The present invention relates to the validation of documents and relates particularly but not exclusively, to validating cheques .

Cheques, which are commonly used to provide payment, have the problem that they can be easily forged. A method currently used in an attempt to prevent such forgery is to print a sequence of digits on each cheque using magnetic ink. Such digits are illustrated on the cheque shown in figure 1. When a cheque 10 is validated, the number sequence 12 on the cheque is read by a magnetic ink character recognition device. This number sequence is then compared to a list of number sequences held by the bank for which the cheque was manufactured or to a list of number sequences which have already been printed on cheques by the manufacturer. If a forger has printed the number sequence on a forged cheque using ink which is not magnetic, the cheque is immediately identified to have been forged. If the number sequence on a forged cheque is infact printed in magnetic ink but the number sequence does not match a valid number sequence held by the bank or cheque manufacturer, the cheque is also deemed to have been forged.

A problem with this method is that the number sequence used in cheque validation is clearly printed on the surface of the cheque allowing a skilled forger to easily forge a valid cheque. A particular problem associated with cheque forgery is that of cloning. In this technique a forger obtains bank account details of a person or company known to have money in their account. An account is then opened by the forger using this name. In order to extract money from the person or companies account it is only necessary to change the account numbers to produce a cheque matching those of the account containing the funds. Once the account has been opened in the person or company name, in order to clone a cheque similar to that in figure 1, all that is required is for a forger to obtain a quantity of magnetic ink, to copy the number sequence printed on a valid cheque and print it on the forged cheque using magnetic ink.

Preferred embodiments of the present invention seek to overcome the above disadvantages of the prior art.

According to an aspect of the present invention, there is provided a printed material comprising: - a substrate;

at least one first printed portion printed on said substrate using a first ink, said first printed portion containing at least one first shape;

at least one second printed portion printed on said substrate using a second ink at least partially obscuring said first printed portion; and

at least one third printed portion printed on said substrate and containing at least one second shape corresponding to at least one said first shape;

wherein at least one of said first and second ink absorbs visible radiation in a first range of frequencies and absorbs non-visible radiation in a second range of frequencies and the other of said first and second ink absorbs visible radiation in a range of frequencies substantially corresponding to said first range and substantially does not absorb radiation in said second range. By hiding a first printed portion, which may be printed in the form of a sequence of characters and/or numbers, provides the advantage that information conveyed by such characters and/or numbers is non-visible to a person viewing the substrate under normal conditions using visible radiation. If the substrate is a cheque or a document, the hidden information may be used in validation purposes, wherein if a forger is unaware that such hidden information is present, a forged cheque on which such hidden information is printed has a higher chance of being recognised as having been so forged.

A further advantage associated with the hiding of information in accordance with an aspect of the present invention, is that a cheque or document becomes more difficult to clone. This is because in order to forge a cheque a person is required to remove a portion of ink from both the first and second printed portions and reapply it, as opposed to the removal and reapplication of a single type of ink as in the case of the prior art.

The use of micro numismatics, as disclosed in UK Patent Number GB2411862 which is incorporated herein by reference, further increases the difficulty of forging a cheque. When information is hidden on a cheque in accordance with the present invention, the cheque incorporating micro numismatics, when a forger removes the ink of the first and second printed portions in an attempt to alter the information printed on the cheque, they also remove the micro numismatics on the surface of the cheque. Therefore the forger is required to reapply the micro numismatics and the alter the cheque. The removal and reapplication of three types of ink is substantially more difficult the removal and reapplication of a single type of ink as in the prior art providing the advantage that a cheque is more difficult to forge . In a preferred embodiment at least one said shape is a digit.

In another preferred embodiment said digit comprises at least part of a bank account number or sort code. In another preferred embodiment at least one said shape is a character .

In a further preferred embodiment said character comprises at least part of the name or address of a person or a bank.

In another preferred embodiment at least one said shape is a logo, currency symbol or a line.

In a further preferred embodiment said substrate is a cheque.

In a preferred embodiment said substrate is a document.

According to another aspect of the present invention, there is provided a method of printing on a substrate, comprising the steps :- printing at least one first printed portion printed on a substrate using a first ink, said first printed portion containing at least one first shape;

printing at least one second printed portion printed on said substrate using a second ink at least partially

printing at least one third printed portion printed on said substrate and the third printed portion containing at least one second shape corresponding to at least one said first shape;

wherein at least one of said first and second ink absorbs visible radiation in a first range of frequencies and absorbs non-visible radiation in a second range of frequencies and the other of said first and second ink absorbs visible radiation in a range of frequencies substantially corresponding to said first range and substantially does not absorb radiation in said second range.

In a preferred embodiment said second printed portion is printed on said substrate before said first printed portion.

In a preferred method at least one shape is a digit.

In another preferred method said digit comprises at least part of a bank account number or sort code.

In another preferred method at least one said shape is a character.

In a further preferred method said character comprises at least part of the name or address of a person or a bank. In another preferred method at least one said shape is a logo, currency symbol or a line.

In a further preferred method said substrate is a cheque. In a preferred method said substrate is a document. According to a further aspect of the present invention there is provided a method of validating the authenticity of a printed material, comprising the steps of:- receiving a printed material as previously discussed; illuminating at least part of the first and second printed portions using radiation of a frequency in said second range;

displaying an image representing radiation in said second range reflected from said substrate; and

comparing said image with said second shape of said third printed portion.

Preferred embodiments of the invention will now be described, by way of example only and not in any limitative sense, with reference to the accompanying drawings in which :-

Figure 1 illustrates a cheque commonly used by banks;

Figure 2 illustrates a cheque on which information has been hidden in accordance with the present invention;

Figure 3 illustrates a range of shapes in which the second printed portion used to obscure the first printed portion, may be printed; and

Figure 4 illustrates an imaging device for revealing hidden information printed on a substrate in accordance with the present invention. Referring to Figure 2, a substrate 100, for example a cheque,

a first ink in the shape of a sequence of digits. The first ink is a standard ink, coloured for example black, and absorbs radiation in a range of visible frequencies and in a non-visible range of frequencies e.g. infra red. Figure 2 also illustrates a second printed portion 104 which has been printed on the cheque 100 over the sequence of digits of the first printed portion 102 using a second ink, such that the sequence of digits is obscured from view. The second ink is also coloured for example black, and absorbs visible radiation but unlike the first ink, transmits radiation in at least a part of the non-visible range of frequencies in which the first ink absorbs. The second ink will be familiar to persons skilled in the art as having been used on bank notes. The second printed portion may be printed in any shape provided that it obscures at least part of and preferably all of the first printed portion. A possible selection of shapes which may be used is illustrated in figure 3. The second printed portion would also be part of the branding or some other printed feature of a document. Figure 2 further illustrates a third printed portion 106 printed on the cheque 100 having a shape corresponding to the sequence of digits of the first printed portion 102. The third printed portion is not obscured by ink of the second printed portion 104 and is printed in a third ink. The third ink can be any form of ink, including being the same as the first and second inks or could be an ink that can only be viewed under certain light such as UV light.

To view the sequence of digits of the first printed portion 102 an imaging device 108, illustrated in figure 4 is utilised. The imaging device 108 comprises a variable frequency radiation source 110 for illuminating a cheque on which information has been hidden in accordance with an aspect of the present invention. In order to reveal the hidden sequence of digits of the first printed portion, radiation with a frequency in the non-visible frequency range in which the first ink absorbs but the second ink does not is to be directed onto the second printed portion 104 covering the sequence of digits of the first printed portion 102. The radiation reflected from the cheque 100 is then captured by a camera 112 and imaged by processor 114, wherein the image is displayed on a screen 116. As the ink in which the sequence of digits of the first printed portion 102 are printed absorbs such radiation, the image will display such digits. The cheque 100 is then validated by comparing the sequence of digits of the third printed portion 106 with the sequence of digits of the first printed portion 102.

It will be appreciated by persons skilled in the art that the above embodiments have been described by way of example only and not in any limitative sense, and that various alterations and modifications are possible without departure from the scope of the invention as defined by the appended claims. For example a sequence of characters or a sequence of characters and digits may also be used to validate a cheque. A shape as opposed to a sequence of characters and/or digits may also be used to validate a cheque. The validation technique outlined in this application may be applied to any document e.g. a purchase order or official letter, and is not exclusively related to the validation of cheques. The first printed portion may also be printed on top of the second printed portion and vice versa. The second printed portion may be printed in the shape of a regular polygon or even a straight line of no particular thickness. The camera of the imaging device may also provide magnification capability to provide a magnified image on the screen of a cheque. Also the inks in which the first and second printed portions are printed need not necessarily be the same colour. The second printed portion 104 may comprise a feature that is normally printed on a cheque so as not to arouse the suspicion of a forger. Such a feature may be one or more of the letters in the account holder's name, the bank's name or any other text which is usually printed on a cheque. Also, such a feature may be one or more of the numbers in the account number, sort code or any other numbers which are usually printed on a cheque. Furthermore, such a feature may be one or more symbols, shapes or markings which are usually printed on a cheque such as the bank's logo, the currency symbol or the lines on which a payee is to write when writing on a cheque. This makes it more difficult for a person to clone a cheque because they are less likely to be aware that any information, such as the first printed portion 102, is hidden on the cheque. However, if they believe such hidden information is present they will be less likely to know where such information is hidden. By, for example, hiding a copy of the account number, a forger must not only replace the account number in magnetic ink, but also replace the copy of the account number where it has been hidden under the second ink that is invisible under IR light.