Adhesive bonding and miscellaneous chemical manufacture – Methods – Surface bonding and/or assembly therefor
Reexamination Certificate
2000-05-25
2001-12-18
Dawson, Robert (Department: 1712)
Adhesive bonding and miscellaneous chemical manufacture
Methods
Surface bonding and/or assembly therefor
C523S461000, C525S452000, C525S528000, C528S059000, C528S067000
Reexamination Certificate
active
06331226
ABSTRACT:
BACKGROUND OF THE INVENTION
1. Field of the Invention
The present invention relates to a method for bonding LCP and, more specifically, to a method for bonding LCP using an adhesive which has heat resistance and excellent adhesion to an LCP.
2. Description of the Related Art
An LCP (Liquid Crystalline Polymer) is attracting much attention even in the field of electronic materials because a highly elastic material is obtained when a molded product is produced therefrom and the LCP has high heat resistance and chemical resistance, due to the high crystallinity of the resin.
Meanwhile, an epoxy resin is widely used as a main raw material in the field of adhesives because a shrinkage of the epoxy resin is small when the epoxy resin is cured and it has excellent adhesion to metals.
However, it is known that a thermosetting adhesive typified by a general-purpose adhesive put on the market has poor adhesion to an LCP. For example, in case an LCP is used as a package material for electronic parts when the parts are mounted on a substrate, there is no thermosetting adhesive having sufficient strength obtained by bonding a substrate to a package. Therefore, its application field is very narrow at the moment.
In contrast to this, attempts have been made to enhance adhesion properties and improve bonding properties by the modification of an LCP itself (Japanese Patent Application Laid-open No. Hei 5-140431). However, this method in which 20 to 1 wt % of an alkylene ether is mixed on 80 to 99 wt % of an LCP impairs heat resistance that is one of the characteristic properties of the LCP and involves problems with solvent resistance and general applicability. Although the improvement of adhesion between an epoxy resin and an LCP by this modification is confirmed, thorough discussions have not been made on interface retention properties that is most important in adhesion between an adhesive and the LCP to be bonded. As an adhesive system having extremely low viscosity has been studied in the above application, the permeation of the adhesive into a molding resin is seen and it is considered that an anchoring effect is exhibited. However, the permeable adhesive is not preferred because it may change the characteristic properties of the LCP resin and the characteristic properties of internal electronic parts packaged with the LCP.
A method for bonding an LCP using a mechanical unit is also reported (Japanese Patent Application Laid-open No. Hei 5-177716). This method relates to a method in which the LCP is physically bonded by engaging or screwing. However, it is troublesome compared with a method using an adhesive, which is a defect of the method.
An adhesive having excellent thixotropic properties and low stringiness is reported, which is obtained by adding polycarbodiimide resin, water and a curing agent with an epoxy resin composition comprising an epoxy resin and a thixotrophy imparting agent and optionally a filler (Japanese Patent Application Laid-open No. Hei 9-53000). However, this publication doesn't say about its specific use and fails to disclose such an idea that it is an adhesive for an LCP.
SUMMARY OF THE INVENTION
It is an object of the present invention to provide a simple bonding method for obtaining a firmly bonding and adhesive site which have excellent adhesion properties to an LCP and excellent heat resistance.
The inventors of the present invention have conducted intensive studies to attain the above object, and have found out that an adhesive having excellent adhesion properties to an LCP can be obtained by adding and mixing a polycarbodiimide resin with an epoxy resin composition comprising an epoxy resin and a curing agent. Then the present invention has been accomplished based on this finding.
That is, the present invention provides a method for bonding LCPs mutually or an LCP and another material comprising the step of bonding the LCPs mutually or an LCP and another material using an adhesive prepared by adding a polycarbodiimide resin with an epoxy resin composition comprising an epoxy resin and a curing agent.
The present invention also provides an adhesive for an LCP which is prepared by adding a polycarbodiimide resin with an epoxy resin composition comprising an epoxy resin and a curing agent.
DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS
A preferred embodiment of the present invention will be described hereinunder.
The method for bonding LCP of the present invention is characterized in that LCPs mutually or an LCP and another material are bonded together using an adhesive prepared by adding a polycarbodiimide resin with an epoxy resin composition comprising an epoxy resin and a curing agent. The adhesive used in this method is preferably an adhesive prepared by adding a polycarbodiimide resin with an epoxy resin composition comprising an epoxy resin and a curing agent and is produced without adding water.
The epoxy resin that can be used in the present invention includes a glycidyl ether type epoxy resin typified by a bisphenol A type epoxy resin, novolak type epoxy resin and cresol-novolak type epoxy resin, and an epoxy resin having at least one epoxy group in the molecule such as an alicyclic epoxy resin, heterocyclic epoxy resin or liquid rubber modified epoxy resin. Any resin called epoxy resin may be used in the present invention.
Out of these, the epoxy resin used in the present invention is preferably liquid at room temperature without a solvent, more preferably a bisphenol type epoxy resin.
Illustrative examples of the curing agent used in the present invention include acid anhydrides such as methyl nadic anhydride, dodecenylsuccinic anhydride, tetrahydrophthalic anhydride, hexahydrophthalic anhydride, methyl endomethylene tetrahydrophthalic anhydride, chlorendic anhydride, ethylene glycol trimellitic anhydride ester, methyl tetrahydrophthalic anhydride and methyl hexahydrophthalic anhydride; imidazole derivatives such as imidazole, 2-methylimidazole, 2-ethyl-4-methylimidazole, 2-phenylimidazole, 2-undecylimidazole, 2-heptadecylimidazole, 1-benzyl-2-methylimidazole, 1-cyanoethyl-2-methylimidazole, 1-cyanoethyl-2-phenylimidazole, 1-cyanoethyl-2-ethyl-4-methylimidazole, 1-cyanoethyl-2-methylimidazole trimellitate, 1-cyanoethyl-2-phenylimidazole trimellitate, 2,4-diamino-6-[2′-methylimidazolyl-(1′)]-ethyl-s-triazine, 2,4-diamino-6-[2′-undecylimidazolyl-(1′)]-ethyl-s-triazine, 2,4-diamino-6-[2′-ethyl-41-methylimidazolyl-(1)] ethyl-s-triazine and 1-dodecyl-2-methyl-3-benzoylimidazolium chloride; dicyandiamide or derivatives thereof; organic acid dihydrazides such as sebacic acid dihydrazide; urea derivatives such as 3-(3,4-dichlorophenyl)-1,1-dimethylurea; polyamideamines, modified polyamines, boron fluoride -monoethylamine complexes and the like. Out of these, amine-based curing agents are preferred.
The amount of the curing agent may be suitably selected according to the type of curing agent used. It is generally 2 to 200 parts by weight based on 100 parts by weight of the epoxy resin. A curing accellorator may be used at this point, which can be easily presumed. They may be used alone or in combination of two or more.
The polycarbodiimide resin used in the present invention may be produced by a method such as a method disclosed in Japanese Patent Application Laid-open No. Sho 51-61599, the method of L. M. Alberino [J. Appl. Polym. Sci., 21, 1999 (1997)], or methods disclosed in Japanese Patent Application Laid-open No. Hei 2-292316 and Japanese Patent Application Laid-open No. Hei 6-56950. That is, the polycarbodiimide resin can be produced from an organic diisocyanate in the presence of a catalyst for promoting the carbodiimidation of the isocyanate.
The organic diisocyanate used in the production of the polycarbodiimide resin may be any type of aliphatic, alicyclic, aromatic or aromatic -aliphatic. These organic diisocyanates may be used solely or in combination of two or more.
The polycarbodiimide resin used in the present invention includes a homopolymer or copolymer compri
Imashiro Yasuo
Itoh Takahiko
Nakamura Norimasa
Tomita Hideshi
Aylward D.
Dawson Robert
Kirkpatrick & Stockton LLP
Nisshinbo Industries Inc.
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