Cholesteric liquid crystal display system

A display responsive to an image wise pattern of illumination to display an image, comprising:

• a) a pair of conductors, at least one conductor being transparent, for forming an electrical field there between;
• b) a layer of cholesteric liquid crystal material disposed between the conductors, the liquid crystal material having multiple stable optical states at zero electrical field and responsive to an electric field between the conductors for changing optical state;
• and
• c) a light absorber for forming an image wise thermal pattern in the cholesteric liquid crystal sufficient to change the optical state of the cholesteric liquid crystal to display the image.

A writing device for writing an image in a display having a pair of conductors, at least one conductor being transparent, for forming an electrical field there between, a layer of cholesteric liquid crystal material disposed between the conductors, the liquid crystal material having multiple stable optical states at zero electrical field and responsive to an electric field between the conductors for changing optical state, and a light absorber for forming an image wise thermal pattern in the cholesteric liquid crystal sufficient to change the optical state of the liquid crystal to display the image, comprising:

• a) a flash light source;
• b) a mask located over the flash light source for forming an image wise pattern of flash light;
• c) a display drive with electrical contacts for applying an electrical field to the conductors of the display;
• and
• d) a controller connected to the light source and the display drive for controlling the intensity of the electrical field and actuating the light source to create an image on the display.

A display system, comprising:

• a) a display including a substrate, a first transparent conductor formed on the substrate, a layer of cholesteric liquid crystal having a plurality of stable optical states at ambient temperatures located over the first conductor, and a light absorbing second conductor located over the layer of cholesteric liquid crystal for forming an image wise thermal pattern in response to an image wise pattern of light;
• and
• b) a writing device including a flash light, a mask for forming the image wise pattern of light, and means for applying an electrical field across the first and second conductors, and a display drive with electrical contacts for applying an electrical field to the conductors of the display;
• and a controller connected to the light source and the display drive for controlling the intensity of the electrical field and actuating the light source to create an image on the display.

A method of writing and erasing an image, comprising the steps of:

• a) providing a layer of polymer dispersed cholesteric liquid crystal material disposed between a pair of unpatterned conductors and a light absorber for forming an image wise thermal pattern in response to an image wise pattern of light;
• b) applying an electrical field having a first magnitude across the unpatterned conductors to erase any image in the polymer dispersed cholesteric liquid crystal material and initializing the material;
• and
• c) applying an electrical field having a second magnitude across the unpatterned conductors and exposing the layer of polymer dispersed cholesteric liquid crystal material to an image wise flash of light to write the image.