JP4077211B2 - Method for producing fine neodymium oxide - Google Patents

Description

[0001]
BACKGROUND OF THE INVENTION
The present invention relates to a process for producing a fine oxide neodymium.
[0002]
[Prior art]
Neodymium oxide (Nd ₂ O _3), such as by utilizing specific light absorption ability and electrical characteristics of it, glass purple colorant, laser materials have been used such as cell Rami' click electric material or a permanent magnet . In recent years, it has been known that the absorption position (wavelength) of this compound improves the separation of the emission spectra of G (green) and R (red) phosphors of displays such as CRT and PDP (plasma display). It can also be applied to other flat panel displays such as LCD (liquid crystal), FED (field emission display), and organic EL (electroluminescence) displays for neutral gray.
[0003]
[Problems to be solved by the invention]
However, neodymium oxide is produced by converting the neodymium content concentrated from a rare earth chloride solution by a solvent extraction method into an oxalate salt and firing it at 1000 ° C. in an oxygen atmosphere. Finer particles having a size as large as μm were not obtained. Therefore, when such a neodymium oxide having a large particle diameter is applied to a film and the transmitted color is observed, the incident light is considerably shielded and cannot be used for an application using the transmitted color.
[0004]
When the transmitted color is measured, neodymium oxide shows a unique spectral curve and relatively strong absorption around 580 nm. This absorption is known to improve the separation of the emission spectrum of G (green) and R (red) phosphors of displays such as CRT and PDP, and increase the contrast of the entire screen. Utilizing this, the neodymium oxide can be applied to other flat panel displays such as LCDs, FEDs, and organic EL displays.
[0005]
However, for that purpose, neodymium oxide is required to have good light transmittance, and a fine particle size is required. In addition, since neodymium oxide is microparticulated to improve the reactivity when mixed with other components, uniformity of the composition can be obtained by firing at a lower temperature, so glass colorants, ceramic materials and electrical materials can be obtained. It can be used for materials.
[0006]
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 diameter which has not been conventionally available.
As a result of various studies to achieve the above-mentioned object, the present inventors have synthesized neodymium oxide by a wet method and adjusted the precipitation conditions and the aging conditions to obtain fine neodymium oxide particles that have not existed before. The present invention has been completed.
[0007]
[Means for Solving the Problems]
According to the present invention, as neodymium was added dropwise at the same time precipitation medium solution and an alkaline solution of salts, the range of 7 to 10 the pH of the precipitation medium during dropping at the same time precipitation medium neodymium salt solution and an alkaline solution and then, the generated precipitate was heat digestion, drying and then pulverizing, neodymium oxide an average particle diameter of 0.2μm or less, the production method of fine neodymium oxide BET specific surface area, wherein to Rukoto and 20 m ² / g or more Provided.
[0008]
DETAILED DESCRIPTION OF THE INVENTION
Next, the present invention will be described in more detail.
The fine neodymium oxide (neodymium) of the present invention can be obtained by simultaneously dropping a neodymium salt solution and an alkaline solution onto a precipitation medium and heat aging the resulting precipitate.
As raw materials used in the production of fine neodymium oxide in the present invention, commercially available neodymium salts such as chlorides, nitrates, carbonates and oxalates can be used, and these neodymium salts are dissolved in water. used. It is also possible to use neodymium oxide by dissolving it in various inorganic acids. In any case, if it is completely dissolved, it can be used without any problem. If the pure content of the raw material is about 99%, it can be used sufficiently. As the alkaline solution used for neutralization, for example, a commonly used alkaline aqueous solution such as caustic soda, sodium carbonate, sodium bicarbonate, and ammonia can be used. Further, water is usually used as the precipitation medium.
[0009]
In order to obtain fine neodymium oxide, first, as described above, a neodymium salt or neodymium oxide is dissolved in water or an inorganic acid, and a neodymium salt solution diluted with about 7 to 15% by weight and an alkali solution are added to the precipitation medium in water. At the same time to precipitate hydrous neodymium. Although depending on the synthesis scale, 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 precipitate tends to agglomerate, and if it is low, the texture of the fine neodymium oxide powder obtained tends to deteriorate. The temperature of precipitation is preferably in the range of 40 to 100 ° C, more preferably in the range of 40 to 90 ° C. When the temperature is near room temperature, the texture of the fine neodymium oxide powder obtained becomes poor and becomes difficult to disperse and becomes opaque. However, in any case, the texture of the fine neodymium oxide powder obtained by the heat aging described below tends to be improved.
[0010]
Next, the hydrous neodymium slurry solution precipitated as described above is heated to age the hydrous neodymium, so that it can be completely crystallized as neodymium oxide to form fine particles. In this case, the aging temperature is preferably in the range of 50 to 100 ° C. If the aging temperature is too low, the texture of the fine neodymium oxide powder obtained is deteriorated. A maturing time of about 1 hour is sufficient, and if it is too long, energy is wasted.
[0011]
The fine neodymium oxide synthesized in this manner is sufficiently washed with decantation or the like until the conductivity of the washing water becomes 300 μs / cm or less in order to remove by-produced salts. After washing with water, a fine powder of neodymium oxide is filtered and dried in a cake state, for example, at 120 ° C. for about 12 hours. Thus neodymium oxide particles obtained are mortar, pot was triturated with other conventional grinding means, fine particles of interest, i.e., the average particle diameter of 0.2μm or less, more preferably 0.1μm or less Thus, fine neodymium oxide having a BET specific surface area of 20 m ² / g or more can be obtained.
The obtained neodymium oxide fine powder can be further improved in crystallinity by heat treatment, but clearly becomes opaque when the heat treatment temperature is 300 ° C. or higher, and the desired fine neodymium oxide with excellent light transmittance is obtained. Because it disappears, attention is necessary.
[0012]
【Example】
Hereinafter, the present invention will be described more specifically with reference to examples and comparative examples. In the following text, “parts” are based on weight unless otherwise specified. The average particle size of neodymium oxide is a value measured using a centrifugal sedimentation particle size distribution measuring device.
[0013]
Example 1
Dissolve 78.5 parts of commercially available neodymium oxide in about 110 parts of concentrated nitric acid, add 500 parts of water to the solution, dilute the neodymium nitrate solution, and dissolve 57 parts of caustic soda as alkali for precipitation neutralization in 600 parts of water. The alkali solutions thus prepared were adjusted, and these solutions were simultaneously added dropwise to 1700 parts of precipitation water prepared in advance. At this time, the precipitation pH was 8.0, and the precipitation temperature was 25 ° C. A light whitish pink precipitate is formed simultaneously with the start of the dropwise addition of both solutions, and the pink becomes darker with time. The dripping was completed in about 40 minutes. After completion of the dropping, aging was performed at 80 ° C. for 1 hour.
[0014]
After aging, the resulting precipitate was washed repeatedly with decantation until the conductivity of the supernatant water reached 300 μs / cm or less. Thereafter, the neodymium oxide cake obtained by filtration was dried at 120 ° C. for 12 hours, and the obtained dried powder was pulverized by a pot mill to obtain fine neodymium oxide. This product had a slightly dark pink color, an average particle diameter of 0.1 μm, a BET specific surface area of 22 m ² / g, and dispersibility was not so bad.
In order to see the light transmission characteristics of the obtained neodymium oxide, it was dispersed in a melamine alkyd resin at a ratio of 30 PHR, and applied to a transparent PET film with a thickness of 100 μm at a thickness of about 10 μm. The evaluation of characteristics was performed by visual observation and measuring a spectral transmittance curve with a wavelength of 400 to 700 nm.
As a result, the visible transmittance was quite good and the back was seen through, the transmittance of the spectral transmittance curve was about 70% on average, and the absorption at 580 nm was relatively strong.
[0015]
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 had an average particle size of 0.08 μm, a BET specific surface area of 31 m ² / g, a slightly dark pink color, good dispersibility, and transmission by a color development test similar to that in Example 1. The transmittance of the spectral transmittance curve increased to about 90% on average.
Spectral transmittance curves and particle size distribution diagrams compared with a commercial product (average particle size 2.5 μm) are shown in FIG. 1 and FIG. The particle size distribution was measured using a particle size distribution measuring apparatus by centrifugal sedimentation, but the sample was pre-dispersed in advance according to a normal procedure and used for the measurement.
[0016]
Example 3
Precipitation 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 slightly hardened state immediately after drying, and a darker pink color than the other examples. . The dispersibility was reasonable, and the transmittance by the color development test similar to that of Example 1 was also relatively good, and the transmittance of the spectral transmittance curve was about 80% on average. Further, the absorption at 580 nm was relatively strong.
[0017]
Example 4
Fine neodymium oxide was prepared 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, permeability and absorption at 580 nm of this product were the same as those of the fine neodymium oxide of Example 2.
[0018]
【The invention's effect】
With the above invention, therefore transparency miniaturization is assigned to neodymium oxide, fine neodymium oxide is not in the conventional neodymium oxide, with a high transmittance, transmission of a relatively strong absorption at a wavelength of around 580nm A spectrum was shown, and these characteristics made it possible to apply fine neodymium oxide to various uses.
More specifically, fine neodymium oxide uses the relatively strong absorption near 580 nm in its transmission spectrum, for example, emission spectra of G (green) and R (red) phosphors of displays such as CRT and PDP. Can be used to improve the separation of the screen and increase the contrast of the entire screen. Moreover, it can be applied to a flat panel display such as LCD, FED, organic EL and the like for neutral gray using the above characteristics. In addition, since the reactivity when mixed with other components is increased by making fine particles, uniformity of the composition is easily obtained by firing at a lower temperature, and for glass colorants, ceramic materials, electrical materials, etc. It can be used.
[Brief description of the drawings]
FIG. 1 shows transmission spectra of fine neodymium oxide of Example 2 and commercially available neodymium oxide.
FIG. 2 shows the particle size distribution of fine neodymium oxide of Example 2 and commercially available neodymium oxide.

Claims (2)

The neodymium salt solution and the alkaline solution are simultaneously dropped onto the precipitation medium, and when the neodymium salt solution and the alkaline solution are simultaneously dropped onto the precipitation medium, the pH of the precipitation medium is in the range of 7 to 10, and the resulting precipitate is heated and aged. , dried and pulverized, neodymium oxide an average particle diameter of 0.2μm or less, the production method of fine neodymium oxide BET specific surface area, wherein to Rukoto and 20 m ² / g or more. Method for producing a fine neodymium oxide according to claim 1, heating aging temperature is in the range of 50 to 100 ° C..

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