JPH1112490A - Green colorant and its production - Google Patents

Abstract

PROBLEM TO BE SOLVED: To obtain a bright green colorant powder prepared by alternatingly laminating a plurality of coating layers having high and low refractive indices on the surface of each basic particle and showing a reflection spectrum having a peak in a specified wavelength region. SOLUTION: There is provided a green pigment prepared by alternatingly laminating a plurality of coating layers having high and low refractive indices on the surface of each basic particle (having a particle diameter of 0.01 μm to several mm and a specific gravity of 0.1-10.5 and made of a metal, a resin or the like) and showing a reflection spectrum having a peak in the range of 450-650 nm. The film having a reflection peak in the range of 450-650 nm can be obtained by repeating at least once an operation comprising forming a coating film having a thickness and a refractive index satisfying the relationship: nd=mλ/4 (wherein n is the refractive index of the substance which forms the coating film, d is the thickness equivalent to m times 1/4 of the wavelength of visible light in the range of 450-650 nm, λ is the reflection or absorption wavelength) and coating a coating film having a different refractive index thereon.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a green pigment and a method for producing the same, and more particularly to a green pigment used for various purposes such as ink, plastic / paper filler, magnetic toner, ink jet printer ink and the like. The present invention relates to the manufacturing method.

[0002]

2. Description of the Related Art In order to provide a powder having a composite function, the powder has a characteristic that only certain powder particles have, in addition to the properties possessed by only certain powder particles. A powder having a metal oxide film or the like having a uniform thickness of 0.01 to 20 μm on the surface thereof was invented (Japanese Patent Laid-Open No.
-228604). Further, the present inventors have further improved the above-mentioned powder, and invented not only a metal oxide film alone but also a powder having a plurality of metal oxide films and metal films alternately (see JP-A-7-1995). -90310).

[0003] In order to produce these powders, it is necessary to provide a plurality of metal oxide films having a uniform thickness on the surface of the substrate. Since it is difficult to precipitate a metal compound that is a body, the present inventors disperse the above-mentioned substrate in a metal alkoxide solution and hydrolyze the metal alkoxide, thereby forming a metal oxide film on the substrate. By developing a method of forming a metal oxide film, a thin and uniform metal oxide film can be formed by this method, and in particular, a multilayer metal oxide film can be formed.

In addition, the inventors of the present invention have proposed a powder having a multilayer film such as a metal oxide film on the surface of a powder particle as a substrate, the combination of substances, refractive index and film thickness of the multilayer film. By controlling, it was found that the reflected light interference waveform of the multilayer film could be adjusted to be a colored powder such as a pigment (WO96 / 28269).

[0005]

However, there is no clear disclosure of a technique for obtaining a colored powder having a desired specific color tone, and the conventional method does not provide a multilayer having a vivid green color. The condition range for developing the color of the film-coated powder was not clear. For example, green color is one of the three primary colors of light and is an important pigment that gives a person a psychologically fresh youth, peace, quiet and security. Obtaining a pigment powder having such a green color tone and a specific function is of great industrial significance. Accordingly, an object of the present invention is to provide a method for forming a multilayer film such as a metal oxide film on the surface of a powder particle as a base, as described above, and a clear green color tone which is industrially useful. An object of the present invention is to provide a pigment which has a specific excellent composite function and a method for producing the pigment efficiently and with high precision.

[0006]

Means for Solving the Problems The inventors of the present invention have conducted intensive studies to achieve the above-mentioned object, and as a result, when forming a multilayer-coated powder, the combination of films and the thickness of each film have been considered. ,
By further improving the method of controlling them, a powder having a higher maximum reflectance and a larger amplitude of the spectral reflection waveform is obtained, the color of the powder itself is improved, and, in the film design, for example, When the range of the wavelength of the maximum value observed when forming each layer of the alternating film of titania and silica was limited to a specific range, it was found that a bright green-colored powder could be obtained. Reached.

That is, the present invention is as follows. (1) a plurality of coating layers in which a coating film having a large refractive index and a coating film having a small refractive index are stacked adjacent to each other on the surface of the base particles;
A green pigment exhibiting a reflection spectrum having a peak at 650 nm. (2) when the refractive index of the base particles is larger than the refractive index of the first layer coating which is in contact with the surface of the base, the coating has an even number of layers;
The green pigment according to the above (1), wherein when the refractive index of the base particles is smaller than the refractive index of the first layer coating, the coating has an odd number of layers. (3) The green pigment according to the above (1), wherein the base particles are inorganic.

(4) In a method for producing a green pigment having a plurality of coating layers having different refractive indices on the surface of substrate particles, a film having a large refractive index and a film having a small refractive index are laminated adjacent to each other on the surface of the substrate particles. Forming a plurality of coating layers,
A method for producing a green pigment, wherein the conditions of the base particles and the coating layer are set so as to show a reflection spectrum having a peak between 650 nm and 650 nm. (5) When the refractive index of the base particles is larger than the refractive index of the first layer coating in contact with the substrate surface, an even-numbered layer coating is formed, and the refractive index of the base particles is higher than the refractive index of the first layer coating. The method for producing a green pigment according to the above (4), wherein an odd-numbered layer is formed when the pigment is too small. (6) The method for producing a green pigment according to the above (4), wherein the base particles are inorganic.

[0009]

DESCRIPTION OF THE PREFERRED EMBODIMENTS In the case where a plurality of layers of a metal oxide, a metal film and the like are formed on the surface of the base particles, the coating film (a layer of a film which covers the base particles and participates in light interference) A special function can be given by adjusting the thickness of each layer. For example, an alternating coating film having a different refractive index is provided on the surface of the base particles so that the refractive index n of the material forming the coating film and the wavelength of visible light between 450 and 650 nm so as to satisfy the following expression (1). Thickness d equivalent to an integer m times 1/4 of
When an appropriate thickness and number of alternating films having
Light having a wavelength λ between 650 nm (using the interference reflection of Fresnel) is reflected or absorbed. nd = mλ / 4 (1)

Utilizing this effect, a film having a film thickness and a refractive index that satisfies the formula (1) is formed on the surface of the substrate particles at a target wavelength of 450 to 650 nm, Further, by alternately repeating coating of a film having a different refractive index once or more thereon, a film having a reflection peak between 450 and 650 nm is formed. At this time, the order of the materials to be formed is determined as follows. First, it is preferable that the first layer be a film having a low refractive index when the refractive index of the base serving as a nucleus is high, and that the first layer be a film having a high refractive index in the opposite relationship.

The change in the optical film thickness, which is the product of the film refractive index and the film thickness, is measured and controlled as a reflected waveform by a spectrophotometer or the like. The thickness of each layer is designed. For example, as shown in FIG. 1, when the peak position of the reflection waveform of each unit film is precisely adjusted to a range of 450 to 650 nm, a green-colored monochromatic colored powder can be obtained without using a dye or a pigment. .

However, in the case of an actual substrate, the particle size of the substrate,
It is necessary to design in consideration of the shape, the phase shift at the mutual interface between the film material and the base particle material, the peak shift due to the wavelength dependence of the refractive index, and the like. For example, when the shape of the base particle is a parallel plate, the Fresnel interference by the parallel film formed on the particle plane is designed under the condition that n in the above formula (1) is replaced by N in the following formula (2). I do. In particular, in the case where a metal film is included even when the shape of the base is a parallel plate, the attenuation coefficient κ is included in the refractive index N of the metal of the formula (2). In the case of a transparent oxide (dielectric), κ is very small and can be ignored. N = n + iκ (i represents a complex number) (2) If this attenuation coefficient κ is large, the phase shift at the mutual interface between the film material and the base material becomes large, and furthermore, interference due to the phase shift occurs in all the layers of the multilayer film. Affects optimum film thickness.

As a result, even if only the geometrical film thickness is adjusted, the peak position is shifted, so that the color becomes pale especially when coloring in a green color system. In order to prevent this, the effects of the phase shift on all the films are taken into consideration, and a computer simulation is designed so that the combination of the film thicknesses is optimized in advance.

Further, there is a phase shift due to the oxide layer on the surface of the substrate and a peak shift due to the wavelength dependence of the refractive index. To correct these, use a spectrophotometer, etc.
The reflection peak is 450 to 6 which is the target wavelength in the final target film number.
It is necessary to find the optimal conditions to be in the range of 50 nm.

The interference of a film formed on a curved surface such as a spherical powder occurs similarly to a flat plate, and basically follows the Fresnel interference principle. Therefore, the coloring method can be designed to be a green color system as shown in FIG. However, for curved surfaces,
Light incident on and reflected by the powder causes complex interference. These interference waveforms are almost the same as a flat plate when the number of films is small. However, as the total number increases, the interference inside the multilayer film becomes more complicated. Also in the case of a multilayer film, the reflection spectral curve can be designed in advance by computer simulation based on the Fresnel interference so that the combination of the film thickness is optimized. In particular, in the case of film formation on the substrate particle surface, taking into account the influence of the phase shift on the substrate particle surface and all films,
A computer simulation is designed to optimize the combination of film thickness in advance. Further, the peak shift due to the oxide layer on the surface of the base particles and the peak shift due to the wavelength dependence of the refractive index are taken into consideration. In the actual sample production, in order to correct these in the actual film with reference to the designed spectral curve, the film thickness is adjusted by a spectrophotometer or the like so that the reflection peak becomes the target wavelength in the range of 450 to 650 nm in the final target film number. It is necessary to find the optimal conditions while changing the conditions.

In the case of coloring an irregularly shaped powder, interference by the multilayer film occurs, and a basic film design is performed with reference to the conditions of the interference multilayer film of the spherical powder. The peak position of each unit film constituting the above-mentioned multilayer film can be adjusted by the film thickness of each layer, and the film thickness can be adjusted in the film forming conditions for forming a solid phase component such as metal oxide on the surface of the base particles. By controlling the composition, solid-phase deposition rate, substrate amount, and the like, the film thickness can be accurately controlled, a film having a uniform thickness can be formed, and a desired green color can be obtained. As described above, the reflection peak is 450 to 650 in the final target film number.
By finding the optimum conditions while changing the film forming conditions such as the film forming solution so that the target wavelength is in the range of nm, a green-colored powder can be obtained. Further, by controlling the combination of the substances constituting the multilayer film and the thickness of each unit film, it is possible to adjust the color development due to the interference of the multilayer film. Thus, the powder can be vividly colored into a desired green color system without using a dye or a pigment.

Hereinafter, the green pigment of the present invention and the method for producing the same will be described in detail. In the green pigment and the method for producing the same according to the present invention, the base particles on which the metal oxide film or the like is formed are not particularly limited, and may be an inorganic substance containing a metal, an organic substance, a magnetic substance,
It may be a dielectric, a conductor, an insulator, or the like. When the base is a metal, any metal such as iron, nickel, chromium, titanium, and aluminum may be used, but when using the magnetism, a magnetic material such as iron is preferable. These metals may be alloys, and when having the above-mentioned magnetism, it is preferable to use ferromagnetic alloys. When the substrate of the powder is a metal compound, a typical example thereof is an oxide of the metal described above.
For example, in addition to iron, nickel, chromium, titanium, aluminum, silicon and the like, oxides such as calcium, magnesium and barium, or composite oxides thereof may be used.
Furthermore, examples of metal compounds other than metal oxides include metal nitrides, metal carbides, metal sulfides, metal fluorides, metal carbonates, and metal phosphates.

Furthermore, as the base particles, other than metal,
It is a semi-metallic or non-metallic compound, especially an oxide, carbide or nitride, and silica, glass beads or the like can be used. Other inorganic substances include inorganic hollow particles such as shirasu balloons (hollow silicate particles), fine carbon hollow spheres (Clekasphere), fused alumina bubbles, aerosil, white carbon, silica fine hollow spheres, calcium carbonate fine hollow spheres, Mica such as calcium carbonate, perlite, talc, bentonite, synthetic mica, muscovite, kaolin and the like can be used.

As the organic substance, resin particles are preferable. Specific examples of the resin particles include cellulose powder, cellulose acetate powder, polyamide, epoxy resin, polyester, melamine resin, polyurethane, vinyl acetate resin, silicon resin, acrylate, methacrylate, styrene, ethylene, propylene and these. Spherical or crushed particles obtained by polymerization or copolymerization of a derivative of the above. Particularly preferred resin particles are spherical acrylic resin particles obtained by polymerization of acrylic acid or methacrylic acid ester. However, when resin particles are used as the substrate, the heating temperature in drying must be lower than the melting point of the resin.

The shape of the substrate may be a sphere, a subsphere, an isotropic body such as a regular polyhedron, a rectangular parallelepiped, a spheroid, a rhombohedron, a plate-like body, a polyhedron such as a needle-like body (a cylinder or a prism), and further a crushing It is also possible to use a completely amorphous powder such as an object. These substrates are not particularly limited in terms of particle size,
Those having a range of 0.01 μm to several mm are preferred. Also,
The specific gravity of the base particles is in the range of 0.1 to 10.5.
5.5 is preferred, more preferably 0.1 to 2.8, and still more preferably 0.5 to 1.8. If the specific gravity of the substrate is less than 0.1, the buoyancy in the liquid is too large, and the film needs to be multilayered or very thick, which is uneconomical. On the other hand, when it exceeds 10.5, the film for floating becomes thick, which is also uneconomical.

The pigment powder of the present invention has a specific gravity of 0.1 to 0.1.
The plurality of coating layers (layers of the film covering the base particles and participating in light interference) formed on the surface of the base particles of 10.5 need to have different refractive indexes from each other, The materials constituting these coating layers are inorganic metal compounds,
It is desirable to arbitrarily select from a metal or an alloy, and an organic substance.

Typical examples of the inorganic metal compound constituting the coating layer include metal oxides, and specific examples thereof include iron, nickel, chromium, titanium, aluminum, silicon, calcium, magnesium, and barium. Oxides or composite oxides of these, such as barium titanate and lead titanate, may be mentioned. Further, as a metal compound other than the metal oxide, magnesium fluoride,
Metal fluorides such as calcium fluoride; metal nitrides such as iron nitride; metal sulfides such as zinc sulfide and cadmium sulfide; metal carbonates such as calcium carbonate; metal phosphates such as calcium phosphate; and metal carbides. Can be

The simple substance of the metal constituting the coating layer includes metallic silver, metallic cobalt, metallic nickel, metallic iron and the like, and metallic alloys include iron / nickel alloy, iron / cobalt alloy, iron / nickel alloy nitride, iron A nickel / cobalt alloy nitride;

The organic substance constituting the coating layer may be the same as or different from the above-mentioned organic substance constituting the core, and is not particularly limited, but is preferably a resin. Specific examples of the resin, cellulose, cellulose acetate, polyamide, epoxy resin, polyester, melamine resin,
Examples include polyurethane, vinyl acetate resin, silicon resin, acrylic acid ester, methacrylic acid ester, styrene, ethylene, propylene and a polymer or copolymer of these derivatives.

As described above, various materials can be used as the material constituting the coating layer, and the combination of these materials is determined by considering the refractive index of each coating layer, It is necessary to select appropriately according to the object to be coated and the like.

As a method of forming the film, the following methods can be mentioned depending on the substance to be formed.
Other methods can also be used. (1) When forming an organic film (resin film) a. Polymerization Method in Liquid Phase A method of forming a resin film on the base particles by dispersing and emulsion-polymerizing the base particles can be used. b. Film forming method in gas phase (CVD) (PVD)

(2) In the case of forming an inorganic metal compound film a. Solid phase deposition method in liquid phase A method of dispersing particles serving as a substrate in a metal alkoxide solution and hydrolyzing the metal alkoxide to form a metal oxide film on the particles is preferable, and a dense metal An oxide film can be formed. Further, a metal oxide film or the like can be formed on the particles by the reaction of the aqueous metal salt solution. b. Film forming method in gas phase (CVD) (PVD) (3) When forming metal film or alloy film a. Method of Reducing Metal Salt in Liquid Phase A so-called chemical plating method of reducing a metal salt in an aqueous solution of a metal salt to deposit a metal to form a metal film is used. b. Film formation method in gas phase (CVD) (PVD) A metal film can be formed on the surface of particles by vacuum evaporation of metal or the like.

Next, as an example, a specific method for forming an alternating multilayer film of a substance having a high refractive index and a substance having a low refractive index in the present invention will be described below. In order to form a film having a high refractive index, for example, the base particles are dispersed in an alcohol solution in which an alkoxide such as titanium or zirconium is dissolved, and a mixed solution of water, alcohol, and a catalyst is dropped with stirring, and By hydrolyzing the alkoxide, a titanium oxide film, a zirconium oxide film, or the like is formed as a high refractive index film on the substrate surface. Thereafter, the powder is subjected to solid-liquid separation, vacuum-dried, and then heat-treated. The drying means may be any of vacuum heating drying, vacuum drying, and natural drying. Further, it is also possible to use a device such as a spray dryer in an inert atmosphere while adjusting the atmosphere. A coating composition that does not oxidize during heat treatment is in air, and a coating composition that easily oxidizes is in an inert atmosphere at 150 to 1100 ° C (when the substrate is an inorganic powder) or 150 to 500 ° C (when the substrate is not an inorganic powder). ) For 1 minute to 3 hours.

Subsequently, the above-mentioned powder having the high refractive index film is dispersed in an alcohol solution in which a metal alkoxide such as silicon alkoxide or aluminum alkoxide, which has a low refractive index when converted to an oxide, is dispersed. A mixed solution of water, an alcohol and a catalyst is added dropwise while the mixture is dropped, and the alkoxide is hydrolyzed to form a low refractive index film such as silicon oxide or aluminum oxide on the surface of the powder. Then, after the powder is solid-liquid separated and dried in vacuum,
Heat treatment is performed in the same manner as described above. By this operation, a powder having two layers of a high refractive index coating and a low refractive index coating on the surface of the base particles is obtained. Further, by repeating the operation of forming this coating, a powder having a multilayer coating on its surface is obtained. At this time, as described above, a powder having a high reflectivity can be obtained by using a powder in which a high-refractive-index coating and a low-refractive-index coating are alternately provided.

In the present invention, after a film of a metal oxide or the like is coated on the substrate particles, the formed metal oxide film is heat-treated to increase the density of the metal oxide constituting the film. In addition, the refractive index of the film is increased, the difference between the metal oxide film having a high refractive index and the metal oxide film having a low refractive index is increased, and the particle diameter is further reduced. In addition, the heat treatment
It may be performed every time the metal oxide film is coated, or after the metal oxide film is coated and the metal oxide film is sequentially coated thereon. Further, after the hydrolysis, the next coating treatment may be performed without drying, or after drying, the next coating treatment may be performed.

[0031]

EXAMPLES The present invention will be described in more detail with reference to the following Examples, which, of course, are not intended to limit the scope of the present invention.

Example 1 (Production of powder coated with a multilayer film) First layer: silica coating Carbonyl iron powder manufactured by BASF (average particle size: 1.8 μm) 10
g was dispersed in 100 ml of ethanol, and the temperature of the liquid was kept at 55 ° C. by heating the container in an oil bath. 6.5 g of silicon ethoxide and ammonia water (29% concentration)
6.5 g was added, and the mixture was reacted for 4 hours while stirring. After drying and heat treatment, the film thickness was adjusted to 96 nm.
After the reaction, the reaction solution was diluted and washed with ethanol, filtered, and dried at 110 ° C. for 3 hours in a vacuum drier. Heat treatment using a dried rotary tubular oven alms 30 minutes at 650 ° C., to obtain a silica-coated powder A _1. The resulting silica dispersion state of the coated powder A ₁ was very good.

Second layer: titania coating After heat treatment, again, 10 g of the obtained silica-coated powder A ₁
Then, 200 ml of ethanol was added and dispersed, and the temperature of the liquid was maintained at 55 ° C. by heating the container in an oil bath. To this, 7.3 g of titanium ethoxide is added and stirred. A mixed solution of 30 ml of ethanol and 7.3 g of water was added dropwise thereto over 60 minutes, and the mixture was allowed to react for 4 hours. After drying and heating, the film thickness was adjusted to 72 nm. After the reaction, the reaction solution was diluted and washed with ethanol, filtered, and dried at 110 ° C. for 3 hours in a vacuum drier. After drying, a heat treatment performed for 30 minutes at 650 ° C. using a rotary tubular furnace to obtain silica-titania-coated powder A _2. Obtained silica / titania coated powder A
₂ had good dispersibility and each was a single particle. silica·
Titania-coated powder A ₂ was a vivid green. The resulting green powder was spherical and had a magnetization of 170 emu / g at a magnetic field of 10 kOe.

The peak wavelength of the spectral reflection curve of the coated powder of the coating film, the reflectance at the peak wavelength, the refractive index of the coating film, and the film thickness were measured by the following methods. (1) The spectral reflection curve was obtained by packing a powder sample into a glass holder using a spectrophotometer with an integrating sphere manufactured by JASCO Corporation and measuring the reflected light. The measuring method was measured according to JISZ8723 (1988). (2) The refractive index and the film thickness were evaluated by measuring the results of measuring the spectral reflection curve of a sample having a film thickness under different conditions by fitting with a curve calculated by an instrument based on the equation of interference. Table 1 shows the refractive index and film thickness of the first and second layers, the peak wavelength of the spectral reflection curve of the coated powder, and the reflectance at the peak wavelength.
Shown in

[0035]

[Table 1]

Example 2 First layer: silica coating Carbonyl iron powder (average particle size 1.8 μm) manufactured by BASF 10
g was dispersed in 100 ml of ethanol, and the temperature of the liquid was kept at 55 ° C. by heating the container in an oil bath. 6.8 g of silicon ethoxide and ammonia water (29% concentration)
6.5 g and 8 g of water were added, and the mixture was reacted for 3 hours with stirring. After drying and heat treatment, the film thickness was adjusted to 98 nm. After the reaction, the mixture is diluted and washed with ethanol, filtered,
It dried at 110 degreeC with a vacuum dryer for 3 hours. After drying, a heat treatment performed for 30 minutes at 650 ° C. using a rotary tubular furnace to obtain silica-coated powder B _1. The resulting silica dispersion state of the coated powder B ₁ represents very good.

Second layer: titania coating 10 g of the obtained silica-coated powder B ₁ again after the heat treatment
Then, 200 ml of ethanol was added and dispersed, and the temperature of the liquid was maintained at 55 ° C. by heating the container in an oil bath. To this, 7.3 g of titanium ethoxide is added and stirred. A mixed solution of 30 ml of ethanol and 8.0 g of water was added dropwise thereto over 60 minutes, reacted for 3 hours, dried, heated, and adjusted to have a thickness of 74 nm. After the reaction, the reaction solution was diluted and washed with ethanol, filtered, and dried at 110 ° C. for 3 hours in a vacuum drier. After drying, a heat treatment performed for 30 minutes at 650 ° C. using a rotary tubular furnace to obtain silica-titania-coated powder B _2. Obtained silica-titania coated powder B
₂ had good dispersibility and each was a single particle. silica·
Titania-coated powder B ₂ was a vivid dark red.
The refractive index and thickness of the coating film, the peak wavelength of the spectral reflection curve of the coating powder, and the reflectance at the peak wavelength were measured.

Third layer: silica coating 10 g of silica / titania coated powder B _{2 was} added to ethanol 1
The solution was dispersed in 00 ml, and the temperature of the solution was kept at 55 ° C. by heating the container in an oil bath. To this, 6.8 g of silicon ethoxide, 7.0 g of aqueous ammonia (29% concentration) and 8 g of water were added, and the mixture was reacted for 3 hours while stirring. After drying and heating, the film thickness was adjusted to 106 nm. .
After the reaction, the reaction solution was diluted and washed with ethanol, filtered, and dried at 110 ° C. for 3 hours in a vacuum drier. After drying, heat treatment was performed at 650 ° C. for 30 minutes using a rotary tube furnace, and silica
To obtain a titania-coated powder B _3. The resulting silica-titania dispersion state of the coated powder B ₃ was very good.

Fourth layer: titania coating 10 g of the obtained silica-coated powder B ₃ again after the heat treatment
Then, 200 ml of ethanol was added and dispersed, and the temperature of the liquid was maintained at 55 ° C. by heating the container in an oil bath. To this, 7.3 g of titanium ethoxide is added and stirred. A mixed solution of 30 ml of ethanol and 10.0 g of water was added dropwise thereto over 60 minutes, reacted for 3 hours, dried, heated, and adjusted to have a thickness of 75 nm. After the reaction, the reaction solution was diluted and washed with ethanol, filtered, and dried at 110 ° C. for 3 hours in a vacuum drier. After drying, heat treatment was performed at 650 ° C. for 30 minutes using a rotary tube furnace to obtain silica-titania-coated powder B ₄ . The resulting silica-titania-coated powder B ₄ has good dispersibility and was an independent particle. The silica-titania-coated powder B ₄ had a bright green color.
The resulting green powder was spherical and had a magnetization of 145 emu / g at a magnetic field of 10 kOe. The refractive index and thickness of the coating film, the peak wavelength of the spectral reflection curve of the coating powder, and the reflectance at the peak wavelength were measured. Table 2 shows the refractive index, the film thickness of the first to fourth layers, the peak wavelength of the spectral reflection curve of the coated powder, and the reflectance at the peak wavelength.

[0040]

[Table 2]

Comparative Example 1 First layer: silica coating Carbonyl iron powder manufactured by BASF (average particle size: 1.8 μm) 10
g was dispersed in 100 ml of ethanol, and the temperature of the liquid was kept at 55 ° C. by heating the container in an oil bath. 6.5 g of silicon ethoxide and ammonia water (29% concentration)
6.5 g was added, and the mixture was reacted for 3 hours with stirring. After drying and heating, the film thickness was adjusted to 96 nm.
After the reaction, the reaction solution was diluted and washed with ethanol, filtered, and dried at 110 ° C. for 3 hours in a vacuum drier. Heat treatment using a dried rotary tubular oven alms 30 minutes at 650 ° C., to obtain a silica-coated powder C _1. The resulting silica dispersion state of the coated powder C ₁ was very good.

Second layer: titania coating 10 g of the obtained silica-coated powder C ₁ again after the heat treatment
Then, 200 ml of ethanol was added and dispersed, and the temperature of the liquid was maintained at 55 ° C. by heating the container in an oil bath. To this, 10.8 g of titanium ethoxide is added and stirred. A mixed solution of 30 ml of ethanol and 8.0 g of water was added dropwise thereto over 60 minutes, followed by a reaction for 12 hours. The film thickness was dried and heat-treated, and adjusted to 156 nm. After the reaction, the reaction solution was diluted and washed with ethanol, filtered, and dried at 110 ° C. for 3 hours in a vacuum drier. After drying, heat treatment was performed at 650 ° C. for 30 minutes using a rotary tube furnace to obtain silica-titania-coated powder C ₂ . The resulting silica-titania-coated powder C ₂ has good dispersibility and was an independent particle. The silica-titania-coated powder C ₂ was magenta.
The resulting green powder was spherical and had a magnetization of 147 emu / g at a magnetic field of 10 kOe. The refractive index and thickness of the coating film, the peak wavelength of the spectral reflection curve of the coating powder, and the reflectance at the peak wavelength were measured. Table 3 shows the refractive index and film thickness of the first and second layers, the peak wavelength of the spectral reflection curve of the coated powder, and the reflectance at the peak wavelength.

[0043]

[Table 3]

[0044]

According to the green color pigment and the method for producing the same of the present invention, a green color composite raw material powder used as a raw material for pigments, powder metallurgy, ceramic raw materials, electronics industry, etc. can be produced without using dyes or pigments. The resulting green pigment retains excellent performance that replaces conventional pigments used in pigments for color inks and fillers for plastics and paper, and has a stable color tone even during long-term storage. Body can be provided. It has good dispersibility, large interference reflection, and enables clear color.Also, the base particles can be changed depending on the application and purpose,
For example, when the base is made of a magnetic material, it becomes a magnetic toner, and when it is made of a dielectric or a conductor, it can provide an ink pigment for an ink jet printer, an electrostatic recording device or the like, which greatly contributes to the industry.

[Brief description of the drawings]

FIG. 1 is a graph showing a spectral waveform of the reflection intensity of each unit film constituting a multilayer film of a powder colored in a green color system.

Claims (6)

[Claims] Claims: 1. A plurality of coating layers in which a coating having a large refractive index and a coating having a small refractive index are stacked adjacent to each other on the surface of a base particle,
A green pigment having a reflection spectrum having a peak between 450 and 650 nm. 2. When the refractive index of the substrate particles is larger than the refractive index of the first layer coating in contact with the substrate surface, the substrate particles have an even number of layers, and the refractive index of the substrate particles is the refractive index of the first layer coating. The green pigment according to claim 1, wherein the pigment has an odd number of layers when the ratio is smaller than the ratio. 3. The green pigment according to claim 1, wherein the base particles are inorganic. 4. A method for producing a green pigment having a plurality of coating layers having different refractive indices on the surface of base particles,
Forming a plurality of coating layers in which a coating film having a large refractive index and a coating film having a small refractive index are stacked adjacent to each other on the surface of the base particles;
A method for producing a green-colored pigment, wherein the conditions of the base particles and the coating layer are set so as to show a reflection spectrum having a peak between 50 nm. 5. When the refractive index of the substrate particles is larger than the refractive index of the first layer coating in contact with the substrate surface, an even-numbered layer coating is formed, and the refractive index of the substrate particles is the refractive index of the first layer coating. The method according to claim 4, wherein an odd-numbered layer is formed when the ratio is smaller than the ratio. 6. The method for producing a green color pigment according to claim 4, wherein the base particles are inorganic.