Positive dielectric anisotropic liquid crystal composition and liquid crystal display device

Abstract

A positive dielectric anisotropic liquid crystal composition includes one or more compounds of formula I and one or more compounds of formula II: ##STR00001##
wherein R1 represents cyclopropyl, cyclobutyl or cyclopentyl, R2, R3 and R4 are as defined in the specification, and a liquid crystal display device. The liquid crystal composition has positive dielectric properties, a high charge retention ratio, a low rotary viscosity, a fast response time, and especially a high transmittance, and is suitable for manufacturing a TFT-LCD with a high transmittance and a fast response.

Claims

1. A positive dielectric anisotropic liquid crystal composition, comprising all negative compounds represented by formulas 13, I6, I13, I14 and I22, one or more neutral compounds represented by formula II1, and one or more positive compounds represented by formulas III-a, III-b, III-g and III-j: ##STR00118## ##STR00119## ##STR00120## ##STR00121## ##STR00122## D.sub.1 represents an alkyl group having a carbon atom number of 1-10 and D.sub.2 represents an alkenyl group having a carbon atom number of 2-10; wherein R.sub.7 represents a linear alkyl group having a carbon atom number of 1-10; and (F) represents hydrogen or fluorine; in said liquid crystal composition, the total mass content of the negative compounds represented by formula I3 is 3%, the total mass content of the negative compounds represented by formula I6 is 3%, the total mass content of the negative compounds represented by formula I13 is 2%, the total mass content of the negative compounds represented by formula I14 is 3% and the total mass content of the negative compounds represented by formula I22 is 4%.

2. The positive dielectric anisotropic liquid crystal composition according to claim 1, wherein, in said liquid crystal composition, a total mass content of the one or more neutral compounds represented by formulas II1 is 20%80%.

3. The positive dielectric anisotropic liquid crystal composition according to claim 1, further comprising one or more compounds represented by formulas VI-b to VI-e below: ##STR00123## wherein R.sub.11 and R.sub.12 each independently represent a linear alkyl group having a carbon atom number of 1-10, ##STR00124## an alkoxy group having a carbon atom number of 1-10 or an alkenyl group having a carbon atom number of 2-10.

4. The positive dielectric anisotropic liquid crystal composition according to claim 1, further comprising one or more compounds represented by formulas VII-c to VII-i below: ##STR00125## wherein R.sub.13 each independently represents a linear alkyl group having a carbon atom number of 1-10, ##STR00126## an alkoxy group having a carbon atom number of 1-10 or an alkenyl group having a carbon atom number of 2-10; and R.sub.14 represents a linear alkyl group having a carbon atom number of 1-5, or an alkyl ether in which an oxygen atom is bonded to a benzene ring.

5. A liquid crystal display device, wherein the liquid crystal display device comprises the positive dielectric anisotropic liquid crystal composition of claim 1, and said liquid crystal display device is an active matrix display device or a passive matrix display device.

Description

DETAILED DESCRIPTION OF EMBODIMENTS

(1) The present invention will be described in further detail below in conjunction with specific examples:

(2) The liquid crystal composition of the present invention may be prepared by means of a method in which liquid crystal compounds are mixed, e.g., by means of a method in which different components are mixed at a high temperature and dissolved in each other, and the liquid crystal composition of the present invention may also be prepared by means of other conventional preparation methods such as using heating, ultrasonication, suspension, etc.

(3) In the present specification, the percentages are mass percentages, the temperatures are in degree Celsius (° C.), and the specific meanings of other symbols and the test conditions are as follows:

(4) Cp represents the clearing point (° C.) of the liquid crystal measured by a DSC quantitative method;

(5) S—N represents the melting point (° C.) for the transformation of a liquid crystal from a crystal state to a nematic phase;

(6) Δn represents optical anisotropy, n.sub.o is the refractive index of an ordinary light, n.sub.e is the refractive index of an extraordinary light, with the test conditions being: 25±2° C. 589 rem and using an abbe refractometer for testing;

(7) Δε represents dielectric anisotropy, with Δε=ε.sub.//−ε.sub.⊥, in which ε.sub.// is a dielectric constant parallel to a molecular axis, and ε.sub.⊥ is a dielectric constant perpendicular to the molecular axis, with the test conditions being 25±0.5° C., a 20 micron parallel cell, and INSTEC: ALCT-IR1 for testing;

(8) γ1 represents a rotary viscosity (mPa.Math.s), with the test conditions being 25±0.5° C., a 20 micron parallel cell, and INSTEC: ALCT-IR1 for testing; and

(9) ρ represents electrical resistivity (Ω.Math.cm), with the test conditions being: 25±2° C., and the test instruments being a TOYO SR6517 high resistance instrument and an LE-21 liquid electrode.

(10) VHR represents a voltage holding ratio (%), with the test conditions being: 20±2° C., a voltage of ±5 V, a pulse width of 10 ms, and a voltage holding time of 16.7 ms. The test equipment is a TOYO Model 6254 liquid crystal performance comprehensive tester.

(11) τ represents response time (ms), with the test instrument being DMS-501 and the test conditions being: 25±0.5° C., a test cell that is a 3.3 micron IPS test cell, an electrode spacing and an electrode width, both of which are 10 microns, and an included angle between the frictional direction and the electrode of 10°.

(12) T (%) represents transmittance, with T (%)=100%* bright state (Vop) luminance/light source luminance, with the test instrument being DMS501, and the test conditions being: 25±0.5° C., a test cell that is a 3.3 micron IPS test cell, an electrode spacing and an electrode width, both of which are 10 microns, and an included angle between the frictional direction and the electrode of 10°.

Comparative Example 1

(13) TABLE-US-00001 Category Structural formula of liquid crystal monomer content (%) Test parameter VI  5 S-N (° C.): ≤ −30 Cp (° C.): 80 γ1 (mPa .Math. s): 60 Δn: 0.1220 Δε: 7.3 III  6 ε.sub.⊥: 3.3 τ (ms): 38.67 T (%): 3.8 III  7 VI  7 II 17 III  7 III 0  8 III 10 III  8

Example 1

(14) TABLE-US-00002 Test Category Structural formula of liquid crystal monomer content (%) parameter VI  5 S-N (° C.): ≤ −30 Cp (° C.): 80 γ1 (mPa .Math. s): 61 Δn: 0.1224 Δε: 6.9 III  6 ε.sub.⊥: 3.6 τ (ms): 33.65 T (%): 4.1 III  5 VI  7 II 42 III  7 III  8 III 0 10 III  8 I  2

(15) It can be seen from the comparison between Example 1 and Comparative Example 1 that, on the basis that Example 1 in which a negative compound represented by formula I and a neutral compound represented by formula II are used in combination maintains clearing point, refractive index, response time, etc. at levels comparable to Comparative Example 1, it has a significantly increased transmittance, thereby obtaining a liquid crystal composition with an excellent performance, i.e., a fast response and a high transmittance.

Example 2

(16) TABLE-US-00003 Structural formula of liquid crystal content Category monomer (%) Test parameter VI 5.5 S-N (° C.): ≤ −30 Cp (° C.): 77 γ1 (mPa .Math. s): 68 Δn: 0.1222 Δε: 6.0 III 20 ε.sub.⊥: 4.0 τ (ms): 28.17 T (%): 4.5 VI 8 II 13.5 II 10 II 5 II 10 III 0 5 III 5 III 5 III 8 I 2 I 3

(17) It can be seen that compared with Comparative Example 1, Example 2 has an increased transmittance and a fast response, is suitable for display applications such as large-size IPS-TV with a low cell thickness, and is advantageous for achieving a wide viewing angle, a high contrast, high-quality dynamic picture play, etc.

Example 3

(18) TABLE-US-00004 content Category Structural formula of liquid crystal monomer (%) Test parameter VI 5 S-N (° C.): ≤ −30 Cp (° C.): 73 γ1 (mPa .Math. s): 74 Δn: 0.1219 Δε: 5.2 III 20 ε.sub.⊥: 4.7 τ (ms): 23.87 T (%): 5.0 VI 8 II 21.5 II 0 10 II 2 II 3 III 5 III 5 III 5 III 5.5 I 2 I 3 I 3 I 0 2

(19) Compared with Comparative Example 1, the refractive index of Example 3 is basically unchanged, the vertical dielectric is increased, the transmittance is further increased, and the high-and-low temperature stability is good; in conjunction with the wide viewing angle advantage of the IPS display modes, it applies to the fields of TV, small and medium size LCD display, etc.

Example 4

(20) TABLE-US-00005 Test Category Structural formula of liquid crystal monomer content (%) parameter VI  3 S-N (° C.): ≤ −30 Cp (° C.): 78 γ1 (mPa .Math. s): 61 Δn: 0.1219 Δε: 7.0 III  6 ε.sub.⊥: 3.6 τ (ms): 33.27 T (%): 4.2 III  5 VI  7 II 30 II 10 III  7 III  8 III 10 III 0  8 I  2

(21) The liquid crystal composition of Example 4 has an appropriate refractive index and clearing point, a high transmittance, and a fast response, and in conjunction with the wide viewing angle advantage of the IPS display modes, it applies to small and medium-sized handheld terminal display applications.

Example 5

(22) TABLE-US-00006 content Category Structural formula of liquid crystal monomer (%) Test parameter III  6 S-N (° C.): ≤ −30 Cp (° C.): 76 γ1 (mPa .Math. s): 62 Δn: 0.1217 Δε: 6.8 ε.sub.⊥: 4.0 τ (ms): 30.72 T (%): 4.7 III  7 VI  7 II 42 III  7 III  8 III 10 III  8 I 0  3 I  2

(23) The liquid crystal composition of Example 5 has an appropriate refractive index and clearing point, a high transmittance, and a fast response, and in conjunction with the wide viewing angle advantage of the IPS display modes, it applies to handheld terminal display applications.

Example 6

(24) TABLE-US-00007 content Category Structural formula of liquid crystal monomer (%) Test parameter III 6 S-N (° C.): ≤ −30 Cp (° C.): 73 γ1 (mPa .Math. s): 66 Δn: 0.1222 Δε: 6.0 ε.sub.⊥: 4.6 τ (ms): 23.10 T (%): 6.2 III 7 VI 5 II 26.5 II 10 II 5 III 7 III 8 III 00 10 III 01 5.5 I 02 2 I 03 3 I 04 3 I 05 2

(25) The liquid crystal compound of Example 6 has an appropriate refractive index and clearing point, a high transmittance, and a fast response, and in conjunction with the wide viewing angle advantage of the IPS display modes, it applies to small-sized display applications such as smart phones.

Example 7

(26) TABLE-US-00008 content Category Structural formula of liquid crystal monomer (%) Test parameter III 06  4 S-N (° C.): ≤ −30 Cp (° C.): 75 γ1 (mPa .Math. s): 66 Δn: 0.1225 Δε: 5.5 ε.sub.⊥: 5.4 τ (ms): 21.22 T (%): 8.1 III 07  5 II 08 50 III 09  7 III 0  8 III  6 III  5 I  2 I  3 I  3 I  3 I  4

(27) The liquid crystal composition of Example 7 has a higher refractive index, which is suitable for low cell thickness displays, as well as a higher clearing point, a wider service temperature, a high transmittance, and a fast response; in conjunction with the wide viewing angle advantage of the IPS display modes, it applies to outdoor display applications.

(28) Although the present invention only lists the specific substances of the above-mentioned eight examples and the proportions thereof in mass percentage, and the performances of the formed liquid crystal compositions are tested, the liquid crystal compositions of the present invention can all achieve the object of the present invention on the basis of the above-mentioned examples by means of the compounds represented by general formulas I, II, III, VI, and VII involved in the present invention and by means of the further expansion and modification of preferred compounds of general formulas I, II, III, VI and VII.