CH651818A5 - 4-N-ALKOXY- (TRANS-4'-N-ALKYL-CYCLOHEXYL) BENZOLE. - Google Patents

Description

The present invention relates to a phenylcyclohexane dielectric material useful as a liquid crystal display material.

PRIOR ART A nematic liquid crystal shows features according to which optical properties, such as light scattering, birefringence and the like, change considerably under the influence of the electric field and are widely used in a display device which uses electro-optical effects, using different display principles . A twisted nematic liquid crystal display device in which a twisted nematic liquid crystal orientation is used, a guest / host effect display device by adding dichroic or pleochroic dye to the above-mentioned twisted nematic liquid crystal display device, a phase transition Guest / host display devices in which the orientation of nematic liquid crystal with the addition of cholesteric liquid crystal or material of optical activity is controlled by the electric field, and the like are well known as typical display devices using the electro-optical effect.

DE-A-26 36 684 describes compounds of the formula ei- (e> © -r2 '

wherein R 1 and R 2 can be alkyl, alkoxy, or cyano. However, preparation and properties are only disclosed for those compounds in which Rt in the formula is alkyl and R2 is cyano. As indicated below in the reaction scheme and under process, these compounds are used as starting materials for the preparation of the compounds according to the invention.

Liquid crystal display materials used in the above-mentioned display devices generally have the following properties:

(1) They should have a wide temperature range, including room temperature, of the liquid crystalline phase.

(2) They should have a low viscosity in order to achieve an excellent response speed.

(3) In order to achieve a high display contrast, they should have a low anisotropy An of the refractive index.

(4) They should be stable against external attack by moisture, light, heat and the like.

(5) They should have high solubility in order to enable easy preparation of liquid crystal mixtures by mixing a number of compounds.

However, a single compound which has all of the properties mentioned above has not yet been known.

Thus, liquid crystal mixtures which can be obtained by mixing some types of compounds are currently used for this purpose. In the prior art, a compound which satisfies the requirements with regard to viscosity, solubility and solubility to a sufficient extent is not known, so that a liquid crystal display device with a satisfactory response speed and sufficient display contrast was not available.

Presentation of the invention

It is an object of this invention to provide liquid crystalline compounds which have some advantages in terms of low viscosity, low viscosity, stability and excellent solubility at the time of mixing with other compounds. The new compounds according to the invention are 4-n-alkoxy- (trans-4'-n-alkylcyclohexyl) benzenes of the formula:

45

r i— (D— © -

wherein R 1 is straight-chain alkyl with 3 to 5 C atoms, and R 2 is straight-chain alkyl with 1 or 3 to 8 C atoms. The reaction process for the preparation of the abovementioned compounds proceeds according to the reaction scheme below and is explained below:

^ - (D— ■ @ - CN

Process 1

KOH, C-Ht-OH O Z *

- (D— © - CNH2

Process 2

Br2 / NaOCH3, CH3OH

3rd

651 818

4th

r1 - (h) —— ® nhcoch3

Process 3

Process 4

koh / 80% c2h5oh (o) nh,

h2so4, hno2

- (d— © —0h

Process 5

R2Br '

koh

® © - 0F4

Process 1: 4- (trans-4 / -n-alkylcyclohexyl) -benzonitriI, which is manufactured by the Merck Patent Gesellschaft and is commercially available, is boiled and decomposed with potassium hydroxide in a mixed solvent of water and ethanol, so that 4 - (Trans-4'-n-alkylcyclohexyl) benzamide is obtained.

Process 2: The 4- (trans-4'-n-alkylcyclohexyl) benzamide mentioned above is dissolved in dewatered methanol in which metallic sodium is dissolved. This solution is then mixed with bromine and heated, so that methyl 4- (trans-4'-n-alkylcyclohexyl) phenyl carbamate is obtained.

Process 3: The above-mentioned methyl 4- (trans-4'-n-alkylcyclohexyl) phenyl carbamate is boiled in 80% ethanol with potassium hydroxide, after which the reaction solution is decomposed so that 4- (trans-4'-n Alkylcyclohexyl) aniline is obtained.

Process 4: The aforementioned 4- (trans-4'-n-alkylcyclohexyl) aniline is mixed with 70% sulfuric acid and reacted with sodium nitrite to form a solution of diazosulfate. This diazo sulfate solution is then hydrolyzed, so that 4- (trans-4'-n-alkylcyclohexyl) phenol is obtained.

Process 5: The above 4- (trans-4'-n-alkylcyclohexyl) phenol and alkyl bromide are condensed using potassium hydroxide in ethanol to give 4-n-alkoxy- (trans-4'-n-alkylcyclohexyl) benzene is obtained.

The compounds according to the invention have a temperature range of the nematic liquid crystal phase of 20-40 ° C. and excellent stability against the external influence of moisture, light, heat and the like. In addition, their viscosity is t | at 20 ° C 10-15 mPa.s, which is much lower than that (25-60 mPa • s) of well-known typical liquid crystal compounds such as those of the biphenyl series, ester series and the like. They thus have the same in liquid crystal display devices and the like the twisted nematic principle excellent effectiveness to achieve higher response speed at low temperature.

In addition, the anisotropy An of the refractive index of the above-mentioned compounds is relatively smaller than that of well-known typical liquid crystal compounds such as those of the biphenyl series, ester series and the like.

A higher display contrast is thus available in phase transition guest / host liquid crystal displays and the like.

In addition, the compounds according to the invention show excellent solubility properties at the time of mixing with other liquid-crystal compounds, since they have a low melting point of 31.5 to 49.0 ° C., low enthalpy AH of the heat of fusion of 16.74-20.93 kJ / mol .

As already mentioned, the compounds according to the invention show excellent properties as liquid crystal display materials which were not known from the prior art.

Thus, a liquid crystal display device with excellent response speed and high display contrast can be obtained by mixing the compounds of the present invention with other well-known liquid crystal compounds which are desired in view of various requirements, and using the obtained liquid crystal mixture.

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50

55

65

Brief description of the drawings

1-15 show IR absorption spectra of each of the compounds of the present invention below.

Figure 1: 4-methoxy- (trans-4'-n-pentylcyclohexyl) benzene

Figure 2: 4-n-Propoxy- (trans-4'-n-pentylcyclohexyl) benzene

Figure 3: 4-n-Butoxy- (trans-4'-n-pentylcyclohexyl) benzene

Fig. 4: 4-n-Pentyloxy- (trans-4'-n-pentylcyclohexyl) benzene

Figure 5: 4-n-Hexyloxy- (trans-4'-n-pentylcyclohexyl) benzene

Figure 6: 4-n-heptyloxy- (trans-4'-n-pentylcyclohexyl) benzene

Figure 7: 4-n-Propoxy- (trans-4'-n-butylcyclohexyl) benzene

Figure 8: 4-n-Butoxy- (trans-4'-n-butylcyclohexyl) benzene

Figure 9: 4-n-Pentyloxy- (trans-4'-n-butylcyclohexyl) benzene

Figure 10: 4-n-Hexyloxy- (trans-4'-n-butylcyclohexyl) benzene

Figure 11: 4-n-HeptyIoxy- (trans-4'-butylcyclohexyl) benzene

651 818

Figure 12: 4-n-Octyloxy- (trans-4'-n-butylcyclohexyl) benzene

Figure 13: 4-n-propoxy- (trans-4'-n-propylcyclohexyl) benzene

Figure 14: 4-n-Butoxy- (trans-4'-n-propylcyclohexyl) benzene

Figure 15: 4-n-Pentyloxy- (trans-4'-n-propylcyclohexyl) benzene

Best way to carry out the invention

4-Methoxy- (trans-4'-n-pentylcyclohexyl) benzene (hereinafter referred to as “Compound No. 1”) is produced by the following reaction process:

Process 1: 25.5 g of commercially available 4- (trans-4'-n-pentylcyclohexyl) benzonitrile and 36 g of potassium hydroxide are dissolved in 750 ml of 70% ethanol and the solution obtained is heated to reflux temperature for 16 h. The crystals formed are then filtered off, washed with water and dehydrated, so that 4- (trans-4'-n-pentylcyclohexyl) benzamide is obtained.

Process 2: 80 g of metallic sodium are dissolved in 3900 ml of dewatered methanol and the solution obtained is cooled to room temperature. Thereafter, 15.2 g of the 4- (trans-4'-n-pentylcyclohexyl) benzamide prepared in process 1 are dissolved in it and 40.5 ml of bromine are added with vigorous stirring. Then the reaction solution is continuously heated for 4 hours. After the reaction, methanol is distilled off. In addition, 3000 ml of water are added to the residue and the precipitate which has separated after mixing is filtered off, washed with water and dehydrated, so that methyl 4- (trans-4'-n-pentylcyclohexyl) phenylcarbamate is obtained.

Process 3: 8.6 g of the methyl 4- (trans-4'-n-pentylcyclohexyl) phenyl carbamate prepared according to process 2 are added to a solution of 250 g of potassium hydroxide in 860 ml of 80% ethanol. The reaction solution is then heated to a reflux temperature with cooling using a condenser which is provided with a nitrogen-containing rubber balloon in the upper part for 24 h. After the reflux treatment, ethanol is distilled off and the residue formed is poured into 300 ml of water. The aqueous solution obtained is extracted with ether. After washing the ether solution several times with water, it is dewatered over sodium sulfate anhydride and ether is distilled off. In addition, the residue obtained is distilled under reduced pressure at bp 150-160 ° C / 2.66 mbar, so that the fraction 4- (trans-4'-n-pentylcyclohexyl) aniline is obtained.

Process 4: 5.7 g of the 4- (trans-4'-n-pentylcyclohexyl) aniline prepared according to process 3 are mixed with 12 ml of concentrated sulfuric acid, mixed with 12 ml of 40% sulfuric acid until a uniform Ge is achieved -mixed and then cooled with ice. On the other hand, a solution of sodium nitrite (2.7 g NaNO 2; 6 ml water) is prepared and added to the above mixture with cooling to obtain a diazosulfate solution. As the diazotization progressed, a 50% sulfuric acid solution was heated to 90 ° C in a water bath, and then the above-mentioned diazosulfate solution was poured in and hydrolyzed after completion of the reaction. After cooling and solidification, the crystals obtained are filtered off, washed with water and dehydrated and then sublimed under reduced pressure (2.66 mbar), giving 4- (trans-4'-pentylcyclo-hexyl) phenol.

Process 5: 1.0 g of the 4- (trans-4'-n-pentylcyclohexyl) phenol prepared according to process 4 and 0.25 g of potassium hydroxide are dissolved in 10 ml of ethanol. Then 0.5 g of methyl bromide is added to this solution and the reaction solution is heated to reflux temperature for 6 h. After the reaction, ethanol is distilled off and the potassium bromide formed is dissolved by adding 20 ml of water, after which the product is extracted with ether. 15 The ether solution is cleaned three times each with 10% sodium hydroxide solution and water and then dehydrated over sodium sulfate anhydride, after which ether is distilled off. In addition, the residue formed is recrystallized from ethanol, so that the above 20 compound No. 1 is obtained.

In a similar manner, compounds No. 2-6 are prepared by reacting propyl bromide, butyl bromide, pentyl bromide, hexyl bromide or heptyl bromide instead of methyl bromide in process 5 above with 4- (trans-4'-n- prepared according to process 4). Pentylcyclohexyl) phenol. Compounds No. 2-6 obtained are: No. 2: 4-n-propoxy- (trans-4'-n-pentylcyclohexyl) -benzene No. 3: 4-n-butoxy- (trans-4'-n- pentylcyclohexyl) benzene No. 4: 4-n-pentyloxy- (trans-4'-n-pentylcyclohexyl) -benzene 30 No. 5: 4-n-hexyloxy- (trans-4'-n-pentylcyclohexyl) -benzene No. 6: 4-n-Heptyloxy- (trans-4'-n-pentylcyclohexyl) -benzene In addition, using commercially available 4- (trans-4'-n-butylcyclohexyl) -benzonitrile as a starting material in a similar manner after the process 4 produced 4- (trans-4'-n-butylcyclohexyl) phenol in process 5 with propyl bromide, butyl bromide, pentyl bromide, hexyl bromide, heptyl bromide or octyl bromide. The following compounds No. 7-12 are obtained: 40 No. 7: 4-n-propoxy- (trans-4'-n-butylcyclohexyl) -benzene No. 8: 4-n-butoxy- (trans-4 '-n-butylcyclohexyl) -benzene No. 9: 4-n-pentyloxy- (trans-4'-n-butylcyclohexyl) -benzene No. 10: 4-n-hexyloxy- (trans-4'-n-butylcyclohexyl) -benzene no. 11: 4-n-heptyloxy- (trans-4 / -n-butylcyclohexyl) -benzene 45 no. 12: 4-n-octyloxy- (trans-4'-n-butylcyclohexyl) -benzene Use of commercially available 4- (trans-4'-n-propylcyclohexyl) benzonitrile as a starting material in a similar manner in process 4 produced 4- (trans-4'-n-propylcyclohexyl) phenol in process 5 with so propyl bromide, butyl bromide or pentyl bromide reacted. The following compounds No. 13-15 are obtained:

No. 13: 4-n-propoxy- (trans-4'-n-propylcyclohexyl) -benzene No. 14: 4-n-butoxy- (trans-4'-n-propylcyclohexyl) -benzene 55 No. 15: 4 -n-Pentyloxy- (trans-4'-n-propylcyclohexyl) -benzene Table 1 shows the transition points of compounds Nos. 1-15, where C is a crystalline phase, N is a nematic phase, Sm is a smectic phase and I is a mean isotropic liquid phase.

Table 1

No.

connection

Transition point ,: C

1 n-C5 H ,, O CH3

2 n-CsH ,, OC, Mr.

(C- »I) 38 (I <= * N) 31 (C-> I) 35 (I <± N) 30

651 818

14

15

Table 1 (continued)

No. Connection transition point, ° C

3 n-C5 HX1 O C4 Hrn (C- »I) 45.5 (feN) 45

4 n-CsH "-®-0-OCsHu-n (C- * N) 33.5 (Ini) 37.5

5 n-C, H "OC6H12-n (C ^) 37 (fei) 44

OC7H15-n (C-> I) 45 (feSm) 44

7 n-C4 H9 O C3 H7-n (C-> I) 45

8 n-C4 H9 0C4Hrn (C-> I) 40 (feN) 29

9 n-C4 H9 OCs brain (C-> I) 33 (feSn) 28

10 n-C4 H9 OC6H15-n (C-N) 31.5 (I? ± I) 33

11 n-C4 H „-®-0- OC7H15-n (C-> I) 38 (I? ± Sm) 36

12 n-C4 H9 - ® - 0 - O C8 H17-n (C- »I) 42 (feSm) 39

13 n-C2 H7 O C3 H7-n (C- »I) 49 n-C2 H7 - ^ - © - O C4 Hg-n (C-> I) 34.5 (I? ± N) 32.5

n-C, H, O C5 H „-n (C-> I) 34 (I? ± N) 28

[Embodiment 1] The liquid crystal mixture obtained in each case is referred to as “mixture B”, “mixture C” or “mixture D”. A liquid crystal mixture (hereinafter referred to as “mixture according to the above-mentioned mixtures A, B, CA”) consists of 13.5% by weight of trans-4-n-propylcy-6o or D, each sealing in an 8 | im -Thick liquid crystal display-clohexane-carboxylic acid-P-ethoxyphenyl ester, 32% by weight ge cell, the vertical alignment of which had been carried out by treatment with trans-4-n-propylcyclohexane-carboxylic acid-Pn-butoxy a Cr complex. Thereafter, phenyl ester, 26.5% by weight trans-4-n-butylcyclohexane under the measurement conditions below, the anisocarboxylic acid P-ethoxyphenyl ester and 28% by weight trans-4-n-tropie An of the refractive index, the dielectric anisotro-pentylcyclohexane-carboxylic acid P-methoxyphenyl ester is made 65 pie As, the operating voltages Vth and Vsat as well as the An and this mixture designated A are speaking speeds xein and x from the mentioned Gemi-20 wt.%, 40 wt.% and 60 respectively % By weight according to the invention see A, B, C and D, respectively. The results obtained are added to 4-n-butoxy- (trans-4'-n-propylcyclohexyl) benzene. summarized in Table 2.

651 818

6

Measurement conditions: On: 589 nm, 20 C

Ae: 1 kHz, 20 C.

Vth, Vsat: 32 Hz, 20 "C xon, xout: 32 Hz, Vsat operation, 20 ° C

Table 2

Mixture A Mixture B

Mixture C

Mixture D

At

0.099

0.107

0.097

0.095

Ae

-1.30

-1.10

-0.87

-0.62

V th (V)

3.8

3.9

4.2

4.7

Vsat (V)

6.2

7.5

8.0

8.7

in (ms)

280

110

185

130

thousand (ms)

110

90

90

85

Embodiment 2

The above-mentioned mixture A is 20% by weight, 40% by weight and 60% by weight according to the invention

4-n-Butoxy- (trans-4'-n-butylcyclohexyl) benzene is added, giving liquid-crystal mixtures which are referred to as “mixture E”, “mixture F” or “mixture G”. With these liquid crystal mixtures obtained, liquid crystal display cells of the same type are produced and the same measured values are determined on them under the same conditions as described above in embodiment 1. The results obtained are summarized in Table 3.

Table 3

Mixture A Mixture B Mixture C Mixture D

At

0.099

0.098

0.097

0.096

As

-1.30

-1.00

-0.87

-0.65

Vth (V)

3.7

3.9

4.1

4.5

Vsat (V)

6.1

7.4

8.0

8.6

xein (ms)

280

220

180

135

xout (ms)

110

95

90

85

5

10th

15

20th

25th

30th

35

40

45

50

55

60

65

S

15 sheets of drawings

Claims (5)

651 818 PATENT CLAIMS 1.4-n-alkoxy- (trans-4'-n-alkyl-cyclohexyl) benzenes of the formula r1 ® © 0r2 wherein Rj denotes straight-chain alkyl with 3-5 C atoms, and R2 denotes straight-chain alkyl with 1 or 3-8 C atoms. 2. Compounds according to claim I, characterized in that R is straight-chain alkyl having 3 C atoms, and R2 is straight-chain alkyl having 3-5 C atoms. 3. Compounds according to claim 1, characterized in that Rj straight-chain alkyl having 4 carbon atoms, and R2 straight-chain alkyl having .3-8 carbon atoms. 4. Compounds according to claim 1, characterized in that R, straight-chain alkyl with 5 carbon atoms, and R2 represent straight-chain alkyl having 1 or 3-7 carbon atoms.