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US 3,938,880 AGranted
Spherulitic liquid crystalline texture
AssigneeXerox Corporation
InventorsWerner E. L. Haas, James E. Adams
Life of this patent
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Abstract
Liquid crystalline compositions comprising dielectrically negative nematic liquid crystalline materials from about 0.4 percent by weight to about 3 percent by weight optically active materials, in contact with an aligning agent, and characterized by a helical pitch to layer thickness ratio of from about 1 to about 10 are transformed from an initially homeotropic or homogeneous texture into a novel stable spherulitic texture upon removal of an applied D.C. or low frequency A.C. electrical field. Erasure and imaging of the novel spherulitic texture are disclosed.
Claims56
A method of producing a stable spherulitic liquid crystalline texture, comprising:
- a. providing an optically negative liquid crystalline composition comprising a dielectrically negative nematic liquid crystalline material and from about 0.4 to about 3 percent by weight of an optically active material, said optically negative composition having a light reflection band centered about .lambda..sub.o equal to 2np, where n equals the index of refraction and p equals the helical pitch of said optically negative liquid crystalline material;
- b. providing on a substrate, a layer of said liquid crystalline composition with at least a portion of said layer in the homeotropic or homogeneous texture of the nematic mesophase;
- said layer having a thickness which provides a ratio of said helical pitch to layer thickness of from about 1 to about 10;
- c. applying a voltage potential across said layer portion at a voltage level and for a period of time wherein upon removal of said applied voltage spherulites are formed;
- and
- d. removing said voltage potential whereby spherulites are produced at least within said layer portion.
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On a substrate:
- a layer of liquid crystalline composition comprising a dielectrically negative nematic liquid crystalline material and from about 0.4 to about 3 percent by weight of an optically active material, said liquid crystalline composition when out of contact with an aligning agent or treated substrate being optically negative and having a light reflection band centered about .lambda..sub.o = 2np where n = index of refraction and p = helical pitch of said liquid crystalline composition, said liquid crystalline composition when in contact with an aligning agent or treated substrate in the homeotropic or homogeneous texture of the nematic mesophase;
- the ratio of said helical pitch to the thickness of said layer being from about 1 to about 10;
- and, an aligning agent or treated substrate in contact with said layer of liquid crystalline composition.
On a substrate:
- a layer of liquid crystalline composition comprising a dielectrically negative nematic liquid crystalline material and from about 0.4 to about 3 percent by weight of an optically active material, said liquid crystalline composition when out of contact with an aligning agent or treated substrate being optically negative and having a light reflection band centered about .lambda..sub.o equal to 2np, where n = index of refraction and p = helical pitch of said liquid crystalline composition, said liquid crystalline composition when in contact with an aligning agent or treated substrate being in the homeotropic or homogeneous texture of the nematic mesophase, said liquid crystalline composition when in the homeotropic or homogeneous texture of the nematic mesophase capable of undergoing electrically induced transition into a spherulitic texture upon removal of an applied voltage;
- the ratio of said helical pitch to the thickness of said layer being from about 1 to about 10;
- an aligning agent or treated substrate in contact with said layer of liquid crystalline composition;
- and, within said layer of liquid crystalline composition, at least one spherulite, said spherulite lacking the optical characteristics of the homoeotropic or homogeneous texture of the nematic mesophase and being surrounded by said liquid crystalline composition having the optical characteristics of the homeotropic or homogeneous texture of the nematic mesophase.
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A method of producing a stable spherulitic liquid crystalline texture, comprising:
- a. providing on a substrate a layer of aligned liquid crystalline composition comprising a dielectrically negative nematic liquid crystalline material and from about 0.4 to about 3 percent by weight of an optically active material, said liquid crystalline composition prior to alignment being optically negative and having a light reflection band centered about .lambda..sub.o = 2np where n = index of refraction and p = helical pitch, the ratio of the helical pitch of the non-aligned liquid crystalline composition to the layer thickness of liquid crystalline composition being from about 1 to about 10;
- b. applying a voltage potential across the layer of liquid crystalline composition;
- and
- c. removing said voltage potential whereupon spherulitic regions of the liquid crystalline composition are formed within the aligned liquid crystalline composition.
1 more element
Dependencies are inferred from the claim text.