JPS60136555A - Ester of 4-isothiocyanatophenol - Google Patents

Abstract

NEW MATERIAL:A compound expressed by the formula (R is 1-10C alkyl). EXAMPLE:4-Isothiocyanatophenyl trans-4-propylcyclohexanecarboxylate. USE:A nematic liquid crystal substance having positive dielectric anisotropy, useful as a component used in liquid crystal materials used in TN type liquid crystal display elements, having not so high melting point and not so low clear point, and capable of assuming the nematic phase. PREPARATION:4-Isocyanatophenol which is a well-known compound is reacted with a trans-4-alkylcyclohexanecarboxylic acid halogenide in a basic solvent, e.g. pyridine, to afford the aimed compound expressed by the formula.

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to novel compounds as a component of liquid crystal mixtures and to liquid crystal compositions containing them.

Liquid crystal display elements utilize the optical anisotropy and dielectric anisotropy of liquid crystal materials, and depending on their display format, TN
It is divided into various types such as type (twisted nematic type), DS type (dynamic scattering type), guest-host type, and DAP type.
The properties of liquid crystal materials suitable for each use vary. All liquid crystal materials have in common that they must be stable against moisture, air, heat, light, etc., and materials that exhibit a liquid crystal phase over as wide a temperature range as possible, centered around room temperature, are desired.

However, at present, there is no single compound that can be put to practical use with excellent characteristics such as liquid crystal temperature range, operating voltage, and response performance. The resulting liquid crystal composition is used.

In other words, in addition to the fact that the liquid crystal composition used in display elements has the above-mentioned liquid crystal phase in a wide temperature range including practical temperatures, it also has a low viscosity and a low operating threshold voltage. Generally, it is required to be driven by electric power and to have a high response speed of operation.

In particular, in order to improve the response speed of a TN type liquid crystal display element, it is desirable to use a liquid crystal material with low viscosity. For this purpose, it is desirable that the constituent components have as low a viscosity as possible, and it is particularly desirable that the main component having positive dielectric anisotropy has a low viscosity. A relatively large positive dielectric anisotropy value, ie Δε=ε1. - Liquid crystal substances with ε of 5 or more, which have been put to practical use in the past, often have cyan groups in the long axis direction of the molecules, and such substances have a tendency to reduce their viscosity due to the presence of cyan groups. has its limits. The present inventors searched for liquid crystal substances having a group in place of the cyano group, and found that a compound having an inthiocyanate group, -N-C=8, is suitable for this purpose. It has arrived.

That is, the first aspect of the present invention is trans-4- of 4-thiocyanatophenol represented by the general formula % (in the above formula, R represents an alkyl group having 1 to 10 carbon atoms). The second is an alkylcyclohexanecarboxylic acid ester, and the second is a liquid crystal composition characterized by containing at least one compound represented by formula (1).

The compound of formula (1) is a nematic liquid crystal material having a very high melting point, a very low clearing point, and a positive dielectric anisotropy, and is suitable as a component of a liquid crystal material used in a TN type liquid crystal display device. It is something.

Until now, liquid crystal substances having isothiocyanate groups have not been completely unknown.

That is, a compound represented by the following formula (a) C high ◇ () N-C-8 (a) becomes a smectic E phase (8E phase) at m, p53tl:', and a Tokichi phase (l phase) at 74.5C. )
(Dabrowski et al., Mol, Cryst, Liq, Oryst, ;
Shadow L109 (1982)) Q The phase transition point of the compound of this formula (a) is the phase transition point of the corresponding cyano compound of both the following formulas, C (crystalline phase) 24 tZ' N c nematic phase) 35. 3U, etc.), it is considered that -N and -C-8 groups have a strong tendency to form a smectic phase in this case. The BE phase shown in L7 (a) has extremely high viscosity.

However, the compounds of formula (I) of the present invention unexpectedly exhibit a nematic phase. The phase transition temperature is shown in Table 1.

The reason why the compound of formula (1) exhibits a smectic phase is unknown, but according to the research of the present inventors, the distinction between exhibiting a nematic phase and a smectic phase is extremely subtle. For example, the compound of the following formula (■), which is similar to the compound of Nakasei, exhibits an osmectic anthropomorphism (SA phase) (in the case of It, If in the above formula, CΣL5■Sat L58A (monotropic)). A compound of the following formula (Ill) having a CN group is a nematic liquid crystal.

R (Oki 0 leaves → -CN ■) This also suggests that those having -N=C=8 groups tend to exhibit a smectic phase.

When the compound of formula (1) of the present invention is compared with the corresponding cyan group-containing compound R (Xcoo@-JjN (M), it is found that -N=
When comparing the physical properties of compounds having C=3 groups, the following characteristics can be mentioned as compounds having -N=O=8 groups.

(i) Dielectric anisotropy Δε - Those with isothiocyanate groups are about 39 smaller than those with cyano groups.

(i) The viscosity is approximately the same for those having isothiocyanate groups.

(The initial refractive index anisotropy Δn is about 0.03 to ()05 thicker for those having inthiocyanate groups.

Table 1 shows Δε, Δn, viscosity (η,
. For comparison, the values of C) are shown together with those of the compound of formula IlI'i (■), and those of the compound of formula Vl1 are also shown as reference values (12).

The compound of formula (1) of the present invention has excellent compatibility with other liquid crystal compounds, such as ship base, azoxy, benzoic acid phenyl ester, cyclohexane carboxylic acid phenyl ester, cyclohexane carboxylic acid phenyl ester, etc. By mixing it with one type of liquid crystal such as carboxylic acid cyclo/xyl ester, biphenyl, phenylcyclohexane, phenylmetadioxane, or a mixture of several types, the viscosity can be reduced significantly. Useful compounds of formula 7.(1) can be obtained by reacting the known compound 4-thiocyanatophenol with trans-4-argylcyclohexanecarboxylic acid norogenides in a basic solution such as dipyridine. Most suitably produced 1
, the details of which are shown in the Examples below.

Performance 11 Example 1 [Production of 4-isothiocyanatoenyltrans-4-propylcyclohexanecarboxylate (with formula (1) where R2 is C, 117)] 4-Inthiocyanatophenol, one of the raw materials J. C. Jochims method (chem, Ber.

101.1746 (1!168)) manufactured by IfC was used. rn, p, 40 Ca 15.19 (0.1 mol) of this substance was dissolved in 100-pyridine and 18.9 g (0.1 mol) of trans-4-propylcyclohexanecarboxylic acid chloride was added to an ice-cooled container.
1) dissolved in 40° of toluene was added dropwise, and then 8
The mixture was heated and stirred at 0C for 2 hours. Ice and 6N hydrochloric acid were added to the mixture to make it acidic, toluene was added to separate the layers, the toluene layer was washed with water, and the toluene was distilled off under reduced pressure. The residue was recrystallized twice from ethanol to give colorless crystals 24.
6. I got f. This material has a melting point of 83C and produces a nematic liquid crystal phase due to a monotropic phase transition below 74.5C. In addition, its infrared absorption spectrum shows a strong characteristic absorption of the -N-C=S group at 4.8 μm.

The elemental analysis values were in good agreement with the theoretical values as shown below.

Analysis value Theoretical value (0+7H210t R8 and 2)C
67.5% 67.29% ■ 6.8% 6.98% N 4.5% 4.62% Examples 2 to 6 In the same manner as in Example 1, other alkyl group compounds of formula (1) were prepared. Manufactured. Its physical property values are shown in Table 1.

The liquid crystal temperature range of the liquid crystal composition consisting of the four components of Example 7 (use example) is -25%
From (below) 72. The viscosity 'hoU of Or, 2Or is 2
7.8 ELL refractive index anisotropy Δ11 is 0.14, dielectric constant anisotropy Δε is 11.6, threshold voltage is 1.75 V, saturation voltage is 2.4 OV when used as a TN type display element, t-
), in this liquid crystal composition, it is c3 in the formula (I) of the present invention.
The nematic temperature range of the compound containing 15 wt-i% of compound n is 12 FI? (below) ~70C, viscosity η2
oC is 26.5Cp, Δ■ is 0.146, and Δε is 10.
9. The threshold voltage was 1.66V, and the saturation voltage was 2.36V. As described above, by adding the compound of formula (1) of the present invention, the viscosity decreased, ΔII increased, and Δε became small. Extrapolating from this experimental result and subtracting Δε and η2oC1Δf1 of the compound of Example 1, each is 69.19 C.
p, 0.18.

These values were determined in the same manner for other compounds of formula (I) and those of comparative examples, and the results are shown in Table 1.

Below

Claims (2)

[Claims] (1) Trans-4-alkylcyclohexanecarboxylic acid ester of 4-inchocyanatophenol represented by the general formula % formula % () (in the above formula, 几 represents an alkyl group having 1 to 10 carbon atoms) . (2) Trans-4-alkylcyclohexanecarboxylic acid ester of 4-isothiocyanatophenol represented by the general formula % formula % () (in the above formula, R represents an alkyl group having 1 to 10 carbon atoms) A liquid crystal composition comprising at least two components, characterized in that it contains at least one component.