DD148676A1 - CRYSTALLINE-LIQUID CHOLESTEROLIC MIXTURES FOR THERMOGRAPHY - Google Patents

Abstract

The invention relates to crystalline-liquid cholesteric mixtures for thermography, in particular for surface temperature measurement. The aim of the invention are mixtures for thermography, which have a high stability against atmospheric oxygen, Oxidtionsmitteln and thermal stress and have a high brilliance of the selective reflection. It has been found that mixtures of optically active 2,5-bis- & 4-n-alkyloxybenzylidene! -3-methylcyclohexanones and optically inactive crystalline liquid substances, which have a nematic or a smectic phase, are outstandingly suitable for thermography are. Thermography, especially surface temperature measurement, is used in many fields of medicine, engineering, material testing and daily life.

Description

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Crystalline liquid cholesteric mixtures for the thermograph! E

Field of application of the invention

The invention relates to cholesteric liquid-crystalline Gemiscne b having a strong selective reflection of circularly Temperaturabhnngigkeit polari8ierten light and are because of this property for temperature measurement, in particular the dimensional temperature measurement (thermograph! E), are suitable. Tnermograph xsx is important in daily life, in technology and in medical diagnostics.

Characteristic of the known technical solutions

It is known that cholesterol mixtures can be used for thermography. The bisphen proposed Gemisehe always contain derivatives of cholesterol, especially esters. The cholesterol molecule is not susceptible to atmospheric oxygen and other oxidants, as well as to thermal stress due to prolonged heating. As a result of this property, the mixtures which contain cholesteryl derivatives as components also change under appropriate conditions, and the temperature ranges of selective reflection are varied. Furthermore, cholesteryl ester mixtures in thermography have only a low brilliance of the selective reflection, which is due to the only weak birefringence.

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Object of the invention

The aim of the invention are cholesteroliscine crystalline liquid mixtures for the temperature measurement, which show a high stability to atmospheric oxygen, oxidizing agents and thermal stress as well as a high brilliance of the selective reflection colors.

Explanation of the invention of the invention

The object of the invention is the replacement of the cholesteryl derivatives in the Tnermographiegemiscnen by substances which are stable to atmospheric oxygen and oxidizing agents and thermal stress and have a high brilliance of the selective reflection.

It has been found that mixtures of optically active 2,5-bis-4-n-alkyloxybenzyiiden_7-3-methyl-cyclohexanonen as well as optically inactive crystalline liquid substances, which in addition to a nematic still have a smektische phase at a lower temperature, for the thermography are excellent. Suitable optically inactive substances are, for example, 4-n-alkyloxybenzoic acid 4'-n-alkyloxyphenyl ester, 4-subst. -Benzoyloxy-7-benzoic acid 4- ^f -substituted-phenyl ester, 2-yl, Substiphenyl_7-5-subst.-pyrimidines in concentrations of 50 to 90 mol%, preferably etv / a 70 mol%, in the mixtures The thermographic mixtures are also stable for a long time and show excellent brilliance of the reflection colors.

The two lowest members of the 2,5-bis-4-n-alkyloxy-benzylidene-7-3-methyl-cyclohexanone are already known / "D.Demus, H. Demus, H. Zascnke, liquid crystals in tables, VEB Deutscher Verlag for Basic Industry, Leipzig 1974, 2nd edition, p. 43_7.

The synthesis of the new members of the homologous series is based on the information in the literature according to the following rule:

1.12 g (0.01 KoI) of (+) - 3-I.Iethyi-cyclohexanone and 0.022 mol of the corresponding 4-n-Alkyloxybenzaldehyds are dissolved in 20 ml of ethanol and 5 drops of 45% sodium hydroxide solution was added. It is allowed to stand for 7 days at room temperature, the precipitated product is filtered off with suction, washed with ethanol and crystallized from dimethylformamide. Yields: 42 - 55 % ·

10 embodiments

example 1

In the table below are some new crystalline liquid 2, S-bis-n-alkyloxybenzyliclen-S-methyl-cyclohexanone recorded with their conversion 3temperaturen.

^C n ^H 2n + 1 ° ~ η melting point 3 104.5 4 128.5 5 108.5 6 101 7 Ö8 8th 80.5

CH =

Clarification point 79.5 85 72 75 71 72.5

^CC n ^H 2n ₊ 1

Example 2

Mixtures of 2,5-bis- / 4-n-aikyloxybenzyliaen_7-3-methyl

cyclohexanones

CH =

/ ^CH 3 = CH-

- ^0C n ^H 2n ₊ 1

and 4-n-decyloxybenzoic acid 4'-n-hexyloxyphenylester (DBHP) show the reflection colors at the temperatures indicated in the table ( ⁰ C).

η = 6; reflection color η = 7i reflection color η = 8; reflection color 21 8 - 4 _ 41 45 408 80 85 85 blue violet blue violet blue violet 70 mol% DBHP 39 43 blue blue blue Temp. ° 38 41 G 76 77 82 turquoise turquoise turquoise 80 37 50 5 70 75 78 green green green 79.5 39 68 72 74 5 green yellow yellow-green yellow-green 77 red yellow orange 75.5 mol% DBHP 70 66 67 71 red red 74 Temp. ⁰ C 60 72.5 63.5 70 mol% DBHP 70 75 80 10 Temp. ⁰ C 67 52 65 64 15 62 47 60 20 25

Claims (2)

invention claim 1, cholesterol crystalline liquid mixtures for thermography, characterized in that J) optically active 2,5-bis-n-alkyloxybenzy ± iaene-3 methyl-cyclohexanones and optically inactive crystalline substances which, in addition to a nematic one, also have a smectic phase at a lower temperature. 2. According to point 1., characterized in that as optically inaictive components 4-n-alkyloxybenzoic acid 4'-n-alkyioxyphenylester, 4- / ~~ 4-Subst.-benzoyloxy_7-benzoic acid ~ 4'-suDst.-phenyl ester and 2 - / "~ 4- Subst.-phenyl__7-5-3-pyrimidines in concentrations of 50 to 90 moi-> S, preferably about 70 moi%, can be used.