HK1258163B - Stretchable electro-optic displays - Google Patents

Description

Stretchable electro-optic displays

Cross Reference to Related Applications

This application claims priority and benefit of U.S. provisional application 62/343,775 filed on 31/5/2016, the contents of which are incorporated herein in their entirety.

Technical Field

The present invention relates to electro-optic displays and related devices and methods. More particularly, in one aspect, the present invention relates to stretchable electro-optic displays.

Background

The term "electro-optic" is used herein in its conventional meaning in the imaging arts when applied to materials or displays to refer to materials having first and second display states that differ in at least one optical property by the material changing from its first display state to its second display state by the application of an electric field to the material. While the optical property is typically a color perceptible to the human eye, it may be another optical property, such as optical transmission, reflection, luminescence, or, in the case of a display for machine reading, a pseudo color in the sense of a change in reflectivity of electromagnetic wavelengths outside the visible range.

The term "gray state" is used herein in its conventional meaning in the imaging art to refer to an intermediate state of two extreme optical states of a pixel, and does not necessarily imply a black-to-white transition between the two extreme states. For example, several of the imperial (E Ink) patents and published applications mentioned below describe electrophoretic displays in which the extreme states are white and dark blue, so that the intermediate "gray state" will actually be pale blue. In fact, as already mentioned, the change in optical state may not be a color change at all. The terms "black" and "white" may be used hereinafter to refer to the two extreme optical states of the display, and should be understood to generally include extreme optical states which are not strictly black and white, such as the white state and the deep blue state described above. The term "monochrome" may be used hereinafter to denote a driving scheme in which a pixel is driven only to its two extreme optical states without an intervening grey state.

The terms "bistable" and "bistability" are used herein in their conventional meaning in the art to refer to displays comprising display elements having first and second display states which differ in at least one optical property and such that, after any given element has been driven to assume its first or second display state by means of an addressing pulse of finite duration, that state will persist for at least several times, for example at least 4 times, the minimum duration of the addressing pulse required to change the state of the display element after the addressing pulse has terminated. It is shown in U.S. patent No. 7,170,670 that some particle-based electrophoretic displays capable of displaying gray scales are stable not only in their extreme black and white states, but also in their intermediate gray states, as is the case for some other types of electro-optic displays. Although for convenience the term "bistable" may be used herein to encompass both bistable and multi-stable displays, such displays are suitably referred to as "multi-stable" rather than bistable.

One type of electro-optic display that has been the subject of intense research and development for many years is a particle-based electrophoretic display in which a plurality of charged particles move through a fluid under the influence of an electric field. Electrophoretic displays can have characteristics of good brightness and contrast, wide viewing angles, state bistability, and low power consumption compared to liquid crystal displays. However, problems with the long-term image quality of these displays have prevented their widespread use. For example, the particles that make up electrophoretic displays tend to settle, resulting in insufficient lifetime of these displays.

A number of patents and applications assigned to or in the name of the Massachusetts Institute of Technology (MIT) and yingke corporation describe various techniques for encapsulating electrophoretic media and other electro-optic media. Such encapsulated media comprise a plurality of capsules, each capsule itself comprising an internal phase containing electrophoretically mobile particles in a fluid medium and a capsule wall surrounding the internal phase. Typically, the capsule itself is held in a polymeric binder to form a tie layer between the two electrodes. The techniques described in these patents and applications include:

(a) electrophoretic particles, fluids, and fluid additives; see, e.g., U.S. Pat. nos. 7,002,728 and 7,679,814;

(b) bladders, adhesives, and packaging processes; see, e.g., U.S. patent nos. 6,922,276 and 7,411,719;

(c) films and sub-assemblies comprising electro-optic material; see, e.g., 6,825,829; 6,982,178; 7,236,292; 7,443,571, respectively; 7,513,813, respectively; 7,561,324, respectively; 7,636,191, respectively; 7,649,666, respectively; 7,728,811, respectively; 7,729,039, respectively; 7,791,782, respectively; 7,839,564, respectively; 7,843,621, respectively; 7,843,624, respectively; 8,034,209, respectively; 8,068,272, respectively; 8,077,381, respectively; 8,177,942, respectively; 8,390,301, respectively; 8,482,835, respectively; 8,786,929; 8,830,553, respectively; 8,854,721, respectively; and U.S. patent No. 9,075,280; and 2009/0109519 th; 2009/0168067, respectively; 2011/0164301, respectively; 2014/0027044, respectively; 2014/0115884, respectively; and U.S. published patent application No. 2014/0340738;

(d) a backplane, adhesive layer and other auxiliary layers and methods for a display; see, e.g., U.S. patent nos. 7,116,318 and 7,535,624;

(e) color formation and color adjustment; see, e.g., U.S. patent nos. 7,075,502 and 7,839,564;

(f) a method of driving a display; see, e.g., U.S. Pat. nos. 7,012,600 and 7,453,445;

(g) an application for a display; see, e.g., U.S. patent nos. 7,312,784 and 8,009,348; and

(h) non-electrophoretic displays, such as 6,241,921; 6,950,220, respectively; 7,420,549, respectively; 8,319,759, respectively; and U.S. patent No. 8,994,705; and U.S. published patent application No. 2012/0293858.

All patents and applications cited herein are incorporated by reference in their entirety.

Many of the above patents and applications recognize that in an encapsulated electrophoretic medium, the walls surrounding the discrete microcapsules can be replaced by a continuous phase, thereby creating a so-called polymer dispersed electrophoretic display, wherein the electrophoretic medium comprises a plurality of discrete droplets of electrophoretic fluid and a continuous phase of polymeric material, and the discrete droplets of electrophoretic fluid in such a polymer dispersed electrophoretic display can be considered as capsules or microcapsules, even if the discrete capsule membranes are not associated with each single droplet; see, for example, the aforementioned U.S. patent No. 6,866,760. Thus, for the purposes of this application, such polymer-dispersed electrophoretic media are considered to be a subcategory of encapsulated electrophoretic media.

A related type of electrophoretic display is the so-called "microcell electrophoretic display". In microcell electrophoretic displays, the charged particles and fluid are not encapsulated in microcapsules, but rather are held in a plurality of cavities formed in a carrier medium, typically a polymer film. See, for example, U.S. patent nos. 6,672,921 and 6,788,449, assigned to Sipix Imaging, inc.

Although electrophoretic media are typically opaque (because, for example, in many electrophoretic media, the particles substantially block the transmission of visible light through the display), and operate in a reflective mode, many electrophoretic displays can be made to operate in a so-called "shutter mode" in which one display state is substantially opaque and one display state is light-transmissive. See, for example, U.S. patent nos. 5,872,552, 6,130,774, 6,144,361, 6,172,798, 6,271,823, 6,225,971, and 6,184,856. Dielectrophoretic displays, which are similar to electrophoretic displays but rely on changes in electric field strength, can operate in a similar mode; see U.S. patent No. 4,418,346. Other types of electro-optic displays can also operate in shutter mode. Electro-optic media operating in shutter mode are useful for multi-layer structures for full color displays; in this configuration, at least one layer adjacent to the viewing surface of the display operates in a shutter mode to expose or hide a second layer further from the viewing surface.

The manufacture of a three-layer electro-optic display typically involves at least one lamination operation. For example, in the above-mentioned several MIT and inck patents and applications, a process for preparing an encapsulated electrophoretic display is described in which an encapsulated electrophoretic medium comprising capsules in an adhesive is applied onto a similar conductive coating on a flexible substrate or plastic film comprising Indium Tin Oxide (ITO), which serves as one electrode of the final display, and the capsule/adhesive coating is dried to form an adhesive layer of the electrophoretic medium that adheres strongly to the substrate. A backplane is separately prepared which includes an array of pixel electrodes and an appropriate arrangement of conductors to connect the pixel electrodes to drive circuitry. To form the final display, the substrate with the bladder/adhesive layer thereon is laminated to a backplane using a laminating adhesive (very similar processes can be used to prepare electrophoretic displays that can be used with a stylus or similar movable electrode that can slide over a simple protective layer, such as a plastic film, by replacing the backplane with a simple protective layer, such as a plastic film). In one preferred form of this method, the backplane is itself flexible and is prepared by printing the pixel electrodes and conductors on a plastic film or other flexible substrate. A well-established lamination technique for large scale production of displays by this method is roll lamination using a lamination adhesive. Similar fabrication techniques may be used for other types of electro-optic displays. For example, the microcell electrophoretic medium or the rotating bichromal element medium may be laminated to the backplane in substantially the same manner as the encapsulated electrophoretic medium.

In some applications, stretchable electro-optic displays may be desirable; however, conventional electro-optic displays include one or more layers that may prevent the display from stretching, even if the display is flexible. For example, in view of an electro-optic display having front and rear electrodes on either side of the electro-optic layer, the front and/or rear electrodes may be formed from a rigid and stretch-resistant material, such as Indium Tin Oxide (ITO). Typically, flexible displays can only bend in a single axis curve, in the same way paper can bend, as stretching may be limited by the most restrictive layers within the electro-optic display. Thus, there is a need for electro-optic displays that are both flexible and stretchable.

Disclosure of Invention

One aspect of the invention provides an electro-optic display comprising a layer of conductive material and an electrophoretic medium laminated to the layer of conductive material. The layer of conductive material may also include a plurality of nodes and stretchable interconnects connecting first and second nodes of the plurality of nodes.

In another aspect of the present invention, a method of making an electro-optic display comprises: patterning a layer of conductive material to define a plurality of nodes and stretchable interconnects connecting first and second nodes of the plurality of nodes, and laminating an electrophoretic medium layer to the layer of conductive material.

These and other aspects of the invention will be apparent in view of the following description.

Drawings

Various aspects and embodiments of the present application will be described with reference to the following drawings. It should be understood that the drawings are not necessarily drawn to scale. The drawings depict one or more embodiments in accordance with the present inventive concept by way of example only and not by way of limitation. In the drawings, like reference characters designate the same or similar elements.

FIG. 1 is a cross-sectional view of an example of an electro-optic display.

FIG. 2 is a schematic diagram illustrating an exemplary method for forming a display capable of conforming to a shape having a compound curve.

FIG. 3A is a schematic diagram illustrating an exemplary display layer structured to stretch in one or more directions.

Fig. 3B is a schematic diagram illustrating an exemplary cross-sectional view of a display having the display layer shown in fig. 3A.

Fig. 3C is a schematic view illustrating an extended state of the display layer illustrated in fig. 3A.

FIG. 4 is a schematic diagram illustrating an exemplary display layer structured to stretch in one or more directions, according to a non-limiting embodiment.

FIG. 5 is a schematic diagram illustrating an exemplary display layer structured to stretch in one or more directions, according to a non-limiting embodiment.

Fig. 6A is a schematic diagram illustrating an exemplary display layer structured to be stretched in one or more directions, according to a non-limiting embodiment.

Fig. 6B is an enlarged version of the schematic diagram of fig. 6A.

Detailed Description

In the following detailed description, numerous specific details are set forth by way of examples in order to provide a thorough understanding of the relevant teachings. It will be apparent, however, to one skilled in the art that the present teachings may be practiced without these specific details.

Referring to the drawings in general, various embodiments of the present invention provide electro-optic displays that include a layer having a plurality of node areas (also referred to herein simply as "nodes") with stretchable interconnections between at least two nodes. While the material of the layer may be non-stretchable or have limited stretchable properties, the shape of the stretchable interconnect may enable the extension of the layer. The stretchable interconnect may be serpentine, coiled, zig-zag, curved or otherwise shaped such that it can expand and contract when properly manipulated. In this way, the distance between the nodes connected by the stretchable interconnect can be changed by manipulating (e.g. pulling) the display. When the nodes are pulled apart, the serpentine interconnect will rotate and bend. The flexibility and extensibility of the display may enable the display to conform to a variety of shapes, including shapes having one or more compound curves. In some embodiments, the electro-optic display is an electrophoretic display, and the layer having nodes and stretchable interconnects is an electrode of the display.

Various features of the displays may help them be used for beneficial purposes, such as in building displays and wearable displays. One such feature is the ability of the display to extend in one or more directions. While the flexibility of the display relates to the ability of the display to bend, the stretchable nature of the display includes the ability of the display to stretch and extend to cover more surface area. The flexibility of the display, combined with its ability to stretch, allows the display to bend and/or conform to a three-dimensional shape. An extendable display may be formed by configuring the display such that portions of the display are configured to extend. The other portions of the display may remain continuous as nodes connected by stretchable interconnects. By extending the interconnects, the distance between adjacent nodes may be increased, resulting in an increased area occupied by the display surface. In some embodiments, the stretchable interconnect and the flexibility of the display cause the display to conform to a shape having one or more compound curves. Another feature relates to the ability to design and structure an electro-optic display to include stretchable interconnects in one or more layers of the display. The electro-optic display layers may be structured to be stretchable using any suitable technique, for example, cutting with a laser cutter or scissors. The resolution of the technique may determine the size of the nodes and stretchable interconnects. Another feature relates to the ability to control the electro-optic display by using drive signals to create colors, patterns, or other visual effects.

Aspects of the present application relate to designing and structuring electro-optic displays in a stretchable manner. An electro-optic display may include an electro-optic medium between front and rear electrodes. In some embodiments, the electro-optic display may have segmented electrodes, and in other embodiments, the electro-optic display may be configured with active matrix pixels. Applicants have appreciated that the nature of the materials used in electro-optic displays may limit the ability of the display to stretch, thereby limiting the types of shapes that can be formed by the electro-optic display. Accordingly, aspects of the present application provide one or more electro-optic display layers having stretchable interconnects that may improve the ability of the display to stretch and conform to different shapes. In some embodiments, the interconnects may be shaped to reduce the strain of the material in the display layer when the interconnects are elongated to a stretched state. In some embodiments, the width of the stretchable interconnect may have a substantially uniform dimension along the length of the stretchable interconnect. In addition, the stretchable interconnect may be structured to increase the active area of the display while still providing the display with the ability to be stretchable.

The above aspects and others will now be described in detail below. It should be understood that these aspects may be used alone, together, or in any combination of two or more, as long as they are not mutually exclusive.

In some embodiments, the expandable display may be an electrophoretic display. A cross-sectional view of an exemplary electrophoretic display configuration is shown in fig. 1. The display 100 comprises an electrophoretic medium layer 101, which electrophoretic medium layer 101 may comprise a plurality of capsules 104, which capsules 104 have a suspending fluid and electrophoretic particles 106 suspended in the fluid. An electrophoretic medium layer 101 is between the electrode 102 and the electrode 110. The electrophoretic particles 106 may be charged and respond to the difference in electric fields generated by the electrodes 102 and 110. Examples of suitable electrophoretic medium layers are described in U.S. Pat. nos. 6,982,178 and 7,513,813. In some embodiments, the electrophoretic medium layer may be relatively more stretchable than other layers in the display, such as electrode 102 and electrode 110, and a stretchable display may be formed by structuring the other layers to include stretchable interconnects. In this way, all layers of the display can be stretched.

Reference to two electrodes may be described based on the viewing surface of the display. For example, if the surface of display 100 proximate electrode 102 is the viewing surface, electrode 102 may be referred to as the front electrode and electrode 110 may be referred to as the back electrode. Electrode 102 and/or electrode 110 may be optically transparent. The electrode 102 may be a single common transparent electrode on one side of the electrophoretic medium layer 101 that extends the length of the display. The electrode 110 is located on the opposite side of the electrophoretic medium layer 101 from the electrode 102. In some embodiments, electrode 110 may also be a common electrode, such as electrode 102, extending the length of display 100. Alternatively, the electrodes 110 may be pixelated to define pixels of the display.

Display 100 also includes a voltage source 108 coupled to electrodes 102 and 110 and configured to provide drive signals to those electrodes. The supplied voltage then creates an electric field between the electrodes 102 and 110. Thus, the electric field experienced by the electrophoretic medium layer 101 may be controlled by varying the voltages applied to the electrodes 102 and 110, and in the case where one or both of those electrodes are pixelated, varying the voltage applied to the desired pixel may provide control of the display pixel. Particles 106 within electrophoretic medium layer 101 may move within their respective capsules 104 in response to an applied electric field generated by a voltage difference between electrodes 102 and 110.

Even if the material forming the electrodes is not itself significantly stretchable, the electrodes 102 and/or 110 may be structured to include stretchable interconnects, providing the display 100 with the ability to be stretchable. For example, the electrodes 102 and/or 110 may be formed of Indium Tin Oxide (ITO) which has limited stretch properties, but by configuring the electrodes 102 and/or 110 to have stretchable interconnections, the stretch properties of the electrodes 102 and/or 110 may be improved. Additionally, electrodes 102 and/or electrodes 110 may be flexible, providing flexibility to display 100. For example, ITO may be flexible at a suitably thin dimension. Thus, in some embodiments, electrode 102 and/or electrode 110 may be a thin layer of ITO. In this case, the ITO may be less than, for example, 15 mils, less than 10 mils, or any value within those ranges, or any other value that provides the desired flexibility in those cases where a flexible display is desired. In those cases where electrode 102 represents the viewing side of display 100, it may be beneficial to use ITO as electrode 102, as the ITO electrode may be transparent. In addition, other electrode materials may be used as alternatives.

Electrode 102 and/or electrode 110 may each optionally be formed on a substrate, such as a substrate of polyethylene terephthalate (PET). Such a substrate may be transparent and thus not negatively affect the display performance of the display 100. As with the electrodes 102 and 110 themselves, any substrate for the electrodes may be formed of a material and structured with stretchable interconnects that provide the desired stretchability. Dimensions similar to those listed above for electrodes 102 and 110 may be used for any substrate to provide the desired display flexibility. For convenience of explanation, the substrate is not separately shown in fig. 1.

Although fig. 1 shows a microcapsule-type electrophoretic display, various types of displays may be used in accordance with the techniques described in this application. In general, electro-optic displays including microcapsule-type electrophoretic displays, microcell-type electrophoretic displays, and polymer dispersed electrophoretic image displays (PDEPIDs) may utilize aspects of the present application. Further, while electrophoretic displays represent a suitable type of display in accordance with aspects of the present application, other types of displays may also utilize one or more aspects of the present application. For example, Gyricon displays, electrochromic displays, and Polymer Dispersed Liquid Crystal Displays (PDLCDs) may also utilize aspects of the present application.

The electro-optic displays described herein may be of any suitable size, and may be small in some embodiments. For example, the display 100 may be small in at least some embodiments, which may contribute to its flexible nature. For example, each of the electrodes 102 and 110 may be between 1 mil (thousandths of an inch) and 10 mils, such as 5 mils each, or between 0.1mm and 0.5 mm. The layer of electrophoretic medium may be between 0.5 mils and 5 mils, such as 1 mil, or between about 0.03mm and 0.06 mm. Thus, in some embodiments, the display 100 may have a total thickness of about 10-15 mils, or about 0.2mm to 0.4 mm. The listed examples of dimensions are non-limiting as other dimensions may be used.

As described above, some or all of the layers in an electrophoretic display may be structured with stretchable interconnects. Since a continuous layer may limit the overall stretch properties of the display, structuring the layers to have stretchable interconnects may improve the ability of the display to stretch. In some embodiments, the material forming the display layers may be relatively inextensible, but the layers may be structured to have extensible interconnections, for example by suitable patterning of the layers. The stretchable electrode layer (e.g. an electrode layer formed of ITO and suitably patterned) may be structured to have nodes connected by stretchable interconnects, while other layers of the display, such as the electrophoretic medium layer, are continuous. In some embodiments, a non-stretchable substrate material (e.g., PET) may be structured into a display layer to have nodes connected by stretchable interconnects. In some embodiments, all layers in a display may be configured with nodes connected by stretchable interconnects. Such displays may have openings through all layers of the display, such that it is a desired purpose for the display to be used for openings in the display, including applications of wearable displays where the display is worn by a person and the openings provide a passage for air and moisture, enabling air permeability similar to fabric. In some embodiments, the display may include an elastomer, such as an elastomeric film layer. The elastomer may provide mechanical structure to the display and/or a structuring that protects one or more layers with stretchable interconnects. The elastomer may optionally be optically obscured by incorporation of scattering fillers or a textured surface of the elastomer layer to hide the cut lines defining the interconnects, which may improve readability of the electro-optic display. Aspects of the present application relate to the manner in which display layers are structured to be stretchable and form stretchable displays of the type described herein. Fig. 2 illustrates an exemplary method 200 for forming an expandable display according to aspects of the present disclosure. The method 200 begins with operation 202 of structuring one or more layers of an electro-optic display to have any suitable configuration of nodes and stretchable interconnections, examples of which are shown in fig. 3A, 3C, and 4 and described in detail below. In some embodiments, the stretchable interconnects are configured to deform when a force is applied to the structured layer and/or a display having the structured layer, while the nodes are continuous regions of the structured layer and have limited ability to deform under the action of the force. In some embodiments, the node is configured to deform. The nodes have at least one interconnect; preferably, at least three interconnects. The shape of the nodes and the location of the interconnect(s) may depend on the extent to which the display needs to be stretched and the direction of stretching. The nodes provide electrical and mechanical connections between the plurality of interconnects. Having multiple interconnects on each node provides fault tolerance to interconnect failures. For example, if an interconnect fails, nodes on either side of the failed interconnect that have connections to other interconnects will continue to be driven and supported by the remaining interconnects. Most likely, only the conductor (e.g., ITO) will crack and the support material (e.g., PET) will still be connected and the electro-optic layer will still function. Even a broken interconnect will continue to function because both ends of the interconnect will still be electrically connected to a node which is still electrically connected to the rest of the display. In other words, the active area will not be lost.

Any suitable node and expandable interconnect dimensions may be used. In some embodiments, the interconnects of the structured layer may be structured to provide uniform deformation when the structured layer is stretched. Both the nodes and the interconnect regions may have similar cross-sectional material compositions, and the ability of the interconnect to deform is primarily based on the shape of the interconnect. The layer may be an electrode layer, an electrophoretic medium layer and/or a substrate layer. The layer may be initially formed as a continuous layer and may be structured to have nodes and stretchable interconnections by removing portions of the layer. Any suitable technique(s) for removing portions of the display layer may be used, such as laser cutting, using scissors, or using other cutting tools. When the layer structured to be stretchable is a layer of electro-optic medium, for example having one or more openings or patterns therein, an optional barrier layer or protective sheet or edge seal may be applied to the display to prevent moisture ingress and/or to prevent leakage of the electro-optic material from the display. Examples of such seals are described in U.S. patent No. 7,649,674.

An electro-optic display may be formed in operation 204 by attaching multiple layers of the display together. An electro-optic display may be manufactured by laminating two electrodes (a front electrode and a back electrode) together with an electro-optic layer therebetween. For example, the front electrode and electro-optic layer may be attached to each other, constituting a front plane laminate, and may have a backing laminate adhesive to which a release sheet is attached. The release sheet may be removed and the front plane laminate material attached to the back electrode. In some embodiments, a roll-to-roll process may be used in which the front electrode and the electro-optic layer are rolled onto the back electrode. Examples of this type of treatment are described in U.S. patent nos. 6,982,178 and 7,513,813. These techniques may be used to fabricate a display, such as display 100 of FIG. 1. Alternative methods for making the display may be used. The techniques used to construct active matrix pixel displays can be used to form electro-optic displays having segmented electrodes as rear electrodes.

The result of operation 204 is an expandable electro-optic display. As previously mentioned, the stretchable electro-optic display may comprise: one or more layers (e.g., electrodes) structured (e.g., patterned) to exhibit stretchability even when formed of material(s) having relatively low inherent stretchability; and one or more layers (e.g., an electro-optic dielectric layer) exhibiting a relatively high stretchability.

One or more monolayers of the stretchable display can be coupled to a drive circuit. According to aspects of the present application, the electrical connection regions on a single display may be coupled to the drive circuitry using any suitable technique, such as by soldering, conductive glue, pinning, and/or other types of electrical connections. Some embodiments may use a rivet connection formed by inserting a conductive connector through an opening in two electrodes and the electro-optic layer of the display. In such embodiments, the connector may be positioned to mechanically and electrically contact one of the two electrodes. In some embodiments, a Printed Circuit Board (PCB) housing drive circuitry for one or more electro-optic displays in a composite display is coupled to electrodes of the one or more displays. Thus, as previously described, control of the individual electro-optic displays of the extendible display may be provided.

The resulting stretchable display may conform to a shape having one or more compound curves. The stretchable interconnect connecting the two nodes may be stretched from an unstretched or relaxed state to a stretched state when the display is conformed to shape. The size of the stretchable interconnect may determine the degree of stretching of the stretchable interconnect. The material properties of the layers with stretchable interconnections may also determine the degree of stretching. In some embodiments, the dimensions of the interconnect may be configured to reduce strain at certain regions of the interconnect when the interconnect is elongated to an extended state. The length of the stretchable interconnect may be elongated from an unstretched state to an stretched state, thereby increasing the distance between the two nodes. In this way, the area of the display may be stretched from an unstretched state to conform to the shape. The display in the extended state may cover a larger surface area than the display in the non-extended state. Similarly, when the display stretched to conform to the shape returns to an unstretched state, the stretched region of the display may contract to a less stretched state or a relaxed state. The interconnects are preferably 3mm wide, but may be as small as 1mm wide or as large as 10mm wide or even wider depending on the size and application of the stretchable display. The lower end of the range of widths is limited by the cutting technique applied. For example, most laser cuts typically have a practical limit of 1mm feature width. The upper range limit of the width is limited by the curvature of the surface of the part to be stretched. A smaller curvature would require finer nodes and interconnects. The length of the interconnect will determine the extent to which the display can be stretched.

It should be understood that the order of conforming to the display and coupling the display to the drive circuitry is not limited to coupling the display before conforming to the display, and some embodiments include conforming the display to a shape having one or more compound curves before coupling the display to the drive circuitry. Any suitable arrangement of nodes and stretchable interconnects may be employed to structure one or more layers to achieve the desired stretchable properties of the resulting display. FIG. 3A shows a layer 300 of an electro-optic display having an exemplary arrangement of nodes 302a-302d and labeled interconnects 304a-304f, as well as other unlabeled interconnects. A display having a layer 300 may be stretched in one or more directions by extending at least a portion of the stretchable interconnect. Layer 300 may be an electrode layer, such as electrodes 102 and 110, and/or a substrate layer. In some embodiments, the display may include multiple layers with structures like nodes and interconnects such that openings are present in the display.

The active area of the display may be defined by the area of the display in which the structured electrode layer has a continuous portion of electrode material. For displays having a structured electrode layer, such as a display having an arrangement of layers 300, the configuration of the nodes and interconnects of the structured electrode layer may define the active surface area of the display, as successive portions of the electrode layer drive the electrophoretic medium. Since such electrode layers are not continuous, the portions of the electrode layers where nodes or interconnects are present may form an effective display area. Openings in the electrode layer, such as areas lacking electrode layer material, create inactive areas of the display because there is no electrode layer to drive the electrophoretic material. The electrode layer may be patterned with nodes and interconnects to achieve a suitable active area of the display. In some embodiments, the configuration of nodes and interconnects may provide sufficient active area of the display such that inactive areas are not apparent to a viewer of the display. Preferably, the active area of the display will be at least 85% when unstretched. More preferably, the active area of the display will be at least 95% when not extended. Most preferably, the display is 100% or almost 100% efficient. In some applications, the amount of active area is less important, and an active area of about 85% or less is acceptable. The inactive area of the display may include the width of any top plate connections and cuts between nodes and interconnects. Laser cutting is the preferred cutting method with a cut width of about 0.1mm, which contributes to the inactive area of the display.

FIG. 3B is a cross-sectional view of the display of FIG. 3 with the electrode layer 306 structured as layer 300 along line A-A'. Electrode layer 306 has continuous portions of electrode material as nodes 302d and 302c and portions forming stretchable interconnects 304c, 304e, and 304 f. In this exemplary embodiment, electrode layer 310 is continuous, as shown in FIG. 3B. An electrophoretic medium layer 308 is located between electrode layers 306 and 310. The active area of the display shown in fig. 3B is where the portion of the electrode layer 306 is present, as the display is controlled by applying a voltage across the electrophoretic medium layer 308. Although fig. 3B shows one structured electrode layer with nodes and interconnects, other layers in the display may have similar structuring. In some embodiments, both electrodes 306 and 310 may be appropriately structured to provide stretch capability to the display. Such an embodiment may be suitable when the material used for both electrode layers has limited stretch properties. In some embodiments, the electrophoretic layer 308 and electrode layers 306 and 310 may be structured with nodes and stretchable interconnects, which may be desirable for applications where the display is both stretchable and able to allow moisture and air to pass through, such as in wearable display applications.

The nodes may be patterned within layer 300 to have any suitable placement, spacing, and shape. For simplicity, only four nodes are shown in fig. 3A, but in practice, the display layer may have more (e.g., greater than 10 nodes, greater than 100 nodes, greater than 1,000 nodes, 10 to 500 nodes, or any number or range of numbers within such a range). The nodes may be uniformly positioned, for example, in an array, but other arrangements are possible. In one embodiment, nodes may be disposed on the backplane of an electro-optic display to provide areas on which delicate active components, such as transistors and storage capacitors, may be positioned.

In FIG. 3A, the nodes 302a-302d are in a square arrangement and connected by interconnects 304a-304d, however, other arrangements of nodes and interconnects may be suitable depending on the desired characteristics of the resulting display. Although the nodes 302a-302d are shaped as squares, the nodes may have any suitable shape and/or size. The spacing between two nodes may be configured by the size of the interconnect connecting the two nodes. For example, length L of interconnect 304a₁Defining the distance between nodes 302a and 302b, and the length L of interconnect 304d₂Defining the distance between nodes 302a and 302 d.

The interconnects may be patterned within layer 300 to have any suitable placement and shape. Although one shape is shown in fig. 3A, the interconnects may be structured to have any suitable shape, such as serpentine, coiled, zigzag, curved, or otherwise shaped such that the layers with the interconnects may expand and contract when properly manipulated. The shape and/or size of the nodes and stretchable interconnects may be selected based on the application of the resulting display. The extent to which the stretchable interconnect may extend may depend on the width of the interconnect material and the lateral dimension of the interconnect shape. As an example, fig. 3A shows the width w and lateral dimension d of the interconnect 304 a. For interconnects, the width and/or dimensions may be varied to provide a desired amount of stretch to the interconnect. The lateral distance and width of the serpentine interconnects determines the amount of extension between the nodes that will be achieved without damaging the electro-optic display. Generally, the longer the lateral distance, the greater the possible extension, as the deformation spreads over a longer path.

The size and shape of the interconnects may be selected based on the material properties of layer 300 to reduce the amount of strain at points along the interconnects. In some embodiments, uniform deformation over the length of the interconnect may be achieved by varying the width and/or lateral dimensions to reduce the area within the interconnect that may limit the elongation of the interconnect. In some embodiments, the electrode layers of the display may be configured with nodes and interconnects to achieve an amount of active surface area with a degree of stretch for the display. Typically, the extendable portion of the display is movable in more than one axis and may move along multiple planes.

The relative distance between nodes may be varied by stretching one or more interconnects. Fig. 3C is an extended state of the layer 300 extended along the x direction. Interconnects 304a and 304c are elongated and have a length L between interconnects 304a and 304c as shown in FIG. 3A₁Has a greater length L in the x-direction in the stretched state shown in fig. 3C than in the less stretched or relaxed state of the layer 300₃. By stretching and extending the interconnect 304a in the x-direction, the distance between the nodes 302a and 302b is greater in the stretched state (fig. 3C) than in the unstretched state (fig. 3A). The structured layer may be unevenly stretched such that some interconnects are elongated from a relaxed state and some interconnects remain in a relaxed state. In this way, the extended state of a layer or display with structured layers may include one or more interconnects with no or limited extension, such as interconnect 304d shown in fig. 3C. Interconnect 304d has a length L due to limited or no stretch in the y-direction in the stretched state depicted in FIG. 3C₄Similar to the length L when the layer 300 is in a relaxed state₂。

FIG. 4 is another exemplary arrangement of nodes 402a-402e and expandable interconnects (some labeled 404a-404d) of a layer 400 of a display. As shown in FIG. 4, node 402e is connected to a central portion of interconnects 404a-404 d. Such an arrangement may increase the amount of material remaining in layer 400 and may be desirable for certain display applications. As an example, an electrode layer configured with the arrangement of layers 400 can produce a display having a desired amount of active surface area, as the surface area of the electrode layer drives the electrophoretic medium in the display. The active area of the display may be defined by an area of the display in which the structured electrode layer has a continuous portion of electrode material.

Fig. 5 is an exemplary arrangement of nodes connected to each other by stretchable interconnects to form a display layer. As shown, the dark black wavy lines represent cut lines that form stretchable interconnections, while the light gray lines represent only hexagonal nodes. As shown in fig. 5, the nodes are arranged in a pattern of hexagonal areas with stretchable interconnects connecting adjacent nodes. The node 502a is connected to stretchable interconnects 504a-504f, which are disposed radially about the node 502 a. The extendable interconnects 504c and 504f connected to node 502a are also connected to nodes adjacent to node 502 a. For example, expandable interconnect 504c is connected to both nodes 502a and 502b, and expandable interconnect 504f is connected to both node 502a and node 502 c. In this way, the active area of the display may be defined by the nodes and the stretchable interconnection connecting the nodes.

Fig. 6A is an exemplary arrangement of interconnects connected to deformable nodes. As shown, the dark black lines represent cut lines and define nodes (squares) 602a, 602b, 602c, and 602 d; the light gray lines also represent cut lines and define interconnects 604a, 604b, 604c, and 604d that connect to the node 602a of the adjacent node.

Fig. 6B is an enlarged version of fig. 6A. Nodes 602a, 602b, 602c, and 602d are adjacent nodes, and each node has four interconnects. Some interconnects are labeled 604a-604 g. When the display is extended, the interconnects (i.e., 604a-604g) remain fairly straight, and the nodes 602a-602d twist to extend the display primarily along the Z-axis. Although the cut lines forming the interconnects 604a-604g are shown as uniformly parallel lines, the spacing between the cut lines and the relative lengths of the cut lines may vary depending on the desired stretchability and/or flexibility of the final display. For example, light gray cut lines that are closer to the dark black cut line may be spaced closer together than light gray cut lines that are relatively farther from the dark black cut line. This will provide more active area in the central area of the node than the periphery of the node.

Having thus described several aspects and embodiments of the technology of the present application, it is to be appreciated various alterations, modifications, and improvements will readily occur to those skilled in the art. Such alterations, modifications, and improvements are intended to be within the spirit and scope of the technology described in this application. For example, various other means and/or structures for performing the function and/or obtaining the result and/or one or more of the advantages described herein will be readily apparent to those of ordinary skill in the art, and each such variation and/or modification is considered to be within the scope of the embodiments described herein. Those skilled in the art will recognize, or be able to ascertain using no more than routine experimentation, many equivalents to the specific embodiments described herein. It is, therefore, to be understood that the foregoing embodiments are presented by way of example only and that, within the scope of the appended claims and equivalents thereto, embodiments of the invention may be practiced otherwise than as specifically described. In addition, any combination of two or more such features, systems, articles, materials, kits, and/or methods, if such features, systems, articles, materials, kits, and/or methods are not mutually inconsistent, is included within the scope of the present disclosure.

Claims (15)

1. An electro-optic display, comprising:

a front electrode;

a back electrode;

an electrophoretic medium located between the front and back electrodes and comprising a suspending fluid and electrophoretic particles suspended in the suspending fluid; and

a voltage source coupled to the front and back electrodes and configured to provide drive signals to the front and back electrodes, thereby generating an electric field that moves electrophoretic particles in a suspending fluid;

wherein the front electrode and/or the back electrode comprise a layer of conductive material having a plurality of cuts forming a plurality of nodes and boundaries of stretchable interconnects, and the stretchable interconnects connect first and second nodes of the plurality of nodes.

2. The electro-optic display of claim 1, wherein the electro-optic display is configured to extend between a first extended state in which the stretchable interconnect is extended and a second unextended state in which the stretchable interconnect is unextended, and wherein at least one of a length or a width of the electro-optic display is greater during the first extended state than during the second unextended state.

3. The electro-optic display of claim 2, wherein a distance between the first and second nodes is greater when the electro-optic display is in a first state than when the electro-optic display is in a second state.

4. The electro-optic display of claim 1, wherein the stretchable interconnects have a sinusoidal shape.

5. The electro-optic display of claim 1, wherein the electro-optic display is configured to conform to a shape having at least one compound curve when the stretchable interconnect is in a stretched state.

6. The electro-optic display of claim 1, wherein the stretchable interconnect has a lateral dimension and a width, and the extent of stretching of the interconnect area is dependent on the lateral dimension and the width.

7. The electro-optic display of claim 1, further comprising an elastomeric film attached to a surface of the display and configured to provide mechanical support to the electro-optic display.

8. A method of making the electro-optic display of any one of claims 1-7, comprising: cutting the first layer of conductive material to define a plurality of nodes and stretchable interconnects connecting first and second nodes of the plurality of nodes;

laminating an electrophoretic medium layer to the first conductive material layer;

laminating a second layer of conductive material onto the electrophoretic medium on a side of the electrophoretic medium opposite the first layer of conductive material; and

a voltage source is coupled to the first layer of conductive material and the second layer of conductive material.

9. The method of claim 8, wherein cutting the layer of conductive material to define a plurality of nodes and stretchable interconnects comprises forming at least two square nodes.

10. The method of claim 8, wherein cutting the layer of conductive material to define a plurality of nodes and stretchable interconnects comprises forming at least two hexagonal nodes.

11. The method of claim 8, wherein cutting the layer of conductive material to define a plurality of nodes and stretchable interconnects comprises forming a serpentine interconnect having a first end coupled to the first node and a second end coupled to the second node.

12. The method of claim 11, wherein cutting the serpentine interconnect further comprises forming the serpentine interconnect to couple to a third node of the plurality of nodes at a point along the serpentine interconnect between the first and second ends.

13. The method of claim 8, wherein cutting the layer of conductive material comprises cutting a front electrode using a laser.

14. The method of claim 8, wherein cutting the layer of conductive material is performed prior to the laminating step.

15. The method of claim 8, wherein cutting the layer of conductive material is performed after the laminating step.