Adhesive bonding and miscellaneous chemical manufacture – Methods – Surface bonding and/or assembly therefor
Reexamination Certificate
1998-04-21
2001-01-09
Sells, James (Department: 1734)
Adhesive bonding and miscellaneous chemical manufacture
Methods
Surface bonding and/or assembly therefor
C156S230000, C156S233000, C156S240000, C156S247000, C156S499000, C156S540000, C427S147000, C427S148000, C428S914000, C428S915000
Reexamination Certificate
active
06171429
ABSTRACT:
This invention relates to printing apparatus, and in particular to such apparatus for carrying out a process commonly known as hot foil stamping.
In security printing apparatus it is known to apply a thin layer of metal foil of predetermined shape and/or pattern to a stock, e.g. a sheet of bank notes, usually as a feature intended to make counterfeiting more difficult. In a typical application the foil is carried as a continuous lamination between a carrier substrate and a layer of hot melt adhesive, the shape or pattern to be applied being determined by a stamp or press. In prior art arrangements the carrier substrate and the stock (e.g. a sheet of bank notes) are placed together beneath a platen-type press carrying an array of stamps which are simultaneously applied to cause an array of hot foil imprints to be applied to the stock. Heat for activating the hot melt adhesive is generally applied from the press, and an inability to transfer heat sufficiently quickly is a factor in limiting the speed of such prior art arrangements.
U.S. Pat. No. 4,340,438 discloses an arrangement for transferring a foil from a carrier substrate to a moving stock in which a thermal belt contacts the rear surface of the carrier substrate in the vicinity of a pressure-applying transfer station, so as to preheat the foil sufficiently to effect separation from the carrier and transfer it to the stock.
Japanese patent publication No. 6115048A discloses an arrangement for bonding a plastic film web to a stock web by passage between presser rolls, the webs passing over pre-heating rolls upstream of the presser rolls.
According to a first aspect of the invention printing apparatus for applying foil to a stock, comprises means for conveying a carrier for the foil towards a printing position, the foil carrying on an outer side an adhesive which is activated by heat, means for conveying a stock towards said printing position, printing means at which the carrier and stock are moved together past said printing position at which pressure is applied to transfer a predetermined pattern and/or shape of foil from the carrier to the stock and so that the adhesive secures the predetermined pattern and/or shape of foil to the stock, and pre-heating means for transferring heat to the carrier before it reaches the printing position and/or before it contacts the stock, wherein the pre-heating means comprises means arranged to apply heat directly to said adhesive layer from said outer side. Preferably the pre-heating means is effective to transfer heat to the carrier immediately upstream of the printing position. For example, where the printing means comprises a nip between a print wheel and a counter wheel the pre-heating means may be located to be effective as close as possible to said nip. The pre-heating means may comprise means directing radiation or hot air at said layer.
In a preferred arrangement the printing means comprises means for applying both pressure and heat at said printing position. For example, the printing means may comprise a print wheel carrying one or more stamps defining said predetermined pattern and/or shape, the wheel carrying heating means in the vicinity of said stamp or stamps.
The printing apparatus may form part of security printing apparatus of the type disclosed in EP 0441596A, the disclosure of which is hereby incorporated herein in its entirety. This apparatus discloses a security printing process in which thin film security material is transported on a carrier ribbon past a printing position together with a moving stock.
According to another aspect of the invention a method of applying foil to a stock by means of pressure and heat to secure the foil to the stock by means of a hot melt adhesive, in which the foil and stock are moved together past a printing position so that successive foil imprints are made at said position, includes a process step in which the adhesive carried with the foil is pre-heated before it reaches said position, wherein said pre-heating step includes directing heat directly at said adhesive from a direction other than through said foil.
According to a further aspect of the invention a method of applying foil to substrate by means of pressure and heat to secure the foil to the substrate by means of a hot melt adhesive, in which the foil and substrate are moved together past a printing position so that successive foil imprints are made at said position, includes the stop of laser etching the shape or pattern of the foil either upstream or downstream of the printing position. Preferably said laser etching is carried out using a suitably shaped or patterned mask which is moved together with the foil.
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patent: 4239569 (1980-12-01), Harvey
patent: 4340438 (1982-07-01), Davis
patent: 4389438 (1983-06-01), Ohtsuki et al.
patent: 4724026 (1988-02-01), Nelson
patent: 5021112 (1991-06-01), Breger
patent: 5520763 (1996-05-01), Johnstone
patent: 5882463 (1982-07-01), Tompkin et al.
patent: 95810302 (1992-11-01), None
patent: 2255317 (1992-11-01), None
Aindow Alan Michael
Cahill Michael John
Santon David
Antonelli Terry Stout & Kraus LLP
Lorengo J. A.
Molins PLC
Sells James
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