JPS5930754B2 - electro-optical display device - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to an electro-optic display device using a novel liquid crystal composition.

Liquid crystal compounds are characterized by the fluidity of liquids within a certain temperature range,
It is a unique compound that has the birefringence of crystals.

A display device using the unique properties of this liquid crystal compound is being considered, and is currently attracting a lot of attention because of its low driving voltage and low power consumption. However, although various display devices using liquid crystal compositions that are not mixed with various liquid crystal compounds have been announced, there are still problems with their reliability. Now, liquid crystal compounds are unique compounds as mentioned above, but
Depending on the form of their molecular arrangement, they can be divided into smectic liquid crystal compounds, cholesteric liquid crystal compounds, and nematic liquid crystal compounds, and liquid crystal compositions containing nematic liquid crystal compounds are mainly used in display devices.

This nematic liquid crystal compound is optically positive, with the maximum speed of light along the long axis of the molecule.

Also, if the permittivity in the long axis direction and the direction perpendicular to the long axis of the molecule are on ε/ and ε, respectively, then it is generally on ε/\ε, and △
Nematic liquid crystal compounds are divided into nematic liquid crystal compounds having positive dielectric anisotropy and nematic liquid crystal compounds having negative dielectric anisotropy depending on the positive and negative values of ε=ε/−ε, and these nematic liquid crystal compounds are mixed. Crystal compositions can similarly be divided into those with positive dielectric anisotropy and those with negative dielectric anisotropy. The display principles can be divided into two types depending on whether the dielectric anisotropy of the liquid crystal composition used is positive or negative, and these two types of display principles are called the DSM method and the FE method, respectively. The display principle of the DSM system will be explained as follows using FIG.

In FIG. 1, 1 is a glass plate with a transparent electrode, 2 is a spacer, 3 is a liquid crystal composition, 4 is an electrode, 5 is an electrode, and 6 is a switch. When a liquid crystal cell as shown in the figure is filled with a liquid crystal composition having negative dielectric anisotropy: the cell is transparent. When an electric field is applied to this transparent cell, the current flowing through the cell disturbs the orientation of the liquid crystal composition, causing light scattering and clouding. If the electrodes are shaped like letters, numbers, or figures, it becomes possible to display the image in a cloudy manner according to the shape. This is the principle of the DSM method. The display principle of the FE method is as follows.

Directionality is imparted to the electrode surfaces by rubbing the surfaces of two glass plates with electrodes for a liquid crystal cell in one direction with gauze or the like, or by depositing SiO or the like from an oblique direction. Next, the liquid crystal cells are assembled so that the rubbing directions are perpendicular to each other. The liquid crystal cell thus created is filled with a liquid crystal composition having positive dielectric anisotropy. The molecules of the filled liquid crystal composition have a 900 spiral structure as shown in FIG. As a result, the liquid crystal cell can rotate the plane of polarization of light by 900 rotations. Furthermore, when an electric field is applied to this liquid crystal cell, since the liquid crystal molecules have a dipole moment in the direction of the long axis of the molecules, the molecules of the liquid crystal composition orient their long axes perpendicularly to the electrode surfaces. As a result, the optical rotation power disappears. If the liquid crystal cell thus produced is sandwiched between two orthogonal or parallel polarizing filters, the passage and blocking of light can be controlled by an electric field. This passage blocking allows any arbitrary shape to be displayed. This is the principle of the FE method. Note that the value of Δε of the liquid crystal composition can be changed by appropriately mixing two types of liquid crystals having positive and negative dielectric anisotropy. Up to now, various displays using liquid crystal compositions have been announced, but they have had the following problems.

Conventional displays have mainly used liquid crystal compositions containing Schiff-type liquid crystal compounds having the general formula R/ and having a Schiff base at the center of the molecule as a main component.

However, this type of liquid crystal compound is affected by even a small amount of water present in the liquid crystal cell, and the molecules are hydrolyzed, resulting in a short display life. Furthermore, conventional liquid crystal compositions have relatively high melting points and cannot be used in low temperature ranges. The present invention has been made in order to eliminate the drawback that conventional displays using liquid crystal compositions containing Schiff-type liquid crystal compounds as a main component have a short lifespan.

The present invention uses a liquid crystal composition mainly composed of a novel azoxy-type liquid crystal compound having different values of n and n' in the general formula, which is different from the conventionally known bilaterally symmetrical azoxy-type liquid crystal compound. It is characterized by:

An example of the properties of this new liquid crystal compound is shown in the following table.

The liquid crystal temperature range was measured using a melting point measuring device sandwiched between orthogonal polarizing plates. The melting point is the melting temperature when the temperature is increased, and the clearing point is the temperature at which the bright field changes to the dark field, and the temperature range between them is defined as the liquid crystal temperature range. This liquid crystal compound can be synthesized as follows.

Suitable alkylaniline (CnH, n+1-<0XNH
) was converted into a nitroso compound (CnH, +1
Ba? ? Change to ChiN blade.

Next, this nitroso compound and alkylaniline (Cn′H2n/+1K○, 〉-NH,) are dehydrated and condensed in an acetic acid solvent to form an azo compound (G
``)toN=Nbe[=]!α锇n) is obtained.

Next, this azo compound is oxidized in acetic acid using hydrogen peroxide to form an azoxy compound.

Alternatively, it can be obtained by dehydrating condensation of the hydroxyamine produced by reducing the above-mentioned nitroso compound and nitro compound.

An actual synthesis example will be explained using P-methyl-Yn-amyl azoxybenzene as an example.

126.99 g of potassium persulfate was added to 72.5 g (39.4 ml) of ice-cooled sulfuric acid, stirred, and left for 1 hour.

Thereafter, crushed ice 4009 was added, and when the ice melted, pure water was added while stirring to form a homogeneous solution. This solution was then neutralized with potassium carbonate solution. Separately, a solution was prepared by dissolving 6 ml of dioxane and 5.4 g of ICP-methylaniline, and this solution was added to the neutralized solution with stirring to cause a reaction.

After the reaction was completed, a nitrosated compound was obtained by steam distillation. After the nitroso compound was extracted with ether, the ether was distilled off, and the residue was used as it was in the next step.

After adding 20 ml of acetic acid to the residue to make a homogeneous solution,
1.7 g of P-n-amylaniline was added, and the mixture was left to stand overnight as a homogeneous solution. After standing, the solution was poured into water to precipitate crystals. After recrystallizing the precipitated crystals with ethanol, 0.52 g of these crystals was dissolved in 10 ml of acetic acid,
0.49% of hydrogen peroxide was added and the mixture was left at 80'C for 4 hours. After being left to stand, the mixture was cooled and poured into water to precipitate crystals. After production, recrystallization was performed with methanol until the melting point became constant. Note that this compound is a mixture of two types of isomers. Using the liquid crystal compound synthesized by the above method, the following liquid crystal composition was prepared and subjected to a life test.

Example 1 When a DSM type liquid crystal cell was filled with a liquid crystal composition as shown in the following table and driven at an alternating voltage of 15 V and 32 Hz, no problem occurred even after 6 months.

Example 2 The liquid crystal composition shown in the following table was filled into a DSM type liquid crystal cell, and the same test as in Example 1 was conducted;
As expected, no problems occurred even after 6 months.

Example 3 When a liquid crystal composition as shown in the following table was filled into an FE type liquid crystal cell and driven with an alternating voltage of 3V, 32Hz,
Even after 6 months had passed, no change in appearance was observed, and there was almost no increase in current.

As described above, it can be seen that the display device using the liquid crystal composition of the present invention is excellent in terms of stability and operating temperature range. This is because the novel azoxy liquid crystal compound according to the present invention has a different number of carbon atoms in the alkyl groups at both ends of the general formula. Since it is a so-called asymmetric compound, two types of isomers always exist, which is thought to widen the liquid crystal temperature range (i.e., the operating temperature range) and improve stability. The display device of the present invention has not yet been put to practical use, but the display device according to the present invention is fully capable of being put to practical use, and when applied to the display section of a watch, calculator, or portable consumer device, it fully exhibits its characteristics. It is something.

[Brief explanation of the drawing]

FIG. 1 is a diagram for explaining the display principle of the DSM method.

Claims (1)

[Claims] 1. A cell consisting of two glass substrates with a transparent electrode formed on one surface and a spacer, a means for applying voltage to the transparent electrode, and an electric cell consisting of a liquid crystal composition filled in the cell. An optical display device, characterized in that the liquid crystal composition is a liquid crystal compound containing a liquid crystal compound ▲A mathematical formula, a chemical formula, a table, etc.▼ or ▲A mathematical formula, a chemical formula, a table, etc.▼ Optical display device.