Stock material or miscellaneous articles – Web or sheet containing structurally defined element or... – Composite having voids in a component
Reexamination Certificate
1999-07-06
2001-08-21
Acquah, Samuel A. (Department: 1711)
Stock material or miscellaneous articles
Web or sheet containing structurally defined element or...
Composite having voids in a component
C525S088000, C525S090000, C525S09200D, C525S094000, C525S100000, C525S101000, C525S107000, C525S185000, C525S234000, C524S081000, C524S403000, C524S442000, C428S221000, C428S304400, C428S305500, C428S312600, C428S312800, C428S317700, C428S319300
Reexamination Certificate
active
06277481
ABSTRACT:
FIELD OF THE INVENTION
The present invention relates to a novel adhesive composition and adhesive sheet. More particularly, the present invention relates to an adhesive composition which is excellent in storage stability and can bond metals, etc. with large bonding strength and whose sheeting enables simplifying bonding steps, and relates to an adhesive sheet comprising the composition.
BACKGROUND OF THE INVENTION
The epoxy resin adhesive has most widely been used to bond metals with each other. However, bonding with satisfactory strength cannot always be accomplished by the epoxy resin adhesive because a lowering of bonding strength may be caused by, for example, the shrinkage of epoxy resin adhesive at the time of curing reaction. In particular, when the epoxy resin adhesive is of one component adhesive type, and a trigger such as heat is employed at the time of curing reaction, the bonding strength tends to decrease because internal stress is centralized at the bonding portion due to the difference in thermal expansion coefficient from those of metals as adherends.
Moreover, the epoxy resin adhesive is generally liquid, so that the bonding step is likely to become burdensome. That is, it is difficult to apply an appropriate amount of adhesive to an adherend surface, and problems such as liquid runs are encountered.
In order to resolve these problems of the liquid adhesive, various sheeted adhesives have been developed and put on the market. However, the conventional sheeted adhesives have drawbacks in that their storage stability is poor and, when bonding and curing are conducted after long-term storage, satisfactory bonding strength (peeling strength) cannot be obtained.
The present invention has been made taking the above prior art into account. Accordingly, the present invention provides an adhesive composition which is excellent in storage stability and can bond metals, etc. with large bonding strength and whose sheeting enables simplifying bonding steps, and provides an adhesive sheet comprising the composition.
SUMMARY OF THE INVENTION
The adhesive composition of the present invention comprises a pressure sensitive adhesive component (A), a thermosetting adhesive component (B) and a compound (C) obtained by addition/condensation reaction of a polysiloxane oligomer with a silane coupling agent.
According to necessity, the adhesive composition of the present invention can further be blended with a flexible component (D), a heat-active latent curing agent (E), a matrix forming component (F) and/or a filler (G). The filler (G) is preferably a conductive filler.
The above adhesive composition of the present invention is excellent in storage stability, can bond metals, etc. with large bonding strength and can be sheeted with the result that an appropriate amount of adhesive can be transferred to an adherend surface and liquid runs can be avoided to thereby enable simplifying the bonding steps.
Thus, the adhesive sheet of the present invention comprises the adhesive composition of the present invention.
DETAILED DESCRIPTION OF THE INVENTION
The adhesive composition of the present invention and the method of using the same will be described in detail below.
The adhesive composition of the present invention comprises, as essential components, a pressure sensitive adhesive component (A), a thermosetting adhesive component (B) and a compound (C) obtained by addition/condensation reaction of a polysiloxane oligomer with a silane coupling agent. According to necessity, the adhesive composition of the present invention can further be loaded with a flexible component (D), a heat-active latent curing agent (E), a matrix forming component (F) and/or a filler (G).
Various common pressure sensitive adhesives can be used as the pressure sensitive adhesive component (A) without any particular limitation. In the present invention, acrylic, rubber and polyester pressure sensitive adhesives are preferably used. Of these, acrylic pressure sensitive adhesives are especially preferred.
Examples of the acrylic pressure sensitive adhesives include (meth)acrylic ester copolymers whose structural units are derived from a (meth)acrylic ester monomer and a (meth)acrylic acid derivative. Cycloalkyl (meth)acrylates, benzyl (meth)acrylate and alkyl (meth)acrylates having an alkyl group of 1 to 18 carbon atoms can be used as the (meth) acrylic ester monomer. Of these, alkyl (meth)acrylates having an alkyl group of 1 to 18 carbon atoms can be used as the (meth)acrylic ester monomer. For example, methyl acrylate, methyl methacrylate, ethyl acrylate, ethyl methacrylate, propyl acrylate, propyl methacrylate, butyl acrylate and butyl methacrylate are especially preferred. The (meth)acrylic acid derivative can be selected from among, for example, (meth)acrylic acid, hydroxyethyl (meth)acrylate and glycidyl (meth)acrylate.
When glycidyl (meth)acrylate is used as the (meth) acrylic acid derivative, the content of units derived from the glycidyl (meth) acrylate in the obtained copolymer is generally in the range of 0 to 80 mol %, preferably 5 to 50 mol %. The incorporation of the glycidyl group increases the compatibility with the below described epoxy resin as the thermosetting adhesive component and also increases the temperature Tg after curing and the heat resistance. When (meth)acrylic acid is used as the (meth)acrylic acid derivative, the content of units derived from (meth)acrylic acid in the obtained copolymer is generally in the range of 0 to 40 mol %, preferably 5 to 20 mol %. The incorporation of a hydroxyl containing monomer such as hydroxyethyl acrylate facilitates the controlling of adherence to adherends and pressure sensitive adhesive properties.
The molecular weight of the acrylic pressure sensitive adhesives is preferably at least 100,000, still preferably in the range of 150,000 to 1,000,000. The glass transition temperature of the acrylic pressure sensitive adhesives is generally up to 20° C., preferably in the range of approximately −70 to 0° C. At ordinary temperature (23° C.), the acrylic pressure sensitive adhesives have pressure sensitive adhesive properties.
The thermosetting adhesive component (B) is capable of forming a three-dimensional network upon being heated, although not cured by energy radiation, to thereby possess properties of bonding adherends with large strength. This thermosetting adhesive component (B) generally consists of a thermosetting resin such as an epoxy resin, a phenolic resin, a resorcinol resin, a urea resin, a melamine resin, a furan resin, an unsaturated polyester resin, a polyurethane resin or a silicone resin. Various thermosetting adhesive components are known, and these can be used in the present invention without any particular limitation. In the present invention, epoxy resins are especially preferably used as the thermosetting adhesive component (B).
Although various common epoxy resins can be used as the above epoxy resin, it is generally preferred to employ those having a molecular weight of about 300 to 2000, especially blends of an ordinarily liquid epoxy resin of 300 to 1000, desirably 330 to 800, in molecular weight and an ordinarily solid epoxy resin of 400 to 2500, desirably 800 to 2000, in molecular weight. The epoxy equivalent of epoxy resins preferably employed in the present invention is generally in the range of 50 to 5000 g/eq. Examples of these epoxy resins include:
glycidyl ethers of phenols such as bisphenol A, bisphenol F, resorcinol, phenylnovolak and cresol novolak;
glycidyl ethers of alcohols such as butanediol, polyethylene glycol and polypropylene glycol;
glycidyl ethers of carboxylic acids such as phthalic acid, isophthalic acid and tetrahydrophthalic acid;
glycidyl or alkylglycidyl epoxy resins obtained by substituting an active hydrogen bonded to a nitrogen atom of aniline isocyanurate or the like with a glycidyl group; and
compounds, known as alicyclic epoxides, obtained by, for example, oxidizing an intramolecular carbon to carbon double bond to thereby incorporate an epoxy group therein, such as vinylcyclohexane diepo
Nakata Yasukazu
Senoo Hideo
Sugino Takashi
Acquah Samuel A.
Lintec Corporation
Webb Ziesenheim & Logsdon Orkin & Hanson, P.C.
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