JP2513259B2 - Liquid crystal composition - Google Patents

Description

TECHNICAL FIELD The present invention relates to a liquid crystal composition, and more particularly to a liquid crystal composition exhibiting good characteristics at low temperatures.

[Prior Art] Conventionally, a liquid crystal composition used in a general liquid crystal display device is a low-viscosity ester cyclohexane (ECH).
-Based liquid crystal compound or phenylcyclohexane (PCH) -based liquid crystal compound as a base, on which a cyanobiphenyl-based liquid crystal compound for increasing Δε, a phenyl ester-based liquid crystal compound, and a tricyclic-type liquid crystal compound for increasing the NI point are used. Contains a liquid crystal compound.

[Problems to be Solved by the Invention] By the way, a liquid crystal compound having an ester bond has a relatively high viscosity and also has poor compatibility with other liquid crystal compounds. Therefore, the conventional liquid crystal composition containing such a liquid crystal compound has a high viscosity. Therefore, the liquid crystal display device using this liquid crystal composition is inferior in operating characteristics at low temperatures. For example, the conventional liquid crystal display element has a guaranteed operation temperature at low temperature of about 0 ° C. at most, and cannot lower the operation temperature on the low temperature side, which hinders its use in cold regions.

Therefore, an object of the present invention is to provide a liquid crystal composition having a sufficiently low C-N point so as not to hinder use at low temperatures.

[Means for Solving the Problems] In order to achieve the above object, the present invention mainly uses a straight ring type liquid crystal compound having a low viscosity, and blends a liquid crystal compound having good compatibility, It is intended to lower the viscosity of the liquid crystal composition and lower the crystallization temperature of the liquid crystal.

That is, according to the present invention, the general formula (Wherein R ¹ is an alkyl group having 3 to 5 carbon atoms, and R ² is an alkyl group having 1 to 4 carbon atoms), 10 to 30% by weight of at least one liquid crystal compound represented by the general formula (Wherein R ³ is an alkyl group having 2 to 5 carbon atoms), and the amount of at least one liquid crystal compound is 10 to 50% by weight. (Wherein R ⁴ is an alkyl group having 2 to 5 carbon atoms), and at least one kind of liquid crystal compound is contained in an amount of 5 to 15% by weight and represented by the general formula: (Wherein R ⁵ is an alkyl group having 3 to 5 carbon atoms, and R ⁶ is an alkyl group having 2 to 5 carbon atoms), at least one kind of which is 10 to 30% by weight and represented by the general formula (Here, R ⁷ is an alkyl group having 3 carbon atoms, and R ⁸ is 4 carbon atoms.
Or 5 to 30% by weight of at least one liquid crystal compound represented by the alkyl group 5), and (Wherein R ⁹ is an alkyl group having 3 to 5 carbon atoms, R ¹⁰
Provides a liquid crystal composition represented by (C3 to C5 alkyl group) optionally mixed in an amount of 10% by weight or less.

The liquid crystal compound represented by the formula (I) is an Nn liquid crystal compound which is a base of the liquid crystal composition of the present invention. This liquid crystal compound has low viscosity and good compatibility with other liquid crystal compounds. Generally, the liquid crystal compound of formula (I) has a C-N point
40 ° C, NI point is 50 ° C or higher, Δn is 0.08 to 0.1, and viscosity is 4 to 10 cP (20 ° C).

The liquid crystal compound represented by the formula (II) is an Np liquid crystal compound for positively increasing Δn of the liquid crystal composition. This liquid crystal compound has a large Δε, good compatibility, and a relatively low viscosity. In general, the liquid crystal compound of formula (II) has a C-N point
40 ° C, NI point is 4 to 55 ° C, Δn is 0.11 to 0.13, Δε is
10-40, viscosity is 20-23cP (20 ℃). Among the liquid crystal compounds represented by the formula (II), those in which R is a propyl group are particularly excellent in compatibility.

Similarly to the liquid crystal compound represented by the formula (II), the liquid crystal compound represented by the formula (III) is also an Np liquid crystal compound for positively increasing Δn of the liquid crystal composition. This liquid crystal compound has a large Δε and a large Δn. The liquid crystal compound represented by the formula (III) generally has a C-N of 75 ° C, an NI point of 22 ° C, and a Δn of 0.
19, Δε is 13, viscosity is 22 cP (20 ° C).

The liquid crystal compounds represented by the formulas (IV), (V) and (VI) are
It is a high temperature liquid crystal compound for increasing the NI point, and has a lower viscosity among the high temperature liquid crystal compounds. The liquid crystal compound represented by the formula (IV) generally has a C-N point of 30 ° C. and an N-I
Point is 160 ℃ or less, Δn is 0.18, Δε is about 0, viscosity is 20 cP
(20 ° C). The liquid crystal compound represented by the formula (V) generally has a C-N point of 50 ° C., an NI point of 190 ° C. or less, and Δn of 0.1.
1, Δε is -1, and viscosity is 40 cP (20 ° C). The liquid crystal compound represented by the formula (VI) generally has a C-N point of 50.
C., NI point is 300.degree. C. or less, .DELTA.n is 0.2, .DELTA..epsilon. Is 0, and viscosity is 50 cP (20.degree. C.). Among these liquid crystal compounds, the liquid crystal compound represented by the formula (V) has a negative Δε and is particularly excellent in compatibility with other liquid crystal compounds.

The liquid crystal composition of the present invention comprises 10 to 30% by weight of at least one liquid crystal compound represented by formula (I) and 10 to 50% by weight of at least one liquid crystal compound represented by formula (II). 5 to 15% by weight of at least one liquid crystal compound represented by formula (III), 10 to 30% by weight of at least one liquid crystal compound represented by formula (IV), and formula (V)
5 to 30% by weight of at least one liquid crystal compound represented by and optionally 10% by weight or less of at least one liquid crystal compound represented by formula (VI).

By blending these specific liquid crystal compounds in the specific ratios described above, a liquid crystal composition exhibiting good characteristics at low temperatures can be obtained.

[Examples] Various liquid crystal compounds shown in Table 1 below were mixed in the proportions (% by weight) shown in the same table to prepare various liquid crystal compositions, and the physical properties thereof were measured. The results are also shown in the table.

As can be seen from Table 1 above, the liquid crystal compositions of Examples A to E all have low viscosities and low crystallization temperatures. For example, the physical properties of the conventional liquid crystal composition having the composition shown in Table 2 below and the liquid crystal composition of Example B are compared and shown in Tables 3 and 4 below.

As can be seen from Tables 3 and 4, the liquid crystal composition of the present invention has extremely excellent temperature characteristics and response at low temperatures.

[Effects of the Invention] As described above, the liquid crystal composition of the present invention is
Very low points and excellent low temperature resistance.

Claims (1)

(57) [Claims] 1. A general formula (Wherein R ¹ is an alkyl group having 3 to 5 carbon atoms, and R ² is an alkyl group having 1 to 4 carbon atoms), 10 to 30% by weight of at least one liquid crystal compound represented by the general formula (Wherein R ³ is an alkyl group having 2 to 5 carbon atoms), and the amount of at least one liquid crystal compound is 10 to 50% by weight. (Wherein R ⁴ is an alkyl group having 2 to 5 carbon atoms), and at least one kind of liquid crystal compound is contained in an amount of 5 to 15% by weight and represented by the general formula (Wherein R ⁵ is an alkyl group having 3 to 5 carbon atoms, and R ⁶ is an alkyl group having 2 to 5 carbon atoms), at least one kind of which is 10 to 30% by weight and represented by the general formula (Wherein, R ⁷ is an alkyl group having 3 carbon atoms, R ⁸ is an alkyl group having 4 to 5 carbon atoms), 5 to 30% by weight of at least one liquid crystal compound represented by the general formula (Wherein R ⁹ is an alkyl group having 3 to 5 carbon atoms, and R ¹⁰ is an alkyl group having 3 to 5 carbon atoms), and a liquid crystal compound is optionally mixed in a proportion of 10% by weight or less. Liquid crystal composition.