New Approach for Securing and Dating Valuable Printed Documents

Abstract This work deals with using a novel approach for securing and dating printed documents, which will detect any forging crime present. In this respect, the coded dots matrices (machine identification code (MIC)) for the used printers are extracted via a binary system of base 2 (0, 1). The UV ink used in the printing process is prepared from novel fluorescence compounds together with polyvinyl alcohol. Different Xerox models of color laser printers are used for printing the document designs. The data obtained reveal that the investigated approach is succeeded in specifying the date of the printing process together with translating the embedded data of the printer to visible information, which can be tracked under a UV lamp. This innovative approach will assist workers in examining the questioned document by specifying the authorized date and position of printed documents from the MIC.


Introduction
In recent years, attention has been focused on developing and enhancing the quality and safety performance of valuable paper documents (checks, receipts, etc.). Many investigators studied the role of paper sheet compositions (type cellulosic fibers and sizing agent), metal complexes, fire retardant additives, coating by biopolymers, as well as surrounding environment on the quality and durability of paper. [1][2][3][4][5][6][7][8] While, for forging purposes, safety paper must be durable and include safety marker resistance to forgery and counterfeiting. [9][10][11][12] Fluorescence active compounds are important materials succeeded to gain the paper document safety property. In this subject, we synthesized 2-alkoxy-3-pyridinecarbonitrile derivatives as well as heterocyclic compounds gathering the whole functional moieties responsible for fluorescence properties. In the synthesis we used variety of pyridine derivatives possessing good yields through cyclocondensation reaction of propenones with aryl hydrazines. The synthesized compounds, which have promising fluorescence properties (quantum yield (Фs) reached 0.86 with respect to quinine sulfate), [21] are candidates in this present work to formulate the UV ink together with polyvinyl alcohol (PVA), as a novel application to translate the embedded data and extract the coded dots matrices (MIC) from the used printer to visible, which can be tracked under the UV lamp. This will serve to detect any forgery present in valuable documents.

UV-Vis Absorption and Fluorescence Spectra
The UV-vis spectra of the synthesized pyrazolines 7-10 were estimated in chloroform with constant concentration (4 mg L −1 ). The maximum absorption wavelength (λ max ) and molar extinction coefficient (ε max ) are recorded in Table 1. It is clear that all investigated pyrazolines have two prominent peaks around 238 and 358 nm, which are related to the π-π* and n-π* transitions, respectively. The effect of introducing different electrondonating (EDG) and withdrawing groups (EWG) in R, R′, and R″ have a remarkable effect on the differences in both the position and intensity of absorption peaks, whereas, the presence of the 2-naphthyl group in compound 9 provided an additional adsorption peak together with a higher absorption peak relative to the other synthesized analogues.
With regard to the fluorescence spectra of synthesized pyrazolines, this test is also undertaken in chloroform with constant concentration (1 × 10 −5 mol L −1 ) ( Table 1). Table 1 shows that the synthesized pyrazolines are excited at 360-370 nm (corresponding to the high wavelength absorption band), affording fluorescence emission in the blue to green regions (emission peak wavelengths 438-471 nm). It has also been noticed that the quantum yield (Ф sample ) value is greatly affected by the substitution-type synthesized pyrazolines. The fluorescence quantum yields were measured relative quinine sulfate using the following equation: It can be seen that the presence of EWG and bulky groups in R′, such as those present in compounds 7 and 10, a higher quantum yield with blue-shifting of emission spectra than the other synthesized compounds occurs. On applying these fluorescence compounds to treat the Bible paper sheets, Table 2 shows that the treated paper sheets are excited at the range of 360-370 nm that corresponding to the absorption band in the solutions. It is noticed that the presence of the 4-chlorophenyl group at pyrazoline moiety for compounds 7 and 9 provides higher intensity; however the lower intensity is illustrated in case of treated paper with compounds including 4-methylphenyl, as the case of compounds 8 and 10.

Fluorescence Compounds as Secure and Dating Markers
To evaluate the role of the investigated approach for translating the machine identification codes to date the printed valuable documents, four fluorescence compounds (7, 8, 9, and 10) with different fluorescence quantum yield фs (0.55-0.86) were used to prepare UV inks. We designed two forms of check and receipt by using Microsoft Office 2016. Then we printed the designed forms on the paper sheets using different color laser printers of Xerox brand. The safety performance of the valuable documents is achieved by the following stages.

Extracting the Authorized Data from Printer
The investigated approach is applied for extracting the authorized data printed from five color laser printers (  approach includes scanning of the printed paper sheets at 1200 dots per inch (DPI). Adobe Photoshop CC 2015 was used as an image processing technique for the extraction step. Finally, we extracted all the machine identification codes that are printed on paper sheets. Figure 1a-d illustrates the distributions of MIC for each type of printer used. It is clear that the authorized data printed on papers are presented in a form of binary system dots that are machine known. Based on this the authorized data are calculated and converted from binary system state to decimal numbers.
From Figure 1a-c, it is observed that all the coded dots matrices (MIC) for the used color lasers consist of a regular grid of dots spread in fifteen columns and eight rows in a defined pattern, and then the area that exhibited the date of the printing is specified. There are three columns numbered 6, 7, and 8 that express the day, month, and year of the printing process, respectively. The date of the printing could simply be calculated from the binary system for base 2 (0, 1), and the calculation direction from down to up. The extraction and the calculation of the date of the printing process are as follows:  * For the unit of the year as present in Figure 1a-c, in row number one and column number eight, one point is found that is calculated as 2 0 and equals one. At the same column but at row number five, it contains another dot that calculated as 2 4 , which is equivalent to sixteen. The specified year 2017 is a result of summation. * From Figure 1b, which is corresponds to the Xerox Docu-Color 250 printer, at column seven and row number four, one point only is observed, which is calculated as 2 3 and is equivalent eight. This is the month of printing. * For Xerox WorkCenter 7132 (Figure 1c), from column number six, it contains two dots at rows number three and four that calculated as 2 2 and 2 3 . The summation represents the day of the printing.

Illustrating the Extracted Date on Printed Paper Documents
The extracted and calculated dates are clear on the valuable document by using the prepared UV via print dater, numerator, and stamp print, using Sirdas print dater 5810, numerator, and stamp print design, respectively. The used UV inks from four selected novel compounds (7, 8, 9, and 10) are colorless. The final images of the designed checks and receipt, under UV light at 365 nm are given in Figures 2a-d and 3.
With regard to designed check model and for improving the safety performance of paper documents, we have created the printed number of the check and micro text in two positions adjacent to two sentences "SIGNATORY NAME" and "AUTHORIZED SIGNATURE." By magnifying at 20× it is Global Challenges 2019, 3, 1800097  examination, through the text messages appeared for both check and receipt as clear in Figure 5.
With regard to check design (Figure 2a-d), the number of the check is printed adjacent to the text "Check No." It is printed with two hidden numbers, using colorless synthesized UV inks, while, the date of the printing process or the creation date of the document is printed in three different positions in both check and receipt with the invisible UV inks. The Eiffel Tower of Paris is also printed as a latent image. Finally, we printed six stars to complete the design for both checks and receipt in different positions with the invisible UV inks to promote the document security and difficulty to forgery. These printed stars indicate * Presence of secured star * Presence of micro print * Presence of fluorescent number of novel check * Presence of fluorescent date of novel check * Presence of static quick barcode Because these security features have not been designed into any check before we believe this work is new in providing a safety measure, and will be provided to help with advanced levels of security, which will help workers in the field of the questioned document examination for detecting the forging crime through specifying the authorized date and position of printed documents from MIC.

Conclusion
In this study, we investigated a new methodology to date the valuable documents (checks and receipt). The approach used was focused on extracting the coded dots matrices (MIC) from color laser printers. For dating the print process, in a binary system for base 2 (0, 1) was used, while novel invisible UV inks based on a pyrazoline derivative were used for printing the date and security information. This approach was succeeded in presenting a new application of fluorescenceactive compounds for dating and securing valuable documents with an advanced level of security.

Experimental Section
Materials-Paper Sample: Durable paper sheets known as Bible paper (45 g m −2 ) were used as substrate for printing the valuable documents. This type was made from 25% cotton and linen in combination with chemical wood pulp.
Materials-Fluorescence Active Compounds: Four pyrazoline derivatives were synthesized [21] and applied in UV ink to print the paper substrate. The methods of synthesizing these fluorescence compounds were summarized in the following scheme. These fluorescence compounds were selected from 21 compounds previously synthesized and have different fluorescence quantum yield (фs). The choice of these fluorescence compounds, numbered 7-10, was based on their quantum yield values (фs), fluorescence intensity of treated paper sheets and it mostly had positive effect on quality number of paper sheets. [21] The general method for synthesizing 4,5-dihydro-1H-pyrazoles (general procedure) is as follows 1,3,5-Triaryl-4,5-dihydro-1H-pyrazoles compounds 7-10, were synthesized through a cyclocondensation reaction of equimolar amounts of 1,3-diaryl-2-propen-1-ones 1-3 with aryl hydrazines 4-6 in refluxing ethanol. The solid separated upon storing the reaction mixture at room temperature overnight and was collected and crystallized from a suitable solvent, affording the corresponding pyrazolines 7-10. The obtained yields are in the range of 69% to 89% and are given in Scheme 1.
Melting points were recorded on a Stuart SMP3 melting point apparatus. IR spectra (KBr) were recorded on a Shimadzu FT-IR 8400S spectrophotometer. 1 H-NMR spectra were recorded on a Varian MERCURY 300 (300 MHz) and Bruker Ascend 400/R (400 MHz) spectrometers. 13C-NMR spectra were recorded on a Bruker Ascend 400/R (100 MHz) spectrometer. Compounds 7-10 were prepared according to the reported procedures. UV spectra were recorded on a Shimadzu UV-1800 spectrophotometer. Emission spectra were determined on LUMINA fluorescence spectrometer.    These synthesized heterocyclic compounds have fluorescence behavior, both in chloroform solution or after surface treating the paper sheets, as reported in Table 1 and 2. UV spectra were recorded on a Shimadzu UV-1800 spectrophotometer. Emission spectra were determined on LUMINA fluorescence spectrometer.
UV Ink Preparation: The formulation of UV ink used in printing the security issues is as follows: 0.5 g polyvinyl alcohol, 0.1 g active fluorescence compound (7, 8, 9, and 10), 30 mL bidistilled water and 2 mL ethanol. First, polyvinyl alcohol was dissolved in 30 mL of hot distilled water with stirring to complete dissolution and formed a very clear, diluted solution. Then, 0.1 g of fluorescence compound (7, 8, 9, or 10) was added after cooling in an ice bath with 2 mL ethanol and stirred until complete dissolution occurred.
Tools for Printing the Security Information: Sirdas print dater 5810, numerator, and stamp print design were purchased from the library. The rubber printing stamp was designed for the special purpose of UV printing. The check and receipt were designed with Microsoft Word 2016.
Tools for Printing the Security Information-Printing Techniques: In our application, we selected the Xerox brand for color laser printers. The reason for this selection was based on the authorized date. All color laser printers used in this application are listed in Table 3. Adobe Photoshop CC 2015 was applied, as nondestructive techniques for extraction the coded dots matrixes.