WO2001017766A1

WO2001017766A1 - Flexible prelaminate

Info

Publication number: WO2001017766A1
Application number: PCT/US2000/024519
Authority: WO
Inventors: Sankar K. Paul
Original assignee: Hunt Graphics Americas Corporation
Priority date: 1999-09-10
Filing date: 2000-09-07
Publication date: 2001-03-15
Also published as: AU7120000A

Abstract

Several embodiments of an improved flexible prelaminate are disclosed, which share the following common characteristics: (1) the prelaminate cover sheet (24) has an overall thickness in the range of about 6-12 mils, of which the exposed layer of heat-activated adhesive (34) for bonding to the graphic, has a thickness in the range of about 2-4 mils, typically 3-4 mils; and/or (2) the bottom sheet (26) of the prelaminate has an overall thickness in the range of 6-12 mils, with the exposed heat activated adhesive layer (36) which will bond to the substrate of the graphic, having a thickness in the range of about 2-4 mils, preferably 3-4 mils. The overall thickness of the prelaminate can be increased substantially by the use of a sled in the form of a board or the like, on which the prelaminate with graphic is placed, to form an assembly which is passed through the rollers.

Description

FLEXIBLE PRELAMINATE

Background of the Invention

The present invention concerns an improvement relative to the type of prelaminate described in U.S. Patent Application No. 08/936,385 filed September 25, 1 997, which has counter-part

(published) European patent application 97/20291 5 filed September 23,

1 997.

Figure 4 of that application shows a flexible prelaminate embodiment in which a cover sheet consisting of a PET film and associated heat activatable adhesive, is joined at one edge to a bottom sheet consisting of another PET film with heat activatable adhesive thereon, such that the adhesive surfaces face each other. The prelaminate can be opened by pulling away the edges opposite to the joined edges to receive a graphics "work piece", i.e., a photograph, poster, computer generated graphics or other form of art work including carrier or substrate, which can be placed within the open prelaminate, with an edge of the graphic abutting the folding edge of the prelaminate, whereupon the cover sheet is set down over the graphic and the substantially flat prelaminate is passed through pressure and/or heated rollers or the like to complete the lamination.

Although the basic flexible prelaminate or pouch described in said application with respect to Figure 4, represents an improvement in the positioning of the graphic within the components of the prelaminate, the features and characteristics of the constituent parts of the prelaminate do not necessarily produce quality results. Accordingly, the need exists for further development of the features and characteristics associated with such flexible prelaminate. Summary of the Invention

In accordance with the present invention, several embodiments of an improved flexible prelaminate are disclosed, which share the following common characteristics: 1 . The prelaminate cover sheet has an overall thickness in the range of about 6-1 2 mils, of which the exposed layer of heat-activated adhesive for bonding to the graphic, has a thickness in the range of about 2-4 mils, typically 3-4 mils; and/or 2. The bottom sheet of the pre-laminate has an overall thickness in the range of 6-1 2 mils, with the exposed heat activated adhesive layer which will bond to the substrate of the graphic, having a thickness in the range of about 2-

4, preferably 3-4 mils. Flexible prelaminates having the thickness range of the constituents in accordance with the invention have greater overall thickness than the flexible laminates using conventional cover and bottom portions, whether or not attached at a common edge such as described in the subject patent application. The overall greater thickness of the present invention provides for a more intimate contact and more uniform distribution of pressure when the prelaminate with graphic is passed through the lamination rollers.

The overall thickness of the prelaminate can be increased substantially, by the use of a sled in the form of a board or the like, on which the prelaminate with graphic is placed, to form an assembly which is passed through the rollers. The overall thickness of this assembly more closely matches the ideal thickness for a typical roller set found in most laminating facilities. Brief Description of the Drawings

The preferred embodiments of the invention will be described below with reference to the accompany drawings, in which:

Figure 1 is a plan view of a portion of a laminating station, showing the inventive prelaminate with graphic therein, carried by a sled immediately prior to passing through a pair of heated pressure rollers;

Figure 2 is an elevation view, somewhat schematic, showing the prelaminate in an opened position with the graphic situated therein, and the sled situated below;

Figure 3 is schematic cross-sectional view of the cover sheet and the bottom sheet of the prelaminate in a first embodiment according to the invention; and

Figure 4 is a view similar to Figure 3, of another, more complex embodiment of the invention.

Description of the Preferred Embodiment

With particular reference to Figures 1 and 2, a laminating station 1 0 is shown, including a top roller of a pair of opposed heated pressure rollers 1 2 adapted to receive the prelaminate pouch 14 according to the invention, which envelopes a graphic 1 8 therein. Preferably, prelaminate 14 has a cover portion or sheet 24 and a bottom portion or sheet 26 which are joined together along common edges as indicated at 20, whereby the graphic 1 8 can be placed so that its leading edge abuts the joined edges at 20. As used herein, "joined along common edges" should be broadly construed to include the variety of joining options described in the disclosure incorporated herein by reference and equivalents thereof, notwithstanding that the actual connections may be spaced from the edges or formed as a series of connection points or the like. It should be appreciated that the cover portion 24 as attached to the lower portion 26 at 20 can be considered a pouch which when lying flat as shown in Figure 1 , is preferably rectangular having dimensions of e.g., 25 inch x 37 inch; 37 x 49 inch; or 49 inch x 61 inch, etc. It is preferable and customary, that the dimensions of the pouch 14 be slightly larger than the dimensions of the graphic 1 8 to be laminated therein.

A sled 22 is formed by a relatively rigid substrate 28 laminated with release paper or the like 30. The substrate is preferably paper board or foam board, having a thickness in the range of 1 /8 inch to 1 /4 inch. The release paper 30 carried thereon resists adhesion of the pouch 14 during processing when adhesive material involved in the hot- lamination extrudes from the sides of the pouch. The sled 22, in conjunction with the flexible pouch 14 and graphic 1 8, provides a large flat surface which achieves a smooth lamination and produces a higher quality finish on the graphic (e.g., print or image) to be encapsulated.

The sled also provides ease of handling of the larger size pouches as shown in Figure 1 . The sled 22 is also preferably rectangular, of a larger size than that of the pouch 14.

Figure 3 is a schematic representation of a first embodiment of a flexible pouch according to the invention, wherein the cover portion

24 is constituted by two layers 32,34 and the bottom portion 26 of the pouch is constituted by two layers 36 and 38. Although in the relevant field of endeavor, the terminology may vary when referring to each of a plurality of stacked sheets, lamination layers, or coated layers within each sheet, for convenience and consistency herein, the order first layer, second layer, third layer, etc. will always correspond to the first layer as the top-most layer of a given composite sheet or laminated sheet. Therefore, in Figure 3, 32 is the first layer and 34 is the second layer, of the cover sheet or portion 24, and layer 36 is the first layer, and layer 38 is the second layer of the composite bottom sheet or portion 26.

In the embodiments to be described below, the cover sheet or portion may have two, three or four layers, and the bottom sheet or portion may likewise have two, three or four layers.

For example, Figure 4 represents another embodiment of the invention in which the cover sheet 24' has three layers 40, 32' and 34', and the bottom sheet or portion 26' has four layers 36', 38', 42' and 44. The six embodiments to be described below may be better understood in relation to each other, by inspection of the table appearing as the Appendix hereto. The first column identifies the relevant components of the pouch, particularly the composition of the layers in the cover sheet, and the respective thicknesses of each layer in the cover, and likewise for the bottom sheet, the material composition of each layer and the respective thickness of each layer are also set forth. It may thus be understood that the embodiment of Figure 3 which has a cover sheet of two layers and a bottom sheet of two layers, can be considered as representing Embodiment 1 , whereas Figure 4 can be considered as representing Embodiment 4.

It should be evident to the reader that the Table inherently discloses how many layers constitute each of the cover and bottom, for each of the embodiments, and therefore a distinct figure for each embodiment is not needed for a full understanding of the various embodiments of the invention.

With respect to the first embodiment, the first layer is heat resistant, dimensionally stable polymeric film, preferably a transparent polyester film (PET), having a thickness of 4 mils, to which has been coated or laminated a second layer of heat activated adhesive (HAA), having a thickness of 3 mils. The bottom sheet likewise has a first layer of about 3 mils thickness of heat activated adhesive, and a second layer of about 4 mils thickness, of PET. In this context, "transparent" means light-transmitting, e.g., clear, translucent, etc.

The PET film thickness can range from about 3 to about 5 mils, whereas the heat activated adhesive thickness can range from 3 to about 4 mils. It should be understood that with a thickness of less than about 3 mils of the PET film, the pouch becomes too flexible (even with the use of the sled) . This creates wrinkles, creases, and other unwanted visual effects in the finished laminate. If the PET film thickness is greater than about 5 mils, the pouch has inadequate heat transfer to create an acceptable bond between the underside of the graphic 1 8 and the PET layer of the bottom sheet.

If the heat activated adhesive has a thickness of less than about 3 mils, there will arise poor adhesion to the visible side (i.e., the print side) of the graphic, whereas with a thickness of more than about 5 mils the transparency and resolution of the print will degrade unacceptably.

As used herein, the term heat activated adhesive should be understood as a single or double layer coating of ethylene vinyl acetate copolymer alone or in admixture with tackifying resins, polyethylene, waxes, ultraviolet light absorbers/inhibitors. These adhesives are non- tacky at ambient conditions and therefore no release liner is needed between the cover sheet 24 and the bottom sheet 26. Suitable adhesive layers have a softening point in the range of 140° - 1 80°F. A softening point below about 140°F can produce tackiness during conditions that arise in normal storage and transportation. With a softening point above about 1 80°F, the adhesive does not provide the full degree of adhesion, due to the limited heating time available with conventional heated rollers. The adhesive in the cover sheet and the adhesive in the bottom sheet can, in most instances, be the same formulation, but this is not necessary and in some situations, particularly as described with respect to the second embodiment, the formulation may preferably be different.

In the second embodiment of the invention, the cover sheet also has two layers, which are substantially identical to those described for the first embodiment. The bottom sheet has three layers, constituted by a first layer of heat activated adhesive having a thickness in the range of about 1 .0 - 2.0 mils, but of a different formulation than the heat activated adhesive of the cover sheet. The bottom layer adhesive contains tackifying resin and waxes whereas the cover layer adhesive does not. This adhesive covers the second layer, of paper having a thickness in the range of 8 - 9 mils. The paper is coated on the underside with polyethylene, thereby in effect constituting a third layer having a thickness of less than about 1 mil. The coating on the paper provides dimensional stability during storage and after lamination, where curling or bowing problems can arise, and prevents penetration of moisture through the underside of the papers. In this embodiment, the overall cover thickness would thus be in the range of about 6 - 9 mils, whereas the overall bottom sheet thickness would be in the range of about 10 -1 2 mils. One advantage of this embodiment is that the paper constituent of the bottom sheet can be selected from a wide variety of colors for compatibility with the coloration of other characteristics of the graphic.

The third embodiment of the invention has four layers in the cover and two layers in the bottom. The cover is constituted by a film release liner having a thickness of about 2 mils, as the first layer, which overlies a layer of pressure sensitive adhesive having a thickness of about 1 mil. The third layer is PET having a thickness of about 2 mils, and the fourth layer is a heat activated adhesive having a thickness of about 3 mils. The bottom sheet has two layers, which can be substantially identical to the bottom sheet described with respect to the first embodiment. The main advantage of the third embodiment is that the pouch can be utilized to secure the laminated graphic to a window or the like. After lamination, the pouch with graphic therein is relocated to the store front or other location, where the first (top) film release liner is peeled away, whereupon the pressure sensitive adhesive layer is secured against the window or the like, such that the graphic can be seen through the transparent PET third layer of the cover sheet.

The fourth embodiment is ideally configured for attaching graphics to a floor or similar surface. The pouch according to

Embodiment 4 has three layers in the cover sheet 24' and four layers in the bottom sheet 26' (as represented in Figure 4) . In the cover sheet 24', the top layer 40 is an embossed or other texturized composite film of polypropylene and PET. In general, the polypropylene layer 40 would have a thickness in the range of about 1 - 2 mils, whereas the PET layer

32' would have a thickness of about 3 mils, but these may not be separately discernable to the extent suggested by Figure 4. The third layer 34' is a 3 mil thick heat activated adhesive. The bottom sheet 26' has a first layer 36' of heat activated adhesive of about 3 mils thickness, a second layer 38' of PET having a thickness of about 2 mils, followed by a third layer 42 of a pressure sensitive adhesive having a thickness of about 1 mil, and a release liner fourth layer 44', having a thickness of about 2-4 mils.

It should be appreciated that in this embodiment, the laminated assembly can be in the form of squares or the like for placement on a floor, in the same manner as the placement of tiles. The release liner 44' is removed, exposing the pressure sensitive adhesive 42, which is then secured to the floor. The graphic, which in the laminate would be situated between the cover sheet 24' and the bottom sheet 26', would be visible through the clear textured layer 40 and PET layer 32' . The embossed or otherwise textured surface 40 provides slip resistance. As an alternative, the embossed and/or second layer 40,32 can be made from polyvinylchloride (PVC) .

The fifth embodiment is especially adapted to resist graffiti. The cover sheet has three layers, wherein the top layer is a silicone or similar coating, the second layer is PET having a thickness of about 4 mils, and the third layer is a heat activated adhesive having a thickness of about 3 mils. Practitioners in this field would recognize other materials that can be substituted for silicone in having the similar property of resisting adhesion of paint, markers, crayons, and the like, to the cover sheet. The bottom sheet can be constituted by any of the bottom sheets previously described with respect to Embodiments 1 -4.

The final embodiment has a cover sheet of two layers, similar to the cover sheet of Embodiments 1 and 2. The bottom sheet has three layers, wherein the first layer is heat activated adhesive having a thickness of about 3 mils, and the second and third layers are a composite having a thickness of about 6 mils and constituted from opaque PET and metalized PET. This type of pouch is especially adapted for so-called "pop-up" and panel displays. The bottom sheet provides minimum light transmission from behind the display, so that the image in the graphic has greater visibility against its background.

SUBSm-UTE SHEET (RULE 26 APPENDIX

SUMMARY OF COVER SHEET AND BOTTOM SHEET MATERIALS AND THICKNESSES

Key HAA = Heat Activatable Adhesive, PSA = Pressure Sensitive Adhesive, PET is substantially transparent unless otherwise indicated, (Parentheses indicate useful range)

Claims

Claims:

1 . A flexible prelaminate comprising : a cover sheet having at least two layers and an overall thickness in the range of about 6-1 2 mils, preferably about 6-9 mils, wherein one layer is a dimensionally stable, transparent film having a thickness in the range of about 2-5 mils and another layer is heat activated adhesive having a thickness in the range of about 2-4 mils; and a bottom sheet having at least two layers and an overall thickness in the range of about 6-1 2 mils, preferably about 6-9 mils, wherein one layer is a dimensionally stable substrate having a thickness in the range of about 2-5 mils and another layer is a heat activated adhesive having a thickness in the range of about 2-4 mils.

2. The flexible prelaminate of claim 1 , wherein the cover sheet and bottom sheet are joined together along respective edges with the adhesive layers facing each other to form a flexible pouch that opens and closes opposite said joined edges for receiving a graphic to be laminated.

3. The flexible pre-laminate of claim 1 , wherein the cover sheet consists of two layers, a first layer of transparent polyester film having a thickness of about 3-4 mils, and a second layer of heat activatable adhesive having a thickness of about 3-4 mils; and the bottom sheet consists of two layers, a first layer of heat activatable adhesive having a thickness of about 3-4 mils and confronting the second layer of the cover sheet, and a second layer of polyester film having a thickness of about 3-5 mils.

4. The flexible prelaminate of claim 1 , wherein the cover sheet consists of two layers, a first layer of transparent polyester film having a thickness of about 4 mils, and a second layer of heat activatable adhesive having a thickness of about 3 mils; and the bottom sheet consists of three layers, a first layer of heat activatable adhesive having a thickness in the range of 1 -2 mils and confronting the second layer of the cover sheet, a second layer of paper having a thickness in the range of 8-9 mils, and a third layer of a polymeric film having a thickness in the range of 0.5 to 1 .0 mils.

5. The flexible prelaminate of claim 1 , wherein the cover sheet has four layers consisting of a first, film release layer having a thickness in the range of 2-3 mils, a second, pressure sensitive adhesive layer having a thickness in the range of 1 .0 to 1 .5 mils, a third, polyester film layer having a thickness in the range of 2-3 mils, and a fourth layer of heat activatable adhesive, having a thickness in the range of 3-4 mils.

6. The flexible prelaminate of claim 1 , wherein the cover sheet has three layers consisting of a first layer of textured polypropylene, a second layer of polyester, which together with the first layer have a thickness in the range of 3-5 mils, and a third layer of heat activatable adhesive having a thickness in the range of 3-4 mils.

7. The flexible prelaminate of claim 1 , wherein the cover sheet consists of three layers, a first layer of release material having a thickness in the range of

0.5- 1 .0 mils, a second layer of polyurethane film having a thickness in the range of 3-4 mils, and a third layer of heat activatable adhesive having a thickness in the range of 3-4 mils.

8. The flexible prelaminate of claim 1 , wherein the bottom sheet consists of three layers, a first layer of heat activatable adhesive having a thickness in the range of 3-4 mils, an opaque polymeric film having a thickness in the range of 3-5 mils, and a metallized polymeric film having a thickness in the range of 2-3 mils.

9. A prelaminate assembly comprising: a cover sheet having at least two layers and an overall thickness in the range of about 6-1 2 mils, wherein one layer is a dimensionally stable, transparent film and another layer is heat activated adhesive having a thickness in the range of about 2-4 mils; a bottom sheet situated substantially congruently beneath the cover sheet and having at least two layers and an overall thickness in the range of about 6-1 2 mils, wherein one layer is a dimensionally stable substrate and another layer is a heat activated adhesive having a thickness in the range of about 2-4 mils; a graphic to be laminated, situated between the cover sheet and the bottom sheet; and a sled formed by a relatively rigid substrate and a layer of release material, having an overall thickness of at least about 1 /8 inch and a surface area which extends beyond the perimeter of the sheets with graphic when placed on the release material, immediately prior to passage of the assembly between a pair of heated pressure rolls.

10. The prelaminate assembly of claim 9, wherein the substrate of the sled is paper board or foam board having a thickness in the range of 1 /8 inch to 1 /4 inch.

1 1 . The prelaminate assembly of claim 9, wherein the release material is release paper.

1 2. The prelaminate of claim 9, wherein the cover sheet and bottom sheet are joined together along respective edges with the adhesive layers facing each other to form a flexible pouch that opens and closes opposite said joined edges for receiving said graphic to be laminated.

1 3. The prelaminate assembly of claim 1 2, wherein the substrate of the sled is paper board or foam board having a thickness in the range of 1 /8 inch to 1 /4 inch.

14. The prelaminate assembly of claim 1 2, wherein the cover sheet consists of two layers, a first layer of transparent polyester film having a thickness of about 3-4 mils, and a second layer of heat activatable adhesive having a thickness of about 3-4 mils; and the bottom sheet consists of two layers, a first layer of heat activatable adhesive having a thickness of about 3-4 mils and confronting the second layer of the cover sheet, and a second layer of polyester film having a thickness of about 3-5 mils.

1 5. The prelaminate assembly of claim 1 2, wherein the cover sheet has three layers consisting of a first layer of textured polypropylene, a second layer of polyester, which together with the first layer have a thickness in the range of 3-5 mils, and a third layer of heat activatable adhesive having a thickness in the range of 3-4 mils.

1 6. The prelaminate assembly of claim 1 2, wherein the cover sheet consists of three layers, a first layer of release material having a thickness of about 0.5-

1 .0 mils, a second layer of polyurethane film having a thickness of about 3-4 mils, and a third layer of heat activatable adhesive having a thickness of about 3-4 mils.