Abstract:
A method of preparing documents for the transmission of secure information comprises the steps of preparing a first laminar element ( 13; 37 ) with a peripheral region ( 15 ) separable from a central region ( 14 ), printing the secure information on the central region ( 14 ) of the first laminar element ( 13; 37 ), or on a central region ( 19 ) of a second laminar element ( 12; 36 ), positioning the two laminar elements ( 13; 37, 12; 36 ) in face-to-face relation, with the face of the element bearing the information facing the said other element, and securing the element together around the peripheral regions. Apparatus for preparing secure composite documents comprises a first storage container ( 25; 47 ) for the first laminar element ( 13; 37 ), a second container ( 24; 50 ) for the said second laminar element ( 12; 36 ), and means ( 27, 28, 48, 49 ) for bringing the first and second laminar elements together in face-to-face relationship after the secure information has been printed on one of them, with the face of the laminar element bearing the printed information facing the other laminar element; and means ( 51; 48, 49 ) for securing the two laminar elements together around their peripheral regions.

Description:
CROSS-REFERENCE TO RELATED APPLICATIONS 
   This application is a divisional of U.S. patent application Ser. No. 10/470,910 filed Jul. 31, 2003, which is a 371 of PCT/GB/02/00400 filed Jan. 30, 2002, which claims priority of United Kingdom Patent Applications 0102414.0 filed Jan. 31, 2001; 0102917.2 filed Feb. 6, 2001; and 0110332.4 filed Apr. 27, 2001. 

   FIELD OF THE INVENTION 
   The present invention relates generally to a composite document for bearing secure information and also to apparatus for producing such a composite document and a method for preparing such a composite document. 
   BACKGROUND OF THE INVENTION 
   There are many circumstances in which it is desirable or necessary to be able to transmit information in documentary form in a secure manner such that the information can be seen only by the intended recipient. The need for such security arises not only from a social and personal perspective, for example in the transmission of payment details on payslips and the like, but also for more serious reasons for the prevention of criminal activity in the transmission of personal information numbers (PIN numbers) associated with credit cards and other such information. 
   A primary consideration in the production of documents bearing such information is that the information must be applied to the document in such a way that no other person, not even the person operating the machinery by which the information is applied to the document, can gain access to it. 
   Prior art attempts to produce satisfactory such documents have included preliminarily closed envelopes bearing, on their inside faces, micro-encapsulated ink particles which, when struck by an impact instrument, rupture and release the ink. In order to apply the information to the document it is, however, necessary to have a so-called impact printer (dot-matrix, daisy wheel or the like) by which the individual letters or numerals of the information can be impressed onto the document in order to cause rupture of the micro-encapsulated ink particles. In order to prevent the information inside the envelope from being viewed from the outside, one face of the document is provided with obscuration printing in the form of swirls and curlicues in an irregular pattern such as to provide a background against which the printed information cannot be distinguished. 
   However, the majority of establishments currently utilise printing equipment other than impact printers, for example laser printers and bubble jet printers which cannot utilise microencapsulated ink materials since they need an impact to rupture them. One attempt at producing a document for secure information which can be printed utilising a laser, ink jet or bubble jet printer comprises a single sheet of material which, after printing, can be folded and secured by adhesive at the periphery to enclose the sensitive information within it in the manner of an envelope. However, this has the disadvantage that it requires a folding machine. Such machines are expensive and unreliable and require constant supervision to ensure that the folding operation is performed properly. 
   SUMMARY OF THE INVENTION 
   The present invention seeks to provide a document for bearing confidential information which overcomes the disadvantages of the prior art, providing a document which can printed with any form of printer, especially a laser, ink jet or bubble jet (non-impact) printer (although, of course, impact printers can be used if they are available) and which does not require folding to conceal the information once it has been applied to the document. 
   According to one aspect of the present invention, therefore, a composite document for bearing secure information comprises a first laminar element having a central region and a peripheral region separable therefrom, a second laminar element of substantially the same perimetral dimensions as the first, and means for securing the second laminar element to the first in a substantially inseparable manner at the said peripheral region of the said first laminar element. 
   Preferably the second laminar element also has a peripheral region separable from a central region thereof, and in a preferred embodiment the peripheral regions are defined from the central regions by a line of perforations between the peripheral region and the central region of the first and/or second laminar element. 
   Confidential information can then be applied to one or other of the laminar elements on that face which, when the two elements are placed face-to-face, is facing the other element in order to be concealed when the composite document is formed by securing the peripheral regions of the first and second laminar elements together. 
   Of course, information, such as address information, may be applied to a face of one or other of the two laminar elements which is on the outside when the two laminar elements are placed together. 
   The means for securing the peripheral region of the said first laminar element to the second laminar element preferably comprises an adhesive. Alternatively, of course, other securing means, including the use of fixing elements may be utilised if appropriate. 
   In embodiments in which the elements are held together by adhesive it is possible for one of a number of different types of adhesive arrangement to be used. For example, a pressure-sensitive adhesive may be applied to only one of the said laminar elements of the document, the two elements lying merely face-to-face until a suitable pressure is applied to cause bonding. The adhesive could in another embodiment be temperature-sensitive adhesive which is substantially non-adhesive at room temperature or may be an adhesive which is rendered tacky and/or cured by irradiation with ultrasound. Alternatively, the adhesive may be a two-part adhesive, one part of which is applied to each of the two laminar elements of the document respectively. 
   Thus, when each of the laminar elements is being handled prior to being placed in the face-to-face operative relationship with one another, the adhesive material does not cause bonding to other surfaces which might cause difficulty in handling the elements. Once the two elements are placed in their operational relationship, however, the adhesive is caused to bond, either by contact with the co-operating part of the two-part adhesive on the other element, or by the application of bonding pressure. This means that the sheet to be printed either has no adhesive (which is preferred) or the adhesive is one which only reacts to a co-operating component but does not exhibit any adhesive effect on its own when in contact with other surfaces. 
   At least one laminar element may be printed or otherwise marked with a pattern of obscuration markings on a face thereof other than that intended to bear the said information. These obscuration markings may be on the ‘inside’ face of the other laminar element such that the “outside” faces can be left blank or carry address information or other publicly available information. 
   According to another aspect of the present invention, there is provided apparatus for preparing secure composite documents as defined hereinabove, comprising a first storage compartment or tray for the said first laminar element of the composite document, a second storage compartment or tray for the said second laminar element of the composite document, and means for bringing together a said first laminar element and a said second laminar element in face-to-face relationship with one face of the one laminar element bearing printed information facing the other laminar element, and means for securing the said two laminar elements together around the peripheral regions thereof. 
   In apparatus of the invention the said means for securing the said two laminar elements together around the periphery thereof may include means for applying an adhesive to the peripheral region of at least one of the said two laminar elements. Such means may be located in advance of the printer or downstream of the printer in relation to the path of movement of the laminar elements in the formation of a composite document depending on the nature of the adhesive. For example, if the adhesive is a heat curing or temperature sensitive or it would be affected by the fuser of a laser printer and therefore cannot be applied to the element which is to bear the printed information before it is printed. The adhesive may, of course, be applied to the element after printing, or may be applied only to the other element, with heat being applied subsequently to join the two elements together. 
   The said means for securing the said two laminar elements together may also include or comprise roller means for pressing together the peripheral regions of the said two laminar elements as they pass there through. This may be associated with heating means if a temperature sensitive adhesive is used. 
   According to another aspect of the present invention, there is provided a method of preparing documents for the transmission of secure information, comprising the steps of: preparing a first laminar element with a peripheral region separable from a central region, providing the said central region of the first laminar element or a central region of a second laminar element with the said information, positioning the said two laminar elements in face-to-face relation with the face of the element bearing the information facing the other said element, and securing the elements around the said peripheral region thereof. 
   The method of the invention may be performed in such a way that the step of securing the elements together is performed by providing an adhesive on the peripheral region of one or both of the said elements and contacting the said peripheral regions together to cause the two elements to adhere to one another around the said peripheral region. In performing the method of the invention the step of applying adhesive to the peripheral region to one or both of the said laminar elements may be performed before the application of the said information and steps may be taken to prevent adhesion of the said peripheral region to any other surface which may come into contact with the element until it is brought into contact with the co-operating face of the other said laminar element. 
   The adhesion of the peripheral region of the said one laminar element may, for example, be prevented until it is brought into contact with the peripheral region of the said other laminar element by the provision of a releasable protective layer over the adhesive at least in the peripheral region of the said one laminar element. Such a layer may, of course, be applied over the entire surface of the laminar element even though it is strictly not necessary other than in the peripheral region, since it facilitates removal of such a release layer if it is in a substantially continuous sheet-like form rather than in a frame-shape form which would be required to cover only the peripheral region of the laminar element. 
   The adhesion of the peripheral region of the said one laminar element may alternatively be prevented by use of an adhesive material which does not exhibit adhesive properties until activated by irradiation with ultrasound. In this case the elements may be collected in face-to-face relationship in preparation for irradiation since this may take longer than it takes for the element to pass an irradiation station. By utilising a batch process this additional time can be accommodated. 

   
     BRIEF DESCRIPTION OF THE DRAWINGS 
     The embodiments of the present invention will now be more particularly described, by way of example, with reference to the accompanying drawings, in which: 
       FIG. 1  is a schematic perspective view of a composite document formed as a first embodiment of the present invention; 
       FIG. 2  is a schematic side view of apparatus for preparing a composite document in accordance with the present invention; 
       FIG. 3  is a schematic perspective view of an alternative embodiment of the invention; 
       FIG. 4  is a schematic perspective view of a further alternative embodiment of the invention using a temperature sensitive adhesive; 
       FIG. 5  is a schematic side view of apparatus for performing the method of the invention using laminar elements having a heat-sensitive adhesive; and 
       FIG. 6  is a schematic side view of apparatus for performing the method of the invention using adhesive cured ultrasonically. 
   

   DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS 
   Referring first to  FIG. 1  there is shown a composite document generally indicated  11 , comprising a first or upper laminar element generally indicated  12  and second or lower laminar element generally indicated  13 . The lower laminar element, which may be considered comparable to the said first laminar element as discussed hereinabove, comprises a generally rectangular sheet of material capable of receiving an image by any conventional printing technique in a central region  14  thereof, as illustrated schematically in  FIG. 1 , and having a peripheral region  15  around the outside of the central region  14  divided therefrom by a closed perforation line  16 . The peripheral region  15  runs parallel to each of the edges of the laminar element  13 , approximately equidistant therefrom. On the reverse face  17  of the laminar element  13  there is formed an obscuration image  18  by a printing of closely spaced curved intersecting and overlapping lines such that the information printed on the central region  14  of the upper face of the laminar element  13  cannot be discerned from the other side, even if the laminar element is held up to the light such that shadows of the printed image could be seen through the thickness of the material, as the obscuration printing completely conceals the letters or numbers of the printed information. 
   The upper or first laminar element  12  likewise has a central region  19  and a peripheral region  20  demarcated by a line  21  of perforations through the material of the element  12  and in a position corresponding approximately to that of the line  16  of perforations in the lower or first laminar element  13 . In this embodiment the upper element has a window  22  through which address information printed on the lower element  12  may be seen. In other embodiments (not shown) instead of a window, this area may be solid and provided with the address information so that there are no openings in the upper element  13 . This offers greater security for the information but means that both sheets have to be printed. In either embodiment the reverse face of the element  12  may also be printed with obscuration markings (not shown) so that the printed information on the inside cannot be read by shining a light through the document. 
   Around the peripheral region  15  of the second or lower element  13  and the under surface of the peripheral region  20  of the upper or first laminar element  12  is provided a layer of adhesive the nature of which is such that it has little or no adhesive effect on its own, but which bonds firmly to the corresponding material on the other element. 
   When two such laminar elements are brought into face-to-face relationship with the adhesive peripheral portions in register they can be secured firmly and permanently together against separation. The nature of the adhesive on the peripheral portions  15  and  20  is such that, once an adhesive bond is made, it cannot be separated without destroying the underlying substrate of the laminar element itself. In use, therefore, confidential information such as a personal identification number or salary details for a payslip, can be printed on the central region  14  of the second or lower laminar element  13  and after this, the information can be completely concealed by overlying the laminar element  13  with the first or upper laminar element  12  with the address information of the intended recipient visible through the window  22 . 
   In another embodiment, not shown, a one-part adhesive is used. This is applied to one of the laminar elements, namely the one which does not bear the printed information. The other element can then be printed without requiring any special arrangements to avoid adhesion problems. Once printed the sheet can be brought into contact with a co-operating sheet bearing adhesive in its perimetral region. Handling of the cooperating sheet is facilitated because it does not have to pass through the printer. 
     FIG. 2  illustrates the main components of a device for assembling laminar elements to form a composite document in accordance with the present invention. The casing of the apparatus is not shown. Within the casing are an upper tray  24  for receiving a stack of upper laminar elements  12 , and a lower tray  25  for receiving a stack of lower laminar elements  13 . 
   The upper tray  24  has exit rolls  26  directing laminar elements taken therefrom to a path comprising guiding rolls  27  and combining rolls  28  at which the laminar elements  12  and  13  are combined by passing through the nip between the rolls themselves. 
   The lower tray  25  has exit rolls  29  guiding laminar elements  13  drawn therefrom to a laser printer  30  which may be of substantially conventional type, receiving input information on a cable  31  from a computer (not shown) connected to the terminal  32 . Upon exit from the laser printer  30  laminar elements  13  are combined with laminar elements  12  by passing through the nip between the pressure rolls  28  as mentioned above. Appropriate commands for operating the rolls  26 ,  27 ,  28  and  29  are generated from an electronic central control unit  33  which also commands operation of the laser printer  30  although the connections from the ECU  33  to the motors (not shown) driving the rolls  26 ,  27 ,  28  and  29  are not shown in detail. 
   A machine operating in this way utilises laminar elements formed as in the embodiment of  FIG. 1 , with a two-part adhesive which has little or no adhesive effect when contacted, for example by corresponding laminar elements of the same type, or when passing through the rolls guiding its passage to or from the printer  30 , or indeed from the printer itself. An alternative embodiment is illustrated in  FIG. 3 , which shows a lower element  13 ′ having a peripheral region similar to that of the embodiment of  FIG. 1 , but in this case coated with an adhesive having a high “grip” which, in order to prevent unwanted attachment to surfaces other than that intended for formation of a composite document, is covered by release layer  34  the under surface  35  of which is coated with a silicone material allowing it to be placed over the adhesive  15 ′ without forming a bond thereto, and to be pulled off immediately prior to contact with the co-operating laminar element  12  in order to form a composite document in the manner described to hereinabove. 
   As a further alternative the present invention may be put into practice by first printing a batch of documents such as the laminar elements  13 , and then placing them in a tray and joining them together using a simple machine having two storage trays and a pair of combining rollers such as the rollers  28 . Embodiments in which the central region  22  of the upper sheets  12  is formed as a window are preferred for this arrangement in order to ensure that the secure information and the address information are always properly matched. Alternatively, of course, the address information may be printed on the reverse face of sheets  13  so that the upper elements  12  serve only as covering elements. Upon arrival at their intended destination the documents can be opened by tearing off the peripheral region to separate the upper and lower elements  12 ,  13 . 
     FIG. 4  shows two co-operating laminar elements  36 ,  37  having respective upper and lower regions separated by respective transverse perforation lines  38 ,  39  into first and second regions, respectively  36   a ,  36   b  and  37   a ,  37   b . The laminar element  36  has an address window  40  in the first region  36   a.    
   On one face of the laminar elements  36  there is a layer of heat-sensitive adhesive  41  extending entirely around the peripheral region of the element  36 . A strip of adhesive  42  also extends transversely across the element  36  from side to side alongside the perforation line  38  between the portions  36   a  and  36   b . A peripheral perforation line  43  runs parallel to the edges of the laminar element  36   b  just inside the peripheral adhesive layer  41 . 
   The other laminar element  37  also has a peripheral perforation line  43 ′ located in substantially the same position in relation to the edges of the portion  37   b  of the element  37  as the perforation line  43  occupies in relation to the edges of the portion  36   b  of the laminar element  36 . The first portion  37   a  of the laminar element  37  has an address panel  44  which is located in relation to the edges of the panel  37  in the same location as the address window  40  in relation to the edges of the panel  36  so that when the two laminar elements  36 ,  37  are superimposed over one another the address panel  44  is visible through the address window  40 . The second portion  37   b  of the laminar element  37  has a region  45  for receiving the secure information. No adhesive is applied to the element  37 , however, and, apart from the perforation lines  39 ,  43 ′ it has no distinguishing physical features from a plain sheet. It may, of course, be marked with indicia showing the regions  44  and  45  although this is not essential and such regions may be no more than nominal areas within the laminar element  37  for reception of printed information. This laminar element can therefore be passed through a laser printer to receive both the address information and the secure information without there being any risk of error or incorrect association of the address information with the secure information since this can be printed at the same time as the secure information. After printing, a laminar element  36  is then superimposed over the laminar element  37  and the two joined by activation of the heat sensitive adhesive strips  41  and  42 . The adhesive strip  42  ensures that the address panel  44  is entirely surrounded by adhesive so that the composite document formed by juxtaposition and union of the two elements  36 ,  37  is totally secure in the sense that the front panel  36  cannot be lifted by inserting a finger under the edge of the address window  40  to allow an observer to gain access to the secure information in the region  37   b . This avoids the necessity for provision of a transparent panel over the window  40  although such panel may be utilised if desired. Alternatively, of course, the address could be printed on the opposite face of element  37 , in which case element  36  would not need an address window. 
     FIG. 5  illustrates the configuration of apparatus suitable for printing and assembling secure documents in accordance with the invention. A laser printer  46  has a magazine  47  bearing a stack of elements  37  for printing with address and secure information in the respective regions  44 ,  45 . The output from the laser printer  46  is then fed on a path towards two pressure rollers  48 ,  49 . Simultaneously elements  36  from a stack in a magazine  50  are fed towards the rollers  48 , 49  so that the two overlie one another. Just in advance of the rollers  48 ,  49  is a heater  51  having upper and lower heating elements which radiate heat onto the two laminar elements as they pass so that the adhesive on the upper laminar element  36  is caused to become tacky or otherwise exhibit its adhesive properties so that, as the two elements pass through the rollers  48 ,  49  they are securely bonded to form a composite document  53 . The documents  53  are then stored in a tray  54  for subsequent dispatch to their addresses. 
     FIG. 6  illustrates apparatus for batch curing composite documents assembled from elements similar to those illustrated in  FIG. 4 , but in which the adhesive is not one sensitive to temperature, but rather exhibits its adhesive properties in response to irradiation with ultrasound. Here, the laser printer  46  and magazine  50  are similar to those illustrated in  FIG. 5 . However, after they have been assembled each pair of elements  36 ,  37  is then passed to a press to form a stack of composite documents  54  which, when sufficient documents have been assembled, receives an upper platen  56  bearing an ultrasonic transducer  57  energised by a suitable generator  58  shown schematically in  FIG. 6 . A further ultrasonic transducer  59  may be positioned at the lower face of the press  55 , driven by a separate generator  60 . The platen  56  applies a light pressure to the documents  54  in the stack to ensure that they are all pressed together when the ultrasonic radiation is generated to cure the adhesive. Since ultrasonically cured adhesive may take a few minutes to develop its adhesive properties this allows the printer  46  to continue printing a further batch of documents, represented schematically by the stack  61  for subsequent transfer into the press  55  once the curing operation is complete and the documents  54  removed.