JP2009173538A - Non-magnetic plate-form particle and method for manufacturing the same - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide zirconium oxide particles having a specified particle form and a particle size, suitable as an abrasive material such as an abrasive tape, or a magnetic tape, or various kinds of functional optical films, and to provide a method for manufacturing the particles. <P>SOLUTION: Zirconium oxide particles are obtained by adding an aqueous solution of a zirconium salt to an alkaline aqueous solution containing oxyalkylamine to produce a precipitate containing zirconium hydroxide, ageing the precipitate in a suspension state, heating the obtained zirconium hydroxide or hydrate at a temperature in a range from 110 to 300°C in the presence of water, followed by filtration and drying, and heating in air at a temperature in a range from 300 to 1,200°C. The obtained zirconium oxide particles have a particle form of a hexagonal plate, with an average particle diameter in a range from 10 nm to 100 nm in the plate face direction of the particle. <P>COPYRIGHT: (C)2009,JPO&INPIT

Description

The present invention includes, for example, abrasives such as abrasive sheets, abrasive tapes, abrasive films, and abrasives, and abrasives such as abrasive liquids, as additives for various coating-type magnetic recording media, and various functions such as optical films. The present invention relates to a plate-like nonmagnetic particle having a novel particle shape suitable as an additive for a conductive film, a method for producing the same, and an application thereof. More specifically, the present invention relates to nonmagnetic oxide particles made of zirconium oxide having a novel particle shape and particle size.

  Nonmagnetic oxide particles such as cerium oxide particles, zirconium oxide particles, aluminum oxide particles, silicon oxide particles, and iron oxide particles are used as abrasives such as abrasive sheets and abrasives such as polishing liquids, and various types of coating type magnetic recording. Used as a media additive in a wide range of applications. Since cerium oxide, zirconium oxide, aluminum oxide, and silicon oxide have high Mohs hardness, they are suitable for applications that require a high polishing rate, and iron oxide has relatively low Mohs hardness, and therefore is suitable for applications that require soft polishing. Various methods are known for producing these nonmagnetic oxide particles.

(1) Cerium oxide:
In general, cerium oxide employs a method of pulverizing cerium oxide produced by a firing method with a ball mill or the like (pulverization method). However, since the cerium oxide particles produced by this method have a wide particle size distribution and are mechanically pulverized, the particle size is limited to the submicron size, and it is difficult to further reduce the particle size.

  On the other hand, a method is also known in which a cerium salt such as cerium carbonate is oxidized by heating in air to form cerium oxide particles. This method has a feature that it is easy to make fine particles as compared with the pulverization method, but interparticle sintering is likely to occur, and there is a problem that it is difficult to uniformly disperse particles particularly when used in a polishing liquid.

For example, in Patent Document 1 and Patent Document 2 , cerium carbonate is heated in the air to form cerium oxide, and then mechanically pulverized into fine particles. In the former Patent Document 1 , ball milling is performed, and the obtained particles are described as having a primary particle diameter of 200 nm. Moreover, it is described that the shape before ball milling is spherical. On the other hand, in the latter patent document 2 , jet milling is performed after firing in order to obtain fine particles, and in addition to small particles having the same size as the primary particle size, the size is 1 μm to 3 μm and 0.5 μm to 1 μm. It is described that the remaining pulverized particles are mixed.

Patent Document 3 describes a method in which cerium carbonate is used as a raw material, the cerium carbonate is pulverized in advance by ball milling, and then heat-treated in air to form cerium oxide particles. In this method, as described in the text, the primary particle diameter is 20 nm, but it is composed of secondary particles of 0.2 μm to 0.3 μm. The details of the shape of the particles are not described. For example, Patent Document 4 describes that the aspect ratio is 1 or more and 2 or less. However, this is considered to be a shape close to a lump or a grain rather than a plate.

  As described above, the conventional manufacturing method basically employs mechanical pulverization in order to obtain fine particles, so that a specific particle shape cannot be obtained, and the particle size distribution is sharp. It was also difficult to get something. Furthermore, when mechanical impact is applied, there is a problem that the cerium oxide particles are easily distorted and the crystallinity is lowered. This crystallinity is extremely important for use as an abrasive, and even if it shows a spectrum based on cerium oxide by X-ray diffraction or the like, it has been satisfactory in terms of crystallinity as an abrasive. There was nothing.

  In addition, although cerium oxide particles depend on the production method, generally, elements other than cerium originally contained in raw materials are likely to be present simultaneously with cerium. That is, there is a problem that it is difficult to obtain high-purity cerium oxide. This purity becomes a problem particularly when cerium oxide particles are used in a chemical polishing liquid or the like.

(2) Zirconium oxide:
Zirconium oxide is used as an abrasive such as a polishing sheet or a polishing liquid. However, zirconium oxide for an abrasive is often made by pulverizing an ingot of zirconium oxide into fine particles. When fine particles are formed by mechanical means, there is a limit to the fine particles. For example, Patent Document 5 describes an example in which the surface of silicon is polished using zirconium oxide particles. The particle diameter of the zirconium oxide particles is 7.0 μm.

Patent Document 6 shows an example of an aqueous dispersion using mixed particles of inorganic particles such as silica, alumina, zirconia, and polymer particles, and in the text, the average particle diameter of the inorganic particles is preferable. The range is 0.12 to 0.8 μm.

  Conventionally, zirconium oxide particles are rarely used as a single abrasive and are often used in combination with other abrasive particles such as aluminum oxide and silicon oxide particles. This is presumably because there has been no satisfactory zirconium oxide particle in the particle diameter and particle shape.

(3) Aluminum oxide:
Aluminum oxide is widely used as an abrasive such as a polishing sheet or a polishing liquid. Various methods are known for producing aluminum oxide particles. Generally, the aluminum oxide produced by the baking method is pulverized by pulverizing with a ball mill or the like. However, the aluminum oxide particles produced by this method have a wide particle size distribution and are further mechanically pulverized. Therefore, the particle size is limited to the submicron size, and it is difficult to further reduce the particle size.

Aluminum oxide particles can be obtained by making a precipitate of aluminum hydroxide by a neutralization reaction and heating the aluminum hydroxide in air. However, with this method, aluminum oxide particles having a small particle diameter can be obtained, but the particle shape is indefinite and the polishing ability sufficient for use as an abrasive cannot be obtained. Furthermore, secondary particles are likely to be formed due to aggregation between particles, and particularly when used in polishing liquids, there is a problem that large energy and extremely long time dispersion are required to obtain a uniform dispersion. For example, Patent Document 7 shows that flat alumina produced by a firing method is finely pulverized for a long time using a nonmetallic medium to break up aggregation. In this method, since fine particles are obtained by pulverization, there is a limit to fine particles and the particle size distribution is essentially widened.

On the other hand, a method for producing plate-like alumina using a hydrothermal synthesis method has been known for a long time. For example, Patent Document 8 and Patent Document 9 describe that plate-like alumina can be obtained. However, the particle size of the plate-like alumina obtained is several microns to several hundred microns, which is problematic in terms of particle miniaturization.

On the other hand, a manufacturing method is known in which aluminum hydroxide whose size has been adjusted in advance to a submicron order is hydrothermally treated in water or an alkaline aqueous solution at a high temperature of 350 ° C. or more to obtain a submicron order plate-like aluminum oxide. (For example, Patent Document 10 and Patent Document 11 ). In this method, aluminum hydroxide is crystal-transformed into aluminum oxide by utilizing a hydrothermal reaction in which plate-like aluminum oxide having excellent crystallinity is easily obtained. For this reason, a special reaction vessel that can react at high temperature and withstand high pressure is required. Furthermore, since this method utilizes a hydrothermal reaction at high temperature, it is suitable for producing aluminum oxide particles having a submicron size and a large particle diameter, but fine aluminum oxide particles of 100 nm or less are used. It is considered unsuitable for manufacturing.

  As described above, finely divided aluminum oxide having a particle size of 100 nm or less with good crystallinity and a sharp particle size distribution has been required for use as a polishing sheet for finish polishing sheets and polishing liquids. Despite this, aluminum oxide particles that satisfy such requirements have not been developed so far.

(4) Silicon oxide:
Silicon oxide is also a well-known material as an abrasive such as a polishing sheet or a polishing liquid. For example, fumed silica and colloidal silica are general-purpose products already commercialized by various companies. An enormous number of patent applications have been filed for polishing sheets and polishing liquids using these silicon oxide particles.

For example, Patent Document 12 and Patent Document 13 relate to a polishing sheet using colloidal silica particles having a size of several tens of nanometers as an abrasive, and are described as being particularly effective for end polishing of an optical connector ferrule. ing. Patent Document 14 describes that a silicon wafer is polished using colloidal silica of 10 to 100 nm as an abrasive. Patent Document 15 also describes polishing a semiconductor wafer using colloidal silica having a specific shape. Furthermore, Patent Document 16 describes that a colloidal silica slurry using colloidal silica having a size of several tens of nm as an abrasive is also effective for polishing a metal surface.

  Thus, it is already known that silicon oxide particles are effective as an abrasive, and as the particle shape, a spherical shape or a shape as close to a spherical shape as possible is effective. Are listed.

  On the other hand, the types of objects to be polished are increasing year by year, and the polishing specifications required for these objects to be polished are also diversifying year by year. In order to meet the demands of these various polishing specifications, for example, silicon oxide particles can be dealt with by devising the composition and surface structure of polishing sheets rather than the particles themselves, and the liquid composition of polishing slurries. This is the current situation. However, as long as silicon oxide particles having a spherical shape and a particle size of several tens of nanometers are used, there is a limit to the response, and it is already difficult to handle polishing for special purposes.

(5) Iron oxide:
In the iron oxide, the present inventors have developed a particle having a novel shape having pores in the thickness direction of the particle at the same time as the particle shape is plate-like. Plate-like iron oxide particles having pores in the vicinity of the center of the particles are known in Patent Documents 17 and 18 , in which plate-like goethite (also called goethite) particles are heated, dehydrated, and reduced to obtain pores. After being made into plate-like magnetite particles with a gap between them, it is modified with cobalt to be used as a magnetic powder for magnetic recording.

Patent Document 19 describes a ring-shaped oxide powder starting from disk-shaped goethite particles, and is used for electronic materials such as magnetic powder, pigments such as paint reinforcing agents, and composite materials. It has been proposed to use it as a reinforcing agent such as medical materials. In this example, an aqueous iron chloride solution is added dropwise to an aqueous solution to which sodium hydroxide and alkylamine are added to precipitate iron hydroxide. After aging, washing and adjusting the pH, hydrothermal treatment is performed, and a disc-shaped gate is obtained. Have gained a site. This plate-like goethite is heated and dehydrated to obtain magnetic powder such as annular hematite particles having a hole in the center, magnetite particles, and gamma iron oxide particles.

Japanese Patent Laid-Open No. 10-106990 JP-A-11-181405 JP 09-027042 A Japanese Patent Laid-Open No. 10-102039 Japanese Patent Application Laid-Open No. 08-113773 JP 2000-204353 A JP 07-315833 A Japanese Patent Publication No. 37-007750 Japanese Patent Publication No. 39-013465 Japanese Patent Laid-Open No. 05-017132 Japanese Patent Application Laid-Open No. 06-316413 Japanese Patent Laid-Open No. 08-336758 JP 09-248771 A JP 08-267356 A JP 07-221059 A Japanese Patent Laid-Open No. 06-313164 JP-A 61-266611 JP-A 61-266313 Japanese Examined Patent Publication No. 03-021489

In light of the above circumstances, the present invention is used as abrasive particles such as abrasives such as abrasive sheets and polishing liquids (slurry abrasives), as additive particles for various coating-type magnetic recording media, and various types. The main object of the present invention is to provide zirconium oxide particles which are non-magnetic oxides having specific particle sizes and particle shapes particularly suitable as additive particles for functional optical films, and a method for producing the same.

As a result of intensive studies to achieve the above object, the present inventors have completed a novel production method that is completely different from the conventional production method of nonmagnetic oxide particles. As a result, they succeeded in developing non-magnetic oxide particles composed of zirconium oxide having a hexagonal plate shape and a particle diameter in the range of 10 nm to 100 nm, which was impossible with the conventional production methods. It is.

That is, the nonmagnetic plate-like particle of the present invention is characterized in that the shape of the particle is a hexagonal plate shape and the particle diameter is in the range of 10 nm to 100 nm. Specifically, the particle shape is a hexagonal plate. And zirconium oxide particles having a particle diameter in the range of 10 nm to 100 nm. In the method of the present invention, an aqueous solution of a zirconium salt is added to an aqueous alkaline solution, and the resulting hydroxide or hydrate of zirconium is heated in the temperature range of 110 to 300 ° C. in the presence of water and filtered. Then, after drying, the zirconium oxide particles having the above specific shape and particle diameter are produced by heat treatment in the temperature range of 300 to 1200 ° C. in the air.

In the method of the present invention, since a high purity zirconium salt such as zirconium chloride or nitrate is used as a starting material, the product hardly contains an element that adversely affects the polishing properties. In addition, since chlorine and nitric acid contained in the starting material are scattered and removed after the heat treatment, it hardly remains in the final zirconium oxide particles, and extremely high purity nonmagnetic oxide particles can be obtained.

As described above, according to the method of the present invention, the particle shape is a hexagonal plate, and the particle diameter in the plate surface direction of the particle is in the range of 10 nm to 100 nm, which is impossible with the conventional manufacturing method. Non-magnetic plate-like particles made of some zirconium oxide are obtained. Thus non-magnetic plate-shaped particles children of the present invention thus obtained is a uniform particle size distribution, sintering, agglomeration is extremely small, has good crystallinity. When such a non-magnetic plate-like particle of the present invention is applied to, for example, a polishing body such as a polishing tape, a polishing sheet, a polishing film and a polishing tool, a magnetic tape, various functional optical films, and the like, conventional oxide particles are used. Compared to the same type used, its characteristics are greatly improved. Thus, the non-magnetic plate-like particle of the present invention opens up a completely new application that has been impossible in the past.

4 is a diagram showing an X-ray diffraction spectrum of cerium oxide particles obtained in Experimental Example 1. FIG. It is the figure which showed the transmission electron microscope photograph (magnification: 200,000 times) of the cerium oxide particle obtained in Experimental example 1. FIG. It is the figure which showed the transmission electron microscope photograph (magnification: 200,000 times) of the cerium oxide particle obtained in Experimental example 2. FIG. It is the figure which showed the transmission electron microscope photograph (magnification: 200,000 times) of the cerium oxide particle obtained in Experimental example 3. FIG. 6 is a diagram showing an X-ray diffraction spectrum of zirconium oxide particles obtained in Experimental Example 8. FIG. It is the figure which showed the transmission electron microscope photograph (magnification: 200,000 times) of the zirconium oxide particle obtained in Experimental example 8. FIG. It is the figure which showed the transmission electron microscope photograph (magnification: 200,000 times) of the zirconium oxide particle obtained in Experimental example 9. FIG. 16 is a diagram showing an X-ray diffraction spectrum of aluminum oxide particles obtained in Experimental Example 15. FIG. It is the figure which showed the transmission electron micrograph (magnification: 200,000 times) of the aluminum oxide particle obtained in Experimental example 15. FIG. 14 is a diagram showing an X-ray diffraction spectrum of aluminum oxide particles obtained in Experimental Example 16. FIG. It is the figure which showed the transmission electron micrograph (magnification: 200,000 times) of the aluminum oxide particle obtained in Experimental example 17. FIG. It is the figure which showed the transmission electron microscope photograph (magnification: 200,000 times) of the aluminum oxide particle obtained in Experimental example 18. FIG. 6 is a diagram showing an X-ray diffraction spectrum of aluminum oxide particles obtained in Experimental Example 20. FIG. It is the figure which showed the transmission electron microscope photograph (magnification: 200,000 times) of the aluminum oxide particle obtained in Experimental example 20. FIG. It is the figure which showed the transmission electron micrograph (magnification: 200,000 times) of the silicon oxide particle obtained in Experimental example 22. FIG. It is the figure which showed the transmission electron microscope photograph (magnification: 200,000 times) of the iron oxide particle obtained in Experimental example 28. It is the figure which showed the transmission electron microscope photograph (magnification: 200,000 times) of the iron oxide particle obtained in Experimental example 29.

In the method of the present invention, as a first step, an aqueous solution of a zirconium salt is added to an alkaline aqueous solution, and the resulting hydroxide or hydrate of zirconium is heated in the temperature range of 110 to 300 ° C. in the presence of water. By processing, the target shape and particle size are adjusted, and then, as a second step, the zirconium hydroxide or hydrate is heat-treated in the air, the particle size distribution is uniform, sintered, Zirconium oxide particles with very little aggregation are obtained.

  In the above method, if a zirconium hydroxide or hydrate aging step is added between the first step and the second step, particles having a more uniform particle size and excellent plate-like properties can be obtained. Can do.

Thus, in the production of non-magnetic oxide particles, the process aimed at adjusting the shape and particle diameter is separated from the process aimed at maximizing the physical properties inherent in the material. Based on a new idea, the present inventors have succeeded in developing zirconium oxide particles having a plate shape and an average particle diameter in the range of 10 nm to 100 nm, which was impossible with the conventional production methods. Here, the plate shape means a plate ratio (maximum diameter / thickness) exceeding 1, and the plate ratio exceeds 2 and is preferably 100 or less. Furthermore, 3 or more and 50 or less are more preferable, and 5 or more and 30 or less are more preferable. The above range is preferable when the plate-like ratio is 2 or less, for example, when a polishing sheet is used, the particles may rise from the coated surface, and the object to be polished may be damaged. This is because there is a case where the object is damaged and the object to be polished is damaged.

The non-magnetic plate-like particles comprising the zirconium oxide of the present invention produced by such a process have the characteristics that the particles are sintered and agglomerated very little, the particle size distribution is sharp, and the particle shape is plate-like. . Because of these characteristics, the nonmagnetic oxide particles of the present invention are used as abrasive particles for abrasive sheets and polishing liquids, additive particles for various coating-type magnetic recording media, and for various optical films. As a material particle, the outstanding performance which was not obtained with these conventional particles is exhibited.

When zirconium oxide particles are used as an abrasive or additive, it is particularly desirable that the particles be crystalline. Even particles showing a spectrum peculiar to these substances by X-ray diffraction etc. have not had sufficient crystallinity so far, and therefore are not always satisfactory when used as an abrasive or additive. It was.

  As a result of examining the shape exhibiting excellent performance as an abrasive, the present inventors have observed so far with an electron microscope or the like. It has been found that it works particularly effectively as particles.

As described above, the present invention is the first successful production of zirconium oxide particles having a specific shape. The oxide particles (zirconium oxide particles) obtained by the present invention are not only optimum abrasive particles for polishing semiconductors, optical fibers, lenses, etc., but also additive particles for various coating-type magnetic recording media, Can be applied to a wide range of applications, such as additive particles for various functional optical films utilizing their unique shapes. The non-magnetic plate-shaped oxide particles, described later cerium oxide particles, aluminum oxide particles, and silicon oxide particles, most the hole without the type of the plate-like oxide particles as zirconium oxide particles of the present invention, will be described later The plate-like oxide particles with pores such as iron oxide are roughly divided, but the former non-magnetic oxide particles with almost no pores are additive particles and functional optical films for coated magnetic recording media. It is more preferably used for the use of. Moreover, since the former does not have coloring, it is used more preferably for the use which dislikes coloring, such as a functional optical film. The plate-like oxide particles having almost no pores are those having 10% or less of oxide particles having pores in the plate thickness direction when 300 particles are observed.

In the method of the present invention, first, a zirconium- containing compound as a raw material is dissolved in water and added dropwise to an alkaline aqueous solution, thereby generating a zirconium hydroxide or hydrate precipitate. The aqueous alkaline solution for producing this precipitate is not particularly limited. However, when oxyalkylamine is added, plate-like particles having a sharp particle size distribution can be easily obtained as the final product. It is preferable to add an alkylamine. The suspension containing the hydroxide or hydrate precipitate is hydrothermally treated using an autoclave or the like. Before this hydrothermal treatment, a suspension containing hydroxide or hydrate precipitate is aged to obtain a final product having better crystallinity and sharp particle size distribution. It is preferable to add an aging step because it is easy to be formed. After hydrothermal treatment, it is washed with water, filtered and dried. Then, the obtained dried product is subjected to a heat treatment to obtain zirconium oxide particles.

Next, a method for producing the nonmagnetic plate-like particles (oxide particles) and uses of the nonmagnetic plate-like particles obtained thereby will be described in more detail. In the following, other metal oxides (specifically, cerium oxide, aluminum oxide, iron oxide) and nonmetal oxides (specifically, silicon oxide) together with nonmagnetic plate-like particles made of zirconium oxide according to the present invention. The non-magnetic plate-like particles made of a metal oxide or non-metal oxide are described as a reference, not as those according to the present invention.

In addition, the expression “metal salt or nonmetal salt” or “metal or nonmetal” in the following is that cerium, zirconium, aluminum, and iron are metal elements, but silicon is not considered to be a metal element. Because. That is, the above “nonmetal” mainly means silicon, and the “nonmetal salt” mainly means “a salt or silicate containing silicon”. However, in the following description, in order to simplify the description, “metal or nonmetal” having the above meaning is simply referred to as “metal”, and “metal salt or nonmetal salt” is simply referred to as “metal salt”. "

(Preparation of precipitate)
For cerium, zirconium, aluminum, and iron, chlorides, nitrates, and sulfates of these metals, and for silicon, sodium silicate is dissolved in water, and an aqueous solution containing these metal ions (metal Salt aqueous solution). Separately, an alkaline solution is prepared. As the alkali, sodium hydroxide, potassium hydroxide, lithium hydroxide, aqueous ammonia solution or the like can be used as a suitable one. Moreover, when alkylamine which is a crystal growth control agent is further added to these alkaline aqueous solutions, it is easy to obtain particles having a good plate shape. Examples of the alkylamine include monoethanolamine, triethanolamine, isobutanolamine, and propanolamine. Among them, monoethanolamine is particularly suitable for obtaining a plate-shaped good particle.

  Next, the metal salt aqueous solution is dropped into the alkali aqueous solution to form a metal hydroxide or hydrate precipitate. The pH of the suspension containing the precipitate is preferably adjusted to a range of 8 to 11, and the suspension is preferably aged at room temperature for about 1 day. This pH adjustment and aging are effective in obtaining particles having a good plate shape and a sharp particle size distribution at a relatively low temperature in the subsequent heat treatment.

(Hydrothermal treatment)
The suspension containing the metal hydroxide or hydrate precipitate is hydrothermally treated using an autoclave or the like. In this hydrothermal treatment, the suspension containing the precipitate may be hydrothermally treated as it is, but the product and the residue other than the precipitate are removed by washing with water, and then the pH is adjusted again with NaOH or the like. It is preferable. The pH value at this time is preferably 7-11. If it is lower than this pH, crystal growth becomes insufficient during hydrothermal treatment, and if it is too high, it becomes difficult to obtain a particle having a small particle size distribution or a desired particle size distribution. A more preferred pH range is 7-10.

  The hydrothermal treatment temperature is preferably in the range of 110 ° C to 300 ° C. If the temperature is lower than this temperature, it is difficult to obtain the metal hydroxide or hydrate having a specific shape. If the temperature is higher than this temperature, the generated pressure becomes high, so that the apparatus becomes expensive and has no merit.

  The hydrothermal treatment time is preferably in the range of 1 hour to 4 hours. If the hydrothermal treatment time is too short, the growth to a specific shape becomes insufficient. Even if the hydrothermal time is too long, there is no particular problem, but only the production cost is increased, and there is no merit.

(Heat treatment)
The metal hydroxide or hydrate particles after hydrothermal treatment are filtered and dried, and then heat-treated. Before filtration, the pH is adjusted to a neutral region around 6 to 9 by washing with water. It is preferable to keep it. This is because sodium and the like remain in a state where the pH is high, and in the subsequent heat treatment process, these residues may cause inter-particle sintering or inhibit crystal growth of the particles. Because there is.

  For cerium, zirconium, aluminum and iron, silica treatment may be performed by adding a silicon compound such as sodium silicate to the hydroxide or hydrate particles of these metals. This silica treatment is effective in maintaining the final target cerium oxide, zirconium oxide, aluminum oxide and iron oxide particles in a specific shape.

  The filtered or dried metal hydroxide or hydrate can be converted into oxide particles by heat treatment. The atmosphere is not particularly limited, but heating in air is preferable because it is the least expensive to manufacture. The heat treatment temperature is preferably in the range of 300 ° C to 1500 ° C. If the temperature is lower than this temperature, it is difficult to obtain oxide particles having good plate-like shape and crystallinity, and if it is too high, the particle size becomes larger due to sintering or the particle size distribution becomes wider. By this heat treatment, oxide particles of cerium oxide, zirconium oxide, aluminum oxide, iron oxide and silicon oxide particles can be obtained. However, if unreacted substances are removed by washing with water or the like, higher purity oxide particles can be obtained. Therefore, in order to use as a polishing material for chemical polishing, it is preferable to wash with water in the final step.

In addition, the above heat treatment is an effective means for obtaining oxide particles having good plate shape and crystallinity. However, in the case of cerium oxide and zirconium oxide, the oxide itself can be obtained without heat treatment. Thus, particles having a fluorite structure, which is a crystal structure of In this case, although it depends on aging and hydrothermal treatment conditions, plate-shaped particles can be obtained without performing heat treatment. In addition, plate-like silicon oxide particles having a composition of SiO ₂ can also be obtained without performing heat treatment on silicon oxide. Since the plate-like particles obtained without going through these heat treatment steps are usually as fine as 10 nm, it is preferable to use them in a slurry state without going through a drying step.

The oxide particles thus obtained have a particle size in the range of 10 nm to 100 nm, and a particle size of 20 nm, which is a particularly preferable range for use as a polishing sheet for finish polishing or polishing liquid. To 90 nm. When the X-ray diffraction spectrum is measured, the peaks corresponding to the crystal structure of CeO ₂ and ZrO ₂ having a fluorite structure are clearly observed in cerium oxide and zirconium oxide, and the crystal wall is also clearly observed in the electron microscope observation. It has been shown that it has extremely good crystallinity that was not obtained by the conventional production methods.

In addition, aluminum oxide is a plate-like crystal having an arbitrary crystal structure such as γ-Al ₂ O ₃ , δ-Al ₂ O ₃ , θ-Al ₂ O ₃ , α-Al ₂ O ₃ depending on the heat treatment temperature. Particles with good properties can be obtained. Specifically, for example, an aqueous solution of an aluminum salt is added to an alkaline aqueous solution, and the obtained aluminum hydroxide or hydrate is heat-treated in the temperature range of 110 to 300 ° C. in the presence of water, filtered, After drying, the obtained boehmite particles are heat-treated in air at a temperature range of 300 to 1200 ° C. or 400 to 1500 ° C., and more preferably by removing products or residues other than aluminum oxide by washing with water, A crystal structure of alumina, δ-alumina, θ-alumina, or α-alumina alone, or a mixture of alumina having two or more of these alumina crystal structures can be obtained.

Further, although it is difficult for silicon oxide to have a clear crystallinity diffraction peak in the X-ray diffraction spectrum, it was confirmed by a fluorescent X-ray analysis or the like that it has an almost SiO ₂ composition.

(Use of non-magnetic plate-like particles)
Nonmagnetic plate-like particles obtained as described above, specifically, oxide particles (cerium oxide particles, zirconium oxide particles, aluminum oxide particles, silicon oxide particles and iron oxide particles) are, for example, polishing bodies and polishing liquids, etc. When used as a polishing material, the unique shape and particle diameter exhibit excellent polishing properties with extremely few scratches on the object to be polished, which could not be obtained with conventional granular abrasive particles. That is, in the case of using conventional granular abrasive particles, it was very difficult to obtain a smooth polished surface without scratching the object to be polished while maintaining the polishing ability. If the oxide particles are used, polishing with very few scratches can be realized by using the flat plate surface of the particles while polishing using the end surfaces of the plate-like particles. The above-mentioned abrasive includes various forms such as a sheet (abrasive sheet), a tape (abrasive tape), a disk (abrasive disk), a card or plate, a rod, and a solid. .

  In addition, according to the method of the present invention, it is possible to obtain oxide particles that easily form holes in the plate thickness direction, such as iron oxide particles, among the non-magnetic plate-like particles as described above. This is because the plate-like hydroxide particles are dehydrated during the heat treatment, and pores are generated. Even in the oxide particles having such pores, the characteristics of the oxide particles of the present invention such as abrasiveness are included. Will not be damaged. In addition, when a part of iron in the iron oxide particles is replaced with other metal elements such as aluminum and zirconium, the hardness of the iron oxide particles can be controlled, and thereby, a delicate polishing ability can be expressed depending on the application.

  By adding and dispersing the nonmagnetic plate-like particles obtained by the method of the present invention in a liquid medium, preferably together with a dispersing agent, a polishing liquid which is a slurry-like abrasive is obtained. The abrasive particles in this case, specifically, cerium oxide particles, silicon oxide particles, zirconium oxide particles, aluminum oxide particles, and iron oxide particles have different hardnesses. Therefore, when these are used in combination, fine hardness can be adjusted, so that it can be used for a wide range of applications. In particular, if a mixture of general-purpose colloidal silica and the above abrasive particles is used, it will be possible to add new polishability to the polishability that was insufficient with colloidal silica alone, enabling a wide range of applications. Become. Even in the case of using such a mixture, the abrasive particles are not sintered and aggregated, and the particle size distribution is extremely uniform, so that different particles are rarely separated, and an extremely stable polishing liquid is obtained. can get.

  The non-magnetic plate-like particles of the present invention are extremely promising as additive particles for various coating-type magnetic recording media. In this case, plate-type particles having no holes are preferred. The reason why this type of plate-like particle is preferred is that if there is a hole, needle-like magnetic particles or the like may be caught in the hole, resulting in problems such as disordered orientation of the magnetic powder. Moreover, there is a possibility of causing thickness unevenness. In the coating-type magnetic recording medium, the magnetic layer is made thinner and thinner with the demand for higher recording density. Conventionally, granular aluminum oxide, silicon oxide, and iron oxide have been used as additives for coating-type magnetic recording media. However, when the magnetic layer is thinned, such granular additives are used as magnetic layers. The protrusion of the additive particles from the surface becomes prominent, the surface smoothness of the magnetic layer is lowered, and noise is increased. On the other hand, when the plate-like particles of the present invention are used, a magnetic recording medium having an extremely smooth magnetic layer surface can be obtained while maintaining the cleaning function of the additive particles by arranging the plate surfaces in parallel with the magnetic layer. It is done.

  Furthermore, when the oxide particles of the present invention are used as additives for various functional films such as an optical film, the optical properties inherent in the substance further exhibit excellent light transmittance based on the plate shape. In other words, when the plate surfaces of the particles are arranged so as to be parallel to the film surface, a functional film exhibiting excellent transparency with good light transmission can be obtained while expressing the interaction with the light inherent in the substance. It is done. For example, many applications such as an antireflection film in which a plurality of types of oxide particles of the present invention having different refractive indexes are applied in multiple layers and a high refractive index coating film with extremely good light transmittance are possible. By utilizing the in-plane isotropic property based on the plate shape, it is possible to realize a coating film having a very small mechanical or thermal deformation rate in a specific direction. In this case, non-colored plate-like particles such as aluminum oxide particles, zirconium oxide particles, cerium oxide particles, and silicon oxide particles are preferable because the film is not colored. In addition, if the plate-like particles have holes, it may cause unevenness in refractive index or decrease in transparency, so a type without holes is preferable.

  As described above, the oxide particles of the present invention are particles having a plate shape and an average particle size in the range of 10 nm to 100 nm and having a very good particle size distribution. Such particles are used. This not only greatly exceeds the characteristics of current products using oxide particles, but also pioneers completely new applications that could not be realized in the past.

Examples of the present invention will be described below together with comparative examples. Of the experimental examples 1 to 55 shown below, experimental examples of the zirconium oxide particles is in the scope of embodiments of the present invention, cerium oxide particles, iron oxide particles, experiments on aluminum oxide particles and silicon oxide particles Examples are given for reference.

(1) Example of cerium oxide particles <Experimental example 1>
An alkaline aqueous solution was prepared by dissolving 0.75 mol of sodium hydroxide and 100 ml of 2-aminoethanol in 800 ml of water. Separately, 0.074 mol of cerium (III) chloride heptahydrate was dissolved in 400 ml of water to prepare an aqueous cerium chloride solution. The latter aqueous cerium chloride solution was dropped into the former alkaline aqueous solution to prepare a precipitate containing cerium hydroxide at about 25 ° C. The pH at this time was 10.8. The precipitate was aged in suspension for 20 hours and then washed with water until the pH reached 7.9.

  Next, after removing the supernatant, the suspension of this precipitate was charged into an autoclave and subjected to hydrothermal treatment at 200 ° C. for 2 hours.

  The obtained hydrothermal treatment product was filtered, dried in air at 90 ° C., and then lightly crushed in a mortar, and heat-treated at 600 ° C. in air for 1 hour to obtain cerium oxide particles. After the heat treatment, in order to remove unreacted substances and residues, they were further washed with an ultrasonic disperser and filtered and dried.

  When the X-ray diffraction spectrum of the obtained cerium oxide particles was measured, a spectrum corresponding to cerium oxide having a fluorite structure was clearly observed (see FIG. 1). The crystallite size was calculated from the peak width corresponding to the (111) plane of cerium oxide using the Scherrer method. The crystallite size was 12.7 nm. Furthermore, when the shape was observed with a transmission electron microscope, it was found to be hexagonal plate-like particles having a particle diameter of 10 to 20 nm.

  An X-ray diffraction spectrum of the cerium oxide particles is shown in FIG. 1, and a transmission electron micrograph taken at 200,000 times is shown in FIG. Table 1 summarizes the synthesis conditions of the cerium oxide particles, the crystal structure investigated by X-ray diffraction, the average particle diameter and shape determined from the transmission electron micrograph, and the crystallite size determined from the X-ray diffraction peak width.

<Experimental example 2>
In the method for synthesizing cerium oxide particles in Experimental Example 1, a precipitate containing cerium hydroxide was prepared in the same manner as in Experimental Example 1, except that the heat treatment temperature of the hydrothermal treatment product was changed from 600 ° C. to 800 ° C. It was produced, washed with water, filtered and dried, and then heat-treated to produce cerium oxide particles.

This cerium oxide particles, was measured X-ray diffraction spectrum, a spectrum corresponding to cerium oxide with a real Kenrei 1 Like fluorite structure was observed. Moreover, the crystallite size calculated | required using the Scherrer method from the peak width corresponding to a (111) plane was 17.2 nm. Further, observation with a transmission electron microscope revealed hexagonal plate-like particles having a particle diameter of 10 to 25 nm.

  A transmission electron micrograph of the cerium oxide particles taken at 200,000 times is shown in FIG. Table 1 summarizes the synthesis conditions, the crystal structure determined by X-ray diffraction, the average particle size and shape determined from transmission electron micrographs, and the crystallite size determined from the X-ray diffraction peak width.

<Experimental example 3>
In the method for synthesizing cerium oxide particles in Experimental Example 1, a precipitate containing cerium hydroxide was prepared in the same manner as in Experimental Example 1, except that the heat treatment temperature of the hydrothermal treatment product was changed from 600 ° C. to 1000 ° C. It was produced, washed with water, filtered and dried, and then heat-treated to produce cerium oxide particles.

  When an X-ray diffraction spectrum was measured for the cerium oxide particles, a spectrum corresponding to cerium oxide having the same fluorite structure as in Experimental Example 1 was observed, and from the peak width corresponding to the (111) plane, the Scherrer method was used. The crystallite size determined using this was 32.4 nm. Further observation with a transmission electron microscope revealed that the particles were hexagonal or quadrangular plate-like particles having a particle diameter of 50 to 100 nm.

  FIG. 4 shows a transmission electron micrograph of the cerium oxide particles taken at 200,000 times. Table 1 summarizes the synthesis conditions, the crystal structure examined by X-ray diffraction, the average particle size and shape determined from the transmission electron micrograph, and the crystallite size determined from the X-ray diffraction peak width.

<Experimental example 4>
In the method for synthesizing cerium oxide particles of Experimental Example 1, after hydrothermal treatment, the suspension was washed with 500 times the volume of the suspension and then filtered and dried. The pH after washing was 7.5. Subsequent steps after the heat treatment were performed in the same manner as in Experimental Example 1 to produce cerium oxide particles.

  When the X-ray diffraction spectrum of this cerium oxide particle was measured, a spectrum corresponding to cerium oxide having a fluorite structure was observed, and the crystal obtained using the Scherrer method from the peak width corresponding to the (111) plane The child size was 11.5 nm. Furthermore, observation with a transmission electron microscope revealed hexagonal plate-like particles having a particle size of 10 to 15 nm.

  Table 1 summarizes the cerium oxide particles, the synthesis conditions, the crystal structure examined by X-ray diffraction, the average particle diameter and shape determined from transmission electron micrographs, and the crystallite size determined from the X-ray diffraction peak width. .

<Experimental example 5>
In the method for synthesizing cerium oxide particles in Experimental Example 1, after hydrothermal treatment, 0.04 g of 4N sodium silicate aqueous solution was added, and then 0.8N hydrochloric acid aqueous solution was added to adjust the pH to 7.4. In the same manner as in Experimental Example 1, a precipitate containing cerium hydroxide was produced, washed with water, filtered, dried, and then heat-treated to produce cerium oxide particles.

  When the X-ray diffraction spectrum of this cerium oxide particle was measured, a spectrum corresponding to cerium oxide having a fluorite structure was observed, and the crystal obtained using the Scherrer method from the peak width corresponding to the (111) plane The child size was 10.6 nm. Furthermore, observation with a transmission electron microscope revealed hexagonal plate-like particles having a particle size of 10 to 15 nm.

  Table 1 summarizes the cerium oxide particles, the synthesis conditions, the crystal structure examined by X-ray diffraction, the average particle diameter and shape obtained from the transmission electron micrograph, and the crystallite size obtained from the X-ray diffraction peak width. Show.

<Experimental example 6>
In the method for synthesizing cerium oxide particles in Experimental Example 1, cerium oxide particles were prepared in the same manner as in Experimental Example 1, except that the heat treatment was performed at 600 ° C. in air for 1 hour, and then washed with an ultrasonic disperser. .

  When the X-ray diffraction spectrum of this cerium oxide particle was measured, a spectrum corresponding to cerium oxide having a fluorite structure was observed, and the crystal obtained using the Scherrer method from the peak width corresponding to the (111) plane The child size was 12.3 nm. Further, observation with a transmission electron microscope revealed hexagonal plate-like particles having a particle size of 10 to 20 nm.

  Table 1 shows the synthesis conditions, the crystal structure investigated by X-ray diffraction, the average particle diameter and shape determined from the transmission electron micrograph, and the crystallite size determined from the X-ray diffraction peak width.

<Experimental example 7>
In the method for synthesizing cerium oxide particles of Experimental Example 1, the amount of sodium hydroxide was changed from 0.75 mol to 0.90 mol, and precipitation was performed in the same manner as in Experimental Example 1 without adding 2-aminoethanol. A product was made. The pH at this time was 10.5. Next, this precipitate suspension was aged, then hydrothermally treated, washed with water, filtered and dried, and further heat treated to produce cerium oxide particles.

  When the X-ray diffraction spectrum of this cerium oxide particle was measured, a spectrum corresponding to cerium oxide having a fluorite structure was observed, and the crystal obtained using the Scherrer method from the peak width corresponding to the (111) plane The child size was 20.1 nm. Furthermore, observation with a transmission electron microscope revealed that the particle size distribution was slightly wide but hexagonal plate-like particles having a particle size of 20 to 30 nm.

  Table 1 shows the synthesis conditions, the crystal structure investigated by X-ray diffraction, the average particle diameter and shape determined from the transmission electron micrograph, and the crystallite size determined from the X-ray diffraction peak width.

<Comparative example 1>
In the method for synthesizing the cerium oxide particles of Experimental Example 1, after producing a precipitate containing cerium hydroxide, the precipitate containing cerium hydroxide is used as it is in the same manner as in Experimental Example 1 without performing hydrothermal treatment. After washing with water, filtering and drying, heat treatment was performed to produce cerium oxide particles.

  When an X-ray diffraction spectrum was measured for the cerium oxide particles, a spectrum corresponding to cerium oxide having a fluorite structure was observed. From the peak width corresponding to the (111) plane, the crystallite size was obtained. The crystallite size was so large that it was observed with a transmission electron microscope. As a result, it was found that the particle size was 1 to 10 μm and the sintered body or coarse particles had a very wide particle size distribution.

  Table 1 summarizes the cerium oxide particles, the synthesis conditions, the crystal structure examined by X-ray diffraction, the average particle diameter and shape obtained from transmission electron micrographs, and the crystallite size obtained from the X-ray diffraction peak width. Show.

(X-ray diffraction spectrum of cerium oxide particles)
FIG. 1 is an X-ray diffraction spectrum of the cerium oxide particles produced in Experimental Example 1 described above. In the figure, peaks corresponding to the crystal structure of cerium oxide having a fluorite structure are shown. Since similar results were obtained in both the powders of the experimental examples and the comparative examples, it was confirmed that the powders prepared in the experimental examples and the comparative examples were cerium oxide particles.

(Transmission electron microscope observation results of cerium oxide particles)
2 to 4 show transmission electron micrographs of the cerium oxide particles produced in Experimental Examples 1 to 3 described above. In Experimental Examples 1 to 3, the heat treatment temperatures after hydrothermal treatment are 600 ° C., 800 ° C., and 1000 ° C., respectively. It can be seen that the average particle diameter increases from about 10 nm to about 100 nm as the heat treatment temperature increases. This indicates that cerium oxide particles grow in the heat treatment process.

  Table 1 summarizes the synthesis conditions of the cerium oxide particles of the above experimental examples and comparative examples, the crystal structure examined by X-ray diffraction, and the average particle diameter and shape estimated from transmission electron micrographs. In addition, the particle diameter estimated from the transmission electron micrograph was calculated | required from the average particle diameter of 300 particle | grains.

  As is apparent from Table 1, the cerium oxide particles obtained in each of the above experimental examples are all plate-like in shape, have a fluorite structure that cerium oxide originally has, and have a particle size of an abrasive sheet or an abrasive liquid. It can be seen that it is in the optimum range for use in magnetic tapes and various optical films by utilizing the plate shape as well as abrasives such as. On the other hand, the cerium oxide particles shown in Comparative Example 1 have a fluorite structure, but have a very large particle size and an extremely wide particle size distribution, and are not suitable for applications such as abrasives.

  Thus, the cerium oxide particles of the present invention have a plate-like shape and simultaneously realize a fine particle diameter of 100 nm or less, and open up a completely new application that has been considered impossible to realize in the past. It is.

(2) Example of zirconium oxide particles <Experimental example 8>
An alkaline aqueous solution was prepared by dissolving 0.75 mol of sodium hydroxide and 100 ml of 2-aminoethanol in 800 ml of water. Separately from this alkaline aqueous solution, 0.074 mol of zirconium (IV) chloride was dissolved in 400 ml of water to prepare an aqueous zirconium chloride solution. The zirconium chloride aqueous solution was dropped into the alkaline aqueous solution to prepare a precipitate containing zirconium hydroxide at about 25 ° C. The pH at this time was 10.8. The precipitate was aged in suspension for 20 hours and then washed with water until the pH reached 7.8.

  Next, after removing the supernatant, the suspension of this precipitate was charged into an autoclave and subjected to hydrothermal treatment at 200 ° C. for 2 hours.

  The obtained hydrothermal treatment product was filtered, dried in air at 90 ° C., and then lightly crushed in a mortar, and heat-treated at 600 ° C. in air for 1 hour to obtain zirconium oxide particles. After the heat treatment, in order to remove unreacted substances and residues, they were further washed with an ultrasonic disperser and filtered and dried.

  When the X-ray diffraction spectrum of the obtained zirconium oxide particles was measured, a spectrum corresponding to zirconium oxide having a fluorite structure was clearly observed. Furthermore, when shape observation was performed with the transmission electron microscope, it turned out that it is a plate-shaped hexagonal particle with a particle diameter of 10-20 nm. FIG. 5 shows an X-ray diffraction spectrum of the zirconium oxide particles, and FIG. 6 shows a transmission electron micrograph taken at 200,000 times. Table 2 summarizes the synthesis conditions of the zirconium oxide particles, the crystal structure examined by X-ray diffraction, and the average particle diameter and shape determined from a transmission electron micrograph.

<Experimental example 9>
In the method for synthesizing zirconium oxide particles in Experimental Example 8, a precipitate containing zirconium hydroxide was prepared in the same manner as in Experimental Example 8, except that the heat treatment temperature of the hydrothermal treatment product was changed from 600 ° C. to 800 ° C. It was produced, washed with water, filtered and dried, and then heat-treated to produce zirconium oxide particles.

  When the X-ray diffraction spectrum of the zirconium oxide particles was measured, a spectrum corresponding to zirconium oxide having a fluorite structure was observed as in Experimental Example 8. Furthermore, observation with a transmission electron microscope revealed hexagonal plate-like particles having a particle diameter of 20 to 30 nm. A transmission electron micrograph of the zirconium oxide particles taken at 200,000 times is shown in FIG. Table 2 summarizes the synthesis conditions, the crystal structure examined by X-ray diffraction, and the average particle diameter and shape determined from transmission electron micrographs of the zirconium oxide particles.

<Experimental Example 10>
In the method for synthesizing zirconium oxide particles in Experimental Example 8, a precipitate containing zirconium hydroxide was prepared in the same manner as in Experimental Example 8, except that the heat treatment temperature of the hydrothermal treatment product was changed from 600 ° C. to 1000 ° C. It was produced, washed with water, filtered and dried, and then heat-treated to produce zirconium oxide particles.

  When the X-ray diffraction spectrum of this zirconium oxide particle was measured, a spectrum corresponding to zirconium oxide having the same fluorite structure as in Experimental Example 8 was observed, and observation with a transmission electron microscope revealed that the particle diameter was 50 to 50. It was found to be 100 nm hexagonal plate-like particles. Table 2 summarizes the synthesis conditions, the crystal structure examined by X-ray diffraction, and the average particle diameter and shape determined from transmission electron micrographs.

<Experimental example 11>
In the method for synthesizing zirconium oxide particles in Experimental Example 8, after hydrothermal treatment, the suspension was washed with 500 times the volume of the suspension, and then filtered and dried. The pH after washing was 7.5. Subsequent steps after the heat treatment were performed in the same manner as in Experimental Example 8 to produce zirconium oxide particles.

  When the X-ray diffraction spectrum of this zirconium oxide particle was measured, a spectrum corresponding to zirconium oxide having a fluorite structure was observed, and when observed with a transmission electron microscope, hexagonal plate-like particles having a particle size of 10 to 15 nm were observed. I found out that Table 2 summarizes the synthesis conditions, the crystal structure examined by X-ray diffraction, and the average particle diameter and shape determined from transmission electron micrographs.

<Experimental example 12>
In the method for synthesizing zirconium oxide particles in Experimental Example 8, after hydrothermal treatment, 0.04 g of 4N sodium silicate aqueous solution was further added, and 0.8N hydrochloric acid aqueous solution was further added to adjust the pH to 7.4. In the same manner as in Experimental Example 8, a precipitate containing zirconium hydroxide was produced, washed with water, filtered, dried and then heat-treated to produce zirconium oxide particles.

  When the X-ray diffraction spectrum of the zirconium oxide particles was measured, a spectrum corresponding to zirconium oxide having a fluorite structure was observed. Further, when observed with a transmission electron microscope, a hexagonal plate shape having a particle size of 10 to 15 nm was observed. It turned out to be a particle. Table 2 summarizes the synthesis conditions, the crystal structure examined by X-ray diffraction, and the average particle diameter and shape determined from transmission electron micrographs of the zirconium oxide particles.

<Experimental example 13>
In the method for synthesizing zirconium oxide particles in Experimental Example 8, zirconium oxide particles were produced in the same manner as in Experimental Example 8 except that after heat treatment at 600 ° C. in air for 1 hour and further washed with an ultrasonic disperser. .

  When the X-ray diffraction spectrum of this zirconium oxide particle was measured, a spectrum corresponding to zirconium oxide having a fluorite structure was observed. Further, when observed with a transmission electron microscope, a hexagonal plate shape having a particle size of 10 to 20 nm was observed. It turned out to be a particle. Table 2 summarizes the synthesis conditions, the crystal structure examined by X-ray diffraction, and the average particle diameter and shape determined from transmission electron micrographs of the zirconium oxide particles.

<Experimental example 14>
In the method for synthesizing zirconium oxide particles in Experimental Example 8, the amount of sodium hydroxide added was changed from 0.75 mol to 0.90 mol, and precipitation was performed in the same manner as in Experimental Example 8 without adding 2-aminoethanol. After aging the precipitate suspension, hydrothermal treatment was performed, followed by washing with water, filtration and drying, followed by further heat treatment to produce zirconium oxide particles.

  When an X-ray diffraction spectrum of the zirconium oxide particles was measured, a spectrum corresponding to zirconium oxide having a fluorite structure was clearly observed. Furthermore, when the shape was observed with a transmission electron microscope, it was found that the particles were hexagonal plate-like particles having a particle size distribution of 15 to 25 nm although the particle size distribution was slightly wide. Table 2 summarizes the synthesis conditions, the crystal structure examined by X-ray diffraction, and the average particle diameter and shape determined from transmission electron micrographs of the zirconium oxide particles.

<Comparative example 2>
In the method for synthesizing the zirconium oxide particles in Experimental Example 8, after the precipitate containing zirconium hydroxide was generated, the precipitate containing zirconium hydroxide was directly used in the same manner as in Experimental Example 8 without performing hydrothermal treatment. Washed with water, filtered and dried, and further heat-treated in the same manner as in Experimental Example 8 to produce zirconium oxide particles.

  When the X-ray diffraction spectrum of this zirconium oxide particle was measured, a peak corresponding to zirconium oxide having a fluorite structure was observed, but when the shape was observed with a transmission electron microscope, the fine particle was sintered or It turned out that the particle size distribution to the coarse particle by aggregation is a sintered body or coarse particle having a very wide particle size distribution with a particle size ranging from 1 to 10 μm. Table 2 summarizes the synthesis conditions, the crystal structure examined by X-ray diffraction, and the average particle diameter and shape determined from transmission electron micrographs of the zirconium oxide particles.

(X-ray diffraction spectrum of zirconium oxide particles)
FIG. 5 is an X-ray diffraction spectrum of the zirconium oxide particles produced in Experimental Example 8. In the figure, peaks corresponding to the crystal structure of zirconium oxide are shown. Since similar results were obtained in any of the powders of the experimental examples, it was found that all the powders prepared in the experimental examples were zirconium oxide particles.

(Transmission electron microscope observation results of zirconium oxide particles)
6 and 7 show transmission electron micrographs of the zirconium oxide particles produced in Experimental Example 8 and Experimental Example 9, respectively. It is clearly observed that plate-like zirconium oxide particles are obtained. In addition, the average particle diameter estimated from the transmission electron micrograph was calculated | required from the average particle diameter of 300 particle | grains.

  As is clear from Table 2, the zirconium oxide particles obtained in each experimental example are all plate-like in shape and excellent in crystallinity, and the particle diameter is not only a polishing material such as a polishing sheet or a polishing liquid, but also a plate It can be seen that the particle diameter is in the optimum range when it is used in applications such as magnetic tape and various optical films utilizing the shape. On the other hand, the zirconium oxide particles shown in Comparative Example 2 have a very large particle size and an extremely wide particle size distribution, which indicates that they are not suitable for applications such as abrasives.

  As described above, the zirconium oxide particles of the present invention have a plate-like shape and simultaneously realize a fine particle diameter of 100 nm or less, and open up a completely new application that has been considered impossible to realize in the past. It is.

(3) Example relating to aluminum oxide particles <Experimental Example 15>
0.75 mol of sodium hydroxide and 100 ml of 2-aminoethanol were dissolved in 800 ml of water to prepare an alkaline aqueous solution. Separately from this alkaline aqueous solution, 0.074 mol of aluminum chloride (III) heptahydrate was dissolved in 400 ml of water to prepare an aqueous aluminum chloride solution. The aluminum chloride aqueous solution was dropped into the alkaline aqueous solution to prepare a precipitate containing aluminum hydroxide at about 25 ° C., and then hydrochloric acid was dropped to adjust the pH to 10.2. This precipitate was aged in a suspension state for 20 hours, and then washed with about 1000 times water.

  Next, after removing the supernatant, the suspension of the precipitate was readjusted to pH 10.0 using an aqueous sodium hydroxide solution, charged into an autoclave, and subjected to hydrothermal treatment at 200 ° C. for 2 hours.

  The obtained hydrothermal treatment product was filtered, dried in the air at 90 ° C., and then lightly crushed in a mortar, followed by heat treatment in the air at 600 ° C. for 1 hour to obtain aluminum oxide particles. After the heat treatment, in order to remove unreacted substances and residues, they were further washed with an ultrasonic disperser and filtered and dried.

  When the X-ray diffraction spectrum of the obtained aluminum oxide particles was measured, a spectrum corresponding to γ-alumina was observed. Furthermore, when shape observation was performed with the transmission electron microscope, it turned out that it is a square-plate-shaped particle | grain with a particle diameter of 30-50 nm.

  FIG. 8 shows an X-ray diffraction spectrum of the aluminum oxide particles, and FIG. 9 shows a transmission electron micrograph taken at 200,000 times. Table 3 summarizes the synthesis conditions, the crystal structure examined by X-ray diffraction, and the average particle diameter and shape determined from transmission electron micrographs of the aluminum oxide particles.

<Experimental example 16>
In the method for synthesizing aluminum oxide particles in Experimental Example 15, a precipitate containing aluminum hydroxide was prepared in the same manner as in Experimental Example 15 except that the heat treatment temperature of the hydrothermal treatment product was changed from 600 ° C. to 1000 ° C. It was produced, washed with water, filtered and dried, and then heat-treated to produce aluminum oxide particles.

  When an X-ray diffraction spectrum was measured for the aluminum oxide particles, a spectrum corresponding to δ-alumina having a peak intensity higher than that of the spectrum in Experimental Example 15 was observed. Further, observation with a transmission electron microscope revealed that it was a square plate-like particle having a particle diameter of 30 to 50 nm, as in Experimental Example 15.

  An X-ray diffraction spectrum of the aluminum oxide particles is shown in FIG. Table 3 summarizes the synthesis conditions, the crystal structure examined by X-ray diffraction, and the average particle diameter and shape determined from transmission electron micrographs of the aluminum oxide particles.

<Experimental Example 17>
In the method for synthesizing aluminum oxide particles in Experimental Example 15, except that the hydrothermal treatment time was changed from 2 hours to 4 hours, a precipitate containing aluminum hydroxide was generated in the same manner as in Experimental Example 15, washed with water, After filtration and drying, heat treatment was performed to produce aluminum oxide particles.

  When the X-ray diffraction spectrum of this aluminum oxide particle was measured, the same spectrum corresponding to γ-alumina as in Experimental Example 15 was observed. Further observation with a transmission electron microscope revealed that the particles were square plate-like particles having a particle diameter of 10 to 20 nm.

  A transmission electron micrograph of this aluminum oxide particle taken at 200,000 times is shown in FIG. Table 3 summarizes the synthesis conditions, the crystal structure examined by X-ray diffraction, and the average particle diameter and shape determined from transmission electron micrographs of the aluminum oxide particles.

<Experimental example 18>
In the method for synthesizing aluminum oxide particles in Experimental Example 15, an aluminum chloride aqueous solution was dropped into an alkaline aqueous solution to prepare a precipitate containing aluminum hydroxide, and then hydrochloric acid was dropped to adjust the pH to 8.3. . After aging, it was washed with about 1000 times water and readjusted to pH 8.1 using an aqueous sodium hydroxide solution. The subsequent steps after hydrothermal treatment were performed in the same manner as in Experimental Example 15 to produce aluminum oxide particles.

  When an X-ray diffraction spectrum was measured for the aluminum oxide particles, a spectrum corresponding to γ-alumina was observed as in Experimental Example 15. Furthermore, when observed with a transmission electron microscope, it was found to be hexagonal plate-like particles having a particle diameter of 65 to 85 nm.

  A transmission electron micrograph of the aluminum oxide particles taken at 200,000 times is shown in FIG. Table 3 summarizes the synthesis conditions, the crystal structure examined by X-ray diffraction, and the average particle diameter and shape determined from transmission electron micrographs of the aluminum oxide particles.

<Experimental Example 19>
In the method for synthesizing aluminum oxide particles in Experimental Example 15, after hydrothermal treatment, 0.04 g of 4N sodium silicate aqueous solution was further added and stirred well, and then 0.8N hydrochloric acid aqueous solution was gradually added with stirring. In the same manner as in Experimental Example 15 except that the pH was adjusted to 7.5, a precipitate containing aluminum hydroxide was produced, washed with water, filtered, dried, and then heat-treated to produce aluminum oxide particles.

  When an X-ray diffraction spectrum was measured for the aluminum oxide particles, a spectrum corresponding to γ-alumina was observed. Furthermore, observation with a transmission electron microscope revealed that it was a square plate-like particle having a particle size of 30 to 50 nm.

  Table 3 summarizes the synthesis conditions, the crystal structure examined by X-ray diffraction, and the average particle diameter and shape determined from transmission electron micrographs of the aluminum oxide particles.

<Experimental example 20>
The aluminum oxide particles obtained in Experimental Example 15 were further heat-treated at 1250 ° C. in air for 1 hour. When the X-ray diffraction spectrum of the obtained aluminum oxide particles was measured, a spectrum corresponding to α-alumina was observed. Furthermore, when the shape was observed with a transmission electron microscope, it was a square plate-like particle having a particle diameter of 40 to 60 nm.

  FIG. 13 shows an X-ray diffraction spectrum of the aluminum oxide particles, and FIG. 14 shows a transmission electron microscope taken at 200,000 times. Table 3 summarizes the synthesis conditions, the crystal structure examined by X-ray diffraction, and the average particle diameter and shape determined from transmission electron micrographs of the aluminum oxide particles.

<Experimental example 21>
In the method for synthesizing aluminum oxide particles in Experimental Example 15, the amount of sodium hydroxide was changed from 0.75 mol to 0.90 mol, and precipitation was performed in the same manner as in Experimental Example 15 without adding 2-aminoethanol. After aging the precipitate suspension, hydrothermal treatment was performed, followed by water washing, filtration and drying, followed by further heat treatment to produce aluminum oxide particles.

  When an X-ray diffraction spectrum was measured for the aluminum oxide particles, a spectrum corresponding to γ-alumina was observed. Furthermore, when the shape was observed with a transmission electron microscope, it was found that the particles were square plate-like particles having a particle size distribution of 40-60 nm, although the particle size distribution was slightly wide.

  Table 3 summarizes the synthesis conditions, the crystal structure examined by X-ray diffraction, and the average particle diameter and shape determined from transmission electron micrographs of the aluminum oxide particles.

<Comparative Example 3>
In the method for synthesizing aluminum oxide particles of Experimental Example 15, it was produced in the same manner as Experimental Example 15 except that the heat treatment temperature was changed from 600 ° C to 300 ° C.

  When the X-ray diffraction spectrum of the particles thus prepared was measured, the crystal structure transformation to aluminum oxide was insufficient, and a spectrum corresponding to aluminum hydroxide oxide (boehmite; AlO (OH)) was observed. It was.

  Table 3 summarizes the synthesis conditions, the crystal structure examined by X-ray diffraction, and the average particle diameter and shape determined from transmission electron micrographs of the aluminum oxide particles.

<Comparative example 4>
In the method for synthesizing aluminum oxide particles of Experimental Example 15, a precipitate containing aluminum hydroxide was produced under the same conditions as in Experimental Example 15, washed with about 1000 times water, and then sodium hydroxide as in Experimental Example 15. The pH was readjusted to 10.0 using an aqueous solution. Next, instead of hydrothermal treatment using an autoclave, this suspension was heat-treated at 90 ° C. for 2 hours. The heated product was filtered, dried in air at 90 ° C., and then lightly crushed in a mortar, and similarly to Experimental Example 1, heat treatment was performed in air at 600 ° C. for 1 hour to obtain aluminum oxide particles. After the heat treatment, in order to remove unreacted substances and residues, they were further washed with an ultrasonic disperser and filtered and dried.

  When an X-ray diffraction spectrum was measured for the aluminum oxide particles, a spectrum corresponding to γ-alumina was observed. The particle size distribution was wide up to the agglomerated particles, and the particle shape was granular or lump-shaped indeterminate.

  Table 3 summarizes the synthesis conditions, the crystal structure examined by X-ray diffraction, and the average particle diameter and shape determined from transmission electron micrographs of the aluminum oxide particles.

(Transmission electron microscope observation results of aluminum oxide particles)
9, 11, 12, and 14 show transmission electron micrographs of the aluminum oxide particles produced in Experimental Examples 15, 17, 18, and 20, respectively.

  In Experimental Example 15 and Experimental Example 17, the hydrothermal treatment time is 2 hours and 4 hours, respectively. As the hydrothermal treatment time increases, the average particle diameter of aluminum oxide particles produced after the heat treatment tends to decrease from about 45 nm to about 16 nm. This is because if crystal growth is sufficiently performed during hydrothermal treatment, crystal growth tends to be suppressed in the subsequent heat treatment, and conversely, if crystal growth during hydrothermal treatment is conserved, crystals will be generated in the subsequent heat treatment. It shows that it tends to grow.

  Thus, in the production method of the present invention, as described above, it is divided into a process aiming at adjusting the shape and particle diameter and a process aiming to maximize the physical properties inherent to the material. One of the characteristics is that the first step by hydrothermal treatment and the subsequent step by heat treatment in air are closely related, and it was also found for the first time by the present invention that this relationship exists. Is.

  Furthermore, in Experimental Example 15 and Experimental Example 18, the pHs during aging and hydrothermal treatment are 10.2 and 8.3, respectively. The particle shape of the aluminum oxide particles is a square plate at pH 10.2, and a hexagonal plate at pH 8.3. The average particle size tends to decrease as the pH increases, and the shape tends to change from a hexagonal plate shape to a square plate shape. The reason why the particle diameter and particle shape change due to the pH during aging and hydrothermal treatment is not clear at present, but the plate shape is maintained depending on the pH value during aging or hydrothermal treatment. The ability to change the particle shape and the average particle diameter is also one of the major features not found in other production methods.

  Table 3 summarizes the synthesis conditions of the aluminum oxide particles of the above experimental examples and comparative examples, the crystal structure of the aluminum oxide particles obtained from the X-ray diffraction spectrum, and the average particle diameter estimated from the transmission electron micrograph. In addition, the average particle diameter estimated from the transmission electron micrograph was calculated | required from the average particle diameter of 300 particle | grains.

(X-ray diffraction spectrum of aluminum oxide particles)
8, 10, and 13 show the X-ray diffraction spectra of the aluminum oxide particles produced in Experimental Examples 15, 16, and 20, respectively. 8, 10 and 13 correspond to the X-ray diffraction spectra of γ-alumina, δ-alumina and α-alumina, respectively. This result shows that aluminum oxide particles having an arbitrary crystal structure can be obtained by controlling the heat treatment conditions without changing the particle diameter and particle shape of the aluminum oxide particles. This is also one of the major features of the present invention.

  As is apparent from Table 3, the aluminum oxide particles obtained in the above experimental examples are all plate-like in shape, and can be controlled to various crystal structures according to heat treatment conditions such as γ, δ, α from X-ray diffraction. It turns out that it is possible.

  On the other hand, in Comparative Example 3, aluminum oxide particles are not obtained, and remain as aluminum hydroxide oxide particles (boehmite particles). Furthermore, it can be seen that the aluminum oxide particles shown in Comparative Example 4 have a very large particle size due to sintering or agglomeration and an extremely wide particle size distribution, and are not suitable for use as additives such as abrasives.

  The particle diameter of the aluminum oxide particles of the present invention is an optimum range not only as an abrasive for polishing sheets and polishing liquids, but also as additive particles for magnetic tape, and further as additive particles for various functional sheets. It is in. Thus, aluminum oxide particles having a plate-like shape and simultaneously realizing a fine particle size of 100 nm or less are unprecedented and open up a completely new application that has been considered impossible to realize in the past.

(4) Example of silicon oxide particles <Experimental example 22>
0.074 mol of sodium metasilicate and 100 ml of 2-aminoethanol were dissolved in 800 ml of water to prepare an alkaline aqueous solution. Apart from this alkaline aqueous solution, 400 ml of 1N aqueous hydrochloric acid solution was prepared. A hydrochloric acid aqueous solution was dropped into the aqueous alkali solution containing sodium silicate and aminoethanol until the pH of the suspension became 8.3, and a precipitate containing silicon hydroxide was produced at about 25 ° C. The precipitate was aged in suspension for 20 hours and then washed with water until the pH reached 7.6.

  Next, after removing the supernatant, the suspension of this precipitate was charged into an autoclave and subjected to hydrothermal treatment at 200 ° C. for 2 hours.

  The obtained hydrothermal treatment product was filtered, dried in air at 90 ° C., and then lightly crushed in a mortar, and heat-treated at 800 ° C. in air for 1 hour to obtain silicon oxide particles.

  When the shape of the obtained silicon oxide particles was observed with a transmission electron microscope, it was found to be a plate-like particle having a particle diameter of 30 to 40 nm, which is close to a circle.

  A transmission electron micrograph of the silicon oxide particles taken at 200,000 times is shown in FIG. Table 4 summarizes the silicon oxide particles, the synthesis conditions, the crystal structure examined by X-ray diffraction, and the average particle diameter and shape determined from a transmission electron micrograph.

<Experimental example 23>
In the method for synthesizing silicon oxide particles of Experimental Example 22, a precipitate containing silicon hydroxide was prepared in the same manner as in Experimental Example 22 except that the heat treatment temperature of the hydrothermal treatment product was changed from 800 ° C. to 600 ° C. It was generated, washed with water, filtered and dried, and then heat-treated to produce silicon oxide particles.

  When this silicon oxide particle was observed with a transmission electron microscope, it was a plate-like particle having a particle diameter of 15 to 25 nm and a nearly circular shape. Table 4 summarizes the synthesis conditions, the crystal structure examined by X-ray diffraction, and the average particle diameter and shape determined from transmission electron micrographs of the silicon oxide particles.

<Experimental example 24>
In the method for synthesizing silicon oxide particles in Experimental Example 22, a precipitate containing silicon hydroxide was prepared in the same manner as in Experimental Example 22 except that the heat treatment temperature of the hydrothermal treatment product was changed from 800 ° C. to 1000 ° C. It was generated, washed with water, filtered and dried, and then heat-treated to produce silicon oxide particles.

  When this silicon oxide particle was observed with a transmission electron microscope, it was a plate-like particle having a particle diameter of 70 to 100 nm and a nearly circular shape. Table 4 summarizes the synthesis conditions, the crystal structure examined by X-ray diffraction, and the average particle diameter and shape determined from transmission electron micrographs of the silicon oxide particles.

<Experimental example 25>
In the method for synthesizing silicon oxide particles of Experimental Example 22, after hydrothermal treatment, the suspension was washed with water 500 times the volume of the suspension, and then filtered and dried. The pH after washing was 7.5. Subsequent steps after the heat treatment were made silicon oxide particles in the same manner as in Experimental Example 22.

  When the obtained silicon oxide particles were observed with a transmission electron microscope, they were found to be plate-like particles having a particle diameter of 30 to 40 nm and nearly circular. Table 4 summarizes the synthesis conditions, the crystal structure examined by X-ray diffraction, and the average particle diameter and shape determined from transmission electron micrographs of the silicon oxide particles.

<Experimental example 26>
In the method for synthesizing silicon oxide particles in Experimental Example 22, silicon oxide particles were produced in the same manner as in Experimental Example 22 except that after heat treatment at 80 ° C. in air for 1 hour and further washed with an ultrasonic disperser. .

  When the obtained silicon oxide particles were observed with a transmission electron microscope, they were found to be plate-like particles having a particle diameter of 30 to 40 nm and nearly circular. Table 4 summarizes the synthesis conditions, the crystal structure examined by X-ray diffraction, and the average particle diameter and shape determined from transmission electron micrographs of the silicon oxide particles.

<Experimental example 27>
In the method for synthesizing silicon oxide particles of Experimental Example 22, instead of adding an alkaline aqueous solution in which 0.074 mol of sodium metasilicate and 100 ml of 2-aminoethanol were dissolved in 800 ml of water, without adding 2-aminoethanol, Except for using an alkaline aqueous solution in which 0.074 mol of sodium metasilicate was dissolved in 800 ml of water, a 1N hydrochloric acid aqueous solution was added to a sodium metasilicate aqueous solution until the pH reached 7.5 in the same manner as in Experimental Example 22. It was dripped and the deposit containing silicon hydroxide was produced. This precipitate was aged in a suspension state for 20 hours and then washed with water to adjust the pH to 7.6.

  Next, after removing the supernatant, the suspension of this precipitate was charged into an autoclave and subjected to hydrothermal treatment at 200 ° C. for 2 hours.

  When the obtained silicon oxide particles were observed with a transmission electron microscope, they were found to be plate-like particles having a slightly wide particle size distribution but a circular shape with a particle size of 20 to 30 nm. Table 4 summarizes the synthesis conditions, the crystal structure examined by X-ray diffraction, and the average particle diameter and shape determined from transmission electron micrographs of the silicon oxide particles.

<Comparative Example 5>
In the method for synthesizing silicon oxide particles in Experimental Example 22, a precipitate containing silicon hydroxide was produced in the same manner as in Experimental Example 22 except that hydrothermal treatment was not performed after producing a precipitate containing silicon hydroxide. After being washed with water, filtered and dried, heat treatment was performed to produce silicon oxide particles.

  When the obtained silicon oxide particles were observed with a transmission electron microscope, they were found to be sintered bodies or aggregated particles having a particle size distribution of 1 to 10 μm and an extremely wide particle size distribution. Table 4 summarizes the synthesis conditions, the crystal structure examined by X-ray diffraction, and the average particle diameter and shape determined from transmission electron micrographs of the silicon oxide particles. The average particle size estimated from the transmission electron micrograph was obtained from the average particle size of 300 particles.

(Transmission electron microscope observation results)
FIG. 15 shows a transmission electron micrograph of the silicon oxide particles produced in Experimental Example 22. It turns out that it is a plate-like particle | grain with a particle diameter of 30-40 nm close to a circle. Thus, the silicon oxide particles having an extremely small particle diameter and a plate-like shape are extremely difficult to obtain by the conventional method, and have been successful for the first time by the method of the present invention.

  As is clear from Table 4, the silicon oxide particles obtained in the above experimental examples have an amorphous crystal structure from the X-ray diffraction spectrum, but all have a plate shape. This silicon oxide particle is realized for the first time by the present invention.

  On the other hand, the silicon oxide particles of Comparative Example 5 have a large particle size due to sintering or aggregation and an extremely wide particle size distribution, and cannot be said to be suitable for applications such as abrasives.

  The particle diameter of the silicon oxide particles of the present invention is in an optimum range not only as an abrasive for polishing sheets and polishing liquids, but also as an additive particle for magnetic tape and various functional sheets. . Thus, there has never been a silicon oxide particle having a unique particle shape such as a plate shape and simultaneously realizing a fine particle size of 100 nm or less, which is completely new and has been considered impossible to realize in the past. It will also open up applications.

(5) Example concerning iron oxide particles <Experimental example 28>
The following two types of aqueous solutions were prepared.
・ A liquid: Ferric chloride (FeCl ₃ .6H ₂ O) 20 g
Water 500cc
-B liquid; Sodium hydroxide 30g
Monoethanolamine 50cc
1000cc water

The above-mentioned A liquid and B liquid were hold | maintained at 12 degreeC, and A liquid was dripped in B liquid over about 1 hour, stirring. After completion of dropping, the mixture was further stirred for 1 hour. The precipitate thus obtained is allowed to stand at room temperature for about 20 hours, washed with pure water, adjusted to pH 11.3 by adding aqueous sodium hydroxide solution, and then at 150 ° C. using an autoclave. A 1 hour hydrothermal treatment was applied. By this treatment, plate-like goethite (αFeOOH) was obtained. Further, a sodium silicate solution was added to the goethite with stirring so as to be 1 wt% in terms of SiO ₂ , the pH was adjusted to 7.3 with hydrochloric acid, and coating treatment with SiO ₂ was performed. After filtering and drying, it was dehydrated by heating at 600 ° C. for 1 hour in air. By this heat treatment, plate-like α iron oxide (α-Fe ₂ O ₃ ) particles were obtained.

  The obtained α iron oxide particles were disk-to-hexagonal plates having an average particle diameter of 65 nm and plate-like particles having a hole with a diameter of about 30 nm near the center. Moreover, it turned out that it is an alpha hematite which has a corundum structure from an X-ray-diffraction spectrum.

  An electron micrograph of the iron oxide particles is shown in FIG. Moreover, about this iron oxide particle, the synthesis | combination conditions, the crystal structure investigated by X-ray diffraction, and the average particle diameter and shape calculated | required from the transmission electron micrograph are collectively shown in Table 5.

<Experimental example 29>
In Experimental Example 28, a precipitate was obtained in the same manner as in Experimental Example 28 except that the holding temperature of both liquids was dropped from 12 ° C. to 18 ° C. when the liquid A was dropped into the liquid B in the iron oxide particle synthesis step. And then hydrothermally treated. Next, heat dehydration treatment was performed in the same manner as in the experimental example to obtain a disc to hexagonal plate-like iron oxide particle having an average particle size of 90 nm and having pores. It was found from the X-ray diffraction spectrum that the iron oxide particles were alpha hematite having a corundum structure.

  An electron micrograph of the iron oxide particles is shown in FIG. Moreover, about this iron oxide particle, the synthesis | combination conditions, the crystal structure investigated by X-ray diffraction, and the average particle diameter and shape calculated | required from the transmission electron micrograph are collectively shown in Table 5.

<Comparative Example 6>
In Experimental Example 28, in the iron oxide particle synthesis step, liquid A was dropped into liquid B to prepare a precipitate, and then a coating treatment with SiO ₂ was performed without hydrothermal treatment, followed by filtration and drying. The mixture was heated and dehydrated at 600 ° C. for 1 hour.

  The iron oxide obtained by this heat treatment was granular with an average particle diameter of 60 nm, and a plate-like shape as in Experimental Example 28 and Experimental Example 29 was not obtained. About this iron oxide particle, the synthesis | combination conditions, the crystal structure investigated by X-ray diffraction, the average particle diameter calculated | required from the transmission electron micrograph, and a shape are put together in Table 5, and are shown.

(Transmission electron microscope observation results)
16 and 17 show transmission electron micrographs of the iron oxide particles produced in Experimental Examples 28 and 29, respectively. The iron oxide particles of Experimental Example 28 shown in FIG. 16 are plate-like particles having an average particle diameter of 65 nm, and the iron oxide particles of Experimental Example 29 shown in FIG. 17 have an average particle diameter of 90 nm. It can be seen that these are plate-like particles. All the particles have pores inside the particles. This is because when plate-like goethite particles obtained after hydrothermal treatment are heat-treated, pores are generated by dehydration. The shape of the pores generated by heating and dehydrating the plate-like hydroxide particles varies depending on the substance, such as those in which relatively large pores are produced from fine micropores like the plate-like iron oxide particles of the present invention. . However, it goes without saying that the formation of such holes does not impair the characteristics such as the abrasive properties of the plate-like particles of the present invention.

  As is apparent from Table 5, the iron oxide particles obtained in the above experimental examples have a corundum structure from the X-ray diffraction spectrum, and the shape is plate-like. The iron oxide particles having such a shape are realized for the first time by the present invention.

  On the other hand, the iron oxide particles of Comparative Example 6 are granular in shape and do not exhibit a plate-like shape as in the present invention. The particle diameter of the iron oxide particles of the present invention is not only suitable as an abrasive for polishing sheets and polishing liquids, but also as an additive particle for magnetic tape, and further as an additive particle for various functional sheets. It is in. Thus, the iron oxide particles having a plate-like shape and simultaneously realizing a fine particle size of 100 nm or less are unprecedented and open up a completely new application that has been considered impossible to realize in the past.

(6) Application Example to Polishing Tape Next, an example in which the plate-like oxide particles of the present invention are applied to a polishing tape as one example of a polishing body will be described. The polishing tape is produced by forming a polishing layer containing an abrasive on the surface of a film-like or sheet-like support, and then cutting the resulting laminate into a tape having a predetermined width. The only difference from the polishing sheet and the polishing film is the tape shape. Therefore, even when the plate-like oxide particles of the present invention are applied to an abrasive sheet or an abrasive film, the same results as in the following examples can be obtained.

<Experimental Examples 30 to 44, Comparative Examples 7 to 16>
A coating liquid for a polishing layer having the following composition was prepared using the plate-like oxide particles of the present invention and the oxide particles shown in the comparative example. The oxide particles used in this experiment were prepared by scaling up the experiment shown in Experimental Example 1 and the like (the same applies hereinafter). In the following experimental examples and comparative examples, “parts” means parts by weight.

<< Coating solution component for polishing layer formation >>
・ 200 parts of non-magnetic oxide particles ・ 30 parts of vinyl chloride-vinyl acetate copolymer (“VAGH” manufactured by UCC) ・ 25 parts of polyurethane resin (“Byron UR8300” manufactured by Toyobo) ・ 150 parts of methyl ethyl ketone ・ 150 parts of toluene・ Cyclohexanone 130 parts

  The above coating liquid components were stirred and mixed, and then dispersed by a sand mill to prepare a coating liquid for forming a polishing layer. This coating solution was applied to one side of a support made of a polyethylene terephthalate film having a thickness of 75 μm so that the thickness after calendering was 10 μm and dried. After being mirror-finished with a calendar, it was cut into a predetermined width to produce an abrasive tape.

  Table 6 shows the types of abrasive tapes produced and the main characteristics of the oxide particles used in those abrasive tapes.

  In the column of “Experimental Example / Comparative Example” in Table 6, the description of the experimental example and comparative example in the right column indicates that the oxide particles obtained in these experimental examples and comparative examples were used. Moreover, in Table 6, the polishing tapes of Comparative Example 8, Comparative Example 10, Comparative Example 12, Comparative Example 14 and Comparative Example 16 are commercially available cerium oxide particles, zirconium oxide particles, aluminum oxide particles, silicon oxide particles and oxides, respectively. Using iron particles, the same components and the same method as those for the coating liquid for forming the polishing layer described above were used. These oxide particles are commercially available oxide particles that are said to be fine particles, and have a spherical shape, a granular shape, or a cubic shape. In order to compare the polishing properties with the abrasive tape using the oxide particles having a plate shape, which is a feature of the present invention, an abrasive tape was prepared using these oxide particles.

  Using each of the polishing tapes shown in the above experimental examples and comparative examples, a glass scratch test was performed by the following method to evaluate the performance. The results were as shown in Table 7.

(Scratch test)
With both ends of the polishing tape fixed on a glass plate and water on the surface, using a surface property measuring machine ("HEIDON-14DR" manufactured by Shinto Kagaku Co., Ltd.), a sliding speed of 3000 mm / min, Under the conditions of a sliding scale of 20 mm and a load of 20 g, a glass ball having a diameter of 5 mm (manufactured by Nikato) is slid 100 times. Thereafter, the degree of wear of the glass sphere was observed with a microscope and evaluated in five stages. In the degree of wear, the larger the number, the greater the degree of wear. Further, the wear scar was evaluated by four stages by observing the glass sphere surface with a microscope. As for the wear scar, “×” indicates that there are 5 or more scratches on the surface, “△” indicates that there are 3 to 4 scratches, “○” indicates that there are 2 or less scratches, and indicates that no scratches occur. Evaluated as “◎”.

  From the results of Table 6 and Table 7, when compared with the same type of oxide particles, the abrasive tape using the plate-like oxide particles of the present invention and the particles that were heat-treated without the hydrothermal treatment of the comparative example The difference is clear with the polishing tape using the tape. That is, the polishing tape using the plate-like particles of the present invention is a well-balanced tape with few scratches while maintaining appropriate polishing properties, whereas the polishing tape using the particles of the comparative example, It can be seen that the larger the particle diameter, the higher the abrasiveness, but the degree of scratching is very large and it is not suitable for polishing tape.

  In addition, when a polishing tape is produced using commercially available oxide particles, which are said to be fine particles, of the same type of oxide, a polishing tape having a good balance between polishing properties and scratches can be obtained. However, compared with the abrasive tape using plate-like particles having a particle diameter in the range of 10 to 100 nm of the present invention, the abrasive sheet produced using commercially available oxide particles is inferior in overall properties. .

  This is probably because the commercially available oxide particles are granular, spherical or cubic, whereas the particles of the present invention are plate-like. That is, when the plate-like particle of the present invention is used, in addition to the polishing property using the edge portion of the plate-like particle, good contact property with the surface to be polished using the plate surface can be obtained. It is considered that excellent polishing ability was obtained.

  It is meaningless to compare the superiority or inferiority between the oxide particles of the present invention, but judging from the abrasiveness alone, aluminum oxide and zirconium oxide are relatively highly abrasive, and cerium oxide, iron oxide and silicon oxide Abrasiveness is relatively gentle. On the other hand, the degree of scratches tends to be opposite to the abrasiveness. Therefore, it is important to select the oxide particles according to the application, but when using any oxide particles, as described above, when using conventional granular, spherical or cubic oxide particles Compared to the above, the polishing tape using the plate-like oxide particles having a particle diameter in the range of 10 to 100 nm of the present invention is superior in overall characteristics.

  In the above experimental example, as an example of utilizing the excellent abrasiveness of the particles of the present invention, an example applied to a polishing sheet has been described. However, it is not always necessary to form a sheet, and it can be used as a polishing liquid or a polishing slurry. Needless to say. That is, by utilizing the unique shape of the nonmagnetic oxide particles of the present invention, excellent characteristics as abrasive particles are exhibited regardless of the final form.

  As described above, by using the plate-like cerium oxide, zirconium oxide, aluminum oxide, silicon oxide and iron oxide particles having a particle diameter of 10 to 100 nm according to the present invention, high polishing ability is maintained. However, it can be seen that a well-balanced polishing sheet with less generation of polishing scratches can be obtained.

(7) Application Example to Coating Type Magnetic Recording Medium (Magnetic Tape) Next, an example in which the plate-like oxide particles of the present invention are applied to the additive of the coating type magnetic tape as an example of the coating type magnetic recording medium. explain. In the following experimental examples and reference examples, “parts” means parts by weight.

<Experimental Examples 45-49, Reference Example 1>
《Coating component for undercoat layer》
(1)
・ Oxide particles (see Table 8 described later) 76 parts ・ Carbon black (average particle size: 25 nm, oil absorption: 55 g / cc) 24 parts ・ Stearic acid (lubricant) 2.0 parts ・ Vinyl chloride-hydroxypropyl acrylate Copolymer 8.8 parts (containing -SO ₃ Na group: 0.7 × 10 ^-4 equivalent / g)
Polyester polyurethane 4.4 parts (containing -SO ₃ Na group: 1.0 × 10 ^-4 equivalent / g)
・ Cyclohexanone 25 parts ・ Methyl ethyl ketone 40 parts ・ Toluene 10 parts (2)
・ Butyl stearate (lubricant) 1 part ・ Cyclohexanone 70 parts ・ Methyl ethyl ketone 50 parts ・ Toluene 20 parts (3)
・ Polyisocyanate (crosslinking agent) 2.0 parts ・ Cyclohexanone 10 parts ・ Methyl ethyl ketone 15 parts ・ Toluene

<Coating component for magnetic layer>
(1)
・ 100 parts of ferromagnetic iron-based metal powder [Co / Fe: 25 wt%,
Y / Fe: 9.3 wt%
Al / Fe: 3.5 wt%,
Ca / Fe: 0 wt%,
σs: 155 A · m ² / kg,
Hc: 188.2 kA / m,
pH: 9.4
Average long axis length: 0.10 μm]
-Vinyl chloride-hydroxypropyl acrylate copolymer 12.3 parts (contained -SO ₃ Na group: 0.7 × 10 ^-4 equivalent / g)
Polyester polyurethane resin 5.5 parts (containing -SO ₃ Na group: 1.0 × 10 ^-4 eq / g)
Α-alumina (average particle size: 0.12 m) 10.0 parts Carbon black 1.0 parts (average particle size: 75 nm, DBP oil absorption: 72 cc / 100 g)
-Metal acid phosphate 2 parts-Palmitic acid amide 1.5 parts-N-butyl stearate 1.0 parts-Tetrahydrofuran 65 parts-Methyl ethyl ketone 245 parts-Toluene 85 parts (2)
・ Polyisocyanate (crosslinking agent) 2.0 parts ・ Cyclohexanone 167 parts

After kneading (1) with the kneader in the above coating component for the undercoat layer, (2) is added, and after stirring, dispersion treatment is performed using a sand mill with a residence time of 60 minutes. After that, a paint for an undercoat layer was obtained. Separately, after kneading the above-mentioned magnetic layer coating component (1) with a kneader, it was dispersed with a sand mill with a residence time of 45 minutes, and after adding the magnetic layer coating component (2), stirring and filtering, A magnetic paint was used. And polyethylene naphthalate film (PEN, thickness 6.2 μm, humidity expansion coefficient = 5.6 × 10 ⁻⁶ /% RH, thermal expansion coefficient = (− 7.4) × 10 ⁻⁶ / ° C., MD = 6 .50 GPa, MD / TD = 0.54, manufactured by Teijin Ltd. Here, MD represents the Young's modulus in the film drawing direction (longitudinal direction), and TD represents the Young's modulus in the direction (width direction) orthogonal to the film drawing direction. The undercoat layer coating is applied to a non-magnetic support made of) so that the thickness after drying and calendering is 1.8 μm, and the above magnetic coating is further applied to the magnetic coating on the undercoat layer. The magnetic layer after orientation treatment, drying and calendering was applied by a wet-on-wet method so that the thickness of the magnetic layer was 0.15 μm, and after magnetic field orientation treatment, it was dried using a dryer to obtain a magnetic sheet. In the magnetic field orientation treatment, an NN counter magnet (5 kG) is installed in front of the dryer, and two NN counter magnets (5 kG) are spaced from each other at a distance of 50 cm from the front 75 cm of the dry coating position of the coating in the dryer. It was installed at. The coating speed was 100 m / min.

《Paint component for back coat layer》
Carbon black (average particle size: 25 nm) 80 parts Carbon black (average particle diameter: 370 nm) 20 parts Nitrocellulose 44 parts Polyurethane resin (containing SO ₃ Na group) 30 parts Cyclohexanone 260 parts Toluene 260 parts 525 parts of methyl ethyl ketone

  After dispersing the coating component for the backcoat layer in a sand mill with a residence time of 45 minutes, adding 13 parts of a polyisocyanate as a crosslinking agent to adjust the coating for the backcoat layer and filtering, the magnetic properties of the magnetic sheet prepared above On the opposite side of the layer, it was applied and dried so that the thickness after drying and calendering was 0.5 μm. The magnetic sheet thus obtained is mirror-finished with a seven-stage calendar made of a metal roll under the conditions of a temperature of 100 ° C. and a linear pressure of 150 × 9.8 N / cm (150 kg / cm). The film was aged at 70 ° C. for 72 hours in a state of being wound on the core.

  Next, using a slitting system, the original magnetic sheet was cut into a 1/2 inch wide magnetic tape. A magnetic tape cartridge (computer tape) for a computer was produced by winding this magnetic tape on a reel and incorporating it in the case body.

  The basic characteristics of computer tapes such as playback output characteristics, error rates, servo characteristics, etc. were evaluated for computer tapes manufactured in this way. An example in which characteristics are evaluated will be described. Since this off-track amount greatly depends on the characteristics of the nonmagnetic particles used for the undercoat layer, and when the various plate-like oxide particles of the present invention are used as the nonmagnetic particles for the undercoat layer, The amount of off-track was compared with the case where conventional acicular α-iron oxide particles were used. In this case, the off-track amount was measured by the following method.

(Measurement of off-track amount)
The off-track amount is recorded using a modified LTO drive (recording track width: 20.6 μm, reproduction track width: 12 μm) at a temperature of 10 ° C. and a humidity of 10% RH (recording wavelength 0.55 μm), and the temperature is 10 ° C. It was determined from the ratio of the reproduction output when regenerated at a humidity of 10% RH, a temperature of 29 ° C., and a humidity of 80% RH. When the recording track width was 80 μm and the reproduction track width was 50 μm, there was almost no decrease in output due to off-track (1% or less).

  Off-track in the state of magnetic tape for the case of using the plate-like oxide particles of the present invention and the case of using the conventional acicular α-iron oxide particles as the oxide particles used for the primer coating The results of measuring the amount are shown in Table 8.

  As is apparent from Table 8, when the non-magnetic oxide particles for the undercoat layer used in the present invention are particles having a particle size in the range of 10 to 100 nm and having a plate shape, The amount of off-track is small compared to the case of using needle-shaped oxide particles.

  In general, off-track is not so problematic when the recording track width is wide, but becomes prominent when the recording track becomes narrow. If the off-track becomes large, an off-track error occurs and normal servo cannot be performed. Such a problem occurs in common in both the magnetic servo system and the optical servo system, but the mass of the entire magnetic head array used in the optical servo system is larger than that in the magnetic servo system. This is even more remarkable.

  By using the plate-like oxide particles of the present invention, PES (standard deviation of positional deviation) is reduced, the recording track width is as narrow as 21 μm or less, and even when there is a temperature change, off-tracking is less likely to occur. A magnetic tape and a magnetic tape cartridge excellent in servo characteristics with a low error rate can be obtained.

  This is thought to be because the shape of the particles is plate-like and it is easy to arrange the plate surface in parallel with the coated surface in the coating film, and as a result, the anisotropy of the elastic modulus within the surface of the tape is small. It is done. At the same time, since the particle diameter is as small as 10 to 100 nm and has a plate-like shape, the surface area of the particles is large, and as a result, the magnetic tape is more firmly bonded to the binder, so that it has excellent thermal and mechanical deformation. This is probably because of

  In the above experimental example, the example in which the plate-like particles of the present invention are used for the undercoat layer has been described. However, the present invention is not limited to the undercoat layer, and the effect can be exhibited even when added to the magnetic layer or the back coat. Needless to say. That is, while these conventional nonmagnetic oxide particles are granular, plate-like needle-like or cubic, the non-magnetic oxide particles of the present invention utilize the plate-like shape which is the greatest feature. Thus, when used for a magnetic tape, a magnetic tape optimal for high-density recording with very little deformation due to temperature and humidity and mechanical deformation can be obtained.

  Furthermore, when added to the magnetic layer of the magnetic tape, not only the above-described tape with less thermal and mechanical deformation can be obtained, but also as an abrasive, as described in the experimental example of the polishing tape. . This action as an abrasive becomes more effective as the magnetic layer becomes thinner. That is, when the thickness of the magnetic layer is as thin as 0.1 μm or less, the granular or spherical particles that have been used as an additive so far project the magnetic layer surface and deteriorate the surface smoothness of the magnetic layer. On the other hand, since the non-magnetic oxide particles of the present invention have a plate-like shape with a particle diameter of 10 to 100 μm, the particles do not protrude from the surface of the magnetic layer, or even if they protrude, The degree and amount are much less than conventional ones. Therefore, excellent surface smoothness can be obtained while maintaining the polishing property.

(8) Application Example to Polishing Liquid Next, an example in which the plate-like oxide particles of the present invention are applied to the polishing liquid will be described.

<Experimental Example 50>
As the abrasive particles, the cerium oxide particles prepared in Experimental Example 1 were used, and a slurry-like polishing liquid was prepared as follows.

  To 300 cc of pure water, 3 g of polyacrylic acid ammonium salt was added and dissolved. To this aqueous solution, 24 g of the plate-like cerium oxide particles prepared by the above method was added and dispersed using a homomixer for 1 hour at a rotational speed of 3000 rpm. The obtained slurry polishing slurry was very stable, and almost no precipitate was formed after standing for 1 day.

<Experimental Example 51>
As the abrasive particles, the silicon oxide particles prepared in Experimental Example 22 were used, and a slurry-like polishing liquid was prepared as follows.

  Similar to Experimental Example 50, 24 g of the above silicon oxide particles were added to an aqueous solution in which 3 g of polyacrylic acid ammonium salt was dissolved in 300 cc of pure water, and a slurry-like polishing liquid was prepared in the same manner as in Experimental Example 50. This slurry-like polishing liquid was extremely stable, and hardly left a precipitate even after being left for one day.

<Experimental Example 52>
As the abrasive particles, the zirconium oxide particles prepared in Experimental Example 8 were used, and a slurry-like polishing liquid was prepared as follows.

  Similarly to Experimental Example 50, 24 g of the zirconium oxide particles were added to an aqueous solution obtained by dissolving 3 g of polyacrylic acid ammonium salt in 300 cc of pure water, and a slurry-like polishing liquid was prepared in the same manner as in Experimental Example 50. The slurry polishing slurry was very stable and hardly produced a precipitate even after being left for one day.

<Experimental Example 53>
As the abrasive particles, the aluminum oxide particles prepared in the above Experimental Example 15 were used, and a slurry-like polishing liquid was prepared as follows.

  Similarly to Experimental Example 50, 24 g of the aluminum oxide particles were added to an aqueous solution in which 3 g of polyacrylic acid ammonium salt was dissolved in 300 cc of pure water, and a slurry-like polishing liquid was prepared in the same manner as in Experimental Example 50. This slurry-like polishing liquid was extremely stable, and hardly left a precipitate even after being left for one day.

<Experimental Example 54>
Instead of the cerium oxide particles in Experimental Example 50, plate-like alpha-iron oxide particles produced by the following method were used.

<Preparation of plate-like alpha-iron oxide particles>
0.75 mol of sodium hydroxide and 100 ml of 2-aminoethanol were dissolved in 800 ml of water to prepare an alkaline aqueous solution. Apart from this alkaline aqueous solution, 0.074 mol of ferric chloride (III) hexahydrate was dissolved in 400 ml of water to prepare an aqueous ferric chloride solution. The alkaline aqueous solution and the ferric chloride aqueous solution were cooled to 5 ° C. The latter ferric chloride aqueous solution was dropped into the former alkaline aqueous solution. Although the temperature of the liquid rises due to the reaction heat due to this dropping, it was dropped while cooling so as not to rise to 8 ° C. or higher, and a precipitate containing ferric hydroxide was produced. The pH at this time was 11.3. This precipitate was aged in a suspension state for 20 hours, and then washed with water until the pH reached 7.5.

  Next, after removing the supernatant, the precipitate suspension was charged into an autoclave and hydrothermally treated at 150 ° C. for 2 hours.

  The hydrothermal treatment product was filtered, dried in air at 90 ° C., and then lightly crushed in a mortar, and heat-treated at 600 ° C. in air for 1 hour to obtain alpha iron oxide particles. After the heat treatment, in order to remove unreacted substances and residues, they were further washed with an ultrasonic disperser and filtered and dried.

  When the X-ray diffraction spectrum of the obtained alpha iron oxide particles was measured, the spectrum of the alpha hematite structure was clearly observed. Furthermore, when the shape was observed with a transmission electron microscope, it was found to be hexagonal plate-like particles having a particle diameter of 30 to 40 nm.

<< Preparation of slurry-like polishing liquid >>
Similarly to Experimental Example 50, 24 g of plate-like alpha iron oxide particles prepared by the above method was added to an aqueous solution in which 3 g of polyacrylic acid ammonium salt was dissolved in 300 cc of pure water. A slurry-like polishing liquid was prepared. This slurry-like polishing liquid was extremely stable, and hardly left a precipitate even after being left for one day.

<Comparative Example 17>
《Cerium oxide particles used as abrasive particles》
In place of the cerium oxide particles used in Experimental Example 50 (prepared in Experimental Example 1), cerium carbonate was used as the cerium salt, and this cerium salt was heated and oxidized in air at 600 ° C. to thereby obtain cerium oxide particles. Was made. Since the cerium oxide particles consisted of coarse particles having a submicron particle diameter, they were further pulverized by ball milling in an aqueous medium. The cerium oxide particles after pulverization were composed of fine particles having a particle size of 0.1 μm and particles having a particle size of 1 μm that seemed to be an aggregate of primary particles. The shape of the cerium oxide particles was a massive indefinite shape.

<< Preparation of slurry-like polishing liquid >>
As in Experimental Example 50, 24 g of the above cerium oxide particles were added to an aqueous solution in which 3 g of polyacrylic acid ammonium salt was dissolved in 300 cc of pure water, and a slurry-like polishing liquid was prepared in the same manner as in Experimental Example 50. . This slurry-like polishing liquid was unstable, and when left after dispersion, it began to settle in a short time, and cerium oxide particles were deposited on the bottom of the container.

<Comparative Example 18>
<< Silicon oxide particles used as abrasive particles >>
Commercially available colloidal silica particles were used. When observed with a transmission electron microscope, the shape of the colloidal silica particles was almost spherical, and the particle diameter was distributed over a range of 10 nm to 100 nm.

<< Preparation of slurry-like polishing liquid >>
Similarly to Experimental Example 50, 24 g of the above colloidal silica particles was added to an aqueous solution in which 3 g of polyacrylic acid ammonium salt was dissolved in 300 cc of pure water, and a slurry-like polishing liquid was prepared in the same manner as in Experimental Example 50. . This slurry-like polishing liquid was quite stable, and a slight amount of precipitate was formed when left for 1 day.

<Comparative example 19>
<< Zirconium oxide particles used as abrasive particles >>
The zirconium oxide particles of Comparative Example 2 were used. That is, in the method for synthesizing zirconium oxide particles of Experimental Example 8, a precipitate containing zirconium hydroxide was produced in the same manner as in Experimental Example 8 without generating hydrous heat treatment after forming a precipitate containing zirconium hydroxide. Was washed with water, filtered and dried as it was, and further heat-treated in the same manner as in Experimental Example 8 to produce zirconium oxide particles.

  When the X-ray diffraction spectrum of this zirconium oxide particle was measured, a peak corresponding to zirconium oxide was observed, but when the shape was observed with a transmission electron microscope, from a fine particle to a coarse particle due to sintering or agglomeration. The particle size distribution was found to be very wide.

  Therefore, in order to make the zirconium oxide particles fine, they were further ball milled in an aqueous medium. The pulverized zirconium oxide particles had a particle diameter distributed over a wide range from 0.1 μm to 1 μm. Further, the shape of the zirconium oxide particles was a blocky indefinite shape.

<< Preparation of slurry-like polishing liquid >>
Similarly to Experimental Example 50, 24 g of the above zirconium oxide particles were added to an aqueous solution in which 3 g of polyacrylic acid ammonium salt was dissolved in 300 cc of pure water, and a slurry-like polishing liquid was prepared in the same manner as in Experimental Example 50. . This slurry-like polishing liquid was unstable, and when it was left after dispersion, it began to settle in a short time, and zirconium oxide particles were deposited on the bottom of the container.

<Comparative Example 20>
<< Aluminum oxide particles used as abrasive particles >>
The aluminum oxide particles of Comparative Example 4 were used. That is, in the method for synthesizing aluminum oxide particles of Experimental Example 15, a precipitate containing aluminum hydroxide was generated under the same conditions as in Experimental Example 15, washed with about 1000 times water, and then subjected to hydrothermal treatment. Filtered and dried in air at 90 ° C. Thereafter, the mixture was lightly crushed in a mortar, and heat-treated at 600 ° C. in air for 1 hour as in Experimental Example 15 to obtain aluminum oxide particles. After the heat treatment, in order to remove unreacted substances and residues, they were further washed with an ultrasonic disperser and filtered and dried.

  The aluminum oxide particles were further ball milled in an aqueous medium. When the X-ray diffraction spectrum was measured for the ground aluminum oxide particles, a spectrum corresponding to γ-alumina was observed. Observation with a transmission electron microscope revealed that the particle size distribution was wide from fine particles with a diameter of about 20 nm to particles that seemed to be 1 μm sintered or aggregates of primary particles, and the particle shape was also indefinite, such as granular or massive. It was.

<< Preparation of slurry-like polishing liquid >>
Similarly to Experimental Example 53, 24 g of the above aluminum oxide particles were added to an aqueous solution in which 3 g of polyacrylic acid ammonium salt was dissolved in 300 cc of pure water, and a slurry-like polishing liquid was prepared in the same manner as in Experimental Example 53. . This slurry-like polishing liquid was unstable, and when it was allowed to stand after dispersion, it began to settle in a short time, and aluminum oxide particles were deposited on the bottom of the container.

<Comparative example 21>
《Alpha iron oxide particles used as abrasive particles》
Commercially available alpha iron oxide particles were used. These alpha-iron oxide particles are commercially available for added abrasive particles such as magnetic tape. The shape observed with a transmission electron microscope is spherical or granular, and the particle diameter is 0.2 μm to 0.3 μm. The particle size distribution was sharp.

<< Preparation of slurry-like abrasive >>
Similarly to Experimental Example 50, 24 g of the above-mentioned alpha iron oxide particles were added to an aqueous solution in which 3 g of polyacrylic acid ammonium salt was dissolved in 300 cc of pure water, and a slurry-like polishing liquid was prepared in the same manner as in Experimental Example 50. did. This slurry-like polishing liquid was relatively stable, and when it was allowed to stand for several hours, the generation of precipitates was small.

<Experimental Example 55>
<< Abrasive particles used >>
The cerium oxide particles used in Experimental Example 50 and the colloidal silica used in Comparative Example 18 were mixed and used. The mixing ratio was 70% for cerium oxide particles and 30% for colloidal silica by weight.

<< Preparation of slurry-like polishing liquid >>
Similar to Experimental Example 50, 16.8 g of the above cerium oxide particles and 7.2 g of colloidal silica were added to an aqueous solution in which 3 g of ammonium polyacrylate was dissolved in 300 cc of pure water. Thus, a slurry-like polishing liquid was prepared. This slurry-like polishing liquid was extremely stable, and even if it was left for 1 day, almost no precipitate was generated.

(Evaluation)
A porous polishing pad made of urethane resin was pasted on a glass plate having a thickness of 10 mm. A surface property measuring device (“HEIDON-14DR” manufactured by Shinto Kagaku Co., Ltd.) was used while dripping the slurry-like polishing liquid prepared in the above experimental examples and comparative examples on the pad at a rate of 10 cc / min. Then, a glass sphere having a diameter of 6.25 mm was rotated for 2 minutes under the conditions of a rotation speed of 30 times / minute and a load of 20 g. Thereafter, the degree of wear of the glass sphere and the wear mark on the surface of the glass sphere were observed with a microscope, and evaluated in four stages, “×”, “Δ”, “◯”, and “◎”. As for the degree of wear, “×” means almost no wear, “◎” means remarkable wear, “△” and “○” are intermediate states, and “○” means a greater degree of wear. It shows that. In addition, as for the wear scar, “x” when there are 5 or more scratches on the surface, “△” when there are 3 to 4 scratches, “○” when there are 2 or less scratches, and no scratches. Was evaluated as “◎”. Table 9 summarizes the evaluation results of the abrasiveness.

  From the results in Table 9, it can be seen that the slurry-like polishing liquid of the above experimental example has very good slurry stability. This is because the particles are not only as small as several tens of nanometers, but also have excellent dispersibility with almost no sintering or aggregation. The abrasiveness is good despite the small particle size. This is presumably because the edge portion increased by making the particle shape plate-like, and as a result, the polishing power was improved. Although some polishing power is slightly low, it is considered that the polishing power is further improved if the polishing conditions such as the number of rotations and the load are adjusted to the optimum conditions for the polishing liquid.

  Moreover, the abrasion trace by grinding | polishing has not generate | occur | produced in the polishing liquid of any experimental example. This is because the particle size is very fine, such as several tens of nm, and the particle size distribution is sharp, so that there are no wear marks caused by coarse particles mixed with fine particles unlike conventional abrasives. .

  On the other hand, in the polishing liquid of Comparative Example, the polishing liquid of Comparative Example 18 using colloidal silica is a balanced polishing liquid with relatively good polishing power and wear marks, but the same silicon oxide in terms of material. Compared with the polishing liquid of Experimental Example 51, the total is inferior.

  Further, the polishing liquid of Comparative Example 21 using alpha-iron oxide particles is also considered to be a relatively balanced polishing liquid, but since the hardness of the iron oxide itself is essentially low, the polishing power beyond this is high. I can't hope. On the other hand, the polishing liquid using the alpha-iron oxide particles of Experimental Example 54 of the present invention has a polishing power and a wear scar as compared with the polishing liquid of Comparative Example 21 due to the edge portion by making the shape of the polishing particles into a plate shape. Both have improved significantly.

  In the polishing liquid using the cerium oxide particles of Comparative Example 17, the polishing properties are relatively balanced, but the polishing liquid is not entirely satisfactory. On the other hand, in the polishing liquid of Experimental Example 50 of the present invention using the same cerium oxide particles, both the polishing power and the wear scars are greatly improved. As the slurry-like polishing liquid, the plate-like cerium oxide particles are particularly suitable. I understand that.

  In the polishing liquids of Comparative Example 19 using zirconium oxide particles and Comparative Example 20 using aluminum oxide particles, although the polishing power is large, wear marks are remarkably generated. This is because zirconium oxide and aluminum oxide are essentially hard and have a high polishing power, and the comparative zirconium oxide particles and aluminum oxide particles are considered to have produced significant wear marks due to the mixed coarse particles. It is done. On the other hand, in the polishing liquid of Experimental Example 52 using the plate-like zirconium oxide particles according to the present invention and Experimental Example 53 using the plate-like aluminum oxide particles, the particle shape is plate-like, the particle diameter is extremely small, and Since the particle size distribution is extremely sharp, an excellent polishing force can be exhibited without generation of wear marks.

  Furthermore, as shown in Experimental Example 55, by mixing and using the plate-like particles of the present invention and general-purpose abrasive particles, various types of objects to be polished can be dealt with finely.

(9) Other application examples In the above examples, the case where the nonmagnetic plate-like particle of the present invention is applied to a polishing tape, a magnetic tape, and a polishing liquid has been described. The oxide particles of the present invention can be applied not only to these applications but also to various functional optical films such as antireflection films, ultraviolet rays, and infrared cut films. That is, since the non-magnetic plate-like particles (particularly oxide particles) have a plate-like shape, the particles are easily arranged so that the plate surface is parallel to the film surface, and as a result, the light transmittance is improved. When light passes through the non-magnetic plate-like particles, the characteristics inherent to the non-magnetic plate-like particles are exhibited by the interaction between the light and the non-magnetic plate-like particles.

  For example, by stacking low refractive index silicon oxide particles and high refractive index zirconium oxide particles or cerium oxide particles, it is not possible to obtain with conventional granular or spherical oxide particles. A membrane is obtained. Moreover, when an iron oxide particle is used, an ultraviolet cut film with good permeability can be obtained. Furthermore, zirconium oxide particles and cerium oxide particles are high refractive index materials. However, when a highly filled coating film is formed using a plate-like shape, it is comparable to a thin film such as a sputtered film even though it is a coating film. A transparent coating film having a very high refractive index is obtained.

Claims (9)

Non-magnetic plate-like particles made of zirconium oxide having a hexagonal plate shape and a particle size in the plate surface direction of 10 to 100 nm. A method for producing the nonmagnetic plate-like particles according to claim 1,
Adding an aqueous solution of a zirconium salt to an aqueous alkaline solution to produce a precipitate containing zirconium hydroxide, and aging the precipitate in a suspension state to obtain a hydroxide or hydrate of zirconium;
And a step of heat-treating the obtained zirconium hydroxide or hydrate in the temperature range of 110 to 300 ° C. in the presence of water . A method for producing the non-magnetic plate-like particles according to claim 1,
Adding a zirconium salt aqueous solution to an alkaline aqueous solution to produce a precipitate containing zirconium hydroxide, and aging the precipitate in a suspension state to obtain a zirconium hydroxide or hydrate;
Heat treating the obtained hydroxide or hydrate of zirconium in the temperature range of 110 to 300 ° C. in the presence of water;
The heat treatment, the product obtained by the process, filtration, after drying, further preparation of a non-magnetic plate-shaped particles, characterized in that it comprises a step of heat treatment in a temperature range of 300 to 1200 ° C. in air Method. The method for producing nonmagnetic plate-like particles according to claim 3, wherein after the heat treatment in the temperature range of 300 to 1200 ° C in air, the product or residue other than the target zirconium oxide is further removed by washing with water . In the step of obtaining a zirconium hydroxide or hydrate by adding a zirconium salt aqueous solution to the alkaline aqueous solution to produce a precipitate containing zirconium hydroxide, and aging the precipitate in a suspension state.
The production of nonmagnetic plate-like particles according to any one of claims 2 to 4, wherein the pH of the suspension after formation of the hydroxide or hydrate of zirconium is adjusted to be in the range of 8-12. Method. Obtaining a hydroxide or hydrate of the zirconium;
The obtained zirconium hydroxide or hydrate is subjected to a heat treatment in the presence of water in a temperature range of 110 to 300 ° C.,
A step of removing a product or residue other than the zirconium hydroxide or hydrate to adjust the pH to a range of 7 to 10 by washing the hydroxide or hydrate of zirconium. The method for producing nonmagnetic plate-like particles according to any one of claims 2 to 5 . The pH of the suspension containing the obtained product is adjusted to a range of 6 to 9 after the step of heat treatment in the temperature range of 110 to 300 ° C in the presence of water. A method for producing the nonmagnetic plate-like particle according to claim 1. The nonmagnetic plate-like particle according to any one of claims 2 to 7, wherein the product obtained is further treated with a silicon compound after the heat treatment in the temperature range of 110 to 300 ° C in the presence of water. Production method. The method for producing nonmagnetic plate-like particles according to any one of claims 2 to 8, wherein the alkaline aqueous solution contains oxyalkylamine .

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