JP2001226673A - Liquid crystal composition - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a liquid crystal composition having a low viscosity, high response speed and excellent steepness. SOLUTION: The liquid crystal composition contains a compound expressed by general formula (1) (R is a 1-10C straight-chain alkyl) and a compound expressed by general formula (2) (R is a 1-10C straight-chain alkyl) as essential components.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a liquid crystal composition used for a liquid crystal display device, and more particularly to a liquid crystal composition containing a specific cyclohexylcyanobenzene compound and a specific cyclohexylcyclohexenyldifluorobenzene compound, having a low viscosity and a high response. High NI with high speed and excellent steepness
The present invention relates to a liquid crystal composition having dots.

[0002]

2. Description of the Related Art A large number of liquid crystal display devices utilizing optical (refractive index) anisotropy (Δn) and dielectric anisotropy (Δε), which are characteristics of liquid crystal compounds, have been produced. It is widely used for watches, calculators, various measuring instruments, automobile panels, word processors, electronic organizers, mobile phones, printers, computers, televisions, etc., and the demand is increasing year by year. Liquid crystal compounds have a unique liquid crystal phase located between the solid phase and the liquid phase, and the phase morphology is roughly classified into a nematic phase, a smectic phase and a cholesteric phase. Of these, the nematic phase is currently used for display devices. Most widely used. In addition, among the methods applied to the liquid crystal display, many display methods have been devised so far. For example, a dynamic scattering type (DS
Type), guest-host type (GH type), twisted nematic type (TN type), super twisted nematic type (STN type), thin film transistor type (TFT type), and ferroelectric liquid crystal (F
LC) and the like, and as a driving method, a static driving method, a time-division driving method, an active matrix driving method, a two-frequency driving method, and the like are known.

Among the above display methods, in recent years, in particular, ST
N-type displays are often used for displays such as personal computers because of their economic advantages such as high display performance and low manufacturing cost. However, even in the case of the STN method, various characteristics are required as the performance of the display element itself is improved. In particular, (1) the response time is short, and (2) the steep threshold voltage (V
It is important that (th) it shows characteristics, (3) it shows a wide operating drive temperature range, and (4) it has low drive power. In order to exhibit these characteristics, it is necessary to improve the characteristics of the liquid crystal composition used for the display device, and for that purpose, it is necessary to improve the liquid crystal compound, which is a component of the liquid crystal composition, to one that gives the above characteristics. It is said.

Further, since liquid crystal display elements are often used under severe conditions such as high temperature and outdoors, the liquid crystal composition and the liquid crystal compound used therein must have sufficiently high chemical stability. . Furthermore, the temperature dependence of each property item is also an important factor in improving the performance of the liquid crystal display device. Incidentally, a practical liquid crystal display element can be used in various environments, particularly in an extremely wide temperature range (−20 to 140).
℃), the display quality must be kept constant. In order to realize this, the liquid crystal composition and the liquid crystal compound used for the same have no temperature dependence or extremely small physical property values. It is necessary to be.

To meet such demands, various STN compounds have been studied so far, and many excellent compounds have been developed. For example, JP-A-5-125363 discloses a liquid crystal composition containing a phenylcyclohexyl compound and a cyclohexenyl compound. Although it has characteristics of low viscosity and fast response speed, it was not sufficiently satisfactory in other performances. Also,
JP-A-58-198428 discloses a cyclohexylcyclohexenyl difluorobenzene derivative, which has a high NI point and a low viscosity, but fails to provide sufficient performance with respect to other properties.

An alkenyl compound having an unsaturated bond at a molecular terminal group (JP-A-59-176221)
However, vinylene compounds (JP-B-7-72148) are well known as having a relatively wide nematic liquid crystal phase temperature range.

[0007] However, none of these compounds can cope with higher quality display. That is, although the alkenyl compound exhibits a relatively large K ₃₃ / K ₁₁ , the viscosity is too large to achieve the required response speed. In addition, this compound, like the vinylene compound, has a problem of compatibility with other components when used as a component of the liquid crystal composition, especially at extremely low temperatures, and cannot maintain a nematic phase, precipitate crystals, or have a smectic phase. There is a drawback that expression of Furthermore, recently STN
In the type display element, the phenomenon of threshold unevenness (burn-in) has become a problem, and various reports have been made. Although the cause of the occurrence is not necessarily clear, it is assumed that the cause is caused by the bias of the impurity ions in the display surface. In order to suppress or reduce these phenomena, it has recently been known that it is effective to use an unsaturated bond-containing compound such as an alkenyl compound or a vinylene compound as a component of a liquid crystal material. Not enough. As described above, in providing a high-quality STN-type liquid crystal display device, the required characteristics of the liquid crystal material are complicated, and the appearance of a new liquid crystal compound that can satisfy this is demanded.

Accordingly, it is an object of the present invention to provide a liquid crystal composition having a low viscosity, a high response speed, and excellent steepness.

[0009]

Means for Solving the Problems The present inventors have developed a liquid crystal composition containing a cyclohexylcyanobenzene compound having a specific structure and a cyclohexylcyclohexenyldifluorobenzene compound having a specific structure as essential components. It has been found that this can be achieved.

The present invention has been made on the basis of the above findings, and comprises a cyclohexylcyanobenzene compound represented by the following general formula (1) and a cyclohexylcyclohexenyldifluorobenzene compound represented by the following general formula (2) as essential components. The present invention provides a liquid crystal composition containing:

Embedded image (Wherein, R represents a linear alkyl group having 1 to 10 carbon atoms)

Embedded image (Wherein, R represents a linear alkyl group having 1 to 10 carbon atoms)

[0011]

BEST MODE FOR CARRYING OUT THE INVENTION Hereinafter, the liquid crystal composition of the present invention will be described in detail.

In the above general formulas (1) and (2), which are essential liquid crystal compounds of the present invention, the compound having 1 carbon atom represented by R in the formulas
Examples of the linear alkyl group of 10 to 10 include linear alkyl groups such as ethyl, propyl, butyl, pentyl, hexyl, heptyl, octyl, nonyl, and decyl.
Particularly, a linear alkyl group having 1 to 6 carbon atoms is preferable.

The liquid crystal composition of the present invention has the general formula (1)
And a cyclohexylcyclohexenyl difluorobenzene compound represented by the general formula (2) as an essential component, and as other components, a conventionally known liquid crystal compound or liquid crystal analog compound, or a mixture thereof ( And a mixture thereof, for example, a compound represented by the following general formula (3) or a mixture thereof.

[0014]

Embedded image (Wherein, Y ₁ represents a hydrogen atom, an alkyl group having 1 to 8 carbon atoms, an alkoxy group, an alkenyl group, an alkenyloxy group, an alkoxyalkyl group, an alkanoyloxy group or an alkoxycarbonyl group, Y ₂ represents a cyano group, A halogen atom, an alkyl group having 1 to 8 carbon atoms, an alkoxy group, an alkenyl group, an alkenyloxy group, an alkoxyalkyl group, an alkanoyloxy group or an alkoxycarbonyl group, wherein Y and Y ₃ are a hydrogen atom, a halogen atom or a cyano group; X ₁ and X ₂ are each independently a direct bond, —CO—O—, —O—CO—, —CH ₂ O—, —O
CH ₂ —, —CH ₂ CH ₂ — or —C≡C—, m
Represents 0, 1 or 2, and ring A and ring B each independently represent a benzene ring, a cyclohexane ring, a cyclohexene ring, a pyrimidine ring or a dioxane ring)

Accordingly, specific examples of the compound represented by the above general formula (3) include the following compounds.
Incidentally, Y ₁ , Y ₂ and Y ₃ in each compound have the same meanings as those in the general formula (3).

[0016]

Embedded image

When the essential liquid crystal compounds of the present invention represented by the above general formulas (1) and (2) are blended and used in the above liquid crystal composition, the content of the essential liquid crystal compounds of the present invention is particularly limited. The compound represented by the general formula (1) is generally 1 to 80 parts by weight, particularly 3 to 60 parts by weight, based on 100 parts by weight of the whole liquid crystal composition, and the compound represented by the general formula (2) Is preferably contained in an amount of 1 to 80 parts by weight, particularly 3 to 50 parts by weight.

[0018]

The present invention will be described in more detail with reference to the following examples. However, the present invention is not limited by the following examples.

Example 1 A liquid crystal composition was prepared by blending the following liquid crystal compounds as in Formulation 1.

[0020]

Embedded image

Comparative Example 1 For comparison, a liquid crystal composition was prepared by blending as in Formula 2 in which cyclohexylcyclohexenyl difluorobenzene represented by the above general formula (2) was not blended.

[0022]

Embedded image

[Test Examples] The physical properties of the liquid crystal compositions of Example 1 [Formulation 1] and Comparative Example 1 [Formulation 2] and the measurement results of the display characteristics of STN liquid crystals obtained by adding a chiral substance to these liquid crystal compositions are shown below. It is shown in Table 1.

[0024]

[Table 1]

From the results shown in Table 1, it was confirmed that the liquid crystal composition of Example 1 had low viscosity, excellent steepness, and high response speed as compared with the liquid crystal composition of Comparative Example 1.

[0026]

The liquid crystal composition of the present invention is an excellent liquid crystal composition having low viscosity, excellent sharpness, and high response speed.

 ────────────────────────────────────────────────── ─── Continuing on the front page (72) Inventor Hirokatsu Shino 5-2-13-Shirahata, Urawa-shi, Saitama F-term in Asahi Denka Kogyo Co., Ltd. 4H027 BA01 BB04 BD03 BD06 BD08 BE05 CM01 CM04 CN02 CU01 DP04

Claims (2)

[Claims] 1. A liquid crystal composition comprising a compound represented by the following general formula (1) and a compound represented by the following general formula (2) as essential components. Embedded image (Wherein, R represents a linear alkyl group having 1 to 10 carbon atoms). (Wherein, R represents a linear alkyl group having 1 to 10 carbon atoms) 2. A compound represented by the general formula (1) is contained in an amount of 1 to 80 parts by weight and a compound represented by the general formula (2) is contained in an amount of 1 to 80 parts by weight based on 100 parts by weight of the whole liquid crystal composition. The liquid crystal composition according to claim 1.