Method for the production of paper protected against forgery, such paper and printing products

Abstract

The invention discloses a process for the production of paper protected against forgery, during which a pigment component is prepared from a granular pigment base material containing rare earth metals, the prepared pigment component is premixed with a starch-based carrier material, and then at least three pigment components are mixed with a carrier in a predetermined ratio to create a color-coded additive. The color-coded additive is mixed with paper pulp, paper is made from the pulp, the finished paper product is illuminated with a radiation source in the wavelength range of 400-1400 nm, the radiation emitted by the additive is detected instrumentally, the physical parameters of the detected radiation are recorded electronically, and the recorded physical parameters are assigned to the color code. The invention also includes paper with anti-forgery protection, as well as a printing product.

Description

[0001] Method for the production of paper protected against forgery, such paper and printing products

[0002] The invention relates to a method for the production of paper protected against forgery provided with an additive containing rare earth metals, and a paper produced by the method according to the invention.

[0003] The protection of the originality of paper carriers is achieved by placing flake fibers or watermarks or other elements visible to the naked eye, or combinations of these on the paper carrier. Paper carriers sometimes contain UV components that become visible when exposed to UV light. However, not all known security features provide adequate protection against counterfeiting, as counterfeiters are aware of these security features and can therefore incorporate or deceptively imitate them in counterfeiting items.

[0004] Patent EP 19970811029 describes a solution in which the paper and printing industry product protected against forgery contains at least one kind of inorganic particles containing at least two chemical elements in a fixed ratio. The fixed ratio of chemical elements is a code or part of a code as a characteristic of the designation. The codes are read back using SEMZEDX X-ray electron-analysis, which is a serious laboratory test - using an electron microscope.

[0005] Publication document W02010037456 Al discloses an infrared absorber built into the product as a safety element (wavelength 800-2500 nm) - added to printing ink.

[0006] Publication document W02020239740 Al describes inks suitable for printing machine-readable security features on a substrate.

[0007] The Czech patent No. CZ17343U1 shows a real progress, the essence of which is that during the production of the paper carrier a safety material based on anti-Stokes compounds is mixed into its raw material, and the emission (afterglow) is checked with naked eye, which afterglow can be white, red, green and orange. Thus, paper with a security feature has the advantage that its authenticity can be verified and identified even if the paper is destroyed, for example burnt. As described in the document CZ17343U1, paper with a safety element is made by adding a safety material radiating in the anti-Stokes range to the raw material during paper production, which is dispersed in the paper pulp. After illuminating the paper with 960- 980 nm wavelength infrared laser diode as a light source, one of the colors mentioned above appears at any point on the paper and can be detected with naked eye. This solution enables a limited number of code generation, and due to the use of a single rare earth pigment, the homogeneity of the additive in the paper and its physical binding to the pulp are not relevant.

[0008] Our goal with the invention is to eliminate the disadvantages of the described solutions and to apply a multi-component paper identification system with an advanced physical, optical-nanotechnological and IT analysis method that enables the application of a large number of codes related to the given paper production batch, and the applied code can be read back instrumentally.

[0009] To achieve the goal set was made possible by perceiving that in order to increase the number of color codes, at least three pigments containing rare earth metals excited in the visible and invisible wavelength range, preferably in the visible wavelength range of 400- 750 nm and in the IR range of 750-1400 nm, producing anti-Stokes scattering, absorbing in the near-infrared and emitting light in the visible range, such as a mixture of gadolinium oxy sulfide-doped yttrium oxysulfide, yttrium oxide-doped lanthanum oxide, yttrium oxysulfide- doped thulium oxide in a predetermined ratio according to RGB or CMYK color model or in an arbitrarily determined ratio, for example, a mixture of 125, 125, 125, i.e. in 1 : 1 : 1 ratio further mixed with a starch-based carrier material, e.g. C18H39CIN4O6 material.

[0010] Our object is achieved by developing a method for the production of paper protected against forgery, containing the step of

[0011] - preparing a pigment component with a particle size of 2-10 microns from a granular pigment base containing rare earth metals,

[0012] - pre-mixing the pigment component thus prepared with a starch-based carrier material in a ratio of 1 : 1,

[0013] - mixing at least three pigment components pre-mixed with the carrier in a pre-fixed ratio, thereby creating a color-coded additive,

[0014] - adjusting the density of the color-coded additive to a density of 0.8-1.5 g / ml fit for paper production technology, by adding an additional starch-based carrier material, if necessary, and then homogenizing the additive, and

[0015] - mixing a color-coded additive in a proportion of 0.05 v% to 1.5 v% to paper pulp,

[0016] - making paper product of the paper pulp mixed with the additive,

[0017] - illuminating the finished paper product with a source of electromagnetic radiation in the wavelength range of 400-1400 nm,

[0018] - detecting instrumentally the radiation emitted by the additive,

[0019] - recording electronically the physical parameters of detected radiation, and - assigning recorded physical parameters to the color code of the additive.

[0020] As a granular pigment base containing rare earth metals granular Gd2Y2O4S2, yttrium oxysulfide doped with gadolinium oxysulfide, lanthanum oxide doped with yttrium oxide, and thulium oxide doped with yttrium oxysulfide are used.

[0021] As a starch-based carrier material C18H39CIN4O6 is used.

[0022] The pre-fixed ratio used during the mixing of the three pigment components premixed with the carrier is selected from RGB color model.

[0023] Setting the density of the color-coded additive to 1.2 g / ml.

[0024] Mixing the color-coded additive with the paper pulp by a ratio of 0.4 v% of the pulp.

[0025] The wavelength and intensity of the radiation are recorded as physical parameters of the detected radiation.

[0026] Our object can be achieved also by a paper protected against forgery, having an additive containing rare earth metal, and a color-coded additive is evenly distributed in the paper in the amount of 0.05% to 1.5% by weight of the paper, which additive contains at least three different pigments with a grain size of 2-10 microns, each containing rare earth metals and a starch-based carrier material in a quantity at least equal to the amount of the pigment.

[0027] The three different pigments containing rare earth metals are yttrium oxysulfide doped with gadolinium oxysulfide, lanthanum oxide doped with yttrium oxide, and thulium oxide doped with yttrium oxysulfide.

[0028] Our object is achieved also by a printed product containing paper produced by a method according to any one of claims 1-7. or a paper according to any one of the claims 8- 9.

[0029] The invention will be described in detail below.

[0030] At least three pigments containing rare earth metals, for example granular Gd2Y2O4S2 yttrium oxysulfide doped with gadolinium oxysulfide, lanthanum oxide doped with yttrium oxide, and thulium oxide doped with yttrium oxysulfide are prepared by sieving and / or grinding according to a 2-10 micron particle size range most suitable for paper production. In one preferred embodiment of the invention, 20 / 15 / 10 / 5 / 2 micron sized sieve inserts were used. The duration of sieving and the setting of the frequency of the vibration of the sieve are determined by the quality and agglomeration of the pigments.

[0031] The pigment component thus prepared having a grain size of 2-10 microns is premixed with a starch-based carrier having a formula C18H39CIN4O6 in a ratio of 1 : 1. The pre- mixing of the prepared pigments with the starch-based carrier was conducted with a rotary mixer.

[0032] Then mixing the at least three premixed pigment components together according to an RGB color model code, e.g. in a ratio of 255, 100, 155, thus creating a so called color- coded additive. Mixing is done with PLC-controlled precision dosing equipment with at least milliliter accuracy.

[0033] The color-coded additive is homogenized, by adding an additional quantity of starch- based carrier material, if necessary, to adjust its density suitable to the paper production technology, e.g. to a density of 0.8-1.5 g / ml, which is conducted with a cross-beater mill.

[0034] Then the additive is exposed to the effect of an exciting radiation source e.g. by using FLAME-S-XR1-E type instrument known and commercially available and produced by the OceanOptics Flame Spectrometer, where the wavelength of the exciting radiation is chosen between 400-1400 nm. The instrument contains a logic circuit, the software installed on it and a memory device, a radiation emitting unit, a data processing unit for evaluation, as well as a LED display for visual display and, where appropriate, a unit for emitting a sound signal. The device can advantageously contain a signal amplifier and various signal filtering units. The wavelength and intensity of the emitted radiation detected by the optical sensor unit of the instrument depends on the ratio of the three pigments mixed in the additive. This relationship, as the code of the additive containing the mixture in the given ratio, is stored for repeatability of subsequent production of the additive material.

[0035] Then, by adding the described additive, a paper pulp is made and paper is produced from it. Since the additive contains at least three compounds containing rare earth metals, the volume homogeneity index of the carrier material and the three different pigments must reach at least HImin: 98.53 % / ml3according to our tests, in order to the same color code to be measured everywhere on the surface of the finished product. The required level of homogeneity can be achieved by adding the carrier material, and therefore it is guaranteed that the pigments containing rare earth metals contained in the safety additive added to the paper pulp during paper production are present in the same distribution as the ratio of color mixing at any point of the paper structure. Applying HImin for the paper mass, the Hlf value for surface homogeneity of the paper is at least 98% / mm2. By arbitrarily changing the mixing ratio of three or more components, similar to the RGB or CMYK color model, millions of invisible but readable variations can be created in such a way that, due to the increased homogeneity, the sufficient amount of safety additive added to the paper pulp during paper production is 0.1 volume% - 0.7 v%, thus the rare earth metal content can be reduced to between 0.04 v% - 0.10 v%, thereby the possibility of deciphering is almost impossible as well, because it can only be realized with extremely expensive laboratory analytical methods.

[0036] The paper protected against forgery according to the invention, therefore, has a color-coded additive uniformly distributed in an amount of 0.05 v% to 1.5 v%, which contains at least three different rare-earth-metal containing pigments with a grain size of 2- 10 microns in a pre-fixed ratio, as well as a starch-based carrier material in an amount at least equal to the amount of the pigment. The three rare earth metal pigments are preferably yttrium oxysulfide doped with gadolinium oxysulfide, lanthanum oxide doped with yttrium oxide, and thulium oxide doped with yttrium oxysulfide. A printing product protected against forgery can be made from the paper according to the invention produced by the process according to the invention.

[0037] Paper manufactured by the use of described additive, or a printing product containing such paper is exposed to the exciting radiation source e.g. by using the instrument mentioned above. The wavelength and intensity of the radiation emitted by the additive in the paper and detected by the optical sensor of the instrument's detector definitely depends on the ratio of the three pigments mixed in the additive. One can store this relationship as the code carried by the paper product for the given production batch, and in case of suspected forgery, it can be checked by using e.g. the instrument mentioned above.

[0038] Paper production can be conducted by using any of the known technologies, using the homogenized additive described in the description as an additive.

[0039] In summary, we have achieved our goal with the invention described. Our solution provides thousands, even millions of unique color combinations as compared to the four combinations disclosed by the document CZ 173430. The method according to the invention is much more accurate compared to the free eye comparison, and during production, the recording and documentation of the wavelength and intensity of the built-in reference signal and its subsequent recovery are also much more precise.

Claims

AMENDED CLAIMS received by the International Bureau on 08 December 2023 (08.12.2023)1. Method for the production of paper protected against forgery, containing the steps of- preparing a pigment component with a particle size of 2-10 microns from a granular pigment base containing rare earth metals,- pre-mixing the pigment component thus prepared with a starch-based carrier material in a ratio of 1 : 1,- mixing at least three different pigment components pre-mixed with the carrier in a pre-fixed ratio, thereby creating a color-coded additive,- adjusting the density of the color-coded additive to a density of 0.8-1.5 g / ml fit for paper production technology, and- mixing a color-coded additive in a proportion of 0.05 v% to 1.5 v% to paper pulp,- making paper product of the paper pulp mixed with the additive,- illuminating the finished paper product with a source of electromagnetic radiation in the wavelength range of 400-1400 nm,- detecting instrumentally the radiation emitted by the additive,- recording electronically the physical parameters of detected radiation, and- assigning recorded physical parameters to the color code of the additive, characterized by adjusting the density of the color-coded additive to a density of 0.8-1.5 g / ml by adding additional starch-based carrier material if necessary, and then homogenizing the additive to reach a volume homogeneity index of the carrier material and the three different pigments of at least HImin: 98.53 % / ml3, and obtaining a paper product having a Hlf value for surface homogeneity of at least 98% / mm2.

2. The method according to claim 1 for the production of paper protected against forgery, characterized by using granular Gd2Y2O4S2, yttrium oxysulfide doped with gadolinium oxysulfide, lanthanum oxide doped with yttrium oxide, and thulium oxide doped with yttrium oxysulfide as granular pigment base containing rare earth metals.

3. The method according to claim 2 for the production of paper protected against forgery, characterized by using C18H39CIN4O6 as a starch-based carrier material.

4. The method according to claim 3 for the production of paper protected against forgery, characterized by the pre-fixed ratio used during the mixing of the three pigment components premixed with the carrier is selected from RGB color model.

5. The method according to claim 4 for the production of paper protected against forgery, characterized by setting the density of the color-coded additive to 1.2 g / ml.

6. The method according to claim 5 for the production of paper protected against forgery, characterized by mixing the color-coded additive with the paper pulp by a ratio of 0.4 v% of the pulp.

7. The method according to claim 6 for the production of paper protected against forgery, characterized in that the wavelength and intensity of the radiation are recorded as physical parameters of the detected radiation.

8. Paper protected against forgery, having an additive containing rare earth metal, a color-coded additive is distributed in the paper in the amount of 0.05% to 1.5% by weight of the paper, which additive contains at least three different pigments with a grain size of 2-10 microns, each containing rare earth metals and a starch-based carrier material, characterized in that the quantity of starch-based carrier material is at least equal to the amount of the pigment, and the color-coded additive is evenly distributed in the paper having a Hlf value for surface homogeneity of at least 98% / mm2.

9. Paper protected against forgery according to claim 8, characterized in that the three different pigments containing rare earth metals are yttrium oxysulfide doped with gadolinium oxysulfide, lanthanum oxide doped with yttrium oxide, and thulium oxide doped with yttrium oxysulfide.

10. Printed product containing paper produced by a method according to any one of claims 1-7. or a paper according to any one of the claims 8-9.