Encapsulated polymer network liquid crystal material, device and applications

• US 8,801,964 B2
• Filed: 12/22/2010
• Issued: 08/12/2014
• Est. Priority Date: 12/22/2010
• Status: Active Grant

• Current Assignee: Orbotech Limited (KLA Corporation)
• Original Assignee: Photon Dynamics Incorporated (KLA Corporation)
• Inventors: Chen, Xianhai
• Primary Examiner(s): WU, SHEAN CHIU
• Application Number:
  US12/976,127
• Publication Number:
  US 20120162596A1
• Time in Patent Office: 1,329 Days
• Field of Search: 349/199, 349/88, 349/90, 252/299.01, 252/299.5
• US Class Current: 252/299.01
• CPC Class Codes: G02F 1/133703 by introducing organic surfactant additives into the liquid crystal material

Abstract

Polymer network liquid crystal materials have improved mechanical properties such as rigidity and hardness and substantially improved electro-optical performance. The PNLC material can be manufactured with an emulsion process so as to simplify substantially the manufacturing process. Each LC droplet can be configured with the polymer network extending substantially across the LC droplet, and the polymer network may comprise a material to lower substantially the switching voltage, such as a fluorinated acrylate that may interact with the liquid crystal so as to lower the surface tension of the LC droplet. The PNLC material may comprise an interfacial layer combined with the polymer network so as to decrease substantially the driving voltage.

Claims

1. A liquid crystal sensor material, comprising:

a plurality of liquid crystal droplets, each droplet comprising a liquid crystal material and a polymer network comprising a plurality of crosslinked polymer chains wherein the polymer network is configured to decrease a light transmission voltage of said sensor material;

a polymer matrix located around each of the plurality of liquid crystal droplets such that said each of the plurality of liquid crystal droplets is located within the polymer matrix; and

an interfacial layer located between the polymer matrix and said each of the liquid crystal droplets so as to encapsulate said each of the plurality of liquid crystal droplets with the interfacial layer and inhibit coupling of the networked polymer with the interfacial layer,

wherein the polymer network comprising the plurality of crosslinked polymer chains extends to the interfacial layer without substantially anchoring to the interfacial layer, and

wherein the polymer network comprising the plurality of crosslinked polymer chains extends substantially across said each droplet from a first portion of the interfacial layer on a first side of said each droplet to a second portion of the interfacial layer on a second side of said each droplet.

2. The liquid crystal sensor material of claim 1, wherein the polymer network decreases a fifty percent light transmission voltage of the plurality of liquid crystal droplets by an amount corresponding to at least about 25% lower than without the polymer network.

3. The liquid crystal sensor material of claim 2, wherein the polymer network comprises a material to decrease a surface tension of said each droplet so as to decrease the fifty percent light transmission voltage of the plurality of liquid crystal droplets by the amount.

4. The liquid crystal sensor material of claim 3, wherein the plurality of cross linked polymer chains comprises carboxylic acid esters having aliphatic carbon chains comprising one or more of unsubstituted aliphatic carbon chains or substituted aliphatic carbon chains to lower the surface tension of said each liquid crystal droplet.

5. The liquid crystal sensor material of claim 4, wherein the substituted aliphatic carbon chains to lower surface tension of said each liquid crystal droplet comprises fluorinated aliphatic carbon chains to lower the surface tension.

6. The liquid crystal sensor material of claim 1, wherein said polymer network of said each droplet comprises a plurality of polyacrylate chains comprising esters of acrylic acid.

7. The liquid crystal sensor material of claim 1, wherein said polymer network of said each droplet comprises silicone acrylate.

8. The liquid crystal sensor material of claim 1 wherein the polymer network comprising the plurality of crosslinked polymer chains comprises fluorinated acrylate so as to decrease surface tension and friction of said each liquid crystal droplet in contact with said interfacial layer.

9. The liquid crystal sensor material of claim 1, wherein the polymer network comprising the plurality of crosslinked polymer chains of said each droplet is coupled to an inner surface of the interfacial layer with no more than weak molecular interactions and without substantial cross-linking chemical bonds extending between the inner surface and the plurality of crosslinked polymer chains.

10. The liquid crystal sensor material of claim 1, wherein the interfacial layer of said each droplet of liquid crystal material comprises a bilayer having an inner hydrophobic side and an outer hydrophilic side, wherein the inner hydrophobic side contacts the polymer network without anchoring and contacts the liquid crystal material so as to decrease substantially a fifty percent light transmission voltage of the plurality of liquid crystal droplets.

11. The liquid crystal sensor material of claim 1, wherein the polymer network comprises a free radical cured monomer or polymer soluble in the liquid crystal material comprising one or more of an acrylate, a di-acrylate, a multi-functional acrylate, a thiol-ene resin, a silicone acrylate or a fluorinated acrylate and wherein the liquid crystal comprises one or more of nematic LC, ferroelectric LC, Blue Phase LC, LC/Dichroic Dye mixture ChLC and wherein the wherein the interfacial layer comprises one or more of diblock copolymer or reactive interfacial agent.

12. The liquid crystal sensor material of claim 1, wherein the polymer matrix comprises one or more of a poly vinyl alcohol (PVA), a water based latex, a water based acrylic latex, or a water based polyurethane latex and wherein the interfacial layer comprises one or more of diblock copolymer or interfacial agent.

19. An electro-optic modulator assembly, comprising:

a transparent substrate; and

,

a liquid crystal sensor material supported with the transparent substrate, wherein the liquid crystal sensor material comprises a liquid crystal sensor material of claim 1.

13. A liquid crystal sensor material, comprising:

a plurality of liquid crystal droplets, each droplet comprising a liquid crystal material and a polymer network comprising a plurality of crosslinked polymer chains;

a polymer matrix located around each of the plurality of liquid crystal droplets such that said each of the plurality of liquid crystal droplets is located within the polymer matrix; and

an interfacial agent located between the polymer matrix and said each of the liquid crystal droplets so as to encapsulate said each of the plurality of liquid crystal droplets with the interfacial agent such that the polymer network is separated from the polymer matrix with the interfacial agent,

wherein the polymer network comprising the plurality of crosslinked polymer chains extends to the interfacial layer without substantially anchoring to the interfacial layer, and

wherein the polymer network comprising the plurality of crosslinked polymer chains extends substantially across said each droplet from a first portion of the interfacial layer on a side of said each droplet to a second portion of the interfacial layer on a second side of said each droplet.

14. A method of manufacturing a sensor material, the method comprising:

making an emulsion comprising a plurality of droplets of a liquid crystal material dispersed in an aqueous liquid, and an interfacial agent, the droplets comprising a prepolymer dissolved in the liquid crystal material, the aqueous liquid comprising a water based polymer, such that the interfacial agent encapsulates said each of the plurality of droplets to form an interfacial layer, wherein the interfacial agent and the polymer network together lower the surface tension of said each droplet;

drying the emulsion such that the water based polymer forms a polymer matrix located around each of the plurality of droplets; and

curing the dried emulsion such that the prepolymer forms a polymer network within said each of the plurality of droplets when the polymer matrix is located around said each of the plurality of droplets,

wherein the polymer network comprising the plurality of crosslinked polymer chains extends to the interfacial layer without substantially anchoring to the interfacial layer, and

wherein the polymer network comprising the plurality of crosslinked polymer chains extends substantially across said each droplet from a first portion of the interfacial layer on a first side of said each droplet to a second portion of the interfacial layer on a second side of said each droplet.

15. The method of claim 14 wherein the polymer network decreases a fifty percent light transmission voltage of the plurality of liquid crystal droplets by an amount corresponding to at least about 25% lower than without the linked polymer network.

16. The method of claim 15 wherein the polymer network lowers a surface tension of said each of the plurality of droplets so as to decrease the fifty percent light transmission voltage of the plurality of liquid crystal droplets by the amount.

17. The method of claim 14 further comprising coating a surface with a layer of the emulsion of droplets of the liquid crystal material in the aqueous solution.

18. The method of claim 14 wherein the droplets of liquid crystal material comprising the dissolved prepolymer are exposed to the aqueous solution comprising the water soluble polymer.