JPH05341289A - Liquid crystal display device - Google Patents

Abstract

PURPOSE:To obtain the liquid crystal display device which switches at a high speed and has a high contrast by adding a surfactant to oriented films. CONSTITUTION:The liquid crystal panel interposed with a liquid crystal having a chiral smectic C phase between substrates 9 and 10 is constituted. The layer structure 13 in the chiral smectic C phase of this liquid crystal is a chevron structure bent to a 'V' shape. The orientation region generated from the relation between a uniaxial orientation direction and the laminar structure of the chiral smectic C phase is on the inner side of the region enclosed by the lightening defect generated in the uniaxial orientation direction or the hairpin defect generated behind this defect or the outer side of the region enclosed by the hairpin defect generated in the uniaxial orientation direction and the lightening defect generated behind this defect. The pretilt angle of the liquid crystal molecules which can be determined by a magnetic field capacity method using a nematic liquid crystal is 8 to 35 deg. and the oriented films 4a, 4b contain the surfactant.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a display device. More specifically, it relates to a liquid crystal display device using a ferroelectric liquid crystal.

[0002]

2. Description of the Related Art A liquid crystal display device using a nematic liquid crystal is a twisted nematic type.
TN type liquid crystal display device, Super twisted type (Supe
rtwisted Birefringence Effect, SBE type) There is a liquid crystal display device. However, in the twisted nematic type liquid crystal display device, the driving margin becomes narrower as the driving method becomes more and more multiplexed, and a drawback that sufficient contrast cannot be obtained occurs. Further, in a super twisted type liquid crystal display device which is an improved version of the twisted nematic type liquid crystal display device and uses a large twist angle, when it is used for a large capacity display, there are drawbacks such as lower contrast and slower response speed. There is.

Therefore, as a device for improving a liquid crystal display device using such a nematic liquid crystal, a liquid crystal display using a chiral smectic C liquid crystal, that is, a ferroelectric liquid crystal by NAClark and Lagerwall in 1980. A device has been proposed (JP-A-56-107)
216, U.S. Pat. No. 4,367,924). This liquid crystal display device is different from the above-mentioned liquid crystal display device that uses the electric field effect that utilizes the dielectric anisotropy of liquid crystal molecules, and has a rotational force that matches the polarity of the spontaneous polarization of the ferroelectric liquid crystal and the polarity of the electric field. It is a liquid crystal display device having the configuration used. Features of this liquid crystal device include bistability, memory property, and high-speed response. That is, when ferroelectric liquid crystal having a layered structure such as chiral smectic C liquid crystal is injected into a cell having a thin gap, the inherent helical structure of the ferroelectric liquid crystal is unraveled by the influence of the interface, and the liquid crystal molecules are smectic layer method. A region in which the line is stable with an inclination angle of θ and a region in which the line is inclined with an angle of −θ in the opposite direction and is stable coexist, and have bistability.
By applying a voltage to the ferroelectric liquid crystal in this cell, the directions of the liquid crystal molecules and their spontaneous polarization can be made uniform, and the orientation of the liquid crystal molecules can be changed by switching the polarity of the applied voltage. It is possible to perform switching to switch from one certain state to another certain state.

With the switching drive, the birefringent light changes in the ferroelectric liquid crystal in the cell, so that the transmitted light can be controlled by sandwiching the cell between two polarizers. Further, even if the voltage application is stopped, the alignment of the liquid crystal molecules is maintained in the state before the voltage application is stopped by the alignment regulating force of the interface, so that the memory effect can be obtained. In addition, the time required for switching drive has a high-speed response of 1/1000 or less of that of a twisted nematic liquid crystal display device because the spontaneous polarization of the liquid crystal and the electric field directly act, and thus high-speed display is possible. Therefore, it has been conventionally attempted to construct a high-resolution liquid crystal display device having a large number of scanning lines by a multiplex drive system by utilizing the memory effect and high-speed response of this ferroelectric liquid crystal.

[0005]

However, the liquid crystal display device proposed by Clark and Lagabal has many problems. First, in the initial model, it was thought that the layer structure of the smectic C phase had a structure perpendicular to the substrates 9 and 10 called bookshelf type as shown in FIG. However, it has been found that when a cell is created by using the conventional alignment method such as rubbing, the expected switching phenomenon and optical characteristics are largely different from each other, and the switching is completely different from the specified model. ..

As one of the causes, it was analyzed by using the X-ray small angle confusion method that the layered structure was bent into a chevron shape called chevron as shown in FIG. TPRiekel, NAClark et al. Phys.Rev.Let
t., 59 , p2658 (1987)). Another difference from the initial model is that not only the spontaneous polarization direction and uniform orientation in which the liquid crystal molecules are aligned in a uniform direction, but also the molecules are twisted in a twisted orientation between the upper and lower substrates. (M.Glogarova and J.Pavel, J.Phys. (France), 45 , p1
43 (1984)).

In particular, it has been known that the ferroelectric liquid crystal display element oriented by rubbing has twist orientation because the regulating force at the interface works strongly. It has been found that, when such an orientation is adopted, generally, the difference in optical molecular axis in switching between two states does not effectively appear, and high contrast characteristics cannot be obtained. In order to solve these drawbacks, several methods for achieving the model initially proposed by Clark et al. Have been proposed. One of them is a method using the SiO oblique deposition method, which has a relatively high pretilt at the substrate interface. It has been reported that the addition of the above to the layer prevents the bending of the layer and achieves the layer structure in which the layer is inclined.

As a second method, a method of applying a high voltage alternating electric field to a cell having a bent structure to change the layer structure to a bookshelf structure has been proposed [Sato et al. Debate (Nagoya), 1st floor
16 (1986)], it was reported that high contrast characteristics were obtained. However, the above-mentioned oblique vapor deposition method has a serious problem in terms of production because it is difficult to obtain a technique for making the vapor deposition angle uniform and has a vacuum process. Further, in the method of applying an electric field, it is difficult to uniformly change the layer structure, and in many cases, the original chevron structure gradually changes with the passage of a long time, and it has not yet been put to practical use.

Therefore, an object of the present invention is to provide a liquid crystal display device having a high contrast characteristic in spite of the chevron structure in order to solve such a problem.

[0010]

According to the present invention, a pair of substrates, on which electrodes are selectively formed on a surface, an insulating film and an alignment film are further formed on the electrodes, and then uniaxial alignment treatment is applied,
The upper and lower substrates are arranged so as to be substantially parallel to each other in the direction of the uniaxial alignment treatment, and a liquid crystal having a chiral smectic C phase is interposed between these substrates to form a liquid crystal panel, which is selective to the electrodes. A drive unit for switching the optical axis of the liquid crystal by applying a voltage to the liquid crystal, and a unit for optically identifying the switching of the optical axis,
The layer structure in the chiral smectic C phase of the liquid crystal is a chevron structure bent in a V shape, and the alignment region generated from the relationship between the uniaxial alignment treatment direction and the layer structure of the chiral smectic C phase is uniaxial. Inside the area surrounded by the lightning defect generated in the alignment treatment direction and the hairpin defect generated behind the defect, or in the area surrounded by the hairpin defect generated in the uniaxial alignment treatment direction and the lightning defect generated behind The pretilt angle θ _P of the above-mentioned liquid crystal molecules, which is outside and is obtained by a magnetic field capacitance method using a nematic liquid crystal, is from 8 degrees to 35 degrees, and the alignment film contains a surfactant. Provided is a ferroelectric liquid crystal display device.

A transparent insulating substrate is used as the substrate of the present invention, and a glass substrate is usually used. The insulating substrate has InO _3, SnO _{2 and} ITO (Indium Tin Ox), respectively.
A transparent electrode having a predetermined pattern made of a conductive thin film such as ide) is formed. An insulating film is formed on it. As the insulating film, for example, an inorganic thin film such as SiO _2, SiNx, Al ₂ O ₃ or the like, an organic thin film such as polyimide, photoresist resin or polymer liquid crystal can be used. When the insulating film is an inorganic thin film, vapor deposition, sputtering, C
It can be formed by a VD (Chemical Vapor Deposition) method or a solution coating method. When the insulating film is an organic thin film, a solution in which an organic substance is dissolved or a precursor solution thereof is used and applied by a spinner coating method, a dip coating method, a screen printing method, a roll coating method, or the like. It can also be formed by a method of curing and forming under the curing conditions (heating, light irradiation, etc.), an evaporation method, a sputtering method, a CVD method, or an LB (Langumuir-Blodgett) method.

An alignment film is formed on the insulating film. The alignment film may be an inorganic layer or an organic layer. When an inorganic alignment film is used, a method often used is oblique vapor deposition of silicon oxide. Alternatively, a method such as rotary evaporation can be used. When an organic alignment film is used, nylon, polyvinyl alcohol, polyimide or the like can be used, and rubbing is usually performed on this. Further, it is also possible to perform alignment by using a polymer liquid crystal or an LB film, alignment by a magnetic field, alignment by a spacer edge method, and the like. Further, it is also possible to use a vapor deposition method of SiO _2, SiNx or the like and a method of rubbing the same.

The uniaxial orientation treatment method of the present invention includes a rubbing method and an oblique vapor deposition method. The rubbing method is advantageous in the case of mass production of a large screen liquid crystal display device. In the case of the rubbing method, the rubbing treatment is performed after forming the alignment film, but the parallel rubbing method (a method of laminating both the pair of substrates so that the rubbing directions are the same) and anti-parallel There are a rubbing method (a method of performing rubbing treatment on both of a pair of substrates and laminating them so that the rubbing directions are opposite to each other), and a single rubbing method (method of performing rubbing treatment on only one of the pair of substrates). In the case of the ferroelectric liquid crystal display device of the present invention, any alignment method can be used.

A surfactant is added to the alignment film. Examples of the addition method include a method in which a surfactant is added to an alignment film solution for forming an alignment film, mixed and homogenized, coated with a spin coater or the like, and then baked to form an alignment film. Any of anionic, cationic and nonionic surfactants can be applied. Specifically, commercially available anionic surfactants include FC-93 (ammonium salt of perfluoroalkylsulfonic acid), FC-95 (potassium salt of perfluoroalkylsulfonic acid), FC-98.
(Potassium salt of perfluoroalkyl sulfonic acid), F
C-129 (potassium salt of perfluoroalkylcarboxylic acid) (all manufactured by Sumitomo 3M Ltd.) and the like are commercially available cationic surfactants such as FC-135 (manufactured by Sumitomo 3M Ltd.) and the like. Examples of nonionic surfactants are FC-170C (perfluoroalkyl polyoxyethylene ethanol), FC-430 (fluorinated alkyl ester), FC-431 (fluorinated alkyl ester) (all manufactured by Sumitomo 3M Limited). Are preferably used. The addition amount is appropriately 0.0001 to 1 ml, and particularly preferably 0.0005 to 0.5 ml per 10 ml of the orientation solution film (concentration of about 3 wt%).

Then, while heating the liquid crystal compound showing the smectic C phase between the substrates, it is injected from the injection port by the vacuum injection method. A liquid crystal compound showing a smectic C phase applied to the present invention is

[0016]

[Chemical 1] The compound represented by this house

[0017]

[Chemical 2] Is preferably applied. Further, these compounds may be appropriately mixed and used. Further, a compound other than the liquid crystal compound exhibiting the smectic C phase may be appropriately mixed. This compound does not necessarily have to exhibit a liquid crystal phase, and (a) a compound for adjusting the temperature range of the liquid crystal phase of the composition to be prepared, (b) exhibiting a large spontaneous polarization in the ferroelectric liquid crystal phase or inducing it. And the optically active compound for adjusting the helical pitch of the liquid crystal phase of the composition to be prepared (c).

After the injection, the injection port is sealed with a UV curable resin such as acrylic resin to obtain a liquid crystal cell. Further, polarizing plates having polarization axes substantially orthogonal to each other were arranged above and below the liquid crystal cell, and one polarization axis of the polarizing plate was made to substantially coincide with one of the optical axes of the liquid crystals of the cell to obtain a liquid crystal display device.

According to the present invention, when the optical axis of the liquid crystal is switched by the driving means, the liquid crystal molecules are not only reversed in the vicinity of the boundary of the bend of the chevron structure which is generated substantially in the center between the pair of substrates, Since the liquid crystal molecules are inverted even near the substrate, the liquid crystal molecules are aligned substantially uniformly between one of the substrates and near the boundary of the bend of the Sieblon structure, and the alignment is slightly different near the boundary due to the bend, but this boundary is slightly different. Are oriented substantially uniformly between the vicinity of and the other side of the substrate. As a result, the liquid crystal molecules between the pair of substrates exhibit an orientation that is hardly twisted (an orientation that is hardly twisted).

As described above, since the liquid crystal molecules are hardly twisted, it is possible to reduce light leakage when light is shielded by using in combination with a means for optically discriminating optical axis switching, for example, a polarizer. It becomes possible to improve the contrast characteristics. Furthermore, the bending direction of the chevron structure of the present invention is inside a region surrounded by a lightning defect occurring in the uniaxial alignment treatment direction and a hairpin defect occurring behind it, or a hairpin defect occurring in the uniaxial alignment treatment direction and thereafter. When the optical axis of the liquid crystal is switched by the driving means in the present invention, as compared with the case of the direction opposite to the bending direction of the present invention, since the direction is outside the region surrounded by the lightning defects that occur in one direction. The difference between the optical molecular axes in the two states, that is, the so-called memory angle is large. Therefore, when the optical axis of the liquid crystal is switched, a means for optically discriminating the switching of the optical axis, for example, between a light transmitting state and a light non-transmitting state when used in combination with a polarizer is used. Since the difference in light transmission amount can be increased, high contrast characteristics are exhibited.

According to the present invention, in the ferroelectric liquid crystal display device in which the pretilt angle θ _{P of the} liquid crystal molecules, which is obtained by the magnetic field capacitance method using nematic liquid crystal, is from 8 degrees to 35 degrees, a suitable amount of the alignment film material is used. By controlling the interaction between the liquid crystal and the substrate interface by adding a surfactant, it is easy to cause a switching process involving inversion of the liquid crystal molecules at the substrate interface, achieving high-speed switching and high contrast characteristics. is there.

[0022]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS This description will be described in detail based on the embodiments shown in the drawings. The present invention is not limited to this.
It is known that the layer structure in the chiral smectic C phase generally has a chevron structure in which the shape of the letter "C" appears. The reason for adopting such a structure becomes small because the liquid crystal molecules tilt when the layer spacing in the liquid crystal phase (generally, the smectic A phase) at a temperature higher than that of the chiral smectic C phase changes to the chiral smectic C phase. On the other hand, molecules near the substrate surface are difficult to move, and in order to maintain the layer spacing in the phase on the high temperature side, it is necessary to reduce the layer spacing while maintaining the layer spacing at the interface,
It is believed that the layers bend. However, the bending direction of this layer is two directions (1
7, 18), and two different orientation states occur with it. At that time, an alignment defect called a zigzag defect occurs at a position where layers are bent in different directions.

As shown in FIG. 2, the zigzag defect has two kinds of defects in the bending direction of the layer, and the layer has a <<<>
Defects that occur in the area in contact with the lightning defect 15,
Hairpin defect 1 is defined as a defect that occurs in the area touching >>><<
It is named as "6", and the bending direction of the layer can be defined by observing this shape [Jpn. J. Appl.
Phys. 28, p. 50 (1988)]. The present invention utilizes this bent structure, and the details thereof will be described below. When the alignment treatment directions are the same in the upper and lower substrates, two different alignment states are obtained depending on whether the layers are bent in the same direction or in the opposite direction with respect to the alignment treatment direction. This relationship is shown in FIG.

Reference numerals 9 and 10 shown in FIG.
Reference numeral 13 denotes a smectic layer, and a conical figure represents an orbit in which the liquid crystal molecules 20 can move during switching, and is an orbit inclined by a tilt angle 26 of the liquid crystal with respect to the layer normal 25. The arrow 19 indicates the rubbing direction. The rubbing direction 19 is a direction when the substrates 9 and 10 are moved and the roller 27 for rubbing the substrates is rotated as shown in FIG. This relationship is also discussed in JP-A-1-158415, and in the case of 23 in FIG. 5 in which the rubbing direction and the layer bending direction are opposite, the C1 orientation (chevron 1), and the rubbing direction and the layer The case of 24 in FIG. 5 in which the bending directions are the same is C2 orientation (chevron 2)
Is defined as Hereinafter, similar names are used in this specification.

The C1 orientation and the C2 orientation show almost equivalent orientation states when there is no pretilt of liquid crystal molecules at the substrate interface. However, when a uniaxial orientation process such as a rubbing process is performed, a pretilt 22 of liquid crystal molecules occurs in the direction as shown in FIG. If this pretilt is increased, C
The difference in the alignment state of the liquid crystal molecules becomes remarkable between 1 and C2. FIG. 9 shows the difference in the alignment state. This figure shows FIG. 5 viewed from the rubbing direction 19.

In FIG. 9, a, b, and c, d are the substrate 9,
The states of the molecules in the memory state of the C1 and C2 orientations when the molecules at the 10 interface are difficult to move are described by the notation method by the C director 21 of the liquid crystal molecule 20. Since the liquid crystal molecules are twisted between the upper and lower substrates, C1 in this case
The orientation is defined as C1T (CITwisted) orientation, and the C2 orientation is defined as C2T (C2Twisted) orientation. Switching when an electric field is applied occurs between ab and cd, respectively. In this case, the memory state switching occurs only at the joint portion 14 of the chevron structure.

In this case, referring to FIG. 5, considering the arrangement on the upper and lower substrates, the n director 20 is in a largely twisted state in the C1T orientation of FIGS. 9a and 9b, and FIGS.
In the C2T orientation of, a small screw state is obtained. Now, when the polarizing plates are arranged above and below the cell so as to be orthogonal to each other and the cell is rotated in the cell, there is a place where the light is extinguished in the C2 orientation. Therefore, the C2T orientation exhibits better contrast characteristics than the C1T orientation. It has been reported. (JP-A-1-
158415).

However, the molecules near the interface are made to move easily,
Considering the case where interface inversion occurs, the situation is different. 9e and 9f and 9g and h show the states of the molecules in the C1 and C2 oriented memory state when interface inversion occurs. Since the twist of the liquid crystal molecules on the upper and lower substrates is eliminated, the molecules are arranged almost uniformly. In this case, the C1 orientation is C1U (C1Uniform) orientation, C2U
(C2Uniform) orientation is defined. Now, the switching when the electric field is applied occurs between ef and gh in FIG. 9, respectively.

In this case, in the C1U orientation, since the optical axis angle (memory angle θ _M ) between the two memory states is wide, not only extinction is possible in the orthogonal Nicols, but also the cell is installed at the extinction position, When the optical axis is switched to another memory state by applying a voltage, a large change in transmitted light intensity can be obtained because the movement of the optical axis angle is large.

However, in the C2 orientation, even if the inversion of molecules near the interface occurs, as can be seen from FIG. 9, the change in the optical axis between the first memory state and the second memory state is large. I can't get it. Therefore, it can be understood that the C1 orientation has better contrast characteristics. From the above, the following relationship is established for the contrast characteristics.

High contrast C1U> C2U ≧ C2T
> C1T Low contrast. The present invention is characterized by using a C1U orientation as a liquid crystal display device based on the above findings, but particularly in the case of switching using interface inversion such as uniform orientation, the movement of bulk liquid crystal is considered. The movement of the liquid crystal near the interface is independent, and normally the bulk molecules tend to move easily, while the interface molecules tend not to move, so that switching accompanied by interface inversion tends to be very slow. However, depending on how to control the state of the interface, it should be possible to switch the inversion of molecules at the substrate interface with a voltage as small as possible and a narrow pulse width.

As a means for suppressing the appearance of C2 orientation and stably obtaining C1 orientation, there is a technique in which the relationship between the layer inclination angle δ and the tilt angle θ is δ / θ ≧ 0.9. Also, C1
As a means for stably obtaining the U orientation, for example, a technique described in Japanese Patent Application No. 3-7879, which has an interface pretilt θ _P >> tilt angle θ, or an interface pretilt of 8 ° to 35 ° has been used. There is technology to do. These techniques are based on the idea of allowing molecules to exist away from the substrate in order to reduce the anchoring constraint due to rubbing.

In the present invention, the interfacial pretilt is 8 ° to 3 °.
Interfacial interaction (anchoring) of the substrate itself by adding an appropriate amount of surfactant to the 5 ° alignment film material
Can be controlled to obtain stable C1U orientation, and high speed switching and high contrast characteristics can be realized. Finally, how to distinguish the alignment state is described below. First, regarding how to distinguish between C1 and C2, the bending direction of the layer can be estimated from the shape of the zigzag defect caused by the spacers and scratches in the cell. That is, it is known that the defect has two types of shapes, lightning and hairpin, the two defects are normally connected and closed, and the bending direction of the layer is different between the area surrounded by the defect and the outside thereof. Therefore, the rubbing direction and the layer bending direction can be estimated. It is generally accepted that the rubbing direction is the pretilt direction of the molecule and has the relationship shown in FIG. 6, so that the C1 orientation and the C2 orientation can be defined from the rubbing direction and the layer bending direction.

Next, a method for discriminating between twist orientation (T) and uniform orientation (U) will be described. In this patent, one of the two states in which the extinction position appears is a uniform, and one in which the extinction position does not appear is a twisted state. The difference between uniform and twisted is as follows.

1. When observing with a microscope while applying a low-frequency triangular wave to the cell, the inversion domain is observed. At that time, domain reversal due to the movement of internal circumflex (which is called a boat-shaped domain) that occurs at the chevron joints (folds) occurs regardless of whether the orientation is twisted or uniform. .. Therefore, if one or more domain inversions are observed in addition to the inversion, the inversion is an inversion at the interface, and it can be determined that the uniform state is passed during switching.

2. Apply a sufficient electric field to the cell (about ± 10V)
It can be said that uniform orientation is obtained when the optical axis angle between the two stable states (no voltage applied state) during memory is 40% or more of the former with respect to the moving angle of the optical axis obtained by applying. Normally, in the twist orientation, only a value in the order of 30% can be obtained.

Embodiment 1 FIG. 1 is a diagram showing a cross section of a liquid crystal display device according to the present invention. In the figure, 300 to 50 are placed on the glass substrate 1a.
A plurality of transparent electrodes 2a having a thickness of 00Å, preferably 1000 to 3000Å are arranged in stripes so as to be parallel to each other (2000Å in this embodiment), and 300 to 5000Å, preferably 500. ~ 200
A 0 Å SiO ₂ electrode protective film 3 a is formed by sputtering (1000 Å in this embodiment), and PSI-A-2001 alignment film solution 1 manufactured by Chisso Petrochemical Co., Ltd. is further formed thereon.
Surfactant (FC manufactured by Sumitomo 3M Limited) per 0 ml
-431) 0.2 ml was added and applied by a spin coater and baked to form an alignment film 4a. After this, uniaxial orientation treatment by rubbing using rayon cloth,
The substrate 9 was formed. On the other hand, on the other side of the glass substrate 1b, a plurality of transparent electrodes 2b are formed in stripes so as to be parallel to each other under the same conditions, and an alignment film 4b is formed on the transparent electrodes 2b via an electrode protective film 3b. Was formed, and thereafter, uniaxial orientation treatment was performed by rubbing to form the substrate 10.

Next, this substrate 10 is replaced with the other substrate 9
And the alignment films 4a and 4b are opposed to each other, the transparent electrodes 2a and 2b are orthogonal to each other, and the rubbing directions are substantially coincident with each other, and the epoxy resin is interposed via the silica spacers 5 at intervals of 1.5 μm. It was pasted with a sealing member 6 made of. A liquid crystal 7 having a chiral smectic C phase (mixture A: composition shown in Table 1) is heated between these substrates 9 and 10 and is injected from an injection port by a vacuum injection method, and then an acrylic UV curing type A liquid crystal cell 11 was produced by sealing the injection port with the resin 8.

[0039]

[Table 1]

Further, polarizing plates 12a and 12b whose polarization axes are substantially orthogonal to each other are arranged above and below the cell 11, and one polarization axis of the polarizing plate substantially coincides with one of the optical axes of the liquid crystals of the cell 11. As a result, a liquid crystal display device was obtained. In addition, the rubbing direction is anti-parallel and the cell thickness is about 50μ with the same cell configuration.
Then, the pretilt angle of the liquid crystal molecules in the nematic phase was measured using the magnetic field capacitance method. The liquid crystal different from the liquid crystal injected this time is used because the liquid crystal having the chiral smectic C phase cannot measure an accurate tilt angle because the liquid crystal molecules are twisted in the cholesteric phase. In general, it is known that there is some dependence of the pretilt angle on the liquid crystal material, but unless it is a special material such as perfluoroalloalkyl, only a variation of about 1 to 2 ° occurs, so a substitute liquid crystal is used. Was used. PSI-A-20
In the case of 01, the pretilt angle obtained by the above method is 15 °
Met.

In the above cell, after confirming the C1U orientation by the above identification method, the optical axis of ± 5 V / μm as shown in FIG.
The / 3 bias drive waveform was applied to the cell to switch the optical axis, and the minimum optical axis switching pulse width (memory pulse width) required for switching between C1 uniforms was measured.
In addition, as a comparative example, a liquid crystal cell was prepared in the same manner as the above cell except that the surfactant was not added to the alignment film, and the same measurement was performed. FIG. 8 shows the temperature dependence of the memory pulse width of the above cell and the temperature dependence of the memory pulse width of the cell in which the surfactant was not added to the alignment film. As can be seen from FIG. 8, the memory pulse width of the cell in which the surfactant was added to the alignment film was shorter than that of the cell in which the surfactant was not added to the alignment film.

Further, the 1/3 bias voltage driving waveforms (FIGS. 10A and 11A) as shown in FIG. 7 with and without addition of the surfactant are shown in FIGS. FIG. 10 shows changes in transmitted light intensity of the cell when applied to the cell.
11 (b) is shown in FIG. 11 (b). Since the voltage pulse width for switching the optical axis can be shortened by adding the surfactant, the fluctuation of the liquid crystal molecules with respect to the bias voltage of the same pulse width is reduced, and high contrast is realized.

The liquid crystal material to be injected into the cell is CS-1014, CS-1022, ZLI-365 shown in Table 1.
Similar results were obtained when changing to 4, ZLI-3489, and FELIX-002. From the above results, it was possible to achieve high-speed switching and high contrast by adding a surfactant to the alignment film.

Example 2 In Example 1, the alignment film material was changed to Chisso Petrochemical Co., Ltd.
Also in the case of PSI-A-2401 manufactured by Pretilt angle 16 °, the same result as in Example 1 was obtained.

Example 3 In Example 1, the alignment film material was LQ-18 manufactured by Hitachi Chemical.
Even when it was set to 00 (pretilt angle 8 °), the same results as in Example 1 were obtained.

Example 4 In Example 1, the alignment film material was changed to Chisso Petrochemical Co., Ltd.
PSI-A-2301 (pretilt angle 13.5 °)
In the case of, the same results as in Example 1 were obtained.

Example 5 In Example 1, the alignment film material was changed to Chisso Petrochemical Co., Ltd.
Also in the case of PSI-A-X005 (pretilt angle 13 °), the same results as in Example 1 were obtained.

Example 6 In Example 1, the alignment film material was changed to Chisso Petrochemical Co., Ltd.
Also in the case of PSI-A-X006 (pretilt angle 13 °), the same result as in Example 1 was obtained.

Example 7 In Example 1, the alignment film material was changed to Chisso Petrochemical Co., Ltd.
Also in the case of PSI-A-X009 (pretilt angle 15 °), the same results as in Example 1 were obtained.

Example 8 In Example 1, the alignment film material was RN-71 manufactured by Nissan Chemical Industries.
Even when it was set to 5 (pretilt angle 13 °), the same results as in Example 1 were obtained.

Example 9 In Example 1, the alignment film material was changed to Chisso Petrochemical Co., Ltd.
Also in the case of PSI-A-S130 (pretilt angle 20 °), the same result as in Example 1 was obtained.

Example 10 In Example 1, the alignment film material was changed to Chisso Petrochemical Co., Ltd.
Also in the case of PSI-A-X018 manufactured by Pretilt angle 10 °, the same results as in Example 1 were obtained.

Example 11 In Example 1, the alignment film material was changed to Chisso Petrochemical Co., Ltd.
Also in the case of PSI-A-X021 manufactured by Pretilt angle 20 °, the same results as in Example 1 were obtained.

Example 12 The same results as in Example 1 were obtained when the surfactant used in Examples 1 to 11 was FC-93 manufactured by Sumitomo 3M Limited.

Example 13 The same results as in Example 1 were obtained when the surfactant used in Examples 1 to 11 was FC-95 manufactured by Sumitomo 3M Limited.

Example 14 The same results as in Example 1 were obtained when the surfactant used in Examples 1 to 11 was FC-98 manufactured by Sumitomo 3M Limited.

Example 15 Similar results as in Example 1 were obtained when the surfactant used in Examples 1 to 11 was FC-129 manufactured by Sumitomo 3M Limited.

Example 16 The same results as in Example 1 were obtained when the surfactant used in Examples 1 to 11 was FC-135 manufactured by Sumitomo 3M Limited.

Example 17 Similar results as in Example 1 were obtained when the surfactant used in Examples 1 to 11 was FC-170C manufactured by Sumitomo 3M Limited.

Example 18 The same results as in Example 1 were obtained when the surfactant used in Examples 1 to 11 was FC-430 manufactured by Sumitomo 3M Limited.

[0061]

From the above results, it was possible to provide a liquid crystal display device having high-speed switching and high contrast by adding a surfactant to the alignment film.

[Brief description of drawings]

FIG. 1 is a sectional view of a liquid crystal display device according to an embodiment of the present invention.

FIG. 2 is a schematic diagram showing a layer structure of a chiral smectic C phase in Examples.

FIG. 3 is a schematic diagram showing a layer structure of a smectic C phase in a conventional example.

FIG. 4 is a schematic diagram showing a layer structure of a smectic C phase.

FIG. 5 is a schematic diagram of C1 orientation and C2 orientation in the examples.

FIG. 6 is an explanatory diagram showing a rubbing process in the example.

FIG. 7 is a waveform diagram showing a 1/3 bias electric field application state in the example.

FIG. 8 is a graph showing the relationship between the memory pulse width and the measured temperature in the example.

FIG. 9 is a projection diagram showing C1 and C2 oriented C directors in Examples.

FIG. 10 shows changes in transmitted light intensity when a 1/3 bias electric field is applied in the example.

FIG. 11 shows a change in transmitted light intensity when a 1/3 bias electric field is applied in a comparative example.

[Explanation of symbols]

1, 1a, 1b Glass substrate 2, 2a, 2b Transparent electrode 3a, 3b Insulating film 4a, 4b Alignment film 5 Spacer 6,8 Sealing member 7 Ferroelectric liquid crystal composition 9,10 Substrate 11 Liquid crystal cell 12a, 12b Polarizing plate 13, 13a, 13b Smectic layer 14 Chevron interface 15 Lightning defect 16 Hairpin defect 17, 18 Bending direction in chiral smectic C phase 19 Rubbing direction 20 N director 21 C director 22 Pretilt angle 23 C1 orientation (chevron 1) 24 C2 orientation (Chevron 2) 25 layer normal 26 tilt angle 27 roller 28 roller 29,30 tilt angle 31 liquid crystal molecule 32 spontaneous polarization 33 applied electric field

Claims (2)

[Claims] 1. A pair of substrates, on each of which an electrode is selectively formed on the surface, an insulating film and an alignment film are further formed on the electrode, and the uniaxial alignment treatment is performed on the pair of substrates. By arranging the substrates so that they are substantially parallel to each other and facing each other, a liquid crystal having a chiral smectic C phase is interposed between these substrates to form a liquid crystal panel, and a voltage is selectively applied to the electrodes. A layer structure in the chiral smectic C phase of the liquid crystal has a chevron structure having a driving means for switching the optical axis of the liquid crystal and a means for optically distinguishing the switching of the optical axis. An alignment region generated due to the relationship between the uniaxial alignment treatment direction and the layer structure of the chiral C phase occurs behind a lightning defect occurring in the uniaxial alignment treatment direction and the defect. Inside the region surrounded by the hairpin defect, or outside the region surrounded by the hairpin defect generated in the uniaxial alignment treatment direction and the lightning defect generated in the rear direction, and determined by the magnetic field capacitance method using nematic liquid crystal. The pretilt angle θ _P of the above liquid crystal molecules is
A ferroelectric liquid crystal display device, characterized in that it is at an angle of 8 to 35 degrees and the alignment film contains a surfactant. 2. The ferroelectric liquid crystal display device according to claim 1, wherein the uniaxial alignment treatment is performed by using a rubbing method.