Stock material or miscellaneous articles – Layer or component removable to expose adhesive – Protective layer
Reexamination Certificate
1998-10-28
2002-10-08
Pyon, Harold (Department: 1772)
Stock material or miscellaneous articles
Layer or component removable to expose adhesive
Protective layer
C428S040100, C428S202000, C428S203000, C156S297000, C156S299000, C040S615000, C160S370210, C296S095100
Reexamination Certificate
active
06461709
ABSTRACT:
FIELD OF THE INVENTION
This invention relates to an article comprising a transparent stack of sheets that may be applied, for example, to protect substrates such as glass or plastic windows, signage or displays. A topmost sheet can be peeled away after it is damaged to reveal an undamaged sheet below. The invention also relates to a method of protecting substrates such as glass or plastic windows, signage and displays from vandalism or other surface damage by adhering the stack of sheets to the substrate to be protected and subsequently pulling a topmost sheet away from the stack after it becomes damaged.
BACKGROUND OF THE INVENTION
Windows and glass in public transportation vehicles such as buses or subway trains can be subjected to a tremendous amount of abuse. The windows can be damaged by both incidental scratching during cleaning or they can be maliciously damaged by vandalism. Vandals damage the windows by scratching or abrading the surface of the window with items such as lava rock, diamonds, abrasive papers or abrasive cloths. Vandals can also damage the window by painting or coloring the surface of the window. Cleaning processes have been defined to eliminate damage by painting or coloring. However, scratching of glass by vandals presents a significant problem. In one major city, for example, approximately 40 percent of the bus windows have been vandalized by scratching and close to 80 percent of the subway train windows. The public transportation officials now call this type of graffiti “scratchiti”. The best approach to stopping graffiti historically has been to remove the graffiti immediately once it appears. This graffiti prevention system which is known as “zero tolerance”, has been extremely successful in eliminating the written and painted vandalism. Scratched glass, however, is extremely difficult and expensive to repair and as a result, the zero tolerance approach to scratchiti prevention and elimination is cost prohibitive. The vandalism issue tarnishes the overall image of an entire city's transportation system. The vandalized glass leads to lower ridership because of the reduced perception of safety on the vehicle by the public. The vandalism ultimately leads to lost revenue for the public transportation system and substantially high repair costs.
Several approaches have been evaluated to combat the scrachiti problem. The first approach has been to repair the glass by a multi-step abrasion/polishing method to remove the scrachiti. The abrasion steps remove glass to the depth of the scratch with diamond abrasives and then with subsequently finer grades of diamond or aluminum oxide abrasives the surface of the glass is polished to its original appearance. The abrasive materials are expensive and the time required to completely abrade and polish the surface of the glass can be several hours depending on the depth of the damaged areas.
A second approach to eliminating the problem has been to apply a single permanent adhesive coated polyester sheet onto the surface of the window. The polyester sheet is thick enough to protect the window from scratching by diamonds, lava rocks and most abrasives. The sheet is typically applied onto the glass with a water solution to eliminate any trapped air. The application process takes about 5 to 10 minutes to complete. The sheet does a good job of protecting the window from most of the damage but the sheet is readily damaged and the damage is visible to the passengers. Removing the sheet is very time consuming taking about 15 to about 60 minutes depending on the amount of residue left on the window after removal of the sheet. Once the damaged sheet is removed, a new permanent adhesive coated polyester sheet needs to be applied. The time required to remove the adhesive coated polyester sheet, remove the adhesive residue from the glass, and apply a new permanent adhesive coated polyester sheet and reinstall the window can be close to 2 hours. Examples of single permanent adhesive coated polyester sheets which can be used to protect a window are 3
M™ Scotchshield™ Safety and Security Window Film and
3
M™ Sun Control Window Films, data sheet number
70-0703-7220-0 published in September 1996 by the 3M Company.
The replaced sheet can be quickly damaged once the vehicle is used again in public thus necessitating another costly and time consuming replacement.
The third approach commonly used to repair and protect windows from scratches is to coat the damaged window with an epoxy coating. (
Enhancement of Vehicle Glazing for Vandal Resistance and Durability,
by Daniel R. Bowman, Mar. 25, 1996, available from the United States Transportation Research Board). The damaged window is typically first scrubbed clean before coating with an epoxy coating. The epoxy coating can be used to fill the defects on the windows and restore the window to a state of clarity where signs can be read through the window. To apply the coating, the window must be removed from the vehicle and the window must be cleaned and primed. The coatings are applied and cured in a clean environment. The coatings currently available however are easily scratched by the same method used to scratch the glass. Once the coating is damaged, it is difficult to apply a subsequent coating due to poor adhesion of the coating to the first layer. The process to replace the damaged coating with a new coating is time consuming and expensive.
Another approach to the problem is to apply a sacrificial window as a shield over an original non-damaged window. The vehicle's window is modified with a frame that has a channel designed for a sheet of polycarbonate or acrylic. The rigid self-supporting sheet is inserted into the channel and acts as a barrier to damage on the base window. The polycarbonate sheet can be easily scratched by intentional methods being used to scratch the glass. This approach requires extensive modification to the window frame. Furthermore, the material cost per repair can be excessive making this approach cost prohibitive.
U.S. Pat. No. 3,785,102 discloses a pad comprising a plurality of very thin polyethylene or polypropylene removable sheets, each sheet bearing a very thin coating of pressure sensitive adhesive on its top surface for removing dirt from shoes and an adhesive at the bottom surface so that each successive layer is removably adhered to successive bottom layers and eventually to the floor. There is no discussion regarding the clarity of such a pad.
3M Masking and Packaging Systems Division sells a stack of sheets with adhesive that removes lint and pet hair under the trade names
Pat It™ Lint and Pet Hair Remover, product data sheet numbers
70-0705-7091-9, 70-0705-0819-0
and
70-0705-7038-0 published by 3M Company in 1994.
Research Disclosure 24109 (May 1984) discloses transmissive strippable plastic sheets stacked on mirror surfaces or stacked reflective (mirror surfaced) strippable plastic sheets that can be removed successively as toner or dust build up on the mirrors used in the optical imaging systems of electrophotographic reproduction apparatus occurs. The adhesive joining the layers to one another are provided only about the border areas of the sheets which are outside the optical image path to minimize image quality losses.
JP 10167765A describes a method of cleaning windows by the application of an optically clear sheet of plastic film on the inner and outer surface of the glass. The film is comprised of polyvinyl chloride, polyacrylic acid, polyester or polycarbonate. The plastic film is thin and only a single sheet of plastic is described on each side of the glass. The sheet is removed when the sheet becomes soiled.
U.S. Pat. No. 5,592,698 discloses a tear away lens stack for maintaining visibility through a transparent protective eye and face shield of a racing vehicle drivers helmet which includes a tab portion having projections formed thereon to assist in grasping the tab portion for rapid tear away. No adhesive is used in the stack; rather the lenses are clipped together.
A need thus exists for an article and a method for
Everaerts Albert I.
Janssen Jeffrey R.
O'Keefe Donald R.
Sheffield William F.
3M Innovative Properties Company
Miggins Michael C.
Pribnow Scott R.
Pyon Harold
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