JPS60146868A - 4-substituted phenyl isothiocyanate - Google Patents

Abstract

NEW MATERIAL:The 4-(trans-4'-alkylcyclohexyl)phenyl isothiocyanate of formula (R is 1-10C alkyl). USE:Useful as a liquid crystal material. It is a nematic liquid crystal substance having low viscosity and positive dielectric anisotropy, and is suitable as a component of a TN-type liquid crystal display element. It has a melting point not too high and a clear point not too low. PREPARATION:The compound of formula can be produced by using 4-(trans-4'- alkylcyclohexyl)aniline as an intermediate, and converting the amino group to -N=C=S group by conventional method.

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.
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. However, 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 being sought.

However, at present, there is no single compound that can be put to practical use because it has excellent properties such as liquid crystal temperature range, operating voltage, and response performance. The liquid crystal composition obtained in this manner is used.

In other words, liquid crystal compositions used in display devices have the aforementioned liquid crystal phase that exists over a wide temperature range, including practical temperatures, as well as low viscosity, low operating threshold voltage, and low power consumption. In general, it is required to be able to drive with high speed and to have a high response speed.

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. Relatively large positive dielectric anisotropy value,
6, that is, △ε-ε/-ε soil is 5 or more, and many of the liquid crystal substances that have been used for secondary fruits have cyan groups in the long axis direction of the molecules; Due to its existence, there is a limit to the reduction of its viscosity. The present inventors searched for liquid crystal substances having a group in place of the cyan group, and found that a compound having an inthiocyanate group, -N-C-8, is suitable for such a purpose. It has arrived.

That is, the first aspect of the present invention is a 4-(tran-4'- The second one is a liquid crystal composition characterized by containing at least one compound represented by the formula (I).

The compound of formula I) has a not very high melting point and not too low clearing point, and is a nematic liquid crystal material with low viscosity and positive dielectric anisotropy, and is a component of a liquid crystal material used in a TN type liquid crystal display device. It is suitable as

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

That is, the compound represented by the following formula (a) csatt-@-o-N-c-s (a) exhibits a smectic E phase (SE phase) at m, p 58°C, and an isokyoshi phase (SE phase) at 74.5°C. 1 phase) was known to occur (R.

Dabrowski et al., Mo1. Crygt, L.
iq, Cryst, 87°109 (1982)
).

The phase transition point of the compound of this formula (a) is the phase transition point of the corresponding cyano compound C3H11-@-@-CN (b) of the following formula (b), C (crystalline phase >24'O, N <Nemachi 8
When compared with 5.3° C. phase) --1→I (isoyoshi phase), it is considered that the --N-C-8 group has a strong tendency to form a smectic phase in this case. Moreover, the SE phase exhibited by compound (a) has extremely high viscosity.

However, the compound of formula (1) of the present invention unexpectedly exhibits a nematic phase and has an extremely low viscosity for a substance exhibiting large positive dielectric anisotropy.

Table 1 shows the phase transition points and other physical properties of representative compounds of formula (1) of the present invention.

Table 1 *1) In each phase of C (solid phase), N (nematic phase), and ■ (transparent phase), the . indicates the phase, and the number on the right side indicates the transition from that phase to the phase on the right side. Indicates transition temperature. or()
indicates the monotropic phase transition temperature, indicating the transition temperature from the phase on the right to that phase.

*2), *8), and *4) are all extrapolated values.

Cyano compound R()@-C corresponding to the compound of formula (1)
N (1) was also previously known as a relatively low-viscosity compound with a large positive dielectric anisotropy; , which is about 3 times smaller than that having a cyano group.

(11) The viscosity is that having an inthiocyanate group,
is about 1/2.

Tsukuda) The refractive index anisotropy Δn is about 0.03 to 0.05 larger in the intiocyanate group-containing one.

The compound of formula (I) of the present invention also has excellent compatibility with other liquid crystal compounds, such as thick base-based, azoxy-based,
Can be mixed with one type of liquid crystal such as benzoic acid phenyl ester type, cyclohexanecarboxylic acid phenyl ester type, cyclohexanecarboxylic acid cyclohexyl ester type, hyphenyl type, phenylcyclohexane type, phenylmetadioxane type, or a mixture of several types of liquid crystals. Yes, it can reduce its viscosity, which is very useful. In particular, when reducing viscosity is important, as long as the N-I point is not extremely lowered, the shorter the complex R in formula (I), the greater the effect, and particularly preferred are ethyl and propyl groups. .

On the other hand, if you want to keep the clearing point as high as possible, a compound with a relatively long R is preferable, but even in that case, the viscosity reduction effect obtained is not possible with conventionally known compounds.
big.

The compound of formula (I) is suitably produced by using 4-(trans-4'-alkylcyclohexyl)aniline as an intermediate raw material and deriving the amino group ff1-N=C-8 group. An example of anilines that are intermediate raw materials is 4-() lance-4'-ethylcyclohexyl)aniline (mp49.5°C).

4-() lance-4'-propylcyclohexyl)aniline (mp58.5°C).

4-() lance-4'-butylcyclohexyl)aniline (mp556C).

4-();yin-4'-pentylcyclohexyl)aniline (mp56.5°C).

4-()Lance-4'-hexylcyclohexyl)aniline (mp 56°C).

4-(trans-4'-hebutylcyclohexyl)aniline (mp 56°C).

etc. can be mentioned. These are for example Mac Miuan
(Mot, Cr7st, Licl, Crest
, +55, 61 (1979)).

Although known chemical methods can be used to induce an amino group into a -N=C-3 group, the simplest method is the method represented by the following formula (J, C, Jochi
ms, Chem, Ber, ; 101 +174
6 (196B)).

R(XMochiNC8+R'-NHCNH-R'1 (1) S Also J, K, Hodgkins et al. (J, Org,
Chem, t 29° 8098 (1964)) can also be applied.

The method for producing the compound of formula (1) and the liquid crystal composition containing the same will be detailed in Examples below.

Example 1 (Preparation of 4-()trans-4'-propylcyclohexyl)phenyl incyanate (formula (I) in which R is C3Hy)) Dicyclohexylcarboniimide 65.5F.

A solution of 63.5 d of pyridine and 127 ml of carbon disulfide was cooled to -10°C, and 4-(trans-4'-7'ropylcyclohexyl)aniline (mp5
8.5°C, a solution obtained by dissolving 69f (produced by the method of Mac Nihlhn et al.) in 100 ml of pyridine is added dropwise while maintaining the liquid temperature at about -10°C. After the dropwise addition, the mixture was kept at that temperature for an additional 8 hours and then at 20°C for 8 hours, and the precipitated dicyclohexylthiourea was filtered out and washed with benzene. Combine the filtrate and washing liquid, distill off the solvent (excess carbon disulfide, benzene, pyridine) under reduced pressure, and then add benzene to the residue. Dicyclohexylthiourea, a by-product, remains undissolved. The benzene layer was washed with 2N salt #L and then with water, and then the benzene was distilled off. The residue was the crude target product (formula (■) where R is C3H7), which was purified by dissolving it in heptane and passing it through an alumina/heptane chromatographic column. It is recrystallized with ethanol to produce colorless crystals 85y, which is the desired ff product.
I got it. This one is rmp (C-N point) 88.9-89
The C1 clearing point (N-I point) was 44.0 to 41.1°C. The heat of fusion was 8.5 Kcat/mot. Furthermore, the elemental analysis values were in good agreement with the theoretical values as shown below.

Analysis value Theoretical value (as C15HztNS) C74.0
% 74.08% H8.2% 8.16% N 5.3% 5.40% Examples 2 to 4 In the same manner as in Example 1, in formula (I), R is C2H[,.

C4He and C5Htt were produced. Its physical property values are also shown in Table 1.

Example 5 (example of use) C3My% CN 24% (graywood, same below) C,H
The liquid crystal temperature range of the liquid crystal composition consisting of four components: ,, (X_CN 86% CrH1s-O-@-CN 25% C3H11a) C4 and CN 15% is -25°C.
(below) to 72℃, 20'G! Viscosity at (η2+1)
is 27.8 cp, and the refractive index anisotropy (Δn) is 0.140.
The dielectric anisotropy (Δε) is 11.6. The threshold voltage when used as a TN type cell is 1.75V.

The saturation voltage is 2.40V.

A liquid crystal composition obtained by adding 5 parts of C3H71N=C=S obtained in Example 1 of the present invention to 85 parts (by weight) of this liquid crystal composition has a nematic temperature range of -25°C (below) to 66°C. .6°C1ga. is 24.8cp, △n is 0.1
45. △ε is 11.6. The L threshold voltage was 1.69V, and the saturation voltage was 2.86V. Thus, by adding the compound of the present invention, the viscosity and driving voltage decreased, and Δn increased. The physical property values shown in Table 1 are obtained by extrapolating the values determined in this way to ΔC9η20+Δn for the single compound of formula (1).

Claims (2)

[Claims] (1) 4-(trans-4'-alkylcyclohexyl) phenyl isothiocyanates represented by the general formula % (in the above formula, R represents an alkyl group having 1 to 10 carbon atoms). (2) 4-(trans-4'-alkylcyclohexyl) phenyl thiocyanates represented by the general formula % formula % (1) (wherein 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 type of.