Infrared absorbing substance, preparation method thereof and ink

Abstract

The invention provides an infrared absorption substance, a preparation method thereof and ink. The preparation method of the infrared absorption substance comprises the following steps: preparing a first solution, a second solution and a third solution, mixing the first solution, the second solution and the third solution to obtain a mixed solution, and standing the mixed solution according to a preset standing duration; the first solution contains copper phosphate, the second solution contains sodium tungstate dihydrate, and the third solution contains cesium carbonate and citric acid; synthesizing the mixed solution by using a hydrothermal synthesis method to obtain a solid-liquid mixture; and carrying out water washing, alcohol washing, centrifugal separation and drying on the solid-liquid mixture to generate an infrared absorption substance, so that the infrared absorption substance has an infrared absorption rate of 85% or above at the infrared band of 850-1250 nm.

Description

[0001] This application is a divisional application of Chinese patent application No. 202310343109.4, filed on March 31, 2023, entitled "Infrared Absorbing Material and Preparation Method Thereof and Ink", the entire contents of which are incorporated herein by reference. Technical Field

[0002] This invention relates to the field of anti-counterfeiting printing technology, and more specifically, to a method for preparing an infrared absorbing material, an infrared absorbing material, and an ink. Background Technology

[0003] In related technologies, dark pigments such as carbon black, phthalocyanine blue, and organic phthalocyanine dyes are used to make inks produce infrared absorption effects. However, adding dark pigments to light-colored inks will cause changes in the ink color, which will significantly increase the color difference between the infrared absorbing ink and the matching infrared non-absorbing ink, reducing the concealment of infrared pairing anti-counterfeiting technology. Summary of the Invention

[0004] The present invention aims to at least solve the technical problems existing in the prior art or related art.

[0005] Therefore, a first aspect of the present invention provides a method for preparing an infrared absorbing material.

[0006] A second aspect of the present invention also provides an infrared absorbing material.

[0007] A third aspect of the invention also provides an ink.

[0008] In view of the above, a first aspect of the present invention provides a method for preparing an infrared absorbing material, comprising: preparing a first solution, a second solution, and a third solution, and mixing the first solution, the second solution, and the third solution to obtain a mixed liquid, and allowing the mixed liquid to stand for a preset standing time; the first solution contains copper phosphate, the second solution contains sodium tungstate dihydrate, and the third solution contains cesium carbonate and citric acid; synthesizing the mixed liquid using a hydrothermal synthesis method to obtain a solid-liquid mixture; and washing the solid-liquid mixture with water, washing with alcohol, centrifuging, and drying to generate an infrared absorbing material.

[0009] The method for preparing the infrared absorbing material provided by this invention specifically comprises the following steps: First, a first solution, a second solution, and a third solution are prepared. The first solution contains copper phosphate, forming a copper phosphate dispersion solution; the second solution contains sodium tungstate dihydrate, forming a sodium tungstate solution; and the third solution contains cesium carbonate and citric acid, forming a mixture of cesium carbonate and citric acid solutions. Further, the first, second, and third solutions are mixed and stirred until homogeneous to obtain a mixed solution, which is then allowed to stand. The prepared mixed solution is subjected to a hydrothermal reaction using a hydrothermal synthesis process to obtain a solid-liquid mixture. The obtained solid-liquid mixture is then washed with water, washed with alcohol, centrifuged, and dried to generate the infrared absorbing material.

[0010] The present invention provides a method for preparing infrared absorbing materials using copper phosphate, sodium tungstate dihydrate, and cesium carbonate as chemical raw materials. A hydrothermal synthesis process is employed in an acidic citric acid solution to obtain a light-colored composite inorganic infrared absorbing powder with high absorbency. Because copper phosphate is light in color, using it as a chemical raw material can produce a light-colored infrared absorbing material, overcoming the shortcomings of using dark pigments such as carbon black as infrared absorbing materials in existing technologies. However, copper phosphate exhibits weak spectral absorption in the 850nm-1250nm infrared band, failing to achieve a high infrared absorption rate. Therefore, based on the preparation of infrared absorbing materials using copper phosphate as a chemical raw material, sodium tungstate dihydrate and cesium carbonate are added as chemical raw materials. Through a hydrothermal synthesis process, the final infrared absorbing material comprises cesium tungsten bronze and copper carbonate, with the cesium tungsten bronze coating the surface of the copper carbonate. Because cesium tungsten bronze has strong absorption in the 850nm-1250nm infrared band, but its color is dark, a hydrothermal synthesis process using copper phosphate, sodium tungstate dihydrate, and cesium carbonate as chemical raw materials in an acidic citric acid solution can coat a small amount of cesium tungsten bronze onto the surface of copper carbonate. This results in a composite infrared absorbing powder that retains a light color while exhibiting excellent infrared absorption performance, thus enabling the infrared absorbing material to have an infrared absorption rate of over 85% in the 850nm-1250nm infrared band.

[0011] The method for preparing the infrared absorbing material according to the present invention may further include the following additional technical features:

[0012] In the above technical solution, the steps for preparing the first solution, the second solution, and the third solution specifically include: adding a second preset amount of deionized water to a first preset amount of copper phosphate salt, stirring and dispersing at a first preset temperature to obtain the first solution; adding a fourth preset amount of deionized water to a third preset amount of sodium tungstate dihydrate, stirring and dissolving to obtain the second solution; and adding a seventh preset amount of deionized water to a fifth preset amount of cesium carbonate and a sixth preset amount of citric acid, stirring and dissolving to obtain the third solution.

[0013] In this technical solution, a single copper phosphate salt is dispersed in deionized water to form a copper phosphate salt dispersion solution, i.e., the first solution. Subsequently, sodium tungstate dihydrate is added to deionized water and stirred to obtain a sodium tungstate solution, i.e., the second solution. Then, cesium carbonate and citric acid are added to deionized water and stirred to react and dissolve, yielding a mixture of cesium carbonate and citric acid solutions, i.e., the third solution.

[0014] It should be noted that the specific values ​​of the first preset amount of copper phosphate, the third preset amount of sodium tungstate dihydrate, the fifth preset amount of cesium carbonate, the sixth preset amount of citric acid, and the corresponding preset amount of deionized water added to each raw material can be selected according to the actual situation and are not limited here. The preset standing time can be between 20 min and 25 min.

[0015] In any of the above technical solutions, the infrared absorbing material specifically includes: the infrared absorbing material includes cesium tungsten bronze nanoparticles and copper phosphate, wherein the cesium tungsten bronze nanoparticles are coated on the surface of the copper phosphate; the infrared absorbing material contains 25% to 42% copper, 12% to 21% phosphorus, 0.1% to 7% cesium and 0.5% to 27% tungsten by mass percentage.

[0016] In this technical solution, the final infrared absorbing material includes cesium tungsten bronze and copper carbonate salt, with the cesium tungsten bronze coating the surface of the copper carbonate salt. Furthermore, energy dispersive spectroscopy (EDS) analysis shows that the chemical composition of the infrared absorbing material, converted to mass percentages, is 25% to 42% copper, 12% to 21% phosphorus, 0.1% to 7% cesium, and 0.5% to 27% tungsten, which meets the requirement of this invention to have an average reflectivity of less than 15% in the wide near-infrared range of 850nm-1250nm.

[0017] In any of the above technical solutions, the synthesis conditions for the hydrothermal synthesis method are: the synthesis temperature is between 160℃ and 240℃, and the synthesis time is between 3 days and 5 days.

[0018] In this technical solution, the synthesis temperature of hydrothermal synthesis is limited to between 160℃ and 240℃, and the synthesis time is limited to between 3 and 5 days, in order to ensure the synthesis effect of hydrothermal synthesis.

[0019] In any of the above technical solutions, the centrifugal rotation speed is between 3000 rpm and 5000 rpm, and the centrifugal separation time is between 30 minutes and 60 minutes; the drying conditions are: the drying temperature is between 60℃ and 80℃, and the drying time is between 6 hours and 12 hours.

[0020] In this technical solution, when centrifuging a solid-liquid mixture, the centrifugal speed is limited to between 3000 rpm and 5000 rpm, and the centrifugal time is limited to between 30 minutes and 60 minutes to ensure the separation effect of the solid-liquid mixture. Specifically, the centrifugal speed can be 3000 rpm, 3500 rpm, 5000 rpm, etc., and the centrifugal time can be 30 minutes, 50 minutes, 60 minutes, etc.

[0021] Furthermore, the drying temperature for drying the solid-liquid mixture is limited to between 60℃ and 80℃, and the drying time is limited to between 6 hours and 12 hours, to ensure that the moisture content of the generated composite infrared absorbing powder is reduced to the minimum.

[0022] In any of the above technical solutions, before synthesizing the mixture using a hydrothermal synthesis method to obtain a solid-liquid mixture, the method for preparing the infrared absorbing material further includes: introducing the mixture into a container, wherein the inner lining of the container is made of polytetrafluoroethylene.

[0023] In this technical solution, the mixture is introduced into a container, and the inner material of the container is polytetrafluoroethylene (PTFE). PTFE has the characteristics of heat resistance and acid and alkali resistance. Using PTFE as the inner lining of the hydrothermal synthesis container improves the corrosion resistance of the container interior, thereby improving the stability of the hydrothermal synthesis reaction.

[0024] In any of the above technical solutions, the copper phosphate salt is a compound composed of one or more of Cu3(PO4)2·2H2O, Cu3(PO4)2, Cu2PO4(OH), Cu3(PO4)(OH)3, Cu5(PO4)3(OH)4, CuAl6(PO4)(OH)8·5H2O, Cu2(P2O7)·3H2O, Cu2(P2O7) and Cu(PO3)2; the average particle size of the copper phosphate salt is between 1 micrometer and 5 micrometers.

[0025] In this technical solution, the copper phosphate salt is a compound group composed of Cu3(PO4)2·2H2O (copper phosphate dihydrate), Cu3(PO4)2 (anhydrous copper phosphate), Cu2PO4(OH) (basic copper phosphate), Cu3(PO4)(OH)3 (commonly known as blue copper phosphate), Cu5(PO4)3(OH)4 (commonly known as pseudomalachite), CuAl6(PO4)(OH)8·5H2O (commonly known as turquoise), Cu2(P2O7)·3H2O [copper pyrophosphate (II) trihydrate], Cu2(P2O7) [anhydrous copper pyrophosphate (II)], and Cu(PO3)2 [copper metaphosphate (II)]. In addition, the average particle size of the copper phosphate salt is limited to between 1 micrometer and 5 micrometers to ensure the uniformity of dispersion of the copper phosphate salt in water.

[0026] In any of the above technical solutions, the molar ratio of the third preset amount of sodium tungstate dihydrate to the fifth preset amount of cesium carbonate is 2:0.33.

[0027] In this technical solution, cesium tungstate dihydrate and cesium carbonate are used as raw materials, and citric acid is used as a reducing agent to synthesize cesium tungstate bronze nanoparticles using a hydrothermal synthesis process. By controlling the molar ratio of sodium tungstate dihydrate to cesium carbonate to 2:0.33, the formation of hexagonal cesium tungstate bronze nanoparticles can be promoted, effectively improving the formation efficiency of cesium tungstate bronze nanoparticles.

[0028] According to a second aspect of the present invention, an infrared absorbing material is provided, which is prepared by the method for preparing an infrared absorbing material proposed in the first aspect; the infrared absorbing material contains copper ions, cesium ions and anions; wherein the anions are composed of one or more of phosphate, hydrogen phosphate, pyrophosphate, metaphosphate, polyphosphate and reduced tungstate.

[0029] The infrared absorbing material provided by this invention contains copper ions, cesium ions, and anions, with the anions being composed of phosphate ions (PO4). 3- ), hydrogen phosphate (HPO4) 2- ), pyrophosphate (P2O7) 4- ), metaphosphate (P3O9) 3- ), polyphosphates and reduced tungstate (WO4) 0.33- One or more components of the above. A highly absorbent, light-colored composite inorganic infrared absorbing powder is obtained through a hydrothermal synthesis process in an acidic citric acid solution using copper phosphate, sodium tungstate dihydrate, and cesium carbonate as chemical raw materials. This improves the overall performance of the infrared absorbing material in terms of appearance and infrared absorption. On the one hand, it overcomes the shortcomings of using dark pigments such as carbon black, expanding the application field of infrared pairing anti-counterfeiting. On the other hand, the generated infrared absorbing material can achieve an absorption rate of over 85% in the 850nm-1250nm infrared band. Compared with currently used light-colored infrared absorbing materials, it exhibits superior infrared absorption performance, preventing criminals from using general infrared materials to counterfeit security products and increasing the technical difficulty of anti-counterfeiting identification.

[0030] According to a third aspect of the present invention, an ink is provided, comprising the infrared absorbing material proposed in the second aspect; when the ink is used for screen printing, the content of the infrared absorbing material in the ink is greater than or equal to 3% by mass; when the ink is used for engraving gravure patterns, the content of the infrared absorbing material in the ink is greater than or equal to 40% by mass.

[0031] The ink provided by this invention contains infrared-absorbing substances, which are used as pigments and ink binders to prepare near-infrared absorbing ink through physical mixing. Specifically, near-infrared absorbing ink is a type of anti-counterfeiting ink. In recent years, near-infrared absorbing ink has been widely promoted and applied as an anti-counterfeiting measure, especially in various currencies, certificates, magnetic cards, and securities. Near-infrared absorbing ink contains substances with near-infrared absorption functions, such as infrared absorbing substances and infrared absorbing materials. The near-infrared absorbing substances create a significant performance difference between anti-counterfeiting inks and ordinary inks. Under certain conditions, the difference in near-infrared absorption function is a reliable basis for distinguishing authenticity.

[0032] The ink proposed in this invention can be used to produce infrared absorbing screen printing inks, especially for screen printing in the field of currency or securities printing. It can provide the optimal effective printing area for the printed pattern, fully reflecting the special and unique characteristics of infrared absorbing materials in the absorption band. It is most suitable for machine-readable anti-counterfeiting in the field of currency and securities.

[0033] Specifically, the ink can be used for screen printing or gravure printing. When the ink is used for screen printing, the content of infrared absorbing material in the ink can be selected to be 3% or more by mass. When the ink is used for gravure printing, the content of infrared absorbing material in the ink can be selected to be 40% or more by mass, so as to provide better anti-counterfeiting printing effect for gravure printing patterns with high line density.

[0034] It is understood that the ink provided by this invention can be printed as an independent anti-counterfeiting feature, or used in conjunction with non-infrared absorbing inks having the same visible hue to form a hidden infrared paired absorption pattern. Furthermore, the infrared absorbing ink provided by this invention can be used in conjunction with other types of infrared absorbing inks on the same document to increase the concealment of machine-readable identification.

[0035] In any of the above technical solutions, further, when the ink is used for screen printing, the ink contains 3% to 19% by mass of infrared absorbing material, 5% to 35% of binder, 5% to 40% of filler and pigment, 0.5% to 10% of wax, 0.1% to 2% of surfactant, 1% to 3% of drying agent and 1% to 25% of solvent.

[0036] In this technical solution, the screen printing ink may contain 3%-19% infrared absorbing material, 5%-35% binder, 5%-40% filler and pigment, 0.5%-10% wax, 0.1%-2% surfactant, 1%-3% drying agent, and 1%-25% solvent. Specifically, for printing currency and securities, considering the contrast effect of red absorption peaks, the content of infrared absorbing material should be above 3%. In ink formulation design, to ensure infrared absorption intensity, the amount of infrared material added can be increased to 19% in areas with smaller pattern surfaces.

[0037] Additional aspects and advantages of the invention will become apparent in the following description or may be learned by practice of the invention. Attached Figure Description

[0038] Figure 1 One of the flowcharts for preparing an infrared absorbing material according to an embodiment of the present invention is shown;

[0039] Figure 2 A second schematic flowchart of the preparation method of the infrared absorbing material according to an embodiment of the present invention is shown;

[0040] Figure 3 The third schematic flowchart illustrates the preparation method of the infrared absorbing material according to an embodiment of the present invention;

[0041] Figure 4 The fourth schematic flowchart illustrates the preparation method of the infrared absorbing material according to an embodiment of the present invention.

[0042] Figure 5 The fifth step in illustrating the process flow diagram of the preparation method of the infrared absorbing material according to an embodiment of the present invention is shown.

[0043] Figure 6 The sixth illustration shows a flowchart of a method for preparing infrared absorbing material according to an embodiment of the present invention. Detailed Implementation

[0044] The technical solutions of the embodiments of the present invention will be clearly and completely described below with reference to the accompanying drawings. Obviously, the described embodiments are only a part of the embodiments of the present invention, and not all of the embodiments. Based on the embodiments of the present invention, all other embodiments obtained by those of ordinary skill in the art without creative effort are within the scope of protection of the present invention.

[0045] It should be noted that in this invention, descriptions involving "first," "second," "third," "fourth," "fifth," "sixth," "seventh," etc., are for descriptive purposes only and should not be construed as indicating or implying their relative importance or implicitly specifying the number of technical features indicated. Therefore, a feature defined with "first," "second," "third," "fourth," "fifth," "sixth," or "seventh" may explicitly or implicitly include at least one of those features. In the description of this invention, "a plurality of" means at least two, such as two, three, etc., unless otherwise explicitly specified.

[0046] Furthermore, the technical solutions of the various embodiments of the present invention can be combined with each other, but only if they are feasible for those skilled in the art. If the combination of technical solutions is contradictory or cannot be implemented, it should be considered that such combination of technical solutions does not exist and is not within the scope of protection claimed by the present invention.

[0047] The following reference Figures 1 to 6 The present invention describes a method for preparing an infrared absorbing material, the infrared absorbing material, and an ink according to some embodiments of the present invention.

[0048] like Figure 1 As shown, according to an embodiment of the present invention, a method for preparing an infrared absorbing material is proposed, the method comprising:

[0049] Step 102: Prepare a first solution, a second solution, and a third solution. The first solution contains copper phosphate, the second solution contains sodium tungstate dihydrate, and the third solution contains cesium carbonate and citric acid.

[0050] Step 104: Mix the first solution, the second solution and the third solution to obtain a mixture, and let the mixture stand for the preset standing time;

[0051] Step 106: The mixture is synthesized using a hydrothermal synthesis method to obtain a solid-liquid mixture;

[0052] Step 108: Wash the solid-liquid mixture with water, alcohol, centrifuge and dry it to generate an infrared absorbing substance.

[0053] The method for preparing the infrared absorbing material provided by this invention specifically comprises the following steps: First, a first solution, a second solution, and a third solution are prepared. The first solution contains copper phosphate, forming a copper phosphate dispersion solution; the second solution contains sodium tungstate dihydrate, forming a sodium tungstate solution; and the third solution contains cesium carbonate and citric acid, forming a mixture of cesium carbonate and citric acid solutions. Further, the first, second, and third solutions are mixed and stirred until homogeneous to obtain a mixed solution, which is then allowed to stand. The prepared mixed solution is subjected to a hydrothermal reaction using a hydrothermal synthesis process to obtain a solid-liquid mixture. The obtained solid-liquid mixture is then washed with water, washed with alcohol, centrifuged, and dried to generate the infrared absorbing material.

[0054] The present invention provides a method for preparing infrared absorbing materials using copper phosphate, sodium tungstate dihydrate, and cesium carbonate as chemical raw materials. A hydrothermal synthesis process is employed in an acidic citric acid solution to obtain a light-colored composite inorganic infrared absorbing powder with high absorbency. Because copper phosphate is light in color, using it as a chemical raw material can produce a light-colored infrared absorbing material, overcoming the shortcomings of using dark pigments such as carbon black as infrared absorbing materials in existing technologies. However, copper phosphate exhibits weak spectral absorption in the 850nm-1250nm infrared band, failing to achieve a high infrared absorption rate. Therefore, based on the preparation of infrared absorbing materials using copper phosphate as a chemical raw material, sodium tungstate dihydrate and cesium carbonate are added as chemical raw materials. Through a hydrothermal synthesis process, the final infrared absorbing material comprises cesium tungsten bronze and copper carbonate, with the cesium tungsten bronze coating the surface of the copper carbonate. Because cesium tungsten bronze has strong absorption in the 850nm-1250nm infrared band, but its color is dark, a hydrothermal synthesis process using copper phosphate, sodium tungstate dihydrate, and cesium carbonate as chemical raw materials in an acidic citric acid solution can coat a small amount of cesium tungsten bronze onto the surface of copper carbonate. This results in a composite infrared absorbing powder that retains a light color while exhibiting excellent infrared absorption performance, thus enabling the infrared absorbing material to have an infrared absorption rate of over 85% in the 850nm-1250nm infrared band.

[0055] like Figure 2 As shown, in the above embodiments, the steps for preparing the first solution, the second solution, and the third solution specifically include:

[0056] Step 202: Add a second preset amount of deionized water to the first preset amount of copper phosphate salt, and stir and disperse at the first preset temperature to obtain the first solution;

[0057] Step 204: Add a fourth preset amount of deionized water to the third preset amount of sodium tungstate dihydrate and stir to dissolve, thus obtaining the second solution;

[0058] Step 206: Add the fifth preset amount of cesium carbonate and the sixth preset amount of citric acid to the seventh preset amount of deionized water and stir to dissolve, to obtain the third solution;

[0059] Step 208: Mix the first solution, the second solution and the third solution to obtain a mixture, and let the mixture stand for the preset standing time;

[0060] Step 210: The mixture is synthesized using a hydrothermal synthesis method to obtain a solid-liquid mixture;

[0061] Step 212: Wash the solid-liquid mixture with water, alcohol, centrifuge and dry it to generate an infrared absorbing substance.

[0062] In this technical solution, a single copper phosphate salt is dispersed in deionized water to form a copper phosphate salt dispersion solution, i.e., the first solution. Subsequently, sodium tungstate dihydrate is added to deionized water and stirred to obtain a sodium tungstate solution, i.e., the second solution. Then, cesium carbonate and citric acid are added to deionized water and stirred to react and dissolve, yielding a mixture of cesium carbonate and citric acid solutions, i.e., the third solution.

[0063] It should be noted that the specific values ​​of the first preset amount of copper phosphate, the third preset amount of sodium tungstate dihydrate, the fifth preset amount of cesium carbonate, the sixth preset amount of citric acid, and the corresponding preset amount of deionized water added to each raw material can be selected according to the actual situation and are not limited here. The preset standing time can be between 20 min and 25 min.

[0064] In a specific embodiment, the synthesis process of an infrared absorbing material is as follows: Step 1, weigh 22.356g of copper pyrophosphate into a beaker, add deionized water, and stir and disperse at a certain temperature to form a copper phosphate salt dispersion solution. Step 2, weigh 2.9685g of sodium tungstate dihydrate, add 20mL of deionized water, and stir to dissolve. Step 3, weigh 0.4907g of cesium carbonate and 8.6055g of citric acid, add 20mL of deionized water, and stir to dissolve. Step 4, mix the two mixtures prepared in Step 2 and Step 3 with the copper phosphate salt dispersion prepared in Step 1, and let stand for 20 minutes. Step 5, transfer the mixture prepared in Step 4 into a polytetrafluoroethylene liner and carry out a high-pressure hydrothermal reaction, wherein the hydrothermal temperature is 180℃ and the hydrothermal time is 3 days. Step 6, wash the solid-liquid mixture obtained in Step 5 with water, wash with alcohol, centrifuge, and dry at 80℃ for 12 hours to obtain the desired composite inorganic infrared absorbing material. Further, the synthesis process of another infrared absorbing material is as follows: Step 1, weigh 9.936g of copper pyrophosphate into a beaker, add deionized water, and stir and disperse at a certain temperature to form a copper phosphate salt dispersion solution. Step 2, weigh 2.9685g of sodium tungstate dihydrate, add 20mL of deionized water, and stir to dissolve. Step 3, weigh 0.4907g of cesium carbonate and 8.6055g of citric acid, add 20mL of deionized water, and stir to dissolve. Step 4, mix the two mixtures prepared in Step 2 and Step 3 with the copper phosphate salt dispersion prepared in Step 1, and let stand for 20 minutes. Step 5, transfer the mixture prepared in Step 4 into a polytetrafluoroethylene liner and carry out a high-pressure hydrothermal reaction, wherein the hydrothermal temperature is 180℃ and the hydrothermal time is 4 days. Step 6, wash the solid-liquid mixture obtained in Step 5 with water, wash with alcohol, centrifuge, and dry at 80℃ for 12 hours to obtain the desired composite inorganic infrared absorbing material.

[0065] In any of the above embodiments, the infrared absorbing material specifically includes: the infrared absorbing material includes cesium tungsten bronze nanoparticles and copper phosphate, wherein the cesium tungsten bronze nanoparticles are coated on the surface of the copper phosphate; the infrared absorbing material contains 25% to 42% copper, 12% to 21% phosphorus, 0.1% to 7% cesium and 0.5% to 27% tungsten by mass percentage.

[0066] In this embodiment, the final infrared absorbing material comprises cesium tungsten bronze and copper carbonate, with the cesium tungsten bronze coating the surface of the copper carbonate. Furthermore, energy dispersive spectroscopy (EDS) analysis shows that the infrared absorbing material, converted to mass percentages, comprises 25% to 42% copper, 12% to 21% phosphorus, 0.1% to 7% cesium, and 0.5% to 27% tungsten, which satisfies the requirement of this invention to have an average reflectivity of less than 15% in the wide near-infrared range of 850nm-1250nm.

[0067] like Figure 3As shown, in any of the above embodiments, the synthesis conditions for the hydrothermal synthesis method are:

[0068] Step 302: Add a second preset amount of deionized water to the first preset amount of copper phosphate salt, and stir and disperse at the first preset temperature to obtain the first solution;

[0069] Step 304: Add a fourth preset amount of deionized water to the third preset amount of sodium tungstate dihydrate and stir to dissolve, thereby obtaining the second solution;

[0070] Step 306: Add the fifth preset amount of cesium carbonate and the sixth preset amount of citric acid to the seventh preset amount of deionized water and stir to dissolve, to obtain the third solution;

[0071] Step 308: Mix the first solution, the second solution and the third solution to obtain a mixture, and let the mixture stand for the preset standing time;

[0072] Step 310: The mixture is synthesized using a hydrothermal synthesis method to obtain a solid-liquid mixture;

[0073] Step 312: The synthesis temperature is between 160℃ and 240℃, and the synthesis time is between 3 days and 5 days;

[0074] Step 314: Wash the solid-liquid mixture with water, alcohol, centrifuge, and dry to generate an infrared-absorbing substance.

[0075] In this embodiment, the synthesis temperature of hydrothermal synthesis is limited to between 160℃ and 240℃, and the synthesis time of hydrothermal synthesis is limited to between 3 days and 5 days, so as to ensure the synthesis effect of hydrothermal synthesis.

[0076] like Figure 4 As shown, in any of the above embodiments, the method for using infrared absorbing materials further includes:

[0077] Step 402: Add a second preset amount of deionized water to the first preset amount of copper phosphate salt, and stir and disperse at the first preset temperature to obtain the first solution;

[0078] Step 404: Add a fourth preset amount of deionized water to the third preset amount of sodium tungstate dihydrate and stir to dissolve, to obtain the second solution;

[0079] Step 406: Add the fifth preset amount of cesium carbonate and the sixth preset amount of citric acid to the seventh preset amount of deionized water and stir to dissolve, to obtain the third solution;

[0080] Step 408: Mix the first solution, the second solution and the third solution to obtain a mixture, and let the mixture stand for the preset standing time;

[0081] Step 410: The mixture is synthesized using a hydrothermal synthesis method to obtain a solid-liquid mixture;

[0082] Step 412: The synthesis temperature is between 160℃ and 240℃, and the synthesis time is between 3 days and 5 days.

[0083] Step 414: Wash the solid-liquid mixture with water, alcohol, centrifuge, and dry it to generate an infrared-absorbing substance;

[0084] Step 416: The centrifugation speed is between 3000 rpm and 5000 rpm, and the centrifugation time is between 30 minutes and 60 minutes; the drying conditions are: the drying temperature is between 60℃ and 80℃, and the drying time is between 6 hours and 12 hours.

[0085] In this technical solution, when centrifuging a solid-liquid mixture, the centrifugal speed is limited to 3000-5000 rpm, and the centrifugal time is limited to 30-60 minutes to ensure the separation effect of the solid-liquid mixture. Specifically, the centrifugal speed can be 3000 rpm, 3500 rpm, 5000 rpm, etc., and the centrifugal time can be 30 minutes, 50 minutes, 60 minutes, etc.

[0086] Furthermore, the drying temperature for drying the solid-liquid mixture is limited to between 60℃ and 80℃, and the drying time is limited to between 6 hours and 12 hours, to ensure that the moisture content of the generated composite infrared absorbing powder is reduced to the minimum.

[0087] like Figure 5 As shown, in any of the above technical solutions, before synthesizing the mixture using a hydrothermal synthesis method to obtain a solid-liquid mixture, the method for preparing the infrared absorbing material further includes:

[0088] Step 502: Add a second preset amount of deionized water to a first preset amount of copper phosphate salt, and stir and disperse at a first preset temperature to obtain a first solution;

[0089] Step 504: Add a fourth preset amount of deionized water to the third preset amount of sodium tungstate dihydrate and stir to dissolve, to obtain the second solution;

[0090] Step 506: Add the seventh preset amount of deionized water to the fifth preset amount of cesium carbonate and the sixth preset amount of citric acid, stir and dissolve to obtain the third solution;

[0091] Step 508: Mix the first solution, the second solution and the third solution to obtain a mixture, and let the mixture stand for a preset standing time;

[0092] Step 510: Pour the mixture into a container lined with polytetrafluoroethylene (PTFE).

[0093] Step 512: The mixture is synthesized using a hydrothermal synthesis method to obtain a solid-liquid mixture;

[0094] Step 514: The synthesis temperature is between 160℃ and 240℃, and the synthesis time is between 3 days and 5 days.

[0095] Step 516: Wash the solid-liquid mixture with water, alcohol, centrifuge, and dry to generate an infrared-absorbing substance;

[0096] Step 518: The centrifugation speed is between 3000 rpm and 5000 rpm, and the centrifugation time is between 30 minutes and 60 minutes; the drying conditions are: the drying temperature is between 60℃ and 80℃, and the drying time is between 6 hours and 12 hours.

[0097] In this technical solution, the mixture is introduced into a container, and the inner material of the container is polytetrafluoroethylene (PTFE). PTFE has the characteristics of heat resistance and acid and alkali resistance. Using PTFE as the inner lining of the hydrothermal synthesis container improves the corrosion resistance of the container interior, thereby improving the stability of the hydrothermal synthesis reaction.

[0098] In any of the above technical solutions, the copper phosphate salt is a compound composed of one or more of Cu3(PO4)2·2H2O, Cu3(PO4)2, Cu2PO4(OH), Cu3(PO4)(OH)3, Cu5(PO4)3(OH)4, CuAl6(PO4)(OH)8·5H2O, Cu2(P2O7)·3H2O, Cu2(P2O7) and Cu(PO3)2; the average particle size of the copper phosphate salt is between 1 micrometer and 5 micrometers.

[0099] In this technical solution, the copper phosphate salt is a compound group composed of Cu3(PO4)2·2H2O (copper phosphate dihydrate), Cu3(PO4)2 (anhydrous copper phosphate), Cu2PO4(OH) (basic copper phosphate), Cu3(PO4)(OH)3 (commonly known as blue copper phosphate), Cu5(PO4)3(OH)4 (commonly known as pseudomalachite), CuAl6(PO4)(OH)8·5H2O (commonly known as turquoise), Cu2(P2O7)·3H2O [copper pyrophosphate (II) trihydrate], Cu2(P2O7) [anhydrous copper pyrophosphate (II)], and Cu(PO3)2 [copper metaphosphate (II)]. In addition, the average particle size of the copper phosphate salt is limited to between 1 micrometer and 5 micrometers to ensure the uniformity of dispersion of the copper phosphate salt in water.

[0100] In any of the above technical solutions, the molar ratio of the third preset amount of sodium tungstate dihydrate to the fifth preset amount of cesium carbonate is 2:0.33.

[0101] In this technical solution, cesium tungstate dihydrate and cesium carbonate are used as raw materials, and citric acid is used as a reducing agent to synthesize cesium tungstate bronze nanoparticles using a hydrothermal synthesis process. By controlling the molar ratio of sodium tungstate dihydrate to cesium carbonate to 2:0.33, the formation of hexagonal cesium tungstate bronze nanoparticles can be promoted, effectively improving the formation efficiency of cesium tungstate bronze nanoparticles.

[0102] like Figure 6 As shown, according to a specific embodiment of the present invention, a method for preparing an infrared absorbing material is proposed, the method comprising:

[0103] Step 602: Disperse a single copper phosphate salt in water to form a first solution;

[0104] Step 604: Take sodium tungstate dihydrate, add it to deionized water and stir to dissolve it to obtain a second solution;

[0105] Step 606: Take cesium carbonate and citric acid, add them to deionized water and stir to react and dissolve, to obtain the third solution;

[0106] Step 608: Mix the first solution, the second solution and the third solution, stir until homogeneous to obtain a mixture, and let the mixture stand.

[0107] Step 610: The mixture is synthesized using a hydrothermal synthesis method to obtain a solid-liquid mixture;

[0108] Step 612: The solid-liquid mixture is washed with water, washed with alcohol, centrifuged and dried to obtain the infrared absorbing material.

[0109] In this embodiment, the infrared absorbing material is a composite inorganic compound obtained directly from copper phosphate, sodium tungstate dihydrate, and cesium carbonate in an acidic citric acid solution via a hydrothermal synthesis process. Specifically, the infrared absorbing material includes cesium tungsten bronze nanoparticles and copper phosphate, with the cesium tungsten bronze nanoparticles loaded on the surface of the copper phosphate. The infrared absorbing material provided in this application exhibits an average infrared absorption rate of over 85% in the wide near-infrared range of 850nm-1250nm, demonstrating excellent infrared absorption performance. Compared with light-colored infrared absorbing materials in the prior art, its comprehensive performance in terms of appearance and infrared absorption will be more advantageous in applications. On the one hand, it can be used in anti-counterfeiting inks of various colors, expanding the application field of infrared pairing anti-counterfeiting, overcoming the shortcomings of using dark pigments such as carbon black, and opening up a broad space for the artistic creation of relevant designers; on the other hand, the main infrared absorption band of infrared absorbing materials is between 850nm and 1250nm, which has obvious band differences compared with the full-band infrared absorption of dark pigments and the narrow-band absorption of organic dyes, effectively distinguishing it from other infrared absorbing materials and enhancing the anti-counterfeiting strength of infrared pairing.

[0110] Furthermore, the infrared absorbing material contains copper ions, cesium ions, and anions. Among these, the anion is phosphate (PO42-). 3- ), hydrogen phosphate (HPO4) 2- ), pyrophosphate (P2O7) 4- ), metaphosphate (P3O9) 3- ), polyphosphates and reduced tungstate (WO4) 0.33- The ion group consists of ).

[0111] Furthermore, the copper phosphate salt is a group of compounds consisting of Cu3(PO4)2·2H2O (copper phosphate dihydrate), Cu3(PO4)2 (anhydrous copper phosphate), Cu2PO4(OH) (basic copper phosphate), Cu3(PO4)(OH)3 (commonly known as blue copper phosphate), Cu5(PO4)3(OH)4 (commonly known as pseudomalachite), CuAl6(PO4)(OH)8·5H2O (commonly known as turquoise), Cu2(P2O7)·3H2O [copper pyrophosphate (II) trihydrate], Cu2(P2O7) [copper pyrophosphate (II) anhydrous], and Cu(PO3)2 [copper metaphosphate (II)].

[0112] Furthermore, the infrared absorbing material contains 25%-42% copper, 12%-21% phosphorus, 0.1%-7% cesium, and 0.5%-27% tungsten by mass percentage.

[0113] Furthermore, the particle size d (0.5) of the copper phosphate salt is 1 micrometer to 5 micrometers.

[0114] Furthermore, the molar ratio of sodium tungstate dihydrate to cesium carbonate is 2:0.33.

[0115] Furthermore, the hydrothermal synthesis temperature is 160℃-240℃, and the hydrothermal time is 3-5 days.

[0116] Furthermore, the centrifugation speed is 3000 r / min-5000 r / min, and the centrifugation time is 30 min-60 min.

[0117] Furthermore, the drying temperature is 60℃-80℃, and the drying time is 6h-12h.

[0118] According to a second aspect of the present invention, an infrared absorbing material is provided, which is prepared by the method for preparing infrared absorbing material proposed in the first aspect; the infrared absorbing material contains copper ions, cesium ions and anions; wherein the anions are composed of one or more of phosphate, hydrogen phosphate, pyrophosphate, metaphosphate, polyphosphate and reduced tungstate.

[0119] The infrared absorbing material provided in this embodiment contains copper ions, cesium ions, and anions. The anions are composed of phosphate ions (PO4). 3- ), hydrogen phosphate (HPO4) 2- ), pyrophosphate (P2O7) 4- ), metaphosphate (P3O9) 3- ), polyphosphates and reduced tungstate (WO4) 0.33- One or more components of the above. A highly absorbent, light-colored composite inorganic infrared absorbing powder is obtained through a hydrothermal synthesis process in an acidic citric acid solution using copper phosphate, sodium tungstate dihydrate, and cesium carbonate as chemical raw materials. This improves the overall performance of the infrared absorbing material in terms of appearance and infrared absorption. On the one hand, it overcomes the shortcomings of using dark pigments such as carbon black, expanding the application field of infrared pairing anti-counterfeiting. On the other hand, the generated infrared absorbing material can achieve an absorption rate of over 85% in the 850nm-1250nm infrared band. Compared with currently used light-colored infrared absorbing materials, it exhibits superior infrared absorption performance, preventing criminals from using general infrared materials to counterfeit security products and increasing the technical difficulty of anti-counterfeiting identification.

[0120] According to a third aspect of the present invention, an ink is provided, comprising the infrared absorbing material proposed in the second aspect; when the ink is used for screen printing, the content of the infrared absorbing material in the ink is greater than or equal to 3% by mass; when the ink is used for engraving gravure patterns, the content of the infrared absorbing material in the ink is greater than or equal to 40% by mass.

[0121] The ink provided in this embodiment contains an infrared-absorbing substance, which is a pigment and ink binder physically mixed to prepare near-infrared absorbing ink. Specifically, near-infrared absorbing ink is a type of anti-counterfeiting ink. In recent years, near-infrared absorbing ink has been widely promoted and applied as an anti-counterfeiting measure, especially on various currencies, certificates, magnetic cards, and securities. Near-infrared absorbing ink contains substances with near-infrared absorption functions, such as infrared absorbing substances and infrared absorbing materials. The near-infrared absorbing substance creates a significant performance difference between anti-counterfeiting inks and ordinary inks. Under certain conditions, the difference in near-infrared absorption function is a reliable basis for distinguishing authenticity.

[0122] The ink proposed in this embodiment is most suitable for producing infrared absorbing screen printing inks, especially for screen printing inks used in the printing of currency or securities. It can provide the best effective printing area for the printed pattern, fully reflecting the special and unique characteristics of infrared absorbing materials in the absorption band. It is most suitable for machine-readable anti-counterfeiting in the field of currency and securities.

[0123] Specifically, the ink can be used for screen printing or gravure printing. When the ink is used for screen printing, the content of infrared absorbing material in the ink can be selected to be 3% or more by mass. When the ink is used for gravure printing, the content of infrared absorbing material in the ink can be selected to be 40% or more by mass, so as to provide better anti-counterfeiting printing effect for gravure printing patterns with high line density.

[0124] It is understood that the ink provided in this embodiment can be printed as an independent anti-counterfeiting feature, or used in conjunction with non-infrared absorbing inks having the same visible hue to form a hidden infrared paired absorption pattern. Furthermore, the infrared absorbing ink provided by this invention can be used in conjunction with other types of infrared absorbing inks on the same document to increase the concealment of machine-readable identification.

[0125] According to one embodiment of the present invention, based on any of the above embodiments, when the ink is used for screen printing, the ink contains 3% to 19% by mass of infrared absorbing material, 5% to 35% of binder, 5% to 40% of filler and pigment, 0.5% to 10% of wax, 0.1% to 2% of surfactant, 1% to 3% of drying agent and 1% to 25% of solvent.

[0126] In this embodiment, the screen printing ink may contain 3%-19% infrared absorbing material, 5%-35% binder, 5%-40% filler and pigment, 0.5%-10% wax, 0.1%-2% surfactant, 1%-3% drying agent, and 1%-25% solvent. Specifically, for printing currency and securities, considering the contrast effect of red absorption peaks, the content of infrared absorbing material should be above 3%. In ink formulation design, to ensure infrared absorption intensity, the amount of infrared material added can be increased to 19% in areas with smaller pattern surfaces.

[0127] In a specific embodiment, as shown in Table 1, 22.356g of copper pyrophosphate, 2.9685g of sodium tungstate dihydrate, 0.4907g of cesium carbonate, and 8.6055g of citric acid were weighed. After generating infrared absorbing substances through an infrared absorbing substance synthesis process, the substances in the proportions shown in Table 1 were weighed into a material tank and premixed for 30 minutes using a disperser. Then, the mixture in the material tank was ground in a sand mill and filtered through a 100-mesh sieve. After the product was tested and found to meet the technical indicators for screen printing ink application, it became the finished infrared absorbing screen printing ink.

[0128] Table 1

[0129] Infrared absorbing materials 10 copies alkyd resin 10 copies Polyvinyl butyral resin 15 copies Ethylene glycol ethyl ether acetate organic solvent 35 copies Oxidized polyethylene wax 5 copies surfactants 1 copy Calcium carbonate 2 copies Titanium dioxide pigment 3 copies Desiccant 0.2 copies

[0130] In a specific embodiment, as shown in Table 2, 9.936g of copper pyrophosphate, 2.9685g of sodium tungstate dihydrate, 0.4907g of cesium carbonate, and 8.6055g of citric acid were weighed. After generating infrared absorbing substances through an infrared absorbing substance synthesis process, the substances in the proportions shown in Table 2 were weighed into a material tank and premixed for 30 minutes using a disperser. Then, the mixture in the material tank was ground in a sand mill and filtered through a 100-mesh sieve. After the product was tested and found to meet the technical indicators for screen printing ink application, it became the finished infrared absorbing screen printing ink.

[0131] Table 2

[0132] Infrared absorbing materials 10 copies alkyd resin 10 copies Polyvinyl butyral resin 15 copies Ethylene glycol ethyl ether acetate organic solvent 35 copies Oxidized polyethylene wax 5 copies surfactants 1 copy Calcium carbonate 2 copies Titanium dioxide pigment 3 copies Desiccant 0.2 copies

[0133] In the description of this specification, the terms "one embodiment," "some embodiments," "specific embodiment," etc., refer to a specific feature, structure, material, or characteristic described in connection with that embodiment or example, which is included in at least one embodiment or example of the present invention. In this specification, the illustrative expressions of the above terms do not necessarily refer to the same embodiment or example. Furthermore, the specific features, structures, materials, or characteristics described may be combined in any suitable manner in one or more embodiments or examples.

[0134] The above are merely optional embodiments of the present invention and are not intended to limit the present invention. For those skilled in the art, the present invention can have various modifications and variations. Any modifications, equivalent substitutions, improvements, etc., made within the spirit and principles of the present invention should be included within the protection scope of the present invention.

Claims

1. A method for preparing an infrared absorbing material, characterized in that, include: Prepare a first solution, a second solution, and a third solution, and mix the first solution, the second solution, and the third solution to obtain a mixture. Let the mixture stand for a preset standing time. The first solution contains copper phosphate, the second solution contains sodium tungstate dihydrate, and the third solution contains cesium carbonate and citric acid; The mixture was synthesized using a hydrothermal synthesis method to obtain a solid-liquid mixture; The solid-liquid mixture is washed with water, washed with alcohol, centrifuged, and dried to generate the infrared absorbing substance. The preset resting time is greater than or equal to 20 minutes and less than or equal to 25 minutes.

2. The method for preparing the infrared absorbing material according to claim 1, characterized in that, The steps for preparing the first solution, the second solution, and the third solution specifically include: Add a second preset amount of deionized water to a first preset amount of copper phosphate, and stir and disperse at a first preset temperature to obtain a first solution; Add a fourth predetermined amount of deionized water to the third predetermined amount of sodium tungstate dihydrate and stir to dissolve, thereby obtaining a second solution; Add a seventh preset amount of deionized water to the fifth preset amount of cesium carbonate and the sixth preset amount of citric acid, and stir to dissolve to obtain a third solution.

3. The method for preparing the infrared absorbing material according to claim 1, characterized in that, The infrared absorbing material specifically includes: The infrared absorbing material includes cesium tungsten bronze nanoparticles and copper phosphate, wherein the cesium tungsten bronze nanoparticles are coated on the surface of the copper phosphate. The infrared absorbing material contains 25% to 42% copper, 12% to 21% phosphorus, 0.1% to 7% cesium and 0.5% to 27% tungsten by mass percentage.

4. The method for preparing the infrared absorbing material according to claim 1, characterized in that, The conditions for the hydrothermal synthesis method are: the synthesis temperature is between 160℃ and 240℃, and the synthesis time is between 3 days and 5 days.

5. The method for preparing the infrared absorbing material according to claim 1, characterized in that, The centrifugal rotation speed is between 3000 rpm and 5000 rpm, and the centrifugal separation time is between 30 minutes and 60 minutes. The drying conditions are as follows: the drying temperature is between 60°C and 80°C, and the drying time is between 6 hours and 12 hours.

6. The method for preparing the infrared absorbing material according to claim 1, characterized in that, Before synthesizing the mixture using a hydrothermal synthesis method to obtain a solid-liquid mixture, the preparation method of the infrared absorbing material further includes: The mixture is introduced into a container, the inner lining of which is made of polytetrafluoroethylene.

7. The method for preparing the infrared absorbing material according to claim 1, characterized in that, The copper phosphate salt is a compound composed of one or more of the following: Cu3(PO4)2·2H2O, Cu3(PO4)2, Cu2PO4(OH), Cu3(PO4)(OH)3, Cu5(PO4)3(OH)4, CuAl6(PO4)(OH)8·5H2O, Cu2(P2O7)·3H2O, Cu2(P2O7), and Cu(PO3)2. The average particle size of the copper phosphate salt is between 1 micrometer and 5 micrometers.

8. The method for preparing the infrared absorbing material according to claim 2, characterized in that, The molar ratio of the sodium tungstate dihydrate in the third preset amount to the cesium carbonate in the fifth preset amount is 2:0.

33.

9. An infrared absorbing material, characterized in that, It is prepared by the method for preparing infrared absorbing material as described in any one of claims 1 to 8; The infrared absorbing material contains copper ions, cesium ions, and anions; The anion is composed of one or more of the following: phosphate, hydrogen phosphate, pyrophosphate, metaphosphate, polyphosphate, and reduced tungstate.

10. An ink, characterized in that, include: The infrared absorbing material as described in claim 9; When the ink is used for screen printing, the infrared absorbing substance in the ink has a mass percentage greater than or equal to 3%; When the ink is used to engrave intaglio printing patterns, the infrared absorbing substance in the ink has a mass percentage greater than or equal to 40%.

11. The ink according to claim 10, characterized in that, When the ink is used for screen printing, the ink contains 3% to 19% by weight of the infrared absorbing material, 5% to 35% of the binder, 5% to 40% of the filler and pigment, 0.5% to 10% of the wax, 0.1% to 2% of the surfactant, 1% to 3% of the desiccant and 1% to 25% of the solvent.

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