company news about Insufficient hardness, sticky surface? Three steps to troubleshoot insufficient UV curing energy

In the UV curing process, the sufficiency of light energy is a key factor affecting the curing effect. Many people may have heard the saying, "This coating didn't cure completely because the light energy was insufficient." However, the problem is that many people don't know exactly how to calculate whether the light energy is sufficient, or how much light energy is needed for effective curing. Today, we will take you through an in-depth analysis of the role of light energy in UV curing, and discuss how to accurately assess whether the light source output is sufficient, helping you avoid curing failures due to insufficient energy in actual production.

In UV curing, light energy refers to the energy emitted by the ultraviolet light source, which, after passing through the coating, effectively initiates a polymerization reaction. Simply put, the role of light energy is to excite the photoinitiator, thereby starting the polymerization reaction in the coating and causing it to harden.

The basic unit of light energy: Light energy is usually measured in joules (J). However, in UV curing, we are more concerned with radiant energy density, that is, the total energy received per unit area, usually expressed in mJ/cm² (millijoules per square centimeter).

How to calculate the required light energy? The required light energy depends on the following factors:

• Light source power (mW): The luminous intensity of the light source, representing the energy output capacity per unit time.
• Irradiation time (s): The time the coating is irradiated by light, measured in seconds.
• Distance from lamp to coating (cm): The distance between the lamp and the coating affects the light intensity; the greater the distance, the lower the light energy per unit area.

The basic formula for calculating the required light energy is: E = P * t, where E is the light energy (mJ), P is the light source power (mW), and t is the irradiation time (seconds). It should be noted that this is only a theoretical calculation; in practical applications, factors such as the matching of the light source spectrum with the coating, the uniformity of the light source, and the light's penetrating power must also be considered.

In practice, many people believe that high power and long curing time guarantee sufficient light energy. However, this is a misconception. Let's look at some common misconceptions:

1. Does higher light source power mean higher light energy? This is a common misunderstanding. While the power of the light source directly affects the output light energy, it is not the only determining factor. In reality, higher light source power certainly provides more energy, but in practice, we must also pay attention to the following points:
   • Wavelength matching: Different photoinitiators have different absorption peaks in the spectrum. If the wavelength of the light source does not match the absorption wavelength of the initiator, even with high light source power, the energy cannot effectively act on the coating.
   • Light source uniformity: Although the power of the light source is high, if the output of the light source is uneven, the energy in some areas may be much lower than in other areas, resulting in incomplete curing.
2. Does longer curing time mean better curing results? Many people believe that as long as the curing time is extended, the coating will be fully cured. However, excessively long curing times do not necessarily mean more thorough curing. Especially in high-speed production lines, prolonged curing times can lead to surface problems such as:
   • Over-curing: the coating surface may become brittle or cracked;
   • Inefficiency: excessively long curing times may waste production resources, resulting in reduced production efficiency.
   Therefore, a reasonable curing time is key to ensuring efficient curing.
3. Is closer proximity necessarily better? The distance between the light source and the coating affects the light intensity. Theoretically, the closer the distance, the higher the light energy per unit area. However, in reality, excessively close proximity can cause the light source to overheat, affecting the coating quality and the lifespan of the light source. Therefore, maintaining an appropriate distance is crucial.

Now that we understand the calculation principle of light energy, the next step is to consider how to determine whether the light energy is sufficient to ensure the curing effect meets expectations.

1. Matching the Light Source and Coating: To assess whether the light energy is "sufficient," we must first ensure that the wavelength of the light source matches the photoinitiator in the coating. Different photoinitiators react differently to different wavelengths of light; therefore, it is necessary to select an appropriate light source wavelength based on the photoinitiator used.
2. Measuring Actual Light Intensity with a Power Meter: During the production process, the power output of the light source gradually decreases over time, especially after the lamp has been used for a period of time. Therefore, measuring the actual light intensity with a power meter is crucial. By measuring the light intensity per unit area (mW/cm²), we can assess whether the current light source is sufficient to meet the curing requirements of the coating.
3. Measuring Actual Energy Density: We must consider not only the light intensity but also the actual energy density. Energy density (mJ/cm²) reflects the light energy per unit area, which directly affects the depth and quality of curing. A photometer can be used to measure the actual energy density received by the coating.
4. Monitoring the curing effect: The cured coating is inspected, such as by testing its hardness, adhesion, and abrasion resistance, to confirm whether the curing is complete. If the coating surface is sticky or powdery, it usually indicates insufficient light energy and incomplete curing.

To ensure sufficient light energy and achieve the desired curing effect, the following measures can be taken:

1. Appropriately Select Light Source and Power: Choose a suitable light source wavelength and power, ensuring it matches the photoinitiator of the coating. For thick coatings or complex substrates, appropriately increase the light source power to ensure sufficient energy is provided.
2. Precisely Control Curing Time: Based on the coating thickness and production line speed, reasonably control the curing time. Avoid excessively long or short curing times to ensure coating stability and quality.
3. Optimize Production Line Configuration: Ensure the matching of lamp spacing, production line speed, and light source power. Regularly check the uniformity of the light source and its actual output to ensure the light energy required during production.

Light energy is one of the key factors affecting UV curing effect. Ensuring sufficient light energy improves production efficiency and guarantees coating quality. In actual operation, reasonably evaluating factors such as light source power, irradiation time, and light source wavelength matching is essential to ensure optimal curing results.

From wavelength matching to energy monitoring, Shenzhen Super-curing Opto-Electronic CO., Ltd. has been deeply involved in the UV curing field for 13 years. We understand the importance of stable output for industrial production. Choose professional equipment to eliminate curing blind spots.