Patent Publication Number: US-11644732-B2

Title: Display device

Description:
CROSS REFERENCE TO RELATED APPLICATIONS 
     This Application is a Continuation of U.S. patent application Ser. No. 15/114,401, filed Jul. 27, 2016, entitled “DISPLAY DEVICE”, which is a 371 U.S. National Stage Application of International Application No. PCT/US2014/014307, filed Jan. 31, 2014, entitled “DISPLAY DEVICE”, both of which are incorporated herein by reference. 
    
    
     BACKGROUND 
     Electronic paper (“e-paper”) is a display technology designed to recreate the appearance of ink on ordinary paper. Some examples of e-paper reflect light like ordinary paper and may be capable of displaying text and images. Some e-paper is implemented as a flexible, thin sheet, like paper. One familiar e-paper implementation includes e-readers. 
    
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
         FIG.  1 A  illustrates a cross-sectional view of one example of a display device. 
         FIG.  1 B  illustrates a top view of one example of the display device illustrated in  FIG.  1 A . 
         FIG.  2 A  illustrates a cross-sectional view of one example of a display device. 
         FIG.  2 B  illustrates a top view of one example of the display device illustrated in  FIG.  2 A . 
         FIG.  3    illustrates a cross-sectional view of one example of an electronic paper (“e-paper”) display. 
         FIG.  4    illustrates one example of a writing module. 
         FIGS.  5 A- 5 C  illustrate one example of a system including a writing module and a display device. 
         FIGS.  6 A- 6 C  illustrate one example of a system including a writing module and a display device. 
         FIGS.  7 A- 7 C  illustrate one example of a system including a writing module and a display device. 
     
    
    
     DETAILED DESCRIPTION 
     In the following detailed description, reference is made to the accompanying drawings which form a part hereof, and in which is shown by way of illustration specific examples in which the disclosure may be practiced. It is to be understood that other examples may be utilized and structural or logical changes may be made without departing from the scope of the present disclosure. The following detailed description, therefore, is not to be taken in a limiting sense, and the scope of the present disclosure is defined by the appended claims. It is to be understood that features of the various examples described herein may be combined, in part or whole, with each other, unless specifically noted otherwise. 
     Electronic paper (“e-paper”) is used in a variety of display applications such as signage, e-books, tablets, cards, posters, and pricing labels. E-paper has several paper-like features. For example, e-paper is a reflective display that uses ambient light as an illumination source. The ambient light strikes the surface and is reflected to the viewer. The usage of pigments similar to those that are used in printing allows the e-paper to be read at a wide range of angles and lighting conditions, including full sunlight. The use of ambient light also eliminates the need for illumination produced by the device, such as a backlight. This minimizes the power used by the e-paper. In addition, the e-paper does not use power to maintain the image. Once the image is written, the image remains on the e-paper for an extended period of time or until the e-paper is rewritten. Thus, a typical e-paper primarily uses power for changing the optical state of the e-paper. 
     E-paper is typically written by generating a charge on a surface in proximately to a layer of microcapsules that contain charged pigment particles. The charge on the surface attracts or repels the charged pigment particles in the microcapsules to create the desired image. To write to e-paper, however, a writing module used to write to the e-paper has to maintain a connection to a ground return path for the e-paper. 
     The following disclosure describes several examples of e-paper display devices that enable a secure electrical connection between a writing module and a ground return path of an e-paper display device. The example display devices also provide for controlled motion through a writing module, provide for proper spacing between the display devices and a writing module, and provide mechanical robustness beyond that provided by the e-paper alone. 
     Accordingly, a display device, such as a gift card, prepaid card, credit card, shelf tag, boarding pass, shipping label, etc., includes a passive electronic paper display. The electronic paper display is imageable by receiving charges on an imaging surface of the electronic paper display from a writing module. The display device includes a ground electrode opposite to the imaging surface of the electronic paper display. The display device includes a ground access stripe on a surface of the display device. The ground access stripe is electrically coupled to the ground electrode. During writing of the electronic paper display, a conductive roller or brush of the writing module makes contact with the ground access stripe to provide a ground return path that allows charges received on the imaging surface to flow to the ground electrode as the writing module and the display device are moved relative to each other. 
       FIG.  1 A  illustrates a cross-sectional view and  FIG.  1 B  illustrates a top view of one example of a display device  100 . Display device  100  includes a support structure  102 , a ground electrode  104 , an electronic paper (“e-paper”) display  106 , and a ground access stripe  108 . Ground access stripe  108  is electrically coupled to ground electrode  104  through a conductor  110  within support structure  102 . In this example, the viewing side of display device  100  is indicated by a viewer  122 . 
     E-paper display  106  includes an imaging surface  114  and a surface  112  opposite imaging surface  114 . Surface  112  contacts ground electrode  104 . Ground electrode  104  and e-paper display  106  are mounted on support structure  102  such that imaging surface  114  of e-paper display  106  is exposed. E-paper display  106  includes an active layer that switches color when a magnetic field or electrical charges are applied to imaging surface  114 . In one example, the active layer contains a switchable pigment or die combination. A resin or polymer may be used to encapsulate the active layer. In addition, e-paper  106  may include a functional coating on the imaging surface  114 . In one example, e-paper display  106  has a thickness between 70 μm and 300 μm. One example of e-paper  106  is further described below with reference to  FIG.  3   . 
     Ground electrode  104  provides a counter-electrode for the imaging of e-paper display  106  by a writing module. Ground electrode  104  allows counter charges to flow to ground electrode  104  from a writing module. Thus, display device  100  remains basically charge neutral despite charges being ejected onto imaging surface  114 . Without a connection between ground electrode  104  and the writing module, no appreciable amount of charges can be ejected onto imaging surface  114  and thus no information can be written to display device  100 . Ground electrode  104  can be composed of a transparent conductive material, such as indium tin oxide, or an opaque conductive material. In one example, ground electrode  104  has a thickness between 5 nm and 1 mm. 
     Support structure  102  can be composed of a transparent material or an opaque material. Support structure  102  can be composed of polyester, plastic, glass, transparent Mylar, or other suitable material. In one example, support structure  102  is shaped to provide a display device  100  in the form of a gift card, prepaid card, credit card, shelf tag, boarding pass, or shipping label. Support structure  102  can include a bar code  130 , text  132 , or other suitable information on its surface. 
     Ground access stripe  108  is arranged on a surface  120  of support structure  102  and is spaced apart from e-paper display  106 . Ground access stripe  108  is arranged parallel to a writing direction of e-paper display  106 . In one example, ground access stripe  108  is partially or completely embedded within surface  120  of support structure  102 . Ground access stripe  108  extends from a first edge  116  of support structure  102  to a second edge  118  of support structure  102  opposite first edge  116 . In this example, ground access stripe  108  and imaging surface  114  of e-paper display  106  are on the same side of display device  100 . In other examples, ground access stripe  108  and imaging surface  114  of e-paper display  106  can be on opposite sides of display device  100 . 
     Ground access stripe  108  is composed of any suitable electrically conductive material, such as a metal or a printed layer (e.g., digitally printed or screen printed) of conductive ink. In one example, ground access stripe  108  and conductor  110  are composed of a conductive polymer. In one example, the width, indicated at  124 , of ground access stripe  108  is between 1 mm and 15 mm and the thickness, indicated at  126 , is between 5 nm and 1 mm. In the example where ground access stripe  108  and conductor  110  are composed of a conductive polymer, the entire support structure  102  may be composed of the conductive polymer. In one example, the conductive polymer has a resistivity between 10 8  Ohm-cm and 10 11  Ohm-cm, which is sufficient for writing and erasing currents between 25 μA and 100 μA. 
       FIG.  2 A  illustrates a cross-sectional view and  FIG.  2 B  illustrates a top view of one example of a display device  200 . Display device  200  includes a support structure  202 , a structural window  228 , a ground electrode  204 , an e-paper display  206 , and a ground access stripe  208 . Ground access stripe  208  is electrically coupled to ground electrode  204 . In this example, the viewing side of display device  200  is indicated by a viewer  222 . E-paper display  206  includes an imaging surface  214  and a surface  212  opposite imaging surface  214 . Surface  212  contacts ground electrode  204 . Ground electrode  204  and e-paper display  206  are surrounded by support structure  202 . 
     Structural window  228  extends through support structure  202  so that a viewer  222  can see the image (e.g., image  236 ) on e-paper display  206 . Structural window  228  can be an air gap or be composed of glass, transparent plastic, or other suitable transparent material. Support structure  202  defines a frame having a thickness indicated at  224  that provides a recessed imaging surface  214  with respect to support structure  202 . In one example, the thickness  224  of the frame is between 100 μm and 300 μm. 
     Ground access stripe  208  is arranged on the outer edge surface  234  of support structure  202  and surrounds support structure  202 . Edge surface  234  of support structure  202  is substantially orthogonal to imaging surface  214 . Ground access stripe  208  is composed of any suitable electrically conductive material, such as a metal or a printed layer (e.g., digitally printed or screen printed) of conductive ink. In one example, ground access stripe  208  is composed of a conductive polymer. In one example, ground access stripe  208  has a thickness, as indicated at  226 , between 5 nm and 1 mm. In the example where ground access stripe  208  is composed of a conductive polymer, the entire support structure  202  may be composed of the conductive polymer. In one example, the conductive polymer has a resistivity between 10 8  Ohm-cm and 10 11  Ohm-cm, which is sufficient for writing and erasing currents between 25 μA and 100 μA. 
     Ground access stripe  208  is likely to be contacted by a user when display device  200  is handled. This contact between a user and ground access stripe  208  provides a positive consequence in that if the user is storing any electrostatic charge, display device  200  will be equipotential with the user, thus minimizing the chance of accidental image modifications due to electrostatic discharges. 
       FIG.  3    illustrates a cross-sectional view of one example of an e-paper display  300 . In one example, e-paper display  300  is used for e-paper display  106  or  206  previously described and illustrated with reference to  FIGS.  1 A- 1 B , and  2 A- 2 B, respectively. E-paper display  300  includes a ground electrode  302 , an active layer  304 , and a transparent charge receiving layer  306 . Active layer  304  includes microcapsules  308  encapsulated by a resin or polymer  314 . In one example, each microcapsule  308  includes black particles  310  and white particles  312  suspended in a fluid medium  316 . Surface  307  of charge receiving layer  306  provides the imaging surface for e-paper display  300  and is also the viewing side for a viewer  318  in this example. 
     Ambient light is transmitted through charge receiving layer  306 , strikes microcapsules  308 , and is reflected back to the viewer  318 . When white particles  312  of a microcapsule  308  are located near charge receiving layer  306 , the microcapsule appears white to the viewer  318 . When black particles  310  of a microcapsule  308  are located near charge receiving layer  306 , the microcapsule appears black to the viewer  318 . The particles  310  and  312  have opposite charges. For example, black particles  310  can be positively charged particles, and white particles  312  can be negatively charged particles. Various shades of gray can be created by varying the arrangement of alternating microcapsules with white and black particles located near charge receiving layer  306  to produce halftoning. 
     Microcapsules  308  exhibit image stability using chemical adhesion between particles and/or between the particles and the microcapsule surface. For example, microcapsules  308  can hold text and images indefinitely without using electricity, while allowing the text or images to be changed later. 
     The structure, materials, and dimensions of the various layers and components of e-paper display  300  can be adapted to specific design criteria. In one example, the transparent charge receiving layer  306  can be composed of a transparent polymer and can have a thickness between 50 μm and 250 μm. The transparent charge receiving layer  306  can also be composed of a material that holds charges or is porous or semi-porous to charges and/or ions. 
     The diameter of each microcapsule  308  is substantially constant within e-paper display  300  and can be in one example between 20 μm and 100 μm, such as 50 μm. Conductive ground electrode  302  can be composed of a transparent conductive material, such as indium tin oxide, or an opaque material. In one example, ground electrode  302  has a thickness between 10 nm and 1 mm, or larger depending on how e-paper display  300  is to be used. 
     In other examples, E-paper display  300  has a variety of other configurations. For example, each microcapsule  308  may include black particles suspended in a white colored fluid. The black particles can be positively charged particles or negatively charged particles. One or more microcapsules form a pixel of black and white images displayed on e-paper display  300 . The black and white images are created by placing black particles near or away from charge receiving layer  306 . For example, the microcapsules with black particles located away from charge receiving layer  306  reflect white light, corresponding to a white portion of an image displayed on e-paper display  300 . In contrast, the microcapsules with black particles located near charge receiving layer  306  appear black to a viewer  318  corresponding to a black portion of the image displayed on e-paper display  300 . Various shades of gray can be created by using halftoning with black particles located near or away from charge receiving layer  306 . 
     Charge receiving layer  306  may be tinted with alternating blue, red, and green regions. Adjacent blue, red, and green regions form color pixels. Color images are created by placing different combinations of white or black particles near charge receiving layer  306 . For example, the microcapsules of a color pixel with white particles located near the red and green regions of charge receiving layer  306  reflect red and green light from e-paper display  300 . The viewer  318  will perceive this combination as a yellow pixel. When the black particles in the microcapsules are located near charge receiving layer  306 , that color pixel will appear black to the viewer  318 . Additionally or alternatively, the black particles  310  of each microcapsule can be replaced by blue, red, or green positively or negatively charged particles. The particles can be used alone or in combination with a tinted charge receiving layer  306  to create a desired color image. 
       FIG.  4    illustrates one example of a writing module  400 . Writing module  400  can be used to write information to display device  100  and/or  200  previously described and illustrated with reference to  FIGS.  1 A- 1 B and  2 A- 2 B , respectively. Writing module  400  includes an imaging unit  401  including a corona writing unit  402  and a corona erasing unit  406 , and conductive roller(s) or brush  412 . Conductive roller(s) or brush  412  is electrically coupled to imaging unit  401  through signal path  410 . Corona writing unit  402  and corona erasing unit  406  are located on the same side of imaging unit  401 . 
     Corona erasing unit  406  selectivity ejects negative ions  408  toward an imaging surface of an e-paper display to erase any text and/or images on the e-paper display by repelling the negatively charged particles and/or by attracting the positively charged particles within the e-paper display toward the imaging surface. Corona writing unit  402  selectively ejects positive ions  404  toward an imaging surface of an e-paper display to write desired text and/or images on the e-paper display by repelling the positively charged particles and/or by attracting the negatively charged particles within the e-paper display toward the imaging surface. 
     Conductive roller(s) or brush  412  makes contact with the ground access stripe of a display device during writing of the display device to provide an electrical connection to the ground electrode of the display device. When using conductive roller(s), the roller(s) can also set the spacing between corona writing unit  402  and corona erasing unit  406  and the display device during writing of the display device. The conductive roller(s) are composed of any suitable electrically conductive material, such as a metal or conductive rubber. When using a conductive brush, the brush is composed of any suitable electrically conductive material, such as a metal or carbon. 
       FIGS.  5 A- 5 C  illustrate one example of a system  420  including a writing module  400   a  and a display device  100 . Writing module  400   a  is similar to writing module  400  previously described and illustrated with reference to  FIG.  4   , and display device  100  was previously described and illustrated with reference to  FIGS.  1 A- 1 B . In this example, writing module  400   a  includes a conductive roller  412   a . To write to display device  100 , writing module  400   a  is brought into contact with display device  100  so that conductive roller  412   a  contacts ground access stripe  108  as best illustrated in the top view of  FIG.  5 B  and the side view of  FIG.  5 C . Conductive roller  412   a  electrically couples imaging unit  401  to ground electrode  104  via ground access stripe  108  and conductor  110 . 
     Writing module  400   a  can be moved in the direction indicated by arrow  422  and display device  100  can be held stationary, display device  100  can be moved in the opposite direction indicated by arrow  422  and writing module  400   a  can be held stationary, or display device  100  and writing module  400   a  can be moved simultaneously with respect to each other. While writing module  400   a  and display device  100  are moved relative to each other, conductive roller  412   a  maintains contact to ground access stripe  108  during the writing of e-paper display  106 . 
     In this example, e-paper display  106  of display device  100  includes microcapsules including positively charged black particles and negatively charged white particles. Corona erasing unit  406  erases any information stored in the microcapsules prior to writing information with corona writing unit  402 . As display device  100  passes under imaging unit  401 , corona erasing unit  406  ejects negative ions  408  onto imaging surface  114 . The negative ions  408  repel negatively charged white particles away from imaging surface  114  and attract positively charged black particles toward imaging surface  114 . By passing corona erasing unit  406  over imaging surface  114 , any information previously written to display device  100  is erased by positioning the positively charged black particles near the top of the microcapsules and pushing the negatively charged white particles to the bottom of the microcapsules. 
     Corona writing unit  402  writes information to the microcapsules. As display device  100  passes under imaging unit  401 , corona writing unit  402  selectively ejects positive ions  404  toward imaging surface  114  when a region of display device  100  is to be changed from black to white. The positive ions  404  repel positively charged black particles away from imaging surface  114  and attract negatively charged white particles toward imaging surface  114 . By passing corona writing unit  402  over imaging surface  114  and selectively ejecting positive ions onto imaging surface  114 , information is written to display device  100  by selectively positioning negatively charged white particles near the top of the microcapsules and selectively pushing the positively charged black particles to the bottom of the microcapsules. 
       FIGS.  6 A- 6 C  illustrate one example of a system  440  including a writing module  400   b  and a display device  100 . Writing module  400   b  is similar to writing module  400  previously described and illustrated with reference to  FIG.  4   , and display device  100  was previously described and illustrated with reference to  FIGS.  1 A- 1 B . In this example, writing module  400   b  includes a conductive brush  412   b . To write to display device  100 , writing module  400   b  is brought into contact with display device  100  so that conductive brush  412   b  contacts ground access stripe  108  as best illustrated in the top view of  FIG.  6 B  and the side view of  FIG.  6 C . Conductive brush  412   b  electrically couples imaging unit  401  to ground electrode  104  via ground access stripe  108  and conductor  110 . System  440  writes to display device  100  similarly to system  420  previously described and illustrated with reference to  FIGS.  5 A- 5 C . 
       FIGS.  7 A- 7 C  illustrate one example of a system  460  including a writing module  400   c  and a display device  200 . Writing module  400   c  is similar to writing module  400  previously described and illustrated with reference to  FIG.  4   , and display device  200  was previously described and illustrated with reference to  FIGS.  2 A- 2 B . In this example, writing module  400   c  includes a plurality of conductive rollers  412   c . To write to display device  200 , writing module  400   c  is brought into contact with display device  200  so that conductive rollers  412   c  contact ground access stripe  208  on opposite sides of display device  200  as best illustrated in the top view of  FIG.  7 B  and the side view of  FIG.  7 C . Conductive rollers  412   c  electrically couple imaging unit  401  to ground electrode  204  via ground access stripe  208 . Conductive rollers  412   c  also constrain the motion of display device  200  so that the display device travels along the desired path. System  460  writes to display device  200  similarly to system  420  previously described and illustrated with reference to  FIGS.  5 A- 5 C . 
     By including a ground access stripe on a display device, an electrical connection between the writing module and the ground electrode of the display device can be maintained during movement of the writing module and the display device relative to each other. The ground access stripe also improves image robustness of the display device by providing a conductive path to ground to prevent accidental electrostatic discharges from users from altering the image. 
     Although specific examples have been illustrated and described herein, a variety of alternate and/or equivalent implementations may be substituted for the specific examples shown and described without departing from the scope of the present disclosure. This application is intended to cover any adaptations or variations of the specific examples discussed herein. Therefore, it is intended that this disclosure be limited only by the claims and the equivalents thereof.