HU227577B1 - Printing-ink, which can be activated in infrared an ultraviolet interval and method for producing it - Google Patents

Abstract

The present invention relates to ultraviolet and infrared bifluorescent printing inks comprising a) a short wavelength UV irradiated organic lanthanide complex pigment, b) an infrared ray excited anti-Stokes pigment; up to 251% and at least 95% of the pigments have a particle size of less than 30 µm. The invention also relates to a process for producing printing ink by homogenizing the pigments in a manner known per se. The printing inks according to the invention have a visible emission of light and can be used for printing paper and plastic media for security purposes.

Description

Ultraviolet and infrared excipient bifluorescence printing inks and process for their production

State Printing House, Budapest, HU

Invent Dr. Lajos Székelyhídi, Hermitage, Süllő u. 20th 1/3 Darvas! Attila, 2Ö84 Nagykovácsi, Kossuth L, u. 105 1/3 Géza Imre, 2151 Main, 12 Lenin Avenue 1/3

Date of filing: 29.08.2003

BACKGROUND OF THE INVENTION The present invention relates to novel ultraviolet and infrared excitation printing inks, which can be excited by organic wavelength UV-irradiated Iantanida complex pigment, and infrared-excited anti-Stok.es. containing a pigment embedded in a suitable binder. The total amount of pigments in printing ink is not more than 251% and the particle size of at least 95% by weight of pigments is less than 30 µm.

The invention further relates to a process for the production of printing inks by homogenizing the pigments with an appropriate offset binder.

The printing ink of the present invention has visible light emission and can be used for printing paper and plastic media for security purposes.

♦ • '♦' φ ♦ V X ♦ * ΦΦΧ

According to current practice, security stone printing products can be divided into two large groups. Securities that represent a value far greater than their material value (banknotes, valuables) and security documents that prove their identity and / or entitlement, such as ID cards, driver's licenses and passports. It is important to mention even non-personal security documents such as various user licenses. It is easy to see that the falsification of security documents can not only result in material damage but can also endanger the security of the state).

Numerous tools have been devised to prevent falsification of content and form, especially in the last thirty years. These are a large group of security printing inks, of which there are many types. The printing ink subject to this application belongs to the family of luminescent inks.

The luminescence is the summary name for the radiation that certain materials exhibit through thermal excitation by suitable excitation. Particularly in document protection, photoluminescence is of practical importance, which is luminescence excited by optical (in this case ultraviolet and infrared) radiation.

The vast majority of phytoluminescence-indicating materials follow Stokes's law, which states that the wavelength of excitation radiation is always lower than that of ernited radiation. In other words, the photons of excited radiation are always higher in energy than the photons of ernited radiation. The so-called. In the case of anti-Stokes luminescence, the opposite is true. Higher wavelength excitation results in lower wavelength emission. The reason for this phenomenon is that the excited electron captures not one but two photons during excitation, so the energy corresponding to the energy of the two photons was taken to the level.

Some of this greater energy is transformed back into electromagnetic radiation, the visible light in our case.

385 nm wavelength ultraviolet radiation and in the visible range emitting fluorescent inks are currently the most widely used specialty inks because they can easily be checked on a security paper using a simple ÖV lamp and are therefore widely used. However, due to their ease of access, they are no longer of significant document protection value in themselves, and are limited by the fact that they are difficult or non-verifiable on ordinary writing and printing papers (containing optical brightener).

Short-wavelength fluorescent printing inks, such as 254 nm and emitting in the visible range, are far less widespread and have only been used so far on priority products (some banknotes, passports). The use of these pigments, which are generally inorganic compounds or organic metal complexes and which have a lower luminescence intensity but higher stability than organic pigments, can significantly increase the security of the document.

The so-called. the printing technology of anti-Stokes luminescence materials can be traced back to just a few years. The reason for this is that only materials that show this phenomenon and meet printing requirements have become known recently.

/ ¾ GB-B 2 258 859 and GB 2 258 680 describe the anti-Stokes luminescence of rare earth compositions contaminated with yttrium oxysulfide. The particle size of the material produced by the authors is typically in the range of 1-10 microns, so that it can be used in printing inks. In WO983992, the authors report the preparation of new materials having anti-Stokes fluorescence. The authors describe several material compositions which emit at different wavelengths than those known hitherto and are suitable for use in printing inks due to their particle size.

The use of these materials represents a major step forward in the manufacture of security products, as they are easy and secure to control by appropriate means, but these devices are not yet widespread, so even the detection of this security mark by a potential counterfeiter is not expected.

The use of biofluorescent inks can provide increased protection for printing products because the common feature of bifluorescence inks is that they are emitted into two different wavelengths by excitation at two different wavelengths, and thus emitted in the visible range. Therefore, the use of a bifluorescent printing ink in security printing products can be a more effective tool than a single wavelength emission printing ink, especially if it has at least one feature that prevents the forger from using it easily. This can be achieved, for example, by using commercially available pigments in the printing ink, which can greatly prevent the reproduction of a given print.

Thus, the main purpose of our investigations was to produce printing inks in which the pigments have the special properties necessary for the production of said fluorescent dyes. In our work, that is, the production of the printing ink according to the invention, several known aspects had to be taken into account and many difficulties had to be overcome, which are described in detail below.

Therefore, it had to be taken into account that the 254 nm radiation emitted by the low-pressure hl * * low vapor lamps, which is intensively emitted by the short-wavelength UV, ie 180-300 nm of the electromagnetic spectrum, is utilized by very widespread fluorescent light sources (fluorescent lamps). , energy-saving lamps, etc.} It is obvious that the materials used in these devices (commonly known as crystalline phosphorus) are used for safety printing inks because of their high availability due to the production of fluorescent lamps, their luminescence is intense, (light and chemical resistance).

There was a fundamental problem with the use of crystalline phosphorus in printing. One problem is that the crystalline phosphorus has been designed with its original purpose in mind, so that its excitation maximum is as close as possible to the 254nm wavelength emitted by the mercury vapor lamp, as it is the most efficient source of energy absorbed by the light source. However, one of the characteristic properties of the binder of printing inks is its extremely intense light absorption in the sub-270 nm range. As a result, excitatory radiation is not or only slightly transmitted to the pigment particles embedded in the binder. As a result of this phenomenon, it is observed that the pigment fluoresces intensively under the appropriate UV lamp, when embedded in a printing ink, or emits little light. Another problem relates to the particle size of crystalline phosphorus. Because the particle size of the pigments used in the production of fluorescent lamps is not suitable for offset technology and is too coarse. It seems obvious that grinding, which can be used in other cases, to reduce the particle size of the pigment. The particle size of crystalline phosphorus can only be reduced within very narrow limits as the surface properties of the material gradually change as the milling progresses, reducing the intensity of its luminescence [6. Wak.efie.ld ,. HA Requeston, <******* V ', ♦ * * ♦ ♦ · ♦ * «. _w * * * ♦ * «'♦

PJ Dobson, and J.L. Hutchlsonf Journal of Coloid and Bacterial Science 215, 179182 (1999), Hasé. T., Kano. T _.: Nakazawa, E., and Yamamoto, H _.; Adv, Electron, Electron Phys. 79, 271 (1990) 1

Maintaining the intensity of the tumorscend is extremely important since, according to practical experience, UV-pigmentable pigments can be present in offset dyes up to 20% by weight. Higher pigmentation results in printing problems. Since the goal of our work was to develop bifluorescent printing inks, we needed a pigment that, when applied at up to 15% by weight, exhibits sufficiently intense luminescence.

It follows from the above that the most important task of the present invention was to produce UV-pigmentable pigments (hereinafter "UV pigments") which are capable of solving the problems detailed above, that are:

- particle size suitable for printing purposes, and

- their luminescence intensity ensures that, when applied to offset printing inks, a maximum of 15% gives a visible luminescence imprint,

- their light and chemical resistance meet the normal requirements for security printing products,

- avoid luminescence (selectivity) when excited by long wavelength UV radiation (365 nm),

- their luminescence is markedly different in color and has surface properties such that the binder of the printing ink can moisten the pigment particles.

In our investigations we have found that the pigments most suitable for the above aspects can be found around certain organic rare earth complexes, especially lanthanide complexes4 4 * 4 4. It has long been known that complexes of certain rare earth ions with organic complexing agents exhibit intense luminescence. The most well-known of these metals are Tb, Ed, Dy and the like.

Chemical analysts have long been known to form complexes that form fluorescent complexes with some rare earths. There are many references in this topic, 8. M, Krasovitskii and BM. Bolotin, Organic Lumineseent Matter! (VCH GmbH, 1988). None of them are suitable for use in printing inks due to the presence of one or more of the following properties:

- water solute,

- freely soluble in organic solvents, luminescent only when dissolved,

However, the aromatic d1- and monocarboxylic acid complexing agents do not have the above properties and their use in printing inks is not impeded since the rare earth complexes formed with the aid of these complexing agents fulfill the conditions for use in printing inks.

In selecting the anti-Stokes pigment, however, we had to take into account that many materials have anti-Stokes luminescent properties but few are suitable for printing applications. For this purpose, crystalline phosphorus having a base lattice of a particular earth metal oxysulfide, in particular Y2O2.S, Gd2.O2'S, La2O2S, may be used. Acceptor ions may be rare earth ions of various oxidation states, primarily Yb. Er, Tm. Combinations of different base lattices and activator ions provide different colored emissions. Of course, excitation wavelengths can also vary.

When selecting the binder we had to take into account that the development of the binder of oxidatively drying offset printing ink is a delicate task because it essentially determines the suitability of the ink for printing. The main weight of the binder is made up of various resins and oils (40-68%) which undergo an oxidative polymerization at the air-oxygen boundary, so that they are firmly attached to the media. The elasticity of the ink layer after printing can be adjusted with different waxes. Inks are usually thickened with calcium carbonate based materials or diluted with diesel to achieve the desired consistency. Drying of the paint is accelerated by the addition of manganese or cobalt octoate.

Detailed Description of the Invention

BACKGROUND OF THE INVENTION The present invention relates to novel security printing inks containing two pigments of up to 25% total volume, a short-wavelength UV-excited pigment, an organic Iantanida complex, and an anti-Stokes pigment, preferably a rare earth oxysulfide Yb or Er complex. containing at least SS% of the pigments having a particle size of less than 3 µm. The invention further relates to a process for the production of printing inks by homogenizing the short-wavelength UV-excited organic Iantanida complex and the anti-Stokes pigment using an appropriate binder, until sufficient homogeneity is achieved.

The printing inks according to the invention thus consist of 3 main components;

- the binder (matrix) constituting the main weight of the inks, which is responsible for the printing properties,

- a luminescent UV pigment which causes fluorescence of dyes under ultraviolet excitation at short wavelengths,

X

- an anti-Stokes pigment that provides green luminescence of dyes by infrared excitation and has the following properties:

· Their print is colorless.

- do not emit light when excited by ultraviolet radiation of long wavelength,

- fluoresce intensively with different colors when excited by ultraviolet radiation of short wavelength, exhibit intense fluorescence when excited by infrared radiation (anti-Stokes fluorescence),

can also be checked on paper containing optical brightener, and

- are capable of mechanical inspection.

The printing inks according to the invention exhibit intense luminescence under short-wavelength ultraviolet light, which can be easily controlled with a medium level of technical skill. A UV lamp capable of emitting a short wavelength of ultraviolet radiation is required for inspection. If the lamp is equipped with a yellow secondary filter (located between the eye of the tester and the test document), it is also possible to test prints on paper containing optical brightener,

The anti-Stokes luminescence pigments of the dyes can only be monitored with a suitable 880 nm IR irradiation device. There are two types of such test tools. One of the devices is actually a handheld IR laser used to illuminate the print with infrared luminescence. The disadvantage of the equipment is that, like all lasers, it is dangerous to the human eye, and it only provides spot-light illumination.

Uses LED. Its intensity is lower than that of a laser diode, however, by using multiple diodes together and using a magnifying glass, a larger area can be examined. This allows you to examine a small amount of print, unlike a laser device where only small, blinking spots are detected. It is also important to mention that LEDs are completely harmless to the human eye.

EXAMPLES

The following examples further illustrate the invention without, however, limiting the scope of the invention to these examples.

The following examples describe the testing of ink and the results of tests where the ink contains the following components.

Binder: Finished colorless offset primer (TW), preferably in a concentration of 75-95%.

254 nm UV excitation luminescent organic metal complexes, the properties of which are summarized in Table 1 below. Their emission and excitation spectra are shown in Annexes 1, 2 and 3. The pigments used are called A, B, C · pigments.

The pigment was selected from the investigated red luminescence materials based on luminescence: intensity, light and chemical stability and good abrasion. According to the pigment composition, europeium3 + ion phthalic acid exe.

lex is insoluble in water and in solvent and exhibits intense red luminescence under shortwave ultraviolet excitation.

ν „8 pigment

The aim of the pigment design was to produce a yellow luminescent pigment, however, such a pigment could not be prepared using a complex containing one type of metal ion, so mixed complexes were investigated. The mixed complex of europium plum3 + / terbiumSe of buccal acid proved to be suitable for our purposes. The desired color was obtained by modifying the Eu / Tb ratio. For the 8 pigments, the Eu: Tb Ions ratio is 35:65% by weight. The complex is insoluble in water and solvent and exhibits intense yellow luminescence under short wavelength ultraviolet excitation.

,, C pigment

Among the metal complexes with green luminescence, the phallic acid complex of ferbium S * ion proved to be the most suitable for the examined parameters.

The complex is insoluble in water and solvent, and exhibits intense green luminescence under short wavelength ultraviolet excitation.

Anfl-Stokes pigment was used as an egv pigment with base lattice Y2O2S and activator ions Vb and Er. This pigment is referred to as AS pigment in the examples. The pigment properties are summarized in Table 2.

Table 1

Fluorescence spectral data of the pigments used

Excitation maximum Emission maximum Hello emi The pigment 315 nm 620 nm red 8 pigments 285 nm 575 nm orange C pigment 265 nm 546 nm green

Luminescence spectra were recorded on a Hitachi 650/60 spectrofluorimeter.

X *

Table 2 Fluorescence spectral data for AS pigment Maximum excitation i Maximum excitation i efficiently luminesiing materials color of the bow i AS pigment 975 nm 1550, 555, 610 nm ΐ : l : ί l z kill

Particle size distribution

The particle size distribution of the luminescent pigments used is critical for both printability and print luminescence intensity. In terms of printability, the finer the pigment, the finer the pigment produces the better the print, and the pigment with a narrow distribution pattern with a maximum around 5 pm is ideal.

The particle size distribution of AS pigment we use is illustrated in Figure 5.

s. Annex.

6, 7 and 8. Annexes A to B represent the particle size distribution of pigments A _: B, C, respectively. Fritsch Anlalysetíe 22 Compaot laser diffraction particle size analyzer was used for the measurements.

Example 1

Composition of the paint:

Pigment 130g AS Pigment 40g TW Primer 830

Preparation of paint

The ingredients were weighed into the paint mixer and the dispersion was reduced for a time appropriate to the mixer parameters. After obtaining sufficient homogeneity, the dense dispersion was triturated using a three-cylinder abrading apparatus. The abrasion friction was checked with a grindometer.

Examination of the paint

The prepared ink was tested using a test print machine (1GT Orange Rroofer). The print media was 100 g / m 2 free of optical bleach. Load paint; 2.5 g / m2

The test prints were checked using a 254 nm UV lamp to determine the homogeneity of the print. The printout must be completely uniform. We checked to see if there were any lighter, star-like points out of the background, indicating the lack of rubbing. The print showed intense red fluorescence, the print was uniform and homogeneous.

Emission spectra were taken from the print using a spectrofluorimeter. No. 9 The spectra of the print at excitation at 315 nm are given in Annex. The spectrum has a peak at 820 nm. Fluorescence of the print was checked with a Chorus 1017 handheld document scanning device.

The prints were subjected to chemical and luminance testing after 48 hours drying. The results of the tests are shown in Table 3 below.

After completion of the above tests, the dye was passed to a field test. The test printing was performed on a Heldelberg GTO printing press. During the trial 1000 pieces. An A4 test sheet was printed. The ink met the general requirements for printing inks during the in-service test, and there was no problem using it.

«.9« · * »9

3, Table

Water way Emission 25-4 nm spin. next to Anti-Stokes quality Soaking in ethanol. 30 min, 25 ° C 10 10 Soaking in ethyl acetate for 30 minutes at 25 ° C 10 10 Soaking in chloroform for 30 minutes at 25 ° C 10 10 Soaking in xylene for 30 minutes at 25 ° C 10 10 Soak in gasoline, 30 minutes, 25 ° C 10 10 Soaking in aceion, 30 minutes, 25'C 10 10 Soaking in carbon tetrachloride for 30 minutes at 25 ° C 10 4 Soaking in sulfuric acid (2%), 30 min, 25 ^° C 10 0 Soaking in potassium hydroxide solution (2%), 30 min, 2 ^: C 10 10 Soak in detergent, 30 minutes, 8 lbs TC cannot be evaluated 10 Soaking in hot water, 30 minutes, 8 * G 10 8 Volatility (high pressure mercury vapor lamp, 50,000 lux, 30 minutes) 10 9

How to evaluate the data in the table

After the tests were performed, the samples were dried and visually compared with a piece of the intact sample using an appropriate light source (254 nm UV lamp) and instrument (Horus 1017 type document examiner). The result of the comparison was evaluated on a scale of 0 to 10. A value of 0 means complete cessation of the property, a value of 10 means that the property being tested has not changed during the test.

Je · ' ^y '<

* »*«

Example 2

Composition of the paint:

8 ”pigment 160 g” AS ^K pigment 40 g

TvV Bodies 800g

The dye preparation was carried out in exactly the same manner as in Example 1 and the dye was also tested in exactly the same manner as in Example 1. Of course, the results obtained were partially varied with the pigment exchange. Only differences are described separately.

The test prints were checked using a 254 nm UV lamp. The print showed intense orange fluorescence and the print was uniform and homogeneous. 10. The spectra of the print at 285 nm excitation are given in Annex. The spectrum has a peak at 575 nm. The anti-Stokes fluorescence of the print is shown in FIG. The results obtained are completely identical. The results of the chemical and light fastness tests of the prints are given in Table 4 below. There was no problem with the paint during the factory test.

1.6

Table 4

Method of examination ! Emission at 254 nm. next to Anti-Stokes quality Soaking in ethanol, 30 minutes, 25 ' ^: ' C 10 10 I Soaking in ethyl acetate, 30 rpm, 25 ° C : 10 10 Soaking in chloroform for 30 minutes at 25 ° C 10 10 Soak in xylene for 30 minutes at 25 ° C 10 10 Soaking in petrol, 30 rpm, 25 ° C 10 10 Soaking in acetone for 30 minutes at 25 ° C 10 10 Soaking szénletraklohoban, 30 min, 25 C ⁿ 10 4 Soaking in sulfuric acid (2%). 30 min, 25 ° C 10 0 Soaking in potassium hydroxide solution (2%), 30 min, 25 ^; 3 10 Soak in detergent for 30 minutes at 8G cannot be evaluated 10 Soaking in hot water, 30 minutes, 8CTC 8 8 Light fastness (high pressure mercury vapor lamp, 50,000 lux, 30 minutes) 8 9

How to evaluate the data in the table

After the tests were performed, the samples were dried and visually compared with a piece of the intact sample using an appropriate light source (254 nm UV lamp) and instrument (Horus 1017 Document Examiner). The result of the comparison was evaluated on a scale of 0-100. A value of 0 means complete disappearance of the property, a value of 10 means that the property being tested has not changed during the test.

* X * «* * ♦« * x * «* ♦♦

Example 3

Composition of the paint;

C pigment 145 g ”AS” pigment 50 g

TW base paint 305 g

The preparation of the dye was carried out in exactly the same manner as in Example 1. The dye was also tested in the same manner as in Example 1. Of course, the results obtained were partially varied with the pigment exchange. Only differences are described separately.

The test prints were checked using a 254 nm UV lamp. The print showed intense green fluorescence, the print was uniform, homogeneous,

Appendix 11 shows the spectra of the print at excitation at 265 nm. The spectrum has a peak at 546 nm. The anti-Stokes fluorescence of the print is shown in FIG. was checked in the same way as the sample. The results were completely identical. The results of the chemical and light fastness tests of the prints are shown in Table 5 below. There was no problem with the paint during the factory test.

* ♦ X * X ♦ »· ♦ * φ *

Table S.

Method of examination Emission at 254 nm. next to Anti-Stokes quality Soaking in ethanol, 30 min, 25 ° C 10 Shoot Soaking in ethyl acetate for 30 min at 25 C. ⁹ 10 10 Soaking in chloroform, 30 minutes, 25 ' ^: C 10 10 Soaking in xylene for 30 minutes at 25 ° C 10 10 Soak in gasoline, 30 minutes, 2FC 10 10 Soaking in acetone for 30 minutes at 25 ° C 10 10 Soaking széntetraklöíídban, 30 min, 25 ^C C 10 4 in Sulfuric Acid (2%), 30 minutes, 25 ° C 10 0 Soaking in potassium hydroxide solution (2%), 30 minutes, 25'C 2 10 Soak in detergent for 30 minutes at 8G cannot be evaluated 10 Soak in hot water, 30 minutes, 8GX 8 8 Light fastness (high pressure mercury vapor lamp, 50,000 lux, 30 minutes) 7 9

After testing, the samples were dried and visually compared to a portion of the intact sample using an appropriate light source (254 nm UV lamp) and instrument (Hcrus 1017 type scanner). The result of the comparison was evaluated on a scale of 0-100. A value of 0 indicates the complete loss of the property. A value of 10 means that the property tested did not change during the test.

φ φ

Summary of results

Thus, in the course of our investigations, using the special UV pigments described, new printing inks with a specific luminescence character were produced. The printing inks produced can be excited in both ultraviolet and infrared light. have visible light emission. To achieve an appreciable light emission, the total concentration of pigment components in the printing ink may be up to 25% by weight, and pigments with a particle size distribution such that at least 95% by weight have a particle size of not more than 30 µm. The printing inks shown in the examples are suitable for printing on paper and plastic (PVC, polycarbonate) substrates,

The printing inks of the present invention are more advantageous than those known in the art because they provide a high level of protection at realistic costs, even at large numbers, and are easy to control. While there are many high-volume, single-use documents that embody less or greater material value or are otherwise in need of protection, due to the high cost of optical bleach-free paper, which is commonly used as a print medium for protected documents. Such documents include medical prescriptions, ballot papers, certificates, etc. A further advantage is that free ink stencils Hl., With the simplest document control tools (magnifying glass, simple UV lamp), are not derlfeffer, which helps to keep the print hidden from the counterfeiter.

If an IR LED is used to excite the anti-Stokes pigments of the dyes, it should be noted that the LEDs are completely harmless to the human eye. Furthermore, the use of infrared detection devices is not widespread, even among document experts, so it is reasonable to assume that this feature is hidden from the counterfeiter. However, anyone who has such a tool can easily and safely decide on the authenticity of a document containing this type of security element.

Another important advantage of using anti-Stokes materials is that they are excellent for automated control. No. 4 The spectrum in Annex II clearly shows that the substance has characteristic emission bands. Such materials can be controlled very effectively because the ratio of well-chosen peaks to each other is always constant, regardless of fluctuations in the pigment content of the ink or printing parameters.

Claims (7)

PATENT CLAIMS 1. Ultraviolet and Infrared excitable · Buoorescent · Printing inks containing a) Organic lantantda complex pigment excitable by UV radiation of short wavelength, b) ani-Stokes pigment that can be infrared; and o) an appropriate offset binder, wherein the total amount of pigments is less than 25% by weight of the total amount of dyes and at least 85% by weight of the pigments is less than 30 µm. The hifluorescent printing inks according to claim 1, comprising 15-22% by weight of pigment. Bifluorescent printing inks according to claim 1, wherein at least 95% by weight of the pigments have a particle size of less than 20 µm. The biflororescent printing ink of claim 1, wherein at least 95% by weight of the pigments have a particle size of less than 10 µm. The biflororescent printing ink of claim 1, which comprises dicarboxylic acid complexes of liberium and europium ion as pigments excited by short-wavelength UV radiation. Hifluorescent printing inks according to claim 1, comprising antiStokes pigments wherein the base lattice Y2O2S and the activator ions Vb and Er, * ♦ 7. Procedure is. For the production of carbon fluorescent inks according to claim 1, characterized in that the pigments, namely the short-wavelength UV-excited organic Iantanida complex pigment and the antl-Stokes pigment, wherein at least 85% of the pigments have a particle size of less than 30 µm and % by weight - homogenize with a suitable offset binder in a known manner.