DD249279A1 - CRYSTALLINE-LIQUID MIXTURES WITH NEGATIVE DIELECTRIC ANISOTROPY - Google Patents

Abstract

The application of crystalline liquid mixtures in optoelectronic components for the modulation of the continuous or reflected light as well as for the colored or black and white reproduction of numbers, characters and images is due to their dielectric and optical anisotropy. The aim is to apply new substances characterized by high negative dielectric anisotropy for large temperature ranges, good miscibility with other liquid crystals and good manufacturability in liquid-crystalline mixtures for electro-optical arrangements. According to the invention, crystalline liquid mixtures containing r-2-subst.-t-5-subst.-c-5-cyano-1,3-dioxanes are used. Cholesteric crystalline liquid compounds or chiral smectic liquid crystals or else non-crystalline liquid substances, in particular dyes, can be added to the substances according to the invention.

Description

Field of application of the invention

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

Characteristic of the known technical solutions

It is known that liquid-crystalline substances can be used for the modulation of light as well as for the display of measured values or for the reproduction of information. These methods are based on the fact that the preferred orientation of thin layers of the crystalline liquid substance can be changed by applying an electric field. The change in the preferential orientation of crystalline liquid substances is associated with a change in optical behavior (birefringence, rotatory power, light absorption) (M. Tobias: International Handbook of Liquid Crystal Displays 1975-76, Ovum Ltd., London 1976).

So far, no pure substance is known, which has even approximately the required technical properties with respect to melting and clearing point, electro-optical threshold voltage, electrical conductivity, optical anisotropy, viscosity and the thermal and chemical stability. Therefore, without exception, mixtures are used whose properties are adapted to the respective intended use by a specific choice of the components.

In order to be able to modify the properties of the mixtures in a targeted manner, new substances with favorable properties are required time and again.

One requirement that can not easily be met with the substances available hitherto is the production of mixtures with negative dielectric anisotropy for a wide temperature range. Here it is particularly important to have a sufficiently large number of mixing components with negative dielectric anisotropy (Δε <-2) and immiscibility in the solid state, so that when mixing a state diagram of eutectic type is formed and thereby the existence of the crystalline liquid phase to low temperatures is extended. Such mixtures are particularly suitable for use in guest host displays (T.Uchida, H. Seki, C.Shishido, M.Wada: Molecular and Liquid Crystals 54, 161 [1979]).

The known laterally substituted cyclohexane derivatives (DE 3231707, DE 3320024) fulfill a part of the stated requirements. Their major disadvantage, however, is on the one hand in too little structural variation possibility and the associated too small number of technically applicable substances and on the other hand in the complicated synthesis.

Furthermore, the dielectric anisotropy of this class of substances is relatively low.

Object of the invention

The object of the invention is the use of novel mixtures of crystalline-liquid substances, which are characterized by a high negative dielectric anisotropy, a good miscibility with other liquid crystals in the crystalline-liquid state and good manufacturability in electro-optical arrangements.

Explanation of the essence of the invention

The object of the invention is to find suitable substances whose dielectric anisotropy is less than -2 and which have good miscibility with other liquid crystals.

It has been found that additions of one or more representatives of the r-2-subst.-t-5-subst.-c-5-cyano-1,3-dioxanes of the general formula

with A = R ⁷ and B = R ¹ or A = COOR ⁴ and B = R ⁷ , wherein the number of rings is 2 to 4 and

cGoY hVr ⁹ ; - / H Y-COO- / H-R ⁹ ;

= _r3; _or ³ ; -OOCR ³ ; -COOR ³ ; -OCOOR ³ ; -COR ³ ; -Halogen

-CN; -CH ₂ -CH-C ₂ H ₅ ; -COO-CH ₂ -CHC ₂ H ₅ ; -COO-cholesteryl;

CH.

CH.

0-CH ₂ -CH-C ₂ H ₅

can be with

; -Cholesteryl;

; -R ³ ;

Z /

X = -COO-; -00C-; Single bond Y = -0-; -SZ = -0-; -SR ⁵ , R ⁶ = H, CH 3 / CH 3, H / H, CN / CN, H / H, H / CN, CN when R ² Φ CN

- - (CH ₂ ) _p

·· - ( ^CH ₂ ) p- \ O) - ^0R8 '

ρ8 _. ρ U

rs = -OR ³ , -CH ₂ OR ³ , -CH ₂ OR ³ , -Cl, -Br, -COOR ³ , -OOCR ³

and with ρ = 0.2, q = 2 to 8 and η = 1 to 16 and m = 1-16, nematic mixtures are suitable for use in optoelectronic components for the modulation of the transmitted or reflected light and for the reproduction of numbers, Characters or images having low negative dielectric anisotropy for large temperature ranges. The r-2-Subst.-t-5-subst.-c-5-cyano-1,3-dioxanes are colorless substances containing nematic (N), smectic (S), and crystalline (K) and isotropic (I) Own phases (Tables 1 to 3). Depending on the intended use, cholesteric crystalline liquid compounds or chiral smectic liquid crystals, but also non-liquid crystalline substances, in particular dyes, can be added to these mixtures.

Table 1 Conversion temperatures of the compounds

No.

1.1 1.2 1.3 1.4 1.5 1.6 1.7 1.8

"(v- ^c 3 ^H ;

6 5 9 9 6

9 - (H) -COOCH

 / η) · - cooch

9 9

- (H) -COO ^ -C ₅ H ₁₁

1.9 6

1.10 9

1.11 9 - <H> -C00

1.12 6 1.1.3 6

1.14 6

1.15 6

1.16 6

1.17 6

1.18 6

1.19 δ

1.20 6 -

, 79 - 68 - -  - 135 I , 77 - 77 - * 4 , 71 (. ) .- - t , 74.5. - " , 165 - 126 - 154 • , 99.5 - • 174 • , 104. • 157 * , 145 - 135 137 • .106 - 141 • 257 • , 118. • 148 • , 92. • 150 • , 139 - (. 120 * , 166 - (. 114 ). , 118 - (. 156 • , 193 - • " , 133 - • , 155 - ). , 130 - ). , 116 - ) · , 121 - •

Continued from Table N r. η Β

1.21 9

1.22 9

1.23 9

1.24 9

1.25 6

1.26 9

1.27 9

- ^> - COO - <^ o) -OOC - <^) - OC ₄ H

- / η \ -ΟΟΟ- / η) -Βγ

Table 2

2.1 2.2 2.3 2.4 2.5 2.6 2.7 2.8 2.9

CH ₀ η 2n + l

COOR '

No. η

3 5 5 3 5 3 3 3 3

C ^ H.

5

h \ -C H

Cholesteryl cholasteryl

-OC ₃ H ₁₇

- <g> -ooc- <Q> -oc ₄ H _g

- <g) -00C- <g> -0C ₆ H ₁₃

2.10 3

2.11 3

2.12 3

2.13 3

2.14 3

2.15 3

2.16 5

- <g) -C00- <g> -Oc ₈ H ₁₇

O) -O) -C ₆ H ₁₃

15

• 216 ) , 244. , 95 (. 132 , 277. , 141 • 232 , 262. , 102 • 166 , 5) , 236. , 119 (. 114 , 5 , 163. , 123 • 234 ) , 246. , 118 (. 56 , 142

, 102 (. 68) -, , 107 - , Ill (. 91) - , 172. 185 , 215. , 130. 219 - , 82 - - , 85 (. 66) - , 146 - , 162. , 132. 169 , 113. 153 , 155. , 150 - , 168. , 129 - , 175. , 103 (. 101) , 102. 146 , 151 - - , 63 - _

Extension of table

2.17 5

2.18 5

2.19 5

2.20 5

2.21 5

2.22 5

2.23 5

2.24 5

2.25 5

- ^0C ₈ ^H 17

-GCH

-COO - ^) - C ₆ H

"(Ö) - <O> CN

, 62 (51) 7 "" 68 "-

, 81. 82 -

, 121 -. 161

, 136. 137. 158

, 138 -. 162

, 99. 159 -

, 92. 158 -

, 130 - (74)

Table 3

Vb

H ₁ -C ₀ -OOC

- (H) -C ₅ H

11

, 119 -. 127. 150. 99 -

embodiments Example 1:

To a basic mix

27 mol% of 4-n-pentyloxybenzoic acid (4-n-octyloxyphenyl ester),

24 mol% of 4-n-methoxybenzoic acid (4-n-hexyloxyphenyl ester), 12 mol% of 4-n-hexyloxybenzoic acid (4-n-heptyloxyphenyl ester) and 37 mol% of 4-n-hexylbenzoic acid (4-n-hexylbenzoic acid) butyloxyphenylester)

in each case 3 mol% of the components indicated in Table 4 below were added. This changed both the

Clarifying temperatures Q _Wi , as well as the dielectric anisotropies Δε at 20 ⁰ C.

mixture

Δε

Δε _Β

GM GM + GM + GM + 1.14 GM + 2.19

70 68 71 72 71

-0.37 - -0.60 -8th -0.60 -8th -0.63 -9 -0.42 -2

The quantity Δε _Β was reduced by assuming a linear dependence Δε = f (X _B )

Δε _Β - calculated. It expresses the effectiveness of the respective doping in the masterbatch at 20 ° C.

Example 2:

To the base mixture from Example 1, 5 mol% of r-2-n-pentyl-c-5-cyano-t-5-carboxylic acid (4-n-octyloxyphenyl ester (No. 2.19), 17 mol% of r-2 ( trans-4-n-heptylcyclohexyl) -c-5-cyano-t-5-n-hexyl-1,3-dioxane (# 1.2), 10 mol% r-2 [4 (4-n-octyloxyphenylcarbonyloxy) phenyl] -c-5-cyano-t-5-n-hexyl-1,3-dioxane (No. 1.14) and 8 mol% of r-2- (4-n-octyloxyphenyl) -c-5-cyano t-5-n-hexyl-1,3-dioxane (no. 1.9) was added. the mixture clears at 62 ° C. Their dielectric anisotropy at 20 ⁰ C is Δε = -3.2. the threshold for the DAP effect was measured with 2.3 V at room temperature.

Example 3:

The mixture indicated in Example 2 was 1 wt .-% of the red dye

/ CH ₂ -CH ₂ OH

added. In homeotropic initial orientation, a color change from pale pink to red at U = 2.2 V in a 15μτη thick sandwich cell was observed (measurement frequency 200Hz, 25 ° C).

Example 4:

A mixture of 33.3 mol% of 2,5-bis (trans-4-n-pentylcyclohexyl) -1,3,4-thiazole, 22.2 mol% of 2- (trans-4-n-propylcyclohexyl ) -5- (4-n-hexylbenzoyl) -1,3,4-thiazole, 13.3 mol% r-2- (trans-4-n-heptylcyclohexyl) -c-5-cyano-t-5 n-hexyl-1,3-dioxane (# 1.2) 14.5 mol% r-2- [4- (4-n-octyloxyphenylcarbonyloxy) phenyl] -c-5-cyano-t-5-n-hexyl- 1,3-dioxane (# 1.14) 11.1 mol% r-2- (4-n-octyloxyphenyl) -c-5-cyano-t-5-n-hexyl-1,3-dioxane (No. 1.9) and 5.6 mol% of r-2-n-pentyl-c-5-cyano-t-5-carboxylic acid (4-n-octyloxyphenyl) ester (Subst.2.19). The mixture melts between 44 and 46 ° C and clears between 93 and 95 ° C. The dielectric anisotropy is Δε = -5.7 at 45 ° C. The threshold voltage for the DAP effect was measured in a 15 / xm sandwich cell at 50 ° C at 2.1V.

Claims (3)

Invention claim: continuous or reflected light and for the reproduction of numbers, characters and images, characterized in that one or more representatives of the r-2-Subst-t-5-subst.-c-5-cyano-1,3-dioxanes as the mixing partner the general formula C
N with A = R ⁷ and B = R ¹ or A = COOR ⁴ and B = R ⁷ , wherein the number of rings is 2 to 4 and pKO) - ^R: R ² = _r3. _or ³ ; -OOCR ³ ; -COOR ³ ; OCOOR ³ ; -COR ³ ; -Halogen H VCOO- / H VR ⁹ Ca /, -COO-CH ₂ -CH-C ₂ H ₅ ; -COO cholesterol; -Q- CH. - C-.fV- CH- C- CH. R - C _n H _2n + \ _y ; -cholesterol; -CH ₀ -CH-C ₀ H,. -R; '2 d ι. ο CH. \
Ο / "« ³ ; - (CH) q-COOR ^: can be with X = -COO-; -0OC-; Single bond Y = -0-; -S-Z = -0-; -S R ⁵ , R ⁶ = H, CH 3 / CH 3, H / H, CN / CN, H / H, H / CN, CN When R ² ΦCN R = C _m H2m + 1 R ⁹ = -OR ³ , -CH ₂ OR ³ , -Cl, -Br, -COOR ³ , -OOCR ³ and with ρ = 0.2, q = 2 to 8 and η = 1 to 16 and m = 1 to 16, are used. 2. crystalline liquid mixtures according to claim 1, characterized in that cholesteric crystalline liquid compounds or chiral smectic liquid crystals are added to these mixtures. 3. crystalline liquid mixtures according to claim 1, characterized in that these mixtures non-liquid-crystalline substances, in particular dyes, are admixed.