Method for making precisely configured flakes useful in optical devices
Precisely configured, especially of geometric shape, flakes of liquid crystal material are made using a mechanically flexible polymer mold with wells having shapes which are precisely configured by making the mold with a photolithographically manufactured or laser printed master. The polymer liquid crystal is poured into the wells in the flexible mold. When the liquid crystal material has solidified, the flexible mold is bent and the flakes are released and collected for use in making an electrooptical cell utilizing the liquid crystal flakes as the active element therein.
1. The method of making flakes or platelets of certain configurations which comprises the steps of:
molding said flakes or platelets in a mold of material more flexible than said flakes or platelets when solid and in wells in a surface of said mold having said certain configuration;
flexing said mold to cause said surface to bend when said flakes or platelets become solid therein so as to release said flakes or platelets from said mold; and
said configuration desired for said flakes or platelets is obtained by the step of molding said mold with the aid of a master having projections and trenches of said configurations to provide an inverse replica of said master.
2. The method according to claim 1 further comprising the step of filling said wells with material in liquid state, which when solid forms said solid flakes or platelets in said mold.
3. The method according to claim 2 further comprising the step of treating surfaces of said wells with a release agent prior to said filling step.
4. The method according to claim 2 further comprising the step of collecting said flakes or platelets when released from said mold.
5. The method of making flakes or platelets of certain configuration which comprises the steps of:
molding said flakes or platelets in a mold of material more flexible than said flakes or platelets when solid and in wells in a surface of said mold having said certain configuration;
flexing said mold to cause said surface to bend when said flakes or platelets become solid therein so as to release said flakes or platelets from said mold; and
carrying out said molding step while elongating said mold in a selected direction or directions generally in the plane of the surface of said mold.
6. The method according to claim 5 wherein said elongating step is carried out by stretching said mold in one or more directions.
7. The method according to claim 1 wherein said certain configurations are selected from the group consisting of square, rectangular, diamond, triangular, circular, elliptical, trapezoidal, and parallelogram configurations.
8. The method according to claim 6 wherein said wells are square along a side parallel to said surface of said mold and said direction is selected from a direction along a side of said square or a direction along a line parallel to or coextensive with a line between the opposite corners of said square to produce flakes or platelets of said rectangular and diamond configuration, respectively.
9. The method according to claim 1 wherein said projections and trenches and said wells and said resulting flakes or platelets are of microscopic dimensions.
10. The method according to claim 1 further comprising the step of photolithographically forming or laser printing said projections and trenches on a surface of said master.
11. The method according to claim 6 wherein said elongating step is carried out in one or more directions related to the shape of said wells.
12. The method according to claim 1 further comprising the step of treating the master to impart a flat, specular, or rough, matte surface to the mold, and thus to the flakes.
13. The method according to claim 1 wherein said mold is made of a moldable elastomeric polymer material.
14. The method according to claim 13 wherein said polymer material is selected from the group consisting of phenol-formaldehyde and polydimethyl-siloxane (PDMS).
15. The method according to claim 1 wherein said mold is mounted on a substrate which is heated to a temperature depending upon the melting temperature and the glass transition temperature of said flake or platelet material.
16. The method according to claim 15 wherein the temperature to which said substrate is heated is above the melting temperature and below the glass transition temperature of said flake or platelet material.
17. The method according to claim 1 wherein said flake or platelet material is a polymer liquid crystal material in a solution thereof when said wells are filled.
18. The method according to claim 17 wherein said wells are filled with said solution in one or more layers.
19. The method according to claim 18 wherein said one or more layers is swept with a knife to align the molecules of said liquid crystal material.
20. The method according to claim 18 wherein said layers are allowed to cure successively in the order in which said layers are formed in said wells.
21. The method according to claim 18 wherein selected ones of said layers may be of material other than said polymer liquid crystal material.
22. The method according to claim 21 wherein said material of said selected ones of said layers may be selected from the group consisting of conductive material, and high dielectric constant particles.
23. The method according to claim 22 wherein said conductive material comprises microscopic carbon black particles.
24. The method according to claim 22 wherein said high dielectric constant particles are microscopic particles of titanium oxide.
25. The method according to claim 5 wherein said configurations desired for said flakes or platelets is obtained by the step of molding said mold with the aid of a master having projections and trenches of said configurations to provide an inverse replica of said master.