Storage device using cholesteric nematic liquid crystals

Claim 2

said composition comprising on a 100 weight percent total composition basis a mixture of from about 51 to 99 weight percent material having nematic liquid crystallinity and correspondingly, from about 1 to 49 weight percent material having cholesteric liquid crystallinity, said composition in said layer displaying a positive dielectric constant anisotropy such that 20 > or = Sigma - Sigma > or = 0.2 where Sigma is the dielectric constant in a direction parallel to the longitudinal axis of the molecules of the liquid composition in a storage device of this invention, and Sigma is the dielectric constant in a direction perpendicular to the helical axis of the liquid composition in a storage device of this invention.

Claim 3

said voltage being either a direct current or an alternating current or both, said composition at the time of said applying having a transparent, planar texture, said voltage being so applied for a time sufficient to generate in said layer a light-scattering, focal-conical, milky texture with a layer-wise helical nematic crystalline formation therein having a screw axis subStantially parallel to said faces and in a pattern representative of said information to be stored, and B. applying across said faces a direct current or an alternating current extinction voltage pulse for a time of less than about 30 microseconds to 30 milliseconds, but which time interval is sufficient to transform the texture of said layer into a transparent, nematically homeotropic form wherein the liquid crystal molecules are aligned in a direction substantially normal to said faces.

Claim 4

The device of claim 1, wherein each of said electrodes is transparent.

Claim 5

The device of claim 1, wherein said other one of said electrodes has a specularly reflecting electrode.

Claim 6

The device of claim 1, wherein said composition comprises from about 90 to 95 weight percent nematic P-methoxy-p''-n-butylazoxybenzene with the balance up to 100 weight percent thereof being cholesterylchloride.

Claim 7

The device of claim 1, wherein said composition in said layer has a specific resistance of at least about 1011 Omega -cm.

Claim 8

An improved method for temporary image storage comprising the sequential steps of A. selectively applying across opposed parallel faces of a layer of a composition a voltage in a pattern representative of information to be stored,

Claim 9

The method of claim 7, wherein said composition comprises from about 90 to 95 weight percent nematic p-methoxy-p''-n-butylazoxybenzene with the balance up to 100 weight percent thereof being cholesterylchloride.

Claim 10

The method of claim 7, wherein after said extinction voltage pulse has died out, the texture of said layer is transformed into said transparent, planar texture wherein a helical cholesteric crystalline structure is formed.

Claim 11

The method of claim 7, wherein said layer has a specific resistance of at least about 1011 Omega -cm.

Claim 12

The method of claim 7, wherein each of said opposed faces is in contact with a layer of surface active material adapted to align the longitudinal axes of the respective individual molecules adjacent thereto in a direction substantially normal to said opposed faces relative to said faces.

Claim 13

The method of claim 11, wherein said surface active layers comprises lecithin.