Adhesive bonding and miscellaneous chemical manufacture – Methods – Surface bonding and/or assembly therefor
Reexamination Certificate
2000-03-17
2002-12-10
Mayes, Curtis (Department: 1734)
Adhesive bonding and miscellaneous chemical manufacture
Methods
Surface bonding and/or assembly therefor
C156S247000, C040S594000
Reexamination Certificate
active
06491781
ABSTRACT:
FIELD OF INVENTION
This invention relates to combined adhesive/substrate systems for placement and removal of image graphics.
BACKGROUND OF INVENTION
Image graphics are omnipresent in modern life. Images and data that warn, educate, entertain, advertise, etc. are applied on a variety of interior and exterior, vertical and horizontal surfaces. Nonlimiting examples of image graphics range from posters that advertise the arrival of a new movie to warning signs near the edges of stairways.
Readily replaceable image graphics are needed for those occasions when the length of time the graphic needs to remain at the intended location is limited to a short duration, often with a replacement image graphic substituting for the image graphic to be removed. An example of an expected replacement image graphic is the movie poster identified above.
Readily replaceable image graphics require both the “staying power” when placed on the horizontal or vertical surface and the “leaving ease” when the image graphic is to be removed.
Among different kinds of readily replaceable image graphics are films that have an image on one major surface and a field of adhesive on the opposing major surface. Again, movie posters and other bills are often adhered to a surface. If the adhesive is pressure sensitive and capable of being readily removed without leaving adhesive residue, then the poster can be posted and has staying power but is removed with ease.
While there are numerous methods of mounting image graphic films to a substrate, two methods that represent the present state-of-the-art are: Pressure Sensitive Adhesive (PSA) coated image-bearing substrates and mechanically fastened graphics. PSA coated substrates typically consist of a PSA coated onto a polymer film such as plasticized polyvinyl chloride (PVC) or high quality paper stock, which are supplied on a siliconized release paper to protect the PSA.
Mechanically fastened graphics can take many forms, examples of which maybe printed paper stock that is simple stapled to a desired substrate, printed cardboard or rigid polymer sheeting such as Plexiglas™ which can be mounted in position using nail, staples, clips or other methods, or even a PSA coated graphic that can be mounted on a rigid carrier such as cardboard and similarly mounted. Such graphics can also be mounted using magnets or small pieces of hook and loop fastener as described in U.S. Pat. No. 4,999,937 (Bechtold). Other mechanical fasteners are disclosed in U.S. Pat. Nos. 5,196,266 and 5,316,849 (both Lu et al.). Alternatively, the hook and loop construction can reside on an opposing major surface of a film that can also be printed on directly, as described in PCT International Patent Publication WO US98/39759 (Loncar).
Additionally, four types of systems bear special mention.
First, the manufacture of double-sided sheets frequently employ a release liner spirally wound with the sheet itself. To the extent that the liner has images or printed information, that liner is interacting with an adhesive but only for the duration of storage until use. Once the sheet is placed in use, the printed release liner is discarded. PCT Publication WO 97/07492 discloses a method of securing a picture on a movable picture carrier using a fastening means comprising a double-sided carrier with differing amounts of adhesion on each of the two sides. This publication uses double-sided sheets in key perimeter locations on picture to secure the picture to the carrier.
Second, 3M Post-It™ Memoboard #558 (Minnesota Mining and Manufacturing Company (“3M”) of St. Paul, Minn., USA) provides a substrate having an exposed major surface of “repositionable” adhesive upon which individual pieces of paper or film as memos or notes can be adhered. The repositionability of notes on the major surface means that the adhesive is designed to have a low and limited amount of holding power.
Further, as the exposed major surface of adhesive becomes contaminated with dirt, oils etc., the adhesive can not be cleaned to restore its original holding power. In contrast, a pressure-sensitive display board is disclosed in U.S. Pat. No. 3,952,133 (Amos et al.), where a bulletin board, display panel, or other posting device has a pressure-sensitive adhesive surface on a thick resilient backing with the pressure sensitive adhesive being preferably a water-washable tacky elastomer. However, this display board is intended to permit adhesion of all types of materials including pens, keys, paper, small notebooks, and other disparate items (both light and heavy in mass). Thus, almost any item could conceivably adhere indiscriminately to the pressure-sensitive adhesive surface.
Third, cling vinyl graphics bear special mention. The substrate to which cling vinyl image graphics bond is limited in adhesion to extremely smooth surfaces such as glass, which makes a bond that has very low adhesive holding power. In addition, while not a PSA, the cling vinyl is generally supplied on a release liner in order to prevent blocking (material sticking to itself), and sticking to smooth surfaces such as metal printer equipment.
Fourth, U.S. Pat. No. 5,462,782 (Su et al.) discloses a target adhesive layer that can only be bonded to the same limited number of surfaces that are available to cling vinyl, where such surfaces have exposed adhesive having a tack that attracts dirt and can not be washed to restore the original adhesion of the adhesive. In another system, PCT Publication WO 95/06692 (Fuji) discloses a self adhesive film, that adheres to itself but not to other materials.
Image graphics using pressure sensitive adhesive surfaces, while extremely versatile, can encounter a number of limitations. First is that the inherent tackiness of the adhesive causes problems in applying the graphic smoothly and evenly to the surface. If the graphic is misaligned or wrinkled during application, the graphic must be removed and reapplied. In the worst case, the graphic can be damaged removing it, which means the graphic needs to be replaced with a new graphic, a considerable expense. Improvements such as contained in Controltac™ branded films sold by 3M have special adhesives to limit the initial adhesion, and thus allow limited repositionability. Repositionability of an adhesive is also described in U.S. Pat. No. 5,296,277 (Wilson et al.). Moreover, a multi-cycle refastenable contact responsive non-tacky fastener system is disclosed in PCT Publication WO 94/21742 (Kobe et al.).
While the use of special adhesive formulations definitely provides assistance in the initial placement of the graphics, these improved adhesives are not designed specifically for problems such as wrinkles that show up after the major portion of a graphic has been applied.
To assist in the removal of wrinkles, the adhesive can be further modified to limit tack, either chemically such as altering the glass transition temperature (Tg) of the adhesive composition, or physically, such as pattern coating or using microspheres. One approach taken using physical modification is disclosed in PCT Patent Publication WO 98/29516 (Sher et al.). However, this approach ends up causing a second limitation in image graphics using pressure sensitive adhesives: the adhesive must bond acceptably to numerous substrates for the intended application.
In most cases, commercially available pressure sensitive adhesives will bond acceptably to some substrates but have high adhesion to others. Moreover, when an adhesive is formulated to be removable, the situation worsens, because the adhesive can have three possible levels of adhesion: too high, too low or acceptable. Therefore, pressure sensitive adhesives are often formulated with a compromise in performance that all too often is not optimum for a particular application.
For the situation when graphics are applied to a variety of substrates, a variety of films with different pressure sensitive adhesive formulations may be needed to complete the job. This results in more logistical problems for the customer.
Another issue facing films that have an image on one majo
Kreckel Karl Werner
Kuester Wilhelm
Mueller Bruno
3M Innovative Properties Company
Christoff James D.
Mayes Curtis
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