DD203561A1 - SUB-COOLABLE NEMATIVE LIQUID GRIQUES - Google Patents

Abstract

The invention relates to unterkuehlbare nematic liquid crystal mixtures for optoelectronic devices. The object of the invention is new nematic crystalline-liquid mixtures for optoelectronic devices that do not crystallize at temperatures below 0 degrees C. The object of the invention is to find suitable crystalline liquid compounds, which greatly reduces its Unterkuehlbarkeit when added to a nematic liquid crystal. It was found that the addition of new crystalline-liquid 6-alkylnaphthalene-2-carboxylic acid & trans-4-alkylclohexyl esters! to crystalline-liquid nematic mixtures, which are suitable for use in optoelectronic components, surprisingly the Unterkuehlbarkeit greatly reduced and the crystallization of the mixtures is prevented at temperatures below 0 degrees C for a long time.

Description

T-Cooling nematic liquid crystal mixtures

Field of application of the invention

The invention relates to supercoolable nematic liquid crystal mixtures for optoelectronic components for the modulation of continuous or incident light and for the display of numbers, characters and images.

Characteristic of the known technical solutions

It has already been proposed to use nematic liquid crystals in optoelectronic components, in particular in cells with a twisted nematic structure (Schadt-Helfrich cells) / G, Meier, E, Sackmann, J _e G. Grabmaier, Applications of Liquid Crystals, Springer-Verlag Berlin-Heidelberg-New York 1975 /.

For practical application in various fields, the components and thus the liquid crystals are subject to different requirements depending on the intended use with regard to melting and clearing point, threshold voltage and operating voltage attack and decay times as well as thermal and chemical stability. So far there is no connection, which in the pure state only approximately meets the stated requirements · Therefore, without exception, mixtures, usually from 3 to 6 components of different properties, used · Newer applications, eg. B, optoelectronic components for vehicles, require low operating and storage temperatures without crystallization of the liquid crystal mixtures, which at temperatures below OC in most cases in the thermodynamic-metastable

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nematic state. Many mixtures that would be suitable for practical use because of their favorable properties ζ · Β · mixtures of several 4-n-Alk7lc7clohexancarbonsäure ^ '- cyanphenylestern or 4-n-alkyl benzoic acid-4 ¹ -cyanphenylestern but know not to be used at low temperatures since they crystallize out at temperatures below 0 ^° C. and thus the necessary orientation of the nematic liquid crystal through the electrodes is no longer ensured even after the melt has reflowed.

Object of the invention

The object of the invention is novel nematic crystalline-liquid mixtures for optoelectronic components which do not crystallize out at temperatures below 0 ^° C.

Explanation of the invention of the invention

The object of the invention is to find suitable crystalline compounds which, when added to a nematic liquid crystal consisting of a compound or a mixture of several ex compounds, greatly reduces its ITcoolability.

It has been found that surprisingly the addition of new crystalline-liquid e-alkylo-pthalene-2-carboxylic acid / trans-4-alkoxycyclohexyl esters to crystalline-liquid-nematic mixtures which are suitable for use in optoelectronic components greatly reduces the undercoolability and the crystallization of the mixtures is prevented at temperatures below 0 ⁰ C for a long time.

The new crystalline-liquid 6-alkylnaphthalene-2-carboxylic acid / "trans ^ -alkylcyclohexylester / are colorless, thermally and chemically stable and already in the pure state strongly supercooled by 10 - 20 E.

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Exemplary embodiments Example 1

The new crystalline liquid 6-alkylnaphthalene-2-carboxylic acid / tertiary-4-alkylcyclohexyl ester / ^r can be prepared according to the following general scheme from the 6-alkylnaphthalene-2-carbonyl chlorides and trans ^ -alkylcyclohexanols according to the unicorn or Schotten Baumann Variant can be made:

η ττ ü'WCO Cl

° ^H 2n + 1

^G n ^H 2n ₊ 1

Example 2

Preparation τοπ o-n-butylnaphthalene ^ -carboxylic acid Z'trans ^ -nbutylcyclohexylester /.

"l" trans-4-n-butylcyclohexanol

120 g (0.8 mol) of 4-n-butylphenol in 300 ml of abs. Ethanol are shaken with 15 g of Raney nickel in an autoclave at 160 ^° C. and 10 to 12 MPa for SO ² until after 60-90 minutes the calculated pressure drop occurred. Thereafter, the catalyst is filtered off and fractionated after removal of the solvent of Bückstaad in vacuo. The main fraction (Ep: 110-116 ° C / 1.3 E Pa) contains 80 % of the theoretically calculated amount of 4-n-butylcyclohexanol (eis-trans-G-etnisch). The complete hydrogenation and the absence of cyclohexanone can be checked by IR spectroscopy. The isomer separation was washed with a ITormag micro Drehbandkoloone (Jo ^ theoretical plates) at a column load of 1 ml / min, a reflux ratio of 1: 50 and at a DestillationsgeschwLndigkeit VOO 1 drop / min led.

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50 ml isomer mixture could be separated in 70 hours,

Yield of trans-product: 31.3 to 37.5 g (25 - 30% of th _e,) Kp: 69 - 70 ° C / EPa 0.65

2. 6-n-3-butylnaphthalene-2-carboxylic acid - / "trans-4-n-butylc-cyclohexyl ester.

To a solution of 7.8 g (0.05 mol) of trans -n-butylcyclohexanol in 50 ml of abs-pyridine was added 12.3 g (0.05 mol) of 6-n-butylnaphthalene-2-Ha. rbonsäurechlorid added dropwise at 0 ⁰ C. The reaction mixture was allowed to stand for 24 hours at room temperature laser-sen-10 "and then heated for 1 hour at 70 ⁰ C. Then poured the cooled batch to 500 g of ice / 30 ml Eonz. H _? S0 ,. The mixture is then re-etherified several times, the ethereal extract is washed thoroughly with water and dilute HCl thoroughly with water, the solvent is distilled off and the residue is recrystallised several times from methanol or ethanol.

Yield: 9.15 g (50 f, d "Th.); K 34.5 N 68 is

Example 3

The following table gives examples of the compounds according to the invention

 Where:

E = crystalline solid state

Έ = nematic

S = smectic

is = isotropic-liquid

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Table 1

6-O-alkyl-2-oaphthaliD oarTjODsäure - / "Trads-4-n-al grlc7clohexylester} /

Verb · R

IS

1a = 4 = 9 O ₂ H ₅ . 31 , 5 - 37 • 1b = 4 = 9 ι 7 * 44 - · 76 » 1c C ₄ H ₉ C ₄ H ₉ . 34 , 5 - 68 O 1d = 4 = 9 57 77 β 1e = 4 = 9 ^C 6 ^H 13 ^# 56 , 5 - 63 5. 2a = 8 = 17 C ₂ H ₅ . 51 - (. 46) • 2 B = 8 = 17 C ₃ H ₇ . 91 , 5 - (ο 73 5). 2c = 8 = 17 C ₄ H ₉ . 52 - · 67, 5. 2d = 8 = 17 ^C 5 ^H 11 * 44 , 5. 65 84 • 2e = 8 = 17 ^C 6 ^H i3 · 46 , 50 37) ♦ 69, 5.

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Example 4

Eα a cell of the type of twisted nematic structure (Schadt-Helfrioh cell), the mixture Mi A of the following composition is used:

34.5 mol % C ₃ H ₇

31.0 mol % C, H _Q - / Ϊ '4 9 \ _

34.5 moles of C $ ₅

The mixture has the following properties:

K 10 Ms 14 N 72 is layer thickness: d = 19,8 / 4n Threshold voltage: TT = 1,7 7 Ί Settling time: t _ß 50 % = 560 ms (20 ⁰ C

Decay side: t _A 50 $ = 180 ms J

In particular, the melting point of 10-14 ⁰ C, which can not be significantly undercooled over a longer period of time, prevents application at low temperatures.

By adding compound no. 1c, which has a melting enthalpy of 23,500 J / mol, is highly subcoolable and thermally very stable, the mixture Mi B has the following properties:

Composition of Mi B

80 mol fo Mi A

20 mol% of compound 1c Fr. clearing point 69.5 C ⁰

Even after 2 weeks, samples of about 200 mg do not crystallize on storage in the refrigerator at -12 ° C, even after 8 hours cooling of small sample quantities on the microscope cooling table

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-20 ⁰ C takes place keioe Kristallisatioa, so that the stable Schmelzpuokt koaote werdeo found because of the strong Uoterkührbarkeit "previously sealing,

Electro-optical parameters at 20 ^° C., layer thickness 21 / im:

SchwellspaoDUDg U ₀ = 1.8 7/500 Hz

ADliming time (50 ^) t _E = 1940 ms decay time (50 S6) t _A = 575 ms

Claims (1)

-a- 237942 £ Erfindungsanspruoh Subcooled nematic liquid crystal mixtures for optoelectronic components, characterized in that the mixtures contain new crystalline liquid 6-alkylnaphthalene-2
bonsäur e / T; ransH - alkylc; yclohe: xylester7 contain ·