JP5444271B2 - Method for producing alkaline earth metal silicate phosphor - Google Patents

Description

The present invention relates to an alkaline earth metal activated by Eu ²⁺ of the composition formula (A, Eu) ₃ SiO ₅ (where A is an alkaline earth metal element), which emits light with high luminance by photoexcitation in the ultraviolet to visible range. The present invention relates to a method for producing a silicate phosphor.

White LEDs are a mixture of LEDs that emit light from near ultraviolet to blue and phosphors to generate white light. Conventionally, white LEDs have been actively developed as LCD backlight sources for small portable devices. As an application, the development of lighting applications is progressing.
Conventionally, as a phosphor for white LED used for this white LED, YAG: Ce ³⁺ which shows yellow fluorescence by blue excitation or (Ba, Sr, Ca) ₂ SiO ₄ : Eu ²⁺ which shows green to yellow fluorescence. Sr ₃ SiO ₅ : Eu ^{2+ and the} like are known, but a phosphor with higher luminance is desired.

On the other hand, alkaline earth metal silicate phosphors activated by Eu ²⁺ can be excited widely from the ultraviolet to the visible range, and the emission wavelength can be changed from green to orange by changing the composition. It is known that it is (refer nonpatent literature 1).

By the way, as a general method for synthesizing phosphors, a method is used in which raw material powders are mixed in a wet or dry manner, then baked at a high temperature and synthesized by a solid phase reaction between the raw materials (see Non-Patent Document 2). As a method for synthesizing the alkaline earth metal silicate phosphor activated with Eu ²⁺ , a solid phase firing method (see Patent Document 1) in which an alkaline earth metal carbonate and SiO ₂ powder are mixed and fired, an alkaline earth metal is used. A method is known in which a precursor is prepared by a sol-gel reaction using an aqueous metal solution and an organosilicon compound such as tetraethoxysilane (TEOS), and then fired (see Patent Document 2).

Further, in order to obtain a high-brightness alkaline earth metal silicate phosphor, it is necessary to increase the crystal phase purity and to uniformly disperse Eu ²⁺ as an activator in the base crystal. In the solid-phase firing method disclosed in Patent Document 1, it is necessary to perform firing at a high temperature for a long time in order to promote diffusion and reaction between raw materials. On the other hand, in the phosphor synthesis from phosphor precursors by liquid phase methods such as sol-gel method and coprecipitation method, the raw material metal elements are uniformly mixed, and element diffusion and reaction compared to solid phase firing method There is an advantage that is easy to proceed.

As the silicon raw material of the alkaline earth metal silicate phosphor by the liquid phase method, an organosilicon compound such as TEOS disclosed in Patent Document 2 is often used. This TEOS is used because it is mixed with other raw materials and then becomes SiO ₂ by hydrolysis and polymerization. However, organosilicon compounds such as TEOS and tetramethoxysilane (TMOS) are generally water-insoluble and cannot be uniformly mixed with an aqueous solution, and when an alkaline earth metal that is a raw material other than silicon is used as an aqueous solution. Is difficult to mix uniformly. Therefore, if the solvent is an organic solvent such as alcohol, the silicon raw material is uniformly dispersed in the solution, but is separated into two phases when water for hydrolysis is added. Further, when the solvent is an organic solvent such as alcohol, there is a problem that it is difficult to dissolve the alkaline earth metal. Furthermore, organosilicon compounds such as TEOS are liable to evaporate, the composition fluctuates during synthesis, and it is difficult to obtain a precursor having a uniform composition.

Therefore, in order to solve these problems, a water-soluble silicon compound (WSS) which is a new silicon raw material has been recently developed, and synthesis of a silicate phosphor using this water-soluble silicon compound (WSS) has been studied. Its usefulness has been confirmed (see Patent Document 3 and Patent Document 4).
Patent Document 4 shows an example in which a silicate phosphor is synthesized by mixing a metal salt aqueous solution and a WSS aqueous solution, and baking the gel obtained by hydrothermal synthesis of the mixture over several stages. . However, when the gel body is synthesized by the hydrothermal synthesis method, the water is separated from the gel body, and the raw material metal salt is dissolved in the water. There is a problem that it is difficult to obtain a body.

JP 2009-173905 A JP 2007-186664 A JP 2010-007032 A JP 2010-188953 A

Philips Research Reports, 1968, VOL. 23, P.I. 189-200 Phosphor Handbook, Ohm, P.A. 166

  As a method for synthesizing a gel body, a wet synthesis method using a water-soluble silicon compound (WSS) requires a large amount of an organic acid such as citric acid. Therefore, it is necessary to remove organic matter, soot and off-flavor during the thermal decomposition of the organic acid, and uniform thermal decomposition is difficult and carbon remains.

In view of the problem in the synthesis of a silicate phosphor using a water-soluble silicon compound as the Si source of such a silicate phosphor, the present invention does not use an organic acid, and the water-soluble silicon compound aqueous solution and the alkaline earth metal element dispersion are used. Are mixed and heated to obtain a uniform gel body, which is further heated and dried to prepare a precursor body, and then emits light with high luminance by calcination and reduction firing (A, Eu) ₃ An object of the present invention is to provide a production method for synthesizing a SiO ₅ (wherein A is an alkaline earth metal element) alkaline earth metal silicate phosphor.

As a result of intensive studies to solve the above problems, the present inventors have found that a composition formula (A, Eu) ₃ SiO ₅ (where A is an alkaline earth metal element) -based Eu ²⁺ activated alkaline earth metal silicate phosphor. Focusing on the fact that when the alkaline earth metal salt is dispersed in water, the particle surface becomes basic and the water-soluble silicon compound (WSS) immediately gels in the basic aqueous solution. The inventors found that a uniform gel body can be produced by mixing and heating an alkaline earth metal salt dispersion and a WSS aqueous solution without using an organic acid, and found that the above problems can be solved. Has been completed.

According to a first aspect of the present invention, there is provided a process for producing a Eu ²⁺ activated alkaline earth metal silicate phosphor of the composition formula (A, Eu) ₃ SiO ₅ (where A is an alkaline earth metal element), the following steps: It consists of 1, step 2, step 3, and step 4.

[Step 1]
An aqueous dispersion of at least one alkaline earth metal carbonate selected from Ba and Sr as constituent metal components, an aqueous dispersion of europium oxide, and a WSS having a water-soluble silicon compound concentration of 2 mol / L or less In this process, the mixed solution with the aqueous solution is heated and stirred at a liquid temperature of 30 to 100 ° C. to obtain a gel body in which the entire amount of the constituent components is uniformly dispersed.

[Step 2]
This is a step of forming a precursor which is a dried product obtained by drying the gel body produced in step 1 and removing the solvent contained therein.

[Step 3]
In this step, the precursor prepared in Step 2 is subjected to a two-stage heat treatment in an air atmosphere at a temperature of 1000 to 1300 ° C. in the first stage and 1100 to 1500 ° C. in the second stage to obtain calcined powder.

[Step 4]
In this step, the calcined powder produced in step 3 is heat-treated at a temperature of 1200 to 1550 ° C. in a reducing atmosphere to obtain a phosphor powder.

In the second invention according to the present invention, a water-soluble silicon compound (WSS) used in Step 1 of the first invention is added with a diol compound to an organosilicon compound, heated, stirred and mixed, and then a small amount of acid. It is a method for producing Eu ²⁺ activated alkaline earth metal silicate phosphor, which is a water-soluble silicon compound to which is added.

3rd invention which concerns on this invention is the process of crushing the calcining powder formed at the process 3 after the process 3 of the 1st invention, classifying, and removing the coarse particle of 100 micrometers or more. It is a manufacturing method of Eu2 ⁺ activated alkaline-earth metal silicate fluorescent substance characterized by including.

In the fourth invention according to the present invention, following step 4 of the first invention, the phosphor powder formed in step 4 is crushed, washed with water, and then decanted using ethanol or isopropyl alcohol. A method for producing an Eu ²⁺ activated alkaline earth metal silicate phosphor, comprising a step of cleaning the surface by drying later and removing fine particles of 5 μm or less.

According to the present invention, an organic acid such as citric acid is used in a method for producing a Eu ²⁺ activated alkaline earth metal silicate phosphor of the composition formula (A, Eu) ₃ SiO ₅ (where A is an alkaline earth metal element). Without mixing, a water-soluble silicon compound (WSS) aqueous solution and an alkaline earth metal element aqueous dispersion are mixed, and a uniform gel body is prepared by maintaining stirring at a predetermined temperature, and further, pyrolysis, calcination, By reducing and firing, a high brightness Eu ²⁺ activated alkaline earth metal silicate phosphor equal to or higher than that of commercially available YAG is obtained.
Also, an industrially easy-to-use manufacturing method that prevents the generation of cracked gases, soot, and off-flavors that have been generated during thermal decomposition when using organic acids, and prevents carbon residue after thermal decomposition is also provided. To do.

It is a figure which shows the fluorescence characteristic of Example 1, and is the figure which showed the emission spectrum excited by 455 nm, and the excitation spectrum which fixed light emission at 585 nm. 2 is a diagram showing an X-ray diffraction pattern of Example 1. FIG. It is a figure which shows the fluorescence characteristic of Example 2, and is the figure which showed the emission spectrum which excited at 455 nm, and the excitation spectrum which fixed light emission at 595 nm. 6 is a diagram showing an X-ray diffraction pattern of Example 2. FIG.

Eu ²⁺ activated alkaline earth metal silicate phosphors of the composition formula (A, Eu) ₃ SiO ₅ (where A is an alkaline earth metal element) based on the present invention are represented by the following formulas (1) and (2) It is shown by the formula.

The Eu ²⁺ activated alkaline earth metal silicate phosphor represented by the general formulas of the above formulas (1) and (2) is manufactured through the following steps 1 to 4.

[Step 1]
An aqueous dispersion of at least one alkaline earth metal carbonate selected from Ba and Sr which are constituent metal components, an aqueous dispersion of europium oxide, and an aqueous WSS solution having a WSS concentration of 2 mol / L or less The process which makes the gel body of the state which the whole quantity of the structural component disperse | distributed uniformly by heating and stirring mixed aqueous solution at the liquid temperature of 30-100 degreeC.

[Step 2]
The process of forming the precursor which is the dried material which removed the solvent contained by drying the gel body produced by the process 1.

[Step 3]
A step of obtaining a calcined powder by subjecting the precursor produced in step 2 to a two-step heat treatment in an air atmosphere at a temperature of 1000 to 1300 ° C in the first step and 1100 to 1500 ° C in the second step.

[Step 4]
A step of heat treating the calcined powder formed in step 3 at a temperature of 1200 to 1550 ° C. in a reducing atmosphere to obtain a phosphor powder.

Below, each process is demonstrated in detail.
[Step 1]
1. Preparation of dispersion of alkaline earth metal carbonate and europium oxide An aqueous dispersion of europium of at least one alkaline earth metal selected from Ba and Sr and an activator element is prepared. Carbonates are used as the alkaline earth metal component. Europium oxide is used as the europium component. The reason is as follows.

  When alkaline earth metal salts and europium salts that can remove acid radicals by thermal decomposition, such as nitrates and acetates, subsequent thermal decomposition does not occur uniformly and the resulting phosphor composition is non-uniform. May be induced. In order to avoid this, for example, it is necessary to add a treatment such as a heat treatment in the middle temperature range of about 300 to 800 ° C. after the step 2, and the process becomes complicated. In addition, when a halide having high solubility in water such as chloride, bromide, iodide, etc. is used as an alkaline earth metal and europium raw material, it is once dissolved in an aqueous solution, and then precipitated as an original salt during the heat treatment. It becomes difficult to produce a liquid phase during the heat treatment in 3 and 4 and obtain a powdery sample.

  The alkaline earth metal carbonate and europium oxide as the activator raw material are weighed so that the composition represented by the general formula of the above formula (1) or (2) is obtained, and 1.7 to 3 times the total weight thereof Add to an amount of water and stir at room temperature to disperse into a dispersion slurry. If the amount of water is less than 1.7 times, the viscosity of the dispersion slurry is high, and sedimentation and lumps of the raw material occur, which is not preferable. Even if it is more than 3 times, there is no difference in the degree of dispersion, and only the time of the drying step for removing the solvent in step 2 becomes very long.

2. Preparation of aqueous solution of water-soluble silicon compound (WSS) The water-soluble silicon compound (WSS) may be prepared by a known production method described in Patent Document 3, but specifically, it may be produced by the method shown below. it can.
The organosilicon compound tetraethoxysilane (TEOS) is used as the Si source material, and TEOS and propylene glycol as the diol compound are weighed to a molar ratio of 1: 4 and mixed at 80 ° C. for 1 hour. Add a small amount of hydrochloric acid or lactic acid as an acid (about 0.2% of the mixed solution) and stir for 1 hour, and dilute with water so that the concentration of WSS obtained is 2 mol / L or less. A WSS aqueous solution is obtained. In addition, when the WSS concentration is higher than 2 mol / L, the liquid viscosity becomes high, so that it becomes uneven when added to the aqueous dispersion of alkaline earth metal salt and europium oxide, and it is difficult to obtain a uniform slurry. This is not preferable because it may cause a typical gelation reaction.

  Here, tetraethoxysilane or tetramethoxysilane is desirable for the organosilicon compound of the Si source material used for the production of the water-soluble silicon compound, and ethylene glycol or propylene glycol is preferably used for the diol compound forming the mixed solution. As the acid added to the mixed solution, hydrochloric acid or lactic acid is preferably used.

3. Mixing of alkaline earth metal, europium oxide aqueous dispersion and WSS aqueous solution, and preparation of gel body Here, the reaction mechanism during gelation will be described.
First, by adding an alkaline earth metal aqueous solution to water-soluble silicon (WSS: Si (OROH) ₄ , R is a divalent alkyl group), the liquid becomes basic and hydrolyzes to form Si (OH) _n. (OROH) _4-n .
Furthermore, it is considered that an OH group dehydration condensation reaction (the following formula (3)) and a dealcoholization condensation reaction (the following formula (4)) progress to form a Si—O—Si network to become a gel body.

At this time, the alkaline earth metal salt and the activator element are uniformly confined in the Si—O—Si network, whereby a uniform gel body is obtained.
The time required for gelation varies depending on the type of alkaline earth metal element and the amount of water in the aqueous solution, but can be implemented within a range not departing from the gelation conditions shown below.

An aqueous WSS solution is added to an aqueous dispersion of alkaline earth metal salt and europium while stirring at room temperature. After stirring for 10 minutes or more and confirming that the entire liquid is in a uniform slurry state, gelation can be achieved by starting heating.
The gelation temperature is preferably 30 to 100 ° C, more preferably 40 to 60 ° C.

Specifically, for example, it is preferable to set the temperature to 50 ° C. At a liquid temperature of 50 ° C., the entire solution gels in about 15 minutes with a mixed liquid amount of 150 ml and becomes a uniform lump. If the liquid temperature is lower than 30 ° C., the time required for gelation becomes as long as 4 hours or longer. If the liquid temperature is higher than 100 ° C., the time required for gelation is shortened to about 5 minutes, but it is difficult to uniformly warm the whole liquid, and this causes local gelation. Absent.
Depending on the volume of the liquid mixture, the heating and stirring method can be selected as appropriate, but it is important to ensure that the whole liquid is uniformly mixed and that the whole liquid is uniformly heated, and that it is uniformly gelled. is there.

[Step 2]
Next, the gel body produced in step 1 is dried to form a precursor, and the contained solvent is removed.
In this process, if moisture moves inside the gel body during drying to form a high-concentration part and precipitates are generated, the phosphor obtained through the subsequent process has a non-uniform composition, resulting in high brightness. In this drying, it is desirable to dry so as not to cause water movement in the gel body.

A drying temperature can be 100-200 degreeC.
The drying method is not particularly limited except for the above precautions, and a general dryer can be used. A hot-air circulating dryer, a vacuum dryer, or a freeze dryer can also be used. When the dry powder is agglomerated, it is preferable to proceed to the next step after crushing.

[Step 3]
In this step, the precursor obtained in step 2 is heat-treated in an air atmosphere to obtain calcined powder.
The thermal decomposition can be performed by a known method such as heating in a box-type electric furnace. Specifically, it is put in an alumina container and heat-treated in the atmosphere.

The heat treatment is performed in two stages, the first stage is carbonate decomposition, and the second stage is to form the desired crystal phase.
The temperature in the first stage is set to 1000 to 1300 ° C. because BaCO ₃ and SrCO ₃ are contained as raw materials.

  The temperature at the second stage is 1100 ° C. to 1400 ° C. when the target phosphor is represented by the above formula (1), and 1400 to 1500 ° C. when the target phosphor is represented by the formula (2). The reason why the temperatures at the second stage are different is that when two or more alkaline earth metal elements are used, the optimum crystal phase formation temperature differs depending on the ratio of the alkaline earth metal elements. .

As a furnace used for the heat treatment, a general box furnace, a belt furnace, or the like can be used.
Furthermore, subsequent to step 3, the calcined powder produced in step 3 is crushed, and the step of removing coarse particles of 100 μm or more by classification is performed first, so that classification after step 4 becomes unnecessary. Thus, a phosphor having higher crystal phase purity and high brightness can be obtained.

[Step 4]
In this step, the calcined powder obtained in step 3 is heat-treated in a reducing atmosphere and subjected to reduction firing to obtain phosphor powder.
The calcined powder obtained in step 3 has a target crystal phase, and is a step of substituting europium as an activator for the site of the alkaline earth metal element. Europium in the calcined powder after step 3 is trivalent as in the raw material, but becomes divalent by heat treatment in a reducing atmosphere in step 4 and is replaced with sites of alkaline earth metal elements. High luminance light emission can be obtained.

The reducing atmosphere uses an inert gas such as N ₂ or Ar mixed with ₁ to 10 vol% H ₂ .
The heat treatment temperature is suitably 1200 to 1550 ° C., although there are some differences depending on the composition, as in Step 3. When the heat treatment temperature is lower than 1200 ° C., Eu reduction and substitution are insufficient, and a high-luminance phosphor cannot be obtained. When the heat treatment temperature is higher than 1550 ° C., particle growth proceeds and coarse particles increase, sintering progresses to form a mass instead of a powder, or melts and forms a mass. Grinding is necessary to obtain a powder, which causes a problem that surface defects increase and emission intensity decreases. As a container at the time of heat treatment, alumina or Mo is desirable.

  Subsequent to Step 4, the phosphor powder formed in Step 4 is crushed, washed with water, decanted with ethanol or isopropyl alcohol and dried to clean the surface and fine particles of 5 μm or less Can be removed. If the fine particles remain, it may cause a decrease in luminance due to oxidative degradation or the like.

In step 3 or step 4, a flux may be added for the purpose of promoting particle growth or lowering the heat treatment temperature. As the flux, alkali metal or alkaline earth metal halides are preferable, and those which melt at the heat treatment temperature are selected. Chlorides such as BaCl ₂ and CsCl and fluorides such as SrF and BaF can be preferably used.

As described above, through the above [Step 1] to [Step 4], the high purity composition formula (A, Eu) ₃ SiO _{5 in which} the purity of the target crystal phase is high and the constituent elements are uniformly dispersed well (however, , A is an alkaline earth metal element) -based Eu ²⁺ activated alkaline earth metal silicate phosphor. In addition, it is easy to put to practical use industrially by preventing the generation of cracked gas, soot, and offensive odor that were generated during the thermal decomposition when using organic acids such as citric acid, and also preventing carbon residue after thermal decomposition. Eu ²⁺ activated alkaline earth metal silicate phosphor can be manufactured by a simple manufacturing method.

Hereinafter, the present invention will be described specifically by way of examples.
As the Eu ²⁺ activated alkaline earth metal silicate phosphor, Sr ₃ SiO ₅ : Eu ²⁺ yellow phosphor in which y = 3 and b = 0.985 in the formula (2) is used, and the production method thereof will be described.
The water-soluble silicon compound (WSS) used was prepared as follows.
First, 22.4 ml of tetraethoxysilane: TEOS (manufactured by Kanto Chemical Co., Ltd.) and propylene glycol (99% manufactured by Kanto Chemical Co., Ltd.) were weighed and mixed at 80 ° C. for 48 hours. Further, 100 μl of hydrochloric acid was added to the mixed solution and stirred at room temperature for 1 hour. Distilled water was added to the stirring solution and the solution was dissolved in 50 ml to prepare a 2 M / L water-soluble aqueous silicon solution (WSS).

[Characteristic evaluation]
Identification and semi-quantification of the crystal phase of the prepared phosphor were performed by X-ray diffraction and Rietveld analysis.
The evaluation of the luminescence characteristics was carried out by measuring excitation and emission spectra using a fluorescence spectrophotometer FP-6500 (manufactured by JASCO Corporation), and using a commercially available yellow phosphor Y ₃ Al ₅ O ₁₂ : Ce ³⁺ (YAG : Ce, manufactured by Phosphor Technology Ltd, model number QMK58), and compared. The emission spectrum was measured at an excitation light wavelength of 455 nm, and the excitation spectrum was measured at the peak wavelength of the emission spectrum.

An Sr ₃ SiO ₅ : Eu ²⁺ Eu ²⁺ activated alkaline earth metal silicate phosphor in which the element A in the formula (2) is Sr, y = 3, and b = 0.985 was produced under the following process conditions. .

[Step 1]
SrCO ₃ (3N, manufactured by Kanto Chemical Co., Inc.) and Eu ₂ O ₃ (3N, manufactured by High-Purity Chemical Laboratory) are weighed as raw materials and added to 1.8 times the total weight of water at room temperature. And stirred for 30 minutes to obtain an aqueous dispersion. Subsequently, a predetermined amount of the 2 mol / L water-soluble silicon (WSS) aqueous solution was weighed to prepare a WSS aqueous solution.
Next, an aqueous WSS solution was added to the aqueous dispersion of SrCO ₃ and Eu ₂ O ₃ and stirred for 10 minutes at room temperature. After confirming that the entire liquid became a uniform slurry, a hot magnetic stirrer was used. Heating was started. The heating temperature was set so that the temperature of the mixed solution was 50 ° C. The whole gelled in 15 minutes from the start of heating and became a uniform gel.

[Step 2]
The gel body obtained in step 1 was put into a hot air dryer set at 120 ° C. and dried for 6 hours, and then taken out and lightly crushed in a mortar to obtain a precursor which was a dried product.

[Step 3]
The precursor, which is a dried product obtained in step 2, was put in an alumina container and heat-treated in the air. As for the heat treatment temperature, the first stage was held at 1000 to 1300 ° C. for 3 hours, and the second stage was held at 1500 ° C. for 3 hours. The heating rate was 10 ° C./min. The fired product after the heat treatment was crushed in a mortar, and coarse particles of 100 μm or more were removed by classification with a sieve to obtain a calcined powder.

[Step 4]
The calcined powder obtained in the step 3 was put in a molybdenum container and heat-treated in a reducing atmosphere. The heat treatment temperature was maintained at 1500 ° C. for 3 hours. The heating rate was 20 ° C./min. As a reducing atmosphere, 4% H ₂ + 96% Ar gas was used, and heat treatment was performed by flowing at 1 L / min. The obtained fired product was crushed with a mortar, further washed with water, and then decanted with ethanol to remove fine particles. The phosphor sample was dried in an oven at 60 ° C. for 5 minutes.
The yield of the prepared phosphor was 98.8%, which is a very high yield, when expressed as a ratio of the phosphor weight calculated from the raw material charge and the amount of the phosphor actually synthesized.

  The result of the fluorescence intensity measurement of the obtained phosphor is shown in FIG. From FIG. 1, the obtained phosphor was a yellow phosphor that showed broad excitation absorption from 300 to 500 nm and showed a peak in the vicinity of 585 nm. The obtained phosphor shows twice the emission intensity as compared with commercially available YAG: Ce, and it can be seen that the phosphor has high luminance.

Moreover, the result of having measured X-ray diffraction is shown in FIG. From FIG. 2, the obtained phosphor was an Sr ₃ SiO ₅ single phase without an impurity phase.
Table 1 summarizes the fluorescence intensity, the presence / absence of a different phase of the target phase, and the presence / absence of an organic odor during heat treatment.

In Example 1, the element A in the formula (2) is Sr and Ba, Ba / (Sr + Ba) = 0.05, y = 3, b = 0.985, (Sr, Ba) ₃ SiO ₅ : An Eu ²⁺ phosphor was produced in the same manner as in Example 1 except for the other conditions.
When the yield of the phosphor was expressed by the ratio of the phosphor weight calculated from the raw material charge amount and the amount of the phosphor actually synthesized, it was a very high yield of 98.4%.

  The result of the fluorescence intensity measurement of the obtained phosphor is shown in FIG. As shown in FIG. 3, the obtained phosphor was an orange phosphor exhibiting broad excitation absorption from 300 to 500 nm and a peak around 595 nm. The obtained phosphor was a high-intensity phosphor having an emission intensity 1.8 times that of commercially available YAG: Ce.

Moreover, the result of having measured X-ray diffraction is shown in FIG. From FIG. 4, it is considered that the obtained phosphor has no impurity phase and is a (Sr, Ba) ₃ SiO ₅ single phase.
Table 1 summarizes the fluorescence intensity, the presence / absence of a different phase of the target phase, and the presence / absence of an organic odor during heat treatment.

(Comparative Example 1)
In Step 1 of Example 1, except that the SrCO ₃ and _Eu 2 _{O 3} SrCO ₃ and the total weight of 1.5 times the amount of _Eu 2 _{O 3} the amount of water to disperse the Example 1 Similarly, a phosphor was produced.
The state of the aqueous dispersion of SrCO ₃ and Eu ₂ O ₃ in Step 1 was non-uniform due to the small amount of water, and many precipitation and aggregation of SrCO ₃ particles and Eu ₂ O ₃ particles were observed.

After Step 3, many hard coarse particles were seen, and after Step 4, many black particles and coarse yellow-green particles were seen.
This is presumably because a heterogeneous phase was generated in Step 3 because the mixture of Sr, Eu and Si was non-uniform because the dispersion was non-uniform in Step 1. The hard coarse particles seen in step 3 turned yellow-green in the subsequent step 4 and are therefore considered to be Sr ₂ SiO ₄ phase. Moreover, it turned out that the black particle which appeared in the process 4 is SrO as a result of the SEM-EDX analysis. This is considered that a part of Sr ₃ SiO ₅ is Sr ₂ SiO ₄ and the remaining Sr is generated as SrO.

The obtained phosphor was a phosphor having a luminance with a luminous intensity 1.3 times that of commercially available YAG: Ce.
Table 1 summarizes the fluorescence intensity, the presence / absence of a different phase of the target phase, and the presence / absence of an organic odor during heat treatment.

(Comparative Example 2)
A phosphor was produced in the same manner as in Example 1 except that in Step 2 of Example 1, the concentration of the WSS aqueous solution was 3 mol / L. In Step 2, when an aqueous WSS solution was added to an aqueous dispersion of SrCO ₃ and Eu ₂ O ₃ , local gelation occurred before everything was mixed. After Step 3, many hard coarse particles were seen, and after Step 4, many black particles and coarse yellow-green particles were seen.

Since the dispersion liquid was non-uniform in step 1, it is considered that the mixing of Sr, Eu, and Si was non-uniform, and a heterogeneous phase was generated in step 3.
The obtained phosphor was a phosphor having a luminance with an emission intensity 1.4 times that of commercially available YAG: Ce.
Table 1 summarizes the fluorescence intensity, the presence / absence of a different phase of the target phase, and the presence / absence of an organic odor during heat treatment.

(Comparative Example 3)
In Step 1 of Example 1, TEOS (95%, manufactured by Kanto Chemical Co., Inc.) was used instead of WSS, and TEOS was diluted with water to 2 mol / L, and acid catalyst for gelling TEOS. As in Example 1, except that 0.01 mol times of lactic acid (special grade, manufactured by Kanto Chemical Co., Inc.) was added to TEOS.

In Step 1, TEOS was separated into two phases from water, and even after being added to the aqueous dispersion of SrCO ₃ and Eu ₂ O ₃ , the entire mixed solution did not gel uniformly in a lump.
After step 4, the obtained sample showed no fluorescence and was found to be SrO.
There appears to be a lot of unreacted TEOS in Step 1 and it was volatilized as TEOS when drying in Step 2. For this reason, it is considered that SrO from which the SiO ₂ component was removed after Step 4 was produced.
Although fluorescence emission is not shown, Table 1 shows the presence / absence of a heterogeneous phase and the presence / absence of an organic odor during heat treatment.

(Comparative Example 4)
The following aqueous solutions were prepared using Sr acetate aqueous solution, Ba acetate aqueous solution, and Eu acetate aqueous solution as starting materials.
An aqueous Sr acetate solution was prepared by dissolving Sr acetate (99.9%, manufactured by Kanto Chemical Co., Ltd.) in water to form a 0.5 M / L aqueous solution. The acetic acid Ba aqueous solution was prepared by dissolving Ba acetate (99.9%, manufactured by Kanto Chemical Co., Ltd.) in water to give a 1 M / L aqueous solution. As the aqueous solution of Eu acetate, 0.1 M / L aqueous solution was prepared by dissolving Eu acetate (manufactured by Furuuchi Chemical Co., Ltd.) in water.

  To the separately prepared water-soluble silicon (WSS), an aqueous solution of Sr acetate, an aqueous solution of Ba acetate, and an aqueous solution of Eu are added so that Si: Sr: Ba: Eu has the composition ratio of Example 2, and the above all metals are further added. 4 times the amount of elemental citric acid was added, stirred for 10 minutes, and completely dissolved to obtain a mixed aqueous solution. Then, when stirring was continued at 50 ° C. for 30 minutes, the solution gelled to form a gel body. Subsequent steps were the same as in Example 1.

In step 3, smoke, a burning odor, and soot were generated due to thermal decomposition of citric acid.
After step 4, the yield of the obtained phosphor was as low as 92.8%.
The obtained phosphor had a luminous intensity twice as high as that of commercially available YAG: Ce and was a high-luminance phosphor, but had a problem of yield and odor accompanying decomposition of organic substances.
Table 1 summarizes the fluorescence intensity, the presence / absence of a different phase of the target phase, and the presence / absence of an organic odor during heat treatment.

As described above, according to the method of the present invention, a uniform gel body can be obtained by mixing a water-soluble silicon (WSS) and alkaline earth metal element carbonate dispersion without using an organic acid such as citric acid. After that, a high-brightness Eu ²⁺ activated alkaline earth metal silicate phosphor can be produced by drying, calcining, and reduction firing. Furthermore, generation of cracked gas, soot and off-flavor generated during pyrolysis when organic acids are used can be eliminated, carbon residue due to non-uniform pyrolysis generated during firing can be prevented, and industrial practical use is easy It is a simple manufacturing method.

Claims (4)

In the process for producing Eu ²⁺ activated alkaline earth metal silicate phosphor of compositional formula (A, Eu) ₃ SiO ₅ (where A is an alkaline earth metal element), the following step 1, step 2, step 3, step 4 are performed. A method for producing an alkaline earth metal silicate phosphor, comprising:
[Step 1]
An aqueous dispersion of at least one alkaline earth metal carbonate selected from Ba and Sr as constituent metal components;
An aqueous dispersion of europium oxide;
A gel in which all components are uniformly dispersed by heating and stirring a mixed solution with a water-soluble silicon compound aqueous solution having a water-soluble silicon compound concentration of 2 mol / L or less at a liquid temperature of 30 to 100 ° C. The process of making a body.
[Step 2]
The process of forming the precursor which is the dried material which dried the said gel body produced by the process 1, and removed the solvent contained.
[Step 3]
A step of obtaining a calcined powder by subjecting the precursor prepared in the step 2 to a two-step heat treatment in an air atmosphere at a temperature of 1000 to 1300 ° C. in the first step and 1100 to 1500 ° C. in the second step.
[Step 4]
A step of obtaining a phosphor powder by heat-treating the calcined powder produced in step 3 at a temperature of 1200 to 1550 ° C. in a reducing atmosphere.   The water-soluble silicon compound used in the step 1 is a water-soluble silicon compound in which a diol compound is added to an organosilicon compound, heated, stirred and mixed, and then a trace amount of acid is added. The manufacturing method of alkaline-earth metal silicate fluorescent substance as described in any one of.   2. The alkali according to claim 1, further comprising a step of crushing the calcined powder formed in Step 3 and performing classification to remove coarse particles of 100 μm or more following Step 3. A method for producing an earth metal silicate phosphor. 2. The method according to claim 1, wherein the phosphor powder formed in step 4 is crushed, washed with water, decanted with ethanol or isopropyl alcohol, and dried after step 4. A method for producing the alkaline earth metal silicate phosphor described.

Images