Polymer dispersed liquid crystals in radiation curable electron-rich alkene-thiol polymer mixtures

• US 5,516,455 A
• Filed: 02/17/1995
• Issued: 05/14/1996
• Est. Priority Date: 05/03/1993
• Status: Expired due to Fees

• Current Assignee: Loctite Corporation (Henkel AG & Co KGaA)
• Original Assignee: Loctite Corporation (Henkel AG & Co KGaA)
• Inventors: Jacobine, Anthony F., Woods, John G., Rakas, Margaret A.
• Primary Examiner(s): Bleutge, John C.
• Assistant Examiner(s): WILSON, DONALD R
• Application Number:
  US08/391,252
• Time in Patent Office: 452 Days
• Field of Search: 252/299.01, 252/299.66, 252/299.67, 522/1, 522/180, 524/205, 524/293, 528/376, 528/360
• US Class Current: 252/299.01
• CPC Class Codes: C08G 75/045 from mercapto compounds and unsaturated compounds
• CPC Class Codes: C08G 75/12 Polythioether-ethers C08G75/0245 takes precedence
• CPC Class Codes: C09K 19/544 as dispersing or encapsulating medium around the liquid crystal

Abstract

A polymer dispersed liquid crystal composite prepared from: (1) at least one multifunctional electron-rich alkene that does not undergo appreciable homopolymerization and is selected from the group consisting of (a) vinyl ethers and vinyl sulfides; (b) keteneacetals, ketenethioacetals and methylene oxathiolanes, wherein the carbon of the carbon-carbon double bond not bearing the electron donating group has bonded to it H or a combination of H and a C1 to C₆ alkyl, preferably a methyl group; (c) ortho or para vinyl phenyl ethers or thioethers (also known as styryloxy or styrylthio ether monomers); or (d) bicylic alkenes which have, as a result of their stereoelectronic configuration, unequal π-electron density above and below the plane of the carbon-carbon double bond axis; (2) a multifunctional thiol; (3) a photoinitiator; and (4) liquid crystal material.

Claims

1. A radiation curable polymerizable mixture comprising:

a multifunctional thiol.

at least one multifunctional electron-rich alkene which does not undergo appreciable homo polymerization and is selected from the group consisting of;

(a) vinyl ethers and vinyl sulfides;

(b) keteneacetals, ketenethioacetals and methylene oxathiolanes wherein the carbon of the carbon-carbon double bond not bearing the electron donating group, has bonded to it H or a combination of H and a C₁ to C₆ alkyl;

(c) ortho or para vinyl phenyl ethers or thioethers; and

(d) bicylic alkenes which have as a result of their stereoelectronic configuration unequal π

-electron density above and below the plane of the carbon-carbon double bond axis,

a photoinitiator, and

a liquid crystal material soluble in said polymerizable mixture in an amount of between about 20 and about 90% by weight of the mixture, said liquid crystal having a molecular weight of less than 1000, wherein

the total reacting functionality of the mixture being greater than 4 and the ratio of equivalents of thiol to electron-rich alkene component being from about 0.5;

1 to about 2.0;

1, and wherein after 100 milliseconds the fraction of the initial voltage sufficient to make a film of the cured mixture clear and transparent, remaining on a pixel element, is 0.82 or higher.

2. The polymerizable mixture of claim 1 wherein the multifunctional electron-rich alkene is selected from the group consisting of vinyl ether functional resins, norbornenyl functional resins and a mixture of both.

3. The polymerizable mixture of claim 1 wherein the multifunctional electron-rich alkene is ethoxylated bisphenol A di(norbornene carboxylate) and the multifunctional thiol is pentaerythritol tetra-(3-mercaptopropionate).

4. The polymerizable mixture of claim 1 wherein the multifunctional electron-rich alkene is polytetrahydrofuran divinyl ether and the multifunctional thiol is pentaerythritol tetra-(3-mercaptopropionate).

5. The polymerizable mixture of claim 1 wherein the equivalent weight ratio of the electron-rich alkene to the multifunctional thiol ranges from about 0.7:

1 to 1.3;

1.

6. The polymerizable composition of claim 1 wherein the equivalent weight ratio of the electron,rich alkene to the multifunctional thiol is about 1:

1.

7. The polymerizable mixture of claim 1 wherein the liquid crystal material is a cyanobiphenyl liquid crystal material and the electron rich alkene comprises a bicylic alkene which has as a result of its stereoelectronic configuration unequal π

-electron density above and below the plane of the carbon-carbon double bond axis.

8. The polymerizable mixture of claim 7 wherein the multifunctional electron-rich alkene comprises a compound containing a plurality of norbornene functional groups.

9. The polymerizable mixture of claim 8 wherein the compound containing a plurality of norbornene functional groups is selected from the group consisting of norbornenecarboxylate esters of the formula:

##STR6## where n is an integer of 2 or more, R² is H or methyl and R³ is the residue of a plural hydroxy compound.

10. The polymerizable mixture of claim 9 wherein said norbornenecarboxylate ester is an ester of 1,6-hexanediol, ethoxylated bisphenol A or polyethylene glycol.

11. The polymerizable mixture of claim 10 wherein the multifunctional electron-rich alkene is ethoxylated hisphenol A di(norbornene carboxylate) and the multifunctional thiol is pentaerythritol tetra-(3-mercaptopropionate).

12. The polymerizable mixture of claim 9 wherein the equivalent weight ratio of the norbornenecarboxylate ester to the multifunctional thiol range from about 0.7:

1 to 1.3;

1.

13. The polymerizable mixture of claim 12 wherein the equivalent weight ratio of the norbornenecarboxylate ester to the multifunctional thiol is about 1:

1.

14. The polymerizable mixture of claim 8 wherein said liquid crystal amount is between about 30% and about 80% of said mixture.

15. The polymerizable composition of claim 14 wherein said liquid crystal amount is between about 40% and about 75% of said mixture.