CN111511572B

CN111511572B - Method for applying a security device to a surface over a hole made in a paper machine

Info

Publication number: CN111511572B
Application number: CN201880080558.1A
Authority: CN
Inventors: G.D.普雷特; M.贾因; K.M.布里格姆
Original assignee: Crane and Co Inc
Current assignee: Crane and Co Inc
Priority date: 2017-12-14
Filing date: 2018-12-14
Publication date: 2022-05-17
Anticipated expiration: 2038-12-14
Also published as: KR20200096544A; JP2023106485A; WO2019118904A1; RU2020123078A3; EP3723996A4; RU2020123078A; JP2021506622A; KR102665889B1; EP3723996A1; CN111511572A

Abstract

A sheet (110) having a security device (112) applied over a through-hole (111) made or "soft-edged" by a paper machine and a method for making such a sheet (110) are provided. By the method of the invention one or more through-holes are formed in the formed fibrous web before it is sufficiently consolidated, and then a security device is applied to the fibrous web, preferably at or near a couch roll or similar tool of a paper machine over the one or more through-holes when the fibrous web constitutes a sufficiently consolidated, fully formed wet web. Applying the safety device at the papermaking stage where the fibers do not shift and then further consolidating the area under the device greatly reduces, if not eliminates, the possibility of one or more through-holes becoming clogged or blocked. Furthermore, paper made according to the method of the present invention exhibits minimal damage at the paper/security device interface when subjected to flow-through simulation testing. Furthermore, the surface-applied security devices showed acceptable levels of intaglio ink adhesion, and the paper had a higher cross-direction (CD) tensile strength and much less show-through on its opposite sides.

Description

Method for applying a security device to a surface over a hole made in a paper machine

Technical Field

In one aspect, the present invention relates to a sheet material having through holes, wherein one or more security devices are coupled to the through holes. The sheet material is exemplarily used to form a security document comprising the above-mentioned through hole and the attached security device. In another aspect, the present invention also relates generally to a method of making such sheets; a method of forming a security document; and means for protecting the documents by coupling the through-hole with one or more security devices. The vias described herein include "soft-sided" vias. Accordingly, another aspect of the present invention also includes a method of forming a soft-edged through-hole in a sheet material, or more particularly in a security document.

Background

Security devices, including non-exclusively strips, bands, threads or ribbons in various forms, are widely used to protect or aesthetically high security and high value documents, providing visual and/or machine detectable means for verifying the authenticity of such documents. These security devices may be fully embedded or partially embedded in the document, or mounted on a surface thereof.

The at least partially embedded security device may be applied to the formed fibrous web by introducing the security device into the fibrous web during the wet stage of the papermaking process. However, the introduction of security devices into the fibrous web at this stage, while suitable for embedded and partially embedded security devices, has heretofore been impractical for surface-applied security devices because the resulting sheet or document would tend to reduce durability (e.g., circulation durability).

It has been found that during the introduction of the security device into the wet stage of the formed fibrous web, when the security device is pressed into the fibrous web, some of the fibres are displaced when flowing around the security device. This results in a certain amount of fiber being displaced from the sub-areas (i.e. the areas of the fiber web underlying or below the security device) and the hinge areas (i.e. the areas of the fiber web lying adjacent to the edges or sides of the security device), which displacement is sufficient to affect the interaction of the security device with the fiber web or with the substrate of the resulting sheet or document. The resulting fiber concentration in the sub-regions and hinge regions is less than the fiber concentration in at least the adjacent one or more body regions. This results in a weak link interaction at the interface of the security device with the substrate of the sheet or document, and in particular at the interface surface and/or edges of the security device. These weak areas are very prone to tearing along the interface edges between the security device and the substrate, or to hinge effects (i.e. separation areas between the interface edges) in the sheet or document during use or circulation of the resulting document. In addition, the document tends to exhibit reverse show-through; that is, when applied on one side of a fibrous web, the applied security device will produce a shadowing effect that can be observed from the opposite side of the fibrous web, any resulting fibrous sheet, or any resulting document. This typically requires the use of a back camouflage coating to address this problem. It has also been observed that the resulting sheet or document exhibits a reduction in cross-direction (CD) tensile strength.

An alternative for obtaining a surface applied security device is to apply the security device to the surface of a fully formed fibrous substrate. However, application to fully formed fibrous substrates is accompanied by other substantial limitations. This substantially limits the range of thicknesses of security devices that can be used, for example. Typically, surface application is limited to the thinnest, such as less than 15 micrometers (μm), of security devices. Thicker security devices are generally excluded from such applications, at least in part because the resulting thickness differences on the resulting sheet affect downstream processing. As used herein, the term "thickness differential" refers to the height differential measured from the upper surface of the body region of the sheet to the upper surface of the security device. Thus, the thickness difference may be negative or positive. For example, in the case where the upper surface of the security device is located below the level of the upper surface of the main body region of the sheet, the difference in thickness is negative. Conversely, where the upper surface of the security device is above the level of the upper surface of the main body region of the sheet, the difference in thickness is positive. Alternatively, a thickness difference of zero indicates that the upper surface of the security device is flush with the upper surface of the body region. Downstream processes such as winding, sheeting, stacking, cutting and processing through ATM are affected in time and cost due to thickness differences created by thicker security devices introduced during the drying stage of the paper making process or during post-application. Importantly, the stacks produced in this manner are not yet ready for pressing or printing.

In view of the above, there remains a need for improved sheets having surface applied security devices regardless of thickness, and for improved methods capable of producing such sheets. There is also a continuing need to provide security documents with additional authenticity features that allow verification of the authenticity of the document while preventing unauthorized copying.

Disclosure of Invention

The present invention addresses at least one of the above needs by providing a sheet, a security document and a method for applying a security device surface to a fibrous sheet or document by introducing the security device to a forming fibrous web during the wet stage of papermaking. In one embodiment, the security device is applied over one or more "soft-edged" through-holes formed in the fibrous web. The security device in this embodiment is made from a structural film and has a thickness of at least about 10 microns, thereby providing the device with sufficient durability across one or more through-holes. As used herein, the term "soft-sided through-holes" means through-holes created during papermaking where fibers in the sheet extend into openings surrounded by the through-holes. The openings of the through holes extend from one side or surface of the web to the opposite side or surface and exhibit a distinct irregularity in the edge region. This unique irregularity is caused by the lack of a sharp cutting edge and includes an irregular accumulation of fibers in the edge region and/or fibers extending into the opening. In the case of such through openings having unique irregularities that vary frequently and are not easily reproduced, these openings serve as authenticity features with a high security value. The method of the invention comprises introducing a security device onto or into the formed fibrous web, optionally over one or more "soft-edged" through-holes formed in the fibrous web, during the wet stage of the papermaking process in which the fibrous web is well consolidated. In one embodiment, the fiber web is sufficiently consolidated when the fiber web has a water or moisture content of less than 98 wt. -%, based on the total weight of the fiber web. Preferably, the fiber web is sufficiently consolidated when the fiber web is at or near a couch roll or similar tool of a paper machine.

The invention also provides a fiber sheet produced by the above method and a resultant document including the fiber sheet. In a first embodiment, a fibrous sheet has: an opposing surface; at least one recess on one surface thereof; a fiber sub-region, the fiber sub-region being a three-dimensional volume disposed below or beneath the recess; and a fiber body region, the fiber body region also being a three-dimensional volume disposed adjacent to the recess and the sub-region; a surface-applied safety device disposed in the recess; and an interface between the surface-applied security device and the body and sub-regions of the sheet material; wherein there are fibers present in substantially equal amounts in the fiber sub-region and the fiber bulk region. The sub-regions of fibres are co-extensive in the transverse or lateral direction with the surface-applied security device. In other words, the three-dimensional sub-area occupies the volume of the fibre sheet that is located below the safety device. The fiber body region is disposed adjacent to the recess and the sub-region and occupies a remaining volume of the fiber sheet.

Confirmation of the presence of substantially equal amounts of fibers in both the sub-regions and the body region of the sheet is achieved by comparing the mass (weight) of the sheet in the three-dimensional region under the security device (after the security device has been removed (see, for example, the region defined by width a, height a and depth dimension (not shown) in figure 11) to the mass (weight) of the three-dimensional region of the sheet adjacent to the security device having equal width (i.e., width equal to the width of the security device) (see, for example, the region defined by width B, height B and depth dimension (not shown) in figure 11). The mass (weight) in the area occupied by the through-hole is first adjusted by adding back the mass (weight) in this area, the mass (weight) of the region (sub-region) is then compared to the mass (weight) of the body region.

In a second embodiment or aspect of the invention, the fibrous sheet material has opposing surfaces and one or more through holes made by the paper machine or "soft-edged". A surface-applied security device is applied over the one or more through-holes, which may be substantially the same or different in shape and size from the one or more through-holes. For example, the surface-applied security device may be shaped differently and larger than the through-hole, or it may be sized similarly and only slightly larger than the through-hole. In both cases, the fibrous sheet and the document formed therefrom will be similar to that described above, except that one or more through-holes will extend from the recess through the opposite surface of the fibrous sheet. The sub-regions of fibre having a three-dimensional volume will therefore be disposed beneath or below those regions of the recess which define the through-hole and extend transversely therefrom to the outer periphery of the surface-applied security device. In other words, as described above, the sub-regions of fibre will occupy the space below the space occupied by the surface-applied security device.

Surprisingly, it has been found that a surface-applied security device can be introduced during the wet stage when the fibrous web is sufficiently consolidated into, for example, a fully formed wet web. By introducing the safety device at this wet stage of the paper making process, the safety device can be pushed into the fiber web sufficiently to consolidate the fibers in the sub-regions further rather than displace them. This in turn helps to provide increased connection interaction between the fibers and the surface applied security device. As a result, at least one of durability, ink adhesion, Cross Direction (CD) tensile strength, and back print through is improved. These surprising advantages avoid the need for further processing steps to improve ink adhesion, improve tensile strength, or camouflage back print-through. Furthermore, since the security device is introduced during the wet stage of sufficient consolidation of the fiber web, it is made possible to force the security device into the fiber web, thereby enabling the use of thicker security devices, since their thickness difference can be significantly reduced. The resulting thickness difference has less influence on the downstream process.

Applicants have also surprisingly discovered, by the methods provided herein, that surface applied security devices can be applied in registration with at least one other feature in a fibrous web, fibrous sheet, or resulting document. In a second aspect of the invention, the surface-applied security device is applied in registration with the one or more through-holes. As will be readily appreciated by those skilled in the art, applying the security device in registration with a further feature in the fibrous web greatly increases the security of the resulting sheet or document. Furthermore, because the safety device is introduced during the wet stage of the fiber web manufacturing process, it is possible to adjust the registration during the paper making process. Thus, further processing steps that would otherwise be required to correct misalignment of the security device with other features are avoided. Introducing the security device in a continuous manner also avoids the need for a carrier substrate, as the security device can be cut/punched and introduced into the fibrous web with a single introduction device. As used herein, the term "introducing means" refers to means for cutting/punching and/or introducing the security device into the fibrous web during the wet stage. Suitable introduction devices are further described herein.

Other features and advantages of the present invention will be recognized by those of ordinary skill in the art upon review of the following detailed description and drawings. Unless defined otherwise, all technical and scientific terms used herein have the same meaning as commonly understood by one of ordinary skill in the art to which this invention belongs. All publications, patent applications, patents, and other references mentioned herein are incorporated by reference in their entirety. In case of conflict, the present specification, including definitions, will control. In addition, the materials, methods, and examples are illustrative only and not intended to be limiting. Moreover, all ranges expressly recited herein also implicitly encompass all subranges.

Drawings

The disclosure may be better understood with reference to the following drawings. The components in the figures are not necessarily to scale, emphasis instead being placed upon clearly illustrating the principles of the present disclosure. While the illustrative embodiments are disclosed in connection with the appended drawings, there is no intent to limit this disclosure to the embodiment or embodiments disclosed herein. On the contrary, the intent is to cover all alternatives, modifications and equivalents.

Certain features of the disclosed invention are explained by reference to the attached drawings, wherein:

FIG. 1 is a cross-sectional side view of a fibrous sheet produced by introducing a security device into a fibrous web in the event that the fibrous web is not sufficiently consolidated during the wet stage of papermaking;

FIG. 2 is a cross-sectional side view of a fibrous sheet produced by introducing a security device onto a fibrous web during or after the drying stage of papermaking when the moisture content is too low to allow the security device to be pressed into the substrate to further consolidate the fibers;

FIG. 3 is a cross-sectional side view of an exemplary embodiment of a fibrous sheet of the present invention having a surface applied security device wherein the security device is introduced into or onto the fibrous web when the fibrous web is sufficiently consolidated;

FIG. 4 is a schematic view of a fourdrinier papermaking machine in which a safety device in the form of a continuous web is introduced into the formed fibrous web on the wire after the wet line and before the couch roll;

FIG. 5 is a top view of an exemplary embodiment of a document having a plurality of discrete surface-applied security devices (patches and strips) applied thereto in accordance with the present invention;

FIG. 6 is a top view of another exemplary embodiment of a document having a plurality of discrete surface applied security devices (patches) applied in registration with another feature in the document, such as a watermark, in accordance with the present invention;

FIG. 7A is a plan view of the front side of a fibrous sheet or document after having been subjected to one (1) cycle through a flow-through simulation test, produced by introducing a security device into the formed fibrous web when the fibrous web is not sufficiently consolidated during the wet stage of papermaking;

FIG. 7B is a plan view of the back side of a fibrous sheet or document after having been subjected to one (1) cycle through a flow-through simulation test, produced by introducing a security device into the fibrous web when the fibrous web is not sufficiently consolidated during the wet stage of papermaking;

FIG. 8A is a plan view of the front side of an exemplary embodiment of a fibrous sheet or document produced by introducing a security device into a formed fibrous web when the fibrous web is sufficiently consolidated during the wet stage of papermaking according to the present invention after having been subjected to one (1) cycle through a flow-through simulation test;

FIG. 8B is a plan view of the back side of an exemplary embodiment of a fibrous sheet or document produced by introducing a security device into a fibrous web while the fibrous web is sufficiently consolidated during the wet stage of papermaking according to the present invention after having been subjected to one (1) cycle through a flow-through simulation test;

FIG. 9A is a plan view of the front side of a fibrous sheet or document after having been subjected to three (3) cycles through a flow-through simulation test, produced by introducing a security device into the formed fibrous web when the fibrous web is not sufficiently consolidated during the wet stage of papermaking;

FIG. 9B is a plan view of the back side of a fibrous sheet or document after having been subjected to three (3) cycles through a flow-through simulation test, produced by introducing a security device into the formed fibrous web when the fibrous web is not sufficiently consolidated during the wet stage of papermaking;

FIG. 10A is a plan view of the front face of an exemplary embodiment of a fibrous sheet or document produced according to the present invention after having been subjected to three (3) cycles through a flow-through simulation test by introducing a security device into the fibrous web while the fibrous web is sufficiently consolidated during the wet stage of papermaking;

FIG. 10B is a plan view of the back side of an exemplary embodiment of a fibrous sheet or document produced by introducing a security device into a fibrous web while the fibrous web is sufficiently consolidated during the wet stage of papermaking according to the present invention after having been subjected to three (3) cycles through a flow-through simulation test;

fig. 11 is a cross-sectional side view of another exemplary embodiment of a fibrous sheet of the present invention (second aspect) produced by introducing a security device into a fibrous web having opposed surfaces and paper machine-made or "soft-sided" through-holes. Introducing a security device into or onto the fiber web once the fiber web is sufficiently consolidated; and

fig. 12 is a schematic view of a fourdrinier papermaking machine in which through-holes are introduced in a formed fibrous web using a patterned forming wire, and then a security device in the form of a continuous web is introduced into the fibrous web after the wet line and before the couch roll. The patterned forming wire is depicted in fig. 12A prior to discharge of the papermaking stock from the headbox onto the forming wire, while the same forming wire is depicted in fig. 12B after discharge of the papermaking stock onto the wire.

Detailed Description

The present invention will be further understood from the following details, which are provided as descriptions of certain exemplary embodiments of the claimed invention.

By the method of the present invention, a fibrous sheet material comprising a surface applied security device is provided. In a first aspect of the invention, a method for applying a security device surface to a fibrous sheet is provided. The method comprises introducing a security device into or onto the fibrous web during papermaking. In a second aspect, the method comprises forming one or more "soft-edge" through-holes in the fibrous web before it becomes sufficiently consolidated during papermaking, and then introducing a security device into or onto the fibrous web above the one or more "soft-edge" through-holes once the fibrous web has become sufficiently consolidated. By forming the through-hole during the paper making, the through-hole is thereby provided with a unique edge irregularity which serves as an authenticity feature having a high security value. Furthermore, by introducing safety devices during the paper making process, the known process steps are uninterrupted and additional process steps are eliminated. Furthermore, by introducing safety devices during the wet stage of the paper making process, it is possible to apply thereby safety devices that are thicker than those that can be applied in the dry stage of the paper making.

In one embodiment, the method further comprises further consolidating the fibers in the sub-region. To further consolidate the fibers in the sub-regions, a surface applied security device is pressed into the fully consolidated (uniform or non-uniform) fibrous web. The fibers are compacted in this region so that the amount of fibers in this region is not displaced despite the reduced volume of this sub-region; at least not by any significant amount. The fact that the fibers in this region are not displaced greatly reduces, if not eliminates, the possibility that one or more of the through-holes will become clogged or blocked as the fibers are further consolidated in this region.

As used herein, with respect to the present disclosure, one of ordinary skill in the art will understand that the term "fully consolidated" means that the fibrous web is in a fully formed, wet web state. In the wet web stage, the fiber web contains less than 98% water and/or moisture. Thus, the fibrous web comprises more than 2% fibers and/or pulp. In another embodiment, the fiber web comprises less than 95% water and/or moisture, the remaining 5% of the ingredients being fibers and/or pulp. In more preferred embodiments, the water and/or moisture in the fibrous web is in the range of about 60% to less than 98%, or about 60% to about 95%. The applicant has found that water and/or moisture content exceeding 98% causes fibre displacement when the safety device is introduced. Significant displacement of the fibers, especially in sub-regions of the substrate, results in weak interaction between the security device and the fibers in the substrate. In particular, the displacement of the fibers reduces the durability and strength of the substrate and reduces the camouflage effect provided in the sub-and hinge regions. As described herein, these weak interactions, especially at the interface edges of the security device, cause the problems identified above. Accordingly, it has also been found that in case the fibrous web has less than 60% water and/or moisture, the introduction of the security device during the papermaking process is not sufficient to allow the security device to be recessed to accommodate a thicker security device, while still maintaining a low thickness difference. Furthermore, at less than 60% water and/or moisture, the fibers in the sub-region cannot further consolidate enough to secure the fibers near the interfacial edges of the security device. As used herein, the term "recessed" refers to pressing the security device into the fibrous web to form a relief/recess in the substrate surface of the fibrous sheet such that at least a portion of the height of the security device is recessed below the surface height of the body region while the top or upper surface region of the security device remains exposed.

The wet stage as defined above can be adjusted to various positions along the paper machine and the invention contemplates all these possibilities. However, in a preferred embodiment, the security device is applied into or onto the formed fibrous web during the wet stage of the papermaking process, e.g. at or near a couch roll or similar tool of a paper machine, when the fibrous web constitutes a fully consolidated or fully formed wet web (i.e. having a moisture or water content of less than 98% of the weight of the fibrous web, preferably from about 60% to less than 98% of the weight of the fibrous web, or more preferably from about 60% to about 95% of the weight of the fibrous web, or from about 60% to about 90% of the weight of the fibrous web, based on the total weight of the fibrous web). At such locations, no further process adjustments are required to accommodate integration of the safety device into the recess. For example, suction boxes are usually located just before the couch roll to remove as much moisture as possible before the web leaves the wet end of the machine in order to minimize the burden on the dryer section of the machine. Similarly, upon exiting the cylinder section of a cylinder mould machine (and after the couch roll), the fibrous web will preferably consist of about 75% to about 95% water and/or moisture and about 5% to about 25% pulp or fibers.

Although it is envisaged to provide sufficient consolidation of the fibrous web (as defined herein) at several papermaking stages on the fourdrinier papermaking machine, in a preferred embodiment the safety device is introduced into the papermaking stage of the fibrous web immediately after the wet line and before the couch roll. This is the point where there is no longer significant surface water on the upper side of the fiber web. In an alternative embodiment, the safety device is introduced into the fibrous web on or before the vacuum box in the wet end, which advantageously helps to set the device into the web. Preferably, the safety device is placed directly to the face of the fibrous web via a transfer wheel, a roller or a contact shoe.

In one embodiment, the fibrous web, while moving past or further over the couch roll, is in a fully formed web with surface applied safety devices when it travels to the dry end of the paper machine, which consists of a press section and a dryer section.

In the press section of both types of paper machines, water and/or moisture is removed by compressing the wet paper between a roll and a felt to reduce the water and/or moisture content to a desired level. The applicant has surprisingly found that compressing the fully formed wet web with the surface applied security devices causes the fibers in the sub-areas (i.e. the areas of the fiber web below or underneath the introduced security devices) to further consolidate as they are compacted rather than displaced. As a result, the strength characteristics of the resulting fibrous sheet or resulting document are improved as well as the back opacity that provides camouflage of the security device to reduce back strike-through.

The security device of the present invention may have various thicknesses. However, it has been found that the method of the present invention advantageously allows for surface application of the security device on the thicker end of the thickness spectrum. In one embodiment, the security device has a thickness of at most 100 micrometers (μm). In another embodiment, the security device has a thickness in the range of 5 μm to 75 μm or more preferably 10 μm to 50 μm. The width of the security device is limited only by the width of the fibrous sheet material. In a preferred embodiment, the width is in the range of 0.25 to 20 millimeters (mm), more preferably 0.5 to 15 mm.

By introducing safety devices during the wet stage of papermaking, these safety devices can be pressed into the fibrous web to create recesses in the surface of the resulting fibrous sheet. The resulting fibrous sheet material comprises a surface applied security device having a thickness differential that does not result in the above-mentioned disadvantages. In one embodiment, the difference in thickness is expressed relative to the thickness of the security device. In this embodiment, the absolute value of the thickness difference is in the range of 0% to about 80% of the thickness of the security device; preferably less than 10% of the thickness of the security device.

In one embodiment, the thickness differential is in the range of-10 μm to about 50 μm. More preferably, the thickness difference is in the range of-5 μm to 30 μm, or 0 μm to 25 μm.

In certain embodiments, the device is sufficiently thin such that the pressing of the security device into the fibrous wet web results in a negative thickness differential (i.e., the thickness or height of the security device is less than the thickness or height of the body region). In such embodiments, the thickness difference is best characterized by reference to the absolute value of the thickness difference relative to the thickness of the security device. For example, in one embodiment, the thickness of the security device is less than 25 μm, such that the absolute value of the difference in thickness of the surface-applied security device when the security device is pressed into the fibrous web is in the range of 0% to about 50%, more preferably 0% to about 30%, even more preferably about 0% to about 10% of the thickness of the security device. In a further embodiment, the thickness of the security device is also less than 25 μm, so that further consolidation of the sub-regions by pressing the security device into the fibrous web results in a thickness difference in the range of-10 μm to 15 μm, preferably-5 μm to 10 μm.

Alternatively, in one embodiment, the thickness of the security device is greater than 25 μm, such that further consolidation of the sub-regions by pressing the security device into the fibrous web produces a thickness difference in the range of-10 μm to 50 μm, preferably-5 μm to 25 μm, or 0 μm to 15 μm. In one other embodiment, wherein the security device also has a thickness greater than 25 μm, the absolute value of the difference in thickness relative to the thickness of the security device is in the range of 0% to about 50%. Preferably, the absolute value of the thickness difference is in the range of 0% to about 20% of the thickness of the security device.

A "couch roll" will be understood by those of ordinary skill in the art to be a guide or turning roll for a fourdrinier wire positioned at the point where the web leaves the wire (i.e., the wet end or paper forming section) and the wire returns to the breast roll on a fourdrinier machine. Couch rolls are used for the same purpose on cylinder mould machines, where the fourdrinier wire section has been replaced by a cylinder mould section. In particular, the couch roll guides and rotates the web as it leaves the cylinder section and travels towards the couch roll.

Although it is also envisaged that the entire fibre web has a uniform consistency in water and/or moisture content and fibre content, it is also within the scope of the invention that the fibre web is not uniformly sufficiently consolidated. For example, in one embodiment, the fiber web is fully consolidated only at or along the point of introduction. As used herein, "introduction point" refers to an area at or along the fibrous web that is at least partially covered by a security device. In another embodiment, the fiber web is only partially sufficiently consolidated or sufficiently consolidated in a gradient or matrix pattern such that at the point of introduction, the fibers are not significantly dispersed resulting in the identified disadvantage. For example, by selective vacuum treatment at locations along the formed fibrous web, a gradient or matrix pattern of sufficient consolidation can be provided. Alternatively, in one embodiment, the moisture content is removed in a gradient or matrix pattern by applying a radiation source (i.e., heat) to remove the top surface water at selected locations along the formed fibrous web.

The introduction of the security device into the fibrous web forms an interface between the security device and the base fibrous web, the resulting fibrous sheet, or the resulting document. As used herein, the term "interface" may be formed by direct or indirect contact between the security device and the substrate. Where the interface is direct, the security device is in direct contact with the fibres in the substrate. However, it is contemplated that the security device forms an indirect interface with the substrate along some or all of the bottom and side surfaces. For example, the interface may include other materials between the security device and the substrate. While a variety of materials are contemplated, additional fibers or polymeric materials (e.g., single and/or multicomponent fibers, alone or in combination, obtained from natural sources such as plant sources or spun from a polymer melt composition, etc.) are particularly suitable. Furthermore, binder materials are preferred for forming the indirect interface. The activatable adhesive may be used to anchor or bond the security device onto or into the recessed surface of the fibrous web. Suitable adhesives are not limited and include, but are not limited to, water activated, heat activated and/or pressure activated adhesives activated in the dryer section of a paper machine where temperatures reach 100 ℃ to 160 ℃. These coatings may be applied in the form of solvent-based polymer solutions or aqueous solutions or dispersions. Suitable dispersions are selected from the group consisting of acrylic resin dispersions, epoxy resin dispersions, natural latex dispersions, polyurethane resin dispersions, polyvinyl acetate resin dispersions, polyvinyl alcohol resin dispersions, urea-formaldehyde resin dispersions, vinyl acetate resin dispersions, ethylene vinyl alcohol resin dispersions, polyester resin dispersions, and mixtures thereof. While moving past the couch roll, the fully formed wet web with surface applied safety devices travels to the dry end of the paper machine, which consists of a press section and a dryer section. The adhesive may alternatively form part of a security device and in such embodiments has a thickness in the range of from 5 μm to about 50 μm, preferably from 5 μm to about 20 μm.

Security devices suitable for use with the present invention include those commonly used by those of ordinary skill in the art to provide security against counterfeiting or forgery. In a second aspect of the invention, the security device is preferably formed from a structural film, for example a polyethylene terephthalate (PET) film, and has a thickness of at least about 10 to 15 microns, which provides sufficient durability to the device to allow it to span one or more through-holes. As used herein, the term "structural film" is intended to mean a film having structural integrity that is an integral part of the structure of the security device, rather than a removable carrier film, such as is typically used with transfer foils, or the transfer foil itself. The security devices may be those adapted to alternatively or additionally apply aesthetic features to the substrate. Suitable security devices may display information that may be perceived by humans, whether directly or by means of the device, or may display information that may additionally or alternatively be perceived by a machine. The security device may employ one or more of the following features: demetallised or selectively metallised, magnetic, combined magnetic and metallic, or embossed regions or layers, colour shifting coatings consisting of colourshifting, iridescent, liquid crystal, photochromic and/or thermochromic materials, coatings of luminescent and/or magnetic materials, holographic and/or diffractive security features, and micro-optical security features. In a preferred embodiment, the security device provides security such that the security or value document can be easily authenticated. In one embodiment, the security device comprises an array of focusing elements and an array of image icons, wherein the array of focusing elements and image icons are arranged such that one or more composite images are projected by the security device. The focusing elements used in the present invention are used to highlight, magnify, illuminate, or emphasize small dots in an array of image icons, and include, but are not limited to, lenticular lenses and non-cylindrical lenses (i.e., microlenses). The composite imaging mentioned above is a form of integral imaging in that the image perceived by the viewer is composed of hundreds or thousands of individual image segments that are magnified by lenses (e.g., microlenses) and projected toward the eyes of the viewer.

In an exemplary embodiment, the security device is a microlens-based security device. Such devices typically include (a) a light transmissive polymer substrate, (b) an arrangement of micro-sized image icons located on or within the polymer substrate, and (c) an arrangement of focusing elements (e.g., microlenses). The image icons and the focusing element arrangement are configured such that one or more composite images are projected when the arrangement of image icons is viewed through the focusing element arrangement. These projected images may show many different optical effects. Material constructions capable of exhibiting such effects are described in the following patents: U.S. patent No. 7,333,268 to Steenblik et al, U.S. patent No. 7,468,842 to Steenblik et al, U.S. patent No. 7,738,175 to Steenblik et al, U.S. patent No. 7,830,627 to Commander, U.S. patent No. 8,149,511 to Kaule et al; U.S. patent No. 8,878,844 to Kaule et al; U.S. patent No. 8,786,521 to Kaule et al; european patent No. 2162294 to Kaule et al; and european patent application No. 08759342.2 to Kaule (or european publication No. 2164713). These references are incorporated herein in their entirety.

In preferred embodiments, the security devices surface-applied by the methods of the present invention include, but are not limited to, micro-optical security devices (such as the MOTION described in, for example, U.S. patent No. 7,333,268)^TMMicro-optical security device), RAPID^TMMicro-optical security devices, holographic security devices (e.g. metallised holographic devices). These devices are commercially available from cane Currency US, LLC, massachusetts, usa. Other suitable devices include, but are not limited to, Optically Variable Devices (OVDs) such as KINEGRAM^TMAn optical data carrier and a colour shifting security device.

Although the security device may be presented in various forms to be incorporated into the fibrous web, it has been found to be most advantageous to provide the security device in the form of a continuous web. By providing the security device in the form of a continuous web, it has been found that the security device can be introduced into the fibrous web in a continuous manner. The continuous web is then segmented or divided into a plurality of discrete security devices. Segmenting the continuous web into discrete security devices may be accomplished by various cutting and/or stamping methods. In a preferred embodiment, the method is a process of applying a plurality of discrete security devices in series to a fibrous web during manufacture on a papermaking machine without the use of a carrier film. The method includes providing a security device in the form of a continuous web; cutting or stamping the continuous web in a continuous manner to form discrete security devices, each security device having a desired shape and size; discrete security devices are then applied to the fibrous web in a continuous manner during papermaking.

It is contemplated herein that additional security devices may be applied to the fibrous sheet material by surface application, partial embedding, or full embedding. For example, in one embodiment, an additional security device is applied to the surface of the fibrous sheet. The attachment means may be introduced into the fibrous web before the introduction of the surface-applied security means or after the introduction of the surface-applied security means. The additional security device may be different from or similar to the surface applied security device. For example, in one embodiment, when one of the discrete security devices has a thickness of 25 μm or less, it is contemplated to incorporate it into the fibrous web at a moisture content of less than 60% by weight, preferably in the range of about 90% to 0%. For example, the safety device is introduced into the fiber web as it travels through the paper machine between the first dryer section and the size press, and is optionally rewetted to increase the water and/or moisture content to between about 4% and about 7%.

The security device may take on a variety of sizes, shapes or colors. For example, it is contemplated that the security device in the form of a discontinuous security device takes the non-limiting form of a strip, band, thread, ribbon, or patch. The total width of these devices may be from about 2mm to about 25mm (preferably, from about 6mm to about 12mm) and the total thickness is from about 10 microns to about 50 microns (preferably, from about 20 microns to about 40 microns). In a preferred embodiment, the security device is a strip or patch. As used herein, "strip" refers to a security device having a longitudinal length dimension that is substantially greater than a transverse width dimension. In contrast, a "patch" may have substantially equal longitudinal and transverse lengths, and may have a uniform or variously non-uniform shape. Various shapes and sizes of strips and patches are contemplated herein. However, while the strips or patches may extend to the edges of the fibrous sheet or resulting document, in a preferred embodiment the strips or patches are located within the perimeter of the fibrous sheet or document and do not extend to the edges of the sheet or document.

As mentioned, various sizes of security devices are considered suitable for the method and fibrous sheet material of the present invention. In one embodiment, the total length of the dimensions is in the range of about 5mm to about 75mm, preferably about 15mm to about 40 mm; and a total width of from about 2mm to about 50 mm, preferably from about 6mm to about 25 mm; and a total thickness of about 10 microns to about 50 microns, preferably about 15 microns to about 40 microns. All ranges mentioned herein include all subranges, including integers and fractions. As noted above, in the second aspect of the invention, the security device is preferably formed from a structural film, for example a polyethylene terephthalate (PET) film, and has a thickness of at least about 10 to 15 microns, which provides sufficient durability to the device to allow it to span one or more through-holes.

As mentioned, various shapes of the safety device are also envisaged; such as patches, strips or lines, geometric shapes such as stars, parallelograms, polygonal (e.g., hexagons, octagons, etc.) shapes, numbers, letters, and various symbols. Simple and complex non-geometric designs are also considered suitable. These shapes and designs can be cut by a rotary die process.

In one embodiment of the method of the present invention, a security device is introduced into the formed fibrous web such that it is in registration with at least one other feature on or in the fibrous web, fibrous sheet, or substrate of the resulting document. In certain embodiments, the security device is introduced such that a particular feature within the security device is registered with another feature in the fibrous web, resulting fibrous sheet, or document. The at least one other feature may be varied as desired with respect to the application. For example, the at least one other feature is a watermark, a printed image, a relief structure, another security device, or a paper feature. In a second aspect of the invention, the security device is introduced such that it is preferably in register with one or more "soft-edged" through-holes. In introducing the security device into the fibrous web so that it is registered, it is envisaged that the security device, which is present in the form of a continuous web, is first delivered to a piece of equipment or system (herein referred to as an introduction device) which can be used to cut/punch the continuous web into discrete security devices. Although it is possible to use a separate device for cutting and then applying the security device to the fibrous web, it is preferred that the system for forming discontinuous security devices is also used for applying the security device into or onto the fibrous web. With a single device, it is possible to apply the safety device in register more accurately, as it requires fewer moving parts.

In a preferred embodiment, in which the continuous web is cut into discrete security devices, which are then introduced into or onto the fibrous web by the same introduction device, it is also contemplated that the placement of the security devices may be adjusted by the introduction device such that the security devices that are not in register (with at least one other feature) may be adjusted to be in register in a continuous manner. By using a single lead-in device to cut, apply and adjust registration in situ during the papermaking process, no additional processing is required to adjust placement. For example, application and adjustment in registration during the papermaking process eliminates the need for secondary processing of the resulting sheet or document prior to printing.

Suitable introduction devices will be apparent to those of ordinary skill in the art after having read this disclosure. However, in a preferred embodiment, the introducing means is a system employing an optical or fiber density sensor that checks the registration between the security device and the fibrous web, fibrous material, or at least one other feature in the resulting document. The introduction means are used to make adjustments in the placement of the security device in view of the identified or calculated position of the security device or the relative position of the security device and the at least one other feature. To make such adjustments, the lead-in device uses a variable speed pusher (e.g., an electric servo with servo drive) that controls the tension on the continuous web so that the discrete safety devices can be applied in registration as needed. Thus, the point of introduction of the safety device is continuously adjusted by adjusting the tension on the continuous web. Alternatively, the introduction device may be a rotary die-cutting and transfer device, such as those used in the label industry for applying labels in registration.

In a second aspect of the invention, a method is provided for forming one or more "soft-edged" through-holes in a formed fibrous web, and then applying a security device to the surface over the one or more through-holes. In the second aspect, the method comprises: one or more "soft-edge" through-holes are formed in the formed fibrous web during papermaking and, once the fibrous web is sufficiently consolidated (uniformly or non-uniformly), a security device is introduced into or onto the formed fibrous web above the one or more "soft-edge" through-holes.

Although the second aspect of the invention is described as having the security device located over the one or more through holes, the security device and the one or more through holes may be otherwise registered or not registered at all. For example, the security device and the one or more through-holes may be registered in a side-by-side configuration, wherein the security device is positioned on/in the fibrous web adjacent to the one or more through-holes.

In one embodiment of the process of the present invention, the process further comprises further consolidating the fibers in a sub-region of the fibrous sheet. To further consolidate the fibers in the sub-regions, a surface applied security device is pressed into the fully consolidated fiber web. The fibres are compacted in this region so that despite the reduced volume of the sub-region, the amount of fibres in this region (surrounding the through-hole or holes) is not displaced, at least not by any significant amount. As described above, the fact that the fibers in this region are not displaced greatly reduces, if not eliminates, the possibility that one or more of the through-holes will become clogged or blocked as the fibers in this region are further consolidated.

One or more through-holes are created during the wet web stage of papermaking before the forming fiber web becomes "fully consolidated". In other words, the fiber web is not in a fully formed wet web state. Thus, the fiber web comprises a water and/or moisture content of more than 98% by weight of the fiber web. In order to be able to create this through-opening, the screen of the paper machine must be provided with at least one waterproofing element which prevents the formation of sheets in this area. The papermaking screen may be a continuous moving forming wire of a fourdrinier machine or a cylinder wire of a cylinder machine.

The through-holes may take any suitable size and shape or profile. For example, the through-holes may be circular, oval, star-shaped, formed like a parallelogram (e.g., square, rectangular), trapezoid, or the like. In an exemplary embodiment, the aperture has at least one cross-dimension that is narrower/smaller than about 1 millimeter (mm) than the security device placed thereover. The cross dimension refers to a line between two points on the aperture that intersect at least a portion of the security device. Thus, if the diameter of the hole is 5mm, the device will have to have a minimum dimension of at least about 6 mm. If the aperture is irregular (e.g., star-shaped), the narrowest edge of the device must be about 1mm from the widest edge of the aperture. The shape or contour of the one or more through-holes may match or coordinate with the shape or contour of the security device and/or the image displayed or projected by the security device.

After the one or more through-holes are formed and the fibrous web is sufficiently consolidated, a security device is applied over the one or more through-holes. As noted above, in a preferred embodiment, the security device is applied into or onto the formed fibrous web when the fibrous web constitutes a fully consolidated or fully formed wet web (i.e., having a moisture or water content of less than 98% by weight of the fibrous web, preferably from about 60% to less than 98% by weight of the fibrous web, or more preferably from about 60% to about 95% by weight of the fibrous web, or from about 60% to about 90% by weight of the fibrous web), during the wet stage of the papermaking process, for example at or near a couch roll or similar tool of a papermaking machine.

The surface-applied security device may be shaped the same as or different from the one or more through-holes, and may be sized to be much larger than or only slightly larger than the one or more through-holes. As described above, the security device may take the non-limiting form of a strip, band, wire, ribbon, or patch, while the through-holes may be circular, oval, star-shaped, formed like a parallelogram (e.g., square/rectangle), trapezoid, or the like. In an exemplary embodiment, the surface-applied security device is an elongated security thread having a width in the range of about 5mm to about 20mm (preferably about 8mm to about 12mm) extending along all or part of the entire length or width of a fibrous sheet made from the fibrous web. In another exemplary embodiment, the through-hole has a circular shape with a maximum diameter in the range between 5mm and 15mm (preferably about 7mm to about 10mm) and the surface applied security device is a patch having a complementary or contrasting shape and a width and length at least 2mm larger than the hole.

In another aspect of the present invention, a fibrous sheet is provided. The fibrous sheet material as described herein is the result of further processing of the fibrous web after the security device has been introduced into the fibrous web. The further processing optionally comprises a drying step applied before or after pressing the security device into the fibrous web. Pressing the security device into the fibrous web produces a fibrous sheet having a fibrous body region and a fibrous sub-region.

In a first aspect, a resulting fiber sheet having opposing surfaces and a recess in one opposing surface includes: a surface-applied safety device disposed in the recess; a fiber sub-region disposed below the recess; a fibrous body region disposed adjacent the security device (disposed in the recess) and the sub-region; and an interface between the security device and at least one surface of the fibrous sheet. In a second aspect, the resulting fiber sheet has one or more "soft-edged" through-holes extending from the recess to the opposite surface of the fiber sheet. As used herein, reference to the body region being adjacent to the security device indicates that the body region is a three-dimensional region adjacent to the security device along the x-axis in the cross-sectional view. As used herein, reference to a sub-region being below the safety device indicates that the sub-region is a three-dimensional region along the y-axis that is at least partially covered by the safety device in cross-sectional view. The thickness of the sub-region is less than the thickness of the body region such that the surface applied security device has a difference in thickness of less than 80% of the thickness of the security device or within the specified range and implicit sub-range as described above.

In one embodiment, the fibers in the sub-region are further consolidated such that the amount of fibers in the sub-region is substantially equal to the fibers in at least the immediately adjacent bulk region. In another embodiment, the amount of fiber in the sub-region is substantially equal to the amount of fiber in the bulk region. As used herein, the term "substantially equal," as it refers to the amount of fiber in the body and sub-regions, means that the amount of fiber in each region is within 80% to 100%, preferably 90% to 100%, of the amount in the other region, as characterized in grams per square meter (gsm) of fiber. In a preferred embodiment, the amount of fibers in the sub-region is equal to an amount in the range of 80% to about 100% of the body region (particularly the immediately adjacent body region).

As described herein, the various thicknesses may be attributable to suitable security devices. Thus, various thickness differences are also contemplated. In one embodiment of the fibrous sheet, the security device has a thickness in the range of about 10 microns to about 75 microns. The thickness difference ranges from about-10 microns to about 30 microns; preferably 0 microns to about 25 microns; preferably about 0um to about 15 um.

In one embodiment of both the first and second aspects of the invention, the fibrous sheet exhibits at least one of: (1) improved durability, (2) acceptable ink adhesion, (3) high cross-direction (CD) tensile strength, or (4) reduced back show through. As used herein, improved durability can be characterized by at least one of: (a) minimal or reduced damage at the interface, or (b) little or no hinge effect, as compared to such sheets produced when the fiber web is not sufficiently consolidated. These effects can be quantified or assessed by known industry techniques that simulate the effects of file circulation. For example, circulation of banknotes can be simulated with a durability test. One such suitable durability test is the "flow through simulation" test (CST). This is a wear test designed to simulate the mechanical and optical degradation experienced by a banknote during its circulation life. The test was performed by attaching rubber washers weighing 7.5 grams each to the four corners of the banknote, and then placing the weighted banknote in a grindstone machine calibrated to 60 Revolutions Per Minute (RPM) speed for a fixed duration of 30 minutes (one (1) cycle). The tumbling action experienced by the weighted note causes mechanical and optical degradation. Controlled amounts of liquid and solid soil agents (e.g., soybean oil and clay) were then added to the grindstone machine to simulate the effects of oil and dirt that the paper currency would normally come into contact with during its life cycle. The banknotes were tested for mechanical degradation (e.g., surface and edge damage in the form of holes, tears, cuts, hinges, separation and rough edges, loss of tensile strength, folding resistance, tear strength and perforation strength), optical degradation (e.g., degradation of the color characteristics of the printing ink), and contamination before and after each simulated degradation. Hinge effects and tearing at the interface are examples of mechanical degradation that is particularly suited for this durability test.

Tests for acceptable ink adhesion are known to those of ordinary skill in the art. For example, ink set-off, which is the amount of ink transferred from one sheet to another in a stacked formation of multiple fibrous sheets or documents, can be quantitatively measured by methods known to those of ordinary skill in the art. Similarly, tensile strength and back print through can be quantified by methods known to those of ordinary skill in the art. For example, show-through can be quantified by known light reflectance or transmittance tests. In use, for example

In the CD tensile strength test of the tensile tester or tensile tester, and as shown in table 2 herein below, the paper made according to the present invention exhibited an increase in CD tensile strength with the measured property having an increase in value ranging from about 90% to about 100% when compared to the application of a security device to a fully formed fibrous web through a conventional cylinder mould.

As mentioned, the fibrous sheet material has a fibrous sub-region beneath the security device and a fibrous body region adjacent the security device and the sub-region. Because the safety device is introduced when the fiber web is sufficiently consolidated, no shifting of the fibers in the area of the fiber web corresponding to the sub-area in the sheet occurs by an amount that leads to the identified disadvantage. In this way, the amount of fibres in the sub-area of fibres is substantially equal to the amount of fibres in at least the immediately adjacent main area. As used herein, the term "immediately adjacent body region" refers to the three-dimensional region of the body region that adjoins the sub-region and the recessed portion of the safety device. The immediately adjacent body region extends radially from the recessed portion and the sub-region to a distance in the cross-sectional x-axis equal to the x-axis length of the sub-region. In view of the volume difference between the immediately adjacent body region and the sub-region, the fiber density in the sub-region is greater than the fiber density in the immediately adjacent body region. The amount of fiber in the immediately adjacent body region and sub-region is substantially equal such that given the difference in volume of the two regions, the density in the sub-region is greater than the density in the immediately adjacent body region. In one exemplary embodiment, the amount of fiber in the body region is in the range of 88.55gsm to 90.15gsm, and the amount of fiber in the sub-region is in the range of 87.26gsm to 90.69 gsm. As used herein, "density" refers to the average amount of fiber in a volume.

In a second aspect of the invention, a fibrous sheet having opposing surfaces, one or more "soft-edged" through-holes, and a recess above the one or more through-holes, comprises: a surface-applied safety device disposed in the recess; a fiber sub-region disposed below the recess, the fiber sub-region defining one or more through-holes; a fibrous body region disposed adjacent the security device (disposed in the recess) and the sub-region; and an interface between the security device and the sub-and main regions of fibres of the fibrous sheet material. The sub-region of fibres extends along an area defined by the outer periphery of the one or more through-holes and one or more outer boundaries of the security device.

As described herein, there are many security devices that are suitable for use with the present invention. However, in one embodiment, the fibrous sheet includes a security device having an array of cylindrical and/or non-cylindrical focusing elements and an array of image icons that optically interact with the focusing elements to produce at least one composite image. In a preferred embodiment, the focusing elements are simply cylindrical lenses or non-cylindrical lenses (e.g., microlenses). However, it is contemplated herein that the lens array includes a mixture of both in various ratios.

As described herein, the security device may be in the form of a strip or patch or other shape or geometry. In one embodiment, the security device is present in the sheet in registration with at least one other feature in the sheet. Suitable additional features are described herein.

In another aspect, the invention is a document comprising a fibrous sheet. The present invention contemplates various files. For example, suitable documents include, but are not limited to, banknotes, bonds, checks, travelers checks, identification cards, lottery tickets, passports, postage stamps, stock certificates, and non-secure documents (such as stationery items and labels, and items for aesthetic purposes). Multiple security devices may be incorporated into the fibrous web and thus may be found applied to the fibrous sheet and any resulting document. Alternatively, in one embodiment, the document includes at least one surface-applied security device and at least one other security device, such as an embedded or partially embedded security device or security feature. The surface-applied security device may be registered with other features of the document, such as other security devices or security or decorative features.

The fibrous sheet material suitable for use in the present invention is paper or a paper-like sheet material. These sheets, which are single-or multi-layer sheets, can be made of a range of fiber types including synthetic or natural fibers or a mixture of both. For example, the sheets can be made from fibers such as abaca, cotton, flax, wood pulp, and blends thereof. As is well known to those skilled in the art, cotton and cotton/linen or cotton/synthetic fiber blends are preferred for banknotes, while wood pulp is commonly used for non-banknote security documents.

As noted above, it is contemplated that the security devices used with the present invention may take a variety of different forms, including but not limited to strips, ribbons, threads, ribbons, or patches (e.g., microlens-based, holographic, and/or color-shifting security threads).

A further understanding of the claimed invention will be facilitated by the following description of the figures, which represent exemplary embodiments.

Conventional techniques are depicted in fig. 1 and 2. Typically, as shown in fig. 1, a security device (11) is introduced during the wet stage of papermaking to embed the device (11) in a fibrous sheet or document (10). When surface applying security devices using this method, the resulting fibrous sheet suffers from low flow through durability, poor CD tensile strength, and high back print through. As mentioned elsewhere herein, it has been found that this is partly due to the displacement of the fibers (15) from the sub-areas (12) when introducing the safety device (11) into the formed fibrous web. It can be seen that the amount of fibres in the hinge region (14) is significantly reduced. This results in a weak interaction at the interface (17) between the security device and the substrate (18) of the fibrous sheet or document (10). This is particularly evident at the interface edge (17 a).

A disadvantage is also found in the conventional embodiment shown in fig. 2, where the safety device (21) is introduced either in the drying stage of the paper making or after the paper making stage where the paper is fully consolidated. The fibers (25) in the partial regions (22) are sufficiently consolidated here that the safety device (21) cannot be pressed into the substrate (28). As a result, the difference in thickness is high. High thickness differences have been associated with poor application of ink on sheets or documents (20). As a result, for embodiments in which the security device is added during the drying stage, the security device must be very thin in order to have a suitable thickness difference.

The present invention addresses at least one of these shortcomings. Fig. 3 depicts an embodiment of the present invention. Here, unlike fig. 1 and 2, the safety device (31) is introduced at the wet stage when the web is sufficiently consolidated, so that a significant amount of fibers (35) are not displaced from the sub-areas (32) when the safety device is pressed into the substrate (38) of the fibrous sheet (30). Instead, the fibers (35) are further consolidated or compacted under the security device (31) and in the hinge region (34). This results in strong fiber interactions at the interface (37) and particularly at the interface edge (37 a). Furthermore, since the security device (31) is introduced during the wet stage, it can be pressed into the substrate (38) to provide a low thickness differential.

Various methods and techniques may be used to introduce the security device (41) into the fibrous web (49). In the preferred embodiment shown in fig. 4, the safety device (41) is present in the form of a continuous web and is continuously applied to the forming fibre web (49) on the fourdrinier machine (40) immediately after the wet line (42) and before the couch roll (44) and between vacuum boxes (45a, 45b) which help to arrange the safety device into the fibre web (49).

Fig. 5 and 6 depict a fibrous sheet or resulting document (50, 60) of the present invention having a plurality of surface applied security devices (52a, 52b, 53, 63a, 63 b). The devices (52a, 52b, 53, 63a, 63b) are presented here in the form of patches (53, 63a, 63b) and strips (52a, 52b) of different sizes and shapes. Although not limited in this regard as to the placement location of the security devices (52a, 52b, 53, 63a, 63b), in one embodiment of the invention, the security devices (e.g., 53, 63a, 63b) are cut or punched during papermaking by an intake device (not shown) and applied to the fibrous web (55) such that they are in registration with at least one other feature (e.g., watermark (61)) in the fibrous web, fibrous sheet, or resulting document (60). Fig. 6 depicts an embodiment in which multiple security devices applied as patches (63a, 63b) are applied in registration with the watermark (61). The first patch (63a) is applied in lateral registration with the watermark (61) and the second patch (63b) is applied in longitudinal registration with the watermark (61). It is also envisaged that the security device (63a, 63b) is aligned with the watermark (61) such that at least one feature (not shown) in the patch (63a, 63b) is in register with the watermark (61) or other feature in the fibrous web, sheet or resultant document (60). The documents (50, 60) have edges (59, 69) which, although depicted here as sides of a parallelogram, may also be depicted in other shapes having other angles. The security device (52a, 52b, 53, 63a, 63b) is applied to the fibrous web, fibrous sheet or document such that it does not extend beyond the edge (59, 69) of the document (50, 60). In a preferred embodiment, the security device is disposed on the surface such that it is positioned away from the edge without contact.

Examples

Comparative example 1: single cycle durability test of surface applied safety devices when fiber webs are not sufficiently consolidated

In a first comparative example, a fibrous sheet was manufactured according to a conventional wet stage process, wherein a security device was introduced into the fibrous web during the paper making process when the water and/or moisture content in the fibrous web was greater than 98%. As a result of the displacement of the fibres in the hinge region (74) and the sub-regions, the fibres are displaced, resulting in a reduced interaction of the security device (71) with the fibre substrate (78) of the fibre sheet (70) in these regions. A fibrous sheet (70) formed according to this process is shown in fig. 7A after passing a single cycle (30min) of the flow-through simulation test. As a result of this single cycle, the fibrous sheet (70) exhibits poor durability, at least as defined by the development of the hinge effect shown in the hinge region (74). The security device (71) is separated from the substrate (78) of the fibrous sheet (70) at a point along the interface edge (77 a).

In addition, surface applied security devices exhibit back print-through. A panel of five (5) people (P1, P2, P3, P4, P5) was asked to rate the degree of back side strike-through from 1 to 5, with 5 having the highest strike-through and 1 having the lowest strike-through. Panelists P1 and P4 rated the back print as 4; panelists P2, P3, and P5 rated a reverse print through of 5. Fig. 7B depicts a fibrous sheet (70) showing reverse side print-through. This would require some sort of back camouflage coating to address this problem.

Also used is model 5965

The tensile tester measures the Cross Direction (CD) tensile strength of the fibrous sheet. The paper sample was cut into dimensions of 125mm wide by 15mm high with the line passing perpendicularly through the center of the sample. The sample was then placed into the jaws of an Instron (model 5965) tensile tester with a set spacing of 40mm between the jaws and the wire centered in the gap. The sample was then stretched at a rate of 38 mm/min until the sample broke. This process was repeated 5 times, and the average of these 5 values is the reported result of the test. The results show that the CD tensile strength is in the range of 5.4 kg to 6.3 kg.

Inventive example 1: single cycle durability test of surface applied safety devices when the fiber web is fully consolidated

In a first inventive example, a fibrous sheet (80) is manufactured according to the invention disclosed herein, wherein a security device (81) is introduced into the fibrous web at a moisture content of the fibrous web of less than 98% during the papermaking process. There is sufficient interaction of the security device (81) with the substrate (88) of the fibrous sheet (80) as a result of reduced fiber displacement from the hinge region and increased fiber consolidation in the sub-region. A fibrous sheet (80) formed according to this process is shown in fig. 8A after passing a single cycle of the flow-through simulation test. It is apparent that the fibrous sheet (80) has improved durability relative to the material produced in comparative example 1. Here, the fibrous sheet (80) does not exhibit a hinge effect with the base (88) of the fibrous sheet (80) along the interface edge (87a) of the security device (81) and is not damaged or separated. The fiber sheet (80) remains intact and exhibits improved durability.

Furthermore, the surface-applied security device (81) showed less back-strike than comparative example 1. A panel of five (5) people (P1, P2, P3, P4, P5) was asked to rate the degree of back side strike-through from 1 to 5, with 5 having the highest strike-through and 1 having the lowest strike-through. Panelist P2 rated the back print as 1; panelists P1, P3, P4 and P5 rated a back print of 2. Fig. 8B depicts a fibrous sheet showing reverse print-through. Alternatively, the back print-through is characterized by measuring cross-line gray scale density. The paper samples were scanned on an Epson V750 Perfection flatbed scanner that had been calibrated using IT8 reference targets. The paper was scanned at 600dpi as a grayscale image in reflected light with a black background behind the sample. Once the scan is captured, a density profile of the selected region is generated. With this functionality, we select a region across the line where the software captures the grayscale value of each pixel in the selected region, for this particular test where the line passes vertically through the center of the selected region, the software averages the vertical pixels within the region, and reports the vertical average data point for each horizontal pixel (e.g., if the region is 20 pixels high by 200 pixels wide, for each horizontal position, the corresponding vertical pixel value will be averaged and will result in an output of 200 data points). The resulting data is then plotted to show whether there are any significant shifts in the gray values within the sample area. The density measurements are provided in table 1. The results of the inventive examples are provided by the top line, while the results of the comparative examples are provided in the bottom line, indicating a significant drop in fiber density measurement as the measuring device traverses the opposite side of the security device. A lower value indicates a high back print-through. It can be seen that with the method of the invention (< 90% water and/or moisture) the density values on the fibrous sheet remained relatively constant, whereas for the comparative examples (> 98% water and/or moisture) the density values had a well-recognized and significant decrease in value. For the comparative example (> 98% water), the average interline grayscale density was 214; whereas for the inventive example (< 90% water) the average interline grayscale density is 226.

Use model 5965

The tensile tester also measures the cross-direction (CD) tensile strength of the fibrous sheet (80). The same process as described above is repeated here. The results show that the CD tensile strength is better than that shown in comparative example 1. The results of the comparative example are depicted as the first bar (> 98% water) in table 2, while the results of the inventive example are (<90% water) is depicted as the second bar in table 2.

Cross-line gray scale density measurement

TABLE 1

The average increase in CD tensile strength was 25%

TABLE 2

Comparative example 2: three cycle durability test of surface applied safety devices when the fiber web is not sufficiently consolidated

In a second comparative example, a fibrous sheet (90) was manufactured according to a conventional wet stage process, wherein a security device was introduced into the fibrous web during the papermaking process when the water and/or moisture content in the fibrous web was greater than 98%. As a result of the displacement of the fibres in the hinge region and the sub-regions, the fibres are displaced during introduction of the security device (91), resulting in a reduced interaction of the security device (91) with the substrate (98) of the fibre sheet (90) in these regions. A fibrous sheet (90) formed according to this process is shown in fig. 9A after passing three cycles of the flow-through simulation test. As a result of these three cycles, the fibrous sheet (90) exhibits poor durability, at least as defined by the development of tears in the sheet along the interface edge (97 a). The fibrous sheet (90) is torn into two pieces along the interface edge (97 a).

Furthermore, the surface applied security device (91) exhibits a back print through. A panel of five (5) people (P1, P2, P3, P4, P5) was asked to rate the degree of back side strike-through from 1 to 5, with 5 having the highest strike-through and 1 having the lowest strike-through. Panelists P1 and P5 rated a back print of 5; panelists P2, P3 and P4 rated a back print of 4. Fig. 9B depicts a fibrous sheet (90) showing tearing and reverse print-through. This would require some sort of back camouflage coating to address this problem.

Inventive example 2: three cycle durability test of surface applied safety devices when the fiber web was fully consolidated

In a second inventive example, a fibrous sheet (100) is manufactured according to the invention disclosed herein, wherein a security device (101) is introduced into the fibrous web at a moisture content of the fibrous web of less than 98% during the papermaking process. There was sufficient interaction of the security device with the substrate (108) of the fibrous sheet (100) as a result of reduced fiber displacement from the hinge region and increased fiber consolidation in the sub-region relative to the situation in comparative example 1. A fibrous sheet (100) formed according to this process is shown in fig. 10A after passing three cycles of the flow-through simulation test. It is apparent that the fiber sheet (100) has improved durability relative to the material produced in comparative example 2. Here, the fibrous sheet (100) exhibits little to no hinge effect or damage along the interface edge (107a) of the security device (101) with the substrate (108) of the fibrous sheet (100). The fiber sheet (100) remains intact and exhibits improved durability.

Furthermore, the surface-applied security device (101) showed less back-strike than comparative example 2. A panel of five (5) people (P1, P2, P3, P4, P5) was asked to rate the degree of back side strike-through from 1 to 5, with 5 having the highest strike-through and 1 having the lowest strike-through. Panelist P1 rated the back print as 2; p2, P4, and P5 rated the back print through as 1; and panelist P3 rated the back print as 3. Fig. 10B depicts a fibrous sheet that exhibits improved back side print-through.

Fig. 11 depicts an embodiment of the second aspect of the present invention. Here, the fiber sheet is marked with reference numeral 110. Before the fibrous sheet (110) becomes sufficiently consolidated in the wet stage of papermaking, "soft-edged" through-holes (111) are formed in the fibrous sheet (110). Then, the security device (112) is introduced over the through-hole (111) when the fibre sheet is sufficiently consolidated such that a significant amount of fibres (113) are not displaced from the sub-areas (114) when the security device is pressed into the substrate (115) of the fibre sheet (110). Instead, the fibers (113) are further consolidated or compacted in the sub-region (114) delimiting the through-hole (111) and in the hinge region (116) below the safety device (112). This results in strong fiber interactions at the interface (117) and particularly at the interface edge (117 a). Furthermore, since the security device (112) is introduced during the wet stage, it may be pressed into the substrate (115) to provide a low thickness differential. Furthermore, since no displacement of the fibers occurs in this state, further consolidation in the sub-regions (114) greatly reduces, if not eliminates, the possibility of the through-holes (111) becoming plugged or blocked.

As described above, various methods and techniques may be used to introduce the through-holes (111) and security devices (112) into the fibrous sheet (110). In particular, the screen of the paper machine may be a continuously moving forming wire of a fourdrinier paper machine or a cylinder wire of a cylinder machine. In the preferred embodiment shown in fig. 12, 12A, 12B, the through-holes 111 are formed using a patterned forming wire 118 on a fourdrinier paper machine 119 provided with at least one water impermeable element 120 that prevents sheet formation in this area. A patterned forming wire (118) is depicted before (fig. 12A) and after (fig. 12B) the papermaking stock is discharged from the headbox onto the forming wire. As shown in fig. 12B, sheet formation is prevented in the region of the water impermeable element (120). After the through-holes (111) are formed and the fibre sheet (110) becomes sufficiently consolidated, the security device (112) is presented in the form of a continuous web and is continuously applied to the formed fibre sheet (110) immediately after the wet line (122) and before the couch roll (123) and between vacuum boxes (124a, 124b) which facilitate the arrangement of the security device into the fibre sheet (110).

While various embodiments of the present invention have been described above, it should be understood that they have been presented by way of example only, and not limitation. Thus, the breadth and scope of the present invention should not be limited by any of the exemplary embodiments.

Claims

1. A fibrous sheet (110) having opposing surfaces, a recess in one opposing surface, and one or more through-holes (111) extending from the recess through the opposing surface of the fibrous sheet, wherein the one or more through-holes are "soft-edged" through-holes, the sheet comprising:

a fiber sub-region (114) disposed below the recess and surrounding the one or more through-holes, and an immediately adjacent body region disposed adjacent to the recess and the sub-region;

a surface-applied security device (112) disposed in the recess over the one or more through-holes; and

an interface (117) between a safety device applied to the surface and the sub-region of fibres and the body region,

wherein the security device applied through the surface further consolidates the fibers in the sub-region such that the amount of fibers in the sub-region is 80% to 100% of the amount of fibers in at least the immediately adjacent body region.

2. The fiber sheet of claim 1, wherein the one or more "soft-sided" through-holes have a unique irregularity in an edge region, a maximum diameter or width in the range of 4 to 15 microns, and a shape or profile selected from the group of circular, elliptical, star-shaped, parallelogram-shaped, and trapezoidal shapes, or combinations thereof.

3. The fibrous sheet material of claim 2, wherein the shape or contoured profile of the one or more "soft-edged" through-holes matches or is coordinated with a shape or contoured profile of the security device, an image displayed or projected by the security device, or both.

4. The fibrous sheet material of claim 1, wherein the security device is formed from a structural film and has a thickness of at least 10 microns.

5. The fibrous sheet material of claim 1, wherein the security device has a thickness in the range of 10 to 75 microns,

or

Wherein the surface applied security device has a thickness differential in the range of-10 microns to 25 microns.

6. The fibrous sheet of claim 1, wherein the fiber density in the sub-regions of fibers is greater than the fiber density in at least the immediately adjacent bulk region.

7. The fibrous sheet of claim 1, wherein the security device comprises an array of cylindrical or non-cylindrical focusing elements and an array of image icons that optically interact with the focusing elements to produce at least one composite image.

8. The fibrous sheet material of claim 1, wherein the security device is in the form of a strip or patch.

9. The fibrous sheet of claim 1, wherein the security device is in registration with at least one other feature on or within the fibrous sheet.

10. The fibrous sheet of claim 9, wherein the at least one other feature on or within the fibrous sheet is selected from the group of a watermark, a printed image, a relief structure, a fiber or group of fibers, another security device, or a combination thereof.

11. The fibrous sheet of claim 1, wherein the fibrous sheet is a banknote, and

wherein the surface-applied security device comprises an array of cylindrical and/or non-cylindrical focusing elements, and an array of image icons that optically interact with the focusing elements to produce at least one composite image,

wherein the thickness of the sub-regions of fibres is less than the thickness of the main region of fibres, such that recesses with side walls are formed in the surface of the sheet,

wherein the surface applied security device is disposed within the recess,

wherein the surface applied security device has a thickness in the range of 10 to 40 microns and a thickness difference in the range of 0 to 15 microns, and

wherein the security device is a strip or patch exposed on at least one side of the banknote.

12. A security or value document comprising the fibrous sheet of claim 1.

13. A security or value document according to claim 12, wherein the security device is introduced such that the security device is in registration with at least one other feature on or within the document, wherein the at least one other feature on or within the document is selected from the group consisting of a watermark, a printed image, a relief structure, a fibre or another security device,

or

Wherein the security or value document is a passport,

or

Wherein the security or value document is a banknote.

14. A method for surface applying a surface-applied security device (112) to a fibrous sheet (110), comprising:

forming one or more "soft-edged" through-holes (111) in the fibrous sheet during papermaking;

introducing the security device into or onto the formed fibrous web above the one or more through-holes at an introduction point during papermaking; and

the safety device applied by the surface further consolidates the fibers in a sub-area (114) of the fibrous sheet such that the amount of fibers in the sub-area is 80% to 100% of the amount of fibers in at least the immediate bulk area of the fibrous web.

15. The method of claim 14, wherein the one or more "softside" through-holes are formed in the fibrous sheet before the fibrous sheet becomes sufficiently consolidated during papermaking such that the level of moisture is greater than 98% by weight based on the total weight of the fibrous web.

16. The method of claim 14, wherein upon introduction of the surface-applied security device, the fibrous web is sufficiently consolidated at least at the point of introduction such that the level of moisture is less than 98% by weight, based on the total weight of the fibrous web.

17. The method of claim 14, wherein the fiber web is sufficiently consolidated such that the moisture is less than 95% by weight based on the total weight of the fiber web.

18. The method according to claim 14, wherein the security device is first presented as a continuous web, which is then cut and placed into or onto the fibrous web,

or

Wherein the security device introduced into or onto the fibrous web is in the form of a strip or patch,

or

Wherein the security device is introduced such that the security device is in registration with at least one other feature on or within the fibrous sheet or document comprising the fibrous sheet, wherein the at least one other feature on or within the fibrous sheet or document is selected from the group consisting of a watermark, a printed image, a relief structure, a fiber, or another security device.

19. The method of claim 14, further comprising

Providing the security device in the form of a continuous web;

cutting or stamping the continuous web in a continuous manner to form patches or strips;

wherein the application of the security device comprises continuously introducing the patch or strip to the fibrous web over the one or more "soft-edged" through-holes such that a fibrous body region, a fibrous sub-region and a negative relief having sidewalls are formed in the fibrous web.

20. The method of claim 14, wherein the introduction point of the safety device is continuously adjusted by adjusting tension on a continuous web.

21. A document comprising a fibrous sheet prepared according to the method of claim 14, wherein the fibrous sheet comprises a surface applied security device.