DD252841A1 - CRYSTALLINE-LIQUID MIXTURES - Google Patents

Abstract

The invention relates to crystalline-liquid mixtures for electro-optical arrangements for the modulation of light and for the representation of numbers, characters and images. The aim of the invention are nematic mixtures with broad mesophase ranges and high thermal and chemical stability. It has been found that novel crystalline liquid trans-4- (trans-5-Subst.-1,3-dithian-2-yl) cyclohexanecarboxylic acid esters of the general formula in mixtures with each other and with other crystalline-liquid and non-crystalline liquids are very well suited for use in optoelectronic displays. formula

Description

- (CH ₂ ) _m -CN, with m = 2 ... 8

R ³ = R ¹ , OR ¹ , COOR ¹ , OCOOR ¹ , COR ¹ , CN, halogen

R ⁴ , R ⁵ = H, H / CH 3, H / H, CH 3 / CN, H / H, CN / CN, CN when R ³ Φ CN R ⁶ = OR ¹ , CH ₂ OR ¹ , CN, halogen, COOR ¹ , OCOR ¹

with X = -COO-, -OOC-, single bond

Y = O, S, Z = O, S

and η = 1 to 12

in mixtures with each other and with other crystalline liquid or non-crystalline liquid substances.

Field of application of the invention

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

Characteristic of the known technical solutions

In order to be able to use liquid crystals in optoelectronic arrangements, they must have certain properties with respect to their melting and clearing temperatures, electrical conductivity, dielectric and optical anisotropy, viscosity and chemical and thermal stability.

There are no pure substances that meet all these requirements even approximately. Therefore, there is a constant search for new substances which allow the properties of mixtures to be changed in a targeted manner. In particular, substances are sought which increase the clearing points in nematic mixtures.

Object of the invention

The aim of the invention are nematic mixtures with broad mesophase ranges and high thermal and chemical stability.

Explanation of the essence of the invention

The object of the invention is to provide suitable substances which increase the clearing points of mixtures.

It has been found that novel trans- ^ trans-B-subst-i-dithianyl-cyclohexanecarboxylic acid esters of the general formula:

X - R ». ^) - R ¹ . ^ O) -R ¹ , ^ O ^ OR ¹

R ¹ = C _n H _{2n +} ! with η = 1 ...

R ⁴ R ⁵

- (CH ₂ ) _B -CN _f - ₁₃

CH with m = 2 .. .8 °

R ³ = R ¹ , OR ¹ , COOR ¹ , OCOOR ¹ , COR ¹ , CN, halogen R ⁴ , R ⁶ = H, H / CH ₃ , H / H, CH ₃ / CN, H / H, CN / CN, CN when R ³ φ CN R ⁶ = OR ¹ , CH ₂ OR ¹ , CN, halogen, COOR ¹ , OCOR ¹ with X = -COO -, - OOC-, single bond Y = O, S, Z = O, S and η = 1 to

in mixtures with one another and with other crystalline liquid and non-crystalline liquid substances for use in optoelectronic displays are very well suited and increase the clearing points of mixtures.

The new substances have high chemical and thermal stability and higher clearing temperatures than comparable dioxane derivatives and substituted phenyldithiane.

Tables 1 and 2 show the transformation temperatures of substances according to the invention. Where:

K = crystalline-solid N = nematic

Sb = smectic B Is = isotropic-liquid

S = smectic phase of unknown structure

Table 1

COOR

-sb

is

• 1/1 1/2 1/3 1/4 Table 2 -C ₂ H ₅ -C ₄ H ₉ -CH-C ₅ H ₁₃ CH ₃ 1.5 - (H) -C ₄ H ₉ 1.6 - (H) -C ₅ H ₁ 1.7 1.8 -CH ₂ CH ₂ CN

• 134 50 • 121.7 • 115.5 60 • 122.5

• 55

• 60 • 85 • 120 • 118 • 120.5 • 125.5

R ¹

R ²

2.1 C ₅ Hn 2.2 CeH 13 2.3 OC ₄ H ₉ 2.4 OC ₅ H ₁₁ 2.5 CN 2.6 CN

H • 45 H • 70 H • 85 H • 95 H • 130 CH ₃ • 100

130 • 157 186.5 • 191 186 »219 187 • 210.5 - - • 228 117.5 • 174.3

13

CN

91

• 102

• 110.5

• 109 • 226

"174

• 238

• 179

• 286

• 315

• 298

• 276

embodiments Example 1:

Substances according to the invention have the following properties:

substance

Enthalpy of fusion [kJ / mol] optical birefringence [at _{b at} 30 ° C]

1/8 2/3

0.11

20.6

The optical birefringence An _b was from a nematic mixture A of the composition 4-methoxybenzoic acid 4-hexyloxyphenylester 22mol-%

4-Pentyloxybenzoic acid 4-octyloxyphenyl ester 29mol%

4-hexylbenzoic acid 4-butyloxyphenyl ester 31 mol%

4-heptyloxybenzoic acid hexyloxyphenyl ester 11 mol%

4,4'-bis-hexylbenzoyloxy-2-ethylbenzene 7 mol%

with the addition of 20 mol% of one of the substances according to the invention by means of the relationship Δη - Χ _Α ΔηΑ

Δη _Α , Χ _Α = birefringence or mole fraction of the mixture A

Δη = birefringence of the total mixture

X _b = molar fraction of the components according to the invention

calculated.

Optical birefringence is an important parameter of nematic liquid crystals used in displays.

The very low values of the enthalpy of fusion of the two substances according to the invention indicate that the substances are readily soluble in mixtures, even at low temperatures, and experience the desired high melting point depression in mixtures with other substances.

Example 2:

The mixture B has the following composition:

4-n-Propylcyclohexanecarboxylic acid 4-cyanophenyl ester 22.4mol%

4-n-butylcyclohexanecarboxylic acid 4-cyanophenyl ester 20.2 mol%

4-n-pentylcyclohexanecarboxylic acid 4-cyanophenyl ester 22.4mol%

4-n-butylcyclohexanecarboxylic acid 4-ethoxyphenyl ester 13.3 mol%

4-n-butylcyclohexanecarboxylic acid 4-n-hexyloxyester 21.7 mol%

This mixture B and a mixture of B and inventive substance were investigated in electro-optical cells in a twisted orientation (Schadt-Helfrich cell). This resulted in the following measured values:

Table 3 MiB No. substance [Mol%] T _n , uo [Ms] τ1 ° mol% - - [ ⁰ C] [V] 38.5 [Ms] 100 2.3 10 68 2.14 27 64 90 89 1.79 38

Operating voltage for the switch-on time τ | ° is 2U ₀ . OFF time = τ _Α ⁵⁰

Temperature: 22 ° C Layer thickness: 10μΓη

Frequency: 500Hz

Claims (1)

Invention claim: Crystalline-liquid mixtures for electro-optical arrangements, characterized in that new trans- ^ itrans-B-subst.-ijS-dithian ^ -yO-cyclohexanecarboxylic acid esters of the general formula: R ¹ = C _n H _2n + imitn = 1 ... 12 o) - ^x - (o) - ^{r 'Ch} olesteryl -