JPH1082980A - Voltage setting method, display device, and electronic apparatus - Google Patents

Abstract

PROBLEM TO BE SOLVED: To improve the display characteristics of a display device by adequately setting the first and second selection voltages to be used in a charge and discharge driving method, etc. SOLUTION: A scanning signal driving circuit 20 applies the first selection voltage VS 1 to scanning lines in a charge mode (first mode). This circuit applies -VPRE which is the precharge voltage of the polarity reverse from the polarity of the first selection voltage VS 1 with the non-selection voltage as a reference to the scanning has in a discharge mode (second mode), then applies the second selection voltage VS 2 of the polarity reverse from the polarity of -VPRE with the non-selection voltage as a reference to the scanning lines. A data signal driving circuit 30 applies various data voltages on data lines. The mode switching between the charge-charge mode (fourth mode) for driving the liquid crystal element by repeating the charge-discharge mode (third mode) at the time of ordinary driving and the charge mode and the discharge- charge mode (fifth mode) of driving the liquid crystal element by repeating the charge mode is made possible.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

The present invention relates to a voltage setting method, a display device, and an electronic device using the same.

[0002]

2. Description of the Related Art In recent years, a liquid crystal display device, which is one of display devices, is a low-power-consumption and lightweight display device, and is an electronic device such as a television, an electronic organizer, a personal computer, and a mobile phone. Widely used for In recent years, MIM elements, back-to-back diode elements, diode ring elements,
In a liquid crystal display device using a non-linear switching element such as a varistor element, a first selection voltage for applying a first selection voltage to a scanning line
And a second mode in which the display element is driven by mixing the second mode in which the preselection voltage is applied and then the second selection voltage is applied to the scanning lines (hereinafter referred to as the charge / discharge driving method). Is in the limelight. This charge / discharge driving method is disclosed in, for example, Japanese Patent Application Laid-Open No. 2-125225.

[0003] On the other hand, this is a driving method existing before the charge / discharge driving method, which uses a binary selection voltage and a binary data voltage.
A driving method called a value driving method is also known. The charge / discharge driving method has various advantages in that display characteristics can be improved as compared with the four-value driving method. However, in this charge / discharge driving method, it is difficult to set the first and second selection voltages, and unless the first and second selection voltages are set to appropriate values, the DC voltage is applied to the liquid crystal element for a long time. Applied,
There are problems such as generation of flicker.

SUMMARY OF THE INVENTION The present invention has been made in view of the above-mentioned problems, and an object thereof is to appropriately set first and second selection voltages used in a charge / discharge driving method or the like. A voltage setting method, a display device, and an electronic device are provided.

[0005]

In order to solve the above problems, the present invention includes a plurality of scanning lines, a plurality of data lines, and a display element driven by using the scanning lines and the data lines, A first mode in which a first selection voltage is applied to a scanning line;
A precharge voltage having a polarity opposite to the first selection voltage with respect to the non-selection voltage is applied to the scanning line, and a second selection voltage having a polarity opposite to the precharge voltage with respect to the non-selection voltage is applied to the scanning line. A voltage setting method used for a display device that drives a display element in a third mode in which the second mode is mixed, wherein the display element is driven in a fourth mode that repeats the first mode, A first selection voltage-transmittance characteristic in the fourth mode is obtained, the display element is driven in a fifth mode in which the second mode is repeated, and a second selection voltage-transmission in the fifth mode is obtained. Rate characteristic is obtained, and based on the first selection voltage-transmittance characteristic in the fourth mode and the second selection voltage-transmittance characteristic in the fifth mode, the third selection voltage-transmittance characteristic is obtained. Determining first and second selection voltages to be used in the mode And it features.

The present invention can be applied to a display device that drives a display element by a so-called charge / discharge driving method or the like. According to the present invention, the first and second selection voltages used in the third mode are obtained based on the first selection voltage-transmittance characteristic and the second selection voltage-transmittance characteristic. Can be For this reason,
When the display element is driven in the third mode in which the first and second modes coexist, the DC component of the voltage applied to the display element can be minimized, and the display characteristics of the display device are improved. Can be achieved.

In the present invention, the precharge voltage may be either positive polarity or negative polarity, and drive using the positive precharge voltage and drive using the negative precharge voltage may be mixed. .

Further, the present invention provides the first selection voltage-transmittance characteristic in the fourth mode and the second selection voltage-transmittance characteristic in the fifth mode having substantially the same transmittance. The first and second selection voltages to be applied are set as first and second selection voltages used in the third mode.

By doing so, even when the display element is driven in the third mode, the transmittance in the first mode and the transmittance in the second mode are substantially equal. And the display characteristics of the display device can be improved.

Further, according to the present invention, the first selection voltage when the transmittance becomes a given value in the fourth mode, and the first selection voltage when the transmittance becomes a given value in the fifth mode. 1 and 2 corresponding to each gradation data when the display element is driven in the third mode based on the second selection voltage.
Is determined.

With this configuration, the first selection voltage when the transmittance becomes 90% in the fourth mode, and the second selection voltage when the transmittance becomes 90% in the fifth mode, for example. With reference to the voltage, the first and second selection voltages corresponding to each gradation data in the third mode can be obtained. Thereby, appropriate and accurate gradation display can be realized by a simple method.

Further, according to the present invention, in the third mode, the average value of the intermediate values of the first and second selection voltages when the same transmittance is obtained in the fourth and fifth modes is obtained. It is characterized in that first and second selection voltages corresponding to each gradation data when driving the display element are obtained.

In this way, it is possible to obtain the first and second selection voltages corresponding to the respective gradation data in the third mode, for example, based on the average value of the intermediate values. Thereby, the DC component of the voltage applied to the display element can be further reduced, and the display characteristics of the display device can be improved.

Further, according to the present invention, there are provided a first mode and a second mode corresponding to each gradation data when driving a display element in the third mode.
When the second selection voltage is obtained, the ratio of the change of the first and second selection voltages to the change of the gradation data is different from each other.

By doing so, the display characteristics can be further improved. When the charge / discharge driving method is used, it is desirable that the rate of change of the second selection voltage be larger than the rate of change of the first selection voltage.

According to another aspect of the present invention, there is provided a display device including a plurality of scanning lines, a plurality of data lines, and a display element driven using the scanning lines and the data lines. A first selection voltage is applied to the scanning line, and in the second mode, a precharge voltage having a polarity opposite to that of the first selection voltage is applied to the scanning line based on the non-selection voltage, and then the non-selection voltage is used as a reference. Scanning signal driving means for applying a second selection voltage having a polarity opposite to the precharge voltage to the scanning lines, data signal driving means for applying a data voltage to the data lines, and display in a mixture of the first and second modes Third driving element
And a means for switching between a fourth mode in which the display element is driven by repeating the first mode and a fifth mode in which the display element is driven by repeating the second mode. And

According to the present invention, it is possible to drive a display element using a so-called charge / discharge driving method or the like. And since the display device of the present invention has the mode switching means,
Based on the display characteristics and the like obtained by the driving in the fourth and fifth modes, it is possible to easily realize appropriate setting of the voltage used in the driving in the third mode.

According to another aspect of the invention, an electronic apparatus includes the above display device. By doing so, it is possible to improve display characteristics, reduce costs, and the like of display devices used in electronic devices such as televisions, remote controllers, calculators, mobile phones, portable information devices, projectors, and personal computers. It becomes possible.

[0019]

Embodiments of the present invention will be described below with reference to the drawings.

Embodiment 1 First, the details of the charge / discharge driving method will be described.

FIG. 1 shows an example of a driving waveform of a conventional four-value driving method, and FIG. 2 shows an example of a driving waveform of a charge / discharge driving method. FIG. 3A shows an equivalent circuit for one pixel of the liquid crystal panel. M, one of the non-linear switch elements
The liquid crystal element, which is one of the IM element and the display element, has
It can be represented by a parallel circuit of a resistor RM and a capacitor CM, and a parallel circuit of a resistor RL and a capacitor CL. 1 and 2 show the waveform of the voltage VD applied to both ends of the MIM element and the liquid crystal element connected in series, and the waveform of the voltage VLC applied to both ends of the liquid crystal element.

In the quaternary driving method shown in FIG. 1, the voltages VA1 and VA2 applied to the liquid crystal element immediately after the end of the selection period (time t1,
(VLC at t2) is as follows: VA1 = (VS1 + VH / 2-VON) -K.VS1 (1) VA2 =-{(VS1 + VH / 2-VON) -K.VS1} (2) Here, VS1 is the selection voltage of the scanning signal, ± VH / 2
Is the ON voltage or OFF voltage of the data signal. Also K
= CM / (CM + CL). VON is VMIM applied to the MIM element immediately before the end of the selection period.
The value depends on the IV characteristic of the MIM element shown in FIG. The VON is when the charging of the liquid crystal element is almost stopped (when the current flowing through the MIM element became 10 ^{@ 9-10 over 8} amperes or so), it is also possible that the voltage applied to the MIM element.

As shown in FIG. 3B, an error occurs in VON. For example, when VON increases by .DELTA.VON, errors also occur in VA1 and VA2, as is apparent from the above equations (1) and (2). , VA1 and VA2 are both reduced by ΔVON. On the other hand, when VON decreases by ΔVON, VA1, V
Both absolute values of A2 increase by ΔVON. Further, even when an error ΔK occurs in K, a considerable error occurs in VA1 and VA2.

On the other hand, in the charge / discharge driving method, as shown in FIG. 2, in the charging mode (for example, the first mode), the first selection voltage VS1 is applied to the scanning line, and the discharging mode (for example, the second mode) is applied. In the mode), after a precharge voltage -VPRE having a polarity opposite to that of VS1 is applied, a second selection voltage VS2 having a polarity opposite to -VPRE is applied. Then, the voltage VB1 (VLC at time t1) applied to the liquid crystal element immediately after the end of the charge mode selection period is the same as in the above equation (1), and VB1 = (VS1 + VH / 2-VON) -K.VS1 (3) On the other hand, in the discharge mode, after the overcharge with the precharge voltage -VPRE, the charged charge is discharged by the second selection voltage VS2, and the voltage applied to the liquid crystal element immediately before the end of the selection period is VS2 + VH / 2-VON. Therefore, the voltage VB2 (VLC at time t2) applied to the liquid crystal element immediately after the end of the selection period is as follows: VB2 =-{(VON-VS2-VH / 2) + K. (VS2 + VH)} (4)

As is apparent from the above equations (3) and (4),
For example, when VON increases by ΔVON, the absolute value of VB1 decreases by ΔVON, but the absolute value of VB2 increases by ΔVON. On the other hand, when VON decreases by △ VON,
The absolute value of VB1 increases by ΔVON, while the absolute value of ΔVB2 decreases by ΔVON. Further, when an error ΔK occurs in K, if the absolute value of VB1 increases due to this error, the absolute value of VB2 decreases, and if the absolute value of VB1 decreases due to this error, the absolute value of VB2 increases.

As described above, according to the charge / discharge driving method, the MIM
Even if the VON of the element fluctuates, the error voltage generated in the liquid crystal applied voltage in the charging mode is effectively canceled by the error voltage generated in the liquid crystal applied voltage in the discharging mode. Therefore, it is possible to effectively prevent the occurrence of display unevenness due to the variation of the VON of the MIM element in the liquid crystal panel. FIG. 4 schematically illustrates the above. Error in VON △
VON occurs, and in the charging mode, the absolute value of the liquid crystal applied voltage increases from E to F in FIG. 4, and the effective voltage applied to the liquid crystal element also increases. As a result, the transmittance of the liquid crystal element decreases and the display becomes dark (in the case of normally white). However, at this time, in the discharge mode, the absolute value of the liquid crystal applied voltage decreases from G in FIG. 4 to H, and the effective voltage applied to the liquid crystal element also decreases. Thereby, the transmittance of the liquid crystal element increases and the display becomes bright. As a result, the total display brightness for one pixel hardly changes. Therefore, even if the VON of the MIM element varies in the liquid crystal panel, the brightness of the display hardly varies, so that display unevenness and the like are prevented. K = C
Even when M / (CM + CL) fluctuates, according to the charge / discharge driving method, display unevenness is similarly prevented.

The driving waveform by the charge / discharge driving method is not limited to the one shown in FIG. 2, but it is sufficient if at least the charge mode and the discharge mode are mixed. For example, as shown in FIGS. 4 and 5 (A), it is also possible to perform a precharge of a positive polarity, or as shown in FIG. 5 (B), to perform a precharge with both positive and negative polarities. Further, the period in which the first and second selection voltages and the precharge voltage are applied may be set to の of the horizontal scanning period 1H, or the gradation display may be performed by pulse height modulation, pulse width modulation, or the like. Further, in addition to the driving by the 1H inversion driving (the driving of inverting the polarity every one scanning line), for example, the nH inversion driving (the driving of inverting the polarity of every n scanning lines) can be used, and the 1H inversion driving is performed. Instead, it is also possible to perform only frame inversion driving.

Next, the details of the first embodiment will be described.

FIG. 6 is a block diagram of a liquid crystal display device capable of realizing the first embodiment. FIG. 7 shows an example of a driving waveform during normal driving of the liquid crystal display device. The liquid crystal panel 10 has a plurality of data lines X1 to Xn and a plurality of scanning lines Y1 to Yn,
Between the data line and the scanning line, for example, as shown in FIG.
The IM element 12 and the liquid crystal element 14 are electrically connected. Note that the connection configuration of the MIM element 12 and the liquid crystal element 14 is not limited to that shown in FIG. 6. For example, a configuration in which the MIM element 12 is connected to a data line and the liquid crystal element 14 is connected to a scanning line, or two MIM elements are connected. A back-to-back structure in which the elements are connected in series in the reverse direction, and various modifications are possible.

In the charging mode (first mode), the scanning signal drive circuit 20 applies the first selection voltage VS1 to the scanning line as shown in FIG. In the discharge mode (second mode), after applying -VPRE which is a precharge voltage having a polarity opposite to that of the first selection voltage VS1 with respect to the non-selection voltage to the scanning line,- VPRE
And a second selection voltage VS2 having the opposite polarity to the scanning line. The data signal drive circuit 30 applies various data voltages to the data lines. As described above, during normal driving, the liquid crystal element is driven in the charge / discharge mode (third mode) in which the charge mode (first mode) and the discharge mode (second mode) are mixed. Of course, the mixed mode of the charging mode and the discharging mode is not limited to the one shown in FIG.
Various modifications can be made, such as the one shown in FIG.

The feature of the first embodiment is that the charge-discharge mode (third mode) during normal driving shown in FIG. 7 and the charge-charge mode (during charge-mode driving the liquid crystal element by repeating the charge mode as shown in FIG. 8). (4th mode) and a discharge-discharge mode (fifth mode) in which the liquid crystal element is driven by repeating the discharge mode as shown in FIG. 9. This mode switching is performed by the mode switching means 31 shown in FIG.

As shown in the above equations (3) and (4), the voltage applied to the liquid crystal element immediately after the end of the selection period in the charging mode is VB1 = (VS1 + VH / 2-VON) -K.multidot.
VS1, and the voltage applied to the liquid crystal element immediately after the end of the selection period in the discharge mode is VB2 = − ｛(VON−VS2−VH
/ 2) + K · (VS2 + VH)}. In order to prevent the DC voltage from being applied to the liquid crystal element for a long time, the relational expression of VB1 + VB2 = 0 (5) needs to be satisfied. The above equation (3),
From (4) and (5), VS2 = -VS1-VH + 2.VON / (1-K) (6) That is, in order to prevent the DC voltage from being applied to the liquid crystal element for a long time, it is necessary to set the first and second selection voltages VS1 and VS2 to values satisfying the above equation (6). However, since VON included in the above equation (6) cannot be directly measured, VON is set to a value that satisfies the above equation (6).
It is not easy to set S1 and VS2. Therefore VS
1. Some method for properly setting VS2 is required.

Therefore, in this embodiment, VS1 and VS2 are set by employing the following method. That is, first, FIG.
Is performed in the charge-charge mode shown in FIG. 1 to obtain a first selected voltage-transmittance characteristic. FIG. 10 shows the VS1 (first selection voltage) -T (transmittance) characteristics obtained in this manner. Further, driving in the discharge-discharge mode shown in FIG. 9 is performed to obtain a second selection voltage-transmittance characteristic. In FIG.
VS2 (second selection voltage) -T thus obtained
(Transmittance) characteristics are shown. In this embodiment, the first and second selection voltages VS1 and VS2 used in the charge / discharge mode shown in FIG. 7 are obtained based on the VS1-T characteristics and the VS2-T characteristics thus obtained. ing.

In the charge / discharge driving method, the liquid crystal element is driven in a charge / discharge mode in which a charge mode and a discharge mode are mixed. Therefore, if the liquid crystal element is driven such that the transmittance in the charging mode is equal to the transmittance in the discharging mode, the DC component of the voltage applied to the liquid crystal element can be made substantially zero. However, if only the drive in the charge / discharge mode can be performed, the first and the second are set so that the transmittances in the charge mode and the discharge mode are equal to each other.
It is almost impossible to set the second selection voltages VS1, VS2.

On the other hand, in the present embodiment, not only the driving in the charge / discharge mode as shown in FIG. 7 but also the driving in the charge-charge mode and the discharge-discharge mode as shown in FIGS. By performing driving in these modes, it is possible to obtain a VS1-T characteristic in a charge-charge mode and a VS2-T characteristic in a discharge-discharge mode. In the VS1-T characteristic, VS1 giving a certain transmittance (referred to as first transmittance), and in the VS2-T characteristic, VS2 giving almost the same transmittance as the first transmittance.
Are used as VS1 and VS2 in the charge / discharge mode. By doing so, it is possible to make the transmittance in the charging mode substantially equal to the transmittance in the discharging mode when driving in the charging / discharging mode shown in FIG. It is possible to make the DC component of the applied voltage almost zero.

In order to perform gradation display using the charge / discharge driving method, it is necessary to find first and second selection voltages VS1 and VS2 corresponding to each gradation data. As a technique for this, for example, first and second techniques described below can be considered. First Method In the first method, first, a VS1-T characteristic and a VS2-T characteristic as shown in FIGS. 10 and 11 are obtained in a charge-charge mode and a discharge-discharge mode. Here, T in FIGS. 10 and 11
(Off) is -VH / 2 (eg-
1.65V) to the data line,
VS2-T characteristics, where T (on) is the ON voltage V
These are the VS1-T characteristics and VS2-T characteristics when H / 2 (for example, 1.65 V) is applied to the data line. Tpp represents the transmittance variation characteristic, and represents the ratio of the 30 Hz component (in the case of 60 Hz per frame) to the DC component of the transmittance. The larger the Tpp, the greater the flicker of the 30 Hz component. Also CR
Represents contrast, and CR = T (off) / T (o
n).

Next, in the first method, in FIGS. 10 and 11, VS1 and VS2 when T (off) becomes a given transmittance, for example, 90%, are obtained, and these are temporarily set as VS1 (90),
VS2 (90). However, a value other than 90% may be selected as the given transmittance, or VS1 and VS2 when T (on) becomes the given transmittance may be obtained. In FIG. 10, VS1 (90) = 21.25 V as shown by E, and in FIG. 11, VS2 (90) = 16.25 V as shown by F.
Then, VS1 (90) = 21.25 V, VS2
Based on (90) = 16.25 V, first and second selection voltages VS1 and VS2 corresponding to each gradation data when driving the display element in the charge / discharge mode are obtained. T in FIG.
(P1) and Tpp (p1) represent the gradation data-transmittance characteristic and the transmittance variation characteristic when the charge / discharge drive is performed using VS1 and VS2 obtained in this manner.
More specifically, the first and second selection voltages VS1 (N) and VS2 (N) corresponding to the gradation data N (the maximum value of the gradation data is assumed to be Nmax = 250) are expressed by the following formula ( 7),
It is obtained as in (8). VS1 (N) = VS1 (90) -VH.N / Nmax = 21.25-3.3.N / 250 (V) (7) VS2 (N) = VS2 (90) + VH.N / 250 = 16. 25 + 3.3 · N / 250 (V) (8) In the above equations (7) and (8), the voltage decrease rate of VS1 (N) and the voltage increase rate of VS2 (N) are the same. These may be different as shown in the following equations (9) and (10). VS1 (N) = VS1 (90) -VH.N / 250 = 21.25-a1.3.3.N / 250 (V) (9) VS2 (N) = VS2 (90) + VH.N / 250 = 16.25 + a2 · 3.3 · N / 250 (V) (10) In this case, it is desirable that the coefficients a1 and a2 have a relationship of a2> a1. As shown in FIGS. 10 and 11, VS1
Is larger than the change in transmittance with respect to VS2, and although the transmittance changes from 10% to 90% (or changes from 90% to 10%),
VS1 requires a change of about 1.25 V, while VS2
This requires a change of about 2.25V.

T (n) and Tpp (n) shown in FIG.
Represents gradation data-transmittance characteristics and transmittance variation characteristics when four-value driving is performed. Tpp (p1)
As can be understood by comparing Tpp (n) with Tpp (p), Tpp (p
The maximum value of 1) is about 1.5 times the maximum value of Tpp (n), which is within an allowable range. Second Method In the second method, first, as shown in FIGS.
The S1-T characteristic and the VS2-T characteristic are obtained.

Next, the charging-charging mode shown in FIG. 10 and the charging mode shown in FIG.
VS1, when obtaining the same transmittance in the discharge-discharge mode of
A value obtained by averaging the intermediate values of VS2 is obtained. Then, based on the average value, the first and second selection voltages VS1 and Vs1 corresponding to each gradation data when the display element is driven in the charge / discharge mode.
Find S2. More specifically, the following is performed.

For example, in FIG. 13, T (off) of FIG.
, A first selection voltage VS1 corresponding to each transmittance is plotted, and a second selection voltage VS2 corresponding to each transmittance is plotted based on T (off) in FIG. . Further, the intermediate value between VS1 and VS2 is plotted as VM. In the second method, an average value of the VM plotted corresponding to each of these transmittances is obtained as a VMM. In FIG. 13, VMM = 18.4V.
Note that the intermediate value VM may be obtained based on T (ON) in FIGS.

Next, this VMM is given a given value, for example, ± V
The value obtained by adding H / 2 (± 1.65 V) is used as the initial value of VS1 and VS2. In this case, the initial values of VS1 and VS2 are respectively
20.05V and 16.75V. Then, for example, the voltage is gradually lowered with respect to VS1 from these initial values,
For VS2, for example, by driving the charge / discharge mode while gradually increasing the voltage by the same value, the VS1-T characteristic in the charge / discharge mode as shown in FIG. 14 is obtained.

Next, VS1 (90) when the transmittance becomes a given value, for example, 90%, is obtained. In FIG. 14, VS1 (90) = 20.75V as shown by G. Also VS2
(90) = VMM- {VS1 (90) -VMM} = 18.
4- (20.75-18.4) = 16.05V.
These VS1 (90) = 20.75V, VS2
Based on (90) = 16.05V, the first and second selection voltages VS1 and VS2 corresponding to each gradation data when the display element is driven in the charge / discharge mode are obtained. T in FIG.
(P2) and Tpp (p2) represent the gradation data-transmittance characteristic and the transmittance variation characteristic when the charge / discharge drive is performed using VS1 and VS2 obtained in this manner.
More specifically, the first and second selection voltages VS1 (N) and VS2 (N) corresponding to the grayscale data N are calculated by, for example, the following equation (1)
1) and (12). VS1 (N) = VS1 (90) -VH.N / Nmax = 20.75-3.3.N / 250 (V) (11) VS2 (N) = VS2 (90) + VH.N / 250 = 16. 05 + 3.3 · N / 250 (V) (12) In the above equations (11) and (12), the voltage decrease rate of VS1 (N) and the voltage increase rate of VS2 (N) are the same.
These may be different as shown in the following equations (13) and (14). VS1 (N) = VS1 (90) -VH.N / 250 = 20.75-a1.3.3.N / 250 (V) (13) VS2 (N) = VS2 (90) + VH.N / 250 = 16.05 + a2 · 3.3 · N / 250 (V) (14) In this case, the coefficients a1 and a2 are set to have a relationship of a2> a1 for the same reason as that described in the first method. Is desirable.

In FIG. 12, Tpp (p2) and Tpp
As can be understood by comparing (n), the maximum value of Tpp (p2) is about 1.5 times the maximum value of Tpp (n),
This is acceptable. Tpp according to the second method
(P2) has a smaller value in a region where the transmittance is lower than Tpp (P1) according to the first method.
Therefore, the use of the second technique can reduce the degree of flicker perceived by a person who actually looks at the liquid crystal display device.

A part of the mode switching means 31 shown in FIG.
0 may be included. For example, circuit elements (selection circuit, switching circuit, and the like) necessary for switching voltage levels when switching between the charge / discharge mode, the charge-charge mode, and the discharge-discharge mode in FIGS. It is included in the circuit 20 and the data signal driving circuit 30. The mode switching by the mode switching means 31 is performed, for example, as shown in FIGS.
Control may be performed by the measurement system that performs various measurements described in the section 4. That is, in this case, for example, mode switching by the mode switching unit 31 is controlled by software or the like included in the measurement system.

In the above description, the present invention has been described mainly on the case where the present invention is applied to a charge / discharge driving method using pulse height modulation, but the present invention employs pulse width modulation as described below. It is also possible to apply to the charge / discharge driving method.

For example, FIG. 15A shows an example of a drive waveform in the charge / discharge mode of the charge / discharge drive method using pulse width modulation.
FIG. 16A shows an example of a driving waveform when pulse width modulation is performed by a conventional four-value driving method. In the driving method of the liquid crystal display device, positive driving and negative driving in which positive and negative voltages are applied are alternately repeated for each frame so that a DC component is not applied to the liquid crystal element for a long time.
At this time, in the conventional four-value driving method, when the pulse widths of the write pulses 40 and 42 in the positive drive and the negative drive that give the same gradation are W1 and W2, FIG.
As shown in (B), the pulse widths W1 and W2 were the same.

On the other hand, in FIG. 15A, in each of the charging mode and the discharging mode, the first and second selection voltages VS1 and VS2 and the data voltages generated by the first and second selection voltages VS1 and VS2 and giving the same gradation are used. When the pulse widths of the second write pulses 44 and 46 are WC and WD, the pulse widths WC and WD are as shown in FIG.
The relationship shown in FIG. That is, WD decreases as WC increases, and W increases as WC increases.
The decrease rate of D becomes smaller. Alternatively, WC decreases as WD increases, and the decrease rate of WC decreases as WD increases. By setting the pulse width in this manner, it is possible to perform appropriate gradation display by pulse width modulation even in the charge / discharge driving method, and prevent a DC voltage from being applied to the liquid crystal element for a long time. . If the concept of pulse width modulation in the conventional four-value driving method is applied as it is, WC and WD will be the same.
In (A) and (B), the concept is not applied, and WC and WD
It is characterized in that the pulse width is set so that one of them increases as the other increases. Further, FIG.
The drive waveform of (B) is conceived based on the knowledge that not only the other is reduced, but also that the reduction rate is gradually reduced, so that appropriate gradation display can be performed. Has the biggest feature.

In the charge / discharge driving method using pulse height modulation, there are problems that it is difficult to control a voltage to obtain a desired gradation and increase the cost of a liquid crystal display device. This problem can be solved.

FIG. 17 shows a measurement result regarding the relationship between the gradation data in the charging mode and the gradation data in the discharging mode. In this measurement, for example, the gradation data in the charging mode is first changed. Then, the first and second selection voltages VS1,
The liquid crystal applied voltage immediately after the selection period by VS2 (t in FIG. 2)
The gradation data in the discharge mode is changed such that VLC at 1, t2) is equal to each other. The relationship thus obtained is the relationship between the charge mode and the discharge mode gradation data shown in FIG. The size of this gradation data corresponds to the size of the pulse width of the write pulse.

As can be understood from FIG. 17, the pulse is applied so that the liquid crystal applied voltages immediately after the selection period by the first and second selection voltages VS1 and VS2 (or at the beginning of the holding period) become substantially equal to each other. By setting the widths WC and WD, it is possible to obtain an appropriate gradation display and prevent a DC voltage from being applied to the liquid crystal element for a long time. By using the various methods described with reference to FIGS. 7 to 14 when setting these WC and WD, it is possible to make the liquid crystal applied voltages immediately after the selection period substantially equal to each other. In this case, the drive waveform in the charge-charge mode as shown in FIG. 8 can be formed by repeating the drive waveform in the charge mode in FIG. 15A, and the drive waveform in the discharge-discharge mode as shown in FIG. 15A can be formed by repeating the drive waveform in the discharge mode shown in FIG.

In FIG. 15A, the first and second write pulses 44 and 46 are shifted in the latter half of the selection period, but both or one of them may be shifted in the first half of the selection period. That is, both or one of the first and second write pulses 44 and 46 may be shifted to the left. By making the first and second write pulses 44 and 46 both right-aligned or left-aligned, even when differential noise occurs due to a change in data voltage, the occurrence of horizontal crosstalk due to the differential noise is effective. Can be prevented. Further, the period in which the first and second selection voltages VS1, VS2 and the precharge voltage VPRE are applied may be set to a half of the horizontal scanning period 1H. In this case, it is desirable that the DC component of the data voltage in the 1H period based on the intermediate voltage between the on-voltage and the off-voltage be substantially zero independent of the gradation. (Embodiment 2) Embodiment 2 is an embodiment relating to an electronic apparatus including the liquid crystal display device described in Embodiment 1, and FIG. 18 shows a configuration example thereof. 18 includes a display information output source 1000, a display information processing circuit 1002, and a drive circuit 100.
4. It includes a liquid crystal panel 1006 which is one of the display panels, a clock generation circuit 1008, and a power supply circuit 1010. The display information output source 1000 is a memory such as a ROM and a RAM,
It includes a tuning circuit and the like, and outputs display information such as a video signal based on a clock from the clock generation circuit 1008. The display information processing circuit 1002 includes a clock generation circuit 1
The display information is processed and output based on the clock from 008. The display information processing circuit 1002 can include, for example, an amplification / polarity inversion circuit, a phase expansion circuit, a rotation circuit, a gamma correction circuit, a clamp circuit, and the like. The driving circuit 1004 includes a scanning signal driving circuit and a data signal driving circuit, and drives the liquid crystal panel 1006. The power supply circuit 1010 supplies power to each of the above-described circuits.

FIG. 19 shows an electronic apparatus having such a configuration.
20, a personal computer (PC) and an engineering workstation (EWS) for multimedia shown in FIG. 20, a pager shown in FIG. 21, and a mobile phone, a word processor, a television, a viewfinder type or a monitor direct view. Type video tape recorder, electronic organizer, electronic desk calculator, car navigation device, POS terminal, device with a touch panel, and the like.

The projector shown in FIG. 19 is a projection type projector using a transmissive liquid crystal panel as a light valve, and uses, for example, a three-plate prism type optical system. In FIG. 19, in a projector 1100, a projection light emitted from a lamp unit 1102 of a white light source is provided inside a light guide 1104 by a plurality of mirrors 1106.
And three active matrix type liquid crystal panels 11 which are divided into three primary colors of R, G, and B by two dichroic mirrors 1108 and display images of respective colors.
10R, 1110G and 1110B. Light modulated by the respective liquid crystal panels 1110R, 1110G, and 1110B is incident on the dichroic prism 1112 from three directions. In the dichroic prism 1112, the red R and blue B lights are bent by 90 °, and the green G light goes straight, so that the images of the respective colors are combined, and a color image is projected on a screen or the like through the projection lens 1114.

The personal computer 12 shown in FIG.
00 is a main body 1204 having a keyboard 1202
And a liquid crystal display screen 1206.

A pager 1300 shown in FIG. 21 includes a liquid crystal display substrate 1304, a light guide 1306 provided with a backlight 1306a, a circuit board 1308, and first and second shield plates 1310, 13 in a metal frame 1302.
12, two elastic conductors 1314 and 1316, and a film carrier tape 1318. Two elastic conductors 1314 and 1316 and film carrier tape 13
Reference numeral 18 denotes a connection between the liquid crystal display substrate 1304 and the circuit board 1308.

Here, the liquid crystal display substrate 1304 has liquid crystal sealed between two transparent substrates 1304a and 1304b, thereby forming at least a dot matrix type liquid crystal panel. The drive circuit 1004 shown in FIG. 18 or the display information processing circuit 1002 can be formed over one of the transparent substrates. Circuits not mounted on the liquid crystal display substrate 1304 are external circuits of the liquid crystal display substrate, and can be mounted on the circuit substrate 1308 in the case of FIG.

FIG. 21 shows the configuration of the pager, and therefore requires a circuit board 1308 in addition to the liquid crystal display substrate 1304. In this case, a liquid crystal display device is used as one component for electronic equipment. When a drive circuit or the like is mounted on a transparent substrate, the minimum unit of the liquid crystal display device is the liquid crystal display substrate 1304. Alternatively, the liquid crystal display substrate 1
What fixed the metal frame 3042 to the metal frame 1302 as a housing can also be used as a liquid crystal display device which is one component for electronic devices. Further, in the case of a backlight type, the liquid crystal display substrate 13 is provided in a metal frame 1302.
04 and a light guide 1306 having a backlight 1306a can be incorporated into a liquid crystal display device. Instead of these, as shown in FIG. 22, two transparent substrates 1304 constituting a liquid crystal display substrate 1304 are provided.
a, 1304b, a TCP (Tape Carrier Package) in which an IC chip 1324 is mounted on a polyimide tape 1322 on which a metal conductive film is formed.
e) 1320 can be connected to be used as a liquid crystal display device, which is one component for electronic equipment.

The present invention is not limited to the first and second embodiments, and various modifications can be made within the scope of the present invention.

For example, drive waveforms in the first to fifth modes to which the present invention is applied are shown in FIGS. 2, 5A, 5B,
Not only those shown in FIG. 7, FIG. 8, FIG. 9, and FIG.
Various modifications are possible.

In the fourth mode, the first selection voltage-
The method of obtaining the first and second selection voltages used in the third mode based on the transmittance characteristics and the second selection voltage-transmittance characteristics in the fifth mode is based on the first and second selection voltages. The method is not limited to the second method, and various other methods can be used.

The present invention can be applied to a liquid crystal display device using a switching element other than the MIM element.

The present invention is particularly preferably applied to a liquid crystal display device.
It is also possible to apply to L (electroluminescence), a plasma display and the like.

The electronic apparatus according to the present invention is not limited to the electronic apparatus described in the second embodiment, but includes various electronic apparatuses including at least the display device according to the present invention.

[0064]

[Brief description of the drawings]

FIG. 1 is a diagram illustrating an example of a driving waveform according to a four-value driving method.

FIG. 2 is a diagram showing an example of a drive waveform in a charge / discharge drive method.

FIG. 3A is a diagram illustrating an equivalent circuit of a pixel of a liquid crystal panel, and FIG. 3B is a diagram illustrating an IV characteristic of a MIM element.

FIG. 4 is a diagram for explaining improvement of display characteristics by a charge / discharge driving method.

FIGS. 5A and 5B are diagrams showing other driving waveform examples of the charge / discharge driving method.

FIG. 6 is an example of a block diagram of a liquid crystal display device that can realize the first embodiment.

FIG. 7 is an example of a drive waveform in a charge / discharge mode (third mode).

FIG. 8 is an example of a drive waveform in a charge-charge mode (fourth mode).

FIG. 9 is an example of a drive waveform in a discharge-discharge mode (fifth mode).

FIG. 10 shows a first selection voltage VS1- in a charging-charging mode.
It is a figure showing an example of transmittance T characteristics etc.

FIG. 11 shows discharge-second selection voltage VS2- in discharge mode.
It is a figure showing an example of transmittance T characteristics etc.

FIG. 12 shows VS1, Vs obtained by the first and second methods and the like.
FIG. 9 is a diagram illustrating an example of gradation data-transmittance characteristics and the like when S2 is used.

FIG. 13 is a diagram for explaining a method of obtaining an intermediate value VM between VS1 and VS2 and an average value VMM of the intermediate value VM.

FIG. 14 is a diagram showing an example of a first selection voltage VS1-transmittance T characteristic when charge / discharge driving is performed using VS1 and VS2 obtained based on the VMM obtained in FIG.

FIGS. 15A and 15B are diagrams for explaining pulse width modulation by a charge / discharge driving method.

FIGS. 16A and 16B are diagrams for explaining pulse width modulation by a quaternary driving method.

FIG. 17 is a diagram showing a measurement result regarding a relationship between gradation data in a charging mode and gradation data in a discharging mode.

FIG. 18 is a diagram illustrating a configuration example of an electronic device according to a second embodiment.

FIG. 19 is a diagram illustrating an example of a projector that is one of the electronic devices.

FIG. 20 is a diagram illustrating an example of a personal computer which is one of electronic devices.

FIG. 21 is a diagram illustrating an example of a pager that is one of the electronic devices.

FIG. 22 is a diagram illustrating a mounting example using TCP.

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 10 Liquid crystal panel 12 MIM element 14 Liquid crystal element 20 Scan signal drive circuit 30 Data signal drive circuit 31 Mode switching means

Claims (7)

[Claims] A first mode that includes a plurality of scanning lines, a plurality of data lines, and a display element driven using the scanning lines and the data lines, and applies a first selection voltage to the scanning lines; ,
A precharge voltage having a polarity opposite to the first selection voltage with respect to the non-selection voltage is applied to the scanning line, and a second selection voltage having a polarity opposite to the precharge voltage with respect to the non-selection voltage is applied to the scanning line. A voltage setting method used for a display device that drives a display element in a third mode in which a second mode is mixed, wherein the display element is driven in a fourth mode that repeats the first mode, A first selection voltage-transmittance characteristic in a fourth mode is obtained, the display element is driven in a fifth mode in which the second mode is repeated, and a second selection voltage-transmission in the fifth mode is determined. Rate characteristics, and based on the first selection voltage-transmittance characteristics in the fourth mode and the second selection voltage-transmittance characteristics in the fifth mode, Find the first and second selection voltages used in the mode. Voltage setting method comprising. 2. The transmission according to claim 1, wherein the first selection voltage-transmittance characteristic in the fourth mode and the second selection voltage-transmittance characteristic in the fifth mode are substantially the same. A voltage setting method, wherein the first and second selection voltages giving the rate are the first and second selection voltages used in the third mode. 3. The method according to claim 1, wherein the first selection voltage when the transmittance becomes a given value in the fourth mode and the transmittance when the transmittance becomes a given value in the fifth mode. A first selection voltage corresponding to each gradation data when driving the display element in the third mode, based on the second selection voltage. 4. The method according to claim 1, wherein the third mode is selected based on an average value of intermediate values of the first and second selection voltages when obtaining the same transmittance in the fourth and fifth modes. A voltage setting method comprising: obtaining first and second selection voltages corresponding to respective gradation data when a display element is driven in a mode. 5. The method according to claim 1, wherein the first and second selection voltages corresponding to each gradation data when the display element is driven in the third mode are obtained. A voltage setting method, wherein the ratio of the change of the first and second selection voltages to the change of the first voltage is different from each other. 6. A display device including a plurality of scanning lines, a plurality of data lines, and a display element driven by using the scanning lines and the data lines, wherein in a first mode, a first mode is provided. In the second mode, a selection voltage is applied to the scanning line, and in the second mode, a precharge voltage having a polarity opposite to that of the first selection voltage is applied to the scanning line based on the non-selection voltage, and then the precharge is performed based on the non-selection voltage. Scanning signal driving means for applying a second selection voltage having a polarity opposite to the voltage to the scanning line; data signal driving means for applying a data voltage to the data line; and driving the display element by mixing the first and second modes Means for switching between a third mode for driving the display element by repeating the first mode and a fifth mode for driving the display element by repeating the second mode. Display characterized by the following: apparatus. 7. An electronic apparatus comprising the display device according to claim 6.