KR810002070B1 - Liquid crystal material - Google Patents

Abstract

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Description

Liquid crystal material

1 Exploded view of staggered nematic display panel

2 is a front view of a watch having a staggered nematic liquid crystal panel made as shown in FIG.

3 is an enlarged cross-sectional view of the part of the watch panel of FIG.

The present invention relates to a liquid crystal material.

Many liquid crystal displays have been known and typically have a thin liquid crystal material between two electrodes sandwiched between two glass slides. Putting an operable voltage through the layers into the two electrodes, the optical properties change visually and these properties are used to display information. The electrodes are arranged, for example, in numerical or matrix form, expressed in time (clockwise units) or in waveforms.

The liquid crystal material is smectic, cholesteric or nematic. The present invention relates to a nematic liquid crystal material or a mixture of nematics and a small amount of cholester material.

The voltage at which the influence of voltage is observed in the liquid crystal is called the threshold voltage. Normally, the threshold is cleared (e.g. about twice the threshold voltage) to make the display clear.

The liquid crystal display should consume a low voltage which is remarkably suitable for battery operation such as wristwatches and pocket calculators. Therefore, it is desirable to reduce the threshold voltage as much as possible to use one low-volt-count battery (eg a standard 1.5V battery).

It is an object of the present invention to provide a liquid crystal capable of operating at low voltages.

The liquid crystal chamber used in the present invention is a liquid crystal layer sandwiched between two substrates, at least one of which is transparent and a substrate in which electrodes are arranged to form an electronic plate in a selected portion of the layer, and a liquid crystal material is a single compound or a mixture of compounds and dyes. It may contain.

The liquid crystal material of the present invention comprises a mixture of at least three liquid crystal materials, at least two of which are selected from the following compounds or compounds substituted with cyclohexane rings instead of benzene rings.

In the compound,

X is a short chain alkyl group C _n H _2n +1 where n is excellent or X is a short chain alkoxy group C _m H _2m +1 where m is an odd number.

The component material may or may not itself be a liquid crystal phase, but when mixed with other liquid crystal substances, it must be a liquid crystal phase.

The mixture may contain components from one or more compounds, but the n and m values must be different, or different compounds of the compounds may be mixed. One or more mixtures are compounds which do not satisfy n = excellent, m = base, and are added to increase the nematic temperature range of the mixture. Such a compound is for example the following 5CT or BB15.

Secondly, the liquid crystal display device operating at low volts number contains the above liquid crystal core containing the (first) mixture.

The liquid crystal material of the following structural formula is described in British Patent Specification No. 1,433,130 and is called a biphenyl material.

In the above structural formula,

X is an alkyl, alkoxy, alkanoyloxy or alkenyl group and CN is a cyano group.

When n is even, the operating voltage is lower than when it is odd, and similarly, it is lower than when it is even. Also, the lower the values of n and m, the lower the operational voltage. In order to lower the operating voltage, the following values are desirable.

n = 2, 4, 6, m = 1, 3, 5

However, materials with low values of n and m have a melting point higher than room temperature, usually higher than the isotropic temperature (temperature to be transparent). (E.g. biphenyl)

TABLE 1

() Indicates the actual short-shift.

Therefore, the mixture contains components with high values of n and m (eg n = 6, m = 5) so that the nematic liquid crystal temperature range of the mixture can be accommodated. For such mixtures the mean values of n and m should be as low as possible, preferably n ≦ 6 and m ≦ 5. The mean values of n and m of the mixture containing alkyl and alkoxy groups should be as small as possible and values less than 6 or 5 are preferred.

The invention can be described in the embodiments associated with the accompanying drawings.

As in FIG. 1, the plate consists of polarizer 1 in which polarization axis 2 is perpendicular. Liquid crystal cell 3 consists of two glass slides 4 and 5 containing six layers of nematic liquid crystals. Electrodes 7, 8 (e.g., stone oxide) are on the inner slides 4 and 5, and behind the liquid crystal chamber 3 is the secondary polarizer 11, in which the analyzer or aza polarization axis 12 is horizontal. Behind the analyzer 11 is a thin wire aluminum reflector 27.

Before assembling the liquid crystal chamber, the slides 4 and 5 are coated with silicon monooxide or magnesium fluoride. At this time, the airflow of the coating body is evaporated and coated. Silicon monooxide, for example, is coated by evaporating the slides at an angle of about 5 ° from the surface as described in British Patent No. 1,454,296. At the time of assembly, the slides are arranged in the same direction as the evaporation directions of the two slides 4 and 5 with each other having a polarization direction of 90 °. The liquid crystal molecules on the coating surface thus coated are placed in a single direction (parallel to the evaporation direction) and at an angle of about 25 ° to 35 °, typically about 30 ° to the slide surface. Alternatively, the slides are cleaned, immersed in a solution of water and 2% by weight of polyvinyl alcohol (P.V.A), dried and wiped in a single direction with a soft tissue. The slide is assembled at right angles to the wiped direction. The liquid crystal molecules move freely from slide 4 to slide 5 when the liquid crystal molecules are placed in the liquid crystal chamber at an angle of about 2 ° with respect to the slide surface. Therefore, when the polarized light is passed through the liquid crystal chamber 3, the molecules on the surfaces of the slides 4 and 5 in the direction of 13 are rotated by 90 ° to be parallel (or perpendicular) to the polarization axes 2 and 12, respectively. When the voltage of the liquid crystal chamber is 0, light passes through the analyzer 1, the liquid crystal chamber 3, and the analyzer 11 and is reflected back to the observer 15 as it is.

When an operational voltage is sent between electrodes 7, 8, they are aligned parallel to the direction of the molecules sent between the electrodes, and the light sent to the polarizer is moved to the analyzer 11 without rotation. Since the polarizer and the analyzer 11 cross each other, no light is transmitted to the reflector, and no light is reflected back to the observer on the side of the liquid crystal chamber 3 between the electrodes 7, 8 so that the back of the bright side is dark. Therefore, electrodes 7 and 8 are each made up of seven separate parts that can be connected to a power source, allowing the numbers from 0 to 6 to be displayed.

In the clock, the display of the second and third degrees and the electrodes 7, 8 are arranged so that the seven bars represent numbers and the period dots reacting once per second.

The voltage required to bring the molecules parallel to the light, ie 'on', depends on the thickness of layer 6, the material used, the temperature and the surface treatment of slides 4 and 5. A typical layer is 12 um thick and the material used should be stable at room temperature, i. Silicon monooxide is evaporated and surface treated at an angle of 5 ° to incline the molecules to 30 °, which reduces the voltage required to turn the liquid crystal chamber on.

In a typical clock display panel using a displaced nematic liquid crystal display panel, the oscillator and the theoretical circuit of the clock are operated by using a 1.5 V battery, and the voltage is raised to 3.0 to 4.5 V using an up converter. It works.

When the nematic liquid crystal material according to the present invention is used, the voltage required to operate the liquid crystal panel is reduced from 1.25 to 1.40V.

Adding a small amount of cholesteric material to the nematic liquid crystal yields a long pitch cholesteric material. In order to prevent the formation of an incongruous appearance, a cholester pitch is attached to the slices 4 and 5 in a relatively straight line as described in British Patent Application No. 1,472,247.

For example, about 1% of C.15 cholesteric cyano biphenyl (commercially available from British Drug Houses) is added to the nematic material.

C.15 The substance has the structure

The following table shows an example of the nematic mixture and an example of the operating voltage required for 10% transmission, that is, the normal light is projected through the manufactured liquid crystal chamber and operated as follows to turn it on completely.

(i) 12um total thickness, slide coated with Sio ₂ , working voltage 1KH ₃ Sine wave bed temperature 22 ℃

(ii) Layer thickness 7um, slide coated and rubbed with PVA, working voltage 100H ₃ square wave 22 ° C percent of bed temperature is weight ratio.

TABLE 2

The display panels of the first, second, and third degrees replace the reflector 27 with a partial reflector, and a beta light or a low power tungsten illuminator is installed behind the partial reflector, and when the ambient light is not available, the display panel is replaced by the reflected light. You can make it visible.

Claims (1)

A liquid crystal material containing a mixture of at least three liquid crystal materials, wherein at least two of the components are selected from the following compounds, or a compound substituted with a cyclohexane ring instead of a benzene ring.

In the compound of the above formula, X is a short chain alkyl group C _n H _2n +1 where n is excellent; or X is a short-chain alkoxy group C _m H _2m +1 where m is an odd number.

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