Canted electric fields for addressing a twisting ball display

• US 5,717,515 A
• Filed: 12/15/1995
• Issued: 02/10/1998
• Est. Priority Date: 12/15/1995
• Status: Expired due to Term

• Current Assignee: Xerox Corporation (Xerox Holdings Corp.)
• Original Assignee: Xerox Corporation (Xerox Holdings Corp.)
• Inventors: Sheridon, Nicholas K.
• Primary Examiner(s): Ben, Loha
• Application Number:
  US08/572,819
• Time in Patent Office: 788 Days
• Field of Search: 359/296, 359/298, 345/111, 345/107, 427/214, 427/282, 349/117, 349/188
• US Class Current: 359/296
• CPC Class Codes: G02B 26/026 based on the rotation of particles under the influence of an external field, e.g. gyricons, twisting ball displays based on orientable dipolar particles G02F1/172; based on electrophoresis G02F1/167
• CPC Class Codes: G09F 9/372 the positions of the elements being controlled by the application of an electric field

Abstract

A method for producing a canted electric field for an electrical twisting ball display device made up of electrically and optically anisotropic spheroidal balls rotatably disposed in a substrate. The display has an array of addressable elements, each array element including at least one spheroidal ball. According to the method, an array element is selected. A preferred direction of orientation is selected for balls of the selected array element, the direction of orientation forming an angle with a vector normal to a planar portion of the substrate surface in a vicinity of the selected array element, the angle being greater than 0 degree and less than 180 degrees. Balls of the selected array element are aligned with the preferred direction of orientation by applying an electric field in the vicinity of the selected array element, the electric field having an electric field vector oriented parallel to the selected preferred direction, thereby causing balls of the selected array element to rotate so as to align with the preferred direction of orientation. Also disclosed are: an electrode assembly for addressing a twisting ball display, capable of producing an electric field adjustable as to the direction of orientation of the field over a continuous angular range of directions; and a twisting ball apparatus incorporating this electrode assembly.

Claims

1. An electrode assembly for a light-modulating apparatus, the apparatus comprising a plurality of electrically and optically anisotropic spheroidal balls rotatably disposed in a substrate, the apparatus having a plurality of addressable elements each occupying a spatial volume bounded by a plurality of edges, each element containing at least one of the spheroidal balls, the electrode assembly comprising:

addressing means for selecting an element from among the plurality of elements;

means for establishing a first electric potential in a vicinity of the selected element along a first edge of the selected element;

means for establishing a second electric potential in a vicinity of the selected element along a second edge of the selected element parallel to the first edge;

means for establishing a third electric potential in a vicinity of the selected element along a third edge of the selected element parallel to the first and second edges; and

means for establishing a fourth electric potential in a vicinity of the selected element along a fourth edge of the selected element parallel to the first, second, and third edges.

2. The electrode assembly of claim 1 and further comprising:

a first planar electrode subassembly incorporating the means for establishing the first and second electric potentials; and

a second planar electrode subassembly, situated parallel to the first planar electrode subassembly and incorporating the means for establishing the third and fourth electric potentials.

3. The electrode assembly of claim 2 wherein each of the first and second electrode subassemblies comprises:

a region of transparent, high-resistivity electrode material disposed in a vicinity of the cell; and

a high-resistivity strip material disposed in a parallelogram about the region of transparent material;

and wherein each of the four means for establishing an electric potential comprises a bus bar disposed at an edge of a region of transparent material.

4. Electrode apparatus for addressing an array of optical elements, each element comprising at least one electrically and optically anisotropic spheroidal ball rotatably disposed in a substrate, the electrode apparatus comprising:

means for choosing an element of the array;

means for generating an electric field in a vicinity of the chosen element, the field having a direction of orientation; and

means for adjusting the direction of orientation of the field over a continuous angular range of directions.

5. Apparatus comprising:

a substrate having a surface;

a plurality of electrically and optically anisotropic spheroidal balls disposed in the substrate; and

means for selectively producing an electric field in a vicinity of at least one ball disposed rotatably in the substrate, the electric field having an electric field vector, the vector being oriented at an orientation angle with respect to a planar portion of the surface proximate to the vicinity, the orientation angle being an angle other than a right angle.

6. The apparatus of claim 5 and further comprising:

control means, coupled to the field-producing means, for adjusting the orientation angle of the electric field vector over a continuous angular range.

7. The apparatus of claim 5 wherein the field-producing means further includes means for selectively producing an electric field having an electric field vector oriented at a right angle with respect to the planar portion of the surface proximate to the vicinity.

8. The apparatus of claim 5 wherein:

the substrate comprises a layer of material having a front surface and a rear surface, the balls of the plurality being disposed within the layer; and

the field-producing means comprises

a first addressing electrode disposed proximately to the front surface of the layer, and

a second addressing electrode disposed proximately to the rear surface of the layer.

9. The apparatus of claim 5 wherein the balls disposed in the substrate include multisegmented balls, each multisegmented ball having a plurality of segments arrayed substantially parallel to one another, each segment being adjacent to at least one other segment and to no more than two other segments, adjacent segments being adjoined to one another at substantially planar interfaces, the plurality of segments including

a first segment having a first thickness and a first optical modulation characteristic,

a second segment having a second thickness and a second optical modulation characteristic, and

a third segment having a thickness different from at least one of the first and second thicknesses and an optical modulation characteristic different from at least one of the first and second optical modulation characteristics,

each multisegmented ball having an anisotropy for providing an electrical dipole moment, the electrical dipole moment rendering the ball electrically responsive such that when the ball is rotatably disposed in the substrate and is subjected to an electric field produced by the field-producing means while the electrical dipole moment of the ball is provided, the ball tends to rotate to an orientation in which the electrical dipole moment aligns with the produced electric field.

10. The apparatus of claim 9 wherein the first segment of each multisegmented ball has an optical modulation characteristic such that the first segment has a chromatic color.

11. The apparatus of claim 5 wherein the balls disposed in the substrate include multisegmented balls, each multisegmented ball having a plurality of segments adjoining one another, each segment being adjacent to at least one other segment and to no more than two other segments, the segments including

a first segment having a first optical modulation characteristic,

a second segment having a second optical modulation characteristic, and

a third segment having an optical modulation characteristic different from at least one of the first and second optical modulation characteristics,

each multisegmented ball having an anisotropy for providing an electrical dipole moment, the electrical dipole moment rendering the ball electrically responsive such that when the ball is rotatably disposed in the substrate and is subjected to an electric field produced by the field-producing means while the electrical dipole moment of the ball is provided, the ball tends to rotate to an orientation in which the electrical dipole moment aligns with the produced electric field,

each multisegmented ball having a plurality of observable aspects, the aspects being observable by an observer situated favorably to observe the surface of the substrate, the aspects including

a first aspect associated with the first optical modulation characteristic, the first aspect being observable when the ball is rotationally oriented in a first orientation with respect to the observer under the influence of a first electric field applied in a vicinity of the ball while the ball is disposed rotatably within the substrate and the electrical dipole moment of the ball is provided, the first electric field having an electric field vector perpendicular to a planar portion of the surface proximate to the vicinity of the ball, and

a second aspect associated with the second optical modulation characteristic, the second aspect being observable when the ball is rotationally oriented in a second orientation with respect to the observer under the influence of a second electric field applied in the vicinity of the ball while the ball is disposed rotatably within the substrate and the electrical dipole moment of the ball is provided, the second applied electric field being produced by the field-producing means and having an electric field vector including an electric field vector component parallel to the planar portion of the surface proximate to the vicinity of the ball.

12. A method for producing a canted electric field for a light-modulating apparatus comprising a plurality of electrically and optically anisotropic spheroidal balls rotatably disposed in a substrate, the apparatus having a plurality of light-modulating elements each occupying a spatial volume bounded by a plurality of edges, each element containing at least one of the spheroidal balls, the method comprising the steps of:

selecting a light-modulating element from among the plurality of elements;

establishing a first electric potential in a vicinity of the selected element along a first edge of the selected element;

establishing a second electric potential in a vicinity of the selected element along a second edge of the selected element parallel to the first edge;

establishing a third electric potential in a vicinity of the selected element along a third edge of the selected element parallel to the first and second edges; and

establishing a fourth electric potential in a vicinity of the selected element along a fourth edge of the selected element parallel to the first, second, and third edges.

13. A method comprising the steps of:

providing light from a light source incident on a modulating device comprising a plurality of electrically and optically anisotropic spheroidal balls rotatably disposed in a substrate, the substrate having a surface;

selectively producing an electric field in a vicinity of at least one ball thus disposed in the substrate, the electric field having an electric field vector, the vector being oriented at an orientation angle with respect to a planar portion of the surface proximate to the vicinity, the orientation angle being an angle other than a right angle; and

modulating with the modulating device at least a portion of the light incident on the modulating device.

14. The method of claim 13 and further comprising the step of:

adjusting the orientation angle of the electric field vector over a continuous angular range.

15. The method of claim 13 wherein the step of selectively producing an electric field in a vicinity of at least one ball comprises:

producing an electric field in a vicinity of a ball having an electrical dipole moment, thereby causing the ball having the dipole moment to rotate under the influence of the electric field so as to align the dipole moment with the electric field vector.

16. In a light-modulating apparatus comprising a plurality of electrically and optically anisotropic spheroidal balls rotatably disposed in a substrate, the substrate having a surface, the apparatus having an array of addressable elements, each array element including at least one ball of the plurality, a method comprising the steps of:

selecting an array element;

selecting a preferred direction of orientation for balls of the selected array element, the direction of orientation forming an angle with a vector normal to a planar portion of the substrate surface in a vicinity of the selected array element, the angle being greater than 0 degree and less than 180 degrees; and

aligning balls of the selected array element with the preferred direction of orientation by applying an electric field in the vicinity of the selected array element, the electric field having an electric field vector oriented parallel to the selected preferred direction, thereby causing balls of the selected array element to rotate so as to align with the preferred direction of orientation.

17. The method of claim 16 and further comprising the steps of:

ceasing to apply the electric field in the vicinity of the selected array element; and

maintaining balls of the selected array element thus aligned with the preferred direction of orientation, notwithstanding cessation of application of the electric field in the vicinity of the selected array element.

18. The method of claim 17 and further comprising the steps of:

selecting a new direction of orientation for balls of the selected array element, the new direction of orientation forming a new angle with the vector normal to the planar portion of the substrate surface in the vicinity of the selected array element, the new angle being greater than or equal to 0 degrees and less than or equal to 180 degrees; and

aligning balls of the selected array element with the new direction of orientation by applying an electric field in the vicinity of the selected array element, the electric field having an electric field vector oriented parallel to the selected new direction, thereby causing balls of the selected array element to rotate through a rotation angle, the rotation angle being other than a multiple of 90 degrees, so as to align with the new direction of orientation.

19. The method of claim 16 wherein each ball of the selected array element comprises a plurality of segments arrayed substantially parallel to one another, each segment being adjacent to at least one other segment and to no more than two other segments, adjacent segments being adjoined to one another at substantially planar interfaces, and wherein the aligning step comprises:

aligning balls of the selected array element so that the planar interfaces are perpendicular to the preferred direction of orientation.

20. The method of claim 16 wherein each ball of the selected array element has a plurality of observable aspects each associated with a degree of color saturation, the degree of color saturation ranging from a minimum degree of color saturation to a maximum degree of color saturation, and wherein the aligning step comprises:

applying the electric field in the vicinity of the selected array element, thereby causing balls of the selected array element to rotate so as to present, to an observer situated favorably to observe the selected array element, an aspect associated with a degree of color saturation intermediate between the minimum and maximum degrees of color saturation.