EP3377593A1 - Material with marker for authentication and sorting of the material - Google Patents

Abstract

The invention relates to a process for producing a modified luminophore, comprising the steps of: a) providing a luminophore, preferably selected from the group consisting of upconversion materials and/or downconversion materials, more preferably upconversion materials; and b) heating the luminophore within a temperature range of 50-2000°C, and/or irradiating the luminophore with high-energy radiation, preferably β radiation and/or γ radiation, for a period of 1-60 minutes, preferably 1-10 minutes, and/or irradiating the luminophore with microwave radiation for a period of 1-60 minutes, preferably 1-10 minutes, and/or altering the size and/or shape of the luminophore, in order to obtain the modified luminophore, and to the modified luminophores thus obtained and to the use of luminophores for simultaneous authentication and sorting of materials present in a mixture.

Description

Material with markers for Authentifi * i * r ^p ng and sorting of the material

The present application relates to a process for the preparation of modified phosphors, the modified phosphors thus obtained and the use of the phosphors for the simultaneous authentication and sorting of materials contained in a mixture.

Methods are known from the prior art to mark materials and thus products homogeneously in order to authenticate them. For example, German application DE 102008 060 675 A1 describes ceramic particles into which specific chemical elements are introduced as marking elements. The ceramic particles can be introduced homogeneously into other materials, in particular plastics. The markers are then detected by chemical analysis of the labeled material. If, for example, X-ray fluorescence spectroscopy is used for this purpose, the authentication of the material and thus of the product can be carried out non-destructively. Disadvantages of this method are the comparatively high cost of detection with X-ray fluorescence spectroscopy.

On the other hand, European patent EP 1 566 837 B1 discloses another method based on fluorescent markers homogeneously mixed into materials to be marked.

For authentication, the fluorescence of the markers is generated and detected. Both spectral and dynamic properties of the fluorescence can be measured here.

The prior art also discloses methods for marking materials so that they can be recognized and sorted in sorting and separation processes. The patent US 8,205,813 B2 describes, for example, that materials of a particular class, in particular plastics, can be specifically marked by fluorescent materials. In this case, in particular, certain emission lines are assigned to the fluorescence of a specific class of materials, products from the marked material and also comminuted Fragments of the marked material can then be detected (detected) by being excited to fluorescence in the sorting process by a radiation source and the fluorescence subsequently evaluated spectrally.

In practice, however, there are several problems. On the one hand, with UV phosphors the excitation sources are relatively expensive. Further excite other components of the materials, so that sometimes unfavorable signal-to-noise ratios result. In this situation, then the concentration of the markers must be increased, which leads to considerable costs

For both applications, authentication and sorting, there is an increasing, permanent need. The structural and global problem of piracy reinforces the interest of many OEMs to mark their products directly, robustly and securely, for example, to defend themselves against unauthorized warranty claims. Likewise, the interest in sustainable sorting and recycling solutions is increasing. Plastic packaging, for example, contributes significantly to the increase in waste generation and is hardly recycled today, because it can not be separated from the waste streams in a pure sort of way.

With respect to the implementation of the illustrated markers discussed above, there are two major disadvantages of the prior art. First, from a technical point of view, the concentrations of the markers should remain as small as possible in order not to change the material properties of the marked material. On the other hand, the marker materials are foreign substances that have to meet the various approval conditions, in particular for food packaging. For this it is important that the foreign substances are present in as low a concentration as possible. A second disadvantage, of course, is the additional cost of the marker materials.

In summary, therefore, the task can also be formulated as follows.

It is the object of the present invention to provide phosphors which overcome the disadvantages of the prior art, in particular to provide phosphors which have an afterglow time, or changed decay behavior, as compared to corresponding phosphors of the prior art. It is likewise the object of the invention To provide a method with which a variety of modified phosphors, each differing in their Nachleuchtzeit, or in their Abklingverhalten, can be provided.

The solution to this problem arises from the subject matter of the independent claims. Preferred AusfOhrungsfonnen result from the dependent claims.

The terms phosphor and markers in the context of the present application, unless otherwise stated, are to be understood as synonymous.

The _phosphors and markers may be selected from the group of fluorescent materials and / or phosphorescent materials and / or Upconvertern and / or down converters and / or materials that re-emit an excitation wavelength upon excitation. Luminescence is the emission of electromagnetic radiation after the entry of energy. It is preferred that the energy input takes place via photons, the observed luminescence is thus photoluminescence. The photoluminescence can occur in the UV and / or VIS and / or IR. Upconverters are luminescent substances which, upon excitation, emit photons whose wavelength is shorter than the wavelength of the excitation photons. Downconverters are luminescent substances which, upon excitation, emit photons whose wavelength is longer than the wavelength of the excitation photons. In the following, the terms fluorescence and luminescence are used interchangeably.

Phosphors which can be modified by means of the method according to the invention are known from the prior art, in particular DE10201410S846A1, EP 1556837 Bl and US Pat. No. 8,205,813 B2. The content of these publications is therefore to be incorporated herein by reference to the publications the relevant content is deemed to be the disclosure content of the present application. The same applies to the phenomena of afterglow, or the decay behavior.

The present invention overcomes disadvantages of the prior art by producing and using fluorescent markers, ie modified phosphors within the meaning of the present application, at the same time providing both the basis for the efficient authentication of many different products as well as an efficient comprehensive sorting of various materials that are present in a mixture, for example.

First of all, it has surprisingly been found that certain properties of the fluorescence, in particular dynamic properties such as the fading constant well known to the person skilled in the art, of many inorganic phosphors, in particular so-called upconversion materials or anti-Stokes crystals, changes after their (primary) production by annealing processes, i. can be modified according to the invention.

It has also been found that also the color or spectral composition of the fluorescence emission of inorganic phosphors is changed by annealing processes, i. can be modified according to the invention.

In the above-mentioned annealing processes, the phosphors after their primary production again in a temperature range of SO - 2000 ° C, 700-1700 ° C, 700 - 1300 ° C or 900-1100 ° C for a period of 1 minute to 24 hours, 1 Minute to 18 hours, 1 minute to 14 hours, 1 minute to 10 hours, 1 minute to 4 hours, 1-120 minutes, preferably 1 -60 minutes, and most preferably heated 1-10 minutes

The annealing processes can take place, for example, in a chamber furnace, continuous furnace or rotary kiln. The annealing process can be carried out continuously or discontinuously.

After the primary production of the phosphors, their properties can also be changed by changing the particle size and / or by changing the particle shape and / or by irradiating the phosphor with high-energy radiation, preferably β-radiation and / or γ-radiation, for a period of 1 -60 minutes, preferably 1-10 minutes, and / or by irradiating the phosphor with microwave radiation for a period of 1-60 minutes, preferably 1-10 minutes.

The change in particle sizes can be achieved by adjusting the phosphors produced by primary production. This can be done by mortars by hand or by technical Mills or Mörecreixirichtungeen done. Subsequently, the ground material can be separated by sieving into fractions of different particle size. These fractions can

From a single phosphor (of the prior art) so numerous variants, ie chemically and / or physically modified modifications can be derived.

Another modifiable feature is the attack behavior. This is understood to mean the excitability of the phosphor for fluorescence emission as a function of the excitation regime. The excitation regime describes the type of excitation of the phosphors. It is described by the spectral composition of the excitation radiation, the intensity of the excitation radiation and the timing of the excitation.

Surprisingly, it has been found, secondly, that the phosphors, in particular the upconversion materials, can be processed in such a way that the intensity of their fluorescence or the intensity of the fluorescence emissions depend very strongly on the correct excitation wavelength. In other words, to generate the maximum fluorescence, it is necessary to excite with an optimal excitation wavelength. Of course, the optimal excitation wavelength depends on the chemical and physical structure of the respective marker and can be determined by the skilled person on the basis of known routine examinations easily and without significant effort. If the excitation wavelength differs by only a few nanometers (about 5 μm) from the optimum excitation wavelength, then the observed intensity corresponds to only a maximum of half the maximum intensity.

Conversely, such fluorescent phosphors allow a particularly efficient use of semiconductor laser diodes for excitation of fluorescence.

The intensity of the excitation radiation may be 0.01-1 W / mm ² , preferably 0, lW / m ² - 0.5 W / mm ² . The timing of the excitation can be in a continuous stimulus or a Excitation with pulses exist. A pulsed excitation can be described by the number of pulses, the duration of the excitation pulses and the duration of the pauses without excitation between the excitation pulses. With multiple excitation, the number of pulses is advantageously 2-10, preferably 2-5. The duration of the excitation is lus-lOOms, 1μ8-5πΐ8, 10us-lms, more preferably 20u5-500us. The duration of excitation can also be in the femtosecond range when using femtosecond lasers.

Processing processes after primary production can modify the mentioned parameters decay constant, spectral composition of fluorescence emission and annealing behavior independently or in combination.

The described processing processes can also be carried out in the context of the primary production of the phosphors. Thus, a phosphor with a defined chemical composition can be annealed already at its primary production at different temperatures and / or for different lengths of time to produce LeuchtstofrVarianten.

To excite the luminescence narrow-band sources, such as lasers, laser diodes, lichtemim ^'erende diodes can broadband and / or (LEDs), xenon lamps, halogen lamps, individually or in combination. The excitation sources can be activated individually or activated simultaneously or sequentially in different combinations. In the excitation devices optical filters such as Ipasspass / Shortpass / Bandpass filters can be used. Furthermore, a variation of the opening width of the excitation sources can be provided in order to modulate the size of an excitation zone through which material to be identified is transported. The excitation zone can also be modulated by arranging a plurality of excitation sources sequentially one behind the other and varying the number of activated excitation sources in this arrangement.

For detecting the fluorescence properties, various detectors such as black-and-white cameras, color cameras, photomultipliers, spectrometers, photocells, photodiodes, phototransistors can be used alone or in combination. In the detection devices, optical filters such as longpass / shortpass / bandpass filters be used. The measuring devices can be designed in stationary or mobile form. They can be integrated in a sorting system or be available as a separate device.

It is preferred that very powerful semiconductor laser diodes are used to excite and measure the fluorescence spectra.

Following these discoveries, the following methods solve the problem described above, which is to be defined by way of example as follows in order to better explain the invention:

There are 10 different materials to be differentiated in sorting processes. In addition, there should be 100 different manufacturers who ^{* market} the 10 different materials and according to which the products should be authenticated.

1st option:

There are 10 different groups of phosphors, each of which can be excited to fluoresce at a different optimal excitation wavelength. No phosphor lights noticeably at one of the other excitation wavelengths than at its optimal wavelength. This means that at excitation wavelengths which deviate by 5 nm from the optimum excitation wavelength, the intensity of the fluorescence emission is at most 50% of the maximum fluorescence emission achievable at the optimum excitation wavelength.

To sort the material types, the excitation wave length is used as a sorting criterion. In this respect, it is a sorting process with 10 sorting stages. In each sorting stage, the sorting material with a different wavelength is excited to fluoresce, preferably by a stationary semiconductor laser optics. For each of the 10 materials then applies that each optimally 100% of the marker excited and used to generate the signal. Luminous pieces of material are detected and separated against all other pieces of dark remaining material. In addition to the sorting of a type of material to allow the authentication of the various manufacturers of this type of material, variants of the phosphors used for this type of material are used in identical material types from different manufacturers. These may be made by the process methods described in this disclosure.

For the referencing of the variants of the phosphor, dynamic and spectral properties of the fluorescence emission are used, which differ in the variants, although they can be excited to fluorescence emission at the same optimal excitation wavelength.

For the production of .noch more variants mixtures of variants of the phosphor can be used in the material type, which results in dynamic and spectral Flucszenzmissionsigenschaften characterized by superposition of the dynamic and spectral fluorescence emission properties of the individual variants, which are characteristic of the variant mixture.

The authentication of the different manufacturers of a type of material can be used to sort the type of material by manufacturer in further sorting stages.

2nd option:

For sorting a variety of materials, phosphors with different emission lines and decay constants are used, but they can all be excited with the same optimal excitation wavelength. In order to differentiate materials in sorting processes, different individual phosphors or mixtures of phosphors are used in the individual material grades, so that the phosphor or the mixtures of phosphors emit for the recognition of a particular material in certain wavelength windows with intensities which are in a fixed ratio , As in option 1, each material optimally uses 100% of the fluorescence markers in the sorting process to generate the signal. The detection of the material takes place in that the fluorescence is recorded differentiated after the wavelength windows. In this respect, a uniform sorting machine with a Excitation wavelength can be used. The differentiation takes over one or more cameras or one or more spectrometers. As in the first option, the dynamic and spectral properties of the phosphor or the mixture of phosphors are measured for authentication.

The methods described in options 1 and 2 in an exemplary form can also represent in their general teaching a teaching according to the invention for achieving the object of the present invention.

Likewise, the features of the invention described in the invention in different combinations may contribute to the advantageous embodiment of the invention.

Example 1:

A phosphor based on gadolinium oxysulfide doped with erbium and ytterbium annealed for 60 minutes at 1650 ° C. This achieves a change in the emission wavelength with maximum intensity of emission (λ max):

Example 2:

A phosphor based on gadolinium oxide doped with ytterbium would be ground by hand in a porcelain crucible and then screened through a sieve of mesh size 45 μm. This results in a change in the decay constant

Claims

Ansprüiche A process for producing a modified phosphor, comprising the steps of: (a) providing a phosphor, preferably selected from the group consisting of upoonversion materials and / or downconversion materials, more preferably upconversion materials; and (B) heating the phosphor in a temperature range of SO - 20O0 ° C and / or irradiating the phosphor with high-energy radiation, preferably β-radiation and / or γ-radiation, for a period of 1-60 minutes, preferably 1-10 minutes and / or irradiating the phosphor with microwave radiation for a period of 1-60 minutes, preferably 1-10 minutes, and / or changing the size and / or shape of the phosphor to obtain the modified phosphor. A process according to claim 1, wherein the temperature range is from 700 to 1300 ° C, preferably from 900 to 1100 ° C. 3. The method of claim 1 or 2, wherein the heating is carried out for a period of 5 minutes to 24 hours, preferably 5 minutes to 2 hours. 4. The method according to any one of the preceding claims, wherein the heating is carried out under an air atmosphere 5. The method according to any one of the preceding claims, wherein the heating is carried out stepwise. 6. The method according to any one of the preceding claims, wherein the heating is carried out in a continuous furnace. A process according to any one of the preceding claims, wherein the heating is carried out batchwise. 8. The method according to any one of claims 1 to 6, wherein the heating is carried out continuously. 9. The method according to any one of the preceding claims, wherein the heating is carried out in a rotary kiln. 10. A modified phosphor obtainable by a process according to any one of claims 1 to 9. 11. Use of a phosphor and / or a modified phosphor according to claim 10 for authenticating a material comprising at least one phosphor and / or a modified phosphor, and / or sorting a mixture of materials, wherein at least one of the materials contained in the mixture is included, a phosphor and / or a modified phosphor comprises; and in the case that more than one of the materials of the mixture comprises a phosphor and / or a modified phosphor, the respective phosphors and / or the modified phosphors in the respective materials are different from each other. 12. Use according to claim 11, wherein the spectral and / or dynamic properties of the fluorescence are measured for authentication and sorting. 13. Use according to one of claims 11 or 12, wherein for the authentication and sorting the fluorescence of at least one of the phosphors and / or the modified phosphors is excited. 14. Use according to any one of claims 11 to 13, wherein for the sorting the relative intensity of specific emission lines of the phosphor and / or the modified phosphor and for the authentication of the dynamic properties of the phosphor and / or the modified phosphor are used. 15. The method according to any one of claims 11 to 14, wherein the material containing the phosphors and / or the modified phosphors, and preferably at least one of widely contained in the mixture before being authenticated and sorted.