DD285105A5 - LIQUID CRYSTALLINE MIXTURES WITH EXTENDED SMEKTIC C-PHASES - Google Patents

Abstract

The invention relates to liquid-crystalline mixtures with extended smectic C phases for electro-optical arrangements for the modulation of the continuous or reflected light and to the colored or black-and-black display of numerals, characters and images. According to the invention, as substances for use in optoelectronic components based on chiral smectic liquid crystals, esters of * with heterocyclic carboxylic acids of the general formula I where R1CnH2n1, CnH2n1O2R2CnH2n1 with n1 to 16A21,4-phenylene, 1,4-cyclohexylene or single bond R3H, CH3 used. Formula I {electro-optics; liquid crystals; mixtures thereof; smectic C phases; negative dielectric anisotropy; extended temperature ranges; ferroelectric liquid crystals; Ester of the *

Description

Field of application of the invention

The invention relates to liquid-crystalline mixtures for electro-optical arrangements for the modulation of the continuous or reflected light as well as for the colored or black-and-white display of numbers, characters and moving or still images.

Characteristic of the known technical solutions

It is known that liquid crystals can be used in optoelectronic components for modulation of light and for displaying measured data or for reproducing information, in such methods the preferred orientation of thin layers of the crystalline liquid substances is changed by applying electric fields. The influence on the preferential orientation of crystalline-liquid substances is associated with a change in the optical behavior (birefringence, rotation, light absorption). Depending on the initial orientation achieved by special pretreatment of the electrodes or by adding certain dopants, dielectric and optical anisotropy, electrical conductivity, spontaneous polarization, dichroism and strength, direction and frequency of the applied electric field, various electro-optical effects are observed and technical (E.Kaneko: Liquid Crystal TV Displays: Principles and Applications of Liquid Crystal Displays, KTK Scientific Publ. Tokyo 1987). N.A. Clark and S.T. Lagerwall proposed a method based on the fact that by applying an electric field to a substance with a chiral smectic C phase, the mean direction of the molecular long axes can be changed by twice the Tilt angle. The occurring rapid switching can be observed in observation between Polaristtoren as a significant change in the intensity of the transmitted or reflected light.

The technical application makes a number of demands on the substances used, especially the following properties are required:

- extended regions of chiral smectic C-; hare with ferroelectric properties

- thermal and chemical stability

- negative "dielectric anisotropy.

For technical applications, since pure substances do not have all the desired properties, only mixtures are used. For these mixtures chemically and thermally stable mixture components are required, on the one hand have high transformation temperatures of the smectic C phases and on the other hand, if possible, have no additional smectic phases at lower temperatures. The chirality may be imparted to a masterbatch having a smectic C-phase by addition of chiral mixture components. However, it is also possible to mix chiral components from the outset, as long as smectic C phases are formed.

Since some additional components lower the upper transition temperature of smectic C phases, the mixture components of the base mixtures should have the highest possible conversion temperatures of the smectic C phase, if possible above 100 ° C.

It has already been proposed (G. W. Gray et al., DE OS 3712995 and WO 88/08019) to use derivatives of 1,3,4-thiadiazole with smectic liquid-crystalline phase in optoelectronic components. The claims of these patents are very general and broad but only some examples are given in WO 88/08010 where the occurrence of smectic C phases is not demonstrated for the majority of the compounds covered by the claims. In particular, none of the substances according to the invention described below are occupied.

Object of the invention

The aim of the invention are new blends for electro-optic applications of smectic C phases, in particular chiral C phases, with negative dielectric anisotropy, not too high melting temperatures, high transformation temperatures and good stability.

Presentation of the essence of the invention

The object of the invention is to find suitable mixture components with smectic C phases, which are either themselves chiral or can be converted by suitable chiral additives into chiral C phases

 According to the invention, liquid-crystalline mixtures with extended smectic C phases and negative average Iris anisotropy contain at least one ester of 2-phenyl-1,3,4-thiadiazole with heterocyclic carboxylic acids of general formula I.

wherein R ¹ = C _n H _{2n + 1} -, C _n H _{2n + 1} O-, R ² = C _n H _{2n + 1} - where n = 1 to 16

^il - -O- Ό-

v = h

, η3

A ² = 1,4-phenylene, 1,4-cyclohexylene or single bond, R ³ = -H, CH ₃ , mean, in addition to liquid-crystalline and / or not

liquid-crystalline substances.

The substances are colorless and thermally and chemically very stable. They have very broad areas of existence of the smectic C phase and are well miscible with each other and with other liquid crystals. They have negative dielectric Anisotropy, which is particularly favorable for use in displays on the Baris ferroelectric C phases. The substances are prepared according to the following reaction scheme:

R ¹ A ^ COCl + HO

R ¹ A ¹ COO

ⁿ -Va ² r ² ι

embodiments example 1 Preparation of 2-n-heptyl-5- / 4-propanoyloxyphenyl / 1,3,4-thiadiazole

0.1 mol (15.8 g) Octansäurehydrazid is in 16OmI absol. Pyridine and dissolved at 0 to 5 "C while stirring with 0.1 mol (21.2 g)

Propanoyloxybenzoylchlorid added dropwise. The reaction mixture is allowed to warm slowly to room temperature

and it is stirred for 2 hours at 20 ⁰ C, then heated for 2 hours at 7O ⁰ C. After cooling to room temperature, the

Reaction mixture poured into 11 ice water. The precipitate is filtered off, washed with water and from Recrystallized ethanol.

Yield 26.7 g (80% of theory).

0.1 mol (33.4 g) of the thus obtained N- (2-n-heptyl) -N- (4-n-propanoyloxyphenyl) hydrazine are dissolved in 300 ml of pyridine and

while stirring with 30 g of PhS ₁₀ added. After the decay of the exothermic reaction is heated to 8O ⁰ C for 2 hours and further 12 hours at 100 ⁰ C stirred. After cooling to room temperature add 100 ml of ethanol and pour

Poured reaction mixture into ice water. The resulting solution is neutralized with 10 parts by mass in% sodium hydroxide, the Suction filtered, washed thoroughly with water and recrystallized from ethanol. Melting point 68 ⁰ C. Yield 25.6 g (77% of theory) According to this regulation, further compounds were synthesized:

C ₉ H ₁₉

-0OCC ₂ H ₅

he 62 is

^{cr 71 is}

-0OCC ₂ H ₅ cr 107 S _c 153 M Isl

Example 2 Preparation of 2-n-heptyl-5- (4-hydroxyphenyl) -1,3,4-thiadiazole

0.05 mol (16.6 g) of 2-n-heptyl-5- (4-propanoyloxyphenyl) -1,3,4-thiadiazole are suspended in 10OmI of methanol and washed with a

Solution of 5.6 g KOH in 10OmI methanol. The mixture is refluxed for 2 hours. Subsequently, the Removed solvent on a rotary evaporator and the residue dissolved in 250 ml of water. The solution is treated with 5% HCl

acidified, the resulting precipitate was filtered off and recrystallized from ethanol.

Yield 10.1 g (95% of theory) According to this regulation, the following compounds were prepared:

-OH

Cr 97 is

CH 4l ^rI 2

-OH

cr 100 is

-OH

cr 152 is

^C 6 ^H 13

-OH cr 178 is

Example 3 Preparation of 6-butyloxypyridazine-3-carboxylic acid To 0.89 mol (150 g) of e-hydroxypyridazine ^ -carboxylic acid ethyl ester was added dropwise with heating to 120 ⁰ C11 POCl ₃ . The The reaction mixture was kept at this temperature for 30 minutes, then cooled to 7O ⁰ C and the excess POCl ₃ distilled off under reduced pressure (1.6 kPa). The residue was poured into ice-water (saturated with Na ₂ CO ₃ ). The

Precipitated product was filtered off and recrystallized from water.

Yield 91 g (55% of theory)

0.1 mol (2.3 g) of Na was dissolved in 150 ml of n-butanol. 0,025mol (4.6 g) was added, e-chloropyridazine-S-carboxylic acid ethyl ester and the reaction mixture heated for 4 hours at 100 ⁰ C. Subsequently, 10 g of NaOH, dissolved in 75 ml of bulanol, were added to the reaction mixture and heated at 100 ° C. for a further 3 hours. The excess solvent was removed on

Removed rotary evaporator, the solid residue dissolved in ethanol and precipitated with dilute hydrochloric acid. The

Precipitated precipitate was recrystallized from water.

Yield 1.5g (30% of theory) Example 4 Preparation of 2-n-heptyl-5- / 4- (6-n-butyloxypyridinyl-3-carbonyloxy) -phenyl / -1,3,4-thiadiazole (# 2)

0.0026 mol (0.5 g) 6-Butyloxynlcotininsäure are mixed with 5 ml of thionyl chloride and heated for 5 hours in a water bath at 30 ° C cerium. The excess thionyl chloride is stripped off on a rotary evaporator and the residue with 0.0024 mol (0.7 g) of 2-n-heptyl-5- (4-hydroxyphenyl) -1,3,4-thiadiazole, dissolved in 10 ml toluene, 2.5 ml of triethylamine and 10 mg of 4-

Dimethylaminopyridine added. The reaction mixture is stirred for 24 hours at room temperature, then with 50 ml of ether

diluted and washed twice with 50 ml of water. After drying with Na ₂ SO ₄ , the solvent is dissolved on

Rotary evaporator distilled off and the residue until the constancy of the transformation temperatures of ethanol

recrystallized.

Yield 0, g (83% of theory).

Example 5 Preparation of 2-n-nonyl-5 - / (2-n-undecyl-6-methylpyrimidinyl-5-carbonyloxy) -phenyl / -1,3,4-thiadiazole (# 17)

0.001 mol (0.3 g) of 2-n-nonyl-5- (4-hydroxyphenyl) -1,3,4-thiadiazole, 0.0011 mol (0.32 g) of 2-n-undecyl-6-methylpyrimidine gerünrt 5-carboxylic acid, 0.0012 mol (0.37 g) EDC Chitos and 10mg of 4-dimethylaminopyridine are suspended in 5 ml of CH ₂ CI ₂ and 20 hours at room temperature. Di 9 obtained solution is diluted with 100 mL CH ₂ Cl _2, washed twice with 100 ml of water undeinmal with 100 mL of 5% NaHCO ₃ solution gowaschen. The solvent is distilled off on a rotary evaporator and the

Residue from ethanol recrystallized to constant transformation temperatures. Yield 0.3 g (53% of theory) Table 1

Mr. R * R ² KS _c S _a N is

C ₇ II ₁₅ * 94 * 136 * 144 * 153 *

C ₇ H ₁₅ * 83 * 144 * 147 * 154 *

3 ^c ₆ ^H ₁₃ 0- \ Vy ~ C ₇ H ₁₅ * 63 * 103 * 171 - - *

C _n H ₂₃ * 90 * 145 * 155 - - *

* ¹⁰ ° * ^U5 ~ * * ²⁶⁵ *

C ₇ Il ₁₅ * 94 - - - - * 132 *

Table 1 (continued)

^{7 0} AVx =

8C,

12 C ₃ I

13 C, l!

14 C ₁ H _n -

^C 11 ^H 23

^C 10 ^H 21

* 87 (* 85) - - * 126 *.

* 88 * 98 - - * 130 *

* 134 * 183 - - * 246 ¹ * * 97 * 249 - - * 273 * * 100 * 245 - - * 265 * * 7 ₉ * 196 * 227 * 270 * * 71 * 189 * 217 * 262

* 103 * 116 - - * 250 *

15 CJI ₁ -O-6 IJ

16 C

15

* 160 ² * 205 - - * 300 ¹ * * 146 * 161 - - * 167 *

* 57 - - * 105 - - *

1 = partial decomposition

2 = complete conversion scheme: 109S ₀ ? 117 sf? 160S ₀ 205S _A 300'is

The substances listed in the table above were prepared according to the instructions of Examples 1 to 5. Where:

he = crystalline-solid

S _A , Sc, S _f , S ₀ = smectic phase of the type A, C, F, G

N = nematic phase

is = isotropic liquid phase

Beseeching 6

Determination of dielectric anisotropy

To the room temperature nematic basic mixture GM, consisting of

Amount of substance

4-n-Pentyloxybenzoic acid 4-n-octyloxyphenyl ester 27

4-Methoxybenzoic acid 4-n-hexyloxyphenyl ester 24

4-n-hexyloxybenzoic acid 4-n-heptyloxyphenyl ester 12

4-n-hexylbenzoic acid 4-n-butyloxyphenyl ester 37

10.7 molar ratios in% of Compound No. 2 were added. For the obtained mixture M and for GM, the static dielectric anisotropies (DKA) were determined at 1 kHz for temperatures 20K below the respective clearing temperature:

DKA (M) =. -0.434 DKA (GM) = -0.314 According to the simple mixing rule DKA (M) = x (GM) * DKA (GM + x (2i-DKA (2) where χ = mass fraction (molar fraction) for the dissolved component ί one DKA = -1.4 determined

 The other substances according to the invention also have a negative DKA.

Example 7

0.30 molar parts in% of substance no. 2 were dissolved in 0.70 molar parts in% of a nematic base mixture (dielectric anisotropy is -0.314 at T - T _n) = -20K). The clearing temperature of the nematic mixture was raised from 70 ⁰ C to 93 ° C and the dielectric anisotropy for T - T _n , "-20K was changed to the value -0.970. Using the simple mixing rule, the dielectric anisotropy of the solute no. 2 is calculated to be -2.5.

Example 8

In order to examine the solubility and the phase behavior of the substances according to the invention with one another, 0.564 molar proportions in% of substance 13 and 0.436 molar proportions in% of substance no. 2 were mixed with one another. The resulting mixture showed the phase transformation scheme: it is 52 S _c 117 S _A 187 N 221 which indicates a pronounced smectic C phase. Therein ¹ It the conversion temperature for the phase transformation smectic C / A for the mixture higher than would be expected assuming additive in behavior.

Example 9 To fix the miscibility of the smectic C phases, 0.531 molar fraction in% of substance no. 1 was 0.469 Substance content% of 2- (4-n-nonyloxyphenyl) -5- (4-n-hexylphenyl) -1,3,4-thiadiazole (he 77 S _c 171 N 175 is). The

resulting mixture has the following conversion behavior:

he 57 Sc 156 N 160 is

which indicates a stabilization of the smectic C phase.

Example 10 As a milder miscibility test, a mixture of derivatives of 2-phenylpyrimidine was used Room temperature has a smectic C phase: S _c 63 S _A 71 N 82 is An addition of 20 mole fractions in% of the substance Nr.4 causes an extension of the state of the

smectic C phase:

Sc 69 S _A 80 N 88 is.

Claims (1)

Liquid-crystalline mixtures with extended smectic C phases and negative dielectric anisotropy, characterized in that at least one ester of 2-phenyl-1,3,4-thiadiazole with heterocyclic carboxylic acids of the general formula I _f as mixture component where R ¹ = C _n H _{2n +} I-, C _n H _{2n +} IO-, R ² = C _n H _{2n + 1} -with η = 1 to 16 A ² = 1,4-phenylene, 1,4-cyclohexylene or single bond, R ³ = -H, CH ₃ , in addition to liquid-crystalline and / or non-liquid-crystalline substances.