Some uses of microencapsulation for electric paper

Abstract

Bichromal balls have two hemispheres, typically one black and one white, each having different electrical properties. Each ball is enclosed within a spherical shell and then a space between the ball and shell is filled with a liquid to form a microsphere so that the ball is free to rotate in response to an electrical field. The microspheres can then be mixed into a substrate which can be formed into sheets or can be applied to any kind of surface. The result is a film which can form an image from an applied electrical field.

Description

BACKGROUND OF THE INVENTIONA "twisting ball" medium for displaying an image comprising internal bichromal balls that rotate to show either black or white hemispheres in response to an externally applied electrical field, and that are contained in individual liquid filled spherical shells that are in turn dispersed in a transparent binder, which is usually solid when used.U.S. Pat. Nos. 4,126,854 and 4,143,103 describe a twisting ball display and are incorporated by reference herein. These patents describe a display system in which the display panel is comprised of spherical balls which have an optical and an electrical anisotropy due to each hemisphere surface having a different color and electrical charge in contact with a liquid. These spherical particles are imbedded in a solid substrate and a slight space between each ball and the substrate is filled with a liquid so that the balls are free to rotate, in a changing electrical field, but can not migrate from one location to anoth...

AI Technical Summary

Benefits of technology

The bichromal balls are individually enclosed in spherical shells with the space between the two spherical surfaces filled with dielectric liquid. The resultant capsules may be dispersed in a second liquid, such as an optically clear epoxy, which may be subsequently hardened. If the hardened liquid, now a solid, is of sufficient strength no further protection is required. The resultant display is then in the form of a thin, paper-like sheet without the bulkiness and optical problems created by the protective cover sheets as in the prior art. Alternatively, the resultant display may be easily conformally coated on a non-planar surface for even greater flexibility of applications.

Problems solved by technology

After being soaked in plasticizer, the gel is soft and lacks durability, and must be bonded between glass or plastic sheets for protection.

This process has the disadvantages that a large number of steps are required for the fabrication, adding to the cost, and that the final product lacks some of the optical and tactile properties of paper, which it emulates in some embodiments.

Such a structure was inherently expensive to make and effectively limited the ball sizes that could be used.

Once again, this is an expensive procedure that would be difficult to implement on large scale.

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