Switchable volume hologram materials and devices

A method for preparing a switchable reflection hologram, comprising the steps of:

• disposing a polymer-dispersed liquid crystal material between transparent plates;
• exposing an interference pattern inside the polymer-dispersed liquid crystal material;
• and
• applying a shear stress field whereby the symmetry axis of the liquid crystal is oriented substantially parallel to the transparent plates.

A switchable reflection hologram comprising:

• a polymer-dispersed liquid crystal material wherein the reflective material is disposed adjacent to the polymer-dispersed material and wherein the hologram is made by exposing an interference pattern inside a polymer-dispersed liquid crystal material, the polymer-dispersed liquid crystal material comprising, before exposure:
• (a) a polymerizable monomer;
• (b) a negative dielectric anisotropy liquid crystal;
• (c) a cross-linking monomer;
• (d) a coinitiator;
• and
• (e) a photoinitiator dye.

A switchable reflection hologram made by exposing an interference pattern inside a polymer-dispersed liquid crystal material in the presence of a magnetic field, the polymer-dispersed liquid crystal material comprising, before exposure:

• (a) a polymerizable monomer;
• (b) a positive dielectric anisotropy liquid crystal;
• (c) a cross-linking monomer;
• (d) a coinitiator;
• and
• (e) a photoinitiator dye;
• wherein the hologram has opposing surfaces and a plurality of polymer regions having a first refractive index and polymer-dispersed liquid crystal regions having a second refractive index disposed substantially parallel to the opposing surfaces of the hologram;
• an electrically conductive material associated with each of the opposing surfaces of the hologram and configured so that an electrical field can be applied across the hologram to modify the refractive index of the polymer-dispersed liquid crystal regions;
• and
• wherein the symmetry axis of the positive dielectric anisotropy liquid crystal is oriented substantially parallel to the opposing surfaces of the hologram.

A switchable reflection hologram made by exposing an interference pattern inside a polymer-dispersed liquid crystal material in the presence of a magnetic field, the polymer-dispersed liquid crystal material comprising, before exposure:

• (a) a polymerizable monomer;
• (b) a positive dielectric anisotropy liquid crystal;
• (c) a cross-linking monomer;
• (d) a coinitiator;
• and
• (e) a photoinitiator dye;
• wherein the hologram has opposing surfaces and a plurality of alternating planes of polymer channels having a first refractive index and polymer-dispersed liquid crystal channels having a second refractive index disposed substantially parallel to the opposing surfaces of the hologram;
• an electrically conductive material associated with each of the opposing surfaces of the hologram and configured so that an electrical field can be applied across the hologram to modify the refractive index of the polymer-dispersed liquid crystal channels;
• and
• wherein the symmetry axis of the positive dielectric anisotropy liquid crystal is oriented substantially parallel to the opposing surfaces of the hologram.

A switchable reflection hologram made by exposing an interference pattern inside a polymer-dispersed liquid crystal material and applying a shear stress field, the polymer-dispersed liquid crystal material comprising, before exposure:

• (a) a polymerizable monomer;
• (b) a positive dielectric anisotropy liquid crystal;
• (c) a cross-linking monomer;
• (d) a coinitiator;
• and
• (e) a photoinitiator dye;
• wherein the hologram has opposing surfaces and a plurality of polymer regions having a first refractive index and polymer-dispersed liquid crystal regions having a second refractive index disposed substantially parallel to the opposing surfaces of the hologram;
• an electrically conductive material associated with each of the opposing surfaces of the hologram and configured so that an electrical field can be applied across the hologram to modify the refractive index of the polymer-dispersed liquid crystal regions;
• and
• wherein the symmetry axis of the positive dielectric anisotropy liquid crystal is oriented substantially parallel to the opposing surfaces of the hologram.

A switchable reflection hologram made by exposing an interference pattern inside a polymer-dispersed liquid crystal material and applying a shear stress field, the polymer-dispersed liquid crystal material comprising, before exposure:

• (a) a polymerizable monomer;
• (b) a positive dielectric anisotropy liquid crystal;
• (c) a cross-linking monomer;
• (d) a coinitiator;
• and
• (e) a photoinitiator dye;
• wherein the hologram has opposing surfaces and a plurality of alternating planes of polymer channels having a first refractive index and polymer-dispersed liquid crystal channels having a second refractive index disposed substantially parallel to the opposing surfaces of the hologram;
• an electrically conductive material associated with each of the opposing surfaces of the hologram and configured so that an electrical field can be applied across the hologram to modify the refractive index of the polymer-dispersed liquid crystal channels;
• and
• wherein the symmetry axis of the positive dielectric anisotropy liquid crystal is oriented substantially parallel to the opposing surfaces of the hologram.