GB2210381A

GB2210381A - Nematic liquid crystals with glass phases

Info

Publication number: GB2210381A
Application number: GB8822184A
Authority: GB
Inventors: Dietrich Demis; Kristina Mohr; Wolfgang Schafer; Renate Schmidt; Wolfgang Wedler; Wolfgang Weissflog
Original assignee: Veb Werk fur Fernsehelektronik Im Vwb Kombinat Mikroelektronik; Werk fuer Fernsehelektronik GmbH
Current assignee: Veb Werk fur Fernsehelektronik Im Vwb Kombinat Mikroelektronik; Werk fuer Fernsehelektronik GmbH
Priority date: 1987-09-24
Filing date: 1988-08-21
Publication date: 1989-06-07
Anticipated expiration: 2008-08-21
Also published as: CH676005A5; GB2210381B; JPH01144490A; DD265155A1; DE3830968A1; GB8822184D0

Description

221038A1 NEMATIC LIQUID CRYSTALS WITH GLASS PHASES The invention relates

to nematic liquid crystals having glass phases as solid, optically anisotropic media for producing optical components, e.g. compensators, prisms, plates with optical rotation, polarisers and for thermo-electrooptical memory displays.

Glass-like liquid crystalline phases have been known for some considerable time (H. Kelker, R. Hatz, Handbook of Liquid Crystals, Verlag Chemie Wel'n'heim 1980; N. Kirov, M.P. Fontana, N. Afanassieva, Mol. Cryst. Liq. Cryst. 89, 193 (1982)).

In the case of the already long-known substances, the glass transition zones lie at temperatures which are too low, which excludes the possibility of using this phase behaviour for practical purposes. For example, the (pbutyl-p'-methoxy)azoxy benzene (N.Grebovicz, B. Wunderlich, Mol. Cryst. Liq. Cryst. 76, 287 (1981)) has a glass transition temperature of around -660C.

A class of compounds having liquid crystalline and non-liquid crystalline homologues which have glass temperatures above or around room temperature, is known from D-D-242 626. All the substances have glass temperatures which are below the melting temperatures, so that the glass state of the pure substances is in the thermodynamically meta-stable range. Therefore, many of these substances tend to crystallise directly they are 2 heated to above the temperature of the glass. In order to prevent crystallisation, suitable mixture partners are used which themselves form nematic glass phases.

The object of the invention is to find nematic liquid crystals which are suitable for the formation of glass phases and which are suitable for producing optical components and for thermoelectrooptical memory displays having good mechanical stability, low temperature dependency of the optical properties and good phase stability at room temperature.

According to the invention, gfass forming 1,4-bis[2,3,4-substituted benzoyloxyl-benzenes to the general formula:- 5COO-X-00C R 2 16 de R R R C(CH 3)3 X C(CH 3)3 C(CH 3)3 zlklc' A. R R 1 # 1z 2 = OC n H 2n+ly "C n H 2n+11 - CNI -C(CH 3)3# -NO 2 R 3, R A c -0CmH2m+l' -C m H 2m+11 "Cl, -Br, -1. -H# -OH R 5 R 6 =---OGH -C H -Cl, -Br, -1, -H, -OH, g; k 2k+l'. k 2k+11 3 -COO(CH2) X -00 1 H21+1. - c 1 H 21+1. -cool,, 1 FI 21+1' -CN, -N C)2' _C(C113)3# - 011 k, 1, m, n, x 1 to 10, in mixtures with one another or with other liquid crystalline or non-liquid crystalline substances are suitable for producing solid optically ani.sotropic media for optical components (compensators, prisms, plates with optical rotation, polarisers) or thermo-electrooptical memory displays.

By the action of external fields, these substances can be orientated so that it is possible to use them as optical compensators and prisms, and also as polarisers when dichroic dye-stuffs have been added. Where twisted orientation is concerned, it is possible to produce plates with optical rotation, as well as thermo-electrooptical memory displays if the appropriate cells are used.

The substances are colourless, can be produced to a high degree of purity and are chemically and thermally stable. Furthermore, with noncrystalline liquid glass forming substances in mixtures with other crystalline liquid glass forming or non-glass forming substances, they produce nematic phases which solidify after the manner of glass. The percentage content of nematic glass forming mixture should be greater than 50 mol-%. Under these conditions, it is possible to reduce the melting points, 4 the clarification points remai.ning suffici.ently high. The durability of the glass phase is si-9nificantly increased and the tendency to crystallise is suppressed both in the glass phase and also under heating beyond the glass transition range.

It is intended to explain the invention in greater detail hereinafter with reference to the followj.ng Examples and the data in the Tables.

Example of Production:

0.01 mol of 2,3-substituted hydroquinone (X) in 20 ml dry pyridi.ne was added dropwj.se, accompanied by agi.tation at room temperature to 0.02 mol of the correspondi.ngly substi.tuted benzoyl chloride in 30 ml of dry pyri.dine. The resulting m!-xture was left to stand for one day and then warmed for one hour under agitati.on to approx. 700C, the reaction soluti. on. It was cooled and poured into a mixture of ice and concentrated sulphuric acid. The precipitate was extracted, washed with dilue sulphuric acid and water and then stirred for one hour with 30 ml of a 5% NaHC03 solution. The crude product was recrystalli.sed after filtering and repeated washi.ng with water. Suitable solvents are alcohol/dioxane mixtures. The acylated 2,3-subst. hydroquinones are formed in yields amounting to 55 to 85% of theory.

Table 1: Thermodynamic data of selected compounds according to formula I.

RI R 2 R 5 R 6 X T Glee/OC T F/OC T Cl/0c C-OC 2 H 5 -OC 2 H 5 H -H 51 215,0 2416 -OC 2 H 5 OC 2 H 5 - Dr -H c-pc h 59 M,OC 2 H 5 -OG 2 H 5 H 11 23 16006 1721B -OC 3 bl 7 - OC 3 11 7 - H -11 142 172t2 217jO -OCH 3 - OCH 3 - H -H 27 139,5 111$8 -OC H OC H H -H 2 5 - 2 5 Z2 143sO 137,6 -Q- C. Me -OC 2 H 5 - 0C 2 11 5 Dr -H 551 210,0 G Me TGlas lower limit of the.glass transition range TF melting point of the most Stable crystal modification T cl nematic-isotropic conversion temperature 6 Examples for Mixtures Example a A eutectic mixture of the substance indicated in Table 1 is produced cl f,0 coo 00C OC H 2 CH- Cl- with the substance NC CH=N N=N CO0C 2 H 5 (b) (hereinafter referred to as mixture I). The physical- chemical parameters of the substance (b) are as follows:- T 3 SoC glass T 188.10c &HF 32.2 kJ/mol.

The corresponding physical-chemical parameters of mixture I are indicated in Table 2.

The result is an homogeneous mixture of red colouring with a melting temperature of 1600C with no liquid crystalline phase. The glass temperature of the mixture is above room temperature. The glass phase which is thus obtained is stable for months.

7 Table 2: Physical data of Mixture I.

Pure components Mixture A - J.

Component kj M01 X Compor T Glee /,C T F /OC TC1/OC- (a) 41,7 0,33 3Z 160YO (b) 32,2 0j67 AHF - fusion enthalpy of the most stable crystal modification xcomp, - mol fraction of the component in the mixture Example b A eutectic mixture of the substances indicated in Table 1 c 2 H 5 COO 0.0e%0C2 HS and C2 H C).rC)0 OOC-0C2 HS (c) are produced (hereinafter referred to as Mixture II), the physical- chemical data for which can be found in Table 3.

Table 3

Pure components Kixture Component DHfkj mor' 5comp Tglaslcl TFO/Oc T CPP c (a) 11.7 0.21 32 128.0 176.5 (c) 39.1 0.79 In contrast to Example a, what is produced here is a colourless homogeneous mixture having a melting temperature of 1280C and a clarification temperature of 176.50C.

The glass temperature of the mixture is above room temperature. When in the molten state, the mixture can be orientated by wall action, electrical and magnetic fields and then frozen into the glass-like state by rapid cooling to temperatures of around OOC. The orientation is retained in the process. By heating to temperatures above the melting temperature it is possible to impose a fresh orientation. The orientation obtained is stable for several months.

Example c

A series of mSxtues of different concentrations are produced from the following substances indicated in Table c 2 H 5 oc CC)C)-QOOC'0C2 HS (d) c and c 2 H 5 O-Q CC)O.QC)OC.QOC 2 E 5.(e) C MC3 E3 r 3r hereinafter referred to as mixtures IIIA, II1B, IIIC and IIID.

The physical-chemical parameters of the mixtures are indicated in Table 4.

Table 4

Mixture No. X (d) Tglass/0c TF/"c TCp/0.c IIIA 0.19 25.0 139.0 133.0 1 IIB 0.40 36.0 130 122.5 I IIC 0.60 43.0 173.0 108.0 IIID 0.80 50.0 192.0 92.0 z (d) - mol f racFlr-o-n of the component (d) Colourless homogeneous mixtures are produced having a nematic phase, although one mixture partner of these binary mixtures is not a carrier having liquid crystalline properties. The glass temperatures of the mixture are around or above room temperature and can be varied between the glass temperatures of the two mixture parameters by varying the mixture compositions.

The characteristic features for practical utilisation of these mixtures are the same as indicated in Example b.

Claims

1. A compound having the general formula:- R

2 COO-X-00C 6 R R wherein C(CH 3)3 X C (CH 3)3 C (CH 3)3 P, R4 Ri and R2 are independently -OCnH2n+11 -CN, -C(CH3)31 -N029 R3 and R4 are independently -OCMH2m+11 -CmH2m+l, -Cl, Br, -I, -H, -OH R5 and R6 are independently -OCkH2k+11 _CkH2k+l -Cl, -Br, -I, -H, -OH, -COO ((,H Ri is OC1H21+11 _ClH21+11 -COOC1H21+11 -CN, -NO C(CH3)31 -OH, wherein k, 1, m, n, x are independently integers from 1 to 10.

12 2. A compound as claimed in claim 1 wherein at least one of Ri and R2 is or are -OCH3. -OC2H5 or -OnC3H7.

3. A compound as claimed in claim 1 or claim 2, wherein R5 is -H or Br.

4. A compound as claimed in any one of the preceding claims wherein R6 is H.

5. A compound as claimed in any one of the preceding claims wherein X is 0 r C Me,

6. A compound as claimed in claim 1 wherein Ri and R2 are -OC2H5. R5 and R6 are H, and X is -S #.- -a

7. A compound as claimed in claim 1, wherein Ri and 2 5 is Br or H, R6 is H, and X R are C2H50- R is 7c MC3

8. A compound according to claim 1 substantially as described hereinbefore.

9. A nematic liquid crystal with glass phases suitable for producing solid optically anisotropi.c media for optical components and for thermoelectrooptical data storage comprising a liquid crystalline compound according to claim 1, mixtures thereof and mixtures with liquid 13 crystalline or non-liquid crystalline substances.

10. A composition as claimed in claim 9 comprising a eutectic mixture of a first component having the general formula of c. 0, c.-- wherein X is and R3 and R4 are H or -CH3, and a second component having the general formula:

0 c, X - 0 PIS wherein X is C, and RS is H or Br.

11. A composition as claimed in claim 10 wherein the mole fraction of the first component is in the range 0.2 to 0.5.

12. A composition as claimed in claim 10 or claim 11 wherein the mole fraction of the second component is in the range of 0.5 to 0.8.

14

13 A composition as claimed in claim 9 substantially as described hereinbefore.

14. A process for the production of a compound as claimed in claim 1 comprising the step of reacting a compound of the general formula:- HO - X - OH with a compound of general formula:- COL.

wherein L is a good leaving group.

15. A process as claimed in claim 14 wherein L is Cl, Br or I.

16. A process as claimed in claim 14 or claim 15 wherein the reaction is performed in the presence of a non-aqueous base.

17. A process as claimed in claim 16 wherein the base is pyridine.

18. A process for the production of a compound as claimed in claim 1 substantially as described hereinbefore.

i Published 1988 at The Patent Oflice. State House. 66'11 High Holborn. London WC1R 4TP Further copies mkv be obtained from The PatentOffice, Salles Branch. S, Me.---yCray. OrpL-gTon. Kent 13R5 3RD Printed by Multiplex techniques ltd. S- Mary Cray. Keni. Con 1,8-,