.

For example, when the selection voltage is a voltage in which the number of data pulses is 0 (no pulse) as shown in FIG. 11,
Voltage Vb-c to be held in the pixel capacitor C _CL becomes the lowest voltage V1 of its control range, the selection voltage 13
When the voltage has a data pulse of the maximum allowable pulse number n such as, the voltage Vb-c held in the pixel capacitance C _CL
Has the highest voltage V3 in its control range.

When the selection voltage is a voltage having a data pulse in a part of the selection period T _S as shown in FIG. 12, the voltage Vb-c held in the pixel capacitor C _CL is controlled by the control. There is a voltage V2 between the lowest and the highest value of the range, which voltage V2 varies with the number of data pulses.

The selection voltage (voltage during the selection period T _S of Va-c) shown in FIG. 12A has a waveform in which the data pulse is superimposed at the end of the selection period T _S. The superimposition timing of the data pulse of the selection voltage may be the initial period or the middle period of the selection period T _S.

The rising angle of the liquid crystal is determined by the voltage (pixel capacitance C _LC applied between the pixel electrode 1 and the counter electrode 4).
Holding voltage) Vb-c, and the pixel transmittance changes according to the rising angle of the liquid crystal.

Therefore, as described above, the selection period T _S
A selection voltage having a pulse number corresponding to image data is applied between the input terminal of the active element 2 and the counter electrode 4 in the active element 2
If a voltage having a value according to the number of data pulses of the selection voltage is applied between the pixel electrode 1 and the counter electrode 4 connected to
It is possible to realize gradation display by controlling the transmittance of the pixels.

The number of gradations of this gradation display is determined by how many steps the value of the voltage Vb-c with which the pixel capacitance C _CL is charged can be selected during the limited selection period T _S , but it is a semiconductor consisting of a diode ring. In the liquid crystal display element using the active element 2, as described in the first embodiment, the current-voltage characteristic of the active element 2 is rapid and the response is high. By controlling the number of pulses of the selection voltage applied between the counter electrode 4 and the counter electrode 4, the applied voltage between the pixel electrode 1 and the counter electrode 4 can be greatly changed.

Since the above-mentioned driving method drives the liquid crystal display element using the active element 2 composed of the diode ring by the modulation method in which the number of data pulses of the selection voltage is changed according to the image data, It is not necessary to use a drive signal of multi-step voltage level unlike the voltage modulation method that has been conventionally adopted as a driving method of a liquid crystal display element.
Therefore, it is possible to cause the liquid crystal display element to perform multi-tone gradation display with a drive circuit having a simple structure.

Also in this embodiment, the current of the diode ring, which is the active element 2, is used as the liquid crystal display element.
If the one having abrupt voltage characteristics (thin film diodes 5 and 6 having a thin I-type semiconductor layer or having a small number of thin film diodes 5 and 6) is used, the selection period T
_{It is possible} to shorten _S and perform time division driving with a larger number of time divisions.

Also, in the driving method of this embodiment, as shown in FIG.
, The scanning signal S _S supplied to the signal line 3 is
During the selection period T _S , the selection potential V of either positive or negative polarity
A data signal to be supplied to the counter electrode 4 as a signal for maintaining _C1 and maintaining the non-selection potential V _C2 which is either positive or negative during the non-selection period T _O and which is lower than the selection potential V _C1 potential during the selection period T _S S _D has a number of pulses according to the image data,
In addition, a signal in which the potential changes with an amplitude substantially equal to the positive side and the negative side with respect to the reference potential V _G in a cycle that divides the selection period T _S into two, that is, the area of the waveform on the positive side around the reference potential V _G And the area of the waveform on the negative side are substantially equal to each other, the voltage applied between the input end of the active element 2 and the counter electrode 4 during the non-selection period T _O is, as described above, The voltage of the waveform is such that the area of the waveform on the positive side and the area of the waveform on the negative side are substantially equal to each other around the non-selection potential V _C2 of the signal S _S.

Therefore, the non-selection voltage applied between the electrodes of the pixel during the non-selection period T _O is divided evenly into the selection period T _S as shown in FIGS. 11 to 13B. In the cycle, the voltage value of the inter-electrode voltage V _LC (hereinafter referred to as the reference holding voltage) V1 at the end of the selection period T _S ,
It is a voltage whose voltage value changes on the positive side and the negative side with V2 and V3 as the center, with substantially the same amplitude (amplitude of fluctuation due to the influence of image data applied to other pixels). In other words, the non-selection voltage applied between the electrodes of the pixel during the non-selection period T _O is such that the area of the positive side waveform and the area of the negative side waveform about the reference holding voltages V1, V2, and V3 are almost the same. The waveforms are equal.

Therefore, the amount of change in the non-selection voltage applied between the electrodes of the pixel during the non-selection period T _O is approximately equal to the amount of change in the negative side, and therefore the positive side and the negative side are equal. since the variation of the voltage is canceled out with each other, the effective value of the voltage between electrodes of the pixels of the non-selection period T _O is the reference holding voltage V1, V
It is kept at 2, V3 and hardly fluctuates.

Therefore, also in the driving method of this embodiment, the pixel transmittance is the voltage value V1 accumulated in the pixel capacitance C _LC according to the number of pulses of the selection voltage applied in the selection period T _S.
, V2, V3, the transmittances of the pixels are hardly changed during the non-selection period T _O , and the display of the correct gradation according to the image data can be obtained. (Other application examples of the present invention)

Although the first and second embodiments are directed to the liquid crystal display element using the diode ring as the active element 2, the driving method of the present invention uses the diode ring as the active element. The present invention can be widely applied to not only the liquid crystal display element, but also an active matrix liquid crystal display element using an active element made of a nonlinear resistance element having a semiconductor, such as an active element having a back-to-back structure made of a thin film diode.

[0153]

According to the present invention, a liquid crystal display element using an active element composed of a non-linear resistance element having a semiconductor is driven by a pulse width or pulse number modulation method instead of the conventional voltage modulation method. , Without using the drive signal of multi-stage voltage level like the conventional drive method,
It is possible to cause the liquid crystal display element to perform multi-tone gradation display.

Further, in the present invention, a selection voltage having either the positive or negative polarity of the pulse width or the number of pulses corresponding to the image data is provided between the drive signal input terminal of the active element and the counter electrode during the selection period. A waveform in which the potential changes in a cycle shorter than the selection period during the non-selection period in which the applied voltage is applied and other pixels are selected, and the areas on the positive side and the negative side of the potential of the scanning signal in the non-selection period are substantially equal to each other. Since the voltage is applied to the pixel, the fluctuation of the inter-electrode voltage of the pixel due to the influence of the image data for driving the other pixels during the non-selection period shifts to the positive side around the potential of the non-selection period of the scanning signal. The fluctuation of the voltage on the negative side and the fluctuation of the voltage on the negative side are almost equal to each other. Therefore, the effective value of the inter-electrode voltage of the pixel during the non-selection period, that is, the holding voltage of the pixel hardly changes, so For driving With less variation in transmittance due to the influence of the image data, it is possible to obtain a display of the correct gradation corresponding to the image data.

[Brief description of drawings]

FIG. 1 is a waveform diagram of a voltage applied between a scanning signal and a data signal, and a signal input end of an active element and a counter electrode according to a first embodiment of the present invention.

FIG. 2 is applied between the input terminal of the active element and the counter electrode when the positive and negative pulse widths of the data signal applied during the selection period are 0/10 (no pulse) of the selection period, respectively. 7 is a waveform diagram of the applied voltage and the voltage applied between the pixel electrode and the counter electrode.

FIG. 3 shows the voltage applied between the input terminal of the active element and the counter electrode when the positive and negative pulse widths of the data signal applied during the selection period are 1/10 of the selection period, respectively. , A waveform diagram of a voltage applied between a pixel electrode and a counter electrode.

FIG. 4 shows a voltage applied between an input terminal of an active element and a counter electrode and a pixel electrode when the positive and negative pulse widths of a data signal applied during a selection period are maximum widths. The wave form diagram of the voltage applied between a counter electrode.

FIG. 5 is a plan view of a part of the liquid crystal display element.

FIG. 6 is an equivalent circuit diagram of one pixel display element of a liquid crystal display element.

FIG. 7 is a current-voltage characteristic diagram of a diode ring and an MIM which are active elements.

FIG. 8 is a charge characteristic diagram of a pixel capacitance with respect to an applied voltage of a liquid crystal display element having a diode ring as an active element.

FIG. 9 is a pulse width-transmittance characteristic diagram of one pixel of the liquid crystal display element when driven by the driving method according to the first embodiment of the present invention.

FIG. 10 is a waveform diagram of a voltage applied between a scanning signal and a data signal, and a signal input end of an active element and a counter electrode according to a second embodiment of the present invention.

FIG. 11 is a diagram illustrating a voltage applied between an input terminal of an active element and a counter electrode when the number of positive and negative pulses of a data signal applied during a selection period is 0, and a voltage applied to a pixel electrode and a counter electrode. The wave form diagram of the voltage applied between an electrode.

FIG. 12 is a diagram illustrating a voltage applied between an input terminal of an active element and a counter electrode when the number of positive and negative pulses of a data signal applied in a selection period is 1, respectively, The wave form diagram of the voltage applied between an electrode.

FIG. 13 shows the case where the positive and negative pulse numbers of the data signal applied during the selection period are the maximum allowable pulse numbers, respectively.
FIG. 3 is a waveform diagram of a voltage applied between an input terminal of an active element and a counter electrode and a voltage applied between a pixel electrode and a counter electrode.

[Explanation of symbols]

1 ... Pixel electrode, 2 ... Active element, 3 ... Signal line, 4 ... Counter electrode, T _S ... Selection period, T _O ... Non-selection period, S _S ... Scan signal, A _D ... Data signal, Va-c ... Active The voltage applied between the input terminal of the element and the counter electrode, Vb-c ... The voltage applied between the pixel electrode and the counter electrode.

Claims (4)

[Claims] 1. A plurality of pixel electrodes arranged in a row direction and a column direction on one substrate of a pair of transparent substrates facing each other with a liquid crystal layer interposed therebetween, and semiconductors connected to each of these pixel electrodes. The liquid crystal display element, in which an active element including a nonlinear resistance element and a signal line for supplying a drive signal to the active element are provided, and a counter electrode facing the pixel electrode is provided on the other substrate, the pixel electrode is provided. In the method of sequentially selecting a plurality of pixels formed by the counter electrode and the liquid crystal between the counter electrode and the time-division driving, in the selection period between the drive signal input terminal of the active element and the counter electrode, In a non-selection period in which a positive or negative polarity selection voltage having a pulse width corresponding to data is applied and other pixels are selected, the potential changes in a cycle shorter than the selection period and the signal Line and oncoming A method for driving a liquid crystal display element, characterized in that a voltage having a waveform in which a positive side area and a negative side area are substantially equal to each other with a potential of a scanning signal supplied to one of the poles in a non-selected period as a center is applied. 2. The potential of one of the positive and negative polarities is maintained on one of the signal line and the counter electrode during the selection period, and is either positive or negative during the non-selection period and is higher than the potential during the selection period. A scan signal that maintains a low potential is supplied, and on the other hand, a pulse having a width corresponding to the image data is provided, and the potential is positive and negative with respect to the reference potential in a cycle in which the selection period is divided into a plurality of potentials. The method for driving a liquid crystal display element according to claim 1, wherein a data signal whose value changes is supplied. 3. A plurality of pixel electrodes arranged in a row direction and a column direction on one of a pair of transparent substrates facing each other with a liquid crystal layer in between, and a semiconductor connected to each of the pixel electrodes. The liquid crystal display element, in which an active element including a nonlinear resistance element and a signal line for supplying a drive signal to the active element are provided, and a counter electrode facing the pixel electrode is provided on the other substrate, the pixel electrode is provided. In the method of sequentially selecting a plurality of pixels formed by the counter electrode and the liquid crystal between the counter electrode and the time-division driving, in the selection period between the drive signal input terminal of the active element and the counter electrode, In a non-selection period in which a positive or negative polarity selection voltage having a number of pulses corresponding to data is applied and other pixels are selected, the potential changes in a cycle shorter than the selection period and the signal Line and oncoming A method for driving a liquid crystal display element, characterized in that a voltage having a waveform in which a positive side area and a negative side area are substantially equal to each other with a potential of a scanning signal supplied to one of the poles in a non-selected period as a center is applied. 4. The potential of one of the positive and negative polarities is maintained on one of the signal line and the counter electrode during the selection period, and has either positive or negative polarity during the non-selection period and is higher than the potential during the selection period. A scanning signal that keeps a low potential is supplied, while the other has a number of pulses according to the image data, and the potential is approximately equal to the positive and negative sides with respect to the reference potential in a cycle in which the selection period is divided into a plurality of potentials. The method for driving a liquid crystal display element according to claim 3, wherein a data signal whose value changes is supplied.