JP2506980B2 - Phosphor - Google Patents

Description

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a phosphor used for a speedometer of an automobile, a cathode ray tube for a color television, a display and the like.

More specifically, zinc oxide (Zn
O) -based phosphor improvement.

2. Description of the Related Art Conventionally, ZnO is the only phosphor that emits light with a low-speed electron beam, and blue-green and red have entered the stage of practical application for the ZnO: Zn system.

Further, attempts have been made to change the emission color by compounding ZnO with Ga, Cd, Eu, Y, S, Ag, Mn, In, Mg, F, O and other elements.

The shape of ZnO used for these is roughly 1 μm.
It was granular or needle-like with a size of m or less.

Problems to be Solved by the Invention However, the general problems of the ZnO-based low-speed electron beam phosphors that have been studied so far are converged on their brightness, lifetime, and poor luminous efficiency.

Means for Solving the Problems In view of the above problems, the inventors of the present invention have invented the following means as a result of intensive research.

That is, the phosphor is mainly composed of ZnO whiskers composed of a core and needle-shaped crystal parts extending in different axial directions from the core. In addition, the diameter of the base of the needle-shaped crystal part is 0.7 ~ 14μ.
m, and the length from the base to the tip of the needle-shaped crystal part is 3 to 200 μm. Furthermore, the number of axes in the multi-axis direction is 4
Mainly ZnO whiskers.

By the above means, an extremely excellent phosphor was realized.

That is, the ZnO whiskers used in the present invention can be produced by heat-treating metallic zinc powder having an oxide film on its surface in an atmosphere containing oxygen. More specifically, metal zinc powder having a particle size of 0.1 μm to 500 μm is used, and a particle size of 10 μm to 300 μm is preferable. The atmospheric oxygen partial pressure during the heat treatment is 0.01 to 11 vol%,
0.1 to 3 vol% is preferred. Further heat treatment is carried out at 700 to 1300 ° C for 20 to 120 minutes, but 900 to 1100 ° C
It is preferable to heat-treat for 30 to 90 minutes. Obtained Zn
O whiskers have an apparent bulk specific gravity of 0.02 to 0.1, 70 wt%
It is highly mass-produced with the above high yield. FIG. 1 shows the electron micrograph. The above-mentioned shape and dimensional features are clearly recognized. (Hereinafter, it is described as a tetrapot structure.) The resistance value of the normal product of the ZnO whiskers of the present invention is 1 to 50 Ω-cm in bulk value, and (powder of 5 kg / cm ² ) in a powder state.
Although it is 0 ³ to 10 ⁶ Ω-cm, it can be changed to a bulk value of 10 ^-2 to 10 ¹¹ Ω-cm by doping Al, Li, Cu or the like. The fluorescence characteristics are particularly remarkable when the bulk value is 10 ^-2 to 10 ³ Ω-cm.

The tetrapot ZnO whiskers of the present invention are themselves Z
It is considered to be an n-excessive n-type semiconductor, and as it is, becomes a ZnO: Zn phosphor.

Furthermore, the fluorescence characteristics and color can be changed by adding or mixing a predetermined amount of another element. That is, as a material for adding other elements, silver nitrate, silver sulfide,
Silver compounds such as silver halides, nitrates and silicates of Mn, gallium nitrates, gallium sulfides, gallium compounds such as gallium halides, alkali metals (Na, K, Li, Rb and Cs) and alkaline earth metals (Ca) , Mg, Sr, Zn, Cd, and Ba) chlorides, bromides, iodides, and fluorides, and aluminum compounds such as aluminum nitrate, aluminum sulfate, aluminum oxide, and aluminum halides, SiO ₂ , Sn
There are metal oxides such as O ₂ , TiO ₂ , ZrO ₂ , praseodymium oxide, and other elements are rare earth elements, halogen group elements, oxygen group elements, manganese group elements, chromium group elements, nitrogen group elements, vanadium group elements, Carbon group element, titanium group element, aluminum group element, zinc group element, copper group element can be added by an appropriate method. Particularly, in this case, it is extremely effective to add gallium element, alkaline earth element and rare earth element.

As a phosphor, a method of applying ZnO whiskers in the shape of a tetrapot directly into a slurry, etc.
A method of mixing ZnO whiskers with the above additives and applying the mixture,
There is a method in which a tetrapot-like ZnO whisker and the above-mentioned additives are sufficiently mixed, a heat treatment (500 ° C to 1500 ° C / several hours) is performed, and then, if necessary, a loosening step and a crushing step are performed and then coating is performed.

However, the needle-like crystal part of ZnO whiskers may be mixed with triaxial, biaxial, or even uniaxial crystal parts, but this is a part of the tetraaxial parts broken in the process. In addition, plate crystals may be observed. X-ray diffractograms of tetrapot ZnO whiskers produced by the usual method showed all zinc oxide peaks, while electron diffraction also showed single crystallinity with few transitions and lattice defects.
The content of impurities was also small, and the result of atomic absorption analysis was 99.98% zinc oxide.

Next, in a system in which large whiskers (having a length of more than 200 μm and a diameter of more than 14 μm) account for a large proportion, the texture of the phosphor screen is rough, which is not preferable. On the other hand, in a system in which small whiskers (length is less than 3 μm and diameter is less than 0.7 μm) account for a large proportion, the brightness, lifetime and luminous efficiency are remarkably reduced, and therefore cannot be used. Further, in terms of characteristics, a product having a length of 3 to 10 μm and a product having a distribution of 10 to 50 μm are superior, and a product having a length of 50 to 200 μm is superior to that of 10 to 50 μm.

Operation Since the phosphor of the present invention has a high-purity resistance value ZnO, it emits light with a low-speed electron beam. In addition, all the particles are tetrapot-shaped single crystals with a regular shape, and are colorless and transparent crystals, so that the light-transmitting property is extremely good, and the light emission in the overlapping deep portion reaches the surface well, so that the brightness and the light emission efficiency are extremely good. Further, since it is a relatively coarse coarse particle and is a perfect single crystal with a small specific surface area, it is extremely small due to deterioration factors and the life is significantly improved.

Examples The present invention will be specifically described below with reference to examples, but the present invention is not limited to these examples.

Example 1 A tetrapot ZnO whisker was obtained in an atmosphere in which the oxygen concentration was controlled. The diameter of the base portion of the needle-shaped crystal portion was distributed to 2 to 8 μm, and the length from the base portion to the tip was distributed to 10 to 80 μm. The resistance value of this whisker is in a powdered state (5 kg / cm ² ).
Was 10 ⁴ Ω-cm.

This whisker was attached to the anode conductor of the fluorescent display tube and mounted on the fluorescent display tube, and the luminance and the luminous efficiency were evaluated when an Anote voltage of 30 V was applied. Further, the deterioration of luminance after continuous use for 500 hours was evaluated and shown in Table 1.

Comparative Example 1 The same evaluation as in Example 1 was performed using a commercially available luminescence grade ZnO powder. The results are shown in Table 1.

Example 2 1 g of whiskers of Example 1, 2.2 g of Ga ₂ O ₃ and 0.2 g of CdCO ₃
And 0.02 g of Eu ₂ O ₃ were mixed, baked at 1300 ° C. for 25 hours, and pulverized to obtain a phosphor.

Next, the same evaluation as in Example 1 was performed. The results are shown in Table 1.

EFFECTS OF THE INVENTION The present invention provides an extremely effective means for automobiles, aircrafts, wall-mounted televisions, fluorescent display tubes, etc., especially in the midst of increasing needs for low-speed electron beam phosphors that emit low voltage. Yes, its industriality is great.

[Brief description of drawings]

FIG. 1 is a photomicrograph showing the crystal structure of zinc oxide whiskers.

 ─────────────────────────────────────────────────── ─── Continuation of the front page (72) Inventor Takeshi Hamabe 1006 Kadoma, Kadoma City, Osaka Prefecture Matsushita Electric Industrial Co., Ltd. (72) Jun Yagi, 1006 Kadoma, Kadoma City, Osaka Matsushita Electric Industrial Co., Ltd. (72) Inventor Takashige Sato 1006 Kadoma, Kadoma-shi, Osaka Prefecture Matsushita Electric Industrial Co., Ltd.

Claims (3)

(57) [Claims] 1. A phosphor mainly composed of a zinc oxide whisker, which comprises a core and needle-shaped crystal parts extending from the core in different axial directions. 2. The needle crystal part has a base diameter of 0.7 to 14 μm, and the needle crystal part has a length from the base to the tip of 3 to 20.
The phosphor according to claim 1, which is 0 μm. 3. The phosphor according to claim 1 or 2, which is mainly composed of zinc oxide whiskers having four axes in the plural axis directions.