The performance of UV lamps that affect curing is completely and accurately related to the four characteristics of ultraviolet spectral distribution, irradiance, radiation and infrared radiation.
1. UV Spectral Distribution It describes the wavelength distribution of phase radiant energy or radiant energy reaching a surface as a function of the wavelength emitted by the lamp. It is usually denoted by an associated standardized term. In order to display the distribution of UV energy, the spectral energy can be combined into a 10nm spectral band to form a distribution table. This allows comparison of different UV lamps and easier calculation of spectral energy and power. UV Wavelength - The effective wavelength for UV curing is 200-400 (nm)
Usually, multi-spectral band ray Detectors are used to test spectral radiance or radiation characteristics online. They obtain relevant information useful for the spectral distribution by sampling the radiant energy in a narrow frequency band (20~60nm). Since the structures of radiation Detectors produced by different manufacturers are different, it is possible to make a comparison, but it is difficult to make a comparison. There is no such standard of comparison between models and manufacturers.
UV lamps. Spectral distribution data for metal halide and mercury lamps:
High-pressure mercury lamp is an effective ultraviolet light-emitting wavelength with 365nm as the main wavelength and a range of about 254nm, 303nm and 313nm. Mainly used for curing UV varnishes and inks; the ultraviolet wavelength of metal halide lamps is mainly in the range of 200-245nm. Compared with high-pressure mercury lamps, long-wavelength UV radiation is more, and it is mainly used to cure UV inks.
2. UV radiation:
Illuminance is the radiant power reaching a surface per unit area. Radiation, expressed in watts or howitzers per square centimeter. It varies with the output power and efficiency of the lamp, the focal point of the reflector system and the distance to the surface. (This is the characteristics and geometry of the lamp, so not dependent on speed.) The high intensity, peak focused power placed directly under the UV lamp is called "peak radiance". Radiance includes all factors related to power supply, efficiency, radiant output, reflectivity, focusing sphere size and geometry.
Due to the absorbing properties of UV curable materials, less light energy reaches the surface than the surface. Curing conditions in these areas can vary widely. Materials with thicker optical thickness (or high absorption, or thicker physical structure, or both) may reduce light efficacy and result in insufficient deep curing of the material. In inks or coatings, a higher surface brightness will provide relatively higher light energy. The curing depth is more affected by the irradiation time (irradiation amount) than the irradiation time (irradiation amount). For highly absorbing (high opacity) films, the effect of brightness is more important.
High irradiance allows the use of less photoinitiator. The increase in photon density increases the collisions between photons and photoinitiator, thereby compensating for the decrease in photoinitiator concentration. This is effective for thicker coatings because the photoinitiator in the surface layer absorbs and prevents photoinitiator molecules of the same wavelength from reaching deeper layers.
3. Ultraviolet radiation
Radiant energy reaching a surface per unit area. Radiance represents the total number of photons reaching a surface (whereas radiance is the rate of arrival). Under any given light source, the amount of radiation is inversely proportional to velocity and directly proportional to exposure. Radiation is the time accumulation of radiation expressed in joules per square centimeter or millijoules per revolution. (Unfortunately, no information about brightness or spectrum is measured brightness. It's just the accumulation of energy at the exposed surface.) Its significance is that it is a characteristic display that includes a parameter of speed and a parameter of exposure time.
4. Infrared radiation density:
Infrared radiation is mainly infrared energy emitted by the quartz bubble of the ultraviolet source. Infrared energy and ultraviolet energy are collected together and focused on the work surface. It depends on the reflectivity of the infrared and the efficiency of the reflector. Infrared energy can be converted into radiation or radiation units. Usually, however, it is the resulting surface temperature that is the point to be aware of. The heat it produces can be harmful or beneficial.
There are many techniques for resolving the relationship between temperature and IR in combination with UV lamps. It can be divided into reducing emissions, transferring and controlling thermal movement. Emission reductions are achieved by using small diameter bulbs, since the surface area of hot quartz emits nearly all of the infrared. Transmission can be reduced by using a dichroic reflector behind the lamp; or by using a hot mirror between the lamp and the target. Thermal motion lowers the temperature of the target, but only after the IR causes the temperature to rise which can be controlled using cool air streams or radiators. Absorption of infrared energy is determined by the material itself – ink, coating or substrate. Velocity has a significant effect on the incident infrared energy and the temperature induced by the absorbed energy on the working surface. The faster this process is, the less infrared energy is absorbed, causing the temperature to rise. The production process can be speeded up by improving efficiency.
