Tailoring material composition for optimization of application-specific switchable holograms

• US 7,175,780 B1
• Filed: 01/17/2006
• Issued: 02/13/2007
• Est. Priority Date: 11/26/2002
• Status: Expired due to Term

• Current Assignee: Leidos, Inc. (Leidos Holdings, Inc.)
• Original Assignee: Science Applications International Corporation
• Inventors: Sutherland, Richard L., Pogue, Robert T., Natarajan, Lalgudi V., Shepherd, Christina K., Brandelik, Donna M.
• Primary Examiner(s): WU, SHEAN CHIU
• Application Number:
  US11/332,247
• Time in Patent Office: 392 Days
• Field of Search: 428/1.1, 252/299.01, 252/299.5, 252/299.1, 349/88, 349/92, 349/93, 349/86
• US Class Current: 252/299.01
• CPC Class Codes: C09K 19/54 Additives having no specific mesophase characterised by their chemical composition
• CPC Class Codes: C09K 19/544 as dispersing or encapsulating medium around the liquid crystal
• CPC Class Codes: C09K 2019/528 Surfactants
• CPC Class Codes: C09K 2323/00 Functional layers of liquid crystal optical display excluding electroactive liquid crystal layer characterised by chemical composition

Abstract

The process described herein offers the optimizing of performance parameters of holograms, such as reducing scattering effects in a polymer-dispersed liquid crystal optical element. In the process, an interfacial tension agent is added to a polymer-dispersed liquid crystal material. The polymer-dispersed liquid crystal material has at least one acrylic acid monomer, at least one type of liquid crystal material, a photoinitiator dye, and a co-initiator. The polymer-dispersed liquid crystal material is subjected to a polymerization. The interfacial tension agent reduces the size of liquid crystal droplets formed within the polymer-dispersed liquid crystal optical element during polymerization.

Claims

1. A process for reducing scattering effects in a polymer-dispersed liquid crystal optical element comprising:

adding an interfacial tension agent to a polymer-dispersed liquid crystal material, the polymer-dispersed liquid crystal material comprising;

at least one acrylic acid monomer;

at least one type of liquid crystal material;

a photoinitiator dye; and

a co-initiator; and

subjecting the polymer-dispersed liquid crystal material to a polymerizing means, wherein the interfacial tension agent reduces the size of liquid crystal droplets formed within the polymer-dispersed liquid crystal optical element during polymerization of the polymer-dispersed liquid crystal material.

2. The process according to claim 1, wherein the interfacial tension agent contains a hydroxyl group.

3. The process according to claim 1, wherein the interfacial tension agent is of the type:

C_nH_(2n+1)COOH wherein n≦

18.

4. The process according to claim 1, wherein the polymer-dispersed liquid crystal material further comprises a reactive diluent.

5. The process according to claim 1, further comprising:

a polymer matrix formed upon polymerization of the polymer-dispersed liquid crystal material containing the at least one acrylic acid monomer in an amount sufficient to increase the conductivity of the polymer matrix and cause a reduction in the switching voltage.

6. The process according to claim 1, wherein the at least one acrylic acid monomer is approximately 1.0–

1.5 percent of the weight of the polymer-dispersed liquid crystal material.

7. The process according to claim 1, wherein the polymer-dispersed liquid crystal optical element further comprises a polymerizable monomer that is polymerized according to a different chemical process than the at least one acrylic acid monomer.

8. The process according to claim 7, wherein the at least one acrylic acid monomer is polymerized using a first polymerizing means and the polymerizable monomer is polymerized using a second polymerizable means.

9. The process according to claim 8, wherein the first and second polymerizing means are selected from the group consisting of:

visible radiation, ultraviolet radiation, heat, electron beam, and reactants.

10. The process according to claim 7, wherein the at least one acrylic acid monomer is polymerized at a first time and the second polymerizable monomer is polymerized at a second time.

11. The process according to claim 7, wherein the polymerizable monomer is a thiol-ene.

12. The process according to claim 7, wherein the at least one acrylic acid monomer comprises approximately 30–

50% of the polymer-dispersed liquid crystal material and the polymerizable monomer comprises approximately 5–

20% of the polymer-dispersed liquid crystal material.

13. The process according to claim 8, wherein the at least one acrylic acid monomer is polymerized by a free-radical chemical reaction and the polymerizable monomer is polymerized by a step-growth chemical reaction.

14. The process according to claim 4, wherein the diluent is selected from the group consisting of decanoic acid and dodecanoic acid.

15. The process according to claim 4, wherein the diluent comprises approximately 3–

4% of the polymer-dispersed liquid crystal material.

16. The process according to claim 1, wherein the interfacial tension agent is a long chain alkyl compound.

17. The process according to claim 1, further comprising the step of adding a co-monomer.

18. The process according to claim 17, wherein the co-monomer is selected from the group consisting of fluorinated mono-acrylates and methacrylates.