Abstract:
A method of introducing discontinuities to an adhesive coated region of a substrate is provided. The method includes the steps of (a) providing a web having upper and lower edges; (b) excising a portion of the web creating open sections interposed between retained sections connected to carrier sections, each including the upper or lower edge of the web to yield a patterned web; (c) perforating the patterned web such that the perforations span from one open section to the next open section to yield a perforated web; (d) contacting the perforated web to the adhesive coated region of the substrate; and (e) removing the carrier sections at the perforations leaving the retained sections on the substrate.

Description:
FIELD OF INVENTION 
   The present invention provides a method of adding non-adhesive discontinuities to a substrate having an adhesive region. In particular, the discontinuities causes the adhesive to be recessed thereby yielding an article having a securing mechanism that exhibits adhesion on demand, i.e., the article exhibits adhesive properties when a consumer applies a pressure activating the securing mechanism to attach the article to an intended surface. 
   BACKGROUND 
   There are various methods to introduce non-adhesive discontinuities to an adhesive backed substrate. For example, U.S. Pat. No. 6,451,149 describes a method where in one step, die cut pieces are produced on a carrier web and in another step, a peeler bar and an moving label applicator are used to transfer the die cut pieces from the carrier web to articles or products. In this particular method, the die cut pieces are generally secured to the carrier web using a pressure sensitive adhesive. Thus, the carrier web is a release liner in order for the die cut pieces to transfer from the carrier web to the second web. 
   In another method, a first web and a second adhesive-coated web are laminated. A controlled depth cut (commonly referred to as a “kiss cut”) is made on the first web to create non-adhesive discontinuities. Thereafter, a continuous portion (i.e., the weed) of the first web is separated thereby leaving the non-adhesive discontinuities laminated to the second web. 
   While these methods have been available, other methods are being sought. 
   SUMMARY 
   The present invention provides a streamlined process for introducing non-adhesive discontinuities into an adhesive backed web, thereby creating a recessed adhesive article. The inventive method and resulting articles do not rely on the use of a release liner, which increases the cost of a product. Because a wide variety of materials can be used and the equipment used does not rely on reciprocating parts, the present method facilitates high speed processing, on the order of hundreds of feet per minute for a line speed. 
   In one aspect, the present invention pertains to a method of adding discontinuities to an adhesive coated region of a substrate comprising the steps of (a) providing a web having upper and lower edges; (b) excising a portion of the web creating open sections interposed with retained sections connected to carrier sections, each including the upper or lower edge of the web to yield a patterned web; (c) perforating the patterned web such that the perforations span from one open section to the next open section to yield a perforated web; (d) contacting the perforated web to the adhesive coated region of the substrate; and (e) removing the carrier sections at the perforations leaving the retained sections on the substrate. Typically, the patterned web has a repeating pattern; although it does not need to be. Typically and as further described below with reference to the drawings, the retained sections are disposed between the perforations and the carrier sections are disposed between an edge of the web and the perforations. While in some embodiments, each retained section can be discrete; each carrier section is continuous to facilitate its removal. 
   In another aspect, the present invention pertains to an article comprising (a) a substrate having a repositionable pressure sensitive adhesive region defined by upper and lower edges; and (b) a plurality of non-adhesive sections disposed on a portion of the adhesive region such that open sections of exposed adhesive are interposed between the non-adhesive sections, a portion of which spans substantially continuously from the upper to the lower edge of the adhesive region. In one embodiment, the non-adhesive sections are discrete. 
   In yet another aspect, the present invention pertains to an easel pad comprising (a) a plurality of sheets stacked on top of one another each having writable opposing first and second surfaces, and upper and lower edges; and (b) a securing mechanism disposed on the second surface of the sheet, the mechanism comprising (i) a repositionable pressure sensitive adhesive having upper and lower edges and disposed proximate to the upper edge of the sheet; and (ii) plurality of non-adhesive sections disposed on the adhesive creating open sections of exposed adhesive interposed between the non-adhesive sections, a portion of which spans substantially continuously from the upper to the lower edge of the adhesive. In one embodiment, the non-adhesive sections are discrete. As used herein, the term “discrete” as used to describe the retained section or the non-adhesive section generally means such sections are individually distinct or unconnected to another section. Thus, the discrete sections can also be described as islands of retained sections or non-adhesive sections. 
   In this document, the term “about” is presumed to modify all numerical dimensions. 

   
     BRIEF DESCRIPTION OF THE DRAWINGS 
     The invention can be better described with reference to the drawings, wherein: 
       FIG. 1  is a top plan view of an exemplary web that may be used according to one method of the present invention; 
       FIG. 2  is a top plan view of the embodiment of  FIG. 1  after the web has been processed to yield a patterned web; 
       FIG. 3  is a bottom plan view of an exemplary an adhesive coated substrate that may be used according to one method of the present invention; 
       FIG. 4  is a bottom plan view of the substrate of  FIG. 3  with the patterned and perforated web of  FIG. 2  attached; 
       FIG. 4   a  is a bottom plan view of another exemplary patterned and perforated web disposed on another exemplary substrate; 
       FIG. 5  is a cross-sectional view of the embodiment of  FIG. 4  taken along line  5 - 5 ; 
       FIG. 6  is a bottom plan view of the embodiment of  FIG. 4  showing carrier sections being removed; 
       FIG. 7  is a bottom plan view of the embodiment of  FIG. 6  after the carrier sections have been removed. 
       FIG. 8  is a top plan view of another exemplary patterned web that may be used according to one method of the present invention; and 
       FIG. 9  is a perspective view of an exemplary easel pad of the present invention. 
   

   These figures are idealized, are not drawn to scale, and are intended merely for illustrative purposes. 
   DETAILED DESCRIPTION 
     FIG. 1  shows an exemplary substantially rectangular shaped web having substantially parallel top and bottom edges,  100   a  and  100   b  that can be used in the present invention. Other starting web configurations can be used. The web can be made from paper or polymeric films. Suitable polymeric films include, but not limited to, polyethylene terephthalate, polypropylene, and polyethylene, and copolymers thereof. In one embodiment, the thickness of the web is less than about 0.2 mm. The web can be light transmissive, meaning that it will allow at least a portion of incident light through, or it can be opaque. Furthermore, the web can be colored. The web material should be able to adhere to the adhesive used on the substrate. 
     FIG. 2  shows a top plan view of the web of  FIG. 1  after a portion of the web has been excised and perforated. A perforated web  110  has an overall length L and an overall width W. The web includes a plurality of open sections or cutouts  112  interposed between a plurality of retained sections  114  connected to carrier sections  116 . The carrier sections of the perforated web include substantially parallel top and bottom edges  110   a  and  110   b  that correspond to the top and bottom edges of the predecessor web  100  of  FIG. 1 , namely edges  100   a  and  100   b.  In this particular embodiment, the perforated web  110  has an upper carrier section that includes the top edge  110   a  to the perforation  118  lying closest to the top edge and the lower carrier section that includes the bottom edge  110   b  to the perforation  118  lying closest to the bottom edge. The retained sections have substantially the same geometry, each in the form of substantially an “X”. While  FIG. 2  shows perforations  118  disposed on the retained sections, they can also be disposed between the carrier section and the retained section, or on the carrier section. The perforations span from one open section to the next adjacent open section. The perforations typically include slits on the web lying between ties. The perforation design should be selected so that the separation of the carrier section does not dislodge the retained sections from the adhesive. 
   In one embodiment, the perforated web based on the design of  FIG. 2  has a first width, W 1 , of about 4 inch (10.2 cm), a second width, W 2 , of about 2.5 inch (6.4 cm), and a third width, W 3 , of about 0.2 inch (5 mm). The third width denotes the distance from an inner surface of the carrier,  116   a,  to the perforation. The web  110  also has a length L 1  of about 2.5 inch and a length L 2 , which denotes one dimension of the retained section, of about 0.27 inch (6.9 mm). In this particular embodiment, the perforation includes two ties, each of 0.010 inch (0.25 mm) in length disposed between three slits. The three slits consist of a long slit, a short slit, and a long slit, with the long slit being 0.078 inch (2.0 mm) in length and the short slit being 0.0321 inch (0.82 mm) in length. Thus, from one open section to the next, the perforation on the retained section can be described as a long slit, a tie, a short slit, a tie, and a long slit. While the foregoing description of the perforation of  FIG. 2  is useful, other designs can be used. For example, another perforation design includes a short slit, a tie, a long slit, a tie, and a short slit. Furthermore, three or more ties can be used along with long and or short slits therebetween. 
     FIG. 3  shows a bottom plan view of an exemplary substantially rectangular shaped substrate having opposing first (not shown) and second  202  surfaces and top and bottom edges,  200   a  and  200   b.  Adhesive  204  is disposed on the second surface proximate to the top edge. In this particular embodiment, the adhesive is in generally in the form of a stripe having substantially parallel upper and lower edges,  204   a  and  204   b  respectively. In one exemplary embodiment, the substrate is a sheet of easel paper. In some embodiments, the width of the adhesive stripe varies from 7.6 to 0.32 cm. In other embodiments, the width of the adhesive stripe varies from 7.6 to 2.5 cm. In one embodiment, the thickness of the substrate is less than about 0.5 mm. 
   Any type of adhesive can be used for the substrate and the adhesive can cover any portion of the substrate. In one embodiment, the adhesive is a microsphere-based repositionable pressure sensitive adhesive. The repositionable adhesive can be solvent based, water based, or can be a solventless, hot melt adhesive. Suitable repositionable adhesives includes those disclosed in the following U.S. Pat. No. 3,691,140 (Silver); U.S. Pat. No. 3,857,731 (Merrill et al.); U.S. Pat. No. 4,166,152 (Baker et al.); U.S. Pat. No. 4,495,318 (Howard); U.S. Pat. No. 5,045,569 (Delgado); U.S. Pat. No. 5,073,457 (Blackwell); U.S. Pat. No. 5,571,617 (Cooprider et al.); U.S. Pat. No. 5,663,241 (Takamatsu et al.); U.S. Pat. No. 5,714,327 (Cooprider et al.); U.S. Pat. RE No. 37,563 (Cooprider et al.); U.S. Pat. No. 5,756,625 (Crandall et al.); U.S. Pat. No. 5,824,748 (Kesti et al.); and U.S. Pat. No. 5,877,252 (Tsujimoto et al.). In another embodiment, the repositionable pressure sensitive adhesive is polyacrylate-based microsphere adhesive. 
     FIG. 4  shows a bottom plan view of the substrate of  FIG. 3  with the perforated web  110  of  FIG. 2  disposed on the adhesive region of the substrate. In one exemplary method, the web  110  is aligned with the adhesive  204  of the substrate such that the perforations  118  on the perforated web substantially coincides with at least one of the upper and lower edges of the adhesive. 
     FIG. 4   a  shows a bottom plan view of a substrate  400 , similar that of substrate  200  of  FIG. 3 , laminated to a perforated web  310 . The substrate has a stripe of adhesive  404  on its second side  402 . The web includes a plurality of open sections or cutouts  312  interposed between a plurality of retained sections  314  connected to upper and lower carrier sections  316 . The retained sections have substantially the same geometry, each in the form of substantially a rectangle. Perforations  318  are disposed between the carrier section, the retained sections. The perforations span from one open section to the next adjacent open section and align with the top and bottom edges of the adhesive stripe of the substrate. Specifically, the patterned and perforated web of this figure includes substantially rectangular open sections, each having dimensions of 2.5 by 2.0 inch (6.4 by 5.1 cm). The distance between one open section to the next adjacent open section is 0.25 inch (6.4 mm). The corners of the open section are rounded to a 0.25 inch radius. And, the distance between a top and a bottom perforation is about 2.1 inch (5.3 cm). The design of the perforations is very similar to that described in  FIG. 2 . Thus, a wide variety of designs can be used for the perforated web. 
     FIG. 5  shows a cross-sectional view of the embodiment of  FIG. 4  taken along line  5 - 5  showing substrate  200  having opposing first and second surfaces,  201  and  202 . Disposed on the second surface of the substrate is adhesive  204  having top and bottom edges  204   a  and  204   b.  The patterned and perforated web includes retained section  114  attached to carrier section  116 . Interposed between the retained sections are open sections  112 . This cross-sectional view better shows that the retained portion  114  has a certain thickness, denoted as S 1 , which function to space or separate an exposed surface  204   c  of adhesive  204  from contacting an adjacent surface. Thus sheet  200  can be handled and moved across the adjacent surface without adhering thereto by adhesive  204 . Examplary adjacent surfaces include, but are not limited to, another sheet, a desktop, or a wall. In this way, the retained sections, which are non-adhesive forms a part of a securing mechanism, allowing the sheet to exhibit adhesion on demand. 
     FIG. 6  shows the embodiment of  FIG. 4  where the upper and lower carrier sections are being removed at the perforation. Typically the carriers are discarded after they have been removed. In one method, after the perforated web  110  has been attached to the adhesive  204  of the substrate, such a composite is laminated together using pressure and or heat to adhere more securely the web  110  to the adhesive. Upon removal of the carrier, the retained sections, which now have been effectively laminated to the adhesive, will not lift off when the carrier section is being removed. 
     FIG. 7  shows the embodiment of  FIG. 6  with both carrier sections removed leaving retained sections  115  (also referred to herein as “non-adhesive sections”) with portions spanning substantially from the upper edge  204   a  to the lower edge  204   b  of the adhesive as well as substantially the entire length of the adhesive stripe. This figure shows that the retained sections are in the form of a plurality of discrete “X”. Here, both legs of the “X” shaped retained section span from the top edge  204   a  of the adhesive to the bottom edge  204   b  of the adhesive. Furthermore, the retained sections span nearly the entire length of the adhesive portion. Other configurations can be used. For example, the retained sections can be in the form of geometric shapes that are substantially circles, squares, rectangles, other polygons, and combinations thereof. Furthermore, the line can be a continuous line a broken line, meaning that adhesive is exposed in between breaks in the line. 
     FIG. 8  shows another exemplary perforated web  510  having a plurality of open sections  512  interposed between a plurality of retained sections  514  connected to carrier sections  516 . The perforated web includes an upper carrier section that includes a top edge  510   a  and a lower carrier section that includes a bottom edge  510   b.  This particular design of the perforated web  510  facilitates the carrier section removal step. 
   In one embodiment, a plurality of substrates such as that of  FIG. 7  is assembled together to form a pad of substrates as shown in  FIG. 9 . Such a construction is typical of an easel pad  700 , typically having 25 to 50 sheets of the substrate  720  stacked and bound together at one end  701 , usually near the end of the adhesive region. The presence of the discrete sections disposed on the adhesive allows the sheets to be stacked without one sheet becoming substantially adhesively attached to the next subsequent sheet and thus the removal of a sheet can be done under substantially lower peel force. Furthermore, as a plurality of these sheets is used, e.g., for transcribing notes of a meeting, they are typically removed and displayed on a wall. At the end of the meeting, one participant usually collects the used sheets, stack them together, and optionally roll the sheets into a cylindrical tube for easy transport. The stacked sheets will typically not adhere to one another, unless a threshold force has been applied to the adhesive region. This adhesive on demand property provides the consumer with an added ease of use feature. 
   EXAMPLES 
   Example 1 
   A patterned and perforated web was made as follows. 
   A rotary die cutting apparatus available from Webtron Corp., Ft. Lauderdale, Fla., equipped with a vacuum trim removal system was used to make a 4.0 inch (10.2 cm) wide and a 0.002 inch (0.05 mm) thick general purpose polyethylene terephthalate available from Grafix Plastics, Cleveland, Ohio perforated web having the pattern shown in  FIG. 2  having open sections and retained sections attached to a carrier. In this example, the excising of the web and the perforation of the web occurred using the same rotary die and done in one step. 
   The perforated web was contacted to an adhesive stripe of a sheet of Post-it® Self-stick Easel Pad, Product No. 559, commercially available from 3M Company, St. Paul, Minn. The perforated web was attached to the sheet of easel paper such that the perforations substantially nearly coincided with a top and a bottom edge of the adhesive stripe. 
   Thereafter, the carrier of the patterned and perforated web was manually separated, collected, and discarded leaving the discrete retained sections behind with the sheet of easel paper. 
   Example 2 
   A patterned and perforated web was made as in Example 1, except that the resulting web had a design substantially similar to web  310  shown in  FIG. 4   a.    
   The patterned and perforated web was laminated to a sheet of Post-it® Self-stick Easel Pad, Product No. 559 as in Example 1 and the carrier of the web was separated leaving discrete retained sections behind with the sheet of easel paper. 
   Although specific embodiments of the present invention have been shown and described, it is understood that these embodiments are merely illustrative of the many possible specific arrangements that can be devised in application of the principles of the invention. Numerous and varied other arrangements can be devised in accordance with these principles by those of ordinary skill in the art without departing from the spirit and scope of the invention. Thus, the scope of the present invention should not be limited to the structures described in this application, but only by the structures described by the language of the claims and the equivalents of those structures.