WO2018186588A1 - Method for preparing inorganic phosphor-coated pearlescent pigment for security and safety application - Google Patents

Abstract

The present invention relates to a method for preparing a security pigment. More specifically, the present invention relates to a method for preparing a security pigment having both aesthetic effects and security characteristics at the same time, the method comprising the steps of: (a) preparing an organic binder solution including inorganic phosphor particles; (b) mixing flake substrates with a solvent, and stirring and dispersing the mixture of the flake substrates and the solvent to prepare a substrate suspension; and (c) mixing the substrate suspension with the organic binder solution to coat the inorganic phosphor particles on the surface of the flake substrates.

Description

Manufacturing method of pearlescent pigment for security and safety coating inorganic phosphor

The present invention relates to a method for preparing a security pigment and a security pigment produced by the same, and more specifically, the fluorescence property using an inorganic phosphor in the pigment as well as an aesthetic effect through the interference color and metal gloss effect of the pearlescent pigment. It relates to a method for producing a security pigment imparted.

In recent years, the importance of imitation and anti-counterfeiting is increasing for all types of products, as well as for high value-added proprietary products. In particular, pharmaceuticals and mechanical replacement parts are part of a family that is easy to imitate and counterfeit, leaving consumers unintentionally exposed to direct or indirect damage.

In order to prevent such imitation and forgery, various typography-based anti-counterfeiting technologies such as holograms that change color depending on the viewing angle and intaglio printing to bend the printing surface have been developed using the micro diffraction structure. Fluorescent inks that fluoresce at wavelength, color changing inks that change color with temperature changes, magnetic inks with magnetic properties, pearlescent inks using pearlescent pigments with interference color effects, etc. It is applied to seals used in articles or articles, such as packaging of raw products, and used to determine whether they are forged.

However, as the counterfeit technology of counterfeiters continues to be sophisticated in recent years, there is a demand for a technology having security features that are more difficult to counterfeit.

It is an object of the present invention to provide a method for preparing a security pigment having simultaneously the aesthetic effect of pearlescent pigments and security properties based on fluorescence.

Method for producing a security pigment according to an embodiment of the present invention for achieving the above object, (a) preparing an organic binder solution containing inorganic phosphor particles; (b) after mixing the flake substrate and the solvent Stirring and dispersing it to prepare a substrate suspension; And (c) mixing the substrate suspension and the organic binder solution to coat the inorganic phosphor particles on the surface of the flake substrate.

In addition, the method for producing a security pigment according to another embodiment of the present invention for achieving the above object, (aa) milling the inorganic phosphor to prepare a pigment comprising an inorganic phosphor powder; And (bb) coating the pigment containing the prepared inorganic phosphor powder on a flake substrate.

The method for producing a security pigment according to the present invention has an advantageous advantage that it is economical and easy to provide a security pigment having a security characteristic by optical properties as well as a unique aesthetic effect of pearlescent pigments by an economical and easy process.

1 is a flow chart showing a method for producing a security pigment according to an embodiment of the present invention.

Figure 2 is a flow chart showing a method for producing a security pigment according to another embodiment of the present invention.

3 is a SEM photograph of a security pigment prepared from a manufacturing method according to an embodiment of the present invention.

Figure 4 is a SEM photograph of the security pigment prepared from the manufacturing method according to another embodiment of the present invention.

5 is a photograph showing the gloss and fluorescence of each sample.

6 is a graph showing emission spectra of respective samples.

Advantages and features of the present invention and methods for achieving them will be apparent with reference to the embodiments described below in detail with the accompanying drawings. However, the present invention is not limited to the embodiments disclosed below, but may be implemented in various different forms, only the present embodiments to make the disclosure of the present invention complete, and common knowledge in the art to which the present invention pertains. It is provided to fully inform the person having the scope of the invention, which is defined only by the scope of the claims. Like reference numerals refer to like elements throughout.

Hereinafter, a method for preparing a security pigment according to the present invention and a security pigment produced by the same will be described in detail.

1 is a flow chart showing a method for producing a security pigment according to an embodiment of the present invention.

Referring to Figure 1, the method for producing a security pigment according to the present invention comprises the steps of (a) preparing an organic binder solution containing inorganic phosphor particles; (b) after mixing the flake substrate and the solvent and stirring and dispersing it Preparing a substrate suspension; And (c) mixing the substrate suspension and the organic binder solution to coat the inorganic phosphor particles on the surface of the flake substrate.

First (a) step (S110) is for the step of preparing an organic binder solution containing inorganic phosphor particles.

The organic binder solution used in step (a) (S110) is cellulose, cellulose acetate, polyamide, epoxy resin, polyester, melamine resin, polyurethane, resin vinyl resin, silicon resin, acrylic acid ester, methacrylic acid ester, Organic binder resins containing one or two or more polymers or copolymers of styrene, ethylene, propylene, acrylic resins and derivatives thereof may be used. However, the organic polymer resins used in the present invention are particularly exemplified above. It is not limited.

* In the organic binder solution, the organic polymer resin is preferably included 5 to 50 parts by weight relative to 100 parts by weight of the organic binder solution. When the organic polymer resin is less than 5 parts by weight, the required resin adhesiveness may not be obtained. On the other hand, when the organic polymer resin is more than 50 parts by weight, the content of the organic polymer resin is too high relative to the amount of the binder resin, thereby agglomeration of particles or substrates. It may cause a phenomenon.

Inorganic phosphors used in the present invention can be used without particular limitation inorganic phosphors known in the art, it is preferable to use inorganic phosphors having strong luminescence properties suitable for security and safety applications.

The inorganic phosphor used in the present invention is not particularly limited as long as it is an inorganic phosphor such as garnet-based, silicate-based, sulfide-based, oxynitride-based or nitride-based, in addition to an oxide-based fluorescent substance having an oxide as a mother crystal. For example, garnet-based phosphors; _{Y 3 Al 5 O 12: Ce} 3 + (YAG: Ce) _{yellow, Tb 3 Al 5 O 12:} Ce 3 + (TAG: Ce) yellow, silica decade based phosphor; (Sr, Ba, Ca) 2 SiO 4: Eu ^{2 +} greenish yellow, (Sr, Ba, Ca, Mg, Zn) 2 Si (OD) 4: Eu 2 +; D = F, Cl, S, N, Br greenish yellow, Ba ₂ MgSi ₂ O ₇ : Eu ^{2 +} green, Ba ₂ SiO ₄ : Eu ²⁺ green, Ca ₃ (Sc, Mg) ₂ Si ₃ O ₁₂ : Ce ^{3 +} Green, sulfide-based phosphors; (Ca, Sr) S: Eu ^{2 +} Red, (Sr, Ca) Ga ₂ S ₄ : Eu ^{2 +} Green, Oxynitrides SrSi ₂ O ₂ N ₂ : Eu ^{2 +} Green, SiAlON: Ce ³⁺ cyan, β-SiAlON: Eu ^{2 +} greenish yellow, Ca-α-SiAlON: Eu 2 + _{orange, Ba 3 Si 6 O 12 N} 2: Eu 2+ green, nitride-based fluorescent material; CaAlSiN ₃ : Eu ^{2 +} red, (Sr, Ca) AlSiN ₃ : Eu ^{2 +} yellow red, Sr ₂ Si ₅ N ₈ : Eu ^{2 +} red, aluminate-based phosphor; _{(Sr, Ba) Al 2 O} 4: Eu 2 + _{blue, (Mg, Sr) Al 2} O 4: Eu 2+ _{blue, BaMg 2 Al 16 O 27:} Eu 2 + blue, oxide-based phosphor; Y ₂ SiO ₅ : Ce blue, Ca ₂ B ₅ O ₉ Cl: Eu blue, BaMgAl ₁₄ O ₂₃ : Eu blue, BaO ₆ Al ₂ O ₃ : Mn blue, Y ₃ Al ₅ O ₁₂ : Ce green, Y ₃ Al ₅ O ₁₂ : Tb green, ZnSiO ₄ : Mn green, InBO ₃ : Tb green, LnPO ₄ : Ce, Tb green, Gd ₂ O ₃ : Eu red, Y ₂ O ₃ : Eu red, CeO ₂ : Eu red, TiO ₂ : Eu red, YVO ₄ : Eu red, MgSiO ₃ : Mn red, Zn ₃ (PO ₄ ) ₂ : Mn red, InBO ₄ : Eu red, (Y, Gd) BO ₃ : Eu red, SrTiO ₃ : Pr Visible light emitting phosphors such as red, ultraviolet light emitting phosphors, and the like.

The inorganic phosphor is preferably contained 5 to 60 parts by weight based on 100 parts by weight of the organic binder solution. When the inorganic phosphor is included in less than 5 parts by weight, the amount of the organic polymer resin and the binder resin is relatively high compared to the inorganic phosphor may cause a problem of low binding efficiency, while the inorganic phosphor is included in excess of 60 parts by weight Since the amount of the organic polymer resin and the binder resin is relatively small, there may be a problem that the required binding effect cannot be obtained.

In addition, the organic binder solution may further include a dispersant and an antifoaming agent as necessary.

The dispersant may be used without limitation, a dispersant known in the art and preferably contains 1 to 5 parts by weight based on 100 parts by weight of the organic binder solution. When the dispersant is included in less than 1 part by weight, the required dispersing effect may not be obtained. When the dispersant is included in an amount exceeding 5 parts by weight, the concentration of the dispersant may be so high that dispersion efficiency may be reduced.

The antifoaming agent may be used without limitation antifoams known in the art, it is preferable that 1 to 5 parts by weight based on 100 parts by weight of the organic binder solution. When the dispersant is included in less than 1 part by weight, the required antifoaming effect may not be obtained. When the dispersant is included in an amount of more than 5 parts by weight, the concentration of the antifoaming agent may be so high that the defoaming efficiency may be reduced.

In addition, the step (a) (S110), (a1) step of introducing the inorganic phosphor particles into the organic binder solution; And (a2) pulverizing the inorganic phosphor particles to prepare an organic binder solution including nano-size inorganic phosphor particles.

The inorganic phosphor particles may be pulverized using a known pulverization method, and are not particularly limited. However, the inorganic phosphor particles contained in the organic binder solution may be pulverized to an appropriate size using a milling equipment having a milling ball. It is preferable in terms of process efficiency.

Preferably, the inorganic phosphor particles have a particle size of 10 to 900 nm, and when the particle size of the inorganic phosphor particles is less than 10 nm, there is no improvement in optical properties during UV irradiation, and when the inorganic phosphor particles exceed 900 nm, adhesion to a flake substrate is exceeded. This can be reduced.

Next (b) step (S120) is to prepare a substrate suspension by mixing the flake substrate and the solvent and then stirring and dispersing it.

The flake substrate is preferably not particularly limited as long as it is a plate-like substrate, but at least one of synthetic mica, natural mica, glass flake, plate iron oxide, plate alumina, aluminum flake, plate silica, talc and bismuth. Including substrates may be used.

The flake substrate may also include a flake substrate coated with one or more metal oxides. The metal oxide may be coated on the flake substrate in a single layer or a plurality of layers of various components such as TiO ₂ , SiO _{2 ,} Fe ₂ O ₃ depending on the required pearl properties.

The solvent may be an organic solvent known in the art, specifically, hydrocarbon solvents such as hexane, octane, decane, isodecane, cyclohexane, methylcyclohexane, toluene, xylene, ethylbenzene; Alcohol solvents such as methanol, ethanol, propanol, isopropanol, butanol, isobutanol, hexanol, benzyl alcohol and cyclohexanol; Ethylene glycol, diethylene glycol, propylene glycol, dipropylene glycol, methyl cellosolve, ethyl cellosolve, butyl cellosolve, propylene glycol monomethyl ether, propylene glycol monoethyl ether, propylene glycol monopropyl ether, diglim, Triglyceride, dipropylene glycol dimethyl ether, butyl carbitol, butyl triethylene glycol, methyl dipropylene glycol, methyl cellosolve acetate, propylene glycol monomethyl ether acetate, dipropylene glycol butyl ether acetate, diethylene glycol monobutyl ether Glycol solvents such as acetates; Ether solvents such as diethyl ether, dipropyl ether, methylcyclopropyl ether, tetrahydrofuran, dioxane and anisole; Methyl ethyl ketone, diethyl ketone, methyl

Ketone solvents such as isobutyl ketone, cyclohexanone, isophorone and acetphenone; Ester solvents such as methyl acetate, ethyl acetate, butyl acetate, propyl acetate, methyl butyrate, ethyl butyrate, caprolactone, methyl lactate and ethyl lactate; Halogenated solvents such as chloroform and dichloroethane; Amide solvents such as dimethylformamide, dimethylacetamide, 2-pyrrolidone, N-methylpyrrolidone, and caprolactam; Dimethyl sulfoxide, sulfolane, tetramethyl urea, ethylene carbonate, propylene carbonate, dimethyl carbonate and the like can be used. However, the kind of organic solvent used for this invention is not specifically limited.

The stirring speed in step (b) (S120) is preferably maintained at 100 ~ 500 rpm. If the stirring speed is less than 100 rpm, there is a problem that the dispersion effect is reduced and the inorganic phosphor particles may aggregate, and if more than 500 rpm, further dispersion efficiency may be reduced.

Next, step (c) (S130) is for mixing the substrate suspension and the organic binder solution to coat the inorganic phosphor particles on the surface of the flake substrate.

Here, it is preferable to adjust the pH of the mixed solution to a range of 7.0 to 10.0 by using a pH adjusting agent in a mixed solution of the substrate suspension and the organic binder solution. When the pH is less than 7.0, the aggregation of particles may occur to reduce the reaction effect, and when the pH exceeds 10.0, a problem may occur in that adhesion of the inorganic phosphor particles is reduced.

The pH adjusting agent used in the present invention is not particularly limited, but may be an acidic solution including one or more mixtures selected from hydrochloric acid, sulfuric acid, acetic acid, acetic acid, and the like, which exhibit acidity.

After step (c), if necessary, (d) washing and dehydrating the flake substrate; (e) drying the washed flake substrate; And (f) screening a separated flake substrate formed larger than a predetermined size among the dried flake substrates.

The drying step according to step (e) is preferably carried out at 60 ~ 180 ℃. If the drying temperature is less than 60 ℃ may take a long time to dry productivity, and if it exceeds 180 ℃, the inorganic phosphor particles may be damaged to reduce the optical properties after drying.

In the screening step according to step (f), it is preferable to separate the flake substrate having a particle size of more than 100 μm. In addition, by passing through the step (f) there is an effect that can remove the aggregated particles formed during the reaction. The screening method of the screening step may be performed using a mesh having a preset size, but is not particularly limited.

Next, a method for preparing a security pigment according to another embodiment of the present invention will be described in detail.

Figure 2 is a flow chart showing a method for producing a security pigment according to another embodiment of the present invention.

Referring to Figure 2, (aa) milling the inorganic phosphor to prepare a pigment comprising the inorganic phosphor powder, and (bb) coating the pigment comprising the prepared inorganic phosphor powder on the flake substrate; includes do.

First, an inorganic phosphor is milled to prepare a pigment including an inorganic phosphor powder.

Thereafter, a pigment containing the inorganic phosphor powder is added to a water-soluble inorganic salt solution, and then the pH is adjusted to a neutral state to prepare a pigment suspension.

The milling may be performed at 20 to 40 Hz for 24 to 72 hours. If the milling time is less than 24 hours, the dispersion of the pigment may be insufficient, and if the milling time is longer than 72 hours, the process time may be long and the efficiency may be reduced without further dispersing effect.

By milling the inorganic phosphor, it is possible to form a pigment containing an inorganic phosphor powder having a nano size. It is preferable that the average particle size of a pigment is 100-300 nm. If the average particle size of the pigment is less than 100nm, there may be no improvement in color saturation after coating the substrate surface with a pigment containing a powder. On the contrary, in the case of exceeding 300 nm, the size of the pigment is large, and thus the adhesion to the substrate is decreased, and the chroma after the reaction may be decreased.

The inorganic phosphor used in the present invention is not particularly limited as long as it is an inorganic phosphor such as garnet-based, silicate-based, sulfide-based, oxynitride-based or nitride-based, in addition to the oxide-based fluorescent substance having an oxide as a mother crystal as described above. For example, garnet-based phosphors; _{Y 3 Al 5 O 12: Ce} 3+ (YAG: Ce) _{yellow, Tb 3 Al 5 O 12:} Ce 3 + (TAG: Ce) Yellow, Cascade silica-based fluorescent material; (Sr, Ba, Ca) 2 SiO 4: Eu ^{2 +} greenish yellow, (Sr, Ba, Ca, Mg, Zn) 2 Si (OD) 4: Eu 2 +; D = F, Cl, S, N, Br greenish yellow, Ba ₂ MgSi ₂ O ₇ : Eu ^{2 +} green, Ba ₂ SiO ₄ : Eu ^{2 +} green, Ca ₃ (Sc, Mg) ₂ Si ₃ O ₁₂ : Ce ^{3 +} Green, sulfide-based phosphors; (Ca, Sr) S: Eu ^{2 +} Red, (Sr, Ca) Ga ₂ S ₄ : Eu ^{2 +} Green, Oxynitrides SrSi ₂ O ₂ N ₂ : Eu ²⁺ Green, SiAlON: Ce ^{3 +} cyan, β-SiAlON: Eu ^{2 +} greenish yellow, Ca-α-SiAlON: Eu 2 + _{orange, Ba 3 Si 6 O 12 N} 2: Eu 2 + green, nitride-based fluorescent material; CaAlSiN _3: Eu ^{2 +} _{red, (Sr, Ca) AlSiN 3} : Eu 2+ yellowish _{red, Sr 2 Si 5 N 8:} Eu 2 + red, aluminate-based phosphor; _{(Sr, Ba) Al 2 O} 4: Eu 2 + _{blue, (Mg, Sr) Al 2} O 4: Eu 2 + _{blue, BaMg 2 Al 16 O 27:} Eu 2 + blue, oxide-based phosphor; Y ₂ SiO ₅ : Ce blue, Ca ₂ B ₅ O ₉ Cl: Eu blue, BaMgAl ₁₄ O ₂₃ : Eu blue, BaO ₆ Al ₂ O ₃ : Mn blue, Y ₃ Al ₅ O ₁₂ : Ce green, Y ₃ Al ₅ O ₁₂ : Tb green, ZnSiO ₄ : Mn green, InBO ₃ : Tb green, LnPO ₄ : Ce, Tb green, Gd ₂ O ₃ : Eu red, Y ₂ O ₃ : Eu red, CeO ₂ : Eu red, TiO ₂ : Eu red, YVO ₄ : Eu red, MgSiO ₃ : Mn red, Zn ₃ (PO ₄ ) ₂ : Mn red, InBO ₄ : Eu red, (Y, Gd) BO ₃ : Eu red, SrTiO ₃ : Pr Visible light emitting phosphors such as red, ultraviolet light emitting phosphors, and the like.

The water-soluble inorganic salt solution is selected from NaOH, KOH, Ca (OH) ₂ , NH ₃ , Mg (OH) ₂ , CH ₃ NH ₂ , CH ₃ CH ₂ NH ₂ , CH ₃ OH, Al (OH) ₃ or It may comprise one or more mixtures.

The pigment concentration in the pigment suspension manufacturing step is preferably adjusted to 5 to 30% by weight based on 100% by weight of the suspension. If the concentration of the pigment is less than 5% by weight, the milling efficiency may decrease during milling due to the low concentration. On the other hand, when the concentration of the pigment exceeds 30% by weight, the amount of the pigment containing the powder relative to the solution is too large, the milling efficiency may be lowered.

Next, the flake substrate is mixed with DI water to form a substrate suspension which is stirred and dispersed. The flake substrate may comprise one or more of synthetic mica, natural mica, glass, plate iron oxide, plate alumina and plate silica, talc, bismuth, aluminum flakes. Alternatively, the flake substrate may be coated with a metal oxide on the surface to further improve the heat resistance of the pigment. As the metal oxide, for example, TiO ₂ , Fe ₂ O ₃ , Cr ₂ O ₃ , SiO ₂ , ZnO, ZnO ₂ , Ce ₂ O ₃ , MgO, Al ₂ O _3, or the like may be used.

In addition, the flake substrate includes the above-described components, and at the same time a metal oxide may be coated on the surface of the substrate.

At this time, the stirring and dispersion may be performed for a predetermined time at 200 ~ 500rpm.

The concentration of the substrate in the substrate suspension forming step may be adjusted to 3 to 25% by weight relative to 100% by weight of the suspension. If the concentration of the substrate is less than 3% by weight, the concentration may be too low to reduce the reaction efficiency. If the concentration is more than 25% by weight, aggregation may occur due to the thick concentration of the substrate suspension.

Next, the acidity regulator and the pigment suspension are mixed with the substrate suspension to coat the inorganic phosphor powder on the surface of the flake substrate.

Acidity regulators include acidic solutions comprising one or more mixtures selected from hydrochloric acid, sulfuric acid, acetic acid, acetic acid, and the like, which exhibit acidity.

The substrate suspension is BaCl ₂ , CaCl ₂ , AlCl ₃ , SnCl ₄ , TiCl ₄ , TiOCl ₂ , TiOSO ₄ , FeCl ₃ , FeSO ₄ , It may further comprise a metal salt comprising one or a mixture of one or more selected from SiCl ₄ , ZrOCl ₂ , Na ₂ O, SiO ₂ 5H ₂ O, MnCl ₂ , MgCl ₂ and CoCl ₂ .

The concentration of the metal salt may be adjusted to 3 to 20% by weight based on 100% by weight of the suspension. When the concentration of the metal salt is less than 3% by weight, the amount of the added solution may increase, resulting in a decrease in efficiency. When the concentration of the metal salt exceeds 20% by weight, the coating state of the substrate may be reduced after the reaction due to the rapid pH change.

The flake substrate coating step may be performed at 100 ~ 500rpm.

If less than 100rpm the dispersion effect during the reaction may be agglomerated between the pigments, if the 500rpm or more can be reduced efficiency only by increasing the rpm without any further dispersion effect.

A flake substrate washing step of washing and dehydrating the flake substrate coated with the inorganic phosphor powder after the flake substrate coating step; A flake substrate drying step of drying the washed flake substrate; And a flake substrate screening step of separating the flake substrate formed larger than a predetermined size among the dried flake substrate using a mesh.

The flake substrate drying step may be performed at 60 ~ 150 ℃. If the temperature is less than 60 ° C., the drying time may be long, resulting in a decrease in productivity. If the temperature is higher than 150 ° C., aggregation may occur due to the fast drying time.

In the flake substrate screening step, the average particle diameter of the separated flake substrate may be 45 μm or less.

In the substrate screening step, a mesh may be used to remove aggregated particles generated during the reaction.

* The security pigment produced by the manufacturing method according to the present invention described above can be used as the authenticity determination object. As mentioned above, by irradiating the object with ultraviolet rays, it is possible to recognize the phosphor and determine the authenticity of the object.

In addition, the security pigments produced by the manufacturing method according to the present invention may be used as well as oil value documents such as banknotes, checks, credit cards, stocks, passports, identity documents, driver's licenses, tickets, stamps, labels, packaging materials, seals, and the like. Security pigments can be used in protected products, such as garments, shoes, household articles, consumer electronics, etc., which are applied directly to the product, and other than the examples listed above, it can be used without limitation for products requiring security.

In particular, the security product to which the security pigment according to the present invention is applied may have any one form of paint, coating, powder coating, printing ink, coating composition, plastic, adhesive, paper stock, building material and rubber composition. The security pigment preferably has a content range of 0.01 to 30% by weight, based on the total weight of the security product.

In addition, the security documents to which the security products are applied include banknotes, checks, bank credit cards, check cards, securities, identification cards, certificates, import stamps, stamps, identification cards, train and plane tickets, admission tickets, telephone cards, labels, It may have any form of test stamps and packaging materials, and the form of the security document is not particularly limited.

Hereinafter, the present invention will be described in more detail with reference to examples according to the present invention, but the scope of the present invention is not limited to the examples given below.

Example 1

1. Preparation of an organic binder solution containing inorganic phosphor particles

36 g of acrylic organic binder resin, 43 g of primary distilled water, 0.5 g of dispersant, and 0.5 g of antifoam were added to a 250 ml beaker, followed by stirring for 1 hour or more using a magnetic bar. After the binder solution was mixed through stirring, 20 g of a Gd ₂ O ₃ : Eu inorganic phosphor was added thereto, followed by stirring for 1 hour using a magnetic bar.

After the organic binder solution prepared through the above process was added with 450 g of ZrO ₂ Ball in a 250 ml PE bottle for ball milling, milling was performed for 35 hours to 72 hours using a milling equipment.

2. Preparation of security pigments comprising flake substrate coated with inorganic phosphor particles

50 g of plate-like alumina substrate and 450 g of methanol were added to a 1 L beaker, and stirred and dispersed at 300 rpm at 20 to 25 ° C. to form a substrate suspension. Next, 12.5 g of the organic binder solution was titrated to the substrate suspension using a pump. After the titration was completed, the pH was adjusted to 7.0 by adding 5% hydrochloric acid solution to the mixed suspension of the substrate suspension and the organic binder solution. Thereafter, the mixture was stirred for 30 minutes to terminate the reaction, washed with water and dehydrated, and then dried at 80 ° C. for 30 minutes. The dried flake substrate was screened using a mesh, and the flake substrate formed larger than a predetermined size was separated or aggregated particles generated during the reaction were removed.

Through the above procedure, a security pigment coated with an inorganic phosphor on the surface of the flake substrate was prepared.

Referring to FIG. 3, it can be seen that the security pigment according to Example 1 includes a flake substrate having inorganic phosphor particles coated on its surface.

<Example 2>

Preparation of security pigments comprising flake substrate coated with inorganic phosphor particles

Gd ₂ O ₃ : Eu inorganic phosphor 10g, primary distilled water 90g was added to a 250mL ball milling bottle, ball milling was performed for 35 Hz and 48 hours, and the inorganic phosphor powder having an average particle size of 100 to 300 nm was included. Pigment was prepared. (The concentration of the pigment containing the inorganic phosphor powder in the solution is 10% by weight.)

Next, a pigment suspension was prepared by mixing the prepared pigment and sodium hydroxide which is a water-soluble inorganic salt solution, and then adjusting the pH to 7.

Next, 30 g of plate-shaped alumina and 270 g of primary distilled water were added to a 2 L beaker as a flake substrate, and stirred and dispersed at 300 rpm at 20 to 25 ° C. to form a substrate suspension.

Next, the pH is adjusted to 12 by adding a 10% solution of sodium hydroxide to the pigment suspension, and mixed with the substrate suspension together with a 5% by weight AlCl ₃ solution to maintain a pH of 5.5. The reaction was terminated by stirring for 10 minutes, washed with water and dehydrated, and dried at 120 ° C. for 2 hours. The dried flake substrate was screened using a mesh, and the flake substrate formed larger than a predetermined size was separated or aggregated particles generated during the reaction were removed.

As a result, an inorganic phosphor powder was coated on the surface of the flake substrate to prepare a security pigment.

Referring to FIG. 4, it can be seen that the security pigment according to Example 2 includes a flake substrate having inorganic phosphor particles coated on its surface.

<Test Example>

1. Preparation of samples

A total of four samples were prepared as follows.

(1) Reference Example 1: Inorganic phosphor

Reference Example 1 is a Gd ₂ O ₃ : Eu inorganic phosphor.

(2) Reference Example 2 Substrate Before Coating

Reference Example 2 is for an alumina flake that is not coated with a metal oxide on the surface.

(3) Comparative Example 1: Mixing

Comparative Example 1 is a mixture of "Gd ₂ O ₃ : Eu inorganic fluorescent substance" according to Reference Example 1 and "alumina flakes not coated with metal oxide on the surface" according to Reference Example 2.

(4) Example 1: Coating

Example 1 means a security pigment according to Example 1 described above.

2. Observation of each sample

FIG. 5 is a photograph showing gloss and fluorescence characteristics of the samples, and FIG. 5 shows characteristics of each sample in daylight and after UV excitation at 254 nm.

Referring to FIG. 5, pearlescent properties in daylight of Reference Example 2 (substrate before coating) and Example 1 (coating) are not easy to distinguish. However, looking at the red light emission after being excited at UV 254nm, it can be seen that Example 1 (coating) has a red light emission characteristics unlike Reference Example 2.

In addition, in Example 1 (coating), inorganic phosphor nanoparticles are uniformly coated on a substrate surface. Therefore, it can be confirmed that Example 1 has a uniform red light emission characteristic.

In contrast, in Comparative Example 1 (Mixing), the inorganic phosphor is not coated on the substrate surface and is present in the form of a mixture of the inorganic phosphor and the substrate. Accordingly, it can be seen that Comparative Example 1 has a non-uniform red light emitting property due to the inferior pearl luster effect and the aggregation phenomenon between the inorganic phosphor particles.

3. Analysis of emission spectrum of each sample

6 is a graph showing emission spectra of respective samples (Reference Example 2, Example 1, and Comparative Example 1).

6 shows the spectral results from 400 nm to 800 nm after UV excitation of each sample. Here, the emission peak of 612 nm corresponds to the light-emission by the transition to a ⁷ F ₂ ground level in the ⁵ D ₀ level of the Eu ^{3 +} ion here.

Referring to Figure 6, Reference Example 2 (substrate before coating) was not observed luminescent properties, Example 1 (coating: inorganic pigment coated security pigment) Comparative Example 1 (Mixing: mixture of inorganic phosphor and flake substrate) It can be seen that the light emission intensity is larger than that of.

Unlike Comparative Example 1 (a mixture of inorganic phosphors and a substrate), Example 1 has an inorganic phosphor uniformly coated on the surface of the substrate, and thus it can be confirmed that it has excellent luminescent properties when irradiated with UV with aesthetic effect peculiar to pearlescent gloss. have.

Accordingly, it can be confirmed that Example 1 according to the present invention has excellent security pigment properties compared to Comparative Example 1.

Although the embodiments of the present invention have been described above with reference to the accompanying drawings, the present invention is not limited to the above embodiments and can be manufactured in various forms, and having ordinary skill in the art to which the present invention pertains. It will be understood by those skilled in the art that the present invention may be embodied in other specific forms without changing the technical spirit or essential features of the present invention. Therefore, it should be understood that the embodiments described above are exemplary in all respects and not restrictive.

Claims (13)

1. (a) preparing an organic binder solution comprising inorganic phosphor particles;

   (b) mixing the flake substrate and the solvent and then stirring and dispersing it to prepare a substrate suspension; And

   (c) mixing the substrate suspension and the organic binder solution to coat the inorganic phosphor particles on the surface of the flake substrate.
2. The method of claim 1,

   Step (a) is

   (a1) adding inorganic phosphor particles to the organic binder solution; And

   (a2) pulverizing the inorganic phosphor particles to prepare an organic binder solution containing nano-size inorganic phosphor particles.
3. The method of claim 1,

   The flake substrate

   A method for producing a security pigment comprising at least one of synthetic mica, natural mica, glass flakes, glass flakes, plate iron oxide, plate alumina, aluminum flakes, plate silica, talc and bismuth.
4. The method of claim 1,

   The flake substrate

   Method for producing a security pigment, characterized in that it comprises a flake substrate coated with at least one metal oxide layer.
5. The method of claim 1,

   After step (c),

   (d) washing and dehydrating the flake substrate;

   (e) drying the washed flake substrate; And

   (f) a screening step of separating the flake substrate formed larger than a predetermined size among the dried flake substrates.
6. (aa) milling the inorganic phosphor to produce a pigment comprising the inorganic phosphor powder; And

   (bb) coating a pigment comprising the prepared inorganic phosphor powder on a flake substrate.
7. The method of claim 6,

   (Bb) step is

   (bb1) preparing a pigment suspension by adding a pigment containing an inorganic phosphor powder to a water-soluble inorganic salt solution and then adjusting the pH to a neutral state;

   (bb2) forming a substrate suspension for mixing the flake substrate with purified water, followed by stirring and dispersion; And

   (bb3) a flake substrate coating step of coating the inorganic phosphor powder on the surface of the flake substrate by mixing an acidity regulator and the pigment suspension in the substrate suspension.
8. The method of claim 7, wherein

   After the flake substrate coating step,

   A flake substrate washing step of washing and dehydrating the flake substrate coated with an inorganic phosphor powder;

   A flake substrate drying step of drying the washed flake substrate; And

   A flake substrate screening step of separating the flake substrate formed larger than a predetermined size of the dried flake substrate using a mesh; The method of producing a security pigment further comprising.
9. The method of claim 7, wherein

   In the step of forming the substrate suspension

   Wherein said flake substrate comprises at least one of synthetic mica, natural mica, glass, flaky iron oxide, flaky alumina and flaky silica, talc, bismuth and aluminum flakes.
10. The method of claim 7, wherein

    In the step of forming the substrate suspension

    The flake substrate is a method for producing a security pigment, characterized in that the surface is coated with a metal oxide.
11. A security pigment, characterized by coating a pigment comprising an inorganic phosphor powder on a surface of a flake substrate.
12. A security product to which the security pigment according to claim 11 is applied,

    The security product has the form of any one of paint, coating, powder coating, printing ink, coating composition, plastic, adhesive, paper stock, building material and rubber composition,

    The security pigment is a security product, characterized in that it has a content range of 0.01 to 30% by weight based on the total weight of the security product.
13. A security document to which a security product according to claim 12 is applied,

    Banknotes, checks, bank credit cards, check cards, securities, identification cards, certificates, import stamps, stamps, identification cards, train and plane tickets, entry tickets, phone cards, labels, test stamps and any form of packaging material. Having a secure document.

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