WO2001047708A1

WO2001047708A1 - Pre-laminate for large graphics

Info

Publication number: WO2001047708A1
Application number: PCT/US2000/014623
Authority: WO
Inventors: K. Paul Sankar
Original assignee: Hunt Graphics Americas Corporation
Priority date: 1999-12-27
Filing date: 2000-05-26
Publication date: 2001-07-05
Also published as: AU5167400A

Abstract

In order to achieve lamination of large graphics (18) with a high quality comparable to that currently available with the lamination of smaller graphics (18), the present innovation has three distinct, but preferably combined inventive features: (1) modifying the mounting board (24) by including a backing sheet to enhance dimensional stability; (2) texturing the adhesive (26) on the mounting board (24) to improve bonding to the graphic sheet (18); and (3) coordinating the adhesives (16) on the cover sheet (12) and the mounting board (24), to achieve strong bonding at a lower temperature range than is conventional for hot roll lamination.

Description

INTERNATIONAL SEARCH REPORT International application No.

PCT US00/14623

A. CLASSIFICATION OF SUBJECT MATTER

IPC(7) :B32B 9/00, 9/06, 33/00; B42D 15/00, 15/10 US CL :Please See Extra Sheet. According to international Patent Classification (IPC) or to both national classification and IPC

FIELDS SEARCHED

Minimum documentation searched (classification system followed by classification symbols) U.S. : NONE

Documentation searched other than minimum documentation to the extent that such documents are included in the fields searched NONE

Electronic data base consulted during the international search (name of data base and, where practicable, search terms used) NONE

DOCUMENTS CONSIDERED TO BE RELEVANT

Category* Citation of document, with indication, where appropriate, of the relevant passages Relevant to claim No.

Y, E US 6,037,028 A (REINDERS) 14 March 2000, abstract, col. 5,line 1-11, 18-22 67 to col. 6, line 1.

Y,E US 6,076,989 A (PEARCE et al) 20 June 2000, abstract, col. 4, 1-11, 18-22 lines 39-44col. 5, lines 43-47.

US 4,064,645 A (WOOD) 27 December 1977, Figure-2, col. l, lines 18-22 51-61, col.2, lines 24 & 37-40.

I I Further documents are listed in the continuation of Box C. I See patent family annex.

* Special categories of cited documents "T" later document published after the international filing date or pπoπty date and not in conflict with the application but cited to understand the

"A" document defining the general state of the art which is not considered pπnciple or theory underlying the invention to be of particular relevance

"E" earlier document published on or after the international filing date "X" document of particular relevance, the claimed invention cannot be considered novel or cannot be considered to involve an inventive step

"L" document which may throw doubts on pπoπty claιm(s) or which is when the document is taken alone cited to establish the publication date of another citation or other special reason (as specified) "Y" document of particular relevance, the claimed invention cannot be considered to involve an inventive step when the document is

"O" document referring to an oral disclosure, use, exhibition or other means combined with one or more other such documents, such combination being obvious to a person skilled in the art

"P" document published pπor to the international filing date but later than the pπoπty date claimed "&" document member of the same patent family

Date of the actual completion of the international search Date of mailing of the international search report

06 AUGUST 2000 24 AUG 2000

Name and mailing address of the ISA/US Authorized officer Commissioner of Patents and Trademarks DEBORAH TH0I Box PCT NASSER AHMAD PARALEGAL SPEC iSIALIST Washington, D C 20231 B ^'

Facsimile No. (703) 305-3230 Telephone No. (703) 308-0661

Form PCT/ISA/210 (second sheet) (July I 998)_ INTERNATIONAL SEARCH REPORT International application No PCT/USOO/ 14623

A CLASSIFICATION OF SUBJECT MATTER US CL

40/630, 661, 661 09, 768, 773, 283/72, 428/40 I, 41 9, 42 1, 141, 200, 201, 203, 204, 217, 346, 347, 354, 913 3

Form PCT/ISA 210 (extra sheet) (July 1998)* PRE-LAMINATE FOR LARGE GRAPHICS

Background of the Invention

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

(published) European Patent Application 97/20291 5 filed September 23,

1 997.

These applications (the disclosures of which are hereby incorporated by reference) show a pre-laminate which is specially adapted for permitting the user to precisely register a graphics sheet, a cover sheet, and a mounting board, which together are passed between heated rolls, thereby activating adhesive layers on each of the cover sheet and board. The cover sheet and board member are fixed together at one end, permitting them to be folded open along a straight line against which the graphic can be placed when the pre-laminate is open.

Thus, the relationship of the graphic to the cover sheet and board member, may be precisely established prior to passing of the enveloped graphic through the rolls. The resulting lamination envelopes and seals the graphic sheet therebetween. Although the innovation described in these prior applications represents a significant improvement with respect to convenience in registering the pre-laminate components, certain problems can arise when such pre-laminate is used with relatively large graphics sheets or boards. In this context, large means that the graphic sheet is to be mounted on a board having a linear dimension of at least 24 inches.

Summary of the Invention

In order to achieve lamination of such large graphics with a high quality comparable to that currently available with the lamination of smaller graphics, the present innovation has three distinct, but 2 preferably combined inventive features:

1 . Modifying the mounting board by including a backing sheet to enhance dimensional stability;

2. Texturing the adhesive on the mounting board to improve bonding to the graphic sheet; and

3. Coordinating the adhesives on the cover sheet and the mounting board, to achieve strong bonding at a lower temperature range than is conventional for hot roll lamination.

The problem addressed by the first inventive feature, arises from the tendency of large fibrous boards to absorb moisture in air, and thereby exhibit warping (bowing) . Excessive bowing may render the board unusable in a nip roll lamination system. Furthermore, upon lamination of a pre-laminate of the type where one end of each of the cover sheet and mounting board are fixed relative to each other, the heat and pressure produce different expansions and stresses on, e.g., a polyester film with associated adhesive constituting the cover sheet and a fiber board with associated adhesive constituting the mounting board. These stresses remain in the laminate and in a relatively short time, tend to induce warping.

In a general solution to this problem according to the first inventive feature, a foldable pre-laminate comprises a large mounting board having an upper, heat activatable adhesive layer and a lower, fibrous board member. A backing sheet of moisture-resistant, preferably, polymeric film material, adheres to the mounting board opposite the mounting board adhesive layer. A substantially transparent cover sheet comprises an upper, film layer, and a lower, adhesive layer and is substantially co-extensive with the mounting board. The cover 3 sheet, mounting board and backing sheet are fixed together along a straight line thereby forming a pre-laminate which can be flexibly folded open opposite the straight line to receive and encapsulate a graphics sheet. In the preferred embodiment, the cover film is polyester, especially PET, at 2-3 mils thickness, and the backing sheet includes a polyester, preferably PET film or polyester composite having a thickness up to about 5 mils. In general, it is preferred that the backing sheet film be of the same material and thickness as the cover film. Although it is not necessarily the case that the same materials will, in their respective roles during lamination and in the completed laminate, expand to the same degree, and that the resulting forces will be exactly balanced between the cover sheet and the backing layer, use of the same materials does contribute to achieving of the dual objective of providing a moisture barrier at the underside of the fibrous board, and achieving dimensional stability both before and after lamination.

It should be appreciated that a large mounting board to which a graphics sheet will be attached by the application of heat and pressure, by means other than a pre-laminate including cover sheet, can also be improved by inclusion of a backing sheet. Thus, in general, the backing sheet can improve moisture-resistance as well as dimensional stability even when the mounting board does not experience the intensity of passage through heated rolls. For example, a backing sheet on a mounting board which is not part of a pre-laminate, would typically be 0.5 mil thick PET adhered to the board with 1 .2 mil thick adhesive, whereas a backing sheet for use in a pre-laminate would typically have a thickness of about 3.0 mil PET and 2.0 mil adhesive.

Although graphic sheets are typically mounted on fibrous boards, and the backing sheet described herein is particularly effective when used with fibrous boards, the inventive concept is also applicable to 4 other mounting substrates which may be subject to dimensional instabilities. In this context, the term "semi-rigid mounting substrate", should be understood as including all substrate material suitable for the mounting of graphic sheets, which by virtue of a high surface area to thickness ratio, may be susceptible to bowing or warping arising from compression, tension, thermal, or other effects which act predominantly on the side of the substrate to which the graphic sheet is adhered. For example, a 24 x 36 inch substrate having a thickness of 1 /4 inch, has an area to thickness ratio of over 3000, whereas at 1 /1 6 inch thickness, the ratio would be nearly 1 5,000, In these circumstances, a backing sheet according to the invention, can act on the opposite side of the substrate to balance out the forces acting on the side to which the graphic sheet adheres, thereby significantly reducing or eliminating warping. The particular problem addressed by the second inventive feature arises from the subtle complexity of the bonding among the various components that is required to achieve high quality for a large graphic. The completed laminate has a transparent, translucent, clear or other light transmission characteristic, which permits the observer to view the image thereunder. For convenience, the term "transparent" will be used hereinafter to include all such variations. The mounting board typically has a thickness in the range of 1/16 to ^ΛA inch and is made of fibrous material, typically foam board or paper board which is typically opaque or translucent and serves as the structural support for the graphic sheet, as well as providing a frame at the perimeter of the graphic sheet. As used herein, the term "fibrous board" includes a board with a foam center made of styrene, and top and bottom layers made of paper, optionally having a coating for improved surface smoothness. The foam and/or the paper layers may be colored. The foam may also be made of other polymeric materials with fibrous layers on the top and 5 bottom. The graphic sheet is constituted by an image carrier, such as ink jet media, Mylar, image paper or the like, on which an image has been fixed by the selective deposition of colored inks, or chemical reaction. Well known examples are color ink jet images, photographs, electrostatic printed image paper, and in general, any other opaque printed matter. The image carrier must bond very strongly to the mounting board. Similarly, the cover sheet must bond firmly to the mounting board beyond the perimeter of the image carrier. Finally, the cover sheet must bond firmly to the visible surface of the image carrier, so that the image may be viewed without flaws or distortions.

The entrapment of air is a significant flaw which can arise in any lamination operation, but is particularly acute when the size of the board member increases beyond a linear dimension of about 24 inches, particularly a width dimension greater than 24 inches. It can be well appreciated thatthe pre-laminate with graphic has a substantial quantity of air between the various layers as the pre-laminate with graphic is being handled by the operator. This air must be squeezed completely out during lamination, i.e., as the heated rolls progress from the straight line at the registration end of the pre-laminate with encapsulated graphics sheet, toward the completion of the lamination at the other end of the pre-laminate. With large mounting boards, it has been virtually impossible to avoid small air pockets or bubbles caused by entrapped air, i.e., air which although squeezed by the rollers, cannot be squeezed out from behind the graphics sheet of the pre-laminate. This is especially true when the graphic sheet image carrier has a smooth or relatively impervious surface, such as a photograph. Particularly with a glossy print, the graphics upper surface is also very smooth and subject to the formation of entrapped air bubbles.

In accordance with applicant's solution of this problem according to the second inventive feature, the adhesive layer on the mounting 6 board is textured, thereby providing surface irregularities forming "peaks" and "valleys" . Strong bonding can occur between the image carrier and the peaks of the adhesive, while air can escape through the valleys. The "peaks" are not necessarily pointed, but can be plateaus rising above the valleys. By the time the adhesive layer is substantially fully melted at the interface with the image carrier, all the air has escaped and the extent of the valleys has been reduced substantially. In general, the peaks in the texturing should not exceed about 5 mm. In a broad aspect of this inventive feature, a foldable pre-laminate is provided for mounting a graphics sheet on a large board. The pre- laminate comprises a mounting board having a linear dimension, especially width dimension, exceeding 24 inches and having an upper, heat-activatable adhesive layer and a lower, fibrous board. A substantially transparent cover sheet comprises an upper, film layer and a lower, heat-activatable adhesive layer. The cover sheet overlies the mounting board substantially co-extensively, and the cover sheet and mounting board are fixed together along a straight line thereby forming a pre-laminate which can be folded open and closed opposite the straight line to receive and encapsulate a graphics sheet. The board adhesive, and optionally the cover adhesive, are textured so as to provide an irregular surface contact between the board adhesive and the underside of the image carrier (and optionally the image) after the graphics sheet has been encapsulated. In the preferred embodiment, the texturing forms valleys covering about 30% of the area of the board adhesive. The texturing can consist of essentially discrete deposits of adhesive, covering up to about 70% of the surface area of the board. The discrete deposits can be considered as distinct "dots". Moreover, other textured regular or irregular patterns can also be utilized.

The problem addressed by the third inventive feature concerns other flaws in appearance of the mounted graphic, which arise from 7 discontinuities or incompatibilities in the adhesives. It can be appreciated that if the combination of temperature, pressure and feed rate through the hot rolls is too intense, the image itself can be distorted. On the other hand, if the temperature at which adhesion begins to occur is too low, the cover adhesive and the board adhesive can become tacky at room temperature and make registration of the graphic sheet in the pre-laminate extremely difficult. Yet, a relatively strong bond is required between the board member and the underside of the image carrier, in order to assure permanent mounting. However, if the melt temperature even in this hidden interface is too high, the board, especially foam board, can have localized melting and extrusion at the edges of the image carrier, thereby producing an irregular and distracting seepage at the edges. Although the bond between the cover sheet and the mounting board surrounding the graphic sheet can be of only modest strength, there must be uniformity in the density and optical characteristics to avoid the appearance of flaws.

Therefore, the third inventive feature coordinates the adhesive on the foam board and the adhesive on the cover sheet to assure ease of handling so that the image carrier can be readily repositioned within the pre-laminate yet be permanently laminated at low temperature to avoid damage to the print.

In general, the third inventive feature is a foldable pre-laminate for mounting a graphics sheet on a large board having a linear dimension exceeding 24 inches and comprising an upper heat-activatable adhesive layer and a lower, fibrous board. A substantially transparent cover sheet comprising an upper, film layer and a lower, heat activatable adhesive layer overlies the mounting board substantially co-extensively. The cover sheet and mounting board are fixed together along a straight line thereby forming a pre-laminate which can be folded open opposite the straight line to receive and encapsulate a graphics sheet. The 8 adhesive layer on the cover sheet has a different formulation from the adhesive layer on the board, although they may include the same ingredient of similar chemistry such as EVA. Both adhesive layers have ambient melt points in the range of about 1 70°F - 21 0°F or pressure melt points (at 50-70 psi and 2.0 ft/min roll feed rate) in the range of about 1 65 °F - 185 °F. Preferably, the cover sheet adhesive has a lower melt point than the board adhesive.

In a particularly preferred embodiment, the melt temperatures can be controlled by utilizing a composite adhesive on the cover sheet, and a different composite adhesive on the board. The cover sheet composite adhesive has a relatively higher melt point adhesive adhered to the cover film and a relatively lower melt point adhesive facing the board member. The board adhesive is a composite with a relatively lower melt point adhesive adhered to the board and a relatively higher melt point adhesive facing the cover sheet.

Brief Description of the Drawings

These and other features and advantages of the invention will be described in greater detail with reference to the accompanying drawings, in which: Figure 1 is a schematic sectional view of the inventive pre- laminate, in relatively simple form, having a cover sheet consisting essentially of a cover film and a cover adhesive layer, connected at one edge to a mounting board having an adhesive layer, with optional protective leaf therebetween, and a graphics sheet which is to be placed between the cover sheet and mounting board after the protective leaf is removed;

Figure 2 is a schematic sectional view of another inventive pre- laminate showing a cover sheet having a composite adhesive layer, a mounting board having a textured, composite adhesive layer, a moisture 9 barrier backing sheet for the mounting board, and no protective leaf; Figure 3 is a perspective view of another pre-laminate embodying the invention, with the cover layer partially opened along a straight weld line; and Figure 4 is a perspective view of yet another pre-laminate embodying the invention, having a mounting board in the form of a foam board, with the cover layer partially opened along a straight weld line.

Description of the Preferred Embodiment(s) A better understanding of the various aspects of the invention may be derived with reference to Figures 1 -4. Figure 1 is a schematic sectional view of the inventive pre-laminate 1 0, in a relatively simple form, having a cover sheet 1 2 consisting essentially of a cover film 1 4 such as polyester, and a cover adhesive layer 1 6. The adhesive may contain a UV absorber to enhance the light fastener of the encapsulated image. A mounting board 24 is spaced from the cover sheet 1 2, and consists of a board adhesive layer 26 on a fibrous board 28, such as card board or foam board. The pre-laminate 10 of Figure 1 is shown with an optional protective leaf 36 of releasible material situated between the adhesive layers 1 6 and 26, but the leaf 36 is not necessary where, as in the present invention, the juxtaposed adhesive layers 1 6,26 are heat-activatable. Nevertheless, the leaf 36 is preferable because the pre-laminate 10 may be subjected to elevated ambient temperatures during transport or storage and the leaf 36 avoids the adhesive layers bonding to each other inadvertently prior to intended usage.

Whether or not the leaf 36 is present, the pre-laminate 10 is adapted to receive a graphics sheet 1 8 consisting essentially of a graphics image 20 bonded to or diffused within the image carrier 22. 10

The adjacent straight leading edges of the cover sheet 1 2 and board member 24 are fixed in position relative to each other by a glue layer 38 such that the sheet 1 2 and board member 24 can be folded apart to receive the graphics sheet 1 8, without disturbing the fixed relationship of the edges. In this context, folding includes flexibly parting the cover sheet 1 2 from the board 24. Moreover, the glue panel 38 provides a stop surface for receiving a similar straight edge of the graphics sheet 1 8 in abutting relationship, thereby establishing a common reference point and colinearity of the leading edges for achieving registration, as described in said prior application.

It should be appreciated that the embodiment shown in Figure 1 is novel with respect to the choice of adhesives in layers 1 6,26 as they dictate the effective melt point temperature during hot roll lamination. Preferably, the exposed surface of the board adhesive layer 26 and optionally of the cover adhesive layer 1 6 are textured, as additional novel features.

Figure 2 illustrates a second embodiment, which differs from the embodiment shown in Figure 1 in three important respects. First, the cover sheet 1 2' consists essentially of a cover film 1 4 which may be the same or similar to that shown in Figure 1 , and a composite adhesive layer consisting of a hidden layer 1 6A and an exposed layer 1 6B. Similarly, the board member 24' consists essentially of board 28 that is the same or similar to that shown in Figure 1 , and a composite adhesive layer consisting of an upper, or exposed layer 26A and an under, or hidden layer 26B. Texturing on the surface of layer 26A is indicated at 52. The constitution of the adhesive layers as composites may be viewed as variations of the inventive features described with respect to the embodiment of Figure 1 , in that the low temperature effectiveness and the texturing, are each achievable independently of one another. It should also be appreciated that other variations (not 1 1 shown) are possible, whereby the cover adhesive layer is constituted from a single adhesive, whereas the board adhesive layer is constituted from two adhesives, or alternatively, the cover adhesive layer is constituted from two adhesives, whereas the board adhesive layer is constituted from a single adhesive. The cover film material can be polyester, but other materials are also usable. The cover film can be embossed or coated with light diffracting particles to provide a lustrous or matte appearance to the image after lamination. Perforated PVC can also be utilized, particularly for the lamination of photographs, where escape of air during lamination needs to be enhanced, especially for the exposed surface of the photograph.

Figure 2 shows another inventive feature, in addition to the low temperature, compatible adhesives and the texturing of the adhesive particularly on the board member, in that a backing sheet 30 is bonded to the underside of the mounting board 24' . In particular, the backing sheet 30 consists essentially of a water-resistant polymeric film 32, preferably polyester and an adhesive layer 34 which effectuates the bond. It is usually preferable that the film 32 be of the same or similar material as that of the cover film 14. In general, low shrinkage material such as zero shrinkage PET is best.

In Figure 2, the space 42 between the cover sheet 1 2' and the mounting board 24' does not have the optional protective leaf 36. However, in a manner similar to that shown in Figure 1 , an adhesive panel 38' maintains the cover sheet 1 2', board member 24' and backing sheet 30 in fixed relation to each other, by aligning and holding the respective straight edges.

Figure 3 is a perspective view of a pre-laminate according to the invention, wherein the cover sheet 1 2 has been folded open 44 relative to the mounting board 24 such that the fold occurs along the weld line 40, which serves substantially the same function as the glue panel 38

Claims

1 2 shown in Figures 1 and 2. The weld line serves two purposes. First, it maintains registration of the cover sheet 1 2 and board member 24 relative to each other, and secondly, it provides a stop surface for receiving in abutting contact, a straight edge of the graphics sheet 1 8. It should be appreciated that, whereas the weld line 40 as shown inFigure 3, spans the full width of the pre-laminate, this is not necessary. For example, the weld line could be interrupted, or other fixation means could be located at a minimum of two points along a straight line, thereby defining the straight line and providing discontinuous but nevertheless effective stop surfaces for registering the graphics sheet1 8. As used herein, the phrase "fixed together along a straight line" includes fixation at two or more points which fall on a straight line.Figure 4 shows a variation which is similar to Figure 3, except that the cover sheet 1 2' is the same as that described with respect to Figure 2, the backing sheet 30' is the same as that shown with respect to Figure 2, but the board member 24" consists essentially of a foam board having a foam layer 48, a paper layer 46, and an opposite paper layer 50. In this embodiment, the adhesive layer 26' on the board is a single material, defining a texture with individual, discrete dots of adhesive material. Optionally, another layer of adhesive could underlie the dots.As previously mentioned, each of the three inventive features, ( 1 ) the backing sheet, (2) texturing the adhesive of the board, and (3) coordinating the adhesives on the cover sheet and the mounting board to achieve high adhesion with a lower temperature range than is conventional, can be implemented individually or in any combination. The novel board with backing can be used apart from the pre- laminate, and is exemplified as Embodiment 1 in the following table. The most effective pre-laminates would combine all of the foregoing three features, as exemplified in Embodiments 2 and 3: 1 3Three Embodiments of the InventionThe cover adhesive material 1 6 for Embodiment 3 is PE or the like (hidden) and EVA or the like (exposed) . The Jet Guard or Deep Crystal brands of material, available from Hunt Graphics American Corporation, or Glenroy 3/2 Dl film, are particularly suited for use in Embodiment 3. The Ecomelt products are available from Ebnoth (Switzerland) . The Proxmelt product is available from Pierce & Steven (U.S.) . 1 4 CLAIMS:

1 . A foldable pre-laminate for mounting a graphics sheet on a large board, comprising: a mounting board having a linear dimension exceeding 24 inches and comprising an upper, heat-activatable adhesive layer and a lower, fibrous board; a backing sheet adhered to the mounting board opposite the mounting board adhesive layer; a substantially transparent cover sheet comprising an upper, film layer and a lower, heat-activatable adhesive layer; wherein the mounting board, backing sheet, and cover sheet are substantially coextensive, with the cover sheet overlying the mounting board, and the cover sheet, mounting board, and backing sheet are fixed together along a straight line thereby forming a pre-laminate which can be folded open opposite said straight line to receive and encapsulate a graphics sheet.

2. The foldable pre-laminate of claim 1 , wherein backing sheet and the cover sheet include polymeric films of substantially the same material.

3. The foldable pre-laminate of claim 1 , where the backing sheet is a polymeric, moisture-resistant film.

4. The foldable pre-laminate of claim 3, wherein the material is polyester. 1 5

5. The foldable pre-laminate of claim 1 , wherein the cover sheet material is a perforated PVC.

6. The foldable pre-laminate of claim 3, wherein the cover sheet film is polyester having a thickness of about 2-3 mils and the cover sheet adhesive has a thickness of about 2-3 mils, and the backing sheet comprises a polyester film having a thickness of about 2-3 mils bonded to the mounting board with an adhesive having a thickness of about 2-3 mils.

7. A foldable pre-laminate for mounting a graphics sheet on a large board, comprising: a mounting board having a linear dimension exceeding 24 inches and comprising an upper, heat-activatable adhesive layer and a lower, fibrous board; a substantially transparent cover sheet comprising an upper, film layer and a lower, heat-activatable adhesive layer; wherein the cover sheet overlies the mounting board substantially coextensively, the cover sheet and mounting board are fixed together along a straight line thereby forming a pre-laminate which can be folded open opposite said straight line to receive and encapsulate a graphics sheet, and the board adhesive is textured.

8. The foldable pre-laminate of claim 7, wherein the cover adhesive is textured. 1 6

9. The foldable pre-laminate of claim 7, wherein the texturing consists essentially of discrete deposits of adhesive covering up to about 70% of the surface area of the fibrous board.

1 0. The foldable pre-laminate of claim 7, wherein the texturing includes a pattern of peaks and valleys with the peaks having a height of less than about 5mm.

1 1 . The foldable pre-laminate of claim 9, wherein the texturing includes a pattern of peaks and valleys with the peaks having a height of less than about 5mm.

1 2. A foldable pre-laminate for mounting a graphics sheet on a large board, comprising: a mounting board having a linear dimension exceeding 24 inches and comprising an upper, heat-activatable adhesive layer and a lower, fibrous board; a substantially transparent cover sheet comprising an upper, film layer and a lower, heat-activatable adhesive layer; wherein the cover sheet overlies the mounting board substantially coextensively, and the cover sheet and mounting board are fixed together along a straight line thereby forming a pre-laminate which can be folded open opposite said straight line to receive and encapsulate a graphics sheet, the adhesive layer on the cover sheet has a different formulation from the adhesive layer on board, and both adhesive layers have ambient melt points in the range of about 1 20-210 deg. F or pressure melt points (50-70 psi) in the 1 7 range of about 165-1 85 deg. F.

1 3. The foldable pre-laminate of claim 1 2, wherein the cover sheet adhesive has a lower melt point than the board adhesive.

1 4. The foldable pre-laminate of claim 1 2, wherein the cover sheet adhesive is a composite with a relatively higher melt point adhesive adhered to the cover film and a relatively low melt point adhesive facing the board member, and the board adhesive is a composite with a relatively lower melt point adhesive adhered to the board and a relatively higher melt point adhesive facing the cover sheet.

1 5. The foldable pre-laminate of claim 1 2, wherein the adhesive layer on the board is a composite with a relatively lower melt point adhesive adhered to the board and a relatively higher melt point adhesive facing the cover sheet.

1 6. A foldable pre-laminate for mounting a graphics sheet on a large board, comprising: a mounting board having a linear dimension exceeding 24 inches and comprising an upper, heat-activatable adhesive layer and a lower, fibrous board; a backing sheet of polymeric film adhered to the mounting board opposite the mounting board adhesive layer; a substantially transparent cover sheet comprising an upper, film layer and a lower, heat-activatable adhesive layer; wherein the mounting board, backing sheet, and cover sheet are substantially coextensive with the cover sheet overlying the mounting