Method of making liquid crystal composite

• US 5,830,385 A
• Filed: 01/24/1997
• Issued: 11/03/1998
• Est. Priority Date: 12/21/1994
• Status: Expired due to Term

• Current Assignee: Tyco Electronics Corporation (TE Connectivity Limited)
• Original Assignee: Raychem Corporation (TE Connectivity Limited)
• Inventors: Di Zio, Kathleen, Vo, Lanchi P., Reamey, Robert H., Lau, Aldrich N. K., Havens, John R.
• Primary Examiner(s): Kelly, C. H.
• Application Number:
  US08/773,803
• Time in Patent Office: 648 Days
• Field of Search: 252/299.01, 252/299.1, 349/187
• US Class Current: 252/299.01
• CPC Class Codes: C09K 19/544 as dispersing or encapsulating medium around the liquid crystal

Abstract

A liquid crystal light composite in which discrete volumes of a liquid crystal material are dispersed in a matrix material is produced by a process in which a reactive additive formulation is added and photopolymerized. The reactive additive formulation includes mono- and multifunctional compounds in specified proportions and a photoinitiator. The reactive additive formulation reduces the operating field and may also improve other electro-optical properties.

Claims

1. A method of making a liquid crystal light composite in which discrete volumes of a liquid crystal material are dispersed in a matrix material and the matrix material and the liquid crystal material are separated from each other by a wall formed by the polymerization of a reactive additive formulation, comprising the steps of:

(a) providing an emulsion comprising plural discrete volumes of a liquid crystal material encapsulated in a matrix material carried in a carrier medium, the emulsion further comprising a reactive additive formulation comprising;

(I) between 83 and 93.3 weight percent of at least two monofunctional compounds of the structure ##STR43## the group --R₁ being --CH₃ or --H and the group --R₂ being an alkyl, aryl, alkylaryl, alkylcycloalkyl, cycloalkylalkyl, hydroxyalkyl, fluoroalkyl, or fluoroaryl group;

wherein (A) each group --R₂ has a chain length of 6 or (B) at least one group --R₂ has a chain length other than six, in which latter event the distribution of chain lengths among the groups --R₂ is according to the following table

space="preserve" listing-type="tabular">______________________________________ Mole Percent Chain Length ______________________________________ 5 to 90 ≦

5 10 to 95 >

5 ______________________________________

the mole percent'"'"'s being based on the total amount of monofunctional compounds;

(II) between 5 and 16.9 weight percent of at least one multifunctional compound having acrylic or methacrylic functionality and being derived from diols or polyols containing aliphatic, aromatic, ester, epoxy, amide, imide, carbamate, or mesogenic segments; and

(III) between 0.1 and 5.0 weight percent of at least one photoinitiator;

the weight percent'"'"'s being based on the combined amounts of monofunctional compounds, multifunctional compound, and photoinitiator;

(b) photopolymerizing the monofunctional and multifunctional compounds in the reactive additive formulation to form the wall separating the matrix material and the liquid crystal material;

(c) applying a coating of the emulsion onto a substrate; and

(d) drying the coating by permitting the carrier medium to evaporate.

2. A method according to claim 1, wherein the at least two monofunctional compounds are selected from the group consisting of n-pentyl acrylate, 2,4,4-trimethylpentyl acrylate, n-hexyl acrylate, n-decyl acrylate, 3,5,5-trimethylhexyl acrylate, 2-ethylhexyl acrylate, and 4-tert-butyl-cyclohexyl acrylate.

3. A method according to claim 1, wherein the at least one multifunctional compound is selected from the group consisting of 1,6hexanediol diacrylate, trimethylolpropane triacrylate, pentaerythritol triacrylate, 1,4-butanediol diacrylate, pentaerythritol tetraacrylate, polyacrylated aliphatic polyester oligomers, and polyacrylated polyurethane oligomers.

4. A method according to claim 1, wherein the multifunctional compound has the structure ##STR44## where n is an integer between 0 and 100, inclusive;

each --R₃ is independently --CH₃ or --H;

each --Q-- is independently alkylene, arylene, or a bond;

each --Z-- is independently oxygen, alkylene, hydroxyalkylene, arylene, or a bond;

X is a bond, oxygen, a carbonyl group, an ester group, an ether group, an amide group, an imide group, a carbamate group, a mesogenic group, or ##STR45## where m is an integer between 1 and 4, inclusive;

--R₄ is a methenyl (.tbd.CH) group, nitrogen, or aromatic nucleus; and

--Z--, --Q--, and --R₃ are as previously defined;

subject to the provisos that Q is not a bond when n is 0, Z is oxygen, or either Z or X is a bond;

that Z is not oxygen when either Q or Z is a bond;

that Z is not a bond when either Q or X is a bond; and

that X is not oxygen when Z is oxygen.

5. A method according to claim 1, wherein the liquid crystal material is operationally nematic and has a positive dielectric anisotropy.

6. A method according to claim 1, wherein the matrix material is selected from the group consisting of poly(vinyl alcohol) and its copolymers, gelatin, polyurethane, latexes, poly(ethylene oxide), poly(vinyl pyrrolidone), cellulosic polymers, natural gums, acrylic and methacrylic polymers and copolymers, epoxies, polyolefins, and vinyl polymers.

7. A method according to claim 1, wherein the reactive additive formulation is used in an amount of 5 to 30 parts by weight per 100 parts by weight of liquid crystal material.

8. A method according to claim 1, wherein the liquid crystal material contains a pleochroic dye dissolved therein.

9. A method according to claim 1, further comprising the step of centrifuging the emulsion and re-dispersing the resulting pellet in a further matrix material.

10. A method according to claim 1, wherein the substrate has electrode material partially or entirely covering it.

11. A method according to claim 1, wherein the carrier medium is aqueous.

12. A method according to claim 1, wherein the photopolymerizing step is performed before the coating step.

13. A method according to claim 1, wherein the coating step is performed before the photopolymerizing step.

14. A method according to claim 1, wherein the at least one monofunctional compound is a combination of 3,5,5-trimethylhexyl acrylate and 2-ethylhexyl acrylate and the multifunctional compound is a tetra-acrylated aliphatic polyester oligomer.

15. A method according to claim 1, wherein the at least one monofunctional compound is a combination of n-pentyl acrylate, 2-ethylhexyl acrylate, and n-decyl acrylate and the multifunctional compound is a tetra-acrylated aliphatic polyester oligomer.

16. A method according to claim 1, wherein the at least one monofunctional compound is a combination of n-pentyl acrylate and n-hexyl acrylate and the multifunctional compound is a tetra-acrylated aliphatic polyester oligomer.

17. A composition of matter comprising

(I) between 83 and 93.3 weight percent of at least two monofunctional compounds of the structure ##STR46## the group --R₁ being --CH₃ or --H and the group --R₂ being an alkyl, aryl, alkylaryl, alkylcycloalkyl, cycloalkylalkyl, hydroxyalkyl, fluoroalkyl, or fluoroaryl group;

wherein (A) each group --R₂ has a chain length of 6 or (B) at least one group --R₂ has a chain length other than six, in which latter event the distribution of chain lengths among the groups --R₂ is according to the following table

space="preserve" listing-type="tabular">______________________________________ Mole Percent Chain Length ______________________________________ 5 to 90 ≦

5 10 to 95 >

5 ______________________________________

the mole percent'"'"'s being based on the total amount of monofunctional compounds;

(II) between 5 and 16.9 weight percent of at least one multifunctional compound having acrylic or methacrylic functionality and being derived from diols or polyols containing aliphatic, aromatic, ester, epoxy, amide, imide, carbamate, or mesogenic segments; and

(III) between 0.1 and 5.0 weight percent of at least one photoinitiator;

the weight percent'"'"'s being based on the combined amounts of monofunctional compounds, multifunctional compound, and photoinitiator.

18. A composition of matter according to claim 17, wherein the at least two monofunctional compounds are selected from the group consisting of n-pentyl acrylate, 2,4,4-trimethylpentyl acrylate, n-hexyl acrylate, n-decyl acrylate, 3,5,5-trimethylhexyl acrylate, 2-ethylhexyl acrylate, and 4-tert-butylcyclohexyl acrylate.

19. A composition of matter according to claim 17, wherein the at least one multifunctional compound is selected from the group consisting of 1,6-hexanediol diacrylate, trimethylolpropane triacrylate, pentaerythritol triacrylate, 1,4butanediol diacrylate, pentaerythritol tetraacrylate, polyacrylated aliphatic polyester oligomers, and polyacrylated polyurethane oligomers.

20. A composition of matter according to claim 17, wherein the multifunctional compound has the structure ##STR47## where n is an integer between 0 and 100, inclusive;

each --R₃ is independently --CH₃ or --H;

each --Q-- is independently alkylene, arylene, or a bond;

each --Z-- is independently oxygen, alkylene, hydroxyalkylene, arylene, or a bond;

X is a bond, oxygen, a carbonyl group, an ester group, an ether group, an amide group, an imide group, a carbamate group, a mesogenic group, or ##STR48## where m is an integer between 1 and 4, inclusive;

--R₄ is a methenyl (.tbd.CH) group, nitrogen, or aromatic nucleus; and

--Z--, --Q--, and --R₃ are as previously defined;

subject to the provisos that Q is not a bond when n is 0, Z is oxygen, or either Z or X is a bond;

that Z is not oxygen when either Q or Z is a bond;

that Z is not a bond when either Q or X is a bond; and

that X is not oxygen when Z is oxygen.