KR102502639B1 - A security pigment coated with green infrared and red ultraviolet fluorescent materials and a preparation method thereof - Google Patents

Abstract

The present invention includes an inorganic plate-shaped substrate and a composite coating layer containing a green near-infrared ray phosphor and a red ultraviolet ray phosphor coated on the surface of the plate-shaped substrate, and a security pigment having double security characteristics of green fluorescence and red fluorescence, and pearls Security having dual fluorescence characteristics of green and red fluorescence and triple security characteristics of pearl luster characteristics at the same time, including a composite coating layer containing a luster pigment and a green near-infrared ray phosphor and a red ultraviolet ray phosphor coated on the surface of the pearl luster pigment As a pigment, the green near-infrared phosphor has a chemical formula of CeO ₂ :Ho _x ,Yb _y (0.001≤x≤0.005, 0.01≤y≤0.07), and the red ultraviolet phosphor has a formula of Gd ₂ O ₃ :Eu _z (0.05≤z ≤0.3) and a method for producing the same.

Description

Security pigment compositely coated with green near-infrared phosphor and red ultraviolet phosphor and method for manufacturing the same

The present invention relates to a security pigment compositely coated with a green near-infrared phosphor and a red ultraviolet phosphor, and a method for manufacturing the same, and more particularly, to an inorganic plate-like substrate or a pearlescent pigment coated with a nano-sized green near-infrared phosphor to coat the surface After coating with a red ultraviolet phosphor to give fluorescence characteristics of two colors, it has a double security characteristic of having a fluorescence characteristic of different colors depending on the type of substrate and a triple security characteristic with the addition of the luster characteristic of pearl luster pigment. It relates to a security pigment with improved security function and a manufacturing method thereof.

In various fields, including pharmaceuticals and machine parts, the use of counterfeit products causes confusion in the market as well as companies, increasing economic losses. It is essential to maintaining order in the market.

Recently, due to the development of similar cloning and counterfeiting technology, crimes related to counterfeiting have increased rapidly, and it has become difficult for even experts to distinguish genuine products from replicas. In order to prevent such counterfeiting, for example, research into anti-counterfeiting products, such as holograms, magnetic materials, and phosphors, which can easily verify genuine products, is being actively conducted. Among them, phosphor is a material that can convert the energy absorbed from the outside into its own light emission. It is mainly used for displays because it can show various colors based on the three main colors of red, green, and blue in the ultraviolet region. Depending on the circle, its application range is widening. A phosphor is composed of a matrix and an activator, and its characteristics depend on the composition, structure, and crystallinity of the phosphor.

As a technology for a security pigment using such a phosphor, Korean Patent Publication No. 10-2018-0112908 discloses a method for producing a security pigment by coating an inorganic phosphor on a flake substrate, and Korean Patent Publication No. 10-1907417 No., discloses a method for producing a security pigment by coating a mixture of organic and inorganic phosphors on a substrate, and in Korean Patent Publication No. 10-1858414, a plurality of metal oxide coating layers are formed on the surface of the substrate, Disclosed is a pearlescent pigment for security in which a phosphor layer containing a phosphor is formed on the surface of the coating layer. However, since the security pigment disclosed in these patent documents exhibits only a single fluorescence characteristic, there may be limitations in exhibiting a security function for various products in various fields, so there is room for further improvement in the security function. .

In addition, a paper by the Korea Research Institute of Chemical Technology (Lee Kyo-gwang et al., "Light emission characteristics of spherical green LaPO ₄ :Tb phosphor prepared by spray pyrolysis", Journal of the Korean Society of Materials Science, 12(9), 2002, pp. 761-766) discloses the preparation of LaPO ₄ :Tb green ultraviolet phosphor by ultrasonic spray pyrolysis. However, the green ultraviolet phosphor produced by the above method requires a high temperature of 1000 ° C. or more in the firing process, and a high temperature of 900 ° C. is required not only in the firing process but also in the manufacturing process itself, so that a lot of cost is consumed in equipment and manufacturing. The phosphor is a phosphor having only green fluorescence characteristics and is unsuitable for use as a security pigment because it has no characteristics in the visible light region.

(Patent Document 1) Korean Patent Publication No. 10-2018-0112908

(Patent Document 2) Korean Patent Publication No. 10-1907417

(Patent Document 3) Korean Patent Publication No. 10-1858414

(Non-Patent Document 1) Kyo-Kwang Lee et al., "Light-emitting characteristics of spherical green LaPO ₄ :Tb phosphor prepared by spray pyrolysis", Journal of the Korean Society of Materials Science, 12(9), 2002, pp. 761-766.

The present invention has been made to solve the problems of the prior art as described above, and an object of the present invention is to coat a green near-infrared phosphor layer on the surface of an inorganic plate-like substrate, and coat a red ultraviolet phosphor layer on the surface of the green near-infrared phosphor layer. It is to provide a composite coating security pigment having double security characteristics of different colors appearing in the green near-infrared region and the red ultraviolet region and a method for manufacturing the same.

Another object of the present invention is to coat the surface of the pearlescent pigment with a green near-infrared phosphor layer, and to coat the surface of the green near-infrared phosphor layer with a red ultraviolet phosphor layer to obtain double colors of different colors appearing in the green near-infrared region and the red ultraviolet region. It is to provide a security pigment with triple security characteristics having both fluorescence and pearl luster and a method for manufacturing the same.

The security pigment of the present invention for achieving the above object includes a plate-shaped substrate and a composite phosphor coating layer containing a green near-infrared ray phosphor and a red ultraviolet ray phosphor coated on the surface of the plate-shaped substrate, wherein the green near-infrared ray phosphor has the following It may have Chemical Formula 1, and the red ultraviolet phosphor may have the following Chemical Formula 2:

[Formula 1]

CeO ₂ :Ho _x ,Yb _y (0.001≤x≤0.005, 0.01≤y≤0.07)

[Formula 2]

Gd ₂ O ₃ :Eu _z (0.05≤z≤0.3).

In the security pigment of the present invention, the mixing weight ratio of the green near-infrared ray phosphor: the red ultraviolet ray phosphor in the composite phosphor coating layer may be 3 to 4:7 to 6.

In the security pigment of the present invention, the composite phosphor may be coated in an amount of 5 to 30 parts by weight based on 100 parts by weight of the plate-shaped substrate.

In the security pigment of the present invention, the plate-like substrate may be selected from inorganic plate-like substrates and pearlescent pigments.

In the security pigment of the present invention, the inorganic plate-like substrate may be at least one selected from the group consisting of natural mica, synthetic mica, glass flake, alumina flake, and Fe ₂ O ₃ flake, , The pearlescent pigment may be a pigment coated with at least one metal oxide selected from TiO ₂ , SiO ₂ , and Fe ₂ O ₃ on the surface of the inorganic plate-like substrate.

The manufacturing method of the security pigment of the present invention may include the following steps:

1) preparing a green near-infrared phosphor nano-dispersion sol by dispersing a green near-infrared phosphor powder having a chemical _formula of CeO ₂ :Ho x ,Yb _y (0.001≤x≤0.005, 0.01≤y≤0.07) in distilled water;

2) preparing a plate-shaped substrate aqueous solution;

3) coating a surface of the plate-shaped substrate with a green near-infrared phosphor coating layer by adding the green near-infrared phosphor nanodispersion sol to the aqueous solution of the plate-shaped substrate;

4) Dispersing the plate-like substrate coated with the green near-infrared phosphor coating layer in distilled water, mixing the red ultraviolet phosphor precursor, and adding a basic aqueous solution, having a chemical formula of Gd ₂ O ₃ :Eu _z (0.05≤z≤0.3) coating a red ultraviolet phosphor coating layer; and

5) Baking the product of step 4) to obtain a security pigment coated with a composite phosphor coating layer containing the green near-infrared phosphor and the red ultraviolet phosphor.

In the manufacturing method of the security pigment of the present invention, in step 1), the green near-infrared phosphor powder is dispersed in distilled water at a concentration of 1 to 20% by weight, and the dispersion may be performed by bead milling or ultrasonic dispersion .

In the manufacturing method of the security pigment of the present invention, in step 2), the plate-like substrate may be selected from inorganic plate-like substrates and pearlescent pigments.

In the manufacturing method of the security pigment of the present invention, in step 2), the concentration of the plate-shaped substrate in the aqueous solution of the plate-shaped substrate may be 1 to 20% by weight.

In the manufacturing method of the security pigment of the present invention, between steps 2) and 3), a step of adjusting the pH of the aqueous solution of the plate-like substrate to 8 or higher may be further included.

In the method for preparing the security pigment of the present invention, in step 3), 1 to 20 parts by weight of the green near-infrared phosphor nanodispersion sol may be added based on 100 parts by weight of the plate-shaped substrate aqueous solution.

In the method for preparing the security pigment of the present invention, in step 3), the green near-infrared phosphor nano-dispersion sol may be added to the aqueous solution of the plate-shaped substrate and stirred at 70 to 90 ° C. for 10 to 30 hours.

In the manufacturing method of the security pigment of the present invention, in step 4), the plate-shaped substrate coated with the green near-infrared phosphor coating layer may be dispersed in distilled water, and then the pH may be adjusted to 8 or higher.

In the method of manufacturing the security pigment of the present invention, in step 4), 1 to 20 parts by weight of the red ultraviolet phosphor precursor may be added based on 100 parts by weight of the plate-shaped substrate coated with the green near infrared phosphor coating layer.

In the manufacturing method of the security pigment of the present invention, in step 5), the firing may be performed at a temperature of 300° C. or more and 900° C. or less for 1 hour or more and 5 hours or less.

According to the present invention, by a simple and economical process of coating a dispersion sol of a green near-infrared phosphor prepared in nano size on an inorganic plate-shaped substrate and then coating a dispersion sol of a red ultraviolet phosphor thereon, depending on the type of plate-shaped substrate , It is possible to provide security pigments with double security characteristics of green near-infrared fluorescence and red ultraviolet fluorescence, or triple security of pearl luster, green near-infrared fluorescence and red ultraviolet fluorescence in an appropriate form according to the application. there is.

1 is a flowchart of a method for manufacturing a security pigment coated with a complex phosphor of the present invention.
Figure 2 shows a FE-SEM image of the security pigment particles coated with the complex phosphor of the present invention.
Figure 3 shows the PL intensity to determine the fluorescence characteristics of the security pigment particles coated with the composite phosphor of the present invention.
Figure 4 shows a photograph of simultaneously measuring a 254nm UV lamp and a 980 IR lamp in order to determine the fluorescence characteristics of the complex phosphor-coated security pigment particles of the present invention.

The advantages and features of the present invention, and how to achieve them, will become clear with reference to the detailed description of the embodiments below. However, the present invention is not limited to the embodiments disclosed below, but may be implemented in various different forms, and only the present embodiments allow the disclosure of the present invention to be complete, and the common knowledge in the art to which the present invention belongs. It is provided to fully inform the holder of the scope of the invention, and the present invention is only defined by the scope of the claims.

Unless otherwise defined, all terms (including technical and scientific terms) used in this specification may be used in a meaning commonly understood by those of ordinary skill in the art to which the present invention belongs. In addition, terms defined in commonly used dictionaries are not interpreted ideally or excessively unless specifically defined explicitly.

Hereinafter, a security pigment and a manufacturing method thereof according to the present invention will be described in detail.

The security pigment of the present invention includes a plate-shaped substrate and a composite phosphor coating layer containing a green near-infrared ray phosphor and a red ultraviolet ray phosphor coated on the surface of the plate-shaped substrate,

A green near-infrared phosphor is coated on the surface of the plate-shaped substrate in the form of an island, and a red ultraviolet phosphor is coated by filling a portion where the green near-infrared phosphor is not coated.

The green near-infrared phosphor may have the following Chemical Formula 1, and the red ultraviolet phosphor may have the following Chemical Formula 2:

[Formula 1]

CeO ₂ :Ho _x ,Yb _y (0.001≤x≤0.005, 0.01≤y≤0.07)

[Formula 2]

Gd ₂ O ₃ :Eu _z (0.05≤z≤0.3)

In Formula 1, when the ranges of x and y are less than the minimum values, the luminescence intensity is low, so that a fluorescence effect cannot be substantially expected. Cost and manufacturing time increase, resulting in poor economic feasibility.

The mixing weight ratio of the green near-infrared phosphor: the red ultraviolet phosphor in the composite phosphor coating layer may be 3 to 4:7 to 6, preferably 3.5 to 3.8:6.5 to 6.2, more preferably 3.2:6.8, and the mixing ratio Outside the range, it is not preferable because the two colors characteristic of the composite phosphor do not appear at the same time.

The composite phosphor may be coated in an amount of 5 to 30 parts by weight, preferably 20 to 30 parts by weight, based on 100 parts by weight of the plate-shaped substrate.

If the ratio of the composite phosphor is less than 5 parts by weight, the fluorescence effect is insignificant and may be practically ineffective, and if it is more than 30 parts by weight, as the concentration of the nano-sized phosphor particles increases, they agglomerate with each other rather than coating. It is not, and the light emitting property is not further improved, so the economic efficiency is lowered.

The plate-like substrate may be selected from inorganic plate-like substrates and pearlescent pigments. The inorganic plate-like substrate may be at least one selected from the group consisting of natural mica, synthetic mica, glass flake, alumina flake, and Fe ₂ O ₃ flake, but is not limited thereto. The pearl luster pigment may be a pigment coated with at least one metal oxide selected from TiO ₂ , SiO ₂ , and Fe ₂ O ₃ on the surface of the inorganic plate-like substrate, but is not limited thereto. Preferably, the pearlescent pigment may be an alumina flake coated with TiO ₂ , which exhibits a special optical effect due to its high refractive index, and is particularly preferable because it has surface properties suitable for coating phosphor nanoparticles.

The manufacturing method of the security pigment of the present invention may include the following steps:

1) preparing a green near-infrared phosphor nano-dispersion sol by dispersing green near-infrared phosphor powder having a chemical formula of CeO ₂ :Ho _x ,Yb _y (0.001≤x≤0.005, 0.01≤y≤0.07) in distilled water and then milling;

2) preparing a plate-shaped substrate aqueous solution;

3) coating a surface of the plate-shaped substrate with a green near-infrared phosphor coating layer by adding the green near-infrared phosphor nanodispersion sol to the aqueous solution of the plate-shaped substrate;

4) Dispersing the plate-like substrate coated with the green near-infrared phosphor coating layer in distilled water, mixing the red ultraviolet phosphor precursor, and adding a basic aqueous solution, having a chemical formula of Gd ₂ O ₃ :Eu _z (0.05≤z≤0.3) coating a red ultraviolet phosphor coating layer; and

5) Baking the product of step 4) to obtain a security pigment coated with a composite phosphor coating layer containing a green near-infrared phosphor and a red ultraviolet phosphor.

In a preferred embodiment of the manufacturing method of the security pigment of the present invention, in the step 1), the green near-infrared phosphor powder may be dispersed in distilled water at a concentration of 1 to 10% by weight, if the concentration is out of the range, the dispersion It is undesirable because particles are agglomerated and rather enlarged due to the heat generated during the process and the attraction of unstable particles.

In step 1), since the green near-infrared phosphor powder is not formed in a size small enough to form a coating layer, a nano-sized dispersion sol may be formed by milling after dispersing in distilled water. At this time, zirconia beads may be used for milling, and for sufficient milling, the milling time may be 10 minutes or more and 30 minutes or less, preferably 20 minutes. In the case of bead milling, it is preferable because it can obtain two effects of reducing the size of particles in a short time and also performing dispersion.

In addition, when bead milling cannot be performed, a nano-sized dispersion sol may be formed through ultrasonic dispersion. In the case of ultrasonic dispersion, the particles are dispersed while reducing the size of the particles by vibration through ultrasonic waves. To be able to disperse, for sufficient dispersion, the dispersion time may be 30 minutes to 2 hours, preferably 40 minutes to 1 hour.

If the bead milling time or the ultrasonic dispersion time is out of the above range, respectively, the particle size does not decrease to the nano size, or the heat generated by the beads or ultrasonic waves causes the particles to aggregate and the particle size may increase, which is not preferable. .

In step 2), the plate-like substrate may be selected from inorganic plate-like substrates and pearlescent pigments, and the concentration of the plate-like substrate in the aqueous solution of the plate-like substrate may be 1 to 20% by weight. If the concentration is out of the above range, the volume is limited. In the case where the particle coating due to the charge difference is not properly performed and rather agglomerates with each other in an unstable state, it is undesirable.

In step 3), 1 to 20 parts by weight, preferably 5 to 15 parts by weight, of the green near-infrared phosphor nano-dispersion sol may be added to 100 parts by weight of the plate-shaped substrate aqueous solution. It is not preferable because the coating on the substrate is not properly performed and the fluorescence characteristics are weak or do not appear.

In step 3), the green near-infrared ray phosphor nano-dispersion sol may be added dropwise to the aqueous solution of the plate-like substrate by stirring. At this time, the stirring speed may be 200 rpm or more and 500 rpm or less, preferably 250 rpm. The stirring temperature may be 70°C or more and 90°C or less, preferably 85°C. The stirring time may be preferably 12 hours or more and 48 hours or less, preferably 24 hours.

After step 3), the obtained solution may be filtered, washed, and dried. A vacuum pump may be used during filtration and washing, and the drying temperature may be 40° C. or more and 80° C. or less, preferably 60° C.

The manufacturing method of the security pigment of the present invention may further include adjusting the pH of the plate-shaped base material solution to 8 or more between steps 2) and 3). If the pH is less than 8, the attractive force between the plate-shaped substrate and the phosphor particles is weakened, so that the surface of the plate-shaped substrate is not effectively coated, which is not preferable.

In the step 4), 1 to 20 parts by weight, preferably 10 to 20 parts by weight of the red ultraviolet phosphor precursor may be added based on 100 parts by weight of the plate-shaped substrate coated with the green near infrared phosphor coating layer. If it is out of the range, it is not preferable because the coating on the plate-shaped substrate is not performed or the particles coated on the plate-shaped substrate are aggregated and the fluorescence characteristics are weak or do not appear.

In step 4), after dispersing the plate-shaped substrate coated with the green near-infrared phosphor coating layer in distilled water, the pH may be adjusted to 8 or higher. If the pH is less than 8, the attractive force between the plate-shaped substrate and the phosphor particles is weakened, so that the surface of the plate-shaped substrate is not effectively coated, which is not preferable.

By the coating process of steps 3) and 4), the green near-infrared phosphor is coated on the surface of the plate-shaped substrate in the form of an island by particle coating, and the red ultraviolet phosphor is coated with room temperature co-precipitation coating, so that the green near-infrared phosphor is not coated. The coating is done while filling the part.

The firing in step 5) may be performed at a temperature of 300 ° C. to 900 ° C., preferably 500 ° C. to 800 ° C. for 1 hour to 5 hours in a hydrogen atmosphere or an air atmosphere. If the firing conditions are out of the above range, it is not preferable because the light emitting characteristic reduced by milling is not recovered at low temperature or the light emitting characteristic is reduced at high temperature because the particles fall due to the difference in thermal expansion rate between the coated particles.

The present invention will be described in more detail through the following Examples and Comparative Examples, but the present invention is not limited by the following Examples.

Example 1

According to the process diagram shown in Figure 1, a security pigment was prepared as follows.

CeO ₂ : Ho _x Yb _y (x = 0.003, y = 0.02) powder, a green near-infrared phosphor prepared by spray pyrolysis, was dispersed in distilled water at a concentration of 2% by weight and milled for 30 minutes using zirconia beads, A nano-dispersed sol of green near-infrared phosphor was prepared. After dispersing 5 g of pearlescent pigment (CQV product A-901K; Alumina coated on the surface with TiO ₂ ) in 100 ml of distilled water as a plate-like substrate serving as a basic base in a 250 ml beaker, the pH was adjusted to 9 using KOH. Based on 100 parts by weight of the pearlescent pigment, 8 parts by weight of the green near-infrared phosphor nano-dispersion sol was added dropwise to the aqueous pearlescent pigment solution at room temperature (23±5° C.) at a rate of 0.2 ml/min using a metering pump and then stirred at 85° C. at 250 rpm. was stirred for 24 hours to coat the surface of the pearlescent pigment with green near-infrared phosphor. After the reaction was completed, the pearlescent pigment solution coated with the green near-infrared phosphor was filtered and washed using a vacuum filter, and dried at 60° C. for 24 hours. After dispersing 5 g of the dried pearlescent pigment coated with the green near-infrared phosphor in 100 ml of distilled water, the pH was adjusted to 9 using KOH. For the production and coating of Gd(OH) ₃ :Eu _z (z=0.1), a red ultraviolet phosphor, Gd(NO ₃ ) ₃ and Eu(NO ₃ ) ₃ were prepared at a molar ratio of Gd to Eu of 0.1 as red ultraviolet phosphor precursors. and dissolved in distilled water, and the result is the pearlescent pigment 100 coated with the green near-infrared ray phosphor. After adding in an amount of 17 parts by weight and stirring at room temperature (23 ± 5 ° C) for 20 minutes, 50 ml of NaOH aqueous solution was added dropwise at a rate of 0.2 ml / min using a metering pump, and then stirred at 250 rpm at 85 ° C for 24 minutes. Time stirring was carried out to coat the red UV phosphor. After the reaction is finished, the resulting pearlescent pigment solution is filtered and washed using a vacuum filter, dried at 60 ° C for 24 hours, and then calcined at 750 ° C for 4 hours to obtain a composite containing a green near-infrared ray phosphor and a red ultraviolet ray phosphor. A security pigment coated with a phosphor was prepared.

Example 2

In the process of preparing the security pigment coated with the complex phosphor of Example 1, the green near-infrared phosphor was used in an amount of 5 parts by weight based on 100 parts by weight of the pearlescent pigment, and the red ultraviolet phosphor was used in an amount of 5 parts by weight based on 100 parts by weight of the pearlescent pigment. It was carried out in the same manner as in Example 1 except that it was adjusted to.

Example 3

In the process of preparing the security pigment coated with the composite phosphor of Example 1, the green near-infrared phosphor was used in an amount of 10 parts by weight based on 100 parts by weight of the pearlescent pigment, and the red ultraviolet phosphor was used in an amount of 10 parts by weight based on the weight of the pearlescent pigment. It was carried out in the same manner as in Example 1 except that it was adjusted.

Example 4

In the process of preparing the security pigment coated with the complex phosphor of Example 1, the green near-infrared phosphor was used in an amount of 15 parts by weight based on 100 parts by weight of the pearlescent pigment, and the red ultraviolet phosphor was used in an amount of 15 parts by weight based on the weight of the pearlescent pigment. It was carried out in the same manner as in Example 1 except that it was adjusted.

Example 5

In the process of preparing the security pigment coated with the complex phosphor of Example 1, the green near-infrared phosphor was used in an amount of 7 parts by weight based on 100 parts by weight of the pearlescent pigment, and the red ultraviolet phosphor was used in an amount of 15 parts by weight based on the weight of the pearlescent pigment. It was carried out in the same manner as in Example 1 except that it was adjusted.

Example 6

In the process of preparing the complex phosphor-coated security pigment of Example 1, the method of Example 1 was carried out except that the process of baking at 750 ° C. for 4 hours was not performed.

Example 7

In the process of preparing the complex phosphor-coated security pigment of Example 1, the method of Example 1 was performed in the same manner as in Example 1, except that an inorganic plate base material (CQV, Mica) was used instead of the pearlescent pigment as the plate base material.

Comparative Example 1

In the process of preparing the security pigment coated with the composite phosphor of Example 1, the same method as in Example 1 was performed except that the green near-infrared phosphor and the red ultraviolet phosphor were simply mixed without coating.

Comparative Example 2

In the process of preparing the security pigment coated with the complex phosphor of Example 1, the green near-infrared phosphor was adjusted in an amount of 20 parts by weight based on 100 parts by weight of the pearlescent pigment, and the red ultraviolet phosphor was not prepared and coated. The same method as in Example 1 was performed.

Comparative Example 3

In the process of preparing the security pigment coated with the composite phosphor of Example 1, the red ultraviolet phosphor was adjusted in an amount of 20 parts by weight based on 100 parts by weight of the pearlescent pigment, and the green near-infrared phosphor was not milled and coated. The same method as in Example 1 was performed.

The working conditions of the Examples and Comparative Examples are summarized in Table 1 below.

Security pigment composition phosphor content
(parts by weight) security characteristics phosphor plate base material Green near-infrared phosphor red ultraviolet phosphor Fluorescent properties ^* Pearl Characteristics ^** Green near-infrared phosphor red ultraviolet phosphor green Red Example 1 CeO ₂ :HO _0.003 ,Yb _0.02 Gd ₂ O ₃ :Eu _0.05 pearl
Polish
pigment 8 17 O O O Example 2 5 5 △ △ O Example 3 10 10 O △ O Example 4 15 15 O O O Example 5 7 15 O O O Example 6 Gd(OH) ₃ :Eu _0.1 8 17 O △ O Example 7 Gd ₂ O ₃ :Eu _0.05 mica 8 17 O O X Comparative Example 1 CeO ₂ :HO _0.003 , Yb _0.02 Gd ₂ O ₃ :Eu _0.05 pearl
Polish
pigment simple mix O X O Comparative Example 2 doesn't exist 20 0 O X O Comparative Example 3 doesn't exist Gd ₂ O ₃ :Eu _0.05 0 20 X O O

main) * In the fluorescence properties, O indicates that excellent fluorescence properties are expressed, Δ indicates that the fluorescence properties are weaker than that of O, and X indicates that the fluorescence properties are non-uniform or non-uniform.

** In the pearl characteristics, O indicates that there is pearl luster, and X indicates that there is no pearl luster.

<Physical property evaluation>

The physical properties of the complex phosphor-coated security pigment were evaluated by drying in the form of powder, and the powder was dried in a vacuum oven at 25 ° C. for 24 hours and used.

1. The shape of each of the security pigments prepared in Example 1 and Comparative Example 1 was confirmed by measuring each dry powder with FE-SEM, which is shown in FIG. 2.

From FIG. 2, it can be seen that the security pigment of Example 1 is coated with particles on the surface of the plate base material, whereas the security pigment of Comparative Example 1 is not coated on the surface of the plate base material, but rather is aggregated in the surrounding area. there is.

2. The PL characteristics of the security pigment prepared in Example 1 were confirmed, and the results are shown in FIG. 3 . The PL analysis was shown by measuring the emission intensity at the maximum central wavelength between 400 and 800 nm in the broadband 254 nm and 975 nm wavelength bands.

3. The fluorescence characteristics of the security pigments prepared in Example 1 and the security pigments prepared by simple mixing without phosphor coating in Comparative Example 1 were measured under a UV lamp at 254 nm, and the results are shown in FIG. 4.

From Figure 4, it can be seen that the security pigment of Example 1 exhibits dual fluorescence characteristics of green fluorescence and red fluorescence, whereas the security pigment of Comparative Example 1 exhibits green fluorescence, but in the case of red fluorescence, it is non-uniform or hardly red. there is.

Claims (15)

A plate-shaped substrate and a composite phosphor coating layer containing a green near-infrared ray phosphor and a red ultraviolet ray phosphor coated on a surface of the plate-shaped substrate, wherein the composite phosphor coating layer has the green near-infrared ray phosphor coated on the surface of the plate-shaped substrate in the form of an island. It consists of a coated green near-infrared phosphor layer and a red ultraviolet phosphor layer coated on the surface of the green near-infrared phosphor layer while filling the portion where the green near-infrared phosphor is not coated, wherein the green near-infrared phosphor has the following formula (1), The red ultraviolet phosphor is a security pigment having the following formula (2):
[Formula 1]
CeO ₂ :Ho _x ,Yb _y (0.001≤x≤0.005, 0.01≤y≤0.07)
[Formula 2]
Gd ₂ O ₃ :Eu _z (0.05≤z≤0.3). The security pigment of claim 1, wherein the mixed weight ratio of the green near-infrared ray phosphor to the red ultraviolet ray phosphor in the composite phosphor coating layer is 3-4: 7-6. The security pigment of claim 1, wherein the composite phosphor is coated in an amount of 5 to 30 parts by weight based on 100 parts by weight of the plate-shaped substrate. The security pigment according to claim 1, wherein the plate-like substrate is selected from inorganic plate-like substrates and pearlescent pigments. The method of claim 4, wherein the inorganic plate-like substrate is one selected from the group consisting of natural mica, synthetic mica, glass flakes, alumina flakes, and Fe ₂ O ₃ flakes, and the pearlescent pigment is applied to the surface of the inorganic plate-like substrate A security pigment that is a pigment coated with at least one metal oxide selected from TiO ₂ , SiO ₂ , and Fe ₂ O ₃ . A method for producing the security pigment of any one of claims 1 to 5, comprising the following steps:
1) preparing a green near-infrared phosphor nano-dispersion sol by dispersing a green near-infrared phosphor powder having a chemical _formula of CeO ₂ :Ho x ,Yb _y (0.001≤x≤0.005, 0.01≤y≤0.07) in distilled water;
2) preparing a plate-shaped substrate aqueous solution;
3) coating the surface of the plate-shaped substrate with a green near-infrared phosphor coating layer in the form of an island by adding the green near-infrared phosphor nano-dispersion sol to the aqueous solution of the plate-shaped substrate;
4) Dispersing the plate-like substrate coated with the green near-infrared phosphor coating layer in distilled water, mixing the red ultraviolet phosphor precursor, and adding a basic aqueous solution, having a chemical formula of Gd ₂ O ₃ :Eu _z (0.05≤z≤0.3) coating a red ultraviolet phosphor coating layer; and
5) Baking the product of step 4) to obtain a security pigment coated with a composite phosphor coating layer containing the green near-infrared phosphor and the red ultraviolet phosphor. The method of claim 6, wherein in step 1), the green near-infrared phosphor powder is dispersed in distilled water at a concentration of 1 to 20% by weight, and the dispersion is performed by bead milling or ultrasonic dispersion. The method of claim 6, wherein in step 2), the plate-like substrate is selected from inorganic plate-like substrates and pearlescent pigments. The method of claim 6, wherein in step 2), the concentration of the plate-shaped substrate in the aqueous solution of the plate-shaped substrate is 1 to 20% by weight. [Claim 7] The method of claim 6, further comprising adjusting the pH of the aqueous solution of the plate-shaped substrate to 8 or higher between steps 2) and 3). The method of claim 6, wherein in step 3), 1 to 20 parts by weight of the green near-infrared phosphor nano-dispersed sol is added to 100 parts by weight of the plate-shaped substrate aqueous solution. The method of claim 6, wherein in step 3), the green near-infrared phosphor nano-dispersion sol is added to the aqueous solution of the plate-shaped substrate and stirred at 70 to 90 ° C. for 10 to 30 hours. The method of claim 6, wherein in step 4), the plate-shaped substrate coated with the green near-infrared phosphor coating layer is dispersed in distilled water and then the pH is adjusted to 8 or higher. The method of claim 6, wherein in step 4), 1 to 20 parts by weight of the red ultraviolet phosphor precursor is added to 100 parts by weight of the plate-shaped substrate coated with the green near infrared phosphor coating layer. The method of claim 6, wherein in the step 5), the firing is performed at a temperature of 300° C. or more and 900° C. or less for a time of 1 hour or more and 5 hours or less.

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