CA2160442C - Durable sheets for printing - Google Patents
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- CA2160442C CA2160442C CA 2160442 CA2160442A CA2160442C CA 2160442 C CA2160442 C CA 2160442C CA 2160442 CA2160442 CA 2160442 CA 2160442 A CA2160442 A CA 2160442A CA 2160442 C CA2160442 C CA 2160442C
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- B—PERFORMING OPERATIONS; TRANSPORTING
- B41—PRINTING; LINING MACHINES; TYPEWRITERS; STAMPS
- B41M—PRINTING, DUPLICATING, MARKING, OR COPYING PROCESSES; COLOUR PRINTING
- B41M5/00—Duplicating or marking methods; Sheet materials for use therein
- B41M5/50—Recording sheets characterised by the coating used to improve ink, dye or pigment receptivity, e.g. for ink-jet or thermal dye transfer recording
- B41M5/502—Recording sheets characterised by the coating used to improve ink, dye or pigment receptivity, e.g. for ink-jet or thermal dye transfer recording characterised by structural details, e.g. multilayer materials
Abstract
Composite durable sheets will print in hot laser printers, or print systems such as rotogravure, lithographic, screen, letterpress, flexographic, and the like, without curling if they comprise at least three layers: A. at least one base layer, B. a printable surface layer on top of the base layer or layers, and C. an optionally printable, optionally strippable protective backing on bottom face on the base layer or layers and if the thermal expansion or contraction characteristics of the printable layer B and the protective backing C are the same or substantially the same.
In preferred embodiments, all or selected portions of the printable surfaces will be coated with a print enhancing coating and one or both major faces of the sheets will include a coating of an antistatic composition.
In preferred embodiments, all or selected portions of the printable surfaces will be coated with a print enhancing coating and one or both major faces of the sheets will include a coating of an antistatic composition.
Description
.
DURABLE SHEETS FOR PRINTING
FIELD OF THE INVENTION
This invention relates to durable printing sheets, such as laser and thermally transfer printable multiple layer sheets, as well as those printed by other printing processes such rotogravure, lithography, screen, letterpress and flexographic techniques. The sheets are of balanced structure and remain curl free under the normal temperature, pressure, tension and environmental conditions of the varied printing processes.
BACKGROUND OF THE INVENTION
Laser printing of label materials is a relatively new development and employs apparatus such as shown and described in Gretchev, U.S. 4,494,129. The high pressures and temperatures employed in laser printing can be accommodated by simple, non-composite paper and synthetic sheets . They will not curl and become di f f icult to feed and stack . I f , however, dual-layer and multi-layer composite sheets, which are necessary components of label or tag sheets, are fed to laser printers, special methods are needed to prevent the composite sheets from curling during and after printing. In one such method, Rutkowski, U.S. 4,913,926, discloses laser printing a dual-layer label sheet having a continuous film of pressure sensitive adhesive between the layers. The resultant sheet is shown to be curled up after passing through the printer.
I f , however, the adhesive is patterned into geometric f figures, such as hexagons and diamonds, during deposition to leave a number of gaps between the patterns, and then the sheets are laser printed, no curling is observed because the melted and squeezed adhesive layer flows into and fills the gaps relieving any stresses developed by heat and pressure. In the method of Rutkowski, special equipment will be necessary for patterned printing and the high degree quality control ~~~0~~.
DURABLE SHEETS FOR PRINTING
FIELD OF THE INVENTION
This invention relates to durable printing sheets, such as laser and thermally transfer printable multiple layer sheets, as well as those printed by other printing processes such rotogravure, lithography, screen, letterpress and flexographic techniques. The sheets are of balanced structure and remain curl free under the normal temperature, pressure, tension and environmental conditions of the varied printing processes.
BACKGROUND OF THE INVENTION
Laser printing of label materials is a relatively new development and employs apparatus such as shown and described in Gretchev, U.S. 4,494,129. The high pressures and temperatures employed in laser printing can be accommodated by simple, non-composite paper and synthetic sheets . They will not curl and become di f f icult to feed and stack . I f , however, dual-layer and multi-layer composite sheets, which are necessary components of label or tag sheets, are fed to laser printers, special methods are needed to prevent the composite sheets from curling during and after printing. In one such method, Rutkowski, U.S. 4,913,926, discloses laser printing a dual-layer label sheet having a continuous film of pressure sensitive adhesive between the layers. The resultant sheet is shown to be curled up after passing through the printer.
I f , however, the adhesive is patterned into geometric f figures, such as hexagons and diamonds, during deposition to leave a number of gaps between the patterns, and then the sheets are laser printed, no curling is observed because the melted and squeezed adhesive layer flows into and fills the gaps relieving any stresses developed by heat and pressure. In the method of Rutkowski, special equipment will be necessary for patterned printing and the high degree quality control ~~~0~~.
necessary should be labor intensive. Another approach to providing adhesive paper labels having curling resistance and applicable to electrostatic and magnetic copying in disclosed by Fuji Xerox Corp in Japanese Patent Publication No.
J59149970-A, August 28, 1984. Such a composite comprises two sheets, a surface paper to receive the printing and a release paper having a ratio of surface paper to release paper elongation and/or contraction of 0.7-1.0:1Ø Furthermore, the release paper has an elongation and/or contraction of below 0.90. If such a composite is used to make laser printed labels comprising wood pulp paper, curling is distinctly not a problem, but the labels do not weather well and cannot be used outdoors, such as to mark lumber, because rain, wind and snow will make them difficult to read and maintain. If, on the other hand, such labels are made of synthetic paper, such as polyvinyl chloride paper, curling is not a problem because the elongation/contraction requirements are met, but the vinyl paper, like wood pulp paper, doesn't weather well and tears readily during application, and has a tendency to give off dangerous gases if burned. Improved weatherability, equivalent printability, high tear resistance and no tendency to elaborate noxious gases during heating can be achieved, if instead of vinyl, tear-resistant synthetic papers are used, such as those based on thermoplastic polyesters and polyolefins, e.g., polypropylene, and the like.
However, the substitution of these for wood pulp paper and vinyl paper in the composite dual-layer label sheets of the Rutkowski and the Japanese Publication, above-mentioned, lead to serious and substantial curling problems during and after laser printing.
It has now been discovered that if a composite sheet is provided having at least three layers and if, further, the top and bottom layers are selected to have the same or substantially the same thermal expansion and contraction 1~~:
J59149970-A, August 28, 1984. Such a composite comprises two sheets, a surface paper to receive the printing and a release paper having a ratio of surface paper to release paper elongation and/or contraction of 0.7-1.0:1Ø Furthermore, the release paper has an elongation and/or contraction of below 0.90. If such a composite is used to make laser printed labels comprising wood pulp paper, curling is distinctly not a problem, but the labels do not weather well and cannot be used outdoors, such as to mark lumber, because rain, wind and snow will make them difficult to read and maintain. If, on the other hand, such labels are made of synthetic paper, such as polyvinyl chloride paper, curling is not a problem because the elongation/contraction requirements are met, but the vinyl paper, like wood pulp paper, doesn't weather well and tears readily during application, and has a tendency to give off dangerous gases if burned. Improved weatherability, equivalent printability, high tear resistance and no tendency to elaborate noxious gases during heating can be achieved, if instead of vinyl, tear-resistant synthetic papers are used, such as those based on thermoplastic polyesters and polyolefins, e.g., polypropylene, and the like.
However, the substitution of these for wood pulp paper and vinyl paper in the composite dual-layer label sheets of the Rutkowski and the Japanese Publication, above-mentioned, lead to serious and substantial curling problems during and after laser printing.
It has now been discovered that if a composite sheet is provided having at least three layers and if, further, the top and bottom layers are selected to have the same or substantially the same thermal expansion and contraction 1~~:
characteristics, then non-vinyl, tear-resistant plastic papers ' such as polyester and polyolefins and the like can be used to provide non-curling sheets, with none of the above-mentioned disadvantages of wood pulp paper and vinyl composite sheets and labels. This result is unexpected in view of the art because the base layer of this invention can have an expansion/contraction ratio substantially different than either the printable top layer and the protective backing layer or coating, whereas the Japanese Patent Publication would teach otherwise.
Accordingly, a principal object of the present invention is to provide printable sheets, e.g., of labels or tags mounted on backing sheets, without the curling problem discussed above. It is a further object of the invention to provide a method for printing sheets without curling. It is a further object to provide printed sheets of such structure which will remain curl free throughout the useful life of the printed piece under varied conditions of temperature and pressure. It is still another object of the invention to provide articles labeled with curl-free printed labels or tagged with curl free printed tags.
These and other objects of the invention will become apparent from the present specification and drawing.
SUMMARY OF THE INVENTION
According to this invention, in one of its major aspects, there are provided durable composite sheets for printing which lay flat and do not curl through out the printing process where temperature, pressure and/or tension can cause curl, i.e., generally all types of printing, the sheets including at least three layers comprised of:
A. at least one base layer comprising a paper or a synthetic paper or a coated film;
Accordingly, a principal object of the present invention is to provide printable sheets, e.g., of labels or tags mounted on backing sheets, without the curling problem discussed above. It is a further object of the invention to provide a method for printing sheets without curling. It is a further object to provide printed sheets of such structure which will remain curl free throughout the useful life of the printed piece under varied conditions of temperature and pressure. It is still another object of the invention to provide articles labeled with curl-free printed labels or tagged with curl free printed tags.
These and other objects of the invention will become apparent from the present specification and drawing.
SUMMARY OF THE INVENTION
According to this invention, in one of its major aspects, there are provided durable composite sheets for printing which lay flat and do not curl through out the printing process where temperature, pressure and/or tension can cause curl, i.e., generally all types of printing, the sheets including at least three layers comprised of:
A. at least one base layer comprising a paper or a synthetic paper or a coated film;
B. at least one print receiving layer comprising a paper or a synthetic paper or a coated film adhered to the top face of base layer or layers A; and C. at least one backing layer comprising a paper or a synthetic paper or a coated film adhered to the bottom face of base layer or layers A, the top layer B and the backing C
having the same or substantially the same thermal elongation or contraction characteristics.
Special mention is made of a preferred aspect of the invention which comprises a composite sheet which does not curl when heated to temperatures normal 1y encountered in . laser printing, the sheet including at least three layers comprised of A. at least one base layer comprising a tear resistant synthetic paper having a pressure sensitive adhesive on the bottom face thereof;
B. a print receiving tear resistant synthetic paper layer permanently adhered to the top face of base layer or layers A; and C. a protective backing comprising a paper layer or a coated film releasably adhered to said pressure sensitive adhesive on the bottom face of base layer or layers A, said top layer B and said protective backing C having the same or substantially the same thermal elongation or contraction characteristics.
In preferred features, the invention contemplates printing sheets as defined above wherein layers A and B
comprise all or subdivided portions thereof; those, wherein layer A comprises a thermoplastic polyester, and layer B and protective backing C comprise a polyolefin; and such sheets wherein layer A comprises a thermoplastic polyester, layer B
comprises a polyolefin and backing C comprises a thermoplastic resin coating. Also contemplated are sheets as defined above which also include a printing enhancing coating on the print receiving face of layer B, especially those wherein the printing enhancing coating comprises an acrylic, polyester or urethane resin filled with finely divided clay, silica, titanium dioxide, zinc oxide, other fillers or blends of fillers, and the like ; those wherein layer B is adhered to layer or layers A through an adhesive layer having high cohesive strength and low shear strength whereby layers B and A can move transversely under the influence of heat without parting. Further preferred embodiments comprise label sheets as defined above wherein backing C can be releasably adhered to the pressure sensitive adhesive on base layer or layers A
through a release coating, especially those wherein the release coating comprises a silicone and the pressure sensitive adhesive layer has high cohesion and low shear strength whereby layers C and A can move transversely under the influence of heat without parting. In addition, the invention includes sheets as defined above wherein layer or layers A include an effective amount of conductive filler for dissipating static changes developed during laser printing whereby sheet feeding and delivery problems are minimized, special mention being made of such sheets wherein the conductive filler comprises carbon black. Best results appear to be obtained with sheets as defined above wherein layer B
has a ratio of thermal elongation or contraction in the range of from about 0.7 to about 1.3 with respect to 1.0 for protective backing C, especially those wherein said layer B
has a ratio or thermal elongation or contraction of about 1.0 with respect to 1.0 for protective backing C. Also contemplated as preferred embodiments are sheets for printing as defined above wherein the outwardly facing major face of layer B, layer C, or layers B and C are provided with a print receiving area or area, and sheets in which the print receiving areas are provided in whole or part with a print enhancing coating. Also contemplated are sheets as above _6_ defined coated in one or both major faces with an antistatic composition so as to avoid jamming in subsequent high speed production printing processes. Such antistatic compositions comprise, for example, amines, quaternary ammonium compounds, anionic or cationic surface active agents, or mixtures of any of the foregoing, and it is preferred to apply them by deposition from an aqueous medium. In an especially preferred embodiment, the invention contemplates also sheets as above defined which, before or after printing, are cut into a plurality of pieces of substantially the same size.
In a broad aspect, then, the present invention relates to a durable sheet for printing, the sheet including at least three layers comprised of: layer A, which comprises at least one base layer consisting of a paper, a synthetic paper or a coated film; layer B, which comprises at least one print receiving layer consisting of a paper, a synthetic paper or a coated film, wherein layer B is adhered to the top face of layer A; and layer C, which comprises at least one backing layer consisting of a paper, a synthetic paper or a coated film, wherein layer C is adhered to the bottom face of layer A; ~ and wherein layer B and the backing C have the same or substantially the same thermal elongation or contraction characteristics; and wherein the top surface of layer A
comprises a release agent, the bottom surface of layer B
comprises a pressure sensitive adhesive and layer C is permanently adhered to layer A.
In another broad aspect, then, the present invention relates to a durable sheet for printing, the sheet including at least three layers comprised of: layer A, which comprises at least one base layer consisting of a paper, a synthetic paper or a coated film; layer B, which comprises at least one print receiving layer consisting of a paper, a synthetic paper or a coated film, wherein layer B is adhered to the top face of layer A, and layer C, which comprises at least one backing - 6a-layer consisting of a paper, a synthetic paper or a coated film, wherein layer C is adhered to the bottom face of layer A; and wherein layer B and the backing C have the same or substantially the same thermal elongation or contraction characteristics; and wherein the top surface of layer C
comprises a release agent, the bottom surface of layer A
comprises a pressure sensitive adhesive and layer B is permanently adhered to layer A.
In yet another broad aspect, then, the present invention relates to a durable sheet for printing, the sheet including at least three layers comprised of: layer A, which comprises at least one base layer consisting of a paper, a synthetic paper or a coated film; layer B, which comprises at least one print receiving layer consisting of a paper, a synthetic paper or a coated film, wherein layer B is adhered to the top face of layer A; and layer C, which comprises at least one backing layer consisting of a paper, a synthetic paper or a coated film, wherein layer C is adhered to the bottom face of layer A; and wherein layer B and the backing C have the same or substantially the same thermal elongation or contraction characteristics; and wherein layer A comprises a thermoplastic resin, and layer B and layer C comprise a polyolefin.
In a further broad aspect, then, the present invention relates to a durable sheet for printing, the sheet including at least three layers comprised of: layer A, which comprises at least one base layer consisting of a paper, a synthetic paper or a coated film; layer B, which comprises at least one print receiving layer consisting of a paper, a synthetic paper or a coated film, wherein layer B is adhered to the top face of layer A; and layer C, which comprises at least one backing layer, consisting of a paper, a synthetic paper or a coated film, wherein layer C is adhered to the bottom face of layer A; and wherein layer B and the backing C have the same or substantially the same thermal elongation or contraction -6b-characteristics; and wherein layer A comprises a thermoplastic polyester, layer B comprises a polyolefin and layer C
comprises a thermoplastic resin coating.
In a still further broad aspect, then, the present invention relates to a durable sheet for printing, the sheet including at least three layers comprised of: layer A, which comprises at least one base layer consisting of a paper, a synthetic paper or a coated film; layer B, which comprises at least one print receiving layer consisting of a paper, a synthetic paper or a coated film, wherein layer B is adhered to the top face of layer A; and layer C, which comprises at least one backing layer consisting of a paper, a synthetic paper or a coated film, wherein layer C is adhered to the bottom face of layer A; and wherein layer B and the backing C
have the same or substantially the same thermal elongation or contraction characteristics; and which also includes a printing enhancing coating on the print receiving face of layer B.
In another broad aspect, then, the present invention relates to a sheet for printing, said sheet including at least three layers comprised of: layer A, which comprises at least one base layer consisting of a tear resistant synthetic paper having a pressure sensitive adhesive on the bottom face thereof; layer B, which comprises a print receiving tear resistant synthetic paper layer permanently adhered to the top face of layer A; and layer C, which comprises a protective backing consisting of a paper layer or a coated film releasably adhered to said pressure sensitive adhesive on the bottom face of layer A, said layer B and said layer C having the same or substantially the same thermal elongation or contraction characteristics.
In yet another broad aspect, then, the present invention relates to a printed sheet including at least three layers comprised of : layer A, which comprises at least one base layer -6c-consisting of a tear resistant synthetic paper having a pressure sensitive adhesive on the bottom face thereof; layer B, which comprises a printed tear resistant synthetic paper layer permanently adhered to the top face of layer A; and layer C, which comprises a protective backing consisting of a paper layer or a coated film releasably adhered to said pressure sensitive adhesive on the bottom face of layer A, said top layer B and said layer C having the same or substantially the same thermal elongation or contraction characteristics.
DESCRIPTION OF THE DRAWINGS
FIG. 1 is a perspective view of a three-layer sheet of printed labels mounted on a backing sheet, a section of the edge being enlarged in FIG. 1A to show detail:
FIG. 2 is a top view of one of the labels from the sheet shown in FIG. 1;
FIG. 3 shows a three-layer sheet having balanced thermal expansion/contraction characteristics in accordance with the invention following printing through a printer, a section of the edge being enlarged in FIG. 3A to show detail; and FIG. 4 shows a three-layer sheet having unbalanced thermal expansion/contraction characteristics not in accordance with this invention, which has been curled up as a result of being printed in a printer, a section of the edge being enlarged in FIG. 4A to show detail.
DETAILED DESCRIPTION OF THE INVENTION
Referring more particularly to the drawings, Figure 1 shows a three-layer sheet 2 including an upper sheet made up of a large number of labels 4 which have been die cut to be separate from one another and which are mounted on backing sheet 6. As will be seen from FIG. 1A, each label comprises printable surface layer 8 alone or on top of base layer 10.
Figure 2 is a front view of one of the labels 4 which has been removed from the backing sheet 6. More specifically, on the front of the label 4 as shown in Figure 2, is some printing or advertising 12, and a bar code configuration 14.
On the back of label 4 .is a continuous layer of pressure sensitive adhesive (not shown) of an entirely conventional type well known to those skilled in the art. There is no need whatsoever to pattern the layer of adhesive into geometric forms as is done in some of the commercial labels in the current state of the art.
Figs. 3 and 3A show a three-layer sheet 16 of the present invention, comprising a top sheet 8 and protective backing 6 having the same thermal expansion/contraction characteristics, in which the sheet 16, following printing, is entirely level and flat. In Figs. 4 and 4A, however, it is shown that a three-layer sheet 18 comprising a top sheet 8a and protective backing 6a having substantially different and unbalanced thermal expansion/contraction characteristics on either side of base layer 10, and, following printing in a printer, it curls up as indicated, particularly at corners 20. This curling is found to be so significant that proper stacking of the printed sheets is not practical, nor is further mechanical processing of the sheets.
Laser printing apparatus, which are well known, are described in U.S. 4,494,129 and 4,913,926, mentioned hereinabove. In general, all such apparatus use electrostatically chargeable drums to form an image and heated rollers to apply moderately high levels of pressure, e.g., greater than about 100 pounds per square inch, and elevated temperatures, e.g., greater than about 250° F, to the sheets during the printing process. It is believed that these relatively high pressures and temperatures produce the curled adhesively bonded label sheets as shown in Figure 4 when no particular attention is paid to selecting top and bottom layers 8a and 6a so that they have the same or substantially the same thermal expansion/contraction characteristics as is required by the present invention.
However, by using a balanced composite as shown in Figure 3A of the drawing, wherein layers 8 and 6 have the same or substantially the same thermal expansion/contraction characteristics, the tension or strain produced downstream in any process where temperature, pressure, and tension can cause curl and flat sheets for printing will be produced.
Suitable materials from the paper sheets comprise thermoplastic polyester, e.g., poly(ethylene terephthalate), poly(acrylonitrile), and the like, as well as polyolefins, such as polypropylene, polyethylene, and the like. For the base layer or layers, polyesters are preferred, and especially polyethylene terephthalate) which is available from a number of sources. For the top layer, monoaxially or biaxially oriented polyolefins are preferred, especially polypropylene, and such papers are available from a number of sources, such as Mobil Chemical Company, Pittsford, N.Y. 14534, U.S.A., tradename "Oppalyte" TW and Toray Plastics, Inc., North Kingston, RI, 02852, U.S.A., tradenames "Treafilms" and "Treax Films".
Thermal elongation and/or contraction characteristics are measured by standard test methods . The values are used to select suitable substrates for use in-this invention. It is important that the relative values rather than their magnitude receive the most attention. It is known for example that polypropylene paper has a shrinkage at 275°F. of -4.5~ in the MD and -5.0~ in the TD. If a composite is prepared having polypropylene on the top and the bottom and polyethylene terephthalate) in the center, curl-free laser printing will be achieved because the top and bottom layers will have the same thermal contraction. If, however, a dual layer composite of polypropylene on top of polyester or a three layer comprising polypropylene (top), polyester(middle) and ~1~0~~
polyester (bottom) is prepared, the composites are unbalanced, as explained above, and they will not print without curling.
The layers can be simply heat-bonded with heat-activated adhesive, but it is preferred to use an adhesive of a permanent type and of a pressure sensitive type. Many adhesives are suitable although it is preferred to select one which has a high cohesive strength and low shear strength to facilitate transverse movement between different layers during heating while precluding parting.
In preferred embodiments, the backing C or layer A will be adhered to the pressure sensitive adhesive through a release coating, such as a poly(tetrafluoroethylene film) or more preferably a silicone resin, as is known in the art, for the labels . Layers B and C may be permanently adhered to layer A by a laminating adhesive for the tags. A release coating is not needed for the tags.
Among the preferred features of the invention are label sheets of the type described wherein the base layer is rendered electrically conductive by including an effective amount of a conductive filler, e.g., a powder such as silver and nickel powders or carbon powders. Conductive fillers can also be put in adhesives instead of base layers and also in printable coatings, without departing from the spirit or scope of the invention. The polyethylene terephalate) base layer, and/ or the other substrates, can for example include 5 to 40 percent by weight of carbon powder, and not only will the sheets not curl during printing, but they also will dissipate static changes developed during printing which can also interfere with feeding, imaging and delivery. For best results, when using polyolefin layers, composite volume resistivity gives best printing at values equal to or less than 1014 ohms-cm.
Concerning the backing, this can be the same or different in terms of material from the top layer so long as 2~.~~~~
the expansion/contraction characteristics are the same or substantially the same, preferably from 0.7-1.3:1 and more preferably 1:1. The backing can even comprise a film coating instead of a sheet, and the backing can even comprise a wood pulp paper sheet, such as a silicone-coated paper sheet, instead of a synthetic paper sheet, without departing from the scope of the invention.
The composites are assembled in conventional ways using conventional equipment. The sheets are consolidated continuously under moderate heat and pressure and cut to any desired size and, if desired, the labels or tags are die-cut into the sheets by means well known to those skilled in this art.
The antistatic agents used herein are applied as surface coatings or are incorporated as additives into print receiving coatings, preferably from an aqueous medium. Such coatings are conveniently applied by gravure, mayer rod, reverse roll, or other techniques known to those skilled in this art. For example, a thin coat of antistatic agent can be applied to one surface of the film or anti-stat additive can be incorporated into a clay coating. Suitable such coatings or additives can be selected from the many commercially-available materials known in this art, such as listed, for example in Modern Plastics Encyclopedia, Mid-October Issue, 1987, "Antistatic Agents" by J. L. Rogers, pages 130 and 132, as well as pages 579-581. Preferred for use herein are commercially-available antistatic coating compositions available, for example, from Akzo Chemie America, Chicago, IL, under the trade name or designation Armostato Aqueous Ethoquad CY12, from Union Carbide Corp., Danbury, CT, under the trade name or designation Silweto L-77, a modified silicone, or from Process Resources Corp., Thornwood, NY, under the tradename or designation PD 945, a proprietary mixture which is gravure -11- lsl-ool-a2 applicable and having the typical properties described in the Table:
TABLE
Solids 4 ~
pH 8.5 - 9.5 Viscosity 10 - 50 CPSo2/20 RPM @ 77 F
Weight / gallon 8.5 LBS / GAL
Color Off White Diluent Water Clean-Up Water Shelf-Life 90 Days The antistatic coating can be applied as part of the gravure printing process using the same techniques for applying any printing enhancing layer and it may be applied either before or after application of any adhesive layer.
Many variations of the present invention will suggest themselves to those skilled in the art in light of the above detailed description and accompanying drawing. For example, instead of oriented polypropylene as the face film, polyethylene terephthalate), cellulose paper, cellulose acetate, polyethylene, polycarbonate, fluoropolymers and polyimide films can be used. Instead of polypropylene as the release film, paper or silicone coated paper can be used. A
printing enhancing coating such as an acrylic or polyester or urethane resin containing finely divided clay, silica, titanium dioxide, zinc oxide, or mixtures of any of them, can be spread on the print receiving face of the top and/ or bottom sheet(s).
All such obvious modifications are within the full intended scope of the appended claims.
having the same or substantially the same thermal elongation or contraction characteristics.
Special mention is made of a preferred aspect of the invention which comprises a composite sheet which does not curl when heated to temperatures normal 1y encountered in . laser printing, the sheet including at least three layers comprised of A. at least one base layer comprising a tear resistant synthetic paper having a pressure sensitive adhesive on the bottom face thereof;
B. a print receiving tear resistant synthetic paper layer permanently adhered to the top face of base layer or layers A; and C. a protective backing comprising a paper layer or a coated film releasably adhered to said pressure sensitive adhesive on the bottom face of base layer or layers A, said top layer B and said protective backing C having the same or substantially the same thermal elongation or contraction characteristics.
In preferred features, the invention contemplates printing sheets as defined above wherein layers A and B
comprise all or subdivided portions thereof; those, wherein layer A comprises a thermoplastic polyester, and layer B and protective backing C comprise a polyolefin; and such sheets wherein layer A comprises a thermoplastic polyester, layer B
comprises a polyolefin and backing C comprises a thermoplastic resin coating. Also contemplated are sheets as defined above which also include a printing enhancing coating on the print receiving face of layer B, especially those wherein the printing enhancing coating comprises an acrylic, polyester or urethane resin filled with finely divided clay, silica, titanium dioxide, zinc oxide, other fillers or blends of fillers, and the like ; those wherein layer B is adhered to layer or layers A through an adhesive layer having high cohesive strength and low shear strength whereby layers B and A can move transversely under the influence of heat without parting. Further preferred embodiments comprise label sheets as defined above wherein backing C can be releasably adhered to the pressure sensitive adhesive on base layer or layers A
through a release coating, especially those wherein the release coating comprises a silicone and the pressure sensitive adhesive layer has high cohesion and low shear strength whereby layers C and A can move transversely under the influence of heat without parting. In addition, the invention includes sheets as defined above wherein layer or layers A include an effective amount of conductive filler for dissipating static changes developed during laser printing whereby sheet feeding and delivery problems are minimized, special mention being made of such sheets wherein the conductive filler comprises carbon black. Best results appear to be obtained with sheets as defined above wherein layer B
has a ratio of thermal elongation or contraction in the range of from about 0.7 to about 1.3 with respect to 1.0 for protective backing C, especially those wherein said layer B
has a ratio or thermal elongation or contraction of about 1.0 with respect to 1.0 for protective backing C. Also contemplated as preferred embodiments are sheets for printing as defined above wherein the outwardly facing major face of layer B, layer C, or layers B and C are provided with a print receiving area or area, and sheets in which the print receiving areas are provided in whole or part with a print enhancing coating. Also contemplated are sheets as above _6_ defined coated in one or both major faces with an antistatic composition so as to avoid jamming in subsequent high speed production printing processes. Such antistatic compositions comprise, for example, amines, quaternary ammonium compounds, anionic or cationic surface active agents, or mixtures of any of the foregoing, and it is preferred to apply them by deposition from an aqueous medium. In an especially preferred embodiment, the invention contemplates also sheets as above defined which, before or after printing, are cut into a plurality of pieces of substantially the same size.
In a broad aspect, then, the present invention relates to a durable sheet for printing, the sheet including at least three layers comprised of: layer A, which comprises at least one base layer consisting of a paper, a synthetic paper or a coated film; layer B, which comprises at least one print receiving layer consisting of a paper, a synthetic paper or a coated film, wherein layer B is adhered to the top face of layer A; and layer C, which comprises at least one backing layer consisting of a paper, a synthetic paper or a coated film, wherein layer C is adhered to the bottom face of layer A; ~ and wherein layer B and the backing C have the same or substantially the same thermal elongation or contraction characteristics; and wherein the top surface of layer A
comprises a release agent, the bottom surface of layer B
comprises a pressure sensitive adhesive and layer C is permanently adhered to layer A.
In another broad aspect, then, the present invention relates to a durable sheet for printing, the sheet including at least three layers comprised of: layer A, which comprises at least one base layer consisting of a paper, a synthetic paper or a coated film; layer B, which comprises at least one print receiving layer consisting of a paper, a synthetic paper or a coated film, wherein layer B is adhered to the top face of layer A, and layer C, which comprises at least one backing - 6a-layer consisting of a paper, a synthetic paper or a coated film, wherein layer C is adhered to the bottom face of layer A; and wherein layer B and the backing C have the same or substantially the same thermal elongation or contraction characteristics; and wherein the top surface of layer C
comprises a release agent, the bottom surface of layer A
comprises a pressure sensitive adhesive and layer B is permanently adhered to layer A.
In yet another broad aspect, then, the present invention relates to a durable sheet for printing, the sheet including at least three layers comprised of: layer A, which comprises at least one base layer consisting of a paper, a synthetic paper or a coated film; layer B, which comprises at least one print receiving layer consisting of a paper, a synthetic paper or a coated film, wherein layer B is adhered to the top face of layer A; and layer C, which comprises at least one backing layer consisting of a paper, a synthetic paper or a coated film, wherein layer C is adhered to the bottom face of layer A; and wherein layer B and the backing C have the same or substantially the same thermal elongation or contraction characteristics; and wherein layer A comprises a thermoplastic resin, and layer B and layer C comprise a polyolefin.
In a further broad aspect, then, the present invention relates to a durable sheet for printing, the sheet including at least three layers comprised of: layer A, which comprises at least one base layer consisting of a paper, a synthetic paper or a coated film; layer B, which comprises at least one print receiving layer consisting of a paper, a synthetic paper or a coated film, wherein layer B is adhered to the top face of layer A; and layer C, which comprises at least one backing layer, consisting of a paper, a synthetic paper or a coated film, wherein layer C is adhered to the bottom face of layer A; and wherein layer B and the backing C have the same or substantially the same thermal elongation or contraction -6b-characteristics; and wherein layer A comprises a thermoplastic polyester, layer B comprises a polyolefin and layer C
comprises a thermoplastic resin coating.
In a still further broad aspect, then, the present invention relates to a durable sheet for printing, the sheet including at least three layers comprised of: layer A, which comprises at least one base layer consisting of a paper, a synthetic paper or a coated film; layer B, which comprises at least one print receiving layer consisting of a paper, a synthetic paper or a coated film, wherein layer B is adhered to the top face of layer A; and layer C, which comprises at least one backing layer consisting of a paper, a synthetic paper or a coated film, wherein layer C is adhered to the bottom face of layer A; and wherein layer B and the backing C
have the same or substantially the same thermal elongation or contraction characteristics; and which also includes a printing enhancing coating on the print receiving face of layer B.
In another broad aspect, then, the present invention relates to a sheet for printing, said sheet including at least three layers comprised of: layer A, which comprises at least one base layer consisting of a tear resistant synthetic paper having a pressure sensitive adhesive on the bottom face thereof; layer B, which comprises a print receiving tear resistant synthetic paper layer permanently adhered to the top face of layer A; and layer C, which comprises a protective backing consisting of a paper layer or a coated film releasably adhered to said pressure sensitive adhesive on the bottom face of layer A, said layer B and said layer C having the same or substantially the same thermal elongation or contraction characteristics.
In yet another broad aspect, then, the present invention relates to a printed sheet including at least three layers comprised of : layer A, which comprises at least one base layer -6c-consisting of a tear resistant synthetic paper having a pressure sensitive adhesive on the bottom face thereof; layer B, which comprises a printed tear resistant synthetic paper layer permanently adhered to the top face of layer A; and layer C, which comprises a protective backing consisting of a paper layer or a coated film releasably adhered to said pressure sensitive adhesive on the bottom face of layer A, said top layer B and said layer C having the same or substantially the same thermal elongation or contraction characteristics.
DESCRIPTION OF THE DRAWINGS
FIG. 1 is a perspective view of a three-layer sheet of printed labels mounted on a backing sheet, a section of the edge being enlarged in FIG. 1A to show detail:
FIG. 2 is a top view of one of the labels from the sheet shown in FIG. 1;
FIG. 3 shows a three-layer sheet having balanced thermal expansion/contraction characteristics in accordance with the invention following printing through a printer, a section of the edge being enlarged in FIG. 3A to show detail; and FIG. 4 shows a three-layer sheet having unbalanced thermal expansion/contraction characteristics not in accordance with this invention, which has been curled up as a result of being printed in a printer, a section of the edge being enlarged in FIG. 4A to show detail.
DETAILED DESCRIPTION OF THE INVENTION
Referring more particularly to the drawings, Figure 1 shows a three-layer sheet 2 including an upper sheet made up of a large number of labels 4 which have been die cut to be separate from one another and which are mounted on backing sheet 6. As will be seen from FIG. 1A, each label comprises printable surface layer 8 alone or on top of base layer 10.
Figure 2 is a front view of one of the labels 4 which has been removed from the backing sheet 6. More specifically, on the front of the label 4 as shown in Figure 2, is some printing or advertising 12, and a bar code configuration 14.
On the back of label 4 .is a continuous layer of pressure sensitive adhesive (not shown) of an entirely conventional type well known to those skilled in the art. There is no need whatsoever to pattern the layer of adhesive into geometric forms as is done in some of the commercial labels in the current state of the art.
Figs. 3 and 3A show a three-layer sheet 16 of the present invention, comprising a top sheet 8 and protective backing 6 having the same thermal expansion/contraction characteristics, in which the sheet 16, following printing, is entirely level and flat. In Figs. 4 and 4A, however, it is shown that a three-layer sheet 18 comprising a top sheet 8a and protective backing 6a having substantially different and unbalanced thermal expansion/contraction characteristics on either side of base layer 10, and, following printing in a printer, it curls up as indicated, particularly at corners 20. This curling is found to be so significant that proper stacking of the printed sheets is not practical, nor is further mechanical processing of the sheets.
Laser printing apparatus, which are well known, are described in U.S. 4,494,129 and 4,913,926, mentioned hereinabove. In general, all such apparatus use electrostatically chargeable drums to form an image and heated rollers to apply moderately high levels of pressure, e.g., greater than about 100 pounds per square inch, and elevated temperatures, e.g., greater than about 250° F, to the sheets during the printing process. It is believed that these relatively high pressures and temperatures produce the curled adhesively bonded label sheets as shown in Figure 4 when no particular attention is paid to selecting top and bottom layers 8a and 6a so that they have the same or substantially the same thermal expansion/contraction characteristics as is required by the present invention.
However, by using a balanced composite as shown in Figure 3A of the drawing, wherein layers 8 and 6 have the same or substantially the same thermal expansion/contraction characteristics, the tension or strain produced downstream in any process where temperature, pressure, and tension can cause curl and flat sheets for printing will be produced.
Suitable materials from the paper sheets comprise thermoplastic polyester, e.g., poly(ethylene terephthalate), poly(acrylonitrile), and the like, as well as polyolefins, such as polypropylene, polyethylene, and the like. For the base layer or layers, polyesters are preferred, and especially polyethylene terephthalate) which is available from a number of sources. For the top layer, monoaxially or biaxially oriented polyolefins are preferred, especially polypropylene, and such papers are available from a number of sources, such as Mobil Chemical Company, Pittsford, N.Y. 14534, U.S.A., tradename "Oppalyte" TW and Toray Plastics, Inc., North Kingston, RI, 02852, U.S.A., tradenames "Treafilms" and "Treax Films".
Thermal elongation and/or contraction characteristics are measured by standard test methods . The values are used to select suitable substrates for use in-this invention. It is important that the relative values rather than their magnitude receive the most attention. It is known for example that polypropylene paper has a shrinkage at 275°F. of -4.5~ in the MD and -5.0~ in the TD. If a composite is prepared having polypropylene on the top and the bottom and polyethylene terephthalate) in the center, curl-free laser printing will be achieved because the top and bottom layers will have the same thermal contraction. If, however, a dual layer composite of polypropylene on top of polyester or a three layer comprising polypropylene (top), polyester(middle) and ~1~0~~
polyester (bottom) is prepared, the composites are unbalanced, as explained above, and they will not print without curling.
The layers can be simply heat-bonded with heat-activated adhesive, but it is preferred to use an adhesive of a permanent type and of a pressure sensitive type. Many adhesives are suitable although it is preferred to select one which has a high cohesive strength and low shear strength to facilitate transverse movement between different layers during heating while precluding parting.
In preferred embodiments, the backing C or layer A will be adhered to the pressure sensitive adhesive through a release coating, such as a poly(tetrafluoroethylene film) or more preferably a silicone resin, as is known in the art, for the labels . Layers B and C may be permanently adhered to layer A by a laminating adhesive for the tags. A release coating is not needed for the tags.
Among the preferred features of the invention are label sheets of the type described wherein the base layer is rendered electrically conductive by including an effective amount of a conductive filler, e.g., a powder such as silver and nickel powders or carbon powders. Conductive fillers can also be put in adhesives instead of base layers and also in printable coatings, without departing from the spirit or scope of the invention. The polyethylene terephalate) base layer, and/ or the other substrates, can for example include 5 to 40 percent by weight of carbon powder, and not only will the sheets not curl during printing, but they also will dissipate static changes developed during printing which can also interfere with feeding, imaging and delivery. For best results, when using polyolefin layers, composite volume resistivity gives best printing at values equal to or less than 1014 ohms-cm.
Concerning the backing, this can be the same or different in terms of material from the top layer so long as 2~.~~~~
the expansion/contraction characteristics are the same or substantially the same, preferably from 0.7-1.3:1 and more preferably 1:1. The backing can even comprise a film coating instead of a sheet, and the backing can even comprise a wood pulp paper sheet, such as a silicone-coated paper sheet, instead of a synthetic paper sheet, without departing from the scope of the invention.
The composites are assembled in conventional ways using conventional equipment. The sheets are consolidated continuously under moderate heat and pressure and cut to any desired size and, if desired, the labels or tags are die-cut into the sheets by means well known to those skilled in this art.
The antistatic agents used herein are applied as surface coatings or are incorporated as additives into print receiving coatings, preferably from an aqueous medium. Such coatings are conveniently applied by gravure, mayer rod, reverse roll, or other techniques known to those skilled in this art. For example, a thin coat of antistatic agent can be applied to one surface of the film or anti-stat additive can be incorporated into a clay coating. Suitable such coatings or additives can be selected from the many commercially-available materials known in this art, such as listed, for example in Modern Plastics Encyclopedia, Mid-October Issue, 1987, "Antistatic Agents" by J. L. Rogers, pages 130 and 132, as well as pages 579-581. Preferred for use herein are commercially-available antistatic coating compositions available, for example, from Akzo Chemie America, Chicago, IL, under the trade name or designation Armostato Aqueous Ethoquad CY12, from Union Carbide Corp., Danbury, CT, under the trade name or designation Silweto L-77, a modified silicone, or from Process Resources Corp., Thornwood, NY, under the tradename or designation PD 945, a proprietary mixture which is gravure -11- lsl-ool-a2 applicable and having the typical properties described in the Table:
TABLE
Solids 4 ~
pH 8.5 - 9.5 Viscosity 10 - 50 CPSo2/20 RPM @ 77 F
Weight / gallon 8.5 LBS / GAL
Color Off White Diluent Water Clean-Up Water Shelf-Life 90 Days The antistatic coating can be applied as part of the gravure printing process using the same techniques for applying any printing enhancing layer and it may be applied either before or after application of any adhesive layer.
Many variations of the present invention will suggest themselves to those skilled in the art in light of the above detailed description and accompanying drawing. For example, instead of oriented polypropylene as the face film, polyethylene terephthalate), cellulose paper, cellulose acetate, polyethylene, polycarbonate, fluoropolymers and polyimide films can be used. Instead of polypropylene as the release film, paper or silicone coated paper can be used. A
printing enhancing coating such as an acrylic or polyester or urethane resin containing finely divided clay, silica, titanium dioxide, zinc oxide, or mixtures of any of them, can be spread on the print receiving face of the top and/ or bottom sheet(s).
All such obvious modifications are within the full intended scope of the appended claims.
Claims (28)
1. A durable sheet for printing, the sheet including at least three layers comprised of:
layer A, which comprises at least one base layer consisting of a paper, a synthetic paper or a coated film;
layer B, which comprises at least one print receiving layer consisting of a paper, a synthetic paper or a coated film, wherein layer B is adhered to the top face of layer A;
and layer C, which comprises at least one backing layer consisting of a paper, a synthetic paper or a coated film, wherein layer C is adhered to the bottom face of layer A; and wherein layer B and the backing C have the same or substantially the same thermal elongation or contraction characteristics;
and wherein the top surface of layer A comprises a release agent, the bottom surface of layer B comprises a pressure sensitive adhesive and layer C is permanently adhered to layer A.
layer A, which comprises at least one base layer consisting of a paper, a synthetic paper or a coated film;
layer B, which comprises at least one print receiving layer consisting of a paper, a synthetic paper or a coated film, wherein layer B is adhered to the top face of layer A;
and layer C, which comprises at least one backing layer consisting of a paper, a synthetic paper or a coated film, wherein layer C is adhered to the bottom face of layer A; and wherein layer B and the backing C have the same or substantially the same thermal elongation or contraction characteristics;
and wherein the top surface of layer A comprises a release agent, the bottom surface of layer B comprises a pressure sensitive adhesive and layer C is permanently adhered to layer A.
2. A durable sheet for printing, the sheet including at least three layers comprised of:
layer A, which comprises at least one base layer consisting of a paper, a synthetic paper or a coated film;
layer B, which comprises at least one print receiving layer consisting of a paper, a synthetic paper or a coated film, wherein layer B is adhered to the top face of layer A, and layer C, which comprises at least one backing layer consisting of a paper, a synthetic paper or a coated film, wherein layer C is adhered to the bottom face of layer A; and wherein layer B and the backing C have the same or substantially the same thermal elongation or contraction characteristics;
and wherein the top surface of layer C comprises a release agent, the bottom surface of layer A comprises a pressure sensitive adhesive and layer B is permanently adhered to layer A.
layer A, which comprises at least one base layer consisting of a paper, a synthetic paper or a coated film;
layer B, which comprises at least one print receiving layer consisting of a paper, a synthetic paper or a coated film, wherein layer B is adhered to the top face of layer A, and layer C, which comprises at least one backing layer consisting of a paper, a synthetic paper or a coated film, wherein layer C is adhered to the bottom face of layer A; and wherein layer B and the backing C have the same or substantially the same thermal elongation or contraction characteristics;
and wherein the top surface of layer C comprises a release agent, the bottom surface of layer A comprises a pressure sensitive adhesive and layer B is permanently adhered to layer A.
3. A durable sheet for printing, the sheet including at least three layers comprised of:
layer A, which comprises at least one base layer consisting of a paper, a synthetic paper or a coated film;
layer B, which comprises at least one print receiving layer consisting of a paper, a synthetic paper or a coated film, wherein layer B is adhered to the top face of layer A;
and layer C, which comprises at least one backing layer consisting of a paper, a synthetic paper or a coated film, wherein layer C is adhered to the bottom face of layer A; and wherein layer B and the backing C have the same or substantially the same thermal elongation or contraction characteristics;
and wherein layer A comprises a thermoplastic resin, and layer B and layer C comprise a polyolefin.
layer A, which comprises at least one base layer consisting of a paper, a synthetic paper or a coated film;
layer B, which comprises at least one print receiving layer consisting of a paper, a synthetic paper or a coated film, wherein layer B is adhered to the top face of layer A;
and layer C, which comprises at least one backing layer consisting of a paper, a synthetic paper or a coated film, wherein layer C is adhered to the bottom face of layer A; and wherein layer B and the backing C have the same or substantially the same thermal elongation or contraction characteristics;
and wherein layer A comprises a thermoplastic resin, and layer B and layer C comprise a polyolefin.
4. A durable sheet for printing, the sheet including at least three layers comprised of:
layer A, which comprises at least one base layer consisting of a paper, a synthetic paper or a coated film;
layer B, which comprises at least one print receiving layer consisting of a paper, a synthetic paper or a coated film, wherein layer B is adhered to the top face of layer A;
and layer C, which comprises at least one backing layer, consisting of a paper, a synthetic paper or a coated film, wherein layer C is adhered to the bottom face of layer A; and wherein layer B and the backing C have the same or substantially the same thermal elongation or contraction characteristics;
and wherein layer A comprises a thermoplastic polyester, layer B comprises a polyolefin and layer C comprises a thermplastic resin coating.
layer A, which comprises at least one base layer consisting of a paper, a synthetic paper or a coated film;
layer B, which comprises at least one print receiving layer consisting of a paper, a synthetic paper or a coated film, wherein layer B is adhered to the top face of layer A;
and layer C, which comprises at least one backing layer, consisting of a paper, a synthetic paper or a coated film, wherein layer C is adhered to the bottom face of layer A; and wherein layer B and the backing C have the same or substantially the same thermal elongation or contraction characteristics;
and wherein layer A comprises a thermoplastic polyester, layer B comprises a polyolefin and layer C comprises a thermplastic resin coating.
5. A durable sheet for printing, the sheet including at least three layers comprised of:
layer A, which comprises at least one base layer consisting of a paper, a synthetic paper or a coated film;
layer B, which comprises at least one print receiving layer consisting of a paper, a synthetic paper or a coated film, wherein layer B is adhered to the top face of layer A;
and layer C, which comprises at least one backing layer consisting of a paper, a synthetic paper or a coated film, wherein layer C is adhered to the bottom face of layer A; and wherein layer B and the backing C have the same or substantially the same thermal elongation or contraction characteristics;
and which also includes a printing enhancing coating on the print receiving face of layer B.
layer A, which comprises at least one base layer consisting of a paper, a synthetic paper or a coated film;
layer B, which comprises at least one print receiving layer consisting of a paper, a synthetic paper or a coated film, wherein layer B is adhered to the top face of layer A;
and layer C, which comprises at least one backing layer consisting of a paper, a synthetic paper or a coated film, wherein layer C is adhered to the bottom face of layer A; and wherein layer B and the backing C have the same or substantially the same thermal elongation or contraction characteristics;
and which also includes a printing enhancing coating on the print receiving face of layer B.
6. A sheet as defend in claim 5 wherein said printing enhancing coating comprises an acrylic, polyester or urethane resin filled with finely divided clay or silica.
7. A sheet for printing, said sheet including at least three layers comprised of:
layer A, which comprises at least one base layer consisting of a tear resistant synthetic paper having a pressure sensitive adhesive on the bottom face thereof;
layer B, which comprises a print receiving tear resistant synthetic paper layer permanently adhered to the top face of layer A; and layer C, which comprises a protective backing consisting of a paper layer or a coated film releasably adhered to said pressure sensitive adhesive on the bottom face of layer A, said layer B and said layer C having the same or substantially the same thermal elongation or contraction characteristics.
layer A, which comprises at least one base layer consisting of a tear resistant synthetic paper having a pressure sensitive adhesive on the bottom face thereof;
layer B, which comprises a print receiving tear resistant synthetic paper layer permanently adhered to the top face of layer A; and layer C, which comprises a protective backing consisting of a paper layer or a coated film releasably adhered to said pressure sensitive adhesive on the bottom face of layer A, said layer B and said layer C having the same or substantially the same thermal elongation or contraction characteristics.
8. A sheet as defined in claim 7 wherein layers A and B are a single label.
9. A sheet as defined in claim 7 wherein layer A comprises a thermoplastic polyester, and layer B and layer C comprise a polyolefin.
10. A sheet as defined in claim 7 wherein layer A comprises a thermoplastic polyester, layer B comprises a polyolefin and layer C comprises a thermoplastic resin coating.
11. A sheet as defined in claim 7 which also includes a printing enhancing coating on the print receiving face of layer B.
12. A sheet as defined in claim 11 wherein said printing enhancing coating comprises an acrylic, polyester or urethane resin filled with finely divided clay or silica.
13. A sheet as defend in claim 7 wherein layer B is permanently adhered to layer A with an adhesive layer which has high cohesive strength and low shear strength, whereby said layers A and B can move transversely under the influence of heat without parting.
14. A sheet has defined in claim 7 wherein layer C is releasably adhered to the pressure sensitive adhesive on layer A with a release coating.
15. A sheet as defined in claim 14 wherein said release coating comprises a silicone and said pressure sensitive adhesive layer has high cohesion and low shear strength whereby said layers C and A can move transversely under the influence of heat without parting.
16. A sheet as defined in claim 5 wherein layer A includes 5%
to 40% by weight of conductive filler for dissipating static charges developed during printing whereby sheet feeding and delivery problems are minimized.
to 40% by weight of conductive filler for dissipating static charges developed during printing whereby sheet feeding and delivery problems are minimized.
17. A sheet as defined in claim 16 wherein said conductive filler comprises carbon black.
18. A sheet as defined in claim 5 wherein layer B has a ratio of thermal elongation or contraction in the range of from 0.7 to 1.3 with respect to 1.0 for layer C.
19. A sheet has defined in claim 18 wherein said layer B has a ratio or thermal elongation or contraction of 1.0 with respect to 1.0 for layer C.
20. A printed sheet including at least three layers comprised of:
layer A, which comprises at least one base layer consisting of a tear resistant synthetic paper having a pressure sensitive adhesive on the bottom face thereof;
layer B, which comprises a printed tear resistant synthetic paper layer permanently adhered to the top face of layer A; and layer C, which comprises a protective backing consisting of a paper layer or a coated film releasably adhered to said pressure sensitive adhesive on the bottom face of layer A, said top layer B and said layer C having the same or substantially the same thermal elongation or contraction characteristics.
layer A, which comprises at least one base layer consisting of a tear resistant synthetic paper having a pressure sensitive adhesive on the bottom face thereof;
layer B, which comprises a printed tear resistant synthetic paper layer permanently adhered to the top face of layer A; and layer C, which comprises a protective backing consisting of a paper layer or a coated film releasably adhered to said pressure sensitive adhesive on the bottom face of layer A, said top layer B and said layer C having the same or substantially the same thermal elongation or contraction characteristics.
21. A sheet as defined in claim 7 wherein layers A and B are subdivided onto a plurality of labels of substantially the same size.
22. A sheet as defined in any one of claims 1, 2 or 3 which also includes a printing enhancing coating on all or a selected part of the print receiving face of layer B.
23. A sheet as defined in claims 3, 4 or 5 wherein layer C is also a print receiving layer.
24. A sheet as defined in claim 23 which also includes a printing enhancing coating on all or a selected part or parts of the print receiving faces of layer B, layer C or layers B
and C.
and C.
25. A sheet as defined in any of claims 1, 2, 3, 4, 5, 7, 20, 23 or 24 that includes a coating made partially or entirely of an antistatic composition on one or both major faces of said sheet.
26. A sheet as defined in claim 25 wherein said antistatic composition comprises an amine, or quaternary ammonium compound, an anionic or cationic surfactant or a mixture of any of them.
27. A sheet as defined in claim 26 wherein said antistatic composition is deposited from an aqueous medium.
28. A sheet as defined in claim 3 which before or after printing is cut into a plurality of smaller pieces of substantially the same size.
Priority Applications (1)
| Application Number | Priority Date | Filing Date | Title |
|---|---|---|---|
| CA 2160442 CA2160442C (en) | 1995-10-12 | 1995-10-12 | Durable sheets for printing |
Applications Claiming Priority (1)
| Application Number | Priority Date | Filing Date | Title |
|---|---|---|---|
| CA 2160442 CA2160442C (en) | 1995-10-12 | 1995-10-12 | Durable sheets for printing |
Publications (2)
| Publication Number | Publication Date |
|---|---|
| CA2160442A1 CA2160442A1 (en) | 1997-04-13 |
| CA2160442C true CA2160442C (en) | 2006-08-15 |
Family
ID=4156758
Family Applications (1)
| Application Number | Title | Priority Date | Filing Date |
|---|---|---|---|
| CA 2160442 Expired - Lifetime CA2160442C (en) | 1995-10-12 | 1995-10-12 | Durable sheets for printing |
Country Status (1)
| Country | Link |
|---|---|
| CA (1) | CA2160442C (en) |
-
1995
- 1995-10-12 CA CA 2160442 patent/CA2160442C/en not_active Expired - Lifetime
Also Published As
| Publication number | Publication date |
|---|---|
| CA2160442A1 (en) | 1997-04-13 |
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