JPH066704B2 - Electron beam excited phosphor and method for producing the same - Google Patents

Description

TECHNICAL FIELD The present invention relates to a novel blue-emitting phosphor having an emission spectrum in both the ultraviolet region and the visible region, which is excited by an electron beam, and particularly, sulfur (S The present invention relates to an oxide-based electron-beam-excited phosphor that does not contain a component), has excellent emission characteristics and has a long life, for example, used as a phosphor for a fluorescent display tube.

[Prior art and its problems]

In general, electron-beam excited phosphors are used for cathode ray tubes that emit light at an accelerating voltage of about several tens of KV and for light-emitting units of large-screen display devices, and for fluorescent display tubes that emit light at a low accelerating voltage of about several V to 10V. It is divided into low-speed electron beam excited phosphors. As the former phosphor for CRT which emits blue light,
ZnS: Ag, Al phosphors, ZnS: Ag phosphors and the like are known. Further, the latter phosphor for a fluorescent display tube is ZnS: Ag, Al + In ₂ O ₂ or ZnS in which a metal oxide such as In ₂ O ₃ or SnO ₂ which is a conductive material is mixed with the phosphor for the cathode ray tube: Ag + In ₂ O ₃ phosphors are known. By mixing the conductive metal oxide as described above, the resistance of the phosphor can be lowered, so that the phosphor can emit light at a low-speed potential line and can be used for a fluorescent display tube.

Further, phosphors such as ZnS: Ag, Al and ZnS: Ag that contain a sulfur (S) component in the phosphor composition are collectively referred to as sulfide phosphors. This sulfide phosphor is often used as a phosphor for a color display other than green of a fluorescent display tube.

However, it is known that the sulfur (S) component of the sulfide phosphor adversely affects the fluorescent display tube and deteriorates the characteristics of the fluorescent display tube.

Therefore, the structure of the fluorescent display tube which is adversely affected by the sulfide phosphor will be described below.

As shown in the plan view of FIG. 1 and the sectional view of FIG. 2, the fluorescent display tube includes a flat box-shaped envelope including a substrate 1 having an insulating property, a side plate 2 and a container portion 4 including a front plate 3. Is formed. The gas in the envelope is exhausted through the exhaust hole, and then the exhaust hole is sealed with a chip tube or a lid member to keep the inside in a high vacuum.

On the substrate 1, the wiring conductor 5 and the anode conductor 6 are patterned by a photolithography method using a metal thin film, for example, an Al thin film. The sulfide phosphor 7 is arranged on the anode conductor 6 by a known means. An anode 8 is formed by the anode conductor 6 and the sulfide phosphor 7. A control electrode 9 is arranged above the anode 8 and a filament cathode 10 is stretched above the control electrode 9 to form a fluorescent display tube.

The operation of the fluorescent display tube configured as described above will be described below.

A cathode voltage is applied to the filamentary cathode 10 to heat the filamentary cathode 10 to emit electrons from the electron emission material layer on the surface. The electrons are attracted by the control electrode 9 to be accelerated, and at the same time, control is performed as to whether or not the electrons are made to strike the anode 8 or be cut. The electrons that have passed through the control electrode 9 impinge on the phosphor layer 7 of the anode 8 to fluorescently display the sulfide phosphor layer 7 to which the anode voltage has been applied.

It is known that when the sulfide phosphor is made to emit light in this way, the emission characteristics representing the electron emission capability of the cathode deteriorate as the light emission time elapses.

The reason for this is that the electrons emitted from the cathode are attracted by the control electrode, the anode, etc., and are accelerated and thus have a large energy. When the electrons impinge on the sulfide phosphor layer 7, the electrons have a function of decomposing the surface of the phosphor layer in addition to the function of causing the phosphor layer 7 to emit light. As a result, the sulfide phosphor is decomposed, and a sulfide-based gas such as S, SO, SO ₂ is scattered, or fine particles containing sulfur (S) are scattered. These sulfide gas and fine particles react with the alkaline earth metal oxide layer that is the electron emission layer of the filamentary cathode 10 to poison or sinter the surface. As a result, the emission characteristics of the filament cathode 10 are deteriorated and the life of the cathode is shortened.

Further, the sulfide is another oxide phosphor, for example ZnO: Z.
There was a problem that the emission brightness of the ZnO: Zn phosphor was also reduced by adhering to the surface of n or the like.

Therefore, color phosphors other than sulfide phosphors have been required as color phosphors used in fluorescent display tubes, especially as light emitters that emit blue light.

As a color phosphor other than the sulfide phosphor, a gallate complex oxide phosphor is known in Japanese Patent Publication No. 31236/1985. The composition formula of this phosphor is A (Zn _1-x M
g _× ) 0 Ga ₂ O ₃ (provided that 0.6 ≦ A ≦ 1.2 and 0 ≦ ×
≦ 0.5. ).

Although it is described that this phosphor emits light with a low-speed electron beam, its emission brightness is low, and there is room for improvement for use as a fluorescent display tube. For example, in the above composition formula, A = 1, X
In the case of ZnO.Ga ₂ O ₃ phosphor with = 0, the cathode voltage is 0.6 V,
Even if the anode voltage of 80 V, which is higher than that of the ordinary voltage, is applied, the emission brightness is 4 ft.
-It was about L. Generally, the brightness of a fluorescent display tube is 50ft-L.
(About 150 Cd / m ² ) or more is necessary, and the conventional example has a problem in terms of brightness.

[Object of the Invention]

The present invention focuses on ZnO.Ga ₂ O ₃ of the above-mentioned known oxide phosphor, and uses this ZnO.Ga ₂ O ₃ as a base material, and by doping the base material with Li and P, a sulfide is contained. It is an object of the present invention to provide a ZnO / Ga ₂ O ₃ -based phosphor that is a blue-emitting phosphor that has a high emission brightness even with a low-speed electron beam and that can be sufficiently used for a fluorescent display tube, and a manufacturing method thereof. Is.

[Structure of Invention]

In order to achieve the above-mentioned object, the present invention has a composition formula of ZnO.Ga ₂ O.
Li ₃ P ₄ as an activator was added to the matrix represented by ₃ in an amount of 5 × 10 ⁻³ to 4 × 10 ⁻¹ mol with respect to 1 mol of the matrix to obtain Li and P.
Is doped.

In addition, ZnO and Ga ₂ O ₃ were mixed well and then baked in the air to obtain ZnO.
The step of making a matrix of Ga ₂ O ₃ and after crushing the matrix, Li ₃ PO
_{4. The process} is well mixed with _4, and is fired in a reducing atmosphere to dope Li and P.

〔Example〕

ZnO and Ga ₂ O ₃ that are the base are equimolar to form the base.
I.e. the 1.6g and Ga ₂ O ₃ ZnO were weighed 3.7 g, placed in an alumina boat after mixing well, carried out for 3 hours at a furnace set at a temperature of 1300 ° C. in an air atmosphere, ZnO and Ga ₂ A solid solution of O ₃ was formed.

Since both ZnO and Ga ₂ O ₃ are oxides, firing in an air atmosphere that is an oxidizing atmosphere improves the crystallinity of the solid solution, that is, the ZnO ・ Ga ₂ O ₃ solid solution that is the matrix of the phosphor. It became clear in the experiment.

After crushing the ZnO.Ga ₂ O ₃ matrix, 5 × 10 ⁻³ to 4 × 10 ⁻¹ mol of Li ₃ PO ₄ is added to 1 mol of the matrix. The Li ₃ PO ₄ of 0.23g case of the present embodiment corresponding to 0.1 mol, the ZnO · Ga
After mixing with the ₂ O ₃ matrix, it was placed in an alumina crucible and the temperature was set to 1000 ° C. in a furnace in a reducing atmosphere containing 1% of H ₂ and baked for 1 hour to dope Li and P.

In addition, a ZnO.Ga ₂ O ₃ matrix was formed by the same method and mixed with different doping amounts of Li ₃ PO ₄ additive to form phosphors with various doping amounts.

After firing, unreacted Li ₃ PO ₄ was removed by washing to obtain a ZnO · Ga ₂ O ₃ : Li, P phosphor.

The obtained phosphor was mixed with an organic binder to form a phosphor paste, and a phosphor layer was formed on the anode electrode on the glass substrate by screen printing. A mesh cathode is provided above the phosphor layer, and a filament cathode is provided further above, and an envelope is constructed by the box-shaped front container covering the electrodes and the glass substrate, and the inside is evacuated to a high vacuum state. Then, a fluorescent display tube was manufactured.

In the fluorescent display tube, cathode voltage 1.7V, grid voltage 12
Light was emitted by applying V and an anode voltage of 0 to 200V. The emission luminance tends to increase as the anode voltage increases, as shown in FIG. Curve A in this is the phosphors 0.1 mol per mol of the Li ₃ PO ₄ additives, for example, 50V in 685Cd / m ^2, the 100V 1100Cd / m ^2, 200V in about 1700Cd / m ² and high intensity Met.

For comparison, a ZnO.Ga ₂ O ₃ phosphor containing no additive Li ₃ PO ₄ was manufactured under the same conditions, mounted on a fluorescent display tube, and light-emitted under the same conditions. Show. As can be seen from this graph, the brightness is low when no additive is added. Even if the anode voltage is increased to 200 V, the brightness is 350 Cd / m ² , which is about 1/7 of the brightness of the present invention.

Next, curve B in FIG. 3 shows the case where 0.01 mol of Li ₃ PO ₄ is added to 1 mol of the ZnO.Ga ₂ O ₃ matrix. The Li
_{Although the} brightness is lower than that of the phosphor containing 0.1 mol of ₃ PO ₄ , the brightness is higher than that of the conventional example of O containing no additive and is 200 Cd / m at 50V.
^2, and a value of 1000 Cd / m ² at 540Cd / m ^2, 200V at 100 V.

However, if the content of Li ₃ PO ₄ is 5 × 10 ⁻³ mol or less, the doping amounts of Li and P, which are the doping agents, are small and no effect is exhibited, which is almost the same as the graph of the additive O of the conventional example.

Also, even if the amount of the additive is 4 × 10 ^-1 mol or more, the doping amount does not increase and Li ₃ PO ₄ remains in the phosphor with self-confidence, which hinders light emission, resulting in a phenomenon that brightness decreases. .

Therefore, the additive amount of Li ₃ PO ₄ is 5 × 10 ⁻³ to 4 × 10 ^−1.
Molar is the preferred range.

Next, FIG. 4 shows the emission spectrum distribution of the conventional phosphor for comparison with the phosphor of the present invention.

In the figure, curve A is the phosphor of the present invention to which 0.1 mol of Li ₃ PO ₄ additive was added, and curve B is the phosphor of the present invention to which 0.01 mol of Li ₃ PO ₄ additive was added. Curve C is for comparison
It is a conventional ZnO.Ga ₂ O ₃ phosphor in which the additive is O.

As is clear from this figure, as the amount of Li ₃ PO ₄ added increases, Li ₃ PO ₄ tends to shift to a longer wavelength side than the conventional example in which O is O, and the emission spectrum distribution becomes broader than in the past. Is.

Next, FIG. 5 shows the emission colors of the phosphor of the present invention and the conventional phosphor.
A comparison and explanation will be given with a CIE chromaticity diagram.

The chromaticity coordinate table C of the conventional additive O phosphor is X = 0.174, Y
= 0.098, Ld = 465, which is a point close to purple in the blue region.

Next, in the chromaticity coordinate table B of the phosphor to which 0.01 mol of the additive of the present invention was added, X = 0.173, Y = 0.129, Ld = 471, which is a point closer to blue than the point C.

Further, in the chromaticity coordinate table A of the phosphor of the present invention to which 0.1 mol of the additive was added, X = 0.176, Y = 0.155, Ld = 474, which is a point closer to the blue side than the point B.

From these, the emission color of the phosphor of the present invention is closer to pure blue (Blue) than the conventional purple blue (Purplish n Blue).

[Effect of the present invention]

As described above, according to the present invention, in order to dope a conventional ZnO / Ga ₂ O ₃ phosphor with Li and P, the first firing is performed by forming a matrix in an oxidizing atmosphere, and then performing the second firing. Since the ZnO.Ga ₂ O ₃ : Li, P phosphor was manufactured by doping in a reducing atmosphere and doping with Li, P, it has the following effects.

(1) The phosphor of the present invention has higher brightness than conventional ones and can be sufficiently used as a phosphor for a fluorescent display tube.

(2) The emission color becomes more pure blue compared to the conventional one, and since it can be used as a blue non-sulfide phosphor, there is no emission of sulfide-based gas and the like, and the characteristics of the fluorescent display tube may be deteriorated. It disappears and can be used as a blue phosphor for various fluorescent display tubes.

(3) Since the phosphor is fired in two steps, the base material having an excellent crystal structure can be formed in the first firing, and the additive is added in the second firing. It has the effect that a purer blue color was obtained because it was not thermally changed and could be doped with pure Li, P.

[Brief description of drawings]

FIG. 1 is a plan view of a general fluorescent display tube, FIG. 2 is a sectional view of the same, and FIG. 3 is a graph showing the correlation between the luminance and the anode voltage of the present invention and a conventional example, FIG. 4 is an emission spectrum distribution diagram of the present invention and a conventional example, and FIG. 5 is a CIE chromaticity diagram of the present invention and a conventional example.

 ─────────────────────────────────────────────────── ─── Continuation of front page (56) Reference JP-A-63-37183 (JP, A) JP-A-63-8475 (JP, A) JP-A-63-135481 (JP, A) JP-A 62- 243679 (JP, A)

Claims (4)

[Claims] 1. An electron-beam-excited phosphor obtained by doping a matrix represented by ZnO.Ga ₂ O ₃ with Li and P as activators. 2. The electron beam excited phosphor according to claim 1, wherein the Li and P are doped with Li ₃ PO ₄ as a supply source. 3. The method according to claim 1, wherein the addition amount of Li ₃ PO ₄ as a source of Li and P is 5 × 10 ⁻³ to 4 × 10 ⁻¹ mol per 1 mol of the base material. Electron-beam excited phosphor. 4. A step of mixing ZnO and Ga ₂ O ₃ well, followed by firing in air to form a matrix of ZnO.Ga ₂ O ₃ , and crushing the matrix, and then mixing well with Li ₃ PO _4. And a step of firing in a reducing atmosphere to dope Li and P, the method for producing an electron beam excited phosphor.