Adhesive bonding and miscellaneous chemical manufacture – Methods – Surface bonding and/or assembly therefor
Reexamination Certificate
1998-12-17
2001-03-27
Ball, Michael W. (Department: 1733)
Adhesive bonding and miscellaneous chemical manufacture
Methods
Surface bonding and/or assembly therefor
C156S302000, C156S303100, C156S306600, C361S737000
Reexamination Certificate
active
06207004
ABSTRACT:
BACKGROUND ART
Thin IC cards have been produced in such a procedure as follows. Electronic components are mounted, by using solder or the like, on lands of a wiring pattern formed on a first cover sheet which is made of vinyl chloride having good self-fusing characteristic. A core sheet made of vinyl chloride, having apertures at positions corresponding to the electronic components mounting positions, is placed over the electronic components. Space around the electronic components in the apertures is filled up with a sealing resin made of a thermosetting resin such as epoxy resin which is cured after filling. Then after placing a second cover sheet made of vinyl chloride on the sealing resin, the assembly of sheets is heated at about 120° C. for 5 to 10 minutes while applying a pressure of 5 kgf/cm
2
by means of a press, thereby completing the thin IC card.
The sealing resin is preferably applied so that the surface is at the same height as the core sheet surface, but the resin changes the volume thereof when curing, and therefore it is difficult to accurately control the amount of the resin to fill. Further, while portions other than the filling resin join with each other through thermal fusion of vinyl chloride, top surfaces of the filling resin are exposed through the cover sheet, resulting in a problem that clear image cannot be printed when printing a pattern on the cover sheet surface.
Thus, it is a first object of the present invention to provide a method for producing a thin IC card with beautiful finish of the cover sheet surface at positions corresponding to the apertures of the core sheet.
Vinyl chloride is capable of self-fusing at a low temperature and is suitable for mass production in a continuous production line. However, vinyl chloride emits a chloride gas when burned, thus polluting the environment. Recently, therefore, it has been proposed to switch the material from vinyl chloride to polyethylene terephthalate (PET). However, polyethylene terephthalate has a melting point above 250° C. and is not self-fusing at a low temperature unlike vinyl chloride. Also in case a thermosetting resin is used as a filling resin of IC cards produced in the continuous production line, such a method cannot be employed as the apertures of the core sheet are filled with the thermosetting resin followed by a period of waiting for the thermosetting resin to cure during the production step. Instead, it is necessary to apply the thermosetting resin on the electronic components in advance. But this method has a problem of causing more impairment of the surface construction of the cover sheet than in the case of the former method.
Thus, it is a second object of the present invention to provide a method for mass producing a thin IC card by using PET which does not have adverse effect on the environment, in a similar way as that for vinyl chloride, while producing the thin IC card of beautiful surface finish.
DISCLOSURE OF THE INVENTION
The present inventors have, through intensive studies, have found that a hot-melt adhesive can be used for filling the apertures instead of the sealing resin without impeding the progress of the step in the continuous production line. The inventor have also found that the thin IC card can be mass-produced with the conventional method of pressurizing while heating at a low temperature, when the hot-melt adhesive of similar nature as that of the cover sheet is applied onto the cover sheet, and that excess or shortage of the filling resin in the apertures can be fine-adjusted thereby producing the thin IC card of beautiful surface, thus completing the present invention.
The present invention provides a method for producing an IC card made by laminating at least a first cover sheet, a core sheet having apertures for housing electronic components and a circuit pattern sheet whereon a wiring pattern is formed and electronic components are mounted, comprising the steps of:
laminating the core sheet on the circuit pattern sheet so that the electronic components mounted on the circuit pattern sheet are located at the positions of the apertures;
filling the apertures housing the electronic components with the hot-melt adhesive;
laminating the first cover sheet on the laminate of the circuit pattern sheet and the core sheet on the opposite side of the circuit pattern sheet, and bonding the sheets via a hot-melt adhesive layer formed on at least one of the opposing bonding surfaces while heating and pressurizing; and
cutting the laminate to a predetermined size.
According to the present invention, because the hot-melt adhesive is used as the filling material, it is made possible to bond the layers while excess or shortage in the amount of hot-melt adhesive filling the apertures and the hot-melt adhesive applied to the layers is compensated for when the laminated layers of the IC card are bonded by heating under a pressure, thereby eliminating the problems encountered when a thermosetting resin is used as the filling material, and it is made possible to mass produce the IC card in a continuous production line without waiting for the thermosetting resin to cure.
While the circuit pattern sheet may be made by forming the wiring pattern with the electronic components mounted thereon directly on the cover sheet (as in a first embodiment shown in FIG.
1
), the second cover sheet may also be bonded separately from the circuit pattern sheet on the back side thereof (as in a second embodiment shown in FIG.
2
).
Although the sheets which have been cut to the finish size may be bonded with each other, it is preferable for the purpose of mass production to supply the sheet materials from rolls of long sheets and repeat the steps described above thereby to continuously produce the thin IC cards (as in the second embodiment shown in FIG.
2
).
The sheets are preferably made of polyethylene terephthalate (PET) when disposal by incineration is taken into consideration. However, since PET sheets do not fuse with each other under pressure and low-temperature heating unlike vinyl chloride, it is desirable to apply a hot-melt adhesive on at least one of the bonding surfaces before bonding.
Since the hot-melt adhesive is inferior in heat resistance, it is desired that a thermosetting resin is mixed with the hot-melt adhesive so that the mixture cures when heated, thereby ensuring enough bonding strength at a high temperature. The thermosetting resin to be mixed is selected by taking the cover sheet material and the kind of hot-melt adhesive, which makes the matrix, into consideration. Proportion of the thermosetting resin to be added is preferably within 50% in volume.
While it is preferable that the hot-melt adhesive be applied to the bonding surfaces of the first and the second cover sheets in advance, it may also be applied in step.
The hot-melt adhesive may be applied as a circuit protection layer to the circuit pattern forming surface of the circuit pattern sheet.
According to the present invention, the IC card may also be produced by the following method. Namely, a method for producing an IC card made by laminating at least the first cover sheet, the core sheet having apertures for housing electronic components and the circuit pattern sheet whereon the wiring pattern is formed and the electronic components are mounted, comprises the steps of:
laminating the core sheet on the circuit pattern sheet so that the electronic components mounted on the circuit pattern sheet are located at the positions of the apertures by using the circuit pattern sheet with the hot-melt adhesive layer formed over the entire surface or a part thereof to cover the electronic components mounted thereon;
laminating the first cover sheet on the surface of the laminate of the circuit pattern sheet and the core sheet and bonding the sheets via a hot-melt adhesive layer formed on at least one of the opposing bonding surfaces while heating and pressurizing; and
cutting the laminate to a predetermined size.
According to the present invention, the IC card may also be produced by the following method. Namely, a
Ball Michael W.
Haran John T.
Mitsubishi Denki & Kabushiki Kaisha
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