DE2257588B2 - USES OF CRYSTALLINE LIQUID NEMATIC DERIVATIVES OF PHENYLPYRIMIDINE - Google Patents

Description

35

The invention relates to the use of the crystalline liquid nematites mentioned in the patent claims Substances, optionally together with customary dichroic dyes or others usual crystalline liquid compounds, for electro-optical arrangements for modulating the continuous or incident light and as a solvent in spectroscopy and as a stationary phase in the Gas chromatography and for the production of nematic layers with a twisted structure.

It is known that nematic crystalline liquid substances are oriented in electric fields can. This possibility for orientation can be used in electro-optical arrangements for light modulation to be used. It is also known that the molecules of added substances orientate in nematic liquids will. This orientation of foreign molecules is in spectroscopic investigations with the help of UV / VIS spectroscopy, nuclear magnetic resonance spectroscopy and electron spin resonance spectroscopy very advantageous for determining the anisotropy properties of the molecules. It has also been suggested that the orientability of dichroic molecules in nematic liquids in electro-optical arrangements to use to modulate the light. Nematic liquids have also been called with success Separating liquids used in gas chromatography.

It is also known that twisted nematic layers are responsible for the structure of electrical components

For the application of liquid nematic crystals it is often necessary only a little above room temperature or even to work at temperatures below room temperature. The ones known so far Substances either have melting points well above room temperature, or they are due sensitive groups in the molecules to thermal and chemical influences as well as electrical Fields unstable, sometimes they have disturbing absorption bands in the visible part of the spectrum. To get to systems with a lower melting point, eutectic mixtures can be used. In the case of some previously known classes of substances, however, the lowering of the melting point can only be achieved small amount.

The object of the invention is the use of low-melting, stable, colorless nematic crystalline Liquids in electro-optical arrangements also with a twisted structure as well as for spectroscopy and for gas chromatography.

It has been found that derivatives of phenylpyrimidine of the general formula

R ₁ -

in which Ri and R _{2 are} identical or different substituents C _n H _{2n + 1} -, C "H _{2n +} iO-, C _n H _{2n + 1} COO- or C _n H _{2n + 1} CO-, where π is 1 to 12 , in electro-optical arrangements for modulating the light passing through or incident, as well as solvents in spectroscopy and as stationary phases in gas chromatography. The substances used according to the invention melt out at low temperatures to form crystalline liquid nematic phases. By producing mixtures, preferably eutectic mixtures, from two or more derivatives of phenylpyrimidine, the melting points are very greatly reduced, while the advantageous properties of the pure substances are retained. In addition to the pure or mixed compounds according to the invention, customary dichroic dyes or other customary crystalline liquid compounds can also be used.

The derivatives of phenylpyrimidine used according to the invention are by condensation of p-substituted benzamidine HCl with n-alkyl malonic esters or n-alkoxymalone esters in the presence of Sodium methylate, conversion of the substituted 4,6-dihydroxypyrimidines into the corresponding dichloropyrimidines and subsequent dehalogenation obtained in good yields as colorless crystals.

The following reaction scheme shows the synthesis route:

NH

NH,

H ₅ C ₂ OOC

HCl +

CH-R,

H ₅ C ₂ OOC
After ₃

POCl ₃

According to the invention, the phenylpyrimidine derivatives mentioned in the claim are used for the preparation of nematic layers with a twisted structure formed by rubbing the electrode surfaces or setting a certain angle of the rubbing direction of the two electrodes, preferably 90 °, is used.

The use of mixtures, preferably eutectic mixtures, is particularly advantageous two or more derivatives of phenylpyrimidine or mixtures with the addition of other customary ones crystalline liquid or non-crystalline liquid substances, e.g. B. p-cyanobenzal-butylaniline, p-chlorobenzalphenetidine, Diphenyl ether, n-octylbenzene. The Liquid crystal substance can be introduced into the cell after the assembly of the rubbed electrode surfaces.

Advantages of the compounds used according to the invention are the low melting points and the strong Lowering of the melting point in mixtures of two or more of these compounds. They are colorless and stable even when heated for hours at temperatures above 100 ° C, do not decompose through air, Moisture or exposure to light and remain even after exposure to electrical fields for days (DC or AC voltage) unchanged In the nematic state, they have a positive anisotropy the dielectric constant. In addition, these compounds are colorless.

The invention is to be explained in more detail below using 7 examples.

example 1
5-n-hexyl-2- (4-n-hexyloxyphenyl) pyrimidine

To dissolve 3.5 g (0.15 mol) of sodium in 100 ml of abs. Methanol are successively 0.05 mol p-n-Hexyloxybenzamidine-HCl (dried over P2O5) and 0.05 mol of n-hexyl malonic ester. With agitation the mixture is heated to 80 ° C. (bath temperature) for 8 hours and then left to stand overnight. With concentrated HCl, the pyrimidine is precipitated, filtered off, filtered off.

washed with water, alcohol and ether and dried at 120 ° C. For the analysis, it is recrystallized from DMF
Yield: 95% of theory, F: 298 to 301 ° C.

0.05 mol of 5-n-hexyl-2- (4-n-hexyloxyphenyl) -4,6-dihydroxypyrimidine (crude product), 12 ml of N-diethylaniline and 100 ml of POCI3 are refluxed for 30 hours the hot oily residue was poured onto a mixture of 40 g NaOH / 100 g ice while stirring. The alkaline solution is extracted with ether. The ether extract is extracted twice with 50 ml of half-concentrated HCl, washed with water, _{dried with Na2SO 4} and then the solvent is distilled off.

The crystal slurry obtained is made from alcohol / activated charcoal recrystallized.

Yield: 91% of theory, F: 46 ° C.
0.05 MoI 5-n-Kexyl-2- (4-n-hexyloxyphenyl) _-4) 6-dichloropyrimidine, 3 g of MgO, 100 mg Pd-activated carbon catalyst, 200 ml of alcohol and 15 ml of water at 6O ⁰ C hydrogenated to saturation with hydrogen.

Then it is filtered off hot and the residue is extracted thoroughly with ether. The combined filtrates are concentrated to dryness and the product is recrystallized from alcohol to a constant KiärpunKt.
Yield: 66% of theory.

Example 2

Table 1 shows examples of the melting and clearing points of the compounds used according to the invention the general formula

specified.

40 Table 1 Ri R ₂ Fp. Etc. KIp. No. ( ⁰ C) ( ⁰ C) - ("C) i smectic / nematic - CeHnO- -CeHi3 30th - 60.5 45 1 C9H19O- -CeHu 37 56.5 61 2 C10H21O- -CeHn 38 - 63 3 C12H25O- -CsHii 52 65 4th CeHu- -OCiH ₉ 40 60.5 5 CsHnO- -OC4H9 82 88 so 6th

Example 3

, In Table 2 are examples of binary mixtures of the Contain compounds used according to the invention.

Table 2

mixture
No. Substance-
No. Mol% Fp.
Γ C) KIp.
(Q 1 1
2 68.5 \
31.5 y 4th 60 II 1
3 74 1
26 y 4.5 59 III 1
4th 64.5 \
35.5 I. 12th 59

Example 4

The compounds used according to the invention and their mixtures can be used in electro-optical Arrangements of the following type take place (Fig. 1):

In a cell made of 2 panes of 2; 3 with electrically conductive transparent electrodes 4; 5 exists, there is the nematic liquid 1. The distance between the electrodes 4; 5 is made by fine Teflon or Polyethylene strips 6 set. The cell can be irradiated with light in the direction indicated which also passes through the polarizer 7 and the analyzer 8. The two conductive electrodes 4; 5 were rubbed evenly before filling the substance and inserted so that the rubbing direction stand parallel to each other. The nematic liquid 1 is then oriented parallel with its preferred direction to the rubbing direction. The direction of friction and the direction of oscillation of the polarizer 7 form an angle of 45 °. A uniformly colored field of view results between the crossed polarizer 7 and the analyzer 8. By applying direct or alternating voltage, the field of view passes through depending on the applied voltage causes a series of interference colors and eventually becomes dark.

Table 3

Mixture 1 shows at 20 ° C. and an electrode spacing of 10 μπι with 50 Hz alternating voltage, the following Behavior:

tension
(V)

colour

order

0
6.1 light yellow \
light green j 6.6
7.5
8.0 light red j
green
blue J 8.6
9.7
IU
13.4 red 1
yellow 1
green I.
blue J 15.6
19.8
20th red ι
yellow I.
gray to I.
black J

and inserted so that the directions of rubbing unite Form an angle of preferably 90 ° with one another.

After filling, the nematic liquid orients itself with its preferred direction in the vicinity of the Electrode areas 4; 5 parallel to the rubbing directions. The overall result is a twisted structure. the Arrangement, which still consists of the polarizer 7 and the analyzer 8, is in the direction indicated shines through with light.

Depending on the angle that the planes of oscillation of polarizer 7 and analyzer 8 form with one another, exist z. B. the following two possibilities for intensity modulation of the light passing through (A b b. 2):

Case a:

If the planes of oscillation of polarizer 7 and analyzer 8 are parallel, then the intensity is emerging light is very small. By applying a direct or alternating voltage of 5 to 7 V. The optical activity disappears on a cell with an electrode spacing of ΙΟμίτι; the continuous light shows maximum brightness.

Case b:

If the planes of oscillation of polarizer 7 and analyzer 8 are crossed, then that has continuous Light maximum brightness when de-energized. When voltage is applied, however, occurs Darkening in the direction of the radiation.

higher orders 3rd order

2nd order 1st order

The cell displays after 2000 hours of operation at 20 ⁰ C no change in Egenschaften.

Example 5

The use of the crystal liquid phenylpyrmüdine derivatives or of mixtures of these compounds for modulating the intensity through or Striking light should also in one embodiment at A b b. 1 to be described.

The ZeDe has a structure as already described in Example 4. The two electrode surfaces 4; 5 are also rubbed before the assembly of the cell and the filling of the nematic liquid In A b b. 2 the intensity of the transmitted light (in arbitrary units) is plotted against the applied voltage for cases a and b. The cell used contains a mixture of 68.5 mol%

5-n-hexyl-2- (4-n-hexyloxyphenyl) pyrimidine and

31.5 mol% of 5-n-hexyl-2- (4-n-nonyloxyphenyl) pyrimidine, which is in the temperature range from 4 ° C to 60 ° C is nematic, in a 10 μm thick layer. Ice cream is made at 20 ° C 50 Hz AC voltage used

The electric field of the arrangement mentioned can be replaced by a magnetic field.

Example 6

The compounds used according to the invention can also be used in a cell operated in incident light with a reflective rear electrode. The electrodes can consist of segments that can be placed individually on the spinning and thus enable the reproduction of colored characters and digits. By using strip-shaped conductors on both electrodes in a crossed arrangement, the nematic liquid can be controlled point by point and enables characters and images to be reproduced.

Example 7

The cell according to Fig. 1, but without polarizer and Analyze jr is made with mixture 1 with the addition of 1% methyl red or buckets of other dicbroitic Dye filled White light irradiated while no voltage is applied after passing through If the cell appears red, the color changes from 50 Hz to yellow with 20 V AC.

1 sheet of drawings

Claims (4)

Patent claims: 1. Use of one or more crystalline liquid nematic derivatives of phenylpyrimidine the general formula in which Ri and R2 are identical or different substituents CA _n +1. Cf ^ -nO-, C _n H2n + iCOO— or CH ^ + iCO—, where π 1 _{] is 5} to 12, for electro-optical arrangements for modulating the passing or incident light and as a solvent in spectroscopy and as a stationary phase in gas chromatography. 2. Use of crystalline liquid nematic substances according to claim 1, characterized in that that mixtures of two or more of the phenylpyrimidine derivatives mentioned in claim 1 can be used. 3. Use of crystalline liquid nematic substances according to claim 1 and 2, characterized characterized in that additionally common dichroic Dyes or other customary crystalline liquid compounds can also be used. 4. Use of crystalline liquid nematic substances according to claims 1 to 3 for the production of nematic layers with a twisted structure.