JP2002194347A - Fluorescent substance, method for producing the same and luminous device - Google Patents

Abstract

PROBLEM TO BE SOLVED: To obtain a fluorescent substance having a raised sphericity so that luminous characteristics can be improved and to provide a method for producing the fluorescent substance by which the fluorescent substance can readily be mass-produced at a low cost. SOLUTION: This fluorescent substance is characterized by comprising many particles prepared by spray-drying a solution containing a fluorescent substance component and then baking the resultant particles and having >=0.95 average value of the sphericity represented by 4πA/L2 when the perimeter of respective particles of a projected image is L and the real area of the projected image is A. The fluorescent substance is produced by spray-dispersing the solution containing the fluorescent substance component, preparing droplets, bringing the resultant droplets into contact with hot air, drying the droplets, providing spherical raw material particles and further baking the obtained raw material particles at 900-1200 deg.C temperature.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a phosphor and a method for producing the same, and more particularly, to a phosphor having a higher sphericity so as to improve emission characteristics, and a phosphor at a low cost and easily. The present invention relates to a manufacturing method that can be mass-produced.

[0002]

2. Description of the Related Art A light emitting device in which a fluorescent film containing a phosphor powder having a predetermined composition is integrally formed on the inner surface of a light emitting surface (translucent airtight container) such as a display screen is known as a CRT (cathode ray tube), FED ( Widely used as field emission display), PDP (plasma display panel), Hg lamp, Xe lamp and the like.

[0003] The conventional phosphor powders used in the light emitting device, component compounds and the active agent constituting the phosphor (reaction promoter) and the about 1200 to 1300 ° C. The raw material mixture formulated with a predetermined ratio It is manufactured by baking at a temperature of and a solid phase reaction. However, since the phosphor particles remain baking is formed into nodular by sintering operation, suitable for practical use phosphor particles after firing was pulverized to have a predetermined particle size phosphor powder It has been.

However, the phosphor powder synthesized and prepared as described above often has a particle shape reflecting the crystal structure of the phosphor, and the particle shape is slightly controlled by additives such as a reaction accelerator. Stay as much as possible. For this reason, the phosphor powder obtained by the conventional synthesis method generally has a large proportion of powder having an irregular shape, making it difficult for the light emission characteristics to become uniform, and also causing the particle surface to be damaged during the pulverization process, thereby lowering the light emission efficiency. there was easy problem to have.

[0005] In order to prevent the emission characteristics from being degraded by the phosphor powder having the irregular shape, for example, Japanese Patent Application Laid-Open No. 2000-2000.
As disclosed in Japanese Patent No. 96048 and Japanese Patent Application Laid-Open No. 2000-109825, a method of obtaining a phosphor powder having an improved sphericity by pulverizing a raw material mixture of a phosphor through a pyrolysis reactor has been tried. . Specifically, an aqueous solution containing the components of the terbium-activated yttrium aluminate phosphor is introduced into the thermal decomposition reactor in the form of droplets,
After heating in a high temperature range of 600 to 1750 ° C, reheating is further performed in a temperature range of 1050 to 1750 ° C.

[0006]

However, in the conventional synthesis method using a thermal decomposition reactor as described above, it is necessary to heat the raw material mixture to a high temperature of 600 ° C. or more during the thermal decomposition. low energy efficiency because it is a manufacturing process that consumes thermal energy, there is a fatal problem that the manufacturing cost of the phosphor powder rises significantly. In addition, in order for the pyrolysis reaction to proceed uniformly, it is necessary to control the operation of the pyrolysis reactor with high accuracy,
There has been a problem that the operation management and handling of the manufacturing apparatus become extremely complicated.

[0007] The present invention has been made to solve the above problems, in particular an inexpensive phosphor and the phosphor enhanced sphericity as capable of improving light emission properties, and easily It is an object of the present invention to provide a manufacturing method which can be mass-produced.

[0008]

Means for Solving the Problems In order to achieve the above object, the present inventors have studied various methods for producing a phosphor capable of increasing the sphericity of the phosphor powder. As a result, particularly when the solution containing the phosphor component is spray-dried into substantially spherical raw material particles and fired at a temperature capable of maintaining the shape of the raw material particles, a phosphor powder having particularly excellent sphericity is obtained. , Inexpensively and easily obtained. The present invention has been completed based on the above findings.

That is, the phosphor according to the present invention is composed of a large number of particles obtained by spray-drying a solution containing the phosphor component and then sintering. The peripheral length of the projected image of each particle is L, and the actual area of the projected image is L. Where A is the average value of the sphericity expressed by 4πA / L ² is 0.95 or more.

In the above phosphor, it is preferable that the phosphor is a manganese-activated zinc silicate phosphor.

Further, the method for producing a phosphor according to the present invention comprises:
A solution containing the phosphor component is spray-dispersed to prepare droplets, and the resulting droplets are contacted with hot air and dried to form spherical raw material particles. The raw material particles are further heated to a temperature of 900 to 1200 ° C.
In and firing.

Further, in the above manufacturing method, the temperature of the hot air is preferably 200 ° C. or less, and the phosphor is preferably a manganese-activated zinc silicate phosphor.

Further, the light emitting device according to the present invention is characterized in that the light emitting layer containing the above-mentioned phosphor is formed integrally with the inner surface of the light-transmitting airtight container.

Although the composition of the phosphor targeted by the present invention is not particularly limited, when the phosphor is a manganese-activated zinc silicate phosphor, the sphericity is particularly high, and the phosphor film is When configured, a phosphor powder having excellent emission characteristics can be obtained.

When the manganese-activated zinc silicate phosphor is manufactured, the following silicate compound, zinc compound and activator (activator) are used. That is, as the silicate compound, silicon alkoxide such as methyl orthosilicate or ethyl orthosilicate or colloidal silica can be used. As the zinc compound, alkoxides and esters of zinc can be used in addition to soluble salts such as zinc nitrate, zinc acetate, zinc chloride, and zinc sulfate. Further, a manganese compound or the like can be used as the activator. As the manganese compound, in addition to soluble salts such as manganese nitrate, manganese acetate, manganese chloride, and manganese sulfate, any of manganese alkoxides and esters can be used.

The phosphor having a true spherical shape according to the present invention is:
It is prepared by the following procedures. First silicate compound in a solvent, zinc compounds, prepared as phosphor ingredient material constituting dissolving or dispersing the by raw material solution, such as active agents. As the solvent, water, alcohols such as methanol and ethanol, and saturated hydrocarbons such as n-hexane can be suitably used.

If the amount of dissolution or dispersion of each component material is too large, it becomes difficult to perform the spraying treatment described below.
It is preferable that each component material is dissolved or dispersed in 2 to 6 liters of a solvent according to the stoichiometric composition required for producing the phosphor of the present invention.

[0018] If the concrete is prepared manganese activated zinc silicate phosphor, a water-soluble zinc, silicon, manganese compounds, for example Zn, readily compounds that may be of element ions in chloride or water Mn It is dissolved in pure water and the composition formula Zn ₂ SiO ₄ : Mn (Mn content is
0.03 to 0.12 mol based on Zn ₂ SiO ₄ matrix
%), Ethyl silicate weighed in stoichiometric ratio is added, and a small amount of nitric acid is further added. Next, a sufficient amount of Zn, M was added by sufficiently stirring until the ethyl silicate was completely dissolved.
An aqueous solution containing n and Si is prepared.

Next, the raw material solution prepared as described above is sprayed and dispersed to prepare spherical droplets. Spraying / dispersing devices (particulateizers) include atomizers using ultrasonic vibration, atomizing devices using a rotating disk, and other general-purpose atomizers, as well as the use of pressurized atomizing gas to generate liquid. It is also effective to use a finely dispersed pressurized two-fluid nozzle.

By controlling the pressure of the atomizing gas supplied to the pressurized two-fluid nozzle and the liquid supply amount, it is possible to adjust the particle size of the droplets in the range of 0.5 to 50 μm. The particle size of the droplet varies depending on the size of the phosphor powder finally formed, but is preferably adjusted to about 2 to 8 μm.

Next, the generated spherical droplets are sent to a drying chamber filled or circulated with hot air heated to a predetermined temperature. In order to increase the thermal efficiency, it is preferable that the atomizing device for generating droplets is directly connected to the drying chamber. The droplets sent to the drying chamber are dried by contacting with hot air to become spherical raw material particles.

Here, the temperature of the hot air for drying the droplets is 2
The temperature is preferably set to 00 ° C. or lower. The hot air temperature is 20
If the temperature exceeds 0 ° C., cracks and defects are likely to be generated on the surface of the raw material particles, the surface roughness of the particles is likely to be rough, the phosphor characteristics are easily deteriorated, and the heat energy cost is greatly increased. By setting the hot air temperature to 200 ° C. or lower, raw material particles having a small surface roughness and few defects can be obtained, and the energy efficiency at the time of producing the phosphor is greatly improved.

Next, the phosphor powder according to the present invention is efficiently produced by firing the obtained spherical raw material particles in the air or in a non-oxidizing atmosphere at a temperature in the range of 900 to 1200 ° C. If the firing temperature is too low, less than 900 ° C., the crystallinity is low and Mn is not activated in the crystal, so that the light emission characteristics are reduced. On the other hand, if the firing temperature is excessively into to exceed 1200 ° C., on the firing while maintaining a true spherical shape of the raw material particles becomes difficult, sphericity of the phosphor is reduced, thermal energy The cost increases, and the production cost of the phosphor tends to increase.

As described in the above manufacturing method, the phosphor according to the present invention is composed of a large number of particles which are obtained by spray-drying a solution containing the phosphor component and then firing, and the peripheral length of the projected image of each particle is L. And 4π when the actual area of the projected image is A
Mean values of sphericity R represented by A / L ² is equal to or is less than 0.95.

The packing density of a phosphor is greatly affected by the particle shape and size of the phosphor in a phosphor film used for a light emitting device such as various displays and lamps. If the particle shape of the phosphor is truly spherical, specifically, if the average value of the sphericity R is 0.95 or more, it is possible to increase the packing density of the phosphor in the phosphor film, Light emission luminance can be greatly improved.

Therefore, the average value of the sphericity R of each phosphor particle constituting the phosphor according to the present invention is specified to be 0.95 or more. Here, the sphericity R is defined as a value given by 4πA / L ² where A is the area of the projected image of each phosphor particle on the plane and L is the peripheral length of the projected image. .

The sphericity R (= 4πA / L ² ) is a coefficient representing the sphericity of the phosphor particles. The closer this coefficient value is to 1, the closer the particle shape is to a true sphere. When the shape is completely spherical, the value is 1.

If the average value of the sphericity R of each of the phosphor particles is less than 0.95, it becomes difficult to fill the phosphor with a high packing density in the phosphor film. The improvement in brightness is insufficient. Therefore, the average value of the sphericity R is specified to be 0.95 or more, more preferably 0.97 or more, and further preferably 0.98 or more.

The average particle size of the sphericity R of the phosphor particles is as follows:
Approximately 100 randomly selected magnetic particles are placed on a flat plate, and a projection image is taken with a scanning electron microscope (SEM), and the obtained particle projection image is image-processed for quick measurement. can do. As an image processing apparatus for performing the above-described image processing, for example, an image processing apparatus manufactured by Pierce (model number: PIAS-III) can be suitably used.

According to the phosphor having the above-described structure, the sphericity of the phosphor particles is defined to be high within a predetermined range, so that the phosphor can be filled in the phosphor film at a high filling density.
The brightness of the light emitting device can be greatly improved.

According to the method for producing a phosphor according to the present invention, the phosphor raw material solution is sprayed, dried with low-temperature hot air, and fired at a temperature that can maintain the shape of the obtained particles. In addition, a phosphor having few defects and excellent sphericity can be easily and efficiently manufactured. Especially by the hot air temperature during drying in 200 ° C. or less, the operation control of the manufacturing apparatus with heat energy consumption is reduced even easier, cheaper phosphor, and can be efficiently manufactured.

[0032]

DESCRIPTION OF THE PREFERRED EMBODIMENTS Next, embodiments of the present invention will be specifically described with reference to the following Examples and Comparative Examples.

Example 1 2 mol of ZnSO ₄ and 0.07 mol of MnCl ₂ were weighed and dissolved in 2 liters of pure water, and a small amount of nitric acid was added and mixed uniformly. 1 mol of S was added to the obtained mixture.
i (OC ₂ H ₅ ) ₄ was added, and the mixture was sufficiently stirred until completely dissolved to prepare a raw material solution. Then, a pressurized two-fluid nozzle, the raw material solution was fed to the particle system which is directly connected to the drying chamber is circulated hot air temperature 200 ° C., hot air droplets simultaneously spraying the raw material solution into droplets , And dried to prepare raw material fine particles. Further, the dried raw material fine particles were calcined in the atmosphere at a temperature of 1000 ° C. for 3 hours to produce the manganese-activated zinc silicate phosphor according to Example 1.

Examples 2 and 3 The firing temperature of the raw material particles of the phosphor was 1050 ° C., respectively.
Except that the temperature was changed to 1100 ° C., the raw material solution was prepared, spray-dried, and fired under the same conditions as in Example 1 to produce manganese-activated zinc silicate phosphors according to Examples 2 to 3.

Example 4 2 mol of ZnSO ₄ and 0.05 mol of MnCl ₂ were weighed and dissolved in 2 liter of pure water, and a small amount of nitric acid was added and mixed uniformly. 1 mol of S was added to the obtained mixture.
i (OC ₂ H ₅ ) ₄ was added, and the mixture was sufficiently stirred until completely dissolved to prepare a raw material solution. Next, the raw material solution is supplied to a fine particle device which has a pressurized two-fluid nozzle and is directly connected to a drying chamber through which hot air at a temperature of 200 ° C. is circulated, and the raw material solution is sprayed into droplets, and at the same time, the droplets are heated with hot air. , And dried to prepare raw material fine particles. The manganese-activated zinc silicate phosphor according to Example 4 was manufactured by firing the dried raw material fine particles at a temperature of 1000 ° C. for 3 hours in the air.

[0036]Comparative Example 1 If the chemical composition of the phosphor is (Zn_0.96Mn_0.04)₂S
iO₄Zinc sulfate (ZnSO₄), Man chloride
Cancer (MnCl₂) And Si (OC₂H₅) ₄Weighed
And mixed well. This raw material mixture is made of alumina crucible
3 hours at 1000 ℃ in nitrogen gas atmosphere
It was during firing. The obtained fired product is pulverized and washed thoroughly with pure water.
After cleaning, the mixture was filtered and dried to produce a phosphor according to Comparative Example 1.
Built.

The chemical composition of Comparative Example 2 phosphor _{(Y 0.96 Tb 0.04) 2} Si
Yttrium nitrate, tetraethyl orthosilicate and terbium nitrate were each dissolved in water so as to become O _4, and a small amount of nitric acid was added to prepare a homogeneous phosphor raw material solution. This liquid was put into an ultrasonic atomizer having a 1.7 MHz vibrator to form droplets, and the droplets were introduced into a tubular furnace maintained at a temperature of 1200 ° C. using air as a carrier gas to form a droplet. A thermal decomposition reaction was performed for 2 seconds to obtain a phosphor according to Comparative Example 2.

Comparative Example 3 29.6 g of zinc nitrate hexahydrate in 100 ml of methanol,
After dissolving 0.144 g of manganese nitrate hexahydrate and 10.96 g of 95% by weight ethyl orthosilicate, the mixture was refluxed and heated at 56 ° C. for 100 hours, and then sprayed into an electric furnace set to a temperature of 500 ° C. with methanol. The obtained amorphous powder was dispersed in water, and a hydrothermal reaction was performed at 250 ° C. for 5 hours in a pressure vessel.
After the reaction, the product was filtered and washed with water to obtain a zinc silicate phosphor according to Comparative Example 3 having a spherical shape with an average particle diameter of 3 μm.

Next, 100 magnetic particles were randomly selected from the phosphor powder according to each of the examples and comparative examples prepared as described above, and were placed on a flat glass plate under a scanning electron microscope (SEM). ), A projection image is taken, and each projection image obtained is processed by an image processing device (Pierce, model number:
The average value of the sphericity (R) and the average particle diameter of the phosphor powder particles were measured by performing image analysis using PIAS-III). Table 1 shows the measurement results.

Next, in order to evaluate the emission characteristics of each phosphor prepared as described above, the wavelength of each phosphor was 254 nm.
The emission spectrum, afterglow time, and chromaticity value (x, y) of the sample under ultraviolet irradiation were measured. Then, the emission intensity of the main emission peak in the emission spectrum was measured. In addition, the afterglow time was measured as a time until the emission luminance after blocking the ultraviolet rays was reduced to 1/10 of the emission luminance immediately before the blocking. The measurement results are shown in Table 1 below.

[0041]

[Table 1]

As is clear from the results shown in Table 1 above,
In the phosphor according to each of the examples manufactured by spray-drying the raw material solution and then firing in a temperature range that can maintain the shape, the average value of the sphericity (R) is extremely high, and the luminous intensity is excellent. and exhibits afterglow characteristics, it was confirmed that the chromaticity characteristics is good.

When the phosphor particles according to each example were observed with an electron microscope, the surface was extremely smooth, the surface roughness was in the range of 0.1 to 0.3 μm based on Rmax, and the width was 0%. or more of crack or recess .1μm it has been found that does not exist. The relative density of each phosphor particle is 96 to
It was in the range of 99%.

On the other hand, the phosphor according to Comparative Example 1 prepared by firing and then pulverizing in a crucible contains a large number of irregularly shaped particles, has a low average value of sphericity, deteriorates light emission characteristics, and cracking is increased by the impact force acting during grinding, phosphor life was also reconfirmed that tends to decrease.

Further, in the phosphor according to Comparative Example 2 formed by the pyrolysis method, although a certain degree of improvement in sphericity is obtained, the light emission characteristics are not sufficient. Further, in the phosphor according to Comparative Example 3 manufactured by performing a hydrothermal reaction after the spraying treatment, the effect of improving the sphericity of the particles is obtained to some extent but is not sufficient, and the surface of the phosphor particles is not sufficient. It has been found that the roughness tends to increase.

[0046]

As described above, according to the phosphor of the present invention, since the sphericity of the phosphor particles is specified to be high within a predetermined range, the phosphor is filled with the phosphor film at a high packing density. And the brightness of the light emitting device can be greatly improved.

According to the method for producing a phosphor according to the present invention, the phosphor raw material solution is sprayed, dried with low-temperature hot air, and fired at a temperature at which the shape of the obtained particles can be maintained. In addition, a phosphor having few defects and excellent sphericity can be easily and efficiently manufactured. Especially by the hot air temperature during drying in 200 ° C. or less, the operation control of the manufacturing apparatus with heat energy consumption is reduced even easier, cheaper phosphor, and can be efficiently manufactured.

Claims (6)

[Claims] 1. A method comprising spraying and drying a solution containing a phosphor component, and then baking a plurality of particles. When the peripheral length of a projected image of each particle is L and the actual area of the projected image is A, 4π
Phosphor average of sphericity represented by A / L ² is equal to or is less than 0.95. 2. The phosphor according to claim 1, wherein said phosphor is a manganese-activated zinc silicate phosphor. 3. A solution containing a phosphor component is spray-dispersed to prepare droplets, and the obtained droplets are contacted with hot air and dried to form spherical raw material particles.
The method for producing a phosphor, characterized by firing at to 1200 ° C.. 4. The method according to claim 3, wherein the temperature of the hot air is 200 ° C. or less. 5. The method according to claim 3, wherein the phosphor is a manganese-activated zinc silicate phosphor. 6. A light-emitting device, wherein a light-emitting layer containing the phosphor according to claim 1 or 2 is integrally formed on an inner surface of a light-transmitting airtight container.