JPH03207787A - Rare earth metal silicate salt fluorescent substance and preparation thereof - Google Patents

Abstract

PURPOSE:To prepare the subject fluorescent substance reduced in the lowering of brightness and highly useful for CRT, fluorescent lights, etc., by subjecting a gel or sol to a hydrothermal reaction to allow a crystal to grow for forming a polyhedron having a clear crystal habit. CONSTITUTION:A homogeneous solution containing rare earth ions for forming the center of emission, other rare earth element ions for forming matrix salts and a silicic acid alkoxide is prepared, and a solvent is removed before or after a gel product is prepared from the solution or after a co-precipitated sol is formed. The prepared gel or sol is subjected to a hydrothermal reaction to form the nuclei of crystals, and evaporative decomposed components are removed to pulverize. The prepared powder is reacted with water in a closed container under high temperature and pressure to allow crystals to grow. The crystals are dehydrated and heated in the atmosphere or in a reducing atmosphere to stabilize the surfaces of the crystals for providing the objective fluorescent substance.

Description

[Detailed Description of the Invention] [Industrial Field of Application] The present invention is a phosphor that emits light when stimulated by electron beams or ultraviolet rays, and is a rare earth phosphor used in the manufacture of cathode ray tubes (CRTs), discharge lamps, plasma displays, etc. This invention relates to a silicate phosphor and its manufacturing method.

[Prior Art] Rare earth silicates, such as yttrium silicate (Y2
Sins) as the mother salt and various activators (Tb%Ce+T
bs Ces Gd, etc.) are known to emit light in the ultraviolet to green range through studies including the synthesis of single crystals (J. Shsul Pitch).
J. Electroches.
Soc. ) J L35 [12] (1988) L314
1-3151). As a typical example, projection type CRT
Y2 810, which is also used as the green component of a three-wavelength phosphor that utilizes the main emission (254 ns) of mercury vapor,
: Explain about Tb green phosphor.

Y2 Sins: Tb phosphor has a main emission peak at 543 ns when excited with an electron beam, and has relatively high brightness.
Even if the stimulation current density increases, the luminescence intensity does not saturate.
Phosphors are characterized by good so-called γ characteristics, but in response to future high-definition televisions (HDTV), higher brightness and lower deterioration are required.

Such Yz SIOs:Tb phosphors are manufactured by solid phase reaction of oxides as described in, for example, US Pat. Added high brightness,
Efforts have been made to reduce deterioration (see Japanese Patent Publication No. 48-37670).

The conventional manufacturing method of Y2SiOs:Tb phosphor will be explained below.

In this manufacturing method, yttrium oxide and terbium oxide are mixed with silicon dioxide and fired at high temperature. In order to improve the uniform dispersion of terbium, the yttrium oxide and terbium oxide are first dissolved in acid, and then oxalic acid is added. was added to obtain an oxalate composite coprecipitate, which was filtered and then fired in the air at around 1000°C to yield a yttrium-terbium composite oxide, and this composite oxide and silicon dioxide were thoroughly mixed. 1600℃ in a slightly reducing atmosphere
This method involves firing at a temperature above, and then crushing and classifying with a ball mill or the like in order to adjust the particle size. Usually, the obtained powdered phosphor is applied to a tube by a suitable means and then used as a lamp.

[Problems to be Solved by the Invention] In the conventional method, Yz SIOs: Tb is obtained by a solid phase reaction represented by formula (I):
A phosphor is manufactured. This reaction involves interdiffusion of ions, and the higher the temperature, the more the reaction proceeds in the right direction, increasing the conversion rate. In addition, sufficient diffusion of terbium ions to the yttrium site occurs, achieving more homogenization and concentration quenching (
Non-luminescent centers and killers are generated due to aggregation of the activator and the formation of ion pairs, leading to a decrease in luminescence brightness). In this sense, it is desirable that the reaction temperature is high enough to prevent melting, but as a result of ion diffusion, macroscopic crystallization is promoted and coarsening occurs. These coarse particles need to be ground to an appropriate particle size using a ball mill or the like in order to be suitable for subsequent processes such as coating. However, methods of grinding using external mechanical energy such as a ball mill cause various defects on the particle surface.
It has recently become clear that there are essential problems such as brightness deterioration and particle size distribution greatly expanding due to deterioration of crystallinity (formation of a non-emissive layer on the surface and formation of various trap centers).

Furthermore, since it is based on a solid-phase reaction, variations in the surface properties of silicon dioxide due to the type of silicon dioxide, lot differences, etc. have an extremely large effect on its reactivity, and there is also the drawback that the luminescent properties are extremely dependent on the raw materials.

The present invention has been made in order to solve the above-mentioned problems, and provides a rare earth silicate phosphor with excellent crystallinity and uniform particle size, and a method for producing the phosphor without employing a high-temperature solid phase reaction. Regarding the method.

[Means for Solving the Problems] In order to solve the above-mentioned problems, the present inventors developed Zn
2 Si04: An example in which Mn was synthesized from an aqueous Zn(NO3)2 solution and tetraethyl orthosilicate to achieve high brightness (R. Moriso et al., “
Material Research Vinylten (Mat. Res
．． Bull. ) J24 (1989) L175-17
9) , YAG: Tb (Y3#sO+r: Tb)
Hydrothermal method to synthesize particles with uniform particle size (T. Takamori (T.
Takamori et al., “American Ceramic Society Bulletin (Aj Cerag+. Soc.
．． Bull. ) J 65 [9] (1986) p. 1
282 - 1286, this report details the case of hydrothermal synthesis from an aqueous solution containing yttrium ions and terbium and aluminum hydroxide by sealing the tube with a gold vibrator. (Although the phosphor properties are unknown), crystals are grown using hydrothermal synthesis, and crystals are scaled due to poor quality using hydrothermal synthesis (for example, Munemiya et al. “Powder Metallurgy J 31 [8] (1984) I). 25
3-259, Somiya et al., “Powder Metallurgy J a6[el (1
9g9) p. 101 to 105), etc., and the present invention was arrived at.

That is, in the present invention, the grain size of crystals grown by hydrothermal reaction is 5 to 20.
A rare earth silicate phosphor having a polyhedral shape in which each crystal face is at least better developed than its pre-hydrothermally-reacted particles and has clear separation; and (A) a light emitting material. Step of preparing a homogeneous solution containing a rare earth element ion that can be the center, other rare earth element ions forming a mother salt, and a silicate alkoxide, (B) (b-1> Spray drying or freezing before the homogeneous solution gels) a step of removing the solvent by drying, (b-2) a step of polymerizing the silicic acid alkoxide in the homogeneous solution to produce a gelled product, and then removing the solvent in the gelled product by heating; or (b-3) a step of removing the solvent in the homogeneous solution. After forming a coprecipitated sol of rare earth element ions and silicate alkoxide by increasing the pH, the solvent in the coprecipitated sol is removed (C) The product obtained in step (B) is heated to crystallize it. Step of generating nuclei, removing volatile decomposition components, and turning into powder; (D) The powder obtained in step (C) is made to interact with water in a closed container at high temperature and high pressure to grow crystals. and (E) dehydrating the obtained crystal and heating it in air or a reducing atmosphere to stabilize the surface.

[Function] In the present invention, all of the raw materials are made into a solution and the rare earth elements are mixed in an ionic state, so that the ion dispersion state is improved, concentration quenching is reduced, and the addition efficiency of the activator is improved.

Moreover, by the steps (B) to (E), crystals with very few surface defects, excellent crystallinity, and uniform grain size can be obtained.

[Example] The phosphor of the present invention contains rare earth element ions (
It is a silicate containing other rare earth element ions (hereinafter also referred to as luminescent center ions) and other rare earth element ions forming the mother salt.

Examples of the luminescent center ions include Tb (terbium), Ce (cerium), Gd (gadolinium), Eu (eurobium), Sl (samarium), and Tb.
Examples include ions such as I (thulium), and one or more of these may be contained.

Other ions forming the mother salt include ions such as Y (yttrium), La (lanthanum), and Cd (gadolinium), and one or more of these ions may be contained.

The composition of the rare earth silicate containing the luminescent center ion is, for example, YzSiOs:Tb,Y2SiO
s:Gd, YzSiOs:Ce%
Y2SiOs: Ts, YzSiOs: Ce
．． Tb s YzSiOs: Cd. Tb%Y
2S10S: Eu%YzSiOs: Eu. Tb
s YzSiOs: Sa, Y2SiOs: Sm
．． Ce, LazSjOs: Tb, GdzS
Examples include, but are not limited to, iOs; Tb.

Since the rare earth silicate is crystal-grown by hydrothermal synthesis, each crystal face is developed better than the particle shape before the hydrothermal reaction, and the quality is clearly seen. Further, the particle size of the rare earth silicate is 5 to 20 mm, preferably 5 to 20 mm. If the particle size is less than 5, the brightness will decrease because there are parts of the surface with low luminous efficiency, and conversely, if the particle size exceeds 20, the efficiency will increase, but the quality of the surface coated by the sedimentation coating method will deteriorate. In particular, a size of about l〇1 is preferable.

Since the rare earth silicate phosphor of the present invention is composed of the crystals described above, it is a phosphor that can be applied to tubes without pulverization and has a luminance deterioration of several to 10% less than conventional phosphors. (See Figure 3).

Next, a method for manufacturing the phosphor of the present invention will be explained.

In the production method of the present invention, first, a homogeneous solution containing ions of a rare earth element that can serve as a luminescence center, ions of other rare earth elements forming a mother salt, and a silicate alkoxide is prepared (containing step).

There is no particular limitation on the method for preparing the homogeneous solution containing the luminescent center ion, the ion forming the mother salt, and the silicate alkoxide, but for example, an oxide of a rare earth element serving as the luminescent center ion, a rare earth element serving as the ion forming the mother salt, etc. Examples include adding a strong acid such as nitric acid, hydrochloric acid, or sulfuric acid to a suspension consisting of an oxide of an element and water, heating it to completely dissolve these rare earths, and then adding and mixing a silicate alkoxide. It will be done. At this time, in order to homogeneously disperse the silicate alkoxide, alcohols, N. N"-dimethylformamide or the like may also be added.

The rare earth element oxides serving as the luminescence center ions include Tb40 7 , CeOz, Gd203, Eu203,
Rare earth element oxides such as Sl203 and Tm203, which become ions forming the mother salt, include Y203 and La20.
3, Gd203, etc.

The silicate alkoxide is not particularly limited, but an alkoxide having an alkoxy group having 1 to 4 carbon atoms, such as a methoxy group, an ethoxy group, an isobroboxy group, a tertiary butyroxy group, etc., and is liquid at room temperature is preferred. Specific examples of the silicate alkoxide include (C2
}IsO)4Si, (CH30)4Si, (1-
C3H 70 )4 ], (t-C+8 90)4S
i, etc., but from a practical point of view (melting point, etc.), especially (C2H sO )4 81, (C}l30
)+Sl, (1-C3H70)4. St is preferred because it is easy to use. A homogeneous solution contains one or more of these.

For example, regarding the YzSiOs:Tb ratio, as mentioned above, the reaction represented by the formula (I): is the final reaction ε, but when preparing a homogeneous solution, the atom ratio of Y and Tb and S1 The atom ratio (molar ratio) of is slightly changed.

Therefore, basically Y/Tb-1.8B/(1
．． 14 (atom ratio), and S1 is (
Y. Tb)/81-1 to about 1.2. That is, Y203 and Tb40y are weighed so that the atom ratio is 1.8670.14, and this is dissolved in acid, and the amount of silicate alkoxide is equal to or slightly increased with respect to the number of moles of both oxides. Added.

Next, the solvent is removed from the homogeneous solution by any of the methods (b-i) to (b-3) below to produce a non-quality dried product (step (03)). Note that the above-mentioned solvent refers to water, alcohol, formamide, etc. used to prepare a homogeneous solution.

Method (b-1) is a method in which the solvent is removed by spray drying or freeze drying before the homogeneous solution gels. This method has the advantage that the solvent can be rapidly removed and homogeneity can be maintained in a microscopic sense.

The spray drying process produces a porous spherical powder with a particle size of about 5 to 50 mm, and the freeze drying process produces a porous spherical powder with a particle size of 1.
A bolus of spherical powder in the range of 0 to 100 can be exchanged.

Method (b-2) is a method in which a gelled product is produced by polymerizing silicate alkoxide in a homogeneous solution, and then the solvent in the gelled product is removed by heating. In this method, uniformity is maintained through gelation, and an amorphous powder with good homogeneity can be obtained very easily by simply removing the solvent by heating.

The gelled product can be produced by heating a homogeneous solution in an oven at about 40° C. for about 24 to 48 hours. The solvent is then removed by raising the temperature to about 120°C. The result is a white powder or a slightly agglomerated lumpy powder aggregate. By removing the solvent from the gelled product in this manner, problems such as the danger of bumping and non-uniformity of the dried product, which occur when the solvent is directly removed from a homogeneous solution, do not occur.

In method (b-3), a coprecipitated sol containing the luminescent center ion, other ions forming the mother salt, and silicate alkoxide is formed by increasing the pH of the homogeneous solution, and the solvent in the coprecipitated sol is This is a method of removing it.

This method has the same advantage as method (b-2) in terms of ease of solvent removal, and is a modified method thereof.

The coprecipitated sol is prepared by adding dilute ammonia water, for example, to a homogeneous solution.
It can be formed by adding concentrated ammonia water or the like to adjust the pH to about 7 to 9. The solvent can then be removed by heating the resulting sol in an oven to about 120°C. The resulting product was an amorphous white powder with some weak agglomerations.

Next, powder is produced by heating the product obtained in step (B). This heat treatment removes volatile decomposition components such as solvent remaining in the dried material, and generates crystal nuclei necessary to obtain a predetermined particle size ((
C) process).

The heat treatment is performed at 500 to 800"C for 12
By heating for ~24 hours to remove residual unused decomposed and volatile components such as alcohol, water, and nitric acid, the powder is of X-ray quality (no clear diffraction peaks appear in the X-ray diffraction pattern, see Figure 1). After producing, it is preferable to further heat the product at 800 to 1200° C. for 2 to 10 hours to crystallize it to some extent by X-rays. By this heat treatment, the X-ray diffraction peaks become progressively stronger and crystallization becomes clearer.

The heating temperature depends on the balance with the hydrothermal reaction conditions in step I)), but crystals with well elongated crystal faces may be heated near the crystallization temperature (temperature in the transition region from non-quality to crystalline). It is preferable to heat at the crystallization temperature. Crystallization temperature is DTA (differential thermal analysis), TG
(Thermobalance), high temperature X-ray equipment, etc. The temperature at which non-quality powder crystallizes varies depending on the type of silicate alkoxide and the type of acid used for dissolution. and the temperature of the test using hydrochloric acid is about 800°C.

Next, crystals are grown to a predetermined size by a so-called hydrothermal reaction in which the powder obtained in step (0) and water (pure water) are reacted at high temperature and high pressure in a closed container (0)
process).

The heating and pressurizing conditions promote crystallization and reduce the particle size to 5.
~2QA! Usually 380-6 to make it about Il1
00℃, more preferably 400-600℃, 30-2
50 MPa, more preferably 50 to 150 MPa
, 3 to 50 hours, more preferably 10 to 30 hours. Note that in consideration of mass productivity, it is preferable to carry out the reaction at as low a pressure and as low a temperature as possible.

In step (g) above, when hydrochloric acid is used to prepare a homogeneous solution, (because the powder obtained in step O contains chlorine ions, these ions promote crystallization and The size of the crystal grains is about one order of magnitude (several hundred and one) larger than that of the uncontained crystals.Also, when performing a hydrothermal reaction, ammonia etc. are added to adjust p}I,
Crystallization may be promoted by adding an alkali ion metal such as Na'' (sodium ion) or K'' (potassium ion).

These ions are added in consideration of their influence on luminescence characteristics. Further, the crystal growth rate can also be changed by changing the proportions of luminescent center ions, ions forming the mother crystal, and silicate alkoxide in the homogeneous solution.

Furthermore, during the hydrothermal reaction, a portion of a water-soluble solvent such as alcohol that can dissolve and precipitate the powder obtained in step (C) may be added.

The hydrothermal reaction can be carried out using the sealed tube method, in which the material is sealed in a brass tube, etc., and then placed in a pressure vessel of a hydrothermal synthesis equipment to heat and pressurize it, or a method that uses a pressure vessel lined with gold or platinum. It is preferable to use a method that can prevent contamination with impurities.

Next, the obtained crystal is heated in the air or in a reducing atmosphere such as an atmosphere containing CO or a mixed gas of nitrogen and hydrogen to dehydrate the rare earth silicic acid whose surface is stabilized. A salt phosphor is manufactured (Step (E)).

It is preferable that the heating is first carried out at about 120°C for about 60 minutes to dehydrate, and then at 300-500''C for about 1-5 hours.

By the manufacturing method of the present invention including the above-mentioned conversion process, a rare earth silicate phosphor having a particle size of 5 to 2 degrees and which is reduced in brightness deterioration is manufactured.

The present invention will be described in more detail below based on Examples.

Example 1 Yttrium oxide (Y203, purity 99.99% or more)
42g and terbium oxide (Tb40y, purity 99.
9% or more) was suspended in water (iDml), 100ml of concentrated nitric acid (HNOs) was slowly added while stirring well using a magnetic stirrer, and the mixture was thoroughly reacted to completely dissolve the two, and then cooled. The obtained solution and TEOS (tetraethoxyorthosilicate (
C2 HSO)4 S1, purity 99.99% or more,
density 0.94g/1) 45.8ml, ethyl alcohol (C2H50H) 50ml and N. N
'-Dimethylformamide ((CHi) 2N CHO
) and a solution obtained by stirring and mixing 25 ml thoroughly. In addition, in this formulation, (Y.Tb)zOs /St02
-1. Ethyl alcohol and N. N'-dimethylformamide was added in consideration of homogeneous dispersibility of TEOS.

After mixing for about 30 minutes and confirming that the solution was homogeneous, it was heated in an oven at about 40° C. for 48 hours to slowly cause a polymerization reaction and form a gel. In order to remove the solvent from this gelled product, the temperature was raised to 120°C and
Dehydration and dealcoholization were performed by heating for about 8 hours. In this state, the solvent has not been completely removed, so the material is transferred to an alumina crucible and heated at 500°C for 24 hours.
Most of the alcohol, nitric acid, water, and other added organic substances were removed to obtain a pale brown powder. The results of X-ray diffraction analysis of the obtained powder are shown in FIG. From FIG. 1, it can be seen that this powder is X-ray amorphous.

Next, the powder was heated at 1000° C. for 4 hours to produce a powder that was X-ray crystallized to some extent.

Next, approximately 5,011 g of the obtained powder and approximately 0.3 ml of pure water were sealed in a brass tube (diameter 4 wa, length 5 ml) sealed at one end by welding.
cm), the ends of the residue were sealed by welding, and this was placed in a pressure vessel of a hydrothermal synthesis equipment and heated at 500°C for 10
After being left at 0 MPa for about 24 hours, the cooling rate was 10°C.
The mixture was cooled to room temperature at a rate of about 1/hr. The contents were taken out from the sealed tube, dried at 120°C for 60 minutes, and then dried at 300°C in the air.
The surface was stabilized by heating at .degree. C. for 2 hours, yielding 40 .mu.m of crystalline powder.

The obtained crystals are 833 in Figs. 4 and 5, respectively.
As shown in the SEX (scanning electron microscope) photograph at 6579 times, the particle size is 5 to 15. It can be seen that the crystal powder has a polyhedral shape with well-grown crystal planes.

On the other hand, the shape of the powder before the hydrothermal reaction (after heating at 500° C. for 24 hours) was not constant as shown in the SEX photograph at 2500 times magnification in FIG. 6, and the crystallinity was extremely poor.

Moreover, the results of examining the X-ray diffraction of the obtained crystal are shown in FIG. From FIG. 2, it was confirmed that the obtained crystal also matched the diffraction pattern of yttrium silicate in terms of X-rays, and was single-phase.

Example 2 and Comparative Example 1 In order to produce a larger amount of phosphor than in Example 1, the same procedure as in Example 1 was carried out by replacing the brass tube with a gold vibrator with an inner diameter of 10 clI and a length of 100 csa, and using a hydrothermal synthesis apparatus with a large internal volume. In the same manner, about 0.3 g of crystal powder was obtained.

The crystalline phase of the obtained powder showed only the diffraction peak of the single phase of Y2SIOs, and the particle shape was polyhedral in size, which was almost the same as that of the powder obtained in Example 1 (small scale example), as observed by SEH. After confirming that
The change in luminescence intensity of this powder by electron beam irradiation was investigated. That is, in order to observe the luminescence of the phosphor itself, the powder was shaped into a pellet and directly irradiated with an electron beam (acceleration voltage 20 kV, current density 1.5 μ^/cd), and the change in brightness was continuously measured. We investigated relative changes over time. The results are shown in FIG. 3 as a solid line. In addition, for comparison, the results of investigating the change in luminescence intensity of powder obtained by the conventional solid-phase sintering method are shown in the third section.
Indicated by dashed lines in the figure. From FIG. 3, it can be seen that the phosphor obtained by the manufacturing method of the present invention exhibits more stable luminance characteristics with less deterioration than the phosphor obtained by the conventional solid phase sintering method.

This seems to be largely due to its crystallinity. For comparison, the conventional solid phase sintering method (Y203(Tb
) + 8102, 1600° C. for 4 hours) SEX photograph of the powder obtained by 2500 times magnification is shown in FIG.

In Examples 1 and 2, phosphors were manufactured and evaluated by adding terbium (Tb) as an activator to yttrium (Y).
b) + Cerium (Ce), gadolinium (Cd), eurobium (Eu), samarium (Ss), or thulium (T■) are changed through the same process, so that each crystal plane is well developed and the crystallinity is improved. The phosphor was replaced with a phosphor with a uniform particle size and improved deterioration characteristics. In addition, similar results were obtained by replacing yttrium with lanthanum, gadolinium, etc., and using different mother salts or mixed crystals of these. Thus, it can be seen that the crystallization method using a hydrothermal reaction is an extremely excellent method for obtaining rare earth silicates with good crystallinity.

Comparative Example 2 A phosphor was produced in the same manner as in Example 1 except that the non-quality powder was not heated at 1000"C for 4 hours. Although it crystallized, the crystal growth rate was low, so the particle size was small and each The growth of crystal planes was also insufficient.This may be related to the establishment of nucleation, but the particle size distribution of the particles was not significantly improved.

Example 3 Yttrium oxide 42g and terbium oxide 5.24g
After dissolving T in 100ml of concentrated nitric acid and BOml of water,
45.8 ml EOS and 50 ml ethyl alcohol
1 of the mixture was added and stirred well. While continuing to stir,
Dilute ammonia water (!N) was slowly added dropwise. Since nitric acid remained, considerable heat of neutralization was generated, so the solution was added dropwise while cooling. As the pH increases, yttrium,
Sudden sedimentation, thought to be terbium hydroxide, began to occur, and p
When H exceeded 7, TEOS itself also began to polymerize and precipitate due to the presence of OH-. There was enough water to form a so-called sol state, but as it was decanted, a precipitate formed. This was heated in an oven at 120° C. for about 24 hours, then transferred to Luppo and heated at 500° C. for 24 hours to obtain non-quality powder.

Next, in the same manner as in Example 1, heating at 1000"C for 4 hours, hydrothermal reaction, 120"C for 6O minutes, 300"C.
Heating was carried out for a period of time to obtain a crystalline powder similar to that of Example 1.

Example 4 After dissolving 42 g of yttrium oxide and 5.24 g of terbium oxide in 100 ml of concentrated nitric acid and a bowl of water, TEO
A mixture of 45.8 ml of S and 50 ml of ethyl alcohol was added and stirred well. While continuing to stir, 120 ml of concentrated ammonia water (reagent grade) was added dropwise.
The entire mixture, including the hydroxide fine powder, became highly viscous and began to gel. At this stage, stirring was no longer possible.

Next, the gelled product was placed in an oven at 120"C for about 48 hours to dry it out, and then transferred to a Lupo oven for about 5 hours.
Heated at 00℃ for 24 hours to remove unnecessary decomposition components,
I received non-quality powder.

Next, in the same manner as in Example 1, heating at 1000"C for 4 hours, hydrothermal reaction, 120"C - 80 minutes, 300"C
- Heating was performed for 2 hours to obtain the same crystalline powder as in Example 1.

Example 5 The solution prepared in Example 1, in which the solution of yttrium oxide and terbium oxide dissolved in nitric acid and the TEOS and ethyl alcohol solution were thoroughly mixed and homogenized, was heated with hot air using an explosion-proof spray dryer (body diameter: approximately In). Dry. The spray dryer uses a disk type, and the disk is made of zirconia (Zr02), considering its strong acidity.
Furthermore, we partially reinforced the spray dryer with Teflon to prevent water droplets atomized by the atomizer from directly adhering to the stainless steel inner cylinder of the spray dryer. Solution dropping speed to disk 20
ml/win (using metering pump), hot air speed 230
"C, atomization was carried out at a rotational speed of about 10 and ODO rpm.

The obtained powder had a porous spherical shape, and the particle size varied slightly with a center of 2o.

Since the obtained powder contained some water, the temperature was once raised to 800° C. to remove volatiles, and the powder was heated for 4 hours to generate nuclei. The obtained powder (partially crystallized) was used to grow crystals by the same hydrothermal reaction as in Example 1, and then heated at 120°C for 60 minutes and 30D"C for 2 hours. A similar crystalline powder was obtained.

Example 6 To a suspension consisting of 42 g of yttrium oxide, 5.24 g of terbium oxide and 60 ml of water, 10 g of concentrated nitric acid was slowly added.
Add 0 ml of ethyl alcohol to completely dissolve them, and then quickly mix the solution with an equal amount of water and the solution of TEOS 45.8 mu and 50 ml of ethyl alcohol. The mixture was atomized using an atomizer equipped with an atomizer, and the mist was blown into hexane cooled with dry ice and trichlene. A solidified solution of water sank into this refrigerant. After cooling a predetermined amount, hexane was removed, ice pieces were collected, and the mixture was sublimated under reduced pressure in a freeze dryer to obtain a powder.

The obtained powder had a particle size of 10 to 100, and was porous spherical particles. Next, heating in the same manner as in Example 5,
A hydrothermal reaction and heating were performed to obtain the same crystalline powder as in Example 1.

[Effects of the Invention] As described above, the production method of the present invention improves the homogeneity of the activator in the rare earth silicate by starting from a solution-like raw material, and also combines the hydrothermal method. This makes it possible to obtain a phosphor with uniform crystal size and excellent crystallinity. The resulting phosphor exhibits little reduction in brightness and is therefore extremely useful for CRTs, fluorescent lamps, and the like.

[Brief explanation of drawings]

Figure 1 is a graph of X-ray diffraction of the non-quality powder from which the solvent has been removed, Figure 2 is a graph of X-ray diffraction of the phosphor of the present invention, and Figure 3 is a graph of the phosphor of the present invention and conventional solid phase sintering. Fig. 4 is a graph showing the change in emission intensity of the phosphor obtained by the method, Fig. 4 is an 833x SEX photograph showing the crystal structure of the phosphor of the present invention, Fig. 5
The figure shows the crystal structure of the phosphor of the present invention with a SE of 6579 times.
M photo, Figure 6 shows the particle structure of the powder before the hydrothermal reaction2
500x SEM photograph, Figure 7 is a 2500x SEM showing the particle structure of the phosphor obtained by the conventional solid phase sintering method.
It's a photo. X-ray intensity X-ray intensity 3 times 0 800 hours (hours) Figure 4 Figure 5

Claims (2)

[Claims] (1) A rare earth silicate phosphor with a grain size of 5 to 20 μm grown by hydrothermal reaction, in which each crystal face is at least better developed than the grain before the hydrothermal reaction, and the crystal cleavage is Rare earth silicate phosphors with distinct polyhedral shapes. (2) (A) Step of preparing a homogeneous solution containing a rare earth element ion that can serve as a luminescence center, other rare earth element ions forming a mother salt, and a silicate alkoxide, (B) (b-1) Gelation of the homogeneous solution (b-2) A step of polymerizing the silicic acid alkoxide in the homogeneous solution to produce a gelled product, and then removing the solvent in the gelled product by heating, or ( b-3) A step of forming a coprecipitated sol of rare earth element ions and silicate alkoxide by increasing the pH of the homogeneous solution, and then removing the solvent in the coprecipitated sol, (C) a step obtained in step (B). (D) The powder obtained in step (C) and water are heated in a closed container at high temperature and under high pressure. (E) dehydrating the obtained crystals and heating them in air or a reducing atmosphere to stabilize the surface of the rare earth silicate phosphor. manufacturing method.