Abstract:
A method of achieving precision registration in a roll to roll process by simultaneously depositing multiple inks onto a printing roll. One of these inks prints a pattern of fiducial marks onto a substrate while another ink prints a predetermined pattern on the same substrate such that the predetermined pattern bears a predictable spatial relationship to the pattern of fiducial marks. Consequently, even if the ink forming the predetermined pattern is invisible, or has such low contrast with the substrate that it is effectively invisible, or even has been dissolved away in a subsequent processing step, it is still possible to know where the predetermined pattern is by referring to the pattern of fiducial marks.

Description:
CROSS REFERENCE TO RELATED APPLICATIONS 
       [0001]    This application claims the benefit of U.S. Provisional Application No. 61/739,992, filed Dec. 20, 2012, the disclosure of which is incorporated by reference herein in its entirety. 
     
    
     BACKGROUND 
       [0002]    The fabrication of articles such as flexible electronic or optical components, can involve the application of layers of material deposited or formed on an elongated substrate or web. In particular, patterns of material may be deposited in layers on an elongated substrate, such as a web, through multiple deposition steps. Some articles require precise registration of features that are applied on one or both sides of the substrate. 
         [0003]    To achieve accurate registration between the layers, lateral (cross web) positioning and longitudinal (down web) positioning must be maintained as the substrate moves through multiple manufacturing steps. Maintaining registration between layers formed on the substrate becomes more complex when the substrate is flexible or stretchable. Some articles are made in multiple steps during which materials or processes are sequentially applied to the substrate, requiring precise position registration for each of the process steps. 
       SUMMARY 
       [0004]    Disclosed is a method of achieving precision registration in a roll to roll process by simultaneously depositing multiple inks onto a printing roll. One of these inks prints a pattern of fiducial marks onto a substrate while another ink prints a predetermined pattern on the same substrate such that the predetermined pattern bears a predictable spatial relationship to the pattern of fiducial marks. Consequently, even if the ink forming the predetermined pattern is invisible, or has such low contrast with the substrate that it effectively invisible, or even has been dissolved away in a subsequent processing step, it is still possible to know where the predetermined pattern is by referring to the pattern of fiducial marks. In some convenient embodiments, the predetermined pattern will define conductive circuit traces after secondary operations. In some other convenient embodiments, the predetermined pattern will define at least one aspect of a tamper-resistant security mark. 
         [0005]    Embodiments where the predetermined pattern is printed in a soluble ink are of particular interest. For example, it is possible to sputter a layer of conductive material onto the printed substrate and then rinse the substrate so as to remove the soluble ink. This also removes the sputtered layer above the soluble ink. If the fiducial marks are not soluble in the solvent, the location of the pattern in the sputtered layer can be known, even if that pattern is invisible, or has such low contrast with the substrate that it is effectively invisible. 
         [0006]    In one embodiment, the invention resides a method of providing a substrate having a predetermined pattern thereon comprising: providing a printing roll, a first ink dispenser, and a second ink dispenser; the first ink dispenser and the second ink dispenser positioned to dispense a first ink and a second ink onto the printing roll in separate first and second zones respectively; dispensing the first ink soluble in a selected solvent into the first zone with the first ink dispenser and dispensing the second ink that is non-soluble in the selected solvent into the second zone with the second ink dispenser; advancing the substrate against the printing roll printing fiducial marks onto the substrate with the second ink, while simultaneously printing the predetermined pattern onto the substrate with the first ink; sputtering a layer of conductive material onto the substrate over the predetermined pattern; and rinsing the substrate with the selected solvent removing the first ink and the predetermined pattern while leaving the fiducial marks on the substrate. 
         [0007]    In another embodiment, the invention resides in a method of providing a substrate having a predetermined pattern thereon comprising: providing a printing roll, a first ink dispenser, and a second ink dispenser, the first ink dispenser and the second ink dispenser positioned to dispense a first and a second ink onto the printing roll in separate first and second zones respectively; dispensing a low contrast ink into the first zone and a visible ink into the second zone; advancing the substrate against the printing roll to print fiducial marks onto the substrate with the visible ink, while simultaneously printing a first predetermined pattern onto the substrate with the low-contrast ink; subsequently placing a secondary pattern in registration with the first predetermined pattern on the substrate using the fiducial marks as a guide. In some convenient embodiments, the secondary predetermined pattern is placed in registration with the first predetermined pattern by a second printing operation. In another embodiment, the secondary predetermined pattern is placed in registration with the first predetermined pattern by laminating an additional layer to the substrate. 
         [0008]    In this application, “contrast” means the degree of dissimilarity of a measured quantity such as luminance of two areas, expressed as a number computed by a specified formula. This definition comes from ASTM Standard E284, “Standard Terminology of Appearance”. In the broadest sense a “low contrast ink” is any ink that is insufficiently optically distinguishable from the substrate to allow a secondary operation on the substrate to be directly registered with predetermined pattern. A more formal definition is presented in connection with the optical test discussed in Example 3 below. 
         [0009]    In this application, “predetermined pattern” means a pattern that can include lines, repeating lines, traces, symbols, letters, figures, graphics, numbers, or combinations thereof by way of example; that is determined or selected in advance to be placed onto the substrate by suitable replicating methods such as printing. The predetermined pattern can include features having a dimension of less than 20, 10, or 5 microns in size. 
         [0010]    In this application “fiducial marks” means a pattern of symbols, lines, points, or other shapes placed onto the substrate for use by an imaging system as a point of reference for obtaining information on web displacement, web speed, or web position. 
         [0011]    Those skilled in the art will more fully understand the nature of the invention upon consideration of the remainder of the disclosure, including the Detailed Description, the Examples, and the appended claims. 
     
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
         [0012]    It is to be understood by one of ordinary skill in the art that the present discussion is a description of exemplary embodiments only, and is not intended as limiting the broader aspects of the present disclosure, which broader aspects are embodied in the exemplary construction. 
           [0013]      FIG. 1  is a perspective view of a printing apparatus including a printing roll adjacent to a doctor blade assembly divided into zones along its cross web width; 
           [0014]      FIG. 2  is a side schematic view of the printing apparatus of  FIG. 1 ; 
           [0015]      FIG. 3  is a perspective view of an alternate printing apparatus according to one embodiment of the present invention; and 
           [0016]      FIG. 4  is a plan view of a web of indefinite length steering that has had a first and second ink printed in first and second zones by an apparatus according the present invention. 
       
    
    
       [0017]    Repeated use of reference characters in the specification and drawings is intended to represent the same or analogous features or elements of the disclosure. 
       DETAILED DESCRIPTION 
       [0018]    Referring now to  FIG. 1 , a printing apparatus  20  suitable for carrying out the present disclosure is illustrated. The printing apparatus  20  includes a printing roll  22  and a doctor blade assembly  24  adjacent to printing roll  22 . In some alternate embodiments roll  22  is a transfer roll such as an anilox roll that inks a separate printing roll indirectly. Printing roll  22  may be either a live shaft roll having a shaft  22   a  or a dead shaft roll. Printing roll  22  is conveniently an anilox roll, but the invention is workable with, e.g. equipment for flexo printing, gravure printing, screen printing, ink jet printing, and dual offset printing. Doctor blade assembly  24  conveniently includes support  25  and blade support  26 . The blade support  26  retains the actual doctor blade  27 . The illustrated blade support  26  includes barriers  28 ,  30 , and  32  that divide the cross web width of the blade support  26  into a first zone  42  and a second zone  40 . The barriers  28 ,  30 , and  32  are conveniently formed from a soft, resilient material that can seal against the side of printing roll  22  without scratching it. 
         [0019]    When the printing roll  22  is a microflexo printing roll, the fabrication methods disclosed in PCT International Pub. No. WO 2013/003412 may be advantageously used. As mentioned there, a micro-contact printing stamp for, e.g. printing electrical circuit predetermined patterns can result in printed traces is less than 20, 10, or even 5 microns. Further, the fiducial marks and the predetermined pattern can be laid down in registration with a dimensional accuracy of less than 20, 10, or even 5 microns. Mounting a microflexo stamp to the printing roll  22  may be advantageously accomplished using the techniques disclosed in PCT International Pub. No. WO 2013/040319. 
         [0020]    Referring now to  FIG. 2 , a side view of the printing apparatus  20  of  FIG. 1  is illustrated. In this side view, it can be better appreciated how the doctor blade  27  is supported by blade support  26 . Also seen in this view is a first ink dispenser  60   a  omitted from  FIG. 1  for visual clarity. First ink dispenser  60   a  is connected to a first ink supply  62  for dispensing a first ink into the first zone ( 42  in  FIG. 1 ) of the blade support  26 . In this view, a similar second ink dispenser  60   b  is disposed behind the first ink dispenser  60   a  and hidden from view for dispensing a second ink into the second zone ( 40  in  FIG. 1 ). Depending on user preferences and/or the type of printing being contemplated, the form of the ink dispensers can take numerous forms such as spouts, sprayers, fed brushes, fed rollers, or the like. 
         [0021]    Referring now to  FIG. 3 , an alternative printing apparatus  120  suitable for carrying out the present invention is illustrated. The printing apparatus  120  includes a printing roll  122 . Printing roll  122  may be either a live shaft roll having a shaft  122   a  or a dead shaft roll. Analogous to printing apparatus  20  above, printing roll  122  is conveniently an anilox roll, but the invention is workable with, e.g. equipment for flexographic printing, gravure printing, screen printing, ink jet printing, and dual offset printing. In the illustrated embodiment, the printing roll  122  is adjacent to a main inking roll  170  which is rotatable about shaft  170   a . The inking roll  170  is inked with a first ink in a first zone  172  by a main inker  174 . The first ink in the first zone  172  is transferred to printing roll  122  in a first receiving zone  176 . 
         [0022]    A support  178  carries at least one (in this illustrated embodiment, two) subsidiary inking rolls  180   a  and  180   b , each inked with a second ink by secondary inkers  182   a  and  182   b , respectively. The second ink is transferred to printing roll  122  in two second receiving zones  184   a  and  184   b . The substrate, in many convenient embodiments a web of indefinite length material, can then be brought into contact with the printing roll  122  in a conventional manner. 
         [0023]    Referring now to  FIG. 4 , illustrated is a plan view of a web  200  of indefinite length that has had a first and second ink printed in first zone  202  and second zone  204  respectively by one of the apparatuses as discussed above. Within first zone  202 , a predetermined pattern  206  has been printed (perhaps a security marking in a low-contrast ink or the pattern of an electronic circuit in a soluble ink). A pair of fiducial marks  208  has been printed in second zone  204 . In various embodiments, the fiducial marks and the predetermined pattern are in registration with a dimensional accuracy of less than 20, 10, or even 5 microns. 
         [0024]    While any pattern of fiducial marks that allows the determination of the position of the predetermined pattern is workable, some possibilities offer distinct advantages. In particular, fiducial marks useful for determining the down web and/or cross web position of a moving web, and methods related to those patterns, can be found in U.S. Patent Application Pub. Nos. 2010/0196607, 2010/0188668, and 2011/0247511. In particular, the fiducial marks illustrated as  208  in  FIG. 4  are disclosed in U.S. Patent Application Pub. No. 2011/0257779. 
       EXAMPLE 1 
       [0025]    A printing apparatus generally as illustrated in  FIGS. 1 and 2  was constructed. The printing roll was 12 cm in diameter. The roll had a predetermined pattern of connected diamonds in both the first and the second zones. On a stainless steel doctor blade, three barriers were formed against the roll from vinyl polysiloxane impression material commercially available as 3M ESPE 7302 EXPRESS from 3M Company of St. Paul, Minn. 
         [0026]    A water soluble ink as disclosed in U.S. Pat. No. 4,895,631 was dispensed onto the doctor blade in the first zone, while a UV curable, non-water-soluble ink, commercially available as 9301 Opaque white UV flexo ink from Nazdar Ink Technologies of Shawnee, Kans., was dispensed onto the doctor blade in the second zone. After a pause to allow the roll to become inked, printing was begun onto a substrate of conventional polyester terephthalate (PET) film, conveyed at a line speed of 2 m/min and at a tension of 1 pound/linear inch (1.75 N/cm). The web was passed through a UV curing station having a microwave light source commercially available as a Model I250B from Fusion UV Systems, Inc. of Gaithersburg, Md., connected to a power supply commercially available as Model VPS-48, also from Fusion UV Systems, Inc. This station was set to 40% power and was supplied with 8 SCFM of nitrogen. This caused the second ink to become non-soluble. 
       EXAMPLE 2  
       [0027]    The film according to Example 1 was passed through a sputter deposition apparatus of conventional type, e.g. a roll-to-roll vacuum chamber similar to the system described in U.S. Pat. Nos. 5,440,446 (Shaw et al.) and 7,018,713 (Padiyath, et al.). A 40 nm thick layer of indium tin oxide (ITO) was deposited on the substrate in the first zone. The film is then rinsed in water, causing the water soluble ink to be dissolved away in the first zone, carrying with it the portion of the sputtered layer above the predetermined pattern. The fiducial marks in the second zone printed with the UV curable ink remained on the film after rinsing with water. Predetermined patterns formed in this way can have features with a dimension less than 20 mils (0.5 mm). 
       EXAMPLE 3 
       [0028]    An apparatus generally as depicted in  FIG. 3  was constructed. A first ink, commercially available as 9301 Opaque white UV flexo ink from Nazdar Ink Technologies was dispensed from the first inker onto a microflexo printing roll in the first zone. The microflexo printing roll had a predetermined pattern of spaced apart rectangles in the first zone. A second ink, commercially available as 9319 Base Process Blue UV flexo ink from Nazdar Ink Technologies, was dispensed from the second inker onto the microflexo printing roll in the second zone. The microflexo printing roll had a predetermined pattern of spaced apart rectangles in the second zone. These inks were printed from the anilox roll onto a substrate of white paper coated with a silicone release liner and then over coated with a thin layer of a pressure sensitive adhesive, specifically a random copolymer of 90% by weight of iso-octyl acrylate and 10% by weight of acrylic acid. After the printing, the web was passed through a UV curing station having a microwave light source commercially available as a Model I250B from Fusion UV Systems, Inc., connected to a power supply commercially available as Model VPS-48, also from Fusion UV Systems, Inc. This station was set to 40% power and was supplied with 8 SCFM of nitrogen. This particular film and ink composition is simulative of certain security mark applications; and, after the inks were dried, the pattern within the first zone was nearly invisible to the naked eye in normal room illumination. However the ink in the second zone was sharp and plainly visible. 
         [0029]    This low-contrast between the inked area and the substrate within zone  1  was assessed by measuring the reflectance of adjacent inked and uninked areas using a MICROMAX photometric camera commercially available from Princeton Instruments of Trenton, N.J. Data was collected at maximum angular apertures of 8.6, 17.5, and 30.0 degrees and under conditions where the cone of illumination was equal to the cone of collection. The results are presented in Table 1 and each entry represents the mean of five experiments in different random portions of the inked substrate. R s  is the reflectance of the substrate in arbitrary units. R i  is the reflectance of the inked area in arbitrary units. Three values were calculated from these values: C c  is R s /R i , C a =(R s −R i )/R i , and C b =(R s −R i )/((R s +R i )/2). 
         [0000]    
       
         
               
               
               
               
               
               
               
               
             
               
               
               
               
               
               
               
               
             
           
               
                 TABLE 1 
               
               
                   
               
               
                 Magnification 
                   
                   
                   
                   
                   
                   
                   
               
               
                 of the camera 
                 Minimum 
                 Maximum 
               
               
                 objective 
                 aperture 
                 aperture 
                 R s   
                 R i   
                 C c   
                 C a   
                 C b   
               
               
                   
               
             
             
               
                   
               
             
          
           
               
                  5X 
                 0.15° 
                 8.6° 
                 28689 
                 24877 
                 1.1532 
                 0.1532 
                 0.1423 
               
               
                 10X 
                 0.30° 
                 17.5° 
                 30244 
                 29130 
                 1.0382 
                 0.0382 
                 0.0375 
               
               
                 20X 
                 0.50° 
                 30.0° 
                 25746 
                 26735 
                 0.9630 
                 −0.0370 
                 −0.0377 
               
               
                   
               
             
          
         
       
     
         [0030]    One definition of “low-contrast ink” may be stated as one where the C c  value calculated when the R s  and R i  values are measured at a 30.0° aperture with the cone of illumination equal to the cone of collection is between about 0.9 and 1.1. 
       EXAMPLE 4 
       [0031]    The printed web of Example 3 was conveyed against a conventional printing roll having a secondary pattern intended to be complimentary for a particular end use to the predetermined pattern. Although the virtually invisible, the position of the first predetermined pattern is known through the visible fiducial marks. A secondary pattern is then applied to the web through, e.g. printing or laminating. The web is the conveniently steered into an appropriate registration between the first predetermined pattern and the secondary pattern using, e.g. the techniques of PCT International Pub. No. WO 2013/090134. 
         [0032]    Other modifications and variations to the present disclosure may be practiced by those of ordinary skill in the art, without departing from the spirit and scope of the present disclosure, which is more particularly set forth in the appended claims. It is understood that aspects of the various embodiments may be interchanged in whole or part or combined with other aspects of the various embodiments. All cited references, patents, or patent applications in the above application for letters patent are herein incorporated by reference in their entirety in a consistent manner. In the event of inconsistencies or contradictions between portions of the incorporated references and this application, the information in the preceding description shall control. The preceding description, given in order to enable one of ordinary skill in the art to practice the claimed disclosure, is not to be construed as limiting the scope of the disclosure, which is defined by the claims and all equivalents thereto.