JP3528449B2 - Liquid crystal display - Google Patents

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a liquid crystal display device capable of time-division driving with high duty, and particularly to a liquid crystal display device using a simple matrix type liquid crystal cell.

[0002]

2. Description of the Related Art Liquid crystal display devices are classified into a transmissive type which uses light from a backlight for display and a reflective type which uses external light such as natural light or room illumination light for display. . In these liquid crystal display devices, polarizing plates are arranged on the front surface side and the back surface side of a liquid crystal cell, and the reflection type liquid crystal display device has a reflection plate arranged on the back surface side of the back side polarizing plate. Is configured. Some reflective liquid crystal display devices are provided with only one polarizing plate. In this reflective liquid crystal display device, a polarizing plate is arranged on the front surface side of the liquid crystal cell and the rear surface side of the liquid crystal cell is arranged. It is configured by arranging a reflector.

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

The above liquid crystal display device is driven for display by applying a drive signal between the electrodes of each pixel portion of the liquid crystal cell. When the drive signal is applied between the electrodes, the liquid crystal molecules are in a state in which no voltage is applied. It operates so as to stand up with respect to the substrate surface while maintaining the alignment state, and the transmission of light is controlled according to the standup state.

By the way, the above-mentioned liquid crystal display devices include those using a simple matrix type liquid crystal cell and those 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.

[0006]

However, in a liquid crystal display device using a simple matrix type liquid crystal cell, an effective value of a drive signal applied between electrodes of each pixel portion of the liquid crystal cell (between the electrodes during one frame is used). RMS value of applied voltage)
Since the display is driven by controlling the, when performing a display in which the light transmission state is controlled stepwise, if the number of time divisions increases,
It becomes impossible to take a large difference in effective value corresponding to each stage. Therefore, when trying to perform time-division driving at high duty, the operating voltage margin (difference in effective value) when driving the liquid crystal cell becomes small, Clear stepwise display is not possible.

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

The present invention uses a simple matrix type liquid crystal cell which is driven by controlling the effective value of a drive signal. An object of the present invention is to provide a liquid crystal display device capable of time-division driving and capable of displaying a high-definition image having a large number of pixels.

[0009]

A liquid crystal display device of the present invention comprises a liquid crystal cell and a polarizing plate disposed on at least the front surface side of the front and back surfaces of the liquid crystal cell, and the liquid crystal cell is provided on the inner surface. A nematic liquid crystal to which a chiral agent is added is sandwiched between a pair of substrates provided with electrodes and subjected to an alignment treatment, and the liquid crystal molecules rise and align almost vertically to the substrate surface. After the reset pulse having the voltage value is applied, the selection pulse having a predetermined voltage value lower than the reset pulse is applied to the first metastable state in which the liquid crystal molecules are aligned in a specific state between the pair of substrates, and the reset is performed. After the application of the pulse, the liquid crystal molecules are aligned between the pair of substrates in a specific state different from the first metastable state by applying a selection pulse having another predetermined voltage value lower than that. 2 has a characteristic of being in a metastable state, and each pixel portion of the liquid crystal cell applies the selection pulse after applying the reset pulse, so that either of the first and second metastable states is achieved. It is characterized in that it is driven by application of a drive signal whose effective value changes in a range lower than the voltage value of the reset pulse in the metastable state.

This liquid crystal display device is provided with a drive circuit for driving the liquid crystal cell, and the drive circuit applies the reset pulse to each pixel portion of the liquid crystal cell, and then, A selection pulse for selecting any one of the second metastable states is applied, and then a driving signal whose effective value changes in a range lower than the voltage value of the reset pulse is applied to drive.

In the liquid crystal display device of the present invention, the liquid crystal molecules of the liquid crystal cell are oriented in either the first or second metastable state, and the rising state of the liquid crystal molecules in the respective metastable states with respect to the substrate surface is driven. This is to control the light transmission state by changing it according to the effective value of the signal. When the first metastable state is selected, a liquid crystal cell in which liquid crystal molecules are aligned in a specific state between a pair of substrates is used. When a second metastable state is selected, which has electro-optical characteristics of a display device including a polarizing plate, liquid crystal molecules are aligned between the pair of substrates in a specific state different from the first metastable state. It has the electro-optical characteristics of a display device including a liquid crystal cell and a polarizing plate.

That is, this liquid crystal display device has the electro-optical characteristics of two display devices in which the alignment states of the liquid crystal molecules of the liquid crystal cell are different from each other.
Controlling a plurality of transmission states among the transmission states to be controlled stepwise by using one electro-optical characteristic, and controlling another plurality of transmission states by using the other electro-optical characteristic. You can

Therefore, according to this liquid crystal display device, the total number of stages of the transmission state is controlled when the electro-optical characteristic of the one side is utilized, that is, when the first metastable state is selected to control the transmission state. And when the other electro-optical characteristic is utilized, that is, when the second metastable state is selected to control the transmissive state. Therefore, the step of driving in each metastable state can be performed. Since the number is reduced, it is possible to perform time-divisional driving with a small number of steps in each metastable state.

Therefore, according to this liquid crystal display device,
Although using a simple matrix type liquid crystal cell that is driven by controlling the effective value of the drive signal, the operating voltage margin is increased with respect to the drive duty to enable time-division drive at high duty, It is possible to display a large number of high-definition images.

[0015]

BEST MODE FOR CARRYING OUT THE INVENTION The liquid crystal display device of the present invention uses a liquid crystal cell in which liquid crystal molecules are aligned in the first metastable state and the second metastable state, and the first and second metastable states are used. In each stable state, by selectively applying a drive signal whose effective value changes corresponding to the display data,
In each of the first and second metastable states, the light transmission state is controlled in a plurality of stages.

The present invention further comprises a drive circuit for supplying the reset pulse, the selection pulse, and a drive signal whose effective value changes in accordance with display data,
The drive circuit drives the liquid crystal cell.

In the liquid crystal display device according to the present invention, the liquid crystal cell is a non-twisted or twisted liquid crystal molecule with a twist angle of approximately 0 ° to approximately 180 ° in one direction with respect to the alignment treatment direction of one of the substrates. There is a liquid crystal layer that is initially aligned in an aligned splay alignment state, and a reset pulse having a sufficiently high voltage value is applied to this liquid crystal layer, and then a voltage value is sufficiently lower than the reset pulse and two different selection values are selected. By selectively applying the pulse,
The first metastable state in which the liquid crystal molecules are further twisted approximately 180 ° from the initial alignment state in one direction to eliminate splay distortion (approximately 180 ° to approximately one direction in one direction with respect to the alignment treatment direction of one substrate). (Twisted orientation with a twist angle of 360 °) and a second metastable state in which splay strain is eliminated by twisting by 180 ° in a direction opposite to the one direction from the initial oriented state (orientation treatment of one substrate). The orientation is a twist orientation or a non-twist orientation with a twist angle of approximately 180 ° to approximately 0 ° in the other direction with respect to the direction.

In one example, the initial alignment state is a splay alignment state in which liquid crystal molecules are twist-aligned in one direction with a twist angle of approximately 90 ° with respect to the alignment treatment direction of one substrate, and the first quasi-first alignment state is used. The stable state is a state in which the liquid crystal molecules are twist-aligned at a twist angle of approximately 270 ° in one direction with reference to the alignment processing direction of the one substrate to eliminate splay distortion, and the second metastable state is The liquid crystal molecules are in a state in which the splay distortion is eliminated by twisting the liquid crystal molecules in a direction opposite to the first metastable state with a twist angle of about 90 ° with respect to the alignment treatment direction of the one substrate.

In another example, the initial alignment state is a splay alignment state in which liquid crystal molecules are twist-aligned in one direction with a twist angle of about 180 ° with respect to the alignment treatment direction of one substrate, and The metastable state 1 is a state in which liquid crystal molecules are twist-aligned in one direction with a twist angle of approximately 360 ° with respect to the alignment treatment direction of the one substrate to eliminate splay strain, and the second quasi-stable state is obtained. The stable state is a state in which the liquid crystal molecules have a twist angle of approximately 0 ° with respect to the alignment processing direction of the one substrate, that is, a state in which the twist of the molecular arrangement is eliminated and the twist distortion is eliminated to eliminate the splay distortion.

Still another example is a splay alignment state in which liquid crystal molecules are non-twisted at a twist angle of approximately 0 ° (there is no twist in the molecular alignment) with respect to the alignment treatment direction of one of the substrates. The first metastable state is a state in which the liquid crystal molecules are twist-aligned in one direction with a twist angle of about 180 ° with respect to the alignment processing direction of the one substrate to eliminate the splay strain, and the second metastable state is the second metastable state. The metastable state is
The liquid crystal molecules are in a state in which the splay distortion is eliminated by twisting the liquid crystal molecules in a direction opposite to the first metastable state with a twist angle of approximately 180 ° with respect to the alignment treatment direction of the one substrate.

[0021]

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. [First Embodiment] FIGS. 1 to 6 show a first embodiment of the present invention. 1A and 1B are perspective views showing a basic configuration of a liquid crystal display device. FIG. 1A shows an initial alignment state, FIG. 1B shows a first metastable state, and FIG. 1C shows 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, polarizing plates 21 and 22 are arranged on the front surface side and the back surface side of the liquid crystal cell 10 and the polarized light on the back surface is polarized. A reflection plate 30 is arranged behind the plate 22, and a driving circuit 40 for driving the liquid crystal cell 10 is further provided.
It is configured by connecting.

As shown in FIG. 2, the liquid crystal cell 10 has a pair of front and back transparent substrates 11 and 14 having transparent electrodes 13 and 14 formed on the inner surfaces thereof and alignment films 15 and 16 having an alignment treatment formed thereon. A liquid crystal 18 is sandwiched between 12 and the pair of substrates 11 and 12 are bonded to each other 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. It is enclosed in a closed area.
The alignment films 15 and 16 are horizontal alignment films made of polyimide or the like, and are subjected to alignment treatment by rubbing the film surface in a predetermined direction.

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

Further, this liquid crystal cell 10 has its liquid crystal 1
8 is a nematic liquid crystal having a twist orientation by adding a chiral agent, and its liquid crystal layer is
In the initial alignment state, the liquid crystal molecules are in a splay alignment state in which the liquid crystal molecules are twisted in one direction with a twist angle of approximately 90 ° with respect to the alignment treatment direction of one of the substrates.

In the liquid crystal cell 10, a reset pulse having a voltage value that causes liquid crystal molecules to rise and align substantially perpendicularly to the surfaces of the substrates 11 and 12 is applied to the liquid crystal layer thereof, and then a predetermined voltage value lower than that is applied. By applying the selection pulse, the liquid crystal molecules are brought into a first metastable state in which the liquid crystal molecules are twist-aligned in one direction with a twist angle of approximately 270 ° with respect to the alignment processing direction of one of the substrates, and the reset pulse is applied. By applying a selection pulse having another predetermined voltage value lower than the applied voltage, the liquid crystal molecules are made to move in a direction approximately 90 degrees in the direction opposite to the first metastable state based on the alignment treatment direction of the one substrate. It has a characteristic of being in a second metastable state in which it is twist-oriented at a twist angle of °.

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

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

In this initial alignment state, liquid crystal molecules are aligned in the respective alignment treatment directions 11 in the vicinity of both substrates 11 and 12.
a and 12a, and a direction indicated by a broken line arrow in FIG. 1A, that is, a chiral agent, with reference to the orientation treatment direction of either one of the substrates, for example, the orientation treatment direction 12a of the back substrate 12. It is a splay alignment state in which the twist alignment is performed at a twist angle of approximately 90 ° in the twist direction given by.

The initial alignment state is a state not actually used for display, and the liquid crystal cell 10 sets the alignment state of the liquid crystal molecules in each pixel portion to the above-mentioned first and second metastable states. It is oriented and driven for display.

In the first metastable state and the second metastable state, the twist angle of liquid crystal molecules is approximately 1 from the initial alignment state.
It 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 is + with respect to the orientation processing direction 12a of the back side substrate 12, and is given by the chiral agent. If the twist angle in the direction opposite to the twist direction (direction to untwist the chiral agent) is −, the first metastable state is the twist orientation in which the twist angle changes by + 180 ° with respect to the initial orientation state. The second metastable state is a twist orientation state in which the twist angle changes by −180 ° with respect to the initial orientation state.

To switch the alignment state from the initial alignment state to the first and second metastable states, liquid crystal molecules are first transferred to the substrate 11 between the electrodes 13 and 14 of each pixel portion of the liquid crystal cell 10.
It is performed by applying a splay distortion eliminating pulse having a voltage value (absolute value) that rises and is oriented almost perpendicularly to the 12th surface, and then applying a selection pulse having a predetermined voltage value between the electrodes 13 and 14. .

That is, after the liquid crystal molecules are risen and aligned substantially perpendicularly to the surfaces of the substrates 11 and 12 by applying the spray distortion eliminating pulse, a predetermined voltage value (absolute value) V _S1 lower than the spray distortion eliminating pulse is applied. When the selection pulse (hereinafter referred to as the first metastable state selection pulse) is applied,
The twist angle of the liquid crystal molecules in the initial alignment state is about 18 more
Twist angle with 90 ° twist (90 ° + 180 ° =
At 270 °), the splay strain is eliminated by orienting in a twisted state, resulting in a first metastable state.

In the first metastable state, the liquid crystal molecules are aligned along the respective alignment treatment directions 11a and 12a in the vicinity of both substrates 11 and 12, and the alignment treatment direction of either one of the substrates, for example, With reference to the orientation processing direction 12a of the back substrate 12, the twist direction shown by the broken line arrow in FIG. 1B, that is, the counterclockwise direction when viewed from the front side (the twisting direction imparted by the chiral agent) is approximately 2
It is in a twisted orientation with a twist angle of 70 °.

Further, after the liquid crystal molecules are risen and aligned substantially perpendicularly to the surfaces of the substrates 11 and 12 by applying the spray distortion eliminating pulse, a predetermined voltage value (absolute value) V _S2 lower than the spray distortion eliminating pulse is applied. Is applied (hereinafter, referred to as a second metastable state selection pulse), a twist angle (90 ° −180 ° = −90) obtained by subtracting a twist of about 180 ° from the twist angle of the liquid crystal molecules in the initial alignment state.
Oriented to a twisted state at (°), the splay strain is eliminated, and the second metastable state is obtained.

In the second metastable state, the liquid crystal molecules are aligned along the respective alignment treatment directions 11a and 12a in the vicinity of the substrates 11 and 12, and the alignment treatment direction of either one of the substrates, for example, With reference to the orientation processing direction 12a of the back substrate 12, the twist direction shown by the broken line arrow in FIG. 1C, that is, the clockwise direction when viewed from the front side (the direction opposite to the twist direction imparted by the chiral agent).
In addition, it is in a twist-oriented state with a twist angle of approximately 90 °.

Further, the first metastable state and the second metastable state can be switched from one to the other, and in any metastable state of the liquid crystal molecules, First, liquid crystal molecules are placed between the electrodes 13 and 14 on the substrate 1.
Liquid crystal molecules can be obtained by applying a reset pulse having a voltage value that causes the liquid crystal molecules to rise and align substantially perpendicularly to the 1st and 12th planes to reset the metastable state, and then applying the first or second metastable state selection pulse. Can be switched from one metastable state to the other metastable state.

The voltage value V _{S1 of} the first metastable state selection pulse and the voltage value V 2 of the second metastable state selection pulse
_S2 is determined by the characteristics of the liquid crystal 18 used, the characteristics of the chiral agent, and the amount added, and the absolute value is, for example, V _S1 <
V _S2, which is the voltage value V of the first metastable state selection pulse
_S1 is a value at which almost no voltage is applied (approximately 0 V), and the voltage value V _{S2 of} the second metastable state selection pulse is almost the same as or close to the pretilt angle with respect to the surfaces of the substrates 11 and 12 for most liquid crystal molecules. It is a low voltage value oriented at a tilt angle.

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

As shown in this schematic diagram, the initial alignment state (the liquid crystal molecules are twist-aligned at a twist angle of about 90 ° counterclockwise when viewed from the front side with reference to the alignment treatment direction 12a of the back substrate 12). (State) is for both substrates 11, 12
The liquid crystal molecules in the vicinity of are oriented so as to rise obliquely with respect to the respective surfaces 11 and 12 of the substrates 11 and 12a at a pretilt angle of about several degrees, but are twisted. The pretilt directions on the substrates 11 and 12 side when the molecules are expanded and viewed so that the major axes of the molecules are on the same plane are opposite to each other. Therefore, the liquid crystal molecules are 1
The tilt angle becomes smaller as the distance from 1 and 12 increases, and the tilt direction 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 °) (spray). It is in a stable twist orientation state in a state with a strain).

In the reset state, both substrates 11,
Liquid crystal molecules in the vicinity of 12 (omitted in the figure) are almost unchanged from the initial alignment state (each substrate 1
Although it is oriented so as to rise obliquely at a pretilt angle of about several degrees toward the orientation treatment directions 11a and 12a with respect to the 1st and 12th surfaces), it is almost apart from the substrates 11 and 12 to some extent or more. Liquid crystal molecules of the substrate 1
It is in a state of being oriented so as to rise almost perpendicularly to the 1st and 12th planes.

Further, in the first metastable state (a state in which liquid crystal molecules are twisted in one direction with a twist angle of approximately 270 °), the liquid crystal molecules in the vicinity of both substrates 11 and 12 are in an initial alignment state. However, the liquid crystal molecules are twisted by about 180 ° more than the initial alignment, and therefore the liquid crystal molecules 18
Since a is oriented with the major axes of the respective molecules oriented in substantially the same direction and the tilt directions of the liquid crystal molecules 18a oriented in the same direction, this second metastable state is a non-twisted orientation state without splay distortion. is there.

The second metastable state (the liquid crystal molecules are the first
The state in which the liquid crystal molecules in the vicinity of both substrates 11 and 12 are almost the same as the initial alignment state, but the twisting of 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 are in a twisted state by twisting by 80 °. Therefore, when the liquid crystal molecules in the twisted orientation are developed so that their long axes are on the same plane, the liquid crystal molecules 18a are tilted in the same direction. Therefore, this second metastable state is a twist orientation state without splay distortion.

The first and second metastable states are, respectively,
In this metastable state, the twist alignment state of the liquid crystal molecules 18a is maintained. In any metastable state, the rising state of the liquid crystal molecules 18a with respect to the surfaces of the substrates 11 and 12 is applied between the electrodes 13 and 14. RMS value of driving signal (RMS value of voltage applied during one frame)
(However, the alignment state of liquid crystal molecules in the vicinity of both substrates 11 and 12 hardly changes).

Among the alignment states of the liquid crystal molecules in the first and second metastable states shown in FIG. 3, in the alignment state shown on the upper side, the effective values of the drive signals are relatively small values V _1-1 , V.
_2-1 shows the rising state of the liquid crystal molecules, and the alignment state shown on the upper side shows the rising states of the liquid crystal molecules when the effective value of the drive signal is V _1-2 and V _2-2 which are high to some extent. In any of the metastable states, the liquid crystal molecules change the rising state according to the effective value of the drive signal while maintaining the twist alignment state in the metastable state.

In the first and second metastable states, the rising state of liquid crystal molecules changes according to the effective value of the drive signal, but the twist alignment state is maintained as it is. The state is also maintained until a metastable state is reset by applying a reset pulse that causes the liquid crystal molecules 18a to rise and align substantially perpendicularly to the surfaces of the substrates 11 and 12.

Further, in FIG. 1, 21a and 22a are
The transmission axes of a pair of polarizing plates 21 and 22 arranged on the front surface side and the back surface side of the liquid crystal cell 10 are shown, and in this embodiment, the front side polarizing plate 21 and the transmission axis 21a thereof are set to the liquid crystal cell. 10 are arranged in a direction substantially parallel to or substantially orthogonal to the alignment treatment direction 11a of the front side substrate 11 (a direction substantially parallel in the figure), and the back side polarizing plate 22 has its transmission axis 22a whose front side is the front side polarizing plate 21. Are arranged in a direction substantially orthogonal to the transmission axis 21a.

On the other hand, the drive circuit 40 includes the liquid crystal cell 10
These scanning electrodes 13 are sequentially selected by sequentially selecting the scanning electrodes 13 of
And a data signal to each signal electrode 14 in synchronism therewith, the potential difference between the scan signal and the data signal is generated between the electrodes 13 and 14 of each pixel portion of the liquid crystal cell 10. This driving circuit 40 applies the reset pulse between the electrodes 13 and 14 of each pixel portion of the liquid crystal cell 10 and then applies the voltage according to the first and second metastable states. Is applied, and then a drive signal whose effective value changes in a range lower than the voltage value of the reset pulse is applied.

The liquid crystal display device of this embodiment uses external light such as natural light or indoor illumination light to reflect light incident from the front surface side by the reflection plate 30 arranged on the rear surface side for display. For display driving, the respective pixel parts of the liquid crystal cell 10 are
After applying the reset pulse between the electrodes 13 and 14, the selection pulse is applied to switch the liquid crystal cell 10 to one of the first and second metastable states, and in the metastable state, the electrodes 13 and 14 are switched. This is performed by applying a drive signal whose effective value changes in a range lower than the voltage value of the reset pulse in between.

In this case, before the driving of the liquid crystal display device is started,
The liquid crystal molecules of the liquid crystal cell 10 are aligned in the above-described initial alignment state (alignment state with splay distortion). However, when the reset pulse is applied, the reset pulse is used as a splay distortion eliminating pulse, and the liquid crystal molecules are applied to the substrate 11. , 12 planes so as to rise almost perpendicularly to the 12 planes, and are oriented in either the first or second metastable state according to the selection pulse applied thereafter.

When the driving of the liquid crystal display device is started, that is, when the power switch is turned on, the above-mentioned spray distortion eliminating pulse is applied from the driving circuit 40 between the electrodes 13 and 14 of all the pixel portions, and thereafter. By applying the selection pulse for selecting one of the first and second metastable states, the display drive can be started after all the pixel portions have the same metastable state.

In the above liquid crystal display device, the liquid crystal molecules of the liquid crystal cell 10 are oriented in either the first or second metastable state, and the substrate 1 of the liquid crystal molecules in each of the metastable states is aligned.
The rising state for the 1st and 12th surfaces is changed according to the effective value of the drive signal to control the light transmission state.
When the first metastable state is selected, the liquid crystal molecule is composed of a liquid crystal cell and a polarizing plate twisted in one direction with a twist angle of approximately 270 ° with respect to the alignment processing direction of one of the substrates. It has the electro-optical characteristics of the device, the second
When the metastable state is selected, a liquid crystal cell in which liquid crystal molecules are twist-aligned at a twist angle of approximately 90 ° in a direction opposite to the first metastable state with respect to the alignment treatment direction of the one substrate is used. It has electro-optical characteristics of a display device including a polarizing plate.

That is, this liquid crystal display device has the electro-optical characteristics of two display devices in which the alignment states of the liquid crystal molecules of the liquid crystal cell are different from each other. Therefore, among the transmission states to be controlled stepwise, The plurality of transmission states can be controlled by utilizing one electro-optical characteristic, and the other plurality of transmission states can be controlled by utilizing the other electro-optical characteristic.

In this case, in the above embodiment, the front polarizing plate 2
The direction of the transmission axis 21a of 1 is the front substrate 11 of the liquid crystal cell 10.
Since the transmission axis 22a of the back side polarizing plate 22 is set to be substantially orthogonal to the transmission axis 21a of the front side polarizing plate 21, The display in the twisted nematic mode (hereinafter referred to as TN mode) is performed both when the metastable state is selected to control the transmissive state and when the second metastable state is selected to control the transmissive state. You can

That is, in both the first and second metastable states, the linearly polarized light that has entered through the front-side polarizing plate 21 and enters the liquid crystal cell 10 undergoes birefringence action of the liquid crystal layer during the process of passing through the liquid crystal cell 10. The light is rotated according to the twist alignment state of the light, and the light is incident on the back side polarizing plate 22, and the transmission is controlled by the back side polarizing plate 22. And the back side polarizing plate 2
The light that has passed through 2 is reflected by the reflection plate 30, passes through the back-side polarizing plate 22, the liquid crystal cell 10, and the front-side polarizing plate 21 in this order, and is emitted.

In this liquid crystal display device, the first
When the metastable state of is selected, the alignment state of liquid crystal molecules is
Since the twist alignment state has a large twist angle of about 270 °, at this time, the optical rotatory power due to the birefringence action of the liquid crystal layer is different for each wavelength light, and therefore, each wavelength light has a different transmittance and the back side polarizing plate 22. The light transmitted through the back side polarizing plate 22 becomes a colored light having a color corresponding to the intensity ratio of the wavelength lights 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 can be obtained, and the display color is the electrodes 13, 1
It changes according to the effective value of the drive signal applied between four.

That is, the liquid crystal molecule changes its rising state while maintaining the alignment state in the metastable state according to the effective value of the drive signal, but when the rising state of the liquid crystal molecule changes, the birefringence of the liquid crystal layer corresponding thereto changes. Since the optical rotatory power of each wavelength changes due to the change of the property, the color of the colored light can be changed by controlling the effective value of the drive signal, and therefore, one pixel portion can display a plurality of colors. You can

The color display uses the birefringence effect of the liquid crystal layer of the liquid crystal cell 10 and the polarization effect of the pair of polarizing plates 21 and 22 to color light. Therefore, a color filter is used. Since light is absorbed less than that which colors light, even in a reflective liquid crystal display device, it is possible to obtain a bright colored display by increasing the transmittance of display light.

On the other hand, when the second metastable state is selected, the alignment state of the liquid crystal molecules is a twist alignment state with a twist angle of about 90 °. Therefore, 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 present invention. In the liquid crystal display device of this embodiment, the front side polarizing plate 21 and the back side polarizing plate 22 are respectively provided with transmission axes 21a,
Since 22a are arranged substantially orthogonal to each other, when the rising angle of the liquid crystal molecules is close to the pretilt angle, white, which is an achromatic bright display, is displayed. The rate is reduced, and finally black, which is an achromatic dark display, is displayed.

In this case, the rising state of the liquid crystal molecules changes according to the effective value of the drive signal, and the birefringence of the liquid crystal layer changes accordingly. Therefore, the effective value of the drive signal is controlled to control the light By controlling the transmission state in stages, it is possible to perform grayscale black and white display.

The above-mentioned initial alignment state, that is, the state in which the liquid crystal molecules are twist-aligned with a splay strain at a twist angle of about 90 ° is not used for actual display, but this initial alignment state is also black and white by the TN mode. It is in a state where the display can be obtained.

4 to 6 show both substrates 1 of the liquid crystal cell 10.
The orientation processing directions 11a and 12a of the liquid crystals 1 and 12 and the transmission axes 21a and 22a of the polarizing plates 21 and 22 on the front and back sides are set as shown in FIG. 1, and Δnd of the liquid crystal cell 10 (refractive index anisotropy Δn of liquid crystal) is set. And the liquid crystal layer thickness d) of the liquid crystal display device selected to have a value of about 1000 nm, the change in the light emission rate and the display color with respect to the applied voltage (effective value of the drive signal) is shown in FIG. ) And (b) are voltage-emission rate characteristic diagrams and CIE chromaticity diagrams in the initial alignment state, and (a) and (b) of FIG.
-Emission rate characteristic diagram and CIE in the metastable state of
The chromaticity diagram and FIGS. 6A and 6B are a voltage-emission rate characteristic diagram and a CIE chromaticity diagram in the second metastable state. In the chromaticity diagram of (b) of each figure, W indicates an achromatic color point.

First, the initial alignment state will be described.
The voltage-emission rate characteristic in the initial orientation state is a characteristic in which the emission rate changes substantially linearly with respect to the voltage change, as shown in (a) of FIG. 4 (b), white when the applied voltage is 0 V (no voltage applied), and black when a voltage of a value (for example, about 5 V) for orienting the liquid crystal molecules in a substantially vertical rising state is applied. is there.

The rising state of the liquid crystal molecules becomes the most vertical when the above-mentioned reset pulse is applied, and the display becomes the blackest at that time, but since the reset pulse application time is extremely short, the reset state The display at is almost unrecognizable to the human eye.

Further, the voltage-emissivity characteristic in the first metastable state shows that the applied voltage is 0 to about 2 V as shown in FIG.
The emission rate is maintained at a high level and hardly changes in the range of, and the emission rate sharply decreases when the voltage becomes higher than that, and the change of the display color with respect to the voltage is as shown in FIG.
As shown in (b) of No. 2, when a voltage of 1.954V is applied, it is red, and when a voltage of 2.979V is applied, it is blue.

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

Further, the voltage-emission rate characteristic in the second metastable state is maintained at a high level in the application voltage range of 0 to about 1.5 V as shown in FIG. 6 (a). The characteristic is that the emission rate sharply decreases when the voltage becomes higher than that, and the display color changes with respect to the voltage by applying a voltage of 1.552 V as shown in FIG. 6B. It is white at times and black when a voltage of 3.071 V is applied.

The white x and y coordinate values are as follows:
x = 0.317, y = 0.341, and the Y value is 34.
41. Also, the black x, y coordinate values are
x = 0.277, y = 0.290, and the Y value is 1.8.
It is 3.

That is, the above liquid crystal display device selects the first metastable state to display red and blue, and selects the second metastable state to display white and black.
In addition to white and black which are the basics of display, two-color display of red and blue can be performed.

When the liquid crystal display device is turned off, the first
Alternatively, the alignment state of the liquid crystal molecules in the second metastable state is
After a few seconds to a few minutes (depending on the characteristics of the liquid crystal 18 to be used and the characteristics and addition amount of the chiral agent) due to spontaneous discharge, the initial alignment state is restored, and the entire screen is in the initial alignment state when no voltage is applied (the above-mentioned examples). Then white).

The liquid crystal display device has the electro-optical characteristics of two display devices in which the alignment state of liquid crystal molecules of the liquid crystal cell are different from each other. Since it is possible to control a plurality of transmission states by using one electro-optical characteristic and control a plurality of other transmission states by using the other electro-optical characteristic, all stages of the transmission state are possible. When one of the electro-optical characteristics is used, that is, when the first metastable state is selected to control the transmission state, and when the other electro-optical characteristic is used, that is, the second metastable state is used. It is possible to select the state and to control the transmission state, and for that reason, since the number of stages driven in each metastable state is small, in each metastable state,
It is possible to perform time-divisional driving with a small number of steps.

Therefore, according to the liquid crystal display device described above, a large operating voltage margin can be secured with respect to the drive duty of the liquid crystal cell 10. That is, in the case of a liquid crystal display device that displays two colors of red and blue in addition to the above-described white and black display, the effective value of the drive signal is set to red by selecting the first metastable state. 1.954 when displaying black
V and 2.979V, and when selecting the second metastable state to display blue and white, 1.552V and 3.
It suffices to set two different values of 071V. Therefore, the difference between the effective values in each metastable state, that is, the operating voltage margin is 1.025V (= 2.
979V-1.954V), 1.5 in the second metastable state
It can be set sufficiently high as 19V (= 3.071V-1.552V).

Therefore, according to the above liquid crystal display device,
Even if the liquid crystal cell 10 is of a simple matrix type that is driven by controlling the effective value of the drive signal, the operating voltage margin is increased with respect to the drive duty, and time-division drive with high duty is possible. It is possible to realize the display of a high-definition image having a large number of pixels.

In the liquid crystal display device described above, the display colors when the first metastable state is selected are red and blue. The display color is obtained by changing the value of Δnd of the liquid crystal cell 10. You can choose arbitrarily.

Further, the liquid crystal display device of the above-mentioned embodiment is the first
The display in the TN mode is performed when either of the first and second metastable states is selected, the display in the first metastable state is a color display, and the display in the second metastable state is black and white. Although it is a display, if at least the direction of the transmission axis 21a of the front-side polarizing plate 21 is diagonally intersecting with the alignment treatment direction 11a of the front-side substrate 11 of the liquid crystal cell 10, the first and second directions are obtained. The display in both metastable states can be color display by the birefringence effect mode.

[Modification of the First Embodiment] The liquid crystal display device of the above embodiment displays by utilizing the birefringence effect of the liquid crystal layer of the liquid crystal cell 10 and the polarization effect of the pair of polarizing plates 21 and 22. In addition to that, the front and back polarizing plates 21 and 22
A retardation plate may be arranged between one or both of the above and the liquid crystal cell 10.

FIG. 7 is a sectional view of a liquid crystal display device showing a modification of the first embodiment. In this display device, a retardation plate 23 is arranged between the front side polarizing plate 21 and the liquid crystal cell 10, and the retardation plate 23 has its optical axis (for example, a slow axis) of the front side polarizing plate 21. It is provided so as to be slanted with respect to the transmission axis 21a. Since this liquid crystal display device is obtained by adding the retardation plate 23 to the liquid crystal display device of the first embodiment, the duplicate description will be given the same reference numerals in the drawings and omitted.

According to the liquid crystal display device of this modification, the linearly polarized light that has passed through the front side polarizing plate 21 and is incident is first converted into elliptically polarized light having different polarization states by the birefringent action of the retardation plate 23. Since the light changes to a different polarization state due to the birefringence effect of the liquid crystal layer of the liquid crystal cell 10 and enters the back-side polarizing plate 22, a clear display color and a large number of colors can be displayed. .

That is, in this liquid crystal display device, light of each wavelength is incident on the back-side polarizing plate 22 after being largely changed in its polarization state by the birefringence action of both the retardation plate 23 and the liquid crystal layer of the liquid crystal cell 10. , The difference in the transmittance of each wavelength light transmitted through the back side polarizing plate 22 becomes large, and therefore the light transmitted through the back side polarizing plate 22 has a large difference in the intensity of each wavelength light constituting the light. In addition, the transmittance of each wavelength light and the difference in the transmittance change significantly with the change in the rising state of the liquid crystal molecules according to the effective value of the drive signal, and the color of the colored light changes. The number of display colors also increases.

The display color and the number of colors of this liquid crystal display device are the conditions that determine the birefringence of the retardation film 23 and the liquid crystal layer of the liquid crystal cell 10, that is, Δnd of the liquid crystal cell 10.
Can be arbitrarily selected by setting the value of, the retardation of the retardation film 23, the direction of its optical axis, and the like.

In this embodiment, when the directions of the transmission axes 21a and 22a of the front and back polarizing plates 21 and 22 are set as shown in FIG. 1, the condition for determining the birefringence is the first. Metastable state (liquid crystal molecules are almost 2 in one direction)
A large birefringence is exhibited in a twisted orientation at a twist angle of 70 °, and a second metastable state (the liquid crystal molecules are twisted at a twist angle of about 90 ° in the opposite direction to the first metastable state). (State), if it is set so as to show only a small amount of birefringence, the display when the first metastable state is selected is a clear color display with a large number of colors, and the second metastable state is selected. The display at this time can be a black and white display which is not so different from the TN mode.

Further, if the condition for determining the birefringence is set so as to exhibit a large birefringence in both the first and second metastable states, the first metastable state is selected. Even when the second metastable state is selected, vivid color display with a large number of colors can be performed.

Further, in the embodiment in which the retardation film 23 is added, as described above, at least the direction of the transmission axis 21a of the front polarizing plate 21 is oblique to the alignment treatment direction 11a of the front substrate 11 of the liquid crystal cell 10. First in the direction of crossing
The present invention can be applied to the case where the display in both the second and second metastable states is a color display in the birefringence effect mode, and in that case, the display color in both the metastable states is made clear and The number can be increased.

[Second Embodiment] FIGS. 8 to 12 show a second embodiment of the present invention. FIG. 8 is a perspective view showing the basic configuration of a liquid crystal display device, in which (a) is an initial alignment state,
(B) shows the first metastable state, and (c) shows the second metastable state.

The liquid crystal display device of this embodiment is similar to that shown in FIG.
As shown in FIG. 3, the polarizing plates 21 and 22 are arranged on the front surface side and the rear surface side of the liquid crystal cell 10 and the reflecting plate 30 is arranged behind the polarizing plate 22 on the back side. 10 is connected to a driving circuit 40 for driving it, and the liquid crystal cell 10 is
The initial alignment state and the alignment states of the liquid crystal molecules in the first and second metastable states are different from those in the first embodiment, but the cell structure is the same.

The liquid crystal of the liquid crystal cell 10 is a nematic liquid crystal added with a chiral agent so as to have a twist alignment property, and the liquid crystal layer has an initial alignment state in which the liquid crystal molecules are aligned in one of the substrates. Is the splay alignment state in which the twist alignment is performed in one direction at a twist angle of approximately 90 °.

In the liquid crystal cell 10, a reset pulse having a voltage value that causes liquid crystal molecules to rise and align substantially perpendicularly to the surfaces of the substrates 11 and 12 is applied to the liquid crystal layer, and then a predetermined voltage value lower than that is applied. By applying the selection pulse, the liquid crystal molecules become the first metastable state in which the liquid crystal molecules are twist-aligned in one direction with a twist angle of approximately 360 ° with respect to the alignment processing direction of one of the substrates, and the reset pulse is applied. A second selection pulse having a predetermined voltage value lower than the applied voltage is applied, whereby the liquid crystal molecules are non-twisted along the alignment treatment direction of the one substrate.
It has the characteristic of becoming a metastable state.

In FIG. 8, 11a and 12a are the alignment treatment directions of the substrates 11 and 12 of the liquid crystal cell 10 (alignment film 15,
16 rubbing directions), and in this embodiment,
The alignment film 15 on the front substrate 11 is aligned in a direction substantially orthogonal to the horizontal axis x of the screen of the liquid crystal display device (direction shifted by about 90 °) from the lower edge side to the upper edge side of the screen. Then, the alignment film 16 on the back substrate 12 is subjected to an alignment treatment in a direction substantially orthogonal to the horizontal axis x and from the upper edge side to the lower edge side of the screen. That is, the alignment treatment directions 11a and 12a of both substrates 11 and 12
Are directions substantially parallel to and opposite to each other.

In this embodiment, as the liquid crystal 18, a liquid crystal to which a chiral agent having a counterclockwise twist orientation when viewed from the surface side is added is used.
In the initial alignment state, the liquid crystal molecules of the liquid crystal cell 10 are twist-aligned with splay strain in a counterclockwise direction (twisted direction given by the chiral agent) at a twist angle of about 180 ° as viewed from the surface side.

In this initial alignment state, liquid crystal molecules are aligned in the respective alignment treatment directions 11 in the vicinity of both substrates 11 and 12.
a, 12a, and the direction indicated by the broken line arrow in FIG. 8A, that is, the chiral agent, based on the orientation treatment direction of either one of the substrates, for example, the orientation treatment direction 12a of the back substrate 12. It is a splay alignment state in which the twist alignment is performed at a twist angle of about 180 ° in the twist direction given by.

The initial alignment state is a state not actually used for display, and the liquid crystal cell 10 is driven for display by aligning the alignment state of liquid crystal molecules to the above-mentioned first and second metastable states. It

In the first metastable state and the second metastable state, the twist angle of liquid crystal molecules is approximately 1 from the initial alignment state.
It 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 is + with respect to the orientation processing direction 12a of the back side substrate 12, and is given by the chiral agent. If the twist angle in the direction opposite to the twist direction (direction to untwist the chiral agent) is −, the first metastable state is the twist orientation in which the twist angle changes by + 180 ° with respect to the initial orientation state. The second metastable state is a non-twisted orientation state in which the twist angle changes by −180 ° with respect to the initial orientation state.

In order to switch the alignment state from the initial alignment state to the first and second metastable states, the liquid crystal molecules are first transferred to the substrate 11 between the electrodes 13 and 14 of each pixel portion of the liquid crystal cell 10.
It is performed by applying a splay distortion eliminating pulse having a voltage value (absolute value) that rises and is oriented almost perpendicularly to the 12th surface, and then applying a selection pulse having a predetermined voltage value between the electrodes 13 and 14. .

That is, after the liquid crystal molecules are risen and aligned substantially perpendicularly to the surfaces of the substrates 11 and 12 by applying the spray distortion eliminating pulse, a predetermined voltage value (absolute value) V _S1 lower than the spray distortion eliminating pulse is applied. When the selection pulse (hereinafter referred to as the first metastable state selection pulse) is applied,
The twist angle of the liquid crystal molecules in the initial alignment state is about 18 more
Twist angle (180 ° + 180 °) with a twist of 0 °
= 360 °), the splay strain is eliminated by orienting in a twisted state, and the first metastable state is obtained.

In the first metastable state, liquid crystal molecules are aligned along the respective alignment treatment directions 11a and 12a in the vicinity of both substrates 11 and 12, and the alignment treatment direction of either one of the substrates, for example, With the orientation processing direction 12a of the back substrate 12 as a reference, the twist direction shown by the broken line arrow in FIG. 8B, that is, the counterclockwise direction when viewed from the front side (the twisting direction imparted by the chiral agent) is approximately 3
It is in a twisted orientation with a twist angle of 60 °.

Further, by applying the spray distortion eliminating pulse, the liquid crystal molecules are risen and aligned almost perpendicularly to the surfaces of the substrates 11 and 12, and then a predetermined voltage value (absolute value) V _S2 lower than the spray distortion eliminating pulse is applied. When a selection pulse (hereinafter, referred to as a second metastable state selection pulse) is applied, liquid crystal molecules have a twist angle of approximately 0 ° (180 ° -180 °- 1
(80 ° = 0 °) state, that is, the twist orientation in the initial orientation state is unwound, the non-twisted state is oriented to eliminate the splay strain, and the second metastable state is obtained.

The second metastable state is a state in which the liquid crystal molecules are non-twisted along the alignment treatment direction of either one of the substrates, for example, the alignment treatment direction 12a of the back substrate 12, and the liquid crystal molecules are both twisted. In the vicinity of the substrates 11 and 12, the alignment is performed along the respective alignment treatment directions 11a and 12a, and the alignment is homogeneous over the entire thickness of the liquid crystal layer without generating twist.

Further, the first metastable state and the second metastable state can be switched from one to the other, and in any metastable state of liquid crystal molecules, First, liquid crystal molecules are placed between the electrodes 13 and 14 on the substrate 1.
Liquid crystal molecules can be obtained by applying a reset pulse having a voltage value that causes the liquid crystal molecules to rise and align substantially perpendicularly to the 1st and 12th planes to reset the metastable state, and then applying the first or second metastable state selection pulse. Can be switched from one metastable state to the other metastable state.

The voltage value V _{S1 of} the first metastable state selection pulse and the voltage value V _S of the second metastable state selection pulse are
_S2 is determined by the characteristics of the liquid crystal 18 used, the characteristics of the chiral agent, and the amount added, and the absolute value is, for example, V _S1 <
V _S2, which is the voltage value V of the first metastable state selection pulse
_S1 is a value at which almost no voltage is applied (approximately 0 V), and the voltage value V _{S2 of} the second metastable state selection pulse is almost the same as or close to the pretilt angle with respect to the surfaces of the substrates 11 and 12 for most liquid crystal molecules. It is a low voltage value oriented at a tilt angle.

FIG. 9 shows the alignment states of the liquid crystal molecules in the initial alignment state, the reset state, and the first and second metastable states in the right edge direction of the liquid crystal cell 10 (direction along the horizontal axis x).
18a is a schematic view seen from the above, and 18a indicates liquid crystal molecules.

As shown in this schematic diagram, the initial alignment state (the liquid crystal molecules are twist-aligned at a twist angle of about 180 ° in the counterclockwise direction when viewed from the front side with reference to the alignment processing direction 12a of the back substrate 12). (State) indicates that both substrates 11 and 1
The liquid crystal molecules in the vicinity of 2 are oriented so as to rise obliquely with respect to the respective surfaces 11 and 12 of the substrates 11 and 12a with a pretilt angle of about several degrees, but twisted. The liquid crystal molecules are in a state where the pretilt directions on the substrates 11 and 12 side are opposite to each other when the liquid crystal molecules are expanded and viewed so that their long axes lie on the same plane. The tilt angle becomes smaller with the distance from the substrates 11 and 12, and the tilt direction with respect to the surfaces of the substrates 11 and 12 is reversed at the middle of the liquid crystal layer thickness (the point where the tilt angle becomes 0 °). It is in a stable twist orientation state with a splay distortion).

In the reset state, both substrates 11,
Liquid crystal molecules in the vicinity of 12 (omitted in the figure) are almost unchanged from the initial alignment state (each substrate 1
Although it is oriented so as to rise obliquely at a pretilt angle of about several degrees toward the orientation treatment directions 11a and 12a with respect to the 1st and 12th surfaces), it is almost apart from the substrates 11 and 12 to some extent or more. Liquid crystal molecules of the substrate 1
It is in a state of being oriented so as to rise almost vertically to the 1st and 12th planes.

Furthermore, in the first metastable state (the state in which the liquid crystal molecules are twist-aligned at a twist angle of about 360 °), the alignment state of the liquid crystal molecules near both substrates 11 and 12 is almost the same as the initial alignment state. However, the twist angle of the liquid crystal molecules is changed by about 180 ° in one direction with respect to the initial alignment state, so that the liquid crystal molecules in the twist alignment are arranged so that their long axes are on the same plane. Since the liquid crystal molecules 18a are tilted in the same direction when viewed in the unfolded state, the first metastable state is a twist alignment state without splay distortion.

In the second metastable state (the state in which the liquid crystal molecules are non-twisted), the alignment state of the liquid crystal molecules in the vicinity of both substrates 11 and 12 is almost the same as the initial alignment state. The twist angle is a state in which the twist angle is changed by about 180 ° in the direction opposite to the first metastable state with respect to the initial alignment state, and therefore, the liquid crystal molecules 18a have their molecular major axes oriented in substantially the same direction. Moreover, since the liquid crystal molecules 18a are aligned with the tilt directions thereof oriented in the same direction, the second metastable state is a non-twisted alignment state having no splay distortion.

The first and second metastable states are, respectively,
In this metastable state, the twist alignment state of the liquid crystal molecules 18a is maintained. In any metastable state, the rising state of the liquid crystal molecules 18a with respect to the surfaces of the substrates 11 and 12 is applied between the electrodes 13 and 14. That varies depending on the effective value of the drive signal (effective value of the voltage applied between the electrodes during one frame)
The alignment state of liquid crystal molecules in the vicinity of is almost unchanged).

Among the alignment states of the liquid crystal molecules in the first and second metastable states shown in FIG. 9, the alignment state shown on the upper side has values V _1-1 and V at which the effective value of the drive signal is relatively small.
_2-1 shows the rising state of the liquid crystal molecules, and the alignment state shown on the upper side shows the rising states of the liquid crystal molecules when the effective value of the drive signal is V _1-2 and V _2-2 which are high to some extent. In any of the metastable states, the liquid crystal molecule maintains the alignment state in the metastable state,
The rising state is changed according to the effective value of the drive signal.

In the first and second metastable states, the rising state of liquid crystal molecules changes according to the effective value of the drive signal, but the alignment state (in the first metastable state, the twist alignment state, In the metastable state of No. 2, the non-twisted alignment state is maintained as it is. In any metastable state, a reset pulse is applied to align the liquid crystal molecules 18a substantially vertically to the surfaces of the substrates 11 and 12. It is held until the metastable state is reset.

Further, in FIG. 8, 21a and 22a are
The transmission axes of a pair of polarizing plates 21 and 22 arranged on the front surface side and the back surface side of the liquid crystal cell 10 are shown, and in this embodiment, the front side polarizing plate 21 and the transmission axis 21a thereof are set to the liquid crystal cell. 10 are arranged so as to be obliquely intersecting with the alignment treatment direction 11a of the front side substrate 11 at a deviation angle of about 45 °, and the rear side polarizing plate 22 has its transmission axis 22a whose transmission axis 22a is the transmission axis of the front side polarizing plate 21. It is arranged in a direction substantially orthogonal to 21a.

On the other hand, the drive circuit 40 includes the liquid crystal cell 10
These scanning electrodes 13 are sequentially selected by sequentially selecting the scanning electrodes 13 of
And a data signal to each signal electrode 14 in synchronism therewith, the potential difference between the scan signal and the data signal is generated between the electrodes 13 and 14 of each pixel portion of the liquid crystal cell 10. This driving circuit 40 applies the reset pulse between the electrodes 13 and 14 of each pixel portion of the liquid crystal cell 10 and then applies the voltage according to the first and second metastable states. Is applied, and then a drive signal whose effective value changes in a range lower than the voltage value of the reset pulse is applied.

The liquid crystal display device of this embodiment uses external light such as natural light and indoor illumination light to reflect light incident from the front surface side by the reflection plate 30 arranged on the back surface side for display. For display driving, the respective pixel parts of the liquid crystal cell 10 are
After applying the reset pulse between the electrodes 13 and 14, the selection pulse is applied to switch the liquid crystal cell 10 to one of the first and second metastable states, and in the metastable state, the electrodes 13 and 14 are switched. This is performed by applying a drive signal whose effective value changes in a range lower than the voltage value of the reset pulse in between.

In this case, before driving the liquid crystal display device,
The liquid crystal molecules of the liquid crystal cell 10 are aligned in the above-described initial alignment state (alignment state with splay distortion). However, when the reset pulse is applied, the reset pulse is used as a splay distortion eliminating pulse, and the liquid crystal molecules are applied to the substrate 11. , 12 planes so as to rise almost perpendicularly to the 12 planes, and are oriented in either the first or second metastable state according to the selection pulse applied thereafter.

When the driving of the liquid crystal display device is started, that is, when the power switch is turned on, the above-mentioned spray distortion eliminating pulse is applied from the driving circuit 40 between the electrodes 13 and 14 of all the pixel portions, and thereafter. By applying the selection pulse for selecting one of the first and second metastable states, the display drive can be started after all the pixel portions have the same metastable state.

In the above liquid crystal display device, the liquid crystal molecules of the liquid crystal cell 10 are oriented in either the first or second metastable state, and the substrate 1 of the liquid crystal molecules in each metastable state is arranged.
The rising state for the 1st and 12th surfaces is changed according to the effective value of the drive signal to control the light transmission state.
When the first metastable state is selected, the liquid crystal molecule is composed of a liquid crystal cell and a polarizing plate twisted in one direction with a twist angle of approximately 360 ° with respect to the alignment treatment direction of one of the substrates. It has the electro-optical characteristics of the device, the second
When the metastable state is selected, the liquid crystal molecule has the electro-optical characteristics of a display device including a liquid crystal cell in which the one of the substrates is not twist-aligned along the alignment treatment direction and a polarizing plate.

That is, this liquid crystal display device has the electro-optical characteristics of two display devices in which the alignment states of the liquid crystal molecules of the liquid crystal cell are different from each other. Therefore, among the transmission states to be controlled stepwise, The plurality of transmission states can be controlled by utilizing one electro-optical characteristic, and the other plurality of transmission states can be controlled by utilizing the other electro-optical characteristic.

In this case, in the above embodiment, the liquid crystal cell 10 is used.
The direction of the transmission axis 21a of the front-side polarizing plate 21 of the pair of polarizing plates 21, 22 arranged with the liquid crystal cell 10 in between.
About 45 with respect to the alignment treatment direction 11a of the front substrate 11.
Since the angle of deviation is set to intersect diagonally,
When the first metastable state is selected to control the transmissive state and when the second metastable state is selected to control the transmissive state, color display in the birefringence effect mode can be performed.

The color display by the birefringence effect mode will be described. In both the first and second metastable states, the linearly polarized light that has passed through the front-side polarizing plate 21 and is incident passes through the liquid crystal cell 10. In the process, due to the birefringence effect of the liquid crystal layer, each wavelength light becomes an elliptically polarized light having a different polarization state, and each wavelength light transmits through the back side polarizing plate 22 at a transmittance corresponding to each polarization state, The light transmitted through the back-side polarizing plate 22 becomes colored light having a color corresponding to the ratio of the light intensities of the respective wavelength light components of the light. This colored light is reflected by the reflection plate 30, passes through the back-side polarizing plate 22, the liquid crystal cell 10, and the front-side polarizing plate 21 in this order and is emitted.

As described above, the color display by the birefringence effect mode colors light by utilizing the birefringence effect of the liquid crystal layer of the liquid crystal cell 10 and the polarization effect of the pair of polarizing plates 21 and 22. Therefore, since light is absorbed less than that in the case where the light is colored by using the color filter, it is possible to obtain a bright color display by increasing the transmittance of the display light even in the reflective liquid crystal display device.

In the liquid crystal display device, the first
Liquid crystal molecules when the metastable state (the state in which the liquid crystal molecules are twist-aligned at a twist angle of about 360 °) is selected and when the second metastable state (the state in which the liquid crystal molecules are non-twisted) is selected. The liquid crystal layer exhibits different birefringence depending on the orientation state of the liquid crystal.

Therefore, when the first metastable state is selected and when the second metastable state is selected, the polarization state of each wavelength light incident on the back side polarizing plate 22 is different, and accordingly, the polarization state is different. Since the light transmitted through the back-side polarizing plate 22 is colored in different colors, the display color when the first metastable state is selected and the display color when the second metastable state is selected are different from each other. is there.

Furthermore, in this liquid crystal display device, the first
In both the second and the second metastable states, the electrodes 13, 1
The birefringence of the liquid crystal layer changes due to the change in the rising state of the liquid crystal molecules according to the effective value of the drive signal applied between the four, and the polarization state of each wavelength light incident on the back side polarizing plate 22 changes accordingly. Therefore, it is possible to change the color of the colored light by controlling the effective value of the drive signal,
Therefore, one pixel portion can display a plurality of colors.

The above-mentioned initial alignment state, that is, the state in which liquid crystal molecules are twist-aligned with a splay strain at a twist angle of about 180 °, is not used for actual display as described above, but this initial alignment state is also not used. This is a state in which a display in the birefringence effect mode can be obtained.

10 to 12, the alignment treatment directions 11a and 12a of both substrates 11 and 12 of the liquid crystal cell 10 and the transmission axes 21a and 22a of the front and back polarizing plates 21 and 22 are set as shown in FIG. The emission of light with respect to the applied voltage (effective value of the drive signal) of the liquid crystal display device in which the value of Δnd (the product of the refractive index anisotropy Δn of the liquid crystal and the liquid crystal layer thickness d) of the liquid crystal cell 10 is selected to be about 900 nm. FIG. 10 shows the change in the rate and the display color.
11A and 11B are voltage-emission rate characteristic diagrams and CIE chromaticity diagrams in the initial alignment state, and FIGS. 11A and 11B are voltage-emission rate characteristic diagrams in the first metastable state and C
The IE chromaticity diagram, and FIGS. 12A and 12B are a voltage-emission rate characteristic diagram and a CIE chromaticity diagram in the second metastable state. In the chromaticity diagram of (b) of each figure, W indicates an achromatic color point.

First, the initial alignment state will be described.
The voltage-emissivity characteristic in the initial alignment state is shown in FIG.
As shown in FIG. 10B, when the applied voltage is 0 V (voltage is It is almost black when no voltage is applied, and purple when a voltage having a value (for example, about 5 V) for orienting liquid crystal molecules in a vertically rising state is applied. The rising state of the liquid crystal molecules becomes the most vertical when the reset pulse is applied, but since the application time of the reset pulse is extremely short, the display in the reset state is hardly recognized by human eyes.

The voltage-emission rate characteristic in the first metastable state is maintained at a high level in the range of applied voltage from 0 to about 2.5 V as shown in FIG. 11 (a). There is almost no change, and the emission rate sharply decreases when the voltage becomes higher than that. The change of the display color with respect to the voltage is as shown in FIG. 11B, when a voltage of 2.506V is applied. It is red at times and black when a voltage of 3.033 V is applied.

The red x and y coordinate values are as follows:
x = 0.418, y = 0.460, and the Y value (brightness) is 30.13. Further, the x and y coordinate values of the black are x = 0.272 and y = 0.291,
The Y value is 11.6.

Further, the voltage-emissivity characteristic in the second metastable state shows that the applied voltage is 0 to about 1.0 V and about 2.0 to about 3.0 V as shown in FIG. Although a high emission rate can be obtained in the two ranges, the emission rate sharply decreases when a voltage in the above two ranges and a voltage exceeding about 3.0 V are applied.
As shown in (b) of 2, it is blue when a voltage of 1.408V is applied, and white when a voltage of 3.018V is applied.

The blue x and y coordinate values are as follows:
x = 0.152, y = 0.138, and Y value is 5.7.
Is. The white x, y coordinate value is x =
0.290, y = 0.314, and the Y value is 26.7.

That is, the liquid crystal display device selects the first metastable state to display red and black, and selects the second metastable state to display blue and white.
In addition to white and black which are the basics 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
Alternatively, the alignment state of the liquid crystal molecules in the second metastable state is
After a few seconds to several minutes (depending on the characteristics of the liquid crystal 18 to be used and the characteristics and addition amount of the chiral agent) by natural discharge, the initial alignment state is restored, and the entire screen is in the initial alignment state when no voltage is applied (the above implementation It becomes almost black in the example).

The liquid crystal display device has the electro-optical characteristics of the two display devices in which the alignment states of the liquid crystal molecules of the liquid crystal cell are different from each other. Since it is possible to control a plurality of transmission states by using one electro-optical characteristic and control a plurality of other transmission states by using the other electro-optical characteristic, all stages of the transmission state are possible. When one of the electro-optical characteristics is used, that is, when the first metastable state is selected to control the transmission state, and when the other electro-optical characteristic is used, that is, the second metastable state is used. It is possible to select the state and to control the transmission state, and for that reason, since the number of stages driven in each metastable state is small, in each metastable state,
It is possible to perform time-divisional driving with a small number of steps.

Therefore, according to the above liquid crystal display device, a large operating voltage margin can be secured with respect to the drive duty of the liquid crystal cell 10. That is, in the case of a liquid crystal display device which displays two colors of red and blue in addition to the display of white and black as described above, the effective value of the drive signal is set to the first value.
2.5 when selecting the metastable state of and displaying red and black
There are two ways of setting 06V and 3.033V, and when selecting the second metastable state and displaying blue and white, it is only necessary to set two ways of 1.408V and 3.018V.
The difference between the effective values in each metastable state, that is, the operating voltage margin, is 0.527V (=
3.033V-2.506V) and 1.610V (= 3.018V-1.408V) in the second metastable state.

Therefore, according to the above liquid crystal display device,
Even if the liquid crystal cell 10 is of a simple matrix type that is driven by controlling the effective value of the drive signal, the operating voltage margin is increased with respect to the drive duty, and time-division drive with high duty is possible. It is possible to realize the display of a high-definition image having a large number of pixels.

The liquid crystal display device of the above-mentioned embodiment is the first
When the metastable state of is selected, the display colors are red and black,
The display colors when the second metastable state is selected are blue and white. The display colors are Δnd of the liquid crystal cell 10.
It can be arbitrarily selected by changing the value of.

[Modification of Second Embodiment] The liquid crystal display device of the above embodiment displays by utilizing the birefringence effect of the liquid crystal layer of the liquid crystal cell 10 and the polarization effect of the pair of polarizing plates 21 and 22. In addition to that, the front and back polarizing plates 21 and 22
A retardation plate may be arranged between one or both of the above and the liquid crystal cell 10.

As an example, the first example shown in FIG. 7 is used.
As in the modification of the embodiment, the retardation plate 23 is provided between the front-side polarizing plate 21 and the liquid crystal cell 10, and its optical axis (eg, slow axis) is oblique to the transmission axis 21a of the front-side polarizing plate 21. It is conceivable to shift the positions.

According to the liquid crystal display device of this modified example, the linearly polarized light that has passed through the front polarizing plate 21 and is incident is first converted into elliptically polarized light having different polarization states due to the birefringence effect of the retardation plate 23. The reflected light changes its polarization state according to the twist alignment state of the liquid crystal molecules by the birefringence effect of the liquid crystal layer of the liquid crystal cell 10 and enters the back-side polarizing plate 22. When the metastable state is selected and displayed, the colored light can be made clearer and the number of colors of the colored light can be increased to realize a multicolor display.

[Third Embodiment] FIGS. 13 to 17 show a third embodiment of the present invention. 13A and 13B are perspective views showing the basic configuration of the liquid crystal display device. FIG. 13A shows an initial alignment state, FIG. 13B shows a first metastable state, and FIG. 13C shows a second metastable state.

The liquid crystal display device of this embodiment is similar to that shown in FIG.
As shown in FIG. 3, the polarizing plates 21 and 22 are arranged on the front surface side and the rear surface side of the liquid crystal cell 10 and the reflecting plate 30 is arranged behind the polarizing plate 22 on the back side. 10 is connected to a driving circuit 40 for driving it, and the liquid crystal cell 10 is
The initial alignment state and the alignment states of the liquid crystal molecules in the first and second metastable states are different from those in the first and second embodiments, but the cell structure is the same.

The liquid crystal of the liquid crystal cell 10 is a nematic liquid crystal in which a chiral agent is added to give a twist alignment property, and the liquid crystal layer thereof is in a splay alignment state in which liquid crystal molecules are in non-twist alignment in an initial alignment state. .

In the liquid crystal cell 10, a reset pulse having a voltage value that causes liquid crystal molecules to rise and align substantially perpendicularly to the surfaces of the substrates 11 and 12 is applied to the liquid crystal layer thereof, and then a predetermined voltage value lower than that is applied. By applying the selection pulse, the liquid crystal molecules are brought into a first metastable state in which the liquid crystal molecules are twist-aligned in one direction with a twist angle of approximately 180 ° with respect to the alignment treatment direction of one of the substrates, and the reset pulse is applied. By applying a selection pulse having a predetermined voltage value lower than the applied voltage after the application, the liquid crystal molecules are rotated by about 180 degrees in the direction opposite to the first metastable state with reference to the alignment treatment direction of the one substrate. It has a characteristic of being in a second metastable state in which it is twist-oriented at a twist angle of °.

In FIG. 13, 11a and 12a are the alignment treatment directions of both substrates 11 and 12 of the liquid crystal cell 10 (alignment film 1).
In this example, the alignment film 15 of the front substrate 11 and the alignment film 16 of the back substrate 12 are parallel to the horizontal axis x of the screen of the liquid crystal display device. The orientation process is performed in the direction from the left edge side to the right edge side of the screen. That is, the alignment treatment directions 11a and 12a of both substrates 11 and 12 are substantially parallel to each other and in the same direction.

In this embodiment, as the liquid crystal 18, a liquid crystal to which a chiral agent having a counterclockwise twist orientation when viewed from the surface side is added is used.
In the initial alignment state, the liquid crystal molecules of the liquid crystal cell 10 are non-twisted with splay strain.

In this initial alignment state, the liquid crystal molecules are twisted over the entire thickness of the liquid crystal layer along the alignment treatment directions 11a and 12a of both substrates 11 and 12, as shown by the broken lines in FIG. It is in a splay alignment state in which it is homogeneously aligned without being generated.

The initial alignment state is a state not actually used for display, and the liquid crystal cell 10 is driven for display by aligning the alignment state of liquid crystal molecules to the above-mentioned first and second metastable states. It

The first metastable state and the second metastable state are the states in which the twist alignment splay strain is eliminated from the initial alignment state at a twist angle of approximately 180 ° of liquid crystal molecules,
Based on the orientation processing direction 12a of the back substrate 12,
When the twist angle in the twist direction imparted by the chiral agent is a + angle, and the twist angle in the direction opposite to the twist direction imparted by the chiral agent (the direction in which the twist by the chiral agent is unwound) is an angle of −, The first metastable state is
The twist orientation state is + 180 ° twisted with respect to the initial orientation state, and the second metastable state is the twist orientation state twisted with −180 ° with respect to the initial orientation state.

To switch the alignment state from the initial alignment state to the first and second metastable states, liquid crystal molecules are first transferred to the substrate 11 and the electrode 13 between electrodes 13 and 14 of each pixel portion of the liquid crystal cell 10.
A splay distortion elimination pulse having a voltage value (absolute value) that rises and is oriented almost perpendicularly to the 12th surface is applied, and then a selection pulse having a predetermined voltage value is applied between the electrodes 13 and 14 between the electrodes 13 and 14. Is applied to

That is, after the liquid crystal molecules are risen and aligned almost perpendicularly to the surfaces of the substrates 11 and 12 by applying the spray distortion eliminating pulse, a predetermined voltage value (absolute value) V _S1 lower than the spray distortion eliminating pulse is applied. When the selection pulse (hereinafter referred to as the first metastable state selection pulse) is applied,
The splay alignment state in which the liquid crystal molecules are in the non-twist alignment which is the initial alignment state is twisted in the twist direction given by the chiral agent at a twist angle of about 180 ° to eliminate the splay strain, and the first quasi Be in a stable state.

In the first metastable state, the liquid crystal molecules are aligned along the respective alignment treatment directions 11a and 12a in the vicinity of both substrates 11 and 12, and the alignment treatment direction of either one of the substrates, for example, With reference to the alignment treatment direction 12a of the back substrate 12, a twist direction shown by a broken line arrow in FIG. 13B, that is, a counterclockwise direction when viewed from the front side (a twisting direction imparted by the chiral agent) is approximately 180. It is in a twisted orientation with a twist angle of °.

Further, after the liquid crystal molecules are risen and aligned almost perpendicularly to the surfaces of the substrates 11 and 12 by applying the spray distortion eliminating pulse, a predetermined voltage value (absolute value) V _S2 lower than the spray distortion eliminating pulse is applied. When a selection pulse (hereinafter, referred to as a second metastable state selection pulse) is applied, the liquid crystal molecules are reversed from the first metastable state from the non-twisted splay alignment state in which the liquid crystal molecules are in the initial alignment state. Direction, that is, in the direction opposite to the twisting direction imparted by the chiral agent, is twisted at a twist angle of about 180 ° to eliminate the splay strain and become the second metastable state.

In the second metastable state, the liquid crystal molecules are aligned along the respective alignment treatment directions 11a and 12a in the vicinity of both substrates 11 and 12, and the alignment treatment direction of one of the substrates, for example, With the orientation processing direction 12a of the back substrate 12 as a reference, in the twist direction shown by the broken line arrow in (c) of FIG. 13, that is, in the clockwise direction when viewed from the front side (the direction opposite to the first metastable state), It is in a twist-oriented state with a twist angle of about 180 °.

Furthermore, the first metastable state and the second metastable state can be switched from one to the other, and in any metastable state of liquid crystal molecules, First, liquid crystal molecules are placed between the electrodes 13 and 14 on the substrate 1.
Liquid crystal molecules can be obtained by applying a reset pulse having a voltage value that causes the liquid crystal molecules to rise and align substantially perpendicularly to the 1st and 12th planes to reset the metastable state, and then applying the first or second metastable state selection pulse. Can be switched from one metastable state to the other metastable state.

It should be noted that the voltage value V _{S1 of} the first metastable state selection pulse and the voltage value V _S of the second metastable state selection pulse.
_S2 is determined by the characteristics of the liquid crystal 18 used, the characteristics of the chiral agent, and the amount added, and the absolute value is, for example, V _S1 <
V _S2, which is the voltage value V of the first metastable state selection pulse
_S1 is a value at which almost no voltage is applied (approximately 0 V), and the voltage value V _{S2 of} the second metastable state selection pulse is almost the same as or close to the pretilt angle with respect to the surfaces of the substrates 11 and 12 for most liquid crystal molecules. It is a low voltage value oriented at a tilt angle.

FIG. 14 shows the alignment states of the liquid crystal molecules in the initial alignment state, the reset state, and the first and second metastable states seen from the lower edge direction of the liquid crystal cell 10 (direction orthogonal to the horizontal axis x). 18a shows a liquid crystal molecule.

As shown in this schematic diagram, in the initial alignment state (the liquid crystal molecules are in non-twist alignment), the liquid crystal molecules in the vicinity of the substrates 11 and 12 are in the respective substrates 11 and 1.
The two surfaces are oriented so as to be obliquely raised at a pretilt angle of several degrees toward the orientation processing directions 11a and 12a, but the pretilt directions on the respective substrates 11 and 12 are opposite to each other. Therefore, the tilt angle of the liquid crystal molecules 18a becomes smaller with the distance from the substrates 11 and 12, and the substrates 11 and 12 are bordered by the middle of the liquid crystal layer thickness (the point where the tilt angle becomes 0 °). It is in a stable non-twist orientation state in a state where the direction of inclination with respect to the surface is reversed (state with splay distortion).

Further, in the reset state, both substrates 11,
Liquid crystal molecules in the vicinity of 12 (omitted in the figure) are almost unchanged from the initial alignment state (each substrate 1
Although it is oriented so as to rise obliquely at a pretilt angle of about several degrees toward the orientation treatment directions 11a and 12a with respect to the 1st and 12th surfaces), it is almost apart from the substrates 11 and 12 to some extent or more. Liquid crystal molecules of the substrate 1
It is in a state of being oriented so as to rise almost vertically to the 1st and 12th planes.

Further, in the first metastable state (the state in which the liquid crystal molecules are twist-aligned with a twist angle of about 180 ° in the counterclockwise direction when viewed from the front side with respect to the orientation processing direction 12a of the back substrate 12), The alignment state of the liquid crystal molecules in the vicinity of the substrates 11 and 12 is almost the same as the initial alignment state, but the liquid crystal molecules 18a are in a twist alignment with a twist angle of about 180 ° in one direction with respect to the initial alignment state. Therefore, when the twisted liquid crystal molecules are expanded and viewed so that their long axes are on the same plane, the tilt directions of the liquid crystal molecules 18a are the same, and thus the first metastable state is obtained. The state is a twist orientation state without splay distortion.

The second metastable state (the state in which the liquid crystal molecules are twist-aligned at a twist angle of about 180 ° in the clockwise direction when viewed from the front side with respect to the alignment treatment direction 12a of the back substrate 12) is The alignment state of the liquid crystal molecules in the vicinity of the substrates 11 and 12 is almost the same as the initial alignment state, but the liquid crystal molecules 18a have an angle of about 180 ° in the direction opposite to the first metastable state with respect to the initial alignment state. The liquid crystal molecules are in a twisted state at a twist angle. Therefore, when the liquid crystal molecules in the twisted orientation are expanded and viewed so that their long axes are on the same plane, the tilt directions of the liquid crystal molecules 18a are the same. Therefore, the second metastable state is a twist orientation state without splay distortion.

The first and second metastable states are, respectively,
In this metastable state, the twist alignment state of the liquid crystal molecules 18a is maintained. In any metastable state, the rising state of the liquid crystal molecules 18a with respect to the surfaces of the substrates 11 and 12 is applied between the electrodes 13 and 14. That varies depending on the effective value of the drive signal (effective value of the voltage applied between the electrodes during one frame)
The alignment state of liquid crystal molecules in the vicinity of is almost unchanged).

Among the alignment states of the liquid crystal molecules in the first and second metastable states shown in FIG. 14, the alignment state shown on the upper side is a value V _{1-1 in} which the effective value of the drive signal is relatively small,
The rising state of the liquid crystal molecules when V _2-1 is shown, and the orientation state shown at the upper side is the rising state of the liquid crystal molecules when the effective value of the drive signal is V _1-2 or V _2-2, which is high to some extent. In any of the metastable states, the liquid crystal molecule changes the rising state according to the effective value of the drive signal while maintaining the alignment state in the metastable state.

In the first and second metastable states, the rising state of liquid crystal molecules changes according to the effective value of the drive signal, but the twist alignment state is maintained as it is. The state is also maintained until a metastable state is reset by applying a reset pulse that causes the liquid crystal molecules 18a to rise and align substantially perpendicularly to the surfaces of the substrates 11 and 12.

Further, in FIG. 13, 21a, 22a
Shows the transmission axes of a pair of polarizing plates 21 and 22 arranged on the front surface side and the back surface side of the liquid crystal cell 10 with the liquid crystal cell 10 interposed therebetween.
In this embodiment, the front polarizing plate 21 has a transmission axis 21a.
Are arranged so as to be obliquely intersecting with the alignment treatment direction 11a of the front side substrate 11 of the liquid crystal cell 10 at a shift angle of about 45 °, and the back side polarizing plate 22 has its transmission axis 22a whose front side is the front side polarizing plate 21. Are arranged in a direction substantially orthogonal to the transmission axis 21a.

On the other hand, the drive circuit 40 includes the liquid crystal cell 10
These scanning electrodes 13 are sequentially selected by sequentially selecting the scanning electrodes 13 of
And a data signal to each signal electrode 14 in synchronism therewith, the potential difference between the scan signal and the data signal is generated between the electrodes 13 and 14 of each pixel portion of the liquid crystal cell 10. This driving circuit 40 applies the reset pulse between the electrodes 13 and 14 of each pixel portion of the liquid crystal cell 10 and then applies the voltage according to the first and second metastable states. Is applied, and then a drive signal whose effective value changes in a range lower than the voltage value of the reset pulse is applied.

The liquid crystal display device of this embodiment uses external light such as natural light or indoor illumination light to reflect the light incident from the front surface side by the reflection plate 30 arranged on the rear surface side for display. For display driving, the respective pixel parts of the liquid crystal cell 10 are
After applying the reset pulse between the electrodes 13 and 14, the selection pulse is applied to switch the liquid crystal cell 10 to one of the first and second metastable states, and in the metastable state, the electrodes 13 and 14 are switched. This is performed by applying a drive signal whose effective value changes in a range lower than the voltage value of the reset pulse in between.

In this case, before driving the liquid crystal display device,
The liquid crystal molecules of the liquid crystal cell 10 are aligned in the above-mentioned initial alignment state (non-twist alignment state with splay distortion). Board 1
Oriented so as to rise almost perpendicularly to the 1 and 12 planes,
Depending on the selection pulse applied thereafter, the first or second metastable state is oriented.

When the driving of the liquid crystal display device is started, that is, when the power switch is turned on, the above-mentioned spray distortion eliminating pulse is applied from the driving circuit 40 between the electrodes 13 and 14 of all the pixel portions, and thereafter. By applying the selection pulse for selecting one of the first and second metastable states, the display drive can be started after all the pixel portions have the same metastable state.

In the above liquid crystal display device, liquid crystal molecules of the liquid crystal cell 10 are aligned in either the first or second metastable state,
Substrate 11, 1 of liquid crystal molecules in each metastable state
The rising state with respect to the two surfaces is changed according to the effective value of the drive signal to control the light transmission state. When the first metastable state is selected, the liquid crystal molecules are aligned on one of the substrates. Almost 1 in one direction based on the processing direction
When the second metastable state is selected with the electro-optical characteristics of the display device including the liquid crystal cell and the polarizing plate that are twist-aligned at a twist angle of 80 °, when the second metastable state is selected, the liquid crystal molecules change the alignment treatment direction of the one substrate. As a reference, it has the electro-optical characteristics of a display device including a liquid crystal cell and a polarizing plate that are twist-aligned in a direction opposite to the first metastable state with a twist angle of about 180 °.

That is, this liquid crystal display device has the electro-optical characteristics of two display devices in which the alignment states of the liquid crystal molecules of the liquid crystal cell are different from each other. Therefore, among the transmission states to be controlled stepwise, The plurality of transmission states can be controlled by utilizing one electro-optical characteristic, and the other plurality of transmission states can be controlled by utilizing the other electro-optical characteristic.

In this case, in the above embodiment, the liquid crystal cell 10
The direction of the transmission axis 21a of the front-side polarizing plate 21 of the pair of polarizing plates 21, 22 arranged with the liquid crystal cell 10 in between.
About 45 with respect to the alignment treatment direction 11a of the front substrate 11.
Since the angle of deviation is set to intersect diagonally,
When the first metastable state is selected to control the transmissive state and when the second metastable state is selected to control the transmissive state, display in the birefringence effect mode can be performed.

The display in the birefringence effect mode will be described. In both the first and second metastable states, the process in which the linearly polarized light that has passed through the front-side polarizing plate 21 and is incident passes through the liquid crystal cell 10. Then, due to the birefringence effect of the liquid crystal layer, each wavelength light becomes elliptically polarized light having a different polarization state, and each wavelength light transmits through the back side polarizing plate 22 at a transmittance corresponding to each polarization state, The light that has passed through the back-side polarizing plate 22 becomes light having a chromaticity corresponding to the ratio of the light intensities of the light of the respective wavelengths that make up the light. This light is reflected by the reflection plate 30, and the back side polarizing plate 22 and the liquid crystal cell 10 are reflected.
And the front side polarizing plate 21 are sequentially transmitted and emitted.

As described above, in the above liquid crystal display device, the birefringence action of the liquid crystal layer of the liquid crystal cell 10 and the pair of polarizing plates 21 and 22 are used.
And the value of Δnd (product of refractive index anisotropy Δn of liquid crystal and liquid crystal layer thickness d) of the liquid crystal cell 10, Polarizing plate 2
By selecting the directions of the transmission shafts 21a and 22a of 1 and 22, it is possible to perform almost achromatic black and white display or color display arbitrarily colored.

In order to display an almost achromatic black and white image, the liquid crystal cell 10 is arranged so that the light transmitted through the back side polarizing plate 22 becomes a light of low chromaticity with a small difference in the light intensity of the respective wavelength lights. Δnd and the transmission axes 21a and 22 of the polarizing plates 21 and 22.
The orientation of a may be selected, and for example, the alignment treatment directions 11a and 12a of both substrates 11 and 12 of the liquid crystal cell 10 and the transmission axes 21a and 22a of the front and back polarizing plates 21 and 22 are set as shown in FIG. In case of doing, Δnd of the liquid crystal cell 10
The value of (product of refractive index anisotropy Δn of liquid crystal and liquid crystal layer thickness d) may be set to about 600 nm.

Further, in the case of performing color display, the light transmitted through the back side polarizing plate 22 has a large difference in the light intensity of each wavelength light, that is, the color is colored according to the ratio of the light intensity of each wavelength light. Δnd of the liquid crystal cell 10 and the polarizing plate 2 so as to become light.
The orientations of the transmission axes 21a and 22a of 1 and 22 may be selected.

When performing this color display, the liquid crystal display device can obtain colored light by utilizing the birefringence action of the liquid crystal layer of the liquid crystal cell 10 and the polarization action of the pair of polarizing plates 21 and 22. Therefore, since light absorption is less than that of the one that colors light using a color filter, it is possible to obtain a bright display by increasing the transmittance of display light even in a reflective liquid crystal display device. .

In the above liquid crystal display device, the first
In both the second and the second metastable states, the liquid crystal cell 10
The birefringence of the liquid crystal layer changes due to the change in the rising state of the liquid crystal molecules according to the effective value of the drive signal applied between the electrodes 13 and 14 of each pixel section, and accordingly the back side polarizing plate 2
Since the polarization state of each wavelength light entering 2 changes, it is possible to change the light transmittance and chromaticity by controlling the effective value of the drive signal, and therefore the display brightness of each pixel unit. Gradation display that changes the value in multiple stages, or 1
It is possible to perform color display in which one pixel section displays a plurality of colors.

The above initial alignment state, that is, the state where the liquid crystal molecules are non-twisted with splay strain,
Although not used for actual display as described above, this initial orientation state is also a state in which display in the birefringence effect mode can be obtained.

15 to 17, the orientation processing directions 11a and 12a of both substrates 11 and 12 of the liquid crystal cell 10 and the transmission axes 21a and 22a of the front and back polarizing plates 21 and 22 are set as shown in FIG. The value of Δnd (product of refractive index anisotropy Δn of liquid crystal and liquid crystal layer thickness d) of the liquid crystal cell 10 is about 600 nm.
FIG. 15A and FIG. 15B show changes in light emission rate and display color with respect to applied voltage (effective value of drive signal) of the liquid crystal display device selected in FIG. Is the voltage-emission rate characteristic diagram and CIE in the initial alignment state.
Chromaticity diagram, (a) and (b) of FIG. 16 are a voltage-emission rate characteristic diagram and a CIE chromaticity diagram in the first metastable state, and FIG.
(A) and (b) are a voltage-emission rate characteristic diagram and a CIE chromaticity diagram in the second metastable state. In the chromaticity diagram of (b) of each figure, W indicates an achromatic color point.

First, the initial alignment state will be described.
The voltage-emissivity characteristic in the initial alignment state is shown in FIG.
As shown in (b) of FIG. 15, the applied voltage is 0 V (voltage It is almost black when no voltage is applied, and blue when a voltage (for example, about 5 V) for vertically aligning liquid crystal molecules is applied (for example, about 5 V).

The rising state of the liquid crystal molecules becomes the most vertical when the above-mentioned reset pulse is applied, but since the reset pulse application time is extremely short, the display in the reset state is not visible to the human eye. Almost unrecognized.

Next, the voltage-emission rate characteristics and the display chromaticity change in the first and second metastable states will be described. The twist alignment state of the liquid crystal molecules in the first metastable state and the second metastable state will be described. The twist alignment state of the liquid crystal molecules in the metastable state has a twist angle of about 180 ° and the twist directions are opposite to each other, and the transmission axis 21a of the front polarizing plate 21 is the front substrate 11 of the liquid crystal cell 10. Since the transmission axis 22a of the back side polarizing plate 22 is substantially perpendicular to the transmission axis 21a of the front side polarizing plate 21, The electro-optical characteristic when the metastable state is selected is substantially the same as the electro-optical characteristic when the second metastable state is selected.

That is, the voltage-emission rate characteristics in the first metastable state are as shown in FIG.
In the range of about 2V, the emission rate temporarily decreases slightly above about 1V, but shows a high emission rate. When the voltage is higher than that, the emission rate gradually decreases. As shown in (b) of FIG. 16, the change in chromaticity is white when a voltage of 1.509 V is applied.
It is black when a voltage of 850 V is applied.

The white x and y coordinate values are as follows:
x = 0.291, y = 0.319, and the Y value (brightness) is 29.4. Further, the x and y coordinate values of the black are x = 0.269 and y = 0.287, and Y
The value is 5.5.

The voltage-emission rate characteristic in the second metastable state is very similar to the voltage-emission rate characteristic in the first metastable state, as shown in FIG. There is also a change in chromaticity of the display with respect to the voltage, as shown in (b) of FIG.
White when a voltage of 1.509V is applied, 4.850V
It is black when the voltage is applied.

The white x and y coordinate values are
x = 0.292, y = 0.320, and the Y value (brightness) is 29.4. Further, the x and y coordinate values of the black are x = 0.269 and y = 0.287, and Y
The value is 5.5.

That is, in the above liquid crystal display device, the emission rate and the chromaticity of the display are as described above in accordance with the applied voltage regardless of whether the first metastable state is selected or the second metastable state is selected. And therefore the first and second
In any of the metastable states, by controlling the effective value of the drive signal in a plurality of stages, it is possible to perform black and white display with gradation.

When the power of the liquid crystal display device is turned off, the first
Alternatively, the alignment state of the liquid crystal molecules in the second metastable state is
After a few seconds to several minutes (depending on the characteristics of the liquid crystal 18 to be used and the characteristics and addition amount of the chiral agent) by natural discharge, the initial alignment state is restored, and the entire screen is in the initial alignment state when no voltage is applied (the above implementation It becomes almost black in the example).

The liquid crystal display device has the electro-optical characteristics of two display devices in which the alignment state of the liquid crystal molecules of the liquid crystal cell are different from each other. Since a plurality of transmission states can be controlled by utilizing one electro-optical characteristic, and a plurality of other transmission states can be controlled by utilizing the other electro-optical characteristic, the one electro-optical characteristic can be controlled. When the characteristics are used, that is, when the first metastable state is selected to control the transmission state, and when the other electro-optical characteristic is used, that is, the second metastable state is selected, the transmission state is changed. The number of steps driven in each metastable state is reduced, and therefore, it is possible to perform time-divisional driving with a small number of steps in each metastable state. Kill.

That is, the liquid crystal display device has a first metastable state (a state in which liquid crystal molecules are twisted in one direction with a twist angle of about 180 °) and a second metastable state (where the liquid crystal molecules are in a first direction). 18 in the direction opposite to the metastable state of 1
The state of twist orientation at a twist angle of 0 ° is a state in which the twist angles of liquid crystal molecules are almost the same and the twist directions are opposite, and the transmission axis 21a of the front polarizing plate 21 is the front substrate 11 of the liquid crystal cell 10. Of the first side metastable state because 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 electro-optical characteristics when selected and the electro-optical characteristics when the second metastable state is selected are almost the same.

For this reason, for example, when performing black and white display with 10 gradations, every other 5 gradations (for example, odd gradations)
Can be displayed by selecting the first metastable state, and every other five gray levels (for example, even gray levels) can be displayed by selecting the second metastable state. , The number of stages of the effective value of the drive signal when the first metastable state is selected to control the transmissive state, and the effective value of the drive signal when the second metastable state is selected to control the transmissive state Since the number of steps may be half of the total number of gradations, a large operating voltage margin can be taken for the drive duty of the liquid crystal cell 10.

In the liquid crystal display device having the voltage-emission rate characteristic and the color change characteristic as shown in FIGS. 15 to 17, every 5th gradation out of 10 gradations is set to the first gradation.
When selecting and displaying the metastable state of, and displaying every other five gradations by selecting the second metastable state, the first metastable state is selected and the transmissive state is selected. The effective value of the drive signal when controlling is from 1.509V (white display voltage) to
Set in 5 steps between 4.850V (black display voltage),
When the second metastable state is selected and the transmission state is controlled, the effective value of the drive signal is 1.509 V (white display voltage) to
It may be set in 5 steps between 4.850 V (black display voltage).

Therefore, according to the above liquid crystal display device,
Even if the liquid crystal cell 10 is of a simple matrix type that is driven by controlling the effective value of the drive signal, the operating voltage margin is increased with respect to the drive duty, and time-division drive with high duty is possible. It is possible to realize the display of a high-definition image having a large number of pixels.

Further, in the above liquid crystal display device, the twist direction of the liquid crystal molecules in the first metastable state and the twist direction of the liquid crystal molecules in the second metastable state are opposite to each other. Since the direction of the viewing angle when the state is selected (the viewing direction in which the display has the highest contrast) and the direction of the viewing angle when the second metastable state is selected are different from each other, each pixel unit is set to 1 ~ If the first metastable state and the second metastable state are alternately selected and driven for every several frames (preferably for each frame), the apparent visual angle characteristic has a visual angle in two directions. Thus, a wide viewing angle display can be performed.

In the liquid crystal display device, as described above, the value of Δnd of the liquid crystal cell 10 and the directions of the transmission axes 21a and 22a of the polarizing plates 21 and 22 are determined by the light transmitted through the back side polarizing plate 22. By selecting so that the light intensity difference between the light beams of the respective wavelengths is large, it is possible to perform color display in which an arbitrary color is applied.

In the case of this color display, the value of Δnd of the liquid crystal cell 10 and the transmission axes 21a and 22a of the polarizing plates 21 and 22.
The display color when the first metastable state is selected and the display color when the second metastable state is selected (any display color depends on the effective value of the drive signal) Can be made to be almost the same, or the display color of each can be made different.

[Modification of Third Embodiment] The liquid crystal display device of the above embodiment displays by utilizing the birefringence effect of the liquid crystal layer of the liquid crystal cell 10 and the polarization effect of the pair of polarizing plates 21 and 22. In addition to that, the front and back polarizing plates 21 and 22
A retardation plate may be arranged between one or both of the above and the liquid crystal cell 10.

As an example thereof, the first example shown in FIG. 7 is used.
As in the modification of the embodiment, the retardation plate 23 is provided between the front-side polarizing plate 21 and the liquid crystal cell 10, and its optical axis (eg, slow axis) is oblique to the transmission axis 21a of the front-side polarizing plate 21. It is conceivable to shift the positions.

According to the liquid crystal display device of this modification, the linearly polarized light that has passed through the front polarizing plate 21 and is incident is first converted into elliptically polarized light having different polarization states due to the birefringence effect of the retardation plate 23. The reflected light changes its polarization state by the birefringence effect of the liquid crystal layer of the liquid crystal cell 10 and enters the back-side polarizing plate 22.
By appropriately selecting the value of d, the retardation of the retardation plate 23 and the direction of the optical axis thereof, it is possible to suppress the banding of white display in black-and-white display and to make the display color sharp and multicolor in color display. You can measure.

That is, even in the liquid crystal display device which is not provided with the above-mentioned retardation plate, the liquid crystal so that the light transmitted through the back side polarizing plate 22 becomes the light of low chromaticity in which the difference in the light intensity of each wavelength light is small. By selecting Δnd of the cell 10 and the directions of the transmission axes 21a and 22a of the polarizing plates 21 and 22, almost achromatic black and white display can be performed, but in the display in the birefringence effect mode, it is incident on the back side polarizing plate 22. Since the light to be emitted is elliptically polarized light having different polarization states due to the birefringence effect of the liquid crystal layer of the liquid crystal cell 10, the transmittance of each wavelength light transmitted through the back side polarizing plate 22 is to some extent. Therefore, the light transmitted through the back-side polarizing plate 22 is slightly colored according to the ratio of the light intensity of each wavelength light, and the white display is colored.

However, as in this embodiment, the retardation film 23
Is added, linearly polarized light that has passed through the front-side polarizing plate 21 and is incident on the back-side polarizing plate 22 changes its polarization state due to the birefringence action of both the retardation plate 23 and the liquid crystal layer of the liquid crystal cell 10. The conditions that determine the polarization state of the light incident on the back side polarizing plate 22, that is, the value of Δnd of the liquid crystal cell 10, the retardation of the retardation plate 23, the direction of the optical axis thereof, and the like are substantially different between the light of each wavelength. If the setting is made so that the light is transmitted through the back-side polarizing plate 22 with no transmittance, it is possible to suppress the banding of the white display and perform better black and white display.

Further, the value of Δnd of the liquid crystal cell 10 and the directions of the transmission axes 21a and 22a of the polarizing plates 21 and 22 are such that the light transmitted through the rear polarizing plate 22 has a large difference in the light intensity of each wavelength light. When the retardation plate 23 is added to the liquid crystal display device which is selected so as to perform the color display, the conditions for determining the polarization state (the value of Δnd of the liquid crystal cell 10, the retardation of the retardation plate 23 and the optical property thereof) are determined. Axis direction etc.)
Can be set so that light of each wavelength transmits through the back side polarizing plate 22 with a transmittance that is significantly different. By doing so, it is possible to perform a clear color display with a large number of colors.

[Other Embodiments] In the liquid crystal display device of the present invention, the liquid crystal cell 10 is not limited to the first to third embodiments, and liquid crystal molecules are aligned on one of the substrates. Almost 0 ° in one direction based on the processing direction
A liquid crystal layer initially aligned in a non-twisted or twisted splay alignment state with a twist angle of about 180 °, and a reset pulse having a sufficiently high voltage value is applied to the liquid crystal layer, and subsequently the voltage value is reset. By selectively applying two kinds of selection pulses whose values are sufficiently lower than the pulse and whose values are different from each other, the liquid crystal molecules are further twisted by about 180 ° in the one direction from the initial alignment state to eliminate the splay distortion. A stable state (a state in which twist orientation is performed in one direction with a twist angle of approximately 180 ° to approximately 360 ° with respect to the orientation processing direction of one substrate) and a state in which the orientation direction is substantially opposite to the one direction from the initial orientation state. The second metastable state in which splay distortion is eliminated by twisting 180 ° (almost 180 ° in the other direction with reference to the orientation processing direction of one substrate).
It may be oriented in a twist orientation or a non-twist orientation at a twist angle of about 0 °.

The liquid crystal display devices of the first to third embodiments are all of the reflection type in which the reflection plate 30 is arranged on the back surface side thereof. Transmission type liquid crystal display device (reflector 3
It can also be applied to those without 0).

Furthermore, the present invention can be applied to a reflection type liquid crystal display device in which only one polarizing plate is provided, the polarizing plate is arranged on the front surface side of the liquid crystal cell, and the reflecting plate is arranged on the rear surface side of the liquid crystal cell. In that case, a reflection plate may be arranged 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 is formed of a metal film, and this electrode also serves as the reflection plate. You may.

[0204]

According to the liquid crystal display device of the present invention, the liquid crystal molecules of the liquid crystal cell are aligned in either of the first and second metastable states, and the liquid crystal molecules in the respective metastable states rise to the substrate surface. Is controlled according to the effective value of the drive signal to control the light transmission state. When the first metastable state is selected, liquid crystal molecules are aligned in a specific state between the pair of substrates. When the second metastable state is selected, which has electro-optical characteristics of a display device including a cell and a polarizing plate, a specific state in which liquid crystal molecules are different from the first metastable state between the pair of substrates. Since it has the electro-optical characteristics of a display device that is composed of a liquid crystal cell and a polarizing plate that are aligned with each other, one of the electro-optical characteristics is used to control a plurality of transmission states among the transmission states to be controlled stepwise. , Other more The control of the transmission state can be performed by using the other electro-optical properties.

Therefore, according to this liquid crystal display device, the total number of stages of the transmissive state is used when the one electro-optical characteristic is utilized, that is, when the first metastable state is selected to control the transmissive state. And when the other electro-optical characteristic is utilized, that is, when the second metastable state is selected to control the transmissive state. Therefore, the step of driving in each metastable state can be performed. Since the number is reduced, it is possible to perform time-divisional driving with a small number of steps in each metastable state.

Therefore, according to this liquid crystal display device,
Although using a simple matrix type liquid crystal cell that is driven by controlling the effective value of the drive signal, the operating voltage margin is increased with respect to the drive duty to enable time-division drive at high duty, It is possible to display a large number of high-definition images.

[Brief description of drawings]

FIG. 1 is a perspective view showing 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 of the liquid crystal display device in a first metastable state.

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

FIG. 7 is a cross-sectional view of a liquid crystal display device showing a modification of the first embodiment.

FIG. 8 is a perspective view showing a basic configuration of a liquid crystal display device according to a second embodiment of the present invention, in an initial alignment state, a first metastable state and a second metastable state.

FIG. 9 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. 10 is a voltage-emission rate characteristic diagram and a CIE chromaticity diagram in the initial alignment state of the liquid crystal display device.

FIG. 11 is a voltage-emission rate characteristic diagram and a CIE chromaticity diagram of the liquid crystal display device in a first metastable state.

FIG. 12 is a voltage-emission rate characteristic diagram and a CIE chromaticity diagram in the second metastable state of the liquid crystal display device.

FIG. 13 is a perspective view showing a basic configuration of a liquid crystal display device according to a third embodiment of the present invention in an initial alignment state, a first metastable state and a second metastable state.

FIG. 14 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. 15 is a voltage-emission rate characteristic diagram and a CIE chromaticity diagram in an initial alignment state of the liquid crystal display device.

FIG. 16 is a voltage-emission rate characteristic diagram and a CIE chromaticity diagram of the liquid crystal display device in a first metastable state.

FIG. 17 is a voltage-emission rate characteristic diagram and a CIE chromaticity diagram in the second metastable state of the liquid crystal display device.

[Explanation of symbols]

10 ... Liquid crystal cell 11a ... Orientation processing direction of front side substrate 12a ... Orientation processing direction of back side substrate 18 ... Nematic liquid crystal added with chiral agent 21, 22 ... Polarizing plate 21a, 22a ... Transmission axis 23 ... Retardation plate 30 ... Reflector 40 ... Drive circuit

─────────────────────────────────────────────────── --Continued from the front page (56) References JP-A-8-95091 (JP, A) JP-A-8-179274 (JP, A) JP-A-8-271934 (JP, A) JP-A-6- 230751 (JP, A) JP-A 2-10 (JP, A) (58) Fields investigated (Int.Cl. ⁷ , DB name) G02F 1/133 560 G02F 1/133 510 G02F 1/133 545 G09G 3 / 36

Claims (3)

(57) [Claims] 1. A liquid crystal cell comprising a liquid crystal cell and a polarizing plate disposed on at least the front surface side of the front and back surfaces of the liquid crystal cell, wherein the liquid crystal cell is provided with an electrode on the inner surface and is subjected to an alignment treatment. A nematic liquid crystal added with a chiral agent is sandwiched between a pair of substrates, the liquid crystal molecules of which are lower than those after application of a reset pulse of a voltage value that rises and is aligned almost perpendicular to the substrate surface. By applying a selection pulse of a predetermined voltage value, the liquid crystal molecules are brought into a first metastable state in which they are aligned in a specific state between the pair of substrates, and after application of the reset pulse, another predetermined lower voltage is applied. By applying a selection pulse of a voltage value, the liquid crystal molecules have a characteristic of becoming a second metastable state in which they are oriented between the pair of substrates in a specific state different from the first metastable state, Serial pixel portions of the liquid crystal cell, the first by applying the selection pulse after applying the reset pulse
And a second metastable state, and in the metastable state, the liquid crystal is driven by applying a drive signal whose effective value changes in a range lower than the voltage value of the reset pulse. Display device. 2. A liquid crystal cell, a polarizing plate disposed on at least the front surface side of the front and back surfaces of the liquid crystal cell, and a drive circuit for driving the liquid crystal cell, wherein the liquid crystal cell is provided on the inner surface. A nematic liquid crystal to which a chiral agent is added is sandwiched between a pair of substrates provided with electrodes and subjected to an alignment treatment, and the liquid crystal molecules rise and align almost vertically to the substrate surface. After the reset pulse having the voltage value is applied, the selection pulse having a predetermined voltage value lower than the reset pulse is applied to the first metastable state in which the liquid crystal molecules are aligned in a specific state between the pair of substrates, and the reset is performed. After the application of the pulse, by applying a selection pulse having another predetermined voltage value lower than that, the liquid crystal molecules are aligned between the pair of substrates in a specific state different from the first metastable state. 2 has a characteristic of becoming a metastable state, and the drive circuit applies one of the first and second metastable states to each pixel portion of the liquid crystal cell, after applying the reset pulse. A liquid crystal display device characterized in that a selection pulse for selection is applied, and then a drive signal whose effective value changes in a range lower than the voltage value of the reset pulse is applied. 3. The liquid crystal cell, wherein the liquid crystal molecules are substantially zero in one direction with respect to the alignment treatment direction of one of the substrates.
The liquid crystal layer is initially aligned in a non-twisted or twisted splay alignment state with a twist angle of approximately 180 ° to 180 °, and the reset pulse is applied to the liquid crystal layer, and then the two selection pulses are successively applied. By selectively applying the liquid crystal molecules, the liquid crystal molecules are twisted further by about 180 ° from the initial alignment state to eliminate the splay strain, and the first alignment state is changed to the one direction. 3. The liquid crystal display device according to claim 1, wherein the liquid crystal display device is oriented in a second metastable state in which splay distortion is eliminated by twisting by approximately 180 ° in the opposite direction.