JP3275128B2 - Manufacturing method of green phosphor for slow electron beam - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention is used in a light-emitting portion of a fluorescent display tube, and emits green at a low acceleration voltage of about several volts to several tens of volts. The present invention relates to a method for manufacturing a phosphor.

[0002]

2. Description of the Related Art A fluorescent display tube can be driven at a low voltage, consumes little power, can be easily miniaturized, and can obtain high luminance.
Widely used as a display. In addition, with the expansion of applications, recently, various emission colors and multi-color within a single tube have been demanded, and some of them have been put into practical use. At present, the emission color most frequently used is green emission, and the phosphor is ZnO: Zn, ZnS: Cu,
Al + In ₂ O ₃ is well known.

[0003] In particular, ZnO: Zn phosphors are used from the initial stage of a fluorescent display tube, are balanced in terms of light emission threshold, light emission efficiency and light emission luminance, and are most often used as green phosphors. Recently, the green color of the ZnO: Zn phosphor has
It is a so-called blue-green-white color, and its color purity is slightly insufficient.
_2. Description of the Related Art A green light-emitting phosphor mainly composed of an a ₂ O ₃ compound, that is, a chlorine gallate compound has been developed.

For example, Japanese Patent Laid-Open Publication No. 51-149772 discloses A (Zn _{1 -X} Mg _X ) O.Ga ₂ O ₃ : BMn (provided that
0.6 ≦ A ≦ 1.2, 0 <B <5 × 10 ⁻² , 0 ≦ X ≦
1.0), and a phosphor of ZnO (Al _X G) is disclosed in JP-A-6-340875.
a _1-X ) ₂ O ₃ : Mn (where X = 0.001 to 0.3 m)
ol) has been proposed.

[0005]

However, when these phosphors based on ZnO.Ga ₂ O ₃ are incorporated in a fluorescent display tube and actually operated, the luminance of the light emission gradually increases after the start of lighting. Increase brightness, typically 1000-20
A tendency to stabilize only after continuous lighting (aging) over 00 hours is recognized. The time required for this stabilization is delicately influenced by various factors during the production of the phosphor, lot differences between the starting materials, the firing position of the kiln, the outside air temperature, and the like. It is often experienced in the business that there is a body and there is a phosphor whose luminance is not stable even after aging for 3000 hours or more.

[0006] Recent fluorescent display tubes have been increased in size as their applications have expanded, and are provided with a variety of symbols, figures, numerical values, and other display portions in the tube, and are constituted by a large number of segments. The lighting frequency at the final demand destination varies depending on the desired display form, and varies greatly depending on the segment. Therefore, in a factory before shipment, aging of several to several tens of hours usually results in a light emission luminance of the entire tube. There is a problem in that the display cannot be completely stabilized uniformly, resulting in an imbalance in luminance at a demand destination and a deterioration in display quality.

[0007] In order to avoid this problem,
Although it is conceivable to perform aging in a factory, it is impossible in many respects to continuously light in a large amount for several thousand hours in the factory as described above.

Accordingly, the present invention has been made to solve the above-mentioned conventional problems, and an object of the present invention is to provide a low-speed electron beam which has a sufficiently high luminance even at the initial stage of lighting and a short time for stabilizing the luminance. A method for producing a green light-emitting phosphor for use.

[0009]

In order to achieve the above object, the present invention provides a method for producing a green phosphor using Mn as an activator in a phosphor matrix represented by the general formula ZnO.Ga ₂ O _3. In the method, the baking is performed with a Zn compound which becomes ZnO by baking.
The phosphor matrix is combined with a Ga compound to become Ga ₂ O _3.
A first step of forming and a second step of doping the phosphor matrix with Mn.
And a second step, a atmosphere reducing to dope Mn in ZnO · Ga ₂ O _3, the heating temperature is 800 to 100
The phosphor is manufactured at a temperature of 650 to 950 ° C. in an inert atmosphere.
By annealing at the temperature range of
The initial luminance is high, and the light emission luminance is stabilized by lighting for a shorter time.

[0010]

Embodiments of the present invention will be described below in detail. ZnO / Ga _{2 serving as} the base of the phosphor
O ₃ (also referred to as ZnGa ₂ O ₄ ) is synthesized by baking in the atmosphere to obtain ZnO and Ga ₂ O _3.
Compound a is appropriately selected as a starting material. For example, Zn
O sources include ZnO, Zn (OH) ₂ , Zn (NO ₃ ) ₂ ,
Inorganic compounds such as ZnCl ₂ or ZnCO ₃ are preferred.

On the other hand, Ga ₂ O ₃ sources include Ga ₂ O ₃ , Ga
Similarly, (OH) ₃ , GaCl ₃ or Ga (NO ₃ ) ₃ may be mentioned, and the purity is as high as 99.9% or more, preferably 99.99% or more in order to increase the emission luminance of the phosphor. Should be used. The starting materials are mixed at a predetermined molar ratio of 1:
1 if mixed, dry or wet if it is difficult to dissolve in solvents such as water, if soluble, dissolve in water,
A mixture is obtained by an operation such as a coprecipitation method.

In the synthesis of ZnO.Ga ₂ O ₃ from ZnO and Ga ₂ O ₃ by dry mixing, the degree of achievement (reaction rate) of the reaction is greatly affected by the particle size and mixing degree of the raw materials used.
To increase the degree of achievement, the temperature during the reaction is increased to a higher temperature (130
0 ° C.), but in general, the higher the temperature, the higher the starting material ZnO or reacted ZnO.G
Since ZnO in a ₂ O ₃ volatilizes out of the system as ZnO gas or Zn gas, and excess Ga ₂ O ₃ remains afterwards.
The performance of the synthesized ZnO.Ga ₂ O _{3 as} a phosphor is remarkably deteriorated. In addition, ZnO.Ga ₂
Although the above-mentioned problems are relatively small in the synthesis of O ₃ , the reaction rate is low because it is also a pure solid-phase reaction, and a high temperature is required to achieve the reaction within a predetermined time.

[0013] For this reason, it is advantageous to add a small amount of flux that can achieve the reaction at a lower temperature. In this case, the flux includes NaCl, NaF, Na ₂ CO ₃ ,
Na-based compounds such as NaNO ₃ , KCl, KF, K ₂ CO
K compounds such as ₃ , KNO ₃ or LiCl, LiF,
Li-based compounds such as LiCO ₃ and LiNO ₃ may be mentioned, but preferably lithium phosphate compounds, LiH ₂ PO ₄ ,
Li ₃ PO ₄ , Li ₄ P ₂ O ₅ , LiPO _{4 and the} like, and more preferably Li ₃ PO ₄ .

Here, when Li ₃ PO ₄ is used as the flux, ZnO.Ga is used at a relatively low temperature of about 1000 ° C.
_{Since 2} O ₃ can be sufficiently synthesized, ZnO is not volatilized, and a compound with a constant ratio can be obtained stably. There is no particular limitation on the amount of Li ₃ PO ₄ to be added, and the excess Li and P components (Li ₃ PO ₄ ) present after the synthesis of ZnO.Ga ₂ O ₃ are factors that lower the emission luminance of the phosphor. Since excess Li ₃ PO ₄ added by acid washing is removed, Zn
The addition of O · Ga ₂ O ₃ of 1mol per 0.01~0.3mol Li ₃ PO ₄ are preferred.

The addition of Li ₃ PO ₄ is 0.01 mol.
If it is less, the achievement rate of the reaction is low, and 0.3 mol
If it exceeds, much labor will be spent on cleaning and removal. The amount of the remaining Li and P varies depending on the amount of addition and the degree of cleaning, but is generally about several thousand ppm to several one ppm.
It is considered to be 0 ppm.

The ZnO.Ga ₂ O ₃ thus synthesized is
Subsequently, Mn is doped into the ZnO.Ga ₂ O ₃ crystal as an activator for emitting green light. Mn sources include:
_{MnO, Mn 3 O 4, Mn} (NO 3) 2, MnSO 4, Mn
Such as Cl ₂ and the like, but the form of an aqueous solution to uniformly doped with a small amount into the crystal are preferred. Here, MnSO
₄ is more preferred.

[0017]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS An embodiment of the present invention will be described below in detail with reference to FIG. First, ZnO.Ga ₂ O _{3 serving as} a base material of the phosphor is used.
To synthesize 99.999% pure ZnO powder to synthesize
0.7 g and 99.999% of Ga ₂ O ₃ powder
3.7 g and 11.6 g of Li ₃ PO ₄ powder having a purity of 99% or more corresponding to 0.1 mol% were weighed, and an appropriate amount of water was added thereto to form a slurry, which was then placed in an agate mortar. 2
Mix for hours.

Next, this was transferred to an oven, kept at 120 ° C. for 5 hours, and dried by evaporating water. The dried product is placed in a high-purity alumina crucible and is placed in an electric furnace for 120 minutes.
Heating was performed at 0 ° C. for 3 hours in an air atmosphere to synthesize ZnO.Ga ₂ O ₃ to be a base of the phosphor. Next, the furnace temperature is about 4
It was left in the furnace until it reached 00 ° C., then it was taken out and cooled in a desiccator to room temperature. Since the sintering proceeded slightly to form a lump, the composite was pulverized in a high-purity alumina mortar so that it could pass through a sieve of about 100 mesh.

The pulverized material contains excess lithium (Li).
And phosphorus (P), which is considered to adversely affect the luminance characteristics of light emission. The removal method is to put these pulverized materials in 0.1N nitric acid aqueous solution,
Excess lithium and phosphoric acid were dissolved, separated by filtration, and finally washed several times with pure water.

Next, since Mn (manganese) acting as an activator is doped into the matrix, Mn is used as a Mn source.
Select SO ₄ and add 30.2g of pure grade 2
000 g, 20.3 g of this solution was fractionated and Zn
Added to 53.8 g of O.Ga ₂ O ₃ synthetic dry powder (ZnO.
0.01 mol of Mn is added to 1 mol of Ga ₂ O ₃ ). The additive was stirred to form a slurry, placed on a hot plate, and heated with constant stirring to evaporate water, and finally dried in an oven at 150 ° C. for 5 hours to obtain Mn.
The SO ₄ was uniformly coated on ZnO · Ga ₂ O _3.

Next, this mixture was transferred to a high-purity alumina container, placed in an electric furnace, and H ₂ (5%)-N ₂ (95%).
%) At a predetermined temperature for 2 hours under a reducing gas atmosphere, and a reduction heat treatment of the synthesized product was performed. This reduction treatment is a step of doping Mn into ZnO.Ga ₂ O ₃ ,
The material thus treated is hereinafter referred to as ZnO.Ga ₂ O ₃ : M
It is called n phosphor. The heating temperature of the reduction treatment was 750 ° C.
The test was performed in the range of 1050 ° C. Further, after cooling to room temperature in a furnace under this gas atmosphere, the H ₂ gas flow path is closed, the temperature is raised again to a predetermined temperature while flowing only N ₂ gas, and the temperature is maintained for 1 hour. Annealed ZnO
Ga ₂ O ₃ : Mn phosphor.

A fluorescent display tube using the phosphor thus synthesized for a light emitting portion was manufactured, and the luminance characteristics were examined. The production of the fluorescent display tube was performed as follows. The synthesized phosphor and an organic solvent (vehicle, ethylcellulose + butyl carbitol acetate) are mixed to form a paste, and the paste is applied by printing on an anode conductor layer formed on a glass substrate. Thereafter, a drying and firing step is performed to remove the organic solvent. As a result, a phosphor screen serving as a light emitting portion of the fluorescent display tube is formed on the anode conductor layer.

After the formation of the phosphor screen, a grid electrode (control electrode) for controlling the flow of electrons is provided on the phosphor screen. After the grid electrode is installed, a filament (cathode) serving as an electron emission source is installed on the opposite side of the phosphor screen across the grid electrode. Thereafter, the entirety including the fluorescent screen, the grid electrode, and the filament is covered with a glass container, and the inside of the glass container is evacuated to thereby assemble a fluorescent display tube.

Next, the luminance of the fluorescent display tube assembled as described above is measured. In this case, the filament voltage the fluorescent display tube V _F = 3.3V, the grid voltage V _G = 30 V, is emitted by the load of the anode voltage V _P = 30 V, measuring the luminance produced by TOPCON BM-7 type luminance measuring device I do.

The following Table 1 shows that the parent ZnO.Ga ₂ O ₃
The relationship between the reduction heating temperature and the initial luminance when doping Mn with Mn is examined. Here, the initial luminance refers to the emission luminance when the fluorescent display tube is first turned on. In addition,
In Table 1, the practical value differs from the practical value depending on the color purity of the light emission. Therefore, the ZnO.Ga ₂ O ₃ : Mn green phosphor is set to 30 fl or more.

[0026]

[Table 1]

FIG. 2 is a rewrite of Table 1, showing relative luminance at each reduction temperature when the practical value of 30 fl is taken as 100%. As shown in FIG. 2, when the reduction temperature is 800 ° C. or lower, the initial luminance is rather lowered, and when the temperature is 1000 ° C. or higher, the luminance tends to decrease. It is necessary to set the heating temperature in the range of 800 to 1000 ° C. in order to obtain 30 fl or more, and preferably in order to secure the luminance of 130% or more, the heating temperature must be in the range of 830 to 970 ° C. well,
It can be seen that the more preferable 150% is in the range of 850 to 950 ° C.

FIG. 3 shows that Zn reduced at heating temperatures of 850 ° C., 900 ° C. and 950 ° C. at which the brightness was highest was obtained.
This graph shows the relationship between the initial luminance and the annealing temperature when the O.Ga ₂ O ₃ : Mn phosphor is further annealed in pure N ₂ gas. In the figure, point C '(without annealing treatment) corresponds to point C' (850 ° C. reduction treatment) in FIG.

In FIG. 3, curve A is a phosphor reduced at 850 ° C., curve B is a phosphor reduced at 900 ° C., and curve C is 950.
The phosphor reduced in ° C is further heated to a temperature of 6 in a pure N ₂ gas atmosphere.
It is a measurement result of the initial relative luminance when annealing was performed in the range of 00 to 1100 ° C., and the 850 ° C. reduced phosphor (curve A) was compared with the phosphor without the annealing at the annealing temperature of 700 to 900 ° C. 30% brightness and 80 more
In the range of 0 to 850 ° C., it is improved by 50%. Similarly 90
The 0 ° C. reduced phosphor (curve B) shows an increase of about 32% at 800 to 900 ° C., particularly at 900 ° C. Similarly 95
The 0 ° C. reduced phosphor (curve C) showed about 20% improvement in luminance at the 850 ° C. annealing temperature.

FIG. 4 shows an annealing temperature of 850 ° C. based on a 850 ° C. reduced phosphor under various inert gases and atmosphere.
FIG. 5 shows the results of the initial relative luminance depending on the type of gas when treated at 1 ° C. for 1 hour. Here, “none” on the horizontal axis indicates that the luminance of the phosphor that was reduced only at 850 ° C. and did not undergo annealing was set to 100%. As shown in FIG.
₂ ) There is no change in luminance due to inert gas species such as argon (Ar) and helium (He).
A value of 50% was obtained, while annealing in air containing 21% oxygen reduced the initial relative brightness to 90%.

Since a fluorescent display tube as a final product is often used continuously for a long period of time, the change with time of the luminance of the phosphor subjected to the annealing treatment was examined. Here, the luminance is shown as a relative value, and the phosphor without annealing was set to 100% as a reference. Change of luminance over time, that is, luminance fluctuation rate (%) = (luminance after continuous lighting for 1000 hours−
It is defined as luminance after lighting for a certain period of time / (luminance after continuous lighting for 1000 hours) × 100. The smaller the fluctuation rate is, the more stable and preferable the phosphor is, but it is difficult to actually manufacture the phosphor. Usually, if the fluctuation rate is within ± 30%, preferably within ± 15%, the phosphor becomes sufficiently practical. Can be served.

FIG. 5 shows a reduction firing at 850 ° C.
FIG. 4 is a diagram showing a change in luminance (variation rate) of a phosphor that has been subjected to an N ₂ gas annealing treatment at 50 ° C. and a phosphor without an annealing treatment after continuous lighting for 1000 hours. The initial luminance immediately after lighting of the phosphor without the color was defined as the initial luminance. Further, a change in luminance of the phosphor at a reduction firing temperature of 1050 ° C., which is out of the range of the present example, is also shown as a comparative example.

As shown in FIG. 5, the phosphor subjected to the annealing treatment has a relative luminance as high as 135% immediately after lighting, 145% after 60 hours, and 150% after 120 hours.
%, 155% after 300 hours, 1 after 1000 hours
It becomes 58%, and after approximately 300 hours, it becomes a completely constant value, and the luminance is extremely stable. Similarly, the luminance of the phosphor of this embodiment without only the annealing treatment is 110% after 60 hours, 120% after 120 hours, and 133% after 300 hours, and the luminance tends to gradually increase thereafter. After 1000 hours, the luminance becomes substantially the same as the luminance of the phosphor described above.

In the case of the phosphor not subjected to the reduction firing at 1050 ° C. and without annealing, which is out of the range of the present embodiment, the initial relative luminance is as low as 68%, 75% after 120 hours, and 98% even after 1000 hours. I understand. Brightness fluctuation rate is 15%
The lighting time required to fall within the range is slightly shorter than the former, from the initial stage for the annealed phosphor, after about 320 hours without annealing, and after 280 hours in the comparative example. Absent.

FIG. 6 shows the results of measuring the relative luminance of the phosphor when reducing at 900 ° C. and performing N ₂ gas annealing at 900 ° C. As shown in FIG. 6, the phosphor annealed has an extremely excellent initial relative luminance of 143%, 162% after 1000 hours, and a luminance variation rate of 11.7%. Further, in this embodiment having only the annealing process, the relative luminance can be increased, but it takes time to keep the variation rate within 15%. As described above, by performing the annealing treatment after the reduction firing, it is possible to obtain a phosphor that has a high luminance from the beginning and has a low luminance variation rate and can be used immediately.

Next, the green light emission characteristics of the phosphor according to the present embodiment will be described with reference to a chromaticity diagram. FIG. 7 shows the measurement results of the chromaticity plotted on the chromaticity diagram, and a ZnO and ZnS-based green phosphor conventionally known as a control is also shown. This is represented by color coordinates as shown in Table 2 below.

[0037]

[Table 2]

As shown in Table 2, green (x = n) which is closer to pure green than ZnO-based or ZnS-based blue-green or yellow-green.
0.13, y = 0.70) was obtained. This green color has substantially the same green light emission characteristics as long as it is a phosphor within the range of the present embodiment.

[0039]

As described above, in the production of the green-emitting ZnO.Ga ₂ O ₃ : Mn phosphor according to the present invention,
The atmosphere in which ZnO.Ga ₂ O _{3 serving} as a base is doped with Mn is reduced, and the firing temperature at that time is set to 800 to 1000.
By setting the temperature in the range of ° C., a phosphor having a high initial luminance was obtained.

Further, this phosphor was placed in an inert atmosphere at 650.
By performing the annealing process in the temperature range of 950 ° C. to 950 ° C., the initial luminance is further increased, and the time required for stabilizing the luminance is reduced to １ ／ of that of the conventional phosphor, and a phosphor having a small luminance variation rate can be obtained. Obtained. As a result, aging can be performed for a short time in the factory before shipment, and an extremely excellent effect that the display quality at the customer's place can be maintained is obtained.

[Brief description of the drawings]

FIG. 1 is a diagram showing a manufacturing process for explaining an embodiment of a method for manufacturing a phosphor according to the present invention.

FIG. 2 is a view showing a relationship between a firing temperature in a reducing atmosphere and initial relative luminance when ZnO.Ga ₂ O ₃ as a base is doped with Mn.

FIG. 3 illustrates a method of manufacturing a phosphor according to the present invention;
FIG. 9 is a diagram showing a relationship between a heat treatment temperature in an inert atmosphere and an initial relative luminance for a phosphor doped with n at about 850 ° C. and about 900 ° C.

FIG. 4 is a diagram showing the relationship between various annealing treatment atmospheres and initial relative luminance.

FIG. 5 is a diagram showing a change over time in luminance with respect to the lighting time of a phosphor which was subjected to an annealing process at 850 ° C. in the method for producing a phosphor according to the present invention.

FIG. 6 is a diagram showing a change over time of luminance with respect to a lighting time of a phosphor which has been subjected to an annealing process at 900 ° C. in the method for producing a phosphor according to the present invention.

FIG. 7 is a diagram showing positions on a chromaticity diagram of a ZnO.Ga ₂ O ₃ : Mn phosphor formed by the phosphor manufacturing method according to the present invention.

──────────────────────────────────────────────────続 き Continued on front page (58) Field surveyed (Int.Cl. ⁷ , DB name) C09K 11/62 CPB C09K 11/08 H01J 29/20

Claims (3)

(57) [Claims] 1. A method for producing a green phosphor using Mn as an activator in a phosphor matrix represented by the general formula ZnO: Ga ₂ O ₃ , wherein a Zn compound which becomes ZnO upon firing and Ga ₂ upon firing.
The phosphor matrix is synthesized with a Ga compound to be O ₃ .
Bei a first step and a second step of doping Mn into the phosphor matrix that
A method of producing a green phosphor for a low-speed electron beam , wherein the doping of the ZnO.Ga ₂ O ₃ with a Mn compound is performed in a reducing atmosphere at a heating temperature of 800 to 1000 ° C. . 2. The method for producing a green phosphor for a low-speed electron beam according to claim 1, wherein annealing is performed in an inert atmosphere at a temperature in the range of 650 to 950 ° C. after the reduction heating. 3. The method according to claim 1, wherein Li ₃ PO ₄ is used for the synthesis of ZnO.Ga ₂ O ₃ .