JPS604857B2 - Nematic liquid crystal composition - Google Patents

Description

[Detailed description of the invention] The present invention relates to novel nematic liquid crystal compositions.

More specifically, the present invention relates to a nematic liquid crystal composition that is white, extremely stable, and has a wide temperature range. In recent years, advances in electronics and other technologies have created a demand for inexpensive display materials that can be driven at low voltages. Liquid crystals are currently seen as a promising display material that satisfies this requirement, and liquid crystals are already being used in some displays. This promising liquid crystal is made of organic compounds, but ordinary compounds are solid →
Liquid crystals undergo a phase change from liquid to gas, but liquid crystals do not directly change from solid to liquid, but instead exhibit a phase that has both solid and liquid properties. Due to the difference in molecular orientation of this phase, liquid crystals
It can be divided into smectic liquid crystal, nematic liquid crystal, and cholesteric liquid crystal. The liquid crystal currently used as a display material is a nematic liquid crystal, and there are two types of display methods for display bodies using this nematic liquid crystal: a light scattering method and a field effect method. The present invention was made regarding a nematic liquid crystal composition used in a field effect type display.

Although liquid crystals are very promising as display materials, conventional liquid crystal materials still have the following drawbacks and points for improvement. 1 Conventional white liquid crystals were mainly compounds having a Schiff base at the center of the molecule.

(Hereinafter, it will be abbreviated as Schiff liquid crystal.) However, this liquid crystal has the drawback that it is extremely susceptible to the influence of moisture, and is therefore extremely difficult to handle and shield. 2. Azoxy compound-based liquid crystals are relatively stable liquid crystals.

(Hereinafter, it will be abbreviated as azoxy liquid crystal.) However, since this liquid crystal absorbs light in the visible region, it has the disadvantage that it deteriorates even when exposed to visible light such as ultraviolet rays. In order to eliminate this drawback, the display section is protected with a colored filter, but this method has the disadvantage that the entire display section is colored in a specific color, which makes it dark and reduces the display ability. 3. As a liquid crystal that does not have the drawbacks 1 and 2 above, there is a white and very stable ester compound liquid crystal (hereinafter abbreviated as ester liquid crystal), but this conventional liquid crystal has a limited temperature range and cannot be used. were constrained in terms of

For example, a liquid crystal composition comprising a liquid crystal represented by the general formula (R is a straight mirror alkyl group) has been considered.

However, this liquid crystal composition had the drawback that the upper limit point (clear point, hereinafter abbreviated as CP) was 50° C. or lower, which was too low. Also, a liquid crystal composition was considered in which a liquid crystal represented by the general formula (R and R' are linear alkyl groups) was mixed with the liquid crystal compound, but this liquid crystal composition also had a CP of 50q.
o or less, which was not satisfactory.

Further, while azoxy liquid crystals and Schiff liquid crystals were able to maintain a supercooled state for a long time, the ester liquid crystal, which is a subordinate liquid crystal, was unable to maintain a supercooled state for a long period of time.

For this reason, it has been difficult to use products using Estel liquid crystal in cold regions. The present invention solves not only the drawbacks mentioned in 1 and 2 above, but also the drawbacks mentioned in 3 above of the conventional Ester liquid crystal by mixing the seven types of Estel liquid crystals shown in Table 1. It is.

Table 1 shows the properties of the Estel liquid crystal used in the present invention.

Table 1 In Table 1, the symbols C, N, and 1 represent crystalline states, respectively.
Represents a nematic liquid crystal state, an isomallic liquid state.

The same applies to the table below. Example 1 shows an example of the components, their proportions, and their properties of a nematic liquid crystal composition of the present invention prepared using the compounds shown in Table 1.

Example 1 From this table, the melting point of the liquid crystal composition of the present invention is -700,
It can be seen that the melting point is much lower than the conventional Estel liquid crystal (melting point 000).

Furthermore, it can be seen that CP sufficiently secures 54qC and 5pi○. In addition, when we conducted a supercooling test, we found that -115
Even if it was left for half a day (one hour) at midnight, it did not crystallize.
As described above, the liquid crystal composition of the present invention is superior to the conventional Estel liquid crystal in terms of temperature characteristics, and has no drawbacks such as the instability of Schiff liquid crystal or the insufficient display ability of azoxy liquid crystal. The composition can be used as a display material with a wide range of applications.

Note that a display using liquid crystal has properties such as low voltage drive and low power consumption, and is suitable as a display for a wristwatch.

When a wristwatch was made using the nematic liquid crystal composition of the present invention, there were no problems with respect to lifespan or contrast even after several months of accelerated deterioration tests.

As for wristwatches, in addition to longevity and contrast, response speed is an issue, so we investigated changes in response speed with respect to temperature, and the results shown in Figure 1 were obtained. Conventionally, the general idea was that ester liquid crystals have a high viscosity and therefore have a slow response time.

Furthermore, experimental results conducted on conventional Estel liquid crystals also supported this idea. However, surprisingly, the response speed of the liquid crystal composition of the present invention was superior not only to the conventional Estel liquid crystal but also to the Schiff liquid crystal, and showed a speed comparable to the conventional azoxy liquid crystal. For comparison, graphs showing the relationship between the response speed and temperature of Schiff liquid crystal and Azoxy liquid crystal are shown in FIGS. 2 and 3. This shows that the liquid crystal composition of the present invention is particularly suitable for use in wristwatches.

[Brief explanation of the drawing]

FIG. 1 shows the response speed and temperature of the liquid crystal composition of the present invention. A diagram showing the relationship with degree. FIG. 2 is a diagram showing the relationship between the response speed and temperature of a secondary Schiff liquid crystal. FIG. 3 is a diagram showing the relationship between response speed and temperature of a conventional azoxy liquid crystal. In FIGS. 1 to 3, the vertical axis is on a logarithmic scale. Hair 1 Figure Hair 2 Figure Winter 3

Claims (1)

[Claims] 1. A compound whose structural formula is ▲There are mathematical formulas, chemical formulas, tables, etc.▼ ▲There are mathematical formulas, chemical formulas, tables, etc.▼ Compounds whose structural formula is represented by ▲There are mathematical formulas, chemical formulas, tables, etc.▼ Compounds represented by ▲ There are mathematical formulas, chemical formulas, tables, etc.▼ Compounds represented by ▲ There are mathematical formulas, chemical formulas, tables, etc. ▼ Compounds represented by ▲ There are mathematical formulas, chemical formulas, tables, etc. ▼ Compounds represented by and , ▲There are mathematical formulas, chemical formulas, tables, etc.▼ A nematic liquid crystal composition characterized by being composed of a compound represented by the following.