UV ink achieves rapid drying effect through UV irradiation. Currently, the main UV light sources are mercury lamps and LEDs. Next, we will compare the characteristics of the two light sources
Mercury lamp ultraviolet light
Mercury lamp, also known as mercury vapor lamp, is one of the commonly used ultraviolet light sources. It consists of a transparent quartz tube encapsulated with mercury and tungsten electrodes at both ends, filled with inert gas argon. When the filament is heated by electricity, the temperature rises, causing the liquid mercury to evaporate and vaporize. The ground state mercury atoms inside the quartz tube are excited and transition to an excited state, and then release photons when returning to the ground state, emitting ultraviolet light.
Mercury lamp is a widely used UV light source that can generate specific wavelengths of ultraviolet light (such as 254nm). When ultraviolet light is irradiated onto UV ink containing photosensitizer, the photosensitizer absorbs light energy and transitions to an excited state, triggering a chemical reaction that transforms the substance from liquid to solid.
LED ultraviolet light
LED ultraviolet light source is a light source that uses LED (Light Emitting Diode) technology to generate ultraviolet light. It relies on the recombination process of electrons and holes in semiconductor materials under the action of current, during which the energy released is emitted in the form of photons, forming ultraviolet light.
In the LED structure, when an appropriate voltage is applied, electrons flow from the n-type semiconductor (electron rich region) to the p-type semiconductor (hole rich region). At the junction, electrons and holes undergo recombination, which is the process of electrons filling holes. This composite process is accompanied by the release of energy, with a portion of the energy being emitted in the form of photons, the magnitude of which depends on the band structure of the semiconductor material. In ultraviolet LEDs, the energy of these photons is high enough to fall within the range of 200 to 400 nanometers in the ultraviolet spectrum, which is LED ultraviolet light.
There are significant differences between mercury lamp curing and LED light sources in multiple aspects, and the following is a detailed comparison of these differences:
1、 Luminescence principle and types
Mercury lamp curing:
Luminous principle: Mercury lamps emit light through the principle of gas discharge, specifically by exciting mercury vapor with current to generate ultraviolet light, which is then converted into visible light through fluorescent powder and other means (mainly used during the curing process).
Luminous type: Mercury lamp emits cold light with a color preference towards cool tones.
LED light source:
Luminescence principle: LED (Light Emitting Diode) emits light through the electroluminescence effect inside the semiconductor, that is, when electrons and holes in the semiconductor material combine, they release energy to produce light.
Luminous type: LED light source is usually considered as thermal light, with a color bias towards warm tones, but in reality, the light emitted by LED does not produce significant heat. Here, "thermal light" refers more to the feeling its light color gives people.
2、 Spectral characteristics and efficiency
Mercury lamp curing:
Spectral characteristics: The light emitted by mercury lamps has a wide wavelength range and may contain unwanted wavelengths, resulting in relatively low efficiency.
Energy conversion efficiency: Mercury lamps consume a high amount of energy during start-up and operation, and require a long preheating time.
LED light source:
Spectral characteristics: LEDs emit light with a more concentrated wavelength, which is usually optimized for specific application requirements, such as the curing wavelength for specific resins in UV curing.
Energy conversion efficiency: LED lights have higher energy conversion efficiency and lower energy consumption.
3、 Environmental friendliness and safety
Mercury lamp curing:
Environmental friendliness: Mercury lamps contain mercury elements and require special treatment after use, otherwise they may cause pollution to the environment and pose significant environmental risks.
Safety: The use and handling of mercury lamps must strictly comply with safety regulations to prevent accidents such as mercury poisoning.
LED light source:
Environmental friendliness: LEDs do not produce pollution during manufacturing and use, meeting the requirements of sustainable development.
Safety: LED light sources are driven by low-voltage direct current, which provides high safety and is less likely to cause accidents such as fires.
4、 Service life and cost
Mercury lamp curing:
Service life: Mercury lamps have a relatively short service life and require more frequent replacement, which increases the cost of use.
Cost: Although the initial purchase cost of mercury lamps may be lower, considering their short lifespan and high energy consumption, the total cost of long-term use may be higher.
LED light source:
Service life: The service life of LED light sources is relatively long, usually tens of thousands to hundreds of thousands of hours, greatly reducing the frequency and cost of replacement.
Cost: With the continuous maturity of LED technology and the increase in production, the cost of LED light sources is gradually decreasing, and the cost-effectiveness is becoming higher and higher.
5、 Application scenarios and curing effects
Mercury lamp curing:
Application scenarios: Suitable for large-scale production scenarios such as wood coating, plastic printing, fiber optic curing, etc.
Curing effect: It can cure thicker materials with a greater curing depth.
LED light source:
Application scenarios: Suitable for fine operations such as surface coating, ink printing, 3D printing, and small-scale production scenarios.
Curing effect: For certain thin layers or surfaces, LED curing speed is fast, but its penetration may not be as good as mercury lamps. However, its high energy conversion efficiency and low energy consumption give LEDs significant advantages in specific applications.
Overall, the trend of LED ultraviolet light replacing mercury lamps has begun, mainly due to LED's lower cost and higher efficiency.
For more knowledge about UV ink, please follow the StarColor website: www.starcolor-ink.com