Multithreshold addressing of a twisting ball display

• US 5,739,801 A
• Filed: 12/15/1995
• Issued: 04/14/1998
• 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): Hjerpe, Richard
• Assistant Examiner(s): TRAN, VUI
• Application Number:
  US08/572,775
• Time in Patent Office: 851 Days
• Field of Search: 345/85, 345/84, 345/107, 345/95
• US Class Current: 345/84
• 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
• CPC Class Codes: G09G 3/3453 based on rotating particles or microelements

Abstract

A multithreshold electrical twisting ball display device. The device is composed of electrically and optically anisotropic spheroidal balls of at least two different rotation thresholds, disposed in an elastomer substrate, together with an addressing electrode assembly. The addressing electrode assembly allows a preferred region of the substrate to be selected in which at least one ball of the first set and at least one ball of the second set are disposed, and first and second electric field to be applied to the preferred region thus selected, each of the first and second electric fields extending throughout the preferred region. The first field facilitates a contemporaneous rotation of balls of both the first and second sets rotatably disposed in the preferred region. The second electric field facilitates a rotation of balls of the second set rotatably disposed in the preferred region, without facilitating a rotation of any ball of the first set rotatably disposed in the preferred region. Also disclosed are the substrate material and electrode assembly for the device, and a method of using the device.

Claims

1. A material comprising:

a substrate; and

a plurality of spheroidal balls disposed in the substrate, each ball having an optical anisotropy and 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 an electric field 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 field, the plurality of balls including

a first set of balls comprising at least one ball, each ball of the first set being associated with a first threshold, and

a second set of balls comprising at least one ball, each ball of the second set being associated with a second threshold, the second threshold being less than the first threshold,

the first and second thresholds being such that

for each ball of each set, a rotation of the ball is facilitated by an application in a vicinity of the ball while the ball is rotatably disposed in the substrate of an electric field having a first electric field strength exceeding the first threshold,

for each ball of the first set, a rotation of the ball is not facilitated by an application in a vicinity of the ball while the ball is rotatably disposed in the substrate of an electric field having a second electric field strength between the first and second thresholds, and

for each ball of the second set, a rotation of the ball is facilitated by an application in a vicinity of the ball while the ball is rotatably disposed in the substrate of an electric field having the second electric field strength.

2. The material of claim 1 wherein each ball of the plurality has a collection of physical characteristics affecting a rotational responsiveness of the ball to applied electric fields while the ball is rotatably disposed within the substrate,

each ball of the first set having a first collection physical characterstics such that when the ball is subjected to an electric field while the ball is stationary and is rotatably disposed within the substrate and the dipole moment of the ball is provided, the ball tends to begin to rotate if the applied electric field substantially exceeds the first threshold and does not tend to begin to rotate if the applied electric field is substantially less than the first threshold,

each ball of the second set having a second collection of physical characterstics such that when the ball is subjected to an electric field while the ball is stationary and is rotatably disposed within the substrate and the dipole moment of the ball is provided, the ball tends to begin rotate if the applied electric field substantially exceeds the second threshold and does not tend to begin to rotate if the applied electric field is substantially less than the second threshold.

3. The material of claim 2 wherein each of the physical characteristics of each of the first and second collections is selected from the group consisting of:

an electrical characteristic, a mechanical characteristic, a structural characteristic, a material characteristic,

dipole moment, monopole moment, dipole moment in the presence of a dielectric fluid, zeta potential distribution in the presence of a dielectric fluid,

mass, moment of inertia, size, mean radius, shape, deviation from spherical shape, coefficient of friction, surface roughness,

size and shape of a component region within the ball, disposition of any component regions within the ball relative to one another,

any material used in the manufacture of any component region within the ball, and any material coating a surface of the ball.

4. The material of claim 1 wherein:

the substrate comprises a plurality of layers, each layer being a nearest neighboring layer with respect to at least one other layer and no more than two other layers, the layers including first and second layers;

each ball of the first set is disposed in the first substrate layer; and

each ball of the second set is disposed in the second substrate layer.

5. The material of claim 1 wherein:

the substrate has a surface and comprises an array of individually addressable image elements, each element including at least one ball of the first set and at least one ball of the second set,

each element having an observable area comprising a portion of the substrate surface in a vicinity of the element, the observable area being observable by an observer situated favorably to observe the substrate surface,

each element having a plurality of operational states including first and second operational states, each operational state being defined by an appearance of the observable area of the element to the observer, each operational state providing an optical modulation of light incident on the element, different operational states providing different optical modulations and thus providing different appearances of the observable area of the element,

each element having a current state, the current state being any one of the operational states, the current state being determined at least in part by a rotational orientation of each ball disposed in the element, the rotational orientation of each ball disposed in the element being defined with respect to a planar portion of the substrate surface proximate to the ball,

a change in the current state of an element being facilitated by applying an electric field in a vicinity of the element while at least one ball of each set is rotatably disposed in the element, so as to facilitate a rotation of at least one ball rotatably disposed in the element,

the first operational state of the element being establishable as the current state by applying an electric field having an electric field strength exceeding the first threshold, thereby facilitating a rotation of at least one ball of the first set rotatably disposed in the element and a rotation of at least one ball of the second set rotatably disposed in the element,

the second operational state of the element being establishable as the current state by applying an electric field having an electric field strength between the first and second thresholds, thereby facilitating a rotation of at least one ball of the second set rotatably disposed in the element without facilitating a rotation of any ball of the first set rotatably disposed in the element.

6. The material of claim 1 wherein each ball of each set comprises a plurality of component regions each having an optical modulation characteristic, each component region of each ball being adjacent to at least one other component region of the ball, the optical modulation characteristics of adjacent component regions being different from one another, the optical anisotropy of each ball arising from a configuration of the component regions in the ball,

each ball of the first set having a first optical anisotropy such that the ball has a first plurality of observable aspects,

each ball of the second set having a second optical anisotropy such that the ball has a second plurality of observable aspects,

each aspect of each ball of each set being associated with at least one of the optical modulation characteristics of the component regions of the ball, each aspect being observable by an observer situated favorably to observe the ball when the ball is rotationally oriented with respect to the observer so as to present the aspect to the observer.

7. The material of claim 6 wherein:

for each ball of the first set, the optical modulation characteristics of the component regions of the ball are such that the first plurality of observable aspects includes an aspect associated with a first color and an aspect associated with a second color; and

for each ball of the second set, the optical modulation characteristics of the component regions of the ball are such that the second plurality of observable aspects includes an aspect associated with a third color and an aspect associated with a color different from the third color.

8. The material of claim 6 wherein each ball of each set comprises a plurality of segments arrayed substantially parallel to one another, each segment of each ball being identified with a component region of the ball, each segment of each ball being adjacent to at least one other segment of the ball and to no more than two other segments of the ball, adjacent segments of each ball being adjoined to one another at substantially planar interfaces, each segment of each ball having an optical modulation characteristic, the optical modulation characteristics of adjacent segments of each ball being different from one another.

9. The material of claim 1 wherein:

the plurality of balls further includes

a third set of balls comprising at least one ball, each ball of the third set being associated with a third threshold, the third threshold being less than the second threshold, the first, second, and third thresholds being such that

for each ball of the first set, a rotation of the ball is not facilitated by an application in a vicinity of the ball of an electric field having a third electric field strength between the second and third thresholds,

for each ball of the second set, a rotation of the ball is not facilitated by an application in a vicinity of the ball of an electric field having the third electric field strength, and

for each ball of the third set, a rotation of the ball is facilitated by an application in a vicinity of the ball of an electric field having any of the first, second, and third electric field strengths.

10. Apparatus comprising:

a piece of the material recited in claim 1;

means for producing an electric field to facilitate a rotation of at least one ball rotatably disposed in the substrate of the piece of material.

11. Apparatus comprising:

a substrate;

first and second sets of electrically and optically anisotropic spheroidal balls disposed in the substrate, each set comprising at least one ball;

means for selecting a preferred region of the substrate, the preferred region including at least one ball of the first set and at least one ball of the second set;

means for applying a first electric field to the preferred region thus selected, the first electric field extending throughout the preferred region and facilitating a rotation of each of a plurality of balls rotatably disposed in the preferred region, including a rotation of a ball of the first set and a rotation of a ball of the second set, the ball rotations thus facilitated being facilitated contemporaneously with one another; and

means for applying a second electric field to the preferred region thus selected, the second electric field extending throughout the preferred region and facilitating a rotation of a ball of the second set rotatably disposed in the preferred region without facilitating a rotation of any ball of the first set rotatably disposed in the preferred region.

12. The apparatus of claim 11 wherein:

for each ball of the first set, a rotation of the ball is facilitated when the ball, while rotatably disposed in the substrate, is subjected to an electric field having an electric field strength exceeding a first threshold;

for each ball of the second set, a rotation of the ball is facilitated when the ball, while rotatably disposed in the substrate, is subjected to an electric field having an electric field strength exceeding a second threshold, the second threshold being less than the first threshold;

the means for applying the first electric field to the preferred region comprises means for applying to the preferred region an electric field having a first electric field strength exceeding the first threshold; and

the means for applying the second electric field to the preferred region comprises means for applying to the preferred region an electric field having a second electric field strength between the first and second thresholds.

13. The apparatus of claim 12 wherein:

the means for selecting the preferred region further comprises means for selecting a preferred electric field strength for an electric field to be applied in the preferred region, the preferred electric field strength being selectable from among a plurality of electric field strengths including the first and second electric field strengths; and

both the means for applying the first electric field and the means for applying the second electric field are provided by a single means for applying an electric field, the single means comprising an electrode assembly for generating in a vicinity of the selected preferred region an electric field having the selected preferred electric field strength, the preferred electric field strength being the first electric field strength when the first electric field is to be applied, the preferred electric field strength being the second electric field strength when the second electric field is to be applied.

14. The apparatus of claim 11 wherein:

the substrate comprises a plurality of layers including first and second layers, each layer of the substrate being adjacent to at least one other layer;

each ball of the first set is disposed in the first substrate layer; and

each ball of the second set is disposed in the second substrate layer.

15. The apparatus of claim 11 wherein:

the substrate has a surface and comprises an array of individually addressable image elements; and

the means for selecting the preferred region comprises means for addressing an element of the array,

each element having an observable area comprising a portion of the substrate surface in a vicinity of the element, the observable area being observable by an observer situated favorably to observe the substrate surface,

the addressed element being identified with the selected preferred region of the substrate and including at least one ball of the first set and at least one ball of the second set.

16. The apparatus of claim 11 wherein each ball of each set comprises a plurality of component regions each having an optical modulation characteristic, each component region of each ball being adjacent to at least one other component region of the ball, the optical modulation characteristics of adjacent component regions being different from one another, the optical anisotropy of each ball arising from a configuration of the component regions in the ball,

each ball of the first set having a first optical anisotropy such that the ball has a first plurality of observable aspects,

each ball of the second set having a second optical anisotropy such that the ball has a second plurality of observable aspects,

each aspect of each ball of each set being associated with at least one of the optical modulation characteristics of the component regions of the ball, each aspect being observable by an observer situated favorably to observe the ball when the ball is rotationally oriented with respect to the observer so as to present the aspect to the observer.

17. The apparatus of claim 11 wherein:

the substrate has a surface;

each ball of each set is associated with a color observable by an observer situated favorably to observe the surface, balls of the first and second sets both being associated with the same observable color, the color being selected from the group consisting of a chromatic color and an achromatic color;

the means for selecting the preferred region further comprises means for selecting a preferred degree to which the observable color is present in the preferred region, the preferred degree of presence being selectable from among a plurality of degrees of presence including first, second, and third degrees;

the means for applying a first electric field to the preferred region comprises

means for establishing the first degree of presence of the observable color in the preferred region by applying as the first electric field an electric field having a first electric field strength and a first direction of orientation with respect to a planar portion of the substrate surface in a vicinity of the preferred region, and

means for establishing the third degree of presence of the observable color in the preferred region by applying as the first electric field an electric field having the first electric field strength and a second direction of orientation with respect to the planar portion of the substrate surface; and

the means for applying a second electric field to the preferred region comprises means for changing the degree of presence of the observable color in the preferred region from the first degree to the second degree by applying as the second electric field an electric field having a second electric field strength and a preferred direction of orietation with respect to the planar portion of the substrate surface.

18. The apparatus of claim 11 and further comprising

a third set of electrically and optically anisotropic spheroidal balls disposed in the substrate, the third set comprising at least one ball;

and

means for applying a third electric field to the selected preferred region, the third electric field extending throughout the preferred region and facilitating a rotation of a ball of the third set rotatably disposed in the preferred region without facilitating a rotation of any ball of the first set rotatably disposed in the preferred region and without facilitating a rotation of any ball of the second set rotatably disposed in the preferred region;

and wherein;

the means for selecting the preferred region includes means for selecting a preferred region including at least one ball of each of the first, second, and third sets;

the means for applying the first electric field comprises means for applying the first electric field to the preferred region so as to facilitate a rotation of a ball of the first set, a rotation of a ball of the second set, and a rotation of a ball of the third set, each ball for which a rotation is thus facilitated being rotatably disposed in the preferred region, the ball rotations thus facilitated being facilitated contemporaneously with one another; and

the means for applying the second electric field comprises means for applying the second electric field to the preferred region so as further to facilitate a rotation of a ball of the second set and a rotation of a ball of the third set, each ball for which a rotation is thus facilitated being rotatably disposed in the preferred region, the ball rotations thus facilitated being facilitated contemporaneously with one another and being facilitated without facilitating a rotation of any ball of the first set rotatably disposed in the preferred region.

19. A method comprising the steps of:

providing light from a light source incident on an optical modulation apparatus comprising a plurality of electrically and optically anisotropic spheroidal balls rotatably disposed in a substrate, the plurality of balls including

a first set of balls comprising at least one ball, each ball of the first set being associated with a first threshold, and

a second set of balls comprising at least one ball, each ball of the second set being associated with a second threshold, the second threshold being less than the first threshold,

the first and second thresholds being such that

for each ball of each set, a rotation of the ball is facilitated by an application in a vicinity of the ball thus rotatably disposed in the substrate of an electric field having a first electric field strength exceeding the first threshold,

for each ball of the first set, a rotation of the ball is not facilitated by an application in a vicinity of the ball thus rotatably disposed in the substrate of

an electric field having a second electric field strength between the first and second thresholds, and

for each ball of the second set, a rotation of the ball is facilitated by an application in a vicinity of the ball thus rotatably disposed in the substrate of an electric field having the second electric field strength;

applying an electric field in a vicinity of a spheroidal ball of one of the first and second sets, the electric field having a strength sufficient to facilitate a rotation of said ball, thereby facilitating a rotation of said ball; and

modulating with the optical modulation apparatus at least a portion of the light incident thereon, the light thus modulated being modulated at least in part by the ball for which the rotation is facilitated.

20. The method of claim 19 wherein the step of applying an electric field comprises:

selecting a preferred region of the substrate, at least one ball of each of the first and second sets being rotatably disposed in the preferred region;

selecting a preferred set of balls from among the first and second sets of balls; and

applying an electric field in a vicinity of the preferred region so as to facilitate a rotation of a collection of balls rotatably disposed in the preferred region, the collection comprising at least one ball, at least one ball of the collection being a ball of the preferred set.

21. The method of claim 20 wherein the substrate comprises a plurality of layers including first and second layers,

each ball of the first set being disposed in the first layer,

each ball of the second set being disposed in the second layer,

and wherein:

the step of selecting a preferred set of balls from among the first and second sets of balls comprises selecting a preferred layer from among the first and second layers; and

the step of applying an electric field in a vicinity of the preferred region comprises applying an electric field to a collection of layers of the substrate, the collection comprising at least two layers including the preferred layer, so as to facilitate a rotation of at least one ball rotatably disposed in the preferred layer.

22. The method of claim 20, wherein the substrate has a surface and each of the first and second sets is associated with a color observable by an observer situated favorably to observe the surface,

each ball of the first set including a component having the color with which the first set is associated,

each ball of the second set including a component having the color with which the second set is associated,

and wherein:

the step of selecting a preferred region comprises selecting a preferred region having an observable area comprising a portion of the substrate surface;

the step of selecting a preferred set of balls from among the first and second sets of balls comprises selecting a preferred color from among the colors of the first and second sets; and

the step of applying an electric field in a vicinity of the preferred region comprises applying an electric field to a ball of the preferred set so as to facilitate a rotation of said ball, thereby facilitating a change in a degree to which the color associated with the preferred set is observably present in the observable area.

23. The method of claim 19 wherein the step of applying an electric field comprises:

selecting a preferred region of the substrate, at least one ball of each of the first and second sets being rotatably disposed in the preferred region;

applying in a vicinity of the preferred region a first electric field having the first electric field strength, so as to facilitate a rotation of a ball of the first set rotatably disposed in the preferred region and a rotation of a ball of the second set rotatably disposed in the preferred region; and

thereafter, applying in a vicinity of the preferred region a second electric field having the second electric field strength, so as to facilitate a rotation of a ball of the second set rotatably disposed in the preferred region without facilitating a rotation of any ball of the first set rotatably disposed in the preferred region.

24. The method of claim 19 wherein the substrate has a surface and each ball of each of the first and second sets has a rotational orientation, the rotational orientation of each ball being defined with respect to a planar portion of the substrate surface proximate to the ball, and wherein the step of applying the electric field comprises:

selecting a preferred region of the substrate, at least one ball of each of the first and second sets being rotatably disposed in the preferred region;

determining a first preferred rotational orientation for balls of the first set rotatably disposed in the preferred region;

determining a second preferred rotational orientation for balls of the second set rotatably disposed in the preferred region; and

applying a series of electric fields, each field of the series being applied in a vicinity of the preferred region, the applying of the entire series of fields serving to facilitate a disposition of the balls of each of the first and second sets in the preferred region in their respective preferred rotational orientations, the series of fields including

a first electric field having the first electric field strength, the first electric field facilitating rotations of balls in each of the first and second sets so as to achieve the preferred rotational orientation of balls in the first set in the preferred region while possibly affecting the rotational orientations of balls of the second set in the preferred region, the first electric field being applied first in the series if the balls of the first set in the preferred region are not already in the first preferred orientation when the step of applying the series of electric fields begins and optionally being applied first in the series if the balls of the first set in the preferred region are already in the first preferred orientation when the step of applying the series of electric fields begins, and

a second electric field having the second electric field strength, the second electric field facilitating rotations of balls in the second set only so as to achieve the preferred rotational orientation of balls in the second set in the preferred region without affecting the rotational orientations of balls of the first set in the preferred region, the second electric field being applied second in the series if the balls of the second set in the preferred region are not already in the second preferred orientation after the application, if any, of the first electric field and optionally being applied second in the series if the balls of the second set in the preferred region are already in the second preferred orientation after the application, if any, of the first electric field.

25. The method of claim 24 wherein:

the step of determining the first preferred rotational orientation comprises selecting a first preferred angle, the first preferred angle being adjustable over a continuous range of angles;

the step of determining the second preferred rotational orientation comprises selecting a second preferred angle, the second preferred angle being adjustable over the continuous range of angles; and

the step of applying the series of electric fields comprises

applying the first field of the series, if at all, by applying an electric field having an electric field vector oriented at the first preferred angle with respect to a reference vector, the reference vector being a vector normal to a planar portion of the substrate surface in a vicinity of the preferred region, the applied first field influencing balls of the first and second sets to rotate, and

applying the second field of the series, if at all, by applying an electric field having an electric field vector oriented at the second preferred angle with respect to the reference vector, the applied second field influencing balls of the second set only to rotate.

26. The method of claim 24 wherein

the first set of balls includes a plurality of balls each associated with a threshold of a first plurality of thresholds, each threshold of the first plurality being less than or equal to the first threshold and greater than the second threshold, the first plurality including at least two different thresholds, a rotation of each ball of the first set being facilitated when the ball thus rotatably disposed in the substrate is subjected to an electric field having an electric field strength exceeding the threshold with which the ball is associated, and

the second set of balls includes a plurality of balls each associated with a threshold of a second plurality of thresholds, each threshold of the second plurality being less than or equal to the second threshold, the second plurality including at least two different thresholds, a rotation of each ball of the second set being facilitated when the ball thus rotatably disposed in the substrate is subjected to an electric field having an electric field strength exceeding the threshold with which the ball is associated,

and wherein:

the step of determining the first preferred rotational orientation comprises

selecting a first intermediate threshold less than or equal to the first threshold and greater than the second threshold so as to determine a first preferred subset of balls, the first preferred subset comprising any balls of the first set rotatably disposed in the preferred region and having associated thresholds less than or equal to the selected first intermediate threshold,

determining as the first preferred rotational orientation a rotational orientation for any balls of the first set not in the first preferred subset and rotatably disposed in the preferred region, and

determining a preferred rotational orientation for balls of the first preferred subset;

the step of determining the second preferred rotational orientation comprises

selecting a second intermediate threshold less than or equal to the second threshold so as to determine a second preferred subset of balls, the second preferred subset comprising any balls of the second set rotatably disposed in the preferred region and having associated thresholds less than or equal to the selected second intermediate threshold,

determining as the second preferred rotational orientation a rotational orientation for any balls of the second set not in the second preferred subset and rotatably disposed in the preferred region, and

determining a preferred rotational orientation for balls of the second preferred subset; and

the step of applying the series of electric fields comprises applying each of the first and second electric fields of the series, and the series further includes

a first additional electric field having an electric field strength between the first and first intermediate thresholds, the first additional electric field facilitating rotations of balls in the first preferred subset and in the second set so as to achieve the preferred rotational orientation of balls in the first preferred subset while possibly affecting the rotational orientations of balls of the second set in the preferred region but without affecting the rotational orientations of balls of the first set not in the first preferred subset, the first additional electric field being applied between the first and second electric fields of the series if the preferred orientation of balls of the first preferred subset is different from the first preferred rotational orientation and the first preferred subset includes at least one ball of the first set and does not include all the balls of the first set in the preferred region, and

a second additional electric field having an electric field strength between the second and second intermediate thresholds, the second additional electric field facilitating rotations of balls in the second preferred subset only so as to achieve the preferred rotational orientation of balls in the second preferred subset without affecting the rotational orientations of balls of the first set and balls of the second set not in the second preferred subset, the second additional electric field being applied after the second electric field of the series if the preferred orientation of balls of the second preferred subset is different from the second preferred rotational orientation and the second preferred subset includes at least one ball of the second set and does not include all the balls of the second set in the preferred region.