Stock material or miscellaneous articles – Layer or component removable to expose adhesive
Reexamination Certificate
1998-10-07
2001-06-12
Ahmad, Nasser (Department: 1772)
Stock material or miscellaneous articles
Layer or component removable to expose adhesive
C423S448000, C428S040200, C428S143000, C428S319100, C428S323000, C428S408000
Reexamination Certificate
active
06245400
ABSTRACT:
BACKGROUND OF THE INVENTION
1. Field of the Invention
The present invention relates to a release lined pressure sensitive adhesive (PSA) flexible graphite product and, in particular, to a release lined PSA flexible graphite sheet article for thermal interface applications wherein the thermal properties of the flexible graphite sheet article are not significantly affected by a pressure sensitive adhesive used to bond the flexible graphite and which release liner is easily removed when the sheet is to be used without any significant delamination of the flexible graphite.
2. Description of Related Art
Flexible graphite is a well-known material used in a variety of industrial, commercial and domestic applications because of its chemical inertness and unique electrical and thermal conduction properties. It is of particular use as a gasketing or sealing material in automobile engines, piping flanges and vessel joints and as a fire proof covering for walls or floors, filtering devices for an air bag for generators, etc. wherein thin flexible graphite sheets between typically 2-70 mil are cut into various sizes to use from the product.
The process for manufacturing flexible graphite is well-known and the typical practice is described in U.S. Pat. No. 3,404,061 to Shane et al., the disclosure of which is incorporated herein by reference. In general, flakes of natural graphite are intercalated in an acid solution. After the flakes are intercalated they are washed and dried and then exfoliated by exposure to a high temperature or under a flame for a short period of time. This causes the flakes to expand or exfoliate in a direction perpendicular to the crystalline planes of the graphite. The exfoliated graphite flakes are vermiform in appearance and are therefore commonly referred to as worms. The worms may be compressed into sheets or foils with a density approaching theoretical density although a density of about 70 lbs/ft
3
is considered typical for most applications. The sheets of flexible graphite can be cut into any desired configuration to suit a particular application.
New applications requiring a low thermal resistance interface sheet material include thermal joints and heat sinks A typical use is to thermally connect a computer chip to a cooling module. Flexible graphite is readily applicable to such applications because of its low thermal resistance and its ability to conform to the surfaces to be interfaced, especially when either or both surfaces are not completely flat. Prior art self bonding flexible graphite sheet articles typically use a PSA backing with a Mylar film as the adhesive carrier. This type sheeting however is not desirable for applications requiring low thermal resistance because the adhesive carrier cannot be cut and processed easily and the adhesive carrier has an extremely high thermal resistance. Additionally, twice the amount of adhesive is needed since there is adhesive on both sides of the Mylar carrier film. The sheeting also lacks mechanical integrity since the carrier film and adhesive typically readily separate from the flexible graphite substrate.
Bearing in mind the problems and deficiencies of the prior art it is therefore an object of the present invention to provide a release lined pressure sensitive adhesive flexible graphite article of manufacture and, in particular, a thermal interface sheet article having a low thermal resistance and which release liner is easily removed when the sheeting is to be used without any significant delamination of the flexible graphite substrate.
It is another object of the present invention to provide a method of making a release lined pressure sensitive adhesive flexible graphite article of manufacture, particularly a thermal interface sheet article having a low thermal resistance and which release liner is easily removed when the sheeting is to be used without any significant delamination of the flexible graphite substrate.
Still other objects and advantages of the invention will in part be obvious and will in part be apparent from the specification.
SUMMARY OF THE INVENTION
The above and other objects and advantages, which are apparent to one of skill in the art, are achieved in the present invention which is directed to, in a first aspect, an article of manufacture having low thermal resistance as a release lined pressure sensitive adhesive flexible graphite thermal interface sheet article having low thermal resistance when compared to a sheet of flexible graphite and flexible graphite PSA prior art sheet articles comprising:
a flexible graphite substrate having a surface for receiving an adhesive primer coating;
an adhesive primer coating on the flexible graphite substrate surface which adheres to the flexible graphite;
a pressure sensitive adhesive coating on the adhesive primer coating which is adherent to the adhesive primer coating; and
a release liner on the pressure sensitive adhesive coating which release liner is easily removed when the sheet is to be used without any significant delamination of the flexible graphite substrate.
In another aspect of the present invention the release lined pressure sensitive adhesive flexible graphite article comprises a pressure sensitive adhesive coating on each side of the flexible graphite substrate providing a double sided pressure sensitive adhesive flexible graphite article of manufacture.
In a further aspect of the invention, a method is provided for making a release lined pressure sensitive adhesive flexible graphite article of manufacture, including thermal interface sheet articles having a low thermal resistance when compared to a sheet of flexible graphite sheet and prior art flexible graphite PSA sheet articles comprising:
supplying a flexible graphite substrate having a surface for receiving an adhesive primer coating;
applying a coating of an adhesive primer on the flexible graphite substrate surface which adheres to the flexible graphite;
applying a pressure sensitive adhesive coating on the adhesive primer coating to adhere the pressure sensitive adhesive coating to the adhesive primer coating; and
applying a release liner on the pressure sensitive adhesive coating which release liner is easily removed when the article is to be used without any significant delamination of the flexible graphite substrate.
In another aspect of the invention, the release liner may be applied as a pressure sensitive adhesive containing transfer tape comprising a liner, a release material such as silicone on the liner and a pressure sensitive transferable adhesive on the release material. Thus, both the pressure sensitive adhesive and release liner may be applied in one step to form the sheet article of the invention.
In a further aspect the present invention relates to a method of using the release lined pressure sensitive adhesive flexible graphite article of manufacture which comprises removing the release liner from the pressure sensitive adhesive surface and then pressing the article onto a surface to which the article is to be bonded.
REFERENCES:
patent: 3404061 (1968-10-01), Shane et al.
patent: 4895713 (1990-01-01), Greinke et al.
patent: 4961991 (1990-10-01), Howard
patent: 5130199 (1992-07-01), Howard
patent: 5149518 (1992-09-01), Mercuri et al.
patent: 5176863 (1993-01-01), Howard
patent: 5198063 (1993-03-01), Howard et al.
patent: 5443894 (1995-08-01), Pollock et al.
patent: 5494506 (1996-02-01), Ford et al.
patent: 1583200 (1969-10-01), None
patent: 03202342 (1991-09-01), None
patent: 05286105 (1993-11-01), None
patent: 08253760 (1996-10-01), None
patent: 11058591 (1999-03-01), None
Getz, Jr. George
Tzeng Jing-Wen
Weber Thomas William
Ahmad Nasser
McCarthy Frederick J.
UCAR Graph-Tech Inc.
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