What is the composition of phosphor on the screen of ordinary color TV?

Classification: Computer/Network >> Computer General Knowledge

Problem description:

Mainly talk about its harm, such as whether there is mercury or lead. The more detailed, the better. Thank you.

Analysis:

First, the enlightenment of "phosphor" luminescence

In order to find out the chemical composition of phosphor, we first thought of the luminescence of fireflies. The luminous principle of fireflies mainly has the following series of processes.

Photoforming protein+photoforming enzyme contains oxygen to form photoforming protein (emitting green light).

Oxyluminescent protein ++H2O luminescent protein.

This is the reason why fireflies can continue to shine, and the light is flashing. It is worth noting that the green light emitted by fireflies is a kind of "cold light" and the conversion rate is as high as 97%.

Secondly, we pay attention to the luminescent properties of luminescent plastics. Luminous plastics are mainly doped with some radioactive substances, such as 14C, 35Sr, 90Sr, Na, th and luminescent materials ZnS and CaS, which are excited to emit visible light (cold light) under the irradiation of radioactive light.

Second, the historical evolution of luminescent materials

At the beginning of the 20th century, Hayward developed a low-voltage mercury discharger, which can be assembled into various fluorescent substances.

19 10, French physicist George Claude invented neon lights according to the principle of gas discharge, and produced a batch of neon lights on the market the following year, but the disadvantage was that the neon lights at that time could only emit red light. Nowadays, this kind of lamp has been greatly improved in material and technology, in which charging mixed gas is a new technology.

During the period of 1927, the U.S. General Electric Company adopted thermoelectric plates as the discharge electrodes of fluorescent lamps, and selected silicate and tungstate which are most suitable for fluorescent lamps from a wide variety of fluorescent substances to make fluorescent lamps with very reliable performance.

Three. Chemical composition of substances in ordinary fluorescent tubes

The main body of a fluorescent lamp is a lamp tube, the inner wall of which is coated with fluorescent powder, and the filaments at both ends are used as hot electrodes, and nitrides of easy-to-emit electronic elements such as Ba, Sr and be are attached to the filaments. When making, the air in the tube is drained first, then a small amount of H2 and mercury is filled in and sealed. If different gases are filled, different colors of light will be emitted. For example, charging Ne emits orange light, and charging Hg emits blue light. Filling the mixture of rare gases such as CO2, he, Ar and Ne can not only reduce the starting voltage, reduce the lamp temperature, improve the luminous efficiency, prolong the service life of the lamp, but also make the color more colorful.

The above materials are preliminary materials, which provide some basis for us to further study the composition and harm of phosphorus. After unremitting efforts and literature retrieval, we finally deepened the chemical composition of phosphorus from vague silicate, tungstate and single element Ba and Sr to standard chemical formula, and its chemical composition is as follows:

kind

chemical formula

colour

density

Red powder

Y2O3: EU

white

5. 1 0.2

Green powder

cemgl 1 1o 19:Tb

white

4.2 0.2

Powder Blue

BaMgAl 10O 17: EU

white

3.7 0.2

Shuangfeng powder blue

BaMgA 10O 17: (EU, Mn)

white

3.8 0.2

Upconversion phosphor, namely infrared excitation phosphor, comprises the following components:

Chemical composition: YErYbF3

Appearance: white inorganic powder

Particle size: 30 nm

Excitation wavelength: 980 nm

Luminous color: green light

Features: high light transmittance, strong solvent resistance, acid and alkali resistance.