As is known to all, the wavelength range of visible light spectrum is 380nm ~ 760nm, which is the seven-color light that the human eye can feel -- red, orange, yellow, green, green, blue and purple, but each of these seven colors is a monochromatic light.
For example, the peak wavelength of red light emitted by leds is 565nm. There is no white light in the spectrum of visible light, because white light is not a monochromatic light, but a composite light synthesized by a variety of monochromatic light, just as the sunlight is a white light synthesized by seven monochromatic light, and the white light in color television is also composed of three primary colors: red, green and blue.
Thus, in order for an LED to emit white light, its spectral characteristics should include the entire visible spectral range. However, it is impossible to manufacture leds with such performance under technological conditions. According to the study of visible light, the white light that the human eye can see requires at least a mixture of two wavelengths (blue + yellow) and three wavelengths (blue + green + red). White light in both modes requires blue light, so blue light has become the key technology to produce white light, namely "blue light technology" pursued by major LED manufacturers. There are only a few manufacturers that master the "blue light technology" in the world, so the promotion and application of white LED, especially the promotion of high-brightness white LED in China still has a process.
The light source
For general lighting, in terms of process structure, white LED is usually formed by two methods. The second is a variety of monochromatic light mixing methods. Both methods have been successful in generating white light devices. The first system for generating white light is shown in figure 1, where the LED GaM chip is seen emitting blue light (lambda p=465nm), which is encapsulated with YAG (yttrium aluminum garnet) phosphors. When the phosphors are excited by blue light, they emit yellow light. The second method USES different color light chip package together, through each color light mixture to produce white light.
In order to explain the characteristics of white LED, first look at the status of the lighting source used. Incandescent lamp and halogen tungsten lamp, the light visual efficiency is 12 ~ 24 lumens/watt; Fluorescent and HID lamps have a luminous efficiency of 50 ~ 120 lumens per watt. For white LED: in 1998, the luminous efficiency of white LED was only 5 lumens per watt; in 1999, it has reached 15 lumens per watt, which is similar to that of ordinary household incandescent lamp; in 2000, the luminous efficiency of white LED has reached 25 lumens per watt, which is similar to that of halogen tungsten lamp. Some companies predict that by 2005, LED light efficiency can reach 50 lumens per watt, and by 2015, LED light efficiency can reach 150 ~ 200 lumens per watt. At that time, the working current of white LED can reach ampere level. Thus it can be seen that the development of white LED writers with lighting sources will become a possible reality.
Incandescent lamps and halogen tungsten lamps for general lighting are cheap, but low light efficiency (the thermal effect of the lamp is a waste of electricity), short life, large maintenance workload, but if the white LED lighting, not only high light efficiency, and long life (continuous working time of more than 10000 hours), almost no maintenance.
LED light source has the advantages of low voltage power supply, low energy consumption, strong applicability, high stability, short response time, no pollution to the environment, multi-color luminescence, etc. Although the price is more expensive than the existing lighting equipment, it is still considered that it will inevitably replace the existing lighting devices.
Characteristics of the LED
The internal characteristics of LED determine that it is the most ideal light source to replace the traditional light source, which has a wide range of USES.
The LED is basically a very small chip enclosed in an epoxy resin, so it's very small, very light.
Low power consumption
LED power consumption is very low, generally speaking, the working voltage of LED is 2-3.6v. The operating current is 0.02-0.03a. This means that it consumes no more than 0.1w of electricity.
Long service life
At the right current and voltage, leds can last up to 100,000 hours
High brightness, low heat
Leds are made of non-toxic materials, unlike fluorescents, which contain mercury and can be recycled.
Strong and durable
Leds are fully encapsulated in epoxy and are stronger than bulbs and fluorescent tubes. There is no loose part inside the lamp, which makes the LED not easily damaged.
The biggest advantage of LED lights is energy saving and environmental protection. The luminous efficiency of light can reach more than 100 lumens per watt, while the ordinary incandescent lamp can only reach 40 lumens per watt, and the energy-saving lamp is hovering around 70 lumens per watt. So, for the same wattage, leds will be much brighter than incandescent and energy efficient bulbs. 1 watt LED light brightness is equivalent to about 2 watts of energy-saving lamps, 5 watt LED lights 1000 hours power consumption 5 degrees, LED life can reach 50,000 hours, LED lights without radiation.
Color temperature color
Color temperature of light source:
People describe the color table of the light source by the absolute temperature of the complete radiator which is equal to or close to the color temperature of the light source (the color seen when the human eye directly observes the light source), which is also called the color temperature of the light source. Color temperature is expressed in terms of absolute temperature K. Different color temperatures will cause different emotional reactions of people. We generally divide the color temperatures of light sources into three categories:
. Warm color light
The color temperature of warm color light is below 3300K. The color of warm color light is close to the color of incandescent light, and the red light has more components, giving a warm, healthy and comfortable feeling.
Also known as the middle color, its color temperature between 3300K-5300K. Warm white light soft light, make people have a pleasant, comfortable, peaceful feeling, suitable for shops, hospitals, offices, restaurants, restaurants, waiting rooms and other places.
Cool color light
Also known as daylight color, its color temperature is above 5300K, the light source is close to natural light, has a bright feeling, make people concentrated, suitable for offices, conference rooms, classrooms, drawing rooms, design rooms, library reading rooms, exhibition Windows and other places.
The degree to which the light source presents the color of the object is called the color performance, that is, the degree to which the color is realistic. The light source with high color performance performs better on the color, so the color we see is closer to the natural color and the color performance
Low light sources have a poor color response, and we see a large color bias.
Why is there a play color of high and low points? The key lies in the spectral characteristics of the light, the wavelength of visible light at 380 nm to 780 nm range, that is we have to see in the spectrum of red, orange, yellow, green, blue, blue, violet light range, if the light source of the light emission by a contained in the proportion of each color close to natural light, then our eyes can see color is more realistic.
We generally take the color rendering index as the color rendering property. Standard color under the radiation of standard light source, the color rendering index is set as 100. When the color standard is irradiated by the experimental light source, the degree of visual distortion of the color is the color rendering index of the light source. The larger the color rendering index, the less distortion; on the contrary, the larger the distortion, the smaller the color rendering index. Different places have different requirements for the color rendering index of the light source. In the international lighting association, the color rendering index is generally divided into five categories:
Category Ra scope of application
1A >90 art galleries, museums and printing industries and places
2B 80 -- 90 families, restaurants, advanced textile technology and similar industries
60-80 lighting for offices, schools and outdoor streets
Heavy industry factory, outdoor street lighting
Outdoor road lighting and some places with low requirements
The difference between
Ordinary fluorescent lamp
A fluorescent lamp has a filament at each end. The tube is filled with trace argon and thin mercury vapor. The inner wall of the tube is coated with fluorescent powder.
Fluorescent lamp working characteristic: lamp tube begins to ignite when need a high voltage, normal when luminescent allow to pass not quite current only, at this moment the voltage of lamp tube both ends is lower than power source voltage.
The LED fluorescent lamp
Led fluorescent lamp is characterized by high quality, durability and energy saving, with a wide range of projection Angle adjustment. The brightness of 15W is equal to that of ordinary 40W fluorescent lamp. Resistance to high temperature, moisture and water, electricity leakage. Operating voltage :110V, 220V optional, optional glass or PC cover material. The lamp holder is the same as ordinary fluorescent lamp.
LED fluorescent lamps adopt the latest LED light source technology, digital appearance design, power saving up to more than 70%, 12W LED daylight intensity is equivalent to 40W daylight tube (for ballasts and starters, 36W fluorescent lamps real power consumption is 42W to 44W). LED fluorescent lamp life is more than 10 times of ordinary tube, almost maintenance-free, no need to change the tube, ballast, starter. Green and environment-friendly semiconductor electric light source, soft light, pure spectrum, is conducive to the user's vision protection and physical health. The cold light source of 6000K gives people a cool and refreshing feeling visually, and the humanized illumination difference design is more conducive to concentration and efficiency.
Compared with ordinary fluorescent lamps, LED fluorescent lamps have the following advantages:
1. Energy saving. 2. Long LED life. 3. Good applicability. Because of the small size of a single LED, it can be made into any shape. 4, the response time is short, which is ns (nanosecond) level response time, while ordinary lamps are ms (ms) level response time. 5, environmental protection, no harmful metals, waste easy recycling. 6. Brilliant color, pure luminous color, narrow spectral range, and can be mixed into seven colors or white light through red, green and blue primary colors.
Cons: 1. Expensive. 2. There is a big gap between the universal light efficiency and the theoretical light efficiency. 3. There is still a big gap between the life that can be achieved and the theoretical life (10w hours). 4. It still has some heat added. 5. The light decay can be greatly reduced.
However, these shortcomings can be overcome through the improvement of technology, so even if the LED light source can not completely replace the existing traditional light source, but with the development of technology, it will be LED in the future.
Applications in advertising
In the advertisement application mainly by the big character primarily. More for large word plug and small lamp source, increase the display effect.