Browse Prior Art Database

Switching of Nematic Liquid Crystals by Surface Waves

IP.com Disclosure Number: IPCOM000077131D
Original Publication Date: 1972-Jun-01
Included in the Prior Art Database: 2005-Feb-24
Document File: 3 page(s) / 57K

Publishing Venue

IBM

Related People

Heidrich, PF: AUTHOR [+5]

Abstract

This description relates to devices based on switching on liquid crystals by piezoelectric surface waves. Liquid crystals are organic molecules, existing in liquid phase and yet exhibiting anisotropic properties of a crystal.

This text was extracted from a PDF file.
At least one non-text object (such as an image or picture) has been suppressed.
This is the abbreviated version, containing approximately 53% of the total text.

Page 1 of 3

Switching of Nematic Liquid Crystals by Surface Waves

This description relates to devices based on switching on liquid crystals by piezoelectric surface waves. Liquid crystals are organic molecules, existing in liquid phase and yet exhibiting anisotropic properties of a crystal.

The liquid crystals may exist in one of three different phases, smectic, nematic and cholesteric. A thin layer of nematic liquid crystal is transparent to white light. However, when an electric field exceeding certain intensity (typically 5 x 10/3/ V/cm) is applied across the thin layer, the liquid scatters light, so that the thin layer becomes opaque.

Switching of liquid crystals from a transparent to a dynamic scattering state can be realized, not by direct application of electric field but by piezoelectric surface waves. Application of this effect is implemented in the following devices.
1. Simple Light Switch.

Fig. 1 shows a thin nematic liquid-crystal layer 1 sandwiched between two plates 2 and 3. One of the plates, for example 3, is a piezoelectric crystal or ceramic, on which interdigital transducers 4 and 5 are fabricated. The transducers 4 and 5 are excited by an AC source 6, whereby two surface waves propagating in opposite direction form a standing wave in the liquid layer device. The piezoelectric field and acoustic field change the liquid crystals to dynamic scattering state. The device which is originally transparent becomes opaque. and thus shuts off the light passing through it. In the device of Fig. 1, the switching is performed by surface waves excited at the transducer of previously known devices because of the size of the transducer is much smaller than the total area of the conventional electrodes. 2. Intensity Variable Light Valve

Fig. 2 shows a configuration where surface waves are propagated on both interfaces of the liquid crystals with the top and bottom plates. The phase of the surface waves in one of the plates can be adjusted with respect to the phase of that on the other plate. Thus, the two waves can interfere either constructively or destructively in the liquid-crystal layer; therefore, the degree of opaqueness or degree of transmission can be a...