JPS608073B2 - luminescent material - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention provides a novel luminescent material for excitation by slow electron beams, more specifically, a luminescent material for excitation by slow electron beams, which is made by mixing appropriate amounts of antimony-doped tin oxide and zinc sulfide phosphor. It is related to.

In recent years, many crab photons using transition metal ions, rare element ions, etc. as activators have been developed.

It has been known for a long time that these metal ions in various solids and liquids exhibit emission line-like emission spectra characteristic of each metal ion when irradiated with electron beams, ultraviolet rays, near-infrared light, etc. In particular, it has attracted attention and research as a laser material. Among these studies, for example, YAG:Nd
While lasers were put into practical use, it was also discovered that cerium, europium, erbium, etc. can be present in various matrix materials and emit light with high efficiency. was studied. As a result, many products have been put into practical use, and among these, yttrium oxide activated with europium, yttrium oxysulfide, and yttrium vanadate are particularly important, and are used as red components in color televisions, high-pressure mercury lamps, etc. These crab photons emit high-intensity light when excited by high-speed electron beams of several kilovolts or more, ultraviolet rays, and the like. However, these crab phosphors hardly emit light when subjected to slow electron beam excitation of several tens of volts or less, so they cannot be used as crab phosphors for crab optical display tubes.
As a result, the applications of crab light display tubes that emit only green light have been limited, and in order to expand the use of display tubes, there has been a strong demand for the development of light-emitting materials that emit bright light other than green.
Conventionally, a self-activated zinc oxide phosphor (
Zn○:Zn) is known.

This crab light emits green-white light when excited by a slow electron beam, and is used as a scale light for crab light display tubes such as calculators and various gold-plated devices. In the laboratory, Y
202S:Eu, ZnS:Ag, etc. with indium oxide (
Although it is known that the material has been imparted with electrical conductivity using 1 mountain 03), it has not been put to practical use in display tubes because the electrical conductivity imparted is insufficient. The conductivity of low-resistance materials varies greatly depending on the amount of chemically adsorbed gas molecules.

For example, in a low-resistance material (in the case of an n-type semiconductor), when oxygen, which is an electron acceptor, is adsorbed and ionized, a new surface quasi & is formed in the forbidden band, and the surface satisfies the electrical neutrality condition. The energy band bends and a surface potential barrier is created. In other words, electrons move from the donor level to the adsorption layer due to chemical adsorption of oxygen molecules, oxygen becomes negatively charged and adsorbed, a space charge layer is formed near the semiconductor surface, the semiconductor's fulumi level decreases, and oxygen electrons Equilibrium is reached when the energy and the Fermi level of the semiconductor become equal. In the case of powdered low-resistance materials, gas molecules are adsorbed at the interface of each particle, forming a potential barrier at the grain boundary and blocking the movement of conduction electrons, resulting in a state in which the overall electrical conductivity is extremely reduced. shows.

Sufficient baking is necessary to prevent the conductivity from decreasing due to the adsorption of gas molecules and to obtain high brightness.

Generally, it is difficult to degas the powder, and baking at high vacuum and high temperatures is required. However, indium oxide has the disadvantage that its properties deteriorate when baked at high temperatures, making it impossible to obtain sufficient brightness. Furthermore, although a certain degree of brightness can be obtained by baking at a low temperature, the lifespan of a practical display tube is short due to insufficient degassing. In order to meet the above-mentioned demands, the present inventor has conducted various studies with the aim of obtaining a luminescent material that exhibits a luminescent color other than green and white when exposed to a slow electron beam, and whose properties do not change even after degassing through sufficient baking. In the process, zinc sulfide fluoride activated with at least one fluoride of praseodymium, samarium, europium, terbium, holmium, thulium, ytterbium, chromium, and manganese was mixed with antimony-doped tin oxide. They discovered that when a luminescent material is excited with a slow electron beam, it emits high-intensity red or blue light, which is characteristic of activated materials. Unlike indium oxide, tin oxide doped with antimony does not change its properties when baked at temperatures up to about 500°C in the production of light display tubes, and is able to release sufficient gas, making it suitable for practical use. It was possible to produce a crab light display tube with a serviceable lifespan.

Examples of the present invention will be described below.

Precipitate zinc sulfide by passing hydrogen sulfide into an aqueous solution of zinc salt, dry this precipitate, and add samarium trifluoride to the powder obtained by ion plating with a gas pressure of 1×io-3Ton, an acceleration voltage of V, and a high-frequency power of 300W. After being deposited with the powder, the particles were thermally diffused in hydrogen sulfide at 600 pm to form luminescent centers of fluoride molecules on the surface layer of the zinc sulfide powder particles, thereby obtaining a zinc sulfide phosphor activated with samarium fluoride. .

At this time, the amount of samarium trifluoride deposited was approximately 6 x 10-5 parts per 1 part of zinc sulfide. On the other hand, tin oxalic acid powder was mixed with an aqueous solution of hydrochloric acid in which antimony oxide was dissolved, and after drying, it was fired at 120,000 ℃ to obtain antimony-doped tin oxide with low resistance.

After thoroughly mixing the thus obtained samarium fluoride-activated zinc sulfide phosphor with antimony-doped tin oxide,
A paste was formed using an aqueous polyvinyl alcohol solution and glycerin, and screen printing was performed on the anode groups 3a to 3n shown in the figure.

This was baked at 500°C in air, a crab light display tube as shown in the figure was assembled, glass-sealed in nitrogen at 50000C, baked at 4500C, and the crab light body was excited to emit light. . The brightness one hour after lighting was 80 foot lamberts at an anode voltage of 50 V.

When the baking temperature is changed, the maximum brightness is 400-50
Obtained at 000. In addition, the luminance changed slowly over time after lighting, and it took more than 500 field hours for the luminance to drop to 50% of the maximum luminance, which was sufficient for practical use. On the other hand, when indium oxide is mixed, the maximum brightness is 200-30
Obtained at 0oo.

At this baking temperature, the degassing of the phosphor powder is not sufficient, and therefore, when it is made into a display tube, the brightness deteriorates quickly due to the influence of the residual adsorbed gas, and the brightness decreases to 50% of the maximum brightness after about 100 steps. It has declined. In this example, zinc sulfide activated with samarium fluoride was described, but zinc sulfide activated with praseodymium, europium, terbium, holmium, thulium, ytterbium, chromium, or manganese, or two or more of these fluorides may also be used. Similar results were obtained with light bodies.

While the only green light-emitting material (Zn○:Zn) was used as a low-speed electron beam-excited light material, the light-emitting material of the present invention emits almost all visible light such as red, yellow, and blue. This luminescent material enables color display by low-speed electron beam excitation, and the industrial value of the present invention is great.

[Brief explanation of drawings]

The figure is a cross-sectional view showing the typical basic structure of a crab light display tube.
2 is a transparent windshield, 2 is a glass substrate, 3a to 3n are anode groups coated with luminescent material, 4 is a cathode filament, and 5
a-5n are control bred sheep.

Claims (1)

[Claims] 1. A zinc sulfide phosphor to which at least one fluoride of praseodymium, samarium, europium, terbium, holmium, thulium, ytterbium, chromium, and manganese is added and tin oxide doped with antimony are mixed. Characteristic luminescent materials.