I. What is UV?

1. In the field of chemical polymers, UV is also used as an abbreviation for radiation curing. Radiation curing encompasses UV curing and EB curing. Since UV curing accounts for over 95% of the market share, UV is similarly used here as the shorthand term for radiation curing.

2. UV curing, or UV ultraviolet curing, is a process that utilizes the medium- and short-wave UV radiation (300–800 nanometers) to stimulate photoinitiators in liquid UV materials, causing them to generate free radicals or cations upon exposure to UV radiation. These free radicals or cations then trigger the polymerization of high-molecular-weight materials (resins) containing reactive functional groups, ultimately forming an insoluble and non-meltable solid coating film. This technology, which emerged in the 1960s, is environmentally friendly and characterized by low VOC emissions. Since the 1980s, it has experienced rapid development in China.

II. What is an LED?

1. A light-emitting diode is commonly referred to as an LED. It is made from compounds containing elements such as gallium (Ga), arsenic (As), phosphorus (P), and nitrogen (N).

2. When electrons and holes recombine, they can emit visible light, making these materials suitable for fabricating light-emitting diodes (LEDs). In circuits and instruments, LEDs are used as indicator lights or to form alphanumeric displays. Gallium arsenide diodes emit red light, gallium phosphide diodes emit green light, silicon carbide diodes emit yellow light, and gallium nitride diodes emit blue light. Based on their chemical properties, LEDs are further classified into organic light-emitting diodes (OLEDs) and inorganic light-emitting diodes (LEDs).

3. What is a UV LED?

1. An UV-LED (or UV Light Emitting Diode) is a solid-state semiconductor device that can directly convert electrical energy into ultraviolet light. It is a type of LED with a wavelength range of 10–400 nm—specifically, it emits monochromatic invisible light typically below 400 nm. The wavelengths commonly used for curing applications are 365 nm and 395 nm. UV adhesives are generally cured using the 365 nm wavelength.

2. UV-LED light sources typically operate at temperatures below 100℃ and boast characteristics such as long service life, high reliability, high luminous efficiency, low power consumption, no thermal radiation, and environmental friendliness. In recent years, they have gradually been adopted in UV curing applications.

IV. Characteristics of UV LEDs

1. Long service life: Over 20,000 hours;

2. Significant energy-saving effect, reaching up to 90%;

3. No infrared thermal radiation: It will not cause thermal stress or thermal deformation in the workpiece.

4. Compact size and flexible configuration: The volume is only 0.1 cm³.

5. Energy Concentration: Over 98% of the light output is in the ultraviolet wavelength range;

6. Narrow and single main emission peak: Over 90% of the light output is concentrated within ±10 nm around the main emission peak.

7. DC low-voltage drive: Suitable for portable UV devices;

8. Stable and continuously adjustable output power;

9. Instant light emission: No warm-up time required; response time is on the microsecond level.

10. The number of opening and closing cycles does not affect the service life; no shutter is required.

11. Environmental Protection: Compliant with RoHS, mercury-free.

V. Classification of UV LED Curing Machines

VI. Structure and Features of UV LED Point Light Sources

1. UV LED point light sources: These are divided into UV LED fan-type point light sources and UV LED pen-type point light sources. The diameter of the light spot can be 3 mm, 4 mm, 6 mm, 8 mm, and 12 mm.

2. UV-LEDs offer numerous advantages, yet there are still many factors that hinder their widespread adoption. Currently, linear UV-LED light sources face challenges such as high costs, low power output per individual LED, complex optical systems, narrow emission peaks, and poor compatibility with photoinitiators.

3. The first application of UV-LEDs to gain acceptance and widespread adoption has been as point light sources.

4. The external dimensions of the UV-LED light-emitting unit are only a few millimeters. The light-emitting elements are mostly cubes with a side length of 1 mm, resulting in small emission points that are ideally suited for achieving excellent focusing effects through optical systems, thus enabling high-intensity ultraviolet irradiation with a small spot size.

5. Point light sources are suitable for applications requiring spot curing with a curing area of only a few millimeters and high UV irradiance intensity—for example, in the manufacturing of laser heads, fiber optic connectors, fiber optic couplers, LCDs, OLEDs, hard drives, smart cards, sensors, micro-motors, encoders, and solder joint reinforcement.

7. Structure and Features of UV LED Line Light Sources

1. The light emitted by UV-LED line sources is typically narrow, elongated, and straight. To achieve this, a specialized optical system must be designed to focus multiple light spots emitted by a row of UV-LEDs into a narrow, uniform, and high-intensity linear beam. The light source has a linear shape, and the length of the linear beam can be customized.

2. Currently, the main types of line light sources are as follows:

(1) This type of linear light source is suitable for curing applications involving slender workpieces. It features high energy and high curing efficiency; however, it is highly sensitive to the working distance and has strict requirements for the irradiation distance—typically ranging from just a few millimeters to around ten millimeters.

(2) This type of linear light source provides uniform illumination and is relatively insensitive to working distance. Its typical beam width is around ten millimeters, though its energy output is slightly weaker.

(3) This type of linear light source has a relatively large illumination range and is less sensitive to working distance; however, compared to the first two types, it has the weakest illumination intensity.

(4) This type of curved linear light source is composed of multiple linear light sources joined together, allowing it to form special shapes and meet the requirements of specific workstations.

8. Structure and Features of UV LED Surface Light Sources

1. UV-LED surface light sources also produce no thermal radiation, allowing the temperature inside the curing oven to be maintained at room temperature. Numerous LED light-emitting points are evenly distributed, and multiple specialized lens groups optimized for ultraviolet irradiation ensure uniform illumination with exceptional consistency in irradiance levels between the edges and the center. Moreover, the shape and size of the illuminated area can be customized according to user requirements. The light source is planar, and its area can be tailored to specific needs, making it widely applicable.

2. Under the same input power, UV-LED area light sources are more expensive to operate than mercury lamps; calculated by output power, their operating costs are higher than those of mercury lamps.

3. Currently, the primary breakthrough for the application and widespread adoption of UV-LED area light sources lies in small-area light sources. Today, the irradiance of these small-area light sources can reach several hundred to over a thousand milliwatts per square centimeter. This high irradiance translates into significantly higher production efficiency. On the other hand, small-area UV-LED light sources concentrate energy efficiently and emit no thermal radiation; as a result, their cooling systems and overall illumination systems tend to be more compact, making them easier to use and integrate into various applications.

4. Compared to point sources and line sources, area light sources are more costly, which has constrained their application and development.

9. The Difference Between UV LED Light Sources and UV Mercury Lamps

1. Service life

2. Thermal radiation

3. Environmental pollution

4. Light source illuminance

5. Energy Consumption

X. Application Fields of UV LED Curing

1. In the electronics field, such as bonding components like optics, mobile phones, touch screens, hard drives, encoders, and more;

2. In the printing field, such as printing on electronic components and offset printing;

3. In the field of handicrafts, such as bonding transparent products like crystal and glass;

4. In the medical field, bonding applications such as injection needles;

5. By application: curing of UV adhesives, UV inks, and UV resins, etc.;

6. Curing of UV adhesives, UV inks, and UV resins, etc.;

7. Glass industry

UV LED inkjet printers can directly print a variety of patterns onto glass surfaces, replacing manual painting. This enables a seamless, efficient, low-cost, and color-rich instant processing procedure. The ease of operation saves glass industry customers significant time, and the use of this equipment has already brought substantial economic benefits to manufacturers.

8. Decoration and interior design industry

UV LED inkjet printers can directly print desired patterns onto the surfaces of various decorative materials, including ceilings, fire-retardant boards, aluminum composite panels, density boards, stone, ceramics, and glass, thereby meeting personalized decoration needs and bringing substantial economic benefits to architectural decoration companies.

9. Construction Materials Industry

UV LED inkjet printers transform building materials such as tiles, glass, wood, fire-rated doors, and stone into high-value-added products.

10. Furniture Industry

UV LED inkjet printers can print vivid patterns on wardrobes, tables and chairs, sofas, and kitchen countertops, meeting consumers’ personalized needs.

11. Signage Industry

UV LED inkjet printers can directly print patterns onto the surfaces of various rigid signage materials, replacing traditional signage processes such as screen printing, etching, and film application. This not only reduces the number of steps involved and lowers costs but also enhances durability. As a result, these printers are an ideal choice for manufacturers of power signs, traffic signs, safety indicator signs, reflective signs, and more.

12. Mural and decorative painting industry

UV LED inkjet printers can directly print patterns onto the surfaces of ceramics and wood products, replacing traditional methods such as hand painting and screen printing. After undergoing post-processing, the resulting products meet stringent requirements for abrasion resistance, water resistance, tolerance to temperature fluctuations, and radiation resistance, while also satisfying personalized decoration needs. This technology enables a highly efficient, low-cost, and on-demand manufacturing process. The advent of inkjet printers has injected greater vitality and artistic expressiveness into the mural and decorative painting industries.

13. Display board production

UV LED inkjet printers can directly print patterns onto the surfaces of ceramics and wood products, replacing traditional methods such as hand painting and screen printing. After undergoing post-processing, the resulting products meet stringent requirements for abrasion resistance, water resistance, tolerance to temperature fluctuations, and radiation resistance, while also satisfying personalized decoration needs. This technology enables a highly efficient, low-cost, and on-demand manufacturing process. The advent of inkjet printers has injected greater vitality and artistic expressiveness into the mural and decorative painting industries.

XI. Summary

As the cost of UV-LEDs continues to decline, the adoption of UV-LEDs is shifting from point light sources toward linear light sources (while widespread adoption of area light sources will still take some time). In the fields of industrial assembly and consumer goods, linear light sources are set to gain increasing prominence. The development trend for linear light sources is toward greater refinement—different categories are emerging based on varying application scenarios (such as wavelength, shape of the illuminated area, and irradiation intensity) to meet the diverse requirements of different operating conditions. Meanwhile, with the ongoing development of photoinitiators tailored specifically for UV-LEDs, the applications of UV-LEDs will expand even further, and their advantages will become increasingly evident.