Optical sensitization and development of liquid crystalline devices

A method of imaging, comprising:

• a. providing, in turn, in sandwich configuration, a first electrode, an insulating layer, a photoconductive layer, a layer of liquid crystalline composition having the optical characteristics of the cholesteric mesophase in the Grandjean texture, and a second electrode;
• the thickness ratio of said photoconductive to insulating layer being at least about 10 to 1;
• b. applying a D.C. voltage across said insulating;
• photoconductive and liquid crystalline layers;
• c. impinging said photoconductive layer with a biasing light having a wavelength within the fundamental absorption band of said photoconductive layer wherein a primary photocurrent is excited within said photoconductive layer;
• d. removing said biasing light at about the charge threshold for gain photocurrent within said photoconductive layer;
• and
• e. impinging said photoconductive layer with gating light having a wavelength within the fundamental absorption band of said photoconductive layer and which excites a primary photocurrent within said photoconductive layer sufficient to provide a total primary photocurrent charge accumulation above the charge threshold for gain photocurrent within said photoconductive layer;
• one of said biasing light and said gating light being in imagewise configuration and the other of said biasing light and gating light impinging said photoconductive layer uniformly.

A method of changing at least one characteristic of a layer of liquid crystalline composition, said characteristic being responsive to applied voltage, comprising:

• a. providing a sandwich structure comprising, in turn, a first electrode, an insulating layer, a photoconductive layer, said layer of liquid crystalline composition, and a second electrode;
• the thickness ratio of said photoconductive layer to said insulating layer being at least about 10 to 1;
• b. applying a D.C. voltage across said insulating photoconductive and liquid crystalline layers;
• c. impinging said photoconductive layer with biasing light having a wavelength within the fundamental absorption band of said photoconductive layer wherein a primary photocurrent is excited within said photoconductive layer;
• d. removing said biasing light at about the charge threshold for gain photocurrent within said photoconductive layer;
• and
• e. impinging said photoconductive layer with a gating light having a wavelength within the fundamental absorption band of said photoconductive layer and which excites a primary photocurrent within said photoconductive layer sufficient to provide a total primary photocurrent charge accumulation above the charge threshold for gain photocurrent within said photoconductive layer;
• said biasing light being in imagewise configuration and said gating light impinging said photoconductive layer in at least one area previously struck by said biasing light.

A method of changing at least one characteristic of a layer of liquid crystalline composition, said characteristic being responsive to applied voltage, comprising:

• a. providing a sandwiched structure comprising, in turn, a first electrode, an insulating layer, a photoconductive layer, said layer of liquid crystalline composition, and a second electrode;
• the thickness ratio of said photoconductive layer to said insulating layer being at least about 10 to 1;
• b. applying a D.C. voltage across said insulating, photoconductive and liquid crystalline layers;
• c. impinging said photoconductive layer with biasing light having a wavelength within the fundamental absorption band of said photoconductive layer wherein a primary photocurrent is excited within said photoconductive layer;
• d. removing said biasing light at about the charge threshold for gain photocurrent within said photoconductive layer;
• and
• e. impinging said photoconductive layer with a gating light having a wavelength within the fundamental absorption band of said photoconductive layer and which excites a primary photocurrent within said photoconductive layer sufficient to provide a total primary photocurrent charge accumulation above the charge threshold for gain photocurrent within said photoconductive layer;
• said biasing light impinging said photoconductive layer uniformly and said gating light being in imagewise configuration.