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(11) | EP 2 781 353 A1 |
| (12) | EUROPEAN PATENT APPLICATION |
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| (54) | Application of adhesives |
| (57) A releasable adhesive 14 is applied to a web of material 6 in a lithographic printing
unit 4. The adhesive 14 is dried in the unit 4. The web 6 may then be folded and opposed
regions of adhesive 14 adhered to one another by activation of the adhesive 14 by
heat and/or pressure.
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[0001] The present invention relates to adhesives and in particular to the application of adhesives to a substrate, and in particular, but not exclusively, to a leaflet.
[0002] It is frequently desirable to apply a releasable or peelable adhesive to a substrate such as a leaflet or other sheet material, to allow the leaflet to be retained in a folded condition and then opened by the consumer without tearing the leaflet. Typically, drops or strips of adhesive are deposited onto the substrate using an adhesive gun or other deposition apparatus. This is done immediately prior to the substrate being folded, so that the adhesive does not have an opportunity to dry out before bonding.
[0003] Typically, the adhesive is applied after the leaflet or sheet material has been printed, and if appropriate varnished, for example by passing through a lithographic or flexographic printing press. In such a press, one or more inks and varnishes are successively applied to the substrate, the ink or varnish being dried by UV light or heat after application. The adhesive is applied to the substrate after printing has been completed in a separate procedure.
[0004] The applicant has recognised that the process of adhesive application can be advantageously incorporated into the printing process and from a first aspect provides a method of applying a releasable, peelable or re-wettable adhesive to a substrate comprising applying the adhesive to the substrate in a printing apparatus and drying the deposited adhesive using UV, IR or heat
[0005] This is particularly advantageous when the substrate is being printed or varnished using a lithographic, flexographic or gravure process, as the adhesive application can take place as a step in the lithographic, flexographic or gravure printing process. It also means that the substrate need not be folded immediately after the adhesive has been applied, but may be stored, with the dried adhesive applied until required.
[0006] From a further aspect, the invention provides a method of printing and/or varnishing a substrate using a lithographic, flexographic or gravure process wherein a releasable, peelable or re-wettable adhesive is applied and dried as a stage in the process.
[0007] The printing of the adhesive could take place in a dedicated lithographic, flexographic, gravure or other printing unit. Such a unit would typically be used to apply and cure or dry an ink or varnish to a substrate as it passes through the unit. In this case, therefore, rather than applying an ink or varnish, it is used instead to apply adhesive.
[0008] Alternatively, however, the adhesive could be applied between first and second units, each with a separate application head and the existing UV, IR or hot air means provided in the second unit acting to dry or cure the applied adhesive as well as the ink or varnish actually deposited by that unit.
[0009] The adhesive may be applied in one or more continuous patterns e.g. strips, or alternatively applied to discrete areas of the substrate, for example in spots.
[0011] The substrate may be supplied to the printing unit as a web from a reel, and the adhesive printed substrate then re-reeled for subsequent handling, for example folding.
[0012] In an alternative process, however, the substrate may be processed e.g. folded after the printing process without the substrate being re-reeled as an intermediate step.
[0013] The adhesive printed substrate may be folded, such that the adhesive may act to hold opposed surfaces of the folded substrate together.
[0014] The adhesive is preferably cold seal, heat and/or pressure activated. Accordingly, the folded substrate may be subjected to heat and/or pressure to effect the adhesion of the opposed surfaces. However, other adhesives, such as re-wettable adhesives can be applied in accordance with the invention. Such an adhesive does not require heat or pressure activation.
[0015] The heat or pressure activation may take place simultaneously with the folding or as a separate operation.
[0016] Adhesive may be applied to just one opposing surface of the substrate, i.e. just one of the surfaces which will be opposed to another after the substrate has been folded. Alternatively and preferably, adhesive is applied to both opposing surfaces.
[0017] The folded and adhered substrate may then subjected to further processing, for example further folding, re-reeling or cutting into individual leaflets.
[0018] The composition of the adhesive used will vary depending upon the particular application. However, the adhesive should be UV, IR or heat curable and have a viscosity which allows it to be applied in a printing unit, more particularly in a lithographic, flexographic or gravure printing unit. The adhesive may, for example, be an acrylic based resin system with suitable viscosity and drying characteristics.
[0019] The substrate used may be any sheet material, but is preferably a paper material. Paper is widely used in leaflet manufacture and is typically not surface coated. Although this may be acceptable for printing purposes, it has been found that this may not be acceptable for receiving a releasable or peelable adhesive. In accordance with a preferred embodiment of the invention therefore, a sealer is applied to at least the surface of the paper substrate which receives the adhesive, prior to application of the adhesive. This allows the absorption of the adhesive into the paper to be controlled to ensure that sufficient adhesive remains on the surface to make a satisfactory bond.
[0020] The sealer may be applied to a whole surface of the substrate or just selected portions thereof which will receive the adhesive.
[0021] The sealer is also preferably applied by flexographic, lithographic or gravure printing. A suitable further printing unit may therefore be provided in the apparatus to effect printing of the sealer.
[0022] The sealer may be applied at any convenient point in the printing process. For example, it may be applied to the paper surface after the paper has been printed. The coating may therefore be transparent so as not to adversely affect the printing. However, in another embodiment, it may be applied prior to printing as a preliminary stage in the printing process. In some embodiments, it may even be possible to incorporate the sealer with the printing ink in one of the ink printing steps.
[0023] In some embodiments, the sealer may be applied on both surfaces of the paper sheet material, for example if adhesive is to be applied to both surfaces.
[0024] In some embodiments a release coating may be applied, again by flexographic, lithographic or gravure printing, onto a surface of the web, for example on a side or region of the web opposite to the side or region receiving the adhesive. This facilitates the release characteristics of the reverse side of the paper thereby reducing the tendency for adhesive to adhere to the reverse contact side when the sheet is reeled up after application of the adhesive prior to its final folding and bonding into a leaflet.
[0025] As discussed above, the invention is applicable particularly in the production of leaflets. The invention therefore extends to a method of manufacturing a leaflet incorporating the methods defined above.
[0026] An embodiment of the invention will now be described by way of example only, with reference to the accompanying drawings in which:
Figure 1 illustrates a lithographic printing apparatus used in the process of the invention;
Figure 2 illustrates a detail of a reel of paper which has been printed and had an adhesive applied thereto in the apparatus of Figure 1; and
Figure 3 illustrates the subsequent folding and sealing of the reel of paper shown in Figure 2.
[0027] With reference to Figure 1, a lithographic printing apparatus 2 comprises a plurality of lithographic printing (litho) units 4. A web of paper 6 is fed from a reel 8 and is sequentially fed through the litho units 4 and, in this embodiment, then re-reeled onto a reel 10. In this embodiment, the web 6 is intended to be made into leaflets. The paper in the web 6 will therefore usually be uncoated.
[0028] In this embodiment, only three litho units 4 are shown, but the apparatus 2 may comprise any number of litho units 4, depending what is being printed onto the web 6. For example if it is desired to print one or more colours onto the web 6 and/or a varnish, more than three litho units may be provided.
[0029] In this embodiment, where the web 6 is destined to be made into leaflets, a first litho unit 4a may apply ink in one colour to provide text or other printed matter 12 on the web. A second litho unit 4b may apply ink in a different colour, or a varnish to some or the entire web. The third litho unit 4c applies a releasable adhesive 14. The adhesive 14 may be heat and/or pressure activated.
[0030] Although not shown, an additional litho unit 4 may be provided for applying a sealant to at least those parts of the web 6 which will receive the adhesive 14 in the subsequent litho unit 4c. Thus the additional unit 4 may apply the sealer to the entire surface of the web 6 or to just selected parts thereof. The additional unit may be provided at any suitable position, for example between the second and third litho units 4b, 4c. However, it could instead be provided before the first litho unit 4a, for example.
[0031] If adhesive 14 is to be applied to both surfaces of the web 6, then a further additional unit may apply the sealer to the other side of the web 6. Again, this may be just in areas which will receive adhesive or over the entire surface. Indeed, even if adhesive 14 is not going to be applied to the other side, it may still be desirable to apply the sealer or release coating to that side.
[0032] The sealer material may be a lithoprintable UV curing primer, such as Sun Cure® ULR 48 primer.
[0033] A yet further litho unit 4 may be provided for applying a release coating to a surface of the substrate as it passes through the apparatus. As is explained further below, this may advantageous where the web 6 is to be reeled into a reel 10.
[0034] In each litho unit 4, the ink, varnish or adhesive is printed on and then dried or cured by UV lights, IR or heaters arranged within the unit. This allows the ink etc. to have dried before the next material is applied in the successive litho unit 4. In another arrangement, not each litho unit 4 may have a drying facility and only selected units 4, for example every other unit 4, have a drying facility. Multiple printings may then be dried at one time.
[0035] In the described embodiment, adhesive 14 is applied in two continuous strips along the respective edges of the web 6. However, other patterns of adhesive 14 can easily be envisaged, depending on the intended use of the web 6.
[0036] As illustrated in Figures 1 and 2, after printing, the web 6 is re-reeled onto a reel 10. It may then be stored and/or transferred to a different location for further processing.
[0037] As discussed above, a release coating may be printed onto the surface of the web 6 which does not have adhesive 14. This means that the adhesive 14 will be less likely to adhere to the web 6 during reeling. This facilitates reeling and also subsequent unreeling of the reel 10.
[0038] A further processing step is illustrated in Figure 3. In this figure, a web 6 which has been printed using the lithographic printing apparatus 2 shown in Figure 1 is folded about a fold line 16, e.g. by a plough or other process. When folded, the strips of adhesive 14 on either edge of the web 6 will overlie one another.
[0039] The folded web 18 is fed into a heat and/or pressure sealing unit 20 where the overlying strips of adhesive 14 will be sealed to one another under heat and pressure. For example, the bonding may take place at room temperature or at a temperature of 120°C at a pressure of 4 bar. The particular bonding parameters may vary depending on the adhesive used. In some embodiments, only temperature or pressure may be used.
[0040] The folded and bonded web 22 is then reeled on to another reel 24 for subsequent further processing, for example further folding or cutting.
[0041] The web 6 may be fed into the sealing unit 20 directly from the litho units 4 or from a reel 10 of material onto which the adhesive has already been applied by the litho units 4.
[0042] While a particular embodiment has been described, it will be appreciated that modifications may be made to the embodiment without departing from the scope of the invention. For example, while two strips of adhesive 14 are shown in Figure 1, it may be possible, depending on the adhesive and the web material 6 to apply adhesive 14 to just one overlapping surface of the web 6, for example a strip of adhesive along just one edge of the web 6. Also, if the end product requires multiple folds, then adhesive may be applied to both sides of the web and at appropriate locations across the web width. Also, if the web is to be folded Into three sections along the length of the web, then adhesive 14 may be applied to both sides of the web in positions arranged to meet and bond together, according to the particular fold lines used.
[0043] Also, while the invention has been described in the context of a reel feeding apparatus, it may equally apply to a sheet feed apparatus in which individual blanks are fed through the lithographic apparatus 2.
[0044] In addition, while a lithographic process has been described in the embodiment, the invention extends to flexographic and other printing processes as well. Thus in other embodiments, the litho units 4 described may be replaced by flexographic, gravure or other printing units.
1. A method of applying a releasable, peelable or re-wettable adhesive to a leaflet substrate
comprising applying the adhesive to the substrate in a printing press and drying or
curing the deposited adhesive using UV, IR or heat.
2. A method as claimed in claim 1 wherein said printing press is a lithographic, flexographic
or gravure printing press.
3. A method as claimed in claim 2 wherein the application of adhesive occurs as a step
in the process of printing and/or varnishing of the substrate.
4. A method as claimed in claim 3 wherein the substrate is paper and wherein a sealer
is applied, for example by flexographic, lithographic or gravure printing, to regions
of the substrate receiving adhesive before application of the adhesive to the substrate.
5. A method as claimed in any preceding claim wherein a release coating is applied to
a region of the web, for example by flexographic, lithographic or gravure printing.
6. A method as claimed in any preceding claim wherein the adhesive, and/or sealer and/or
release coating is applied in one or more continuous patterns e.g. strips.
7. A method as claimed in any preceding claim wherein the adhesive and/or sealer and/or
release coating is applied to one or both sides of the substrate.
8. A method as claimed in any preceding claim wherein the substrate is supplied to the
adhesive printing unit as a web from a reel, and wherein, optionally, the web is re-reeled
after application of the adhesive.
9. A method as claimed in any preceding claim wherein the adhesive printed substrate
is folded and wherein, optionally, the folding occurs prior to any re-reeling of the
web.
10. A method as claimed in any preceding claim wherein the adhesive is heat and/or pressure
activated, or is rewettable.
11. A method as claimed in claims 9 and 10 wherein the heat or pressure activation occurs
simultaneously with the folding.
12. A method as claimed in any preceding claim wherein adhesive is UV, IR or heat curable
and has a viscosity which allows it to be applied in a printing unit, for example
a lithographic, flexographic or gravure printing unit.
13. A method as claimed in any preceding claim wherein the adhesive is an acrylic based
resin system.
14. A method as claimed in any preceding claim comprising cutting the substrate into a
leaflet, the cutting optionally being effected after the folding of the substrate
and/or activation of the adhesive.
15. A method of manufacturing a leaflet using a method as claimed in any preceding claim.