Liquid crystal driving system

#This invention relates to a liquid crystal driving system.

#Conventionally, the liquid crystal device wherein electrodes are disposed on the inner wall surfaces of a transparent receptacle such as a transparent glass-made receptacle; and a liquid crystal, for example, a nematic liquid crystal is provided between the electrodes is driven by applying thereto a square wave pulse voltage readily obtained using, for example, an oscillator having the digital integrated circuit construction.

#That is, upon applying a voltage to the liquid crystal, it is brought to a dynamic scattering state. When a light incides into the resulting liquid crystal, the incident light is subjected to scattering, so that this liquid crystal looks whitish to the eyes.

#FIG. 1 is a prior art voltage waveform for being applied to a liquid crystal to drive the same;

#FIG. 2 is a curve diagram illustrating the light scattering strength characteristic of the liquid crystal relative to the frequency of a voltage applied;

#FIG. 3 is a curve diagram illustrating the light scattering strength characteristic of the liquid crystal relative to the ambient temperature thereof;

#There will now be described an embodiment of the invention by reference to the accompanying drawings. A liquid crystal device may be one having a known construction. To take an example, a pair of electrodes are disposed opposed to each other between the mutually opposed inner wall surfaces of an airtight receptacle made of transparent material such as glass and having a size of, for example 50 mm .times. 50 mm, and a liquid crystal layer 20 .mu.m in thickness which consists of nematic liquid crystal, for example, a mixed liquid crystal composed of MBBA (P-methoxy benzylidene-P'-n-butyl aniline) and EBBA (P-ethoxy benzylidene-P'-n-butyl aniline) is provided between said pair of electrodes to obtain a liquid crystal device.

#Conventionally, the liquid crystal is generally driven by applying across said electrodes such a square wave pulse voltage as illustrated, for example, in FIG. 1 and thereby applying this voltage to the liquid crystal.

#Generally, the AC voltage e(t) whose cyclical period T is expressed by 2.pi./W and which contains no DC component is expanded into a Fourier series as below. ##EQU1## where ##EQU2## m is an integer; and bm represents the amplitude of the m th harmonics wave. Accordingly, the square wave pulse voltage illustrated in FIG. 1 is expanded into the following Fourier series. ##EQU3## As apparent from the above equation, such a square wave pulse voltage as illustrated in FIG. 1 contains many harmonics wave components as well as the fundamental wave component whose frequency For example, the third harmonics wave component has an amplitude equal to 1/3 of that of the fundamental wave component. If, in case liquid crystal driving is effected by applying such a square wave pulse voltage as illustrated in FIG. 1 to the liquid crystal, its repetitive frequency is raised up to a level of more than 800 Hz as seen from FIG. 2, or the ambient temperature of the liquid crystal is reduced below 5.degree. C as seen from FIG. 3, the liquid crystal will cease to present a dynamic scattering state.