DD258243A1 - LIQUID CRYSTALLINE MIXTURES (ESTER) - Google Patents

Abstract

The invention relates to liquid-crystalline mixtures with low optical anisotropy, negative electrical anisotropy and low viscosity for electro-optical arrangements for modulation of the continuous or reflected light and for colored or black-and-white display of numbers, characters and moving or still images. According to the invention nematic mixtures 1 to 80 mol% of one or more representatives of the esters of v- (trans-4-hydroxycyclohexyl) -alkansaeurealkylester added.

Description

Z = -COO-, -OCO-, -CH ₂ -CH ₂ -, -CH ₂ -, and R ¹ = -C _n H _2n + ^ and R ² = R ¹ , -OC _n H _{2n + 1} with η = 1 to 12, к = 1 to 12 and m = 1 to 4 are added.

Liquid crystalline mixtures (esters)

The invention relates to liquid-crystalline 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 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 the optical behavior (birefringence, rotatory power, light absorption). Depending on the initial orientation achieved by special pretreatment of the electrodes or by addition of suitable substances, the dielectric and optical anisotropy, the conductivity, the dichroism and strength, direction and frequency of the applied electric field, various electro-optical effects are observed and used technically (M.Tobias: International Handbook of Liquid Crystal Displays 1975-76, Ovum Ltd., London 1976; G. Meier, E. Sackmann, JG Graber: Applications of Liquid Crystals, Springer-Verlag, Berlin-Heidelberg-New York 1975; H.Kresse: Dielectric Behavior of Liquid Crystals, Progress of Physics 30 (Issue 10), p.573 ff. [1982] Akademieverlag Berlin).

For example, a known method is based on the fact that the optical rotation of a layer of twisted structure is abolished by applying an electric field, and permeability (extinction) for incident light is found between parallel (crossed) polarizers (M. Schadt, W. Heifrich: Applied Physics Letters 18 127 [1971]). Exact calculations revealed that the contrast of such a cell depends on the optical path length difference in the cell (C.H.Gooch, H.A. Tarry, J. Phys., D Appl. Phys., 81575 [1975]). For the adaptation of crystalline-liquid mixtures to existing technologies and the new or further development of displays substances are required, which have a low optical anisotropy, a negative dielectric anisotropy, a low viscosity and a sufficient solubility in the base mixture to be modified. Those by K. Praefcke, D. Schmidt and R. Eidenschink (EP 56113, DE 3100142) as well as MA Osman and L. Revesz (Mol Cryst. Liq. Cryst. [Lett] 56157 [1980]) and MA Osman and T. Although Huynh-Ba (HeI, Chim. Acta 67 [1984] 959) esters of trans-4-Cyancyclohexanols have some of the required properties, but are only in the supercooled liquid-crystalline. The same restriction applies to the esters described by H.Tatsuta, M. Fukai, K. Asai and H.Takahashi (DE 2352664; DE 2353315) as well as I.M. Lohar and G.H. Patel (Mol.Cyst. 7419 [1981]). With the help of the esters of cyclohexanecarboxylic acids (DDWP 105701) one is not able to achieve the desired variation of technical properties.

Object of the invention

The object of the invention are novel mixtures of liquid-crystalline substances, which are characterized by a low optical anisotropy and a negative dielectric anisotropy and low viscosity for electro-optical arrangements.

Explanation of the essence of the invention

The object of the invention is to find suitable substances with low optical anisotropy, a negative dielectric anisotropy and low viscosity. According to the invention nematic mixtures for use in electro-optical components for modulation of the transmitted or reflected light and for the reproduction of numerals, characters and images 1-80Mol .-% of one or more representatives of the esters of co-itrans-'i-hydroxycyclohexyl) -alkansäurealkylester the general formula

2k + 1

With

and Z = -COO-, -OCO-, -CH ₂ -CH ₂ -, -CH ₂ -, and R ¹ = C _n H _2n + , and R ² = R ¹ , -OC _n H _{2n +} , where η = 1 to 12, к = 1 to 12 and m = 1 to 4 added.

Depending on the intended use, these mixtures can not be mixed with liquid-crystalline substances, in particular with dyes. The advantage of the substances according to the invention is that surprisingly stable liquid-crystalline phases occur and a good solubility in nematic mixtures.

embodiments example 1

The mixture components according to the invention are prepared by esterification of the corresponding substituted cyclic and aromatic acids with üMtrans-'l-hydroxy-cyclohexyD-alkansäurealkylestern. The following synthesis scheme illustrates the most important steps known per se in the synthesis of the substituted cyclohexanols in three different variants (a, b, c): where V is heating, RT-room temperature, Me-methyl and Ac-acetyl, Ph-phenyl. -

+ CH ₃ -COCl

AlCl ₃ ;

or CHCl

-10 ^U C Ms RT

CO-CH

s ₈ , ^ 7,

Morpholine or Me ₃ NH HCl

CH ₃ -O

CH ₂ -COOH

HBr / Ac OH

+ CH = CH-CN AlCl ₃ , HCl (g)

CH ₂ -CH ₂ -CN NaOH (35 #

CH ₃ -

0-10

0

CO-CH-CH-COOH Zn amalgam; HCl

CH ₂ -CH ₂ -CH-COOH

(CH ₂ ) I _n -COCH R-OH (H ₂ SO ₄ ), (CH ₂ ) _m -COO-R

-s H0- / ~~ \ - (CH ₂ ) ^ COO-R

H, Ra - Ni 12-15 MPa

Examples of the substances to be used according to the invention are mentioned below. In this case, mean: K-crystalline solid, S-smectic, N-nematic and l-isotropic liquid (temperatures in ⁰ C

1. 1 2 trans-4-n-heptylcyclohexyl 28 Second 1 2 4-n-Butyl-biphenyl-4-yl 88 Third 1 2 4- (4n-Hexyloxybenzoyloxy) -phenyl- 86 4th 2 2 trans-4-n-butylcyclohexyl 42 5th 2 2 trans-4-n-pentylcyclohexyl 51 6th 2 2 trans-4-n-Heptylcyclohexyl- 61 7th 2 2 4-n-pentylphenyl 46 8th. 2 2 trans-4-n-propylcyclohexylethyl 46 9th 2 2 4-n-octyloxyphenyl 67 10th 2 2 4-n-Butyl-biphenyl-4-yl 79 11th 2 2 4- (4-n-Pentylbenzoyloxy) -phenyl- 54 12th 2 2 4- (4-n-Hexyloxybenzoyloxy) -phenyl- 83 13th 2 2 4- (4-n-butylbenzoyloxy) -phenyl- 59 14th 3 2 trans-4-n-hexyl Heptylcyclo = 45 15th 3 2 4-n-Buyl-biphenyl-4-yl 64

17

19) 84) 121

13) - -

(51)

(· 45)

48 -

Because of the low melting temperatures, the substances mentioned are readily soluble in nematic phases.

33) 110 118 145 145

111

Example 2

To a basic mixture (GM)

27Mol .-% of 4-n-pentyloxybenzoic - (- 4-n-Octyloxyphenyl ester)

24Mol .-% of 4-methoxybenzoic acid (4-n-hexyloxyphenylester)

12Mol .-% of 4-n-Hexyloxybenzoesäure- (4-n-heptyloxyphenylester)

37 mol% of 4-n-hexylbenzoic acid (4-n-butyloxyphenyl ester)

were dissolved 35 mol. yotrans ^ -n-butylcyclohexanecarboxylic acid-1β-ftrans ^ -hydroxycyclohexyl-D-propionic acid ethyl ester] (Subst.4). In this case, the clearing point fell from 70 ° C down to 45 ⁰ C.

After the formula

ΔΕ _ΓβΙ =

ΔΕ-X (GM) AE (GM) 1-X (GM)

ΔΕ = Δε, Δη, Χ = mole fraction

From the measured dielectric and optical anisotropies Δε and Δη and those of the basic mixture (A8 [GM], Δη [GM]) and the mole fraction of the basic mixture X (GM), the relative anisotropies Δε _Γβ | and Δη _Γβ! determined. It was obtained

temperature Δε _Γβ ι Δη _Γβ ι T _n - T = 20 K -2.2 0,042 20 ⁰ C -2.3 0.047

Example 3

Analogously to Example 2 were added to the masterbatch GM ISMol .- ^ otrans ^ -n-Heptylcyclohexancarbonsäure-tß-ftrans ^ - hydroxycyclohexyD-propionic acid ethyl ester] (Subst.6). The mixture clears at 55 ° C. The relative anisotropies Δε _{Γβ) and} An _re i were

temperature Δε _Γβ , Δη _Γβ ι GM η / mPa  s T _NI -T = 20K -1.6 0,035 - Subst. 6 20 ° C -1.9 0,045 8.5 10.1 the viscosity of GM and Subst. 6 in i 6.9 7.6 O / ° C 5.6 5.8 28 4.5 70 23 80 90 100 Ед / KJmor ¹

The activation energy corresponding to a simple Arrhenius relationship for Subst. 6 is significantly lower and can expect better switching properties at lower temperatures.

Claims (1)

Patent Attention: Liquid-crystalline mixtures with low optical anisotropy, negative dielectric anisotropy and low viscosity for modulation of the transmitted or reflected light and for the reproduction of numbers, characters and images, characterized in that nematic mixtures as the mixing partner one or more representatives of the esters of u> ( Trans-4-hydroxycyclohexyl) -alkansäurealkylester of the general formula R-CCCH / V (CH ₀₎ -COOC ₁ HX ₁ f 2k + 1