DD140358A1 - METHOD FOR ADJUSTING THE TEMPERATURE DISPLAY AREA OF CHOLESTERIC LIQUID CRYSTALS - Google Patents

Abstract

Method for adjusting the temperature display range of cholesteric liquid crystals for thermography by varying the composition of the thermographic mixture by the addition of further cholesteric liquid crystals, nematic liquid crystals or chemically neutral organic substances, characterized in that benzoic acid phenyl esters or their mixtures substituted as nematic liquid crystals for a stock solution, as cholesteric additive cholesteryl-PC-pelargonat or as a chemically neutral organic substance di-iso-octylphthalat or iso-nonylphenol, are added. FIG.

Description

However, in order to adjust the temperature reading range, it tends to oil liquids

The application came into being .

The invention relates to a method for adjusting the temperature display range of cholesteric liquid crystals, which are used for temperature measurement (thermography).

Characteristics of the known technical solutions

Temperature measurement (thermography) with cholesteric liquid crystals is a method increasingly used to solve problems of medical diagnostics, materials testing, microelectronics and other fields. One of the most important forms of application is the use of solutions of cholesterol-containing mixtures in volatile solvents.

The temperature range of a Therraogi aphielösung arises from their composition. Depending on the percentages of the individual cholesterol tern, the reflection colors show up at different temperatures. The reproducibility of the temperature-color display behavior depends essentially on the purity of the cholesterol derivatives used.

In the industrial production of cholesterol derivatives, their chemical purity is subject to a considerable fluctuation range j, e.g. through quality

2 0 970 9

In addition, the shelf life of some cholesterol esters is limited, e.g. These fluctuations in the melting, conversion and clearing points of the individual components naturally result in correspondingly altered temperature ranges when mixed into thermographic solutions. Consequently, the production of thermographic mixtures for defined temperature ranges according to the methods known hitherto results in difficulties in which can only be remedied by a new, complex determination of the percentage composition ".

Object of the invention

The ^z iel of the invention consists in an easy-to-use method for adjusting the temperature display "range of cholesteric liquid crystals, in which the time-consuming accurate determination of the total composition is avoided ·

Explanation of the essence of the invention

It has been found that by adding nematic liquid crystals, oysteric liquid crystals, which do not show any reflection in the required display region, ohemically neutral organic substances, e.g. Di-octyl phthalate or iso-nony! Phenol, the target temperature range of roughly cholesteric ther-. mogsaphiegemlsche within an interval of many. Celsius degrees can be adjusted so that from a stock solution several solutions can be made with different temperature display ranges.

As additives are basically all known chemical. Substances or mixtures thereof capable of meeting the following .Forderungen '

a) chemical stability

b) stability against oxidative influences and UV

Radiation. ,

ο) chemically inert behavior towards cholesterol derivatives

d) The temperature indication behavior of the thermographic device shall not be adversely affected with regard to brilliance, spectral distribution, etc. ,

e) Good solubility of the additive in the hermographiemisohirag

Exemplary embodiments

Example 1: ^:

The effect of the addition of nematic liquid crystals on ohoiesterin © thermographic substances shall be clarified by the following table.

substance

Mass Reflection Temp, parts color ⁰ C

Cholesteryl nonanoate cholesteryl undecyl carbonate

Cholesteryl chloride 2.7

Cholesteryl oleate 2,6

The substances correspond in purity to the usual requirements, which were checked in their melting and clearing points.

red yellow green violet

30 31 32 33.5

Pen tyloxyb enzoic acid eoc tyloxyphenyls t er

Methoxybsnzoesäurehexyloxyphenylester

Hexyloxybenso it is eh-eptyloxyphenyles ter

Hexylbenzoic acid butyl oxyphenyl © s ter

1.88

0.82 2.14

-4- 209709

Continuation of the table

substance %> £ -

Mixture of 97% by weight, # A. and 3% by weight # B

red 27 yellow 28 green 29 violet 30.5

Example 2:

The setting of the temperature display range can be advantageously carried out by cholesterol-based substances or mixtures which themselves do not show any reflection in the required display range. In particular, the substances are cholesteryl PC-pelargonat (cholesteryl esters, prepared using a mixture of n-car- produced by VEB Deutsche Hydrierwerke Rodleben).

15 bonsäuren G "to C.q),

A thermographic mixture C with the following composition shows the reflection colors in the specified temperature range. Addition of cholesteryl PC-pelargonate shifts the indicator to lower values:

₉ λ ο -V ₀₊ ^ mass reflection temp,

Substance _{parts color Ος} Λ

cholesterylnonanoate

Choles terylundecylcarbonate

Cholesteryl chloride cholesteryl oleate

25 Mixture of 11.6% by mass and 2.5 parts by mass of hydrochloric acid PC-pelargonat:

2.5 red red 32.5 * 29.5 4.0 yellow yellow 33 30 1.6 green green 34 31 3.5 violet violet 35.5 32.5 η mixture C Eryl-PC

Example 3 t , '^

A variant of Example 2 "is that, for example, in mixture C, the cholesteryl nonanoate is exchanged for cholesteryl PC-pelargonate, resulting in mixture Ds

9 substance

Mass parts

Reflection color

Cholesteryl PC D Cholesteryl oleate. 2.5 T o 21 pelargonate XWV Cholesteryl undecyl carbonate 4.0 yellow 22 cholesteryl 1.6 green 23 3.5 violet 25

Blending of the mixtures C and D can be made any display area, which lies between those of the mixtures C and D.

Example 4:

Duxoh chemically neutral substances, such as "di-iso-octyl phthalate or iso-nonylphenol, the ranges can be varied within very wide limits. The lowering of the temperature range of the stazar solution is proportional to the amount of the additive. An addition of 1 # Di ~ iso ~ octylphtalat lowers the temperature range around etvia 3 ⁰ C, iso-nonyl phenol, about 7 ⁰ C. Starting from the mixture A of Example 1 (or other mixture) viird this effect in the graphs Fig 1 and Fig. 2 deactivating t.

Claims (4)

209709 claim for invention 1. A method for adjusting the Temperatuxanzeigeigebeses Gholesterinischer liquid crystals for thermography, characterized in that to a stock solution nematic liquid crystals, cholesteric liquid crystals in the required display area would be no reflection, or chemically neutral organic substances are added « 2 · procedure according to point 1 *,
characterized by that as nematic liquid crystals e.g. substituted benzoic acid phenyl esters or their mixtures used • nexden. " 3 · Procedure according to point 1., characterized in that as a gholesterinic additive, e.g. Cholesteryl PC-pelargonat, which is used in the required temperature range if no reflection. 4 · procedure according to point 1.,
indicates that chemically neutral organic substances are, for example, di-iso-octylphthalate or isononylphenol.