JP3032927B2 - Metal or metal compound powder having a metal oxide film on the surface - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

The present invention relates to a thick metal oxide film on the surface relates metal or metal compound powder having multiple several layers, in particular metal oxides of the thick foreign to the surface of the metal or metal compound powder The present invention relates to a new metal or metal compound powder having a composite property by having a film so as to perform a composite function.

[0002]

2. Description of the Related Art Conventionally, even if a metal material or product is polished cleanly, it is often difficult for its surface to be oxidized in air and covered with a thin metal oxide film. It is known. In addition, many types of means such as coating, deposition, anodic oxidation, sputtering, and vacuum deposition are known as a coating technique for protecting the surface of an article or forming a thin film on the surface of an article. Although the coating method and the like can obtain a thick film, the coating method and the like have a non-uniform film thickness and poor adhesion, and the anodic oxidation method, sputtering, vacuum evaporation method, etc. Although the film has good adhesion and a composition having a uniform composition to some extent can be obtained, there is a drawback that only a thin film can be obtained. In the anodization method, when the substrate is aluminum, an aluminum oxide layer is formed, but the structure is not dense.

[0003] However, such a coating technique can be easily performed when the article has a certain size, but when the article to be coated is a powder, most of the techniques are directly applied. However, it is difficult to form a film having a uniform thickness on the powder even if some additional means are taken. Forming a metal oxide film on the surface of a metal powder can be achieved by placing the metal powder in an oxidizing atmosphere.
Since the metal on the surface of the metal powder is oxidized and a naturally thin oxide film is formed on the surface, it is not difficult, but the metal is easily oxidized,
Alternatively, when the particle size of the powder is small, the reaction is fast, and the oxidation proceeds at a stretch to ignite, so that this means cannot be employed. Even if an oxide film is formed by controlling the degree of oxidation, the film is thin and not suitable for practical use. The method of oxidizing the surface of a metal powder with an oxidizing agent in a liquid cannot be carried out on average because of the heterogeneous system, so that a metal oxide film having a uniform thickness can be obtained. Was difficult to form.

Further, it is more difficult to uniformly form an oxide film of a metal different from the metal on the metal powder. Although there is a technique for coating silicon oxide or titanium oxide very thinly on the surface of a metal powder for the purpose of surface treatment, it has been difficult to increase the film thickness to a uniform thickness. The deposition method and the coating method can form a thick film on a metal object, but when these methods are applied to a metal powder, the metal powder must be maintained in a dispersed state. In addition, particles (powder) of only the coating material are easily formed outside the coated metal powder, and a mixture thereof is formed. For this reason, there has been no method of thickly coating the surface of a metal powder with a different kind of metal oxide and not producing single fine particles of the metal oxide to be coated.

[0005] Even when the powder is composed of a metal compound, it is difficult to form an oxide film of another metal on the powder because of various problems. For example, when a method of depositing a metal compound on a powder from a metal salt aqueous solution and heating the deposit to change the metal oxide to the metal oxide is adopted, the aqueous solution is impregnated into the metal compound of the substrate,
At the time of the precipitation reaction, there is a risk that a state in which a different metal oxide is mixed in the metal compound, for example, the metal oxide, by the above-described reaction is generated, and the intended product cannot be obtained.

[0006]

With the progress in various technical fields, there has been an increasing demand for metal powders or metal compound powders having unique properties, and only metal powders or metal compound powders have been developed. There is a demand for metal or metal compound powders that have different properties in addition to the provided properties and have a composite function. For example, in the raw magnetic powder of the color magnetic toner, the color of the magnetic metal powder, which has not been a problem in the conventional black magnetic toner, cannot be used as it is. In addition, Toka for the protection of the powder has been known traditional,
In order to improve the surface of the powder, for example, in order to facilitate the mixing with the synthetic resin, etc., the means by which a thin metal oxide film is formed on the surface of the powder, It cannot withstand new demands. In this respect, it is necessary to provide a powder having a new composition not found in conventional powders.

[0007] An object of the present invention is to provide a metal or metal compound powder having composite properties which can meet such new requirements and which can fulfill a composite function. Another object of the present invention is to provide a metal or metal compound powder having a metal oxide film on its surface, and in particular, a raw material magnetic powder for a color magnetic toner used in an electrophotographic copying machine or the like, An object of the present invention is to provide a heat conductive powder having an insulating property. It is a further object of the present invention to provide a new production method capable of producing a metal or metal compound powder having such composite properties and capable of fulfilling the composite function.

[0008]

In order to achieve the above object, the present inventor has studied various means for producing a powder capable of satisfying the above-mentioned conditions. When dispersed in an alkoxide solution and hydrolyzing the metal alkoxide, it is possible to form a thick and uniform metal oxide film on the powder, thereby making it thicker and thicker than previously possible. Metal or metal compound powder having a uniform metal oxide film , and furthermore, the metal oxide film
A unique optical function can be obtained if there are multiple layers with different folding rates.
And reached the present invention on the basis thereof.

The above object of the present invention is achieved by the following means. (1) A metal oxide film having a uniform thickness of 0.01 to 20 μm per layer and composed of a metal different from the metal constituting the metal or the metal compound is formed on the surface of the metal or metal compound powder. A white powder comprising a plurality of layers, wherein the metal oxide films which are in contact with each other have different refractive indexes and totally reflect light. (2) The white powder as described in (1) above, wherein the thickness of the metal oxide film is 1/4 times the wavelength of visible light. (3) The white powder as described in the above (1) or (2), wherein the metal oxide films having mutually different metal oxide films having different refractive indexes are alternately provided. (4) A metal or metal compound powder is dispersed in a metal alkoxide solution, and the metal alkoxide is hydrolyzed to form a metal oxide on the surface of the metal or metal compound powder, and a uniform layer is formed per layer. 0.01-20μ
forming a metal oxide film having a thickness of m and then using another metal alkoxide solution to form a metal oxide film. A method for producing a white powder having a metal oxide film on the surface of a metal or metal compound powder, the method comprising obtaining a powder having a plurality of object films and totally reflecting light.

In the present invention, when the base material of the powder on which the metal oxide film is to be formed is a metal, iron, nickel, chromium, titanium, aluminum, etc.
Any metal may be used, but those utilizing magnetism are preferably those having magnetism such as iron. These metals may be alloys, and when having the above-mentioned magnetism, it is preferable to use ferromagnetic alloys. Also,
When the substrate of the powder is a metal compound, typical examples thereof include oxides of the above-mentioned metals.For example, iron, nickel, chromium, titanium, aluminum, silicon, etc., calcium, Oxides such as magnesium and barium or composite oxides thereof may be used. Furthermore, examples of metal compounds other than metal oxides include metal nitrides and metal carbides, and specifically, iron nitrides and the like are preferable. 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 is 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 these powders is not particularly limited, but is preferably in the range of 0.01 μm to several mm.

The metal oxide constituting this metal oxide film includes, for example, iron, nickel, chromium, titanium, zinc, aluminum, cadmium, zirconium, silicon and the like, as well as oxides such as calcium, magnesium and 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. Metal oxide film may be provided multiple several layers. When two or more layers are provided, each of the layers has a thickness of 0.1 mm.
The thickness is set to 01 to 20 μm. When two or more layers are provided, a film of a different metal oxide is formed on the surface of the powder serving as the core, and then a film of the same or different metal oxide as the metal oxide of the film is sequentially formed thereon. It can be made as follows. When the powder is a metal oxide, it is preferable to provide two or more metal oxide films.

In forming a metal oxide film, a metal or metal compound powder is dispersed in a solution of a metal alkoxide which is a component of the metal oxide, and the metal alkoxide is hydrolyzed to form the powder. To form an oxide of the metal on the surface of the metal. This method of producing a metal oxide by hydrolysis is called a sol-gel method, and an oxide having a fine and uniform composition is formed. By applying this method to powder, a uniform thickness is obtained. In addition, it was found that a thick film was obtained. As the metal alkoxide, an alkoxide of a metal corresponding to a required metal oxide such as zinc, aluminum, cadmium, titanium, zirconium, and silicon is selected. In many cases, a magnetic powder for a magnetic toner is formed by forming an oxide of titanium or silicon as a metal oxide on the surface. In this case, an alkoxide of silicon or titanium is used.

The metal alkoxide is used as a solution in an organic solvent because it is decomposed by water. 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.

A metal or metal compound powder is dispersed in the metal alkoxide solution, and water is added to the metal alkoxide to hydrolyze the metal alkoxide to form a metal oxide. An oxide film is generated. The powder on which the metal oxide film is formed is taken out of the solution and dried to obtain a strong metal oxide film. 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 to precipitate a metal oxide on the powder surface. In the case of a single-layer coating, the coated powder is obtained by drying the metal oxide film coated on the surface of the powder to be treated. Drying is preferably performed under vacuum. In order to produce a coated powder having a plurality of layers, a reaction step of forming a metal oxide layer may be repeated, and finally, drying may be performed.

In the hydrolysis of the metal alkoxide,
First, a metal oxide sol is formed and then gelled,
After the hydrolysis reaction, gelation proceeds after a while, and in some cases, gelation is completed by drying. In the reaction, the sol is generated on the surface of the powder, so that a continuous film is formed, whereby a uniform metal oxide film having a uniform thickness and a uniform composition is easily formed. It is considered something. 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 speed is high and fine metal oxide particles are easily formed, but alkanolamines and the like can be added to slow the reaction. In order to accelerate the reaction, a catalyst such as an acid or an amine can be used. In this method for producing a powder, a metal oxide film having excellent properties different from a metal oxide film obtained by simply oxidizing the surface of the metal powder is obtained. It is also useful when forming a metal oxide film containing the same metal as the metal or the metal constituting the metal compound, so that the metal or metal compound powder having such a metal oxide film The present invention is also applied to the case of manufacturing and is included in the present invention.

The metal or metal compound powder having a metal oxide film on the surface manufactured as described above is made of the metal or metal compound of the powder selected to constitute the powder and the metal oxide of the surface film. It has various properties depending on the material of the object, and can be used for each purpose. For example, magnetic metal iron, triiron tetroxide, etc. are used as 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. If used, a magnetic powder having a high degree of whiteness is obtained, and silver or copper is used as the powder, and if aluminum oxide is used as the metal oxide of the film thereon, a thermally conductive powder having an electrically insulating surface layer Is obtained.

Further, when the metal oxide film formed on the surface of the powder has a plurality of layers, a special function can be provided by adjusting the thickness of each layer of the film. For example, when coating films having different refractive indices are provided on the surface of the object by a thickness corresponding to a quarter wavelength of light,
Since all light is reflected (using Fresnel reflection), this effect is used to make a magnetic material such as iron, cobalt, nickel or other metal powder or metal alloy powder, or iron nitride powder as the core. By providing a silicon oxide layer having a thickness of a quarter wavelength (95 to 195 nm) of visible light on the surface of the particles, the color of the powder of the magnetic material is concealed, and the thickness of visible light Quarter wavelength (95-
By repeating once or more times coating a titanium oxide layer having a thickness of 195 nm) and having a uniform thickness, a magnetic powder for a magnetic toner that shines white by total reflection of light is produced. be able to. If a colored layer is provided on the powder and a resin layer is further provided thereon, a color magnetic toner can be manufactured. Since the wavelength of visible light has a wide range, the thickness of the silicon oxide layer and the thickness of the titanium oxide layer fall within the above-mentioned quarter wavelength range, but a plurality of different thicknesses may be alternately provided. FIG. 1 is a cross-sectional view illustrating such a powder particle.
, And a plurality of metal oxide films A and three metal oxide films B are provided on the surface thereof.

The method of using the magnetic toner obtained as described above will be schematically 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 positively charged image is transferred to a support such as paper, and a magnetic brush opposite to the positively charged image of the present invention is attached to the support from a magnetic brush formed of a magnetic toner or the like, and the non-attached portion When the magnetic toner is removed, a magnetic toner image corresponding to the original image is obtained on the photoreceptor. When this magnetic toner image is printed, a copy image is obtained on paper. If the paper is white and the magnetic toner colored by using the powder of the present invention as a raw material is colored, a new copy image that has never been obtained before will be obtained.

[0019]

EXAMPLES The single-layer and multiple-layer metal oxide film-coated powder of the present invention and the method for producing the same will be described with reference to examples.
However, the present invention is not limited only to the following examples. Example 1 Dehydrated ethanol: The dehydrated ethanol to be used was obtained by dehydrating ordinary dehydrated ethanol with a molecular sieve 3A1 / 8 for one day or more, then filtering in a glove box replaced with Ar gas, and placing it in a stoppered glass bottle. save. Slurry 1: 100 g of carbonyl metal iron powder (average particle size: 1.8 μm) manufactured by BASF was placed in a glass container equipped with a high-speed stirrer, and 300 ml of the dehydrated ethanol was added thereto.
And sufficiently stirred with a high-speed stirrer to obtain slurry 1.

Solution 1: In a glove box replaced with Ar gas, 300 ml of the above dehydrated ethanol and 33 g of tetraethyl orthosilicate are weighed and mixed in a glass bottle with a stopper, and the mixture is sealed to form a solution 1. -Slurry 2: The container of the solution 1 is taken out of the glove box, the solution 1 is poured into the container containing the slurry 1 at a stretch, and sufficiently stirred at a high speed to obtain the slurry 2. -Solution 2: 2.7 g of pure water in 200 ml of dehydrated ethanol
Solution.

The solution 2 is dropped using a burette over 1 hour with stirring to such an extent that the powder to be coated in the slurry 2 does not precipitate, whereby the hydrolysis is gradually performed.
After the dropping, the resulting slurry (slurry 3) is stirred for about 8 hours. After the stirring, the slurry 3 is centrifuged, and the supernatant is removed to obtain a solid 1. The solid 1 was dried under vacuum to obtain a sample 1. This sample 1 is a silicon oxide-coated iron powder. The content of silicon oxide (SiO ₂ ) in the obtained sample 1 was 6.3%. Therefore, the thickness of the silicon oxide is calculated to be 0.18 μm. Further, the obtained silicon oxide-coated iron powder is put into 300 ml of dehydrated ethanol, and sufficiently stirred and dispersed. A mixed solution of 42 g of tetraethyl orthotitanate and 300 ml of dehydrated ethanol prepared in advance is added thereto, and the mixture is further stirred to obtain a slurry 4. While the slurry 4 is being stirred, a mixed solution of 3.3 g of pure water prepared in advance by burette and 200 ml of dehydrated ethanol is dropped over 1 hour. After dropping, stirring was continued for 8 hours, followed by solid-liquid separation with a centrifuge, and the precipitate was dried to obtain Sample 2. The content of titanium oxide (TiO ₂ ) in Sample 2 was 11.1%. Therefore, the thickness of the titanium oxide is calculated to be 0.16 μm.

Example 2 100 g of iron nitride powder (average particle size: 0.8 μm: manufactured in-house) was put into 300 ml of dehydrated ethanol with a high-speed stirrer in the same manner as in Example 1, and sufficiently stirred to obtain a slurry 5. To this slurry 5, a solution obtained by mixing 105 g of tetraethyl orthosilicate with 300 ml of dehydrated ethanol was added, and the mixture was stirred and mixed. Then, a solution obtained by adding 8.6 g of pure water to 300 ml of dehydrated ethanol was added for 1 hour. To mix. After completion of the dropwise addition, stirring was continued for 10 hours, and after standing still, solid-liquid separation was performed, followed by vacuum drying to obtain Sample 3. The silicon oxide content of this sample 3 was 24.4%, from which the thickness of the silicon oxide was calculated to be 0.11 μm. Next, the sample 3 is dispersed in 300 ml of dehydrated ethanol to obtain a slurry 6. This slurry 6 is mixed with dehydrated ethanol 3
A mixed solution obtained by mixing 163 g of tetraethyl orthotitanate in 00 ml was added and dispersed, and a solution obtained by adding 12.8 g of pure water to 300 ml of dehydrated ethanol was added dropwise over 1 hour and mixed. After dropping, 10
Stirring was continued for a period of time, and after standing, solid-liquid separation was performed, followed by vacuum drying to obtain Sample 4. The titanium oxide content of this sample 4 was 31.3%, from which the thickness of the titanium oxide was calculated to be 0.10 μm.

Reference Example 1 600 g of atomized metallic copper powder (average particle size: 6.0 μm) was placed in 300 ml of dehydrated ethanol in the same manner as in Example 1,
The mixture is sufficiently stirred with a high-speed stirrer to obtain slurry 7. A solution obtained by mixing 83 g of tetraethyl orthotitanate with 300 ml of dehydrated ethanol was added to the slurry 7 at a stretch, and the mixture was sufficiently stirred and mixed at a high speed. Then, 6.5 g of pure water was added to 200 ml of dehydrated ethanol. 1
Drop and mix over time. After completion of the dropwise addition, stirring was continued for 8 hours, and after standing still, solid-liquid separation was performed, followed by vacuum drying to obtain a sample 5. The average particle diameter of the obtained sample 5 is 6.4 μm.
m. The titanium oxide content of Sample 5 was 2.2%, from which the thickness of the titanium oxide was calculated to be 0.3 μm.

[0024]

According to the present invention, it is possible to obtain a metal or metal compound powder having a plurality of properties and capable of performing a composite function. Since this powder has a thick metal oxide film on the surface, which has not been obtained conventionally, the properties of the metal oxide film can be sufficiently and effectively utilized. Further, by providing a plurality of such metal oxide films, unique properties can be given. For example, a white powder can be obtained without providing an extremely thick colored layer. Further, since the metal oxide film has a uniform thickness and a strong bond, the metal oxide film is hard to peel off and can form a useful surface layer. Specific applications include magnetic powders for white magnetic toners and thermally conductive powders with electrical insulation. The latter is used for filling materials used in resin for semiconductor encapsulants or for insulating electronic components. It is used as a heat dissipation sheet for heat dissipation.

[Brief description of the drawings]

FIG. 1 is a cross-sectional view of a magnetic powder particle for a color magnetic toner of the present invention.

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 1 Magnetic particle 2 Metal oxide film A 3 Metal oxide film B

Continuation of front page (56) References JP-A-59-25901 (JP, A) JP-A-3-250702 (JP, A) JP-A-4-29302 (JP, A) JP-A-63-3402 (JP) JP-A-59-9101 (JP, A) JP-A-4-74833 (JP, A) (58) Fields investigated (Int. Cl. ⁷ , DB name) B22F 1/02

Claims (4)

(57) [Claims] 1. A metal oxide having a uniform thickness of 0.01 to 20 μm per layer and a metal different from the metal constituting the metal or metal compound on the surface of the metal or metal compound powder. A white powder comprising a plurality of films, wherein the metal oxide films which are in contact with each other have different refractive indices and totally reflect light. 2. The metal oxide film according to claim 1, wherein the thickness of the metal oxide film is １ ／ of the wavelength of visible light.
White powder. 3. The white powder according to claim 1, wherein the metal oxide films are arranged such that metal oxide films in contact with each other have different refractive indexes. 4. A metal or metal compound powder is dispersed in a metal alkoxide solution, and the metal alkoxide is hydrolyzed to form a metal oxide on the surface of the metal or metal compound powder. Uniform 0.01 ~
By forming a film of the metal oxide having a thickness of 20 μm and then using another metal alkoxide solution to form a film of the metal oxide, the metal oxide films in contact with each other have different refractive indices. A method for producing a white powder having a metal oxide film on the surface of a metal or metal compound powder, the method comprising obtaining a powder having a plurality of object films and totally reflecting light.