3-D flexible display structure

[0002] This invention relates to flexible electro-optic displays, in particular to displays based on flexible fabrics and other flexible permeable materials.

[0003] An electro-optic display is a device that changes its optical state when electric or electromagnetic signals are applied to it. The display may change as a whole unit or in parts constituting a visible image. The image on such displays is formed from a plurality of display elements including an electro-optically active (EOA) substance. “EOA substance” shall mean here a substance that changes its color, transparency, reflectivity or other optic properties, or emitting light, when subjected to changes of electric or electromagnetic field.

[0004] Flexible electro-optic displays may be made of flexible polymer films, where the EOA substance and patterns of electrodes are laid in thin layers over a polymer substrate, or may be based on flexible fibers or strips woven or knitted into fabric or textile material where the electrodes are in the constituent fibers. Woven displays have certain advantages since they may be produced using known weaving techniques which do not limit their length. Woven displays are more flexible and robust than integral film displays.

[0005] U.S. Pat. No. 5,962,967 and JP 2001-034195 disclose woven displays made of two sets of transverse fibers, each fiber including a longitudinal conductor, and at least fibers of one set including a coating of light-emitting or other EOA substance. At each junction where a fiber of one set overlaps a fiber of the other set, an EOA zone is formed from the EOA substance between the fibers. Each EOA zone is an individually controllable display element (pixel). The visible images are formed from a plurality of such pixels. The EOA zones (pixels) in such displays are of the size of the fiber diameter.

[0006] WO 99/19858 describes a woven display produced from flat fibers or strips in basket weave. The display comprises two intersecting sets of stripes. One of these sets may consist of display stripes with electroluminescent layer, while the other set consists of conductive stripes, or both sets may comprise display stripes and conductive stripes. The display stripes have a back conductive layer laid in separated areas defining display elements (pixels). The pixels effectively use the entire area of the applied electroluminescent layer.

[0007] U.S. Pat. No. 6,229,265 discloses a rigid electroluminescent display with display elements of EOA substance laid in grooves. The grooves are made in a common base electrode while individual electrodes are very narrow strips integral with a transparent layer covering the base electrode and the EOA substance.

[0008] In accordance with one aspect of the present invention, there is provided an electro-optical display comprising a flexible three-dimensional structure including at least two layers of electrode structures, which are held together but spaced apart by at least one skeletal layer formed of fibers transverse to the layers of electrode structures. The skeletal layer has empty space among the transverse fibers, filled with an electrooptically active (EOA) substance, whereby an electrooptically active zone (EOA zone) is formed by the EOA substance between the electrode structures. The 3D structure preferably comprises network layers made of fibers, or flexible film layers which carry the electrode structures, and are secured to the fibers of the skeletal layer.

[0009] The network layers may be formed of a plurality of woven or knitted fibers, or of a plurality of overlapping (non-woven) fibers. Hereinafter, a “fiber” shall mean any elongated and flexible element capable of being woven or knitted or sewn. A fiber may have round, flat, or other cross-section form. The electrode structures may be formed of flexible conductive layers or of conductive fibers. Hereinafter, a “conductive fiber” shall mean any elongated flexible element suitable for conducting electricity. For example, it may have round, flat or other section form; be made of solid metal; be in the form of a dielectric fiber or strip covered or intertwined with a conductive wire or layer; multiple-core twisted, spun, plaited wire; etc.

[0010] The network layers of the flexible 3-D display structure of the present invention may be made of a plurality of woven or knitted fibers, where in each network layer are interwoven non-conductive fibers protruding from one or both sides thereof in the form of Velcro hooks and loops or plush pile, and the skeletal layer is formed by the hooks and loops or the pile of two network layers snapped together.

[0011] In the electro-optical display of the present invention, the EOA zone may comprise a plurality of distinctive display elements constituting an image. According to one embodiment, the display elements are formed by separated areas of EOA substance or by areas of EOA substance with different electro-optic properties. According to another embodiment, a first electrode structure is formed from separated areas with individual wiring, and these areas, together with a second electrode structure, constitute display elements.

[0012] According to still another embodiment of the invention, the electrode structures are made of sets of conductive fibers interwoven with the network layers which are made of woven or knitted fibers. One electrode structure may comprise a first set of parallel conductive fibers, and another electrode structure may comprise a second set of parallel conductive fibers transverse to the first set. Thereby the EOA zone is constituted by a matrix of individually controllable EOA zones (pixels), each defined in the overlapping of a conductive fiber of the first set with a conductive fiber of the second set.

[0013] According to a further embodiment of the invention, the electrode structure may further comprise a conductive transparent or translucent layer in contact with the set of parallel conductive fibers. This layer may be in the form of separated strips parallel to the conductive fibers, each strip being in contact with at least one conductive fiber; or the layer may be continuous but of predetermined limited conductivity, such that the effective electric field of each conductive fiber is expanded over a strip of predetermined width disposed along said fiber. When a second conductive layer is applied to a second transverse electrode structure in a similar manner, a matrix of individually controllable enlarged pixels is formed, each pixel being defined in an overlapping of two transverse strips.

[0014] According to another aspect of the present invention, there is provided a three-dimensional spacer fabric comprising at least two woven or knitted network layers spaced by a skeletal layer made of non-conductive fibers predominantly transverse to and interwoven with the network layers, wherein the network layers comprise conductive fibers. The conductive fibers in one network layer may be arranged in a conductive network or in a set of parallel fibers. The two network layers may have transverse sets of parallel fibers adapted for forming a matrix structure. Each network layer may further comprise a second set of conductive fibers transverse to and in contact with the first set of parallel conductive fibers, where the fibers of the second set have a lower predetermined conductivity than the fibers of the first set and play the role of the above-mentioned layer with limited conductivity.

[0015] The 3-D structure of the present invention can be easily produced by known warp-knitting process. Not only the 3-D structure but also the electrode structure may be manufactured in the same time by the same process. The present invention allows for the manufacture of multi-layered 3-D display structures which can be used i.e. for two-sided displays. The EOA substance is very reliably accommodated in the skeletal layers of the structure due to the numerous surfaces of contact and adhesion. The thickness of the skeletal layer and hence of the EOA layer is not limited by the thickness of the constituent fibers as in the prior art. The electrode structures are reliably kept at predetermined distance from each other thus preventing electrical breakdown of the display.

[0016] In order to understand the invention and to see how it may be carried out in practice, preferred embodiments will now be described, by way of non-limiting example only, with reference to the accompanying drawings, in which:

[0017] FIG. 1 is a perspective view of a generalized 3-D structure of an electro-optical display of the present invention.

[0018] FIGS. 2A and 2B are front and back plan views of an animated display structure in accordance with the present invention.

[0019] FIG. 3 is a perspective view of an electro-optical display structure based on 3-D spacer fabric.

[0020] FIG. 4 is a perspective view of a matrix display structure with enlarged pixels in accordance with the present invention.

[0021] FIG. 5 is a schematic illustration of the operative electric voltage distribution in a display pixel.

[0022] FIGS. 6A and 6B are a plan and a sectional view of a double-layered display structure in accordance with the present invention.

[0023] FIG. 7 is a sectional view of a sewn display structure in accordance with the present invention.

[0024] FIGS. 8A and 8B are front and back plan views of a combined electro-optical display structure in accordance with the present invention.

[0025] FIG. 9 is a perspective view of another generalized 3-D structure of an electro-optical display of the present invention.

[0026] FIG. 10 is a schematic sectional view of an electro-optical display structure based on a Velcro-like fabric.

[0027] With reference to FIG. 1, there is shown in a perspective sectional view an electro-optical display 10 of the present invention. It comprises a flexible three-dimensional structure 12 built of generally parallel flat network layers 14 and 16 made of fibers 18, and a skeletal layer 22 formed preferably of non-conductive fibers 24, having empty space 26 therebetween. The fibers 24 may be also conductive, as far as they do not shortcut the electrode structures below.

[0028] The network layers 14 and 16 carry electrode structures 30 and 32 integrated therewith. The electrode structures are made of individual conductive-fibers or of conductive fiber networks as shown in FIG. 1. They also may be in the form of a transparent or translucent conductive layer or a combination of a conductive layer and conductive fibers.

[0029] The empty space 26 of the skeletal layer 22 is filled with EOA substance 36, in intimate contact with the electrode structures 30 and 32. Thus, an EOA zone 40 is formed between the electrode structures 30 and 32. Upon applying a suitable electric signal on electrodes 30 and 32, the EOA substance therebetween will change its optic properties, i.e. may emit light in the case of electroluminescent substance.

[0030] The skeletal layers may be more than one, each skeletal layer being sandwiched between a pair of adjacent network layers (see FIGS. 6 and 10 below). Such structure may be used for a two-sided display or a light-transmissive display.

[0031] Preferably, the network layers are made of polymer material but may be made also of inorganic fibers. The skeletal layers have plenty of penetrable space between their fibers and are adapted to generally preserve a predetermined distance between the network layers when the whole flexible display 10 is bent, rolled, etc.

[0032] The EOA substance in the skeletal layer may be laid as areas 44 and 46 separated by gaps 48 filled with optically inactive substance, or as areas 46, 50 and 52 having different electro-optic properties, for example, different color. These areas represent distinctive display elements forming a static image when a suitable electric signal is applied to the electrode structures 30 and 32.

[0033] The electrode structures also may have separated conductive areas with individual wiring, as illustrated by the front and back views in FIGS. 2A and 2B. Here, a 3-Delectrooptic display 60 comprises one skeletal layer 62 sandwiched between a front transparent network layer 64 and a back network layer 66. A front electrode structure 68 is integrated in the front layer 64. An EOA substance 72 fills the skeletal layer 62 being laid therein in areas 72ato 72hof different color. A rear electrode structure 74 is applied on the back network layer 66 in separated areas 74ato 74g.

[0034] The conductive areas 72ato 72ggenerally coincide, in plan view, with the respective EOA substance areas 72ato 72g, thereby forming a display element between each conductive area 74 and the front electrode structure 68. Using a suitable wiring and controller, the display elements may be switched on and off in a desired order, thus forming a dynamic image. It should be understood that the electrooptic display 60 will work also in the case when the boundaries of the areas of EOA substance 72ato 72gdo not coincide with the boundaries of the areas of the rear electrode structure 72ato 74g.

[0035] The skeletal layers are preferably made of non-conductive fibers generally transverse to the network layers, such as, for example, in the electrooptic display 80 shown in FIG. 3. The electrooptic display 80 comprises two network layers 82 and 84 made of woven or knitted fibers 86, and a skeletal layer 88 made of filaments 90 interwoven with and connecting the network layers 82 and 84. Such 3-D structure is known in textiles manufacture as 3-dimensional spacer fabrics (SpaceTec(®, Duotex(®, 3 mesh®, etc.) and is produced in a single knitting process, whereby skeletal layers of different thickness may be obtained. Electrode structures 92 and 94 are created by weaving or knitting conductive fibers 92ato 92dand 94ato 94dinto the network layers 82 and 84, respectively, either as additional fibers or as constituent fibers. Electrode structures may be also created by coating the knitted or woven network layers with conductive layers 98, or may include both conductive layers and conductive fibers. The skeletal layer 88 is impregnated with an EOA substance 96, forming, together with the electrode structures, an EOA zone similar to the zone described with reference to FIG. 1.

[0036] In each of the electrode structures 92 and 94, the conductive fibers (wires) are generally parallel to each other and separated from each other. The wires in the electrode structure 92 are transverse to the wires in the electrode structure 94. Thereby, the adjacent electrode structures 92 and 94 form, with the EOA substance therebetween, a matrix of EOA zones (pixels) 97. Each pixel is defined in the overlapping of a wire of the electrode structure 92 with a wire of the electrode structure 94. It will be appreciated that the size of such pixel is limited by the wires diameter and the thickness of the skeletal layer 88. The pixels are individually controllable. For example, the shown pixel 97 is activated when electric signal is applied to wires 92aand 94a. Thereby, a display structure is obtained that is capable of visualizing dynamic images such as running text, animation, TV sequence, movies, etc.

[0037] The electrooptic display 120 in FIG. 4 is similar to the one in FIG. 3 but has enlarged pixels. The display 120 comprises two network layers (not seen) made of woven or knitted fibers carrying electrode structures 92 and 94, and a skeletal layer 88 made of filaments 90 connecting and spacing apart the network layers. The skeletal layer is filled with EOA substance 96. The electrode structure 92 is covered with a transparent conductive layer laid in separated strips 122a, 122bgenerally parallel to the wires 92ato 92d. Each strip may be in contact with one or more wires. The electrode structure 94 is covered in a similar way by separated conductive strips 124a, 124bgenerally parallel to the wires 94ato 94dand transverse to the strips 122a, 122b. It will be appreciated that in this case a pixel 126 is defined in the overlapping of the strip 122aand the strip 124aand its dimensions are defined by the width of these strips.

[0038] The same effect is obtained by a continuous conductive layer 132 laid over the electrode structure 92, as also shown in FIG. 4. In this case, the conductivity of the layer 132 is limited in such a manner that the effective electric field at both sides of the conductive wire 92dfalls under a threshold value at a predetermined distance d from the wire, thereby defining the size of pixel 128. The process is illustrated in the graph of FIG. 5 showing the distribution of the operative electric voltage U between the layer 132 and the strip 124ain the vicinity of the wire 92d, assuming that the EOA substance is electroluminescent. Light is emitted when and where this voltage exceeds a threshold value U_t. It will be appreciated that for a different EOA substance, a different characteristic of the electric field may be relevant, such as current, frequency, etc.

[0039] Instead of laying special layers of limited conductivity over the electrode structures, the network layers may be knitted or woven from fibers with limited conductivity, yielding the same effect of spreading the electric field in a predetermined vicinity of the conductive fibers (wires) 92 or 94.

[0040] A different 3-D electrooptical display, according to the present invention, is shown in FIGS. 6A and 6B. The display 140 is assembled of longitudinal strips 142, comprising transparent or translucent conductive strips 146 and a layer of EOA substance 150, and transverse conductive strips 152. The flexible 3-D structure is knitted preferably from non-conductive fibers 156 which in this case belong in parts 156ato the network layers (at the surface), and in parts 156b, to the skeletal layer. It will be appreciated that EOA zones (pixels) 160 are formed at the overlapping of one longitudinal strip 142 with one transverse conductive strip 152. The display in FIGS. 6A and 6B is shown with a second set of longitudinal strips 144 under the transverse conductive strips 152, forming a second EOA layer. In this case either the conductive strips 148 or the transverse conductive strips 152 should be transparent. The conductive strips 146, 148 and 152 themselves may have various structure. For example, the strip 146 comprises conductive fibers 162 in a layer of limited conductivity 164, as described under number 132 in FIG. 5, or it may comprise conductive fibers interwoven in a network of non-conductive fibers.

[0041] A similar electrooptic display 170 is shown in cross-section in FIG. 7. It comprises two fabric layers 172 and 174, for example woven or non-woven, or knitted, with conductive fibers 176 and 178, a layer of EOA substance 180 and a plurality of fibers 182 sewn through the above layers in stitches. The surface parts 182aof the fibers 182, together with the fabric layers 172 and 174, constitute network layers of the 3-D stricture, while the transverse parts 182bconstitute the skeletal layer. In case the conductive fibers 176 and 178 form connected network electrode structures in the respective network layers, the display 170 will operate as the static image display 10 shown in FIG. 1. If the conductive fibers 176 and 178 are arranged in sets of parallel conductors, the two sets being transverse to each other, then a matrix of pixels will be obtained, similar to the one shown in FIG. 3. The pixels may be further enlarged by adding flexible layers of limited conductivity or conductive strips as shown in FIG. 4.

[0042] With reference to FIGS. 8A (front view) and 8B (back view), an electrooptic display 190 is presented, combining a static and a dynamic display in one unit. The combined display 190 comprises a front network layer 192 with electrode structure of wires 194, a skeletal layer 198 filled with EOA substance, and a back network layer 200. A transparent conductive layer 202 covers the front electrode structure 194, and a second conductive layer 204 covers the back network layer 200.

[0043] The display 190 is divided into two or more areas of two kinds. The area I is organized in a manner similar to FIG. 2: a layer of EOA substance is laid in separated areas or in areas of different electro-optic properties 208, 210, 212, and 214. The transparent conductive layer 202 covers the area I as one continuous area, while the second conductive layer 204 is laid in separated areas 204a, 204b, 204c. Thereby, the area I constitutes a display with a number of static pictures.

[0044] The area II is organized in a manner similar to FIG. 4. The transparent conductive layer 202 is laid in longitudinal strips 218 parallel to the conductive wires 194, in electric contact with them. The second conductive layer 204 is laid in strips 220 transverse to the longitudinal conductive strips 218. Thereby, a dynamic matrix of individually controllable pixels 222 is formed in the area II. The EOA substance in the area II may be uniform, yielding a monochromatic matrix display, or the pixels may have different colors, yielding a color display. Thus, one flexible display may contain both static pictures such as logos, decorative luminous panels, and dynamic images such as animation and/or running text.

[0045] The electrode structures of the displays of the present invention are not necessarily supported by network layers. Thus, FIG. 9 shows in a perspective sectional view a generalized electrooptic display design 230 comprising a flexible three-dimensional structure 232 built of a front transparent layer 234 and back layer 236 made of flexible polymer film, and a skeletal layer 238 formed of fibers 240, having empty space 242. Fibers of the skeletal layer are bonded or welded or otherwise connected to the film layers 234 and 236.

[0046] The film layers 234 and 236 carry conductive electrode layers 244 and 246 bonded thereto. The front electrode layer 244 is transparent and may also comprise thin narrow conductive strips 248.

[0047] The empty space 242 of the skeletal layer 238 is filled with EOA substance. Thus, an EOA zone is formed between the electrode layers 244 and 246. The display 230 operates in the same way as the one described with reference to FIG. 1, hence the same numerals are used hereafter.

[0048] The EOA substance in the skeletal layer 238 may be laid as areas 44 and 46 separated by gaps 48 filled with optically inactive substance, or as areas 46, 50 and 52 having different electro-optic properties, for example, different color. These areas represent distinctive display elements forming a static image when a suitable electric signal is applied to the electrode layers 244 and 246.

[0049] According to the present invention, another type of 3-D electrooptic display 300, shown by sectional view in FIG. 10, may be obtained from network layers 302, 304 and 306 which are formed from a plurality of woven or knitted fibers as in FIGS. 1, 3 and 4. However, in each network layer, there are interwoven non-conductive fibers 310, 312 and 314 protruding from one or both sides of the network layer in the form of Velcro hooks and loops or plush pile. Skeletal layers 316 and 318 are formed by the hooks and loops or pile of two adjacent network layers snapped together. In this case, the EOA substance 319 may be impregnated into the skeletal layers before assembling the display structure.

[0050] Although a description of specific embodiments has been presented, it is contemplated that various changes could be made without deviating from the scope of the present invention. For example, display structures shown here with one or two skeletal layers may be complemented with more skeletal layers and respective network layers and electrode structures.