JPS5945019B2 - 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 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 meets this demand, 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 exhibiting such properties are classified into nematic liquid crystals, smectic liquid crystals, and cholesteric liquid crystals, depending on the orientation of liquid crystal molecules. Currently, the liquid crystal 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 in order for liquid crystal to be used as a display material, the following requirements are required.

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 these things are required of liquid crystal materials, conventional liquid crystal materials have the following drawbacks and points that need to be improved. 1. 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 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. One way to eliminate this drawback is to protect the display section with a colored filter. However, this method has the drawback that the entire display section is colored in a specific color, which makes it dark and reduces the display ability. 3. Above 1
．． As a liquid crystal that does not have the drawbacks mentioned in 2, there is a white and very stable liquid crystal that has 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 they do not have a sufficient temperature range. Another drawback was that the response speed was slow. The present invention uses an ester liquid crystal that does not have the drawbacks mentioned in 1.2 that Schiff liquid crystals and azoxy liquid crystals have, and in order to improve the shortcomings of conventional ester liquid crystals, such as a 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-alkoxyphenyl ester of 4-n-alkylbenzoic acid has 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-alkylphenyl ester has the property of increasing the response speed of a liquid crystal display.

4-(4-n-alkoxybenzoyloxy)monobenzoic acid-2/-chloro-41-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. be.

Typical characteristics of the four types of liquid crystals mentioned above are shown in Table 1. By mixing these four types of liquid crystals, liquid crystals with good characteristics were always obtained.

Preparation examples will be described below with reference to Examples.

Example 1 As can be seen from the example, the nematic ivy 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 of the present invention did not crystallize even after being left at -20°C for half a day. This shows that it can withstand use 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).

As a result of the test, all the nematic liquid crystal compositions of the present invention
．． I found out that it can be driven with 5V. As an example of test results, the contrast characteristics of a display using the nematic liquid crystal composition of Example 1 are shown in FIG. In this figure, the horizontal axis represents the drive voltage ( ), and the vertical axis represents the light transmittance (%). The contrast characteristics shown in the figure are from the direction of 85 degrees with respect to the normal to the glass substrate.
Using a cell made from a glass substrate deposited with
Measured in °C. This figure shows that the display using the nematic liquid crystal composition of the present invention can be sufficiently driven at 1.5V. 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 the display parts of wristwatches, calculators, etc., but also as display materials for various consumer appliances. This is particularly suitable for wristwatches that are required to be more compact. A prototype wristwatch was made using the nematic liquid crystal composition of the present invention and an accelerated test for several months was conducted, but no problems were found in terms of lifespan, contrast, etc.

Figures 2 and 3 show the general appearance of this wristwatch and its block diagram.

[Brief explanation of drawings]

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. ▲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'- 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-alkoxybenzoyloxy) monobenzoic acid-2'-chloro-4'-cyanophenyl ester}
(However, in the above formula, R and R' represent a straight chain alkyl group having 3 to 9 carbon atoms.)