In recent years, the development of LED technology in my country has been very rapid, The light source is getting brighter, and the light efficiency has become higher and higher. According to Maslow’s hierarchy of needs theory, after solving the underlying needs of "whether there is light", people gradually turn their attention to the problem of "lighting and uncomfortable", and then whether light affects human health and whether it is suitable The environment has put forward higher requirements.
So, why should we pay attention to healthy light sources? What is a healthy light source? What is the basis for judging a healthy light source? Follow Yenhualighting, then look down and you will understand.
Why promote healthy light sources?
As the saying goes, the eyes are the windows of the soul, and the unhealthy light source is like a storm outside the window, exerting tremendous pressure on the windows all the time. Discomforts such as dry eyes and swelling may occur, and irreparable injuries such as retinal atrophy and damage may occur. Blue light hazards, visual fatigue, bulbar atrophy, glaucoma and other diseases are the four common hazards of harmful light sources.
The harm to the light source should not be underestimated. A healthy light source is very important!
The case map is too horrible, so let's not put it...
What is a healthy light source?
What kind of light source is considered healthy?
A healthy light source is usually defined as: all visible light that conforms to what humans have been able to bear since evolution, does not harm the body, does not harm the vision, and makes humans feel happy.
We tend to feel that the sun is more comfortable at 8 o'clock in the morning and 5 o'clock in the afternoon. The strong light at noon can make people feel dazzling and uncomfortable, which is unhealthy for people. Therefore, sunlight is not a purely healthy light source, and the time period must be considered.
Healthy light sources can often be evaluated from the following aspects:
1. Wave length
Determine the color of light, such as three primary colors: red light (630nm) green light (550nm) blue light (450nm);
Commonly used light intensity (Cd) and illuminance (lx) to measure, international and domestic have clear regulations on the light intensity of lighting products, too strong or weak will cause damage to eyesight;
3. Color temperature
Determine the basic color of the light (there are many in the market are positive white, warm white, cool white, etc.), the color temperature range that the human eye can perceive is 1500K-12000K. The color temperature needs to be compatible with the environment. For example, in a hospital, cold white light makes patients feel irritable, while warm white light makes patients feel more comfortable (an important factor).
4. Color rendering
Color rendering refers to the characteristics of different colors when light sources of different spectrums are illuminated on objects of the same color. The color rendering index (Ra) is usually used to express the color rendering of the light source. The color rendering on the market is not much above 75, and the real color above 80 is very small. A light source with a color rendering property of 97 has been developed in the laboratory, and the color rendering property can be improved a lot when the light efficiency is not reduced a lot;
How can we achieve a healthy light source?
So how to make a very cost-effective healthy light source while reducing costs or not increasing costs? Let’s take a look at the methods!
In the color matching process, the color temperature can be analyzed and adjusted by using the spectrogram. Take the main light source cold white light on the market as an example:
Figure: Cold white light spectrum
It can be seen from the spectrogram that the blue light of cold white light is stronger and the red light is weaker. The color temperature is about 6500-7000K, which is still slightly whiter for human eyes.
Another common light-warm white light, as shown below:
Figure: Warm white light spectrum
Compared with cold white light, the blue of warm white light is relatively weaker, and the red and yellow are relatively prominent. The color temperature of the upper right picture is about 1700-2000K, and the color temperature of the upper left picture is about 3500K.
It can be seen that judging color temperature by spectrum is an important criterion for measuring light source.
The combination of phosphor, glue, and chips is the key to making a cost-effective and healthy light source while reducing costs or not increasing costs.
Optimize packaging technology
The four major material factors that affect the light-emitting quality and effect of the light source during the packaging process are the chip, the bracket, the phosphor, and the sealing compound. The complexity of packaging is that these four are interrelated and affect each other, which requires us to consider the following technologies in packaging:
1. Matching of chip and bracket
Any bracket is designed for a specific chip, and the bracket must match the chip;
2. Matching of chip and phosphor
The mechanism of chip light emission is to use the blue light emitted by the chip to excite the phosphor to make it emit the light we need. The emission wavelength of the chip must be able to effectively excite the phosphor.
3. Matching of chip and glue
The light guide, compactness and other properties of the glue will affect factors such as color drift, dead light, water vapor permeability, and blackening. In addition, chips, especially high-power chips, often need to dissipate heat up and down, so the heat dissipation of the glue and whether it matches the chip should be considered when packaging.
4. The matching of phosphor powder and light source quality
The poor ratio of phosphors will cause the light source to appear colors that we don't need to see, or the color accuracy and purity are not enough, and the width is not enough.
For example: using a 450nm blue chip and a phosphor with an effective excitation of 454nm, the wavelength difference between the two is 4nm, which will cause the phosphor to lose 2%-5% of luminous efficiency;
5. Matching of different materials and different processes
To achieve a healthy light source, packaging technology is the most critical.
Mimic the sunlight spectrum
Generally speaking, the human eye is more adapted to the solar spectrum
Solar spectrum range: 400-750nm, green light is strong, red light is slightly weak
Sun white temperature: 3500K-5500K,
Color rendering: above 85.
Compared with sunlight, the biggest weakness of LED light lies in the huge lack of blue and green parts.
Picture: Sunlight spectrum
Figure: LED light source spectrum (blue and green parts are missing)
Fortunately, the experiment has developed a healthy spectrum that is very close to sunlight:
The lack of blue and green light in the LED light source can be compensated by adding blue and green phosphors. In fact, there is a lot of knowledge in the increase of phosphors. Experiments have proved that the amount of blue and green powder has a significant impact on the color temperature, CRI and luminous efficiency of the COB LED packaged light source:
Most of the light sources on the market are cold white light, and the color temperature is not conducive to the living environment. The LED light source without visual system harm is matched with a variety of phosphors in the package, and green phosphors are added. The finished product has improved color temperature, color rendering, and light efficiency.
It can be seen from this that finding the appropriate amount of phosphor through the COB experiment can make the light source reach the appropriate color temperature and improve the color rendering index and light efficiency of the light source.
The design of the light source must match the environment
The picture below is the lighting design of McDonald's. The light is close to warm white, which makes people very appetizing, very comfortable and relaxed. At the same time, the intensity of the light source complies with the universal standards of the world, so that the light can be effectively illuminated on the desktop, but it will not be dazzling.
Picture: McDonald's lighting design
Therefore, different environments and places (such as hospitals, classrooms, shopping malls, etc.) need to be considered when designing the light source to make the light source effect meet the environmental requirements.
to sum up
1. Healthy light sources are of great significance to human health;
2. Through the deployment of LED packaging glue and a variety of phosphors, the sun-like health spectrum can be obtained;
3. The design of a healthy light source needs to consider the pertinence of its use;
4. The development of light source packaging technology for human health may become a widely optimistic development direction in the next five-year cycle.
The development of healthy light source technology is not only a market demand, but also a trend of industry development.