JP2003253153A - Water-resistant rare earth pigment - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a rare earth pigment improved in water resistance. <P>SOLUTION: The water-resistant rare earth pigment has a composition represented by A<SB>x</SB>B<SB>(0.5-x/2)</SB>LnM<SB>2</SB>O<SB>8</SB>. In the composition, 0<x≤1; A is at least one selected among alkali metals; B is at least one selected among alkaline earth metals; Ln is at least one selected among rare earth elements; and M is at least one selected from molybdenum and tungsten. <P>COPYRIGHT: (C)2003,JPO

Description

Detailed Description of the Invention

[0001]

TECHNICAL FIELD The present invention relates to a rare earth pigment having improved water resistance.

[0002]

2. Description of the Related Art Since inorganic pigments are excellent in heat resistance and weather resistance, they are used in high-temperature molding materials such as engineering plastics and construction materials, paints, paints, ceramics, and so on. Further, since rare earth elements have unpaired electrons in the 4f orbit, they are used in pigments and light emitting materials.

[0003]

However, many of the inorganic pigments contain heavy metals and transition metals, and when these metal ions flow out, there is a risk of affecting the environment and the human body. Especially, the use of pigments containing cadmium and lead is severely restricted. In order to solve this problem, a yellow pigment using a rare earth element has been researched and developed and proposed. However, this compound has a problem that it is weak in water resistance because it contains an alkali metal ion. In addition, since it contains an alkali metal ion, there is a risk that the alkali metal ion may elute under outdoor use or in an environment where water is present, which poses a problem that the range of use is limited.

The present invention has been made in order to solve the above problems, and reduces the content of alkali metal ions highly soluble in water while maintaining the crystal structure, and conventional inorganic pigments are used. It is an object of the present invention to provide a water resistant rare earth pigment which is useful in various fields such as coloring of general resins and engineering plastic resins, paints, inks, ceramics, building materials, and fields used as light emitting materials.

[0005]

[Means for Solving the Problems] As a result of preparing and examining compounds having various compositions in order to achieve the above object, the present inventors have found that the composition is A _x B _{(0.5-x / 2)} LnM ₂ O ₈ It was clarified that the rare earth compound represented by the formula (3) gives a color unique to the rare earth ion, and that the water resistance can be improved by reducing the content of the alkali metal.

The water resistant rare earth pigment according to the present invention is ALnM ₂ O.
₈ (A in the composition is at least one selected from the group consisting of alkali metals, Ln is at least one selected from rare earth elements, and M is at least one selected from molybdenum and tungsten. The water resistance can be increased by substituting the alkaline earth metal of (1)) with an alkaline earth metal.

That is, the water resistant rare earth pigment according to the present invention has a composition of A _x B _{(0.5-x / 2)} LnM ₂ O ₈ (where 0 <x ≤ 1,
A is at least one selected from alkali metals (Li, Na, K, Rb, Cs, Fr), and B in the composition is from alkaline earth metals (Ca, Sr, Mg, Ba, Be, Ra). At least one chosen
Ln is at least one selected from the group consisting of rare earth elements).

The above A _x B _{(0.5-x / 2)} LnM ₂ O ₈ (where 0 <x ≦
1, A in the composition is at least 1 selected from alkali metals
B is at least one selected from alkaline earth metals, Ln is at least 1 selected from rare earth elements
And M is at least one selected from molybdenum and tungsten).
Solid phase reaction method, precipitation method, hydrothermal synthesis method, glycothermal method,
A sol-gel method, a spray pyrolysis method and the like are conceivable, but the method is not limited to either method. Further, when firing is carried out, the target compound can be obtained by firing at 500 ° C. to 1300 ° C. in the solid phase reaction method, but a structure of A _x B _{(0.5-x / 2)} LnM ₂ O ₈ is generated. The firing temperature is not limited as long as it is the firing temperature and the holding time.

[0009]

BEST MODE FOR CARRYING OUT THE INVENTION Embodiments of the present invention will be described below with reference to the following examples.

[0010]

Example 1 In the composition A _x B _{(0.5-x / 2)} LnM ₂ O ₈ , lithium (Li) was used as the alkali metal of A, calcium (Ca) was used as the alkaline earth metal of B, and the rare earth element of Ln was used. Li _x Ca _{(0.5-x / 2)} CeM ₂ O ₈ is formed by using cerium (Ce) as
Stoichiometric ratios of lithium carbonate (Li ₂ CO ₃ ), calcium carbonate (CaCO ₃ ), x = 0, 0.25, 0.50, 0.75, 1.0
Molybdenum oxide (MoO ₃ ) and cerium oxide (CeO ₂ ) were accurately weighed and uniformly mixed using a ball mill to prepare a raw material mixture. Next, the obtained raw material mixture was put into an alumina crucible and fired at a temperature of 600 ° C. to 900 ° C. for 6 hours. The obtained calcined product was sufficiently crushed in an alumina mortar to obtain the target compound.

It has been found that a high firing temperature is required due to an increase in the amount of calcium (Ca) blended. LiCeMo
₂ O ₈ can obtain a single phase at 600 ℃, but Ca _0.5 CeMo ₂ O ₈ is 90
Baking above 0 ° C was required. The obtained compound is LiC
Since it showed the same X-ray diffraction pattern as eMo ₂ O ₈ , it was confirmed that they had the same crystal structure. And FIG.
As shown in Fig. 5, when compared with cadmium sulfide (CdS) in the spectral reflectance curve, Ca _0.5 CeMo ₂ O ₈ shows weak absorption at a wavelength of less than 550 nm, but exhibits a reflectance comparable to that of cadmium sulfide at a wavelength of 550 nm or more. . Ca _0.5 CeMo ₂ O ₈ has a brightness of 64.7.
%, Stimulation purity 75.7%, main wavelength 579.0 nm, a bright yellow color, and it was found to be useful as an inorganic pigment by improving the water resistance by reducing the content of alkali metal elements.

[0012]

Example 2 Similar to Example 1 above, the composition A _x B _{(0.5-x / 2)} L
In nM ₂ O ₈ , lithium (Li) as the alkali metal of A
, Calcium (Ca) as alkaline earth metal of B, L
Li _x Ca using europium (Eu) as the rare earth element of n
_{(0.5-x / 2)} EuM ₂ O ₈ is composed, and calcium carbonate (CaCO ₃ ), molybdenum oxide (MoO ₃ ), europium oxide (Eu ₂ O _{8 )} are formed in a stoichiometric ratio so as to be Ca _0.5 EuMo ₂ O _{8. 3} ) was accurately weighed and uniformly mixed in ethanol using a ball mill to prepare a raw material mixture. Next, the obtained raw material mixture,
It was placed in an alumina crucible and baked at a temperature of 900 ° C. for 6 hours.
The obtained calcined product was sufficiently crushed in an alumina mortar to obtain the target compound.

Since it has not been registered in the ICDD card yet,
Although the product could not be identified, it is considered to have the same structure as shown in FIG. 4, because it shows the same X-ray diffraction pattern as the compound using cerium (Ce) as the rare earth element in Example 1 described above. To be From this, it was confirmed that Ca _0.5 EuMo ₂ O ₈ was generated. As a result of measuring this compound with a spectrofluorometer, red emission having a peak at 615 nm was observed as shown in FIG. Further, as shown in FIG. 2, sharp excitation bands having peaks at 361 nm, 381 nm, 394 nm, 415 nm, 464 nm, and 535 nm were confirmed, and light sources having these wavelengths, for example, ultraviolet LED, blue LED, green LED,
It can be suitably used for a cathode tube and the like.

[0014]

Example 3 In the composition A _x B _{(0.5-x / 2)} LnM ₂ O ₈ , lithium (Li) is used as the alkali metal of A, calcium (Ca) is used as the alkaline earth metal of B, and a rare earth element of Ln is used. Li _x Ca _{(0.5-x / 2)} NdM ₂ O ₈ is formed by using neodymium (Nd) as a material, and calcium carbonate (CaCO ₃ ) and molybdenum oxide are used in a stoichiometric ratio so that Ca _0.5 NdMo ₂ O ₈ is obtained. (MoO ₃ ) and neodymium oxide (Nd ₂ O ₃ ) were accurately weighed and uniformly mixed in ethanol using a ball mill to prepare a raw material mixture. Next, the obtained raw material mixture was put into an alumina crucible and 900
It was baked at a temperature of ° C for 6 hours. The obtained calcined product was sufficiently crushed in an alumina mortar to obtain the target compound.

Since it has not been registered in the ICDD card yet,
Although the product could not be identified, as shown in FIG. 4, the compound showed the same X-ray diffraction pattern as the compound using cerium (Ce) of Example 1 and europium (Eu) of Example 2. It is considered to have the same structure. Then, as a result of measuring the spectral reflectance with a spectrophotometer, as shown in FIG.
A partial absorption band due to Nd ³⁺ ions was confirmed. From this, it can be easily inferred that when this pigment is used for a filter, the transmittance of the three primary colors of light, blue, green, and red, is high, and intermediate colors (blue-green, yellow, etc.) are easily absorbed. Therefore, when it is used for a display such as a liquid crystal, a color television, an EL display, and a PDP, it is possible to enhance the contrast and it can be effectively used.

[0016]

Example 4 Molybdenum oxide (MoO ₃ ), cerium oxide (CeO ₂ ), and Ca _0.5 CeMo ₂ O ₈ having a stoichiometric composition
Accurately weigh calcium oxide (CaCO ₃ ), Ca _0.5 CeMo ₂ O
₈ diammonium hydrogen phosphate to _{((NH 4) 2 HPO 4} ) 0m
It was added in an ol% to 20 mol% external formulation. These reagents were uniformly mixed in ethanol using a ball mill to prepare a raw material mixture. Next, the obtained raw material mixture was put into an alumina crucible and baked at a temperature of 900 ° C. for 6 hours. The obtained calcined product was sufficiently crushed in an alumina mortar to obtain the target compound.

The compound obtained was analyzed by X-ray diffraction in Example 1.
The compound has the same X-ray diffraction pattern as the compound using cerium (Ce) as the rare earth element, and it is confirmed that it has the same crystal structure. The spectral reflectance increased from 600 nm to 700 nm, and the hue shifted to the reddish direction. From this, it was found that the addition of phosphorus (P) can increase the reflectance from 600 nm to 700 nm and shift the hue in the reddish direction. The results are shown in [Table 1].

[0018]

[Table 1]

[0019]

As described above, according to the water resistant rare earth pigment of the present invention, no harmful substances are contained, high coloring power or luminescence intensity is obtained, and conventional inorganic pigments are used. For example, it is possible to provide a yellow pigment useful in the fields of coloring of general resins and engineering plastic resins, paints, inks, ceramics, building materials or light-emitting materials, displays, etc., and also to reduce water resistance by reducing the content of alkali metal elements. Can be improved.

[Brief description of drawings]

FIG. 1 is a graph showing the spectral reflectance of the compound according to Example 1.

FIG. 2 is a graph showing the excitation wavelength and the emission wavelength of the compound according to Example 2.

FIG. 3 is a graph showing the spectral reflectance of the compound according to Example 3.

FIG. 4 is a graph showing X-ray diffraction patterns of the compounds according to Examples 1 to 3.

Claims (6)

[Claims] 1. A water resistant rare earth pigment having a composition represented by A _x B _{(0.5-x / 2)} LnM ₂ O ₈ . However, 0 <x ≦ 1, A in the composition is at least one selected from alkali metals, B is at least one selected from alkaline earth metals, and Ln is at least 1 selected from rare earth elements. M is at least one selected from molybdenum and tungsten. 2. The water resistant rare earth pigment according to claim 1, wherein calcium is used as the alkaline earth metal. 3. The water resistant rare earth pigment according to claim 1, wherein cerium is used as the rare earth element. 4. The water resistant rare earth pigment according to claim 1, wherein europium is used as the rare earth element. 5. The water resistant rare earth pigment according to claim 1, wherein neodymium is used as the rare earth element. 6. The water resistant rare earth pigment according to any one of claims 1 to 5, wherein an element other than the constituent elements is added.