DD247694A1 - CRYSTALLINE-LIQUID MIXTURES - 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 object of the invention is the use of novel substances characterized by a negative dielectric anisotropy, a low melting temperature and a high Klaertemperatur or by a positive dielectric anisotropy and a high Klaertemperatur in liquid-crystalline mixtures for electro-optical arrangements. According to the invention, crystalline-liquid mixtures containing 2-subst.-5- (trans-4-n-alkylcyclohexyl) -1,3,4-thiadiazoles are used. Non-crystalline liquids, in particular dyes, can be added to the mixtures according to the invention.

Description

^C n ^H 2n + l

where R denotes substituents,

and

with Ri: C _m H2m +1, X is a single bond or an oxygen atom

and R ₂ : H, Br or CH 3 and η and m from O to 12, wherein R _{2 is} not H when X is an oxygen atom.

2. Crystalline-liquid mixture according to claim 1, characterized in that cholesteric crystalline 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 added.

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 the color or black-and-white display of numerals, characters and moving or still images in the one and two-frequency method.

Characterization of the known technical solutions

Liquid crystals which are used in passive optoelectronic components (displays) must have certain properties with regard to melting and clearing point, electro-optical threshold voltage, electrical conductivity, optical anisotropy, viscosity and the thermal and chemical stability.

So far, no pure substance is known, which even approximately meets these requirements. 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 more favorable properties are required time and again. A requirement that can not be easily met with the previously available substance classes, is a large temperature range in which the substance mixtures can be used. This is especially true for guest-host mixtures (T. Uchida, H. Seki, C.Shishido, M.Wada: Molecular Crystals and Liquid Crystals 54161 [1979]) which require substances with negative dielectric anisotropy. Especially for substances that have no dipole moment in the direction of the molecular longitudinal axis, the field of application is an application in two-frequency mixtures for symmetrizing the dielectric anisotropy.

Although the known 2-phenyl-5- [4-n-alkyloxyphenyl] -1,3,4-thiadiazoles (DD-WP 117014) have high clearing points, usually above 100 ⁰ C, and high contrasts in the dynamic scattering effect, but their melting temperatures are too high. The result of this is their great disadvantage, the insufficient solubility at lower temperatures and consequently the inadequate ability to modify the properties of mixtures. This property is particularly important for substances used in liquid crystalline mixtures for the dielectric orientation effects described above.

Object of the invention

The object of the invention are new mixtures of crystalline-liquid substances for electro-optical arrangements, which are characterized by a negative dielectric anisotropy, low melting temperatures and high clearing temperatures or a positive dielectric anisotropy and high clearing temperatures.

Explanation of the essence of the invention

The object of the invention is to find suitable substances. It has been found that additions of one or more representatives of the ^ -Subst.Shltrans ^ -n-alkylcyclohexyD-I.S ^ -thiadiazoles of the general formula

° ^H 2n + l

where R denotes the following substituents:

and R

with R ₁ : C _m H _2m +1, X is a single bond or an oxygen atom and R ₂ ; H, Br, Cn or CH ₃ and η and m from 0 to 12, wherein R _{2 is} not H, when X is an oxygen atom, are suitable for use in optoelectronic components for the modulation of the transmitted or reflected light and for the reproduction of numbers , Signs and pictures. Depending on the intended use, cholesteric crystalline liquid compounds, chiral smectic liquid crystals or non-liquid crystalline substances, in particular dyes, can be added to these mixtures. So far, of the 2- (4-substituted-phenyl) -5- (trans-4-n-alkylcyclohexyl) -1,3,4-thiadiazoles only the compound

, N-N

^C 6 ^H 13 ° -

(K. Dimitrowa, J. Hausschild, H. Zaschke, H. Schubert: J. prakt. Chem. 322, 933 [1980]). Due to its melting point of 103 ° C, it is not very suitable for use in electro-optical arrangements. Therefore, it was surprising that the present 2- (4-substituted-phenyl) -5- (trans-4-n-alkylcyclohexyl) -1,3,4-thiadiazoles had such low melting points

(see Table 1) and are therefore suitable for use in electro-optical arrangements.

Examples of the substances to be used according to the invention are contained in Tables 1 to 4. In the tables, K = crystalline solid, S ₁ , S ₂ , S ₃ = unspecified smectic phases, S _A , S _B = smectic A and B,

N = nematic, I = isotropic-liquid.

Table 1

Verb.

N-N.

^C m ^H 2rn + l ^X

^C n ^H 2n ₊ l

1.1 4 3 1.2 4 4 1.3 4 5 1.4 4 6 1.5 6 2 1.6 6 3 1.7 6 4 1.8 6 5 1.9 6 6 1.10 9 4 Table 2

H H H H H H H H Br

^C n ^H 2n + l

76 71 52 58 50 61 47 50 50 81

96 150 120 146 115 136 117 151 77 115 126 146 133 139 146 150 145 - - 114 117

Verb.

2.1 2.2

4 6

169

202 199

Table 3

N-N.

^C m ^H 2rn + l

^H > - ^C n ^H 2n ₊ l

m = n

S ₁

2 3 4 5 6

118

126

39

49

55

55

64

66

143 162 180 181

144

Table 4

N-N

^C m ^H 2rn + l

Verb.

^H > - ^C n ^H 2n ₊ l

κ ¹¹

4.1 4.2 4.3

4 6 3

7 8 8

D D 1)

174 182 174

1) Did not crystallize even after storage for 20 days at -20 ⁰ C.

embodiments

Example 1 To a masterbatch GM of 27 mol% of 4-n-pentyloxybenzoic acid (4-n-octyloxyphenyl ester) 24 mol% of 4-n-methoxybenzoic acid (4-n-hexyloxyphenylester) 12 mol% of 4-n-hexyloxybenzoic acid - (4-n-heptyloxyphenyl ester) 37 mol% 4-n-hexylbenzoic acid (4-n-butyloxyphenyl ester)

15 mole percent 2- (trans-4-n-butylcyclohexyl) -5- (4-n-hexylphenyl) -1,3,4-thiadiazole (Compound 1.7) was added. Here, the clearing point is increased from 70 to 88 ⁰ C. The dielectric anisotropy of the nematic mixtures is reduced from Δε (master batch) = -0,37aufA8 = -1.02 at 23 ° C. This corresponds to an effective dielectric anisotropy of Δε = -4.8

for substance

Example 2 The basic mixture GM was admixed with 10 mol% of 2,5-bis (trans-4-n-butylcyclohexyl) -1,3,4-thiadiazole (compound 3.3) or 10 mol% of 2,5-bis- (trans-4-n-hexylcyclohexyl) -1,3,4-thiadiazole (Comp 3.5) or

10 mol% of 2 (trans-4-n-hexylcyclohexyl) -5- (trans-4-n-octylcyclohexyl) -1,3,4-thiadiazole (Compound 4.2)

added.

The dielectric anisotropy of the nematic mixtures decreased from Δε (basic mixture) = -0.36 to Δε = -0.84 (compound 3.3) or Δε = -0.91 (compound 3.5) and Δε = -0.82 (Verb 3.2) at 25 ° C. This corresponds to an effective dielectric anisotropy of -5.2 (verb 3.3) and -5.9 (verb 3.5) and -5.0 (verb 4.2). The clearing temperatures increased by 5 ⁰ C.

by adding the respective substances.

Example 3

43 mol% of a mixture of 8.1 mol% of 2- (trans-4-n-butylcyclohexyl) -5- (3-bromo-4-n-nonyloxyphenyl) -1 to the basic mixture GM mentioned in Example 1, 3,4-thiadiazole (Comp 1.10) 45.4 mol% of 2- (trans-4-n-pentylcyclohexyl) -5- (4-n-hexylphenyl) -1,3,4-thiadiazole (Comp.1.8) 46 , 5 mol% of 2- (trans-4-n-butylcyclohexyl) -5- (4-n-hexylphenyl) -1,3,4-thiadiazole (Comp. 1.7) was added. The colorless mixture is nematic at 2O ⁰ C and turns at 95 ⁰ C in the isotropic phase to. The dielectric anisotropy of the mixture is at 20 ⁰ C Δε = -2.7. The threshold voltage for the DAP effect is 58 ° C

1.8V and at 20 ° C 2V. The dynamic scattering effect occurs only above U = 15V.

Example 4

The mixture indicated in Example 3 is mixed with 1% by weight of the red dye

In the case of homeotropic initial orientation, a color change from pale pink to red at U = 2V is observed at room temperature.

Example 5

To the basic mixture mentioned in Example 1 are respectively

3 mol% of 2- (trans-4-n-butylcyclohexyl) -5- (4-cyanophenyl) -1,3,4-thiadiazole (Compound 2.1)

or. '

3 mol% of 2- (trans-4-n-hexylcyclohexyl) -5- (4-cyanophenyl) -1,3,4-thiadiazole (Comp 2.2) added. The dielectric anisotropy increases to -0.05 and -0.07 at 20 ⁰ C. The effective dielectric anisotropy of the dissolved components is Δε = 11 (comp. 2.1) and Δε = 10.3 (comp. 2.2). The clearing points increase by 5grd.

Example 6

52 mol% of a mixture of 52 mol% of 2,5-bis (trans-4-n-butylcyclohexyl) -1,3,4-thiadiazole (compound 3,3) are added to the base mixture indicated in example 1.

48 mol% of 2,5-bis (trans-4-n-hexylcyclohexyl) -1,3,4-thiadiazole (Compound 3.5)

added. The clearing temperature of the mixture increases compared to the base mixture by 26 ⁰ C. The dielectric anisotropy decreases from Δε (basic mix) = -0.33 to Δε = -2.6 at 46 ° C. The threshold voltages for the reorientation of a homeotropic to the planar orientation (DAP effect) are 1.6 V at 8O ⁰ C and 2.5 V at 46 ° C (measuring frequency: 200 Hz). At 8O ⁰ C the dynamic scattering effect is observed above 15V, whereas at 46 ° C it is only above 30 V (measuring frequency:

20Hz) occurs. Dielectric relaxation effects that could be caused by compounds 3.3 and 3.5 are not observed up to frequencies of 10OkHz.

Example 7

In order to demonstrate the good miscibility with other substances, which also have a high negative dielectric anisotropy, a mixture of 22.39 mol% of compound 3.4 72.76 mol% of the basic mixture of Example 1 and 4.85 mol%

~ ^{0C H} 5. 13

manufactured.

At 25 ⁰ C was found for the mixture ε \\ = 4.4 and Δε = -2.2. The threshold voltage for the DAP effect is 2.1 V.

The mixture was transformed at 80.5 ⁰ C from the nematic to the isotropic phase to.

Claims (2)

Invention claim: 1. Crystalline-liquid mixtures with negative dielectric anisotropy, low melting temperatures and high clearing temperatures or with positive dielectric anisotropy and high clearing temperatures for the modulation of the transmitted or reflected light and for the reproduction of numbers, characters and images, both in the single-frequency and the two-frequency method, characterized in that one or more representatives of the 2-Suβ.-5- (trans-4-n-alkylcyclohexyl) -1,3,4-thiadiazoles of the general formula