In the early 1990s, the blue LED chip came out, and then the white LED light source made by using the blue chip to excite the yellow light phosphor was born. White LED lamps are used in the field of general lighting. Compared with traditional incandescent lamps and fluorescent lamps, they have the advantages of high luminous efficiency, long life, and adjustable light. It is a great change in the field of lighting. Under the country's vigorous promotion and support, the domestic LED industry has developed extremely rapidly. At present, LEDs have been widely used in the field of indoor and outdoor lighting. There are many domestic LED lighting manufacturers, with uneven technical levels, great disparity in product quality, and many problems in application, which are not yet fully accepted by people. Among them, the problems of glare and light color are the most prominent, and there have been some domestic articles discussing blue light. This article first briefly describes the characteristics of LED, and then discusses the impact of light color on human vision, hoping to arouse the full understanding of producers and users, so that the LED lighting industry can develop healthily.

1. LED lighting source

It has been more than 130 years since the incandescent lamp was invented, and the fluorescent lamp has a history of more than 70 years. People have become accustomed to living in this kind of light and color environment. Therefore, in order to improve the light color characteristics of LED lighting, we should try our best to get close to the two types of light sources to obtain the LED light color that people can fully accept. Fluorescent lamps use mercury atoms to generate 254 nm ultraviolet rays in the excited ionization discharge to irradiate the three primary color phosphors to obtain a light color with a color temperature of 2700-6500K. The highest luminous efficiency is about 110 lm/W, generally 60-80 lm/W. Generally, light sources with high color temperature have high luminous efficiency; light sources with low color temperature have low luminous efficiency.

1. Working characteristics of LED light source

Gallium Nitride (GaN) chips are used in popular LED light sources, and the peak value of the emitted blue light is about 450nm. The blue light and the yellow light radiated by the phosphor excited by it can be synthesized into white light. This kind of LED is characterized by high color temperature, high luminous efficiency and poor color rendering, and the output light contains nearly 50% blue light. In order to obtain LED light sources with medium and low color temperatures, the blue light beam can be irradiated onto the red and green rare earth phosphors, and the light source with high color rendering (Ra≥80) can be obtained by adjusting the ratio of phosphors of various colors. The blue light in the light will be reduced, but the light effect is significantly lower than that of high color temperature light sources. The LED light source has high luminous efficiency with high color temperature, and low luminous efficiency with low color temperature, which is opposite to the characteristics of fluorescent lamps.

The LED light source has a small light-emitting area, high surface brightness, directional radiation with a small solid angle, and contains a lot of blue light. It will make people feel uncomfortable to use it directly for lighting. Blue light will have many effects on human beings, such as photochemical, physiological, physical, psychological and other effects, which is the so-called "blue light effect".

2. Application of LED lighting source

At present, the highest luminous efficiency of LED light source has reached more than 200 lm/W, and the working life is about 30,000 hours or more. If LED bulbs are used to replace incandescent bulbs, the energy-saving effect is huge; if compared with energy-saving fluorescent lamps, the luminous efficiency is not greatly improved. Compared with fluorescent tubes, straight-tube LED lamps can double the light efficiency at most. LED lamps can be continuously dimmed, which is beneficial to energy saving, but the distribution of illuminance is uneven.

The working characteristics of LED light sources are large dispersion and poor stability. When the working current or ambient temperature changes, its luminous efficiency and color temperature will change accordingly. During the lifetime, the light efficacy will decrease and the color temperature will drift. Secondly, the semiconductor PN junction has poor heat resistance. Once the junction temperature is too high, the working stability will deteriorate, the life will be shortened, and even failure will occur. LED light sources cannot be used in higher temperature environments.

Compared with energy-saving fluorescent lamps, some commercially available LED light sources have poorer light color quality, which often makes people feel dazzling. Especially for indoor lighting, there are not many high-quality LED lighting products in the domestic market at present. If low-priced and low-quality products flood the market, it will definitely endanger human health.