JPH0250890B2 - - Google Patents

Description

[Detailed description of the invention]

The present invention relates to a novel colorless liquid crystal substance, a liquid crystal composition containing the colorless liquid crystal substance, and a liquid crystal display element having the liquid crystal composition as a liquid crystal layer. In this specification, a colorless liquid crystal substance means a liquid crystal substance that does not absorb visible light. Further, the liquid crystalline substance includes a substance that does not exhibit a liquid crystal layer by itself at room temperature but is useful as a compounding component of a liquid crystal composition. In order to obtain a liquid crystal display element with excellent response characteristics not only at room temperature but also in low-temperature environments, it is necessary to extend the liquid crystal temperature range to the low-temperature region. This becomes possible if the viscosity of the liquid crystal composition is reduced. Typical conventional liquid crystalline substances (m, n are integers) has a high viscosity for the above purpose. On the other hand, compounds with similar general formula

[Formula] has a low viscosity but does not exhibit a liquid crystal phase. Based on the difference between the two, the inventor came to the following conclusion. like the former

Oxygen atom is directly bonded to [Formula] Well then

The π electrons in [Formula] and the unshared electrons of oxygen move together, increasing the dielectric constant and resulting in high viscosity. On the other hand, the latter has a low dielectric constant, so its viscosity is low, but since it does not have polar atoms or groups like oxygen atoms, the polarity of the molecule as a whole is small, and therefore it cannot exhibit a liquid crystal phase. Therefore, we conducted further research and arrived at the present invention in the process of investigating a molecular structure that could provide properties intermediate between the two. In addition, the general formula described in Japanese Patent Application Laid-open No. 52-68881 The compound represented by (R is CH ₃ , C ₂ H ₅ , n-C ₃ H ₇ , n-C ₄ H ₉ ) is a low-viscosity liquid crystal substance that can widen the liquid crystal temperature range. It is. However, this compound is a colored Schiff base liquid crystalline substance. An object of the present invention is to provide a colorless liquid crystal material and a liquid crystal composition that can extend the liquid crystal temperature range to a low temperature region, and furthermore, it is an object of the present invention to provide a colorless liquid crystal material and a liquid crystal composition that can extend the liquid crystal temperature range to a low temperature region. The present invention provides a display element. In the present invention, the colorless liquid crystal substance has the general formula (In the formula, R and R' represent an alkyl group having not more than 12 carbon atoms, and X represents CO ₂ or OCO or an empty direct bond.) Among these, when X is a direct bond with no element and R and R' have 8 or less carbon atoms, the improvement in response characteristics due to lower viscosity is particularly excellent. By the way, one of the physical property values of liquid crystal materials is refractive index anisotropy (hereinafter abbreviated as Δn. Δn is the difference between the extraordinary ray refractive index and the normal ray refractive index). Δn
has a large influence on the display quality of liquid crystal display elements, and depending on the driving method, liquid crystals with a large Δn or liquid crystals with a small Δn are required. It is well known that the display quality of a liquid crystal display element can be improved by using these. The present invention confirmed that Δn changes by changing the distance between the benzene ring and the oxygen atom. The colorless liquid crystal substance according to the present invention is also a compound that makes the Δn of the liquid crystal composition smaller. In the above general formula, R and R' may have the same or different numbers of carbon atoms, and may be linear or branched. The compound represented by this general formula can be produced by a conventional method. In particular, the combination of Williamson's ether synthesis method, Friedel-Crafts reaction, and Bayer-Villiger method is the easiest. It should be noted that not only Schiff base-based colored liquid crystalline substances such as those of the conventional example, but also colored liquid crystalline substances such as azo and azoquine-type substances are of course outside the scope of the present invention. The liquid crystal composition of the present invention is characterized in that it contains a liquid crystal substance represented by the above general formula as a compounding component. Further, since the liquid crystal material of the present invention can be mixed with any known type of liquid crystal material, the obtained liquid crystal composition can be applied to all liquid crystal display methods. Further, in the liquid crystal composition of the present invention, the colorless liquid crystal substance represented by the above general formula can be used in any composition ratio as desired, and it is also possible to consist only of the compound represented by the above general formula. Furthermore, the liquid crystal display element of the present invention is characterized by a structure in which the above colorless liquid crystal composition of the present invention is sandwiched between two opposing electrode substrates as a liquid crystal layer, and a voltage is applied between the electrode substrates to display the colorless liquid crystal composition of the present invention. This is an optical device that optically modulates a liquid crystal layer. The liquid crystal display element of the present invention includes:
It is effective for various display methods such as TN type, phase transition type, and guest-host type. Hereinafter, the present invention will be explained more specifically in Examples. In the following explanation, the value of phase transition temperature is subject to slight variations depending on the measurement method and purity. Further, the transition temperature from the crystalline to the nematic phase is indicated by the symbol T _CN , and the transition temperature from the nematic phase to the isotropic liquid phase is indicated by the symbol _TNI . In the case of a monotropic transition in which a liquid crystal phase is exhibited only upon cooling, the transition temperature from an isotropic liquid phase to a nematic phase is shown in <>. Example 1 <General formula

Manufacturing method and physical properties of colorless liquid crystal substance represented by the formula> 20 g of metallic sodium is dissolved in 600 c.c. of anhydrous methanol, and 120 g of γ-bromopropylbenzene is added dropwise while heating and refluxing. 6 hours later,
The reaction solution was poured into ice water 2, and the separated oil was extracted with benzene. After removing the benzene, γ-methoxypropylbenzene can be obtained by distillation under reduced pressure.
The boiling point of this compound is 96-98°C/15mmHg. Next, in 1.5 g of methylene chloride, 195 g of anhydrous aluminum chloride and γ-methoxypropylbenzene were added.
Add 100g and cool on ice while stirring. 79 g of acetyl chloride was added dropwise little by little to this, and stirring was continued for 6 hours under ice cooling. After confirming that the generation of hydrogen chloride gas has stopped, the reaction solution is poured into dilute hydrochloric acid 1, the methylene chloride layer is separated, the methylene chloride is distilled off, and then distilled under reduced pressure to obtain 4-(γ-methoxypropyl). -Acetophenone is obtained. The boiling point of this compound is 94-95°C/0.3mmHg. 67 g of 4-(γ-methoxypropyl)-acetophenone and 620 c.c. of 88% formic acid are mixed and stirred, and then 310 ml of acetic anhydride, 4 ml of concentrated sulfuric acid, and 110 ml of 35% hydrogen peroxide are added dropwise in this order. After heating to a temperature of 40-50°C and stirring for 8 hours, the reaction solution is poured into water. After extracting the separated oil and distilling off the solvent, add 100ml of methanol and a 2N caustic soda aqueous solution.
Add 250 ml and heat under reflux for 2 hours. After cooling, the oil is separated by acidifying the reaction solution with hydrochloric acid. This is extracted with benzene, the benzene is distilled off, and then distilled under reduced pressure to obtain 4-(γ-methoxypropyl)phenol. The boiling point of this compound is 106-108℃/
It is 10mmHg. 4-(γ-methoxypropyl)-phenol 10
g was dissolved in 100 ml of benzene and 5 ml of pyridine, 14 g of trans-pentylcyclohexylcarboxylic acid chloride was added dropwise with stirring, and the mixture was dissolved at room temperature for 30 g.
Continue stirring for an hour. The reaction solution is poured into water, extracted with benzene, and the residue after distilling off the benzene is recrystallized with acetone to obtain 4-(γ-methoxypropyl)phenyl-4'-pentylcyclohexanecarboxylate. As shown in Figure 1, the infrared absorption spectrum of the compound obtained by this method shows absorption of ester bonds at 1750 cm ^-1 and absorption of ether bonds at 1120 cm ^-1 . Furthermore, in the mass spectrum, a molecular ion peak appears at m/e346. Based on both facts and the relationship with the raw material compounds, the compound synthesized here is 4-(γ-methoxypropyl)phenyl-4'-pentylcyclohexanecarboxylate (hereinafter abbreviated as MPCE) shown by the following formula. It was confirmed that The phase transition temperature of this compound is mp.=42℃, (T _IN )
It was 32℃. Similarly, compounds such as those exemplified below can be produced. (1) 4-(γ-methoxypropyl)phenyl-
4'-Propylcyclohexanecarboxylate (2) 4-(γ-methoxypropyl)phenyl-
4'-Butylcyclohexanecarboxylate (3) 4-(γ-methoxypropyl)phenyl-
4'-Hexylcyclohexanecarboxylate (4) 4-(γ-methoxypropyl)phenyl-
4'-heptylcyclohexanecarboxylate (5) 4-(γ-methoxypropyl)phenyl-
4'-Octylcyclohexanecarboxylate (6) 4-(γ-ethoxypropyl)phenyl-
4'-Propylcyclohexanecarboxylate (7) 4-(γ-ethoxypropyl)phenyl-
4'-Pentylcyclohexanecarboxylate (8) 4-(γ-ethoxypropyl)phenyl-
4'-heptylcyclohexanecarboxylate (9) 4-(γ-propoxypropyl) phenyl-
4'-Propylcyclohexanecarboxylate (10) 4-(γ-propoxypropyl)phenyl-
4'-Butylcyclohexanecarboxylate (11) 4-(γ-propoxypropyl)phenyl-
4'-Pentylcyclohexanecarboxylate (12) 4-(γ-propoxypropyl)phenyl-
4'-heptylcyclohexanecarboxylate (13) 4-(γ-butoxypropyl)phenyl-
4'-Ethylcyclohexanecarboxylate (14) 4-(γ-butoxypropyl)phenyl-
4'-Pentylcyclohexanecarboxylate (15) 4-(γ-pentyloxypropyl)phenyl-4'-ethylcyclohexanecarboxylate (16) 4-(γ-pentyloxypropyl)phenyl-4'-pentylcyclohexanecarboxylate implementation Example 2 <Characteristics of a liquid crystal composition containing the colorless liquid crystal substance produced in Example 1 above as a compounding component>
MPCE produced in was added. The viscosity of the liquid crystal composition re-prepared in this way is compared with the viscosity of the sample without addition (i.e., only the base liquid crystal) in Table 2.
Shown below.

【table】

[Table] As is clear from Table 2, the liquid crystal compositions according to the present examples have a viscosity of 15% compared to the corresponding base liquid crystal.
~35% lower. Example 3 <Response characteristics of a liquid crystal display element using the liquid crystal composition according to the present invention prepared in Example 2> 20 weight of MPCE manufactured in Example 1 was added to the base liquid crystal B shown in Example 2. A TN-type liquid crystal display device was prepared using the liquid crystal composition containing % of the above as a liquid crystal layer.
This liquid crystal display element has transparent NESA electrodes formed inside each of the upper and lower glass substrates, and an alignment control film of an organic polymer compound for aligning liquid crystal molecules. The thickness of the liquid crystal layer between the upper and lower substrates is approximately 10μm.
Gap control was performed so that When a voltage of 6V was applied to this liquid crystal display element at an ambient temperature of -30°C, the response time was 1.8 seconds. still,
In the liquid crystal display element using only the base liquid crystal B, the response time under the same conditions was 3.6 seconds. That is, according to this embodiment, there is an effect that the response time of the liquid crystal display element can be greatly improved. Example 4 <General formula Manufacturing method and properties of colorless liquid crystal substance represented by > 500 c.c. of methylene chloride, 80 g of anhydrous aluminum chloride, and 130 g of trans-4-pentylcyclohexanecarboxylic acid chloride are placed in a flask and stirred. Then, 100 g of (γ-bromopropyl)benzene was added dropwise under ice cooling. After 6 hours, the reaction solution was poured into a dilute aqueous hydrochloric acid solution to decompose the complex. If the methylene chloride layer is washed with water, dehydrated, and filtered, methylene chloride is removed and recrystallized with ligroin, trans-4-
Pentylcyclohexyl-4'-(γ-bromopropyl)phenyl is obtained. The melting point of this compound is
It is 38-39℃. Next, put 40 g of trans-4-pentylcyclohexyl-4'-(γ-bromopropyl) phenyl ketone and 200 c.c. of methanol into a flask and stir.
Then, metallic sodium in anhydrous methanol 80 c.c.
A solution of 3.5 g of sodium methylate in methanol is added dropwise and refluxed. After 6 hours, the reaction solution was concentrated, poured into ice water, and the separated oil was extracted with benzene. If benzene is distilled off and then distilled under reduced pressure, trans-4-pentylcyclohexyl-
4′-(γ-methoxypropyl)phenyl ketone is obtained. The boiling point of this compound is 168-171℃/0.08
mmHg. Mix and stir 24 g of trans-4-pentylcyclohexyl-4'-(γ-methoxypropyl) phenyl ketone and 130 c.c. of 88% formic acid in a flask.
Next, 65 c.c. of acetic anhydride, 1 c.c. of concentrated sulfuric acid, and 20 c.c. of 35% hydrogen peroxide solution were added dropwise in this order. Heat to 40-50℃ 13
After stirring for an hour, the reaction solution was poured into water. The separated oil is extracted with benzene, the solvent is distilled off, distilled under reduced pressure, and recrystallized with methanol to obtain 4-(γ-
methoxypropyl)-4'-pentylcyclohexyloxycarbonylbenzene is obtained. The boiling point of this compound is 181-188°C/0.15mmHg. As shown in Figure 2, the infrared absorption spectrum of the compound obtained by this method shows absorption of ester bonds at 1720 cm ^-1 and absorption of ether bonds at 1120 cm ^-1 . Furthermore, in the mass spectrum, a molecular ion peak appears at m/e346. From both facts and the relationship with the raw material compounds, the compound synthesized here is 4-(γ-methoxypropyl)-4'- shown by the following formula.
Pentylcyclohexyloxycarbonylbenzene (hereinafter abbreviated as MPCC) It was confirmed that The phase transition temperature of this compound is mp.=30℃, (T _IN )
It was 13℃. Similarly, compounds such as those exemplified below can be produced. (1) (γ-methoxypropyl)-4'-propylcyclohexyloxycarbonylbenzene (2) 4-(γ-methoxypropyl)-4'-butylcyclohexyloxycarbonylbenzene (3) 4-(γ-methoxypropyl)- 4'-Hexylcyclohexyloxycarbonylbenzene (4) 4-(γ-methoxypropyl)-4'-heptylcyclohexyloxycarbonylbenzene (5) 4-(γ-methoxypropyl)-4'-octylcyclohexyloxycarbonylbenzene (6 ) 4-(γ-ethoxypropyl)-4'-propylcyclohexyloxycarbonylbenzene (7) 4-(γ-ethoxypropyl)-4'-pentylcyclohexyloxycarbonylbenzene (8) 4-(γ-ethoxypropyl)- 4'-heptylcyclohexyloxycarbonylbenzene (9) 4-(γ-propoxypropyl)-4'-propylcyclohexyloxycarbonylbenzene (10) 4-(γ-propoxypropyl)-4'-butylcyclohexyloxycarbonylbenzene (11 ) 4-(γ-propoxypropyl)-4'-pentylcyclohexyloxycarbonylbenzene (12) 4-(γ-propoxypropyl)-4'-heptylcyclohexyloxycarbonylbenzene (13) 4-(γ-butoxypropyl)- 4'-Ethylcyclohexyloxycarbonylbenzene (14) 4-(γ-butoxypropyl)-4'-pentylcyclohexyloxycarbonylbenzene (15) 4-(γ-pentyloxypropyl)-
4'-Ethylcyclohexyloxycarbonylbenzene (16) 4-(γ-pentyloxypropyl)-4'-
Pentylcyclohexyloxycarbonylbenzene Example 15 <Characteristics of a liquid crystal composition containing the colorless liquid crystal substance produced in Example 4 above as a compounding component> The liquid crystal composition of Example 4 described above was added to the liquid crystal composition having the composition shown in Table 1.
MPCC manufactured by was added. The viscosity of the liquid crystal composition re-prepared in this way is shown in Table 3 in comparison with the viscosity of the sample without addition.

[Table] As is clear from Table 3, the liquid crystal compositions according to the present examples have a higher viscosity than the corresponding parent liquid crystals.
It has fallen by 15-30%. Example 6 <Response characteristics of a liquid crystal display element using the liquid crystal composition according to the present invention prepared in Example 5> 20 weight of MPCC manufactured in Example 4 was added to the base liquid crystal B shown in Example 2. A TN-type liquid crystal display device was prepared using the liquid crystal composition containing % of the above as a liquid crystal layer.
This liquid crystal display element has transparent NESA electrodes formed inside each of the upper and lower glass substrates, and an alignment control film of an organic polymer for aligning liquid crystal molecules. Gap control was performed between the upper and lower substrates so that the thickness of the liquid crystal layer was approximately 10 μm. When a voltage of 6V was applied to this liquid crystal display element at an ambient temperature of -30°C, the response time was 1.8 seconds. In addition, in the liquid crystal display element using only the base liquid crystal B, the response time under the same conditions was 3.6 seconds. That is, this embodiment also has the effect that the response time of the liquid crystal display element can be greatly improved, similar to the third embodiment. Example 7 <General formula

Production method and physical properties of colorless liquid crystal substance represented by [Formula]>4-n-pentyl-(4'-acetylphenyl)
Add 300 ml of methyl alcohol to 40 g of cyclohexane, 20 g of thallium nitrate, and 87 g of perchloric acid (70%), and stir at room temperature for 4 hours. After that, it is filtered, and the filtrate is extracted with benzene, washed with water, and then dehydrated.
Thereafter, it is recrystallized from methyl alcohol to obtain the desired product, 4-n-pentyl-4' (methoxycarbonylmethylphenyl)cyclohexane. This compound has a melting point of 46-47°C. Next, 400 ml of dry ethyl ether was added to 6 g of lithium aluminum hydride and stirred. While cooling the mixture with water, 36 g of the above-mentioned 4-n-pentyl-(4'-methoxycarbonylmethylphenyl)cyclohexane was added dropwise very slowly, and after the dropwise addition was completed, stirring was continued at 30° C. or below for 3 hours. Filter and extract the filtrate with benzene. After distilling off the benzene, recrystallization was performed using n-hexane to obtain 4-n-pentyl-
{4′-(β-hydroxyethyl)phenyl}cyclohexane is obtained. The melting point of this compound is 44-46℃
It is. 20g of this compound, 18g of thionyl chloride and pyridine
Add 0.6 g and 300 ml of benzene and reflux for 5 hours. When distilled after removing excess thionyl chloride, 4-
n-pentyl-{4'-(β-chloroethyl)phenyl} is obtained. The boiling point of this compound is 174-176
℃/1mmHg. 9 g of this 4-n-pentyl-{4'-(β-chloroethyl)phenyl}cyclohexane and
100ml of DMSO and 2.3g of sodium cyanide at 140-150℃
Stir for 2 hours. After cooling, add sodium dichlorate aqueous solution (10%). Further, water is poured into this and the precipitate is recrystallized with ligroin to obtain 4-n-pentyl-{4'-(β-cyanoethyl)phenyl}cyclohexane. The melting point of this compound is 44-46
It is ℃. 6g of this compound, 11g of caustic potassium, 80ml of water,
Add 130 ml of ethyl alcohol and reflux for 10 hours.
Ethyl alcohol is distilled off, extracted with ethyl ether, and then the extract is washed with water. After distilling off ethyl ether, the residue was recrystallized with ligroin, resulting in 4
-n-pentyl-{4-(β-hydroxylcarbonylethyl)phenyl}cyclohexane is obtained. It was confirmed that this compound exhibits a liquid crystal phase in the range of 128.8 to 164.3°C. Next, 0.82 g of lithium aluminum hydride was added to 50 ml of dry ethyl ether and stirred. 4-
Slowly add 5 g of n-pentyl-{4'-(β-hydroxylcarbonyl)phenyl}cyclohexane. Thereafter, the mixture was stirred for 5 hours and filtered.
Ethyl ether was distilled off from the filtrate and the residue was recrystallized from n-hexane to give 4-n-pentyl-{4
-(γ-hydroxypropyl)phenyl}cyclohexane is obtained. The melting point of this compound is 70.7 ~
It is 72.5℃. 3.6g thionyl chloride, 1 drop of pyridine, benzene
Add 4-n-pentyl-{4'-(γ) obtained above to 50 ml.
-Hydroxypropyl)phenyl}cyclohexane (4.3 g) was added and refluxed for 5 hours. Thereafter, excess thionyl chloride is distilled off to obtain 4-n-pentyl-{4-(γ-chloropropyl)phenyl}cyclohexane. The melting point of this compound is 70.7
~72.5℃. Next, add 1 g of metallic sodium to 50 ml of dry methyl alcohol and dissolve. Add to this the 4 obtained above.
-n-pentyl-{4'-(γ-chloropropyl)
Add 4.3g of phenyl cyclohexane. reflux
After 62 hours, the methyl alcohol was distilled off, and the residue was washed with water, dried, and distilled to give 4-n
-Pentyl-{4'-(γ-methoxypropyl)phenyl}cyclohexane is obtained. As shown in Figure 3, the infrared absorption spectrum of this compound shows ether absorption at 1120 cm ^-1 and
The absorption of --CH ₂ -- group increases at 3000 cm ^-1 . Also, in the mass spectrum, the molecular ion peak is m/e302
It appears in From both facts, the compound synthesized here has the following formula: 4-n-pentyl-{4'-
(γ-methoxypropyl)phenyl}cyclohexane (hereinafter abbreviated as 5PC1) It was confirmed that The phase transition temperature of this compound is mp.=2.0℃, (T _IN )
= -16℃. Similarly, the compounds shown below can be synthesized. (1) 4-ethyl-{4'-(γ-butoxypropyl)phenyl}cyclohexane (2) 4-ethyl-{4'-(γ-propyloxypropyl)phenyl}cyclohexane (3) 4-n-propyl- {4′-(γ-methoxypropyl)phenyl}cyclohexane(4) 4-n-propyl-{4′-(γ-ethoxypropyl)phenyl}cyclohexane(5) 4-n-propyl-{4′-(γ -Propyloxypropyl)phenyl}cyclohexane (6) 4-n-propyl-{4'-(γ-butoxypropyl)phenyl}cyclohexane (7) 4-n-butyl-{4'-(γ-methoxypropyl)phenyl }Cyclohexane (8) 4-n-butyl-{4'-(γ-ethoxypropyl) phenyl} cyclohexane (9) 4-n-butyl-{4'-(γ-propyloxypropyl) phenyl} cyclohexane (10) 4-n-pentyl-{4'-(γ-ethoxypropyl)phenyl}cyclohexane (11) 4-n-pentyl-{4'-(γ-propyloxypropyl)phenyl}cyclohexane (12) 4-n-hexyl -{4'-(γ-methoxypropyl)phenyl}cyclohexane (13) 4-n-hexyl-{4'-(γ-ethoxypropyl)phenyl}cyclohexane (14) 4-n-hexyl-{4'-( γ-propyloxypropyl)phenyl}cyclohexane (15) 4-n-heptyl-{4′-(γ-methoxypropyl)phenyl}cyclohexane (16) 4-n-heptyl-{4′-(γ-ethoxypropyl) phenyl}cyclohexane (17) 4-n-heptyl-{4'-(γ-propyloxypropyl)phenyl}cyclohexane (18) 4-n-octyl-{4'-(γ-methoxypropyl)phenyl}cyclohexane (19) ) 4-n-octyl-{4'-(γ-ethoxypropyl)phenyl}cyclohexane (20) 4-n-octyl-{4'-(γ-propyloxypropyl)phenyl}cyclohexane Example 8 <Above example Characteristics of a liquid crystal composition containing the colorless liquid crystal material produced in Example 7 as a compounding component>
5PC1 manufactured by was added. The physical properties of the liquid crystal composition thus re-prepared are shown in Table 4 in comparison with the viscosity of the sample without addition (that is, only the base liquid crystal).

[Table] From No. 4, the viscosity of the liquid crystal composition according to this example is 36 to 41% lower than that of the base liquid crystal, and Δn is 23%.
~30% smaller. Example 9 <Response characteristics of a liquid crystal display element using the liquid crystal composition according to the present invention prepared in Example 8> 20 ml% of 5PC1 obtained in Example 7 was added to the base liquid crystal B used in Example 2. Using the formulated liquid crystal composition
Created a TN type liquid crystal display element. The element structure is the same as in Example 3. The gap between the glass substrates, that is, the thickness of the liquid crystal layer was adjusted to about 10 μm. When a voltage of 6V was applied to this liquid crystal display element at -30°C and the response time was measured, it was 1.4 seconds. Similarly, when only the base liquid crystal B was measured, the time was 3.6 seconds under the same conditions. That is, this embodiment also has the effect that the response time of the liquid crystal display element can be greatly improved in the same manner as in the third embodiment. As explained above, the colorless liquid crystal material of the present invention has a wide liquid crystal temperature range from room temperature to warm environments to high temperature environments,
Moreover, it becomes possible to obtain a colorless liquid crystal composition with a small Δn. In addition, it has the effect of imparting excellent response characteristics to a liquid crystal display element using this colorless liquid crystal composition.

[Brief explanation of drawings]

1 to 3 are infrared absorption spectrum diagrams of various colorless liquid crystal materials according to the present invention.

Claims (1)

[Claims] 1. General formula (In the formula, R and R' represent an alkyl group not exceeding 12 carbon atoms, and X represents CO ₂ or OCO or an empty direct bond.) 2 If the above general formula is (In the formula, R and R' represent an alkyl group whose number of carbon atoms does not exceed 8.)
Colorless liquid crystalline substance described in Section 1. 3 General formula (In the formula, R and R' represent an alkyl group with a carbon number not exceeding 12, and X represents CO ₂ or OCO or an empty direct bond.) A liquid crystal composition characterized by: 4. In a liquid crystal display element in which a liquid crystal layer is sandwiched between two opposing electrode substrates and a voltage is applied between the electrode substrates to optically modulate the liquid crystal layer, the liquid crystal composition forming the liquid crystal layer is , general formula (In the formula, R and R' represent an alkyl group with a carbon number not exceeding 12, and X represents CO ₂ or OCO or an empty direct bond.) LCD display element.