FI80638B - Document, method for preventing photocopying of the document and paper unsuitable for photocopying - Google Patents

Description

1 80038

Document, a method of preventing photocopying of a document and paper unsuitable for photocopying

Divided by application No. 831891 5

The present invention relates to a document, a method for preventing photocopying of a document, and a paper unsuitable for photocopying.

With the proliferation of photocopiers, it has been necessary to consider how to make documents or certain parts of them such that they cannot be photocopied. Today, anyone can very easily take a photocopy of a document containing confidential information, provided that it is not a paper unsuitable for photocopying. That is why, in order to prevent the taking of unauthorized photocopies, a number of proposals have been made to make documents inaccessible. The information contained in the document is then covered with a translucent film so that it can be read normally, but cannot be read from a photocopy. U.S. Patent Nos. 3,887,742 and 4,118,122 disclose such proposals, but for some reason it has not been possible in either case to develop a fully satisfactory solution for rendering such documents unsuitable for photocopying.

It is an object of the present invention to provide an improved method for rendering a document or a portion thereof incapable of being photocopied.

The document according to the invention is characterized in that the information-containing part on the front of the document is colored in such a way that a sufficiently small reflection spectral response is produced when said copier is substantially sensitive below 650 nanometers, so that said part of the document is not 2 30638 can be photocopied legibly, and that said portion of the document is capable of transmitting visible light from the reverse side to the front, providing sufficient contrast between the relatively opaque data and the information-free background so that the data can normally be read by the human eye from the front of the document. from the reverse side to the front side, wherein the reflection spectral response is substantially zero for light having a wavelength below about 625 nanometers.

The preferred reflection spectral response is approximately zero for light having a wavelength not exceeding about 625 nanometers, as well as approximately zero for light having a wavelength not exceeding about 650 nanometers, and preferably also about zero for light having a wavelength of up to about 700 nanometers.

The non-photocopying part of the document has an average transmittance of 3% in visible light. It is preferred that the transmittance range 20 begins at approximately zero (for light having a wavelength not exceeding about 450 nanometers) and end at about 5% (for light having a wavelength not exceeding about 700 nanometers). The text is usually black, a relatively opaque ink.

The document according to the invention is very difficult to photocopy because photocopiers require that the paper to be reproduced has a sufficient reflection spectral response at a wavelength of light to which they are able to react. Namely, most photocopiers 30 do not respond to light having a wavelength greater than 650 nanometers. As a result, the document according to the invention is indeed very difficult to photocopy.

Instead, such a document is very easy to read with visible light directed through it from behind. The visible light may be daylight or other ambient light, or it may also be light specifically intended for reading a document according to the invention. A low reflection spectral response can be obtained by attaching a suitable color film to a paper suitable for this purpose.

The structures of the invention will now be described, by way of example, with reference to the accompanying drawings, in which Figure 1 shows graphically readability of the existing text by means of light transmitted through the paper.

Figure 1 shows graphically a document which is colored paper. Its transmission coefficient is shown as a line T and the reflection spectral response as a line R. In Fig. 1, curve E shows the typical spectral response of the eye and curve P again the possible spectral response of a photoresist machine.

20 From curve P it can be seen that the spectral response of the photocell machine decreases to zero with a wavelength of about 650 nanometers and a cut-off of about 625 nanometers. The term cut-off is commonly used to describe a wavelength at which the spectral response is less than about 10%.

25 The paper transmittance T increases mainly linearly from zero (wavelength approx. 450 nanometers) to approx. 5% (wavelength approx. 700 nanometers). The average is then approx. 3% in the visible light range (curve E). Above the visible light range, the transmittance increases approximately linearly to about 10% when the wavelength of the light is about 1000 nanometers.

The reflection spectral response R is very small (almost zero) at a wavelength below about 700 nanometers, i.e. less than about 1% and remains the same even in the range of 700 to 1000 nano-35 meters.

4,80638

The paper may be, for example, UV ULTRA II from Kimberley Clark Corporation, which has a matt black ink on the front surface (manufactured by Cal / Ink Limited or Sinclair & Valentine Limited) to give the desired permeation layer.

The data is transferred to the front of the paper either by typewriter, printing, or otherwise in black or a corresponding dark color, making the paper relatively opaque. The information can, of course, be different, e.g. printed, written or drawn text, curves or images. They can also be transferred to paper on a photocopier from an original document that can be photocopied. In this case, the paper according to the invention is used as the copy paper, which again cannot be reproduced light-15. The information is displayed on paper as black, dry carbon spots.

If such a document is attempted to be photocopied, the copy is not readable because the data and their background merge together, i.e., the photocopy presents the background 20 in the same color as the data on the paper because the paper has approximately zero reflection spectral response at about 700 nanometers.

Instead, if the paper is illuminated from the back by positioning it so that the surrounding daylight or artificial light passes through it from front to front, the information can be easily read in the usual way from the front of the paper because black or almost black text provides sufficient contrast to the paper. is illuminated by the light that has passed through it.

Figure 2 shows the relative response (sensitivity) of the eye when reading a document. Curve 1 shows the response of the eye when the paper is viewed in the light transmitted through it, and curve 2 again depicts the response of the eye when the paper is viewed in reflected surface light. The light 35 transmitted through the paper is easily seen as a contrast to the text 5 80638 on the paper, specifically at the wavelengths to which the eye reacts most sensitively. When using reflected light, the eye sees the paper almost black, making the text and paper little different.

The invention can, of course, be applied to various securities, including lotteries, tickets for theaters and sports competitions, stamps and tax stamps, shares and bonds, credit cards, various checks and banknotes.

It will be appreciated by those skilled in the art that other modifications may be made to the invention. The scope of the invention is defined in the appended claims.

Claims (15)

1. Document containing information, in which at least part of the information is on a certain part p on its front, characterized in that said part p on the front has such a color that the photocopier is substantially sensitive to less than 650 nanometers. sufficient spectral reflection sensitivity (F), in that the said portion of the document cannot be photocopied in a readable manner, and that said portion of the document causes passing of visible light from the back to the front, thereby providing a sufficient contrast between the relatively opaque information and the background without i.e., the information can be read by a human eye normally from the front of the document, i.e. the visible light emits through the document from its back to the front, the spectral reflection sensitivity being essentially zero for light, whose wavelength is below about 625 nanometers. 2. A document according to claim 1, characterized in that the spectral reflection sensitivity is approximately zero for light, whose wavelength does not exceed approx. 700 nanometers. 3. Document according to claim 1, characterized in that the average transmission factor of the above-mentioned part is approx. 3% within the range of visible light. 4. Document according to any of claims 1-3, characterized in that the transmission factor of the aforementioned part varies from about zero to light, whose wavelength is approx. 450 nanometers to about 5% for light, whose wavelength is approx. 700 nanometers. 5. A document according to any of claims 1-4, characterized in that the information has a substantially black and relatively opaque color. 35 A method by which the document containing information becomes sideways that it cannot be photocopied, the method comprising preserving the information on a certain part on the front of the document, characterized in that said part on the front has such a color that the copier is substantially sensitive below 650 nanometers, a sufficiently low spectral reflection sensitivity is provided, such that said portion of the document cannot be photocopied in a readable manner, and that it avoids passing visible light from the back to the front, so that sufficient contrast is provided between the the relatively opaque information and the background without information, wherein the information can be read by a human eye normally from the front of the document, the visible light passing through the document from its back to the front, the spectral reflection sensitivity being essentially zero for light whose path length is about 625 nanomete r. Method according to claim 6, characterized in that the spectral reflection sensitivity is approximately zero for light, whose path length does not exceed approx. 700 nanometers. 20 8. A method according to claim 6 or 7, characterized in that the transmission factor for the above-mentioned part of the document is an average of approx. 3% within the range of visible light. Method according to any one of claims 6-8, characterized in that the transmission factor for the above-mentioned part of the document varies from about zero to light, whose path length is approx. 450 nanometers to approx. 5% for 1 light, whose path length is approx. 700 nanometers. Method according to any of claims 6-9, 30, characterized in that the color used for the information is substantially black and relatively opaque. 11. Paper which is not suitable for light copying, characterized in that its free side has such a color that the copying machine is substantially sensitive under 650 nanometers, a sufficiently low spectral n 80038 reflection sensitivity, so that the said part of the document cannot be photocopied on a readable way where the information is written or otherwise added to its front page, and that said portion of the document obscures transmitting visible light from the back to the front, thereby providing a sufficiently large contrast between the relatively opaque information and the background without information; so that the information can be read by a human eye normally from the front of the document, where the visible light passes through the document 10 from its front to back, the spectral reflection sensitivity being essentially zero for light, whose path length is about 625 nanometers. 12. Paper according to claim 11, characterized in that the spectral reflection sensitivity is approximately zero for light, the path length of which does not exceed approx. 700 nanometers. 13. Paper according to claim 11 or 12, characterized in that the average transmission factor of the above-mentioned part of the document is approx. 3% within the range of visible light. Paper according to any of claims 11-13, characterized in that the transmission factor for the above-mentioned part of the document varies from about zero to light, the path length of which is approx. 450 nanometers to approx. 5% 25 for light whose path length is approx. 700 nanometers. Paper according to any one of claims 11-14, characterized in that the color used for the information is essentially black and relatively opaque. 30