UV UV Curing Analysis (Part 2)

UV lamp parameters

The effects of curing UV lamps can be fully and accurately linked by four characteristics: UV spectral distribution, irradiance, radiation dose and infrared radiation.

1. Spectral distribution It describes the phase radiant energy that is one of the functions of the lamp's emission wavelength.

The wavelength distribution of the radiant energy that arrives or reaches the surface. It is often expressed in a related standardized terminology. To show the distribution of UV energy, the spectral energy can be combined into 10 nm spectral bands to form a distribution table. This allows comparison between different UV lamps and easier calculation of spectral energy and power. Lamp manufacturers publish their spectral distribution data.

On-line detection uses a multispectral ray detector to characterize the spectral radiance or radiation. They obtain relative information useful for spectral distribution by sampling radiant energy in a relatively narrow (20-60 nm) frequency band. Due to the different construction of radiation detectors from different manufacturers, it is possible to compare them with each other, but it is difficult. There is no such standard to compare models and manufacturers.

2. Irradiance: Irradiance is the radiated power per unit area of ​​the surface reached. The degree of radioactivity is expressed in watts per square centimeter or watts. It varies with lamp output power, efficiency, focusing of the reflective system, and distance to the surface. (It is a characteristic of the lamp and its geometry, so it is not related to speed.) The high-intensity, peak-focus power reference placed directly under the UV lamp is referred to as "peak radiation." Radiosity includes all factors related to power supply, efficiency, radiant output, reflectivity, focused bulb size, and geometry.

Due to the UV-curable material's absorption characteristics, less energy is reached below the surface than in the surface layer. Curing conditions in these areas may be significantly different. A material with a thick optical thickness (either high absorptivity, or a thick physical structure, or both) may reduce light efficiency, resulting in insufficient solidification of the material. In inks or coatings, higher surface radiances provide relatively high light energy. The depth of solidification is more affected by the radiation than the longer exposure time (irradiation). The influence of radioactivity is more important for highly absorbent (high opacity) films.

High radiation allows the use of less light triggers. The increase in photon density increases the photon-light trigger collision, thus compensating for the decrease in photo-trigger concentration. This works for thicker coatings because the photo-trigger in the skin absorbs and blocks the same wavelength from reaching deeper photo-trigger molecules.

3. UV radiation

Radiation energy reaching the unit area of ​​the surface. The amount of radiation represents the total amount of photons that reach the surface (and the rate of radiation is the rate of arrival). Under any given source, the amount of radiation is inversely proportional to speed and is proportional to the amount of exposure. The amount of radiation is the cumulative time of radiation, expressed in terms of Joules per square centimeter or miliJoules. (Unfortunately, there is no information about the radiometric or spectral content being replaced by the amount of radiation measured. It is simply the accumulation of energy at the exposed surface. Its significance is that it is the only feature that includes the speed parameter and the exposure time parameter.

4. Infrared Radiation Density: Infrared radiation is mainly infrared energy emitted by a quartz bubble of a UV source. Infrared energy and UV energy are collected together and focused on the work surface. This depends on the IR reflectivity and reflector efficiency. IR energy can be converted to radiation or radiometric units. But usually, the surface temperature it produces is important for attention. The heat it generates can be harmful and may also be beneficial.

There are many technologies that combine UV lamps to solve the relationship between temperature and IR. Can be divided into reduced emission, transmission and control of heat movement. The reduction in emission is achieved by using small diameter bulbs because it is the surface area of ​​hot quartz that emits almost all of the IR. The reduction in transfer can be achieved by using a cold mirror behind the lamp; or use a hot mirror between the lamp and the target. Heat movement reduces the temperature of the target - but only after IR has caused a temperature rise - cooling airflow or heat sinks can be used to control heat movement. The absorption of IR energy is determined by the material itself—ink, coating, or substrate. The speed has a significant effect on the temperature caused by the incident IR energy and the energy absorbed by the work surface. The faster the process, the less IR energy is absorbed, causing the temperature to rise. It can speed up the production process by improving efficiency.

UV drying technology data

1. Most UV rays contain two UV wavelengths, both of which work simultaneously. Short waves work on the surface, longer waves act on the deep layer of ink or Lacquer. This is because short-wave energy is absorbed by the surface and cannot enter deep layers. Short-wavelength underexposure can cause the surface to become sticky, while insufficient long-wave energy can cause adhesion difficulties. 2. UV drying in CD production is used in two ways - namely protective adhesive drying and printing ink drying.

A. Protective Glue: Coverage of protective glue is almost always carried out by spraying - spinning. Then exposed under UV. There are many ways of exposure, which can be roughly divided into: rotating or not rotating; focusing, defocusing or no focus.

B. Rotation mode: In this mode, the DISC is fixed under the UV lamp and rotated so that its surface is within a certain distance from the in-focus or out-of-focus UV lamp. Although the rotation method seems to be a good way to provide uniform exposure to the DISC surface, it is not always the case. If the UV lamp is within or near the focal point, a strong light will pass through the center of the CD. As the disc rotates, its center continues to be exposed while the edges receive only two short-term "burst" UV lights. This can lead to poor drying of the edges.

Source: Huashi Wire Mesh