JPS5945020B2 - Nematic liquid crystal composition - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to a novel nematic liquid crystal composition, and more particularly to a nematic liquid crystal composition that is white, very stable, and has a wide temperature range.

In recent years, advances in electronics technology have created a demand for inexpensive display materials that can be driven at low voltages.

Liquid crystals are currently attracting attention as a display material that satisfies this requirement, and liquid crystals are already being used in some products. The liquid crystals that are attracting attention are made of organic compounds, but while ordinary organic compounds undergo a phase change from crystal to liquid, liquid crystals do not directly change from crystal to liquid; Indicates a phase that also has birefringence. Liquid crystals having such properties are classified into linematic liquid crystals, smectic liquid crystals, and cholesteric liquid crystals, depending on the orientation of liquid crystal molecules. The liquid crystal currently mainly used as a display material is a nematic liquid crystal, and there are two types of display methods using this nematic liquid crystal: a light scattering method and a field effect method.

The nematic liquid crystal composition of the present invention is a liquid crystal used in a field effect type system. Now, liquid crystal is very promising as a display material, but the following requirements are required for liquid crystal to be used as a display material.

1. Liquid crystals must be chemically stable and will not decompose or deteriorate due to heat, light, oxygen, etc.

2. Wide liquid crystal temperature range.

Although this is at least required for liquid crystal materials, conventional liquid crystal materials have the following drawbacks and points that need to be improved.

*]. Conventional liquid crystals mainly have a Schiff base at the center of the molecule (hereinafter abbreviated as Schiff liquid crystal). However, Schizophrenic liquid crystals are easily affected by moisture, making them difficult to handle and shield. 2. Azoxy compound-based liquid crystals are relatively stable liquid crystals (hereinafter abbreviated as azoxy liquid crystals).

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, it is necessary to protect the display section with a colored filter. However, this method has the disadvantage that the entire display section is colored in a specific color, becomes dark, and the display performance deteriorates. 3. As a liquid crystal that does not have the drawbacks mentioned in 1 and 2 above, there is a white and very stable liquid crystal having an ester bond in the center of the molecule (hereinafter abbreviated as ester liquid crystal).

However, ester liquid crystals have not been used in conventional displays because a sufficient liquid crystal temperature range cannot be secured. Another drawback was that the response speed was slow. The present invention uses an ester liquid crystal that does not have the disadvantages mentioned in 1 and 2 of Schiff liquid crystals and azoxy liquid crystals, and improves the disadvantages of conventional ester liquid crystals such as narrow temperature range and slow response speed. It was done.

The nematic liquid crystal composition of the present invention is a liquid crystal composition containing at least the following four types of liquid crystals.

The above liquid crystals each have the following properties. 4-n-alkylbenzoic acid-4'-cyanophenyl ester is a liquid crystal with positive dielectric anisotropy, and is an essential liquid crystal for field effect liquid crystals.

4-n-alkylbenzoic acid-41-n-alkoxyphenyl ester is a liquid crystal with a narrow liquid crystal temperature range but a low melting point, and is necessary to lower the melting point of the nematic liquid crystal composition.

4-n-alkoxybenzoic acid-4! -n-alkyl phenyl ester has the property of increasing the response speed of a liquid crystal display.

4-(4-n-alkylbenzoyloxy)monobenzoic acid-27-chloro-47-cyanophenyl ester has a high melting point but a wide liquid crystal temperature range, so it is necessary to widen the temperature range of nematic liquid crystal compositions. .

Typical characteristics of the four types of liquid crystals mentioned above are shown in Table 1.

Very good characteristics were obtained by mixing these four types of liquid crystals. Preparation examples will be described below with reference to Examples.

Example 1 Example 2 A nematic liquid crystal composition in which 4-n-hebutyl-4'-cyanobiphenyl was mixed in place of the 4-n-butylbenzoic acid-4''-cyanophenyl ester of Example 1.

The liquid crystal temperature range of this liquid crystal composition is 5 to 60°C. Example 3 A nematic liquid crystal composition obtained by adding 5 weight percent of P-anisonitrile to the liquid crystal composition of Example 1.

As can be seen from the examples, the nematic liquid crystal composition of the present invention has a very wide temperature range, which is sufficient for ordinary displays. Furthermore, conventional ester liquid crystals could not maintain a supercooled state for a long period of time, making it difficult to use them in cold regions. However, the nematic liquid crystal composition of the present invention is -20
No crystallization occurred even after being left at ℃ for half a day. This shows that the liquid crystal composition of the present invention can be satisfactorily used even in cold regions. The purpose of the present invention is to create a liquid crystal that is stable and has a wide temperature range, but another purpose is to create a liquid crystal that can be driven at 1.5V (one battery).

The liquid crystal of Example 1 was filled in a cell made of a glass substrate on which SiO was vapor-deposited from 85 directions with respect to the normal line of the glass substrate, a display was made, and the contrast characteristics were measured. The results are shown in FIG. In this figure 2, the driving voltage (V) is plotted on the horizontal axis, and the light transmittance (V) is plotted on the vertical axis.
%) is set aside. From the figure, the display using this liquid crystal is 1
．． It can be seen that 5 is sufficient for driving. As described above, the nematic liquid crystal composition of the present invention is superior to conventional liquid crystal compositions in various respects.

The excellent nematic liquid crystal composition of the present invention can be applied not only to display parts of wristwatches, calculators, etc., but also as display materials for various consumer appliances. Furthermore, since the display using the nematic liquid crystal composition of the present invention can be driven at 1.5V, there is an advantage that the booster circuit required in the conventional display is not required. For this reason, the nematic liquid crystal composition of the present invention is suitable for wristwatches that must be made compact. A prototype wristwatch was made using the nematic liquid crystal composition of the present invention and accelerated testing was conducted for several months.
There were no problems with life contrast, etc.

This wristwatch and its program diagrams are shown in Figures 2 and 3.

[Brief explanation of the drawing]

FIG. 1 shows the relationship between voltage and contrast.

Claims (1)

[Scope of Claims] 1. A nematic liquid crystal composition comprising at least the following four types of liquid crystals. 1, ▲ There are mathematical formulas, chemical formulas, tables, etc. ▼ (4-n-alkylbenzoic acid-4'-cyanophenyl ester) 2, ▲ There are mathematical formulas, chemical formulas, tables, etc. ▼ (4-n-alkylbenzoic acid-4 '-n-alkoxyphenyl ester) 3, ▲ There are mathematical formulas, chemical formulas, tables, etc. ▼ (4-n-alkoxybenzoic acid -4'-n-alkylphenyl ester) 4, ▲ There are mathematical formulas, chemical formulas, tables, etc. ▼ 4-(4-n-alkylbenzoyloxy)-benzoic acid-2'-chloro-4'-cyanofnyl ester) (However, in the above formula, R and R' represent a straight-chain alkyl group having 3 to 9 carbon atoms. ).