JPH10186307A - Liquid crystal display device and liquid crystal cell driving method therefor - Google Patents

Abstract

PROBLEM TO BE SOLVED: To perform a high time division driving of liquid crystal cell and to easily and surely perform the selection of quasi-stable states of the liquid crystal cell by enlarging an operating voltage margin with respect to a driving duty. SOLUTION: An liquid crystal cell 10 having such characteristics that liquid crystal molecules are oriented in either a first or a second quasi-stable state according to quasi-stable state selection voltages to be impressed on them after impressing a reset voltage on them and oriented states of the liquid crystal molecules being in the quasi-stable states are changed according to the effective values of a driving voltage is used and pixel parts of respective rows are respectively rewritten by impressing a write voltage for controlling effective values of the driving voltage on them after successively impressing the reset voltage and the quasi-stable selection voltages on them and, also, voltages of waveforms whose voltages are the same and whose pulse widths are different with each other are impressed on them as the first and second quasi-stable state selection voltages.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

[0001] 1. Field of the Invention [0002] The present invention relates to a liquid crystal display device capable of high-duty time-division driving and a method of driving a liquid crystal cell thereof.

[0002]

2. Description of the Related Art There are two types of liquid crystal display devices: a transmissive type that displays by using light from a backlight, and a reflective type that displays by using external light such as natural light or indoor illumination light. .

In these liquid crystal display devices, a polarizing plate is disposed on the front side and the back side of a liquid crystal cell. In a reflection type liquid crystal display device, a reflecting plate is provided on the back side of the back side polarizing plate. Are arranged. Some reflection-type liquid crystal display devices include only one polarizing plate. In this reflection-type liquid crystal display device, a polarizing plate is arranged on the front side of a liquid crystal cell, and on the back side of the liquid crystal cell. It is configured by disposing a reflection plate.

The liquid crystal cell used in these liquid crystal display devices has a structure in which an electrode is provided on the inner surface and a liquid crystal is sandwiched between a pair of substrates on which an alignment film subjected to an alignment process is formed. The liquid crystal molecules are aligned in a predetermined alignment state (for example, a twist alignment state) with the alignment direction in the vicinity of each substrate being regulated by the alignment film.

In the above liquid crystal display device, display driving is performed by applying a drive voltage according to display data between electrodes of each pixel portion of a liquid crystal cell. When a voltage is applied between the electrodes, the liquid crystal molecules are turned off. The orientation state is changed so as to rise from the initial orientation state in the applied state to the substrate surface, and the transmission of light is controlled according to the orientation state.

There are two types of liquid crystal display devices, one using a simple matrix type liquid crystal cell and the other using an active matrix type liquid crystal cell.
The simple matrix method is advantageous in that the structure of the liquid crystal cell is extremely simple and can be obtained at low cost.

[0007]

However, in a liquid crystal display device using a simple matrix type liquid crystal cell, a writing voltage is applied between electrodes (between a scanning electrode and a signal electrode) of each pixel portion of the liquid crystal cell. Since the display is driven by controlling the effective value of the drive voltage generated between the electrodes, when performing display in which the transmission state of light is controlled in a stepwise manner, if the number of time divisions is increased, the effective value corresponding to each step is increased. The difference cannot be made large. Therefore, when time-division driving is attempted with a high duty, the operating voltage margin (difference in effective value) when driving the liquid crystal cell becomes small, and a clear step-by-step display becomes impossible. .

Therefore, in a liquid crystal display device using a liquid crystal cell of a simple matrix system, it is difficult to perform high-duty time-division driving, and it is therefore difficult to increase the number of pixels to achieve high definition of a display image. Was.

According to the present invention, there is provided a liquid crystal display device capable of increasing the operating voltage margin with respect to the drive duty, enabling time-division driving at a high duty, and realizing the display of a high-definition image having a large number of pixels. It is intended to provide a method for driving the liquid crystal cell as well as the method for driving the liquid crystal cell.

[0010]

A liquid crystal display device according to the present invention comprises a liquid crystal cell having a nematic liquid crystal layer sandwiched between a pair of substrates having electrodes formed on opposing surfaces, and at least one of the liquid crystal cells. At least one polarizing plate disposed on the front side, and a drive system for supplying a voltage between the electrodes of the liquid crystal cell, wherein the liquid crystal layer includes liquid crystal molecules between the electrodes of the pair of substrates. After applying a reset voltage for orienting the major axis substantially perpendicular to the substrate surface, a lower value of the first metastable state selection voltage and a second metastable state selection voltage different from the first metastable state selection voltage. A first metastable state in which the liquid crystal molecules are aligned in a predetermined alignment state by selective application of a stable state selection voltage, and a second metastable state in which the liquid crystal molecules are aligned in an alignment state different from the first metastable state When,
A writing alignment state induced by an electric field in which the alignment of liquid crystal molecules changes according to the effective value of the voltage applied to the liquid crystal layer in each of the first metastable state and the second metastable state; A system for selectively applying the reset voltage, the first and second metastable state selection voltages having the same voltage value and different pulse widths from each other, and a voltage having a predetermined effective value to the liquid crystal layer. And a driving means for sequentially supplying a writing voltage between the opposed electrodes of the liquid crystal cell.

In this liquid crystal display device, the liquid crystal molecules of the liquid crystal cell are aligned in one of the first and second metastable states, and the alignment state of the liquid crystal molecules in each metastable state is determined by the effective value of the driving voltage. The first and second metastable states are controlled by changing the state according to the following.
The switching is performed by applying the reset voltage to cause the liquid crystal molecules to rise substantially vertically and reset the alignment state before the liquid crystal molecules, and then apply a metastable state selection voltage for selecting the first or second metastable state. .

When the first metastable state is selected, the liquid crystal display device has electro-optical characteristics of a display device including a liquid crystal cell in which liquid crystal molecules are aligned in the first metastable state and a polarizing plate. When the second metastable state is selected, the display device has electro-optical characteristics of a liquid crystal cell in which liquid crystal molecules are aligned in the second metastable state and a polarizing plate.

That is, this liquid crystal display device has the electro-optical characteristics of two display devices having different alignment states of liquid crystal molecules of a liquid crystal cell.
Control of a plurality of transmission states of the transmission state of light to be controlled stepwise is performed using one electro-optical characteristic, and control of other plural transmission states is performed using the other electro-optical characteristic. Can do it.

For this reason, according to this liquid crystal display device, the total number of stages of the transmission state is determined when the one electro-optical characteristic is used, that is, when the transmission state is controlled by selecting the first metastable state. Using the other electro-optical characteristic, that is, selecting the second metastable state to control the transmission state, and for that, driving each metastable state. Since the number is reduced, time-division driving with a small number of stages can be performed in each metastable state.

Therefore, according to this liquid crystal display device,
The operating voltage margin is increased with respect to the driving duty of the liquid crystal cell, enabling time-division driving at high duty.
The display of a high-definition image having a large number of pixels can be realized.

Further, the liquid crystal display device has a driving system for driving the liquid crystal cell, and the driving system causes the reset voltage and the reset voltage to be applied between the electrodes of the pixel portion of each pixel row of the liquid crystal cell. By applying the metastable state selection voltage sequentially and applying the write voltage, the pixel portion of each pixel row is rewritten to display an image.

In this liquid crystal display device, the rewriting is performed by first resetting the alignment state of the previous liquid crystal molecules and selecting the next metastable state, and then applying a write voltage for obtaining the next write state. In this case, the resetting of the alignment state and the selection of the metastable state can be performed in a short time.

In this liquid crystal display device, the first
Further, since the voltages having the same voltage value and different pulse widths from each other are applied as the second metastable state selection voltage, the metastable state can be selected easily and reliably. .

In the liquid crystal display device according to the present invention, one of the electrodes formed on each of the substrates facing each other of the liquid crystal cell has a plurality of scanning electrodes extending in one direction, and the other electrode extends in a direction intersecting the scanning electrodes. When the driving means comprises a plurality of extending signal electrodes, the driving means sets a period in which all of the plurality of scanning electrodes are sequentially selected and a driving signal is supplied as one frame, and the first metastable state selection voltage and the second It is preferable that the driving circuit further comprises a driving circuit for selectively supplying the metastable state selection voltage between the opposed electrodes for one or more frames.

Further, the driving method of the liquid crystal cell of the present invention is as follows.
After the reset voltage is supplied for a predetermined period, the first and second metastable state selection voltages having the same voltage value and different pulse widths are selectively supplied, and then a predetermined effective voltage is supplied to the liquid crystal layer. A writing voltage for applying a value voltage is sequentially supplied between the opposed electrodes of the liquid crystal cell.

According to this driving method, it is possible to cause the liquid crystal display device to perform an image display in which the pixel portion of each pixel row of the liquid crystal cell is rewritten, and the metastable state can be selected easily and easily. It can be performed reliably.

[0022]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS A liquid crystal display device according to the present invention uses a liquid crystal cell in which liquid crystal molecules are oriented in a first metastable state and a second metastable state, and resets each pixel portion between electrodes. A first in which the voltage and the absolute value are equal and the pulse widths are different from each other
And the second metastable selection voltage is selectively applied.
And the second metastable state is selected, and after the selection of the metastable state, the effective value of the driving voltage is controlled by applying a write voltage to orient the liquid crystal molecules in a desired state, thereby obtaining the second state. In each of the first and second metastable states, the light transmission state is controlled in a plurality of stages.

That is, this liquid crystal display device has a drive system for driving the liquid crystal cell, and the drive system applies the reset voltage to the pixel portion of each pixel row of the liquid crystal cell before the drive to apply the reset voltage. After resetting the alignment state of the liquid crystal molecules, a metastable state selection voltage is applied to align the liquid crystal molecules to one of the first and second metastable states, and thereafter, rewriting is performed by applying a write voltage. In addition to displaying an image by applying a voltage having the same voltage value and a different pulse width from each other as the first and second metastable state selection voltages, the metastable state can be easily selected. Moreover, it is intended to be surely performed.

In the liquid crystal display device according to the present invention, the initial alignment state of the liquid crystal molecules in the liquid crystal cell is approximately 0 ° to approximately 180 ° in one direction with respect to the alignment processing direction of one of the substrates. A non-twisted or twisted splay alignment state with a twist angle, wherein the first metastable state is such that liquid crystal molecules are further twisted by about 180 ° in the one direction from the initial alignment state to eliminate splay distortion. The second metastable state is a state in which the liquid crystal molecules are twisted from the initial alignment state by approximately 180 ° in a direction opposite to the one direction to eliminate the splay distortion.

Further, the driving method of the liquid crystal cell of the present invention is as follows.
After the reset voltage is supplied for a predetermined period, the first and second metastable state selection voltages having the same voltage value and different pulse widths are selectively supplied, and then a predetermined effective voltage is supplied to the liquid crystal layer. By sequentially supplying a write voltage for applying a voltage of a value between the opposed electrodes of the liquid crystal cell, the metastable state can be selected easily and reliably.

In this driving method, it is desirable to drive the pixel portions of each pixel row of the liquid crystal cell by rewriting the pixel portions of one pixel row every predetermined number of frames. In the rewrite frame to be performed, the reset voltage and the metastable state selection voltage are sequentially applied between the electrodes of the pixel unit, and then the write voltage is applied. In other frames, the write voltage is applied in a rewrite frame before the frame. What is necessary is just to apply the write voltage whose absolute value is the same as the written write voltage.

In this driving method, all the pixel rows of the liquid crystal cell are divided into groups of a plurality of rows, and the resetting of the pixel portion of each pixel row of one group and the selection of the metastable state are performed for each frame. It is desirable to write the pixel portions of all the pixel rows.

In this case, the pixel rows are grouped as follows:
It is desirable to choose to change the organization of the pixel rows of each group every cycle of resetting and metastable selection and writing of the pixel rows of all groups.

[0029]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS An embodiment in which the present invention is applied to a reflection type liquid crystal display device will be described below with reference to the drawings.

FIGS. 1A and 1B are perspective views showing the basic structure of a liquid crystal display device according to a first embodiment of the present invention. FIG. 1A shows an initial alignment state, FIG. 1B shows a first metastable state, and FIG. Indicates a second metastable state. FIG. 2 is a sectional view of the liquid crystal display device.

In the liquid crystal display device of this embodiment, as shown in FIGS. 1 and 2, the polarizing plates 21 and 22 are arranged on the front side and the back side of the liquid crystal cell 10 and the back side polarizing plate. A reflection plate 30 is arranged behind the plate 22, and a driving system 40 for driving the liquid crystal cell 10 is connected to the liquid crystal cell 10.

As shown in FIG. 2, the liquid crystal cell 10 has a pair of front and back transparent substrates 11, 16 on which transparent electrodes 13 and 14 are provided on the inner surface and alignment films 15 and 16 on which an alignment process is performed are formed thereon. A liquid crystal 18 is sandwiched between the substrates 12, and the pair of substrates 11 and 12 are joined via a frame-shaped sealing material 17, and the liquid crystal 18 is surrounded by the sealing material 17 between the substrates 11 and 12. Is enclosed in a closed area.
The alignment films 15 and 16 are horizontal alignment films made of polyimide or the like, and the alignment is performed by rubbing the film surfaces in a predetermined direction.

The liquid crystal cell 10 is of a simple matrix type, and a transparent electrode 13 provided on a front substrate 11 has a plurality of scanning electrodes formed along one direction (left and right directions in FIG. 2). The transparent electrodes 14 provided on the electrodes and the back substrate 12 are a plurality of signal electrodes formed along a direction substantially orthogonal to the scanning electrodes 13.

Further, the liquid crystal cell 10 has the liquid crystal 1
8, using a nematic liquid crystal having a twist orientation by adding a chiral agent, and the liquid crystal layer is
In the initial alignment state, the liquid crystal molecules are in a non-twist alignment or a splay alignment state with a twist angle of 0 ° to 180 ° in one direction with respect to the alignment processing direction of one of the substrates.

The liquid crystal cell 10 has a first metastable state after a reset voltage having a voltage value high enough to cause liquid crystal molecules to rise and align substantially perpendicular to the surfaces of the substrates 11 and 12 is applied to the liquid crystal layer. By applying the selection voltage, the liquid crystal molecules are further twisted by approximately 180 ° from the initial alignment state in the one direction (the same direction as the twist alignment direction in the initial alignment state) to cancel the splay distortion. After the reset voltage is applied, the second metastable state selection voltage is applied to cause the liquid crystal molecules to move from the initial alignment state in a direction opposite to the one direction (the first metastable state). Twist direction at an angle twisted by approximately 180 ° to the second metastable state in which the splay distortion has been eliminated by twisting at an angle of approximately 180 °
The alignment state of the liquid crystal molecules in the first and second metastable states has an alignment state induced by an electric field that changes according to an effective value of a driving voltage applied according to display data.

In this embodiment, the twist angle of the liquid crystal molecules in the initial alignment state is set to approximately 90 °. Therefore, the first metastable state is a state in which the liquid crystal molecules are aligned by one of the substrates. A state in which the liquid crystal is twist-oriented in one direction with a twist angle of approximately 270 ° based on the direction,
The second metastable state is a state in which the liquid crystal molecules are twist-aligned with a twist angle of about 90 ° in a direction opposite to the first metastable state with respect to the alignment processing direction of the one substrate.

In FIG. 1, reference numerals 11a and 12a denote alignment directions of the substrates 11 and 12 of the liquid crystal cell 10 (the alignment films 15 and 12).
16 rubbing directions), and in this embodiment,
The alignment film 15 of the front substrate 11 is subjected to an alignment process in a direction shifted approximately 45 ° counterclockwise as viewed from the front side with respect to the horizontal axis x of the screen of the liquid crystal display device and from the lower left to the upper right of the screen. The orientation film 16 of the rear substrate 12 is oriented in a direction deviated clockwise by approximately 45 ° from the horizontal axis x when viewed from the front side and in a direction from the upper left to the lower right of the screen. That is, the orientation direction 11 of both substrates 11 and 12
a and 12a are directions substantially orthogonal to each other.

In this embodiment, a liquid crystal 18 to which a chiral agent having a counterclockwise twist orientation is added as viewed from the surface side is used. Therefore, the liquid crystal molecules of the liquid crystal cell 10 are: In the initial alignment state, the liquid crystal is twist-aligned with a splay distortion in a counterclockwise direction (the twist direction given by the chiral agent) with a twist angle of about 90 ° when viewed from the surface side.

In this initial alignment state, the liquid crystal molecules are aligned in the respective alignment processing directions 11 near the substrates 11 and 12.
a, 12a, and the direction indicated by the broken line arrow in FIG. 1A with reference to the alignment processing direction of one of the substrates, for example, the alignment processing direction 12a of the back substrate 12, that is, the chiral agent. Is a splay alignment state in which the liquid crystal molecules are twist-oriented at a twist angle of about 90 ° in the twist direction given by.

The initial alignment state is a state that is not actually used for display. The liquid crystal cell 10 changes the alignment state of the liquid crystal molecules in each pixel portion to the first and second metastable states described above. The display is driven while being oriented.

In the first metastable state and the second metastable state, the twist angle of the liquid crystal molecules is substantially 1 from the initial alignment state.
This is a state in which the splay distortion is eliminated by changing by 80 °, and the twist angle in the twist direction given by the chiral agent with respect to the orientation processing direction 12a of the backside substrate 12 is +, and the twist angle is given by the chiral agent. Assuming that the twist angle in the direction opposite to the twist direction (direction in which the twist by the chiral agent is released) is minus, the first metastable state is a twist orientation in which the twist angle is changed by + 180 ° with respect to the initial orientation state. The second metastable state is a twist alignment state in which the twist angle has changed by -180 ° with respect to the initial alignment state.

The switching of the alignment state from the initial alignment state to the first and second metastable states is performed between the electrodes (between the scanning electrode 13 and the signal electrode 14) of each pixel portion of the liquid crystal cell 10.
First, a splay distortion elimination voltage of a sufficiently high voltage value at which the liquid crystal molecules rise and align substantially perpendicular to the surfaces of the substrates 11 and 12 is applied, and then a selection voltage of a predetermined value is applied between the electrodes. Done by

That is, after the liquid crystal molecules are vertically aligned with respect to the surfaces of the substrates 11 and 12 by the application of the splay distortion eliminating voltage, the first metastable state selection voltage is applied. Torsion angle (90 ° + 1
(80 ° = 270 °), the film is oriented in a twisted state, the splay distortion is eliminated, and a first metastable state is set.

In the first metastable state, the liquid crystal molecules are aligned along the respective alignment processing directions 11a and 12a near the two substrates 11 and 12, and the alignment processing direction of one of the substrates, for example, With reference to the orientation processing direction 12a of the back substrate 12, in the twist direction indicated by the broken arrow in FIG. 1B, that is, in the counterclockwise direction (the twist direction given by the chiral agent) when viewed from the front side, approximately 2
It is in a state of being twist-oriented at a twist angle of 70 °.

Further, after the liquid crystal molecules are vertically aligned with respect to the surfaces of the substrates 11 and 12 by applying the spray distortion canceling voltage, the second metastable state selection voltage is applied. 18 from the twist angle at
Twist angle minus 90 ° twist (90 ° -180 °
(= −90 °), the film is oriented in a twisted state, the splay distortion is eliminated, and the state becomes the second metastable state.

In the second metastable state, the liquid crystal molecules are aligned along the respective alignment processing directions 11a and 12a near the two substrates 11 and 12, and the alignment processing direction of one of the substrates, for example, With reference to the orientation processing direction 12a of the back substrate 12, the twist direction indicated by the broken arrow in FIG. 1C, that is, the clockwise direction as viewed from the front side (the direction opposite to the twist direction given by the chiral agent)
In addition, it is in a state of being twist-oriented at a twist angle of about 90 °.

Further, the first metastable state and the second metastable state can be switched from one to the other, and even if the liquid crystal molecules are oriented in either metastable state, First, liquid crystal molecules are placed between the electrodes 13 and 14 on the substrate 1.
By resetting the metastable state by applying a reset voltage of a sufficiently high voltage that rises and orients substantially perpendicular to the 1,12 planes, and then applies the first or second metastable state selection voltage, In addition, the alignment state of the liquid crystal molecules can be switched from one metastable state to the other metastable state.

The first metastable state selection voltage and the second metastable state selection voltage are determined by the characteristics of the nematic liquid crystal used, the characteristics of the chiral agent, and the amount added. The state selection voltage is a voltage that generates an electric field that causes most liquid crystal molecules to be aligned in an alignment state when no voltage is applied (an alignment state in which the liquid crystal molecules fall down at a pretilt angle in the initial alignment state). The second metastable state selection voltage is a voltage that generates an electric field in which most liquid crystal molecules are aligned at an inclination angle close to the pretilt angle in the initial alignment state, and the generated electric field is the first metastable state. This value is larger than the electric field generated by the steady state selection voltage.

FIG. 3 shows the alignment state of the liquid crystal molecules in the initial alignment state, the reset state, and the first and second metastable states as viewed from the lower edge direction of the liquid crystal cell 10 (the direction orthogonal to the horizontal axis x). FIG. 18a is a schematic diagram, and 18a indicates liquid crystal molecules.

As shown in this schematic diagram, the initial alignment state (the liquid crystal molecules are twist-aligned with a twist angle of approximately 90 ° counterclockwise as viewed from the front side with respect to the alignment processing direction 12a of the back substrate 12). State) indicates that both substrates 11 and 12
Are aligned so as to rise obliquely at a pretilt angle of about several degrees toward the alignment processing directions 11a and 12a with respect to the surfaces of the substrates 11 and 12 respectively, but the twisted liquid crystal is aligned. This is a state in which the tilts of the pretilts on the respective substrates 11 and 12 are opposite to each other when the molecules are developed so that the respective molecular long axes are on the same plane. A state in which the tilt angle decreases as the distance from the substrates 11 and 12 increases, and the direction of inclination with respect to the surfaces of the substrates 11 and 12 is reversed with respect to the middle of the liquid crystal layer thickness (point where the tilt angle becomes 0 °) ( (With splay distortion).

In addition, the reset state is set between the two substrates 11,
The liquid crystal molecules (not shown in the figure) near 12 are in a state that is almost the same as the initial alignment state (for each substrate 1).
1 and 12 surfaces are oriented so as to rise obliquely at a pre-tilt angle of about several degrees toward the alignment processing directions 11a and 12a), but almost at least a certain distance from the substrates 11 and 12 Liquid crystal molecules of the substrate 1
It is in a state of being oriented so as to rise almost perpendicularly to the 1 and 12 planes.

Further, the first metastable state (the state in which the liquid crystal molecules are twisted in one direction at a twist angle of about 270 °) corresponds to the state in which the liquid crystal molecules in the vicinity of the substrates 11 and 12 are in the initial alignment state. It is almost the same as the above, but the liquid crystal molecules are twisted by about 180 ° more than the initial alignment state and are in a twisted state. Therefore, the liquid crystal molecules in the twisted state are aligned such that their respective molecular long axes are on the same plane. Since the tilt direction of the liquid crystal molecules 18a is the same when viewed in a developed state, the first metastable state is a twist alignment state without splay distortion.

In the second metastable state (when the liquid crystal molecules are in the first
Is a state in which the liquid crystal molecules are twisted at a twist angle of about 90 ° in the direction opposite to the metastable state of the liquid crystal molecules). The angle is approximately 1 in the direction opposite to the twist direction in the first metastable state from the initial orientation state.
The liquid crystal molecules 18a are twisted and twisted by 80 °, and therefore, when the liquid crystal molecules in the twisted alignment are developed so that the respective molecular major axes are on the same plane, the tilt direction of the liquid crystal molecules 18a is the same. Therefore, the second metastable state is also a twist alignment state having no splay distortion.

The first and second metastable states are respectively
In this metastable state, the twist angle of the liquid crystal molecules 18a is maintained, but in any metastable state,
The tilt angle of the liquid crystal molecules 18a, that is, the rising angle with respect to the surfaces of the substrates 11 and 12 changes according to the effective value of the drive voltage applied between the electrodes 13 and 14 (however, the two substrates 1
The alignment state of the liquid crystal molecules near 1 and 12 hardly changes).

Of the alignment states of the liquid crystal molecules in the first and second metastable states shown in FIG. 3, the alignment state shown on the upper side corresponds to the case where the effective value of the driving voltage is a relatively small value. Of the liquid crystal molecules (first writing state) when the effective value of the driving voltage is a certain high value. In any metastable state, the liquid crystal molecules are aligned in accordance with the effective value of the driving voltage while maintaining the twist alignment state in the metastable state.

The driving voltage is a voltage whose effective value changes within a range lower than the voltage value of the reset voltage, and the first and second metastable states correspond to the effective value of the driving voltage. Although the tilt angle of the liquid crystal molecules changes, the twist alignment state is maintained as it is. In any metastable state, the liquid crystal molecules 18a are made almost perpendicular to the substrates 11 and 12 by applying the reset voltage. It is reset by the rising orientation.

In FIG. 1, 21a and 22a are:
The transmission axes of a pair of polarizing plates 21 and 22 disposed on the front side and the back side with the liquid crystal cell 10 interposed therebetween are shown. In this embodiment, the front polarizing plate 21 is connected to the transmission axis 21a by the liquid crystal cell. 10 are arranged in a direction substantially parallel to or substantially perpendicular to the orientation processing direction 11a of the front substrate 11 (direction substantially parallel in the figure), and the rear polarizing plate 22 is connected to the front polarizing plate 21 by the transmission axis 22a. Are arranged in a direction substantially perpendicular to the transmission axis 21a.

This liquid crystal display device uses external light such as natural light or indoor illumination light to reflect light incident from the front side by a reflecting plate 30 arranged on the back side to display an image. The driving is performed by driving the liquid crystal cell 10 by the driving system 40.

The driving system 40 has a pixel section of each pixel row of the liquid crystal cell 10 and a reset voltage and a metastable state selection voltage between its electrodes 13 and 14, respectively. Are sequentially applied, and a write voltage for controlling the effective value of the drive voltage is applied to rewrite, and a voltage is selected as a metastable state selection voltage for selecting the first and second metastable states. It is configured to apply voltages of waveforms having the same value and different pulse widths.

That is, the first metastable state and the second metastable state can be selected by controlling the value (absolute value) of the applied metastable state selection voltage. In this liquid crystal display device, By setting the first and second metastable state selection voltages to voltages having the same voltage value and different pulse widths from each other, by applying a voltage having a small pulse width, the liquid crystal molecules are brought into a state where no voltage is applied. The first metastable state to be aligned is selected, and the second metastable state in which liquid crystal molecules are aligned at an inclination angle close to the pretilt angle in the initial alignment state by the application of a voltage having a large pulse width is selected. I have.

The molecules of the liquid crystal in each pixel portion of the liquid crystal cell 10 are oriented so as to rise almost vertically by the application of the reset voltage from the driving system 40 to the frame in which the pixel portion is rewritten. The previous alignment state is reset, and the liquid crystal molecules are oriented to one of the first and second metastable states according to the metastable state selection voltage applied thereafter, and
In the metastable state, the alignment state is changed according to the effective value of the drive voltage controlled by the application of the write voltage.

Prior to the start of driving of the liquid crystal display device, the liquid crystal molecules in all the pixel portions of the liquid crystal cell 10 are aligned in the above-described initial alignment state (alignment state having splay distortion). At the start, when the first reset voltage is applied, the voltage is used as the splay distortion elimination voltage to orient the liquid crystal molecules so as to rise almost vertically, which is the same state as when the metastable state is reset.

In the liquid crystal display device, the liquid crystal molecules in each pixel portion of the liquid crystal cell 10 are aligned in one of the first and second metastable states, and the tilt angle of the liquid crystal molecules in each metastable state is driven. The light transmission state is controlled by changing the effective value of the voltage. When the first metastable state is selected, the liquid crystal molecules are turned on one side with reference to the alignment processing direction of one of the substrates. The display device has electro-optical characteristics of a display device comprising a liquid crystal cell and a polarizing plate twisted with a twist angle of about 270 ° in the direction, and when the second metastable state is selected, the liquid crystal molecules are aligned with the one substrate. In the direction opposite to the first metastable state with respect to the processing direction, approximately 9
It has electro-optical characteristics of a display device comprising a liquid crystal cell twisted at a twist angle of 0 ° and a polarizing plate.

That is, this liquid crystal display device has the electro-optical characteristics of two display devices having different alignment states of the liquid crystal molecules of the liquid crystal cell. Can be controlled using one electro-optical characteristic, and the other plural transmission states can be controlled using the other electro-optical characteristic.

In this case, in the above embodiment, the front side polarizing plate 2
1 with respect to the direction of the transmission axis 21a.
And the transmission axis 22a of the back-side polarizing plate 22 is set to a direction substantially perpendicular to the transmission axis 21a of the front-side polarizing plate 21. Display in a twisted nematic mode (hereinafter referred to as TN mode) both when the metastable state is selected to control the transmission state and when the second metastable state is selected to control the transmission state. Can be.

That is, in any of the first and second metastable states, the linearly polarized light transmitted through the front polarizing plate 21 and incident on the liquid crystal cell 10 is transmitted by the liquid crystal cell 10 due to the birefringence of the liquid crystal layer. Is rotated in accordance with the twist alignment state of the above, and the light is incident on the rear polarizing plate 22, and the transmission is controlled by the rear polarizing plate 22. And the back side polarizing plate 2
The light transmitted through 2 is reflected by the reflection plate 30 and is transmitted through the back-side polarizing plate 22, the liquid crystal cell 10, and the front-side polarizing plate 21 in order and emitted.

In the liquid crystal display device, the first
When the metastable state of is selected, the alignment state of the liquid crystal molecules is
Since the twist angle is as large as about 270 ° in the twisted state, the optical rotation differs for each wavelength light due to the optical rotation dispersion in the birefringence action of the liquid crystal layer. The light transmitted through the plate 22 and transmitted through the back-side polarizing plate 22 becomes colored light having a color corresponding to the intensity ratio of each wavelength light constituting the light.

As described above, when the first metastable state is selected, the display in the TN mode is a color display in which a colored display is obtained, and the display color is the electrode 13, 1
It changes according to the effective value of the drive voltage applied between the four.

That is, the liquid crystal molecules rise and align in accordance with the effective value of the driving voltage while maintaining the alignment state in the metastable state. When the alignment state of the liquid crystal molecules changes in this manner, the liquid crystal layer changes its orientation. Since the optical rotation of each wavelength is changed by the change of optical rotation dispersion according to the change of birefringence, the color of the colored light can be changed by controlling the effective value of the drive voltage, and therefore, one pixel Can display multiple colors.

The color display uses the birefringence of the liquid crystal layer of the liquid crystal cell 10 and the polarization of the pair of polarizing plates 21 and 22 to color light. Since light absorption is smaller than that of coloring light, even a reflective liquid crystal display device can increase the transmittance of display light to obtain a bright colored display.

On the other hand, when the second metastable state is selected, the alignment state of the liquid crystal molecules is a twist alignment state in which the twist angle is substantially 90 °, and the display in the TN mode at this time is a normal TN mode. This is basically the same as the case of the liquid crystal display device of the type. In the liquid crystal display device of this embodiment, the front-side polarizing plate 21 and the rear-side polarizing plate 22 are respectively connected to the transmission axes 21a, 21a.
When the tilt angles of the liquid crystal molecules are close to the pretilt angle, white, which is an achromatic bright display, is displayed when the tilt angle of the liquid crystal molecules is close to the pretilt angle. The rate decreases, and black, which is an achromatic dark display, is finally displayed.

In this case, the liquid crystal molecules rise and align in accordance with the effective value of the driving voltage, and the birefringence of the liquid crystal layer changes accordingly. Therefore, by controlling the effective value of the driving voltage, the effective value of the light is controlled. By controlling the transmission state in a stepwise manner, monochrome display with gradation can be performed.

The above-mentioned initial alignment state, that is, the state in which the liquid crystal molecules are twist-aligned at a twist angle of about 90 ° with splay distortion is not used for actual display. In this state, the display can be obtained.

FIGS. 4 to 6 show both substrates 1 of the liquid crystal cell 10.
The orientation directions 11a and 12a of the liquid crystal cells 1 and 12 and the transmission axes 21a and 22a of the front and back polarizing plates 21 and 22 are set as shown in FIG. 4 (a) and 4 (b) show changes in light emission rate and display color with respect to the drive voltage of the liquid crystal display device in which the value of (product of liquid crystal layer thickness d) is selected to be about 1000 nm. Voltage-emission rate characteristic diagram and CIE chromaticity diagram in the state,
5A and 5B are a voltage-emission rate characteristic diagram and a CIE chromaticity diagram in the first metastable state, and FIGS.
(B) is a voltage-emission rate characteristic diagram and a CIE chromaticity diagram in the second metastable state. In the chromaticity diagrams of (b) of each drawing, W indicates an achromatic color point.

First, the initial alignment state will be described.
The voltage-emission ratio characteristic in the initial alignment state is a characteristic as shown in FIG. 4A, and the change in the display color with respect to the driving voltage is such that the effective value of the driving voltage is 0 V as shown in FIG. White (when no voltage is applied) and black when an effective value (for example, about 5 V) voltage at which the liquid crystal molecules rise and align substantially vertically is applied.

The rising alignment state of the liquid crystal molecules is almost vertical when the reset voltage is applied, and the display becomes blackest at that time. However, since the reset voltage application time is extremely short, the reset alignment state is low. The display in the state is hardly recognized by human eyes.

The voltage-emission rate characteristics in the first metastable state are as shown in FIG. 5A, and the change of the display color with respect to the driving voltage is as shown in FIG. 5B. Red when an effective value of 1.95 V is applied, and 2.9 effective value.
It is blue when a voltage of 8 V is applied.

Note that the red coordinate values of x and y are as follows:
x = 0.353, y = 0.350, and the Y value (brightness) is 28.54. The x, y coordinate values of the blue are x = 0.274, y = 0.296,
The Y value is 11.64.

Further, the voltage-emission rate characteristics in the second metastable state are as shown in FIG. 6A, and the change of the display color with respect to the driving voltage is as shown in FIG. 6B. White when an effective value of 1.55 V was applied, and an effective value of 3.
It is black when a voltage of 07 V is applied.

The x, y coordinate values of the above white are:
x = 0.317, y = 0.341, and the Y value is 34.
41. Further, the x, y coordinate values of the above black are:
x = 0.271, y = 0.290, and the Y value is 1.8
3.

That is, the liquid crystal display device displays red and blue by selecting the first metastable state and displays white and black by selecting the second metastable state.
In addition to white and black display, which is the basis of display, two color display of red and blue can be performed.

When the power of the liquid crystal display device is turned off, the first
Or, the alignment state of the liquid crystal molecules in the second metastable state is
The liquid crystal returns to the initial alignment state in a few seconds to several minutes (depending on the characteristics of the nematic liquid crystal used and the characteristics and addition amount of the chiral agent) due to spontaneous discharge, and the entire screen is in the initial alignment state when no voltage is applied (see the above embodiment). Then it becomes white).

The liquid crystal display device has the electro-optical characteristics of two display devices having different alignment states of liquid crystal molecules in a liquid crystal cell. Since a plurality of transmission states can be controlled using one electro-optical characteristic and another plurality of transmission states can be controlled using the other electro-optical characteristic, all stages of the transmission state can be controlled. The number is determined when the one electro-optical characteristic is used, that is, when the transmission state is controlled by selecting the first meta-stable state, and when the other electro-optical characteristic is used, that is, when the second meta-stable state is used. When the state is selected and the transmission state is controlled, it can be sorted, and therefore, the number of stages driven in each metastable state decreases, so in each metastable state,
Time-division driving with a small number of stages can be performed.

Therefore, according to the above liquid crystal display device, it is possible to increase the operating voltage margin with respect to the driving duty of the liquid crystal cell 10. That is, in the case of a liquid crystal display device that performs two-color display of red and blue in addition to the above-described white and black display, the effective value of the drive voltage is changed to red by selecting the first metastable state. 1.95V when displaying black
1.55V and 3.07V when the second metastable state is selected to display blue and white.
Therefore, the difference between the effective values of the two drive voltages in each metastable state, that is, the operating voltage margin, is set to 1.03 V in the first metastable state.
(= 2.98V-1.95V) and 1.52V (= 3.07V-1.55V) in the second metastable state, which is sufficiently large.

Therefore, according to the above liquid crystal display device,
Even if the liquid crystal cell 10 is of a simple matrix type driven by controlling the effective value of the driving voltage, the operating voltage margin is increased with respect to the driving duty, and time-division driving at a high duty is enabled. The display of a high-definition image having a large number of pixels can be realized.

In the liquid crystal display device, when the first metastable state is selected, the display colors become red and blue. The display color is obtained by changing the value of Δnd of the liquid crystal cell 10. Can be chosen arbitrarily.

Further, the liquid crystal display device of the above embodiment performs the display in the TN mode when any of the first and second metastable states is selected, and performs the display in the first metastable state. Is a color display, and the display in the second metastable state is a black-and-white display. At least the direction of the transmission axis 21a of the front polarizing plate 21 is set to the alignment processing direction 11a of the front substrate 11 of the liquid crystal cell 10. If the direction is obliquely intersected, the display in both the first and second metastable states can be color display in the birefringence effect mode.

FIGS. 7A and 7B are perspective views showing the basic structure of a liquid crystal display device according to a second embodiment of the present invention. FIG. 7A shows an initial alignment state, FIG. 7B shows a first metastable state, and FIG. Indicates a second metastable state.

The liquid crystal display device of this embodiment has a liquid crystal cell 1
The twist angle of the liquid crystal molecules in the initial alignment state of 0 is approximately 3
The other configuration is the same as that of the first embodiment.

In this embodiment, as shown in FIG. 7, the orientation direction 11a of the front substrate 11 of the liquid crystal cell 10 is substantially counterclockwise with respect to the horizontal axis x of the screen of the liquid crystal display device when viewed from the front side. The direction is shifted by 15 ° from the lower left to the upper right of the screen.
a is approximately 1 clockwise with respect to the horizontal axis x when viewed from the front side.
The direction is shifted by 5 ° and is directed from the upper left to the lower right of the screen. That is, the alignment processing directions 11a and 12a of the substrates 11 and 12 are directions intersecting each other at an angle of about 30 °.

In this embodiment, the liquid crystal cell 1
The liquid crystal of 0 is a liquid crystal added with a chiral agent having a counterclockwise twist alignment as viewed from the surface side. Therefore, in the initial alignment state, the liquid crystal molecules have a splay distortion when viewed from the surface side. It is twist-oriented with a twist angle of about 30 ° in the counterclockwise direction (the twist direction given by the chiral agent).

In this initial alignment state, the liquid crystal molecules are aligned in the respective alignment processing directions 11 near the substrates 11 and 12.
a, 12a, and the direction indicated by the dashed arrow in FIG. 70 (a), ie, the chiral agent, based on the alignment processing direction of one of the substrates, for example, the alignment processing direction 12a of the back substrate 12. Is a splay alignment state in which the liquid crystal molecules are twist-oriented at a twist angle of about 30 ° in the twist direction given by the above.

In each of the first and second metastable states, the twist angle of the liquid crystal molecules is approximately 18 degrees from the initial alignment state.
In this embodiment, the twist angle of the liquid crystal molecules in the initial alignment state is almost 3 °.
In the first metastable state, the liquid crystal molecules are twist-aligned at a twist angle of about 210 ° in the twist direction given by the chiral agent with respect to the alignment processing direction of one of the substrates. In the metastable state of 2, the liquid crystal molecules are twist-aligned with a twist angle of about 150 ° in a direction opposite to the twist direction given by the chiral agent with respect to the alignment processing direction of the one substrate.

That is, in the first metastable state, the liquid crystal molecules are aligned along the respective alignment processing directions 11a and 12a in the vicinity of the substrates 11 and 12, and
The orientation processing direction of one of the substrates, for example, the back substrate 1
2, the twist direction indicated by the broken line arrow in FIG. 7B, that is, the counterclockwise direction as viewed from the surface side (the twist direction given by the chiral agent) with reference to the second alignment processing direction 12a.
In addition, it is in a twist-oriented state with a twist angle of about 210 °.

Further, the second metastable state is that the liquid crystal molecules are:
In the vicinity of the two substrates 11 and 12, the alignment is performed along the respective alignment processing directions 11a and 12a, and based on the alignment processing direction of one of the substrates, for example, the alignment processing direction 12a of the back substrate 12, (FIG. In the twist direction indicated by the dashed arrow in c), that is, in the clockwise direction (the direction opposite to the twist direction given by the chiral agent) when viewed from the surface side, the twist is oriented at a twist angle of about 150 °.

The first metastable state and the second metastable state are the same as in the first embodiment.
Resetting the meta-stable state by applying a reset voltage having a value that causes the liquid crystal molecules to rise and orient substantially perpendicular to the 1,12 surfaces,
Thereafter, by applying the first or second metastable state selection voltage, one metastable state is switched to the other metastable state.

Also in this liquid crystal cell 10, the first metastable state selection voltage is a voltage that generates an electric field that causes most of the liquid crystal molecules to be aligned in the alignment state when no voltage is applied, and the second metastable state is selected. The state selection voltage is a voltage that generates an electric field in which most liquid crystal molecules are aligned at a tilt angle close to the pretilt angle in the initial alignment state.

In this embodiment, the front side polarizing plate 21
Is arranged so that its transmission axis 21a is displaced substantially 45 ° counterclockwise as viewed from the front side with respect to the horizontal axis x of the screen, and the back-side polarizing plate 22 has its transmission axis 22a set to the horizontal axis x. On the other hand, they are arranged in a direction shifted clockwise by approximately 45 ° clockwise when viewed from the front surface side.
1a is the alignment processing direction 1 of the front substrate 11 of the liquid crystal cell 10.
1a (approximately 15 ° counterclockwise with respect to the horizontal axis x when viewed from the front side)
(The direction shifted) at a crossing angle of about 30 ° with respect to the oblique direction, and the transmission axis 22a of the back-side polarizing plate 22 is substantially orthogonal to the transmission axis 21a of the front-side polarizing plate 21. .

The liquid crystal display device of this embodiment has a liquid crystal cell 1
Since the initial alignment state of the liquid crystal molecules of 0 is a splay alignment state in which the liquid crystal molecules are twist-aligned with a twist angle of about 30 ° in one direction with reference to the alignment processing direction 12a of one substrate (here, the back substrate) 12, When the metastable state of 1 is selected, a display comprising a liquid crystal cell and a polarizing plate in which liquid crystal molecules are twist-aligned in one direction with a twist angle of about 210 ° in one direction with respect to the alignment processing direction 12a of the one substrate 12. When the device has the electro-optical characteristics and selects the second metastable state, the liquid crystal molecules are substantially aligned in the direction opposite to the first metastable state with respect to the alignment processing direction 12a of the one substrate 12. It has electro-optical characteristics of a display device comprising a liquid crystal cell twisted at a twist angle of 150 ° and a polarizing plate.

In this embodiment, the direction of the transmission axis 21a of the front-side polarizing plate 21 is set to a direction obliquely shifted at an intersection angle of about 30 ° with respect to the alignment processing direction 11a of the front-side substrate 11 of the liquid crystal cell 10. , The transmission axis 22a of the rear polarizing plate 22
Since the direction is set substantially perpendicular to the transmission axis 21a of the front polarizing plate 21, the second metastable state is selected even when the transmission state is controlled by selecting the first metastable state. Also, when controlling the transmission state by using the display device, color display in the birefringence effect mode can be performed.

The color display by the birefringence effect mode will be described. In either of the first and second metastable states, the linearly polarized light transmitted through the front polarizer 21 and transmitted through the liquid crystal cell 10. In the process, each wavelength light becomes elliptically polarized light having a different polarization state due to the birefringence action of the liquid crystal layer, and each wavelength light passes through the back-side polarizing plate 22 at a transmittance according to each polarization state, The light transmitted through the back-side polarizing plate 22 becomes colored light having a color corresponding to the light intensity ratio of each wavelength light constituting the light. This colored light is reflected by the reflection plate 30, and is transmitted through the rear-side polarizing plate 22, the liquid crystal cell 10, and the front-side polarizing plate 21 in order and emitted.

As described above, the color display in the birefringence effect mode uses the birefringence of the liquid crystal layer of the liquid crystal cell 10 and the polarization of the pair of polarizing plates 21 and 22 to color light. Therefore, since light absorption is smaller than that in which light is colored using a color filter, a bright color display can be obtained by increasing the light transmittance even in a reflective liquid crystal display device.

The above-mentioned initial alignment state, that is, the state in which the liquid crystal molecules are twist-aligned at a twist angle of about 30 ° with a splay distortion is not used for an actual display as described above. In this state, a display in the birefringence effect mode can be obtained.

In the liquid crystal display device, the first
(A state where liquid crystal molecules are twisted at a twist angle of about 210 ° in one direction) is selected.
The alignment state of the liquid crystal molecules is different from that when the second metastable state (the state in which the liquid crystal molecules are twisted at a twist angle of about 150 ° in the opposite direction to the first metastable state) is selected,
Accordingly, the liquid crystal layer exhibits different birefringence,
Different colors can be displayed when the metastable state is selected and when the second metastable state is selected.

Further, in this liquid crystal display device, the electrodes 13, 14 are provided in any of the first and second metastable states.
The birefringence of the liquid crystal layer changes due to a change in the tilt angle of the liquid crystal molecules in accordance with the effective value of the driving voltage applied between them, and the polarization state of each wavelength light incident on the back-side polarizing plate 22 changes accordingly. Therefore, by controlling the effective value of the driving voltage, the color of the colored light can be changed, and therefore, a plurality of colors can be displayed in one pixel portion.

FIGS. 8 to 10 show that the twist angle of the liquid crystal molecules in the initial alignment state of the liquid crystal cell 10 is set to approximately 30 ° as in this embodiment, and the alignment direction 11 of the substrates 11 and 12 is changed.
a, 12a and the transmission axes 21a of the front and back polarizing plates 21, 22;
The direction of 22a is set as shown in FIG. 7, and the change of the light emission rate and the display color with respect to the driving voltage of the liquid crystal display device in which the value of Δnd of the liquid crystal cell 10 is set to about 800 nm is shown. 8A and 8B are a voltage-emission rate characteristic diagram and a CIE chromaticity diagram in an initial alignment state,
9A and 9B are a voltage-emission rate characteristic diagram and a CIE chromaticity diagram in the first metastable state, and FIGS.
(B) is a voltage-emission rate characteristic diagram and a CIE chromaticity diagram in the second metastable state. In the chromaticity diagrams of (b) of each figure, W is an achromatic color point.

First, the initial alignment state will be described.
The voltage-emission rate characteristic in the initial alignment state is a characteristic as shown in FIG. 8A, and the change in the display color with respect to the driving voltage is such that the effective value of the driving voltage is 0 V as shown in FIG. It is yellow-green when (voltage is not applied) and black when an effective value (for example, about 5 V) voltage at which liquid crystal molecules rise and align almost vertically is applied.

The voltage-emission rate characteristics in the first metastable state are as shown in FIG. 9A, and the change in display color with respect to the drive voltage is as shown in FIG. 9B. Red when an effective value of 1.46 V is applied, and an effective value of 2.0
It is white when a voltage of 0 V is applied.

Note that the red x, y coordinate value is x
= 0.432, y = 0.391, and the Y value (brightness)
Is 20.29. The x, y coordinate values of the white are x = 0.290, y = 0.319, and the Y value is 29.70.

Further, the voltage-emission rate characteristics in the second metastable state are as shown in FIG. 10A, and the change of the display color with respect to the drive voltage is as shown in FIG. 10B. And red when an effective value of 1.46 V is applied, and blue when an effective value of 2.00 V is applied.

Note that the red x, y coordinate value is x
= 0.424, y = 0.399, and the Y value is 21.3.
It is one. Also, the x, y coordinate values of the blue are x =
0.249, y = 0.267, and the Y value is 11.32.
It is.

That is, the liquid crystal display device displays red and white by selecting the first metastable state, and displays red and blue by selecting the second metastable state.
For example, color display in which an image is displayed in red and blue on a white background can be performed.

In the liquid crystal display device of this embodiment, the effective value of the drive voltage is changed to the second metastable state even when the first metastable state is selected and red and white are displayed. When displaying red and blue, it is sufficient to set the two values of 1.46 V and 2.00 V. Therefore, the difference between the effective values of the two drive voltages in each metastable state, that is, the operating voltage margin, is set. , 0.51 V (= 2.00 V-1.46 V) in any of the first and second metastable states.

The two effective values when the first metastable state is selected and displayed and the two effective values when the second metastable state is selected and displayed are the same (1). .46V and 2.00V), so that display driving is also facilitated.

FIGS. 11A and 11B are perspective views showing the basic structure of a liquid crystal display device according to a third embodiment of the present invention. FIG. 11A shows an initial alignment state, FIG. 11B shows a first metastable state, and FIG. Is the second
Shows a metastable state.

The liquid crystal display device of this embodiment has a liquid crystal cell 1
The twist angle of the liquid crystal molecules in the initial alignment state of 0 is approximately 7
The other configuration is the same as that of the first embodiment.

In this embodiment, as shown in FIG.
The orientation direction 11a of the front substrate 11 of the liquid crystal cell 10 is
The direction is approximately 35 ° counterclockwise when viewed from the front side with respect to the horizontal axis x of the screen of the liquid crystal display device, and is a direction from the lower left to the upper right of the screen.
2a is a direction deviating clockwise by approximately 35 ° from the horizontal axis x when viewed from the front side, and a direction from the upper left to the lower right of the screen. That is, the alignment processing directions 11a and 12a of the substrates 11 and 12 are directions intersecting each other at an angle of about 70 °.

In this embodiment, the liquid crystal cell 1
The liquid crystal of 0 is a liquid crystal added with a chiral agent having a counterclockwise twist alignment as viewed from the surface side. Therefore, in the initial alignment state, the liquid crystal molecules have a splay distortion when viewed from the surface side. It is twist-oriented with a twist angle of approximately 70 ° in the counterclockwise direction (the twist direction given by the chiral agent).

In this initial alignment state, the liquid crystal molecules are aligned in the respective alignment processing directions 11 near the substrates 11 and 12.
a, 12a, and the direction indicated by the dashed arrow in FIG. 11A with respect to the alignment processing direction of one of the substrates, for example, the alignment processing direction 12a of the back substrate 12, that is, the chiral agent. Is a splay alignment state in which the liquid crystal molecules are twist-oriented at a twist angle of about 70 ° in the twist direction given by (1).

The first and second metastable states each have a twist angle of liquid crystal molecules of about 18 from the initial alignment state.
This is a state in which the splay distortion is eliminated by changing by 0 °. In this embodiment, the twist angle of the liquid crystal molecules in the initial alignment state is set to about 7 °.
Therefore, in the first metastable state, the liquid crystal molecules are twist-aligned at a twist angle of about 250 ° in the twist direction given by the chiral agent with respect to the alignment processing direction of one of the substrates. In the metastable state of 2, the liquid crystal molecules are twist-aligned with a twist angle of about 110 ° in a direction opposite to the twist direction given by the chiral agent with respect to the alignment processing direction of the one substrate.

That is, in the first metastable state, the liquid crystal molecules are aligned along the alignment processing directions 11a and 12a in the vicinity of the substrates 11 and 12, respectively.
The orientation processing direction of one of the substrates, for example, the back substrate 1
(B) of FIG. 11 on the basis of the second alignment processing direction 12a.
In the twist direction indicated by the dashed arrow, that is, in the counterclockwise direction (the twist direction given by the chiral agent) when viewed from the front surface side, in a twisted state with a twist angle of about 250 °.

The second metastable state is that the liquid crystal molecules are
In the vicinity of both substrates 11 and 12, the alignment is performed along the respective alignment processing directions 11a and 12a, and the alignment processing direction of one of the substrates, for example, the alignment processing direction 12a of the back substrate 12, is used as a reference (FIG. 11). In the twist direction indicated by the dashed arrow in c), that is, in the clockwise direction as viewed from the surface side (the direction opposite to the twist direction given by the chiral agent), the twist is oriented at a twist angle of about 110 °.

The first metastable state and the second metastable state are the same as those in the first embodiment.
By resetting the metastable state by applying a reset voltage having a voltage value that causes the liquid crystal molecules to rise and orient substantially perpendicular to the surfaces 1 and 12 and then applying the first or second metastable state selection voltage, Is switched from the metastable state to the other metastable state.

Note that the first metastable state selection voltage is:
The second metastable state selection voltage is a voltage that generates an electric field that causes most of the liquid crystal molecules to be aligned in the alignment state when no voltage is applied. Is a voltage that produces an electric field oriented in

In this embodiment, the front side polarizing plate 21
Is arranged so that its transmission axis 21a is displaced substantially 45 ° counterclockwise as viewed from the front side with respect to the horizontal axis x of the screen, and the back-side polarizing plate 22 has its transmission axis 22a set to the horizontal axis x. On the other hand, they are arranged in a direction shifted clockwise by approximately 45 ° clockwise when viewed from the front surface side.
1a is the alignment processing direction 1 of the front substrate 11 of the liquid crystal cell 10.
1a (approximately 35 ° counterclockwise as viewed from the front side with respect to the horizontal axis x)
The transmission axis 22a of the rear-side polarizing plate 22 is in a direction substantially orthogonal to the transmission axis 21a of the front-side polarizing plate 21. .

The liquid crystal display device of this embodiment has a liquid crystal cell 1
Since the initial alignment state of the liquid crystal molecules of 0 is a splay alignment state in which the liquid crystal molecules are twist-aligned with a twist angle of about 70 ° in one direction with reference to the alignment processing direction 12a of one substrate (here, the back substrate) 12, When the metastable state of 1 is selected, a display comprising a liquid crystal cell and a polarizing plate in which liquid crystal molecules are twist-aligned in one direction with a twist angle of approximately 250 ° with respect to the alignment processing direction 12a of the one substrate 12 as a reference. When the device has the electro-optical characteristics and selects the second metastable state, the liquid crystal molecules are substantially aligned in the direction opposite to the first metastable state with respect to the alignment processing direction 12a of the one substrate 12. It has electro-optical characteristics of a display device comprising a liquid crystal cell twisted at a twist angle of 110 ° and a polarizing plate.

In this embodiment, the direction of the transmission axis 21a of the front-side polarizing plate 21 is set to a direction obliquely shifted at an intersection angle of about 10 ° with respect to the alignment processing direction 11a of the front-side substrate 11 of the liquid crystal cell 10. , The transmission axis 22a of the rear polarizing plate 22
Since the direction is set substantially perpendicular to the transmission axis 21a of the front polarizing plate 21, the second metastable state is selected even when the transmission state is controlled by selecting the first metastable state. Also, when controlling the transmission state by using the display device, color display in the birefringence effect mode can be performed.

In the liquid crystal display of this embodiment,
The first metastable state (when the liquid crystal molecules are almost 2 in one direction)
When a twist orientation of 50 ° is selected) and a second metastable state (state in which liquid crystal molecules are twisted in a direction opposite to the first metastable state with a twist angle of approximately 110 °) When the first metastable state is selected and when the second metastable state is selected, the alignment state of the liquid crystal molecules is different from when the liquid crystal layer is selected, and the liquid crystal layer exhibits different birefringence accordingly. Thus, different colors can be displayed.

Further, in this liquid crystal display device, the electrodes 13, 14 are provided in either of the first and second metastable states.
The birefringence of the liquid crystal layer changes due to the change in the tilt angle of the liquid crystal molecules according to the effective value of the drive signal applied between them, and the polarization state of each wavelength light incident on the back-side polarizing plate 22 changes accordingly. Therefore, the color of the colored light can be changed by controlling the effective value of the drive signal, so that a single pixel portion can display a plurality of colors.

FIGS. 12 to 14 show that the torsion angle of the liquid crystal molecules in the initial alignment state of the liquid crystal cell 10 was set to approximately 70 ° as in this embodiment, and the alignment processing direction 1 of both substrates 11 and 12 was changed.
1a, 12a and transmission axes 21 of front and back polarizing plates 21, 22
a and 22a are set as shown in FIG. 11, and the change of the light emission rate and the display color with respect to the driving voltage of the liquid crystal display device in which the value of Δnd of the liquid crystal cell 10 is set to about 900 nm is shown. FIGS. 12A and 12B show the voltage-emission rate characteristic diagram and the CIE chromaticity diagram in the initial alignment state, and FIGS. 13A and 13B show the voltage-emission ratio in the first metastable state. 14A and 14B are a voltage-emission rate characteristic diagram and a CIE chromaticity diagram in the second metastable state. In the chromaticity diagrams of (b) of each figure, W is an achromatic color point.

First, the initial alignment state will be described.
The voltage-emission rate characteristic in the initial alignment state is a characteristic as shown in FIG.
As shown in FIG. 12B, when the effective value of the drive voltage is 0 V (no voltage is applied), when a voltage of an effective value (for example, about 5 V) at which the liquid crystal molecules rise and rise almost vertically is applied. Is black.

The voltage-emission rate characteristics in the first metastable state are as shown in FIG. 13 (a), and the change of the display color with respect to the drive voltage is as shown in FIG. 13 (b). Red when an effective value of 1.53 V is applied, and orange when an effective value of 2.03 V is applied.

The red x, y coordinate value is x
= 0.343, y = 0.322, the Y value is 24.31, and the orange x, y coordinate value is x = 0.32.
2, y = 0.378, and the Y value is 31.98.

Further, the voltage-emission ratio characteristic in the second metastable state is a characteristic as shown in FIG. 14A, and the change of the display color with respect to the drive voltage is as shown in FIG. And white when an effective value of 1.53 V is applied, and blue when an effective value of 2.03 V is applied.

The x, y coordinate values of the white are x
= 0.320, y = 0.349, the Y value is 34.36, and the blue x, y coordinate values are x = 0.260, y =
0.278, the Y value is 9.05.

That is, the liquid crystal display device displays red and orange by selecting the first metastable state, and displays white and blue by selecting the second metastable state. For example, a color display in which an image is displayed in red, orange, and blue on a white background can be performed.

In the liquid crystal display device of this embodiment, the effective value of the driving voltage is changed to the second metastable state even when the first metastable state is selected and red and orange are displayed. 1.53V and 2.03 when displaying white and blue
V. Therefore, the difference between the effective values of the two drive voltages in each metastable state, that is, the operating voltage margin is set to 0.50 V in both the first and second metastable states. (= 2.03V-1.53V)
Can be taken sufficiently large.

The two effective values when the first metastable state is selected and displayed and the two effective values when the second metastable state is selected and displayed are the same (1). .53V and 2.03V), so that the display driving becomes easy.

As described above, the liquid crystal display devices of the second and third embodiments are also similar to those of the first embodiment.
It has the electro-optical characteristics of two display devices having different alignment states of liquid crystal molecules in a liquid crystal cell. Therefore, it is possible to control a plurality of transmissive states of one of the transmissive states to be controlled in a stepwise manner. Since the characteristics can be controlled and the other plurality of transmission states can be controlled using the other electro-optical characteristics, even if the liquid crystal cell 10 is of a simple matrix type, its driving duty is As a result, the operating voltage margin can be increased, and time-division driving at a high duty can be performed, so that a high-definition image with a large number of pixels can be displayed.

The liquid crystal display device of the second embodiment selects the first metastable state to display red and white, and
Is selected to display blue and black.
The liquid crystal display device according to the third embodiment displays the red and orange colors by selecting the first metastable state, and displays white and blue by selecting the second metastable state. The display color is determined by the value of Δnd of the liquid crystal cell 10 and the polarizing plates 21 and
The direction can be arbitrarily selected by changing the directions of the transmission axes 21a and 22a.

Further, in the liquid crystal display device of the present invention,
The initial alignment state of the liquid crystal cell 10 is not limited to the above-described first to third embodiments, and the liquid crystal molecules are oriented by approximately 0 ° in one direction with respect to the alignment processing direction of one of the substrates.
A non-twisted or twisted splay alignment state with a twist angle of about 180 ° is sufficient.

Incidentally, for example, the initial alignment state is such that all the liquid crystal molecules are aligned along the alignment processing direction of one substrate.
In a non-twist orientation state in which the twist angle is almost 0 °,
The first metastable state is a state in which the splay distortion is eliminated by twist orientation in one direction with a twist angle of about 180 ° in one direction with reference to the orientation processing direction of the one substrate, and the second metastable state is , Approximately 180 degrees in a direction opposite to the first metastable state with respect to the orientation processing direction of the one substrate.
This is a state in which splay distortion is eliminated by twist orientation at a twist angle of °.

For example, when the initial alignment state is a twist alignment state in which liquid crystal molecules are aligned in one direction with a twist angle of about 180 ° with respect to the alignment processing direction of one substrate, the first metastable state is obtained. The state is a state where the splay distortion is eliminated by twist alignment with a twist angle of about 360 ° in one direction based on the alignment processing direction of the one substrate, and the second metastable state is a state where all the liquid crystal molecules are aligned. Is a state in which non-twist alignment is performed along the alignment processing direction of the one substrate to eliminate splay distortion.

As described above, even when the initial alignment state and the first and second metastable states of the liquid crystal cell 10 are selected, at least the front side of the pair of polarizing plates 21 and 22 having the liquid crystal cell 10 interposed therebetween. If the direction of the transmission axis 21a of the polarizing plate 21 is set to a direction obliquely intersecting with the alignment processing direction 11a of the front substrate 11 of the liquid crystal cell 10, the first metastable state is selected and the transmission state is controlled. In both cases, the color display in the birefringence effect mode can be performed when the transmission state is controlled by selecting the second metastable state.

Further, the liquid crystal display device of each of the above embodiments is
Birefringence action of liquid crystal layer of liquid crystal cell 10 and pair of polarizing plates 2
The display is performed by utilizing the polarizing action of the liquid crystal cell 10 in addition to the polarizing action of the liquid crystal cell 10. Is also good.

This addition of a retardation plate is particularly effective in a liquid crystal display device which performs color display in the birefringence effect mode. Due to the birefringence of both the retardation plate and the liquid crystal layer of the liquid crystal cell 10, the polarization state of each is greatly changed and incident on the back-side polarizing plate 22.
The difference in the transmittance of each wavelength light passing through becomes large, so that the light transmitted through the back-side polarizing plate 22 becomes sharp colored light in which the difference in the intensity of each wavelength light constituting the light is large,
Further, with the change of the alignment state of the liquid crystal molecules according to the effective value of the driving voltage, the transmittance of each wavelength light and the difference between the transmittances greatly change, and the color of the colored light changes. Also increase.

The liquid crystal display devices according to the first to third embodiments are of a reflection type in which a reflection plate 30 is disposed on the back surface side. Transmission type liquid crystal display device (reflection plate 3
0) can also be applied.

Further, the present invention can be applied to a reflection type liquid crystal display device in which only one polarizing plate is provided, a polarizing plate is arranged on the front side of the liquid crystal cell, and a reflecting plate is arranged on the back side of the liquid crystal cell. In this case, a reflector may be provided on the outer surface of the back substrate of the liquid crystal cell, or an electrode provided on the inner surface of the back substrate may be formed of a metal film, and this electrode may also serve as the reflector. May be.

Next, an example in which the drive system 40 and the method of driving the liquid crystal cell 10 by the drive system 40 are applied to the liquid crystal display device of the second or third embodiment will be described.

As described above, the drive system 40 controls the pixel portion of each pixel row of the liquid crystal cell 10 to the electrode 1
After a reset voltage and a metastable state selection voltage are sequentially applied between 3 and 14, a rewrite is performed by applying a write voltage for controlling an effective value of a drive voltage.
By setting the metastable state selection voltage to a voltage having the same voltage value and a different pulse width from each other, the application of a voltage having a small pulse width allows the liquid crystal molecules to be in a predetermined alignment state (here, when no voltage is applied). The first metastable state in which the liquid crystal molecules are oriented in the (orientated state) is selected, and by applying a voltage having a large pulse width, the liquid crystal molecules are in a predetermined alignment state different from the first metastable state (here, the initial alignment state). The second metastable state is selected in which the liquid crystal molecules are oriented at an inclination angle close to the pretilt angle.

In this embodiment, the driving system 40
To the pixel portion of each pixel row of the liquid crystal cell 10,
The pixel portion of one pixel row is rewritten and driven every predetermined number of frames, and a reset voltage and first and second reference voltages are applied between the electrodes of the pixel portion in a rewrite frame for rewriting the pixel portion. After sequentially applying a metastable state selection voltage for selecting one of the stable states, a write voltage for controlling the effective value of the voltage applied to the liquid crystal layer is applied. , A write voltage having the same absolute value as the write voltage applied in the rewrite frame is applied.

FIG. 15 shows the structure of the drive system 40. This drive system 40
, A column driver 42 for supplying a data signal to each signal electrode 14 of the liquid crystal cell 10, a power supply unit 43 of these drivers, and a write / control data generation circuit 44. Has become.

The power supply section 43 controls the reference potential V0 of the scanning signal, the reset potential VR for applying a reset voltage between the electrodes of the liquid crystal cell 10, and the effective value of the drive voltage between the electrodes. A write period potential VC that defines a write period for applying the write voltage is supplied to the row driver 41.

Further, the power supply section 43 includes a reference potential VS0 for the data signal and a metastable state selection potential VS for applying the first and second metastable state selection voltages between the electrodes of the liquid crystal cell 10. Then, write potentials VD1 and VD2 for applying the write voltage between the electrodes are generated, and the respective potentials are supplied to the column driver 42.

In the case of the liquid crystal display device according to the second or third embodiment, the two effective values when the first metastable state is selected and displayed and the second metastable state are displayed. Since the two effective values when selecting and displaying are the same,
The write potential may be only two potentials VD1 and VD2.

In this embodiment, since the liquid crystal cell 10 is driven by the frame inversion method, the reference potential V of the scanning signal is used.
With respect to 0, a reset potential + VR, -VR and a write period potential + VC, -VC of a positive (+) potential and a negative (-) potential (the same absolute value) are supplied from the power supply unit 43 to the row driver 41. , Metastable state selection potentials + VS, -VS of + potential and-potential (the same absolute value) with respect to the reference potential VS0 of the data signal, and write potentials + VD1, -VD1 and + V.
D2 and -VD2 are supplied from the power supply unit 43 to the column driver 42.

On the other hand, the write / control data generation circuit 44
Generates control data for controlling the application of a reset voltage and write data for selecting the first or second metastable state and performing subsequent writing based on display data supplied from the outside. Then, the control data is supplied to the row driver 41 and the write data is supplied to the column driver 42.

The row driver 41 uses a clock signal supplied from a clock signal generation circuit (not shown) to reset the reset potential VR (+ VR or -VR) at a predetermined cycle with reference to the reference potential V0.
And the write period potential VC (+ VC or -VC) are sequentially generated, and the generation of the reset potential VR (+ VR or -VR) is suppressed according to the control data from the write / control data generation circuit 44. The scanning signal having the waveform is generated and supplied to each scanning electrode of the liquid crystal cell 10.

Each of the scanning signals supplied from the row driver 41 to each scanning electrode of the liquid crystal cell 10 uses the reference potential V0 during periods other than the reset period and the writing period of the pixel row corresponding to the scanning electrode supplying the scanning signal. A signal having a pulse waveform of the reset potential VR during the reset period, and a pulse waveform of the write period potential VC during the write period.
The waveform is inverted with respect to the reference potential V0 every predetermined frame, for example, every frame.

The column driver 42 applies the reference potential VS0 and the metastable state selection potential VS (+ VS or −VS) of the data signal according to the clock signal and the write data from the write / control data generation circuit 44. VS) and write potentials VD1 (+ VD1 or -VD1) and VD2 (+ VD2 or -VD2) are selected at a predetermined timing, and a data signal of the waveform is supplied to each signal electrode of the liquid crystal cell 10.

Each of the signal electrodes of the liquid crystal cell 10 from the column driver 42 has the same absolute value and one of two types of pulse widths in each metastable state selection period immediately after the reset period of each pixel row. Is supplied, and a signal having a pulse waveform having an absolute value of one of two write potentials VD1 and VD2 is supplied for each write period of each pixel row. The polarity of the signal is inverted every predetermined frame (one frame in this embodiment) with reference to the intermediate value (reference potential V0) of the metastable state selection potentials + VS and -VS.

Here, the metastable state selection potential VS of 2
One of the pulse waveforms, that is, the first
The first pulse waveform for selecting the meta-stable state of the data signal becomes the meta-stable state selection potential VS for a predetermined time in the meta-stable state selection period, and the remaining time is the reference potential V S of the data signal.
The other pulse waveform, ie, the second pulse waveform for selecting the second metastable state, is a waveform that becomes the metastable state selection potential VS over the entire period of the metastable state selection period. It is.

The driving method of the liquid crystal cell 10 by the driving system 40 will be described. In this embodiment, in order to increase the frame frequency and eliminate the flickering of the screen, all the pixel rows of the liquid crystal cell 10 are divided into groups of a plurality of rows. For each frame, reset of the writing state (metastable state and alignment state of liquid crystal molecules in the pixel state) of the pixel portion of each pixel row of one group, selection of the next metastable state, and all pixels By writing the pixel units in a row, during one frame, reset of the writing state of the pixel units in each row of one pixel row group, selection of the next metastable state, and subsequent new writing are performed. Only the rewriting for maintaining the written state is performed on the pixel rows in the group.

That is, as a method of driving the liquid crystal cell 10, resetting of all pixel rows and selection of a metastable state are sequentially performed during one frame, and then writing to each pixel row is performed sequentially. However, it takes a certain amount of time to reset the pixel row and select the metastable state, so that it takes a long time to reset and select the metastable state, so that one frame becomes longer and the frame frequency becomes lower. .

In addition, in this method, the resetting of all the remaining pixel rows and the selection of the metastable state are completed for the pixel row for which the metastable state has been selected, and then the sequential writing to each pixel row is started. Until the writing period to the pixel row is started, new writing is not performed.Particularly, the pixel row for which the metastable state is selected earlier has a longer duration, so that the screen flickers. Occur.

Therefore, in this embodiment, all the pixel rows of the liquid crystal cell 10 are divided into groups of a plurality of rows, and the resetting of the pixel portion of each row of one pixel row group and the selection of the metastable state are performed for each frame. , The writing of the pixel portions of all the pixel rows is performed.
Since the reset and metastable state selection time to be secured in one frame need only be the time required for resetting and metastable state selection of each pixel row in one group, it is possible to shorten one frame and increase the frame frequency. it can.

According to the method of this embodiment, writing to the pixel row whose metastable state has been selected is completed, resetting of the remaining pixel rows of the group and selection of the metastable state are completed, and thereafter, the group of this group is metastable. Since writing to each pixel row is sequentially started and a writing period to the pixel row is started, new writing is performed even in a pixel row in which resetting and metastable state selection are first performed in a group. The time in which nothing is done is very short, so that no screen flicker occurs.

When the pixel rows of the liquid crystal cell 10 are driven in a group of a plurality of rows as described above, only one group of pixel rows is rewritten for each frame, and in that frame, pixels of other groups are rewritten. Since the row is only rewritten to maintain its written state,
Rewriting of an image for one screen is performed with the same number of frames as the number of groups of pixel rows. Therefore, if the number of frames required to rewrite an image for one screen is large, switching between screens is delayed. Become.

Therefore, the grouping of pixel rows is 1
It is desirable to select the number of pixel rows of a group so as to obtain a high frame frequency, and to select the number of groups so that the number of frames required to rewrite an image for one screen is not so large.

To give an example, simple matrix type liquid crystal cells include those having 32, 64, 128, etc. pixel lines. For example, the liquid crystal cell has 64 pixel lines. In such a case, it is preferable to divide the pixel rows into groups of eight rows, and if the number of pixel rows in one group is about eight, a sufficiently high frame frequency can be obtained.
If 64 lines are divided into groups of 8 lines, an image for one screen is rewritten in about 8 to 9 frames, so that screen switching is good.

That is, for example, when the frame frequency is 1/3
If it is 0 sec, if the number of frames required to rewrite an image for one screen is 8 to 9 frames, about 3 to 4 screens can be rewritten per second, so that the screen switching is good. Can be

However, the grouping of the pixel rows is 1
It is desirable that the organization of the pixel rows of each group be changed every time the image for the screen is rewritten, that is, every cycle of resetting and metastable state selection and writing of the pixel rows of all groups.

This is because the previous writing state is reset, the next metastable state is selected, and the area corresponding to the pixel row group to be rewritten by applying the writing voltage (hereinafter referred to as the rewriting area) is reset from the time of writing. Is different from the display state of a region (hereinafter, referred to as a non-rewrite region) corresponding to a pixel row group for maintaining the previous write state without performing the rewrite, so that the organization of the pixel rows of each group is always performed. If they are the same, the boundary between the rewritable area and the non-rewritable area appears at the same place every cycle, and display unevenness is conspicuous.

That is, for example, as described above, the total number of pixel rows of a liquid crystal cell is 64, and the total number of pixel rows is one group. If the number is divisible by, 1 to 8 lines, 9 to
When the pixel rows are grouped into 16 rows, 17 to 24 rows... 57 to 64 rows, the organization of the pixel rows in each group is always the same, and the boundaries of each pixel row group are fixed.
The boundary between the rewrite area and the non-rewrite area appears at the same place every cycle.

On the other hand, as described above, if the pixel rows are divided into groups so that a part of the organization of the pixel rows of each group is changed every cycle, the rewrite area and the non-rewrite area are changed every cycle. , The display unevenness due to the difference between the display states of these areas can be made inconspicuous.

An example will be described in which 64 pixel rows are divided into groups of 8 rows. For example, the last pixel row of each group and the first pixel row of the next group are overlapped and grouped. The first cycle is 1-8 rows,
Lines 8 to 15, lines 15 to 22,..., Lines 57 to 64 are sequentially rewritten one by one in one frame. In the second cycle, lines 64 to 7, lines 7 to 14, and lines 14 to 2
1 row... Rewriting of each pixel row group of 56 to 63 rows is sequentially performed one group at a time in one frame.
Lines 3 to 6, lines 6 to 13, lines 13 to 20,..., 55 to 62 are sequentially rewritten one frame at a time in one frame, and the boundary between the rewrite area and the non-rewrite area is provided every cycle. Can be shifted by one pixel row.

Note that the overlap number of the pixel rows in each group is not limited to one row, and may be a plurality of rows. For example, if the overlap number of the pixel rows in each group is two rows, the overlap between the rewrite area and the non-rewrite area every one cycle is possible. The boundary with the rewriting area is shifted by two lines.

However, if the total number of pixel rows of the liquid crystal cell is not divisible by the number of pixel rows of one group, the rewrite area is changed every cycle even if some of the pixel rows of each group do not overlap. The boundary with the non-rewritable area can be shifted.

FIG. 16 shows a liquid crystal cell in which the total number of pixel rows is 64. The pixel rows are divided into groups of 8 rows, and 1
The boundary between the rewrite area and the non-rewrite area is set to 1 every cycle.
FIG. 7 is a waveform diagram of a scanning signal and a data signal when driven by a method of shifting by pixel rows. Here, a scanning signal C1 supplied to scanning electrodes of a first row, a second row, an eighth row, and a ninth row.
, C2, C8, C9 and the data signal S1 supplied to the signal electrodes in the first column.

As shown in FIG. 16, in this driving method,
The initial period of all frames T1, T2,.
Reset / metastable state selection period T for one pixel row group
S, and the remaining period is the writing period TD of all of the 1 to 64 pixel rows.

In this embodiment, the reset /
The metastable state selection period TS is set to the first to ninth periods TS1 to TS9.
The first row of the pixel row (8 rows) of one group is reset in the first division period TS1 and the metastable state of the first row is selected in the second division period TS2. The reset of two rows is performed, the reset of each pixel row and the selection of the metastable state are performed in the same manner, and the metastable state of the seventh row and the reset of the eighth row are performed in the eighth divided period TS8. During the ninth division period TS9, the metastable state of the eighth row is selected. In each of the above periods, for example, the reset / metastable state selection period TS is about 300 ms.
c, and each of the divided periods TS1 to TS9 is approximately 3
3 msec.

In this driving method, the writing period TD is set to 64 periods TD1 to TD1 which is the same as the number of pixel rows of the liquid crystal cell 10.
TD64, and each period TD1, TD2, TD3 ... TD64
Each pixel row is written sequentially one by one. In each of the above periods, for example, the writing period TD is about 10 msec, and the equally divided periods TD1 and TD1
D2, TD3... TD64 are each about 0.16 msec.

The scanning signal and the data signal will be described. Each of the scanning signals supplied to each of the scanning electrodes of the liquid crystal cell 10 is, as described above, a reset period of the pixel row corresponding to the scanning electrode to which the signal is supplied. And a period other than the address period, the waveform is set to the reference potential V0, the reset potential VR is supplied during the reset period, and the address period VC is supplied during the address period. This signal is inverted with reference to V0.

The reset potential VR is supplied to each scanning signal when the last pixel row of each group is overlapped with the first pixel row of the next group, and the first pixel row of each group is supplied. Once every nine frames (one cycle) except for the row, the last pixel row of each group is supplied with the reset potential VR once at the end of the reset period of one frame and once at the beginning of the next frame. You.

Further, the writing period potential VC is supplied to each scanning signal once every frame, and the period during which the reset potential VR is supplied is shifted by one reset period every nine frames. The period during which the writing period potential VC is supplied is the same period (selection period of the pixel row corresponding to the scanning electrode to which the scanning signal is applied) in any frame.

On the other hand, each data signal supplied to each signal electrode of the liquid crystal cell 10 is basically a metastable state selection period immediately after the reset period of each pixel row, that is, a reset / In each of the second to ninth divided periods TS2 to TS9 of the metastable state selection period TS, the potential is equal to the metastable state selection potential VS in one of the two pulse widths. It has a certain pulse waveform,
For each writing period of each pixel row, two writing potentials VD1,
This signal is a signal having any pulse waveform of VD2, and the waveform is inverted every frame. In this embodiment, the configurations of the column driver 42 and the power supply unit 43 of the drive system 40 are simplified. Therefore, the potential of each data signal is set to VS0 and + like the data signal S1 shown in FIG.
The signal has a simple waveform that changes in three ways, VSD and -VSD.

Each potential VS0, + VSD, −
Of VSD, VS0 is a reference potential of the data signal. The reference potential VS0 is equal to the reference potential V0 of the scanning signal.
It is desirable to select almost the same as that described above. In this way, the number of potentials output from the power supply circuit can be reduced, the drive circuit can be simplified, and both substrates of the liquid crystal cell 10 by applying data signals can be used. It is possible to reduce the bias of the charge due to the voltage applied therebetween.

The other two potentials + VSD and -VSD are potentials having the same value (absolute value) with respect to the reference potential VS0, and the potential difference between the scanning signal and the reference potential V0 is the second metastable potential. This is a value for aligning liquid crystal molecules in a state.

In this embodiment, the second to ninth embodiments
Among the pulse waveforms of the metastable state selection potential VS applied in each of the divided periods TS2 to TS9, the first pulse waveform for selecting the first metastable state is one of the first half of the divided period. / 2 becomes the metastable state selection potential VS,
The remaining half of the time has a waveform that becomes the reference potential VS0 of the data signal, and the second pulse waveform for selecting the second metastable state becomes the metastable state selection potential VS over the entire division period. It has a waveform.

Further, in this embodiment, the absolute value of the writing period potential VC (+ VC and -VC) of the scanning signal is set according to the potential of + VSD and -VSD of the data signal.

That is, in this embodiment, of the writing period potential VC of the scanning signal, the + writing period potential + VC
The upper alignment state (the effective value of the drive voltage) of the liquid crystal molecule alignment state corresponding to the effective value of the drive voltage in the first and second metastable states shown in FIG. Is the same as the write voltage for obtaining the alignment state when is a relatively small value, and the potential difference of the data signal with respect to -VSD is a lower alignment state (the effective value of the drive voltage is a somewhat high value). At the same time as the write voltage for obtaining the orientation state).
The negative write period potential -VC is used because the potential difference of the data signal with respect to + VSD becomes the same as the write voltage for obtaining the lower alignment state, and the potential difference of the data signal with respect to -VSD obtains the upper alignment state. Is set to the same value as the write voltage of

Note that the absolute value of the reset potential VR of the scanning signal has a potential difference (sufficient to make the liquid crystal molecules rise almost vertically and align with any of the potentials of the data signal VS0, + VSD and -VSD). Reset voltage).

FIG. 17 shows the scanning signals C1, C2 and C8.
, C9 and the data signal S1 have the waveforms shown in FIG. 16, the scan electrodes in the first row, the second row, the eighth row, and the ninth row of the first column, and the signal electrodes in the first column. FIG. 3 is a waveform diagram of a voltage applied between the scan electrodes of the first row and the signal electrodes, and C1-S1 is a voltage applied between the scan electrodes of the first row and the signal electrodes. C8-S1 is the voltage applied between the scanning electrode in the eighth row and the signal electrode, and C9-S1 is the voltage applied between the scanning electrode in the ninth row and the signal electrode. The applied voltage is shown.

The driving of the pixel units in each row of the liquid crystal cell 10 is performed by applying a scanning signal and a data signal having a waveform as shown in FIG. 16 to the scanning electrodes and signal electrodes for the pixel units in the first column of each row. FIG. 17 shows the case of supplying
This will be described with reference to FIG. Note that this example is an example in which rewriting of an image for one screen in the first cycle (first to ninth frames) is started from the first pixel row.

First, the rewriting of an image for one screen in the first one cycle will be described. In the first frame (hereinafter, referred to as the first frame) T1 in the figure, the first frame T1 of the reset / metastable state selection period TS is shown. During the division period TS1,
The reset potential VR of the scanning signal C1 and the data signal S are applied between the electrodes of the pixel portion of the first row in the pixel row group of 1 to 8 rows.
A reset voltage corresponding to the difference from the potential of 1 is applied, and the liquid crystal molecules in this pixel portion rise almost vertically and are aligned, and the previous writing state, that is, the previous metastable state and the liquid crystal molecules in that state Is reset.

The reset of the previous alignment state of the liquid crystal molecules is performed not only when the next writing is performed by selecting a metastable state different from the previous metastable state but also in the same metastable state as the previous metastable state. This is also performed when selecting and performing.

Next, during the second divided period TS2 of the reset / metastable state selection period TS, the difference between the reference potential V0 of the scanning signal C1 and the potential of the data signal S1 is applied between the electrodes of the pixel unit in the first row. Is applied, and the alignment state of the liquid crystal molecules in this pixel portion is selected to be the first or second metastable state,
The reset potential V of the scanning signal C2 is applied between the electrodes of the pixel unit in the row.
A reset voltage corresponding to the difference between R and the potential of the data signal S1 is applied, and the pixel unit in the second row is reset.

Next, during the third divided period TS3 of the reset / metastable state selection period TS, the reference potential V0 of the scanning signal C2 and the data signal S1 are applied between the electrodes of the pixel section in the second row.
, A metastable state selection voltage having a pulse waveform corresponding to the potential difference between the first row and the second row is selected, and at the same time, the pixels in the third row are selected in the first or second metastable state. The reset voltage is applied between the electrodes of the
The pixel unit in the row is reset.

Similarly, in each of the divided periods of the reset / metastable state selection period Ts, the metastable state selection of the pixel unit in one row and the reset of the pixel unit in the next row are sequentially performed. In the last ninth divided period TS9, the pixel unit on the eighth row, which is the last row of one group, is selected in the first or second metastable state.

Note that the reset /
Each of the scanning signals C1, C2... C8 during the metastable state selection period TS.
Reset potential VR is either one of + or-with respect to the reference potential V0 (-VR in FIG. 16), and the data signal S1 is VS0, + during the first divided period TS1.
VSD or −VSD, and the potential is + V in each of the second to ninth divided periods TS2 to TS9.
At S or -VS2, the pulse width becomes the first pulse waveform having a half of the divided period or the second pulse waveform having the same pulse width as the divided period. In this embodiment, as described above, Since the absolute value of the reset potential VR is set to a value that can provide a sufficient potential difference to cause liquid crystal molecules to rise almost vertically and be aligned with respect to any of the data signals VS0, + VSD, and -VSD. In the first to eighth divided periods TS1 to TS8, it is possible to surely reset the pixel units in each row.

A metastable state selection voltage of the selected waveform (the difference between the reference potential V0 of the scanning signals C1, C2... C8 and the potential of the data signal S1) is applied to each pixel section after the reset, and The liquid crystal molecules are aligned in either the first or second metastable state according to the waveform of the metastable state selection voltage.

That is, the liquid crystal molecules that rise and align almost vertically by the application of the reset voltage are set in accordance with the effective value of the metastable state selection voltage applied in the division period immediately thereafter.
When the effective value is lower than a threshold voltage Vth, the device is oriented to a first metastable state, and when the effective value is higher than the threshold voltage Vth, the device is oriented to a second metastable state.

When the data signal S1 has a waveform as shown in FIG. 16, the waveform of the data signal in the second divided period TS2 for selecting the metastable state of the pixel unit in the first row has the above-mentioned pulse width. The metastable state selection voltage applied to the pixel unit in the first row has a small pulse width as shown in FIG. 17 (the first pulse waveform is ２ of the divided period). / 2), the effective value of the applied voltage in the divided period TS2 is lower than the threshold voltage Vth, and therefore, the liquid crystal molecules in the pixel portion are in the first metastable state selection voltage. Orient to a metastable state.

In the waveform of the data signal S1 in FIG. 16, the waveform of the data signal in the third divided period TS3 for selecting the metastable state of the pixel portion in the second row is the second pulse having the same pulse width as the divided period. Therefore, the metastable state selection voltage applied to the pixel unit in the second row is a second metastable state selection voltage having a waveform with a large pulse width (the same width as the divided period) as shown in FIG. Therefore, the effective value of the applied voltage in the divided period TS3 is higher than the threshold voltage Vth, and therefore, the liquid crystal molecules in this pixel portion are oriented in the second metastable state.

After the metastable state of the pixel units in the first to eighth rows is selected in this manner, the pixel units in the first row are set in the first row write period TD1 of the next write period TD. A writing voltage corresponding to the difference between the writing period potential VC of the scanning signal C1 and the potential of the data signal S1 is applied between the electrodes and writing is performed. Similarly, the pixels of the second row are similarly written in the second row writing period TD2. , The third row pixel section in the third row writing period TD3...
In the row writing period TD64, the pixel units in all rows are rewritten in the order of the pixel units in the 64th row.

Note that each of the writing period potentials VC of the respective scanning signals in the writing period TD of the first frame T1 is:
It is either + or − potential (+ VC in FIG. 16) with respect to the reference potential V0, and the data signal S during this period TD
The waveform 1 is a waveform in which one of the potentials + VSD and -VSD is selected in accordance with the write data in each of the write periods TD1, TD2,.

Therefore, for example, as shown in FIG. 16, when the writing period potential VC of each scanning signal is + VC and the data signal potential in the first row writing period TD1 is -VSD,
A write voltage corresponding to the potential difference between + VC and -VSD is applied to the pixel portion on the first row, and the next frame (hereinafter, referred to as a second frame) is applied.
The effective value of the drive voltage until the first row writing period TD1 of T2 reaches a certain high value, and this pixel portion has a high effective value of the alignment state in the metastable state shown in FIG. The first state in which the liquid crystal molecules are aligned in the alignment state when a voltage is applied (the lower alignment state in FIG. 3).
Write state.

In the waveform of the data signal S1 shown in FIG. 16, the data signal potential in the second row writing period TD2 is + VSD, and therefore, the pixels of the second row have + VC and + VSD.
Is applied, the effective value of the drive voltage until the second row writing period TD2 of the next second frame T2 becomes a relatively small value, and the pixels in the second row In the second writing state in which the liquid crystal molecules are aligned in the alignment state (upper alignment state in FIG. 3) when a low effective value voltage is applied among the alignment states in the metastable state shown in FIG. Become.

This is the same in the pixel units in other rows, and the data signal potential in the writing period TD2 of that row is -V.
If it is SD, the pixel section is in the first write state, and if the data signal potential is + VSD, the pixel section is in the second write state.

Further, when the writing of the pixel portion of the 64th row, which is the last row, is completed and the next second frame T2 starts, in the second frame T2, during the reset / metastable state selection period TS, the above-mentioned second frame T2 is set. In one frame T1, the pixel portions of each row of the 8 to 15 pixel row groups including the last pixel row of the pixel row group (1 to 8 rows) for which reset and selection of the metastable state have been performed are sequentially reset, and 1st or 2nd
In the metastable state, and during the subsequent writing period TD,
The pixel units in rows 1 to 64 are sequentially written.

In the second frame T2, the waveforms of the scanning signals and the data signals are inverted with respect to the waveforms of the first frame T1, but the resetting of the pixel portion in each row, the selection of the metastable state, and the subsequent writing are performed. Is performed in the same manner as in the first frame T1.

That is, for example, the pixel portion on the eighth row is
Subsequent to the frame T1, also in the second frame T2, the reset / metastable state selection period TS is reset in the first divided period TS1 of the selected period, and the metastable state is selected in the second divided period TS2. Writing is performed in the eighth row writing period TD8 of TD, and as shown in FIG. 16, the pixel portion of the eighth row is set in the second divided period TS2 for selecting the metastable state of the row. A stable state is selected, and a second write state is applied in which a low effective value voltage is applied during an eighth row write period TD8 in which writing of the row is performed.

The pixel portion on the ninth row is the pixel portion of the first frame T
In 1 the reset and the metastable state selection are not performed, but only the writing is performed. In the second frame T2, the reset and the metastable state selection period are reset in the second divided period TS2 of the reset / metastable state selection period TS, and in the third divided period TS3, The stable state is selected, and the ninth row write period TD9 of the next write period TD
Then, as shown in FIG. 16, the pixel portion of the ninth row selects the first metastable state in the third divided period TS3 for selecting the metastable state of the row, and In the ninth row writing period TD9 in which writing is performed, the first writing state in which a high effective value voltage is applied.

The pixel portion of the eighth row, which is the first row of the pixel row group of 8 to 15 rows for which the reset and the metastable state selection are performed in the second frame T2, is once performed in the previous first frame T1. Reset and metastable state selection and writing are performed, and in the second frame T2, the first frame T1
Is reset, the meta-stable state is selected again, and then the data is written again.
The writing state according to the effective value of the drive voltage until the row writing period TD8 is reached.

The write voltage applied to the pixel units in all the rows except for the pixel row group of 8 to 15 rows for performing the reset and the selection of the metastable state in the second frame T2 is as follows:
This is a rewriting voltage for maintaining the written state in the first frame T1, and the rewriting voltage applied to the pixel portion in these rows is the same as the writing voltage in the first frame T1.

Hereinafter, similarly, for each frame, 1
One pixel row group is reset, a metastable state is selected, and all pixel rows are written.
The reset of the pixel row group of 7 to 64 rows, the selection of the metastable state, and the writing of all the pixel rows are performed, and the image for one screen is rewritten.

In the next one cycle (the tenth to eighteenth frames), 64 to 7 rows, 7
..., 14, 21 to..., One of the 56 to 63 pixel row groups is reset, the metastable state is selected, and all the pixel rows are written, and the image for one screen is rewritten. .

Furthermore, in the next one cycle (the 19th to 27th frames), 63 to 6
Row, 6 to 13 rows, 13 to 20 rows... 55 to 62 rows, one of the pixel row groups is reset, the metastable state is selected, and all the pixel rows are written. Is rewritten.

Further, the next one cycle (the 28th cycle)
To the thirty-sixth frame).
-5, 5-12, 12-19..., One of the pixel row groups 54-61, reset and metastable state selection, and writing of all pixel rows are performed.
The image for one screen is rewritten.

In these cycles, the rewriting of display is performed in one of the nine frames because the reset and metastable states are selected in that frame, and the pixels of eight rows of the group to be written thereafter are selected. And a pixel portion of another row is applied with a rewrite voltage having the same absolute value as the write voltage applied in the previous rewrite frame as described above, and thereafter, the rewrite voltage is applied to each subsequent frame. Is applied, and the write state written in the previous rewrite frame is maintained until the next rewrite frame in which the pixel row is rewritten.

In each pixel row, rows overlapping two groups (for example, rows 1 to 8 in the first cycle,
In the grouping of 8 to 15 rows, 15 to 22 rows... 57 to 66 rows, the pixel units of 8 rows, 15 rows, 22 rows.
Reset and metastable state selection and writing are performed twice in two consecutive frames, and a rewrite voltage is applied in each subsequent frame to write in a later frame of the two consecutive frames. The inserted write state is maintained until the next frame in which the pixel row is reset and the metastable state is selected.

Note that the metastable state selection and writing in the previous frame of the two consecutive frames for the pixel units in these rows are temporary ones until reset in the next frame. However, the metastable state selection and writing in the previous frame should be the same as the previous metastable state and writing state, or the same as the metastable state and the writing state selected in the next frame. It is desirable to do.

As described above, the driving method of the liquid crystal cell is as follows.
The liquid crystal cell 10 is driven by rewriting a pixel portion of each pixel row in a pixel row of one pixel row every predetermined number of frames, and rewriting for rewriting between electrodes of the pixel portion. To the frame, a reset voltage and a metastable state selection voltage for selecting one of the first and second metastable states are sequentially applied, and then a write voltage for controlling the effective value of the drive voltage is applied. , A write voltage having the same absolute value as the write voltage applied in the rewrite frame preceding the frame is applied.

Therefore, the liquid crystal display device rewrites the written state written in the rewrite frame by applying the same absolute value of the write voltage in each frame until the next rewrite frame. By repeating the above operation, the pixel portion of each pixel row is rewritten every predetermined number of frames to display an image.

Note that the above-mentioned liquid crystal display device has a liquid crystal cell 10
In the rewriting frame, first, the orientation state (writing state) of the previous liquid crystal molecules is reset by applying a reset voltage to the rewriting frame, and the next metastable state is selected. This is performed by applying a write voltage for obtaining a write state. In this case, the reset of the alignment state and the selection of the metastable state can be performed in a short time.

In the liquid crystal display device, as in the above driving method, as the first and second metastable state selection voltages, voltages having the same voltage value and different pulse widths from each other are applied. Therefore, there is no need to control the voltage value of the metastable state selection voltage as in the case where the first and second metastable states are selected by applying voltages having different absolute values. The selection can be made easily and reliably.

That is, the first and second metastable states can also be selected by controlling the voltage value of the metastable state selection voltage in two ways. , Two types of metastable state selection potentials (a total of four types of metastable state selection potentials on the + side and two types of metastable state selection potentials on the − side when driven by the frame inversion method)
Seed potential).

On the other hand, in the case of the above driving method, the first metastable state selection voltage and the second metastable state selection voltage may have the same voltage value. The metastable state selection potential to be applied may be only one value (the potential on the + side and the potential on the − side when driven by the frame inversion method). Therefore, the metastable state can be selected easily and reliably. Can be.

In the driving method of the above embodiment,
All the pixel rows of the liquid crystal cell 10 are divided into groups of a plurality of rows, and for each frame, resetting and selection of a metastable state of a pixel portion of each pixel row of one group and writing of pixel portions of all the pixel rows are performed. As described above, the frame frequency can be increased to eliminate the flicker on the screen, as described above.

In this case, in the above embodiment, the grouping of the pixel rows is changed in each group in which the resetting of the pixel rows of all groups and the selection and metastable state selection and writing are performed. Therefore, in each cycle, the previous write state is reset, and the next metastable state is selected, and the rewrite area corresponding to the pixel row group to be rewritten by the application of the write voltage is rewritten. Instead, the boundary between the pixel row group that maintains the previous written state and the corresponding non-rewritable area is shifted, so that display unevenness due to the difference in display state between these areas can be made inconspicuous.

In the above driving method, the liquid crystal cell 1
Pixel rows of 0 are 1 to 8 rows, 8 to 15 rows, 15 to 22 rows ...
As described above, the pixels are grouped so that one group is formed by a predetermined number of adjacent pixel rows.
Grouping may be performed such that one group is formed by a predetermined number of pixel rows every other row or every other row.

In each frame, the order of selection of the reset and metastable states and the selection of the pixel row groups in which the new writing is performed may be every other group or every plural groups. By performing the selection, resetting of each pixel row of the group, selection of the metastable state, and subsequent new writing, flickering of the screen can be further reduced.

Further, in the above driving method, in order to simplify the configuration of the column driver 42 and the power supply unit 43 of the driving system 40, the data signal supplied to each signal electrode of the liquid crystal cell 10 is changed as shown in FIG. Although the signal has a simple waveform in which the potential changes in two ways, + VSD and -VSD, in addition to the reference potential VS0, as shown in FIG.
Reference potential VS0, metastable state selection potential VS, and write potential V
D1 and VD2 are supplied to the column driver 42.
2, the respective VS0, VS, VD according to the write data.
A data signal having a waveform selected from 1, VD2 may be supplied to each scanning electrode of the liquid crystal cell 10.

The above driving method can be applied to the driving of the liquid crystal cell of the liquid crystal display device of the first embodiment. In this case, when the first metastable state is selected and displayed. Since the effective values of the two drive voltages are different from the effective values of the two drive voltages when the second metastable state is selected and displayed, four write potentials are generated by the power supply unit 43. Then, each potential may be supplied to the row driver 41.

[0235]

The liquid crystal display device of the present invention has the electro-optical characteristics of two display devices in which the liquid crystal molecules of the liquid crystal cell have different alignment states from each other. A plurality of transmission states among the states can be controlled using one electro-optical characteristic, and the other plurality of transmission states can be controlled using the other electro-optical characteristic.

For this reason, according to this liquid crystal display device, the total number of stages of the transmission state is determined when the one electro-optical characteristic is used, that is, when the transmission state is controlled by selecting the first metastable state. Using the other electro-optical characteristic, that is, selecting the second metastable state to control the transmission state, and for that, driving each metastable state. Since the number is reduced, time-division driving with a small number of stages can be performed in each metastable state.

Therefore, according to this liquid crystal display device,
Increase operating voltage margin with respect to drive duty,
By enabling time-division driving at a high duty, it is possible to realize display of a high-definition image having a large number of pixels.

This liquid crystal display device has a drive system for driving the liquid crystal cell. The drive system allows a reset voltage and a metastable voltage to be applied between the electrodes of the pixel portion of each pixel row of the liquid crystal cell. By applying the write voltage after sequentially applying the state selection voltage, the pixel portion of each pixel row is rewritten to display an image. In the present invention, the first and second metastables are provided. As the state selection voltage,
Since voltages having the same voltage value and different pulse widths from each other are applied, the first and second metastable states are selected by applying voltages having different absolute values, as in the case of selecting the first and second metastable states. There is no need to control the value of the selection voltage,
Therefore, the metastable state can be easily and reliably selected.

Further, the method of driving the liquid crystal cell of the present invention is as follows.
After applying the reset voltage between the electrodes thereof to reset the alignment state of the liquid crystal molecules before the pixel portion of each pixel row of the liquid crystal cell, the metastable state selection voltage is applied to apply a reset voltage to the liquid crystal molecules. Is oriented in one of the first and second metastable states, and thereafter, is rewritten by applying a write voltage for controlling an effective value of the drive voltage,
According to this driving method, the first and second metastable state selection voltages are applied with voltages having the same voltage value and different pulse widths. In addition, an image display in which the pixel portion of each pixel row of the liquid crystal cell is rewritten can be performed, and the metastable state can be easily and reliably selected.

[Brief description of the drawings]

FIG. 1 is a perspective view of an initial alignment state, a first metastable state, and a second metastable state, showing a basic configuration of a liquid crystal display device according to a first embodiment of the present invention.

FIG. 2 is a sectional view of the liquid crystal display device.

FIG. 3 is a schematic diagram showing an alignment state of liquid crystal molecules in an initial alignment state, a reset state, and first and second metastable states of the liquid crystal display device.

FIG. 4 is a voltage-emission rate characteristic diagram and a CIE chromaticity diagram in an initial alignment state of the liquid crystal display device.

FIG. 5 is a voltage-emission rate characteristic diagram and a CIE chromaticity diagram in a first metastable state of the liquid crystal display device.

FIG. 6 is a voltage-emission rate characteristic diagram and a CIE chromaticity diagram in a second metastable state of the liquid crystal display device.

FIG. 7 is a perspective view showing the basic configuration of a liquid crystal display device according to a second embodiment of the present invention, showing an initial alignment state, a first metastable state, and a second metastable state.

FIG. 8 shows a voltage-emission ratio characteristic diagram and a CIE chromaticity diagram in an initial alignment state of the liquid crystal display device.

FIG. 9 is a voltage-emission ratio characteristic diagram and a CIE chromaticity diagram in a first metastable state of the liquid crystal display device.

FIG. 10 shows a voltage-emission ratio characteristic diagram and a CIE chromaticity diagram in a second metastable state of the liquid crystal display device.

FIG. 11 is a perspective view showing a basic configuration of a liquid crystal display device according to a third embodiment of the present invention, showing an initial alignment state, a first metastable state, and a second metastable state.

FIG. 12 shows a voltage-emission rate characteristic diagram and a CIE chromaticity diagram in an initial alignment state of the liquid crystal display device.

FIG. 13 is a voltage-emission rate characteristic diagram and a CIE chromaticity diagram in a first metastable state of the liquid crystal display device.

FIG. 14 is a voltage-emission ratio characteristic diagram and a CIE chromaticity diagram in a second metastable state of the liquid crystal display device.

FIG. 15 is a block diagram showing a configuration of a drive system for driving a liquid crystal cell.

FIG. 16 is a waveform diagram of a scanning signal and a data signal supplied to the liquid crystal cell.

FIG. 17 is a waveform diagram of a voltage applied between a scanning electrode and a signal electrode of the liquid crystal cell.

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 10 ... Liquid crystal cell 11a ... Orientation processing direction of a front side substrate 12a ... Alignment processing direction of a back side substrate 18 ... Nematic liquid crystal added with a chiral agent 21, 22 ... Polarizing plates 21a and 22a ... Transmission axis 30 ... Reflecting plate 40 ... Drive system 41 row driver 42 column driver 43 power supply

Claims (3)

[Claims] 1. A liquid crystal cell having a nematic liquid crystal layer sandwiched between a pair of substrates having electrodes formed on respective surfaces facing each other, and at least one polarizing plate disposed on at least the surface side of the liquid crystal cell. And a drive system for supplying a voltage between the electrodes of the liquid crystal cell, wherein the liquid crystal layer is arranged between the electrodes of the pair of substrates such that the major axis of the liquid crystal molecules is substantially perpendicular to the substrate surface. After applying a reset voltage to be applied, the liquid crystal is selectively applied by a first metastable state selection voltage having a lower value and a second metastable state selection voltage different from the first metastable state selection voltage. A first metastable state in which the molecules are oriented in a predetermined orientation state, a second metastable state in which the molecules are oriented in an orientation state different from the first metastable state, a first metastable state and a second metastable state. In the liquid crystal layer in each metastable state A writing alignment state induced by an electric field in which the orientation of liquid crystal molecules changes according to the effective value of the applied voltage, wherein the drive system selectively resets the reset voltage and the voltage value to be equal and pulsed with each other. The first and second metastable state selection voltages having different widths and a writing voltage for applying a voltage of a predetermined effective value to the liquid crystal layer are sequentially supplied between the opposed electrodes of the liquid crystal cell. A liquid crystal display device comprising driving means. 2. An electrode formed on each of the substrates facing each other of the liquid crystal cell includes a plurality of scanning electrodes, one of which extends in one direction, and a plurality of signal electrodes, which extends in a direction intersecting the scanning electrodes. The driving unit sets the first metastable state selection voltage and the second metastable state selection voltage in a period in which all of the plurality of scan electrodes are sequentially selected and a driving signal is supplied as one frame. 2. The liquid crystal display device according to claim 1, further comprising a drive circuit for selectively supplying between the opposing electrodes every one or a plurality of frames. 3. The method for driving a liquid crystal cell of a liquid crystal display device according to claim 1, wherein after the reset voltage is supplied for a predetermined period, the first voltage having the same voltage value and different pulse widths from each other. And a second metastable state selection voltage, and then sequentially applying a writing voltage for applying a voltage of a predetermined effective value to the liquid crystal layer between the opposed electrodes of the liquid crystal cell. A method for driving a liquid crystal cell, comprising: