WO1995003178A1

WO1995003178A1 - Embossing

Info

Publication number: WO1995003178A1
Application number: PCT/GB1994/001554
Authority: WO
Inventors: James John Cook; Christopher Stephen Cook; Laurence David Cook
Original assignee: James John Cook; Christopher Stephen Cook; Laurence David Cook
Priority date: 1993-07-20
Filing date: 1994-07-18
Publication date: 1995-02-02
Also published as: GB9315045D0

Abstract

A counter-force for use in an embossing of foil-embossing operation comprises a substrate (10) which carries up-standing portions (12) corresponding in shape and cross-sectional profile to the recesses of a die with which the counter-force is to be used. The substrate (10) comprises a flexible, substantially transparent plastics material sheet such as of polyester resin; the up-standing portions (12) are of synthetic resin moulded directly on to the substrate (12), which resin is also substantially transparent when cured.

Description


  
 



   EMBOSSING
 This invention relates to a counter-force for use in a foil-embossing or blind-embossing operation on a sheet-like workpiece, and to methods of preparing a press for foil-embossing or blind-embossing a sheetlike workpiece, using such a counter-force. The invention further relates to a process for making a counter-force for use in conjunction with a die for performing a foil-embossing or operation.



   For aesthetic reasons, it is frequently desirable to subject a paper or paper-like sheet material (hereinafter referred to as   a "workpiece")    to a foilembossing or blind-embossing operation, as a part of a printing process, whereby printed or foiled characters or graphics, or plain unprinted areas are raised out of the general plane of the workpiece. For example, a book jacket may have the title foil-embossed so that each letter of the title is of a gold colour and is raised out of the general plane of the workpiece.



   The operations of foiling, foil-embossing and blind-embossing will now be described in greater detail.



  (1) Foiling is the application of a thin metallic foil with a heat sensitive adhesive backing to the surface of a workpiece using a die with raised portions in the form of letters or designs and which is mounted on a heated platen of a press and brought down upon the workpiece, sandwiching the metallic foil between the die and the workpiece. The heat is transferred only through the raised areas of the die in contact with the workpiece, and this causes the metallic foil with its heat sensitive adhesive backing (now in contact with the workpiece) to bond in those areas only. In this way, the letters or design on the die is transferred to the workpiece in metallic foil, such as can be seen on  greetings cards or book jackets. This process is called foiling, foil blocking, hot foil blocking or sometimes gold blocking, although metallic foil comes in many colours other than gold.



  (2) Foil embossing applies foil in the same fashion as above but at the same time and in the same operation raises (embosses) the area being foiled from the general plane of the workpiece. This is achieved with a die similar to that for foiling, but with the printing or foiling surfaces of the letters or design recessed in a concave fashion, so that when used with a counter-force (which will be described in detail later), the workpieces and foil can be sandwiched between the appropriate areas on the die and the counter-force, forcing the workpiece into the concave printing or foiling recesses and so embossing the surface of the workpiece at the same time as applying the foil to the surface. This process is called foil embossing.



  (3) Blind embossing (or just embossing) is the raising from the general plane of the workpiece any design or letters without applying foil at the same time. No heat is necessary and because foil is not being applied in a heat transfer process, the area around the detail or design on the die does not need to be cleared away to prevent it touching the surface of the workpiece. An embossing or die need be no more than a solid plate with the area of the letters or design recessed into the die so that the image is sunk into the plate rather than raised out of the plate.



  With the use of a counter-force, the workpiece is sandwiched between the die and counter-force, forcing the workpiece into the recessed areas of the die and raising the letters or designs from the general plane of the workpiece.



   In order to perform a foil-embossing operation, a  die has to be prepared which has portions upstanding from the general plane of the die and which define those parts which are to be raised out of the general plane of the workpiece. The upstanding portions of the die have recesses   (or "flutes")    into which the parts of the workpiece to be raised may be pressed. The die is mounted on one platen of a press, and on the opposed platen of the press a so-called counter-force is mounted, which counter-force has raised portions generally corresponding to the recesses of the die.



  When a workpiece is positioned between the die and the counter-force and the platens are moved together, the material of the workpiece is driven into the recesses of the die, so raising the required parts of the workpiece.



   A foil-embossing operation is performed by positioning between the die and the workpiece a film carrying a suitable metallic foil, which foil is transferred to the workpiece by the application of heat. The foil adheres to the workpiece only in the region of the upstanding portions, where heat is applied to the foil, and the workpiece is pressed into the recesses by the counter-force.



   The manufacture of the counter-force is difficult since the raised portions thereof must precisely correspond to the recesses of the die. If the thickness of the workpiece is significant, then an allowance must be made for that thickness, during the manufacture of the counter-force. Moreover, the setting-up of a press to perform a foil-embossing operation using such a counter-force must be performed with great care. Once the die has been mounted on one platen, the counter-force must properly be positioned on the other platen, accurately aligned with and opposed to the die mounted on the one platen. If the alignment is not perfect, either the die or the  counter-force is likely to be damaged during the first pressing operation. In the case of a press having at least one platen in the form of a press-cylinder, the problems of obtaining accurate alignment are even greater.



   In view of the above, the manufacture of a counter-force for use with a die is expensive, and the setting-up for subsequent printing of a plurality of workpieces also is relatively expensive. It is a principal aim of the present invention to address at least some of these problems associated with known processes for foil-embossing or blind-embossing workpieces, and particularly to simplify the setting-up of a press so as to minimise the time (and so costs) required, as well as to reduce the likelihood of damage to a counter-force or die.



   According to one aspect of the present invention, there is provided a counter-force for use in conjunction with a die having at least one recessed part to perform a foil-embossing or blind-embossing operation on a sheet material to produce an embossed region on that sheet material, which counter-force comprises a substrate which carries on one surface thereof a raised portion the shape and cross-sectional profile of which corresponds to the recessed part of the die with which the counter-force is to be used, characterised in that said substrate is substantially transparent.



   It will be appreciated that the setting-up of a press to perform a foil-embossing or blind-embossing operation may be much simplified, by using a counterforce of this invention. The die may be mounted on one press platen and used to make a light impression on the other platen or packing material on or around the other platen - for example by lightly inking the die and then relatively moving the platens to contact the die on the  opposed platen. Then, the platens may be separated and the counter-force attached to the opposed platen - but since the counter-force of this invention has a substantially transparent substrate, the alignment of the raised portions thereof with the printed impression is very simple.

   An operator may view the printed impression through the transparent substrate of the counter-force and achieve an exact alignment very easily and quickly, whereafter the counter-force may be secured to the other platen by any suitable technique for example by use of adhesives, adhesive tape, or the like.



   Taking the foregoing into account, according to a second aspect of this invention there is provided a method of preparing a press for an embossing operation on a workpiece, comprising the steps   of:    mounting on one platen of the press an embossing die having at least one recessed part; printing on the other platen of the press an image of the recessed part of the die; mounting on the other platen a counter-force having a substantially transparent substrate which carries on one surface thereof a raised portion the shape and cross-sectional profile of which corresponds to the recessed part of the die, so that the raised portion overlies the appropriate part of printed image; and securing the counter-force in that position.



   The securing of the counter-force in the required position may be assisted by the counter-force having a substantially transparent substrate which is also flexible. In this way, the substrate may be flexed to permit one side edge of the substrate to be secured to a press platen for example by means of double-sided adhesive tape whilst a significant area of the substrate is held firmly in the required position.



  Then, with said one side edge secured, the substrate may again be flexed and the opposed side edge secured,  using double-sided adhesive tape. A further advantage of a counter-force having a flexible substrate is that the substrate may be mounted on a press-cylinder which co-operates with a die mounted on a flat press platen.



   From the above, it will be appreciated that the counter-force may be used on a press having flat platens, or having at least one platen in the form of a press cylinder. The term platen as used herein should therefore be construed in a broad sense, to refer to either of the two opposed parts of a press between which a workpiece is located in order to be embossed, and either one or both platens may be flat, curved or drum-like.



   Conveniently, the substrate of the counter-force may be made from a substantially transparent plastics film material, such as of polyester sheet. A typical thickness for such a film-like substrate is in the range of 250 microns to 500 microns.



   It is preferred for the raised portion of the counter-force also to be substantially transparent, and to comprise a cured synthetic resin, such as an epoxy or polyester resin, moulded in position on one surface of the substrate so as to have a shape and crosssectional profile which corresponds to the shape and cross-sectional profile of the recessed part of the die. If required, an appropriate allowance may be made for the thickness of the workpiece, when moulding the raised portion of the counter-force.



   When a counter-force of this invention is employed in a press to perform an embossing operation, the substantially transparent substrate may be mounted directly or indirectly on one of the press platens.



  For example, a resilient blanket may be laid over and secured to the press platen on which the counter-force is to be mounted, the counter-force then being secured to the blanket which is itself held against movement.  



  In such a case, the impression made by the die will be made on the blanket, rather than on the platen itself, whereafter the counter-force is aligned with that impression.



   The counter-force of this invention may be made by using the die itself as a mould for the resin which is to be moulded on to one surface of the substrate. In the case of an embossing die, the counter-force may be made simply by a moulding operation on the die itself, using for example a synthetic resin which, when cured, is substantially transparent.

   In the case of a foilembossing die, the counter-force may be made by the following steps:
 - manufacturing a die by any known processes, including forming recesses (often referred to as "flutes") in up-standing portions of the die;
   moulding    a matrix on to the die so as wholly to cover the upstanding portions;
 - machining the matrix back to form a flat and level surface co-planar with the upper edges of the fluted up-standing portions of the die;
 - removing the matrix material from the flutes themselves;
 - filling the exposed flutes with a curable synthetic resin (which is itself preferably substantially transparent, when cured) and laying a substantially transparent substrate over the matrix surface;
 - curing the resin or allowing the resin to cure so as to bond to the substrate;

  
 - removing the substrate together with the cured resin bonded thereto so that the substrate has upstanding portions corresponding in shape and crosssectional profile to the flutes of the die; and
 - removing the remaining matrix from the fluted die so as to restore the die to its original condition.  



   The counter-force could be made using other processes, for example employing an intermediate mould, which is used both for the manufacture of the counterforce and also for the manufacture of the die, by appropriate processes which will be understood by those skilled in the art.



   In order that the invention may better be understood, it will now be described in greater detail and certain specific examples thereof given, reference being made to the accompanying drawings, in   which   
 Figure 1 is a general perspective view of a counter-force of this invention;
 Figure 2 is a cross-section taken on line II-II marked on Figure 1;
 Figure 3 is a general perspective view of a die mounted on one platen of a press and a counter-force of this invention mounted on an opposed platen; and
 Figures 4 to 6 illustrate three steps in the manufacture of a counter-force of this invention, from a fluted die.



   Referring initially to Figures 1 and 2, there is shown a counter-force of this invention. The counterforce comprises a transparent substrate 10 made for example from polyester sheet or plastics film of a thickness of about 250 microns. On its upper surface 11 the film supports raised portions 12 each of a substantially transparent cured synthetic resin material. The raised portions 12 have a crosssectional profile and shape (when viewed in plan) corresponding to the profile and shape of the flutes in an embossing die with which the counter-force is to be used.



   Typically, that embossing die may be arranged to imprint letters on a workpiece, such as of paper or a light card, and so have the letters upstanding from a base area. Each of the letters is fluted in a manner    nown    in the art, and thus is recessed with a generally arcuate profile, within the area of the letter upstanding from the base area. Conventionally, the flutes (recesses) in the letters are produced manually, which is a highly skilled and time-consuming task.



  Once completed, the die may then be used as a mould for the production of the counter-force, as will be described below.



   Figure 3 illustrates diagrammatically a part of a printing press, for use in an embossing operation using a counter-force as illustrated in Figures 1 and 2. The press has a flat lower platen 15 and an upper platen in the form of a print cylinder 16 which, during operation of the press, rolls over the lower platen 15. Such a press is well-known and understood in the art and forms no part of the present invention and will not therefore be described in further detail here.



   Mounted on the lower platen 15 is a foil-embossing die 17. This foil-embossing die comprises a base plate 18 of magnesium, from which up-stand raised letters 19.



  The upper surface of each raised letter 19 is recessed to define a flute 20, within the thickness of the raised letter. Each flute has a concave profile, when considered about any cross-section.



   Mounted on the cylinder 16 is a counter-force 21 for the die 17. This counter-force has a transparent substrate which is attached to the cylinder 16 for example by means of a double-sided adhesive tape.



  Upstanding from the surface of the substrate facing the die 17 are raised portions 22 each of which corresponds in cross-sectional profile and shape to the flutes of the die 17.



   It will be appreciated that the counter-force 20 must be mounted in exactly the correct position in order that the raised portions 22 may precisely enter the flutes of the die, as the cylinder 16 rolls over  the lower platen 15. This may be achieved by lightly inking the die 17 and then imprinting a light impression on the cylinder 16. Thereafter, the counter-force 21 may be precisely aligned with the impression on the cylinder 16, by viewing that impression through the transparent substrate 10. Once accurately aligned, one side of the counter-force may be firmly held against movement whilst the opposite side is raised from the cylinder and double-sided adhesive tape is adhered to the cylinder. The counterforce may then be flexed back on to that tape, so as to secure that other side in the required position.

   This operation may then be repeated for said one side of the counter-force.



   Referring now to Figures 4 to 6, there is shown the steps of a method for producing a counter-force such as that illustrated in Figures 1 and 2. The first stage of the process is the production of a fluted die 25. This may be made by any conventional process and has raised portions 26 defining letters or other characters or graphics which are to be embossed on a workpiece. The upper surface of these raised portions 26 are fluted, as shown at 27. The die is typically made of magnesium, and is produced by an etching process, the flutes then being cut by hand into the raised portions.



   A matrix material 28, for example of bakelite, is cast on to the upper surface of the base plate 29 of the die, so as completely to cover the fluted raised portions 26, as illustrated in Figure 4. Once set, the matrix material is machined back until its upper surface is precisely flat and level with the upper parts of the raised portions 26 of the die, as shown in
Figure 5. The bakelite material is then removed from the flutes and an appropriate release agent is spread over the exposed top surface of the matrix and the  flutes. A thermo-setting plastics material, such as an epoxy resin, is spread into the exposed flutes of the die and then a transparent substrate 30 is pressed on to the top of the matrix material. Once the resin has cured, the substrate 30 is peeled off the matrix, with the set resin adhering to the face of the substrate.



   The process is completed by removing the matrix material 28 from the die, so restoring the die to its original condition. Thereafter, the die may be mounted on one platen of a press and the substrate on the other platen by the process described above with reference to
Figure 3, to allow an embossing operation to be performed.

Claims

CLAIMS 1. A counter-force for use in conjunction with a die having at least one recessed part to perform a foil-embossing or blind-embossing operation on a sheet material to produce an embossed region on that sheet material, which counter-force comprises a substrate which carries on one surface thereof a raised portion the shape and cross-sectional profile of which corresponds to the recessed part of the die with which the counter-force is to be used, characterised in that said substrate is substantially transparent.

2. A counter-force according to claim 1, characterised in that the raised portion is also substantially transparent.

3. A counter-force according to claim 1 or claim 2, characterised in that the raised portion is moulded from a synthetic resin.

4. A counter-force according to any of the preceding claims, characterised in that the substrate comprises a flexible sh-eet of a plastics material.

5. A counter-force according to claim 4, characterised in that the substrate comprises a polyester film and in that the raised portions comprised a moulded epoxy or polyester resin, moulded and cured directly onto the substrate.

6. A method of preparing a press for an embossing operation on a workpiece, comprising the steps of: mounting on one platen of the press an embossing die having at least one recessed part; printing on the other platen of the press an image of the recessed part of the die; mounting on the other platen a counter-force having a substantially transparent substrate which carries on one surface thereof a raised portion the shape and cross-sectional profile of which corresponds to the recessed part of the die, so that the raised portion overlies the appropriate part of the printed image; and securing the counter-force in that position.

7. A method according to claim 6 and in which a counter-force having a flexible substrate is employed, in which one edge region of the substrate is flexed away from the press platen whilst a significant area of the substrate is held firmly in the required position, the flexed-away edge region then being adhered to the press platen.

8. A counter-force according to claim 7, wherein the flexed-away edge region is adhered to the platen by means of a strip of double-sided adhesive tape, laid in the space between the platen and the flexed-away edge region.

9. A counter-force according to claim 7 or claim 8, wherein following the adhering on said one edge region to the press platen, the opposed edge region of the substrate is flexed away from the platen and is then adhered to the platen.

10. A method according to any of claims 6 to 9, wherein the counter-force is indirectly mounted on one of the press platens.

11. A method according to claim 10, wherein a resilient blanket is laid over and secured against movement with respect to the press platen on which the counter-force is to be mounted, the counter-force then being secured to the blanket.

12. A method of manufacturing a counter-force according to claim 1 and for use in an embossing operation, which method comprises the steps of: - manufacturing an embossing die having at least one embossing recess; - filling the recess with a curable synthetic resin and laying a substantially transparent substrate over the upper surface of the die; - curing the resin or allowing the resin to cure so as to bond to the substrate; and - removing the substrate together with the cured resin bonded thereto so that the substrate has an upstanding portion corresponding in shape and crosssectional profile to the recess of the die.

13. A method of manufacturing a counter-force according to claim 1 and for use in a foil-embossing operation, which method comprises the steps of: - manufacturing a die by any known processes, including forming recesses in up-standing portions of the die; moulding a matrix on to the die so as wholly to cover the up-standing portions; - machining the matrix back to form a flat and level surface co-planar with the upper edges of the recessed up-standing portions of the die; - removing the matrix material from the recesses themselves; -filling the exposed recesses with a curable synthetic resin and laying a substantially transparent substrate over the matrix surface; - curing the resin or allowing the resin to cure so as to bond to the substrate;

- removing the substrate together with the cured resin bonded thereto so that the substrate has upstanding portions corresponding in shape and crosssectional profile to the recesses of the die; and - removing the remaining matrix from the die so as to restore the die to its original condition.

14. A method according to claim 12 or claim 13, wherein the synthetic resin is, when cured, substantially transparent.