DE60203541T4 - Rare earth compounds and their mixtures - Google Patents

Description

The invention relates to rare earth metal compounds and mixtures of these, which are suitable due to their luminescence, when irradiated with UV light excellent for marking objects, such as data carriers and documents.

Fluorescent rare earth metal compounds, such as salts or complexes, are known in the art.

For applications in which a red fluorescence effect is required, so far mainly europium-diketonate complexes (see HG Brittain and FS Richardson, J. Amer. Chem. Soc., 99, 65-70 (1977)) and europium-carboxylic acid Compounds (see G. Kallistratos, Chemika Chronika, New Series, 11, 249-266 (1982; EP Diamandis, Analyst, 117, 1879-1884 (1992)).

The europium-diketonate complexes can be excited both in solid form and in the form of solutions or mixtures in organic solvents or polymer systems with UV light of a wavelength of 366 nm or 254 nm to emit an intense red fluorescent light (see GA Crosby et al. , J. Phys. Chem., 66, 2493-2499 (1962)). Also from the US-A-5-118349 are soluble rare earth-diketonate complexes known. Decisive disadvantages of these complexes, however, are their low light stability and their low thermal stability.

Europium-carboxylic acid complexes usually have the desired thermal stability. However, it turns out that in the presence of these complexes in finely divided or amorphous form intense fluorescence only when irradiated with very short-wave UV light, z. B. with light of a wavelength of 254 nm, can be achieved. When grinding these carboxylic acid complexes z. B. for the production of offset printing inks, therefore, there is a shift of the excitation maximum in the short-wave range, ie the fluorescence intensity is significantly higher when irradiated with short-wave UV light than when irradiated with long-wave UV light. Furthermore, the luminescence effect in these complexes is due to their crystal structure, as is known in inorganic luminescent pigments. Destruction of the crystals therefore has a direct influence on the luminescence properties (cf. DE-A-30 32 611 ).

• – farblos bei Tageslicht
• – hohe Intensität des emittierten Fluoreszenzlichtes bei Bestrahlung mit UV-Licht einer Wellenlänge von 366 nm
• – hohe thermische Stabilität
• – hohe Lichtechtheit
• – keine Veränderung der Fluoreszenzeigenschaften (Intensität und CIE-Farbkoordinaten) bei Vermahlung.

As a result of the aforementioned disadvantages of the known materials, the object of the invention was to provide fluorescent rare earth metal compounds having the following properties:

• - colorless in daylight
• - High intensity of the emitted fluorescent light when irradiated with UV light of a wavelength of 366 nm
• - high thermal stability
• - high lightfastness
• - no change in fluorescence properties (intensity and CIE color coordinates) when ground.

This object is surprisingly achieved by the rare earth metal compounds and the mixtures of these compounds according to claims 1 to 7. The invention further relates to a process for the preparation of the rare earth metal compounds and the mixtures of these according to claims 8 to 11, their use according to claims 12 to 17 and the labeled compounds containing the rare earth metal compounds or mixtures thereof according to claim 18 ,

The compounds according to the invention are rare earth metal compounds of at least one rare earth metal and 2-hydroxyquinoline-4-carboxylic acid of the formula (I)

Wherein L ¹ , L ² , L ³ , L ⁴ and L ⁵ independently represent a substituent or H.

The compounds according to the invention or mixtures of these are colorless under the influence of daylight, but upon excitation with ultraviolet light they fluoresce, depending on the metal ion used, in different colors. Because of these properties, they can be used in a variety of applications, and examples of possible applications are z. B. in the DE-A-30 32 611 disclosed.

The rare earth metal compounds of the present invention are the result of extensive investigations in the field of organic rare earth metal salts in order to find luminescent compounds capable of exhibiting the aforementioned properties.

For this purpose, in particular europium chelate complexes with differently substituted quinolinecarboxylic acids were investigated in more detail. For this purpose, reference is made to Examples 1 to 11 and Table 1 listed there. It was found that the complexes with the majority of the quinolinecarboxylic acids investigated still have the described disadvantages of the materials known from the prior art. In contrast, it is surprising that only those complexes which are substituted in the 2-position of the quinoline carboxylic acid with a hydroxy group, have all the desired properties.

Preferred rare earth metal compounds and mixtures of these have at least two different rare earth metals. Such materials are capable of emitting different fluorescent light as the temperature is changed. This behavior and the resulting advantages when using the compounds and mixtures according to the invention in particular for labeling and authentication, d. H. the determination of the authenticity of objects will be explained below.

wobei
A und B für unterschiedliche Seltenerdmetalle aus der Gruppe Europium, Terbium, Gadolinium, Samarium, Yttrium, Neodym, Lanthan und Cer stehen,
C ein Erdalkalimetall aus der Gruppe Calcium, Strontium und Barium ist,
L¹, L², L³, L⁴ und L⁵ unabhängig voneinander für einen Substituenten oder H stehen,
x + y eine Zahl ergibt, die größer als 0 und kleiner oder gleich 1 ist, und
N = x + y + 2 ist.Particularly preferred rare earth metal compounds and mixtures of these correspond to the general formula (II)

in which
A and B represent different rare earth metals from the group europium, terbium, gadolinium, samarium, yttrium, neodymium, lanthanum and cerium,
C is an alkaline earth metal from the group calcium, strontium and barium,
L ¹ , L ² , L ³ , L ⁴ and L ⁵ independently represent a substituent or H,
x + y gives a number greater than 0 and less than or equal to 1, and
N = x + y + 2.

It should be noted that the formula (II) indicates only the ratio of the individual components of the compounds to each other. The nature of the bond between the 2-hydroxy-quinoline-4-carboxylic acid and the metals has not been definitively elucidated. However, it is believed that this is a complex-like bond and the 2-hydroxy-quinoline-4-carboxylic acid is present as the anion and the metals as cations. In such a complex, bonding of the metals via both the carboxylate group, the hydroxyl group and the lone pair of electrons of the nitrogen atom would be conceivable.

It is preferable that the rare earth metals A and B are independently selected from the group consisting of europium, terbium, gadolinium and neodymium. It is particularly preferred that A or B is europium or terbium.

Further investigations have surprisingly shown that in the presence of two different rare earth metals, ie when x is greater than 0 and y is greater than 0, the compounds of the invention emit a fluorescent light when excited with UV light, the color of which depends on the temperature. For example, compounds according to the invention which contain europium with terbium showed an intense orange-red fluorescence upon irradiation with UV light at room temperature, which turns green when cooled to -20 to -30 ° C. This surprising feature of sending out different fluorescent light depending on the temperature is very useful especially when using the compound according to the invention for marking objects. In conventional pigments which emit a substantially independent of the temperature of the type of fluorescent light, in marked with objects such. As credit cards, only one type of fluorescent light to be tested by irradiation with UV light. In contrast, labeled with the compounds of the invention objects, for. B. at temperature decrease, z. B. by spraying with conventional cold spray, emit a fluorescent light completely different color, and this behavior then confirms the user that the examined object is actually marked and thus authentic, ie genuine. The imitation of the mark by counterfeiters is made even more difficult.

It is further preferred that the substituents L ¹ , L ² , L ³ , L ⁴ and L ⁵ present in the 2-hydroxy-quinoline-4-carboxylic acid are independently of one another H, halogen, C ₁ -C ₆ -alkoxy, C C ₁ -C ₆ -alkyl, C ₆ -C ₁₂ -aryl, OH, CN, C ₁ -C ₆ -alkylamino, CO-C ₁ -C ₆ -alkyl or CO-NH ₂ .

The rare earth metal compounds of the present invention and mixtures thereof are preferably prepared by reacting at least one rare earth metal salt with 2-hydroxyquinoline-4-carboxylic acid of the formula (I) optionally in the presence of an alkaline earth metal salt. The rare earth metal salt is preferably a rare earth metal halide, such as. B. a chloride.

The reaction usually takes place in an aqueous medium and in particular in water.

Particularly preferably, the 2-hydroxy-quinoline-carboxylic acid is first reacted with alkaline substances to form 2-hydroxy-quinoline-4-carboxylate. In particular, potassium hydroxide or sodium hydroxide, but also organic amines, such as ethanolamines or alkylamines, are used as alkaline substances. Also, mixtures of alkaline substances can be used.

The product which usually precipitates after the reaction is isolated and dried in the customary manner and can then be used in this form for the intended applications.

The rare earth metal compounds according to the invention and mixtures of these show the already mentioned property of emitting fluorescent light in the visible in the visible range upon irradiation with UV light. In the case of the use of two different rare earth metals in the compounds or even in mixtures of compounds each having a rare earth metal, the particularly advantageous property may occur that the wavelength of the emitted fluorescent light depends on the temperature. In this way, z. B. to detect a change in the color of the fluorescent light obtained at irradiation with UV light at room temperature to another color, for. B. when the material is cooled to lower temperatures.

Also, the compounds of the invention to solvents are much more stable because they show pigment-like character. Furthermore, the fluorescence properties of the compound and in particular the intensity of the emitted fluorescent light do not change when the compounds are ground. They are also highly thermally stable and usually colorless upon exposure to daylight. Because of these properties, they can be used in a variety of luminescent applications. Examples are in the DE-A-195 12 773 specified.

Preferably, the rare earth metal compounds of the invention and the mixtures of these compounds are used to label articles by providing the article with the compounds or mixtures thereof.

Above all, these items are data carriers or documents, with smart cards, check cards or credit cards being used as data carriers, and badges, banknotes and documents as documents.

Since the compounds of the invention are colorless when exposed to sunlight, they produce in this use a unrecognizable to the viewer marker, which is just important for such objects that, such. As chip cards, check cards or credit cards and ID cards, banknotes and documents, often counterfeiting attempts are exposed. The irradiation of these objects with UV light, however, produces a characteristic fluorescent light, which in the particular embodiment described in more detail above, even with temperature change, such as cooling, z. B. by spraying the article with a commercially available cryogenic spray, changed color. Each of special Compounds according to the invention and mixtures of these generated colors of the fluorescent light at room temperature and modified, z. B. lowered temperature, then for the verifier of a marked object is a sure indication that it has been marked with the compounds. Thus, the compounds of the invention are used to prevent counterfeiting or the detection of counterfeiting and the determination of the authenticity of objects.

The compounds of the invention or mixtures of these can be incorporated as such into the articles to be marked in a conventional manner. However, it is also conceivable that they be used in the form of compositions containing the compounds or mixtures of these together with a binder. Suitable binders are, in particular, acrylic polymers, polyamides, polyurethanes, polyesters and polyethylene terephthalates and the corresponding monomers and oligomers. It is also possible to add customary auxiliaries to these compositions.

Furthermore, the compounds according to the invention can also be used in films, such as polymer films, or fibers, such as spin-dyed fibers.

It is also conceivable that the compounds of the invention together with a liquid carrier, for. B. be used in the form of dispersions.

Such dispersions can then be used, for example, for impregnating the articles to be marked. Such an approach is z. B. for the production of marked security threads possible, then z. B. in ID cards, banknotes, checks and documents are incorporated.

Finally, the invention also relates to marked articles which contain the rare earth metal compounds according to the invention and mixtures of these.

The invention will be explained in more detail below with reference to examples.

A series of compounds of europium and differently substituted quinolinecarboxylic acids were prepared to check the influence of the kind of substitution of the quinolinecarboxylic acid on the properties of the obtained compounds.

The compounds were prepared analogously to the instructions given below for Examples 1 and 9.

The resulting quinolinecarboxylic acid europium compounds, which are believed to be chelate complexes, were visually examined for the intensity of fluorescent light emitted upon irradiation with UV light of wavelength 366 nm. In each case, the solid, a solution in toluene and a composition applied to a substrate and containing 5% by weight of the compound in a binder system were tested.

Furthermore, the UV stability of the compounds prepared was tested by exposing the prepared spreads in a SOL 2 device from D. Höhnle to radiation of daylight D65 for several hours and then visually under UV light, the brightness of each emitted fluorescent light was observed and evaluated in the comparison of compounds with each other and with literature-known rare earth metal complexes.

The results obtained are shown in Table 1 below.

• 1. Sowohl die Europium-Verbindungen mit 3-Hydroxy-4-chinolincarbonsäure (Beispiele 2 und 3) als auch diejenigen mit Hydroxy-2-chinolin-carbonsäure (Beispiele 7 und 8) zeigen keine oder nur eine sehr geringe Fluoreszenz.
• 2. Fehlt die Hydroxy-Gruppe völlig in der Chinolincarbonsäure, so erhält man Verbindungen mit nur geringer Intensität des Fluoreszenzlichtes (Beispiele 5, 6 und 10). Eine Ausnahme ist lediglich die Verbindung mit 2-Phenyl-4-Chinolincarbonsäure (Beispiel 9), die sowohl in Lösung als auch im Aufstrich eine sehr intensive Fluoreszenz zeigt. Diese Verbindung hat jedoch als entscheidenden Nachteil, dass sie nur eine sehr geringe UV-Stabilität, d. h. eine sehr geringe Lichtechtheit aufweist.
• 3. Die Verbindung gemäß Beispiel 4 zeigt, dass allein durch die Hydroxy-Gruppe in der 2-Position nur eine geringfügig fluoreszierende Verbindung gebildet wird.
• 4. Nur die erfindungsgemäße Verbindung gemäß Beispiel 1, in der sowohl die Hydroxy- aus auch die Carbonsäuregruppe an der richtigen Position im Chinolingrundkörper vorhanden sind, zeigt die gewünschten Eigenschaften.

From the results given in the table, the following can be read.

• 1. Both the europium compounds with 3-hydroxy-4-quinolinecarboxylic acid (Examples 2 and 3) and those with hydroxy-2-quinoline-carboxylic acid (Examples 7 and 8) show little or no fluorescence.
• 2. If the hydroxy group is completely absent in the quinoline carboxylic acid, compounds with only low intensity fluorescent light are obtained (Examples 5, 6 and 10). An exception is only the compound with 2-phenyl-4-quinolinecarboxylic acid (Example 9), which shows a very intense fluorescence both in solution and in the spread. However, this compound has as a significant disadvantage that it has only a very low UV stability, ie a very low light fastness.
• 3. The compound according to Example 4 shows that only a slightly fluorescent compound is formed solely by the hydroxy group in the 2-position.
• 4. Only the compound according to the invention according to Example 1, in which both the hydroxy and the carboxylic acid group are present at the correct position in Quinolingrundkörper shows the desired properties.

example 1

A europium compound according to the invention was prepared.

To this was suspended 30 g (0.1585 mol) of 2-hydroxyquinoline-4-carboxylic acid in 420 ml of water in a 1 liter three-neck round bottom flask and dissolved by adding 6.34 g of sodium hydroxide.

To the resulting clear solution, a solution of 9.31 g of europium in 15.64 g of 37% hydrochloric acid and 100 ml of water was added dropwise with stirring at 20-100 ° C within 20 minutes.

The precipitating europium compound was isolated and dried. It showed a reddish-orange fluorescence when irradiated with long-wave UV light (366 nm).

Example 9

For comparison, a europium-2-phenylquinoline-4-carboxylic acid compound was prepared.

For this purpose, 19.75 g (0.0792 mol) of 2-phenylquinoline-4-carboxylic acid were dissolved in a solution of 5.23 g of potassium hydroxide in 420 ml of water in a 1 three-necked round bottom flask.

To this solution was added a solution of 4.65 g of europium oxide in 7.95 g of 37% hydrochloric acid and 150 ml of water.

The resulting precipitated compound was isolated and dried. It was readily soluble in common organic solvents, so there would generally be an opportunity to use them in printing systems that still rely on unwanted organic solvents.

However, a very great disadvantage is the strong migration from the binder used, since the compound is soluble, and the very low light resistance, which is reflected in a very large drop in the intensity of the fluorescent light after irradiation with daylight.

For outdoor use, the connection is therefore not suitable.

Examples 12-15

Other rare earth metal compounds according to the invention or mixtures thereof were prepared.

The materials obtained according to these examples had a pronounced pigment character, i. H. they are insoluble in common organic solvents. By appropriate grinding colorless, but under UV light of 366 nm very strongly colored fluorescent light emitting materials were obtained under normal light.

This makes it possible, with the compounds of the invention, all known printing systems, eg. As water-dilutable, oxidatively dried and UV-reactive printing systems with high light resistance produce.

Example 12

A europium-gadolinium compound according to the invention was prepared.

To this was dissolved in a 1 L three-neck round bottom flask 30 g (0.1585 mol) of 2-hydroxyquinoline-4-carboxylic acid in a solution of 6.34 g of sodium hydroxide in 420 ml.

To the resulting clear solution, a solution of 8.376 g of europium oxide and 0.959 g of gadolinium oxide in 15.64 g of 37% hydrochloric acid and 120 ml of water was added dropwise with stirring at 20-100 ° C within 15-30 minutes.

The resulting precipitated compound was isolated and dried.

Example 13

A europium-terbium compound according to the invention was prepared.

To this was dissolved 30 g (0.1585 mol) of 2-hydroxyquinoline-4-carboxylic acid in a solution of 6.34 g of sodium hydroxide in 400 ml of water in a 1 liter three-necked round bottom flask.

To the resulting solution was added dropwise with stirring at 20-100 ° C, a solution of 8.376 g of europium oxide and 0.989 g of terbium in 15.89 37% hydrochloric acid and 100 ml of water within 30 minutes.

The resulting precipitate was isolated and dried. A sample of the compound obtained when irradiated with UV light of a wavelength of 366 nm, an intense orange-red fluorescence, which changed on cooling to -20 to -30 ° C in a green fluorescence.

Example 14

A gadolinium-terbium compound according to the invention was produced.

To this was suspended 30 g (0.1585 mol) of 2-hydroxyquinoline-4-carboxylic acid in 400 ml of water in a 1 liter three-necked round bottom flask and dissolved by adding 10.46 g of potassium hydroxide.

A solution of 8.63 g of gadolinium oxide and 0.989 g of terbium oxide in 15.89 g of 37% strength hydrochloric acid and 100 g of water was slowly added dropwise to this solution at 20-100 ° C.

It then formed a fine precipitate, which was isolated by suction and then dried.

A sample of the precipitate showed no visible fluorescence in a spread in commercial, water-borne acrylic paint after drying and irradiating with UV light (366 nm). However, when the spread is cooled to about -20 ° C, intense green fluorescence was visible.

Examples 15 and 16

For comparative purposes, metal compounds of cinnamic acid and 2-phenylquinoline-4-carboxylic acid with terbium europium, as well as gadolinium europium and gadolinium terbium, were also prepared according to Example 9.

However, none of the obtained compounds showed a color change of fluorescence when irradiated with UV light of 366 or 254 nm when cooled down to -50 ° C.

Claims (18)

Rare earth metal compounds of at least one rare earth metal and 2-hydroxy-quinoline-4-carboxylic acid of the formula (I),

wherein L ¹ , L ² , L ³ , L ⁴ and L ⁵ independently represent a substituent or H, as well as mixtures of these compounds. Rare earth metal compounds and mixtures of these according to claim 1 which comprise at least two different rare earth metals. Rare earth metal compounds and mixtures of these according to claim 1 or 2 which correspond to the general formula (II)

wherein A and B are different rare earth metals from the group europium, terbium, gadolinium, samarium, yttrium, neodium, lanthanum and cerium, C is an alkaline earth metal from the group calcium, strontium and barium, L ¹ , L ² , L ³ , L ⁴ and L ⁵ independently represent a substituent or H, y + y gives a number greater than 0 and less than or equal to 1, and N equals x + y + 2. Rare earth metal compounds and mixtures of these according to claim 3, wherein x is greater than 0 and y is greater than zero. Rare earth metal compounds and mixtures of these according to claim 3 or 4, wherein A and B independently represent a rare earth element selected from the group consisting of europium, terbium, gadolinium and neodymium. Rare earth metal compounds and mixtures of any one of claims 3 to 5 wherein A or B is europium or terbium. Rare earth metal compounds and mixtures of any of claims 3 to 6 wherein L ¹ , L ² , L ³ , L ⁴ and L ^{5 are} independently H, halo, C ₁ -C ₆ alkoxy, C ₁ -C ₆ Alkyl, C ₆ -C ₁₂ aryl, OH, CN, C ₁ -C ₆ alkylamino, CO-C ₁ -C ₆ alkyl or CO-NH ₂ . A process for producing the rare earth metal compounds and mixtures thereof according to any one of claims 1 to 7, wherein at least one rare earth metal salt is reacted with 2-hydroxyquinoline-4-carboxylic acid of the formula (I), optionally in the presence of an alkaline earth metal salt. The method of claim 8, wherein the rare earth metal salt is a rare earth metal halide. Process according to claim 8 or 9, wherein the 2-hydroxyquinoline-4-carboxylic acid (I) is first converted to 2-hydroxy-quinoline-4-carboxylate by reaction with alkaline substances. A method according to claim 10, wherein potassium hydroxide or sodium hydroxide, an ethanolamine or an alkylamine is used as the alkaline substance. Use of the rare earth metal compounds and mixtures of these according to claims 1 to 7 for marking articles by providing the article with the compounds or mixtures thereof. Use according to claim 12, wherein the articles are data carriers or documents. Use according to claim 13, wherein smart cards, check cards or credit cards are used as data carriers. Use according to claim 13, whereby documents, passports, banknotes and documents are used. Use according to any one of claims 12 to 15, wherein the rare earth metal compounds and mixtures of these are used in the form of compositions containing them together with a binder. Use according to claim 16, wherein acrylic polymers, polyamides, polyurethanes, polyesters and polyethylene terephthalates are used as binders. Marked articles containing the rare earth metal compounds or mixtures of any of claims 1 to 7.