Abstract:
A liquid crystal composition obtained by mixing a phenylalkyl dioxaborinane derivative, an isothiocyanate derivative, a tolan derivative and a pyrimidine-phenyl derivative in an appropriate ratio, and a liquid crystal display using the same are provided. The liquid crystal composition reveals a nematic phase at a wide range of a temperature including room temperature and having optical anisotropies and dielectric anisotropies of various magnitudes. Also, a twisted nematic (TN) type liquid crystal display manufactured using the liquid crystal composition can be driven in a multiplexed manner.

Description:
BACKGROUND OF THE INVENTION 
     1. Field of the Invention 
     The present invention relates to a liquid crystal composition and a liquid crystal display using the same, and more particularly, to a liquid crystal composition which reveals a nematic phase over a wide range of temperatures including room temperature, and which has optical anisotropies and dielectric anisotropies of various magnitudes, and a liquid crystal display using the liquid crystal composition which can be driven in a multiplexed manner. 
     2. Description of the Related Art 
     A phenyl alkyl dioxaborinane derivative represented by the following formula is a polar liquid crystalline compound having a high dielectric anisotropy Δ.di-elect cons.. The method for synthesizing the dioxaborinane derivative represented by the following formula is described in detail in U.S. Pat. No. 4,853,150 allowed to Bezborodov et al. and now assigned to the applicant of the present invention. ##STR1## where R1 represents an alkyl group having 1 to 12 carbon atoms, Y represents a cyano group, a halogen group, OR, ##STR2## X, V and W represent simultaneously or independently hydrogen, a halogen, a cyano group, an alkyl group having 1 to 12 carbon atoms, or an alkoxy group having 1 to 12 carbon atoms, and R represents an alkyl group having 1 to 12 carbon atoms. 
     An isothiocyanate derivative represented by the following formula is a polar liquid crystalline compound having a low viscosity and a high dielectric anisotropy. The characteristics thereof are described in detail in PL 241,286 and U.S. Pat. No. 4,528,116. ##STR3## where R1 represents an alkyl group having 1 to 12 carbon atoms, C and D represent simultaneously or independently a phenyl group, a biphenyl group, a cyclohexyl group or a cyclohexylphenyl group, and W represents a single bond (i.e., directly connected) or an ethylene group (--CH 2  CH 2  --). 
     A compound represented by the following formula is a non-polar liquid crystalline compound having a low viscosity. The characteristics thereof are described in detail in DE-OS 2,638,634 and DDR 171,971. ##STR4## where R1 and R2 represent simultaneously or independently an alkyl group having 1 to 12 carbon atoms or an alkoxy group having 1 to 12 carbon atoms, A and B represent simultaneously or independently a phenyl group, a biphenyl group, a cyclohexyl group or a biphenyl group having a methyl group, and Z represents a single bond (i.e., directly connected) or an ester bond (--COO--). 
     A tolan derivative represented by the following formula is a non-polar liquid crystalline compound having a high optical anisotropy Δn. The characteristics thereof are described in detail in U.S. Pat. No. 3,529,482. ##STR5## where R1 and R2 simultaneously or independently represent an alkyl group having 1 to 12 carbon atoms or an alkoxy group having 1 to 12 carbon atoms. 
     A pyrimidine-phenyl derivative represented by the following formula is a liquid crystal having a low elastic constant. A method for synthesizing the same is described in detail in Mol.Cryst. Liq.Cryst., 68, 57 (1981) and DDR 95892. ##STR6## where R1 and R2 simultaneously or independently represent an alkyl group having 1 to 12 carbon atoms, an alkoxy group having 1 to 12 carbon atoms or a cyano (--CN--) group. 
     SUMMARY OF THE INVENTION 
     It is an objective of the present invention to provide a liquid crystal composition which reveals a nematic phase over a wide range of temperature, including room temperature, and which has optical anisotropies and dielectric anisotropies of various magnitudes. 
     It is another objective of the present invention to provide a twisted nematic (TN) liquid crystal display using the liquid crystal composition, which can be driven in a multiplexed manner. 
     Accordingly, to achieve the first objective, there is provided a nematic liquid crystal composition comprising: 
     a compound represented by a formula (1); ##STR7##  where R1 represents an alkyl group having 1 to 12 carbon atoms, and Y represents a cyano group, a halogen, OR, ##STR8##  or in which X, V and W represent simultaneously or independently hydrogen, a halogen, a cyano group, an alkyl group having 1 to 12 carbon atoms, an alkoxy group having 1 to 12 carbon atoms, or an unsubstituted or substituted aryl group, and R represents an alkyl group having 1 to 12 carbon atoms, 
     a compound represented by a formula (2); ##STR9## where R1 represents an alkyl group having 1 to 12 carbon atoms, C and D represent simultaneously or independently a phenyl group, a biphenyl group, a cyclohexyl group or a cyclohexylphenyl group, and W represents a single bond or an ethylene group (--CH 2  CH 2  --), 
     at least one selected from the group consisting of a compound represented by a formula (3) and a compound represented by a formula (4): ##STR10##  where R1 and R2 represent simultaneously or independently an alkyl group having 1 to 12 carbon atoms or an alkoxy group having 1 to 12 carbon atoms, A and B represent simultaneously or independently a phenyl group, a biphenyl group, a cyclohexyl group or a biphenyl group having a methyl group, and Z represents a single bond or an ester group(--COO--), ##STR11## where R1 and R2 represent simultaneously or independently an alkyl group having 1 to 12 carbon atoms or an alkoxy group having 1 to 12 carbon atoms. 
     The liquid crystal composition according to the present invention may further include a compound represented by a formula (5): ##STR12## where R1 and R2 represent simultaneously or independently an alkyl group having 1 to 12 carbon atoms, an alkoxy group having 1 to 12 carbon atoms, or a cyano group. 
     The content of the compound represented by the formula (5) is 1.0˜20.0 parts by weight. If the content of the compound represented by the formula (5) exceeds 20.0 parts by weight, the viscosity of the liquid crystal composition becomes too high. 
     To achieve the second objective, there is provided a liquid crystal display which is manufactured by inserting the nematic liquid crystal composition according to the present invention into a pair of electrode. 
     DESCRIPTION OF THE PREFERRED EMBODIMENTS 
     The liquid crystal composition according to the present invention includes as essential components a compound represented by a formula (1), a compound represented by a formula (2) and at least one selected form the group consisting of a compound represented by a formula (3) and a compound represented by a formula (4). ##STR13## where R1 represents an alkyl group having 1 to 12 carbon atoms, and Y represents a cyano group, a halogen, OR, ##STR14## in which X, V and W represent simultaneously or independently hydrogen, a halogen, a cyano group, an alkyl group having 1 to 12 carbon atoms, an alkoxy group having 1 to 12 carbon atoms, or an unsubstituted or substituted aryl group, and R represents an alkyl group having 1 to 12 carbon atoms, ##STR15## where R1 represents an alkyl group having 1 to 12 carbon atoms, C and D represent simultaneously or independently a phenyl group, a biphenyl group, a cyclohexyl group or a cyclohexylphenyl group, and W represents a single bond or an ethylene group(--CH 2  CH 2  --), ##STR16## where R1 and R2 represent simultaneously or independently an alkyl group having 1 to 12 carbon atoms or an alkoxy group having 1 to 12 carbon atoms, A and B represent simultaneously or independently a phenyl group, a biphenyl group, a cyclohexyl group or a biphenyl group having a methyl group, and Z represents a single bond or an ester group(--COO--), ##STR17## where R1 and R2 represent simultaneously or independently an alkyl group having 1 to 12 carbon atoms or an alkoxy group having 1 to 12 carbon atoms. 
     Also, the liquid crystal composition according to the present invention may further include a compound represented by a formula (5): ##STR18## where R1 and R2 represent simultaneously or independently an alkyl group having 1 to 12 carbon atoms, an alkoxy group having 1 to 12 carbon atoms, or a cyano group. Here, the contents of the respective compounds may slightly differ depending on characteristics of a device to be manufactured. However, preferably, the contents of the compounds represented by the formulas (1), (2), (3) and (4) are 1.0˜65.0 parts by weight, 1.0˜65.0 parts by weight, 1.0˜50.0 parts by weight, and 1.0˜20.0 parts by weight, respectively. If the contents of the compounds represented by the formulas (1) and (2) exceed 65.0 parts by weight, respectively, the viscosity of the liquid crystal composition becomes too high. If the content of the compound represented by the formula (3) exceeds 50.0 parts by weight, the nonpolarity of the liquid crystal composition increases so that the threshold voltage V th  of the liquid crystal composition becomes too high. If the content of the compound represented by the formula (4) exceeds 20.0 parts by weight, the nonpolarity of the liquid crystal composition increases so that the threshold voltage V th  of the liquid crystal composition becomes too high and the optical anisotropy Δn becomes too high. 
    
    
     The present invention will be described in more detail through the following examples, but without limiting the scope of the invention. 
     EXAMPLE 1 
     As shown in Table 1, a liquid crystal composition was prepared by mixing 24.7 wt % of a compound represented by a formula 3b, 12.3 wt % of a compound represented by a formula 3c, 14.3 wt % of a compound represented by a formula 1b, 9.4 wt % of a compound represented by a formula 1c, 6.7 wt % of a compound represented by a formula 1d, 4.8 wt % of a compound represented by a formula 2b, 11.4 wt % of a compound represented by a formula 2d, 2.8 wt % of a compound represented by a formula 2f and 13.6 wt % of a compound represented by a formula 4a. The liquid crystal composition was heated to a temperature higher than that at which it revealed an isotropic phase, stirred, and then cooled to room temperature, thereby obtaining a uniformly mixed liquid crystal composition. 
     The thus-obtained liquid crystal composition was injected into a 90° twisted nematic cell of 6 μm thickness and then its electrooptical properties were measured at room temperature. Table 2 summarizes the measured electrooptical properties. Referring to Table 2, the nematic phase formation temperature of the liquid crystal composition, T N-1 , was 75 ° C. Thus, it was understood that the liquid crystal composition according to this embodiment revealed a nematic phase up to 75° C., which includes room temperature. The optical anisotropy Δn was 0.1406, the dielectric anisotropy Δ.di-elect cons. was 9.9, the threshold voltage V 10  (the voltage at which the cell passes 10% of the light falling on it) was 1.48 V, the saturation voltage V 90  (the voltage at which the cell passes 90% of the light falling on it) was 2.11 V, and the number of duties N 90  defined as below was 8.62. ##EQU1## 
     EXAMPLES 2 THROUGH 45 
     The liquid crystal composition was manufactured in the same manner as in Example 1, except that the components of the liquid crystal composition were changed as listed in Table 1. 
     The thus-obtained liquid crystal compositions were injected into a 90° twisted nematic cells of 6 μm thickness and then their electrooptical properties were measured at room temperature. Table 2 summarizes the measured electrooptical properties. Referring to Table 2, the nematic phase formation temperature of the liquid crystal compositions, T N-1 , was 63.3˜110.7° C. That is, it was understood that the liquid crystal compositions according to these embodiments revealed a nematic phase over a wide range of temperatures, including room temperature. Also, referring to Tables 1 and 2, it is understood that the optical anisotropy and the dielectric anisotropy of the liquid crystal compositions of the present invention were adjustable by controlling the ratios of the components. Also, since the number of duties N 90  of the liquid crystal compositions of the present invention is in the range of 6.51 to 8.95, a liquid crystal display which can be driven in a multiplexed manner can be manufactured using the liquid crystal compositions of the present invention. The alkyl group and the alkyl group in the alkoxy group listed in Table 1 are both of normal structure. 
     
         TABLE 1   - Example   Component 1 2 3 4 5 6 7 8 9   (3a)  ##STR19##   4.5 4.2 4.6 4.3 3.5  2.5 (3b)  ##STR20##  24.7 8.1 7.5 8.3 7.7 6.3 23 4.5 18 (3c)  ##STR21##  12.3 19.3 17.9 19.8 18.5 15.1 12 10.7 7 (3d)  ##STR22##   13.1 12.1 13.3 12.5 10.1  7.3 (1a)  ##STR23##    3  3 (1b)  ##STR24##  14.3 16.5 16.5 17 17 10 10 10 10 (1c)  ##STR25##  9.4     10 10 10 10 (1d)  ##STR26##  6.7     10 10 10 10 (1e)  ##STR27##  10 10 10 10 (2a)  ##STR28## (2b)  ##STR29##  4.8 (2c)  ##STR30## (2d)  ##STR31##  11.4 9.4 20 20 15 15 15 15 15 (2e)  ##STR32## (2f)  ##STR33##  2.8 (2g)  ##STR34##   6.8 7 7 7   10 10 (5a)  ##STR35## (4a)  ##STR36##  13.6 12.6 12.6 (4b)  ##STR37##10 10 10 10 10 10 Example   Component 10 11 12 13 14 15 16 17 18   (3a)  ##STR38##    2.5     3.5 3.5 (3b)  ##STR39##    4.5 18  23 23 6.3 6.3 (3c)  ##STR40##    10.7 7  12 12 15.1 15.1 (3d)  ##STR41##    7.3     10.1 10.1 (1a)  ##STR42## (1b)  ##STR43##  15.4 13.3 15 15 20 10 10 10 10 (1c)  ##STR44##  15.4 13.3 10 10 13.3 10 5 10 5 (1d)  ##STR45##  15.4 13.3 10 10 13.3 10 10 10 10 (1e)  ##STR46##  15.4 13.3 (2a)  ##STR47## (2b)  ##STR48##  5 4 8 8 10.7 5 5 5 5 (2c)  ##STR49## (2d)  ##STR50##  15 13 17 17 25.7 15 15 15 15 (2e)  ##STR51## (2f)  ##STR52##  3 3 5 5 6.7 5 5 5 5 (2g)  ##STR53##   13.3 10 10 13.3 5 5  5 (5a)  ##STR54## (4a)  ##STR55## (4b)  ##STR56##  15.4 13.5    10 10 10 10 Example   Component 19 20 21 22 23 24 25 26 27   (3a)  ##STR57##3.3 3.4 1.5 (3b)  ##STR58##  22 22 23 6.0 6.1 2.7 10 23 22 (3c)  ##STR59##  10 10 12 14.3 14.6 6.5 5 12 10 (3d)  ##STR60##9.7 9.9 4.3 (1a)  ##STR61##  3 3   2    3 (1b)  ##STR62##  10 10 10 15 15 13 13 10 10 (1c)  ##STR63##  10 5 5 5 5 7 7 5 5 (1d)  ##STR64##  10 10 10 9.5 9.5 10 10 10 10 (1e)  ##STR65## (2a)  ##STR66##  12 12.7 7.9 7.9 (2b)  ##STR67##  5 5 5 4 3 5.2 5.2 3.2 3.2 (2c)  ##STR68##  2.0 2.0 1.3 1.3 (2d)  ##STR69##  15 15 15 14.7 14 13.3 13.3 8.3 8.3 (2e)  ##STR70##  3.2 3.2 2.0 2.0 (2f)  ##STR71##  5 5 5 4 3 3.6 3.6 2.3 2.3 (2g)  ##STR72##   5 5 5 5 5 5 5 5 (5a)  ##STR73## (4a)  ##STR74##    3 (4b)  ##STR75##  10 10 7 9.5 9.5 10 10 10 10 Example   Component 28 29 30 31 32 33 34 35 36   (3a)  ##STR76##  3.5 3.2 3.0 4.0 3.5  3.2 3.2 3.9 (3b)  ##STR77##  6.3 5.8 5.4 7.2 6.3 23 5.8 5.8 7.0 (3c)  ##STR78##  15.1 13.7 12.9 17.2 15.1 12 13.7 13.7 16.7 (3d)  ##STR79##  10.1 9.3 8.7 11.6 10.1  9.3 9.3 11.3 (1a)  ##STR80##   3     3 (1b)  ##STR81##  10 10 12 10 10 10 10 12 11.1 (1c)  ##STR82##  5 5 6 5 5 5 5 5 5.5 (1d)  ##STR83##  10 10 10 10 10 10 10 11 11.1 (1e)  ##STR84## (2a)  ##STR85##  7.9 7.9 7.9 6.3 9.4 9.4 9.4 9.4 (2b)  ##STR86##  3.2 3.2 3.2 2.6     5.5 (2c)  ##STR87##  1.3 1.3 1.3 1.0 (2d)  ##STR88##  8.3 8.3 8.3 6.7 11.2 11.2 11.2 11.2 16.7 (2e)  ##STR89##  2.0 2.0 2.0 1.6 (2f)  ##STR90##  2.3 2.3 2.3 1.8 4.4 4.4 4.4 4.4 5.5 (2g)  ##STR91##  5 5 7 5 5 5 5 5 5.7 (5a)  ##STR92## (4a)  ##STR93## (4b)  ##STR94##  10 10 10 10 10 10 10 10 Example   Component 37 38 39 40 41 42 43 44 45   (3a)  ##STR95##  3.9 3.9 3.3 3.2 2.5 1.5 2.0 2.0 2.2 (3b)  ##STR96##  7.0 7.0 6.0 5.7 4.5 2.7 3.6 3.6 4.0 (3c)  ##STR97##  16.7 16.7 14.3 13.5 10.7 6.5 8.6 8.6 9.6 (3d)  ##STR98##  11.3 11.3 9.7 9.1 7.3 4.3 5.8 5.8 6.4 (1a)  ##STR99## (1b)  ##STR100##  11.1 11.1 9.5 9 10 10 10 10 11.3 (1c)  ##STR101##  5.5 5.5 4.7 4.5 5 5 5 5 5.5 (1d)  ##STR102##  11.1 11.1 9.5 9 10 10 10 10 11.1 (1e)  ##STR103## (2a)  ##STR104##  8.8 10.4 8.8 8.4 13.1 16.8 12.7 14.9 14.1 (2b)  ##STR105##  3.6      5.2  5.7 (2c)  ##STR106##  1.4      2.0  2.2 (2d)  ##STR107##  9.2 12.8 10.9 10.4 16.1 20.7 13.3 18.4 14.8 (2e)  ##STR108##  2.3      3.2  3.6 (2f)  ##STR109##  2.5 4.6 4.0 3.7 5.8 7.5 3.6 6.7 4.0 (2g)  ##STR110##  5.6 5.6 4.8 4.5 5 5 5 5 5.5 (5a)  ##STR111##    5 10 (4a)  ##STR112## (4b)  ##STR113##    9.5 9 10 10 10 10 
    
     
                       TABLE 2______________________________________Electrooptical                                        Properties  Example T.sub.N-1 (° C.) Δn Δε V.sub.10 (V)                                       V.sub.90 (V) N.sub.90______________________________________ 1       75.0      0.1406   9.90                           1.48  2.11  8.62   2 84.4 0.1426 10.58 1.61 2.35 7.66   3 74.8 0.1388 10.42 1.48 2.15 7.67   4 80.0 0.1400 11.24 1.58 2.31 7.60   5 73.4 0.1345 11.18 1.51 2.20 7.73   6 68.7 0.1345 13.51 2.23 2.33 6.89   7 63.3 0.1318 13.18 1.51 2.23 7.25   8 82.4 0.1503 14.74 1.47 2.16 7.42   9 79.7 0.1471 14.98 1.61 2.39 7.08  10 66.0 0.1658 13.35 1.86 2.80 6.65  11 64.0 0.1781 20.38 1.56 2.36 6.51  12 94.0 0.1511 14.28 1.48 2.12 8.41  13 91.6 0.1474 14.87 1.47 2.13 7.94  14 110.7  0.1750 20.46 1.36 1.98 7.76  15 76.5 0.1453 10.97 1.51 2.15 8.68  16 71.1 0.1469 10.46 1.58 2.23 9.09  17 68.0 0.1468 10.25 1.54 2.18 8.95  18 77.2 0.1454 11.01 1.56 2.21 8.91  19 61.2 0.1377 11.32 1.47 2.09 8.75  20 71.5 0.1388 11.22 1.51 2.16 8.47  21 73.6 0.1419 10.92 1.59 2.27 8.56  22 85.0 0.1523 13.82 1.46 2.10 8.24  23 78.9 0.1475 13.29 1.44 2.08 8.07  24 79.4 0.1742 13.85 1.50 2.19 7.65  25 84.1 0.1730 13.69 1.51 2.20 7.73  26 78.5 0.1452 11.53 1.62 2.36 7.74  27 76.0 0.1390 11.29 1.48 2.13 8.21  28 86.2 0.1457 11.27 1.63 2.33 8.50  29 79.0 0.1380 12.04 1.51 2.17 8.28  30 90.0 0.1507 12.91 1.52 2.16 8.77  31 84.0 0.1480 11.57 1.59 2.26 8.76  32 79.8 0.1457 11.11 1.61 2.31 8.34  33 80.5 0.1460 10.57 1.65 2.39 7.95  34 87.5 0.1387 11.96 1.54 2.21 8.33  35 90.1 0.1501 14.07 1.58 2.31 7.60  36 76.2 0.1351 11.56 1.48 2.13 8.21  37 77.5 0.1349 12.71 1.51 2.19 7.91  38 78.0 0.1346 12.43 1.50 2.18 7.83  39 71.2 0.1543 12.66 1.51 2.18 8.09  40 67.3 0.1569 13.19 1.45 2.10 7.96  41 72.0 0.1649 12.86 1.56 2.25 8.13  42 71.3 0.1713 13.96 1.48 2.15 7.84  43 73.5 0.1662 12.33 1.52 2.19 8.17  44 71.8 0.1676 13.57 1.52 2.21 7.93  45 73.3 0.1513 15.10 1.40 2.05 7.55______________________________________ 
    
     As described above, the liquid crystal composition according to the present invention reveals a nematic phase over a wide range of temperature, including room temperature, and has optical anisotropies and dielectric anisotropies of various magnitudes. Also, a twisted nematic (TN) type liquid crystal display manufactured using the liquid crystal composition can be driven in a multiplexed manner.