Anti-counterfeiting color-changing particles for ceramic ink, anti-counterfeiting ink and preparation method

Abstract

The invention relates to the technical field of printing ink for ceramics, in particular to anti-counterfeiting color-changing particles for ceramic printing ink, anti-counterfeiting printing ink and a preparation method of the anti-counterfeiting printing ink. The anti-counterfeiting color-changing particle for the ceramic ink comprises a clay core layer, a middle layer and a protective shell layer from inside to outside, the middle layer is a SiO2 layer containing amino groups; the outer side face of the middle layer is connected with a plurality of fluorescent quantum dots. The anti-counterfeiting color-changing particle has high temperature resistance and good structural stability, can be applied to ceramics, and has a fluorescent anti-counterfeiting effect when irradiated by ultraviolet rays.

Description

Technical Field

[0001] The invention relates to the technical field of ceramic ink, and in particular to anti-counterfeiting color-changing particles for ceramic ink, anti-counterfeiting ink and a preparation method thereof. Background Art

[0002] Counterfeiting is an endless stream in the field of building ceramics. Building ceramics are an important component of building materials and are widely used in indoor and outdoor floors, walls, decorations, etc. However, counterfeit and shoddy building ceramic products have caused a series of negative impacts on consumers. The quality of counterfeit building ceramic products cannot be guaranteed, and their materials and processes often do not meet standards and specifications, which leads to a decline in the service life and quality of the products, such as cracking, falling off, discoloration, etc., which seriously affect the appearance and use function of the building. In addition, counterfeit and shoddy building ceramic products have potential risks in terms of safety. Because manufacturers often ignore safety testing and quality control, these products may have safety hazards such as radioactive pollution and release of harmful substances, posing a threat to human health. The use of counterfeit and shoddy products will also bring unnecessary economic losses to consumers. Due to its low-cost production and low price, the quality and performance of building ceramics often cannot meet the needs. Consumers may be misled by false propaganda and need additional repairs and replacements after purchasing inferior products, which increases the economic burden. For the problem that counterfeit and shoddy building ceramics cause serious economic losses and negative impacts on consumers and enterprises, the development of new optical anti-counterfeiting technology is an effective way to solve this problem.

[0003] Research based on optical anti-counterfeiting is in a stage of continuous development and innovation. However, conventional optical anti-counterfeiting technologies (such as organic fluorescent inks, watermarks and lasers, etc.) cannot withstand the high temperature of ceramic firing. In addition, the composition and structure of the anti-counterfeiting materials are significantly different from those of ceramic raw materials, making them difficult to integrate into the ceramic system, resulting in poor concealment of anti-counterfeiting labels, low bonding strength with ceramic products and falling off, which essentially makes the anti-counterfeiting labels lose their anti-counterfeiting function. Due to the above reasons, current ceramic anti-counterfeiting is often added to the surface of packaging materials, but there are still anti-counterfeiting loopholes. The best anti-counterfeiting technology is that the anti-counterfeiting material can be directly embedded in the array of ceramic products, and the anti-counterfeiting color-changing material is sintered with the ceramic by means of the high temperature during the ceramic firing process, so as to achieve strong bonding strength and excellent anti-counterfeiting effect.

[0004] Therefore, how to develop a new type of ink that has good integration with ceramic products, is resistant to high temperatures, and has excellent anti-counterfeiting properties has become one of the urgent problems to be solved in this field. Summary of the invention

[0005] In view of the above-mentioned deficiencies in the prior art, the purpose of the present invention is to provide an anti-counterfeiting color-changing particles, anti-counterfeiting ink and a preparation method for ceramic ink, aiming to provide a new type of ink that has good integration with ceramic products, high temperature resistance and excellent anti-counterfeiting performance.

[0006] In order to achieve the above object, the present invention adopts the following technical solutions:

[0007] The first aspect of the present invention provides an anti-counterfeiting color-changing particle for ceramic ink, which includes a clay core layer, an intermediate layer and a protective shell layer from the inside to the outside; the intermediate layer is a SiO2 layer containing amino groups; and the outer side of the intermediate layer is connected to a plurality of fluorescent quantum dots.

[0008] The anti-counterfeiting color-changing particles for ceramic ink, wherein the protective shell layer is a silicon dioxide layer or a titanium dioxide layer.

[0009] The anti-counterfeiting color-changing particles for ceramic ink, wherein the fluorescent quantum dots include at least one of CdTe, CdS, ZnS, PbS, and HgTe.

[0010] The anti-counterfeiting color-changing particles for ceramic ink, wherein the average particle size of the fluorescent quantum dots is 2nm to 20nm, the polydispersity index is 1.01 to 1.15, and the luminescent wavelength is 400nm to 800nm.

[0011] The anti-counterfeiting color-changing particles for ceramic ink, wherein the raw materials for preparing the clay core layer include magnesium aluminum silicate; and the particle size of the clay core layer is 5 μm to 100 μm.

[0012] The second aspect of the present invention provides a method for preparing anti-counterfeiting color-changing particles, which is used to prepare the anti-counterfeiting color-changing particles for ceramic ink as described above, comprising the following steps:

[0013] Using clay particles as cores, the sol-gel method is used to generate an amino-containing SiO2 layer on the surface of the clay particles, thereby obtaining positively charged clay colloid particles.

[0014] The positively charged clay colloidal particles and the fluorescent quantum dots are mixed in proportion;

[0015] The protective shell layer is coated to obtain the anti-counterfeiting color-changing particles for ceramic ink.

[0016] The third aspect of the present invention provides a high temperature resistant anti-counterfeiting ink for ceramics, comprising the following components: the anti-counterfeiting color-changing particles for ceramic ink as described above, a solvent, a conductive agent and a viscosity regulator.

[0017] The high temperature resistant anti-counterfeiting ink for ceramics, wherein the solid content of the high temperature resistant anti-counterfeiting ink for ceramics is 2% to 8%, the viscosity is 20 to 1000 mPa·s, and the conductivity is 10 -4 ~10 3 S / cm.

[0018] The high temperature resistant anti-counterfeiting ink for ceramics, wherein the conductive agent includes one or more of sodium chloride, polyaniline, polycarbazole, polypropylene imidazole, polystyrene sulfonic acid, silver powder, copper powder, aluminum powder, carbon nanotubes, graphene, and tetrabutylammonium hydrochloride.

[0019] A fourth aspect of the present invention provides a method for preparing a ceramic ink, which is used to prepare the high temperature resistant anti-counterfeiting ink for ceramics as described above, comprising the following steps:

[0020] The anti-counterfeiting color-changing particles for ceramic ink, solvent, conductive agent and viscosity regulator as described above are mixed to prepare the high temperature resistant anti-counterfeiting ink for ceramics.

[0021] Beneficial effects: The first aspect of the present invention provides an anti-counterfeiting color-changing particle for ceramic ink, wherein the anti-counterfeiting color-changing particle uses clay particles of ceramic raw materials as a core layer structure, constructs an intermediate layer fixed with fluorescent quantum dots, and finally protects the fluorescent quantum dots through a protective shell layer. The anti-counterfeiting color-changing particle of the present invention is composed of high-temperature resistant inorganic materials, can be deeply integrated with ceramics after high sintering temperature, and shows a pattern under ultraviolet light, thereby achieving an excellent anti-counterfeiting effect.

[0022] The second aspect of the present invention provides a method for preparing anti-counterfeiting color-changing particles. The method first uses a sol-gel method to obtain positively charged clay colloid particles, so that fluorescent quanta are adsorbed on the surface of the clay colloid particles to form an intermediate layer, and finally a protective shell layer is coated. The obtained anti-counterfeiting color-changing particles have a small particle size and high structural stability, and can be well used as the main component of high-temperature resistant anti-counterfeiting ink for ceramics. BRIEF DESCRIPTION OF THE DRAWINGS

[0023] Figure 1 Schematic diagram of the preparation process of anti-counterfeiting color-changing particles for ceramic inks.

[0024] Figure 2 This is a diagram showing the effect of using the high temperature resistant anti-counterfeiting ink for ceramics of Example 1.

[0025] Figure 3 This is a diagram showing the effect of using the high temperature resistant anti-counterfeiting ink for ceramics of Example 2.

[0026] 1-clay core layer, 2-middle layer, 3-protective shell layer, 4-fluorescent quantum dots, 5-anti-counterfeiting color-changing particles. DETAILED DESCRIPTION

[0027] The present invention provides an anti-counterfeiting color-changing particle for ceramic ink, an anti-counterfeiting ink and a preparation method. In order to make the purpose, technical scheme and effect of the present invention clearer and more specific, the present invention is further described in detail with reference to the accompanying drawings and examples. It should be understood that the specific embodiments described herein are only used to explain the present invention and are not used to limit the present invention.

[0028] See also Figure 1 In a first aspect, the present invention provides an anti-counterfeiting color-changing particle for ceramic ink, which includes a clay core layer, an intermediate layer and a protective shell layer from the inside to the outside; the intermediate layer is a SiO2 layer containing amino groups; and the outer side of the intermediate layer is connected to a plurality of fluorescent quantum dots.

[0029] Specifically, the material of the clay core layer can be various common ceramic clay raw materials, such as magnesium aluminum silicate. The surface of the SiO2 layer containing amino groups has a positive charge, and the fluorescent quantum dots with instantaneous ultraviolet light response color change characteristics can be attached to the surface by electrostatic attraction, and the protective shell layer acts as a coating to protect it. The anti-counterfeiting color-changing particles can be further used to form ceramic inks, which can be sprayed on the surface of the ceramic embryo according to a preset pattern (QR code, etc.). After high-temperature sintering, the anti-counterfeiting color-changing particles can be well integrated with the ceramic, without affecting the appearance of the ceramic product, giving the ink / ceramic anti-counterfeiting system ultraviolet light response color change performance and excellent structural fastness, achieving an excellent anti-counterfeiting effect.

[0030] Preferably, the protective shell layer is a silicon dioxide layer or a titanium dioxide layer. The protective shell layer is used to prevent the fluorescent quantum dots from falling off.

[0031] Preferably, the thickness of the protective shell layer is 5 nm to 20 nm.

[0032] Preferably, the fluorescent quantum dots include at least one of CdTe, CdS, ZnS, PbS, and HgTe.

[0033] Preferably, the average particle size of the fluorescent quantum dots is 2 nm to 20 nm, the polydispersity index is 1.01 to 1.15, and the emission wavelength is 400 nm to 800 nm.

[0034] Fluorescent quantum dots can be synthesized by a hydrothermal method. By adjusting the ligand, raw material concentration, type of metal salt, and synthesis temperature, the size and crystal form of the fluorescent quantum dots can be controlled to obtain fluorescent quantum dots of different colors.

[0035] Preferably, the raw material for preparing the clay core layer includes magnesium aluminum silicate.

[0036] The second aspect of the present invention provides a method for preparing anti-counterfeiting color-changing particles, which is used to prepare the anti-counterfeiting color-changing particles for ceramic ink as described above, comprising the following steps:

[0037] S001. Using clay particles as cores, a sol-gel method is used to generate an amino-containing SiO2 layer on the surface of the clay particles to obtain positively charged clay colloid particles;

[0038] Specifically, the particle size of the clay particles is optimally 5 μm to 100 μm, and large particles can be processed into small-sized clay particles by grinding, ball milling or high-speed shearing technology.

[0039] S002. Mixing positively charged clay colloidal particles and fluorescent quantum dots in proportion;

[0040] S003. Coating with a protective shell layer to obtain the anti-counterfeiting color-changing particles for ceramic ink.

[0041] Preferably, the fluorescent quantum dots are negatively charged and can be spontaneously adsorbed on positively charged clay colloid particles by electrostatic force. The optimal charge range of the fluorescent quantum dots is -25mV to -45mV. Correspondingly, the optimal charge range of the clay colloid particles is 20mV to 40mV.

[0042] Preferably, in S002, the mass ratio of the fluorescent quantum dots to the clay colloid particles is 1:20 to 5:20.

[0043] The third aspect of the present invention provides a high temperature resistant anti-counterfeiting ink for ceramics, comprising the following components: the anti-counterfeiting color-changing particles for ceramic ink as described above, a solvent, a conductive agent and a viscosity regulator.

[0044] Preferably, the high temperature resistant anti-counterfeiting ink for ceramics has a solid content of 2% to 8%, a viscosity of 20 to 1000 mPa·s, and a conductivity of 10 -4 ~10 3 S / cm.

[0045] Preferably, the solvent includes but is not limited to ethanol, acetone, tetrahydrofuran, and ethylene glycol.

[0046] Preferably, the volume of ethylene glycol accounts for 5% to 20% of the volume of the solvent.

[0047] Preferably, the conductive agent includes, but is not limited to, one or more of sodium chloride, polyaniline, polycarbazole, polypropylene imidazole, polystyrene sulfonic acid, silver powder, copper powder, aluminum powder, carbon nanotubes, graphene, and tetrabutylammonium hydrochloride.

[0048] Preferably, the amount of the conductive agent used accounts for 0.05% to 0.1% of the total mass of the high temperature resistant anti-counterfeiting ink for ceramics.

[0049] Preferably, the viscosity modifier includes, but is not limited to, one or more of polyacrylates, polyamides, polymer colloids, gelling agents, polyacrylamide and polyesters.

[0050] Preferably, the amount of the viscosity regulator is 0.5% to 2% of the total mass of the high temperature resistant anti-counterfeiting ink for ceramics.

[0051] A fourth aspect of the present invention provides a method for preparing a ceramic ink, which is used to prepare the high temperature resistant anti-counterfeiting ink for ceramics as described above, comprising the following steps:

[0052] The anti-counterfeiting color-changing particles for ceramic ink, solvent, conductive agent and viscosity regulator as described above are mixed to prepare the high temperature resistant anti-counterfeiting ink for ceramics.

[0053] The present invention is further described below with reference to specific examples.

[0054] Example 1

[0055] A high temperature resistant anti-counterfeiting ink for ceramics, the preparation method of which comprises the following steps:

[0056] Step (1): clay raw material from a mine in Kunming is selected, and the clay particles are ground to 5 μm by using spheroidal graphite technology for 24 hours to obtain clay particles. The sol-gel method is used to hydrolyze and condense ethyl orthosilicate in a mixed solution of water and ethanol using the catalytic effect of ammonia water to generate SiO2, and then 3-aminopropyltriethoxysilane (APS) is used to hydrolyze and condense the silanol groups on the surface of SiO2 to introduce amino groups (-NH2) to obtain clay colloidal particles (clay@SiO2-NH2) with the surface modified by SiO2-NH2. The surface amino groups are protonated in a weakly acidic solution to make them carry a positive charge with a potential of 35 mV.

[0057] Step (2): adopting a hydrothermal method, using CdCl2 as a Cd source and mercaptopropionic acid as a ligand, the two are prepared into a mixed solution in a certain molar ratio, and the pH of the solution is adjusted to 9, and an appropriate amount of NaHTe solution obtained by reacting Te powder and NaBH4 solution is quickly added under N2 protection, and the solution is transferred to a hydrothermal reactor, and reacted at 185°C to generate CdTe fluorescent quantum dots; the particle size of the obtained CdTe fluorescent quantum dots is 10nm, the surface potential of the CdTe fluorescent quantum dots is -25mV, and the peak of its fluorescence emission spectrum is 600nm;

[0058] Step (3): In a weakly acidic environment of pH = 5, clay colloid particles and fluorescent quantum dots are mixed at a mass ratio of 10:1, and the fluorescent quantum dots are spontaneously adsorbed onto the surface of the clay colloid particles;

[0059] Further coating the outer side to form a protective shell layer, wherein the protective shell layer is a SiO2 shell layer structure with a thickness of about 5nm, to obtain anti-counterfeiting color-changing particles;

[0060] Step (4): mixing the anti-counterfeiting color-changing particles, the solvent, the conductive agent and the viscosity modifier to obtain the high temperature resistant anti-counterfeiting ink for ceramics;

[0061] The high temperature resistant anti-counterfeiting ink for ceramics comprises the following components in parts by mass: 60 parts of ethanol, 20 parts of acetone, 10 parts of tetrahydrofuran, 5 parts of ethylene glycol, 5 parts of anti-counterfeiting color-changing particles, 0.05 parts of conductive agent tetrabutylammonium hydrochloride, and 0.5 parts of polymethyl methacrylate.

[0062] The viscosity of the high temperature resistant anti-counterfeiting ink for ceramics is 50mPa·s and the conductivity is 5×10 -4 S / cm.

[0063] Figure 2 This is a diagram showing the effect of using the high temperature resistant anti-counterfeiting ink for ceramics of Example 1. It can be seen that under ultraviolet light, the anti-counterfeiting ink on the ceramic produces a clear fluorescent pattern.

[0064] Example 2

[0065] A high temperature resistant anti-counterfeiting ink for ceramics, the preparation method of which comprises the following steps:

[0066] Step (1): clay raw material from a mine in Guangxi is selected, and the clay particles are ground to 20 μm by hydraulic grinding technology for 12 hours to obtain clay particles. The KH580 aqueous aminosilane coupling agent is hydrolyzed and condensed in a mixed solution of water and ethanol by the catalytic effect of ammonia water to generate an amino-containing SiO2 shell layer, thereby obtaining modified clay colloid particles (clay@SiO2-NH2) whose surface is modified by SiO2-NH2. The surface amino groups are protonated in a weakly acidic solution to make them carry a positive charge with a potential of 40 mV.

[0067] Step (2): using a hydrothermal method, ZnSO4 is used as a Zn source, and citric acid is used as a ligand. The two are prepared into a mixed solution in a certain molar ratio, and the pH of the solution is adjusted to 10. Under the protection of N2, an appropriate amount of Na2S aqueous solution is quickly added, and the mixture is transferred to a hydrothermal reactor to react at 185°C to generate ZnS fluorescent quantum dots; the particle size of the obtained ZnS fluorescent quantum dots is 15nm, the surface potential of the fluorescent quantum dots is -30mV, and the peak of its fluorescence emission spectrum is at 400nm;

[0068] Step (3): In a weakly acidic environment of pH = 4, clay colloid particles and fluorescent quantum dots are mixed at a mass ratio of 20:1, and the quantum dots are spontaneously adsorbed onto the surface of the clay colloid particles;

[0069] Further coating the outer side to form a protective shell layer, wherein the protective shell layer is a SiO2 shell structure (sol-gel method can be used) with a thickness of about 10 nm, to obtain anti-counterfeiting color-changing particles;

[0070] Step (4): mixing the anti-counterfeiting color-changing particles, the solvent, the conductive agent and the viscosity modifier to obtain the high temperature resistant anti-counterfeiting ink for ceramics;

[0071] The high temperature resistant anti-counterfeiting ink for ceramics comprises the following components by mass: 70 parts of ethanol, 15 parts of acetone, 5 parts of tetrahydrofuran, 5 parts of ethylene glycol, 5 parts of anti-counterfeiting color-changing particles, 0.05 parts of conductive agent tetrabutylammonium hydrochloride, and 0.5 parts of polymethyl methacrylate.

[0072] The viscosity of the high temperature resistant anti-counterfeiting ink for ceramics is 500mPa·s and the conductivity is 20×10 -4 S / cm.

[0073] Figure 3 This is a diagram showing the effect of using the high temperature resistant anti-counterfeiting ink for ceramics of Example 2. It can be seen that under ultraviolet light, the anti-counterfeiting ink on the ceramic produces a clear fluorescent pattern.

[0074] Example 3

[0075] A high temperature resistant anti-counterfeiting ink for ceramics, the preparation method of which comprises the following steps:

[0076] Step (1): using clay raw material from a mine in Guangdong, grinding clay particles to 3 μm by ball milling technology for 36 hours, obtaining clay particles by sol-gel method, and hydrolyzing and condensing 3-aminopropyltrimethoxysilane in a mixed solution of water and ethanol by the catalytic effect of ammonia water to generate SiO2 with amino groups on the surface, thereby obtaining clay colloidal particles (clay@SiO2-NH2) with the surface modified by SiO2-NH2, wherein the amino groups on the surface are protonated in a weakly acidic solution to make them carry a positive charge with a potential of 39 mV;

[0077] Step (2): using a hot injection method, a mercury source (such as mercuric acetylacetonate) and a tellurium source (such as trimethyl telluride) are rapidly mixed in a high-temperature organic solvent (such as trioctylphosphine oxide or oleylamine) to obtain HgTe fluorescent quantum dots; the size and shape of the quantum dots can be controlled by controlling the temperature and reaction time; the size of the obtained HgTe fluorescent quantum dots is 15 nm, the surface potential of the quantum dots is -28 mV, and the peak of its fluorescence emission spectrum is at 600 nm;

[0078] Step (3): In a weakly alkaline environment of pH = 8, clay colloid particles and fluorescent quantum dots are mixed at a mass ratio of 15:1, and the fluorescent quantum dots are spontaneously adsorbed onto the surface of the clay colloid particles;

[0079] Further, a protective shell layer is formed on the outside, wherein the protective shell layer is a SiO2 shell layer structure with a thickness of about 5 nm, to obtain an anti-counterfeiting color-changing unit;

[0080] Step (4): mixing the anti-counterfeiting color-changing particles, the solvent, the conductive agent and the viscosity modifier to obtain the high temperature resistant anti-counterfeiting ink for ceramics;

[0081] The high temperature resistant anti-counterfeiting ink for ceramics comprises the following components by mass: 70 parts of ethanol, 15 parts of acetone, 10 parts of tetrahydrofuran, 5 parts of ethylene glycol, 3 parts of anti-counterfeiting color-changing particles, 0.05 parts of conductive agent tetrabutylammonium hydrochloride, and 0.5 parts of polymethyl methacrylate.

[0082] The viscosity of the high temperature resistant anti-counterfeiting ink for ceramics is 65mPa·s and the conductivity is 6.5×10 -4 S / cm.

[0083] It is understandable that those skilled in the art can make equivalent substitutions or changes based on the technical solution and inventive concept of the present invention, and all these changes or substitutions should fall within the protection scope of the claims attached to the present invention.

Claims

1. An anti-counterfeiting color-changing particle for ceramic ink, characterized in that: From the inside to the outside, it includes a clay core layer, an intermediate layer and a protective shell layer; the intermediate layer is a SiO2 layer containing amino groups; and the outer side of the intermediate layer is connected to a plurality of fluorescent quantum dots.

2. The anti-counterfeiting color-changing particles for ceramic ink according to claim 1, characterized in that: The protective shell layer is a silicon dioxide layer or a titanium dioxide layer.

3. The anti-counterfeiting color-changing particles for ceramic ink according to claim 1, characterized in that: The fluorescent quantum dots include at least one of CdTe, CdS, ZnS, PbS, and HgTe.

4. The anti-counterfeiting color-changing particles for ceramic ink according to claim 1, characterized in that: The average particle size of the fluorescent quantum dots is 2nm to 20nm, the polydispersity index is 1.01 to 1.15, and the luminescent wavelength is 400nm to 800nm.

5. The anti-counterfeiting color-changing particles for ceramic ink according to claim 1, characterized in that: The raw materials for preparing the clay core layer include magnesium aluminum silicate; the particle size of the clay core layer is 5 μm to 100 μm.

6. A method for preparing anti-counterfeiting color-changing particles, used for preparing the anti-counterfeiting color-changing particles for ceramic ink as claimed in any one of claims 1 to 5, characterized in that: The steps include: Using clay particles as cores, the sol-gel method is used to generate an amino-containing SiO2 layer on the surface of the clay particles, thereby obtaining positively charged clay colloid particles. The positively charged clay colloidal particles and the fluorescent quantum dots are mixed in proportion; The protective shell layer is coated to obtain the anti-counterfeiting color-changing particles for ceramic ink.

7. A high temperature resistant anti-counterfeiting ink for ceramics, characterized in that: The invention comprises the following components: the anti-counterfeiting color-changing particles for ceramic ink as described in any one of claims 1 to 5, a solvent, a conductive agent and a viscosity regulator.

8. The high temperature resistant anti-counterfeiting ink for ceramics according to claim 7, characterized in that: The high temperature resistant anti-counterfeiting ink for ceramics has a solid content of 2% to 8%, a viscosity of 20 to 1000 mPa·s, and a conductivity of 10 -4 ~10 3 S / cm.

9. The high temperature resistant anti-counterfeiting ink for ceramics according to claim 7, characterized in that: The conductive agent includes one or more of sodium chloride, polyaniline, polycarbazole, polypropylene imidazole, polystyrene sulfonic acid, silver powder, copper powder, aluminum powder, carbon nanotubes, graphene, and tetrabutylammonium hydrochloride.

10. A method for preparing ceramic ink, characterized in that: The method for preparing the high temperature resistant anti-counterfeiting ink for ceramics as claimed in any one of claims 7 to 9 comprises the following steps: The anti-counterfeiting color-changing particles for ceramic ink as described in any one of claims 1 to 5, a solvent, a conductive agent and a viscosity regulator are mixed to obtain the high-temperature resistant anti-counterfeiting ink for ceramics.

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