What are the main advantages of LED compared to traditional lighting?

In the past decade, many lighting devices have used LEDs because LEDs have more advantages than traditional lighting devices:

Longer service life, lower cost and maintenance costs

Unit power can generate more light, more efficient

On-off operation is faster and has no adverse effects

Smaller size, bringing more potential for use

Higher stability in the face of shock, vibration and mechanical stress

LEDs are everywhere in our lives, whether it's a gas mask at a gas station or a retail location for food and clothing. The white light illuminates our world, accompanied by red, green and blue light, giving us a new perspective to look at life.

At the same time, LEDs have changed in the spectral range that we can't detect with the naked eye, and he has changed our application. In addition to visible seven colors, LEDs have made a huge leap forward, and they are subverting the application of ultraviolet and infrared spectroscopy, which is beyond the reach of human rods and cells.

The human eye's ability to perceive color is approximately in the wavelength range of 400 nm to 700 nm. People have known since childhood that the rainbow consists of six basic colors: red, orange, yellow, green, blue, and purple. When a light wave having a wavelength of 430 nm to 495 nm is taken into the human eye, blue is seen, and light having a wavelength of less than 430 nm is displayed in purple. When the wavelength is around 400 nm, the naked eye can't see the purple color, and the color can no longer be distinguished. (figure 1)

Blue 430nm-495nm

UV-A long-wave UV 360nm-430nm

Figure 1: Wavelengths of blue and violet light (Source: Mouser Electronics)

The shorter light than the purple light is ultraviolet (UV), which covers approximately three lightwave areas:

UV-A (long-wave UV): 315nm-400nm

UV-B (medium wave UV): 280nm–315nm

UV-C (short-wave UV): 100nm–280nm

Short-wave ultraviolet light is mainly used for sterilization and disinfection. The photons of these high-frequency light waves have higher energy than the low-frequency spectrum. They are mainly used to break down biological factors that are difficult to handle. The application fields mainly include the cleaning work of air, water and medical equipment. . However, due to the band gap level of the semiconductor material, it is very difficult to obtain a light wave having a short wavelength. Therefore, the application of medium wave and short-wave ultraviolet light is limited, and long-wave ultraviolet light is more widely used.

UV lamps occupy a place in the industrial field thanks to the application of long-wave UV, because semiconductor manufacturers are better at producing such semiconductor materials and products that emit long-wave light. Long-wave UV LEDs are mainly used in three areas: UV treatment, inkjet printing, and scientific equipment. Let's take a look at how long-wave UV LEDs are used in inkjet printing applications.

Inkjet printing is a method of transferring high quality digital images onto a variety of media such as paper and plastic. The ink used in inkjet printing is either dried or cured. Conventional inks are typically ink or ink solvents. Drying of the ink or ink solvent is achieved by oxidation and evaporation, respectively. Both processes require a certain amount of heat (infrared heating), which not only increases the printing time, but also tends to cause shrinkage and distortion. In order to avoid such a result, inkjet manufacturers have developed a method of curing ink by long-wave ultraviolet rays, that is, when ultraviolet rays illuminate the binder and the pigment, polymerization occurs and the pigment is cured. This is because the energy from the long-wave ultraviolet rays causes the reactants to generate free radicals that bind to other elements that bind the binder firmly to the pigment. The advantage of this method is that the cured ink no longer needs to be completely exposed to high temperatures, so the image is smooth and uniform. In addition, this method is very environmentally friendly, and the ink cured by ultraviolet rays retains the ink raw material 100%, and does not cause evaporation and oxidation residues, thereby reducing pollution and promoting environmental protection.

Ultraviolet light has been produced by ultraviolet mercury lamps for many years. Thanks to the broad-spectrum UV wavelength output, these UV-cursors accelerate the inkjet printing process while maximizing the active ingredients of the ink. Long-wave UV-lit LED lamps are inherently monochromatic, which limits their curing capabilities. However, the advantages of the LED lamp as described above still exist. Manufacturers continue to improve inks to match the latest long-wave UV LED lamps. This makes inkjet printing technology more suitable for low-productivity devices than for high-efficiency and high-performance systems. So far, with the continuous development of higher power long-wave UV lamps, they will continue to influence the industry.

Many LED lighting companies are expanding their supply of UV LED lamps, including Lumileds, Led Engin, Luminus Devices, Everlight Electronics and Wurth Electronics . For example: Lumileds LUXEON UV U Line LEDs are a high-power, high-efficiency device (Figure 2). They are designed to be very small, suitable for places where previous UV LEDs could not be embedded, and without a lamp cap, can be mounted on the surface of the object, arranged in an array with only 0.2 mm gap between them. Their small size allows for precise optical control. These LEDs provide light wavelengths from 380nm–400nm and 400nm–420nm and can be used in a variety of applications such as curing reactions, medical applications, analytical instruments, and UV photochemical reactions.

Figure 2: Lumileds LUXEON UV U Line LEDs (Source: Lumileds)

For high-power UV LEDs, LED Engin has developed small-sized, high-brightness UV LED components with wavelengths ranging from 385nm to 410nm. It can be used in the curing of inks and adhesives, dental treatment, tooth whitening, identification of counterfeit documents, and equipment. Disinfection and medical applications. The LZ4 series is packaged on a 7mm*7mm substrate, the LZC package is mounted on a 9mm*9mm substrate, and the LZP series is packaged on a 12mm*12mm substrate. As the size increases, more die can be placed on the substrate. (image 3)

Figure 3 LED Engin's LZP00UB00 Series LED Transmitter

Seven-color light has two ends. Below the blue color, there is ultraviolet light shorter than the blue light wavelength. On the other end of the seven-color light, above the red light, there is another wave frequency - infrared light. Ultraviolet rays have a wide range of applications due to their inherent advantages. Similarly, infrared applications are widely used. Let's take a look at the application of infrared LEDs.

Where is the edge of red light in the seven-color light? Let us start with this. When light having a wavelength of 610 nm to 740 nm is incident on the eye, it is red, but it is difficult to see the naked eye of a person having a wavelength of 700 nm or more. When it comes to the boundary between red and infrared, there will be some overlap. According to the actual situation, we usually define this part as light between 700nm and 740nm.

Red light 610nm-740nm

Near infrared ray 700nm-1500nm

Figure 4 Red and infrared light waves (Source: Mouser Electronics)

Unlike ultraviolet light, which has three lightwave regions, infrared rays cover five lightwave regions:

Near infrared: 700nm-1500nm

Short-wave infrared: 1.5μ–3μ

Medium wave infrared: 3μ–1,000μ

Long wave infrared: 8μ–8μ

Far infrared: 15μ–1,000μ

Infrared rays in each area are used in industrial and commercial applications. Here, we only discuss near-infrared LEDs, which are especially suitable for scenes that need to be illuminated and are invisible to the human eye, and these scenes are easily perceived electronically. The role of near-infrared LEDs is so powerful that they have many electronic sensors, such as silicon detectors, which have very good response curves in the near-infrared spectrum.

Near-infrared LEDs are used in a wide range of applications. For example, near-infrared LEDs are particularly well-monitored for monitoring security systems, closed-circuit television, and machine vision. Near-infrared LEDs are also used to collect tags and license plate information on the highway. In biostatistics, near-infrared LED lights are used for access control and identification. Together with silicon detectors, it can be used for touch screens, gesture recognition systems and smoke detectors. If you've ever seen the popular TV series "CSI," you'll be familiar with getting clues, and the process takes advantage of spectroscopy, including short-infrared spectroscopy. Near-infrared spectroscopy also has an exciting new application for identifying the quality and properties of the substances we consume, including foods and drugs.

Just as humans can see objects through visible light reflected from objects, near-infrared spectroscopy uses near-infrared LED lamps as light sources to illuminate materials in experiments that absorb and reflect light based on their inherent physical properties. Experiments with the provision of a wavelength selective detector to observe these reflected light provide information on the subject. In this way, the system and the user can determine the presence or absence of a material by comparison with known materials.

In the past, people used large and cumbersome spectroscopy machines, but as NIR LEDs became smaller and more powerful, NIR LEDs will be more used in handheld devices and portable devices. .

To meet this trend, suppliers including Lumileds and Osram Opto Semiconductors have developed their own products such as Lumileds LUXEON IR LED (Figure 5) and IR OSLON® Black Series (Figure 6).

Figure 5 Lumileds LUXEON IR LED

Figure 6 Osram Opto Semiconductors IR OSLON® Black Series LEDs

How do companies like Osram produce high-power NIR LEDs? One of the secrets is through phosphor conversion. The LED will input most of the light energy into the visible spectrum, such as blue light. When these visible light hits the phosphor on the LED or the like, cold light is generated, which changes the wavelength of the light. Through careful design and program control, a variety of near-infrared wavelengths are produced, including wavelengths ranging from 850 nm to 940 nm. The shade further determines the orientation of the light emitting position. The bandwidth and performance of near-infrared spectroscopy can be improved by using more than one wavelength in the system design.

LED lights make life better, and its potential advantages have prompted designers to design a large number of products to meet people's needs. Ultraviolet lamps cover three wavelength regions other than blue light, and long-wave UV light enables them to work in curing, inkjet printing, and scientific instrument sterilization. At the other end of the spectrum, the infrared light covers five wavelength regions, and the near-infrared spectrum has a perfect application.

The transition from incandescent light to LEDs has revolutionized the world of illumination, and LED lighting has moved forward at a faster rate. Many of these lighting applications come from the edge of the seven-color light. LED lights incorporate UV and near-infrared light into the design. Although the human eye can't see the light, it helps us see the world beyond the colorful light.