JPS5932508B2 - electro-optical element - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to mesomorphism
) and exhibits a nematic liquid crystal phase at or near room temperature, and relates to an electro-optical element, particularly a liquid crystal display element, using a new and stable ester compound.

Display elements using so-called nematic liquid crystal materials exhibiting a nematic liquid crystal phase are known, which elements are generally controlled by an electric field.

That is, when a nematic liquid phase material is placed between a pair of substrates with electrodes and no electric field is applied between the electrodes, a liquid crystal display element containing a thin layer of this material is transparent to light;
When a voltage higher than a certain level determined by the liquid crystal material is applied, a display is performed by causing clouding in the area to which the electric field is applied. This is because when an electric field is applied, the arrangement of liquid crystal molecules is disturbed and light is scattered. The electro-optical effect based on the arrangement of nematic liquid crystal molecules in such an electric field is useful not only in display devices that display numbers and letters using patterned electrodes, but also in light shielding devices that simultaneously turn on and off the entire surface of the device. can also be applied. Some of the conventional liquid crystals used herein have relatively high nematic transition temperatures (the lower temperature limit at which a nematic liquid crystal phase occurs). Since nematic liquid crystals must be operated in their nematic liquid crystal phase, such liquid crystals require heating to achieve a temperature range in which they exhibit a nematic liquid crystal phase. Other conventional liquid crystals often exhibit inherent coloration, such as those based on Schiff bases, which exhibit an inherent yellow color and also lack long-term stability, such as in the presence of moisture or It also has the disadvantage of decomposing under ultraviolet irradiation. The present invention uses a liquid crystal that does not have the above drawbacks, that is, an ester compound that has a low nematic transition temperature (lower limit temperature for forming a nematic liquid crystal phase), is colorless, and is not easily deteriorated by water, oxygen, or ultraviolet rays. The object of the present invention is to provide a liquid crystal compound whose periodic characteristics are not easily deteriorated, and thereby to provide an excellent electro-optical element, particularly a display element.

That is, in the present invention, R1, which is an ester compound having a nematic liquid crystal phase, is a linear alkyl group having 5 to 8 carbon atoms, a linear alkoxy group, or a linear alkoxycarbonyloxy group, and R2 is an ester compound having 6 to 8 carbon atoms. Straight chain alkoxy group and R
Between the substrates with electrodes, an ester compound having the general formula V where the total number of carbon atoms of 1 and R2 is 14 or less and Y is a fluorine atom or a chlorine atom is mixed with another liquid crystal substance. This is an electro-optical element arranged in a.

It has been reported that some ester compounds having an ester group in the center of the molecule are nematic liquid crystals, but all of these have a high nematic transition temperature, such as pure 4-n-hexyloxy. The liquid crystal of carbonyloxybenzoic acid-4'-amyloxyphenyl ester exhibits a nematic liquid crystal phase in the temperature range of 41 to 89°C, and it is difficult to form a practical device using such a liquid crystal. I can't.

However, the liquid crystals of the ester compounds of the present invention have significantly lower and stable nematic transition temperatures. There is no simple relationship between the properties of the liquid crystal phenomenon and the molecular structure, nor between the substituents on the molecule and the temperature range in which the nematic liquid crystal phase is exhibited. Therefore, the fact that the liquid crystal of the ester compound of the present invention has a significantly low and stable nematic transition temperature as described above is a phenomenon that is difficult to predict from conventional ester compound liquid crystals. In the liquid crystal of the ester compound of the present invention, R1 in the general formula above is a linear alkyl group, a linear alkoxy group, or a linear alkoxycarbonyloxy group having a substituent having 5 to 8 carbon atoms, and R2 is a substituent. When is a linear alkoxy group having 6 to 8 carbon atoms and the total number of carbon atoms of R and R2 is 14 or less, the resulting liquid crystal has a significantly low nematic transition temperature and is stable, and its color It is also colorless and has particularly high stability against degradation by water, oxygen, and ultraviolet light.
Note that Rl and R2 may be the same group, and Y is a fluorine atom or a chlorine atom.

The ester compound of the present invention can be synthesized, for example, by the following esterification reaction.

(However, Rl, R2, and Y represent the groups described above.) Next, more specific synthesis examples will be shown.

Synthesis Example 1 4-n-hexyloxybenzoic acid-3'-chloro-4'
-Synthesis of n-hexyloxyphenyl ester 4-n-
A mixture of 0.001 mol of hexyloxybenzoic acid, 0.002 mol of thionyl chloride, and carbon tetrachloride 5a is heated under reflux for 6 hours, and then the solvent and excess thionyl chloride are distilled off using a rotary evaporator.

0.0% of 3-chloro-4-hexyloxyphenol was added to the residue.
0011 mol and further added 3 mol of benzene as a solvent.
0.0015 mol of pyridine was added to the mixture with stirring, and the product obtained after heating and refluxing at 80° C. for 3 hours was purified through alumina (309)-toluene column chromatography. This was further recrystallized twice from hexane so as to exhibit a constant melting point. This results in 4-n-
0.0008 mol of hexyloxybenzoic acid-3'-chloro-4'-n-hexyloxyphenyl ester was obtained.

Yield 80(f). R spectrum of this ester compound (
KBr tablet) has a strong ester absorption VC=0 of 1734
It was recognized in CTIL-1. Synthesis Example 2 In the same manner as in Synthesis Example 1, 4-n-hexylbenzoic acid and 3
-chloro-4-n-octyloxyphenol to 4-
N-hexylbenzoic acid-3'-chloro-4'-n-octyloxyphenyl ester was synthesized.

Synthesis Example 3 In the same manner as in Synthesis Example 1, 4-n-octylbenzoic acid and 3
-chloro-4-n-hexyloxyphenol to 4-
N-octylbenzoic acid-3'-chloro-4'-n-hexyloxyphenyl ester was synthesized.

Synthesis Example 4 In the same manner as in Synthesis Example 1, 4-n-heptylbenzoic acid and 3
-fluoro-4-n-hexyloxyphenol to 4
-n-heptylbenzoic acid-3'fluoro-4'-n-hexyloxyphenyl ester was synthesized.

Synthesis Example 5 In the same manner as in Synthesis Example 1, 4-n-butyloxycarbonyloxybenzoic acid-3'-fluoro- 4'-n-hexyloxyphenyl ester was synthesized.

Synthesis Example 6 In the same manner as in Synthesis Example 1, 4-n-hexyloxycarbonyloxybenzoic acid-3'fluoro-4 was prepared from 4-n-hexyloxycarbonyloxybenzoic acid and 3-fluoro-4-n-hexyloxyphenol. '-n-hexyloxyphenyl ester was synthesized.

Synthesis Example 7 In the same manner as in Synthesis Example 1, 4-n-heptylbenzoic acid and 3
-chloro-4-n-hexyloxyphenol to 4-
n-heptylbenzoic acid-3'-chloro-4'-n-hexyloxyphenyl ester was synthesized.

Table 1 summarizes the characteristics of the ester compounds synthesized in Synthesis Examples 1 to 7, and R1 and R2 each represent a substituent in the general formula having the same meaning as above.

All of the liquid crystals in Table 1 above of the present invention are colorless, have at least a transition point to a nematic liquid crystal and a transition point to an isotropic liquid, and exhibit a nematic liquid crystal phase surrounded by the two transition points. Contains useful temperature ranges.

For example, as the ester compound of Synthesis Example No. 4 is heated, it becomes a smectic liquid crystal state at 22°C, and at 24°C
When heated to 36° C., an isotropic liquid is formed. Furthermore, the nematic temperature range of the ester compound of Synthesis Example No. 1 is slightly high at 41 to 53.5°C, but even in this ester compound, the nematic temperature range of the Y position is hydrogen is significantly high at 63.5 to 92°C. By introducing a chlorine atom at the Y position, the nematic temperature range could be significantly lowered. The liquid crystal of the ester compound of the present invention is
It can be mixed with other families of liquid crystals to obtain an expanded temperature range exhibiting useful nematic liquid crystal phases.

Typical crystals of other types that can be mixed include p'-ethoxybenzylidene-p-n-butylaniline, 4-ethoxy-4/-n-butyl-β-chlortolan\stilbene, and 4-n-hexyloxybenzoic acid. Acid-4'-n-amyloxyphenyl ester, 4-methoxy-4'-n-
Examples include butylazoxybenzene. For example, 50 mol% of P7-methoxybenzylidene-p-n-butylanilide and p'-ethoxybenzylidene-p-n-
If a liquid crystal mixture with 50 mol% of butylaniline is cooled to -14C, it will solidify in 3 hours, but a liquid crystal mixture of 40 mol% of each of these two compounds and 20 mol% of the compound of Synthesis Example No. 7 above will solidify in 3 hours. , it does not solidify for more than a week even when cooled to -14°C. One example of an electro-optical element to which the above-mentioned ester compound liquid crystal is applied is to apply the above-mentioned liquid crystal compound in a sufficiently thin layer, preferably 5 to 300 microns, between transparent substrates that face each other and have parallel surfaces adjacent to each other. There are display elements in which the optical properties of the liquid crystal compound are abruptly changed through electrodes, such as metal oxides, provided on the internal surface of each substrate.

The display element may be of a transmissive type, a reflective type, or an absorptive type. When the ester compound liquid crystal of the present invention is applied to such a liquid crystal display element, the element can operate at or near room temperature, and the compound is colorless and highly stable, making it superior to conventional elements. There are significant advantages to When the liquid crystal of the present invention is used, an appropriate doping agent, for example, an ionic substance such as trimethylhexadecyl ammonium bromide or dodecylpyridinium-p-toluenesulfonate, can be added to improve the properties of the liquid crystal. The structure of the electro-optical element of the present invention will be explained in more detail.The electro-optical element of the present invention may have various known structures and may be driven by various known driving methods.

A specific example of this is to form electrodes of a desired shape on the surface of a substrate such as glass or plastic, arrange them with a desired gap so that the electrode surfaces face each other on the inside, and seal the periphery. There is an electro-optical element in which a cell is formed, liquid crystal is injected through an injection port, and the injection port is sealed.

In this case, the front substrate must be at least a transparent substrate, and usually both substrates are transparent. Further, known applications such as adding a polarizing plate and a reflecting plate as necessary are also possible. Example 1 Compound 19 of Synthesis Example No. 4 and 4-n-
Butylbenzoic acid-4'-n-hexyloxyphenyl ester 19 was mixed, heated to 60°C to melt, then cooled and solidified, and the phase transition temperature was measured.The transition temperature from solid to nematic liquid crystal was measured. was -8°C, and the transition temperature from nematic liquid crystal to isotropic liquid was 42°C.

This mixture was mixed with 0.1 wt % of trimethylhexadecyl ammonium bromide, and the composition was sandwiched between glass substrates coated with tin oxide to give conductivity to a thickness of 1.0 μm.
A sandwich cell was made, and a 50 Hz alternating current voltage was applied to this cell at 20°C. When the voltage was gradually increased, the cell became slightly cloudy due to the application of a voltage of 8 V.
At No. 15, it became completely cloudy.

As described above, the electro-optical element using the specific ester compound of the present invention has a temperature range showing a low nematic liquid crystal phase, is stable, and can be used in various applications in the future.

Claims (1)

[Scope of Claims] 1 R_1 is a straight-chain alkyl group, a straight-chain alkoxy group, or a straight-chain alkoxycarbonyloxy group having 5 to 8 carbon atoms, R_2 is a straight-chain alkoxy group having 6 to 8 carbon atoms, and The total number of carbon atoms of R_1 and R_2 is 14 or less, and Y
An electro-optic system in which an ester compound having the general formula ▲mathematical formula, chemical formula, table, etc. is available▼ where is a fluorine atom or a chlorine atom is mixed with other liquid crystal substances and arranged between substrates with electrodes as a nematic liquid crystal substance. element.