Flexible timepiece in multiple environments

Details Flexible timepiece in multiple environments Flexible timepiece in multiple environments

2001-08-01

2003-09-16

Martin, David (Department: 2841)

Horology: time measuring systems or devices

Chronological

With electro-optical display

C368S010000, C368S084000, C368S226000, C368S227000, C368S242000, C368S276000, C368S281000, C368S282000

Reexamination Certificate

active

06621766

ABSTRACT:

BACKGROUND OF THE INVENTION
1. Technical Field of the Invention
The present invention relates generally to a timepiece having a reflective and flexible display, and specifically to the mechanical solutions involved in implementing such a watch and to the multiple environments in which such a watch could be implemented.
2. Description of Prior Art
Watches come in a variety of shapes and sizes. The watch display is usually either mechanical with at least two hands that sweep around a marked dial or a liquid crystal display. In either case, one common constraint for prior art watches is the rigidity of the display. It is common for the display to have a metal casing and either a glass or hard plastic crystal.
FIG. 1A
illustrates a standard prior art watch
10
. The watch has a thick case
12
that contains the time keeping mechanism. The case can be anywhere from a few millimeters thick to well over a centimeter. The case can be made of metal or a hard plastic; but in either case, it must be rigid to protect the time keeping mechanism. Likewise,
FIG. 1B
illustrates a generic digital watch
20
. The watch also has a display. In many instances the display is a liquid crystal display (LCD)
22
. An LCD display provides several advantages including generally low power requirements. The LCD is a reflective display. In other words, selected segments of the LCD display are biased to either a black or a gray state. The gray segments are approximately 15-25% reflective; so approximately one sixth to one quarter of the incident light produces either light or dark segments in the shape of numbers or letters. Ambient or supplemental light reflects off of the segments and the user can determine the time or date. LCD displays must also incorporate a hard display cover
A need exists for a flexible display for watches. A flexible display would allow for a number of significant advancements in the design and mechanical implementation of watches. Despite much effort directed to developing highly flexible, reflective display media, there are relatively few examples of displays formed on semi-flexible substrates, and these examples have found only moderate success. For example, plastic-based liquid crystal displays, including twisted nematic (TN), supertwisted nematic (STN), polymer dispersed liquid crystal (PDLC), and bistable cholesteric liquid crystals have been developed. Nevertheless, problems remain with liquid crystal alignment in TN and STN displays, cholesteric displays are sensitive to changes in their cell gap, and local stress can cause changes in the scattering or absorbance of PDLC and cholesteric films. As such, only moderate flexibility can be achieved with these displays.
Emissive electroluminescent films and organic light emitting diode films can be deposited on flexible substrates to create flexible displays. However, these devices require continuous power consumption for operation, and thus are not practical for many applications.
The concept of electronic ink, or e-ink, is disclosed in U.S. Pat. No. 6,118,426, owned by E-Ink Corp. of Cambridge Mass. An encapsulated electrophoretic display can be constructed so that the optical state of the display is stable for some length of time. When the display has two states that are stable in this manner, the display is said to be bistable. If more than two states of the display are stable, then the display can be said to be multistable. The term bistable indicates a display in which any optical state remains fixed once the addressing voltage is removed. The definition of a bistable state depends on the application for the display. A slowly-decaying optical state can be effectively bistable if the optical state is substantially unchanged over the required viewing time. For example, in a display that is updated every few minutes, a display image which is stable for hours or days is effectively bistable for that application. The term bistable also indicates a display with an optical state sufficiently long-lived as to be effectively bistable for the application in mind. Alternatively, it is possible to construct encapsulated electrophoretic displays in which the image decays quickly once the addressing voltage to the display is removed (i.e., the display is not bistable or multistable). Whether or not an encapsulated electrophoretic display is bistable, and its degree of bistability, can be controlled through appropriate chemical modification of the electrophoretic particles, the suspending fluid, the capsule, and binder materials.
An encapsulated electrophoretic display may take many forms. The display may comprise capsules dispersed in a binder. The capsules may be of any size or shape. The capsules may, for example, be spherical and may have diameters in the millimeter range or the micron range, but is preferably from ten to a few hundred microns. Particles may be encapsulated in the capsules. The particles may be two or more different types of particles. The particles may be colored, luminescent, light-absorbing or transparent, for example. The particles may include neat pigments, dyed (laked) pigments or pigment/polymer composites, for example. The display may further comprise a suspending fluid in which the particles are dispersed.
Referring to
FIG. 2A
, a display
30
is created by printing a first conductive coating
32
on a substrate
34
, printing an electronic ink
36
on the first conductive coating
32
, and printing a second conductive coating
38
on the electronic ink
36
. Conductive coatings
32
,
38
may be Indium Tin Oxide (ITO) or some other suitable conductive material. The conductive layers
32
,
38
may be applied from a vaporous phase, by electrolytic reaction, or deposition from a dispersed state such as spray droplets or dispersions in liquids. Conductive coatings
32
,
38
do not need to be the same conductive material. For example, the substrate
34
is a polyester sheet having a thickness of about 4 mil, and the first conductive coating
32
is a transparent conductive coating such as ITO or a transparent polyaniline. The second conductive coating
38
may be an opaque conductive coating, such as a patterned graphite layer. Alternatively, the second conductive coating
38
can be polymeric. The polymer can be intrinsically conductive or can be a polymer carrier with a metal conductor such as a silver-doped polyester or a silver-doped vinyl resin. Conductive polymers suitable for use as the second electrode include, for example, polyaniline, polypyrole, polythiophene, polyphenylenevinylene, and their derivatives. These organic materials can be colloidally dispersed or dissolved in a suitable solvent before coating. Of course, for the pixel orientation to be visible, it is preferable that the second conductive coating
38
be transparent.
The display
30
can also be created by printing a first conductive coating
32
on a first substrate
34
, printing an electronic ink
36
on the first conductive coating
32
, printing a second conductive coating
38
on a second substrate
34
′ (not shown), and configuring the substrates
34
,
34
′ such that the second conductive coating
38
is in electrical communication with the electronic ink
36
.
The electronic ink
36
comprises a plurality of capsules. The capsules, for example, may have an average diameter on the order of about 100 microns. Capsules this small allow significant bending of the display substrate without permanent deformation or rupture of the capsules themselves. The optical appearance of the encapsulated medium itself is more or less unaffected by the curvature of these capsules.
FIG. 2B
illustrates one example of the display media
40
. A microcapsule or cell
42
, filled with a plurality of metal sol
46
and a clear fluid
44
. Metal sol
46
is particles, which are smaller than a wavelength of light. In one detailed embodiment, the metal sol
46
comprises gold sol. When an electric field is applied across the microcapsule or cell
42
, sol particles
46
agglomerate and scatter light. When the applied electric field is redu

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