JPH0223596B2 - - Google Patents

Description

[Detailed description of the invention]

The present invention relates to a liquid crystal composition containing a phenylpyrimidine derivative. In recent years, a large number of products using liquid crystal displays, such as wristwatches and calculators, have been on sale, and liquid crystal displays are becoming more and more developed. The advantages of liquid crystal displays over other display elements, such as low power consumption and low voltage drive, remain problems that must be improved in the future, and the stability of liquid crystals remains a problem. In other words, the lifespan of liquid crystal displays must also be improved. In general, the liquid crystal of liquid crystal displays used in watches, calculators, etc. is a nematic liquid crystal that exhibits positive dielectric anisotropy (hereinafter abbreviated as _Np liquid crystal), and _Np liquid crystal is used in watches, calculators, etc. It is made of a composition that is a mixture of several types of liquid crystal compounds in order to ensure the operating temperature. On the other hand, it is known that the driving voltage of a liquid crystal display depends on the dielectric anisotropy (Δε) of the liquid crystal composition and is inversely proportional to the square root of Δε. dielectric anisotropy must be increased. One method is to mix a liquid crystal compound exhibiting positive dielectric anisotropy into a liquid crystal composition, and the other is to mix a liquid crystal compound exhibiting positive dielectric anisotropy into a liquid crystal composition exhibiting negative dielectric anisotropy. There are a method of mixing and a method of mixing a non-liquid crystal compound that imparts positive dielectric anisotropy to the liquid crystal composition. In either method, a liquid crystal composition exhibiting large positive dielectric anisotropy is required, and the liquid crystal composition must of course be stable. Hitherto, a stable liquid crystalline composition that exhibits such a large positive dielectric anisotropy has not been discovered. For example, for liquid crystalline compounds with large dielectric anisotropy, the general formula is

There is a composition containing a compound represented by the formula (R represents a straight-chain alkyl). However, this composition has the disadvantage that there is a risk of decomposition such as hydrolysis, and there is an upper limit to the amount that can be mixed into the composition, and that it cannot be mixed very much. On the other hand, as a stable liquid crystal compound with positive dielectric anisotropy, the general formula is

There is a biphenyl liquid crystal composition containing the formula: (R' represents a straight-chain alkyl group or a straight-chain alkoxy group). However, since this liquid crystal has a small dielectric anisotropy, there is a drawback that the driving voltage cannot be lowered even if a large amount is mixed. An object of the present invention is to provide a stable liquid crystal composition with large dielectric anisotropy. That is, the liquid crystal composition of the present invention has the general formula:

[Formula] A compound represented by

[Formula] or

[Formula] or

It is characterized by the addition of one of the components in the formula. (however
R ₁ is a linear alkyl group having 3, 4, or 5 carbon atoms, R ₂
represents an alkyl group having 1 or 2 carbon atoms or a straight-chain alkyl group having 4 carbon atoms. ) Below, 2- used in the liquid crystal composition of the present invention will be described.
A method for synthesizing (4-cyanophenyl)-5-n-alkylpyridine is shown. (However, R represents a straight-chain alkyl group having 2 to 4 carbon atoms.) Although the compound synthesized by the above reaction formula does not exhibit a liquid crystal phase, by mixing this compound into a liquid crystal composition, dielectric anisotropy can be achieved. A liquid crystal composition with high properties can be obtained. In general, compounds with positive dielectric anisotropy are more unstable than compounds with negative dielectric anisotropy, so it is not preferable to add them in large amounts to liquid crystal compositions due to aging problems. Therefore, the additive that imparts dielectric anisotropy must have as large a dielectric anisotropy as possible. In general, as has been revealed in Schiff-type liquid crystals, the shorter the length of the alkyl group in the molecule, the greater the dielectric anisotropy, which is more suitable for meeting the above requirements. In the composition of the present invention, the dielectric anisotropy becomes extremely large due to the addition of short alkyl groups. Therefore, by adding only a small amount to the liquid crystal composition, the dielectric anisotropy of the liquid crystal composition can be increased and the driving voltage can be lowered. Also, there are no problems with stability. Next, as a substance used in the liquid crystal composition of the present invention, 2
The method for producing -(4-cyanophenyl)-5-n-alkylpyrimidine will be explained in detail. Commercially available P-cyanobenzoic acid was reacted with ethanol in the presence of sulfuric acid to form ethyl P-cyanobenzoate. This ethyl P-cyanobenzoate and hydrochloric acid gas are reacted in ethanol to synthesize 4-ethoxycarbonylbenziminoether hydrochloride, which is then reacted with ammonia gas in ethanol to synthesize 4-ethoxycarbonylbenzamidine hydrochloride. Synthesized salt. On the other hand, commercially available diethyl malonate was reacted with an alkyl bromide in sodium ethoxide to give n-alkyl diethyl malonate. Subsequently, the above 4-ethoxycarbonylbenzamidine hydrochloride and diethyl n-alkylmalonate were reacted in methanol in the presence of sodium methoxide to form 2-(4-methoxycarbonylphenyl)- 4,6-dihydroxy-5-n-
2-(4-methoxycarbonylphenyl)-4,6-dichloro-5-n-alkylpyrimidine was synthesized by reacting the alkylpyrimidine with phosphorus oxychloride. Subsequently, 2-(4-methoxycarbonylphenyl)-4,6-dichloro-5-n-alkylpyrimidine was reacted with hydrogen gas in the presence of magnesium oxide and palladium carbon in a mixed solvent of ethanol and water. and dehalogenated to 2-(4-
methoxycarbonylphenyl)-5-n-alkylpyrimidine. This 2-(4-methoxycarbonylphenyl)
-5-N alkylpyrimidine is hydrolyzed with thorium hydroxide in a mixed solvent of ethanol and water,
P-(5-n-alkyl-2-pyrimidyl)benzoic acid chloride was obtained, and P-(5-n-alkyl-2-pyrimidyl)benzoic acid amide was obtained by reacting this with ammonia in dioxane. Subsequently, P-(5-n-alkyl-2-pyrimidyl)benzoic acid amide is dehydrated with phosphorus oxychloride to obtain the final target product, 2-(4-cyanophenyl)-5-n-alkylpyrimidine. Can be done. 2- used in the liquid crystal composition of the present invention below.
A production example of (4-cyanophenyl)-5-n-alkylpyrimidine will be shown in detail, and the physical properties of each substance will be shown. Production example 1 [2-(4-cyanophenyl)-5-
Synthesis of n-propylpyrimidine] Commercially available P-cyanobenzoic acid 200g (1.36mol)
was dissolved in 1000 ml of ethanol, 10 ml of concentrated sulfuric acid was added thereto, and the mixture was refluxed under stirring for 18 hours. Subsequently, ethanol was distilled off, and the residue was dissolved in ether, washed with a saturated aqueous sodium carbonate solution and water, and then dried over anhydrous sodium sulfate. Next, the ether was distilled off, the residue was recrystallized from ethanol, and the obtained crystals were dried in vacuum. Now, ethyl P-cyanobenzoate is
194.7g (1.11mol) was obtained, with a yield of 81.8%. The infrared absorption spectrum of this product is shown in FIG. Next, the obtained ethyl P-cyanobenzoate
194.7 g was dissolved in 800 ml of ethanol, and hydrochloric acid gas was passed through the solution while stirring under ice cooling until the reaction mixture solidified white. After standing for one day, the reaction mixture was filtered to obtain 4-ethoxycarbonylbenziminoether hydrochloride. Add 600 ml of ethanol to the iminoether hydrochloride, add 1000 ml of ammonium ethanol solution at room temperature, and pass ammonia gas into the reaction mixture for 1 hour at room temperature.
I left it for a day. After the reaction mixture was filtered to remove ammonium chloride, ethanol was distilled off, and the precipitated 4-ethoxycarbonylbenzamidine hydrochloride was filtered. The resulting amidine hydrochloride was dried in vacuo and dried over phosphorus pentoxide. This gives 149.97g of 4-ethoxycarbonylbenzamidine hydrochloride.
(0.67 mol) was obtained, and the yield was 59.1%. Moreover, the infrared absorption spectrum of this amidine hydrochloride is shown in FIG. Meanwhile, add 18.4 g of sodium metal to 400 ml of dry ethanol that has been dried over sodium metal.
(0.8 mol) was added to form sodium ethoxide, and then 128 g (0.8 mol) of diethyl malonate and 98.4 g (0.8 mol) of propyl bromide were added dropwise with stirring and the mixture was refluxed with stirring for 7 hours. Thereafter, ethanol was distilled off, water was added to the residue, and the mixture was extracted with ether. The ether layer was washed with water and dried over sodium sulfate. Subsequently, the ether was distilled off and the residue was distilled under reduced pressure. Then, it was distilled under reduced pressure again for purification. b _p 60-62℃/2mmHg The obtained diethyl n-propylmalonate is
The yield was 66% at 106.6g. Moreover, this infrared absorption spectrum is shown in FIG. Next, 20.05 g of sodium metal was added to 580 ml of dry methanol dried over sodium metal to form sodium methoxide, and then 57.6 g of diethyl propylmalonate and 66.6 g of 4-ethoxycarbonylbenzamidine hydrochloride were added with stirring. The mixture was refluxed under stirring for 8 hours. After standing overnight, 500 ml of hydrochloric acid (36%) was added to the reaction mixture, the resulting white precipitate was filtered, and the resulting crystals were washed successively with water, ethanol, and ether, and dried under vacuum. 2-(4-methoxycarbonylphenyl)-4,6-dihydroxy-5-n
-Propylpyrimidine was obtained in an amount of 81.7g with a yield of 93.3.
It was %. Moreover, this infrared absorption spectrum is shown in FIG. Subsequently, the obtained 2-(4-methoxycarbonylphenyl)-4,6-dihydroxy-5-n-
81.7g (0.27mol) of propylpyrimidine, N,
79ml of N-diethylaniline and phosphorus oxychloride
540 ml was added and refluxed for 30-40 hours. Next, phosphorus oxychloride is distilled off, and the residue is dissolved in sodium hydroxide.
A 10% aqueous solution 2 was added and extracted with ether. The ether layer was washed with 18% hydrochloric acid and water, dried over anhydrous sodium sulfate, the ether was distilled off, and the residue was recrystallized from ethanol and dried under vacuum. The resulting 2-(4-methoxycarbonylphenyl)
The amount of -4,6-dichloro-5-n-propylpyrimidine was 68.9g, and the yield was 75.3%. This infrared absorption spectrum is shown in FIG. Next, 34.8 g of magnesium oxide was added to 68.9 g of the obtained 2-(4-methoxycarbonylphenyl)-4,6-dichloro-5-n-propylpyrimidine.
g, 11.6 g of palladium carbon (5%), 840 ml of ethanol, and 63 ml of water were added, and hydrogen gas was absorbed at 60° C. until it was saturated. Subsequently, the reaction mixture was filtered and the filtrate was added to a Soxhlet extractor;
Extracted with ethanol. The ethanol solution extracted with Soxhlet and the previous filtrate were mixed, the ethanol was distilled off, and the residue was recrystallized with ethanol. 2
-(4-methoxycarbonylphenyl)-5-n
-35.2g of propylpyrimidine was obtained, and the yield was
It was 65.5%. This infrared absorption spectrum is shown in FIG. Next, 65.4 g of sodium hydroxide was dissolved in 429 ml of water, 87 ml of ethanol was added, and the obtained 2-(4-methoxycarbonylphenyl)-5-
After adding 35.2 g of n-propylpyrimidine and refluxing for 3 hours, the mixture was cooled to room temperature, and 350 ml of 36% hydrochloric acid was added to the reaction mixture. The white precipitate thus separated was filtered, washed with water, and dried under vacuum. I got this P-
The amount of (5-n-propyl-2-pyrimidyl)benzoic acid was 31.9 g, and the yield was 95.5%. This infrared absorption spectrum is shown in FIG. Next, the obtained P-(5-n-propyl-2-
(pyrimidyl) benzoic acid 31.9g to thionyl chloride 215
After refluxing for 4 hours, thionyl chloride was distilled off. To remove the thionyl chloride that could not be completely distilled off, toluene was added to the residue to dissolve it, and the toluene was distilled off together with the remaining thionyl chloride. This residue, P-(5-n-propyl-2-pyrimidyl)benzoic acid chloride, was dissolved in 420 ml of dioxane, and 400 ml of an ammonia dioxane solution was added under stirring at room temperature. Furthermore, ammonia gas was passed through the reaction mixture. . Dioxane was distilled off from the reaction mixture, 18.4 ml of water was added to the residue and stirred, and the white precipitate was filtered and washed well with water. The obtained crystals were dried in vacuum to obtain 31.3 g of P-(5-n-propyl-2-pyrimidyl)benzoic acid amide. The yield is
It was 98.4%. This infrared spectrum is shown in FIG. Subsequently, the obtained P-(5-n-propyl-2
300 ml of phosphorus oxychloride was added to 31.3 g of -pyrimidyl)benzoic acid amide, and after refluxing for 3 hours, the phosphorus oxychloride was distilled off. Water was added to the residue and the precipitate was filtered. This filtrate was recrystallized from ethanol and dried under vacuum. The final target product, 2-(4-cyanophenyl)-5-n-propylpyrimidine, is 20.8
g was obtained, with a yield of 71.7%. This infrared spectrum is shown in FIG. Furthermore, measurement of H'-NMR spectrum confirmed that this product was 2-(4-dianophenyl)-5-n-propylpyrimidine. Furthermore, as a result of mass spectrometry, fragments 194 and 223 were detected and could be confirmed. 2-(4-cyanophenyl)
-5-n-propylpyrimidine has a mp of 124.5℃, and a differential calorimeter shows that ΔH is 8.8KCal/
It is mol. Production example 2 [2-(4-cyanophenyl]-5-
Synthesis of n-butylpyrimidine] The synthesis of 2-(4-cyanophenyl]-5-n-butylpyrimidine was carried out in the same manner as in Production Example 1. Sodium metal was added to 200 ml of dry ethanol that had been dried over sodium metal. After adding 9.2 g to make sodium methoxide, 64.3 g of diethyl malonate and 54.8 g of butyl bromide were added dropwise with stirring and refluxed for 7 hours with stirring.Then, ethanol was distilled off, water was added to the residue, After extraction with ether, the ether layer was washed with water and dried over sodium sulfate.Then, the ether was distilled off and purified by distillation under reduced pressure. b _p 55°C/0.5mmHg 49.3g of diethyl n-butylmalonate was obtained. ,
The yield was 57%. This infrared absorption spectrum is shown in FIG. Next, add sodium metal to 120ml of dry methanol.
After adding 4.6g to make sodium methoxide,
Furthermore, diethyl n-butylmalonate and Production Example 1
After adding 13.9 g of 4-ethoxycarbonylbenzamidine hydrochloride synthesized in step 1 and refluxing for 8 hours, the same operation as in Production Example 1 was performed to obtain 2-(4-methoxycarbonylphenyl)-4,6-dihydroxy-5.
13.05g of -n-butylpyrimidine was obtained, with a yield of 68.8%. This infrared absorption spectrum is shown in FIG. Subsequently, in the same manner as in Production Example 1, 13.05 g of 2-(4-methoxycarbonylphenyl)-4,6-dihydroxy-5-n-butylpyrimidine and 82 ml of phosphorus oxychloride were added to N,N-diethylaniline 12
7.65 g of 2-(4-methoxycarbonylphenyl)-4,6-dichloro-5-n-propylpyrimidine was obtained from the reaction in 52.9% yield. This infrared absorption spectrum is shown in FIG. Next, in the same manner as in Production Example 1, 2-(4-methoxycarbonylphenyl)-4,6-dichloro-5-n-
When 7.65 g of butylpyrimidine is reacted with hydrogen gas in the presence of 3.66 g of magnesium oxide and 0.61 g of palladium carbon (5%) in a mixed solvent of ethanol and water, 2-(4-methoxycarbonylphenyl)-5- 1.62 g of butylpyrimidine was obtained, with a yield of 26%. This infrared absorption spectrum is shown in FIG. Next, when 1.62 g of 2-(4-methoxycarbonylphenyl)-5-n-butylpyrimidine was hydrolyzed with sodium hydroxide in a mixed solvent of water and ethanol, P-(5-n-butyl-2- 1.46 g of (pyrimidyl)benzoic acid was obtained, with a yield of 100%. This infrared spectrum is shown in FIG. Subsequently, 1.46 g of P-(5-n-butyl-2-pyrimidyl)benzoic acid was converted into acid chloride with 10 ml of thionyl chloride, and this was reacted with ammonia in dioxane to form P-(5-n-butyl-2-pyrimidyl)benzoic acid. 1.34g of benzoic acid amide (pyrimidyl) was obtained, and the yield was
It was 92.5%. This infrared absorption spectrum is shown in FIG. Next, 1.34 g of P-(5-n-butyl-2-pyrimidyl)benzoic acid amide was added to 20 g of phosphorus oxychloride.
ml, and perform a dehydration reaction in the same manner as in Production Example 1 to obtain the desired product, 2-(4-cyanophenyl)-5-.
0.13g of n-butylpyrimidine was obtained, and the yield was
It was 10.2%. This infrared spectrum is the 16th
As shown in the figure. In addition, H'-NMR spectroscopy revealed that this product was 2-(4-cyanophenyl)-
It was confirmed that it was 5-n-butylpyrimidine. mp60-61℃. Production example 3 [2-(4-cyanophenyl)-5-
Synthesis of Ethylpyrimidine] 2-(4-cyanophenyl)-5-ethylpyrimidine was synthesized in the same manner as in Production Examples 1 and 2. 14.5 g of sodium metal in 420 ml of dry methanol
was added to obtain sodium methoxide, and then 39.5 g of diethyl ethylmalonate synthesized in the same manner as in Examples 1 and 2 and 4 synthesized in Production Example 1.
-Ethoxycarbonylbenzamidine hydrochloride 48.0
g was added and refluxed for 8 hours. The same operation as in Production Example 1 was performed to obtain 46.1 g of 2-(4-methoxycarbonylphenyl)-4,6-dihydroxy-5-ethylpyrimidine, with a yield of 76.2%. It was hot. This infrared absorption spectrum is shown in FIG. Subsequently, in the same manner as in Production Examples 1 and 2, 46.1 g of 2-(4-methoxycarbonylphenyl)-4,6-dihydroxy-5-ethylpyrimidine and 320 ml of phosphorus oxychloride were added to 46.8 ml of N,N-diethylaniline.
The reaction therein yielded 31.5 g of 2-(4-methoxycarbonylphenyl)-4,6-dichloro-5-ethylpyrimidine, with a yield of 58.1%.
This infrared absorption spectrum is shown in FIG. Next, in the same manner as in Production Examples 1 and 2, 2-(4-methoxycarbonylphenyl)-4,6-dichloro-
When 31.5 g of 5-ethylpyrimidine is reacted with hydrogen gas in the presence of 15.4 g of magnesium oxide and 5.1 g of palladium carbon (5 g) in a mixed solvent of ethanol and water, 2-(4-methoxycarbonylphenyl)-5-ethyl is produced. 20.8 g of pyrimidine was obtained, with a yield of 92.5%. This infrared absorption spectrum is shown in FIG. Next, 20.8 g of 2-(4-methoxycarbonylphenyl)-5-ethylpyrimidine was hydrolyzed with sodium hydroxide in a mixed solvent of water and ethanol, resulting in P-(5-ethyl-2-pyrimidyl)benzoic acid. 16.9g of was obtained, and the yield was 86.0%.
This infrared absorption spectrum is shown in FIG. Then, P-(5-ethyl-2-pyrimidyl)
16.9 g of benzoic acid was converted into acid chloride with 119 ml of thionyl chloride, and this was reacted with ammonia in dioxane to obtain P-(5-ethyl-2-pyrimidyl)benzoic acid amide. This infrared absorption spectrum is shown in FIG. Next, P-(5-ethyl-2-pyrimidyl)benzoic acid amide was dehydrated with 38 ml of phosphorus oxychloride in the same manner as in Production Examples 1 and 2, resulting in the desired product, 2-(4-cyanophenyl). 15.2 g of )-5-ethylpyrimidine was obtained, with a yield of 98.3%. This infrared spectrum is shown in FIG.
Further, measurement of H'-NMR spectrum confirmed that this product was 2-(4-cyanophenyl)-5-ethylpyrimidine. m _p is 147℃. Using a differential calorimeter, ΔH is 7.6KCal/
It is mol. Example 1 The compound synthesized in Production Example 1 was prepared as a liquid crystal composition shown in Table 1, filled into a liquid crystal cell for a twisted nematic display, and its contrast characteristics were measured. The liquid crystal compositions shown in Table 1 are liquid crystal compositions with negative dielectric anisotropy in which the compound 2-
It is a mixture of (4-cyanophenyl)-5-n-propylpyrimidine.

[Table] Figure 23 shows the contrast characteristics at 25°C of a liquid crystal cell (cell thickness: 9 μm) filled with the liquid crystal composition shown in Table 1. In the figure, the horizontal axis shows the applied voltage, and the vertical axis shows the light transmittance. Vth (light transmittance 90%
The voltage when the light transmittance is 10%) was 4.15V, and the Vsat (voltage when the light transmittance was 10%) was 5.75V. In Table 1, 2
Since liquid crystal compositions other than -(4-cyanophenyl)-5-n-propylpyrimidine have negative dielectric anisotropy, liquid crystal compositions containing no such compounds are filled into liquid crystal cells for twisted nematic displays. However, by adding only 5% of 2-(4-cyanophenyl)-5-n-propylpyrimidine to this liquid crystal composition, the dielectric anisotropy of the liquid crystal composition becomes positive and the liquid crystal cell does not operate at 6V. It becomes possible to drive. Example 2 In order to confirm the degree of dielectric anisotropy imparting effect of the compound synthesized in Production Example 2, the liquid crystal composition shown in Table 2 was prepared in the same manner as in Example 1, and a liquid crystal cell for twisted nematic display was prepared. The contrast characteristics were measured. This contrast characteristic is expressed as
As shown in the figure. In the figure, the horizontal axis shows the applied voltage, and the vertical axis shows the light transmittance. Vth (voltage at 90% light transmittance) was 4.88V, and Vsat (voltage at 10% light transmittance) was 6.86V.

【table】

【table】

[Table] As mentioned above, in Table 2, liquid crystal compositions other than 2-(4-cyanophenyl)-5-n-butylpyrimidine have negative dielectric anisotropy, so liquid crystal compositions containing no such compounds have negative dielectric anisotropy. Even if it is filled into a liquid crystal cell for a twisted nematic display, it will not work, but by adding just 5% of the above compound to this liquid crystal composition, the dielectric anisotropy of the liquid crystal composition becomes positive, and 7V
It becomes possible to drive with. Example 3 In order to confirm the degree of dielectric anisotropy imparting effect of the compound synthesized in Production Example 3, the liquid crystal composition shown in Table 3 was prepared in the same manner as in Examples 1 and 2, and a liquid crystal for twisted nematic display was prepared. It was filled into a cell and its contrast characteristics were measured. This contrast characteristic is shown in FIG. In the figure, the horizontal axis shows the applied voltage, and the vertical axis shows the light transmittance. Vth (light transmittance 90%
The voltage when the light transmittance was 10%) was 4.29V, and the Vsat (voltage when the light transmittance was 10%) was 5.93V. As previously mentioned,
In Table 3, since the liquid crystal compositions other than the compound 2-(4-cyanophenyl)-5-n-ethylpyrimidine have negative dielectric anisotropy, liquid crystal compositions not containing the compound are used for twisted nematic displays. However, by adding just 5% of the compound to this liquid crystal composition, the dielectric anisotropy of the liquid crystal composition becomes positive and it becomes possible to drive at 6V. As described above in Examples 1 to 3, all of the liquid crystal compositions of the present invention have positive dielectric anisotropy and are excellent as liquid crystal compositions. For reference, 2-(4-cyanophenyl)-5
A comparison will be made between the liquid crystal composition of the present invention and a liquid crystal composition in which a compound in which an alkyl group is longer than that of the compound used in the liquid crystal composition of the present invention is added to n-alkylpyrimidine. As shown in Table 4, similar to Examples 1 to 3,
A liquid crystal composition was prepared by mixing 2-(4-cyanophenyl)-5-n-heptylpyrimidine having a long alkyl group with a liquid crystal composition having negative dielectric anisotropy.

[Table] This liquid crystal composition was filled into a liquid crystal cell for a twisted nematic display, and the contrast characteristics were measured and the results are shown in FIG. In the figure, the horizontal axis shows the applied voltage, and the vertical axis shows the light transmittance. Vth
(voltage at 90% light transmittance) was 5.84V, and Vsat (voltage at 10% light transmittance) was 8.05V. this
The values of Vth and Vsat were higher than those of any of the liquid crystal compositions of the present invention (Examples 1 to 3), indicating that the liquid crystal composition of the present invention can be driven at low voltage. That is, it was found that the liquid crystal composition of the present invention in which phenylpyrimidine with a short alkyl group was added had a greater dielectric anisotropy imparting effect than the phenylpyrimidine compound with a long alkyl group. As described above, according to the present invention, the general formula having a predetermined alkyl group is

Represented by [formula] A compound that

【formula】

[Formula] or

It is very stable when mixed with a non-liquid crystal compound with a short alkyl group of [Formula], and as can be seen from the results of measuring and comparing Vth and Vsat, the present invention In example 1, Vth is a little over 4V,
Vsat is a little less than 6V, Vth is a little less than 5V in Example 2, and Vsat is a little less than 6V.
In Example 3, Vth is a little over 4V and Vsat is a little under 6V, and when a phenylpyrimidine compound with a long alkyl group is added, the Vth is 6.84V and the Vsat is 8.05V.
It is possible to provide a liquid crystal composition with positive dielectric anisotropy that can be driven at a voltage 1 to 2 V lower than that of the liquid crystal composition. Furthermore, since the base liquid crystal is made of the same material, it can be manufactured at low cost, and the liquid crystal composition of the present invention can be provided at low cost.

[Brief explanation of drawings]

1 to 22 are diagrams showing infrared absorption spectra of the following compounds, respectively. Figure 1: Ethyl P-cyanobenzoate (nujiol method), Figure 2:
Ethoxycarbonylbenzamidine hydrochloride (Nudiyol method), Figure 3: Diethyl n-propylmalonate (Nudiyol method), Figure 4: 2-(4-methoxycarbonylphenyl)-4,6-dihydroxy-5-n -Propylpyrimidine (Nujiol method), Figure 5: 2-(4-methoxycarbonylphenyl)-4,6-dichloro-5-n-propylpyrimidine (Nujiol method), Figure 6: 2-(4
-Methoxycarbonylphenyl)-5-n-propylpyrimidine (nujiol method), Figure 7: P-
(5-n-propyl-2-pyrimidyl)benzoic acid (Nujiol method), Figure 8: P-(5-n-propyl-2-pyrimidyl)benzoic acid amide (Nujiol method), Figure 9: 2-( 4-cyanophenyl)-
5-n-propylpyrimidine (nujiol method),
Figure 10: Diethyl n-butylmalonate (nujiol method) Figure 11: 2-(4-methoxycarbonylphenyl)-4,6-dihydroxy-5-n
Butylpyrimidine (nujiol method), Figure 12:
2-(4-methoxycarbonylphenyl)-4,
6-dichloro-5-n-butylpyrimidine (Nujiol method), Figure 13: 2-(4-methoxycarbonylphenyl)-5-n-butylpyrimidine (Nujiol method), Figure 14: P-(5-n -butyl-2-pyrimidyl) benzoic acid (nujiol method),
Figure 15: P-(5-n-butyl-2-pyrimidyl)benzoic acid amide (Nujiol method), No. 16
Figure: 2-(4-cyanophenyl)-5-n-butylpyrimidine (KBr method), Figure 17: 2-(4-
methoxycarbonylphenyl)-4,6-dihydroxy-5-ethylpyrimidine (Nujiol method),
Figure 18: 2-(4-methoxycarbonylphenyl)-4,6-dichloro-5-ethylpyrimidine (nujiol method), Figure 19: 2-(4-methoxycarbonylphenyl)-5-ethylpyrimidine ( KBr method), Figure 20: P-(5-ethyl-2-
pyrimidyl) benzoic acid (nujiol method), No. 21
Figure: P-(5-ethyl-2-pyrimidyl)benzoic acid amide (KBr method), Figure 22: 2-(4-cyanophenyl)-5-ethylpyrimidine (KBr method).
23 to 25 are contrast characteristic diagrams measured by filling a twisted nematic type liquid crystal cell with the liquid crystal composition of the present invention.
2-(4-cyanophenyl)-5-n-propylpyrimidine, Figure 24: 2-(4-cyanophenyl)-5-n-butylpyrimidine, Figure 25: 2
-(4-cyanophenyl)-5-n-ethylpyrimidine, Figure 26 shows a liquid crystal composition in which a conventional liquid crystal composition mixed with 2-(4-cyanophenyl)-5-n-heptylpyrimidine is filled into a twisted nematic liquid crystal cell. FIG.

Claims (1)

[Scope of Claims] 1. A liquid crystal composition characterized in that a compound represented by the general formula [Formula] is added with any component of [Formula], [Formula], or [Formula]. (However, R ₁ represents a straight-chain alkyl group with 3, 4, or 5 carbon atoms, and R ₂ represents an alkyl group with 1 or 2 carbon atoms or a straight-chain alkyl group with 4 carbon atoms.)