Liquid crystal composition and liquid crystal display device

Abstract

A liquid crystal composition includes a polymerizable compound (or polymer) and a polar compound, where the homeotropic alignment of liquid crystal molecules can be achieved by the action of these compounds, and a liquid crystal display device includes such a composition. A nematic liquid crystal composition has positive dielectric anisotropy and includes a polymerizable compound as a first additive and a polar compound as a second additive, and the composition may include a specific liquid crystal compound having a large positive dielectric anisotropy and a specific liquid crystal compound having a high maximum temperature or a small viscosity, and a liquid crystal display device includes such a composition.

Claims

1. A liquid crystal composition having positive dielectric anisotropy and including at least one polymerizable compound represented by formula (1) as a first additive, and at least one polar compound represented by formula (5) as a second additive: ##STR00065##
MES-R.sup.5(5) in formula (1), ring A and ring C are independently cyclohexyl, cyclohexenyl, phenyl, 1-naphthyl, 2-naphthyl, tetrahydropyran-2-yl, 1,3-dioxane-2-yl, pyrimidine-2-yl or pyridine-2-yl, and in these rings at least one hydrogen may be replaced by fluorine, chlorine, alkyl having 1 to 12 carbons, alkoxy having 1 to 12 carbons or alkyl having 1 to 12 carbons in which at least one hydrogen has been replaced by fluorine or chlorine; ring B is 1,4-cyclohexylene, 1,4-cyclohexenylene, 1,4-phenylene, naphthalene-1,2-diyl, naphthalene-1,3-diyl, naphthalene-1,4-diyl, naphthalene-1,5-diyl, naphthalene-1,6-diyl, naphthalene-1,7-diyl, naphthalene-1,8-diyl, naphthalene-2,3-diyl, naphthalene-2,6-diyl, naphthalene-2,7-diyl, tetrahydropyran-2,5-diyl, 1,3-dioxane-2,5-diyl, pyrimidine-2,5-diyl or pyridine-2,5-diyl, and in these rings at least one hydrogen may be replaced by fluorine, chlorine, alkyl having 1 to 12 carbons, alkoxy having 1 to 12 carbons or alkyl having 1 to 12 carbons in which at least one hydrogen has been replaced by fluorine or chlorine; Z.sup.1 and Z.sup.2 are independently a single bond or alkylene having 1 to 10 carbons, and in the alkylene at least one CH.sub.2 may be replaced by O, CO, COO or OCO, and at least one CH.sub.2CH.sub.2 may be replaced by CHCH, C(CH.sub.3)CH, CHC(CH.sub.3) or C(CH.sub.3)C(CH.sub.3), and in these groups at least one hydrogen may be replaced by fluorine or chlorine; P.sup.1, P.sup.2 and P.sup.3 are a polymerizable group; Sp.sup.1, Sp.sup.2 and Sp.sup.3 are independently a single bond or alkylene having 1 to 10 carbons, and in the alkylene at least one CH.sub.2 may be replaced by O, COO, OCO or OCOO, and at least one CH.sub.2CH.sub.2 may be replaced by CHCH or CC, and in these groups at least one hydrogen may be replaced by fluorine or chlorine; a is 0, 1 or 2; and b and d are 1; c is independently 0, 1, 2, 3 or 4, with the proviso that a is 1 or 2 when ring A and ring C are phenyl and that Sp.sup.1 and Sp.sup.3 are a single bond when a is 1; in formula (5), MES is a mesogenic group having at least one ring; and R.sup.5 is a group represented by any one of formula (A2) to formula (A4): ##STR00066## in formula (A2) to formula (A4), Sp.sup.4, Sp.sup.6 and Sp.sup.7 are independently a single bond or group (-Sp-X), where Sp is alkylene having 1 to 20 carbons, and in the alkylene at least one CH.sub.2 may be replaced by O, S, NH, N(R.sup.0), CO, COO, OCO, OCOO, SCO, COS, N(R.sup.0)COO, OCON(R.sup.0), N(R.sup.0)CON(R.sup.0), CHCH or CC, and in these groups at least one hydrogen may be replaced by fluorine, chlorine or CN, and X is O, S, CO, COO, OCO, OCOO, CON(R.sup.0), N(R.sup.0)CO, N(R.sup.0)CON(R.sup.0), OCH.sub.2, CH.sub.2O, SCH.sub.2, CH.sub.2S, CF.sub.2O, OCF.sub.2, CF.sub.2S, SCF.sub.2, CF.sub.2CH.sub.2, CH.sub.2CF.sub.2, CF.sub.2CF.sub.2, CHN, NCH, NN, CHCR.sup.0, CY.sup.2CY.sup.3, CC, CHCHCOO, OCOCHCH or a single bond, where R.sup.0 is hydrogen or alkyl having 1 to 12 carbons, and Y.sup.2 and Y.sup.3 are independently hydrogen, fluorine, chlorine or CN; Sp.sup.1 is a trivalent group or a tetravalent group (namely, >CH, >CR.sup.11, >N, >C<); X.sup.3 is OH, OR.sup.11, COOH, NH.sub.2, NHR.sup.11, N(R.sup.11).sub.2, SH, SR.sup.11, ##STR00067## where R.sup.0 is hydrogen or alkyl having 1 to 12 carbons; X.sup.4 is O, CO, NH, NR.sup.11, S or a single bond; R.sup.11 is alkyl having 1 to 15 carbons, and in the alkyl at least one CH.sub.2 may be replaced by CC, CHCH, COO, OCO, CO or O, and in these groups at least one hydrogen may be replaced by fluorine or chlorine; ring J is an aromatic group having 6 to 25 carbons or an alicyclic group having 3 to 25 carbons, and these groups may be a condensed ring, and in these groups one to three hydrogens may be replaced by R.sup.L; R.sup.L is OH, (CH.sub.2).sub.iOH, fluorine, chlorine, CN, NO.sub.2, NCO, NCS, OCN, SCN, C(O)N(R.sup.0).sub.2, C(O)R.sup.0, N(R).sub.2, (CH.sub.2).sub.iN(R).sub.2, SH, SR.sup.0, aryl having 6 to 20 carbons, heteroaryl having 6 to 20 carbons, alkyl having 1 to 25 carbons, alkoxy having 1 to 25 carbons, alkylcarbonyl having 2 to 25 carbons, alkoxycarbonyl having 2 to 25 carbons, alkylcarbonyloxy having 2 to 25 carbons or alkoxycarbonyloxy having 2 to 25 carbons, and in these groups at least one hydrogen may be replaced by fluorine or chlorine, where R.sup.0 is hydrogen or alkyl having 1 to 12 carbons, i is 1, 2, 3 or 4; and k is 2, 3, 4 or 5.

2. The liquid crystal composition according to claim 1, wherein the first additive is at least one polymerizable compound selected from the group of compounds represented by formula (1-1) to formula (1-7) and formula (1-9) to formula (1-12): ##STR00068## ##STR00069## in formula (1-1) to formula (1-7) and formula (1-9) to formula (1-12), P.sup.1, P.sup.2 and P.sup.3 are independently a polymerizable group selected from the group of groups represented by formula (P-1) to formula (P-3), where M.sup.1, M.sup.2 and M.sup.3 are independently hydrogen, fluorine, alkyl having 1 to 5 carbons or alkyl having 1 to 5 carbons in which at least one hydrogen has been replaced by fluorine or chlorine; and ##STR00070## Sp.sup.1, Sp.sup.2 and Sp.sup.3 are independently a single bond or alkylene having 1 to 10 carbons, and in the alkylene at least one CH.sub.2 may be replaced by O, COO, OCO or OCOO, and at least one CH.sub.2CH.sub.2 may be replaced by CHCH or CC, and in these groups at least one hydrogen may be replaced by fluorine or chlorine.

3. The liquid crystal composition according to claim 1, wherein the ratio of the first additive is in the range of 0.03% by weight to 10% by weight based on the weight of the liquid crystal composition.

4. The liquid crystal composition according to claim 1, including at least one compound represented by formula (2) as a first component: ##STR00071## in formula (2), R.sup.1 is alkyl having 1 to 12 carbons, alkoxy having 1 to 12 carbons or alkenyl having 2 to 12 carbons or alkenyl having 2 to 12 carbons in which at least one hydrogen has been replaced by fluorine or chlorine; ring D is 1,4-cyclohexylene, 1,4-phenylene, 2-fluoro-1,4-phenylene, 2,3-difluoro-1,4-phenylene, 2,6-difluoro-1,4-phenylene, 3,5-difluoro-1,4-phenylene, pyrimidine-2,5-diyl, 1,3-dioxane-2,5-diyl or tetrahydropyran-2,5-diyl; Z.sup.3 is a single bond, CH.sub.2CH.sub.2, CH.sub.2O, OCH.sub.2, COO, COC, CF.sub.2O or OCF.sub.2; X.sup.1 and X.sup.2 are independently hydrogen or fluorine; Y.sup.1 is fluorine, chlorine, alkyl having 1 to 12 carbons in which at least one hydrogen has been replaced by fluorine or chlorine, alkoxy having 1 to 12 carbons in which at least one hydrogen has been replaced by fluorine or chlorine, or alkenyloxy having 2 to 12 carbons in which at least one hydrogen has been replaced by fluorine or chlorine; and e is 1, 2, 3 or 4.

5. The liquid crystal composition according to claim 4, including at least one compound selected from the group of compounds represented by formula (2-1) to formula (2-46) as the first component: ##STR00072## ##STR00073## ##STR00074## ##STR00075## ##STR00076## in formula (2-1) to formula (2-46), R.sup.1 is alkyl having 1 to 12 carbons, alkoxy having 1 to 12 carbons, alkenyl having 2 to 12 carbons or alkenyl having 2 to 12 carbons in which at least one hydrogen has been replaced by fluorine or chlorine.

6. The liquid crystal composition according to claim 4, wherein the ratio of the first component is in the range of 10% by weight to 90% by weight based on the weight of the liquid crystal composition.

7. The liquid crystal composition according to claim 1, including at least one compound represented by formula (3) as a second component: ##STR00077## in formula (3), R.sup.2 and R.sup.3 are independently alkyl having 1 to 12 carbons, alkoxy having 1 to 12 carbons, alkenyl having 2 to 12 carbons, alkyl having 1 to 12 carbons in which at least one hydrogen has been replaced by fluorine or chlorine, or alkenyl having 2 to 12 carbons in which at least one hydrogen has been replaced by fluorine or chlorine; ring E and ring F are independently 1,4-cyclohexylene, 1,4-phenylene, 2-fluoro-1,4-phenylene or 2,5-difluoro-1,4-phenylene; Z.sup.4 is a single bond, CH.sub.2CH.sub.2, CH.sub.2O, OCH.sub.2, COO or OCO; and f is 1, 2 or 3.

8. The liquid crystal composition according to claim 7, including at least one compound selected from the group of compounds represented by formula (3-1) to formula (3-13) as the second component: ##STR00078## ##STR00079## in formula (3-1) to formula (3-13), R.sup.2 and R.sup.3 are independently alkyl having 1 to 12 carbons, alkoxy having 1 to 12 carbons, alkenyl having 2 to 12 carbons, alkyl having 1 to 12 carbons in which at least one hydrogen has been replaced by fluorine or chlorine, or alkenyl having 2 to 12 carbons in which at least one hydrogen has been replaced by fluorine or chlorine.

9. The liquid crystal composition according to claim 7, wherein the ratio of the second component is in the range of 10% by weight to 90% by weight based on the weight of the liquid crystal composition.

10. The liquid crystal composition according to claim 1, including at least one compound represented by formula (4) as a third component: ##STR00080## in formula (4), R.sup.7 and R.sup.8 are independently alkyl having 1 to 12 carbons, alkoxy having 1 to 12 carbons, alkenyl having 2 to 12 carbons or alkenyloxy having 2 to 12 carbons; ring Q and ring V are independently 1,4-cyclohexylene, 1,4-cyclohexenylene, 1,4-phenylene, 1,4-phenylene in which at least one hydrogen has been replaced by fluorine or chlorine or tetrahydropyran-2,5-diyl; ring U is 2,3-difluoro-1,4-phenylene, 2-chloro-3-fluoro-1,4-phenylene, 2,3-difluoro-5-methyl-1,4-phenylene, 3,4,5-trifluoronaphthalene-2,6-diyl or 7,8-difluorochroman-2,6-diyl; Z.sup.7 and Z.sup.8 are independently a single bond, CH.sub.2CH.sub.2, CH.sub.2O, OCH.sub.2, COO or OCO; p is 1, 2 or 3, q is 0 or 1; and the sum of p and q is 3 or less.

11. The liquid crystal composition according to claim 10, including at least one compound selected from the group of compounds represented by formula (4-1) to formula (4-21) as the third component: ##STR00081## ##STR00082## in formula (4-1) to formula (4-21), R.sup.7 and R.sup.8 are independently alkyl having 1 to 12 carbons, alkoxy having 1 to 12 carbons, alkenyl having 2 to 12 carbons or alkenyloxy having 2 to 12 carbons.

12. The liquid crystal composition according to claim 10, wherein the ratio of the third component is in the range of 3% by weight to 25% by weight based on the weight of the liquid crystal composition.

13. The liquid crystal composition according to claim 1, including at least one compound represented by formula (5-1) as the second additive: ##STR00083## in formula (5-1), ring G and ring I are independently an aromatic group having 6 to 25 carbons, a heteroaromatic group having 5 to 25 carbons, an alicyclic group having 3 to 25 carbons or a heteroalicyclic group having 4 to 25 carbons and these groups may be a condensed ring, and in these groups at least one hydrogen may be replaced by group T, where group T is OH, (CH.sub.2).sub.iOH, halogen, CN, NO.sub.2, NCO, NCS, OCN, SCN, C(O)N(R.sup.0).sub.2, C(O)R, N(R.sup.0).sub.2, (CH.sub.2).sub.iN(R.sup.0).sub.2, aryl having 6 to 20 carbons, heteroaryl having 6 to 20 carbons, alkyl having 1 to 25 carbons, alkoxy having 1 to 25 carbons, alkylcarbonyl having 2 to 25 carbons, alkoxycarbonyl having 2 to 25 carbons, alkylcarbonyloxy having 2 to 25 carbons or alkoxycarbonyloxy having 2 to 25 carbons, in these groups at least one hydrogen may be replaced by fluorine or chlorine, where R.sup.0 is hydrogen or alkyl having 1 to 12 carbons, i is 1, 2, 3 or 4; Z.sup.5 is O, S, CO, COO, OCO, OCOO, OCH.sub.2, CH.sub.2O, SCH.sub.2, CH.sub.2S, CF.sub.2O, OCF.sub.2, CF.sub.2S, SCF.sub.2, (CH.sub.2).sub.i, CF.sub.2CH.sub.2, CH.sub.2CF.sub.2, (CF.sub.2).sub.i, CHCH, CFCF, CC, CHCHCOO, OCOCHCH, C(R.sup.0).sub.2 or a single bond, where R.sup.0 is hydrogen or alkyl having 1 to 12 carbons, and i is 1, 2, 3 or 4; R.sup.5 is alkyl having 1 to 25 carbons, and in the alkyl at least one CH.sub.2 may be replaced by NR.sup.0, O, S, CO, COO, OCO, OCOO or cycloalkylene having 3 to 8 carbons, where R.sup.0 is hydrogen or alkyl having 1 to 12 carbons, at least one tertiary carbon (>CH) may be replaced by nitrogen (>N), and at least one hydrogen may be replaced by fluorine or chlorine; R.sup.6 is hydrogen, halogen, alkyl having 1 to 25 carbons, and in the alkyl at least one CH.sub.2 may be replaced by NR.sup.0, O, S, CO, COO, OCO, OCOO or cycloalkylene having 3 to 8 carbons, and at least one tertiary carbon (>CH) may be replaced by nitrogen (>N), and in these groups at least one hydrogen may be replaced by fluorine or chlorine, where R.sup.0 is hydrogen or alkyl having 1 to 12 carbons; and h is 0, 1, 2, 3, 4 or 5.

14. The liquid crystal composition according to claim 13, wherein the second additive is at least one compound selected from the group of compounds represented by formula (5-1-2) to formula (5-1-4): ##STR00084## in formula (5-1-2) to formula (5-1-4), ring G and ring I are independently 1,4-cyclohexylene, 1,4-phenylene, 2-fluoro-1,4-phenylene, 2-fluoro-1,3-phenylene, 2-ethyl-1,4-phenylene, 2,6-diethyl-1,4-phenylene, 2-trifluoromethyl-1,4-phenylene, 2,3-difluoro-1,4-phenylene, 2,5-difluoro-1,4-phenylene, 2,6-difluoro-1,4-phenylene or 2,3,5,6-tetrafluoro-1,4-phenylene; ring J is cyclohexyl or phenyl; Z.sup.5 is a single bond, CH.sub.2CH.sub.2, COO or OCO; Sp.sup.4 is a single bond, ethylene, propylene or methyleneoxy; Sp.sup.7 is a single bond or alkylene having 1 to 5 carbons, and in the alkylene CH.sub.2 may be replaced by O or NH; R.sup.6 is alkyl having 1 to 8 carbons or fluorine; h is 0, 1, 2, 3, 4 or 5; X.sup.3 is OH, COOH, SH, OCH.sub.3 or NH.sub.2; and X.sup.4 is a single bond or O.

15. The liquid crystal composition according to claim 1, wherein the ratio of the second additive is less than 10% by weight based on the weight of the liquid crystal composition.

16. A liquid crystal display device including the liquid crystal composition according to claim 1.

17. A liquid crystal display device having no alignment films and including a liquid crystal composition according to claim 1, where the polymerizable compound in the liquid crystal composition has been polymerized.

Description

EXAMPLES

(1) The invention will be explained in more detail by way of examples. The invention is not limited to the examples. The invention includes a mixture of composition (M1) and composition (M2). The invention also includes a mixture prepared by mixing at least two compositions in Examples. Compounds prepared herein were identified by methods such as NMR analysis. The characteristics of the compounds, compositions and devices were measured by the methods described below.

(2) NMR Analysis: A model DRX-500 apparatus made by Bruker BioSpin Corporation was used for measurement. In the measurement of .sup.1H-NMR, a sample was dissolved in a deuterated solvent such as CDCl.sub.3, and the measurement was carried out under the conditions of room temperature, 500 MHz and the accumulation of 16 scans. Tetramethylsilane was used as an internal standard. In the measurement of .sup.19F-NMR, CFCl.sub.3 was used as the internal standard, and 24 scans were accumulated. In the explanation of the nuclear magnetic resonance spectra, the symbols s, d, t, q, quin, sex, m and br stand for a singlet, a doublet, a triplet, a quartet, a quintet, a sextet, a multiplet and line-broadening, respectively.

(3) Gas Chromatographic Analysis: A gas chromatograph Model GC-14B made by Shimadzu Corporation was used for measurement. The carrier gas was helium (2 milliliters per minute). The sample injector and the detector (FID) were set to 280 C. and 300 C., respectively. A capillary column DB-1 (length 30 meters, bore 0.32 millimeter, film thickness 0.25 micrometers, dimethylpolysiloxane as the stationary phase, non-polar) made by Agilent Technologies, Inc. was used for the separation of component compounds. After the column had been kept at 200 C. for 2 minutes, it was further heated to 280 C. at the rate of 5 C. per minute. A sample was dissolved in acetone (0.1% by weight), and 1 microliter of the solution was injected into the sample injector. A recorder used was Model C-R5A Chromatopac Integrator made by Shimadzu Corporation or its equivalent. The resulting gas chromatogram showed the retention time of peaks and the peak areas corresponding to the component compounds.

(4) Solvents for diluting the sample may also be chloroform, hexane and so forth. The following capillary columns may also be used in order to separate the component compounds: HP-1 made by Agilent Technologies Inc. (length 30 meters, bore 0.32 millimeter, film thickness 0.25 micrometers), Rtx-1 made by Restek Corporation (length 30 meters, bore 0.32 millimeter, film thickness 0.25 micrometers), and BP-1 made by SGE International Pty. Ltd. (length 30 meters, bore 0.32 millimeter, film thickness 0.25 micrometers). A capillary column CBP1-M50-025 (length 50 meters, bore 0.25 millimeter, film thickness 0.25 micrometers) made by Shimadzu Corporation may also be used for the purpose of avoiding an overlap of peaks of the compounds.

(5) The ratio of the liquid crystal compounds included in the composition may be calculated according to the following method. A mixture of the liquid crystal compounds was analyzed by gas chromatography (FID). The ratio of peak areas in the gas chromatogram corresponds to the ratio of the liquid crystal compounds. When the capillary columns described above are used, the correction coefficient of respective liquid crystal compounds may be regarded as 1 (one). Accordingly, the ratio (percentage by weight) of the liquid crystal compounds can be calculated from the ratio of peak areas.

(6) Samples for measurement: A composition itself was used as a sample when the characteristics of the composition or the device were measured. When the characteristics of a compound were measured, a sample for measurement was prepared by mixing this compound (15% by weight) with mother liquid crystals (85% by weight). The characteristic values of the compound were calculated from the values obtained from measurements by an extrapolation method: (Extrapolated value)=(Measured value of sample)0.85(Measured value of mother liquid crystals)/0.15. When a smectic phase (or crystals) deposited at 25 C. at this ratio, the ratio of the compound to the mother liquid crystals was changed in the order of (10% by weight: 90% by weight), (5% by weight: 95% by weight) and (1% by weight: 99% by weight). The values of the maximum temperature, the optical anisotropy, the viscosity and the dielectric anisotropy regarding the compound were obtained by means of this extrapolation method.

(7) The mother liquid crystals described below were used. The ratio of the component compounds were expressed as a percentage by weight.

(8) ##STR00044##

(9) Measurement methods: The characteristics of compounds were measured according to the following methods. Most are methods described in the JEITA standards (JEITA-ED-2521B) which was deliberated and established by Japan Electronics and Information Technology Industries Association (abbreviated to JEITA), or the modified methods. No thin film transistors (TFT) were attached to a TN device used for measurement.

(10) (1) Maximum Temperature of a Nematic Phase (NI; C.): A sample was placed on a hot plate in a melting point apparatus equipped with a polarizing microscope and was heated at the rate of 1 C. per minute. The temperature was measured when a part of the sample began to change from a nematic phase to an isotropic liquid. The upper limit of the temperature range of a nematic phase is sometimes abbreviated to the maximum temperature.
(2) Minimum Temperature of a Nematic Phase (Tc; C.): A sample having a nematic phase was placed in glass vials and then kept in freezers at temperatures of 0 C., 10 C., 20 C., 30 C. and 40 C. for 10 days, and then the liquid crystal phases were observed. For example, when the sample maintained the nematic phase at 20 C. and changed to crystals or a smectic phase at 30 C., Tc was expressed as <20 C. A lower limit of the temperature range of a nematic phase is sometimes abbreviated to the minimum temperature.
(3) Viscosity (bulk viscosity; ; measured at 20 C.; mPa.Math.s): An E-type viscometer made by Tokyo Keiki Inc. was used for measurement.
(4) Viscosity (rotational viscosity; 1; measured at 25 C.; mPa.Math.s): The measurement was carried out according to the method described in M. Imai, et al., Molecular Crystals and Liquid Crystals, Vol. 259, 37 (1995). A sample was poured into a TN device in which the twist angle was 0 degrees and the distance between the two glass substrates (cell gap) was 5 micrometers. A voltage was applied to this device and increased stepwise with an increment of 0.5 volt in the range of 16 to 19.5 volts. After a period of 0.2 seconds with no voltage, a voltage was applied repeatedly under the conditions of a single rectangular wave alone (rectangular pulse; 0.2 seconds) and of no voltage (2 seconds). The peak current and the peak time of the transient current generated by the applied voltage were measured. The value of rotational viscosity was obtained from these measured values and the calculating equation (8) on page 40 of the paper presented by M. Imai, et al. The value of dielectric anisotropy necessary for this calculation was measured by the method described in measurement (6).
(5) Optical anisotropy (refractive index anisotropy; n; measured at 25 C.): The measurement was carried out using an Abbe refractometer with a polarizing plate attached to the ocular, using light at a wavelength of 589 nanometers. The surface of the main prism was rubbed in one direction, and then a sample was placed on the main prism. The refractive index (n) was measured when the direction of the polarized light was parallel to that of rubbing. The refractive index (n) was measured when the direction of polarized light was perpendicular to that of rubbing. The value of the optical anisotropy (n) was calculated from the equation: n=nn.
(6) Dielectric anisotropy (; measured at 25 C.): A sample was poured into a TN device in which the distance between the two glass substrates (cell gap) was 9 micrometers and the twist angle was 80 degrees. Sine waves (10 V, 1 kHz) were applied to this device, and the dielectric constant () in the major axis direction of liquid crystal molecules was measured after 2 seconds. Sine waves (0.5 V, 1 kHz) were applied to this device and the dielectric constant () in the minor axis direction of the liquid crystal molecules was measured after 2 seconds. The value of dielectric anisotropy was calculated from the equation: =.
(7) Threshold voltage (Vth; measured at 25 C.; V): An LCD evaluation system Model LCD-5100 made by Otsuka Electronics Co., Ltd. was used for measurement. The light source was a halogen lamp. A sample was poured into a TN device having a normally white mode, in which the distance between the two glass substrates (cell gap) was 4.45/n (micrometers) and the twist angle was 80 degrees. A voltage to be applied to this device (32 Hz, rectangular waves) was stepwise increased in 0.02 V increments from 0 V up to 10 V. During the increase, the device was vertically irradiated with light, and the amount of light passing through the device was measured. A voltage-transmittance curve was prepared, in which the maximum amount of light corresponded to 100% transmittance and the minimum amount of light corresponded to 0% transmittance. The threshold voltage was expressed as voltage at 90% transmittance.
(8) Voltage Holding Ratio (VHR-1; measured at 25 C.; %): A TN device used for measurement had a polyimide-alignment film, and the distance between the two glass substrates (cell gap) was 5 micrometers. A sample was poured into the device, and then this device was sealed with a UV-curable adhesive. A pulse voltage (60 microseconds at 5 V) was applied to this device and the device was charged. A decreasing voltage was measured for 16.7 milliseconds with a high-speed voltmeter, and area A between the voltage curve and the horizontal axis in a unit cycle was obtained. Area B was an area without the decrease. The voltage holding ratio was expressed as a percentage of area A to area B.
(9) Voltage Holding Ratio (VHR-2; measured at 80 C.; %): The voltage holding ratio was measured by the method described above, except that it was measured at 80 C. instead of 25 C. The resulting values were represented by the symbol VHR-2.
(10) Voltage Holding Ratio (VHR-3; measured at 25 C.; %): The stability to ultraviolet light was evaluated by measuring a voltage holding ratio after irradiation with ultraviolet light. A TN device used for measurement had a polyimide-alignment film and the cell gap was 5 micrometers. A sample was poured into this device, and then the device was irradiated with light for 20 minutes. The light source was an ultra-high-pressure mercury lamp USH-500D (produced by Ushio, Inc.), and the distance between the device and the light source was 20 centimeters. In the measurement of VHR-3, a decreasing voltage was measured for 16.7 milliseconds. A composition having a large VHR-3 has a high stability to ultraviolet light. The value of VHR-3 is preferably 90% or more, and more preferably 95% or more.
(11) Voltage Holding Ratio (VHR-4; measured at 25 C.; %): A TN device into which a sample was poured was heated in a constant-temperature bath at 80 C. for 500 hours, and then the stability to heat was evaluated by measuring the voltage holding ratio. In the measurement of VHR-4, a decreasing voltage was measured for 16.7 milliseconds. A composition having a large VHR-4 has a high stability to heat.
(12) Response Time (; measured at 25 C.; millisecond): An LCD evaluation system Model LCD-5100 made by Otsuka Electronics Co., Ltd. was used for measurement. The light source was a halogen lamp. The low-pass filter was set at 5 kHz. A sample was poured into a FFS device having no alignment films, in which the distance between the two glass substrates (cell gap) was 3.5 micrometers. This device was sealed with a UV-curable adhesive. The device was irradiated with ultraviolet light (28 J) of 78 mW/cm.sup.2 (405 nanometers) for 359 seconds, while a voltage of 30 V was applied. A multi-metal lamp for UV curing M04-L41 made by Eye Graphics Co., Ltd. was used for irradiation with ultraviolet light. Rectangular waves (120 Hz) were applied to this device. The device was vertically irradiated with light simultaneously, and the amount of light passing through the device was measured. The transmittance was regarded as 100% when the amount of light reached a maximum. The transmittance was regarded as 0% when the amount of light reached a minimum. The maximum voltage of the rectangular waves was adjusted in order that the transmittance was 90%. The minimum voltage of the rectangular waves was adjusted to 2.5 V where the transmittance was 0%. The response time was expressed as the time (fall time; millisecond) for change from 90% transmittance to 10% transmittance.
(13) Elastic constants (K; measured at 25 C.; pN): A LCR meter Model HP 4284-A made by Yokokawa Hewlett-Packard, Ltd. was used for measurement. A sample was poured into a homogeneous device in which the distance between the two glass substrates (cell gap) was 20 micrometers. An electric charge of 0 volts to 20 volts was applied to this device, and the electrostatic capacity and the applied voltage were measured. The measured values of the electric capacity (C) and the applied voltage (V) were fitted to equation (2.98) and equation (2.101) on page 75 of Ekisho Debaisu Handobukku (Liquid Crystal Device Handbook, in English; The Nikkan Kogyo Shimbun, Ltd., Japan) and the values of K11 and K33 were obtained from equation (2.99). Next, the value of K22 was calculated from equation (3.18) on page 171 of the book and the values of K11 and K33 thus obtained. The elastic constant K was expressed as an average of K11, K22 and K33.
(14) Specific Resistance (p; measured at 25 C.; cm): A sample of 1.0 milliliter was poured into a vessel equipped with electrodes. A DC voltage (10 V) was applied to the vessel, and the DC current was measured after 10 seconds. The specific resistance was calculated from the following equation: (specific resistance)=[(voltage)(electric capacity of vessel)]/[(DC current)(dielectric constant in vacuum)].
(15) Pretilt Angle (degree): A spectroscopic ellipsometer, Model M-2000U (made by J. A. Woollam Co., Inc.) was used for measurement of a pretilt angle.
(16) Alignment stability (Stability of liquid crystal alignment axis): In the liquid crystal display device, the change of a liquid crystal alignment axis in the side of the electrode was evaluated. A liquid crystal alignment angle [ (before)] before stressed in the side of the electrode was measured, and rectangular waves (4.5 V, 60 Hz) were applied to the device for 20 minutes, and no voltages for 1 second, and then a liquid crystal alignment angle [ (after)] in the side of the electrode was measured after 1 second and 5 minutes. The change (, deg.) of the liquid crystal alignment angle after 1 second and 5 minutes was calculated from these values by the following equation:
(deg.)=(after)(before)
These measurements were carried out by referring J. Hilfiker, B. Johs, C. Herzinger, J. F. Elman, E. Montbach, D. Bryant, and P. J. Bos, Thin Solid Films, 455-456, (2004) 596-600. The smaller value of means a smaller change ratio of the liquid crystal alignment axis, which means that the stability of liquid crystal alignment axis is better.

(11) Examples of compositions will be shown below. Component compounds described in Examples were expressed in terms of symbols according to the definition in Table 3 described below. In Table 3, the configuration of 1,4-cyclohexylene is trans. In Examples, a parenthesized number next to a symbolized compound represents the chemical formula to which the compound belongs. The symbol () means any other liquid crystal compound. The ratio (percentage) of a liquid crystal compound means the percentages by weight (% by weight) based on the weight of the liquid crystal composition. Last, the values of characteristics of the composition are summarized.

(12) TABLE-US-00003 TABLE 3 Method of Description of Compounds using Symbols R(A.sub.1)Z.sub.1 . . . Z.sub.n(A.sub.n)R 1) Left-terminal Group R Symbol C.sub.nH.sub.2n+1 n- C.sub.nH.sub.2n+1O nO C.sub.mH.sub.2m+1OC.sub.nH.sub.2n mOn- CH.sub.2CH V C.sub.nH.sub.2n+1CHCH nV CH.sub.2CHC.sub.nH.sub.2n Vn- C.sub.mH.sub.2m+1CHCHC.sub.nH.sub.2n mVn- CF.sub.2CH VFF CF.sub.2CHC.sub.nH.sub.2n VFFn- FC.sub.nH.sub.2n Fn- 2) Right-terminal Group R Symbol C.sub.nH.sub.2n+1 -n OC.sub.nH.sub.2n+1 On CHCH.sub.2 V CHCHC.sub.nH.sub.2n+1 Vn C.sub.nH.sub.2nCHCH.sub.2 -nV C.sub.nH.sub.2nCHCHC.sub.mH.sub.2m+1 -nVm CHCF.sub.2 VFF COOCH.sub.3 -EMe F F Cl CL OCF.sub.3 OCF3 CF.sub.3 CF3 CN C 3) Bonding Group Z.sub.n Symbol C.sub.2H.sub.4 2 COO E CHCH V CC T CF.sub.2O X CH.sub.2O 10 4) Ring A.sub.n Symbol H Dh dh B B(F) 0 B(2F) B(F,F) B(2F,5F) G Py B(2F,3F) 5) Examples of Description Example 1. VHHB-1 Example 2. 3-BB(F)B(F,F)F Example 3. 3-HGB(F,F)F Example 4. 3-HHEBH-5
Examples of the Device
1. Starting Materials

(13) A device having no alignment films was produced, and the homeotropic alignment of liquid crystal molecules and the conversion of a polymerizable compound were studied. First, starting materials will be explained. The starting materials were liquid crystal compositions (M1) to (M10), polymerizable compounds (RM-1) to (RM-8) and polar compounds (PC-1) to (PC-33) will be listed in this order.

(14) TABLE-US-00004 Composition M1 3-HHB(F,F)-F (2-12) 10% 3-HBB(F,F)-F (2-24) 40% 2-HHBB(F,F)-F (2-42) 2% 3-HHBB(F,F)-F (2-42) 5% 4-HHBB(F,F)-F (2-42) 4% V-HH-3 (3-1) 25% V-HHB-1 (3-5) 8% 2-BB(F)B-3 (3-8) 6% NI = 78.9 C.; Tc <20 C.; n = 0.105; = 5.7; Vth = 1.62 V; = 15.5 mPa .Math. s.

(15) TABLE-US-00005 Composition M2 5-H2B(F)-F (2-4) 7% 3-HHB-OCF3 (2-8) 10% 3-HHEB-F (2-17) 7% 5-HHEB-F (2-17) 5% 2-HBEB(F,F)-F (2-30) 3% 3-HBEB(F,F)-F (2-30) 3% 3-BB(F,F)B(F)-OCF3 (2-34) 8% 3-BBB(F,F)-F (2-35) 3% 3-BB2B(F,F)-F (2-39) 3% V-HH-3 (3-1) 31% 1V-HH-4 (3-1) 6% V-HHB-1 (3-5) 3% 5-HBBH-3 (3-11) 6% 5-HB(F)BH-3 (3-12) 5% NI = 90.5 C.; Tc <20 C.; n = 0.093; = 4.3; Vth = 2.07 V; = 12.2 mPa .Math. s.

(16) TABLE-US-00006 Composition M3 3-HB-CL (2-1) 10% 3-HHB-CL (2-7) 4% 3-HHB(F)-F (2-11) 7% 3-HBB(F,F)-F (2-24) 25% 3-HHEBB-F (2-40) 3% 3-HH2BB(F,F)-F (2-44) 6% 4-HH2BB(F,F)-F (2-44) 4% 3-HH-O1 (3-1) 15% 1V-HH-3 (3-1) 18% 3-HBB-2 (3-6) 3% 1-BB(F)B-2V (3-8) 5% NI = 84.2 C.; Tc <20 C.; n = 0.104; = 4.2; Vth = 1.94 V; = 15.9 mPa .Math. s.

(17) TABLE-US-00007 Composition M4 3-HHB(F,F)-F (2-12) 10% 4-HHB(F,F)-F (2-12) 6% 5-HHB(F,F)-F (2-12) 6% 3-HBB(F,F)-F (2-24) 30% 2-HHBB(F,F)-F (2-42) 3% 3-HHBB(F,F)-F (2-42) 4% 4-HHBB(F,F)-F (2-42) 2% 3-HH-V (3-1) 25% 1V2-HH-3 (3-1) 6% V2-HHB-1 (3-5) 4% 3-HHEBH-3 (3-9) 4% NI = 93.1 C.; Tc <20 C.; n = 0.091; = 5.3; Vth = 1.83 V; = 14.0 mPa .Math. s.

(18) TABLE-US-00008 Composition M5 3-HHB(F)-OCF3 (2-10) 7% 3-HBB(F,F)-F (2-24) 12% 2-HB(F)B(F,F)-F (2-25) 4% 3-HB(F)B(F,F)-F (2-25) 12% 3-H2BB(F,F)-F (2-27) 5% 3-HHB(F)B(F,F)-F (2-43) 4% 5-HHB(F)B(F,F)-F (2-43) 3% 3-HH-5 (3-1) 20% 2-HH-3 (3-1) 4% 3-HB-O2 (3-2) 6% 3-HHEH-5 (3-4) 3% VFF-HHB-1 (3-5) 10% 3-HHB-1 (3-5) 5% 1V-HBB-2 (3-6) 5% NI = 81.1 C.; Tc <20 C.; n = 0.091; = 5.6; Vth = 1.76 V; = 12.0 mPa .Math. s.

(19) TABLE-US-00009 Composition M6 1V2-BB-CL (2) 3% 7-HB(F)-F (2-2) 5% 7-HB(F,F)-F (2-3) 7% 3-HHB(F,F)-F (2-12) 10% 3-H2HB(F)-F (2-13) 6% 5-H2HB(F)-F (2-13) 4% 3-H2HB(F,F)-F (2-14) 6% 4-H2HB(F,F)-F (2-14) 5% 3-HH2B(F,F)-F (2-16) 12% 3-HBB-F (2-22) 5% V-HH-5 (3-1) 17% V2-HH-2V (3-1) 8% V2-BB(F)B-1 (3-8) 4% 5-HBB(F)B-3 (3-13) 8% NI = 75.0 C.; Tc <20 C.; n = 0.088; = 4.5; Vth = 1.89 V; = 14.0 mPa .Math. s.

(20) TABLE-US-00010 Composition M7 3-HGB(F,F)-F (2-19) 3% 3-H2GB(F,F)-F (2-20) 5% 5-GHB(F,F)-F (2-21) 10% 3-HBB(F,F)-F (2-24) 10% 2-HHBB(F,F)-F (2-42) 3% 3-HHBB(F,F)-F (2-42) 4% 2-HH-3 (3-1) 20% 3-HH-VFF (3-1) 9% 1V-HH-3 (3-1) 7% 1V2-BB-1 (3-3) 4% V-HHB-1 (3-5) 7% 1-BB(F)B-2V (3-8) 4% 2-BB(F)B-2V (3-8) 6% 3-HHEBH-5 (3-9) 4% 1O1-HBBH-5 () 4% NI = 93.0 C.; Tc <20 C.; n = 0.103; = 5.4; Vth = 1.83 V; = 12.7 mPa .Math. s.

(21) TABLE-US-00011 Composition M8 5-HEB-F (2-5) 3% 5-HEB(F,F)-F (2-6) 5% 3-HHB-F (2-9) 5% 2-HHEB(F,F)-F (2-18) 4% 3-HHEB(F,F)-F (2-18) 7% 3-HBB(F)-F (2-23) 9% 5-HBB(F)-F (2-23) 6% 5-HBEB-F (2-29) 4% 2-BB(F)B(F,F)-F (2-36) 4% 3-BB(F)B(F,F)-F (2-36) 10% 3-HHBB(F)-F (2-41) 4% 5-HHBB(F)-F (2-41) 4% 3-HH-O1 (3-1) 3% 3-HH-4 (3-1) 6% 2-HH-5 (3-1) 6% F3-HH-V (3-1) 20% NI = 77.7 C.; Tc <20 C.; n = 0.097; = 5.7; Vth = 1.68 V; = 17.1 mPa .Math. s.

(22) TABLE-US-00012 Composition M9 3-HHB(F,F)-F (2-12) 10% 3-HH2B(F)-F (2-15) 8% 3-H2BB(F)-F (2-26) 7% 3-HB(F)EB-OCF3 (2-28) 8% 3-HH2BB(F,F)-F (2-44) 5% 4-HH2BB(F,F)-F (2-44) 3% 1V2-HH-V (3-1) 6% 1V-HH-V (3-1) 8% 7-HB-1 (3-2) 3% 1-BB-5 (3-3) 9% V2-BB-1 (3-3) 4% 1V2-BB-1 (3-3) 6% 3-HHB-O1 (3-5) 5% V2-HHB-1 (3-5) 5% 1-BB(F)B-2V (3-8) 6% 2-BB(F)B-2V (3-8) 3% 3-BB(F)B-2V (3-8) 4% NI = 90.9 C.; Tc <20 C.; n = 0.131; = 5.0; Vth = 1.84 V; = 13.6 mPa .Math. s.

(23) TABLE-US-00013 Composition M10 3-H2HB(F,F)-F (2-14) 6% 3-HBB(F,F)-F (2-24) 18% 3-BB(F,F)B-F (2-33) 4% 3-BB(F)B(F,F)-F (2-36) 10% 3-B2BB(F,F)-F (2-38) 5% 3-HHB(F)B(F,F)-F (2-43) 4% 3-HH2BB(F,F)-F (2-44) 4% V-HH-3 (3-1) 25% 1V-HH-3 (3-1) 5% 7-HB-1 (3-2) 5% V2-HHB-1 (3-5) 5% 1-BB(F)B-2V (3-8) 5% 5-HBB(F)B-3 (3-13) 4% NI = 80.2 C.; Tc <20 C.; n = 0.118; = 6.2; Vth = 1.53 V; = 15.1 mPa .Math. s.

(24) TABLE-US-00014 Composition M11 3-HHB-F (2-9) 3% 3-GHB(F,F)-F (2-21) 4% 3-HBB(F)-F (2-23) 3% 3-GB(F)B(F)-F (2-31) 8% 3-BB(F)B(F,F)-CF3 (2-37) 3% 3-GB(F)B(F)B(F)-F (2-45) 2% 4-GBB(F)B(F,F)-F (2-46) 3% 3-HH-V (3-1) 30% F3-HH-V (3-1) 8% 3-HB-O2 (3-2) 5% 1-BB-5 (3-3) 4% V-HBB-2 (3-6) 6% 1-BB(F)B-2V (3-8) 4% 2-BB(F)B-2V (3-8) 6% 3-BB(F)B-2V (3-8) 3% 5-HBBH-3 (3-11) 3% 3-dhBB(2F,3F)-O2 (4-16) 5% NI = 82.4 C.; Tc <20 C.; n = 0.125; = 2.7; Vth = 2.10 V; = 17.1 mPa .Math. s.

(25) The following polymerizable compounds (RM-1) to (RM-8) were used as the first additive.

(26) ##STR00060##

(27) The following polar compounds (PC-1) to (PC-33) were used as the second additive.

(28) ##STR00061## ##STR00062## ##STR00063##
2. Homeotropic Alignment of Liquid Crystal Molecules
Run Number 1

(29) Polymerizable compound (RM-1) and polar compound (PC-1) were added to composition (M1) in the ratios of 0.5% by weight and 5% by weight, respectively. The mixture was poured into a device having no alignment films, in which the distance between the two glass substrates (cell gap) was 4.0 micrometers, on a hot stage at 100 C. The polymerizable compound was polymerized by irradiating the device with ultraviolet light (28 J) using an ultra-high-pressure mercury lamp USH-250-BY (produced by Ushio, Inc.). The device was placed on the stage of a polarizing microscope where the polarizer was orthogonal to the analyzer, and irradiated from below with light, and the presence or absence of light leak was observed. The homeotropic alignment was judged as excellent when light did not pass through the device because of a sufficient alignment of liquid crystal molecules. It was judged as poor when light passed through the device was observed.

(30) Run Numbers 2 to 33

(31) A device having no alignment films was produced using a mixture combining the composition, the polymerizable compound and the polar compound. The presence or absence of the light leak was observed in the same manner as with Run Number 1. The results were summarized in Table 4.

(32) TABLE-US-00015 TABLE 4 Homeotropic Alignment of Liquid Crystal Molecules Liquid Polymerizable Polar Run Crystal Compound Compound Homeotropic Number Composition (0.5% by weight) (5% by weight) Alignment 1 M1 RM-1 PC-1 excellent 2 M2 RM-2 PC-2 excellent 3 M3 RM-3 PC-3 excellent 4 M4 RM-4 PC-4 excellent 5 M5 RM-5 PC-5 excellent 6 M6 RM-6 PC-6 excellent 7 M7 RM-7 PC-7 excellent 8 M8 RM-8 PC-8 excellent 9 M9 RM-1 PC-9 excellent 10 M10 RM-2 PC-10 excellent 11 M11 RM-3 PC-11 excellent 12 M1 RM-4 PC-12 excellent 13 M2 RM-5 PC-13 excellent 14 M3 RM-6 PC-14 excellent 15 M4 RM-7 PC-15 excellent 16 M5 RM-8 PC-16 excellent 17 M6 RM-1 PC-17 excellent 18 M7 RM-2 PC-18 excellent 19 M8 RM-3 PC-19 excellent 20 M9 RM-4 PC-20 excellent 21 M10 RM-5 PC-21 excellent 22 M11 RM-6 PC-22 excellent 23 M1 RM-7 PC-23 excellent 24 M2 RM-8 PC-24 excellent 25 M3 RM-1 PC-25 excellent 26 M4 RM-2 PC-26 excellent 27 M5 RM-3 PC-27 excellent 28 M6 RM-4 PC-28 excellent 29 M7 RM-5 PC-29 excellent 30 M8 RM-6 PC-30 excellent 31 M9 RM-7 PC-31 excellent 32 M10 RM-8 PC-32 excellent 33 M11 RM-1 PC-33 excellent
3. Conversion of Polymerizable Compound

(33) A polymerizable compound was added to the composition together with a polar compound. The polymerizable compound was consumed by polymerization and gave a polymer. In the extent of conversion of the reaction, the larger is preferable. This is because a smaller amount of the residual amount of the polymerizable compound (the amount of unreacted polymerizable compound) is desirable in view of image burn-in. When a device with a polymer sustained alignment is produced, it is irradiated with ultraviolet light generally in two steps for the purpose of optimizing the pretilt angle of liquid crystal molecules. In the next experiments, the residual amount of a polymerizable compound was measured after irradiation with ultraviolet light in the first step, and the conversion was calculated. Polymerizable compound (RM-9) described below was selected for comparison. This compound is excluded from compound (1) by the definition of the symbols.

(34) ##STR00064##

(35) Polymerization was carried out as follows. A device having no alignment films was produced by the method described in the paragraph of Homeotropic Alignment of Liquid Crystal Molecules. The device was irradiated with ultraviolet light (28 J) of 78 mW/cm.sup.2 (405 nanometers) for 359 seconds, while a voltage of 30 V was applied. A multi-metal lamp M04-L41 for UV curing made by Eye Graphics Co., Ltd. was used for ultraviolet irradiation. The residual amount of a polymerizable compound was measured by HPLC and the conversion was calculated. The results were summarized in Table 5. The conversion in Run number 1 to 8 was in the range of 38% to 46%. In Comparative Example 1, polymerizable compound (RM-1) used in Run number 1 was replaced by polymerizable compound (PM-9), which was then polymerized. In this case, the conversion was 18%. It can be concluded that the composition of the invention is excellent in view of the conversion based on this comparison.

(36) TABLE-US-00016 TABLE 5 Conversion of Polymerizable Cpmpounds Polymerizable Polymerizable Liquid Crystal Compound Polar Compound Compound Remained Run Number Composition (0.5% by weight) (5% by weight) (% by weight) Conversion 1 M1 RM-1 PC-1 0.29 42% 2 M2 RM-2 PC-2 0.30 40% 3 M3 RM-3 PC-3 0.31 38% 4 M4 RM-4 PC-4 0.27 46% 5 M5 RM-5 PC-5 0.28 44% 6 M6 RM-6 PC-6 0.27 46% 7 M7 RM-7 PC-7 0.29 42% 8 M8 RM-8 PC-8 0.30 40% Comparative M1 RM-9 PC-1 0.41 18% Example 1

(37) The results indicated by Table 4 and Table 5 show that liquid crystal molecules are aligned stably without any alignment films by using a liquid crystal composition including a polymerizable compound and a polar compound, although the type of each component is different. This is a feature of the invention and is worthy of special mention.

INDUSTRIAL APPLICABILITY

(38) The liquid crystal composition of the invention can adjust the alignment of liquid crystal molecules in a device having no alignment films. The composition satisfies at least one of characteristics such as a high maximum temperature, a low minimum temperature, a small viscosity, a suitable optical anisotropy, a large positive dielectric anisotropy, a large specific resistance, a high stability to ultraviolet light, a high stability to heat and a large elastic constant, or is suitably balanced between at least two of the characteristics. A liquid crystal display device including the composition can be used for a liquid crystal projector, a liquid crystal television and so forth, since it has characteristics such as a short response time, a large voltage holding ratio, a low threshold voltage, a large contrast ratio and a long service life.