JPH09278414A - Production of multilayer metal oxide film coated powder - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a producing method without causing mutual binding of particles and prevented from generating a defect, which causes the lowering of reflectance of the particle surface, at the time of forming a metal oxide film in the production of the powder having plural layers of the metal oxide films. SOLUTION: The multilayer different kind metal oxide film coated powder is produced by dispersing the powder of a base body in a metallic alkoxide solution, forming a metal oxide by the hydrolysis of the metallic alkoxide to cover the surface of the powder with the metal oxide film and to obtain a metal oxide film coated powder and repeating the metal oxide film forming process with the metallic alkoxide having the same or different metal component. At least one layer of the metal oxide film in the multilayer different kind metal oxide film coating is formed by dividing the metal oxide film forming process into plural times to form plural layers of the same metal oxide films.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a method for producing a powder having a composite coating layer structure and capable of performing a characteristic function, and particularly to a raw material for a color magnetic material such as a color magnetic toner or a color magnetic ink. The present invention relates to a method for producing a magnetic powder having a multilayer film on the surface thereof.

[0002]

2. Description of the Related Art There are many known coating techniques for forming a film on the surface of an article, such as coating, deposition, sputtering, vacuum deposition, electrodeposition and anodic oxidation. It is difficult to make the thickness of the film uniform by the deposition method or the deposition method, and it is difficult to obtain a thick film by the sputtering or the vacuum evaporation method. Further, the electrodeposition method and the anodic oxidation method are not suitable for treating powder because the object to be treated is used as an electrode.

Regarding the method of forming a coating film of a metal oxide on the surface of a metal powder, when forming a film of the same kind of metal oxide, the metal powder may be placed in an oxidizing atmosphere. When a fine metal powder is placed in an oxidizing atmosphere, the oxidation proceeds rapidly and the temperature rises, which may lead to ignition in extreme cases. Generally, the reaction is fast and it is difficult to obtain a dense oxide film.
Further, it is not easy to uniformly form a dense film to a desired film thickness, for example, it is difficult to increase the film thickness by this method in order to form a dense oxide film. Further, it is more difficult to form a film of a metal oxide different from the metal on the surface of the metal powder. not to mention,
It is extremely difficult to form a thick film of metal oxide on the surface of glass beads.

As a method of forming a film of a metal oxide different from the constituent metal on the surface of a metal powder or a metal oxide powder, for example, a coating treatment is performed with an aqueous salt solution of a metal to be a metal oxide. Immerse metal powder or metal oxide powder,
As described above, a method is considered in which the metal salt is reduced to precipitate a metal, which is then converted into an oxide by heating or the like, but such a method produces a dense, uniform and thick film. I can't let that happen.

First, the present inventors disperse a metal powder or a metal compound powder in a metal alkoxide solution and hydrolyze the metal alkoxide to form a metal oxide on the surface of the powder. And thereby forming a metal oxide film on the surface of the powder, and repeating this operation to form a plurality of layers of metal oxide film on the surface of the powder. This method is disclosed in Japanese Patent Application Laid-Open No. 6-228.
No. 604. Further, the present inventors
A metal powder or a metal compound powder is dispersed in a metal alkoxide solution, and the metal alkoxide is hydrolyzed to form a metal oxide film on the surface of the powder, and a metal film is formed on the metal oxide film. Inventing a method of forming a metal oxide film on the metal film, and repeating such an operation to alternately form a plurality of metal oxide films and metal films on the surface of the metal powder or the metal compound powder. However, this method is disclosed in JP-A-7-9.
No. 0310.

By the method of forming a plurality of layers of metal oxide films on the surface of the metal powder or the like, for example, the functionality such as the powder having a high thermal conductivity and the electric insulation is provided. It is possible to develop high-quality powder. Further, the refractive index of each layer is adjusted by changing the kind of the metal constituting the metal oxide of a plurality of layers and each layer on the surface of the magnetic metal powder or the magnetic metal compound powder. Alternatively, it is possible to develop a color magnetic powder as a raw material for color magnetic ink. In the color powder used as a raw material for toner or ink, it is desirable that the powder has a small particle size and high whiteness, but in the case of particles that do not necessarily need to have magnetism, metal powder or metal compound powder The use of glass beads as the base particles makes it possible to inexpensively produce color powder having a better color tone than the body particles as the base particles.

[0007]

In the course of research on improving the characteristics such as color tone and saturation of color powder, there is a phenomenon that the saturation of manufactured color powder becomes poor and the color tone changes. It could happen. Such a phenomenon is a phenomenon that occurs because the reflectance of the manufactured color powder partially or totally decreases. Such phenomena have also been experienced in the production of color magnetic powders. Generally, in order to form a metal oxide layer having a high reflectance, the thickness of the metal oxide layer must be considerably increased. However, if a thick metal oxide layer is formed as a single layer, it will be adjacent in the process of forming the film. There is a case where the metal oxide films of the powders adhere to each other, and if the metal oxide films of the powders adhere to each other, the metal oxide film coating on the powder surface is damaged when the powders are separated. When the coating of the metal oxide film on the surface of the color magnetic powder is partially damaged in this way, the reflectance of the manufactured color powder is reduced. It is considered that since no reflection occurs at the damaged portion of the particles, the reflectance of the whole powder is reduced.

According to the present invention, a metal oxide layer having a uniform and excellent characteristic can be obtained even when a thick metal oxide layer is formed in the production of a powder having a plurality of metal oxide coatings. It is an object of the present invention to provide a method capable of producing a powder having a plurality of layers of metal oxide films, which does not cause the problem that the reflectance is lowered, which has been observed in the production of color magnetic powder.

[0009]

As a result of earnest research, it has been found that the above-mentioned object can be achieved by the method for producing a multilayer metal oxide film-coated powder according to the present invention. That is, it is the following manufacturing method. (1) Dispersing a powder of a substrate in a metal alkoxide solution, hydrolyzing the metal alkoxide to generate a metal oxide, and coating the surface of the powder with the metal oxide, A film made of the metal oxide is formed,
It is dried to obtain a metal oxide film-coated powder, and then the metal oxide film forming step is repeated using a metal alkoxide having the same or different metal components to produce a multilayer heterogeneous metal oxide film-coated powder. In the method, the metal oxide film of at least one layer of the multi-layered different metal oxide film coating is formed by performing the formation process of the metal oxide film in multiple steps to form a multi-layered metal oxide film. A method for producing a multi-layer metal oxide film-coated powder, comprising:

(2) The metal oxide film of at least one layer of the multi-layered different kind metal oxide film coating is formed into the same metal oxide film by performing the forming process of the metal oxide film in plural times. In the case of forming a coating in multiple layers, the step of forming each metal oxide film comprises the steps of forming a coating of the metal oxide film, followed by drying and heat treatment. A method for producing a multi-layer metal oxide film-coated powder according to claim 1. (3) The multi-layer metal oxide film-coated powder according to item (1) or (2), wherein the powder of the base is made of one substance selected from glass, metal, and metal compound. Body manufacturing method. (4) The multi-layer metal oxide film-coated powder according to item (3), wherein the powder of one substance selected from the metal and the metal compound of the substrate is a substance having magnetism. Manufacturing method.

In the method for producing a multi-layer metal oxide film-coated powder according to the present invention, each layer of the metal oxide film coated on the surface of the powder in multiple layers is a metal oxide film constituting an adjacent layer. , May be composed of metal oxide films having the same metal composition or different kinds of metals, but the target metal oxide film has a defect in its formation because it is thick. It is a thing. Therefore, the metal oxide film formed according to the present invention has a form in which at least two layers of the same metal oxide film are adjacent to each other when viewed after being manufactured. The metal film may be provided on the surface of the powder, that is, at the bottom of the multilayer, or between the metal oxide films. The structure and manufacturing means of the metal film can be as described in JP-A-7-90310.

Without using the present invention, a metal oxide film layer consisting of a considerably thick layer is formed on the surface of the powder by one film formation (or the surface of the powder having an already existing metal oxide film layer). ), The unreacted material remains on the surface of the coated metal oxide layer gel when it is dried, and the unreacted material on the surface of the coated metal oxide layer gel of the adjacent powder adheres to each other. ,
When the adjacent powders separate after drying, the coating film on either powder may be destroyed. In a portion where such a coating film is broken, for example, in the case of a color magnetic powder, the reflectance decreases, the saturation of the color magnetic powder deteriorates, and the color tone changes. Such a problem is that the film thickness after drying is easily fixed at 50 to 70 nm in the case of titania, and is easily fixed at 30 to 70 nm in the case of silica. Although the cause of this is unknown, it is considered that, for example, when the hydrolysis is insufficient, the film itself becomes soft, and the hydrolysis is slow and unreacted groups are likely to remain.
This can prevent sticking to some extent by taking sufficient time to reduce unreacted substances in the film, but it is not practical. In the present invention, when the film thickness is such that sticking occurs, the formation of the metal oxide film layer is
By dividing into more than one time, the problem of sticking can be avoided.

The gist of the present invention is such that such a metal oxide film layer is divided into a plurality of times to be coated and formed on the powder,
By reducing the film thickness formed by one-time film formation, reducing the unreacted substances remaining on the gel surface of the coated metal oxide film layer, and reducing the contact area between particles, the coating film during drying can be formed. By eliminating aggregation and sticking, the particles can be easily separated and the dispersion of the particles can be improved. A further emphasized feature of the present invention is that the powder is dispersed in a metal alkoxide solution, the metal alkoxide is hydrolyzed to generate a metal oxide, and a coating of the metal oxide is formed on the surface of the powder. The effect is remarkable when a metal oxide film is formed on the surface of the powder, dried, and then further heat-treated. When the heat treatment is performed, the coating films do not aggregate and stick to each other at all, and the heat treatment increases the density of the metal oxides that form the film and reduces the diameter of the coated particles, increasing the refractive index of the film. .

[0014]

BEST MODE FOR CARRYING OUT THE INVENTION Examples of the metal oxide constituting the coating film on the surface of the powder include iron, nickel, chromium, titanium, zinc, aluminum, cadmium, zirconium, silicon and the like, calcium, magnesium, An oxide of a metal such as barium can be used. As the kind of the metal oxide, one suitable for the property to be imparted to the surface of the powder is selected. It should be noted that silicon and the like are not included in metals in a narrow sense but may be referred to as semimetals. However, in the present invention, the metal in the metal oxide includes silicon and the like.

In the present invention, the thickness of the metal oxide film for forming the film in a plurality of times is set in the range of 0.005 to 5.0 μm. Is preferred. In the case of the above-mentioned color magnetic powder, the total thickness of the metal oxide film formed in a plurality of times is equivalent to that of the metal oxide layer in order to form a metal oxide layer having a high reflectance due to the interference. Thick layer, preferably in the range of 0.01 to 20 μm, more preferably 0.0
The thickness is preferably in the range of 2 to 5.0 μm. The thickness is preferably in the range of 0.02 to 2.0 μm in order to interfere and reflect visible light with a particularly thin film thickness, for example, when the particle size is limited. The thickness of each of the other metal oxide films formed on the powder having the multilayer metal oxide film of the present invention is not particularly limited, but is preferably in the range of 0.01 to 20 μm, and more preferably 0.1 to 20 μm. 02 to 10 μm. As already described above, in the case of the color magnetic powder which is the characteristic product of the present invention, in order to form a thin metal oxide film layer having a good reflectance in the visible light range, the range is 0.02 to 5.0 μm. The thickness is preferably

In the present invention, when a metal oxide film is formed on the surface of a powder, the powder is dispersed in a solution of a metal alkoxide which is a component of the metal oxide to hydrolyze the metal alkoxide. This produces an oxide sol of the metal on the surface of the powder. The generated sol deposits on the surface of the powder and gels, and a metal oxide gel film is uniformly formed on the powder. The first metal oxide film is used.
At the time of forming the metal oxide film at the second time, the powder is the powder of the substrate, but at the time of forming the metal oxide film after the second time, the powder is a powder having the surface covered with the metal oxide film. There will be. In this way, using a solution of metal alkoxide,
A method of forming a metal oxide sol by hydrolyzing a solution of a metal alkoxide by hydrolysis and forming a metal oxide sol by gelling the sol is called a sol-gel method, which has a fine and uniform composition. It is characterized in that a metal oxide is produced. In the present invention, this sol-gel method is applied to generate a metal oxide layer on the surface of powder, and a film having a uniform composition, a dense structure and a uniform thickness can be obtained. However, when the film is thick, unreacted substances may remain on the gel surface when the metal oxide gel film on the powder is dried. In the present invention,
This problem can be prevented by dividing the formation of one metal oxide film into a plurality of times.

In the present invention, a substance selected from one of glass, metal and metal compound is used as the powder substrate. One example of a glass powder is called glass beads. When the substrate is a metal or a metal compound, they may be magnetic. When the substrate is a metal, any metal such as iron, nickel, chromium, titanium, and aluminum may be used. Preferred examples of the metal whose substrate has magnetism include metallic iron, nickel, and chromium. These metals may be alloys, and it is preferable to use ferromagnetic alloys as those having magnetism. In addition, when the substrate of the powder is a metal compound, examples of the metal compound include various metals and silicon, calcium, magnesium, barium and other oxides described above,
In addition to the composite oxide, a metal nitride, a metal carbide, and the like can be given. In addition, examples of the metal compound whose base is magnetic include magnetic substances such as ferrite and chromium oxide. As a metal oxide film formed on the surface of these powders, a metal whose metal oxide is different from the metal of the powder or the metal that is a component of the metal compound can be used. For example, when the powder is a metal oxide, the formation of the same metal oxide film does not result in the formation of films having different properties, so that there is not much technical advantage. The particle size of the powder is not particularly limited, but is preferably in the range of 0.01 μm to several mm.

The metal alkoxide used for forming the film includes alkoxides of metals such as zinc, aluminum, cadmium, titanium, zirconium and silicon. In forming the film, an alkoxide of a metal corresponding to the metal oxide forming the coating is selected and provided for forming a metal oxide film. The metal alkoxide is used as a solution in an organic solvent so that the decomposition with water is carried out uniformly. As the organic solvent, alcohols such as ethanol and methanol, ketones and the like are used. It is preferable to use a dehydrated organic solvent. The concentration of the metal alkoxide solution varies depending on the type of metal alkoxide to be dissolved and the type of organic solvent, but optimal conditions are set. The thickness of the metal oxide film on the powder is determined by the concentration of the metal alkoxide solution and the amount of the metal alkoxide solution used for the powder.

The powder of the substrate is dispersed in this metal alkoxide solution, water is added thereto (preferably added as a liquid mixed with alcohol) to hydrolyze the metal alkoxide to form a metal oxide, and A metal oxide film is formed by depositing on the powder. To specifically form the metal oxide film, the powder is dispersed in dehydrated alcohol, a metal alkoxide solution is added and mixed with sufficient stirring, and alcohol and water are gradually added to the uniform mixture. The mixed solution is added to hydrolyze the metal alkoxide, and the metal oxide sol is deposited on the surface of the powder in the form of a film. In addition, in the case of silicon alkoxide or zirconium alkoxide having a relatively low hydrolysis rate among metal alkoxides, the metal alkoxide is added after the raw alkoxide and the catalyst and water are simultaneously added or the mixture of water and the catalyst is added first instead of the above method. You can also.

In the hydrolysis of the metal alkoxide of the present invention, a sol of the metal oxide is first formed on the surface of the powder and then gels, but after the hydrolysis reaction, gelation proceeds after a while, In some cases, drying completes gelation. In the hydrolysis reaction, the above sol is generated on the surface of the powder, so that a continuous film is formed, thereby easily forming a uniform metal oxide film having a uniform thickness and a uniform composition. It is thought to be done. A metal oxide film having such properties cannot be obtained by a conventional deposition method or the like. In the hydrolysis reaction,
When the amount of water is large, the reaction rate is fast and fine metal oxide particles are easily formed, but an alkanolamine or the like can be added to slow the reaction. Further, in order to accelerate the above reaction, a catalyst such as acid, amine, base such as ammonia can be used.

A coated powder is obtained by drying the metal oxide gel film coated on the surface of the powder. Drying may be any of vacuum heating drying, vacuum drying, and natural drying, but preferably vacuum drying. Further, it is also possible to use a device such as a spray dryer in an inert atmosphere while adjusting the atmosphere. After coating the surface of the powder with a metal oxide film and drying it, increase the density of the coated metal oxide film,
In order to increase the strength and reduce the particle size of the coated particles,
It is preferable to heat-treat the formed metal oxide film. If the metal oxide film is heat-treated in this way, even if unreacted substances remain on the gel surface when the gel film is dried, aggregation and fixation of the coating film between adjacent metal oxide film-coated particles occurs. This can be completely prevented.

The temperature in the heat treatment is the heating temperature or higher usually used for drying, and it is sufficient if the organic substances are removed.
0 ° C. or higher and up to 1000 ° C. or lower, preferably 3 ° C.
00 to 600 ° C, more preferably 400 to 55 ° C.
0 ° C. The lower one may be 200 ° C or 250 ° C. The heat treatment time is appropriately determined in the range of 1 minute to 3 hours. The atmosphere in the heat treatment may be air, but since the oxidation state does not change in a nitrogen atmosphere or an inert gas atmosphere, if it is desirable that the oxidation state does not change, the atmosphere is a nitrogen or inert gas atmosphere or the like. be able to. Further, the heat treatment is preferably performed for each coating step of the metal oxide film formation, but may be performed after the metal oxide film is coated and the metal oxide film is sequentially coated thereon.

The metal or metal compound powder having a metal oxide film on the surface produced in this manner is the powder metal or metal compound material selected to constitute it, and the metal oxide of the surface film. Since it has various properties depending on the material, it can be used for each purpose. For example, if silver is used as the powder base and a film layer of aluminum oxide is provided as a film thereover, an insulating powder having good thermal conductivity can be provided. Also, for example, magnetic powder metal iron, triiron tetraoxide, etc. are used as the powder, silicon oxide having a lower refractive index is used as the metal oxide of the film thereon, and titanium oxide having a higher refractive index is used as the outer film. With
Magnetic powder with high whiteness can be obtained.

In the case where the metal oxide film formed on the surface of the powder has a plurality of layers, the thickness of each layer of the film is adjusted, and the alternating coating films having different refractive indexes are expressed by the following formula (1). If a suitable thickness and number of alternating films having a refractive index n of the material forming the covering film and a thickness d corresponding to an integer m times a quarter of the wavelength of visible light are provided so as to satisfy the condition (1). , Specific wavelength λ
Light (using Fresnel interference reflection) is reflected. nd = mλ / 4 (1) Utilizing this action, for example, metal powder or metal alloy powder of iron, cobalt, nickel or the like, or magnetic material such as iron nitride is used as the base particles, and the target visible For example, a silicon oxide film or a titanium oxide film is formed twice in a thickness of 0.5 μm or less so as to satisfy the formula (1) with respect to the wavelength of light, so that the dispersion of particles is improved and the visible light range is improved. It is possible to make the particles of the reflective and bright color peculiar to. It is more preferable to design so that the peak shift due to the complex refractive index and the shape of powder such as metal is corrected by the film thickness.

In the present invention, as a means for providing the metal film on the surface of the metal or metal compound powder or on the metal oxide film layer, it is possible to use not only the electroless plating method but also the contact electroplating method. It can be provided by a sputtering method. However, in the contact electroplating method, the powder is not plated when the powder does not come into contact with the electrodes, and in the sputtering method, the metal vapor is not uniformly applied to the powder. different. On the other hand, the electroless plating method is preferable because a dense and uniform film can be formed and the film thickness can be easily adjusted. The metal film can be provided alternately with the metal oxide film, but it is preferably used in a layer that is most effective in increasing the reflectance of the powder. As the metal forming the metal film, iron, nickel, silver, gold or the like and alloys thereof such as iron-nickel alloy, iron-cobalt alloy and the like can be used. When the metal film is provided, the reflection efficiency is improved, and the whiteness can be increased particularly when white particles are obtained. Further, since the film may be thin, there is an advantage that the particle size of the particles can be reduced.

Further, in the present invention, by further heat treating the produced powder in an inert gas atmosphere at a temperature of 300 to 600 ° C., a stronger powder can be obtained. If a colored layer is further provided on the powder and a resin layer is further provided thereon, color magnetic toners of various colors can be manufactured. Since the wavelength of visible light has a wide range, the thickness of each of the oxide and metal layers of the particles constituting the magnetic toner is determined by the product of the refractive index of the substance and the thickness of the film is a quarter wavelength of visible light. May be alternately provided in a plurality of portions slightly different from each other within a range close to the thickness.

FIG. 1 is a flow chart showing a method of forming a silica-titania multilayer oxide film-coated powder described below. That is, the powder is dispersed in ethanol, the silicon ethoxide solution prepared as a coating solution and ammonia water are added thereto, and the mixture is reacted with stirring to form a coating. Diluted and washed with ethanol, filtered, dried in a vacuum drier, heat-treated by heating after drying to obtain a silica-coated powder, and the obtained silica-coated powder is again dispersed in ethanol. By repeating the same operation, the silica film is
Cover once. The silica-coated powder obtained by coating the silica film twice was dispersed in ethanol, titanium ethoxide prepared as a coating solution was added to this, and a mixed solution of ethanol and water was added dropwise to the mixture, followed by reaction, and the coated film after the reaction. The powder in which is formed is diluted and washed with ethanol, filtered, dried in a vacuum drier, and heat-treated by heating after drying to obtain a silica-titania powder. Further, the silica-titania powder is again dispersed in ethanol in the same manner as in the first titania coating, and the same operation as above is repeated to coat the second titania film. Thus, a silica-titania multilayer oxide film-coated powder is formed.

A method of using the magnetic toner obtained as described above will be briefly described. For example, a metal deposition layer is provided on a polyester film to form a conductive layer, and a fine particle of a photoconductive semiconductor such as zinc oxide in a binder such as an acrylic resin, a photosensitizing dye, a color sensitizer, A photoreceptor having a photoconductive layer formed by dispersing and applying a dispersing agent or the like is prepared. When a corona charge is uniformly applied to the photosensitive member and reflected light from an image to be copied is irradiated on the charged photosensitive member, a positive charged image of an original image is formed on the photosensitive member. The magnetic brush composed of the magnetic powder of the present invention charged in the opposite direction to the above positively charged image is adhered to the photoreceptor from the magnetic brush on the positively charged image. A magnetic toner image corresponding to the original image is obtained. When this magnetic toner image is transferred to paper and fixed, a copied image is obtained on paper. The paper is white,
By using the colored magnetic toner obtained by using the powder obtained by the present invention as a raw material, a clear and excellent copy image which has never been obtained can be obtained.

[0029]

[Examples] An example of producing a powder having a plurality of metal oxide films on the surface of a base powder according to the present invention will be specifically described with reference to an example. However, the present invention is not limited to the examples below.

Example 1 (when coated twice) First layer: silica coating Carbonyl iron powder made by BASF (average particle size 1.8 μm) 20
g was dispersed in 200 ml of ethanol, 8 g of silicon ethoxide and 8 g of aqueous ammonia (29% concentration) were added thereto, and the mixture was reacted for 5 hours while stirring. After the reaction, the reaction solution was diluted and washed with ethanol, filtered, and dried in a vacuum dryer at 110 ° C. for 3 hours. After drying, heat treatment was performed at 650 ° C. for 30 minutes using a rotary tube furnace to obtain silica-coated powder A.
After the heat treatment, 20 g of the obtained silica-coated powder A is dispersed again in 200 ml of ethanol, 6 g of silicon ethoxide and 8 g of ammonia water (29% concentration) are added thereto, and the mixture is reacted for 5 hours with stirring, the first time. Vacuum drying and heat treatment were performed in the same manner as in 1. to obtain silica-coated powder B.
The silica-coated powder B obtained had good dispersibility and was a single particle.

Second layer: titania coating The silica-coated powder B 8 was added to 250 ml of ethanol.
g was dispersed, 3 g of titanium ethoxide was added thereto, and a mixed solution of 30 ml of ethanol and 3.0 g of water was added dropwise over 30 minutes, and then reacted for 3 hours. After the reaction, the reaction solution was diluted and washed with ethanol, filtered, and dried in a vacuum dryer at 110 ° C. for 3 hours. After drying, heat treatment was performed for 30 minutes at 650 ° C. using a rotary tube furnace to obtain silica-titania powder A.
I got Further, for the silica-titania powder A, 8 g of the powder A was dispersed in 250 ml of ethanol in the same manner as in the case of the first titania coating, 3 g of titanium ethoxide was added thereto, and 30 ml of ethanol and 3.0 g of water were further added.
The mixed solution of (1) was added dropwise over 30 minutes, and then the mixture was reacted for 3 hours, vacuum-dried and heat-treated to obtain silica-titania powder B. The obtained powder had good dispersibility and was a single particle. A micrograph of the particle structure of the powder is shown in FIG. This micrograph has a magnification of 10,000 times,
It can be seen that few particles are bound to each other. The peak wavelength of the spectral reflection curve of this powder is 552 nm.
The reflectance at the peak wavelength was 40%, and the color was vivid green.

Comparative Example 1 (in the case of coating once) Carbonyl iron powder made by BASF (average particle size 1.8 μm) 16
g was dispersed in 400 ml of ethanol, and 16 g of silicon ethoxide and 16 g of ammonia water (29% concentration) were dispersed therein.
Was added and reacted for 5 hours with stirring. After the reaction, dilute and wash with ethanol, filter, and dry in a vacuum dryer at 110 ° C 3
Dried for hours. After drying, heat treatment was performed at 650 ° C. for 30 minutes using a rotary tube furnace to obtain a silica-coated powder C. Ethanol 500 against this silica-coated powder C
Add ml and disperse in the ethanol, add 7.2 g of titanium ethoxide, and add ethanol 30
A mixed solution of ml and water (3.6 g) was added dropwise over 30 minutes, and the reaction was performed for 3 hours. After the reaction, the reaction solution was diluted and washed with ethanol, filtered, and dried in a vacuum drier at 110 ° C. for 3 hours. After drying, heat treatment was performed at 650 ° C. for 30 minutes using a rotary tube furnace to obtain silica-titania powder C. The obtained powder had poor dispersibility. A micrograph of the particle structure of the powder is shown in FIG. This micrograph has a magnification of 10,000
It is twice as many, and there are quite a few solidified particles that are bound to each other, and there are many missing parts on the particle surface that are thought to be due to the binding of the particles to each other. The peak wavelength of the spectral reflection curve of the obtained powder was 550 nm, the reflectance at the peak wavelength was 22%, and it was dark green.

Example 2 (in the case of coating twice without heat treatment) First layer: silica coating Carbonyl iron powder made by BASF (average particle size 1.8 μm) 20
g was dispersed in 200 ml of ethanol, and 60 g of silicon ethoxide and 4.5% of aqueous ammonia (29% concentration) were dispersed in this.
g was added and reacted for 24 hours with stirring. After the reaction, wash well with ethanol, wash, filter and vacuum-dry 1
It was dried at 10 ° C. for 3 hours to obtain a silica-coated powder D. 20 ml of the obtained silica-coated powder D was added to 200 ml of ethanol.
Dispersed in the solution, to which 6.0 g of silicon ethoxide and 4.5 g of ammonia water (29% concentration) were added, reacted for 24 hours while stirring, and vacuum dried in the same manner as the first time,
Silica-coated powder E was obtained. The resulting silica-coated powder E had good dispersibility and was a single particle.

Second layer: titania coating 8 g of the silica-coated powder E was added to 250 ml of ethanol.
Dispersed in it, and then added 2.2 g of titanium ethoxide,
Further, add 6 ml of a mixed solution of 30 ml of ethanol and 2.2 g of water.
After dropping for 0 minutes, the reaction was performed for 24 hours. After the reaction, the mixture is diluted and washed with ethanol, filtered, and dried in a vacuum drier.
Silica / titania powder D was obtained by drying at ℃ for 3 hours. Further, for the silica-titania powder D, 8 g of the powder D was added to 25 parts of ethanol in the same manner as in the first titania coating.
Disperse in 0 ml, add 2.2 g of titanium ethoxide, add dropwise a mixed solution of 30 ml of ethanol and 3.0 g of water over 60 minutes, react for 3 hours, vacuum dry, and then silica-titania. A powder E was obtained. The obtained powder had good dispersibility and was a single particle. Also,
The peak wavelength of the spectral reflection curve of this powder was 544 nm, the reflectance at the peak wavelength was 32%, and it was vivid green. Further, this powder was subjected to heat treatment at 650 ° C. for 30 minutes using a rotary tube furnace, and the peak wavelength of the spectral reflection curve of the powder was 456 nm, and the reflectance at the peak wavelength was 41%, which was vivid. It was blue.

Example 3 (Twice Treatment without Heat Treatment and Drying) First Layer: Silica Coating Carbonyl iron powder made by BASF (average particle size 1.8 μm) 20
g was dispersed in 200 ml of ethanol, and 6.0 g of silicon ethoxide and 8.5 g of ammonia water (29%) were dispersed therein.
Was added and reacted for 48 hours with stirring. After the reaction, a silica-coated powder F was obtained by sufficiently diluting and washing with ethanol. After washing this, it was dispersed in 200 ml of ethanol, and 6.0 g of silicon ethoxide and ammonia water (29
%) 8.5 g, and reacted for 48 hours with stirring. After the reaction, the product was thoroughly diluted with ethanol and washed to obtain a silica-coated powder G.

Second layer: titania coating 8 g of the silica-coated powder G was added to 250 ml of ethanol.
Dispersed in it, and added 3.0 g of titanium ethoxide to it,
Further, add 6 ml of a mixed solution of 30 ml of ethanol and 3.5 g of water.
After dropping over 0 minutes, the reaction was carried out for 48 hours. After the reaction, silica / titania powder F was obtained by diluting and washing with ethanol. Silica-titania powder F 8g ethanol 250
2.5 g of titanium ethoxide was added thereto, and a mixed solution of 30 ml of ethanol and 3.5 g of water was added dropwise over 60 minutes, followed by reacting for 48 hours, and after the reaction, sufficiently diluted with ethanol and washed. , Filter and vacuum dryer 11
Dry at 0 ° C for 3 hours and 650 ° C 30 in a rotary tube furnace.
Heat treatment was performed for a minute to obtain silica-titania-coated powder G. The obtained powder had good dispersibility and was a single particle. The peak wavelength of the spectral reflection curve of this powder is 555 nm, the reflectance at the peak wavelength is 40%,
It was bright green.

[0037]

According to the present invention, it is possible to produce a multi-layer metal oxide film-coated powder having a large interference reflection and a bright color. The surface of the obtained powder is smooth because the multilayer metal oxide film has no defects. Especially in the manufacturing process,
Powder particles having a metal oxide film formed from a metal alkoxide on the surface do not bind to each other or are few, so there is no defect on the surface and therefore powder with high reflectance can be obtained. . Further, according to the present invention, by selecting the kind of the metal oxide film forming the multilayer metal oxide film, it is possible to obtain a powder having a plurality of properties and capable of performing a composite function. The heat-treated powder was a powder having good dispersibility because the metal oxide film was dense and had a small particle size. Also,
The color powder obtained by the present invention has a large interference reflection,
It was a bright color.

[Brief description of drawings]

FIG. 1 is a flow chart illustrating a method for producing a multi-layer metal oxide film-coated powder according to the present invention.

FIG. 2 shows a micrograph of the particle structure of a powder obtained by the method for producing a multilayer metal oxide film-coated powder according to the present invention.

FIG. 3 shows a micrograph of the particle structure of a powder obtained by the method for producing a multilayer metal oxide film-coated powder of Comparative Example.

Claims (4)

[Claims] 1. A powder of a substrate is dispersed in a metal alkoxide solution, a metal oxide is produced by hydrolyzing the metal alkoxide, and the surface of the powder is coated with the metal oxide. Then, a film made of the metal oxide is formed and dried to obtain a metal oxide film-coated powder, and then the metal oxide film forming step is performed using a metal alkoxide having the same or different metal components. In the method for producing the multi-layered heterogeneous metal oxide film-coated powder by repeating, the metal oxide film of at least one layer of the multi-layered heterogeneous metal oxide film coating is formed by performing the forming process of the metal oxide film a plurality of times. A method for producing a multi-layer metal oxide film-coated powder, characterized in that the same metal oxide film is formed into a multi-layer coating by performing the steps separately. 2. The metal oxide film of at least one layer of the multi-layered different kind metal oxide film coating is formed into a same metal oxide film by performing the forming process of the metal oxide film in plural times. When forming the coating on the layer, the step of forming each metal oxide film is performed after the coating of the metal oxide film is formed.
The method for producing a multi-layer metal oxide film-coated powder according to claim 1, comprising a step of drying and heat treatment. 3. The multilayer metal oxide film-coated powder according to claim 1, wherein the powder of the substrate is made of one substance selected from glass, metal, and metal compound. Manufacturing method. 4. The multilayer metal oxide film-coated powder according to claim 3, wherein the powder of one substance selected from the metal and the metal compound of the substrate is a substance having magnetism. Manufacturing method.