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EP 1 860 128 B12510152025303540455055DescriptionTECHNICAL FIELD[0001] The present invention relates to a method for temporarily fixing a member in processing of various members,and an adhesive composition and an adhesive suitable for the fixation. More particularly, the present invention relatesto a method for temporarily fixing an optical member in processing the member and a photocurable adhesive suitablefor the application.BACKGROUND ART[0002] Two-sided tapes and hot-melt type adhesives are used as adhesives for temporary fixation method of opticallenses, prisms, arrays, silicon wafers, semiconductor packaging parts, and so on, and members bonded or laminatedwith use of these adhesives are cut into a predetermined shape, followed by removal of the adhesive to produce processedmembers. With respect to the semiconductor packaging parts, for example, they are fixed on a substrate with a two-sided tape and then cut into desired parts, and the two-sided tape is irradiated with ultraviolet rays to be separated fromthe parts. Furthermore, in the case of the hot-melt type adhesive, members are bonded therewith and heated to let theadhesive penetrate into their interspace, and then the members are cut into desired parts, followed by removal of theadhesive in an organic solvent.[0003] However, in the case of the two-sided tape, there were problems that it was difficult to achieve satisfactorythickness accuracy; that it was inferior in the chipping property in processing of parts because of weak adhesive strength;that it was impossible to separate the tape without heating at 100°C or more; and that, where it was separated byirradiation with ultraviolet rays, it was impossible to separate the tape if an adherend had a poor UV transmittance.[0004] In the case of the hot-melt type adhesive, it could not be effective in bonding without heating at 100°C or more,so that there was a restriction on the members to be used. Furthermore, it was necessary to use an organic solvent inremoval of the adhesive, and washing steps with an alkali solvent and a halogen type organic solvent were cumbersomeand also problematic from the viewpoint of working environments.[0005] In order to overcome these drawbacks, there were proposals on photocurable or heat-curable adhesives fortemporary fixation method containing a water-soluble compound such as a water-soluble vinyl monomer. These adhesivecompositions solved the problem of the removability in water but they still had problems that the adhesive strength waslow in fixation of parts and that the members after cut had poor dimensional accuracy. Furthermore, there were proposalson adhesives for temporary fixation method improved in adhesion with use of a specific, highly hydrophilic (meth)acrylate,and, also improved in removability by swelling and partial dissolution. However, a cutting process involves generationof frictional heat between the parts and a cutting jig such as a blade or a diamond cutter and thus is carried out whilecooling the parts with a large amount of water. Therefore, a cured resin of the above highly hydrophilic compositionswells to become soft during the cutting, whereby higher dimensional accuracy cannot be achieved. In addition, thecured resin dissolved in part remains as a residual adhesive on the members after the removal, which causes a problemin appearance (cf. Patent Documents 1, 2 and 3).Patent Document 1: JP-A-06-116534Patent Document 2: JP-A-11-71553Patent Document 3: JP-A-2001-226641DISCLOSURE OF THE INVENTIONPROBLEM TO BE SOLVED BY THE INVENTION[0006] In order to improve the dimensional accuracy of the members after cutting, there are desires for a photocurableadhesive hydrophobic, high in adhesive strength, excellent in removability in water, free of an adhesive residue on themembers after removal, and environmentally excellent in working, particularly, in application fields of optical members.[0007] The inventors of the present invention have conducted extensive studies to solve the above problems in theprior art, and as a result, have found that an adhesive composition having a high adhesive strength and a good removabilityin water or in warm water is obtained with use of specific hydrophobic (meth)acryl monomers in combination, and thatthe object of the present invention could be attained. The present invention has been accomplished on the basis of sucha discovery.