JPH08313877A - Liquid crystal device - Google Patents

Abstract

PURPOSE: To prevent monostabilization and the degradation in contrast. CONSTITUTION: An information signal is impressed from an information signal impression circuit (not shown in Fig.) to a liquid crystal panel P and ferroelectric liquid crystals attain a first optically stable state or second optically stable state with every pixel when an liquid crystal device 400 is driven. The respective pixels display either of a bright state or dark state when the pixels are irradiated with rays from a back light device 10. At this time, the absorption axis of a polarizer 9b is aligned to the direction of the first optically stable state. A motor M is driven and an analyzer 9a and the polarizer 9b are rotated by a prescribed angle and the absorption axis of the polarizer 9b is aligned to the direction of the second optically stable state when the prescribed time elapses in this state. The signal from the information signal impression circuit to the liquid crystal panel P is changed over and all the optically stable states of the ferroelectric liquid crystals are changed. As a result, the dark state or bright state is continuously displayed. The optically stable states of the ferroelectric liquid crystals are properly changed over even in the case the bright state or the dark state is continuously displayed and, therefore, the monostabilization is prevented.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention generally relates to a liquid crystal device using a ferroelectric liquid crystal, and more particularly to prevention of a monostabilization phenomenon.

[0002]

2. Description of the Related Art In recent years, a display element (hereinafter referred to as a "liquid crystal panel") of a type in which transmitted light rays are controlled by using a chiral smectic liquid crystal, particularly a ferroelectric liquid crystal, in combination with a polarizing element by utilizing a refractive index anisotropy. ) Is Clark
And Lagerwall (JP-A-56-107216, US Pat. No. 4,367,924, etc.).

This ferroelectric liquid crystal generally has a non-helical chiral smectic C phase (SmC ^* ) or H phase (SmH ^* ) in a specific temperature range, and responds to an electric field applied in this state. Has either a first optical stable state or a second optical stable state, and has the property of maintaining that state when no electric field is applied, that is, bistability, and is resistant to changes in the electric field. It responds quickly and is expected to be widely used for high-speed and memory type display devices.

FIG. 1 shows the structure of the liquid crystal panel.
It is explained along.

This liquid crystal panel P, as shown in FIG.
A pair of glass substrates 1a, 1b arranged in parallel (hereinafter,
“Upper substrate 1a” and “lower substrate 1b”) are provided, and a large number of stripe-shaped transparent electrodes 2a, ..., 2b, ... Are formed on the surfaces of these upper substrate 1a and lower substrate 1b, respectively. (Hereinafter, referred to as “information electrode 2a, ...” And “scan electrode 2b, ...”). In addition, these information electrodes 2
The scanning electrodes 2b, ... Are covered with insulating films 3a, 3b, respectively, and the insulating films 3a, 3b are covered with alignment control films 5a, 5b. In addition,
The surfaces of these orientation control films 5a and 5b are subjected to a rubbing treatment so that the rubbing direction is the direction indicated by D. Further, a large number of spacers 6, ... Are arranged in the gap between the upper substrate 1a and the lower substrate 1b to define the gap size, and the ferroelectric liquid crystal 7 is arranged. The information electrodes 2a, ... And the scanning electrodes 2b ,.
Form a matrix electrode and form a large number of pixels at each intersection.

Further, on both sides of the liquid crystal panel P, an analyzer 9a as a second polarizing means and a polarizer 9b as a first polarizing means are respectively arranged. Here, as shown in FIG. 2, the analyzer 9a and the polarizer 9b become crossed Nicols, and their respective absorption axes 11a,
11b are orthogonal to each other, and the polarizer absorption axis 11b
Are arranged so as to coincide with the molecular long axis direction of the ferroelectric liquid crystal 7 in the first optical stable state A (in other words, form an angle θ with the rubbing direction D). Also,
A backlight device (illuminating means) 1 is provided below the polarizer 9b.
0 is attached.

By the way, the ferroelectric liquid crystal molecule takes either one of the first optically stable state A and the second optically stable state B for each pixel.

Then, in the pixel in which the ferroelectric liquid crystal molecules are in the first optical stable state A, the light rays passing from the backlight device 10 through the polarizer 9b are birefringent by the ferroelectric liquid crystal molecules. However, since the analyzer absorption axis 11a is orthogonal to the direction of the first optical stable state A (see FIG. 2), the pixel displays a dark state.

On the other hand, in the pixel in which the ferroelectric liquid crystal molecule is in the second optical stable state B, the light beam passing from the backlight device 10 through the polarizer 9b is birefringent by the ferroelectric liquid crystal molecule. And then passes through the analyzer 9a. In this case, the pixel displays a bright state.

The liquid crystal panel P described above displays various images depending on the combination of the bright state and the dark state.

[0011]

By the way, in the liquid crystal panel P as described above, there is no particular problem when switching is performed at relatively short intervals, but when the bright state or the dark state is continuously written. Had various problems.

That is, when the bright state or the dark state is continuously written, the ferroelectric liquid crystal molecules are in the first optically stable state A.
Alternatively, one of the second optical stable state B and the second optical stable state B is continuously held, and as a result, the switching threshold from the first optical stable state A to the second optical stable state B There was a difference in the threshold value from the optical stable state B to the first optical stable state A. Specifically, when the ferroelectric liquid crystal molecules are held in the first optical stable state A for a long time, the threshold value from the second optical stable state B to the first optical stable state A decreases, On the contrary, the threshold value from the first optical stable state A to the second optical stable state B was increased, and there was a difference between these two threshold values. When the ferroelectric liquid crystal molecules are held in the second optical stable state B for a long time, the threshold value from the first optical stable state A to the second optical stable state B is lowered, and conversely the second optical stable state B is lowered. Optically stable state B
To the first optically stable state A from
There was a difference between the two thresholds. Then, due to the difference in the threshold value, the ferroelectric liquid crystal molecules cannot be stably positioned in the opposite monostable state,
There is a problem that the bistable memory property is lost (such a phenomenon is hereinafter referred to as "monostabilization phenomenon").

When such a monostabilization phenomenon occurs, the fluctuation amount of the liquid crystal molecules with respect to the information signal during matrix driving differs between the first optically stable state A and the second optically stable state B, There is a problem that light leakage in the dark state becomes large and the contrast is remarkably lowered depending on how to set the crossed Nicols.

Further, when the driving pulse width for switching to each state is large, there is a problem that the limit value for maintaining each stable state is also affected.

The present inventor investigated the monostabilization phenomenon (that is, the change in the threshold value) by experiments. The contents of the experiment will be briefly described below.

The present inventor created a plurality of liquid crystal panels P during an experiment, and for the created liquid crystal panels P, a threshold value from the first optically stable state A to the second optically stable state B, and the second The threshold values from the optical stable state B to the first optical stable state A were measured respectively, and it was confirmed that they were bistable.

Next, a predetermined voltage is applied to these liquid crystal panels P to hold the specific pixels in the first optically stable state A, and the remaining pixels in the second optically stable state B. Each of them was kept at that temperature for 3 days at a temperature of 30 ° C. Further, in the other liquid crystal panel P, the light and dark are inverted at intervals of 1 minute, and the ferroelectric liquid crystal molecules have a constant optical stable state (the first optical stable state A or the second optical stable state B). ) Was kept for more than 1 minute. This reversal was repeated at a temperature of 30 ° C. for 3 days.

Thereafter, * Pixels held in the first optical stable state A for 3 days * Pixels held in the second optical stable state B for 3 days * First optical stable state A and second optical stable state A Steady state B
The threshold was measured for each of the pixels for which the and were switched.

The measured threshold value is V _{I (AB)} ; from the first optically stable state A to the second optical stability state in the initial state.
Threshold value V _{I (BA)} required to invert to the optically stable state B of;
Threshold value V _{A (AB)} required to invert to the optical stable state B of the first optical stable state A to the second optical stable state in a pixel held in the first optical stable state A for 3 days Threshold required to invert to state B V _{A (BA)} ; Inversion from second optically stable state B to first optically stable state A in a pixel held in first optically stable state A for 3 days Threshold V _{B (AB)} required to make it necessary to invert from the first optical stable state A to the second optical stable state B in a pixel held in the second optical stable state B for 3 days Threshold value V _{B (BA)} ; a threshold value required to invert from the second optical stable state B to the first optical stable state A in a pixel held in the second optical stable state B for 3 days. . Then, based on these thresholds V _{A (AB)} , ...
The parameters P _AB and P _BA of the following equation were calculated.

[0020]

(Equation 1) Table 1 shows the values of the parameters P _AB and P _BA . In addition,
As the parameters P _AB and P _BA are smaller, there is less difference in the threshold value, and the monostabilization phenomenon is less.

[0021]

[Table 1] From this experiment, in the case of the inverted sample which was repeatedly switched every minute, although the parameters were small and the monostabilization phenomenon was small, in the case of the retained sample which was kept in the specific optical stable states A and B without repeating the switching. , It was understood that the monostabilization phenomenon occurred with each parameter increasing.

In view of this, the present invention secures the bistability of the ferroelectric liquid crystal by preventing the threshold value from changing when a bright state or a dark state is continuously written for a long time, and at the same time prevents the deterioration of the contrast. It is intended to provide.

[0023]

SUMMARY OF THE INVENTION The present invention has been made in view of the above circumstances, and includes a ferroelectric liquid crystal element having a pair of substrates and a ferroelectric liquid crystal sandwiched between the pair of substrates. An illuminating means that is provided along with the ferroelectric liquid crystal element to illuminate the ferroelectric liquid crystal element, a first polarizing means disposed between the ferroelectric liquid crystal element and the illuminating means, and the ferroelectric A second polarizing means arranged on the light emission side of the liquid crystal element and in a crossed Nicols pattern with the first polarizing means; and a control means for inputting a drive signal to the ferroelectric liquid crystal element. In the liquid crystal device provided, a polarization axis switching means for switching the polarization axes of the first and second polarization means is provided, and the first and second polarization means are maintained in a state where the crossed Nicols are maintained. The polarization axis of the polarizing means
When the polarization axis is switched by the polarization axis switching means at the same time as the polarization axis is switched by the polarization axis switching means, the control means outputs the drive signal at the same time as the direction of the long axis of the molecule of the ferroelectric liquid crystal in the first or second optically stable state. It is characterized in that the optical stable state of the ferroelectric liquid crystal is changed by switching.

In this case, the polarization axis switching means is a motor that rotationally drives the first and second polarization means, and the polarization axes are changed by rotating the first and second polarization means. You may make it switch.

Further, the first polarizing means and the second polarizing means are arranged so as to oppose the ferroelectric liquid crystal element, and a nematic liquid crystal element is provided side by side with the nematic liquid crystal element. And a polarization circuit for linearly polarizing light, the polarization axis switching means is a drive circuit for turning on / off the nematic liquid crystal element, and the first and second are turned on / off by turning on / off the nematic liquid crystal element. The polarization axis of the polarizing means may be switched. In this case, the nematic liquid crystal element is composed of a pair of transparent substrates and a nematic liquid crystal arranged in a gap between the substrates, and both of the transparent substrates are arranged so that the rubbing directions of the pair of transparent substrates form a predetermined angle. It is preferable that the substrate is subjected to a rubbing treatment. The polarization direction of the polarizing plate in the first polarizing means is a first polarization direction, and the polarization direction of the polarizing plate in the second polarizing means is a second polarization direction. And the rubbing direction of the transparent substrate adjacent to the polarizing plate is defined as a first outer rubbing direction, and the rubbing direction of the transparent substrate adjacent to the ferroelectric liquid crystal element in the first polarizing means is defined as a first rubbing direction. 1, and the rubbing direction of the transparent substrate adjacent to the polarizing plate in the second polarizing means is defined as the second outer rubbing direction, and the ferroelectric liquid crystal element in the second polarizing means is formed. Set the rubbing direction of the transparent substrate on the adjacent side to the second
, The first polarization direction and the first outer rubbing direction, and the second polarization direction and the second outer rubbing direction respectively match, The outer rubbing direction and the first inner rubbing direction of the first and second optically stable states of the ferroelectric liquid crystal in the first or second optically stable state are alternatively coincident with each other, and It is preferable that the inner rubbing direction and the first inner rubbing direction, and the second outer rubbing direction and the first outer rubbing direction each form a right angle.

Further, the control means has a first signal for keeping the ferroelectric liquid crystal in a first optically stable state and a second signal for keeping the ferroelectric liquid crystal in a second optically stable state. And, and when the polarization axis is switched by the polarization axis switching means, a second signal is output instead of the first signal and a first signal is output instead of the second signal. ,
It is preferable to do so.

[0027]

According to the above construction, when a drive signal is input from the control means to the ferroelectric liquid crystal element, the ferroelectric liquid crystal is in either the first optical stable state or the second optical stable state for each pixel. Take something On the other hand, the light beam from the illumination means is applied to the ferroelectric liquid crystal element via the first polarization means. Here, for example, assuming that the polarization axis of the first polarizing means is aligned with the molecular long axis direction of the ferroelectric liquid crystal in the first optically stable state, the ferroelectric liquid crystal has the first optical axis. Pixels in the optically stable state display the dark state, and pixels in which the ferroelectric liquid crystal is in the second optically stable state display the bright state. And
Various information will be displayed depending on the combination of the bright state and the dark state.

Next, when the polarization axis switching means is activated, the polarization axes of the first and second polarization means are switched and the first and second polarization means are switched.
The polarization axis of the polarizing means is aligned with the molecular long axis direction of the ferroelectric liquid crystal in the second optically stable state. At the same time, the control means switches the drive signal to change the optically stable state of the ferroelectric liquid crystal. That is, the ferroelectric liquid crystal in the first optical stable state is switched to the second optical stable state, and conversely, the ferroelectric liquid crystal in the second optical stable state is switched to the first optical stable state. To the stable state. Therefore, the pixel that was displaying the bright state before switching the polarization axis continues to display the bright state after switching, and the pixel that was displaying the dark state continues to display the dark state after switching. This means that the image of the ferroelectric liquid crystal element does not change even if the polarization axis is switched.

[0029]

Embodiments of the present invention will be described below with reference to the drawings. The same parts as those shown in FIGS. 1 and 2 are designated by the same reference numerals and the description thereof will be omitted.

First, FIG. 3 shows the first embodiment of the present invention.
It will be described with reference to FIG.

FIG. 3 is a block diagram showing the overall configuration of the liquid crystal device 400 according to this embodiment. In this embodiment, the scanning electrode 2 of the liquid crystal panel (ferroelectric liquid crystal element) P is used.
A scanning signal applying circuit 402 is connected to b, ...
An information signal application circuit (control means) 403 is connected to the other information electrodes 2a, .... In addition, these circuits 40
A scanning signal control circuit 404, an information signal control circuit 406, a drive control circuit 405, and a graphic controller 407 are sequentially connected to 2, 403. And
From the graphic controller 407 to the drive control circuit 40
Data and various signals are transmitted to the scan signal control circuit 5 from the scan signal control circuit 404 to the scan signal application circuit 40.
2 includes scanning line address data and the like, the information signal control circuit 4
Display data is transmitted from 06 to the information signal application circuit 403. Further, the scanning signal application circuit 402 applies a scanning signal having a waveform determined by the scanning method signal to the scanning electrodes 2b, ... Determined by the address data, and the information signal application circuit 403 displays white or black displayed by the display data. It is configured to apply an information signal having a waveform determined by two of the content and the scanning method signal.

By the way, in this embodiment, the information signal has a waveform as shown in FIG. 4, and in the pixel to which the information signal (driving signal) S _A is applied, the ferroelectric liquid crystal molecules are the first. In the pixel to which the information signal (driving signal) S _B is applied, the ferroelectric liquid crystal molecules take the second optical stable state B.

On the other hand, the polarizer (first polarization means) 9b is
As shown in FIG. 5, it is configured to be connected to a motor (polarization axis switching means) M so as to be rotationally driven by an angle 2θ around the screen central axis o, and its absorption axis 9b is the first optical axis. A position that coincides with the molecular long axis direction of the ferroelectric liquid crystal 7 in the stable state A (a position inclined by −θ with respect to the rubbing direction D; hereinafter referred to as “−θ position”) (FIGS. 2 and 5). A position where the absorption axis 9b coincides with the molecular long axis direction of the ferroelectric liquid crystal 7 in the second optical stable state B (a position inclined by + θ with respect to the rubbing direction D. Hereinafter, referred to as “+ θ position”). Yes) and (see FIGS. 6 and 7).

On the other hand, the analyzer (second polarization means) 9a
Is also connected to the motor M in the same manner as the polarizer 9b and is driven to rotate about the screen central axis o by an angle 2θ, so that the crossed Nicols of the analyzer 9a and the polarizer 9b are maintained. It has become. The motor M is activated at regular intervals (for example, every 3 minutes), whereby the analyzer 9a and the polarizer 9b are configured to selectively take the positions shown in FIGS. 5 and 6. . Further, θ is within 1 °. The analyzer 9a and the polarizer 9b are rotated as described above, but the liquid crystal panel P and the backlight device 10 remain stationary at predetermined positions.

By the way, the above-mentioned information signals S _A and S _B
Is selected and applied for each pixel based on whether to display the dark state or the bright state as shown in Table 2. These signals S _A and S _B are switched at the same time when the motor M is activated. is, the information signal S _a is the information signal S _B is applied to the pixel that has been applied, the information signal S _a is to be applied to the pixel in which the information signal S _B has been applied.

[0036]

[Table 2] Next, the operation of this embodiment will be described.

Now, when the liquid crystal device 400 is driven, the information signal S is sent from the information signal applying circuit 403 to the liquid crystal panel P.
_A and S _B are input, and the scanning signal is input from the scanning signal applying circuit 402 to the liquid crystal panel P. Then, the ferroelectric liquid crystal 7 takes either the first optical stable state A or the second optical stable state B for each pixel.

Here, the analyzer 9a and the polarizer 9b are -θ.
It is assumed that the polarizer absorption axis 11b at the position is aligned with the molecular long axis direction of the ferroelectric liquid crystal 7 in the first optically stable state A as shown in FIG. In this case,
In the pixel in which the ferroelectric liquid crystal molecule is in the first optical stable state A, the backlight device 10 is connected to the polarizer 9 in the pixel.
The light beam that has passed through b undergoes birefringent interaction by the ferroelectric liquid crystal molecules, but the analyzer absorption axis 11a has the first
Since it is orthogonal to the direction of the optically stable state A, the pixel displays the dark state (see Table 2). On the other hand, in the pixel in which the ferroelectric liquid crystal molecule is in the second optical stable state B, the light beam that has passed through the polarizer 9b from the backlight device 10 is birefringently interacted by the ferroelectric liquid crystal molecule. And then passes through the analyzer 9a. in this case,
The pixel displays a bright state (see Table 2). Then, various kinds of information are displayed depending on the combination of the bright state and the dark state.

After 3 minutes have passed in this state, the motor M
Is activated, the analyzer 9a and the polarizer 9b are rotated by the angle 2θ to the + θ position, and the polarizer absorption axis 11b is in the second optically stable state B as shown in FIG. Coincides with the long axis direction of the molecule. At the same time,
Information signal S _A from the information signal application circuit 403, S _B is switched, the pixel information signal S _A has been applied information signal S _B is applied, the pixel information signal S _B has been applied The information signal S _A is applied (see Table 2). By switching this information signal, the optically stable state of the ferroelectric liquid crystal 7 is changed between the first optically stable state A and the second optically stable state B. That is, the ferroelectric liquid crystal 7 in the first optical stable state A is switched to the second optical stable state B, and conversely, the ferroelectric liquid crystal 7 in the second optical stable state B is switched. Is switched to the first optically stable state A. Then, in the pixel in which the ferroelectric liquid crystal molecule is in the first optical stable state A, the light ray passing through the polarizer 9b from the backlight device 10 is birefringently interacted by the ferroelectric liquid crystal molecule. And then passes through the analyzer 9a. In this case, the pixel displays a bright state (see Table 2). On the other hand, in the pixel in which the ferroelectric liquid crystal molecule is in the second optical stable state B, the light beam that has passed through the polarizer 9b from the backlight device 10 is birefringently interacted by the ferroelectric liquid crystal molecule. However, since the analyzer absorption axis 11a is orthogonal to the direction of the second optically stable state B, the pixel displays a dark state (see Table 2).

Therefore, the pixel which was displaying the bright state before the switching of the polarization axis continues to display the bright state after the switching, and the pixel which displayed the dark state continues to the dark state after the switching. LCD panel P
The image does not change even if the polarization axis is switched.

Next, the effect of this embodiment will be described.

According to the present embodiment, the ferroelectric liquid crystal molecules are in the same position (first optically stable state A or second optically stable state B) in the pixel which continues to display the bright state or the dark state. Therefore, it is possible to prevent the fluctuation of the threshold value (occurrence of the mono-stabilization phenomenon) because it is not continuously held at. Therefore, the bistability of the ferroelectric liquid crystal 7 is ensured, and the deterioration of the contrast can be prevented.

Next, another embodiment of the present invention will be described with reference to FIGS. The same parts as those shown in FIGS. 1 and 2 are designated by the same reference numerals and the description thereof will be omitted.

In this embodiment, as shown in FIG.
The first polarizing means 20a is arranged between the liquid crystal panel P and the backlight device 10, and the second polarizing means 20b is arranged on the light emitting side of the liquid crystal panel P. These polarizing means 20a and 20b are used for the nematic liquid crystal element 2
1a and 21b (hereinafter, "TN liquid crystal elements 21a and 21b")
And a polarizing plate 22a, 22b.
A drive circuit (polarization axis switching means) C is connected to the liquid crystal elements 21a and 21b, and two TN liquid crystal elements 21a and 21 are provided.
It is configured to turn on and off b at the same time. Specifically, the drive circuit C includes the TN liquid crystal elements 21a and 21b.
The voltage is applied for a certain time (for example, 3 minutes), and after the lapse of the time, the voltage is cut off and the cutoff state is continued for the same time. The TN liquid crystal elements 21a and 21b are arranged so as to face the liquid crystal panel P in both the first polarizing means 20a and the second polarizing means 20b, and the polarizing plates 22a and 22b are arranged outside. ing.

In this embodiment, the polarizing means 20
a, 20b, liquid crystal panel P, and backlight device 10
Both remain stationary in place.

[0046] Also in this embodiment, has become a circuit configuration as shown in FIG. 3, data electrodes 2a from the information signal application circuit 403, to the ..., information signal having a waveform as shown in FIG. 4 S _A And S _B are applied. Then, these information signals S _A and S _B are O of the drive circuit C.
N · OFF simultaneously switched, the information signal S _A information signal S _B is applied to the pixel that has been applied, as the pixel information signal S _B has been applied information signal S _A is applied Has become.

Here, the detailed structure of the polarization means 20a will be described with reference to FIGS.

In the polarization means 20a, the TN liquid crystal element 2
1a is a substrate 23a, 25a (hereinafter,
The "outer substrate 23a" and the "inner substrate 25a" are provided, and a nematic liquid crystal 26a is arranged in a gap between the two substrates 23a and 25a. Although rubbing treatment is applied to each of the two substrates 23a and 25a, the rubbing direction of the outer substrate 23a (hereinafter, referred to as "first outer rubbing direction") is shown in FIG.
7a, and the rubbing direction of the inner substrate 25a (hereinafter, referred to as "first inner rubbing direction") is shown in FIG. 29a.
Direction. In addition, these rubbing directions 27a, 2
9a is configured to be offset by an angle 2θ, and the outer rubbing direction 27a is the polarization direction 30a of the polarizing plate 22a.
It is set to match without twisting. And
The nematic liquid crystal 26a of the TN liquid crystal element 21a, as shown in FIG.
a, 25a, and rubbing directions 27a, 29
When a voltage is applied so as to be twisted with the relative twisting of a, it is arranged vertically to the substrates 23a and 25a as shown in FIG.

The second polarizing means 20b also has the same structure as the first polarizing means 20a. In the second polarizing means 20b, the rubbing direction 27b of the outer substrate 23b is the "second outer rubbing direction 27b" and the rubbing direction 29b of the inner substrate 25b is the "second inner rubbing direction 29b". Furthermore, the first polarization means 20
The polarization direction 30a in a is "first polarization direction 30a"
Then, the polarization direction 30b in the second polarization means 20b is referred to as "second polarization direction 30b".

Next, the relationship between the rubbing directions 27a, 27b, 29a and 29b in the polarizing means 20a and 20b will be described with reference to FIGS.
Note that the liquid crystal panel P is omitted in FIGS. 11 and 12 for convenience of description.

In this embodiment, the first inner rubbing direction 29a coincides with the direction of the second optically stable state B of the ferroelectric liquid crystal 7 in the liquid crystal panel P, and the first polarized light is polarized. The direction 30a and the first outer rubbing direction 27a are the first direction of the ferroelectric liquid crystal 7 in the liquid crystal panel P.
Is set so as to coincide with the direction of the optical stable state A. Further, the second inner rubbing direction 29b is perpendicular to the first inner rubbing direction 29a, and the second polarization direction 3b
0b and the second outer rubbing direction 27b form a right angle with the first polarization direction 30a and the first outer rubbing direction 27a. That is, the polarization axis of the first polarization unit 20a and the polarization axis of the second polarization unit 20b are configured to always have a crossed Nicol relationship even if the polarization plane of the transmitted light beam is switched. .

Next, the operation of this embodiment will be described.

When the liquid crystal device 500 according to this embodiment is driven, the information signal applying circuit 403 causes the liquid crystal panel P to be driven.
The information signals S _A and S _B are input to the liquid crystal panel, and the scanning signals are input to the liquid crystal panel P from the scanning signal applying circuit 402. Then, the ferroelectric liquid crystal 7 takes either the first optical stable state A or the second optical stable state B for each pixel.

Further, the drive circuit C to the TN liquid crystal element 21
A predetermined voltage is applied to a and 21b for a predetermined time, and the nematic liquid crystals 26a and 26b, as shown in FIG.
It rises perpendicularly to the substrates 23a, 25a and 23b, 25b.

On the other hand, a light beam is emitted from the backlight device 10, and the emitted light beam is linearly polarized by the polarizing plate 22a. The linearly polarized light passes through the TN liquid crystal element 21a without rotating the polarization plane because the nematic liquid crystal 26a rises vertically to the substrates 23a and 25a as described above. The polarization axis of the first polarization means 20a in this case is the direction along the first polarization direction 30a and the first outer rubbing direction 27a. Also in the second polarizing means 20b, since the nematic liquid crystal 26b rises vertically to the substrates 23b and 25b, the plane of polarization of the transmitted light beam is not rotated.

Since the first polarization direction 30a coincides with the major axis direction of the ferroelectric liquid crystal 7 in the first optically stable state A, the ferroelectric liquid crystal molecules are in the first optical direction. In the pixel in the statically stable state A, the light beam that has passed through the first polarization unit 20 from the backlight device 10 undergoes birefringent interaction with the ferroelectric liquid crystal molecules, but has the second polarization direction. 30b is the first optical stable state A
Since it is orthogonal to the direction of, the pixel displays a dark state. On the other hand, the ferroelectric liquid crystal molecules are in the second optically stable state B.
In the pixel taking the light, the light beam from the backlight device 10 undergoes birefringent interaction by the ferroelectric liquid crystal molecules, and then passes through the second polarizing means 21b. In this case, the pixel displays a bright state. Then, various kinds of information are displayed depending on the combination of the bright state and the dark state.

When a predetermined time (3 minutes) elapses in this state, the voltage from the drive circuit C to the TN liquid crystal elements 21a and 21b is cut off, and the nematic liquid crystals 26a and 26b are changed to those shown in FIG.
As shown in 1, the twisted state is obtained. Therefore, in the first polarizing means 20a, the light beam from the backlight device 10 is linearly polarized by the polarizing plate 22a, and
The polarization plane is 2θ according to the alignment state of the nematic liquid crystal 26a.
It is only rotated and emitted from the TN liquid crystal element 21a.

Meanwhile, the information signal S _A, S _B from the information signal application circuit 403, the drive circuit switched switched simultaneously C to OFF, the information signal S _A information signal to the pixel which has been applied is S _B Is applied, and the information signal S _A is applied to the pixel to which the information signal S _B was applied. By switching this information signal, the optically stable state of the ferroelectric liquid crystal 7 is changed between the first optically stable state A and the second optically stable state B. That is, the ferroelectric liquid crystal 7 in the first optically stable state A is changed to the second optically stable state B.
The ferroelectric liquid crystal 7 in the second optically stable state B is switched to the first optically stable state A.

Since the first inner rubbing direction 29a coincides with the molecular long axis direction of the ferroelectric liquid crystal 7 in the second optically stable state B, the ferroelectric liquid crystal molecules are in the first optical direction. In the pixel in the statically stable state A, the light beam emitted from the first polarizing means 20a undergoes birefringent interaction by the ferroelectric liquid crystal molecules as described above, and then the second polarizing means 20b. Pass through. In this case, the pixel displays a bright state. On the other hand, in the pixel in which the ferroelectric liquid crystal molecule is in the second optical stable state B, the light beam emitted from the first polarizing means 20a undergoes birefringent interaction by the ferroelectric liquid crystal molecule. But rubbing direction 2
Since 9b is orthogonal to the direction of the second optically stable state B, the pixel displays the dark state.

Therefore, the pixels that were displaying the bright state before the switching of the polarization axis continue to display the bright state after switching, and the pixels that were displaying the dark state continue to be in the dark state after switching. LCD panel P
The image does not change even if the polarization axis is switched.

Next, the effect of this embodiment will be described.

According to this embodiment, the ferroelectric liquid crystal molecules are in the same position (first optically stable state A or second optically stable state B) in the pixel which continues to display the bright state or the dark state. Therefore, it is possible to prevent the fluctuation of the threshold value (occurrence of the mono-stabilization phenomenon) because it is not continuously held at. Therefore, the bistability of the ferroelectric liquid crystal 7 is ensured, and the deterioration of the contrast can be prevented.

Further, according to the present embodiment, the switching of the polarization axes is electrically performed by turning on / off the TN liquid crystal elements 21a ,. Therefore, the screen does not flicker when the polarization axes are switched. Furthermore, vibration resistance, durability, and response performance can be improved.

[0064]

As described above, according to the present invention,
Since the switching of the polarization axes of the first and second polarizing means and the switching between the first optical stable state and the second optical stable state are performed at the same time, the pixels displaying the bright state are the same. The pixel that was displaying the bright state and the dark state is displayed in the dark state. Therefore, the bright state or the dark state can be continuously displayed. Further, even though the bright state or the dark state is continuously displayed in this way, the optically stable state of the ferroelectric liquid crystal is appropriately changed, so that the threshold value does not change unlike the conventional case. As a result, the so-called mono-stabilization phenomenon can be avoided and the reduction in contrast can be prevented.

Such an effect can be obtained by rotatably driving the first and second polarizing means with a motor. However, when the first and second polarizing means are formed by a nematic liquid crystal element. Can achieve switching of polarization axes in a short time. Therefore, the screen does not flicker when the polarization axes are switched. Furthermore, vibration resistance, durability, and response performance can be improved.

[Brief description of drawings]

FIG. 1 is a cross-sectional view for explaining a structure and the like of a liquid crystal panel.

FIG. 2 is a diagram for explaining the operation of the liquid crystal panel.

FIG. 3 is a block diagram illustrating an overall configuration of a liquid crystal device.

FIG. 4 is a waveform chart for explaining a waveform of an information signal.

FIG. 5 is a perspective view for explaining an operation (operation when the analyzer and the polarizer are at the −θ position) in the first embodiment of the present invention.

FIG. 6 is a perspective view for explaining an operation (operation when the analyzer and the polarizer are at the + θ position) in the first embodiment of the present invention.

FIG. 7 is a diagram for explaining an operation (operation when the analyzer and the polarizer are at + θ position) in the first embodiment of the present invention.

FIG. 8 is a sectional view illustrating a structure of a liquid crystal device according to a second embodiment of the invention.

FIG. 9 is a perspective view for explaining the operation of the second embodiment of the present invention.

FIG. 10 is a perspective view for explaining the operation of the second embodiment of the present invention.

FIG. 11 is a perspective view for explaining a rubbing direction.

FIG. 12 is a perspective view for explaining a rubbing direction.

[Explanation of symbols]

1a, 1b Glass substrate (substrate) 7 Ferroelectric liquid crystal 9a Analyzer (second polarization means) 9b Polarizer (first polarization means) 10 Backlight device (illumination means) 11a Polarization axis of second polarization means 11b Polarizing axis of first polarizing means 20a First polarizing means 20b Second polarizing means 21a, 21b Nematic liquid crystal elements 22a, 22b Polarizing plates 23a, 23b Outer substrate (transparent substrate) 25a, 25b Inner substrate (transparent substrate) 26a, 26b Nematic liquid crystal 27a First outer rubbing direction 27b Second outer rubbing direction 29a First inner rubbing direction 29b Second inner rubbing direction 30a First polarization direction 30b Second polarization direction 400 Liquid crystal device 403 Information Signal application circuit (control means) A First optical stable state B Second optical stable state C Drive circuit (polarization Axis switching means M Motor (polarization axis switching means) P Liquid crystal panel (ferroelectric liquid crystal element) S _A information signal (driving signal, first signal) S _B information signal (driving signal, second signal)

 ─────────────────────────────────────────────────── ─── Continuation of the front page (72) Inventor Yukio Hanyu 3-30-2 Shimomaruko, Ota-ku, Tokyo Canon Inc. (72) Inventor Hirohide Munekata 3-30-2 Shimomaruko, Ota-ku, Tokyo Canon Within the corporation

Claims (6)

[Claims] 1. A ferroelectric liquid crystal device having a pair of substrates and a ferroelectric liquid crystal sandwiched between the pair of substrates,
Illuminating means that is provided in parallel with the ferroelectric liquid crystal element to illuminate the ferroelectric liquid crystal element, first polarization means disposed between the ferroelectric liquid crystal element and the illuminating means, and the ferroelectric property. Second polarizing means arranged on the light emitting side of the liquid crystal element so as to be in crossed Nicols with the first polarizing means, and control means for inputting a drive signal to the ferroelectric liquid crystal element,
A liquid crystal device including: a polarization axis switching unit that switches polarization axes of the first and second polarization units, and the first and second polarization units are maintained in a state where crossed Nicols are maintained. The polarization axis of the polarization means is selectively made to coincide with the molecular long axis direction of the ferroelectric liquid crystal in the first or second optically stable state, and at the same time the polarization axis is switched by the polarization axis switching means. ,
A liquid crystal device, wherein the control means switches a drive signal to change an optically stable state of the ferroelectric liquid crystal. 2. The polarization axis switching means is a motor that rotationally drives the first and second polarizing means, and switches the polarization axes based on rotating the first and second polarizing means. The liquid crystal device according to claim 1, wherein 3. A nematic liquid crystal element in which the first polarizing means and the second polarizing means are arranged so as to face the ferroelectric liquid crystal element, respectively, and a light beam is provided adjacent to the nematic liquid crystal element. A polarizing plate that performs linear polarization of
The polarization axis switching means turns on the nematic liquid crystal element.
The drive circuit is turned off, and the first circuit is turned on and off by turning on and off the nematic liquid crystal element.
The liquid crystal device according to claim 1, wherein the polarization axes of the second polarization means are switched. 4. The nematic liquid crystal element comprises a pair of transparent substrates and a nematic liquid crystal arranged in a gap between the substrates, and the rubbing directions on the pair of transparent substrates form a predetermined angle. The liquid crystal device according to claim 3, wherein both transparent substrates are subjected to a rubbing treatment. 5. The polarizing direction of the polarizing plate in the first polarizing means is a first polarizing direction, and the polarizing direction of the polarizing plate in the second polarizing means is a second polarizing direction.
The rubbing direction of the transparent substrate of the first polarizing means adjacent to the polarizing plate is a first outer rubbing direction, and the transparent side of the first polarizing means adjacent to the ferroelectric liquid crystal element is transparent. The rubbing direction of the substrate is a first inner rubbing direction, the rubbing direction of the transparent substrate of the second polarizing means adjacent to the polarizing plate is a second outer rubbing direction, and the rubbing direction of the second polarizing means is the same. When the rubbing direction of the transparent substrate adjacent to the ferroelectric liquid crystal element is the second inner rubbing direction, the first polarization direction and the first outer rubbing direction,
And the second polarization direction and the second outer rubbing direction respectively match, and the first outer rubbing direction and the first inner rubbing direction are the first or second optically stable state. Of the ferroelectric liquid crystal, the second inner rubbing direction, the first inner rubbing direction, and the second outer rubbing direction and the first inner rubbing direction. 5. The liquid crystal device according to claim 3, wherein the outer rubbing directions of the liquid crystal and the outer rubbing direction are at right angles to each other. 6. The first signal for keeping the ferroelectric liquid crystal in a first optically stable state and the second signal for keeping the ferroelectric liquid crystal in a second optically stable state. And, and outputs the second signal instead of the first signal and the first signal instead of the second signal when the polarization axis is switched by the polarization axis switching means. The liquid crystal device according to any one of claims 1 to 5, wherein: