Stock material or miscellaneous articles – Layer or component removable to expose adhesive
Reexamination Certificate
1997-10-24
2001-01-16
Robinson, Ellis (Department: 1772)
Stock material or miscellaneous articles
Layer or component removable to expose adhesive
C428S040900, C428S041500, C428S041700, C428S041800, C428S343000, C428S354000, C428S3550RA, C428S461000, C428S446000, C428S450000, C156S275100, C156S275700, C156S307700, C264S241000, C264S603000
Reexamination Certificate
active
06174578
ABSTRACT:
FIELD OF THE INVENTION
The invention relates to an adhesive tape useful in the manufacture of ceramic articles, and particularly ceramic electronic components such as capacitors.
BACKGROUND OF THE INVENTION
Certain types of ceramic capacitors are manufactured by laying up multiple thin layers of a ceramic insulator material alternating with thin electrically conductive layers. The conductive layer may, for example, take the form of a pattern screen printed with a conductive ink composition. The ceramic insulator layer is typically composed of inorganic and organic materials in an unfired or “green” form. The layered conductor/insulator structure is then heated fire or sinter the ceramic composition and the alternating layered conductor/insulator structure fuses into a monolithic article.
To facilitate handling during the manufacturing operation, an adhesive tape has been used to adhere a first green ceramic layer to a rigid carrier such as a metal plate. Then, alternating conductive layers and green ceramic insulating layers are stacked upon the first ceramic layer, and the layered structure is pressed and consolidated. Subsequently, the layered structure may be cut or diced to form individual discrete capacitors. Thereafter, the layered structures are fired or sintered to harden the ceramic and unite the layered structure.
In the manufacturing process, the adhesive tape is relied upon to firmly hold the layered structure to the carrier during the various processing steps of laying up, printing, dicing, etc. Before the ceramic articles have been fired however, they must be removed from the carrier without damage.
Conventional adhesive tapes used heretofore for this purpose have typically employed a heat curable adhesive. The adhesive loses its adhesive characteristic when heated under certain time and temperature conditions, thus allowing for release of the ceramic material from the adhesive tape. However, with this type of tape, the temperatures which can be used during the laminating or drying operations are limited by the properties of the tape. Laminating the ceramic layers at higher temperatures would better adhere the layers to one another. However, these higher temperatures that would help the ceramic layers adhere to one another can also cause the adhesive tape to prematurely release the ceramic articles from the carrier. Also, the time required to effect deactivation of the adhesive and release of the ceramic articles by heating is a limitation upon manufacturing throughput.
It is an object of the present invention to overcome the limitations of the prior conventional adhesive tapes just described. More particularly, it is an object of the present invention to provide an adhesive tape which can be used at higher temperatures than heretofore without allowing the tape to prematurely release from the carrier.
SUMMARY OF THE INVENTION
The present invention provides an adhesive Tape which is capable of withstanding high temperatures and wherein its adhesive characteristics can be deactivated by exposure to actinic radiation, such as ultraviolet light. Broadly, an adhesive tape in accordance with the present invention comprises a substrate and a first adhesive layer on one surface of the substrate. This adhesive layer comprises a heat stable adhesive composition. A second adhesive layer is provided on the opposite surface of the substrate, with this second adhesive layer comprising a heat stable radiation curable adhesive composition which loses its adhesive characteristics upon exposure to radiation. The tape is adhered to a rigid carrier by the first adhesive layer, and a green ceramic article is adhered to the second adhesive layer. The adhesive tape firmly holds the ceramic layer in place on the carrier during the manufacturing operation. After dicing of the ceramic article, when it is desired to release the ceramic articles from the carrier, the second adhesive layer may be exposed to radiation, thereby causing the adhesive properties of the second adhesive to be deactivated and allowing for release o the ceramic articles.
In one embodiment of the invention, the adhesive tape employs a substrate formed of a heat stable polyester film having a reflective metallized coating on one surface thereof. On one surface of the film substrate, there is provided a first adhesive layer of a heat stable pressure sensitive acrylic adhesive composition. This adhesive layer is intend for adhering the tape to a rigid carrier, such as a metal plate. On the opposite surface of the polyester film substrate, a second adhesive layer is provided. This second adhesive layer comprises a heat stable, radiation curable acrylic pressure sensitive adhesive composition in which the pressure sensitive adhesive characteristics are deactivated upon exposure to radiation. Preferably, this second adhesive layer has dispersed in it a finely divided particulate filler which serves for scattering light and thus facilitates distributing ultraviolet light throughout the second adhesive layer when the tape is exposed to ultraviolet light for curing. This makes it possible to cure the second adhesive by exposing ultraviolet light to the tape from the top side, i.e. the side to which the ceramic articles are adhered. Preferably, the ceramic articles are adhered to the tape with marginal edges of the tape protruding beyond the perimeter of the ceramic article. When exposed to ultraviolet radiation these protruding marginal edge portions, coupled with the presence of the light dispersing filler, allows the radiation to be dispersed laterally throughout the second adhesive layer to achieve deactivation of the adhesive.
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Alston & Bird LLP
Figueroa John J.
Rexam Industries Corp.
Robinson Ellis
LandOfFree
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