JP7551985B2 - Pearl colored scale-like particles, inks, and coatings - Google Patents

Description

The present invention relates to pearlescent colored scale-like particles, ink, and coating film.

Conventionally, various light interference pearl pigments have been used in the fields of paints, plastics, printing inks, cosmetics, etc. Known examples of the pearl pigment include those in which the surface of a scaly powder base material is coated with titanium oxide, iron oxide, etc.

Patent Document 1 also discloses that optically variable flakes with a three-layer structure of ZnS/MgF ₂ /ZnS exhibit pearl coloring (see paragraph [0010], Table 1). Patent Document 1 also discloses that the total average thickness of the three layers of ZnS/MgF ₂ /ZnS is 0.5 μm (500 nm) or less, and that the average particle size of the flakes is within the range of 2 μm to 20 μm (see paragraph [0037]). Patent Document 1 further discloses that deposition and sputtering methods are used to form the three-layer structure of ZnS/MgF ₂ /ZnS (see paragraph [0024]).

Japanese Patent Application Publication No. 8-58224

However, the flakes of the three-layer structure of ZnS/MgF ₂ /ZnS in the above Patent Document 1 are mainly used for cards for preventing counterfeiting, and the ink is applied by bar-coat printing, screen printing, etc. (see paragraph [0037]), and is not used for inkjet printing. When inkjet printing is performed using ink containing flakes with an average particle size of 2 μm to 20 μm as in the above Patent Document 1, the ejection stability may be extremely deteriorated due to the influence of the nozzle diameter of the inkjet printer head and the dispersion stability. Furthermore, the flakes of the three layers of ZnS/MgF ₂ /ZnS in the above Patent Document 1 are described as having a total average thickness of the three layers of 0.5 μm (500 nm) or less, but there is no description of the average thickness of each of the three layers, and no attempt is made to optimize the thickness of each of the three layers suitable for pearl coloring.

The present invention aims to solve the above-mentioned problems in the prior art and to achieve the following objectives. That is, the present invention aims to provide pearlescent coloring scale-like particles, ink, and coating film that can achieve excellent pearlescent coloring by optimizing the thickness of each layer in a three-layer structure having a first zinc sulfide layer, a magnesium fluoride layer, and a second zinc sulfide layer in that order.

The means for solving the above problems are as follows.
<1> A zinc sulfide layer, a magnesium fluoride layer, and a zinc sulfide layer in this order,
The first zinc sulfide layer has an average thickness of 30 nm or more;
The magnesium fluoride layer has an average thickness of 25 nm or more,
The second zinc sulfide layer has an average thickness of 30 nm or more;
The pearlescent colored scaly particles are characterized in that the total average thickness of the three layers, namely, the first zinc sulfide layer, the magnesium fluoride layer and the second zinc sulfide layer, is 330 nm or less.
<2> The average thickness of the first zinc sulfide layer is 30 nm or more and 130 nm or less,
The magnesium fluoride layer has an average thickness of 25 nm or more and 60 nm or less,
The pearlescent colored scaly particle according to <1>, wherein the second zinc sulfide layer has an average thickness of 30 nm or more and 190 nm or less.
<3> The pearlescent colored scaly particles according to any one of <1> and <2>, wherein a cumulative 50% volume particle diameter D ₅₀ is 1.8 μm or less.
<4> The pearlescent colored scaly particles according to any one of <1> to <3>, which are for inkjet printing.
<5> An ink containing the pearlescent colored scaly particles according to any one of <1> to <4>.
<6> A coating film comprising the pearlescent colored scale-like particles according to any one of <1> to <4>.

The present invention can solve the above-mentioned problems of the prior art and achieve the above-mentioned objectives, and can provide pearlescent coloring flake particles, ink, and coating film that can realize excellent pearlescent coloring by optimizing the thickness of each layer in a three-layer structure having a first zinc sulfide layer, a magnesium fluoride layer, and a second zinc sulfide layer in that order.

FIG. 1 is a schematic diagram showing an example of the pearlescent colored scale-like particles of the present invention. FIG. 2 is a front view of the coating film of Configuration 1. FIG. 3 is a view of the coating film of the configuration 1 as viewed from an oblique direction. FIG. 4 is a front view of the coating film of configuration 2. FIG. 5 is a front view of the coating film of Configuration 3. FIG. 6 is a front view of the coating film of Configuration 4. FIG. 7 is a diagram showing a method for measuring the absolute reflectance in the 5° specular reflection direction and the absolute reflectance in the 45° specular reflection direction for the evaporated films of Configurations 1 to 4. FIG. 8 is a graph showing the results of simulation and actual measurement of the 5° regular reflectance of the evaporated film of the configuration 1. FIG. 9 is a graph showing the results of simulation and actual measurement of the 5° regular reflectance of the evaporated film of the configuration 2. FIG. 10 is a graph showing the results of simulation and actual measurement of the 5° regular reflectance of the evaporated film of the third configuration. FIG. 11 is a graph showing the results of simulation and actual measurement of the 5° regular reflectance of the evaporated film of the configuration 4. FIG. 12 is a graph showing the results of simulation and actual measurement of the 45° regular reflectance of the evaporated film of the configuration 1. FIG. 13 is a graph showing the results of simulation and actual measurement of the 45° regular reflectance of the evaporated film of the configuration 2. FIG. 14 is a graph showing the results of simulation and actual measurement of the 45° regular reflectance of the evaporated film of the configuration 3. FIG. 15 is a graph showing the results of simulation and actual measurement of the 45° regular reflectance of the evaporated film of the configuration 4. FIG. 16 is a graph showing the results of a simulation of the 5° regular reflectance of Example 1, Example A, Example D, Example E, Comparative Example F, Comparative Example G, Comparative Example H, and Comparative Example I. FIG. 17 is a graph showing the results of a simulation of the 5° specular reflectance of Comparative Example A, Comparative Example B, Comparative Example C, Comparative Example D, and Comparative Example E. FIG. 18 is a graph showing the relationship between the total average thickness of the first to third layers and the cumulative 50% volume particle size D ₅₀ after pulverization. FIG. 19 is a schematic diagram showing a method for taking a photograph of the appearance of a coating film. FIG. 20 shows the results of external appearance photographs of the coating films of Configurations 1 to 4, the coating films of Configurations 5 to 8, and a coating film of a competitor's product. FIG. 21 shows cross-sectional SEM photographs of scaly particles obtained by pulverizing the vapor-deposited films of Configurations 1 to 4, scaly particles obtained by pulverizing the vapor-deposited films of Configurations 5 to 8, and a competitor's powder. FIG. 22 is an enlarged cross-sectional SEM photograph of scaly particles obtained by pulverizing the vapor-deposited film of Configuration 2. FIG. 23 is an enlarged cross-sectional SEM photograph of scaly particles obtained by pulverizing the vapor-deposited film of Configuration 7. FIG. 24 is an enlarged cross-sectional SEM photograph of a powder of a competitor's product (SXB). FIG. 25 is a SEM photograph of the particle shapes of the finely pulverized scaly particles of Configurations 1 to 4, the finely pulverized scaly particles of Configurations 5 to 8, and a competitor's product. FIG. 26 is a diagram showing the particle size distribution of the finely pulverized scaly particles of Configurations 1 to 4. FIG. 27 is a diagram showing the particle size distribution of the finely pulverized scaly particles of Compositions 5 to 8 and particles of a competitor's product. FIG. 28 is a diagram showing the 5° specular reflection spectrum of each coating film of Configurations 1 to 4. FIG. 29 is a diagram showing the 45° specular reflection spectrum of each coating film of Configurations 1 to 4.

(Pearl-colored scale-like particles)
The pearlescent colored scaly particle of the present invention has a first zinc sulfide layer, a magnesium fluoride layer, and a second zinc sulfide layer in this order, the first zinc sulfide layer having an average thickness of 30 nm or more, the magnesium fluoride layer having an average thickness of 25 nm or more, the second zinc sulfide layer having an average thickness of 30 nm or more, and the total average thickness of the three layers, the first zinc sulfide layer, the magnesium fluoride layer, and the second zinc sulfide layer, being 330 nm or less.

Conventionally, examples of pearl pigments include flakes in which the surface of mica or glass flakes is coated with a metal oxide (such as _TiO2 ), and scaly particles having a three-layer structure of _TiO2 / _SiO2 / _TiO2 (high refractive index layer/low refractive index layer/high refractive index layer).
The flakes obtained by coating the surface of the mica or glass flakes with a metal oxide (such as _TiO2 ) have a large thickness, and it is difficult to finely divide the flakes to a level suitable for inkjet printing, resulting in a noticeable graininess.Furthermore, the flakes obtained by coating the surface of the mica or glass flakes with a metal oxide (such as _TiO2 ) have a problem in that they cannot achieve the seamless feel and moist feel of scale-like particles obtained by finely pulverizing a vapor deposition film with a three-layer structure of ZnS/ _MgF2 /ZnS.

The ZnS/ _MgF2 /ZnS triple-layered scaly particles of the present invention are superior in pearl coloring compared to the conventional _TiO2 / _SiO2 / _TiO2 triple-layered scaly particles. This is because, in the case of deposition, the crystalline structure of the deposited film obtained is an amorphous structure of _TiO2 / _SiO2 / _TiO2 , and therefore the refractive index is lower than that of the bulk. On the other hand, since ZnS/ _MgF2 /ZnS has a crystalline structure, the refractive index is close to the literature value, and therefore the refractive index difference is large, the reflectance is high, and the pearl coloring is good.

Therefore, according to the present invention, by having a first zinc sulfide (ZnS) layer, a magnesium fluoride ( _MgF2 ) layer, and a second zinc sulfide (ZnS) layer in this order and optimizing the average thickness of each of the three layers, it is possible to realize scale-like particles that exhibit good pearl coloring within the visible light wavelength range.

As shown in FIG. 1, the pearlescent colored scaly particle 10 of the present invention has a three-layer structure in which a first zinc sulfide layer 1, a magnesium fluoride layer 2, and a second zinc sulfide layer 3 are laminated in this order, and the average thickness of each layer is designed so as to obtain good pearlescent coloring, and the particles are finely pulverized to a cumulative 50% volume particle diameter D of ₅₀ suitable for inkjet printing.

<First zinc sulfide layer and second zinc sulfide layer>
The content of zinc sulfide (ZnS) in the first and second zinc sulfide layers is preferably 98 mass % or more, more preferably 99 mass % or more, and even more preferably 99.9 mass % or more.
The zinc sulfide content in the first and second zinc sulfide layers can be measured by, for example, X-ray fluorescence analysis (XRF).

The average thickness of the first zinc sulfide layer is 30 nm or more, preferably 30 nm or more and 130 nm or less, and more preferably 30 nm or more and 120 nm or less.
The average thickness of the second zinc sulfide layer is 30 nm or more, preferably 30 nm or more and 190 nm or less, and more preferably 30 nm or more and 170 nm or less.

The average thickness of the first and second zinc sulfide layers is the same as the average deposition thickness obtained by measuring the thickness at 5 to 10 points on the first and second zinc sulfide layers and averaging them, for example, when the layers are produced by a physical vapor phase method.
Examples of methods for measuring the average thickness of the first and second zinc sulfide layers include scanning electron microscope (SEM) observation, X-ray fluorescence analysis (XRF), and ultraviolet-visible spectroscopy.
When the average thickness is determined by the scanning electron microscope (SEM) observation, a cross-section of the vapor-deposited film or scaly particles containing the first and second zinc sulfides is observed using the scanning electron microscope (SEM), the thicknesses of the first and second zinc sulfide layers are measured at 5 to 10 points, and the average vapor deposition thickness is determined as the average thickness.
When the average thickness is determined by the X-ray fluorescence analysis (XRF), the thicknesses of the first and second zinc sulfide layers are measured at 5 to 10 locations by quantitative analysis, and the average value can be used as the average thickness.

<Magnesium fluoride layer>
The content of magnesium fluoride (MgF ₂ ) in the magnesium fluoride layer is preferably 98 mass % or more, more preferably 99 mass % or more, and further preferably 99.9 mass % or more.
The content of magnesium fluoride in the magnesium fluoride layer can be measured, for example, by X-ray fluorescence analysis (XRF).
The average thickness of the magnesium fluoride layer is 25 nm or more, preferably 25 nm or more and 60 nm or less, and more preferably 35 nm or more and 50 nm or less.

The total average thickness of the three layers, the first zinc sulfide layer, the magnesium fluoride layer, and the second zinc sulfide layer, is 330 nm or less, and preferably 130 nm or more and 290 nm or less.

<Other demographics>
The other layers include, for example, a release layer for releasing the laminate consisting of the first and second zinc sulfide layers and the magnesium fluoride layer from the substrate by dissolving.

The pearlescent coloring particles of the present invention having the magnesium fluoride layer between the first zinc sulfide layer and the second zinc sulfide layer are scaly particles, and may also be called thin plate-like particles, flat particles, flake-like particles, etc.
In the present invention, the scale-like particles refer to particles having a substantially flat surface and a substantially uniform thickness in the direction perpendicular to the substantially flat surface.
The shape of the approximately flat surface is not particularly limited and can be appropriately selected depending on the purpose. Examples of the shape include polygonal shapes such as approximately circular, approximately elliptical, approximately triangular, approximately rectangular, approximately pentagonal, approximately hexagonal, approximately heptagonal, and approximately octagonal, and random, indefinite shapes.

The cumulative 50% volume particle diameter _D50 of the pearlescent colored scale-like particles is preferably 1.8 μm or less, more preferably 0.8 μm or more and 1.8 μm or less, even more preferably 0.7 μm or more and 1.7 μm or less, and particularly preferably 0.5 μm or more and 1.6 μm or less.
The cumulative 50% volume particle diameter _D50 is a particle diameter corresponding to 50% of the cumulative volume distribution of the particle diameter distribution curve obtained by the laser diffraction method, and is the average length of the major axis and minor axis of the non-spherical scale-like particle when the non-spherical scale-like particle is measured assuming that the non-spherical scale-like particle is a perfect sphere. However, the actual scale-like particle is not spherical, but has a scale shape having a long side and a short side. Therefore, the _D50 is a value different from the actual length in the long side direction (major axis) and the length in the short side direction (minor axis) of the scale-like particle.
Examples of the means using the laser diffraction method include a laser diffraction/scattering type particle size distribution measuring instrument.

The ratio of the scaly particles (cumulative 50% volume particle diameter D ₅₀ (nm)/total average thickness of the three layers (nm)) is preferably 5 or more, and more preferably 10 or more.
In the present invention, the ratio of " _D50 (nm)/total average thickness of three layers (nm)" is a ratio calculated by dividing _D50 measured by a laser diffraction method by the average thickness obtained by observation with a scanning electron microscope (SEM) or fluorescent X-ray analysis. Therefore, the ratio of " _D50 (nm)/average thickness (nm)" is a ratio different from a parameter generally called the aspect ratio.

<Method of manufacturing pearl-colored scale-like particles>
The method for producing pearlescent colored scaly particles of the present invention includes forming a release layer on a substrate, forming a first zinc sulfide layer on the release layer by a vapor phase method, forming a magnesium fluoride layer on the first zinc sulfide layer by a vapor phase method, forming a second zinc sulfide layer on the magnesium fluoride layer by a vapor phase method to obtain a laminate, peeling the laminate from the substrate, and pulverizing the laminate. This allows for efficient production of pearlescent colored scaly particles 10 as shown in FIG. 1.

The method for producing the pearl-colored scale-like particles of the present invention specifically includes a peeling layer forming step, a first zinc sulfide layer forming step, a magnesium fluoride layer forming step, a second zinc sulfide layer forming step, a peeling step, and a grinding step, and may further include other steps as necessary.

<Release Layer Forming Step>
The release layer forming step is a step of providing the release layer on the substrate.

- Substrate -
The substrate is not particularly limited as long as it has a smooth surface, and various substrates can be used. Among these, a resin film, a metal, or a composite film of a metal and a resin film having flexibility, heat resistance, solvent resistance, and dimensional stability can be appropriately used.
Examples of the resin film include a polyester film, a polyethylene film, a polypropylene film, a polystyrene film, and a polyimide film.
Examples of the metal include copper foil, aluminum foil, nickel foil, iron foil, and alloy foil.
The composite film of the metal and the resin film may be a film obtained by laminating the resin film and the metal.

-Release layer-
The peeling layer can be made of various organic substances that can be dissolved in the subsequent peeling step, or solvents such as water, etc. In addition, if an organic material constituting the peeling layer is appropriately selected, the organic substances attached to or remaining on the magnesium fluoride layer or the first and second zinc sulfide layers can be made to function as a protective layer for the scale-like particles, which is preferable.
The protective layer has a function of suppressing aggregation, oxidation, elution into a solvent, etc. of the scale-like particles. In particular, by utilizing the organic material used in the release layer as the protective layer, it is preferable since it becomes unnecessary to provide a separate surface treatment step.
The organic material constituting the release layer that can be used as the protective layer can be, for example, cellulose acetate butyrate (CAB), other cellulose derivatives, polyvinyl alcohol, polyvinyl butyral, polyethylene glycol, polyacrylic acid, polyacrylamide, acrylic acid copolymer, modified nylon resin, etc. These can be used alone or in combination of two or more. Among these, cellulose acetate butyrate (CAB) is preferred from the viewpoint of high functionality as the protective layer.

The method for forming the release layer is not particularly limited and can be appropriately selected depending on the purpose. Examples of the method include inkjet method, blade coating method, gravure coating method, gravure offset coating method, bar coating method, roll coating method, knife coating method, air knife coating method, comma coating method, U comma coating method, AKKU coating method, smoothing coating method, microgravure coating method, reverse roll coating method, four-roll coating method, five-roll coating method, dip coating method, curtain coating method, slide coating method, and die coating method. These may be used alone or in combination of two or more.

<First zinc sulfide layer forming step>
The first zinc sulfide layer forming step is a step of forming a first zinc sulfide layer on the release layer by a vapor phase method.

The vapor phase method includes deposition method and sputtering method, which are collectively called physical vapor deposition (PVD).

<Magnesium fluoride layer forming process>
The magnesium fluoride layer forming step is a step of forming a magnesium fluoride layer on the first zinc sulfide layer by a vapor phase method.

The vapor phase method includes deposition method and sputtering method, which are collectively called physical vapor deposition (PVD).

<Second zinc sulfide layer forming step>
The second zinc sulfide layer forming step is a step of forming a second zinc sulfide layer on the magnesium fluoride layer by a vapor phase method.
As a result of the above, a laminate is formed in which the first zinc sulfide layer, the magnesium fluoride layer, and the second zinc sulfide layer are laminated in this order on the release layer of the substrate.

The vapor phase method includes deposition method and sputtering method, which are collectively called physical vapor deposition (PVD).

<Peeling process>
The peeling step is a step of peeling off the laminate by dissolving the release layer.
The solvent capable of dissolving the release layer is not particularly limited as long as it is capable of dissolving the release layer, and may be appropriately selected depending on the purpose.

The solvent capable of dissolving the release layer is not particularly limited and can be appropriately selected according to the purpose. Examples of the solvent include alcohols such as methanol, ethanol, propanol, isopropanol, butanol, octanol, dodecanol, ethylene glycol, and propylene glycol; ethers such as tetrahydrone; ketones such as acetone, methyl ethyl ketone, and acetylacetone; esters such as methyl acetate, ethyl acetate, butyl acetate, and phenyl acetate; ethyl cellosolve, butyl cellosolve, ethyl carbitol, butyl carbitol, ethylene glycol monomethyl ether, ethylene glycol monoethyl ether, ethylene glycol monoisopropyl ether, ethylene glycol monobutyl ether, ethylene glycol monohexyl ether, ethylene glycol monophenyl ether, diethylene glycol monomethyl ether, diethylene glycol monoethyl ether, diethylene glycol monobutyl ether, diethylene glycol dimethyl ether, diethylene glycol diethyl ether, and triethylene glycol monomethyl ether. Examples of the phenol include glycol ethers such as glycol monomethyl ether, triethylene glycol monoethyl ether, triethylene glycol monobutyl ether, propylene glycol monomethyl ether, propylene glycol monoethyl ether, dipropylene glycol monomethyl ether, dipropylene glycol monoethyl ether, and diethylene glycol monomethyl ether acetate; phenols such as phenol and cresol; aliphatic or aromatic hydrocarbons such as pentane, hexane, heptane, octane, dodecane, tridecane, tetradecane, pentadecane, hexadecane, octadecane, octadecene, benzene, toluene, xylene, trimesine, nitrobenzene, aniline, and methoxybenzene; aliphatic or aromatic chlorinated hydrocarbons such as dichloromethane, chloroform, trichloroethane, chlorobenzene, and dichlorobenzene; sulfur-containing compounds such as dimethyl sulfoxide; nitrogen-containing compounds such as dimethylformamide, dimethylacetamide, acetonitrile, propionitrile, and benzonitrile; and water. These may be used alone or in combination of two or more.

<Crushing process>
The pulverization step is a step of pulverizing the laminate peeled off from the substrate in the peeling step. By carrying out this pulverization step, the pearlescent colored scale-like particles of the present invention can be obtained.

The method used in the pulverization step is not particularly limited and can be appropriately selected depending on the purpose. Examples of the method include a jet mill, a ball mill, a bead mill, a vibration mill, and an ultrasonic homogenizer.
Furthermore, if necessary, various treatments may be carried out to recover the pearlescent colored scaly particles or adjust their physical properties. For example, the particle size of the pearlescent colored scaly particles may be adjusted by classification, the scaly particles may be recovered by centrifugation, suction filtration, or the solid content concentration of the dispersion may be adjusted. In addition, solvent replacement may be carried out, and viscosity adjustment may be carried out using additives.

<Other processes>
Examples of the other steps include a step of extracting the pulverized pearl colored scale-like particles as a dispersion liquid, and a step of recovering the scale-like particles from the dispersion liquid.

<Dispersion>
The dispersion used in the present invention contains the pearlescent colored scaly particles of the present invention, and preferably contains an organic solvent and water, and further contains other components as required.
The dispersion may be either aqueous or solvent-based, but is preferably aqueous from the standpoint of environmental friendliness.

The content of the pearl-colored scale-like particles is preferably 0.1% by mass or more and 50% by mass or less based on the total amount of the dispersion liquid.

- Organic solvents -
The organic solvent is not particularly limited and can be appropriately selected depending on the purpose, and examples thereof include polyhydric alcohols, polyhydric alcohol alkyl ethers, polyhydric alcohol aryl ethers, nitrogen-containing heterocyclic compounds, amides, amines, sulfur-containing compounds, etc. These may be used alone or in combination of two or more.

Examples of the polyhydric alcohols include ethylene glycol, diethylene glycol, 1,2-propanediol, 1,3-propanediol, 1,2-butanediol, 1,3-butanediol, 1,4-butanediol, 2,3-butanediol, 3-methyl-1,3-butanediol, triethylene glycol, polyethylene glycol, polypropylene glycol, 1,2-pentanediol, 1,3-pentanediol, 1,4-pentanediol, Examples include glycerin, 2,4-pentanediol, 1,5-pentanediol, 1,2-hexanediol, 1,6-hexanediol, 1,3-hexanediol, 2,5-hexanediol, 1,5-hexanediol, glycerin, 1,2,6-hexanetriol, 2-ethyl-1,3-hexanediol, ethyl-1,2,4-butanetriol, 1,2,3-butanetriol, and 2,2,4-trimethyl-1,3-pentanediol.

Examples of the polyhydric alcohol alkyl ethers include ethylene glycol monoethyl ether, ethylene glycol monobutyl ether, diethylene glycol monomethyl ether, diethylene glycol monoethyl ether, diethylene glycol monobutyl ether, tetraethylene glycol monomethyl ether, and propylene glycol monoethyl ether.

Examples of the polyhydric alcohol aryl ethers include ethylene glycol monophenyl ether and ethylene glycol monobenzyl ether.

Examples of the nitrogen-containing heterocyclic compounds include 2-pyrrolidone, N-methyl-2-pyrrolidone, N-hydroxyethyl-2-pyrrolidone, 1,3-dimethyl-2-imidazolidinone, ε-caprolactam, and γ-butyrolactone.

Examples of the amides include formamide, N-methylformamide, N,N-dimethylformamide, 3-methoxy-N,N-dimethylpropionamide, and 3-butoxy-N,N-dimethylpropionamide.

Examples of the amines include monoethanolamine, diethanolamine, and triethylamine.
Examples of the sulfur-containing compound include dimethyl sulfoxide, sulfolane, and thiodiethanol.

-Other ingredients-
The other components are not particularly limited and can be appropriately selected depending on the purpose. Examples of the other components include water, polymers, crosslinking agents, antiaging agents, fillers, polymerization inhibitors, surface conditioners, antistatic agents, antifoaming agents, viscosity modifiers, light resistance stabilizers, weather resistance stabilizers, heat resistance stabilizers, antioxidants, leveling agents, antiseptics/fungal agents, rust inhibitors, and pH adjusters.

-water-
As the water, for example, pure water such as ion-exchanged water, ultrafiltered water, reverse osmosis water, distilled water, or ultrapure water can be used.

(ink)
The ink of the present invention contains the pearlescent colored scaly particles of the present invention, and preferably contains a binder, and further contains other components as required.
The ink of the present invention may be either water-based or solvent-based.

- Pearl colored scale-like particles -
The content of the pearlescent colored scaly particles relative to the total amount of the ink is not particularly limited, and can be appropriately selected depending on the purpose.
The ink of the present invention may contain other luster pigments in addition to the pearlescent colored scaly particles, as necessary, such as metallic pigments (e.g., aluminum pigments), pigments obtained from natural mica (e.g., pearl pigments), glass flake pigments, etc.

-binder-
The binder is not particularly limited and can be appropriately selected depending on the purpose. Examples of the binder include polyurethane resin, polyester resin, acrylic resin, vinyl acetate resin, styrene resin, butadiene resin, styrene-butadiene resin, vinyl chloride resin, acrylic-styrene resin, acrylic-silicone resin, polyvinyl alcohol resin, polyether resin, alkyd resin, polyvinylpyrrolidone, and cellulose.
When the ink contains the binder, an ink having excellent fixability and dispersibility can be obtained.
The content of the binder is not particularly limited and can be appropriately selected depending on the purpose.

The organic solvent and water in the ink may be the same as those in the dispersion.

-Other ingredients-
The other components are not particularly limited and may be appropriately selected depending on the purpose. Examples of the other components include surfactants, antifoaming agents, antiseptic and antifungal agents, rust inhibitors, and pH adjusters.

The ink of the present invention can be used for coating methods such as the inkjet method, gravure coating method, screen printing method, spray coating method, spin coating method, blade coating method, gravure offset coating method, bar coating method, roll coating method, knife coating method, air knife coating method, comma coating method, U comma coating method, AKKU coating method, smoothing coating method, microgravure coating method, reverse roll coating method, four-roll coating method, five-roll coating method, dip coating method, curtain coating method, slide coating method, and die coating method. Among these, the inkjet method, bar coating method, spray coating method, gravure coating method, and screen printing method are preferred.

(Coating film)
The coating film of the present invention contains the pearlescent colored scaly particles of the present invention, and preferably contains a binder, and further contains other components as required.
The coating film may be used alone, but may also be a coated product formed on a substrate by the above-mentioned coating method using the ink of the present invention.
The substrate is not particularly limited and can be appropriately selected depending on the purpose. Examples of the substrate include plain paper, glossy paper, special paper, cloth, film, OHP sheet, general-purpose printing paper, automobile window glass and film, building window glass and film, agricultural film, and the like.

<Applications>
The pearlescent colored scaly particles of the present invention can realize excellent pearlescent coloring and can be used in a wide variety of fields, such as paints, plastics, printing, food, cosmetics, and automobiles.

The following describes examples of the present invention, but the present invention is not limited to these examples.

(Experimental Example 1)
<Optimization of the average thickness of each layer in a three-layer structure of ZnS/MgF ₂ /ZnS by simulation>
The optimum setting value for the average thickness of each layer in the three-layer structure of ZnS/MgF ₂ /ZnS in compositions 1 to 4, which produces good pearl coloring, was found by simulation. The results are shown in Table 1.
As a simulator, optical thin film design software (TFV ver. 3, manufactured by Nally Software Co., Ltd.) was used, and the reflectance was determined by simulation.
The color tone was evaluated from the obtained reflectance spectrum using the CIE Lab color system.

(Experimental Example 2)
<Preparation of pearl-colored scale-like particles>
(1) As described above, a simulation of a vapor deposition film having a three-layer structure was performed, and the lower limit of the average thickness of each layer of configurations 1 to 4 was determined. As will be described later, it has been confirmed that the optical characteristics (reflection spectrum) of the simulation and the actually manufactured sample are almost identical. Therefore, there is no problem in optimally designing the average thickness of each layer by simulation.

(2) Using the average thickness of each layer of the ZnS/MgF ₂ /ZnS three-layer structure determined by simulation, compositions 1 to 4 of evaporated films having a three-layer structure were actually produced.
Specifically, a solution containing 5% by mass of cellulose acetate butyrate (CAB) was applied to a polyethylene terephthalate (PET) film having an average thickness of 25 μm by a gravure coating method in a coating amount of 0.06 g/ ^m2 ±0.01 g/ ^m2 , and then dried at 110°C or higher and 120°C or lower to form a release layer.
Next, a first zinc sulfide layer having an average thickness of 40 nm was formed on the release layer by vacuum deposition of zinc sulfide. The average thickness of the first zinc sulfide layer was determined by measuring the thickness of the first zinc sulfide layer at five locations by quantitative analysis using X-ray fluorescence analysis (XRF) and averaging the measured values.
Next, magnesium fluoride was deposited on the first zinc sulfide layer by vacuum deposition to form a magnesium fluoride layer having an average thickness of 50 nm.
Next, a second zinc sulfide layer having an average thickness of 40 nm was formed on the magnesium fluoride layer by the same method as for the first zinc sulfide layer.
As a result, a vapor-deposited film having a configuration 1 was obtained in which a release layer, a first zinc sulfide layer, a magnesium fluoride layer, and a second zinc sulfide layer were laminated in this order on a PET film.
The evaporated films of the compositions 2 to 4 were also prepared in the same manner as above.

(3) Each vapor-deposited film was pulverized (pulverized as finely as possible) for inkjet printing to a cumulative 50% volume particle diameter D ₅₀ of 1.8 μm or less, to obtain pearlescent colored scale-like particles of compositions 1 to 4.
Specifically, butyl acetate was sprayed onto the PET film surface on which the vapor-deposited film was formed to dissolve the release layer, and the vapor-deposited film was scraped off with a doctor blade.
Next, the mixture of the vapor-deposited film and butyl acetate thus obtained was subjected to a fine pulverization process in order to adjust the particle size, and was pulverized until the target cumulative 50% volume particle size D ₅₀ became 1.8 μm or less.

(4) The above pearlescent colored scale-like particles were dispersed in butyl acetate to prepare pearlescent colored inks of compositions 1 to 4.
(5) The pearl coloring inks of compositions 1 to 4 were applied onto a polyethylene terephthalate (PET) film (transparent) using a bar coater.
(6) Black tape was attached to half of the surface of the PET film opposite to the ink-coated surface, and the coating films of Constructions 1 to 4 were visually observed and various data were measured.

Here, Fig. 2 is a front view of the coating film of the configuration 1. Fig. 3 is a diagonal view of the coating film of the configuration 1. As shown in Figs. 2 and 3, when the visual direction is changed from the front to an oblique direction, it is recognized that the peak wavelength of the reflected light of the pearl color shifts and the color changes.
FIG. 4 is a front view of the coating film of the configuration 2, and the left side shows a coating film coated with a pearl coloring ink having a high solids concentration of scaly particles using a bar coater.
FIG. 5 is a front view of the coating film of the third embodiment, and the left side shows a coating film coated with a pearlescent ink having a high solids concentration of scaly particles using a bar coater.
FIG. 6 is a front view of the coating film of Configuration 4, and the left side shows a coating film coated with a pearlescent ink having a high solids concentration of scaly particles using a bar coater.

(Experimental Example 3)
<Comparison between simulation and actual measurement (evaporated film)>
-simulation-
As a simulator, optical thin film design software (TFV ver. 3, manufactured by Nally Software Co., Ltd.) was used to determine simulated values of reflectance.
The reflectance is the absolute reflectance in the 5° regular reflection direction when light is incident at an angle of 5° from the normal direction of each film. The absolute reflectance is calculated by the following formula.
Absolute reflectance = (amount of light reflected by the sample/amount of light used) x 100
The absolute reflectance is the reflectance when the reflectance of air is taken as 100%.

- Actual measurement (evaporated film) -
When the reflectance was actually measured, the reflectance of a sample in which a black tape 12 was provided on the back of a vapor-deposited film 11 as shown in FIG. 7 was measured.
The reflectance was measured using an ultraviolet-visible-near infrared spectrophotometer (SolidSpec-3700, manufactured by Shimadzu Corporation).
As shown in Fig. 7, the absolute reflectance in the 5° specular reflection direction when light was incident at an angle inclined by 5° from the normal direction of each of the evaporated films of the above-mentioned configurations 1 to 4, and the absolute reflectance in the 45° specular reflection direction when light was incident at an angle inclined by 45° from the normal direction of each of the evaporated films of the above-mentioned configurations 1 to 4 were measured. The results are shown in Figs. 8 to 15.
From the results of FIGS. 8 to 15, it was found that the simulation and actual measurements (evaporated film) were almost in agreement in the reflection spectrum at visible light wavelengths, and the optimum design of the average thickness of each layer could be performed by simulation.

(Examples 1 to 4, Examples A to D, and Comparative Examples A to I)
<Setting the lower limit of the average thickness of each of the three layers by simulation (evaporated film)>
The visual color was evaluated for Examples 1, A, D, E, F, G, H, and I in which the average thicknesses of the three layers were changed as shown in Table 2, and the results of a simulation of the 5° regular reflectance are shown in Table 2 and FIG. 16.
For Comparative Examples A, B, C, D, and E in which the average thickness of each of the three layers was changed as shown in Table 2, the visual color was evaluated, and the results of a simulation of the 5° regular reflectance are shown in Table 2 and FIG. 17.

- Visual color -
The visual color was evaluated using the reflection spectrum obtained from a simulation and the CIE Lab color system, and was judged according to the following criteria.
[Evaluation Criteria]
OK: good visual color NG: poor visual color

Next, the results of a simulation of 5° regular reflection for Example 1 (Structure 1), Example A (lower limit of Structure 1), Example E, and Comparative Examples A to I are shown in Tables 3-1 to 3-3.
The lower limit of the average thickness of each of the three layers in the blue region must satisfy both (1) and (2) below.
(1) The value of (maximum reflectance in the wavelength range of 380 nm to 530 nm) / (minimum reflectance in the wavelength range of 420 nm to 630 nm) is 3.0 or more. (2) In the reflection spectrum in the wavelength range of 380 nm to 780 nm, the minimum reflectance is in the wavelength range of 420 nm to 630 nm. By simultaneously satisfying the above (1) and (2), the color is easily recognized as blue by the naked eye.

The results in Tables 3-1 to 3-3 show that there is a boundary between Comparative Example I and Example E for the lower limit of the average thickness of each of the three layers.

(Experimental Example 4)
<Setting the upper limit of the average thickness of the three layers>
The upper limit of the total average thickness of the three layers was set in order to pulverize each evaporated film into a range of cumulative 50% volume particle diameter _D50 that can be used for inkjet printing. The results are shown in FIG. 18 and Tables 4 and 5.
The average thickness of each layer is calculated by measuring the thickness of each layer at five locations by quantitative analysis using X-ray fluorescence analysis (XRF) and averaging the measured values.

From the results of FIG. 18 and Tables 4 and 5, it was found that the upper limit of the total average thickness of the three layers was 330 nm or less.
The relationship between the total average thickness of the three layers and the cumulative 50% volume particle size _D50 after pulverization is considered to be independent of the material of each layer. The thicker the total average thickness of the three layers is, the less fine the particles will be even after pulverization.
In the range indicated by A in FIG. 18, clogging of the head occurred when printing was performed with an inkjet printer.

(Experimental Example 5)
<Appearance of coating film>
As shown in FIG. 19, the exterior photographs of the coatings of the configurations 1 to 4, which are coatings using three layers of finely pulverized scaly particles of ZnS/MgF ₂ /ZnS, the configurations 5 to 8, which are coatings using three layers of finely pulverized scaly particles of TiO ₂ /SiO ₂ /TiO ₂ , and the coatings of other companies' products (products of Nihon Koken Kogyo Co., Ltd., TiO ₂ embedded in natural mica, SXB, YXB) were taken with an iPhone (registered trademark) (manufactured by Apple Inc.) from a vertical line at a light source D65. The results are shown in FIG. 20. The left half of each photograph in FIG. 20 corresponds to the left half of FIG. 19, and the right half of each photograph in FIG. 20 corresponds to the right half of FIG. 19.
From the results in Figure 20, the products of other companies (Nihon Koken Kogyo Co., Ltd., _TiO2 embedded in natural mica, SXB, YXB) are large particle size flake powders, not finely ground particles, and therefore the coating film has a grainy texture (roughness) that is not preferable. In contrast, the coating film of configurations 1 to 8 obtained by the bar coating method had a moist visibility.

(Experimental Example 6)
<SEM Observation of Powder Cross Section>
The cross sections of the powders of configurations 1 to 4, which are three-layered evaporated films of ZnS/MgF ₂ /ZnS, configurations 5 to 8, which are three-layered evaporated films of TiO ₂ /SiO ₂ /TiO ₂ , and products of other companies (products with TiO ₂ embedded in natural mica, SXB and YXB, manufactured by Nihon Koken Kogyo Co., Ltd.) were observed using a scanning electron microscope (SEM) HITACHI S-4700 (manufactured by Hitachi, Ltd.). The results are shown in FIG.
An enlarged cross-sectional SEM photograph of scaly particles obtained by pulverizing the vapor-deposited film of Configuration 2 is shown in Fig. 22. An enlarged cross-sectional SEM photograph of scaly particles obtained by pulverizing the vapor-deposited film of Configuration 7 is shown in Fig. 23. An enlarged cross-sectional SEM photograph of the powder of a competitor's product (SXB) is shown in Fig. 24.
21 to 24, it can be seen that ZnS/ _MgF2 /ZnS and _TiO2 / _SiO2 / _TiO2 have a three-layer structure from the cross section, and that the three-layer evaporated film was pulverized into powder. In contrast, the competitor's product has no cross section, and the entire powder surface is uniformly coated.
Figure 24 is an enlarged SEM photograph of a competitor's powder, where the surface coating layer ( _TiO2 ) has partially peeled off, revealing the mica inside. The competitor's product is fully coated with large-particle-size mica in a post-processing step, so the particle size is basically large (no crushing process is carried out after coating).
It can also be seen that the powders of structures 1 to 8 obtained by pulverizing the evaporated films of three layers of ZnS/MgF ₂ /ZnS and TiO ₂ /SiO ₂ /TiO ₂ have smaller particle sizes when the total thickness of the three layers is smaller.

(Experimental Example 7)
<SEM Observation of Powder Shape>
The powder shapes of flakes of Configurations 1 to 4, which are finely pulverized scaly particles of three layers of ZnS/MgF ₂ /ZnS, Configurations 5 to 8, which are finely pulverized scaly particles of three layers of TiO ₂ /SiO ₂ /TiO ₂ , and products of other companies (products of Nihon Koken Kogyo Co., Ltd., in which TiO ₂ is embedded in natural mica, SXB and YXB) were observed using a scanning electron microscope (SEM: Scanning Electron Microscope) HITACHI S-4700 (manufactured by Hitachi, Ltd.). The results are shown in FIG.
From the results in FIG. 25, it can be seen that in the ZnS/MgF ₂ /ZnS three-layer structure, even if the first zinc sulfide layer and the second zinc sulfide layer have different thicknesses, no curling due to film stress is observed and the film remains flaky.

(Experimental Example 8)
<Measurement of particle size distribution>
The particle size distribution of flakes of Configurations 1 to 4, which are finely pulverized scaly particles having three layers of ZnS/ _MgF2 /ZnS, Configurations 5 to 8, which are finely pulverized scaly particles having three layers of _TiO2 / _SiO2 / _TiO2 , and products of other companies (products of Nihon Koken Kogyo Co., Ltd., natural mica with _TiO2 embedded, SXB, YXB) was measured using a laser diffraction/scattering type particle size distribution analyzer (LSM-2000e, Seishin Enterprise Co., Ltd.), and the cumulative 10% volume particle size _D10 , cumulative 50% volume particle size _D50 , and cumulative 90% volume particle size _D90 were obtained. The results are shown in Figures 26 and 27.
From the results of Figs. 26 and 27, it is seen that the finely pulverized scaly particles having a three-layer structure of ZnS/MgF2/ZnS have a cumulative 50% volume particle diameter _D50 of 1.8 µm or less.

(Experimental Example 9)
<Optical data of coating film>
0.40 g of the finely pulverized scaly particles of Constitutions 1 to 4, 0.04 g of a binder (S-LEC B, manufactured by Sekisui Chemical Co., Ltd.), and 3.64 g of butyl acetate were mixed using a mixer (rotation/revolution type mixer ARE-310, manufactured by Thinky Corporation) to prepare inks of Constitutions 1 to 4.
Next, each ink was applied to a polyethylene terephthalate (PET) film having an average thickness of 100 μm using an applicator so that the average thickness was 5 μm or less. After natural drying at room temperature, the ink was dried at 120° C. for 3 minutes using a dryer to produce each coating film of Constructions 1 to 4.

Next, for the coating films of the obtained compositions 1 to 4, L ^* a*b*, Y, x, and y were measured at absolute reflection angles of 5° and 45° under the following measurement conditions using an ultraviolet-visible-near ^{infrared spectrophotometer} (SolidSpec-3700, manufactured by Shimadzu Corporation). The results are shown in Table 7.
[Measurement conditions]
Lighting: D65
Visual field: 2 degrees. The 5° specular reflection spectra of the coating films of Configurations 1 to 4, measured using an ultraviolet-visible-near infrared spectrophotometer (SolidSpec-3700, manufactured by Shimadzu Corporation), are shown in FIG. 28, and the 45° specular reflection spectra of the coating films of Configurations 1 to 4 are shown in FIG. 29.

From the results in Table 7, Figure 28, and Figure 29, when the absolute reflectance was measured by irradiating light at angles inclined at 5° and 45° to the normal direction of each coating film, it was found that the reflected and absorbed wavelengths were different at 5° and 45°, with the 45° angle being shifted to the shorter wavelength side.

REFERENCE SIGNS LIST 1 First zinc sulfide layer 2 Magnesium fluoride layer 3 Second zinc sulfide layer 10 Pearl colored scale-like particles

Claims (4)

The coating film has a three-layer structure including a first zinc sulfide layer, a magnesium fluoride layer, and a second zinc sulfide layer in this order,
The first zinc sulfide layer has an average thickness of 30 nm or more and 130 nm or more ;
The magnesium fluoride layer has an average thickness of 25 nm or more and 60 nm or less ,
The average thickness of the second zinc sulfide layer is 30 nm or more and 190 nm or less ,
The cumulative 50% volume particle size D50 _is 1.8 μm or less;
the first zinc sulfide layer, the magnesium fluoride layer, and the second zinc sulfide layer are all vapor-deposited films;
A pearlescent colored scaly particle, characterized in that the total average thickness of the three layers, namely, the first zinc sulfide layer, the magnesium fluoride layer and the second zinc sulfide layer, is 330 nm or less. 2. The pearlescent colored scaly particles according to claim 1 , which are for inkjet printing. 3. An ink comprising the pearlescent colored scaly particles according to claim 1. A coating film comprising the pearlescent colored scale-like particles according to claim 1 or 2 .