JP2002038144A - Method for producing zinc silicate phosphor - Google Patents

Abstract

(57) [Abstract] [Object] It is an object of the present invention to provide a method for producing a manganese-activated zinc silicate phosphor having a narrow particle size distribution, a uniform shape, a uniform chemical composition, and excellent emission characteristics. SOLUTION: An aqueous solution containing at least manganese, silicon and zinc is prepared, formed into droplets, introduced into a thermal decomposition reactor together with a carrier gas, and is heated to 1050 ° C to 143 ° C.
A method for producing a manganese-activated zinc silicate phosphor, which comprises heating at a temperature of 0 ° C. for 1 second to 10 minutes to thermally decompose.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION The present invention relates to a cathode ray tube (CRT),
The present invention relates to a method for producing a manganese-activated zinc silicate phosphor suitable for use in displays such as a plasma display panel (PDP) and a field emission display (FED), and a fluorescent film such as a fluorescent lamp.

[0002]

2. Description of the Related Art Composite oxide phosphors used as fluorescent films for displays such as CRTs, PDPs, and FEDs and fluorescent lamps are conventionally prepared by mixing raw material powders and placing them in a firing vessel such as a crucible at a high temperature. It has been manufactured by heating for a time to cause a solid-phase reaction, which is finely pulverized by a ball mill or the like.

However, the phosphor produced by this method is
It is composed of powder in which irregularly shaped particles are aggregated. When this phosphor is used for the above-mentioned applications, the phosphor film obtained by coating is inhomogeneous and has a low packing density. Could not get. In addition, the phosphor was subjected to physical and chemical shocks in the fine pulverization treatment such as a ball mill after the solid-phase reaction, causing defects in and inside the phosphor particles, resulting in a decrease in luminous intensity. . Furthermore, since it is placed in a baking vessel such as a crucible and heated at a high temperature for a long time, impurities are mixed in from the crucible to lower the light emission characteristics, or the solid phase reaction does not proceed sufficiently depending on the particle size of the raw material powder, resulting in In some cases, an impurity phase is mixed in the obtained phosphor, resulting in deterioration of light emission characteristics. In addition, since the energy consumed when heating at a high temperature for a long time is large, the manufacturing cost of the phosphor has been increased.

By the way, manganese-activated zinc silicate phosphor is one of the complex oxide phosphors that have been practically used as green light-emitting phosphors for displays and fluorescent lamps for a long time. Like the composite oxide phosphor,
It has the above-mentioned problems, and its improvement has been desired.

[0005]

DISCLOSURE OF THE INVENTION The present invention has been made to solve the above-mentioned problems, and is directed to a manganese compound having a narrow particle size distribution, a uniform shape, a uniform chemical composition, and excellent light emission characteristics. An object of the present invention is to provide a method for producing an activated zinc silicate phosphor.

[0006]

Means for Solving the Problems The present inventors have studied the production conditions of a manganese-activated zinc silicate phosphor in detail, and as a result, have replaced the conventional production method in which each raw material mixture powder is heated and reacted between solids. Thus, the above-mentioned problem can be solved by once dissolving and uniformly mixing the phosphor raw material compounds to form droplets, and heating and thermally decomposing.

The structure of the present invention is as follows. (1) An aqueous solution containing at least manganese, silicon, and zinc is prepared, and the resulting solution is dropped into a pyrolysis reactor together with a carrier gas. The solution is heated at a temperature of 1050 ° C to 1430 ° C for 1 second to 10 minutes. A method for producing a manganese-activated zinc silicate phosphor, wherein the phosphor is heated and thermally decomposed. (2) The method for producing a manganese-activated phosphor according to the above (1), wherein manganese nitrate, tetraethyl orthosilicate and zinc nitrate are used as raw materials of the manganese, silicon and zinc, respectively.

(3) The number of moles of silicon Ms, the number of moles of zinc Mz and the number of moles of manganese Mm contained in one liter of the aqueous solution are 1.6 ≦ (Mz + Mm) /Ms≦2.2 and 0.2. The method for producing a manganese-activated phosphor according to the above (1) or (2), wherein a relationship of 005 ≦ Mm / (Mz + Mm) ≦ 0.09 is satisfied.

(4) The number of moles of silicon Ms, the number of moles of zinc Mz and the number of moles of manganese Mm contained in 1 liter of the aqueous solution are 1.7 ≦ (Mz + Mm) /Ms≦2.0 and 0. The method for producing a manganese-activated phosphor according to the above (1) or (2), wherein a relationship of 02 ≦ Mm / (Mz + Mm) ≦ 0.06 is satisfied. (5) The total C (= Mm + Ms + Mz) of moles of manganese, silicon and zinc in 1 liter of the aqueous solution is 0.03 to
15. The method for producing a manganese-activated phosphor according to any one of the above (1) to (4), wherein the manganese-activated phosphor is in a range of 15 and preferably in a range of 0.1 to 10.

(6) The method for producing a phosphor according to any one of the above (1) to (5), wherein ultrasonic waves are used as a means for forming droplets of the aqueous solution. (7) The method for producing a manganese-activated phosphor according to any one of (1) to (6), wherein an oxidizing gas or an inert gas is used as the carrier gas.

(8) The method for producing a manganese-activated phosphor according to the above (7), wherein air is used as the oxidizing gas. (9) The method for producing a manganese-activated phosphor according to the above (7), wherein a nitrogen gas is used as the inert gas.

[0012]

BEST MODE FOR CARRYING OUT THE INVENTION Hereinafter, the present invention will be described in more detail. In the method for producing a phosphor of the present invention, first, as starting materials, a compound of zinc and silicon, which are metals constituting a base of the manganese-activated zinc silicate phosphor, and manganese which is an activator of the phosphor, Dissolve the compound in water, manganese,
A raw material aqueous solution containing silicon and zinc is prepared. These phosphor starting materials are halides, hydroxides, sulfates, acetates containing zinc, silicon and manganese elements,
Any material can be used as long as it is a raw material that is soluble in water, such as oxalate, carbonate or the like, or an organometallic compound, and that decomposes to an oxide when heated to a high temperature. . Note that the phosphor starting material is not necessarily a water-soluble compound, but may be used after previously dissolved in nitric acid, hydrochloric acid, or the like, and then appropriately diluted.

[0013] Among the above phosphor starting materials, zinc nitrate, tetraethyl orthosilicate, manganese nitrate, zinc nitrate, silicon and manganese nitrate and organic metal which are easily decomposed by heating to easily synthesize the phosphor. Compounds are more preferred. Note that in order to obtain favorable light-emitting characteristics, it is necessary to use a raw material containing a small amount of impurity elements such as iron or nickel which serves as a killer center.

Number of moles of silicon M per liter of raw material aqueous solution
s, the number of moles of zinc Mz, and the number of moles of manganese Mm
It is necessary to satisfy the following relationship in order to obtain a phosphor having good emission characteristics. 1.6 ≦ (Mz + Mm) /Ms≦2.2 and 0.005 ≦ Mm / (Mz + Mm) ≦ 0.09 A more preferable relationship is as follows. 1.7 ≦ (Mz + Mm) /Ms≦2.0 and 0.02 ≦ Mm / (Mz + Mm) ≦ 0.06

When the above-mentioned mole number is blended in such a ratio that the total mole number of zinc and manganese to silicon is made smaller than the stoichiometric amount, a manganese-activated zinc silicate fluorescent material having higher brightness can be obtained. You can get the body. However, the amount of zinc relative to silicon is too small, that is, [(Mz + Mm) / M
If s] is less than 1.6, if the mixing ratio is set so that the above relationship is not satisfied, the proportion of the generated phosphor is reduced and the emission luminance is significantly reduced. Conversely, if the amount of zinc is too large than the stoichiometric amount, [(Mz + Mm) / M
When s] is more than 2.2, the obtained phosphor has a body color, and its emission luminance is undesirably reduced.

Further, the ratio of the droplet diameter of the raw material aqueous solution to the phosphor particle diameter depends on the solute concentration of the raw material aqueous solution. If the ratio of the droplet diameter to the phosphor particle diameter is large, the solution The phosphor having a desired particle size can be obtained by lowering the solute concentration in the medium and, if the ratio is small, adjusting the solute concentration to be high. In order to obtain a manganese-activated zinc silicate phosphor having a desired particle size while adjusting the particle size of the droplets of the raw material aqueous solution in this manner, zinc, silicon and manganese contained per liter of the raw material aqueous solution are required. Is defined as C, the solute concentration C in the raw material aqueous solution is preferably in the range of 0.03 ≦ C ≦ 15, and more preferably in the range of 0.13.
≦ C ≦ 10. When a small amount of flux is added to the raw material aqueous solution, it becomes easy to generate spherical phosphor particles having high crystallinity at a relatively low temperature in a short time during the thermal decomposition reaction. The flux may be dissolved in the raw material aqueous solution in advance.

Next, the raw material aqueous solution thus prepared is formed into droplets. Droplet formation can be performed by various spraying methods. For example, a method of forming droplets of 1 to 50 μm by spraying while sucking up liquid with pressurized air, a method of spraying droplets of 4 to 10 μm by applying ultrasonic waves of about 2 MHz from a piezoelectric crystal, A 10-20 μm orifice is vibrated by a vibrator, and a liquid supplied to the orifice at a constant speed is discharged from a hole by a constant amount in accordance with a vibration frequency.
A method of forming a droplet of 50 μm, a method in which a liquid is dropped on a rotating disk at a constant speed, and 20 to 1 is removed from the rotating disk by centrifugal force.
A method of forming a droplet of 00 μm, a method of generating a droplet of 0.5 to 10 μm by applying a high voltage to the liquid surface, or the like can be appropriately adopted.

Among them, a manganese-activated zinc silicate phosphor having a particle size of submicron to micron order and having a uniform particle size suitable for forming a fluorescent film such as a display such as a CRT, PDP, FED or a fluorescent lamp. For this purpose, a spraying method using ultrasonic waves is preferable.

The droplets thus formed are introduced into a thermal decomposition reaction furnace by a carrier gas and heated to become phosphor particles. By adjusting the type of the raw material aqueous solution, the type of the carrier gas, the flow rate of the carrier gas, the temperature in the pyrolysis reaction furnace, etc., a hollow spherical, porous,
Alternatively, solid particles, crushed particles, and the like can be generated, and the morphology and surface state of the particles can be adjusted.

As the carrier gas used in the production method of the present invention, air, oxygen, nitrogen or argon containing a small amount of oxygen can be used, but a manganese-activated silicate fluorescent material having high luminance and good luminous characteristics can be used. In order to obtain a body, air or an oxidizing gas such as oxygen or an inert gas such as nitrogen is preferable, and in order to reduce the production cost, air is more preferable.

The thermal decomposition reaction of the droplet of the raw material aqueous solution is 105
If the temperature is lower than 0 ° C., the crystallinity of the phosphor cannot be sufficiently ensured, and manganese cannot be activated in the crystal, so that only an extremely weak light emission intensity of the phosphor can be obtained. On the other hand, if the thermal decomposition reaction temperature is too high, unnecessary energy is wasted, and depending on the abundance ratio of zinc and silicon in the raw material aqueous solution, if the heating temperature exceeds 1430 ° C, the phosphor melts and the liquid phase Is generated, which is not preferable because it hinders the precipitation of a crystal phase and volatilizes zinc. Therefore, the thermal decomposition reaction of the droplets of the raw material aqueous solution needs to be performed at a temperature of 1050 to 1430 ° C, and it is more preferable to perform the thermal decomposition reaction of the droplets at a temperature of 1200 to 1410 ° C.

The residence time of the droplets in the pyrolysis reactor is preferably in the range of 1 second to 10 minutes. If the residence time (reaction time) is too short, the resulting phosphor will have low crystallinity and manganese will not be activated in the crystal, resulting in low light emission characteristics. On the other hand, if the residence time (reaction time) is too long, unnecessary energy will be wasted.

[0023]

The present invention will be described below with reference to examples. Example 1 The number of moles Mz of zinc was 1.9 moles, the number of moles of manganese Mm was 0.01 mole, and the number of moles of silicon Ms was 1.
0 mol of tetraethylorthosilicate, zinc nitrate and manganese nitrate are dissolved in water, a small amount of nitric acid is added thereto, and the mixture is sufficiently stirred to obtain a solute concentration (the number of moles of solute per liter of aqueous solution). Total C = Mz + Mm + M
s) A homogeneous phosphor raw material aqueous solution having a ratio of 0.9 was prepared. This raw material aqueous solution 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 1200 ° C. using air as a carrier gas to form a droplet.
The thermal decomposition reaction is carried out by staying for 2 seconds, and the chemical composition is (Zn
A phosphor of _0.95 Mn _0.05 ) ₂ SiO ₄ was obtained.

The obtained phosphor was irradiated with CuKα ray and examined for powder X-ray diffraction pattern. As a result, it showed good crystallinity. The phosphor had a spherical surface with a smooth surface and a uniform particle size, and the average particle size was 0.8 μm. When the emission spectrum of this phosphor was measured under irradiation of ultraviolet light at 254 nm, it showed good green light emission.

[Embodiment 2] In the embodiment 1, the liquid droplets were introduced.
The maximum temperature in the furnace of the tubular furnace to be
Chemical composition under the same conditions as in Example 1 except that the temperature was changed to 0 ° C.
Is (Zn_0.95Mn _0.05)_TwoSiO_FourOf the phosphor
Was. The obtained phosphor has good crystallinity as in Example 1.
showed that. Further, as shown in FIG.
Spherical with uniform diameter, average particle size is 0.8μm
Was. And the emission spectrum under 254 nm UV irradiation
Measurement showed very good green emission.
Do you get it.

Example 3 In Example 2, the zinc
The number of moles Mz is 1.73 mol, and the number of moles of manganese Mm is 0.
So that the number of moles Ms of silicon becomes 1.0 mole.
Tetraethyl orthosilicate, zinc nitrate and man nitrate
Mix gun and dissolve in water to prepare phosphor solution aqueous solution
Except that the chemical composition was (Zn) under the same conditions as in Example 2._0.96
Mn_0.04) _1.8SiO_3.8Was synthesized. Obtained
The phosphor thus obtained exhibited good crystallinity as in Example 1.
The phosphor has a spherical shape with a uniform particle size.
The average particle size was 0.8 μm. And 254 nm UV
When the emission spectrum was measured under irradiation,
It was found that the phosphor emitted green light of higher luminance than the phosphor.

[Comparative Example 1] In Example 1, droplets were introduced.
The maximum temperature in the furnace of the tubular furnace to be
Chemical composition under the same conditions as in Example 1 except that the temperature was changed to 0 ° C.
Is (Zn_0.95Mn _0.05)_TwoSiO_FourOf the phosphor
Was. The obtained phosphor was spherical with uniform particle size,
Crystallinity was low. In addition, under 254 nm ultraviolet irradiation,
The emission spectrum of the phosphor of
No light was emitted.

[Comparative Example 2] In Example 1, droplets were introduced.
The maximum temperature in the furnace of the tubular furnace to be
Chemical composition under the same conditions as in Example 1 except that the temperature was changed to 0 ° C.
Is (Zn_0.95Mn _0.05)_TwoSiO_FourOf the phosphor
Was. The resulting phosphor is amorphous and spherical with a uniform particle size.
Emission spectrum of this phosphor under 254 nm UV irradiation.
The light emission was extremely weak green light emission
Was.

[0029]

According to the present invention, a manganese-activated zinc silicate fluorescent material having a narrow particle size distribution, a small number of agglomerated particles, a high purity and a uniform chemical composition is obtained by employing the above-described structure. The body can be manufactured at low cost, and the obtained phosphor is suitable for a display such as a CRT or a PDP or a fluorescent film such as a fluorescent lamp. It is possible to form a uniform and dense high-brightness fluorescent film.

[Brief description of the drawings]

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

 ──────────────────────────────────────────────────続 き Continuing on the front page (72) Inventor Kikuo Okuyama 2-365 Kagamiyama, Higashihiroshima City, Hiroshima Pref. 2-401 First-rate occupant's dormitory 2-401 (72) Inventor Naoto Kijima 1000 Kamoshidacho, Aoba-ku, Yokohama-shi, Yokohama, Mitsubishi Chemical Research Institute Yokohama Research Laboratory F-term (reference) 4H001 CF02 XA05 XA14 XA30 YA25

Claims (6)

[Claims] An aqueous solution containing at least manganese, silicon and zinc is prepared, formed into droplets, introduced into a thermal decomposition reactor together with a carrier gas, and is heated to 1050 ° C. to 143 ° C.
A method for producing a manganese-activated zinc silicate phosphor, which comprises heating at a temperature of 0 ° C. for 1 second to 10 minutes to thermally decompose. 2. The method for producing a manganese-activated phosphor according to claim 1, wherein manganese nitrate, tetraethyl orthosilicate and zinc nitrate are used as raw materials of said manganese, silicon and zinc, respectively. 3. The molar number Ms of silicon, the molar number Mz of zinc and the molar number Mm of manganese contained in 1 liter of the aqueous solution are 1.6 ≦ (Mz + Mm) /Ms≦2.2 and 0.005. 3. The method for producing a manganese-activated phosphor according to claim 1, wherein a relationship of ≦ Mm / (Mz + Mm) ≦ 0.09 is satisfied. 4. 4. The method according to claim 1, wherein the total C (= Mm + Ms + Mz) of the number of moles of manganese, silicon and zinc in 1 liter of the aqueous solution is in the range of 0.03 to 15.
The method for producing a manganese-activated phosphor according to any one of claims 3 to 3. 5. The method for producing a phosphor according to claim 1, wherein an ultrasonic wave is used as a means for forming a droplet of the aqueous solution. 6. The method for producing a manganese-activated phosphor according to claim 1, wherein an oxidizing gas or an inert gas is used as the carrier gas.