JP2000087033A - Production of phosphor - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a process for inexpensively producing a cerium-activated yttrium aluminate phosphor having a high purity and a homogeneous chemical composition, having a narrow particle size distribution, a low agglomerate content, and excellent sphericity, and suited for the formation of a homogenous dense high-luminance fluorescent film for e.g. a cathode-ray tube, a fluorescent lamp, PDP(plasma display panel) or FED(field emission display). SOLUTION: This process comprises: preparing an aqueous solution containing yttrium, cerium, and aluminum; introducing the solution in the form of liquid drops carried by a gas into a thermal cracking reactor; heating the feed at a temperature range of 600-1,900 deg.C for an in-oven residence time of 1 sec to 10 min, and further heating it at a temperature range of 950-1,450 deg.C for 1 sec to 24 hr.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

The present invention relates to a cathode ray tube, a fluorescent lamp, a plasma display panel (PDP), and
The present invention relates to a method for producing a cerium-activated yttrium aluminate phosphor that can be used for a field emission display (FED) and the like.

[0002]

2. Description of the Related Art A cathode ray tube, a fluorescent lamp, a PDP, and
Conventionally, composite oxide phosphors used in FEDs and the like are prepared by mixing a raw material powder into a firing vessel such as a crucible and then heating the mixture at a high temperature for a long time to cause a solid-phase reaction, which is then converted to a ball mill or the like. It has been manufactured by finely pulverizing.

[0003] However, the phosphor produced by this method is composed of powder in which irregularly shaped particles are aggregated. When this phosphor is used for the above-mentioned purpose, the phosphor film obtained by coating is inhomogeneous. In this case, the light-emitting characteristics were low because the packing density was low. In addition, physical and chemical impacts are applied to the phosphor during the fine pulverization treatment by a ball mill or the like after the solid-phase reaction, so that defects are generated in the particles or on the surface, and the luminous intensity is reduced. Was. Furthermore, since the mixture is placed in a firing vessel such as a crucible and heated at a high temperature for a long time, the emission characteristics may be reduced due to the contamination of impurities from the crucible, or the solid phase reaction may sufficiently proceed depending on the particle size of the raw material powder. However, the impurity phase may be mixed and the emission characteristics may be deteriorated. Further, since the energy consumed when heating at a high temperature for a long time is large, the manufacturing cost of the phosphor has been increased.

[0004]

SUMMARY OF THE INVENTION The present invention has been made to solve the above problems, and has a narrow particle size distribution, a small amount of agglomerated particles, and a spherical shape.
When used in fluorescent lamps, PDPs, and FEDs, it is possible to form a uniform and dense high-luminance fluorescent film,
In addition, it is an object of the present invention to provide a method for inexpensively producing a cerium-activated yttrium aluminate phosphor having excellent emission characteristics because of its high purity and uniform chemical composition.

[0005]

The present invention has succeeded in solving the above-mentioned problems by adopting the following constitution. (1) An aqueous solution containing yttrium, cerium and aluminum is prepared, and the aqueous solution is dropped into a pyrolysis reaction furnace together with a carrier gas, and 600 to 190
After heating for 1 second to 10 minutes in the furnace at a temperature range of 0 ° C., and further heating at a temperature range of 950 to 1450 ° C. for 1 second.
A method for producing a cerium-activated yttrium aluminate phosphor, wherein the phosphor is heated again in a range of seconds to 24 hours.

(2) The method for producing a cerium-activated yttrium aluminate phosphor according to the above (1), wherein yttrium nitrate, cerium nitrate, and aluminum nitrate are used as raw materials for the yttrium, cerium, and aluminum.

(3) The cerium-activated aluminum according to (1) or (2), wherein the mixing ratio of yttrium, cerium, and aluminum in preparing the aqueous solution is adjusted to the range of the following formula. Method for producing yttrium oxide phosphor. 0.54 ≦ (My + Mc) /Ma≦0.66 0.001 ≦ Mc / (My + Mc) ≦ 0.1 (wherein, My, Mc, and Ma indicate the number of moles of yttrium, cerium, and aluminum, respectively) .)

(4) The method for producing a cerium-activated yttrium aluminate phosphor according to (3), wherein the mixing ratio of yttrium and cerium in preparing the aqueous solution is adjusted within the range of the following formula: . 0.005 ≦ Mc / (My + Mc) ≦ 0.02 (5) The solute concentrations C of yttrium, cerium, and aluminum in the aqueous solution are adjusted to be within the range of the following formulas (1) to (4). ) The method for producing a cerium-activated yttrium aluminate phosphor according to any one of the above. 0.01 ≦ C ≦ 5 (where C is １ ／ of the total number of moles of yttrium, cerium, and aluminum contained in 1 liter of the aqueous solution)
It is. )

(6) The aqueous solution is introduced into the furnace in the form of droplets using ultrasonic waves.
(5) The method for producing a cerium-activated yttrium aluminate phosphor according to any one of the above (5).

[0010]

BEST MODE FOR CARRYING OUT THE INVENTION Hereinafter, the present invention will be described in more detail. In the method for producing a phosphor of the present invention, at least yttrium, cerium, and a raw material used for preparing an aqueous solution containing aluminum are soluble in water, such as salts and organometallic compounds containing these elements. ,
In addition, any material can be used as long as it is a material that undergoes a decomposition reaction to an oxide when heated to a high temperature. However, in order to facilitate the synthesis of the phosphor, a raw material that is easily decomposed by heating, such as yttrium nitrate, cerium nitrate, or aluminum nitrate, is preferable. In addition, in order to obtain good emission characteristics, a raw material containing a small amount of an impurity element such as iron or nickel which serves as a killer center is preferable.

The mixing ratio of yttrium, cerium, and aluminum when preparing the aqueous solution is within a range represented by 0.54 ≦ (My + Mc) /Ma≦0.66 0.001 ≦ Mc / (My + Mc) ≦ 0.1. Then, a phosphor having good emission characteristics can be obtained. Here, My, Mc, and Ma represent the number of moles of yttrium, cerium, and aluminum, respectively. Further, when the mixing ratio of yttrium and cerium is set to 0.005 ≦ Mc / (My + Mc) ≦ 0.02, a phosphor exhibiting better emission characteristics can be obtained.

[0012] These raw materials are put into water and stirred to be sufficiently dissolved. The element concentration in the solution is adjusted according to the diameter of a droplet formed by ultrasonic spraying or the like with respect to the diameter of a desired phosphor particle. That is, if the ratio of the droplet diameter to the phosphor particle diameter is large, the solute concentration in the solution is lowered, and if the ratio is small, the solute concentration is adjusted high. In order to synthesize a good phosphor, the solute concentration C of yttrium, cerium, and aluminum in the aqueous solution is preferably in the range of 0.01 ≦ C ≦ 5. Here, C is 1/8 of the total mole number of yttrium, cerium, and aluminum contained in 1 liter of the aqueous solution.

When a small amount of flux is added to an aqueous solution, phosphor particles having high crystallinity are generated in a short time at a relatively low temperature during the thermal decomposition reaction. Therefore, the flux is dissolved in the aqueous solution in advance. Is also good. The formation of the droplets can be performed by various spraying methods. For example, a method of forming droplets of 1 to 50 μm by spraying while sucking up liquid with pressurized air, a method of forming droplets of 4 to 10 μm using ultrasonic waves of about 2 MHz from a piezoelectric crystal, a hole diameter A method in which a 10-20 μm orifice is vibrated by a vibrator, and a liquid supplied to the orifice at a constant speed is discharged from a hole by a constant amount according to the frequency to form a 5-50 μm droplet, A method in which a liquid is dropped at a constant speed on a circular plate and a droplet of 20 to 100 μm is formed from the liquid by centrifugal force, and a high voltage is applied to the surface of the liquid to form a droplet of 0.5 to 10 μm. The method of occurrence can be adopted. For the production of terbium-activated yttrium silicate phosphors having a uniform particle size on the order of submicron to micron which can be used for cathode ray tubes, fluorescent lamps, PDPs, FEDs, etc. A spraying method using ultrasonic waves capable of forming droplets of 10 μm to 10 μm is preferable.

The formed droplets are introduced into a pyrolysis reaction furnace by a carrier gas and heated to become phosphor particles. Due to factors that affect the heating rate, such as the type of solution, the type of carrier gas, the flow rate of the carrier gas, and the temperature in the pyrolysis reactor, they are formed as hollow spheres, porous, clogged particles, crushed particles, etc. The morphology and surface state of the particles change. As the carrier gas, air, nitrogen, argon, hydrogen, or the like can be used. In order to activate trivalent cerium and obtain good emission characteristics, a neutral or reducing gas such as nitrogen, argon, or hydrogen is used. preferable.

[0015] The pyrolysis reaction is carried out at a temperature in the range of 600 ° C to 1900 ° C. If the pyrolysis reaction temperature is too low,
The reaction does not proceed sufficiently. On the other hand, if the thermal decomposition reaction temperature is too high, unnecessary energy is consumed. The pyrolysis reaction is 1
It is preferable to carry out with a residence time in the range of not less than seconds and not more than 24 hours. If the reaction time is too short, the reaction does not proceed sufficiently. On the other hand, if the reaction time is too long, unnecessary energy is consumed.

After the step of heating in the thermal decomposition reaction furnace, the temperature is further increased to 950 ° C. to 1450 ° C. for 1 second or more for 24 seconds.
The reheating treatment is performed for a time within the range of the time or less. If the reheating temperature is too low or the time is too short, the crystallinity is low and cerium is not activated in the crystal, so that the light emission characteristics are low. On the other hand, if the temperature is too high or the time is too long, a large number of agglomerated particles will be generated, so that the fluorescent film will not be formed densely when formed, and desired light emitting characteristics cannot be obtained.

[0017]

The present invention will be described in more detail with reference to the following examples. (Example 1) The chemical composition of the phosphor is (Y _0.99 Ce _0.01 ) 3
Yttrium nitrate, cerium nitrate, and aluminum nitrate were dissolved in water to obtain Al ₅ O _12, and a small amount of nitric acid was added to prepare a homogeneous solution having a solute concentration of 0.4 mol / liter. This liquid was placed in an ultrasonic atomizer having a 1.7 MHz vibrator to form droplets, and the droplets were introduced into a tubular furnace maintained at a maximum temperature of 900 ° C. using nitrogen as a carrier gas. A thermal decomposition reaction was performed for 1.6 seconds to synthesize precursor particles. The particles were allowed to stand in a muffle furnace and reheated at 1300 ° C. for 5 hours in the atmosphere to obtain a phosphor. When the powder X-ray diffraction pattern of the obtained phosphor was examined, a crystal of (Y _0.99 Ce _0.01 ) 3Al ₅ O ₁₂ showing good crystallinity was formed in a single phase as shown in FIG. I was The shape of the particles was spherical with uniform particle size as shown in the scanning electron micrograph of FIG. 2, and the average particle size was 0.62 μm. When the emission spectrum was measured under irradiation of ultraviolet rays at 254 nm, the emission intensity of the main emission peak observed at a wavelength of 527 nm was 194, indicating that good green emission was exhibited.

Example 2 A phosphor was synthesized under the same conditions as in Example 1 except that the reheating temperature was changed to 1400 ° C. The obtained phosphor showed good crystallinity. The shape of the particles was spherical with uniform particle diameter, and the average particle diameter was 0.62 μm. 25
When the emission spectrum was measured under the same conditions as in Example 1 under irradiation with 4 nm ultraviolet light, the emission intensity of the main emission peak observed at a wavelength of 527 nm was 297, indicating that good green emission was exhibited.

Example 3 A phosphor was synthesized under the same conditions as in Example 2 except that the solute concentration of the aqueous solution was changed to 0.03 mol / L. The obtained phosphor showed good crystallinity. The shape of the particles was spherical with a uniform particle size, and the average particle size was 0.48 μm. When the emission spectrum was measured under the same conditions as in Example 1 under irradiation of ultraviolet rays at 254 nm, it was found that the emission intensity of the main emission peak observed at a wavelength of 527 nm was 181 and good green emission was exhibited.

Example 4 Example 2 was the same as Example 2 except that the solute concentration of the aqueous solution was changed to 1.5 mol / L.
A phosphor was synthesized under the same conditions as described above. The obtained phosphor is
It showed good crystallinity. The shape of the particles was spherical with a uniform particle size, and the average particle size was 1.2 μm. The emission spectrum was measured under the same conditions as in Example 1 under irradiation of ultraviolet rays at 254 nm. As a result, it was found that the emission intensity of the main emission peak observed at a wavelength of 527 nm was 256, indicating good green emission.

Comparative Example 1 A phosphor was synthesized under the same conditions as in Example 1 except that the reheating temperature was changed to 900 ° C. Although the obtained phosphor has a spherical shape with uniform particle diameter, as shown in FIG.
_0.99 Ce _0.01 ) In addition to 3Al ₅ O ₁₂ crystals, YAM and Y
It was found that other crystals indicated by AP were mixed. 254
When the emission spectrum was measured under the same conditions as in Example 1 under irradiation with ultraviolet light of nm, the emission intensity was extremely low.

Comparative Example 2 A phosphor was synthesized under the same conditions as in Example 1 except that the reheating treatment was not performed. The obtained phosphor was spherical with uniform particle size, but had extremely low crystallinity as shown in FIG. 2 (3). When the emission spectrum was measured under the same conditions as in Example 1 under irradiation of ultraviolet rays at 254 nm, no emission was observed.

Comparative Example 3 A phosphor was synthesized under the same conditions as in Example 1 except that the reheating temperature was changed to 1600 ° C. The resulting phosphor was irregularly shaped particles with very strong aggregation.

[0024]

According to the present invention, a cathode ray tube, a fluorescent lamp, a PDP, and a FE can be obtained by adopting the above-mentioned structure because the particle size distribution is narrow, the agglomerated particles are small, and the shape is spherical.
A cerium-activated yttrium aluminate phosphor that can form a uniform and dense high-brightness fluorescent film when used for D, etc., and has excellent emission characteristics because of its high purity and uniform chemical composition. It has become possible to provide an inexpensive manufacturing method.

[Brief description of the drawings]

FIG. 1 is a diagram showing powder X-ray diffraction patterns of phosphors obtained in Example 1 and Comparative Examples 1 and 2.

FIG. 2 is a scanning electron micrograph of the phosphor obtained in Example 1.

 ──────────────────────────────────────────────────続 き Continuing on the front page (72) Inventor Takashi Komiya 4267 Saijocho, Higashihiroshima-shi, Hiroshima Green Forest A-23 (72) Inventor Kikuo Okuyama 2-21-15 Mikadai, Kawachinagano-shi, Osaka (72) Invention Person Katsuaki Park 107-701 F-term (reference) 4H001 CA06 CA07 CF01 XA08 XA13 XA39 YA58

Claims (6)

[Claims] An aqueous solution containing yttrium, cerium and aluminum is prepared, and the aqueous solution is introduced into a pyrolysis reactor in the form of droplets together with a carrier gas.
Cerium characterized by heating at a temperature in the range of 0 to 1900 ° C. for the residence time in the furnace for 1 second to 10 minutes, and then heating again in a temperature range of 950 to 1450 ° C. in the range of 1 second to 24 hours. A method for producing an activated yttrium aluminate phosphor. 2. The method for producing a cerium-activated yttrium aluminate phosphor according to claim 1, wherein yttrium nitrate, cerium nitrate, and aluminum nitrate are used as a raw material of said yttrium, cerium, and aluminum. 3. The cerium-activated yttrium aluminate phosphor according to claim 1, wherein the mixing ratio of yttrium, cerium, and aluminum in preparing the aqueous solution is adjusted to the range of the following formula. Manufacturing method. 0.54 ≦ (My + Mc) /Ma≦0.66 0.001 ≦ Mc / (My + Mc) ≦ 0.1 (wherein, My, Mc, and Ma indicate the number of moles of yttrium, cerium, and aluminum, respectively) .) 4. The method for producing a cerium-activated yttrium aluminate phosphor according to claim 3, wherein a mixing ratio of yttrium and cerium in preparing the aqueous solution is adjusted to the range of the following formula. 0.005 ≦ Mc / (My + Mc) ≦ 0.02 5. The aqueous solution of yttrium, cerium,
The method for producing a cerium-activated yttrium aluminate phosphor according to any one of claims 1 to 4, wherein the solute concentration C of aluminum is adjusted within the range of the following equation. 0.01 ≦ C ≦ 5 (where C is 1 of the total number of moles of yttrium, cerium, and aluminum contained in 1 liter of the aqueous solution)
/ 8. ) 6. The method according to claim 1, wherein the aqueous solution is introduced into the furnace in the form of droplets using ultrasonic waves.
The method for producing a cerium-activated yttrium aluminate phosphor according to any one of the above.