Stock material or miscellaneous articles – Layer or component removable to expose adhesive
Reexamination Certificate
1997-07-15
2001-10-23
Ahmad, Nasser (Department: 1772)
Stock material or miscellaneous articles
Layer or component removable to expose adhesive
C428S041800, C428S041900, C428S345000, C428S352000, C428S354000, C428S409000, C428S913000, C503S226000
Reexamination Certificate
active
06306475
ABSTRACT:
TECHNICAL FIELD
The present invention generally relates to pressure-sensitive adhesive laminates wherein the silicone layer of a silicone-coated release liner is in direct contact with a pressure sensitive adhesive. More particularly, the present invention relates to regulation of the adhesive-silicone interface in order to control the release strength thereof. Specifically, the invention relates to regulation of such release strength through irradiation of the silicone-adhesive interface by ultraviolet (UV) light.
BACKGROUND OF THE INVENTION
It is generally known that pressure-sensitive adhesives (PSAs) can be applied to the back of a face material, known as a face sheet or face stock, and subsequently be laminated to the silicone coating of a backing sheet to form a pressure-sensitive adhesive laminate, referred to herein simply as a laminate. The adhesive can be applied onto a siliconized backing and then sandwiched onto the face material by lamination. These laminates typically have four layers: a face sheet, a PSA, also referred to herein as an adhesive, a silicone release coating and a backing sheet. The cured silicone is typically bonded strongly to the backing sheet to form what is collectively called a release liner, and the PSA bonds strongly to the face sheet. The PSA and silicone layers, however, bond relatively weakly and can be pulled apart easily.
Typically, it is desirable for the release liner to be easily removable, thereby exposing the free adhesive surface. Therefore, the release strength, which is a measure of the amount of force (the “release force”) required to remove the release liner, is generally very low. However, sometimes it is desirable to have higher release strength, or even permanent bonding of the release liner to the face sheet, in selected areas.
The patent literature discloses PSA laminates where the release strength is purported to be “controlled” by altering the composition of the adhesive or the release liner. By exposure of the silicone layer to UV light, bonding of the adhesive-silicone interface can be strengthened for some combinations of adhesive and silicone. Once the composition is manufactured and cured, however, the release strength can no longer be altered. Furthermore, there is no incremental control of release strength.
For example, Reding, U.S. Pat. Nos. 4,952,657, Kobayashi, 5,198,476, and Kessel, 5,217,805, each discloses a UV-cured silicone release coating with a release strength that is controllable by modiifing the silicone composition.
Yoshimura, U.S. Pat. No. 5,560,796, discloses UV curing an adhesive after applying it to a substrate. Although it also discloses coating the substrate with a silicone solution, it does not suggest controllable release of adhesive-silicone interface bonding based on relative amounts of UV exposure.
Another problem encountered in the prior art is that control of the geometric configuration of the areas of specific release strength is difficult to attain. Yet another problem encountered in the prior art is that control of a gradient of release in a specific zone of the PSA laminate is difficult to attain.
SUMMARY OF THE INVENTION
It is therefore an object of the present invention to provide a PSA laminate with an adhesive-silicone interface, the release strength of which can be increased with each increment of UV light exposure.
It is another object of the present invention to provide a PSA laminate that can be masked from UV light in any desired shape, thereby providing zones of high release and low release within the laminate.
It is yet another object of the present invention to provide a PSA laminate that is stable over time in the absence of UV light.
It is still another object of the present invention to provide a PSA laminate whose adhesive can be selectively cleaved by delamination into two sticking labels.
It is another object of the present invention to provide a PSA laminate whose ungummed areas can be designed by irradiation of UV light onto the laminate through a mask.
It is still another object of the present invention to provide a PSA laminate whose release at the two adhesive-silicone interfaces can be independently and selectively increased in specific zones by irradiation of UV light through two masks.
It is still yet another object of the present invention to provide a PSA laminate with a UV-written signature that is invisible until the label is removed from the substrate.
It is yet another object of the present invention to provide a PSA laminate whose free adhesive zones can be selectively designed by UV light.
It is still another object of the present invention to provide a PSA laminate with a gradient of release strength in a specific zone.
It is yet a further object of the present invention to provide a PSA laminate whose release strength can be controllably enhanced long after production of the laminate.
At least one or more of the foregoing objects, together with the advantages thereof over the known art relating to the controlled release strength of PSA laminates, which shall become apparent from the specification which follows, are accomplished by the invention as hereinafter described and claimed.
In general, the present invention provides a pressure-sensitive adhesive laminate comprising an adhesive layer, a first face sheet contacting one side of the adhesive layer, and a first silicone layer contacting the side of the adhesive layer opposite the face sheet wherein the force required to separate the adhesive layer and the first silicone layer increases upon application of ultraviolet light to the interface between the adhesive layer and the first silicone layer. The present invention also provides a method of enhancing the release strength between an adhesive layer and a silicone layer using ultraviolet light.
REFERENCES:
patent: 4952657 (1990-08-01), Riding et al.
patent: 5198476 (1993-03-01), Kobayashi et al.
patent: 5217805 (1993-06-01), Kessel et al.
patent: 5560796 (1996-10-01), Yoshimura
Francois Jean-Marc C.
Stocq Robert G.
Ahmad Nasser
Morgan Adhesives Company
Renner Kenner Greive Bobak Taylor & Weber
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