Abstract:
A display system includes a light writable display associated with an identification code and arranged to receive an image wise pattern of light to form an image on the display; a display writer for producing the image wise pattern of light for writing the image on the display; a scanner connected to the display writer for sensing the identification code; and a processor linked to the scanner and the display writer and responsive to the identification code for programming the display writer to write an image associated with the identification code.

Description:
FIELD OF THE INVENTION  
       [0001]     The present invention relates to an apparatus for updating memory displays.  
       BACKGROUND OF THE INVENTION  
       [0002]     Retail stores offer goods for sale and need to provide customers with information on item pricing. Price labels typically provide information describing an item, the price for that item, and a machine readable code for the item, typically in UPC bar code format. The price of items often changes rapidly, requiring that printed retail labels be manually changed. Items that are on sale often have a larger secondary label, called a shelf-talker, that highlights items on sale for customers. The process of writing and changing retail pricing is costly, primarily in the labor required to replace tags. Systems have been proposed to address the problem of using digital data transmission to electrically changeable retail labels known as Electronic Shelf Labels (ESL).  
         [0003]     U.S. Pat. No. 5,448,226, issued Sep. 5, 1995 to Failing, Jr. et al. describes an ESL system having a plurality of electronic price labels fitted into rails. The rails provide power and communication to each label. Connection to the rail can be provided through direct electrical connection to a conductor in the rail or a radio frequency (RF) interface. The label can be powered though direct electrical connection to power conductors in the rail, a battery or solar cell. Such a system requires expensive complex electronic and communication structures.  
         [0004]     U.S. Pat. No. 6,186,555, issued Feb. 13, 2001 to Rawlings describes paper shelf-talkers that can be attached to conventional paper shelf labels to identify items on sale. Adhesive strips are applied to a perforated substrate that is printed to align text with the adhesive label. Attaching such a shelf-talker to a label requires the assembly to be discarded when pricing is changed. U.S. Pat. No. 5,771,005, issued Jun. 23, 1998 to Goodwin III describes an auxiliary electronic display that can be attached to an electronic price label (sic). The auxiliary display acts as an electronic shelf talker to identify special prices on goods.  
         [0005]     U.S. Pat. No. 6,130,603, issued Oct. 10, 2000 to Briechle provides a good reference for current Electronic Shelf Labels. Independent modules contain a power supply, antenna and controller. The controller is attached to a conventional liquid crystal display that requires periodic refreshing to maintain an image. Displays in ESLs currently display data on simple seven segment numeric data. An internal power supply expends about half its power maintaining the display image and the other half of the power maintaining the RF link. Such displays have limited display resolution, and must incorporate expensive and bulky controller and transmission electronics. Such displays further must incorporate a power supply which further increases cost and size.  
         [0006]     U.S. Pat. No. 5,751,257 issued May 12, 1998 to Sutherland shows an electronic shelf label having first and second substrates. Sutherland omits the expensive controller and power portions of the ESL, using a programming device translated across a series of pins and to write segments of an electronic display formed between the two glass substrates. The Sutherland apparatus requires the device to be positioned at a specific initial position, and translate specific sequence and rate to update the shelf tag. The information displayed in the Sutherland apparatus is limited to low resolution images.  
         [0007]     There is a need therefore for an improved display system having a low cost rewritable shelf label with high resolution.  
       SUMMARY OF THE INVENTION  
       [0008]     The need is met according to the present invention by providing a display system that includes a light writable display associated with an identification code and arranged to receive an image wise pattern of light to form an image on the display; a display writer for producing the image wise pattern of light for writing the image on the display; a scanner connected to the display writer for sensing the identification code; and a processor linked to the scanner and the display writer and responsive to the identification code for programming the display writer to write an image associated with the identification code. 
     
    
     BRIEF DESCRIPTION OF THE DRAWINGS  
       [0009]      FIG. 1  is a schematic view of a label writing system in accordance with the present invention;  
         [0010]      FIG. 2  is a partial perspective view of a display incorporated into a label in accordance with the present invention;  
         [0011]      FIG. 3  is a schematic sectional view of optical states of cholesteric material in accordance with the present invention;  
         [0012]      FIG. 4  is a plot of the response of a polymer dispersed cholesteric material, originally in the planar state, to constant flash unit lamp energy and various voltages;  
         [0013]      FIG. 5  is a side view of a label in accordance with the invention;  
         [0014]      FIG. 6  is a front view of a written label in accordance with the present invention;  
         [0015]      FIG. 7  is a schematic view of a label and a writer in accordance with the invention;  
         [0016]      FIG. 8  is a schematic view of a writer employed with the present invention;  
         [0017]      FIG. 9  is a schematic view of a writer scanning an object identity code according to the present invention;  
         [0018]      FIG. 10  is a schematic view of a writer obtaining label information for a specific object identity code from a central processor using wireless transmission according to the present invention; and  
         [0019]      FIG. 11  is a schematic view of a writer writing a display using label information for a specific object according to the present invention.  
     
    
     DETAILED DESCRIPTION OF THE INVENTION  
       [0020]      FIG. 1  is a schematic view of a label writing system in accordance with the present invention. A label  19  displays information about an object  100 . Objects  100  can be objects for retail sale or inventory items. Objects  100  have an associated object identity code  102 . The code  102  can be attached to individual items or adjacent to a set of one or more objects. Scanner/writer  80  contains means to scan an identification code  102  and write label  19 .  
         [0021]     Scanner/writer  80  has means to scan an object identity code  102  and select label image data for label  19  associated with a specific object  100 . Scanner/writer  80  further contains memory means to create label image data associated with an identification code  102  or access such data via writer antenna  88  to retrieve label image data from a central processor  90  using a conventional wireless network. Central processor  90  receives requests for label image data from processor antenna  92  from the wireless network. Central processor  90  retrieves label image data from central memory  94 , and transmits the data via processor antenna  92  to the scanner/writer  80  that made the request.  
         [0022]      FIG. 2  is a perspective of a display incorporated into a label in accordance with the present invention. Display  10  includes a flexible display substrate  15 , which is a thin transparent polymeric material, such as Kodak Estar film base formed of polyester plastic that has a thickness of between 20 and 200 microns. In an exemplary embodiment, display substrate  15  can be a 125-micron thick sheet of polyester film base. Other polymers, such as transparent polycarbonate, can also be used.  
         [0023]     A first conductor  20  is formed on display substrate  15 . First conductor  20  can be tin-oxide, indium-tin-oxide (ITO), or a transparent organic conductor such as polythiophene, with ITO being the preferred material. Typically the material of first conductor  20  is sputtered or coated as a layer over display substrate  15  having a resistance of less than 1000 ohms per square. First conductor  20  can also be formed by printing a transparent organic conductor such as PEDT/PSS, PEDOT/PSS polymer, which materials are sold as Baytron® P by Bayer AG Electronic Chemicals. A portion  22  of first conductor  20  does not contain subsequent layers to provide exposed first conductor.  
         [0024]     Cholesteric liquid crystal light modulating layer  30  overlays first conductor  20 . Cholesteric liquid crystal light modulating layer  30  contains cholesteric liquid crystal material, such as those disclosed in U.S. Pat. No. 5,695,682 issued Dec. 9, 1997 to Doane et al., the disclosure of which is incorporated by reference. Such materials are made using highly anisotropic nematic liquid crystal mixtures and adding a chiral doping agent to provide helical twist in the planes of the liquid crystal to the point that interference patterns are created that reflect incident light. Application of electrical fields of various intensity and duration can be employed to drive a chiral nematic material (cholesteric) into a reflective state, to near transparent state, or an intermediate state. These materials have the advantage of having stable optical states in the absence of an electrical field. The materials can maintain a given optical state indefinitely after the field is removed. Cholesteric liquid crystal materials can be formed using a two component system such as MDA-00-1444 (undoped nematic) and MDA-00-4042 (nematic with high chiral dopant concentrations) available from E.M. Industries of Hawthorne, N.Y.  
         [0025]     In a preferred embodiment, cholesteric liquid crystal light modulating layer  30  is a cholesteric liquid crystal dispersed in de-ionized photographic gelatin. The liquid crystal material is mixed at 8% cholesteric liquid crystal in a 5% gelatin aqueous solution. The mixture is dispersed to create an emulsion having 8-10 micrometer diameter domains of the liquid crystal in aqueous suspension. The domains can be formed using the limited coalescence technique described in U.S. Pat. No. 6,423,368 issued Jul. 23, 2002 to Stephenson et al. The emulsion is coated over first conductor  20  on a polyester display substrate  15  and dried to provide an approximately 9-micrometer thick polymer dispersed cholesteric coating. Other organic binders such as polyvinyl alcohol (PVA) or polyethylene oxide (PEO) can be used in place of the gelatin. Such emulsions are machine coatable using coating equipment of the type employed in the manufacture of photographic films. A gel sub-layer can be applied over first conductor  20  prior to applying cholesteric liquid crystal light modulating layer  30  as disclosed in U.S. Pat. No. 6,423,368 referenced above.  
         [0026]      FIG. 3  is a schematic side sectional view of a chiral nematic material in a planar and focal conic state responding to incident light. In the figure on the left, after a high voltage field has been applied and quickly switched to zero potential, the liquid crystal molecules become planar liquid crystal  72 , which reflect portions of incident light  60  as reflected light  62 . In the figure on the right side of  FIG. 2 , upon application of a lower voltage field, the molecules of the chiral nematic material break into weakly forward scattering cells known as focal conic liquid crystal  74 . Increasing the time duration of a low voltage pulse creates optical states between reflective planar liquid crystal  72  and light scattering focal conic liquid crystal  74 .  
         [0027]     A light absorber  35  is positioned on the side opposing the incident light  60 . Light absorber can be dark second conductor  40 . Light absorber  35  can be a thin layer of light absorbing, sub-micron carbon in a gel binder as disclosed in U.S. Pat. No. 6,639,637 issued Oct. 28, 2003 to Stephenson. As fully evolved focal-conic liquid crystal  74 , the cholesteric liquid crystal is forward light scattering and incident light  60  is absorbed by light absorber  35  to create a black image. Progressive evolution towards the focal-conic state causes a viewer to perceive reflected light  62  that transitions to black as the cholesteric material changes from reflective planar liquid crystal  72  to a fully evolved light scattering focal-conic liquid crystal  74 . When the field is removed, cholesteric liquid crystal light modulating layer  30  maintains a given optical state indefinitely. The states are more fully discussed in U.S. Pat. No. 5,437,811 issued Aug. 1, 1995 to Doane et al.  
         [0028]      FIG. 4  shows a plot of the response of a polymer dispersed cholesteric material, originally in the planar state, to constant flash unit lamp energy and various voltages. The curve for the masked material (filled boxes) is the same response of materials in the absence of the thermal pulse provided by flash unit  82 . The clear curve is the same display in the presence of the heat pulse from the flash unit combined with an electrical field. Hysteresis between the masked and unmasked curves, at approximately 20 and 60 volts are two conditions that permit writing of displays using a combination of light and electric field. Many operating states can be found to write displays. Such states are more thoroughly discussed in copending U.S. Ser. No. 10/256,930 filed Sep. 27, 2002 by Stephenson et al. The combination of high intensity light under an electric field permits high resolution images without patterning conductors. The process eliminates the need for many drives on many conductive traces.  
         [0029]     Returning to  FIG. 2 , second conductor  40  overlays or can be light absorber  35 . Second conductor  40  has sufficient conductivity to provide an electric field between the first transparent conductor  20  and second conductor  40  strong enough to change the optical state of the cholesteric material in cholesteric liquid crystal light modulating layer  30 . Second conductor  40  can be formed, for example, by the well known technique of vacuum deposition for forming a layer of conductive material such as aluminum, tin, silver, platinum, carbon, tungsten, molybdenum, tin or indium or combinations thereof. The layer of conductive material can be patterned using well known techniques of photolithography, laser etching or by application through a mask.  
         [0030]     In a preferred embodiment, second conductor  40  is formed by screen printing a conductive ink such as Electrodag 423SS screen printable electrical conductive material from Acheson Corporation. Such screen printable conductive materials comprise finely divided graphite particles in a thermoplastic resin. Screen printing is preferred to minimize the cost of manufacturing the display. The light absorbing properties of the printed carbon material reduces the need for light absorber  35 .  
         [0031]     The presence of light absorber  35  permits second conductors to be formed of reflective materials. Second conductors  40  can be formed of metal, for example, by vacuum deposition of conductive materials such as aluminum, chrome or nickel. Second conductors  40  are formed by screen printing a reflective and conductive formulation such as UVAG© 0010 from Allied Photochemical of Kimball, Mich. Such screen printable conductive materials comprise finely divided silver in ultra violet curable resin. After printing, the material is exposed to ultra violet radiation greater than 0.40 Joules/cm{circumflex over ( )}2, the resin will polymerize in 2 seconds to form a durable surface. The fast cure process time is advantageous in manufacturing.  
         [0032]     Alternatively, second conductors  40  can be formed by screen printing thermally cured silver bearing resins. An example of such a material is Acheson Electrodag© 461 SS, a heat cured silver ink In the case of reflective second conductor  40 , light absorber  35  can be used as a light absorbing layer that provides alternative colors, as described in copending U.S. Ser. No. 10/455,050 filed Jun. 5, 2003 by Stephenson et al.  
         [0033]     The use of a flexible support for display substrate  15 ; unpatterned first conductor  20 ; machine coated cholesteric liquid crystal light modulating layer  30 ; and unpatterned second conductor  40  permits the fabrication of a low cost flexible display. The opto-electrical writing process eliminates the need for attached, expensive electronics. Small displays according to the present invention can be used as electronically rewritable tags for inexpensive limited rewrite applications.  
         [0034]      FIG. 5  is a side view of a label  19  in accordance with the invention. Display support  17  carries a display  10 . Display support  17  can be a sheet of material having printed support contacts  16 . Display support  17  can be made of paper or white plastic and can have an area to carry printed information. Two support contacts  16  are positioned under first conductor  20  and second conductor  40  respectively, and extend outside the perimeter of an attached display  10 . A display  10 , formed in accordance with  FIG. 4  is positioned over support contacts  16  and bonded to display support  17  so that support contacts  16  provide an exposed electrical connection to display  10 . In a preferred embodiment, an anisotropic adhesive, such 3M 9703 Electrically Conductive Tape is used, which permits electrical conduction through an adhesive but not across the adhesive.  
         [0035]     Anisotropic adhesives consist of a conductive particle having a diameter near the thickness of adhesive binder, and dispersed at a concentration that does not conduct laterally. When display  10  is pressed onto support contacts  16 , conductive particles form an electrical connection between conductors on the back of display  10  and support contacts  16 . The adhesive can be thermally cured with an applied pressure to provide a permanent connection between conductors on the back of display  10  and support contacts  16 .  
         [0036]      FIG. 6  is a front view of a label in accordance with the present invention. Two support contacts  16  are exposed for front connection of an electric field to first conductor  20  and second conductor  40  within display  10 . The use of a flexible display support  17  and display  10  permit printing into areas of label  19 . An additional area of display support  17  is free of display  10  to permit writing of printing  14  on display support  17 .  
         [0037]     Ink jet printers are useful in this application because ink jet print heads are spaced from a dye receiving surface by about 1.00 millimeter. Display  10  is typically less than 0.25 millimeters thick and is flexible, permitting display assembly  17  to pass through an ink jet printer an not interfere with the motion of an ink jet head over display assembly  17 . Display support  17  can further include and adhesive backing and release liner. Such structures are more thoroughly discussed in copending U.S. Ser. No. 10/134,185 filed Apr. 29, 2002 by Stephenson et al.  
         [0038]      FIG. 7  is a schematic view of a label and light writer used with the present invention. Writer controller  81  acquires image data corresponding to an image to be printed on display  10 . Masking display  83  receives image data from writer controller  81  and creates and image wise pattern of light transmitting and light blocking areas that correspond to the desired image pattern. Masking display  83  can be a simple twisted-nematic (TN) or super-twisted-nematic (STN) liquid crystal display of conventional design. Pixels on masking display  83  can be formed in an array of uniform pixels, or contain electrodes patterned to conform to types of specific images, such as seven segment digital images. Writer controller  81  provides an electrical field to writer contacts  86  which are pressed against support contacts  16  to provide an electrical field to display  10 . Flash unit  82  is triggered by writer controller  81  in conjunction with application of the electrical field to form a pattern wise image on display  10  using masking display  83 . By using the masking display to write onto a simple unpatterned label, an image having the higher resolution of the masking display can be provided on the label without the need for complex electrode structures in the label and corresponding contacts in the writer, thereby significantly reducing the cost of the label.  
         [0039]     An example of a display useful as a masking display in the present invention is a dot-matrix super-twisted-nematic (STN) display, part number TM 13164 BCHG-1 from Tianma Corporation in Taiwan. The display has an array of 63 by 131 pixels at a 0.50 mm pitch. The display has a 4:1 contrast ratio, which provides modulation of high intensity light sufficient to create an image-wise pattern of high intensity light across display  10 .  
         [0040]      FIG. 8  is a schematic view of a hand held scanner/writer  80  used with the present invention. As shown in  FIG. 9 , scanner  84  in scanner/writer  80  can determine an object identification code  102 . Scanner  84  can be a conventional bar code reader that can read a bar code from an object to determine the object identification code. Alternatively, scanner  84  can be an radio frequency (RF) tag scanner that retrieves object identification code  102  from an object having an attached RF data storage element. Writer controller  81  can contain internal memory means that provides a label image for one or more object identification codes  102 , or can use writer antenna  88  to access label data wirelessly from an external data source. Scanner/writer  80  further incorporates flash unit  82  to provide high intensity light. High intensity light emitted by flash unit  82  is masked by a masking display  83  connected to writer controller  81 . Writer contacts  86  are connected to writer controller  81  to permit application of an electric field in conjunction with flash unit  82  to electro-optically writer data image associated with object identification code  102  to display  10 .  
         [0041]      FIG. 9  is a schematic view of the scanner/writer scanning an object identity code. Writer controller is activated to acquire an object identification code  102 . Object identification code  102  can be received as an optical or radio signal from storage means attached or unattached to object  100 .  FIG. 10  is a schematic view of the scanner/writer  80  obtaining label information for a specific object identity code  102  from a central processor  90  using wireless transmission. Writer controller  81  obtains an object identification code  102  as shown in  FIG. 9  and transmits the object identification code  102  though a wire (not shown), or wirelessly through writer antenna  88 , to central processor  90 . Central processor operates on the object identification code  102  to retrieve a label image from memory  94 . Image data can contain pricing information, date and time information, a quantity or location data. Central processor  90  can transmit the image data back to scanner/writer  80  wirelessly using processor antenna  92  to both receive and send data.  
         [0042]      FIG. 11  is a schematic view of scanner/writer  80  imprinting display  10  using label information for an object identification code  102 . Writer controller  81  contains image data for an object identification code  102  and is prepared to write to label  19 . Scanner/writer  80  and label  19  are brought together using conventional means. In a first case, label  19  can be removed from a holder (not shown) and inserted into the body of scanner/writer  80 . In a second case, scanner/writer  80  or portions containing flash unit  82 , masking display  83  and writer contacts  86  are pressed against label  19 . Contacts  85  of scanner/writer  80  are pressed against support contacts  16  to provide an electrical field to display  10 . Masking display  83  is brought into alignment with an area to be written onto a display  10  attached to label  19 . Sensors connected to writer controller  81  can verify that the correct alignment has been made between label  19  and scanner/writer  80 .  
         [0043]     Writer controller  81  first transmits image data corresponding to an image for object identification code  102  to masking display  83 . Writer controller  81  then applies an electrical field across display  10  using writer contacts  86  and fires flash unit  82  to imprint the label image on masking display  83  onto display  10 . Scanner/writer  80  can be disengaged from fixed labels, providing an inexpensive electrically rewritable ESL. A label  19  that has been removed from a holder can be disengaged from scanner/writer  80  and re-mounted onto the holder.  
         [0044]     The method and apparatus of this invention provides low cost, simple and rapidly written shelf labels with high information content. The scanner/writer provides a simple and accurate means for identifying an object associated to be labeled and for retrieving an image for the label associated with the object. The labels are inexpensive, having a few simple, unpatterned, mass produced layers. The writing apparatus itself is simple, requiring a low cost flash unit system, an inexpensive masking display and a 2 wire electrical exciter for the display  10 . Separating the drive from the display permits many inexpensive labels  19  to be written by a single, simple display writer  90 .  
         [0045]     The invention has been described in detail with particular reference to certain preferred embodiments thereof, but it will be understood that variations and modifications can be effected within the spirit and scope of the invention.  
       Parts List  
       [0000]    
       
           10  display  
           14  printing  
           15  display substrate  
           16  support contacts  
           17  display support  
           19  label  
           20  first conductor  
           22  exposed portion of first conductor  
           30  cholesteric liquid crystal light modulating layer  
           35  light absorber  
           40  second conductor  
           60  incident light  
           62  reflected light  
           72  planar liquid crystal  
           74  focal conic liquid crystal  
           80  scanner/writer  
           81  writer controller  
           82  flash unit  
           83  masking display  
           84  scanner  
           86  writer contacts  
           88  writer antenna  
           90  central processor  
           92  processor antenna  
           94  central memory  
           100  object  
           102  object identification code