Abstract:
A method for fabricating electrical storage cell including providing a photopolymer; providing a pre-patterned mask wherein the pre-patterned mask includes masked regions and unmasked regions; attaching the pre-patterned mask on top of the photopolymer; applying collimated ultraviolet radiation on the masked substrate wherein areas of the photopolymer underneath of the unmasked regions are solidified or cross linked and areas of the photopolymer underneath the masked are not solidified or cross linked to form an imaged substrate with perforated holes; developing the imaged substrate; cleaning residual material from the perforated holes; forming a thin film over the surface of a substrate area to define an anode, a cathode; and forming a solid electrolyte disposed between the anode and the cathode, wherein the thin film comprising a final layer which is formed so as to fill the perforated holes.

Description:
CROSS REFERENCE TO RELATED APPLICATIONS 
       [0001]    Reference is made to commonly-assigned copending U.S. patent application Ser. No. ______(Attorney Docket No. K001863US01NAB), filed herewith, entitled SYSTEM FOR FABRICATING AN ELECTRICAL STORAGE CELL, by Goldstein; the disclosure of which is incorporated herein. 
     
    
     FIELD OF THE INVENTION 
       [0002]    The present invention relates generally to the field of electrical energy sources and specifically to a substrate for thin film microbatteries. 
       BACKGROUND OF THE INVENTION 
       [0003]    U.S. Pat. No. 7,527,897 (Nathan et al.) presents a three-dimensional storage cell, such as a microbattery. The storage cell is produced by forming multiple thin film layers on a microchannel plate (MCP) structure. The thin film layers cover the inner surfaces of the microchannel tubes. Typically, the thin film layers also cover the upper and/or lower surfaces of the plate in order to provide electrical continuity of the layers over the entire MCP. The layers inside the tubes completely fill the volume of the tube. The MCP may be made from glass or from other suitable materials, as described above, and the thin film layers may be deposited using a variety of liquid or gas-phase processes. 
         [0004]    Although MCPs themselves are well known in the art of radiation and electron detection, their use as a substrate for energy-storage devices is novel. Because of the processes by which MCPs are made by fusing together multiple tubes they can be made with very small channel diameters, high channel density and high channel aspect ratio. As a result, MCP-based microbatteries have a larger electrode area/volume ratio, and thus higher electrical capacity, than microbatteries known in the art, such as those described in the above-mentioned U.S. Pat. No. 6,197,450 (Nathan et al.). The term “microbattery” as used herein simply denotes small-scale electrical batteries, in which certain features of the present invention are particularly advantageous, but the principles of the present invention are generally applicable to batteries and other electrical storage cells regardless of scale. 
         [0005]    The energy storage device will typically include a micro channel plate (MCP) having channels formed therein, the channels having surface areas; and thin films formed over the surface areas and defining an anode, a cathode, and a solid electrolyte disposed between the anode and the cathode. 
         [0006]    Typically, the MCP includes a plurality of tubes, which are fused together and cut to define the MCP, the tubes having lumens, which define the channels. The tubes may include glass or carbon. The MCP may include a non-conductive material or a conductive material. The MCP has top and bottom surfaces, and the thin films are further formed over at least one of the top and bottom surfaces. 
         [0007]    The current invention discloses a method and an article of a substrate with perforated channels adapted for microbatteries based MCP. 
       SUMMARY OF THE INVENTION 
       [0008]    Briefly, according to one aspect of the present invention a method for fabricating electrical storage cell including providing a photopolymer; providing a pre-patterned mask wherein the pre-patterned mask includes masked regions and unmasked regions; attaching the pre-patterned mask on top of the photopolymer; applying collimated ultraviolet radiation on the masked substrate wherein areas of the photopolymer underneath the unmasked regions are solidified or cross linked and areas of the photopolymer underneath the masked are not solidified or cross linked to form an imaged substrate; developing the imaged substrate; cleaning residual material from the areas which are not solidified to form perforated holes; forming a thin film over the surface of a substrate area to define an anode; and forming a solid electrolyte over the anode and the cathode, wherein the thin film comprising a final layer which is formed so as to fill the perforated holes. 
         [0009]    The invention and its objects and advantages will become more apparent in the detailed description of the preferred embodiment presented below. 
     
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
         [0010]      FIG. 1  represents in diagrammatic form of a digital front end driving an imaging device (prior art); 
           [0011]      FIG. 2  represents in diagrammatic form a laser imaging head mounted on an imaging carriage which images on a plate mounted on an imaging cylinder (prior art); 
           [0012]      FIG. 3  represents in diagrammatic form a honeycomb shape used to form an image on a film mask; 
           [0013]      FIG. 4  represents in diagrammatic form a film mask with a honeycomb shape image which will be attached to a photopolymer plate; 
           [0014]      FIG. 5  represents in diagrammatic form a substrate built from a pre-patterned mask attached to a photopolymer plate; 
           [0015]      FIG. 6  depicts a top view matrix of perforated holes made by collimated UV exposure of a substrate; 
           [0016]      FIG. 7A  shows a top view of perforated holes made by collimated UV exposure of a substrate; 
           [0017]      FIG. 7B  shows a close up view of perforated holes made by collimated UV exposure of the substrate shown in  FIG. 7A ; 
           [0018]      FIG. 8  shows a side view of the perforated holes made by collimated UV exposure of the substrate shown in  FIGS. 7A and 7B , showing the depth of the perforated holes; 
           [0019]      FIG. 9  shows a photopolymer plate after imaging and development, being treated by water jets to remove debris from non solidified regions; 
           [0020]      FIG. 10  shows micro battery structure showing several perforated holes filled with battery material (current collector, cathode and electrolyte layers); 
           [0021]      FIG. 11  shows an anode layer added to structure of  FIG. 10 ; 
           [0022]      FIG. 12  shows a second current collector added to structure of  FIG. 11 ; and 
           [0023]      FIG. 13  shows a cutaway view of honeycomb structure cells with deposited micro battery materials. 
       
    
    
     DETAILED DESCRIPTION OF THE INVENTION 
       [0024]    In the following detailed description, specific details are set forth in order to provide a thorough understanding of the disclosure. It will be understood, however, by those skilled in the art that the teachings of the present disclosure may be practiced without these specific details. In other instances, well-known methods, procedures, components and circuits have not been described in detail so as not to obscure the teachings of the present disclosure. 
         [0025]      FIG. 1  shows a an imaging device  108 . The imaging device is driven by a digital front end (DFE)  104 . The DFE receives printing jobs in a digital form from desktop publishing (DTP) systems (not shown), and renders the digital information for imaging. The rendered information and imaging device control data are communicated between DFE  104  and imaging device  108  over interface line  112 . 
         [0026]      FIG. 2  shows an imaging system  200 . The imaging system  200  includes an imaging carriage  232  an imaging head  220 . Imaging head  220  are controlled by controller  228 . The imaging head  220  is configured to image on a film substrate  208 . The substrate may be a film to be attached as a mask to a flexographic plate, or alternatively a flexographic plate that will be directly imaged by imaging system  200 .  FIG. 2  shows a substrate  208  mounted on a rotating cylinder  204  for exposure, the imaging device can be based on a flat bed imaging head as well. The carriage  232  is adapted to move substantially parallel to cylinder  204  guided by an advancement screw  216 . The substrate  208  is imaged by imaging head  220  to form imaged data  212  on substrate  208 . 
         [0027]      FIG. 3  shows a honeycomb image  212 . The rendered image  212  was prepared by DFE  104 , to be further imaged on film mask  208 . 
         [0028]      FIG. 4  shows an exposed film mask  208  with honeycomb image shape  304 . The exposed film mask  208  is pre-patterned where the boundaries or the walls  308  represent the non masked areas and the holes  312  represent the masked area when UV radiation will be applied. 
         [0029]    Mask  208  is attached on top of the photopolymer plate  504  to form substrate  508  as is shown in  FIG. 5 . Plate  504  is made of a photo sensitive layer comprising a binder, a monomer and a photo initiator. The binder is usually made from a thermoplastic elastomeric block copolymer such as an SBS (styrene butadiene styrene), natural rubber or a styrene-isoprene. The monomer is usually a poly functional acrylate such as isobornyl acrylate, 2-phenoxyethyl acrylate or hexane diol diacrylate. The photo initiator is an ultra violet (UV) light triggered to start the photopolymer reaction. The photo initiator is usually a benzophenone, benzoin which is known by commercial name such as Irgacure 651. 
         [0030]    Collimated ultra violet (UV) radiation is applied on substrate  508  to solidify or crosslink areas under the unmasked areas  308 , and not change the properties of the masked areas  312 , thereby to produce straight perforated holes under the masked areas  312  of substrate  508  (the UV emission process is not shown). The collimated emission can be applied by UV light. 
         [0031]      FIG. 6  and  FIG. 7A  show a top view of the perforated holes  604  produced by the collimated UV light source after removal of the residual material. UV light sources are described at http://www.oainet.com/oai-lightsrcGrande-pp.html. The holes  604  are formed under masked areas  204 , shown in  FIG. 5 . 
         [0032]      FIG. 7B  shows a close up view of the perforated holes  604 . The perforated holes have an approximated holes diameter  708  of 60 micrometers and distance between holes  704  of 20 micrometers. 
         [0033]      FIG. 8  shows a side view of the perforated holes depth structure  804 . The shown perforated holes depict a pattern of 60 by 20 micrometer pattern. The diameter  812  is 60 micrometer in size whereas the distance between holes are shown to be around 20 micrometer, the depth of the holes  808  shown to be around 300 micrometers. The shown pattern  804  was achieved by 5 minutes exposure followed by 10 minutes development at room temperature. 
         [0034]    Following the applied collimated UV radiation the exposed parts are cross linked and the masked parts are removed by solvent using a development processor  120  (shown in  FIG. 1 ). The solvents that can be used are aromatic or aliphatic hydrocarbons such as diisopropyl benzene. 
         [0035]    Referencing  FIG. 9 , non-solidified material  908  on imaged and developed plates  904  is cleaned to form straight holes in the substrate. The cleaning process may utilize means such as water jets, brushes or by ultra sonic means.  FIG. 9  shows water jets  912  applied on plate  904  to remove the non-solidified areas  908  to form perforated holes  816  as is shown in  FIG. 8 . 
         [0036]      FIG. 10  shows several perforated holes  816  filled with microbattery material which forms first current collector layer  1004  the perforated holes. Layer  1004  typically comprises a metallic layer, which is deposited over substrate  1000  using any suitable thin-film deposition process known in the art (not shown). Typically, collector  1004  forms a hollow structure or crust that coats the entire surface area of the perforated substrate. 
         [0037]    A cathode layer  1008  is formed over the first current collector layer  1004 . The cathode layer  1008  may be formed using an electrochemical deposition process or using any other suitable method, such as electroless deposition and chemical vapor deposition. 
         [0038]    An electrolyte separator layer  1012  is applied over cathode layer  1008  to form the separator layer of the microbattery, as is known in the art. In some embodiments, the electrolyte separator layer comprises an ion-conducting electrolyte membrane  1012 . 
         [0039]    An anode layer  1016  as is shown in  FIG. 11  is formed on or otherwise attached to the outer surface or surfaces of electrolyte separator  1012 . The anode layer  1016  comprises a substantially flat layer or film of conductive material. The anode may be deposited onto the outer surface of the membrane using a thin- or thick-film deposition process. Alternatively, the anode may comprise a thin foil made of anode material and attached to the surface of the membrane. The anode layer may either be attached to one or both outer surfaces of electrolyte separator  1012 . 
         [0040]    A second current collector layer  1020  of conductive material as is shown in  FIG. 12  is optionally attached to the anode layer  1016 . 
         [0041]      FIG. 13  is a schematic, cutaway view of micro battery substrate  1000  showing details of thin film structure in the interior of perforated holes  816 , in accordance with an embodiment of the present invention. The relative thickness of the thin film layers is exaggerated in the figure for clarity of illustration. It can be seen in the figure that the layers both cover the interior walls  308  of perforated holes  816  and extend over the upper or lower surfaces or both of the substrate  1000 . The thin film layers may be deposited using any suitable processes known in the art, such as wet processes or chemical vapor deposition (CVD) processes. Some specific fabrication examples are described herein below. 
         [0042]    In the embodiment shown in  FIG. 13 , a current collector layer  1004  is deposited over the substrate and thus coats wall  308 . An cathode layer  1008 , which may be either the anode or the cathode of perforated substrate  1000 , is deposited over current collector layer  1004 . Alternatively, the current collector layer may be eliminated if cathode layer  1008  is capable of serving the current collection function, or if wall  308  is itself made of conductive material, such as a suitable form of carbon. In an alternative embodiment, the battery substrate also serves as one of the electrodes, such as the anode. In this case, both cathode layer  1008  and anode layer  1016  may be eliminated from structure. 
         [0043]    Cathode layer  1008  is overlaid by an electrolyte layer  1012 , typically a solid electrolyte in a polymer matrix. A second (cathode or anode) electrode layer  1016  is formed over electrolyte layer  1012 . If necessary, electrode layer  1016  is followed by another (optional) current collector layer  1020 . Alternatively, if electrode layer  1016  is sufficiently conductive (for example, if layer  1016  comprises a graphite anode), current collector layer  1020  is not required. 
         [0044]    While the present invention is described in connection with one of the embodiments, it will be understood that it is not intended to limit the invention to this embodiment. On the contrary, it is intended to cover all alternatives, modifications and equivalents as covered by the appended claims. 
         [0045]    While the invention has been described with respect to a limited number of embodiments, these should not be construed as limitations on the scope of the invention, but rather as exemplifications of some of the preferred embodiments. Other possible variations, modifications, and applications are also within the scope of the invention. Accordingly, the scope of the invention should not be limited by what has thus far been described, but by the appended claims and their legal equivalents. The principles of the present invention may similarly be applied to other types of electrical storage cells, such as energy-storage capacitors. 
         [0046]    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 scope of the invention. 
       PARTS LIST 
       [0000]    
       
           104  digital front end (DFE) 
           108  imaging device 
           112  interface line 
           120  development processor 
           200  imaging system 
           204  rotating cylinder 
           208  imaged film mask with honeycomb shape image 
           212  imaged data on film (honeycomb shape image) 
           216  screw 
           220  imaging head 
           228  controller 
           232  carriage 
           304  honeycomb image 
           308  walls of the holes (unmasked areas) 
           312  holes (masked areas) 
           504  photopolymer plate 
           508  substrate for imaging 
           604  perforated holes showing holes diameter from top view 
           704  distance between perforated holes 
           708  perforated holes diameter 
           804  perforated holes pattern showing holes depth from side view 
           808  side view of perforated holes depth 
           812  side view of perforated holes diameter 
           816  perforated holes 
           904  plate after imaging and development 
           908  non-solidified areas 
           912  water jets 
           1000  perforated substrate 
           1004  first current collector 
           1008  cathode layer 
           1012  electrolyte layer 
           1016  anode layer 
           1020  second current collector