JP3239310B2 - Ferroelectric liquid crystal display device - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a ferroelectric liquid crystal display. More specifically, the present invention relates to a ferroelectric liquid crystal display device capable of gradation display and a ferroelectric liquid crystal display device driven by using a thin film transistor.

[0002]

2. Description of the Related Art At present, liquid crystal display devices are used in a wide range of fields such as clocks and calculators, OA equipment such as word processors and personal computers, pocket televisions, and the like. It is a thing using. As a liquid crystal display device using a nematic liquid crystal, a twisted nematic type (Twisted Nema type) is used.
tic TN type liquid crystal display device, super twisted type (S
(uppertwisted Birefringence Effect, SBE type) liquid crystal display devices.

However, a twisted nematic (TN) type liquid crystal display device has a drawback that a drive margin becomes narrower with an increase in the number of scanning lines and a sufficient contrast cannot be obtained. Have difficulty. Super twisted nematic (STN) to improve this TN type liquid crystal display element
Type liquid crystal display device and double layer super twisted nematic (DSTN) type liquid crystal display device have been developed, but as the number of lines increases, the contrast and response speed decrease, so the display capacity of about 800 x 1024 lines is currently limited. It is. In addition, TN type, STN type, DSTN
A display element using a nematic phase such as a mold has a large drawback that a viewing angle is narrow. In addition, sufficiently good values for contrast and response speed cannot be obtained.

On the other hand, a thin film transistor (TF) is formed on a substrate.
An active matrix type liquid crystal display element with an array of T) has also been developed, which has enabled large-capacity display of 1000 × 1000 lines, etc., and high contrast has been obtained. However, there was a problem in response speed. Therefore, as a device for improving such a liquid crystal display device using a nematic liquid crystal, a liquid crystal display device using a chiral smectic C liquid crystal, that is, a ferroelectric liquid crystal was proposed by NAClark and STLagerwall in 1980. (JP-A-56-107216; U.S. Pat.
367924). This liquid crystal display device is different from the above-mentioned liquid crystal display device using an electric field effect utilizing the dielectric anisotropy of liquid crystal molecules, in that a rotational force for matching the polarity of the spontaneous polarization of the ferroelectric liquid crystal with the polarity of the electric field is used. This is a liquid crystal display device having a configuration used. Characteristics of this liquid crystal device include improved bistability, memory properties, and high-speed response. That is,
When ferroelectric liquid crystal is injected into a cell with a reduced gap,
Under the influence of the interface, the helical structure of the ferroelectric liquid crystal is released,
As shown in FIG. 1A, a region where the liquid crystal molecules 18 are stabilized by inclining by + θ19 with respect to the smectic layer normal 17 and a region where the liquid crystal molecules 18 are stabilized by inclining by −θ20 in the opposite direction coexist. Has the property. By applying a voltage 16 to the ferroelectric liquid crystal in this cell, FIG.
As shown in (1), the directions of the liquid crystal molecules and their spontaneous polarization can be made uniform. Further, by switching the polarity of the applied voltage, the orientation of the liquid crystal molecules can be aligned in a direction opposite to that of FIG. 1B as shown in FIG.

Since the birefringent light of the ferroelectric liquid crystal in the cell changes with this switching drive, the transmitted light can be controlled by sandwiching the cell between two polarizers. Further, as shown in FIG. 1D, even if the application of the voltage is stopped, the alignment of the liquid crystal molecules is maintained in the state before the stop of the application of the voltage due to the alignment regulating force at the interface, so that a memory effect can be obtained. . In addition, the time required for the switching drive has a high-speed response of 1/1000 or less of that of the TN-type liquid crystal display device because the spontaneous polarization of the liquid crystal and the electric field act directly, thereby enabling a high-speed display. However, it is difficult to obtain a uniform orientation showing high contrast,
It also has disadvantages such as difficulty in gradation display.

Further, as a display device using a ferroelectric liquid crystal, a short pitch bistable ferroelectric liquid crystal display device (SBF-LCD) is used.
Abbreviation; Short Pitch Bistable Ferroelectric LCD) is a display device called J. Fuenfschill
ing) and M.Schadt (SID
90 Digest (1990) 106-109). This display device uses a principle similar to that of the above-mentioned Clark-Ragabal ferroelectric liquid crystal display device, but differs in that a ferroelectric liquid crystal having a helical pitch shorter than a substrate interval is used. That is, the Clark-Ragabal display device generally uses a ferroelectric liquid crystal having a helical pitch larger than the cell thickness, and unwinds the helical structure by the regulating force from the substrate interface. SBF-LCD, on the other hand,
A ferroelectric liquid crystal having a helical pitch shorter than the substrate interval is used.

For this reason, the helical structure cannot be unraveled and the bistability (memory effect) cannot be obtained. However, depending on the liquid crystal material, the fin filing and the shutting may be performed even when the helical pitch is shorter than the substrate interval. It was found that the helical structure was unwound and bistability (memory effect) was obtained. In this case, as shown in FIG.
Are observed in two regions inclined from each other by ± γ. Since the region 1 and the region 2 repeatedly appear alternately in the direction 23, a fine stripe pattern is observed under a polarizing microscope. In each of the region 1 and the region 2, as shown in FIG. 2A, the liquid crystal molecules 24 are tilted at an inclination angle + θ25 with respect to the smectic layer normals 21 and 22, and the liquid crystal molecules 24 are tilted at −θ26 in the opposite direction. And stable regions are mixed and have bistability. By applying a voltage 27 to the ferroelectric liquid crystal in this cell, as shown in FIG. 2 (b), the liquid crystal molecules and the direction of the spontaneous polarization of each of the regions 1 and 2 are made uniform. Can be aligned.

Further, by switching the polarity of the applied voltage, the alignment of the liquid crystal molecules in each of the regions 1 and 2 is reversed in the direction opposite to that in FIG. 2B, as shown in FIG. 2C. Can be. With this switching drive, the optical axis of the macro birefringence of the ferroelectric liquid crystal region 1 and region 2 in the cell changes to + β28 and −β29, so that the cell is sandwiched between two polarizers. Thereby, transmitted light can be controlled.

In the following, the optical axis of the macro birefringence in which the region 1 and the region 2 are combined is referred to as the apparent optical axis. As shown in FIG. 2 (d), even when stopping the application of voltage, regions 1 and 2
Since the boundary portion 30 prevents the spiral structure from being generated and is maintained in the state before the voltage application is stopped, a memory effect can also be obtained. Since the spontaneous polarization of the liquid crystal and the electric field act directly on the time required for the switching drive, it has a high-speed response of 1/1000 or less of that of the TN type liquid crystal display device, thereby enabling high-speed display.

This SBF-LCD can easily obtain a defect-free uniform alignment having an extinction position by a very common rubbing method and has a very large memory angle, even when compared to a Clark-Ragabal display device. Therefore, there is an advantage that a bright display is possible.

[0011]

A display device using a ferroelectric liquid crystal has an advantage that high-speed display is possible.
There are a number of issues that need to be resolved. Typical examples are Clark-Ragabal display devices, SBF-LC
D is a point that it is difficult to perform gradation display because it has bistability. In Clark-Ragabal display,
Various methods have been proposed for gradation display. One of the promising methods is disclosed in JP-A-3-242624, JP-A-3-243915 Mori, et al., 16th Liquid Crystal Discussion, 3K111 (1990) Toyoda, et al. , The 16th Liquid Crystal Symposium, 3K112 (199
0) Matsui, et al., 17th Liquid Crystal Discussion, 3F301 (199
1) There is a method disclosed in K. Nito et al., Proc. IDRC, 179 (1991).

In these methods, an intermediate voltage is displayed by applying an AC voltage to a monostable Clark-Ragabal cell and by changing the direction of the molecular axis of the liquid crystal molecules uniquely according to the magnitude of the voltage. FIG. 3 shows the principle of this mode. When no voltage is applied, the molecule is at position 101, and when a voltage is applied to it, the molecule moves right or left depending on its polarity. When a sufficiently high voltage is applied, the molecule becomes 102
Or, it moves to the position of 103, but if the voltage is lower than that, the molecule stays at an intermediate position. So, for example, 1
The halftone display can be obtained by aligning the polarization axis of one of the polarizers with the position 01 and the polarization axis of the other polarizer at right angles. It should be noted here that FIG. 3 is a simplified diagram for understanding this mode. In an actual ferroelectric liquid crystal cell, the direction of the molecular axis of the liquid crystal molecules is measured from the upper surface of the substrate. It must be mentioned that the lower surface is not uniform but twisted. FIG. 4 shows the relationship between the voltage and the tilt angle, and FIG. 5 shows the relationship between the voltage and the amount of transmitted light. According to the technology disclosed so far, the use of a monostable ferroelectric liquid crystal is described, but halftone display is possible in either case, either monostable or bistable.

However, the use of this halftone display mode does not solve another disadvantage of the Clark-Ragabal ferroelectric liquid crystal display device in that uniform alignment exhibiting high contrast is hardly obtained. In general, an alignment defect called a zigzag defect easily occurs in a Clark-Ragabal type ferroelectric liquid crystal display device subjected to parallel rubbing. This is because the layer structure in the SmC * phase is bent in the shape of a "ku", and the "ku"
The orientation of the liquid crystal molecules is divided into the C1 orientation and the C2 orientation depending on which direction the character is bent. FIG. 6 shows the definitions of the C1 orientation and the C2 orientation. The boundary between the C1 orientation and the C2 orientation becomes a defect called a zigzag defect. Also, Clark
The Lagabal type also has two types of molecular orientation states called uniform orientation and twist orientation. Uniform alignment refers to a state in which liquid crystal molecules are substantially uniformly aligned from one substrate to the other substrate, and twist alignment refers to a state in which liquid crystal molecules are twisted between one substrate and the other substrate. Call (FIG. 7). In general, it is known that uniform orientation has an extinction position and twist orientation has no extinction position. In order to achieve high contrast in a Clark-Ragabal ferroelectric liquid crystal display device, a uniform alignment having at least one extinction position without zigzag defects must be used.

Several methods have been proposed for obtaining a uniform alignment exhibiting high contrast in the Clark-Ragabal display device as described above. One of them is Si
There is a report that an O oblique vapor deposition method is used, in which a relatively high pretilt is applied to a substrate interface to prevent the layer from being bent and to achieve an obliquely inclined layer structure. As a second method, a method has been proposed in which a layer structure is changed to a bookshelf structure by applying a high-voltage AC electric field to a cell having a "<" shape (Sato et al., The 12th Liquid Crystal). Discussions (Nagoya), 1F16 (1986).) All report that high contrast characteristics were obtained. However, the oblique deposition method has a serious problem in terms of production because it is difficult to make the deposition angle uniform, and has a vacuum process. In addition, it is difficult to uniformly change the layer structure of the method of applying an electric field, and many methods gradually change to the original chevron structure over a long period of time, and have not yet been put to practical use. Also,
As a third method, there is an attempt to realize a high contrast without changing the layer having the "<" shape (for example, Japanese Patent Application Laid-Open No. 3-252624). This uses a Clark-Ragabal display device in which θ <α + δ (θ: tilt angle, α: pretilt angle, δ: layer tilt angle), and it is said that a C1 uniform orientation showing high contrast can be obtained. . However, although it has been reported that a uniform C1 orientation can be easily obtained by satisfying the relationship of θ <α + δ, a definitive means for obtaining a uniform uniform orientation having an extinction position has been found. At present, there is no such method, and it is very difficult to obtain high-contrast uniform alignment even with the third method.

Matsui et al., 17th Liquid Crystal Discussion, 3F301 (199)
1) In K. Nito et al., Proc. IDRC, 179 (1991), an anti-parallel rubbing cell is used. However, anti-parallel rubbing is generally difficult to obtain a uniform orientation without defects.

The present invention has been made under such circumstances, and by changing the apparent tilt angle of the SBF-LCD according to the voltage value, production is easy, high contrast is exhibited, and gradation display is possible. A high-speed display device is provided.

[0017]

According to the present invention, a crossed Nicols state is arranged before and after a liquid crystal cell filled with a ferroelectric liquid crystal between a pair of substrates having at least an electrode film and an alignment control layer. In a liquid crystal display device in which a pair of polarizing plates is installed and the polarization direction of the polarizing plate is adjusted to one of the extinction positions when no electric field is applied, the ferroelectric liquid crystal is a short pitch bistable ferroelectric liquid crystal (Short Pitch Bistable). Ferroelectric Liquid
Crystal SBF-LC), the applied voltage is a rectangular wave, and gradation display can be performed by changing the peak value, and the liquid crystal has a helical pitch in the chiral smectic C phase that is equal to the distance between the pair of substrates. Despite being shorter, a ferroelectric liquid crystal display device characterized in that its helical structure is unraveled is provided.

Further, as a system to which this SBF-LC is applied,
A plurality of scanning electrodes and a plurality of signal electrodes are formed in a matrix on one of the pair of substrates, active elements are provided at intersections of the electrodes, and both of the pair of substrates are electrode films for applying an electric field. And a liquid crystal cell having an alignment control layer and a liquid crystal cell filled with ferroelectric liquid crystal, and a ferroelectric liquid crystal display device provided with a pair of polarizing plates arranged in a crossed Nicols state before and after the liquid crystal cell.

Among them, as a preferable system, a method for driving an active element uses a method for driving a thin film transistor using amorphous silicon or polysilicon as a semiconductor film, and the orientation control layer is made of an organic polymer film;
A ferroelectric liquid crystal display device characterized in that alignment is controlled by a rubbing method. Furthermore, preferably, the alignment control by the rubbing method is performed substantially equally to the substrates on both sides, the rubbing direction of each substrate is substantially parallel or substantially antiparallel, and / or the alignment control by the rubbing method is
A ferroelectric liquid crystal display device characterized in that a rubbing treatment is performed only on the polymer film of a substrate on which a thin film transistor is not provided or on a substrate on which both surfaces are asymmetrically provided.

The ferroelectric liquid crystal of the present invention is SBF-LC, wherein the helical pitch in the chiral smectic C phase is shorter than the interval between the pair of substrates, and the helical structure is unraveled. Liquid crystal
For example, FLC-6430 (manufactured by Hoffman-La Roche) and the like can be mentioned. Conventionally, in the SBF-LCD, it has been known that the helix is untwisted and two bistable states appear and the electric field can switch between the two states.
It has been generally believed that intermediate states between two states cannot be created. However, the inventors have found that an intermediate state can be created in an electric field applied state. That is,
The applied voltage was a rectangular wave, and gradation display could be performed by changing the peak value.

This intermediate state can be considered to be due to the apparent tilt angle change induced by the electric field. FIG. 8 shows the relationship between the memory angle and the tilt angle of the apparent optical axis of the SBF-LCD. The memory angle is half the angle between the two apparent extinction positions
Which is usually smaller than the apparent tilt angle of the liquid crystal. The tilt angle θ is half the angle between the apparent extinction positions when a sufficient electric field is applied (± 20 V). 201, 20
Reference numerals 2 and 203 denote apparent optical axis positions in a memory state, a state where a sufficient voltage is applied in a positive direction, and a state where a sufficient voltage is applied in a negative direction, respectively. Initially, when the memory state 201 has an apparent optical axis and a voltage is applied in the negative direction, if a sufficiently large voltage is applied for a sufficient time, the apparent optical axis reaches 203, but this is not the case. In this case, the apparent optical axis moves to an arbitrary position between 201 and 203 according to the magnitude of the voltage and the voltage application time. That is, the angle formed between the polarizer and the apparent optical axis changes according to the magnitude of the voltage and / or the time during which the voltage is applied, so that gray scale display is possible. It can be seen that infinite gradation is possible by using this characteristic.

The polarization direction of the polarizing plate installed in the crossed Nicols state is matched with the apparent extinction position of the SBF-LCD in which one memory state is obtained by applying an electric field, and a 60 Hz rectangular wave is applied to transmit the transmitted light intensity. Was measured. FIG. 9 shows the applied voltage dependence of the amount of transmitted light at this time. The transmitted light intensity in the figure is obtained by averaging the amount of transmitted light during one cycle of the applied voltage.
As can be seen from the figure, the amount of transmitted light continuously increases as the voltage increases. In this method, the applied voltage waveform has no positive or negative bias, and there is no problem in reliability.

The characteristic shown in FIG. 9 is an example using a bistable SBF-LCD. However, a monostable element may be used, and a monostable ferroelectric liquid crystal element is more stable. Is easy to obtain. It is known that rubbing in the parallel direction is performed on both surfaces of the substrate as a means for obtaining the one-side stability in the SBF-LCD (Jpn. J. Appl. Phys. 30 (1991) 741-746).
However, depending on the alignment film / reorientation conditions, one-sided rubbing or anti-parallel rubbing may cause one-sided stability. Changing the rubbing conditions between the two substrates is also an effective means.

As a driving method utilizing such characteristics, there is an active matrix driving. In particular, driving using a thin film transistor is preferable. FIG. 10 shows an equivalent circuit of an active matrix liquid crystal display element using a thin film transistor (TFT). When driving the liquid crystal, a signal is sent from a scanning line to apply an electric field to the gate electrode G to turn on the TFT. When a signal is sent from the signal line to the source electrode S in synchronization with this, electric charges are accumulated in the liquid crystal LC through the drain electrode D, and the liquid crystal responds by an electric field generated by this.

The embodiment of the present invention will be described by using one scan electrode G1,
G2,. . . , Gn-1, Gn, Gn + 1, Gn + 2,. . . , Gl
-1, Gl and k signal electrodes S1, S2,. . . , Sm, Sm +
1,. . . , Sk-1, and Sk are formed in a matrix, and a liquid crystal display element as shown in FIG. 11 is used in which a ferroelectric liquid crystal is combined with an active matrix substrate in which thin film transistors (TFTs) are arranged at respective intersections. The gate electrode of the TFT at each intersection is connected to the scanning electrode, and the source electrode is connected to the signal electrode. P1 / 1, P1 / 2,. . . P
1 / m, P1 / m + 1,. . . Pn / 1, Pn / 2,. . . Pn / m, Pn
/ m + 1,. . . And the like indicate pixels connected to the drain electrode of the TFT formed at each intersection. FIG. 12 shows drive waveforms for driving this liquid crystal display element.

First, for a time t1, a signal is sent from the scanning electrode G1 to turn on the TFT. In synchronization with this, the pixels connected to G1 (P1 / 1, P1 / 2, P1 / m, P1 / m + 1, P1 / k-
1, P1 / k, etc.) is applied from the signal electrode to a zero or positive voltage corresponding to the display required. At the next time t1, a signal is sent from G2 to turn on the TFT, and a signal is sent from the signal electrode in synchronization with this. Thereafter, similarly, the TFTs connected to the respective scanning electrodes are sequentially turned on.

After the signals are transmitted from all the scanning electrodes, the signals are transmitted again from the scanning electrodes G1 for the time t1, and the TFTs are transmitted.
Turn on. In synchronization with this, it corresponds to the display required for the pixels (P1 / 1, P1 / 2, P1 / m, P1 / m + 1, P1 / k-1, P1 / k, etc.) connected to G1. Zero or negative voltage is applied from the signal electrode. At the next time t1, a signal is sent from G2 to turn on the TFT, and in synchronization with this, a zero or negative signal is sent from the signal electrode. Thereafter, similarly, the TFTs connected to the respective scanning electrodes are sequentially turned on. FIG. 12 shows an example of a voltage waveform applied to the pixel at this time and a change in transmitted light amount at that time. Large positive and negative electric fields are alternately applied to the pixel P1 / 1 for each frame, and this pixel performs white display. The voltage applied to pixel P12 is less than the voltage applied to pixel P1 / 1 in the first four frames,
Therefore, P1 / 2 is darker than P1 / 1 and a halftone display is obtained. In the fifth and sixth frames, the applied voltage becomes zero, and this pixel changes to black display. Here, one important thing is the relationship between the method of aligning the polarizing plates and the sign of the electric field application. Figure in the case of 12 must align the polarization direction of the polarizing plate on the extinction position of the memory state occurs upon application of a negative electric field. In other words, if the voltage applied to the pixel is reduced to zero after the positive voltage is applied, white display is desired although black display is desired. Therefore, in FIG. 12, one set is formed in two frames, and the voltage value must be changed only in the first frame of a pair of frames formed in two frames.

A color display can be obtained by combining color filters. The use of the ferroelectric liquid crystal device of the present invention as described above has the following advantages.
First, when a black state is required, a high contrast is obtained because no electric field is applied to the liquid crystal. Second, the amount of transmitted light can be changed by changing the voltage applied to each pixel, and gray scale display can be easily performed. Third, 1 high liquid crystal element of unpolarized reliable charge for switching the polarity of every frame to the applied voltage is Ru obtained. In addition, there are advantages that the response speed is faster and the viewing angle is wider than an element in which a nematic liquid crystal is combined with a TFT.

As a method for forming the alignment treatment layer, there are a rubbing method, an oblique vapor deposition method, and the like. In the case of mass production of a large-screen liquid crystal display device, the rubbing method is advantageous. In the case of the rubbing method, a rubbing treatment is performed after forming an alignment film, and a parallel rubbing method (a method in which both substrates are rubbed and bonded so that the rubbing directions are the same), an anti-parallel method. There are a rubbing method (a method in which rubbing is performed on both of a pair of substrates and bonding is performed so that the rubbing directions are reversed), and a single rubbing method (a method in which rubbing is performed on only one of the pair of substrates).

In the case of the ferroelectric liquid crystal device of the present invention, any orientation method can be used, but a single rubbing method in which a rubbing treatment is performed only on a substrate on which a thin film transistor is not formed is particularly preferable. The following two reasons can be cited. First, a substrate on which a thin film transistor is not formed is flatter, and uniform rubbing can be easily performed. Second, when a rubbing treatment is performed on a substrate on which a thin film transistor is formed, static electricity generated by the rubbing treatment easily changes characteristics of the thin film transistor and causes dielectric breakdown between wirings.

[0031]

【Example】

Example 1 An insulating film was formed on each of a pair of glass substrates on which a patterned ITO film was formed, nylon 6/6 was spin-coated, and only one substrate was rubbed. The pair of glass substrates are bonded together with a cell thickness of 1.2 μm, and FLC-6430 (Hoff
man-La Roche) was vacuum injected. Table 1 shows the physical properties of the liquid crystal.

The prepared ferroelectric liquid crystal cell was set in a polarizing microscope, and the transmitted light intensity was measured at 20.5 ° C. while applying a 60 Hz rectangular wave. FIG. 13 shows the results. It can be seen that the amount of transmitted light changes continuously with the voltage.

Example 2 In Example 1, the same result was obtained when the orientation film was PSI-A-2101 (manufactured by Chisso Petrochemical Co., Ltd.) and the measurement temperature was 21.5 ° C. FIG. 14 shows the voltage dependency of the amount of transmitted light when a 60 Hz rectangular voltage is applied. It can be seen that the amount of transmitted light changes continuously with the voltage.

Example 3 An insulating film was formed on each of a pair of glass substrates on which a patterned ITO film was formed, and PSI-A-2101 (manufactured by Chisso Petrochemical Co., Ltd.) was spin-coated and rubbed. The pair of glass substrates are bonded to each other with a cell thickness of 1.2 μm so that the rubbing directions are substantially antiparallel, and FLC-6430 (Hoffman-
La Roche) was injected under vacuum. FIG. 15 shows the voltage dependence of the amount of transmitted light when a 60-Hz rectangular wave voltage is applied. It can be seen that the amount of transmitted light changes continuously with the voltage.

Example 4 The cell used in Example 1 was driven by a TFT. FIG. 16 shows the frequency dependence of the capacitance of this cell. FIG. 17 shows the gate voltage, the source voltage, the drain voltage, and the transmitted light intensity when driven by changing the gate pulse width TON.
However, at this time, the polarizing plate is arranged so as to be in a dark state when a positive voltage is applied. FIG. 18 shows the source voltage dependence of the transmitted light intensity at this time. When TON is short,
The change in drain voltage is large, and the dependence of transmitted light intensity on source voltage is small. However, when the TON is set to 100 μsec, the change in the drain voltage becomes small, and the source voltage dependence of the transmitted light intensity is also good.

[0036]

By using the ferroelectric liquid crystal device of the present invention, continuous gradation can be realized. Active matrix driving of this display device enables large capacity, wide viewing angle, high contrast, infinite gradation display (full color display)
, A liquid crystal display device capable of performing the above can be obtained.

[Brief description of the drawings]

FIG. 1 is a principle diagram of a Clark-Ragabal ferroelectric liquid crystal display device.

FIG. 2 is a principle diagram of an SBF-LCD.

FIG. 3 is a schematic diagram for explaining switching of a ferroelectric liquid crystal element.

FIG. 4 is a diagram showing a relationship between a voltage and a tilt angle of a Clark-Ragabal ferroelectric liquid crystal element.

FIG. 5 is a diagram showing a relationship between a voltage applied to a Clark-Ragabal ferroelectric liquid crystal element and a change in transmitted light amount.

FIG. 6 is a schematic diagram of definitions of C1 orientation and C2 orientation and zigzag defects.

FIG. 7 is a molecular orientation model of a uniform orientation and a twist orientation.

FIG. 8 is a schematic diagram for explaining switching of the SBF-LCD of the present invention.

FIG. 9 is a diagram showing a relationship between an applied voltage and a change in transmitted light amount in a ferroelectric liquid crystal element in an SBF-LCD of the present invention.

FIG. 10 is an equivalent circuit diagram for describing an active matrix liquid crystal display.

FIG. 11 shows an active matrix type ferroelectric liquid crystal device.
It is a figure for explaining.

FIG. 12 is a diagram for explaining a driving method according to the present invention.

FIG. 13 is a graph showing the transmission intensity of the ferroelectric liquid crystal of the example.

FIG. 14 is a graph showing the transmission intensity of the ferroelectric liquid crystal of another example.

FIG. 15 is a graph showing the transmission intensity of the ferroelectric liquid crystal of another example.

FIG. 16 is a graph showing the frequency dependence of the capacitance of the liquid crystal cell of Example 1.

FIG. 17 is a graph showing transmitted light intensity at a gate voltage, a source voltage, and a drain voltage.

FIG. 18 is a graph showing source voltage dependence of transmitted light intensity.

Continued on the front page (72) Inventor Hiroshi Goda 22-22 Nagaikecho, Abeno-ku, Osaka-shi, Osaka Inside Sharp Corporation (72) Inventor Naofumi Kondo 22-22 Nagaikecho, Abeno-ku, Osaka-shi, Osaka Inside Sharp Corporation (72 ) Inventor Mikio Katayama 22-22 Nagaikecho, Abeno-ku, Osaka City, Osaka Prefecture Inside Sharp Corporation (56) References JP-A-1-152430 (JP, A) (58) Fields investigated (Int. Cl. ⁷ , DB Name) G02F 1/137 G02F 1/141

Claims (8)

(57) [Claims] 1. A pair of polarizing plates arranged in a crossed Nicols state before and after a liquid crystal cell filled with a ferroelectric liquid crystal is provided between a pair of substrates having at least an electrode film and an alignment control layer. In a liquid crystal display device in which the polarization direction of the polarizing plate is adjusted to one of the extinction positions upon application, the ferroelectric liquid crystal is a short-pitch bistable ferroelectric liquid crystal, the applied voltage is a rectangular wave, and the By changing the peak value, gradation display can be performed, and the helical structure of the liquid crystal is unraveled even though the helical pitch in the chiral smectic C phase is shorter than the interval between the pair of substrates. Ferroelectric liquid crystal display. 2. A plurality of scanning electrodes and a plurality of signal electrodes are formed on a matrix on one of a pair of substrates, an active element is provided at each intersection of the electrodes, and both of the pair of substrates have an electric field. In a ferroelectric liquid crystal display device in which a pair of polarizing plates arranged in a crossed Nicols state is installed before and after a liquid crystal cell filled with a ferroelectric liquid crystal in a liquid crystal cell having an application electrode film and an orientation control layer, The dielectric liquid crystal is a short-pitch bistable ferroelectric liquid crystal. For two consecutive frames, a positive or zero voltage is applied to the liquid crystal in a first frame, and a negative or zero voltage is applied in a second frame. A gradation display can be performed by applying a voltage to the liquid crystal and changing the peak value thereof, and the liquid crystal has a helical structure in which the helical pitch in the chiral smectic C phase is shorter than the interval between the pair of substrates. Ferroelectric liquid crystal display device characterized by being solved. 3. The ferroelectric liquid crystal display device according to claim 2, wherein the driving method of the active element uses a driving method of a thin film transistor using amorphous silicon or polysilicon as a semiconductor film. 4. The ferroelectric liquid crystal display device according to claim 1, wherein the alignment control layer is formed of an organic polymer film, and the alignment is controlled by a rubbing method. 5. The ferroelectric device according to claim 4, wherein the alignment control by the rubbing method is performed substantially equally on the substrates on both sides, and the rubbing directions of the respective substrates are substantially parallel or substantially antiparallel. Liquid crystal display device. 6. The ferroelectric liquid crystal display device according to claim 4, wherein the alignment control by the rubbing method is performed asymmetrically on the substrates on both sides. 7. The method according to claim 2, wherein the orientation control layer is made of an organic polymer film, and the rubbing treatment is applied only to the polymer film on the substrate on which the thin film transistor is not provided. Dielectric liquid crystal display. 8. The method according to claim 4, wherein the orientation control layer is made of an organic polymer film, and only the polymer film on the substrate on which the thin film transistor is not provided is subjected to a rubbing treatment.
Item 7. The ferroelectric liquid crystal display device according to item 1.