KR102399617B1 - A security pigment coated with green fluorescent material and a preparation method thereof - Google Patents

Abstract

The present invention provides a security pigment or pearlescent pigment having a single green fluorescence property comprising an inorganic plate-shaped substrate, a coating layer containing a green phosphor coated on the surface of the plate-shaped substrate, and a green phosphor coated on the surface of the pearlescent pigment As a security pigment having dual properties of green _fluorescence and _{pearlescent properties} at _the same time, including a coating layer containing 0.08) to a security pigment having the chemical formula and a method for preparing the same.

Description

Green phosphor-coated security pigment and manufacturing method thereof

The present invention relates to a security pigment in which fluorescence properties are imparted to an inorganic plate-like substrate or pearlescent pigment by coating a nano-sized green phosphor on the surface by a particle coating method, and a method for manufacturing the same. The security pigment of the present invention can be manufactured with single or double security characteristics depending on the type of substrate, so it can be applied to various products such as printing inks, paints, building materials, automobiles, etc. can be used advantageously.

In various fields, the use of counterfeit products causes confusion in the market as well as companies, increasing economic losses, and distinguishing genuine products with legitimate rights from counterfeit products is important to protect legitimate rights holders and consumers and maintain market order. It is essential.

Recently, with the development of cloning and counterfeiting technologies similar to genuine products, crimes related to counterfeiting have rapidly increased, and it has become difficult for even experts to identify genuine and counterfeit products. In order to prevent such forgery, for example, research on anti-counterfeiting products, such as holograms, magnetic materials, phosphors, etc. Among them, phosphor is a material that can convert energy absorbed from the outside into unique light emission. It can express various colors based on the three main colors of red, green, and blue in the ultraviolet region, so it is mainly used in displays, but the excitation energy According to the circle, the scope of its application is expanding. A phosphor is composed of a parent and an activator, and its properties depend on the composition, structure, and crystallinity of the phosphor.

Among them, there is LaPO ₄ :Tb as a phosphor that can be used as a green phosphor, and the manufacturing method thereof has been disclosed in a thesis of the Korea Research Institute of Chemical Technology (Non-Patent Document 1). In the above paper, the green phosphor is manufactured by ultrasonic spray pyrolysis, and it is disclosed that six ultrasonic vibrators, a temperature of 900°C, and a temperature of 700°C to 1150°C for activation are required.

The green phosphor manufactured 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 firing but also in the manufacturing process itself. In addition, the green phosphor is a phosphor having only green fluorescence characteristics, and is not suitable for use as a pigment because it has no characteristics in the visible ray region.

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

The present invention has been devised to solve the problems of the prior art as described above, and an object of the present invention is to provide a single-property security pigment having only green fluorescence properties by coating a green phosphor on the surface of an inorganic plate-shaped substrate, and a method of manufacturing the same will provide

Another object of the present invention is to provide a double-property security pigment having a green fluorescence and pearl luster at the same time by coating a green phosphor on the surface of the pearlescent pigment, and a method for manufacturing the same.

The security pigment of the present invention for achieving the above object includes a coating layer containing a green phosphor coated on the surface of a plate-shaped substrate, wherein the green phosphor may have the following chemical formula:

La _1-xy Tb _x Ce _y PO ₄ (0.05≤x≤0.3, 0≤y≤0.08)

In the security pigment of the present invention, the green phosphor may be coated in an amount of 5 to 20 parts by weight based on 100 parts by weight of the plate-like substrate.

In the security pigment of the present invention, the plate-like substrate may be selected from inorganic plate-shaped 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, and , The pearlescent pigment may be a pigment coated with one or more metal oxides selected from TiO ₂ , SiO ₂ , and Fe ₂ O ₃ on the surface of the inorganic plate-like substrate.

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

1) preparing a green phosphor powder having a formula of La _1-xy Tb _x Ce _y PO ₄ (0.05≤x≤0.3, 0≤y≤0.08);

2) dispersing the green phosphor powder in distilled water to prepare a green phosphor nano-dispersion sol;

3) preparing a plate-shaped substrate aqueous solution; and

4) coating the green phosphor coating layer on the surface of the plate-shaped substrate by adding the green phosphor nano-dispersed sol to the aqueous solution of the plate-shaped substrate.

In the manufacturing method of the security pigment of the present invention, the step 1) comprises:

a) mixing a La(NO ₃ ) ₃ solution, a Tb(NO ₃ ) ₃ solution, a KH ₂ PO ₄ solution, and optionally a Ce(NO ₃ ) ₃ solution, and then administering KOH to impregnate the green phosphor, and

b) filtering, washing, drying, and calcining the resulting solution to prepare a green phosphor powder.

In the method for producing a security pigment of the present invention, in step 2), the green phosphor powder may be dispersed in distilled water at a concentration of 1 to 10% by weight, and the dispersion may be performed by bead milling or ultrasonic dispersion. there is.

In the method for producing a security pigment of the present invention, in step 3), the plate-like substrate may be selected from inorganic plate-shaped substrates and pearlescent pigments.

In the manufacturing method of the security pigment of the present invention, in step 3), 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 3) and 4), the step of adjusting the pH of the aqueous solution of the plate-like substrate to 8 or more may be further included.

In the manufacturing method of the security pigment of the present invention, the step of calcining the result of step 4) in a hydrogen atmosphere or an air atmosphere at a temperature of 300 ° C or more and 900 ° C or less for 1 hour or more and 5 hours or less. can

According to the present invention, by a simple and economical process that can control the fluorescence characteristics by particle-coating the dispersed sol of a green phosphor prepared in nano size on a plate substrate in various amounts, green fluorescence characteristics, or pearlescent characteristics A security pigment having both and green fluorescence characteristics can be manufactured in an appropriate form according to the use.

1 shows a flowchart for a method of manufacturing the security pigment of the present invention.
Figure 2 shows FE-SEM images of the security pigment particles of Examples 1, 8 and Comparative Example 2 of the present invention.
Figure 3 shows the PL intensity in order to examine the fluorescence characteristics of the security pigment particles of Example 1 of the present invention.
4 shows photographs measured under a 254 nm UV lamp in order to examine the fluorescence characteristics of the security pigment particles of Examples 1, 6, 8 and Comparative Example 2 of the present invention.

Advantages and features of the present invention, and methods for achieving them, will become apparent with reference to the embodiments described below in detail. However, the present invention is not limited to the embodiments disclosed below, but may be implemented in various different forms, and only these embodiments allow the disclosure of the present invention to be complete, and common knowledge in the technical field to which the present invention pertains. It is provided to fully inform the possessor 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 herein may be used with the meaning commonly understood by those of ordinary skill in the art to which the present invention belongs. In addition, terms defined in the dictionary used in general are not to be 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 coating layer containing a green phosphor coated on the surface of the plate-shaped substrate, wherein the green phosphor is La _1-xy Tb _x Ce _y PO ₄ (0.05≤x≤0.3, 0≤y≤0.08).

In the above formula, when the range of x is less than 0.05, the luminescence intensity is low and substantially no fluorescence effect can be expected. increase, and the economy declines.

In the above formula, when the range of y is greater than 0.08, the doping of Tb is affected, so that there is a problem in the light emitting characteristic.

The green phosphor may be coated in an amount of 5 to 20 parts by weight, preferably 10 to 20 parts by weight, based on 100 parts by weight of the plate-like substrate.

When the proportion of the green phosphor is less than 5 parts by weight, the fluorescence effect is insignificant and thus the utility may be substantially lost, and when it is more than 20 parts by weight, as the concentration of the nano-sized phosphor particles increases, rather than coating, they are agglomerated and coated and the luminous properties are 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 pearlescent pigment may be a pigment in which at least one metal oxide selected from TiO ₂ , SiO ₂ , and Fe ₂ O ₃ is coated on the surface of the inorganic plate-like substrate, but is not limited thereto. Preferably, the pearlescent pigment may be alumina flakes coated with TiO ₂ , which has a high refractive index and exhibits special optical effects, and has surface properties suitable for coating phosphor nanoparticles, which is particularly preferable.

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

1) preparing a green phosphor powder having a formula of La _1-xy Tb _x Ce _y PO ₄ (0.05≤x≤0.3, 0≤y≤0.08);

2) dispersing the green phosphor powder in distilled water to prepare a green phosphor nano-dispersion sol;

3) preparing a plate-shaped substrate aqueous solution; and

4) coating the green phosphor coating layer on the surface of the plate-shaped substrate by adding the green phosphor nano-dispersed sol to the aqueous solution of the plate-shaped substrate.

In a preferred embodiment of the method for producing a security pigment of the present invention, the step 1) comprises:

a) mixing a La(NO ₃ ) ₃ solution, a Tb(NO ₃ ) ₃ solution, a KH ₂ PO ₄ solution, and optionally a Ce(NO ₃ ) ₃ solution, and then administering KOH to impregnate the green phosphor, and

b) filtering, washing, drying, and calcining the resulting solution to prepare a green phosphor powder.

In step a), the mixing ratio (molar ratio) of the La(NO ₃ ) ₃ solution, the Tb(NO ₃ ) ₃ solution, and the KH ₂ PO ₄ solution may be preferably 1:0.15:0.4, or La( The mixing ratio (molar ratio) of the NO ₃ ) ₃ solution, the Tb(NO ₃ ) ₃ solution, the KH ₂ PO ₄ solution, and the Ce(NO ₃ ) ₃ solution may be preferably 1:0.1:0.4:0.05. If the mixing ratio is out of the above-mentioned mixing ratio, the structure of the matrix that can be doped with the activator ions is not smoothly formed, so that the color purity and light emitting characteristics of the phosphor may be reduced, which is not preferable.

In a preferred embodiment of the method for producing a security pigment of the present invention, in step 2), the green phosphor powder may be dispersed in distilled water at a concentration of 1 to 10% by weight, which is dispersed outside the concentration range Due to the heat generated in the process and the attraction of the unstable particles, the particles agglomerate and become rather large, which is undesirable.

In step 2), since the green phosphor powder is not formed in a size small enough to form a coating layer, it is possible to form a nano-sized dispersed sol 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 to obtain two effects of making the particle size small in a short time while also dispersing.

In addition, when bead milling cannot be performed, a nano-sized dispersed sol may be formed through ultrasonic dispersion. In the case of ultrasonic dispersion, the particles are separated by 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.

When the bead milling time or the ultrasonic dispersion time is out of the above range, the particle size does not decrease to a nano size, or the particles are aggregated by heat generated on the particles by the beads or ultrasonic waves, which is not preferable because the particle size may increase. .

In step 3), the plate-shaped substrate may be selected from inorganic plate-shaped substrates and pearlescent pigments, and the concentration of the plate-shaped substrate in the aqueous plate-shaped substrate may be 1 to 20% by weight. In this case, particle coating due to the difference in charge is not performed properly and rather they aggregate among themselves in an unstable state, which is undesirable.

In step 4), the green phosphor nano-dispersion sol may be added dropwise to the aqueous solution of the plate-like substrate and stirred. 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 higher and 90°C or lower, preferably 85°C. The stirring time may be preferably 12 hours or more and 48 hours or less, preferably 24 hours.

After step 4), the obtained solution may be filtered, washed, and dried, and a vacuum pump may be used for filtration and washing, and the drying temperature may be 40°C or higher and 80°C or lower, preferably 60°C.

The method for producing a security pigment of the present invention may further include, between steps 3) and 4), adjusting the pH of the plate-shaped aqueous solution to 8 or more. If the pH of the aqueous solution of the plate-shaped substrate is less than 8, the attractive force between the plate-shaped substrate and the phosphor particles is weakened, so that it is not coated on the surface of the plate-shaped substrate, which is not preferable.

The method for producing a security pigment of the present invention may further include calcining the result of step 4) at a temperature of 300° C. or higher and 900° C. or lower for 1 hour or more and 5 hours or less under a hydrogen atmosphere or an air atmosphere. there is. If the firing conditions are out of the above range, it is not preferable because the luminescent properties reduced by milling are not recovered at low temperatures or the particles fall due to the difference in thermal expansion coefficient between the coated particles at high temperatures, so that the luminescent properties are reduced.

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

Example 1

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

Lanthanum oxide and terbium oxide were dissolved in nitric acid, respectively, and used in the form of La(NO ₃ ) ₃ and Tb(NO ₃ ) ₃ solutions. In addition, potassium phosphate (potassium phosphate) was dissolved in distilled water. At this time, the content of La(NO ₃ ) ₃ and Tb(NO ₃ ) ₃ fixed the molar ratio of La to Tb to 0.15, and the content of La(NO ₃ ) ₃ and K _H 2P _O4 was the molar ratio of La to PO ₄ . was fixed to 0.4 and the experiment was carried out. After mixing the three solutions using ultrasound for 20 minutes, KOH was administered using a metering pump at a rate of 14 ml/min to impregnate the phosphor. Then, after filtering and washing using a vacuum pump, dried at 60 ℃ for 24 hours, and calcined at 600 ℃ for 2 hours LaPO ₄ :Tb (Formula La _1-x Tb _x PO ₄ , x ₌ 0.15) powder was prepared. The prepared LaPO ₄ :Tb was dispersed in distilled water at a concentration of 2% by weight, and then milled for 20 minutes using zirconia beads to prepare a nano-sized dispersion sol. After dispersing 5 g of a pearlescent pigment (CQV product A-901K; Alumina coated with TiO ₂ on the surface) in 100 ml distilled water as a plate-like substrate serving as a base material in a 250 ml beaker, the pH of the obtained pearlescent pigment aqueous solution was adjusted to 9 using KOH. was adjusted with LaPO ₄ :Tb was added dropwise to an aqueous pearlescent pigment solution at room temperature in an amount of 20 parts by weight based on 100 parts by weight of the pearlescent pigment at a rate of 0.5 ml/min using a metering pump, and then stirred at 250 rpm at 85° C. for 24 hours. and coated on the surface of the pearlescent pigment. Upon completion of the reaction, the aqueous pearlescent pigment solution was filtered and washed using a reduced pressure filter, dried at 60° C. for 24 hours, and calcined at 650° C. for 2 hours under a hydrogen atmosphere to prepare a security pigment.

Example 2

A security pigment was prepared in the same manner as in Example 1, except that the pH of the aqueous pearlescent pigment solution was adjusted to 8 in Example 1.

Example 3

A security pigment was prepared in the same manner as in Example 1, except that the pH of the aqueous pearlescent pigment solution was adjusted to 10 in Example 1.

Example 4

A security pigment was prepared in the same manner as in Example 1, except that LaPO ₄ :Tb was added dropwise in an amount of 5 parts by weight based on 100 parts by weight of the pearlescent pigment.

Example 5

A security pigment was prepared in the same manner as in Example 1, except that LaPO ₄ :Tb was added dropwise in an amount of 10 parts by weight based on 100 parts by weight of the pearlescent pigment.

Example 6

A security pigment was prepared in the same manner as in Example 1, except that in Example 1, firing was performed in an air atmosphere.

Example 7

In Example 1, the method of Example 1, except that a Ce(NO ₃ ) ₃ solution obtained by dissolving CeO ₂ in nitric acid was used together with a La(NO ₃ ) ₃ solution and a Tb(NO ₃ ) ₃ solution when preparing the phosphor in Example 1 In the same manner, LaPO ₄ :Tb,Ce (La _1-x Tb _x PO ₄ ,Ce _y , x ₌ 0.15, y=0.05) powder was prepared, and a security pigment was prepared in the same manner as in Example 1 using this powder. prepared.

Example 8

When dispersing the phosphor in Example 7, a security pigment was prepared in the same manner as in Example 7, except that instead of milling for 20 minutes using zirconia beads, it was treated with ultrasonic waves for 40 minutes.

Example 9

A security pigment was prepared in the same manner as in Example 1, except that in Example 1, an inorganic plate material (CQV product, Mica) was used instead of the pearlescent pigment as the plate-shaped substrate.

Comparative Example 1

A security pigment was prepared in the same manner as in Example 1, except that in Example 1, LaPO ₄ :Tb phosphor was not used and an inorganic plate material (CQV product, Mica) was used instead of the pearlescent pigment.

Comparative Example 2

In Example 1, LaPO ₄ : Tb phosphor was prepared without milling the dispersion, and then a security pigment was prepared in the same manner as in Example 1, except that it was simply mixed (not coated) with an aqueous pearlescent pigment solution. did.

Comparative Example 3

A security pigment was prepared in the same manner as in Example 1, except that in Example 1, the process of milling the LaPO4:Tb phosphor was not performed.

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

main) * In the fluorescence characteristics, O indicates excellent fluorescence characteristics, and X indicates weak or non-uniform fluorescence characteristics.

** In the pearl properties, O indicates pearlescent luster, and X indicates no pearlescent luster.

<Evaluation of properties>

LaPO ₄ : Evaluation of physical properties of the Tb phosphor-coated security pigment was evaluated by drying it in the form of a powder, and the powder was dried in a vacuum oven at 25° C. for 24 hours.

1. The shape of each of the security pigments prepared in Example 1, Example 8 and Comparative Example 2 was confirmed by measuring each dry powder by FE-SEM, which is shown in FIG. 2 .

From Figure 2, it can be confirmed that the security pigments of Examples are coated with particles on the surface of the plate substrate, whereas the security pigment of Comparative Example 2 is not coated with any particles on the surface of the plate substrate or is separately aggregated around the surface. can

2. The PL characteristics of the LaPO ₄ :Tb phosphor-coated security pigment prepared in Example 1 were confirmed, and the results are shown in FIG. 3 . PL analysis showed the emission intensity at the maximum central wavelength between 400 and 800 nm in the broadband 254 nm wavelength band.

3. LaPO ₄ :Tb phosphor coated security pigment prepared in Examples 1 and 6, LaPO ₄ :Tb,Ce phosphor coated security pigment prepared in Example 8, and LaPO prepared in Comparative Example 2 ₄ : The fluorescence characteristics of the simple mixture of Tb were measured under a UV lamp at 254 nm, and the results are shown in FIG. 4 .

From FIG. 4 , it can be seen that the security pigments of Examples exhibit excellent green fluorescence properties, while the security pigments of Comparative Example 2 do not exhibit any fluorescence properties or exhibit non-uniform fluorescence properties.

Claims (10)

A security pigment comprising a plate-shaped substrate and a coating layer containing a green phosphor coated on the surface of the plate-shaped substrate, wherein the green phosphor is La _1-xy Tb _x Ce _y PO ₄ (0.05≤x≤0.3, 0＜y≤ 0.08), a security pigment having a chemical formula. The security pigment according to claim 1, wherein the green phosphor is coated in an amount of 5 to 20 parts by weight based on 100 parts by weight of the plate-like substrate. The security pigment according to claim 1, wherein the plate-like substrate is selected from inorganic plate-shaped substrates and pearlescent pigments. According to claim 3, wherein the plate-like substrate is at least 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 the surface of the inorganic plate-shaped substrate. A security pigment in which at least one metal oxide selected from TiO ₂ , SiO ₂ , and Fe ₂ O ₃ is coated. A method for producing a security pigment according to any one of claims 1 to 4, comprising the steps of:
1) preparing a green phosphor powder having a formula of La _1-xy Tb _x Ce _y PO ₄ (0.05≤x≤0.3, 0<y≤0.08);
2) dispersing the green phosphor powder in distilled water to prepare a green phosphor nano-dispersion sol;
3) preparing a plate-shaped substrate aqueous solution, and adjusting the pH of the plate-shaped substrate aqueous solution to 8 or more; and
4) coating the green phosphor coating layer on the surface of the plate-shaped substrate by adding the green phosphor nano-dispersed sol to the aqueous solution of the plate-shaped substrate. The method of claim 5, wherein step 1) comprises:
a) mixing La(NO ₃ ) ₃ solution, Tb(NO ₃ ) ₃ solution, and KH ₂ PO ₄ solution, or La(NO ₃ ) ₃ solution, Tb(NO ₃ ) ₃ solution, KH ₂ PO ₄ solution , and a step of impregnating the green phosphor by administering KOH after mixing the Ce(NO ₃ ) ₃ solution, and
b) filtering, washing, drying and calcining the resulting solution to prepare a green phosphor powder. The method of claim 5, wherein in step 2), the green phosphor powder is dispersed in distilled water at a concentration of 1 to 10 wt%, and the dispersion is performed by bead milling or ultrasonic dispersion. The method of claim 5, wherein in step 3), the concentration of the plate-shaped substrate in the aqueous solution of the plate-shaped substrate is 1 to 20% by weight. delete The method of claim 5, further comprising calcining the resultant of step 4) at a temperature of 300°C or higher and 900°C or lower for a period of 1 hour or more and 5 hours or less under a hydrogen atmosphere or an air atmosphere. .

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