Bichromal balls
Disclosed is a technique for producing bichromal balls that are adapted for use in high temperature applications. The bichromal balls find particular application in signs and display devices that can be used in environments in which the temperature exceeds 40° C.
1. A process for forming bichromal balls adapted for display applications at temperatures greater than 40° C., said process comprising: providing a polyethylene wax having a molecular weight distribution of about 200 to about 3000; providing an isoparaffin solvent; extracting said polyethylene wax with said isoparaffin solvent to remove a fraction of said polyethylene wax from a remaining purified portion of said polyethylene wax, said fraction having an average molecular weight of less than 700; and forming bichromal balls adapted for display applications at temperatures greater than 40° C. from said purified portion of said polyethylene wax, wherein said forming of the bichromal balls from said purified polyethylene wax includes: mixing said purified polyethylene wax with a first pigment to produce a first wax material; mixing said purified polyethylene wax with a second pigment to produce a second wax material; heating said first wax material to a temperature greater than the melting temperature of said first wax material; heating said second wax material to a temperature greater than the melting point of the second wax material; depositing said heated first wax material and said second wax material onto a spinning disk to produce bichromal balls adapted for use in display applications at temperatures greater than 40° C.
2. The process of claim 1 , wherein said polyethylene wax has a melting point of about 100° C. to about 150° C.
3. The process of claim 1 , wherein said polyethylene wax has a melting point of from about 113° C. to about 126° C.
4. The process of claim 1 , wherein said extraction is performed a number of times, said number selected from the group consisting of 1, 2, 3, 4, and 5 times.
5. The process of claim 1 , wherein said extraction is performed at an elevated temperature.
6. The process of claim 1 , wherein said extraction is performed at a temperature of about 80° C.
7. The process of claim 1 further comprising:
providing a silicone fluid;
providing a shell material;
encapsulating said bichromal balls and said silicone oil within a shell of said shell material.