Adhesive bonding and miscellaneous chemical manufacture – Methods – Surface bonding and/or assembly therefor
Reexamination Certificate
1999-11-29
2001-09-25
Ball, Michael W. (Department: 1733)
Adhesive bonding and miscellaneous chemical manufacture
Methods
Surface bonding and/or assembly therefor
C156S105000, C156S275700, C156S285000, C118S052000, C427S240000, C269S020000, C269S305000
Reexamination Certificate
active
06294035
ABSTRACT:
BACKGROUND OF THE INVENTION
1. Field of the Invention
The present invention relates to a method of fabricating a thin-sheet-coated composite substrate that fabricates a thin-sheet-coated composite substrate by bonding a thin sheet or a film, such as a thin glass sheet, to a substrate formed by laminating optical films or the like with an adhesive and, more particularly, to a method of fabricating a thin-sheet-coated composite substrate having a thin sheet having an improved flatness.
2. Description of the Related Art
Functional substrates coated with a thin glass sheet are employed in electronic parts and optical parts. A conventional method of fabricating a thin-sheet-coated composite substrate superposes a substrate and a thin sheet with an adhesive placed between the substrate and the thin sheet to form a layered structure, holds the layered structure between a pair of highly flat pressure plates, and compresses the layered structure so that the adhesive is spread in an adhesive layer of a predetermined thickness, and then cures the adhesive layer. When the layered structure is compressed between the pressure plates, the adhesive is squeezed out of the space between the substrate and the thin sheet. The squeezed adhesive spreads over portions not to be coated with the adhesive of the substrate, and the thin sheet, and the pressure plates are smeared with the adhesive. Therefore, the pressure plates must be cleaned to remove the adhesive before using the same again. This method is unable to adjust the thickness of the adhesive layer in a satisfactory accuracy and has a difficulty in applying a fixed pressure uniformly to the layered structure in case that the substrate is larger than the thin sheet. Since the layered structure is compressed between the pressure plates, the components of the layered structure are firmly bonded together and it is difficult to separate the bonded components.
A method proposed in JP-A 55-68040 comprises the steps of supporting a substrate by a vacuum chuck on a spinner, dripping a liquid adhesive onto the substrate, putting a thin glass sheet on the adhesive, blowing air against the thin glass sheet to spread the adhesive in an adhesive layer over the entire surface of the substrate, driving the spinner to rotate the substrate so that a surplus portion of the adhesive is scattered and the substrate and the thin glass sheet are bonded firmly together to form a composite substrate, and removing the composite substrate from the vacuum chuck.
Although this previously proposed method eliminated drawbacks in the conventional techniques to a considerable extent, this method has a drawback that the flatness of the thin glass sheet of the composite substrate fabricated by this method is unsatisfactory. The substrate has an irregular thickness and does not have satisfactory flatness unless the substrate is finished by polishing. When a thin glass sheet is attached to the surface of a substrate having an irregular thickness or to a layer formed on such a substrate, the surface of the thin glass sheet reflects the irregular shape of the surface of the substrate underlying the thin glass sheet.
SUMMARY OF THE INVENTION
Accordingly, it is an object of the present invention to provide a method of fabricating a thin-sheet-coated substrate comprising a substrate and a thin sheet laminated to the substrate, capable of reducing irregularities in the surface of the thin sheet laminated to the substrate which unavoidably has an irregular surface to the least possible extent.
According to the present invention, a thin plate is placed under a substrate. If the thin plate is held by a pneumatic chuck, the thin sheet will be bent or broken. The present invention places a thin sheet on a surface plate fixedly held by a pneumatic chuck or the like in close contact with a surface of the surface plate to keep the thin sheet flat, forms an adhesive layer over the upper surface of the thin sheet and bonds the substrate to the thin sheet with the adhesive layer. Thus, the present invention eliminates the serious drawback of the prior art method.
According to the present invention, a thin-sheet-coated composite substrate fabricating method comprises the sequential steps of: fixing a surface plate having a flat surface of a high flatness to a workpiece holding chuck included in a rotary coating machine with the flat surface facing upward; placing a thin sheet on the surface plate in close contact with the flat surface; dropping a liquid adhesive onto the thin sheet; placing a substrate on the surface of the thin sheet wetted by the liquid adhesive; and rotating the chuck to remove a surplus portion of the liquid adhesive.
Since the flatness of the thin sheet is corrected by the highly flat surface of the surface plate, the substrate can be coated with the thin sheet having a high flatness.
In this method of fabricating a thin-sheet-coated composite substrate, the adhesive may be curable, and a curing step of curing the adhesive may be performed after the completion of the step of rotating the chuck to scatter a surplus portion of the liquid adhesive.
Since the adhesive is cured, the flatness of the surface of the composite substrate formed by laminating the thin sheet to the substrate can be stably maintained.
In this method of fabricating a thin-sheet-coated composite substrate, the adhesive may be an ionizing-radiation-curable adhesive, and the curing step may employ an ionizing radiation.
Since the adhesive is ionizing-radiation-curable and can be cured in a very short time by irradiating the adhesive with the ionizing radiation, the corrected flatness of the thin sheet cannot deteriorate even if stress induced in the thin sheet when correcting the flatness remains in the thin sheet because the adhesive is cured.
In this method of fabricating a thin-sheet-coated composite substrate, a liquid layer may be formed between the surface plate and the thin sheet in the step of placing the thin sheet on the surface plate in close contact with the flat surface.
The liquid facilitates holding the thin sheet in close contact with the surface plate.
In this method of fabricating a thin-sheet-coated composite substrate, air may be blown against the thin sheet placed on the surface plate from the side of the thin sheet in the step of placing the thin sheet on the surface plate in close contact with the flat surface.
The thin sheet can be surely brought in close contact with the surface plate without touching the thin sheet.
The above and other objects, features and advantages of the present invention will become more apparent from the following description taken in connection with the accompanying drawings.
REFERENCES:
patent: 5744193 (1998-04-01), Kitano
patent: 55-68040 (1980-05-01), None
Ball Michael W.
Dai Nippon Printing Co. Ltd.
Parkhurst & Wendel L.L.P.
Tolin Michael A.
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