Abstract:
An electrooptical display comprising an electrooptically active (EOA) element, a first electrode element having a pattern of separated electrodes, a second electrode element, and a picture element having a pattern of picture parts which may be transparent, translucent, re-emitting, refractive or reflective. The pattern of the separated electrodes matches the pattern of picture parts in a predetermined way; for example, they may coincide, be nested, or overlap each other. The electrode elements and the EOA element form a plurality of EOA zones. The patterned elements are changeable by detaching and attaching and thereby allow the display to show different images.

Description:
FIELD OF THE INVENTION 
     This invention relates to backlight panels, in particular to panels with changeable pictures. 
     BACKGROUND OF THE INVENTION 
     There are known electrooptic displays with static or semi-dynamic pictures or signs comprising a plurality of display elements and based on various electrooptically active (EOA) substances. Hereinafter, “EOA substance” is meant to denote any substance capable of changing its optic properties such as color, transparency, reflectivity, etc., or capable of emitting light, in response to changes of applied electric or electromagnetic field, and thereby suitable for displaying images. 
     For example, U.S. Pat. Nos. 3,531,676 and 3,571,647 disclose electroluminescent panels with one common grid electrode and a plurality of separated grid electrodes which may be in the form of bars, letters, or decorative designs. Those separated electrodes may be powered independently, by a suitable electronic driver, thereby producing light effects of display elements going on and off. 
     The electrodes may be made of transparent conductive materials such as indium tin oxide layer deposited on a polymer film, as disclosed in WO 97/48254. 
     The display elements of such electrooptic display may be numerous and may form quite complex pictures capable of presenting animated images or alpha-numeric characters, such as LCD of calculators or hand-held computer games. 
     These displays, however, are static in the sense that the individual pictures cannot be changed but only the display elements&#39; optic effect can be controlled. Once manufactured, they can show permanently or periodically only one picture defined by the pattern of its display elements. 
     An ultimate solution to obtain dynamically changeable image is the matrix display where each picture element is formed of a plurality of pixels which may be controlled individually. However, these displays are very expensive. They have relatively low brightness due to the very process of pixel control (scanning) which limits the time during which a pixel can emit light. 
     SUMMARY OF THE INVENTION 
     In accordance with the present invention, there is provided an electrooptical display comprising two patterned elements: a picture element having a pattern of transparent translucent, re-emitting or reflective picture parts and a first electrode element having a pattern of separated electrodes. The pattern of separated electrodes matches the pattern of picture parts in a predetermined way. The display further comprises a carrying element, an electrooptically active (EOA) element and a second electrode element. Hereinafter, an EOA element is understood as a layer of EOA substance with or without a carrying substrate. The electrode elements and the EOA element form a plurality of EOA zones corresponding to the pattern of separated electrodes and define, together with the picture parts, a visible image. The patterned elements are detachably attachable, preferably by means of adhesive layers, and thereby allow the electrooptic display to display different images using the same carrying element and the same EOA element. The patterned elements may also consist of a plurality of parts that can be arranged and attached in various ways. 
     The patterned picture elements may be organized in changeable pairs with matching patterned electrode elements. Moreover, a picture element and an electrode element may be integrated in one changeable element. The electrode elements may be transparent or translucent, for example made of indium tin oxide, or may be formed as a network of thin metal strips deposited on a polymer substrate. 
     In accordance with one aspect of the invention, the electrode elements are disposed on different sides of the EOA element. The second electrode is a common electrode for all separated electrodes, whereby each of the separated electrodes defines an EOA zone including a portion of the EOA substance and a portion of the common electrode. 
     In accordance with another aspect of the invention, the first and the second electrode elements are both patterned and are disposed on one side of the EOA element, in the form of conductive paths running parallel to each other and free of contact with each other. The conductive paths preferably have the form of spirals or of combs inserted into each other. Both electrode elements and the picture element may be integrated in one changeable element. In this case EOA zones are formed in that part of the EOA element which is penetrated by the electric field formed by two adjacent conductive paths belonging to different electrodes. 
     The adhesive layers are preferably transparent and conductive. A conductive adhesive layer on the pattered electrode is laid in separated spots corresponding to the electrode pattern. Two adhesive layers intermediate to the changeable patterned element and one of the other elements may be used, where each adhesive layer is firmly attached to one element and the attaching and detaching takes place between the two adhesive layers. 
     To provide for better electrical contact between the electrode elements and the EOA element, one or more z-conductive layers may be disposed therebetween. A z-conductive layer is characterized by good conductivity across its thickness and zero or low conductivity parallel to the layer. Such material is described, for example, in WO/0036649 and WO98/57226. The z-conductive layers may also be transparent and/or adhesive. 
     The electrooptic display of the present invention provides for an efficient and cheap display device with versatile functions. The same EOA element and the same carrying element may be used to obtain various images with attractive optic effects. Pictures or parts thereof may be peeled off and attached as easy as wallpaper. All elements of such pictures may be individually controlled by a suitable electronic circuitry, such as digital controllers, computers, etc. 
    
    
     BRIEF DESCRIPTION OF THE DRAWINGS 
     In order to understand the invention and to see how it may be carried out in practice, a preferred embodiment will now be described, by way of non-limiting example only, with reference to the accompanying drawings, in which: 
     FIG. 1A is a schematic exploded view of a basic electrooptic display in accordance with one aspect of the invention. 
     FIG. 1B is a sectional view of the electrooptic display shown in FIG.  1 A. 
     FIG. 2A is a schematic exploded view of another embodiment of the electrooptic display shown in FIG.  1 A. 
     FIGS. 2B and 2C are alternative sectional views of the electrooptic display shown in FIG.  2 A. 
     FIG. 3 is a sectional view of yet another embodiment of the electrooptic display shown in FIG.  1 A. 
     FIG. 4 is a schematic exploded view of the electrooptic display shown in FIG.  3 . 
     FIG. 5 is a schematic exploded view of a basic electrooptic display in accordance with a second aspect of the invention. 
     FIG. 6 is a schematic exploded view of a basic electrooptic display in accordance with a third aspect of the invention. 
     FIGS. 7A and 7B are partial views of the electrooptic display shown in FIG.  6 . 
     FIGS. 8A and 8B are sectional views of the electrooptic display shown in FIG.  6 . 
    
    
     DETAILED DESCRIPTION OF THE INVENTION 
     With reference to FIG. 1A, it is shown, in an exploded schematic view, an electrooptic display  10  with changeable pictures, according to the present invention. The display  10  comprises a transparent carrying element  12 , an electrooptically active (EOA) element  13 , a front transparent electrode element  14  with a common electrode  15 , a back flexible patterned electrode element  16  with separated electrodes  18 ,  20 ,  22  and  24 , and a flexible patterned picture element  26  with picture parts  28 ,  30 ,  32  and  34 . The EOA element  13  may be a layer of EOA substance on a suitable substrate such as a thin mesh or polymer film or just a layer laid on the electrode element  14 . The common electrode  15  and the separated electrodes  18 ,  20 ,  22  and  24  are connected to a driver or controller  36 . When the display is assembled, the EOA element  13  is sandwiched between the electrode elements  14  and  16  forming EOA zones, such as zone  38 , between each of the separated electrodes  18 ,  20 ,  22  and  24 , and the common electrode  15 . The picture parts  28 ,  30 ,  32  and  34  on the picture element  26  match the separated electrodes  18 ,  20 ,  22  and  24  on the front electrode element  16  in a desired manner, for example they may coincide, be nested, overlap each other, etc. The picture parts may have different optical properties, e.g. different color, transparency, etc. The carrying element  12  may be flat, cylindrical or shaped otherwise in a manner suitable for covering and adhesion of flexible patterned elements, such as the electrode element  16  and the picture element  26 . The carrying element may be integrated with the electrode element  14  and the EOA element  13 . In particular, patterned pictures and electrodes may be assembled from separate thin flat fragments or may be extendable, for example to cover a spherical carrying element. 
     When a suitable electric signal is applied by the controller  36 , e.g. to electrodes  20  and  15 , the EOA zone  38  is activated, e.g. starts to emit light, and the picture part  30  becomes visible to the viewer  39  as a shining display element. A desired optical effect such as animation may be achieved by activating the EOA zones in a programmed sequence. 
     The electrooptic device described above may be connected to a computerized driver, for example for real-time control by an external input signal, to visualize current temperature, humidity, sound level, etc. 
     As shown in the sectional view of FIG. 1B, the patterned electrode element  16  and the patterned picture element  26  of the display  10  may be attached to the EOA element  13  and to the carrying element  12 , respectively, by means of transparent adhesive layers  40  and  42 . The adhesive is sensitive to pressure and allows peeling off and reattaching the patterned picture element  26  and the patterned electrode element  16 . The electrooptical display may be supplied to users as a kit containing a plurality of matching changeable pairs  16 - 26 , allowing an easy and rapid change of the displayed picture or animation. Each changeable pair may have its own programmed sequence loaded into the controller  36 . 
     With reference to FIG. 2A, it is shown, in an exploded schematic view, a vacation of the electrooptic display of FIG. 1A, with somewhat different order of elements. The display  48  comprises a carrying element  12 , an electrooptically active (EOA) element  13 , a back electrode element  14  with a common electrode  15 , a front transparent flexible patterned electrode element  16  with separated electrodes  18 ,  20 ,  22  and  24 , and a flexible patterned picture element  26  with picture parts  28 ,  30 ,  32  and  34 . 
     As shown in the sectional view of FIG. 2B, the patterned electrode element  16  and the patterned picture element  26  of the display  10  are attached to each other and to the EOA element  13  by means of the transparent adhesive layers  40  and  42 . As shown in FIG. 2C, the patterned picture element  26  and the patterned electrode element  16  may be integrated in one changeable flexible film element  44 , while the adhesive layer  40  may be firmly attached to the EOA element  13 . Also, two touching adhesive layers may be used, one attached firmly to the EOA element, the other one attached to the changeable element. 
     To provide for better electrical contact between the patterned electrode element  16  and the EOA element  13 , the adhesive layers  40  and  42  may be conductive. In this case, the adhesive layer  40 , which is in contact with the patterned electrode element  16 , is laid in separated spots matching the pattern of the separated electrodes. 
     A better electrical contact may be also provided by an adhesive layer made of z-conductive material which is characterized by good conductivity across its thickness and zero or low conductivity parallel to the layer. In this case, the adhesive layer on the patterned electrode element may be continuous. 
     Reverting to FIGS. 1A and 2A, picture parts, such as  28 ,  30 ,  32  and  34 , may be printed on the front or on the back side of a carrying transparent film. The picture parts may be transparent or may be capable of re-emitting light, i.e. be printed in fluorescent dyes. The flexible transparent electrode element  16  may have an electrode pattern of conductive material such as indium-tin oxide (ITO) printed on a flexible transparent polymer film. Also, the picture element and the patterned electrode element may consist of respective parts adapted to be independently attached in different order. This option is illustrated in FIG. 4 with exchanged places of parts  28  and  34  and respective electrodes  18  and  24 , but it is applicable to all embodiments. 
     According to another embodiment of the present invention shown as display  50  in FIG. 4, the carrying element, the second electrode and the EOA element are integrated in a flexible fabric  52 . The fabric comprises a plurality of fibers and may be woven, non-woven or knitted. At least part of the fibers is conductive and they form a connected conductive network. As it is shown in the sectional view of FIG. 3, the fabric  52  constitutes a carrying element and is impregnated with EOA substance  13 . Conductive fibers  54  constitute a second (common) electrode. A flexible patterned electrode  56  with separated electrodes  18 ,  20 ,  22 , and  24  is detachably attached to the back of the fabric  52  by means of an insulating adhesive layer  42 . A flexible picture element  26  with picture parts  28 ,  30 ,  32 , and  34  is detachably attached to the front side of the fabric  52  by means of a transparent adhesive layer  40 . EOA zones are formed in the vicinities of the conductive fibers  54  adjacent the separated electrodes. For example, FIGS. 3 and 4 show such zones excited by the electrode  20 . 
     Still another embodiment of an electrooptic display with changeable pictures in accordance with the present invention is shown in the exploded view of FIG.  5 . The designation of the elements in FIG. 5 is the same as in FIG. 1, where applicable. In FIG. 5, the display  70  comprises a transparent carrying element  72 , a transparent back common, electrode  64  with EOA substance  74  which is of electro-modulating type, e.g. capable of changing its refractive index (transparency), for example, a liquid crystal. The display  70  further comprises a front transparent flexible patterned electrode element  16  with separated electrodes  18 ,  20 ,  22  and  24 , and a flexible patterned picture element  76  at the back of the display, with picture parts  78  which reflect light thereby forming display elements. The common electrode  64  and the separated electrodes  18 ,  20 ,  22  and  24  are connected to the controller  36 . When a suitable electric signal is applied by the controller  36 , an EOA zone, for example  38 , is activated, e.g. becomes transparent, and a display element becomes visible to the viewer  39  in reflected light. It should be understood that the common electrode  64 , the carrying element  72 , and the EOA element (substance) may be united in one element. 
     An electrooptic display  80  with changeable pictures in accordance with another aspect of the present invention is shown in the exploded view of FIG.  6 . The display  80  comprises a carrying element  12  with EOA substance  13 , a transparent front electrode element  82  having a first system of separated electrodes  84 ,  86 ,  88  and  90 , and a second system of separated electrodes  92 ,  94 ,  96  and  98 , the two systems being free of contact therebetween, and a flexible patterned picture element  26  with picture parts  28 ,  30 ,  32  and  34 . The electrodes of the first system may be connected into a common electrode  100 , and all electrodes are connected to the controller  36 . As shown in detail in FIG. 7A, each electrode of the first system, e.g.  84 , is complemented by an electrode of the second system, i.e.  92 , to form a pattern matching a display element, e.g.  28  (FIG. 6) of the picture  26 . While the electrodes in FIG. 7A are shaped like combs opposingly inserted into each others other configurations are possible, provided the electrodes of the first system are uniformly spaced from the electrodes of the second system. A possible spiral shape of the electrodes is shown in FIG.  7 B. 
     When the display  80  is assembled, the EOA substance  13  remains at one side of the electrode element  82 . In this case, EOA zones between the electrodes of the two systems are formed as shown in the enlarged sectional view of FIG. 8A taken along the lie A—A of FIG.  7 B. The picture element and the electrode element are shown in FIG. 8A integrated in one changeable picture. The picture parts, e.g.  28  are printed on one side of a flexible transparent substrate  104 , while electrodes, e.g.  84  and  92 , are disposed on the other side of the substrate. An adhesive layer  40  is applied between the changeable picture and the EOA element  13 . When a suitable electric signal is applied by the controller  36 , for example between the electrodes  92  and  84 , the electric field formed between them penetrates the EOA substance  13  and an EOA zone matching the picture part  28  is activated, e.g. starts to emit light, making it visible to the viewer  39  as a display element. 
     As shown in the sectional view of FIG. 8B, the picture element  26  and the electrode element  82  may be disposed at different sides of the carrying element  12 . In this case the electrode element  82  may not be transparent. 
     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, the reflective display of FIG. 5 may be built with the electrode element of FIG. 6, or all combinations of adhesive and conductive layers described with reference to the embodiments of FIGS. 1A and 2A may be applied to the other embodiments.