Process for manufacture of a laminated sheet

Details Process for manufacture of a laminated sheet Process for manufacture of a laminated sheet

1999-04-27

2001-06-19

Mayes, Curtis (Department: 1734)

Adhesive bonding and miscellaneous chemical manufacture

Methods

Surface bonding and/or assembly therefor

C156S220000, C156S277000, C428S209000, C428S211100

Reexamination Certificate

active

06248198

ABSTRACT:

The present invention relates to a laminated sheet and to a process for manufacturing the laminated sheet.
In particular the present invention relates to a laminated sheet comprising sheets of metal foil and paper and a process for manufacturing the laminated sheet.
Laminated sheets, such as those made of sheets of metal foil and paper, can be used for a variety of functions including wrapping or packaging. Consumer items, such as confectionary, are often wrapped individually or in bundles in laminated sheets, and cigarettes and cigars are often sold in tins or boxes having laminated sheets as a liner. Laminated sheets are particularly useful as liners because the metal foil forms a barrier to light and moisture which could degrade the tobacco.
Laminated sheets are often printed or embossed with “images” such as trade marks, logos or company names of manufacturers or distributors, or other information in order to enhance the presentation of goods wrapped or packaged in the laminated sheets.
In general, laminated sheets are printed or embossed on one side only. Usually, the paper is printed or the metal foil is embossed, but occasionally both the metal foil is printed and the paper is embossed. The printing and embossing is carried out by processes which are well known in printing technology, such as roll to roll embossing and intaglio printing.
While it is well known in the printing and paper industry to produce a laminated sheet comprising an embossed metal foil and printed paper, it has not hitherto been known to provide a laminated sheet on which the printing and embossing are in registration, that is, on which there is exact correspondence of the printed and embossed images.
An object of the present invention is to provide a laminated sheet comprising printed paper and embossed metal foil wherein the printing and embossing are in registration.
A further object of the present invention is to provide a process for manufacturing such a laminated sheet.
According to the present invention there is provided a process for manufacturing a laminated sheet comprising the steps of:
(i) adhering together a sheet of metal foil and a sheet of paper;
(ii) printing an image on an outer surface of the paper, and
(iii) embossing a mirror of the image on the metal foil in registration with the printed image on the paper.
According to the present invention there is provided a process for manufacturing a laminated sheet comprising the steps of:
(i) adhering together a sheet of metal foil and a sheet of paper;
(ii) embossing an image on the metal foil; and
(iii) printing a mirror of the image on the outer surface of the paper in registration with the embossed image on the metal foil.
As noted above, the order of the printing and embossing steps is not essential. However, it is preferred that the embossing step precede the printing step.
It is particularly preferred that the process comprises detecting the first formed of the printed and embossed images and controlling the subsequent embossing/printing step to ensure registration of the subsequently formed printed and embossed images.
The step of adhering together the sheets of paper and metal foil may be carried out by any suitable method. In a preferred embodiment, the metal foil is passed over a coating roller which applies adhesive to one surface of the metal foil. The paper and metal foil are then passed between a pair of rolls which press the paper and the adhesive coated surface of the metal foil together to form the laminated sheet.
The embossing step may be carried out by any suitable method. In one method of embossing, a workpiece (such as a roller) and embossing die is located on either side of the laminated sheet and brought together so that the die contacts and embosses the foil. In another method of embossing, the workpiece is stationery and the die is moved up and down against the metal foil of the laminated sheet. In another method of embossing, the workpiece is moved against the paper of the laminated sheet, thus pressing the metal foil against the embossing die.
It is preferred that the embossing step comprises feeding the laminated sheet between the nip of two rolls, with one roll acting as a workpiece and being formed from a relatively soft material such as paper, and the other roll acting as a die and being formed from metal, such as steel.
The printing step may be carried out by any suitable method. For example, the printing step may comprise relief or letterpress printing, planographic printing or intaglio printing, such as photogravure or roll to roll gravure.
The laminated sheet of the present invention may have physical characteristics appropriate for the intended use. For example, where it is intended for wrapping confectionery, the laminated sheet may need to be very flexible. Alternatively, where it is intended to line cigarette boxes, it may be necessary that the laminated sheet be relatively rigid so that it can be folded and maintain the folds.
Different physical characteristics of the laminated sheet may be provided in part by choice of adhesive and the grade and type of paper and/or metal foil.
It is preferred that the metal foil comprise a metal chosen form the main group of the periodic table.
It is particularly preferred that the metal foil comprises or consists of aluminium.
Optionally, the process of the present invention comprises colouring the metal foil. Preferably, the colouring step comprises a roll to roll gravure printing process in which the whole surface of the metal foil is coloured by being passed across an inked gravure roll. The coloured ink deposited on the metal foil by the gravure roll may be dried by passing the metal foil through a hot air chamber or the like.


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