JP2003238153A - Fine neodymium oxide and method for producing the same - Google Patents

Abstract

(57) [Problem] To provide neodymium oxide having a fine particle size which has not been conventionally provided. SOLUTION: A fine neodymium oxide powder having an average particle size of 0.2 μm or less and a BET specific surface area of 20 m ² / g or more and a solution of a neodymium salt and an alkaline solution are simultaneously dropped into a precipitation medium, and the resulting precipitate is heated and aged. A method for producing fine neodymium oxide, characterized by comprising:

Description

Detailed Description of the Invention

[0001]

TECHNICAL FIELD The present invention relates to fine neodymium oxide and a method for producing the same.

[0002]

_2. Description of the Related Art Neodymium oxide (Nd ₂ O ₃ ) is used in purple colorants for glass, laser materials, ceramic electrical materials, permanent magnets, etc., due to its unique light absorption ability and electrical characteristics. Has been done. In recent years, the absorption position (wavelength) of this compound is known to improve the separation of the emission spectra of G (green) and R (red) phosphors in displays such as CRTs and PDPs (plasma displays). It is also applicable to other flat panel displays such as LCD (liquid crystal), FED (field emission display) and organic EL (electroluminescence) display for neutral gray.

[0003]

However, neodymium oxide is prepared by converting a neodymium component, which is concentrated from a rare earth chloride solution by a solvent extraction method, into an oxalate salt, and the neodymium oxide is mixed in an oxygen atmosphere at 100
Since it was produced by firing at 0 ° C., the particle size after pulverization was as large as several μm, and finer particles could not be obtained. Therefore, when neodymium oxide having such a large particle size is applied to a film and the transmitted color is observed, the incident light is considerably shielded, and it cannot be used for applications utilizing the transmitted color.

When the transmitted color is measured, neodymium oxide shows a unique spectral curve and exhibits a relatively strong absorption near 580 nm. It is known that this absorption improves the separation of the emission spectra of the G (green) and R (red) phosphors of a display such as a CRT or PDP and improves the contrast of the entire screen. Use neodymium oxide for other flat panel displays such as LC
Application to D, FED, organic EL display, etc. is also possible.

However, for that purpose, neodymium oxide needs to have a high light transmittance, and a fine particle size has been demanded. In addition, since neodymium oxide is made into fine particles, the reactivity when mixed with other components is improved, so that uniformity of composition can be obtained by lower temperature firing,
It can be used as a coloring agent for glass, a material for ceramics and an electric material.

The present invention has been made in consideration of such a situation, and an object of the present invention is to provide neodymium oxide having a fine particle size which has never been obtained. We have
As a result of various studies to achieve the above-mentioned object, it was found that fine neodymium oxide particles which have never existed can be obtained by synthesizing neodymium oxide by a wet method and adjusting the precipitation conditions and aging conditions. .

[0007]

According to the present invention, the average particle size is 0.2 μm or less and the BET specific surface area is 20 m ² / g.
A method for producing fine neodymium oxide is provided, in which the solution of the fine neodymium oxide powder and the neodymium salt and the alkaline solution are simultaneously added dropwise to the precipitation medium, and the resulting precipitate is heat-aged.

[0008]

BEST MODE FOR CARRYING OUT THE INVENTION The present invention will now be described in more detail. The fine neodymium oxide (neodymium) of the present invention can be obtained by simultaneously dropping a solution of a neodymium salt and an alkaline solution into a precipitation medium and aging the resulting precipitate by heating. As the raw material used for the production of fine neodymium oxide in the present invention, commercially available neodymium salts, for example, chlorides, nitrates, carbonates, oxalates and the like can be used, and these neodymium salts are dissolved in water. used. It is also possible to dissolve neodymium oxide in various inorganic acids before use. In any case, if it is completely dissolved, it can be used without any problem, and if the pure content of the raw material is about 99%,
It is fully usable. As the alkali solution used for neutralization, for example, an aqueous solution of a commonly used alkali such as caustic soda, sodium carbonate, sodium bicarbonate, and ammonia can be used. Water is usually used as the precipitation medium.

To obtain fine neodymium oxide, first, the neodymium salt or neodymium oxide is dissolved in water or an inorganic acid as described above, and a neodymium salt solution and an alkaline solution diluted to about 7 to 15% by weight are precipitated. At the same time, it is dropped into water as a medium to precipitate neodymium hydroxide. Although depending on the scale of synthesis, both solutions are usually added dropwise in about 30 minutes to 1 hour.
The pH of the precipitation medium during precipitation of hydrous neodymium is 7-10.
If the pH is too high, the precipitates tend to agglomerate, and if the pH is too low, the texture of the obtained fine neodymium oxide powder tends to be poor. The temperature of precipitation is 40 to 1
The range of 00 ° C is preferable, and more preferably 40 to 90.
It is in the range of ° C. At around room temperature, the texture of the obtained fine neodymium oxide powder deteriorates, making it difficult to disperse and becoming opaque. However, in any case, the texture of the fine neodymium oxide powder obtained by the heat aging described below tends to be improved.

Next, by heating the hydrous neodymium hydroxide slurry solution deposited as described above and aging the hydrous neodymium hydroxide, this is completely crystallized as neodymium oxide to form fine particles. You can The aging temperature at this time is preferably in the range of 50 to 100 ° C., and if the aging temperature is too low, the texture of the obtained fine neodymium oxide powder becomes poor. A maturing time of about 1 hour is sufficient,
If it is too long, it wastes energy.

The fine neodymium oxide synthesized in this manner is sufficiently washed by decantation or the like to remove the by-produced salts until the electric conductivity of the washing water becomes 300 μs / cm or less. After washing with water, the fine neodymium oxide powder slurry is filtered and in a cake state, for example, 120
Dry at ℃ for about 12 hours. The neodymium oxide particles thus obtained are crushed with a mortar, pot mill, or other ordinary crushing means, and the desired fine particles, preferably having an average particle size of 0.2 μm or less, more preferably 0.1 μm.
Below, fine neodymium oxide having a BET specific surface area of 20 m ² / g or more can be obtained. Although the crystallinity of the obtained neodymium oxide fine powder can be further improved by heat treatment, it becomes apparently opaque at a heat treatment temperature of 300 ° C. or higher, and the desired fine neodymium oxide excellent in light transmittance can be obtained. You need to be careful because it will disappear.

[0012]

EXAMPLES The present invention will be described more specifically with reference to Examples and Comparative Examples below. The "parts" in the following text are based on weight unless otherwise specified. The average particle size of neodymium oxide is a value measured using a centrifugal sedimentation method particle size distribution measuring device.

Example 1 78.5 parts of commercially available neodymium oxide was dissolved in about 110 parts of concentrated nitric acid, and 500 parts of water was added to this solution to dilute the solution, and caustic soda 57 was used as an alkali for precipitation neutralization.
Part of water was prepared by preliminarily preparing an alkaline solution prepared by dissolving 600 parts of water in 600 parts of water.
It was added dropwise to 0 part at the same time. At this time, the precipitation pH was 8.0 and the precipitation temperature was 25 ° C. A pale whitish pink precipitate is formed at the same time when the above two solutions are started to be added, and the pink color becomes darker with time. The dropping was completed in about 40 minutes. After the completion of dropping, aging was carried out at 80 ° C. for 1 hour.

After aging, the obtained precipitate was repeatedly washed by decantation until the electric conductivity of the supernatant water was 300 μs / cm or less. After that, the neodymium oxide cake obtained by filtration is dried at 120 ° C. for 12 hours,
The obtained dry powder was ground with a pot mill to obtain fine neodymium oxide. This one has a slightly dark pink color,
The average particle size is 0.1 μm and the BET specific surface area is 22 m ² /
At g, the dispersibility was acceptable. In order to examine the light transmission characteristics of the obtained neodymium oxide, it was dispersed in a melamine alkyd resin at a ratio of 30 PHR to give a transparent 1
It is applied to a PET film with a thickness of 00 μm to a thickness of about 10 μm, and the transmittance and spectral characteristics are evaluated visually and at wavelengths of 400 to 7
This was done by measuring the spectral transmission curve at 00 nm. As a result, the visual transmittance was fairly good, the rear part was transparent, the transmittance of the spectral transmittance curve was about 70% on average, and the absorption at 580 nm was relatively strong.

Example 2 A fine neodymium oxide powder was obtained in the same manner as in Example 1 except that the precipitation temperature was 50 ° C. and the aging temperature was 80 ° C.
The obtained fine powder has an average particle size of 0.08 μm and BET
It has a specific surface area of 31 m ² / g, has a slightly deep pink color, has good dispersibility, has good transmittance in the same color development test as in Example 1, and has an average transmittance of the spectral transmittance curve. 9
It rose to about 0%. Commercial product (average particle size 2.5μ
The spectral transmittance curve and the particle size distribution chart in comparison with m) are shown in FIGS. 1 and 2. The particle size distribution was measured using a particle size distribution measuring device by the centrifugal sedimentation method, and the sample was predispersed in advance according to the usual procedure and used for the measurement.

Example 3 Precipitated neodymium oxide powder was obtained in the same manner as in Example 1 except that the precipitation temperature was 50 ° C., the precipitation pH was 10.5, and the aging temperature was 80 ° C. The obtained fine powder had an average particle size of 0.09 μm, a BET specific surface area of 26 m ² / g, a state of being slightly hardened immediately after drying, and a darker pink color than those of the other examples. . The dispersibility was fair, and the transparency in the same color development test as in Example 1 was relatively good.
The transmittance of the spectral transmittance curve was about 80% on average.
The absorption at 580 nm was relatively strong.

Example 4 Fine neodymium oxide was produced in the same manner as in Example 2 except that the nitric acid solution of neodymium oxide was replaced with an aqueous solution of neodymium chloride. The average particle size, BET specific surface area, color, dispersibility, transmittance and absorption at 580 nm of this product were the same as those of the fine neodymium oxide of Example 2.

[0018]

According to the present invention described above, transparency is imparted to neodymium oxide by miniaturization, and fine neodymium oxide is
High transmittance, 580 nm, not found in conventional neodymium oxide
It showed a transmission spectrum showing a relatively strong absorption in the vicinity wavelength, and these characteristics made fine neodymium oxide applicable to various applications. More specifically, fine neodymium oxide takes advantage of its relatively strong absorption near 580 nm in its transmission spectrum, for example, in CRT and PDP.
It can be used to improve the separation of the emission spectra of the G (green) and R (red) phosphors of the display, and to increase the contrast of the entire screen. Further, by utilizing the above characteristics, it can be applied to flat panel displays such as LCDs, FEDs and organic ELs for neutral gray. Also, by making it finer,
Since the reactivity when mixed with other components is increased, it is easy to obtain compositional uniformity in lower temperature firing, a glass colorant,
It can also be used for ceramic materials, electrical materials, etc.

[Brief description of drawings]

FIG. 1 shows transmission spectra of fine neodymium oxide of Example 2 and commercially available neodymium oxide.

FIG. 2 shows particle size distributions of fine neodymium oxide of Example 2 and commercially available neodymium oxide.

   ─────────────────────────────────────────────────── ─── Continued front page    (72) Inventor Hiromi Terada             1-7-6 Nihonbashi Bakurocho, Chuo-ku, Tokyo Large             Within Nissei Chemical Co., Ltd. F-term (reference) 4G076 AA02 AB18 BA13 BA45 BD01                       BD02 CA26 DA07 DA30

Claims (3)

[Claims] 1. A fine neodymium oxide powder having an average particle size of 0.2 μm or less and a BET specific surface area of 20 m ² / g or more. 2. A method for producing fine neodymium oxide, which comprises simultaneously dropping a solution of a neodymium salt and an alkaline solution into a precipitation medium, and aging the formed precipitate by heating. 3. The method for producing fine neodymium oxide according to claim 2, wherein the heat aging temperature is in the range of 50 to 100 ° C. 4. The solution of the neodymium salt and the alkaline solution are simultaneously added dropwise to the precipitation medium. PH of precipitation medium is 7-10
The method for producing fine neodymium oxide according to claim 2, wherein