Liquid crystal device and liquid crystal apparatus

A liquid crystal device having a pair of electrode substrates, and a liquid crystal composition disposed between the substrates. At least one of the substrates is provided with an alignment control layer having a thickness of at most 200 .ANG. and having been subjected to a rubbing uniaxial aligning treatment. The liquid crystal composition contains at least 30 wt. % of (i) at least one species of a fluorine-containing mesomorphic compound (B) represented by a formula (II) having smectic C phase and providing a tilt angle below 30 degrees at a temperature 15.degree. C. below an upper limit temperature of said smectic C phase ##STR1## (ii) at least one species of compound (C) in an amount at least 5 wt. % represented by the formula (II) having a smectic C phase and which provides a tilt angle of at least 30 degrees at a temperature 15.degree. C. below an upper limit temperature of said smectic C phase.

FIELD OF THE INVENTION AND RELATED ART
 The present invention relates to a liquid crystal device including a liquid
 crystal composition used as a light-valve for flat-panel displays,
 projection displays, printers, etc. The present invention also relates to
 a liquid crystal apparatus using the liquid crystal device.
 There has been known a cathode ray tube (CRT) as a display device. The CRT
 has widely been used as a display terminal for outputting motion pictures
 of a television receiver or a video tape recording (VTR) apparatus or used
 as a monitor for a personal computer. However, the CRT encounters problems
 when outputs still images, in view of its characteristics, such that
 recognizability is liable to be lowered due to flickering and scanning
 fringes caused by an insufficient resolution and that degradation or
 deterioration of a fluorescent substance due to burning is caused to occur
 in some cases. In recent years, it has been found that an electromagnetic
 wave generated by the CRT adversely affects human body. As a result, the
 CRT can break health of video display terminal (VDT) operators in some
 cases. In addition, the CRT has a structure including a large volume
 behind a picture area (display portion), whereby space-saving utilization
 of an office or a house in which the CRT is used is hindered and there is
 a possibility that the CRT fails to sufficiently play a part in displays
 in an advanced information-oriented society.
 Liquid crystal devices have been used as a display device having solved the
 above-mentioned problems of the CRT. For instance, there have been known
 liquid crystal devices using use TN (twisted nematic) type liquid
 crystals, as shown in "Voltage-Dependent Optical Activity of a Twisted
 Nematic Liquid Crystal" by M. Schadt and W. Helfrich "Applied Physics
 Letters" Vol. 18, No. 4 (Feb. 15, 1971) pp. 127-128.
 One of the above-mentioned TN-type liquid crystal devices is a simple
 matrix-type liquid crystal device having the advantage of inexpensive
 production costs. When the liquid crystal device is driven by using an
 electrode matrix structure with an improved pixel density in accordance
 with a multiplex driving scheme, the liquid crystal device is liable to
 encounter a problem of occurrence of crosstalk, so that the number of
 pixels is restricted. Further, the uses of the device as a display device
 is also limited since the response speed is too slow, i.e., on the order
 of at least several ten milli-seconds.
 In recent years, there have been proposed liquid crystal devices using a
 thin film transistor (TFT). These liquid crystal devices can control a
 display state pixel by pixel since each pixel is provided with a
 transistor, whereby the devices solve problems of crosstalk and response
 speed. However, as these devices have a larger picture area, it is
 industrially more difficult to prepare a liquid crystal device with no
 defective pixels. Even if it is possible to prepare such a liquid crystal
 device, the device is more expensive.
 To overcome the above-mentioned drawbacks of such conventional liquid
 crystal devices, the use of liquid crystal devices using a liquid crystal
 material having bistability has been proposed by Clark and Lagerwall (e.g.
 Japanese Laid-Open Patent Appln. (JP-A) No. 56-107216; U.S. Pat. No.
 4,367,924, etc.). In this instance, as the liquid crystal material having
 bistability, a ferroelectric liquid crystal having chiral smectic C-phase
 (SmC*) or H-phase (SmH*) is generally used. The ferroelectric liquid
 crystal can effect inversion switching due to its spontaneous
 polarization, thus showing a very high response speed. Further, the
 ferroelectric liquid crystal shows at least two stable states including
 bistable states providing a memory characteristic and is excellent in view
 angle characteristics, so that a liquid crystal device using a
 ferroelectric liquid crystal is considered suitable for a display device
 or light-valve having properties including high-speed responsiveness, high
 resolution and a large picture area. In recent years, there has been
 proposed an anti-ferroelectric chiral smectic liquid crystal device
 assuming three stable states, as described in "Japanese Journal of Applied
 Physics" vol. 27, p. L729 (1988) by Chanani and Takezoe et al.
 Such a liquid crystal device using a chiral smectic liquid crystal,
 however, encounters a problem such that a contrast ratio is lowered by
 occurrence of zig-zag alignment defects in some cases, as described in
 "Structures and Properties of Ferroelectric Liquid Crystals" (1990) by
 Atsuo Fukuda and Hideo Takezoe issued by Corona Publishing Co. Ltd. (Tokyo
 Japan). The reason why the zigzag defect occurs may be attributable to the
 fact that a layer of a chiral smectic liquid crystal disposed between a
 pair of substrates constituting a cell structure includes two kinds of
 chevron layer structures.
 On the other hand there has been the recent trend in layer structure of a
 (chiral smectic) liquid crystal wherein a high contrast ratio is intended
 to be realized by suppressing a chevron layer structure resulting in a low
 contrast ratio and providing the liquid crystal with a bookshelf layer
 structure (hereinafter referred to as "bookshelf structure") in which
 boundaries of each liquid crystal layer are disposed in parallel with each
 other or with a structure closer to the bookshelf structure (e.g., Atsuo
 Fukuda (Editor)) "Future Liquid Crystal Display and Its Materials" (1992),
 issued by K. K. CMC (Tokyo Japan). One of methods for realizing a
 bookshelf structure is a method of using a naphthalene-based liquid
 crystal material having a particular structure. In this method, however,
 the resultant liquid crystal device has a tilt angle of about 10 degrees,
 which is considerably smaller than an ideal tilt angle of 22.5 degrees
 providing a maximum transmittance, thus resulting in a low transmittance
 or a low contrast. In addition, such a liquid crystal material fails to
 exhibit a bookshelf structure reversibly with respect to temperature in
 many cases. Another method for giving a bookshelf structure may include
 one inducing a bookshelf structure by externally applying an electric
 field to a liquid crystal device. Such a method, however, involves a
 problem of unstability against external stimuli such as temperature. In
 addition, various other problems to be solved are presumably present in
 order to put a liquid crystal material exhibiting a bookshelf structure
 into practical use since such a material has quite recently been
 discovered or proposed.
 Further, in quite recent years, there have been proposed a mesomorphic
 (liquid crystal) compound having a perfluoroether terminal portion (U.S.
 Pat. Nos. 5,082,587 and 5,262,082 and International Publication No.
 WO93/22396) and a liquid crystal composition (Marc D. Radcliffe et al: The
 4th International Ferroelectric Liquid Crystal Conference, P-46 (1993)) as
 materials exhibiting a bookshelf structure or a structure closer thereto.
 By using these liquid crystal materials, it is possible to provide a
 bookshelf structure or a structure showing a small layer inclination angle
 closer to the bookshelf structure without using external fields such as an
 external electric field. Accordingly, these liquid crystal materials are
 suitable for a liquid crystal device and display apparatus providing high
 speed responsiveness, high definition and large picture area.
 However, these liquid crystal materials (compounds and compositions) still
 leave room for improvement in several characteristics, such as response
 speed, alignment characteristic, contrast and driving stability, singly or
 in combination thereof for the purpose of providing a high performance
 liquid crystal device or apparatus.
 SUMMARY OF THE INVENTION
 An object of the present invention is to provide a liquid crystal device
 using a chiral smectic liquid crystal composition showing an alignment
 state exhibiting a bookshelf structure or a structure, having a small
 layer inclination angle, closer to the bookshelf structure with respect to
 a smectic layer structure, in order to realize a large-area liquid crystal
 device having improved properties such as high responsiveness, high
 contrast, high definition, high brightness and high reliability, and
 capable of retaining the above structure (alignment state) and these
 properties in a wider temperature range.
 Another object of the present invention is to provide a liquid crystal
 apparatus using the liquid crystal device.
 According to the present invention, there is provided a liquid crystal
 device, comprising: a pair of substrates each having thereon at least an
 electrode, and a liquid crystal composition disposed between the
 substrates so as to assume at least two optically stable states,
 wherein at least one of the substrates is provided with an alignment
 control layer having a thickness of at most 200 .ANG., and
 the liquid crystal composition comprises at least one species of a
 fluorine-containing mesomorphic compound (A) in an amount of at least 70
 wt. % comprising a fluorocarbon terminal portion and a hydrocarbon
 terminal portion, the terminal portions being connected with a central
 core, and having smectic mesophase or latent smectic mesophase, wherein
 the fluorine-containing mesomorphic compound (A) comprises at least one
 species of a compound (B) having a fluorocarbon terminal portion
 containing at least one catenary ether oxygen atom in an amount of at
 least 30 wt. % based on the liquid crystal composition, and the compound
 (B) comprises at least one species of a compound (C) having a smectic C
 phase and providing a tilt angle of at least 30 degrees at a temperature
 below an upper limit temperature of said smectic C phase by 15.degree. C.
 in an amount of at least 5 wt. % based on the liquid crystal composition.
 The present invention also provides a liquid crystal device, comprising: a
 pair of substrates each having thereon at least an electrode, and a liquid
 crystal composition disposed between the substrates so as to assume at
 least two optically stable states,
 wherein at least one of the substrates is provided with an alignment
 control layer comprising a polyimide film, and
 the liquid crystal composition comprises at least one species of a
 fluorine-containing mesomorphic compound (A) in an amount of at least 70
 wt. % comprising a fluorocarbon terminal portion and a hydrocarbon
 terminal portion, the terminal portions being connected with a central
 core, and having smectic mesophase or latent smectic mesophase, wherein
 the fluorine-containing mesomorphic compound (A) comprises at least one
 species of a compound (B) having a fluorocarbon terminal portion
 containing at least one catenary ether oxygen atom in an amount of at
 least 30 wt. % based on the liquid crystal composition, and the compound
 (B) comprises at least one species of a compound (C) having a smectic C
 phase and providing a tilt angle of at least 30 degrees at a temperature
 below an upper limit temperature of said smectic C phase by 15.degree. C.
 in an amount of at least 5 wt. % based on the liquid crystal composition.
 The present invention further provides liquid crystal apparatus including
 the above-mentioned liquid crystal devices, respectively.

DETAILED DESCRIPTION OF THE INVENTION
 The liquid crystal device according to the present invention is
 characterized by a specific cell structure wherein a liquid crystal
 composition comprising specific components in particular proportions,
 respectively, is sandwiched between a pair of electrode plates (substrates
 having thereon electrodes, respectively) at least one of which is provided
 with an alignment control layer having a thickness of 200 .ANG. or
 comprising a polyimide film.
 The liquid crystal composition may be a chiral smectic (or ferroelectric)
 liquid crystal composition.
 The liquid crystal composition used in the present invention comprises at
 least one species of a fluorine-containing mesomorphic compound (A) in an
 amount of at least 70 wt. %.
 The fluorine-containing mesomorphic compound (A) comprises at least one
 species of a compound (B) having fluorocarbon terminal portion containing
 at least one catenary ether oxygen atom in an amount of at least 30 wt. %,
 preferably at least 50 wt. %, based on the liquid crystal composition in
 order to provide a bookshelf structure or a structure closer thereto
 having a small layer inclination angle.
 The compound (B) comprises at least one species of a compound (C) having a
 smectic C phase and providing a tilt angle .theta. of at least 30 degrees,
 preferably at least 35 degrees, at a temperature (T) lower than an upper
 limit temperature (Tc) in its smectic C phase-providing temperature region
 by 15.degree. C. (Tc-T=15.degree. C.). The compound (C) is contained in
 the liquid crystal composition in an amount of at least 5 wt. %,
 preferably at least 10 wt. %.
 Herein, the term "catenary ether oxygen atom" means an ether oxygen atom
 present in a perfluoroether chain and located between adjacent carbon
 atoms.
 The fluorine-containing mesomorphic compound (A) contains a fluorocarbon
 terminal portion, a hydrocarbon terminal portion, and a central core
 connecting the terminal portions and assumes a smectic (mesomorphic) phase
 or a latent smectic (mesomorphic) phase. Herein, the compound having a
 latent smectic mesophase (or latent smectic phase) means a compound not
 showing (exhibiting) a smectic (meso)phase by itself but showing a smectic
 (meso)phase when used together with a compound showing a smectic
 (meso)phase or another compound having a latent smectic (meso)phase under
 an appropriate condition.
 The term "mesomorphic compound" used herein covers not only a compound
 assuming a mesomorphic phase (mesophase) but also a compound not assuming
 a mesomorphic phase per se as long as a liquid crystal composition
 containing such a compound assumes a mesomorphic phase.
 The tilt angle .theta. referred to herein will be explained with reference
 to FIG. 8.
 In case where the compound (C) described above is a chiral smectic
 mesomorphic compound (liquid crystal) showing ferroelectricity, liquid
 crystal molecules form plural smectic liquid crystal layers 82 and each of
 liquid crystal molecules is placed in at least two states 81a and 81b by
 switching under application of an appropriate voltage. A half of an angle
 (2.theta.) formed between the above two states 81a and 81b is defined as a
 tilt angle .theta..
 In case where the compound (C) is not chiral compound, the tilt angle
 .theta. can be determined in the following manner.
 Three chiral liquid crystal compositions are prepared by mixing a sample
 compound (compound (C)) with a chiral compound of the formula (i) shown
 below in weight ratios 99:1, 98:2 and 97:3, respectively.
 ##STR2##
 These compositions containing the chiral compound (1 wt. %, 2 wt. % and 3
 wt. %, respectively) are subjected to measurement of a tilt angle
 according to a prescribed method (described hereinafter) to obtain three
 values of the tilt angle from which a tilt angle of the sample (a chiral)
 compound is obtained by extrapolation.
 Hereinbelow, the liquid crystal device of the present invention will be
 described specifically with reference to FIG. 1.
 FIG. 1 is a schematic sectional view of an embodiment of the liquid crystal
 device for explanation of the structure thereof.
 Referring to FIG. 1, the liquid crystal device includes a liquid crystal
 layer 1 comprising a chiral smectic liquid crystal composition containing
 at least one species of a perfluoroether-type mesomorphic compound (as
 main components) disposed between a pair of substrates 2 each having
 thereon a group of transparent electrodes 3 and an alignment control layer
 4. In the present invention, however the alignment control layer 4 may be
 formed on one of the substrates 2. The substrates 2 are placed or arranged
 opposite each other. The periphery of the substrates 2 is sealed up with a
 sealing agent 5. Outside the substrates 2, a pair of polarizers 8 are
 disposed so as to modulate incident light I.sub.0 from a light source 9 in
 cooperation with the liquid crystal 1 to provide modulated light I.
 The liquid crystal layer 1 may preferably have a thickness (corresponding
 to a cell gap) of at most 5 .mu.m, more preferably about 0.5-3 .mu.m, in
 order to exhibit at least two optically stable states. Each of two
 substrates 2 comprise glass or plastic and is coated with a transparent
 electrode 3 having a prescribed pattern (e.g., stripe pattern) and
 comprising a film of SnO.sub.2, In.sub.2 O.sub.3 or ITO (indium-tin-oxide)
 to form an electrode plate. On at least one of the substrates 2, the
 alignment control layer 4 is formed via an insulating layer (not shown),
 as desired, by applying a solution containing a material for the alignment
 control layer or by vapor deposition or sputtering of a material for the
 alignment control layer. Examples of the material for the alignment
 control layer 4 may include: an inorganic material, such as silicon
 monoxide, silicon dioxide, aluminum oxide, zirconium oxide, magnesium
 fluoride, cerium oxide, cerium fluoride, silicon nitride, silicon carbide,
 or boron nitride; and an organic material, such as polyvinyl alcohol,
 polyimide, polyamide-imide, polyester, polyamide, polyester-imide,
 polyparaxylylene, polycarbonate, polyvinyl acetal, polyvinyl chloride,
 polystyrene, polysiloxane, cellulose resin, melamine resin, urea resin or
 acrylic resin. The surface of thus prepared alignment control layer 4 is
 subjected to a prescribed (uniaxial) aligning treatment, as desired, e.g.,
 by rubbing the surface with a fibrous material such as velvet, cloth or
 paper. The alignment control layer 4 may be formed by an oblique vapor
 deposition method wherein a film of an oxide such as SiO.sub.2 or an
 nitride is vapor-deposited on the electrode plate(s) from an oblique
 direction to the electrode plate.
 The liquid crystal device of the invention may further comprise a short
 circuit-preventing layer for the pair of substrates such as an insulating
 layer, an inorganic material layer and an organic material layer other
 than those for the above-mentioned alignment control layer. The pair of
 substrates 2 are held to have a prescribed (but arbitrary) gap (e.g., at
 most 5 .mu.m, preferably 0.5-3 .mu.m) with a gap-controlling spacer (not
 shown) of, e.g., silica beads or alumina beads. A voltage is applied to
 the liquid crystal layer 1 in accordance with a switching signal from a
 signal power supply (not shown), thus effecting switching. As a result,
 the liquid crystal device functions as a light valve such a display
 device. Further, in case where two groups of electrodes are arranged in
 matrix (so as to intersect with each other, e.g., at right angles) on the
 pair of substrates, it is possible to perform pattern display and pattern
 exposure, so that the liquid crystal device is used as a display device
 for a personal computer, a word processor, etc., or a light valve for a
 printer.
 In the liquid crystal device of the present invention, as described above,
 the pair of substrates may preferably be subjected to different aligning
 treatments including no aligning treatment in order to appropriately
 control an alignment (orientation) state, particularly an initial
 alignment state, of liquid crystal molecules of the chiral smectic liquid
 crystal composition containing the fluorine-containing mesomorphic
 compound. Specifically, for example, one of the substrates is provided
 with a rubbing-treated alignment control layer and the other substrate is
 provided with an alignment control film not subjected to rubbing and
 comprising a material identical to or different from that of the
 rubbing-treated alignment control layer.
 In the present invention, the liquid crystal composition containing the
 fluorine-containing mesomorphic compound(s) does not assume cholesteric
 phase in some cases. Particularly, in this instance, the liquid crystal
 composition causes a phase transition from isotropic phase to mesomorphic
 (e.g., smectic) phase on temperature decrease. If such a liquid crystal
 composition is disposed between a pair of electrode plates each provided
 with an alignment film subjected to mutually different aligning
 treatments, particularly including one electrode plate having an alignment
 film subjected to a uniaxial aligning treatment, batonnets (e.g., is
 islands of smectic phase) are generated from the uniaxial aligning-treated
 alignment film side and gradually grow toward the other alignment film
 side smoothly. For this reason, the liquid crystal molecule are finally
 aligned uniformly between the electrode plates, thus also exhibiting good
 performances when the resultant liquid crystal device is driven.
 The liquid crystal device of the present invention includes at least one
 alignment control layer having a thickness of at most 200 .ANG. or at
 least one alignment control layer consisting of a polyimide film.
 The former alignment control layer may preferably have a thickness of at
 most 100 .ANG., more preferably at most 50 .ANG., in order to allow good
 driving characteristics, a high reliability and a driving stability in a
 wide temperature range.
 This may be attributable to, e.g., an improvement in switching
 characteristic by using a thin alignment control layer since a certain
 permittivity of the alignment control layer is ensured and an alleviation
 of reverse electric field due to a spontaneous polarization of the liquid
 crystal composition used is enhanced. Particularly, when a chiral smectic
 liquid crystal composition for providing good and high-speed switching
 characteristic is used, such a liquid crystal composition generally has a
 spontaneous polarization of at least 10 nC/cm.sup.2 in many cases. In
 addition, the thin alignment control layer can suppress contact charging
 caused at a boundary between an electrode and the alignment control layer,
 so that we presume that irregularities in switching and alignment caused
 by the contact charging are suppressed. This is particularly noticeable in
 the case of employing the mutually different aligning treatments as
 described above.
 The latter alignment control layer (polyimide alignment control layer) may
 generally be prepared by applying a polyamic acid (polyimide precursor)
 solution onto the surface (electrodes) of the substrate(s), heating the
 applied (coating) layer and subjecting it to the above-described rubbing
 treatment.
 In the present invention, when the polyimide alignment control layer is
 used in combination with a chiral smectic liquid crystal composition
 disposed between the pair of substrates subjected to different aligning
 treatments, it is possible to attain a liquid crystal device providing
 good driving characteristics, a high reliability and a driving stability
 in a very wide temperature range. Particularly, by using a polyimide
 alignment control layer having a small thickness (at most 200 .ANG.)
 subjected to rubbing treatment formed on one substrate and an alignment
 control layer consisting of other materials (e.g., a layer of a silane
 coupling agent) not subjected to rubbing treatment on the other substrate
 in combination, it is possible to provide a particularly stable alignment
 control ability and excellent drive characteristics.
 In view of ease of formation and a high alignment control ability, the
 alignment control layer 4 may preferably comprise a polyimide film
 represented by the following formula (III) as a recurring unit.
 ##STR3##
 in which
 K is
 ##STR4##
 L.sup.11 and L.sup.12 independently denote
 ##STR5##
 or an alkylene group having
 1-20 carbon atoms;
 M.sup.11 is a single bond or --O--; and
 a is 0, 1 or 2.
 Specific examples of the polyimide of the formula (III) include those
 having the following recurring units shown below.
 ##STR6##
 The compound (B) containing a fluorocarbon terminal pattern having at least
 one catenary ether oxygen atom may include compounds described in U.S.
 Pat. No. 5,262,082, WO93/22396, and The 4th Int'l FLC conference, P-46
 (1993) (Marc D. Radcliffe et al).
 The compound (B) may preferably contain a fluorocarbon terminal portion
 (perfluoroether group) represented by the following structure:
 --D.sup.2 --(C.sub.xb F.sub.2xb --O).sub.za --C.sub.ya F.sub.2ya+1, where
 xb is independently 1-10 for each (C.sub.xb F.sub.2xb --O); ya is 1-10; za
 is 1-10; --D.sup.2 -- is --CO--O--C.sub.rc H.sub.2rc, --O--C.sub.rc
 H.sub.2rc --, --C.sub.rc H.sub.2rc --, --O--(C.sub.sa H.sub.2sa
 --O).sub.ta --C.sub.rd H.sub.2rd --, --O--SO.sub.2 --, --SO.sub.2 --,
 --SO.sub.2 --C.sub.rc H.sub.2rc --, --C.sub.rc H.sub.2rc --N(C.sub.pb
 H.sub.2pb+1)--SO.sub.2 --, --C.sub.rc H.sub.2rc --N(C.sub.pb
 H.sub.2pb+1)--CO--, or a covalent bond where rc and rd are independently
 1-20; sa is independently 1-10 for each (C.sub.sa H.sub.2sa --O); ta is
 1-6; and pb is 0-4.
 In general, the fluorine-containing mesomorphic compound (A) having the
 perfluoroether group (particularly by the compound (B)) has a central core
 comprised of at least two rings independently selected from aromatic,
 heteroaromatic, cycloaliphatic, or cycloaliphatic rings, connected one
 with another by a covalent bond or by groups selected from --COO--,
 --COS--, --NC.dbd.N--, --COSe--. Rings may be fused or non-fused.
 Heteroatoms within the heteroaromatic ring comprise at least one atom
 selected from N, O, or S. Non-adjacent methylene groups in cycloaliphatic
 rings may be substituted by O or S atoms.
 In this case, the central core may more preferably be one containing a
 benzene ring and a pyrimidine ring.
 The compound (B) may more preferably be represented by the following
 general formula (II):
 ##STR7##
 where A.sup.4, A.sup.5 and A.sup.6 are each independently denote
 ##STR8##
 gb, hb and ib are each independently an integer of 0-3 with the proviso
 that the sum of gb+hb+ib be at least 2;
 each L.sup.3 and L.sup.4 are independently a single bond, --CO--O--,
 --O--CO--, --CO--S--, --S--CO--, --CO--Se--, --Se--CO--, --CO--Te--,
 --Te--CO--, --(CH.sub.2 CH.sub.2).sub.ka --(ka is 1-4), --CH.dbd.CH--,
 --C.dbd.--C--, --CH.dbd.N--, --N.dbd.CH--, --CH.sub.2 --O--, --O--CH.sub.2
 --, --CO--or --O--;
 X.sup.2, Y.sup.2 and Z.sup.2 are each a substituent of A.sup.4, A.sup.5
 A.sup.6, respectively, and each X.sub.2, Y.sub.2 and Z.sub.2 independently
 --H, --Cl, --F, --Br, --I, --OH, --OCH.sub.3, --CH.sub.3, --CF.sub.3,
 --O--CF.sub.3, --CN or --NO.sub.2 ; each jb, mb and nb are independently
 an integer of 0-4;
 J.sup.2 is --CO--O--C.sub.rc H.sub.2rc --, --O--C.sub.rc H.sub.2rc --,
 --C.sub.rc H.sub.2rc --, --O--(C.sub.sa H.sub.2sa --O).sub.ta --C.sub.rd
 H.sub.2rd --, --O--SO.sub.2 --, --SO.sub.2 --, --SO.sub.2 --C.sub.rc
 H.sub.2rc --, --C.sub.rc H.sub.2rc --N(C.sub.pb H.sub.2pb+1)--SO.sub.2
 --or --C.sub.rc H.sub.2rc --N(C.sub.pb H.sub.2pb+1)--CO--where rc and rd
 are independently 1-20; sa is independently 1-10 for each (C.sub.sa
 H.sub.2sa --O), ta is 1-6; pb is 0-4;
 R.sup.4 is --O--(C.sub.qc H.sub.2qc --O).sub.wa --C.sub.qd H.sub.2qd+1,
 --(C.sub.qc H.sub.2qc --O).sub.wa --C.sub.qd H.sub.2qd+1, --C.sub.qc
 H.sub.2qc --R.sup.6, --O--C.sub.qc H.sub.2qc --R.sup.6, --CO--O--C.sub.qc
 H.sub.2qc --R.sup.6, or O--CO--C.sub.qc H.sub.2qc --R.sup.6 which may be
 either straight chain or branched where R.sup.6 is --O--CO--C.sub.qd
 H.sub.2qd+1 ; --CO--O--C.sub.qd H.sub.2qd+1, --Cl, --F, --CF.sub.3,
 --NO.sub.2, --CN or --H; qc and qd are independently 1-20; wa is 1-10;
 R.sup.5 is (C.sub.xb F.sub.2xb --O).sub.za --C.sub.ya F.sub.2ya+1, wherein
 xb is independently 1-10 for each (C.sub.xb F.sub.2xb --O); ya is 1-10;
 and za is 1-10.
 The compound (B) represented by the formula (II) may be synthesized through
 processes similar to those descried in JP-A (Kohyo) 7-506368 and
 WO93/22396. Specific examples of such compounds of the formula (II) may
 include those (Example Compound Nos. II-1 to II-45) shown below.
 ##STR9##
 ##STR10##
 ##STR11##
 ##STR12##
 The above-described compound (C) providing a tilt angle .theta. of at least
 30 degrees (preferably 35 degrees) at a temperature T (Tc-T=15.degree. C.)
 is contained in an amount of at least 5 wt. % (preferably at least 10 wt.
 %) based on the liquid crystal composition, so that the resultant liquid
 crystal device is improved in a stability of a layer structure against
 temperature change to stably maintain a bookshelf structure or a layer
 structure closer thereto. Further, the liquid crystal device comprising
 the above liquid crystal composition provides a good alignment
 characteristic (good bistability) to ensure a high-speed drive, a high
 brightness, a high contrast and a high reliability.
 The compound (C) may preferably be represented by the above-mentioned
 formula (II). The compound represented by the formula (II) may
 particularly preferably be those of the formula (II) wherein R.sup.4 is
 --O--(C.sub.qc H.sub.2qc --O).sub.wa --C.sub.qd H.sub.2qd+1, --O--C.sub.qc
 H.sub.2qc --R.sup.6 or --O--CO--C.sub.qc H.sub.2qc --R.sup.6 where qc, qd,
 wa and R.sup.6 have the meanings defined above.
 Specific examples of the preferred compounds of the compound (C) may
 include those shown below.
 ##STR13##
 In the liquid crystal composition used in the present invention, the
 fluorine-containing mesomorphic compound (A) may include a
 fluorine-containing mesomorphic compound having a perfluoroalkyl group
 (hereinafter, called "perfluoroalkyl-type mesomorphic compound) in view of
 a high mutual solubility with the compounds (B) and/or (C).
 The perfluoroalkyl-type mesomorphic compound may include compounds
 described in, e.g., JP-A 2-142753.
 The perfluoroalkyl-type mesomorphic compound (as the compound (A)) may
 preferably comprise a fluorocarbon terminal portion represented by the
 formula --D.sup.1 --C.sub.xa F.sub.2xa --X, where xa is 1-20; X is --H or
 --F; --D.sup.1 -- is --CO--O--(CH.sub.2).sub.ra --, --O--(CH.sub.2).sub.ra
 --, --(CH.sub.2).sub.ra --, --O--SO.sub.2 --, --SO.sub.2 --, --SO.sub.2
 --(CH.sub.2).sub.ra --, --O--O(CH.sub.2).sub.ra --O--(CH.sub.2).sub.rb --,
 --(CH.sub.2).sub.ra --N(C.sub.pa H.sub.2pa+1)--SO.sub.2 -- or
 --(CH.sub.2).sub.ra --N(C.sub.pa H.sub.2pa+1)--CO-- where ra and rb are
 independently 1-20; and pa is 0-4.
 In the case of the perfluoroalkyl-type mesomorphic compound, the
 mesomorphic compound may preferably have a central core comprising at
 least two aromatic, heteroaromatic, cycloaliphatic, or cycloaliphatic
 rings. The aromatic or heteroaromatic ring may be selected from fused
 aromatic, heteroaromatic, or non-fused aromatic or heteroaromatic rings,
 and the rings may connected one with another by means of functional groups
 selected from --COO--, --COS--, --HC.dbd.N--, --COSe--. Heteroatoms within
 the heteroaromatic ring comprise at least one atom selected from N, or S.
 In this case, the central core may preferably contain a benzene ring and a
 pyrimidine ring.
 The perfluoroalkyl-type mesomorphic compound may more preferably be
 represented by the following general formula (I):
 ##STR14##
 wherein A.sup.1, A.sup.2 and A.sup.3 are each independently
 ##STR15##
 ga, ha and ia are independently an integer of 0-3 with the proviso that the
 sum of ga+ha+ia be at least 2;
 L.sup.1 and L.sup.2 are independently a covalent bond, --CO--O--,
 --O--CO--, --COS--, --S--CO--, --CO--Se--, --Se--CO--, --CO--Te--,
 --Te--CO--, --CH.sub.2 CH.sub.2 --, --CH.dbd.CH--, --C.tbd.C--,
 --CH.dbd.N--, --N.dbd.CH--, --CH.sub.2 --O--, --O--CH.sub.2 --, --CO--or
 --O--;
 X.sup.1, Y.sup.1 and Z.sup.1 are each a substituent of A.sup.1, A.sup.2 and
 A.sup.3, respectively, and each X.sup.1, Y.sup.1 and Z.sup.1 are
 independently --H, --Cl, --F, --Br, --I, --OH, --OCH.sub.3, --CH.sub.3,
 --CN or --NO.sub.2 ;
 each ja, ma and na are independently an integer of 0-4;
 J.sup.1 is --CO--O--(CH.sub.2).sub.ra --, --O--(CH.sub.2).sub.ra --,
 --(CH.sub.2).sub.ra --, --O--SO.sub.2 --, --SO.sub.2 --, --SO.sub.2
 --(CH.sub.2).sub.ra --, --O--(CH.sub.2).sub.ra --O--(CH.sub.2).sub.rb --,
 --(CH.sub.2).sub.ra --N(C.sub.pa H.sub.2pa+1)--SO.sub.2 -- or
 --(CH.sub.2).sub.ra --N(C.sub.pa H.sub.2pa+1)--CO--where ra and rb are
 independently 1-20, and pa is 0-4;
 R.sup.1 is --O--C.sub.qa H.sub.2qa --O--C.sub.qb H.sub.2qb+1, --C.sub.qa
 H.sub.2qa --O--C.sub.qb H.sub.2qb+1, --C.sub.qa H.sub.2qa --R.sup.3,
 --O--C.sub.qa H.sub.2qa --R.sup.3,--CO--O--C.sub.qa H.sub.2qa --R.sup.3,
 or --O--CO--C.sub.qa H.sub.2qa --R.sup.3 which may be either straight
 chain or branched where R.sup.3 is --O--CO--C.sub.qb H.sub.2qb+1,
 --CO--O--C.sub.qb H.sub.2qb+1, --H, --Cl, --F, --CF.sub.3, --NO.sub.2 or
 --CN; and qa and qb are independently 1-20;
 R.sup.2 is C.sub.xa F.sub.2xa --X, wherein X is --H or --F, xa is an
 integer of 1-20.
 The perfluoroalkyl-type mesomorphic compound represented by the formula (I)
 may be synthesized through processes similar to those described in JP-A
 (Kokai) 2-142753 and U.S. Pat. No. 5,082,587. Specific examples of such a
 mesomorphic compound of the formula (I) may include those (Example
 Compound Nos. I-1 to I-103) shown below.
 ##STR16##
 ##STR17##
 ##STR18##
 ##STR19##
 ##STR20##
 The liquid crystal composition may further contain another mesomorphic
 compound having no fluorocarbon terminal portion ("hydrocarbon-type
 mesomorphic compound") in an appropriate amount, preferably in an amount
 of at most 30 wt. %.
 The liquid crystal composition may preferably contain at least one species
 of an optically active (chiral) compound which may have a fluorocarbon
 terminal portion.
 Specific examples of the hydrocarbon-type mesomorphic compound (free from a
 perfluorocarbon chain) as another mesomorphic compound may include those
 shown below.
 ##STR21##
 ##STR22##
 ##STR23##
 ##STR24##
 ##STR25##
 ##STR26##
 ##STR27##
 ##STR28##
 Specific examples of the optically active compound may preferably include
 those shown below.
 TABLE A
 (for Compounds Nos. A-1 to A-105)
 R.sup.6 "--A.sup.6 "--X.sup.6 "--A.sup.7 "--A.sup.8 "--X.sup.7 "--R.sup.7
 "--.EPSILON.**-R.sup.9 "
 No. R.sup.6 " A.sup.6 " X.sup.6 " A" A.sup.8 " X.sup.7 " R.sup.7 "
 .EPSILON.** R.sup.8 " R.sup.9 "
 1 C.sub.6 H.sub.13 -- -- Ph Ph -- M1 .EPSILON. H
 C.sub.8 H.sub.17
 2 C.sub.8 H.sub.17 O -- -- Ph Ph -- M1 .EPSILON. H
 C.sub.18 H.sub.37
 3 C.sub.5 H.sub.11 O -- -- Ph Ph2F -- M1 .EPSILON. H
 C.sub.6 H.sub.13
 4 CH.sub.3 O -- -- Ph Ph -- M1 .EPSILON. H
 C.sub.6 H.sub.13
 5 C.sub.6 H.sub.13 CH(CH.sub.3)(CH.sub.2).sub.2 O -- -- Ph Ph
 -- M1 .EPSILON. H C.sub.6 H.sub.13
 6 C.sub.7 H.sub.15 O -- -- Ph P23F -- M1 .EPSILON. H
 C.sub.6 H.sub.13
 7 C.sub.6 H.sub.13 -- -- Ph Ph -- M1 .EPSILON. H
 C.sub.9 H.sub.19
 8 C.sub.7 H.sub.15 O -- -- Ph Ph -- M1 .EPSILON. H
 C.sub.5 H.sub.11
 9 C.sub.8 H.sub.17 O -- -- Ph Ph -- M1 .EPSILON. H
 C.sub.6 H.sub.13
 10 C.sub.8 H.sub.17 -- -- Pr1 Ph -- M1 .EPSILON. H
 C.sub.8 H.sub.17
 11 C.sub.10 H.sub.21 -- -- Pr2 Ph -- M1 .EPSILON. H
 C.sub.4 H.sub.9
 12 C.sub.11 H.sub.23 -- -- Pr2 Ph -- M1 .EPSILON. H
 C.sub.6 H.sub.13
 13 C.sub.12 H.sub.25 -- -- Pr2 Ph -- M1 .EPSILON. H
 C.sub.8 H.sub.17
 14 C.sub.4 H.sub.9 O -- -- Py1 Ph -- M1 .EPSILON. H
 C.sub.10 H.sub.21
 15 C.sub.13 H.sub.27 -- -- Py2 Ph -- M1 .EPSILON. H
 C.sub.5 H.sub.11
 16 C.sub.6 H.sub.13 -- -- Py2 Ph -- M1 .EPSILON. H
 C.sub.8 H.sub.17
 17 C.sub.6 H.sub.13 CH(CH.sub.3)CH.sub.2 O -- -- Py2 Ph -- M1
 .EPSILON. H C.sub.9 H.sub.19
 18 C.sub.6 H.sub.11 O -- -- Py2 P23F -- M1 .EPSILON. H
 C.sub.4 H.sub.9
 19 C.sub.10 H.sub.21 -- -- Py2 Ph -- M1 .EPSILON. H
 C.sub.6 H.sub.13
 20 C.sub.8 H.sub.17 -- -- Py2 Ph3F -- M1 .EPSILON. H
 C.sub.8 H.sub.17
 21 C.sub.6 H.sub.13 -- -- Cy Ph -- M1 .EPSILON. H
 C.sub.4 H.sub.9
 22 C.sub.3 H.sub.7 -- -- Cy Ph -- M1 .EPSILON. H
 C.sub.5 H.sub.11
 23 C.sub.5 H.sub.11 -- -- Cy Ph -- M1 .EPSILON. H
 C.sub.14 H.sub.29
 24 C.sub.10 H.sub.21 -- -- Cy Ph -- M1 .EPSILON. H
 C.sub.10 H.sub.21
 25 C.sub.6 H.sub.13 -- -- Pa Ph -- M1 .EPSILON. H
 C.sub.10 H.sub.21
 26 C.sub.7 H.sub.15 OCO -- -- Pd Ph -- M1 .EPSILON. H
 C.sub.3 H
 27 C.sub.6 H.sub.13 -- -- Dt2 Ph -- M1 .EPSILON. H
 C.sub.6 H.sub.13
 28 C.sub.8 H.sub.17 -- -- Tn Ph -- M1 .EPSILON. H
 C.sub.9 H.sub.19
 29 C.sub.5 H.sub.11 -- -- Tz1 Ph -- M1 .EPSILON. H
 C.sub.9 H.sub.19
 30 C.sub.9 H.sub.19 O -- -- Tz2 Ph -- M1 .EPSILON. H
 C.sub.6 H.sub.13
 31 C.sub.2 H.sub.5 -- -- Td Ph -- M1 .EPSILON. H
 C.sub.7 H.sub.15
 32 C.sub.10 H.sub.21 -- -- Dx2 Ph -- M1 .EPSILON. H
 C.sub.8 H.sub.17
 33 C.sub.6 H.sub.13 -- -- Boa2 Ph -- M1 .EPSILON. H
 C.sub.10 H.sub.21
 34 C.sub.15 H.sub.31 -- -- Bob2 Ph -- M1 .EPSILON. H
 C.sub.10 H.sub.21
 35 C.sub.7 H.sub.15 -- -- Bta2 Ph -- M1 .EPSILON. H
 C.sub.6 H.sub.13
 36 C.sub.16 H.sub.33 O -- -- Btb2 Ph -- M1 .EPSILON. H
 C.sub.9 H.sub.19
 37 C.sub.6 H.sub.13 -- -- Np Ph -- M1 .EPSILON. H
 C.sub.6 H.sub.13
 38 C.sub.5 H.sub.11 -- -- Np Ph -- Cb .EPSILON. H
 C.sub.4 H.sub.9
 39 C.sub.8 H.sub.17 CH(CH.sub.3)CH.sub.2 O -- -- Ep1 Ph -- Cb
 .EPSILON. H C.sub.6 H.sub.13
 40 C.sub.4 H.sub.9 -- -- Ep2 Ph -- M1 .EPSILON. H
 C.sub.8 H.sub.17
 41 C.sub.6 H.sub.13 -- -- Gp1 Ph -- M1 .EPSILON. H
 C.sub.6 H.sub.13
 42 C.sub.7 H.sub.15 -- -- Gp2 Ph -- M1 .EPSILON. H
 C.sub.12 H.sub.25
 43 C.sub.6 H.sub.13 -- -- Cm1 Ph -- M1 .EPSILON. H
 C.sub.10 H.sub.21
 44 C.sub.8 H.sub.17 -- -- Io1 Ph -- M1 .EPSILON. H
 C.sub.12 H.sub.25
 45 C.sub.18 H.sub.37 -- -- Id1 Ph M1 M1 .EPSILON.
 H C.sub.6 H.sub.13
 46 C.sub.11 H.sub.23 -- -- Id1 Ph -- M1 .EPSILON. H
 C.sub.5 H.sub.11
 47 C.sub.8 H.sub.17 -- -- Id1 Ph -- M1 .EPSILON. H
 C.sub.5 H.sub.11
 48 C.sub.5 H.sub.11 -- -- Id1 Ph2F -- M1 .EPSILON. H
 C.sub.6 H.sub.13
 49 C.sub.6 H.sub.13 -- -- Tn Ph -- M1 .EPSILON. H
 C.sub.6 H.sub.13
 50 C.sub.4 H.sub.9 O -- -- Tz2 Ph -- M1 .EPSILON. H
 C.sub.8 H.sub.17
 51 C.sub.12 H.sub.25 -- -- Btb2 Ph -- M1 .EPSILON. H
 C.sub.10 H.sub.21
 52 C.sub.6 H.sub.13 O -- -- Btb2 Ph -- M1 .EPSILON. H
 C.sub.6 H.sub.13
 53 CH.sub.2 .dbd.CH(CH.sub.2).sub.3 O -- -- Ep2 Ph -- M1
 .EPSILON. H C.sub.5 H.sub.11
 54 C.sub.9 H.sub.19 -- -- Gp2 Ph -- M1 .EPSILON. H
 C.sub.6 H.sub.13
 55 C.sub.5 H.sub.11 -- -- Np Ph -- M1 .EPSILON. H
 C.sub.6 H.sub.13
 56 C.sub.6 H.sub.13 Ph -- Ph Ph Cb M1
 .EPSILON. H C.sub.6 H.sub.13
 57 C.sub.8 H.sub.17 COO Pr2 -- Ph Ph -- M1 .EPSILON.
 H C.sub.5 H.sub.11
 58 C.sub.3 H.sub.7 Py2 -- Ph Ph -- M1 .EPSILON.
 H C.sub.4 H.sub.9
 59 C.sub.5 H.sub.11 -- -- Ha2 Ph -- M1 .EPSILON. H
 C.sub.4 H.sub.9
 60 C.sub.6 H.sub.13 Ph COO Pr2 Ph -- M1
 .EPSILON. H C.sub.6 H.sub.13
 61 C.sub.9 H.sub.19 Ph -- Pr1 Ph -- Cb .EPSILON.
 H C.sub.6 H.sub.13
 62 C.sub.13 H.sub.27 Ph -- Cy P3Br M1 Cb
 .EPSILON. H C.sub.5 H.sub.11
 63 C.sub.10 H.sub.21 O Ph OCO Py1 Ph -- M1
 .EPSILON. My C.sub.6 H.sub.13
 64 C.sub.7 H.sub.15 Ph -- Py2 Ph -- M1 .EPSILON.
 H C.sub.5 H.sub.11
 65 C.sub.4 H.sub.9 Ph3TF COO Pa Ph -- M1
 .EPSILON. H C.sub.6 H.sub.13
 66 CH.sub.3 -- -- Hb2 Ph -- M1 .EPSILON. H
 C.sub.8 H.sub.17
 67 C.sub.8 H.sub.17 Ph -- Tn Ph -- M1 .EPSILON.
 H (CH.sub.2).sub.3 CH(CH.sub.3).sub.2
 68 C.sub.2 H.sub.5 Ph -- Tz1 Ph2M -- M1 .EPSILON.
 H C.sub.8 H.sub.17
 69 C.sub.6 H.sub.13 Ph -- Ph Ph -- M1 .EPSILON.
 H C.sub.8 H.sub.17
 70 C.sub.10 H.sub.21 Ph -- Td Ph -- M1 .EPSILON.
 H (CH.sub.2).sub.3 CH(CH.sub.3).sub.2
 71 C.sub.10 H.sub.21 -- -- Ph Py1 -- M1 .EPSILON. H
 C.sub.6 H.sub.13
 72 C.sub.6 H.sub.13 -- -- Ph Py1 -- M1 .EPSILON. H
 C.sub.4 H.sub.9
 73 C.sub.6 H.sub.13 OCO -- -- Ph Py1 -- M1 .EPSILON. H
 C.sub.6 H.sub.13
 74 C.sub.7 H.sub.15 -- -- Ph Pr2 -- M1 .EPSILON. H
 C.sub.5 H.sub.11
 75 C.sub.9 H.sub.19 -- -- Ph Pr2 -- M1 .EPSILON. H
 (CH.sub.2).sub.3 CH(CH.sub.3).sub.2
 76 C.sub.7 H.sub.15 -- -- Ph Pr2 -- M1 .EPSILON. H
 C.sub.6 H.sub.13
 77 C.sub.5 H.sub.11 O -- -- Py2 Cy -- M1 .EPSILON. H
 C.sub.10 H.sub.21
 78 C.sub.4 H.sub.9 -- -- Ph Cy -- M1 .EPSILON. H
 C.sub.12 H.sub.25
 79 C.sub.12 H.sub.25 -- -- Ph Cy -- M1 .EPSILON. H
 C.sub.5 H.sub.11
 80 C.sub.6 H.sub.13 C.tbd.C -- -- Ph Pa -- M1 .EPSILON.
 H C.sub.10 H.sub.21
 81 C.sub.8 H.sub.17 O -- -- Ph Pd -- M1 .EPSILON. My
 C.sub.6 H.sub.13
 82 C.sub.3 H.sub.7 -- -- P2Cl Tn -- M1 .EPSILON. H
 C.sub.10 H.sub.21
 83 C.sub.4 H.sub.9 -- -- Ph Tn -- M1 .EPSILON. H
 C.sub.8 H.sub.17
 84 C.sub.8 H.sub.17 -- -- Ph Tz1 -- M1 .EPSILON. H
 C.sub.8 H.sub.17
 85 C.sub.4 H.sub.9 OCH(CH.sub.3)COO -- -- Ph Tz1 -- M1
 .EPSILON. H C.sub.7 H.sub.15
 86 C.sub.6 H.sub.13 -- -- Ph2F Td -- M1 .EPSILON. My
 (CH.sub.2).sub.3 CH(CH.sub.3)C.sub.6 H.sub.13
 87 C.sub.5 H.sub.11 -- -- Py2 Np -- M1 .EPSILON. H
 C.sub.9 H.sub.19
 88 CH.sub.3 -- -- Ph Np -- M1 .EPSILON. H
 C.sub.12 H.sub.25
 89 C.sub.11 H.sub.23 -- -- Ph Np -- M1 .EPSILON. H
 C.sub.6 H.sub.13
 90 C.sub.5 H.sub.11 -- -- Py1 Ep1 -- M1 .EPSILON. H
 C.sub.5 H.sub.11
 91 C.sub.8 H.sub.17 OC.sub.2 H.sub.4 -- -- Ph Ep1 -- M1
 .EPSILON. H C.sub.5 H.sub.11
 92 C.sub.6 H.sub.13 -- -- Ph Ep1 -- M1 .EPSILON. H
 C.sub.8 H.sub.17
 93 C.sub.9 H.sub.19 -- -- Py1 Gp1 -- M1 .EPSILON. H
 C.sub.5 H.sub.11
 94 C.sub.8 H.sub.17 -- -- Ph Gp1 -- M1 .EPSILON. H
 C.sub.6 H.sub.13
 95 C.sub.3 H.sub.7 COO -- -- Ph Gp1 -- M1 .EPSILON. H
 C.sub.8 H.sub.17
 96 C.sub.4 H.sub.9 -- -- Ph Id1 -- M1 .EPSILON. H
 C.sub.8 H.sub.17
 97 C.sub.12 H.sub.25 -- -- Ph Io1 Cb M1 .EPSILON.
 H C.sub.6 H.sub.13
 98 C.sub.10 H.sub.21 -- -- Ph Cm1 -- M1 .EPSILON. H
 C.sub.8 H.sub.17
 99 C.sub.6 H.sub.13 -- -- Ph Ph -- M1 .EPSILON. H
 C.sub.8 H.sub.17
 100 C.sub.4 H.sub.9 Ph OCH.sub.2 Ph Py1 -- M1
 .EPSILON. H C.sub.12 H.sub.25
 101 C.sub.4 H.sub.9 Ph2CN -- Ph Pr1 -- M1 .EPSILON.
 H C.sub.10 H.sub.21
 102 C.sub.5 H.sub.11 Ph CH.sub.2 O Ph3F Tz1 Cb M1
 .EPSILON. H C.sub.6 H.sub.13
 103 C.sub.6 H.sub.13 Ph -- Ph Tn -- M1 .EPSILON.
 H C.sub.8 H.sub.17
 104 C.sub.7 H.sub.15 Tn -- Ph Py1 -- M1 .EPSILON.
 H C.sub.8 H.sub.17
 105 C.sub.10 H.sub.21 Ph -- Ph Cy1 -- M1 .EPSILON.
 H C.sub.5 H.sub.11
 In Table A, the respective abbreviations (symbols) mean the following
 groups, respectively.
 ##STR29##
 ##STR30##
 TABLE B
 for Compounds Nos. B-1 to B-105
 ##STR31##
 No. R.sub.31 ' A.sub.31 ' A.sub.41 ' X.sub.3 ' A.sub.51 ' L
 R.sub.41 '
 1 C.sub.6 H.sub.13 -- -- -- Ph L C.sub.8 H.sub.17
 2 C.sub.8 H.sub.17 O -- -- -- Ph L C.sub.18 H.sub.37
 3 C.sub.5 H.sub.11 O -- -- -- Ph2F L C.sub.6 H.sub.13
 4 CH.sub.3 O -- Ph -- Ph L C.sub.6 H.sub.13
 5 C.sub.6 H.sub.13 *CHF(CH.sub.2).sub.2 O -- Ph -- Ph L
 C.sub.6 H.sub.13
 6 C.sub.7 H.sub.15 O -- Ph -- Ph23F L C.sub.6 H.sub.13
 7 C.sub.6 H.sub.13 -- Ph --OCH.sub.2 -- Ph L C.sub.9
 H.sub.19
 8 C.sub.6 F.sub.13 CH.sub.2 O -- Ph --C.tbd.C-- Ph L C.sub.5
 H.sub.11
 9 C.sub.8 H.sub.17 O -- Ph --COO-- Ph L C.sub.6 H.sub.13
 10 C.sub.8 H.sub.17 -- Pr1 -- Ph L C.sub.8 H.sub.17
 11 C.sub.10 H.sub.21 -- Pr2 -- Ph L C.sub.4 H.sub.9
 12 C.sub.11 H.sub.23 -- Pr2 -- Ph L C.sub.6 H.sub.13
 13 C.sub.12 H.sub.25 -- Pr2 --COO-- Ph L C.sub.8 H.sub.17
 14 C.sub.4 H.sub.9 O -- Py1 -- Ph L C.sub.10
 H.sub.21
 15 C.sub.13 H.sub.27 -- Py2 -- Ph L C.sub.5 H.sub.11
 16 C.sub.6 H.sub.13 O -- Py2 -- Ph L C.sub.8 H.sub.17
 17 C.sub.6 H.sub.13 *CHFCH.sub.2 O -- Py2 -- Ph L
 C.sub.9 H.sub.19
 18 C.sub.5 H.sub.11 O -- Py2 -- Ph23F L C.sub.4 H.sub.9
 19 C.sub.10 H.sub.21 -- Py2 -- Ph L C.sub.6 H.sub.13
 20 C.sub.8 H.sub.17 -- Py2 -- Ph3F L C.sub.7 H.sub.15
 21 C.sub.6 H.sub.13 -- Cy -- Ph L C.sub.4 H.sub.8
 OC.sub.4 H.sub.8
 22 C.sub.7 H.sub.15 OCO -- Cy -- Ph L C.sub.14
 H.sub.29
 23 C.sub.6 H.sub.13 -- Cy --CH.dbd.CH-- Ph L C.sub.10
 H.sub.21
 24 C.sub.3 H.sub.7 -- Cy --COO-- Ph L C.sub.6 H.sub.13
 25 C.sub.5 H.sub.11 -- Pa -- Ph L C.sub.8 H.sub.17
 26 C.sub.10 H.sub.21 -- Pd -- Ph L C.sub.6 H.sub.13
 27 C.sub.6 H.sub.13 -- Dt2 -- Ph L (CH.sub.2).sub.7
 CH.dbd.CH.sub.2
 28 C.sub.8 H.sub.17 -- Tn -- Ph L C.sub.9 H.sub.19
 30 C.sub.5 H.sub.11 -- Tz1 -- Ph L C.sub.8 H.sub.17
 31 C.sub.9 H.sub.19 O -- Tz2 -- Ph L C.sub.5 H.sub.11
 32 C.sub.2 H.sub.5 -- Td -- Ph L C.sub.8 H.sub.17
 33 C.sub.10 H.sub.21 -- Dx2 -- Ph L C.sub.7 H.sub.15
 34 C.sub.6 H.sub.13 -- Boa2 -- Ph L C.sub.10
 H.sub.21
 35 C.sub.7 H.sub.15 -- Bob2 -- Ph L C.sub.6 H.sub.13
 36 C.sub.16 H.sub.33 O -- Bta2 -- Ph L C.sub.6
 H.sub.13
 37 C.sub.6 H.sub.13 -- Btb2 -- Ph L C.sub.14
 H.sub.29
 38 C.sub.5 H.sub.11 -- Np --COO-- Ph L C.sub.7 H.sub.15
 39 C.sub.8 H.sub.17 *CFHCH.sub.2 O -- Ep1 -- Ph L
 C.sub.10 H.sub.21
 40 C.sub.4 H.sub.9 -- Ep2 -- Ph L C.sub.6 H.sub.13
 41 C.sub.6 H.sub.13 -- Gp1 -- Ph L C.sub.12
 H.sub.25
 42 C.sub.7 H.sub.15 -- Gp2 -- Ph L C.sub.6 H.sub.13
 43 C.sub.6 H.sub.13 -- Cm1 -- Ph L C.sub.8 H.sub.17
 44 C.sub.8 H.sub.17 -- Io1 -- Ph L C.sub.6 H.sub.13
 45 C.sub.20 H.sub.41 -- Id1 --COO-- Ph L C.sub.4 H.sub.9
 46 C.sub.11 H.sub.23 -- Id1 -- Ph L C.sub.8 H.sub.17
 47 C.sub.8 H.sub.17 -- Id1 -- Ph L C.sub.8 H.sub.17
 48 C.sub.5 H.sub.11 -- Id1 -- Ph2F L C.sub.6 H.sub.13
 49 C.sub.6 H.sub.13 -- Tn -- Ph L C.sub.7 H.sub.15
 50 C.sub.4 H.sub.9 O -- Tz2 -- Ph L C.sub.9 H.sub.19
 51 C.sub.12 H.sub.25 -- Btb2 -- Ph L C.sub.6 H.sub.13
 52 C.sub.6 H.sub.13 O -- Btb2 -- Ph L C.sub.9 H.sub.19
 53 CH.sub.2 .dbd.CH(CH.sub.2).sub.3 O -- Ep2 -- Ph L
 C.sub.6 H.sub.13
 54 C.sub.9 H.sub.19 -- Gp2 -- Ph L C.sub.5 H.sub.11
 55 C.sub.5 H.sub.11 O -- Np -- Ph L C.sub.10
 H.sub.21
 56 C.sub.6 H.sub.13 Ph Ph -- Ph L C.sub.3
 H.sub.7
 57 F Pr2 Ph -- Ph L C.sub.6
 H.sub.13
 58 C.sub.3 H.sub.7 Py2 Ph -- Ph L C.sub.8
 H.sub.17
 59 C.sub.5 H.sub.11 -- Ha2 -- Ph L C.sub.11
 H.sub.23
 60 C.sub.6 H.sub.13 Ph Pr2 -- Ph L C.sub.6
 H.sub.13
 61 C.sub.9 H.sub.19 Ph Pr1 -- Ph L C.sub.5
 H.sub.11
 62 C.sub.13 H.sub.27 Ph Cy -- Ph3Br L C.sub.7
 H.sub.15
 63 C.sub.10 H.sub.21 O Ph Py1 -- Ph L C.sub.6
 H.sub.13
 64 C.sub.7 H.sub.15 Ph Py2 -- Ph L C.sub.10
 H.sub.21
 65 C.sub.4 H.sub.9 Ph3TF Pa -- Ph L
 (CH.sub.2).sub.3 CH(CH.sub.3).sub.2
 66 H -- Hb2 -- Ph L C.sub.6 H.sub.17
 67 C.sub.8 H.sub.17 Ph Tn -- Ph L C.sub.5
 H.sub.11
 68 C.sub.2 H.sub.5 Ph Tz1 -- Ph2M L C.sub.3
 H.sub.7
 69 C.sub.6 H.sub.13 Ph Tz2 -- Ph L C.sub.6
 H.sub.13
 70 C.sub.10 H.sub.21 Ph Td -- Ph L C.sub.7
 H.sub.15
 71 C.sub.10 H.sub.21 -- Ph -- Py1 L C.sub.6 H.sub.13
 72 C.sub.6 H.sub.13 -- Ph -- Py1 L C.sub.6 H.sub.13
 73 C.sub.6 H.sub.13 OCO -- Ph -- Py1 L C.sub.5
 H.sub.11
 74 C.sub.7 H.sub.15 -- -- -- Pr2 L C.sub.10 H.sub.21
 75 C.sub.9 H.sub.19 -- Ph -- Pr2 L C.sub.8 H.sub.17
 76 C.sub.3 H.sub.7 -- Ph -- Pr2 L C.sub.6 H.sub.13
 77 C.sub.5 H.sub.11 O -- -- -- Cy L C.sub.4 H.sub.9
 78 C.sub.4 H.sub.9 -- Ph --CH.sub.2 O-- Cy L C.sub.7
 H.sub.15
 79 C.sub.12 H.sub.25 -- Ph -- Cy L C.sub.3 H.sub.7
 80 C.sub.6 H.sub.13 C.tbd.C -- Ph -- Pa L C.sub.6
 H.sub.13
 81 C.sub.8 H.sub.17 O -- Ph -- Pd L C.sub.5 H.sub.11
 82 C.sub.3 H.sub.7 -- Ph2Cl -- Tn L C.sub.10
 H.sub.21
 83 C.sub.4 H.sub.9 -- Ph -- Tn L C.sub.7 H.sub.15
 84 C.sub.8 H.sub.17 -- Ph -- Tz1 L C.sub.12
 H.sub.25
 85 C.sub.4 H.sub.9 OCH(CH.sub.3)COO -- Ph -- Tz1 L
 C.sub.5 H.sub.11
 86 C.sub.6 H.sub.13 -- Ph2F -- Td L (CH.sub.2).sub.3
 CH(CH.sub.3)C.sub.6 H.sub.13
 87 C.sub.5 H.sub.11 -- -- -- Np L C.sub.9 H.sub.19
 88 C.sub.8 H.sub.17 OCH.sub.2 CH.sub.2 -- Ph -- Np L
 C.sub.5 H.sub.11
 89 C.sub.11 H.sub.23 -- Ph -- Np L C.sub.6 H.sub.13
 90 C.sub.5 H.sub.11 -- -- -- Ep1 L C.sub.4 H.sub.9
 91 CH.sub.3 -- Ph -- Ep1 L C.sub.7 H.sub.15
 92 C.sub.6 H.sub.13 -- Ph -- Ep1 L C.sub.6 H.sub.13
 93 C.sub.9 H.sub.19 O -- -- -- Gp1 L C.sub.8 H.sub.17
 94 C.sub.8 H.sub.17 -- Ph -- Gp1 L C.sub.10
 H.sub.21
 95 C.sub.3 H.sub.7 COO -- Ph -- Gp1 L C.sub.11
 H.sub.23
 96 C.sub.4 H.sub.9 -- Ph -- Id1 L C.sub.7 H.sub.15
 97 C.sub.12 H.sub.25 -- Ph -- Io1 L C.sub.6 H.sub.13
 98 C.sub.10 H.sub.21 -- Ph -- Cm1 L C.sub.5 H.sub.11
 99 C.sub.6 H.sub.13 -- Ph -- Ph L (CH.sub.2).sub.4
 C.sub.3 F.sub.7
 100 C.sub.3 H.sub.7 Ph Ph -- Py1 L C.sub.7
 H.sub.15
 101 C.sub.4 H.sub.9 Ph2CN Ph -- Pr1 L C.sub.4
 H.sub.9
 102 C.sub.5 H.sub.11 Ph Ph3F -- Tz1 L C.sub.3
 H.sub.7
 103 CN Ph Ph -- Tn L CH.sub.3
 104 C.sub.7 H.sub.15 Tn Ph -- Py1 L C.sub.8
 H.sub.17
 105 C.sub.10 H.sub.21 Ph Ph -- Cy L C.sub.6
 H.sub.13
 In Table B, the respective abbreviations mean the following groups,
 respectively.
 ##STR32##
 ##STR33##
 ##STR34##
 ##STR35##
 ##STR36##
 ##STR37##
 ##STR38##
 The (chiral smectic) liquid crystal composition used in the invention may
 further contain additives such as an antioxidant, an ultraviolet
 ray-absorbing agent, dyes and pigments.
 The liquid crystal device according to the present invention is used as a
 display element (medium), for various liquid crystal apparatus, one
 embodiment of which is described below.
 Based on an arrangement appearing hereinbelow and data format comprising
 image data accompanied with scanning line address data and by adopting
 communication synchronization using a SYNC signal as shown in FIGS. 2 and
 3, there is provided a liquid crystal display apparatus of the present
 invention which uses the liquid crystal device according to the present
 invention as a display panel portion.
 Referring to FIG. 2, a chiral smectic liquid crystal display apparatus 101
 includes a graphic controller 102, a display panel 103, a scanning line
 drive circuit 104, a data line drive circuit 105, a decoder 106, a
 scanning signal generator 107, a shift resistor 108, a line memory 109, a
 data signal generator 110, a drive control circuit 111, a graphic central
 processing unit (GCPU) 112, a host central processing unit (host CPU) 113,
 and an image data storage memory (VRAM) 114.
 Image data are generated in the graphic controller 102 in an apparatus body
 and transferred to a display panel 103 by signal transfer means. The
 graphic controller 102 principally comprises a CPU (central processing
 unit, hereinafter referred to as "GCPU") 112 and a VRAM (video-RAM, image
 data storage memory) 114 and is in charge of management and communication
 of image data between a host CPU 113 and the liquid crystal display
 apparatus (FLCD) 101. The control of the display apparatus is principally
 performed by the graphic controller 102. A light source (not shown) is
 disposed at the back of the display panel 103.
 The liquid crystal display apparatus of the present invention employs the
 above-described liquid crystal device showing a good switching
 characteristic as a display panel (medium), so that the display apparatus
 exhibits excellent drive characteristics and reliability and provides
 high-definition and large-area display images at high speed.
 The liquid crystal device using the chiral smectic liquid crystal
 composition according to the present invention may be driven by driving
 methods as disclosed in, e.g., JP-A 59-193426, JP-A 59-193427, JP-A
 60-156046 and JP-A 60-156047.
 FIGS. 6A and 6B are waveform diagrams showing an example set of driving
 waveforms used in such a driving method. FIG. 5 is a plan view showing an
 electrode matrix used in a chiral smectic liquid crystal panel 51 of a
 simple matrix-type. The liquid crystal panel 51 shown in FIG. 5 includes
 scanning electrodes 52 (S.sub.1, S.sub.2, S.sub.3, . . . S.sub.m) and data
 electrodes 53 (I.sub.1, I.sub.2, I.sub.3, . . . I.sub.n) intersecting each
 other so as to constitute a pixel at each intersection together with a
 chiral smectic liquid crystal disposed between the scanning electrodes 52
 and data electrodes 53.
 Referring to FIG. 6A, at S.sub.S is shown a selection scanning signal
 waveform applied to a selected scanning line, at S.sub.N is shown a
 non-selection scanning signal waveform applied to a non-selected scanning
 line, at I.sub.S is shown a selection data signal waveform (providing a
 black display state) applied to a selected data line, and at I.sub.N is
 shown a non-selection data signal waveform applied to a non-selected data
 line. Further, at I.sub.S -S.sub.S and I.sub.N -S.sub.S in the figure are
 shown voltage waveforms applied to pixels on a selected scanning line,
 whereby a pixel supplied with the voltage I.sub.S -S.sub.S assumes a black
 display state and a pixel supplied with the voltage I.sub.N -S.sub.S
 assumes a white display state. FIG. 6B shows a time-serial waveform used
 for providing a display state as shown in FIG. 4.
 In the driving embodiment shown in FIGS. 6A and 6B, a minimum duration
 (application time) .DELTA.t of a single polarity voltage applied to a
 pixel on a selected scanning line corresponds to the period of a writing
 phase t.sub.2, and the period of a one-line clearing phase t.sub.1 is set
 to 2.DELTA.t.
 The parameters V.sub.S, V.sub.I and .DELTA.t in the driving waveforms shown
 in FIGS. 6A and 6B are determined depending on switching characteristics
 of a liquid crystal material used.
 FIG. 7 shows a V-T characteristic, i.e., a change in transmittance T when a
 driving voltage denoted by (V.sub.S +V.sub.I) is changed while a bias
 ratio as mentioned hereinbelow is kept constant. In this embodiment, the
 parameters are fixed at constant values of .DELTA.t=50 .mu.s and a bias
 ratio V.sub.I /(V.sub.I +V.sub.S)=1/3. On the right side of FIG. 7 is
 shown a result when the voltage (I.sub.N -S.sub.S) shown in FIG. 6A is
 applied to a pixel concerned, and on the left side of FIG. 8 is shown a
 result when the voltage (I.sub.S -S.sub.S) is applied to a pixel
 concerned, respectively while increasing the voltage (V.sub.S +V.sub.I).
 On both sides of the ordinate, the absolute value of the voltage (V.sub.S
 +V.sub.I) is separately indicated. At (I.sub.N -S.sub.S) and (I.sub.S
 -S.sub.S), a previous (display) state is cleared by applying a voltage
 V.sub.R and a subsequent (display) state is determined by voltages
 V.sub.B.sup.1 and V.sub.B.sup.2, respectively. Referring to FIG. 8, a
 relationship of V.sub.2 &lt;V.sub.1 &lt;V.sub.3 holds. At this time, (V.sub.3
 -V.sub.1)/(V.sub.3 +V.sub.1) is referred to as a voltage margin parameter
 M2 (V) as to a voltage range allowing a matrix drive. The voltage V.sub.1
 may be referred to as a threshold voltage in actual drive and the voltage
 V.sub.3 may be referred to as a crosstalk voltage. More specifically, as
 shown in FIG. 6A, a voltage V.sub.1 denotes a voltage value causing
 switching by applying a voltage signal V.sub.B.sup.2 and a voltage V.sub.3
 denotes a voltage value causing switching by applying a voltage signal
 V.sub.B.sup.1. Further, a voltage V.sub.2 denotes a voltage value required
 for clearing the previous state by applying a voltage signal V.sub.R. The
 crosstalk voltage V.sub.3 is generally present in actual matrix drive of a
 ferroelectric liquid crystal device. It is of course possible to increase
 the value of V.sub.3 by increasing the bias ratio (i.e., by causing the
 bias ratio to approach a unity). However, a large bias ratio corresponds
 to a large amplitude of a data signal and leads to an increase in
 flickering and a lower contrast, thus being undesirable in respect of
 image quality. According to our study, a bias ratio of about 1/3-1/4 was
 practical. On the other hand, when the bias ratio is fixed, the voltage
 margin parameter M2 (V) strongly depends on the switching characteristics
 of a liquid crystal material and the cell (device) structure, and it is
 needless to say that a liquid crystal device providing a large M2 (V) is
 very advantageous for matrix drive.
 Further, it is also possible to drive the liquid crystal device by changing
 a voltage application time (duration) t while keeping the driving voltage
 (V.sub.I +V.sub.S) so as to provide a certain (constant) value. In this
 case, the drive characteristic of the liquid crystal device can be
 evaluated in terms of a duration margin parameter (voltage application
 time margin parameter) M2 (.DELTA.T)=(.DELTA.t.sub.2
 -.DELTA.t.sub.1)/(.DELTA.t.sub.2 +.DELTA.t.sub.1) wherein .DELTA.t.sub.1
 denotes a threshold duration and t.sub.2 denotes a crosstalk duration.
 The upper and lower limits of application voltages or durations and a
 difference therebetween (driving voltage margin .DELTA.V=V.sub.3 -V.sub.1
 or duration margin .DELTA.T=.DELTA.t.sub.2 -.DELTA.t.sub.2) by which
 selected pixels are written in two states of "black" and "white" and
 non-selected pixels can retain the written "black" and "white" states at a
 constant temperature as described above, vary depending on and are
 intrinsic to a liquid crystal material used and a cell structure employed.
 Further, the driving margin (voltage or duration margin) is fluctuated
 according to a change in environmental temperature, so that optimum
 driving conditions should be required of an actual display apparatus in
 view of a liquid crystal material used, a cell (device) structure and an
 environmental temperature.
 Hereinbelow, the present invention will be described more specifically
 based on Examples. It is however to be understood that the present
 invention is not restricted to these Examples.
 In the following examples, chiral smectic liquid crystal compositions were
 prepared by mixing the following mesomorphic compounds indicated
 proportions (shown in respective examples).
 &lt;Perfluoroalkyl-Type Mesomorphic Compound&gt;

Compound Structural formula
 (1)
 ##STR39##
 (2)
 ##STR40##
 (3)
 ##STR41##
 (4)
 ##STR42##
 (5)
 ##STR43##
 (6)
 ##STR44##
 (7)
 ##STR45##
 Optically active compound Structural formula
 (a)
 ##STR46##
 (b)
 ##STR47##
 (c)
 ##STR48##
 In the above compounds, compounds falling under the category of the
 fluorine-containing mesomorphic compound (B) and/or the compound (C) are
 the compounds (4)-(7).
 In order to identify the compound (C) providing a tilt angle .theta. of at
 least 30 degrees at a temperature T(T=Tc-15.degree. C., Tc: upper limit
 temperature of smectic C phase-providing temperature), each of the
 compounds (4)-(7) was subjected to measurement of tilt angle .theta. in
 the following manner.
 Three liquid crystal compositions were prepared by mixing one of the
 compounds (4)-(7) with an optically active compound of the formula (i):
 ##STR49##
 in a mixing ratio of 99:1, 98:2 and 97:3 (by weight), respectively.
 Each of these compositions was injected into a spacing (about 1 .mu.m) of a
 blank cell including a pair of substrates provided with ITO electrodes to
 prepare a liquid crystal cell (device).
 Then, each of the liquid crystal compositions contained in the respective
 liquid crystal devices was controlled to have a temperature below its
 upper limit temperature of smectic C phase by 15.degree. C.
 Each of the liquid crystal device was sandwiched between right angle-cross
 nicol polarizers and rotated horizontally relative to the polarizers under
 application of an AC voltage of .+-.30 V to .+-.50 V and 1 to 100 Hz
 between the upper and lower substrates of the device while measuring a
 transmittance through the device by a photomultiplier (available from
 Hamamatsu Photonics K.K.) to find a first extinction position (a position
 providing the lowest transmittance) and a second extinction position. A
 tilt angle .theta. was measured as a half of the angle between the first
 and second extinction positions.
 With respect to each of the compounds (4)-(7), a tilt angle .theta. of the
 compound alone was obtained from three measured data of the respective
 three liquid crystal compositions (optically active compound content: 1
 wt. %, 2 wt. %, 3 wt. %) by extrapolation.
 The thus-obtained tilt angles of the compounds (4)-(7) per se are shown in
 Table 1.
 TABLE 1
 Tilt angle .THETA.
 Compound (at Tc-T = 15.degree. C.)
 (4) 24
 (5) 15
 (6) 30.5
 (7) 35
 Accordingly, the compounds (6) and (7) correspond to the compound (c)
 described above.
 EXAMPLE 1
 Each of three blank cells was prepared as follows.
 To one of 1.1 mm-thick glass plates provided with an ITO film having a
 prescribed pattern, a solution of 6,6-nylon in formic acid was applied by
 spin coating, followed by drying and subjecting the resultant nylon film
 to rubbing treatment to form a 50 .ANG.-thick alignment control layer.
 To the other glass plate provided with an ITO film having a prescribed
 pattern, a solution of a silane coupling agent comprising
 octadecyltriethoxysilane was applied by spin coating, followed by hot
 curing to form a 20 .ANG.-thick alignment control layer.
 After silica beads (average particle size: about 2 .mu.m) as a spacer were
 dispersed on the other glass plates, the two glass plates were applied to
 each other so that the alignment control layers constituted inner
 (opposite) surfaces to prepare a blank cell having a cell gap of 1.8
 .mu.m.
 Chiral smectic liquid crystal compositions A to C were prepared by mixing
 the above-mentioned mesomorphic compounds and optically active compounds
 in the indicated proportions (wt. parts) shown in Table 2 below,
 respectively.
 TABLE 2
 Compo- Compounds (wt. parts)
 sition (1) (2) (3) (4) (5) (6) (7) (a) (b) (c)
 A 10 10 10 30 30 5 -- 3 2 --
 B 6 10 7 30 30 -- 10 -- 7 --
 C 5 10 10 30 30 10 -- 3 2 --
 Each of the thus prepared liquid crystal compositions A to C was injected
 in the blank cell in isotropic liquid phase and gradually at a rate of
 0.5.degree. C./min cooled to a temperature at which chiral smectic phase
 was assumed, thus preparing liquid crystal devices 1-1, 1-2 and 1-3,
 respectively.
 Each of the liquid crystal devices 1-1, 1-2 and 1-3 was evaluated with
 respect to the following items.
 Alignment Characteristic
 The liquid crystal device after cooling (at a rate of 0.5.degree. C./min
 for isotropic phase) was subjected to observation of an alignment state of
 liquid crystal molecules at 25.degree. C.
 "Good": A random alignment region was not observed.
 "Inferior": A random alignment region was observed.
 Bookshelf (BS) Characteristic
 A bookshelf (BS) characteristic was evaluated as a degree of a layer
 inclination angle (angle formed between the smectic layer and a normal to
 the substrate).
 The layer inclination angle was measured by using a method by Clark and
 Lagerwall (Japanese Display '86, Sep. 30-Oct. 2, 1986, p.p. 456-458) or
 the method of Ohuchi et al (J.J.A.P., 27 (5) (1988), p.p. 725-728).
 Specifically, the measurement was performed by using a rotary cathode-type
 X-ray diffraction apparatus (available from MAC Science), and 80
 .mu.m-thick microsheets (glass sheet) (available from Corning Glass Works)
 were instead of the 1.1 mm-thick glass plates.
 "Good": an inclination angle of at most 8 degrees.
 "Inferior": an inclination angle of above 8 degrees.
 Transmittance (T %)
 The liquid crystal device was sandwiched between cross nicol polarizers. By
 using a light source (backlight) disposed behind the liquid crystal
 device, a transmittance (transmitted light quantity) T.sub.1 through the
 device with the polarizers was measured by a photomultiplier (available
 from Hamamatsu Photonics K.K.). Similarly, a transmittance T.sub.2 through
 the polarizers (not through the device per se) was measured.
 A transmittance (T) was evaluated as a ratio of T.sub.1 /T.sub.2 (i)
 Contrast Ratio (C/R)
 The liquid crystal device wa sandwiched between cross nicol polarizers
 arranged so as to provide one of extinction positions (where a minimum
 transmittance was attained) under no voltage (electric field) application.
 The liquid crystal device was driven at 25.degree. C. by using a drive
 waveform as shown in FIGS. 6A and 6B (bias ratio=1/3.0, drive voltage
 (V.sub.S +V.sub.1)=10 volts) and a light source providing a certain light
 quantity source providing a certain light quantity to effect a display of
 "white" and "black" states while measuring a transmittance in the states
 to obtain a contrast ratio (C/R) between those in the "white" and "black"
 states.
 Contrast Keeping Temperature Range (CK Range)
 After measuring a contrast ratio (C/R).sub.1 at 25.degree. C. according to
 the above method, the liquid crystal device was cooled to a prescribed
 temperature (T.sub.1) at a rate of 1.degree. C./min and left standing for
 1 hour at T.sub.1 and then was restored to 25.degree. C. Thereafter, the
 liquid crystal device was again subjected to measurement of a contrast
 ratio (C/R).sub.2. When the contrast ratio (C/R).sub.2 was within .+-.20%
 of the contrast ratio (C/R).sub.1, a temperature range from T.sub.1 to a
 phase transition temperature T.sub.CA (smectic C phase/smectic A phase)
 was evaluated as a contrast-keeping temperature range (CK range) allowing
 a substantially stable contrast ratio without being adversely affected by
 temperature decrease and temperature increase (temperature history).
 The results are shown in Table 3.
 TABLE 3
 Compo- Align- BS charac- T CK
 Device sition ment teristic (%) C/R range (.degree. C.)
 1-1 A Good Good 85 65 40
 1-2 B Good Good 85 57 50
 1-3 C Good Good 88 55 50
 EXAMPLE 2
 Each of three blank cells was prepared as follows.
 To one of 1.1 mm-thick glass plates provided with an ITO film having a
 prescribed pattern, a solution of a polyimide precursor (providing a
 polyimide having a recurring unit of the formula (III) shown below in a
 mixture solvent (n-methylpyrrolidone (NMP)/n-butylcellosolve (nBC)=2/1)
 was applied by spin coating. The thus coated glass plate was subjected to
 hot curing treatment and a rubbing treatment to form a 100 .ANG.-thick
 polyimide alignment control layer.
 ##STR50##
 To the other glass plate provided with an ITO film, a solution of a silane
 coupling agent comprising octadecyltriethoxysilane was applied by spin
 coating, followed by hot curing to form a 20 .ANG.-thick alignment control
 layer.
 After silica beads (average particle size: about 2 .mu.m) as a spacer were
 dispersed on the other glass plate, the two glass plates were applied to
 each other so that the alignment control layers constituted inner surfaces
 to prepare a blank cell having a cell gap of 1.8 .mu.m.
 Into the thus prepared blank cells, the liquid crystal compositions A to C
 prepared in Example 1 were injected in a similar manner to prepare three
 liquid crystal devices 2-1, 2-2 and 2-3, respectively.
 Each of the thus prepared liquid crystal devices 2-1, 2-2 and 2-3 was
 evaluated in the same manner as in Example 1.
 The results are shown in Table 4.
 TABLE 4
 Compo- Align- BS charac- T CK
 Device sition ment teristic (%) C/R range (.degree. C.)
 2-1 A Good Good 90 75 40
 2-2 B Good Good 90 68 50
 2-3 C Good Good 85 60 50
 Further, three liquid crystal devices were prepared and evaluated in the
 same manner as in this example (Example 2) except that the thickness of
 the polyimide film was changed to 50 .ANG.. Evaluation results were
 similar to those shown in Table 4.
 Reference Example 1
 Three liquid crystal devices 1-4, 1-5 and 1-6 were prepared and evaluated
 in the same manner as in Example 1 except that three liquid crystal
 compositions C, D and E shown in Table 5 below were used, respectively.
 TABLE 5
 Compo- Compounds (wt. parts)
 sition (1) (2) (3) (4) (5) (6) (7) (a) (b) (c)
 D 3 3 4 80 -- -- -- 5 -- --
 E 20 25 25 10 13 -- -- 2 5 --
 F 15 10 15 50 -- -- -- 5 -- --
 The results are shown in Table 6.
 TABLE 6
 Compo- Align- BS charac- T CK
 Device sition ment teristic (%) C/R range (.degree. C.)
 1-4 D Good Good 50 27 25
 1-5 E Good Inferior 60 10 40
 1-6 F Good Inferior 55 10 40
 Reference Example 2
 Liquid crystal devices 1-7 and 1-8 using liquid crystal compositions A and
 B, respectively, were prepared and evaluated in the same manner as in
 Example 1 except that the nylon alignment control layer was changed to a
 250 .ANG.-thick polyvinyl alcohol alignment control film (polyvinyl
 alcohol, available from Aldrich Co.).
 Both of the liquid crystal devices 1-7 and 1-8 provided a remarkably
 inferior alignment characteristic, so that a meaningful evaluation could
 not be effected with respect to other evaluation items.
 Reference Example 3
 A liquid crystal device 2-4 was prepared and evaluated in the same manner
 as in Example 2 except that a 50 .ANG.-thick rubbing-treated polyimide
 alignment control layer was provided to both of the glass plates and the
 liquid crystal composition C was used.
 The results are shown in Table 7.
 TABLE 7
 Compo- Align- BS charac- T CK
 Device sition ment teristic (%) C/R range (.degree. C.)
 2-4 C Inferior Inferior 75 50 50
 Reference Example 4
 Liquid crystal device 2-5 and 2-6 were prepared and evaluated in the same
 manner as in Example 2 except that the 100 .ANG.-thick polyimide alignment
 control layer was changed to a 300 .ANG.-thick polyimide alignment control
 layer and the liquid crystal compositions A and B were used, respectively.
 Both of the liquid crystal devices 2-5 and 2-6 provided a poor bistability
 and a contrast ratio (C/R) of at most 5.
 EXAMPLE 3
 Liquid crystal device 3-1 and 3-2 were prepared and evaluated in the same
 manner as in Example 2 except that a 100 .ANG.-thick polyimide alignment
 control layer was formed by using a polyimide having the following
 recurring unit:
 ##STR51##
 and that the liquid crystal compositions A and B were used.
 The results are shown in Table 8.
 TABLE 8
 Compo- Align- BS charac- T CK
 Device sition ment teristic (%) C/R range (.degree. C.)
 3-1 A Good Good 85 55 40
 3-2 B Good Good 85 45 50
 Reference Example 5
 Liquid crystal device 2-7, 2-8 and 2-9 were prepared and evaluated in the
 same manner as in Example 2 except that the liquid crystal compositions D,
 E and F prepared in Reference Example 1 were used, respectively.
 The results are shown in Table 9.
 TABLE 9
 Compo- Align- BS charac- T CK
 Device sition ment teristic (%) C/R range (.degree. C.)
 2-7 D Good Good 50 30 25
 2-8 E Good Inferior 60 20 40
 2-9 F Good Inferior 60 20 40
 As described hereinabove, according to the present invention, there is
 provided a liquid crystal device using a specific cell structure and a
 specific liquid crystal composition capable of exhibiting a bookshelf
 structure or a structure closer thereto having a small layer inclination
 angle, so that it is possible to provide improved display characteristics
 including a high brightness (high transmittance) and a high contrast
 ratio. In the liquid crystal device, the cell structure includes at least
 one thin (at most 200 .ANG.) alignment control film or at least one
 polyimide film and preferably includes a pair of substrates (electrode
 plates) provided with alignment control layers subjected to different
 aligning treatments (e.g., only one of the alignment control layers is
 subjected to rubbing), thereby allowing a high reliability and a
 temperature stability with respect to the display characteristics and the
 layer structure.