JP2001083943A - Liquid crystal display device and drive method - Google Patents

Abstract

PROBLEM TO BE SOLVED: To simplify the structure of an output circuit and make the potential of one value variable so that a bright regulation can be realized by synchronizing a common electrode line driving circuit with a scanning line drive circuit, and setting the output binary. SOLUTION: The output of a common electrode line drive circuit 112 is binary, and it is arranged on the same side as a scanning line drive circuit 110. A scanning line waveform Vg and a signal line waveform Vs are changed in IH time unit and repeated in IV period. This is repeated, whereby an amplitude larger than the signal waveform Vs can be obtained. Since the common line electrode potential is binary, the positive side and the negative side have the same amplitude, and the common electrode Vc of a liquid crystal 107 is set lower than the center value of the signal line waveform Vs by the portion of the slight shift to the negative side according to the Voff change of a scanning line waveform Vg, whereby the application of DC to the liquid crystal 107 can be prevented, and a problem such as flicker or seizure is never caused. Accordingly, the common electrode line drive circuit 112 can reconcile the increase in picture element electrode potential Vd and the suppression of the scanning line waveform Vg.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an active matrix type liquid crystal display device and a driving method, which simultaneously reduce the amplitude of a signal side driving circuit and the amplitude of a scanning side driving circuit, and improve the practicality. .

[0002]

2. Description of the Related Art In an active matrix type liquid crystal display device, a fixed capacitance coupling driving method for forming a storage capacitor between a preceding scanning line and a pixel and applying a bias voltage to the liquid crystal from the former is provided. There is a method called (for example, Nikkei BP Flat Panel Display '93 P128-P131). This aims at suppressing the maximum amplitude on the signal side (5 V is sufficient), suppressing the internal DC voltage, and the like. On the other hand, in order to prevent an increase in the amplitude on the scanning side, which is a drawback of this method, the auxiliary capacitance is not connected between the preceding gates but is connected to an independent auxiliary electrode. There has been proposed a method of adding (JP-A-10-39277). FIG. 8 shows its configuration, and FIG. 5 shows its operation waveforms.

[0003] In FIG. 8, a plurality of signal lines 101, a plurality of scanning lines 102 orthogonal to the signal lines 101, and a switching element 103 provided near an intersection thereof are provided in an image display unit.
And the pixel electrode 104 connected thereto and the scanning line 102
A common electrode line 105 which is paired with the common electrode line 105, a storage capacitor 106 having one end connected to the pixel electrode 104 and the other end connected to the common electrode line 105, and a common electrode Vc opposed via a liquid crystal 107. Are located.

The switching element is generally made of amorphous silicon (a-Si), and recently, polycrystalline polysilicon (p-Si).
If the application is limited to a reflective projection type panel or the like, it is formed of single crystal silicon (c-Si) used for an IC. They have a gate-drain capacitance 108 due to the structure of the device, which causes a phenomenon that a gate pulse from the scanning line 102 shifts the pixel electrode 104 to the negative side.

In areas other than the pixel display portion, a signal line driving circuit 109 for driving the signal lines 101, a scanning line driving circuit 110 for driving the scanning lines 102, and a common electrode line driving circuit 111 for driving the common electrode lines 105 are provided. It is arranged around.
The scan driving circuit 110 is composed of a shift register and a buffer for generating binary values of Voff and Von based on the start signal VS and the clock signal Vclk. Similarly, the common electrode line driving circuit 111 is composed of a shift register and a switch that generate three values of Ve−, Ve and Ve + based on the start signal VS and the clock signal Vclk.

Next, the operation will be described with reference to the waveform diagram of FIG. The waveform Vg of a certain scanning line is Von with an H period width,
The next field period (= V period) is held at Voff,
Later, Von is output for the H period, and this is repeated. The signal line driving circuit 109 differs depending on the video signal, but assuming that a uniform signal is input, a signal Vs whose polarity is inverted every H period is output as shown in FIG. Pixel electrode 104
Of the switching element 1 during the period when Vg is Von.
03 conducts and has the same potential as the signal line waveform Vs (in this case, negative polarity). During this period, the potential of the common electrode line 105 is set to Ve.
To Ve +. At the moment when Vg becomes Voff, the pixel electrode potential shifts slightly negatively through the gate-drain capacitance 108 (gate-drain capacitance 1).
08 is one digit smaller than the sum of the capacity of the liquid crystal 107 and the storage capacity 106). After that, the potential of the common electrode line 105 becomes Ve.
Since the voltage drops from + to Ve, the pixel electrode potential Vd substantially shifts to the negative side of the potential difference, and is held until the next Vg becomes Von because the switching element is in the cutoff state. During the next Von, Vs is positive and Vd is charged from the negative side to the positive side Vs. During this period, the potential of the common electrode 105 is changed from Ve to Ve−. And similarly Von
After a slight negative shift at the moment from Voff to Voff, the potential of the common electrode 105 rises from Ve− to Ve, and Vd shifts by this potential difference to the positive side and is held.

By repeating this, it becomes possible to give an amplitude larger than the amplitude of the signal line Vs to the pixel electrode. At this time, in order to efficiently transmit the amplitudes of Ve + and Ve- to Vd, it is desirable to increase the storage capacitance and increase the ratio to the liquid crystal capacitance several times. By the operation described above, the scanning line waveform Vg has an effect of being suppressed to the amplitude from Von to Voff.

[0008]

However, in the conventional configuration and method, since the output value of the common electrode is three-valued first, the configuration of the common electrode driving circuit cannot be made with a simple buffer configuration, and becomes complicated. When forming the output of the common electrode, Ve + and Ve- are used to adjust the brightness of the liquid crystal panel.
It is necessary to adjust the amplitude in conjunction with each other. Usually, since a plurality of operational amplifiers having low output impedance are used, the mounting area and the power consumption increase. Furthermore, if the scanning line driving circuit and the common electrode driving circuit are formed on both sides, the signal lines and the power supply of the circuit must be drawn, which may increase the peripheral size of the panel and increase the number of connection points with external circuits. In addition, there is another problem that when the storage capacity is increased, the aperture ratio of the panel is reduced and the panel becomes dark.

[0009]

According to a first aspect of the present invention, a plurality of signal lines provided on a first substrate, a signal line driving circuit for driving the plurality of signal lines, and a plurality of signal lines orthogonal to the signal lines are provided. A scanning line, a scanning line driving circuit for driving the scanning line, a switching element provided near an intersection of the signal line and the scanning line, a pixel electrode connected to the switching element, and a pair with the scanning line. A common electrode line arranged substantially in parallel, a storage capacitor having one end connected to the pixel electrode and the other end connected to the common electrode line, a common electrode driving circuit for driving the common electrode, and the first substrate And a second substrate having a common electrode facing each other via a liquid crystal layer. The common electrode driving circuit synchronizes with the scanning line driving circuit and outputs a binary value.

According to a second aspect of the present invention, a plurality of signal lines provided on a first substrate, a signal line driving circuit for driving the plurality of signal lines, a plurality of scanning lines orthogonal to the signal lines, and A scanning line driving circuit to be driven; a switching element provided near an intersection of the signal line and the scanning line; a pixel electrode connected to the switching element; An electrode line, a storage capacitor having one end connected to the pixel electrode and the other end connected to the common electrode line,
A common electrode driving circuit for driving the common electrode;
Having a common electrode opposed to the substrate through a liquid crystal layer
The scanning line driving circuit and the common electrode driving circuit are arranged on one side of a display screen and share an input signal.

According to a third aspect of the present invention, a plurality of signal lines provided on a first substrate, a signal line driving circuit for driving the plurality of signal lines, a plurality of scanning lines orthogonal to the signal lines, and A scanning line driving circuit to be driven; a switching element provided near an intersection of the signal line and the scanning line; a pixel electrode connected to the switching element; An electrode line, a storage capacitor having one end connected to the pixel electrode and the other end connected to the common electrode line,
A common electrode driving circuit for driving the common electrode;
Having a common electrode opposed to the substrate through a liquid crystal layer
And the pixel electrode is a reflective electrode.

[0012]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS A first embodiment of the present invention is shown in FIG. Basically, components having the same functions as those in FIG. The signal line driving circuit 109, the scanning line driving circuit 110, and the pixel display section perform operations equivalent to those in FIG. The common electrode line driving circuit 112 is different from FIG. 8 in that the output is binary, and is further arranged on the same side as the scanning line driving circuit 110. FIG. 2 shows waveforms, and the operation will be described. The scanning line waveform Vg and the signal line waveform Vs change in 1H period units as in FIG. 5, and repeat the 1V period cycle. During the first Von period, the pixel electrode potential Vd becomes the same potential as the negative signal line waveform Vs, and a slight negative shift occurs when Vg subsequently changes to Voff. Up to this point, it is the same as FIG. During this period, the common line electrode potential keeps Ve + from the previous field period, and after this Vg becomes Voff, it falls from Ve + to Ve-, and this amplitude Vd is shifted to the negative side. Then, this state is maintained during the field period (= V period), and Vd is charged to the positive side of Vs in the next Von period. After the next slight negative shift of Vd, the common line electrode potential is raised from Ve− to Ve +, and the amplitude Vd is shifted to the positive side by this amplitude.

By repeating this, the signal line waveform V
It is possible to obtain an amplitude larger than s. In this case, since the common line electrode potential has two values, the positive side and the negative side have the same amplitude, and the common electrode Vc of the liquid crystal 107 is shifted to the center value of the signal line waveform Vs by a slight negative side shift accompanying the Voff change of Vg. If the temperature is lowered further, no DC is applied to the liquid crystal, and no problems such as flicker and burn-in occur. As a result, even when the common electrode line drive circuit 112 has a binary output, it is possible to achieve both an increase in Vd and a suppression of Vg.

Since the scanning line driving circuit 110 and the common electrode line driving circuit 112 are arranged on the same side as shown in FIG. 1, the start signal VS and the clock signal Vclk can be used in common. Although not shown, power supply wiring and the like can be shared in addition to the above, so that there are advantages that wiring can be shortened, and connection of an external circuit is basically required at one place.

Next, another aspect of the present invention will be described. As described in FIG. 2, for a pair of a certain scanning line and a common electrode line,
There is one change of the common electrode line during the field period, and the writing of the entire screen is performed while this pair shifts in the vertical direction. That is, for the common electrode line driving circuit 112, only one common electrode line changes during the 1H period, and the other common electrode lines are in a holding state. The inventors paid attention to this and found the allowable value of the output impedance of the common line electrode drive circuit 112, and found that the allowable value was on the order of several kΩ, depending on the panel size. Because of this and the binary output, the brightness adjustment can be performed by one variable resistor. The so-called bright adjustment in which the brightness of the image is changed by adjusting the magnitude of the liquid crystal applied voltage is conventionally performed by using the amplitudes of common electrode lines, Ve + and Ve + shown in FIG.
This was done by changing the amplitude of-. This Ve + and Ve
Changing the-amplitude in conjunction means that the operational amplifier
I had to take a complicated configuration that uses more than one.

In the present invention, this is possible with the simple configuration shown in FIG. In FIG. 3, reference numeral 201 denotes a variable resistor;
It is connected between the power supply Vdd and the ground potential Vss of the existing circuit, and the middle point is connected to the output circuit of the common line electrode drive circuit 112 as Ve +. In a normal twisted nematic liquid crystal, Vss is about 5V, and the amplitude of Ve + and Ve- is 4V.
Since a normal screen can be obtained from 5 V, a common +5 V power supply can be used as Vdd. If the brightness adjustment is unnecessary or the signal line driving circuit 109 has the function, it is natural that Ve- and Ve + may be connected to a fixed power supply.

Although Vss is commonly used in FIG. 3, Vdd may be commonly used and Ve- side may be varied, and the effect is not changed. And at one moment 1
Considering further that only one of the common electrode lines changes and the other common electrode lines are in a holding state, the other common electrode lines themselves operate as smoothing capacitors, and the variable resistor 2 shown in FIG.
It has been found that it is practically unnecessary to add a separate smoothing capacitor to the midpoint of 01. This has further simplified the configuration. These advantages are particularly significant when the signal line driving circuit 109 has a digital input configuration, so that it is difficult to perform overall brightness adjustment.

This output impedance and the fact that a smoothing capacitor is not required are based on the conventional ternary output common electrode line driving circuit 11.
Even 1 can be applied. FIG. 4 shows the overall configuration. Components having the same functions as those in FIG. 1 are denoted by the same reference numerals and description thereof will be omitted. The difference from FIG. 1 is that the common electrode line drive circuit 113 has three values, Ve−, Ve and Ve +. This specific example is shown in FIG. V is applied to the variable resistor 202 and the variable resistor 203 in FIG.
Create e + and Ve-. The point where a smoothing capacitor is unnecessary is the same as the above.

Another embodiment of the present invention is shown in FIG. 7 and will be described with reference to the drawings. FIG. 7 is a plan view of one pixel when applied to a reflection type liquid crystal, wherein 101 is a signal line, 102 is a scanning line, 103 is a switching element, 104 is a pixel electrode,
Reference numeral 05 denotes a common electrode line, and a hatched portion 106 denotes a storage capacitor. Here, the pixel electrode 104 is usually formed on the uppermost portion with a reflecting plate structure of aluminum. On the other hand, a pixel electrode of a general transmissive liquid crystal is made of a transparent conductor such as ITO, and when the common electrode line 105 is made thicker, the common electrode line is shielded from light by a metal and becomes dark. In the reflective liquid crystal configuration, the area of the storage capacitor 106 can be effectively used for display.
In other words, it is possible to achieve a configuration that is not disadvantageous in that the aperture ratio is reduced when the storage capacitor is increased and the amplitude of the common electrode line driving circuit is reduced.

Since the present invention is driven by a pair of a scanning line and a common electrode line, a driving circuit having twice the number of ordinary scanning lines is required. For this reason, a configuration in which the switching elements of the pixel display unit are built in the same substrate with polycrystalline silicon or single crystal silicon has a smaller number of connection points and is more practical than a case where these driving circuits are externally provided. Of course, since the operation speed is 10 kHz to 30 kHz, it is possible to operate even with amorphous silicon.

[0021]

According to the first embodiment of the present invention, the output of the common electrode line drive circuit is binary, so that the configuration of the output circuit is simplified, and one of the potentials is made variable. The brightness adjustment can be realized with.

According to the second embodiment of the present invention, by arranging the scanning line driving circuit and the common line driving circuit adjacent to one side, connection lines and power supply lines can be shared, and the area of the peripheral circuit portion can be increased. It is possible to reduce the number of connections and the number of connections to external circuits to one.

According to the third embodiment of the present invention, since the pixel electrodes are of the reflection type, the aperture ratio is reduced as compared with reducing the amplitude of the common electrode line drive circuit by increasing the storage capacitance. A configuration without disadvantage can be obtained.

From another viewpoint, there is an advantage that the brightness can be adjusted with a simple configuration of the variable resistor. Further, by forming the scanning line driving circuit and the common electrode line driving circuit on the same substrate as the switching elements of the screen display portion on the same substrate in the same process, the practicality is further enhanced.

[Brief description of the drawings]

FIG. 1 is a configuration diagram of a first present invention.

FIG. 2 is an explanatory diagram of the operation of the first present invention.

FIG. 3 is a configuration diagram of voltage generation.

FIG. 4 is a block diagram of the second invention.

FIG. 5 is a diagram for explaining the operation of the second invention.

FIG. 6 is a configuration diagram of the voltage generation according to the second invention.

FIG. 7 is a pixel configuration diagram according to the third invention.

FIG. 8 is a conventional configuration diagram.

[Explanation of symbols]

 Reference Signs List 101 signal line 102 scanning line 103 switching element 104 pixel electrode 105 common electrode line 106 storage capacitance 107 liquid crystal 108 gate-drain capacitance 109 signal line driving circuit 110 scanning line driving circuit 111, 112, 113 common electrode line driving circuit 201, 202 , 203 Variable resistor

 ──────────────────────────────────────────────────続 き Continued on front page F term (reference) 2H093 NA16 NB13 NC03 NC09 NC18 NC21 NC34 NC35 ND07 ND10 ND38 5C006 AF44 AF52 BB16 BC03 BC12 BC20 BF25 BF37 FA43 FA47 FA54 5C080 AA10 BB05 DD03 EE28 FF11 JJ02 JJ03 JJ04

Claims (27)

[Claims] 1. A plurality of signal lines provided on a first substrate, a signal line driving circuit for driving the signal lines, a plurality of scanning lines orthogonal to the signal lines, and driving the scanning lines A scanning line driving circuit, a switching element provided near an intersection of the signal line and the scanning line, a pixel electrode connected to the switching element, and a common electrode line paired with the scanning line and arranged substantially in parallel with the scanning line A storage capacitor connected to the pixel electrode at one end and the other end connected to the common electrode line, a common electrode line driving circuit for driving the common electrode line, and the first substrate and the liquid crystal layer. A liquid crystal display device comprising a second substrate having common electrodes facing each other, wherein the common electrode line driving circuit is synchronized with the scanning line driving circuit and has a binary output. 2. The liquid crystal display device according to claim 1, wherein one of binary outputs of said common electrode line drive circuit is variable. 3. The liquid crystal display device according to claim 2, wherein said signal line drive circuit is a digital signal input. 4. The liquid crystal display device according to claim 1, wherein one or both of the outputs of the common electrode line drive circuit are connected to a fixed power supply via a resistor. 5. A smoothing capacitor is not connected to an output of said common electrode line driving circuit.
The liquid crystal display device as described in the above. 6. The liquid crystal display device according to claim 1, wherein said scanning line driving circuit and said common electrode line driving circuit are made of polycrystalline silicon and formed on a first substrate. 7. The liquid crystal display device according to claim 1, wherein said scanning line driving circuit and said common electrode line driving circuit are made of amorphous silicon and formed on a first substrate. 8. The liquid crystal display device according to claim 1, wherein said scanning line driving circuit and said common electrode line driving circuit are formed of single crystal silicon and formed on a first substrate. 9. A plurality of signal lines provided on a first substrate, a signal line driving circuit for driving the signal lines, a plurality of scanning lines orthogonal to the signal lines, and driving the scanning lines. A scanning line driving circuit, a switching element provided near an intersection of the signal line and the scanning line, a pixel electrode connected to the switching element, and a common electrode line paired with the scanning line and arranged substantially in parallel with the scanning line A storage capacitor connected to the pixel electrode at one end and the other end connected to the common electrode line, a common electrode line driving circuit for driving the common electrode line, and the first substrate and the liquid crystal layer. Consisting of a second substrate facing
The common electrode applies a constant bias voltage to the pixel electrode through an auxiliary capacitor by changing from a certain potential A to another potential B after a pair of scanning electrodes change from on to off, and the common electrode potential B is By maintaining one field period and returning the common electrode to the potential A after the next scanning electrode changes from on to off, a reverse bias voltage is applied to the pixel electrode, and flicker adjustment adjusts the DC common electrode potential. A method for driving a liquid crystal display device, comprising: 10. A driving method for a liquid crystal display device according to claim 9, wherein one of the potentials A and B of said common electrode is made variable to have a brightness adjusting function. 11. A plurality of signal lines provided on a first substrate, a signal line driving circuit for driving the signal lines, a plurality of scanning lines orthogonal to the signal lines, and driving the scanning lines. A scanning line driving circuit, a switching element provided near an intersection of the signal line and the scanning line, a pixel electrode connected to the switching element, and a common electrode line paired with the scanning line and arranged substantially in parallel with the scanning line A storage capacitor connected to the pixel electrode at one end and the other end connected to the common electrode line, a common electrode driving circuit for driving the common electrode, and the first substrate facing the first substrate via a liquid crystal layer. A second substrate having a common electrode, wherein the common electrode driving circuit synchronizes with the scanning line driving circuit and outputs a pulse having an a value giving a positive bias voltage to the pixel electrode and a negative bias potential applied to the pixel electrode. B pulse giving Becomes, the liquid crystal display device where most of the period consists of three values is a constant value c, a value and b value, characterized in that provided through the resistor from a fixed power source. 12. The liquid crystal display device according to claim 11, wherein a smoothing capacitor is not connected to an output of said common electrode line driving circuit. 13. A plurality of signal lines provided on a first substrate, a signal line driving circuit for driving the signal lines, a plurality of scanning lines orthogonal to the signal lines, and driving the scanning lines. A scanning line driving circuit, a switching element provided near an intersection of the signal line and the scanning line, a pixel electrode connected to the switching element, and a common electrode line paired with the scanning line and arranged substantially in parallel with the scanning line A storage capacitor connected to the pixel electrode at one end and the other end connected to the common electrode line, a common electrode line driving circuit for driving the common electrode line, and the first substrate and the liquid crystal layer. The scanning line driving circuit and the common electrode line driving circuit are collectively arranged on one side with respect to a display screen;
A liquid crystal display device characterized by partially sharing an input signal. 14. The liquid crystal display device according to claim 13, wherein said scanning line driving circuit and said common electrode line driving circuit are formed of polycrystalline silicon and formed on a first substrate. 15. The liquid crystal display device according to claim 13, wherein said scanning line driving circuit and said common electrode line driving circuit use amorphous silicon and are formed on a first substrate. 16. The liquid crystal display device according to claim 13, wherein said scanning line driving circuit and said common electrode line driving circuit are formed of single crystal silicon and formed on a first substrate. 17. A plurality of signal lines provided on a first substrate, a signal line driving circuit for driving the signal lines, a plurality of scanning lines orthogonal to the signal lines, and driving the scanning lines. A scanning line driving circuit, a switching element provided near an intersection of the signal line and the scanning line, a pixel electrode connected to the switching element, and a common electrode line paired with the scanning line and arranged substantially in parallel with the scanning line A storage capacitor connected to the pixel electrode at one end and the other end connected to the common electrode line, a common electrode line driving circuit for driving the common electrode line, and the first substrate and the liquid crystal layer. A liquid crystal display device comprising a second substrate having a common electrode facing each other, wherein the pixel electrode is a reflective electrode. 18. The liquid crystal display device according to claim 17, wherein said common electrode line driving circuit is synchronized with said scanning line driving circuit and has a binary output. 19. A liquid crystal display device according to claim 18, wherein one of binary outputs of said common electrode line drive circuit is variable. 20. The liquid crystal display device according to claim 19, wherein said signal line drive circuit is a digital signal input. 21. An output of the common electrode line driving circuit,
19. The liquid crystal display device according to claim 18, wherein one or both are connected to a fixed power supply via a resistor. 22. The liquid crystal display device according to claim 18, wherein a smoothing capacitor is not connected to an output of said common electrode line driving circuit. 23. The liquid crystal display device according to claim 17, wherein said scanning line driving circuit and said common electrode line driving circuit are formed of polycrystalline silicon and formed on a first substrate. 24. The liquid crystal display device according to claim 17, wherein said scanning line driving circuit and said common electrode line driving circuit are made of amorphous silicon and formed on a first substrate. 25. The liquid crystal display device according to claim 17, wherein said scanning line driving circuit and said common electrode line driving circuit are formed of single crystal silicon and formed on a first substrate. 26. The common electrode line driving circuit synchronizes with the scanning line driving circuit and outputs a pulse having an a value giving a positive bias voltage to the pixel electrode and a pulse having a b value giving a negative bias potential to the pixel electrode. Consisting of a constant c
18. The liquid crystal display device according to claim 17, wherein the liquid crystal display device comprises three values, and the a value and the b value are provided from a fixed power supply through a resistor. 27. The liquid crystal display device according to claim 26, wherein a smoothing capacitor is not connected to an output of said common electrode line driving circuit.