JP2007002086A - Method for producing electron beam-excited red phosphor - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a phosphor that emits light by electron beam excitation, especially a red phosphor suitably used for a field emission display (FED). <P>SOLUTION: In a method for producing the electron beam-excited red phosphor, a mixture of a yttrium compound and a europium compound or a yttrium-europium complex compound is fired in a non-reducing atmosphere to obtain a crude phosphor which is subsequently ground and re-fired in the atmosphere. The phosphor which is excellent in emission luminance achieved by electron beam radiation, has a small median diameter and is suitably made into a paste form can be obtained through the method. <P>COPYRIGHT: (C)2007,JPO&INPIT

Description

  The present invention relates to a method for producing a red phosphor used for an electron beam excited light emitting device such as a field emission display (FED).

As a red phosphor used for an electron beam-excited light emitting element, yttrium oxide (Y _1-x Eu _x ) ₂ O ₃ activated with europium is known. This one emits red light when irradiated with an electron beam by substituting a part of yttrium with europium, but its light emission characteristics are not sufficient, aiming at improving the light emission luminance, lowering the light emission start voltage, etc. Consideration has been made. For example, a manufacturing method in which re-firing (annealing) is performed in a reducing atmosphere is known for lowering the light emission starting voltage (see Patent Document 1). Further, for example, a technique using zinc as a co-activator is known (see Patent Document 2).

JP 2000-265168 A JP 2000-319654 A

  Although the red phosphor described in Patent Document 1 can reduce the light emission start voltage, further improvement in light emission luminance is required for use as a red light emitting element of a field emission display (FED). .

  The present inventor has made various studies to find a red phosphor having further improved emission luminance. As a result, in the europium-activated yttrium oxide red phosphor, the phosphor material is obtained by firing in a non-reducing atmosphere. After the obtained crude phosphor was pulverized, it was found that the luminance of light emitted by electron beam irradiation was further improved by re-baking in the same atmosphere as that during the baking, and the present invention was completed.

  That is, the present invention provides a crude phosphor by firing a mixture of yttrium compound and europium compound or yttrium-europium composite compound in a non-reducing atmosphere, and then pulverizing the crude phosphor and then the atmosphere during the firing. It is a manufacturing method of the electron beam excitation red fluorescent substance characterized by rebaking in the same atmosphere.

  The method for producing an electron beam-excited red phosphor of the present invention is a method for producing a phosphor suitable for making into a paste, which is further excellent in emission luminance by electron beam irradiation and has a small median diameter.

  The present invention relates to a method for producing an electron beam-excited red phosphor, which is obtained by firing a mixture of an yttrium compound and a europium compound or an yttrium-europium complex compound in a non-reducing atmosphere, and then obtaining a crude phosphor. After the body is pulverized, it is re-fired in the same atmosphere as that at the time of firing.

In the production method of the present invention, first, a mixture of yttrium compound and europium compound or yttrium-europium composite compound is used as a raw material, and this is fired in a non-reducing atmosphere to obtain a crude phosphor. Yttrium compounds that can be used include yttrium oxide, yttrium hydroxide, yttrium oxalate, and yttrium carbonate. Europium compounds include europium oxide, europium hydroxide, europium oxalate, europium carbonate, europium chloride, and europium nitrate. Can be mentioned. As the yttrium-europium complex _{compound, (Y 1-x Eu X} ) (OH) 3, (Y 1-x Eu X) 2 O 3 · nH 2 O, (Y 1-x Eu X) 2 (C ₂ O ₄ ) _{3 and the} like. Furthermore, when the blending ratio of yttrium and europium is expressed in terms of molar ratio (Eu / Y) and is in the range of 0.03 to 0.20, light emission luminance corresponding to the blending amount of europium is obtained, and the color purity of the luminescent color. In addition, it is preferable because an excellent product is obtained.

The composite compound, for example, (Y _1-x Eu _X ) (OH) ₃ neutralizes a nitrate solution containing yttrium and europium with aqueous ammonia, (Y _1-x Eu _X ) ₂ O ₃ .nH ₂ O is (Y _1-x Eu _X ) (OH) ₃ is filtered and washed with water, and then partially dehydrated by heating. (Y _1-x Eu _X ) ₂ (C ₂ O ₄ ) ₃ is a oxalic acid solution in a nitrate solution containing yttrium and europium. It can manufacture by adding.

  The firing atmosphere is a non-reducing atmosphere, for example, an oxidizing atmosphere containing oxygen such as air, or a neutral atmosphere containing a non-oxidizing / non-reducing gas such as nitrogen.

  In obtaining the crude phosphor, it is preferable to granulate a mixture of yttrium compound and europium compound or yttrium-europium complex compound and then calcinate it, since it is easy to obtain a crude phosphor with uniform particle size. As a granulation method, a known granulator / dryer such as a spray dryer, a flash jet dryer, a slurry dryer, or Omtex can be used. In the present invention, it is preferable to use a spray dryer because mixing with the flux becomes uniform as will be described later, and a granulated product having a uniform spherical particle size is obtained.

Firing the raw material in the presence of a flux is preferable because crystallization of the resulting crude phosphor is promoted. Examples of the flux that can be used include lithium fluoride, sodium fluoride, potassium fluoride, potassium phosphate, sodium phosphate, sodium chloride, lithium chloride and the like. These can be used alone or in combination. be able to. Among these, it is preferable to use lithium fluoride because the flux hardly remains in the crude phosphor obtained after firing. It is preferable to use lithium fluoride and potassium phosphate together because the particle shape tends to be spherical.
The amount of the flux used is preferably in the range of 1 to 15 mol% relative to the raw material. Further, it is preferable that the flux is sufficiently mixed with the raw material in advance before firing. For example, the raw material and the flux are sufficiently mixed in a solid phase in advance, or the raw material and the flux are mixed in an aqueous system. After thoroughly mixing to make a slurry, the slurry may be dried. In particular, a product dried by a spray drying method is preferable because a dried product (secondary particle) having a uniform particle size is easily obtained.

  The firing temperature is not particularly limited as long as it is in a range in which the starting compound reacts to produce yttrium oxide doped with europium, but a range of 800 to 1500 ° C. is preferable. When firing in the presence of a flux, a preferred temperature range is 850 to 1400 ° C.

  Next, the coarse phosphor obtained by firing is pulverized to uniform the particle size. The degree of pulverization is preferably 15 μm or less when the particle size is expressed in median diameter. However, when pulverized to make the particle size uniform, there is usually a problem that the emission luminance is lowered. In the present invention, the emission luminance reduced by such pulverization is refired in the same atmosphere as at the time of firing, so that the emission luminance exceeds the emission luminance of the crude phosphor before pulverization and the particle size is uniform. A phosphor can be obtained.

  The re-baking temperature is preferably in the range of 400 to 1200 ° C, more preferably in the range of 600 to 1100 ° C. If the re-baking temperature is lower than the above range, the emission luminance is not sufficiently improved. If re-baking at a temperature higher than the above range, the particles are easily sintered again, and further improvement in the emission luminance is expected. It is also difficult to do.

  Since the phosphor of the present invention obtained by refiring has a uniform particle size, further pulverization or the like is not always necessary, but light pulverization such as crushing may be performed. In addition, when a flux is used during firing, an operation of washing the phosphor after re-baking with an aqueous system may be performed in order to remove the flux remaining on the phosphor.

  There is a field emission display (FED) as a flat panel display using the electron beam excitation light emission phenomenon. This is a low voltage type using an electron beam accelerated by a voltage of 100 to 3000 V as an excitation source and a voltage of 3000 V or more. Two types of high-voltage type using an electron beam accelerated by the above as an excitation source have been studied. The red phosphor of the present invention can be used in any of the above-mentioned types because good light emission can be obtained even with an electron beam accelerated at least at about 1000V.

  EXAMPLES Hereinafter, although an Example demonstrates this invention, this invention is not limited to these Examples.

Comparative Example 1
400 ml of pure water was added to a slurry of 125 g of yttrium oxide (Y ₂ O ₃ ) and 19.482 g of europium oxide (Eu ₂ O ₃ ). To this was added 268 ml of concentrated nitric acid (concentration 61%) and dissolved, and then diluted with pure water to make the volume 8 l. Next, the temperature was raised to 60 ° C., 283 ml of concentrated aqueous ammonia (12.62N) was added with stirring, the mixture was aged for 5 hours, washed with filtered water and double hydroxide (Y _0.909 Eu _0.091 ) (OH) ₃ Got.
(Y _0.909 Eu _0.091 ) The double hydroxide corresponding to 90 g in terms of ₂ O ₃ was redispersed in 3 liters of pure water, 0.723 g of lithium fluoride was further added, and the mixture was stirred for 1 hour to give a slurry (sample a) was obtained. Sample a was evaporated to dryness at a temperature of 120 ° C. After adjusting the particle diameter (median diameter) to 15 μm by pulverization, firing was performed in the atmosphere at a temperature of 950 ° C. for 5 hours, and subsequently at a temperature of 1350 ° C. for 5 hours, followed by washing to obtain a crude phosphor (sample A).

Comparative Example 2
The crude phosphor (sample A) obtained in Comparative Example 1 was pulverized using a centrifugal pulverizer (type ZM100, manufactured by Retsch) to obtain a phosphor (sample B).

Example 1
The phosphor (sample B) obtained in Comparative Example 2 was refired at a temperature of 900 ° C. for 2 hours in the same air atmosphere as the firing atmosphere to obtain the phosphor of the present invention (sample C).

Comparative Example 3
The crude phosphor (sample A) obtained in Comparative Example 1 was refired at 900 ° C. for 2 hours in the same air atmosphere as the firing atmosphere to obtain a phosphor (sample D).

Comparative Example 4
Comparative Example 1 The resulting slurry (sample a) a spray dryer (Niro Inc., desk atomizer - type) to obtain spherical particles of median size 12 [mu m was spray dried using. Subsequently, after baking at a temperature of 950 ° C. in the atmosphere for 5 hours and subsequently at a temperature of 1350 ° C. for 5 hours, washing was performed to obtain a crude phosphor (sample E).

Comparative Example 5
The crude phosphor (sample E) obtained in Comparative Example 4 was pulverized using a centrifugal pulverizer (Retsch, type ZM100) to obtain a phosphor (sample F).

Example 2
The phosphor (sample F) obtained in Comparative Example 5 was refired at a temperature of 900 ° C. for 2 hours in the same air atmosphere as the firing atmosphere to obtain the phosphor of the present invention (sample G).

Comparative Example 6
The crude phosphor (sample E) obtained in Comparative Example 4 was refired at a temperature of 900 ° C. for 2 hours in the same air atmosphere as the firing atmosphere to obtain a phosphor (sample H).

  Using the samples A to H obtained in Examples 1 and 2 and Comparative Examples 1 to 6, electron beam excitation light emission luminance, specific surface area, and median diameter were measured. The results are shown in Table 1. In addition, electron beam excitation luminescence brightness and median diameter were measured by the following methods.

(Measurement method of luminance excited by electron beam)
The sample thinly coated on an aluminum plate was placed in a high vacuum container with a pressure of 10 ⁻⁵ Pa or less, and the emission from the sample was measured by irradiating an electron beam from an electron gun. The electron gun used thermoelectrons emitted from a heated cathode. The acceleration voltage of the electron beam and the amount of current of the electron beam flowing into the sample can be adjusted independently. The luminance was measured by irradiating the sample with an electron beam accelerated at an acceleration voltage of 5 kV, and measuring the emission spectrum from the sample using a multichannel spectrometer. The current density passed through the sample is 150 μA / cm ² . The Y value (emission luminance) in the CIE 1931 color system was determined from the obtained emission spectrum. In Table 1, the light emission luminance of Sample A is expressed as a relative value with 100.

(Measurement method of median diameter)
It was measured with a laser diffraction / scattering particle size distribution measuring apparatus LA-950 manufactured by Horiba.

  From Table 1, it was found that the red phosphor obtained by the production method of the present invention is excellent in light emission luminance by electron beam excitation and has a small median diameter and is suitable for pasting.

The phosphor of the present invention is useful as a red phosphor for an electron beam-excited light emitting device such as a field emission display (FED).

Claims (7)

A mixture of yttrium compound and europium compound or yttrium-europium composite compound is fired in a non-reducing atmosphere to obtain a crude phosphor, and then the crude phosphor is pulverized and then re-reacted in the same atmosphere as that for firing. A method for producing an electron beam-excited red phosphor, characterized by firing. The method for producing an electron beam-excited red phosphor according to claim 1, wherein re-baking is performed at a temperature in the range of 400 to 1200 ° C. 2. The method for producing an electron beam-excited red phosphor according to claim 1, wherein the mixture is sintered after granulating a mixture of an yttrium compound and a europium compound or an yttrium-europium composite compound. 4. The method for producing an electron beam-excited red phosphor according to claim 3, wherein the granulation is performed using a spray dryer. The method for producing an electron beam-excited red phosphor according to claim 1, wherein firing is performed in the presence of a flux. The method for producing an electron beam-excited red phosphor according to claim 5, wherein lithium fluoride and / or potassium phosphate is used as a flux. The method for producing an electron beam-excited red phosphor according to claim 1, wherein the firing and re-firing atmosphere is an oxidizing atmosphere.