CH653983A5 - CRYSTALLINE LIQUID, 6N ALKYLNAPHTHALINE-2-CARBONIC ACID (TRANS-4N ALKYLCYCLOHEXYL ESTER). - Google Patents

Description

The invention will be explained in more detail below using exemplary embodiments.

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example 1

The new crystalline-liquid 6-alkylnaphthalen-2-car-bonic acid (trans-4-alkylcyclohexyl ester) can be prepared according to the following general scheme from the 6-alkylnaphtha-i5 lin-2-carboxylic acid chlorides and trans-4-alkylcyclohexanols according to the unicorn or Schotten-Baumann variant can be produced:

The invention relates to crystalline-liquid 6-n-alkylnaphthalene-2-carboxylic acid (trans-4-n-alkylcyclohexyl ester) which is used in subcoolable nematic liquid crystal mixtures for optoelectronic components for modulating the continuous or striking light and for representing numbers, characters and images are used.

It is known to use nematic liquid crystals in optoelectronic components, in particular in cells with a twisted nematic structure (Schadt-Helfrich cells) (G. Meier, E. Sackmann, JG Grabmaier, Applications of Liquid Crystals, Springer-Verlag Berlin-Heidelberg- New York 1975).

For practical use in various fields, the components and thus the liquid crystals, depending on the intended use, have different requirements with regard to melting and clearing point, threshold voltage and operating voltage, rise and decay times and thermal and chemical stability. So far there is no connection that even meets the stated requirements in the pure state. For this reason, mixtures are used without exception, mostly consisting of 3 to 6 components with different properties. New applications, e.g. Optoelectronic components for vehicles require low operating and storage temperatures without crystallization of the liquid crystal mixtures, which are in thermodynamic-metastable nematic state in most cases at temperatures below 0 ° C. Many mixtures that would be suitable for practical use due to their favorable properties, e.g. Mixtures of several 4-n-alkylcyclohexane carboxylic acid -4'-cyanophenyl esters or 4-n-alkylbenzoic acid -4'-cyanophenyl esters cannot be used at low temperatures because they crystallize at temperatures below 0 ° C and thus the necessary orientation of the nematic liquid crystal is no longer guaranteed by the electrodes even after the mixture has melted again.

The aim of the invention consists in new nematic crystalline-liquid mixtures for optoelectronic components which do not crystallize out at temperatures below 0 ° C.

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

It has been found that by adding new crystalline liquid 6-n-alkylnaphthalene -2-carboxylic acid (trans-4-n-alkylcyclohexyl ester) to crystalline liquid nematic mixtures which are suitable for use in optoelectronic components.

COCI

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+ HCM

CA ,, CO "000-® ^" "1

2m + l + HCI

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Example 2

30 Preparation of 6-n-butylnaphthalene-2-carboxylic acid (trans-4-n-butylcyclohexyl ester)

1. trans-4-n-butylcyclohexanol 120 g (0.8 mol) 4-n-butylphenol in 300 ml abs. Ethanol is shaken with 15 g Raney nickel in an autoclave at 160 ° C and 10 to 15 MPa until the calculated pressure drop has occurred after 60-90 minutes. The catalyst is then filtered off and, after the solvent has been removed, the residue is fractionated in vacuo. The main fraction (bp: 110-116 ° C / 1.3 KPa) contains 80% of the theoretically calculated amount of 40 4-n-butylcyclohexanol (cis-trans mixture). The complete hydrogenation and the absence of cyclohexanone can be checked by IR spectroscopy. The isomer separation was carried out using a Normag micro-rotating column column (55 theoretical plates) at a column load of 1 ml / min, 45 at a reflux ratio of 1:50 and at a distillation rate of 1 drop / min. cited. 30 ml of isomer mixture could be separated in 70 hours. Yield of trans product: 31.3-37.5 g (25-30% of theory); Bp: 69-70 ° C / 0.65 KPa.

50

2,6-n-butylnaphthalene-2-carboxylic acid (trans-4-n-butylcyclohexyl ester)

Dropwise at 0 ° C to a solution of 7.8 g (0.05 mol) of trans-4-n-butylcy-çlohexanaphthalene -2-carboxylic acid chloride. 55 The reaction set was left to stand at room temperature for 24 hours and then heated to 70 ° C. for one hour. The cooled mixture is then poured onto 500 g of ice / 30 ml of conc. H2S04. The mixture is then etherified several times, the ether extract is washed with 5% NaHC03 solution, diluted 60 HCl and thoroughly with water, the solvent is distilled off and the residue is recrystallized several times from methanol or ethanol.

Yield: 9.15 g (50% of theory); K 34.5 N 68 is.

65

Example 3

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

653 983

Here: K = crystalline solid state N = nematic S = smectic is = isotropic liquid

Table 1

6-n-alkyl-naphthalene-2-carboxylic acid (trans-4-n-alkylcy-clohexyl ester)

-COO-

^ H ^> - R2

Verb.

R1

R2

K

S

N

la c4h9

c2h5

• 31.5

-

• 37

lb c4h9

c3h7

• 44

-

■ 76

lc c4h9

c4h9

• 34.5

-

• 68

ld c4h9

c5Hm

■ 57

-

• 77

le c4h9

c6h, 3

• 56.5

-

• 63.5

2a cghlv c2h5

■ 51

_

(• 46)

2 B

C8Hiv c3h7

• 91.5

-

(• 73.5)

2c c8h17

c4h9

• 52

-

• 67.5

2d c8h17

c5h "

• 44.5

• 65

• 84

2e c8hi7

c6h, 3

• 46.5

(• 37)

• 69.5

Example 4

The mixture Mi A of the following composition is used in a cell of the twisted nematic structure type (Schadt-Helfrich cell):

34.5 mol% C3H7 - -eoo- -CN

-eoo-

5 31.0 mol% C4H9 -34.5 mol% C

-CN -CN

Is

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30th

35

The mixture has the following properties:

K 10 to 14 N 72 is layer thickness: d = 19.8 µm

Threshold voltage: U0 = 1.7 V 20 ° C

Response time: tE 50% = 560 ms 20 ° C

Cooldown: tA 50% = 180 ms 20 ° C

In particular, the melting point of 10-14 ° C, which cannot be subcooled noticeably over a long period, prevents use at low temperatures.

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

Composition of Mi B 80 mol% Mi A 20 mol% Compound No. lc clearing point 69.5 ° C

Even after two weeks, samples of approx. 200 mg mass do not crystallize when stored in the refrigerator at -12 ° C, even after eight hours of cooling small sample amounts on the microscope cooling table at - 20 ° C, there is no crystallization, so that the stable melting point due to the strong subcoolability could not be determined so far.

Electro-optical parameters at 20 ° C, layer thickness 21 Jim: Threshold voltage: U0 = 1.8 V / 500 Hz Response time: (50%) tE = 1940 ms Response time: (50%) tA = 575 ms

C.

Claims (2)

653 983 PATENT CLAIMS 1. Crystalline liquid 6-n-alkylnaphthalene-2-carboxylic acid (trans-4-n-alkylcyclohexyl ester) of the formula I CnH2n + l CnH2n + l 2. Subcoolable nematic liquid crystal mixtures for optoelectronic components, characterized in that the mixtures contain crystalline-liquid 6-n-alkylnaphthalene -2-carboxylic acid (trans-4-n-alkylcyclohexyl ester). are suitable, surprisingly the supercoolability is greatly reduced and the crystallization of the mixtures at temperatures below 0 ° C is prevented for a long time. The new crystalline-liquid 6-n-alkylnaphthalene -2-car-5 bonic acid (trans-4-n-alkylcyclohexyl esters) are colorless, thermally and chemically stable and can be subcooled by 10-20 K in their pure state.